CN100387592C - Process for preparing lactide using microwave radiation pressure reducing catalystic method - Google Patents
Process for preparing lactide using microwave radiation pressure reducing catalystic method Download PDFInfo
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- CN100387592C CN100387592C CNB2006100098607A CN200610009860A CN100387592C CN 100387592 C CN100387592 C CN 100387592C CN B2006100098607 A CNB2006100098607 A CN B2006100098607A CN 200610009860 A CN200610009860 A CN 200610009860A CN 100387592 C CN100387592 C CN 100387592C
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- lactide
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- lactic acid
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Abstract
The present invention discloses a method for preparing lactide by utilizing a microwave radiation decompressing catalytic process, which relates to a preparation method for lactide. In order to achieve the purpose for reducing the production cost of lactide by shortening the preparation time, reducing the energy consumption and enhancing the production rate, the following method is adopted: if the raw material is lactic acid aqueous solution, the lactic acid aqueous solution is dewatered under the condition of decompression; if the raw material is lactic acid, the next step is carried out without the dewatering step; a catalyst is added in the system, and the system is polymerized by microwaves under the condition of decompression to obtain oligomerization lactic acid; then, under the condition of decompression, the oligomerization lactic acid is decomposed by microwaves to obtain a coarse product; pure lactide is obtained after the coarse product is purified. The preparation of the coarse lactide needs no more than two hours by using the method under the condition of microwave radiation, and the preparation process does not need to use nitrogen flow protection. The method can remarkably shorten the reaction time and reduce the energy consumption on the premise of ensuring higher lactide production rate, and thereby, the production cost of the lactide is reduced.
Description
Technical field
The present invention relates to a kind of preparation method of rac-Lactide, be specifically related to a kind of method of utilizing the microwave radiation pressure reducing catalysis method to prepare rac-Lactide.
Background technology
Poly(lactic acid) is a kind of novel high polymer material with excellent biological compatibility, biological degradability and environmental friendliness performance, has wide application and development prospect in environmental protection, medicine and other fields.High molecular and highly purified poly(lactic acid) are mostly synthetic by rac-Lactide ring-opening polymerization method (being called for short the open loop method) at present.Because the open loop method will be the feedstock production intermediate lactide with lactic acid at first, its synthetic route is tediously long, and productive rate is lower, causes the rac-Lactide preparation cost higher.Therefore, high-level efficiency, high yield, prepare the important technology key that rac-Lactide becomes the poly(lactic acid) suitability for industrialized production at low cost.Produce rac-Lactide and generally adopt two kinds of normal pressure air-flow method and decompression methods.Though the operation of normal pressure air-flow method is more safe and reliable, its weak point is that preparation time is long, efficient is low, and air-flow can be taken away portion of product and cause productive rate low.Though the dehydration of decompression method is shorter with polymerization time, the efficient height, at depolymerization later stage system thickness, charing is serious, and rac-Lactide is difficult for distillating, and often produces some indefinite by products.Generally speaking, the preparation rac-Lactide all is faced with long reaction time, energy consumption is big, productive rate is low defective under the traditional heating condition, thereby makes that the preparation cost of rac-Lactide is very high.
Microwave radiation promotes that the chemical reaction technology is a kind of novel high polymer synthetic technology, and the traditional method incomparable advantage is arranged: it can shorten the reaction times greatly, enhances productivity; Do not have thermograde in the reaction process, reaction evenly also can suppress production of by-products.In this experimental system, the specific inductivity of water and lactic acid is big (water 78.3, lactic acid 22.0) all, belongs to high loss material, and the microwave heating effect is very outstanding.Microwave radiation has reduced energy consumption by shortening the reaction times, so can reduce cost, is suitable for production-scale expansion.People such as Liu Lijian (CN 1583740A) adopt microwave radiation pressure reducing air-flow legal system to be equipped with rac-Lactide, under the nitrogen gas stream atmosphere, are catalyzer with the zinc-tin compound system, and microwave radiation 6h prepares crude lactide, and the rac-Lactide productive rate is 45～48% after purifying.
Summary of the invention
The present invention proposes a kind of method of utilizing the microwave radiation pressure reducing catalysis method to prepare rac-Lactide, this method is by selecting suitable catalyst system and processing condition, under no nitrogen gas stream condition, prepare rac-Lactide fast, shorten preparation time to reach, cut down the consumption of energy, improve productive rate, thereby reduce the purpose of lactide production cost.Above-mentioned purpose of the present invention can realize by following two kinds of technical schemes:
With lactic acid is raw material, the compound system that in lactic acid, adds catalyzer tin salt and tosic acid, the consumption of control tin salt is 0.1～1% of a lactic acid quality, the ratio of the amount of substance of tin salt and tosic acid (TSA) is 1: 0.1～5, at pressure is that 1～20kPa, microwave power are polymerization 20～50min under the condition of 50～400W, obtains viscosity-average molecular weight and be 1000～8000 lact-acid oligomer; Be that 0.1～10kPa, microwave power are cracking 20～70min under the condition of 100～600W at pressure then, obtain the rac-Lactide crude product; Crude product obtains pure rac-Lactide after purifying; Wherein said tin salt is SnCl
22H
2O, Sn (Oct)
2Or SnSO
4
With the lactic acid aqueous solution is raw material, is to dewater under the condition of 100～1000W at 10～60kPa, microwave power with it, obtains lactic acid; The compound system that in lactic acid, adds catalyzer tin salt and tosic acid, the consumption of control tin salt is 0.1～1% of a lactic acid quality, tin salt is 1: 0.1～5 with the ratio of the amount of substance of tosic acid, at pressure is that 1～20kPa, microwave power are polymerization 20～50min under the condition of 50～400W, obtains viscosity-average molecular weight and be 1000～8000 lact-acid oligomer; Be that 0.1～10kPa, microwave power are cracking 20～70min under the condition of 100～600W at pressure then, obtain the rac-Lactide crude product; Crude product obtains pure rac-Lactide after purifying; Wherein said tin salt is SnCl
22H
2O, Sn (Oct)
2Or SnSO
4
But the filtrate reuse after the above-mentioned crude product washing is as the raw material of preparation rac-Lactide.
The present invention prepares crude lactide required time≤2h under microwave radiation, be equipped with the crude lactide time than traditional heating legal system and shortened 1/2～4/5; Be equipped with the rac-Lactide time than the microwave radiation pressure reducing air-flow legal system among the CN 1583740A and shortened more than 1/2, and preparation process need not adopt the nitrogen gas stream protection.The present invention cuts down the consumption of energy guaranteeing can significantly to shorten the reaction times under the higher rac-Lactide productive rate prerequisite, thereby reduces the production cost of rac-Lactide.
Embodiment
Embodiment one: present embodiment prepares rac-Lactide according to following steps: be raw material with lactic acid, the compound system that in lactic acid, adds catalyzer tin salt and tosic acid, the consumption of control tin salt is 0.1～1% of a lactic acid quality, tin salt is 1: 0.1～5 with the ratio of the amount of substance of tosic acid, at pressure is that 1～20kPa, microwave power are polymerization 20～50min under the condition of 50～400W, obtains viscosity-average molecular weight and be 1000～8000 lact-acid oligomer; Be that 0.1～10kPa, microwave power are cracking 20～70min under the condition of 100～600W at pressure then, obtain the rac-Lactide crude product; Crude product obtains pure rac-Lactide after purifying.
In the present embodiment, described tin salt is SnCl
22H
2O, Sn (Oct)
2Or SnSO
4The method of purification of described rac-Lactide crude product is: the rac-Lactide crude product is used dehydrated alcohol recrystallization 2～5 times after washing, filtering, obtain pure rac-Lactide after filtration, the drying.
Embodiment two: present embodiment is with D, and L-lactic acid is raw material: with 270g D, L-lactic acid places the 500mL flask, adds the SnCl that accounts for lactic acid massfraction 0.4%
22H
2O adds and SnCl again
22H
2The ratio of O amount of substance is that 1: 2 TSA makes catalyzer.At system pressure is that 5kPa, microwave power are polyase 13 0min under the 170W condition, obtains the lact-acid oligomer intermediates; Subsequently, be that 1kPa, microwave power are under the 200W condition at pressure, lact-acid oligomer to be carried out the cracking preparation collect crude lactide, collection time is 60min; The cold slightly back of the crude lactide product of collecting adds distilled water wash, behind the filtration drying, with the dehydrated alcohol recrystallization, obtains colourless sheet rac-Lactide crystal behind the filtration drying, and productive rate is 35.7%.With filtrate recycle, final that the rac-Lactide overall yield is 52%.
Embodiment three: present embodiment prepares rac-Lactide according to following steps: being raw material with the lactic acid aqueous solution, is to dewater under the condition of 100～1000W at 10～60kPa, microwave power with it, obtains lactic acid; The compound system that in lactic acid, adds catalyzer tin salt and tosic acid, the consumption of control tin salt is 0.1～1% of a lactic acid quality, tin salt is 1: 0.1～5 with the ratio of the amount of substance of tosic acid, at pressure is that 1～20kPa, microwave power are polymerization 20～50min under the condition of 50～400W, obtains viscosity-average molecular weight and be 1000～8000 lact-acid oligomer; Be that 0.1～10kPa, microwave power are cracking 20～70min under the condition of 100～600W at pressure then, obtain the rac-Lactide crude product; Crude product obtains pure rac-Lactide after purifying.
In the present embodiment, described tin salt is SnCl
22H
2O, Sn (Oct)
2Or SnSO
4The method of purification of described rac-Lactide crude product is: the rac-Lactide crude product is used dehydrated alcohol recrystallization 2～5 times after washing, filtering, obtain pure rac-Lactide after filtration, the drying.
Embodiment four: present embodiment is with D, and the L-lactic acid aqueous solution is a raw material: with 370ml D, L-lactic acid solution (34.1%) places the 500mL flask, is that 30kPa, microwave power are that 50min sloughs free water under the 600W irradiation at pressure.Add that to account for the lactic acid massfraction be 0.4% SnCl
22H
2O adds and SnCl again
22H
2The ratio of O amount of substance is that 1: 2 TSA makes catalyzer, is that 5kPa, microwave power are polyase 13 0min under the condition of 150W at system pressure, obtains the lact-acid oligomer intermediates.Subsequently, be that 1kPa, microwave power are under the 200W condition at pressure, lact-acid oligomer to be carried out the cracking preparation collect crude lactide, collection time is 40min.The cold slightly back of the crude lactide product of collecting adds distilled water wash, behind the filtration drying, with the dehydrated alcohol recrystallization, obtains colourless sheet rac-Lactide crystal behind the filtration drying, and productive rate is 38%.With filtrate recycle, final that the rac-Lactide overall yield is 50%.
Claims (4)
1. utilize the microwave radiation pressure reducing catalysis method to prepare the method for rac-Lactide, it is characterized in that described method prepares rac-Lactide according to following steps: be raw material with lactic acid, the compound system that in lactic acid, adds catalyzer tin salt and tosic acid, the consumption of control tin salt is 0.1～1% of a lactic acid quality, tin salt is 1: 0.1～5 with the ratio of the amount of substance of tosic acid, at pressure is that 1～20kPa, microwave power are polymerization 20～50min under the condition of 50～400W, obtains viscosity-average molecular weight and be 1000～8000 lact-acid oligomer; Be that 0.1～10kPa, microwave power are cracking 20～70min under the condition of 100～600W at pressure then, obtain the rac-Lactide crude product; Crude product obtains pure rac-Lactide after purifying; Wherein said tin salt is SnCl
22H
2O, Sn (Oct)
2Or SnSO
4
2. the method for utilizing the microwave radiation pressure reducing catalysis method to prepare rac-Lactide according to claim 1, the method of purification that it is characterized in that described rac-Lactide crude product is: the rac-Lactide crude product is after washing, filtering, with dehydrated alcohol recrystallization 2～5 times, filter, obtain pure rac-Lactide after the drying.
3. utilize the microwave radiation pressure reducing catalysis method to prepare the method for rac-Lactide, it is characterized in that described method prepares rac-Lactide according to following steps: be raw material with the lactic acid aqueous solution, with it is to dewater under the condition of 100～1000W at 10～60kPa, microwave power, obtains lactic acid; The compound system that in lactic acid, adds catalyzer tin salt and tosic acid, the consumption of control tin salt is 0.1～1% of a lactic acid quality, tin salt is 1: 0.1～5 with the ratio of the amount of substance of tosic acid, at pressure is that 1～20kPa, microwave power are polymerization 20～50min under the condition of 50～400W, obtains viscosity-average molecular weight and be 1000～8000 lact-acid oligomer; Be that 0.1～10kPa, microwave power are cracking 20～70min under the condition of 100～600W at pressure then, obtain the rac-Lactide crude product; Crude product obtains pure rac-Lactide after purifying; Wherein said tin salt is SnCl
22H
2O, Sn (Oct)
2Or SnSO
4
4. the method for utilizing the microwave radiation pressure reducing catalysis method to prepare rac-Lactide according to claim 3, the method of purification that it is characterized in that described rac-Lactide crude product is: the rac-Lactide crude product is after washing, filtering, with dehydrated alcohol recrystallization 2～5 times, filter, obtain pure rac-Lactide after the drying.
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|---|---|---|---|
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| CNB2006100098607A CN100387592C (en) | 2006-03-24 | 2006-03-24 | Process for preparing lactide using microwave radiation pressure reducing catalystic method |
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|---|---|
| CN1821240A CN1821240A (en) | 2006-08-23 |
| CN100387592C true CN100387592C (en) | 2008-05-14 |
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| CN112250661B (en) * | 2020-11-18 | 2021-11-02 | 南京大学 | Method for catalytically synthesizing lactide |
| CN114456145A (en) * | 2021-12-29 | 2022-05-10 | 江苏金聚合金材料有限公司 | Method for preparing glycolide by microwave pyrolysis of glycolic acid oligomer |
| CN115232102B (en) * | 2022-09-06 | 2024-02-13 | 中国科学院长春应用化学研究所 | Preparation method and production device of lactide |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6277951B1 (en) * | 1992-01-24 | 2001-08-21 | Cargill, Incorporated | Continuous process for manufacture of lactide polymers with controlled optical purity |
| CN1583740A (en) * | 2004-05-26 | 2005-02-23 | 武汉大学 | Method for preparing lactide by microwave radiation |
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2006
- 2006-03-24 CN CNB2006100098607A patent/CN100387592C/en not_active Expired - Fee Related
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6277951B1 (en) * | 1992-01-24 | 2001-08-21 | Cargill, Incorporated | Continuous process for manufacture of lactide polymers with controlled optical purity |
| CN1583740A (en) * | 2004-05-26 | 2005-02-23 | 武汉大学 | Method for preparing lactide by microwave radiation |
Non-Patent Citations (4)
| Title |
|---|
| 熔融缩聚法制备聚乳酸. 任杰等.塑料工业，第32卷第5期. 2004 |
| 熔融缩聚法制备聚乳酸. 任杰等.塑料工业，第32卷第5期. 2004 * |
| 聚D,L-丙交酯的常压微波辐射合成. 舒静等.高校化学工程学报，第19卷第4期. 2005 |
| 聚D,L-丙交酯的常压微波辐射合成. 舒静等.高校化学工程学报，第19卷第4期. 2005 * |
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