US3835207A
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Method for forming reverse osmosis membranes composed of polyamic acid salts
Assignee: Graftech Technology LLC
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Filing: 1972-05-03
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Granted: 1974-09-10
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Expires: 1992-05-03
Abstract
Abstract A polymeric membrane is prepared by reacting a suitable derivative of a tri or tetracarboxylic acid with a diamine to form a polyamic acid, forming a film from the polyamic acid, imidizing the polyamic acid film to form a polyamide-imide film, treating the polyamide-imide film to open the imide rings, to form a permselective membrane comprising water insoluble polyamic acid salt polymers.
Inventors
- 👤 L Frost
- 👤 L Scala
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 20:16
CPC Classifications
B; B01; B01D; B01D71/00; B01D71/06; B01D71/58; B01D71/62; B01D71/64; B01D71/641
Claims Analysis
Total Claims: 27
Claim 1
Independent Claim
66 words
The method of claim 1 wherein the solution which is used to open the imide rings is an aqueous solution of a base containing an ion selected from the group consisting of Na, K, Ba and trimethylbenzylammonium and the polyimide film is derived from about 4 moles pyromellitic dianhydride, about 9 moles of isophthaloyl chloride, about 3 moles terephthaloyl chloride and about 16 moles of m-phenylenediamine.
Claim 2
Dependent Claim
15 words
The method of claim 1 wherein the polyamic acid salt has the following structural formula:
Claim 3
Dependent Claim
21 words
The method of claim 3, wherein R is at least one tetravalent carbocyclic organic radical selected from the group consisting of:
Claim 4
Dependent Claim
46 words
The method of claim 2 wherein, as a last step the polyamic acid salt membrane is reacted with an aqueous metal salt solution containing an ion selected from the group consisting of Mg, Ca, Fe, Ag, Co, Pb, Cu, Li, Mn, Ni, Zn, Hg, and Al.
Claim 5
Dependent Claim
47 words
The method of claim 2 wherein, as a last step the polyamic acid salt membrane is reacted with a solution selected from the group consisting of MgSO4, CaCl2, FeCl2, FeCl3, CuSO4, Co(NO3)2, AgNO3, Pb(NO3)2, LiCl, MnSO4, Ni(NO3)2, ZnCl2, Hg(NO3)2, NH4Cl, (CH3)4 NCl, (CH3)3(C6H5CH2-)NCl and ClN (CH3)3-(CH2)6-N (CH3)Cl.
Claim 6
Dependent Claim
13 words
The method of claim 1 wherein the film is a hollow fiber film.
Claim 7
Independent Claim
165 words
A method of making a permselective polymeric membrane consisting essentially of water insoluble polyamic acid salt polymers comprising the steps of: A. reacting at least one aromatic dicarboxylic acid halide with an aromatic diamine to form an amine-terminated aromatic polyamide, B. reacting the amine-terminated aromatic polyamide with an aromatic dianhydride in a solvent comprising organic aprotic solvent to form a polyamic acid, C. casting a film from the polyamic acid, D. heating the polyamic acid film to evaporate solvent and form a solid water insoluble polyimide film containing imide rings and having a thickness between about 0.01-10 mils, and k E. contacting the polyimide film with an aquEous solution of a base containing an ion selected from the group consisting of Na, K, Ba and trimethylbenzylammonium to open a substantial portion of the imide rings in the film to form a water insoluble permselective polyamic acid salt polymeric membrane having a thickness between about 0.01-10 mils containing a high concentration of hydrophilic carboxylate salt groups.
Claim 8
Dependent Claim
58 words
The method of claim 8 wherein the alkali solution used to contact the polyimide film is selected from the group consisting of aqueous NaOH, KOH, Ba (OH)2 and trimethylbenzylammonium hydroxide, the polyamic acid, is cast as a film in step (C) on a porous support, and where after step (D) the imidized film is stripped from the support.
Claim 9
Dependent Claim
31 words
The method of claim 8 wherein the film is cast on the inside of a tubular support comprising resin bonded filler particles, and the film has a relatively uniform cross section.
Claim 10
Dependent Claim
57 words
The method of claim 10 wherein the resin bonding the filler particles is selected from the group consisting of epoxy resin, phenolic resin, polyester resin and melamine formaldehyde resin, the filler particles are sand particles having a particle size between about 40-500 microns, and the resin constitutes about 1 to 18 weight percent based on resin-filler weight.
Claim 11
Independent Claim
211 words
A method of making a permselective polymeric membrane consisting essentially of water insoluble polyamic acid salt polymers comprising the steps of: A. contacting a solid polyimide film containing imide rings and having a thickness between about 0.01-10 mils with an aqueous solution of a base containing an ion selected from the group consisting of Na, K, Ba and trimethylbenzylammonium to open a substantial portion of the imide rings in the film to form a water insoluble permselective polyamic acid salt polymeric membrane having a thickness between about 0.01-10 mils containing a high concentration of hydrophilic carboxylate salt groups containing an ion selected from the group consisting of Na, K, Ba and trimethylbenzylammonium, and B. reacting the polyamic acid salt membrane with an aqueous metal salt solution containing an ion selected from the group consisting of Mg, Ca, Fe, Ag, Co, Pb, Cu, Li, Mn, Ni, Zn, Hg and Al to substitute the metal portion of the metal salt for all or part of the ions contained in the hydrophilic carboxylate salt groups of the polyamic acid salt polymeric membrane by an ion exchange reaction to provide a water insoluble permselective polyamic acid salt polymeric membrane having a thickness between about 0.01-10 mils containing a high concentration of hydrophilic carboxylate salt groups.
Claim 12
Independent Claim
224 words
A method of making a reverse osmosis liquid treatment system comprising a supported membrane comprising the steps of: A. reacting an aromatic diamine with an aromatic diacyl halide to form an amine- terminated aromatic polyamide, and then the amine-terminated aromatic polyamide is reacted with a compound selected from the group consisting of aromatic dianhydrides, aromatic anhydride monoacyl halides, aromatic diester diacyl halides and aromatic monoester diacyl halides and mixtures thereof in a solvent comprising an organic aprotic solvent to form a polyamic acid, B. casting a film from the polyamic acid on the inside of a porous tubular support comprising resin bonded filler particles, C. heating the polyamic acid film cast on the support to evaporate solvent and form a solid water insoluble polyimide film containing imide rings and having a thickness between about 0.01-10 mils, and D. contacting the polyimide film on the support with an alkali solution of a base containing an ion selected from the group consisting of Na, K, Ba and trimethylbenzylammonium to open a substantial portion of the imide rings in the polyimide film to provide a reverse osmosis liquid treatment system comprising a supporting porous tube comprising resin bonded fillEr particles and a supported water insoluble permselective polyamic acid salt polymeric membrane having a thickness between about 0.01-10 mils containing a high concentration of hydrophilic carboxylate salt groups.
Claim 13
Dependent Claim
21 words
The method of claim 13 wherein the liquid treatment system also contains liquid feed inlet means and treated liquid outlet means.
Claim 14
Dependent Claim
24 words
The method of claim 13 wherein, in step (A) the amine-terminated aromatic polyamide is reacted with an aromatic dianhydride to form a polyamic acid.
Claim 15
Dependent Claim
66 words
The method of claim 15 wherein the solution which is used to open the imide rings is an aqueous solution of a base containing an ion selected from the group consisting of Na, K, Ba and trimethylbenzylammonium and the polyimide film is derived from about 4 moles pyromellitic dianhydride, about 9 moles isophthaloyl chloride, about 3 moles terephthaloyl chloride and about 16 moles of m-phenylene diamine.
Claim 16
Dependent Claim
22 words
The method of claim 16 wherein the aqueous base solution contacts the polyimide film at a temperature between about -10* to 40*C.
Claim 17
Dependent Claim
57 words
The method of claim 16 wherein the resin bonding the filler particles is selected from the group consisting of epoxy resin, phenolic resin, polyester resin and melamine formaldehyde resin, the filler particles are sand particles having a particle size between about 40-500 microns, and the resin constitutes about 1 to 18 weight percent based on resin-filler weight.
Claim 18
Dependent Claim
46 words
The method of claim 18 wherein, as a last step the polyamic acid salt membrane is reacted with an aqueous metal salt solution containing an ion selected from the group consisting of Mg, Ca, Fe, Ag, Co, Pb, Cu, Li, Mn, Ni, Zn, Hg, and Al.
Claim 19
Dependent Claim
43 words
The method of claim 18 wherein, as a last step the polyamic acid salt membrane is reacted with a solution selected from the group consisting of MgSO4, CaCl2, FeCl2, FeCl3, CuSO4, Co(NO3)2, AgNO3, Pb(NO3)2, LiCl, MnSO4, Ni(NO3)2ZnCl2, Hg(NO3)2, NH4Cl, (CH3)4NCl, (CH3)3(C6H5CH2-NCl and CIN(CH3)3-(CH2)6-N(CH3)Cl.
Claim 20
Dependent Claim
35 words
The method of claim 12 wherein the polyimide film is derived from about 4 moles pyromellitic dianhydride, about 9 moles of isophthaloyl chloride, about 3 moles terephaloyl chloride and about 16 moles of m-phenylene diamine.
Claim 21
Dependent Claim
21 words
The method of claim 12 wherein the aqueous base solution contacts the polyimide film at a temperature between about -10* 40*C.
Claim 22
Dependent Claim
18 words
The method of claim 12 wherein the concentration of the aqueous base solution is between about 0.5-20 percent.
Claim 23
Independent Claim
181 words
A method of making a permselective polymeric membrane comprising water insoluble polyamic acid salt polymers comprising the steps of: A. reacting about 12 moles of at least one aromatic dicarboxylic acid halide and about 16 moles of an aromatic diamine to form an amine terminated polyamide, B. reacting the amine terminated polyamide with about 4 moles dianhydride in a solvent comprising an organic aprotic solvent to form a polyamic acid, C. casting a film from the polyamic acid, D. heating the polyamic acid film to evaporate solvent and form a solid water insoluble polyimide film containing imide rings and having a thickness between 0.01-10 mils, and E. contacting the polyimide film with an aqueous solution of a base containing an ion selected from the group consisting of Na, K, Ba and trimethylbenzylammonium to open a substantial portion of the imide rings in the film to form a water insoluble permselective polyamic acid salt polymeric membrane having a thickness between about 0.01-10 mils containing a high concentration of hydrophilic carboxylate salt groups, said membrAne being effective to reject salts in applied solutions.
Claim 24
Dependent Claim
14 words
The method of claim 24 wherein the dianhydride and dicarboxylic acid halide are aromatic.
Claim 25
Dependent Claim
29 words
The method of claim 25 wherein the dianhydride is pyromellitic dianhydride, the dicarboxylic acid halide is a mixture of isophthaloyl chloride and terephthaloyl chloride and the diamine is m-phenylenediamine.
Claim 26
Dependent Claim
17 words
The method of claim 25 where after step (C) the imidized film is stripped from the support.
Claim 27
Dependent Claim
22 words
The method of claim 25 where the film is cast on the inside of a tubular support comprising resin bonded filler particles.
References Cited (Backward Citations)
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US3518219A
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US3598241A
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US3676193A
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US3737478A
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US3778411A
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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) | 1977-09-09 | 1978-03-11 | 1978-09-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-09-09 | 1982-03-11 | 1982-09-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-09-09 | 1986-03-11 | 1986-09-10 | $7700.00 | Window Closed / Lapsed |