Linear polyester mfr. from ethylene glycol and terephthalic acid - by adding paste of acid and glycol to preheated glycol

摘要

In the prodn. of linear polyesters (I) by discontinuous direct esterification of HOCH2CH2OH (II) and terephthalic acid (III) in 1.1-2.0:1 molar ratio, in which (III) is added to preheated (II), the reactor contains 0.1-1.4, pref. 0.3-0.8 mole (II)/mole (III) and is heated above 200 degrees C at excess pressure, a paste of (III) with 1.9-0.6, pref. 1.4-0.9 mole (II)/mole (III) is added and esterification is carried out at 200-290, pref. 240-270 degrees C and an initial pressure of 1-15, pref. 4-8 atmos.g., which falls as the reaction proceeds. Pref. (II) with a water content of 0.1-20, esp. 2-6% is used in both cases. During esterification, additional (II) is pref. added in amts. is not 500g/gh-kg (III). Esterification can take place in the presence of a modifier. Polycondensn. is carried out in the same reactor to a degree of polycondensn. of 3-20. The process is simple, gives extremely homogeneous distribution of the reactants and results in a high space-time yield, with minimum by-prod. formation, in a short reaction time.