Irradiated expanded polytetrafluoroethylene composites, and devices using them, and processes for making them

• US 5,019,140 A
• Filed: 12/21/1988
• Issued: 05/28/1991
• Est. Priority Date: 12/21/1988
• Status: Expired due to Fees

• Current Assignee: W. L. Gore & Associates (W.L. Gore & Associates)
• Original Assignee: W. L. Gore & Associates (W.L. Gore & Associates)
• Inventors: Hyde, Christopher T., Bowser, John J.
• Primary Examiner(s): Spitzer, Robert
• Application Number:
  US07/287,811
• Time in Patent Office: 888 Days
• Field of Search: 55/159, 55/485-488, 55/524, 55/528, 428/286, 428/287, 428/480
• US Class Current: 96/6
• CPC Class Codes: A61F 5/441 having venting or deodorant means, e.g. filters ; having antiseptic means, e.g. bacterial barriers
• CPC Class Codes: B01D 19/0031 by filtration
• CPC Class Codes: B01D 63/087 Single membrane modules
• CPC Class Codes: B01D 69/1071 Woven, non-woven or net mesh
• CPC Class Codes: B01D 69/108 Inorganic support material
• CPC Class Codes: B01D 71/36 Polytetrafluoroethene
• CPC Class Codes: B32B 2262/0276 Polyester fibres
• CPC Class Codes: B32B 2262/103 Metal fibres
• CPC Class Codes: B32B 2305/026 Porous
• CPC Class Codes: B32B 2307/73 Hydrophobic
• CPC Class Codes: B32B 2310/0881 using ion-radiation, e.g. alpha-rays
• CPC Class Codes: B32B 27/12 next to a fibrous or filamentary layer
• CPC Class Codes: B32B 38/0008 Electrical discharge treatment, e.g. corona, plasma treatment; wave energy or particle radiation heat treatment B32B38/0036
• CPC Class Codes: B32B 5/26 another layer next to it also being fibrous or filamentary relative arrangement of fibres or filaments of different layers B32B5/12
• CPC Class Codes: B32B 7/12 using interposed adhesives or interposed materials with bonding properties
• CPC Class Codes: Y10T 428/31544 Addition polymer is perhalogenated
• CPC Class Codes: Y10T 428/31786 Of polyester [e.g., alkyd, etc.]
• CPC Class Codes: Y10T 442/339 Metal or metal-coated strand

Abstract

Radiation resistant composites made of adjacent layers of a microporous hydrophobic polytetrafluoroethylene layer and one or more supporting layers made of woven metal material or woven synthetic organic polymeric material and a microporous hydrophobic polytetrafluoroethylene membrane are described. Filtration devices containing the composite are described.

Claims

1. A radiation-resistant polytetrafluoroethylene composite comprising:

(a) a layer of woven metal material which has an elongation of less than 25% after 100 hours under a load of 2.0 pounds per inch, and

(b) a layer of microporous hydrophobic polytetrafluoroethylene membrane,

wherein the properties of the layers are such that the composite is capable of withstanding either (i) at least 20 pounds per square inch of pressure, or (ii) the water entry pressure of the membrane, whichever is less, for 100 hours in the Pressurization Test without rupturing.

2. A composite of claim 1 in the form of a laminate.

3. A composite of claim 1 wherein the material of the layer (a) is a woven metal screen.

4. A filtration device containing the composite of claim 1.

5. Process for preparing a laminated composite of claim 1 which comprises bonding layers (a) and (b) together with a hot melt bonding adhesive.

6. Process for irradiating an unirradiated composite of claim 1 which comprises subjecting the composite to ionizing radiation of between 0.5 to 10 Megarad.

7. A radiation resistant polytetrafluoroethylene composite comprising:

(a) a layer of an synthetic organic polymeric material having an elongation of less than 25% elongation after 100 hours under a load of 2.0 pounds per inch, and

(b) a middle layer of a compliant synthetic organic polymeric material that is porous and substantially smooth, and has a basis weight of between 1 and 6 ounces per square yard, and

(c) a layer of microporous hydrophobic polytetrafluoroethylene membrane,

wherein the properties of the layers are such that the composite is capable of withstanding either (i) at least 20 pounds per square inch of pressure, or (ii) the water entry pressure of the membrane, whichever is less, for 100 hours in the Pressurization Test without rupturing.

8. A composite of claim 7 in the form of a laminate.

9. A composite of claim 7 wherein layer (a) is a woven polyester screen, layer (b) is a nonwoven of fine polyester filaments which has a basis weight of 1 to 6 ounces per square yard, and layer (c) is a microporous polytetrafluoroethylene membrane which has a pore size of between about 0.01 to 100 micrometers and a thickness of between 2 to 250 micrometers.

10. A filtration device containing the composite of claim 7.

11. The filtration device of claim 10 wherein the device contains rounded edges so as to provide strain relief to the filtration medium.

12. The filtration device of claim 10 wherein the device contains one or more additional cross members which have rounded supporting edges so as to provide strain relief to the filtration medium.

13. Process for preparing a laminated composite of claim 7 which comprises bonding the layers together with a hot melt bonding adhesive.

14. Process for irradiating an unirradiated composite of claim 7 which comprises subjecting the laminate to ionizing radiation of between 0.5 to 10 Megarad.