MXPA97005238A - Absorbent foam materials for aqueous fluids, made of useful high-phase emulsions that have very high relations of water to ace - Google Patents

Abstract

Absorbent, crushed, low density foam materials which, upon contact with aqueous fluids, in particular urine, can expand and absorb these fluids. These low density foams typically have an expanded thickness of about 6 to about 10 times their thickness of the foams in their crushed state. These low density foams are made by polymerizing high internal phase emulsions (HIPEs), where the volume to weight ratio of the water phase to the oil phase is on the scale of about 55.1 to about 100.

Description

ABSORBENT FOAM MATERIALS FOR ACUTE FLUIDS.

FACTS OF USEFUL INTERNAL HIGH-PHASE EMULSIONS THAT THEY HAVE VERY HIGH RELATIONS OF WATER TO OIL TECHNICAL FIELD OF THE INVENTION This application relates to polymeapous, open cell, microporous, flexible foam materials that have fluid absorption and retention characteristics that make them particularly suitable for absorbing charged fluids, eg, urine. This application particularly pertains to materials of absorbent foam made of high internal phase emulsions that have very high water-to-oil ratios BACKGROUND OF THE INVENTION The development of highly absorbent articles to be used as disposable diapers, incontinence pads and panties for adults, and catamenial products and sanitary napkins, is the subject of substantial commercial interest. A highly desired feature for such articles is thinness. For example, diapers thinner they are less bulky to the user, fit better under the clothes, and are less noticeable Also, these are more compact in the package, making the diapers easier for the consumer to carry and store The compactez in the packaging and the reduced weight also result in reduced distribution costs for the manufacturer and distributor, including less shelf space required in the warehouse per unit diaper The ability to provide thinner absorbent articles, such as diapers, has been contingent on the ability to develop cores or structures relatively absorbent that can be acquired, distribute and store large quantities of body waste fluids, particularly urine In this regard, the use of certain particulate absorbent polymers, usually referred to as "hydrogel", "superabsorbent" or "hydrocolloid" materials, has been particularly important v'er, for example, United States of America patent 3,699, 103 (Harper et al.), issued June 13, 1972 and United States of America patent 3,770,731 (Harmon), issued June 20, 1972 , which describe the use of such particulate absorbent polymers in absorbent articles Actually, the development of thinner diapers has been the direct consequence of thinner absorbent cores which have the advantage of the ability of these absorbent particulate polymers to absorb large amounts of aqueous body fluids, discarded, typically when used in combination with a fibrous matrix See, for example, patent of the United States of America 4,673,402 (Weisman et al.) Issued June 16, 1987 and United States of America 4,935,022 (Lash et al.) Issued June 19, 1990, which describe dual layer core structures comprising a fibrous matrix and particulate absorbent polymers useful for manufacturing thin, compact non-bulky diapers These particulate absorbent polymers have previously not been exceeded in their ability to retain large volumes of fluids, such as urine. A representative example of such particulate absorbent polymers are lightly entangled polyacrylates. Like many other absorbent polymers, these slightly interlaced polysaccharides comprise a multitude of ammonium carboxy groups (charged) attached to the base structure of the polymer It is in these charged carboxy groups that the polymer can absorb aqueous fluids from the body as a result of osmotic forces Capillary strength-based absorbency is also important in many articles absorbent, including diapers. The capillary forces in various everyday phenomena, as exemplified by a paper towel that imbibes spilled liquids. Capillary absorbents can offer superior performance in terms of acquisition speed and conduction due to fluid wicking, that is, the ability to move the aqueous fluid away from the initial point of contact. Actually, the two-layer core absorbent structures, observed above, use the fibrous matrix as the primary capillary transport vehicle to move the aqueous fluid of the initially acquired body through the absorbent core, so that it can be absorbed and retained. by the absorbent polymer in particles placed in layers or zones of the nucleus. Other absorbent materials capable of providing capillary fluid transport are open cell polymeric foams. In fact, certain types of polymeric foams have been used in absorbent articles for the purpose of embedding, wicking and / or actually retaining aqueous body fluids. See, for example, U.S. Patent 3,563,247 (Lindquist), issued February 6, 1971 (absorbent pad for diapers and the like, wherein the primary absorbent is a sheet of hydrophilic polyurethane foam); U.S. Patent 4,554,297 (Dabi), issued November 19, 1985 (cellular polymers that absorb fluid from the body, which can be used in diapers or catamenial products); U.S. Patent 4,740,520 (Garvey et al.), issued April 26, 1988 (absorbent composite structure, such as diapers, feminine care products and the like, containing sponge absorbers made from certain types of polyurethane foams) interlaced, superimpregnated). The use of absorbent foams in absorbent articles such as diapers can be highly desirable. If done properly, open-cell hydrophilic polymer foams can provide capillary fluid acquisition, transport and storage characteristics required for use in high-performance absorbent cores. Absorbent articles containing such foams may possess desirable moisture integrity; provide adequate adjustment during the entire period in which the article is used, and may minimize changes in form during use (v gr, (-non-controlled lining, or stacking) In addition, absorbent articles containing such structures can be easier to manufacture on a commercial scale. For example, diaper absorbent cores can simply be printed on continuous foam sheets and can be designed to have considerably greater integrity and uniformity than absorbent fibrous webs. Many absorbent cores made from said fibrous webs are They fall apart during use. Such foams can also be prepared in any desired form, or even more can be formed into one-piece diapers. Absorbent foams particularly suited for absorbent products such as diapers, have been made from High Internal Phase Emulsions ( hereinafter referred to as "HIPE") See, for example, United States of America patent 5,260,345 (DesMarais et al., issued November 9, 1993 and United States of America patent 5,268,224 (DesMarais et al.) issued. on December 7, 1993. These absorbent HIPE foams provide desirable fluid handling properties, including (a) relatively good penetration and fluid distribution characteristics to transport the imbibed urine or other body fluid away from the initial impact zone and toward the unused balance of the foam structure to allow subsequent jets of fluid to be accommodated s, and (b) a relatively high storage capacity with a relatively high fluid capacity under load, i.e. under compressive forces. These HIPE absorbent foams are also flexible and soft enough to provide a high degree of comfort to the user of the article. absorbent, some can be made relatively thin until they are subsequently moistened by absorbed body fluid An important benefit in the manufacture of absorbent HIPE foams is commercially attractive for use in absorbent products such as diapers, is the economical The economics of the foams of HIPE absorbents depend on the amount and cost of the monomers used per unit of fluid absorbed, as well as the cost of converting the monomers to a usable polymer foam. Making the absorbent absorbent HIPE foams economically, you may need to use (1) lower total monomer per unit volume of e spuma, (2) less expensive monomers, (3) a less expensive process to convert these monorres to a usable absorbent HIPE foam, or (4) combinations of these factors »At the same time the absorbent HIPE foam can satisfy desirable characteristics for the capacity and absorbent strength under loading conditions without sacrificing the shear strength or elasticity to an unacceptable degree The reduction to reduce the cost of such absorbent foams, especially in terms of the reduction of the total amount of monomer used, it may be very difficult to achieve these desired mechanical and absorbency properties. As noted above, the thinner absorbent core is usually a requirement to make relatively thin absorbent articles, such as as diapers Providing relatively thin absorbent HIPE foams that quickly absorb body fluids when wetted, can be very challenging This is especially true if the relatively thin HIPE foam is made economically, while at the same time satisfying the desired criteria for absorbent capacity, hardening and strength under compression loading For example, it has been found that when less monomer is used per unit volume, the resulting absorbent HIPE foam may be too weak to function properly. Therefore, it would be desirable to be chap az of making a polymeric, absorbent, open-cell foam material that: (1) has adequate or preferably superior fluid handling characteristics, including capillary fluid transport capacity and total absorbent capacity for discharged body fluids for be desirable for use in absorbent articles such as diapers, pads or trusses for adult incontinence, sanitary napkins and the like; (2) it can be relatively thin and light during storage and normal use until it is moistened with these fluids; (3) have sufficient elasticity, hardness and strength under compression load to rapidly absorb these body fluids; and (4) can be manufactured economically without sacrificing these desired absorbency and mechanical properties to an unacceptable degree.

BRIEF DESCRIPTION OF THE INVENTION The present invention relates to polymer foam materials, in a crushed state, which upon contact with aqueous fluids (in particular aqueous body fluids such as urine), can expand and absorb these fluids. These absorbent polymeric foam materials comprise a flexible, hydrophilic, nonionic, interconnected open-cell polymeric foam structure. This foam structure has: (A) a specific surface area per volume of foam of at least about 0.025 m2 / cm 3; (B) at least about 0.1% by weight of a hydrated, hydroscopic, toxicologically acceptable salt incorporated herein; (C) in its collapsed state, an expansion pressure of approximately 30 kPa c lower; and (D) a free absorbent capacity of from about 50 to about 100 rpL'gr, (E) an expanded to crushed thickness ratio of at least about 6 1, (F) a resistance to compression deflection of about 40. % or less when measured under a confining pressure of 0 052022 kgrms per cm2 The present invention provides absorbent foams of very low density For a given expanded thickness, these foams of less density are thinner in their crushed state than the foams of HIPE Prior Absorbents These lower density foams more efficiently utilize the available pohmeric material and ultimately produce less waste than previous absorbent HIPE foams. As a result, the bulk density absorbent foams of the present invention provide an economically attractive means of achieving cores. Thinner absorbers for absorbent articles such as diapers, pillow or trusses for adult incontinence, sanitary napkins, and the like This is achieved while maintaining the desired absorbency and mechanical properties. The present invention further relates to a process for obtaining these lower density absorbent foams by polymerizing a specific type of water in oil emulsion or HIPE, having a relatively small amount of an oil phase and a relatively larger amount of a water phase This process comprises the steps of A) forming a water-in-oil emulsion of 1) an oil phase comprising a) from about 85 to about 98% by weight of a monomer component capable of forming a copolymer having a Tg of about 35 ° C or less, the monomer component comprising: i) from about 45 to about 70% by weight of at least one monofunctional monomer substantially insoluble in water , capable of forming an atactic amorphous polymer having a Tg of about 25 ° C or less; ii) from about 10 to about 30% by weight of at least one monofunctional comonomer substantially insoluble in water, capable of imparting strength approximately equivalent to that provided by the styrene; iii) from about 5 to about 25% by weight of a first polyfunctional crosslinking agent, substantially insoluble in water, selected from divinylbenzenes, trivinylbenzenes, divinyl-toluenes, divinyl-xylenes, divinylnaphthalenes, divinyl-alkylbenzenes, divinyl-phenanthrenes, divinylbiphenyls, divinyl-diphenylmethanes, divinylbenzyl, ethers divinylphenyls, divinyl-diphenyl sulfides, divinylfurans, divinyl sulfide, divinyl sulfone, and mixtures thereof; and iv) from 0 to about 15% by weight of a second polyfunctional crosslinking agent, substantially insoluble in water, selected from polyfunctional acrylates, methacrylates, acrylamides, methacrylamides, and mixtures thereof; and b) from about 2 to about 15% by weight of an emulsifying component, which is soluble in the oil phase, and which is suitable for forming a stable water-in-oil emulsion, the emulsion component comprising: a primary emulsifier having at least about 40% by weight of emulsifying components selected from diglycerol monoesters of branched C16-C24 fatty acids, diglycerol monoesters of linear unsaturated C16-C22 fatty acids, and diglycerol monoesters of saturated C12-C14 fatty acids , linear; sorbitan monoesters of branched C 16 -C 24 fatty acids, sorbitan monoesters of unsaturated linear C 16 -C 22 fatty acids, sorbitan monoesters of saturated, linear C 12 -C 14 fatty acids; monoaliphatic diglycerol ethers of branched alcohols, monoaliphatic diglycerol ethers of linear unsaturated C 16 -C 22 fatty alcohols, diglycerol monoaliphatic ethers of linear saturated C 12 -C 14 alcohols, and mixtures thereof; and 2) a water phase comprising an aqueous solution containing: (a) from about 0.2 to about 20% by weight of a water soluble electrolyte; and (b) an effective amount of a polymerization initiator; 3) a volume to weight ratio of water phase to oil phase in the range of about 55: 1 to about 100: 1; and B) polymerizing the monomer component in the oil phase of the oil in water emulsion to form a polymeric foam material. The polymeric foam material can be dehydrated subsequently to the point that a crushed, polymeric foam material is formed which will re-expand upon contact with aqueous fluids. The process of the present invention allows the formation of these low density HIPE foams as the result of a combination of two factors. One is the use of more robust emulsifiers, in particular diglycerol monooleate, diglycerol monoisostearate and sorbitan monooleate emulsifiers which have higher levels of interfacially active components. These more robust emulsifiers can stabilize the HIPE at these very high water to oil ratios, even when the HIPE is emptied and / or polymerized at relatively high temperatures. The other is a balanced formulation of the monomer component with more polyfunctional crosslinking agent and less monomer that confers stiffness similar to polystyrene to achieve the desired resistance objectives under compression load without sacrificing shear strength or elasticity to an unacceptable degree . The inclusion of a second crosslinking agent, and in particular the diacrylates and dimethylacrylates of a diol having at least two, more preferably at least 4, very preferably 6 carbon atoms, is particularly useful in the manufacture of foams with the desired properties.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 of the drawings is a photomicrograph (250 X amplification) of an edge view of a cutting section of an absorbent, representative polymer foam, according to the present invention, in its expanded state, made of HIPE having a weight ratio of water to oil of 56: 1 and is emptied at 44 ° C, and wherein the monomer component consists of a weight ratio of 7: 22: 63: 8 styrene: technical grade divinylbenzene (approximately 55% DVB and approximately 45% ethyl styrene): 2-ethylhexyl acrylate (EHA): 1,4-butanediol dimethylacrylate, and where emulsifier was used in 6% (by weight of the oil phase) of diglycerol monoleate (DGMO). Figure 2 of the drawings is a photomicrograph (1000 X amplification) of the foam of Figure 1. Figure 3 of the drawings is a photomicrograph (250 X amplification) of an edge view of a section of cut of another polymer foam , absorbent, representative, according to the present invention, in its expanded state, made of HIPE having a weight ratio of water to oil of 56: 1 and emptied at 44 ° C, and having the same weight ratio from water to oil, weight ratio of the monomer and emulsifier component in 6% of (DGMO) as the HIPE of Figure 1 Figure 4 of the drawings is a photomicrograph (1000 X amplification) of the foam of Figure 3 Figure 5 of the drawings is a cut-away representation of a disposable diaper utilizing the absorbent polymer foam of the present invention as an hourglass-shaped fluid storage / redistribution component in an absorbent diaper core. Double layer configuration Figure 6 of the drawings depicts a sectional view of a shape fitting article such as a disposable training pant that employs a polymeapca absorbent foam according to the present invention as an absorbent core Figure 7 of the drawings represents a separate view of the components of a diaper structure also of a multi-layer core configuration, having a fluid acquisition / distribution foam layer, in the form of an hourglass, covering a storage / redistribution layer of fluid with a modified hourglass shape DETAILED DESCRIPTION OF THE INVENTION I. Polymeric Absorbing Foams A. General Characteristics of the Foam The polymembrane foams according to the present invention, useful in absorbent articles and structures, are those that are relatively open cell. This means that the individual cells of the foam are in complete communication. , not obstructed with the adjacent cells The cells, in said substantially open cell foam structures, have intercell openings or "windows" that are large enough to allow easy transfer of fluid from one cell to another, within the structure of the cell. foam These foam structures of substantially open cell will generally have a cross-linked character, the individual cells being defined by a plurality of mutually connected, three-dimensionally branched webs The strands of the polymeric material forming these branched webs may be referred to as "poles" The foams of cell that have a typical pole-like structure are shown by way of example in the photomicrographs of Figures 3 and 4 For purposes of the present invention, a foam material is "open cell" if at least 80% of the cells in the foam structure that are at least Vm in size, are in fluid communication with at least one adjacent cell. In addition to having open cells, these polymeric foams are sufficiently hydrophilic to allow the foam to absorb fluids Aqueous in the quantities specified below The internal surfaces of the foam structures are made hydrophilic through residual hydrophilizing surfactants left in the foam structure after polymerization, or through selected post-polymerization foam treatment procedures, as described below. The degree to which these polymeric foams are "hydrophilic" can be quantified through the value of "adhesion stress" exhibited when in contact with an absorbable test liquid The adhesion stress exhibited by these foams can be determined experimentally using a method wherein the consumption of a test liquid by weight, for example, synthetic urine, is measured for a sample of known dimensions and area of capillary suction specific surface Said procedure is described in detail in the Test Methods section of the application of the United States of America sene No 989,270 (Dyer et al.), filed on December 1, 1992, which is incorporated Here by reference The foams, which are useful as absorbers in the present invention, are generally those that ex They have an adhesion strength value of about 15 to about 65 dynes / cm, preferably about 20 to 65 dynes / cm, approximately, as determined by the capillary absorption of synthetic urine having a surface tension of 65 + 5 dynes / cm. The polymeric foams of the present invention can be prepared in the form of crushed polymeric foams (ie without expanding) which, upon contact with aqueous fluids, expand and absorb said fluids. The crushed polymeric foams are usually obtained by squeezing the water phase of the polymerized HIPE foam through compression sleeves and / or thermal drying and / or vacuum dewatering. After compression and / or thermal drying / vacuum dehydration, the polymeric foam is in a crushed or unexpanded state. The cellular structure of a crushed, representative HIPE foam from which the water has been squeezed out by compression is shown in the photomicrograph of Figures 3 and 4. As shown in these figures, the cellular structure of the foam is distorted, especially when compared to the expanded HIPE foam structures shown in Figures 1 and 2. Also, as can be seen in Figures 3 and 4, the voids or pores (dark areas) in the crushed foam structure have been flattened or elongated. Following compression and / or thermal drying / vacuum dewatering, the crushed polymer foam can be re-expanded when wetted with aqueous fluids.

Surprisingly these polymeric foams remain in their crushed state 0 not expanded, for significant periods of time, up to at least approximately 1 year. The ability of these polymeric foams to remain in this crushed / unexpanded state is believed to be due to capillary forces, and in particular to the capillary pressures developed within the foam structure. As used herein, "capillary pressures" refers to the pressure differential across the liquid / air interface due to the half-moon curvature within the narrow boundary of the pores in the foam [See Chatterjee, "Absorbencv." Textile Science and Technology, Vol 7, 1985, p 36] After compression and / or thermal drying / vacuum dehydration to a practicable limit, these polymeric foams have residual water that includes both the water of hydration associated with the hydrated, hygroscopic salt incorporated there, as well as the free water absorbed within the foam This waste water (aided by the hydrated salts) is believed to exert capillary pressures on the foam structure, crushed, resulting in the crushed polymeric foams of the present invention may have wastewater of at least about 4%, typically from about 4 to about 40%, by weight of the foam when stored at conditions a Environmental temperatures of 22 ° C and 50% relative humidity Preferred crushed polymer foams have residual water contents of about 5 to about 25% by weight of the foam. A key parameter of these spunns is their glass transition temperature (Tg). Tg represents the midpoint of the transition between the vitreous and elastic states of the polymer. Foams that have a Tg greater than the temperature of use, can be very strong, but they will also be very rigid and potentially susceptible to fracture. Such foams typically also take a lot time to recover the expanded state when wetted with cooler aqueous fluids than the Tg of the polymer after being stored in the crushed state for extended periods The desired combination of mechanical properties, specifically strength and elasticity, typically needs a fully selective scale of types and levels of monomer to obtain these properties For the foams of the present invention, the Tg should be as low as possible, provided that the foam has an acceptable resistance to the temperatures of use. Therefore, the monomers are selected to provide as much as possible corresponding homopolymers having Tgs more It has been found that the chain length of the alkyl group in the acrylate and meta-platelet comonomers may be longer than that which could be predicted from the Tg of the homologous homopolymer series. Specifically, it has been found that homologous homopolymer sene of alkylacline or meta-plate has a minimum Tg at a chain length of 8 carbon atoms. In contrast, the minimum Tg of the copolymers of the present invention occurs at a chain length of about 12 carbon atoms (Since styrene monomers can be used substituted with alkyl instead of the alkylacplatos and metacplatos, its availability is currently extremad limited) The shape of the glass transition region of the polymer can also be important, that is, if it is narrow or wide as a function of temperature This shape of the glass transition region is particularly relevant when the temperature in use (usually ambient or body temperature) of the polymer is at or near the Tg. For example, a wider transition region may represent an incomplete transition at temperatures of use. Typically, if the transition is incomplete at the use temperature, the polymer it will present greater rigidity and less elasticity In reverse form, if the transition is complete at the temperature of use, then the polymer will exhibit a more rapid recovery of compression when wetted with aqueous fluids. Therefore, it is desirable to control the Tg and the width of the transition region of the polymer to obtain the desired mechanical properties. polymer is at least about 10 ° C lower than the temperature of use (The Tg and the width of the transition region are derived from the curve of tangent against temperature, of loss, of a measurement of dynamic mechanical analysis (DMA), as described in the Test Methods section below B. Pressures and Capillary Forces within the Foam Structure In its collapsed state, the capillary pressures developed within the foam structure at least equal to the forces exerted by the recovery or elastic modulus of the compressed polymer. In other words, the capillary pressure needed to keep the relatively thin collapsed foam is determined by the compensating force exerted by the compressed polymeric foam as it intends to "return to its previous state". The tendency in elastic recovery in polymeric foams can be estimated from stress / strain experiments where the expanded foam is compressed to approximately 17% of its original thickness, expanded, and then maintained in this compressed state until it is measured a relaxed tension value. Alternately, and for the purposes of the present invention, the relaxed stress value is estimated from the measurements in the polymer foam in its crushed state when placed in contact with aqueous fluids, eg, water. This value of alternating relaxed tension is hereinafter referred to as the "expansion pressure" of the foam. The expansion pressure for the crushed polymeric foams of the present invention is about 30 kiloPascals (kPa) or less and typically about 7 to about 20 kPa. A detailed description of a method for estimating the expansion pressure of the foams is set forth in the Test Methods section of the United States patent application, copending Serial No. 989,270 (Dyer et al.), Filed on April 1. December 1992, which is incorporated by reference. For the purposes of the present invention, it has been found that the specific surface area by volume is particularly useful for defining empirically the foam structures that will remain in a crushed state. See United States patent application, copending Serial No. 989,270 (Dyer et al.), Filed December 11, 1992 (incorporated herein by reference), where the specific area by volume of foam is discussed in detail. The "specific surface area per unit volume" refers to the specific surface area of capillary suction of the foam structure multiplied by its foam density in the expanded state. This value of specific surface area per volume of foam is characterized as "empirical" in that it is derived from (a) the specific surface area of capillary suction that is measured during wetting of the dry foam structure, and ( b) the density of the expanded foam structure after wetting to saturation, instead of the direct measurement of the crushed, dry foam structure. Even though, it has been found that certain values of specific surface area per minimum foam volume are correlatable to the ability of the foam structure to remain in a crushed state. Polymeric foams according to the present invention having specific surface area values per foam volume of at least about 0.025 m2 / cm3, preferably at least about 0.05 m2 / cm3, most preferably at least about 0.07 m2 / cm3 , have been found empirically to remain in a crushed state. The "capillary suction specific surface area" is, in general, a measurement of the surface area accessible to the test liquid of the polymer network that forms a particular foam per unit mass of the volume of foam material (polymeric structural material plus the residual solid material). The particular surface area of suction is determined both by the dimensions of the cell units in the foam and by the density of the polymer, and thus is a way of quantifying the total amount of solid surface provided by the foam network to such degree that said surface participates in the absorbency. The specific surface area of capillary suction is particularly relevant per se the appropriate capillary pressures within the foam structure are developed to keep it in a crushed state until it is wetted with aqueous fluids. The capillary pressure developed within the foam structure is proportional to the specific surface area of capillary suction. Assuming that other factors such as foam density and adhesive tension are constant, this means that, as the specific capillary suction surface area increases (or decreases), the capillary pressure within the foam structure also increases (or decreases) proportionally. For the purposes of this invention, the specific surface area of capillary suction is determined by measuring the amount of capillary consumption of a liquid of a low surface tension (e.g., ethanol), which occurs within a foam sample of a mass and known dimensions. A detailed description of said method to determine the specific surface area of the foam through the capillary suction method is established in the Test Methods section of the co-pending United States of America patent application No. 989,270 (Dyer and others), filed on December 11, 1992, which is incorporated herein by reference. Any reasonable alternative method can also be used to determine the specific surface area of capillary suction. The foams of the present invention useful as absorbers are those having a capillary suction specific surface area of at least about 3 m2 / g. Typically, the capillary suction specific surface area is in the range of about 3 to about 15 m2 / g, preferably about 4 to about 13 m2 / g, most preferably about 5 to 1 1 pT / g, approximately. Foams having versed values specific surface area of capillary suction (with densities in the expanded state of about 0.010 to about 0.018 g / cm3) will generally possess a balance of absorbent capacity, characteristics of fluid retention and wicking fluid or distribution, especially desirable, for aqueous fluids such as urine. In addition, foams having said specific surface area of capillary suction may develop sufficient capillary pressure to keep the foam in a crushed, unexpanded state, until it is moistened with aqueous fluids.

C. Absorbent Free Capacity Another important property of absorbent foams according to the present invention is their absorbent free capacity. "Absorbent free capacity" is the total amount of test fluid (test urine) which a sample of given foam will absorb into its cell structure per unit mass of solid material in the sample. To be especially useful in absorbent articles for absorbing aqueous fluids such as urine, the absorbent foams of the present invention should have a free capacity of about 55 to about 100 mL, preferably about 55 to about 75 mL, of synthetic urine per gram. of dry foam material. The procedure for determining the free absorbent capacity of the foam is described later in the Test Methods section.

D. Expansion Factor When exposed to aqueous fluids, the crushed foams of the present invention expand and absorb fluids. The foams of the present invention contain in their expanded state, more fluid than most other foams. When these foams are dehydrated by compression to a thickness of approximately (17%) or less of their expanded total thickness, they remain in even thinner states as is possible with the previous HIPE foams, with an increase with comitant in efficiency and storage flexibility. This is attributable to the low density of expanded foams. The "expansion factor" for these foams is at least about 6X, that is, the thickness of the foam in its expanded state is at least about 6 times the thickness of the foam in its collapsed state. The collapsed foams of the present invention typically have an expansion factor in the range of about 6X to about 10X. In comparison, the higher density foams above typically have an expansion factor of only 4X to 5X. For the purposes of the present invention, the relationship between expanded and collapsed thickness for dewatered foams by compression can be empirically predicted from the following equation: thickness expanded = thickness thickness x 0.133 x W: 0 ratio where thickness expanded is the thickness of the foam in its expanded state; apical thickness 0 is the thickness of the foam in its crushed state; and the ratio of W: 0 is the water-oil ratio of the HIPE from which the foam is made. In this way, a typical foam made of an emulsion with a water-oil ratio of 60: 1 would have a predicted expansion factor of 8.0, that is, a thickness expanded 8 times to the crushed thickness of the foam. The procedure for measuring an expansion factor is described hereinafter in the Test Methods section.

E. Resistance to Compression Deflection An important mechanical aspect of the polymeric absorbent foams of the present invention is its strength in its expanded state, as determined by its resistance to compression deflection (RTCD). The RTCD exhibited by the foams herein is a function of the polymer module, as well as the density and structure of the foam network. The polymer module is, in turn, determined by: a) the composition of the polymer; b) the conditions under which the foam was polymerized (for example the polymerization integrity obtained, specifically with respect to the entanglement); c) the degree to which the polymer is plasticized by the residual material, v. gr, emulsifiers, left in the foam structure after processing. To be useful as absorbers in absorbent articles such as diapers, the foams of the present invention must be suitably resistant to deformation or compression by forces encountered when such absorbent materials are coupled in fluid absorption and retention. Foams that do not have sufficient foam resistance in terms of RTCD may be able to acquire and store acceptable amounts of body fluid under no-load conditions, but too easily deliver said fluid under compression stress originated by the movement and activity of the user of the absorbent article containing the foam. The RTCD exhibited by the polymeric foams of the present invention can be quantified by determining the amount of stress produced in a saturated foam sample held under a certain confining pressure for a specific period of time and temperature. The method for carrying out this particular type of test is described later in the Test Methods section. The foams useful as absorbent are those that exhibit an RTCD so that a confining pressure of 5.1 kPa produces a voltage typically of approximately 40% or less of compression of the foam structure, when this has been saturated to its absorbent free capacity. with synthetic urine that has a surface tension of 65 ± 5 dynes / cm. Preferably, the stress produced under such conditions will be in the range of about 2 to about 25%, preferably about 4 to about 15%, most preferably about 6 to about 10%.

F. Other Properties of Polymer Foam Foam cells, and especially cells that are formed by polymerizing an oil phase containing monomer surrounding water phase droplets relatively free of monomer, will often have a substantially spherical shape. The size or "diameter" of said spherical cells is commonly used to characterize foams in general. Since the cells in a given sample of polymeric foam will not necessarily be of approximately the same size; the average cell sizes, ie the average cell diameters, will usually be specified. A number of techniques are available to determine the average cell sizes of the foams. The most useful technique involves a simple measurement based on the scanning electron photomicrograph of a foam sample. Fig. 1, for example, shows a typical HIPE foam structure, according to the present invention, in its expanded state. Superimposed on the photomicrograph is a scale representing a dimension of 20 μ. Said scale can be used to determine the average cell sizes through an image analysis procedure. The average cell measurements given herein are based on the average cell size in number of the foam in its expanded state, for example, as shown in Figure 1. The foams useful as absorbers for aqueous fluids, in accordance with The present invention will preferably have a number average cell size of about 50μ or less, and typically about 5 to 35μ. The "foam density" (ie in grams of foam per cubic centimeter of foam volume in air) is specified here on a dry basis. The amount of water-soluble waste materials, absorbed, for example, residual salts and liquids left in the foam, for example, after the polymerization, washing and / or hydrophilization of the HIPE, are not considered in the calculation and expression of the density of foam. The foam density does not, however, include other water-soluble waste materials such as emulsifiers present in the polymerized foam. Such residual materials can, in fact, contribute significant mass to the foam material. Any suitable gravimetric procedure that will provide a mass determination of the solid foam material per unit volume of foam structure can be used to measure the density of the foam. For example, an ASTM gravimetric process described more fully in the Test Methods section of the co-pending United States of America patent application No. 989,270 (Dyer et al.), Filed on December 11, 1992 (incorporated herein by reference) is a method that can be used for density determination. In their crushed state, the polymeric foams of the present invention useful as absorbers have dry basis density values in the range from about 0.1 to about 0.2 g / cm3, preferably from about 0.11 to about 0.15 g / cm3, and most preferably from 0.12 to 0.14 g / cm, approximately. In its expanded state, the polymeric foams of the present invention useful as absorbers have dry basis density values in the range from about 0.010 to about 0.018 g / cm3, preferably from about 0.013 to about 0.018 g / cm3. Suitable absorbent foams will in general exhibit in a particularly desirable and useful manner absorbency and aqueous fluid handling characteristics. The fluid handling and absorbency characteristics that are most relevant for the absorbent foams are: A) the vertical wicking effect of the fluid through the foam structure; B) the absorptive capacity of the foam at the specific reference wick effect heights; e C) the capacity of the absorbent foam structures to drain (distribute) the fluid of the rival absorbent structures with which the foam is brought into contact. The vertical wicking effect, ie the conduction by fluid wicking in a direction opposite to the gravitational forces, is an attribute of performance especially important for the absorbent foams herein. These foams will often be used in absorbent articles, in such a way that the fluid to be absorbed must move within the article from a relatively lower position to a relatively higher position within the absorbent core of the article. Accordingly, the ability of these foams to wick the fluid against gravitational forces is particularly relevant to their operation as fluid acquisition and distribution components in absorbent articles. The vertical wicking effect is determined by measuring the time taken for a color test liquid (e.g., synthetic urine) in a tank to wick a vertical distance of 5 cm through a foam test strip. specific size. The vertical wicking effect procedure is described in more detail in the Test Methods section of the co-pending United States of America application No. 989,270 (Dyer et al.), Filed on December 11, 1992 (incorporated herein by reference), but is done at 31 ° C, instead of 37 ° C. To be especially useful in absorbent articles for absorbing urine, the foam absorbent articles of the present invention will preferably vertically wick the synthetic urine (65 + 5 dynes / cm) 5 cm in no more than about 30 minutes. Most preferably, the preferred foam absorbers of the present invention will vertically wick this synthetic urine 5 cm in no more than about 5 minutes. Another important property of the absorbent foams useful in accordance with the present invention is its capillary absorption pressure. The capillary absorption pressure refers to the ability of the foam to wick the fluid vertically. [See, P. K. Chatterjee and H. V. Nguyen in "Absorbency", Textile Science and Technology Vol. 7; P. K. Chatterjee, Ed .; Elsevier: Amsterdam, 1985; Episode 2]. For the purposes of the present invention, the capillary absorption pressure of interest is the hydrostatic head, at which the vertically driven fluid load by wicking effect is 50% of the absorbent capacity under equilibrium conditions at 31 ° C. The hydrostatic head is represented by a column of fluid (eg, synthetic urine) of height h. To be especially useful in absorbent articles for absorbing charged fluids, the preferred absorbent foams of the present invention will generally have capillary absorption pressures of at least about 24.1 cm. (The foams of the present invention typically have absorption pressures of about 30 to about 40 cm).

II. Preparation of Polymeric Foams from HIPE having Very High Water to Oil Ratio A. In General Polymeric foams according to the present invention can be prepared by polymerizing certain water-in-oil emulsions having a relatively high ratio of water phase to oil phase commonly known in the art as "HIPEs". Polymeric foam materials, which result from the polymerization of such emulsions, are referred to hereafter as "HIPE foams". The relative amounts of the water and oil phases used to form the HIPEs are, among many other parameters, important for determining the structural, mechanical and performance properties of the resulting polymeric foams. In particular, the water to oil ratio in the emulsion can influence the density, the cell size and the specific surface area of capillary suction of the foam and dimensions of the poles that form the foam. The emulsions for preparing the HIPE foams of this invention will generally have a volume to weight ratio of water to oil phase in the range of about 55 1 to about 100 1, more preferably about 55 1 to about 75 1 , and most preferably from about 55 1 to about 65 1 1. Oil Phase Components The continuous oil phase of the HIPE comprises monomers that are polymetered to form the solid foam structure. This monomer component is formulated to be capable of forming a copolymer having a Tg of about 35 ° C or less. , and typically from 15 ° to 30 ° C, approximately (The method for determining Tg by Dynamic Mechanical Analysis (DMA) is described later in the Test Methods section) This monomer component includes (a) at least one functional monomer whose atactic amorphous polymer has a Tg of about 25 ° C or less (see Brandup, J, Immergut, EH, "Polymer Handbook", 2nd edition, W law-Interscience, New York, NY, 1975, 111-139) (b) at least one monofunctional comonomer to improve the stiffness or breaking strength of the foam, (c) a first functional interlacing agent, and (d) optionally a second functional crosslinking agent. Individuals and quantities of monofunctional monomers and comonomers and polyfunctional crosslinking agents may be important for the performance of HIPE absorbent foams, which have the desired combination of structure, mechanical, and fluid handling properties, which make these materials are suitable for use in the present invention The monomer component comprises one or more monomers that tend to impart rubber-like properties to the resulting polymeric foam structure. Such monomers can produce high molecular weight atactic amorphous polymers (greater than 10,000), having a Tg of about 25 ° C or less Monomers of this type include, for example, the alkylactlates (C4-C14) such as butyl acrylate, hexyl acrylate, octyl acrylate., 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, dodecyl (lauryl) acrylate, isoclecyl acrylate, tetradecyl acrylate, aryl acrylates and alkaryl acrylates such as benzyl acrylate, nonylphenyl acrylate, alkyl methacrylates ( C6-C16) such as hexyl methacrylate, octyl methacrylate, nonyl methacrylate, decyl methacrylate, isodecyl methacrylate, dodecyl (lauryl) methacrylate, tetradecyl methacrylate, alkyl styrenes (C4-C12) such as pn-octylstyrene, acrylamides such as N-octadecyl acrylamide, isoprene, butadiene, and combinations of such monomers. Of these monomers, the most preferred are isodecyl acrylate, dodecyl acrylate, and 2-ethylhexyl acrylate. The monofunctional monomers will generally comprise from 45 to about 70%, most preferably from about 50 to 65%, by weight of the monomer component. The monomer component used in the oil phase of the HIPEs also comprises one or more monofunctional comonomers capable of imparting rigidity approximately equivalent to that provided by styrene to the resulting polymeric foam structure. The stiffer foams exhibit the ability to deform substantially without failure. These types of monofunctional comonomer may include styrene-based comonomers (eg, styrene and ethyl styrene), or other types of monomers such as methyl methacrylate, wherein related homopolymer is known for its illustrative rigidity. The preferred monofunctional comonomer of this type is a styrene-based monomer, the most preferred monomers of this type being styrene and ethyl styrene.

The monofunctional "stiffness" comonomer will usually comprise about 10 to 30%, preferably 15% to 23%, most preferably about 18% to about 22%, by weight of the monomer component, In certain cases, the comonomer of "Stiffness" can also impart the desired rubber type properties to the resulting polymer. C4-C12 alkyl styrenes, and in particular p-n-octyl styrene, are examples of such comonomers. For said comonomers, the amount of these that can be included in the monomer component will be that of the typical monomer and comonomer combination. The monomer component also contains a first polyfunctional crosslinking agent (and optionally a second agent.) As with the monofunctional monomers and comonomers, the selection of the particular type and amount of the crosslinking agent is very important for the final realization of the preferred polymeric foams having the desired combination of structural, mechanical, and fluid handling properties The first polyfunctional crosslinking agent can be selected from a wide variety of comonomers containing 2 or more activated vinyl groups, such as divinylbenzenes, trivinylbenzenes, divinyl toluenes, divinylxylenes, divinylnaphthalenes, divinyl-alkylbenzenes, divinylphenanthrenes, divinylbiphenyls, divinyl-diphenylmethans, divinylbenzyl, divinylphenyl ethers, divinyl diphenyl sulfides, dikvinylfurans, divinyl sulfide, divinyl sulfone, and mixtures thereof Divinylbenzene is typically available as a mixture with ethylene glycol. il styrene in proportions around 55:45 These proportions can be modified in order to enrich the oil phase with one or the other component. In general, it is advantageous to enrich the mixture with the ethyl styrene component, while simultaneously reducing the amount of styrene in the monomer mixture. The preferred ratio of divinylbenzene to ethyl styrene is approximately 30:70 and 55:45, most preferably from 35:65 to 45:55, approximately. The inclusion of higher levels of ethyl styrene imparts the required rigidity without increasing the Tg of the resulting copolymer to the extent that the styrene does. This first interlacing agent in general can be included in the oil phase of the HIPE in an amount from about 5% to about 25%, preferably from about 12% to 18%, and most preferably from 12% to 16%, approximately, by weight of the monomer component.

The second optional crosslinking agent can be selected from polyfunctional acrylates, methacrylates, acrylamides, methacrylamides and mixtures thereof. These include di-, tri-, and tetra-acrylates, as well as di-, tri-, and tetra-methacrylates, di-, tri-, and tetra-acrylamides, as well as di-, tri-, and tetra-methacrylamides; and mixtures of these crosslinking agents. Suitable acrylate and methacrylate crosslinkers can be derived from diols, triols and tetraols including 1,1,10-decanediol, 1,8-octanediol, 1,6-hexanediol, 1,4-butanediol, 1,3-butanediol, 1, 4-but-2-eneodiol, ethylene glycol, diethylene glycol, trimethylolpropane, pentaerythritol, hydroquinone, catechol, resorcinol, triethylene glycol, polyethylene glycol, sorbitol, and the like. (The acrylamide and methacrylamide crosslinking agents can be derived from the equivalent diamines, triamines, and tetrarnins). Preferred diols have at least 2, preferably at least 4, and most preferably 6 carbon atoms. This second crosslinking agent can generally be included in the oil phase of the HIPE in an amount of from 0 to about 15%, preferably from 7 to about 13%, by weight of the monomer component. Without being bound by theory, it is believed that this second interlacing agent generates a more homogeneously interlaced structure that develops resistance more efficiently than using either the first or the second interleaver only at comparable levels. The second interlacing also has the effect of extending the transition region from glass to rubber. This wider transition region can be designed to meet the requirements of strength and elasticity at temperatures of use by controlling the relative amount of the two types of interleaver used. In this way, a foam containing only the first type of interlayer will exhibit a relatively narrow transition region, which may be useful if greater elasticity is desired and if the Tg is very close to the final temperature of use. The increase in the amount of the second interleaver serves to extend the transition region, even if the actual transition temperature has not changed.

The main portion of the oil base of the HIPEs will comprise the aforementioned monomers, comonomers and crosslinking agents. It is essential that these monomers, comonomers and crosslinking agents are substantially insoluble in water, so that they are mainly soluble in the oil phase and not in the water phase. The use of said substantially insoluble monomers in water ensures that HIPEs of appropriate characteristics and stability will be obtained. Of course, it is highly preferred that the monomers, comonomers and crosslinking agents used herein are of the type such that the resulting polymeric foam is suitably non-toxic and appropriate and chemically stable. These monomers, comonomers and crosslinking agents should preferably have little or no toxicity if present at very low residual concentrations, during the processing and / or use of the post-polymerization foam. Another essential component of the oil phase of the HIPE is an emulsifying component that allows the formation of stable HIPEs. This emulsifying component comprises at least one primary emulsifier. It has been found that the suitable primary emulsifiers are those which: (1) are soluble in the oil phase of the HIPE; (2) provide an oil phase / water phase interfacial tension (IFT) of from about 1 to about 10 dynes / cm, preferably from 2 to 8, approximately, dynes / cm; (3) provide a critical aggregate concentration (CAC) of about 5% by weight or less, preferably about 3% by weight or less; (4) form HIPEs that are sufficiently stable against coalescence at the relevant drop sizes and relevant process conditions (eg, formation and polymerization temperatures of HIPE); and (5) desirably have a high concentration of "interfacially active" components capable of reducing the interfacial tension between the oil and water phases of the HIPE. Although not intended to be bound by theory, it is believed that the concentration of interfacially active components needs to be sufficiently high to provide at least a roughly monolayer envelope to the internal oil phase droplets to the preferred droplet sizes, water ratios: oil, and emulsifier levels. It is also believed that a combination of the oil phase / high minimum water phase, IFT and CAC facilitates the formation of stable HIPE having suitably large droplet sizes, for the formation of a foam having preferred averaged cell and hole sizes. of the present invention. Typically, these primary emulsifiers: (6) have melt and / or crystalline phase transition temperatures from solid to liquid of about 30 ° C or less; (7) are dispersible in water; and (8) are substantially insoluble in water or at least not appreciably divided in the water phase under the conditions of use. It is preferred that the primary emulsifier provides a sufficient wetting capacity when it extends over the hydrophobic surface (eg, the polymeric foam), so that the advancing contact angle for the synthetic urine is less than (preferably and substantially) less than 90. The method for measuring IFT and CAC is described in the Test Methods section below). These emulsifiers also preferably hydrophilize the resulting polymeric foam. These primary emulsifiers typically contain at least about 40%, preferably at least 50%, most preferably at least about 70%, of emulsifying components selected from diglycerol monoesters of branched C16-C24 fatty acids, diglycerol monoesters. unsaturated, linear, C16-C22 fatty acids, or diglycerol monoesters of saturated C12-C14 fatty acids (ie, diglycerol monoesters of C18 fatty acids 1), diglycerol monomiristate, diglycerol monoisostearate, diglycerol monoesters of coconut fatty acids; sorbitan monoesters of branched C16-C24 fatty acids, sorbitan monoesters of C16-C22 unsaturated, linear fatty acids, and sorbitan monoesters of C12-C fatty acids such as sorbitan monooleate, sorbitan monomiristate and monoesters of sorbitan derived from coconut fatty acids; monoaliphatic diglycerol ethers of branched C16-C24 alcohols, diglycerol monoaliphatic ethers of linear unsaturated C16-C22 alcohols, diglycerol monoaliphatic ethers of saturated, linear C12-C14 alcohols, and mixtures of these emulsifying components. Preferred primary emulsifiers are glycerol monooleate (eg, preferably greater than about 40%, preferably greater than about 50%, and most preferably greater than about 70% glycerol monooleate) and sorbitan monooleate (v. gr., preferably greater than 40%, preferably greater than about 50%, and most preferably greater than about 70% sorbitan monooleate), and glycerol monoisostearate (eg, preferably greater than about 40%, preferably greater than about 50%, and most preferably greater than about 70% glycerol monoisostearate). The glycerol monoesters of saturated, linear unsaturated and branched linear fatty acids useful as emulsifiers in the present invention can be prepared by esterifying diglycerol with fatty acids, using procedures well known in the art. See, for example, the method for preparing polyglycerol esters, described in copending application of the United States of America series No. 989,270 (Dyer et al.), Filed December 1, 1992, which is incorporated herein by reference. The diglycerol can be obtained commercially or can be separated from polyglycerols that have a high content of diglycerol. Linear, saturated linear and branched unsaturated fatty acids can be commercially obtained. The ester product composed of the esterification reaction can be fractionally distilled under vacuum one or more times to produce distillation fractions having a high content of diglycerol monoesters. For example, a continuous 35.56 cm centrifugal molecular distillation still can be used for fractional distillation, A CMS-15A (C.V.C. Products Inc., Rochester, N.Y.). Typically, the supply line of the polyglycerol ester, while hot, is first dosed through a degassing unit and then into the hot evaporator cone of the molecular distillation still, where vacuum distillation occurs. The distillate is collected on the surface of the glass bell, which can be heated to facilitate the removal of the distillate. The distillate and the residue are continuously removed through transfer pumps. The fatty acid composition of the resulting composite ester product can be determined using high resolution gas chromatography. See, application of the co-pending United States of America series No. 989,270 (Dyer et al.), Filed on December 1, 1992, which is incorporated herein by reference. The distribution of polyglycerol and polyglycerol ester of the resulting composite ester product can be determined by capillary supercritical chromatography. See, request of the States United of Copendent Series No. 989,270 (Dyer et al.), Filed on December 1, 1992, which is incorporated herein by reference. Also, linear, unsaturated, linear, or branched, saturated, diglycerol monoaliphatic ethers can be prepared, and their composition is determined using methods well known in the art. See also request of the United States of America co-pending series No. 08/370920 (Stephen A. Goldman et al.), Filed on January 10, 1995, case No. 5540, which is incorporated herein by reference. The sorbitan monoesters of linear, branched saturated linear unsaturated fatty acids can be obtained commercially or prepared using methods well known in the art. See, for example, patent of the United States of America 4, 103, 047 (Zaki et al.), Issued July 25, 1978 (incorporated herein by reference), especially column 4, line 32 to column 5, line 13. The product of sorbitan ester compound can be fractionally distilled under vacuum to produce compositions having a high content of sorbitan monoesters. The sorbitan ester compositions can be determined by methods well known in the art, such as small molecule gel permeation chromatography. See also request of the United States of America co-pending series No. 08/370920 (Stephen A. Goldman et al.), Filed on January 10, 1995, case No. 5540, (which is incorporated herein by reference), which describes the use of this method for polyglycerol aliphatic ethers. In addition to these primary emulsifiers, secondary emulsifiers may optionally be included in the emulsifying component. These secondary emulsifiers are at least co-soluble with the primary emulsifier in the oil phase, and may be included for: (1) increasing the stability of the HIPE against coalescence of the dispersed water droplets, especially at higher water ratios to oil and higher HIPE formation and polymerization temperatures, (2) modify the minimum of IFT between oil and water phases within the range of approximately 0.06 to approximately 5 dynes / cm, (3) reduce the component CAC emulsifier, or (4) increase the concentration of interfacially active components. Suitable secondary emulsifiers may be of zwitterionic types, including phosphatidyl choline and phosphatidyl choline containing compositions such as lecithins and aliphatic betaines such as lauryl betaine; cationic types, including long chain C 12 -C 22 dialiphatic quaternary ammonium salts, short chain C, -C 4 dialiphatic salts, such as dimethyl ammonium ditallow chloride, bistridecyl dimethyl chloride; ammonium, dimethyl ammonium ditallow methylsulfate, quaternary ammonium salts of dialkoyl (alkenoyl) -2-hydroxyethyl C12-C22 long chain, dialiphatic short chain C1-C4, such as ditallow-2-hydroxyethyl dimethyl chloride ammonium, the long chain C12-C22 dialiphatic imidazolino quaternary ammonium salts, such as methyl-1-tallowamido ethyl-2-tallow imidazolino methylsulfate and methyl-1-oleylamido ethyl-2-oleyl imidazolino methyl sulfate; dialkyl benzyl quaternary ammonium salts of C, -C4 short chain, long chain C12-C22 monoaliphatic, such as dimethyl stearyl benzyl ammonium chloride and dimethyl tallow benzyl ammonium chloride, dialkoyl (alkenoyl) -2-aminoethyl C12-C22 long-chain, short-chain CrC4 monoaliphatic, short-chain CrC4 monohydroxyaliphatic ammonium salts such as methyl d-tallow sulfate-l-2-amidoethexyl 2-h? Drox? propylene ammonium and methyl diloleum sulfate? l-2-aminoethyl ethyl 2-hydroxy? ammonium, anionic types which include the C6-C18 dialiphatic esters of sodium sulfosuccinic acid such as the dioctyl ester of sodium sulfosuccinic acid and the sodium bicarbonate ester of sodium sulfosuccinic acid, the amine salts of dodecylbenzene sulfonic acid, and mixtures of these secondary emulsifiers. These secondary emulsifiers can be obtained commercially or prepared using methods known in the art. The preferred secondary emulsifiers are dimethyl ammonium dichloride methylsulfate and dimethyl ammonium dichloride methylchloride. When these emulsifiers Optional secondary materials are included in the emulsifying component, they are in a weight ratio of primary to secondary emulsifier from about 50 1 to about 1 4, preferably from 30 1 to 2 1, approximately The oil phase used to form the HIPEs comprises from about 85 to about 98% by weight of the monomer component and from about 2 to about 15% by weight of the emulsifier component. Preferably, the oil phase will comprise from about 90 to about 97% by weight of a monomer component and from about 3. to approx 10% by weight of the emulsifying component The oil phase can also contain other optional components. One such optional component is an oil-soluble polymerization initiator of the general type well known to those skilled in the art, as described in the patent. of the United States of America 5,290,820 (Bass et al.), Issued March 1, 1994, which is incorporated herein by reference A preferred optional component is an anti-oxidant such as an anti-oxidant such as Amined Light Stabilizer (HALS) such as bis- (1, 2,2,5,5-pentamet? Lp? Pepd? No) sebacate (T? nuv? n-765®) or a Handicapped Phenolic Stabilizer (HPS) such as lrganox-076®, and t-butylhydroquinone. Another optional component includes plasticizers such as cioctyl azelate, dioctyl sebacate or dioctyl adipate. Other optional components include fillers, dyes, agents chain transfer, dissolved polymers and the like. 2. Components of the Water Phase The discontinuous water internal phase of the HIPE is generally an aqueous solution containing one or more dissolved components. A dissolved essential component of the water phase is a water soluble electrolyte. The dissolved electrolyte minimizes the tendency of monomers, comonomers and crosslinkers that are mainly soluble in oil to also dissolve in the water phase. This, in turn, is believed to minimize the degree to which the polymeric material fills the cell windows in the adjoining oil / water surfaces formed by the droplets of the water phase during polymerization. Thus, the presence of the electrolyte and the ionic strength resulting from the water phase is believed to determine if and to what degree the resulting preferred polymeric foams can be open cell. Any electrolyte capable of imparting ionic resistance to the water phase can be used. Preferred electrolytes are mono-, di- or trivalent organic salts, such as water-soluble halides, for example, chlorides, nitrates and sulfates of alkali metals or alkaline earth metals. Examples include sodium chloride, calcium chloride, sodium sulfate and magnesium sulfate. Calcium chloride is most preferred for use in the present invention. Generally, the electrolyte will be used in the water phase of the HIPEs at a concentration in the range of about 0.2 to about 20% by weight of the water phase. Most preferably, the electrolyte will comprise from about 1 to about 20% by weight of the water phase. The HIPEs will also typically contain an effective amount of a polymerization initiator. Said initiator component is generally added to the water phase of the HIPEs and can be any free radical, water soluble, conventional initiator. These include peroxygen compounds such as sodium, potassium and ammonium persulfates, hydrogen peroxide, sodium peracetate, sodium percarbonate and the like. Conventional redox initiator systems may also be used. Such systems are formed by combining the above peroxygen compounds with reducing agents such as sodium bisulfite, L-ascorbic acid or ferrous salts The initiator may be present in an amount of up to 20 mole% based on the total moles of polymembrane monomers present in the oil phase. Most preferably, the initiator is present in an amount of about 0.001 to about 10 mol% based on the total moles of the polymerizable monomers in the oil phase 3. Hydrophilizing Surfactants and Hydratable Salts The polymer that forms the HIPE foam structure will preferably be substantially free of polar functional groups. This means that the polymeric foam will have a relatively hydrophobic character. These hydrophobic foams can find utility when the absorption of hydrophobic fluids is desired. Uses of this class include those in which an oily component is mixed with water and it is desired to separate and isolate the oily component, such as in the case of marine oil spills. When these foams are to be used as absorbers for aqueous fluids such as spills of juice, milk, and urine, these usually require additional treatment to make the foam relatively more hydrophobic. This can be achieved by treating the HIPE foam with a hydrophilizing surfactant, as described below. These surfactants Hydrophilization can n be any material that improves the water moistening capacity of the polymer foam surface These are well known in the art, and include a variety of surfactants, preferably of the non-ionic type. Generally, they will be in liquid form, and will dissolve or disperse in a hydrophilizing solution that is applied to the HIPE foam surface. In this way, the hydrophilizing surfactants can be absorbed by the preferred HIPE foams in suitable amounts so that their surfaces become substantially hydrophilic, but without substantially damaging the desired flexibility and compression deflection characteristics of the foam. Such surfactants may include all those previously described for use as the oil phase emulsifier for HIPE, such as glycerol monooleate, sorbitan monooleate and diglycerol monoisostearate. Said hydrophilizing surfactants may be incorporated in the foam during the formation and polymerization of the HIPE, or they may be incorporated by treatment of the polymeric foam with a solution or suspension of the surfactant in a suitable vehicle or solvent. In preferred foams, the hydrophilizing surfactant is incorporated so that residual amounts of the agent, which remain in the foam structure, range from about 0.5% to about 10%, preferably from about 0.5 to about 6% in weight of the foam. Another material that is typically incorporated into the foam structure of HIPE is a water soluble, hydratable, and preferably hygroscopic or deliquescent inorganic salt. Such salts include, for example, toxicologically acceptable alkaline earth metal salts. Salts of this type and their use with oil-soluble surfactants such as the foam hydrophilizing surfactant are described in greater detail in U.S. Patent 5,352,711 (DesMarais), issued October 4, 1994, the description of which is incorporated herein by reference. Preferred salts of this type include calcium halides such as calcium chloride which, as previously noted, can also be employed as the water phase electrolyte in the HIPE.

The hydratable inorganic salts can be incorporated by treating the foams with aqueous solutions of such salts. These salt solutions can generally be used to treat the foams after the end of or as part of the removal procedure of the residual water phase of the just polymerized foams. The treatment of foams with said solutions preferably deposits hydratable inorganic salts such as calcium chloride in residual amounts of at least 0.1% by weight of the foam, and typically in the range of about 0.1 to 12%, preferably from 7 to 10. % by weight of the foam, approximately. The treatment of these foams and relatively hydrophobic with hydrophilicizing surfactants (with or without hydratable salts) will typically be carried out to the extent necessary to impart a suitable hydrophilic character to the foam. Some preferred HIPE foams, however, are suitably hydrophilic in preparation, and may have sufficient amounts of hydratable salts incorporated therein, thus requiring no further treatment with hydrophilizing surfactants or hydratable salts. In particular, such preferred HIPE foams include those wherein certain previously described oil phase emulsifiers and calcium chloride are used in the HIPE. In those cases, the polymeric foams will be suitably hydrophilic, and will include residual water phase liquid containing or depositing sufficient quantities of calcium chloride to make them hydrophilic, even after the polymeric foams have been dehydrated or dried as described below.

B. Processing Conditions for Obtaining HIPE Foams The preparation of foams typically involves the steps of: 1) forming a highly stable internal phase emulsion (HIPE); 2) polymerizing / curing this suitable emulsion to form a solid polymeric foam structure; 3) optionally washing the solid polymeric foam structure to remove the original wastewater phase from the polymeric foam structure and, if necessary, treating the polymeric foam structure with a hydrophilizing agent and / or hydratable salt to deposit any agent hydrophilizing surfactant / hydratable salt required; and 4) then dehydrating this polymeric foam structure. 1. HIPE Formation HIPE is formed by combining the oil and water phase components in the weight ratios previously specified. The oil phase will typically contain the requisite monomers, comonomers, trainers and emulsifiers, as well as optional components such as plasticizers, antioxidants, flame retardants, and chain transfer agents. The water phase will typically contain electrolytes and polymerization initiators, as well as optional components such as water-soluble emulsifiers. The HIPE can be formed from the combined oil and water phases by subjecting them to shear agitation. The shear agitation is also applied to such a degree and for a time necessary to form a stable emulsion. Said process can be conducted in either intermittent or continuous form, and is generally carried out under suitable conditions to form an emulsion, wherein the droplets of the water phase are dispersed to such an extent that the resulting polymeric foam will have the requisite characteristics. of cell size and other structural characteristics. Emulsification of the oil and water phase combination will often involve the use of a mixing or stirring device, such as a pin propellant. A preferred method for forming said HIPEs involves a continuous process that combines and emulsifies the oil and water phases of requirement. In said process, a liquid stream comprising the oil phase is formed.

Consequently, a separate liquid stream comprising the water phase is also formed. Then, the two streams are combined in a suitable mixing chamber or zone, so that the pre-specified water-to-oil phase weight ratios are obtained. In the mixing zone or chamber, the combined streams are generally subjected to low shear agitation provided, for example, through a pin driver of suitable configurations and dimensions. The shear stress will typically be applied to the combined oil / water phase stream at an appropriate speed. Once formed, the stable liquid HIPE can then be removed from the mixing zone or chamber. This preferred method for forming HIPEs through a continuous process is described in more detail in U.S. Patent 5, 149,720 (DesMarais et al.), Issued September 22, 1992, which is incorporated herein by reference . See also application of the co-pending United States of America series No. 08/370694 (Thomas A. DesMarais), filed on January 10, 1995. Case No. 5543 (incorporated herein by reference), which describes an improved continuous procedure that has a recirculation loop for the HIPE. 2. Polymerization / Healing of HIPE The formed HIPE will generally be collected or emptied into a suitable container, container or reaction region, which will be polymerized or cured. In one embodiment, the reaction vessel comprises a tray constructed of polyethylene, from which finally the polymerized / cured solid foam material can be easily removed for further processing after the polymerization / cure has been carried out to the desired degree. The temperature at which the HIPE is emptied into the vessel is approximately equal to the polymerization / cure temperature. Suitable polymerization / curing conditions will vary depending on the monomer and other development of the oil and water phases of the emulsion (especially the emulsifier systems used), and the type and amounts of polymerization initiators used. Frequently, however, suitable polymerization / cure conditions will involve maintaining the HIPE at elevated temperatures approximately above 30 ° C, preferably above 35 ° C., during a period ranging from about 2 to 64 hours, most preferably from 4 to 48 hours, approximately. HIPE can also be cured in stages as described in U.S. Patent 5,189,070 (Brownscombe et al.), Issued February 23, 1993, which is incorporated herein by reference. A particular advantage of the more robust emulsifier systems used in these HIPEs is that the mixing conditions during the formation and emptying of the HIPE can be carried out at higher temperatures of about 50 ° C or more, preferably 60 ° C or more. plus. Typically, HIPE can be formed at a temperature from about 60 ° to about 99 ° C, very typically from about 65 ° to 95 ° C. An open-cell, porous, water-filled HIPE foam is typically obtained after polymerization / cure in a reaction vessel, such as a tray. This polymerized HIPE foam is typically cut or sliced into a sheet-like shape. Polymerized HIPE foam sheets are easier to process during the subsequent steps of treatment / washing and dehydration, as well as to prepare the HIPE foam for use in absorbent articles. The polymerized HIPE foam is typically cut / sliced to provide a cut thickness in the range of about 0.08 to about 2.5 cm. Subsequent dehydration will compress the foam in the Z direction typically leading to crushed HIPE foams having a thickness in the range of about 10 to about 17% of their cut thickness. 3. Treatment / Washing of the HIPE Foam The solid polymerized HIPE foam formed will generally be filled with the wastewater phase material to prepare the HIPE. The residual water phase material (generally an aqueous electrolyte solution, residual emulsifier, and polymerization initiator) must be at least partially removed prior to the processing and use of the foam. The removal of this original water phase material will usually be done by compressing the foam structure to compress the residual liquid, and / or by washing the foam structure with water or other aqueous washing solutions. Frequently, several compression and washing steps will be used, v. gr., from 2 to 4 cycles. After the original water phase material has been removed to the required degree, the HIPE foam, if needed, can be treated, v. g., by continuous washing, with an aqueous solution of a hydrophilizing surfactant and / or suitable hydratable salt. Hydrophilizing surfactants and hydratable salts that can be used have been previously described. As noted, the treatment of the HIPE foam with the hydrophilizing surfactant / hydratable salt solution continues, if necessary, until the desired amount of hydrophilizing surfactant / hydratable salt has been incorporated, and until the foam display the desired value of adhesion tension for any test liquid of choice. 4. Dehydration of the Foam After the HIPE foam has been treated / washed, it will generally be dehydrated. Dehydration can be achieved by compressing the foam to squeeze the residual water, subjecting the foam and water at the same temperature from about 60 ° to about 200 ° C, or by microwave treatment, by thermal dehydration in vacuum or by a combination of compression and drying / microwave / vacuum dewatering techniques. These HIPE foams are typically dehydrated in a compressed manner to a thickness of 17% or less of their expanded total thickness. The dehydration step will generally be performed until the HIPE foam is ready to use and is as dry as practicable. Frequently, such compression dehydrated foams will have a water content (moisture) of from about 50 to about 500%, most preferably from about 50 to 200% by weight, on a dry weight basis. Subsequently, the compressed foams can be thermally dried to a moisture content of about 5 to about 40%, most preferably 5 to 15% by weight, about a dry weight basis. lll. Uses of Polymeric Foams A. In General Polymeric foams according to the present invention are widely useful in absorbent cores of disposable diapers, as well as in other absorbent articles. These foams can also be used as absorbers of environmental waste oil; as absorbent components in bandages or bandages; to apply paint to various surfaces; in heads of molasses for dust; in wet mopping heads; in fluid jets; in packaging; in shoes as odor / moisture absorbers; on cushions; in gloves, and for many other uses.

B. Absorbent Articles The absorbent foams of the present invention are particularly useful as at least a portion of the absorbent structures (eg, absorbent cores) for various absorbent articles. By "absorbent articles" herein is meant a product of the consumer that is capable of absorbing significant amounts of urine, or other fluids (ie, liquids) such as aqueous fecal matter (soft stools), discarded by an incontinent user or user of the article . Examples of such absorbent articles include disposable diapers, incontinence garments, catamenials such as tampons and sanitary napkins, disposable trainers, night pillows, and the like. The absorbent foam structures herein are particularly suitable for use in articles such as diapers, sanitary napkins, incontinent pads or garments, protective clothing, and the like. In its simplest form, an absorbent article of the present invention only needs to include a backsheet, typically and relatively impervious to the liquid, and one or more absorbent foam structures associated with this backsheet. The absorbent foam structure and the backsheet will be associated in such a way that the absorbent foam structure is placed between the backsheet and the fluid discharge region of the wearer of the absorbent article. The liquid impervious backing sheets can comprise any material, for example polyethylene or polypropylene, having a thickness of about 0.038 mm, which will help retain the fluid within the absorbent article. More conveniently, these absorbent articles will also include a sheet superior to the liquid that curves the side of the absorbent article that touches the user's skin. In this configuration, the article includes an absorbent core comprising one or more structures of absorbent foam structures of the present invention placed between the back sheet and the top sheet. The liquid permeable upper sheets may comprise any material such as polyester, polyolefin, rayon and the like which are substantially porous and allow the body fluid to pass rapidly through it and into the underlying absorbent core. The sheet material of the topsheet it will preferably not have a propensity to maintain aqueous fluids in the contact area between the topsheet and the wearer's skin.

The absorbent core of the absorbent article embodiments of the present invention may consist of only one or more of these foam structures. For example, the absorbent core may comprise a single unit piece of foam formed as desired or needed for the best fit of the type of absorbent article in which it is to be used. Alternatively, the absorbent core can comprise a plurality of pieces of foam or particles that can be adhesively bonded together or that can simply be compressed into a non-bonded aggregate or understood together by an envelope of wrapping tissue or by means of the sheet upper and the backing sheet of the absorbent article. The absorbent core of the absorbent articles herein may also comprise others, for example, conventional materials or elements, in addition to one or more absorbent structures of the present invention. For example, the absorbent articles may use an absorbent core comprising a combination, for example, a mixture placed in air, of particles or pieces of the absorbent foam structure of the present and conventional absorbent materials such as a) wood pulp or other cellulosic fibers, and / or, b) particles or fibers of polymeric gelling agents. In an embodiment involving a combination of the absorbent foam of the present and other absorbent materials, the absorbent articles can employ a multi-layer absorbent core configuration wherein a core layer containing one or more foam structures of the present invention it can be used in combination with one or more additional separated core layers comprising other absorbent structures or materials. These or other absorbent structures or materials, for example, can be air-laid or wet-laid plies of wood pulp or other cellulosic fibers. These other absorbent structures may also comprise other types of foams, for example, absorbent foams or even sponges useful as fluid acquisition / distribution components such as those described in the United States patent application, copending No. 08 / 370695 (Keith J. Stone et al.), Filed on January 10, 1995. Case No. 5544, which is incorporated by reference. These other absorbent structures may also contain, for example, up to 80% by weight of particles or fibers of polymeric gelling agent of the type commonly used in absorbent articles that are for acquiring and retaining aqueous fluids. Polymeric gelling agents of this type and their use in absorbent articles are more fully described in reissued United States Patent 32,649 (Brandt et al.), Reissued on April 19, 1988, which is incorporated by reference. One embodiment of these absorbent articles utilizes a multi-layer absorbent core having a fluid handling layer positioned in the discharge regions of the article user. This fluid handling layer may be in the form of a high-floor non-woven web, but is preferably in the form of a fluid acquisition / distribution layer comprising a layer of modified cellulose fibers, eg fibers hardened, curled cellulosics, and optionally makes 10% by weight of this fluid fluid acquisition / distribution layer of gelling polymeric agent. The modified cellulosic fibers used in the fluid acquisition / distribution layer of said preferred absorbent article are preferably wood pulp fibers that have been hardened and crimped by thermal and / or chemical treatment. Said modified cellulosic fibers are of the same type as used in the absorbent articles described in U.S. Patent No. 4,935,622 (Lash et al.), Issued June 19, 1990, which is incorporated by reference. These multi-layer absorbent cores also comprise a second, that is, lower, fluid storage / redistribution layer comprising a foam structure of the present invention. For purposes of the present invention, a "super-layer" of a multi-layer absorbent core is a layer that is relatively closer to the wearer's body, eg, the narrower layer to the topsheet of the article. The term "lower layer" adversely means a layer of a multi-layer absorbent core that is relatively further from the wearer's body, for example, the layer closest to the backsheet of the article. This lower layer of fluid storage / redistribution is typically placed within the absorbent core to cover the (upper) fluid handling layer and to be in fluid communication with it. Absorbent articles utilizing the absorbent foam structures of the present invention in a lower fluid storage / redistribution layer that covers an upper acquisition / distribution layer of fluid containing curled, hardened cellulosic fibers are described in more detail in U.S. Patent 5,147,345 (Young et al.), issued September 15, 1992, which is incorporated by reference. Also, multi-layer absorbent cores can be made according to co-pending United States patent application Serial No. 08/370900 (Gary Dean Lavon et al.), Filed on January 10, 1995.

No. 5547 (incorporated herein by reference), wherein the fluid storage / redistribution layer comprises an absorbent foam according to the present invention. The disposable diapers comprising the absorbent foam structures of the present invention can be made using conventional diaper manufacturing techniques, but by replacing or supplying the wood pulp fiber web ("air filter") or the cellulose core absorbers modified typically used in conventional diapers with one or more foam structures of the present invention. The foam structures of the present invention can thus be used in diapers in a single layer or in several multi-layer core configurations as described above. One embodiment of disposable diaper representative of the present invention is illustrated by Figure 5 of the drawings. Said diaper includes an absorbent core 50, comprising a fluid acquisition upper layer 51, and an underlying fluid storage / redistribution layer comprising an absorbent foam structure of the present invention. A topsheet 53 is superimposed and is coextensive with one side of the core, and a backsheet impervious to liquid 54 is superposed and coextensive with the side of the core set to the face covered by the topsheet. The backsheet preferably has a width greater than that of the core, thereby providing lateral marginal portions of the backsheet extending beyond the core. The diaper is preferably constructed in an hourglass configuration. Another type of absorbent article that can utilize the absorbent foam structures of the present invention comprises shaped fit products such as training pants. Such shape adjustment articles will generally include a flexible, non-woven substrate, adapted in a frame in the form of shorts or trusses. An absorbent foam structure according to the present invention can then be fixed in the crotch area of said frame for the purpose of serving as an "absorbent core". This absorbent core will often be overwrapped with an envelope fabric or other non-woven material, permeable to liquid. Said overwrap of the core in this manner serves as the "top sheet" for the shape-adjusting absorbent article. The flexible substrate forming the frame of the shape adjustment article may comprise fabric or paper or other type of nonwoven substrate or formed films, and may be elasticized or otherwise capable of stretching. The leg bands or waistbands of said training pants article may be elasticized in any conventional manner to improve the fit of the article. Said substrate will generally be made relatively impermeable to the liquid, or at least not easily permeable to liquids, treating or coating the surface of the same or laminating this flexible substrate with another substrate relatively impervious to the liquid in order to make the overall frame relatively impermeable to the liquid. In this example, the frame itself serves as the "backsheet" for the shape adjustment article. Typical training pants products of this type are described in U.S. Patent 4,619,649 (Roberts), issued October 28, 1986, which is incorporated by reference. An adjustment article of typical shape in the form of a disposable training pant is shown in Figure 6 of the drawings. Said article comprises an outer layer 60 fixed to a lining layer 61 by adhering along its peripheral zones. For example, the inner liner 61 can be attached to the outer layer 60, along the periphery of a leg band area 62, along the periphery of the other leg band area 63, and along from the periphery of the waistband area 64. Attached to the crotch area of the article is a generally rectangular absorbent core 65 comprising an absorbent foam structure of the present invention.

IV. Test Methods A. Dynamic Mechanical Analysis (DMA) The DMA was used to determine the Tgs of the polymers including the polymeric foams. Samples of the foams were sliced into blocks with a thickness of 3-5 mm, and washed 3-4 times in distilled water, expressing the fluid through press rolls between each wash. The resulting foam blocks were allowed to air dry.

The slices of dry foam were applied to a core to produce cylinders with a diameter of 25 mm. These cylinders were analyzed using Rheometrics RSA-II dynamic mechanical analyzer equipment, in a compression mode using parallel plates with a diameter of 25 mm. The instrument parameters used were the following: Temperature step from approximately 85 ° C to -40 ° C in steps of 2.5 ° C Soaking intervals between temperature changes of 125-160 seconds Dynamic voltage setting from 0.1% to 1.0% (usually 0.7%) Frequency setting at 1.0 radians / second Setting of self-tension in dynamic force mode of static force tracking with an initial static force setting at 5 g. The glass transition temperature was taken as the maximum point of the tangent curve of loss versus temperature.

B. Resistance to Compression Deflection (RTCD) The resistance to compression deflection can be quantified by measuring the tension (% reduction in thickness) produced in a foam sample, which has been saturated with synthetic urine, after which a confining pressure of 5.7 kPa has been applied to the sample. Measurements of compressive deflection resistance are typically made on the sample concurrently with the Absorbent Free Capacity measurement, as described above. Jayco synthetic urine, used in this method, was prepared by dissolving a mixture of 2.0 g of KCl, 2.0 g of Na2S04, 0.85 g of NH4H2P04, 0.15 g of (NH4) 2HP04, 0.19 g of CaCl2, and 0.23 g of MgC | to 1.0 liters with distilled water. The salt mixture can be purchased from Endovations, Reading, Pa (Cat. No. JA-00131 -000-01). The foam samples, the Jayco synthetic urine and the equipment used to make the measurements were all equilibrated at a temperature of 31 ° C. All measurements were also made at this temperature. A sheet of foam sample was expanded and saturated, in its crushed state, to its free absorbent capacity by soaking it in a Jayco synthetic urine bath. After 3 minutes, a cylinder with a circular surface area of 6.5 cm 2, of the saturated, expanded sheet, was cut with a sharp circular die. The cylindrical sample was soaked in synthetic urine at 31 ° C for 6 more minutes. The sample was removed after the synthetic urine and placed on a base of flat, low granite or suitable gauge to measure the thickness of the sample. The gauge was set to exert a pressure of 0.55 kPa on the sample. Any calibrator equipped with a limb having a circular surface area of at least 6.5 cm2 and capable of measuring a thickness of 0.025 mm) may be used. Examples of such calibrators are Ames model 482 (Ames Co., Waltham, MA) or one Ono-Sokki model EG-225 (Ono-Sokki Co., Ltd., Japan) After 2 to 3 minutes, the expanded thickness (X1) was recorded, then a force was applied to the extremity, so that the sample of Saturated foam was subjected to a pressure of 5.1 kPa for 15 minutes.After this, the calibrator was used to measure the final thickness of the sample (X2) .From the initial and final thickness measurements, the percentage of induced stress for the samples, as follows: [(X1-X2) / X1] x100 =% reduction in thickness.

C. Absorbent Free Capacity (FAC) Absorbent free capacity can be quantified by measuring the amount of synthetic urine absorbed in a foam sample, which has been saturated and expanded with synthetic urine. Typically, the measurements of free absorbent capacity are made in the same sample concurrently with the measurement of the deflection resistance by compression and the expansion factor. The foam samples and Jayco synthetic urine were equilibrated at a temperature of 31 ° C. The measurements are made at room temperature. A foam sample sheet in its collapsed state was expanded and saturated to its free absorbent capacity by soaking it in a Jayco synthetic urine bath. After 3 minutes, a cylinder with a circular surface area of 6.5 cm 2, of the saturated, expanded sheet, was cut with a sharp circular die. The cylindrical sample was soaked in synthetic urine at 31 ° C for 3 more minutes. The sample was removed after the synthetic urine and placed on a digital scale. Any balance equipped with a tray for weighing that has an area larger than that of the sample and with a resolution of one milligram or less can be used. Examples of such balances are Mettler PM 480 and Mettler PC 440 (Mettler Instrument Corp., Hightstown NJ). After determining the weight of the wet foam sample (Ww), it was placed between two thin plastic mesh sieves on top of 4 disposable paper towels. The sample was compressed three times by firmly rolling a plastic roller over the upper screen. The sample was then stirred, soaked in distilled water for approximately 2 minutes, and compressed between the mesh sieves as previously done. Then, it was placed between 8 layers of disposable paper towels (4 on each side) and compressed with a force of 9080 kg in a Carver laboratory press. The sample was removed after the paper towels, dried in an oven at 82 ° C for 20 minutes, and its dry weight (Wd) was recorded. The free absorbent capacity (FAC) is the wet weight (Ww), minus the dry weight (Wd) divided by the dry weight (Wd), that is, FAC = [(Ww-Wd) / Wd].D. EXPANSION FACTOR The expansion factor can be quantified by measuring the thickness of a foam sample in the crushed state and in the expanded state. The ratio of the expanded thickness to the crushed initial thickness is the expansion factor. It is convenient to run the two measurements on the same sample concurrently with the measurement of the RTCD and free absorbent capacity as described above. The foam samples, the Jayco synthetic urine and the equipment used to make the measurements were all equilibrated at a temperature of 31 ° C. All measurements were also made at this temperature.

The sample foam is placed in its collapsed state on a flat granite base under a suitable meter to measure the thickness of the sample. The gauge was set to exert a pressure of 0.55 kPa on the sample. Any calibrator equipped with a limb having a circular surface area of at least 6.5 cm2 and capable of measuring a thickness of 0.025 mm) may be used. Examples of such calibrators are Ames model 482 (Ames Co., Waltham, MA) or an Ono-Sokki model EG-225 (Ono-Sokki Co., Ltd., Japan.) The initial thickness (XO) is recorded. foam is then expanded and saturated, to its free absorbent capacity by soaking it in a Jayco synthetic urine bath After 3 minutes, a cylinder with a circular surface area of 6.5 cm2, of the saturated, expanded sheet, was cut with a die The sample was then removed from the synthetic urine and placed on a flat granite base under a suitable meter to measure the thickness of the sample as a circular urine. Previously, after 2 to 3 minutes, the expanded thickness was recorded (X1) The expansion factor (EF) is calculated as EF = X1 / XO.

E. Interfacial Tension Method (IFT) (Turning Drop) The interfacial tension (IFT) was measured at 50 ° C through the spin drop method described in the co-pending United States of America application No. 989,270 ( Dyer et al.), Filed December 1, 1992 (incorporated herein by reference) except that: (1) the monomer mixture used to prepare the oil phase contains styrene, divinylbenzene (55% technical grade), acrylate 2-ethylhexyl, and 1,4-butanediol dimethacrylate, in a weight ratio of 14: 14:60:12; (2) The concentration of the emulsifier in the oil phase is varied by the dilution of a generally higher concentration of about 5-10% by weight below a concentration where the IFT is increased to a value that is at least about 10 dynes / cm greater than the minimum IFT, or about 18 dynes / cm, whichever is smaller; (3) a smooth line plotted through an IFT plot against the log emulsifier concentration was used to determine the minimum IFT; (4) Critical Aggregation Concentration (CAC) was determined by extrapolating the low concentration, usually a linear portion of the IFT against the log concentration graph (ie, the portion of the curve typically used to calculate the surface area per molecule on the adjoining surface, see, for example, Surfactants and Interfacial Phenomena, Second Edition, Milton J. Rosen, 1989, pp. 64-69) at a higher concentration; the concentration of emulsifier in this extrapolated line, corresponding to the minimum IFT, was taken as the CAC. Generally, a higher emulsifier concentration of about 5-10% by weight was used. Desirably, the concentration of the higher emulsifier used is at least about twice (more desirably at least about 3 times) the CAC of the emulsifier. For emulsifiers having a solubility in the oil phase at an ambient temperature of less than 5% by weight, the upper concentration limit can be reduced as long as this concentration remains at least about twice the CAC of the emulsifier at 50 ° C. .

F. Capillary Absorption Pressures A capillary absorption isotherm curve was generated using the Vertical Mecha Effect Absorbing Capacity test, described in the Methods section of Proof of the co-pending application of the United States of America series No. 989,270 (Dyer et al.), Filed on December 1, 1992, which is incorporated herein by reference, except that at 31 ° C instead of 37 ° C . The curve is a graph of the absorbent capacity of each segment as a function of the height driven by the wick effect, using the distance from the top of the water tank to the midpoint of each segment for height, h. The capillary absorption pressure is taken as the height of the foam having an absorbing capacity of half the free absorbent capacity of the foam.

IV. Specific Examples These examples illustrate the specific preparation of crushed HIPE foams, in accordance with the present invention.

EXAMPLE 1: Preparation of Foam from HIPE A) Preparation of HIPE The 378 liters of anhydrous calcium chloride water (36.32 kg) and potassium persulfate (189 g) were dissolved. This provides the water phase stream that will be used in a continuous process to form a HIPE emulsion. To a combination of monomer comprising styrene (420 g), divinylbenzene 55% technical grade (1320 g), 2-ethylhexyl acrylate (3780 g), and 1,4-butanediol dimethylacrylate (480 g) was added monooleate diglycerol of high purity (360 g) and antioxidant Tinuvin 765 [bis (1, 2,2,5,5-pentamethylpiperidinyl) sebacate] (30 g). This diglycerol monooleate emulsifier was prepared following the general procedure for preparing esters polyglycerol in the application of the United States of America co-pending series No. 989, 270 (Dyer et al.), filed on December 11, 1992. A polyglycerol composition comprising about 97% or more of diglycerol and 3% or less of triglycerol (Solvay Performance Chemicals, Greenwich, Conn.) Was esterified with fatty esters having a fatty acid composition comprising about 71% C18: 1, 4% of C18: 2, 9% of C16: 1, 5% of C16: 0, and 11% of other fatty acids (Emersol-233LL; Emery / Henkel) in a weight ratio of approximately 60:40, using sodium hydroxide as a catalyst at about 225 ° C under conditions of mechanical agitation, introduction of nitrogen, gradual increase of vacuum, with subsequent neutralization with phosphoric acid, cooling to about 85 ° C, and sedimentation to reduce the level of unreacted polyglycerols. The reaction product of polyglycerol ester is first fractionally distilled through two CMS-15A centrifugal molecular distillation stills connected in series to reduce the levels of unreacted polyglycerols and fatty acids, and then distilled again through the stills to produce distillation fractions with a high content of diglycerol monoesters. Typical conditions for the final distillation are a feed rate of approximately 6.81 kg / h, a desgacification vacuum of approximately 21 -26 microns, a glass bell vacuum of approximately 6-12 microns, a temperature of 170 ° C, and a residue temperature about 180 ° C. The distillation fractions with a high content of diglycerol monoesters were combined, yielding a reaction product (determined by supercritical fluid chromatography) comprising approximately 50% diglycerol monooleate, 27% other diglycerol monoesters, 20% polyglycerols, and 3% of other polyglycerol esters. The resulting diglycerol mololeate emulsifier imparts a minimum oil phase / phase phase interfacial tension value of approximately 1.0 dynes / cm, and has a critical aggregation concentration of approximately 0.95 by weight. After mixing, the reaction product was allowed to settle overnight. The supernatant was removed and the oil phase was used as the emulsifier to form the HIPE.

(Approximately 20 g of a sticky residue was discarded). The separate streams of the oil phase (25 ° C) and the water phase (42 ° -44 ° C) were fed to a dynamic mixing apparatus. The complete mixing of the combined streams in the dynamic mixing apparatus was achieved through a pin impeller. In this scale of operation, a suitable pin propellant comprises a cylindrical arrow with a length of approximately 21.6 cm with a diameter of approximately 1.9 cm. The arrow holds 4 rows of pins, two rows having 17 pins and two rows having 16 pins, each having a diameter of 0.5 cm extending outward from the center axis of the arrow to a length of 1.6 cm. The pin propeller is mounted on a cylindrical sleeve which forms the dynamic mixing apparatus, and the pins have a clearance of 0.8 mm from the walls of the cylindrical sleeve. A spiral static mixer is mounted downstream of the dynamic mixing apparatus to provide back pressure in the dynamic mixer and to provide improved incorporation of the components in the emulsion that is ultimately formed. Said static mixer has a length of 35.6 cm with an external diameter of 1.3 cm. The static mixer is one of TAH Industries Model 070-821, modified by a cut of 6 1 cm. The fixing of the combined mixing apparatus is filled with oil phase and water phase at a ratio of two parts of water to one part of oil. The dynamic mixing apparatus is vented so that air can escape while the apparatus is fully filled. The flow rates during filling are 3.78 g / sec of oil phase and 7. 56 cc / sec of water phase. Once the apparatus is full, agitation begins in the dynamic mixer, with the propeller spinning at 1800 rpm. The flow rate of the water phase was then increased steadily at a rate of 45.4 cm3 / sec, and the flow rate of the oil phase was reduced to 0.82 g / sec over a period of about 2 minutes.

The back pressure created by the dynamic and static mixers at this point is 92 kPa. The speed of the propellant was then stably reduced at a speed of 1200 rpm for a period of 120 sec. The back pressure of the system drops to 37 kPa. At this point, the speed of the propellant is instantaneously increased to 1800 rpm. The back pressure of the system increases to 44 kPa and remains constant afterwards. The resulting HIPE has a water to oil ratio of about 55: 1.

B) Polymerization / Healing of HIPE The HIPE of the static mixer was collected in a round polypropylene tray, with a diameter of 43 cm and a height of 7.5 cm, with a concentric insert made of Celcon plastic. The insert has a diameter of 12.7 cm at its base and a diameter of 12 cm in its upper part, and a height of 17.1 cm. The trays containing HIPE are kept in a room at 65 ° C for 18 hours to cure and provide a polymeric HIPE foam.

C. Foam Washing and Dehydration The cured HIPE foam was removed from the trays. The foam at this point has a residual water phase (containing dissolved emulsifiers, electrolyte, initiator residues, and initiator) of about 50-60 times (50-60 X) the weight of the polymerized monomers. The foam was sliced with a saw blade with a sharp reciprocal movement, in sheets with a thickness of 0.368 cm. These sheets were then subjected to compression in a series of two porous press rolls equipped with a vacuum, which gradually reduces the residual water phase content of the foam to approximately 6 times (6X) the height of the polymerized monomers. At this point, the sheets are then resaturated with a 1.5% CaCl2 solution at 60 ° C, compressed into a series of three porous press rolls equipped with vacuum at a water phase content of about 4X. The CaCl2 content of the foam is between 8 and 15%. The HIPE foam remains compressed after the final pressing to a thickness of approximately 0.048 cm. The foam is then dried with air for about 16 hours. Said drying reduces the moisture content to approximately 9-17% by weight of the polymerized material. In this point, the foam sheets are very drapable. In the co-drawn state, the density of the foam is approximately 0.14 gr / cm3. When expanded with Jayco synthetic urine, its absorbent free capacity is approximately 54 mL / g and has a glass transition temperature of 19 ° C.

EXAMPLE 2: Preparation of the Foam from a HIPE A) Preparation of HIPE The 378 liters of anhydrous calcium chloride water (36.32 kg) and potassium persulfate (189 g) were dissolved. This provides the water phase stream that will be used in a continuous process to form a HIPE emulsion. To a combination of monomer comprising distilled divinylbenzene (40% divinylbenzene and 60% styrene) (2100 g), 2-ethylhexyl acrylate (3300 g), and hexanediol diacrylate (600), high purity diglycerol monooleate (360 g) and Tinuvin antioxidant were added. 765 (30 g). The diglycerol monooleate emulsifier (Grindsted Products, Brabrand, Denmark) comprising approximately 81% diglycerol monoolet, 1% other diglycerol monoesters, 3% polyglyceroles, and 15% other polyglycerol esters, imparts a minimum value of interfacial phase tension of oil / water phase of approximately 2.5 dynes / cm, and has a critical aggregation concentration of approximately 2.9% by weight. After mixing, the reaction product was allowed to settle overnight. No visible residue was formed and all of the mixture was removed and used in the oil phase as the emulsifier to form the HIPE. The separated streams of the oil phase (25 ° C) and the water phase (53 ° -55 ° C) were fed to a dynamic mixing apparatus, as in Example 1. A portion of the output material of the mixing apparatus The dynamic is removed and recirculated by a recirculation line as shown and described in Figure 6 of copending US Patent Application Serial No. 08 / 370,694 (Thomas A. DesMarais), filed January 10. of 1995, Case No. 5543 (incorporated herein by reference) to the point of entry of the flow streams of the oil phase and of the water phase into the dynamic mixing zone. The combined mixing and recirculation apparatus is filled with the oil phase and the water phase in a ratio of 3 parts of water to 1 part of oil. The dynamic mixing apparatus is vented so that air can escape while the apparatus is fully filled. Flow rates during filling are 3.78 g / sec of oil phase and 11.35 crrrVseg of water phase, with approximately 15 cm3 / sec in the recirculation line. Once the apparatus is full, the flow rate of the water phase is cut in half to reduce the formation pressure while closing the vent. Agitation begins in the dynamic mixer, with the propeller spinning at 1800 rpm. The flow rate of the water phase was then stably increased at a rate of 45.4 cm3 / sec over a period of about 1 minute, and the flow rate of the oil phase was reduced to 0.757 g / sec during a period of time. approximately 2 minutes. The recirculation rate was stably increased to approximately 45 cm3 / sec during the last period of time. The back pressure created by the dynamic and static mixers at this point is 69 kPa. The speed of the Waukesha pump is then stably reduced to a recirculation rate performance of about 1 1 cm 3 / sec.

B) Polymerization / Healing of HIPE The formed emulsion resulting from the static mixer at this point was collected in a round polypropylene tube, with a diameter of 43 cm and a height of 10 cm, with a concentric insert made of Celcon plastic. The insert has a diameter of 12.7 cm at its base and a diameter of 12 cm at the top, and a height of 17.14 cm. The tubes containing HIPE are kept in a room at 65 ° C for 18 hours to achieve the polymerization of the emulsion in the containers and thereby form the polymeric foam.

C. Foam Washing and Dehydration The cured HIPE foam was removed from the trays. The foam at this point has a residual water phase (containing dissolved emulsifiers), electrolyte, initiator residues, and initiator) of about 50-60 times (50-60 X) the weight of the polymerized monomers. The foam was sliced with a saw blade with a sharp reciprocal movement, in sheets with a thickness of 0.406 cm. These sheets were then subjected to compression in a series of two porous press rolls equipped with a vacuum, which gradually reduces the residual water phase content of the foam to approximately 6 times (6X) the height of the polymerized monomers. At this point, the sheets are then resaturated with a 1.5% CaCl2 solution at 60 ° C, compressed into a series of three porous press rolls equipped with vacuum at a water phase content of about 4X. The CaCl2 content of the foam is between 8 and 15%. The HIPE foam remains compressed after the final pressing to a thickness of approximately 0.053 cm. The foam is then dried with air for about 16 hours. Said drying reduces the moisture content to approximately 9-17% by weight of the polymerized material. At this point, the foam sheets are very drapable. The foam also contains about 5% by weight of the residual diglycerol moleleate emulsifier. In the co-drawn state, the density of the foam is about 0.14 gr / cm3. When expanded with Jayco synthetic urine, its absorbent free capacity is approximately 60 mL / g and has a glass transition temperature of 23 ° C.

Example 3: Preparation of HIPE Foams of Different Monomers. The HIPE absorbing foams having variable monomer components are prepared using similar procedure to those described in Example 1 or 2 above. The monomer formulations, water-to-oil ratios (W: 0), and the physical properties of these foams (RTCD, Expansion Factor and Tg) are shown in Table 1 below: Table 1 * STY = styrene EST = ethyl styrene DVB = divinyl benzan EHA = 2-ethylhexyl acrylate BDMA = 1,4-butadoniol dimethylacrylate EGDMA = ethylene glycol dimethylacrylate HDDA = 1,6-hexanediol diacrylate ** volume by weight *** by DMA Example 4: Diaper Made with HIPE Foam A disposable diaper was prepared using the configuration and components shown in the expanded and separated representation of Figure 7. Such diaper comprises an upper sheet 70, a fluid impermeable back sheet 71, and a double layer absorbent core placed between the upper sheet and the backing sheet The double layer absorbent core comprises a layer of storage / redistribution of the fluid 72, in the form of a modified hourglass, comprising the collapsed foams according to examples 1, 2, or 3, placed below the acquisition layer of the second layer. fluid 73 in the form of a modified hourglass Approximately 10 grams of this crushed HIPE foam was used to form this storage / distribution layer 72 having a surface area of about 339 cm 2 and a thickness of about 0 25 cm in its collapsed state The topsheet 70 contains two substantially parallel strips of elastic leg barrier folds 74 Fixed to the backsheet of the diaper 71, there are two elastified, rectangular waistband members 75 Also fixed to each end of the backsheet are two waist protection elements 76, constructed of polyethylene. Also fixed to the backsheet are two parallel strips of leg elastics. polyethylene 78 to the outside of the backsheet as to a fastening surface dedicated by two pieces Y-tape 79 that can be used to hold the diaper around the user The acquisition layer 73 of the diaper core can comprise a mixture of 92% or 8% wet-laid curly, twisted, hardened cellulose fibers, and conventional cellulose fibers unhardened fibers The cellulose fibers, curled, twisted, hardened, are made from a kraft pulp of southern softwood (Foley lint) that has been entangled with glutraldehyde up to the limit of approximately 2 5% mole on a dry basis of fiber cellulose anhydroglucose The fibers are interlaced according to the "dry entanglement process" as described in U.S. Patent 4,822,453 (Dean et al.), issued April 18, 1989. These hardened fibers are similar to the fibers that have the characteristics described as follows in Table 2: Table 2 Curled Cellulose Fibers. Crooked Hardened (STCC) Type = Southern softwood kraft pulp interlaced with glutraldehyde to the limit of 1.41% mole on an anhydroglucose base of dry fiber cellulose Dry Twist Count = 6.8 nodes / mm Wet Twist Count = 5.1 nodes / m Retention Value of 2-Propanol = 24% Water Retention Value = 37% Curl Factor = 0.63 The conventional unhardened cellulose fibers used in combination with the STCC fibers are also made from the Foley fluff. These uncured cellulose fibers are refined to approximately 200 CSF (Canadian Standard Riñes). The acquisition layer 73 has a dry average density of approximately 0.01 gr / cm3, an average saturation density with the synthetic line, a dry basis weight package of approximately 0.08 gr / cm2, and a base average weight of approximately 0.03 gr / cm2. Approximately 8 grams of the fluid acquisition layer of the diaper core was used. The surface area of the acquisition layer is approximately 302 cm2. This has a thickness of approximately 0.44 cm. Similar results can be obtained if the hardened fibers placed in air are replaced by the hardened fibers wet placed in the acquisition layer 73 of the absorbent core. The acquisition layer 73 may also comprise an acquisition / distribution foam made according to the examples 1, 2, or 3, of copending United States patent application Serial No. 08/370695 (Keith J. Stone et al.), Filed on January 10, 1995. Case No. 5544, which is incorporated by reference.

Claims (6)

1. - A polymeric foam material, crushable, which upon contact with accusative fluids, can expand and absorb said fluids, said polymeric foam material comprising a polymeric, non-ionic, flexible, hydrophilic foam structure of interconnected open cells, characterized because the foam structure has: (A) a specific surface area per volume of foam of at least 0.025 m2 / cm3, preferably of at least 0.05 m2 / cm3; (B) at least 0.1% by weight of a hydrated, hydroscopic, toxicologically acceptable salt incorporated herein; (C) in its crushed state, an expansion pressure of about 30 kPa or less; and (D) a free absorbent capacity of 50 to 100 mL / g, (E) a ratio of expanded to crushed thickness of at least about 6: 1; (F) a resistance to compression deflection of 40% or less, preferably from 4 to 15%, when measured under a confining pressure of 0.052022 kgrms per cm

2. 2. The foam material according to claim 1, further characterized in that said structure has: (A) a specific capillary suction surface area of 3 to 15, preferably 5 to 11 m2 / g; (B) A residual water content of at least 4%, preferably from 2 to 25% by weight; (C) from 1 to 10% by weight of calcium chloride, and from 0.5 to 10% by weight of a hydrophilicizing surfactant herein incorporated to make the surface of the foam structure hydrophilic; (D) in its collapsed state, an expansion pressure of 7 to 20 kPa; (E) a free absorbing capacity of 55 to 75 mL / g; (E) a ratio of expanded thickness to crushed of 6; 1 to 10: 1; (F) a resistance to compression deflection of 2 to 25%.

3. The foam material according to any of claims 1 or 2, further characterized in that it comprises a water-in-oil polymerized emulsion having: 1) an oil phase comprising: a) from 85 to 98%, preferably from 90 to 97%, by weight of a monomer component capable of forming a copolymer having a Tg of 35 ° C or less, preferably from 15 to 30 ° C, the monomer component comprising: i) from 45 to 70% by weight of at least one monofunctional monomer substantially insoluble in water, capable of forming an atactic amorphous polymer having a Tg of 25 ° C or less; ii) from 10 to 30% by weight of at least one monofunctional comonomer substantially insoluble in water, capable of imparting resistance equivalent to that provided by styrene; iii) from 5 to 25% by weight of a first polyfunctional crosslinking agent, substantially insoluble in water, selected from divinylbenzenes, trivinylbenzenes, divinyl-toluenes, divinyl-xylenes, divinylnaphthalenes, divinyl-alkylbenzenes, clivinyl-phenanthrene, divinylbiphenyls, divinyl-diphenylmethanes, divinylbenzyl, divinylphenyl ethers, divinyl-diphenyl sulfides, dikvinylfurans, divinyl sulfide, divinyl sulfone, and mixtures thereof; and iv) from 0 to 15% by weight of a second polyfunctional crosslinking agent, substantially insoluble in water, selected from polyfunctional acrylates, methacrylates, acrylamides, methacrylamides, and mixtures thereof; and b) from 2 to 15%, preferably from 3 to 10%, by weight of an emulsifying component, which is soluble in the oil phase, and which is suitable to form a stable water-in-oil emulsion; 2) a water phase comprising 0.2 to 20%, preferably 1 to 10%, by weight of a water-soluble electrolyte, preferably calcium chloride; 3) a volume to weight ratio of water phase to oil phase in the range of 55: 1 to 100: 1, preferably 55: 1 to 75: 1. 4.- The foam material in accordance with the claim 3, further characterized in that said comonomer component comprises: i) from 50 to 65% by weight of monomer selected from the group consisting of C4-C14 alkyl acrylates, aryl and alkaryl acrylates, C16 alkyl methacrylates, acrylamides, show us C4-C12 alkyl and their mixtures; ii) from 15 to 23% by weight of comonomer selected from the group consisting of styrene, ethyl styrene and mixtures thereof; iii) from 12 to 18% by weight of divinylbenzenes; and iv) from 7 to 13% by weight of said second crosslinker selected from the group consisting of 1,4-butanediol dimethacrylate, ethylene glycol dimethacrylate, 1,6-hexanediol diacrylate, and mixtures thereof. 5. The foam material according to claim 4, further characterized in that said monomer (i) is selected from the group consisting of butyl acrylate, hexyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate , decyl acrylate, dodecyl acrylate, isodecyl acrylate, tetradecyl acrylate, benzyl acrylate, nonylphenyl acrylate, hexyl methacrylate, octyl methacrylate, nonyl methacrylate, decyl methacrylate, isodecyl methacrylate, dodecyl methacrylate, methacrylate of tetradecyl, pn-octylstyrene, N-octadecyl acrylamide, and mixtures thereof. 6. An absorbent article especially suitable for absorbing and retaining aqueous body fluids, said article comprising: I) a backing sheet; and II) an absorbent core associated with the backsheet, such that said absorbent core is placed between said backsheet and the fluid discharge region of the article user, said absorbent core characterized in that it comprises the foam material of either of claims 1 to 5. The absorbent article according to claim 6, further characterized in that said absorbent core comprises: (1) a fluid handling layer positioned in the fluid discharge region; and (2) a fluid storage / redistribution layer in fluid communication with the fluid handling layer, and which comrpenses the foam material. 8. A diaper useful for absorbing aqueous fluids from the body discarded by an incontinent individual, said diaper article comprising: I) a backing sheet relatively impermeable to liquid; II) a topsheet relatively permeable to liquid; III) an absorbent core placed between said backing sheet and the upper sheet, said absorbent core characterized in that it comprises the foam material of any of claims 1 to 5. 10.- A process for the preparation of a polymeric foam material, characterized in that it comprises the steps of: A) forming a water-in-oil emulsion of: 1) an oil phase comprising: a) from 85 to 98%, preferably from 90 to 97%, by weight of a monomer component capable of forming a copolymer having a Tg of 35 ° C or less, preferably 15 to 30 ° C, the monomer component comprising: i) from 45 to 70% by weight of at least one monofunctional monomer substantially insoluble in water, capable of forming a polymer amorphous atactic that have a Tg of 25 ° C or less; ii) from 10 to 30% by weight of at least one monofunctional comonomer substantially insoluble in water, capable of imparting resistance equivalent to that provided by styrene; iii) from 5 to 25% by weight of a first water-insoluble polyfunctional crosslinking agent selected from divinylbenzenes, trivinylbenzenes, divinyl-toluenes, divinyl-xylenes, divinylnaphthalenes, divinyl-alkylbenzenes, divinyl-phenanthrene, divinyl-biphenyls, divinyl-diphenyl-methanes, divinyl-benzyl, di-vinyl-phenyl ethers. , divinyl-diphenyl sulfides, divinylfurans, divinyl sulfide, divinyl sulfone, and mixtures thereof; and iv) from 0 to 15% by weight of a second polyfunctional, substantially water insoluble crosslinking agent, selected from polyfunctional acrylates, methacrylates, acrylamides, methacrylamides, and mixtures thereof; and b) from 2 to 15%, preferably from 3 to 10%, by weight of an emulsifying component, which is soluble in the oil phase, and which is suitable to form a stable water-in-oil emulsion; the emulsion component comprising: a primary emulsifier having at least about 40% by weight of emulsifying components selected from diglycerol monoesters of branched C 16 -C 24 fatty acids, diglycerol monoesters of linear, unsaturated C 16 -C 22 fatty acids, and diglycerol monoesters of saturated C12-C14 fatty acids, linear; sorbitan monoesters of branched C 16 -C 24 fatty acids, sorbitan monoesters of unsaturated linear C 16 -C 22 fatty acids, sorbitan monoesters of saturated, linear C 12 -C 14 fatty acids; monoaliphatic diglycerol ethers of branched, branched alcohols, monoaliphatic diglycerol ethers of linear unsaturated C 16 -C 22 fatty alcohols, diglycerol monoaliphatic ethers of linear saturated C 12 -C 14 alcohols, and mixtures thereof; and 2) a water phase comprising an aqueous solution containing: (a) from 0.2 to 20%, preferably from 1 to 10%, by weight of a water-soluble electrolyte, preferably calcium chloride; and (b) an effective amount of a polymerization initiator; 3) a volume to weight ratio of water phase to oil phase in the range of 55: 1 to 100: 1, preferably 55: 1 to 75: 1, and most preferably 55: 1 to 65: 1; and B) polymerizing the monomer component in the oil phase of the oil in water emulsion to form a polymeric foam material. 10. The method according to claim 9, further characterized in that it comprises the additional step of dehydrating the polymeric foam material of step B) to a limit such that a crushed polymeric foam material is formed which will re-expand upon contacting with aqueous fluids. 11. The process according to any of claims 9 or 10, further characterized in that said comonomer component comprises: i) 50 to 65% by weight of monomer selected from the group consisting of C4-C14 alkyl acrylates, acrylates of aryl and alkaryl, C16 alkyl methacrylates, acrylamides, C4-C12 alkyl styrenes and mixtures thereof; I) from 15 to 23% by weight of comonomer selected from the group consisting of styrene, ethyl styrene and their mixtures; iii) from 12 to 18% by weight of divinylbenzenes; and iv) from 7 to 13% by weight of said second crosslinking agent selected from the group consisting of 1,4-butanediol dimethacrylate, ethylene glycol dimethacrylate., 1,6-hexanediol diacrylate, and mixtures thereof. 12. The process according to claim 11, further characterized in that said monomer (i) is selected from the group consisting of butyl acrylate, hexyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, acrylate. decyl, dodecyl acrylate, isodecyl acrylate, tetradecyl acrylate, benzyl acrylate, nonylphenyl acrylate, hexyl methacrylate, octyl methacrylate, nonyl methacrylate, decyl methacrylate, isodecyl methacrylate, dodecyl methacrylate, tetradecyl methacrylate , pn-octylstyrene, N-octadecyl acrylamide, and mixtures thereof. 13. The process according to any of claims 9 to 12, further characterized in that said primary emulsifier comprises at least 70% of emulsification components, selected from the group consisting of diglycerol monooleate, diglycerol monoisostearate, diglycerol monoesters of coconut fatty acids, sorbitan monooleate, sorbitan monomiristate, sorbitan monoesters of coconut fatty acids and mixtures thereof. 1

4. The method according to any of the claims 9 to 13, characterized in that it further comprises a secondary emulsifier selected from the group consisting of phosphatidyl choline and compositions containing phosphatidyl choline such as aliphatic lecithins and betaines, dialiphatic quaternary ammonium salts of C12-C22 long chain, dialiphatic CrC4 short chain, quaternary ammonium salts of dialkyl (alkenoyl) -2-hydroxyethyl-C12-C22 long-chain, dialiphatic of C, -C4 short chain, dialiphatic imidazolino quaternary ammonium salts of C12-C 22 chain long, the dialiphatic quaternary ammonium salts of short chain C4, monoaliphatic Q, -Q, long chain, quaternary ammonium salts of short chain C, -C4 monohydroxyaliphatic; and mixtures of these secondary emulsifiers; in a weight ratio of primary to secondary emulsifier is from 50: 1 to 1: 4. 1

5. The process according to claim 14, characterized in that said secondary emulsifier is selected from the group consisting of dimethyl ammonium ditallow methylisulfate, dimethyl ammonium ditallow chloride, and mixtures thereof, and wherein the weight ratio of primary emulsifier to secondary is from 30: 1 to 2: 1.