Method for producing water absorbent polyacrylic acid (salt) resin powder, and water absorbent polyacrylic acid (salt) resin powder

摘要

An object of the present invention is to provide a method for producing water absorbent resin powder in which permeability potential (SFC) is improved while a water absorbing rate (FSR) is being kept. The method is a method for producing water absorbent polyacrylic acid (salt) resin powder including the steps of: (i) polymerizing an acrylic acid (salt) monomer aqueous solution; (ii) during or after the step of (i), performing gel grinding of a hydrogel crosslinked polymer obtained by the polymerization, wherein the hydrogel crosslinked polymer has resin solid content of 10 wt % to 80 wt %, and the gel grinding is carried out with gel grinding energy (GGE) of 18 [J/g] to 60 [J/g]; (iii) drying a particulate hydrogel crosslinked polymer obtained by the gel grinding, wherein the drying is performed at 150° C. to 250° C.; and (iv) carrying out a surface treatment to the particulate hydrogel crosslinked polymer thus dried.

主权项

1. Water absorbent polyacrylic acid (salt) resin having:
95 wt % or more of particles whose diameter is not less than 150 μm and less than 850 μm; logarithmic standard deviation (σζ) of particle size distribution of 0.25 to 0.50; absorption against pressure (AAP) of 20 [g/g] or more; a water absorbing rate (FSR) of 0.30 [g/g/s] or more; a saline flow conductivity (SFC) of 20[×10−7·cm3·s·g−1] or more; and an internal cell ratio of greater than 1.0% to 2.5%, which is calculated by {(real density)−(apparent density)}/(real density)×100, the water absorbent polyacrylic acid (salt) resin containing a polyvalent metal salt.