Polyacrylic acid (salt)-type water absorbent resin and method for producing of same

Abstract

Disclosed is a method for producing a water absorbent resin, by which a surface-crosslinked water absorbent resin having excellent physical properties can be efficiently obtained at low cost, while assuring high productivity. When the production scale is increased to a continuous production on a huge scale (for example, 1 t/hr or more), the physical properties are improved and stabilized (for example, standard deviation of the physical properties is reduced) by a surface-crosslinking treatment, and the absorption against pressure (AAP) and liquid permeability (SFC) are further improved. Specifically disclosed is a method for producing a polyacrylic acid (salt)-type water absorbent resin, which comprises: a step of preparing an aqueous monomer solution using an acrylic acid (salt); a step of continuously polymerizing the aqueous monomer solution; shedding step of a hydrous gel-like crosslinked polymer during or after the polymerization; a step of drying the thus-obtained particulate hydrous gel-like crosslinked polymer; and a surface treatment step in which a surface-crosslinking agent is added to and reacted with the dried water absorbent resin powder. In the surface treatment step, the continuous mixing apparatus for the surface treatment agent and the continuous heating device are connected and periodic shielding is performed between the mixing apparatus and the heating device.