Wrapped composite gasket material

• US 5,494,301 A
• Filed: 04/20/1993
• Issued: 02/27/1996
• Est. Priority Date: 04/20/1993
• Status: Expired due to Term

• Current Assignee: W. L. Gore & Associates (W.L. Gore & Associates)
• Original Assignee: W. L. Gore & Associates (W.L. Gore & Associates)
• Inventors: Lubin, Cindy B., Waterland, Alfred F. III, Lalli, Eric W., Sparks, Wanda F., Hamilton, Elizabeth M.
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): Beres, John L.
• Application Number:
  US08/050,903
• Time in Patent Office: 1,043 Days
• Field of Search: 277/227, 277/229, 277/230, 277/DIG. 6
• US Class Current: 277/652
• CPC Class Codes: B29C 53/58 helically
• CPC Class Codes: B29C 55/005 characterised by the choice of materials
• CPC Class Codes: B29C 55/023 using multilayered plates or sheets
• CPC Class Codes: B29C 63/00 Lining or sheathing, i.e. applying preformed layers or sheathings of plastics; Apparatus therefor B29C73/00 takes precedence; by blowing B29C49/00; by thermoforming B29C51/00
• CPC Class Codes: B29K 2027/18 PTFE, i.e. polytetrafluorethene , e.g. ePTFE, i.e. expanded polytetrafluorethene
• CPC Class Codes: F16J 15/022 characterised by structure or material
• CPC Class Codes: F16J 15/104 characterised by structure
• CPC Class Codes: F28F 3/10 Arrangements for sealing the margins
• CPC Class Codes: Y10S 277/944 Elastomer or plastic
• CPC Class Codes: Y10S 277/946 PTFE

Abstract

A composite gasket material composed of a core of elongated polytetrafluoroethylene wrapped with a high strength porous expanded polytetrafluoroethylene film is provided. The composite gasket material exhibits increased resistance to creep while in use so that thickness of the composite gasket material and thus gasket stress is maintained.

Claims

1. A composite gasket material comprising:

(a) a core of elongated non-felted polytetrafluoroethylene, and

(b) means to prevent substantial lateral flow and creep of the core under load, said means comprising a first porous expanded polytetrafluoroethylene film wrapped upon said core of polytetrafluoroethylene so as to restrain said core;

said first porous expanded polytetrafluoroethylene film having in at least one direction a tensile strength of at least 13.8 MPa.

2. The composite gasket material as described in claim 1, wherein said core of elongated polytetrafluoroethylene is expanded polytetrafluoroethylene .

3. The composite gasket material as described in claim 1, wherein said core of elongated polytetrafluoroethylene has been compressed and restrained so that it has a cross-sectional surface area that is 90 percent or less of an initial cross-sectional area.

4. The composite gasket material as described in claim 3, wherein said core of elongated polytetrafluoroethylene has been compressed and restrained so that it has a cross-sectional surface area that is 80 percent or less of an initial cross-sectional area.

5. The composite gasket material as described in claim 4, wherein said core of elongated polytetrafluoroethylene has been compressed and restrained so that it has a cross-sectional surface area that is 60 percent or less of an initial cross-sectional area.

6. The composite gasket material as described in claim 1, wherein the first porous expanded polytetrafluoroethylene film is coated with a layer of melt-processible thermoplastic fluoropolymer;

said layer of melt-processible thermoplastic fluoropolymer adhering said first porous expanded polytetrafluoroethylene film to the core of elongated polytetrafluoroethylene.

7. The composite gasket material as described in claim 6, wherein the layer of melt-processible thermoplastic fluoropolymer is selected from the group consisting of copolymer of tetrafluoroethylene and hexafluoropropylene, copolymer of tetrafluoroethylene and perfluoro(propyl vinyl ether), homopolymers of polychlorotrifluoroethylene and its copolymers with TFE or VF2, ethylene-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, and polyvinylfluoride.

8. The composite gasket material as described in claim 1, wherein the core of elongated polytetrafluoroethylene contains a particulate filler.

9. The composite gasket material as described in claim 1, wherein the first porous expanded polytetrafluoroethylene film contains a particulate filler.

10. The composite gasket material as described in claim 1, further comprising a second porous expanded polytetrafluoroethylene film wrapped upon said first porous expanded polytetrafluoroethylene film.

11. The composite gasket material as described in claim 10, wherein the second porous expanded polytetrafluoroethylene film is coated with a layer of melt-processible thermoplastic fluoropolymer;

said layer of melt-processible thermoplastic fluoropolymer adhering said second porous expanded polytetrafluoroethylene film to said first porous expanded polytetrafluoroethylene film.

12. A composite gasket material comprising:

(a) a core of elongated non-felted polytetrafluoroethylene, and

(b) means to prevent substantial lateral flow and creep of the core under load, said means comprising a first porous expanded polytetrafluoroethylene film wrapped upon said core of polytetrafluoroethylene so as to restrain said core;

said first porous expanded polytetrafluoroethylene film having in at least one direction a 2% secant tensile modulus of 172 MPa or greater.

13. The composite gasket material as described in claim 12, wherein said core of elongated polytetrafluoroethylene is expanded polytetrafluoroethylene.

14. The composite gasket material as described in claim 12, wherein said core of elongated polytetrafluoroethylene has been compressed and restrained so that it has a cross-sectional surface area that is 90 percent or less of an initial cross-sectional area.

15. The composite gasket material as described in claim 14, wherein said core of elongated polytetrafluoroethylene has been compressed and restrained so that it has a cross-sectional surface area that is 80 percent or less of an initial cross-sectional area.

16. The composite gasket material as described in claim 15, wherein said core of elongated polytetrafluoroethylene has been compressed and restrained so that it has a cross-sectional surface area that is 60 percent or less of an initial cross-sectional area.

17. The composite gasket material as described in claim 12, wherein the first porous expanded polytetrafluoroethylene film is coated with a layer of melt-processible thermoplastic fluoropolymer;

said layer of melt-processible thermoplastic fluoropolymer adhering said first porous expanded polytetrafluoroethylene film to the core of elongated polytetrafluoroethylene.

18. The composite gasket material as described in claim 17, wherein the layer of melt-processible thermoplastic fluoropolymer is selected from the group consisting of copolymer of tetrafluoroethylene and hexafluoropropylene, copolymer of tetrafluoroethylene and perfluoro(propyl vinyl ether), homopolymers of polychlorotrifluoroethylene and its copolymers with TFE or VF2, ethylene-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, and polyvinylfluoride.

19. The composite gasket material as described in claim 12, wherein the core of elongated polytetrafluoroethylene contains a particulate filler.

20. The composite gasket material as described in claim 12, wherein the first porous expanded polytetrafluoroethylene film contains a particulate filler.

21. The composite gasket material as described in claim 12, further comprising a second porous expanded polytetrafluoroethylene film wrapped upon said first porous expanded polytetrafluoroethylene film.

22. The composite gasket material as described in claim 21, wherein the second porous expanded polytetrafluoroethylene film is coated with a layer of melt-processible thermoplastic fluoropolymer;

said layer of melt-processible thermoplastic fluoropolymer adhering said second porous expanded polytetrafluoroethylene film to said first porous expanded polytetrafluoroethylene film.

23. A composite gasket material comprising:

(a) a core of elongated non-felted polytetrafluoroethylene, and

(b) means to prevent substantial lateral flow and creep of the core under load, said means comprising a first porous expanded polytetrafluoroethylene film wrapped upon said core of polytetrafluoroethylene so as to restrain said core;

said first porous expanded polytetrafluoroethylene film having in at least one direction a tensile strength of at least 13.8 MPa and a 2% secant tensile modulus of 172 MPa or greater.

24. The composite gasket material as described in claim 23, wherein said core of elongated polytetrafluoroethylene is expanded polytetrafluoroethylene.

25. The composite gasket material as described in claim 23, wherein said core of elongated polytetrafluoroethylene has been compressed and restrained so that it has a cross-sectional surface area that is 90 percent or less of an initial cross-sectional area.

26. The composite gasket material as described in claim 25, wherein said core of elongated polytetrafluoroethylene has been compressed and restrained so that it has a cross-sectional surface area that is 80 percent or less of an initial cross-sectional area.

27. The composite gasket material as described in claim 26, wherein said core of elongated polytetrafluoroethylene has been compressed and restrained so that it has a cross-sectional surface area that is 60 percent or less of an initial cross-sectional area.

28. The composite gasket material as described in claim 23, wherein the first porous expanded polytetrafluoroethylene film is coated with a layer of melt-processible thermoplastic fluoropolymer;

said layer of melt-processible thermoplastic fluoropolymer adhering said first porous expanded polytetrafluoroethylene film to the core of elongated polytetrafluoroethylene.

29. The composite gasket material as described in claim 28, wherein the layer of melt-processible thermoplastic fluoropolymer is selected from the group consisting of copolymer of tetrafluoroethylene and hexafluoropropylene, copolymer of tetrafluoroethylene and perfluoro(propyl vinyl ether), homopolymers of polychlorotrifluoroethylene and its copolymers with TFE or VF2, ethylene-chlorotrifluoroethylene copolymer, ethylene-tetrafluoroethylene copolymer, polyvinylidene fluoride, and polyvinylfluoride.

30. The composite gasket material as described in claim 23, wherein the core of elongated polytetrafluoroethylene contains a particulate filler.

31. The composite gasket material as described in claim 23, wherein the first porous expanded polytetrafluoroethylene film contains a particulate filler.

32. The composite gasket material as described in claim 23, further comprising a second porous expanded polytetrafluoroethylene film wrapped upon said first porous expanded polytetrafluoroethylene film.

33. The composite gasket material as described in claim 32, wherein the second porous expanded polytetrafluoroethylene film is coated with a layer of melt-processible thermoplastic fluoropolymer;

said layer of melt-processible thermoplastic fluoropolymer adhering said second porous expanded polytetrafluoroethylene film to said first porous expanded polytetrafluoroethylene film.