US3756990A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Late process for increasing the molecular weight of polyethylene terephtha
Assignee: Glanzstoff AG
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Filing: 1971-08-09
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Granted: 1973-09-04
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Expires: 1991-08-09
Abstract
Abstract PROCESS FOR INCREASING THE MOLECULAR WEIGHT OF POLYETHYLENE TEREPHTHALATE OR SIMILAR LINEAR, FIBER-FORMING POLYESTERS BY THERMAL TREATMENT IN THE SOLID PHASE WHEREIN THE INITIAL LOW MOLECULAR WEIGHT POLYESTER PRECONDENSATE IS SLOWLY DISCHARGED OR WITHDRAWN AS A COHERENT GRANULAR BED OR LAYER DOWNWARDLY THROUGH A VERTICAL HEATING ZONE IN STABILIZED COUNTERCURRENT FLOW TO AN INERT GAS, PREFERABLY NITROGEN, WHILE BEING NON-ISOTHERMALLY HEATED TO A MAXIMUM TEMPERATURE OF ABOUT 210-240*C., PREFERABLY 220-235*C. AND FOR A PERIOD OF TIME SUFFICIENT TO CAUSE AFTER-CONDENSATION TO A DESIRED HIGHER MOLECULAR WEIGHT.
Inventors
- 👤 F Jaeger
- 👤 H Koepp
- 👤 F Wiloth
- 👤 R Eismann
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 22:21
CPC Classifications
C; C08; C08G; C08G63/00; C08G63/78; C08G63/80
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) | 1976-09-03 | 1977-03-05 | 1977-09-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-09-03 | 1981-03-05 | 1981-09-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-09-03 | 1985-03-05 | 1985-09-04 | $7700.00 | Window Closed / Lapsed |