Processes for producing highly water absorptive resins

A process for producing a highly water absorptive amorphous resin, which comprises

• (a) suspending an aqueous solution of partially neutralized alkali metal acrylate wherein about 50 to 100% by mole of the carboxyl group has been neutralized to its alkali metal salt and at least one water soluble radical polymerization initiator, in a hydrocarbon solvent containing a surfactant having a HLB value of 8.about.12;
• (b) subjecting the mixture to inverse suspension polymerization while raising the internal temperature of the reactor successively to 70.degree. C., to 60.degree..about.67.degree. C., and then to 75.degree. C., to undergo phase-transition;
• (c) during or after the polymerization, separating the moisture from the produced polymer by azeotropic distillation to reduce the water content to about 15 to 55% by weight, and filtering to remove the solvent;
• (d) adding a crosslinking agent having three or more reactive epoxy groups which is dissolved in methanol, wherein the amount of the crosslinking agent is 0.005.about.15% by weight based on the produced polymer, and incubating for 1.about.2 hours at temperatures 70.degree. to 85.degree. C.;
• and
• (e) washing with methanol, filtering, and drying at temperatures of 90.degree. to 175.degree. C. to obtain the water absorptive resin.