Hydrophilic polyacrylic acid (salt) resin and manufacturing method thereof

• US 9,518,133 B2
• Filed: 02/08/2010
• Issued: 12/13/2016
• Est. Priority Date: 02/06/2009
• Status: Active Grant

• Current Assignee: Nippon Shokubai Company Limited
• Original Assignee: Nippon Shokubai Company Limited
• Inventors: Fujino, Shinichi, Matsumoto, Satoshi, Ishizaki, Kunihiko
• Primary Examiner(s): Peters, Monique
• Application Number:
  US13/148,359
• Publication Number:
  US 20120010372A1
• Time in Patent Office: 2,500 Days
• Field of Search: 525/384, 525/329.4, 525/330.1, 525/329.7, 524/556, 526/317.1
• US Class Current: 1/1
• CPC Class Codes: C08F 2/44 Polymerisation in the presence of compounding ingredients, e.g. plasticisers, dyestuffs, fillers
• CPC Class Codes: C08F 220/06 Acrylic acid; Methacrylic acid; Metal salts or ammonium salts thereof

Abstract

The physical properties of a water-absorbing resin with low residual monomer content are improved or stabilized, without sacrifices in productivity, production cost, stability, etc. Provided is a water-absorbing resin with low residual monomer content and excellent whiteness, wherein a water-absorbing resin consumed in large quantities in disposable diapers, etc., is preferably a sustainable and renewable water-absorbing resin that does not require excessive purification of the acrylic acid, particularly acrylic acids derived from non-fossil sources, that is the starting material of the water-absorbing resin. Disclosed is a method of manufacturing a hydrophilic polyacrylic acid (salt) resin, which is a method of manufacturing a water-absorbing polyacrylic acid resin that comprises a step in which a monomer is prepared from acrylic acid, a step in which said monomer is polymerized, and a step in which the resulting hydrous gel is dried. The polymerization is performed such that the content of hydroxypropionic acid (salt) in the monomer is 2000 ppm or less and/or the content of saturated organic carboxylic acid in the monomer is 2% by mass or less, and at least a portion of the saturated organic carboxylic acid is volatilized during and after the drying step.

Claims

1. A method of manufacturing a hydrophilic polyacrylic acid (salt) resin selected from the group consisting of a water-absorbent resin and a water-soluble resin, comprising the steps of:

a preparation step in which a monomer is prepared from acrylic acid,

a polymerization step in which the monomer is polymerized, and

optionally a drying step in which an obtained hydrogel is dried,

wherein

acrylic acid obtained by dehydration reaction of hydroxypropionic acid (salt) obtained from a non-fossil raw material is used as the acrylic acid; and

the acrylic acid obtained by dehydration reaction of hydroxypropionic acid (salt) has a water content of 1 mass % or lower; and

the preparation step in which the monomer is prepared from acrylic acid is conducted within 72 hours after purification; and

polymerization is carried out with the content of the hydroxypropionic acid (salt) in the monomer being adjusted to 2000 ppm or lower; and

/or

acrylic acid obtained by dehydration reaction of hydroxypropionic acid (salt) obtained from a non-fossil raw material is used as the acrylic acid and the amount of a saturated organic carboxylic acid in the monomer is adjusted to more than 1000 ppm to 2 mass % or lower to carry out polymerization; and

at least a portion of the saturated organic carboxylic acid is volatilized and optionally trapped in the drying step and thereafter.

2. The manufacturing method according to claim 1, wherein the hydrophilic polyacrylic acid (salt) resin is a polyacrylic acid (salt)-based water-absorbent resin;

acrylic acid obtained by dehydration reaction of hydroxypropionic acid (salt) obtained from a non-fossil raw material is used as the acrylic acid and polymerization is carried out with the content of the hydroxypropionic acid (salt) in the monomer being adjusted to 2000 ppm or lower;

and/or at least a portion of the saturated organic carboxylic acid is volatilized and optionally trapped in the drying step and thereafter.

3. The manufacturing method according to claim 1, wherein the content of one or more of protoanemonin, allyl acrylate, allyl alcohol, an aldehyde component, maleic acid, and benzoic acid in the acrylic acid is 0 to 20 ppm;

or the saturated organic carboxylic acid in the acrylic acid is 300 ppm or more;

or 3-hydroxypropionic acid is 200 ppm or lower in the monomer.

4. The manufacturing method according to claim 1, wherein a polymerization inhibitor is used in the dehydration step and further the inhibitor is removed.

5. The manufacturing method according to claim 1, wherein an acrylic acid derived from a fossil raw material and an acrylic acid other than the acrylic acid obtained by dehydration reaction of hydroxypropionic acid (salt) derived from the non-fossil raw material are further used in combination as the monomer.

6. The manufacturing method according to claim 1, wherein the monomer contains 10 to 200 ppm of a polymerization inhibitor besides phenol (C₆H₅OH);

or Fe (in terms of Fe₂O₃) in the monomer is 0.002 to 2 ppm.

7. The manufacturing method according to claim 1, wherein the acrylic acid contains the saturated organic carboxylic acid and a saturated aliphatic carboxylic acid is volatilized until the content reaches 2000 ppm or lower, and optionally trapped in the drying step and thereafter.

8. The manufacturing method according to claim 1, wherein a residual monomer in the obtained water-absorbent resin is 400 ppm or lower.

9. The manufacturing method according to claim 1 further comprising the step of surface-crosslinking the water-absorbent resin with a surface cross-linking agent of a compound derived from a non-fossil raw material.

10. The manufacturing method according to claim 1, further comprising the step of surface-crosslinking the water-absorbent resin with a surface cross-linking agent containing propanediol or lactic acid.

11. The manufacturing method according to claim 1, further comprising the step of adding a basic substance after the drying step.

12. The manufacturing method according to claim 1, wherein an acrylic acid other than the acrylic acid obtained by dehydration reaction of hydroxypropionic acid (salt) is used in combination as the monomer.

13. The manufacturing method according to claim 1, further comprising a neutralization step, wherein the neutralization step is conducted within 72 hours after refining the acrylic acid.