Claims
- 1. A method for the enrichment of the amount of a gaseous organic compound in a gaseous admixture of said organic compound and at least one of oxygen and nitrogen, said method comprising:
- (a) providing in a membrane separation cell a selectively permeable membrane having a feed side and a permeate side, said membrane being virtually defect-free with an oxygen/nitrogen selectivity of at least 1.4 and formed from an amorphous polymer of perfluoro-2,2-dimethyl-1,3-dioxole, and feeding said admixture to the feed side of said membrane, said membrane being at a temperature of less than the glass transition temperature of the polymer; and
- (b) removing from the feed side of the membrane, a gaseous admixture of said organic compound that is enriched in the amount of organic compound.
- 2. The method of claim 1 in which a pressure differential is applied across the membrane.
- 3. The method of claim 1 in which the temperature of the membrane is at least 30.degree. C. lower than the glass transition temperature of the polymer.
- 4. The method of claim 1 in which the membrane has a selective permeation of nitrogen over the organic compound of at least 10:1.
- 5. The method of claim 1 in which the organic compound is a gaseous fluorocarbon.
- 6. The method of claim 1 in which the organic compound is a gaseous hydrocarbon.
- 7. The method of claim 1 in which the polymer is a copolymer of perfluoro-2,2-dimethyl-1,3-dioxole.
- 8. The method of claim 7 in which the polymer is a copolymer of perfluoro-2,2-dimethyl-1,3-dioxole and a complementary amount of at least one monomer selected from the group consisting of tetrafluoroethylene, perfluoromethyl vinyl ether, vinylidene fluoride and chlorotrifluoroethylene.
- 9. The method of claim 1 in which the polymer is a homopolymer of perfluoro-2,2-dimethyl-1,3-dioxole.
- 10. The method of claim 1 in which the polymer is a dipolymer of perfluoro-2,2-dimethyl-1,3-dioxole and a complementary amount of tetrafluoroethylene.
- 11. The method of claim 10 in which the polymer is a dipolymer containing 65-99 mole % of perfluoro-2,2-dimethyl-1,3-dioxole and having a glass transition temperature of at least 140.degree. C.
- 12. The method of claim 11 in which the membrane has a permeability to oxygen of at least 100 Barrers.
- 13. The method of claim 12 in which the permeability to oxygen is at least 200 Barrers.
- 14. The method of claim 12 in which the permeability to oxygen is at least 500 Barrers.
- 15. A method for the enrichment of the amount of a gas in a gaseous admixture with another gas, said method comprising:
- (a) providing in a membrane separation cell a selectively permeable membrane having a feed side and a permeate side, said membrane being virtually defect-free with an oxygen/nitrogen selectivity of at least 1.4 and formed from an amorphous polymer of perfluoro-2,2-dimethyl-1,3-dioxole, and feeding said admixture to the feed side of said membrane, said membrane being at a temperature of less than the glass transition temperature of the polymer; and
- (b) removing from the permeate side of the membrane, a gaseous admixture that is enriched in the amount of one gas.
- 16. The method of claim 15 in which a pressure differential is applied across the membrane.
- 17. The method of claim 15 in which the temperature of the membrane is at least 30.degree. C. lower than the glass transition temperature of the dipolymer.
- 18. The method of claim 15 in which the polymer is a copolymer of perfluoro-2,2-dimethyl-1,3-dioxole.
- 19. The method of claim 18 in which the polymer is a copolymer of perfluoro-2,2-dimethyl-1,3-dioxole and a complementary amount of at least one monomer selected from the group consisting of tetrafluoroethylene, perfluoromethyl vinyl ether, vinylidene fluoride and chlorotrifluoroethylene.
- 20. The method of claim 19 in which the polymer is a dipolymer of perfluoro-2,2-dimethyl-1,3-dioxole and a complementary amount of tetrafluoroethylene.
- 21. The method of claim 20 in which the polymer is a dipolymer containing 65-99 mole % of perfluoro-2,2-dimethyl-1,3-dioxole and having a glass transition temperature of at least 140.degree. C.
- 22. The method of claim 15 in which the polymer is a homopolymer of perfluoro-2,2-dimethyl-1,3-dioxole.
- 23. The method of claim 15 in which the gases are oxygen and nitrogen.
- 24. The method of claim 15 in which the gaseous admixture is air.
- 25. The method of claim 15 in which the gases are at least two gases selected from the group consisting of oxygen, nitrogen, hydrogen, helium, methane, ammonia, carbon monoxide and carbon dioxide.
- 26. The method of claim 15 in which the gases additionally contain water.
- 27. The method of claim 15 in which the membrane has a permeability to oxygen of at least 100 Barrers.
- 28. The method of claim 17 in which the permeability to oxygen is at least 200 Barrers.
- 29. The method of claim 17 in which the permeability to oxygen is at least 500 Barrers.
- 30. A selectively permeable membrane for the separation of gaseous mixtures comprising a film or coating of an amorphous polymer of perfluoro-2,2-dimethyl-1,3-dioxole on a porous support, said membrane exhibiting an oxygen/nitrogen selectively of at least 1.4.
- 31. The membrane of claim 30 having a permeability to oxygen of at least 100 Barrers.
- 32. The membrane of claim 31 in which the permeability to oxygen is at least 200 Barrers.
- 33. The membrane of claim 31 in which the permeability to oxygen is at least 500 Barrers.
- 34. The membrane of claim 31 in which the polymer is a copolymer of perfluoro-2,2-dimethyl -1,3-dioxole.
- 35. The membrane of claim 34 in which the polymer is a copolymer of perfluoro-2,2-dimethyl -1,3-dioxole and a complementary amount of at least one monomer selected from the group consisting of tetrafluoroethylene, perfluoromethyl vinyl ether, vinylidene fluoride and chlorotrifluoroethylene.
- 36. The membrane of claim 35 in which the polymer is a dipolymer of perfluoro-2,2-dimethyl -1,3-dioxole and a complementary amount of tetrafluoroethylene.
- 37. The membrane of claim 36 in which the polymer is a dipolymer containing 65-99 mole % of perfluoro-2,2- dimethyl-1,3-dioxole and having a glass transition temperature of at least 140.degree. C.
- 38. The membrane of claim 30 in which the membrane is monolithic membrane.
- 39. The membrane of claim 30 in which the membrane is in the form of a hollow fibre.
- 40. The membrane of claim 30 in which the film or coating and the porous support are different polymers.
- 41. The membrane of claim 30 in which the polymer is a homopolymer of perfluoro-2,2-dimethyl -1,3-dioxole.
FIELD OF THE INVENTION
This is a continuation-in-part of Application Ser. No. 07/366,400, filed 1989 June 15, now abandoned.
The present invention relates to selectively permeable membranes formed from a polymer, especially a dipolymer, of a perfluorodioxole. The membranes may be used in a variety of end-uses, two examples of which are oxygen enrichment of gaseous admixtures of oxygen and nitrogen e.g. air, and enrichment of the amount of gaseous organic compounds in admixtures with oxygen and/or nitrogen e.g. air. In embodiments, the gaseous organic compound may be a gaseous fluorocarbon or a volatile organic compound.
Methods for the enrichment and/or separation of gaseous organic compounds from gaseous admixtures, including gaseous admixtures with oxygen and/or nitrogen e.g. air, are known. For example, D. L. Roberts and G. D. Ching discuss the recovery of fluorocarbon gases using silicone rubber membranes, specifically a silicone rubber on a polysulfone backing, in I&EC Process Design and Development, 1986, 25 971. It was found that the permeability of gaseous fluorocarbons varied substantially with the structure of the fluorocarbon, with some fluorocarbons exhibiting greater permeability through the membrane than nitrogen whereas other fluorocarbons exhibited lower permeability than nitrogen. For example, whereas carbon tetrafluoride exhibited a permeability through the silicone rubber membrane that was 15 times less than that of nitrogen, the permeability of dichlorodifluoromethane i.e. the fluorocarbon available commercially as Freon.RTM. 12, was greater than that of nitrogen.
A process for the recovery and concentration of organic vapours from a stream of air containing no more than 20 000 ppm of the organic vapour is described in U.S. Pat. No. 4 553 983 of R. W. Baker et al, which issued 1985 Nov, 19. Such a process requires a selectivity for the organic vapour over air, as measured by nitrogen, of at least 50. The membrane that was exemplified was a silicone rubber membrane. Separation of organic vapours from air is also discussed by R. W. Baker et al in Journal of Membrane Science 31 (1987) 259-271.
Copolymers of perfluoro-2,2-dimethyl-1,3-dioxole, especially dipolymers with tetrafluoroethylene, are known for use as cladding materials in optical fibre constructions as well as certain electronics applications, and as moulded articles and films. Such dipolymers and uses thereof are described in U.S. Pat. No. 4 754 009 of E. N. Squire, which issued 1988 June 28, as well as in U.S. Pat. No. 4 530 569 of E. N. Squire, which issued 1985 July 23. Perfluorinated dioxole monomers and polymers are disclosed in U.S. Pat. No. 4 565 855 of B. C. Anderson, D. C. England and P. R. Resnick, which issued 1986 Jan. 21.
Films formed from polymers containing fluorine and having a ring structure in the main polymer chain are disclosed in published Japanese patent application No. 63 60 932 of Asahi Glass KK, published 1988 Oct. 27. The films have a thickness of less than 50 microns. Gas or liquid selectively permeable membranes formed from fluoropolymers having a ring structure in the main polymer chain are disclosed in published Japanese patent application No. 63 264 101 of Asahi Glass KK, published 1988 Nov. 01. The membrane that is exemplified was formed from perfluoroallyl vinyl ether and had fluxes, in cm.sup.3.cm/cm.sup.2.sec.cm Hg (Barrers), as follows: He =106; H.sub.2 =26; CO.sub.2 =8.2; O.sub.2 =3.9: N.sub.2 =0.87 and CH.sub.4 =0.24. The separation coefficients were calculated to be as follows: O.sub.2 /N.sub.2 =4.4; CO.sub.2 /CH.sub.4 =35; He/CH.sub.4 =452; He/N.sub.2 =122 and H.sub.2 /N.sub.2 =30.
A selectively permeable membrane that may be used in, for example, oxygen enrichment of gaseous admixtures containing oxygen and in the enrichment of gaseous organic compounds in admixture with oxygen and/or nitrogen e.g. air, has now been found. The membrane exhibits preferential permeability of oxygen at a high flux rate.
Accordingly, the present invention provides a selectively permeable membrane for the separation of gaseous mixtures, said membrane being formed from an amorphous polymer of perfluoro-2,2- dimethyl-1,3-dioxole and exhibiting an oxygen/nitrogen selectivity of at least 1.4.
In a still further embodiment, the membrane is a supported membrane, in the form of a film or coating on a porous support, or in the form of a hollow fibre.
The present invention further provides a membrane separation device containing a selectively permeable membrane formed from an amorphous polymer of perfluoro-2,2-dimethyl-1,3-dioxole.
In another embodiment, the membrane is a supported membrane.
In addition, the present invention provides a method for the enrichment of the amount of a gaseous organic compound in a gaseous admixture of said organic compound and at least one of oxygen and nitrogen, said method comprising:
(a) providing in a membrane separation cell a selectively permeable membrane having a feed side and a permeate side, said membrane having an oxygen/nitrogen selectivity of at least 1.4 and formed from an amorphous polymer of perfluoro-2,2- dimethyl-1,3-dioxole, and feeding said admixture to the feed side of said membrane, said membrane being at a temperature of less than the glass transition temperature of the polymer;
(b) optionally applying a pressure differential across the membrane; and
(c) removing from the feed side of the membrane, a gaseous admixture of said organic compound that is enriched in the amount of organic compound.
In a preferred embodiment of the method of the present invention, the selective permeation of nitrogen over the organic compound is at least 10:1.
In a further embodiment, the organic compound is a gaseous fluorocarbon.
In another embodiment, the organic compound is a hydrocarbon.
Furthermore, the present invention provides a method for the enrichment of the amount of a gas in a gaseous admixture with another gas, especially oxygen in a gaseous admixture of oxygen and nitrogen, said method comprising:
(a) providing in a membrane separation cell a selectively permeable membrane having a feed side and a permeate side, said membrane having an oxygen/nitrogen selectivity of at least 1.4 and formed from an amorphous polymer of perfluoro-2,2- dimethyl-1,3-dioxole, and feeding said admixture to the feed side of said membrane, said membrane being at a temperature of less than the glass transition temperature of the polymer;
(b) optionally applying a pressure differential across the membrane; and
(c) removing from the permeate side of the membrane, a gaseous admixture that is enriched in the amount of one gas.
In a preferred embodiment of the method of the present invention, the selective permeation of oxygen over nitrogen is at least 1.7:1.
In preferred embodiments of the membranes and methods of the present invention, the polymer is a copolymer of perfluoro-2,2-dimethyl-1,3-dioxole, especially a copolymer having a complementary amount of at least one monomer selected from the group consisting of tetrafluoroethylene, perfluoromethyl vinyl ether, vinylidene fluoride and chlorotrifluoroethylene.
In other embodiments, the polymer is a homopolymer of perfluoro-2,2-dimethyl-1,3-dioxole.
In further embodiment, the polymer is a dipolymer of perfluoro-2,2-dimethyl-1,3-dioxole and a complementary amount of tetrafluoroethylene, especially a dipolymer containing 65-99 mole % of perfluoro-2,2-dimethyl-1,3-dioxole and having a glass transition temperature of at least 140.degree. C.
US Referenced Citations (11)
Foreign Referenced Citations (2)
| Number |
Date |
Country |
| 0111343 |
Jun 1984 |
EPX |
| 0181850 |
May 1986 |
EPX |
Non-Patent Literature Citations (2)
| Entry |
| Roberts et al., "Recovery of Freon Gases with Silicon Rubber Membranes", Ind. Eng. Chem. Process Design Dev., 25 (1986), pp. 971-973. |
| Baker et al., "Separation of Organic Vapors from Air", Journal of Membrane Science, 31 (1987), pp. 259-271. |
Continuation in Parts (1)
|
Number |
Date |
Country |
| Parent |
366400 |
Jun 1989 |
|
Patent Grant
5051114
