Super absorbent polymer and method for preparing the same

• US 10,450,425 B2
• Filed: 11/11/2015
• Issued: 10/22/2019
• 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
• Primary Examiner(s): Rabago, Roberto
• Application Number:
  US15/107,297
• Publication Number:
  US 20170009026A1
• Time in Patent Office: 1,441 Days
• 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 method of preparing a superabsorbent polymer comprising:

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 non-circular 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 area of the upper surface of the chopper die with a unit mm², n is the number of holes, and c is the total circumference of the plurality of holes, and

wherein the value of c is 500 to 800 mm.

2. The method of claim 1, wherein the thickness of the chopper die is 5 to 15 mm.

3. The method of claim 1, wherein the n-holes have the identical shape with each other.

4. The method of claim 1, wherein n is an integer of 10 to 30.

5. The method of claim 1, 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.

6. The method of claim 1, wherein

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

C.

7. The method of claim 1, wherein

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

m.

8. The method of claim 1, wherein the surface-crosslinking in Step 5) is carried out at a temperature of 100 to 250°

C.

9. The method of 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 C₂-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.

10. The method of claim 1, wherein

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

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, 2-(meth)acrylamide-2-methyl propane sulfonic acid, (meth)acrylamide, N- substituted (meth)acrylate, 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, methoxy polyethylene glycol (meth)acrylate, polyethylene glycol (meth)acrylate,(N,N)-dimethylaminoethyl(meth)acrylate, and (N,N)-dimethylaminopropyl(meth)acrylamide.

11. The method of 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.