Improvements relating to the production of linear aromatic polyesters

Polyesters, suitable for the manufacture of fibres and photographic film-bases, are made by reacting (a) an aqueous solution of a metal phenolate of a bis-phenol with (b) a di-acid halide of one or more of terephthalic, isophthalic and fumaric acids dissolved in a water-immiscible organic liquid which is a solvent for the polyesters formed by the reaction. The bis-phenol (a) may be partly replaced by another dihydric phenol, e.g. hydroquinone or resorcinol and the acids (b) may be partly replaced by a dicarboxylic acid having two phenylene rings as described in the parent Specification. The bis-phenol used may have the formula HO-Ar-R-Ar-OH wherein each Ar represents a para- or meta-phenylene radical or a methyl-substituted phenylene radical and R represents a direct link, an alkyl- or aryl-substituted methylene group, an alkyl- and aryl-substituted methylene group, a halogen-substituted methylene group, a halomethyl substituted methylene group, a sulphone group, a carbonyl group or a carbon atom forming part of a cycloaliphatic ring. Polyesterification is preferably effected in the presence of a quaternary ammonium compound as catalyst. The polyesters are soluble in organic solvents such as methylene chloride, chloroform, 1:2-dichloroethane, tetrachloroethane, methylchloroform, 1:1:2-trichloroethane, benzene, toluene, dioxane and tetrahydrofurane. Those of fumaric acid may be made insoluble by heating them at above 200 DEG C. or by effecting condensation in the presence of a vinyl compound. In examples, polyesters were obtained by reacting in a medium containing aqueous sodium hydroxide solution together with dioxane or methylene chloride and/or 1:1:2-trichloroethane (1)-(3) fumaroyl chloride with 1,1-(4,41-dihydroxy-diphenyl) propane, 2,2-(4,41-dihydroxy-diphenyl) butane or 1,1-(4,41-dihy droxy-diphenyl) cyclohexane; (4)-(7) isophthaloyl chloride and 2,2-(4,41-dihydroxy-diphenyl) butane, 1,1-(p,p1-dihydroxy-diphenyl)-1,1-(diphenyl) methane, 1,1-(p,p1-dihydroxy-diphenyl)-1-phenyl ethane or 2,2-(4,41-dihydroxy-diphenyl) propane; (8) isophthaloyl chloride, terephthaloyl chloride and 2,2-(4 41-dihydroxy-diphenyl) propane; (9)-(13) terephthaloyl chloride and 2,2-(4,41-dihydroxy-3,31-dimethyl-diphenyl) propane, 3,3-(4,41-dihydroxy-diphenyl) pentane, 4,41-dihydroxy-diphenyl methylphenyl methane, 1,1,1 - trichloro - 2,2 - (4,41 - dihydroxy - diphenyl) ethane or 2,2-(4,41-dihydroxy-diphenyl) propane. The polyesters may be recovered from the organic solutions thus