Method for producing polyacrylic acid (salt)-based water absorbent resin

Abstract

The purpose of the present invention is to provide a method for producing a water absorbent resin having improved physical properties, particularly, improved saline flow conductivity (SFC) and less amount of fine powder. The present invention provides a method for producing a polyacrylic acid (salt)-based water absorbent resin, the method comprising: a polymerization step of supplying as a base material an aqueous solution containing an acrylic acid and/or an acrylic acid salt as a monomer component and polymerizing the monomer in the presence of a polymerization initiator, wherein in the polymerization step, there is used a polymerization apparatus which comprises a polymerization part covered with a case, said polymerization part comprising at least a supply line for supplying the aqueous solution, an external gas supply port, and a gas discharge port, and has a structure that a liquid contact part in contact with the aqueous solution and a gas supplied from the outside of the polymerization apparatus are brought into contact with the aqueous solution during a polymerization, and assuming that a controlled temperature of the liquid contact part is set as TS, a temperature of the gas part is set as TG, and TT is (TS+TG)/2, the polymerization is carried out under temperature conditions satisfying the following Equations 1 to 3: Equation 1: 35° C.≦TS≦85° C., Equation 2: 40° C.≦TG≦90° C., Equation 3: 47° C.≦TT≦73° C.

Dependencies are inferred from the claim text.