Particulate, absorbent, polymeric compositions containing interparticle crosslinked aggregates

Field of the Invention

The present invention relates to improved particulate absorbent polymeric compositions. Such polymeric compositions are those which, upon contact with fluid (i.e. liquids), such as water or body exudate liquids, swell and soak up such fluids. These polymeric compositions are especially useful on their own or as absorbent parts such as fibrous web structures that may be incorporated into absorbent articles such as diapers, incontinent adult pads, sanitary pads and the like. The present invention also relates to processes for producing such polymeric compositions.

General Framework of the Invention

Absorbent and particulate polymeric compositions can absorb large amounts of fluids such as water and exudate body fluids and are still capable of retaining such fluids under moderate pressures. Such absorption characteristics of such polymeric compositions make them especially useful for incorporation into absorbent articles such as diapers. For example, U.S. Patent No. 3,699,103, issued to Harper et al. on June 13, 1972 and U.S. Patent No. 3,670,731, issued to Harmon on June 20, 1972, refer to the use of particulate absorbent polymeric compositions (also known as hydrogels, hydrocolloids or superabsorbent materials) in absorbent articles.

However, the polymeric compositions absorbed

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Conventional particulates and particulates have the limitation that their fluid absorption rate is much lower than that of conventional cellulosic fiber webs due to the smaller proportion between surface area and mass of the particles constituting the polymeric composition. The surface area to particle mass ratio of the particulate absorbent polymer composition is important as it can control the overall fluid absorption rate of the bulk polymer composition. The surface area to mass ratio and thus the rate of fluid absorption can be substantially increased by decreasing the average mass particle size in the bulk polymeric composition. However, when these small or fine particles swell upon contact with liquids, the particles, when incorporated into a fiber web, tend to be easily forced into the capillaries between the web fibers. The swollen or partially swollen fine particles may also form a coagulated gel mass held together by the surface tension forces of the fluid, thereby forming a gel barrier. In either case, the resistance to fluid flow through the structure is increased, as the fluid flow channels are blocked within the fiber web or gel mass, resulting in a marked decrease in permeability. These phenomena are commonly referred to as gel blocking.

An attempt to break this balance between the rate of fluid absorption and gel blockage is to agglomerate a multiplicity of small particles into larger core particles by water. These water agglomeration techniques are disclosed in Published Japanese Patent Application SHO 61 (1986) -97,333 and Published Japanese Patent Application SHO 61 (1986) -101,586. While agglomeration with water of the particles results in a modest increase in the rate of fluid absorption due to the increased surface area to water ratio.

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mass of the larger particles, the water-agglomerated particles dissociate upon contact and / or swelling with an aqueous solution. This results in a concentration of swollen or partially swollen free fine particles that will contribute to the increased gel blocking effect by virtue of the mechanism described above.

Another attempt to solve the problem is to treat the surface of the distinct particles. A specific surface treatment is to crosslink the surface of the distinct particles so that each individual particle had a higher crosslink density between or near the polymer chains. surface of the particles. Such surface crosslinking techniques are described in U.S. Patent 4,666,983 issued to Tsubakimoto et al. On May 19, 1987 and U.S. Patent 4,734,478 issued to Tsubakimoto et al. col, 29 March 1988. Surface crosslinking of the particles results in a modest reduction in the above-mentioned gel blocking form, reducing the tendency of the separated particles to coagulate to form an impermeable gel mass during swelling. However, the particle fluid absorption rate does not increase as the ratio of surface area to particle mass remains relatively constant.

Therefore, the present invention seeks to solve the above problems by providing improved absorbent and particulate polymeric compositions with a high fluid absorption rate and a minimum of gel blocking properties.

Thus, it is an object of the present invention to provide particulate absorbent polymeric compositions with a high fluid absorption rate.

It is still another object of the present invention to provide particulate absorbent polymeric compositions.

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- ') them, which have minimum gel blocking properties.

It is a further object of the present invention to provide particulate absorbent polymeric compositions which have a high compressive strength during use (i.e. during swelling) so as to maintain and / or increase the permeability of the absorbent products incorporating such polymeric compositions.

It is also an object of the present invention to provide particulate absorbent polymeric compositions having minimal fine particle dissociation upon contact with the fluid or after swelling.

It is yet another object of the present invention to provide particulate absorbent polymeric compositions having a minimum of free fines in the dry state.

It is a further object of the present invention to provide particulate absorbent polymeric compositions which achieve predefined rates of fluid absorption by selecting specific precursor particle characteristics such as the average particle size or absorption capacity thereof. .

It is a further object of the present invention to provide a process for producing such particulate absorbent polymeric compositions.

It is also an object of the present invention to provide improved absorbent products, absorbent parts and absorbent articles (such as diapers or sanitary napkins) incorporating the particulate absorbent polymeric compositions of the present invention.

Summary of the Invention 30

The present invention provides improved particulate absorbent polymeric compositions comprising particulate cross-linked aggregates. The particulate cross-linked aggregates comprise precursor particles of substantially inorganic absorbent polymeric material.

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Water soluble hydrogel forming; and, a particle crosslinking agent that is reacted with the polymeric material of the precursor particles to form crosslinked bonds between the precursor particles. When the average particle size of the resulting polymeric composition by mass has increased by at least about 25% relative to the average mass particle size of the precursor particles, a sufficient number of interparticle crosslinked aggregates is formed. that the resulting polymeric composition has improved properties. The cross-linked aggregates between the particles have improved structural integrity (i.e. the aggregate remains intact when swollen and has relatively high compressive strength), increased absorption rate, and minimal gel blocking properties.

When contacted with a liquid, the crosslinked aggregates between the particles generally swell isotropically (i.e., they also swell in all dimensions), even under confining moderate pressures, and absorb these liquids. 0 Isotropic swelling of particulate cross-linked aggregates is achieved since particle cross-linked aggregates maintain the structural and spatial relationships of the precursor particles even after swelling (i.e. the aggregates maintain their integrity in both dry and swollen state) .Like this, precursor particles forming cross-particle cross-link aggregates do not dissociate as contact with liquids or after swelling in liquids (such that cross-particle cross-link aggregates are fluid stable) so that gel blocking is minimized . In addition, the particulate crosslinked aggregates have relatively high fluid absorption rates to provide rapidly absorbing polymeric compositions due to the high surface to mass ratio of the particulate crosslinked aggregates. Thus, the particulate cross-linked aggregates of the presence of

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Mod. 71 - 20,000 ex. This invention provides a polymer composition capable of rapidly absorbing liquids while minimizing gel blocking properties.

The present invention also relates to improved particulate absorbent polymeric compositions comprising crosslinked aggregates between particles formed of precursor particles having a relatively small particle size (i.e. fine precursor particles) using fine precursor particles to form crosslinked aggregates. between particles, the surface area to mass ratio of the aggregates is increased relative to the surface area to mass ratio of precursor particles of the same particle size as the aggregate, so that the resulting polymeric compositions incorporating such particulate crosslinked aggregates have particularly high fluid absorption rates (swelling rate), their gel blocking properties are minimized by removing the free fines from the swollen or partially swollen polymer composition. These particulate crosslinked aggregates also provide an efficient way to reduce the fines of the dry bulk polymeric composition which improves the handling and behavioral characteristics of such polymeric compositions.

The present invention further relates to absorbent products, absorbent parts and absorbent articles incorporating the polymeric compositions of the present invention comprising particulate cross-linked aggregates. The behavior of such products is improved by providing polymeric compositions that have high fluid absorption rates with minimal gel blocking properties.

In addition, the larger size of the particulate cross-linked aggregates helps to open fibrous web capillary channels incorporating such polymeric compositions. On the other hand, particle cross-linked aggregates minimize the migration of swollen or dried particles through the structures.

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absorbent due to their structural integrity (ie the finer particles are bonded together).

The present invention further relates to processes for producing such polymeric compositions comprising interparticle crosslinked aggregates. In the process of the present invention, an interparticle crosslinking agent is applied to the precursor particles; the precursor particles are physically associated to form a multiplicity of aggregates; and the interparticle crosslinking agent is reacted with the polymeric material of the aggregate precursor particles while maintaining the physical association of the precursor particles to form crosslinked bonds between the precursor particles and form interparticle crosslinked aggregates. The interparticle crosslinked aggregates are formed to such an extent that the average mass size of the particles of the polymeric composition is at least about 25% larger than the average mass size of the precursor particles. In a preferred process, the interparticle crosslinked aggregates are also surface crosslinked.

Brief Description of the Drawings

Although the specification is concluded with claims that specifically point out and distinctly claim the present invention, it is assumed that it will be better understood from the following description, made in conjunction with the accompanying drawings, in which:

Figure 1 is a sectional plan view);

Figure 2 is a longitudinal sectional view of only the disposable diaper absorbent core in one embodiment of a disposable diaper in accordance with the present invention, wherein most of the topsheet has been cut to more clearly show the diaper absorbent core underneath (an embodiment of an absorbent part according to the present invention)._t . . &gt; - -1 * - / 5 · &amp;. . —- i - '4'&gt; · Λ- * '2 *. ·' · .- (* &amp; .. &lt;&lt; 4 -, - -: - '' · -&gt;

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taken along line 2-2 of Figure 1;

Figure 3 is a cross-sectional view of only the absorbent core of the disposable diaper taken along section line 3 - 3 of Figure 1;

Figure 4 is a perspective view of an absorbent article according to the present invention used as an absorbent core in the disposable diaper shown in Figure 1;

Figure 5 is an enlarged fragmentary cross-sectional view of a layered (laminate) absorbent piece according to the present invention;

Figure 6 is a perspective view of another embodiment of a double layer absorbent piece according to the present invention;

Figure 7 is a cross-sectional view of the double layer absorbent part of Figure 6 taken along the cut line 7 - 7 of Figure 6;

Figure 8 is a plan view of an alternate embodiment of an absorbent piece according to the present invention;

Figure 9 is a perspective view of another alternative embodiment of an absorbent part according to the present invention;

Figure 10 is a cross-sectional perspective view of an embodiment according to the present invention of a disposable diaper containing the absorbent piece shown in Figure 9;

Figure 11 is a top view of a portion of an absorbent part according to the present invention depicting a preferred shape of the absorption zone;

Figure 12 is a approximately 30-fold enlarged photomicrographic view of a particulate absorbent polymer composition made in accordance with the present invention as described in Example 6 of this specification;

Figure 13 is a photomicrograph, enlarged

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approximately times of an interparticle crosslinked aggregate according to the present invention chosen from the sample shown in Figure 12;

Figure 14 is a approximately 40-fold enlarged photomicrograph view of a particulate absorbent polymeric composition made in accordance with the present invention as described in Example 11 of this specification, wherein the mass median particle size of the precursor particles equals about 84 micrometers;

Figure 15 is an approximately 110-fold enlarged photomicrograph of an interparticle crosslinked aggregate according to the present invention chosen from the sample shown in Figure 14;

Figure 16 is a perspective view of an absorbent product according to the present invention comprising a support and the interparticle crosslinked aggregate of the present invention joined to the support;

Figure 17 is a partially sectioned plan view of an embodiment of a sanitary napkin according to the present invention;

Figure 18 is a side view of the apparatus used to measure the gel expansion pressure of absorbent particulate polymer compositions;

Figure 18a is a side view of the stage mounting platform of the apparatus of Figure 18;

Figure 18b is a top view of the stage mounting platform of the apparatus of Figure 18;

Figure 18c is a top view of the sample alignment console of the apparatus of Figure 18;

Figure 18d is a top view of the sample holder of the apparatus of Figure 18;

Figure 18e is a side view of the sample holder of the apparatus of Figure 18;

Figure 18f is a side view of the compression shoe of the apparatus of Figure 18; and _ what _

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Figure 18g is a top view of the compression shoe of the apparatus of Figure 18.

Detailed Description of the Invention

The particulate absorbent polymeric compositions of the present invention are materials capable of absorbing large amounts of fluids (i.e. liquids), such as water and / or exudate body fluids (e.g., urine or menstrual fluids) and capable of retaining these fluids under moderate pressures. Typically, particulate absorbent polymer compositions according to the present invention swell and rapidly absorb fluids with little or no gel blockage.

As shown in Figures 12 and 14, the polymeric compositions according to the present invention are in particulate form. The term particulate is used herein to mean that the elements that make up the polymer composition are in the form of separate units called particles. The particles may be in the form of granules, powders, spheres, flakes, fibers, aggregates or agglomerates. Thus, the particles may have any desired geometric shape, such as cubic; rod-like; polyhedral; spherical; rounded; angular; irregular; irregularly sized irregular shapes (e.g., powdery products resulting from a grinding or spraying operation, or in the form of aggregates) or shapes that have a large difference between larger / smaller size, such as similar and needles or flake-like or fibrous forms and the like. As shown in Figures 12 and 14, the particles preferably comprise irregularly-shaped and irregularly sized interparticle crosslinked aggregates.

The polymeric compositions of the present invention are referred to herein as comprising. '•' Λλ ·^:···. ··&gt; «· '-ί ··; .ι '“•' ί &lt;ή&gt; ι» ·, · ί ·· »

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I endorse particles. It should be noted, however, that the term particles includes aggregates. As used herein, the term aggregate means a single particle formed from two or more previously independent particles (i.e. precursor particles) bonded together. Although it is relatively easy for those skilled in the art to determine which particles of the polymeric composition are aggregated, a specific procedure for identifying these aggregates is described later in this specification in the chapter entitled Test Method. Thus, throughout this specification, the term particles is used to mean the resulting units that make up the polymeric position, including aggregates, while the term precursor particles refers to the initial units used in forming the resulting particles of the composition. especially the aggregates. Particles that are formed from a single precursor particle will be specifically referred to as unaggregated particles.

Although particles and precursor particles may have sizes within a wide range, particles with specific size distributions and particle size are preferred.

For the purposes of the present invention, particle size is defined as the size of a precursor particle or particle which is determined by sieving particle size analysis. Thus, for example, a particle that is retained in a number 30 standard sieve with apertures of 600 micrometers is considered to have a particle size greater than 600 micrometers; a particle passing through sieve n². 30, with apertures of 600 micrometres and retained in standard sieve number 35, with apertures of 500 micrometres, is considered to have a particle size of between 500 and 600 micrometres; and a particle that passes through sieve number

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35, with apertures of 500 micrometres, is considered to have a particle size of less than 500 micrometres. In preferred embodiments of the present invention, the particles are generally about 1 to about 2000 micrometers in diameter or in cross section; more preferably, the particles have a particle size of from about 20 to about 1,000 micrometers.

Furthermore, for the purposes of the present invention, the average particle size, mass, or precursor particles is important for determining the characteristics and properties of the polymer composition.

Average particle size, mass, of a given particulate sample or precursor particle is defined as the particle size which is the average particle size of the sample on a mass basis. The process for determining the average mass particle size of a sample is described later in the present Testing chapter. In preferred embodiments of the present invention, the average particle size by weight is from about 100 to about 1500 micrometers, but more preferably from about 200 to about 1000 micrometers.

The polymeric compositions of the present invention are formed from polymeric materials capable of absorbing large amounts of liquids. (These polymeric materials are commonly referred to as hydrogels, hydrocolloids or superabsorbent materials). The polymeric compositions preferably comprise particles of substantially water-insoluble, hydrogel-forming, polymeric material. Polymeric materials useful for particles of polymeric compositions can vary widely. Specific polymeric materials useful in the present invention will be described below with reference to the polymeric materials that form the precursor particles.

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The polymeric, absorbent and particulate compositions of the present invention comprise particulate cross-linked aggregates. Cross-particle aggregates are aggregate particles formed by joining two or more previously independent precursor particles. The precursor particles are linked together by particulate cross-linking agents applied to them and are subjected to conditions sufficient to react such inter-particle cross-linking agents with the polymeric material of the precursor particles so as to form cross-linking bonds between the precursor particles which are present. form the aggregate while maintaining the physical association of the same particles. Figures 13 and 15 show photomicrographs of particle cross-linked aggregates in accordance with the present invention.

Precursor particles form the particulate cross-linked aggregates of the present invention. The precursor particles comprise substantially water-insoluble, hydrogel-forming absorbent polymeric material. Examples of polymeric materials suitable for use as precursor particles of the present process (and thus the particles of the resulting polymeric composition) include those prepared from polymerizable, unsaturated acid-containing monomers. Thus, such monomers include olefinically unsaturated acids and anhydrides that contain at least one olefinic double bond between one carbon atom and another carbon atom. More specifically, such monomers may be chosen from olefinically unsaturated and anhydrous acid carboxylic acids, olefinically unsaturated sulfonic acids and mixtures thereof.

Some non-acidic monomers may also be used to prepare the precursor particles of the present invention. Such non-acidic monomers may include, for example, water-soluble or water-dispersible esters of acid function-containing monomers as well as

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·. ......... ·. * &lt;£ * · -wtf of monomers containing neither carboxyl nor sulfonic acid groups. Optional non-acidic monomers may therefore include monomers containing the following types of functional groups: carboxylic acid or sulfonic acid esters, hydroxyl groups, amide groups, amine groups, nitrile group and quaternary ammonium salt groups. These non-acidic monomers are well known materials, and described in greater detail, for example, in U.S. Patent No. 4,076,663, issued to Masuda et al. on February 28, 1978 and U.S. Patent No. 4,062,817, issued to Westerman on December 13, 1977, which are incorporated herein by reference.

Carboxylic acid monomers and olefinically unsaturated carboxylic acid anhydrides include acrylic acids, typified by acrylic acid itself, methacrylic acid, ethacrylic acid, alpha-chloro-acrylic acid, alpha-cyano-acrylic acid, beta-methyl-acrylic acid (crotonic acid), alpha-phenyl acrylic acid, beta-acryloxypropionic acid, sorbic acid, alpha-chloro-sorbic acid, angelic acid, cinnamic acid, p-chloro-cinnamic acid, beta-stearyl-acrylic acid, itaconic acid, citraconic acid, mesaconic acid, glutaconic acid, aconitic acid, maleic acid, fumaric acid, tricarboxyethylene and maleic acid anhydride.

Olefinically unsaturated sulphonic acid monomers include aliphatic or aromatic vinyl sulphonic acids, such as vinyl sulphonic acid, allyl sulphonic acid, vinyl toluenesulphonic acid and styrene sulphonic acid; sulfonic acrylic and methacrylic acid, such as sulfoethyl acrylate, sulfoethyl methacrylate, sulfopropyl acrylate, sulfopropyl methacrylate, 2-hydroxy acid^-3-Acryloxypropyl sulfonic acid, 2-hydroxy-3-methacryloxypropyl sulfonic acid and 2-acrylamido-2-methylpropane sulfonic acid.

Preferred polymeric materials for use_Μ·., . ·’.

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The present invention has a carboxyl group. These polymers include grafted hydrolyzed starch-acrylonitrile grafted copolymers, partially neutralized starch-acrylonitrile grafted copolymer, acrylic starch-grafted copolymer, partially neutralized acrylic acid starch-grafted copolymer, saponified vinyl acetate copolymer, hydrolyzed acrylonitrile or acrylamide copolymers, lightly cross-linked products of any of the abovementioned copolymers, partially neutralized polyacrylic acid and slightly crosslinked partially neutralized polyacrylic acid products. These polymers may be used either independently or in the form of a mixture of two or more monomers, compounds or similar products. Examples of such polymeric materials are referred to in U.S. Patent Nos. 3,661,875; 4,076,663;

093 776; 4,666,983 and 4,734,498.

The most preferred polymeric materials for use as precursor particles are slightly cross-linked products of partially neutralized polyacrylic acids and their starch derivatives. More preferably, the particles comprise from about 50 to about 95%, preferably about 75% of slightly cross-linked, neutralized polyacrylic acid (e.g. poly (sodium acrylate / acrylic acid)).

As described above, the precursor particles are preferably slightly cross-linked polymeric materials. Crosslinking serves to make the precursor particles substantially insoluble in water and also partly serves to determine the characteristics of the precursor particles and the resulting polymeric composition for absorption capacity and extractable polymer content. Polymer crosslinking processes and typical crosslinking agents are described in more detail in

U.S. Patent No. 4,076,663, previously mentioned herein.

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The individual precursor particles may be formed in any conventional manner. Typical and preferred processes for producing the individual precursor particles are described in Republished U.S. Patent Re. 32 649, titled Hydrogel-Forming Polymer Compositions for Use in Absorbent Structures, by Kerryn A. Brandt, Steven A. Goldman and Thomas A. English on April 19, 1988; U.S. Patent No. 4,666,983, entitled Absorbent Article, issued to Tsuneo Tsubakimoto, Tadao Shimomura, and Yoshio Iris on May 19, 1987; and U.S. Patent No. 4,625,001, entitled Process for the Continuous Production of Cross-Linked Polymer, issued to Tsuneo Tsubakimoto, Tadao Shimomura and Yoshio Irie on July 25. November 1986. These patents are incorporated herein by reference.

Preferred processes for forming the precursor particles are those comprising polymerization processes in aqueous solution or in other solutions. As described in U.S. Patent Re.

649 above, aqueous solution polymerization involves the use of an aqueous reaction mixture to carry out the polymerization that forms the precursor particles. This aqueous reaction mixture is then subjected to polymerization conditions capable of producing the reaction mixture. a substantially water-insoluble and slightly cross-linked polymeric material. The mass of polymeric material thus formed is then pulverized or cut to form the individual precursor particles used in forming the interparticle crosslinked aggregates and the polymeric compositions of the present invention.

More specifically, the aqueous solution polymerization process for the production of the particles is pre-IA · &amp; · ”- '', ·· ... . J. '- - ·' · 7 ·,&gt; · »Κ &lt;£ ί. .

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Individual cursors comprise the preparation of an aqueous reaction mixture in which polymerization is carried out to form the desired precursor particles. One element of this reaction mixture is an acidic group-containing monomeric material, which forms the backbone of the precursor particles to be produced. The reaction mixture generally comprises about 100 parts by weight of the monomeric material. Another component of the aqueous reaction mixture comprises a crosslinking agent. Crosslinking agents useful in forming the precursor particles are described in more detail in U.S. Patent Re. 32,449 above, issued to Brandt et al; U.S. Patent No. 4,666,983 issued to Tsubakimoto et al. and U.S. Patent No. 4,625,001 issued to Tsubakimoto et al. 0 The crosslinking agent is generally present in the aqueous reaction mixture in an amount from about 0.001 to about 5 mol%, based on the total number of moles of the monomer present in the aqueous mixture (about 0.01 to about 20 parts by weight based on 100 parts by weight of monomeric material). An optional component of the aqueous reaction mixture comprises a free radical initiator including, for example, peroxygen compounds such as sodium, potassium and ammonium persulfates, caprylic peroxide, benzoyl peroxide, hydrogen peroxide, hydroperoxide of cumene, tertiary butyl diperphthalate, butyl perbenzoate. tertiary, sodium peracetate, sodium percarbonate and the like. Other optional components of the aqueous reaction mixture comprise the various non-acidic comonomer materials, including esters of the monomers containing essential unsaturated acidic functional groups or other comonomers which do not contain carboxyl or sulfonic acid functional groups.

The aqueous reaction mixture is subjected to polymerization conditions which are capable of producing na. ...

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mixes absorbent and substantially water-insoluble hydrogel-forming polymeric materials. Polymerization conditions are also further developed in the three above-referenced patents. Such polymerization conditions generally involve heating (thermal activation techniques) to a polymerization temperature of from about 0 to about 100 ° C, more preferably from about 5 to about 40 ° C.

C. The polymerization conditions under which the aqueous reaction mixture is maintained may also include, for example, subjecting the mixture or portions thereof to any conventional form of polymerization activating irradiation. Radioactive, electronic, ultraviolet or electromagnetic radiation are alternative conventional polymerization techniques.

The acid functional groups of the polymeric materials formed in the aqueous reaction mixture are also preferably neutralized. The neutralization may be carried out in any conventional manner which results in at least about 25 mol% or more preferably at least about 50 mol% of the total monomer used to form the material. The polymeric composition is comprised of acid group-containing monomers which are neutralized with a salt-forming cation. Such salt-forming cations include, for example, alkali metal, ammonium, substituted ammonium and amine cations, as more fully disclosed in U.S. Patent Re 32,649 issued to Brandt et al., And mentioned above.

While it is preferred that the precursor particles be produced by an aqueous solution polymerization process, it is also possible to carry out the polymerization process using multi-phase polymerization processing techniques such as reverse emulsion polymerization or suspension polymerization. inverse. In reverse emulsion polymerization or reverse suspension polymerization processes, the aqueous reaction mixture. · &amp;. .; &lt;».. - · *. ; - .. '' #&gt; '·

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: iff '*. The invention described above is suspended as fine droplets in a matrix of a water immiscible inert organic solvent such as cyclohexane. The resulting precursor particles generally have a spherical shape. Reverse suspension polymerization procedures are described in more detail in U.S. Patent No. 4,340,706, issued to Obaysashi et al. on July 20, 1982; U.S. Patent No. 4,506,052 issued to Flesher et al. on March 19, 1985; and U.S. Patent No. 4,735,987 issued to Morita et al. on April 5, 1988; each of these patents is incorporated herein by reference.

In preferred embodiments of the present invention, the precursor particles used to form the interparticle crosslinked aggregates are substantially dried. The term substantially dried is used herein to mean that the precursor particles have a liquid content, typically water or other solution content, of less than about 50% but preferably less than about 20% and, more preferably less than about 10% by weight relative to the precursor particles. Typically, the liquid content of the precursor particles is within the range of from about 0.01 to about 5% by weight of the precursor particles. The individual precursor particles may be dried by any conventional method, such as by heating. Alternatively, when the precursor particles are formed using an aqueous reaction mixture, water may be removed from the reaction mixture by azeotropic distillation.

The aqueous reaction mixture containing the polymer may also be treated with a dehydrating solvent, such as methanol. Combinations of these drying processes may also be used. The dehydrated mass of polymeric material may then be cut or pulverized to form substantially dried precursor particles of a polymeric material. '··&gt; \ -Γη * 4? · “' .. · 3 • ... * - ··&gt; .--. · ** ι · ν&gt; · 63,387

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which forms hydrogel, absorbent and substantially water-insoluble.

Preferred precursor particles in the present invention are those having a high absorption capacity, so that the resulting polymeric composition formed from such precursor particles also has a high absorption capacity. Absorption capacity refers to the ability of a given polymeric material to absorb liquids with which it comes into contact. Absorption capacity may vary significantly with the nature of the liquid being absorbed and the manner in which the liquid contacts the polymeric material. For purposes of the present invention, the absorptive capacity is defined e.g. the amount of synthetic urine (as further defined herein) absorbed by any polymeric material in terms of grams of synthetic urine per gram of polymeric material, in a process defined later in this chapter in the chapter on Test Methods. Preferred precursor particles in the present invention are those having an absorption capacity of at least about 20 grams, but more preferably equal to at least about 25 grams of synthetic urine per gram of polymeric material. Typically, the polymeric materials used in the present invention have an absorption capacity of from about 40 to about 70 grams of synthetic urine per gram of polymeric material. Precursor particles having this relatively high absorptive capacity are especially useful in absorbent parts and articles, since interparticle crosslinked aggregates formed from such precursor particles can, by definition, conserve satisfactorily high amounts of discharged body liquids such as urine.

The individual precursor particles may optionally be surface treated. For example, U.S. Patent No. 4,824,901, 63,387

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to Alexander et al. April 25, 1989, concerns the surface treatment of polymeric particles with a quaternary polyamine. If surface treated, the precursor particles are preferably surface crosslinked, as disclosed in U.S. Patent No. 4,666,983, Absorbent Articls, issued to Tsubakimoto et al. May 1987; and U.S. Patent No. 4 734,478, entitled Water Absorbing Agent, issued to Tsubakimoto et al. On March 29, 1988; which patents are incorporated herein by reference. As referred to in U.S. Patent No. 4 666 983, assigned to Tsubakimoto, the individual precursor particles may be surface crosslinked by applying a surface crosslinking agent to the precursor particles and allowing the surface crosslinking agent to react with the polymeric material on the surface of the particles.

Although all precursor particles of a given interparticle crosslinked aggregate or the resulting polymeric composition are preferably formed of the same polymeric material with the same properties, this need not always be so. For example, some precursor particles may comprise a polymeric material of a starch / acrylic acid grafted copolymer, while other precursor particles may comprise a polymeric material derived from slightly cross-linked partially neutralized polyacrylic acid products. In addition, the precursor particles of a specific interparticle crosslinked aggregate or present in the resulting polymeric composition may vary in shape, absorbability or any other properties or characteristics of the precursor particles. According to a preferred embodiment of the present invention, the precursor particles comprise a polymeric material consisting essentially of slightly crosslinked acidic products.

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partially neutralized lycrylic acid; all precursor particles having similar properties.

Precursor particles may comprise granules, powders, spheres, flakes, fibers, aggregates, agglomerates or the like. Thus, the precursor particles may have any desired geometric shape, such as cubic shape; rod-like; polyhedral; spherical; rounded; angular; irregular; irregularly sized irregular shapes (i.e. powder products resulting from grinding or spraying operations) or needle-like, flake-like or fibrous forms. Preferably, as shown in Figures 12 to 15, the precursor particles are in the form of a finely divided powder consisting of randomly sized, irregularly shaped granules or powdery flakes.

The precursor particles may also have a size that varies over a wide range. Preferably, the precursor particles have sizes ranging from about 1 to about 2000 micrometers in diameter or cross section. More preferably, the precursor particles have a particle size of from about 20 to about 1000 micrometers. The average mass particle size of the precursor particles is generally from about 20 to about 1500 micrometers; more preferably between about 50 and about 1000 micrometers. In the preferred embodiments of the present invention, the precursor particles preferably have a mass average particle size of less than about 1000 micrometres, preferably less than about 600 micrometres and most preferably less than about 60 microns. of 500 micrometers.

The interparticle crosslinked aggregates of the present invention also comprise an interparticle crosslinking agent. The interparticle crosslinking agent is applied to the precursor particles and is reacted with the polymeric material of the precursor particles.¹#,*·**- -;»

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Mod. 71 - 20,000 ex. -90/08 while maintaining the physical association between the same particles. This reaction forms crosslinked bonds between the precursor particles. Thus, the crosslinked bonds are interparticle in nature (that is, between different precursor particles). Without wishing to be bound by any theory or in any way limiting the present invention, the reaction of the interparticle crosslinking agent with the polymeric material of the precursor particles is assumed to be crosslinked bonds between the polymer chains of different precursor particles (i.e. (interparticle crosslinking bonds). For the preferred polymers of the present invention, the interparticle crosslinking agent is supposed to react to form crosslinking bonds between the carboxyl groups of the precursor particles. Without intending to be bound by any theory or limiting the scope of the present invention, for preferred carboxyl group-containing polymeric materials, it is assumed that the interparticle crosslinking agent reacts with the carboxyl groups of the polymeric materials to form chemical crosslinking bonds. covalent bonds between the polymeric chains of the different precursor particles. Covalent chemical crosslinking bonds are generally obtained as a result of the formation of ester, amide (imide) or urethane groups by reacting the functional groups of the crosslinking agents with the carboxyl groups of the polymeric material. In preferred embodiments, ester bonds are supposed to form. Thus, preferred interparticle crosslinking agents are agents which are capable of reacting with the carboxyl groups of the preferred polymers to form ester bonds.

Interparticle crosslinking agents useful in the present invention are those which react with the peripheral material of the precursor particles used to form the interparticle crosslinked aggregates. Suitable interparticle crosslinking agents may comprise a number of miscellaneous agents, such as, for example, as a cross-linker.

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halogen epoxy stations such as epichlorohydrin and alpha-methyl fluorohydrin; polyaldehyde compounds such as glutaraldehyde and glyoxazole; polyamine compounds such as ethylene diamine, diethylene triamine, triethylene tetramine, tetrethylene pentamine, pentaethylene hexamine and polyethylene imine; and polyisocyanate compounds such as 2,4-toluene diisocyanate and hexamethylene diisocyanate.

An interparticle crosslinking agent, or two or more substantially non-mutually reactive inter-particle crosslinking agents selected from the above group may be used. Particularly preferred interparticle crosslinking agents for use in the present invention with carboxyl-containing polymer chains are ethylene glycol, glycerol, trimethylol propane, 1,2-propanediol and 1,3-propanediol.

The proportion of interparticle crosslinking agent to be used in the process of the present invention is from about 0.01 part to about 30 parts by weight, preferably from about 0.5 to about 10 parts by weight. more preferably from about 1 to about 5 parts by weight per 100 parts by weight of precursor particles.

In the process of the present invention, other materials or agents may be used in conjunction with the interparticle crosslinking agent (s) as aids in the production of interparticle crosslinking aggregates or in the production or support of the interparticle crosslinking agent with polymeric material of the precursor particles.

For example, water may be used in combination with the interparticle crosslinking agent. Water functions to promote uniform dispersion of the interparticle crosslinking agent on the surface of the precursor particles and permeation of the interparticle crosslinking agent into the surface region of the precursor particles. Water also promotes a stronger physical association between the precursor particles of the aggregates that repre-

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Case: 4124X posts having at least two polymerizable double bonds; compounds having at least one polymerizable double bond and at least one functional group reactive with the polymeric material; compounds with at least two functional groups reactive with the polymeric material; polyvalent metal compounds; or monomers as previously described herein. Specific cross-linking agents useful in the present invention are described in the aforementioned U.S. Patent No. 4,076,663 and U.S. Patent No. 32,649, which are incorporated herein by reference.

When carboxyl groups are present on or within the polymeric materials (i.e. polymer chains) of the precursor particles, the preferred interparticle crosslinking agents have at least two functional groups per molecule capable of reacting with the group. carboxyl. Preferred interparticle crosslinking agents include polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, glycerol (1,2,3-propanotriol), polyglycerol, propylene glycol, 1 , 2-propanediol, 1,3-propanediol, trimethylol propane, diethanolamine, triethanolamine, polyoxypropylene oxyethylene oxypropyl block copolymer fatty acid sorbitan esters, polyoxyethylene sorbitan fatty acid esters, pentaerythritol and sorbitol; polyglycidyl ether compounds such as ethylene glycol glycidyl ether, polyethylene glycol diglycidyl ether, glycecylglycidyl ether, ether diglycerol-polyglycidyl ether, polyglycerol-polyglycidyl ether, sorbitol-polyglycidyl ether-polyglycyl ether-polyglycyl ether diglycidyl and propylene glycol diglycidyl ether; polyazyldine compounds such as 2,2-bishydroxymethylbutancttris- [3- (i-azidine) propionate], 1,6-hexamethyl toluene diethylene urea and diphenyl methane bis 4,4'-Ν, N'-diethylene urea; how/. _

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I

The rotations are pre-rotated, and the dryness or swelling integrity of the resulting interparticle crosslinked aggregates.

In the present invention the water is used in a ratio of less than about 20 parts by weight (0 to about 20 parts by weight), preferably from about 0.01 to 20 parts by weight, more preferably from about 0.1 to 10 parts by weight based on 100 parts by weight of precursor particles. The actual amount of water to use varies depending on the species of polymeric material and the size of the precursor particles.

Organic solvents may also be used in association with the interparticle crosslinking agent. Organic solvents are used to remove uniform dispersion of interparticle crosslinking agent on the surface of the precursor particles. The organic solvents are preferably hydrophilic organic solvents. Hydrophilic organic solvents useful in the present invention include lower alcohols, such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, secondary butanol and tertiary butanol; ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; ethers, such as dioxane, tetrahydrofuran and diethyl ether; amides, such as α, β-dimethyl formamide and N, N-diethyl formamide; and sulfoxides, such as dimethyl sulfoxide.

hydrophilic organic solvent is used in the present invention in a ratio of less than about 60 parts by weight (between 0 and about 60 parts by weight), preferably between about 0.01 and 60 parts by weight, and more. preferably from about 1 to about 20 parts by weight based on 100 parts by weight of precursor particles. The actual amount of hydrophilic organic solvent to be used varies depending on the species of polymeric material and the size of the precursor particles.

The interparticle crosslinking agent may also be used in admixture with water and one or more hydrophilic organic solvents. it has been found to use c.

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The formation of an interparticle / water crosslinking solution provides the maximum penetration of the crosslinking agent into the surface region of the precursor particles while a solution of interparticle crosslinking agent / hydrophilic organic solvent provides minimal penetration of the crosslinking agent. However, mixing of the three agents is preferred to control the proportion of interparticle crosslinking agent penetration into the surface region of the precursor particles. Specifically, it was found that the higher the ratio of water to the component used as organic solvent, the deeper the cross-linking agent penetration, the greater the stability in the presence of stress aggregates, and the greater the reduction in absorption capacity resulting from interparticle crosslinked aggregates. Typically, the ratio of water to hydrophilic organic solvent present in the solution should be from about 10: 1 to about 1:10. The interparticle crosslinking agent / water / hydrophilic organic solvent solution is used in a ratio of less than about 60 parts by weight (between 0 and about 60 parts by weight), preferably between about 0.01 and about 1%. 60 parts by weight and more preferably from about 1 to about 20 parts by weight based on 100 parts by weight of precursor particles.

Other optional components may also be mixed with the solution containing the interparticle crosslinking agent. For example, a starting agent, a catalyst or non-acid comonomer materials may be added. Examples of such materials suitable for use in the process of the present invention are described in Republished U.S. Patent Re. 32,649, hereinbefore referred to.

The process for producing polymeric compositions containing interparticle crosslinked aggregates involves the use of precursor particles of the type 7, 7,. ,.,: · ·_Λ, »«!,.&gt;

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believed in the present specification; applying an interparticle crosslinking agent to the precursor particles; the physical association of the precursor particles to form a multiplicity of aggregates; and reacting the interparticle crosslinker with the aggregate precursor particle polymeric material while maintaining the physical association of the precursor particles to form crosslink bonds between the precursor particles.

Interparticle crosslinking agent is applied to the precursor particles. The interparticle crosslinking agent may be applied by any of a variety of techniques and equipment used to apply to materials solutions including coating, pouring, pouring, dripping, spraying, atomizing, condensing, or dipping the crosslinking agent. interparticles on par. precursor particles. As used herein, the expression applied on means that at least a portion of the surface area of ​​at least one of the precursor particles to be bound to form the aggregate is coated with the interparticle crosslinking agent. Thus, the interparticle crosslinking agent may be applied to only a few precursor particles, to all precursor particles, to only a part of the surface of some or all of the precursor particles or to the entire surface of some or all of the precursor particles: Preferably, the interparticle crosslinking agent covers the entire surface of most of the pre. of all precursor particles, so as to improve the efficiency, mechanical strength and density of interparticle crosslinking bonds between the precursor particles.

In preferred embodiments of the process of the present invention, after the interparticle crosslinking agent has been applied to the precursor particles, the interparticle crosslinking agent is admixed.

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with the precursor particles by any of a number of mixing techniques to ensure that the precursor particles are completely coated with the interparticle crosslinking agent. When the precursor particles are completely coated with the interparticle crosslinking agent, and efficiency, the mechanical strength and density of the crosslinking bonds between the precursor particles are enhanced. The mixing operation can be performed using various techniques and equipment including various mixers or kneaders as is known in the art.

Prior to, during or after application of the interparticle crosslinking agent onto the precursor particles, the precursor particles are physically associated with each other to form a multiplicity of aggregates. The term physically associated is used herein to mean that the precursor particles are brought together and remain in contact as component parts in various spatial ways and relationships to form single units (aggregates).

Preferably, the precursor particles are physically associated with each other by applying an associating agent on the precursor particles and by promoting physical contact between the precursor particles on at least the part of their surface on which the associating agent has been applied. Preferred associating agents cause the polymeric material of the precursor particles, when they are contacted with each other, to adhere by the action of fluid surface tension forces and / or by entanglement of the polymer chains due to external swelling. The associating agents used in the present invention include hydrophilic organic solvents, typically low molecular weight alcohols, such as methanol, ethanol or isopropanol; Water; a mixture of hydrophilic organic solvents and water; certain agen

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interparticle crosslinking agents as previously described herein; volatile hydrophobic compounds such as hexane, octane, benzene or toluene; or mixtures thereof. Preferred associating agents are water, methanol, isopropanol, ethanol, interparticle crosslinking agents such as glycerol, or mixtures thereof. Typically, the coupling agent comprises a mixture comprising an interparticle crosslinking agent such that the interparticle crosslinking agent application operation is carried out simultaneously with the coupling agent application operation.

The coupling agents may be applied to the precursor particles by any of a variety of techniques and equipment used to apply to materials solutions including coating, pouring, pouring, spraying, atomizing, condensing or dipping the coupling agent onto the precursor particles. . The associating agent is applied over at least a portion of the surface area of ​​at least one of the precursor particles to be joined to form the aggregate. Preferably, the pooling agent is coated over the entire surface of the may. and preferably all precursor particles. The coupling agent is generally mixed with the precursor particles by any of a number of mixing techniques and mixing equipment to ensure that the precursor particles are completely coated with coupling agents.

When the associating agent has been applied to the precursor particles, the precursor particles may be physically contacted with each other in any of a number of different ways to proceed. For example, the binding agent alone may keep the particles in contact with each other. Alternatively, gravitational forces may be used to ensure contact between the precursor particles. In addition, the items can be placed in a container.

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Mod. 71 - 20,000 ex. - W / 08 be aware that it has a fixed volume to ensure contact between the precursor particles.

The precursor particles may, as a variant, be physically associated with each other by being constrained physically so that they are in contact with each other. For example, the precursor particles may be tightly packed in a fixed container with a fixed volume such that the precursor particles physically contact each other. Alternatively, or in combination with the above described process, the forces of gravity may be used to physically associate the precursor particles. They may also be physically associated with each other by electrostatic attraction or by introducing an adhesive agent (e.g., a water soluble adhesive material) that adheres them to each other. The precursor particles may also be attached to a third member (a substrate) such that the precursor particles are brought into contact with each other via that substrate.

The precursor particles may be associated with each other in various special relationships to form aggregates having a wide variety of shapes and sizes. For example, one or more precursor particles may be associated with a central or nuclear precursor particle; the precursor particles may be randomly associated such that a particular precursor particle is associated with one, two or more precursor particles; or the precursor particles may be associated according to a particular plane, shape or geometric model.

Although the precursor particles may be contacted according to a number of special relationships, the precursor particles must be made contactable by their surfaces on which the interparticle crosslinking agent or agents and / or the associating agent or agents have been or will be applied. Typically, the interparticle crosslinking agent or dq associating agent

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4BR1S9I coats the entire surface of the precursor particles so that they can be associated anywhere on their surfaces. However, if the interparticle crosslinking agent or coupling agent is applied only to a part of the surface of one or more precursor particles, measures shall be taken to ensure that the precursor particles are associated with each other on that surface.

Simultaneously or after the interparticle crosslinking agent has been applied and the precursor particles have been associated with each other, the interparticle crosslinking agent is reacted with the polymeric material of the aggregate precursor particles while maintaining the physical association of the particles. precursor particles to form cross-linked bonds between the precursor particles when interparticle cross-linked aggregates.

The reaction between the interparticle crosslinking agent and the polymeric material must be activated and completed to form the crosslinking bonds between different precursor particles, generating the interparticle crosslinked aggregates. Although crosslinking can be activated by irradiation (e.g., ultraviolet radiation, gamma radiation or X-radiation) or by a catalyst, the crosslinking reaction is preferably thermally activated (by heating). 0 active heating causes reaction and evaporates any volatile products present in the mixture. Such reaction conditions generally comprise heating the associated precursor particles and the interparticle crosslinking agent for certain time intervals and at certain temperatures. The heating operation may be carried out by use of the of a number of different devices known to include the various greenhouses or dryers known in the art.

Generally, the reaction is effected by heating

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the reaction mixture at a temperature above about 90 ° C for the time necessary to complete the crosslinking reaction. For each specific set of interparticle cross-linking agent or agents and precursor particle polymeric materials used, if the temperature is too low or the time is too short, the reaction will not be sufficiently developed, resulting in less interparticle crosslinking bonds and weaker bonds, the desired amount of interparticle crosslinked aggregates could not be produced. If the temperature is too high, the absorption capacity of the precursor particles may be degraded or the cross-links of the precursor particles, depending on the specific polymeric materials, may be degraded to the point that the resulting aggregates will not absorb large amounts of liquid. . In addition, if the times and temperatures are not correct, the extractable levels of the resulting aggregates may increase, thereby increasing the incidence of those forming gel block. Thus, the reaction should generally be carried out at a temperature of from about 120 to about 300 ° C, and more preferably from about 150 to 250 ° C.

The reaction between the interparticle crosslinking agent and the polymeric material of the precursor particles is complete until complete. The time required to complete the reaction varies depending upon the specific crosslinking agents, polymeric materials, additives and reaction conditions and the equipment chosen. One process for determining whether the reaction is complete is by measuring the loss of absorbency of the polymeric composition compared to the absorptive capacity of the precursor particles. The reaction has generally been found to be complete when the absorption capacity of the polymer composition has decreased from about 5 to about 70%. Although it is considered ideal that the ability to

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absorption of the polymeric composition did not decrease, it is assumed that the formation of crosslinked bonds decreases the absorption capacity such that the greater the loss of absorption capacity, the greater the strength and number ⁵ resulting aggregates). More specifically, the completion of the reaction can be verified by the following equation:

£ (100 + R) Q / P &lt;95

Mod. 71 - 20,000 ex. - 70/08 where P represents the absorption capacity of the precursor particles; Q represents the absorption capacity of the reaction product; and R represents the amount, expressed in parts by weight, of the interparticle crosslinking agent used per 100 parts by weight of precursor particles. In certain embodiments, the decrease in absorption capacity is from about 15 to about 60%. Thus, for the present invention, the time required to complete the reaction in the absence of catalysts is generally from about five minutes to about six hours, but more preferably from about ten minutes to about three hours. by decreasing the absorption capacity as defined above.

For the preferred polymeric material of the precursor particles, mildly cross-linked products of partially neutralized polyacrylic acid, and for preferred interparticle crosslinking agents such as glycerol or trimethylol propane, the conditions of the reaction involve a temperature of from about 1 ° C to about 10 ° C. 170 and about 220 ° C for about two hours to about twenty minutes respectively. More preferably, the reaction is carried out at temperatures from about 190 to about 210 ° C for about forty-five minutes to about thirty minutes, respectively. Actual times and temperatures used vary depending on the specific polymeric materials used for the precursor particles, the specifically used interparticle crosslinking agents, and the presence or absence of catalyst.

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accelerating reaction.

The crosslinking reaction may be performed by acidifying an initiator and / or catalyst to the interparticle crosslinking agent to decrease the time and / or temperature and / or the amount of interparticle crosslinking agent required to join the precursor particles together. . However, the reaction is generally carried out without catalyst.

The physical association of the precursor particles needs to be maintained during the reaction phase so that the interparticle crosslinked aggregates of the present invention form at especially high percentages. If, during the reaction phase, there are sufficient forces or stresses. In order to dissociate the precursor particles, the crosslinking bonds between the precursor particles (interparticle crosslinking bonds) may not form. The physical association of the precursor particles is typically maintained by causing a minimum of dissociation forces or stresses during the reaction operation.

As an optional and preferred step in the process of forming the polymer compositions comprising interparticle crosslinked aggregates, at least the interparticle crosslinked aggregates and preferably the remaining unaggregated particles of the polymer composition are superficially treated. For example, U.S. Patent No. 4 No. 824,901 issued to Alexander on April 25, 1989 relates to the surface treatment of the polymeric particles with a quaternary polyamine. In a method described by way of example, the polymeric material existing at least in the vicinity of the surface of the precursor particles is superficially cross-linked, as set forth in U.S. Patent No. 4 666 983, entitled Absorbent Articls, issued to Tsubakimoto et al on May 19, 1987; and U.S. Patent No. 4,734,478, entitled Water Absorbing Agent, issued to Tsubakimoto et al.

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on March 29, 1988; These patents are incorporated herein by reference. Using a surface crosslinking operation in the present invention, the creep resistance of the resulting interparticle crosslinked aggregates is improved and thus the polymeric composition, when swollen, is improved. 0 The interparticle crosslinking agent applied to the precursor particles should preferably also serve as a surface crosslinking agent such that the interparticle crosslinked aggregates are simultaneously formed and surface crosslinked.

As noted above, the operations of the interparticle crosslinked aggregate production process need not be performed in any specific order. In addition, the operations may be performed simultaneously. In the present specification, the following describes, by way of example, processes using the operations identified above.

In a preferred embodiment, the interparticle crosslinking agent is applied to the precursor particles when they are physically associated with each other to form a multiplicity of aggregates. 0 The interparticle crosslinking agent is then reacted with the associated precursor particle aggregates either immediately after the above operations are completed or after the mixture has been allowed to stand for a while to simultaneously form. and superficially cross-linking the interparticle crosslinked aggregates. Typically, the precursor particles are mixed with a mixture of an interparticle crosslinking agent, water and a hydrophilic organic solvent. The solution ie interparticle crosslinking agent, water and hydrophilic organic solvent also serves as a precursor particle binding agent. The interparticle crosslinking agent also preferably serves as a surface crosslinking agent. The precursor particles are physically

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Mod. 71 - 20,000 ex. - 90/08 associated with each other when the mixture is applied on them. 0 crosslinking agent is subsequently made re? rotating with the associated precursor particle aggregates by heating at the temperature and time required to form cross-linked bonds between different precursor particles and simultaneously surface cross-linking the resulting interparticle cross-linked aggregates and a significant, if not all, of the unaggregated particles. of the polymer composition.

In an alternative embodiment, the interparticle crosslinking agent is applied to the precursor particles; the precursor particles are then physically associated with each other; and the interparticle crosslinking agent is subsequently reacted with the precursor particles to form interparticle crosslinked aggregates.

In another embodiment which may be used as a variant, the precursor particles are associated with each other and subsequently an interparticle crosslinking agent is applied to the associated precursor particles. The interparticle crosslinking agent is then reacted with the precursor particles to form the interparticle crosslinked aggregates.

In yet another alternative embodiment of the present invention, these operations are performed simultaneously, producing interparticle crosslinked aggregates.

The interparticle crosslinked aggregates of the present invention should be present in the polymer composition in an amount sufficient to provide the benefits referred to herein. One method for determining if sufficient quantities of particulate crosslinked aggregates are present in the polymeric composition is to determine the deviation of the mean particle size value, in mass, between the precursor particles and the resulting polymeric composition. Preferably,

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3 The variation in mass average particle size should be such that the resulting polymeric composition has an average mass particle size of at least about 25%, preferably about 30%. more preferably about 40% and more preferably about 50% larger than the average mass particle size of the precursor particles. In preferred embodiments of the present invention, the mass average particle size of the precursor particles is less than about 1000 micrometers, preferably less than about 600 micrometers, and most preferably less than about 1000 micrometers. 500 micrometers.

In especially preferred embodiments of the present invention, the mass average particle size of the precursor particles ⁹and realistically small (that is, the precursor particles are fine particles). The use of large amounts of fine precursor particles has been found to form interpair crosslinked aggregates. particularly high surface to mass ratio to give high swelling rates. Figure 14 represents an embodiment of such a polymeric composition, while Figure 15 represents an interparticle crosslinked aggregate comprising such fine precursor particles. In these especially preferred embodiments, the mass average particle size of the precursor particles is less than about 300 micrq meters. In preferred embodiments, the mass average particle size of the precursor particles is less than about 180 micrometres, preferably less than 150 micrometres or more preferably less than about 106 micrometres. In an exemplary embodiment, at least about 90% of precursor particles have a particle size of less than about 300 micrometers, and preferably less than about 150 micrometers. Since interparticle cross-linked aggregates formed from such small precursor particles typically integrate many precursor particles, the deviation in grain

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average mass nullometry is much larger than the deviations found when using larger precursor particles. The deviation in mass average particle size is such that the resulting polymeric composition has an average mass particle size of at least about 50%, preferably about 75%, more preferably about 100% and more preferably. still about 150% larger than the average mass particle size of the precursor particles.

The amount of interparticle crosslinked aggregates within the polymer composition may also be defined in terms of the weight percent of interparticle crosslinked aggregates within the polymer composition. For the preferred polymeric compositions of the present invention, at least about 25% by weight of the particles of the polymeric composition, but more preferably at least about 30% by weight, and most preferably at least about 25% by weight. 40% by weight comprises interparticle crosslinked aggregates. In the most preferred embodiments, at least about 50% by weight, but more preferably at least about 75% by weight, and most preferably at least about 90% by weight of the particles. of the polymeric composition comprise interparticle crosslinked aggregates.

An indication that crosslinked bonds are being formed between the previously independent precursor particles is the fact that the resulting interparticle crosslinked aggregates are generally stable in the presence of fluids (i.e.^:liquids). The term fluid stable is used herein to mean a unit of aggregates which, upon contact with an aqueous liquid fluid or upon swelling (with and / or without tension) in an aqueous fluid, remain substantially intact (i.e. at least two of the previously independent component precursor particles remain attached to one another). Although the definition of fluid presence stability considers that at least two of the

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Since the precursor moieties remain attached to each other, it is preferable that all precursor particles used to make the specific interparticle crosslinked aggregate remain together. However, it should be recognized that some precursor particles may dissociate from the interparticle crosslinked aggregate if, for example, certain particles have subsequently been agglomerated with water to the interparticle crosslinked aggregate.

The fluid stability of the interparticle crosslinked aggregates of the present invention allows the interparticle crosslinked aggregate to maintain its structure in both the dry and wet (swollen) state, to immobilize the component precursor particles and minimize particle migration, and to maintain an accelerated rate of fluid absorption. In an end product such as an absorbent part, fluid stability is beneficial as it reduces gel blockage as the precursor particles remain aggregated even when in contact with excess liquids, allowing the use of previously independent fine particles in aggregate form. , and increasing the fluid absorption level of the resulting polymeric composition, while minimizing the incidence of gel blockage. In addition, larger particles of interparticle crosslinked aggregates open capillary channels in the absorbent organ, providing better liquid handling characteristics.

The stability of the aggregates in the presence of fluids can be determined by a two step process. The initial dynamic response of the aggregate unit is observed upon contact with an aqueous fluid (synthetic urine) and then the equilibrium condition of the completely swollen aggregate is observed. A test method for determining fluid stability based on these criteria is described later in this specification in the Test Methods chapter.

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As noted above, interparticle crosslinked aggregates retain their structural integrity even after swelling. This structural integrity can be measured in terms of the gel expansion pressure of the sample. Gel expansion pressure of the polymeric composition refers to the ability of a sample of an absorbent, particulate and partially swollen polymeric composition to maintain its structural integrity, resisting deformation and widening. The expansion pressure of the gel may vary as a function of particle size, the solution used to swell the polymeric material, the relative amount of absorbed synthetic urine (eg charge X) and the geometrometry of the test apparatus. Charge X refers to the number of grams of synthetic urine added per gram of absorbent and particulate polymeric composition. Gel expansion pressure, as used herein, is defined in terms of the net force exerted by a partially swollen polymeric material when trying to reclaim with relative elasticity its relative structural geometry in the section. when it is being volumetrically constrained in a partially swollen state. It has been found desirable to use particles having a gel expansion pressure as high as possible in absorbent parts to minimize gel blockage and to ensure fluid distribution within the structure. Gel expansion pressure is measured in terms of kilodines per square centimeter. A process for determining gel expansion pressure is described later in the present Assay Methods chapter.

Interparticle crosslinked aggregates provide a polymer composition with a high fluid absorption rate measured by its swelling rate. The swelling rate of a polymer composition refers to the average rate of fluid absorption for a given amount of synthetic urine per sample of the polymer composition. The swelling rate as defined in

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Mod. 71 - 20,000 ex. · 90/08

In this specification, it is a measure of the rate of diffusion of liquid into the absorbent polymer, modified by the permeability of the overall gel mass. Thus, the permeability of the gel mass can become the limiting factor by limiting the rate at which free fluid can reach other particles of the mixture. The swelling rate is measured and defined in terms of grams of synthetic urine per gram of polymer per second. The swelling rate can be determined using a method described hereinafter in the Assay Method chapter.

Preferred absorbent and particulate polymeric compositions, which comprise interparticle crosslinked aggregates according to the present invention, have a gel expansion time of thirty minutes under a 28X charge (i.e. as defined above, and 28 grams of urine). added per gram of polymer) greater than or equal to about 20 kilodines per square centimeter, but preferably greater than or equal to about 25 kilodines per square centimeter. At a load of 15X, the thirty-minute gel expansion pressure of the preferred polymer compositions is greater than or equal to about 45 kilodines per square centimeter, but more preferably greater than or equal to about 60 kilodines per square centimeter. square centimeter. The swelling rate of the polymeric compositions of the present invention at a load of 28X is preferably greater than or equal to about 0.3 g / gf, but more preferably greater than or equal to about 0.5 g / g / s. For especially preferred embodiments of the polymer compositions of the present invention, the swelling rate at a load of 28X is preferably greater than or equal to about 1.0 g / g / s, but more preferably greater than or equal to about 1.1 g / g / s, more preferably greater than or equal to about 1.25 g / g / s.

As noted above, the ratio of surface area to mass of a given particle is a

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Particle fluid rate and inlet indication. The greater the surface area to particle mass ratio, the more area there is for the diffusion of the liquid to be absorbed. Thus, particles having a larger portion of surface area to mass are preferred when the gel expansion pressure characteristics (i.e. without loss of high gel expansion pressure values) and the other properties are similar. The surface area to mass ratio is defined as a ratio of square meters per gram of material. The surface area to mass ratio of a given polymer composition can be determined according to the method described herein in the Test Methods chapter. In the absorbent and particulate polymeric compositions of the present invention, the surface area to mass ratio of the interparticle crosslinked aggregates is greater than the surface area to mass ratio of unaggregated particles of the same size, such that the swelling rate of the particulate matter. polymeric compositions containing interparticle crosslinked aggregates is increased. In addition, the swelling rate of interparticle crosslinked aggregates is generally greater than the swelling rate of precursor particles forming interparticle crosslinked aggregates.

Another characteristic feature of the polymeric compositions of the present invention which is especially useful in the absorbent parts and articles referred to herein is the level of extractable polymeric material present in such compositions. Levels of extractable polymer may be determined by contacting a sample of polymeric composition with synthetic urine for a substantial period of time (e.g. at least sixteen hours) that is required to achieve the extraction equilibrium, then filtering the hydrogel formed from the supernatant liquid and finally determining the polymer content of the filtrate. The process used in determining the extractable polymer content of pof f

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Mod. 71 - 20,000 ex. 90/08 Limerics is referred to in Republished U.S. Patent No. Re. 32,649, previously referred to in the present specification. Polymeric compositions having a synthetic urine equilibrium extractable content of not more than about 17%, preferably not more than about 10% by weight of the polymeric material, are particularly preferred in the present invention.

In use, particulate absorbent polymer compositions comprising interparticle crosslinked aggregates are contacted with liquids such that the particles swell and absorb such liquids. Generally, the interparticle crosslinked aggregates of the present invention swell isotropically, even under moderate confinement pressures, so that the interparticle crosslinked aggregate retains its relative geometry and spatial relationships even after swelling. The precursor particles which form the interparticle crosslinked aggregate do not dissociate upon contact with or after swelling in the liquid to be absorbed (i.e., the interparticle crosslinked aggregates are fluid stable) such that the fine particles do not rupture. nor do they actually block gel to acquire liquids. Interparticle crosslinked aggregates have relatively high fluid absorption rates to provide rapid acquisition materials due to the high surface to mass ratio of interparticle crosslinked aggregates.

Although the use of the polymeric compositions of the present invention are specifically presented in terms of their use in absorbent products, absorbent parts and absorbent articles, it is to be understood that particulate absorbent polymer compositions comprising interparticle crosslinked aggregates may be used. be used for many purposes and in many other fields of use. For example, the polymeric compositions of the present invention may be used in containers containing

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Mod. 71 - 20,000 ex. - »/ 08 bullet; drug delivery devices; wound cleaning devices; burn treatment devices; materials for ion exchange columns; Construction Materials; agricultural or horticultural materials, such as seed protection or water retention sheets; and industrial uses, such as sludge or oil dehydrating agents, materials for preventing dew formation, drying agents and moisture control materials.

Interparticle crosslinked aggregates or polymeric compositions comprising interparticle crosslinked aggregates according to the present invention are useful when attached to a support. Figure 16 depicts one embodiment of an absorbent product 1600, wherein an individual interparticle crosslinked aggregate 1610 is attached to a support 1620. The supports 1620 useful in the present invention include absorbent materials such as cellulose fibers. The supports 1620 may also be any other supports known in the art, such as nonwoven webs, fabric webs, foams, superabsorbent fibers such as polyacrylate fibers or FIBERSORB fibers (sold by Arco Chemical Company of Wilmington, DE ., United States of America), apertured polymeric webs, modified cellulose film, warp webs, synthetic fibers, metallic sheets, elastomers and the like. 0 Interparticle cross-linked aggregate 1610 may be attached directly or indirectly to the supports 1620 or may be attached thereto by a chemical or physical bond, for example by known processes including adhesives or reacting chemicals to adhere the interparticle crosslinked aggregate 1610 to the supports. 1620.

As shown in Figures 1 to 11, the particulate absorbent polymeric compositions of the present invention comprising interparticle cross-linked aggregates, either of the broadly defined type or of the preferred or especially preferred types (

I

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described above may be employed in combination with fibrous materials to form improved absorbent products such as absorbent parts. The absorbent parts of the present invention are described herein in relation to their use in absorbent articles; However, it should be borne in mind that potential applications of absorbent parts should not be limited to absorbent articles.

The absorbent parts of the present invention are generally compressible, conformable, non-irritating to the skin and capable of absorbing and retaining liquids and certain body exudations, it is to be understood that for the purposes of the present invention, an absorbent part is not necessarily limited to , to a single layer or to a single sheet of material. Thus, an absorbent piece may comprise laminates, webs or combinations of various sheets or webs of the types of material already described herein. Therefore, as used herein, the term piece includes the term pieces or layers or layers. Preferred absorbent parts herein. The invention is webs or wads comprising tangled masses of fibers (fibrous material or fiber material) and the absorbent and particulate polymeric compositions comprising the interparticle crosslinked aggregates of the present invention. Most preferred absorbent parts comprise a web of a mixture of fibrous materials and specific amounts of the particulate absorbent polymer composition comprising the interparticle crosslinked aggregates described herein.

In the absorbent parts of the present invention, various types of fiber materials may be used. Any type of fiber material that is suitable for use in conventional absorbent products is also suitable for use in the absorbent parts of the present invention. Specific examples of such fiber materials include cellulose fibers, modified cellulose fibers, rayon, polypropylene.

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pylene and polyester fibers such as polyethylene terephthalate (DACRON), hydrophilic nylon (HYDROFIL) and the like. Other fiber materials include polyvinyl fluoride cellulose acetate, polyvinylidene chloride, acrylic fibers, polyvinyl acetate, polyamides (such as nylon), bicomponent fibers, tricomponent fibers, mixtures thereof, and the like. Hydrophilic fiber materials are preferred. Examples of suitable hydrophilic fiber materials include, in addition to some fibers already mentioned, hydrophilized hydrophobic fibers, such as surfactant-treated or silica-treated thermoplastic fibers, derived for example from polyolefins, such as polyethylene or polypropylene, polyacrylic fibers, polyamides, polystyrenes, polyurethanes and the like. Indeed, hydrophobic hydrophobic fibers which are not in themselves and very absorbent, and which therefore do not provide webs of sufficient absorbent capacity to be useful in conventional absorbent products, are suitable for use in the absorbent parts of the fabric. present invention by virtue of its ability to act as a wick. This is because, in the structures of the present invention, the ability of the fibers to act as a wick is as important if not even more important than the absorbent capacity of the fiber material itself due to the high fluid absorption rate and the lack of gel-blocking properties of the absorbent and particulate polymer compositions of the present invention used in such absorbent parts. Hydrophobic synthetic fibers may also be used, but are less preferred.

For reasons of availability and cost, cellulosic fibers are generally preferred for use as hydrophilic fiber material of absorbent parts.

Most preferred are wood pulp fibers, which are also referred to as air-deposited felt.

-Kl _

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<img file="PT97236B_D0048.tif" />

Other cellulosic fiber materials which may be useful in certain absorbent parts according to the present invention are chemically stiffened cellulosic fibers. Chemically stiffened cellulosic fibers pre. Wounds are the twisted, twisted and twisted cellulosic fibers that can be produced by internal crosslinking of the cellulose fibers with a crosslinking agent. The types of fi. Coiled, twisted and stiffened cellulosic arms useful as hydrophilic fiber material of the absorbent parts of the present invention are described in detail in U.S. Patent No. 4,822,453 entitled Absorbent Structure Containing. Individualized Crosslinked Fibers), issued to Dean et al, April 18, 1989; in U.S. Patent No. 4 888 093, entitled Individualized Reticulated Fibers and Process for the Fa. Individualized Crosslinked Fibers and Process for Making Said Fibers, granted to Dean et al. on December 19, 1989; U.S. Patent No. 4,889,595, entitled Process for Making Individually Crosslinked Fibers Having Processes and Their Fibers, Crosslinked Fibers Having Reduced Residuals and Fibers Thereof, issued to Herron et al. on December 26, 1989; in U.S. Patent No. 4 889 596, entitled Process for Making Individualized Crosslinked Fibers and their Fibers (Crosslinked Fibers and Thereof Fibers Thereof). granted to Shoggen et al. on December 26, 1989; in U.S. Patent No. 4 889 597, entitled Process for Making Wetted Structures Containing Individualized Stiffened Fibers (Process for Making Wet-Laid Structures), granted to Bourbon et al. on December 26, 1989; and U.S. Patent No.

898 642, entitled Twisted Cellulosic Fibers, Chemistry_ Aft _

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<img file="PT97236B_D0049.tif" />

Mod. 71 · 20,000 ex. · »/ 08 Stiffened, and Made-Up Absorbent Structures (Twisted, Chemically Stiffened Cellulosic Fibers and AbsoBent Structures Made Therefrom), issued to Moore et al. February 6, 1990. All of these patents are incorporated herein by reference.

As used herein the term hydrophilic refers to fibers or fiber surfaces that are wetted by the liquids deposited on the fibers (i.e. when water or aqueous body liquids readily spread over or throughout fiber surface, without regard to whether the fiber is soaked in fluid or gel), 0 The current state of the art for wetting materials allows the definition of hydrophobicity (and wetting) in terms of contour angles and surface tension of the liquids and solids involved. This is further elaborated in the American Chemical Society Publication, Contact Angle, Wettability and Adhesion, edited by Robert F. Gould and copyrighted 1964. A fiber or the surface of a fiber is said to be wetted by a liquid or when the contact angle between the liquid and the fiber or its surface is less than 90 degrees, or when the liquid tends to spontaneously spread over the surface. long fiber surface; normally both of these conditions are coexistent.

The relative amount of fiber material and absorbent and particulate polymeric composition used in the absorbent parts of the present invention may be more conveniently expressed in terms of weight percent relative to the absorbent part. The absorbent parts preferably contain from about 2 to about 98%, but more preferably from about 5 to about 75% and most preferably from about 10 to about 60% by weight. absorbent piece of particulate absorbent polymer composition. This concentration of particulate absorbent polymer composition may be expressed in terms of proportion. Ω _

'.-,·. ,. &lt;·&gt;$

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by weight of particulate fiber. This ratio can range from about 98: 2 to about 2: 98. For the largest parent¹Of the absorbent parts, the optimum weight ratio of fiber to particle is from about 95: 5 to about 25: 75, and more preferably from about 90: 10 to about 40.60.

In addition, the particulate absorbent polymer composition may be dispersed in various weight proportions in the different regions and thicknesses of the absorbent part. For example, the mixture of fiber material and particulate absorbent polymer composition may be placed only in certain parts of the absorbent part. Preferably, the absorbent part contains a uniformly distributed mixture of hydrophilic fiber material and particulate absorbent polymer composition. The polymer composition may be substantially uniformly dispersed (completely dispersed) throughout the absorbent part, as disclosed in U.S. Patent 4,610,678, High-Density Absorbent Structures. ), issued to Paul T. Weisman and Etephan A. Goldman on September 9, 1986, which patent is incorporated herein by reference. The polymer composition may, as a variant, be distributed in regions or zones with higher concentrations of polymer composition than other regions or zones.

For example, U.S. Patent No.

699 823, issued to Kellenberger et al. on October 13, 1987, refers to an absorbent part having the particulate absorbent polymer composition distributed on a positive gradient across at least part of the thickness of the absorbent part. Preferably, the concentration gradient across the thickness has the minimum concentration at or near the surface of the absorbent piece receiving liquids (i.e. the upper surface) and the maximum concentration at or near the lower surface of the part. absorbent. That patent is incorporated herein. . '· »- ·&gt; · * - · - *,. . . · - · '*** «

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descriptive memory as reference.

As indicated above, the absorbent and particulate polymeric compositions of the present invention may have a particle size that varies over a wide range. However, when using absorbent parts, other considerations may exclude the use of very small particles or very large particles. For reasons of industrial hygiene, particles having a particle size of less than about 30 micrometers are less desirable. Particles having a particle size greater than about 2 millimeters are also undesirable because they may cause a feeling of granularity in the absorbent part, which is undesirable from the consumer's point of view. Preferred particles for use in the present invention are those having a particle size of from about 45 to about 1,000 micrometers.

The density of the absorbent parts of the present invention may be of some importance in determining the absorbent properties of the absorbent parts and the absorbent articles in which such parts are employed. The density of the absorbent parts of the present invention is generally from about 0.06 to about 0.5 g / cm3 and more preferably from about 0.09 to about 0.30 g / cm3. cm. The density values ​​of these structures are calculated from their base weight and the caliper-measured dimensions. The measured dimensions are determined under a light load of 10 g / cm. The basis weight is determined by slicing a sample of a certain size and weighing the sample on a normal scale, the basis weight being determined from the weight and area of ​​the sample. Density and basis weight values ​​include the weight of the particles of the polymeric composition.

The absorbent parts of the present invention may contain a wide variety of optional materials in addition to the fiber materials and components of the polymer composition. Such optional materials may include, for example,

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pio, auxiliaries for fluid distribution, antimicrobial agents, pH control agents, odor control agents, perfume, etc. If present, these optional components generally do not constitute more than about 30% by weight of the absorbent part of the present invention.

The absorbent parts of the present invention comprising a mixture of fiber material and particulate absorbent polymer composition according to the present invention may be prepared by any process or technique._Lwhich provides a web comprising a combination of the fibers and particles of the polymeric composition. The absorbent parts of the present invention are preferably formed by air-laying a substantially dry mixture of fiber and particles of the polymeric composition and, if desired or necessary, increasing the density of the web. This procedure is described in more detail in U.S. Patent No. 4 No. 610,678, previously mentioned herein, and incorporated by reference herein. As indicated in U.S. Patent No. 4,610,678, air-laid webs formed by this procedure preferably comprise substantially unbound fibers, and preferably have a moisture content of 10%. % or less. In preparing webs by an air setting process or any other conventional procedure, care should be taken in handling and transporting the particles of the polymer composition to avoid breaking these particles into smaller particles. That is, valid even when the particles are made of interparticle crosslinked aggregates, although interparticle crosslinked aggregates have relatively high structural integrity in the dry state.

In an alternative embodiment of the absorbent parts of the present invention, the absorbent part comprises a laminate (a layered absorbent part) which comprises_ν. .··; \ ···' · &lt; ,. &lt;-·/, - , - : ,'· ' - ’ -~'·*· &lt;·'*'/

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13A contains at least one and optionally two or more layers of dispersed particles of the polymeric composition. The laminates preferably comprise layers or webs of fibrous materials (preferably a sheet of absorbent material) such as paper tissue. These layered absorbent structures are more fully described in U.S. Patent No. 4 No. 578,068, entitled Absorbent Laniinate Structure, issued to Timothy A. Kramer, Gerald A. Young, and Ronald K. Kock on March 25, 1986, incorporated herein by reference. Other processes and devices for the manufacture of such laminates are described in U.S. Patent No.

551 191, entitled Process for the Uniform Distribution of Distinct Particles on a Moving Porous Web (Method for Uniformly Distributing Discrete Particles on a Moving Porous Web) granted to Ronald K. Kock and John A. Esposito on November 5, 1985, which patent is incorporated herein by reference.

Figure 5 is an exemplary embodiment of a laminated layered absorbent piece 70 in accordance with the present invention. The layered absorbent piece 70 preferably comprises four webs of fibrous material: upper web 81, lower web 84 and intermediate webs 82 and 83. The layered absorbent piece 70 has inner faces 86, 87 and 88 between adjacent webs with the particles 75 of the absorbent and particulate polymeric composition of the present invention forming a continuous layer on each of the inner faces 86, 87 and 88. As follows. As shown in Figure 5, the layered absorbent part 70 preferably still has conical projections 90 on the upper surface 71 and the corresponding conical recesses 91 on the lower surface 72.

The layered absorbent pieces 70 of the present invention are produced comprising the following components: not substantially planar webs of fibrous materials, each web having two substantial surfaces53.

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Mod. 71 - 20,000 ex. - 90/08 are parallel, where n is an integer equal to or greater than 2; and particles of the absorbent and particulate polymeric composition according to the present invention. The absorbent layered pieces 70 of the present invention have a superstructure. upper surface 71 and lower surface 72. The layered absorbent pieces 70 comprise n webs of fibrous materials, n being an integer equal to or greater than 2. The webs are layers such that there is an upper web 81, a lower web 84, n-2 intermediate webs 82 and 83, and nl interfaces 86, 87, 88 of the two opposite and contacting adjacent surfaces of the adjacent webs. Each of the interfaces has a surface area. The particles 75 of the polymeric composition form a discontinuous layer at one or more of the interfaces.

The layered absorbent pieces 70 of the present invention may have from two to a large number of webs of fibrous material. The number of webs is generally limited by the thickness of the webs. It is preferred that there are from about two to about two webs of fibrous material, but more preferably from about two to about five webs of fibrous material. The particles 75 of the absorbent and particulate polymeric composition may be placed between each adjacent web of fibrous material as shown in Figure 5; however, particles 75 may be included between each other in some of the adjacent webs of fibrous material.

As used herein, the term fibrous material web refers to a sheet of thin and substantially contiguous material having two substantially parallel surfaces. Although a web of fibrous material need not be flat or smooth, it is or can be placed in a substantially planar two-dimensional arrangement of indefinite length and indefinite width extending in both dimensions. Examples of fibrous material webs used in the layered absorbent pieces 70 of the present invention include many paper materials and nonwoven materials. Mate30's webs

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The fibrous materials used in the present invention are preferably webs of absorbent materials, but more preferably webs of absorbent paper and most preferably absorbent tissue. The webs of fibrous materials may all be of the same fibrous material or may be of different fibrous materials.

In the layered absorbent pieces 70 of the present invention, the webs of fibrous materials are preferably substantially fractionally bonded in their entirety by entangling the fibers of the adjacent web contact surfaces at interfaces where the particles 75 are located. find gifts. Particles can be disabled at the interfaces by the action of the fibers. Alternatively, the particles 75 of the polymeric composition may be linked to one or more webs in various ways. For example, a fine spray of glue may be deposited on the webs to adhere the particles to the webs. Alternatively, the glue may be deposited on the fibrous webs in a defined pattern, such as a spiral pattern, which adheres the webs of fibrous material to one another to form pockets in which the particles are enclosed. In yet another way, the webs may be bonded to the particles by hydrogen point bonding, by spraying a haze of water onto the webs, adding the particles, compressing the webs against each other, and drying the resulting layered absorbent piece. As shown in Figure 5, the fibrous webs are preferably creased between two folding surfaces with geometric protrusions in the corresponding z-direction, providing multiple protrusions 90 in the z-direction 91 to the layered pile of webs. An exemplary process for producing such layered absorbent members is described in the above-mentioned U.S. Patent No.

578 068, incorporated herein by reference.

An alternative embodiment of parts 63,387

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<img file="PT97236B_D0055.tif" />

The absorbent layered fabrics of the present invention is a pouch containing the absorbent and particulate polymeric composition. The pouch is a layered absorbent part as described above, wherein the number of fibrous webs is equal to two. each other by their periphery so as to form a large pocket in the middle of the pouch. The particles of the polymeric composition are enclosed in the pouch between fibrous webs. Thus, the pouch is similar to a tea bag wherein the absorbent polymeric composition is particulate can freely swell and absorb liquids within the pouch. The fibrous pouch webs preferably comprise a nonwoven material as known in the art, the nonwoven webs being heat sealed around their periphery, although other means for sealing the webs are known in the art. the other, such as adhesive or ultrasound bonding, which means may also be used.

Due to the exceptional absorbent properties of the absorbent and particulate polymeric compositions referred to herein, the absorbent parts of the present invention are especially suitable for use as absorbent cores in absorbent articles, especially disposable absorbent articles. As used herein, the term absorbent article refers to articles that absorb and retain exudate body fluids, more specifically, articles that are placed against or near the user's body to absorb and retain the various exudate liquids discharged by the body. Additionally, disposable absorbent articles are those which are intended to be disposed of after single use (ie the original absorbent article as a whole is not intended to be washed or otherwise restored or reused as an absorbent article). although certain materials or the entire absorbent article may be recycled, reused or redone). An embodiment pr ~ _ ς a _ .387 is shown in Fig. 1.

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<img file="PT97236B_D0056.tif" />

wound of an absorbent article, the diaper 20. As used herein, the term diaper refers to a piece of fabric commonly used by newborn children and incontinent persons, being worn around the bottom of the diaper. from the wearer's trunk. It should be understood, however, that the present invention also applies to other absorbents, such as incontinent pads, incontinent pads, tracksuits, diaper inserts, sanitary tampons, facial tissues, paper towels and similar articles.

Figure 1 is a plan view of the diaper 20 of the present invention in its flat, non-contracted state (i.e., with all contraction caused by eliminated elastics) with cut parts of the frame to show more clearly the construction of the diaper. diaper 20 and the portion of the diaper 20 contacting the wearer facing the observer. As shown in Figure 1, the diaper 20 has a waistband anterior region 22, a waistband posterior region 24, a groin region 26 and a periphery 28 which is defined by the outer edges of the diaper, wherein the longitudinal edges are denoted by 30 and the outer edges are denoted by 32. In addition, the diaper has a transverse centerline denoted by 34 and a longitudinal centerline denoted by 36.

Preferably, the diaper 20 comprises a liquid permeable topsheet 38; a liquid impervious backsheet 40 joined to the topsheet 38; an absorbent core 41 (absorbent part 42) positional between the topsheet 38 and the backsheet 40; elastic parts 44; and clip latches 46. Although the topsheet 38, the backsheet 40, the absorbent core 41 and the elastic parts 44 may be assembled according to a variety of well-known shapes, it is generally described in U.S. Patent No. 3,860,003, incorporated Contractable Side Portions for Disposable Diapers

7 '·· ·&gt;; ·· »- · .. · · ν ·.

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(Contractable Side Portions for Disposable Diaper), issued to Kenneth B. Buell on January 14, 1975, and which is incorporated herein by reference as a preferred embodiment. Other alternative embodiments, also preferred for the disposable diapers of the present invention, are referred to in U.S. Patent No. 4 808 178, entitled Disposable Absorbent Article Having Elastic Clips With Pej Resistant Parts? Disposable Absorbent Article Having Elasticized Flaps Provided with Leakage Resistant Portions, issued to Mohammed I. Aziz and Ted L. Blaney on February 28, 1989; U.S. Patent No. 4,695,278, entitled Absorbent Article Having Dual Cuffs, issued to Michael I. Lawson on September 22, 1987; and in U.S. Pat. No. 4,816,025 entitled Absorbent Article Having a Containment Pocket, issued to John H. Foreman on March 28, 1989, These patents are incorporated herein by reference.

Figure 1 represents a preferred embodiment of the diaper 20, wherein the topsheet 38 and backsheet 40 have the same generally larger extension and length and width than those of the absorbent core 41. The topsheet 38 is associated with it is superimposed on the poster sheet 40, thus forming the periphery 28 of the diaper 20. The periphery 28 defines the outer perimeter or the margins of the diaper 20. The periphery 28 comprises the longitudinal edges 30 and the edge edges 32.

The diaper 20 has the fore and aft regions surrounding the waist 22 and 24, respectively, which extend from the edges of the edges 32 of the diaper periphery 28 towards the transverse centerline 34 of the diaper in a distance preferably equal to about 5% of the length of the diaper 20. The waistband regions comprise the upper portions of the diaper.

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<img file="PT97236B_D0058.tif" />

diaper 20 which, when worn, surrounds the wearer's waist. The groin region 26 is the part of the diaper 20 which lies between the waist regions 22 and 24, and which comprises the part of the diaper 20 which, in use, is positioned between the wearer's legs and covers the lower part of the diaper. the user's trunk. Thus, the groin region 26 defines the typical liquid deposition area of ​​a diaper 20 or other disposable absorbent article.

The topsheet 38 is adaptable, soft and non-irritating to the wearer's skin. In addition, the topsheet 38 is permeable to liquids, allowing them to easily penetrate through its thickness. A suitable topsheet 38 may be made of a wide variety of materials, such as porous foams, crosslinked foams, apertured plastic films, natural fibers (e.g. wood or cotton fibers), synthetic fibers (e.g. polyester or polypropylene fibers) or combinations of natural and synthetic fibers. Preferably, the sweat sheet 38 is made of a hydrophobic material to isolate the wearer's skin from liquids retained in the absorbent core 42.

A particularly preferred topsheet 38 comprises normal length fiber polypripylene fibers having a denier of about 1.5 such as Hercules type 151 polypropylene, marketed by Hercules Inc. of Wilmington, Delaware, United States of America. As used herein, the expression fibers of normal fiber length refers to fi. bras that have a length of at least about 15.9 millimeters (0.62 inches).

There are a number of manufacturing techniques that can be used to manufacture the topsheet 38. For example, the topsheet 38 may be woven, nonwoven, weaved, carded or the like. A preferred topsheet is carded and thermally bonded by means known to those skilled in the art of fabrics. Preferably

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Mod. 71 - 20,000 ex. - 90/08 te, the topsheet 38 has a weight of from about 18 to about 25 grams per square meter, a minimum dry tensile strength of at least 400 grams per centimeter in the machine direction, and a mechanical wet tensile strength of at least about 55 grams per centimeter in the transverse direction of the machine.

Backsheet 40 is liquid impermeable and is preferably made from a thin plastic film, although other flexible liquid impervious materials may also be used. Backsheet 40 prevents the exudate liquids absorbed and retained in the absorbent core 41 from wetting articles in contact with the diaper 20, such as sheets and underwear. Preferably, the backsheet 40 is a polyethylene film about 0.012 millimeters (0.5 millimeters in) thick to about 0.051 centimeters (2.0 millis inch), although other flexible materials may be used. impermeable to liquids. As used herein, the term flexible refers to materials that are adaptable to the body and easily conform to the overall shape and contours of the wearer's body.

A suitable polyethylene film is manufactured by Monsanto Chemical Corporation and is marketed as Film No.². 8020. Backsheet 40 is preferably embossed and / or has a matt finish to give a fabric-like appearance. In addition, the backsheet may allow vapors to escape from the absorbent core while preventing exudate from passing through it.

Backsheet size 40 is dictated by the size of the absorbent core 41 and the exact design chosen for the diaper. In a preferred embodiment, the backsheet 40 is in the form of a modified hourglass extending beyond the absorbent core 41 at a distance

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<img file="PT97236B_D0059.tif" />

minimum of at least about 1.3 centimeters to about

2.5 centimeters (about 0.5 to about 1.0 inch) around the entire periphery of the diaper 28.

The top diaper 38 and back sheet 40 are joined together in any appropriate manner. As used herein, the term coupled encompasses configurations wherein the topsheet 38 is directly joined to the backsheet 40 by directly securing the topsheet to the backsheet 40, and configurations wherein the topsheet 38 is indirectly joined to the backsheet 40. backsheet 40 by attaching the topsheet 38 to intermediate members which are in turn attached to the backsheet 40. In a preferred embodiment, the topsheet 38 and backsheet 40 are fixed directly to each other on the periphery of the diaper 28 by bonding means (not shown), such as adhesive or any other bonding means known in the art. For example, a continuous and uniform layer of adhesive, a layer of adhesive conforming to a given pattern, or a set of separate lines or points of adhesive may be used to secure the topsheet 38 to the backsheet 40.

Normally, securing clips 46 are applied to the back of waist 24 of the diaper 20 to provide diaper securing means to the wearer's body. Only one of these clips is shown in Figure 1. The retaining clip 46 may be any of the tapes known in the art, such as the retaining tape described in U.S. Patent No. 3,848,594, issued to Kenneth B. Buell on November 19, 1974, patent incorporated herein by reference. Es. Such fastening clips 46 or any other diaper attachment means are usually applied near the corners of the diaper 20.

The elastic members 44 are placed adjacent to the periphery 28 of the diaper 20, preferably to the longest.

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<img file="PT97236B_D0060.tif" />

Mod. 71 - 20,000 βχ. 90/08 go from each longitudinal edge 30 so that the elastic pieces 44 close and hold the diaper 20 against the wearer's legs. Alternatively, the elastic members 44 may be placed adjacent to either or both packs. end members 32 of the diaper 20 to provide a waist band as well as or instead of leg bands. For example, an appropriate waist band is described in U.S. Patent No. 4 515 595 entitled Disposable Diapers Wette Elasticlly Contractable Waistbands, issued to David J. Kievit and Thomas F. Osterhage on May 7, 1985, which patent is incorporated herein as reference . In addition, a suitable process and device for making a disposable diaper with resiliently contractible elastic parts is described in US Patent No. 4 081 301 entitled Process and Device for Continuously Binding Distinct Parts of Stretched Elastic to Isolated and Predetermined Portions of Disposable Absorbent Products, which has been issued to Kenneth B. Buell on March 28, 1978, and which is incorporated herein by reference.

The elastic members 44 are secured to the diaper 20 in an elastically contractable condition, so that in a normally unrestrained configuration, the elastic members 44 actually contract or tighten the diaper 20. The elastic members 44 may be secured in an elastically contractible condition. at least two different ways. For example, the elastic members 44 may be stretched and secured while the diaper 20 is in the non-contracted state. Alternatively, the diaper 20 may be contracted, for example by pre-empting it and the elastic members 44 being secured and bonded to the diaper 20 when they are in condition.

O

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63.387

Case: 4124 X tion relaxed or not stretched.

In the embodiment shown in Figure 1, the elastic members 44 essentially extend the length of the diaper 20 in the groin region 26. Alternatively, the elastic members 44 may extend the entire length of the diaper 20 or any other suitable length to provide a elastically contractible line. The length of the elastic members 44 is dictated by the design of the diaper.

Elastic members 44 may take a variety of configurations. For example, the width of the elastic members 44 may range from about 0.25 mm (0.01 inch) to about 25 mm (1.0 inch) or more. The elastic members 44 may comprise a single strip of elastic material or may comprise several parallel or non-parallel strips of elastic material; the elastic members 44 may be rectangular or curvilinear. Moreover, the elastic members 44 may be diapered by one of several methods known in the art. For example, the elastic members 44 may be ultrasonically bonded, or heat or pressure sealed to the diaper 20 using a series of bonding patterns, or the elastic members 44 may simply be glued to the diaper 20.

The absorbent core 41 of the diaper 20 is positioned between the topsheet 38 and the backsheet 40. The absorbent core 41 can be manufactured in a wide variety of sizes and shapes (e.g. rectangular, shaped like hourglass or asymmetric, etc.) and from a wide variety of materials. The total absorbent capacity of the absorbent core 41 should, however, be compatible with the net load designed for the intended use of the absorbent article or diaper. In addition, the size and absorbency of the absorbent core 41 may vary depending on the type of wearers, which may range from newborn children to adults. The absorbent core 41 preferably comprises the parts.

<img file="PT97236B_D0062.tif" />

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Mod. 71 · 20,000 ex. The absorbent materials of the present invention, which comprise a mixture of fiber material and specific amounts of particles of the absorbent and particulate polymer compositions of the present invention containing inter-particle crosslinked aggregates.

A preferred embodiment of the diaper 20 has a modified hourglass-shaped absorbent core 41. The absorbent core 41 is preferably an absorbent product 42, which comprises a web or pad of air-laid wood pulp fibers and the absorbent and particulate polymeric composition disposed therein.

Alternatively, the absorbent cores of the present invention may consist only of absorbent and particulate polymeric compositions of the present invention, in combination with layers including the polymeric compositions of the present invention (including the laminate materials described herein) or any other embodiment of the present invention. absorbent core known in the art. Examples of suitable absorbent core configurations are described, for example, in U.S. Patent No. 3,670,731 issued to Harmon on June 20, 1972 in U.S. Patent No. 3,669,114 issued to Morane on June 15, 1972; U.S. Patent No. 3,888,257, Cook et al., issued June 10, 1975; U.S. Patent No. 3,901,231 to Assarson et al. on August 26, 1975; in U.S. Patent No.

102 340, issued to Mesek et al., On July 25, 1978; and U.S. Patent No. 4,500,315 issued to Pieniak et al. February 19, 1985. All of these patents are incorporated herein by reference.

One embodiment of an absorbent core

41, which may be considered as an example, comprises a web formed of hydrophilic fiber material and the absorbent and particulate polymer composition of the present invention.

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such as the absorbent part described in U.S. Patent No. 4,610,678, entitled High-Density Absorbent Structure, which was issued to Paul T Weisman and Stephen A. Goldman on 9 May. September 1986 and which is incorporated herein by reference. Another alternative embodiment of an absorbent core 41 is a double-layer absorbent core of a preferred embodiment which, as generally described in U.S. Patent No. 4,673, 402, entitled Absorbent Article Absorbent Article With Dual-Layered Colors, awarded to Paul T, Weisman, Dawn I. Houghton and Dale A. Gellert on June 16, 1987, and incorporated herein by reference, has an asymmetrically shaped upper layer and a lower layer. A particularly preferred embodiment of the absorbent core 41 useful in the present invention is described in U.S. Patent No. 4 834 735, titled High Density Absorbent Parts Having Lower Density and Lower Absorbent Members Having Lower Dendity and Lower Basis Weight Acquisition Zones, granted to Miguel Alemany and Charles J. Berg on May 30, 1989, which features absorbent parts having a storage zone and an absorption zone that has a lower average density and a lower average weight per unit area than the storage zone, so that the absorption zone can effectively and efficiently acquire the discharged liquid quickly. This patent is incorporated herein by reference.

Figure 4 is a perspective view of a preferred embodiment of the absorbent core 41 (absorbent member 42) of the present invention as described in U.S. Patent No. 4,834,773, referred to herein. . The absorbent member 42 shown in Figure 4 comprises a

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Mod. 71 - 20,000 ex. These materials are incorporated in the present specification, although other structures with high capillarity may also be used.

Storage zone 58 preferably has a relatively high density and high basis weight per unit area relative to the acquisition zone 56. The density and base weight values ​​of storage zone 58 include the weight of the particles. of the polymeric composition such that the density and basis weight values ​​vary as a function of the amount of particles dispersed through the absorbent part 42.

Although the storage zone 58 may have a number of sizes and shapes, it is preferred that the storage zone 58 comprises at least that portion of the deposition region 54 where there is no absorption zone 56 (i.e. total deposition region 54 comprises a storage zone 58, except absorption zone 56). Although rear section 48 and end region 52 need not have storage zones, in the particularly preferred embodiments of the absorbent part 42 shown in Figures 2, 3 and 4, the absorbent part 42, except the absorption zone 56 consists entirely of one or more storage areas 58. Furthermore, although the storage zone 58 need not completely surround the sides of the absorption zone 56 (i.e., in liquid communication with at least a portion of the lateral area of ​​the absorption zone 56), in the Preferred embodiments of the present invention, the storage zone 58 laterally surrounds the absorption zone 56 so as to be able to take advantage of the capillary difference between them.

Absorption zone 56 has a relatively smaller capillarity, thus preferably has a lower average density and average base weight per unit area less than storage zone 58. Absorption zone 56 serves to quickly collect and store temporarily discharged liquids. As these liquids are generally discharged in gulps, absorption zone 56 should be

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rear section 48 and an anterior section 50. The anterior section 50 shown has an end region 52 and a deposition region 54. The deposition region 54 comprises an absorption zone 56 (represented by dashed lines) and a storage zone 58. Furthermore, the anterior section 50 is transversely divided into three regions comprising two transversely spaced tab-shaped regions 60 and 62 respectively and a central region 64.

The absorbent part 42 additionally has a transverse centerline which is designated 66, and a longitudinal axis which is designated 68.

The absorbent part 42 has a rear section 48 and an anterior section 50 which adjoins the rear section 48.

The back section 48 and the front section 50 of the absorbent part 42 extend respectively from the edges: terminals 67 of the absorbent part 42 towards the transverse centerline 66, the front section 50 extending a distance of about half to about three quarters, preferably about two thirds, of the length of the absorbent member 42. The front section 50 is preferably greater than half of the total length of the absorbent piece 42 so that it covers the entire typical liquid deposition area of ​​the absorbent piece 42 when it is placed in a diaper or other absorbent article.

The front section 50 has an end region 52 and a deposition region 54. The end region 52 comprises the part of the front section 50 extending from the end margin 70 of the absorbent piece 42 towards the transverse center mesh 66 in a from about 2 to about 10%, preferably about 5% of the length of the absorbent piece 42. The deposition region 54 comprises the front section portion 50 which adjoins and is positioned between the end region 52 and the rear section 48, and encompasses the typical Liquid deposition area of ​​the absorbent part 42.

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The front section 50 further has two transversely spaced tab-like regions 60 and 62 respectively and a central region 64 disposed between the tab regions 60 and 62. The tab regions 60 and 62 comprise the portions generally extending from the longitudinal edges 30 of the periphery 28 towards the longitudinal centerline at a distance of about one tenth to about one third of the width of the absorbent piece 42. Thus, the regions of the flaps 60 and 62 are the portions that engage the sides of the wearer's waist and torso, while the central region 64 fits the middle waist and tror region. of the user. The central region 64 thus defines the typical liquid deposition cross-sectional area.

The deposition region 54 comprises an absorption zone 56 and a liquid communicating storage zone 58 with at least a portion of the lateral area of ​​the absorption zone 56. The absorption zone 56 comprises portions of the deposition region 54 designated by dashed lines in Figure 4. Storage zone 58 generally comprises the remainder of the deposition region 54 and preferably the remainder of the absorbent portion 42.

Storage zone 58 is the relatively high capillary (high density and high basis weight) portion of at least the deposition region 54. The main functions of the storage zone 58 are to absorb discharged liquids which are either deposited directly on the storage zone 58, or transferred to the storage zone 58 by means of the capillary force gradients established between the absorption zone. 56 and storage area 58, and retain such liquids under pressures resulting from the movements of the wearer. Preferably, the storage zone 58 consists essentially of the structure described in U.S. Patent No. 4,610,678, above, and the lower fluid storage layer described in U.S. Patent No. 4,610,678. 4,673,407, pa 63,387

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Mod. 71 - 20,000 ex. - 90/08

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capable of rapidly acquiring and conveying the liquid from the point of contact with the liquid to the other parts of the absorbent part 42.

Although portions of the absorption zone 56 may be positioned in the rear section 48 of the absorbent part 42, the absorption zone 56 is preferably positioned generally in the anterior section 50 of the absorbent part 42, so that the absorption zone 56 is placed in the typical liquid deposition area, that is, in the position region 54. Thus, the absorption zone 56 is located in the vicinity of the liquid discharge point, so as to be able to quickly acquire such liquids in its contact zone. Generally forward positioning of the absorption zone 56 can be defined by specifying the percentage of the area. from the upper surface of the absorption zone 56 which faces in front of specific points along the length of the absorbent part 42. Although the positioning of the absorption zone 56 may alternatively be defined. With respect to the volume of the absorption zone positioned in front of certain points, it has been found that the upper surface area of ​​the absorption zone 56 provides a more desirable definition because the upper surface area actually defines the initial available area for liquid demand. . of. Furthermore, since the thickness of the absorbent part 42 is preferably uniform in the deposition region 54, and the absorption zone 56 has a generally rectangular cross-sectional area, the definition of the upper surface area is equal to a volumetric definition, in a preferred embodiment. Thus, the positioning of the absorption zone 56 is referred to throughout the specification as relating to its upper surface area (i.e., the percentage of the upper surface area of ​​the absorption zone positioned in a given area).

Thus, according to the present invention, at least part of the absorption zone 56 should be placed in the

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deposition region 54, even though the remaining portion may be positioned elsewhere in the absorbent part 42, including the rear section 48 and the end regions 52. (It should be understood that if multiple absorption zones are used, at least a part of one of the absorption zones must be positioned in the deposition region 54). However, the absorption zone 56 should preferably be positioned relative to the absorbent part 42 such that the upper surface area of ​​the absorption zone 56 is completely positioned within the anterior section 50 of the absorbent part 42. More preferably, the absorption zone 56 should be positioned relative to the absorbent part 42 such that the upper surface area of ​​the absorption zone 56 is completely positioned within the deposition region 54 of the absorbent part 42. Even more preferably. At least 30% of the upper surface area of ​​the absorption zone 56 should be positioned in the front half of the anterior section (approximately 1/3 front of the total absorbent part 42) of the absorbent part.

The absorption zone 56 may be of any desired shape which is consistent with the absorption requirements of the absorbent piece 42 or diaper 20, including, for example, circular, rectangular, triangular, trapezoidal, oblong, hourglass, funnel, in dog bone, fox head or oval. Preferred forms for the absorption zone 56 are those which increase the perimeter of the interface between the absorption zone 56 and the storage zone 58, so that the relative capillary difference between the zones is fully utilized. In the embodiment shown in Figures 1 to 4, the absorption zone has an oval shape and an upper surface area of ​​about 45 square centimeters (about 7 square inches).

In order to maintain a minimum level of absorption in the anterior section of the absorbent part 42, the upper surface area or the volume of the storage area 58 must comprise a minimum percentage of the upper surface area or

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Thus, it has been found that the absorption zone 56 should preferably comprise less than the total area of ​​the upper surface and / or the volume of the anterior section 50 of the absorbent part 42. According to a preferred embodiment, the absorption zone 56 has a generally uniform thickness and cross-sectional area, the volume may be replaced by the upper surface area as a point of definition. The upper surface area of ​​the absorption zone portion 56 positioned in the anterior section 50 of the absorbent part 42 preferably comprises less than about 50% of the upper surface area of ​​the anterior section 50. More preferably, the area of ​​the The upper surface of the absorption zone 56 comprises less than about 35% of the upper surface area of ​​the anterior section 50 of the absorbent part 42, especially a percentage of less than about 20% is preferred. In addition, the upper surface area of ​​the absorption zone 56 preferably comprises less than about 50% of the upper surface area of ​​the deposition region 54, but more preferably less than about 35% and most preferably. , less than about 20%.

Absorption zone 56 may also have a number of different cross-sectional areas and configurations, including those wherein the portion area of ​​the absorption zone 56 is smaller or larger than its upper surface area (i.e. absorption zone 56 is smaller or larger below the upper surface of the absorbent part 42). For example, the absorption zone 56 may have tapered, trapezoidal, T-shaped or rectangular cross-sectional areas. As shown in Figures 2 and 3, the absorption zone 56 preferably has a rectangular cross-sectional area so as to provide a uniform absorption zone 56.

Moreover, the absorption zone 56 need not comprise the full thickness of the absorbent member 42; may extend to only part of its total thickness. Absorption zone 56 may also have a different thickness

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that of the storage area 58 surrounding it laterally. However, in a preferred embodiment shown in FIGS. 2 and 3, the absorption zone 56 preferably extends over the entire thickness of the absorbent part 42 and has a thickness equal to the thickness of the storage zone 58 which in the deposition region 54.

Although the absorption zone 56 may be transversely positioned at any point along the absorbent part 42, it has been found that the absorption zone 56 functions most efficiently when it is transversely centered within the anterior section 50 or the deposition region 54 of the absorber. Thus, the absorption zone 56 is preferably centered with respect to the longitudinal axis 68 of the absorbent part 42. More preferably, the absorption zone 56 is positioned transversely only in the central region 64 of the anterior section 50 or of the absorbent piece deposition region 42 such that no absorption zone 56 is located in the regions of the flaps 60 and 62.

This absorbent piece 42 is preferably obtained by air-seating a profiled thickness absorbent piece preform and then calendering the absorbent piece 42 into a fixed thickness calender roll to effect the preparation. densification of the absorbent part 42. The profiled thickness absorbent part 42 initially has areas of higher basis weight defining storage zone 58 and lower base weight defining absorption zone 56. The absorbent piece 42 is then calendered, preferably to at least a uniform thickness in the deposition region. Thus, an absorption zone 56 of lower average density and average basis weight per unit area is created relative to the highest average density and highest average base weight of the storage zone 58. In addition, the absorbent and particulate polymeric composition is added to an air-entrained fiber stream prior to its deposition in the preform to ensure an even distribution.

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uniform composition of the polymeric composition through the preformed absorbent part 42.

Figures 6 and 7 represent an alternative embodiment of an absorbent core according to the present invention. An absorbent acquisition layer 674 is positioned over an absorbent part 642 to form a double layer absorbent core. An example of a similar double-layer absorbent core is described in more detail in U.S. Patent No.

673 402, mentioned above, and incorporated herein by reference.

This absorbent acquisition layer 674 serves for. to collect rapidly and store liquids temporarily. discharged, and for transporting, by wick from the initial contact point to other parts of the absorbent acquisition layer 674. As the main function of the absorbent acquisition bed 674 is to receive the liquids which can be passed through the topsheet 38 and to transport them to other areas of the absorbent acquisition layer 674 and, eventually, to the absorbent part 642 the Absorbent acquisition layer 674 may be substantially free of the composition. polymeric reaction. Preferably, the absorbent acquisition layer 674 consists essentially of hydrophilic fibrous material. Alternatively, the absorbent acquisition layer 674 may contain specific amounts of polyether composition. Thus, the absorbent acquisition layer 674 may contain, for example, up to about 50% by weight of polymer composition. In preferred embodiments, the absorbent acquisition core contains from 0 to about 8% by weight of the polymer composition. In preferred alternative embodiments, the absorbent acquisition layer 674 comprises chemically stiffened cellulosic fibers, as noted hereinbefore.

The absorbent acquisition layer 674 in its unfolded configuration may be of any desired shape, such as rectangular, oval, oblong, asymmetrical shape. &lt;: # · * ♦ ·· '

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Mod. 71 20,000 ex. - 90/08 'ejj / ca or hourglass. The shape of the absorbent acquisition layer 674 may define the overall shape of the resulting diaper 20.

In preferred embodiments of the present invention shown in Figure 6, the absorbent acquisition layer 674 is hourglass-shaped.

The absorbent part 642 of the present invention need not be the same size as the absorbent acquisition layer 674, and may in fact have a substantially smaller or larger upper surface area than the upper surface area of ​​the absorbent acquisition layer 674. As shown in Figure 6, the absorbent part 642 is smaller than the absorbent acquisition layer 674, and has a larger surface area of ​​about 0.25 to about 1.0 times that of the absorbent acquisition layer 674. Preferably, the upper surface area of ​​the absorbent part 642 is only about 0.25 to about 0.75 and more preferably still about 0.3 and about 0.5 times the size. of the absorbent acquisition layer 674. In an alternative embodiment, the absorbent acquisition layer 674 is smaller than the absorbent part 642, and has a surface area of ​​about 0.25 to about 1.0 times, more preferably about 0.3 times. about 0.95 times that of the absorbent member 642. In this alternative embodiment, the absorbent acquisition layer 642 preferably comprises chemically stiffened cellulosic fibers.

The absorbent piece 642 is preferably placed in the diaper or other absorbent article, in a specific position relation to the backsheet 40 and / or the absorbent acquisition layer 674. More particularly, the absorbent piece 642 is positioned generally towards the pad. The front of the diaper, so that the polymeric composition is placed more effectively to acquire and store the discharged liquids from the absorbent acquisition layer 674.

Advanced positioning of absorbent part 642 can be defined by specifying percentage of compo35

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total polymeric position in front of terminated points along the length of the diaper or any other absorbent article. Thus, according to the present invention, absorbent part 642 is positioned relative to the backsheet and / or absorbent acquisition layer 674 such that (1) at least about 75% of the total polymer composition of absorbent part 642 is within the two-thirds portion of the diaper or any other absorbent article and (2) at least about 55% of the total polymer composition of the absorbent article 642 is within the front half of the diaper or any other absorbent article. More preferably, the absorbent part 642 is positioned relative to the backsheet 38 and / or the absorbent acquisition layer 674 such that at least about 90% of the total polymer composition of the absorbent member 642 is in the front portion: a. two thirds, and at least about 60% of the total polymer composition is on the front equal to half of the diaper or any other absorbent article. (For purposes of the present invention, the term portions of a diaper or any other absorbent article may be defined with reference to the upper surface area of ​​the unfolded diaper 20 or absorbent article that is in front of a particular point on the line defining the length of the diaper 20 or the absorbent article).

The absorbent part 642 of the double-layer absorbent core may be of any desired shape which is consistent with a comfortable fit, including, for example, the hourglass-shaped, hourglass-shaped, circular, rectangular, trapezoidal, oblong shape. If desired, the absorbent piece 642 may be wrapped in a high moisture-resistant envelope web such as paper tissue or a fine-pore synthetic material (e.g. a non-woven material) to minimize the possible migration of the particles of the polymer composition out of the absorbent part 642. Another objective "7 C" ----- ......

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such wrapping is to increase, as desired, the integrity of the double layer absorbent core during use. The web may in fact be glued to the absorbent part 642. Suitable means for performing this sizing operation include the glue spraying process described in U.S. Patent No. 4,573,986 issued to Minetola and Tucker March 4, 1986, which patent is incorporated herein by reference.

In preferred embodiments, such as co. As shown in Figure 6, the absorbent part 642 of the double layer absorbent core is oblong. In especially preferred embodiments, an oblong absorbent piece 624 wrapped in adhesive spray bonded fabric is employed.

Figure 8 represents yet another alternative embodiment of an absorbent core comprising the absorbent part 842 of the present invention. The absorbent part 842 is asymmetrical in shape (i.e. the absorbent part 842 is not symmetrical with respect to its transverse centerline). In addition, the density and basis weight values ​​of the flap regions 860 and 862 and the rear section 848 are different from the storage zone 858 positioned in the central region 864 by virtue of the method by which the absorbent part 842 is formed. . The flap regions 860 and 862 and the back section 848 are preferably made with a lower base weight than the storage region 858 of the central region 864, since the extra material in this embodiment is not. provides any significant added benefits in loss protection, and thus the cost of the absorbent part 842 is reduced. The absorbent part 842 is calendered to a uniform thickness; storage area 858 of central region 864 therefore has a higher average density than rear section 848 and flap regions 860 and 862. (It should be understood that all or part of rear section 848 and regions of tabs 860 and 862 may alternatively be calan -. 'Λ · V' · '-W' t, 4, .-.&gt; í “W ', ··.' * '- ··'. &lt; · »- · ·· 63,387

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to a thickness less than the central region 864 so as to have approximately an average density equal to or greater than that of the storage area 858). In addition, as shown in Figure 8, section 848 preferably contains tabs although it is not necessary to contain them.

The absorption zone 856 of the absorbent member 842 is in the form of a funnel. The funnel shape is defined by a generally triangular portion 884 in combination with a rod or rectangular portion 886. The triangular portion 884 is especially effective in absorbing liquids discharged by a male user, while the rod portion 886 is effective. in the case of a female user. In order to re. If the rod portion 884 of the absorption zone 856 is closed during manufacture or use, the rod portion 884 must have a minimum width; preferably at least about 3/8 inch for the fibrous material is preferably used in the present invention. The acquisition zone shape 856 may also vary according to the type of intended user, such as preferably a triangular shape 884 for a male user.

Figure 9 represents another alternative embodiment of the present invention, wherein the absorbent core may comprise the absorbent part 942 having a stratified matrix of fiber material and a mixture of fiber and particle material 900 of the polymeric composition of FIG. present invention. The absorbent part 942 thus comprises a storage zone 958 (designated by dashed lines) and a dusting layer 902 (acquisition / distribution layer). Preferably, the storage area 958 is positioned only on the front section 850 of the absorbent part 942 such that the rear section 48 does not comprise a storage area 958 (i.e. the rear section 48 does not comprise a mixture of fibrous material and polymeric composition). This configuration saves material costs while at the same time providing the benefit of absorbent end tip losses 942. In addition, 7:, * · + · **. ? · »'..« f »..: 72§73fArí (

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Mod. 71 - 20,000 ex. 0/06 alone, both the storage zone 958 and the absorption zone 956 do not cover the total thickness of the absorbent part 942, but extend only by a fraction (preferably between about 25 and about 95% but more preferably between about 75 and about 95%) of the total thickness of the absorbent part 942. Thus, the dusting layer 902 is preferably relatively thinner in thickness than the absorption zone 956 and the storage zone 958 of the absorbent part 942, and is formed from at least the portion of the thickness of absorbent part 942 not comprising absorption zone 056 and storage zone 958; more preferably, the dusting layer 902 is also formed from the rear section 48 of the absorbent part 942. In the embodiment shown, both the absorption zone 956 and the sprinkling layer 902 preferably consist essentially of hydrophilic fiber material having limited amounts (from about 0 to about 2%) of the polymer composition dispersed therein. In addition, the absorption zone 956 and the dusting layer 902 are made of the same materials and have the same density and basis weight, so that the absorbent member 942 has essentially an overall absorption zone surrounding the storage zone. 958.

Body liquids that are deposited in the absorption zone 956 are readily acquired and pass into the absorbent part 942 where they are either transported to the storage zone 958 by the capillary gradient between the storage zone 958 and the absorption zone 956, along its interface, either they are dragged by a wick or pushed by gravity to the sprinkle layer 902 after which the liquids are rapidly transported by wick, from the initial contact point in the absorption zone 956 to the other parts of the sprinkling layer 902, where the capillary difference between the sprinkling layer 902 and the storage zone 958 causes the liquid to be transported to the storage zone 958. Thus, there is a larger capillary gradient area between zo '&lt;r'

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Mod. 71 - 20,000 ex. 908 and other portions of the absorbent part 942, so that the storage area 958 and, more particularly, the particles 900 of the polymeric composition are used most effectively. Thus, although the absorption zone 956 and the sprinkling layer 902 may have different characteristics and constructions, such as being made of different materials, having different densities or having polymeric composition particles dispersed in both, they prefer. the absorption zone 956 and the dusting layer 902 consist of the same material, have the same density and are essentially devoid of particles of the polymeric composition, so that the liquids can be swiftly transported to and through the absorbent part 942.

The absorbent part 942 of this alternative embodiment is preferably manufactured by the processes and devices described in U.S. Patent No. 4,888,231 entitled Absorbent Colors Having a Dustinj Layer, Issued to John J. Angstadt on December 19, 1989 and incorporated herein by reference. Thus, the absorbent part 942 is preferably made by laying in a draft a layer of fibrous material only in a preform consisting of a profiled absorbent part to form what will be the sprinkling layer 902 and the absorption zone 956. The zone The storage unit 956 is then laid in an air stream over the dusting layer and the absorbent part is calendered to a uniform thickness.

Figure 10 is a perspective view of an alternative embodiment of the diaper of the present invention, wherein the absorbent member 942 of Figure 9 is seated between a topsheet 1002 and a backsheet 1004 to form disposable diaper 1000. The absorbent part 942 is preferably placed such that the dusting layer 902 is positioned adjacent HA · W '

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to backsheet 1004, so that absorbent part 942 may function as previously described herein. Although not preferred, the storage zone 958 may alternatively be positioned adjacent to the backsheet 1004 so that the sprinkling layer 902 acts as a fluid distribution / acquisition layer and the storage zone 958 acts as a layer. lower fluid storage, such as the structure described in U.S. Patent No. 4,673,402, previously referenced herein.

Figure 11 represents an embodiment 1A. As an embodiment of the present invention, the shape of the absorption zone 1156 (represented by the dotted lines) has the shape of a fox head. (And so called because it looks like the frontal profile of a fox head). As noted above, it has been found that a triangular absorption zone is especially effective with male users.

However, such an absorption zone does not behave as well for female users. The optimum absorption zone shape for female users has been found to be the fox head shape shown in Figure 11. The head shape increases the perimeter of the interface between the absorption zone 1156 and the storage zone. 1158

In addition, the fox head shape is positioned farther from the front end of the absorbent piece 1142 than the triangular absorption zone used by male wearers and is placed closer to the unloading point, given the anatomical difference between wearers. male and female users. Thus, the fox-head absorption zone 1156 improves fluid distribution for female wearers.

Yet another alternative to the above embodiments of the absorbent parts is to vary the pore size of the fibers without necessarily varying the fiber density to form an absorption zone and a storage zone. For example, they may use • λ 'Jríí ·;

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Advantageously, the dimensions of fine hardwood fibers may be replaced by at least about 50%, and preferably about 80 to 100% of downy hardwood fibers of approximately the same size. density than the lower density of softwood fibers, softwood fibers in the storage zone. This can be because thin hardwood fibers have smaller pore sizes than softwood fibers. As a result, a capillarity difference is also obtained covering the scope of the present invention, even if the density of each zone is equal. Thus, for example, an absorbent piece having a predominantly softwood pulp with fine pore structure can be obtained to define the absorption zone and with a predominantly hardwood fine fiber pulp to define the storage zone. .

In use, the diaper 20 is applied to the wearer by positioning the waistband region of the back waist 24 under the wearer's back and pulling the remaining portion of the diaper 20 between the wearer's legs so that the waistband region of the front waist 22 is positioned in front of the wearer. The securing clips made of pieces of tape 46 are then attached to preferably areas of the outer face of the diaper 20.

As the absorbent and particulate polymeric compositions, and hence the absorbent parts of the present invention have a high absorption capacity of menstrual fluids as well as urine, these structures, although defined in terms of relative capacity to synthetic urine, are also suitable for use in sanitary towels.

Figure 17 represents an alternative embodiment of the present invention, wherein the disposable absorbent article is a sanitary napkin 1720, provided for receiving and containing vaginal discharges such as menstrual fluids. The disposable sanitary napkins are designed in ma81

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to be held together with the human body through use. wearing a garment, such as a garment or underpants, or by means of a specially designed belt. Examples of the types of sanitary napkins to which the present invention easily fits are set forth in U.S. Patent No. 4,687,478 entitled Shaped Sanitary Napkin With Flaps, issued to Kees J. Van Tilburg on August 18, 1987; U.S. Patent No. 4,589,876, entitled Sanitary Napkin, issued to Kees J. Van Tilburg on May 20, 1986; U.S. Patent No. 4,681,578, entitled Pantiliner With Ventilation Areas, issued to Arthur B. Anderson and Sherry L. Brandt on July 20, 1987; and in Invention Patent Nor. te-American No. 4 690 680, entitled Adhesive Attachment Means for Absorbent Articles, issued to Maureen L. Higgins on September 1, 1987. All of these patents are incorporated herein by reference.

It is apparent from the following description that the absorbent and particulate polymeric conditions and the absorbent parts described herein may be used as the absorbent core of such sanitary towels. On the other hand, it should be understood that the present invention is not limited to any specific sanitary napkin structure or configuration.

Figure 17 is a plan view of a sanitary napkin 1720 embodying the present invention before being placed on the wearer's underwear. As shown in Figure 17, a preferred sanitary napkin construction comprises a liquid-permeable topsheet 1726, an absorbent core 1728, a liquid-impermeable backsheet 1730 and a fastening system 1724 for securing the sanitary napkin 1720 to underwear. of the user. Despite the *

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topsheet 1726, absorbent core 1728 and backsheet 1730 may be made in accordance with a number of well-known embodiments, a preferred sanitary napkin embodiment is shown and described generally in the above-mentioned U.S. Patent No. 4,687,478, wherein the sanitary napkin 1720 has, in addition. optionally tabs 1732 and 1732 '.

Figure 17 represents a preferred embodiment of sanitary napkin 1720, wherein topsheet 1726 and backsheet 1730 are cohesive and have length and width dimensions generally larger than those of absorbent core 1720 to form tabs 1732. and 1732 '. The topsheet 1726 is joined to and overlapped with the backsheet 1730 to form the periphery of the sanitary napkin 1720. The sanitary napkin 1720 has an inner surface 1734 and an outer surface 1736. In general, the outer surface 1736 extends from one extreme edge 1738 to the other extreme edge 1738 and from one longitudinal edge 1740 to the other longitudinal edge 1740, and is the furthest surface from the wearer during use of the sanitary napkin. 1720, designed to fit the wearer's underwear. When using a backsheet 1730, this typically forms the outer surface 736. The inner surface 1734 is the surface opposite the outer surface 736 and in the embodiment shown is typically formed by the topsheet 1726. In general, the inner surface 734 is the co-extensive surface of the outer surface 1736 which is in its mostly in contact with the wearer when the sanitary napkin 1720 is in use.

In the preferred embodiment of the sanitary napkin 1720 as shown in Figure 17, the fastening system 1724 comprises a connecting member 1724 positioned on the outer surface 1736 of the sanitary napkin 1720 and a release plug (not shown) which , as is known in the art, is attached to the adhesive of the bonding member 1742 and may be loosened.

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As one of the preferred embodiments of the sanitary napkin 1720 of the present invention comprises connecting flaps 1732 and 1732 ', one or both flaps 1732 and 1732' are also provided with a flap connecting member 1746 for holding the flaps. 1732 and 1732 'in position after the same 1732 and 1732' have been arranged around the edges of the groin region of the inner garment. Also, a release sheet (not shown) is placed over each of the flap attachment members 1746 to protect the adhesive until the sanitary napkin 1720 is used, the release sheet is then removed and the flap wrapped around. vol. groin region edges of the garment.

The topsheet 1726 may be made of any of the above topsheet materials regarding diapers. In a preferred embodiment, the topsheet 1726 preferably comprises a thermoplastic film formed as described in U.S. Patent No. 4,342,314, entitled Resillient Plastic Web Exhibiting. Fiber-Like Properties), granted to Clifford J. Radel and Hugh A. Thompson on August 3, 1982; and U.S. Patent No.

463 045, entitled Macro-Copically Expanded Three-Dimensional Plastic Web That Has a Non-Glossy Visible Surface and Tissue-Like Touch (Macros ^ copically Expanded Three-Dimensional Plastic Web Exhibiting Non-Glossy Visible Surface and Cloth-Like Tactile Impression), issued to Nicholas A. Ahr, William I. Mullane, Jr. and William R. Quellette, July 31, 1984; patents which are incorporated herein by reference.

Backsheet 1730 may be made of any of the backsheet materials referred to in respect of diapers. The backsheet preferably comprises a polyethylene film.

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absorbent core 1728 is positioned between topsheet 1726 and backsheet 1730, and may be made. any of the absorbent parts of the present invention or only the particulate absorbent polymer compositions of the present invention. In an alternative embodiment of the sanitary napkin 1726, the absorbent core 728 comprises a laminate (a layered absorbent part) as described herein.

In use, the sanitary napkin 1720 is secured to the inner side of an inner garment in the groin region with the adhesive-fastened side of the sanitary napkin 1720 pressure sensitive towards the groin region of the inner garment. . Thus, the inner garment serves as the receiving member of the web system. xation 1724. The release sheet is removed from the connecting member 1742 and the sanitary napkin 1720 is secured in position by firmly compressing the pressure sensitive adhesive fastener 1742 against the groin area material of the inner garment.

Synthetic Urine

Specific synthetic urine used in the assay methods of the present invention is referred to herein as synthetic urine. Synthetic urine is commonly known as Jayco Synurine and can be obtained from Jayco Pharmaceuticals Company. Camp Hill, Pennsylvania, United States of America. The synthetic urine formulation is as follows: 2.0 g / liter KCl; 2.0 g / 1 Na₂S0₄; 0.85 g / l of (NH₄)H₂P0₄; 0.15 g / l of) NH₄)₂HPO₄; 0.19 g / 1 CaCl₂and 0.23 g / l MgCl₂· All chemicals are reagent grade. The pH of synthetic urine ranges from 6.0 to 6.4.

Assay Methods

A. Sample Selection and Screening

In order to test representative samples of the

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polymeric positions in the assays described hereinafter, sample specific fractions are produced. The specific fraction chosen for the assays according to the present invention is a sample of about 300 micrometers (standard sieve number 50) to about 850 micrometers (normal sieve number 20). Thus, the test amps according to the present invention are designated as fraction 20/50. In order to obtain the 20/50 fraction if stopped and sieved, a sample or a plurality of particles are separated and then sieved through a set of decreasing aperture sieves.

Approximately 40 fractions of a representative bulk sample of the polymer composition are divided into eight equal fractions. The sample is trimmed according to the manufacturer's instructions with a Rotary Microriffler model RR-4, available from Quantossrome Co. of Syosset, NY, United States of America. One of these fractions is then transferred to a sieve set, the sieve set contains, from top to bottom, a number 20 standard sieve (850 micrometres), a number 50 standard sieve (300 micrometres) and a receiving vessel. The quarter fraction is sieved following the manufacturer's instructions with an agitated 7.6 mm (3 inch) vibrating sieve model SS-5. 0 sieve shaker, standard sieve number 20 (300 micrometres), standard sieve number 50 (850 micrometres) and collection vessel can be obtained from Gilson Company, Inc. of Worthington, OH, United States. The quarter fraction is shaken for three minutes at approximately 2,100 vibrations per minute (6 on the instrument marker) to obtain a sample with a particle size of 300 to 850 micrometres; that is, a sample consisting of particles which pass through a 20 mesh screen (sieve number 20) and which are retained in a 50 mesh screen (sieve number 50) and which in this specification may simply be designated , as a 20/50 fraction.

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Β Swelling Speed

A sample of the 20/50 fraction of the polymer composition is placed in a test tube, a specific amount of synthetic urine is added thereto, and the time taken for the sample to absorb the synthetic urine is measured. The rate of fluid absorption of the sample determines the swelling rate. The swelling rate measures the average rate of fluid uptake by a 20/50 fraction sample and at a load of 28 grams per gram, in the presence of potential gel blocking conditions. As the mass of the gel expands upward into the fluid contained in the tube, the gel bed height increases. For polymer compositions especially prone to gel blocking, a point is reached at which the permeability of the gel bed limits the swelling of the interior gel particles. That is, the rate at which fluid can penetrate and travel through the bed is less than the rate at which fluid can diffuse through particles, for polymeric compositions: with minimal gel-blocking properties, this method will point to for results virtually unaffected by bed properties.

The subsequent procedure develops under normal laboratory conditions of 23 ° C (73 ° F) and 50% relative humidity. Using a standard scale to three decimal places, a 0.358 gram sample, plus or minus 0.001 gram, is weighed from a sample of the 20/50 fraction of the polymer composition and placed on the bottom of a standardized test tube of 16 mm in diameter, as obtainable from Fisher Scientific Co., Pittsburgh, PA, United States of America. To the test tube held vertically 10.0 ml of synthetic urine is added and a timer is started at the same time. The stopwatch is stopped at a time when the swelling polymer mass of swollen polymer reaches the bottom of the synthetic urine meniscus present in the test tube. Tie" *"

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The swelling rate (sr) of the polymer composition is calculated as follows:

sr = (the amount of synthetic urine per gram of polymeric composition added to the sample, in this case 28), divided by (elapsed time in seconds).

The swelling rate used in this specification corresponds to the average swelling rate of three samples.

It should be noted that the swelling rate of multi-ear polymer (not only 28 x ear) polymer compositions can be determined by varying the amount of synthetic urine added to the 20/50 fraction sample. For example, a 15 x swelling rate may be calculated by adding 5.36 ml of synthetic urine to a sample weighing 0.358 grams.

C. Gel Expansion Pressure

A sample of a 20/50 polymer fraction is placed in a special gel expansion pressure apparatus as described hereinafter and contacted with a specific amount of synthetic urine. The liquid force exerted by the expanded gel mass of the sample is then measured with the apparatus and then converted to gel expansion pressure.

Figure 18 shows a side view of the apparatus used to measure gel expansion pressure of the polymeric compositions of the present invention. The apparatus generally comprises a test holder 1810, a storage rack 1812, a storage rack 1814, a sample alignment console 1816, a sample holder 1818, an absorption cell 1820, a 1822 compression and an 1824 force gauge.

Assay holder 1810 comprises a base 1826. · · · · 63,387

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A column 1828 attached to the base 1826, a mobile test platform 1820 attached to the column 1828 and a force gauge mounting console 1832 attached to the column 1828 above the test platform 1830. Assay 1830 is operated by a rack and pinion lever system As shown in Figure 18, the rack and pinion lever system comprises a rack 1834, a lever 1836 and a locking screw 1838. 0 Assay holder comprises an Ametek Model RP number ML-3656 test holder, available from Crown Tool &amp; Supply Co. of Solon, OH, United States of America.

The mounting rack of the storage rack 1812 is shown in Figures 18a and 18b and comprises a 7.6 by 7.6 cm (3 by 3 inch) blade having two 1842 threaded holes in the plate at a distance of 1.11 cm (7/16 inch) from a first edge 1844 of plate 1840, with its centers spaced 2.5 cm (1 inch) from opposite sides 1846 of plate 1840. A support rod that is 1.3 cm (1/2 inch) long and 0.64 cm (1/4 pole in) in diameter is attached to the bottom of the 1840 plate. The 1812 Object Holder Mounting Platform It is made of aluminum.

Rack 1814 is secured to the rack mounting platform 1812 by bolts that pass through the threaded holes 1842. Rack 1814 provides microscope-like motion control. The storage case 1814 is thus provided with a rough fit 1850, a fine fit 1852 and a adjusting screw 1854. 0 1814 comprises a precision moving platform storage case number J36O8, available from Edmund Scientific Co. of Barrington, NJ, United States of America.

The sample alignment console 1816 is shown in Figure 18c and comprises a U-shaped part consisting of a rectangular part approximately 90 by 60 millimeters. U 1856 studs each have

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one, approximately 25 by 60 millimeters, with the base 1858 having approximately 40 by 10 millimeters, such that the U aperture is approximately 40 by 50 mm. At the specimen alignment console, four 3.5mm diameter tapped holes are drilled at 20mm from the 1862 side edges and 5mm from the 1864 end margins. The 1816 sample alignment console is made of LEXAN sheet material. 0.64cm (1/4 inch). The sample alignment console 1816 is secured to the top of the storage case 1814 by means of threaded holes and screws.

The sample holder 1818 is held loosely by the sample alignment console 1816 at opening U. The sample holder 1818 is shown in Figures 18d and 18e. The sample holder 1818 is formed by a block about 40 mm wide by 40 mm long and 38 mm high. In the sample holder 1818, a central cylindrical aperture 1866 having a diameter of 25 mm and a length of 25 mm is formed. The sample holder is made of LEXAN.

The absorption cell 1820 is loosely mounted to the sample holder 1818 by placing the absorption cell 1820 in the central cylindrical opening 1866. The absorption cell 1820 must have an inside diameter of 23 mm. Absorption cell 1820 comprises a standard absorption cell number 07-102 available from Fisher Scientific of Pittsburg, PA., United States of America.

1824 force gauge is attached to the mounting bracket of the 1810 test case holder force gauge. The 1824 force gauge is the Accuforce Cadet 0-500 Gauge AFC-1 reverse reading, RS 232 number ML-5801 -4, available from Crown Tool &amp; Supply Co. of Solon, OH, United States.

The compression shoe 1822, as shown in Figures 18f and 18g, is attached to the force gauge.

1824 The compression shoe 1822 comprises a base 1868 and a shank 1870. The base 1868 is formed of a circular plate.

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v ^ · ·

Mod. 71 - 20,000 ex. · 90/08 home that has the diameter of 20.5 mm and the thickness of

2.5 millimeters. Rod 1870 is a rod with a diameter of

6.5 mm and length of approximately 80 mm. An 1872 meter (12 inch) long, 12.7 mm (1 inch) long connecting hole with an inner thread 10-32 is placed at the end of the rod 1870 that opposes the base 1868 to hold the 1822 compression shoe to 1824 force gauge. The 1822 compression shoe is made of aluminum.

In the test holder an illuminator (not shown) may also be used. The illuminator comprises an optical fiber illuminator number N-09745-00, available from Cole-Parmer of Chicago, II., United States of America.

The following procedure is performed under normal laboratory conditions at 25 ° C (73 ° F) and 50% relative humidity. Using a normal scale to three decimal places, a sample of 0.358 grams is weighed, plus or minus 0.001 grams of a sample of fraction 20/50 of composition po. 1020 ml of synthetic urine (a charge equal to 28 x) is added to the absorption cell 1820. The absorption cell 1820 is placed in the sample holder 1818, which is placed in the sample alignment console 1816 in the test holder 1810. The illuminator is turned on using the lever 1836 on the test platform 1830 of the test holder 1810, the sample is raised until the compression shoe 1822 is almost touching the fluid. Using the coarse / fine adjustments 1850 and 1852 in item 1814, the sample is raised until the fluid level is aligned with the top of the base 1868 of the compression shoe 1822. This is accomplished by looking at through the upper part of the base of the shoe 1868. The fluid that is in the absorption cell wall due to surface tension appears as a white band. As the sample rises, this band moves closer to the base of the 1868 shoe, and eventually blocks the silver color of the base of the 1868 shoe. When the white band is above

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Mod. 71 · 20,000 ex. - 90/08 from the top of the base of the 1868 shoe, a silver band appears. At this point, the sample is lowered until the silver band simply disappears. When the gel mass reaches the base of the 1868 shoe, a timer is set.⁵ for thirty minutes and goes into operation. The timer is a Desktop Dual Timer chronometer Number N-08610-14, available from Cole-Palmer of Chicago, II., United States of America. After 30 minutes, the force in grams indicated on the force gauge shall be recorded.

1824 (There is also the peak of force). Gel expansion pressure (gep), in dynes per square centimeter, is cal. as follows:

gep = (strength after 30 minutes in grams ₅ multiplied by (981 dynes per gram); The result is divided by (3.14 cm 2, where 3.14 cm 2 is the base area of ​​the 1868 shoe).

This procedure is repeated with two additional samples. The gel expansion pressure of the polymer composition is the average of three gep values ​​obtained as described above.

It should be noted that the gel expansion pressure of the polymeric compositions under various loads (not just 28x loads) can be determined by varying the amount of synthetic urine added to the 20/50 fraction samples. For example, a 15 X gel expansion pressure can be calculated by adding 5.36 ml of synthetic urine to a 0.358 gram sample.

D. Absorption Capacity

The polymeric composition is placed in a tea bag, dipped in a synthetic urine remnant for a spaced time, and then centrifuged for a specific period of time. The pro35 • f - · &lt;_and ·

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The portion between the final weight of the polymer composition after centrifugation minus the initial weight (net fluid gain) and the initial weight determines the absorption capacity.

The following procedure is performed under normal laboratory conditions at 23 ° C (73 ° F) and 50% relative humidity. Using a 6 by 12 centimeter die cut, the tea bag material is cut in half lengthwise and sealed on two sides with a T-bar seal to give a Square tea bag with 6 by 6 inches. The tea bag material used is a heat sealable grade 1234 material obtainable from CH Dexter, Division of the Dexter Corp., Windsor Locks, Connecticut, United States of America, or equivalent material. If you wish to retain the particles fi. less porosity tea bag material should be used. 0.200 grams, approximately 0.005 grams, of the polymeric composition is weighed on a weighing paper and transferred to the tea bag. Seal the top (open end) of the tea bag. An empty tea bag is sealed at the top and used as a blank test. Approximately 300 ml of synthetic urine is poured into each. It is poured into a 1,000 ml precipitation beaker. Dip the empty tea bag into the synthetic urine. The tea bag containing the polymeric composition (sample tea bag) is held horizontally so that the material is evenly distributed through the tea bag. This is placed on the surface of synthetic urine. The tea bag is allowed to soak for not more than one minute and then completely submerged and soaked for 60 minutes. Approximately two minutes after the first sample has been dipped, a second set of tea bags, similarly prepared to the first set of sample and empty tea bags, is dipped and soaked for sixty minutes. same way as the first set. After the prescribed soak time for each sample set in the tea bags has elapsed,

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tea bags are promptly removed from synthetic urine (using tweezers). The samples are then centrifuged as described below. The centrifuge used is a Delux Dynac II Fisher model centrifuge.². 05-100-26, available from Fisher Scientific Co. of Pittsbrugh, PA, USA, or the equivalent. The centrifuge must be equipped with a direct reading tachometer and an electric brake. The centrifuge is further equipped with an inserted cylindrical basket that is approximately 6.35 centimeters (2.5 inches) in outer wall height, 21.425 centimeters (8.435 inches) in outer diameter, 20.1555 (7.935 inches) in inner diameter , nine rows of circular holes about 3/32 inch (0.238 cm) in diameter, equally spaced around the circumference of the outer wall, and a bottom with 6 0.635 cm (1/4 inch) diameter circular drainage holes, equally spaced around the circumference of the basket bottom, with a distance of 1.27 cm (1/2 inch) between inner surface of the outer wall and the center Drainage holes or equivalent. The basket is mounted on the centrifuge so that it can rotate as well as lock in unison with the centrifuge. Tea bags containing the sample are placed in the centrifuge basket with one end of the tea bags bent in the direction of rotation of the centrifuge to absorb the initial force. Empty tea bags are placed on either side of the corresponding tea bags. Tea with sample. 0 tea bag with sample from the second set should be placed opposite to the tea bag from the first set; and the empty tea bag of the second set should be opposite the empty tea bag of the first set to balance the centrifuge. The centrifuge is started and its speed is raised rapidly to a stable value of 1,500 revolutions per minute. Once the centrifuge has stabilized at 1,500 revolutions per minute, the timer is set to three minutes. After the three minutes /.

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c &lt;W. &lt;13, the centrifuge is switched off and the brake applied. The first sample tea bag is removed · the first empty tea bag and weighed separately. The procedure is repeated with the second sample tea bag and the second empty tea bag. The absorption capacity (ac) of each sample is calculated as follows:

ac = (weight of the sample tea bag after centrifugation minus the weight of the empty tea bag after centrifugation, minus the weight of the dry polymeric composition) divided by (dry weight of the polymeric composition).

The absorption capacity value for use in the present specification is the average absorption capacity of the two samples.

E. BET Surface Area Measurement by Mass Unit

The specific surface area per unit mass (m / g) of the polymeric composition is determined using the Brunauer-Emmet-Teller gas adsorption method (BET. This method includes the adsorption of a monomolecular gas layer ( krypton) in a known mass of a sample of the polymer composition at the temperature of the liquid nitrogen. The adsorbed krypton is then demoted by raising the sample temperature (thermal desorption), and is detected by means of a thermal conductivity detector (TCD), the output of which is connected to an integrated recorder. The area of ​​unabsorbed krypton peak is thus known. From each sample, duplicate desorption peaks are recorded. After sample analysis, the instrument response is determined by preparing a calibration curve. Known quantities of gaseous nitrogen (99.99% +) are injected into the system and the response of the instrument is recorded via the integrated recorder. A ΰβνκ · ”·. ν'Τ

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Linear regression analysis of instrument response (peak area) compared to the amount of sample injected yields a calibration curve. This information is then used to determine the specific area of ​​the various samples using a BET single point calculation.

Specific equipment used to perform these analyzes can be obtained from Quantachrome Corporation (Syosset, NY, United States) and consists of the Quantector Outgassing Station and the Quantasorb Sample Analysis Unit. These units are used as described in the respective operating manuals, which are incorporated herein by reference. The adsorbed gas mixture is 0.10% krypton in helium. (This gas mixture can be obtained from Alphagaz and is realistically certified to its concentration such that the gas is used without further analysis).

Weigh 3.0 grams, plus or minus 0.01 g / g, into a glass vial of the apparatus. The glass vial containing the sample is then placed in the gas stream of the instrument. Samples are degassed for a minimum of four hours at 30 ml / minute of helium stream flow using the Quantector. After degassing, the gas stream is passed to a 0.10% helium krypton stream. 0 Glass vial is dipped in liquid nitrogen allowing to reach equilibrium. This generates an adsorption curve. The adsorbed krypton is then desorbed by removing the liquid nitrogen bath and immersing the glass vial in hot tap water. The adsorbed krypton yields a desorption curve and a peak value. Duplicate adsorption / desorption measurements are sealed over each sample. The total surface area of ​​the sample (S_fc) according to the following formula:

s_t = (1-P / P_O) (A / A_ç) V_ç ((AT_cgP_The) / RT) where P equals the partial pressure of the adsorbed; Ρθ is equal to the saturated pressure of the adsorbed (2.63 mm Hg for cri35

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(roipton); A is equal to the signal area; A equals cali area^ç 3 arm; V is equal to calibration volume (cm); N is equal^ç 23 to Avogadro's number ie 6.02 x 10; THE_cg is equal to the cross-sectional area of ​​the adsorbed molecule in square meters, which is 20.5 x 19 m for krypton; P is equal to ambient pressure (atmosphere); R is equal to the perfect gas constant of 82.1 eni atm / K ° m; and T is equal to the temperature of the calibration volume (room temperature in K °). To transform the calibration volume of nitrogen to krypton, the ratio is used:

kr

0.752 V_N2

By constructing a calibration curve of the instrument response (peak area) compared to the injected volume, V can be determined._ç and A = A_ç At 25 ° C, the pressure of 1 atmosphere (ambient laboratory conditions), and using 0.10% krypton in helium, the relationship to surface area is given by the expression:

s_t (m₂) = ((A - C) / B) x 2.7343 where A equals the peak area of ​​the desorbed sample; B is equal to the slope of the calibration curve; and C is equal to the y-intercept of the calibration curve. This total surface area value is then divided by the sample mass to obtain the surface area to mass ratio. 0 The surface area divided by mass value for use in the present invention is the average surface area values ​​for mass for the two samples in duplicate. market. (Specific BET single-point calibration values ​​are given in the instrument manuals, incorporated herein by reference).

F. Aggregate Percentage Method

The percentage of aggregate particles in a sample of the polymeric composition may be determined using a technique. · Y &amp; çvx .. ·. ·

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microscopy cases with small magnification (10 to 60 times). A particle is considered to be an aggregate if it appears to be made of more than one precursor particle. By carefully observing the individual particles, the observer can distinguish aggregates from simple unaggregated particles. Aggregate particles have typically been found to have many uneven edges and many faces when viewed under the light microscope, whereas single unaggregated particles are typically smooth and without special features. In addition, due to the diffusion of light around the particles, the aggregate particles appear more opaque, whereas the unaggregated single particles typically have a translucent appearance, unless their surfaces are severely scratched or notched.

A sample of the 20/50 fraction of the polymer composition is analyzed under the optical microscope. The optical microscope used is a model SMZ-2T stereoscopic optical microscope available from Nikon in Garden City, NJ, United States of America. After mounting a microscope slide to find the field of view on the microscope plate, a sample of about 300 particles of the 20/50 fraction is placed on the slide. While illuminating the particles with an illuminator, at least about 50 individual particles are observed at a magnification of 10 to 60 x. The illuminator used is a fiber optic illuminator obtainable from Bausch &amp; Lomb Company of Rochester, NY., United States of America. If a particle is clearly formed of smaller individual particles bound together, that particle is recorded as an aggregate. If it is not evident whether or not the particle is formed of more than one particle, or if the particle is clearly only one particle, then the particle is re. registered as a single unaggregated particle. After at least 50 particles are observed, the total number of aggregates is divided by the total number of particles counted and multiplied by 100% to give a percentage percentage value.

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aggregates in a given sample. On a weight percent basis, the total number of aggregates is separately weighed on a normal scale and the aggregate weight is di.

It is due to the total weight of the counted particles and multiplied! per 100 to give a weight percent aggregation value for a given sample.

G. Fluid Stability The objective of this method is to determine the stability. individual particle aggregate after exposure to synthetic urine.

About 300 particles of a sample of the 20/50 fraction are placed on a standard 2.5 cm x 7.6 cm (1 by 3) microscope slide. The slide can be obtained from Fisher Scientific Co., Pittsburgh, PA., United States of America. The particles are analyzed under the optical microscope. The optical microscope used is a model SMZ-2T stereoscopic optical microscope available from Nikon of Garden City, NJ, United States of America. The particles are illuminated. The illuminator used is a fiber optic illuminator obtainable from Bausch &amp; Lomb of Rochester, NY, United States of America.

The particles are studied at a magnification of 10 to 60 times. Three relatively large particles with exceptional aggregate qualities (i.e. comprising a multiplicity of precursor particles) are placed on separate microscopic observation slides. One of the slides containing a single aggregate particle is placed on the optical microscope stage. Three drops of synthetic urine are added to the side and about 2 millimeters above the aggregate particle. The swell of the aggregate particle is observed for three minutes. (If necessary, the microscope can be continually refocused so that the aggregate particle or any separate particles are in focus). When observing the swollen aggregate particle, the aim is to observe the possible rupture of small particles of the particulate

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Case: 4124 X 1a main aggregate; moving away from floating platelet-like particles from the main aggregate particle; the expansion of the particles in the two-dimensional xy plane only 30Λ particles breaking with and floating away from the main aggregate particle; or the establishment of individual particles at the blade / water interface. A particle is considered unstable if the aggregate particle has a large number of component precursor particles disrupting and receding. After five minutes, a dissecting needle is used to experiment around the particle. The Dissecting Needle is a Brich Handy Sample Pointer available from Fisher Scientific of Pittsburgh, PA, United States of America. The main aggregate particle (if it still exists) is carefully displaced by the dissecting needle to determine whether or not particles separate from the main aggregate particle. The dissecting needle can also carefully investigate closely the main aggregate particle to determine whether or not this particle remains intact. If the main aggregate particle breaks after gentle testing, or if there are separate particles, the particle is considered unstable. After analyzing the particle, two more drops of synthetic urine of approximately 1 cm height are directly added above the swollen main aggregate particle. The principal aggregate particle is observed for any additional instability. If the instability is excessive, the particle is considered unstable. If the aggregate particle remains relatively stable after each test procedure, the aggregate particle is considered stable. The test is repeated with the remaining two aggregate particles.

H. Particle Size and Average Mass Particle Size

The distribution of the particle size is determined on a percentage by weight basis of a bulk sample of 10

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Case: 4124 X grams of polymer composition sieving the sample with a set of nineteen sieves ranging in size from standard sieve number 20 (850 micrometres) to standard sieve number 400 (38 micrometres). Sieves are standard sieves obtainable from Gilson Company, Inc. of Uorthinton, OH, United States of America. 0 This procedure is carried out on three sieve sets at a time, as the equipment cannot support all nineteen sieves at the same time. A first set contains sieves numbers 20, 25, 30. 35, 40, 45 and 50, plus the sieve receiving container; the second set contains sieves numbers 60, 70, 80, 100, 120 and 140, plus the sieving container; The third set contains sieves numbers 170, 200, 230, 270, 325 and 400, plus the sieving container. The particles retained on each of these screens are then weighed to determine the particle size distribution on a weight percent basis.

The first set of sieves is mounted on a shaker and placed on sieve number 20 with about 0.01 grams of a representative bulk sample. The shaker used is a sieve shaker vi. 7.6 cm (3 inch) model SS-5, available from Gilson Company, Inc. of Wothington, OH, United States. The set is shaken for three minutes at approximately 2,100 vibrations per minute (6 on the instrument controller). The sieve receiving container is then removed and the sieve assembly set aside for subsequent weighing. Using a soft brush, the received sample is passed into the sieving container onto a weighing paper. The second set of sieves are mounted on the shaker, and sample on the weighing paper is transferred to sieve number 60. The second set is shaken for three minutes at approximately 2,100 vibrations per minute, with the sample remaining in the sieving vessel transferred to a weighing paper and the sieve assembly set aside. Mounts the third

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shaker set and the sample from the weighing paper is transferred to No. 170 sieve. The third sieve set is shaken for three minutes at approximately 2,100 vibrations per minute. A soft brush transfers the contents of each sieve to a previously weighed weighing paper. The sample shall be weighed on a normal scale of three decimal places and the weight of the sample on each specific sieve shall be noted. This operation is repeated using fresh weighing paper for each sample, for each sieve and for the sample in the sieving container after the third set of sieves has been shaken. The process is repeated for two additional pieces of 10 grams each. The average weights of the three samples on each sieve determine the average distribution of the grabulometry on a weight percent basis for each sieve size.

Average particle size by mass of the 10 gram bulk sample is calculated by the following expression:

(Di x M_±) maps = ^ M.

where maps is the average mass particle size; Mi is the weight of the particles in each specific sieve; and Di is the size parameter for each specific sieve. The sieve size parameter Di is defined by the size (expressed in micrometres) of the immediately larger sieve. For example, a standard sieve number 50 has a size parameter of 355 micrometres, which corresponds to the size of the apertures in a standard sieve number 45 (the immediately larger sieve). 0 Average mass particle size for use in the present invention is the average average mass particle size of the three samples.

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<img file="PT97236B_D0100.tif" />

EXAMPLES

Comparative Example 1

A 10-liter twin-arm stainless steel kneader with a lid measuring 220 x 240 mm in opening and 240 mm deep with two Sigma-type blades with a diameter of 10 mm. rotation equal to 120 mm. An aqueous monomer solution consisting of 37% by weight of monomers is prepared.

Monomer consists of 75 mol% sodium acrylate and 25 mol% acrylic acid. 5,500 grams of the aqueous monomer solution is charged into the kneading vessel which is subsequently purged with nitrogen gas to remove trapped air. Then the two Sigma-type blades are rotated at a speed of 46 revolutions per minute and the jacket is heated by passing water at 35 ° C. As polymerization initiators, 2.8 grams of persulphate are added. of sodium and 0.14 grams of L-ascorbic acid. Polymerization begins about four minutes after the addition of the starting agents. In the reaction system, a peak temperature of 82 ° C is reached fifteen minutes after the addition of the primers. The hi gel polymer is divided. dripped into particles about 5 millimeters in size while stirring. The lid of the kneader is removed sixty minutes after the start of polymerization and the material is removed from the kneader.

The hydrated aqueous gel polymer thus obtained is spread over a standardized metal mesh of TA. No. 50, and is dried with hot air at 150 ° C for ninety minutes. The dried particles are sprayed with a hammer mill type sprayer, and sieved with a standard number 20 sieve (850 micrometers) to obtain particles passing through the standard size 20 sieve. mass of these particles is 405 micrometres.

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EXAMPLE 1

A solution consisting of 24.0 grams of methanol and 6.0 grams of glycerol is prepared. In a standard precipitation beaker, this solution is applied to and mixed with 300 grams of precursor particles made according to Comparative Example 1. The size distribution of the precursor particles is such that 75% by weight passes through a standard sieve number 100 (150 micrometres) and is retained on the standard sieve number 170 (90 micrometres); and 25% by weight passes through a standard sieve number 170 (90 micrometres). The average mass size of the precursor particles is 84 micrometers. This mixture is stirred until all precursor particles are wetted by the solution (approximately one minute). The resulting mixture is then spread on a Pyrex dish to stand still and allowed to stand unheated for five minutes to allow the precursor particles to physically associate. The mixture is then heated in a forced-air oven at 200 ° C for forty-five minutes. The resulting particles are then allowed to cool to ambient temperature. The resulting particles are passed through a number 20 standard sieve (850 micrometres) to limit the size of the larger particles.

EXAMPLE 2

A solution consisting of 18.0 grams of isopropanol, 12.0 grams of distilled water and 6.0 grams of glycerol is prepared. In a normal precipitation beaker, this solution is applied to and mixed with 300 grams of precursor particles made according to Comparative Example 1.

The size distribution of the precursor particles is such that 10% by weight passes through a standard sieve number (850 micrometres) and is retained on a standard 30 number sieve (600 micrometres); 25% by weight passes through a sieve. - * «* V '»

L ..V · '

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<img file="PT97236B_D0102.tif" />

standard number 30 (600 micrometres) and is retained by a standard number 40 (425 micrometres); 25% by weight passes through a standard sieve number 40 (425 micrometers) and is retained on a standard sieve number 50 (300 micrometers); 30% by weight passes through a number 50 standard sieve (300 micrometres) and is retained on a number 100 standard sieve (150 micrometres); and 10% by weight passes through a standard 100 number sieve (150 microns). 0 Average mass size of the precursor particles is 421 micrometers. This mixture is stirred until all precursor particles are wetted by the solution (approximately one minute). The resulting mixture is then spread on a PYREX dish so that it is loose and allowed to stand unheated for forty-five minutes to allow the precursor particles to physically associate. The mixture is then heated in a forced air oven at 200 ° C for forty-five minutes. The resulting particles are then allowed to cool to room temperature.

The resulting particles are passed through a number 20 standard sieve (850 micrometres) to limit the size of the larger particles.

EXAMPLE 3

A solution consisting of 18.0 grams of isopropanol, 12.0 grams of distilled water and 6.0 grams of glycerol is prepared. This solution is introduced and mixed in a standard precipitation beaker, the solution is applied to and mixed with 300 grams of precursor particles prepared according to Comparative Example 1. The size distribution of the precursor particles is such that 50 wt% is passed through a standard sieve number 40 (425 micrometers) and is retained on a standard sieve number 50 (300 micrometers); 30% by weight passes through standard sieve number 50 (300 micrometres) and is retained on standard sieve number 100 (150 micrometres); and 20% by weight passes through standard sieve number 100 (150 micrometres). 0 average mass size,

........· ·- ·.

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<img file="PT97236B_D0103.tif" />

of the precursor particles equals 322 micrometers. This mixture is stirred until all precursor particles are wetted by the solution (approximately one minute). The resulting mixture is then soaked in PYREX silver and allowed to stand unheated for forty-five minutes to allow the precursor particles to physically associate. The forced air circulation is then heated in an oven at 200 ° C for forty-five minutes and the resulting particles are then allowed to cool to room temperature. The resulting particles are passed through standard screen number 20 (850 micrometres) to limit the size of the larger particles).

EXAMPLE 4

A solution consisting of 18.0 grams of isopropanol, 12.0 grams of distilled water and 6.0 grams of glycerol is prepared. In a standard precipitation beaker, the solution is applied to and mixed with 300 grams of precursor particles prepared according to Comparative Example 1. The size distribution of the precursor particles is such that 60% by weight passes through a number 50 standard sieve (300 micrometres) and is retained on the number 100 standard sieve (150 micrometres); and 40 wt.% passes through standard sieve number 100 (150 micrometres). The average mass size of the precursor particles is 205 micrometers. I did This mixture is stirred until all precursor particles are wetted by the solution (approximately one minute). The resulting mixture is then spread loosely in a PYREX dish and allowed to stand unheated for ten minutes to allow the precursor particles to physically associate. The mixture is then heated in a forced air oven at 200 ° C for forty-five minutes, then allowed to cool to room temperature. These particles are ugly. pass through a number 20 standard sieve (850 micron

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O.1S9í meters) to limit the size of the larger particles.

EXAMPLE 5

Mod. 71 - 20,000 ex. · 90/08

A solution consisting of 18.0 grams of isopropanol, 12.0 grams of distilled water and 6.0 grams of glycerol is prepared. In a standard precipitation beaker, the solution is applied to and mixed with 300 grams of precursor particles prepared according to Comparative Example 1. The size distribution of the precursor particles is such that 60% by weight passes through a number 50 standard sieve (300 micrometres) and is retained by a number 100 standard sieve (150 micrometres); and 40 wt.% passes through a number 100 standard sieve (150 micrometers). The average mass size of the precursor particles is 205 micrometers. This mixture is stirred until all precursor particles are wetted by the solution (approximately one minute). The resulting mixture is then spread loosely in a PYREX dish and allowed to stand unheated for ten minutes to allow the precursor particles to physically associate. The mixture is then heated in a forced air oven at 180 ° C for forty-five minutes. The resulting particles are then allowed to cool to room temperature. These particles are passed through a number 20 standard sieve (850 micrometres) to limit the size of the larger particles).

EXAMPLE 6

In a mixing apparatus, 100 parts of a bulk sample of precursor particles made according to Comparative Example 1 are carefully mixed with a solution containing 2 parts by weight of glycerol and 4 parts by weight of water per 100 parts by weight of precursor particles. The average mass size of the precursor particles is 405 micrometers. 700 grams of the resulting mixture is introduced into a cylinder dipped in an oil bath. ·· * «. · · Rw ^ W® ·, χχΛΛί ^ ί³:*'·'.'

· .- *. · .- &lt;'ΛΓ ·. - '· · * - {. · «.

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(80 ° C), and heat for eighty minutes while gently shaking, the resulting particles are passed through a number 18 standard wire mesh (1,000 micrometers).

Comparative Example 2

In a mixer, 100 parts of the precursor particles produced according to Comparative Example 1 are mixed with a solution containing 0.5 parts by weight of glycerol, 2 parts by weight of water and 0.5 parts by weight of isopropanol per 100 parts by weight of precursor particles. The average mass size of the precursor particles is 405 micrometers. The resulting mixture is heated in a continuous dryer. 0 average resistance time in the dryer is about fifty minutes and the temperature of the material at the dryer outlet is approximately 190 ° C. The resulting particles are passed through a number 20 wire mesh (850 micrometers). The resulting particles have the following particle size distribution: retained on a number 20 screen; 0% retained on a number 25 sieve; 0% retained on sieve number 20; 0% retained on sieve 35;

0.3% retained in sieve number 40; 1.1% retained in sieve number 45; 2.2% retained in sieve number 50; 4.4% retained in sieve number 60; 9.4% retained in sieve number 70; 10.9% retained in sieve number 80; 10.4% retained in sieve number 100; 10.9% retained in sieve number 120; 12.6% ret. sieve number 140; 5.4% retained on sieve number 170; 7.2% retained on sieve number 200; 6.3% retained in sieve number 230; 5.0% retained in sieve number 270; 3.5% retained on sieve number 325; 3.3% retained on sieve number 400; and 4.7% retained in the final collection container. The average mass particle size is 465 micrometers.

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<img file="PT97236B_D0107.tif" />

EXAMPLE 7

With a lid, a 10 liter capacity double arm stainless steel kneader with a cannon, which measures 220 x 240 mm in opening and 240 mm in depth, and has two Sigma-type blades that have a rotation diameter equal to 120 mm. An aqueous solution consisting of 37% by weight of monomer is prepared. The monomer consists of 75 mole% sodium acrylate and 25 mole% acrylic acid. 5,500 grams of the aqueous monomer solution is introduced into the whirlpool which is subsequently purged with nitrogen gas to remove the contained air. The two Sigma blades are then rotated at a speed of 46 revolutions per minute and the jacket is heated by passing water at 35 ° C. As polymerization initiators, 2.8 grams of sodium persulfate and 0.14 grams of L-ascobic acid are added. Polymerization begins about four minutes after addition of the initiators. Within the reaction system, a maximum temperature of 82 ° C is reached fifteen minutes after the addition of the primers. The polymer comprising the hydrated gel is divided into particles about 5 millimeters in size while stirring is continued. The lid of the kneader is removed sixty minutes after polymerization has commenced, and the kneading material is removed.

The hydrated aqueous gel polymer thus obtained is spread over a number 50 standard metal mesh (300 micrometres) and dried with hot air at 150 ° C for ninety minutes. The dried particles are sprayed (stronger than in the case of the particles produced in Comparative Example 1) with a hammer-type mill, and sieved through a number 20 standard wire mesh (850 micrometres) to obtain particles. passing through standard screen number 20 (850 micrometres). The average mass size of these precursor particles is 153 micrometers.

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In a mixer, 100 parts of the precursor particles produced according to the procedure described above are mixed with a solution containing 4 parts by weight glycerol, 8 parts by weight water and 2 parts by weight isopropanol per 100 parts by weight. Precursor particles 500 grams of the resulting mixture are introduced into a cylinder dipped in an oil bath (210 ° C) and heat-treated for ninety-five minutes while stirring gently. The resulting particles are passed through tenth number 18 standard metal mesh (1,000 micrometers).

Comparative Example 3

A 10 liter capacity twin-arm stainless steel kneader 220 x 240 mm opening and 240 mm deep with two Sigma-type blades with a rotational diameter of 120 mm is sealed with a lid. An aqueous solution consisting of 37% by weight of monomer is prepared. The monomer consists of 75 mole% sodium acrylate and 25 mole% acrylic acid. 5,500 grams of aqueous monomer solution is introduced into the kneading vessel, which is subsequently purged with nitrogen gas to remove any air which has been trapped therein. The two Sigma-type blades are then rotated at a speed of 46 revolutions per minute and, at the same time, the layer is heated by passing water at 35 ° C. As polymerization initiators, 2.8 grams of sodium persulfate and 0.14 grams of L-ascorbic acid are added. Polymerization begins four minutes after the addition of the initiating agents. Within the reaction system, a maximum temperature of 82 ° C is reached fifteen minutes after the addition of the initiating agents. The hydrated gel polymer is divided into about 5 millimeters in particle size while stirring is continued. Re. the kneader lid is removed sixty minutes after

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<img file="PT97236B_D0109.tif" />

initiate polymerization, and the material is removed from the kneader The particles are hydrated particles resulting from the aqueous gel polymer are spread on a standard 50 µm wire mesh (300 micrometers and dried with hot air at 150 ° C for ninety minutes. The dried particles (more violently than for the particles produced in Comparative Example 1) are sprayed with a hammer-type sprayer, and sieved with a standard No. 20 (850 micrometer) wire mesh to obtain particles that will pass through a standard number 20 sieve (850 micrometres). The mass average particle size of these precursor particles is 319 micrometres.

In a mixer, 100 parts of the precursor particles produced according to the above procedure are mixed with a solution containing 0.5 parts by weight of glycerol, 2 parts by weight of water and 0.5 parts by weight of isopropanol per 100 µl. parts by weight of precursor particles. The resulting mixture is heated in a continuous drawer.

Average residence time in the dryer is about fifty minutes, and the temperature of the material leaving the dryer is approximately 195 ° C. In a mixer, 100 parts of the material thus obtained are mixed with 5 parts of water, the mixture is allowed to stand for 30 minutes in a heated atmosphere at 80 ° C to agglomerate the particles and to disintegrate (ground). and granulate) to obtain particles passing through standard sieve number 20 (850 micrometres).

The results of the various tests exemplified above are shown in the following Table 1:

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TABLE

<td>1 • rl &lt;HO pu &lt;d (XO Ocm · -.</td><td></td><td></td><td>ο</td><td></td><td>σ&gt;</td><td>QC</td><td>CN</td><td></td><td>THERE</td><td>QC</td><td></td><td>i — 1</td><td>THE*</td><td></td><td>r-</td>

<td>CQ OC</td><td></td><td></td><td>CN</td><td></td><td>Ό</td><td>cq</td><td>&lt;r</td><td>M&gt;</td><td>MO</td><td>QC</td><td></td><td>CN</td><td>M0</td><td></td><td>QC</td>

<td> —</td><td></td><td></td><td>ο</td><td></td><td>Γ * 4</td><td>ο</td><td>O</td><td>O</td><td>O</td><td>O</td><td></td><td>O</td><td>O</td><td></td><td>O</td>

<td>CO ι — 1 CM</td><td></td><td></td><td></td><td></td><td>Λ</td><td>•s</td><td></td><td> *</td><td> ·*</td><td> *&gt;</td><td></td><td> *</td><td> *</td><td></td><td> •</td>

<td>CD CO Ή Ή B * co</td><td></td><td></td><td>ο</td><td></td><td>ο</td><td>ο</td><td>O</td><td>O</td><td>O</td><td>O</td><td></td><td>O</td><td>O</td><td></td><td>O</td>

<td>CD</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>• H | O 1 the co</td><td>oo</td><td></td><td>CN</td><td></td><td>οο</td><td>Μ0</td><td>THERE</td><td>CN</td><td>r-</td><td>QC</td><td></td><td></td><td> 00</td><td></td><td>ι — 1</td>

<td>The J3 CD</td><td>4-&gt; LA 00 ·</td><td></td><td>CN</td><td></td><td>ο</td><td>HERE</td><td>&lt;r</td><td> 00</td><td>oo</td><td>QC</td><td></td><td>r — 1</td><td>σ '</td><td></td><td>CN</td>

<td>rl Ό CJ</td><td>C 60</td><td></td><td> *.</td><td></td><td>• V</td><td> ·*</td><td></td><td>Λ</td><td>*s</td><td></td><td></td><td> ·»</td><td> **</td><td></td><td> *»</td>

<td>CD CO C</td><td>&lt;DO 60 CD</td><td></td><td>ο</td><td></td><td>γΗ</td><td>ο</td><td>O</td><td>O</td><td>O</td><td>O</td><td></td><td>O</td><td>O</td><td></td><td>O</td>

<td>&gt; Ό -H</td><td>B &lt;M CQ</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>cl</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>O (0 single (X o</td><td>CD</td><td></td><td>CM</td><td></td><td>Ό</td><td>CN</td><td>co</td><td>CN</td><td> 00</td><td> &gt;-</td><td></td><td>r — 1</td><td>Oh</td><td></td><td>CN</td>

<td>03 X T3</td><td>OB</td><td></td><td>r.</td><td></td><td> ·*</td><td></td><td> »&gt;</td><td></td><td></td><td>Λ</td><td></td><td></td><td> *</td><td></td><td> *</td>

<td>W φ</td><td>LA · Η / -s</td><td></td><td>σι</td><td></td><td>&lt;r</td><td>σ '</td><td>σ '</td><td>σ '</td><td>σ&gt;</td><td>co</td><td></td><td>M3</td><td>THERE</td><td></td><td> 00</td>

<td>CD O</td><td>1—1 T3N</td><td></td><td></td><td></td><td>ι-H</td><td>QC</td><td>QC</td><td>CN</td><td>CN</td><td>QC</td><td></td><td>ι — 1</td><td>CN</td><td></td><td>i — 1</td>

<td>P (D 1 (0</td><td>CD O m E</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>CX T3 03</td><td>OOCM CJ</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>«| P | ΤΟ O</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>• HW The eO</td><td>O -.</td><td></td><td>ο</td><td></td><td> 00</td><td>THERE</td><td>r-</td><td>σ '</td><td>THERE</td><td>r-</td><td></td><td>&lt;D</td><td>O&gt;</td><td></td><td></td>

<td>CO &lt;</td><td>iro 00</td><td></td><td>Γ \</td><td></td><td>Λ</td><td>x</td><td></td><td> *.</td><td>¡</td><td></td><td></td><td></td><td> *&gt;</td><td></td><td> *</td>

<td>cx o</td><td> \</td><td></td><td>Μ3</td><td></td><td>ΜΟ</td><td> 00</td><td></td><td>QC</td><td>QC</td><td>THERE</td><td></td><td>CN</td><td>&lt;r</td><td></td><td> 00</td>

<td>(fl (D IC)</td><td>O 60</td><td></td><td>&lt;Τ</td><td></td><td>QC</td><td>QC</td><td>QC</td><td>QC</td><td>QC</td><td>QC</td><td></td><td>&lt;r</td><td>QC</td><td></td><td>QC</td>

<td>OU QC</td><td>CN</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>ro | ι Ό CD</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>• Η Ρ O</td><td>O</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>rl cxo</td><td>ICO</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>• r4</td><td>the</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td colspan="2">mo ε co tj o CO CD CZ'rl IZO C</td><td></td><td> &lt;</td><td></td><td>ε</td><td>B</td><td>B</td><td>Ξ</td><td>B</td><td>B</td><td></td><td>B</td><td>AND</td><td></td><td>O</td>

<td>4-&gt; C</td><td>3 -H</td><td></td><td></td><td></td><td>• Η</td><td>•H</td><td>• r4</td><td>• rd</td><td>• r4</td><td>•H</td><td></td><td>•H</td><td>• r4</td><td></td><td>iro</td>

<td colspan="2">CQ CD CD —1 o CO Cd TO 03 &lt;H CM</td><td></td><td>ζ</td><td></td><td>CZ3</td><td>co</td><td>co</td><td>co</td><td>co</td><td>co</td><td></td><td>czo</td><td>cn</td><td></td><td>is</td>

<td>CD</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>CO ε Μ Ό O</td><td>B</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>CZ rH</td><td>CD</td><td></td><td></td><td></td><td> &amp;?</td><td> 6«</td><td>ê-S</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>ro ro 3</td><td>ASS</td><td></td><td></td><td></td><td>Ο</td><td></td><td>MO</td><td>THERE</td><td>O</td><td>MO</td><td></td><td> 00</td><td>O</td><td></td><td> 00</td>

<td>• rl -rl C</td><td>ro cq</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td> *&gt;</td><td></td><td> ·»</td>

<td>P TO eO</td><td>• rl CQ</td><td></td><td>&lt;c</td><td></td><td></td><td>O</td><td>THERE</td><td>O</td><td>O</td><td>CM</td><td></td><td>&lt;r</td><td>co</td><td></td><td>&lt;r</td>

<td>CO 'CD P</td><td>ρ ro</td><td></td><td></td><td></td><td>THERE</td><td>&lt;r</td><td>THERE</td><td>M3</td><td></td><td>QC</td><td></td><td>r — 1</td><td>σ \</td><td></td><td>CN</td>

<td colspan="2">&gt; s Mxi ε</td><td></td><td>ζ</td><td></td><td>π-4</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>1 ass</td><td> 1 1</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>0) -H</td><td>ρ ro ι</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>Efl co</td><td>3 P CD</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>o '&lt;D ω</td><td>O 60 B</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>rH ε m</td><td>CD Ό</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>3 CO</td><td>pro p</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>c co ε</td><td>CJ CD</td><td>z-s</td><td>&lt;c</td><td></td><td>&lt;Τ</td><td>i — 4</td><td>CN</td><td>THERE</td><td>THERE</td><td>THERE</td><td></td><td>THERE</td><td>QC</td><td></td><td>OO</td>

<td>CO -rl</td><td>P rl P</td><td>ο</td><td>«X.</td><td></td><td>οο</td><td>CN</td><td>CN</td><td>O</td><td>O</td><td>O</td><td></td><td>O</td><td>THERE</td><td></td><td>1 — I</td>

<td>Ρ Ρ B</td><td>OO CD B</td><td>Ρ</td><td>ζ</td><td></td><td></td><td>&lt;r</td><td>QC</td><td>CN</td><td>CN</td><td>&lt;r</td><td></td><td>&lt;r</td><td>ι — 1</td><td></td><td>QC</td>

<td>The 4J CD</td><td>TO 03 C '</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>1 co co</td><td>O </td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>CD * rl</td><td>P</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>ΒΌ CO</td><td>4-J</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>O 'CD CQ</td><td>CD</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td>rl B CQ</td><td>Ή S</td><td></td><td>THERE</td><td></td><td>Ό</td><td>CN</td><td>ι — 1</td><td>CJh</td><td>CO</td><td>r *</td><td></td><td>THERE</td><td>QC</td><td></td><td>oo</td>

<td>3 co</td><td>φ Ό</td><td></td><td>ο</td><td></td><td>ι — 4</td><td>σ '</td><td>O</td><td>CN</td><td>CN</td><td>QC</td><td></td><td>M0</td><td>O</td><td></td><td>OO</td>

<td rowspan="2">C co B CO * rl PPBO 4J (D</td><td rowspan="2">3 P co O Ρ Ή 60 ε</td><td></td><td>&lt;r</td><td></td><td>CN</td><td>THERE</td><td>THERE</td><td>QC</td><td>QC</td><td>THERE</td><td></td><td>&lt;r</td><td>QC</td><td></td><td>QC</td>

<td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td>

<td></td><td></td><td></td><td></td><td></td><td>γ— (</td><td>CM</td><td>m</td><td>&lt;r</td><td>THERE</td><td>M3</td><td></td><td></td><td></td><td></td><td></td>

<td></td><td></td><td></td><td>ο</td><td>ASS</td><td>ο</td><td>O</td><td>O</td><td>O</td><td>O</td><td>O</td><td>O</td><td>ro |</td><td>O</td><td>O</td><td>ral</td>

<td></td><td></td><td></td><td>ι — 1</td><td>kl 1—1</td><td>ρΗ</td><td>iH</td><td>r-4</td><td>ι-1</td><td>1 — f</td><td>r — 1</td><td> »—4</td><td>P CM</td><td>r— |</td><td>f — l</td><td>P CO</td>

<td></td><td></td><td></td><td>(X</td><td>Λ</td><td>(X</td><td>cx</td><td>(X</td><td>IX</td><td>(X</td><td>(X</td><td>(X</td><td>ro</td><td>(X</td><td>cx</td><td>ro</td>

<td></td><td></td><td></td><td>ε</td><td>cx Ο</td><td>ε</td><td>s</td><td>B</td><td>B</td><td>s</td><td>s</td><td>B</td><td>(X o</td><td>S |</td><td> 6</td><td>CD o</td>

<td></td><td></td><td></td><td>CD</td><td>Β&gt;</td><td>CD</td><td>ID</td><td>CD</td><td>CD</td><td>CD</td><td>(D</td><td>CD</td><td>B&gt;</td><td>CD</td><td>ID</td><td>B&gt;</td>

<td></td><td></td><td></td><td>X</td><td>Ο · Η</td><td>X</td><td>X</td><td>X</td><td>X</td><td>X</td><td>X</td><td>X</td><td>O-tl</td><td>X</td><td>X</td><td>O -rl</td>

<td></td><td></td><td></td><td>CD</td><td>J 4J</td><td>CD</td><td>CD</td><td>CD</td><td>CD</td><td>CD</td><td>CD</td><td>CD</td><td>C-0 4-1</td><td>CD</td><td>CD</td><td>C 3 d</td>

O 1 O. , /. ', - ··· ·. · V

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<img file="PT97236B_D0111.tif" />

Table 1 shows that the polymeric compositions of the present invention have mass average particle size at least about 25% greater than the mass average particle size of the precursor particles used to form such polymeric compositions. Particle size variations of this value and sense are indicative of the formation of large numbers of aggregates and aggregates having a large number of component precursor particles. In addition, Table 1 shows that the aggregates formed in Examples 1 to 7 are stable in the presence of fluid, indicating the presence of large number of particle cross-linking bonds of the aggregates. Table 1 also shows that the polymeric compositions of the present invention, exemplified by Examples 1 to 7, have higher compressive strength (i.e., higher gel expansion pressure) and higher swelling rates than the corresponding precursor particles. .

Table 1 also shows that Comparative Examples 2 and 3 give smaller particle size variations relative to their precursors than Examples 1 to 7, indicating the creation of fewer aggregates. In addition, the aggregates of Comparative Example 3, a sample agglomerated with water, demonstrate the overall tendency for fluid instability, meaning that the actual particle size variation due to any interparticle cross-linking is significantly less than the 24% variation. , 8% shown in Table 1. Table 1 also shows that the swelling rates of Comparative Examples 2 and 3 are lower than those of the polymeric compositions of the present invention.

The above properties refer to the behavior of the polymeric compositions in absorbent products, so that the polymeric compositions according to the present invention should provide better behavior with respect to the corresponding precursor particles and / or the comparative examples described above when used. in absorbent products, such as absorbent parts or articles. · '• · Ίβίί' · ιίί (, ·. *. '4-. «►? -'« tóefe! Í, · '? -' 'Sje -; *^í? «ÍíÈÍs5Sjp&gt; í^í®S '·.,. , '··.' · .._ · ••• χ * ·, ». · .Ί .- -J f .f y63.387

Case: 4124 X

<img file="PT97236B_D0112.tif" />

absorbent diapers.

While particularly described and illustrated, embodiments of the present invention are apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention. It is therefore intended to cover, in the appended claims, all such changes and modifications that fall within the scope of the present invention.