To provide a method for producing a resin reduced in residual monomer without spoiling the physical property of the resin, and to provide a water- absorbing resin having a high absorbing ability, little in water-soluble component and reduced in residual monomer.
This method for producing a resin by radical-polymerizing an aqueous polymerization liquid comprising a hydrophilic radical polymerizable monomer and water, if necessary, in the presence of a copolymerizable crosslinking agent, comprises: using a polymerization initiator producing free radicals at ≤40°C together with a polymerization initiator having the relation of (T-25<T1/2<T) between the 10 hors. half-life period temperature (T1/2) and the temperature (T) when a polymerization rate reaches 98%, if necessary, by adding a polymerization initiator to the resultant water-containing polymer after polymerized and by surface-crosslinking the thus obtained particular water- absorbing resin so as to improve its water-absorbing ability under load.
TAKAI HITOSHI
IWASAKI YOSHIYUKI
TANAKA KEIJI
