High stiffness absorbent polymers having improved absorbency rates and method for making the same

• US 6,939,914 B2
• Filed: 11/08/2002
• Issued: 09/06/2005
• Est. Priority Date: 11/08/2002
• Status: Expired due to Fees

• Current Assignee: Kimberly-Clark Worldwide Incorporated (Kimberly-Clark Corporation)
• Original Assignee: Kimberly-Clark Worldwide Incorporated (Kimberly-Clark Corporation)
• Inventors: Ranganathan, Sridhar, Zhang, Xiaomin, Qin, Jian, Uttecht, Cathleen M., Dodge, Richard Norris II
• Primary Examiner(s): Zalukaeva, Tatyana
• Application Number:
  US10/291,237
• Publication Number:
  US 20040092658A1
• Time in Patent Office: 1,033 Days
• Field of Search: 524/800, 604/358, 604/372, 604/368, 525/329.5, 526/318.3, 526/323, 526/326, 526/330
• US Class Current: 524/800
• CPC Class Codes: A61F 2013/530569 characterized by the particle size
• CPC Class Codes: A61F 2013/530729 by the swelling rate
• CPC Class Codes: A61L 15/60 Liquid-swellable gel-forming materials, e.g. super-absorbents
• CPC Class Codes: C08J 2300/14 Water soluble or water swellable polymers, e.g. aqueous gels
• CPC Class Codes: C08J 3/12 Powdering or granulating

Abstract

Superabsorbent polymer materials are provided including absorbent polymers having a fast vortex time, desirably about 10 seconds or less, and a stiffness index of at least about 0.7, as determined by test procedures described herein. The absorbent polymers can be modified to obtain a faster vortex time by a method including providing an absorbent polymer having a first vortex time, absorbing water with the absorbent polymer, freeze-drying the swollen absorbent polymer to remove at least a portion of the absorbed water, and obtaining a modified absorbent polymer having a second vortex time. The ratio of the first vortex time to the second vortex time is at least about 5, and desirably the modified absorbent polymer has a stiffness index of at least about 0.7.

Claims

1. A superabsorbent material, comprising:

an absorbent polymer having a vortex time of about 10 seconds or less and a stiffness index of at least about 0.7.

2. The superabsorbent material of claim 1, wherein the absorbent polymer has a vortex time of about 5 seconds or less.

3. The superabsorbent material of claim 2, wherein the absorbent polymer has a vortex time of about 3 seconds or less.

4. The superabsorbent material of claim 1, wherein the absorbent polymer has a stiffness index of at least about 0.8.

5. The superabsorbent material of claim 4, wherein the absorbent polymer has a vortex time of about 5 seconds or less.

6. The superabsorbent material of claim 5, wherein the absorbent polymer has a vortex time of about 3 seconds or less.

7. The superabsorbent material of claim 1, wherein the absorbent polymer has a stiffness index of at least about 0.9.

8. The superabsorbent material of claim 7, wherein the absorbent polymer has a vortex time of about 5 seconds or less.

9. The superabsorbent material of claim 8, wherein the absorbent polymer has a vortex time of about 3 seconds or less.

10. The superabsorbent material of claim 1, wherein the absorbent polymer is a modified absorbent polymer, and the absorbent polymer has a first vortex time greater than about 10 seconds before modification and a second vortex time of about 10 seconds or less after modification.

11. The superabsorbent material of claim 10, wherein the modified absorbent polymer is a freeze-dried absorbent polymer.

12. The superabsorbent material of claim 1, wherein the absorbent polymer includes a polymer selected from the group including an anionic polymer, a cationic polymer, an acidic polymer, a basic polymer, and combinations thereof.

13. The superabsorbent material of claim 12, wherein the absorbent polymer is selected from the group including sodium polyacrylate, polyvinyl amine salt, polyacrylic acid, polyvinyl amine, and combinations thereof.

14. The superabsorbent material of claim 1, wherein the absorbent polymer is a modified absorbent polymer, the absorbent polymer having a first vortex time before modifying and a second vortex time after modifying, wherein a ratio of the first vortex time to the second vortex time is at least about 5.

15. A method for forming the modified absorbent polymer of the superabsorbent material of claim 14, the method comprising:

providing an absorbent polymer having the first vortex time;

absorbing water with the absorbent polymer;

removing at least a portion of the absorbed water from the absorbent polymer; and

obtaining the modified absorbent polymer having the second vortex time.

16. The method of claim 15, further comprising absorbing water to obtain an absorbent polymer swelling level of at least about 5 grams water/gram absorbent polymer.

17. The method of claim 16, wherein the absorbent polymer includes a particle size of about 850 micrometers or less before absorbing water.

18. The method of claim 16, further comprising absorbing water to obtain an absorbent polymer swelling level of at least about 10 grams water/gram absorbent polymer.

19. The method of claim 18, wherein the absorbent polymer includes a particle size of about 600 micrometers or less before absorbing water.

20. The method of claim 18, further comprising absorbing water to obtain an absorbent polymer swelling level of at least about 20 grams water/gram absorbent polymer.

21. The method of claim 15, wherein the ratio of the first vortex time to the second vortex time is at least about 10.

22. The method of claim 21, wherein the ratio of the first vortex time to the second vortex time is at least about 20.

23. The method of claim 15, wherein the modified absorbent polymer has a stiffness index of at least about 0.8.

24. The method of claim 23, wherein the modified absorbent polymer has a stiffness index of at least about 0.9.

25. The method of claim 15, wherein the portion of the water is removed by freeze-drying.

26. The superabsorbent material of claim 14, wherein the modified absorbent polymer is a freeze-dried absorbent polymer, the freeze-dried absorbent polymer having the first vortex time before freeze-drying and the second vortex time after freeze-drying.

27. The superabsorbent material of claim 26 wherein the freeze-dried absorbent polymer comprises sodium polyacrylate.

28. A method for forming the modified absorbent polymer of the superabsorbent material of claim 10, the method comprising:

providing an absorbent polymer having the first vortex time of greater than about 10 seconds;

absorbing water with the absorbent polymer to obtain a swollen absorbent polymer;

freeze-drying the swollen absorbent polymer to remove at least a portion of the absorbed water; and

obtaining the modified absorbent polymer having the second vortex time of about 10 seconds or less and the stiffness index of at least about 0.7.

29. The method of claim 28, further comprising absorbing water to obtain an absorbent polymer swelling level of at least about 5 grams water/gram absorbent polymer.

30. The method of claim 28, wherein the modified absorbent polymer has a second vortex time of about 5 seconds or less.

31. The method of claim 30, wherein the modified absorbent polymer has a second vortex time of about 3 seconds or less.

32. The method of claim 28, wherein the modified absorbent polymer has a stiffness index of at least about 0.8.

33. The method of claim 32, wherein the modified absorbent polymer has a stiffness index of at least about 0.9.

34. The superabsorbent material of claim 27, wherein the absorbent polymer has a stiffness index of at least about 0.8.

35. The superabsorbent material of claim 34, wherein the absorbent polymer has a stiffness index of at least about 0.9.

36. The superabsorbent material of claim 27, wherein the ratio of the first vortex time to the second vortex time is at least about 10.

37. The superabsorbent material of claim 36, wherein the absorbent polymer has a stiffness index of at least about 0.8.

38. The superabsorbent material of claim 37, wherein the absorbent polymer has a stiffness index of at least about 0.9.

39. An absorbent composite comprising about 5 percent to 95 percent by weight of the superabsorbent material of claim 27.

40. An absorbent article comprising the superabsorbent material of claim 27.

41. An absorbent composite comprising about 5 percent to 95 percent by weight of the superabsorbent material of claim 1.

42. An absorbent article comprising the superabsorbent material of claim 1.