CN101434594A - Method for preparing lactide by mixed solvent process - Google Patents
Method for preparing lactide by mixed solvent process Download PDFInfo
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- CN101434594A CN101434594A CNA2008100801945A CN200810080194A CN101434594A CN 101434594 A CN101434594 A CN 101434594A CN A2008100801945 A CNA2008100801945 A CN A2008100801945A CN 200810080194 A CN200810080194 A CN 200810080194A CN 101434594 A CN101434594 A CN 101434594A
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Abstract
The invention relates to a method for preparing lactide by a component solvent method. The method adopts D, L-lactic acid as raw material; D, L-lactide is synthesized by cyclodehydration in the environment of pressure reduction by using a catalyst in a mixed solvent. The method is divided into two steps: Step 1, a lactic acid oligomer is obtained by the direct condensation polymerization of lactic acid; Step 2, the lactic acid oligomer is depolymerized at relatively high temperature to generate the lactide; the conditions of the reaction are that: the usage of the catalyst is 1.5 percent of the lactic acid; the mixed solvent adopts a low boiling point solvent and a high boiling point solvent; the adding quantity of the low boiling point solvent is 10 percent to 20 percent of the lactic acid while that of the high boiling point solvent is 15 percent to 25 percent of the lactic acid; decomposition temperature is kept between 250 DEG C and 280 DEG C and decomposition time is 2 hours to 3 hours; the degree of vacuum is 600mm Hg to 760mm Hg. The method has the advantages of relatively high yield; the yield of the lactide can reach 23.6 percent; besides, the purity of the lactide is also relatively high.
Description
Technical field
The present invention relates to a kind of method of preparing lactide by mixed solvent process.
Background technology
Rac-Lactide ring-opening polymerization under catalyst system generates PLA, PLA is a kind of important biodegradable high molecular polymer, with its good biocompatibility and Bioabsorbable and be widely used in controlled drug delivery system and medical engineering material, and obtained the approval of food and drug administration (FDA).Up to now, the chemosynthesis of rac-Lactide mainly is raw material with lactic acid, main synthetic method has single stage method and two-step approach, wherein two-step approach is to prepare the most frequently used method of rac-Lactide, and the concrete grammar step of two-step approach is as follows: a) lactic acid generates the poly(lactic acid) oligopolymer: the first step reaction is the polycondensation that generates polyester between the carboxyl of lactic acid and the hydroxyl.Polyesterification is a kind of reversible balanced reaction, and the equilibrium constant is very little.The timely discharge of the water that water in the lactic acid and reaction generate is necessary for the generation of oligopolymer.Therefore reaction is normally carried out under the condition that heating (180 ℃) vacuumizes, and catalyzer can not be used in this step reaction, and the molecular weight of gained oligopolymer is generally in 500～200 scopes.The reaction of second step can be carried out or suspend continuously, and the oligopolymer of generation can separate or store.B) the oligopolymer depolymerization generates rac-Lactide: the depolymerization of lactic acid oligomers claims the hot-drawn chain reaction again.This reaction also is the reversed reaction of lactic acid polycondensation.In fact, this also just why the lactic acid direct condensation can only obtain the major cause of low molecular weight product.This moment, required temperature often reacted higher than the first step, and vacuum tightness is also bigger.Catalyzer is used in this step reaction usually, and the effect of catalyzer is to reduce temperature of reaction, makes it not only can quicken zippering reaction but also can drop to the degree of high temperature pyrolysis reaction minimum.The catalyzer that uses mainly contains oxide compound, metal oxide, as Vanadium Pentoxide in FLAKES, phosphorus trioxide, zinc oxide and tin compound such as stannous sulfate, stannous octoate, stannous octoate, lactic acid tin etc.The yield of above-mentioned rac-Lactide synthetic method is very low, thereby costs an arm and a leg.Influenced the development of China's pharmaceutical industry.Its major cause is to prepare in the cracking process of rac-Lactide with lactic acid, produces charing owing to temperature is high.
Summary of the invention
Technical problem to be solved by this invention is at existing problem in the above-mentioned prior art, and the method for all higher preparing lactide by mixed solvent process of a kind of productive rate and purity is provided.
The present invention adopts following technical scheme:
Method steps of the present invention is as follows:
(1) lactic acid passes through direct condensation obtain lactic acid oligopolymer:
With 85% D of 200 grams-300 grams, L lactic acid is added in the four-hole boiling flask, and electronic stirring and heating when being heated to 120 ℃, begin to have water to steam, and slowly increase Heating temperature, and solution is thickness gradually;
When Heating temperature rises to 160 ℃, add catalyzer for the first time, the catalyzer add-on is 0.7%-0.8% for the first time; And adding low boiling point solvent, the add-on of low boiling point solvent is the 10-20% of lactic acid, when temperature rises to 220 ℃ rapidly, add for the second time catalyzer, the add-on of catalyzer is 0.7-0.8% for the second time, start vacuum pump and carry out underpressure distillation this moment, and in still-process, temperature remains 120-160 ℃; Thereby generation lactic acid oligomer;
(2) the lactic acid oligomer depolymerization is generated D, the L-rac-Lactide:
Intensification limit, the lactic acid oligomer limit gas clean-up that above-mentioned steps (1) is generated, when temperature is 160 ℃-200 ℃, when vacuum tightness was 600-760mm Hg, reaction mass became brown or black by dark yellow, and described lactic acid oligomer begins cracking, when temperature arrives 250-280 ℃, and reaction adds high boiling solvent after 2-3 hour, and the add-on of high boiling solvent is the 15-25% of lactic acid, and underpressure distillation is 4 hours then, get crude product D, the L-rac-Lactide;
(3) with D, ethyl alcohol recrystallization 3 times of L-rac-Lactide crude product, standby after vacuum-drying.
Described catalyzer is selected from any in following: zinc oxide, antimonous oxide.
Described low boiling point solvent is selected from any in following: n-Heptyl alcohol, butanols, amylalcohol.
Described high boiling solvent is selected from any in following: hexadecanol, stearyl alcohol.
One of reason that productive rate of the present invention is higher is to add low boiling point solvent to reaction vessel early stage at cracked, as butanols or amylalcohol etc., the rac-Lactide that generates is taken out of; The reaction later stage adds high boiling solvent such as hexadecanol or stearyl alcohol, thereby prevents the charing of rac-Lactide.
The invention has the beneficial effects as follows that productive rate is higher, the rac-Lactide productive rate can reach 39.01%, and in addition, the purity of rac-Lactide is also higher.
Description of drawings
Fig. 1 be the catalyst consumption to D, the influence of the thick productive rate of L-rac-Lactide.
Fig. 2 be dehydration temperaturre to D, the influence of the thick productive rate of L-rac-Lactide.
Fig. 3 is product D of the present invention, the infrared spectrogram of L-rac-Lactide.
Among Fig. 1-2, X1 is catalyst levels/%, X2 be dehydration temperaturre/℃, Y is productive rate/%.
Embodiment
Embodiment 1:
With 85% D of 300 grams, L-lactic acid is added in the four-hole boiling flask, and electronic stirring and heating slowly increase Heating temperature after being heated to 120 ℃, during Heating temperature life to 160 ℃, adds catalyst oxidation zinc for the first time and adds 2.4 grams; And add low boiling point solvent n-Heptyl alcohol 60 grams, and when temperature rises to 220 ℃ rapidly, adding catalyst oxidation zinc 2.4 grams for the second time, start vacuum pump and carry out underpressure distillation this moment, and in still-process, temperature remains 120-160 ℃; Thereby generation lactic acid oligomer, with intensification limit, back gas clean-up, when temperature is 160-200 ℃, when vacuum tightness was 600-760mm Hg, lactic acid oligomer began cracking, when temperature arrives 250-280 ℃, and reaction adds high boiling solvent hexadecanol 75 grams after 2-3 hour, underpressure distillation is 4 hours then, gets crude product D, the L-rac-Lactide.With D, ethyl alcohol recrystallization 3 times of L-rac-Lactide crude product, standby after vacuum-drying.
Embodiment 2:
With 85% D of 260 grams, L-lactic acid is added in the four-hole boiling flask, and electronic stirring and heating slowly increase Heating temperature after being heated to 120 ℃, during Heating temperature life to 160 ℃, adds catalyst oxidation zinc for the second time and adds 2 grams; And add low boiling point solvent butanols 42 grams, and when temperature rises to 220 ℃ rapidly, adding catalyst oxidation zinc 2 grams for the second time, start vacuum pump and carry out underpressure distillation this moment, and in still-process, temperature remains 120-160 ℃; Thereby generation lactic acid oligomer, with intensification limit, back gas clean-up, when temperature is 160-200 ℃, when vacuum tightness was 600-760mm Hg, lactic acid oligomer began cracking, when temperature arrives 250-280 ℃, and reaction adds high boiling solvent stearyl alcohol 58 grams after 2-3 hour, underpressure distillation is 4 hours then, gets crude product D, the L-rac-Lactide.With D, ethyl alcohol recrystallization 3 times of L-rac-Lactide crude product, standby after vacuum-drying.
Embodiment 3:
With 85% D of 240 grams, L-lactic acid is added in the four-hole boiling flask, and electronic stirring and heating slowly increase Heating temperature after being heated to 120 ℃, during Heating temperature life to 160 ℃, adds catalyst oxidation zinc 1.75 grams for the first time; And add low boiling point solvent amylalcohol 32 grams, and when temperature rises to 220 ℃ rapidly, adding catalyst oxidation zinc 1.75 grams for the second time, start vacuum pump and carry out underpressure distillation this moment, and in still-process, temperature remains 120-160 ℃; Thereby generation lactic acid oligomer, with intensification limit, back gas clean-up, when temperature is 160-200 ℃, when vacuum tightness was 600-760mm Hg, lactic acid oligomer began cracking, when temperature arrives 250-280 ℃, and reaction adds high boiling solvent hexadecanol 48 grams after 2-3 hour, underpressure distillation is 4 hours then, gets crude product D, the L-rac-Lactide.With D, ethyl alcohol recrystallization 3 times of L-rac-Lactide crude product, standby after vacuum-drying.
Embodiment 4
With 85% D of 200 grams, L-lactic acid is added in the four-hole boiling flask, and electronic stirring and heating slowly increase Heating temperature after being heated to 120 ℃, during Heating temperature life to 160 ℃, adds The catalytic antimony trioxide for the first time and adds 1.4 grams; And add low boiling point solvent n-Heptyl alcohol 20 grams, and when temperature rises to 220 ℃ rapidly, adding The catalytic antimony trioxide 1.4 grams for the second time, start vacuum pump and carry out underpressure distillation this moment, and in still-process, temperature remains 120-160 ℃; Thereby generation lactic acid oligomer, with intensification limit, back gas clean-up, when temperature is 160-200 ℃, when vacuum tightness was 600-760mm Hg, lactic acid oligomer began cracking, when temperature arrives 250-280 ℃, and reaction adds high boiling solvent hexadecanol 30 grams after 2-3 hour, underpressure distillation is 4 hours then, gets crude product D, the L-rac-Lactide.With D, ethyl alcohol recrystallization 3 times of L-rac-Lactide crude product, standby after vacuum-drying.
In the various embodiments described above, the process that generates rac-Lactide mainly was divided into for two steps: the first step is that lactic acid obtains lactic acid oligomer by direct condensation, polyesterification is a kind of reversible balanced reaction, and the equilibrium constant is very little, the present invention adds low boiling point solvent to reaction vessel, as butanols and amylalcohol etc., the rac-Lactide that generates in time can be taken out of to separate and be impelled balance to shuffle with water system; Second step caused high temperature carbonization for lactic acid oligomer depolymerization under comparatively high temps generates rac-Lactide for avoiding the reaction system thickness, and the present invention adds high boiling solvent such as hexadecanol and stearyl alcohol etc. in system.Experimental results show that the rac-Lactide productive rate through this mixed solvent method preparation can improve 20%-30%.
The factor that influences the rac-Lactide productive rate is discussed below:
(1) catalyzer and consumption thereof influence (see figure 1):
Fig. 1 be catalyst levels to D, the influence of L-rac-Lactide productive rate.Along with catalyst levels ground increases, D, L-rac-Lactide productive rate increases afterwards earlier and reduces, and these can be from 2 considerations: the one, owing to zinc oxide is not only the catalyzer of polycondensation phase, also will play katalysis to cracking in the depolymerization stage; The 2nd, scission reaction has certain selectivity [to see the Zhejiang Academy of Medical Sciences journal to the relative molecular mass of poly(lactic acid), 1992,3 (3): 32-35] average molecular mass prepares D in the suitable thermo-cracking of the poly(lactic acid) of 500-2000, L-third hands over acid, the too high or too low difficulty that scission reaction is become of relative molecular mass.Take all factors into consideration D, the amount of steaming of L-lactic acid and this two aspects factor of residue amount, as shown in Figure 1, and when catalyst levels (massfraction) is 1.5%, the remnant minimum of system, the D that steams, the L-lactic acid production is also less, so productive rate is the highest.
In numerous optional catalyzer, the applicant has been the contrast experiment with zinc oxide and ANTIMONY TRIOXIDE SB 203 99.8 PCT respectively, and the result is shown in subordinate list 1.Finding in the experiment that zinc oxide (ZnO) is to the excellent catalytic effect of this reaction, and with reactive system good consistency is arranged, is preparation high yield D, and the L-rac-Lactide is the ideal catalyzer comparatively.When catalyst levels (massfraction) when being about 1.5%, the residue of system is minimum, and the lactic acid production that steams is also less, so productive rate is the highest.
(2) dehydration temperaturre influence (see figure 2):
Under the condition of 150g lactic acid, 3.0g catalyzer, in 120 ℃-150 ℃, regulate D, L-third hands over the dehydration temperaturre of lactic acid, D, the thick productive rate of L-rac-Lactide changes as shown in Figure 2.Similar with the rule of catalyst levels, with the rising of dehydration temperaturre, D, the thick productive rate of L-rac-Lactide also are elder generation and increase near the trend (reaching maximum value 140 ℃) that afterwards reduces, and the discussion of its reason and front is similar.Because D, the polycondensation of L-lactic acid is one and has temperature dependent process, so temperature is high more, and glue is thorough more, and when temperature was too high, one step of relative molecular mass increased equally, and it is difficult that cracking becomes, thereby productive rate is descended.
(3) reaction times influences (seeing attached list 2) to the rac-Lactide synthetic:
Fixing lactic acid consumption 150g in the rac-Lactide compound experiment, zinc oxide 2.25g, dewatering time are 3 hours.Productive rate that under different cracking time conditions, obtains such as subordinate list 2.
The preparation of rac-Lactide is made of dehydration and cyclisation two-step reaction, so there is certain influence in the reaction times to rac-Lactide synthetic.In general, the dehydration time should be longer as far as possible, comes out to guarantee water that water in the material acid and reaction the generate distillation of can trying one's best, and makes lactic acid generate oligopolymer simultaneously as far as possible, and vacuum tightness should slowly raise in order to avoid cause damage.Cyclization process should be suitably fast under the prerequisite that guarantees sufficient reacting, because at high temperature, crosses the charing that causes lactic acid oligomer for a long time on the contrary, and final cyclisation temperature should be no more than 250 ℃, otherwise product will have darker color.
(4) the oligopolymer cracking temperature should not be low excessively, otherwise the cracking process is slow, transforming degree ground; Although the too high scission reaction that makes of temperature has been accelerated, side reaction speed such as oxidation, charing are also accelerated simultaneously, and in addition, the rac-Lactide that has generated also can produce and be decomposed to form by product because of having little time the discharge system, has finally reduced the rac-Lactide yield.In the experiment we fixedly the lactic acid consumption be 150mL, zinc oxide 3.5g, the cracking time is 3h, vacuum tightness is 500mmHg.Obtain result such as subordinate list 3.
The D of the present invention's preparation, the infrared measurement (see figure 3) of L-rac-Lactide:
The infrared spectra of synthetic rac-Lactide as shown in Figure 3.In the infrared spectra of rac-Lactide, 1752.19cm
-1The place is the stretching vibration peak of ester carbonyl group C=0: 2943.56cm
-1And 2878.98cm
-1The place is C-H stretching vibration peak, 1386.91cm
-1The place is C-H flexural vibration peak; 1055.1cm
-1, 1098.44cm
-1, 1131.62cm
-1The place is the stretching vibration peak of C-O-C, proves that the C-O-C group exists; 934.917cm
-1The place is ring skeletal vibration peak.
Subordinate list 1: different catalyzer and different amounts are to the influence of productive rate
Subordinate list 2: the cracking time is to the influence of productive rate
Subordinate list 3: cracking temperature is to the influence of productive rate
Claims (4)
1, the method for preparing lactide by mixed solvent process is characterized in that its method steps is as follows:
(1) lactic acid passes through direct condensation obtain lactic acid oligopolymer:
With 85% D of 200 grams-300 grams, L-lactic acid is added in the four-hole boiling flask, and electronic stirring and heating when being heated to 120 ℃, begin to have water to steam, and slowly increase Heating temperature, and solution is thickness gradually;
When Heating temperature rises to 160 ℃, add catalyzer for the first time, the catalyzer add-on is 0.7%-0.8% for the first time; And adding low boiling point solvent, the add-on of low boiling point solvent is the 10-20% of lactic acid, when temperature rises to 220 ℃ rapidly, add for the second time catalyzer, the add-on of catalyzer is 0.7-0.8% for the second time, start vacuum pump and carry out underpressure distillation this moment, and in still-process, temperature remains 120-160 ℃; Thereby generation lactic acid oligomer;
(2) the lactic acid oligomer depolymerization is generated D, the L-rac-Lactide:
Intensification limit, the lactic acid oligomer limit gas clean-up that above-mentioned steps (1) is generated, when temperature is 160 ℃-200 ℃, when vacuum tightness was 600-760mm Hg, reaction mass became brown or black by dark yellow, and described lactic acid oligomer begins cracking, when temperature arrives 250-280 ℃, and reaction adds high boiling solvent after 2-3 hour, and the add-on of high boiling solvent is the 15-25% of lactic acid, and underpressure distillation is 4 hours then, get crude product D, the L-rac-Lactide;
(3) with D, ethyl alcohol recrystallization 3 times of L-rac-Lactide crude product, standby after vacuum-drying.
2, the method for preparing lactide by mixed solvent process according to claim 1 is characterized in that described catalyzer is selected from any in following: zinc oxide, antimonous oxide.
3, the method for preparing lactide by mixed solvent process according to claim 2 is characterized in that described low boiling point solvent is selected from any in following: n-Heptyl alcohol, butanols, amylalcohol.
4, the method for preparing lactide by mixed solvent process according to claim 3, base are characterised in that described high boiling solvent is selected from any in following: hexadecanol, stearyl alcohol.
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Cited By (8)
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| CN102863420A (en) * | 2012-09-29 | 2013-01-09 | 上海绿色盛世生态材料有限公司 | Method for preparing medical lactide |
| CN103300120A (en) * | 2013-06-25 | 2013-09-18 | 南京工业大学 | Environment-friendly hair removal agent for poultry and livestock and preparation method of hair removal agent |
| CN104781248A (en) * | 2012-10-26 | 2015-07-15 | 伍德-伊文达-菲瑟股份有限公司 | Process for preparing cyclic diesters, especially dilactide |
| CN107118200A (en) * | 2016-02-24 | 2017-09-01 | 香港纺织及成衣研发中心有限公司 | A kind of method that utilization lactic acid catalyzes and synthesizes lactide |
| WO2018045941A1 (en) * | 2016-09-07 | 2018-03-15 | 南京大学 | Method for synthesizing glycolide |
| CN111589178A (en) * | 2020-05-29 | 2020-08-28 | 吉林中粮生化有限公司 | Falling film evaporator and lactide production system |
| CN114315788A (en) * | 2021-12-29 | 2022-04-12 | 普立思生物科技有限公司 | Preparation method of lactide |
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| US5274127A (en) * | 1990-09-18 | 1993-12-28 | Biopak Technology, Ltd. | Lactide production from dehydration of aqueous lactic acid feed |
| CN101054371A (en) * | 2007-05-24 | 2007-10-17 | 复旦大学 | Preparation method for glycolide |
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| CN102863420A (en) * | 2012-09-29 | 2013-01-09 | 上海绿色盛世生态材料有限公司 | Method for preparing medical lactide |
| CN104781248A (en) * | 2012-10-26 | 2015-07-15 | 伍德-伊文达-菲瑟股份有限公司 | Process for preparing cyclic diesters, especially dilactide |
| US9428484B2 (en) | 2012-10-26 | 2016-08-30 | Uhde Inventa-Fischer Gmbh | Method for the production of cyclic diesters, in particular dilactide |
| CN104781248B (en) * | 2012-10-26 | 2017-09-12 | 伍德-伊文达-菲瑟股份有限公司 | Method for preparing cyclic diester especially lactide |
| CN103300120A (en) * | 2013-06-25 | 2013-09-18 | 南京工业大学 | Environment-friendly hair removal agent for poultry and livestock and preparation method of hair removal agent |
| CN107118200A (en) * | 2016-02-24 | 2017-09-01 | 香港纺织及成衣研发中心有限公司 | A kind of method that utilization lactic acid catalyzes and synthesizes lactide |
| CN107118200B (en) * | 2016-02-24 | 2020-02-28 | 香港纺织及成衣研发中心有限公司 | Method for catalytically synthesizing lactide by using lactic acid |
| WO2018045941A1 (en) * | 2016-09-07 | 2018-03-15 | 南京大学 | Method for synthesizing glycolide |
| JP2019529532A (en) * | 2016-09-07 | 2019-10-17 | 南京大学Ｎａｎｊｉｎｇ Ｕｎｉｖｅｒｓｉｔｙ | Glycolide synthesis method |
| CN111589178A (en) * | 2020-05-29 | 2020-08-28 | 吉林中粮生化有限公司 | Falling film evaporator and lactide production system |
| WO2023071865A1 (en) * | 2021-10-31 | 2023-05-04 | 中国石油化工股份有限公司 | Method and system for continuously preparing lactide by step control |
| CN114315788A (en) * | 2021-12-29 | 2022-04-12 | 普立思生物科技有限公司 | Preparation method of lactide |
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