Patent ID: 8487048

Claim:
A water-absorbent resin, which is a water-absorbent resin comprising sodium polyacrylate obtained by a process including the step of polymerizing and crosslinking a monomer component including acrylic acid and/or its sodium salt (neutralized material) as a main component, wherein the water-absorbent resin has a mass-average particle diameter of 380 to 550 μm; includes a powder having particle diameters of smaller than 150 μm in an amount of 0 to 3 mass % relative to the water-absorbent resin; and includes a powder having particles of not smaller than 300 μm comprising not less than 60 mass % of the entirety of the water-absorbent resin; has an uncrosslinked water-extractable component content (water-soluble polymer content) of 0 to 25 mass % relative to the water-absorbent resin, and exhibits an absorption capacity of not less than 35 g/g without load, a total absorption capacity of not less than 70 (g/g) and an absorption efficiency of not less than 70% under load, wherein the total absorption capacity and the absorption efficiency under load are defined by the following equations based on values given by absorption of a 0.90 mass % aqueous sodium chloride solution (25° C.) for 1 hour: total absorption capacity(g/g)=absorption capacity(g/g)without load+monolayer absorption capacity(g/g)under load; and absorption efficiency(%)under load=monolayer absorption capacity(g/g)under load×100/absorption capacity(g/g)without load.