Patent ID: 6573330
Filing Date: 2003-06-03
Classification: C08F

Abstract:
A process for preparing a water-absorbent resin by polymerization of a water-soluble ethylenic unsaturated monomer, comprising;adding an aqueous solution of the water-soluble ethylenic unsaturated monomer to a hydrocarbon solvent and dispersing the aqueous solution therein; adding a water-absorbent resin having a water-absorbing rate different from that of a water-absorbent resin resulting from polymerization of the water-soluble ethylenic unsaturated monomer to the hydrocarbon solvent; and polymerizing the water-soluble ethylenic unsaturated monomer in the presence of the water-absorbent resin added to the hydrocarbon solvent, wherein the water-soluble ethylenic unsaturated monomer is at least one member selected from the group consisting of acrylic-acid, methacrylic acid, 2-acrylamide-2-methylpropanesulfonic acid, 2-methacrylamide-2-methylpropanesulfonic acid, and alkali salts thereof; acrylamide, methacrylamide, N,N -dimethylacrylamide, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, N-methylol acrylamide, and N-methylol methacrylamide; and diethylaminoethyl acrylate, diethylaminoethyl methacrylate, diethylaminopropyl acrylate, diethylaminopropyl methacrylate, diethylaminopropyl acrylanride, diethyl aminopropyl methacrylamide, and quaternary compounds thereof, the water absorbent resin to be present during the polymerization is at least one member selected from the group consisting of a hydrolyzate of a graft copolymer of starch and acrylonitrile, a neutralized graft copolymer of starch and acrylic acid, a saponified copolymer of vinyl acetate and acrylic acid ester, partially neutralized polyacrylic acid, a copolymer of maleic anhydride and isobutylene, and a polymer of a water-soluble ethylenic unsaturated monomer, and a water-absorbing time of the water-absorbent resin to be present during polymerization is less than 10 seconds or longer than 20 seconds.