Process for producing water-absorbent resin

Patent metadata

Field	Value
Publication number	US-10065173-B2
Application number	US-201414759762-A
Country	US
Kind code	B2
Filing date	Nov 4, 2014
Priority date	Jul 11, 2014
Publication date	Sep 4, 2018
Grant date	Sep 4, 2018

Abstract

The present invention provides a process for producing a water-absorbent resin, characterized in that a reverse-phase suspension polymerization of a water-soluble ethylenically unsaturated monomer is carried out in a hydrocarbon dispersion medium comprising a dispersion stabilizer while an azo-based compound and a peroxide are combined in the presence of an internal-crosslinking agent, in that the following formulae are satisfied,

0.10≤ B /( A+B )  (1), and

0.055≤ B +9× C ≤0.120  (2),
wherein A mol, B mol and C mol represent used amounts of the azo-based compound, the peroxide and the internal-crosslinking agent, respectively, relative to 100 mol of the water-soluble ethylenically unsaturated monomer used in the polymerization, and in that a post-crosslinking reaction is carried out by adding a post-crosslinking agent after the polymerization. The present invention also relates to a water-absorbent resin having specific performance and produced by the process.

First claim

The invention claimed is:

1. A process for producing a water-absorbent resin comprising:
a reverse-phase suspension polymerization of water-soluble ethylenically unsaturated monomers, and then
a post-crosslinking reaction,
wherein the reverse-phase suspension polymerization of water-soluble ethylenically unsaturated monomers is carried out in a hydrocarbon dispersion medium comprising a dispersion stabilizer,
wherein an azo-based compound and a peroxide are combined in the presence of an internal-crosslinking agent in aqueous solution comprising the water-soluble ethylenically unsaturated monomers,
wherein the water-soluble ethylenically unsaturated monomers comprise one or more of the group consisting of (meth)acrylic acid and the salt thereof, 2-(meth)acrylamide-2-methylpropanesulfonic acid and the salt thereof, (meth)acrylamide, N,N-dimethyl(meth)acrylamide, 2-hydroxyethyl (meth)acrylate, N-methylol (meth)acrylamide, polyethylene glycol mono(meth)acrylate; N,N-diethylaminoethyl(meth)acrylate, N,N-diethylaminopropyl(meth)acrylate and diethylaminopropyl (meth)acrylamide, as well as the quaternary compounds thereof,
wherein the following formulae are satisfied:
0.25≤ B /( A+B )≤0.50  (1),

0.055≤ B+ 9× C≤ 0.120  (2), and

0.0005 mol≤ B≤ 0.10 mol,

wherein the A is representative of the amount of the azo-based compound in mol; the B is representative of the amount of the peroxide in mol; and C is representative of the amount of the internal-crosslinking agent in mol, relative to 100 mol of the water-soluble ethylenically unsaturated monomers in the reverse-phase suspension polymerization step,
wherein the post-crosslinking reaction is carried out by adding a post-crosslinking agent, and
wherein the water-absorbent resin satisfies all of the following characteristics (A) to (D):
(A) a water-retention capacity of physiological saline of 36 to 60 g/g,
(B) a water-absorption capacity of physiological saline under a load of 4.14 kPa, of 15 ml/g or higher,
(C) a vertical diffusion water-absorption capacity of 4.0 ml/g or higher, and
(D) a content of residual monomers of 180 ppm or lower.

2. The process for producing a water-absorbent resin according to claim 1 , wherein the azo-based compound is at least one selected from the group consisting of 2,2′-azobis(2-amidinopropane) dihydrochloride, 2,2′-azobis{2-[1-(2-hydroxyethyl)-2-imidazolin-2-yl]propane} dihydrochloride, and 2,2′-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] tetrahydrate.

3. The process for producing a water-absorbent resin according to claim 1 , wherein the peroxide is at least one selected from the group consisting of potassium persulfate, ammonium persulfate, sodium persulfate and hydrogen peroxide.

4. The process for producing a water-absorbent resin according to claim 1 , wherein the internal-crosslinking agent is at least one selected from the group consisting of (poly)ethylene glycol diglycidyl ether, (poly)propylene glycol diglycidyl ether, (poly)glycerin diglycidyl ether and N,N′-methylenebis(meth)acrylamide.

5. The process for producing a water-absorbent resin according to claim 1 , wherein the azo-based compound and the peroxide simultaneously coexist in an aqueous solution before the start point of polymerization in the reverse-phase suspension polymerization step.

6. The process for producing a water-absorbent resin according to claim 1 ,
wherein the azo-based compound is at least one selected from the group consisting of 2,2′-azobis(2-amidinopropane) dihydrochloride, 2,2′-azobis{2-[1-(2-hydroxyethyl)-2-imidazolin-2-yl]propane} dihydrochloride, and 2,2′-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] tetrahydrate,
wherein the peroxide is at least one selected from the group consisting of potassium persulfate, ammonium persulfate, sodium persulfate and hydrogen peroxide, and
wherein the internal-crosslinking agent is at least one selected from the group consisting of (poly)ethylene glycol diglycidyl ether, (poly)propylene glycol diglycidyl ether, (poly)glycerin diglycidyl ether and N,N′-methylenebis(meth)acrylamide.

7. The process for producing a water-absorbent resin according to claim 1 , wherein the azo-based compound is 0.005 to 1 mol relative to 100 mol of the water-soluble ethylenically unsaturated monomers in the reverse-phase suspension polymerization step.

8. The process for producing a water-absorbent resin according to claim 1 , wherein the internal-crosslinking agent is 0.001 to 0.13 mol relative to 100 mol of the water-soluble ethylenically unsaturated monomers in the reverse-phase suspension polymerization step.

9. The process for producing a water-absorbent resin according to claim 1 , wherein the post-crosslinking agent is 0.001 to 1 mol relative to 100 mol of the water-soluble ethylenically unsaturated monomers in the reverse-phase suspension polymerization step.

10. The process for producing a water-absorbent resin according to claim 1 ,
wherein the azo-based compound is 0.005 to 1 mol relative to 100 mol of the water-soluble ethylenically unsaturated monomers in the reverse-phase suspension polymerization step,
wherein the internal-crosslinking agent is 0.001 to 0.13 mol relative to 100 mol of the water-soluble ethylenically unsaturated monomers in the reverse-phase suspension polymerization step, and
wherein the post-crosslinking agent is 0.001 to 1 mol relative to 100 mol of the water-soluble ethylenically unsaturated monomers in the reverse-phase suspension polymerization step.

11. The process for producing a water-absorbent resin according to claim 1 ,
wherein the internal-crosslinking agent is at least one selected from the group consisting of (poly)ethylene glycol diglycidyl ether and (poly)propylene glycol polyglycidyl ether.

12. The process for producing a water-absorbent resin according to claim 1 ,
wherein the post-crosslinking agent is at least one selected from the group consisting of (poly)ethylene glycol diglycidyl ether, (poly)glycerin diglycidyl ether, (poly)glycerin triglycidyl ether, (poly)propylene glycol polyglycidyl ether and (poly)glycerol polyglycidyl ether.

13. The process for producing a water-absorbent resin according to claim 1 ,
wherein the reverse-phase suspension polymerization is carried out in multi-stages having two or more stages.

Assignees

• Sumitomo Seika Chemicals

Inventors

• Hinayama Tetsuhiro
• Murakami Masahiro
• Takatori Junichi

Classifications

• A61L15/60

  Liquid-swellable gel-forming materials, e.g. super-absorbents · CPC title

• C08J2333/02

  Homopolymers or copolymers of acids; Metal or ammonium salts thereof · CPC title

• B01J20/261 Primary

  obtained by reactions only involving carbon to carbon unsaturated bonds (macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds per se C08F) · CPC title

• B01J20/3085

  Chemical treatments not covered by groups B01J20/3007 - B01J20/3078 · CPC title

• C08F2/32

  Polymerisation in water-in-oil emulsions · CPC title