Method and apparatus for producing polyacrylic acid (salt)-based water absorbent resin

Patent metadata

Field	Value
Publication number	US-9580519-B2
Application number	US-201214112774-A
Country	US
Kind code	B2
Filing date	Apr 20, 2012
Priority date	Apr 20, 2011
Publication date	Feb 28, 2017
Grant date	Feb 28, 2017

Abstract

The purpose of the present invention is to provide a method for producing a water absorbent resin in which a water absorbent resin having excellent properties can be obtained effectively. The present invention relates to a method for producing a polyacrylic acid (salt)-based water absorbent resin, which includes a polymerization step of polymerizing an aqueous monomer solution containing a polymerization inhibitor, acrylic acid (salt) and an internal cross-linking agent to produce a water-containing gel-like cross-linked polymer, a gel-crushing step of performing the gel-crushing of the water-containing gel-like cross-linked polymer simultaneously with or subsequent to the polymerization to produce a particulate water-containing gel-like cross-linked polymer, and a drying step of supplying the particulate water-containing gel-like cross-linked polymer to a continuous through-flow belt-type dryer by a traverse conveyor to dry the particulate water-containing gel-like cross-linked polymer, in which the belt temperature of the traverse conveyor is 40 to 120° C. and/or the water soluble component in the particulate water-containing gel-like cross-linked polymer on the traverse conveyor is 10% by weight or less and the water soluble component is increased after the drying step.

First claim

The invention claimed is:

1. A method for producing a polyacrylic acid (salt)-based water absorbent resin, the production process comprising:
a polymerization step of polymerizing an aqueous monomer solution containing a polymerization inhibitor, acrylic acid (salt) and an internal cross-linking agent to produce a water-containing gel-like cross-linked polymer;
a gel-crushing step of performing the gel-crushing of the water-containing gel-like cross-linked polymer simultaneously with or subsequent to the polymerization to produce a particulate water-containing gel-like cross-linked polymer;
a gel transporting step of supplying the particulate water-containing gel-like cross-linked polymer to a continuous through-flow belt-type dryer by a traverse conveyor; and
a drying step of drying the particulate water-containing gel-like cross-linked polymer by the continuous through-flow belt-type dryer,
wherein the belt temperature of the traverse conveyor is 40 to 120 C.

2. The method according to claim 1 , wherein a water soluble component in the particulate water-containing gel-like cross-linked polymer is 10% by weight or less and the water soluble component is increased after the drying step, and
wherein the water soluble component is measured by adding 1.000 g of the particulate water-containing gel-like cross-linked polymer into 200 ml of 0.9% by weight aqueous sodium chloride solution, stirring for 16 hours at 500 rpm and measuring by pH titration, an amount of dissolved polymer (unit; by weight).

3. The method according to claim 2 , wherein the internal cross-linking agent has a thermally degradable skeleton or a (poly)ethylene glycol skeleton.

4. The method according to claim 2 , wherein the water soluble component is increased within the range of 1 to 10% by weight.

5. The method according to claim 2 , wherein the particulate water-containing gel-like cross-linked polymer has a water absorption capacity without load (CRC) of less than 30 [g/g].

6. The method according to claim 1 , wherein the main body of the traverse conveyor is connected to the dryer while the traverse conveyor being in a practically covered state.

7. The method according to claim 6 , wherein the main body of the traverse conveyor is under atmosphere of 30 C or higher.

8. The method according to claim 1 , wherein the particulate water-containing gel-like cross-linked polymer has a temperature of 50 C or higher.

9. The method according to claim 1 , wherein the neutralization rate of acrylic acid in the aqueous monomer solution exceeds 60% by mol.

10. The method according to claim 1 , further comprising a pulverizing step, a classification step, and a surface cross-linking step after the drying step, and
further comprising a fine powder recycling step of recycling fine powder obtained from the classification step to a step in or prior to the drying step.

11. The method according to claim 1 , wherein the difference between the belt temperature of the traverse conveyor and the temperature of the particulate water-containing gel-like cross-linked polymer is 0 to 30 C.

12. The method according to claim 1 , wherein air contact time of the particulate water-containing gel-like cross-linked polymer obtained from the gel-crushing step till the supply to the continuous through-flow belt-type dryer is within 180 seconds.

13. The method according to claim 1 , wherein the belt width of the traverse conveyor is 0.1 to 1 m and the area occupancy ratio of the particulate water-containing gel-like cross-linked polymer is 10 to 90% in the width direction of the belt.

14. The method according to claim 1 , wherein the belt tilt angle of the traverse conveyor is less than −10 when the horizontal direction is assumed to be 0.

15. The method according to claim 1 , wherein the belt surface roughness (Rz) of the traverse conveyor is 800 nm or less.

16. The method according to claim 1 , wherein the belt surface material of the traverse conveyor has a contact angle with respect to water of 60 or more and a heat deflection temperature of 20 C or higher.

17. The method according to claim 1 , wherein the belt surface of the traverse conveyor is coated with a resin.

18. The method according to claim 17 , wherein the belt surface material of the traverse conveyor is one selected from polyethylene, polypropylene, polyester, polyamide, polyimide, polyurethane, polyacetal, a fluoro resin, polyvinyl chloride, an epoxy resin, and a silicon resin.

19. The method according to claim 1 , wherein the particulate water-containing gel-like cross-linked polymer is obtained by gel-crushing during kneader polymerization or gel-crushing after polymerization by using a screw type extruder having a porous plate.

Assignees

• Nogi Kozo
• Kanzaki Syuji
• Ishizaki Kunihiko
• Fujino Shinichi
• Matsumoto Satoshi
• Nippon Catalytic Chem Ind

Inventors

• Nogi Kozo
• Kanzaki Syuji
• Ishizaki Kunihiko
• Fujino Shinichi
• Matsumoto Satoshi

Classifications

• C08J3/12 Primary

  Powdering or granulating · CPC title

• C08J2333/02

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

• C08F220/06

  Acrylic acid; Methacrylic acid; Metal salts or ammonium salts thereof · CPC title

• C08F2/18 Primary

  Suspension polymerisation · CPC title