Arakawa Kagaku Kogyo Kabushiki Kaisha

Jun-ichi Maeno

Shozo Tanioku

Muneharu Makita

Kiyoshi Sato

Nobuyuki Oshima

This invention provides a process for preparing a water-absorbing resin which comprises the steps of mixing powder of an inorganic inactive substance with a water-absorbing resin having carboxylate-containing monomer units, and adding water and a high molecular-weight cross-linking agent to the mixture to perform cross-linking reaction and evaporation of water, the cross-linking agent being selected from a specified copolymer (1) and a specified mixture of copolymers (2), and also provides a water-absorbing resin prepared by the process. The process of the invention gives water-absorbing resins improved not only in water-absorbing ability, rate of water absorption, gel strength after water absorption and unlikelihood of affording a wetty feeling after water absorption but also in capability of retaining water under pressure.

Process for preparing water-absorbing resin

A process for preparing a highly water-absorbent resin by a reversed-phase suspension polymerization method using an aqueous solution of a monomer containing an alkali metal salt of acrylic or methacrylic acid, water-soluble polymerization initiator, protective colloid, hydrophobic organic solvent and if required, dispersing agent, the process being characterized in that the protective colloid is a copolymer comprising: (A) about 50 to about 97 mole % of styrene and/or alkyl-substituted derivative thereof, (B) 0 to about 50 mole % of dialkylaminoalkyl acrylate or methacrylate and/or dialkylaminoalkyl acrylamide or methacrylamide, (C) about 3 to about 15 mole % of glycidyl acrylate and/or glycidyl methacrylate and (D) 0 to about 30 mole % of an unsaturated monomer which can be copolymerized with the component A, B or C.

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Osaka, Japan

Jun-ichi Maeno