Solid state polymerization method for preparing polylactic acid

Abstract

The invention relates to a solid phase polymerization method used for preparing polylactic acid. Low molecular weight lactic acid is taken as starting raw material, is heated to the final temperature from the starting temperature under the condition of vacuum or inertia atmosphere by the constant temperature rise, the staggered temperature rise or the combination way of the constant temperature rise and the staggered temperature rise and performs the solid phase polymerization reaction under one solid phase polymerization temperature or a plurality of solid phase polymerization temperatures. The invention inhibits the production of lactide and prevents preformed polymer from being melted by adjusting the constant temperature rise and the staggered temperature rise. The method effectively enhances the reaction efficiency by the control of the limiting temperature, has quick polymerization speed, has little subsidiary product such as the lactide after the reaction, and has high productive rate, simple equipment and lower cost.

Description

technical field [0001] The invention belongs to the field of macromolecular materials, and in particular relates to a method for preparing high-molecular-weight polylactic acid by a solid-phase polymerization method. Background technique [0002] With the development of science and society, people pay more and more attention to environmental and resource issues and become global issues. Petroleum-based plastic materials are widely used, and such materials are difficult to recycle after use, resulting in a relatively serious "white pollution" problem; moreover, resources such as petroleum are non-renewable resources, and a large number of unreasonable uses have brought human There is a serious shortage of resources. The emergence of degradable materials, especially the recyclability of raw materials for degradable materials, provides an effective means to solve this problem. [0003] Polylactic acid (PLA) is a degradable material that has been researched and applied relativ...

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Problems solved by technology

[0024] However, so far, there are still many problems to be overcome in the process of preparing polylactic acid by direct method melting + solid phase polymerization, such as: the amount of lactide produced in the reaction is large, resulting in too low yield; the polymerization time is too long and the efficiency Not high; the prepolymer powder is prone to sticking during solid-state polymerization, making it difficult to remove water, affecting the increase in molecular weight and product quality

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