US3789993A
Expired / Lapsed
US
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Cellulosic reverse osmosis membranes having high flux and high salt rejection
Assignee: Eastman Technology Inc
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Filing: 1972-01-06
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Granted: 1974-02-05
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Expires: 1992-01-06
Abstract
Abstract Using cellulose ester dope compositions in which the solvent portion contains a high proportion of formic acid, cellulosic reverse osmosis membranes can be manufactured. These membranes have surprisingly high flux and salt rejection properties, an unexpected resistance to compaction at high pressures over prolonged periods of time and salt rejection properties that are practically independent of applied pressure.
Inventors
- 👤 B Brown
- 👤 E Ray
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 23:46
CPC Classifications
B; B01; B01D; B01D71/00; B01D71/06; B01D71/08; B01D71/12; B01D71/14; B01D67/00; B01D67/0002; B01D67/0023; B01D67/003; B01D69/00; B01D69/02; B01D2323/00; B01D2323/15; B01D2323/18; B01D2325/00; B01D2325/02; B01D2325/022; B01D61/00; B01D61/02; B01D61/025; Y; Y02; Y02A; Y02A20/00; Y02A20/124; Y02A20/131
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
45 words
An asymmetric cellulose ester reverse osmosis membrane as in claim 1, wherein the amount of combined acetyl is from about 37.5 to about 40.5 percent, and the intrinsic viscosity of said cellulose ester is from about 0.5 to about 1.2 measured in acetone at 25*C.
Claim 2
Dependent Claim
23 words
An asymmetric cellulose acetate reverse osmosis membrane as in claim 2, wherein the acetyl content of said cellulose acetate is about 40 percent.
Claim 3
Dependent Claim
64 words
A clear dope composition comprising (a) from about 20 to about 35 weight percent cellulose acetate having an acetyl content of from about 36 to about 41 percent and an intrinsic viscosity (measured in acetone at 25*C.) of at least about 0.5 and (b) a pore producing material dissolve in a solvent medium which consists essentially of a blend of formic acid and acetone.
Claim 4
Dependent Claim
39 words
A clear dope composition as in claim 4, wherein said pore producing material is an effective amine salt of an inorganic acid; the amount of said amine salt in said dope composition being at least about 0.5 weight percent.
Claim 5
Dependent Claim
29 words
A clear dope composition as in claim 5, wherein said formic acid and said acetone are present in a weight ratio, respectively of from about 60 to about 40.
Claim 6
Dependent Claim
37 words
A clear dope composition as in claim 6, wherein said cellulose acetate has from about 37.5 to about 40.5 percent acetyl and an intrinsic viscosity of from about 0.8 to about 1.2 measured in acetone at 25*C.
Claim 7
Dependent Claim
31 words
A clear dope composition as in claim 5, wherein said amine salt of an inorganic acid is selected from the group consisting of di-pyridine sulfate, di-triethylamine sulfate, and di-triethanol ammonium sulfate.
Claim 8
Dependent Claim
13 words
A composition as in claim 8, wherein said amine salt is di-triethylamine sulfate.
Claim 9
Dependent Claim
13 words
A composition as in claim 8, wherein said amine salt is di-pyridine sulfate.
Claim 10
Dependent Claim
29 words
A composition as in claim 5, wherein the amount of said amine salt in said dope composition is from about 0.5 to about 10 weight percent of said composition.
Claim 11
Dependent Claim
103 words
A clear dope composition consisting essentially of: a. from about 20 to about 35 weight percent of cellulose acetate or a mixture thereof having an acetyl content of from about 36 to about 41 percent and an intrinsic viscosity measured in acetone at 25*C of from about 0.5 to about 1.2; b. from about 0.5 to about 10 weight percent of a pore producing amine salt of an inorganic strong acid; and c. at least about 55 weight percent of a solvent blend which consists essentially of formic acid and acetone and contains from about 45 to 80 weight percent of formic acid.
Claim 12
Dependent Claim
107 words
A composition as in claim 12, wherein (a) the cellulose acetate has an acetyl content of from about 37.5 to about 40.5 percent and an intrinsic viscosity of from about 0.8 to about 1.2 measured in acetone in 25*C., (b) the formic acid represents from about 60 to 75 weight percent of a fraction of the dope composition which is volatile at 105*C. at atmospheric pressure, (c) the acetone constitutes from about 25 to about 40 weight percent of said composition, and (d) the pore producing amine salt of an inorganic strong acid is selected from the group consisting of di-pyridine sulfate, di-triethylamine and di-triethanol ammonium sulfate.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-02-04 | 1977-08-06 | 1978-02-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-02-04 | 1981-08-06 | 1982-02-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-02-04 | 1985-08-06 | 1986-02-05 | $7700.00 | Window Closed / Lapsed |