CN100528860C - Method for lactide recrystallization using gradient concentration style - Google Patents

Method for lactide recrystallization using gradient concentration style Download PDF

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CN100528860C
CN100528860C CNB2005100953376A CN200510095337A CN100528860C CN 100528860 C CN100528860 C CN 100528860C CN B2005100953376 A CNB2005100953376 A CN B2005100953376A CN 200510095337 A CN200510095337 A CN 200510095337A CN 100528860 C CN100528860 C CN 100528860C
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lactide
rac
solution
quality concentration
crystallization
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CN1763034A (en
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刘晓宁
魏荣卿
魏军
刘迎
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Nanjing Tech University
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Abstract

The present invention is lactide re-crystallizing process with gradiently change solution mass concentration. The process includes dissolving coarse lactide product in solvent, changing the mass concentration of the solution gradiently for multiple times of re-crystallization to obtain high purity crystallized product ultimately. The process features the first high mass concentration solution for initial re-crystallization in high yield and the subsequent low mass concentration solution for subsequent re-crystallization in high purity. The process can obtain both high product purity and high product yield.

Description

A kind of method of utilizing gradient concentration style to carry out lactide recrystallization
Technical field
The present invention relates to a kind of purification process of cyclic ester class organic compound.Specifically, a kind of exactly crude lactide that makes gives preliminary recrystallization with high quality concentration solution earlier in the process of recrystallization, obtain high yield; By the crystallization of inferior quality concentration solution weight, obtain highly purified purification process again.
Background technology
Rac-Lactide is a kind of cyclic ester that is generated by two molecule lactic acid, has four kinds of forms: the L-rac-Lactide that two molecule L-lactic acid forms; The D-rac-Lactide that two molecule D-lactic acid form; The Study of Meso-Lactide that a part L-lactic acid and a part D-lactic acid form; And the rac-lactide of L-rac-Lactide and the formation of D-rac-Lactide.Rac-Lactide is a kind of important compound that can be used for preparing poly(lactic acid) and multipolymer thereof.
As everyone knows, poly(lactic acid) and multipolymer thereof are as Biodegradable material, and have two big outstanding advantages: its raw material---lactic acid can be obtained by fermentation, belongs to renewable resources; Its finished product can be become carbonic acid gas and water by microbiological degradation, reach degraded fully, can not produce environment and pollute.Therefore, the research of relevant polylactic acid-based material causes extensive concern.
High molecular weight polylactic acid is normally obtained by highly purified rac-Lactide ring-opening polymerization.Usually, rac-Lactide by aqueous lactic acid through low molecular weight as intermediate, obtain by the cracked method again.Patent CN1212343, CN1369490, AU2003231482, DE3232103, DE3708915, FR2843390, JP63101378, JP2004149418, US1095205, US5053522, US2002132967 etc. have introduced the building-up process of rac-Lactide.
In the rac-Lactide that above-mentioned patented method obtains, also contain impurity (rac-Lactide that hereinafter will contain these impurity is called crude lactide) such as a small amount of lactic acid monomer, lactic acid dipolymer (lactyllactic acid) and water.
Contained above-mentioned impurity can have a negative impact to the polyreaction of rac-Lactide: the existence of water can make the rac-Lactide hydrolysis obtain lactic acid, and can make polylactic acid molecule chain hydrolytic cleavage; The existence of acid such as lactic acid and dimer thereof can make the polylactic acid molecule chain be degraded etc. because of acidolysis.Therefore, crude lactide need be through purifying to remove the impurity that it contains.
The purification process of crude lactide generally has evaporation method of air aided, hydrolysis method and recrystallization method etc.
Evaporation method of air aided can make such as rac-Lactide or glycollide or and composition thereof cyclic ester be separated with impurity as the steam component in the air-flow.Relevant patent has AU2003295252, US5274073, US6277951 etc.But evaporation method of air aided sepn process complexity, and yield is generally not high.
Thereby hydrolysis method is a kind of method that mesoisomer obtains the high-optical-purity rac-Lactide of removing from crude lactide, and relevant patent has CN1112559, JP10025288, US5502215 etc.But after the hydrolysis treatment, generally still need recrystallization to be further purified.
And recrystallization method is few because of its operation steps, technology is used comparatively extensive than maturation.Patent CN1488628, FR2843390, WO9315069 etc. introduce recrystallization method purifying rac-Lactide.But the research for recrystallization method purifying rac-Lactide mostly is choice of Solvent greatly at present, adopt ethyl acetate, JP10279577 to adopt lower member ester class, US6313319 to use alcohols, JP6279435 application lower alcohol, ketone, ester class or its mixture etc. as patent US4727163, CN1583740, and the influence factor of lactide recrystallization technology is not studied.
In fact, for a certain solvent (be as a kind of or total carbon atom number in the alcohols of C1~C4 in the ester class of C2~C6 a kind of), under the different condition of solution quality concentration, solution quality concentration is low more, its crystallized product purity is high more, but corresponding yield is low more; Though and the concentration that improves the quality can reach high yield, purity is relatively poor, needs to increase the crystallization number of times and obtains highly purified product.This patent is in the repeatedly recrystallization process of rac-Lactide, utilize gradient control break mass concentration recrystallization method promptly: crystallization obtains the high yield of product in high quality concentration solution earlier, crystallization obtains the high purity of product in inferior quality concentration solution again, finally can be under identical recrystallization time said conditions, when obtaining highly purified crystallized product, improve the recrystallized product yield.
Summary of the invention
Purpose of the present invention i.e. technology by the mass concentration of the rac-Lactide solution of different recrystallization number of times is carried out gradient control, and making increases the crystallized product yield when improving product purity under identical recrystallization time said conditions.
Purpose of the present invention can reach by following measure:
A is dissolved in crude lactide a kind of or total carbon atom number in the alcohols of C1~C4 and is a kind of in the ester class of C2~C6 under 50 ℃~95 ℃, obtain crude lactide solution, and the mass concentration of control solution is in a higher scope.
B is cooled to 0 ℃~30 ℃ with solution, and the rac-Lactide crystallization is separated out and filtration drying, obtains the rac-Lactide crystal.
C repeats above-mentioned two step operations, but reduces the mass concentration of the rac-Lactide solution of being controlled, and obtains secondary or the rac-Lactide crystal behind the recrystallization repeatedly.
In further of the present invention, along with the increase of crystallization number of times, the mass concentration of the rac-Lactide solution that a back recrystallization is controlled should be lower than the mass concentration of rac-Lactide solution last time.
When solvent was selected a kind of in the alcohols of C1~C4, the variation range of its mass concentration of rac-Lactide solution of high quality concentration was 50%~120%, preferred mass change in concentration scope 70%~100%; The variation range of its mass concentration of rac-Lactide solution of inferior quality concentration is 15%~55%, preferred mass change in concentration scope 25%~50%.
Solvent is selected total carbon atom number when being a kind of in the ester class of C2~C6, and the variation range of its mass concentration of rac-Lactide solution of high quality concentration is 150%~210%, preferred mass change in concentration scope 170%~200%; The variation range of its mass concentration of rac-Lactide solution of inferior quality concentration is 40%~90%, preferred mass change in concentration scope 50%~75%.
Advantage of the present invention: the method for carrying out lactide recrystallization by gradient concentration style is promptly controlled the mass concentration of the rac-Lactide solution of different recrystallization number of times in the recrystallization process, can effectively improve the yield and the purity of crystallized product simultaneously.
Embodiment
Embodiment 1
Getting the 20.0g crude lactide, is solvent with methyl alcohol, adopts successively decrease mode recrystallization three times of solution quality concentration gradient, the solution quality concentration of each recrystallization and the results are shown in Table 1.
Table 1
Figure C20051009533700051
Embodiment 2
Getting the 20.0g crude lactide, is solvent recrystallization three times with ethanol, adopts successively decrease mode recrystallization three times of solution quality concentration gradient, the solution quality concentration of each recrystallization and the results are shown in Table 2.
Table 2
Embodiment 3
Getting the 20.0g crude lactide, is solvent with ethanol, adopts shift gears recrystallization three times of solution quality concentration, the solution quality concentration of each recrystallization and the results are shown in Table 3.
Table 3
Figure C20051009533700053
Embodiment 4
Getting the 20.0g crude lactide, is solvent with ethanol, adopts the solution weight crystallization three times of different mass concentration, the solution quality concentration of each recrystallization and the results are shown in Table 4.
Table 4
Figure C20051009533700061
Embodiment 5
Getting the 20.0g crude lactide, is solvent with the Virahol, adopts the solution quality concentration gradient to reduce the mode recrystallization three times, the solution quality concentration of each recrystallization and the results are shown in Table 5.
Table 5
Figure C20051009533700062
Embodiment 6
Getting the 20.0g crude lactide, is solvent with the methyl acetate, adopts successively decrease mode recrystallization three times of solution quality concentration gradient, the solution quality concentration of each recrystallization and the results are shown in Table 6.
Table 6
Figure C20051009533700063
Embodiment 7
Getting the 20.0g crude lactide, is solvent with the ethyl acetate, adopts successively decrease mode recrystallization three times of solution quality concentration gradient, the solution quality concentration of each recrystallization and the results are shown in Table 7.
Table 7
Figure C20051009533700064
Embodiment 8
Getting the 20.0g crude lactide, is solvent with the ethyl acetate, adopts shift gears recrystallization three times of solution quality concentration, the solution quality concentration of each recrystallization and the results are shown in Table 8.
Table 8
Figure C20051009533700071
Embodiment 9
Getting the 20.0g crude lactide, is solvent with the butylacetate, adopts successively decrease mode recrystallization three times of solution quality concentration gradient, the solution quality concentration of each recrystallization and the results are shown in Table 9.
Table 9
Figure C20051009533700072
Embodiment 10
Getting the 20.0g crude lactide, is solvent with ethanol, adopts shift gears recrystallization three times of solution quality concentration, the solution quality concentration of each recrystallization and the results are shown in Table 10.
Table 10
Figure C20051009533700073

Claims (5)

1. method that begins the purifying rac-Lactide from the crude lactide that contains impurity, the method is characterized in that: with the increase of crystallization number of times, reduce the recrystallization that mass concentration that mode changes the solution of being controlled is carried out rac-Lactide with gradient, the mass concentration of described solution is the quality of every 100g dissolution with solvents rac-Lactide, and this method comprises:
A is dissolved in crude lactide a kind of or total carbon atom number in the alcohols of C1~C4 and is a kind of in the ester class of C2~C6 under 50 ℃~95 ℃, obtain crude lactide solution;
B is cooled to 0 ℃~30 ℃ with solution, and the rac-Lactide crystallization is separated out and filtration drying, obtains the rac-Lactide crystal;
C repeats above-mentioned A, B operation, adopts the crystallization of high quality concentration solution weight once or for several times, reduces the mass concentration of the rac-Lactide solution of being controlled, and obtains the secondary or the rac-Lactide crystal of recrystallization repeatedly;
When utilizing the crystallization of high quality concentration solution weight, when solvent is selected a kind of in the alcohols of C1~C4, the rac-Lactide solution quality concentration of being controlled is 50%~120%, when solvent when to select total carbon atom number be a kind of in the ester class of C2~C6, the rac-Lactide solution quality concentration of being controlled is 150%~210%; When utilizing the crystallization of inferior quality concentration solution weight, when solvent is selected a kind of in the alcohols of C1~C4, the rac-Lactide solution quality concentration of being controlled is 15%~55%, when solvent when to select total carbon atom number be a kind of in the ester class of C2~C6, the rac-Lactide solution quality concentration of being controlled is 40%~90%.
2. according to the method for claim 1, when it is characterized in that utilizing the crystallization of high quality concentration solution weight, when solvent was selected a kind of in the alcohols of C1~C4, the rac-Lactide solution quality concentration of being controlled was 70%~100%.
3. according to the method for claim 1, when it is characterized in that utilizing the crystallization of inferior quality concentration solution weight, when solvent was selected a kind of in the alcohols of C1~C4, the rac-Lactide solution quality concentration of being controlled was 25%~50%.
4. according to the method for claim 1, when it is characterized in that utilizing the crystallization of high quality concentration solution weight, when solvent when to select total carbon atom number be a kind of in the ester class of C2~C6, the rac-Lactide solution quality concentration of being controlled is 170%~200%.
5. according to the method for claim 1, when it is characterized in that utilizing the crystallization of inferior quality concentration solution weight, when solvent when to select total carbon atom number be a kind of in the ester class of C2~C6, the rac-Lactide solution quality concentration of being controlled is 50%~75%.
CNB2005100953376A 2005-11-09 2005-11-09 Method for lactide recrystallization using gradient concentration style Expired - Fee Related CN100528860C (en)

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CN103664866A (en) * 2012-09-05 2014-03-26 中国石油化工股份有限公司 Method for purifying glycolide
CN109400574B (en) * 2018-12-13 2021-03-02 中国科学院长春应用化学研究所 Purification method and application of crude lactide

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D,L-丙交酯的合成与纯化. 李南,姜文芳,赵京波,杨万泰.石油化工,第32卷第12期. 2003 *
丙交酯单体的制备及纯化. 张子勇,陈燕琼.高分子材料科学与工程,第19卷第2期. 2003
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