Co-production process of lactide and preparation method of polylactic acid

By controlling the conversion rate of lactic acid oligomers and the secondary depolymerization process, combined with refining and purification, the problem of low waste utilization in lactide production has been solved, achieving efficient preparation of high-purity lactide and racemic lactide, improving raw material utilization and product yield, and is suitable for preparing polylactic acid with different melting points.

CN120865140APending Publication Date: 2025-10-31ZHEJIANG NHU NYLON MATERIALS CO LTD +2
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Patent Information

Application Number
CN202410535795.X
Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
Filing Date
2024-04-30
Publication Date
2025-10-31

AI Technical Summary

Technical Problem

In the existing technology, the utilization rate of waste materials in the production process of lactide is low, resulting in low utilization rate of raw material lactic acid, low yield and optical purity of lactide products, and high process complexity.

Method used

A co-production process for lactide is adopted, which controls the conversion rate of lactic acid oligomers during the first depolymerization and carries out a second depolymerization under the action of a racemic second catalyst. Combined with a refining and purification process, high-purity lactide and racemic lactide are obtained. Their ratio is adjusted to improve the utilization rate of raw materials and the product yield.

Benefits of technology

It improves the utilization rate of raw material lactic acid and the yield and optical purity of lactide products, reduces waste discharge and treatment costs, and enables the preparation of polylactic acid products with different melting points.

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Abstract

The invention relates to a co-production process of lactide and a preparation method of polylactic acid. The co-production process comprises the following steps: dehydrating lactic acid, and carrying out polycondensation to obtain a lactic acid oligomer; a lactic acid oligomer is subjected to primary depolymerization under the action of a first catalyst, a first coarse material and a leftover material are obtained, and the conversion rate of the first coarse material formed by depolymerization of the lactic acid oligomer is 50%-90%; refining and purifying the first coarse material to obtain lactide; the leftovers are subjected to secondary depolymerization under the action of a second catalyst, a racemic second coarse material is obtained, the second coarse material is refined and purified, racemic lactide is obtained, and the second catalyst is selected from alkaline ionic liquid. According to the co-production process, the utilization rate of the lactic acid raw material and the yield and the optical purity of the lactide product are effectively improved, meanwhile, the proportion of the lactide and the racemic lactide prepared in the co-production process can be regulated and controlled, so that polylactic acid products with different melting points are obtained, and the method has a wide application prospect.
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