Method for preparing lactide

A lactide, free technology, applied in the direction of organic chemistry, etc., can solve the problems of difficult to clean the residue in the reactor, affecting the optical purity of the product, reducing the yield of lactide, etc., to improve the output rate and the chemical purity of the product. , The effect of shortening the production cycle and reducing the viscosity

Inactive Publication Date: 2016-06-08
DONGHUA UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

During the cracking process, the viscosity of the reaction system continues to increase, resulting in slow heat transfer, and the local temperature of the system is too high, which easily leads to carbonization of the material, a decrease in the yield of lactide, and serious waste; prolonged heating at high temperature will also lead to racemization of lactide Chemical reaction, which affects the optical purity of the product; and the residue in the reactor is difficult to clean

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0026] A method for preparing lactide, the specific steps are:

[0027] (1) Add 300g L-lactic acid (labeled purity ≥ 85%) into the reactor, carry out the dehydration reaction under the pressure of 0.1MPa, 105°C, the reaction time is 2h, and receive 60g of free water.

[0028] (2) under nitrogen protection, after adding 0.48g (0.2% based on lactic acid mass percent) stannous octoate catalyst in reactor, be that 137 ℃, the condition of pressure 0.1MPa carry out polycondensation reaction debinding water at temperature, react in Under stirring conditions, the stirring speed is 100rpm, the reaction time is 3h, and the lactic acid oligomer is obtained;

[0029] (3) Add 100 mL [bmim] BF to about 190 mL of the lactic acid oligomer obtained in step (2) to remove bound water 4 As a solvent, the temperature was raised to 210°C at a rate of 5°C / min for depolymerization reaction, and the pressure was 0.02MPa. At the same time, the crude product was collected by vacuum distillation until n...

Embodiment 2

[0032] A method for preparing lactide, similar to Example 1, the difference is that the 100mL [bmim]BF added in step (3) 4 It is recovered in Example 1. If the recovered ionic liquid is less than 100ml, it will be replenished. Other experimental conditions remain unchanged.

[0033] The yield of crude lactide is 97.8%, and the purity of the lactide product after recrystallization and purification is 99.5%.

Embodiment 3

[0035] A method for preparing lactide, similar to Example 1, the difference is that the lactic acid in step (1) is 300g D-lactic acid (purity ≥ 88%), and the ionic liquid used in step (3) is 100mL [hmim] PF 6 , and other experimental conditions remained unchanged. The yield of crude lactide was 97.3%.

[0036] The purity of lactide after recrystallization and purification is 99.6%.

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Abstract

The invention provides a method for preparing lactide. The method is characterized by including the steps of firstly, performing free water-removing reaction on lactic acid; secondly, adding catalyst into the lactic acid after the free water-removing reaction to perform condensation polymerization so as to obtain lactic acid oligomer; thirdly, adding ionic liquid into the lactic acid oligomer to serve as solvent, heating to perform depolymerization, and performing reduced-pressure distillation to collect crude product; fourthly, purifying the crude product to obtain the finished-product lactide. The method has the advantages that the method is improved on the basis of an existing synthesizing process, the recyclable high-boiling-point ionic liquid is added during the depolymerization to greatly lower the viscosity of a reaction system, the lactide can be fast distilled favorably, carbonization is reduced, the yield and chemical purity of the lactide are increased evidently, purification times are reduced, the production cycle is shortened, and the method is an efficient method for preparing the high-purity lactide.

Description

technical field [0001] The invention belongs to the field of polymer material manufacture, and in particular relates to a high-yield preparation method of lactide. Background technique [0002] Polylactic acid is a green and environmentally friendly polymer material with good biocompatibility and biodegradability. It has good application prospects in engineering plastics, biomedicine, repair materials and daily necessities. The preparation methods mainly include one-step method and two-step method. One-step method is direct dehydration polycondensation of lactic acid to prepare lower molecular weight polylactic acid. The two-step method is to use lactic acid as a raw material to prepare a lactide intermediate, and then perform ring-opening polymerization of lactide to obtain polylactic acid with a higher molecular weight. At present, the two-step method is commonly used at home and abroad, but there are problems such as complex process, low purity and yield in the process ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C07D319/12
CPCC07D319/12
Inventor 常悦陈支泽
Owner DONGHUA UNIV
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