EP0125908A2
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EP
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Asymmetric polyimide reverse osmosis membrane, method for preparation of same and use thereof for organic liquid separations
Assignee: ExxonMobil Technology and Engineering Co
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Filing: 1984-05-11
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Granted: —
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Expires: 2004-05-11
Abstract
Abstract Asymmetric polyimide reverse osmosis membranes of high flux and selectivity for organic liquid separations are described. These membranes are prepared from undegraded polyimide by dissolving from 14-30 wt.% of the undegraded polymer in a dual solvent system comprising a polymer pro- solvent/anti-solvent wherein the pro-solvent is DMF and the anti-solvent is dioxane, wherein the ratio of anti-soivent/pro- solvent ranges from about 10:1 or more - 1:1, preferably about 8:1 - 1.5:1, most preferably about 7:1 - 3:1; the polymer-solvent mixture is spread into a thin film of the desired thickness and permitted to evaporate for a time just sufficient to permit formation of an asymmetric dense active layer, i,e,, within the range 2-120 seconds, preferably 2-60 seconds, most preferably 2 - 20 second before being immersed in a gelation bath. The membranes may be fabricated in the form of sheets, tubes, hollow fibers, etc. Mixtures of organic liquids, and especially mixtures of dewaxing solvents and dewaxed oils, are separated one from the other after completion of dewaxing operations, using the asymmetric polyimide reverse osmosis membrane described above.
Inventors
- 👤 Harry Franklin Shuey
- 👤 Wankei Wan
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-02 09:46
CPC Classifications
B; B01; B01D; B01D71/00; B01D71/06; B01D71/58; B01D71/62; B01D71/64; B01D61/00; B01D61/02; B01D61/025; B01D61/10; B01D63/00; B01D63/10; B01D63/107; B01D67/00; B01D67/0002; B01D67/0009; B01D67/0011
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
139 words
A high flux, high selectivity reverse osmosis asymmetric polyimide membrane prepared by the process comprising: (a) dissolving from 14-30 wt.% of an undegraded polyimide copolymer derived from the coconden- sation of benzophenone 3, 3', 4, 4'-tetracarboxylic acid dianhydride (BTDA) and a mixture of di (4 amino-phenyl) methane and toluene diamine, or 4, 4' methylenebis(-phenyl isocyanate) and toluene diisocyanate in a dual solvent system comprising dioxane antisolvent and N, N-dimethylformamide (DMF) pro-solvent at an antisolvent to prosolvent ratio of from about 10:1 to 1:1 to produce a casting solution; (b) generating a thin layer of the polyimide co-polymer/dual solvent solution mixture; (c) partially evaporating the solvent from the polyimide polymer-solvent thin layer for a time sufficient to permit formation of a thin active layer; (d) immersing the evaporated polymer-solvent thin layer in a gelation bath to form the asymmetric membrane.
Claim 2
Dependent Claim
139 words
A high flux, high selectivity reverse osmosis asymmetric polyimide membrane prepared by the process comprising: (a) dissolving from 14-30 wt.% of an undegraded polyimide copolymer derived from the coconden- sation of benzophenone 3, 3', 4, 4'-tetracarboxylic acid dianhydride (BTDA) and a mixture of di (4 amino-phenyl) methane and toluene diamine, or 4, 4' methylenebis(-phenyl isocyanate) and toluene diisocyanate in a dual solvent system comprising dioxane antisolvent and N, N-dimethylformamide (DMF) pro-solvent at an antisolvent to prosolvent ratio of from about 10:1 to 1:1 to produce a casting solution; (b) generating a thin layer of the polyimide co-polymer/dual solvent solution mixture; (c) partially evaporating the solvent from the polyimide polymer-solvent thin layer for a time sufficient to permit formation of a thin active layer; (d) immersing the evaporated polymer-solvent thin layer in a gelation bath to form the asymmetric membrane.
Claim 3
Dependent Claim
27 words
The asymmetric polyimide reverse osmosis membrane of claim 1 wherein the undegraded co-polymer is dissolved in the dual solvent system, at a concentration of from 16-25 wt.%
Claim 4
Dependent Claim
28 words
. The asymmetric polyimide reverse osmosis membrane of claim 2 wherein the undegraded copolymer is dissolved in the dual solvent system at a concentration of from 18-22 wt.%.
Claim 5
Dependent Claim
34 words
. The assymetric polyimide reverse osmosis membrane of any one of claims 1, 2 or 3 wherein the dual solvent system is employed at an anti-solvent to pro-solvent ratio of from 7:1 to 1.5:1.
Claim 6
Dependent Claim
27 words
The asymmetric polyimide reverse osmosis membrane of claim 4 wherein the dual solvent system is employed at an anti-solvent to pro-solvent ratio of from 7:1 to 3:1.
Claim 7
Dependent Claim
30 words
The asymmetric polyimide reverse osmosis membrane of any one of claims 1, 2, 3,4 or 5 wherein the polyimide polymer-solvent thin layer is evaporated for from 2 to 120 seconds.
Claim 8
Dependent Claim
24 words
The asymmetric polyimide reverse osmosis membrane of claim 6 wherein the polyimide polymer- solvent thin layer is evaporated for from 2 to 60 seconds.
Claim 9
Dependent Claim
32 words
The asymmetric polyimide reverse osmosis membrane of any one of claims 1 to 7 wherein the undegraded polyimide copolymer employed comprises from 10 to 90% of and from 90 to 10% of
Claim 10
Dependent Claim
50 words
The asymmetric polyimide reverse osmosis membrane of claim 8 wherein the undegraded polyimide copolymer employed comprises about 20% of and about 80% of produced by precipitation in a non aqueous crystallization solvent from which it is recovered by means of a nonaqueous anti-solvent prior to preparation of the casting solution.
Claim 11
Independent Claim
185 words
A method for separating mixtures of organic solutions by reverse osmosis by contacting the organic solution to be separated with the dense side of an asymmetric membrane at a pressure sufficient to overcome the osmotic pressure wherein the asymmetric membrane is a high flux, high selectivity reverse osmosis polyimide membrane prepared by the process comprising: (a) dissolving from 14-30 wt.% of an undegraded polyimide copolymer derived from-the co-condensation of benzophenone 3, 3', 4, 4' - tetracarboxylic acid dianhydride (BTDA) and a mixture of di (4 amino-phenyl) methane and toluene diamine, or 4, 4' methylene/bis(-phenyl isocyanate) and toluene diisocyanate in a dual solvent system comprising dioxane antisolvent and N, N-dimethyl formamide (DMF) prosolvent at an antisolvent to prosolvent ratio of from about 10:1 to 1:1 to produce a casting solution; (b) generating a thin layer of the polyimide co polymer dual solvent solution mixture; (c) partially evaporating the solvent from the polyimide co-polymer/solvent thin layer for a time sufficient to permit formation of a thin active layer; (d) immersing the evaporated copolymer- solvent thin layer in a gelation bath to form the asymmetric reverse osmosis membrane.
Claim 12
Independent Claim
185 words
A method for separating mixtures of organic solutions by reverse osmosis by contacting the organic solution to be separated with the dense side of an asymmetric membrane at a pressure sufficient to overcome the osmotic pressure wherein the asymmetric membrane is a high flux, high selectivity reverse osmosis polyimide membrane prepared by the process comprising: (a) dissolving from 14-30 wt.% of an undegraded polyimide copolymer derived from-the co-condensation of benzophenone 3, 3', 4, 4' - tetracarboxylic acid dianhydride (BTDA) and a mixture of di (4 amino-phenyl) methane and toluene diamine, or 4, 4' methylene/bis(-phenyl isocyanate) and toluene diisocyanate in a dual solvent system comprising dioxane antisolvent and N, N-dimethyl formamide (DMF) prosolvent at an antisolvent to prosolvent ratio of from about 10:1 to 1:1 to produce a casting solution; (b) generating a thin layer of the polyimide co polymer dual solvent solution mixture; (c) partially evaporating the solvent from the polyimide co-polymer/solvent thin layer for a time sufficient to permit formation of a thin active layer; (d) immersing the evaporated copolymer- solvent thin layer in a gelation bath to form the asymmetric reverse osmosis membrane.
Claim 13
Dependent Claim
32 words
The method of claim 10 wherein the pressure is a net driving force of about 100 to.1500 psi over the osmotic pressure and the temperature is about -50 to +150 0 C.
Claim 14
Dependent Claim
32 words
The method of claim 11 wherein the organic solutions to be separate comprise dewaxed oil and dewaxing solvent wherein the dewaxing solvent constitutes the permeate a.nd the dewaxe6 oil constitutes the retentate.
Claim 15
Dependent Claim
52 words
The method of claim 12 wherein the dewaxing solvent is a ketone having from 3-6 carbons and mixtures thereof, C 6 -C 9 aromatic hydrocarbons, mixtures of C 3 -C 6 ketones and C 6 -C 9 aromatic hydrocarbons, halogenated C 1 -C 4 hydrocarbons, ethers and mixtures of ethers and ketones.
Claim 16
Dependent Claim
22 words
The method of claim 13 wherein the asymmetric reverse osmosis polyimide membrane is used in the form of a spiral wound element.
References Cited (Backward Citations)
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