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, comprising
a step of polymerizing an aqueous acrylic acid (salt)-based monomer solution,
a step of drying the resulting polymer,
an optional grinding·classifying step, and
a 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.
从减少表面交联后的不合规格产品的角度出发,特别是使用
碳酸亚烷基化合物作为表面
交联剂时,受空气温度的影响很大,有必要减少作为副产品产生的
乙二醇,提供了一种生产聚
丙烯酸(盐)基吸
水性
树脂粉末的工艺,包括
聚合
丙烯酸(盐)基单体
水溶液的步骤、
干燥所得聚合物的步骤、
可选的研磨分级步骤,以及
表面交联步骤、
其中在表面交联步骤中
(1) 将含有
碳酸亚烷基酯化合物和多元醇化合物的表面
交联剂混合到吸
水性
树脂粉末中,对混合物进行热反应,并在混合的同时或单独混合离子反应表面
交联剂,和/或
(2) 将表面
交联剂溶液与含有至少一种或多种离子活性表面
交联剂的吸
水性
树脂粉末进行两次或多次混合处理。