| abstract |
A process is described for producing a high molar mass polylactic acid, which comprises the following steps: a) polycondensation in a reactor (R1) of a lactic acid solution, by heating in the form of temperature gradients and under controlled pressure, resulting in a polylactic acid oligomer within the range of 300 to 5000 g/mol; b) conversion, in reactor (200), of the polylactic acid of low molar mass obtained in step a) to a lactide, in the presence of a depolymerization catalyst; c) separation of the volatile fractions; d) recrystallization of the lactide in the vessel (R3), in order to obtain ethanol; e) polymerization, in a tube reactor (300), of the recrystallized lactide obtained in step d), via ring opening in the presence of the catalyst, producing a high molar mass polylactic acid; f) devolatilization, at (400), of the polymeric mass obtained in step e); and g) recovery of the final polylactic acid product with a high degree of purity, with a molar mass of between 50 000 and 200 000 g/mol and a reaction conversion of between 70% and 95%. Also described are the depolymerization reactor (200), polymerization reactor (300) and devolatilization reactor (400) used in the process of the invention. |