Pressure-resistant absorbent resin, disposable diaper using the resin, and absorbent resin, and method for production thereof

An absorbent resin produced by adding a compound having a plurality of functional groups capable of reacting with a group represented by formula —COOR in which each R is independently hydrogen atoms, metal atoms or ammonium to an absorbent cross-linked polymer having a —COOR group of 12 mmol/g or more and a molecular ratio of —COOH/—COOR of not more than 0.5.

An absorbent resin having the proximity of the surface thereof subjected to a cross-linking treatment with a compound having plural of functional groups capable of reacting with a group represented by formula —COOR in which each R is independently hydrogen atoms, metal atoms or ammonium, having a —COOR group in a concentration of 12 mmol/g or more and a molecular ratio of —COOH/—COOR of not more than 0.5.

An absorbent resin having a BET specific surface area of 0.03 m2/g or more and a ratio of water absorption capacity under high pressure of 25 g/g or more to artificial urine under a load of 100 g/cm2.

A pressure-resistant absorbent resin manifesting a ratio of water absorption capacity under pressure of 30 g/g or more to artificial urine under a load of 50 g/cm2, and a pressure-resistant absorption ratio of 0.6 or more, wherein said pressure-resistant absorption ratio is defined as the ratio of said ratio of water absorption capacity under high pressure to artificial urine under a load of 100 g/cm2 to a ratio of water absorption capacity under pressure to artificial urine under a load of 50 g/cm2.

A method for the production of an absorbent resin, characterized by adding a compound having a plurality of functional groups capable of reacting with a group represented by formula —COOR in which each R is independently hydrogen atoms, metal atoms or ammonium to an absorbent cross-linked polymer having a —COOR group of 12 mmol/g or more and a molecular ratio of —COOH/—COOR of not more than 0.5 and heating the resultant mixture.