High-density absorbent structures

• US 4,610,678 A
• Filed: 09/06/1983
• Issued: 09/09/1986
• Est. Priority Date: 06/24/1983
• Status: Expired due to Fees

• Current Assignee: The Procter & Gamble Company
• Original Assignee: The Procter & Gamble Company
• Inventors: Goldman, Stephen A., Weisman, Paul T.
• Primary Examiner(s): Pellegrino, Stephen C.
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US06/529,900
• Time in Patent Office: 1,099 Days
• Field of Search: 604/368, 604/379, 604/380
• US Class Current: 604/368
• CPC Class Codes: A61F 13/15203 Properties of the article, e.g. stiffness or absorbency chemical aspects A61L15/00
• 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 2013/530481 having superabsorbent materials, i.e. highly absorbent polymer gel materials
• CPC Class Codes: A61F 2013/530489 being randomly mixed in with other material
• CPC Class Codes: A61F 2013/530496 being fixed to fibres
• CPC Class Codes: A61L 15/60 Liquid-swellable gel-forming materials, e.g. super-absorbents

Abstract

Absorbent structures comprising a mixture of hydrophilic fibers and discrete particles of a water insoluble hydrogel are disclosed. The fiber/hydrogel ratios range from about 30:70 to about 98:2. The absorbent structures have a density of from about 0.15 g/cm³ to about 1 g/cm³. The structures are flexible, and have superior absorption capacities for water and body fluids.

Claims

1. A flexible, substantially unbonded, absorbent structure comprising an air-laid, substantially dry mixture of hydrophilic fibers and discrete particles of a water-insoluble, cross-linked polymeric hydrogel, in a fiber/hydrogel weight ratio from about 30:

70 to about 98;

2;

said absorbent structure having a density of from about 0.15 to about 1 g/cm³, a moisture content of less than about 10% by weight of the dry absorbent structure and a Gurley Stiffness value of less than 2 grams.

2. An absorbent structure according to claim 1, having a fiber/hydrogel weight ratio of from about 50:

50 to about 95;

5.

3. An absorbent structure according to claim 1, having a fiber/hydrogel weight ratio of from about 75:

25 to about 90;

10.

4. An absorbent structure according to claim 1, having a density of from about 0.15 to about 0.6 g/cm³.

5. An absorbent structure according to claim 1, having a density of from about 0.25 to about 0.44g/cm³.

6. An absorbent structure according to claim 1 wherein the hydrophilic fibers are wood pulp fibers.

7. An absorbent structure according to claim 1, further comprising from about 0.01% to about 0.5% by weight of the hydrophilic fibers of a quaternary ammonium compound of the formula ##STR3## wherein R₁ and R₂ are hydrocarbyl groups containing from about 8 to about 22 carbon atoms, R₃ and R₄ are alkyl having from 1 to 6 carbon atoms;

n and m are integers from 2 to about 10, and X is halogen.

8. An absorbent structure according to claim 1 which the has a Gurley Stiffness value of less than 1 g.

9. An absorbent structure according to claim 1, wherein the hydrogel particles have an average particle size of from about 30 microns to about 4 mm.

10. An absorbent structure according to claim 1, wherein the hydrogel particles have an average particle size of from about 50 microns to about 1 mm.

23. An absorbent product comprising the absorbent structure of claim 1.

24. A disposable diaper, comprising:

(a) a liquid impervious backing sheet;

(b) a hydrophobic top sheet;

(c) an absorbent structure according to claim 1, said structure being placed between the backing sheet and the top sheet.

25. A disposable diaper, comprising:

(a) a liquid impervious backing sheet;

(b) a hydrophobic topsheet; and

(c) an absorbent structure according to claim 7, said structure being placed between the backing sheet and the topsheet.

26. A disposable diaper according to claim 24, wherein the absorbent structure has a basis weight of from about 0.01 to about 0.05 g/cm².

27. A disposable diaper according to claim 24 wherein the absorbent structure is wrapped in envelope tissue.

28. A disposable diaper according to claim 27 wherein the absorbent structure has a thickness of from about 0.3 mm to about 2 mm.

29. A disposable diaper according to claim 27 wherein the absorbent structure has a thickness of from about 0.5 mm to about 1 mm.

30. A disposable diaper according to claim 24 wherein the absorbent structure is hourglass-shaped.

31. A disposable diaper according to claim 24 further comprising a wood pulp fiber absorbent core which is placed between the hydrophobic top sheet (b) and the absorbent structure (c).

32. A disposable diaper according to claim 31 wherein the wood pulp fiber absorbent core is hourglass shaped and the absorbent structure (c) is rectangular.

33. A sanitary napkin comprising:

(a) a liquid impervious backing sheet;

(b) a hydrophobic top sheet;

(c) an absorbent structure according to claim 1, said structure being placed between the backing sheet and the top sheet.

11. A flexible, substantially unbonded, absorbent structure comprising an air-laid, substantially dry mixture of wood pulp fibers and discrete particles of a water-insoluble, cross-linked polymeric hydrogel in a fiber/hydrogel weight ratio of from about 75:

25 to about 90;

10, said cross-linked polymeric hydrogel being selected from the group consisting of hydrolyzed acrylonitrile grafted starch, acrylic acid grafted starch, polyacrylate, co-polymers of isobutylene and maleic anhydride, and mixtures thereof, said particles having an average particle size of from about 50 microns to about 1 mm;

said structure having a density of from about 0.15 to about 0.6 g/cm³ and a Gurley Stiffness value of less than 2 grams.

12. A process for making a continuous, flexible absorbent structure, comprising the following steps:

(a) air-laying into a web a dry mixture of hydrophilic fibers and particles of a water-insoluble, cross-linked polymeric hydrogel, said mixture having a fiber/hydrogel weight ratio of from about 30;

70 to about 98;

2 and a moisture content of less than about 10% by weight of the mixture; and

,

(b) compressing the web to a density of from about 0.15 to about 1 g/cm³ and a Gurley Stiffness value of less than 2 grams.

13. A process according to claim 12, whereby the mixture of hydrophilic fibers and hydrogel particles has a fiber/hydrogel weight ratio of from about 50:

50 to about 95;

5.

14. A process according to claim 12, whereby the mixture of hydrophilic fibers and hydrogel particles has a fiber/hydrogel weight ratio of from about 75:

25 to about 90;

10.

15. A process according to claim 12 whereby the web is compressed to a density of from about 0.15 to about 0.6 g/cm³.

16. A process according to claim 12 whereby the web is compressed to a density of from about 0.25 to about 0.4 g/cm³.

17. A process according to claim 12, wherein the hydrophilic fibers are wood pulp fibers.

18. A process according to claim 12, wherein the cross-linked polymeric hydrogel is selected from the group consisting of hydrolyzed acrylonitrile grafted starch, acrylic acid grafted starch, polyacrylates, copolymers of isobutylene and maleic anhydride, and mixtures thereof.

19. A process according to claim 12, wherein the hydrogel particles have an average particle size of from about 30 microns to about 4 mm.

20. A process according to claim 12 wherein the hydrogel particles have an average particle size of from about 50 microns to about 1 mm.

22. An absorbent structure made according to the process of claim 12.

21. A process for making a flexible, substantially unbonded, absorbent structure, comprising the following steps:

(a) dry mixing of hydrophilic fibers and particles of a water-insoluble, cross-linked polymeric hydrogel in a weight ratio of from about 75;

25 to about 90;

10, said particles having an average size of from about 50 microns to about 1 mm, and said cross-linked polymeric hydrogel being selected from the group consisting of hydrolyzed acrylonitrile grafted starch, acrylic acid grafted starch, polyacrylates, copolymers of isobutylene and maleic anhydride, and mixtures thereof to form a fiber/hydrogel mixture having a moisture content of less than 10% by weight;

(b) air-laying of the mixture obtained in step (a) into a web; and

(c) compressing the web into a density of from about 0.15 to about 0.6 g/cm³ and a Gurley Stiffness value of less than 2 grams.