Mechanically stable hydrogel-forming polymers

• US 6,414,214 B1
• Filed: 10/04/1999
• Issued: 07/02/2002
• Est. Priority Date: 10/04/1999
• Status: Expired due to Term

• Current Assignee: BASF AG (BASF SE)
• Original Assignee: BASF AG (BASF SE)
• Inventors: Riegel, Ulrich, Herfert, Norbert, Weismantel, Matthias, Heide, Wilfried, Frenz, Volker, Engelhardt, Friedrich
• Primary Examiner(s): Weiss, John G.
• Assistant Examiner(s): Stephens, Jacqueline F.
• Application Number:
  US09/411,644
• Time in Patent Office: 1,002 Days
• Field of Search: 523/206, 523/201, 523/105, 524/916, 526/930, 424/402, 424/484, 424/486, 424/487, 604/365, 604/368, 604/374, 604/375, 604/372, 604/367, 428/327, 428/290, 428/339
• US Class Current: 604/368
• CPC Class Codes: C08F 20/10 Esters
• CPC Class Codes: C08F 8/00 Chemical modification by after-treatment graft polymers, block polymers, crosslinking with unsaturated monomers or with polymers C08F251/00 - C08F299/00; of conjugated diene rubbers C08C
• CPC Class Codes: C08J 3/126 Polymer particles coated by polymer, e.g. core shell structures
• CPC Class Codes: C08J 3/245 Differential crosslinking of one polymer with one crosslinking type, e.g. surface crosslinking

Abstract

Hydrogel-forming polymers which have:

(i) a Saline Flow Conductivity of at least 40×10⁻⁷ cm³s/g;

(ii) an AUL 0.7 psi (4826.5 Pa) of at least 20 g/g; and

(iii) a Frangibility Index of at least 60%,

are useful in hygienic articles such as incontinence briefs for adults and diapers for infants.

Claims

1. Hydrogel-forming polymer having

(i) a Saline Flow Conductivity (SFC) of at least 40×

10<sup>−

7</sup> cm³s/g

(ii) an AUL 0.7 psi (4826.5 Pa) of at least 20 g/g

(iii) a Frangibility Index of at least 60%.

2. Hydrogel-forming polymer as claimed in claim 1, possessing a Saline Flow Conductivity (SFC) of at least 50×

10<sup>−

7</sup> cm³s/g.

3. Hydrogel-forming polymer as claimed in claim 1 or 2, possessing an AUL 0.7 psi (4826.5 Pa) of at least 22 g/g.

4. The hydrogel-forming polymer of claim 1, which has a Frangibility Index of at least 70%.

5. The hydrogel-forming polymer of claim 2, which has a Frangibility Index of at least 70%.

6. The hydrogel-forming polymer of claim 3, which has a Frangibility Index of at least 70%.

7. A process for producing a hydrogel-forming polymer having:

(i) a Saline Flow Conductivity of at least 40×

10<sup>−

7</sup> cm³s/g;

(ii) an AUL 0.7 psi (4826.5 Pa) of at least 20 g/g; and

(iii) a Frangibility Index of at least 60%;

wherein said process comprises;

(a) subjecting a polymer to a surface postcrosslinking step, to obtain a surface-postcrosslinked polymer; and

(b) treating said surface-postcrosslinked polymer, to obtain a residual moisture content of at least 3% by weight.

8. The process of claim 7, wherein said hydrogel-forming polymer has a Saline Flow Conductivity of at least 50×

10<sup>−

7</sup> cm³s/g.

9. The process of claim 7, wherein said hydrogel-forming polymer has an AUL 0.7 psi (4826.5 Pa) of at least 22 g/g.

10. The process of claim 7, wherein said hydrogel-forming polymer has a Frangibility Index of at least 70%.

11. The process of claim 7, wherein said treating said surface-postcrosslinked polymer, to obtain a residual moisture content of at least 3% by weight, comprises adding water to said surface-postcrosslinked polymer.

12. The process of claim 11, wherein water is added to said surface-postcrosslinked polymer in a cooler downstream of a surface postcrosslinking dryer.

13. The process of claim 11, wherein said hydrogel-forming polymer has a Saline Flow Conductivity of at least 50×

10<sup>−

7</sup> cm³s/g.

14. The process of claim 11, wherein said hydrogel-forming polymer has an AUL 0.7 psi (4826.5 Pa) of at least 22 g/g.

15. The process of claim 11, wherein said hydrogel-forming polymer has a Frangibility Index of at least 70%.

16. The process of claim 11, wherein said water comprises a surfactant having an HLB value ≧

3.

17. The process of claim 11, wherein said water comprises an ethanolamine of the general formula (I)

18. A hygiene article comprising

(A) a fluid-pervious topsheet

(B) a fluid-impervious backsheet

(C) a core positioned between (A) and (B) and comprising

(C1) 10-100% by weight of a hydrogel-forming polymer;

and

(C2) 0-90% by weight of hydrophilic fiber material;

wherein said hydrogel-forming polymer has;

(i) a Saline Flow Conductivity (SFC) of at least 40×

10<sup>−

7</sup> cm³s/g;

(ii) an AUL 0.7 psi (4826.5 Pa) of at least 20 g/g; and

(iii) a Frangibility Index of at least 60%.

19. The hygiene article of claim 18, wherein said hydrogel-forming polymer has a Saline Flow Conductivity of at least 50×

10<sup>−

7</sup> cm³s/g.

20. The hygiene article of claim 18, wherein said hydrogel-forming polymer has an AUL 0.7 psi (4826.5 Pa) of at least 22 g/g.

21. The hygiene article of claim 18, wherein said hydrogel-forming polymer has a Frangibility Index of at least 70%.

22. The hygiene article of claim 18, further comprising:

(D) a tissue layer positioned directly above and below said core (C).

23. The hygiene article of claim 22, wherein said hydrogel-forming polymer has a Saline Flow Conductivity of at least 50×

10<sup>−

7</sup> cm³s/g.

24. The hygiene article of claim 22, wherein said hydrogel-forming polymer has an AUL 0.7 psi (4826.5 Pa) of at least 22 g/g.

25. The hygiene article of claim 22, wherein said hydrogel-forming polymer has a Frangibility Index of at least 70%.

26. The hygiene article of claim 18, further comprising:

(E) optionally an acquisition layer positioned between (A) and (C).

27. The hygiene article of claim 26, wherein said hydrogel-forming polymer has a Saline Flow Conductivity of at least 50×

10<sup>−

7</sup> cm³s/g.

28. The hygiene article of claim 26, wherein said hydrogel-forming polymer has an AUL 0.7 psi (4826.5 Pa) of at least 22 g/g.

29. The hygiene article of claim 26, wherein said hydrogel-forming polymer has a Frangibility Index of at least 70%.