US3718722A
Expired / Lapsed
US
⏱️ 0.0 years remaining
A method of forming a porous cellulose acetate membrane
Assignee: Celanese Corp
•
Filing: 1970-09-17
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Granted: 1973-02-27
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Expires: 1990-09-17
Abstract
Abstract In the method of preparing a porous membrane adapted to separate a solute from a solution comprising: (a) dissolving a filmforming cellulosic ester in a solvent for said ester, (b) casting the resulting solution to form a membrane of substantially uniform thickness, (c) evaporating a portion of said solvent for a period of 0.5 to 5 minutes, (d) immersing the thus cast membrane in water, the steps which comprise: (e) annealing the membrane by initially heating it under tension to a temperature between about 70* and 90*C., which is about 5* - 10*C. below the final annealing temperature and then by a final heat treatment without tension at the final annealing temperature from about 75* to 95*C.
Inventors
- 👤 L Lee
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 22:08
CPC Classifications
B; B01; B01D; B01D71/00; B01D71/06; B01D71/08; B01D71/12; B01D71/14; B01D71/16; B01D67/00; B01D67/0002; B01D67/0009; B01D67/00091; B01D67/0081; B01D67/0083
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
16 words
The method of claim 1 wherein the final annealing temperature is from about 75* to 85*C.
Claim 2
Dependent Claim
20 words
The method of claim 1 wherein the casting and evaporating are accomplished with said solution being at about room temperature.
Claim 3
Dependent Claim
42 words
The method of claim 1 wherein said cellulose acetate is dissolved with said solvent in an aqueous solution of a perchlorate salt pore producing agent wherein the weight ratio of cellulose acetate to pore producing agent is between about 10:1 and 20:1.
Claim 4
Dependent Claim
13 words
The method of claim 4 wherein said pore producing agent is magnesium perchlorate.
Claim 5
Dependent Claim
10 words
The method of claim 4 wherein the solvent is dioxane.
Claim 6
Dependent Claim
11 words
The method of claim 1 wherein the solvent is dimethyl formamide.
Claim 7
Dependent Claim
20 words
The method of claim 1 wherein the resultant porous membrane is subject to a rolling step in a roll mill.
Claim 8
Dependent Claim
129 words
In the method of preparing a porous membrane adapted to separate a solute from a solution comprising: a. dissolving a film-forming Cellulose acetate in a solvent for said cellulose acetate wherein the weight ratio of solvent to ester is between about 1:1 and 10:1; b. casting the resulting solution to form a membrane of substantially uniform thickness; c. evaporating a portion of said organic solvent for a period of from 0.5 to 5 minutes, and d. immersing the thus cast membrane in water, the step which comprises: e. annealing the membrane by heating it under tension to a temperature between about 70* and 95*C. for a period of from about 0.5 to 1 hour and then rolling the annealed membrane in a roll mill to produce an opalescent film.
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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) | 1976-02-27 | 1976-08-28 | 1977-02-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-02-27 | 1980-08-28 | 1981-02-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-02-27 | 1984-08-28 | 1985-02-27 | $7700.00 | Window Closed / Lapsed |