Porous, absorbent macrostructures of bonded absorbent particles surface crosslinked with cationic amino-epichlorohydrin adducts

Porous and absorbent macroscopic structure on the surface of bonded absorbent particles cross-linked with cationic amine-epichlorohydrin adducts

This patent application relates to a porous, absorbent macrostructure. When it comes in contact with liquids such as water or body exudates (such as urine), it will swell and absorb this liquid, and it can be used on absorbent articles, such as Diapers, adult incontinence pads, sanitary napkins, etc. This patent application particularly relates to the porous macrostructure of the combined absorbent particles, the particles being the surface cross-linked with cationic, preferably polymerizable, amine-epichlorohydrin adducts.

The particulate absorbent polymer composition can absorb a large amount of liquid, such as water and body exudates (such as urine), and can further maintain the absorbed liquid under a moderate pressure. The absorbent properties of this polymer composition make it particularly useful for incorporation into absorbent articles, such as diapers. See, for example, U.S. Patent 3,699,103 (Harper et al.), issued on June 13, 1972, and U.S. Patent 3,770,731 (Harmon), issued on June 20, 1972, which disclose the use of particulate, Absorbent, polymer composition (usually called "hydrogel", "superabsorbent", or "hydrocolloid material").

However, conventional particulate, absorbent, and polymer compositions have the limitation that the particles are not fixed and migrate freely during handling and/or use. The migration of this particle can lead to loss of material handling during manufacturing, and the uneven incorporation of this particle into the structure using the particle. When these particulate matter migrate, more serious problems will occur during use or after expansion. This mobility will result in high resistance to liquids flowing through the material due to the lack of stable inter-particle capillary action or liquid transport channels. This phenomenon is a form commonly referred to as "gel blocking effect".

In order to overcome the performance limitations associated with the mobility of absorbent particles during use in absorbent articles, one of the attempts is to infiltrate particulate, absorbent, and polymer compositions into the tissue layer, which means layered absorption. Sexual structure. By covering the particles between the tissue layers, the mobility of the overall particles in the absorbent structure will be reduced. However, when in contact with a liquid, the particles in the laminate often move freely relative to each other, causing any pre-existing capillary channels between the particles to collapse.

Another attempted solution is to fix the particulate, absorbent, polymer composition by adding a large amount of liquid polyhydroxy compound, which acts as an adhesive to fix the particles together or to the base. Material. See, for example, U.S. Patent 4,410,571 (Korpman) issued on October 18, 1983. Although this research approach does limit migration before and to every degree during the expansion of the particles, in the presence of excess liquid, the particles will eventually become separated from each other, again causing any pre-existing particles between the particles. The capillary channel collapsed.

Another attempted solution to overcome the mobility problem of absorbent particles is to extrude a linear absorbent polymer solution and then crosslink it to produce a super absorbent film. See, for example, U.S. Patent 4,861,539 (Allen et al.) issued on August 29, 1989 (cross-linked with a polyhydroxy compound such as glycol or glycerin); and U.S. Patent 4,076,673 issued on February 28, 1978 (Burkholder) (with polyamine-polyamide epichlorohydrin adduct (e.g. Kymene^®) Cross-linking). Although these superabsorbent films can absorb a large amount of liquid, they have limited liquid transport properties because they are basically non-porous, meaning that they lack internal capillary channels. In fact, due to the lack of internal capillary channels, such superabsorbent films are particularly prone to gel blocking.

In order to overcome the mobility problem of absorbent particles, a relatively recent solution proposed is to make these particles form an aggregated macroscopic structure, which is typically a thin sheet of combined absorbent particles. See U.S. Patent 5,102,597 (Roe et al.) issued on April 7, 1992. These aggregate macrostructures are made in the following manner. First, the absorbent particles are mixed with a solution consisting of a non-ionic crosslinking agent, water and a hydrophilic organic solvent (such as isopropanol). These nonionic crosslinking agents include polyhydric alcohols (such as glycerin), polyaziridine compounds (such as 2,2-bishydroxymethylbutanol-tris[3-(1-aziridine) propionate) ]), halogenated epoxy compounds (e.g., epichlorohydrin), polyaldehyde compounds (e.g., glutaraldehyde), polyamine compounds (e.g., ethylene diamine), and polyisocyanate compounds (e.g., 2,4-toluene diamine) Isocyanate), preferably glycerin. See column 11, lines 22-54 of the Roe et al. patent.

The type of particulate absorbent polymer composition used to make these aggregated macrostructures usually contains multiple carboxyl groups, and is typically derived from polycarboxyl compounds, such as polyacrylates. When glycerol is used as a crosslinking agent, the hydroxyl groups of the glycerol typically react with the carboxyl groups of the polymer present in the absorbent particles through an esterification reaction. The cross-linked ester bond formed by glycerin not only occurs on the surface of the absorbent particles, but also occurs inside the particles. This is due to the fact that glycerol is a non-ionic, relatively small molecule that can penetrate the interior of absorbent particles. The resulting internal cross-linking will result in a lower absorptive capacity of the aggregated macrostructure of the bound particles.

Furthermore, the cross-linking reaction between the hydroxyl group of glycerin and the carboxyl group of the polymer present in the absorbent particles is relatively slow. In fact, glycerin-treated absorbent particles are typically heated at 200°C for 50 minutes. This results in a relatively brittle flake of bonded absorbent particles, which is more difficult to handle, especially in the manufacture of the final desired absorbent structure. Therefore, these flakes must be treated with a plasticizer, such as a mixture of water and glycerin, to make them relatively soft and therefore easier to handle in the manufacture of absorbent structures.

Therefore, it is generally desirable to be able to use a crosslinking agent when manufacturing such aggregated macrostructures of bonded absorbent particles. (1) It will rapidly react with the carboxyl groups of the polymer present in the absorbent particles, and mainly on the surface, so as to minimize the effect of absorption; (2) Provide improved aggregate macrostructures The absorbent and mechanical (tension) properties; (3) The flexible sheet with the macroscopic structure is provided so that it can be easily made into an absorbent structure and used in diapers, adult incontinence pads, sanitary napkins and other On the analog; and (4) no organic solvent, such as isopropanol, is required.

The present invention relates to improved porosity, absorptivity, and macrostructures, which include aggregates bound between particles. These aggregates include multiple precursor absorbent particles bound to each other on their surfaces. The particles include a substantially water-insoluble polymer material with anionic functional groups that can form absorbent hydrogels. These aggregates further include a cationic (preferably polymeric) amino-epichlorohydrin adduct that reacts with the absorbent polymer material on the surface of the precursor particles, and the amount is sufficient to achieve surface cross-linking effect. These aggregates also have pores between adjacent precursor particles. These pores are connected to each other by interconnecting channels, so as to form a liquid-permeable macrostructure. The surrounding dry volume of the macrostructure is It is larger than about 0.008 mm cubic.

The present invention further provides a method for manufacturing such a porous absorbent macrostructure by providing multiple precursor absorbent particles, and then using a sufficient amount of cationic (preferably polymeric) amine-epichloride Treat it with alcohol adducts. Then, the treated precursor particles are physically associated to form aggregates, and the adduct is allowed to react with the absorbent polymer material of the precursor particles to cause effective surface cross-linking. The obtained porous, absorbent macrostructure, used alone or in combination with other absorbent materials, can be used in absorbent structures for various absorbent articles, including diapers, adult incontinence pads, and sanitary napkins And its analogues.

The porous absorptive macrostructure of the present invention, and its preparation method, provide many important advantages over the previous porous absorptive macrostructure made by using a nonionic crosslinking agent (especially glycerin). The use of cationic (preferably polymeric) amine-epichlorohydrin adducts as the crosslinking agent according to the present invention will improve the maturation rate and enhance this by reducing or eliminating intra-particle crosslinking Absorbability of particles. This is due to the fact that these adducts, especially polymer resin variants, are relatively large cationic molecules that cannot penetrate the interior of the absorbent particles. In addition, it is believed that the cationic functional groups of these adducts (such as tertiary methylimine salts) will react extremely quickly with the anionic (typically carboxyl) functional groups of the polymer material constituting the absorbent particles. , Even at ambient room temperature, for example at 18-25°C. As a result, compared with typically 4% by weight of glycerin as a cross-linking agent, only a lower content of cross-linking agent is required, for example as low as 1% of the weight of the absorbent particles.

The use of these cationic (preferably polymeric) amine-epichlorohydrin adducts will provide other significant advantages over the porous absorbent macrostructure made by using glycerin as a crosslinking agent. The porous absorbent macrostructure of the present invention has improved absorption capacity and mechanical (tension) properties. Unlike the absorbent macrostructure cross-linked with glycerol, the flexible absorbent macrostructure (such as a sheet) according to the present invention can be made by a basically one-step method, without the need for plasticizers for subsequent steps. Treatment (for example, adding a mixture of water and glycerin). In addition, when manufacturing the absorbent macrostructure according to the present invention, organic solvents such as isopropanol are not required.

Figure 1 is a photomicrograph of a cross-section of the porous and absorbent macrostructure according to the present invention (34.9 times magnification).

Fig. 2 is an enlarged part of the macro structure shown in Fig. 1 (magnification 75 times).

Fig. 3 is a further enlarged part of the macro structure shown in Fig. 2 (magnification 200 times).

Fig. 4 is a further enlarged part of the macro structure shown in Fig. 3 (magnification 400 times).

Figure 5 is a perspective view of a specific embodiment of a disposable diaper according to the present invention, in which a part of the top sheet has been cut off to more clearly show the absorbent core layer underneath the diaper (absorbent element according to the present invention) The specific embodiment), wherein the absorbent element includes a porous, absorbent macrostructure according to the present invention; Figure 6 is the diaper shown in Figure 5, taken along the line 6-6 of Figure 5 7 is a perspective view of a specific embodiment of a disposable diaper according to the present invention, in which a part of the top sheet has been cut off to show an alternative double-layer absorbency more clearly Specific embodiment of the core layer. Figure 8 is a blow-up view of the various components of a diaper structure. One of the components is an alternative double-layer absorbent core, in which the absorbent structure is in the form of multiple sheets. Figure 9 is a simplified perspective view of a device for manufacturing the absorbent macrostructure of the present invention in the form of a sheet.

Detailed description of the invention

A.

Porous absorptive macrostructure

The porous, absorbent macrostructure according to the present invention is a structure capable of absorbing a large amount of liquid, such as water and/or body exudate (such as urine or menstrual fluid), and then holding this liquid under moderate pressure. Due to the microparticle nature of the precursor particles, this structure has pores between adjacent precursor particles. These pores are connected to each other by interconnecting channels, so that the macrostructure is liquid-permeable (that is, it has capillary transport channels).

Due to the bonds formed between the precursor particles, the resulting aggregate macrostructure has improved structural integrity, increased liquid availability and distribution rate, and minimal gel blocking properties. It has been found that when the macrostructure is in contact with liquid, the macrostructure usually expands in an isotropic manner, even under a moderately confined pressure. The liquid is absorbed into the pores between the precursor particles, and then the macrostructure will expand in an isotropic manner. These liquids are sucked into the particles. The isotropic expansion of this macrostructure allows the precursor particles and their pores to maintain their relative geometrical shape and spatial relationship, even when expanded. Therefore, this macroscopic structure has considerable "fluid stability". The reason is that the precursor particles will not dissociate from each other, so that the gel blocking effect is minimized, and the capillary channel can be maintained and expanded Amplify so that this macroscopic structure can capture and transport the subsequently loaded liquid, even if there is excess liquid.

The term "macro structure" as used herein means a structure that has a surrounding volume when substantially dry (meaning the surrounding dry volume) of at least about 0.008 mm cubic, preferably at least about 10.0 mm Cubic, more preferably at least about 100 millimeters cubic, most preferably at least about 500 millimeters cubic. Typically, the macrostructure of the present invention has a surrounding dry volume that is greater than about 500 mm cubic. In a preferred embodiment of the present invention, the macro structure has a surrounding dry volume between about 1000 mm cube and about 100,000 mm cube.

Although the macrostructure of the present invention can have many shapes and sizes, it is typically in the form of sheets, films, cylinders, agglomerates, spheres, fibers, monofilaments, or other shaped elements. This macro structure usually has a thickness or diameter between about 0.2 mm and about 10.0 mm. When this macro structure is used in absorbent products, it is preferably in the form of a sheet. As used herein, the term "sheet" describes a macro structure having a thickness of at least about 0.2 mm. The sheet preferably has a thickness between about 0.5 mm and about 10 mm, typically about 1 mm to about 3 mm.

As shown in Figures 1 to 4, the porous and absorbent macrostructure of the present invention includes aggregates bound between particles. The aggregates of these inter-particle associations usually contain about 8 or more previously independent precursor particles. For the preferred surrounding dry volume and size of the individual precursor particles used herein, the aggregates of these inter-particle associations are typically formed by about 100,000 or more individual precursor particles. These individual precursor particles may include particles, powders, spheres, flakes, fibers, aggregates or clumps.

As can be particularly seen in Figures 1 and 2, the individual precursor particles can have a variety of shapes, such as cubes, rods, polyhedrons, spheres, circles, angles, irregular shapes, irregular shapes of any size For example, the powdery product of the grinding or pulverization step, or the shape with a large maximum size/minimum size ratio, so that it is needle-like, flake-like or fibrous.

As particularly shown in Figs. 3 and 4, the aggregates of the bonds between the particles constituting the macrostructure of the present invention are basically formed by connecting or bonding adjacent particles together. The adhesive is basically a polymer substance present on the surface of these particles. When these precursor particles are processed and physically associated as described later, the polymer material present on the surface of these particles has sufficient plasticity and cohesion (such as viscosity) so that adjacent particles Will stick together, typically becoming a discontinuous link between particles. Therefore, the cross-linking reaction between the amino-epichlorohydrin adduct and the polymer substance of the particle will establish such a bonded structure, so that the particles in the aggregate are still bound together in a cohesive manner.

B.

Absorbable precursor particles

The macrostructure of the present invention is formed from a polymer material capable of absorbing a large amount of liquid (this polymer material is often called a "hydrogel", a "hydrocolloid material", or a "superabsorbent" material). The macrostructure preferably includes substantially water-insoluble polymer materials that can form absorbent hydrogels. This special polymer material will be discussed in this article for the material that forms the precursor particles.

Although the precursor particles can have a wide range of sizes, the specific particle size distribution and size are preferred. For the purpose of the present invention, the particle size defined by the precursor particles does not have a large maximum size/minimum size ratio. Like fibers (such as particles, flakes or powder), the size of the precursor particles is analyzed by screen size Measured. Therefore, for example, the precursor particles retained on the standard #30 sieve with 600 micron openings are considered to have a particle size greater than 600 micrometers, passing through the #30 sieve with 600 micron openings, and retained in the #30 sieve with 600 micron openings. The precursor particles on the standard #35 screen with micron openings are recognized as having a particle size between 500 and 600 microns, and the precursor particles passing through the #35 screen with 500 micron openings are recognized as having The particle size is less than 500 microns. In a preferred embodiment of the present invention, the size of the precursor particles generally ranges from about 1 micrometer to about 2000 micrometers, more preferably from about 20 micrometers to about 1000 micrometers.

Furthermore, for the purpose of the present invention, the mass average particle size of the precursor particles is very important in determining the characteristics and properties of the macrostructure formed. The mass average particle size of a given particle sample is defined as its particle size, which is the average particle size of the sample on a mass basis. A method for determining the mass average particle size of a sample is described in the test method section below. The mass average particle size of the precursor particles is usually about 20 microns to about 1500 microns, more preferably about 50 microns to about 1000 microns. In a preferred embodiment of the present invention, the mass average particle size of the precursor particles is less than about 1000 microns, more preferably less than about 600 microns, and most preferably less than about 500 microns. In a particularly preferred embodiment of the present invention, the mass average particle size of the precursor particles is relatively small (that is, the precursor particles are finer). In these embodiments, the mass average particle size of the precursor particles is less than about 300 microns, and more preferably less than about 180 microns. In an illustrative embodiment, at least about 95% by weight of the precursor particles have a particle size between about 150 microns and about 300 microns. In an alternative embodiment, at least about 95% by weight of the precursor particles have a particle size between about 90 microns and about 180 microns. Narrow precursor particle size distribution is better because it will result in a higher porous macrostructure. This is because for a wider precursor particle size distribution with the same mass and average particle size, there is Higher gap part.

The particle size of a substance with a large maximum size/minimum size is typically defined by its maximum size. For example, if absorbent and polymeric fibers (meaning superabsorbent fibers) are used in the macrostructure of the present invention, the length of this fiber is used to define its "particle size" (it can also specify the single and / Or diameter). In the illustrated embodiment of the present invention, the fiber has a length greater than about 5 mm, preferably between about 10 mm and about 100 mm, and more preferably between about 10 mm and about 50 mm.

The precursor particles include substantially water-insoluble polymer materials that can form absorbent hydrogels, which have multiple anionic functional groups, such as sulfonic acid groups, and more typically carboxyl groups. Examples of polymer substances suitable for use as precursor particles herein include those made from polymerizable, unsaturated, acid-containing monomers. Therefore, such monomers include olefinic unsaturated acids and anhydrides containing at least one carbon-to-carbon olefin double bond. In more detail, these monomers can be selected from olefin-based unsaturated carboxylic acids and acid anhydrides, olefin-based unsaturated sulfonic acids, and mixtures thereof.

In the preparation of the precursor particles herein, some non-acid monomers may also be included, usually a small amount. Such non-acid monomers may include, for example, water-soluble or water-dispersible esters of the acid-containing monomers, and monomers that do not contain carboxylic acid groups or sulfonic acid groups. The selected non-acid monomers can therefore include monomers containing the following types of functional groups: carboxylic acid or sulfonate, hydroxyl, amide, amine, cyano and quaternary ammonium salt groups. These non-acid monomers are known substances and are described in more detail in, for example, U.S. Patent 4,076,663 (Masuda et al.) issued on February 28, 1978, and U.S. Patent 4,062,817 issued on December 13, 1977 ( In Westerman), both patents are incorporated herein for reference.

Olefin-based unsaturated carboxylic acid and carboxylic anhydride monomers, including acrylic Acid), α-phenyl acrylic acid, β-acryloyloxypropionic acid, hexadienoic acid, α-chlorohexadienoic acid, angelic acid, cinnamic acid, p-chlorocinnamic acid, β-stearyl acrylic acid, decomposing aconitic acid, methyl Maleic acid, methyl fumaric acid, glutaconic acid, aconitic acid, maleic acid, fumaric acid, tricarboxyethylene and maleic anhydride.

Olefinic unsaturated sulfonic acid monomers, including aliphatic or aromatic vinyl sulfonic acids, such as vinyl sulfonic acid, allyl sulfonic acid, vinyl toluene sulfonic acid and styrene sulfonic acid; acrylic and methacrylic Sulfonic acid, such as sulfonate ethyl acrylate, sulfonate ethyl methacrylate, sulfonate propyl acrylate, sulfonate propyl methacrylate, 2-hydroxy-3-methacryloyloxypropyl Sulfonic acid and 2-propenamide-2-methylpropane sulfonic acid.

The preferred polymer materials for use in the present invention contain carboxyl groups. These polymers include hydrolyzed starch-acrylonitrile graft copolymer, partially neutralized starch-acrylonitrile graft copolymer, starch-acrylic acid graft copolymer, partially neutralized starch-acrylic acid graft copolymer Compounds, saponified vinyl acetate-acrylate copolymers, hydrolyzed acrylonitrile or acrylamide copolymers, lightly networked crosslinked polymers of any of the foregoing copolymers, partially neutralized polyacrylic acid, and partially Slightly reticulated crosslinked polymer of neutralized polyacrylic acid. These polymers can be used alone or in the form of a mixture of two or more different polymers. Examples of these polymeric substances are disclosed in U.S. Patent 3,661,875, U.S. Patent 4,076,663, U.S. Patent 4,093,776, U.S. Patent 4,666,983, and U.S. Patent 4,734,478.

The best polymer material for the production of precursor particles is the slightly reticulated cross-linked polymer of partially neutralized polyacrylic acid and its starch derivatives. In the best case, the precursor particles comprise about 50 to about 95%, preferably about 75%, neutralized and slightly reticulated cross-linked polyacrylic acid (meaning, poly(sodium acrylate/acrylic acid)).

As mentioned above, the precursor particles are preferably made from a polymer material that has been slightly cross-linked in the form of a network. The network cross-linking effect is used to make the polymer material of the precursor particles substantially water-insoluble, and, in part, determine the characteristics of the absorption capacity of the precursor particles and the extractable polymer content. And the macro structure formed. The method for performing network crosslinking between this polymer and a typical network crosslinking agent is described in more detail in the aforementioned US Patent 4,076,663.

The individual precursor particles can be made in any conventional way. A representative and preferred method for producing individual precursor particles is described in U.S. Patent Re. 32,649 (Brandt et al.) issued on April 19, 1988, and U.S. Patent 4,666,983 issued on May 19, 1987 ( Tsubakimoto et al.), and US Patent 4,625,001 (Tsubakimoto et al.) issued on November 25, 1986, all of which are incorporated herein by reference.

The preferred method for forming this precursor particle is a method involving aqueous solution or other solution polymerization. As described in the above-referenced US Patent Re. 32,649, aqueous solution polymerization involves the use of an aqueous reaction mixture to carry out the polymerization reaction to form the precursor particles. The aqueous reaction mixture is then subjected to polymerization conditions sufficient to produce a substantially water-insoluble, slightly network-crosslinked polymer material in the mixture. Then the agglomerates of this polymer material are crushed or shredded to form individual precursor particles.

In more detail, the aqueous polymerization method used to produce the individual precursor particles includes preparing an aqueous reaction mixture and performing polymerization reaction therein to form the desired precursor particles. One component of this reaction mixture is a monomeric substance containing acid groups, which will form the "skeleton" of the precursor particles to be produced. The reaction mixture usually contains about 100 parts by weight of monomer material. Another component of the aqueous reaction mixture includes a network crosslinking agent. The network cross-linking agent that can be used to form the precursor particles is described in more detail in the above-referenced U.S. Patent Re. 32,649, U.S. Patent 4,666,983, and U.S. Patent 4,625,001. This network crosslinking agent is usually present in the aqueous reaction mixture in an amount of about 0.001 mol% to about 5 mol%, based on the total number of moles of monomers present in the aqueous mixture (based on 100 The parts by weight of the monomers are based on the amount of about 0.01 to about 20 parts by weight). An optional component of the aqueous reaction mixture includes a free radical initiator, which includes, for example, peroxy compounds such as sodium, potassium, and ammonium peroxy, octyl peroxide, benzyl peroxide, hydrogen peroxide, hydrogen Cumene peroxide, t-butyl diperoxyphthalate, t-butyl peroxybenzoate, sodium peracetate, sodium percarbonate, and the like. Other optional components of this aqueous reaction mixture include various non-acidic comonomers, including esters of monomers containing substantially unsaturated acidic functional groups, or other comonomers that do not contain carboxylic acid or sulfonic acid functional groups. .

The aqueous reaction mixture is subjected to polymerization conditions, which are sufficient to produce a substantially water-insoluble, absorbent, and slightly network-like cross-linked polymer material capable of forming a hydrogel in the mixture. This polymerization reaction conditions are also discussed in more detail in the three patents referred to above. These polymerization reaction conditions generally involve heating (thermal activation technique) to the polymerization temperature, from about 0°C to about 100°C, more preferably from about 5°C to about 40°C. The polymerization reaction conditions (the aqueous reaction mixture is maintained under these conditions) can also include, for example, subjecting the reaction mixture or a part thereof to any conventional form of polymerization activation irradiation. Radioactive, electronic, ultraviolet, or electromagnetic radiation are alternative conventional polymerization techniques.

The acid functional groups of the polymeric material formed in the aqueous reaction mixture are preferably also neutralized. Neutralization can be carried out in any conventional manner, which will result in at least about 25 mol%, and preferably at least about 50 mol%, of all monomers used to form the polymer material and which are acid group-containing monomers. , Neutralize with a cation that can form a salt. Such salt-forming cations include, for example, alkali metals, ammonium, substituted ammonium, and amines, as discussed in more detail in U.S. Patent Re. 32,649, which is incorporated by reference above.

Although the precursor particles are preferably produced using an aqueous solution polymerization process, they can also be processed using heterogeneous polymerization processing techniques, such as inverse emulsion polymerization or inverse suspension polymerization. In the inverse emulsion polymerization or inverse suspension polymerization process, the aqueous reaction mixture as described above is suspended in a matrix of an inert organic solvent immiscible with water (such as cyclohexane) in the form of tiny droplets. The formed precursor particles are usually spherical. The inverse suspension polymerization process is described in more detail in U.S. Patent 4,340,706 (Obaysashi et al.) issued on July 20, 1982, U.S. Patent 4,506,052 (Flesher et al.) issued on March 19, 1985, and April 5, 1988 The issued US Patent No. 4,735,987 (Morita et al.) is incorporated herein by reference in its entirety.

In a preferred embodiment of the present invention, the precursor particles used to form the aggregates of bound particles are substantially dry. As used herein, the term "substantially dry" means the liquid content of the precursor particles, typically water or other solution content, less than about 50%, preferably less than about 20%, more Preferably, it is less than about 10%, based on the weight of the precursor particles. Generally speaking, the liquid content of the precursor particles is in the range of about 0.01% to about 5% based on the weight of the precursor particles. The individual precursor particles can be dried by any conventional method, such as by heating. Alternatively, when the precursor particles are formed using an aqueous reaction mixture, azeotropic distillation can be used to remove water from the reaction mixture. It is also possible to treat the polymer-containing aqueous reaction mixture with a dehydrating solvent (such as methanol). A combination of these drying procedures can also be used. The dehydrated mass of the polymer material can then be chopped or pulverized to form a substantially dried precursor particle of the polymer material that is substantially water-insoluble, absorbent, and gelable.

The preferred precursor particles of the present invention are those that exhibit high absorptive capacity, so that the final macrostructure formed from such precursor particles also has high absorptive capacity. Absorptive capacity refers to the ability of a given polymer substance to absorb the liquid in contact with it. Absorption capacity can vary significantly with the nature of the liquid being absorbed and the way the liquid comes into contact with the polymeric substance. For the purpose of the present invention, the absorptive capacity is defined in terms of the amount of synthetic urine (as defined below) absorbed by any given polymer substance, in the procedure defined in the test method section below , Expressed in grams of synthetic urine per gram of polymer substance. The preferred precursor particles of the present invention have an absorption capacity of at least about 20 grams, more preferably at least about 25 grams of synthetic urine per gram of polymer material. Typically, the polymer material of the precursor particles herein has an absorption capacity of about 20 to about 70 grams of synthetic urine per gram of polymer material. The precursor particles with such relatively high absorptive properties will produce macrostructures that are particularly useful in absorbent products, absorbent elements and absorbent articles, because the final macrostructure made from such precursor particles , By definition, can fix a desired high amount of body exudate (such as urine) that is excreted.

Although all precursor particles are preferably made from the same polymeric material with the same properties, it does not have to be the case. For example, a portion of the precursor particles may include a starch-acrylic acid graft copolymer, while other precursor particles may include a slightly network cross-linked polymer partially neutralized with polyacrylic acid. Furthermore, the precursor particles can change size, shape, absorption capacity, or any other properties or characteristics. In a preferred embodiment of the present invention, the precursor particles are basically composed of a slightly reticulated cross-linked polymer that partially neutralizes polyacrylic acid, and each precursor particle has similar properties.

C.

Cationic amino-epichlorohydrin adduct

One of the important components of the polymer that forms the interparticle bonding of the porous macrostructure of the present invention is the adduct of epichlorohydrin and a certain type of monomeric amine or polymeric amine. These amine-epichlorohydrin adducts will react with the polymeric substances of the absorbent precursor particles, and especially the anionic (typically carboxylic acid) functional groups of these polymeric substances, and Form a covalent ester type bond. In other words, the amino-epichlorohydrin adduct is used to cross-link the polymer material present in the absorbent precursor particles. (The part of absorbent particles containing polymer substances that have been effectively cross-linked with the amino-epichlorohydrin adduct will swell in the presence of aqueous body fluids relative to other non-cross-linked parts of this particle Less).

It is believed that these reacted amine-epichlorohydrin adducts mainly provide cross-linking on the surface of the absorbent precursor particles. This is due to the fact that these adducts, and especially the polymer resin variants of these adducts, are relatively large cationic molecules. Therefore, it cannot penetrate the interior of the absorbent particles, and therefore can only react with the polymer substance on its surface. In addition, it is believed that these adducts (especially polymer resin variants) will react very quickly with the anionic (typically carboxyl) functional groups of the polymer material of the absorbent particles, even at room temperature ( For example, at about 18°C to about 25°C). Therefore, a fairly moderate content (for example, as low as about 1% based on the weight of the particles) of these amino-epichlorohydrin adducts is required to provide an effective surface for the polymeric substances present in the absorbent precursor particles. Cross-linking.

As used herein, "cationic amine-epichlorohydrin adduct" refers to the reaction product between epichlorohydrin and a monomeric or polymeric amine, so that the resulting reaction product has at least two Kind of cationic functional group. These adducts may be in the form of monomeric compounds (for example, the reaction product of epichlorohydrin and ethylenediamine), or may be in polymeric form (for example, epichlorohydrin and polyamide-polyamine or polyamine). The reaction product between ethyleneimine). The polymer variants of these cationic amino-epichlorohydrin adducts are typically called "resins".

An amine-based compound type that can react with epichlorohydrin to form the adduct used in the present invention, which includes monomeric di-, tri-, and higher amines with primary or secondary amine groups in its structure kind. Examples of diamines of this type that can be used include bis-2-aminoethyl ether, N,N-dimethylethylenediamine, hexahydropyridine<img file="TW366287B_D0001.tif" />, And ethylenediamine. Examples of useful triamines of this type include N-aminoethylhexahydropyridine<img file="TW366287B_D0002.tif" />, And secondary alkyl triamines, such as diethylene triamine, and dipropylene triamine.

This amine substance reacts with epichlorohydrin to form a cationic amine-epichlorohydrin adduct which can be used as a crosslinking agent herein. For the preparation of these adducts and a more complete description of the adducts themselves, please refer to U.S. Patent 4,310,593 (Gross) issued on January 12, 1982, and Ross et al.,<u style="single">J. Organic</u><u style="single">Chemistry</u>, Volume 29, Pages 824-826 (1964). Both documents are incorporated in this article for reference.

In addition to monomeric amines, polymerizable amines such as polyethyleneimine can also be used as this amine-based compound. A particularly desirable amine-based compound that can react with epichlorohydrin to form a preferred cationic polymerizable addition resin that can be used herein, including those derived from polyalkylene polyamines and saturated C₃-C₁₀Certain polyamide-polyamines of dibasic carboxylic acid. Such epichlorohydrin/polyamide-polyamine adducts are water-soluble, thermosetting cationic polymers, which are users of wet-strength resins known in the art as paper products.

In the preparation of polyamide-polyamine used to form this kind of preferred cationic polymerizable resin, a dicarboxylic acid and a polyalkylene polyamine are first reacted, preferably in an aqueous solution, and then Under the above conditions, so as to produce a repetitive group -NH(C_nH_2nNH)_x-CORCO- water-soluble long-chain polyamide, wherein n and x are each 2 or greater, and R is the C of the dicarboxylic acid₁To C₈Alkylene.

A variety of polyalkylene polyamines, including polyethylene polyamines, polypropylene polyamines, polybutylene polyamines, etc., can be used to prepare the polyamide-polyamines, among which polyethylene polyamines represent an economically better type . In more detail, the preferred polyalkylene polyamine used to prepare the cationic polymer resin herein is a polyamine containing two primary amine groups and at least one secondary amine group, wherein the nitrogen atom is represented by the formula -C_nH_2n-Groups are connected together, where n is an integer smaller than one large, and the number of such groups in the molecule ranges from two to up to about eight, and preferably up to about four. Its nitrogen atom can be connected to -C_nH_2n-Adjacent carbon atoms in a group, or connected to a more separate carbon atom, but not connected to the same carbon atom. It is also intended to be covered by the use of such polyamines, such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, dipropylenetriamine, etc., which can be obtained in a reasonably pure form. Among all the foregoing, the best is a polyethylene polyamine containing two to four ethylene groups, two primary amine groups, and one to three secondary amine groups.

For the users of this document, what is also intended to be covered is a polyamine precursor material containing at least three amine groups, and at least one of these groups is a tertiary amine group. Suitable polyamines of this type include methylbis(3-aminopropyl)amine, methylbis(2-aminoethyl)amine, N-(2-aminoethyl)hexahydropyridine<img file="TW366287B_D0003.tif" />, 4,7-Dimethyltriethylenetetramine and so on.

It can react with the aforementioned polyamines to form the polyamide-polyamine precursor dicarboxylic acid that can be used in the preferred cationic polymerizable resin herein, including saturated aliphatic C₃-C₁₀Dicarboxylic acid. More preferable ones are those containing 3 to 8 carbon atoms, such as malonic acid, succinic acid, glutaric acid, adipic acid, etc., and oxydiacetic acid. Among them, oxidized diacetic acid and saturated aliphatic dicarboxylic acids having 4 to 6 carbon atoms in the molecule (meaning succinic acid, glutaric acid, and adipic acid) are the best ones. Blends of two or more of these dicarboxylic acids, and blends of one or more of them with high-carbon saturated aliphatic dicarboxylic acids (such as azelaic acid and sebacic acid) can also be used, as long as The long-chain polyamide-polyamine formed may be water-soluble or at least water-dispersible.

The polyamide-polyamine material prepared from the aforementioned polyamine and dicarboxylic acid is reacted with epichlorohydrin to form a cationic polymerizable amino-epichlorohydrin resin which is preferably used herein as a crosslinking agent. The preparation of this substance is described in more detail in U.S. Patent 2,926,116 (Keim) issued on February 23, 1960, U.S. Patent 2,926,116 (Keim) issued on February 23, 1960, and U.S. Patent issued on July 25, 1967 Patent 3,332,901 (Keim), all of which are incorporated herein by reference.

The cationic polyamide-polyamine-epichlorohydrin resin, which is preferably used herein as a crosslinking agent, is produced by Hercules under the trade name Kymene^®Commercially available. Especially useful is Kymene^® 557H, Kymene^® 557LX and Kymene^® 557⁺It is the epichlorohydrin adduct of polyamide-polyamine (which is the reaction product of diethylenetriamine and adipic acid). It is typically sold in the form of an aqueous solution of a cationic resin material containing about 10% to about 33% by weight of the resin active.

D.

Preparation of aggregates and macrostructures combined between particles

In preparing the aggregates of the interparticle bonding that constitute the porous and absorbent macrostructure of the present invention, the absorbent precursor particles are treated with a sufficient amount of cationic amine-epichlorohydrin adducts, so that the particles On the surface, it reacts with the polymer material to cause effective cross-linking, which means that the cross-linked surface of the particle will swell less in the presence of an aqueous liquid compared to its uncross-linked part. The matters that constitute the "sufficient" adduct depend on many factors, including the specific absorbent precursor particles to be processed, the specific amino-epichlorohydrin adduct used, and the formation of interparticle aggregates The specific role expected on the above, and similar factors. In the case of monomeric amino-epichlorohydrin adducts, for example, a hexahydropyridine<img file="TW366287B_D0004.tif" />-Epichlorohydrin adducts, the adducts used, such as methanol and ethanol; amides, such as N,N-dimethylformamide and N,N-diethylformamide; and sulfenites , Such as dimethyl sulfide. If a hydrophilic solvent is used, its amount is less than about 20 parts by weight (meaning 0 to about 20 parts by weight, preferably in the range of about 5 to about 15 parts by weight, and more preferably in the range of about 8 to about 15 parts by weight). Within the range of about 12 parts by weight, based on the weight of 100 parts of precursor particles. The actual amount of hydrophilic solvent can be used to form the polymer material of the precursor particles according to the adduct used. The particle size and similar factors change.

As mentioned above, it is not necessary to use a hydrophilic organic solvent to prepare the bound particle aggregates of the present invention. In fact, it may be desirable to avoid the use of such organic solvents. Typically, the solvent must be removed from the aggregate before it is suitable for its intended use. The removal of organic solvents is often energy and process intensive, and will increase additional processing costs. Some hydrophilic solvents, such as isopropanol or tertiary-butanol, can cause the amino-epichlorohydrin adduct to precipitate out of the solution, so it is not applicable. In fact, typically the only solvent used to prepare the combined particle aggregates of the present invention is lower alcohols, such as methanol and ethanol, which are not too energy-intensive or process-intensive to remove, and will not cause the amine group. -The epichlorohydrin adduct precipitates out as an aqueous solution.

Other optional ingredients can also be used with the cationic amino-epichlorohydrin adduct, and especially its aqueous treatment solution. It is particularly preferable that the treatment solution containing the cationic amino-epichlorohydrin adduct includes a plasticizer, especially when the treated precursor particles are cured at ambient temperature as described below Time is true. When a plasticizer is not used, the processed precursor particles may be relatively brittle when they are made into aggregates of inter-particle bonding. Therefore, the amount is calculated based on the weight of 100 parts of absorbent precursor particles. The range can be about 0.1 to about 3 parts by weight, preferably about 0.5 to about 1.5 parts by weight, and most preferably about 0.8 to about 1.2 parts by weight. In the case of better polymerized amino-epichlorohydrin resins, such as Kymene^® 557H, 557LX or 557⁺, The amount of resin used can be about 0.1 to about 5 parts by weight per 100 parts of absorbent precursor particles, preferably about 0.5 to about 2.5 parts by weight, and most preferably about 1 to about 2 parts by weight. Parts by weight.

In addition to the absorbent precursor particles and the cationic amine-epichlorohydrin adduct, other ingredients or reagents can be used as auxiliary agents for the preparation of the aggregates bound between the particles. For example, water is typically used with such adducts to form its aqueous treatment solution. Water will promote the uniform dispersion of the adduct on the surface of the precursor particles and cause the adduct to penetrate into the surface area of the particles. Water will also promote a stronger physical association between the processed precursor particles and provide greater integrity of the cross-linked aggregates formed between the particles. In the present invention, the amount of water used per 100 parts by weight of precursor particles is less than about 25 parts by weight (meaning 0 to about 25 parts by weight), preferably about 3 to about 15 parts by weight. It is in the range of parts by weight, more preferably in the range of about 5 to about 10 parts by weight. The actual water consumption depends on the type of adduct used, the type of polymer material used to form the precursor particles, the particle size of these precursor particles, the addition of other optional ingredients (such as glycerol), and similar factors. Variety.

Although not absolutely necessary, organic solvents can be used, which are usually used to promote the uniform dispersion of the cationic amino-epichlorohydrin adduct on the surface of the precursor particles. These organic solvents are typically hydrophilic, and may include lower alcohols which are more difficult to handle, especially when manufacturing the final desired absorbent structure. Adding a plasticizer to the treatment solution can ensure that the formed aggregates between the particles (when the ambient temperature is cured), forming a relatively soft porous and absorbent macrostructure, especially the aggregates between the particles Body soft, porous, absorbent sheet. These soft sheets are relatively easy to handle when manufacturing the final desired absorbent structure.

Appropriate plasticizers, including water, used alone or in combination with other ingredients, such as glycerol, propylene glycol (meaning 1,2-malonic acid), 1,3-propanediol, ethylene glycol, sorbus, sucrose, polymer solution , Such as those involving polyvinyl alcohol, ester precursors of polyvinyl alcohol, or polyethylene glycol, or mixtures thereof. These other ingredients, in terms of plasticizers, such as glycerin, are believed to be used as wetting agents, co-plasticizers, or both, with water as the main plasticizer. The preferred plasticizer for use in the present invention is a mixture of glycerin and water, especially when added as part of the aqueous treatment solution of the cationic amino-epichlorohydrin adduct, the glycerin reacts to water The weight ratio is about 0.5:1 to about 2:1, preferably about 0.8:1 to about 1.7:1.

The actual amount of the plasticizer can be changed according to the specific plasticizer used, the type of polymer material used to form the precursor particles, and the specific softness desired from the plasticizer. Typically, the amount of plasticizer is about 5 to about 100 parts by weight, preferably about 5 to about 60 parts by weight, more preferably about 10 to about 30 parts by weight, most preferably about 15 to about 20 parts by weight. Parts by weight are based on the weight of each 100 parts of precursor particles.

In the method of the present invention, the absorbent precursor particles can be treated with a cationic amine-epichlorohydrin adduct, which is typically an aqueous solution, by any of a variety of techniques. It includes any method of applying the solution to the material, including the cationic amino-epichlorohydrin adduct or its solution, coating, pouring, pouring, dripping, spraying, atomizing, condensing or soaking the absorbent The first plasmid. The term "coating" as used herein means that at least part of the surface area of at least some of the precursor particles to be combined has an effective amount of adducts on it to cause surface cross-linking. . In other words, the cationic adduct can be applied this in some precursor particles, the precursor particles of all, some or one of the upper surface portion of the precursor particles all, or to the entire surface of some or all of the particles being superior. Preferably, this adduct is coated on most (preferably all) of the entire surface of the absorbent precursor particles to enhance the efficiency, strength, and strength of the interparticle bonding between the precursor particles. Density, and the expected surface cross-linking of the polymer material on the surface of these precursor particles.

In a specific embodiment of the method of the present invention, after the processing solution has been coated on the precursor particles, the processed precursor particles are mixed or mixed by any of a number of mixing or coating techniques. Coating together to ensure that the precursor particles are fully coated by the treatment solution. Since the precursor particles are sufficiently coated by the treatment solution, the density of the bonds between the precursor particles is strengthened, and the surface interaction caused by the reaction between the cationic adduct and the polymer material constituting the precursor particles The joint effect has also been strengthened. Such mixing operations can be achieved using various techniques and devices, including various mixers or kneaders, as known in the art.

Before, during, and after applying the solution here, the precursor particles are physically associated together to form aggregate macrostructures. The term "physical association" used in this article means that the precursor particles are joined together, and still in any of many different ways and spatial relationships, as if they are part of each other, to form a single Unit (a macroscopic structure of aggregates).

The precursor particles are preferably physically associated together by coating an associating agent on the precursor particles, and on at least part of the surface of the precursor particles on which the associating agent has been applied, Physically bring the precursor particles into contact. The preferred associating agent will cause the polymer material of the precursor particles to stick together by the action of the surface tension of the fluid and/or the entanglement of the polymer chains due to external expansion. The associative agent that can be used in the present invention includes hydrophilic organic solvents, typically low molecular weight alcohols, such as methanol or ethanol; water; a mixture of hydrophilic organic solvents and water; the aforementioned cationic amino-epichlorohydrin plus The finished product, or a mixture thereof. The preferred associating agent is water, methanol, ethanol, cationic polymeric amino-epichlorohydrin resin, such as Kymene^® 557H, or 557LX or +, or a mixture thereof. Typically, the associative agent includes a mixture containing a cationic amine group-epichlorohydrin adduct, so that the step of applying the adduct is performed simultaneously with the step of applying the associative agent.

The associative agent can be applied to the precursor particles by any of the various techniques and devices used to apply the solution to the material, which includes coating, pouring, pouring, spraying, atomizing the associating agent, Condensed or soaked on the precursor particles. The associating agent is applied to at least a part of the surface of at least some precursor particles to be combined together. Preferably, the associating agent is coated on the entire surface of most (preferably all) precursor particles. Usually, the associative agent is mixed with or sprayed on the precursor particles by any of many mixing/spraying techniques and mixing/spraying devices to ensure that the precursor particles are fully coated by the associative agent.

When the associative agent has been applied to the precursor particles, the precursor particles can be brought into physical contact together in many different ways. For example, using the associative agent alone can make the particles contact and fix them together. Alternatively, gravity can be used to ensure contact between the precursor particles, for example by coating the precursor particles. Furthermore, the particles can be placed in a container with a fixed volume to ensure the contact between the precursor particles.

Alternatively, the precursor particles can be physically restricted, so that the precursor particles are physically associated with each other so that they contact each other. For example, the precursor particles can be tightly packed in a container having a fixed volume, so that the precursor particles physically contact each other. Alternatively, gravity (e.g., coating) can be used, or it can be used in combination with the aforementioned procedures to physically associate the precursor particles. It is also possible to use electrostatic attraction to physically associate the precursor particles together, or to introduce a binder (for example, an adhesive substance, such as a water-soluble adhesive) to bind them together. It is also possible to adhere the precursor particles to the third element (a substrate), so that the precursor particles contact each other through the substrate.

In an alternative method of manufacturing the macrostructure of the present invention, the precursor particle aggregates are made into various geometric shapes, spatial relationships and densities to form aggregates with defined shapes, sizes and/or densities. This aggregate can be formed by any conventional forming technique known in the art. The preferred method of forming the polymer includes casting, molding or forming operations. Casting and molding techniques usually involve introducing precursor particles into a prepared cavity and applying pressure (compression) to the aggregate to cause the aggregate to conform to the shape of the cavity. Examples of the special molding techniques used here include compression molding, injection molding, extrusion, or lamination. For example, many precursor particles can be added to a container with a fixed volume of the cavity, and the aggregates can be compressed to conform to the shape of the cavity, so that the formed macrostructure has the same shape. The forming technique involves performing various operations on the aggregate to modify its shape, and/or size, and/or density. Examples of special forming techniques for use herein include rolling, forging, extrusion, drawing, coating or stretching operations. For example, an aggregate mixture of precursor particles and at least a cationic amine-epichlorohydrin adduct can be passed between a pair of compaction rollers to form aggregate flakes. Alternatively, the aggregate mixture can be pressed out through an orifice to form an aggregate having a shape corresponding to the orifice. Furthermore, the aggregate mixture can be molded on a surface to form aggregates having a desired shape or surface morphology. Any or all of these techniques can also be used in combination to form the shaped aggregate. Any suitable device, known in the art, can be used to perform this operation, which can be performed with the material or part of the device, regardless of whether it is hot and/or cold.

In a specific embodiment of the method of the present invention, the precursor particles, cationic amino-epichlorohydrin adducts, water, wetting agent/co-plasticizer (optional) and hydrophilic organic solvent are aggregated The body mixture is added to the feeding funnel of a conventional extruder device. An example of an extruder device is shown in<u style="single">Principles of Polymer Materials, Second Edition</u>(McGraw Hill Book Company, 1982), in Figures 12-14 on page 331, this publication is incorporated herein for reference. The aggregate mixture is extruded through the orifice of the extruder device and fed into a pair of driven compaction rollers with a fixed (but variable) gap between the rollers to press the aggregate into a sheet shape. This sheet is then processed to a specific length to provide a macro structure with a specially designed size, shape and/or density.

When the aggregated macrostructure of the present invention is made into a specific shape (especially a sheet), its density should be carefully controlled. If the density of the formed aggregate macrostructure is too high, it may be more likely to cause gel blocking. Conversely, if the density is too low, the aggregate macrostructure that has been formed may have insufficient tensile strength and integrity. The formed aggregate macrostructure of the present invention generally has a density of about 0.7 to about 1.3 g/cc, preferably about 0.8 to about 1.1 g/cc, and most preferably about 0.9 to about 1.0 g/cc.

A preferred method and device for continuously making thin sheets of the aggregated macrostructure of the present invention is described in the award to Michael S. Kolodesh et al.'s U.S. patent application serial number , titled "Method and Apparatus for Manufacturing Cohesive Sheets from Particulate Absorbent Polymer Compositions", case number 4732, application date , the disclosure of which is incorporated herein by reference . This continuous method of manufacturing aggregate flakes can be best understood with reference to Figure 9, which shows an apparatus 301 for performing this method. The device 301 has a frame 302 to support its various components. The device 301 includes a supporting device, such as a moving conveyor belt 303 as shown in FIG. 9, which moves in the direction of arrow 310. The conveyor belt 303 first passes under an initial sprayer 304a. After passing under the initial sprayer 304a, the conveyor belt 303 passes under at least one device to continuously coat a predetermined amount of precursor particles on the conveyor belt. This is shown in the feeders 305a to 305e in FIG. The conveyor belt 303 also passes under at least one device to spray a predetermined amount of treatment solution on the precursor particle layer on the conveyor belt. This is shown in the sprayers 304b to 304f in FIG. 9. The device 301 further includes a pair of non-planar back pressure feed rollers, which are located downstream of the feeder 305 and the sprayer 304. The pressure feed rollers shown in FIG. 9 are a pair of compaction rollers 306. Also shown in FIG. 9 as part of the device 301 are the cutting and conveying belt 307, the doctor and anvil roller 308, and the sheet accumulator 309.

The conveyor belt 303 may be a flat belt-shaped conveyor belt with good release properties, such as polyurethane, which is commonly used in the food industry. The width of the conveyor belt is determined by the desired sheet size. This conveyor belt usually starts at point 311 where the sprayer 304a is initially located, and moves in the direction of arrow 310 to point 312 where the scraper and anvil roller 308 are located. The conveyor 303, as shown in FIG. 9, is typically an endless conveyor belt.

The conveyor belt 303 first passes under the initial sprayer 304a, where a predetermined amount of treatment solution is sprayed to the conveyor belt to cover the predetermined area of the conveyor belt. This initial spraying operation is to ensure that the bottom part of the initial precursor particle sublayer is exposed to the treatment solution. Moreover, the surface of the wet conveyor belt will prevent the subsequently fed particles from bouncing off from their desired position. However, this initial spraying step is not absolutely necessary, especially when the first layer of particles to be placed on the conveyor belt is relatively thin, or when the conveyor belt is running at a slower speed.

The sprayer 304a (and the sprayers 304b to 304f) must deliver a substantially uniform hazy atomized spray, and should have a low impact force to avoid possible blowing away of the precursor particles. A sprayer that has been found to work well is the 6218-1/4 JAU atomizing air start nozzle assembly provided by Spraying Systems, Wheaton, IL 60188.

Then, the conveyor belt 303 passes under the feeder 305a, where a predetermined amount of dried precursor particles are coated on a predetermined area of the conveyor belt. The amount of precursor particles to be coated on the conveyor belt 303 depends on many factors, including (but not limited to) the desired density of the formed flakes, the number of coating steps to be performed, the size of the particles used and the formation The desired width of the sheet. In the lowest case, the predetermined amount should be enough to cover the predetermined area of the conveyor belt using the thickness of a layer of particles.

The feeder 305a (and the feeders 305b to 305e) must be able to distribute the precursor particles in a thin and preferably wide layer. The thinner layer on the conveyor belt ensures that all particles are processed during the subsequent spraying step, while the wider layer will increase throughput. The vibrating feeder has been shown to be suitable for coating the dried precursor particles on the conveyor belt. An example of a suitable vibrating feeder is Super Feeder #2106E-003S4, which is commercially available from Solids Flow Control, PO Box 410767, 14201-A South Lakes Drive, Charlotte, NC 28241-0767. This feeder has a weight feedback control system to provide accuracy.

Then, the conveyor belt 303 passes under the second sprayer 304b. On the conveyor belt 303 of the predetermined area with the first layer of precursor particles, a predetermined amount of the same treatment solution used in the initial sprayer 304a is sprayed. Generally speaking, the predetermined amount of treatment solution is related to the amount of particles in the layer. The greater the amount of particles in the layer, the more treatment solution that must be used to treat virtually all particles.

Therefore, this metering and spraying step can be repeated many times (for example, using feeders 305b to 305e, and sprayers 304c to 304f), depending on the desired density of the final sheet. When the metering and spraying steps are repeated multiple times and the initial spraying step as described above is performed, the first layer of particles is exposed to two spray coating operations. Therefore, the initial spraying step and the first post-coating spraying step each only need to spray half the amount of the following treatment solution, which is required to treat the amount of particles in the first layer on the conveyor belt 303. The other sprayers 304c to 304f will spray the normal amount of treatment solution, which means twice the spray amount of the initial or first coating.

After all the coating and spraying steps have been performed, the processed precursor particles are typically loosely bonded together to form a thin plate. Then, the conveyor belt 303 moves the thin plate and conveys it to a pair of counter-pressure feed rollers. The pressure feed roller in FIG. 9 also takes the form of a compaction roller 306. However, as those familiar with the art will understand, an intermittent conveyor belt method can be used with opposing plates or pressure plates for compressing the thin plates.

The compaction roller 306 may have a non-planar, rough surface. When the thin plate passes through the compaction roller 306, the pressure on the thin plate will cause it to expand. The rough surface of the roller 306 reduces the sliding effect between the roller and the thin plate when the thin plate is in contact with the roller. Thus, this will reduce the expansion of the sheet in both the machine direction 310 and the cross-machine direction. The machine direction expansion is undesirable because it requires the compaction roller 306 to speed up to match the machine direction expansion. By the compaction effect of the roller 306, the thin plate of the free deposition layer of the precursor particles and the sprayed treatment solution will be compacted and become a thin sheet.

The compaction roller 306 may be in the form of a cylindrical stainless steel roller, which is coated with a plasma coating, so that the roller obtains a rough surface and makes it easier to release the sheet after compaction. Suitable coatings include coatings No. 934 and No. 936, available from Plasma Coatings Company, Waterbury, CT 06702. The gap between the compaction rollers can determine the amount of compaction applied to the sheet.

The device 301 may include a strip cutter to trim the edge of the sheet before compaction. The edge of the sheet may have a less uniform density than the rest of the sheet, and is typically subjected to inconsistent coating of the processing solution and particles. This is caused by the movement of the conveyor belt in the cross-machine direction, thus making it possible to expect Way to remove. The slitting machine can be a regular circular blade that works against a hard surface, such as a transfer conveyor belt, as shown in 307.

After the sheet passes through the compaction roller 306, a sheet is formed and collected on the storage 309. The accumulator 309 may take the form of a take-up roll, which will wind the sheet into a single roll of the desired size. In order to obtain the desired size of the roll, the device 301 may have a second slitting machine to cut the sheet. This second slitter may take the form of a doctor blade and anvil roll 308.

After the cationic amine-epichlorohydrin adduct has been applied, the precursor particles have been physically associated together to form an aggregate, and at the same time or after the aggregate has been formed, the adduct system and the precursor The polymer material of the particles reacts while maintaining the physical association of the precursor particles to provide effective surface cross-linking in the precursor particles on the macroscopic structure of the aggregate. Due to the relatively reactive cationic functional group of the amine-epichlorohydrin adduct used in the present invention, the cross-linking reaction between the adduct and the polymer material of the precursor particles is Can occur at relatively low temperatures. In fact, this cross-linking reaction (curing) can occur at ambient room temperature. When the treatment solution containing the adduct additionally contains a plasticizer (for example, a mixture of water and glycerin), this ambient temperature maturation is particularly desirable. Maturation at significantly higher than ambient temperature, due to the volatility of the plasticizer, can cause the plasticizer to be driven away, so additional steps must be taken to plasticize the aggregates formed between the particles. Such environmental aging operations are typically carried out at a temperature of about 18°C to about 35°C for about 12 to about 48 hours. Preferably, this environmental curing operation is performed at a temperature of about 18°C to about 25°C for about 24 to about 48 hours.

Although the cross-linking reaction between the cationic amine-epichlorohydrin adduct and the polymer material of the precursor particles can occur at ambient temperature, this maturation reaction can also be carried out at a higher temperature. Speed up this reaction. Maturation at a higher temperature typically involves heating the treated and associated precursor particles to cause a cross-linking reaction between the adduct and the polymer material of the precursor particles, which occurs in a relatively short period of time, typically It takes a few minutes. This heating step can be performed using many conventional heating devices, including various ovens or dryers known in the art.

Generally speaking, heat curing can be carried out at a temperature higher than about 50°C for a period of time, which is sufficient to complete the cross-linking reaction between the polymer material of the adduct and the precursor particles. The specific temperature and time used in heating and curing depends on the specific cationic amino-epichlorohydrin adduct used and the polymer substance present in the precursor particles. If the aging temperature is too low or the aging time is too short, the reaction will not be fully driven, resulting in a macro structure with insufficient integrity and poor absorption. If the aging temperature is too high, the absorbability of the precursor particles may be degraded, or depending on the special polymer material used, the network cross-links of these precursor particles may be degraded to a certain degree, so that the giant particles formed The structure is relatively unsuitable for absorbing a large amount of liquid. In addition, if the maturation time and temperature are not appropriate, the degree of extractability of the formed aggregates may be higher, thus increasing the incidence of blocking by a specific form of gel. Therefore, heat curing is generally carried out at a temperature ranging from about 50°C to about 205°C for about 1 to about 20 minutes. The heat curing is preferably performed at a temperature of about 180°C to about 200°C for about 5 to about 15 minutes. The actual time and temperature used may depend on the specific polymer material used to make the precursor particles, the specific adduct used, the thickness or diameter of the macrostructure involved, and similar factors.

The cross-linking reaction between the cationic amine-epichlorohydrin adduct and the polymeric substance of the precursor particles is fast enough, even at ambient temperature, so that it can be used without initiator and/or Under the catalyst. However, an important factor related to the reactivity of the amino-epichlorohydrin adduct is the pH of the treatment solution containing the adduct. Typically, the pH of the treatment solution is about 4 to about 9, preferably about 4 to about 6. Keeping the pH of the treatment solution within these ranges can ensure that the amino-epichlorohydrin adduct has sufficient reactivity, even at ambient temperature.

The physical association of the processed precursor particles must be maintained during the maturation step so that when cross-linking occurs, adjacent precursor particles become cohesively bound together. If the force or stress present during the cross-linking reaction is sufficient to dissociate the precursor particles, insufficient binding of the precursor particles may occur. This can result in aggregates with poor structural integrity. The physical association of the precursor particles is typically maintained by ensuring that a minimum dissociation force or stress is introduced during maturation.

As mentioned above, the steps for manufacturing the macrostructure in the method of the present invention do not need to be performed in any specific order, but can be performed at the same time. For example, the application of cationic amine-epichlorohydrin adducts can be carried out simultaneously with the physical association of precursor particles to form a better shape and typically desired density, and then make the adduct and the precursor The polymer material reaction of the plasmid is carried out immediately after completing the above steps, or after the aggregate has been left for a period of time, so as to cross-link the surface of the precursor particles and form the macroscopic structure of the aggregate at the same time. Typically, a solution of precursor particles and adduct, water, wetting agent and/or co-plasticizer (such as glycerin) and hydrophilic organic solvent (such as methanol) are mixed together or sprayed with the mixture, and Form a kind of aggregates that stick together. The adduct, water, wetting agent/co-plasticizer, and hydrophilic organic solvent act as an associative agent for the precursor particles, and the adduct also acts as a crosslinking agent. Then, using the extrusion and rolling techniques as described above, the bonded aggregates (that is, the associated precursor particles and the aqueous mixture) are made into dense sheets. Then, through the environment or heating and curing, the adduct reacts with the polymer material to cause the cross-linking at the surface of the precursor particles at the same time, and the macroscopic structure of the aggregates of the cohesive particles is formed.

In some cases, especially if the processed precursor particles have been heat-cured, the resulting macrostructure may be slightly less flexible and potentially brittle. In this case, it can be treated with a plasticizer to make the macro structure more flexible. Suitable plasticizers include water, used alone or in combination with the aforementioned wetting agent/co-plasticizer (preferably glycerin). The plasticizer can be applied to the macrostructure in many different ways, including spraying, coating, atomizing, soaking, or pouring the plasticizer on the macrostructure. Alternatively, in the case of using water alone, the macrostructure can be placed in a high humidity environment (for example, greater than 70% relative humidity). The amount of plasticizer applied to the macrostructure can be selected, depending on the specific plasticizer used and the desired effect. Typically, the amount of plasticizer applied is about 5 to about 100 parts by weight, preferably about 5 to about 60 parts by weight, based on the weight per 100 parts of the macrostructure. A particularly preferred plasticizer system includes a mixture of glycerin and water in a weight ratio of about 0.5:1 to about 2:1, preferably about 0.8:1 to about 1.7:1.

As shown in Figures 1 to 4, and particularly Figures 3 and 4, the macrostructure formed by the method of the present invention has holes (dark areas in the photomicrograph) between adjacent precursor particles. This hole is the space between adjacent precursor particles, which allows liquid to pass through into the interior of the macrostructure. This hole is formed in the macrostructure because the precursor particles are not tightly "annotated" or stacked, even when compressed to eliminate the hole. (The accumulation efficiency of this precursor is lower than 1). This hole is generally smaller than the formed precursor particles, and a capillary is provided between the precursor particles to transport liquid into the interior of the macrostructure.

This hole is connected to each other by the interconnecting channels between the holes. These channels allow the liquid in contact with the macrostructure to be transported to other parts of the macrostructure through capillary forces (that is, to form capillary channels), so that the entire volume of the macrostructure is used to absorb the liquid. Furthermore, when expanded, the hole and the communicating channel will allow the liquid to pass through the macrostructure, reach the precursor sublayer away from the point of contact of the liquid, or reach other structures in contact with the macrostructure. Therefore, due to the hole and the connecting channel, it is believed that this macroscopic structure is liquid permeable.

The void part (meaning the total volume of the macrostructure including the hole and channel) has a minimum value for a given particle size distribution. Generally speaking, the narrower the particle size distribution of this precursor, the higher the gap part will be. Therefore, in order to provide a higher void portion in a dense state, the precursor particles should preferably have a relatively narrow particle size distribution.

Another feature of the macrostructure of the present invention is that when liquid is deposited on or in contact with it, it usually expands isotropically, even under a moderately restricted pressure. Isotropic expansion as used here means that when wetted, the macrostructure usually expands equally in all directions. Isotropic expansion is an important property of this macroscopic structure. This is because the precursor particles and pores can maintain their relative geometrical shape and spatial relationship, even when they are expanded, so that they remain during use (if If not expanded) the existing capillary channels. (The pores and precursor particles will both become larger during the expansion period). Therefore, the macro structure can absorb and/or transport additional loads of liquid through itself without causing gel blocking.

Cross-linking bonds are all formed on the surface of the precursor particles, which is that the macroscopic structure formed is fluid (meaning liquid) and stable. As used herein, "fluid stability" means a macroscopic structure including aggregates bound between particles, which remains substantially when contacted with or swelled in an aqueous fluid (with and/or unused stress) Intact (meaning that most of the previously independent components of the precursor particles are still combined). Although this definition of fluid stability assumes that most (preferably all) of the precursor particles are still combined together, it should be understood that if, for example, other particles are subsequently condensed on it by water, part of The precursor particles may dissociate themselves from the macrostructure.

Fluid stability is an important feature of the macrostructure of the present invention, because it allows the aggregate to maintain its relative structure in both dry and swollen states, and it will fix the component precursor particles. In a final product, such as an absorbent element or an absorbent article, fluid stability is beneficial to reduce the gel blocking effect, because the precursor particles are still aggregated, even when in contact with liquid, and allow us The previously independent fine particles in the form of aggregates are used to increase the fluid absorption rate of the formed macrostructure without introducing gel blocking elements.

Fluid stability can be measured in the aggregate macrostructure by a two-step procedure. Observe the initial dynamic response of the aggregated macrostructure when it comes into contact with the aqueous fluid, and then observe the complete expansion equilibrium of the aggregated macrostructure. Based on these standards, a test method used to determine fluid stability is described in the test method section below.

When in use, the liquid deposited on the macrostructure or in contact with the macrostructure is absorbed by the precursor particles, or passed into the hole and transferred to other parts of the macrostructure, where it is taken up by other precursors The particles are absorbed or transported through the macrostructure to other absorbent elements nearby.

Various types of fiber materials can be used as reinforcing elements in the macro structure of the present invention. It is applicable to any type of fiber material in conventional absorbent products, and also applicable to the macro structure in this article. Specific examples of such fiber materials include cellulose fibers, modified cellulose fibers, rayon, polypropylene, and polyester fibers, such as polyethylene terephthalate (DACRON), hydrophilic nylon (HYDROFIL) ), and its analogues. In addition to some of the already discussed, other fiber materials for use in the present invention, examples of which are hydrophilized hydrophobic fibers, such as thermoplastic fibers that have been treated with surfactants or silicone, which are derived from For example, polyolefins (such as polyethylene or polypropylene), polyacrylates, polyamides, polystyrene, polyurethane, etc. In fact, the hydrophilized hydrophobic fiber is not very absorbent by itself or in it. Therefore, it cannot provide a sheet with sufficient absorption capacity that can be used in conventional absorbent structures. However, due to its good wicking properties, it is suitable for In the macro structure of the present invention. This is because in the macro structure in this article, the wicking tendency of the fiber is as important as (if not more important) the absorption capacity of the fiber material itself. This is due to the high rate fluid absorption and fluid absorption of the macro structure of the present invention. Not due to gel blocking properties. Synthetic fibers are usually preferentially used here as the fiber component of this macro structure. The most preferred are polyolefin fibers, and of these, polyethylene fibers are preferred.

Other cellulosic fiber materials that can be used in some macrostructures herein are cellulosic fibers that are chemically stiffened. Preferably, chemically stiffened cellulose fibers are stiffened, twisted, and crimped cellulose fibers, which can be made by internally cross-linking the cellulose fibers using a cross-linking agent. Appropriately stiffened, twisted, and crimped cellulose fibers that can be used as the hydrophobic fibrous material herein are described in more detail in U.S. Patent 4,888,093 (Dean et al.), issued on December 19, 1989; U.S. Patent 4,889,595 (Herron et al.) People), issued on December 26, 1989; U.S. Patent 4,889,596 (Schoggen et al.), issued on December 26, 1989; U.S. Patent 4,889,597 (Bourbon et al.), issued on December 26, 1989; and U.S. Patent 4,898,647 ( Moore et al.), issued on February 6, 1990, all incorporated herein for reference.

As used herein, the term "hydrophilic" refers to the surface of the fiber or fiber, which is wetted by the liquid deposited on the fiber (that is, if water or water-containing body fluid is easy to spread on or cover the surface of the fiber It has nothing to do with whether the fiber actually absorbs fluid or forms a gel). This technique allows the definition of hydrophobicity (and wetting effect) from the viewpoint of the contact angle and surface tension of the liquid and solid involved in the current state of the wetting effect of the material. This series was discussed in detail in a publication of the American Chemical Society, titled "Contact Angle, Wetting Ability, and Adhesion", edited by Robert F. Gould, and copyrighted in 1964. When the contact angle between the liquid and the fiber or the surface is less than 90, or when the liquid is easy to spontaneously spread on the surface of the fiber (the two cases usually coexist), we call the fiber or fiber surface is Liquid wetting.

This fiber material can be added to the macrostructure by introducing the fiber into a solution with cationic amino-epichlorohydrin adduct, and mixing it with precursor particles before applying the adduct, or The fiber material is added to the adduct/precursor particle mixture. For example, the fibrous material can be kneaded in the adduct/precursor particle mixture. It is best to thoroughly mix the fibrous material with this solution so that the fibrous material is evenly dispersed throughout the macrostructure. This fiber is also preferably added before the polymer material of the adduct reacts with the precursor particles.

The relative amount of fibrous material mixed with the precursor particles can vary widely. The preferred addition amount of this fiber material is in the range of about 0.01 part to about 50 parts, more preferably in the range of about 0.5 part to about 5 parts, based on the weight of 100 parts of precursor particles.

E.

The purpose of macro structure

This porous absorptive macro structure can be used in many application areas and for many purposes. For example, this macro structure can be used for filling containers; drug delivery devices; wound cleaning devices; combustion treatment devices; ion exchange column materials; construction materials; agricultural or gardening materials, such as seeding flakes or water-holding materials; Or oil dehydrating agent, material to prevent the formation of dew, desiccant, and humidity control material.

The porous absorbent macrostructure of the present invention is useful when combined with a carrier. The carrier that can be used in the present invention includes absorbent materials, such as cellulose fibers. The carrier can also be any other carrier known in the art, such as non-woven sheets, tissue boards, foams, polyacrylate fibers, perforated polymer sheets, synthetic fibers, metal foils, elastomers, etc. . This macrostructure can be directly or indirectly bonded to the carrier, and can be bonded together, for example, by chemical or physical bonding methods known in the art, including adhesives or chemicals, which react to make the macrostructure Bonded to this carrier.

Due to the unique absorption properties of the porous and absorbent macrostructure of the present invention, it is particularly suitable for use in absorbent articles as an absorbent core layer, especially disposable absorbent articles. The term "absorbent article" as used in this article refers to an article that can absorb and contain body exudates. More specifically, it refers to an article that is placed against or close to the wearer's body to absorb and contain the body. All kinds of exudate objects discharged. In addition, "disposable" absorbent articles are articles that are intended to be discarded after a single use (that is, the original absorbent articles are not intended to be restored or reused by washing or other means for absorption). Sexual objects, but some or all of the materials in this absorbent article can be remanufactured, reused or mixed). A preferred embodiment of a disposable absorbent article, diaper 20, is shown in FIG. 5. The term "diaper" used in this article refers to a piece of clothing usually worn by infants and incontinent persons, which is worn near the lower body of the wearer. However, it should be understood that the present invention can also be applied to other absorbent articles, such as incontinence tights, incontinence pads, sports pants, diaper inserts, sanitary napkins, beauty fabrics, paper towels, and the like.

Fig. 5 is a perspective view of the diaper 20 of the present invention in its uncontracted state (that is, all elastics that cause contraction are removed), and part of the structure is cut away to show the structure of the diaper 20 more clearly. And 20 parts of the diaper that are in contact with the wearer and face the observer. The diaper 20 shown in FIG. 5 preferably includes a liquid-permeable top sheet 38; a back sheet 40 connected to the top sheet 38 and impervious to liquid; and an absorbent located between the top sheet 38 and the back sheet 40 Core layer 42; elastic element 44; Although the top sheet 38, the back sheet 40, the absorbent core layer 42 and the elastic element 44 can be combined in a variety of conventional forms, a preferred diaper form is generally described in the U.S. Patent issued on January 14, 1975 3,860,003 (Buell) and included in this article for reference. Other preferred forms of disposable diapers are also disclosed in U.S. Patent 4,808,178 (Aziz et al.) issued on February 28, 1989; U.S. Patent 4,695,278 (Lawson) issued on September 22, 1987; and 1989 U.S. Patent 4,816,025 (Foreman) issued on March 28, 2005, is incorporated herein by reference in its entirety.

FIG. 5 shows a preferred embodiment of the diaper 20, in which the top sheet 38 and the back sheet are coextensive, and the length and width dimensions of the top sheet 38 and the back sheet are generally larger than the size of the absorbent core layer 42. The top sheet 38 is connected and overlapped on the back sheet 40 to form the periphery of the diaper 20. This perimeter defines the outer perimeter or edge of the diaper 20. This periphery includes a terminal edge 32 and a longitudinal edge 30.

The top sheet 38 has flexibility, a soft feel, and is non-irritating to the wearer's skin. Furthermore, the top sheet 38 is liquid permeable, allowing liquid to penetrate through its thickness immediately. The appropriate top sheet 38 can be made from a wide range of materials, such as porous foams, reticulated foams, porous plastic films, natural fibers (e.g., wood or cotton fibers), synthetic fibers (e.g., polyester or polypropylene fibers). ) Or a combination of natural and synthetic fibers. The top sheet 38 is preferably made of a hydrophobic material to isolate the wearer's skin from the liquid in the absorbent core layer 42.

A particularly preferred top sheet 38 includes polypropylene fibers having a staple length of about 1.5 deniers, such as Hercules 151 polypropylene sold by Hercules (Wilmington, Delaware). As used herein, the term "staple length fiber" refers to fibers having a length of at least about 15.9 mm (0.62 inches).

There are many manufacturing techniques that can be used to manufacture the top sheet 38. For example, the top sheet 38 may be woven, unwoven, spunbonded, carded, or the like. A preferred top sheet is combed and thermally bonded by means familiar in textile technology. Preferably, the top sheet 38 has a weight of about 18 to about 25 grams per square meter, a minimum dry tensile strength of at least about 400 grams per centimeter in the machine direction, and a wet tensile strength of at least about 55 grams per centimeter in the machine direction. tensile strength.

The back sheet 40 is liquid impermeable, and is preferably made of a thin plastic film, but other soft liquid impermeable materials can also be used. The back sheet 40 prevents the exudate absorbed and contained in the absorbent core layer 42 and prevents the objects in contact with the diaper 20 from wetting, such as bed sheets and underwear. The back sheet 40 is preferably a polyethylene film having a thickness of about 0.012 mm (0.5 mil) to about 0.051 cm (2.0 mil), but other flexible, liquid-impermeable materials can also be used. The term "softness" used in this article refers to materials that are flexible and easily conform to the general shape and contour of the wearer's body.

A suitable polyethylene film is manufactured by Monsanto Chemical Company and sold under the film number 8020 as the trade name. The back sheet 40 is preferably embossed and/or matted to provide a more cloth-like appearance. Furthermore, the back sheet 40 may allow vapor to escape the absorbent core layer 42 but still prevent exudate from passing through the back sheet 40.

The size of the back sheet 40 depends on the size of the absorbent core layer 42 and the actual diaper design selected. In a preferred embodiment, the back sheet 40 has a modified hourglass pattern, and extends beyond the absorbent core layer 42 by a minimum distance of at least about 1.3 cm to about 2.5 cm (about 0.5 to about 1.0 inches), surrounding the entire Around the diaper.

The top sheet 38 and the back sheet 40 are connected together in any suitable manner. The term "connected" as used herein includes the form of directly attaching the top sheet 38 to the back sheet 40, and the top sheet 38 is directly connected to the back sheet 40, and the form of attaching the top sheet 38 to the intermediate element , And then sequentially attached to the back sheet 40, so that the top sheet 38 is indirectly connected to the back sheet 40. In a preferred embodiment, the top sheet 38 and the back sheet 40 are directly attached to each other by an attachment method (not shown), such as an adhesive or any other attachment method known in the art. On the periphery of the diaper. For example, a uniform continuous adhesive layer, a patterned adhesive layer, or an arrangement of individual adhesive lines or dots can be used to attach the top sheet 38 to the back sheet 40.

The drape fastener 46 is typically applied to the waistband area of the diaper 20 to provide a hook and loop device to secure the diaper to the wearer. The strap fastener 46 can be any person known in the art, such as the hook and loop fastener disclosed in US Patent 3,848,594 (Buell) issued on November 19, 1974, which is incorporated herein by reference. These flap fasteners 46 or other diaper fastening devices are typically applied close to the corners of the diaper 20.

The elastic elements 44 are arranged adjacent to the periphery of the diaper 20, preferably along each longitudinal edge 30, so that the elastic elements 44 are easy to stretch and secure the diaper 20 against the leg of the wearer. Alternatively, the elastic element 44 may be disposed on either end or both ends adjacent to the end edge 32 of the diaper 20 to provide a waistband and trouser opening or not. For example, a suitable waist belt is disclosed in U.S. Patent 4,515,595 (Kievit et al.) issued on May 7, 1985, and is incorporated herein by reference. In addition, a method and device suitable for manufacturing disposable diapers with elastic shrinkable elastic elements are described in U.S. Patent 4,081,301 (Buell) issued on March 28, 1978, which is incorporated herein by reference.

The elastic element 44 is fixed to the diaper 20 in an elastically contractible state, so that in a normal unrestricted configuration, the elastic element 44 will effectively shrink or crease the diaper 20. The elastic element 44 can be fixed in at least two ways, and is in an elastic and contractible state. For example, the elastic element 44 can be stretched and fixed, while the diaper 20 is in an uncontracted state. Alternatively, the diaper 20 can be contracted by, for example, pleating, and the elastic element 44 is fixed and connected to the diaper 20, and the elastic element 44 is in its unslack or unstretched state.

In the specific embodiment shown in FIG. 5, the elastic element 44 extends along a part of the length of the diaper 20. Alternatively, the elastic element 44 may extend over the entire length of the diaper 20, or any other length suitable for providing elastic shrinkable threads. The length of the elastic element 44 depends on the design of the diaper.

The elastic element 44 can take various forms. For example, the width of the elastic element 44 may vary from about 0.25 mm (0.01 inch) to about 25 mm (1.0 inch) or more; the elastic element 44 may include a single strand of elastic material, or may include several parallel or non-parallel strips. The elastic material bundle; or the elastic element 44 may be rectangular or curvilinear. Furthermore, the elastic element 44 can be attached to the diaper in any of several ways known in the art. For example, a variety of bonding styles can be used, the elastic element 44 can be ultrasonically bonded, heat and pressure sealed in the diaper 20, or the elastic element 44 can be simply glued to the diaper 20.

The absorbent core layer 42 of the diaper 20 is located between the top sheet 38 and the back sheet 40. The absorbent core layer 42 can be made of a wide variety of sizes and shapes (for example, rectangular, hourglass, asymmetric, etc.), and can be made from a wide variety of materials. However, the full absorbent capacity of the absorbent core layer 42 should be compatible with the liquid load design of the intended use of the absorbent or the diaper. Furthermore, the size and absorptive capacity of the absorbent core 42 can be changed to adapt to wearers ranging from infants to adults. The absorbent core layer 42 includes the porous absorbent macrostructure of the present invention.

A preferred embodiment of the diaper 20 has a rectangular absorbent core 42. As shown in FIG. 6, the absorbent core layer 42 preferably includes an absorbent element 48 including an envelope sheet 50 and a porous absorbent macrostructure 52 disposed in the envelope sheet 50. The macro structure 52 is installed in the envelope sheet 50 to minimize the potential for precursor particles to migrate through the top sheet, and another liquid transport layer is provided between the top sheet 38 and the macro structure 52 to enhance liquid acquisition Function and minimize rewetting. As shown in FIG. 6, the single-piece envelope sheet 50 is wrapped around the macro structure 52 by folding it to form the first layer 54 and the second layer 56. The edge 58 of the envelope sheet 50 is sealed around its periphery by any conventional means, such as adhesive 59 (as shown in the figure), ultrasonic bonding, or heat/pressure bonding to form a bag. The envelope sheet 50 may include many materials, including an unwoven sheet, a paper sheet, or a sheet of absorbent material, such as tissue paper. The envelope sheet 50 preferably includes an unwoven sheet similar to the sheet used to form the top sheet 38. The unwoven sheet is preferably hydrophilic to allow liquid to pass through the envelope sheet 50 quickly. A similar layered absorbent element (laminate) is more fully described in U.S. Patent 4,578,068 (Kramer et al.) issued on March 25, 1986, and is incorporated herein by reference.

Alternatively, the absorbent core layer 42 of the present invention may be composed of one or more porous absorbent macrostructures of the present invention alone; may include a combined layer containing the macrostructure of the present invention; or include one or more macrostructures of the present invention Any other absorbent core form of the structure.

Figure 7 shows another specific embodiment, a diaper 120, which includes a double-layer absorbent core layer 142, which contains an improved hourglass type absorbent element 60 and a porous absorbent macrostructure located adjacent to the absorbent element 60 The sheet 62 (that is, located between the absorbent element 60 and the back sheet 40).

The absorbent element 60 is used to quickly collect and temporarily hold the liquid discharged from the residence, and transport this liquid by wicking, from the initial contact point to other parts of the absorbent element 60, and to the macro structure sheet 62. The absorbent element 60 preferably includes a sheet or batt of fibrous material. Various types of fiber materials can be used in the absorbent element 60, such as the fiber materials discussed above. Cellulose fibers are generally preferably used here, and wood pulp fibers are particularly preferred. The absorbent element 60 may also contain a specific amount of particulate, absorbent, polymer composition. For example, the absorbent element 60 may contain up to about 50% of its weight polymer composition. In the most preferred embodiment, the absorbent element 60 contains 0% to about 8% by weight of the particulate absorbent polymer composition. In another preferred embodiment, the absorbent element 60 includes chemically stiffened cellulose fibers as discussed above. Specific examples of the absorbent element 60 that can be used in the present invention are described in U.S. Patent 4,673,402 (Weisman et al.) issued on June 16, 1987; and U.S. Patent 4,834,735 (Alemany et al.) issued on May 30, 1989. ), both cases are incorporated in this article for reference. A particularly good absorbent element for use herein is an absorbent element having a storage area and an acquisition area, wherein the acquisition area has a lower average density than the storage area and has a lower average basis weight per unit area, so that The acquisition area can effectively and efficiently quickly acquire the discharged liquid.

The absorbent element 60 may have any desired shape, for example, rectangular, oval, oblong, asymmetrical or hourglass-shaped. The shape of the absorbent element 60 can define the general shape of the diaper 120 formed. In the preferred embodiment shown in FIG. 7, the absorptive element 60 is in the shape of an hourglass.

The macrostructure sheet 62 of the present invention does not have to be the same size as the absorbent element 60, and in fact may have a top surface, which is substantially smaller or larger than the top surface area of the absorbent element 60. As shown in FIG. 7, the macrostructure sheet 62 is smaller than the absorbent element 60 and has a top surface area of about 0.10 to about 1.0 times the area of the absorbent element 60. In the best case, the surface area of the top layer of the macrostructure sheet 62 is only about 0.10 to about 0.75 times the area of the absorbent element 60, and most preferably about 0.10 to about 0.5 times. In another embodiment, the absorbent element 60 is smaller than the macrostructure sheet 62, and has a top layer surface area of about 0.25 to about 1.0 times the area of the macrostructure sheet 62, more preferably about 0.3 to about 0.95 times. In this alternative embodiment, the absorbent element 60 preferably comprises chemically stiffened cellulose fibers as described above.

The macro structure sheet 62 is preferably placed in a special positional relationship with respect to the back sheet 40 and/or the absorbent element in the diaper. More specifically, the macro structure sheet 62 is located at a position generally facing the front of the diaper, so that the macro structure sheet 62 is most effectively positioned to capture and fix the discharged liquid.

In another preferred embodiment, several macrostructures, preferably two to six macrostructure strips or sheets, can be used instead of the single macrostructure sheet 62 shown in FIG. 7. Furthermore, other absorbent layers, elements or structures can be placed in the absorbent core layer 142. For example, other absorbent elements can be placed between the macro structure sheet 62 and the back sheet 40 to provide the storage capacity of the absorbent core layer 142, and/or provide a layer to pass through the macro structure sheet 62 The liquid is distributed to other parts of the absorbent core layer 142 or to the macrostructure sheet 62. The macro structure sheet 62 can also be placed above the absorbent element 60 in another way, so as to be placed between the top sheet 38 and the absorbent element 60.

Figure 8 shows another specific embodiment, a diaper 220 containing alternating double absorbent core layers 242, which includes a rectangular absorbent element 260, and three elongated parallel spaced macrostructure strips 262, located on the absorbent element 260 And the back sheet 40 between.

The absorbent element 260 is used to quickly collect and temporarily fix the liquid discharged from the residence, and transport this liquid by wicking, from the initial contact point to other parts of the absorbent element 260, and to the macro structure bar 262. The absorbent element 260 preferably comprises a sheet or cotton roll of fibrous material, most preferably a chemically stiffened cellulose fiber as discussed above. The macro structure bars 262 are used together to capture and hold the discharged liquid. With the macro structure bars 262 spaced apart from each other, a more effective surface area is presented to capture and maintain the discharged liquid. This is particularly true because the spaced macro structure strips 262 can expand and expand in the width direction without disturbing the ability of adjacent strips to obtain the discharged liquid.

In use, the diaper 20 is applied to the wearer by placing the back waistband area behind the wearer and stretching the rest of the diaper 20 between the wearers legs so that the front waistband area is located Across the front of the wearer. Then, the drape fastener 46 is preferably fixed to the outward facing area of the diaper 20. When in use, the disposable diapers or other absorbent articles combined with the porous absorbent macrostructure of the present invention are easy to distribute and store liquids more quickly and efficiently, and still remain dry. This is due to the macrostructure High absorptive capacity. The disposable diaper combined with the macro structure of the present invention can also be thinner and more flexible.

Synthetic urine

The special synthetic urine used in the test method of the present invention is referred to herein as "synthetic urine". This synthetic urine is often referred to as Jayco SynUrine and is obtained from Jayco Pharmaceuticals (Camp Hill, Pennsylvania). The formula of synthetic urine: 2.0 g/L KCl; 2.0 g/L Na₂SO₄; 0.85 g/L (NH₄)H₂PO₄; 0.15 g/L (NH₄)₂HPO₄; 0.19 g/L CaCl₂And 0.23 g/L MgCl₂. All chemicals are reagent grade. The pH value of this synthetic urine is in the range of 6.0 to 6.4.

experiment method

A.

Absorption capacity of precursor particles

The polymer composition is placed in a "tea bag", soaked in excess synthetic urine for a specified period of time, and then centrifuged for a specified period of time. After centrifugation, the final weight of the polymer composition minus the initial weight (net fluid gain), and the ratio of the initial weight determines its absorption capacity.

The following procedures are performed under standard laboratory conditions at 23°C (73°F) and 50% relative humidity. Using a 6 cm x 12 cm cutting die, cut the tea bag material, fold it in half the length, and seal it with a T-bar heat sealer along both sides to produce a 6 cm x 6 cm square tea bag. The tea bag material used is a grade 1234 heat-sealable material, available from Dexter's CH Dexter Department (Windsor Locks, Connecticut, USA), or its equivalent. If you need to retain fine particles, you should use a lower porosity tea bag. Weigh out 0.200 g ± 0.005 g of polymer composition on a weighing paper and transfer it to a tea bag, and then seal the top (open end) of the tea bag. Seal an empty tea bag at the top and use it as a blank test. Pour approximately 300 ml of synthetic urine into a 1,000 ml beaker. The blank test tea bag is immersed in synthetic urine. Keep the tea bag (sample tea bag) containing the polymer composition level so that the material is evenly distributed throughout the tea bag. Lay the tea bag horizontally on the surface of the synthetic urine. Wet the tea bag for no more than one minute, then completely submerge and soak for 60 minutes. About 2 minutes after the first sample was sunk, the second set of tea bags (made in the same way as the first set of blank and sample tea bags) was sunk and soaked for 60 minutes in the same manner as the first set. After the designated soaking time of each group of tea bag samples has passed, the tea bag is quickly removed (using a clamp) to synthesize urine. Then these samples were centrifuged as follows. The centrifuge used was a Delux Dynac II centrifuge, Fisher model number 05-100-26, available from Fisher Technology Company (Pittsburgh, PA), or its equivalent. This centrifuge should be equipped with a tachometer that can be directly read and an electric brake. This centrifuge is further equipped with a cylindrical insert basket, which has an outer wall of about 2.5 inches (6.35 cm) high, 8.435 inches (21.425 cm) outer diameter, 7.935 inches (20.155 cm) inner diameter, and 9 rows each Approximately 106 3/32 inch (0.238 cm) diameter circular holes, which are equally spaced around the outer wall, and have a basket bottom plate, in which there are six 1/4 inch (0.635 cm) diameter circular drainage holes, etc. The interval surrounds the bottom of the basket, and the distance from the inner surface of the outer wall to the center of the drainage hole is 1/2 inch (1.27 cm), or its equivalent. This basket is loaded in the centrifuge so that it is consistent with the centrifuge when rotating and braking. The sample tea bag is placed in the centrifuge basket, and the folded end of the tea bag is in the direction of the centrifuge rotation to absorb the initial force. Place the blank teabag on either side of the corresponding sample teabag. The sample tea bags of the second group must be placed opposite to the sample tea bags of the first group; and the blank tea bags of the second group are also opposite to the blank tea bags of the first group to balance the centrifuge. Start the centrifuge and make it spin quickly up to a steady speed of 1,500 rpm. Once this centrifuge has reached 1,500 When stable at rpm, immediately set the timer to 3 minutes. After 3 minutes, turn off the centrifuge and apply the brakes. Remove the first sample tea bag and the first blank tea bag and weigh them individually. Repeat this procedure for the second sample teabag and the second blank teabag. Calculate the absorption capacity (ac) of each sample as follows: ac=(the weight of the sample tea bag after centrifugation minus the weight of the blank tea bag after centrifugation minus the weight of the dry polymer composition) divided by (the weight of the dry polymer composition). Regarding the absorption capacity value used in this article, it is the average absorption capacity of the two samples.

B.

Fluid stability

The purpose of this method is to determine the stability of aggregates when exposed to synthetic urine.

Place the macrostructure sample in the shallow dish. Add excess synthetic urine to this macro structure. Observe the expansion of this macro structure until a balance is reached. During the observation of the macroscopic structure in expansion, the macroscopic structure is to observe the small particles that are broken from the main body of the aggregate, the plate-shaped particles that float away from the main body of the aggregate, or that the particles expand only in two directions in the xy plane. There are particles that break off and float away from the main body of the aggregate. If the aggregate has a large number of broken and detached component particles, it is considered that the macrostructure is unstable. The isotropic expansion effect of this macroscopic structure should also be observed. If after this test procedure, the aggregate is still quite stable, and the relative geometric shape and spatial relationship of the precursor particles and pores are still maintained, the macrostructure is considered to be stable. Preferably, the macroscopic structure of fluid stability is such that it can be picked up in its expanded state without breaking apart.

C.

Precursor particle size and mass average particle size

On the basis of weight percentage, the particle size distribution of the whole sample of 10 grams of precursor particles is determined by passing the sample through a set of 19 sieves. The size of the sieves ranges from the standard #20 sieve (850 Micrometers) to standard #400 mesh (38 micrometers). These screens are standard screens, available from Gilson Company (Worthington, Ohio). This procedure is performed on three stacks of screens at a time, because the equipment used cannot fix all 19 screens at once. The first pile contains screens #20, 25, 30, 35, 40, 45, and 50, plus screen trays; the second stack contains screens #60, 70, 80, 100, 120, and 140, plus Upper screen tray; the third stack contains screens #170, 200, 230, 270, 325 and 400, plus screen trays. The first particles remaining on each of these sieves are then weighed to determine the particle size distribution on a weight percentage basis.

Install the first stack of sieves on the shaker, and place 10.0 g ± 0.00 g sample on the #20 sieve. The oscillator used was a vibrating 3-inch screen shaker SS-5, available from Gilson Company (Worthington, Ohio). Under about 2100 vibrations per minute ("6" on the dial of this instrument), the pile is oscillated for 3 minutes. Then remove the screen tray and set this stack aside for later weighing. Using a soft brush, transfer the sample remaining on the screen tray to the weighing paper. Install the second stack of screens on the shaker, and transfer the sample on the weighing paper to #60 screen. At about 2,100 vibrations per minute, shake the second stack for 3 minutes, transfer the sample remaining on the screen tray to the weighing paper, and set the stack aside. Install the third stack of screens on the shaker, and transfer the sample left on the weighing paper to #170 screen. At about 2,100 vibrations per minute, the third stack was oscillated for 3 minutes. Use a soft brush to transfer the contents of each given screen to the tare weighing paper. Weigh the sample on a standard three-digit balance, and record the weight of the sample on a specific sieve. For each sample, for each screen, and for the sample remaining on the screen tray, after the third stack of screens has been shaken, use a new weighing paper to repeat this step. Repeat this method for the other two 10 g samples. For each screen, the average of the weight of the three samples determines the average particle size distribution of each screen based on the weight percentage.

The mass average particle size of 10 g of the whole sample is calculated as follows:<maths><img file="TW366287B_D0005.tif" /></maths>Where maps is the mass average particle size; M₁Is the weight of particles on a specific screen; and D₁It is the "size parameter" of a specific screen. The size parameter of a screen D₁, Is defined as the size of the next high screen (expressed in microns). For example, a standard #50 screen has a size parameter of 355 microns, which corresponds to the size of the openings in the standard #45 screen (the next highest screen). The mass average particle size used in this article is the average of the mass average particle sizes of three samples.

Examples of precursors

A 10-liter double-arm stainless steel kneader equipped with a jacket. The size at the opening is 220 mm × 240 mm, and it has a depth of 240 mm. It has two Σ-shaped fins and a rotating diameter of 120 mm. A lid seals this kneader. Prepare a monomer aqueous solution composed of 37% by weight monomer. This single system is a combination of 75 mol% sodium acrylate and 25 mol% acrylic acid. 5500 g of the monomer aqueous solution was fed into the kneader container, followed by purging with nitrogen gas to remove the remaining trapped air. Then, set the two Σ-shaped fins to rotate at a speed of 46 rpm and pass water at 35°C to heat the jacket. 2.8 g of sodium persulfate and 0.14 g of L-ascorbic acid were added as a polymerization initiator. The polymerization reaction started about four minutes after the addition of the initiator. 15 minutes after adding the initiator, the inside of the reaction system reached a peak temperature of 82°C. While continuously stirring, the hydrated gel polymer is divided into particles of about 5 mm in size. 60 minutes after the start of the polymerization reaction, the lid was removed from the kneader, and the material was removed from the kneader.

The hydrated hydrogel polymer thus obtained was spread on a standard #50 size metal net and dried under hot air at 150°C for 90 minutes. The dried particles are crushed with a hammer crusher and filtered with a standard #20 mesh (850 microns) to obtain particles that pass the standard #20 mesh. The mass average particle size of these particles is 405 microns.

<u style="single">Special instructions for preparing macrostructures according to the present invention</u>

<u style="single">Example 1</u>

One hundred parts of the precursor particles prepared according to the example of the precursor particles were placed in a 5-quart vertical kitchen mixer. The particle size of the precursor particles is such that the precursor particles pass through the standard number 50 mesh (300 microns) and remain on the standard number 100 mesh (150 microns). An aqueous treatment solution is made from a mixture of 4.3 parts Kymene+ (30% resin active), 2.6 parts water and 10.0 parts methanol. Use a Preval sprayer (available from Precision Valve Company (Yonkers, NY)), spray the treatment solution on the precursor particles. Spray the treatment solution on the precursor particles while operating the mixer at a low speed for about 4 minutes, which means until all the solution is sprayed on the particles. After spraying, mix the mixture of moist precursor particles at the highest speed, set for 2 to 5 minutes. During this high-speed mixing, the methanol evaporates, thereby increasing the viscosity of the processed precursor particle mixture so that it still sticks together. This viscous mixture of processed precursor particles is then fed into an extrusion/compaction unit. The extruder screw has a length of 8 inches (20.3 cm) and contains 5 threads, each of which is 1.5 inches (3.8 cm) long. The outer diameter of the extruder screw is 1.75 inches (4.45 cm), and the gap between the screw and the casing is 0.20 inches (0.51 cm). Start this unit so that the extruder screw rotates at a rate of 47 rpm. The mixture is pressed out between two smoothly polished steel compaction rolls (kneading rolls) with a fixed (but variable) gap. This compaction roller has a diameter of 8.975 inches (22.8 cm) and is driven at a speed of 5.4 rpm. The gap between the compaction rollers is 0.015 inches (0.38 mm). Then, the formed aggregate sheet is separated into approximately 12 to 15 inches (30 to 40 cm) in length. Heat the formed aggregate flakes in a forced air convection oven at 200°C for about 10 minutes, so that Kymene⁺Reacts with the polymer material on the surface of the precursor particles, thus causing effective cross-linking. The oven-cured sheet has a thickness (curved foot gauge) of about 0.031 inches (0.8 mm) and a width of about 1.95 inches (4.95 cm). A plasticizer solution containing 65 parts of glycerin and 35 parts of distilled water was sprayed on the oven-cured flakes at a ratio of 0.9 g of the plasticizer solution per 1.0 g of the oven-cured flakes. About 1/2 hour after treatment with this plasticizer solution, the sheet has sufficient flexibility and tensile strength that can be picked up.

<u style="single">Example 2</u>

In this example, 100 copies of the precursor particles prepared according to the example of the precursor particles are used, and they have the particle size characteristics described in Example 1. Also used a Kymene made from 6.0 parts⁺(30% resin active), an aqueous treatment solution of a mixture of 3.5 parts of water and 8.5 parts of glycerin.

Use a reciprocating table or shuttle, and connect a pair of sprayers for applying treatment solution, and a vibrating feeder for placing precursor particles. The sprayer and the feeder are placed on the reciprocating surface of the table. When the surface of the table moves below the sprayer, the treatment solution is sprayed on the table (or particle layer) in a predetermined pattern. When the surface of the table moves further in the same direction and is under the feeder, a predetermined amount of precursor particles are deposited on the table or on the previously processed particle layer. After the particles have been deposited from the feeder to form one of its layers, the table top moves backward in the opposite direction, so that the sequence of applying the treatment solution/depositing the particle layer can be repeated.

Initially, a predetermined amount of treatment solution was sprayed on the moving table. After the table top has been sprayed with the treatment solution for the first time, five layers of precursor particles (0.2 g particles per square inch per layer) are deposited from the feeder. After the precursor particles of each layer have been deposited, a predetermined amount of treatment solution is sprayed on top of each layer. The amount of treatment solution sprayed on the desktop and the first layer of precursor particles for the first time is about 0.018 g/in². The amount of treatment solution sprayed on the other four layers of precursor particles is about 0.036 g/in². In fact, the precursor particles of each layer are treated with an equal amount of solution.

After the precursor particles are laminated and sprayed with the treatment solution, a relatively cohesive particle flake is formed. This cohesive sheet is then fed to the compaction roller by means of a conveyor belt. This compaction unit consists of two coated steel compaction rolls (kneading rolls) with a fixed (but variable) gap. The compaction roller has a diameter of about 8 inches (20 cm) and is driven at a rate of about 20 rpm. The gap between the compaction rollers is 0.035-0.040 inches (0.9-1.0 mm). Store the formed aggregate sheet (density 0.9-1.0 g/cc) in a plastic bag at ambient room temperature (about 65-75°F, 18.3-22.2°C) for about 24 hours. During aging at this ambient temperature, Kymene⁺It will react with the polymer material on the surface of the precursor particles, thus causing effective cross-linking. A sheet cured at ambient temperature has a thickness of about 0.050-0.060 inches (1.3-1.5 mm) (curved foot gauge) and a width of about 4 inches (10 cm). These sheets cured at ambient temperature have sufficient flexibility and tensile strength so that they will not break or tear during handling.

<u style="single">Example 3</u>

In this example, the device 301 shown in FIG. 9 is used. The precursor particles used are made according to the examples of precursor particles, and have a size between 150-250 microns. An aqueous treatment solution is made from 5.0 parts of Kymene⁺(30% resin active), a mixture of 7.1 parts of water and 12.7 parts of glycerin. The feeder 305 is a Super Feeder #210 model SE-00354 vibrating feeder, available from Solids Flow Control (Charlotte, NC). The sprayer 304 is a model 6218-1/4 JAU atomizing air priming nozzle combination, available from Spray Systems (Wheaton, IL). For the first two coatings, the sprayers 304a and 304b deliver the treatment solution to the conveyor belt 303 at a rate of 39.8 g/min. For the subsequent coating, the sprayers 304c to 304f deliver the treatment solution to the conveyor belt 303 at a rate of 79.6 g/min. The conveyor belt 303 is a mobile conveyor belt made of polyurethane and runs at a speed of 27 feet per minute. The pressure feed rollers are a pair of compaction rollers 306 with a diameter of 8 inches (20 cm) and a width of 12 inches (30.5 cm). The upper and lower rollers 306 are coated with #934 plasma coating, available from the plasma coating company (Waterbury, CT).

This example is carried out according to the following steps: Step 1: Spray the predetermined area of the conveyor belt with the treatment solution for the first time, the amount of which is substantially equal to 0.025 grams of solution per square inch of the conveyor belt.

Step 2: In a substantially continuous manner, 0.2 grams of precursor particles per square inch of the conveyor belt are coated on the same predetermined area.

Step 3: Spray the treatment solution on the first layer of precursor particles on the conveyor belt of a predetermined area, the amount of which is substantially equal to 0.025 grams of solution per square inch of the conveyor belt.

Step 4: In a substantially continuous manner, 0.2 grams of precursor particles per square inch of the conveyor belt are coated on the same predetermined area.

Step 5: Spray the second layer of precursor particles on the conveyor belt of a predetermined area with the treatment solution, the amount of which is substantially equal to 0.050 grams of solution per square inch of the conveyor belt.

Step 6: Repeat steps 4 and 5 in sequence for more than three times to obtain: (a) a total of one initial spraying step and five post-coating spraying steps, resulting in a total of 0.25 grams of treatment solution per square inch of conveyor belt; and (b) ) A total of five coating steps, resulting in a total of 1 gram of precursor particles per square inch of conveyor belt. Thus, a thin plate is formed.

Step 7: Pass the sheet through the compaction roller. The gap between the compaction rollers is 0.035 inches (0.9 mm). This produces flakes with a density of 0.995 g/cc.

Step 8: Put this sheet in a plastic bag and place it at ambient temperature (72°F, 22.2°C) and mature for 48 hours.

The formed sheet has good flexibility, gel blocking and wetting integrity.