Method of producing water absorbent resin

Patent metadata

Field	Value
Publication number	US-9453091-B2
Application number	US-201113635045-A
Country	US
Kind code	B2
Filing date	Mar 17, 2011
Priority date	Mar 17, 2010
Publication date	Sep 27, 2016
Grant date	Sep 27, 2016

Abstract

A method for producing a water absorbent resin, the method including a polymerization step, a drying step, a classification step, and a surface crosslinking step. The classification step carried out before or after the surface crosslinking step requires use of a metal sieve mesh having stretch tension from 35 to 100 N/cm, in which an air jet cleaner or an air jet brush cleaner and plural tapping balls or tapping blocks are installed below the metal sieve mesh, a classification aid particle having specific gravity different from that of the water absorbent resin powder is added, and a fine powder of the water absorbent resin and the classification aid particle are removed.

First claim

The invention claimed is:

1. A method for producing a water absorbent resin comprising:
a polymerization step of polymerizing an aqueous solution of acrylic acid (salt) to obtain a water-containing gel-like crosslinked polymer;
a drying step of drying the water-containing gel-like crosslinked polymer to obtain a water absorbent resin powder;
a classification step of classifying the water absorbent resin powder; and
a surface crosslinking step of surface crosslinking the water absorbent resin powder,
wherein in the classification step that is carried before the surface crosslinking step and/or after the surface crosslinking step, stretch tension (tension) of a metal sieve mesh used in the classification step is from 35 [N/cm] to 100 [N/cm],
the method satisfying one or more of the following three requirements:
(1) an airbrush is installed below the metal sieve mesh used in the classification step, in which the airbrush uses dry air having a dew point of 0° C. or lower, and the classifying apparatus is heated at 40° C. to 80° C.;
(2) in the classification step, a classification aid particle having specific gravity larger than that of the water absorbent resin powder is added, and a fine powder of the water absorbent resin and the classification aid particle are removed, in which the classification aid particle is an inorganic fine particle or an organic fine particle; and
(3) plural tapping balls or tapping blocks are installed below the metal sieve mesh used in the classification step, in which a gas stream passes through in the classification step, and the dew point of the gas stream is 15° C. or lower.

2. The method according to claim 1 , wherein the material of the metal sieve mesh is SUS304 or SUS316, and the surface roughness (Rz) of the inner surface of the metal sieve mesh is 800 nm or less.

3. The method according to claim 1 , wherein requirement (2) or (3) is satisfied and the metal sieve mesh is heated or kept warm to a temperature of 40° C. or higher.

4. The method according to claim 1 , wherein requirement (2) is satisfied, a gas stream passes through in the classification step, and the dew point of the gas stream is 15° C. or lower.

5. The method according to claim 1 , wherein in the classification step, removal of electricity is carried out by a ground connection with a ground resistance value of 100Ω or less.

6. The method according to claim 1 , wherein the classification step is carried out under reduced pressure.

7. The method according to claim 1 , wherein the damage to the metal sieve mesh is monitored by an acoustic emission (AE) method.

Assignees

• Okuda Sumio
• Kanzaki Syuji
• Ishizaki Kunihiko
• Fujino Shinichi
• Nogi Kozo
• Nippon Catalytic Chem Ind

Inventors

• Okuda Sumio
• Kanzaki Syuji
• Ishizaki Kunihiko
• Fujino Shinichi
• Nogi Kozo

Classifications

• B07B1/54

  with beating devices · CPC title

• B07B1/28

  Moving screens not otherwise provided for, e.g. swinging, reciprocating, rocking, tilting or wobbling screens · CPC title

• C08F6/008

  Treatment of solid polymer wetted by water or organic solvents, e.g. coagulum, filter cakes · CPC title

• G01N15/0272

  with screening; with classification by filtering (B01D takes precedence) · CPC title

• C08F220/06 Primary

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