| 摘要 |
A continuous polycondensation apparatus comprises a vertical column (52) containing upper and lower tube sets (62, 78) providing surfaces over which condensing material flows as a thin film, said tube sets having associated distributors (56) and weirs (60, 76) at the upper parts thereof; a heat exchanger positioned between the inlet at the top of the column and the outlet in the lower portion; and a vacuum pump to reduce the pressure therein. As illustrated in the Fig. (not shown) a polymethylene glycol ester of dimethylterephthalic acid is passed from reactor 36 of the kind claimed in Specification 1,039,233 [Also in Division B1] through line 58 into the upper part of the precondensation apparatus 52, where it flows over baffle 56 and is directed over weirs 60 into tubes 62 down which it flows as a thin film. Heat exchange medium is passed round the outside of said tubes to provide a temperature of 180-210 DEG C. Thereafter the product flows on to a second baffle 56 and into similarly arranged tubes 78 heated to 240-280 DEG C. and is finally passed to finisher 86 which is connected to vacuum line 92. Excess ethylene glycol is recovered by passing the vapour effluent through bubble cap column 75 (removing any terephthalate) to condenser 70, connected to vacuum line 74. |
