PROCESS FOR PREPARING CYCLIC DIESTERS, ESPECIALLY DILACTIDE

摘要

The present invention relates to a process for preparing cyclic carboxylic esters, especially intramolecular lactones, for example dilactide, wherein these cyclic esters are prepared from oligomeric carboxylic acids by cyclizing depolymerization. The reaction gives, as a by-product, a condensation product of these oligomeric carboxylic acids, i.e. a mixture of high molecular weight oligomeric carboxylic acids, which are hydrolysed in a further step and thus recovered. This hydrolysate can be added again to the cyclizing depolymerization conducted in the first stage.