Patent US4902423A successfully refreshed from Google Patents.
US4902423A
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Highly air permeable expanded polytetrafluoroethylene membranes and process for making them
Assignee: W.L. Gore and Associates Inc
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Filing: 1989-02-02
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Granted: 1990-02-20
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Expires: 2009-02-02
Abstract
Abstract A thin, low density porous polytetrafluoroethylene membrane having very large pores and heretofore unknown high air permeabilities is described. The membrane is produced by a particular series of longitudinal and transverse stretching steps carried out under particular conditions.
Inventors
- 👤 John E. Bacino
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 19:32
CPC Classifications
C; C08; C08J; C08J5/00; C08J5/18; B; B01; B01D; B01D39/00; B01D39/14; B01D39/16; B01D39/1692; B01D67/00; B01D67/0002; B01D67/0023; B01D67/0025; B01D67/0027; B01D71/00; B01D71/06; B01D71/30; B01D71/32; B01D71/36; B29; B29C; B29C55/00; B29C55/005; B01D2239/00; B01D2239/10; B01D2325/00; B01D2325/04; B01D2325/20; B29K; B29K2027/00; B29K2027/12; B29K2027/18; B29K2105/00; B29K2105/04; B29K2995/00; B29K2995/0037; B29K2995/0065; C08J2327/00; C08J2327/02; C08J2327/12; C08J2327/18
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
49 words
A thin, low density, porous polytetrafluoroethylene membrane having an open structure defined by small nodes interconnected with fibrils, said membrane characterized by having a porosity equal to or greater than 90%, a density of 0.2 g/cc or less, and permeabilities to air between Frazier numbers of 100 and 350.
Claim 2
Dependent Claim
49 words
A thin, low density, porous polytetrafluoroethylene membrane having an open structure defined by small nodes interconnected with fibrils, said membrane characterized by having a porosity equal to or greater than 90%, a density of 0.2 g/cc or less, and permeabilities to air between Frazier numbers of 100 and 350.
Claim 3
Dependent Claim
46 words
The membrane of claim 1 wherein the majority of the nodes are arranged in series of generally aligned parallel rows across the membrane, and are connected node to node by fibrils and bundles of fibrils and the rows are connected to each other by long fibrils.
Claim 4
Dependent Claim
19 words
The membrane of claim 2 wherein the membrane is a film of a thickness of less than 1 mil.
Claim 5
Dependent Claim
18 words
The membrane of claim 3 wherein the permeability to air is between Frazier numbers of 150 to 300.
Claim 6
Dependent Claim
19 words
An air filtration device comprising a frame and a membrane defined as in claim 1 held in said frame.
Claim 7
Dependent Claim
19 words
The membrane of claim 1 wherein the membrane is a film of a thickness of less than 1 mil.
Claim 8
Dependent Claim
19 words
An air filtration device comprising a frame and a membrane defined as in claim 1 held in said frame.
References Cited (Backward Citations)
US3953566A
Cited
US3962153A
Cited
US4187390A
Cited
US4096227A
Cited
US4025679A
Cited
US4248924A
Cited
US4482516A
Cited
US4598011A
Cited
US4814412A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-02-19 | 1993-08-21 | 1994-02-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-02-19 | 1997-08-21 | 1998-02-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-02-19 | 2001-08-21 | 2002-02-20 | $7700.00 | Window Closed / Lapsed |