CA2226408C - Foams made from high internal phase emulsions useful as absorbent members for catamenial pads - Google Patents

Abstract

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

Description

FDAMS MADE FROM HIGH INTERNAL PHASE EMULSIONS USEFtI AS
ABSORBENT MEMBERS FOR CATAMENLAL PADS
s to TLis application relates to flexible. microporous, open-celled polymeric foam materials made 5rarn high internal phase emulsions that can absorb blood and blood-based fluids such as menses. This application particularly relates to absorbent foam materials that is are useful as absorbent members for catameaial pads, tampons, , bandages wound dressings, surgical drapes and the h7ce.
The development of highly absorbent articles for blood and blood-based fluids such as catameniaJ-pads (e.g., sanitary napkins), tarnporu, wound dressings, bandages and surgical 20 drapes can be challenging. Corr>pared to water and urine, blood and blood based fluids such as menses are relatively complex mixtures of dissolved and uadissolvod components (e.g., erythrocytes or red blood cells). In particular, blood-bsiad fluids such as messes arc much more viaca~ than water and urine. This higher viscosity hampers the ability of conventional alraorb~t materials to efficieady sad rapidly transport these blood-based fluids to regions 25 remote ftorn the point of initial discharge. Undissolved elements in these blood-bzsed fluids as also poo~alty clog the capillaries of these absorbent rrrataials. This makes tlu design of appropriate absorbent systems for blood-based fluids such as meow particularly difficult.
In the cax of catamenia! pads, women have came to expect a high level of performance in terms of Comfort and 5t, retention of fluid, and minimal seining. Above all.
3o leakage of fluid from the pad onto undergarrrrents is rqgarded a totally unacceptable.
Improving the perfvrnrance of such catamenial pads dues to be a formidable undertaking, although a number of improvements have been made in both catamenial struedrres, and materials used in such swctures. However, eliminating leakage.
particularly along the inside of the thighs, without compromising 6t and comfort. has not always met the 35 desired ands of the consumer.
The users of sanitary napkins, and the like. have also come to expect the surface of .I.
such produce to provide a cleaner. more sannaw and deer aspect than common cloth or nonwoven materials have historicallv_ provided. Current sanitan~ napkin products are ripically provided with nonwoven or formed-film permeable topsheets that are designed to move discharged menstrual fluids rapidly through and into an underlying absorbent structure.
5 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 10 structures for relatively thin versions of prior catameaial 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 tops6at is the main absorbent core that is typically made from air-laid or wet-laid tissue. The absorbent core often contains a 15 particulate absorbent gelling material that can be wed or enveloped within this tissue.
Such encased or enveloped cons are often rcferned 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 cons used in sanitary napkin products.
2o Prior catameaial absorbent structure made from fibrous layers have a number of problems. One is the di~culty in ensuring adequate topsheet dryness. 1n particular, the acquired matstrual fluid can pot~ially leak back through the main topsheet.
This phenomenon is oRea 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 2s se~ary topaz, 'I~ ~ the di sparity in fluid capillary Pressure brtwxrt core and topabea elane~, the greater the potential for providing a dry topshat surface in contact ~ ~ b°d5'~ ~ Pte. however, can only be realized if the kinetics of fluid movement throughout the core is sufficiently fast.
Prior casanteaial absorbent structures, and in particular catameaial pads using such 30 structure. 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 tack of resilieaa, and consequent bunching, has also caused these prior catameaial pads to provide poorer fit and comfort for the user.
Act alternative to conventional catameaial absorbent structures are absorbent foams.
35 Absorbent foams can possess desirable wet integrity, can Provide suitable fit throughout the entire period the article is worn, and can minimize chaoga in shape during ux (e.g., uncontrolled swelling, bunching, etc.). In addition. cammeniai products containing such foam structures'can be easier to manufacture on a commercial scale. For example.
absorbent cores can simply be stamped out from continuous foam sheets and can be designed to have considerably greater 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 absorbers article used to absorb blood or blood-base fluids such as tampons, wound dressings, bandages and surgical drapes.
Foams of various types have bees suggested for ux in tampons, sanitary napkins and other articles that absorb blood and blood-bayed fluids. See for example U.S.
Patent 4,110.276 (DesMacais), issued August 29, 1978 (soft; flexible, open celled foams made from 10 polyurethanes, cellulose, or sty~ene/butadiene rubber that can be used is tampons and sanitary pads); U.S. Patent 4,752,349 (Gebel), issued June 21, 1988 (foams of "medium cell size" hydrophilized by surfactant treatment ark having a density within the range of 0.1 to 0.8 glee); U.S. Patent 4,613.543 (Dabs), issued September 28, 1986 (hydrophilic cxUular polymers used in catarneaial products); U.S. Patent 3,903,232 (Wood et al.), issued 15 September 2, 1975 (ccxnprased hydrophilic polyurethane foams useful in biomedical aPPh~~, ~lud~8 devices): U. S. Pate:u 4,049,592 (Merest et al.) issued September 20, 1977 (biodegradable hydrophilic polyu~ i~ 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 all size. As a result, these 20 prior foams do not exert su~cieat fluid capillary pressure for blood and blood-baxd fluids to acquire discharged metutrval fluids quickly from and through the tops6at of catamenial products such a sanitary napkins. 'Iris results is undesirable cawet since the surface is immediate contact with the body retains some of the fluid that is not absorbed into the core and is availsbk to be transferred back onto the body of the wearer.
25 Suitable absorbent foams for absorbent products have also been made from high I~ P~ i~ to as "HIDE"). See, for example, U.S. Patent 5,260,345 (De~Ma:ais et al), issued November 9, 1993 and U.S. Patent 5,268,224 (DaMarais et al), issued Decanter 7, 1993. Tbex absorbent HIDE fosrns provide desirable fluid handling properties, including: (a) relatively good wiclang and fluid distribution 30 characteristics to transport fluid away from the initial impingerrrent zone and into the unused balance of the foam strucNre 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 coarpressive forces. Tbese HIPS absorbent foams are also su$rciently flexible and soft so as to provide a high degrte of comfort to the wearer of the absorbent article: some of 35 thex 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 ei al), issued June 7, 1994, which disclox absorbent cores havurg 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 storagelredistribution component that is a HIPS-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 rewet.
However, it has been found that the residual hydratable salts such as calcium chloride typically present in prior HIDE 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 HIDE foams typically have a foam microstructure too small to admit readily the undissolved components of blood and blood-based fluids such as red blood cells.
Accordingly, it would be desirable to be able to make an open-celled absorbent polymeric foam material, in particular an absorbent HIPS foam, that: (1) can rapidly absorb blood and blood-based fluids such as menses; (2) can be usod as absorbent members for relatively thin catamenial pads (e.g., sanitary napkins) and other catamenial products such as ~p~~ ~ ~ll ~. ~,ound dressings; bandages, surgical drapes and the like; (3) allow storage components having high~c papillary :r osmotic absorption pressures to partition away this-fluid: (4) keep-the source of the Mood-based fluids relatively free of mwet, even in "gush"
situations and under compressive load; (5) are soft, flexible, resilient, and comfortable to the wearer of the absorbent article, and (6) have a relatively high capacity for fluid to provide efficient in their utilization of costly components.
While thin casarneaial products are desired by many users, there is significant demand for relatively thick products. For example, a thick product may provide a perceived ability to better absorb and retain fluid. Also, a thick product may offer improved fit. It would therefore be desirable to have a relatively thin absorbent foam materials) as the absorbent core of a catamenial product that allows the use of inexpensive filler materials (e.g., airfelt) to provide bulk/thickness.
3o DISCLOSURE OF THE INVENTION
The present invention relates to polymeric foam materials that are capable of absorbing blood and blood-based fluids such as menses and then moving these absorbed fluids e»ciently to other regions of the foam. These absorbent polymeric foam materials comprise a hydrophilic, flexible, cionionic polymeric foam structure of interconnected open-cells. This foam structure has:
A) the ability to wick artificial menstrual fluid (AMF) vertically to a height of p cm in _j_ 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 hvdratable salts.
A particularly important attribute of the foams of the present invention is that the connecting passages (holes) between the cells of these foams are sufficiently large to pass to insoluble solids such as erythrocytes (mean diameter 8 pcn). 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 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 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 about 20 to about 180 Vim, while the holes between these cells have a number average hole size of from about 4 to about 30 Eun.
The present invention further relates to a process for obtaining these absorbent foams by polymerizing a specific type of water-in~il emulsion or HIPS having a relatively small amount of an oil phase and a relatively greater amount of a water phase. This process comprises the steps of A) forming a water-in-oil emulsion at a temperature of about 50°C or higher and under low shear mixing from:
1) an oil phase comprising:
a) finm 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 monofunctionat comonomer capable of imparting toughness about equivalent to that provided by' styrene;

iii) from about ~ to about 25% by weight of a first substannallv water-uuoluble, pohfunctional crosslinking agem selected from divinyl bertzenes. tnvinyl benzenes. divinyl toluenes, divine l xylenes. divinyl naphthaleaes divinyl alkylbenzenes, divuwl phenanthrenes, divinyl biphenyls. divinyl diphenvUnethanes.
divinyl beazyls, divinyl phenylethers, divinyl diphenylsulfides, divinyl furacu. diviny) sulfide, divinyl sulfone, and mixtures thereof and iv) from 0 to about 15% by weight of a second substantially water-10 insoluble, polyfunctional croSSlia~
8 agent selected from polvfunctional acrylates, methacryiates, actylamides.
methacrytamides, and mixtures thereof. aad b) from about 2 to about 15% by weight of as emulsifier component which is soluble in the oil phase aad w bich is suitable for fornung a 15 stable water-in~il emulsion, the emulsion component ccu:iprisiag: (;) a prirrrary emulsifier having at least about 40% by weight emulsifying ~po~ selected from diglyctrol monoesters of linear unsaturated C ! 6-C22 ~Y acids, dtglycerol monoaters of branched C 16-C24 fatty acids, diglyceml moooaliphatic ethers of braac6ed C 16-C24 20 alcobols, diglycxrol moDOaiiphatic ethers of linear unsaturated C 16 C22 alco6ols, diglycerol moooalipbatic ethers of linear saturated C 12'C 14 ~~ls, sorbima moooesters of linear unsawrated C 16 C22 fauy acids, sorbitaa monoGSters of branched C 16-C24 ~' ~, a~ ~~s thereof, or (ii) the combination a primary emulsifier having at least 20% by weight of these emulsifying ~P°°~ ~d certata secondary emulsifiers in a weight ratio of PAY to sa~ndary emulsifier of from about 50:1 to about 1:4; and 2) a water phase comprising as aqueous solution containing from about 0.2 to about 20% by weight of a water-soluble electrolyte;
30 3) a volume to weight ratio of water phase to oil phase is the range of from about 20:1 to about 125:1;
PolYnre~g the monomer component in the oil phase of the water-in~il emulsion to form a polymeric foam material:
C) ~"~8 ~ polymeric foam material to lower the' level of residual 35 electrolytes less than about 2%;
) ~ washed foam with an effective amount of a suitable hY~p~ng surhaaat; and _7_ E) dewatering the washed foam to a moisture content of about 40% or less.
The process of the present invention allows these absorbent foams to have cells and holes small enough to provide a high capillary absorptive pressure but large enough to prevent or minimize blockage by the insoluble components of these fluids. In addition, this process removes most of the residual electrolytes (i.e., hydratable salts) from the foam.
While these hydratable salts are typically needed during initial formation of the HIPE, their presence in the resulting foam can adversely affect its ability to absorb blood and blood-based fluids such as menses, especially as the concentration of these salts in the foam to increases. Accordingly, it is desirable to reduce the level of these hydratable salts in the foam.
The present invention also relates to catamenial products containing one or more foam materials of the present invention as the absorbent core.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 of the drawings is a top-plan view of a catamenial product having HIPE
foams of the present invention as absorbent members.
Figure 2 of the drawings is a cross-sectional view take along line 2-2 of Figure 2.
Figure 3 of the drawings is a photomicrograph (250 X magnification) of a section of a representative absorbent polymeric foam according to the present invention made from HIPE having a 50:1 water-to-oil weight ratio and poured at 74°C, and where the monomer component consisted of a 5:21:14:60 weight ratio of styrene (S'I'~:ethyl styrene (EtS):divinyl benzene (DVB):2-e~thylhexyl acrylate (EHA), and where 5.5% (by weight of the oil phase) of diglycerol monooleaxe (DGMO) and 1 % of disallow dimethyl ammonium methylsulfate emulsifiers are usod.
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 HIDE having a 62.4:1 water-to-oil weight ratio and poured at 156°F and 1300 RPM, where the monomer component consisted of a 19:14:55:12 weight ratio of ethyl styrene (EtS):divinyl benzene (DVB):2~thylhexyl acrylate (EHA):1,6-hexanedioldiacrylate (HDDA), and where 8% (by weight of the oil phase) of sorbitan mvristate 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.

_g.
DETAILED DESCRIPTION OF'rf.~ (ll~rE~,~fION
I. -PoIvTnenc Absorbent Foams A. General Foam Characteristics Polymeric foams according to the praent invention useful in absorbent articles and 5 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-cellod foam structures have intercellular openings or "windows" (holes) that provide passagtways large enough to permit free and ready movement of blood and blood basod fluids such as menses from one cell to another within the foam structure, even l0 though these fluids contain certain insoluble components. On the other hand, these cells and connecting Passages are small enough to provide t>~ necessary high caprllary absorption pressure (i.e., capillary specific surface area per volume) to effectively move these fluids throughout the foam.
'I~se substantially open-celled foam structura will generally have a reticulated 15 character with the individual cells being de5ned by a plurality of mutually connoted, three dimensionally branched webs. The strands of polymeric material making up these branched WCbs Can be t~fCfrOd t0 aS "SWLR.~ ~pEn~ellCa lITdIIiS h3VUlg 8 typIC81 SVUt-typC SWCtufe are shown by way of example in the photomicrograph shown Figures 3. For purposes of the present invention, a foam material is ~,"opea~elled" if at least 80% of the cells in the foam 2o structure that are at least 1 Eurt size are in fluid carrtmuairation 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-bayed fluids. The internal surfaces of the foam structures are r~ered hydrophilic by residual hvdrophilizing surfa~ats IeR is the foam strucdrre aRer polymairation, or by selected post-polymeriration ZS foam treattrtent procedures, as described het'eafter.
'The polymeric foams useful in the present invention also have so<rxwhat interrelated and iaterdepeadeat struuural and mxhanical properties, features andJor characteristics. It should be understood that these foams can have different properties, features and/or characteristics at difl~t times prior to contact baweea the foam and the blood or blood 30 based fluid to be absorbed. For example, during their manufacdire, shipping, storage, etc., these foams can have density andlor cell size values outside the ranges set forth hereafter for these parameters. for example if they are storod in a collapsed state or are compressed by packaging. However, such foams are nevertheless still within the scope of this invention if ~~5' ~ ~dm8o 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.

.g_ 'Ihe foams of the presenmnvennon may also be used m rhea collapsed state surular to the condition described in U.S. 5.387.207 (Dver 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 5 wetting agents. and drying. Unlike the foams described within U.S.
5.387,207. the present foams may be reexpanded by application of modest amounu 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 gad blood-based fluids, these collapsed foams regain their original thickness and fluid capacities. These foams are also useful in distributing blood and blood-l0 basod fluids effectively from the point of insult since the fluid capillary pressure exerted by the unexpended regions of these foams excads that of the wettod, expaadod area of the foam.
These materials generally serve well whey positioned be~ih 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 arc those of the foams in their expaadod 15 state unless otherwise noted.
B. Foam Characteristics Imnortaat to Absorbing and Traasnorang Blood and Blood-Based Fluids 1. Vertical Wickin~~~
Vertical wicking (i.e., fluid wicking in a direction opposite from gravitational forces) 20 of a given of fluid within a set period of time is as especially important performance attribute for absorbent foams herein. The rate of fluid wicking through a porous structure is generally a fimcriao of the openness of the structure, the affinity of the fluid for the surface of the structure, gad the viscosity of the fluid. This is conveniently measured as the time taken for a test fluid, i.e., Artificial Menstrual Fluid (Ally, in a reservoir to wick a vertical 25 distance of 5 an through a test strip of foam of specified size at 22°C. Such a vertical wiclang test is described 6eraRer in the TEST METHODS suction. To be especially useful is catameaial products for absorbing menses, the foam absorbents of the present invention vertically wick the AMF 5 cm in less than about 60 mimrtes. More preferably, the preferred foam absorbents of the praeat invention vertically wick AMF 5 cm is less than about 20 30 minutes, gad most preferably in less than about 15 minutes.
The foam absorbents of the present invention will also preferably pick a high capacity of the test fluid to a particular height at equilibrium. Preferably, these foams will wick at least about 30 glg AMF (g of AMF/g dry foam) to a height of about ~
cm. more preferably at !cart about 40 g/g of AMF. Particulariy prefrrred foam absorbents will wick at 35 least about 45 g/g of AMF to a height of about 5 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. Capillan~ 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 specsfic 5 surface area is determined both by the dimensions of the cellular uniu 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 pu:poses of the present invention, capillary suction specific surface area is determined by the method is set forth in the TEST METHODS section of U.S. Parrnr 5,387,207 (Dyer et 10 al.) issued Feb. 7. 1995, Generally, the surface area of the foam at a constant volume uicrrases as the cellular structure becomes smaller cellod ("finer"). Higher surface arms are highly desirable in rapidly moving blood and blood-baxd fluids such as menses within the foam.
However, the surface area of the foam can reach the point that the rate of fluid absorption becomes 15 limiting, as well as increasing the likelihood that insoluble components within the fluid can no longer pass readily from ooe all to another. Acoordiagly, the sur>>ace area of the foam creeds to be xlected within a particular range to balance tbex ootnpetiag factors.
The polymeric foams of the present invention uxful as absorbent manbers iw catameaial products arz those that have a capillary suction spoci5c surfa~x arcs in the range of from about 0.0080 to about 20 0.040 rr>Zlcc. Typically, the capillary suction specific surface area is in the range from about 0.010 to about 0.030 m2/cc, preferably from about 0.012 to about 0.026 m2/cc.
For absorbent pores where two layers of absorbent foam are usod, it is preferred that the upper foam layer (facing the body of the weartt) have a Iowa capillary suction spxi5c surfa~x acres, for example from about 0.012 to about 0.020 rrtZ/cc, while the lower foam layer 25 hat a higfeet capillary suction spxific surface area, for example from about 0.020 to about 0.026 ~Ix. In this way, the lower foam layer will have a higher fluid capillary pressure, allowing it to drain fluid from the upper foam layer, thus koepiag the body of the wearer relatively frx >iom contact with the fluid. (It follows that where more than two foam layers are employed, the capillary suction spxi5c surface area of the rapxtive foams preferably 30 will inertase as the foams are locatod mort remotely (i.e., lower in the absorbent product) from the user.) 3. Resistance to Compression Deflection An important mechanical feature of the foams of the present invention are their strength as determiaod by resistance to compression deflection (RTCD). The RTCD
35 exhibited by the foams herein is a firnction of the polymer modulus. as well as the drruity and structure of the foam netwotlc. The polymer modulus is, in turn, determined by a)~ the poivmer~nposiuon: b) the conditions under wtuch the foam was polyTnenzed (for e.Yampie.
the completeness of polvmenzanon obtained, specifically with respect to crosslinking); and c) the extent to which the polymer is plasticized bv_ residual materials, e.g..
emulsifiers. left m 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 suitabiv_ 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 l0 produced in a sample of saturated foam held under a certain confining pressure for a specified period of time. The method for earning out this particular type of test is described hereafter in the . TEST METHODS section. Foams useful as absorbents members for ~~ P~u~ ~ ~ which exhibit a RTCD such that a confining pressure of 0.74 psi (5.1 kPa) produces a swain 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 ~itv Another important property of absorbent foams according to the present invention is their free absorbent, capacity. For absorbent members useful in catarnenial products, free absorbent capacity is the total amount of test fluid (i.e., synthetic urine) that a given foam sample wiU 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 caramenial products will at least meet a minimum free absorbent capacity. The free absorbent capaciy 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 apeaaliy rueful as absorbent members for catairteaial products, the foams of the present invention should Gave 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 Imp~rti~ 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 espxially cells that are formed by polymerizing a monomer-containing oil phase 33 that surrounds relatively monomer-free water~phase droplets, will frequently be substannaUv spherical in shape. The size or "diameter" of such spherical cells is a commonly used parameter for charactenzmg foams in general. Since cells in a given sample of pohtnenc foam W Il not necessarily be of approximately the same sue. an average cell size. i.e., number average cell diameter. will often be specified.
Cell size is a foam parameter that can unpact a number of important mechanical and 5 performance features of the absorbent foams according to the present invention. Since cell sizt 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 deveiopcd within the foam structure.
l0 A number of techniques are available for determining the average cell size of foams.
The most useful technique for determining cell size is foams involves a simple measurement based on the scaruring electron photomicrograph of a foam sample. Figure 3, for example.
shows a typical HIPS foam structure according to the present invention.
Superimposed on the photomicrograph is a scale r~epraenting a dimension of 20 Wrr. Such a scale can be used i5 to determine average cell size via visual inspection or an image analysis procedure.
The cell size measurerrunts given lu;rzia are based on the number average cell size of the foam. The foams useful as absorbent members for cataraeaial products according to the present inveatioa will preferably have a number average all size of from about 20 to about l80 Eurt, and typically from about 35 to about 130 Eua.
20 Another feature useful in de&ning these preferred foams is hole size. The holes arc the openings betwear adjacent cells that maintain fluid communication betty ~een these cells.
The foams of the present invention have hole sizes sufficiently large to allow passage of the insoluble components of blood, especially the red blood cells, to avoid blockage of these fluid P
25 The preferred txhnique for determining hole size is image analysis based on scanning electron micrograpbs of the foams as discussed above and shown in Figure 3. The bol size meaturert>ents gives herein are based on the number average hole sim of the foam.
The foams useful as absorbent members for catameaial products according to the present inveati~ will preferably have a number average hole size of from about 4 to about 30 Wn, 30 sad prr;faably from about l0 to about 28 Eun. While fozrr>S having hole sizes larger than about 30 Eun will allow passage of blood cells, thry will ~t have the fine microstructure necessary to provide the fluid capillary absorbent pressure of the foams of the present mveauon.
2. Foam Density 35 "Foam density" (i.e., in grams of foam per cubic centimeter of foam volume in air) is specified lutein 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 _ l i.
the RTCfl of absorbent foams. lmporrantly also. the densny of the foam controls the absorbent capaciy of such foams in units of glg. This influences the cost effecnveness and utility of such foams as absorbent members for catamenial produce.
Any suitable gravimetric procedure that will provide a determination of mass of solid 5 foam material per unit volume of foam structure can be used to measure foam denstn~. An ASTM gravimetric procedure described more fully in the TEST METHODS section of U.S.
Patent 5,387,207 (Dyer et al.) issuod 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 10 from about 0.008 to about 0.05 g/cc, preftrably from about O.Ol4 to about 0.024 g/cc. and most preferably about 0.02 g/cc.
3. Horiiontal Gravimetric Wicking One of the prunary 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
15 foam of insufficient strength (RTCD) will exptrss excess fluid readily during use. Under mechanical pressure from the weartr of the catamenia! product, this mobile fluid can be pumped out of the absorbent core and upwards through the topsheet. As a result. the ~Psh~ " " with this pumpod fluid such that there is not adequate topshoet 20 The ability of the foams of the present invention to miainuze rewet can be correlated to their ability to retain absorbed fluids. The ability of these foams to retain absorbed fluids can be measured by ~orinontal ~ravimetric Wicbag (HGW), the Procedure for which is described hereafter in the Test Methods scctioo. For the purposG~ of the present invention this HGW measunaneat is expressed as the percentage of the Retained Uptake of AMF.
25 relative to the Initial Uptake of AMf, or "% Resained/Initial Uptake of AMF." The foams of the press ikon typically have a % Retainod/Initial Uptake of AMF of at least about 50% and preferably at least about 65%.
30 II. Polymeric Faam Barrier Layer As indicated herein, many users of catamenial products prefrr relatively thick pads.
With such pads, iaeacpeasive filler materials. which may possess pore absorbent/wet integtly properties, may be preferred. However. whey such materials are used, the resulting absorbent products may suffer from an aesthetic aadlor performance standpoint.
Because the 35 absorbart polymeric foams of the present invention provide high fluid acquisitionlstorage 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 bunching and/or roping m use This results in better core and product integntyn use. To further facilitate mamtanence of a relatively dw filler layer. !n a preferred embodiment of the present invention a polwrteric 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 5 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 ~tm, preferably from about 25 to about 35 Eun: and an average hole size from about 4 to about 9 Eun.
l0 preferably fiom about 5 to about 7 Eun. These relatively small ceU 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 adrnitttd into the barrier layers is further retained by the relatively high fluid cap~Uary Pressure associated with such structures. Thus, whey the absorbent foam core is ptacod oa top of, e.g., an air laid 5brous core, the barrier 15 layer serves to prevent contamination of the air laid care with fluid which would cause the air laid core to change its dimensions and lose its integrity and/or be stainod 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 possrssa the ability to move fluid away from the wearer. Thus, it is preferred that barrier layer have a higher capillary specific 20 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 spcctfic surface areas as described in section I-b herein, it is preferred that the barrier layer will have a capillary suctimr spxific surface area of from about 0.040 to about 0.080 m2/cc. In this way, the fa~am layers of the absorbent core have successively higher fluid capi!)ary pressure 25 Providing draioag~e away from the wearers body. The barrier layer's ability to acquire and store fluid may alb~w for eahanad fluid retention by the article under circumstances where the absorbent foam nrateri:tls (discussed above) have reached their capacity or where fluid is "squeezed out" of the foam layers overlying the barrier layer.
III. Peon of Polymeric Foams From HIPS
30 A.
Polymeric foams according to the present imKation can be prcparcd by polymerization of certain water-in-oil emulsions having a relatively high ratio of water phase ~ od P~ Y ~ ~ t~ art as "HIPEs." Polymeric foam materials which result from the polyrrKrization of such emulsions arc referred to herein as "HIPS
foams."
35 The relative amounts of the water and oil phases used to form the I-flPEs are, among many other parameters, important in determining the structural, mechanical and perfom~ance properties of the resulting pohTnenc foams. In particular. the ratio of water to oil (W O1 ~, the HIPEs varies inversely with ultimate foam densm according to the equation:
Density = l/(W:0 ratio + 1 ).
This can influence the cell size and capillary specific surface area of the foam and. dimensions 5 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: I.
1. Oil Phase Comuonents l0 The continuous oil phase of the HIPS 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 determining Tg by Dymarnic Mechanical Analysis~(DMp) is described hereafter in the TEST METHODS section.) This monomer component includes:
15 (a) at least one monofunctional monomer capable of fonrdng as atacsic amorphous polymer having a Tg of about 35°C or lower (see Braadup, 1.: Immergut, E.H.
"Polymer Handbook".
2nd ed., Wiley-Interscience New York, NY, 1975, III-139.): (b) at least one monofiiactional comonomer to improve the toughness or tear resistance of the foam; (c) a first polyfunctional crosslinkiag agent; and (d) optionally a second polvfunetional crosslinking agent. Selection 20 of particular types and amounts of monofunctional monomer(s), corrionomer(s) and polvfunctiooal crnasliniang ageat(s) can be important to the realization of absorbent HIPS
foams having the desired combination of strucxure. mechanical, and fluid handbag Properties.
The monomer component comprises one or more monomers that lead to impart rubber-like ptnperbes to the resulting polymeric foam structure. Such monomers can 25 produce high molecular weight (grrrater than 10,000) atactic amorphous polymers having Tg's of about 35°C or Iower. Monomers of this type include, for example, the (C4-C 141 alkyl acrylates such as butyl acrylate, 6exy1 acrylate, octyi acrylate, 2~thylhexyl acrylate, nonyl acrylate, Beryl acrylate, dodecyl (lauryl) acrylate, isoderyl acrylate taradecyl acrylate, aryl and atkaryl acrylates such as benzyl acrytate, and nonylphenyl acrylate, the (C6-C 16) 30 alkyl methacrylates such as hexyl methacrylate, octyl methacrylate, tinny!
methacrylate, decyl methacrylate, isodecyl rrretlracrylate, dodccyl (lauryl) methacrylate, tetradecyl methacrylate:
acrylamides such as N-octadecyl acrylamide: (C4-C 12) alkyl styra>a such as p-n-octylstyrzae, isopr>:ae, butadiene, and combinations of such monomers. Of these monomers.
isodecyl acrytate, dodecyl acrylate and 2~tltylhexyl acrylate are the most preferred. The 35 monofunctional monomers) will generally comprise 45 to about 70%. more preferably from about 50 to about 65%. by weight of the monomer component.
The monomer component utilized in the oil phase of the I-IIPEs also compnses one or more monofuncuonal comonomers capable of imparting toughness about equivalent to that provided by styrene to the resulting polymeric foam structure. Tougher pohTrters eattibit the 5 ability to deform substantially without failure. These monofunctional comonomer types can include styrene-based comonomers (e.g., styrene and ethyl styrene) or other monomer types such as methyl methacrylate when the related homopolvmer is well Irnown as exemplifying toughness. The preferred monofunctional comonomer of this type is a styrene-based monomer with styrene and ethyl styrene being the most preferred monomers of this kutd. The 10 monofunctional "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 styrtaes, and in particular p-n I S octYlstvnae, are examples of such comonomers. For such comonmrters, the amount that can be inclu~d in the monomer component will be that of the typical monomer and-comonomer combined.
The monomer component also contains a first (and optimally socond) polvfunctional crosslinking agent. As with the moaofitnctional monomers and comonomers, selection of the 20 particular type and amount of crosslinking ageat5 is very important to the eventual realization of preferred polymeric foams having the desired combinati~ of structural, mechanical, and fluid-handling Properties.
The first polyfirnctional crossliaking agent can be seixtod from a wide variety of polyvinyl aromatic and related polyvinyl materials such as divi~rlbeauaes.
trivinylbenzenes.
25 divinyltolueaes, divinybryleaes, divinylnapbthale~s divinylalkylbenunes.
diviaylpbmarr<hrvra, divinylbiphenyls, divitryldipbemnnethat>GS, divinylbenzyls, dtvmylpbeayla6ers, divimrldipbeayisutfides, divinylfuraas. divinyrlsulfide, divinylsulfone, and mixtures thereof. Divi~rl brae is typically available as a mixture with tthyl stmne in Proportions of about 55:45. These proportions can be modified so as to enrich the oil phase 30 with ~e or the other cxrrtpooeat. Generally, it is advantageous to enrich the mixture with the ethyl styrene component while simuhaneousiy reducing the amount of stvttne is the monomer blend. The preferred ratio of divinyi benzene to ethyl stytrae is betwoen from about 30:70 and 55:45, most preferably front betwaa 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 is the oil phase of the I~PE is an amount of from about 8% to about 22%, more preferably from about 10% to about l8% most preferably from about 12% to about 16%, by weight of the monomer component the optional second crosslirtking agent can be selected from pohfunctional acrvlates and methacrvlatts, acrylamides and methacrylamides. and rruxtures thereof These include di-. tri-, and tetra-acrylates, as well as di-, tri-. and tetra-methacrvlates: di-, tn-. and tetra-s acrylamides, as well as di-. tri-, and tetra- methacrvlamides: and mixtures of these crosslinking agents. Suitable acrylate and methacrylate crosslinking agenu can be derived from diols, triols and tetraols that include 1.10-decanediol, l,g-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 .g~ly be inciudod in the oil phax of the hBPE
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 theory, it is believed this second crvsslinking agent generates a more homogeaoously crosslinked structure that develops soreagth more efficiently 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 spxific strength and railience requirements at in-use tanperatures by controlling the relative amount of the two crossliaker types empioyod. Thus, a foam containing only the first type of crosslinker will exhibit a relatively narrow transition region. increasing the amount of the xcond crosslinker xrves to broaden the traruitian region, eves if the actual transition temperature itself has not changed.
25 The major portion of the oil phase of the HIPEs will c~mprix the aforementioned monomers, camooomers and crosslinking agents. It is aseatial that thex monomers.
conanomers and ccoasliakiog agents be substantially water-insoluble so that they are prirnatily soluble in the oil phax and not the water phase. Ux of such substantially wacer-insoluble m~omers ensures that E-~Es of appropriate characteristics and stability will be 30 rcalimd. It is, of course, highly prsfer:ed that thex monomers, comonorrrers and crosslinking agents be of the type such that the resulting polymeric foam is suitably non-toxic and aPP~P~Iy ~~y ale. Thex monomers, comonomers and cross-linking agents should preferably have little or no toxicity if present at very low residual concentrations during post-polymerirrtion foam processing andlor ux.
35 Another essential component of the oil phase is an emulsifier component that petmiu the formation of stable HIPEs. This emulsifier component comprises a primary emulsifier and optionally a secondary emulsifier. Especially whey used alone. these prirnary emulsifer .Ig_ typically comprise at least about 'i0%. preferably at least about 70%, emulsifying components selected from diglycerol monoesters of linear unsaturated C l6-CZZ
fam~ ands.
diglycerol monoesters of branched C 16-C24 fatty acids, diglycerol monoaliphatic ethers of branched C l6-C24 alcohols, diglycerol monoaliphatic ethers of linear unsaturated C l6-CZ~
5 alcohols, digtycerol monoaliphatic ethers of linear saturated C 12-C 14 alcohols. sorbitan monoesters of linear unsaturated C 16-C22 fatty acids. sorbitan monoesters of branched C 16' C24 fatty acids, and mixtures thereof. Preferred prvnary cmulsi8crs include diglycerol monooieate (e.g.. Preferably greater than about 40%, more preferably greater than about 50%, most preferably greater than about 70% diglycerol monooleate), sorbitan monooleate 10 (e.g., preferably greater than about 40%, more preferably greater thaw about 50%, most preferably greater than about 70% sorbitan mronooimte), sorbitaa monopalmitatc, and diglyccrol moooisostearate (e.g., Preferably greater thaw about 40%, more preferably greater thaw about 50%, most preferably greater theses about 70% digiycerol moooisostearace).
Diglycerol monoesters of tincar unsatutatred and braaclxd fatty acids useful as is emulsifiers in the prs~seat inventiar can be prepared by aterifyiag diglycerol with Fatty acids, using procedures well lmowa in the art. Sec, for exarrtQle, the method for preparing polyglycerol esters disclosed is U.S. Patent 5.389,207 (Dyer a al.) issued Feb. 7, 1995.
Diglycerol can be obtained comtrrercially or can be separated from polyglyceroLs that are high in diglycerol. Linen. btaached, and unsaturated fatty acids can be obtained commercially.
20 The mixed ester product of the esterifiruion reaction can be fractionally distilled under vacuum one or more times to yield distillation fraaioas that are high is diglycerol moooestert. For example, a A CMS-15A (C.V.C. Products Inc.: Rochester, N.Y.) continuous l4 inch oeatrifugal molecular stiD can be used for fracaoaal distillation.
Typinlly, tht polyglyatol ester feedstock. while being heated, is first metered through a 2s degasset unit and t6ea to the heated evaporator cone of the still, where the vacuum distillation taloes place. Distillate is collected on the beU jar surface, which can be heated to facilitate distillate ranoval. Distillate and residue are continuously removed by transfer pumps. The fauy acid composition of the resultant mixed ester product can be determined using high resolution gas chrorrratograpby. See U.S. Paient 5,387,207 (Dyer et al.) issued Feb. 7, 1995.
30 Polyglycerol and polygiycerol ester distribution of the resultant mixed ester product can be determined by capillary supercMtca! chromatography.
Linear satsrrated, lirsnr uasatrrrated, or branched diglycerol monoaliphatic ethers can also be prepared and their composition deurmined using procedures wdl Imown in the art .
3s Sorbitaa rrronoesters of linear unsaturated and breached fax<y acids can be obtained commercially or prepsced using methods lQrown is the art. See, for example, U.S. Patent -19~
4.103,047 (Zulu et al). issued July 2~. 1978, cspec~aliv column 4. line 32 to column ~, line 13. The rtuxed sorbitan ester product can be fracuonallv vacuum distilled to yield composiuons that are high ui sorb~tan monoesters.
Sorbitan ester compositions can be determined by methods well known in the art such as small molecule gel permeation chromatography, When these primary emulsifiers are used in combination with certain secondary emulsifiers, the primary emulsifier can compnsc lower levels of these emulsifying components, i.e., as low is about 20% of these emulsifying components. These secondary 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 12-C22 ~iP~uc, short chain C 1-C4 dialiphatic quaternary ammonium salts such as disallow dimethyl ammonium chloride, bistridecyl dimethyl ammonium chloride, and disallow dim~thyl ammonium meshyisulfate, the long chain C l2-CU dialkoyl(alkmoyl~2-bydroxyethyl, short chain C 1-C4 dialiphatic quaternary ammonium sails such as dinllowoyl-2-hydroxyethyl dimethyl ammonium chloride, the long chain C 12-CU dialiphatic imida~olinium quaternary ammonium salts such as methyl-1-tallow amido ethyl-2-tallow imidazoliaium methylsulfate and methyl-1-oleyl amido ethyl-2-oleyl imidazolinium mediylsulfate, the short chain C 1-C4 dialiphatic. long chain C i2-C~ monoaliphatic benzyl quaternary arrunonium salts such at dimethyi stearyl benryl ammonium chloride: anionic types inciudiag the C6-C 18 ~P~o esters of sodium sulfosuccioic acid such as the dioctyl ester of sodium sulfosuccinic acid and the bistridocvl ester of sodium sulfosucciaic acid; and mixtures of these secondary emulsifiers. These secondary emulsifiers can be obtained cottunercially or prepared using methods kao~wo is the art. The preferred secondary emulsifiers are ditaUow dimethyl amrraoium methyl sulfate and ditallow dimethyl ammonium methyl chloride. Whcn these optional secondary anulsifiers are included in the emulsifier component, it is typically at a weight ratio of primary to secondary emulsifier of from about 50:1 to about 1:4, preferably fiom about 30:1 to about 2: l .
-1~e o~ p>~se usod to form the EIIpFs comprises from about 85 to about 98% by weight mooonxr component and from about 2 to about 15% by weight emulsifier component.
Preferably, the oil phase will comprise from about 90 to about 97% by weight monomer cmnponent and from about 3 to about 10% by weight emulsifier component. The oil phase also can contain other optional compooatts. One such optional component is an oil soluble polyrrxrimtion initiator of the genes! type well blown to those skilled in the art, such as 33 describod in U.S. patent 5.290,820 (Bass a al), issued March 1. 1994, Another preferred optional component is an antioxidant such as a Hindered Amide Light Stabilizer (HALS) and Hinderod Phenolic Stabilizers (ID'S) or any other ~20-antioxidant compatible W th the initiator system to be employed. ether optional components include-plasticizers, fillers. colorants. chain transfer agents, dissolved polymers, and the like.
2. Water Phase Com The discontinuous water internal phase of the I-IIpE is generally an aqueous solution containing one or more dissolved components. One essential dissolved component of the water phase is a water-soluble elecuolvte. The dissolved electrolyte minimizes the tendency of monomers, comonomers, and crosslinkers that are primarily oil soluble to also dissolve in the water phase. 'Ibis, in turn, is believed to minimize the extent to which polymeric material fills the cell windows at the oiUwater interfaces fornud by the water phase droplets during to 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 prtFerr~d polymeric foams can be open~elled.
Any electrolyte capable of imparting ionic sttmgth to the water pl~e c~ be ~.
Preferred electrolytes are mono-, di-, or trivalent inorganic salt: such as the water-soluble halides, e.g., chlorides, nitrstea and sulfates of alkali metals and alkaline earth metals.
Examples include sodium chloride, calcium chloride, sodium sulfate sad ntagoGSium sulfate.
Calcium chloride is the moat preferred for use in the present invention.
Generally the electrolyte will be utilized in the water phase of the HIPEs in a ooncattration in the range of from about 0.2 to about 20% by weight of the water phax. Mots prekrably, the electrolyte will comprise from about 1 to about 10% by weight of tire water phase.
The HIPEs will also typically contain a polymerirrtioo initiator. Such an initiator component is geoeraUy added to the water phase of the I-flPEs and can be arty conventional water-soluble 5~e radical initiator. These include peroxyget< compounds such as sodium, potassium and ammonium petsulfates, hydtogea perwcide, sodium per, sodium percarbaoate and the like. Conventional redox initiator systans can also be used. Such sysoa~ arse f~onned by combining the foregoing permrygm compounds with roducing agents strc~r as sodium bisul5te, L-axorbic acid or ferrous salts.
The ioitaamr can be present at up to about 20 mole percent based on the total moles of polr<naizsbk monomers present in the oil phase. More preferably, the initiator is present in an amount of lsom about 0.001 to about 10 mole percent based on the total moles of polvmetizabie monomers in the oil phase.
3.
The polymer forming the I-iIPE foam swcturc will preferably be substantially free of polar firnetia~al groups. This meant the polymeric foam will be relatively hydrophobic in character. To be useful at absorbents for blood and blood-baxd fluids such as menses, these foams geaenlly require further treaanem to rer>der the foam relatively more hydrophilic.

_o [.
Hvdrophiliiauon of the foam. ~f necessary. can generally be accomplished bs treating the HIPS foam with a hvdrophiliung surfactant in a manner described more fully hereafter These hydrophilizing .surfactants can be am~ material that enhances the water wettability of the polymeric foam surface. Suitable surfactants should be non-to~uc and non 5 imtaung to mucus membranes. It should be soluble or dispersible in warm water Preferably, the hydrophilinrtg surfactant is a liquid at temperatures near ambient for ease of incorporation during the foam making process. Suitable surfactants include ethoxvlates of C 11'C l5 ~~hols, rttarketed by Shell Chemical Co., in particular NEODOLT 25-(condensation product of C 12-C 15 ~ ~oohols with 12 moles of ethylene o~cide).
l0 NEODOL 23-6.ST (condensation product of C 12-C 13 linear alcohols with 6.p moles of ethylene oxide that has been distilled (topped) to remove certain impurities), and NEODOL
23-3 (condtasa:ion product of C 12-C 13 ~ ~o°h°ls '''"th 3 rnola of ethylene oxide);
TM
ethoxytates of C 11-C 15 ~' ~r~ sold undo the PEGOSPERSE designation by Stepan Chemical Corp., NorthSeld, IL: condensation products of ethylene oxide and/or propylene t 5 oxide having molecular weights greater than about 2000, and condensation products of propylene oxide and propylene glycol sold under the PLUROMC daigaation by BASF
Parisspany, NJ: modified oxyethylated straight chain alcohols sold under the Plurafac desig~nstion by BASF. Corp., Parsippatry, Nl: sulfated alcohol ethoxylates and alkyl ether sulfates such as those -sold by Elarcos Chemicals, Kariszs. KS, braac>~ed and linear alkyl aryl 20 ethoxylates such as Triton X-60, Triton X-100, Triton N-57, and the like marketed by Union TM
Carbide. Inc. Danbury, CT, silicone-glycol copolymers sold under the SILWET
designation by OSI Speciattia, Danbury, CT, as well as mixtures of these surfacsaau.
Particularly preferred surfacmnts are PEGOSPERSE 200 ML. an ~oxylate of lauric acid having an average of 4.5 etboxy waits.
25 These hydrophiliziag surfactants can be dissolved or dispcrxd in a hydrophilinng sdution bust is applied to the HIDE foam surface. In this manner, hydmphiliring surfactanu c~a be adsorbed by the petferred RIPE foams in amounts suitable for rendering the surfaces tbaeof substantially hydrophilic, but without substantially impairing the desired flexibility and compression deflection characteristics of the foam. In preferred foams, the 30 hydrophili>'ag surfactant is iaearporated such that residual amounts of the surfactant that ~ ;n ~ foam, suueture are typically in the range from aboui O.OS% to about 5%.
preferably from about 0.5 to about 1%, by weight of the foam.
B. ~T'~-~sisni Cv~sditinnc fOr Obtaining HIPS Foams Foam preparation typically involves the steps of: 1) forming a stable high internal 35 phase emulsion (HIDE): 2) polyrneriang/curing thrs stable emulsion under conditions suitable for forming a solid polymeric foam structure: 3) slicing or otherwise cutting the water-tilled polymeric foam and then washing the sliced or cut foam to remove the original residual water phase. and especially the residual hvdratable salts, from the polvTnenc foam structure: .t) treating -the polymeric foam structure wth a hvdrophilizing surfactant; and thereaRer dewatering this polymeric foam structure.
Formation of HIDE
5 The HIDE is formed by combining the oil and water phase components in the previously specified weight ratios. The oil phase will typically contain the requisite monomers, comonomers, crosslinkert, and emulsifiers, as well as optional components such as solvents and polymerisation initiators. The water phase will typically contain clectrolvtes.
as well as optional components such as water-soluble emulsi5ets, and/or polymerization 10 initiators.
The HIPS can be formed from the combined oil and water phases by subjecting these combinod phases to shear agitation. Shear agitation is generally appliod to the extent and for a time period trecasary to form a stable emulsion. Such a process can be conducted in either batchwise or continuous fashion and is gmeraUy carried out undo conditions suitable for 15 forming as emulsion where the water phase droplets are dispasod to such an extent that the resulting polymeric foam will have the requisite cxll sine and outer structural characteristics.
Suitable mixing or agitation devices are those that are capable of forming as emulsion wader conditions of low shear mixing. Emulsification of the oil and water phase combination will frequently involve the use of a mixing or agitation device such as a pin impeller.
20 One preferred method of forming such HIPEs involves a continuous process that combines and emulsifies the requisite oil and water phases. Ia such a process, a liquid stream comprising the oil phase is fonrted. Concurrently. a liquid suzam comprising the water phase is also formed. The two stseamt are then combined in a suitable mixing chamber or zone such that the requisite water to oil phase weight ration previously speci>hod are achievod.
25 Ia the mixing chamber or zone, the combi~d stttauis are generally subjected to shear agitation provided, for exaatple, by a Pin impeUet of suitable con5guratioa and dimeasioru.
Spar will typically be applied to the combinod oil/wata phase stream at at a tare of about 4000 sx'1 or less, preferably about 3000 sec'1 or less. Once formod, the stable liquid RIPE
can then be withdrawn from the mixing chamber or zone. This preferred method for forming 30 HIPEs via a continuous procGSS is described in greater detail in U.S.
Patent 5.149,720 (DesMarais et al). issued September 22, 1992. - . .
35 The degree of sheu appGod and/or the water to oil phase ratio during HIPE
formation noed not be constant throughout. For example, HIPS making can be carried out under "pulsed" conditions or varied rhythmically. 'Ibis is especially useful when the HIPE is _i ;.
collected m a rotating cylindrical container as successive layers to form foams hav,ng heterogeneous structures. Pulsed conditions can produce HIPEs compnsu~g regioru 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 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 RIPE formation and pouring can be carried out at more elevattd temperatures of about 50°C or higher, preferably 60°C
or higher. Typically, the to I-flPE can be formod at a temperature of from about 60° to about 99°C, more typically from about 65° to about 85°C.
2. Polvmeriration/Curing of the HIDE
The HIDE formed will generally be collected or poured into a suitable reaction vesxl, container or region to be polvmerizad or curod. In o~ embodiment , the rzacaoo vase! comprises a tub conswctad of polyethylene from which the eventually polymerized/cured solid foam material can be easily removod for further proccssiag after polvmerirrtionlcuring has bxa carriod out to the extent desired. It is usually preferred that the temperature at which the HIDE is poured into the vesxl be apprrncimasely the same as the polvmeriration/curing temperature.
Suitable polyn>crizationlcuring conditions will vary depending upon the monomer and other makeup of the oil and water phaxs of the emulsion (especially the emulsifier systems usod), and the type and amounts of polvmerirdtioa initiators used.
Frequently.
however, suitable poiymeri:atiodcuring conditions will involve maintaining the HIDE at elevated temperanrra above about 50°C, more preferably above about 65°C, and most prtf~ably above about 80°C, for a tune period ragging fran about 2 to about 64 hours, more preferably from about 2 to about 48 hours. The HIDE can also be cured in stages such as daaribed in U.S. patent 5,,189,070 (Browascombe et al), issued February 23, 1993.
A porous water-filled open-celled I~PE faam is typically obtained after polymeriratiodcuring in a reaction vessel, such as a tub. 'Ibis polymerized HIDE foam is typically cut or sliced into a sheet-like form. Sheets of polyrrrerizod HIDE
foam are easier to proaess during subsequent treating/washing and devvaieting steps, as well as to prepare the HIPS foam for ux is absorbent article. The polymerized HIDE foam is typically cut/sliced to provide a wt thickness in the range of from about 0.08 to about 2.5 cn~
preferably from about 0.15 and about 1 cm. The polymerized HIDE foam can also be cubed or sliced into this spaghetti~like sections or can be stamped into shapes such as a continuous tube (e.g., for ux in tampons) at this point.

3. Siicina and Washtna HIPE Foam The solid pohmenzed HIPS 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 polvmetization initiator) should be at 5 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 sheen of from about 0.15 to about 0.4 cm in thickrsess. These sheen arc dewateted by compressing the foam structure to squeeze out residual liquid and/or by washing the foam swcture 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 sale) from the foam is particulariy important. As tested previously, these hydratable salty arc typically included during initial formation of the HIPS to minimize the tendency of cnotmtners, votnotwmers, and crosslinkers that are primarily oil soluble to also dissolve in the water phase. However, 15 after poiyn>etvaaon of the HIPS, the pceseacx of these salts is uaneassary and can adversely a.>ToCt the ability of the foam to absorb blood and blood-baud fluids such as rttertses, especially as the conoatnation of these sale is the foam increases.
Accordingly, it desirable to reduce the level of tlxse hydeatable salu in the foam as much as possible during this washing step. After washing, the foams of the present inverttioo have less thaw about 2% of 2o such residual hydratable salts. Preferably, the foams of the prtsent inventi~ have less than about 0.5% of such residual salts.
4. Twith Hvdrot~hilizimr Surfacmat and Foam Dewaterintt After the original water phase material has bun ratwved to the extent required, the HIDE foam is typically treated with as effe~ve amoutn of a suitable hydrophilizing 23 sur6c~t. Hydtophilizing surfactants that can be employed have been previously described and particularly include ethOxyiates of C I 1-C 15 fatty acids wch as Pegoaperse 200 ML.
branched and linear alkyl aryl ethoxylat~es such as Triton X-100, and ethoxylates of C 11-C I S
aliphatic alcobols such as NEODOL 23-6.ST. Treatment of the H>pE foam with the hydrophiliang sur6c~at co~aues until the foam exhibits the desired degree of wettability.
30 After the HIDE foan bat been hydrophilized, it will geaecally be dewatered.
Devvatering can be achieved by compressing the foam (preferably in the z-dirx:;on) 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/rnicrowavdvacuum dewateriag techniques.
35 The dig step will generally be carried out until the RIPE foam is ready for use and is as dry as practicable. Frequently such compression dewatercd foams will have a water (moisture) content of from about 50 to about 500%. more preferably from about 50 to about 200%, by weight on a dw weight basis. Subsequently. the compressed foams can be themtally deed to a moisture content of about .t0% or less. preferably in the range of from about ~ to about l5%, on a dry weight basis.
After the HIPS foam has been dewatered. it can be slitted in various patterns.
~ese 5 include patterns that conform to the shape of the catamenial product in which the slated foam is used as an absorbent member. Slitting can be especially desirable when the foam ~s intended to confer superior fit in a cammenial pad such as a sanitary napkin.
N. Use of Polymeric Foams in Catam~sal Prr~m.rc The polymeric foams of the present invention are useful in a variety of absorbent l0 articles for absorbing blood acrd blood-based fluids.
A. Catamenial Products The polymeric foams of the present invention are particularly useful as absorbent members in a variety of catameaial products such as catamenial pads. An embodiment of a catamenial pad or sanitary napkin l0 according to the prasent i»tion is shown in Figure 1.
15 As used herein, the term "sanitary napkin" rrfers . to as absorbart article that is wore by females adjacent to the pudeadal region, generally external to the a tal which is intended to absorb and contain menswal fluids and other vaginal discharges from the wearer's body (e.g., blood, mensal, and urine). Interlabial devices that reside partially within and parrially external of the wearer's vatibuk are also within the scope of the present 20 invention. As used herein, the term "pudeadal" refers to the eraernally visible female genitalia. It should be understood, however, that the prrseat invention is also appGcabie to other feminine hygiene or catameoiai pads such as paadlinen, or other catarrrenial products such as incar<iaeace pads, tampons and the like.
The poiytnaic foams of the prexat invention are particularly useful in sheet form.
25 'This re>aies to care of nraaufuarre and shipping as weU as for general utility in the product.
'I1e sheet or sheets used can be of any thickness desired according to the capacity required for the surface aria available. Generally, the sheets will be from about 0.1 to about 1 cm in thici~ss. These sheds can be perforated of slit, either to further enhance the rate of fluid absorptiar by incrryuing the surface area of the foam exposed to the fluid or to increase the 30 stretchability of the foarrr. Alternatively. these foams can be in the form of diced cubes.
strands (e.g. spaghemi-like material), this strips, and the like that can be assembled into absorbent carts of various shapes dtperrding on the spxi5c needs of the product.
As particularly shown in Figure 2, catarrrenisl pad l0 is cronstructed of fluid pervious primary topsheet 12, an absorbent core consisting of an optional fluid acquisition layer 14 35 corrrrnonly referred to as a "secondary topsheet", a fluid storage absorbent member 16 made of one or more polymeric foams according to the presort invention, and a fluid impernous -36~
backsheet 18. The fluid storage absorbent member ! 6 may also compnse a pohmenc foam barrier layer of the present invention. The backsheet l8 and the topsheet l2 are positioned adjacent the garment surface and the body surface, respectively. of pad 10 and are preferably domed to each other. For example, the backsheet l8 and the topsheet l2 can be secured to 5 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 backshea can be joined to each other by heat bonding, pressure bonding, ultrasonic bonding, dynamic mechanical bonding, or any other suitable method for joining topsheeu and backsheets imown is the art.
to A suitable method for joining topsheet 12 and baclc~heet 18 together is by a seal that forms border segment 20. As shown in Figure l, the inner portion of this border segment 20 defines a perimeter 22. Perimeter 22 encircles the secondary topshett l4 and absorbent mattber l6. 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 1 s width of border 20 can be uniform or vary about the perimaa of pad 10.
Border 20 prrncides a fluid impermeable seal that surrounds pain>eter 22. The seal is preferably formed by the simultaneous appGcatioa of pressure, with or without heat, to melt topsheet 12 and backshcet l8, thereby forming border segerteat 20..
In addition to providing fluid acquisition benefits, the secondary topsheet 14 may 20 enhance the integrity of the product by stabilising the positioning (e.g., by reducing bunching) of the fluid strorage absorbent member 16. The secondary topsheet cart include nonwoven or woven webs of syntbeac fibers including polyester, polypropylene, or polyethylene; natural fibers including cxmoo or cellulose: blends of such fiber:; or nay equivalent materials or combinations of materials. Suitable secondary topsheets can also be made fin mixtures of 2s fibers with tberraoplastic materials to form thermally hooded matrices.
These therrttoplanic materials can be is any of a variay of forma including particulates, fibers, or combinations of particulates a~ fibers. T~era>oplastic fiber are a particularly prekrred form bxause of their ability to form numerous iaterfiber hood sites. Other altert>ativa for the secondary topsbeet are the use of wood pulp surfa,oe-splayed with latex and air laid wood pulp structure 30 bonded with latex.
The backt6xt 18 is impervious to fluids (e.g., menses) and is preferably manufacatred fi~om a thin plastic film, 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 htunaa body. The backchat 18 prevents 3 s the exudates absorbed and cooz$inod in the absorbent strucurre from wetting articles that cmttact the sanitary napkin 10 such as pants, Pajamas and undergartnatts. The backsheet 18 can comprise a woven or nonwoven material, polymeric films such as thermoplastic films of .W.
polyethylene or polypropylene, or composite materials such as a film-coated nonwoven material. Preferably. the backsheet is a polyethylene film having a thickness of from about 0.012 mm (0.~ mil) to about 0.051 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 des~gnat~on XP-39385. The backsheet is preferably embossed and/or matte finished to provide a more clothlike appearance. Further. the backsheet l8 can permit vapors to escape from the absorbent core (i.e., is breathable) while still preventing exudates from passing through the backsheet l8.
to The topsheet 12 is compliant, soft feeling, and non-imtauag to the wearer's skin.
Further, the topsheet 12 is fluid pervious permitting fluids (e.g., menses) to readily penetrate through its thiclmas. A suitable topsheet l2 can be manufactirrod from a wide range of materials such as woven and nomvoven materials; polymeric materials such as apertured formed thecrmoplastic films. bred Plastic films, and hydroformod thermoplastic films:
15 porous foams; reticulated foams; reticulated thermoplastic films; and thermoplastic scrims.
Suitable woven and aonwoven materials can be comprised of natural fibers (c.g., wood or cottom fiber:), synthetic fibers (e.g., polymeric fiber such as polyester, polypropylene. or polyethylene fibers) or from a combination of natural and synthetic fibers.
PrcFerod topshoets for use is the prexmt are selecsod firm high loft nonwoven 20 topsh~et~ and aperture fonrad filth topsheets. Apertured formed films are especially prefernd for the tops6eet because 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 wears skin.
Thus, the sur6ce of the formed film that is in contact with the body remairu dry. thereby reducing body soiling and creating a morn comfortable feel for the v~rrarrr.
Suitable formed 25 films are described is U.S. Patent 3,929,135 (Thormpson), issued Decearber 30, 1975; U.S.
Patent 4,324,246 (Mullane, et al.), issuod April 13, 1982; U.S. Patent 4,342,3 l4 (Radel. et al.), issued August 3, 1982; U.S. Patent 4,463,045 (Ahr et al.), issued Julv 3l. 1984; and U.S. 5,006,394 (Baud), issued April 9, 1991, Particularly pttferred microapetured formed film topsheeu are oascrosed in 30 U.S. patent 4,609,518 (Curro et al), issue September 2, 1986 and U.S. pauat 4,629,643 (Curro et al), issuod December 16, 1986. The preferred tops6eet for the prexat invention is the torma~ mnr ascribed tit one or more of the above patents and marketed cra sanitary napkiru by The Procter & Crumble Company of Cincinnati, TM
Ohio as "DRI-WEAVE."
33 The body surface of the formed film topsheet can be hydrophilic so as to help liquid to transfer through the topshect faster than if the body surface was not hydrophilic so as to diminish the likelihood that menstrual fluid will flow off the topsheet rather than flowing mto _~g.
and beutg absorbed by the absorbent structure. In a preferred embodiment.
surfactant is incorporated mto the pohntenc matenals of the formed film toosheet, .4.lter~atively, the body surface of the topsheet care be mane 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 thick catamenial pad is desired, a filler material can be positioned betwan the fluid storage absorbent member 16 and the backsheet 18 l0 Useful filler materials, many of which are known in the art, include but are not limited to airklt (e.g., chemi-thermo-mechanical pulp, southern softwood crag. rerycled pulp), foams (~~B~, PolYu. cellulose, polystyrene), sawdust, Paper wadding, recycled newspaper. etc.
Alternatively, the foam materials of the present invention can be cut in layers of sufficient thickness to provide increased product thickness, typically between about t and about 2 cm.
is In use, pad 10 can be held in place by nay support or at:arhment device (not shown) weU-latovvn for such purpoxs. Preferably, pad 10 is placed in the uxr's uadeor Panty and secured thereto by a fastener such as an adhesive. The adhesive provides a means ~r ~~B ~ Pad k ~ o~ portion of the panty. Thus, a portion or all of the outer surface of the bacicsixet l 8 is canted with adhesive. Any adhesive or glue used in the art for 20 such purposes can be used for the adhesive herein. with pressure-sensitive adhesives being TM
preferred. Suitable adhesives are Century A-305-IV manufactured by the Century Adhesives Corporation of Columbus. Ohio: and Instant Lxk 34-2823 manufactured by the National Starch and Chemical Company of Bridgewater, Nl. Suitable adhesive Fasteners are also described io U.S. Patent 4,917,697. Before pad 10 is placed in ux, the pressure-xnsiuve 23 adhesive is typically covered with a removable release liner in order to keep the adhesive from drying out or adba~ievg to a surtax other than the crotch portion of the panty prior to ux.
Suitsbk release liras are also described in the above-referraad U.S. Patent 4,9!7,697. Any commercially available releax liners cacrurmnly used for such purposes can be utilized hewn. Non-limiting exempla of suitable release liner: are BL30MG-A Silox EI/0 and 30 HL30MG-A Silax 4P/O both of which are manufa~ued by the Akrosil Corporation of Meaashs, WI. The pad IO is put in ux by removing the release liner and thereafter placing the pad is a panty so that the adhesive contacu the panty. The adhesive maintains the pad 10 in its position within the panty during use.
The absorbent foams of the present invention arc also useful as the upper 35 acquisitioddistribution component in a "multi-layer" absorbent core that additionally contains a lower fluid storage/redistnbuuon component, where the absorbent core ~s positioned betwxa the topsheet and backsheet to form the catamenial pad. For purposes of _og_ the present mvenuon. an "upper" layer of a mule-layer absorbent core ~s a layer that ~s relatively closer to the body of the wearer, e.g.. the (aver closest to the topsheet 'i~se term "lower" !aver conversely means a layer of a mula-!aver absorbent core that a relauvelv further away from the body of the wearer, e.g., the layer closest to the backsheet. 'This tower fluid storageJredistnbution layer is typically posinoned within the absorbent core so as to underlie the (upper) fluid acquisition/distribution layer and be in fluid commumcat~on therewith. This lower storagdredistribution layer can comprise a vaney of fluid storagelredistribution components including those wntaining absorbent gelling macenals such as disclosed in U.S. Patent 5.061,259 (Goldmaa et. al), issued October 29, 1991. U.S. Patent 4,654,039 (Brartdt et al), issued March 31, 1987 (reissued April 19, 1988 as Re. 32.649), U.S. Patent 4,666.983 (Tsubalcimoto et al), issued May 19, 1987, and U.S.
Patent 4,625.001 (Tsubakimoto et al), issued November 25, 1986.
absorbent microstructures made from these absorbent gelluig matenals such as those disclosed is U.S. Patent 5.102,597 (Roe et al), issuod April 7, 1992, and U.S.
Patent 5,324,561 (Rerai et al), issued June 23, 1994, and absorbent gelling materials laminated brtwan two tissue layers such as those disclosed in U.S. Patent 4,260,443 (Lindsay et al), issued April 7, 1981, U.S. Patent 4,467,012 (Pedersen et al), issued August 21, 1984, U.S. Patent 4,715,918 (Lang), issued December 29, 1987, U.S. Patent 4,851,069 (Paclcard et al), issued July 25; 1989, U.S.
Patent 4,950,264 (Osborn), issuod August 21, 1990; U.S. Patent 4,994,037 (Hernardin), issued Febnuuy 19, 1991: U.S. Patent 5,009,650 (Bernardin), issued April 23, 1991; U.S. Patent 5.009,653 (Osborn), issued April 23, 1991; U.S. Patent 5,128,082 (Makoui), July 7, 1992;
U.S. Patent 5.149,335 (Kelleaberger et al), issued September 22, 1992; and U.S. Patent 5,176,668 (Beraardia), issued January 5, 1993.
There is oo particular criticality with respect to the posmonat reunonsmp or the fluid acquisitioddisttibution foam component and the fluid stotagdrsdistribution component within these mufti-layer absorbent cores so long as these components are in effective fluid raaurtuaication with each other and so long as each component is large enough to effectively bold and/or vaatport the amount of aquoous body fluid that is expected to be discharged into the casamarial pad. The mast preferred relatioathip bawoea the fluid acquisitioddistribution foam compooaoi and the fluid storagelredistributioo component within the absorbent core is to place these caenporxats in a laversd configuration. In such a layered con5guration, the fluid acquisitioddistribution foam component comprises as upper foam layer which overlies a subjacent fluid storagelredistribuaon component in the form of a lower layer. It should be understood that these two types of layers refer merely to the upper and lower zones of the absorbent wre and are not neeestanly lirruted to single layers or sheets. Both the fluid acquisitioddistribution zone, e.g., upper layer. and the fluid storagelredistribution zone.~e.g..

-;0-lower layer, can comprise several layers the requisite type. Thus. as used herein. the term "layer" includes the terms "layers" and "layered".
B. Byes and Wound Dress~a~
Absorbent foams of the present invention are also useful in bandages and dressings 5 for wounds. Thex include articles ranging from simple bandaids to large surgical dressings and bandages. A bandage or dressing can simply comprix 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 l0 area with modia that are conducive to microbiological growth. Potential wound healing benefits can be conferred by prctreating the absorbent foam with any of a wide variety of antimicrobial and/or antiseptic compounds well know to those skilled is the art.
C. yvt~pes Absorbent foams of the present invention are also useful in surgical drapes.
These 15 are sheets of material that catch blood during surgical proc~rra. They typically co<nprix 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 placxrttent is surgery.
The foam of the present invention is particularly easy to form into such articles. Further, the inherent 2o integrity of such foams prevents contamination of the area by loox n>aurials such as might be found in traditional 5ber-based absorbent structures. The absorbent properties are well suited to captttrutg splattered blood quickly and preventing its spread, e.g.
to the floor thus producing a slipping harird. Smaller sizes of thex laminates may also be used as wipes for blood and blood based fluids.
25 V. Test Methods for Polymeric Faams A. Vertical Wicking C~ ilitv 1.
Artificial Meosava! Fluid (AMF) is prepanad by combining oqual volumes of gastric mutts solution and Erah., sterile defibrinated sheep blood (Cleveland Scienti5c, American 3o Biomedical, Bath, OIL. The gastric mucin solution is preparod by combining the following in the proportiaos and order shown:
- 450 mL of aqueous sodium dihydrogrn phosphate (.138 wt.%) solution containing sodium chloride (0.85 wt.%) adjusted to pH 7.210.1:
- 7.5 mL potassium hydroxide aquoous solution:
35 - 31 g sta~ilized gastric mucin (1CN Biomedical Inc.. Cleveland, OED:
heated 2.5 _;l_ hours to completely dissolve the aastnc muctn. The solution ~s allowed to cool to less than .t0°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. Samrle P
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-Her sealer (Model T-7, 115VAC, 65 W Haneil Company, Santa Monica, California). The 0.5 centimeter at the bottom of the material snip remains cxposcd.
The ouuide 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. Eauioment Preparation The AMF is stirred for 30 minutes at 21°C. Approximately 300 mL of the equilibrated AMF is poured into a 500 mL rarystalliang dish. The filled dish is stirred ma~rically at low speed.
A rylindrical Plexiglas bar (30.5 cm cylindrical bar with at least two attached Plexiglas plates (25 cm x 0.5 cm x 3 em) aitac6ed at the end with the spacing being adjustable) is clamped onto a ring stand. Ttx clamp should tentatively be set approximately I 8 - 20 inches above the base of the stand. Allow enough space between the Plexiglas plates on the end of the rylindrical bar is prrnrided to flt the tbidmess of the samples to be tested.
4. Test Procedure The sealed top side of the sample is placed baween two of the Plexiglas plates, and then the plates ate tied togaher 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.
If not, additioml plates can be used to position the samples one behind the other. After suspeadiog aU samples, the bottom and top of t>se samples should all be level with respect to the Plexiglas plates and each other.
The stir plate and dish of AMF is placed direuly underneath the suspended samples.
The samples art towrered 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 iaterfaoa 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 appro~urnated. The heterogenem within the samples promdes channels of wicked fluid with no clear leading edge. The m~dpo~nt of the wicked height is taken as the value to be recorded. The average of the final vertical wiclung 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 Wicking l0 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 caxamenial 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, cantainiag the test fluid (ice this case, AMF at 22°C) and coaneetcd to a fluid reservoir at zero hydrostatic head rrlative to the test sample, is allowed to contact the lower surface of the sample as a point source aced the .
increase in weight of the sample is used as a measure of fluid uptake versus time. The test prods for 3900 sx~onds. During the test, the sample is consaained under 0.18 psi (1.2 kPa) pressure by a conformable water-filled plastic bag covered by a metal weight. This conformable systan provides a hydrostatic pressure to the sample to allow the pressure on the sample to r~rtain relatively caistaat over the entire sample area.
"initial Uptake" is de5aed as the weight of AMF absorbed by the system after seconds. "Rewet" is subsequently measured on the absorbent member or catamenial pad to 5nd out the amount of fluid that eaa be repeatedly blotted from the strucdtrelpad with Whaintan fiber paper at 0.25 psi (1.7 kPa) until the core will give up less than 0.5 g of AMF.
"R~imd Uptake" is calculated as the differs between "initial Uptake" and "Rewet".
C.
Resistance to compression deflection can be quanti5ed by mnsttriog the amount of strain (% reduction in thicloseas) produced it a foam sample which has bees saturated with syntheoic urine, after a confining pressure of 0.74 psi (5.1 kPa) has bees applied to the 3o sample.
Jayco srotheric urine used in this rnrtbod is prepanod by dissolving a mixture of 2.0 g KCI, 2.0 g Na2S04, 0.85 g NH4H2P04, 0.15 g (Ni~)2HP04, 0.19 g CaCl2, and 0.23 g MgCl2 to 1.0 liters with distilled water. The salt mixture can be purchased from Eadovations, Reading, Pa (cat No. JA-00131-000-01).
The foam samples, synthetic urine and equipment used to make measunmaus are all equilibrated to a temperature of 31°C. All measurarseau are also performed at this .; ; _ temperature.
A foam sample sheet is saturated to its free absorbent capacity by soalung m a bath of synthetic urine. After 3 mututes. 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 cvlindncal sample is soaked in sythetic unite at 31 °C for a further 6 minutes.
The sample is then removod from the synthetic urine and is placed on a flat granite base under a gauge suitable for measuring the sample thickness. The gauge is sa 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 inZ
(6.5 cm2) and capable of measuring thiclatess to 0.001 in (0.025 mm) can be employed.
Examples of such gauges are as Amen ,node( 482 (Amen Co.: Waltham, MA) or an Ono-Sokki model EG-225 (Ono-Sokki Co., Ltd.: Japan).
After 2 to 3 ruin., 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 usod to measure the final sample thickness (X2). From the initial and final thiclmess measurements, the percent strain induced can be calculated for the sample as follows: [(Xl-X2)/X1]x100 = % reduction in thickness.
D. Free Absorbent C ~~c:.., Free absorbent capacity can be quaatifiod by measuring the amount of sythetic uric absorbed in a foam sample which has beg saturated with synthetic urine.
2o The foam samples and synthetic urine are equilibrated to a temperature of 31 °C.
Measurements are performed at ambient temperature.
A foam sample sleet is saturated to its free absorbent capacity by soaking in a bath of synthetic urine. ARer 3 minutes, a ~c~rtinder baring a 1.0 ia2 (6.5 cm2) circular surface era is cut out of the sasurated sheet with a sharp circular die. The ryiiadrical sample is soaked in syo~C urine at 3l°C for a further 3 minute. 'I~e sample is then removod from die sync urine and is placed on a digital balance. Any balance fitted with a weighing P~
hsviag an aces larger than that of the sample and with a rtsolutioa of 1 milligram or less can be employed. Examples of such balances are the Metder PM 480 and Mettler PC

(Menler Iatwrrteat Corp; Hightstawn Nn.
3o ARer daaminiog the weight of the wet foam sample (Ww), it is placed betwatt 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 oa each side) and pressed with 20.000 Iba. of force in a Carver Laboratory Press. The sample is then removed from the paper towels, dried is a Fisher convection oven at 82°C for 20 minutes. and its dn_ weight recorded (Wd).

.;4.
The free absorbent capacm (FAC) is the wet weight (Ww), less the drv_ .;eight (Wd) divided by the dw weight (Wd), i.e., FAC = ((Ww-Wd)/Wd]
E. Dwamic Mechanical Analysis (DM~e,) DMA is used to determine the Tgs of polymers including polymeric foams.
Sawples 5 of the foams are sliced into blocks 3-5 mm in thiclmess and washed 3-4 times in dis,:lled water, expttssing the fluid through roller tops between each washing. The resulting foam blocks are allowed to dry in air. The dried foam slices are cored to yield a cylinders 25- rrui in diameter. These cylinders are analyzed using a Rheometrics RSA-II dynamic mechanica~
analyzer set in compression mode using parallel plates 25 tnm in diameter.
Instrument to parameters used were as follows:
'Temperature step from ca. 85°C to -40°C in steps of 2.5°C
Soak intervals between tempetaturt changes of 125-160 seconds Dynarntc strain set at 0.1% t0 1.0% (usually 0.7%) 15 Ft~equency set at 1.0 radianals~d Autoteasion set in static force hacking dynamic force made with initial static force set at 5 g.
The glass transition tentperatitre is taken as the maximum point of the loss tangent versus 20 temperature curve.
VI. Stxcisc Examp~
These examples illustrate the specific preparation of collapsed RIPE foams according the present invention.
25 A) Anhydrous calcium chloride (36.32 kg) and potassium persulfate (567 g) are dissolved is 378 liters of water. This provides the water phase stream to be usod in a continuous process for forming a HIDE emuisioo.
To a monomer combination comprising 400 g styrene, 2900 g divim~lba~ (40%
30 divinylbeazene and 60% ethyl styrene), and 4800 g 2tthylbexylacrylate is added 480 g of high purity diglycerol tnonooleate and Tintrvia 765 [bis( 1,2.2.5,5 pentan~rthylpiperidinyl)sobacateJ antioxidant (41 g).
This diglycerol tnooooleste emulsifier is prepared following the general procedure for PnP~'in8 PoIYBlYa~1 ~~ ~ in U.S. Patent 5,387.207 (Dyer et al.) issued Feb. 7, 35 1995. A polyglycerol composition comprising approximately 97% or greater diglycerol and .;;_ 3°~° or less tnglycerol (Solvav Performance Chertucals:
Greenwich. Conn) is estenfied with fatty acids having a fam acid composition comprising appro~umately 71% C
18:1,. :i% C 18.x.
9% Clb:l, 5% C16:0, and I1% 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 conditiocts 5 of mechanical agitation. nitrogen sparging, and gradually increasing vacuum.
with subsequent phosphoric acid neutralisation, cooling to about 85°C, and settling to reduce the level of unreacted polyglycerols. The polyglycerol ester reaction product is first fiactionallv distilled through two CMS-15A centrifugal molecular stills conneetod in series to roduce the levels of unreactod polyglycerols and fatty acids and then redistilled through the stills to yield l0 distillation fractions high in diglycerol monoesters. Typical conditions for the final distillation pass are a feed rate of about 15 lblhr, a degauer vacuum of about 21-26 microns, a bell jar vacuum of about 6-12 microns, a fad temperature of about 170°C, and a residue temperature of about 180°C. Distillation flactions high in diglycerol monoesters are combined, yielding a reaction product (as determined by supercritical fluid chron~aphy) 13 comprising approximately 50% diglycerol monooleate, 27% other diglycerol monoesters, 20% polyglycerols, sad 3% Other polyglycerol esters. After mixing, the reaction product is allowed to settle overnight. The supernatant is withdrawn sad usod in the oil phase as the emulsifier in forming the ICE. (About 20 g of a sticky residue is discarded.) Separate strearru of the oil phase (25°C) and water phase (65°-70°C) are fcd to a 20 dynamic mixing apparatus. Thorough mixing of the combined streams in the dynamic mixing apparatus is achieved by mesas of a pin impeller. At this scale of operation, an appropriate pin impeller comprises a rylindrical shaft of about 21.6 cm in length witb a dianxter of about l.9 cm. The shaft holds 4 rows of pins, 2 rows having 17 pins sad 2 rows having 16 pins, each having a dian~ter of 0.5 cm extending outwardly from the central axis of the shaft to a 25 length of 1.6 cm. The pin impeller is mountod in a cylindrical sloeve which forms the dynamic mixing apparatus, and the pint have a clearance of 0.8 mm firom the walls of the cylindrical sleeve.
A spiral static mixer is mouatod dowuuream from the dynamic nuxing apparatus to provide back pressure in the dynamic mixer sad to provide improved incorporation of 30 composts into the emulsion that is eve~ally formed. Such a static mixer is 14 inches (35.6 cm) long with a 0.5 inch ( 1.3 cm) outside diarruxer. The static mixer is a TAH
Industries Modd 070-821, modified by cutting off 2.4 inches (6.1 cm).
The cAmbined 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 35 escape while filling the apparatus completely. 'Ihe flow ratrx during filling are 3.78 g/sx oil phase and 7.56 ccJsec water phase.
Once the apparatus set-up is fillod, agitation is begun in the dynamic mixer, with the -3 ti-unpeller cuttuttg at 800 RPM. The flow' rate of the water phase is then steadily increased to a rate of 44. I cclsec in a time period of about 30 sec. and the oil phase flow rate is reduced to 1.25 glsec 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 I-IIPE has a water-to-oil ratio of 5 about 50:1.
B) Polvmerization/Curing of RIPE
The 1~PE 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 l0 is 6.75 in. ( 17.14 cm) high. The E~PE-containing tubs are kept in a room maintained at 65°C for l8 hours to cure and provide a polymeric HIPS foam.
C) Foam Washing and Dewaterina The cured HIDE foam is removed from the tubs. The foam at this point has residual water phase (containing dissolved emulsifiers, elxd~olyte, initiator raidues, gad initiator) l5 about 32-38 times (32-38X) the weight of polymerized monomers. The foam is slicxd with a sharp reciprocating saw blade into sheets which are 0.15 inches (0.38 cm) in thiclatess.
These shits are then subjected to comprasion in a series of 2 porous nip rolls equippod with vacuum which gradually reduces the residual water phase coat of the foam to about 2 times (2X) the weight of the polymerized monomers. At this point, the sheets are then 20 rrsaarrated with a 1% solution of Pegospecse 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 faom is then dried in air for about l6 hours. Such drying reduces the moisture oor~t to about 4-10 % by weight of polycrxrized material.

EIRE foams are preparzd using various pour tanpaaatres, cure times and tanperanires, water to oil (W:O) ratios, gad impeller mixer speeds. These foams and their propatia are shown in Tables 1 gad 2 below:
Table l : Hole Sizes vs. Pour Tang Example Pour Mixer W:O Cure TempCure Hole Temp Speed Ratio (C) Time Size (C) ( m) (ltrs) ( ) 2a 65 800 45:1 65 16 I1.8 2b 74 800 50:1 65 t6 13 2c 65 800 50:1 65 l6 11 -Zd 65 800 SS:I 65 16 111 2e 82 800 50: l 82 2 l7 - 2f 82 800 45:1 82 2 16.4 Table 2. Foam Caoacitv a_~~_~~ ctrr.,~h vs W~0 Ratio Example W:O RTCD FAC
RatlO

la 45:1 32.3% 44.7 lb 50:1 55.7% 46.0 lc 50:1 57.0% 50.1 Id 55:1 64.9% 52.7 le 50:1 68.8% 49.2 if 45:1 54.5% 43.0 5 Table 3 shows the effect on the vertical wic)ung ,ate and capacity of residual calcium chloride salt in the foam relative to a washed foam sample that has been rehydrophilized according to the prrsent invention. The foam sample labeled "Unwas~d" is the unwasbcd HIPS foam of Example 2b containing residual calcium chloride sah. The foam sample labeled "Washed" is the HIDE foam of Example 2b that has been washed to remove the salt to and rrhydrophilixed with PEGOSPERSE 200 ML. The columns relating to "Wicking Rate"
show the time required to wide A11~ to the indicated heights: the columns relating to "Capacity" show the amount of Albff wicked to that height after a period of 18 hours:
Table 3: Wicking Rate and C,~acitv at l~uilibrium Height Wicking Rate Capacity Height Umvashod Washed Unwashed Washcd (cm) (min) (min) (g/gj ( ) 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 85 I : 40.3 44 s ._ 8_ 6' 120 30 39.2 42 s 7 33.3 39.5 8 19.1 22.7 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 is the foam relative to a washed foam sample that has bees rehydrophilized according to the present invention. The foam sample labeled "Unwashed" is the unwashed HIPS foam of Example 2b containing residual calcium chloride salt. The foam sample labeled "Washed" is the HIPS foam of Example 2b that has boen washed to ranove the salt and t~ehydrophilined with PEGOSPERSE 200 ML.:
la Table 4: HGW
Foam Sample Initial UptakeRetained Uptake% Retaincd/Initial (glg) (g/g) U take Unwashed l4 12 86%

W~~d 24 19 79a/o Table.4 above shows that the preseact calcium chloride in the foam inhibits the HGW, relative to the same foam that has been was>rod and crhydrophilizcd.
3.
HIDE foams are prepared according to the procedure of Example 1. The HIPEs are poured at 74°C and 800 RPM and curod at~ 82°C for 2 hours.
Differences is water to oil (W:O) ratio and corresponding differences in properties are shown in Table 5.
Table 5. Foam Canacitv and Strensnh vs. W:O Ratio Example W:0 RTCD FAC
Ratio 3a 30I 5.7% 29.8 3b 40:1 22.5% 39 4 3c 40I 12.0% 39.6 -~9.
3d 50 l ;o ~a~ ,17 ~
Example a~ Preparation of Bamer Lover from I-llPEs A foam material useful as the optional bamer 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 bamer lav_ er are mixing at a temperature 5 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 step 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 as absorbent member or layer between a fluid impernous to backsheet and an apertured film tops6eet (such as DRI-WEAVE). Optionally, a nonwoven sheet can be used as the topsheet in place of the aperturod film. Prcferabiy, a secondary topsheet is positioned between the foam absorbent member gad the apertured topshoet.
Example 6: Catamenial Pad Having '~'wo Foam Absorbent embers A piece of polymeric foam according to any of Examples 2a, 2b, 2c, or 2d is cut into 15 a strip having a width of 6.4 em, a length of I O cm, gad a thickness of 0.19 cm (volume = l2 cc). A second piece of polynxric foam according to Examples le 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 arc assembled as described is Example 5 into a catarnenial pad with the upper layer (adjacent to the tops6at) being the smaller of the two pieta of foam.
Preferably the two 20 foam pieta are lightly bonded together with gay suitable bonding adhesive applied in specific points to maintain contact between the pieta without restricting fluid flow.
~~~le 7: Camrnenial Pad Having a Barrier L,a ~~er A r~tamenial pad having an absorbent core comprising three absorbent foams of the prcseat invention and a filler material between the foam absorbent core and the backsheet is 25 prepared as follows. A piece of polymeric foam according to gay 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 le or if is cut into a strip that will be the middle !aver 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 30 material, which is optioaaUy airfelt) of the absorbent core. This barrier layer will have a number average ceU size of from about 15 to about 50 pin gad a number average hole size of from about 4 to about 9 Erin.
For a thick product, the filler material (e.g., airfelt) is located between the absorbent .QU_ core and the backslteet. TEte pieces are assembled as described ut Example ~
into a catamenial pad. Preferably the three foam pieces are lightly bonded together with aav suitable bonding adhesive applied in specific points to maintain contact between the pieces without restricting fluid flow.
5 E~cam~le 8 v Catamenial Pad Containing Foam and Absorbent Gelling_Matenal A piece of polymeric foam according to any of Examples 2a, 2b, 2c, or 2d is cut into a step having a width of 6.4 cm, a length of 10 cm, and a thiclmess of 0.19 cm (volume = 12 cc). 'Ibis is assembled over a web consisting of cellulosic fibers and absorbent gelling material or absorbent gelling material laminated between two layers of tissue.
l0 Example 9. Bandaste 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 acposed edges of this strip are coated with gay suitable contact adhesive and cover with a release paper and packagod in, a sanitary l5 wrapper. Optionally, a fluid pervious tops6eet such as DRI-WFAVE or a noawovea can be attached on top of the foam.
Example 10. Sury ~~tte Having Foam Comp 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 impernxable backsheet using any 20 suitable adhesive. The oppasutg side of the backtheei can be trrated with any suitable contact adhesive gad covered with release paper so as to provide for stability in application to a particular arts when in use.
Any of the foams of Example 2 can be cored to provide a tube having a radius of 1.2 cm 25 gad a length of 8 cm. The tube is wrapped~in a fluid permeable aonwoven covershoet and attached to a suing for easy ranoval.

Claims (25)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A polymeric foam material which is capable of absorbing blood and blood-based fluids, said polymeric foam material comprising a hydrophilic, flexible. nonionic polymeric foam structure of interconnected cells, which foam structure has:
A) the ability to wick artificial menstrual (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.

2. The foam material of Claim 1 wherein said foam structure has:
A) the ability to vertically wick AMF to a height of 5 cm in less than about 20 minutes;
B) a capillary specific surface area in the range of from about 0.010 to about 0.030 m2/cc;
C) a free absorbent capacity of from about 40 to about 70 g/g.

3. The foam material of Claim 2 wherein said foam structure has:
B) a capillary specific surface area in the range of from about 0.012 to about 0.026 m2/cc.

4. The foam material of Claim 3 wherein said foam structure has about 0.5% or less of said residual hydratable salts.

5. The foam material of Claim 2 wherein said foam structure has the ability to wick at least about 30 g/g of AMF to a height of about 5 cm at equilibrium.

6. The foam material of Claim 2 wherein said foam structure has % Retained/Initial Uptake of AMF of at least about 50%.

7. The foam material of Claim 2 which has a number average cell size of from about 20 to about 180 µm and a number average hole size of from about 4 to about 30 µm.

8. The foam material of Claim 7 which has a number average cell size of from about 35 to about 130 µm and a number average hole size of from about 10 to about 28 µm.

9. The foam material of Claim 1 which has a dry basis density of from about 0.014 to about 0.024 g/cc.

10. A catamenial pad especially suitable for absorbing menstrual fluids, said pad comprising:
I) a fluid pervious topsheet;
II) a backsheet; and III) an absorbent core positioned between said topsheet and said backsheet and the fluid discharge region of the wearer of the pad, said absorbent core comprising an absorbent member made from the foam material of Claim 1.

11. The pad of Claim 10 wherein said absorbent core further comprises a fluid acquisition layer between said topsheet and said absorbent member.

12. The pad of Claim 10 wherein said absorbent member comprises an upper foam layer having a capillary suction specific surface area from about 0.012 to about 0.020 m2/cc and a lower foam layer having a capillary suction specific surface area higher than that of said upper foam layer and in the range of from about 0.020 to about 0.026 m2/cc.

13. The pad of Claim 10 wherein said absorbent member comprises:
(a) an upper foam layer having a capillary suction specific surface area from about 0.012 to about 0.020 m2/cc;
(b) a middle foam layer having a capillary suction specific surface area higher than that of said upper foam layer and in the range of from about 0.020 to about 0.026 m2/cc; and (c) a lower foam layer having a having a capillary suction specific surface area higher than that of said middle foam layer and in the range of from about 0.04 to about0.08 m2/cc, and a number average cell size of from about 20 to about 50 µm and a number average hole size of from about 4 to about 9 µm.

14. The pad of Claim 10 wherein said absorbent member is an upper acquisition/distribution component and wherein said absorbent core further comprises a lower fluid storage/redistribution component in fluid communication with said upper component and comprising absorbent gelling material.

15. The pad of claim 14 wherein said lower component comprises absorbent gelling material laminated between two tissue layers.

16. An absorbent article selected from the group consisting of tampons, bandages, wound dressing and surgical drapes which comprises the foam material of Claim 1.

17. 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, divinylphenan-threnes, divinylbiphenyls, divinyldiphenylmethanes, divinylbenzyls, divinylphenylethers, divinyldiphenyl-sulfides, divinylfurans. divinylsulfide, divinysulfone, 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 quatemary ammonium salts, long chain C12-C22 dialkoyl(alkenoyl)-2-hydroxyethyl, short chain C1-C4 dialiphatic quatemary ammonium salts, long chain C12-C22 dialiphatic imidazolinium quatemary ammonium salts, short chain C1-C4 dialiphatic, long chain C12-C22 monoaliphatic benzyl quatemary 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.

18. The process of Claim 17 wherein the polymeric foam of step B) is sliced into a sheet prior to step C).

19. The process of Claim 17 wherein the polymeric foam material is dewatered in step E) to a moisture content of from about 5 to about 15%.

20. The process of Claim 17 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.

21. The process of Claim 17 wherein:
I) 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.

22. The process of Claim 17 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-octadecylacrylamide, p-n-octystyrene, and mixtures thereof.

23. The process of Claim 21 wherein the emulsifier component comprises a primaryemulsifier having at least about 70% by weight emulsifying components selected from the group consisting of diglycerol monooleate, sorbitan monooleate, diglycerol monoisostearate, sorbitan palmitate, sorbitan myristate, sorbitan laurate, and mixtures thereof.

24. The process of Claim 17 wherein the hydrophilizing 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 etboxylates; silicone-glycol copolymers; and mixtures thereof.

25, The process of Claim 24 wherein from about 0.05 to about 5% of the hydrophilizing surfactant remains in the foam material after step D).