GB974604A - Improvements in and relating to polymers - Google Patents

Abstract

<PICT:0974604/C3/1> In a continuous process for the further polymerization of an intermediate molecular weight polyester of a dicarboxylic acid compound and an alkanediol by elimination of some alkanediol by vaporization and evacuation at elevated temperature and low pressure, the polyester is fed to an upper zone at a pressure of up to 5 cm. Hg where it flows through a series of receptacles equipped with overflows leading from one receptacle to the next and through a liquid seal into a lower zone at a lower pressure where the polyester flows as a thin film over a series of evaporative surfaces dropping from one surface to the next below. The polyester starting material has an inherent viscosity measured in a solution of 40% tetrachloroethane +60% phenol of from 0.05 to 0.4 and the material recovered at the bottom of the lower zone has an inherent viscosity at least 0.2 greater. The temperature should not exceed 350 DEG C. The polyester enters a heated upper zone at line 48 (Fig. 2), drops on to a tray 50, passes through an overflow pipe 52 to a tray 54, through an overflow pipe 56 and through a liquid 58 into a heated lower zone. The upper zone is maintained at a reduced pressure by a pump attached to line 62 and the lower zone is maintained at a lower pressure by a pump attached to line 80. In the lower zone the polyester flows over a series of plates 66 and is removed at a line 68. In examples polyesters prepared from dimethyl terephthalate, 1,4-cyclohexanedimethanol, dibutyl glutarate, dibutyl isophthalate, ethylene, glycol and dimethyl isophthalate, are further polymerized.