TEREPHTHALIC ACID ETHYLENE GLYCOL ESTERS, THEIR PRODUCTION AND USE IN THE PRODUCTION OF POLYESTER POLYMERS

摘要

Terephthalic acid ethylene glycol esters solid at ambient temperature are disclosed which have a solidification point in the range of from 180 to 220.degree.C, a reduced viscosity of from 0.07 to 0.14 dl/g, a melt viscosity not higher than 250 cP,an oligomeric ester content of at least 80% by weight, a free ethylene glycol content of at most 5% by weight and an average degree of condensation of from 2.2 to 6.7. A process for the production of these esters is disclosed which requires the use of a column reactor in which transesterification of dimethyl terephthalate with ethylene glycol is carried out at elevated temperature, the reaction mixture employed passing downwardly through the column from an upper chamber in which the reactants are first provided. The transesterification product is then subjected to condensation to produce an oligomer by heating under reduced pressure in a separate chamber or chambers until a predetermined amount of glycol has been distilled off from the transesterification product. The liquid product thus obtained is allowed to impinge on a surface on which it can solidify and be obtained therefrom in for example flake or pellet form. The ester produced is particularly suitable for subsequent condensation to produce polyesters and a variety of other ester group-containing polymers.