Process for production of polyester

摘要

A process for production of a polyester comprising units of ethylene terephthalate as the major repeating units by supplying terephthalic acid and ethylene glycol continuously or intermittently to bis(beta-hydroxyethyl) terephthalate or its oligomer so as to carry out esterification under a pressure of not more than about 1.0 kg/cm2, followed by polycondensation, which is characterized in that at least one magnesium compound is incorporated into the reaction system in an amount of about 30 to 400 ppm in terms of Mg to the polyester when the esterification rate in the step of esterification reaches about 20-80% and at least one phosphorus compound is incorporated into the reaction system in an amount as satisfying the following equation (I) at the stage after the esterification rate reaches not less than about 91% and before the termination of the initial condensation in the step of esterification: 1.2