METHOD FOR OBTAINING POLYHYDROXYCARBOXYLIC ACID Russian patent published in 2016 - IPC C07D319/12 C08G63/08 B01D9/00 B01D9/02 B01D9/04 

FIELD: chemistry.

SUBSTANCE: invention relates to method for obtaining polylactic acid and device for said method realisation. Method includes the following stages: realisation of polymerisation with ring opening with application of catalyst and either catalyst deactivator compound or additive, blocking terminal groups, to obtain non-purified polylactic acid with molecular weight higher than 10000 g/mol. After that method includes stage for purification of non-purified polylactic acid by removal and separation of low-boiling compounds, including lactide and admixtures, from non-purified polylactic acid, by removal of volatile low-boiling compounds in form of gas-phase flow. Further, follows stage of purification of lactide from stage of removal of volatile components, and removal of admixtures from gas-phase flow of evaporated low-boiling compounds by condensation of evaporated gas-phase flow with obtaining condensed flow and further crystallisation from melt of condensed flow. Lactide is purified, and admixtures, which include catalyst residue and compound, which contains at least one hydroxyl group, are removed so that purified lactide is polymerised by its resupply into ring opening polymerisation.

EFFECT: provision of improved method for obtaining polylactic acid with increased product output in comparison with known level of technology, with reduction of equipment, required for inert gas processing.

13 cl, 2 tbl, 10 dwg, 2 ex