Patent ID: 8383747
Filing Date: 2013-02-26
Classification: B01J,C08F,C08J,C08L

Abstract:
1. A method for producing a water absorbent resin, comprising the steps of: (i) polymerizing in a reactor having a crushing means a monomer including an unsaturated monomer containing a carboxyl group, in the presence of an internal cross-linking agent (A) having two or more radically polymerizable unsaturated groups in its single molecule and in the presence of a non-polymeric internal cross-linking agent (B) having in its single molecule two or more functional groups each of which allows formation of an ester bond or an amide bond by reacting with a carboxyl group, while crushing a produced cross-linked polymer hydrogel in the reactor having crushing means; and (ii) drying the crushed cross-linked polymer hydrogel obtained in the step (i) so that an amount of the internal cross-linking agent (B) remaining in the water absorbent resin obtained in the step (ii) is not more than 1.0×10 an amount of the internal cross-linking agent (A) is 0.01 mol % or more and 0.2 mol % or less relative to an amount of the unsaturated monomer containing a carboxyl group, and a molar ratio (B)/(A) of the internal cross-linking agent (A) and the non-polymeric internal cross-linking agent (B) is 0.01 or more and 1.8 or less.