Water-absorbent resin, water-absorbent material, and water-absorbent article

Patent metadata

Field	Value
Publication number	US-10265226-B2
Application number	US-201314426940-A
Country	US
Kind code	B2
Filing date	Aug 1, 2013
Priority date	Sep 10, 2012
Publication date	Apr 23, 2019
Grant date	Apr 23, 2019

Abstract

One purpose of the present invention is to provide a water-absorbent resin having excellent water absorption characteristics and being capable of improving the shape-retaining characteristics of a water-absorbent material when used in the water-absorbent material. A water-absorbent resin obtained by performing reversed phase suspension polymerization of a water-soluble ethylenically unsaturated monomer in a hydrocarbon dispersion medium, using a radical polymerization initiator, said resin being capable of having both excellent absorption performance and shape retention in a water-absorbent material using the water-absorbent resin, as a result of fulfilling the conditions of: (1) having a water-retention capacity of physiological saline of at least 38 g/g; (2) having a water-absorption capacity of physiological saline under a load of 4.14 kPa of at least 15 ml/g; and (3) having a tan δ of a 50-fold swollen gel of at least 2.10×10 −2 .

First claim

The invention claimed is:

1. A method for producing a water-absorbent resin, wherein the water-absorbent resin has the following characteristics (1) to (3):
(1) the water-retention capacity of physiological saline thereof is 38 g/g or more,
(2) the water-absorption capacity of physiological saline under a load of 4.14 kPa thereof is 15 ml/g or more, and
(3) the tan δ of a 50-fold swollen gel thereof is 2.10×10 −2 or more, and

wherein the method comprises a first step and a second step each defined below:
the first step of performing reversed phase suspension polymerization of a water-soluble ethylenically unsaturated monomer in the presence of a radical polymerization initiator and an internal-crosslinking agent in a hydrocarbon dispersion medium, wherein an amount of the internal-crosslinking agent used is 0.000015 to 0.00020 mol per mol of the water-soluble ethylenically unsaturated monomer subjected to the polymerization; and
the second step of crosslinking suspension polymerized particles obtained in the first step with a single addition of post-crosslinking agent, wherein an amount of the post-crosslinking agent used is 0.00025 to 0.0010 mol per mol of the water-soluble ethylenically unsaturated monomer subjected to the polymerization.

2. The method for producing a water-absorbent resin according to claim 1 , wherein the water-soluble ethylenically unsaturated monomer is at least one selected from the group consisting of (meth)acrylic acid and salts thereof, (meth)acrylamide, and N,N-dimethylacrylamide.

3. The method for producing a water-absorbent resin according to claim 1 , wherein the internal-crosslinking agent and the post-crosslinking agent are polyglycidyl compounds.

4. The method for producing a water-absorbent resin according to claim 1 , wherein the amount of the internal-crosslinking agent to be used in the first step is 0.000030 to 0.000080 mol per mol of the water-soluble ethylenically unsaturated monomer subjected to the polymerization, and wherein the amount of the post-crosslinking agent used in the second step is 0.00044 to 0.00076 mol per mol of the watersoluble ethylenically unsaturated monomer subjected to the polymerization.

Assignees

• Sumitomo Seika Chemicals

Inventors

• Watanabe Ayaka
• Kondo Kimihiko
• Takatori Junichi

Classifications

• C08F2/32

  Polymerisation in water-in-oil emulsions · CPC title

• A61F13/53 Primary

  characterised by the absorbing medium (A61F13/20 takes precedence) · CPC title

• A61L15/60

  Liquid-swellable gel-forming materials, e.g. super-absorbents · CPC title

• C08J3/075

  Macromolecular gels · CPC title

• C08J3/245

  Differential crosslinking of one polymer with one crosslinking type, e.g. surface crosslinking · CPC title