| 摘要 |
PROBLEM TO BE SOLVED: To obtain a water absorbing agent having a high absorbing rate and excellent in magnification in absorption under a pressurized condition, liquid permeability under a pressurized condition and impact resistance, by adding a crosslinking agent to water absorptive resinous powder and then by crosslinking the resultant composition. SOLUTION: This water absorbing agent is obtained by adding a crosslinking agent to water absorptive resinous powder having a weight average particle diameter of 200-1000μm while grinding tire powder, followed by surface crosslinking of the water absorptive resin. It is preferable that the weight average particle diameter is reduced by a factor of 1-50% through grinding the resinous powder, the content of arisen particulate having a particle diameter of <=150μm becomes 10 wt.% or below and the BET specific surface area of the water absorptive resin is increased by 1.05-10 times. It is preferable that the grinding of the resinous powder is conducted by a reduction index of >=1,000 under a load of 20 g/cm<3> or in the presence of a ball mill. The surface crosslinking agent contains a polyhydric alcohol, and the resinous powder pref. has a low absorption power of 35 g/g or below in terms of an absorption magnification in an isotonic sodium chloride solution.
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