GB1422676A - Production of polyesters - Google Patents

Abstract

1422676 Polyester resins GENERAL ELECTRIC CO 4 Oct 1973 [29 Nov 1972] 46285/73 Heading C3R A high molecular weight, linear poly (1,4- butylene terephthalate) resin is prepared by (a) heating a bis ester of 1,4-butane-diol and terephthalic acid at from 250-275‹ C. under a vacuum of from 0À1-25 mm. Hg., and removing the 1,4-butane-diol as it is formed, and continuing the heating until the intrinsic viscosity of the intermediate polyester product reaches at least 0À65 dl./g., as calculated from the measured value in a 60 : 40 mixture of phenol and tetrachloroethane at 30‹ C.; (b) adding from 0À5-3 moles of a diaryl carbonate per 100 moles of the intermediate polyester product; and (c) applying a high vacuum of from 0À01-1À0 mm. Hg. and continuing the heating until the intrinsic viscosity of the polyester product reaches at least 1À2 dl./g. Suitable diaryl carbonates are diphenyl carbonate, di-o-tolyl carbonate and di-#-naphthyl carbonate. The bis-ester is preferably prepared by reacting 1,4- butane-diol and dimethyl terephthalate at a molar ratio of at least 2 : 1 under alcoholysis conditions. Preferably the alcoholysis is carried out at atmospheric pressure and step (a) is carried out in 2 stages by (i) heating the bisester under the specified temperature and vacuum conditions only until a prepolymer which has an intrinsic viscosity of at least 0À2 dl./g. and normally solid at 25‹ C. is obtained, cooling the mixture and recovering the solid prepolymer; and (ii) remelting the solid prepolymer and heating under the conditions specified in step (a) until the intermediate polyester product is obtained. The linear polyester may comprise up to 15 mol per cent of groups derived from other glycols, e.g. ethylene glycol, 1,3-propane diol and 1,4-dimethylol cyclohexane, and/or up to 15 mol per cent of groups derived from other dicarboxylic acids, e.g. isophthalic acid, succinic acid and naphthalene dicarboxylic acid. Uses.-Moulding powders either alone or mixed with other polymers and fillers such as glass filaments, wood flour, cloth fibres and clays, as well as conventional additives.