POLYACRYLIC ACID-TYPE WATER ABSORBENT RESIN AND METHOD FOR PRODUCING SAME

摘要

Provided is a method for producing a water absorbent resin, which promotes the formation of interconnected voids (continuous gas bubbles) in a foamed polymer (foam-like water absorbent resin) by a more convenient method, and produces with high efficiency a water absorbent resin which exhibits a high water absorption rate even when stepped into a sheet form or a powder form in hygiene articles and the like. Disclosed is a method for producing a polyacrylic acid-type water absorbent resin, comprising (A) a step of obtaining an aqueous solution of acrylic acid-type monomers containing gas bubbles dispersed therein; (B) a step of polymerizing the aqueous monomer solution and thereby obtaining a foamed polymer; and (C) a step of heating and drying the foamed polymer,
wherein gas bubbles are incorporated such that the volumetric expansion factor defined by the following formula (1);;[Formula 1];Volumetric expansion factor=(Volume of aqueous monomer solution after gas bubble dispersion)/(volume of aqueous monomer solution before gas bubble dispersion)  Formula (1);; exceeds 1.1 times, and the aqueous monomer solution having a monomer concentration defined by the following formula (2);;[Formula 2];Monomer concentration [wt %]=(Weight of a monomer)/{(weight of a monomer)+(weight of solvent)}×100  Formula (2);; of 40% by weight or greater is boiling polymerized at a temperature of 100° C. or higher.

主权项

1. A polyacrylic acid-type water absorbent resin having an open gas bubble ratio of 5% or greater and the content of p-methoxyphenol is 60 ppm or less.