Patent ID: 7790823

Claim:
A process for preparing a hydrogel-forming polymer capable of absorbing aqueous fluids, comprising a step of surface postcrosslinking a base polymer having a pH of not more than 5.7 with a surface postcrosslinking agent consisting of a di- or polyglycidyl compound, a polyamine, a polyamidoamine, a polyamidoamine reaction product with epichlorohydrin, a polyamide reaction product with epichlorohydrin, or 2-oxazolidinone, wherein said hydrogel-forming polymer is an acrylic acid (co)polymer partially neutralized with an alkali metal, alkaline earth metal, ammonium, or amine salt and having a pH absorbency index pH AI of at least 90 and a pH of not more than 5.7, wherein pH AI is calculated as follows: pH AI =ΔpH(AUL 0.7 psi +CRC), wherein ΔpH=7−pH of product, AUL 0.7 psi is an absorbency under pressure at 0.7 psi, and CRC is a centrifuge retention capacity.