Patent US3640970A successfully refreshed from Google Patents.
US3640970A
Expired / Lapsed
US
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Process for preparation of polyamides
Assignee: Teijin Ltd
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Filing: 1969-02-14
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Granted: 1972-02-08
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Expires: 1989-02-14
Abstract
Abstract A PROCESS FOR PREPARATION OF POLYAMIDES WHICH COMPRISES REACTING SUBSTANTIALLY EQUIMOLAR AMOUNTS OF AT LEAST ONE DIAMINE AND A DIHALIDE OF A LEAST ONE DICARBOXYLIC ACID AND IN AN INERT, NON-BASIC ORGANIC MEDIUM TO FORM A PRE-CONDENSATE, AND THEREAFTER CONTACTING SAID PRE-CONDENSATE IN SAID MEDIUM WITH AN AQUEOUS SOLUTION OF A WATER-SOLUBLE ACID ACCEPTOR. THUS HIGH MOLECULAR-WEIGHT AROMATIC POLYAMIDES SUITABLE FOR HIGH TEMPERATURE USES INCLUDING CO-POLYAMIDES HAVING EITHER RANDOM OR BLOCK STRUCTURE CAN BY OBTAINED WITH PRACTICAL EASINESS EVEN IN LARGE SCALE OPERATIONS.
Inventors
- 👤 Shuji Ozawa
- 👤 Hiroshi Fujie
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 20:39
CPC Classifications
C; C08; C08G; C08G69/00; C08G69/02; C08G69/26; C08G69/32
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) | 1975-02-07 | 1975-08-09 | 1976-02-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-02-07 | 1979-08-09 | 1980-02-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-02-07 | 1983-08-09 | 1984-02-08 | $7700.00 | Window Closed / Lapsed |