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

摘要

From a view point of reduction in an out of spec product after surface crosslinking, particularly, when an alkylene carbonate compound is used as a surface crosslinking agent, influence by an air temperature is great, and it is necessary to reduce ethylene glycol which is produced as a byproduct, and there is provided a process for producing a polyacrylic acid (salt)-based water absorbent resin powder, comprisinga step of polymerizing an aqueous acrylic acid (salt)-based monomer solution,a step of drying the resulting polymer,an optional grinding•classifying step, anda surface crosslinking step,wherein in the surface crosslinking step,(1) a surface crosslinking agent containing an alkylene carbonate compound and a polyhydric alcohol compound is mixed into a water absorbent resin powder, the mixture is heat-reacted and, further, simultaneously with, or separately from the mixing, an ion reactive surface crosslinking agent is mixed, and/or(2) mixing treatment of mixing a surface crosslinking agent solution into a water absorbent resin powder containing at least one or more kinds of ion reactive surface crosslinking agents is performed two or more times.