US3679614A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for making porous fibrous sheets containing polytetrafluoroethylene
Assignee: Wyeth Holdings LLC
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Filing: 1969-11-24
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Granted: 1972-07-25
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Expires: 1989-11-24
Abstract
Abstract IN THE MANUFACTURE OF POLYTETRAFLUOROETHYLENE FIBER SHEETS AN INTERMEDIATE SHEET WAS RIGID UNITIL A CONTINUOUS PHASE OF POLYMETHYLMETHACRYLATE (PMMA) HAS BEEN EXTRACTED WITH SOLVENTS. THE INVENTION EMPLOYS HIGH CONCENTRATION OF PLASTICIZER (E.G. TEREPHTHALATE DIESTERS) IN THE PMMA PHASE TO RENDER THE INTERMEDIATE SHEET NONRIGID HENCE EASIER TO HANDLE. ALSO PLASTICIZER REDUCES WORKING TEMPERATURE FOR MAKING THE INTERMEDIATE SHEET, ENABLING INCORPORATION OF HEAT-SENSITIVE FILLERS E.G. HEAT SENSITIVE CATALYST OR LOW-MELTING POLYPYROPYLENE INCORPORATED FIBERS.
Inventors
- 👤 Girish Chandulal Shah
- 👤 Mahesh Shantilal Shroff
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 07:57
CPC Classifications
D; D04; D04H; D04H13/00; B; B29; B29C; B29C66/00; B29C66/70; B29C66/71; C; C08; C08J; C08J9/00; C08J9/26; B29K; B29K2027/00; B29K2027/12; B29K2027/18; Y; Y10; Y10T; Y10T428/00; Y10T428/31504; Y10T428/3154; Y10T428/31855; Y10T428/31938; Y10T442/00; Y10T442/20; Y10T442/2139
Claims Analysis
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References Cited (Backward Citations)
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-07-25 | 1976-01-24 | 1976-07-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-07-25 | 1980-01-24 | 1980-07-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-07-25 | 1984-01-24 | 1984-07-25 | $7700.00 | Window Closed / Lapsed |