A kind of method for preparing lactide from lactic acid oligomer

A technology of lactic acid oligomer and lactide, applied in the direction of organic chemistry and the like, can solve the problems of too high production, unfavorable production, long dehydration polycondensation time, etc., and achieves the effect of simple process

Active Publication Date: 2020-09-25
CHANGCHUN INST OF APPLIED CHEMISTRY - CHINESE ACAD OF SCI
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AI Technical Summary

Problems solved by technology

[0003] In order to reduce the free acid content in the crude lactide product, it is possible to increase the molecular weight of lactic acid oligomers, but the increase in the molecular weight of oligomers needs to greatly increase the time of dehydration polycondensation reaction of lactic acid, and in the later stage of dehydration, due to the lactic acid oligomers The sharp increase of melt viscosity, the water produced by polycondensation is not easy to remove from the system, making it difficult to make the molecular weight of the oligomer too high, and the dehydration polycondensation time is too long, which also leads to the production of L- or D-propane The content of meso-lactide in lactide products is significantly increased, which is not good for production

Method used

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  • A kind of method for preparing lactide from lactic acid oligomer
  • A kind of method for preparing lactide from lactic acid oligomer
  • A kind of method for preparing lactide from lactic acid oligomer

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0044] In the three-necked flask (5000 mL) with a magnetic stirrer and a thermometer, add 3.0 kg of L-lactic acid (the content of lactic acid is 93%), and add stannous benzoate according to 0.3 wt % of the amount of lactic acid. Dehydrate under the stirring condition of vacuum degree of -0.095~-0.1MPa, slowly raise the temperature to 160℃~170℃, and then continue dehydration at 160~170℃ for 10h to obtain lactic acid oligomers, and measure the number average of lactic acid oligomers Molecular weight (M n ) is 3984 g / mol.

Embodiment 2

[0046] The lactic acid oligomer 140g of embodiment 1 is dissolved with an appropriate amount of dichloromethane, joins in pre-dried three-necked bottle with magnetic stirrer and thermometer, and adds active compound isophorone diisocyanate (IPDI) The molar ratio of the isocyanate group (-NCO) to the oligomer is 1.90:1, and the reaction is stirred at room temperature for 8h, then most of the dichloromethane is distilled off, and the remaining dichloromethane is extracted by vacuum, heated to Keep at 180°C for 10 minutes, and crack the lactic acid oligomers under the condition of the temperature of 190°C to 210°C and the vacuum degree of -0.095 to -0.1MPa until there is no more lactide distilled out in the three-necked bottle. The lactide produced by the cracking is condensed in the tube and collected.

[0047] The obtained lactide was detected, and the content of free acid was 88ppm, and the yield of lactide was 87.4%.

Embodiment 3

[0049] According to Example 2, the difference is that the addition of active compound IPDI is that the molar ratio of isocyanate group (-NCO) to oligomer is 2.46:1, and the content of free acid in the obtained lactide is 79ppm, and the production of lactide The rate is 85.6%.

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Abstract

The invention provides a method for preparing lactide from a lactic acid oligomer, comprising: mixing and reacting a lactic acid oligomer with an active compound, and then performing a cracking reaction to obtain lactide; the active compound is capable of oligomerizing with lactic acid The organic compound that reacts with the terminal hydroxyl or carboxyl group of the compound. Compared with the prior art, the present invention utilizes the active substance to react with the terminal hydroxyl or carboxyl group of the lactic acid oligomer to increase the molecular weight of the lactic acid oligomer without affecting its cracking activity, the process is simple, and the obtained lactide The content of free acid in the medium is far less than that of lactide obtained by direct cracking of lactic acid oligomers, and the yield of lactide is equivalent to that of lactide obtained by direct cracking of lactic acid oligomers.

Description

technical field [0001] The invention belongs to the technical field of organic chemical industry, in particular to a method for preparing lactide from lactic acid oligomers. Background technique [0002] Polylactic acid (PLA) is a very promising biodegradable polymer material. The production of high-molecular-weight PLA usually adopts a two-step method: the first step is to prepare lactic acid oligomers through dehydration polycondensation of lactic acid, and the lactic acid oligomers are cracked into rings under the action of a catalyst to obtain crude lactide; Lactide is purified and polymerized to obtain high molecular weight PLA. The crude lactide prepared by cleavage of lactic acid oligomers has a relatively high free acid content, and cannot be directly polymerized into high-molecular-weight PLA. Therefore, crude lactide needs to be purified to obtain high-purity polymerization grade lactide before it can be passed Ring-opening polymerization to obtain high molecular...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C07D319/12
CPCC07D319/12
Inventor 冯立栋边新超孙彬项盛刘焱龙李杲陈学思
Owner CHANGCHUN INST OF APPLIED CHEMISTRY - CHINESE ACAD OF SCI
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