Verfahren zur Aufarbeitung von Dihydroxyverbindungen enthaltenden Rückständen

摘要

The invention concerns a process for preparing residues which contain dihydroxy compounds and occur during the production of polyesters, in that: a) in a first step, a dicarboxylic acid or its ester or esterifying derivatives are esterified or transesterified with a molar excess of a dihydroxy compound; b) in at least a second step, the esterification product obtained in a) is polycondensed; and c) the vapours occurring during the reactions according to a) and b) are subjected to a treatment for recovering the starter substances. The invention is characterized in that: 1) the vapour occurring in step a) and some of the vapour of step b) of the process are combined in at least one column (A), the low-boiling components of the vapours are separated at the top and the base product, which predominantly contains the excess dihydroxy compounds and oligomer and polymer reaction products, is returned to step a); and 2) the other vapour portion of step b) of the process is transferred to at least one column (B), the low-boiling components of the vapours are separated at the top and the base product is discharged from the column and subsequently subjected to a further treatment for recovering the dihydroxy compound.