AU749640B2 - Sponge - Google Patents

Description

-1- Regulation 3.2

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT

(ORIGINAL)

Name of Applicant: Actual Inventors: Address for Service: Holbray Pty Ltd JAY, William Harold DAVIES COLLISON CAVE, Patent Attorneys, 1 Little Collins Street, Melbourne, 3000.

Invention Title: "Sponge" Details of Associated Provisional Application(s) No(s): PO 9461 The following statement is a full description of this invention, including the best method of performing it known to us: Q:\OPER\MLA\HOLBRAY.CM 25/9/98 P:\OPER\MLA\SPONGE.COM 25/9/98 -2-

SPONGE

The present invention relates to absorbent sponges. In particular to highly water absorbent sponges which exhibit improved mechanical properties. The present invention also relates to processes for producing such sponges.

Solid materials capable of absorbing and retaining aqueous fluids have for many years found utility in numerous applications. Natural sea sponges were formerly used for this purpose.

However, these sponges have in the main, been replaced by synthetic sponges. The advantages of synthetic sponges is their ability to be produced in a variety of shapes and in accordance with market demands. Synthetic sponges are produced from a wide range of polymeric materials, and a particularly useful synthetic sponge is produced from reconstituted cellulose.

Cellulose-based sponges are widely used for many domestic and industrial cleaning applications. Cellulose-based sponges exhibit poor wet cut tear strength. Manufacturers of S cellulose-based sponges report that the product is biodegradable. However other important environmental aspects, namely that the process by which cellulose sponges are manufactured is environmentally disadvantageous due to the production of toxic gaseous and liquid byproducts resultant from such manufacture.

Polyurethane foams are well-known and a voluminous body of literature has accumulated over the years as attempts have been made to modify the physical properties of polyurethane foams, or to prepare specialised foams with unique properties for specific applications. Much of this work has focussed upon various combinations of starting materials and the correlation of these starting materials with physical properties. Polyether-based polyols using propylene oxide as the predominant raw material has become the industry norm. Conventional polyurethane foams as a group are hydrophobic. These flexible polyurethane foams in general only exhibit bulk hydrophilicity. They have poor surface hydrophilicity and do not exhibit the desirable absorbency and wiping properties exhibited by cellulosic sponges.

P:\OPER\MLA\SPONGE.COM 25/9/98 -3- U.S. Patents 3,988,268 and 4,558,149 both describe sulphonate polyurethane prepolymers useful for the preparation of foams. U.S. Patent 4,638,017 also relates to a water absorbing sponge which comprises at least one of a sulpho-group containing polyurea and polyurethane, the polymer containing at least one sulphonate equivalent per 20,000 molecular weight units.

The use of sulphonated polyurethanes have in the main, been restricted to the synthesis of watersoluble or water dispersible materials, such as given in U.K. Patent 1,483,687.

Hydrophilic horticultural foams are described in U.S. Patent 3,889,417 and as mentioned above and also, in U.S. Patent 3,988,268. In the latter patent, it is reported that the rate of 10 ion exchange increases as the hydrophilic character, proportion of open cells and size of the cells of the product increases. Polyester-based polyols containing carboxylic or sulphonic acid groups are one preferred group. The preferred polyisocyanates are those which contain urethane groups, biuret groups, allophanate groups, isocyanurate groups or uretidinedione imine groups and have the advantage over unmodified isocyanates of having a greater affinity for hydrophilic polyols. The water content used for expansion of the foams is in the order of 5% of the formulation.

U.S. Patent 4,156,592 and U.S. Patent 4,292,412 disclose the use of reticulated hydrophilic polyurethane foams in compressed form and formulated as described in U.S. Patent 3,861,993 for the preparation of expandable fabric softener-containing articles and hydrophilic fabric softener foam compositions, respectively.

Superabsorbent polyurethane foams differ from the above polyurethane foams in that they are normally produced by the reaction of a suitably formulated polyurethane prepolymer with a very significant excess of water. The polyol portion of the prepolymer is generally based upon poly(oxyethylene) glycol, and the isocyanate component is generally TDI, MDI or MDI-based isocyanates or mixtures of both isocyanates. However, as a class, these superabsorbent polyurethanes are characterised by inadequate wet tear strength, large changes in dimensional volume on wetting, poor stiffness, and low compressive strength.

P:\OPER\MLA\SPONGE.COM -25/9/98 -4- According to the present invention there is provided an absorbent foam comprising a superabsorbent polyurethane embedded in the cellular network of an open cell foam matrix.

According to a second aspect of the present invention there is provided a process for the manufacture of an absorbent foam comprising the steps of: 1) providing an open cell foam matrix; 2) introducing an aqueous solution and/or suspension of the precursors to a 10 superabsorbent polyurethane foam into the open cell foam matrix; and S' 3) curing said precursors to form a superabsorbent polyurethane foam embedded in the cellular network of the open cell foam matrix.

We have now found that by embedding a superabsorbent polyurethane into an open cell foam matrix a sponge may be produced which advantageously provides high retention of water, reduced volumetric swelling, improved wet cut tear strength, improved tensile strength, improved stiffness, good dimensional stability, and good wiping properties.

The superabsorbent polyurethane which is embedded in the cellular network may partially or totally fill the cellular network of the open cell foam matrix.

The open cell foam matrix may be selected from a wide variety of open cell foam available and have desirable mechanical properties for the proposed use of the absorbent foam.

Preferably the open cell foam is an open cell polyurethane or polyurethane/urea foam.

Suitable open cell foams may be either hydrophobic or hydrophilic in character.

P:\OPER\MLA\SPONGE.COM 25/9/98 Open Cell Foams Conventional polyurethane foams may be employed as the open cell foam. Conventional polyols for flexible polyurethane foams are usually made by the reaction of a polyhydric alcohol with an alkylene oxide, usually propylene oxide and/or ethylene oxide, to a molecular weight number average of about 2,000 to 4,000 and above. These polyols are then reacted with a di- or higher functionality isocyanate in the presence of water (normally less than based upon the polyol content), surface active agents (generally polysiloxane-polyoxyalkylene *copolymers), a secondary blowing agent (particularly methylene chloride), colourants, fillers, etc. to produce the desired polyurethane foam. The water reacts with the isocyanate groups producing carbon dioxide gas which forms the cells or trapped bubbles when the polyurethane gels and cures. These polyurethane foams are generally hydrophobic, and therefore repel water; they do not wipe smooth surfaces dry, and do not rapidly wick water. However, in water they exhibit a very low volumetric swell and thus advantageously, do not change significantly in volume.

A resilient, crosslinked, hydrophilic, open-celled polyoxyalkylene urea/urethane foam with hydrophilic and hydrophobic segments of relatively high molecular weight such as is disclosed in U.S. Patent 3,793,241 may be used as open cell foams. This patent discloses a mixture comprising a hydrophilic isocyanate-terminated prepolymer, a polymeric isocyanate and a surfactant when intimately blended with a second mixture which comprised a hydrophobic hydroxyl-terminated prepolymer dissolved in a large volume of ice water produces foams suitable for cushioning. These foams are suitable for use as the open cell matrix.

Hydrophilic polyurethanes which have been based upon a formulation strategy described above are not generally "superabsorbent". In this class of polyurethanes the resulting polymer may, for example, be a hydroxy-terminated polyurethane consisting of polyoxyethylene units (soft segments) and ethylene and/or diethylene units (hard segments), connected through urethane linkages. Also present in the polymer chain may be urea segments which originate P:\OPER\MLA\SPONGE.COM -25/9/98 -6from the reaction of the water with isocyanate groups. In a number of formulations, a portion of the polyoxyethylene glycol may be replaced with polyoxypropylene glycol to increase tensile strength. This, reduces the hydrophilicity of the final product, but does serve to improve its tensile and tear strength. Hydrophilicity is generally a function of the polyoxyethylene segments. The amount and/or the molecular weight of the polyoxyethylene controls the degree of hydrophilicity. The added water constitutes about 0.3% of the total formulation.

U.S. Patent 4,158,087 describes a low resiliency polyurethane foam made from a 10 polyoxyalkylene urethane prepolymer containing at least 40 mole percent of oxyethylene units, water and at least about 50 parts, based on the prepolymer, of a synthetic polymer latex. Such polyurethane foams are suitable for use as the open cell foam matrix in the absorbent foams of the present invention.

U.S. Patent 4,201,846, U.S. Patent 4,258,137, and U.S. Patent 4,309,509 describe the incorporation of hydrophilic vinyl alcohol polymer and copolymer fibres, an epoxy resin, and an odorant, respectively into a polymer as described in U.S. Patent 4,137,200. The reinforced foams have improved tensile and tear properties, reduced shrinkage upon drying, and also exhibit reduced swelling upon contact with water. In U.S. Patent 4,258,137, rigidising the polymer is accomplished by post-curing the epoxy resin included in the foaming step. These polyurethane foams may be used advantageously as the open cell foam matrix.

Polyurethanes incorporating acrylic monomers containing carbamate functionality are described in U.S. Patent Nos. 3,297,745, 3,425,988, 4,129,667, 4,279,833. As disclosed in these patents, the production technique adopted provides for the preparation of interpenetrating polymer networks preferably should not include any grafting of one polymer to the other although some grafting may accidentally occur. These polyurethane foams are also suitable for use as the open cell foam matrix.

Slightly hydrophilic polyurethane foams have been described in U.S. Patent 4,435,527 are P:\OPER\MLA\SPONGE.COM 25/9/98 -7also suitable for use as the open cell foam matrix. This patent describes a polyether polyol, polyester polycarbonate and polyisocyanate reaction product and subsequently foamed. It is claimed that these foams have offer better water absorption and retention and a lesser tendency to yellow. The water content proposed to be used in the foaming step was from to 10.0 parts per 100 parts of polyol.

Flexible polyurethane foams may be provided with a hydrophilic surface, such as is disclosed in U.S. Patent 4,654,234. The hydrophilic coating preferably does not penetrate the surface to a depth greater than 50%. A polyethylene glycol-isocyanate terminated prepolymer is described. The coating typically contains antifoaming agents and is cured by the application of heat and a catalyst. This coated surface may be used to improve the wet cut tear strength of the foam, to improve the water absorption, and to assist in the controlled release of cleaning and sanitizing agents.

U.S. Patent 4,181,770 describes the preparation of hydrophilic polyurethane foams from an isocyanate-terminated branched polyethylene polyol, an isocyanate-terminated polyester prepolymer, MDI/polycarbodiimide liquid condensation product which has 30% free isocyanate groups and water. The foam may be used to impregnate fabrics non-wovens, to produce reinforced sheets of foam of high absorbency and improved scuff (abrasion) resistance and firmness. Preferred polyesters are condensation products of adipic acid plus one or more alkane diols or a polycaprylactone.

Suitable Superabsorbent Polyurethanes U.S. Patent 4,731,391 discloses a method for preparing a superabsorbent polyurethane foam suitable for use in the present invention. Polyurethane foam precursors are mixed and reacted under foaming and free radical conditions with an ethylenically unsaturated compound such as an acrylate, methacrylate or acrylamide. Addition polymerisation can take place during or after foam formation. Reactants and reaction conditions are selected so as to essentially avoid grafting of addition polymer to the polyurethane. The polyurethane is preferably derived from P:\OPER\MLA\SPONGE.COM 25/9/98 -8an isocyanate-terminated poly(oxyalkylene) glycol having an isocyanate functionality greater than two and the addition polymer is the polymerisation product of at least one compound selected from the group consisting of acrylamide, substituted acrylamides, and acrylate and methacrylate salts, alkali metal and ammonium salts of acrylic and methacrylic acid.

These superabsorbent, hydrophilic polyurethane polymers are chemical entities which are well known to those skilled in the art. Methods for the preparation or application of these polymers are typically described in U.S. Patent Numbers 3,793,241; 3,854,535; 3,861,993; 3,890,254; 3,900,030; 3,903,232, 3,904,557; 4,110,508; 4,127,516; 4,137,200; 4,158,087; 4,160,076; 4,181,770; 4,266,043; 4,292,412; 4,314,034; 4,365,025; 4,337,645; 4,384,050; 4,384,051; 4,717,738; 4,725,628; 4,731,391; 4,740,528; 4,789,720; 4,798,876; 4,828,542; 5,065,752;5,296,518; 5,591,779 and 5,624,971, which are incorporated herein by reference.

The procedure for the manufacture of the prepolymers described in the above patents is either given within the description, or can be produced according to typical procedures as described in various publications relating to polyurethane chemistry, or as disclosed in U.S. Patent Nos.

2,726,219: 2,948,691; 2,993,013; 3,805,532 and 4,137,200.

In U.S. Patent 4,725,629 a superabsorbent polyurethane foam based upon an interconnecting polymer network of a crosslinked polyurethane and a cross-linked addition polymer containing a plurality of chain segments made up of functional groups containing repeating units which may be the same or different. These superabsorbent polymers are recommended for the manufacture of absorbent articles, especially disposable absorbent articles, such as nappies, sanitary napkins, bedpads, incontinent pads, and the like.

Superabsorbent polyurethane foams preferably derived from an isocyanate-terminated poly(oxyalkylene) polyol having an isocyanate functionality greater than two and containing an addition polymer such as acrylamides, acrylate and methacrylate salts, etc. are disclosed in U.S. Patent 4,731,391 P:\OPER\MLA\SPONGE.COM -25/9/98 -9- Polyurethanes such as those described in U.S. Patent 4,127,516 having good wet strength are preferred. The foam is prepared by reacting a urethane prepolymer with large amounts of water containing a poly(amino)urea and optionally, surfactants, etc. The poly(amino)urea is a water-soluble reaction product of a polyamine with a urethane prepolymer; said reaction product being further reacted with a cross-linking agent such as epichlorhydrin The basic formulation used is as disclosed in U.S. Patent 4,110,508. The poly(amino)urea, for example, may be prepared by reacting a linear poly(oxyethylene) polyol which is capped with a Spolyisocyanate and a polyamine in an organic solvent.

Hydrophilic cross-linked polyurethane foams such as disclosed in U.S. Patent 4,137,200 may be prepared by reacting a blend of a monomeric polyol and a polyoxyalkylene glycol (the OH groups of said blend being capped with a polyisocyanate) with large amounts of an aqueous reactant. The resultant foams were claimed to exhibit a broad spectrum of improved properties including hydrolytic stability and tensile strength and are suitable for use as open cell foam matrices.

Resilient foamed polymer obtained by reacting a mixture of an isocyanate-terminated prepolymer and a polyisocyanate with 15-150% by weight of water is disclosed in U.S. Patent 4,266,043 and may also be used. The polyether polyol has an oxyethylene content of 15 to by weight and the additional polymerisation product includes either a diol or higher functionality hydroxyl containing material. The polyisocyanate portion of the formulation being about 5 to 15% of the prepolymer weight.

U.S. Patent 4,273,913 and 4,297,482 disclose isocyanate-capped urethane-containing prepolymers prepared from polyols obtained from an epihalohydrin. For example, the polyol may be a polyalkylene glycol composed of the same or different oxyalkylene units or a mixture of different oxyalkylene units.

U.S. Patent 4,314,034 describes an open cell polyurea polyurethane foamed sponge which P:\OPER\MLA\SPONGE.COM 25/9/98 is produced by mixing together a prepolymer made from a hydrophilic oxyalkylene polyol which is capped with isocyanate groups (containing from 1 to 30% by weight of a polymeric isocyanate such as MDI and in particular PAPI) and an aqueous phase. The aqueous phase may contain reinforcing fibres, surfactants, thickening agents and preferably up to 40% by weight of diatomaceous earth. The resultant foam is said to exhibit reduced volume swell, rapid wet out and improved strength. U.S. Patent Nos. 4,314,034, 4,365,025, 4,377,645, 4,384,050 and 4,384,051 describe variations of the general concept of mixing an aqueous phase and a resin phase in which the resin phase comprises an isocyanate-capped Spoly(oxyethylene) glycol of the type disclosed in U.S. Patent 3,903,232 and related patents.

MDI and/or polymeric forms or isocyanate-containing derivatives thereof comprise the isocyanate component.

MDI-based absorbent polyurethane foams are described in U.S. Patent 4,337,645. The foams comprise a prepolymer derived from an alkylene diol, an MDI containing isocyanate product having a functionality greater than two and a monomeric polyol cross-linking agent having 3 or 4 hydroxyl equivalents per mole. The foam is said to exhibit minimal swell when wet and does not curl on drying. The foams however, do not have adequate load-bearing or stiffness properties for many applications.

U.S. Patent 4,365,025 describes flexible polyurethane foams which are made from isocyanate terminated prepolymers where the isocyanate is a mixture of diphenylmethane diisocyanate (MDI) and polymeric forms of MDI. The polyols which are reacted with the isocyanate are diols and triols having at least 50% by weight of oxyethylene groups. The foams are produced by reacting the prepolymer with water.

U.S. Patents 4,384,050 and 4,384,051 disclose flexible, hydrophilic polyurethane foams which are produced by mixing together an aqueous phase and a resin phase comprising a prepolymer derived from a poly (oxy C(2-4))alkylene) diol having a molecular weight of at least 1100, an MDI-containing isocyanate (preferably Isonate 143L) and a monomeric polyol crosslinking agent having 3 or 4 hydroxyl equivalents per mole. Trimethylolpropane is the P:\OPER\MLA\SPONGE.COM -25/9/98 11 preferred polyol. The isocyanate component should comprise less than 50% by weight of the prepolymer.

A method for the manufacture of multicoloured polyurethane sponge is described in U.S.

Patent 3,904,557. A poly(oxyethylene) polyol having a weight average molecular weight of from 200 to about 20,000 and a hydroxy functionality of from about 2 to about 8 is capped with a polyisocyanate. At least two different colouring agents is added to at least two different portions of isocyanate-capped polyol or water. The coloured portions are then separately .o*o reacted with the required other component to form at least two differently coloured reaction mixtures. These mixtures are then mixed together under laminar flow conditions to yield multicoloured variegated polyurethane foam.

U.S. Patent 4,717,738 relates to a hydroxyl containing polymer polyol and a method for the production of a polyurethane foam.

British Patent 1,209,058 discloses a hydrophilic polyurethane foam in which a polyether polyol containing a block of ethylene oxide capped with propylene oxide to obtain hydrolytic stability is reacted with a polyisocyanate. Again, only small quantities of water are used. The foams produced by this method have very poor wiping properties.

A superabsorbent polyurethane foam into which microcapsules of active ingredients are formed is described in U.S. Patent 4,828,542. The hydrophilic polyurethane prepolymer is foamed by mixing with water in the range of at least approximately 0.2/1 or greater and preferably 1/1 or greater.

U.S. Patent 5,065,752 describes a superabsorbent, hydrophilic foam composition for wound dressings. The polyurethane foam is produced by the in-situ reaction product of an isocyanatecapped polyether prepolymer, a polymeric hydrophilic agent capable of absorbing water (such as starch grafted copolymers of acrylate salts, or acrylamide salts), an adjuvant comprising a water-soluble alcohol, a wetting agent, and water.

P:\OPER\MLA\SPONGE.COM 25/9/98 -12- U.S. Patent 5,591,779 discloses a process for preparing a superabsorbent polyurethane foam by reacting a suitable polyurethane prepolymer with water in the presence of a superabsorbent polymer. The polyurethane prepolymer contains an oxyethylene content of at least 50% by weight. The amount of water required being 15 to 500 parts by weight of the weight of the prepolymer. At the start of the reaction, the temperature of the water being 10°C to higher than the temperature of the prepolymer.

The preferred absorbent foam should have a volumetric swell in water of less than 30 and preferably, nil, or little volumetric change between wet and dry states. The open cell foam matrix should preferably have open cells which may range in size from about 3 cm to less than 1 micron and should preferably exhibit good cut tear strength particularly when wet, good tensile strength and stiffness. The absorbent foam wipe surfaces dry, and rapidly wick exhibit a rapid rate of water absorption.

To overcome the problems enumerated above, it has been found that significantly improved physical properties are obtained when the isocyanate-terminated polyoxyethylene glycol *...prepolymers are mixed with large volumes of water and then foamed in the presence of a conventionally manufactured hydrophobic or hydrophilic polyurethane foam. This procedure is conducted in a manner such that the hydrophilic foaming mass penetrates through the pores of the hydrophobic foam partially or totally filling them. Composite foams of this type have been shown to be stiffer, have significantly improved wet and dry cut tear strength, improved tensile strength, and better load-bearing properties. Surprisingly, it has been also noted that the wiping properties of the absorbent foam are equal to, or superior to that of the same hydrophilic polyurethane foam, but without the polyurethane foam reinforcement. This is considered to be due to the better dimensional stability of the wet composite foam.

To enable the hydrophilic rising foam to better fill the cells within the block of polyurethane foam it is desirable, but not a requirement, that the foam be pretreated with one or more suitable wetting agents. Thispretreatment can also be advantageously used to enable the cell P:\OPER\MLA\SPONGE.COM 25/9/98 13structure of the rising foam to be further modified.

In the process of the present invention it is desirable for the superabsorbent polyurethane to be formed at a temperature below the temperature at which the open cell matrix foam decomposes or exhibits thermal degradation of the foam or its properties.

Hydrophobic polyurethanes show better absorbency for organic compounds than the S. hydrophilic polyurethane foams described herein. Thus, the hydrophobic polyurethane may be impregnated with a suitable adjuvant such as therapeutic agents, cosmetic agents, bactericide, fungicide, medicaments, or have such adjuvants incorporated into the foaming composition. Such incorporation will enhance the retention properties of the adjuvant.

Furthermore, if each of the foams are coloured differently, then resultant foam can be provided with additional visual appeal. Such colouring agents used would be those which are well known to those skilled in the art of manufacture of flexible polyurethane foams.

In a further modification, carbon, and in particular, activated carbon, may be included into the hydrophilic polymer formulation prior to it being foamed through the pre-cut blocks of polyurethane foam. If desired, the formulation may also contain suitable bactericides. The finished foam may then be suitably cut for insertion into footwear for comfort, and also serving as moisture and perspiration absorbents.

The present invention is further described by reference to the following non-limiting examples.

EXAMPLE ONE A reticulated hydrophobic flexible polyurethane foam, manufactured by Joyce Corporation, Moorebank, N.S.W. was suitably cut to size to fit a predetermined mould shape and size. The surfaces of the mould had been pre-treated with a suitable release-agent to assist in P:\OPER\MLA\SPONGE.COM 25/9/98 14demoulding the cured foam.

A hydrophilic prepolymer was prepared by reacting together a 1000 MW poly(oxyethylene) glycol with toluene diisocyanate to produce an isocyanate-terminated prepolymer with a free NCO content of 9.5 using the methodology previously identified.

PEG 1000 100 pbw TDI 44 pbw MDI to provide NCO content of 10 1 gram of Pluronic L62 (a surfactant manufactured by BASF) was dissolved into 100 grams 0 of water. 50 grams of the prepolymer described above was then added to this aqueous mixture, and both components were rapidly mixed together for 15 seconds. The creaming mixture was then poured into the mould, the block of polyurethane foam placed on top, and a lid containing air holes for vapour release was then fitted to the container. After the foam had cured, it was demoulded, cut to size and able to be packaged.

The resultant foam exhibited exceptional tensile, wet and dry tear strengths, almost no volumetric change between wet and dry states, was stiff, wiped water from a smooth surface without beading and was highly water absorbent.

EXAMPLE TWO A reticulated hydrophobic flexible polyurethane foam manufactured by Joyce Corporation, Moorebank, N.S.W. was suitably cut to size to fit a predetermined mould shape and size.

This block of foam was then soaked in a solution containing 2% of Crillet 1, removed from the solution, and excess water squeezed out. The surfaces of the mould had been pre-treated with a suitable release-agent to assist in demoulding the cured foam.

grams of the hydrophilic prepolymer used in Example 1 was reacted with 200 grams water containing 2 grams of Pluronic L62 (a surfactant manufactured by BASF) and both P:\OPER\MLA\SPONGE.COM 25/9/98 components were rapidly mixed together for 15 seconds. The creaming mixture was then poured into the mould, the block of polyurethane foam placed on top, and a lid containing air holes for vapour release was then fitted to the container. After the foam had cured, it was demoulded, cut to size and able to be packaged.

The resultant foam exhibited exceptional tensile, wet and dry tear strengths, almost no volumetric change between wet and dry states, was stiff, wiped water from a smooth surface without beading and was highly water absorbent.

**o EXAMPLE THREE A flexible polyurethane foam manufactured by Joyce Corporation, Moorebank, NSW in which the polyol component of the polyurethane foam consisted of a glycerine-based triol containing both poly(propylene oxide) and poly(ethylene oxide) to introduce some hydrophilicity into the foam was suitably cut into sheet form. These sheets of foam were then passed through pinch rolls in a manner such that an aqueous solution containing 2% of Crillet 1 wet the foam surfaces and to remove excess water.

50 grams of the hydrophilic prepolymer used in Example 1 was added to 200 grams of water containing 2 grams of Pluronic L62 (a surfactant manufactured by BASF) and both components were rapidly mixed together for 15 seconds. The creaming mixture was then poured onto the surface of the wet sheet of polyurethane foam and again passed through pinch rolls. The resultant sheet of foam was supported on a sheet of waxed paper until the superhydrophilic foam had gelled and become tack-free. After the foam had cured, it was cut to size and able to be packaged.

EXAMPLE FOUR A flexible polyurethane foam manufactured by Joyce corporation, Moorebank, NSW in which the polyol component used in the manufacture of the polyurethane foam consisted of a P:\OPER\ Ad2 106953.RES .d4)705/O2 -16glycerine-based triol containing both poly(propylene oxide) and poly(ethylene oxide) was reticulated and then suitably cut into sheet form. These sheets of foam were then passed through pinch rolls in a manner such that an aqueous solution containing 2% of Crillet 1 wet the foam surface and to remove excess water.

The hydrophilic prepolymer used in Example 1 was placed in one raw material tank of a polyurethane dispensing machine. Water containing 2 grams of Pluronic L62 (a surfactant manufactured by BASF) was placed in the other tank of the dispensing machine. Both components were pumped into the mixing chamber where they were rapidly mixed together in the ratio of 1:3 prepolymer:water. The creaming mixture was dispensed onto the surface of the wet sheet of polyurethane foam and again passed through pinch rolls.

The resultant sheet of foam was supported on a sheet of waxed paper until the superhydrophilic foam had gelled and become tack-free. After the foam had cured, it was cut to size and able to be packaged.

S Throughout this specification and the claims which follow, unless the context requires S"otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

:The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that that prior art forms part of the common general knowledge in Australia.

Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. It is to be understood that the invention includes all such variations and modifications which fall within its spirit and scope. The invention also includes all of the steps, features, compositions and compounds referred to or indicated in this specification, individually or collectively, and 3 any and all combinations of any two or more of said steps or features.

Claims (9)

1. An absorbent foam comprising a superabsorbent polyurethane embedded in the cellular network of an open cell foam matrix.

2. An absorbent foam according to claim 1 wherein said absorbent foam has a volumetric swell between wet and dry states of less than

3. An absorbent foam according to either claim 1 or claim 2 wherein said absorbent foam exhibits substantially no volumetric swell between wet and dry states.

4. An absorbent foam according to any one of claims 1 to 3 wherein the open cell foam matrix comprises open cells of up to 3 cm in diameter.

5. An absorbent foam according to any one of claims 1 to 4 wherein the open cell foam matrix comprises a reticulated cell structure.

6. An absorbent foam according to any one of claims 1 to 5 wherein the open cell foam matrix is of a colour different to the colour of the superabsorbent polyurethane.

7. An absorbent foam according to any one of claims 1 to 6 wherein the open cell foam matrix and/or the superabsorbent polyurethane are impregnated with an adjuvant selected from the groups consisting of therapeutic agents, cosmetic agents, bactericide, fungicide, medicaments, activated carbon or have such adjuvants incorporated into the foaming composition.

8. A process for the manufacture of an absorbent foam comprising the steps of: 1) providing an open cell foam matrix; J 0 P:\OPER\MLA\SPONGE.COM 25/9/98

18- 2) introducing an aqueous solution and/or suspension of the precursors to a superabsorbent polyurethane foam into the open cell foam matrix; and 3) curing said precursors to form a superabsorbent polyurethane foam embedded in the cellular network of the open cell foam matrix. 9. An absorbent foam substantially as hereinbefore described with reference to the examples. 10 10. A process substantially as hereinbefore described with reference to the examples. DATED this 25th day of SEPTEMBER, 1998 Holbray Pty Ltd S S 05*5 59 S S S S. 0 S S S S S. S 50 by DAVIES COLLISON CAVE Patent Attorneys for the Applicant(s)