Patent ID: 9428484
Filing Date: 2016-08-30
CPC Classification: C07D

Claim Text:
1. A method for the production of cyclic esters of general formula I in which respectively R being selected, in formulae I to II, from linear or branched aliphatic radicals with 1 to 6 carbon atoms and, in formula II, the average value for n being between 2 and 40, is catalytically converted by cyclising depolymerisation into the cyclic diester of general formula I, wherein the catalyst is a tin containing catalyst, wherein the cyclic depolymerisation is implemented at temperatures between 100 and 300° C., and the thereby produced cyclic diester of general formula I is separated, the part of the oligomeric carboxylic acid of formula II, which is not converted into the cyclic diester of general formula I, is made to react to form a residue during the cyclising depolymerisation, which residue comprises a mixture of oligomeric carboxylic acids of formula II with a higher average value for n than the mixture of oligomeric carboxylic acids of formula II fed into the first step, or a mixture of oligomeric carboxylic acids of formula II with an average value for n between 1 and 20 and an alpha-hydroxycarboxylic acid of formula III, and wherein the cyclising depolymerisation of the first step is implemented until at most 98% by weight of the mixture of oligomeric carboxylic acids of formula II, which is utilized, is converted by the cyclising depolymerisation into the cyclic diester of general formula I.