Superabsorbent polymers providing long-term generation of free volume in partially hydrated absorbent cores

• US 6,710,224 B2
• Filed: 04/10/2001
• Issued: 03/23/2004
• Est. Priority Date: 10/25/1999
• Status: Expired due to Term

• Current Assignee: Paragon Trade Brands, LLC (Medtronic Plc)
• Original Assignee: Paragon Trade Brands Inc. (Johnson Controls International plc)
• Inventors: Baker, Andrew, Chmielewski, Harry J.
• Primary Examiner(s): Lo, Weilun
• Assistant Examiner(s): Anderson, Catharine L
• Application Number:
  US09/828,846
• Publication Number:
  US 20020035353A1
• Time in Patent Office: 1,078 Days
• Field of Search: 604/367-8, 604/368, 604/359
• US Class Current: 604/368
• CPC Class Codes: A61F 13/15658 Forming continuous, e.g. composite, fibrous webs, e.g. involving the application of pulverulent material on parts thereof
• CPC Class Codes: A61F 13/15699 Forming webs by bringing together several webs, e.g. by laminating or folding several webs, with or without additional treatment of the webs
• CPC Class Codes: A61F 13/53 characterised by the absorbing medium A61F13/20 takes precedence
• CPC Class Codes: A61F 13/531 having a homogeneous composition through the thickness of the pad A61F13/538, A61F13/539 take precedence
• CPC Class Codes: A61F 2013/15463 Absorbency
• CPC Class Codes: A61F 2013/530481 having superabsorbent materials, i.e. highly absorbent polymer gel materials
• CPC Class Codes: A61F 2013/530744 by the absorbency under load
• CPC Class Codes: A61L 15/18 containing inorganic materials
• CPC Class Codes: A61L 15/60 Liquid-swellable gel-forming materials, e.g. super-absorbents

Abstract

An absorbent composition providing unexpectedly high fluid capacity with minimal gel-blocking, articles comprising the absorbent composition and methods of preparing the absorbent composition are disclosed. The absorbent composition optionally comprises a surface crosslinked polymer disbursed within a fibrous matrix of wettable fibers. The surface crosslinked polymer has an FVAUL value of at least about 60 cc after 10 minutes.

Claims

1. An absorbent composition comprising:

about 5% by weight to about 30% by weight of a fibrous matrix comprising wettable fibers;

about 70% by weight to about 95% by weight of a surface crosslinked polymer, said surface crosslinked polymer being disbursed within said fibrous matrix;

wherein the absorbent composition has a Finite Volume Absorbency Under Load FVAUL value of at least about 60 cc after 10 minutes, said FVAUL value being determined by the formula FV_s=20.268·

T_s−

[R·

W/ρ

_sap]−

[(1−

R)·

W/ρ

_pulp]; and

T_s is thickness of the sample (cm), R is ratio of SAP to sample weight (g/g), W is mass of the sample (g), ρ

_sap is density of SAP (g/cm³), and ρ

_pulp is density of pulp(g/cm³).

2. The absorbent composition of claim 1, wherein the surface crosslinked polymer is bipolar.

3. The absorbent composition of claim 1, wherein the surface crosslinked polymer provides minimal gel-blocking properties upon absorption of liquid.

4. The absorbent composition of claim 1, wherein the surface crosslinked polymer constitutes about 85% by weight to about 95% by weight of the combined weight of the fiberous matrix and the surface crosslinked polymer.

5. The absorbent composition of claim 1, wherein the surface crosslinked polymer constitutes about 90% by weight to about 95% by weight of the combined weight of the fiberous matrix and the surface crosslinked polymer.

6. The absorbent composition of claim 1, wherein said wettable fibers constitute about 5% by weight to about 15% by weight of the combined weight of the fiberous matrix and the surface crosslinked polymer.

7. The absorbent composition of claim 1, wherein said wettable fibers constitute about 5% by weight to about 10% by weight of the combined weight of the fiberous matrix and the surface crosslinked polymer.

8. The absorbent composition of claim 1, wherein the surface crosslinked polymer comprises a mixed-bed ion-exchange superabsorbent polymer composition.

9. The absorbent composition of claim 1, wherein the FVAUL free volume of the absorbent composition is about 20% to about 70%.

10. The absorbent composition of claim 1, wherein the FVAUL free volume of the absorbent composition is about 20% to about 60%.

11. The absorbent composition of claim 1, wherein the FVAUL free volume of the absorbent composition is about 20% to about 50%.

12. The absorbent composition of claim 1, wherein the FVAUL free volume of the absorbent composition is about 25% to about 50%.

13. The absorbent composition of claim 1, wherein the surface crosslinked polymer is evenly disbursed within the fibrous matrix.

14. The absorbent composition of claim 1, wherein the surface crosslinked polymer is poly(acrylic acid).

15. The absorbent composition of claim 1, wherein the surface crosslinked polymer comprises about 95% by weight of poly(acrylic acid) and about 3% by weight of a crosslinking agent.

16. The absorbent composition of claim 15, wherein the crosslinking agent is methylene bisacrylamide.

17. The absorbent composition of claim 15, wherein the surface crosslinked polymer additionally comprises a neutralizing agent.

18. The absorbent composition of claim 17, wherein the neutralizing agent is triethanol amine.

19. The absorbent composition of claim 1, wherein the wettable fibers are selected from the group consisting of natural fibers, synthetic fibers, and combinations thereof.

20. The absorbent composition of claim 1, wherein the wettable fibers are selected from the group consisting of wood pulp (fluff), cotton linters, polyethylene, polypropylene, polyesters, copolymers of polyesters and polyamides, and combinations thereof.

21. The absorbent composition of claim 1, wherein the wettable fibers are selected from the group consisting of wood pulp fibers, meltblown synthetic fibers and combinations thereof.

22. An absorbent composition prepared by the process comprising:

providing a first layer of wettable fibers;

distributing on the first layer of wettable fibers a layer of surface crosslinked polymer;

providing a second layer of wettable fibers on top of the layer of surface crosslinked polymer; and

calendaring said layers to form the wettable fibers into a fibrous matrix having the surface crosslinked polymer disbursed therein, said surface crosslinked polymer comprising about 70% by weight to about 95% by weight the absorbent composition and said wettable fibers comprising about 5% by weight to about 30% by weight of the absorbent composition, said absorbent composition having a Finite Volume Absorbency Under Load (FVAUL) value of at least about 60 cc after 10 minutes, said FVAUL value being determined by Finite Volume Absorbency Under Load Method.

23. The absorbent composition of claim 22, wherein the surface crosslinked polymer is bipolar.

24. The absorbent composition of claim 22, wherein the surface crosslinked polymer provides minimal gel-blocking properties upon absorption of liquid.

25. The absorbent composition of claim 22, wherein the surface crosslinked polymer constitutes about 85% by weight to about 95% by weight of the combined weight of the fiberous matrix and the surface crosslinked polymer.

26. The absorbent composition of claim 22, wherein the surface crosslinked polymer constitutes about 90% by weight to about 95% by weight of the combined weight of the fiberous matrix and the surface crosslinked polymer.

27. The absorbent composition of claim 22, wherein said wettable fibers constitute about 5% by weight to about 15% by weight of the combined weight of the fiberous matrix and the surface crosslinked polymer.

28. The absorbent composition of claim 22, wherein said wettable fibers constitute about 5% by weight to about 10% by weight of the combined weight of the fiberous matrix and the surface crosslinked polymer.

29. The absorbent composition of claim 22, wherein the surface crosslinked polymer comprises a mixed-bed ion-exchange superabsorbent polymer composition.

30. The absorbent composition of claim 22, wherein the FVAUL free volume of the absorbent composition is about 20% to about 70%.

31. The absorbent composition of claim 22, wherein the FVAUL free volume of the absorbent composition is about 20% to about 60%.

32. The absorbent composition of claim 22, wherein the FVAUL free volume of the absorbent composition is about 20% to about 50%.

33. The absorbent composition of claim 22, wherein the FVAUL free volume of the absorbent composition is about 25% to about 50%.

34. The absorbent composition of claim 22, wherein the surface crosslinked polymer is evenly disbursed within the fibrous matrix.

35. The absorbent composition of claim 22, wherein the surface crosslinked polymer is poly(acrylic acid).

36. The absorbent composition of claim 22, wherein the surface crosslinked polymer comprises about 95% by weight of poly(acrylic acid) and about 3% by weight of a crosslinking agent.

37. The absorbent composition of claim 36, wherein the crosslinking agent is methylene bisacrylamide.

38. The absorbent composition of claim 36, wherein the surface crosslinked polymer additionally comprises a neutralizing agent.

39. The absorbent composition of claim 38, wherein the neutralizing agent is triethanol amine.

40. The absorbent composition of claim 22, wherein the wettable fibers are selected from the group consisting of natural fibers, synthetic fibers, and combinations thereof.

41. The absorbent composition of claim 22, wherein the wettable fibers are selected from the group consisting of wood pulp (fluff), cotton linters, polyethylene, polypropylene, polyesters, copolymers of polyesters and polyamides, and combinations thereof.

42. The absorbent composition of claim 22, wherein the wettable fibers are selected from the group consisting of wood pulp fibers, meltblown synthetic fibers and combinations thereof.

43. An absorbent composition comprising:

a surface crosslinked polymer;

wherein the absorbent composition has a Finite Volume Absorbency Under Load FVAUL value of at least about 60 cc after 10 minutes, said FVAUL value being determined by the formula FV_s=20.268·

T_s−

[R·

W/ρ

_sap]−

[(1−

R)·

W/ρ

_pulp]; and

T_s is thickness of the sample (cm), R is ratio of SAP to sample weight (g/g), W is mass of the sample (g), ρ

_sap is density of SAP (g/cm³), and ρ

_pulp is density of pulp(g/cm³).

44. An absorbent article comprising:

a permeable topsheet;

a substantially impermeable backsheet; and

an absorbent core disposed between the permeable topsheet and the substantially impermeable backsheet, said absorbent core comprising an absorbent composition comprising about 5% by weight to about 30% by weight of a fibrous matrix comprising wettable fibers and about 70% by weight to about 95% by weight of a surface crosslinked polymer, said surface crosslinked polymer being disbursed within said fibrous matrix;

wherein the absorbent composition has a Finite Volume Absorbency Under Load FVAUL value of at least about 60 cc after 10 minutes, said FVAUL value being determined by the formula FV_s=20.268·

T_s−

[R·

W/ρ

_sap]−

[(1−

R)·

W/ρ

_pulp]; and

T_s is thickness of the sample (cm), R is ratio of SAP to sample weight (g/g), W is mass of the sample (g), ρ

_sap is density of SAP (g/cm³), and ρ

_pulp is density of pulp(g/cm³).

45. The absorbent article of claim 44, wherein the surface crosslinked polymer is bipolar.

46. The absorbent article of claim 44, wherein the surface crosslinked polymer provides minimal gel-blocking properties upon absorption of liquid.

47. The absorbent article of claim 44, wherein the surface crosslinked polymer constitutes about 85% by weight to about 95% by weight of the combined weight of the fiberous matrix and the surface crosslinked polymer.

48. The absorbent article of claim 44, wherein the surface crosslinked polymer constitutes about 90% by weight to about 95% by weight of the combined weight of the fiberous matrix and the surface crosslinked polymer.

49. The absorbent article of claim 44, wherein said wettable fibers constitute about 5% by weight to about 15% by weight of the combined weight of the fiberous matrix and the surface crosslinked polymer.

50. The absorbent article of claim 44, wherein said wettable fibers constitute about 5% by weight to about 10% by weight of the combined weight of the fiberous matrix and the surface crosslinked polymer.

51. The absorbent article of claim 44, wherein the surface crosslinked polymer comprises a mixed-bed ion-exchange superabsorbent polymer composition.

52. The absorbent article of claim 44, wherein the FVAUL free volume of the absorbent composition is about 20% to about 70%.

53. The absorbent article of claim 44, wherein the FVAUL free volume of the absorbent composition is about 20% to about 60%.

54. The absorbent article of claim 44, wherein the FVAUL free volume of the absorbent composition is about 20% to about 50%.

55. The absorbent article of claim 44, wherein the FVAUL free volume of the absorbent composition is about 25% to about 50%.

56. The absorbent article of claim 44, wherein the surface crosslinked polymer is evenly disbursed within the fibrous matrix.

57. The absorbent article of claim 44, wherein the surface crosslinked polymer is poly(acrylic acid).

58. The absorbent article of claim 44, wherein the surface crosslinked polymer comprises about 95% by weight of poly(acrylic acid) and about 3% by weight of a crosslinking agent.

59. The absorbent article of claim 58, wherein the crosslinking agent is methylene bisacrylamide.

60. The absorbent article of claim 58, wherein the surface crosslinked polymer additionally comprises a neutralizing agent.

61. The absorbent article of claim 60, wherein the neutralizing agent is triethanol amine.

62. The absorbent article of claim 44, wherein the wettable fibers are selected from the group consisting of natural fibers, synthetic fibers, and combinations thereof.

63. The absorbent article of claim 44, wherein the wettable fibers are selected from the group consisting of wood pulp (fluff), cotton linters, polyethylene, polypropylene, polyesters, copolymers of polyesters and polyamides, and combinations thereof.

64. The absorbent article of claim 44, wherein the wettable fibers are selected from the group consisting of wood pulp fibers, meltblown synthetic fibers and combinations thereof.

65. The absorbent article of claim 44, wherein the absorbent article is a nighttime diaper.

66. The absorbent article of claim 44, wherein the absorbent article is a long-term use diaper.

67. The absorbent article of claim 44, wherein the absorbent article is a travel diaper.

68. An absorbent composition comprising:

about 5% by weight to about 30% by weight of a fibrous matrix comprising wettable fibers;

about 70% by weight to about 95% by weight of a surface crosslinked polymer, said surface crosslinked polymer being disbursed within said fibrous matrix;

wherein the absorbent composition has a Finite Volume Absorbency Under Load (FVAUL) value of at least about 60 cc after 10 minutes, said FVAUL value being determined by the formula FV_s=20.268·

T_s−

[R·

W/ρ

_sap]−

[(1−

R)·

W/ρ

_pulp]; and

T_s is thickness of the sample (cm), R is ratio of SAP to sample weight (g/g), W is mass of the sample (g), ρ

_sap is density of SAP (g/cm³), and ρ

_pulp is density of pulp(g/cm³);

wherein the surface crosslinked polymer comprises about 95% by weight of poly(acrylic acid) and about 3% by weight of a crosslinking agent; and

wherein the surface crosslinked polymer additionally comprises a neutralizing agent;

said neutralizing agent is triethanol amine.

69. An absorbent composition prepared by the process comprising:

providing a first layer of wettable fibers;

distributing on the first layer of wettable fibers a layer of surface crosslinked polymer;

providing a second layer of wettable fibers on top of the layer of surface crosslinked polymer; and

calendaring said layers to form the wettable fibers into a fibrous matrix having the surface crosslinked polymer disbursed therein, said surface crosslinked polymer comprising about 70% by weight to about 95% by weight the absorbent composition and said wettable fibers comprising about 5% by weight to about 30% by weight of the absorbent composition, said absorbent composition having a Finite Volume Absorbency Under Load (FVAUL) value of at least about 60 cc after 10 minutes, said FVAUL value being determined by Finite Volume Absorbency Under Load Method;

wherein the surface crosslinked polymer comprises about 95% by weight of poly(acrylic acid) and about 3% by weight of a crosslinking agent; and

wherein the surface crosslinked polymer additionally comprises a neutralizing agent, said neutralizing agent being triethanol amine.

70. An absorbent article comprising:

a permeable topsheet;

a substantially impermeable backsheet; and

an absorbent core disposed between the permeable topsheet and the substantially impermeable backsheet, said absorbent core comprising an absorbent composition comprising about 5% by weight to about 30% by weight of a fibrous matrix comprising wettable fibers and about 70% by weight to about 95% by weight of a surface crosslinked polymer, said surface crosslinked polymer being disbursed within said fibrous matrix;

wherein the absorbent composition has a Finite Volume Absorbency Under Load (FVAUL) value of at least about 60 cc after 10 minutes, said FVAUL value being determined by the formula FV_s=20.268·

T_s−

[R·

W/ρ

_sap]−

[(1−

R)·

W/ρ

_pulp]; and

T_s is thickness of the sample (cm), R is ratio of SAP to sample weight (g/g), W is mass of the sample (g), ρ

_sap is density of SAP (g/cm³), and ρ

_pulp is density of pulp(g/cm³);

wherein the surface crosslinked polymer comprises about 95% by weight of poly(acrylic acid) and about 3% by weight of a crosslinking agent; and

wherein the surface crosslinked polymer additionally comprises a neutralizing agent, said neutralizing agent being triethanol amine.