CA2208642C

CA2208642C - Foams made from high internal phase emulsions useful as absorbent members for catamenial pads

Info

Publication number: CA2208642C
Application number: CA002208642A
Authority: CA
Inventors: John Collins Dyer; Susan Nicole Lloyd
Original assignee: Procter and Gamble Co
Current assignee: Procter and Gamble Co
Priority date: 1995-01-10
Filing date: 1996-01-11
Publication date: 2004-04-13
Anticipated expiration: 2016-01-11
Also published as: TW460302B; FI972917A; CA2226408A1; NO973186L; HK1004140A1; MX9705239A; EP0802930A1; TR199700615T2; US5795921A; ES2171654T3; DE69618174D1; CA2226408C; CN1177359A; JPH10512168A; WO1996021682A1; BR9606735A; US5899893A; CZ218197A3; AU713687B2; JP3432828B2

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

WO 96121682 ' PCTILS96100388 FOAMS MADE FROM HIGH INTERNAL PHASE EMULSIONS USEFtJI AS
ABSORBENT MEMBERS FOR CATAMENIAL PADS

t=IELD OF THE INVENTION
"Ibis application relates to flexible. microporous, opm-celled pohmeric foam rnataials made from high intecna! phase anulsi~s that can absorb blood and blood-based fluids such as menses. 'This application particularly relates to absorbent foam materials that 15 are useful as absorbent membea for catamenial pads, tampons, bandages, wound dressings.
surgical drapes and the fke.
BACKGROUND OF THE IhNENTION
The development of highly absorbent articles for blood and blood-based fluids such as catarnenial pads (e.g., sanitary napkins), tampons, wound dressings, bandages and surgical 20 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., erytbrocytea or red blood cells). In particular, blood-based fluids such as menses are much more viscous than water and urine. This higher viscosity bumpers the ability of conventional abx~rbe~ manaials to e~cieatly and rapidly transport these blood-based fluids to regions 25 rrsnote from the point of initial discharge. Undissolved elest~ats in these blood-based fluids can also potrntially clog the capillaries of these absorbent materials. This makes the design of appropriate absorbent sysc~tts for blood-based fluids such as menses particularly difficult.
In the case of catameaial pads, women have come to expect a high level of perforatanx in terms of comfort and 1n. reteatiau of fluid, and minima!
staining. Above all.
30 leakage of fluid from the pad onto undergarments is r~ardad as totally unacceptable.
Improving the performance of such catamatial pads continues to be a formidable undertaking, although a number of improvements have been made in both caramcniat strucdrres, and materials used in such swctura. However, etin>inating leakage, particularly along the inside of the thighs, without compromising fit and comfort, has not alw'avs met the 35 desired needs of the consumer.
The users of saattacy napkins, and the like. have also come to expect the surface of _2_ such products to provide a cleaner, more sanitary 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 the wearer of the product.

The absorbent structures of current catamenial (e.g., sanitary napkin) pads have . typically comprised 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 thin versions of prior catamenial 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 main absorbent core that is typically made from air-laid or wet-laid tissue. The absorbent core often contains a particulate 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 (Osborn), issued August 21, 1990 and U.S. patent 5,009,653 - (Osborn), issued April 23, 1991, that disclose tissue laminate cores used in sanitary napkin products.

Prior catamenial 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 main and secondary topsheet. The greater the disparity 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.

Prior catamenial absorbent structure's, and in particular catamenial pads using such structures, have also had a greater chance of causing panty and body soiling. 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 prior catamenial pads to provide poorer fit and comfort for the user.

An alternative to conventional catamenial absorbent structures are absorbent foams.

Absorbent foams can possess desirable wet integrity, can provide suitable fit throughout the entire period the article is worn, and can minimize changes in shape during use (e.g., uncontrolled swelling, bunching, etc.). In addition, catamenial products containing such foam _.

W O 96121682 PCTlUS96/00388 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 integrity and uniformity than conventional absorbent fibrous webs.
Such foams can also be prepared in any desired shape, or even formed into single-piece , 5 catamenial pad, or other absorbent article used to absorb blood or blood-base fluids such as tampons, wound dressings, bandages and surgical drapes.
Foams of various 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 4,110,276 (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 in catamenial products); U.S. Patent 3,903,232 (Wood et al.), issued September 2, 1975 (compressed hydrophilic polyurethane foams useful in biomedical applications, including catamenial devices); U. S. Patent 4,049,592 (Mayans et al.) issued September 20, 1977 (biodegradable hydrophilic polyurethane foams highly absorptive upon contact with liquids or bodily fluids having utility in sanitary napkins and the like). Prior foams used in these products have tended to have relatively large cell sizes.
As a result, these prior 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 catamenial 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 into 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 HIDE foams provide desirable fluid handling properties, including: (a) relatively good wicking and fluid distribution characteristics to transport fluid away from the initial impingement zone and into 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 thin until subsequently wetted by the absorbed body 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.
HIPS 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 l0 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 the presence of these salts.
Moreover, prior HIPE foams typically have a foam microstructure too small to admit readily the ur_dissolved 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) has a relatively high capacity for fluid to provide. efficiency in the utilization of costly components.
While thin catamenial products are desired by many users, 5 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 materials) as the absorbent core of a catamenial product that allows the use of inexpensive filler materials (e. g., airfelt) to provide bulk/thickness.
DISCLOSURE OF THE INVENTION
Various aspects of the invention are as follows:
A catamenial pad especially suitable for absorbing menstrual fluids, said pad comprising:
I) a fluid pervious topsheet;
II) a backsheet;
III) a volume filling material located adjacent said backsheet; and IV) an absorbent core positioned between said topsheet and said filling material and the fluid discharge region of the wearer of the pad, said absorbent core comprising an absorbent member made from a polymeric foam material which is capable of absorbing blood and blood-based fluids, said polymeric foam material comprising a hydrophilic, flexible, non-ionic polymeric foam structure of interconnected open cells, which 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;

-5a-B) a capillary specific surface area in the range of from about 0.0080 to about 0.040 m2/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 minutes;
D) a free absorbent capacity of from about 20 to about 125 g/g; and 10 E) less than about 2% residual hydratable salts.
A catamenial pad especially suitable for absorbing menstrual fluids, said pad comprising:
I) a fluid pervious topsheet;
II) a backsheet;
15 III) a filler material located adjacent said backsheet; and IV) an absorbent core positioned between said topsheet and said filler material, said absorbent core comprising a polymeric foam 2o material which is capable of absorbing blood and blood-based fluids, said polymeric foam material comprising a hydrophilic, flexible, non-ionic polymeric foam structure of interconnected open cells, which 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 m2/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% residual hydratable salts.

5b In an aspect of the present invention, there is provided 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, non-ionic polymeric foam structure of interconnected open-cells.
This foam structure has:
A) the ability to wick artificial menstrual 1o 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 m2/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 attribute of the foams is that the connecting passages (holes) between the cells of these foams are sufficiently large to pass insoluble solids such as erythrocytes (mean diameter 8 Vim). As a result, these holes do not become blocked or obstructed by blood and blood-based fluids absorbed by the foam.
Even though the cells and holes are large enough to allow free movement of insoluble components in blood and blood-based fluids, they are sufficiently small so as to 3o produce the necessary high capillary absorption pressure required of absorbents used in catamenial products. In other words, these foams combine high capillary absorption pressure with sufficient openness to allow 5c free movement of the insoluble components in blood and blood-based fluids such as menses. Typically, the cells of these foams have a number average cell size of from 20 to about 180 Vim, while the holes between these cells have a number average hole size of from about 4 to about 30 Vim.
In another aspect, there is provided a process for obtaining these absorbent foams by polymerizing a specific type of water-in-oil emulsion or HIPE having a 1o relatively small amount of an oil phase and a relatively greater amount of a water phase. This process comprising 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 comprising:
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 comprising 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, ii) from about l0 to about 40% by weight of at least one substantially water-insoluble monofunctional comonomer capable of imparting toughness about equivalent to that provided by styrene;

_6_ iii) from about 5 to about 25% by weight of a first substantially water-insoluble, polvfunctional crosslinking agent selected from divinyl benzenes, trivinyl benzenes, divinyl toluenesa , divinyl xylenes, divinyl naphthalenes divinyl alkylbenzenes, divinyl :.. ~ phenanthrenes, divinyl biphenyls, divinyl diphenylmethanes, divinyl benzyls, divinyl phenylethers, diviilyl diphenylsulfides, divinyl furans, divinyl sulfide, divinyl sulfone, and mixtures thereof; and a iv) from 0 to about 15% by weight of a second substantially water-insoluble, polyfunctional crosslinking agent selected from polyfunctiona.l acrylates, methacrylates, acrylamides, 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 comprising: (i) a primary emulsifier having at least about 40% by weight emulsifying components 'selected from diglycerol monoesters of linear unsaturated C 16-022 fatty acids, diglycerol monoesters of branched C 16-024 fatty acids, diglycerol monoaliphatic ethers of branched 016-024 ' alcohols, diglycerol monoaliphatic ethers of linear unsaturated C 16-022 alcohols, diglycerol monoaliphatic ethers of linear saturated C 12-014 alcohols, sorbitan monoesters of linear unsaturated C 16-022 fatty acids, sorbitan monoesters of branched C 16-024 fatty acids, and mixtures thereof or (ii) the combination a primary emulsifier having at least 20% by weight of these emulsifying -i, - components and certain secondary emulsifiers in a weight ratio of primary to secondary emulsifier of from about 50:1 to about 1:4; and 2) a water phase comprising an aqueous solution containing 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) polymerizing the monomer component in the oil phase of the water-in-oil emulsion to form a polymeric foam material;

C) washing the polymeric foam material to lower the level of residual electrolytes less than about 2%;
D) treating the washed foam with an effective amount of a suitable hydrophilizing surfactant; and .g.

E) dewatering the washed foam to a moisture content of about 40% or less.
In yet another aspect, there is provided a process for the preparation of an absorbent polymeric foam material capable of absorbing blood and blood-based fluids, which comprises the steps of:
A) forming a water-in-oil emulsion under from:
1) an oil phase comprising:
a) from about 85 to about 98% by weight of a monomer component capable of forming a copolymer having a Tg of about 50°C or lower, the monomer component comprising:
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;
ii) 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 by styrene;
iii) from about 5 to about 25% by weight of a first substantially water-insoluble, polyfunctional crosslinking agent selected from the group consisting of divinylbenzenes, trivinylbenzenes, divinyltoluenes, divinylxylenes, divinylnaphthalcnes divinylalkylbenzenes, divinylphenanthrenes, divinylbiphenyls, 7a divinyidiphenylmethanes, divinylbenzyls, divinylphenylethers, divinyidiphenylsulfides, divinylfurans, divinylsulfide, divinylsulfone, and mixtures thereof; and iv) from 0 to about I5% 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 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 comprising:
(i) a primary emulsifier having at least about 40% by weight emulsifying components selected from diglycerol monoesters of linear unsaturated C16-Czz fatty acids, diglycerol monoesters of branched C16-Cz4 fatty acids, diglycerol monoaliphatic ethers of branched C16-C24 alcohols, diglycerol monoaliphatic ethers of linear unsaturated C16-Czz alcohols, diglycerol monoaliphatic ethers of linear saturated Clz-C14 alcohols, sorbitan monoesters of linear unsaturated C16-C22 fatty acids, sorbitan monoesters of branched C16-Cz4 fatty acids, sorbitan monoesters of linear saturated Clo-C14 fatty acids, and mixtures thereof, or 7b (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-C2z dialiphatic, short chain C~-C4 dialiphatic quaternary ammonium salts, long chain Cla-C22 dialkoyl(alkenoyl)-2-hydroxyethyl, short chain C1-C4 dialiphatic quaternary ammonium salts, long chain C12-Czz dialiphatic imidazolinium quaternary ammonium salts, short chain C1-C4 dialiphatic, long chain C12-C22 monoaliphatic benzyl quaternary ammonium salts, and mixtures thereof; and 2) a water phase comprising 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; 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 about 2%;
D) treating the washed foam with an effective amount of a hydrophilizing surfactant;

E) dewatering the washed foam to a moisture content of about 40% or less.
This process 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 the level of these hydratable salts in the foam.
The present invention as indicated above relates to catamenial products containing one or more such foam materials as the absorbent core.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 of the drawings is a top-plan view of a catamenial product having HIPE foams of the present invention as absorbent menders.
Figure 2 of the drawings is a cross-sectional view taken along line 2-2 of Figure 1.
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 HIPS having a 50:1 water-to-oil weight ratio and poured at 74°C, and where the monomer component consisted of a 5:21:14:60 weight ratio of styrene (STY) :ethyl -~d-styrene (EtS):divinyl benzene (DVB):2-theylhexyl 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 materials) 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 (DVE3):2-ethylhexyl acrylate (EHA):1,6-hexanedioldiacrylate (HDDA), and where 8% (by weight of the 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.

a . ~ WO 96!21682 PCT/US96/00388 _g_ DETAILED DESCRIPTION OF THE INVENTION
I. Polymeric Absorbent Foams r A. General Foam Characteristics Polymeric 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 another within the foam structure, even though these fluids contain certain insoluble components. On the other hand, these cells and connecting passages are small enough to provide the 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 individual cells being defined by a plurality of mutually connected, three dimensionally branched webs. The strands of polymeric material 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 invention, a foam material is "open-celled" if at least 80% of the cells in the foam structure that are at least 1 ucn size are in fluid communication with at least one adjacent cell.
In addition to being open-celled, these polymeric 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 hydrophilizing surfactants left in the foam structure after polymerization, or by selected post-polymerization foam treatment procedures, as described hereafter.
' The polymeric foams useful in the present invention also have somewhat interrelated and interdependent structural and mechanical properties, features and/or characteristics. It - should be understood that these foams can have different properties, features and/or characteristics at different times prior to contact between the foam and the blood or blood based fluid to be absorbed. For example, during their manufacture, shipping, storage, etc., these foams can have density and/or cell size values outside the 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 invention if - they later undergo physical changes so that they have the requisite values specified hereafter - , 35 for these properties, features and/or characteristics at least some point prior to and/or during . , contact with the blood or blood based fluid to be absorbed.
n:a~::.4 W O 96121682 PCTlUS96/00388 The foams of the present invention may also be used in their collapsed state similar to the condition described in U.S. x,387,207 (Dyer et al.) issued Feb. 7.
1995. Such foams generally comprise those having finer microstructure (higher capillary specific surface areas) and which are relatively weak. These foams remain collapsed after washing, treating with wetting agents, and drying. Unlike the foams described within 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 the product prior to use.
When exposed to blood and blood-based fluids, these collapsed foams regain their original thickness and fluid capacities. These foams are also useful in distributing blood and blood-based fluids effectively from the point of insult since the fluid capillary pressure exerted by the unexpended regions of these foams exceeds that of the wetted, expanded area of the foam.
These materials generally serve well when positioned beneath a larger celled foam of the present invention which serves to acquire rapidly the blood and blood-based fluid. The properties of these collapsed foams stated herein are those of the foams in their expanded state unless otherwise noted.
B. Foam Characteristics Important to Absorbing and Transporting Blood and Blood-Based Fluids Vertical Wicking Capability Vertical wicking (i.e., fluid wicking in a direction opposite from gravitational forces) of a given amount of fluid within a set period of time is an especially important performance attribute for absorbent foams herein. The rate of fluid wicking through a porous structure is generally a function of the openness of the structure, the affinity of the fluid for the surface of the structure, and the viscosity of the fluid. This is conveniently measured as the time taken for a test fluid, i.e., Artificial Menstrual Fluid (AMF), in a reservoir to wick a vertical distance of 5 cm through a test strip of foam of specified size at 22°C. Such a vertical wicking test is described hereafter in the TEST METHODS section. To be especially useful in catamenial products for absorbing menses, the foam absorbents of the present invention vertically wick the AMF 5 cm in less than about 60 minutes. More preferably, the preferred foam absorbents of the present invention vertically wick AMF 5 cm in less than about 20 minutes, and most preferably in less than about 15 minutes.
The foam absorbents of the present invention will also preferably wick a high capacity of the test fluid to a particular height at equilibrium. 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 preferred foam absorbents w111 wick at least about 45 g/g of AMF to a height of about ~ cm. The procedure for measuring the ability to wick fluid to a particular height at equilibrium is described hereafter in the TEST

METHODS section.
2. Sanillaw Specific Surface Area "Capillary suction specific surface area" is a measure of the test-liquid-accessible surface area of the polvmenc network accessible to a test fluid. Capillary suction specific 5 surface area is determined both by the dimensioru of the cellular units in the foam and by the density of the polymer, and is thus a way of quantifying the total amount of solid surface provided by the 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 sectircs of U.S. Patent 5,387,207 (Dyer et to al.) issued Feb. 7, 1995, Crenerally, the surface area of the foam at a constant volume increases as the cellular swcdrrc become smaller celled ("finer"). Higher surface areas arc highly desirable in rapidly moving blood and blood-baxd fluids such as menses within the foam.
However, the surface arcs of the foam can reach the point that the rate of Said absorption becomes 15 limiting, as well as increasing the likelihood that insoluble corrrponeats within the fluid can an longer pass readily from aoe cell to another. Accordingly, the sur>Fxe area of the foam treads to be xlected within a particular range to balance these competing factors.
The polymeric foams of the present invention useful as absotbau nranbers in-catameaial products are those that have a capillary suction specific surface area in the range of from about 0.0080 to about 20 0.040 m2/cc. Typically, the capillary suction spocific surface arcs is is the range from about 0.010 to shout 0.030 m2/cc, preferably from about 0.012 to about 0.026 m2lcc.
For absorbent cores where two layer: of absorbent foam arc uxd, it is preferred that the upper foam layer (facing the body of the wearer) have a lo~w~a capillary suction specific sur>Faoe area, for exaarpk from about 0.012 to about 0.020 m2/crc, while the lower foam layer 25 has a higher capillary sucrion specific surface area, for example fiarr about 0.020 to about 0.026 m2/ee. 1a this way, the lower foam layer will have a higher fluid capillary Pressure, :!lowing it to drain fluid from the upper foam byet, thus keeping the body of the wearer relatively See 5onr contact with the fluid. (It follows that w6erc more than two form layers are anpkrysd, the capillary suction spocisc surface area of the rcspoctive foam.: preferably 30 will iocrea~e as the foams are located more remotely (i.e., lower in the absmbeat product) from the user.) 3. Resistance to Com~msion Deflection Aa important mxhaoical feature of the foams of the present invention are their stra>g~ as detsrmincd by resistance to compression deflection (RTCD). The RTCD
35 exhibited by the foams herein is a function of the polymer modulus, as well as the density sad strucdrre of the foam network. The polymer modulus is, in turn, determined by a)~ the WO 96/21682 PCTlL1S96/00388 polymer composition; b) the conditions under which the foam was polymerized (for example, the completeness of polymerization obtained, specifically with respect to crosslinking); and c) the extent to which the polymer is plasticized by residual materials, e.g., emulsifiers, left in the foam structure after processing.
To be useful as absorbent members in catamenials products, as well as other absorbent articles, the foams of the present invention must be suitably resistant to deformation or compression by forces encountered when such absorbent members are engaged in the absorption and retention of fluids. The RTCD exhibited by the polymeric foams of the present invention can be quantified by determining the amount of strain to produced in a sample of saturated foam held under a certain confining pressure for a specified period of time. The method for carrying out this particular type of test is described hereafter in the TEST METHODS section. Foams useful as absorbents members for catamenial products are those which exhibit a RTCD such that a confining pressure of 0.74 psi (5.1 kPa) produces a strain of typically from about 5 to about 95%
compression of the foam structure. Preferably the strain produced under such conditions will be in the 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 invention is their free absorbent capacity. For absorbent members useful in catamenial products, free absorbent capacity is the total amount of test fluid (i.e., synthetic urine) that a given foam sample will absorb at equilibrium into its cellular structure per unit mass of solid material in the sample. The foams that are especially useful as absorbent members in catamenial products will at least meet a minimum free absorbent capacity. The free absorbent capacity of the foams of the present invention can be determined using the procedure described 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 catamenial products, the foams of the present invention 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 urine per gram of dry foam.
C. Other Important Properties of Polymeric Foam 1. Cell and Hole Sizes A feature that can be useful in defining preferred polymeric foams is cell size. Foam cells, and especially cells that are formed by polymerizing a monomer-containing oil phase that surrounds relatively monomer-free water-phase droplets, will frequently be substantially spherical in shape. The size or "diameter" of such spherical cells is a commonly used WO 96!21682 PCT/US96/00388 - 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 the present invention. Since cell size contributes to capillary suction specific surface area that, together with foam hydrophilicity, determines the 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 the scanning electron photomicrograph of a foam sample.
Figure 3, for example, shows a typical HIPE foam structure according to the present invention.
Superimposed on the photomicrograph is a scale representing a dimension of 20 pm.
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 the number average cell size of the foam. The foams useful as absorbent members for catamenial products according to the - present invention will preferably have a number average cell size of from about 20 to about ' 180 lun; and typically from about 35 to about 130 Nm.

Another feature useful in defining these preferred foams is hole size. The holes are - the openings between adjacent cells that maintain fluid communication between these cells.

The foams of the present invention have hole sizes sufficiently large to allow passage of the __A . insoluble components of blood, especially the 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 the number average hole size of the foam.

The foams useful as absorbent members for catamenial products according to the present invention will preferably have a number average hole size of from about 4 to about 30 fun, 4 30 and preferably from about 10 to about 28 N,m. While foams having hole sizes larger than about 30 Eun will allow passage of blood cells, they will not have the fine microstructure necessary to provide the fluid capillary absorbent pressure of the 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 the foam, like capillary suction specific surface area, can influence a number of performance and mechanical characteristics such as WO 96!21682 PCT/US96/00388 the RTCD of absorbent foams. Importantly also, the density of the 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 catamenial products.
Any suitable gravimetric procedure that will provide a determination of mass of solid foam material per unit volume of foam structure can be used to measure foam density. An ASTM gravimetric procedure described more fully in the TEST METHODS section of U.S.
Patent 5,387,207 (Dyer et al.) issued Feb. 7, 1995 is the preferred method that can be employed for density determinations. Polymeric foams of the present invention useful as absorbent members for catamenial 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. Horizontal Gravimetric Wicking One of the primary benefits of the foams of the present invention is their ability to retain absorbed blood and blood-based fluids, even when subjected to compressive load. A
i5 foam of insufficient strength (RTCD) will express excess fluid readily during use. Under mechanical pressure from the wearer of the catamenial product, this mobile fluid can be pumped out of the absorbent core and upwards through the topsheet. As a result, the topsheet becomes" rewetted" with this pumped fluid such that there is not adequate topsheet dryness.
The ability of the foams of the present invention 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 Horizontal Gravimetric Wicking (HGW), the procedure for which is described hereafter in the Test Methods section. For the purposes of the present invention this HGW measurement is expressed as the percentage of the Retained Uptake of AMF, relative to the Initial Uptake of AMF, or "% Retained/Initial Uptake of AMF."
The foams of the present invention typically have a % Retained/Initial Uptake of AMF of at least about 50%, and preferably at least about 65%.
II. Polymeric Foam Barrier Layer - As indicated herein, many users of catamenial products prefer relatively thick pads.
With such pads, inexpensive filler materials, which may possess pore absorbent/~~et integrity - properties, may be preferred. However. when such materials are used, the resulting absorbent products may suffer from an aesthetic and/or performance standpoint.
Because the absorbent polymeric foams of the present invention provide high fluid acquisition/storage capabilities, such filler materials can be used without compromising performance. For example, keeping the filler material (e.g., airfelt) relatively free from liquid results in less -1.1_ bunching and/or roping in use. This results in better core and product integrity in use. To further facilitate maintanence of a relatively dry filler layer, in a preferred embodiment of the present invention a polymeric foam material (referred to herein as a "barrier layer") is used as the lowest layer of the absorbent core material. This optional barrier layer is useful in that it significantly limits passage of blood/fluid into optional materals (e.g., fillers such as air felt) below the absorbent foam core material.
To prevent fluid flow into filler material located immediately above the backsheet, the barrier layer preferably has an average cell size from about 15 to about 50 wm, preferably from about 25 to about 35 Nm; and an average hole size from about 4 to about 9 p,cn, preferably from about 5 to about 7 Nrn. These relatively small cell sizes tend to filter out the red blood cells in blood and blood based fluids, thus preventing passage of this color into - lower layers of filler material. The fluid which is admitted into the barrier 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, the barrier .. . 15 layer serves to prevent contamination of the air laid core with fluid which would cause the air laid core to change its dimensions and lose its integrity and/or be stained with the red color.
While the primary function of the barrier layer is to inhibit fluid (especially blood) flow to lower product layers, this foam material preferably possesses the ability to move fluid away from the wearer. Thus, it is preferred that barrier 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 invention having capillary specific surface areas as described in section I-b herein, it is preferred that the barrier 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 providing drainage away from the wearers body. The barrier layer's ability to acquire and - store fluid may allow for enhanced fluid retention by the article under circumstances where the absorbent foam materials (discussed above) have reached their capacity or where fluid is "squeezed out" of the foam layers overlying the barrier layer.
III. Preparation of Polymeric Foams From HIPE
t A. In General Polymeric foams according to the present invention can be prepared by polymerization of certain water-in-oil emulsions having a relatively high ratio of water phase , to oil phase commonly lrnown in the art as "HIPEs." Polymeric foam materials which result from the polymerization of such emulsions are referred to herein as "HIDE
foams."
The relative amounts of the water and oil phases used to form the HIPEs are, among many other parameters, important in determining the structural, mechanical and performance . i -> . .., W O 96(21682 PCTlUS96/00388 -i~-properties of the resulting polymeric foams. In particular, the ratio of water to oil (W:0) in the HIPEs varies inversely with ultimate foam density according to the equation:
Density = 1/(W:0 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 the foams of the present invention will generally have a volume to weight ratio of water phase to oil phase in 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 to The continuous oil phase of the HIPE comprises monomers that are polymerized to form the solid foam structure. This monomer component is formulated to be capable of forming a copolymer having a Tg of about 50°C or lower, and typically from about 15° to about 30°C. (The method for detennining Tg by Dynamic Mechanical Analysis-(DMA) is described hereafter in the TEST METHODS section.) This monomer component includes:
(a) at least one monofunctiona.l 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 agents) can be important to the realization of absorbent HIPE
foams having the desired combination of structure, mechanical, and fluid handling properties.
The monomer component comprises one or more monomers that tend to impart rubber-like properties to the resulting polymeric foam structure. Such monomers can produce high molecular weight (greater than 10,000) atactic amorphous polymers having Tg's of about 35°C or lower. Monomers of this type include, for example, the (C4-C 14) 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 (C6-C 16) alkyl methacrylates such as hexyl methacrylate, octyl methacrylate, nonyl methacrylate, decyl methacrylate, isodecyl methacrylate, dodecyl (lauryl) methacrylate, tetradecyl methacrylate;
acrylamides such as N-octadecyl acrylamide; (C4-C 12) alkyl styrenes such as p-n octylstyrene, isoprene, butadiene, and combinations of such monomers. Of these monomers, isodecyl acrylate, dodecyl acrylate and 2-ethylhexyl acrv_ late are the most preferred. The monofunctional monomers) will generally comprise 45 to about 70%, more preferably from WO 96!21682 PCT/ITS96/00388 about 50 to about 65%, by weight of the monomer component.
The monomer component utilized in the oil phase of the HIPEs also comprises one or more monofunctional comonomers capable of imparting toughness about equivalent to that provided by styrene to the resulting polymeric foam structure. Tougher polymers exhibit the ability to deform substantially without failure. These monofimctional comonomer types can include styrene-based comonomers (e.g., styrene and ethyl styrene) or other monomer types such as methyl methacrylate where the related homopolvmer is well known as exemplifying toughness. The preferred monofimctiona.l comonomer of this type is a styrene-based monomer with styrene and ethyl styrene being the most preferred monomers of this kind. The l0 monofimctional "toughening" comonomer will normally comprise 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 certain cases, the "toughening" comonomer can also impart the desired rubber-like properties to the resultant polymer. The (C4-C 12) alkyl styrenes, and in particular p-n octylstyrene, are examples of such comonomers. For such comonomers, the amount that can be included in the monomer component will be that of the typical monomer and comonomer combined.
The monomer component also contains a first (and optionally second) polvfimctional _ crosslinking agent. As with the monofiuictional monomers and comonomers, selection of the particular type and amount of crosslinking agents is very important to the eventual realization of preferred polymeric foams having the desired combination of structural, mechanical, and fluid-handling properties.
The first polyfimctiona.l crosslinking agent can be selected from a wide variety of polyvinyl aromatic and related polyvinyl materials such as divinylbenzenes, trivinylbenzenes, divinyltoluenes, divinylxylenes, divinyhiaphthalenes divinylalkylbenzenes, divinylphenanthrenes, divinylbiphenyls, divinyldiphenylinethanes, divinylbenzyls, ' divinylphenylethers, divinyldiphenylsulfides, divinylfurans, divinylsulfide, divinylsulfone, and mixtures thereof. Divinyl benzene is typically available as a mixture with ethyl styrene in proportions of about 55:45. These proportions can be modified so as to enrich the oil phase with one or the other component. Generally, it is advantageous to enrich the mixture with the _ ethyl styrene component while simultaneously reducing the amount of styrene in the monomer blend. The preferred ratio of divinyl 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 - 35 resulting copolymer to the degree that styrene does. This first crosslinking agent can generally be included in the oil phase of the HIPS in an amount of from about 8% to about 22%, more preferably from about 10% to about 18%, most preferably from about 12% to WO 96121682 PCT/US96/o0388 about 16%, by weight of the monomer component.
The optional second crosslinking agent can be selected from polyfunctional acrylates and methacrylates, acrylamides and methacrylamides. and mixtures thereof.
These include d1-, tri-, and tetra-acrylates, as well as d1-, tri-, and tetra-methacrylates; d1-, tri-, and tetra-- 5 acrylamides, as well as d1-, tri-, and tetra- methacrylamides; and mixtures of these crosslinking agents. Suitable acrylate and methacrylate crosslinking agents can be derived from diols, triols and tetraols that include 1,10-decanediol, 1,8-octanediol, 1,6-hexanediol, 1,4-butanediol, 1,3-butanediol, 1,4-but-2-enediol, ethylene glycol, diethylene glycol, trimethylolpropane, pentaerythritol, hydroquinone, catechol, resorcinol, triethylene glycol, l0 polyethylene glycol, sorbitol, and the like. (The acrylamide and methacrylamide crosslinking agents can be derived .from the equivalent diamines, triamines and tetramines). The preferred diols have at least 2, more preferably at least 4, most preferably 6, carbon atoms. This second cross-linking agent can generally be included in the oil phase of the HIDE in an amount of from 0 to about 15%, preferably from 0 to about 13%, by weight of the monomer 15 component.
Without being bound by theorv_ it is believed this second crosslinking agent generates ..______ ____a _____ _, ___,,~ _ _ _ a more homogeneously crosslinked structure that develops strength more e~ciently than using either the first or the second crosslinker alone at comparable levels.
The second crosslinker also has the effect of broadening the glass-to-rubber transition region. This 20 broader transition region can be tailored to meet specific strength and resilience requirements at in-use temperatures by controlling the relative amount of the two crosslinker types employed. Thus, a foam containing only the first type of crosslinker will exhibit a relatively narrow transition region. Increasing the amount of the second crosslinker serves to broaden the transition region, even if the actual transition temperature itself has not changed.
25 The major portion of the oil phase of the HIPEs will comprise the aforementioned monomers, comonomers and crosslinking agents. It is essential that these monomers, comonomers and crosslinking agents be substantially water-insoluble so that they are primarily soluble in the oil phase and not the water phase. Use of such substantially water-insoluble monomers ensures that HIPEs of appropriate characteristics and stability will be 30 realized. It is, of course, highly preferred that these monomers, comonomers and crosslinking agents be of the type such that the resulting polymeric foam is suitably non-toxic and appropriately 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-polymerization foam processing and/or use.
35 Another essential component of the oil phase is an emulsifier component that permits the formation of stable HIPEs. This emulsifier component comprises a primary emulsifier and optionally a secondary emulsifier. Especially when used alone, these primary emulsifer WO 96121682 pC1'/US96~00388 .18_ typically comprise at least about 40%, preferably at least about 70%.
emulsifying components selected from diglycerol monoesters of linear unsaturated C 16-C22 Vim' acids, diglycerol monoesters of branched C 16-C24 fatty acids, diglycerol monoaliphatic ethers of branched C 16-C24 .alcohols. diglycerol monoaliphatic ethers of linear unsaturated C 16-C22 5 alcohols, diglycero! monoafiphatic ethers of linear saturated C 12-C 14 alcohols, sorbitan monoesters of linear unsaturated C 16-C22 ~Y acl~~ sorbitan monoesters of branched C 16-C24 fatty acids, and mixtures thereof. Preferred primary emulsifiers include diglycerol monooleate (e.g., Preferably greater than about 40%, more prekrabty greater than about 50%, most preferably greater than about 70% diglyarol monooleaze), sorbitao monooleate 10 (e.g., preferably grater than about 40%, more preferably greater than about 50%, most preferably greater than about 70% sorbitan monooleate), sorbitaa monopatmitate, and diglycerol moooisostearate (e.g., preferably gs~ater than about 40%, more preferably grater rhea about 50°/., most preferably grater than about 70% diglycsrvl monoisostearate).
Diglycerol moooesters of linear uasat~rramd and branched fatty acids useful as 15 emulsifiers in the present invention can be prepared by aterifyiaig digiyeer~ol with fatty acids, using procedures well lmowo in the art. See, for example, the method for prepanag polyglyeerot esters disclosed in U.S. Patent 5,387,207 (Dyer a al.) issued Feb. 7, t995.
Diglycad as be obdi~ed commercially or can be separated from polyglyatols that arc high in diglycaoi. Liar, branched, and unsawrated faay acids can be obtained cammerciaUy.
20 'Ibe mixed ester product of the esteri5catioa raction can be fractionally distilled under vacuum one or hare times to yield distillation fractions that era high in diglycerol monoesters. For example, a A CMS-15A (C.V.C. Products Inc.: Rocha~er, N.Y.) c~tiouous l4 inch ~orifugai molecular still can be used for fractiaoal diswlation.
TYP~YY. ~' P~YHIY~ ~ ~ while being 6a8ed, is first nwtered through a 25 degas unit and rhea to the hated evaporator cone of the still, where the vacuum distillation taiaes pboe. Di:tilialoe is odkcted on the bell jar surface, which can be bated to facilitate distillate reanoval. Distillate-and residue are cooamrouaiy ranovod by transfer pumps. 'the forty acid oompositioo of the resultant mixed ester product can be determined using high rasolutian gas chrornatogtaphy. See U.S. Patent 5,387,207 (Dyer et al.) issued Feb. 7, 1995.
30 Polyglyard and potyglyaad ester distribution of the raulnat mixed ester product can be detetmitted by capillary supercritical chromatographY-Lioar sa~rat~ed. linear unsaturated, or branched diglyarol manoaliphatic ethers can also be prepared and their composition determined using procedures well lmown in the art .
See also U.S. Patent No. 5,500,451, issued March 19, 1996.

Sorbitaa monoacers of linear unsaturated and branched fatty acids can be obtaicsed corrunercially or prepared using methods Imown in the art. See, for example, U.S. Patent WO 96111682 ~ PCTIU59d100388 _19.
4.103,047 (Zaki et al), issued lulu 25. 1978, especially column 4. line 32 to column ~. line 13. The muted sorbitan ester product can be fractionally .vacuum distilled to yield compositions that are high in sorbitan mmtoaters.
Sorbitan ester compositions can be determined by methods well Imown in the art such as small molecule gel permeation chromatography. See U.S. Patent No. 5,500,451, issued March 19, 1996, which describes the use of this method for polyglycerol aliphatic ethers.
When these primary emulsifiers are used in combination with certain secondary emulsifiers, the primary emuisi5er can comprise lower levels of these emulsifying components, i.e.. as low as about 20% of these emulsifying components. 'Ibex secondary 10 emulsifiers are at least cosoluble with the primary emulsifier in the oil phase. Suitable secondary emulsifiers can be cationic types, including the long chain C!2-C22 ~~iP~tic, short chain C 1-C4 dialiphatic quaternary ammonium salts such as ditsllow dimetttyl ammonium chloride, bistridecyl dimethyl amm~ium chloride, and ditallow dimethyl ammonium methylsulfate. the long chain C 12-C22 dtalicoyl(alkenoyl~2-hYdt~oxyrthyl. short 15 chain C l-C4 dialiphatic quaternary ammonium salts such as ditallow~oyl-2-hydroxyethyl dimethyl ammonium chloride. the long chain C 12-C22 ~P~c ~damlinium quatetaary amrno~uittm salts such as methyl-1-tallow amido ethyl-2-tallow imidazolinium methylsulfate and methyl-l-oleyl amido ethyl-2-oleyl imidamlinium medtylsulfate, the short chain C 1-C4 dialipbatic. long chain C l2-C22 "'P~ beaayl quaternary anunooium salts such as 20 dimethyl stearyl bearyl ammonium chloride: anionic typo including the C6-Clg dialiphatic esters of sodium sulfosucciaic acid such as the dioctyl ester of sodium sulfosuccinie acid and the bist:idecvl ester of sodium sulfosucxiaic acid; and miamrres of these sxondary emulsi5as. These secondary emulsifiers can be obtained carurrercially or prepsrod using ntethoda laao~wn in the art. 7lte preferred secondary emulsifiers are ditallow ditnethyl 25 atttrrionium rt~ryt sulfate and ditallow ditnethyl ammonium methyl chloride. Whrn these optiaml se~ary anulsi5ers are includod in the emulsifier component, it is typically at a weight tstio of prirttary to scary emulsifier of from about 50:1 to about 1:4, preferably from about 30:1 to about 2: l .
'Ibe oil phase used to form the HIFF.s comprises from about 85 to about 98% by 30 weight monomer component and from about 2 to about 15% by weight anulsi5er component.
Preferably, the oil plisse will comprix from about 90 to about 97% by weight monomer catnpottertt acrd from about 3 to about 10% by weight emulsifies component.
The oil phase ~ ~ ~~ ~ options! components. One such optional component is as oil soluble poiyrrrerizanoa initiator of the gerxral type well Ioaown to those skilled in the art, such as 33 described in U.S. patent 5,290,820 (Bass et al), issued March 1. 1994, Another preferred optional component is as antioxidant such as a Hindered Amide Light Stabilizer (HALS) and Hindered Pheaolic Stabilizers (HPS) or arrv other WO 96!21682 PCT/US96/00388 antioxidant compatible with the initiator system to be employed. Other optional components include plasticizers. fillers, colorants, chain transfer agents, dissolved polymers. and the like.
2. Water Phase Components The discontinuous water internal phase of the HIPE is generally an aqueous solution containing one or more dissolved components. One essential dissolved component of the water phase is a water-soluble electrolyte. The dissolved electrolyte minimizes the tendency - of monomers, comonomers, and crosslinkers that are primarily oil soluble to also dissolve in the water phase. This, in turn, is believed to minimize the extent to which polymeric material fills the cell windows at the oil/water interfaces formed by the water phase droplets during polymerization. Thus, the presence of electrolyte and the resulting ionic strength of the water phase is believed to determine whether and to what degree the resulting preferred polymeric foams can be open-celled.
Any electrolyte capable of imparting ionic strength to the water phase can be used.
Preferred electrolytes are mono-, di-, or trivalent inorganic salts such as the water-soluble halides, e.g., chlorides, nitrates and sulfates of alkali metals and alkaline earth metals.
Examples include sodium chloride, calcium chloride, sodium sulfate and magnesium sulfate.
:' Calcium chloride is the most preferred for use in the present invention.
Generally the electrolyte will be utilized in the water phase of the HIPEs in a concentration in the range of from about 0.2 to about 20% by weight of the water phase. More preferably, the electrolyte will comprise from about 1 to about 10% by weight of the water phase.
The HIPEs will also typically contain a polymerization initiator. Such an initiator - component is generally added to the water phase of the HIPEs and can be any conventional water-soluble free radical initiator. These include peroxygeh compounds such as sodium, potassium and ammonium persulfates, hydrogen peroxide, sodium peracetate, sodium percarbonate and the like. Conventional redox initiator systems can also be used. Such . systems a,re formed by combining the foregoing peroxygen compounds with reducing agents such as sodium bisulfite, L-ascorbic acid or ferrous salts.
The initiator can be present at up to about 20 mole percent based on the total moles of polvmerizable monomers present in the oil phase. More preferably, the initiator is present in an amount of from about 0.001 to about 10 mole percent based on the total moles of polvmerizable monomers in the oil phase.
3. Hvdrophilizing Surfactants The polymer forming the HIPE foam structure will preferably be substantially free of polar functional groups. This means the polymeric foam will be relatively hydrophobic in character. To be useful as absorbents for blood and blood-based fluids such as menses, these foams generally require further treatment to render the foam relatively more hydrophilic.
-~~:y- -WO 96121682 PC'f/LS96~00388 Hydtophiliiation of the foam. ~f necessary. can generally be accomplished by treating the RIPE foam with a hvdrophiliung surfactant in a manner described more fully hereafter.
These hydrophiliang surfactants can be any material that enhances the water wettability of the polymeric foam surface. Suitable surfactants should be non-to~uc and non 5 imtating to mucus membranes. It should be soluble or dispersible in warm water.
Preferably, the hydrophilizing surfactant is a liquid at temperatures near ambient for ease of incorporation during the foam making process. Suitable surfactants include ethoxvlates of .*
C l 1'C 15 ~~hols, marketed by Shell Chtmica! Co., in particular NEODOL 25-12 (coadauation product of C 12-C l5 luxar alcohols with 12 moles of ethylene oxide).
to NEODOL*23-6.ST (condensation product of C12-C13 ~ alcohols '"nth 6_~ moles of ethylene oxide that has been distilled (topped) to remove certain impurities), and NEODOL*
23-3 (condensation product of C 12-C 13 ~ ~~ols ~"nth 3 mold of ethylene oxide);
ethoxylata of C 11-C IS ~5' acids sold under the PEGOSPERSE~*designation by Stepan Chemical Corp., Northfield, IL; condensation products of ethylene oxide and/or propylene 15 oxide having molectriar weights greater than about 2000. dad condensation products of propylene oxide and propylene glycol sold under the PLURONIC *daigaation by BASF
Parisspany, NJ; modified oxyethylatod straight chain alcohots sold under the Plurafac design by BASF. Corp., Panippatry, NI; sutfatod ako6ol ethoxylates and alkyl ether sulfates such as those sold by Hateos Chemicals, Kansas, KS., branched and linear alkyl aryl 2o ethoxylates such a Triton X-60, Triton X-100, Triton N-57, and the like marketed by Union Carbide, lac. Danbury, CT. silicone-glycol copolyrr>ers sold udder the SILWET
designation by OSI Speciaitia, Daobury, CT, as web as mixtures of these surlactaats.
Particularly *
preferred surfactants arc PEGOSPERSE 200 ML, as ethoxylatt of Laurie acid having an average of 4.5 etboxy units.
25 These h~ydrop6iliriog surfactaott can be dissolved or dispersed in a hydrophiliang solution that is applied to the HIDE foam surface. In this manner.
hydrophilizing surfactants cad be adsorbed by the preferrzd HIDE foams in amounts suitable for reoderirrg the surfaces tbaoo~f subs~ally hydrophilic, but without substantially bnpair>n8 the desired flexibility and compression deflection characteristics of the foam. In preferred foams, the 30 hydroQh~ixing surfaetaat is incorporated such that residual amounts of the surfactant that rarrain is the foarrr strucarre are typically in the range from about 0.05% to about 5%-preferably From about 0.5 to about 1 %, by weight of the foam.
B. ,~10CCSSL~Q Conditions for Obtaining HIPS Foams Foam preparation typically involves the steps of. l) forming a stable high internal 33 phase emulsion (HIDE): 2) poiymeri>'nglcuring this stable emulsimr under conditions suitable for forming a solid polymeric foam structure; 3) slicing or otherwise cutting the water-filled polymeric foam acrd then washing the sliced or cut foam to remove the original residual water * = TM

phase, and especially the residual hvdratabte salts, from the polymeric foam structure: 4) treating nhe polymeric foam structure with a hydrophilizing surfactant: and thereafter dewatering this polymeric foam structure.
Formation of HIDE
The HIDE is formed by combining the oil and water phase components in the previously specified weight ratios. The oi) phase will typically contain the requisite monomers, comonomers, crosslinkets, and emulsifiers, as welt as optional components such as solvents and polymerization initiators. The water phase will typically contain electrolytes, as well as optional components such as water-soluble emuLtifiers, and/or polymerization initiators.
The HIPS can be formed from the combined oil and water phases by subjecting these combined phasts to shear agitation. Shear agitation is generally applied to the extent and for a time period necessary to form a stable emulsion. Such a process can be conducted in either batchwix or continuous fashion and is generally carried out under conditions suitable for forming as emulsion where the water phase droplets are dispersed to such an extent that the resulting polymeric foam will have the requisite cell size and other structural characteristics.
Suitable mixing or agitation devices are those that src capable of forming an avulsion under conditions of low shear mixing. Emulsification of the oil and water phase combination will frequently involve the use of a mixing or agitation devicr such as a pin impeller.
Une preferred method of forming such HIPEs involves a continuous process that combines and emulsifies the requisite oil and water phases. In such a pr~oass.
a liquid scram comprising the oil phax is formed. Concurrently, a liquid stream comprising the water phase is also formed. The two streams arc then combined in a suitable mixing chamber or zone such that the requisite water to oil phase weight ration previously specified are achieved.
23 In the ndxing charrtber or zone, the combined sues are generally subjected to shear agi~an Provyded, for example, by a Pin impeller of suitable configuration and dimeasiotu.
Shear will typically be applied to the combined oillwater phase stream at at a rate of about 4000 sec'/ ~ less, Preferably about 3000 xc'1 or less. Once formed, the stable liquid RIPE
can then be withdrawn from the mixing chamber or zone. This preferred mahod for forming HIPEs via a continuous process is described in grtater derail in U.S. Patent 5.149.720 (DesMarais et al.), issued September 22, 1992. See also U.S. Patent No.
5,827,909, issued October 27, 1998, which describes an improved continuous process having a recirculation loop for the HIPE.
33 'Ihe degree of shear applied and/or the water to oil phase ratio during HIDE
formation need not be consmat throughout. For example. HIDE making can be carried out under "pulsed" cattditioas or varied rhythmically. This is especially useful wham the HIPS is collected in a rotating cylindrical container as successive layers to form foams having heterogeneous structures. Pulsed conditions can produce HIPEs comprising regions of larger and smaller celled foam in an alternating sequence. After curing and slicing as described hereafter, this can provide foams having the ability to control the direction of movement of r 5 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 the more robust emulsifier systems used in these HIPEs is that the mixing conditions 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. Polymerization/Curin~ 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 , the reaction vessel comprises a tub constructed of polyethylene from which the eventually polymerized/cured solid foam material can be easily removed for further processing after polvmerization/curing has been carried out to the extent desired. It is usually preferred that the temperature at which the HIPE is poured into the vessel be approximately the same as the polymerization/curing temperature.
Suitable polymerization/curing conditions will vary depending upon the monomer and other makeup of the oil and water phases of the emulsion (especially the emulsifier systems used), and the type and amounts of polymerization initiators used.
Frequently, however, suitable polymerization/curing conditions 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 polvmerization/curing in a reaction vessel, such as a tub. This polymerized HIPS foam is typically cut or sliced into a sheet-like form. Sheets of polymerized HIPS
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 thickness in the range of from about 0.08 to about 2.5 cm, preferably from about 0.15 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.

-2-t-3. Slicing and Washing HIPE Foam The solid polymerized HIPE foam formed will generally be filled with residual water phase material used to prepare the HIPS. This residual water phase material (generally an aqueous solution of electrolyte, residual emulsifier, and polymerization initiator) should be at least partially removed prior to further processing and use of the foam.
Removal of this original water phase material will usually be carried out after slicing the foam into sheets of from about 0.15 to about 0.4 cm in thickness. These sheets are dewatered by compressing the foam structure to squeeze out residual liquid and/or by washing the foam structure with water or other aqueous washing solutions. Frequently several compressing and washing - 10 steps, e.g., from 2 to 4 cycles, will be used.
The removal of most of the residual electrolyte (i.e., hydratable salts) from the foam is particularly important. As noted previously, these hydratable salts are typically included during initial formation of the HIPE to minimize the tendency of monomers, comonomers, and crosslinkers that are primarily oil soluble to also dissolve in the water phase. However, .: 15 after polymerization 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 the level of these hydratable salts in the foam as much as possible during this washing step. After washing, the foams of the present invention have less than about 2% of 20 such residual hydratable salts. Preferably, the foams of the present invention have less than about 0.5% of such residual salts.
4. Treatine with Hvdrophilizing Surfactant and Foam Dewaterin~
After the original water phase material has been removed to the extent required, the HIPE foam is typically treated with an effective amount of a suitable hydrophilizing _- 25 surfactant. Hydrophilizing surfactants that can be employed have been previously described and particularly include ethoxylates of C 11-C 15 fatty acids such as Pegosperse 200 ML, branched and linear alkyl aryl ethoxylates such as Triton X-100, and ethoxylates of C 11-C 15 aliphatic alcohols such as NEODOL 23-6.ST. Treatment of the HIDE foam with the ., hydrophilizing surfactant continues until the foam exhibits the desired degree of wettability.
30 After the HIDE foam has been hydrophilized, it will generally be dewatered.
Dewatering can be achieved by compressing the foam (preferably in the z-direction) to -,-. squeeze out residual water, by subjecting the foam and the water therein to temperatures of from about 60° to about 200°C, or to microwave treatment, by vacuum dewatering or by a combination of compression and thermal drving/microwave/vacuum dewatering techniques.
35 The dewatering step will generally be carried out until the HIDE 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 ~.~ v <i -2~-200%, by weight on a dry weight basis. Subsequently, the compressed foams can be thermally dried to a moisture content of about 40% or less, preferably in the range of from about ~ to about 15%, on a dry weight basis.
After the HIPE foam has been dewatered, it can be slitted in various patterns.
These include patterns that conform to the shape of the catamenial product in which the slitted foam is used as an absorbent member. Slitting can be especially desirable when the foam is intended to confer superior fit in a catamenial pad such as a sanitary napkin.
IV. Use of Polymeric Foams iri Catamenial Products The polymeric foams of the present invention are useful in a variety of absorbent articles for absorbing blood and blood-based fluids.
A. Catamenial Products The polymeric foams of the present invention are particularly useful as absorbent members in a variety of catamenial products such as catamenial pads. An embodiment of a catamenial pad or sanitary napkin 10 according to the present invention is shown in Figure 1.
As used herein, the term "sanitary napkin" refers to an absorbent article that is worn by females adjacent to the pudendal region, generally external to the urogenital region, and which is intended to absorb and contain menstrual fluids and other vaginal discharges from the wearer's body (e.g., blood, menses, and urine). Interlabial devices that reside partially within and partially external of the wearer's vestibule are also within the scope of the present invention. As used herein, the term "pudendal" refers to the externally visible female genitalia. It should be understood, however, that the present invention is also applicable to other feminine hygiene or catamenial pads such as pantiliners, or other catamenial products such as incontinence pads, tampons and the like.
The polymeric foams of the present invention are particularly useful in sheet form.
2S This relates to ease of manufacture and shipping as well as for general utility in the product.
The sheet or sheets used can be of any thickness desired according to the 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 of slit, either to further enhance the rate of fluid absorption by increasing the surface area of the foam exposed to the fluid or to increase the stretchability of the foam. Alternatively, these foams can be in the form of diced cubes, strands (e.g. spaghetti-like material), thin strips, and the like that can be assembled into absorbent cores of various shapes depending on the specific needs of the product.
As particularly.shown in Figure 2, catamenial 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 polymeric foams according to the present invention, and a fluid impervious backsheet 18. The fluid storage absorbent member 16 may also comprise a polymeric foam barrier layer of the present invention. The backsheet 18 and the topsheet 12 are positioned adjacent the garment surface and the body surface, respectively, of pad 10 and are preferably joined to each other. For example, the backsheet 18 and the topsheet 12 can be secured to each other by adhesive. Suitable adhesives tare manufactured by H. B. Fuller Company of St. Paul, Minnesota under the designation HL-1258 or H-2031. Alternatively, topsheet 12 and backsheet can be joined to each other 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 method for joining topsheet 12 and backsheet 18 together 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 narrow, and can extend a distance of - approximately 0.25 to 6 mm. and preferably is approximately 3 mm. wide.
However, the width of border 20 can be uniform or vary about the perimeter of pad 10.
Border 20 provides a fluid impermeable seal that surrounds perimeter 22. The seal is preferably formed by the simultaneous application of pressure, with or v~ithout heat, to melt topsheet 12 and backsheet 18, thereby forming border segment 20..
In addition to providing fluid acquisition benefits, the secondary topsheet 14 may enhance the integrity of the product by stabilizing the positioning (e.g., by reducing bunching) of the fluid strorage absorbent member 16. The secondary topsheet can include nonwoven or woven webs of synthetic fibers including polyester, polypropylene, or polyethylene; natural fibers including cotton or cellulose; blends of such fibers; or any equivalent materials or combinations of materials. Suitable secondary topsheets can also be made from mixtures of 2~ fibers with thermoplastic materials to form thermally bonded matrices.
These thermoplastic - materials can be in any of a variety of forms including particulates, fibers, or combinations of - particulates and fibers. Thermoplastic fibers are a particularly preferred form because of their ability to form numerous interfiber bond sites. Other alternatives for the secondary topsheet are the use of wood pulp surface-splayed with 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 thin plastic film, although other flexible liquid impervious materials may also be used.
As used herein, the term "flexible" refers to materials that are compliant and will readily conform to the general shape and contours of the human body. The backsheet 18 prevents the exudates absorbed and contained in the absorbent structure from wetting articles that contact the sanitary napkin 10 such as pants, pajamas and undergarments. The backsheet 18 can comprise a woven or nonwoven material, polymeric films such as thermoplastic films of WO 96121682 PtrTIL'S96/00388 .2;_ polyethylene or polypropylene. or composite materials such as a film-coated nonwoven material. Preferably. the backsheet is a polyethylene film having a thiclaress of from about 0.012 mm (0.5 mil) to about 0_0S 1 mm (2.0 mils). Exemplary polyethylene films are manufactured by Clopay Corporation of Cincinnati, Ohio. under the designation 5 and by Ethyl Corporation, Visqueen Division. of Terre Haute, Indiana. under the designation XP-39385. The backsheet is preferably embossed andlor 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 preventing exudat~es from passing through the backs6eet 18.
10 The topsheet 12 is compliant, soft feeling, and non-irritating to the wearer's skin.
Further, the topsheet 12 is fluid pervious permitting fluids (e.g., menxs) to readily penetrate through its thiclaxss. A suitable topsheet 12 can be manufactured from a wide range of materials such as woven and nonwovea materials; polymeric materials such as apertured formed thenmoplastic films, apertured plastic films. and hydrofonrred thermoplastic films:
t5 porous foams; reticulated foams; r~eticulatod thermoplastic films; and thermoplastic scrims.
Suitable woven sad nonwovea materials can be comprised of natural fibers (e.g., wood or cotton fibers), synthetic fibers (e.g., polymeric fibers such as polyester, polypropylene, or polyethylene fibers) or fran a combination of natural sad syrrtbetic fibers.
Prrfen~d topshoets for ux in the presort are xloctod firm high loft nonwoven 20 topshoets sad aperture formed film topsbeets. Aperturod forn>ed films are especially preferred for the topsheet bxaux they are pervious to body exudates and yet non-absorbent and have a reduced tendency to allow fluids to pass back through and rewet the wearer's skin.
Thus, the surface of the formed film that is in contact with the body remains dry, thereby reducing body soiling and creating a more comfortable feel for the wearer.
Suitable formed 25 films are described is U.S. Patent 3,929,135 ('Ihompson), issued Dexmber 30, 1975; U.S.
Patent 4,324,246 (MuUane, et al.), issued April 13, 1982; U.S. Patent 4,342,314 (Radel. et al.), issued August 3, 1982; U.S. Patent 4,463,045 (Ahr et al.), issued July 31, 1984; and U.S. 5,006,394 (Baud), issued April 9, 1991.
Particularly preferred microapetured formed film topsheets are disclosed in 30 U.S. patent 4,609,518 (Curro et al), issue Septanber 2, 1986 and U.S.
patsnt 4,629,643 (Curro et al), issued Dooember 16. 1986, which are incorporated by . The preferred topaheet for the prexat invention is the formed film described in one or more of the above patents sad rtrarlteted oo sanitary napkins by The Procter & Gamble Company of Cincinnati.
Ohio as "DRI-WEAVEt"'"
33 '1be body surface of the formed film topsheet carr be hydrophilic so as to help liquid to transfer through the topsheet Faster than if the body surface was not hydrophilic so as to diminish tire likelihood that menstrual fluid will flow off the topsheet rather than flowing into .og.
and being absorbed by the absorbent structure. In a preferred embodiment, surfactant is incorporated into the polymeric materials of the formed film topsheet such as is described in PCT Publication WO 93/09741, published May 27, 1993, "Absorbent Article Having a Nonwoven and Apertured Film Coversheet" by Aziz, et al. Alternatively, the body surface of 5 the topsheet can be made hydrophilic by treating it with a surfactant such as is described in the above referenced U.S. 4,950,254.
In a preferred embodiment. where a duck catamenial pad is dairerl. a filler maccrial can be positiocud between the fluid storage absorbent member 16 and the backsheet t 8.
to Useful filler materials, many of which are known is the art, include but are not limited to airfett (e.g., chemi-thermo-mechanical pulp, southern softwood crag recycled pulp), foams (c.g., polyurethane, cellulose, polystyrene), sawdust, paper wadding, recycled newspaper, etc.
Alternatively, the foam materials of the present invention coo lx cut in layers of sufficient thiclaness to provide increased product thickrxss, typically between about 1 and about 2 cm.
15 In ux, pad 10 can be fold in place by any support or attacbmeat device (not shown) well-knovvn for such purposes. Preferably, pad l0 is placed in the uses undergarma~t or panty and sxuted thereto 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 backsbeet 18 is coated with adhesive. Any adhesive or glue used in the art for 20 such purposes can be used for the adhesive herein, with pressure-sensitive adltaives being preferred. Suitable adhesives are Century A-305~fV manufactured by the Century Adhesives Corporation of Columbus, Ohio; and Instant Lock 34-2823 maaufacaued by the National Starch and Chanieai Company of Hridge~raLer, Nl. Suitable adhesive i~rs are also described is U.S. Patent 4,917,697. Before pad 10 is placed in ux, the pressure-sensitive 23 adhesive is typically covered with a removable release liner in order to keep the adhesive from drying out or adbai~og to a surface other than the crotch portion of the panty prior to use.
Suitable release liners are also described in the above-referenced U.S. Patent 4,917.697. Any coauna~eially available rekise liners corturmnly used for such purpoxs can be utilized heron. Non-limiting examples of suitable itlesx liners are BL30MG-A Silox El/0 and 30 8L30MG-A Silox 4P/0 both of which are manuby the Akrosil Corporation of Msaas6a, WI. The pad 10 is put in ux by removing the rtleax liner and thereafter placing the pad in a panty so that the adhesive contacts the panty. The adhesive maintains the pad 10 in its position within the panty during use.
The absorbent foams of the present invention are also useful as the upper 3s acquisitioddistributioo component in a "mufti-layer" absorbent core that additionally contains a lower fluid storagrJredistribuuon component, where the absorbent core is positioned bawxo the topsheet and backsheet to form the catamenial pad. For purposes of WO 961Z168Z - PCT/U596r00388 _og.
the present invention. an "upper" layer of a mufti-lever absorbent core is a layer that ~s relatively closer to the body of the wearer, e.g.. the layer closest to the topsheet. The term "lower" layer conversely means a layer of a mufti-layer absorbent core that is relatively further away from the body of the wearer, e.g., the layer closest to the backsheet. 'This lower 5 fluid storage/redistribution layer is typically positioned within the absorbent core so as to underlie the (upper) fluid acquisitionldistribution layer arid be in fluid communication therewith. This lower storagelrcdistribution layer can comprise a variey of fluid storageJrodistribution components including those containing absorbent gelling materials such as dixlosed in U.S. Patent 5.061,259 (Goldrnaa et. al), issued October 29, 1991. U.S. Patent 10 4,654,039 (Brands et al), issued March 31, 1987 (reissued April 19, 1988 as Re. 32.649), U.S. Patent 4,666,983 (Tsubakirrwto et al), issued May l9, 1987, and U.S.
Patent 4,625,001 (Tsubakimoto et al), issued November 25, 1986;
absorbent macroswctures made from these absorbent gelling materials such as those disclosed in U.S. Patent 5,102,597 (Roe et al), issued April 7, 1992, and U.S.
Patent 15 5,324,561 (Rezai et al), issued June 23, 1994;
and absorbent gelling materials laminated betw«n two tissue layers such as those dixlosed in U.S. Patmt 4,260,443 (Lindsay a al), issued April 7, 1981, U.S. Patent 4,467,012 (Pedersen et a!), issued August 21, 1984, U.S. Paroart 4,715,918 (hang), issued Daxmber 29, 1987, U.S. Patent 4,851,069 (Packard et al), issued July 25: 1989, U.S. Patent 4,950,264 20 (Osborn), issued August 21. 1990; U.S. Patent 4.994,037 (Berrrardin), issued February 19, 1991; U.S. Patsat 5,009,650 (Bernardin), issued April 23, 1991; U.S. Patent 5,009,653 (Osborn), issued Apri123, 1991; U.S. Patent 5,128,082 (Makoui), July 7, 1992:
U.S. Patent 5,149,335 (KeUenberger et al), issued Septsmber 22, 1992; a~ U.S. Patent 5,176,668 (Beraardia), issued January 5, 1993;
25 There is no particular criticality with respect to the positional relationship of the fluid acquiaitiooJdistribution foam component and the fluid storagrJredistribution component within thex mufti-layer absorbent cores so long as these components are in effective fluid communication with each other and so long as each oompooeut is large enough to effectively bold and/or transport the amount of aqueous body fluid that is expected to be dixharged into 30 the catameaial pad. The most preferred rclatiooship be~eea the fluid aoquiaitioddistribution foam component and the fluid storagelredistribution campo»t within the absorbent core is to place these carnpar~ats in a layered configuration. In such a tayerod con5guration, the fluid acquisitioddistribution foam component comprises as upper foam layer winch overlies a subjacent fluid storagdredisVibution component in the form of a lower layer.
It should be 35 understood that these two types of layers refer merely to the upper and lower zones of the absorbent core and ate not necessarily limited to single layer: or sheets.
Both the flmd acquisitioddistribution zone, e.g., upper layer, and the fluid stotagelredistribution zone,~e.g..

-j~-lower layer, can comprise several layers the requisite type. Thus, as used herein. the term "layer" includes the terms "layers" and "layered".
B. Bandages and Wound Dressings .
Absorbent foams of the present invention are also useful in bandages and dressings for wounds. These include articles ranging from simple bandaids to large surgical dressings .
and bandages. A bandage or dressing can simply comprise a topsheet, an absorbent foam of the present invention, and a fluid impervious backsheet optionally attached to adhesive strips in various shapes and sizes. The foams of the present invention are particularly good at absorbing fluids from suppurating wounds and preventing or reducing contact of the healing area with media that are conducive to microbiological growth. Potential wound healing benefits can be conferred by pretreating the absorbent foam with any of a wide variety of antimicrobial and/or antiseptic compounds well know to those skilled in the art.
C. Surgical Drapes Absorbent foams of the present invention are also useful in surgical drapes.
These are sheets of material that catch blood during surgical procedures. They typically comprise a thin layer of absorbent material, in this case the foam of the present invention, a fluid impervious backsheet, typically a 1-2 mil thick sheet of polyethylene. The polyethylene can optionally be treated with an adhesive to secure its placement in surgery. The foam of the present invention is particularly easy to form into such articles. Further, the inherent integrity of such foams prevents contamination of the area by loose materials such as might be found in traditional fiber-based absorbent structures. The absorbent properties are well .. suited to capturing splattered blood quickly and preventing its spread, e.g. to the floor thus -- producing a slipping hazard. Smaller sizes of these laminates may also be used as wipes for blood and blood based fluids.
V. Test Methods for Polymeric Foams A. Vertical Wickinu Capability 1. Preparation of Artificial Menstrual Fluid - Artificial Menstrual Fluid (AMF) is prepared by combining equal volumes of gastric mucin solution and fresh, sterile defibrinated sheep blood (Cleveland Scientific, American Biomedical, Bath, OIL. The gastric mucin solution is prepared by combining the following in the proportions and order shown:
- 450 mL of aqueous sodium dihydrogen phosphate (.138 wt.%) solution containing sodium chloride (0.85 wt.%) adjusted to pH 7.2~0.1;
- 7.5 mL potassium hydroxide aqueous solution;
- 31 g sterilized gastric mucin (ICN Biomedical Inc., Cleveland, OH); heated 2.5 - p;
:~ , .' WO 96!21682 PCTlUS961~~388 hours to completely dissolve the gastric mucin. The solution is allowed to cool to less than 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 within 7 days.
2. Sample Preparation Foam samples are cut into 2.54 cm width strips about 25 cm long. Two samples are cut for each material to be tested. The samples are sealed in plastic on the top and on both long sides using a T-Bar sealer (Mode( T-7, 115VAC, 65 W Harwil Company, Santa Monica, California). The 0.5 centimeter at the bottom of the material strip remains exposed.
The outside of the plastic is graduated with marks each centimeter along the length of the sample, starting at the bottom of the plastic (not the bottom of the sample).
3. Eauipment Preparation The AMF is stirred for 30 minutes at 22°C. Approximately 300 mL of the equilibrated AMF is poured into a 500 mL recrystallizing dish. The filled dish is stirred magnetically at low speed.
A cylindrical Plexiglas bar (30.5 cm cylindrical bar with at least two attached Plexiglas plates (25 cm x 0.5 cm x 3 cm) attached at the end with the spacing being adjustable) is clamped onto a ring stand. The clamp should tentatively be set approximately 18 - 20 inches above the base of the stand. Allow enough space between the Plexiglas plates on the end of the cylindrical bar is provided to fit the thiclrness of the samples to be tested.
4. Test Procedure The sealed top side of the sample is placed between two of the Plexiglas plates, and then the plates are tightened together until the sample is completely suspended. There should be enough room along the width of the plates to fit 2-3 samples without the samples touching.
T~ ...,+ .alit:+:~...,1 ..!.,to.. .. .. 1~0 ....oil +n ., ni4inn +~n cnmr~pe nna aching tha ntltar ~~ar a u~~, auuauwaaaa ~la(aIGJ rail UG liJG4 W ~JVJ1L1V11 111v ocuaalJaW V11V
waauau uaV Vuava. ~.......
suspending all samples, the bottom and top of the samples should all be level with respect to the Plexiglas plates and each other.
The stir plate and dish of AMF is placed directly underneath the suspended samples.
The samples are lowered such that 0.5 cm of each sample is submerged in the AMF. (The plastic covered portion of the samples should not be submerged., as fluid will tend to wick in the interfaces of the seal instead of within the sample). Adjustments to level the bar and samples are made, if necessary, so that each sample bottom is equally submerged in the AMF.
The absorbent foam samples are suspended in the stirred AMF to the bottom of the plastic. The time elapsed when the 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 leading edge. The midpoint of the 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 the vertical wicking value for the material. At the conclusion of the measurement, the sample is sectioned into 1 cm pieces and weighed to obtain (after subtraction of the weight of the sample) the capacity of the material at varying heights.
B. Horizontal Gravimetric Wickine Horizontal Gravimetric Wicking (HGW) is an absorbency test that measures the uptake of fluid by a 2.5 in by 7.5 in absorbent member or catamenial pad sample as a function of time. In this method, the sample is held upside down horizontally in a holder suspended from an electronic balance. A glass supply tube, containing the test fluid (in this case, AMF at 22°C) and connected to a fluid reservoir at zero hydrostatic head relative to the test sample, is allowed to contact the lower surface of the sample as a point source and the increase in 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 the sample to remain relatively constant over the entire sample area.
"Initial Uptake" is defined as the weight of AMF absorbed by the system after seconds. "Rewet" is subsequently measured on the absorbent member or catamenial pad to - , find out the amount of fluid that can be repeatedly blotted from the structure/pad with ' Whatrnan filter. paper at 0.25 psi ( 1.7 kPa) until the core will give up less than 0.5 g of AMF.
"Retained Uptake" is calculated as the difference between "Initial Uptake" and "Rewet".
C. Resistance to Compression Deflection (RTCD) Resistance to compression deflection can be quantified by measuring the amount of strain (% reduction in thickness) produced in a foam sample which has been saturated with synthetic urine, after a confining pressure of 0.74 psi (5.1 kPa) has been applied to the sample.
Jayco synthetic urine used in this method is prepared by dissolving a mixture of 2.0 g KCI, 2.0 g Na2S04, 0.85 g NH4H2P04, 0.15 g (NHq,)2HP04, 0.19 g CaCl2, and 0.23 g MgCl2 to 1.0 liters with distilled water. The salt mixture can be purchased from "
Endovations, Reading, Pa (cat No. JA-00131-000-01 ).
- 35 The foam samples, synthetic urine and equipment used to make measurements are all equilibrated to a temperature of 31°C. All measurements are also performed at this WO 96/21682 PCTlUS96/00388 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 in2 (6.~ cm2) circular surface area is cut out of the saturated, expanded sheet with a sharp circular die.
The cylindrical sample is soaked in synthetic urine at 31°C for a further 6 minutes.
The sample is then removed from the synthetic 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 with a foot having a circular surface area of at least 1 in2 (6.5 cm2) 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 (X1) is recorded. A force is then applied to the foot so that the saturated foam sample is subjected to a pressure of 0.74 psi (5.1 kPa) for 1~ 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: [(X1-X2)/X1]x100 = % reduction in thickness.
D. Free Absorbent Capacity Free absorbent capacity can be quantified by measuring the amount of synthetic urine absorbed in a foam sample which has been saturated with synthetic urine.
The foam samples and synthetic 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 synthetic urine. After 3 minutes, a cylinder having a 1.0 in2 (6.5 cm2) circular surface area is cut out of the saturated sheet with a sharp circular die. The cylindrical sample is soaked in synthetic 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 with a weighing pan having an area larger than that of the sample and with a resolution of 1 milligram or less can be employed. Examples of such balances are the Mettler PM 480 and Mettler PC

(Mettler Instrument Corp; Hightstown NJ).
After determining the weight of the wet foam sample (Ww), it is placed between fine plastic mesh screens on top of 4 disposable 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 disposable paper towels (4 on each side) and pressed with 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 dr~~
weight recorded (Wd).

WO 96/21682 PCT~'L'S96I00388 .;;_ 'The free absorbent capacy (FAC) is the wet weight (Ww). less the dry weight (Wd) divided by the dw weight (Wd). i.e-. FAC = [(Ww-Wd)/Wd]
E. Drnantic Mechanical Analysis (DMA) DMA is used to determine the Tgs of polymers including polymeric foams.
Samples 5 of the foams are sliced into blocks 3-5 mm in thicla~ess and washed 3-4 times in disz:lled water, expressing the fluid through 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 mr~
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 10 parameters used were as follows:
Temperature step from ca. 85°C to -40°C in steps of 2.5°C
Soak intervals betvveen temperature changes of 125-1.60 seconds Dynamic strain set at 0.1% to !.0% (usually 0.7%) I S Frequency set at 1.0 radians/seeond - Autotension set in static force tracking dynamic force mode with initial static force set at 5 g.
The glass transition temperature is taken as the maximum point of the loss tangent versus ZO temperature curve.
VI. SyeciSc Examples These examples illustrate the specific preparation of collapsed I~PE foams accor~diog the present invention.
is A) I~PE Prec~aration Anhydrous calcium chloride (36.32 kg) and potassium persutfate (567 g) are dissolved is 378 liters of water. This provides the water phase stream to be used in a continuous process for forming a HIDE emulsion.
To a monomer combination comprising 400 g styrene, 2900 g divinylba~zene (40%
30 divinylband 60% ethyl styr~e), and 4800 g 2,~thylbexylaerylate is added 480 g of high purity diglycerol monooleate and Tinuvin TM 765 [his( 1,2.2.5.5 pratart~hylPtperidinyl)sebacate] antioxidant (41 g).
This diglycerol mooooleate emulsifier is prepared following the general procedure for preparing polygiycerol esters described in U.S. Patent 5,387,207 (Dyer et al.) issued Feb. 7.
35 1995. A polyglycerol composition comprising approximately 97% or greater digfycerol and WO 96121682 PCTlUS96100388 -3 ~-3% or less triglycerol (Solvay Performance Chemicals; Greenwich, Corn) is esterified with fatty acids having a fatty acid composition comprising approximately 71% C
18:1, 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, using sodium hydroxide as a catalyst at about 225°C under conditions - 5 of mechanical agitation, nitrogen sparging, and gradually increasing vacuum, with subsequent phosphoric acid neutralization, cooling to about 85°C, and settling to reduce the level of unreacted polyglycerols. The polyglycerol ester reaction product is first fractionally distilled thraugh two CMS-15A centrifugal molecular stills connected in series to reduce the levels of unreacted polyglycerols and fatty acids and then redistilled through the stills to yield distillation fractions high in diglycerol monoesters. Typical conditions 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 in diglycerol monoesters are combined, yielding a reaction product (as determined by supercritical fluid chromatography) comprising approximately 50% diglycerol monooleate, 27% other diglycerol monoesters, 20% polyglycerols, and 3% other polyglycerol esters. After mixing, the reaction product is allowed to settle overnight. The supernatant is withdrawn and used in the oil phase as the emulsifier in forming 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 mixing apparatus. Thorough mixing of the combined streams in the dynamic mixing apparatus is achieved by means of a pin impeller. At this scale of operation, an appropriate pin impeller comprises a cylindrical 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 having 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 pin impeller is mounted in a cylindrical sleeve which forms the dynamic mixing apparatus, and the pins have a clearance of 0.8 mm from the walls of the cylindrical sleeve.
A spiral static mixer is mounted downstream from the dynamic mixing apparatus to provide back pressure in the dynamic mixer and to provide improved incorporation of components into the emulsion that is eventually formed. Such a static mixer is 14 inches (35.6 cm) long with a 0.5 inch (1.3 cm) outside diameter. The static mixer is a TAH
Industries Model 070-821, modified by cutting off 2.4 inches (6.1 cm).
r The combined mixing apparatus set-up is filled with oil phase and water phase at a ratio of 2 parts water to 1 part oil. The dynamic mixing apparatus is vented to allow air to escape while filling the apparatus completely. The flow rates during filling are 3.78 g/sec oil phase and 7.56 cc/sec water phase.
Once the apparatus set-up is filled, agitation is begun in the dynamic mixer, with the impeller turning at 800 RPM. The flow rate of the water phase is then steadily increased to a rate of 44.1 cc/sec in a time period of about 30 sec. and the oil phase flow rate is reduced to 1.25 g/sec over a time period of about 1 min. The back pressure created by the 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) Polvmerization/Curing of HIPE
The HIPE from the static mixer is collected in a round polypropylene tub, 17 in. (43 cm) in diameter and 7.5 in. (10 cm) high, with a concentric insert made of Celcon plastic. The insert is 5 in. ( 12.7 cm) in diameter at its base and 4.75 in ( 12 cm) in diameter at its top and is 6.75 in. ( 17.14 cm) high. The HIPS-containing tubs are kept in a room maintained at 65°C for 18 hours to cure and provide a polymeric HIPE foam.
C) Foam Washing and Dewatering The cured HIPE foam is removed from the tubs. The foam at this point has residual water phase (containing dissolved emulsifiers, electrolyte, initiator residues, and initiator) about 32-38 times (32-38X) the weight of polymerized monomers. The foam is sliced with a sharp reciprocating saw blade into sheets which are 0.15 inches (0.38 cm) in thickness.
These sheets are then subjected to compression in a series of 2 porous nip rolls equipped with vacuum which gradually reduces the residual water phase content of the foam to about 2 times (2X) the weight of the polymerized monomers. At this point, the sheets are then resaturated with a 1°!° solution of Pegosperse 200 ML in water at 60°C and are squeezed in a series of 3 porous nip rolls equipped with vacuum to a water phase content of about 4X. The CaCl2 content of the foam is below 2%.
The HIDE foam is then dried in air for about 16 hours. Such drying reduces the moisture content to about 4-10 % by weight of polymerized material.
Example 2: Preparation of Foams from HIPEs HIDE foams are prepared using various pour temperatures, cure times and temperatures, water to oil (W:0) ratios, and impeller mixer speeds. These foams and their properties are shown in Tables 1 and 2 below:
Table 1: Hole Sizes vs. Pour Temperature Example Pour Mixer W:O Cure Temp Cure Hole Temp Speed Ratio (C) Time Size (C) ( m) (~'S) ( ) 2a 65 800 45:1 65 16 11.8 2b 74 800 50:1 65 16 13.8 L - 2c 65 ~ 800 ~ 50:165 ~ 16 ~ 11.7 I ~

-v_:_.

WO 96(21682 PCT/LTS96/00388 2d 65 800 55:1 65 16 11.1 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:O RTCD FAC
Ratio la 45:1 32.3% 44.7 1b 50:1 55.7% 46.0 lc 50:1 57.0% 50.1 1d 55:1 64.9% 52.7 1e 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 the unwashed HIPE foam of Example 2b containing residual calcium chloride salt. The foam sample labeled "Washed" is the HIPE foam of Example 2b that has been washed to remove the salt and rehydrophilized with PEGOSPERSE 200 ML. The columns relating to "Wicking Rate"
show the time required to wick AMF to the indicated heights. The columns relating to "Capacity" show the amount of AMF wicked to that height after a period of 18 hours:
Table 3: Wicking Rate and Capacity at Equilibrium Height Wicking Rate Capacity Height Unwashed (min)Washed Unwashed (g/g)Washed (cm) ~~n) ( ) 1 8.3 .5 53.0 45.9 2 15.3 1.2 41.5 50.5 3 25.5 3.5 45.7 48.6 4 40.5 6.5 40.0 42.2 5 85 13 40.3 44.5 6 120 30 39.2 42.4 7 33.3 39.5 8 19.1 22.7 9 4.6 5.4 ' 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 5 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 the unwashed HIDE foam of Example 2b containing residual calcium chloride salt. The foam sample labeled "Washed" is the HIPE foam of Example 2b that has been washed to remove the salt and rehydrophilized with PEGOSPERSE 200 ML.:

10 Table 4: HGW
Foam Sample Initial UptakeRetained Uptake% Retained/Initial (g/g) (g/g) U take Unwashed 14 12 86%

I W~h~ 24 19 79%

Table _ 4 above shows that the presence calcium chloride in the foam inhibits the 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 the 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 corresponding differences in properties are shown in Table 5.
Table 5. Foam Capacity and Strength vs. W:0 Ratio Example W:O RTCD FAC
Ratio 3a 30:1 5.7% 29.8 36 40:1 22.5% 39.4 3c 40:1 12.0% 39.6 3d 50:1 59.2% 47.2 Example 4: Preparation of Barrier Layer from HIPEs A foam material useful as the optional barrier layer is prepared according to the general process described in Example 1. The only modifications needed to obtain the relatively smaller cell and hole sizes desired for the barrier layer are mixing at a temperature of 156°F and using a mixer speed of about 1300 RPM.
Example 5: Catamenial Pad Having A Foam Absorbent Member A piece of polymeric foam according to any of Examples 2a-2f is cut into a strip having a width 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 the topsheet in place of the apertured film. Preferably, a secondary topsheet is positioned between the foam absorbent member and the apettured topsheet.
Example 6: Catamenial Pad Having Two Foam Absorbent Members A piece of polymeric foam according to any of Examples 2a, 2b, 2c, or 2d is cut into a strip having a width of 6.4 cm, a length of 10 cm, and a thickness of 0.19 cm (volume = 12 cc). A second piece of polymeric foam according to Examples 1e or if is cut into a strip having a width of 6.4 cm, a length of 19 cm, and a thickness of 0.19 cm (volume 23 cc). The pieces are assembled as described in Example 5 into a catamenial pad with the upper layer (adjacent to the topsheet) being the smaller of the two pieces of foam.
Preferably the two foam pieces are lightly bonded together with any suitable bonding adhesive applied in specific points to maintain contact between the pieces without restricting fluid flow.
Example 7: Catamenial Pad Having a Barrier Layer A catamenial pad having an absorbent core comprising three absorbent foams of the present invention and a filler material between the foam absorbent core and the backsheet is prepared as follows. A piece of polymeric foam according to any of Examples 2a, 2b, 2c, or 2d is cut into a strip which will be the upper layer (adjacent the topsheet) of the absorbent core. A second piece of polymeric foam according to Examples 1e or if is cut into a strip that ~~ill be the middle layer of the absorbent core. A third piece of polymeric foam according to Example 4 is cut into a strip that will be the barrier layer (adjacent the filler material, which is optionally airfelt) of the absorbent core. This barrier layer will have a number average cell size of from about 15 to about 50 Eun and a number average hole size of from about 4 to about 9 Vim.
For a thick product, the filler material (e.g., airfelt) is located between the absorbent WO 96/21682 PCTlUS96/00388 core and the backsheet. The pieces are assembled as described in Example ~
into a catamenial pad. Preferably the three foam pieces are lightly bonded together with any suitable bonding adhesive applied in specific points to maintain contact between the pieces , without restricting fluid flow.
Example 8: Catamenial Pad Containing Foam and Absorbent Gelling_Material A piece of polymeric foam according to any of Examples 2a, 2b, 2c, or 2d is cut into a strip having a width of 6.4 cm, a length of 10 cm, and a thickness of 0.19 cm (volume = 12 cc). This is assembled over a web consisting of cellulosic fibers and absorbent gelling material or absorbent gelling material laminated between two layers of tissue.
Example 9. Bandage Having Foam Component.
Any of the foams of Example 2 can be cut into a piece 2.5 cm square and 0.2 cm thick. This piece of foam is attached to a fluid impermeable backsheet strip having a width of 2.8 cm and a length of 7 cm using an adhesive. The exposed edges of this strip are coated - with any suitable contact adhesive and cover with a release paper and packaged in a sanitary wrapper. Optionally, a fluid pervious topsheet such as DRI-WEAVE or a nonwoven can be attached on top of the foam.
Example 10. Surgical Drape Having Foam Component.
Any of the foams of Example 2 can be sliced into a piece 1 m square and 0.13 cm thick. This piece of foam is attached to a 1 m square fluid impermeable backsheet using any suitable adhesive. The opposing side of the backsheet can be treated with any suitable contact adhesive and covered with release paper so as to provide for stability in application to a particular area when in use.
Example 11. Tampon Having 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 process for the preparation of an absorbent polymeric foam material capable of absorbing blood and blood-based fluids, which comprises the steps of:
A) forming a water-in-oil emulsion under from:
1) an oil phase comprising:
a) from about 85 to about 98% by weight of a monomer component capable of forming a copolymer having a Tg of about 50°C
or lower, the monomer component comprising:
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;
ii) 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 by styrene;
iii) from about 5 to about 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, divinyidiphenylmethanes, divinylbenzyls, divinylphenylethers, divinyidiphenylsulfides, divinylfurans, divinylsulfide, divinylsulfone, and mixtures thereof; and iv) from 0 to about 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 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 comprising:
(i) a primary emulsifier having at least about 40% by weight emulsifying components selected from diglycerol monoesters of linear 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 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, sorbitan monoesters of linear saturated C10-C14 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 dialiphatic, short chain C1-C4 dialiphatic quaternary ammonium salts, long chain C12-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 monoaliphatic benzyl quaternary ammonium salts, and mixtures thereof; and 2) a water phase comprising 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; 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 about 2%;
D) treating the washed foam with an effective amount of a hydrophilizing surfactant;
E) dewatering the washed foam to a moisture content of about 40% or less.

2. The process of claim 1 wherein the polymeric foam of step B) is sliced into a sheet prior to step C).

3. The process of claim 1 wherein the polymeric foam material is dewatered in step E) to a moisture content of from about 5 to about 15%.

4. The process of claim 1 wherein the volume to weight ratio of water phase to oil phase is in the range of from about 40:1 to about 70:1.

5. The process of claim 1 wherein:
1) the oil phase comprises:
a) from about 90 to about 97% by weight of a monomer component capable of forming a copolymer having a Tg value from about 15° to about 30°C, said monomer component comprising:
i) from about 50 to about 65% by weight monomer selected from the group consisting of C4-C14 alkyl acrylates, aryl acrylates, C6-C16 alkyl methacrylates, acrylamides C4-C12 alkyl styrenes, and mixtures thereof;
ii) from about 15 to about 40% by weight comonomer selected from the group consisting of styrene, ethyl styrene and mixtures thereof; and iii) from about 12 to about 18% by weight divinyl benzene; and b) from about 3 to about 10% by weight of said emulsifier component;
and 2) the water phase comprises from about 1 to about 10% calcium chloride.

6. The process of claim 1 wherein 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, p-n-octylstyrene, and mixtures thereof.

7. The process of claim 5 wherein the emulsifier component comprises a primary emulsifier having at least about 70% by weight emulsifying components selected from the group consisting of diglycerol monooleate, sorbitan monooleate, diglycerol monoisostearate, sorbitan palinitate, sorbitan myristate, sorbitan laurate, and mixtures thereof.

8. The process of claim 1 wherein the hydrophilizing surfactant is selected from the group consisting of ethoxylates of C11-C15 alcohols; ethoxylates of C11-C15 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.

9. The process of claim 8 wherein from about 0.05 to about 5% of the hydrophilizing surfactant remains in the foam material after step D).