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 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 mononer 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 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, in which the gas bubbles that are dispersed are formed by an inert gas,
Wherein the 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.