Method for producing particulate water—absorbing agent composed principally of water absorbing resin

• US 8,138,292 B2
• Filed: 03/13/2009
• Issued: 03/20/2012
• Est. Priority Date: 03/13/2008
• Status: Active Grant

• Current Assignee: Nippon Shokubai Company Limited
• Original Assignee: Nippon Shokubai Company Limited
• Inventors: Matsumoto, Koji, Ishizaki, Kunihiko, Okuda, Sumio
• Primary Examiner(s): CHOI, LING SIU
• Application Number:
  US12/922,011
• Publication Number:
  US 20110009590A1
• Time in Patent Office: 1,103 Days
• Field of Search: 526/317.1, 526/318.2, 526/223
• US Class Current: 526/317.1
• CPC Class Codes: B01J 20/26 Synthetic macromolecular compounds
• CPC Class Codes: B01J 20/267 Cross-linked polymers
• CPC Class Codes: B01J 20/30 Processes for preparing, regenerating, or reactivating
• CPC Class Codes: B01J 2220/68 Superabsorbents
• CPC Class Codes: B29B 2009/125 Micropellets, microgranules, microparticles
• CPC Class Codes: B29B 7/002 Methods chemical aspects C08J3/00
• CPC Class Codes: B29B 7/48 with intermeshing devices, e.g. screws
• CPC Class Codes: B29B 7/726 Measuring properties of mixture, e.g. temperature or density B29B7/724 takes precedence
• CPC Class Codes: B29B 7/748 Plants B29B7/7433, B29B7/7485, B29B7/7495 take precedence
• CPC Class Codes: B29B 7/82 Heating or cooling
• CPC Class Codes: B29B 7/885 with means for treating, e.g. milling, the charges B29B7/905 takes precedence
• CPC Class Codes: B29B 9/02 by dividing preformed material
• CPC Class Codes: B29B 9/12 characterised by structure or composition
• CPC Class Codes: B29B 9/16 Auxiliary treatment of granules
• CPC Class Codes: B65B 1/06 by gravity flow
• CPC Class Codes: B65B 1/08 by vibratory feeders
• CPC Class Codes: B65B 1/22 by vibration
• CPC Class Codes: B65B 37/04 by vibratory feeders
• CPC Class Codes: C08F 20/06 Acrylic acid; Methacrylic acid; Metal salts or ammonium salts thereof
• CPC Class Codes: C08J 3/245 Differential crosslinking of one polymer with one crosslinking type, e.g. surface crosslinking

Abstract

Provided is a production method for the particulate water-absorbing agent, which can contribute to property enhancement, and further improvement of productivity or the like, as well. One example of the production method for the particulate water-absorbing agent relevant to the present invention includes the polymerization step for obtaining a polymer gel; the drying step for drying the polymer gel to obtain a dried substance; the pulverization step for pulverizing the dried substance or the polymer gel to obtain the particulate water-absorbing resin; the classification step for sieving the particulate water-absorbing resin; the granule sizing step for granule sizing the particulate water-absorbing agent obtained from the particulate water-absorbing resin; and the transporting step for transporting the products produced in each of the steps to other steps. Preferably, one or more steps selected from the pulverization step, the classification step, the granule sizing step and the transporting step after the pulverization step are set under reduced pressure state.

Claims

1. A method for producing a particulate water-absorbing agent comprising:

a polymerization step for obtaining a polymer gel;

a drying step for drying the polymer gel to obtain a dried substance;

a pulverization step for pulverizing the dried substance under a reduced pressure to obtain a particulate water-absorbing resin, wherein the reduced pressure is lower than atmospheric pressure by no more than 10 kPa;

a classification step for sieving the particulate water-absorbing resin; and

a transporting step for transporting the products produced in each of the steps to other steps.

2. The method for producing the particulate water-absorbing agent according to claim 1, wherein equal to or more than 50% of the time required from the pulverization step to the packaging step is set under a reduced pressure state.

3. The method for producing the particulate water-absorbing agent according to claim 1, wherein 50% or more of the total time required for the steps including and subsequent to the pulverization step is set under a reduced pressure state.

4. The method for producing the particulate water-absorbing agent according to claim 1, wherein the transporting step performed next to the pulverization step is set under a reduced pressure state.

5. The method for producing the particulate water-absorbing agent according to claim 1, wherein all steps including and subsequent to the pulverization step are set under a reduced pressure state.

6. The method for producing the particulate water-absorbing agent according to claim 1, wherein the transporting step comprises the transporting step by pressurization.

7. The method for producing the particulate water-absorbing agent according to claim 6, wherein all steps other than the pulverization step are set under a reduced pressure state or a pressurized state.

8. The method for producing the particulate water-absorbing agent according to claim 1, further comprising a granulation step.

9. The method for producing the particulate water-absorbing agent according to claim 1, wherein the particulate water-absorbing resin is an irregular pulverized shaped particle of a polyacrylic acid (salt)-based water-absorbing resin.

10. The method for producing the particulate water-absorbing agent according to claim 1, wherein the polymerization step is performed by continuous kneader polymerization or continuous belt polymerization.

11. The method for producing the particulate water-absorbing agent according to claim 1, wherein the surface cross-linking step is performed using a surface cross-linking agent, having dehydration esterification reactivity of one or more kinds selected from a group consisting of an oxazolidinone compound, an alkylene carbonate compound, a polyvalent alcohol compound, and an oxetane compound, at a temperature in the range of 150 to 250°

C.

12. The method for producing the particulate water-absorbing agent according to claim 1, wherein absorbency against non-pressure (CRC) of the particulate water-absorbing agent is equal to or higher than 15 g/g, and saline flow conductivity (SFC) thereof is equal to or higher than 30 (×

10<sup>−

7</sup>·

cm³·

s·

g<sup>−

1</sup>).

13. The method for producing the particulate water-absorbing agent according to claim 1, wherein the content of fine powders with a weight average particle diameter of below 150 μ

m, contained in the particulate water-absorbing agent, is below 1% by weight relative to the total weight of the particulate water-absorbing agent.

14. The method for producing the particulate water-absorbing agent according to claim 1, wherein one or more of the classification step, and the transporting step after the pulverization step are performed under a reduced pressure.

15. A method for producing a particulate water-absorbing agent comprising:

a polymerization step for obtaining a polymer gel;

a drying step for drying the polymer gel to obtain a dried substance;

a pulverization step for pulverizing the dried substance under a reduced pressure to obtain a particulate water-absorbing resin, wherein the reduced pressure is lower than atmospheric pressure by no more than 10 kPa;

a classification step for sieving the particulate water-absorbing resin;

a granule sizing step for granule sizing a particulate water-absorbing agent obtained from the particulate water-absorbing resin obtained in the classification step; and

a transporting step for transporting the products produced in each of the steps to other steps.

16. The method for producing the particulate water-absorbing agent according to claim 15, wherein one or more of the classification step, the granule sizing step, and the transporting step after the pulverization step are performed under a reduced pressure.

17. A method for producing a particulate water-absorbing agent comprising:

a polymerization step for obtaining a polymer gel;

a drying step for drying the polymer gel to obtain a dried substance;

a pulverization step for pulverizing the dried substance under a reduced pressure to obtain a particulate water-absorbing resin, wherein the reduced pressure is lower than atmospheric pressure by no more than 10 kPa;

a classification step for sieving the particulate water-absorbing resin;

a surface cross-linking step for cross-linking the neighborhood of the surface of the particulate water-absorbing resin obtained in the classification step to obtain a particulate water-absorbing agent;

a packaging step for filling a packaging material container with the particulate water-absorbing agent for packaging; and

a transporting step for transporting the products produced in each of the steps to other steps.

18. The method for producing the particulate water-absorbing agent according to claim 17, wherein one or more of the classification step, the surface cross-linking step, the packaging step, and the transporting step after the pulverization step are performed under a reduced pressure.

19. A method for producing a particulate water-absorbing agent comprising:

a polymerization step for obtaining a polymer gel;

a drying step for drying the polymer gel to obtain a dried substance;

a pulverization step for pulverizing the dried substance under a reduced pressure to obtain a particulate water-absorbing resin, wherein the reduced pressure is lower than atmospheric pressure by no more than 10 kPa;

a classification step for sieving the particulate water-absorbing resin;

a surface cross-linking step for cross-linking the neighborhood of the surface of a particulate water-absorbing resin obtained in the classification step to obtain a particulate water-absorbing agent;

a granule sizing step for granule sizing the particulate water-absorbing agent;

a packaging step for filling a packaging material container with the particulate water-absorbing agent, obtained in the granule sizing step for packaging; and

a transporting step for transporting the products produced in each of the steps to other steps.

20. The method for producing the particulate water-absorbing agent according to claim 19, wherein equal to or more than 50% of the time required from the pulverization step to the packaging step is set under a reduced pressure state.

21. The method for producing the particulate water-absorbing agent according to claim 19, wherein one or more of the classification step, the surface cross-linking step, the granule sizing step, the packaging step, and the transporting step after the pulverization step are performed under a reduced pressure.