Dense polytetrafluoroethylene articles

• US 5,374,473 A
• Filed: 08/19/1992
• Issued: 12/20/1994
• Est. Priority Date: 08/19/1992
• 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: Knox, John B., Delaney, William E. III, Connelly, John M. Jr.
• Primary Examiner(s): Ryan, Patrick J.
• Assistant Examiner(s): WEISBERGER, RICHARD C
• Application Number:
  US07/932,441
• Time in Patent Office: 853 Days
• Field of Search: 428/34.5, 428/34.6, 428/35.7, 428/35.9, 428/36.5, 428/71, 428/218, 428/219, 428/220
• US Class Current: 428/218
• CPC Class Codes: B29C 2791/006 Using vacuum
• CPC Class Codes: B29C 43/003 characterised by the choice of material
• CPC Class Codes: B29C 43/006 Pressing and sintering powders, granules or fibres
• CPC Class Codes: B29C 43/18 incorporating preformed parts or layers, e.g. compression moulding around inserts or for coating articles B29C43/206 takes precedence
• CPC Class Codes: B29C 43/20 Making multilayered or multicoloured articles B29C43/14 takes precedence
• CPC Class Codes: B29C 70/04 comprising reinforcements only, e.g. self-reinforcing plastics
• CPC Class Codes: B29C 70/06 Fibrous reinforcements only
• CPC Class Codes: B29C 70/342 using isostatic pressure
• CPC Class Codes: B29D 99/0053 Producing sealings B29D99/0085 takes precedence
• CPC Class Codes: B29K 2027/18 PTFE, i.e. polytetrafluorethene , e.g. ePTFE, i.e. expanded polytetrafluorethene
• CPC Class Codes: B29K 2105/0809 Fabrics
• CPC Class Codes: B29L 2031/26 Sealing devices, e.g. packaging for pistons or pipe joints
• CPC Class Codes: B29L 2031/755 Membranes, diaphragms
• CPC Class Codes: B32B 37/1018 using only vacuum
• CPC Class Codes: F16J 3/02 Diaphragms
• CPC Class Codes: Y10T 428/1314 Contains fabric, fiber particle, or filament made of glass, ceramic, or sintered, fused, fired, or calcined metal oxide, or metal carbide or other inorganic compound [e.g., fiber glass, mineral fiber, sand, etc.]
• CPC Class Codes: Y10T 428/1317 Multilayer [continuous layer]
• CPC Class Codes: Y10T 428/1352 Polymer or resin containing [i.e., natural or synthetic]
• CPC Class Codes: Y10T 428/1359 Three or more layers [continuous layer]
• CPC Class Codes: Y10T 428/1376 Foam or porous material containing
• CPC Class Codes: Y10T 428/233 : Foamed or expanded material encased
• CPC Class Codes: Y10T 428/24992 : Density or compression of components

Abstract

This invention provides a densified previously expanded PTFE article having remnants of a fibril and node structure and a process for producing the article. A PTFE shape is compressed through the application of heat and pressure while the shape itself is under a vacuum, thus forming the densified ePTFE article. The densified PTFE article exhibits increased flexural strength.

A diaphragm containing the densified ePTFE article as one layer is also disclosed.

Claims

1. A material consisting essentially of a sintered, densified expanded polytetrafluoroethylene having remnants of a fibril and node structure as characterized by peaks at about 327°

C. and about 380°

C. in a thermogram of differential scanning calorimetry in the course of temperature rise of 10°

C./min, having a density of 2.10 gm/cc or greater and being substantially free of pores.

2. The material of claim 1 wherein the material has a density of 2.14 cm/cc or greater.

3. The material of claim 1 wherein the material has a density of 2.175 g/cc or greater.

4. The material of claim 1 in which the material is in the form of a plurality of layers of sheets.