Continuous polymerization devolatilization method and device for polylactic acid

Abstract

The invention discloses a polylactic acid continuous polymerization devolatilization method and device, and the method comprises the following steps: a polylactic acid melt from a lactide polymerization system firstly enters a falling film evaporation heater at the upper part of a devolatilization reaction device which is vertically arranged, and the melt is heated; low-boiling-point substances and lactide gas generated in the devolatilization reaction process are changed into lactide liquid after passing through a condensing device, and the lactide liquid flows back to the lactide buffer tank; non-condensable gas and low-boiling-point substances are sucked into a vacuum buffer tank to be further condensed and crystallized, and are discharged into a sewage system under the action of spraying water; and the devolatilized polymer melt is extruded to an inlet of the devolatilization discharging pump by the devolatilization device screw, is mixed with the modified additive from the additive feeding screw, and is conveyed to a granulation system by the devolatilization discharging pump. The chemical components of the polylactic acid melt are distributed more uniformly, the expected effect can be achieved by stirring for 30 minutes under the normal condition, and the problems of crystallization, carbonization, melt wall hanging and the like are effectively avoided.

Description

technical field [0001] The invention belongs to the technical field of chemical production equipment, and in particular relates to a method and a device for continuous polymerization and devolatilization of polylactic acid. Background technique [0002] Polylactic acid is a polymer obtained by polymerizing lactic acid as the main raw material. The raw materials are mainly plant straw and corn starch. The source is sufficient and the product is biodegradable. It is very friendly to the environment and is an ideal green polymer material. The process usually uses industrial-grade L-lactic acid to dehydrate under high temperature and high vacuum to undergo esterification to generate linear dimer lactic acid-based lactic acid, and further dehydration and condensation reaction to generate high molecular weight lactic acid oligomers and lactide. , and then depolymerize and degrade the high molecular weight oligomer to generate lactide, and the crude lactide after depolymerization i...

AI Technical Summary

Problems solved by technology

The reaction generally takes place in a horizontal stirring reaction device. In this type of equipment, the molecular weight of the product is difficult to further increase after the melt polycondensation of the material reaches a certain stage. The material is prone to uneven heating, thermal oxidation degradation and other side reactions, and the residence time distribution is wide.

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