Patent ID: 7745537

Claim:
A particulate water absorbing agent comprising: (A) a water-swelling crosslinked polymer having a constitutional unit derived from an unsaturated monomer containing an acid group and/or a salt thereof; and (B) water, said particulate water absorbing agent having: (a) centrifuge retention capacity (CRC) for a 0.90% by weight aqueous sodium chloride solution being 28 to 50 g/g; (b) absorbency against pressure (AAP: 0.90 g) being 20 to 40 g/g; (c) moisture content determined on the basis of the weight loss in drying at 105° C. for 3 hrs being 2 to 10% by weight; (d) positive frictional charge when the moisture content determined on the basis of the weight loss in drying at 105° C. for 3 hrs is not higher than 0.5% by weight; and (e) permeability potential under pressure (PPUP) being 60 to 100% specified by the following formula (I): PPUP(%)=(AAP: 5.0 g)/(AAP: 0.90 g)*100 (I) wherein (AAP: 0.90 g) is the absorbency against pressure measured with 0.90 g of the particulate water absorbing agent for a 0.90% by weight aqueous sodium chloride solution under a pressure of 4.8 kPa for 60 min; and (AAP: 5.0 g) is the absorbency against pressure measured with 5.0 g of the particulate water absorbing agent for a 0.90% by weight aqueous sodium chloride solution under a pressure of 4.8 kPa for 60 min.