US3837500A
Expired / Lapsed
US
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Diaphragm for inverse osmosis and method of making same
Assignee: Bpifrance Financement SA
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Filing: 1971-04-16
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Granted: 1974-09-24
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Expires: 1991-04-16
Abstract
Abstract The invention relates to a method of preparation of semipermeable diaphragms, especially for use in inverse osmosis and enabling substantially pure water to be extracted from aqueous solutions of dissolved substances of low molecular weight, such as sodium chloride, saccharose, etc. The diaphragms for inverse osmosis essentially consist of a film-producing polymer having a sufficient number of mobile hydrogen groups to give, after reticulation, compounds which are insoluble in water. The method covers the preparation of ultra-thin layers which can be employed for hyper-filtration purposes, and also includes the superficial reticulation of a dry film of polymers which include, inter alia, the polyvinyl alcohols and polyvinyl pyrrolidone. The reticulation agent is preferably chosen from the di-isocyanates and may comprise a solvent for a swelling agent for the polymer and a catalyst for the reticulation reaction. An important feature of the invention is that the degree of reticulation of such diaphragms varies progressively throughout the thickness of the film, the most highly reticulated layer being a very thin superficial layer of the diaphragm.
Inventors
- 👤 L Nicolas
- 👤 R Dick
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 00:53
CPC Classifications
B; B01; B01D; B01D67/00; B01D67/0081; B01D67/0093; C; C08; C08G; C08G18/00; C08G18/06; C08G18/28; C08G18/40; C08G18/62; C08G18/6212; C08G18/6283; C08G18/64; C08G18/6415; C08G18/6423; B01D2323/00; B01D2323/30
Claims Analysis
Total Claims: 34
Claim 1
Independent Claim
31 words
A process as claimed in claim 1, in which the recticulation agent is selected from such agents having a high speed of reaction and a high diffusion rate into said film.
Claim 2
Dependent Claim
32 words
A process according to claim 1, wherein the film producing polymer has groupings with mobile hydrogen in a number sufficient to form compounds being insoluble in water after reticulation by a dissocyanate.
Claim 3
Dependent Claim
17 words
A process according to claim 1, wherein the film producing polymer has a substantially high molecular weight.
Claim 4
Dependent Claim
34 words
A process according to claim 4, wherein the average molecular weight of the film producing polymer is such that a 4 percent aqueous solution has a viscosity of 50 to 150 centipose at 20*C.
Claim 5
Dependent Claim
29 words
A process according to claim 1, wherein the film producing polymer is selected from the group consisting of the polyvinyl alcohols, polyethylene glycol, the imine polyethylenes, and polyvinyl pyrrolidone.
Claim 6
Dependent Claim
17 words
A process according to claim 6, wherein the polyvinyl alcohol has a viscosity of approximately 5000 centipoise.
Claim 7
Dependent Claim
18 words
A process according to claim 1, wherein the solution containing the film producing polymer includes a reticulation catalyst.
Claim 8
Dependent Claim
23 words
A process according to claim 1, wherein the reticulating solution includes one of a solvent and swelling agent of the film producing polymer.
Claim 9
Dependent Claim
14 words
A process according to claim 1, wherein the reticulating solution includes a reticulation catalyst.
Claim 10
Dependent Claim
20 words
A process according to claim 1, wherein the reticulating solution includes as a reticulation agent a diisocyanate, or tolylene dissocyanate.
Claim 11
Dependent Claim
29 words
A process according to claim 1, further including hot-drying with rapid evapOration of the solvent after the reticulated film has been removed from the presence of the reticulation solution.
Claim 12
Dependent Claim
15 words
A process according to claim 1, wherein the rinsing solvent is benzene or ethyl acetate.
Claim 13
Dependent Claim
25 words
A process according to claim 1, further comprising heating said film producing polymer in water between 30*C and 100*C prior to dissolving said non-reticulated remainder.
Claim 14
Dependent Claim
22 words
A process according to claim 1, further comprising fixing the reticulated layer on a porous support prior to dissolving said non-reticulated remainder.
Claim 15
Dependent Claim
21 words
A process according to claim 1, further comprising fixing the reticulated layer on a porous support after dissolving said non-reticulated remainder.
Claim 16
Dependent Claim
22 words
A process according to claim 1, further comprising fixing the reticulated layer on a permeable support prior to dissolving said non-reticulated remainder.
Claim 17
Dependent Claim
21 words
A process according to claim 1, further comprising fixing the reticulated layer on a permeable support after dissolving said non-reticulated remainder.
Claim 18
Dependent Claim
55 words
A process according to claim 1, wherein the preparation of the polymeric film from the solution of the film producing polymer comprises rapid evaporation of the solvent from the solution to produce a film having an assymetrical structure, said film being more dense in the vicinity of the surface from which the evaporation takes place.
Claim 19
Dependent Claim
33 words
A process according to claim 19, wherein the more dense face of the polymeric film is subjected to the vapors of the reticulation solution comprising diisocyanate in a swelling agent for said film.
Claim 20
Dependent Claim
14 words
A process according to claim 19, wherein the reticulation takes place under controlled humidity.
Claim 21
Dependent Claim
20 words
A process according to claim 1, wherein said film producing polymer is soluble in hot water in the non-reticulated condition.
Claim 22
Dependent Claim
124 words
A process for manufacturing a membrane for inverse osmosis including at least one layer of a film producing reticulated polymer having a degree of reticulation which varies progressively from one face of the layer to the other comprising preparing a film by drying a thin layer of a solution containing a film producing polymer; placing one face of the film in contact with reticulating reactants present in a reticulating solution to thereby effect reticulation of a portion of the film; removing the reticulated film from the presence of the reticulating solution; rinsing the film in a solvent of the reagents of the reticulating solution; and dissolving the non-reticulated remainder of the film producing polymer in a solvent of the polymer in the non-reticulated condition.
Claim 23
Dependent Claim
38 words
A membrane for inverse osmosis made by the process of claim 23 comprising at least one layer of a reticulated polymer film having a degree of reticulation varying progressively from one face of the layer to the other.
Claim 24
Dependent Claim
32 words
A membrane according to claim 24, wherein said layer is a superficial thin layer and said membrane further comprises a thicker and more porous sub-layer, said sub-layer supporting said superficial thin layer.
Claim 25
Dependent Claim
15 words
A membrane according to claim 24 wherein the layer is deposited on a porous support.
Claim 26
Dependent Claim
18 words
A membrane according to claim 26, wherein the face having the higher degree of recticulation contacts the support.
Claim 27
Dependent Claim
15 words
A membrane according to claim 26, wherein the support is a polymer wettable by water.
Claim 28
Dependent Claim
15 words
A membrane according to claim 24, wherein the layer is deposited on a permeable support.
Claim 29
Dependent Claim
44 words
A membrane according to claim 24, wherein the film producing reticulated polymer is selected from the group consisting of polyvinyl alcohol, polyvinyl alcohol containing a small amount of polyvinyl acetate, polyoxyethylene glycol, polyethylene imine, polyvinyl-pyrrolidone and a copolymer of polyvinyl alcohol and vinyl acetate.
Claim 30
Dependent Claim
21 words
A membrane according to claim 24, wherein the membrane has a rejection coefficient for sea salt of 98 to 99 percent.
Claim 31
Dependent Claim
15 words
A membrane according to claim 24, having a thickness of from 0.5 to 10 microns.
Claim 32
Dependent Claim
12 words
A membrane according to claim 24, wherein the polymer is polyvinyl alcohol.
Claim 33
Dependent Claim
12 words
A membrane according to claim 24, wherein the polymer is polyvinyl pyrrolidone.
Claim 34
Dependent Claim
39 words
A membrane according to claim 24, wherein said film is an asymmetrical reticulated layer, with the structure of said film being dense close to said one major face and less dense in the vicinity of said other major face.
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) | 1977-09-23 | 1978-03-25 | 1978-09-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-09-23 | 1982-03-25 | 1982-09-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-09-23 | 1986-03-25 | 1986-09-24 | $7700.00 | Window Closed / Lapsed |