VALORISATION OF D-LACTIC ACID STREAM BY L/D SEPARATION IN THE PRODUCTION PROCESS OF L-POLYLACTIC ACID

• Main Authors: COSZACH, Philippe, MORLOT, Julien
• Format: Patent
• Language: English; French; German
• Published: 03.07.2024
• Subjects: ACYCLIC OR CARBOCYCLIC COMPOUNDS; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F,C08G; CHEMISTRY; COMPOSITIONS BASED THEREON; GENERAL PROCESSES OF COMPOUNDING; MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONSONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS; METALLURGY; ORGANIC CHEMISTRY; ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; WORKING-UP

The present invention discloses a valorisation method of a flux containing undesired D-lactic acid (ester(s)) in the production process of L-polylactic acid, the production thereof comprising: oligomerisation (30) of a substantially pure L-lactic acid; cyclisation (40) of the lactic acid oligomers, thereby obtaining lactides and a first residual stream transferred, at least partially, to a transesterification (80) and a hydrolysis (90) step; lactide purification (50), thereby obtaining purified lactides comprising L-lactide and meso-lactide, a second and a third residual stream, wherein the second residual stream is transferred, at least partially, to the oligomerisation (30) step and the third residual stream is transferred, at least partially, to a transesterification (80) and a hydrolysis step (90); polymerisation (60) of the purified lactides into polylactic acid; purification (70) of the polylactic acid, thereby obtaining purified polylactic acid comprising substantially L-polylactic acid and unreacted L-lactide, unreacted meso- lactide and impurities transferred, at least partially, to the lactide purification step (50); transesterification (80) and hydrolysis (90) of the at least partially transferred first and third residual streams, thereby obtaining a fourth and a fifth residual stream, wherein the lactic acid of the fourth residual stream and the one or more lactic acid esters of the fifth residual stream are subjected to (a) concentration (100) and optionally distillation (105), thereby obtaining a concentrated lactic acid solution having a total acid content of at least 90% by weight and a content of monomeric lactic acid of at least 80% by weight based on the total weight of the concentrated lactic acid solution; (b) crystallization (110) of the concentrated lactic acid solution, thereby obtaining crystallized L-lactic acid with a higher chiral purity, and a sixth residual stream.