Patent US3773534A successfully refreshed from Google Patents.
US3773534A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for preparing a dry semi-permeable cellulose acetate membrane
Assignee: Kalle GmbH and Co KG
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Filing: 1971-11-30
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Granted: 1973-11-20
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Expires: 1991-11-30
Abstract
Abstract A dry semi-permeable cellulose acetate membrane is processed from a wet cellulose acetate membrane having an active separating layer and a porous supporting layer. In the process, the wet membrane is immersed in an aqueous solution containing Two to 20 per cent by weight of an organic carboxylic acid having one to three carbon atoms, and 20 TO 40 PER CENT BY WEIGHT OF A POLYHYDRIC ALCOHOL HAVING TWO OR THREE CARBON ATOMS, AND DRIED AT A TEMPERATURE IN THE RANGE OF ABOUT 25* TO 100* C.
Inventors
- 👤 W Kaiser
- 👤 F Schwarzer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 09:48
CPC Classifications
B; B01; B01D; B01D67/00; B01D67/0081; B01D67/0095
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
15 words
A process according to claim 1 in which the organic carboxylic acid is acetic acid.
Claim 2
Dependent Claim
13 words
A process according to claim 1 in which the polyhydric alcohol is glycerol.
Claim 3
Dependent Claim
13 words
A dry semi-permeable cellulose acetate membrane produced by the process of claim 1.
Claim 4
Dependent Claim
11 words
A membrane according to claim 4 reinforced by a fibrous support.
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) | 1976-11-19 | 1977-05-21 | 1977-11-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-11-19 | 1981-05-21 | 1981-11-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-11-19 | 1985-05-21 | 1985-11-20 | $7700.00 | Window Closed / Lapsed |