US3639665A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process of preparing a gellable collodial cellulose sulfate
Assignee: Kelco Co
•
Filing: 1969-04-10
•
Granted: 1972-02-01
•
Expires: 1989-04-10
Abstract
Abstract PROCESS FOR PREPARING CELLULOSE SULFATE HAVING A DEGREE OF SUBSTITUTION RANGING FROM 1 TO 3, PREFERABLY 2 TO 3 AND VISCOSITY IN A 1% AQUEOUS SOLUTION IN EXCESS OF 20 CPS., THE PROCESS COMPRISING PRESOAKING THE CELLULOSE IN A LOWER N-DIALKYL AMIDE FOR AT LEAST ABOUT 10 MINUTES AT A TEMPERATURE OF ABOUT 0 TO 28*C. AND THEN REACTING THE PRESOAKED CELLULOSE WITH A LOWER N-DALKYL AMIDESULFUR TRIOXIDE COMPLEX FOR ABOUT 20 TO 60 MINUTES AT TEMPERATURES OF ABOUT 0 TO 35*C. PRESOAKING OF THE CELLULOSE IS CARRIED OUT UNDER AGITIATION AND THE CELLULOSE MAY CONTAIN UP TO ABOUT 10% BY WEIGHT OF WATER.
Inventors
- 👤 Richard G Schweiger
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 19:52
CPC Classifications
C; C08; C08B; C08B5/00; C08B5/14
Claims Analysis
Total Claims: 0
No claims parsed yet. Click Sync Now above to re-index claims from Google Patents.
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) | 1975-01-31 | 1975-08-02 | 1976-02-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-01-31 | 1979-08-02 | 1980-02-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-01-31 | 1983-08-02 | 1984-02-01 | $7700.00 | Window Closed / Lapsed |