GB1296242A - - Google Patents

Abstract

1296242 Linear polyesters FIBER INDUSSTRIES Inc 25 Feb 1970 [26 Feb 1969 (2)] 9051/70 Heading C3R [Also in Divisions B1 and C2] Linear polyesters are prepared by (A) direct esterification of a glycol, e.g. ethylene glycol with a dicarboxylic acid, e.g. terephthalic acid in a molar ratio of 1À01 to 2À5 at 197-300‹ C. under a partial pressure above that of the partial pressure of the glycol at the reaction temperature until esterification is at least 90% complete (B), reducing the pressure and further esterifying at 197-300‹ C. until esterification is at least 95% complete and (C) polycondensing the resultant polyester to give a product having an intrinsic viscosity of at least 0À5, the process being carried out continuously with the vapours from the first esterification step recycled to the initial reactants. The dicarboxylic acid may be in particulate form and introduced into step A as a pumpable paste formed with the glycol. The polymerization is conducted (A) in a " low " polymerizer consisting of a plurality of chambers with connecting pipes from the vapour space of one to below the liquid level of the next, and (B) in a "high" polymerizer consisting of a horizontal tube fitted with a rotatable shaft carrying foraminous members such that the polyester is lifted in films and exposed to a subatmospheric pressure. The polyester product is extracted by a screw with a converging section such that the pressure is increased thus removing the volatile materials therein.