Sumitomo Seika Chemicals Co., Ltd.

Sachi Kikuno

Atsushi Heguri

Nobuhiro Maeda

Hideki Yokoyama

Masayoshi Handa

The present invention provides a method for producing water-absorbing resin particles having high equilibrium swelling capacity, a high water-absorption rate or high initial swelling capacity, and an appropriate particle size that achieves good handling performance; water-absorbing resin particles obtained by the method; and a water blocking material and an absorbent article which include the water-absorbing resin particles. The present invention is a method for producing water-absorbing resin particles, which comprises: preparing a hydrogel polymer by reversed-phase suspension polymerization of a water-soluble ethylenically unsaturated monomer in a hydrocarbon solvent in the absence of an internal crosslinking agent but in the presence of a surfactant with an HLB of 8 to 12; carrying out a post-crosslinking reaction of the hydrogel polymer whose moisture content is adjusted to 30 to 110 mass % based on a water-soluble ethylenically unsaturated monomer component that composes the hydrogel polymer.

Process for production of water-absorbing resin particles, water-absorbing resin particles, water-stopping material, and absorbent article

A method for producing a water-absorbent resin comprising at least two stages of reversed-phase suspension polymerization, wherein the first stage of the at least two stages of reversed-phase suspension polymerization comprises the following steps of: (A) performing a primary dispersion by stirring to mix in the absence of surfactants an aqueous solution of a water-soluble ethylenically unsaturated monomer containing a hydrophilic polymeric dispersion agent with a petroleum hydrocarbon dispersion medium in which a hydrophobic polymeric dispersion agent dissolves or disperses; (B) further performing a secondary dispersion by adding a surfactant to the resultant dispersion liquid; and (C) performing a polymerization by using a water-soluble radical polymerization initiator to obtain a water-absorbent resin as particles in a hydrous gel state which disperse in the petroleum hydrocarbon dispersion medium, and a water-absorbent resin obtained by the method.

Method for producing a water-absorbent resin

A method for producing a water-absorbent resin by performing a reversed-phase suspension polymerization of a water-soluble ethylenically unsaturated monomer in a petroleum hydrocarbon dispersion medium, comprising the following steps of: (A) performing a primary dispersion in the absence of surfactants by adding an aqueous solution of a water-soluble ethylenically unsaturated monomer containing a hydrophilic polymeric dispersion agent to a petroleum hydrocarbon dispersion medium in which a hydrophobic polymeric dispersion agent was heat-dispersed or heat-dissolved, under stirring; (B) further performing a secondary dispersion by adding a surfactant to a dispersion liquid obtained after the primary dispersion; and (C) performing the reversed-phase suspension polymerization by using a radical polymerization initiator; and the water-absorbent resin obtained by the method.

A method for producing a water-absorbent resin having a further reduced odor as compared with a water-absorbent resin obtained by a conventional method as well as a water-absorbent resin produced by the same method, by maintaining the addition rate V from the pouring nozzle for the aqueous solution of the water-soluble ethylenically unsaturated monomer in a polymerization reaction tank not more than 0.30 [min], in the first stage polymerization step which is within the step of the conventional method upon performing multi-stages such as two or more stages of reversed-phase suspension polymerizations in a method for producing a water-absorbent resin, and thereby by being able to reduce the amount of the petroleum hydrocarbon dispersion medium remaining in the above water-absorbent resin.

The present invention provides a method for producing a water-absorbent resin by a reversed-phase suspension polymerization method, wherein an odor originating from a raw material component, in particular, a petroleum hydrocarbon dispersion medium, was reduced, and a water-absorbent resin obtained by the method. More specifically, the present invention provides a method for producing a water-absorbent resin comprising performing a reversed-phase suspension polymerization of a water-soluble ethylenically unsaturated monomer in a petroleum hydrocarbon dispersion medium by using a surfactant, wherein an aqueous solution of the water-soluble ethylenically unsaturated monomer is dispersed in the dispersion medium at a specific pouring rate to reduce an odor, and a water-absorbent resin obtained by the method, are provided.

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Kurobe, Japan

Sachi Kikuno