Patent GB-588833-A (GB)
Title: Preparation of linear polyesters
IPC: C08G63/692
Filed: 1944-08-21
Abstract: In forming polyesters of high molecular weight (above 5000) and unit chain length of at least 7 from one or more dicarboxylic acids and one or more dihydric alcohols, the reaction is performed at 150-300 DEG  C. preferably under reduced pressure in presence of less than .004 gm-mol./kgm. of polyester, of a compound selected from the group consisting of phosphorous acid, its alkyl or aryl esters or inorganic salts, and the alkyl or aryl esters of thio-phosphorous acid, said compound being added initially to the polyester-forming reactants or to a monomeric ester formed therefrom.  Suitable dihydric alcohols are ethylene, trimethylene, propylene, butylene, hexylene, octylene, dodecylene, 2,2-dimethyl trimethylene, diethylene, or tetraethylene glycol, the cyclohexanediols, 1,2-di-b -hydroxyethyl benzene, di-b -hydroxyethoxybenzene, 2,2-(di-b -hydroxyethoxyphenyl) propane, xylylene glycols, b -thiodiglycol.  The use of branched chain glycols gives polymers free from crystallinity.  Suitable dicarboxylic acids are oxalic, succinic, glutaric, a -methyl glutaric, a  - ethyl glutaric, adipic, b  - methyl adipic, pimelic, suberic, azelaic, sebacic, brassilic, tetradecanedioic, paraphenylene diacetic, phthalic, terephthalic, hexahydroterephthalic, isophthalic, diglycollic, thiodibutyric or diphenic acid or 2,2-dicarbomethoxyphenyl propane.  Unsaturated acids, e.g. maleic, fumaric, or dihydromuconic may be used particularly in mixtures. Acid anhydrides may be used, or a salt of the acid may be reacted with a dihalogen compound corresponding with the dihydric alcohol. Suitable stabilizers are triphenyl, tricresyl, tritert.-butylphenyl, trioctylphenyl, trinaphthyl, tri-, di- or mono-phenoxyethyl, tert.-butylphenoxyethyl, trimethyl, triethyl, tributyl, tricapryl, dibutyl, dioctyl, butyl, dodecyl, amyl, dicyclohexyl, benzyl, methylbenzyl, amyl phenyl, glycol, glyceryl, or methyl glyceryl phosphites, phosphorous acid, or inorganic salts thereof.  The reaction may be initiated under reflux condenser, if desired with a solvent such as xylene, or high-boiling petroleum solvent to aid removal of water, and continued under reduced pressure.  Acidic catalysts and an inert atmosphere may be employed.  According to the examples: (1) a polyester from sebacic acid and ethylene glycol in presence of zinc chloride is stabilized with triamyl phosphite and compared with a similar one prepared without its use; (2) is similar to (1) with triphenyl phosphite as stabilizer; (3) a viscous liquid polyester is prepared from succinic acid, maleic anhydride, propylene glycol and ethylene glycol in presence of tricresyl phosphite.  Mixed with sulphur and pigments it could be vulcanized to a rubbery solid; (4) is similar to (3), but uses zinc chloride as a catalyst and the initial refluxing is performed in presence of xylene; (5) and (6) are similar to (4); (7) a polyester from phthalic anhydride, sebacic acid, maleic anhydride and ethylene glycol in presence of zinc chloride is stabilized with triphenyl phosphite; (8) a polyester from succinic acid, sebacic acid, fumaric acid, ethylene glycol, and propylene glycol in presence of zinc chloride is stabilized with tricapryl phosphite; (9) a polyester from sebacic acid and 2,2-dimethyl trimethylene glycol in presence of zinc chloride is stabilized with triphenyl phosphite; (10) a polyester from sebacic acid, maleic anhydride, propylene glycol and ethylene glycol in presence of zinc chloride is stabilized with phosphorous acid.  The products may be cured with agents such as benzoyl peroxide or butyl hydroperoxide to rubbery-like solids which are suitable for use in engine connections, for gaskets or diaphragms, for flexible tubing and couplings used in hydraulic lines in aircraft. Specifications 510,899 and 588,834 are referred to.  The Specification as open to inspection under Sect. 91 includes the use of a trivalent phosphorus compound as the stabilizer and mentions alkylamine phosphites, arylamine phosphites, phosphorus trichloride, phosphorus trioxide, phosphorus bromide, phosphorus sulphide, esters of the form (RO)2PCl or (RO)PCl2, an aliphatic, aromatic, alicyclic or heterocyclic phosphine, including primary, secondary, tertiary or halogen substituted phosphines, phosphinous acid or its derivatives such as RPHO(OH), where R is a hydrocarbon radical.  This subject-matter does not appear in the Specification as accepted.