WO1996021682A1 - Foams made from high internal phase emulsions useful as absorbent members for catamenial pads - Google Patents

Abstract

Foams capable of absorbing blood and blood-based fluids, especially menses. These absorbent foams have high capillary absorption pressures required of absorbents used in catamenial products, yet have sufficient openness to allow free movement of the insoluble components in blood-based fluids such as menses. These absorbent foams are made by polymerizing high internal phase emulsions (HIPEs) where the volume to weight ratio of the water phase to the oil phase is in the range of from about 20:1 to about 125:1. These foams are particularly useful as absorbent members for catamenial pads.

Description

FOAMS MADE FROM HIGH INTERNAL PHASE EMULSIONS USEFUL AS ABSORBENT MEMBERS FOR CATAMENIAL PADS

This application is a continuation-in-part application of U.S.S.N. 08/370.697. filed January 10, 1995 by J. Dyer.

FIELD OF THE INVENTION

This application relates to flexible, microporous, open-celled polymeric foam materials made from high internal phase emulsions that can absorb blood and blood-based fluids such as menses. This application particularly relates to absorbent foam materials that are useful as absorbent members for catamenial pads, tampons, bandages, wound dressings, surgical drapes and the like.

BACKGROUND OF THE INVENTION

The development of highly absorbent articles for blood and blood-based fluids such as catamenial pads (e.g., sanitary napkins), tampons, wound dressings, bandages and surgical drapes can be challenging. Compared to water and urine, blood and blood based fluids such as menses are relatively complex mixtures of dissolved and undissolved components (e.g., erythrocytes or red blood cells). In particular, blood-based fluids such as menses are much more viscous than water and urine. This higher viscosity hampers the ability of conventional absorbent materials to efficiently and rapidly transport these blood-based fluids to regions remote from the point of initial discharge. Undissolved elements in these blood-based fluids can also potentially clog the capillaries of these absorbent materials. This makes the design of appropriate absorbent systems for blood-based fluids such as menses particularly difficult.

In the case of catamenial pads, women have come to expect a high level of performance in terms of comfort and fit, retention of fluid, and minimal staining. Above all. leakage of fluid from the pad onto undergarments is regarded as totally unacceptable. Improving the performance of such catamenial pads continues to be a formidable undertaking, although a number of improvements have been made in both catamenial structures, and materials used in such structures. However, eliminating leakage, particularly along the inside of the thighs, without compromising fit and comfort, has not always met the desired needs of the consumer.

The users of sanitary napkins, and die like, have also come to expect the surface of such products to provide a cleaner, more sanitarv and drier aspect than common cloth or nonwoven materials have historically provided Current sanitary napkin products are typically provided with nonwoven or formed-film permeable topsheets that are designed to move discharged menstrual fluids rapidly through and into an underlying absorbent structure This rapid movement of acquired menstrual fluids is designed to provide a drier and cleaner surface adjacent die wearer of the product

The absorbent structures of current catamenial (e g , sanitary napkin) pads have typically compnsed one or more fibrous layers for acquiring the discharged menstrual fluid from the permeable topsheet and distributing it to an underlying storage area Absorbent structures for relatively thm versions of pπor catamemal products usually comprise a fluid acquisition layer (often called a "secondary topsheet") that is adjacent to the permeable topsheet This "secondary topsheet" typically is made from an air-laid-tissue web or a synthetic nonwoven Underlying this secondary topsheet is the mam absorbent core that is typically made from air-laid or wet-laid tissue The absorbent core often contains a paniculate absorbent gelling material that can be encased or enveloped within this tissue Such encased or enveloped cores are often referred to as tissue laminate cores See, for example, U S patent 4,950,264 (Osbom), issued August 21, 1990 and U S patent 5,009,653 (Osbom), issued April 23, 1991, that disclose tissue laminate cores used in sanitary napkin products Pπor catamemal absorbent structures made from fibrous layers have a number of problems One is the difficulty in ensuring adequate topsheet dryness In particular, the acquired menstrual fluid can potentially leak back through the main topsheet This phenomenon is often referred to as "rewet " Rewet can be significantly reduced by increasing the fluid capillary pressure exerted by the absorbent core for fluid relative to the mam and secondary topsheet The greater the dispaπty in fluid capillary pressure between core and topsheet elements, the greater the potential for providing a dry topsheet surface in contact with the body This potential, however, can only be realized if the kinetics of fluid movement throughout the core is sufficiently fast

Pπor catamemal absorbent structures, and m particular catamemal pads using such structures, have also had a greater chance of causmg panty and body soilmg This is because the absorbent structure lacks resilience, leading to bunching of the pad This lack of resilience, and consequent bunching, has also caused these pπor catamemal pads to provide poorer fit and comfort for the user

An alternative to conventional catamemal absorbent structures are absorbent foams Absorbent foams can possess desirable wet integnty, can provide suitable fit throughout the entire peπod the article is worn, and can minimize changes in shape duπng use (e g , uncontrolled swelling, bunching, etc ) In addition, catamemal products containing such foam structures can be easier to manufacture on a commercial scale For example, absorbent cores can simply be stamped out from continuous foam sheets and can be designed to have considerably greater uitegπty and uniformity than conventional absorbent fibrous webs Such foams can also be prepared in any desired shape, or even formed mto single-piece catamemal pad, or other absorbent article used to absorb blood or blood-base fluids such as tampons, wound dressings, bandages and surgical drapes

Foams of vaπous types have been suggested for use in tampons, sanitary napkins and other articles that absorb blood and blood-based fluids See for example U S Patent 4J 10,276 (DesMarais), issued August 29, 1978 (soft, flexible, open celled foams made from polyurethanes, cellulose, or styrene/butadiene rubber that can be used in tampons and sanitary pads), U S Patent 4,752,349 (Gebel), issued June 21, 1988 (foams of "medium cell size" hydrophilized by surfactant treatment and having a density within the range of 0 1 to 0 8 g cc), U S Patent 4,613,543 (Dabi), issued September 28, 1986 (hydrophilic cellular polymers used m catamemal products), U S Patent 3,903,232 (Wood et al ), issued September 2, 1975 (compressed hydrophilic polyurethane foams useful m biomedical applications, mcludmg catamemal devices), U S Patent 4,049,592 (Marans et al ) issued September 20, 1977 (biodegradable hydrophilic polyurethane foams highly absorptive upon contact with liquids or bodily fluids having utility m sanitary napkins and the like) Pπor foams used in these products have tended to have relatively large cell sizes As a result, these pπor foams do not exert sufficient fluid capillary pressure for blood and blood-based fluids to acquire discharged menstrual fluids quickly from and through the topsheet of catamemal products such as sanitary napkins This results in undesirable rewet since the surface in immediate contact with the body retains some of the fluid that is not absorbed mto the core and is available to be transferred back onto the body of the wearer Suitable absorbent foams for absorbent products have also been made from High

Internal Phase Emulsions (hereafter 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 absorbent HIPE foams provide desirable fluid handling properties, mcludmg (a) relatively good wicking and fluid distribution characteπsUcs to transport fluid away from the initial unpmgement zone and mto the unused balance of the foam structure to allow for subsequent gushes 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 sufficiently flexible and soft so as to provide a high degree of comfort to the wearer of the absorbent article, some of these foams can be made relatively thm until subsequently wetted by die absorbed bodv fluids See also U S Patent 5,147,345 (Young et al), issued September 15, 1992 and U S Patent 5,318,554 (Young et al), issued June 7, 1994, which disclose absorbent cores having a fluid acquisition distribution component that can be a hydrophilic. flexible, open-celled foam such as a melamine-formaldehyde foam (e.g., BASOTECT made by BASF), and a fluid storage redistribution component that is a HIPE-based absorbent foam.

HIPE foams can provide the fluid capillary pressure necessary to remove most of the menstrual fluid from the body, or topsheet adjacent to the body, thus minimizing rewet. However, it has been found that the residual hydratable salts such as calcium chloride typically present in prior HIPE foams can impair the rapid acquisition blood and blood-based fluids by these foams, and especially the wicking of such fluids within these foams. As noted above, blood and blood-based fluids such as menses are more highly viscous than water and especially urine. The higher viscosity of these fluids is further increased by die presence of these salts. Moreover, prior HIPE foams typically have a foam microstnicture too small to admit readily the undissolved components of blood and blood-based fluids such as red blood cells.

Accordingly, it would be desirable to be able to make an open-celled absorbent polymeric foam material, in particular an absorbent HIPE foam, that: (1) can rapidly absorb blood and blood-based fluids such as menses; (2) can be used as absorbent members for relatively thin catamenial pads (e.g., sanitary napkins) and other catamenial products such as tampons, as well as wound dressings, bandages, surgical drapes and the like; (3) allow storage components having higher capillary or osmotic absorption pressures to partition away this fluid; (4) keep the source of the blood-based fluids relatively free of rewet, even in "gush" situations and under compressive load; (5) are soft, flexible, resilient, and comfortable to the wearer of the absorbent article, and (6) have a relatively high capacity for fluid to provide efficient in their utilization of costly components.

While thin catamenial products are desired by many users, there is significant demand for relatively thick products. For example, a thick product may provide a perceived ability to better absorb and retain fluid. Also, a thick product may offer improved fit. It would therefore be desirable to have a relatively thin absorbent foam material(s) as the absorbent core of a catamenial product diat allows the use of inexpensive filler materials (e.g., airfelt) to provide bulk/thickness.

DISCLOSURE OF THE INVENTION

The present invention relates to polymeric foam materials that are capable of absorbing blood and blood-based fluids such as menses and then moving these absorbed fluids efficiently to other regions of the foam. These absorbent polymeric foam materials comprise a hydrophilic, flexible, nonionic polymeric foam structure of interconnected open-cells. This foam structure has:

A) the ability to wick artificial menstrual fluid (AMF) vertically to a height of 5 cm in less than about 60 minutes.

B) a capillary specific surface area in the range of from about 0 0080 to about 0 040 m^/cc,

C) a resistance to compression deflection of from about 5 to about 95% when measured under a confining pressure of 0 74 psi at 31 °C after 15 minutes.

D) a free absorbent capacity of from about 20 to about 125 g/g, and

E) less than about 2% of residual hydratable salts

A particularly important attπbute of the foams of the present invention is diat the connecting passages (holes) between the cells of these foams are sufficiently large to pass msoluble solids such as ervthrocytes (mean diameter 8 μm) As a result, these holes do not become blocked or obstructed by blood and blood-based fluids absorbed by die foam Even though the cells and holes are large enough to allow free movement of msoluble components in blood and blood-based fluids, they are sufficiently small so as to produce the necessary high capillary absorption pressure required of absorbents used in catamemal products In other words, these foams combme high capillary absorption pressure with sufficient openness to allow free movement of the insoluble components m blood and blood-based fluids such as menses Typically, the cells of these foams have a number average cell size of from about 20 to about 180 μm, while the holes between these cells have a number average hole size of from about 4 to about 30 μm The present invention further relates to a process for obtaining these absorbent foams by poly eπzing 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 compπses the steps of

A) forming a water-in-oil emulsion at a temperature of about 50°C or higher and under low shear mixing from

1) an oil phase compnsing a) from about 85 to about 98% by weight of a monomer component capable of forming a copolymer having a Tg of about 50°C or lower, the monomer component compnsing i) from about 45 to about 70% by weight of at least one substantially water-insoluble monofunctional monomer capable of forming an atactic amorphous polymer having a Tg of about

35°C or lower, u) from about 10 to about 40% by weight of at least one substantially water-insoluble monofunctional comonomer capable of imparting toughness about equivalent to that provided b styrene, in) from about 5 to about 25% by weight of a first substantially water-insoluble, polyfunctional crosslinking agent selected from divinyl benzenes, tπvinyl benzenes, divinyl toluenes, divinyl xylenes, divinyl naphthalenes divinyl alkylbenzenes, ώvinyl phenanthrenes, divmyl biphenyls, divinyl diphenylmethanes. divinyl benzyls, divinyl phenylethers, divinyl diphenylsulfides, divinyl furans, ώvinyl sulfide, divinyl sulfone, and mixtures thereof, and

IV) from 0 to about 15% by weight of a second substantially water- msoluble, polyfunctional crosslinking agent selected from polyfunctional acrylates, methacrylates, acrvlamides, methacrylamides, and mixtures thereof, and b) from about 2 to about 15% by weight of an emulsifier component which is soluble in the oil phase and which is suitable for forming a stable water-in-oil emulsion, the emulsion component compnsing (i) a primary emulsifier having at least about 40% by weight emulsifying components selected from diglycerol monoesters of lmear unsaturated C16-C22 fatty acids, diglycerol monoesters of branched C16-C24 fatty acids, diglycerol monoaliphatic ethers of branched C16-C24 alcohols, diglycerol monoaliphatic ethers of lmear unsaturated C g-

C22 alcohols, diglycerol monoaliphatic ethers of lmear saturated Cj2~C}4 alcohols, sorbitan monoesters of lmear unsaturated C1 - C22 fatt acids, sorbitan monoesters of branched C16-C24 fatty acids, and mixtures thereof, or (11) the combination a primary emulsifier having at least 20% by weight of these emulsif ing components and certain secondary emulsifiers m a weight ratio of primary to secondary emulsifier of from about 50 1 to about 1 4, and 2) a water phase compnsing an aqueous solution containing from about 0 2 to about 20% by weight of a water-soluble electrolyte, 3) a volume to weight ratio of water phase to oil phase in the range of from about 20 1 to about 125 1,

B) polymeπzing the monomer component in the oil phase of the water-in-oil emulsion to form a polymeπc foam mateπal,

C) washmg the polymeπc foam mateπal to lower the level of residual electrolytes less than about 2%,

D) treating the washed foam with an effective amount of a suitable hydrophilizmg surfactant, and E) dewatering die washed foam to a moisture content of about 40% or less.

The process of the present invention allows these absorbent foams to have cells and holes small enough to provide a high capillary absorptive pressure but large enough to prevent or minimize blockage by the insoluble components of these fluids. In addition, this process removes most of the residual electrolytes (i.e., hydratable salts) from the foam. While these hydratable salts are typically needed during initial formation of the HIPE, their presence in the resulting foam can adversely affect its ability to absorb blood and blood- based fluids such as menses, especially as the concentration of these salts in the foam increases. Accordingly, it is desirable to reduce die level of these hydratable salts in the foam.

The present invention also relates to catamemal products containing one or more foam materials of the present invention as the absorbent core.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 of the drawings is a top-plan view of a catamemal product having HIPE foams of the present invention as absorbent members.

Figure 2 of the drawings is a cross-sectional view take along line 2-2 of Figure 2. Figure 3 of the drawings is a photomicrograph (250 X magnification) of a section of a representative absorbent polymeric foam according to the present invention made from HIPE having a 50: 1 water-to-oil weight ratio and poured at 74°C, and where die monomer component consisted of a 5:21:14:60 weight ratio of styrene (STY):ethyl styrene (EtS):divinyl benzene (DVB):2-ethylhexyl acrylate (EHA), and where 5.5% (by weight of the oil phase) of diglycerol monooleate (DGMO) and 1% of ditallow dimethyl ammonium methylsulfate emulsifiers are used. Figure 4 is a photomicrograph (50 X magnification) of a section of a representative polymeric foam that is useful as the optional barrier layer beneath absorbent foam material(s) of the present invention. The foam is made from a HIPE having a 62.4: 1 water-to-oil weight ratio and poured at 156°F and 1300 RPM, where the monomer component consisted of a 19:14:55: 12 weight ratio of ethyl styrene (EtS):divinyl benzene (DVB):2-ethylhexyl acrylate (EHA)J,6-hexanedioldiacrylate (HDDA), and where 8% (by weight of die oil phase) of sorbitan myristate and 1% of ditallow dimethyl ammonium methyl sulfate emulsifiers are used.

Figure 5 is a photomicrograph of the foam shown in Figure 4, but at 250 X magnification. Figure 6 is a photomicrograph of the foam shown in Figure 4, but at 1000 X magnification. DETAILED DESCRIPTION OF THE INVENTION

I Polvmenc Absorbent Foams

A General Foam Charactenstics

Polvmenc foams according to the present invention useful in absorbent articles and structures are those which are highly open-celled This means the individual cells of the foam are in complete, unobstructed communication with adjoining cells The cells in such substantially open-celled foam structures have intercellular openings or "windows" (holes) that provide passageways large enough to permit free and ready movement of blood and blood based fluids such as menses from one cell to anod er within the foam structure, even though these fluids contam certam insoluble components On the other hand, these cells and connecting passages are small enough to provide die necessary high capillary absorption pressure (I e , capillary specific surface area per volume) to effectively move these fluids throughout the foam

These substantially open-celled foam structures will generally have a reticulated character with the mώvidual cells be g defined by a plurality of mutually connected, three dimensionally branched webs The strands of polymeπc mateπal making up these branched webs can be referred to as "struts " Open-celled foams having a typical strut-type structure are shown by way of example in the photomicrograph shown Figures 3 For purposes of the present mvention, a foam mateπal is "open-celled" if at least 80% of the cells in the foam structure that are at least 1 μm size are in fluid communication with at least one adjacent cell

In adώtion to bemg open-celled, diese polymeπc foams need to be rendered sufficiently hydrophilic to permit the foam to absorb blood and blood-based fluids The internal surfaces of the foam structures are rendered hydrophilic by residual hydrophi zing surfactants left in the foam structure after polymerization, or by selected post-polymeπzation foam treatment procedures, as descnbed hereafter

The polvmenc foams useful in the present mvention also have somewhat inteπelated and interdependent structural and mechanical properties, features and/or charactenstics It should be understood diat these foams can have different properties, features and/or charactenstics at different times pnor to contact between the foam and die blood or blood based fluid to be absorbed For example, duπng dieir manufacture, shipping, storage, etc , these foams can have density and/or cell size values outside die ranges set forth hereafter for these parameters, for example if they are stored in a collapsed state or are compressed by packaging However, such foams are nevertheless still within the scope of this mvention if they later undergo physical changes so that they have d e requisite values specified hereafter for these properties, features and/or charactenstics at least some pomt pnor to and/or during contact with the blood or blood based fluid to be absorbed The foams of the present mvention may also be used m their collapsed state similar to the condition descnbed m U S 5,387.207 (Dyer et al ) issued Feb 7. 1995 Such foams generally compπse those havmg finer microstructure (higher capillary specific surface areas) and which are relatively weak These foams remain collapsed after washmg, treating with wetting agents, and drying Unlike the foams descnbed widun U S 5,387,207, the present foams may be reexpanded by application of modest amounts of heat (e g 60°C for several hours) Or, they may be used so as to maintain the thinness of die product pπor to use When exposed to blood and blood-based fluids, diese collapsed foams regain their oπginal thickness and fluid capacities These foams are also useful m ώstπbuting blood and blood- based fluids effectively from the pomt of insult since the fluid capillary pressure exerted by d e unexpanded regions of these foams exceeds diat of the wetted, expanded area of the foam These materials generally serve well when positioned benead a larger celled foam of the present mvention which serves to acquire rapidly die blood and blood-based fluid The properties of these collapsed foams stated herein are those of die foams their expanded state unless otherwise noted

B Foam Charactenstics Important to Absorbing and Transporting Blood and

Blood-Based Fluids

1 Vertical Wickuig Capability

Vertical wicking (i e , fluid wicking in a direction opposite from gravitational forces) of a given amount of fluid within a set peπod of time is an especially important performance attnbute for absorbent foams herein The rate of fluid wicking through a porous structure is generally a function of die openness of the structure, die affinity of die fluid for the surface of the structure, and d e viscosity of the fluid This is conveniently measured as die time taken for a test fluid, l e , Artificial Menstrual Fluid (AMF), m a reservoir to wick a vertical ώstance of 5 cm through a test stπp of foam of specified size at 22°C Such a vertical wicking test is descnbed hereafter in the TEST METHODS section To be especially useful m catamemal products for absorbing menses, the foam absorbents of the present mvention vertically wick the AMF 5 cm m less than about 60 minutes More preferably, the prefened foam absorbents of the present mvention vertically wick AMF 5 cm in less than about 20 minutes, and most preferably m less than about 15 minutes

The foam absorbents of the present mvention will also preferably ick a high capacity of the test fluid to a particular height at equi bπum Preferably, these foams will wick at least about 30 g/g AMF (g of AMF/g dry foam) to a height of about 5 cm. more preferably at least about 40 g/g of AMF Particularly prefened foam absorbents will wick at least about 45 g/g of AMF to a height of about 5 cm The procedure for measurmg the ability to wick fluid to a particular height at equi bπum is descnbed hereafter in the TEST METHODS section.

2. Capillary Specific Surface Area

"Capillary suction specific surface area" is a measure of the test-liquid-accessible surface area of the polymeric network accessible to a test fluid. Capillary suction specific surface area is determined bodi by the dimensions of die cellular units in the foam and by die density of die polymer, and is dius a way of quantifying the total amount of solid surface provided by die foam network to the extent that such a surface participates in absorbency. For purposes of the present invention, capillary suction specific surface area is determined by the method is set forth in the TEST METHODS section of U.S. Patent 5,387,207 (Dyer et al.) issued Feb. 7, 1995, which is incorporated by reference.

Generally, the surface area of the foam at a constant volume increases as the cellular structure becomes smaller celled ("finer"). Higher surface areas are highly desirable in rapidly moving blood and blood-based fluids such as menses within the foam. However, the surface area of the foam can reach d e point that the rate of fluid absorption becomes limiting, as well as increasing the likelihood dat insoluble components within the fluid can no longer pass readily from one cell to another. Accordingly, die surface area of the foam needs to be selected within a particular range to balance these competing factors. The polymeric foams of the present invention useful as absorbent members in catamemal products are those that have a capillary suction specific surface area in the range of from about 0.0080 to about 0.040 m^/cc. Typically, the capillary suction specific surface area is in the range from about 0.010 to about 0.030 m²/cc, preferably from about 0.012 to about 0.026 m²/cc.

For absorbent cores where two layers of absorbent foam are used, it is prefeπed that the upper foam layer (facing the body of die wearer) have a lower capillary suction specific surface area, for example from about 0.012 to about 0.020 π cc, while the lower foam layer has a higher capillary suction specific surface area, for example from about 0.020 to about 0.026 m²/cc. In this way, the lower foam layer will have a higher fluid capillary pressure, allowing it to drain fluid from the upper foam layer, thus keeping the body of d e wearer relatively free from contact with the fluid. (It follows d at where more than two foam layers are employed, die capillary suction specific surface area of d e respective foams preferably will increase as the foams are located more remotely (i.e., lower in the absorbent product) from the user.)

3. Resistance to Compression Deflection

An important mechanical feature of the foams of the present invention are their strength as determined by resistance to compression deflection (RTCD). The RTCD exhibited by die foams herein is a function of the polymer modulus, as well as the density and structure of the foam network. The polymer modulus is, in turn, determined by a) die polymer composition, b) the conditions under which the foam was polymeπzed (for example, the completeness of polymeπzation obtained, specifically with respect to crosslinking), and c) die extent to which the polymer is plasticized by residual matenals, e g , emulsifiers, left in the foam structure after processing To be useful as absorbent members catamenials products, as well as other absorbent articles, die foams of the present mvention must be suitably resistant to deformation or compression by forces encountered when such absorbent members are engaged m die absorption and retention of fluids The RTCD exhibited by the polymeπc foams of the present mvention can be quantified by determining the amount of stra produced m a sample of saturated foam held under a certam confining pressure for a specified penod of time The method for carrying out this particular type of test is descnbed hereafter m the TEST METHODS section Foams useful as absorbents members for catamemal products are those which exhibit a RTCD such that a confining pressure of 0 74 psi (5 1 kPa) produces a stram of typically from about 5 to about 95% compression of the foam structure Preferably the stram produced under such conώtions will be m die range from about 10 to about 85%, most preferably from about 15 to about 80%

4 Free Absorbent Capacity

Another important property of absorbent foams according to the present mvention is their free absorbent capacity For absorbent members useful m catamemal products, free absorbent capacity is the total amount of test fluid (I e , syndietic unne) that a given foam sample will absorb at equilibπum mto its cellular structure per unit mass of solid mateπal in the sample The foams that are especially useful as absorbent members in catamemal products will at least meet a minimum free absorbent capacity The free absorbent capacity of the foams of the present mvention can be determined using the procedure descnbed in the TEST METHODS section of U S Patent 5,387,207 (Dyer et al ) issued Feb 7, 1995 To be especially useful as absorbent members for catamemal products, die foams of the present mvention should have a free capacity of from about 20 to about 125 g/g, preferably from about 40 to about 70 g/g, and most preferably about 50 g/g, of synthetic unne per gram of dry foam

C Other Important Properties of Polvmenc Foam

1 Cell and Hole Sizes

A feature that can be useful in defining prefened polymeπc foams is cell size Foam cells, and especially cells diat are formed by polymenzing a monomer-containing oil phase that sunounds relatively monomer-free water-phase droplets, will frequently be substantially spheπcal m shape The size or "diameter" of such spheπcal cells is a commonly used parameter for characterizing foams in general. Since cells in a given sample of polymeric foam will not necessarily be of approximately the same size, an average cell size. i.e.. number average cell diameter, will often be specified.

Cell size is a foam parameter that can impact a number of important mechanical and performance features of the absorbent foams according to die present invention. Since cell size contributes to capillary suction specific surface area that, together with foam hydrophilicity, determines d e capillarity of the foam, cell size is a foam structure parameter that can directly affect the fluid wicking properties of absorbent foams, as well as the capillary pressure that is developed within the foam structure. A number of techniques are available for determining the average cell size of foams.

The most useful technique for determining cell size in foams involves a simple measurement based on die scanning electron photomicrograph of a foam sample. Figure 3, for example, shows a typical HIPE foam structure according to die present invention. Superimposed on die photomicrograph is a scale representing a dimension of 20 μm. Such a scale can be used to determine average cell size via visual inspection or an image analysis procedure.

The cell size measurements given herein are based on die number average cell size of the foam. The foams useful as absorbent members for catamemal products according to the present invention will preferably have a number average cell size of from about 20 to about 1 0 μm, and typically from about 35 to about 130 μm. Another feature useful in defining diese prefeπed foams is hole size. The holes are the openings between adjacent cells diat maintain fluid communication between these cells. The foams of the present invention have hole sizes sufficiently large to allow passage of the insoluble components of blood, especially d e red blood cells, to avoid blockage of these fluid passages. The preferred technique for determining hole size is image analysis based on scanning electron micrographs of the foams as discussed above and shown in Figure 3. The hole size measurements given herein are based on die number average hole size of the foam. The foams useful as absorbent members for catamemal products according to die present invention will preferably have a number average hole size of from about 4 to about 30 μm, and preferably from about 10 to about 28 μm. While foams having hole sizes larger than about 30 μm will allow passage of blood cells, they will not have the fine microstructure necessary to provide the fluid capillary absorbent pressure of die foams of the present invention.

2. Foam Density "Foam density" (i.e., in grams of foam per cubic centimeter of foam volume in air) is specified herein on a dry basis. The density of die foam, like capillary suction specific surface area, can influence a number of performance and mechanical characteristics such as the RTCD of absorbent foams Importantly also, the density of die foam controls the absorbent capacity of such foams in units of g/g This influences the cost effectiveness and utility of such foams as absorbent members for catamemal products

Any suitable gravimetπc procedure d at will provide a determination of mass of solid foam mateπal per unit volume of foam structure can be used to measure foam density An ASTM gravimetnc procedure descnbed more fully in the TEST METHODS section of U S Patent 5,387,207 (Dyer et al ) issued Feb 7, 1995 is die prefened mediod diat can be employed for density determinations Polymeπc foams of the present mvention useful as absorbent members for catamemal products have dry basis density values in the range of from about 0 008 to about 0 05 g/cc, preferably from about 0 014 to about 0 024 g/cc, and most preferably about 0 02 g/cc

3 Hoπzontal Gravimetnc Wicking

One of the primary benefits of the foams of the present mvention is their ability to retain absorbed blood and blood-based fluids, even when subjected to compressive load A foam of insufficient strength (RTCD) will express excess fluid reaώly duπng use Under mechanical pressure from the wearer of the catamemal product, diis mobile fluid can be pumped out of die absorbent core and upwards through the topsheet As a result, die topsheet becomes" rewetted" with this pumped fluid such diat there is not adequate topsheet dryness The ability of the foams of the present mvention to minimize rewet can be correlated to their ability to retain absorbed fluids The ability of these foams to retain absorbed fluids can be measured by Hoπzontal Gravimetnc Wicking (HGW), the procedure for which is descnbed hereafter the Test Methods section For die purposes of the present mvention this HGW measurement is expressed as d e percentage of the Retained Uptake of AMF, relative to the Imtial Uptake of AMF, or "% Retained/Initial Uptake of AMF " The foams of the present mvention typically have a % Retained/Initial Uptake of AMF of at least about 50%, and preferably at least about 65%

II Polvmenc Foam Barner Layer

As indicated herein, many users of catamemal products prefer relatively thick pads With such pads, inexpensive filler mateπals, which may possess pore absorbent/wet integπty properties, may be prefened However, when such mateπals are used, die resulting absorbent products may suffer from an aesthetic and/or performance standpoint Because the absorbent polymeπc foams of the present mvention provide high fluid acquisition/storage capabilities, such filler mateπals can be used without compromising performance For example, keeping the filler mateπal (e g , airfelt) relatively free from liquid results in less bunching and/or rop g in use This results m better core and product uitegnty in use To further facilitate maintanence of a relatively dry filler layer, in a prefened embodiment of d e present mvention a polymeπc foam mateπal (refened to herein as a "bamer layer") is used as the lowest layer of the absorbent core matenal This optional bamer layer is useful m that it significantly limits passage of blood/fluid mto optional materals (e g , fillers such as air felt) below the absorbent foam core matenal

To prevent fluid flow mto filler matenal located immediately above d e backsheet, the bamer layer preferably has an average cell size from about 15 to about 50 μm, preferably from about 25 to about 35 μ-m. and an average hole size from about 4 to about 9 μm, preferably from about 5 to about 7 μm These relatively small cell sizes tend to filter out d e red blood cells in blood and blood based fluids, dius preventing passage of this color mto lower layers of filler matenal The fluid which is admitted mto d e bamer layers is further retained by the relatively high fluid capillary pressure associated with such structures Thus, when the absorbent foam core is placed on top of, e g , an air laid fibrous core, die bamer layer serves to prevent contamination of the air laid core with fluid which would cause die air laid core to change its dimensions and lose its uitegnty and/or be stained with d e red color

While the primary function of die bamer layer is to inhibit fluid (especially blood) flow to lower product layers, d s foam mateπal preferably possesses the ability to move fluid away from the wearer Thus, it is prefened diat bamer layer have a higher capillary specific suction surface area than the absorbent foam layers located above (closer to the user) it For example, where two foam layers of the present mvention having capillary specific surface areas as descnbed in section I-b herem, it is prefened diat die bamer layer will have a capillary suction specific surface area of from about 0 040 to about 0 080 m²/cc In this way, the foam layers of the absorbent core have successively higher fluid capillary pressure providmg drainage away from the wearers body. The bamer layer's ability to acquire and store fluid may allow for enhanced fluid retention by die article under circumstances where the absorbent foam mateπals (ώscussed above) have reached dieir capacity or where fluid is "squeezed out" of die foam layers overlying the bamer layer

III Preparation of Polvmenc Foams From HIPE A In General

Polymenc foams according to the present mvention can be prepared by polymerization of certam water-in-oil emulsions having a relatively high ratio of water phase to oil phase commonly known in the art as "HIPEs " Polymenc foam mateπals which result from the polymenzation of such emulsions are refened to herem as "HIPE foams " The relative amounts of the water and oil phases used to form the HIPEs are, among many other parameters, important determining die structural, mechanical and performance properties of the resultmg polymeπc foams In particular, the ratio of water to oil (W O) ιn the HIPEs vanes mversely with ultimate foam density according to die equation

Density = 1/(W O ratio + 1)

This can influence the cell size and capillary specific surface area of the foam and dimensions of the struts that form the foam The HIPEs used to prepare die foams of the present mvention will generally have a volume to weight ratio of water phase to oil phase the range of from about 20 1 to about 125 1. more preferably from about 40 1 to about 70 1, most preferably about 50 1

1 Oil Phase Components The continuous oil phase of the HIPE compπses 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 50°C or lower, and typically from about 15° to about 30°C (The method for determining Tg by Dynamic Mechanical Analysis (DMA) is descnbed hereafter m the TEST METHODS section ) This monomer component includes (a) at least one monofunctional monomer capable of forming an atactic amorphous polymer having a Tg of about 35°C or lower (see Brandup, J , Immergut, E H "Polymer Handbook", 2nd ed , Wiley-Interscience New York, NY, 1975, III- 139 ), (b) at least one monofunctional comonomer to improve the toughness or tear resistance of the foam, (c) a first polyfunctional crosslinking agent, and (d) optionally a second polyfunctional crosslinking agent Selection of particular types and amounts of monofunctional monomer(s), comonomer(s) and polyfunctional crosslinking agent(s) can be important to the realization of absorbent HIPE foams having the desired combination of structure, mechanical, and fluid handling properties

The monomer component compπses one or more monomers that tend to impart rubber-like properties to the resultmg polymeπc foam structure Such monomers can produce high molecular weight (greater than 10,000) atactic amorphous polymers having Tg's of about 35°C or lower Monomers of this type clude, for example, the (C4-C14) alkyl acrylates such as butyl acrylate, hexyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, dodecyl (lauryl) acrylate, isodecyl acrylate tetradecyl acrylate, aryl and alkaryl acrylates such as benzyl acrylate, and nonylphenyl acrylate, the

alkyl methacrvlates such as hexyl methacrylate, octyl methacrylate, nonyl methacrylate, decyl methacrylate, isodecyl methacrylate, dodecyl (lauryl) methacrylate, tetradecyl methacrylate, acrylanudes such as N-octadecyl acrylamide, (C4-C12) alkyl styrenes such as p-n- octylstyrene, isoprene, butadiene, and combinations of such monomers Of these monomers, isodecyl acrylate, dodecyl acrylate and 2-ethylhexyl acrylate are the most prefened The monofunctional monomer(s) will generally compnse 45 to about 70%, more preferably from about 50 to about 65%, by weight of the monomer component

The monomer component utilized m die oil phase of the HIPEs also compnses one or more monofunctional comonomers capable of imparting toughness about equivalent to diat provided by styrene to the resultmg polymeπc foam structure Tougher polymers exhibit the ability to deform substantially without failure These monofunctional comonomer types can clude styrene-based comonomers (e g , styrene and ediyl styrene) or other monomer types such as methyl methacrylate where the related homopolymer is well known as exemplifying toughness The prefened monofunctional comonomer of dus type is a styrene-based monomer widi styrene and ediyl styrene bemg the most prefened monomers of dus kind The monofunctional "toughening" comonomer will normally compnse from about 10 to about 40 %, preferably from about 15% to about 40%, most preferably from about 18% about 28%, by weight of the monomer component

In certam cases, the "toughening" comonomer can also impart the desired rubber-like properties to the resultant polymer The (C4-C12) alkyl styrenes, and m particular p-n- octylstyrene, are examples of such comonomers For such comonomers, the amount diat can be mcluded m die monomer component will be diat of die typical monomer and comonomer combined

The monomer component also contains a first (and optionally second) polyfunctional crosslmkmg agent As with die monofunctional monomers and comonomers, selection of the particular type and amount of crosslmkmg agents is very important to the eventual realization of prefened polymeπc foams having the desired combination of structural, mechanical, and fluid-handling properties

The first polyfunctional crosslmkmg agent can be selected from a wide vaπety of polyvuiyl aromatic and related polyvmyl matenals such as vinylbenzenes, tnvuiylbenzenes, ώvinyltoluenes, ώvmylxylenes, ώvmylnaphthalenes ώvmylalkylbenzenes, divmylphenanthrenes, divmylbiphenyls, divmylώphenylmethanes, ώvmylbenzyls, vmylphenylethers, divmylώphenylsulfides, ώvmylfurans, ώvmylsulfide, divmylsulfone, and mixtures thereof Divinyl benzene is typically available as a mixture with ethyl styrene proportions of about 55 45 These proportions can be modified so as to ennch the oil phase with one or the other component Generally, it is advantageous to ennch the mixture with the ediyl styrene component while simultaneously reducmg die amount of styrene in the monomer blend The preferred ratio of ώvinyl benzene to ethyl styrene is between from about 30 70 and 55 45, most preferably from between about 35 65 to about 45 55 The inclusion of higher levels of ethyl styrene imparts the required toughness without increasing the Tg of the resulting copolymer to the degree diat styrene does This first crosslmkmg agent can generally be mcluded in die oil phase of the HIPE in an amount of from about 8% to about 22%, more preferably from about 10% to about 18%, most preferably from about 12% to about 16%, by weight of the monomer component

The optional second crosslmkmg agent can be selected from polyfunctional acrylates and mediacrylates, acrylamides and mediacrylamides, and mixtures thereof These mclude ώ-, tπ-, and tetra-acrylates, as well as ώ-, tπ-, and tetra- mediacrylates, ώ-, tπ-, and tetra- acrylamides, as well as di-, tπ-, and tetra- mediacrylamides, and mixtures of these crosslmkmg agents Suitable acrylate and methacrylate crosslmkmg agents can be deπved from ώols, tπols and tetraols that mclude 1,10-decaneώol, 1,8-octaneώol, 1,6-hexaneώol, 1,4-butaneώol, 1,3-butanedιol, l,4-but-2-eneώol, ethylene glycol, ώethylene glycol, tπmethylolpropane, pentaerythπtol, hydroqumone, catechol, resorcmol, tnethylene glycol. polyethylene glycol, sorbitol, and the like (The acrylamide and methacrvlamide crosslmkmg agents can be deπved from the equivalent ώamines. tnamines and tetraπunes) The prefened ώols have at least 2, more preferably at least 4, most preferably 6, carbon atoms This second cross-linking agent can generally be mcluded die oil phase of the HIPE m an amount of from 0 to about 15%, preferably from 0 to about 13%, by weight of the monomer component

Without bemg bound by theory, it is believed this second crosslmkmg agent generates a more homogeneously crosslinked structure diat develops strength more efficiently than usmg either die first or the second crosslinker alone at comparable levels The second crosslmker also has the effect of broadening die glass-to-rubber transition region This broader transition region can be tailored to meet specific strength and resilience requirements at in-use temperatures by controlling the relative amount of die two crosslinker types employed Thus, a foam containing only the first type of crosslinker will exhibit a relatively nanow transition region Increasing the amount of the second crosslinker serves to broaden die transition region, even if the actual transition temperature itself has not changed The major portion of the oil phase of the HIPEs will compnse the aforementioned monomers, comonomers and crosslmkmg agents It is essential that these monomers, comonomers and crosslmkmg agents be substantially water-insoluble so that they are pπmanly soluble in the oil phase and not die water phase Use of such substantially water- insoluble monomers ensures that HIPEs of appropπate charactenstics and stability will be realized It is, of course, highly prefened diat these monomers, comonomers and crosslmkmg agents be of the type such that the resultmg polymenc foam is suitably non-toxic and appropnately chemically stable These monomers, comonomers and cross-linking agents should preferably have little or no toxicity if present at very low residual concentrations during post-polymenzation foam processing and/or use Another essential component of the oil phase is an emulsifier component diat permits the formation of stable HIPEs This emulsifier component compπses a primary emulsifier and optionally a secondary emulsifier Especially when used alone, these primar emulsifer typicallv compnse at least about 40%, preferably at least about 70%, emulsifying components selected from diglycerol monoesters of lmear unsaturated C16-C22 fatty acids, diglycerol monoesters of branched C 16-C24 fatty acids, diglycerol monoaliphatic ethers of branched CJ6- 24 alcohols, diglycerol monoaliphatic ethers of lmear unsaturated C16-C22 alcohols, diglycerol monoaliphatic ethers of lmear saturated C12-C14 alcohols, sorbitan monoesters of lmear unsaturated C 16-C22 fatty acids, sorbitan monoesters of branched C _jg- C24 fatty acids, and mixtures thereof Prefened primary emulsifiers mclude ώglycerol monooleate (e g , preferably greater than about 40%, more preferably greater than about 50%. most preferably greater than about 70% ώglycerol monooleate), sorbitan monooleate (e g , preferably greater dian about 40%, more preferably greater than about 50%. most preferably greater than about 70% sorbitan monooleate), sorbitan monopalmitate, and ώglycerol monoisostearate (e g , preferably greater than about 40%, more preferably greater than about 50%, most preferably greater than about 70% ώglycerol monoisostearate)

Diglycerol monoesters of lmear unsaturated and branched fatty acids useful as emulsifiers m the present mvention can be prepared by esteπfying ώglycerol with fatty acids, using procedures well known m the art See, for example, the mediod for preparing polyglycerol esters ώsclosed m U S Patent 5,387,207 (Dyer et al ) issued Feb 7, 1995 Diglycerol can be obtained commercially or can be separated from polyglycerols that are high m ώglycerol Lmear, branched, and unsaturated fatty acids can be obtained commercially The mixed ester product of die esteπfication reaction can be fractionally distilled under vacuum one or more times to yield distillation fractions that are high in ώglycerol monoesters For example, a A CMS-15A (C V C Products Inc , Rochester, N Y ) continuous 14 inch centnfugal molecular still can be used for fractional distillation Typically, the polyglycerol ester feedstock, while bemg heated, is first metered dirough a degasser umt and then to the heated evaporator cone of the still, where the vacuum distillation takes place Distillate is collected on die bell jar surface, which can be heated to facilitate distillate removal Distillate and residue are continuously removed by transfer pumps The fatty acid composition of die resultant mixed ester product can be determined using high resolution gas chromatography See U S Patent 5,387,207 (Dyer et al ) issued Feb 7, 1995 Polyglycerol and polyglycerol ester ώstnbution of die resultant mixed ester product can be determined by capillary supercntical chromatography

Lmear saturated, lmear unsaturated, or branched ώglycerol monoaliphatic ethers can also be prepared and dieir composition determined usmg procedures well known in the art See also copending U.S. application Serial No. 08/514,346 (Stephen A. Goldman et al), filed August 9, 1995 (P&G Case No. 5540C), which is incorporated by reference

Sorbitan monoesters of lmear unsaturated and branched fatty acids can be obtained commercially or prepared us g mediods known in the art See, for example, U S Patent 4,103,047 (Zaki et al). issued July 25. 1978 (herem incorporated by reference), especially column 4. line 32 to column 5, line 13 The mixed sorbitan ester product can be fractionally vacuum distilled to yield compositions diat are high in sorbitan monoesters Sorbitan ester compositions can be determined by methods well known in the art such as small molecule gel permeation chromatography See copending U.S. application Serial No. 08/514,346 (P&G Case 5540C), which descπbes die use of dus mediod for polyglycerol aliphatic ethers

When diese primary emulsifiers are used in combination with certam secondary emulsifiers, the primary emulsifier can compnse lower levels of these emulsifying components, i e , as low as about 20% of these emulsifying components These secondary emulsifiers are at least cosoluble with the primary emulsifier m the oil phase Suitable secondary emulsifiers can be cationic types, mcludmg the long chain C12-C22 diahphatic, short chain CJ-C4 diahphatic quaternary ammomum salts such as ώtallow dimethyl ammomum chlonde, bistπdecyl dimethyl ammomum chlonde, and ώtallow dimethyl ammomum methylsulfate, the long chain C12-C22 ώalkoyl(alkenoyl)-2-hydroxyethyl, short chain C1-C4 diahphatic quaternary ammomum salts such as ώtallowoyl-2-hydroxyethyl dimethyl ammomum chlonde, die long chain C12-C22 ώaliphatic imidazolinium quaternary ammomum salts such as methyl-1 -tallow amido ethyl-2-tallow imidazolinium methylsulfate and medιyl-1-oleyl amido edιyl-2-oleyl imidazolinium methylsulfate, die short chain CJ-C4 diahphatic. long chain C12-C22 monoaliphatic benzyl quaternary ammomum salts such as dimethyl stearyl benzyl ammomum chlonde, amomc types mcludmg die Cg-C 1 g diahphatic esters of sodium sulfosucciruc acid such as die ώoctyl ester of sodium sulfosuccinic acid and die bistπdecyl ester of sodium sulfosuccinic acid, and mixtures of these secondary emulsifiers These secondary emulsifiers can be obtained commercially or prepared usmg methods known m the art The prefened secondary emulsifiers are ώtallow dimethyl ammomum methyl sulfate and ώtallow dimethyl ammomum methyl chlonde When diese optional secondary emulsifiers are mcluded m die emulsifier component, it is typically at a weight ratio of primary to secondary emulsifier of from about 50 1 to about 1 4, preferably from about 30 1 to about 2 1

The oil phase used to form the HIPEs compπses from about 85 to about 98% by weight monomer component and from about 2 to about 15% by weight emulsifier component Preferably, die oil phase will compnse from about 90 to about 97% by weight monomer component and from about 3 to about 10% by weight emulsifier component The oil phase also can contam other optional components One such optional component is an oil soluble polymeπzation initiator of the general type well known to diose skilled die art, such as descnbed m U S patent 5,290,820 (Bass et al), issued March 1, 1994, which is incorporated by reference Another prefened optional component is an antioxidant such as a Hindered Amide Light Stabilizer (HALS) and Hindered Phenolic Stabilizers (HPS) or any other antioxidant compatible with die initiator system to be employed Other optional components mclude plasticizers. fillers, colorants, cham transfer agents, dissolved polymers, and the like

2 Water Phase Components

The ώscontmuous water internal phase of the HIPE is generally an aqueous solution containing one or more dissolved components One essential ώssolved component of die water phase is a water-soluble electrolyte The ώssolved electrolyte minimizes the tendency of monomers, comonomers, and crosslinkers that are pnmanly oil soluble to also ώssolve in the water phase This, m turn, is believed to minimize the extent to which polymenc mateπal fills the cell windows at die oil water interfaces formed by die water phase droplets duπng polymenzation Thus, the presence of electrolyte and die resultmg lo c strength of the water phase is believed to determine whedier and to what degree die resultmg prefened polymeπc foams can be open-celled

Any electrolyte capable of imparting ionic strength to die water phase can be used Prefened electrolytes are mono-, ώ-, or tπvalent inorganic salts such as the water-soluble halides, e g , chlondes, nitrates and sulfates of alkali metals and alkaline earth metals Examples mclude sodium chlonde, calcium chlonde, sodium sulfate and magnesium sulfate Calcium chlonde is die most prefened for use m the present mvention Generally the electrolyte will be utilized in the water phase of the HIPEs a concentration in the range of from about 0 2 to about 20% by weight of the water phase More preferably, the electrolyte will compnse from about 1 to about 10% by weight of the water phase

The HIPEs will also typically contam a polymerization mitiator Such an mitiator component is generally added to die water phase of the HIPEs and can be any conventional water-soluble free radical mitiator These mclude peroxygen compounds such as sodium, potassium and ammomum persulfates, hydrogen peroxide, sodium peracetate, sodium percarbonate and die like Conventional redox mitiator systems can also be used Such systems are formed by combining the foregoing peroxygen compounds widi reducing agents such as sodium bisulfite, L -ascorbic acid or fenous salts

The mitiator can be present at up to about 20 mole percent based on die total moles of polymeπzable monomers present m the oil phase More preferably, the mitiator is present an amount of from about 0 001 to about 10 mole percent based on die total moles of polymenzable monomers in the oil phase

3 Hγdrr>phιli7.ιng Surfactants

The polymer forming the HIPE foam structure will preferably be substantially free of polar functional groups This means the polymeπc foam will be relatively hydrophobic in character To be useful as absorbents for blood and blood-based fluids such as menses, diese foams generally require further treatment to render die foam relatively more hydrophilic Hydrophihzation of the foam, if necessary, can generally be accomplished by treating the HIPE foam with a hydrophihzing surfactant m a manner descnbed more fully hereafter

These hydrophihzing surfactants can be any mateπal diat enhances the water wettabihty of the polymeπc foam surface Suitable surfactants should be non-toxic and non- nutating to mucus membranes It should be soluble or ώspersible n warm water Preferably, the hydrophihzing surfactant is a liquid at temperatures near ambient for ease of incorporation during the foam making process Suitable surfactants mclude edioxylates of C 11 -C j 5 alcohols, marketed by Shell Chemical Co , particular NEODOL 25-12 (condensation product of Cj2-Cj5 lmear alcohols with 12 moles of ethylene oxide), NEODOL 23-6 5T (condensation product of C12-C13 lmear alcohols with 6 5 moles of ethylene oxide diat has been distilled (topped) to remove certam impuπties), and NEODOL 23-3 (condensation product of C12-C13 linear alcohols with 3 moles of ediylene oxide), edioxylates of Cj j-C^ fatty acids sold under the PEGOSPERSE designation by Stepan Chemical Corp , Northfield, IL, condensation products of ediylene oxide and or propylene oxide having molecular weights greater than about 2000, and condensation products of propylene oxide and propylene glycol sold under the PLURONIC designation by BASF Paπsspany, NJ, modified oxyediylated straight chain alcohols sold under the Plurafac designation by BASF, Corp , Parsippany, NJ, sulfated alcohol edioxylates and alkyl ether sulfates such as those sold by Harcos Chemicals, Kansas, K.S, branched and lmear alkyl aryl ethoxylates such as Tnton X-60, Tnton X-100, Tnton N-57, and die like marketed by U on Carbide, Inc Danbury, CT, sihcone-glycol copolymers sold under the SILWET designation by OSI Specialties, Danbury, CT, as well as mixtures of these surfactants Particularly prefened surfactants are PEGOSPERSE 200 ML, an ethoxylate of lauπc acid hav g an average of 4 5 ethoxy units These hydrophihzing surfactants can be ώssolved or dispersed m a h drophihzing solution that is applied to die HIPE foam surface In this manner, hydrophihzing surfactants can be adsorbed by die preferred HIPE foams amounts suitable for rendering the surfaces thereof substantially hydrophilic, but without substantially impairing the desired flexibility and compression deflection charactenstics of the foam In prefened foams, the hydrophihzing surfactant is incorporated such that residual amounts of the surfactant that remain m the foam structure are typically m the range from about 0 05% to about 5%, preferably from about 0 5 to about 1%, by weight of the foam

B Processing Conώtions for Obtaining HIPE Foams

Foam preparation typically involves the steps of 1) forming a stable high mtemal phase emulsion (HIPE), 2) polymeπzmg/cuπng this stable emulsion under conώtions suitable for forming a solid polymenc foam structure, 3) slicing or otherwise cutting the water-filled polymeπc foam and dien washmg the sliced or cut foam to remove the oπginal residual water phase, and especially die residual hydratable salts, from the polymenc foam structure, 4) treating the polymeπc foam structure with a hydrophihzing surfactant, and diereafter dewateπng this polymeπc foam structure

1 Formation of HIPE The HIPE is formed by combining the oil and water phase components the previously specified weight ratios The oil phase will typically contam the requisite monomers, comonomers, crosslinkers, and emulsifiers, as well as optional components such as solvents and polymerization initiators The water phase will typically contam electrolytes, as well as optional components such as water-soluble emulsifiers, and/or polymeπzation initiators

The HIPE can be formed from the combined oil and water phases by subjecting these combmed phases to shear agitation Shear agitation is generally applied to die extent and for a tune penod necessary to form a stable emulsion Such a process can be conducted in either batchwise or contmuous fashion and is generally earned out under conώtions suitable for formmg an emulsion where the water phase droplets are ώspersed to such an extent that the resultmg polymenc foam will have the requisite cell size and odier structural charactenstics Suitable mixing or agitation devices are those that are capable of formmg an emulsion under conώtions of low shear mixing Emulsification of the oil and water phase combination will frequently volve the use of a mixing or agitation device such as a pm impeller One prefened mediod of formmg such HIPEs volves a contmuous process diat comb es and emulsifies die requisite oil and water phases In such a process, a liquid stream compnsing the oil phase is formed Concunently, a liquid stream compnsing the water phase is also formed The two streams are then combmed in a suitable mixing chamber or zone such that the requisite water to oil phase weight ratios previously specified are achieved In the mixing chamber or zone, the combmed streams are generally subjected to shear agitation provided, for example, by a p impeller of suitable configuration and dimensions Shear will typically be applied to die combmed oil/water phase stream at at a rate of about 4000 sec"* or less, preferably about 3000 sec^** or less Once formed, the stable liquid HIPE can then be withdrawn from the mixing chamber or zone This prefened mediod for formmg HIPEs via a continuous process is descnbed m greater detail m U S Patent 5,149,720 (DesMarais et al), issued September 22, 1992, which is incorporated by reference See also copending U.S. application Serial No. 08/370,694 (Thomas A. DesMarais), filed January 10, 1995 (P&G Case No. 5543) (herem incorporated by reference), which descπbes an improved continuous process hav g a recirculation loop for the HIPE The degree of shear applied and/or the water to oil phase ratio during HIPE formation need not be constant throughout For example, HIPE making can be earned out under "pulsed" conώtions or vaned rhythmically This is especially useful when die HIPE is collected in a rotating cylindrical container as successive layers to form foams having heterogeneous structures. Pulsed conώtions can produce HIPEs comprising regions of larger and smaller celled foam in an alternating sequence. After curing and slicing as described hereafter, diis can provide foams having the ability to control the ώrection of movement of the absorbed fluid within the foam. For example, fluid movement can be induced to occur along the line of pour of the foam.

One particular advantage of die more robust emulsifier systems used in these HIPEs is that the mixing conώtions during HIPE formation and pouring can be carried out at more elevated temperatures of about 50°C or higher, preferably 60°C or higher. Typically, the HIPE can be formed at a temperature of from about 60° to about 99°C, more typically from about 65° to about 85°C.

2. Polvmerization/Curing of the HIPE

The HIPE formed will generally be collected or poured into a suitable reaction vessel, container or region to be polymerized or cured. In one embodiment , die reaction vessel comprises a tub constructed of polyediylene from which the eventually polymerized/cured solid foam material can be easily removed for further processing after polymerization/curing has been carried out to die extent desired. It is usually prefened that the temperature at which the HIPE is poured into the vessel be approximately the same as the polymerization/curing temperature. Suitable polymerization/curing conώtions will vary depending upon die monomer and other makeup of the oil and water phases of the emulsion (especially die emulsifier systems used), and die type and amounts of polymerization initiators used. Frequently, however, suitable polymerization/curing conώtions will involve maintaining the HIPE at elevated temperatures above about 50°C, more preferably above about 65°C, and most preferably above about 80°C. for a time period ranging from about 2 to about 64 hours, more preferably from about 2 to about 48 hours. The HIPE can also be cured in stages such as described in U.S. patent 5,189,070 (Brownscombe et al), issued February 23, 1993, which is herein incorporated by reference.

A porous water-filled open-celled HIPE foam is typically obtained after polymerization/curing in a reaction vessel, such as a tub. This polymerized HIPE foam is typically cut or sliced into a sheet-like form. Sheets of polymerized HIPE foam are easier to process during subsequent treating/washing and dewatering steps, 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 diickness in the range of from about 0.08 to about 2.5 cm, preferably from about 0J5 and about 2 cm. The polymerized HIPE foam can also be cubed or sliced into thin spaghetti-like sections or can be stamped into shapes such as a continuous tube (e.g., for use in tampons) at this point. 3 Slicing and Washmg HIPE Foam

The solid polymeπzed HIPE foam formed will generally be filled with residual water phase matenal used to prepare the HIPE This residual water phase mateπal (generally an aqueous solution of electrolyte, residual emulsifier, and polymenzation mitiator) should be at least partially removed pnor to further processing and use of die foam Removal of this oπgmal water phase mateπal will usually be earned out after slicing the foam mto sheets of from about 0 15 to about 0 4 cm in thickness These sheets are dewatered by compressmg die foam structure to squeeze out residual liquid and/or by washmg the foam structure with water or odier aqueous washmg solutions Frequently several compressmg and washmg steps, e g , from 2 to 4 cycles, will be used

The removal of most of the residual electrolyte (l e , hydratable salts) from the foam is particularly important As noted previously, diese hydratable salts are typically mcluded during initial formation of the HIPE to minimize the tendency of monomers, comonomers, and crosslinkers that are pπmaπly oil soluble to also ώssolve in the water phase However, after polymenzation of the HIPE, the presence of these salts is unnecessary and can adversely affect the ability of the foam to absorb blood and blood-based fluids such as menses, especially as the concentration of these salts in the foam increases Accordingly, it desirable to reduce die level of diese hydratable salts in the foam as much as possible during this washmg step After washmg, the foams of the present mvention have less than about 2% of such residual hydratable salts Preferably, the foams of the present mvention have less than about 0 5% of such residual salts

4 Treating with Hydrophilizmg Surfactant and Foam Dewateπng After the oπgmal water phase matenal has been removed to die extent required, die

HIPE foam is typically treated with an effective amount of a suitable hydrophilizmg surfactant Hydrophilizmg surfactants diat can be employed have been previously descnbed and particularly mclude edioxylates of C_j J-C15 fatty acids such as Pegosperse 200 ML, branched and linear alkyl aryl ethoxylates such as Tnton X-100, and edioxylates of C i [-C 15 aliphatic alcohols such as NEODOL 23-6 5T Treatment of the HIPE foam with die hydrophilizmg surfactant continues until the foam exhibits the desired degree of wettabihty After the HIPE foam has been hydrophilized, it will generally be dewatered

Dewatenng can be achieved by compressmg die foam (preferably in the z-ώrection) to squeeze out residual water, by subjecting die foam and die water therein to temperatures of from about 60° to about 200°C, or to microwave treatment, by vacuum dewatenng or by a combination of compression and thermal drying/microwave/vacuum dewatenng techniques The dewatenng step will generally be earned out until die HIPE foam is ready for use and is as dry as practicable Frequently such compression dewatered foams will have a water (moisture) content of from about 50 to about 500%, more preferably from about 50 to about 200%, by weight on a dry weight basis Subsequently, the compressed foams can be thermally dπed to a moisture content of about 40% or less, preferably in the range of from about 5 to about 15%, on a dry weight basis

After the HIPE foam has been dewatered. it can be shtted m vaπous patterns These mclude patterns that conform to the shape of the catamemal product m which the shtted foam is used as an absorbent member Slitting can be especially desirable when the foam is intended to confer supenor fit m a catamemal pad such as a samtary napk

IV Use of Polvmenc Foams Catamemal Products

The polymeπc foams of the present mvention are useful m a vaπety of absorbent articles for absorbmg blood and blood-based fluids

A Catamemal Products The polymeπc foams of the present mvention are particularly useful as absorbent members m a vaπety of catamemal products such as catamemal pads An embodiment of a catamemal pad or samtary napkm 10 according to die present mvention is shown in Figure 1 As used herem, die term "samtary napkm" refers to an absorbent article that is worn by females adjacent to die pudendal region, generally external to the urogenital region, and which is mtended to absorb and contam menstrual fluids and other vaginal discharges from the wearer's body (e g , blood, menses, and unne) Interlabial devices diat reside partially within and partially external of the wearer's vestibule are also within the scope of the present mvention As used herem, die term "pudendal" refers to the externally visible female genitaha It should be understood, however, diat the present mvention is also applicable to other feminine hygiene or catamemal pads such as pantiliners. or other catamemal products such as incontinence pads, tampons and die like

The polymeπc foams of the present mvention are particularly useful in sheet form This relates to ease of manufacture and shipping as well as for general utility m the product The sheet or sheets used can be of any thickness desired according to die capacity required for the surface area available Generally, the sheets will be from about 0 1 to about 1 cm in thickness These sheets can be perforated or slit, either to further enhance the rate of fluid absorption by mcreasmg the surface area of the foam exposed to die fluid or to increase the stretchabi ty of the foam Alternatively, these foams can be in the form of ώced cubes, strands (e g spaghetti-like matenal), thm stnps, and die like that can be assembled mto absorbent cores of vaπous shapes depending on die specific needs of die product

As particularly shown in Figure 2, catamemal pad 10 is constructed of fluid pervious primary topsheet 12, an absorbent core consisting of an optional fluid acquisition layer 14 commonly referred to as a "secondary topsheet", a fluid storage absorbent member 16 made of one or more polymeπc foams according to die present mvention, and a fluid impervious backsheet 18 The fluid storage absorbent member 16 may also compnse a polymenc foam bamer layer of the present mvention The backsheet 18 and die topsheet 12 are positioned adjacent die garment surface and the body surface, respectively, of pad 10 and are preferably jomed to each odier For example, the backsheet 18 and die topsheet 12 can be secured to each odier by adhesive Suitable adhesives tare manufactured by H B Fuller Company of St Paul, Minnesota under die designation HL-1258 or H-2031 Alternatively, topsheet 12 and backsheet can be jomed to each odier by heat bonding, pressure bonding, ultrasonic bonding, dynamic mechanical bonding, or any other suitable method for joining topsheets and backsheets known in the art A suitable mediod for joining topsheet 12 and backsheet 18 togedier is by a seal that forms border segment 20 As shown in Figure 1, the inner portion of this border segment 20 defines a perimeter 22 Perimeter 22 encircles the secondary topsheet 14 and absorbent member 16 Border segment 20 is generally relatively nanow, and can extend a ώstance of approximately 0 25 to 6 mm and preferably is approximately 3 mm wide However, die widdi of border 20 can be uniform or vary about the perimeter of pad 10 Border 20 provides a fluid impermeable seal that sunounds perimeter 22 The seal is preferably formed by die simultaneous application of pressure, with or without heat, to melt topsheet 12 and backsheet 1 , thereby formmg border segment 20

In adώtion to providmg fluid acquisition benefits, the secondary topsheet 14 may enhance the mtegnty of the product by stabilizmg the positionmg (e g , by reducmg bunching) of the fluid strorage absorbent member 16 The secondary topsheet can mclude nonwoven or woven webs of synthetic fibers mcludmg polyester, polypropylene, or polyethylene, natural fibers mcludmg cotton or cellulose, blends of such fibers, or any equivalent matenals or combinations of matenals Suitable secondary topsheets can also be made from mixtures of fibers with thermoplastic mateπals to form thermally bonded matnces These thermoplastic matenals can be m any of a vanety of forms mcludmg particulates, fibers, or combinations of particulates and fibers Thermoplastic fibers are a particularly prefened form because of their ability to form numerous interfiber bond sites Other alternatives for the secondary topsheet are die use of wood pulp surface-sprayed widi latex and air laid wood pulp structure bonded with latex

The backsheet 18 is impervious to fluids (e g , menses) and is preferably manufactured from a un plastic film, although other flexible liquid impervious matenals may also be used As used herem, the term "flexible" refers to matenals that are compliant and will reaώly conform to the general shape and contours of die human body The backsheet 18 prevents the exudates absorbed and contamed in the absorbent structure from wetting articles that contact the samtary napkm 10 such as pants, pajamas and undergarments The backsheet 18 can compnse a woven or nonwoven mateπal, polymenc films such as thermoplastic films of polyethylene or polypropylene, or composite matenals such as a film-coated nonwoven mateπal Preferably, the backsheet is a polyethylene film having a thickness of from about 0 012 mm (0 5 mil) to about 0 051 mm (2 0 mils) Exemplary polyethylene films are manufactured by Clopay Corporation of Cincinnati, Ohio, under die designation PI 8-0401 and by Ediyl Corporation, Visqueen Division, of Tene Haute, Indiana, under die designation XP-39385 The backsheet is preferably embossed and/or matte finished to provide a more clothlike appearance Further, the backsheet 18 can permit vapors to escape from the absorbent core (I e , is breathable) while still preventmg exudates from pass g through the backsheet 18 The topsheet 12 is compliant, soft feelmg, and non-irntating to the wearer's skin

Further, the topsheet 12 is fluid pervious permitting fluids (e g , menses) to reaώly penetrate through its thickness A suitable topsheet 12 can be manufactured from a wide range of mateπals such as woven and nonwoven matenals, polymeπc matenals such as apertured formed diermoplastic films, apertured plastic films, and hydroformed diermoplastic films, porous foams, reticulated foams, reticulated diermoplastic films, and diermoplastic scrims Suitable woven and nonwoven materials can be compπsed of natural fibers (e g , wood or cotton fibers), synthetic fibers (e g , polymeπc fibers such as polyester, polypropylene, or polyethylene fibers) or from a combination of natural and synthetic fibers

Prefened topsheets for use die present are selected from high loft nonwoven topsheets and aperture formed film topsheets Apertured formed films are especially prefened for the topsheet because diey are pervious to body exudates and yet non-absorbent and have a reduced tendency to allow fluids to pass back through and rewet die wearer's skin Thus, the surface of the formed film that is contact with die body remains dry, thereby reducmg body soilmg and creating a more comfortable feel for the wearer Suitable formed films are descnbed in U S Patent 3,929,135 (Thompson), issued December 30, 1975, U S Patent 4,324,246 (MuUane, et al ), issued Apπl 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 U S 5,006,394 (Baird), issued April 9, 1991 Each of these patents are incorporated herem by reference Particularly prefened microapetured formed film topsheets are ώsclosed in U S patent 4,609,518 (Cuno et al), issue September 2, 1986 and U S patent 4,629,643 (Cuno et al), issued December 16, 1986, which are incorporated by reference The prefened topsheet for the present mvention is the formed film descnbed m one or more of die above patents and marketed on samtary napkins by The Procter & Gamble Company of Cincinnati, Ohio as "DRI-WEAVE " The body surface of die formed film topsheet can be hydrophilic so as to help liquid to transfer through the topsheet faster than if the body surface was not hydrophilic so as to dimmish die likelihood diat menstrual fluid will flow off die topsheet rather than flowing mto and bemg absorbed by die absorbent structure In a prefened embodiment, surfactant is incoφorated mto the polymeπc matenals of the formed film topsheet such as is descnbed in U S Patent Application Seπal No 07/794,745, "Absorbent Article Havmg A Nonwoven and Apertured Film Coversheet" filed on November 19, 1991 by Aziz, et al . which is incoφorated by reference Alternatively, the body surface of the topsheet can be made hydrophilic by treating it with a surfactant such as is descnbed in the above referenced U S 4,950,254, mcoφorated herem by reference

In a prefened embodiment, where a duck catamemal pad is desired, a filler mateπal can be positioned between the fluid storage absorbent member 16 and die backsheet 18 Useful filler matenals, many of which are known m the art, mclude but are not limited to airfelt (e g , chemi-thermo-mechanical pulp, southern softwood craft, recycled pulp), foams (e g , polyurethane, cellulose, polystyrene), sawdust, paper wadding, recycled newspaper, etc Alternatively, the foam matenals of the present mvention can be cut layers of sufficient thickness to provide increased product duckness, typically between about 1 and about 2 cm In use, pad 10 can be held place by any support or attachment device (not shown) well-known for such puφoses Preferably, pad 10 is placed die user's undergarment or panty and secured diereto by a fastener such as an adhesive The adhesive provides a means for securing the pad in the crotch portion of the panty Thus, a portion or all of the outer surface of the backsheet 18 is coated widi adhesive Any adhesive or glue used in the art for such puφoses can be used for the adhesive herem, widi pressure-sensitive adhesives bemg prefened Suitable adhesives are Century A-305-IV manufactured by die Century Adhesives Corporation of Columbus, Ohio, and Instant Lock 34-2823 manufactured by die National Starch and Chemical Company of Bndgewater, NJ Suitable adhesive fasteners are also descnbed m U S Patent 4,917,697 Before pad 10 is placed in use, the pressure-sensitive adhesive is typically covered with a removable release Imer order to keep the adhesive from drying out or adhering to a surface other than the crotch portion of the panty pπor to use Suitable release liners are also descnbed the above-referenced U S Patent 4,917,697 Any commercially available release liners commonly used for such puφoses can be utilized herem Non-limiting examples of suitable release liners are BL30MG-A Silox El/0 and BL30MG-A Silox 4P/0 bodi of which are manufactured by die Akrosil Coφoration of Menasha, WI The pad 10 is put m use by removing die release Imer and thereafter placing the pad m a panty so that the adhesive contacts the panty The adhesive maintains the pad 10 its position within the panty duπng use

The absorbent foams of the present mvention are also useful as the upper acquisition/distribution component m a "multi-layer" absorbent core that additionally contains a lower fluid storage/reώstπbution component, where the absorbent core is positioned between the topsheet and backsheet to form the catamemal pad For puφoses of the present invention, an "upper" layer of a multi-layer absorbent core is a laver that is relatively closer to the body of die wearer, e g , die layer closest to the topsheet The term "lower" layer conversely means a layer of a multi-layer absorbent core that is relatively further away from the body of die wearer, e g , die layer closest to die backsheet This lower fluid storage/reώstπbution layer is typically positioned widun the absorbent core so as to underlie die (upper) fluid acquisition/ώstπbution layer and be m fluid communication therewith This lower storage/reώstπbution layer can compnse a vanety of fluid storage/reώstπbution components mcludmg those containing absorbent gelling mateπals such as ώsclosed m U S Patent 5,061,259 (Goldman et al), issued October 29, 1991. U S Patent 4,654,039 (Brandt et al), issued March 31, 1987 (reissued Apπl 19, 1988 as Re 32,649), U S Patent 4,666,983 (Tsubakimoto et al), issued May 19, 1987, and U S Patent 4,625,001 (Tsubakimoto et al), issued November 25, 1986, all of which are incoφorated by reference, absorbent macrostructures made from these absorbent gelling mateπals such as those ώsclosed m U S Patent 5,102,597 (Roe et al), issued Apπl 7, 1992, and U S Patent 5,324,561 (Rezai et al), issued June 23, 1994, bodi of which are incoφorated by reference), and absorbent gelling mateπals laminated between two tissue layers such as those ώsclosed m U S Patent 4,260,443 (Lindsay et al), issued Apnl 7, 1981, U S Patent 4,467,012 (Pedersen et al), issued August 21, 1984, U S Patent 4,715,918 (Lang), issued December 29, 1987, U S Patent 4,851,069 (Packard et al), issued July 25, 1989, U S Patent 4,950.264 (Osbom), issued August 21, 1990, U S Patent 4,994,037 (Bemarώn), issued February 19, 1991, U S Patent 5,009,650 (Bemarώn), issued Apnl 23, 1991, U S Patent 5,009,653 (Osbom), issued Apπl 23, 1991, U S Patent 5,128,082 (Makoui), July 7, 1992, U S Patent 5,149,335 (Kellenberger et al), issued September 22, 1992, and U S Patent 5, 176,668 (Bernardin), issued January 5, 1993, all of which are uicoφorated by reference There is no particular cπticahty with respect to the positional relationship of the fluid acquisition/ώstπbution foam component and die fluid storage/reώstπbution component within these multi-layer absorbent cores so long as diese components are m effective fluid communication with each other and so long as each component is large enough to effectively hold and/or transport the amount of aqueous body fluid diat is expected to be discharged mto die catamemal pad The most prefened relationship between the fluid acquisition/ώstπbution foam component and die fluid storage/reώstπbution component within the absorbent core is to place these components m a layered configuration In such a layered configuration, the fluid acquisition/ώstπbution foam component compπses an upper foam layer which overlies a subjacent fluid storage/reώstπbution component in die form of a lower layer It should be understood diat these two types of layers refer merely to the upper and lower zones of die absorbent core and are not necessanly limited to smgle layers or sheets Both the fluid acquisition/ώstπbution zone, e g , upper layer, and die fluid storage/reώstπbution zone, e g . lower layer, can compnse several layers the requisite type Thus, as used herem. die term "layer" mcludes the terms "layers" and "layered"

B Bandages and Wound Dressings

Absorbent foams of the present mvention are also useful in bandages and dressings for wounds These mclude articles ranging from simple bandaids to large surgical dressings and bandages A bandage or dressing can simply compnse a topsheet, an absorbent foam of the present mvention, and a fluid impervious backsheet optionally attached to adhesive stnps vaπous shapes and sizes The foams of the present mvention are particularly good at absorbmg fluids from suppurating wounds and preventmg or reducmg contact of die healmg area widi media that are conducive to microbiological growth Potential wound healmg benefits can be confened by pretreating the absorbent foam with any of a wide vaπety of antimicrobial and or antiseptic compounds well know to those skilled in the art

C Surgical Drapes

Absorbent foams of the present mvention are also useful in surgical drapes These are sheets of mateπal that catch blood during surgical procedures They typically -compnse a thm layer of absorbent matenal, m this case the foam of the present mvention, a fluid impervious backsheet, typically a 1-2 mil thick sheet of polyethylene The polyethylene can optionally be treated widi an adhesive to secure its placement m surgery The foam of the present mvention is particularly easy to form mto such articles Further, the inherent mtegnty of such foams prevents contamination of die area by loose matenals such as might be found m traditional fiber-based absorbent structures The absorbent properties are well suited to capturing splattered blood quickly and preventmg its spread, e g to the floor thus producmg a slipping hazard Smaller sizes of these laminates may also be used as wipes for blood and blood based fluids

V Test Methods for Polvmenc Foams

A Vertical Wicking Capability

1 Preparation of Artificial Menstrual Fluid

Artificial Menstrual Fluid (AMF) is prepared by combining equal volumes of gastnc mucm solution and fresh, stenle defibnnated sheep blood (Cleveland Scientific, Ameπcan Biomeώcal, Bath, OH) The gastnc mucm solution is prepared by combmmg the followmg the proportions and order shown

- 450 mL of aqueous sodium ώhydrogen phosphate ( 138 wt %) solution containing sodium chlonde (0 85 wt %) adjusted to pH 7 2±0 1 ,

- 7 5 mL potassium hydroxide aqueous solution, - 31 g steπlized gastnc mucm (ICN Biomeώcal Inc , Cleveland, OH), heated 2 5 hours to completely dissolve the gastnc mucm The solution is allowed to cool to less an 40°C,

- 2 0 mL of 8 wt % aqueous lactic acid solution

The mixture is autoclaved at 121°C for 15 minutes, then allowed to cool to room temperature This mixture should be refrigerated and should be used widun 7 days

2 Sample Preparation

Foam samples are cut mto 2 54 cm widtii stπps about 25 cm long Two samples are cut for each matenal to be tested The samples are sealed m plastic on die top and on bodi long sides usmg a T-Bar sealer (Model T-7, 115VAC, 65 W Harwil Company, Santa Mo ca, California) The 0 5 centimeter at the bottom of the mateπal stπp remains exposed The outside of die plastic is graduated widi marks each centimeter along the length of die sample, starting at the bottom of the plastic (not the bottom of the sample)

3 Equipment Preparation

The AMF is stined for 30 minutes at 22°C Approximately 300 mL of the equilibrated AMF is poured mto a 500 mL recrvstallizmg ώsh The filled ώsh is stined magnetically at low speed

A cyhndncal Plexiglas bar (30 5 cm cylindπcal bar with at least two attached

Plexiglas plates (25 cm x 0 5 cm x 3 cm) attached at die end with the spacing bemg adjustable) is clamped onto a ring stand The clamp should tentatively be set approximately 18 - 20 mches above the base of the stand Allow enough space between the Plexiglas plates on the end of die cylindπcal bar is provided to fit die thickness of the samples to be tested

4 Test Procedure

The sealed top side of die sample is placed between two of the Plexiglas plates, and then die plates are tightened together until the sample is completely suspended There should be enough room along the widdi of the plates to fit 2-3 samples without die samples touching If not, additional plates can be used to position die samples one behind die odier After suspending all samples, die bottom and top of die samples should all be level widi respect to the Plexiglas plates and each odier

The stir plate and ώsh of AMF is placed ώrectly underneath die suspended samples The samples are lowered such that 0 5 cm of each sample is submerged the AMF (The plastic covered portion of die samples should not be submerged , as fluid will tend to wick die interfaces of the seal instead of widun the sample) Adjustments to level die bar and samples are made, if necessary, so that each sample bottom is equally submerged the AMF The absorbent foam samples are suspended in the stined AMF to the bottom of the plastic The tune elapsed when die fluid height reaches each 1 cm marking is recorded The average height of the fluid front in these samples is approximated The heterogeneity within the samples provides channels of wicked fluid with no clear leadmg edge The midpomt of die wicked height is taken as the value to be recorded The average of the final vertical wicking values recorded for the samples (n=2) is used as die vertical wicking value for the mateπal At the conclusion of die measurement, die sample is sectioned mto 1 cm pieces and weighed to obtain (after subtraction of the weight of the sample) die capacity of the matenal at varying heights

B Honzontal Gravimetnc Wicking Honzontal Gravimetnc Wicking (HGW) is an absorbency test that measures the uptake of fluid by a 2 5 in by 7 5 m absorbent member or catamemal pad sample as a function of tune In this method, die sample is held upside down horizontally m a holder suspended from an electronic balance A glass supply tube, containing the test fluid ( this case, AMF at 22°C) and connected to a fluid reservoir at zero hydrostatic head relative to die test sample, is allowed to contact the lower surface of the sample as a pomt source and die increase m weight of the sample is used as a measure of fluid uptake versus time The test proceeds for 3900 seconds During the test, the sample is constrained under 0 18 psi (1 2 kPa) pressure by a conformable water-filled plastic bag covered by a metal weight This conformable system provides a hydrostatic pressure to the sample to allow the pressure on die sample to remain relatively constant over the entire sample area

"Imtial Uptake" is defined as the weight of AMF absorbed by die system after 3900 seconds "Rewet" is subsequently measured on die absorbent member or catamemal pad to find out die amount of fluid diat can be repeatedly blotted from the structure/pad widi Whatman filter paper at 0 25 psi (1 7 kPa) until die core will give up less than 0 5 g of AMF "Retained Uptake" is calculated as die difference between "Imtial Uptake" and "Rewet"

C Resistance to Compression Deflection (RTCD)

Resistance to compression deflection can be quantified by measurmg the amount of stram (% reduction thickness) produced in a foam sample which has been saturated widi synthetic unne, after a confining pressure of 0 74 psi (5 1 kPa) has been applied to die sample

Jayco syndietic unne used dus method is prepared by dissolving a mixture of 2 0 g KC1, 2 0 g Na S0₄, 0 85 g NH4H2PO4, 0 15 g (NH₄)₂HP0₄, 0 19 g CaCl₂, and 0 23 g MgCl to 1 0 liters with distilled water The salt mixture can be purchased from Endovations, Reading, Pa (cat No JA-00131-000-01) The foam samples, synthetic unne and equipment used to make measurements are all equilibrated to a temperature of 31°C All measurements are also performed at dus temperature.

A foam sample sheet is saturated to its free absorbent capacity by soaking in a bath of synthetic urine. After 3 minutes, a cylinder having a 1.0 in^ (6.5 cπ J circular surface area is cut out of the saturated, expanded sheet widi a shaψ circular die. The cylindrical sample is soaked in syndietic urine at 31°C for a further 6 minutes. The sample is then removed from the syndietic urine and is placed on a flat granite base under a gauge suitable for measuring the sample thickness. The gauge is set to exert a pressure of 0.08 psi (0.6 kPa) on the sample. Any gauge fitted widi a foot having a circular surface area of at least 1 in^ (6.5 cm^) and capable of measuring thickness to 0.001 in (0.025 mm) can be employed. Examples of such gauges are an Ames model 482 (Ames Co.; Waltham, MA) or an Ono- Sokki model EG-225 (Ono-Sokki Co., Ltd.; Japan).

After 2 to 3 min., the expanded thickness (XI) is recorded. A force is then applied to die foot so that the saturated foam sample is subjected to a pressure of 0.74 psi (5.1 kPa) for

15 minutes. At the end of this time, the gauge is used to measure the final sample thickness (X2). From the initial and final thickness measurements, the percent strain induced can be calculated for the sample as follows: [(Xl-X2)/Xl]xl00 = % reduction in thickness.

D. Free Absorbent Capacity

Free absorbent capacity can be quantified by measuring the amount of syndietic urine absorbed in a foam sample which has been saturated widi syndietic urine. The foam samples and syndietic urine are equilibrated to a temperature of 31°C.

Measurements are performed at ambient temperature.

A foam sample sheet is saturated to its free absorbent capacity by soaking in a bath of syndietic urine. After 3 minutes, a cylinder having a 1.0 in^ (6.5 cm^) circular surface area is cut out of the saturated sheet widi a shaφ circular die. The cylindrical sample is soaked in syndietic urine at 31°C for a further 3 minutes. The sample is then removed from the synthetic urine and is placed on a digital balance. Any balance fitted widi a weighing pan having an area larger than that of the sample and widi a resolution of 1 milligram or less can be employed. Examples of such balances are the Mettler PM 480 and Mettler PC 440 (Mettler Instrument Coφ; Hightstown NJ). After determining die weight of the wet foam sample (Ww), it is placed between 2 fine plastic mesh screens on top of 4 ώsposable paper towels. The sample is squeezed 3 times by firmly rolling a plastic roller over the top screen. The sample is then removed, soaked in distilled water for approximately 2 minutes, and squeezed between mesh screens as before. It is then placed between 8 layers of ώsposable paper towels (4 on each side) and pressed widi 20,000 lbs. of force in a Carver Laboratory Press. The sample is then removed from the paper towels, dried in a Fisher convection oven at 82°C for 20 minutes, and its dry weight recorded (Wd). The free absorbent capacity (FAC) is the wet weight (Ww), less the dry weight (Wd) ώvided by the dry weight (Wd), i.e., FAC = [(Ww-Wd)ΛVd]

E. Dynamic Mechanical Analysis (DMA)

DMA is used to determine the Tgs of polymers including polymeric foams. Samples of the foams are sliced into blocks 3-5 mm in thickness and washed 3-4 times in distilled water, expressing the fluid dirough roller nips between each washing. The resulting foam blocks are allowed to dry in air. The dried foam slices are cored to yield a cylinders 25 mm in diameter These cylinders are analyzed using a Rheometrics RSA-II dynamic mechanical analyzer set in compression mode using parallel plates 25 mm in diameter Instrument parameters used were as follows:

Temperature step from ca. 85°C to -40°C in steps of 2.5°C Soak intervals between temperature changes of 125-160 seconds Dynamic strain set at 0.1% to 1.0% (usually 0.7%) Frequency set at 1 0 radians/second

Autotension set in static force tracking dynamic force mode widi initial static force set at 5 g.

The glass transition temperature is taken as the maximum point of the loss tangent versus temperature curve.

VI. Specific Examples

These examples illustrate die specific preparation of collapsed HIPE foams according die present invention.

Example 1. Preparation of Foam from a HIPE A) HIPE Preparation

Anhydrous calcium chloride (36.32 kg) and potassium persulfate (567 g) are ώssolved in 378 liters of water. This provides die water phase stream to be used in a continuous process for forming a HIPE emulsion.

To a monomer combination comprising 400 g styrene, 2900 g ώvinylbenzene (40% ώvinylbenzene and 60% ediyl styrene), and 4800 g 2-edιylhexylacrylate is added 480 g of high purity ώglycerol monooleate and Tinuvin 765 [bis( 1,2,2, 5,5- pentamethylpipendιnyl)sebacate] antioxidant (41 g).

This ώglycerol monooleate emulsifier is prepared following the general procedure for preparing polyglycerol esters described in U.S. Patent 5,387,207 (Dyer et al.) issued Feb. 7, 1995. A polyglycerol composition comprising approximately 97% or greater ώglycerol and 3% or less tπglycerol (Solvay Performance Chemicals, Greenwich. Conn) is esteπfied with fatty acids havmg a fatty acid composition compπsmg approximately 71% C18 1, 4% C 18 2, 9% C16 1, 5% C16 0, and 11% other fatty acids (Emersol-233LL, Emery/Henkel) in a weight ratio of 62 38, usmg sodium hydroxide as a catalyst at about 225°C under conώtions of mechanical agitation, nitrogen sparging, and gradually increasing vacuum, with subsequent phosphoπc acid neutralization, cooling to about 85°C, and settling to reduce die level of unreacted polyglycerols The polyglycerol ester reaction product is first fractionally distilled through two CMS-15A centnfugal molecular stills connected in senes to reduce die levels of unreacted polyglycerols and fatty acids and then redistilled through the stills to yield distillation fractions high m ώglycerol monoesters Typical conώtions for the final distillation pass are a feed rate of about 15 lb/hr, a degasser vacuum of about 21-26 microns, a bell jar vacuum of about 6-12 microns, a feed temperature of about 170°C, and a residue temperature of about 180°C Distillation fractions high m ώglycerol monoesters are combmed, yielding a reaction product (as determined by supercntical fluid chromatography) compπsmg approximately 50% ώglycerol monooleate, 27% other ώglycerol monoesters, 20% polyglycerols, and 3% odier polyglycerol esters After mixmg, the reaction product is allowed to settle overnight The supernatant is withdrawn and used die oil phase as the emulsifier formmg the HIPE (About 20 g of a sticky residue is discarded )

Separate streams of the oil phase (25°C) and water phase (65°-70°C) are fed to a dynamic nux g apparatus Thorough mixmg of the combmed streams the dynamic mixmg apparatus is achieved by means of a pm impeller At this scale of operation, an appropnate p impeller compnses a cylmdπcal shaft of about 21 6 cm in length with a diameter of about 1 9 cm The shaft holds 4 rows of pins, 2 rows havmg 17 pins and 2 rows having 16 pins, each having a diameter of 0 5 cm extending outwardly from the central axis of the shaft to a length of 1 6 cm The p impeller is mounted a cyhndπcal sleeve which forms the dynamic mixmg apparatus, and the p s have a clearance of 0 8 mm from the walls of the cyhndncal sleeve

A spiral static mixer is mounted downstream from the dynamic mixmg apparatus to provide back pressure m die dynamic mixer and to provide improved uicoφoration of components mto the emulsion that is eventually formed Such a static mixer is 14 mches (35 6 cm) long with a 0 5 mch (1 3 cm) outside diameter The static mixer is a TAH Industπes Model 070-821, modified by cutting off 2 4 mches (6 1 cm)

The combmed nuxmg apparatus set-up is filled widi oil phase and water phase at a ratio of 2 parts water to 1 part oil The dynamic mixmg apparatus is vented to allow air to escape while fillmg the apparatus completely The flow rates duπng fillmg are 3 78 g/sec oil phase and 7 56 cc/sec water phase

Once the apparatus set-up is filled, agitation is begun m die dynamic mixer, with die unpeller turning at 800 RPM The flow rate of the water phase is then steadily increased to a rate of 44 1 cc/sec a time penod of about 30 sec and die oil phase flow rate is reduced to 1 25 g/sec over a tune penod of about 1 nun The back pressure created by die dynamic and static mixers at this point is 2 psi (14 kPa) The resultant HIPE has a water-to-oil ratio of about 50 1

B) Polvmeπzation/Cuπng of HIPE

The HIPE from the static mixer is collected a round polypropylene tub. 17 m (43 cm) m diameter and 7 5 m (10 cm) high, with a concentnc insert made of Celcon plastic The insert is 5 (12 7 cm) diameter at its base and 4 75 m (12 cm) m diameter at its top and is 6 75 m (17 14 cm) high The HIPE-containing tubs are kept m a room mamtamed at

65°C for 18 hours to cure and provide a polymeπc HIPE foam

C) Foam Washmg and Dewatenng

The cured HIPE foam is removed from the tubs The foam at this pomt has residual water phase (containing ώssolved emulsifiers, electrolyte, mitiator residues, and mitiator) about 32-38 tunes (32-38X) die weight of polymerized monomers The foam is sliced widi a shaφ reciprocating saw blade mto sheets which are 0 15 mches (0 38 cm) in thickness These sheets are then subjected to compression a senes of 2 porous nip rolls equipped widi vacuum which gradually reduces die residual water phase content of the foam to about 2 tunes (2X) d e weight of the polymenzed monomers At this pomt, the sheets are then resaturated widi a 1% solution of Pegosperse 200 ML m water at 60°C and are squeezed m a senes of 3 porous nip rolls equipped widi vacuum to a water phase content of about 4X The CaCl2 content of the foam is below 2%

The HIPE foam is then dπed m air for about 16 hours Such drying reduces die moisture content to about 4-10 % by weight of polymenzed mateπal

Example 2 Preparation of Foams from HIPEs

HIPE foams are prepared usmg vanous pour temperatures, cure tunes and temperatures, water to oil (W O) ratios, and impeller mixer speeds These foams and dieir properties are shown m Tables 1 and 2 below

Table 1 Hole Sizes vs Pour Temperature

2d 65° 800 55: 1 65° 16 1 1 1

2e 82° 800 50: 1 82° 2 17.4

2f 82° 800 45: 1 82° 2 16.4

Table 2. Foam Capacity and Strength vs. W:0 Ratio

Example W:0 RTCD FAC Ratio % R/g la 45: 1 32.3% 44.7 lb 50:1 55.7% 46.0 lc 50: 1 57.0% 50J

Id 55: 1 64.9% 52.7 le 50: 1 68.8% 49.2

If 45: 1 54.5% 43.0

Table 3 shows the effect on the vertical wicking rate and capacity of residual calcium chloride salt in the foam relative to a washed foam sample that has been rehydrophilized according to the present invention. The foam sample labeled "Unwashed" is die unwashed HIPE foam of Example 2b containing residual calcium chloride salt. The foam sample labeled "Washed" is die HIPE foam of Example 2b that has been washed to remove the salt and rehydrophilized widi PEGOSPERSE 200 ML. The columns relating to "Wicking Rate" show the time required to wick AMF to the inώcated heights. The columns relating to "Capacity" show the amount of AMF wicked to diat height after a period of 18 hours:

Table 3: Wicking Rate and Capacity at Equilibrium Height

6 120 30 39.2 42.4

7 33.3 39.5

8 19J 22.7

9 4.6 5.4

10 0.8 1.6

11 0.0 0.4

12 0.0 0.0

Table 3 above shows that removal of the calcium chloride salt speeds up the wicking rate without adversely affecting capacity.

Table 4 shows the effect on Horizontal Gravimetric Wicking (HGW) of residual calcium chloride salt in the foam relative to a washed foam sample that has been rehydrophilized according to die present invention. The foam sample labeled "Unwashed" is die unwashed HIPE foam of Example 2b containing residual calcium chloride salt. The foam sample labeled "Washed" is die HIPE foam of Example 2b that has been washed to remove the salt and rehydrophilized widi PEGOSPERSE 200 ML.:

Table 4: HGW

Foam Sample Initial Uptake (g/g) Retained Uptake (g/g) % Retained/Initial Uptake

Unwashed 14 12 86%

Washed 24 19 79%

Table 4 above shows that the presence calcium chloride in the foam inhibits die HGW, relative to the same foam that has been washed and rehydrophilized.

Example 3. Preparation of Foams from HIPEs HIPE foams are prepared according to die procedure of Example 1. The HIPEs are poured at 74°C and 800 RPM and cured at 82°C for 2 hours. Differences in water to oil (W:0) ratio and conesponding differences in properties are shown in Table 5.

Table 5. Foam Capacity and Strength vs. W:Q Ratio

Example W O RTCD FAC Ratio %

3a 30: 1 5.7% 29.8

3b 40: 1 22.5% 39.4

3c 40: 1 12.0% 39.6 3d 50 1 59 2% 47 2

Example 4 Preparation of Bamer Layer from HIPEs

A foam mateπal useful as the optional bamer layer is prepared accordmg to die general process descnbed m Example 1 The only modifications needed to obtain the relatively smaller cell and hole sizes desired for the bamer layer are mixmg at a temperature of 156°F and usmg a mixer speed of about 1300 RPM

Example 5 Catamemal Pad Having A Foam Absorbent Member

A piece of polymenc foam accordmg to any of Examples 2a-2f is cut mto a stπp having a vviddi of 6 4 cm , a length of 19 cm , and a thickness of 0 51 cm (volume = 62 cc) This piece of foam is positioned as an absorbent member or layer between a fluid impervious backsheet and an apertured film topsheet (such as DRI-WEAVE) Optionally, a nonwoven sheet can be used as die topsheet in place of the apertured film Preferably, a secondary topsheet is positioned between the foam absorbent member and die apertured topsheet

Example 6 Catamemal Pad Having Two Foam Absorbent Members

A piece of polymenc foam accordmg to any of Examples 2a, 2b, 2c, or 2d is cut mto a stπp havmg a widdi of 6 4 cm, a length of 10 cm, and a thickness of 0 19 cm (volume = 12 cc) A second piece of polymeπc foam accordmg to Examples le or If is cut mto a stπp havmg a widdi of 6 4 cm, a length of 19 cm, and a duckness of 0 19 cm (volume 23 cc) The pieces are assembled as descnbed in Example 5 mto a catamemal pad widi die upper layer (adjacent to die topsheet) bemg the smaller of the two pieces of foam Preferably the two foam pieces are lightly bonded together with any suitable bondmg adhesive apphed specific points to maintain contact between the pieces widiout restπctmg fluid flow

Example 7 Catamemal Pad Having a Bamer Layer

A catamemal pad having an absorbent core compπsmg three absorbent foams of the present mvention and a filler mateπal between the foam absorbent core and die backsheet is prepared as follows A piece of polymenc foam accordmg to any of Examples 2a, 2b, 2c. or 2d is cut mto a stπp which will be die upper layer (adjacent the topsheet) of the absorbent core A second piece of polymenc foam accordmg to Examples le or If is cut mto a stnp that will be the middle layer of the absorbent core A third piece of polymeπc foam accordmg to Example 4 is cut mto a stπp that will be the bamer layer (adjacent the filler mateπal, which is optionally airfelt) of the absorbent core This bamer layer will have a number average cell size of from about 15 to about 50 μm and a number average hole size of from about 4 to about 9 μm

For a thick product, die filler matenal (e g , airfelt) is located between die absorbent core and die backsheet The pieces are assembled as descnbed m Example 5 mto a catamemal pad Preferably the diree foam pieces are lightly bonded togedier widi any suitable bondmg adhesive applied m specific points to maintain contact between the pieces widiout restnctmg fluid flow

Example 8 Catamemal Pad Containing Foam and Absorbent Gelling Mateπal

A piece of polymeπc foam accordmg to any of Examples 2a, 2b, 2c, or 2d is cut mto a stπp having a widdi of 6 4 cm, a length of 10 cm, and a duckness of 0 19 cm (volume = 12 cc) This is assembled over a web consisting of cellulosic fibers and absorbent gelling mateπal or absorbent gelling matenal laminated between two layers of tissue

Example 9 Bandage Having Foam Component

Any of the foams of Example 2 can be cut mto a piece 2 5 cm square and 0 2 cm duck This piece of foam is attached to a fluid impermeable backsheet stπp having a widdi of 2 8 cm and a length of 7 cm usmg an adhesive The exposed edges of dus stπp are coated witii any suitable contact adhesive and cover widi a release paper and packaged in a samtary wrapper Optionally, a fluid pervious topsheet such as DRI-WEAVE or a nonwoven can be attached on top of die foam

Example 10 Surgical Drape Having Foam Component

Any of the foams of Example 2 can be sliced mto a piece 1 m square and 0 13 cm duck This piece of foam is attached to a 1 m square fluid impermeable backsheet usmg any suitable adhesive The opposmg side of die backsheet can be treated with any suitable contact adhesive and covered widi release paper so as to provide for stability m application to a particular area when m use

Example 1 1 Tampon Havmg Foam Component

Any of the foams of Example 2 can be cored to provide a tube having a radius of 1 2 cm and a length of 8 cm The tube is wrapped in a fluid permeable nonwoven coversheet and attached to a string for easy removal

Claims

What is Claimed is:

1. A polymeric foam material which is capable of absorbing blood and blood-based fluids, said polymeric foam material comprising a hydrophilic, flexible, nonionic polymeric foam structure of interconnected open cells, characterized in that the foam structure has:

A) the ability to wick artificial menstrual fluid (AMF) vertically to a height of 5 cm in less than 40, preferably less than 20, minutes;

B) a capillary specific surface area in the range of from 0.0080 to 0.040, preferably from 0.010 to 0.030, most preferably from 0.014 to about 0.026, m²/cc;

C) a resistance to compression deflection of from 5 to 75%, preferably from 10 to 65%, most preferably from 15 to 60%, when measured under a confining pressure of 5J kPa at 31°C after 15 minutes;

D) a free absorbent capacity of from 20 to 125 g/g;

E) less than 2%, preferably less than 0.5%, residual hydratable salts.

2. The foam material of Claim 2 characterized in that said foam structure has the ability to wick at least 30 g/g of AMF to a height of about 5 cm at equilibrium and has % Retained/Initial Uptake of AMF of at least about 50%.

3. The foam material of any of Claims 1 to 2 characterized in that it has a number average cell size of from 30 to 130, preferably from 35 to 60, μm and a number average hole size of from 8 to 30, preferably from 10 to 20, μm.

4. The foam material of Claims 1 to 3 characterized in that it has a dry basis density of from 0.014 to 0.024 g/cc.

5. A catamenial pad especially suitable for absorbing menstrual fluids, said pad comprising:

I) a fluid pervious topsheet;

II) a backsheet; and

III) an absorbent core positioned between said topsheet and said backsheet and the fluid discharge region of the wearer of the pad, said absorbent core characterized in that it comprises an absorbent member made from the foam material of any of Claims 1 to 5.

6. The pad of Claim 5 characterized in that said absorbent core further comprises a fluid acquisition layer between said topsheet and said absorbent member.

7. The pad of Claim 5 characterized in that said absorbent member comprises an upper foam layer having a capillary suction specific surface area from 0.014 to 0.020 m^/cc and a lower foam layer having a capillary suction specific surface area higher than that of said upper foam layer and in the range of from 0.020 to 0.026 m^/cc.

8. The pad of Claim 5 characterized in that said absorbent member is an upper acquisition/distribution component and wherein said absorbent core further comprises a lower fluid storage/redistribution component in fluid communication with said upper component and comprising absorbent gelling material, said lower component preferably comprising absorbent gelling material laminated between two tissue layers.

9. An absorbent article selected from the group consisting of tampons, bandages, wound dressing and surgical drapes characterized in that it comprises the foam material of any of Claims 1 to 4.

10. A process for the preparation of an absorbent polymeric foam material capable of absorbing blood and blood-based fluids, characterized in that it comprises the steps of:

A) forming a water-in-oil emulsion under from: 1) an oil phase comprising: a) from 85 to 98%, preferably from 90 to 97%, by weight of a monomer component capable of forming a copolymer having a Tg of 50°C or lower, preferably from 15° to 30°C, the monomer component comprising: i) from 45 to 70% by weight of at least one substantially water-insoluble monofunctional monomer capable of forming an atactic amorphous polymer having a Tg of 35°C or lower; ii) from 10 to 40% by weight of at least one substantially water-insoluble monofunctional comonomer capable of imparting toughness about equivalent to that provided by styrene; iii) from 5 to 25% by weight of a first substantially water- insoluble, polyfunctional crosslinking agent selected from the group consisting of divinylbenzenes, trivinylbenzenes, divinyltoluenes, divinylxylenes, divinylnaphthalenes divinylalkylbenzenes, divinylphenanthrenes, divinylbiphenyls, divinyldiphenylmethanes, divinylbenzyls, divinylphenylethers, divinyldiphenylsulfides, divinylfurans, divinylsulfide, divinylsulfone, and mixtures thereof; and iv) from 0 to 15% by weight of a second substantially water-insoluble, polyfunctional crosslinking agent selected from the group consisting of polyfunctional acrylates, methacrylates, acrylamides, methacrylamides, and mixtures thereof; and b) from 2 to 15%, 3 to 10%, by weight of an emulsifier component which is soluble in the oil phase and which is suitable for forming a stable water-in-oil emulsion, the emulsion component comprising: (i) a primary emulsifier having at least 40% by weight emulsifying components selected from diglycerol monoesters of linear unsaturated C ] 6-C22 fatty acids, diglycerol monoesters of branched C 15- C24 fatty acids, diglycerol monoaliphatic ethers of branched C16-C24 alcohols, diglycerol monoaliphatic ethers of linear unsaturated C16-C22 alcohols, diglycerol monoaliphatic ethers of linear saturated C12-C14 alcohols, sorbitan monoesters of linear unsaturated C16-C22 fatty acids, sorbitan monoesters of branched C16-C24 fatty acids, and mixtures thereof; or (ii) a combination of a primary emulsifier having at least about 20% by weight of said emulsifying components and a secondary emulsifier in a weight ratio of primary to secondary emulsifier of from about 50: 1 to about 1 4, said secondary emulsifier being selected from the group consisting of long chain C12-C22 diahphatic, short chain C 1-C4 dialiphatic quaternary ammonium salts, long chain C 12-C22 dialkoyl(alkenoyl)-2-hydroxyethyl, short chain C1-C4 dialiphatic quaternary ammonium salts, long chain C12-C22 dialiphatic imidazolinium quaternary ammonium salts, short chain C1 -C4 dialiphatic, long chain C12-C22 rnonoaliphatic benzyl quaternary ammonium salts, and mixtures thereof; and

2) a water phase comprising an aqueous solution containing from 0.2 to 20%, preferably from 1 to 10%, by weight of a water-soluble electrolyte, preferably calcium chloride;

3) a volume to weight ratio of water phase to oil phase in the range of from 20: 1 to 125: 1, preferably from 40: 1 to 70 J; and

B) polymerizing the monomer component in the oil phase of the water-in-oil emulsion to form a polymeric foam material that is capable of acquiring and distributing blood based fluids;

C) washing the polymeric foam material to lower the level of residual electrolytes to less than 2% ;

D) treating the washed foam with an effective amount of a hydrophilizing surfactant;

E) dewatering the washed foam to a moisture content of 40% or less, preferably from 5 to 15%.

11. The process of Claim 10 characterized in that the polymeric foam of step B) is sliced into a sheet prior to step C).

12. The process of any of Claims 10 to 11 characterized in that said monomer component comprises: i) from 50 to 65% by weight monomer selected from the group consisting of C4-C14 alkyl acrylates, aryl acrylates, Cg-Cjg alkyl methacrylates, acrylamides C4-C12 alkyl styrenes, and mixtures thereof; ii) from 15 to 40% by weight comonomer selected from the group consisting of styrene, ethyl styrene and mixtures thereof; and iii) from 12 to 18% by weight divinyl benzene.

13. The process of Claim 12 characterized in that 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, tetradecyl methacrylate, N-octadecyl acrylamide, ?-n-octylstyrene, and mixtures thereof.

14. The process of any of Claims 10 to 13 characterized in that the emulsifier component comprises a primary emulsifier having at least 70% by weight emulsifying components selected from the group consisting of diglycerol monooleate, sorbitan monooleate, diglycerol monoisostearate, and mixtures thereof.

15. The process of any of Claims 10 to 15 characterized in that the hydrophilizing surfactant is selected from the group consisting of ethoxylates of C11-C 15 alcohols; ethoxylates of C 11-C J 5 fatty acids; condensation products of ethylene oxide, propylene oxide, and mixtures thereof having molecular weights greater than about 2000; condensation products of propylene oxide and propylene glycol; sulfated alcohol ethoxylates; alkyl ether sulfates; branched and linear alkyl aryl ethoxylates; silicone-glycol copolymers; and mixtures thereof.

16. The process of Claim 15 characterized in that from 0.1 to 5% of the hydrophilizing surfactant remains in the foam material after step D).