Verfahren zur Herstellung von Polyestern

摘要

Ethylene glycol esters of terephthalic acid are made by reacting terephthalic acid with ethylene oxide in the absence of an inert liquid medium or in the presence of an inert organic liquid in an amount at most equal in weight to that of the terephthalic acid. The organic liquid may be a ketone or an aromatic hydrocarbon. Preferably 1 to 2 moles of ethylene oxide are used per mole of terephthalic acid and the latter preferably has a bulk density of at least 0.6. Reaction is preferably effected at a temperature of 80-160 DEG C., a pressure of 5 to 15 kg./sq. cm. gauge and in the presence of a catalyst, e.g. a primary, secondary or tertiary amine or a salt thereof, a quaternary ammonium salt or an amide, amino acid or lactam. Suitable auxiliary catalysts are isophthalic acid and lower alkyl isophthalates. Bis-(2-hydroxyethyl)-terephthalate may also be present. Up to 15 mole per cent of the terephthalic acid may be replaced by another difunctional acid, e.g. isophthalic, sebacic, adipic or p-hydroxybenzoic acid or lower alkyl or hydroxyalkyl esters thereof. At the end of the reaction, the reaction product may be dissolved in water which is cooled to below 20 DEG C. whereby impurities are dissolved out. The glycol terephthalates are polycondensed to polyethylene terephthalate (see Division C3).