(US5165963-A)      Mfg. a composite F-contg. polyimide membrane comprises coating a support material with a fluorine-contg. polyimide resin consisting mainly of repeating units of formula (I), with a first organic solvent compatible with water.    In (I), R1 = divalent aromatic, alicyclic or aliphatic hydrocarbon gp., or a divalent organic gp. comprising divalent aromatic, alicyclic or aliphatic hydrocarbon gps. bonded to each other by a divalent organic bonding gp.. The material is, then, dipped in a second organic solvent in which the resin is insoluble, but which is compatible with the first organic solvent and water. Finally, the material is dipped in water, whereby a fluorine-contg. polyimide supporting film having an anisotropic structure is formed on the material. A thin film of an elastomeric polymer is then formed on the supporting film.    USE/ADVANTAGE -   The membranes have high gas permeability and selectivity as well as good heat and chemical resistances, and mechanical strength.    (US5178940-A)      A composite fluorine-contg. polyimide membrane comprises (I) a supporting film of a fluorine-contg. polyimide resin consisting mainly of repeating units of formula (II) and a thin film of an elastomeric polymer formed on the supporting film. (In (II), R' = a divalent aromatic, alicyclic or aliphatic hydrocarbon gp., or a divalent organic gp. comprising divalent aromatic, alicyclic or aliphatic hydrocarbon gps. bonded to each other by a divalent organic bonding gp.).    USE/ADVANTAGE -   The composite has high gas permeability and selectivity as well as good heat and chemical resistances and mechanical strength. It finds use for gas sepn..    (US5391219-A)      The sepn. and concn. of gases comprises bringing a mixt. of two or more gases into contact with a composite F-contg polyimide membrane comprising a supporting film of a F-contg polyimide resin consisting of repeating units of general formula (I), and thin film of an elastomeric polymer formed on the supporting film, so that a particular component of the mixt. may selectively be allowed to pass through the membrane. R1 is a divalent alicyclic hydrocarbon gp., a divalent aliphatic hydrocarbon gp. or gps. of formulae in (II).    Pref. the mixt contains CO2 and membrane and the CO2 is allowed to pass through the membrane while the methane is concd. Most pref. the mixt. contains steam, and oxygen or nitrogen or air and the steam is allowed to pass through the membrane and is concd.    ADVANTAGE -   The membrane is highly selective.    (EP509260-B1)      Membrane comprises (a) a supporting film of a fluorine-contg. polyimide resin of formula (I) where R1 is divalent aromatic, alicyclic or aliphatic hydrocarbon, or a divalent gp. consisting of hydrocarbon gps. e.g. gps.(i)-(iii) bonded to each other by the divalent gp.; and (b) a thin film of an elastomeric polymer formed on (a).    Also claimed are: (1) prepn. of the described membranes by coating a supporting material with the resin of formula (I), and with a solvent compatible with H2O; dipping the material in a further solvent in which the resin is insol. but compatible with the first solvent and H2O; dipping the material in H2O to form a supporting film having an anisotropic structure; and forming a thin elastomeric polymer film on the supporting film.    USE/ADVANTAGE -   Useful for the sepn. of CO2 and CH4 to concentrate CH4, while allowing CO2 to pass, or for removing steam from oil. The membrane has high gas permeability and selectivity, as well as good heat and chemical resistances and mechanical strength.    .D