Absorbent foams made from high internal phase emulsions useful for acquiring and distributing aqueous fluids

Claim 1

A process for the preparation of an absorbent polymeric foam material capable of acquiring and distributing aqueous fluids, which 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) from about 85 to about 98% by weight of a monomer component capable of forming a copolymer having a Tg of about 35° C. or lower, the monomer component comprising: i) from about 30 to about 80% by weight of at least one substantially water-insoluble monofunctional monomer capable of forming an atactic amorphous polymer having a Tg of about 25° C. or lower; ii) from about 5 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 divinyl benzenes, trivinyl benzenes, divinyl toluenes, divinylxylenes, divinylnaphthalenes divinylalkylbenzenes, divinylphenanthrenes, divinylbiphenyls, divinyldiphenylmethanes, divinylbenzyls, divinylphenylethers, divinyldiphenylsulfides, divinylfurans, divinylsulfide, divinyl sulfone, 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 the group consisting of diglycerol monoesters of linear unsaturated C 16 -C 22 fatty acids, diglycerol monoesters of branched C 16 -C 24 fatty acids, diglycerol monoaliphatic ethers of branched C 16 -C 24 alcohols, diglycerol monoaliphatic ethers of linear unsaturated C 16 -C 22 fatty alcohols, diglycerol monoaliphatic ethers of linear saturated C 12 -C 14 alcohols, sorbitan monoesters of linear unsaturated C 16 -C 22 fatty acids, sorbitan monoesters of branched C 16 -C 24 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 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 C 12 -C 22 dialiphatic, short chain C 1 -C 4 dialiphatic quaternary ammonium salts, long chain C 12 -C 22 dialkoyl(alkenoyl)-2-hydroxyethyl, short chain C 1 -C 4 dialiphatic quaternary ammonium salts, long chain C 12 -C 22 dialiphatic imidazolinium quaternary ammonium salts, short chain C 1 -C 4 dialiphatic, long chain C 12 -C 22 monoaliphatic benzyl quaternary ammonium salts, and mixtures thereof, and 2) a water phase containing: (a) from about 0.2 to about 20% by weight of a water-soluble electrolyte; and (b) an effective amount of a polymerization initiator; 3) the weight ratio of the water phase to the oil phase being in the range of from about 12:1 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.