Process for preparing polyethylene terephthalate and its low molecular weight oligomers

摘要

A process for preparing bis(hydroxyethyl)terephthalate and its low molecular weight oligomers in a reactor equipped with a rectifying column which comprises suspending or dissolving terephthalic acid in molten bis(hydroxyethyl)terephthalate and its low molecular weight oligomers at a temperature above the dew point of ethylene glycol and feeding gaseous or liquid ethylene glycol into the suspension or the solution to react it with the terephthalic acid, where the amount of ethylene glycol fed into the reactor is controlled so as to maintain the temperature inside the rectifying column at a temperature at which the ethylene glycol does not substantially distill off from the rectifying column and the partial pressure of the ethylene glycol is maximized.