Patent ID: 6107356
Filing Date: 2000-08-22
Classification: A61L,C08F,C08J,C08K

Abstract:
A process for making a collapsible polymeric foam structure of interconnected open-cells which, upon contact with aqueous fluids, can expand and absorb the fluids, the process comprising the steps of:A) forming a water-in-oil emulsion, at a shear rate of not more than about 6000 sec.sup.-1, 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.degree. 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 25.degree. C. or lower;ii) from about 10 to about 30% 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 divinylbenzenes, trivinylbenzenes, divinyltoluenes, divinylxylenes, divinylnaphthalenes divinylalkylbenzenes, divinylphenanthrenes, divinylbiphenyls, divinyldiphenylmethanes, divinylbenzyls, divinylphenylethers, divinyldiphenylsulfides, divinylfurans, divinylsulfide, divinylsulfone, tetrakis[2-ethoxyacryloxy]silane, and mixtures thereof; andiv) from 0 to about 15% by weight of a second substantially water-insoluble, polyfunctional crosslinking agent selected from polyfunctional acrylates, methacrylates, acrylamides, methacrylamides, and mixtures thereof; andb) from about 2 to about 15% by weight of an emulsifier component which is soluble in the oil phase and which is capable of forming a stable water-in-oil emulsion, the emulsifier component comprising a primary emulsifier having at least about 40% by weight emulsifying components selected from diglycerol monoesters of branched C.sub.16 -C.sub.24 fatty acids, linear unsaturated C.sub.16 -C.sub.22 fatty acids, and linear saturated C.sub.12 -C.sub.14 fatty acids; sorbitan monoesters of branched C.sub.16 -C.sub.24 fatty acids, linear unsaturated C.sub.16 -C.sub.22 fatty acids, linear saturated C.sub.12 -C.sub.14 fatty acids; diglycerol monoaliphatic ethers of branched C.sub.16 -C.sub.24 alcohols, linear unsaturated C.sub.16 -C.sub.22 alcohols, and linear saturated C.sub.12 -C.sub.14 alcohols, and mixtures thereof; and2) a water phase comprising an aqueous solution 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) a volume to weight ratio of water phase to oil phase in the range of from about 30:1 to about 100:1; andB) polymerizing the monomer component in the oil phase of the water-in-oil emulsion to form a polymeric foam material.