Patent ID: 7183456

Claim:
A water-absorbent resin, which is surface-crosslinked with a surface-crosslinking agent including at least a polyhydric alcohol, wherein the water-absorbent resin before surface-crosslinking is obtained by polymerizing hydrophilic monomers comprising a major proportion of either or both of acrylic acid and its salt (neutralized product), and where the water-absorbent resin has a particle size distribution such that the ratio of particles having particle diameters of smaller than 150 μm is not more than 5 weight %, and exhibits an absorption capacity without a load of not less than 30 g/g, with the water-absorbent resin being characterized in that: a single-layer absorption capacity (10 min.) of particles having particle diameters of 600 to 300 μm is not less than 30 g/g under a load; the single-layer absorption capacity (60 min.) of particles having particle diameters of 600 to 300 μm is not less than 30 g/g under a load; the single-layer absorption capacity (10 min.) of particles having particle diameters of 300 to 150 μm is not less than 30 g/g under a load; and the single-layer absorption capacity (60 min.) of particles having particle diameters of 300 to 150 μm is not less than 30 g/g under a load, wherein the single-layer absorption capacity is measured under the following conditions: (a) the liquid being absorbed is a synthetic urine (comprising 0.2 weight % of sodium sulfate, 0.2 weight % of potassium chloride, 0.05 weight % of magnesium chloride 6 hydrates, 0.025 weight % of calcium chloride dihydrate, 0.085 weight % of ammonium dihydrogen phosphate, 0.015 weight % of diammonium hydrogen phosphate, and 99.425 weight % of deionized water) at 25±2° C., (b) the load applied to the measurement sample during the absorption is 50 g/cm 2 (4.83 kPa). (c) the amount of the water-absorbent resin as a measurement sample is 0.055±0.005 g, and (d) the water-absorbent resin as a measurement sample is uniformly spread on the wire net made of stainless steel attached to the bottom of the cylinder having an internal diameter of 60 mm, wherein the absorption capacity without a load is measured with a sample drained with a centrifuge after immersed into an aqueous sodium chloride solution of 0.9 weight % for 30 minutes.