Patent US3718722A successfully refreshed from Google Patents.
US3718722A
Expired / Lapsed
US
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A method of forming a porous cellulose acetate membrane
Assignee: Celanese Corp
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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
2026-11-05 15:07
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.
References Cited (Backward Citations)
US2897546A
Cited
US3133137A
Cited
US3364288A
Cited
US3310488A
Cited
US3344214A
Cited
US3373056A
Cited
US3285765A
Cited
US3290286A
Cited
US3412184A
Cited
US3497072A
Cited
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 |