Textured, porous, expanded PTFE

• US 5,466,509 A
• Filed: 01/15/1993
• Issued: 11/14/1995
• Est. Priority Date: 01/15/1993
• Status: Expired due to Term

• Current Assignee: Bard Peripheral Vascular Incorporated (Becton, Dickinson & Co)
• Original Assignee: IMPRA Incorporated (Becton, Dickinson & Co)
• Inventors: Bibeau, John M., Taylor, Howard H., Kowligi, Rajagopal R.
• Primary Examiner(s): Lesmes, George F.
• Assistant Examiner(s): COPENHEAVER, BLAINE R
• Application Number:
  US08/005,482
• Time in Patent Office: 1,033 Days
• Field of Search: 428/304.4, 428/422, 428/315.7, 428/543, 428/141, 428/152, 521/145, 521/919
• US Class Current: 428/141
• CPC Class Codes: B29C 44/5627 by mechanical deformation, e.g. crushing, embossing, stretching
• CPC Class Codes: B29C 48/00 Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor extrusion blow-moulding B29C49/04
• CPC Class Codes: B29C 48/022 characterised by the choice of material
• CPC Class Codes: B29C 48/08 flexible, e.g. films
• CPC Class Codes: B29C 48/10 flexible, e.g. blown foils
• CPC Class Codes: B29C 55/005 characterised by the choice of materials
• CPC Class Codes: B29C 55/22 of tubes B29C61/08 takes precedence
• CPC Class Codes: B29C 59/04 using rollers or endless belts
• 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: B32B 5/18 characterised by features of a layer of foamed material
• CPC Class Codes: Y10T 428/24355 Continuous and nonuniform or irregular surface on layer or component [e.g., roofing, etc.]
• CPC Class Codes: Y10T 428/24446 Wrinkled, creased, crinkled or creped
• CPC Class Codes: Y10T 428/249953 Composite having voids in a component [e.g., porous, cellular, etc.]
• CPC Class Codes: Y10T 428/249979 Specified thickness of void-containing component [absolute or relative] or numerical cell dimension
• CPC Class Codes: Y10T 428/31544 Addition polymer is perhalogenated
• CPC Class Codes: Y10T 428/8305 Miscellaneous [e.g., treated surfaces, etc.]

Abstract

A more porous PTFE is obtained by impressing a pattern into extruded PTFE and then expanding the PTFE. The pattern can be impressed by knurling or, preferably, by rolling the sheet between rollers having a pseudo-random pattern formed on the surface of the roller. The uniformity of the pores is controlled by the pattern; viz. a coarse pattern produces a wider distribution of internodal distances than a finer pattern.

Claims

1. An expanded polytetrafluoroethylene sheet produced by the process of extruding a mixture of polytetrafluoroethylene and a lubricant into a sheet;

forming a pattern of defect sites in said sheet by one of impressing an external pattern into said sheet;

high energy bombardment with solids, etching, laser irradiation and actinic irradiation;

expanding said sheet; and

sintering said sheet, whereby the expanded polytetrafluoroethylene sheet is characterized by having internodal distances non-uniformly distributed across the range of 10-200 microns.

2. The expanded polytetrafluoroethylene sheet produced by the process of claim 1 wherein said expanding step further comprises expanding said sheet sequentially in different directions.

3. A sheet of expanded polytetrafluoroethylene as set forth in claim 1 wherein said internodal distances are distributed in the range of 10-50 microns.

4. A sheet of expanded polytetrafluoroethylene as set forth in claim 3 wherein said internodal distances are distributed in the range of 20-40 microns.

5. The sheet of expanded polytetrafluoroethylene according to claim 1, wherein said pattern of defect sites is formed by imparting a plurality of sacrificial sites in said sheet and removing said sacrificial sites before expanding said sheet.

6. The expanded polytetrafluoroethylene sheet produced according to the process of claim 5, wherein said texturing step further comprises application of a textured surface to at least one surface of said sheet and applying positive pressure to said textured surface thereby imparting the plurality of defect sites in said sheet.

7. The expanded polytetrafluoroethylene sheet produced according to the process of claim 5, wherein said step of applying positive pressure further comprises calendaring.

8. The expanded polytetrafluoroethylene sheet produced according to the process of claim 5, wherein said texturing step further comprises high energy bombardment of external matter directed toward at least one surface of said sheet whereupon impact of said external matter imparts the plurality of defect sites in the sheet.

9. The expanded polytetrafluoroethylene sheet produced according to the process of claim 5, wherein said texturing step further comprises etching said sheet.

10. The expanded polytetrafluoroethylene sheet produced according to the process of claim 9, wherein said etching further comprises one of chemical or plasma etching.

11. The expanded polytetrafluoroethylene sheet produced according to the process of claim 5, wherein said texturing step further comprises exposing at least one surface of said sheet to one of laser or actinic irradiation.

12. An expanded polytetrafluoroethylene material produced by the process of extruding a mixture of polytetrafluoroethylene and a lubricant into a predetermined shape;

forming at least one region of non-uniformly distributed nodes and fibrils in said shape, said nodes and fibrils having internodal distances non-uniformly distributed across the range of 10-50 microns, by one of impressing an external texturing pattern into said sheet, high energy bombardment with solids, etching, laser irradiation and actinic irradiation;

expanding said shape; and

sintering said shape.

13. The expanded polytetrafluoroethylene sheet produced by the process of claim 12 wherein said expanding step further comprises expanding said shape sequentially in different directions.

14. A sheet of expanded polytetrafluoroethylene as set forth in claim 12 wherein said internodal distances are distributed in the range of 20-40 microns.