# US 9,517,446 B2 · Super absorbent polymer and a preparation method thereof

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- Number: US 9,517,446 B2
- Document ID: US9517446B2
- Status: Granted
- Kind: B2
- Application number: 14/394,685
- Filed: 2013-04-23
- Published: 2015-03-26
- Granted: 2016-12-13
- Earliest claimed: 2012-04-25
- Assignees: LG Chem, Ltd.
- Applicants: LG Chem, Ltd.
- Inventors: Tae-Young Won; Chang-Sun Han; Gi-Cheul Kim; Yong-Hun Lee; Sang-Gi Lee; Kyu-Pal Kim; Sung-Soo Park; Gyu Leem
- Web page: https://patentgrep.com/patent/US9517446B2

## CPC

- B01J 20/267: {Cross-linked polymers}
- 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 20/28004: {Sorbent size or size distribution, e.g. particle size}
- B01J 20/28016: {Particle form}
- B01J 20/3085: {Chemical treatments not covered by groups B01J20/3007 - B01J20/3078}
- B01J 20/3208: {Polymeric carriers, supports or substrates}
- B01J 20/3248: {the functional group or the linking, spacer or anchoring group as a whole comprising at least one type of heteroatom selected from a nitrogen, oxygen or sulfur, these atoms not being part of the carrier as such}
- C08F 220/06: Acrylic acid; Methacrylic acid; Metal salts or ammonium salts thereof
- C08J 3/075: Macromolecular gels
- C08J 3/12: Powdering or granulating
- C08J 3/126: {Polymer particles coated by polymer, e.g. core shell structures}
- C08J 3/24: Crosslinking, e.g. vulcanising, of macromolecules (mechanical aspects B29C35/00; crosslinking agents C08K)
- C08J 3/245: {Differential crosslinking of one polymer with one crosslinking type, e.g. surface crosslinking}
- B01J 2220/68: Superabsorbents
- C08J 2300/14: Water soluble or water swellable polymers, e.g. aqueous gels
- C08J 2333/02: Homopolymers or copolymers of acids; Metal or ammonium salts thereof
- B01J: CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- 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)
- C08F: MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- 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)

## Abstract

The present invention relates to a super absorbent polymer (SAP) and a preparation method thereof. More specifically, the present invention provides a SAP satisfying the overall properties required to a SAP and especially the superior initial absorbency and absorbing rate under load at the same time, and a preparation method thereof, by treating the surface of the SAP with a surface treatment solution including water and a diol-based or glycol-based surface crosslinking agent.

## Claims

### Claim 1

A super absorbent polymer (SAP), comprising
a base polymer powder comprising a crosslinked polymer of at least partially neutralized water-soluble ethylenic unsaturated monomer of acrylic acid; and
a surface crosslinking layer formed on the base polymer powder,
wherein the surface crosslinking layer is obtained by crosslinking the surface of the base polymer powder with a C2-C8 diol-based or glycol-based compound, and the surface crosslinking is performed by spraying a surface treatment aqueous solution comprising the C2-C8 diol-based or glycol-based compound on the base polymer powder with the spray angle of 10 to 30° and carrying out the surface crosslinking reaction at 120 to 250° C. for 10 to 120 minutes,
wherein the SAP has the SPAN value of 1.2 or less, represented by the following Mathematical Formula 1, and
satisfies the absorbing rate under load (ARUL) represented by the following Mathematical Formula 2:
SPAN=[D(90%)−D(10%)]/D(50%)≦1.2 [Mathematical Formula 1]
in Mathematical Formula 1,
D(90%) is the diameter of the particle when the accumulated weight from the smallest particle becomes 90%, when the SAP particles are arranged in order of particle diameter measured according to EDANA method WSP 220.2,
D(10%) is the diameter of the particle when the accumulated weight from the smallest particle becomes 10%, when the SAP particles are arranged in order of particle diameter measured according to EDANA method WSP 220.2, and
D(50%) is the diameter of the particle when the accumulated weight from the smallest particle becomes 50%, when the SAP particles are arranged in order of particle diameter measured according to EDANA method WSP 220.2,
1.0>ARUL=AUP(10 min)/AUP(60 min)>0.70 [Mathematical Formula 2]
in Mathematical Formula 2,
AUP (10min) is the absorbency under pressure after 10 mins represented by the following Mathematical Formula 3, and AUP (60 min) is the absorbency under pressure after 60 mins represented by the following Mathematical Formula 3,
AUP(g/g)=[Wb(g)−Wa(g)]/weight of absorbent polymer(g) [Mathematical Formula 3]
in Mathematical Formula 3,
Wa (g) is the sum of the weight of the absorbent polymer and the weight of the device capable of providing load to the absorbent polymer, and
Wb (g) is the sum of the weight of the absorbent polymer in which moisture is absorbed under load (0.7 psi) for a given time of 10 mins or 60 mins and the weight of the device capable of providing load to the absorbent polymer.

### Claim 2 (depends on 1)

The super absorbent polymer according to claim 1, the base polymer powder comprises:
the powder having the diameter of 300 to 600 μm in an amount of 50 weight % or more.

### Claim 3 (depends on 2)

The super absorbent polymer according to claim 2, the base polymer powder comprises:
the powder having the diameter of 600 to 850 μm in an amount of 7 weight % or more; and
the powder having the diameter of 150 to 300 μm in an amount of 7 weight % or more.

### Claim 4 (depends on 1)

A sanitary fitting including the super absorbent polymer of claim 1.

### Claim 5 (depends on 1)

A diaper including the super absorbent polymer of claim 1.

### Claim 6 (depends on 1)

A product including the super absorbent polymer of claim 1, wherein the product is a water combination soil for horticulture, a water-stop material for civil engineering and construction, a nursery sheet, a freshness preservation in a food distribution field or a poultice material.