| abstract |
An object of the present invention is to provide a particle-shaped water absorbing agent having a remarkably improved surface color and excellent water-absorbing properties (better water absorption capacity, and lower water soluble content and residual monomer content) at the same time. In order to attain the object, a particle-shaped water absorbing agent according to the present invention is a particle-shaped water absorbing agent whose main component is a polyacrylic acid and/or a salt thereof, the particle-shaped water absorbing agent having a surface color of Hunter b value in a range of −5 to 10, and having a cross-linking absorption property index (CPI) in a range of 1 to 100, the CPI defined by the following two equations: n GEX =( GVs +17)/Ln (water soluble content) Equation 1; n CPI =( GEX /residual monomer content)×100 Equation 3 where GVs is gel volume in saline, Ln (water soluble content) is a logarithm natural of water soluble content. |