Verfahren zur Herstellung von linearen omega-Hydroxycarbonsäureeinheiten enthaltenden Copolyestern

摘要

The prodn. of linear copolyesters (I) contg. omega-hydroxy-carboxylic acid ( omega -OHCA) units from polyesters (II) contg. at least 90 mole% polyethylene terephthalate (PET) units, normal amts. of diethylene glycol (DEG) units and opt. catalysts and stabilisers, comprises (a) intensively mixing the polyester melt (II) with up to 10 mole% lactone(s) and opt. other additives, but without adding more catalyst, for less than 30 mins. at 265-310 degrees C at a pressure higher than the lactone vapour pressure, in a gastight system consisting of a tube fitted with an inlet and a downstream mixer, and (b) working up, discharging or granulating and then further processing the prod. to give (I) with a statistical distribution of omega -OHCA units and a viscosity equal to that of (II). Also claimed are post-condensed linear copolyesters with statistically-distributed omega -OHCA units (I) obtd. by this process.