| abstract |
A method according to the present invention for producing water absorbent resin powder is a method for producing water absorbent resin having a surface cross-linked structure, and includes: a polymerization step in which an unsaturated monomer aqueous solution is polymerized; a drying step in which a hydrogel cross-linked polymer obtained in the polymerization step is dried; a surface treatment step in which the hydrogel cross-linked polymer or a dried hydrogel cross-linked polymer is subjected to a surface treatment; and a sorting step, carried out after the drying step, in which a foreign matter included in a water absorbent resin is color-sorted from the water absorbent resin entirely or partially. As a result, it is possible to obtain a water absorbent resin which has high properties and is less likely to be colored. In this way, there is provided the water absorbent resin powder production method in which the color sorting technique is used to remove foreign matters from the water absorbent resin. |