Liquid purification or separation – Processes – Liquid/liquid solvent or colloidal extraction or diffusing...
Patent
1986-12-29
1989-09-12
Thurlow, Jeffery
Liquid purification or separation
Processes
Liquid/liquid solvent or colloidal extraction or diffusing...
21050042, 21050043, 264 22, 264 41, 26433114, 26433116, 264340, 264344, 427 44, 522116, 522118, 522120, 522124, 522149, B01D 1300
Patent
active
048657433
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method for the production of solution-diffusion membranes, wherein homogeneous dense films of synthetic polymers produced by melt extrusion or casting are irradiated with accelerated electrons and thereupon submitted to a radical graft copolymerization with monomers, which contain functional groups capable of salt formation or groups which easily can be converted into groups capable of salt formation, and their application for pervaporation.
Such manufacturing methods are described by N. D. Rozenblyum et al., Khim. Vys. Energ. 8 (1974) 339, I. Ishigaki et al, Radiat. Phys. Chem. 18 (1981) 899, Y. Haruvy. A. L. Rajbenback, J. Appl. Polym. Sci. 26 (1981) 3065 and S. Shkolnik, D. Behar, J. Appl. Polym. Sci. 27 (1982) 2189. Therein grafting of polyethylene is performed with acrylic acid, styrene, acrylonitrile, 2,3-epoxypropylacrylate, Na-vinylsulfonate or p-Na-styrene sulfonate, or of nylon-6 with acryl amide, methacryl amide, hydroxyethyl acrylate, hydroxyethyl methacrylate, methacrylic acid or acrylic acid.
Besides, also the .sup.60 Co-.gamma.-initiated grafting is known.
The majority of publications on solutiondiffusion membranes for pervaporation deal with the grafting according to the simultaneous irradiation technique with .sup.60 Co-.gamma.radiation, a method suited to laboratory scale but not to technical scale production because of difficult handling (polymer film and graft monomer are simultaneously irradiated) and long duration of the graft reaction. In addition, the separation factors of the known solutiondiffusion membranes prepared by radiation-initiated graft polymerization are too small by about one order of magnitude.
Therefore, it is an object of the invention to provide solution-diffusion membranes suitable for pervaporation, having simultaneously high selectivity and permeability for one component of a mixture, e.g., water in solvent/water mixtures, and which can be prepared by a technically feasible process.
Thus the subject of the invention is a method for the production of solution-diffusion membranes, wherein homogeneous dense films produced by melt extrusion or casting from synthetic polymers are irradiated with accelerated electrons and thereupon submitted to a radical graft copolymerization with monomers, which contain functional groups capable of salt formation or groups which easily can be converted into groups capable of salt formation (e.g., esters), which is characterized by the fact that films of synthetic polymers are used, which have a melting temperature above 140.degree. C., a glass transition temperature above 0.degree. C., and long-time stability against boiling ethanol, and by means of which the functional groups of the graft polymer are converted into dissociated salts after graft polymerization.
The process of the invention is suited for performance in technical scale. The solution-diffusion membranes prepared hereby are excellently suited for the pervaporation of water-containing mixtures and have simultaneously high selectivity and permeability for water.
In accordance with the present invention synthetic polymers are used, which have a melting temperature (Fp) above 140.degree. C., preferably above 180.degree. C., and a glass transition temperature (Tg) above 0.degree. C., preferably above 15.degree. C. and particularly above 20.degree. C. or higher.
If a polymer exhibits two glass transitions, the upper glass transition temperature is meant (cf. R. F. Boyer, J. Polym. Sci., Polym. Symp. 50 (1975) 189).
In accordance with the present invention appropriate examples are polyvinyl fluoride (PVF) (Fp.about.185.degree. C.; Tg.about.45.degree. C.), polyvinylidene fluoride (PVF.sub.2) (Fp.about.170.degree. C.; Tg.about.20.degree. C.), polytetrafluoroethylene-co-hexafluoropropene (PFEP) (Fp.about.260.degree. C.; Tg.about.80.degree. C.) and polyacrylonitrile (PAN) (Fp.about.317.degree. C.; Tg.about.85.degree. C.).
In a preferred embodiment films of fluorine-containing polymers are used among which polyvinyl fluoride again is particularly p
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Rautenbach and Albrecht "membrantrennverfahren" 1981, p. 27.
"Ullmanns Enzyklopadie der Technischen Chemie", vol. 16 (1978), pp. 521 and 522.
Brueschke Hartmut E. A.
Ellinghorst Guido
Goetz Bernd
Niemoeller Axel
Scholz Horst
GFT Gesellschaft fur Trenntechnik mbH
Tentoni Leo B.
Thurlow Jeffery
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