High-purity lactide and preparation method thereof

Abstract

The invention discloses high-purity lactide and a preparation method thereof. The preparation method comprises the steps of raw material addition, free water removal, polycondensation, depolymerization, distillation and secondary distillation. The raw material addition step refers to that a catalyst is added into L-lactic acid or D-lactic acid, wherein the catalyst is one or more of zinc oxide, stannous oxide and stannous octoate. In the preparation process, the use of an organic solvent, N2 and inert gas and environmental pollution are avoided, the vacuum degree is moderate, purification loss is reduced, the production cost is reduced, and the method is suitable for industrial production. The L-lactide or D-lactide product prepared by the method is high in yield, optical purity and quality, the yield is more than or equal to 97 percent, and the optical purity of the purified lactide is 99.45 percent or above.

Description

technical field [0001] The invention relates to a high-purity lactide and a preparation method thereof, belonging to the field of fine chemicals. Background technique [0002] Polylactic acid material is a kind of bio-based degradable material. It is prepared by chemical synthesis from lactic acid fermented by microorganisms from biomass raw materials (cassava, sugar beet, straw fiber, sugarcane, etc.). Polylactic acid material products can be quickly degraded into carbon dioxide and water under composting conditions after use, and do not pollute the environment. [0003] Polylactic acid was first prepared by American scientist Nef in 1913 by direct dehydration condensation method under low pressure and high temperature conditions, commonly known as one-step method, but the molecular weight of polylactic acid prepared by this method is too small, the performance is too poor, and has no application performance. In 1932, Carothers of DuPont Company proved that high molecular ...

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Problems solved by technology

At present, ethanol, ethyl acetate, ethyl acetate and toluene are mixed for solvent recrystallization, but this method consumes a large amount of organic solvent, and it is difficult to remove it in the product, which will affect the polymerization. At the same time, it will dissolve in the solvent Some products cause product loss, increase production cost and reduce yield

[0008] Generally speaking, the preparation conditions of high-gloss pure L-lactide (or D-lactide) in China are relatively harsh: high vacuum requirements, high purity requirements for raw lactic acid, use of organic solvents for preparation or purification, N 2 , inert gas, etc., high production and processing costs, polluting the environment, and at the same time, L-lactide (or D-lactide) has low optical purity and low yield, which seriously restricts its large-scale production

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