US3745202A
Expired / Lapsed
US
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Method of preparing an asymmetric membrane from a cellulose derivative
Assignee: United States Department of the Interior
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Filing: 1971-03-17
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Granted: 1973-07-10
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Expires: 1991-03-17
Abstract
Abstract ASYMMETRIC MEMBRANES ARE PREPARED FROM NON-SELECTIVE THERMALLY GELLED SUBSTRATES OF A CELLULOSE DERIVATIVE. AFTER LEACHING, THE SUBSTRATE IS ANNEALED AND THEN TREATED IN A DILUTE AQUEOUS SOLUTION OF EITHER P-DIOXANE, FORMIC ACIDS OR NITROMETHANE AT AN ELEVATED TEMPERATURE. THE RESULTING SEMIPERMEABLE MEMBRANE IS PARTICULARLY SUITED FOR DESALINATION BY REVERSE OSMOSIS.
Inventors
- 👤 B Riggleman
- 👤 M Cohen
- 👤 M Grable
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-22 23:52
CPC Classifications
B; B01; B01D; B01D67/00; B01D67/0002; B01D67/0023; B01D67/003; B01D67/0025; B01D67/0027; B01D69/00; B01D69/08; C; C08; C08J; C08J9/00; C08J9/28; C08J2201/00; C08J2201/04; C08J2201/054; C08J2201/0542; C08J2201/0543; C08J2201/0545; C08J2201/0546; C08J2301/00; C08J2301/08; Y; Y10; Y10S; Y10S264/00; Y10S264/14
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) | 1976-07-09 | 1977-01-08 | 1977-07-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-07-09 | 1981-01-08 | 1981-07-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-07-09 | 1985-01-08 | 1985-07-10 | $7700.00 | Window Closed / Lapsed |