GRANULAR WATER ABSORBER AND METHOD OF PRODUCING THE SAME

摘要

It is intended to simultaneously establish the following two characteristics, i.e., a high water absorptivity (improvement in water absorption ratio and reduction of water-soluble matters and residual monomers) and an elevated grain surface whiteness. This object is achieved by providing a granular water absorber comprising polyacrylic acid (or its salt) as the main component, characterized in that the b value in Hunter Lab surface color system of the grains is from -5 to 10 and the crosslinkage property index (CPI) defined by the following formulae (1) and (3) is from 1 to 100: Formula (1): GEX=(GVs+17)/Ln(amount of water-soluble matters) Formula (3): CPI=(GEX/amount of residual monomers) x 100 wherein GVs stands for the absorption ratio without loading any pressure, while Ln(amount of water-soluble matters) stands for the logarithm natural of the amount of water-soluble matters.