Process for production of water-absorbent resin

A process for the production of water-absorbent resin by reversed phase suspension polymerization of a water-soluble ethylenic unsaturated monomer, which comprises the steps of:

• A. subjecting an aqueous solution of the water-soluble ethylenic unsaturated monomer to a reversed phase suspension polymerization reaction of a first stage in a petroleum hydrocarbon solvent in the presence of a surfactant and/or polymeric protective colloid by using a radical polymerization initiator optionally in the presence of a crosslinking agent,
• B. cooling the solution to precipitate the surfactant and/or polymeric protective colloid,
• C. adding an aqueous solution of a water soluble-ethylenic unsaturated monomer solution containing a radical polymerization initiator and optionally a crosslinking agent to the first polymerization reaction system to absorb it on gel formed in the first polymerization reaction,
• D. then, heating the reaction mixture to carry out a second reversed phase suspension polymerization reaction, and
• E. optionally, repeating the above steps B, C, D at least once.