Absorbent articles containing absorbent foam materials for aqueous body fluids

description

ABSORBENT FOAM STRUCTURES FOR WATER BODY FLUIDS AND ARTICLES

ABSORBENTS CONTAINING SUCH MATERIALS

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Scope of the Invention

The present invention relates to flexible, absorbent microporous open cell polymeric foam materials and retention characteristics that make such materials particularly suitable for use in body fluids, i.e. urine, absorbent articles such as diapers. , parts. de = incontinent adult clothing, bed covers, hygienic protectors, sweat bands, insoles and the like.

Background of the Invention The development of highly absorbent materials and structures for use in diapers, catamenial products, bandages and the like is of substantial commercial interest. Originally, such products rely on various fabric or cotton fibers to provide the absorbing power. 0 The development of multiple layers of cellulose pulp in contact with air has brought further progress in the field of absorbent materials and structures, which generally absorb up to 5-6 times their own weight of aqueous body fluids such as urine. More recently, the use of absorbent gelling materials such as polyacrylates in combination with cellulosic fibers has substantially increased the absorbent capacity of absorbent articles such as diapers, enabling the manufacture of relatively thin diapers that are currently for sale on the market. However, even with these improvements, the search for better absorbent materials and continuous structures continues.

It may seem reasonable to those of ordinary skill in the art to suggest that normal sponge materials in general may be considered open-celled foams to be reasonably useful for absorbent articles and structures. For example, both natural sponges and artificial cellulosic sponges have been used to rinse water and other fluids since time immemorial. However, on a deeper approach, it should be noted that such sponges are not particularly suitable for high acting body fluid absorbent articles of the currently used type. For example,

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The absorbent articles are initially used in the dry state. It is well known that many dry sponge materials are somewhat hard (rigid) and have a rough touch to the skin and are therefore not very suitable for use on diapers and other incontinence products. In addition, many common sponge materials do not have uniform cell sizes and have fully or partially closed cells, which retard running and flowing fluid. be held back by the sponge. Finally, while ordinary sponge materials may soak in subtle amounts of aqueous fluids, they may also release soaked fluids with very little pressure. Similarly, such sponge materials would be totally unsuitable for use in situations where the absorbent structure is used under pressure conditions, for example when a child with diapers sits.

In addition to common sponges, the industry literature and commercial practice is full of descriptions of various types of polymeric foams that may soak in a variety of. fluid for a wide range of purposes. The use of certain types of polymeric foam materials as absorbent article elements such as diapers and catamenial flow products is also known. For example, Karami, US Patent 4,029,100, of June 14, 1977, discloses a retention diaper so that a foam element may be used in the crotch area of ​​the absorbent padding to provide high dry elasticity. to the filling zone.

Certain types of foam materials which are useful in absorbent articles for soaking, conducting and / or retaining aqueous body fluids are described. For example, US Patent 3,563,243 of February 16, 1971, discloses an absorbent diaper-like filler in which the primary absorbent is a hydrophilic foam sheet formed from hydrophilic polymers. Such foam sheets are formed by combining poly (oxyethylene) glycols with diisokinates. Dabi, U.S. Patent 4,554,297 of November 19, 1985 discloses body fluid absorbing cellular polymers that can be used in diapers or catamenial products. Such cellular polymers comprise reaction products of at least one epoxy resin and one poly (alkylene) (oxide) with

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amino termination. Garvey et al, US Patent 4,740,528, April 26, 1988, disclose absorbent composite structures such as diapers, feminine hygiene products, and the like, which contain an absorbent sponge composition made from a certain type of cross-linked polyurethane foam. super deviation.

Despite the known uses of various types of polymeric foam as elements in body fluid absorbent articles, there is a continuing need to identify additional absorbent foam materials with a good combination of characteristics that make such foams particularly useful in commercially available absorbent products. , such as diapers. It has been determined that the best absorbent sponges for body fluids, and especially foams for use in diapers and adult incontinent products, must have the following characteristics:

(a) flexibility and preferably compression recovery for improved comfort and performance;

(b) an acceptable fluid acquisition rate such that the foam readily accepts and soaks urine or other fluids;

(c) relatively good drift and good fluid distribution characteristics such that the foam conveys the soaked urine or any other fluid out of the area where the fluid is initially soaked in the foam and for the unusual balance of the foam structure, thus allowing subsequent spurts to be accommodated;

(d) a relatively high storage capacity with a capacity of. relatively high fluid under load; that is, under compressive pressure; and (e) a relatively low density for the foam to exhibit a highly adequate storage capacity and to compress a thin soft material;

(f) a relatively higher affinity for absorbing body fluids than that manifested by any other components of absorbent articles so that the foam material can drain (divide) fluids from these other components and

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keep such fluid stored inside the foam structure.

It should be noted that the absorbent foams with the above characteristics provide the characteristics of acquisition, transport, storage of fluid that are required for use in high performance absorbent articles. The best foams should preferably also be soft to the touch. Of course, absorbent foams for contact or proximity to the skin should not cause any damage or irritation to the skin or expose the user to toxic chemicals. Since they are intended for use in disposable articles such as diapers, the preferred ideal foams should also be relatively inexpensive and easy to make and should be compatible with solid waste transmission systems such as filler, incineration It is also noted that the manufacturer of absorbent articles improving absorbent foam materials of the type described represents a substantial advance in the industry. Absorbent articles containing such foams must have a desirable dry integrity, allow for adaptation during the entire period in which. The article is worn, does not degrade in shape during use and provide the skin to remain dry in a desirable manner.

Absorbent articles containing such foam structures should also be easier to manufacture on an industrial scale. For example, diaper product cores may simply be stamped from continuous foam sheets and may be designed to have considerably higher integrity and more uniformity than ready-to-dry absorbent cores. Such foams may further be molded in any shape desired, or even formed into integral unitary or underwear-shaped diaper structures. Alternatively, such foam materials may be combined, for example, bonded with other conventional absorbent structure components.

The present invention identifies the parameters that define the ideal absorbent foam materials that are particularly suited for use in body fluid absorbent articles such as urine. This invention also provides absorbent foams which

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There are a number of disadvantages to the foam materials used hitherto in body fluid absorbent articles.

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SUMMARY OF THE INVENTION

In aspects of the composition, the present invention relates to a certain type of polymeric foam material which is particularly suitable for the absorption and retention of aqueous body fluids, for example urine. Such foam material comprises a flexible hydrophilic structure formed from a plurality of interconnected open cells. This cellular foam structure has, when used as an absorbent material, a pore volume of from about 12 to 100 mL / g and a specific surface area of ​​from about 0.5 to 5.0 m / g such as is determined by suction. capillary. The foam structure also has a compressive deflection resistance such that there is one. 5.1 kPa limiting pressure which produces, after 15 minutes, a tension between about 5Z to 95Z of compression of the structure when it is saturated to its free absorbing capacity with 65-5 dynes / cm of synthetic urine at 37 ° C.

Preferred absorbent foam materials with these characteristics may be prepared by polymerizing a specific type of water-in-oil emulsion with a relatively small amount of one oil phase and a relatively large amount of a water phase. This type of polymerizable emulsion is generally known as a High Internal Phase Emulsion or HIPE ”(High Initial Phase Emulsion”).

The oil phase that forms the particular HIPE water-in-oil emulsions. which may be used to prepare the preferred absorbent foams comprises from about 3Z to 41Z by weight of a water-insoluble monofunctional glassy monomer component, from about 27Z to 73Z by weight of an insoluble monofunctional rubbery comonomer component in water; from about 8Z to 30Z by weight of a water-insoluble polyfunctional crosslinked bonding component and from about 2Σ to 33Z by weight of an emulsifying component which is soluble in the oil phase and which allows an emulsion to be made. stable

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I 20 for polymerization. The water or internal phase that forms the water-in-oil HIPE emulsions that can be used to prepare such preferred foams comprises an aqueous solution containing from about 0.2 to 40% by weight of a water-soluble electrolyte. The weight ratio of the water phase to the oil phase in these HIPE water in oil emulsions ranges from about 12: 1 to 100: 1.

Water-in-oil emulsions that can be used to prepare the preferred absorbent foam material of this invention are polymerized under conditions that provide open cell foam structures with. the structure and resistance to the above mentioned compression deflection characteristics. Subsequent post-polymerization treatment of such foams should often be necessary to make the hydrophilically suitable foam materials ready to absorb aqueous body fluids.

In aspects of this article, the present invention relates to incontinence absorbent articles, such as diapers using these polymeric foam absorbent materials as at least a part of their core fluid absorbing element. The absorbent articles of the present invention generally comprise a liquid impervious backsheet (or water impervious skin on the foam itself) and a polymeric foam absorbent material of the type described above. 0 absorbent polymeric foam material is associated with the bottom sheet such that the foam absorbent material. It is located between the bottom sheet and the user fluid discharge region of the absorbent article.

BRIEF DESCRIPTION OF THE RECORDS

Figure I of the engravings is a photomicrograph of the interstices of a typical absorbent HIPE foam of this invention.

Figure 2 is a sectional representation of a disposable diaper utilizing the absorbent foam material of this invention as an hourglass-shaped fluid storage / dispensing component in a double layer configuration absorbent diaper core.

Figure 3 is a cross-sectional view of an adapted article.

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such as the disposable underwear using the absorbent HIPE foam structure of this invention as the absorbent core.

Figure 4 is a separate view of the components of a diaper structure also having a double layer core configuration with an hourglass-shaped fluid acquisition layer on an absorbent foam-shaped fluid storage / distribution layer. modified hourglass.

DETAILED DESCRIPTION OF THE INVENTION

As already mentioned the present invention is based on the use of a certain type of polymeric foam material very specifically defined as one. absorbent for downloadable aqueous body fluids such as urine. These polymeric foam pads can thus be used in whole or in part as absorbent cores of absorbent articles such as diapers, incontinent pads, training pads and the like.

Polymeric foams can generally be characterized as structures obtainable when a relatively monomer-free gas or relatively monomer-free liquid is dispersed in a liquid containing polymerizable monomers, followed by polymerization of the polymerizable monomers in the liquid containing surrounding monomers. the bubbles. The resulting polymerized dispersion may be in the form of a porous solidified structure which is an aggregate of cells whose walls and boundaries comprise solid polymerized material. The cells themselves contain the relatively monomer-free gene or relatively monomer-free liquid, which prior to polymerization bubbles into the liquid dispersion. As will be described in more detail below, the preferred polymeric foam materials useful as absorbents for this invention are those prepared by polymerizing a particular type of oil-in-water emulsion. Such an emulsion is formed from a relatively small amount of a polymerizable monomer-containing oil phase and a relatively larger amount of a relatively monomer-free water phase. The water phase

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Mod. / 1 ​​* 2U.OUU and '. The relatively discontinuous inner monomer-free inner shape thus forms the dispersed bubbles surrounded by the polymerizable monomer-containing oil phase. Subsequent polymerization of the monomers in the continuous oil phase forms the cellular foam structure. The aqueous liquid remaining in the foam structure formed at the time of polymerization may be removed by pressing and / or drying the foam.

Polymeric foams, including ideal foams prepared from these oil-in-water emulsions, may have relatively open or relatively closed cells, depending on the extent to which cell walls or windows, ie cell windows, are formed. filled with polymeric material. The polymeric foam materials useful in the absorbent articles and structures of this invention are those with relatively open cells, the individual cells being the foam. most of the time not completely isolated from each other by polymeric material from the cell walls. Thus, the cells in. such substantially open cell foam structures have intercellular openings or windows which are large enough to allow rapid transfer of fluid from one cell to another cell within the foam structure.

In substantially open cell structures of the type useful in this case, the foam should have a cross-linked character, the individual cells being defined by a plurality of closely spaced 3-dimensionally connected webs. The strands of the polymeric material forming the branched webs of the open cell foam structure may be referred to as supports. Open cell foams with a typical backing type structure are shown as. In the photomicrographic example of Figure 1. For the present invention, the foam material is open cell with at least 80% of the cells in the foam structure being in place. fluid communication with at least one adjacent cell. Alternatively, a foam material may be considered to be substantially open cell if it has an available pore volume, as described below, which exceeds □ minimum value. for this parameter, also described below.

In addition to having open cells, the polymeric foam pads of this invention have a hydrophilic character. These foams have to

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hydrophilic enough to allow the foam to absorb aqueous body fluids in the amounts specified below. As discussed below with respect to the ideal foam types and methods for foam preparation, the inner surfaces of these foam may be rendered hydrophilic through the particular monomers selected for use in the preparation of polymeric foam, by the action of the residual hydrophilizing agents left on the foam structure after polymerization or by the action of selected post-polymerization foam treatment procedures which may be used to alter the surface energy of the foam structure forming material.

The extent to which polymeric foam structures such as those referred to in this invention are hydrophilic can be quantified by reference to the stress of adhesion manifested on such foams in contact with an absorbable test liquid. A. adhesion stress is defined by the formula

Where AT is the tack stress in dynes / cm;

is the surface tension of a test liquid absorbed by the foam material in dynes / cm;

is the contact angle in degrees between the surface of the foam polymer material and the vector that is tangent to the test liquid at the point at which the test liquid contacts the foam polymer surface.

For a given hydrophilic foam material. The adhesion stress manifested by the foam can be determined experimentally using a procedure in which the weighting of one. Test liquid, for example synthetic urine, is measured by a foam sample of known dimensions and specific surface area of ​​capillary suction. This procedure is described in more detail in the following section TESTING METHODS. Useful absorbent foams in this invention are usually those which have been taken hydrophilic to the extent that they have an adhesion stress of from about 15 to 65 dynes / cm, more preferably from about 20 to 65 dynes / cm as determined. by taking synthetic urine capillary suction having a j

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In addition to being open cell and hydrophilic. The polymeric foam materials useful in this invention are those having a specific set of characteristic properties or mechanical and structural capacities. It has been found that polymeric foams with such characteristic properties or selected structural and mechanical capacities will, as a result, have performance, for example fluid handling, properties which make such foams particularly suitable and useful as absorbent for body fluids.

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I) STRUCTURAL ASPECTS

The somewhat interrelated and interdependent specific structural properties have been identified as being essential for the realization of foam absorbents that are particularly suitable for the absorption of aqueous body fluids. It should be noted that the materials of: foam^- of the present invention may have structural properties which are different from those specified below. at some point before contact between the foam and aqueous body fluid has to be absorbed. For example, during manufacture, transport, storage, etc., these foams may have a pore volume, specific surface area, density and / or cell size values ​​in addition to the values ​​set forth below for these parameters. However, such foam absorbent structures are, however, within the scope of this invention, if they later undergo physical or rheological changes, so that they then have the required values ​​specified below for these, structural properties at least in some respects. point during the subsequent contact period between the absorbent structure and the aqueous body fluid to be absorbed by such means. foam can be summarized as follows:

A) PORE VOLUME pore volume is the measurement of the volume of the openings or cells in a porous foam structure per unit mass of solid material (polymer structure plus any residual solid) forming the foam structure. Pore ​​volume may be important in influencing

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in a number of performances and mechanical capacities of these absorbent foams. Such performances and mechanical capabilities include the absorbent capacity of aqueous body fluid foams, the point and rate of fluid distribution within the structure by conducting absorbed aqueous fluids from one part of the absorbent foam to another, foam flexibility and characteristics. compression deflection foam.

pore volume may be determined by any suitable experimental method which gives an accurate indication of the actual pore volume of the structure. Such experimental methods will generally entail measuring the volume and / or mass of a test liquid that can be introduced into the foam structure and is therefore representative of the volume occupied by open foam cells. For this reason, the pore volume parameter of these foams may also be referred to as the available pore volume.

A conventional way to terminate the available pore volume. experimentally entails introducing a low surface tension liquid such as isopropanol into the foam structure from outside the foam structure. A procedure for determining the available pore volume using isopropanol is set forth below in the TEST METHODS section. Note, however, that alternative test liquids and other procedures may be used to determine the available pore volume.

pore volume of the absorbent foams useful herein can be influenced &amp; controlled by adjusting one. number of foam composition and processing characteristics. For example, with these ideal HIPE emulsion based foams, these pore volume influencing aspects may include an oil to water ratio of the HIPE emulsion, type e- amount of water phase electrolyte used, type and amount- gives. phase of: emulsified oil used post-polymerization foam compression phases for foam washing and / or densification purposes and degree of recovery of the polymerized foam structure after such compression phases.

The foam materials of this invention generally have a pore volume of from about 12 to 100 mL / g; preferably between about

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at 70 mL / g, more preferably between about 25 to 50 mL / g. Such pore volume scales are intended to be an inclusive definition of the theoretical pore volume for the foams covered by this invention. Thus, if any experimental method that can reasonably give theoretical approximate pore volume measurements gives values ​​within the stated values, then the foam materials tested by such method are within the scope of this invention.

B) SPECIFIC HAIR SUCTION SURFACE AREA

Another essential structural aspect of these foam materials is a certain specific surface area of ​​capillary suction. The capillary suction-specific surface area is generally a measure of the polymer network liquid-accessible surface area that forms a particular foam per unit mass of the volume foam material (Mayan polymer structural material residual matter). solid). The specific surface area of ​​capillary suction is determined by the dimensions (i.e. diameter) of the cell units in the foam and the size (length, width and thickness) of the supports forming such cell units. The specific surface area of ​​capillary suction is thus a way of quantifying the total amount of solid surface provided by the foam network to the extent that such surface participates in absorption.

The specific surface area of ​​capillary suction of an open cell foam structure such as these absorbent foams and the appearance of the foam are. influences capillary (or capillary suction) manifested by: foam. It turned out that the capillarity of. foam has to. controlled and selected so that these foam materials have sufficient capillarity to provide acceptable fluid retention while allowing some fluid conduction within the foam structure. Surface area adjustment capillary suction, as well as the control of the hydrophilicity of the foam polymer surfaces, is thus how to provide the required degree of capillarity for the absorbent foams of this invention. Foams with a relatively high capillary suction specific surface area provide a very desirable combination of high capacity (and low density) and high capillarity. The high specific surface area and a consequence of the fineness of the supports.

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that form the foam structure.

The specific surface area of ​​capillary suction of these foam absorbents is influenced and controlled by adjusting various similar composition and processing parameters, which affect the pore volume of the foam. For HIPE emulsion based foams, composition parameters include the oil / water ratio of the HIPE emulsion, and the type and amounts of monomers, emulsifiers, and electrolytes used in the HIPE emulsion: Process parameters that affect specific surface area. Suction capillaries include mixing energy and temperature.

As noted, for the purposes of this invention, the specific surface area of ​​any foam material contemplated for use in the present invention can and will normally be determined by the procedure involving the principle of capillary suction. In such a procedure, the specific surface area of ​​capillary suction is measured by measuring the amount of capillary uptake of a low surface tension liquid (e.g., ethanol) that occurs within a foam sample. with a given mass and dimensions. A detailed description of such a procedure for determining a specific foam surface area is established by the capillary suction method in the TESTING METHODS section below. Any reasonable alternative method for determining the specific surface area of ​​capillary suction may also be used.

The open cell porous absorbent foams useful in the present invention are those prepared to have a certain type of capillary suction specific surface area characteristics. In particular, these foams have a specific suction surface area.

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which ranges from about 0.5 to 5.0 m / g, preferably from about 0.75 to 4.5 m / g, more preferably from about 1.0 to about

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at 4.0 m / g- Hydrophilic foams having such capillary suction-specific surface area values ​​have been found to typically have an especially desirable balance of absorbent capacity, fluid retention, and fluid conduction or distribution characteristics for body liquids. aqueous as urine.

C) ADDITIONAL OR ALTERNATIVE STRUCTURAL ASPECTS

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There are two additional structural aspects of these absorbent foams that are interrelated to the pore volume and specific surface area of ​​capillary suction and which can be used as supplementary or alternative forms to characterize the foams of this invention, which are the foam density. and the average size or diameter of the foam cells. Each of these additional / alternative structural aspects are described as follows:

1) FOAM DENSITY

The density of these foam materials, such as pore volume and capillary suction specific surface area, may influence a number of mechanical characteristics and performance of these absorbent foams. These include absorbent capacity for aqueous body fluids, foam interior flow rate and distribution rate, foam flexibility, and characteristics. deflection, and compression. Also important is the density of the foam absorbent structures which may determine the cost effectiveness of such structures.

Foam density in grams per cm of airborne foam volume is specified herein on a dry basis. Thus, the amount of absorbed aqueous liquid, for example, that residual liquid which may be left in the foam, for example after HIPE emulsion polymerization, washing and / or hydrophilization, is not taken into account in the calculation and expression of foam density. The foam density as specified herein does not, however, include residual solid material such as electrolyte, emulsifiers, hydrophilizing agents, etc. in the polymerized foam. Such residual material may in fact contribute a significant mass. for foam material.

Any suitable gravimetric procedure which provides a mass determination of solid foam material per foam structure unit volume can be used to measure foam density. For example, the ASTM gravimetric procedure described in more detail in the following section. TEST METHODS is a method that can be used to determine density. For situations where foam sample preparation procedures (drying, aging, pre-bending, etc.) may inadvertently alter the obtained density measurements, den30 * AG0.19 'determination tests may also be used. ?

alternating power. Such alternative methods, for example, may include gravimetric density measurements using a test liquid absorbed within the foam material. This type of density determination method may be useful for characterizing very low density foams, such as the foams of this invention where the drying density approximates the inverse pore volume in the foam [see CHATTERJEE, Absorbency]. , Textile Science and Technology, Vol. 7, 1985, p. 41 ]. As with. pore volume and capillary suction-specific surface area, the foam density limits set forth below are intended to be inclusive, ie they are supposed to follow density values ​​that can be determined by any reasonable experimental test method. .

The foam absorbents of this invention should have base drying density values ​​of from about 0.01 to 0.08 g / cm, preferably from about 0.014 to about 0.05 g / cm and most preferably from about 0.01 to about 0.05 g / cm. from 0.02 to 0.04 g / cm, at which time such foam absorbers find the aqueous fluids to be absorbed. The density of the foam materials may be adjusted within such ranges by controlling many of the same processing and foam composition parameters set forth for pore volume adjustment. The density of these absorbent foam structures does not have to be uniform throughout the structure. Some portions or areas of the foam structure may have relatively higher or lower densities. than others, portions or zones2) CELL SIZE

Another alternative structural aspect or. A supplementary feature of these absorbent foams, which is not essentially an established parameter but which may be useful in the optimal definition of the foam materials of this invention, is cell size. The foam cells, and in particular the cells formed by polymerization of an oil phase containing monomers surrounding bubbles of the relatively monomer-free water phase, would normally have a substantially spherical shape. 0 size or f

The diameter of such substantially spherical cells is thus another parameter commonly used to characterize the overall foams as well as to characterize certain preferred absorbent foams of the type.

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used in this invention. Since the cells in a given polymeric foam sample will not necessarily be the same size, an average cell size, i.e. an average cell diameter will often be specified.

Such pipe foam density, specific surface area of ​​capillary suction and pore volume, cell size is a foam parameter that can have a certain impact on a number of important mechanical aspects and performances of the foam material. absorbent material of this invention. Since cell size is a factor which, together with the specific surface area of. Capillary suction, pore volume, and foam hydrophilicity determine the foam capillarity, cell size is a foam structure parameter that can directly affect the absorbent capacity and internal fluid conduction properties of these foam absorbents. Cell size may further affect the mechanical properties of these foam absorbents including aspects of flexibility, strength and recoverability of compression deflection.

There are a large number of techniques available for determining the average size of cells in foams. These techniques include mercury porosimetric methods well known in the art. The most useful technique, however, for determining cell size in foams involves a simple photographic measurement of a foam sample. Figure 1, for example, is a photomicrograph of a fracture surface of. A typical HIPE foam absorbent structure of this invention. There is a scale representing a dimension of 10 microns. TaL scaling can be used to determine the average cell size through an image analysis procedure. Photomicrographic image analysis of foam samples is, in fact, a commonly used analytical instrument that can be used to determine the average cell size of these foam structures. Such a technique is described in more detail in US Patent 4,788,225, to Edwards et al, November 29, 1988. This patent is incorporated herein by reference.

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As determined by direct photographic measurement, foams useful as absorbent for aqueous body fluids in accordance with this invention should have an average cell size of from about 5 to about 5%.

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100 microns. More preferably, the cell size ranges from about 10 to 90 microns. Most preferably, the cell size should be between about 15 to 80 microns.

The size or diameter of the cells in these foam pads can be influenced and controlled by variation of the same type of foam. foam composition and processing aspects that influence the specific surface area of ​​capillary suction and the available pore volume. For preferred HIPE-based foams, these primarily include those factors that determine the size of the water phase bubbles in the precursor HIPE emulsion of these polymeric foam structures. Thus, cell size can be varied by adjusting the oil-water ratio of the HIPE emulsion and the type and amount of emulsifier used to form the HIPE emulsion. Cell size can also be altered by simply compressing the solid foam structures after they have been prepared.

As indicated, the cell sizes in these absorbent foams are generally not uniform, so an average cell size can be calculated for any foam sample or zone in the foam sample. It is, of course, possible to use absorbent foams having discrete and identifiable zones with relatively smaller or relatively larger average cell sizes.

II) MECHANICAL ASPECTS

Absorbent foams of a suitable polymeric composition and structural aspects described generally have mechanical properties, eg compressive deflection strength, flexibility, compression deflection recovery, integrity _f softness, etc., which take such gspmnas suitable for use as absorbent structures in. absorbent articles such as disposable diapers. Within the said structural limits, however, it is possible to select certain combinations of parameters and / or certain foam preparation techniques &amp; conditions which make foam absorbents to have particularly desirable mechanical properties. The specific, somewhat interconnected, mechanical properties that have been identified as contributing to the realization of absorbent foams particularly suitable for use in incontinent absorbent articles.

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80 / Μ · · »· 000'0 ?: · 1 / pow can be summarized as follows: A) RESISTANCE TO COMPRESSION DEFLECTION The most important mechanical aspect of these polymeric foams and the strength of the foam absorber as determined by their resistance to compression deflection. The compressive deflection resistance manifested by these foam absorbents is a function of polymeric wool modulus and the dimensions of the supports forming the foam network. 0 The elastic modulus of the supports is in turn determined by a) the polymeric composition of the supports, and b) the extent to which the supports may be plasticized by residual material, eg emulsifiers, water phase synthesis or subsequently hydrophilizing agents. added, left on the foam structure after processing.

In order to be useful as absorbent structures in absorbent articles such as diapers, the absorbent foam materials of the present invention must be suitably resistant to deformation or compression by forces encountered when such absorbent materials are implicated in the absorption and retention. of fluids. Foams that do not have sufficient foaming strength on. terms of deflection resistance; Compressors may be able to acquire and store acceptable amounts of body fluid under no-load conditions, but will very easily yield such fluid under compressive pressure caused by the user's movement and activity of the foam-containing absorbent articles.

The compressive deflection resistance manifested by the foam absorbers used in this invention can be quantified by the. Determining the Amount of: Stress Produced in a Sample of Saturated Foam Material Maintained at a Limiting Pressure for a Period of Time For the purposes of this invention, such measurements may be made on a sample of standard size (cylinders). with a thickness of 0.8 cm and a circular cross-sectional area of ​​6.5 cm). Such samples are saturated with a synthetic urine with + ^f surface tension of 65 - 5 dynes / cm and then subjected to a limiting pressure of 5,1 kPa over a period of 15 minutes at a temperature of 37 ° C. The amount of voltage produced in such)

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Mod. 71 - 20,000 ex. · 90/08 i

Testing is reported as a percentage of the original sample thickness that the compressed sample thickness represents. The method for carrying out this particular type of test to quantify compressive deflection resistance is set forth below in more detail in the TEST METHODS section .

The absorbent foams useful herein are those which have a compressive deflection resistance such that there is a limiting pressure of 5.1 kPa which produces a tension between about 5Z to 95Z of compression of the foam structure when saturated until its free absorbent capacity with synthetic urine having a surface tension of 65 + 5 dynes / cm. The voltage produced under such conditions should preferably range from about 5Z to 75Z, more preferably from about 5Z to 50Z. For the preferred HIPE foams of this invention, the compressive deflection resistance can be adjusted to stress values ​​within the stated 1 magnets by an appropriate selection of monomer types, comonomers and crosslinking types and concentrations in combination with a selection of appropriate emulsion formation and emulsion polymerization conditions and techniques. Thus, such preferred foams may be formed from materials with elastic modules large enough to provide adequate deflection resistance even if such foams have a low density and very thin supports to provide a high specific surface area. B) FLEXIBILITY

The absorbent foams of this invention must be sufficiently flexible of shape a. can be used in. absorbent products that are adapted to the shape of the wearer's body. The characterization of these absorbent foams as flexible therefore means that these foams may be deformed; or folded to the point necessary for use. absorbent articles without significant damage to their structural integrity or significant loss of absorbent properties

Preferred absorbent foams of this invention must also be sufficiently flexible to withstand the compressive and deforming forces encountered during the preparation, processing, packaging, transport and storage of absorbent articles containing such materials.

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Foam materials. Disposable diapers, for example, are usually packaged and marketed in a folded condition wherein the diaper core is folded longitudinally and transversely. Disposable diapers are also marketed in stacks. of folded diapers, which stacks are contained and would compress by the packaging surrounding them. Similarly, the compressive and deforming forces to which these foam absorbers may be subjected during processing and commercialization may be even greater than those which. are applied to the foam materials in use. Given the nature of the treatment of these absorbent foams, the preferred absorbent foam materials of this invention have flexibility characteristics that can be quantified by reference to their ability to withstand bending without suffering; significant damage to its structural integrity. The following TESTING METHODS section describes a procedure for determining the flexibility of these absorbent foams by determining whether a; how many times a foam sample of a given size can be folded around a cylindrical mandrel at a specific rate without breaking. Preferred foams of this invention are those sufficiently flexible that, when used as an absorbent for body fluids, the saturated foam material at 37 ° C may be subjected to this folding test without breaking (i.e. manifold®; folding at least one cycle). Preferably, the preferred foams may be folded at least 2 times, preferably at least 5 times without breaking when there is a test procedure. C) ADDITIONAL OR PREFERRED MECHANICAL PROPERTIES

In addition to the deflection, compressive strength and flow characteristics, the ideal foam absorbers of this invention also have several additional types of mechanical attributes. These preferred mechanical attributes include compression deflection relative to desirable recovery (i.e. elasticity), foam integrity and softness of touch. Each of these ideal mechanical properties is described in more detail as follows:

1) COMPRESSION DEFLECTION RECOVERY

The recovery from deflection '. compression refers to the tendency or

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propensity of a piece of foam material to return to its original dimensions after being deformed or compressed under forces. encountered during manufacture, storage or use. For the purposes of the present invention, the recovery of compression deflection of these preferred foam absorbers should be determined in the foams which, at their proper point of use density and often under such conditions, will contain the absorbed body fluid. . Similarly, recovery from compression deflection can be measured in foams that are dry or saturated with synthetic urine.

A suitable procedure for determining compression deflection recovery is set out in the METHODS section. Such a procedure generally involves compressing and releasing a standard sized foam sample that is dry or saturated to its full extent. free capacitor absorbent with synthetic urine. The samples are kept at a compression of 50Z for a certain period of time and then released from the compression. 0 point, as far as the sample regains its own. thickness within one minute after release of compressive force and taken as a measure of recovery a. from the propensity of the compression deflection (strength) of the sample.

Ideal absorbent foams of this invention generally exhibit a recovery of at least 85Z of the original gauge when dry and / or at least 75Z of the original gauge when wet after one minute. Preferably, such ideal foam materials will have a recovery from. At least 90Z dry and / or 80Z wet compression ratio.

2) FOAM AND SOFT INTEGRITY

Although not. is absolutely essential for the construction of operable absorbent structures or. Useful, the HIPE foam absorbers of this invention should have the additional mechanical attributes of structural integrity in use and softness (no irritation) to the touch. For example, the foam materials to be used in. Such absorbent articles, such as child diapers, must often be subjected to the dynamic and static forces that arise when the user walks, runs, hops or jumps. Such forces may not only tend to compress the foam pads and expel the fluid therefrom, but forces may also tend to tear or shred from any material.

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Mod. / 1 ​​- AI.OIXJ ex. The other form is the foam structure. Of course, it would be advantageous for foam structures that are used in this form to have sufficient structural integrity to minimize the incidence of foam tearing or breaking during use.

The foam elements of this invention may also be used in absorbent articles as described below in configurations wherein the surface of the foam material may be in contact with or in proximity to the wearer's skin. Similarly, it is highly advisable for the surface of these foam pads to be acceptably soft and non-irritating to the skin.

III) FLUID ABSORPTION AND HANDLING CHARACTERISTICS

Absorbent foams of a suitable polymeric composition and the structural characteristics and mechanical aspects referred to herein generally exhibit desirable and useful body fluid absorption and handling characteristics. Such fluid absorption and handling characteristics are in themselves. In turn, the attributes of these ideal foam materials make the foams particularly suitable for use as absorbent structures in. absorbent articles designed to acquire and maintain aqueous body fluids.

The most relevant fluid absorption and handling characteristics for the realization of these absorbent foams are, A) the absorbent equilibrium capacity of the foam, especially under pressure, B) a. vertical conduction rate of the fluid through the foam, C) the absorptive capacity of the foam at specific reference driving heights, and D) the ability of the absorbent foam structures to conduct (divide) the fluid from the absorbent structures with which the foam may be in contact. Each of these features is described in more detail below:

A) ABSORBENT CAPACITY AND ABSORBENT CAPACITY UNDER PRESSURE

Absorbent capacity is the total amount of test fluid (synthetic urine) that a given foam sample absorbs: for its cell structure per unit mass of solid material in the sample. Pressure absorbing capacity refers to the amount of fluid retained without any pressure (free capacity) at which the foam retains within its cellular structure when the foam sample is subjected to

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Mod. 71 - 2OO00 ex. - 90/08 a compressive force. Such absorbent capacity measurements are calculated for these purposes under equilibrium, ie after the foam sample has been allowed to acquire and / or maintain all possible fluid for the period of time required to form a foam sample. completely saturated with the test liquid. Foam materials particularly useful as absorbent in absorbent articles such as diapers exceed a minimum free absorbent capacity and also exceed a minimum pressure capacity.

Using the procedure described in more detail below, in the TEST METHODS section, the free absorbent capacity and the pressure absorbent capacity can both be determined for any foam sample given by a gravimetric analysis technique. In such a technique, a foam sample of a specific known size and weight is placed onto the test fluid plate (synthetic urine) and allowed to absorb the test fluid to equilibrium. After removal of the saturated fluid sample, the amount of fluid maintained per gram of foam, that is, the free hold capacity is then calculated. This sample of. Saturated foam is then phased to compressive pressure. progressing in various increments, the expressed fluid being conducted outward in each phase. The amount of fluid retained in the sample at each pressure fill is about 0.1 psi (6.9 kPa) and is determined gravimetrically.

To be particularly useful in the urine absorbent absorbent articles, the foam absorbents of this invention should have a free balance capacity of at least about 12, preferably at least about 20 mL. of synthetic urine per gram of dried foam material. The capacity of such materials to foam under a limiting pressure of about 0.74 psi (5.1 kPa) maintained for 15 minutes at 37 ° C should be at least about 5Z, preferably at least about 20Z, of free capacity. of equilibrium of such foams. B) VERTICAL DRIVING ACTION

Another fluid handling attribute of these absorbent foams useful herein relates to their ability to rapidly move or conduct acceptable amounts of body fluids through their foam structures. Vertical conduction, ie fluid conduction

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in a direction opposite to that of gravitational force, is one of the particularly acceptable performance attributes for these absorbent foam materials. This is because such materials are often used in absorbent articles so that in order for fluid to be absorbed, it has to be moved within an article from a relatively lower position to a relatively higher position within the absorbent core of the article.

The vertical driving action is related to the magnitude of the capillary suction driving force that moves the liquid through the foam and keeps it in the foam structure. The parameters characterizing the foam related to the vertical conduction propensity thus provide an indication of how the ideal foams herein will act as absorbent structures in absorbent articles. For the foam absorbers of this invention, the fluid conduction propensity can: be quantified. by reference to the vertical conduction rate test and the driving absorbency test.

1) RATE OF. VERTICAL DRIVING vertical conduction rate test measures the time taken for a colored test liquid (eg synthetic urine) from a reservoir to travel a vertical distance of 5 cm across a foam test strip of a given size when The test is performed at 37 ° C. Such a vertical conduction rate test is described in more detail in the TEST METHODS section. To be particularly useful in urine absorbent absorbent articles, foam absorbents. of this invention should preferably have a vertical conduction rate of 5 cm to no more than about 30 minutes when carrying synthetic urine (65-5 dynes / cm). Preferably, the ideal conductive pads of this invention should have a conduction rate 5 cm vertical not more than about 5 minutes when carrying synthetic urine.

2) CAPACITY. VERTICAL DRIVING ABSORBENT 'vertical conduction absorbing capability test carried out in conjunction with the vertical transport rate test. The vertical conductive absorbent capacity measures the amount of test fluid per gram of absorbent foam that is carried for each 1 inch (2.54 cm) vertical section of the same standard sample size.

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Mod. 71 · 20,000 · κ. &lt;^ 0/06

Ο cougar in the vertical driving rate test. Such determination is usually made after the sample has been allowed to transport the test fluid vertically to an equilibrium state (e.g., after about 18 hours). As with the vertical conduction rate test, the vertical absorbency test is described in more detail below in the TEST METHODS section.

To be particularly useful in the urine absorbent absorbent articles, the preferred foam absorbents of this invention must have a water. absorbent, vertical capacity such as mnna. At a height of 11.4 cm (4.5 inches), the foam test strip has an absorbent capacity of at least about 10 mL of synthetic urine (65-5 dynes / cm) per gram of absorbent foam. Preferably,. These ideal foam absorbers have a vertical conduction-absorbent capacity of 11.4 cm (4.5 cm) between about. 20 to 45 mL of synthetic urine per gram of foam.

C) DIVISIONS

These absorbent foam structures will often be used in absorbent articles with other types of absorbent structures, which may also participate in the acquisition, distribution and / or storage of discharged body fluids. In contexts where these foam structures serve primarily as a fluid storage / redistribution component in absorbent articles, it is advisable for such foams to have one. propensity to pull body fluids into the foam structure from other absorbent components that also absorb such fluids. Such a propensity for conducting fluid from other absorbent article components is known in the art as division. The concept of dividing certain procedures for determining splitting is described, for example, in Weisman / Goldman patent, . USA. 4,610,678, September 9, 1986 .. When tested by splitting action using procedures similar to those disclosed in U.S. Patent 4,610,678, the absorbent foam structures of this invention exhibit particularly desirable fluid splitting characteristics.

IV) IDEAL HYPE ABSORBENT FOAMS

As mentioned, the ideal absorbent foam materials that are

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«0 (04 · '» »ΟΟΟΌδ · ΙΖ P ° W can be prepared to meet the required and ideal characteristics in terms of structure, mechanics and fluid handling, as mentioned above, are the products that result from the polymerization of certain water-based emulsions. having a relatively high ratio of water phase to oil phase. Emulsions of this type, which have these relatively high water to oil phase ratios are known in the art as high internal phase emulsions [HIPEs or HIPE emulsions cf. the original British expression High Internai Phase Emulsion]. Ideal polymeric foam materials that result from the polymerization of such emulsions are referred to as: HIPE foams.

The relative amounts of the water and oil phases used to form the HIPE polymeric foam precursor emulsions are, among other parameters, important in determining the action, mechanical and structural properties of the resulting ideal polymeric foams. In particular, the water to oil ratio in the foam forming emulsion may influence the foam density, cell size, specific surface area of ​​the foam and the dimensions of the foam forming pads. The emulsions used to prepare the ideal polymeric HIPE foam materials of this invention should generally have a water to oil phase ratio of from about 12: 1 to 100: 1, preferably from about 20: 1 to 70: 1, more preferably. between about 25: 1 and 50: 1.

The continuous oil phase of the emulsions used to prepare these ideal HIPE emulsions comprises the monomers that will be polymerized to. The monomer comprises a major monomer component, a component; comonomer and a braiding agent component. The selection of particular types and amounts of monomer (s) and monofunctional major comonomer (s) and agent (s). polyfunctional braiding (s) may be important for the realization of HIPE 'absorbent foam materials; with the combination of mechanical structure and desired fluid handling properties that make such materials suitable for use in this invention.

The major monofunctional monomer component used in the oil phase of ideal foam precursor HIPE emulsions comprises one or more monomers which tend to impart glazing properties to the resulting foam structure. Such monomers are hereinafter referred to as ο

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as glazed monomers and are, for the purposes of this invention, defined as monomeric material which will produce high molecular weight homopolymers (greater than 6000) with a glass transition temperature, Tg, above 402 ° C. The ideal monofunctional glass monomer type is a styrene based monomer, with styrene itself being the most advised monomer of its kind. Substituted styrene may also be used, for example monosubstituted. such as methyl styrene-p. 0 The monofunctional glass monomer component typically comprises from about 32 to 412, more preferably from about 72 to 402 by weight of the oil phase used, to form the HIPE emulsion to be. polymerized.

The monofunctional comonomer component, which will also be present in the Oil phase of the HIPE emulsion with the glassy main monomer material, comprises one or more comonomers which tend to impart rubbery properties to the foam structure therefrom. it works. Such comonomers are hereinafter referred to as rubbery comonomers and are, for the purposes of this invention, defined as monomeric materials which will produce a high molecular weight (greater than 10,000) in the homopolymers having a glass transition temperature, Tg, of about 40 ° C, or any less. The mohunctional rubbery comonomers of this type include, for example, alkyl acrylates, alkyl methacrylates, allylacrylate, butadiene, substituted butadienes, vinylidine halides and combinations of such comonomers and types of comonomers. Ideal rubbery comonomers include butylacrylate, ethylhexylacrylate-2, butadiene. isoprene and combinations of these comonomers. Of all these types, the most recommended are butylacrylate and ethylhexylacrylate-2. 0 monofunctional rubbery comonomer component comprises in. generally from about 272 to 732, preferably from about 272 to 662, by weight of the oil phase.

In HIPE emulsions used to form these ideal absorbent foams, either the main glazing monomer (s) or: the monofunctional rubbery tenter (s) comonomer (s) be present in the oil phase at the above concentration parameters. In addition, the molar ratio of the monofunctional glassy monomer component to the monofunctional rubbery component will generally be from about 1:25 to 1.5: 1, more preferably from about 1: 9 to 1.5: 1.

Since the polymer chains formed from monomer (s)

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The glassy number (s) and the rubbery comonomer (s) must be braided, the oil phase of the emulsions used to form these ideal HIPE foams must also contain a polyfunctional braiding agent. As with monofunctional monomers and comonomers, it is very important to select a type and amount of braiding agent for the eventual realization of ideal polymeric foams with the desired combination of structural, mechanical and fluid absorption properties.

Depending on the type and amounts of monofunctional monomers and comonomers used, and depending on the desired characteristics of the ideal polymeric foams eventually made, the component of the polyfunctional braiding agent for use in the ideal HIPE emulsion foam precursor may be selected from. from a wide range of polyfunctional, preferably difunctional, monomers. Thus, the braiding agent may be a divinyl aromatic material such as divinylbenzene, divinyltolulene or. diallylphthalate. Alternatively, divinyl aliphatic braids, such as any of the diacrylic acid esters of the polyols, may be used. The most suitable foaming agent for preparing the most acceptable foam from these HIPE emulsions is divinylbenzene.

braiding agent of any kind will normally be used in the oil phase of these ideal foam-forming emulsions in an amount of about 87%. 40%, more preferably from about 10% to 255; by weight. Amounts of plaiting agent (s) within these limits usually provide a plaiting molar concentration of from about 5 mole% to about 60 mole%, based on the total monomers present in the oil phase.

The major portion of the oil phase of these ideal HIPE emulsions comprises the said monomers, comonomers and braiding agents which eventually form ideal polymeric foam absorbers. It is therefore essential. that these monomers, comonomers and braking agents are substantially insoluble in water, so that they are primarily soluble in the Oil phase and not in the water phase. The use of such water insoluble monomer materials ensures that the emulsions

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HIPE ideals have the proper characteristics and their stability to be realized.

It is, of course, highly advised that monomers, comonomers and agents

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braids used to form these ideal polymeric foam materials are of a type which makes the eventually formed foam polymer suitably non-toxic and suitably chemically stable. Thus, such monomers, comonomers and braiding agents should have little or no toxicity at very low residual concentrations, which may be encountered during post-polymerization foam processing and / or during use.

Another essential oil phase component of the HIPE emulsions used to form the ideal polymeric foams of this invention comprises an emulsifier which allows the formation of stable HIPE emulsions. Such emulsifiers are those which are soluble in the oil phase used to form the emulsion. The emulsifiers used may be nonionic, cationic, anionic or amphoteric as long as the emulsifier or combination of emulsifiers forms a stable emulsion. The types of emulsifiers. which may be used to provide an emulsion component—

Mod. 71 · 20,000 βκ. Suitable characteristics include sorbitan fatty acid esters, polyglycerol fatty acid esters, polyoxyethylene fatty acid (POE) esters. Particularly preferred are sorbitan fatty acid esters such as sorbitan monolaurate (SPAN®20), sorbitan monooleate (SPAN® 80) and combinations of sorbitan trioleate (SPAi® 85) and sorbitan monooleate (SPA1®80). A particularly preferred emulsion combination comprises the combination of sorbitan monooleate and sorbitan trioleate in a ratio of. greater than or equal weight. to about 3.1, preferably about 4: 1. Other operable emulsifiers include TRIODAN® 20, which is marketed as polyglycerol in the form of. an ester by Grindsted and EMSORB 2502. which is a sorbitan skioleate marketed by Henkel.

The emulsifying component generally comprises from about 2 to about 2%. 33Z by weight of the oil phase used to form the. HIPE emulsions. which, in turn, are used to prepare these ideal polymeric foams. More preferably, the emulsifying component comprises from about 4Z to 25Z by weight of the oil phase._r

In addition to the monomeric and emulsifier components described above, the oil phase used to form these polymerizable HIPE emulsions may also contain additional optional components. A phase component

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Mod. 21 · 20,000 βκ. 90/08 of optional oil may be an oil soluble polymerization initiator of the general type described below. Another possible optional oil phase component may be a substantially water-insoluble solvent for the oil phase monomer and emulsifying components. Such a solvent must, of course, be unable to dissolve any optionally polymerized monomers. 0 The use of such a solvent is not ideal, but if such a solvent is used, it will generally comprise no more than about 10% by weight of the oil phase.

As indicated, the above described HIPE oil phase is a continuous phase in the emulsions to be polymerized to realize the ideal foams of this invention. The discontinuous internal phase of the polymerizable HIPE emulsions is the water phase which is generally an aqueous solution containing one or more dissolved components. An essential dissolved component of the water phase is a water soluble electrolyte. 0 The electrolyte dissolved in the water phase of the HIPE emulsion serves to minimize the tendency of monomers and plaiters that are primarily oil soluble as well. dissolve in the water phase. This in turn can minimize the extent to which, during emulsion polymerization, the. polymeric material fills the cell windows at the oil / water interfaces formed by the water phase bubbles. Thus, the presence of the electrolyte and the resulting ionic strength of the water phase can determine if and to what extent the resulting ideal polymeric foams may have open cells.

Any electrolyte providing ionic species to provide ionic strength to the water phase may be used. Ideal electrolytes are mono-, di- or trivalent inorganic salts such as water-soluble halides, for example chlorides, nitrates to alkali metal sulfates and alkaline earth metals. Examples include sodium chloride, calcium chloride, sodium sulfate and magnesium sulfate. 0 Calcium chloride is most advisable for use in these ideal embodiments of this invention.

In general, the electrolyte will be used in the water phase of HIPE emulsions, which are precursors of these ideal polymeric foams at a concentration ranging from about 0.2% to about 40% by weight of the water phase. Preferably, the electrolyte comprises from about 0.5Z to 20Z by weight of the oil phase.

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HIPE emulsions used to prepare these ideal polymeric foams generally contain a polymerization initiator. Such initiator component is usually added to the water phase of the HIPE emulsions and can be any conventional water soluble free radical initiator. Materials of this type include compounds, peroxygen, such as sodium, potassium and ammonium per-sulfates, caprylyl peroxide, benzoyl peroxide, hydrogen peroxide, cumene hydroperoxides, butyl diperphlate, tertiary butyl perbenzoate, sodium peracetate, sodium percarbonate and the like. Conventional redox starter systems may also be used. Such systems are formed by combining said peroxygen compounds with reducing agents such as bisulfite, L-ascorbic acid or ferrous salts.

Starter material may comprise up to about 5 moleZ based. total moles of the polymerizable monomers present in the oil phase. Preferably, the initiator comprises from about 0.001 to 0.5 mole Z with. based on the total moles of polymerizable monomers in the oil phase. When used in the oil phase, such initiator concentrations may be achieved by adding initiate E to the water phase to a point between about 0.02Z to 0.4Z, preferably about 0.1Z to 0.2Z. by weight of the oil phase.

By the process described in more detail below, the oil and water phases as above are combined under stirring to form an emulsion in the form of a stable foam. This HIPE foam is then subjected to polymerization conditions which are sufficient and suitable to cause the polymerization of the monomers in the oil phase and thus to form a solid cellular foam structure.

The chemical nature, formation and morphology of the polymer material forming these foam structures are determined by the type and concentration of the monomers. _x comonomers and braiding. HIPE emulsion and the emulsion polymerization conditions used. Such polymeric material will normally not be swellable in aqueous liquids, so that the material itself does not significantly plasticize or soak in aqueous liquids that it contacts. However, regardless of the particular monomeric constitution, molecular weight or morphology of the polymeric material, the resulting ideal polymeric material will, in

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Ύού. / 1 · AJUUU »Χ. · Yo / υβ is generally a viscoelastic character. Thus, the polymer of these ideal foam structures will have viscous, i.e. fluid, and elastic, i.e., spring characteristics. It is important that the polymeric material that forms the cellular foam structure has physical, rheological and morphological attributes which, in use, confer one. adequate flexibility, deflection resistance.) Compression, and dimensional stability to the absorbent foam material.

braiding polymer material which forms these ideal absorbent foam structures: should be substantially free of polar functional groups in their polymeric structure. Thus, immediately after the polymerization phase, the polymeric material forming the foam structure surfaces of such ideal absorbent foams will normally have a relatively hydrophobic character. Similarly, freshly polymerized foams may have to be even longer. treated to make the foam frame surfaces relatively more hydrophilic so that such foams can be used as absorbents for aqueous body fluids. Hydrophilization of the foam surfaces, if necessary, can be accomplished by treating the HIPE foam structures as hydrophilizing agent polymerized as follows in detail.

Hydrophilizing agents are any materials that enhance the wettability of water on the polymer surfaces with which they are in contact and on which they are deposited. The hydrophilizing agents are fine. Such agents commonly known include surfactants of the anionic, cationic or nonionic type. Hydrophilizing agents are generally used in liquid form, typically dissolved in water to form an aqueous hydrophilizing solution, which is applied to them. HIPE Foam Surfaces- Thus, the hydrophilizing agents; may be absorbed on polymer surfaces; The ideal HIPE foam structures have adequate amounts to render such surfaces substantially hydrophilic, but without altering the desired flexibility and compression characteristics of the foam. In ideal foams that have been treated with hydrophilizing agents, the hydrophilizing agent is incorporated into the foam structure so that the residual amounts of the agent remaining in the foam structure are present.

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foam size ranges from about 0.1 LZ to LOZ by weight of the foam.

A suitable type of hydrophilizing agent comprises mild non-irritating surfactants applied to the foam structure in amounts sufficient to provide a residual censoring agent in the foam of from about 0.5Z to 5Z by weight, preferably from about 1Z to 3Z by weight based on the weight of the foam. Such surfactants may include, for example, alkyl sulfates and alkyl ethoxylylphosphites of the type used in dishwashing liquids, such as for example JOY LIQUID DETERGENT. Aqueous solutions of such surfactants are usually used to wash the HIPE foam structure after removal of the wastewater phase material left from the foam polymerization operation or preferably as part of the wash treatment serves to remove this wastewater phase material.

Another ideal type of hydrophilizing agent comprises hydratable, and preferably hygroscopic, water-soluble organic salts. These materials include, for example, alkaline earth metal salts. toxicologically acceptable. Materials of this type and their use in conjunction with water-insoluble surfactants, such as hydrophilic foam agents, are described in more detail in the application of the Thomas A. patent. DesMarais with Serial No. 2 (P&amp;G No. 3354), incorporated herein by reference. Ideal salts of this type include calcium and magnesium halides, such as calcium chloride, which, as noted below, may also be used as the electrolyte in the water phase of HIPE emulsions used to prepare the ideal absorbent foams.

Hydrophilizing agents in. In the form of hydratable inorganic salts can easily be incorporated into these absorbent foams by treating the foams with. aqueous solutions of such salts► Such conux with surfactant hydrophilizing agents_r Hydratable inorganic salt solutions may generally be used to treat and hydrophilize hydrophobic foams after completion, or as part of the process of removing the wastewater phase from freshly polymerized foams. Contact of the foams with each solution should preferably be used to deposit hydratable inorganic salts such as calcium chloride in residual amounts ranging from about 0.1 to 7% by weight of the solution.

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Mod. 71 - 20,000 βκ. · 6/20 puma.

Hydrophilizing treatment thereof into ideal foam structures which are relatively hydrophobic when polymerized will be carried out to the extent necessary to impart adequate hydrophilicity to the ideal HIPE foams of the present invention. Some ideal HIPE emulsion type foams, however, may be hydrophilic when prepared and thus may not require any additional treatment with hydrophilizing agents. In particular, such HIPE foams may be those wherein sorbitan fatty acid esters are used as emulsifiers added to the oil phase and wherein calcium chloride is used as an electrolyte in the water phase of HIPE emulsion foam precursors. . In such a case, the residual phase liquid kept within the foams after polymerization may contain or deposit sufficient amounts of calcium chloride to render the residual emulsifier-containing internal foam surfaces adequately hydrophilic even after the polymerized emulsion foams have been devoid of water. ..

V) ABSORBENT FOAM PREPARATION METHODS

The absorbent foam materials of this invention may be prepared using any suitable polymerization and post-polymerization process steps and using any suitable combination of monomeric materials, provided hydrophilic foams result, which has been described as essential, e.g. with ideal structural and mechanical characteristics. As noted, an ideal method of carrying out polymeric foams with; required structural and mechanical characteristics, and with the desired fluid handling properties, entails the polymerization of High Internal Phase Emulsions [(HIPEs) cf. High Internal Phase Emulsion], The preparation of absorbent foams using this ideal procedure will be described to illustrate how such foams can be made.

This ideal foam preparation method involves the steps of A) forming a stable high inner phase emulsion (HIPE), B), and then polymerizing this stable emulsion under conditions suitable for forming a solid polymeric foam structure. C) washing and, if necessary, hydrophilizing a polymeric foam structure

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Mod. 71 20,000 οκ. · »08/08 ϊ

solid by treating the structure with water and / or liquid hydrophilizing agents to remove the original wastewater phase from the polymeric foam structure and depositing any necessary hydrophilizing agent, and D) removing all water from it. polymeric foam structure to the extent necessary to make the foam material useful as an absorbent for aqueous body fluids. Each of these phases of. The basic process is most promisingly described as follows:

A) HIPE EMULSION FORMING The HIPE emulsion precursor for these ideal absorbent materials can be formed by combining an oil phase as described with a water phase also described. The weight ratio of. water phase. for. The. oil phase and such a combination will normally be from about 12: 1 to 100: 1. preferably from about 20: 1 to 70: 1.

The phase of. The oil used to form these HIPE emulsions must contain the above specified essential components such as the required monomers, comonomers, braids and emulsifiers. The oil phase may also contain optional components such as solvents and polymerization initiators. The water phase used to form these HIPE emulsions contains the aforesaid electrolyte as an essential component, and may also contain optional components such as water soluble emulsifiers, and / or polymerization initiators.

The HIPE emulsion may be formed from the combined oil and water phase by subjecting this phase combination to. a, shear agitation ~ The shear agitation is normally applied to the extent and for the time necessary to form a stable emulsion from. combined oil and water phases ► This process can be conducted in. series, or from. It is carried out under conditions suitable for the formation of an emulsion in which the drops of the oil phase are dispersed to a point where the foam is polymerized. which is optionally formed from the emulsion, has a required pore volume and other structural characteristics. Emulsification of the water and oil phase combination often involves the use of a mixing or stirring device such as a pin propellant.

An ideal method for forming HIPE emulsions can be here)

<img file="PT101759B_D0053.tif" />

Mod. / 1-20,000 χ. - 90/00)

used implies a continuous process for combining and emulsifying the required oil and water phases. In such a process, a liquid stream comprising the oil phase is formed as above, with a flow rate between about 0.08 to 1.5 mL / sec. On the other hand, a liquid stream is also formed comprising the water phase as described above, with a flow rate between about 4 to 50 ml / sec. With flow rates within the stated limits, these two strokes are then combined in a mixing chamber or zone to obtain and maintain the phase to oil to water phase weight ratios.

The combined strokes are generally subjected to shear agitation in a mixing zone or chamber, for example by a pin impeller of suitable size and configuration. Shear is usually applied to the point between about 1000 and 4000 sec. —1— The residence times in the mixing chamber vary usually. about 5 to 30 sec. . Once formed, the stable HIPE emulsion in liquid form can be removed from the mixing chamber or zone at a fluid rate of from about 4 to 52 mL / sec. .

This ideal method for forming useful HIPE emulsions through a continuous process is described in more detail in the Thomas A. DesMarais, Stephen T. Dick and Thomas M. Shiveley U.S. Patent Application Serial No. _________ (P&amp;G No. 4453 ). This application is included herein by reference.

B) POLYMERIZATION OF. HIPE EMULSION

A. HIPE emulsion. formed as described above is usually placed in one. reaction container or reaction region to be polymerized. In one embodiment of this invention, the reaction container comprises a tube constructed of polyethylene from which the polymerized solid foam material can be easily removed for further processing after polymerization has been made to the desired point.

The polymerization conditions under which the HIPE emulsion is subjected to vary according to the monomeric or other oil and water phases of the emulsion and the type and amounts of polymerization initiators used. However, often the polymerization conditions

<img file="PT101759B_D0054.tif" />

9θ / Μ · '«» ΟΟΟ'Οί - ΙΖ P^noW comprise the maintenance of the HIPE emulsion at elevated temperatures from about 55 ° C to 90 ° C, preferably from about 60 ° C to 662 ° C for a period of time from about 4 to about 24 hours, preferably from about 4 to 12 hours. .

C) WASH AND HYDROPHILIZATION OF HYPER FOAM

The solid HIPE foam formed after the end of the described polymerization phase will generally be flexible, with an open cell pore structure with the cells filled with the wastewater phase material used to prepare the HIPE emulsion before, of polymerization. This wastewater phase material, which usually comprises an aqueous electrolyte solution, residual emulsifier and polymerization initiator, should be removed from the foam structure at this point prior to further processing and prior to use of the foam. Removal of the original water phase material is usually accomplished by compressing the foam structure to squeeze out residual liquid and / or by washing the foam structure with water or any other aqueous wash solution. Various compression and washing steps are often used, for example, 2 cycles.

After the original water phase material has been removed from the foam structure to the required extent, the HIPE foam may need to be treated, i.e. by continuous washing with a suitable aqueous hydrophilizing agent solution. Hydrophilizing agents that may be used are referred to in this patent. As noted, HIPE foam treatment with the hydrophilizing agent solution is continued until necessary until the required amount of hydrophilizing agent is incorporated and until the foam has a desired tack stress value for any hydrophilizing liquid. test the choice.

D) REMOVE FOAM WATER.

After. foam. HIPE has been treated to the extent necessary to: render the foam; suitably hydrophilic, dry. the foam must be dried before being cut or made ready for use as an absorbent structure in an absorbent article. Water can be removed by compressing the foam to squeeze out the residual water by subjecting the foam or water therein to elevated temperatures, for example at temperatures between about 60 ° C to 2002 ° C or under micro-treatment.

<img file="PT101759B_D0055.tif" />

Mod. 71 - 2OOOO · «. ? Ο / ΰβ)

- Round combined with water compression and heating techniques. The dewatering phase of the HIPE foam is usually carried out until the HIPE foam is ready for use in its dry form. Such waterless foams after compression often have a water content (moisture) of from about 50Z to 500Z, preferably from about 50Z to 200Z by weight relative to a dry weight basis. Subsequently, the heated foams may be dried to a moisture content of from about 5Z to 40Z, preferably from about 5Z to 15Z, on a dry weight basis.

VI) ABSORBENT ARTICLES

This invention also relates to body fluid absorbent articles utilizing these foam absorbent structures at least a portion of their fluid absorbent core member. The term absorbent article means in this context a consumable product capable of absorbing significant amounts of urine or other fluids (i.e. liquids), such as aqueous fecal matter, discharged by an incontinent user or user of the article. Examples of such pads include disposable diapers, incontinent clothing, disposable training protectors, bed covers, and the like. These absorbent foam structures are particularly useful for use in articles such as diapers, incontinent garment fillers, garment protectors and the like.

In its simplest form, an absorbent article of the present invention need only include a relatively liquid impermeable backsheet and one or more foam absorbent structures associated with this backsheet. such that the foam absorbent structure material is located between the backsheet and the user fluid discharge zone of the absorbent article. The liquid impermeable backsheets may comprise any material, for example polyethylene or polypropylene, having a caliber of about 1.5 mils (Q.038 mm), which helps to retain fluid within the absorbent article.

More conventionally, these absorbent articles also include a liquid permeable topsheet element that covers the side of the absorbent article that touches the user's skin. In this case, the article)

<img file="PT101759B_D0056.tif" />

Mod. / 1-20,000 x. O / OB includes an absorbent core comprising one or more foam absorbent structures of this invention disposed between the backsheet and the topsheet. The liquid permeable topsheets may comprise any material such as polyester, polyolefin, rayon and the like which are substantially porous and allow body fluid to rapidly pass therethrough toward the underlying absorbent core. 0 Topsheet material should have no affinity for maintaining aqueous body fluids in the contact area between the topsheet and the user's skin.

The absorbent core of the absorbent article embodiments of this invention may consist solely of one or more of these foam structures. For example, the absorbent core may comprise a single piece of foam of the desired shape or shape that best suits the type of absorbent article in which it is used. Alternatively, the absorbent core may comprise a plurality of pieces or particles of foam. foam which may be bonded by adhesives or which may be only in a group held together by an envelope tissue surrounding them, or by a topsheet and one. backsheet of the absorbent article. zv

The absorbent core of these absorbent articles may also comprise other conventional elements or materials, in addition to one or more foam absorbent structures of this invention, for example, these absorbent articles may utilize an absorbent core comprising a combination of, for example, a mixture, in particular. contact with air of particles or pieces of these foam absorbent structures and conventional absorbent materials, such as a) wood pulp or other cellulosic fibers, and / or, b) particles or fibers of polymeric gelling agents.

In a form of embodiment involving one. In combination with this foam absorbent material and other absorbent materials, these absorbent articles may use a multi-layer absorbent core configuration, wherein a core layer containing one or more foam structures of this invention may be used in combination with one or more additional separate core layers comprising conventional absorbent structures or materials. Such conventional absorbent structures or materials, e.g. - yv / υΰ

<img file="PT101759B_D0057.tif" />

<img file="PT101759B_D0058.tif" />

<img file="PT101759B_D0059.tif" />

for example, they may include air-contacting or ready-to-dry webs of wood pulp or any other cellulosic fiber. Such conventional structures may also comprise large cell foam or even absorbent sponges. Conventional absorbent structures used with this foam absorbent may also contain, for example, up to 80% by weight of particles or fibers of a polymeric gelling agent commonly used in absorbent articles that are supposed to acquire and retain aqueous body fluids. Polymeric gelling agents of this type and their use in absorbent articles are described in more detail in Brandt / Goldman / Inglin Patent No. 32,649, reissued April 19, 1988, incorporated herein by reference.

A preferred type of absorbent article herein is that which uses a multilayer absorbent core with a fluid acquisition / distribution top layer comprising a layer of mixed cellulosic fibers, e.g. 10Z by weight of this polymeric gelling agent fluid acquisition / distribution layer. Such a multilayer absorbent core comprises a second lower fluid storage / redistribution layer comprising a foam structure of this invention. (For purposes of this invention, an upper multi-layer absorbent core is a layer relatively closer to the wearer's body, for example, the layer closest to the top sheet of the article. The term lower layer in turn means a multi-layer absorbent core layer which is relatively further from the wearer's body (e.g., the closest layer to the backsheet of the article). The modified cellulosic fibers used in the fluid acquisition / distribution layer of such an ideal absorbent article should be wood pulp fibers which have been reinforced and made of spirals by chemical and / or thermal treatment means. Such modified cellulosic fibers are of the same type as those used in the absorbent articles described in US Patent No. 4,935,622 to Lash and Thompson of June 19, 1990, incorporated herein by reference. Absorbent articles utilizing absorbent foam structures of this invention in a fluid storage / redistribution layer underlying the fluid storage / redistribution layer containing reinforced spiral cellulosic fibers are described below.

<img file="PT101759B_D0060.tif" />

Mod. 21 - 20,000 ex. - TODAY

<img file="PT101759B_D0061.tif" />

in more detail in Gerald A. Young's US Patent, Gary D. LaVon and Gregory W. Taylor, Serial No. _________ (P&amp;G Νθ 4452), incorporated herein by reference.

As indicated above, the mechanical and fluid handling characteristics of these specific foam absorbent structures make such structures particularly suitable for use in absorbent articles in the form of disposable diapers. Disposable diapers comprising the foam absorbent structures of this invention may be made using conventional diaper making techniques, either by replacing or changing the wood pulp fiber web (felt air) or the cellulosic core pads. Modified material typically used in conventional diapers with one or more foam structures of this invention. The foam structures of this invention may thus be used in single-layer diapers or, as noted, in various multi-layer core configurations. Articles in the form of; disposable diapers are described in more detail in US patent. Duncan and Baken, no. 26,151. January 31, 1967; Duncan US Patent 3,592,194, July 13, 1971; Duncan and Gellert, Patent 3,489,148 issued January 13, 1970; Buell, U.S. Patent 3,860,003, January 14, 1975; and Alemany and Berg, US Patent 4,834,735, May 30, 1989; included herein by reference.

An ideal disposable diaper embodiment of this invention is shown in Figure 2. Such a diaper includes an absorbent core, 50, comprising an upper fluid acquisition layer, 51, and an underlying fluid storage / dispensing layer, 52, comprising a foam-absorbent structure of this invention. A topcoat, coextensive with a core phase, is superimposed. waterproof back sheet, 54, co-extensive with. the core face facing the face covered by the topsheet. The backsheet should be wider than the core, thus providing lateral marginal zones of the backsheet extending beyond the core. The diaper should preferably be made with an hourglass configuration.

Γ

Another ideal type of absorbent article that can use the foam absorbent structures of this invention comprises anatomically shaped products such as training clothes. Such articles generally include a basis for

<img file="PT101759B_D0062.tif" />

Mod. 71 20,000 · χ. 90/08 j

Flexible non-woven in the form of shorts. A foam absorbent structure according to the present invention may then be attached to the area between legs to serve as an absorbent core. This absorbent core will often be overlaid with fabric or any liquid permeable nonwoven material. Such a core thus serves as the topsheet for the anatomical absorbent article.

The flexible base forming the chassis of this article may comprise fabric or. paper or any kind of non-woven base or formed films and may be elastic or otherwise extendible. The leg or waist straps of such training articles may be stretched in the conventional manner to improve the adaptability of the article. Such a base will be made relatively liquid impermeable, or at least not immediately liquid permeable, by treating or coating a flexible base or surface with another relatively liquid impermeable base, making the entire chassis relatively impermeable. liquid. In these cases, the chassis itself serves as the backsheet for the anatomical article. if described by Roberts in US Patent 4,619,649, October 28, 1986, Included herein by reference.

A typical article in. Disposable training garment form is shown in Figure 3. Such a product comprises an outer layer 60 attached to a cover layer 61 which adheres to its peripheral areas. For example, the inner liner 61 may be affixed to the outer layer 60 along the periphery of a legband area 62; along the periphery of the other strip. leg 63; and along the periphery of the waistband area, 64. There is usually a rectangular absorbent core attached to the crotch area of ​​article 65 comprising a foam absorbent structure of the present invention.

TEST METHODS

A number of characteristics of HIPE foam absorbent structures are set forth in the description of the present invention. These characteristics may be determined by the use of the following test fluids, and test methods.

<img file="PT101759B_D0063.tif" />

<img file="PT101759B_D0064.tif" />

<img file="PT101759B_D0065.tif" />

15’

Mod. 21 - 20,000. - 90/08

I) TEST FLUIDS AND PREPARATION OF A FOAM SAMPLE

A) TEST FLUID - SYNTHETIC URINE

Many of the measurements described in the tests involve the use of a test fluid, such as synthetic urine, ethanol or isopropanol. The synthetic urine used in a number of tests described herein is made from a commercially available synthetic urine preparation by Jayco Pharmaceuticals (Mechaniscsburg, PA, 17 055). This synthetic urine made from this preparation comprises KCl, 0.2Z; Na2 SO4 0.2Z; NH₄H₂POWDER₄0.085Z; (NH₄)₂HPO₄0.015Z; CaCl₂* 2H₂0, 0.025Z and MgCl₂* 6H₂0.05Z (weight percentages). Synthetic urine specimens are prepared according to label instructions using distilled water. To aid dissolution, the Jayco salt mixture is slowly added to the water. The sample is. filtered if. necessary to remove any particles. Any unused synthetic urine is discarded after one week. To improve fluid visibility, 5 drops of blue food coloring can be added. for every liter of synthetic urine solution .. The used Jayco synthetic urine has. a surface tension of 65 - 5 dynes / c.

B) PREPARATION OF THE FOAM SAMPLE

A large number of the following tests involve the preparation and basketing of foam samples of a particular specific size. Unless. otherwise specified, foam samples of the required size should be cut from large foam blocks using a sharp reciprocating knife (saw). 0 Use of this or another equivalent type of foam cutting device serves to substantially eliminate sample edges that could have an adverse impact on certain measurements made during the various test procedures described below.

The size specification of the. The sample also generally includes a dimension for the gauge and thickness of the sample. Size or thickness is measured for the purposes of the present invention when the sample is; foam is under a pressure of (0.05 psi) 350 Paddle.

II) DETERMINATION OF STRUCTURAL CHARACTERISTICS

A) AVAILABLE PORE VOLUME

Any procedure for determining available pore volume

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<img file="PT101759B_D0066.tif" />

This involves measuring an amount of isopropanol (key point 122C) which can be introduced into the structure of an absorbent foam sample. The equipment and materials used to make such measurements are balanced at 22 - 22 ° C. Measurements are also made at this temperature.

Dry foam samples are cut into (1 inch ^) 2 cylinders

6.5 cm x (0.3 inches) 0.8 cm thick, or equivalent. Such cylindrical specimens may be prepared using a 2.87 cm (1.13 inch) diameter punch on a 0.3 cm (0.3 inch) foam sheet. Each of the dried foam samples are weighed to determine a dry weight (dw). Three of these samples are weighed to determine the average dry weight (DW).

The measured free capacity (MFC) of these samples is then determined according to the following steps:

1) The foam samples are immersed in isopropanol in a crystalline dish and allowed to saturate. At this point, the sample may be squeezed a few times to expel air. I

2) Each sample is removed without squeezing the isopropanol. Excess fluid is allowed to drip from the sample in a flat position for about 30 seconds. Each sample is then weighed wet to determine a wet weight (ww).

3) Phases 1) and 2) are repeated twice more and then an average wet weight (WW) is calculated.

The measured free capacity (MFC; g / g) is the weight of isopropanol in saturated foam per unit mass of dry foam. CFR is calculated according to the formula

MFC = (WW (g) - DW (g)]

DW (g) available portion volume is then calculated by dividing the foam MFC for isopropanol by the isopropanol density, which is 0.785 g / mL. This gives an available pore volume for the foam in ml / g. * ·

B) SPECIFIC HAIR SUCTION SURFACE AREA

The specific surface area of ​​capillary suction of these foam absorbents can be determined from the weighting of the foam.

<img file="PT101759B_D0067.tif" />

Mod. 71 - 20,000 · κ. - 90/08 lily of a test liquid of known low surface tension. In this case, absolute ethanol is used (key point at 102 ° C).

To perform the test, a properly sized tare foam sample strip (eg 25 cm long x 2 cm wide x 0.8 cm thick) is equilibrated to 22 - 22 ° by vertically placing being immersed in a 1-2 mm tip in an ethanol reservoir using a laboratory device. Ethanol is allowed to rise in the foam range to its equilibrium height, which should be less than the sample length. The ethanol-containing strip is then weighed while still in contact with the reservoir to determine the weight of the total ethanol uptake. During this process, the sample should be protected, for example, with a coated glass cylinder to prevent ethanol from evaporating.

The specific area of. The surface of the foam sample can be calculated. from the following formula:

^sand V. where S_ç = specific surface area of ​​capillary suction in cm3 / gm; M_and = mass of EtOH liquid intake in grams; G = the gravitational constant, which is 980 cm / sec; = total sample length in centimeters; M ^ = dry sample mass in grams; and γ = EtOH surface tension, which is 22.3 dynes / cm. The values ​​obtained can then be divided by 10 000 cm 2 / mA to provide a specific surface area of: capillary suction in m 2 / g.

C) FOAM DENSITY.

One of the procedures that can be used to determine foam density is that described in the ASTM method. no. D3574—86, Test which is designed primarily for testing urethane foams, but. which may also be used for density measurement of the ideal HIPE type absorbent foams of this invention. In particular, density measurements made according to the ASTM procedure are performed on foam samples that have been preconditioned to some extent as specified in the test.

The density is determined by measuring the dry mass of a given foam sample and its volume at 22 - 22 ° C. The volume determination

<img file="PT101759B_D0068.tif" />

<img file="PT101759B_D0069.tif" />

Mod. 71 - 20,000 ««. -? 0 / 0β in larger foam samples is calculated from measurements of sample sizes made in the absence of any pressure. The dimensions of smaller foam samples can be measured using a marker type gauge using a foot pressure of 350 Pa (0.05 psi). Density is calculated as mass per unit volume. For purposes of this invention, density is generally expressed in terms of g / cm³.

III) A. DETERMINATION OF MECHANICAL CHARACTERISTICS

A) RESISTANCE TO COMPRESSION DEFLECTION

Compression deflection resistance can be quantified for the purposes of this invention by measuring the amount of pressure (Z caliber reduction) produced in a foam sample which has been saturated with synthetic urine after one. Stress in the form of 0.74 psi (5.1 kPa) of pressure applied to the sample The test to make such measurements can be performed on sample v cylinders prepared as described for the available pore volume test. In such samples, synthetic urine test fluid and the equipment used for such measurements are all equilibrated at a constant room temperature of 992F (372C). Measurements are also made in this environment.

The foam samples are placed in a crystallizing dish and saturated to their own. Jayco synthetic urine free absorbent capacity. A given saturated sample to be tested is then placed on a mesh screen 25 over a crucible, and a dial-type device suitable for gauge measurements is placed on the sample. Any device fitted with a foot with a surface area of ​​at least 1 inch³-) 6.5 cm³- a able: to measure gauge dimensions up to (0, OOL inches³·), 0.025 mm can be used- Examples of such^--devices are the Ames 482 model (Ames Co., Walthaç, MA) or an Ono-Sokki EG-225 model (Ono-Sokki Co. Lcd .; Japan). Weights may also be used which may be used with the dialing device to produce a standing pressure in the foam sample up to (1.0 psi) 6.9 kPa

The saturated foam sample on the screen is then subjected to a pressure of (0.74 psi) 5.1 kPa for 15 minutes. At the end of this time, use ·

<img file="PT101759B_D0070.tif" />

X. J

15Mod. 71 · 20,000 βκ. · 90/00

<img file="PT101759B_D0071.tif" />

a marking device for measuring the change in sample gauge that occurs as a result of applying pressure. From these initial and final gauge measurements, a percentage of induced strain may be calculated for the sample.

B) FLEXIBILITY, /

Foam flexibility can be quantified by reference to a test procedure which is a modification of the ASIM D 3574-86, 3.3 test used to determine the flexibility of foam products. cellular organic polymer. This modified test uses a foam sample that is 7x0.8x0.8 cm in size and has been saturated to its free absorbent capacity with Jaycd synthetic urine at 37 ° C. It is important that the process of. The cutting used to make these samples does not introduce edge defects into the foam strip. The synthetic urine saturated foam strip is folded around a cylindrical mandrel with a diameter of 0.8 cm at a uniform rate of · 1 turn in 5. seconds- until the ends of the strip meet- The foam is considered flexible if it does not bend or break during this test, ie if a folding cycle has passed.

C) COMPRESSION DEFLECTION RECOVERY

To test compression deflection recovery, foam samples similar to those prepared for the available pore volume test described above are reused. These samples are d &amp; 0.3 cm cylinders. “thickness with a circular cross-sectional area of ​​6.45 cm? - (1 inch ^ -) - These simple samples can be tested in a dry state or after being saturated to their free absorbent capacity with synthetic urine. Jayco

With the help of. a dial-type device, consisting of an east sample, dried thoroughly, for 10 seconds to 50Z of its original thickness, remaining in the continuous state for 1 minute. The pressure is then withdrawn. , and is allowed to foam. recover thickness for 1 minute- Percent recovery is based on the original height of the uncompressed foam.

To test the dried samples, use room temperature, for example 22 22C. To test wet samples, the foam sample is saturated to its free absorbent capacity at 37 ° C with Jayco synthetic urine in a 5 cm diameter dish. 0 plate acts as reser—

<img file="PT101759B_D0072.tif" />

Mod. 71 - 20,000 X. · OJ / Ofl is used to contain the fluid expressed during compression and also serves as a reservoir from which the sample can re-absorb fluid when recovering from compression.

IV) DETERMINATION OF FLUID HANDLING CHARACTERISTICS

A) ABSORBENT CAPACITY

Free absorbing capacity and pressure absorbing capacity * may be determined by gravimetric analytical techniques using synthetic urine as the fluid for which the absorbent capacity of the foam is calculated.

1) ABSORBING CAPACITY TESTING PRINCIPLE

In this test, a foam sample is saturated with synthetic urine test liquid to measure under no load the free absorbent capacity of the foam sample— Pressure is applied in various increments to determine the absorbent capacity under load. This pressure absorbing capacity is measured after the foam sample has been kept in a compressed state for a certain period of time.

2) SCOPE OF. TESTING

This test measures the absorbent capacity of a pressure foam sample of interest, namely between (0 and 1.0 lb) 0.453 g per (inch ^) 2.54 cm ^ (psd) 0 to 6.9 kPa at temperature of interest, for example, from (992F) 372C □

3) EQUIPMENT

Fabric, mesh 25 ,. 8 cm in diameter; crystallizing plate, 15 cm in diameter x 7.5 cm in height; crucible .. 50 mL; analytical balance; dial-type device adapted with a foot of at least C 1 inch ^ '

6.5 cm2 and capable of measuring up to (0.001 inches) 0.025 mm, for example Ames 482 (Ames Co., Waltham, MA) or Ono-Sokki EG-225 from Ono-Sokki, Ltd. ' Japan; weights of. dial-type device capable of producing pressures of (0.2, 0.74- and 1.0 psi) 1.4, 5, L.

and 6.9 kPa.

4) MATERIALS.

Jayco synthetic urine; Foam samples. r

5) PROCEDURE

(i) The equipment and materials described are equilibrated in a constant temperature room heated to (992F) 372C. The measurements are

')

<img file="PT101759B_D0073.tif" />

Mod. 71 - 20,000 ex. - 90/00

The also made in this room.

ii) Foam samples similar to those prepared in the available pore volume test are cut into cylinders with a thickness of (1 inch ^) 6.5 cm ^ x (0.3 inches) 0.8 cm. These samples are weighed to provide an average dry weight (DW).

iii) the free sorbent capacity of each foam sample is. determined as follows;

a) dives a. foam sample in synthetic urine in the crystallizing dish, allowing to saturate. The sample may be expressed several times to expel air.

b) the foam is removed without squeezing the fluid. Excess fluid is allowed to drip from the sample horizontally for about 30 seconds, and then the dried sample is weighed.

c.) stages a) and b) are repeated twice more, calculating an average wet weight (WW).

d) the free absorbent capacity (FAC, g / g is calculated as FAC = weight of saturated synthetic foam urine / dry weight foam = [WW (g) -DW (g)] / DW (g) iv ) The pressure absorbing capacity (pressure disruption) for each foam sample is determined as follows:

(a) Place the 50 ml. crucible with the screen on top of it over the center of the foot of the dialing device, resting the foot on the. screen.

b) the saturated sample is placed at the top of the screen, certifying that a. The sample is located over the center of the crucible and the dial-type device is positioned to apply pressure to the foam sample. '

c) weights are placed on the device to apply one. (0.2 psi) 1.4 kPa pressure in the sample.

d) After 15 minutes, the foam sample is weighed (WW, 0.2).

e) re-saturate the same sample, then repeat the phases

a) -d), except that 0.74 and 1.0 psi are used to determine WW, 0.74 and WW, 1.0.

f) using new samples, repeat steps a) - e) twice

<img file="PT101759B_D0074.tif" />

Mod. / 1 ​​20,000 x. -? 0 | 0β

Further to determine the average wet weights after the samples have been kept under different pressures.

g) the pressure absorbing capacities (x-load, g / g) are calculated as follows.

(X load under a given pressure is the weight of synthetic urine in wet foam / dry foam)

Capacity below 0.2 psi

X = 0.2 (g / g) [WW, 0.2 (g) - DW, (g).] / DW (g).

Capacity below 0.74 psi

X, 0.74 (g / g) - [WW, 0.74 (g) - DW (g) - DW (g)] / DW (g)

Capacity below 1.0 psi

X, 1.0 (g / g) - [WW, 1.0 (g) - DW (g) I / DW (g)

Synthetic urine absorbent capacity values ​​per gram of dry foam can be obtained by dividing the FAC and X-load values ​​by the specific gravity of Jayco synthetic urine, which is about 1g / ml.

B) VERTICAL DRIVING RATE AND CAPACITY. VERTICAL DRIVING ABSORBENT

Vertical conduction rate and absorbent vertical conduction capacity are measures of the ability of a dry foam to conduct fluid vertically from a reservoir. The time required for the front fluid to conduct through a vertical length of 5 cm of a foam strip is measured to give a vertical conduction rate. After the fluid has been conducted to its equilibrium height, the amount of fluid maintained by the foam strip at a particular vertical conduction height for example (4.5 inches) or 11.4 cm is determined to give an absorbent capacity of. vertical driving »

Jayco synthetic urine is used with. a blue dye in the following methods for determining the vertical conduction rate; and a. absorbent capacity for vertical driving. In this test procedure the materials are equilibrated at 37 ° C and the test performed at the same temperature.

1) SAMPLE PREPARATION

i) a foam strip of about 25 cm x 2 cm x 0.8 cm is prepared as in the capillary suction specific surface area test.

<img file="PT101759B_D0075.tif" />

Mod. 71 20,000 οχ. - 90/08)

(ii) a fluid reservoir is placed on top of a laboratory device and the foam sample is attached; at one end such that it is suspended vertically over the fluid reservoir.

iii) a ruler is attached near the foam sample so that the base (0 cm) of the ruler is about 1-2 mm above the foam sample base. iv) the fluid reservoir is filled to about 3/4 with the colored synthetic urine solution.

2) RATE. VERTICAL DRIVING

i) the. reservoir is; raised to the base of the foam sample with the laboratory device. A stopwatch is turned on as soon as the fluid touches the base of the foam sample.

The reservoir is immediately raised until the liquid touches the base of the tank. scale..

iii) the time taken for the top fluid to reach cm is recorded.

iv) The foam is allowed to drive until it reaches equilibrium (eg about 18 hours). The laboratory device may need to be adjusted to keep 1 - 2 mm of the sample immersed and the sample should be protected to prevent evaporation.

3) ABSORBENT CAPACITY (mL / g) BY VERTICAL FOAM LENGTH

i) remove a. The foam sample is quickly placed on a non - absorbent surface. separate 1 inch (2.5 inch) pieces, using an instrument sharp enough not to compress^- the sample of foam, each being a heavy piece.

iii) squeeze yourself. the biggest^- fluid portion of each piece, each piece being placed on a towel, absorbent, iv) each piece is allowed to dry completely.

v) each piece is then weighed, so that an absorbent capacity is calculated for each piece based on the difference between wet and dry weights.

For the purposes of this invention, the absorbent capacity of the one inch segment which represents 4.5 inches 11.4 cm υ

Mod. 71-20,000 βχ. - »0/08

S —- 25 of the driving height is the desired parameter.

C) ADHESIVE TENSION

The adhesion stress manifested by the hydrophilization of foam samples which soak the test fluids by capillary suction is the product of the surface tension, y, of the test fluid times the contact angle cosine, 9, shown by the test fluid in contact with the inner surfaces of the foam sample. The bonding stress can be determined experimentally by measuring the capillary suction balance weighting manifested by two test samples of the same foam using two different test liquids. In the first phase of such a procedure the specific surface area of ​​the foam sample is determined using ethanol as the test fluid as described herein in the discussion of specific surface area in this section of TEST METHODS.

The capillary suction procedure is then repeated in the same manner as the ethanol procedure. except Jayco synthetic urine is used as the test fluid and the test is performed at a temperature of 37 ° C. The contact angle of synthetic urine may be calculated as follows from the known specific surface area and synthetic urine outlet data:

cos9u ⁼ MyGL ^ ^MNAKED^shundred. where 9 = contact angle of Jayco synthetic urine in degrees; My »- Jayco synthetic urine fluid-taking mass in grams; G «• gravitational constant which is 980 cm / sec ^; Mjj = mass of dry foam sample in grams; ·) * 'jj = Jayco urine surface tension of 65 dynes / cm; s_ç »Specific surface area of ​​the foam sample in cm -1 - / gm as determined by the e-tanol take-up procedure and» length of foam sample in cm ..

When a surfactant is present (on the foam sample surfaces and / or the advanced test liquid), the characterization of the advanced type liquid is defined by applying the tack stress (AT) equation:

AT ³ M_tGL_no m_nos_ç

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ftnfnx · · »· rrrvrw í 20

O

<img file="PT101759B_D0077.tif" />

where Μψ is the mass of the test liquid taken by the foam sample, where G, Ljj, and S_ç as defined above. [See Hodgson and Berg, J. Coll. Inc. Sci., 121 (1), 1988, pp 22-31].

In determining the bond stress for any test liquid, no reference is made to the numerical value of the surface tension at any point such that they are: immaterial any possible changes in surfactant concentration on the sample surfaces and / or in the advanced liquid during driving. The experimental value of the tack stress (ycosO) is particularly useful when viewed as a percentage of the maximum tack stress, which is the surface tension of the test liquid (eg the maximum adhesion stress using JAYCO synthetic urine would be [.65 lbs 5 dynes / cm]).

EXAMPLES

The preparation of HIPE absorbent foam materials, the characteristics of such foam materials, and the use of such foam absorbents, in particular. disposable diapers are illustrated in the following examples.

EXAMPLE I The following example illustrates the preparation of an ideal HIPE foam absorber on a semi-pilot plant scale.

EMULSION PREPARATION

Calcium chloride (320 g) and potassium persulphate (48 g) are dissolved in 32 liters of distilled water. This causes the water phase to form: a HIPE emulsion.

Joins one: monomer combination comprising styrene (420g). divinylbenzene (, 660 g) and ethylhexylacrylate - 2 (1920 g) to sorbitan monooleate (450 g as SPAli® 80) and sorbitan trioleate (150 g with SPAlí® 85). After mixing, this comprises the oil phase used to form the HIPE emulsion.

At liquid temperatures ranging from 55 ° C to 65 ° C, separate oil phase and water phase bands are fed into a dynamic mixing chamber. Mixing through the combined strips in the dynamic mixing chamber is accomplished by a pin thruster. At this stage of operation, there is a pin thruster comprising a cylindrical shaft

<img file="PT101759B_D0078.tif" />

©

<img file="PT101759B_D0079.tif" />

about 18 cm long with a diameter of about 1.9 cm. The shaft has two rows of 17 and two rows of 16 cylindrical pins, each having a diameter of 0.5 cm radially outwardly from the central axis to a length of 1.6 cm. The four rows are positioned at 902 angles around the drive shaft circumference *. The rows that are perpendicular to each other are placed along the length of the axis so that no pins that are perpendicular to each other are in the same radial plane projecting from the axis. The pin thruster is mounted on a cylindrical sleeve forming the dynamic mixing chamber and the pins on the thruster have a distance of 0.8 mm from the cylindrical sleeve walls. The propellant is operated at a speed of 900 revolutions per minute.

£. mounted one. static mixer (S inches) long by 0./4 of. inch. ) outer diameter by (0.190 inch) inner diameter - 20.32-cm. / 0.635 cm / 0.4826 cm, respectively, in the lower region from the dynamic mixing chamber to help provide some back pressure. This helps the dynamic mixing chamber comprising the cylindrical sleeve with its full pin thruster. This also helps to ensure proper and complete mixing of the oil and water phases.

An emulsion with the required ratio of oil to water phases is obtained. First, the flow rates are adjusted so that 3 parts by weight of the water phase and 1 part by weight of the. oil phase enters the dynamic mixing chamber with the pin impeller. The ratio of the water phase to the oil phase is increased over a period of only a few minutes until the ratio of 12 - 13 parts of the water phase to 1 part of the oil phase changes to the dynamic mixing chamber. · a. at a rate of 15 ml / sec. Gradually, the flow rate of oil decreases so that the water / oil phase is by weight; be almost 25: 1. At this stage, the emulsion viscosity comes out of the static mixture droplets. (Visually, this mixture becomes more translucent at this stage). * ”

The flow rate of the oil phase is then decreased to the extent that the water phase / oil phase, in its weight ratio, is 30-33: 1. Visually the emulsion flows at this stage from the orifice of the mixer i

/ u 17

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Mod. 71 · 20,000 · «. - »0/08 static with the consistency of a whipped cream and set with a consistency reminiscent of a creamy yogurt.

EMULSION POLYMERIZATION

At this stage, the emulsion emerging from the static mixer is ready to cure. The emulsion is fed to a generally rectangular mold made of polyethylene which is 38 cm long, 25 cm wide and 22 cm deep. The emulsion is emptied into such molds until each mold contains about 20,000 ml of the emulsion to be cured.

Curing is effected by placing the emulsion-containing molds in the oven to cure at a temperature of 60 ° C for a period of about 16 hours. Thereafter, the solid polymerized foam material contains up to 98Z of water and is soft. wet to the touch »

FOAM WASHING AND HYDROLIZATION Wet cured foam material is removed from the curing mold and subjected to further processing. The wastewater phase in the foam is expressed by applying sufficient pressure to the foam material or thin slices of foam material to squeeze at least 90% of the original retained waste water phase material. Interestingly, when the foam prepared according to the above procedure is squeezed, the foam edges do not protrude outward, and the foam cells do not stretch. Instead, the foam appears to collapse under pressure in the foam. Z-direction, then bouncing back to its original shape, either as rolling the soaked water or when heat is applied as described herein.

The foam sample is then washed for 20 seconds in 60 ° C water containing a detergent as a hydrophilizing agent. In this case, the JOY liquid dishwashing detergent is used and dissolved in. water up to 5 g · / liter. The JOY-active hydrophilizing agents comprise a mixture of coconut alkyl sulfate and anionic coconut ethoxylate sulfate anionic surfactants, as described in more detail in Pacheri U.S. Patent 4,316. 824 23 February 1982 (incorporated herein by reference). During this treatment, the foam returns to its original form.

The JOY solution used for the first wash is again expressed using

<img file="PT101759B_D0080.tif" />

Mod. 71 - 20,000 ex. · 90/08 pressure, the foam is then treated with a second wash with the JOY solution at 60 ° C. This second rinse is supposed to leave a detergent residue in the foam, thus taking the relatively hydrophilic internal foam surfaces.

TAKE WATER FROM FOAM

The twice hydrophilized foam is again pressed to squeeze excess detergent solution from inside its porous structure. The foam samples are then dried by drying them in the oven for 12 hours at room temperature.^L60 ° C. After drying, the foam samples are further cut if necessary and subjected to further testing or incorporation into diaper products of the type described in Example IV.

EXAMPLE II

Another type of HIPE foam material may be prepared in the same manner as set forth in Example I. In this case, the emulsion preparation and polymerization procedures are performed as in Example I, but with the following differences. in materials, concentrations and conditions:

1) An emulsifying mixture of 480 g SPAN @ 80 and 120 grams SPAN ^ 85 is used in the oil phase.

2) a static mixer (14 inches) in length xx (3/8 inch) 0 is used. D. 35.6 cm x 0.95 cm for a. lower zone from the. mixing chamber.

3) The pin thruster is operated at a speed of 850 revolutions per minute.

4) The thin weight ratio! of water to the oil phase is 31: 1.

5) A cure temperature of 662C is used.

In this example, the polymerized HIPE foam is hydrophilized through one. treatment with an aqueous sodium chloride solution as agentx. hydrophilizing agent. The hydrophilizing agent solution contains 1 Z by weight of calcium chloride and is applied twice to the foam samples in the same manner as in Example I. After drying, the foam samples in this example are cut again according to. additional testing required and for incorporation into diaper products of the type described in example IV.

EXAMPLE III

<img file="PT101759B_D0081.tif" />

<img file="PT101759B_D0082.tif" />

V

In this example, HIPE foam materials prepared according to the general procedures of Examples I and II are tested for their structural, mechanical and fluid handling properties. Testing for these properties is performed using the procedure described in US Patent 4,788,225, cited above, or the various procedures set forth above in the TEST METHODS section. The results of such tests are summarized in table I.

ASPECT

TABLE I

FOAM / EXAMPLE I

FOAM / EXAMPLE II

Mod. 71 - 20,000 βχ. · 90/08

Q

STRUCTURAL ASPECTS UNITS

<td>pore volume</td><td> 36,8</td><td> 31,8</td><td>mL / g</td>

<td>Specific surface area</td><td></td><td></td><td></td>

<td>gets hair suction</td><td> 1,35</td><td> 1,25</td><td>m²/ g</td>

<td>Density</td><td> 0,029</td><td> 0,032</td><td>g / cm³</td>

<td>Medium cell size</td><td> 40</td><td> 37</td><td></td>

<td>MECHANICAL ASPECTS</td><td></td><td></td><td></td>

<td>Voltage under 5.1 kPa / Pressure</td><td>52Z</td><td>31Z</td><td>Ί</td>

<td>Flexibility</td><td> &gt; 1</td><td></td><td>cycles of</td>

<td>50Z Recovery Z</td><td></td><td></td><td></td>

<td>95Z compression</td><td></td><td>94Z</td><td>Z</td>

<td colspan="2">FLUID HANDLING PROPERTIES</td><td></td><td></td>

<td colspan="2">Absorbing capacity at a pressure of:</td><td></td><td></td>

<td>0.0 kPa (0.0 psi)</td><td> 35,9</td><td> 31,5</td><td>mL / g</td>

<td>1.4 kPa (0.2psi)</td><td> 34,0</td><td> 29,1</td><td>mL / g</td>

<td>5.1 kPa (0.74 psi)</td><td> 23,4</td><td> 25,1</td><td>mL / g</td>

<td>6.9 kPa (1.0 psi)</td><td> 13,0</td><td> 14,8</td><td>mL / g</td>

<td>Z cf acfdaie kPa of 0.0</td><td></td><td></td><td></td>

<td>at 5.1 kPa</td><td> 65,2</td><td> 79,7</td><td>Z</td>

<td>Driving license</td><td></td><td></td><td></td>

<td>up to 5 cm</td><td> 105</td><td> 120</td><td>seconds</td>

<td>Absorbing capacity at</td><td>height up to:</td><td></td><td></td>

<td>1.3 cm (0.5 in 1</td><td> 30,9</td><td> 26,7</td><td>mL / g</td>

<td>3.8 cm (1.5 in)</td><td> 30,7</td><td> 26,4</td><td>mL / g</td>

<td>6.4 cm (2.5 in)</td><td> 28,0</td><td> 25,3</td><td>mL / g</td>

<td>8.9 cm (3.5 in)</td><td> 26,6</td><td> 24,8</td><td>mL / g</td>

<img file="PT101759B_D0083.tif" />

<img file="PT101759B_D0084.tif" />

yu / υο

<img file="PT101759B_D0085.tif" />

<img file="PT101759B_D0086.tif" />

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<img file="PT101759B_D0089.tif" />

described below in Table II.

TABLE II

STRENGTHED AND STRENGTHED SPIRAL CELLULOSE FIBERS (STCC) Type ~ Southern softwood pulp braided with glutaldehyde up to 1.41 mole Z on an anhydroglucose basis of dry fiber cellulose

Dry Count ³ 6.8 knots / mm

Wet count = 5.1 knots / mm

Isorpopol alcohol retention value = »24Z

Water retention value = 37Z

Spiral Factor = * 0.63

Conventional unreinforced cellulose fibers used in combination with STCC fibers are also made of foley. These unreinforced cellulose fibers are refined to about 200 CSF (. FREE STATE. CANADIAN STANDARD).

The acquisition layer has a mean dry density of about 0.07 g / cm3, a synthetic mean dry weight basis under density of about 0.08 g / cm3 and a weight of about average base of about 0.03 g / cm 2. About 9.2 are used. grams of the branch of the acquisition of. fluid in the diaper core. The surface area of ​​the acquisition layer is about (46.8 inches ^) 302 cm ^. It has a caliber of about 0.44 cm.

The diaper core fluid redistribution / storage layer comprises a HIPE foam modified hourglass shape of the type described in Examples II and III. About 12 grams of HIPE foam is used to form this storage / distribution layer which attempts a surface area of ​​about 65.9 inches 425. gauge and about 0.325 inches caliber 0.826 cm. .

A diaper with this particular core configuration exhibits a desirable and effective use of the core to maintain discharged urine, thereby providing an exceptional low incidence of leakage when worn by a child in normal form.

EXAMPLE V ^r

Substantially similar to those described in Example IV are tested for effectiveness in a panel test where 75 boys use Example IV type diapers and baby diaper products.

<img file="PT101759B_D0090.tif" />

i 10

<img file="PT101759B_D0091.tif" />

Mod. 71 20,000 ex. 90/06 conventional configuration trolley in a noctuma situation. In such a test, each uses medium size diapers 7 for consecutive noctumo use, 4 of the type IV example and 3 of the type that corresponds to the commercially equivalent LUVS Deluxe for boys. The LUVS product has a standard male absorption zone and contains 39.1 grams of absorbent material.

Each uses one diaper per night, and the incidence of night leakage from each diaper used should be recorded. The resulting escape from all is then gathered and analyzed. As a result of this analysis, it can be determined that in such a panel test, 13.1Z of Example IV type diapers are leaky, while 14.00Z of LUVS diapers are leaky.

This panel test indicates that diapers using the absorbent foam materials of this invention as a fluid storage element may provide a leakage action comparable to the control diaper products marketed, even though the diapers of this invention contain slightly less. absorbent material than · control diaper products.

EXAMPLE VI

This example illustrates the preparation of another type of HIPE foam material within the scope of this invention.

EMULSION PREPARATION

Calcium chloride (36.32 kg) and potassium persulphate (568 g) are dissolved in 378 liters of water. This causes the water phase chain to be used in a continuous process for forming a HIPE emulsion.

Joins a monomer combination. comprising styrene (1600 g), technical grade divinylbenzene 55Z (1600 g), and ethylhexylacrylate-2 (4800 g) sorbitan monolaurate (960 g as SPAl · / ® 20). After mixing, this combination of materials is left to stand overnight. The supernatant material is removed and used as an oil phase in a continuous process for forming a HIPE emulsion. (about 75g of a sticky residue is discharged).

At an aqueous phase temperature of 48 - 50 ° C and an oil phase temperature of 22 ° C, separate oil phase and water phase chains are fed to a dynamic mixing apparatus. Mixing of the combined strands in the dynamic mixing apparatus is accomplished by

<img file="PT101759B_D0092.tif" />

Mod. 71 20,000 ex. - 90/00 of a pin thruster. At this stage of operation, there is a suitable pin thruster comprising a cylindrical shaft about 21.6 cm long with a diameter of about 1.9 cm. As described in example I, the shaft has four rows of pins, 2 rows of 17 pins and 2 rows of 16 pins, each with a diameter of 0.5 cm extending outwards from a central axis to a length of 1.6 cm. 0 pin driver is mounted on a cylindrical sleeve forming the dynamic mixing apparatus, the pins having a gap of 0.8 mm from the walls of the cylindrical sleeve.

A static spiral mixer is mounted in the lower part of a dynamic mixing apparatus to provide back pressure to the dynamic mixer and to provide improved incorporation of components into the emulsion which may be formed. Such a static mixer is (14 inches) long 35.6 cm with an outer diameter of 0.5 inches) 1.3 cm .0 static mixer is an industry model TAH 070-821, modified with the cut of (2, 4 inches) 6.1 cm.

Said combined mixing apparatus is filled with the oil phase and the water phase at one. ratio of 2 parts water to 1 part oil. The dynamic mixing apparatus is vented to let air out while filling the apparatus completely. Flow rates during filling are 1.127 g / sec oil phase and 2.19 cm 2 / sec water phase.

An. Once the apparatus is full, stirring is started in the dynamic mixer, with the impeller rotating at 1800 RPM. The flow rate of the water phase. It is then uniformly increased to a rate of 35.56 cm 2 / sec over a period of 130 sec. The back pressure created by the dynamic and static mixers at this time is (7.5 psi) 51.75 kPa. The thruster speed is then uniformly decreased to a speed of 1200 RPM over a time period of 60 sec. A. low back pressure up to (4.5 PSl) 31.05 kPa At this point, the throttle speed is instantly decreased to 1800 RPM. The system back pressure remains constant thereafter at (4,5 PSl) &lt;-31,05 kPa

EMULSION POLYMERIZATION

The formed emulsion flowing from the static mixer at this point is collected in Rubbermaid Economy cold food storage boxes,

<img file="PT101759B_D0093.tif" />

Mod. 7l 20,000 οχ. · 90/00

Model 3500. These boxes are made of food grade polyethylene and have the nominal dimensions of (18 x 26 x 9) 45.7 cm x 66 cm x 22.9 cm .The actual internal dimensions of these boxes are (15 xx 23 x 9) 38.1 cm x 58.4 cm x 22.9 cm. These boxes are pre-treated with a film of. a solution that. comprises a 20 AN solution of SP AN in an equal weight solvent mixture of xylene and isorpopanol. The solvent mixture is allowed to evaporate to leave only SPAN®20. 47 liters of emulsion are collected in each box.

The boxes containing the emulsion are kept in a room maintained at 6520 ° C for 18 hours in order to bring the emulsion polymerization into the boxes to thereby form polymeric foam material.

WASH, HYDROPHILIZATION AND DRYING OF FOAM

Once cured, the wet cured foam material is removed from the curing boxes. At this stage, the foam contains about 30-40 times the weight of the polymerized material (30-40X) of the wastewater phase. containing dissolved emulsifiers, electrolytes and initiators. The spirit material is cut with a reciprocating saw blade with a caliber of 0.350 inches (0.89 inches). These sheets are then compressed in series of 3 tooth rollers which gradually reduce the foam wastewater phase content to about 6 times (6X) the weight of the polymerizable material. At this stage, the leaves are then resaturated with a solution of Ca 12) at 60 ° C, squeezed into a tooth to a water phase content of about 10X. resaturated with CaC solution) 2^The 60 ° C, again being squeezed into a tooth to a water phase content of about 10X.

Foam sheets now containing about 10x of what is essentially a CaCl ^12 solution pass through a final vacuum tooth. The last tooth reduces the CaCl2 solution content up to about 5 times (5X). The weight of the polymer . A. The foam remains compressed after the last tooth to a caliber of about (0_?080 inches) 0.2 cm. The foam is then dried in a vacuum oven. air at about 60 ° C for about 3 hours. This drying reduces the moisture content to about 5-7µm weight of the polymerized material. At this stage, the foam sheets have a caliber of about (0.755 inches') 0.19 cm and are very foldable. The foam also contains about 11Z by weight of a sorbi monolaurate emulsifier.

<img file="PT101759B_D0094.tif" />

<img file="PT101759B_D0095.tif" />

Mod. 71 · 20.OCO ex. · JOfCB residual tetanus and about 5Z by weight (anhydrous basis) of residual hydrated calcium chloride as hydrolyzing agents. When collapsed, the foam density is about 0.17 g / cm3. When expanded to its free absorbent capacity (26.5 ml / g) in JAYCO synthetic urine, the expanded foam has a specific surface area. of capillary suction of about 2.24 m 2 / g, a pore volume of about 29.5 cc / g and an average cell size of about 15 microns.

Foam sheets prepared as in example VI represent an ideal fine-dry embodiment of this invention, as these foam sheets are in the form of collapsing foam material that expands in contact with aqueous body fluids. Once expanded, the foam materials are useful for absorbing body fluids that caused the foam to expand. These ideal collapsing foams are those formed from an unhydrolyzed polymeric material having a specific capillary suction surface area of ​​from about 0.5 to 5.0 m / g, containing from about 0.5Z to 20Z. by weight of the waste water-insoluble emulsifier foam material, and from about 0.1 Z to 7 Z by weight (anhydrous base) of the toxically acceptable hygroscopic hydrated salt foam material, which should preferably be calcium chloride or magnesium chloride as the hydrolyzing agent.

At this stage of collapse, such foam material has a residual water content of from about 4Z to 15Z by weight of polymerized material when stored under ambient conditions of (722) 222C and 50Z relative humidity. This water content includes hydration water associated with hygroscopic and hydrated salt as well as Free water absorbed inside.^- of the foam. This collapsing foam material also has a dry base density of from about 0-08 to 0.3 g / cm3.

In yours. In such a state of expansion, these ideal fine to dry foam materials have a pore volume of about 12 to 100 ml / g and have a compressive deflection resistance such that there is a pressure of 5.1 kPa which, after 15 minutes, produces a there is between about 5Z to 95Z of frame compression, when there is saturation at 37 ° C. until its free absorbent capacity with synthetic urine having a surface tension of 65 5 dynes / cm. 0 average cell size of these

Mod. 71 - 21) .000 βχ. · 90/08 Thin to dry ideal foam materials in the expanding state range from about 5 to 30 microns. The dry base density of the expanded foam material under saturation to its free absorbent capacity in this synthetic urine ranges from about 9Z to 28Z of its collapsed dry base density.

EXAMPLE VII

A substantially similar diaper is prepared in configuration as described in Example IV, using a thin to dry collapsible absorbent foam sheet of the type described in Example VI as the fluid storage / redistribution layer. In this diaper, the fluid acquisition / distribution layer comprising reinforced, twisted and spiral cellulosic fibers is used in an amount of about 13 grams. The thin to dry fluid storage / redistribution layer is also used in an amount of about 13 grams.

A diaper of this particular configuration exhibits an especially desirable and effective use of the absorbent core for maintaining discharged urine, thereby providing a relatively low leakage rate when worn by a child in normal situations.

<img file="PT101759B_D0096.tif" />

17 ÃG0.1995

Lisbon,

By THE. PROCTER &amp; GAMBLE COMPANY

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