MXPA97005187A - Absorbent foams made of internal high-end emulsions useful to acquire and distribute flui - Google Patents

Abstract

Absorbent materials are described which are capable of acquiring and distributing aqueous fluids, especially fluids discarded by the body, such as urine. These absorbent foams combine relatively high capillary absorption pressures and weight capacity properties that allow them to acquire fluids, with or without the help of gravity. These absorbent foams also deliver this fluid efficiently to higher absorption pressure storage materials, including foam-based absorbent fluid storage components, without crushing. These absorbent foams are made by polymerizing high internal phase emulsions (HIPE

Description

ABSORBENT FOAMS MADE OF HIGH-PHASE EMULSIONS INTERNAL USEFUL TO ACQUIRE AND DISTRIBUTE FLUIDS TECHNICAL FIELD OF THE INVENTION This application relates to polymeric, absorbent, open cell, microporous, flexible foam materials. This application particularly relates to absorbent foam materials made of high internal phase emulsions which are capable of acquiring and distributing fluids v. gr., urine.

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 such as sanitary napkins, is the subject of substantial commercial interest. The ability to provide high-performance absorbent articles, such as diapers, has been contingent on the ability to develop relatively absorbent cores or structures that can acquire, distribute and store large quantities of discarded body 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. See, 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 said absorbent polymers in particles in absorbent articles. In fact, the development of high performance diapers has been the direct consequence of thinner absorbent cores which have the advantage of the ability of these absorbent polymers in oarticles to absorb large quantities of aqueous, waste body fluids, typically when used in combination with a fibrous matrix. See, for example, 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 structures of double layer core comprising a fibrous matrix and particulate absorbent polymers useful for manufacturing high performance diapers. These particulate absorbent polymers have not previously been exceeded in their ability to retain large volumes of fluids, such as urine. A representative example of such particulate absorbent polymers are slightly interlaced polyacrylates. Like many of the other absorbent polymers, these slightly entangled polyacrylates comprise a multitude of anionic (charged) carboxy groups 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 the osmotic forces. Absorbency based on capillary strength is also important in many absorbent articles, including diapers. The hair absorbent articles can offer superior performance in terms of acquisition speed and conduction by fluid wicking, ie the ability to move the aqueous fluid away from the initial point of contact. In fact, the two-layer core absorbent structures, noted above, use the fibrous matrix as the primary capillary transport vehicle to move the aqueous fluid from 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). 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 a desirable moisture integrity, may provide adequate fit throughout the period in which the article is used, and may minimize changes in shape during use (eg. , uncontrolled swelling, or stacking). In addition, absorbent articles containing such foam structures may be easier to manufacture on a commercial scale. For example, the diaper absorbent cores can simply be printed on continuous foam sheets and can be designed to have considerably greater integrity and uniformity than the absorbent fibrous webs. Such foams can also be prepared in any desired form, or even more can be formed into one-piece diapers. Absorbent foams particularly suitable for absorbent products such as diapers, have been made from High Internal Phase Emulsions (hereinafter referred to as "HIPE"). See, for example, U.S. Patent 5,260,345 (DesMarais et al.), Issued November 9, 1993 and U.S. Patent 5,268,224 (DesMarais et al.) Issued December 7, 1993. These foams HIPE absorbers provide desirable fluid handling properties, including: (a) relatively good fluid penetration and 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; 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 wearer of the absorbent article; some can be made relatively thin until they are subsequently moistened by the absorbed body fluid. See also, U.S. Patent 5,318,544 (Young et al.), Issued June 7, 1994, which describes absorbent cores having a fluid acquisition / distribution component that can be an open cell, flexible foam , hydrophilic, such as a melamine-formaldehyde foam (eg, BASOTECT made by BASF), and a fluid storage / redistribution component, which is an absorbent foam based on HIPE.

These acquisition / distribution components, based on foam, must allow a rapid acquisition of fluid, as well as an efficient division or distribution of the fluid towards other components of the absorbent core that have absorption pressures greater than the desorption pressure of the foam acquisition / distribution. This property of desorbing fluid to other components of the core is important to provide the ability to accept repeated discharges or loads of fluid and to maintain the dryness of the user's skin. It also allows the acquisition / distribution foam to serve as a hollow volume reservoir, or buffer zone, to temporarily maintain the fluid that can be expressed from the core storage components when extraordinarily high pressures are encountered during the use of the absorbent article. By providing this fluid to other core components, these foam-based acquisition / distribution components must do this without densifying or collapsing. Foam-based acquisition / distribution components must also readily accept the fluid, with or without the aid of gravity. The acquisition / distribution components based on foam must also provide good aesthetics, be soft and elastic in structure, and have a good physical integrity in both wet and dry states. Accordingly, it would be desirable to be able to make an absorbent, open cell polymeric foam material, in particular a HIPE absorbent foam, which: (1) can function as an acquisition / distribution component in an absorbent core; (2) allowing other core components having absorption pressures greater than the desorption pressure of the acquisition / distribution foam, to separate the fluid, without the acquisition / distribution foam collapsing; (3) keep the user's skin dry, even in "jet" situations and even when subjected to a compressive load; (4) that is soft, flexible and comfortable for the user of the absorbent article; and (5) having a relatively high capacity for the fluid, to provide diapers and other absorbent articles that efficiently utilize core components.

DESCRIPTION OF THE INVENTION The present invention relates to polymeric foam materials that are capable of acquiring and distributing aqueous fluids, especially fluids discarded from the body, such as urine. These absorbent polymeric foam materials comprise a non-ionic, flexible, hydrophilic polymeric structure of interconnected open cells. This foam structure has: A) the ability to vertically wick synthetic urine at a height of 5 cm in less than about 120 seconds; B) a capillary absorption pressure (ie, height at 50% capacity) of about 5 to about 25 cm; C) a capillary desorption pressure (ie, height at 50% capacity) of from about 8 to about 40 cm; D) a resistance to compression deflection from about 5 to about 85% when measured under a confining pressure of 0. 052022 kg / cm2; E) an absorbent free capacity of approximately 12 to approximately 125 g / g. In addition to rapidly acquiring and distributing body fluids, the absorbent foams of the present invention distribute this fluid efficiently to other fluid storage components, including foam-based fluid storage components. The absorbent foams of the present invention combine relatively high capillary absorption pressures and capacity properties by weight (compared to conventional foams) that allow them to acquire fluid, with or without the help of gravity. The absorbent foams of the present invention can also provide good aesthetics due to their soft, elastic structure and physical integrity. As a result, the absorbent foams of the present invention are particularly attractive for high performance absorbent articles such as diapers, adult incontinence pads, sanitary napkins and the like. A particularly important attribute of the foams of the present invention is that they do not collapse when they are desorbed by other components in the absorbent core. Without intending to be bound by theory, it is believed that this resistance to compression (i.e. resistance to crushing) by hydrostatic forces is due to the desorption pressure of these foams in their expanded state, being less than the pressure required for the compression deflection. An important related attribute, when wetted, is that they spontaneously expand again after the application and release of mechanical compression, even without the foams do not re-absorb fluid. This means that these foams imbibe air when dehydrated either by desorption, by mechanical compression, or a combination thereof, when they expand or when they return to an expanded state. As a result, the ability of these foams to rapidly acquire fluids is restored, and the foam is able to provide a drier feel. The present invention further relates to a process for obtaining these 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 greater amount of a water phase. This process comprises the steps of: A) forming a water-in-oil emulsion at a temperature of about 50 ° C or higher, and under low shear mixing of: 1) an oil phase comprising: a) of about 85 to about 90% by weight of a monomer component capable of forming a copolymer having a Tg of about 35 or less, the monomer component comprising: i) from about 30 to about 80% by weight of at least one monofunctional monomer substantially insoluble in water, capable of forming an atactic amorphous polymer having a Tg of about ° C or less; ii) from about 5 to about 40% 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, substantially water-insoluble crosslinking agent selected from divinylbenzenes, trivinylbenzenes, divinyl-toluenes, divinyl-xylenes, divinylnaphthalenes, divinyl-alkylbenzenes, divinyl-phenanthrenes, divinylbiphenyls, divinyl-diphenylmethanes, divinylbenzyl, ethers divinyl phenyl, 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 to form a stable water-in-oil emulsion, the emulsion component comprising: (i) a primary emulsifier having at least about 40% by weight of emulsifying components selected from diglycerol monoesters of linear unsaturated C16-C22 fatty acids, diglycerol monoesters of branched dC24-C fatty acids, monoaliphatic diglycerol ethers of alcohols of C16-C24 branched, monoaliphatic diglycerol ethers of linear unsaturated C16-C22 fatty alcohols, diglycerol monoaliphatic ethers of saturated, linear C12-C14 alcohols, sorbitan monoesters of linear unsaturated C16-C22 fatty acids, sorbitan monoesters C16-C24 branched fatty acids, and mixtures thereof; or, (ii) the combination of a primary emulsifier having at least 20% by weight of these emulsification components and certain secondary emulsifiers in a weight ratio of primary to secondary emulsifier of from about 50: 1 to about 1: 4; and 2) a water phase comprising an aqueous solution containing, (i) from about 0.2 to about 20% by weight of a water-soluble electrolyte; (ii) an effective amount of a polymerization initiator; 3) a volume to weight ratio of water phase to oil phase in the range of about 12: 1 to about 125: 1; and B) polymerizing the monomer component in the oil phase of the oil-in-water emulsion to form a polymeric foam material; C) optionally dehydrate the polymeric foam material. The present invention allows the formation of these absorbent foams which are capable of acquiring and rapidly distributing fluids as a result of a combination of two factors. One is the use of low shear mixing during the formation of HIPE. The other is the use of more robust emulsifier systems that allow the HIPE to be formed and emptied at relatively high temperatures, for example, about 50 ° C or higher.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 of the drawings is a graphic representation of the absorption curves of four HIPE foams emptied at different temperatures. Figure 2 of the drawings is a graphic representation of the desorption curves of these same four HIPE foams. Figure 3 of the drawings is a photomicrograph (50 X amplification) of a representative, absorbent, polymeric foam section in accordance with the present invention, made of HIPE having a water to oil weight ratio of 60: 1 and it is emptied at 93 ° C, and where the monomer component consists of a weight ratio of 21: 14: 55: 10 of ethylstyrene (EtS): divinylbenzene (DVB): 2-ethylhexyl acrylate (EHA): diacrylate of hexanediol (HDDA), and where emulsifiers were used in 5.5% (by weight of the oil phase) of diglycerol monoleate (DGMO) and 1% of dimethyl ammonium ditallow methylisulfate. Figure 4 of the drawings is a photomicrograph (250 X amplification) of the foam of Figure 3. Figure 5 of the drawings is a graphic representation illustrating the fluid holder (desorption pressure) as a function of the cell structure (hole size between cells) for several HIPE foams. Figures 6 and 7 of the drawings represent, respectively, a top view and a side view of a multi-layer core configuration, wherein a fluid storage / redistribution component covers an underlying fluid acquisition / distribution component. Figure 8 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 shape of an hourglass, covering a storage layer / redistribution of fluid with a modified hourglass shape.

DETAILED DESCRIPTION OF THE INVENTION I. Polymeric Absorbing Foams A. General Characteristics of Foam Polymeric 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 such 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 foam structure. 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 frames. The strands of the polymeric material forming these branched webs can be referred to as "poles". Open cell foams having 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 an "open cell" if by at least 80% of the cells in the foam structure that are at least 1μm 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 aqueous fluids. The internal surfaces of the foam structures are rendered hydrophilic through residual hydrophilicizing surfactants left in the foam structure after polymerization, or through selected post-polymerization foam treatment processes, 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 tension 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 specific surface area of capillary suction. . Said process is described in detail in the Test Methods section of the application of the United States of America series No. 989,270 (Dyer et al.), Filed on December 11, 1992, which is incorporated herein by reference. The foams, which are useful as absorbers in the present invention, are generally those that exhibit an adhesion tension value of from about 15 to about 65 dynes / cm, preferably from 20 to 65 dynes / cm, approximately, as determined by the capillary suction consumption of synthetic urine that has a surface tension of 65 + 5 dynes / cm. An important aspect of these foams is their glass transition temperature (Tg) The 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 useThey can be very strong, but they will also be very rigid and potentially susceptible to fracture. Such foams typically also take a long time to respond when used at cooler temperatures than the Tg of the polymer. The desired combination of mechanical properties, specifically strength and elasticity, typically requires a completely selective scale of types and levels of monomer to obtain these desired properties. For foams of the present invention, the Tg should be as low as possible, as long as the foam has an acceptable strength. Accordingly, the monomers are selected to provide as much as possible corresponding homopolymers having lower Tgs. It has been found that the chain length of the alkyl group in the acrylate and methacrylate comonomers may be longer than would be predicted from the Tg of the homologous homopolymer series. Specifically, it has been found that the homologous series of alkyl acrylate or methacrylate homopolymers 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 alkyl-substituted styrene monomers can be used instead of alkyl acrylates and methacrylates, their availability is currently extremely limited). The shape of the glass transition region of the polymer can also be important, i.e., whether 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 will exhibit greater rigidity and less elasticity. Conversely, if the transition is complete at the use temperature, then the polymer will exhibit a more rapid recovery of compression. Accordingly, it is desirable to control the Tg and the width of the transition region of the polymer to obtain the desired mechanical properties. Generally, it is preferred that the g of the polymer is at least about 10 ° C lower than the use temperature. (The Tg and the width of the transition region are derived from the tangent versus temperature, loss curve, of a dynamic mechanical analysis (DMA) measurement, as described in the Test Methods section below.

B. Important Characteristics of the Foam to Acquire and Distribute Aqueous Fluids without Crushing 1. Vertical Wick Effect The vertical wicking effect, that is, the conduction by fluid wicking in a direction opposite to the gravitational forces, of an amount given fluid within a set period, is an attribute of performance especially important for absorbent foams of the present. 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 120 seconds. Most preferably, the preferred foam absorbers of the present invention will vertically wick this synthetic urine 5 cm in no more than about 70 seconds, and most preferably in no more than about 50 seconds. 2. Capillary Absorption and Desorption Pressures 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. As illustrated in Figure 1, for foams of the present invention, this is typically the inflection point in the capillary absorption curve. Figure 1 represents the absorption curves for four foams identified as P161, P170, P180 and P194, which correspond to HIPEs emptied at 72 ° C, 77 ° C, 82 ° C and 90 ° C, respectively. The absorption pressures were determined from these absorption curves and are summarized in Table 1 below: TABLE 1 Of particular importance to the ability of the absorbent foams of the present invention to function as useful fluid acquisition and distribution components is their capillary desorption pressure. Capillary desorption pressure refers to the ability of the foam to maintain fluid at several hydrostatic heads at equilibrium conditions at 22 ° C. For the purposes of the present invention, the capillary desorption pressure of interest is the hydrostatic head (ie, height), at which the fluid load is 50% of the absorbent free capacity under conditions of equilibrium at 22 °. C. As illustrated in Figure 2, for foams of the present invention, this is typically the inflection point in the capillary desorption curve. Figure 2 represents the desorption curves of the same four foams identified as P161, P170, P180 and P184, which correspond to HIPEs emptied at 72 ° C, 77 ° C, 82 ° C and 90 ° C, respectively. The desorption pressures were determined from these desorption curves and are summarized in Table 2 below: TABLE 2 The capillary desorption pressure is important in relation to the absorption pressure of other absorbent components, especially those intended to store fluid. If the fluid acquisition component of the absorbent article keeps the acquired fluid too tenacious, this will inhibit the ability of these other components to divide the fluid. This can cause the acquisition component to remain very heavily loaded with fluid, whereby the absorbent article is more susceptible to spillage. The foams of the present invention have sufficiently low desorption pressures, so that the fluid storage components can effectively dry (ie, desorb) these foams. This restores the ability of the foam to accept more "jets" of fluid (either from the user or from the compression of the storage components) and maintains the layer that is close to the wearer's skin (e.g., top sheet) comparatively dry. The data in Table 2 above show how this property can be adjusted through the selection of appropriate processing conditions (eg, dump temperature). The absorbent foams of the present invention can be readily desorbed by other components of the absorbent core that store such fluids, including those comprising conventional, absorbent gelling materials, such as those described in, for example, United States of America 5,061,259 (Goldman et al.), Issued October 29, 1991, United States of America patent 4,654,039 (Brandt et al.), Issued March 31, 1987 (reissued on April 19, 1988 as Re. 32,649), patent of the United States of America 4,666,983 (Tsubakimoto et al.), issued May 19, 1987), and United States of America 4,625,001 (Tsubakimoto et al.), issued November 25, 1986, all incorporated herein by reference; as well as absorbent macrostructures made from these absorbent gelling materials, such as those described in, for example, United States of America patent 5,102,597 (Roe et al.), issued April 7, 1982, and U.S. Patent 5,324,561 (Rezai et al.), Issued June 23, 1994, all incorporated herein by reference. Actually, these absorbent foams can be easily desorbed by other absorbent polymeric foams that store the purchased fluid, such as those described in, for example, United States of America 5,268,224 (DesMarais et al.), Issued December 7, 1993, application of the co-pending United States of America series No. 989,270 ( et al.), Filed in December 1992, and request of the United States of America co-pending series No. 08/37092 (Thornas A. DesMarais, and others) , filed on June 10, 1995. Case No. 5541, all of which are incorporated herein by reference. Accordingly, the absorbent foams of the present invention work very well in multiple "jets" situations, to rapidly move the purchased fluid to other storage components of the absorbent structure. Capillary absorption pressures can be measured using a vertical wicking absorbent capacity test, as described in more detail in the Test Methods section of the co-pending United States of America application No. 989,270 ( et al. others), filed in December 1992, which is incorporated herein by reference, except at 31 ° C instead of 37 ° C. The data of the conduction absorbent capacity test by vertical wicking effect provides the curve from which the capillary absorption pressure is determined. The capillary desorption pressure can be measured using the procedure described in the Test Methods section. To generate the data of a desorption curve, a sample of foam is saturated with water, hangs vertically, and then lets it desorb until it reaches a balance. Then, the fluid load is plotted as a function of height. The capillary desorption pressure, that is, the hydrostatic head at which the fluid load is 505 of the free absorbent capacity, is determined from this curve. The absorbent foams according to the present invention have capillary absorption pressures from about 5 to about 25 cm, and capillary desorption pressures from about 8 to about 40 cm. Particularly preferred absorbent foams have capillary absorption pressures from about 5 to about 15 cm, and capillary desorption pressures from about 8 to about 25 cm. 3. Resistance to Compression Deflection An important mechanical aspect of the absorbent foams of the present invention is its resistance 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 (e.g., 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 fluid acquisition / distribution components, in absorbent cores of 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 the absorption and fluid retention. This is particularly important since the fluids are divided, either due to a gradient of absorption or compression pressure, of the acquisition / distribution components and to other fluid storage components in the absorbent core. Actually, the acquisition / distribution foams of the present invention provide a balance of capillary desorption pressure and foam resistance to avoid undesirable crushing during division. If the capillary desorption pressure of the foam is greater than its RTCD and / or its resistance to re-expansion (i.e., expansion pressure at a particular compression ratio), it will tend to collapse after desorption and this shape will leave the foam in a saturated, densified state. In this state, the acquisition / distribution foam may feel wet to the touch, moistening the wearer's skin. It could also impede the acquisition speed of additional fluid spills. If the foams are too strong, however, they will look and feel stiff, leading to poor aesthetics. Also, a mechanism by which the foams of the present invention can distribute and divide the fluid, involves mechanical pumping, thus, it may be advantageous for the acquisition / distribution foam to be compressed to some degree by normal pressures experienced by the user during use to promote its additional mechanism of division. 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. The method for carrying out this particular type of test is described later in the Test Methods section. The foams useful as absorbers for acquiring and distributing fluids are those that exhibit a resistance to compression deflection, so that a confining pressure of 5.1 kPa produces a voltage typically of to 85% compression of the foam structure. Preferably, the stress produced under such conditions will be in the range of about 5 to about 65%, preferably about 5 to 50%, approximately. 4. Recovery of Wet Compression Recovery of wet compression (RFWC) refers to the tendency or propensity of a piece of wet foam material to quickly return to its original dimensions after being deformed or compressed under forces encountered during fabrication or use, without having a free fluid reservoir for extraction during re-expansion. Many high pressure capillary foams, such as those described in U.S. Patent 5,268,224 (DesMarais et al.), Issued December 7, 1993, and in the co-pending United States of America application No. 989,270 ( Dyer and others), presented on December 11, 1992, will not be easily re-expanded. It has also been found that re-expansion is even more difficult for an acquisition / distribution foam, when in fluid competition with a higher absorption pressure component, such as is typically found in absorbent cores.

A suitable procedure for determining the recovery of wet compression is established in the Test Methods section. Said process in general, involves the compression of a foam sample that has been previously saturated to its absorbent free capacity with synthetic urine, while being placed on top of a high pressure capillary absorption material. The samples are maintained on a tension of 75% compression at a constant temperature (31 ° C) for a period of 5 minutes, after which the compression is released. After competing two minutes for the fluid with the upper absorption pressure material (the sample having had the opportunity to re-expand, the sample is separated and its thickness is measured.) The degree to which the sample recovers its thickness is taken as a measure of the recovery of wet compression of the sample.

Preferred absorbent foams of the present invention will generally exhibit a recovery of at least about 60% of the fully expanded thickness, within two minutes of being released from compression. Most preferably, such preferred foam materials will have a wet compression recovery of at least about 755, most preferably at least about 90%, of the fully expanded thickness within one minute of being released from compression.

. Absorbent Free Capacity Another important property of absorbent foams according to the present invention is its free absorbent 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. Foams that are especially useful in absorbent articles, such as diapers, will satisfy at least a minimum absorbent free capacity. To be especially useful in absorbent articles for absorbing urine, the absorbent foams of the present invention should have a free capacity of from about 12 to about 125 g / g, preferably from about 20 to about 90 g / g, and most preferably from 45 to 75 g / g, approximately, 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.

C. Other Properties of Polymer Foam 1. Cell and Hole Sizes One aspect that may be useful for defining preferred polymer foams is the cell structure. The foam cells, and especially the 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. These spherical cells are connected to each other through openings, which are hereinafter referred to as holes between cells. Both the size or "diameter" of said spherical cells and the diameter of the openings (holes) between the cells are commonly used to characterize foams in general. Since the cells, and the holes between the cells, in a given sample of polymeric foam will not necessarily be of approximately the same size; the average cell and hole sizes, ie the average cell and hole diameters, will usually be specified. The cell and hole sizes are parameters that can impact a number of mechanical aspects and performance of the foams according to the present invention, including the fluid wicking properties of these foams, as well as the capillary pressure that It is developed inside the foam structure. A number of techniques are available to determine the average cell and hole sizes of the foams. The most useful technique involves a simple measurement based on the scanning electron photomicrograph of a foam sample. Figures 3 and 4, for example, show a typical HIPE foam structure, according to the present invention. Superimposed on the photomicrograph of Figure 4 is a scale representing a dimension of 20 μm. This scale can be used to determine the average cell and hole sizes through an image analysis procedure.

The foams useful as absorbers for aqueous fluids, in accordance with the present invention, will preferably have a number average cell size of from about 20 to about 200 μm, and typically from about 30 to 130 μm, and an average hole size in number from about 5 to about 30 μm, and typically from about 8 to 25 μm. The relationship between the fluid holding capacity and the cell structure for these HIPE foams is shown in Figure 5. Figure 5 depicts a graph of desorption pressures against average number hole size for a series of HIPE foams . As stated above, the desorption pressure of the foams of the present invention is one of the key factors that prevent these foams from collapsing when they are desorbed or dehydrated. The graph in Figure 5 shows how one aspect of the foam structure (the hole size between cells) has an impact on this important aspect. Actually, as shown through this graph, as the average size hole size increases, the desorption pressure is reduced in an essentially linear fashion. 2. Specific area of capillary suction "Surface area of capillary suction" is a measurement of the surface area accessible to the test liquid of the polymer network accessible to the test fluid. 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. 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 0. 2 m2 / g. Typically, the capillary suction specific surface area is in the range of about 0.3 to about 4 m2 / g, preferably about 0. 3 to approximately 2.5 m2 / g, most preferably from 0.3 to 1.5 m2 / g, approximately. 3. Surface Area by Volume of Foam The specific surface area by volume of foam can be useful to define empirically foam structures that will not crush, or will remain in a crushed state, when they are desorbed, v. gr., dried or compressed while in a wet state. See co-pending United States of America patent application No. 989,270 (Dyer et al.), Filed December 11, 1992 (hereby incorporated by reference), where the specific area by volume of foam is discussed in detail. to crushed foams. As used in the present, "specific surface area per volume of foam" refers to the specific surface area of capillary suction of the foam structure times its foam density in the expanded state. It has been found that certain values of maximum specific surface area per volume of foam correlate with the ability of the foam structure to maintain itself in an expanded state when it is desorbed, or rapidly return to an expanded state after being compressed while in the expanded state. a humerus state. The foams according to the present invention have specific surface area values per foam volume of about 0.06 m2 / cc or less, preferably from about 0.01 to about 0.04 m / cc, most preferably from 0.01 to 0.03 m2 / cc, approximately. 4. Foam Density "Foam density" (ie in grams of foam per cubic centimeter of foam volume in the air) is specified here on a dry basis. The density of the foam, such as the specific surface area of capillary suction, can influence a number of performance and mechanical characteristics of the absorbent foams.

These include the absorbent capacity for aqueous fluids and the characteristics of compression deflection. 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, a gravimetric procedure ASTM 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 It can be used for density determination. The polymeric foams of the present invention useful as absorbers have dry weight density values in the range from about 0.0079 to about 0.077 g / cc, preferably from about 0.011 to about 0.028 g / cc, and most preferably from 0.013 to 0.022 g. / cc, approximately.

II. Preparation of Polymeric Foams from HIPE A. In General Polymeric foams according to the present invention can be prepared by the polymerization of certain water-in-oil emulsions having a relatively high ratio of water phase to oil phase commonly known in the technique 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 varies inversely with the last foam density and can influence 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 12: 1 to about 125: 1, and most typically of about 35: 1 to approximately 90: 1. Particularly preferred foams can be made of HIPEs having ratios from about 45: 1 to about 75: 1. 1. Components of the Oil Phase The continuous oil phase of the HIPE comprises monomers that are polymerized 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 about 15 ° to 30 ° C. (The method for determining Tg by Dynamic Mechanical Analysis (DMA) is described later in the section on Test Methods). 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, Wiley -lnterscience, 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 polyfunctional interlacing agent; and (d) optionally a second polyfunctional crosslinking agent. The selection of particular types and amounts of monofunctional monomers and comonomers and polyfunctional crosslinking agents can be important for the realization of the absorbent foams of HIPE, having the desired combination of structure, mechanical, and fluid handling properties, which make these materials 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 atactic amorphous polymers of high molecular weight (greater than 10,000), having a Tg of about 25 ° C or less. Monomers of this type include, for example, (C4-C14) alkyl acrylates such as butyl acrylate, hexyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, (lauryl) acrylate, dodecyl, isodecyl acrylate, tetradecyl acrylate, aryl acrylics and alkaryl acrylates such as benzyl acrylate, nonylphenyl acrylate, alkyl methacrylates (C6-C16) such as hexyl methacrylate, octyl methacrylate, nonyl methacrylate, methacrylate decyl, 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 30 to about 80%, 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, where 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 "stiff" monofunctional comonomer will typically comprise about 5 to 40%, preferably 15% to 25%, most preferably about 18% to about 24%, by weight of the monomer component. In certain cases, the "stiffness" comonomer may 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, divinyl phenanthrenes, divinylbiphenyls, divinyl diphenylmethanes, divinylbenzyl, divinylphenyl ethers, divinyl diphenyl sulfides, divinylfurans, divinyl sulfide, divinyl sulfone, and mixtures thereof Divinylbenzene is typically available as a mixture with the 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 can generally be included in the oil phase of the HIPE in an amount of about 5% to about 25%, preferably about 12% to 20%, and most preferably 12% to 18%, 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 1,10-dekanediol, 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 tetramines). 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 0 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 interleaver will exhibit a relatively narrow transition region. The increase in the amount of the second interleaver serves to extend the transition region, even if the actual transition temperature itself 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 is an emulsifying component that allows the formation of stable HIPEs. This emulsifying component comprises a primary emulsifier and optionally a secondary emulsifier. 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 "substantially 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 interferingly active components needs to be sufficiently high to provide at least an approximately monolayer envelope to the internal oil phase droplets at 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 melting 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 provide sufficient wetting capacity when it is spread over the hydrophobic surface (v. gr., the polymeric foam), so that the advancing contact angle for synthetic urine is less than (preferable and substantially less than 90 °.) The method for measuring IFT and CAC is described in the Methods section Further, especially when used alone, 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. C16-C22 linear unsaturated fatty acids, diglycerol monoesters of branched C16-C24 fatty acids, diglycerol monoaliphatic ethers of branched C16-C24 alcohols, diglycerol monoaliphatic ethers of linear, unsaturated C16-C22 alcohols, monoaliphatic diglycerol ethers of alcohols C12-C14 saturates, linear, sorbitan monoesters of unsaturated C16-C22 fatty acids, linear, mono sorbitan esters of branched C 16 -C 24 fatty acids, and mixtures thereof. Preferred primary emulsifiers include 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, greater than about 40%, preferably greater than about 50%, and most preferably greater than about 70). % glycerol monoisostearate). Glycerol monoesters of linear, unsaturated and branched 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 11, 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. The unsaturated, linear and branched 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 11, 1992, which is incorporated herein by reference. The distribution of polyglycerol and polyglycerol ester of the resulting composite ester product can be determined through capillary supercritical chromatography. See application of the co-pending United States of America series No. 989,270 (Dyer et al.), Filed on December 11, 1992., which is incorporated herein by reference. Also, linear, unsaturated, linear, or branched saturated linear monoaliphatic ethers can be prepared, and their composition is determined using methods well known in the art. See also application of the co-pending United States of America 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 and branched unsaturated fatty acids can be obtained commercially or prepared using methods well known in the art. See, for example, 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 application of the co-pending United States of America series No. 08/370920 (Stephen A. Goldman et al.), Filed on January 10, 1995. Case No. 5540, (which is hereby broken by reference), which describes the use of this method for polyglycerol aliphatic ethers. When these primary emulsifiers are used in combinations containing secondary emulsifiers, the primary emulsifier may comprise lower levels of these emulsifying components, ie, as low as about 20% of these emulsifying components. 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) raise the oil phase / water phase IFT, (3) reduce the CAC of the emulsifying component, or (4) increase the concentration of the etherically active components. Although not intended to be bound by theory, it is believed that the ability of the secondary emulsifier to maintain a high oil phase / IFT phase and a low CAC for the emulsifying component extends the temperature scale of HIPE formation and emptying ( for example, at approximately 50 ° C or more) on which HIPEs can be made with a high ratio of water: stable oil, having the large droplet sizes suitable for the formation of polymeric foams having cell and cell sizes. preferred average hole of the present invention. Suitable secondary emulsifiers can be of cationic types, including C12-C22 dialiphatic, long-chain dialiphatic, C-C4 short-chain quaternary ammonium salts, such as dimethyl ammonium ditallow chloride, bistridecyl dimethyl ammonium chloride, and methylisulfate of dimethyl ammonium disodium, quaternary ammonium salts of dialkoyl (alkenoyl) -2-hydroxyethyl-C12-C22 long-chain, dialiphatic short-p-chain, such as ditallowyl-2-hydroxyethyl dimethyl ammonium chloride, the salts of long-chain C12-C22 dialiphatic imidazolino quaternary ammonium, such as methyl-1-seboamido ethyl-2-tallow imidazolino methylisulfate and methyl-1-oleylamido ethyl-2-oleyl imidazolino methyl sulfate, the quaternary ammonium salts of Dialiphatic benzyl of short chain CrC4, monoaliphatic C12-C22 long chain, such as dimethyl stearyl benzyl ammonium chloride; anionic types which include the C6-C18 diatic esters of sodium sulfosuccinic acid such as the dioctyl ester of sodium sulfosuccinic acid and the bistridecyl ester of sodium sulfosuccinic acid; and mixtures of these secondary emulsifiers. These secondary emulsifiers can be obtained commercially or prepared using methods known in the art. Preferred secondary emulsifiers are dimethyl ammonium ditallow methylisulfate and dimethyl ammonium dichloride methylchloride. When these optional secondary emulsifiers 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 about 30: 1 to 2: 1. 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 about 10% by weight of the emulsifier 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, such as described in U.S. Patent 5,290,820 (Bass et al.), Issued on the 1st. March 1994, which is incorporated herein by reference. Another preferred optional component is an antioxidant such as a Disabled Amine Light Stabilizer (HALS) and Stolen Phenolic Stabilizers (HPS) or any other antioxidant compatible with the initiator system used. Other optional components include plasticizers, fillers, colorants, chain transfer agents, dissolved polymers and the like. 2. Components of the Aaua 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 the 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 in a concentration on the scale 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 contain 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 can 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 mol% based on the total moles of polymerizable 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, or the like, for cleaning, and / or body fluids such as urine, they generally require additional treatment to make the foam relatively more hydrophilic. . The hydrophilization of the foam, if necessary, can generally be achieved by treating the HIPE foam with a hydrophilizing surfactant, in the manner described below. These hydrophilizing surfactants may be any material that improves the water wettability of the polymeric 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. In preferred foams, the hydrophilizing surfactant is incorporated so that residual amounts of the agent, which remain in the foam structure, are in the range of from about 0.5% to about 15%, preferably from about 0.5 to about 6% in foam weight. Another material that is typically flaked to the HIPE foam structure 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 such 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%. 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 the same, sufficient quantities of hydratable salts entrapped, 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 surfaces of internal polymerized foam will be adequately hydrophilic, and will include residual water phase liquid containing or depositing sufficient amounts of chloride, even after the polymeric foams have been dehydrated to a practicable liking.

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) polymerize / cure this suitable emulsion to form a solid polymeric foam structure 3) optionally wash the solid polymeric foam structure to remove the original residual water phase from the polymeric foam structure and, if necessary, treat the structure of the polymeric structure. polymeric foam with a hydrophilizing agent and / or hydratable salt to deposit any 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, crosslinkers 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. Suitable mixing or agitating devices are those that are capable of forming an emulsion under low shear mixing conditions. 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 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 a rate of about 4000 sec "1 or less, preferably about 3000 sec" 1 or less. 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 the patent of the United States of America ,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 (hereby incorporated by reference), which describes an improved continuous procedure that has a recirculation loop for the HIPE. 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, the HIPE: can be formed at a temperature of about 60 ° to about 99 ° C, very typically about 65 ° to 95 ° C. 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. It is usually preferred that 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 above about 50 ° C, preferably above 65 ° C, and most preferably above 80 ° C, during a period ranging from about 2 to 64 hours, most preferably from 2 to 48 hours, approximately. An advantage of the most robust emulsifier systems used is that coalescence is minimized when the polymerization / cure is carried out at higher temperatures. HIPE can also be cured in stages as described in the United States of America patent ,189,070 (Brownscombe et al.), Issued February 23, 1993, which is incorporated herein by reference. 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. HIPE polymerized 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. 3. HIPE Foam Treatment / Washing 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 hydrofixing surfactant / hydratable salt has been incorporated, and until the foam display the desired value of adhesion tension for any test liquid of choice. For certain uses, it may be desirable to remove most of the residual electrolyte (ie, hydratable salts) of the foam. For example, the removal of these salts is particularly important when the foam is to be used in an absorbent core (as described below) which also has a float storage component containing absorbent gelling materials. Under these circumstances, the level of residual hydratable salts in the foam is reduced as much as possible during this washing step, typically to about 2% or less, preferably to about 0.5% or less. After removal of these salts, the HIPE foam will typically require treatment with an effective amount of a hydrophilizing surfactant to rehydrate the foam. 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 (preferably in the z direction) to squeeze the waste water, subjecting the foam and water at the same temperature from about 60 ° to about 200 ° C, or by microwave treatment, by thermal dehydration to vacuum or by a combination of compression and drying / microwave / vacuum dehydration techniques. 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 consumer product that is capable of absorbing significant amounts of urine, or other fluids such as aqueous fecal matter (accelerated evacuations), discarded by an incontinent user or user of the item. Examples of such absorbent articles include disposable diapers, incontinence garments, catamenials such as tampons and sanitary napkins, disposable trainers, night pads, and the like. The absorbent foam structures herein are particularly suitable for use in articles such as diapers, sanitary napkins, tampons, incontinent pads or garments, protective clothing, and the like. The absorbent foams of the present invention provide good aesthetics due to their soft, elastic structure and physical integrity. In the sheet form, these absorbent foams are also relatively easy to configure for use in a variety of absorbent articles. In contrast to the fibrous absorbent components, these absorbent foams remain greatly unchanged in overall appearance and structure during use, i.e., density, shape, thickness, etc. These absorbent foams are not plasticized by the aqueous fluids, their mechanical properties remain enormously unchanged when they are wetted. Since the foams of the present invention rapidly acquire and distribute the aqueous fluids, they are particularly useful as the fluid acquisition / distribution component of an absorbent core. These acquisition / distribution foams combine relatively high capillary absorption pressures and weight capacity properties that allow them to acquire fluid with or without the aid of gravity, thus keeping the user's skin dry. This high capacity (by given weight) can lead to efficient, lightweight products. In addition, since the absorbent foams of the present invention can deliver this efficiently acquired fluid to other absorbent components, these foams are particularly useful as the upper acquisition / distribution component in a "multi-layer" absorbent core that also contains a lower fluid storage / redistribution component, wherein the absorbent core is placed between the top sheet and the sheet of backing to form the absorbent article. For purposes of the present invention, an "upper" layer of a multi-layer absorbent core is a layer that is relatively closer to the wearer's body, v. gr., the layer closest to the top sheet of the article. The term "bottom" layers in inverse form means a layer of a multi-layer absorbent core that is relatively further from the wearer's body, v. gr., the layer closest to the backing sheet of the article.

This lower storage / fading redistribution layer is typically placed within the absorbent core in order to be below the (upper) acquisition / redistribution layer of fluid and may be in fluid communication therewith. This lower storage / redistribution layer may comprise a variety of fluid storage / redistribution components including those containing absorbent gelling materials such as described in U.S. Patent 5,061,259 (Goldman et al.), Issued Oct. 29. October 1991; U.S. Patent 4,654,039 (Brandt et al.), issued March 31, 1987 (reissued on April 19, 1988 as Re. 32,649); United States of America 4,666,983 (Tsubakimoto et al.), issued May 19, 1987; and United States of America 4,625,001 (Tsubakimoto et al.), issued November 25, 1986, all incorporated herein by reference; absorbent macrostructures made of these absorbent gelling materials such as those described in U.S. Patent 5,102,597 (Roe et al.), issued April 7, 1992; and U.S. Patent 5,324,561 (Rezai et al.), issued June 23, 1994, both incorporated herein by reference; absorbent gelling materials laminated between two layers of gauze such as those described in United States of America 4,260,443 (Lindsay et al.), issued April 7, 1981; U.S. Patent 4,467,012 (Pedercen et al.), issued August 21, 1984; U.S. Patent 4,715,918 (Lang) issued December 29, 1987; patent of the United States of America 4,951,069 (Packard et al.), Issued July 25, 1989; U.S. Patent 4,950,264 (Osborn), issued August 21, 1991; United States of America patent 4,994,037 (Bemardin), issued February 19, 1991; U.S. Patent 5,009,650 (Bernardin), issued April 23, 1991; United States of America patent 5,009,653 (Osborn), issued April 23, 1991; U.S. Patent 5,128,082 (Makoui), July 7, 1992; U.S. Patent No. 5,149,335 (Kellenberger et al.), issued September 22, 1992; and U.S. Patent No. 5,176,668 (Bernardin), issued January 5, 1993, all incorporated herein by reference; and absorbent foams capable of storing purchased fluids such as those described in U.S. Patent 5,268,224 (DesMarais et al.), issued December 7, 1993; Application of the United States of America Copendent Series No. 989,270 (Dyer et al.), filed on December 11, 1992, and application of the United States of America series No. 08/370922 (Thomas A. DesMarais et al.), filed on January 10, 1995. Case No. 5541, all of which are incorporated herein by reference. There is no critical aspect with respect to the positional relationship of the fluid acquisition / distribution foam component and the fluid storage / redistribution component within these multi-layer absorbent cores, provided that these components are in effective fluid communication between yes, and as long as each component is large enough to maintain and / or effectively transport the amount of aqueous fluid from the body that is expected to be discharged to the absorbent article. An appropriate relationship between the foam component of fluid distribution acquisition and the fluid storage / redistribution component within the absorbent core, is to place these components in a layered configuration. In such a layered configuration, the fluid acquisition / distribution foam component comprises a top foam layer, which covers a component of storage / redistribution of underlying fluid in the form of a lower layer. It should be understood that these two types of layers merely refer to the upper and lower areas of the absorbent core and are not necessarily limited to individual layers or sheets. Both the fluid acquisition / distribution zone, v. gr., top layer, such as the fluid storage / redistribution zone, v. gr., lower layer, may comprise several layers of the requisite type. Thus, as used herein, the term "layer" includes the terms "layers" and "layers". The absorbent articles typically comprise a fluid impermeable backsheet, a fluid pervious top sheet bonded to, or otherwise associated with, the backsheet, and an absorbent core according to the present invention, placed between the backsheet and the upper sheet. The topsheet is positioned adjacent to the body surface of the absorbent core. The topsheet is preferably attached to the backsheet through attachment means such as those well known in the art. As used herein, the term "attached" encompasses configurations by which one element is directly secured to the other element by attaching the element directly to the other element, and configurations by which the element is indirectly secured to the other element by fixing the element to intermediate members, which in turn are fixed to the other element. In preferred absorbent articles, the topsheet and the backsheet are directly bonded together at the periphery thereof. The backsheet is typically impervious to body fluids and is preferably manufactured from a thin plastic film, although other flexible fluid impervious materials may also be used. As used herein, the term "flexible" refers to materials that are condescending and that will readily conform to the configuration and general contours of the human body. The backsheet prevents the body fluids absorbed and contained in the absorbent core from wetting the garments that are in contact with the articles, such as panties, pajamas, underwear, and the like. The backsheet may comprise a woven or non-woven material, polymeric films such as polyethylene or polypropylene thermoplastic films, or composite materials such as a film-coated nonwoven material. Preferably, the backing sheet is a polyethylene film having a thickness of about 0.012 mm to about 0.051 mm. Illustrative polyethylene films are manufactured by Clopay Coforation of Cincinnati, Ohio, under the designation P18-0401 and by Ethyl Corporation, Visqueen Division, of Terre Haute, Indiana, under the designation XP-39385. The backsheet is preferably engraved and / or finished in matte to provide an appearance more of a type of clothing. In addition, the backsheet can allow vapors to escape from the absorbent (ie, breathable) core while still preventing body fluids from passing through the backsheet. The upper sheet is condescending, soft feeling and non-irritating to the user's skin. In addition, the top sheet is permeable to the fluid allowing the fluids of the core to easily penetrate through its thickness. A suitable topsheet can be manufactured from a wide variety of materials such as woven and nonwoven materials; polymeric materials such as thermoplastic films formed with apertures, apertured plastic films, and hydroformed thermoplastic films; porous foams; cross-linked foams; reticuted thermoplastic films and thermoplastic screens. Suitable woven and nonwoven materials may be composed of natural fibers (eg, wood and cotton fibers), synthetic fibers (eg, polymer fibers such as polyester, polypropylene, or polyethylene fibers), or a combination of natural and synthetic fibers. The preferred sheets for use in absorbent articles of the present invention are selected from high-flux non-woven upper sheets and upper sheets formed with openings. Films formed with openings are especially preferred for the topsheet, since they are permeable to body fluids and are non-absorbent, and have a reduced tendency to allow fluids to pass through and re-moisten the wearer's skin. In this way, the surface of the formed film that is in contact with the body remains dry, thus reducing the staining of the body and creating a more comfortable feeling for the user. Suitable shaped films are described in U.S. Patent 3,929,135 (Thompson), issued December 30, 1975; U.S. Patent 4,324,246 (Mullane et al.), issued April 13, 1982; U.S. Patent 4,342,314 (Radel et al.), issued August 3, 1982; U.S. Patent 4,463,045 (Ahr et al.), issued July 31, 1984; and United States of America patent 5,006,294 (Baird), issued April 9, 1991; each of these patents is disclosed here by reference. Suitable upper film laminations with micro apertures are described in United States of America 4,609,518 (Curro et al.), Issued September 2, 1986, and United States of America 4,629,643 patent (Curro et al. and others), issued on December 16, 1986, which will be listed here by reference. The foamed surface of the formed film topsheet can be hydrophilic in order to help the body fluids to be transferred through the topsheet faster than if the body surface were not hydrophilic, in order to decrease the probability that fluid will flow out of the topsheet instead of flowing into and being absorbed by the absorbent structure. In a preferred embodiment, the surfactant is incorporated into the polymeric materials of the formed film topsheet, as described in the application of the United States of America series No. 07 / 794,745, "Absorbing Article Having a Nonwoven and Apertured Film Coversheet "(Absorbent article having a cover sheet of non-woven film with openings), filed November 19, 1991 by Aziz et al., Which is hereby uncoded by reference. Alternatively, the body surface of the topsheet can be rendered hydrophilic by treating it with a surfactant such as is described in U.S. Patent 4,950,254, cited above, incorporated herein by reference. In some embodiments according to the present invention, the acquisition / distribution layer of the absorbent core will be placed in a specific positional relationship with respect to the topsheet and the storage / redistribution layer of the absorbent core. More particularly, the acquisition / distribution layer of the core is positioned so that it is effectively located to acquire the fluid discarded by the body, and to transport said fluid to other regions of the core. In this way, the acquisition / distribution layer can encompass the near point of discharge of body fluids. These areas could include the crotch area and, preferably for items used by men, also the region where the urination discharges that occur in the front of the diaper occur. For a diaper, the front part of the absorbent articles represents the portion of the absorbent article, which is intended to be placed on the front of the user. further, for male users, it is desirable for the acquisition / distribution layer to expand close to the front waist area of the wearer to effectively acquire the relatively high fluid load that occurs in the front of the diapers of male users, and to compensate the Directional variations of downloads. The regions of the corresponding absorbent article may vary depending on the design and fit of the absorbent article. For diaper runs, the acquisition / distribution layer of the core can be placed in relation to an elongated topsheet and / or the storage / redistribution layer, so that the acquisition / distribution layer is of sufficient length to extend toward areas corresponding to at least about 50%, preferably 75%, of the length of the topsheet, and / or from about 50 to about 120% of the length of the storage / redistribution layer. The acquisition / distribution foam layer must have a width sufficient to acquire jets of fluid from the body and prevent direct discharge of the fluid onto the storage / redistribution layer. Generally, for diapers, the width of the acquisition / distribution layer will be at least about 5 cm, preferably at least 6 cm. For the purpose of determining the placement of the acquisition / distribution foam layer, the length of the absorbent article will be taken as the normal longest longitudinal dimension of the backing sheet of the elongated article. This normal longer dimension of the elongate backsheet can be defined with respect to the article when applied to the user. When used, the opposite ends of the backing sheet are held together, so that these joined ends form a circle around the wearer's waist. The normal length of the backing sheet will thus be the length of the line running through the backing sheet from, a) the point on the edge of the backing sheet in the middle part of the back waist of the user, through the crotch, towards b) the point on the opposite edge of the backing sheet in the middle part of the user's front waist. The size and shape of the topsheet will generally correspond substantially to the backsheet. In the usual case, the storage / redistribution layer of the absorbent cores, which generally defines the shape of the absorbent article and the normal length of the topsheet of the elongate article, will be close to the longest longitudinal dimension of the storage layer / redistribution of the nucleus. However, in some articles (eg, incontinence articles for adults), where volume reduction or minimum cost is important, the storage / redistribution layer could generally be placed to cover only the user's genital region. and a reasonable area close to the genital area. In this case, both the fluid acquisition / distribution layer and the storage / redistribution layer could be placed towards the front of the article as defined by the upper sheet, so that the acquisition / distribution and storage / redistribution layers typically they could be found two-thirds of the front of the article's length. The acquisition / distribution foam layer can be of any desired shape consistent with the comfortable fit and dimension limitations discussed above. These shapes include, for example, circular, rectangular, trapezoidal, or oblong, v. gr, shaped like an hourglass, shaped like a dog's bone, shaped like a dog's bone, oval or irregularly shaped. The acquisition / distribution foam layer can be in a similar way or a different shape to that of the storage / redistribution layer. The storage / redistribution layer of the preferred absorbent core configuration can also be of any desired shape consistent with the comfortable fit, including, for example, circular, rectangular, trapezoidal or oblong, v. gr., shaped like an hourglass, shaped like a dog's bone, shaped like a dog's bone, oval, or with an irregular shape. The storage / redistribution layer need not be physically separated from the acquisition / distribution layer, or completely disconnected from the storage / redistribution layer. Figures 6 and 7 show a multi-layer absorbent core configuration, wherein the fluid storage / redistribution component comprises an upper layer 64 generally rectangular in shape, which is placed on a lower acquisition / distribution foam layer 65. of fluid, hourglass-shaped, underlying. The fluid storage / redistribution layer contains a fluid acquisition opening 66 through which body fluid is discarded, in order to collide with the underlying acquisition / distribution lower layer 65. Figure 8 shows a diaper disposable having another multi-layer absorbent core configuration. Said diaper comprises an upper sheet 70, a fluid impermeable backing sheet 71, and a double layer absorbent core, placed between the upper sheet and the backing sheet, the double layer absorbent core comprises a storage / redistribution layer. fluid 72, in the form of a modified hourglass, placed below a layer of fluid acquisition / distribution foam 73, with a modified hourglass shape. The upper sheet contains two strips of folds 74 for the legs, of substantially parallel barrier, with elastic. Attached to the back sheet of the diaper are two elastic waistband members 75 with elastic, rectangular. Also fixed to each end of the backing sheet are two waist protection elements 76. Also attached to the back sheet are two parallel elastic strips 77, for the legs. A sheet 78 is affixed to the outside of the backsheet as a dedicated fastening surface for two Y-shaped tape pieces 79, which can be used to hold the diaper around the wearer's waist. The multi-layer absorbent cores can also be made in accordance with the request of the co-pending United States of America series No. 08/370900 (Gary Dean LaVon et al.), Filed on January 10, 1995, case No. 5547 (incorporated here by reference), wherein one or more layers comprise an absorbent foam according to the present invention.

IV. Test Methods A. Capillary Absorption Pressure A capillary absorption isotherm curve was generated using the Vertical Mecha Effect Absorbing Capacity test, described in the Test Methods section of the co-pending application of the United States of America series No. 989,270 (Dyer et al.), Filed December 11, 1992, which is incorporated herein by reference, except 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.

B. Pressure of Hair Loss The capillary desorption test is a measure of the ability of the foam to hold the fluid as a function of several hydrostatic heads. The sample strip of adequate dimensions, v. gr., 40 cm long x 2 5 cm wide x 0.2 cm thick, and the test liquid (distilled water, optionally containing a small amount of food grade dye as indicator), were balanced in a quarter to 22+ 2 C. The measurement was carried out at the same temperature. The foam strip is saturated with water, then placed vertically, so that the lower end is immersed 1-2 mm in a water tank. The water is allowed to drain from the sample until an equilibrium is reached, typically 16-24 hours. During this procedure, the sample and the deposit should be protected, for example, using a glass cylinder and an aluminum sheet, to avoid water loss due to evaporation. The sample was then quickly removed and placed on a non-absorbent surface, where it was cut to 2.5 cm segments, after discharging the portion of the sample that was submerged in the reservoir. Each piece was weighed, washed with water, dried and then weighed again. The absorbent capacity was calculated for each piece. An isotherm curve of capillary desorption was generated by plotting the absorbent capacity of each segment as a function of height. The curve is a graph of the absorbent capacity of each segment as a function of height of that of the desorbed test fluid, using the distance from the top of the water reservoir to the midpoint of each segment for height, h. The capillary desorption pressure is taken as the height of the foam having an absorbent capacity of half the free absorbent capacity of the foam.

C. 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 a confining pressure of 5.7 kPa has been applied to the sample. Measurements of resistance to compression deflection are typically made on the sample concurrently with the measurement of the Absorbent Free Capacity, 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 Na2SO4, 0.85 g of NH4H2PO4, 0.15 g of (NH4) 2HPO4, 0.19 g of CaCl2, and 0.23 g of MgCl2 at 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 foam sample sheet was saturated to its free absorbent capacity by soaking in a Jayco synthetic urine bath. After 3 minutes, a cylinder with a circular surface area of 6.5 cm2 was cut from the saturated sheet 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, expanded thickness was recorded. (X1) Then, a force was applied to the limb, so that the saturated foam sample 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 voltage for the samples can be calculated, as follows: [(X1-X2) / X1] x100 =% reduction in thickness.

D. Recovery of Wet Compression fRFWC) The foam samples, the Jayco synthetic urine and the equipment used to make measurements were all equilibrated at 31 ° C and at a relative humidity of 50%. All measurements were also made at this temperature and humidity. Thickness measurements were made under a pressure of about 0.55 kPa using a calibrator such as an Ames model 482 or an Ono-Sokki model EG-225.

A foam cylinder with a thickness of approximately 2 mm and a diameter of 29 mm was punched in a foam sheet. It was saturated to its absorbent free capacity with Jayco synthetic urine, then a Whatman grade No. 3 paper filter (particle retention: 6 μm) was placed on top of three sheets with a diameter of 9 cm. The role of filter paper is to simulate the high absorption pressures typically associated with storage components in absorbent articles. The foam / paper composite is immediately compressed to 75% of the thickness of the wet foam (1.5 mm for a sample with a thickness of 2 mm), using a rigid plate with a larger area than the foam sample. This tension was maintained for 5 minutes, during which most of the synthetic urine was divided into the foam and into the filter paper. After the 5 minute period, the confinement plate was removed from the paper foam composite material, and the foam was able to imbibe air and re-expand. Two minutes after removing the confinement plate, the sample was separated from the paper and its thickness was measured. The degree to which the sample recovers its thickness, expressed as a percentage of its initial thickness, is taken as a measure of the wet compression recovery of the sample. The average of at least three measurements was used to determine the RFWC.

E. 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 with synthetic urine. Typically, measurements of free absorbent capacity are made in the same sample concurrently with the measurement of resistance to compression deflection. 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 was 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 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 Mettier PM 480 and Mettier PC 440 (Mettier Instrument Cof., 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].

F. 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.

G. Interfacial Tension Method (IFT. (Turning Drop) The interfacial tension (IFT) was measured at 50 ° C through the spin drop method described in the request of the United States of America co-pending series No. 989,270 (Dyer et al.), Filed December 11, 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 was determined (CAC) 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 is used. Desirably, the concentration of the higher emulsifier used is at least about twice (most desirably at least about 3 times) of the emulsifier's CAC. . 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. .

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 (567 g) were dissolved. This provides the water phase stream that will be used in a continuous process to form a HIPE emulsion. To a monomer combination comprising styrene (1600 g), divinylbenzene 55% technical grade (1600 g), to 2-ethylhexyl acrylate (4800 g), high purity diglycerol monooleate (480 g) and antioxidant Tinuvin 765 [bis (1, 2,2,5 sebacate) was added , 5-pentamethylpiperidinyl)] (40 g). This diglycerol monooleate emulsifier was prepared following the general procedure for preparing polyglycerol esters in the co-pending United States of America application 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 polyglycerol ester reaction product is first functionally distilled through two CMS-15A centrifugal molecular distillation stills connected in series to reduce the levels of unreacted polyglycerols and fatty acids, and then re-distilled 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 / hr, a desgacizer vacuum of approximately 21-26 microns, a glass bell vacuum of approximately 6-12 microns, a temperature of 170 ° C, and a residue temperature of approximately 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 (70 ° -74 ° 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 lilacs of pins, two rows having 17 pins and two rows having 16 pins, each having a diameter of 0.5 cm extending out from the central 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 incoforation 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 starts in the dynamic mixer, with the propeller rotating at 1200 fm. The flow rate of the water phase was then increased steadily at a rate of 44.1 cc / sec over a period of about 30 seconds, and the flow rate of the oil phase was reduced to 1.25 g / sec over a period of about 1 minute. The back pressure created by the dynamic and static mixers at this point is 35 kPa. The speed of the propellant was then stably reduced at a speed of 600 rpm for a period of 120 sec. The back pressure of the system is reduced to 12 kPa and remains constant afterwards. The resulting HIPE has a water to oil ratio of about 36: 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. Washing and Dewatering the Foam 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 32-38 times (32-38 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 0.19 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 2 times (2X) the height of the polymerized monomers. At this point, the sheets are then resaturated with a solution of 0.75% CaCl2 at 60 ° C, compressed in 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 2 and 5%. Then, the HIPE foam was dried with air for about 16 hours. Said drying reduces the moisture content to about 4-10% by weight of the polymerized material.

EXAMPLE 2 Preparation of Foam from a HIPE A) Preparation of HIPE Anhydrous calcium chloride (36.32 kg) and potassium persulfate (189 g) were dissolved in 378 liters of water. This provides the water phase stream that will be used in the continuous process to form a HIPE emulsion. To a combination of monomer comprising styrene (600 g), technical grade divinylbenzene (700 g), 2-ethylhexyl acrylate (3100 g), and 1,4-butanediol dimethacrylate (600 g), was added monooleate diglycerol (250 g), 2-octyldodecyl diglycerol ether (50 g) and antioxidant (30 g) Tinuvin 765 (41 g). The glycerol monooleate emulsifier is the same as that used in Example 1 The co-emulsifier of 2-octyldodecyl diglycerol ether was prepared as follows: ether was prepared 2-octyldodecyl glycidyl, using the aliphatic glycidyl ether method described in the co-pending United States of America application No. 08/370920 (Stephen A. Goldman et al.), Filed on January 10, 1995, case No. 5540 , which is incorporated herein by reference. To a stirred mixture of about 1.5 kg of 2-octyldodecanol (Jarcol I-20; Jarchem Industries) and about 10 g of stannic chloride, about 360 g of epichlorohydrin was added. After the resulting exotherm heated the reaction mixture to about 70 ° C, the mixture was stirred under nitrogen for about an additional 6 hours at about 65 ° C. After, approximately 190 g of sodium hydroxide, prediluted in approximately 28 g of distilled water, were added and reacted for about 6 hours at about 65 ° C. After separating the aqueous layer, the organic layer was washed with water three times, heated to 95 ° C, nitrogen was introduced to dry, and distilled on the scale of about 185 ° -210 ° C and < 1 mm Hg to produce about 1.1 kg of 2-octyldodecyl glycidyl ether.

Approximately 8.1 g of sodium methoxide (25% by weight in methanol) and approximately 1400 g of anhydrous glycerin were reacted together for about 3 hours under nitrogen at about 130 ° C. After heating the resulting mixture to about 185 ° C, 2-octyldodecyl glycidyl ether was added dropwise over a period of about 2 hours. The resulting mixture was stirred for about 4 hours at about 185 ° C under nitrogen and then allowed to cool without mixing. A layer of glycerin settled on the bottom and was removed by siphoning. Volatile products were distilled from the remaining material by heating to approximately 150 ° C to 2 mm Hg, producing approximately 1.3 kg of the product. Approximately 700 g of the product was dissolved in an excess of compound hexanes. This phase of hexane is multiplied by extracting 90:10 (v: v) methanol: water. The methanol extracts were combined and the solvent was removed using a rotary evaporator. The resulting residue was heated to about 70 ° C and filtered through a glass microfiber filter, yielding approximately 380 g of the 2-octyldodecyl diglycerol ether emulsifier. The product was analyzed by gel permeation chromatography and found to be approximately 82% monoaliphatic diglyceryl ether and about 5% diallyl triglyceryl ether. This imparts a minimum value of interfacial tension of oil phase / water phase of approximately 3.9 dynes / cm, and has a critical aggregation concentration of approximately 0.5% by weight. After mixing, this combination of materials was allowed to settle overnight. No visible residue formed and the entire mixture was removed and used as the oil phase in a continuous process to form a HIPE emulsion. At an aqueous phase temperature of 85 ° -90 ° C and an oil phase temperature of 23 ° C, the separated streams of the oil phase and the water phase 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, as in Example 1. As in Example 1, a spiral static mixer was also mounted downstream of the dynamic mixing apparatus for provide counter pressure and an improved incorporation of components to the emulsion that was finally formed. The Fixation of the combined mixing apparatus was filled with oil phase and water phase at a ratio of two parts of water to one part of oil. The dynamic mixing apparatus was ventilated to allow air to escape, while the apparatus is completely filled. The flow rates during filling are 3.78 g / sec of the oil phase and 7.56 cc / sec of the water phase. Once the apparatus is filled, the flow rate of the water phase is cut to 25% to reduce pressure buildup while closing the vent. Then, the agitation was started in the dynamic mixer, with the propeller rotating at 1800 rpm. The flow rate of the water phase was stably increased at a rate of 37.8 cc / sec over a period of about 1 minute, and the flow rate of the oil phase was reduced to 0.84 g / sec over a period of about 2 minutes. When the flow rate of the water phase reaches 37.8 cc / sec, the speed of the propellant is instantly reduced to 1200 rpm, and then stably reduced for a period of 1 minute at 900 rpm. The back pressure created by the dynamic and static mixers at this point is approximately 16 kPa. The speed of the propellant is then stably reduced to approximately 850 rpm for a period of 1 minute. The back pressure created by the dynamic and static mixers at this point is approximately 15 kPa. The resulting HIPER has a water to oil ratio of about 45: 1.

B) Polymerization of the Invention The formed emulsion flowing from the static mixer at this point is collected in polypropylene round trays, as in Example 1. The trays containing the emulsion are kept in a room at 82 ° C for 4 hours for carry out the polymerization of the emulsion in the containers, to form the polymeric foam.

C) Washing and Dehydration of the Foam After completing the cure, the wet cured foam is removed from the healing trays. The foam at this point contains approximately 40-50 times the weight of the polymerized material (40-50X) of the wastewater phase containing dissolved emulsifiers, electrolyte, initiator residues, and initiator. The foam was sliced with a saw blade with a sharp reciprocal movement, in sheets with a thickness of 0.19 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 3 times (3X) the weight of the polymerized material. 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 1X. The CaCl2 content of the foam is between 2 and 5%.

The foam was then dried with air for about 16 hours. Said drying reduces the moisture content to about 4-10% by weight of the polymerized material.

EXAMPLE 3 Preparation of the Foam from a HIPE A) Preparation of HIPE Anhydrous calcium chloride (36.32 kg) and potassium persulfate (1.13 kg) were dissolved in 378 liters of water. 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% ethyl styrene) (1750 g), 2-ethylhexyl acrylate (2750 g) and 1,4-hexanediol diacrylate (500 g), it is added diglycerol monooleate (250 g), dihydrogenated tallow dimethyl ammonium methylisulfate (50 g) and Tinuvin 765 antioxidant (25 g). The glycerol monooleate emulsifier (Grindsted Products, Brabrand, Denmark) comprises approximately 82% glycerol monooleate, 1% other diglycerol monoesters, 7% polyglycerols, and 11% other polyglycerol esters, imparts a minimum interfacial tension value of oil phase / water phase of approximately 2.4 dynes / cm, and has a critical aggregation concentration of about 3.0% by weight. Dihydrogenated tallow methylisulfate dimethylammonium was obtained from Witco / Sherex Chemical Co. This imparts a minimum oil phase / phase phase interfacial tension value of approximately 2.5 dynes / cm and has a critical aggregation concentration of approximately 0.065 by weight. After mixing, this combination of materials was allowed to settle overnight. Only a small visible residue was formed and almost all of the mixture was removed and used as the oil phase in a continuous process to form a HIPE emulsion. At an aqueous phase temperature of 85 ° -90 ° C and an oil phase temperature of 20 ° C, the separated streams of the oil phase and the water phase were fed to a dynamic mixing apparatus. The complete mixing of the combined streams in the dynamic mixing apparatus was achieved through a pin propellant, as in Example 1. As in Example 1, a spiral static mixer was also mounted downstream of the dynamic mixing apparatus to provide back pressure and an improved incoforation of components to the emulsion that was finally formed. The Fixation of the combined mixing apparatus was filled with oil phase and water phase at a ratio of two parts of water to one part of oil. The dynamic mixing apparatus was ventilated to allow air to escape, while the device is completely filled. The flow rates during filling are 3.78 g / sec of the oil phase and 7.6 cc / sec of the water phase. Once the apparatus is filled, the flow rate of the water phase is cut to 25% to reduce pressure buildup while closing the vent. Then, agitation was started in the dynamic mixer, with the propeller rotating at 1200 fm. The flow rate of the water phase was stably increased at a rate of 37.8 cc / sec over a period of about 1 minute, and the flow rate of the oil phase was reduced to 0.63 g / sec over a period of about 3 minutes. The back pressure created by the dynamic and static mixers at this point is approximately 21 kPa. The speed of the propellant was steadily reduced to 800 rpm for a period of approximately 2 minutes and the back pressure fell to 16 kPa. The resulting HIPE has a water to oil ratio of 60: 1.

B) Polymerization of Emulsion The formed emulsion flowing from the static mixer at this point is collected in polypropylene round trays, as in Example 1. The trays containing the emulsion are kept in a room at 82 ° C for 2 hours to carry out the polymerization of the emulsion in the containers, to thereby form the polymeric foam.

C) Foam Washing and Dehydration After the cure is completed, the wet cured foam is removed from the healing trays. The foam at this point contains approximately 50-60 times the weight of the polymerized material (50-60X) of the wastewater phase containing dissolved emulsifiers, electrolyte, initiator residues, and initiator. The foam was sliced with a saw blade with a sharp reciprocal movement, in sheets with a thickness of 0.127 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 3 times (3X) the weight of the polymerized material. 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 1X. The CaCl2 content of the foam is between 1 and 4%. The foam was then dried with air for about 16 hours. Said drying reduces the moisture content to about 3-12% by weight of the polymerized material.

Claims (16)

1. - A polymeric foam material, which is capable of acquiring and distributing aqueous fluids, said polymeric foam material comprising a polymeric, non-ionic, flexible, hydrophilic foam structure of interconnected open cells, characterized in that the foam structure has: ) the ability to vertically wick synthetic urine at a height of 5 cm in less than about 120 seconds, preferably less than 70 seconds; B) a capillary absorption pressure of about 5 to 25 cm, preferably 5 to 15 cm; C) a capillary desorption pressure of 8 to 40 cm, preferably of 8 to 25 cm; D) a resistance to compression deflection of 5 to 85%, preferably 5 to 65%, most preferably 5 to 50%, when measured under a confining pressure of 5.1 kPa; E) an absorbent free capacity of 12 to 125 g / g, preferably 35 to 90, most preferably 45 to 75 g / g; F) a wet compression recovery of at least 60%, preferably at least 75%.

2. The foam material according to claim 1, further characterized in that it has a number average cell size of 20 to 200, preferably 30 to 130 μm, and a number average hole size of 5 to 30, preferably from 8 to 25 μm.

3. The foam material according to any of the claims 1 to 2, further characterized in that said foam structure has a specific surface area per volume of foam from 0.01 to 0.06, preferably from 0.01 to 0.04 m2 / ce.

4. The foam material according to any of claims 1 to 3, further characterized in that it is made of a water-in-oil emulsion, polymerized, having: 1) an oil phase comprising: a) from 85 to 90%, preferably 90 to 97% by weight of a monomer component capable of forming a copolymer having a Tg value of 35% or less, preferably 15 ° to 30 ° C, the monomer component comprising: i) from 30 to 80% by weight of at least one monofunctional monomer substantially insoluble in water, capable of forming a polymer having a Tg of 25 ° C or less; ii) from 5 to 40% by weight of at least one monofunctional comonomer substantially insoluble in water, capable of imparting resistance approximately 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 the group consisting of divinylbenzenes, trivinylbenzenes, divinyl-toluenes, divinylxylenes, divinylnaphthalenes, divinyl-alkylbenzenes, divinyl-phenanthrenes, divinylbiphenyls, divinyl-diphenylmethanes, divinylbenzyl, ethers divinyl phenyl, divinyl diphenyl sulfides, divinylfurans, divinyl sulfide, divinyl sulfone, and mixtures thereof; and iv) from 0 to 15% by weight of a second, polyfunctional, substantially insoluble water-binding agent selected from the group consisting of polyfunctional acrylates, methacrylates, acrylamides, methacrylamides and mixtures thereof; 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 for forming a stable water-in-oil emulsion; and 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 at a weight ratio of water phase to oil phase in the range of 35: 1 to 90: 1, preferably 45: 1 to 7'4: 1.

5. The foam material according to claim 4, further characterized in that said monomer component comprises: i) from 50 to 65% by weight of a monomer selected from the group consisting of C4-C14 alkyl acrylates, acrylates of aryl and alkaryl, C6-C16 alkyl methacrylates, alkyl styrenes of -C, 2, acrylamides and mixtures thereof; ii) from 15 to 25% by weight of a comonomer selected from the group consisting of styrene, ethyl styrene, and mixtures thereof; iii) from 12 to 20% by weight of divinylbenzene; and iv) from 0 to 13% by weight of said second crosslinking agent selected from the group consisting of 1,4-butenediol dimethacrylate, ethylene glycol dimethacrylate, 1,6-hexanediol diacrylate and mixtures thereof.

6. The foam material according to claim 5, 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.

7. An absorbent article especially suitable for absorbing and retaining aqueous fluids of the body, 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 user of the article, said absorbent core characterized in that it comprises the foam material of either of claims 1 to 6.

8. The absorbent article according to claim 7, further characterized in that said absorbent core comprises: (1) a fluid handling layer comprising the foam material placed in the discharge region of fluid; and (2) a fluid storage / redistribution layer in fluid communication with the fluid handling layer.

9. A diaper useful for absorbing aqueous fluids from the body discarded by an incontinent individual, said diaper article comprising: I) a backing sheet relatively impervious 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 6. 10.- A process for the preparation of a polymeric foam material, absorbent, capable of acquiring and distributing aqueous fluids, which comprises the steps of: A) forming a water-in-oil emulsion at a temperature of 50 ° C or higher, preferably in the range of about 60 ° to about 99 ° C, and under low shear mixing of: 1) an oil phase comprising : a) from 85 to 90%, preferably from 90 to 97% by weight of a monomer component capable of forming a copolymer having a Tg of 35 or less, preferably from 15 ° to 30 ° C, the monomer component comprising i) from about 30 to about 80% 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 5 to 40% by weight of at least one monofunctional comonomer substantially insoluble in water, capable of imparting resistance approximately 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, divinylxylenes, divinylnaphthalenes, divinyl alkylbenzenes, divinylphenanthrenes, divinylbiphenyls, divinyl diphenylmethanes, divinylbenzyl, divinylphenyl ethers, divinyl sulfides diphenyl, divinylfurans, 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 for forming a stable emulsion of water in oil, the emulsion component comprising: (i) a primary emulsifier having at least 40% by weight of emulsifying components selected from the group consisting of diglycerol monoesters of linear unsaturated C16-C22 fatty acids, diglycerol monoesters of branched C16-C24 fatty acids, monoaliphatic diglycerol ethers of branched C16-C24 alcohols, diglycerol monoaliphatic ethers of linear unsaturated C16-C22 fatty alcohols, diglycerol monoaliphatic ethers of saturated, linear C12-C14 alcohols, sorbitan monoesters of unsaturated C16-C22 fatty acids, linear, sorbitan monoesters of branched C 16 -C 24 fatty acids, and mixtures thereof; or, (ii) the combination of a primary emulsifier having at least about 20% by weight of these emulsification components and a secondary emulsifier in a weight ratio of primary to secondary emulsifier of from about 50: 1 to about 1: 4; and said secondary agent being selected from the group consisting of dialiphatic quaternary ammonium salts of long chain C12 C22, short chain of C1-C4, dialcoyl (alkenoyl) -2-hydroxyethyl long chain of C12-C22, quaternary ammonium salts short-chain dialiphatics, C12-C22 dialiphatic long-chain imidazolino quaternary ammonium salts, short chain dialklytic benzyl quaternary ammonium salts of CrC4, long-chain monoaliphatic C12-C22 salts, and mixtures thereof; and 2) a water phase 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) the weight ratio of water phase to oil phase in the scale from 12: 1 to 125: 1, preferably from 35: 1 to 90: 1, most preferably from 45: 1 to 75: 1; and B) polymerizing the monomer component in the oil phase of the oil in water emulsion to form a polymeric foam material. 11. The method according to claim 10, further characterized in that it comprises the additional step of dehydrating the polymeric foam material of step B) to such a degree that a polymeric foam material is formed which is capable of acquiring and distributing aqueous fluids. 12. The method according to claim 10, further characterized in that said monomer component comprises: i) from 50 to 65% by weight of the monomer selected from the group consisting of C4-C14 alkyl acrylates, aplo-acrylates and alkaryl, alkyl methacrylates of G, -C8, C4-C12 alkyl styrenes, acrylamides and mixtures thereof; ii) from 15 to 25% by weight of a comonomer selected from the group consisting of styrene, ethyl styrene and mixtures thereof; iii) from 12 to 20% by weight of divinylbenzene; and iv) from 0 to 13% by weight of said second cronker selected from the group consisting of 1,4-butanediol dimethacrylate, ethylene glycol dimethacrylate, 1,6-hexanediol diacrylate, and mixtures thereof. 13. The process according to claim 13, further characterized in that the 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, and mixtures thereof. 14. The process according to any of claims 10 to 13, further characterized in that said primary emulsifier comprises at least 70% of emulsification components, selected from the group consisting of diglycerol monooleate, diglycerol monoisostearate, sorbitan monooleate and mixtures thereof. 15. The process according to any of claims 10 to 14, further characterized in that said secondary emulsifier is selected from the group consisting of dimethyl ammonium dichloride chloride, bistridecyl dimethyl ammonium chloride, dital dimethyl ammonium methylisulfate, ditallow chloride -2-hydroxyethyl dimethyl ammonium, methyl-1-tallow amido ethyl-2-tallow imidazolino methylisulfate, methyl-1-oleyl amido ethyl-2-oleyl imidazolino methylisulfate, dimethyl stearyl benzyl ammonium chloride and mixtures thereof. 16. The process according to claim 15, further characterized in that said second emulsifier is selected from the group consisting of dimethyl ammonium dichloride chloride and dimethyl ammonium ditallow methylisulfate.