SUPER ABSORBENT POLYMER AND METHOD FOR PREPARING THE SAME

• US 20170009026A1
• Filed: 11/11/2015
• Published: 01/12/2017
• Est. Priority Date: 11/24/2014
• Status: Active Grant

• Current Assignee: LG Chem Limited (LG Corporation)
• Original Assignee: LG Chem Limited (LG Corporation)
• Inventors: Nam, Hye Mi, Lee, Sang Gi, Jang, Tae Hwan, Hwang, Min Ho, Lee, Soo Jin
• Granted Patent: US 10,450,425 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: A61L 15/60 Liquid-swellable gel-forming materials, e.g. super-absorbents
• CPC Class Codes: B02C 18/365 Perforated discs
• CPC Class Codes: C08F 220/06 Acrylic acid; Methacrylic acid; Metal salts or ammonium salts thereof
• CPC Class Codes: C08F 2800/20 as weight or mass percentages
• CPC Class Codes: C08F 2810/20 leading to a crosslinking, either explicitly or inherently
• CPC Class Codes: C08J 2300/14 Water soluble or water swellable polymers, e.g. aqueous gels
• CPC Class Codes: C08J 2333/02 Homopolymers or copolymers of acids; Metal or ammonium salts thereof
• CPC Class Codes: C08J 3/075 Macromolecular gels
• CPC Class Codes: C08J 3/12 Powdering or granulating
• CPC Class Codes: C08J 3/245 Differential crosslinking of one polymer with one crosslinking type, e.g. surface crosslinking

Abstract

The present invention relates to a super absorbent polymer and a method for preparing the same. The present invention has features that it is possible to prepare a super absorbent resin that can have an improved centrifuge retention capacity (CRC) and a high absorbency under load (AUL) by controlling the shape and size of the chopper die holes during coarse pulverization of a hydrous gel phase polymer.

Claims

1. A super absorbent polymer comprising a crosslinked polymer, the crosslinked polymer being obtained by surface-crosslinking a base polymer prepared by polymerizing a water-soluble ethylene-based unsaturated monomer including an acidic group in which at least a part of the acidic group is neutralized, wherein the super absorbent polymer has

a centrifuge retention capacity (CRC) of more than 20 g/g,

an absorbency under 0.9 psi load (AUL) of more than 18 g/g, and

ARUL shown in the following Equation 1 of 60% to 85%:

ARUL=0.3AUL(5 min)/0.3AUL(60 min) 

 

[Equation 1]

in Equation 1,

0.3AUL (5 min) and 0.3AUL (60 min) are the values of absorbency under load (AUL) at 5 minutes and 60 minutes shown in the following Equation 2, respectively,

0.3AUL(g/g)=[Wb(g)−

Wa(g)]/weight(g) of the absorbent polymer 

 

[Equation 2]

in Equation 2,

Wa(g) is the sum of the weight of the absorbent polymer and the weight of the device capable of providing a load for the absorbent polymer, and

Wb(g) is the sum of the weight of the absorbent polymer in which moisture is absorbed after supplying water for the absorbent polymer under a load (0.3 psi) for 5 minutes or 60 minutes, and the weight of the device capable of providing a load for the absorbent polymer.

2. The super absorbent polymer according to claim 1 wherein

the water-soluble ethylene-based unsaturated monomer is a compound represented by the following Chemical Formula 1:

R₁-COOM¹ 

 

[Chemical Formula 1]

in Chemical Formula 1,

R₁ is a C₁-C₅ alkyl group including an unsaturated bond, and

M¹ is a hydrogen atom, a monovalent or divalent metal, an ammonium group, or an organic amine salt.

3. The super absorbent polymer according to claim 1 wherein

the water-soluble ethylene-based unsaturated monomer includes one or more selected from the group consisting of:

an anionic monomer such as acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloylethane sulfonic acid, 2-methacryloylethane sulfonic acid, 2-(meth)acryloylpropane sulfonic acid, or 2-(meth)acrylamide-2-methyl propane sulfonic acid, and salts thereof;

a nonionic hydrophilic monomer such as (meth)acrylamide, N-substituted (meth)acrylate, 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, methoxy polyethylene glycol (meth)acrylate, or polyethylene glycol (meth)acrylate; and

an amino group-containing unsaturated monomer such as (N,N)-dimethylaminoethyl(meth)acrylate or (N,N)-dimethylaminopropyl(meth)acrylamide, and a quaternary compound thereof.

4. The super absorbent polymer according to claim 1 wherein

the surface crosslinking is carried out by reacting one or more crosslinking agents selected from the group consisting of ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol polyglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, ethylene carbonate, ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, tetraethylene glycol, propanediol, dipropylene glycol, polypropylene glycol, glycerin, polyglycerin, butanediol, heptanediol, hexanediol, trimethylolpropane, pentaerythritol, sorbitol, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, iron hydroxide, calcium chloride, magnesium chloride, aluminum chloride, and iron chloride.

5. The super absorbent polymer according to claim 1 wherein

the absorbency under 0.9 psi load (AUL) is represented by the following Equation 3:

0.9AUL(g/g)=[Wb(g)−

Wa(g)]/weight(g) of the absorbent polymer 

 

[Equation 3]

in Equation 3,

Wa(g) is the sum (g) of the weight of the absorbent polymer and the weight of the device capable of providing a load for the absorbent polymer, and

Wb(g) is the sum (g) of the weight of the absorbent polymer in which moisture is absorbed after supplying water for the absorbent polymer under a load (0.9 psi) for 60 minutes, and the weight of the device capable of providing a load for the absorbent polymer.

6. The super absorbent polymer according to claim 1 wherein

the centrifuge retention capacity (CRC) is represented by the following Equation 4:

CRC(g/g)={[W₂(g)−

W₁(g)]/W₀(g)}−

1 

 

[Equation 4]

in Equation 4,

W₀(g) is a weight (g) of the absorbent polymer,

W₁(g) is a weight (g) of the device which is measured after draining water off at 250 G for 3 minutes with a centrifuge, without using the absorbent polymer, and

W₂(g) is a weight (g) of the device including the absorbent polymer, which is measured after immersing the absorbent polymer in 0.9% by weight of the physiological saline solution at room temperature for 30 minutes and then draining water off at 250 G for 3 minutes with a centrifuge.

7. The super absorbent polymer according to claim 1 wherein

the super absorbent polymer is prepared by a method comprising the steps of:

1) carrying out thermal polymerization or photopolymerization of a monomer composition including a water-soluble ethylene-based unsaturated monomer and a polymerization initiator to form a hydrous gel phase polymer;

2) passing the hydrous gel phase polymer through a chopper die and pulverizing the polymer;

3) drying the pulverized hydrous gel phase polymer;

4) pulverizing the dried polymer; and

5) surface-crosslinking the pulverized polymer,

wherein the chopper die is provided with a plurality of holes,

the chopper die has an opening/closing rate of 30 to 40%, and

the chopper die satisfies the following Mathematical Formula 1;

c>

2×

√

{square root over (0.4×

π

×

n×

A)} 

 

[Mathematical Formula 1]

wherein

A is the overall width of the upper surface of the chopper die, n is the number of holes, and c is the total circumference of the plurality of holes.

8. The super absorbent polymer according to claim 7 wherein

the thickness of the chopper die is 5 to 15 mm.

9. The super absorbent polymer according to claim 7 wherein

the value of c is 500 to 800 mm.

10. The super absorbent polymer according to claim 7 wherein

the n-holes have the identical shape with each other.

11. The super absorbent polymer according to claim 7 wherein

n is an integer of 10 to 30.

12. The super absorbent polymer according to claim 7 wherein

the pulverizing in step 2) is a step of pulverizing the hydrous gel phase polymer into a particle size of 2 to 10 mm.

13. The super absorbent polymer according to claim 7 wherein

the drying in step 3) is carried out at a temperature of 120 to 250°

C.

14. The super absorbent polymer according to claim 7 wherein

the pulverizing in step 4) is carried out so that the particle size of the pulverized polymer becomes 150 to 850 μ

m.

15. The super absorbent polymer according to claim 7 wherein

the surface-crosslinking in Step 5) is carried out at a temperature of 100 to 250°

C.