Super absorbent polymer and method for producing same

Patent metadata

Field	Value
Publication number	US-12053757-B2
Application number	US-202217742548-A
Country	US
Kind code	B2
Filing date	May 12, 2022
Priority date	Dec 23, 2016
Publication date	Aug 6, 2024
Grant date	Aug 6, 2024

Abstract

The present invention relates to a super absorbent polymer exhibiting more improved absorption under pressure and liquid permeability, even while basically maintaining excellent centrifuge retention capacity and absorption rate, and a method for producing the same. The super absorbent polymer comprises: a base polymer powder including a first crosslinked polymer of a water-soluble ethylenically unsaturated monomer having at least partially neutralized acidic groups; and a surface crosslinked layer formed on the base polymer powder and including a second crosslinked polymer in which the first crosslinked polymer is further crosslinked via a surface crosslinking agent, wherein the surface crosslinking agent includes at least two compounds having a solubility parameter value (σ) of 12.5 (cal/cm3)1/2 or more, and wherein at least one of the surface crosslinking agents is an alkylene carbonate-based compound, and the remainder is selected from the group consisting of an alkylene carbonate-based compound and a polyhydric alcohol-based compound.

First claim

The invention claimed is:

1. A method for producing a super absorbent polymer comprising the steps of:
performing crosslinking polymerization of a water-soluble ethylenically unsaturated monomer having at least partially neutralized acidic groups in the presence of an internal crosslinking agent, to form a hydrogel polymer containing a first crosslinked polymer;
drying, pulverizing and classifying the hydrogel polymer to form a base polymer power; and
heat-treating and surface-crosslinking the base polymer powder in the presence of a surface crosslinking agent to form a super absorbent polymer particle,
wherein the surface crosslinking agent includes at least two compounds having a solubility parameter value (σ) of 12.5 (cal/cm 3 ) 1/2 or more,
wherein at least one of the surface crosslinking agents is an alkylene carbonate-based compound, and the remainder is selected from the group consisting of an alkylene carbonate-based compound and a polyhydric alcohol-based compound,
wherein the surface-crosslinking step includes a first reaction step in which the reaction is performed at a temperature within a range of 170° C. to 190° C. for 3 to 10 minutes and a second reaction step in which the reaction is performed at a higher temperature than that of the first reaction step, within a range of 190° C. to 220° C. for 20 to 40 minutes.

2. The method for producing a super absorbent polymer according to claim 1 , wherein the water-soluble ethylenically unsaturated monomer includes at least, one selected from the group consisting of anionic monomers of acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2-acryloylethanesulfonic acid, 2-methacryloylethanesulfonic acid, 2-(meth)acryloylpropanesulfonic acid or 2-(meth)acrylamido-2-methylpropanesulfonic acid, and their salts; non-ionic, hydrophilic group-containing monomers of (meth)acrylamide, N-substituted (meth)acrylate, 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, methoxypolyethylene glycol(meth)acrylate or polyethylene glycol (meth)acrylate; and amino group-containing unsaturated monomers of (N,N)-dimethylaminoethyl(meth)acrylate or (N,N)-dimethylaminopropyl(meth)acrylamide, and their quaternary product.

3. The method for producing a super absorbent polymer according to claim 1 , wherein the internal crosslinking agent includes at least one selected from the group consisting of a bis(meth)acrylamide having 8 to 12 carbon atoms, a polyol poly(meta)acrylate having 2 to 10 carbon atoms and a polyol poly(meth)ally ether having 2 to 10 carbon atoms.

4. The method for producing a super absorbent polymer according to claim 1 , wherein the base polymer powder is produced and provided so as to have a particle diameter of 150 to 850 μm.

5. The method for producing a super absorbent polymer according to claim 1 , wherein the surface crosslinking of the base polymer powder is carried out in the presence of the surface crosslinking agent and a polycarboxylic acid-based polymer.

6. The method for producing a super absorbent polymer according to claim 1 , wherein before the first and second reaction steps, a temperature raising step for reaching the maximum reaction temperature is further included,
the temperature raising step before the first reaction step is performed at a temperature raising rate of 1.5° C./min to 3.0° C./min, and
the temperature raising step before the second reaction step is performed at a temperature raising rate of 1.2° C./min to 2.3° C./min.

Assignees

• Lg Chemical Ltd

Inventors

• Lee Yong Hun
• Sohn Jung Min
• Lee Hyemin
• Han Chang Sun

Classifications

• C08J3/24

  Crosslinking, e.g. vulcanising, of macromolecules (mechanical aspects B29C35/00; crosslinking agents C08K) · CPC title

• C08K5/11

  of acyclic polycarboxylic acids · CPC title

• C08J3/12

  Powdering or granulating · CPC title

• C08J3/075

  Macromolecular gels · CPC title

• C08F2/44

  Polymerisation in the presence of compounding ingredients, e.g. plasticisers, dyestuffs, fillers · CPC title