(EP444690-A3)      New gas separation membrane comprises a thin layer consisting mainly of a polyester or copolyester deriving from the reaction of an aromatic dicarboxylic acid or derivative and 50% mole or more of tetrabromobisphenol A (I). The dicarboxylic cpd. comprises (a) isophthalic acid or its dichloride and/or 4 bromoisophthalic acid or its dichloride and (b) terephthalic acid or its dichloride and/or 2 bromoterephthalic acid or its dichloride and the molar ratio of iso/tere dicarboxylic cpds. is 80/20 to 20/80, pref. 30/70 to 20/80.    The (co)polyester can derive from aromatic dicarboxylic acid or derivative and a mixt. of diols comprising 50% mole or more of tetrabromobisphenol A (I) and 50% mole or less of another bisphenol, pref. 4,4(2,2,2trifluoro-1(trifluoromethyl -ethylide bis(2,6-dibromophenol).    USE -   /ADVNTAGE - The membrane has exceptional gas separation properties e.g. O2/N2, CO2/CH4 and He/CH4 and has enhanced O2, CO2 and He permeabilities. It is useful for the selective permeation of one component from a gas mixt. @(14pp Dwg.No 0/0)@    (RU2026727-C1)      New gas separation membrane comprises a thin layer consisting mainly of a polyester or copolyester deriving from the reaction of an aromatic dicarboxylic acid or derivative and 50% mole or more of tetrabromobisphenol A (I). The dicarboxylic cpd. comprises (a) isophthalic acid or its dichloride and/or 4 bromoisophthalic acid or its dichloride and (b) terephthalic acid or its dichloride and/or 2 bromo-terephthalic acid or its dichloride and the molar ratio of iso/tere dicarboxylic cpds. is 80/20 to 20/80, pref. 30/70 to 20/80.    The (co)polyester can derive from aromatic dicarboxylic acid or derivative and a mixt. of diols comprising 50% mole or more of tetrabromobisphenol A (I) and 50% mole or less of another bisphenol, pref. 4,4(2,2,2-tri-fluoro-1(trifluoromethyl -ethylide bis(2,6-dibromophenol).    USE/ADVANTAGE -   The membrane has exceptional gas separation properties e.g. O2/N2, CO2/CH4 and He/CH4 and has enhanced O2, CO2 and He permeabilities. It is useful for the selective permeation of one component from a gas mixt.    (JP95114936-B2)      New gas separation membrane comprises a thin layer consisting mainly of a polyester or copolyester deriving from the reaction of an aromatic dicarboxylic acid or derivative and 50% mole or more of tetrabromobisphenol A (I). The dicarboxylic cpd. comprises (a) isophthalic acid or its dichloride and/or 4 bromoisophthalic acid or its dichloride and (b) terephthalic acid or its dichloride and/or 2 bromoterephthalic acid or its dichloride and the molar ratio of iso/tere dicarboxylic cpds. is 80/20 to 20/80, pref. 30/70 to 20/80.    The (co)polyester can derive from aromatic dicarboxylic acid or derivative and a mixt. of diols comprising 50% mole or more of tetrabromobisphenol A (I) and 50% mole or less of another bisphenol, pref. 4,4(2,2,2trifluoro-1(trifluoromethyl -ethylide bis(2,6-dibromophenol).    USE/ADVANTAGE -   The membrane has exceptional gas separation properties e.g. O2/N2, CO2/CH4 and He/CH4 and has enhanced O2, CO2 and He permeabilities. It is useful for the selective permeation of one component from a gas mixt.