| 摘要 |
PROBLEM TO BE SOLVED: To obtain a water-absorbing resin having a high absorption rate, reduced in a water-soluble component content and a residual monomer content, and having excellent quality in high productivity by effecting static aqueous solution polymerization comprising using an initiator containing a persulfate and maintaining the reaction mixture at a specified temperature for a specified time after reaching a specified peak polymerization temperature. SOLUTION: After a peak temperature of at least 80 deg.C is reached, the obtained water-containing get-like polymer is maintained at 40-90 deg.C for at least 60 min. The polymerization initiator used is a persulfate alone or in combination with a polymerization initiator such as an azo compound or a peroxide or may be combined with a reducing agent to form a redox system. The relative humidity used when the gel-like polymer is maintained for at least 60 min is desirably at least 50% RH. When the water-containing gel-like polymer is maintained for at least 60 min, its specific surface area is desirably 10 cm2/g or below. It is desirable that the monomer component is based on acrylic acid or its salt, and it is desirable that 40-100 mol.% of the acidic groups have been neutralized.
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