Patent ID: 8841395

Claim:
A method for producing a water-absorbent resin comprising performing a reversed-phase suspension polymerization of a water-soluble ethylenically unsaturated monomer in a petroleum hydrocarbon dispersion medium by using a surfactant, a pouring rate upon dispersing an aqueous solution of the water-soluble ethylenically unsaturated monomer in the dispersion medium, is satisfied with the following conditions: (a) an addition rate V i of the aqueous solution is 0.30 [min −1 ] or less upon dispersing an aqueous solution of the water-soluble ethylenically unsaturated monomer in the dispersion medium, wherein the addition rate [min −1 ] V i is defined by Equation (I): V i =F i ×A i /T wherein i: Nozzle number (1 to n), n: Number of nozzles (1≦n≦10), F i : Average linear flow rate from nozzle [m/min], A i : Cross-section area of nozzle [m 2 ], and T: Total amount [m 3 ] of the aqueous monomer solution charged in a polymerization reaction tank; and (b) a total addition rate [min −1 ] V total of the aqueous monomer solution of the water-soluble ethylenically unsaturated monomer charged in the polymerization reaction tank, is 0.04 [min −1 ] or more, wherein the total addition rate [min −1 ] V total is defined by the following Equation (II): V total =ΣV i ( i= 1 to n ) polymerization tank wherein V i : Addition rate of each nozzle [min −1 ], and i and n are as defined in Equation (I), and V total =V 1 when the polymerization equipment has one nozzle (n=1).