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Lactide separation and purification method

A purification method and technology of lactide, applied in the direction of organic chemistry, etc., can solve the problems of complex equipment, cumbersome operation, and high cost

Active Publication Date: 2021-03-16
WANHUA CHEM (SICHUAN) CO LTD +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

In addition, the existing melt crystallization process, especially the crystallizer, still has problems such as cumbersome operation, low processing capacity, complicated equipment, and high cost. Industrially, intermittent operations are often used, which limits the processing capacity and keeps the production cost high.

Method used

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  • Lactide separation and purification method

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0063] Use as attached figure 1 The shown separation and purification process takes L-lactide as the main product.

[0064] Step 1: Crystallization process. Use as attached Figure 6 The suspended crystallizer shown has a diameter of 270mm and a height of 3m, and is equipped with 7-stage push-up propellers. The crude lactide prepared in the reaction process is used for melt crystallization. Calculated based on the total flow rate of the crude lactide stream, the total residence time is 4 hours, where the temperature of the hot oil in the heating zone is 98°C, and the temperature of the cooling medium in the cooling zone is 70°C.

[0065] The relevant results are shown in the table below, where L-LD stands for L-lactide, m-LD stands for m-lactide, D-LD stands for D-lactide, and LA stands for lactic acid.

[0066]

Embodiment 2

[0068] Use as attached figure 1 The shown separation and purification process takes L-lactide as the main product.

[0069] Step 1: The crystallization process adopts the attached Figure 6 In the suspension crystallizer shown, the crude lactide prepared in the reaction process is used for melt crystallization. Calculated based on the total flow rate of the crude lactide stream, the total residence time is 2.5h, and the temperature of the hot oil in the heating area is 120°C. The temperature of the regional cooling medium is 50°C.

[0070] The relevant results are shown in the table below.

[0071]

[0072] Analysis of the results of Examples 1 and 2: After crystallization and purification, m-lactide, lactic acid, and oligomers in the crude lactide all decreased significantly.

Embodiment 3

[0074] Use as attached figure 1 The shown process is a separation process with L-lactide as the main product.

[0075] Steps 2 and 3: Rectification process. The rectification column is filled with 3 sections of Pro-Pak Bulletin-fillers from American POPE Company, each with a height of 50cm, and the feeding position is between the first and second packings from top to bottom, and the target product is extracted from the side line, and the extraction position is From top to bottom between the second and third sections of packing.

[0076] L-LD / % m-LD / % D-LD / % LA / % Oligomer / % Optical purity / % starting material 89.4 5.6 0.4 2.8 1.85 93.7

[0077] The operating conditions of the rectifying tower are as follows:

[0078] Oil bath / ℃ Kettle temperature / ℃ Top temperature / ℃ Reflux ratio Pressure PaA stream a rectification column 135 120 104 4:1 500 Stream b rectification column 165 150 120 4:1 500

[0...

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Abstract

The invention discloses a lactide separation and purification method. According to the method, crude lactide in a reaction process is firstly subjected to melt crystallization and then is purified through a rectification step. The process can efficiently remove acid and isomers which have remarkable influence on the downstream polylactic acid polymerization process, remarkably improve the qualityof the lactide product, reduce impurities and remarkably reduce the energy consumption and the production cost of the whole lactide separation and purification process.

Description

technical field [0001] The invention relates to the field of separation and purification of synthetic products, in particular to a method for separation and purification of lactide. Background technique [0002] Polylactic acid (PLA), also known as polylactide, is a typical biodegradable polymer material prepared by chemical synthesis from renewable plant resources. At present, the PLA global market is growing rapidly, and the annual demand will increase at a rate of 20,000-30,000 tons, and the premium can reach 20%-30%, and it is expected that the supply will be in short supply for a long time. The global plastic ban and garbage sorting have brought a huge potential market for degradable plastics, especially disposable plastic products. [0003] At present, the industrial production of PLA generally adopts the lactide ring-opening polymerization method. Lactide is the key intermediate for the synthesis of PLA, and its synthesis process and key equipment are the key directi...

Claims

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Application Information

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IPC IPC(8): C07D319/12
CPCC07D319/12Y02W30/62
Inventor 何岩田博杨颖范天熙刘英俊张红涛朱小瑞马朋成张永振乔小飞
Owner WANHUA CHEM (SICHUAN) CO LTD
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