US4145295A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Cellulose ester ultra-filtration membranes and their manufacture
Assignee: National Research Council Canada
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Filing: 1977-08-15
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Granted: 1979-03-20
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Expires: 1997-08-15
Abstract
Abstract A process for preparing ultra-filtration membranes and the product thereof, in which a selected cellulosic-ester polymer solution is cast into a thin film, at about ambient temperature, partially dried and immersed in a gelation bath at -20 ° to +30° C. The gelation bath contains a sufficient percentage by volume of ethyl alcohol or other organic polar compound to ensure that a flux rate in excess of the initial minimum is achieved. In this way, ultra-filtration membranes having water flux rates selected from within the approximate range 14-10,000 gals./sq.ft./day at 100 psig and a molecular weight cut off above about 15,000, can be produced.
Inventors
- 👤 Oleh Kutowy
- 👤 William L. Thayer
- 👤 Srinvasa Sourirajan
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 05:20
CPC Classifications
B; B01; B01D; B01D71/00; B01D71/06; B01D71/08; B01D71/12; B01D71/14; B01D71/16; B01D67/00; B01D67/0002; B01D67/0009; B01D67/0011; B01D61/00; B01D61/14; B01D61/145
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
125 words
In a process for producing a cellulosic ester semi-permeable membrane wherein a thin film is cast from a mixture comprising cellulosic ester polymer, pore-forming additive and casting solvent, a portion of the casting solvent may be removed from the film and the film is immersed in a gelation bath containing a polar organic compound which is miscible with said casting solvent, the improvement, for producing an ultra-filtration membrane, comprising controlling the temperature of said gelation bath at a selected temperature in the range -20° C. to +30° C. and selecting said polar organic compound to be an alcohol in a concentration, in said gelation bath greater than that required to produce an initial minimum flux for said membrane, equivalent to point B in FIG. 2a.
Claim 2
Dependent Claim
125 words
In a process for producing a cellulosic ester semi-permeable membrane wherein a thin film is cast from a mixture comprising cellulosic ester polymer, pore-forming additive and casting solvent, a portion of the casting solvent may be removed from the film and the film is immersed in a gelation bath containing a polar organic compound which is miscible with said casting solvent, the improvement, for producing an ultra-filtration membrane, comprising controlling the temperature of said gelation bath at a selected temperature in the range -20° C. to +30° C. and selecting said polar organic compound to be an alcohol in a concentration, in said gelation bath greater than that required to produce an initial minimum flux for said membrane, equivalent to point B in FIG. 2a.
Claim 3
Dependent Claim
26 words
A process as claimed in claim 1 wherein said alcohol is selected from the group comprising lower monohydric alcohols, dihydric alcohols, trihydric alcohols and mixtures thereof.
Claim 4
Dependent Claim
18 words
A process as claimed in claim 2 wherein said gelation bath comprises an aqueous solution of said alcohol.
Claim 5
Dependent Claim
22 words
A process as claimed in claim 3 wherein said alcohol in said solution is present in an amount from 25-100% by volume.
Claim 6
Dependent Claim
19 words
A process as claimed in claim 4 wherein said gelation bath comprises 25-95% by volume ethyl alcohol in water.
Claim 7
Dependent Claim
21 words
A process as claimed in claim 4 wherein said thin film is cast at a temperature in the range 18°-26° C.
Claim 8
Dependent Claim
22 words
A process as claimed in claim 6 wherein said gelation bath is at a temperature in the range -20° to +30° C.
Claim 9
Dependent Claim
21 words
A process as claimed in claim 1 wherein said film is immersed in a separate leaching bath following said gelation bath.
Claim 10
Dependent Claim
36 words
A cellulosic ester ultra-filtration membrane produced by the process of claim 1 having a water flux rate in the range 14-10,000 gals/sq.ft./day at 100 psig, and a magnesium sulphate rejection at 100 psig below about 40%.
Claim 11
Dependent Claim
35 words
An ultra-filtration membrane as claimed in claim 9 wherein said film is cast from a mixture comprising: 13-19 weight % cellulose acetate 58-68 weight % acetone 14-22 weight % water 1.3-3.3 weight % magnesium perchlorate.
Claim 12
Dependent Claim
19 words
An ultra-filtration membrane as claimed in claim 10 having a molecular weight cut off in excess of about 15,000.
Claim 13
Dependent Claim
24 words
A process as claimed in claim 2 wherein said alcohol is selected from the group consisting of ethyl alcohol, methyl alcohol and mixtures thereof.
Claim 14
Dependent Claim
23 words
A process as claimed in claim 7 wherein said gelation bath is at a temperature in the range 0° C. to 20° C.
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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) | 1982-03-19 | 1982-09-18 | 1983-03-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-03-19 | 1986-09-18 | 1987-03-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-03-19 | 1990-09-18 | 1991-03-20 | $7700.00 | Window Closed / Lapsed |