Patent ID: 7803880

Claim:
A water absorbent comprising water-absorbing resin particles, which are surface cross-linked and prepared from a water-absorbing resin having a cross-linked structure prepared by polymerizing a monomer including at least one of an acrylic acid and a salt of the acrylic acid, the water absorbent satisfying: (a) 90% by weight or more of the particles have a diameter less than 850 μm but not less than 150 μm; (b) a logarithmic standard deviation (σζ)of the particle size distribution is in a range of 0.25 to 0.45; (c) AAPs for 0.9 wt % saline is 20 g/g or more; (f) CRCs for 0.9 wt % saline is not less than 15 g/g but less than 29 g/g; (g) a chemical cross-linking index against pressure is 100 or more, the chemical cross-linking index against pressure represented by Formula (2): Chemical Cross-Linking Index Against Pressure =( CRCs )+( AAPdw ) (2), where CRCs (g/g) is an absorbency for 0.9 wt % saline, and AAPdw (g/g) is an absorbency against pressure for deionized water.