A process for the purification of crude dimethyl terephthalate which has been recovered by the depolymerisation of polythylene terephthalate

摘要

A process for the purification of crude dimethyl terephthalate which has been recovered by the depolymerisation of polyethylene terephthalate by heating the polyethylene terephthalate in the presence of methanol at a temperature of substantially 200 DEG C. and a pressure of substantially 40 atmospheres, comprises crystallising the crude ester while hot in a first stage in the presence of methanol at a temperature of from 58 DEG C. to 50 DEG C. until at least 50% of the dimethyl terephthalate contained in the crude ester has precipitated, continuing the crystallisation at a temperature of 48 DEG C. until no more. dimethyl terephthalate precipitates, separating the resulting crystal magma at a temperature of at least 27 DEG C. and immediately centrifuging the separated crystal magma. An example is furnished.