US3884801A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Preparation of reverse osmosis membranes by complete evaporation of the solvent system
Assignee: United States Department of the Interior
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Filing: 1973-09-26
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Granted: 1975-05-20
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Expires: 1993-09-26
Abstract
Abstract A method for preparing asymmetric reverse osmosis membranes by preparing a dilute solution of cellulose acetate in a solvent system consisting of a solvent and at least one pore-forming material selected from the nonsolvents for cellulose acetate, casting the solution to form a thin film, and allowing the solvent system to evaporate completely. The dry membranes so formed can be stored in the absence of water and rewet when necessary for use in reverse osmosis separations. The membranes can be repeatedly dried and rewet without any special treatment steps and without harm to the membrane.
Inventors
- 👤 Robert Emil Kesting
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 18:00
CPC Classifications
B; B01; B01D; B01D71/00; B01D71/06; B01D71/08; B01D71/12; B01D71/14; B01D67/00; B01D67/0002; B01D67/0009; B01D67/0011; B01D67/0023; B01D67/003; B01D61/00; B01D61/02; B01D61/025
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
106 words
A PROCESS FOR FORMING AN ASYMMETRIC REVERSE OSMOSIS MEMBRANE CONSISTING ESSENTIALLY OF THE STEPS: A. PREPARING A DILUTE SOLUTION CONSISTING OF A CELLLULOSE ESTER IN AN AMOUNT LESS THAN OR EQUAL TO 15 PERCENT BY WEIGHT OF THE SOLUTION, A SOLVENT FOR THE CELLULOSE ESTER CONSISTING OF ACETONE OR DIOXANE, AND AT LEAST ONE PORE-FORMING MATERIAL, THE SOLVENT HAVING A BOILING POINT AT LEAST 30*C LOWER THAN THE BOILING POINT OF THE PORE-FORMING MATERIAL AND THE PORE-FORMING MATERIAL BEING A NONSOLVENT FOR THE CELLULOSE ESTER, B. CASTING SAID DILUTE SOLUTION TO FORM A THIN FILM, AND C. ALLOWING THE SOLVENT AND PORE-FORMING MATERIAL TO EVAPORATE COMPLETELY.
Claim 2
Dependent Claim
106 words
A PROCESS FOR FORMING AN ASYMMETRIC REVERSE OSMOSIS MEMBRANE CONSISTING ESSENTIALLY OF THE STEPS: A. PREPARING A DILUTE SOLUTION CONSISTING OF A CELLLULOSE ESTER IN AN AMOUNT LESS THAN OR EQUAL TO 15 PERCENT BY WEIGHT OF THE SOLUTION, A SOLVENT FOR THE CELLULOSE ESTER CONSISTING OF ACETONE OR DIOXANE, AND AT LEAST ONE PORE-FORMING MATERIAL, THE SOLVENT HAVING A BOILING POINT AT LEAST 30*C LOWER THAN THE BOILING POINT OF THE PORE-FORMING MATERIAL AND THE PORE-FORMING MATERIAL BEING A NONSOLVENT FOR THE CELLULOSE ESTER, B. CASTING SAID DILUTE SOLUTION TO FORM A THIN FILM, AND C. ALLOWING THE SOLVENT AND PORE-FORMING MATERIAL TO EVAPORATE COMPLETELY.
Claim 3
Dependent Claim
54 words
The process of claim 1 wherein said cellulose ester is selected from the group consisting of cellulose acetate, cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose butyrate, cellulose cyanoethylate, cellulose methacrylate, blends of at least two of said cellulose esters, and cellulose mixed esters having at least two of the acid moieties of said esters.
Claim 4
Dependent Claim
25 words
The process of claim 2 wherein the pore-forming material is selected from the group consisting of isopropanol, ethanol, methanol, water, and isomeric butanols and pentanols.
Claim 5
Dependent Claim
12 words
The process of claim 1 wherein the cellulose ester is cellulose acetate.
Claim 6
Dependent Claim
25 words
The process of claim 1 wherein the pore-forming material is selected from the group consisting of isopropanol, ethanol, methanol, water, and isomeric butanols and pentanols.
Claim 7
Dependent Claim
106 words
An asymmetric reverse osmosis membrane prepared by the process consisting essentially of the steps: a. preparing a dilute solution consisting of a cellulose ester in an amount less than or equal to 15 percent by weight of the solution, a solvent for the cellulose ester consisting of acetone or dioxane, and at least one pore-forming material, the solvent having a boiling point at least 30*C lower than the boiling point of the pore-forming material and the pore-forming material being a nonsolvent for the cellulose estEr, b. casting said dilute solution to form a thin film, and c. allowing the solvent and pore-forming material to evaporate completely.
Claim 8
Dependent Claim
106 words
An asymmetric reverse osmosis membrane prepared by the process consisting essentially of the steps: a. preparing a dilute solution consisting of a cellulose ester in an amount less than or equal to 15 percent by weight of the solution, a solvent for the cellulose ester consisting of acetone or dioxane, and at least one pore-forming material, the solvent having a boiling point at least 30*C lower than the boiling point of the pore-forming material and the pore-forming material being a nonsolvent for the cellulose estEr, b. casting said dilute solution to form a thin film, and c. allowing the solvent and pore-forming material to evaporate completely.
Claim 9
Dependent Claim
28 words
In a reverse osmosis process for separating solute from solvent employing a semipermeable membrane, the improvement which comprises employing as the semipermeable membrane the membrane of claim 6.
Claim 10
Dependent Claim
19 words
The method of claim 7, wherein the solute is one or more salt compounds and the solvent is water.
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) | 1978-05-19 | 1978-11-18 | 1979-05-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-05-19 | 1982-11-18 | 1983-05-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-05-19 | 1986-11-18 | 1987-05-20 | $7700.00 | Window Closed / Lapsed |