Very highly stretched polytetrafluoroethylene and process therefor

• US 3,962,153 A
• Filed: 06/14/1973
• Issued: 06/08/1976
• Est. Priority Date: 05/21/1970
• 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: Gore, Robert Walton
• Primary Examiner(s): Turer, Richard B.
• Application Number:
  US05/369,814
• Time in Patent Office: 1,090 Days
• Field of Search: 260/2.5 R, 260/2.5 M, 260/2.5 E, 260/92.1 S, 264/210 F, 264/41
• US Class Current: 521/79
• CPC Class Codes: B01D 67/0027 by stretching
• CPC Class Codes: B01D 71/36 Polytetrafluoroethene
• CPC Class Codes: B29C 55/005 characterised by the choice of materials
• CPC Class Codes: B29C 55/12 biaxial
• CPC Class Codes: B29C 55/18 by squeezing between surfaces, e.g. rollers
• CPC Class Codes: B29K 2027/18 PTFE, i.e. polytetrafluorethene , e.g. ePTFE, i.e. expanded polytetrafluorethene
• CPC Class Codes: B29K 2105/04 cellular or porous
• CPC Class Codes: C08J 2327/18 Homopolymers or copolymers of tetrafluoroethylene
• CPC Class Codes: C08J 5/124 using adhesives based on a macromolecular component
• CPC Class Codes: C08J 5/18 Manufacture of films or sheets
• CPC Class Codes: H01B 3/445 from vinylfluorides or other fluoroethylenic compounds
• CPC Class Codes: Y10T 428/2975 Tubular or cellular
• CPC Class Codes: Y10T 428/31544 Addition polymer is perhalogenated

Abstract

This invention provides a tetrafluoroethylene polymer in a porous form which has an amorphous content exceeding about 5% and which has a micro-structure characterized by nodes interconnected by fibrils. The material has high porosity and high strength. It can be used to produce all kinds of shaped articles such as films, tubes, rods, and continuous filaments. Laminations can be employed and impregnation and bonding can readily be used to produce a large variety of articles. Compressed articles of very high strength can also be produced from these porous forms.

Claims

1. A porous product consisting essentially of polytetrafluoroethylene produced by a process comprising:

a. stretching an unsintered extrudate of said polymer made by a paste-forming extrusion technique, said stretching being performed after removal of lubricant extrusion aid from said extrudate;

b. said stretching being performed at a rate exceeding about 2000% per second;

c. said stretching being performed at an elevated temperature but below the melt point of said polymer; and

,

d. said extrudate being stretched to such an extent that the final length of the stretched product after stretching exceeds 50 times the original length of said extrudate prior to stretching.

2. The product produced according to claim 1 in which said final length is about 56.5 times said original length.

3. The product produced according to claim 1 in which said final length exceeds 100 times said original length.

4. The product produced according to claim 1 in which said final length is about 120 times said original length.

5. The product produced according to claim 1 in which said final length exceeds 200 times said original length.

6. The product produced according to claim 1 in which said final length is about 240 times said original length.

7. The product produced according to claim 1 in which said final length exceeds 1500 times said original length.

8. The product produced according to claim 1 in which said final length is about 1760 times said original length.

9. The product of claim 1 which has never been heated to a temperature above 327°

C and has a crystallinity greater than about 98%.

10. The product of claim 1 which has been heated following stretching to a temperature above 327°

C and has a crystallinity below about 98%.