Porous PTFE materials and articles produced therefrom

• US 8,757,395 B2
• Filed: 09/16/2008
• Issued: 06/24/2014
• Est. Priority Date: 07/18/2005
• Status: Active Grant

• Current Assignee: W. L. Gore & Associates (W.L. Gore & Associates)
• Original Assignee: W. L. Gore & Associates (W.L. Gore & Associates)
• Inventors: Bacino, John E., Hobson, Alex R., Strid, Jason J.
• Primary Examiner(s): Menon, Krishnan S
• Application Number:
  US12/211,311
• Publication Number:
  US 20090032470A1
• Time in Patent Office: 2,107 Days
• Field of Search: 210/650, 210/500.1, 210/321.6, 210/500.36, 210/500.27, 210/489, 428/319.9, 428/318.4, 264/288.8, 264/127, 264/291, 264/294, 96/4, 96/10, 95/45
• US Class Current: 210/500.22
• CPC Class Codes: B01D 2325/00 Details relating to properties of membranes
• CPC Class Codes: B01D 2325/02 Details relating to pores or porosity of the membranes
• CPC Class Codes: B01D 2325/021 Pore shapes
• CPC Class Codes: B01D 2325/0283 Pore size
• CPC Class Codes: B01D 2325/20 Specific permeability or cut-off range
• CPC Class Codes: B01D 2325/24 Mechanical properties, e.g. strength
• CPC Class Codes: B01D 2325/43 Specific optical properties
• CPC Class Codes: B01D 39/1692 Other shaped material, e.g. perforated or porous sheets
• CPC Class Codes: B01D 67/0027 by stretching
• CPC Class Codes: B01D 69/02 characterised by their properties
• CPC Class Codes: B01D 69/12 Composite membranes; Ultra-thin membranes
• CPC Class Codes: B01D 71/36 Polytetrafluoroethene
• CPC Class Codes: B32B 2264/0257 Polyolefin particles, e.g. polyethylene or polypropylene homopolymers or ethylene-propylene copolymers
• CPC Class Codes: B32B 2307/414 Translucent
• CPC Class Codes: B32B 2307/54 Yield strength; Tensile strength
• CPC Class Codes: B32B 2307/72 Density
• CPC Class Codes: B32B 2307/724 Permeability to gases, adsorption
• CPC Class Codes: B32B 2307/726 Permeability to liquids, absorption
• CPC Class Codes: B32B 2307/732 Dimensional properties
• CPC Class Codes: B32B 27/12 next to a fibrous or filamentary layer
• CPC Class Codes: B32B 27/322 : comprising halogenated polyolefins, e.g. PTFE
• CPC Class Codes: B32B 3/02 : characterised by features of form at particular places, e.g. in edge regions non-uniform thickness B32B3/263
• CPC Class Codes: B32B 3/26 : characterised by a particular shape of the outline of the cross-section of a continuous layer; characterised by a layer with cavities or internal voids foam layer B32B5/18; layer of synthetic resin characterised by fillers that create voids or cavities B32B27/205; characterised by an apertured layer
• CPC Class Codes: B32B 5/022 : Non-woven fabric
• CPC Class Codes: B32B 5/024 : Woven fabric
• CPC Class Codes: B32B 5/026 : Knitted fabric
• CPC Class Codes: B32B 5/16 : characterised by features of a layer formed of particles, e.g. chips, powder or granules layer formed of natural mineral particles B32B19/00; layer being formed of wood fibres, chips or particles B32B21/02
• CPC Class Codes: B32B 5/245 : another layer next to it being a foam layer
• CPC Class Codes: B32B 7/05 : the layers not being connected over the whole surface, e.g. discontinuous connection or patterned connection using interposed adhesives or bonding materials applied in spaced arrangements B32B7/14
• CPC Class Codes: B32B 7/12 : using interposed adhesives or interposed materials with bonding properties
• CPC Class Codes: Y10T 428/249954 : With chemically effective material or specified gas other than air, N, or carbon dioxide in void-containing component
• CPC Class Codes: Y10T 428/269 : including synthetic resin or polymer layer or component
• CPC Class Codes: Y10T 442/2139 : Coating or impregnation specified as porous or permeable to a specific substance [e.g., water vapor, air, etc.]

Abstract

Novel porous PTFE membranes are described possessing a unique combination of high strength, low flow resistance, and small pore size. Additionally, unique constructions with superior filtration and venting properties incorporating porous PTFE membranes are described.

Claims

1. An article comprising:

an expanded polytetrafluoroethylene (ePTFE) membrane having a Gurley versus bubble point equal to or below the line defined by the equation log(Gurley)=2.6×

10<sup>−

3</sup>(Bubble Point)−

0.59, said ePTFE membrane having a surface area of at least 20 m²/g,

wherein the bubble point of said ePTFE membrane is greater than or equal to the intersection of the line defined by the equation log(Gurley)=2.6×

10<sup>−

3</sup>(Bubble Point)−

0.59 and the line defined by the equation log(Gurley) 5.13×

10<sup>−

3</sup>(Bubble Point))−

1.58, and

wherein the bubble point of said ePTFE membrane is less than or equal to about 877 kPa.

2. The article of claim 1, wherein the ePTFE membrane has a ratio of matrix tensile strength in two orthogonal directions of 2:

1 or less.

3. The article of claim 1, wherein said ePTFE membrane has a light transmission through the ePTFE membrane of greater than 50%.

4. The article of claim 1, wherein said ePTFE membrane has a product of matrix tensile strengths in two orthogonal directions of at least 1.3×

10⁵ MPa².

5. An article comprising:

an expanded polytetrafluoroethylene (ePTFE) membrane having a Gurley versus bubble point equal to or below the line defined by the equation log(Gurley)=2.6×

10<sup>−

3</sup>(Bubble Point)−

0.59 and a product of matrix tensile strengths in two orthogonal directions of at least 1.3×

10⁵ MPa², said ePTFE membrane having a first side and a second side,

wherein the bubble point of said ePTFE membrane is greater than or equal to the intersection of the line defined by the equation log(Gurley)=2.6×

10<sup>−

3</sup>(Bubble Point)−

0.59 and the line defined by the equation log(Gurley) 5.13×

10<sup>−

3</sup>(Bubble Point))−

1.58, and

wherein the bubble point of said ePTFE membrane is less than or equal to about 877 kPa.

6. The article of claim 5, further comprising at least one layer on at least one of said first side and said second side of said ePTFE membrane, said at least one layer being selected from the group consisting of non-wovens, scrims and fabrics.

7. The article of claim 6, wherein said at least one layer comprises at least one layer on said first side and said second side of said ePTFE membrane.

8. The article of claim 6, wherein said at least one layer comprises at least one porous membrane.

9. The article of claim 8, wherein said at least one layer comprises an ePTFE membrane.

10. The article of claim 5 in the form of a filter.

11. The article of claim 5 in the form of a vent.

12. The article of claim 5 in the form of a filter cartridge.

13. An article comprising:

an expanded polytetrafluoroethylene (ePTFE) membrane having a Gurley versus bubble point equal to or below the line defined by the equation log(Gurley)=2.6×

10<sup>−

3</sup>(Bubble Point)−

0.59 and a light transmission of at least 50%,

wherein the bubble point of said ePTFE membrane is greater than or equal to the intersection of the line defined by the equation log(Gurley)=2.6×

10<sup>−

3</sup>(Bubble Point)−

0.59 and the line defined by the equation log(Gurley) 5.13×

10<sup>−

3</sup>(Bubble Point))−

1.58, and

wherein the bubble point of said ePTFE membrane is less than or equal to about 877 kPa.

14. The article of claim 13, wherein said ePTFE membrane has a surface area of at least 27 m²/g.

15. The article of claim 13, wherein said ePTFE membrane has a product of matrix tensile strengths in two orthogonal directions of at least 1.3×

105 MPa².

16. The article of claim 13, wherein the product of matrix tensile strength in two orthogonal directions is greater than 1.9×

10⁵ MPa².

17. An article comprising:

an expanded polytetrafluoroethylene (ePTFE) membrane having a Gurley versus bubble point equal to or below the line defined by the equation log(Gurley)=2.6×

10<sup>−

3</sup>(Bubble Point)−

0.59, said ePTFE membrane having a first side and a second side,

wherein the bubble point of said ePTFE membrane is greater than or equal to the intersection of the line defined by the equation log(Gurley)=2.6×

10<sup>−

3</sup>(Bubble Point)−

0.59 and the line defined by the equation log(Gurley) 5.13×

10<sup>−

3</sup>(Bubble Point))−

1.58,

wherein the bubble point of said ePTFE membrane is less than or equal to about 877 kPa,

wherein said ePTFE membrane has a surface area of at least 20 m²/g,

wherein said ePTFE membrane a light transmission of at least 50%, and

wherein a product of matrix tensile strengths in two orthogonal directions of at least 1.3×

10⁵ MPa².

18. The article of claim 17, wherein the product of matrix tensile strength in two orthogonal directions is greater than 1.9×

10⁵ MPa².

19. The article of claim 17, wherein said ePTFE membrane has a surface area of at least 27 m²/g.

20. The article of claim 17, wherein said ePTFE membrane has a ratio of matrix tensile strength in two orthogonal directions of 2:

1 or less.

21. The article of claim 17, further comprising at least one layer on at least one of said first side and said second side of said ePTFE membrane.

22. The article of claim 21, wherein said at least one layer comprises at least one member selected from the group consisting of non-waving scrims and fabrics.

23. The article of claim 21, wherein said at least one layer comprises at least one porous membrane.

24. The article of claim 23, wherein said at least one layer comprises ePTFE.

25. The article of claim 17 in the form of a filter.

26. The article of claim 17 in the form of a vent.

27. The article of claim 17 in the form of a filter cartridge.