Absorbent structure containing individualized, polycarboxylic acid crosslinked wood pulp cellulose fibers

• US 5,137,537 A
• Filed: 10/17/1990
• Issued: 08/11/1992
• Est. Priority Date: 11/07/1989
• Status: Expired due to Term

• Current Assignee: The Procter & Gamble Company
• Original Assignee: Procter & Gamble Cellulose Company
• Inventors: Cooper, David J., Herron, Carlisle M.
• Primary Examiner(s): Clingman, A. Lionel
• Application Number:
  US07/596,607
• Time in Patent Office: 664 Days
• Field of Search: 8/120, 8/116.1
• US Class Current: 8/120
• CPC Class Codes: A61L 15/28 Polysaccharides or their derivatives A61L15/225 takes precedence
• CPC Class Codes: C08L 1/02 Cellulose; Modified cellulose
• CPC Class Codes: D04H 1/587 characterised by the bonding agents used
• CPC Class Codes: D04H 1/64 the bonding agent being applied in wet state, e.g. chemical agents in dispersions or solutions
• CPC Class Codes: D06M 13/192 Polycarboxylic acids; Anhydrides, halides or salts thereof D06M13/1845 takes precedence
• CPC Class Codes: D21C 9/005 organic compounds

Abstract

Disclosed are absorbent structures containing individualized, crosslinked fibers. The individualized, crosslinked fibers preferably have a C₂ -C₉ polycarboxylic acid crosslinking agent reacted with the fibers in the form of intrafiber crosslink bonds. Preferably, the crosslinking agent is citric acid, and between about 0.5 mole % and about 10.0 mole % crosslinking agent react to form the intrafiber crosslink bonds. Also preferably, the absorbent structures have actual dry densities greater than their corresponding equilibrium wet densities, and expand upon wetting. The absorbent structures may also contain hydrogel-forming material.

Claims

1. An absorbent structure comprising individualized, crosslinked wood pulp cellulosic fibers having between about 0.5 mole % and about 10.0 mole % of a C₂ -C₉ polycarboxylic acid crosslinking agent, calculated on a cellulose anhydroglucose molar basis, reacted with said fibers in an intrafiber ester crosslink bond form, wherein said crosslinked fibers have a water retention value of from about 25 to about 60, and wherein said C₂ -C₉ polycarboxylic acid crosslinking agent is selected from the group consisting of:

(i) aliphatic and alicyclic C₂ -C₉ polycarboxylic acids having at least three carboxyl groups per molecule; and

(ii) aliphatic and alicyclic C₂ -C₉ polycarboxylic acids having two carboxyl groups per molecule and having a carbon-carbon double bond located alpha, beta to one or both of the carboxyl groups, wherein one carboxyl group in said C₂ -C₉ polycarboxylic acid crosslinking agent is separated from a second carboxyl group by either two or three carbon atoms.

2. The absorbent structure of claim 1 wherein said fibers have between about 1.5 mole % and about 6.0 mole % crosslinking agent, calculated on a cellulose anhydroglucose molar basis, reacted therewith in the form of intrafiber ester crosslink bonds.

3. The absorbent structure of claim 1 wherein said crosslinking agent is selected from the group consisting of citric acid, 1, 2, 3, 4 butane tetracarboxylic acid, and 1, 2, 3 propane tricarboxylic acid.

4. The absorbent structure of claim 3 wherein said crosslinking agent is citric acid.

5. The absorbent structure of claim 2 wherein said crosslinking agent is selected from the group consisting of citric acid, 1,2,3,4 butane tetracarboxylic acid, and 1,2,3 propane tricarboxylic acid.

6. The absorbent structure of claim 5 wherein said crosslinking agent is citric acid.

7. The absorbent structure of claim 6 wherein said water retention value is between about 28 and about 50.

8. The absorbent structure of claim 1 wherein said crosslinking agent is selected from the group consisting of oxydisuccinic acid, tartrate monosuccinic acid having the formula ##STR3## and tartrate disuccinic acid having the formula ##STR4## .

9. The absorbent structure of claim 8 wherein said crosslinking agent is oxydisuccinic acid.

10. The absorbent structure of claim 8 wherein said fibers have between about 1.5 mole % and about 6.0 mole % crosslinking agent, calculated on a cellulose anhydroglucose molar basis, reacted therewith in the form of intrafiber crosslink bonds.

11. The absorbent structure of claim 10 wherein said water retention value is between about 28 and about 50.

12. The absorbent structure of claim 1, 4, 7, or 8, having a dry density and an equilibrium wet density calculated on a dry fiber weight basis, said dry density being greater than said equilibrium wet density.

13. The absorbent structure of claim 1, 4 or 8 wherein said absorbent structure has a dry density of less than about 0.60 g/cc.

14. The absorbent structure of claim 1, 4 or 8 wherein said absorbent structure has a dry density of between about 0.05 g/cc and about 0.15 g/cc.

15. The absorbent structure of claim 7 wherein said absorbent structure has a dry fiber density of between about 0.12 g/cc and about 0.60 g/cc and an equilibrium wet density, calculated on a dry fiber basis, which is less than said actual dry fiber density.

16. The absorbent structure of claim 11 wherein said absorbent structure has a dry fiber density of between about 0.12 g/cc and about 0.60 g/cc and an equilibrium wet density, calculated on a dry fiber basis, which is less than said actual dry fiber density.

17. The absorbent structure of claim 1 wherein said structure comprises between about 70% and about 95% individualized crosslinked fibers, and between about 30% and about 5% uncrosslinked cellulosic fibers.

18. The absorbent structure of claim 1 further comprising a hydrogel-forming material disposed upon said fibers.

19. The absorbent structure of claim 1 further comprising a hydrogel-forming material disposed within said absorbent structure.

20. The absorbent structure of claim 19 wherein said hydrogel-forming material is substantially homogeneously blended throughout at least part of said absorbent structure.

21. The absorbent structure of claim 19 wherein said hydrogel-form material is disposed upon a sheet, said sheet being placed against said fibers.

22. The absorbent structure of claim 17 further comprising a hydrogen-forming material disposed within said absorbent structure.

23. A disposable absorbent article comprising a topsheet, a backsheet connected to said topsheet, and an absorbent structure as recited in claim 1, 15, 16, 18, 19, or 22, disposed between said topsheet and said backsheet.

24. The absorbent structure of claim 1 wherein said absorbent structure has a basis weight of less than about 800 g/m², and a dry density of less than about 0.60 g/cc.

25. The absorbent structure of claim 19 having a dry density and an equilibrium wet density, calculated on a dry fiber weight basis, said dry density being greater than said equilibrium wet density.

26. The absorbent structure of claim 25 wherein said absorbent structure has a dry density of between about 0.12 g/cc and about 0.60 g/cc.

27. The absorbent structure of claim 26 wherein said fibers have between about 1.5 mole % and about 6.0 mole % crosslinking agent, calculated on a cellulose anhydroglucose molar basis, the water retention value of said fibers is from about 28 to about 50, and wherein said crosslinking agent is citric acid.