US3558764A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for preparing microporous film
Assignee: Celanese Corp
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Filing: 1969-06-23
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Granted: 1971-01-26
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Expires: 1989-06-23
Abstract
Abstract A METHOD IS DISCLOSED AND CLAIMED FOR THE PRODUCTION OF POLYMERIC FILMS (E.G. POLYETHYLENE, POLYPROPYLENE OR POLYACETAL FILMS) CHARACTERIZED BY AN OPEN-CELL STRUCTURE AND AN APPARENT DENSITY LOWER THAN THE ACTUAL DENSITY OF THE ORIGINAL POLYMERS. SUCH PRODUCTS ARE PREPARED BY FIRST EXTRUDING A FILM, NEXT DRAWING DOWN THIS FILM AT A HIGH RATE, THEN ANNEALING IT AND COLD DRAWING IT AND FINALLY HEAT-SETTING THE COLD DRAWN FILM. THE THUS-PRODUCED POLYMERIC FILMS ARE PARTICULARLY USEFUL FOR SUCH APPLICATIONS AS MICROPOROUS MEMBRANES.
Inventors
- 👤 Robert B Isaacson
- 👤 Harvey S Bierenbaum
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-22 22:21
CPC Classifications
B; B29; B29C; B29C67/00; B29C67/20; Y; Y10; Y10S; Y10S264/00; Y10S264/13; Y10S264/62
Claims Analysis
Total Claims: 0
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References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-01-25 | 1974-07-27 | 1975-01-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-01-25 | 1978-07-27 | 1979-01-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-01-25 | 1982-07-27 | 1983-01-26 | $7700.00 | Window Closed / Lapsed |