Method for producing particulate water-absorbent resin

摘要

A production of a water-absorbent resin by which a particle diameter of the water-absorbent resin can be controlled simply and conveniently, and a content of fine powder can be decreased, without necessity of change of raw materials or expensive facility investment is to be provided. The method is a continuous production method of a polyacrylic acid (salt)-based water-absorbent resin, comprising a polymerization step of an aqueous solution containing acrylic acid (salt), a drying step of the resultant hydrogel-like polymer, a pulverization step of the dried substance, a classification step of the pulverized substance, and optionally a surface cross-linking step of the classified substance, wherein (a) the drying step and the pulverization step are connected via a storage step and a transportation step; and (b) a time of holding the dried substance from a time of completing the drying step to a time of starting the pulverization step is set at 3 minutes or longer.

主权项

1. A continuous production method of a polyacrylic acid (salt)-based water-absorbent resin, comprising a polymerization step of an aqueous solution containing acrylic acid (salt), a drying step of the resultant hydrogel-like polymer, a pulverization step of the dried substance, a classification step of the pulverized substance, and optionally a surface cross-linking step of the classified substance, wherein
(a) the drying step and the pulverization step are connected via a storage step and a transportation step; (b) a time of holding the dried substance from a time of completing the drying step to a time of starting the pulverization step is set at 3 minutes or longer; (c) prior to the pulverization step, a classification step of the dried substance is further performed, and different times of holding the dried substance are applied based on the particle diameters of the dried substance classified, in which, prior to pulverization, at least 50% by weight of the dried substance is composed of particles each having a particle diameter of 850 μm or larger, and a time of holding the dried particles each having a particle diameter of 850 μm or larger is 3 minutes or longer; and (d) in the storage step, the dried substance after the drying step is stored while being heated at 40 to 90° C.