Abstract: Process for preparing a water-absorbent resin comprising carrying out a reversed-phase suspension polymerization in multi-steps of two or more steps. The water-absorbent resin is prepared by subjecting a water-soluble ethylenically unsaturated monomer to the reversed phase suspension polymerization. This process for preparing a water-absorbent resin involves adding an aminocarboxylic acid compound to at least one step in the second and subsequent steps to carry out the polymerization reaction. The resulting water-absorbent resin can be suitably used in a hygienic material. The water-absorbent resin has a high degree of water-retention, including a high degree of water absorption under pressure. It also has a high water absorption rate, and contains only a small amount of water-soluble substances.

Abstract: A process for producing a water-absorbent resin particle comprising subjecting a water-soluble ethylenically unsaturated monomer to a reverse phase suspension polymerization, characterized in that the process for producing a water-absorbent resin particle comprises the steps of (A) subjecting the water-soluble ethylenically unsaturated monomer to a first-step reverse phase suspension polymerization in a hydrocarbon-based solvent using a water-soluble radical polymerization initiator in the presence of a surfactant and/or a polymeric protective colloid, and optionally an internal crosslinking agent; (B) carrying out at least one step of the procedures of adding an aqueous solution of a water-soluble ethylenically unsaturated monomer containing a water-soluble radical polymerization initiator and optionally an internal crosslinking agent to a reaction mixture after the termination of the first-step reverse phase suspension polymerization in a state that the surfactant and/or the polymeric protective colloid is

Abstract: [Problems] To provide a process for preparing a water-absorbent resin which can be suitably used in a hygienic material, the water-absorbent resin having a large amount of water-retention, a large amount of water absorption under pressure, a high water absorption rate, and a small amount of water-soluble substance. [Solving Means] A process for preparing a water-absorbent resin comprising carrying out a reversed phase suspension polymerization in multi-steps of two or more steps when the water-absorbent resin is prepared by subjecting a water-soluble ethylenically unsaturated monomer to the reversed phase suspension polymerization, said process for preparing a water-absorbent resin being characterized by adding an aminocarboxylic acid compound to at least one step in the second and subsequent steps, to carry out the polymerization reaction.

Abstract: The present invention provides a process for producing a water-absorbing resin with less coloring wherein only a small amount of a polymerization inhibitor remains, and the water-absorbing resin. More particularly, the present invention provides a process for producing a water-absorbing resin, comprising polymerizing a water-soluble ethylenic unsaturated monomer and, then, drying a hydrous gel of the resulting polymer at a pressure of 5 to 90 kPa under the atmosphere having no oxygen, or having an oxygen concentration of not higher than 5% by volume. In addition, by such the process, a water-absorbing resin having Yellow Index of not more than 20 is obtained, wherein an amount of a remaining polymerization inhibitor is not more than 30 ppm.

Abstract: A process for producing a water-absorbent resin particle comprising subjecting a water-soluble ethylenically unsaturated monomer to a reverse phase suspension polymerization, characterized in that the process for producing a water-absorbent resin particle comprises the steps of (A) subjecting the water-soluble ethylenically unsaturated monomer to a first-step reverse phase suspension polymerization in a hydrocarbon-based solvent using a water-soluble radical polymerization initiator in the presence of a surfactant and/or a polymeric protective colloid, and optionally an internal crosslinking agent; (B) carrying out at least one step of the procedures of adding an aqueous solution of a water-soluble ethylenically unsaturated monomer containing a water-soluble radical polymerization initiator and optionally an internal crosslinking agent to a reaction mixture after the termination of the first-step reverse phase suspension polymerization in a state that the surfactant and/or the polymeric protective colloid is