Patent ID: 7435477

Claim:
A particulate water absorbent containing a water absorbent resin prepared by crosslinking a water-soluble unsaturated monomer mainly containing an acrylic acid and/or a salt (neutralizer) of acrylic acid, the water absorbent resin being particular in shape and containing particles of a particle size in a range of not less than 106 μm and less than 850 μm in an amount of not less than 90 mass percent with respect to a total mass of the water absorbent resin, the particulate water absorbent having a first salt concentration absorption index of not less than 0.60 as measured by a formula below when ion exchange water is used as an aqueous solution of a constant salt concentration: (salt concentration absorption index)=(absorbency for an aqueous solution of a constant salt concentration against a pressure of 4.83 kPa)/(absorbency for an aqueous solution of a constant salt concentration against no pressure), where the numerator is absorbency against a pressure of 4.83 kPa when the particulate water absorbent is impregnated with the aqueous solution of a constant salt concentration for 60 minutes, and the denominator is absorbency against no pressure when the particulate water absorbent is impregnated with the aqueous solution of a constant salt concentration for 60 minutes.