SUPERABSORBENT POLYMER COMPOSITIONS HAVING COLOR STABILITY

• US 20090023848A1
• Filed: 07/16/2007
• Published: 01/22/2009
• Est. Priority Date: 07/16/2007
• Status: Active Grant

• Current Assignee: Evonik Corporation
• Original Assignee: Evonik Stockhausen, LLC (Rag-Stiftung)
• Inventors: Walden, Mirko, Smith, Scott J., King, Brian, Ahmed, Iqbal, Schmidt, Harald
• Granted Patent: US 7,816,426 B2
• Time in Patent Office: Days
• US Class Current: 524/422
• CPC Class Codes: A61L 15/56 Wetness-indicators or colourants
• CPC Class Codes: A61L 15/60 Liquid-swellable gel-forming materials, e.g. super-absorbents
• CPC Class Codes: C08F 220/06 Acrylic acid; Methacrylic acid; Metal salts or ammonium salts thereof
• CPC Class Codes: C08F 222/103 of trialcohols, e.g. trimethylolpropane tri(meth)acrylate
• CPC Class Codes: C08K 3/30 Sulfur-, selenium- or tellurium-containing compounds

Abstract

The invention relates to absorptive, crosslinked polymeric compositions that are based on partly neutralized, monoethylenically unsaturated monomer carrying acid groups wherein the absorptive, crosslinked polymeric composition further includes an antioxidant and is color stable.

Claims

1. A superabsorbent polymer composition comprising a superabsorbent polymer comprising:

a) from about 55% to about 99.9% by weight of the superabsorbent polymer of polymerizable unsaturated acid group containing monomer based on the superabsorbent polymer; and

b) from about 0.001% to about 5% by weight of internal crosslinking agent based on the polymerizable unsaturated acid group containing monomer;

c) from about 50 to 1000 ppm of a thermal initiator based on the polymerizable unsaturated acid group containing monomer;

wherein the superabsorbent polymer has a degree of neutralization of greater than about 25%;

wherein elements a), b) and c) are polymerized into a crosslinked hydrogel, which is then prepared into superabsorbent polymer particles;

the superabsorbent polymer composition further comprising the following additives to form superabsorbent polymer composition particles

i) from about 0.001% to about 5% by weight of surface crosslinking agent based on the superabsorbent polymer composition; and

wherein from about 0.01% to about 5% by weight of an antioxidant based on the superabsorbent polymer composition is added to the polymerized product whether in crosslinked hydrogel or subsequent superabsorbent polymer particles or superabsorbent polymer composition particle form wherein the superabsorbent polymer composition has a free swell gel bed permeability of at least about 6 Darcy as measured by the Free Swell Gel Bed Permeability Test.

3. The superabsorbent polymer composition according to claim 1 wherein the superabsorbent polymer composition, after storage for 49 days at 40°

C. and 80% relative humidity, exhibits a Whiteness Index of at least about 7.5 as measured by the Whiteness Index Test.

7. The superabsorbent polymer composition according to claim 1 wherein the thermal initiator comprises sodium persulfate.

12. The superabsorbent polymer composition according to claim 1 wherein the antioxidant comprises sodium bisulfite.

15. The superabsorbent polymer composition according to claim 1 wherein the additives further comprises iii) from about 0.01% to about 5% by weight of a polymeric coating based on the superabsorbent polymer composition.

16. The superabsorbent polymer composition according to claim 1 wherein said polymeric coating comprises iii) from about 0.01% to about 0.5% by weight of a thermoplastic polymer based on the dry superabsorbent polymer composition.

18. The superabsorbent polymer composition of claim 16 wherein the polymeric coating comprises a maleated polypropylene.

19. The superabsorbent polymer composition according to claim 15 wherein the polymeric coating comprises a cationic polymer.

25. The superabsorbent polymer composition of claim 1 wherein at least about 50% by weight of the superabsorbent polymer composition have a particle size from about 300 μ

m to about 600 μ

m.

2. (canceled)

4-6. -6. (canceled)

8-11. -11. (canceled)

13-14. -14. (canceled)

17. (canceled)

20-24. -24. (canceled)

26-28. -28. (canceled)

29. The superabsorbent polymer composition comprising a superabsorbent polymer comprising superabsorbent polymer particles surface treated with i) from about 0.01% to about 5% by weight of a polymeric coating based on the superabsorbent polymer composition;

and ii) from about 0.01% to about 5% by weight of an antioxidant based on the superabsorbent polymer composition wherein the antioxidant is added to the polymerized product whether in crosslinked hydrogel or subsequent superabsorbent polymer particles or superabsorbent polymer composition particle form.

33. The superabsorbent polymer composition according to claim 29 wherein the superabsorbent polymer composition, after storage for 84 days at 40°

C. and 80% relative humidity, exhibits a Whiteness Index of at least about 7.5 as measured by the Whiteness Index Test.

35. The superabsorbent polymer composition according to claim 29 wherein the thermal initiator comprises sodium persulfate.

40. The superabsorbent polymer composition according to claim 29 wherein the antioxidant comprises sodium bisulfite.

46. The superabsorbent polymer composition according to claim 29 wherein said polymeric coating comprises from about 0.01% to about 0.5% by weight of a thermoplastic polymer based on the dry superabsorbent polymer composition.

30-32. -32. (canceled)

34. (canceled)

36-39. -39. (canceled)

41-45. -45. (canceled)

47-54. -54. (canceled)

55. A method to make a superabsorbent polymer composition comprising the steps of:

a) preparing a superabsorbent polymer by the process of polymerizing from about 55% to about 99.9% by weight of polymerizable unsaturated acid group containing monomer based on the superabsorbent polymer, and from about 0.001% to about 5% by weight of an internal crosslinking agent based on the polymerizable unsaturated acid group containing monomer, and from about 50 to 1000 ppm of a thermal initiator based on the polymerizable unsaturated acid group containing monomer, wherein the superabsorbent polymer has a degree of neutralization of greater than about 25%;

b) polymerizing the components of a) into a hydrogel;

c) preparing superabsorbent polymer particles from the superabsorbent polymer;

d) treating the superabsorbent polymer particles with surface additives including;

i) from about 0.001% to about 5% by weight of surface crosslinking agent based on the superabsorbent polymer composition;

wherein from about 0.01% to about 5% by weight of an antioxidant based on the superabsorbent polymer composition is added to the polymerized product whether in crosslinked hydrogel or subsequent superabsorbent polymer particles or superabsorbent polymer composition particle form wherein the superabsorbent polymer composition has a free swell gel bed permeability of at least about 6 Darcy as measured by the Free Swell Gel Bed Permeability Test.

56. The method to make the superabsorbent polymer composition of claim 55 wherein the superabsorbent polymer composition, after storage for 42 days at 40°

C. and 80% relative humidity, exhibits a Whiteness Index of at least about 7.5 as measured by the Whiteness Index Test.

71. The method to make the superabsorbent polymer composition of claim 55 wherein the additives further comprises iii) from 0% to about 5% by weight of a polymeric coating based on the superabsorbent polymer composition.

72. The method to make the superabsorbent polymer composition according to claim 71 wherein said polymeric coating is from about 0.01% to about 0.5% by weight of a thermoplastic polymer based on the dry superabsorbent polymer composition.

74. The method to make the superabsorbent polymer composition according to claim 71 wherein the polymeric coating comprises maleated polypropylene.

76. The method to make the superabsorbent polymer composition according to claim 71 wherein the polymeric coating comprises polyvinylamine.

77. The method to make the superabsorbent polymer composition of claim 55 wherein the high-capacity superabsorbent polymer composition has at least about 40% by weight of the dry superabsorbent polymer have a particle size from about 300 μ

m to about 600 μ

m.

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73. (canceled)

75. (canceled)

78-80. -80. (canceled)

81. A superabsorbent polymer composition comprising a superabsorbent polymer comprising:

a) from about 55% to about 99.9% by weight of the superabsorbent polymer of polymerizable unsaturated acid group containing monomer based on the superabsorbent polymer; and

b) from about 0.001% to about 5% by weight of internal crosslinking agent based on the polymerizable unsaturated acid group containing monomer;

c) from about 50 to 1000 ppm of a thermal initiator based on the polymerizable unsaturated acid group containing monomer;

wherein the superabsorbent polymer has a degree of neutralization of greater than about 25%;

wherein elements a), b) and c) are polymerized into a crosslinked hydrogel, which is then prepared into superabsorbent polymer particles;

the superabsorbent polymer composition further comprising the following additives to form superabsorbent polymer composition particles

i) from about 0.001% to about 5% by weight of surface crosslinking agent based on the superabsorbent polymer composition; and

wherein from about 0.01% to about 5% by weight of an antioxidant selected from sulfinic acid, 2-hydroxy-2-sulfinatoacetic acid, 2-hydroxy-2-sulfonatoacetic acid or sulfonic acid, and salts or derivatives of the foregoing, based on the superabsorbent polymer composition is added to the polymerized product whether in crosslinked hydrogel or subsequent superabsorbent polymer particles or superabsorbent polymer composition particle form.

82. The superabsorbent polymer composition of claim 81 wherein the superabsorbent polymer composition after storage for 42 days at 40°

C. and 80% relative humidity, exhibits a Whiteness Index of at least about 7.5 as measured by the Whiteness Index Test.

83-103. -103. (canceled)