US3669954A
Expired / Lapsed
US
⏱️ 0.0 years remaining
A process for producing semipermeable membranes
Assignee: United States Department of the Interior
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Filing: 1970-05-04
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Granted: 1972-06-13
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Expires: 1990-05-04
Abstract
Abstract Semipermeable membranes having improved reverse osmosis properties are prepared by crosslinking cellulose acetate methacrylate membranes in an aqueous persulfate-bisulfite redox system. The resulting membranes exhibit superior long-term reverse osmosis properties and find particular utility in desalination of water.
Inventors
- 👤 Otto S Schaeffler
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-10 01:25
CPC Classifications
C; C08; C08L; C08L1/00; C08L1/08; C08L1/10; C08L1/14; B; B01; B01D; B01D71/00; B01D71/06; B01D71/08; B01D71/12; B01D71/14; B01D71/18; C08B; C08B3/00; C08B3/22; B01D2323/00; B01D2323/30
Claims Analysis
Total Claims: 2
Claim 1
Independent Claim
18 words
The method of claim 1 in which the cellulose acetate methacrylate membrane is heat treated prior to crosslinking.
Claim 2
Dependent Claim
35 words
The method of claim 1 in which the cellulose acetate methacrylate has an average degree of acetate substitution of about 2.0 to 2.5 and an average degree of methacrylate substitution of about 0.1 to 0.4.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-06-13 | 1975-12-13 | 1976-06-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-06-13 | 1979-12-13 | 1980-06-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-06-13 | 1983-12-13 | 1984-06-13 | $7700.00 | Window Closed / Lapsed |