From a viewpoint 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.