# US 9,518,180 B2 · Method for producing polyacrylic acid (salt)-based water absorbing agent, and water absorbing agent

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- Number: US 9,518,180 B2
- Document ID: US9518180B2
- Status: Granted
- Kind: B2
- Application number: 14/426,539
- Filed: 2013-08-20
- Published: 2015-07-30
- Granted: 2016-12-13
- Earliest claimed: 2012-09-11
- Assignees: Nippon Shokubai Co., Ltd.
- Applicants: Nippon Shokubai Co., Ltd.
- Inventors: Kazuki Kimura; Yusuke Watanabe; Sayaka Machida; Taku Fujimoto; Kenji Kadonaga
- Web page: https://patentgrep.com/patent/US9518180B2

## CPC

- C08J 3/245: {Differential crosslinking of one polymer with one crosslinking type, e.g. surface crosslinking}
- A61L 15/24: Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds; Derivatives thereof {(A61L15/225 takes precedence)}
- A61L 15/60: Liquid-swellable gel-forming materials, e.g. super-absorbents
- B01J 20/267: {Cross-linked polymers}
- C08F 220/06: Acrylic acid; Methacrylic acid; Metal salts or ammonium salts thereof
- C08L 33/02: Homopolymers or copolymers of acids; Metal or ammonium salts thereof
- C08J 2333/02: Homopolymers or copolymers of acids; Metal or ammonium salts thereof
- C08L 2203/02: for biomedical use
- C08J: WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H (working, e.g. shaping, of plastics B29)
- A61L: METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES (preservation of bodies or disinfecting characterised by the agents employed A01N; preserving, e.g. sterilising, food or foodstuffs A23; preparations for medical, dental or toiletry purposes A61K)
- B01J: CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- C08F: MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08L: COMPOSITIONS OF MACROMOLECULAR COMPOUNDS (compositions based on polymerisable monomers C08F, C08G; artificial filaments or fibres D01F; textile treating compositions D06)

## Abstract

The present invention relates to an absorbent suitable for use in a thin sanitary material/absorbent article having a high absorbent content and not prone to gel blocking, the absorbent having excellent liquid diffusibility (e.g. SFC) and minimal decrease in absorption ratio under pressure (e.g., AAP or PUP) even when a liquid permeation enhancer is added, and to a method for manufacturing the high-performance absorbent stably during actual production. The method is a method for manufacturing a polyacrylic acid (salt)-based absorbent, having a surface-crosslinking agent addition step for adding a solution of a surface-crosslinking agent, and a liquid permeation enhancer addition step for adding a liquid permeation enhancer, the liquid permeation enhancer addition step being performed after and/or at the same time as the surface-crosslinking agent addition step, the method characterized in that a surface crosslinking step for performing heat treatment in an atmosphere having a dew point of 45° C. to 100° C. is performed after or at the same time as the surface-crosslinking agent addition step.

## Claims

### Claim 1

A polyacrylic acid (salt)-based water absorbing agent having a surface, a periphery of which surface is cross-linked by an organic surface crosslinking agent and is provided with a liquid permeability enhancer, the polyacrylic acid(salt)-based water absorbing agent satisfying the following requirements (A) through (D):
(A) CRC is 25 g/g to 35 g/g;
(B) SFC is not less than 10(×10−7 cm3·sec/g);
(C) soluble component is 5 mass % to 20 mass %; and
(D) surface-crosslinked layer strength index is not more than 40 provided that surface-crosslinked layer strength index is defined by the following equation: surface-crosslinked layer strength index=surface soluble component (%)/soluble component (%)×100.

### Claim 2 (depends on 1)

The water absorbing agent as set forth in claim 1, wherein
the water absorbing agent further satisfies the following requirement (E): (E) 0.58 psi PUP is not less than 30 (g/g).

### Claim 3 (depends on 1)

The water absorbing agent as set forth in claim 1, wherein
the water absorbing agent further satisfies the following requirement (F): (F) surface soluble component is in a range of 0 mass % to 4.5 mass %.

### Claim 4 (depends on 1)

The water absorbing agent as set forth in claim 1, wherein
the liquid permeability enhancer is a cationic polymer compound.