CN109776482A - The method of the continuous preparation high-purity lactide of industrialization - Google Patents
The method of the continuous preparation high-purity lactide of industrialization Download PDFInfo
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Abstract
The invention discloses a kind of methods of the continuous preparation high-purity lactide of industrialization, include the following steps: the evaporation of (1) crude lactide and (2) fusion-crystallization；(1) crude lactide evaporation includes the following steps: for crude lactide to be sent into the evaporation equipment for being equipped with secondary condenser, and the lactide intermediate products for being stripped of most of high boiling product component are collected in heated under vacuum evaporation from first-stage condenser；(2) fusion-crystallization includes the following steps: that product among lactide will be collected in first-stage condenser, and be sent into melting crystallizer, mother liquor is discharged in melting crystallizer decrease temperature crystalline；The crystal that will be left in melting crystallizer carries out crystal sweating, collects the high-purity lactide.New technological flow of the present invention is brief, easy to operate, and low energy consumption, and product yield and quality are high, and the optical purity and chemical purity of lactide can reach 99.6% or more, purifies yield 90% or more.
Description
Technical field
The present invention relates to the preparation methods of lactide.
Background technique
Polylactic acid is a kind of important Biodegradable high-molecular, has huge applications in the fields such as plastics, weaving, medical
Prospect, raw materials for production come from crops through lactic acid made of biofermentation.Polylactic acid have it is nontoxic, nonirritant, with
And good biocompatibility, it can be by biological decomposition and absorption.
The production of current polylactic acid mainly uses two step method technology, is first made thick third through pre- poly- cracking by lactic acid monomer and hands over
Ester, then it is purified lactide is made, last ring-opening polymerisation obtains polyphosphazene polymer lactic acid.In this course, the purity of lactide
The quality of polylactic acid is directly affected, no high-purity lactide can not just produce qualified polylactic acid, and the country is in this link one
Solution is not directly industrialized effectively, to affect the development of China's polylactic acid industry.
The crude lactide ingredient also contains other impurities such as water, lactic acid, Study of Meso-Lactide, cream in addition to lactide
Acid oligomer and pigment and coke object etc..Lactide containing impurity has to pass through purification, keeps its optical purity and chemistry pure
Degree is greater than 99.5% requirement for being just able to satisfy polymerization.
Currently, there are three types of the representative methods of purification of domestic lactide, i.e., Multi-stage high-vacuum rectification method, Hydrolyze method,
Solvent recrystallization method.It facts have proved that the first two kind purification process (Multi-stage high-vacuum rectification method, Hydrolyze method) of single use can not still reach
To lactide purification of target, the third method (solvent recrystallization method) although high-purity lactide can be obtained, inefficiency and
A large amount of solvents are needed to cannot achieve large-scale production.
Since lactide purification requirements are especially high, and lactide has thermal sensitivity and invertibity and lactide common
Easily moisture is absorbed in environment and is decomposed, and difficult point of the lactide in purification process has been in turn resulted in.So simply using single
Process means can not obtain high-purity lactide.As single selection WATER-WASHING METHOD can largely remove meso and lactic acid and part
Pigment and oligomer can also remove most of water by drying means.But it is unable to reach the requirement of high-purity lactide.It is more
Grade high-vacuum rectification is main method that current China industrially uses, may be implemented in theory to it is high in crude lactide,
Low boilers efficiently separate, but in the actual process since thick third hands over containing a certain amount of acid and moisture content, and in hot conditions
The thermal sensitivity of lower lactide will be so that lactide be extremely easy in decomposition with invertibity；Secondly although lactide, meso, lactic acid have centainly
Boiling-point difference but relatively to realize requirement of the high-purity separation to equipment, energy consumption, operation difficulty or ease in high vacuum conditions
Degree is all greatly to challenge, and therefore, rectification process technology is not very successful at present in terms of lactide purifying.
Summary of the invention
The purpose of the present invention is disclosing a kind of method of continuous preparation high-purity lactide of industrialization, to overcome the prior art
Existing defect.
Method of the invention, in turn includes the following steps: (1) crude lactide evaporation and (2) fusion-crystallization；
(1) the crude lactide evaporation includes the following steps:
The crude lactide is sent into the evaporation equipment for being equipped with the condenser that second level is connected in series, heated under vacuum
Evaporation removes most oligomer, lactic acid polymer and pigment and coke object, vacuum degree 100-1000Pa, evaporating temperature
For 130-160, the lactide intermediate products for being stripped of most of high boiling product component are collected from first-stage condenser, yield exists
The 90%~95% of total amount is evaporated, the weight content of the lactide intermediate products is 96-98.5%, remaining is low boiling point group
Divide and micro high boiling component；
The evaporant that surplus is collected in secondary condenser is sent into postprocessing working procedures and is handled, wherein lactide contains
Amount is 75-85%；
The evaporation equipment is selected from common falling film type, rises membrane type, scraper-type inspissator and distillation reactor；
It is 90-100 DEG C that the first-stage condenser, which obtains temperature, and the temperature of secondary condenser is 80-90 DEG C；
Evaporating remaining raffinate is about 5%-8%, and main component is oligomer, polymeric lactic acid and pigment and coke object, is sent
Enter postprocessing working procedures to be handled.
The crude lactide includes the component of following mass percent:
Lactide: 92-94%
Low boilers: 2.8-4.2%
High boiling substance: 3.2-3.8%
Described (2) fusion-crystallization includes the following steps:
Product among lactide will be collected in first-stage condenser, be sent into the melting crystallizer that temperature is 100-120 DEG C, fused junction
Brilliant device starts decrease temperature crystalline, and rate of temperature fall is 2-8 DEG C/h, and temperature is down to 70-90 DEG C, mother liquor is discharged, at this time containing big in mother liquor
Part meso, acid, water and a small amount of pigment, are sent to postprocessing working procedures and are handled, and recycle；
Then the crystal that will be left in melting crystallizer carries out crystal sweating: specific step is as follows:
For heating rate in 2-8 DEG C/h, sweating temperature rises to 93-100 DEG C, and sweating is discharged, then heats up and melts crystal
It collects, what is be collected into is high-purity lactide, 99.6% or more quality purity；
Contain meso, acid and water in sweating, be sent to postprocessing working procedures and handled, recycles；
(2) fusion-crystallization is a kind of static ontology fusion-crystallization technology, and melting crystallizer is cold by similar vertical pipe type
The crystallizer of condenser reaches lactide purifying using the fusing point difference of different material by primary crystallization and first sweating process
Purpose.Crystallization and sweating are all a kind of purification process, control crystallographic form and mother liquor ratio and sweating temperature and speed
It is the key point of technological operation.High-purity lactide can be obtained by optimised process operation and improves purification efficiency, while also can
The decomposition of lactide is effectively reduced.
The beneficial effects of the present invention are:
The coupling technique combined using kinds of processes, in different phase, using different disposal technique.With efficient low energy
The characteristics of consumption, main body of the present invention use two kinds of purifying process technologies, and first using evaporation purifying process, the purpose is to greatest extent
Removing crude lactide in high and low boilers, especially high boiling substance and stickum are conducive to mitigate fused junction
The burden of brilliant purification process improves product purity.Evaporation is compared with rectifying, when having vacuum degree height in reaction kettle, material processing
Between it is short, low energy consumption, the simple small investment of equipment is also beneficial to the protection of heat sensitive material the features such as can operating continuously.Second step is adopted
With fusion-crystallization technology, it is current more advanced generally acknowledged low energy consumption industrialization product method of purification, mainly utilizes substance
Between fusing point difference reach efficiently separating for each component, had using fusion-crystallization technology than the purification of rectification process technology obvious excellent
Gesture, the lactide after pervaporation handle by fusion-crystallization, are fully able to reach high-purity lactide product requirement.The operation
In atmospheric conditions, temperature is not high, does not have transmission system, and the processing is simple for equipment, strong operability, and low energy consumption, to thermal sensitivity object
Material protection is advantageous.This technology utilization lactide fusing point (96 DEG C) and water (0 DEG C) lactic acid (52 DEG C) Study of Meso-Lactide fusing point (54
DEG C) difference, by static ontology crystallization with two processes of sweating solve the problems, such as preparation of industrialization high-purity lactide.
The present invention proposes the treatment process and recycling method of taking the mother liquor and intermediate of different phase auxiliary,
It can achieve the effect that get twice the result with half the effort, be the key that the important technology guarantor for improving the act of purifying yield, and reducing waste discharge
Card.
Feature of the present invention: high energy consumption, complicated multistage rectification technology and equipment have been abandoned, has not also had solvent treatment process.
New technological flow is brief, and operating aspect, equipment investment is few, and operation energy consumption is low, and product yield and quality are high, the object in purification process
Material can be recycled, and generate substantially without waste, complies fully with environmentally protective technique production feature, can embody technology comprehensively
The novelty of route and the effect got twice the result with half the effort.Product quality, which is entirely capable of reaching, both at home and abroad wants the index of high optical purity lactide
It asks.
Compared with prior art, the present invention mainly there is following advantage:
(1) process through the invention: the optical purity and chemical purity of lactide can reach 99.6% or more, far
Much higher than the level of purification (99%) of current rectifying equipment, requirement of the polylactic acid industry to lactide is complied fully with；Purify yield
90-95% (process materials can full recycling and reusing).
(2) two sets of technological equipment manufactures of main body are easy, and small investment, easy to operate, low energy consumption, operates item in present invention process
Under part, be conducive to the protection to heat sensitive material, whole material, can Reusability, generated substantially without waste, Ke Yiyou
Effect ground reduces production cost.
(3) main process process of the present invention does not introduce solvent, and the pollution problem of solvent or waste water is substantially not present, close to zero
Discharge technology complies fully with environment protection requirement.
Between 90-95%, mother liquor in the process substantially passes through processing and can circulate in purifying total recovery of the invention
It recycles.
Term " purifying total recovery " is defined as follows:
N: purifying total recovery；N1: product lactide weight；S: the lactide weight in the total feed before processing；
Specific embodiment
Embodiment 1
Crude lactide to be processed includes the component of following mass percent:
Lactide 92.9%
High boiling product 3.6%
Low boilers 3.5%
Evaporation equipment is common downward film evaporator:
(1) it by the crude lactide of processing, is sent into downward film evaporator, material is at 160 DEG C of temperature, vacuum degree 100Pa
Under conditions of continuous evaporation, lactide rapid evaporation with this condition, and being distilled out of together with moisture along with meso, acid,
Lactide crude product is collected by first-stage condenser, temperature control is 90 DEG C, and the lactide crude product that first-stage condenser is collected is evaporation
The 90% of gross mass is directly entered melting crystallizer, fusion-crystallization separation；
Secondary condenser temperature is 90 DEG C, collects the 10% of evaporation total amount, is sent to postprocessing working procedures and is handled, recycling benefit
With；
It is evaporated to light component no longer to come out, remaining raffinate is about 5%, and main component is oligomer, polymeric lactic acid and color
Element and coke object.
Evaporation yield is 90%, while raffinate is sent to postprocessing working procedures and is handled, and is recycled.
Melting crystallizer is made of crystallizer, material basin, the heat-conducting oil system of similar vertical tube type condenser:
(2) the lactide crude product for collecting first-stage condenser, is squeezed into melting crystallizer with pump, at this time in melting crystallizer
Temperature be 100 DEG C；
Melting crystallizer starts decrease temperature crystalline, and for rate of temperature fall in 2 DEG C/h, crystallization temperature is down to 70 DEG C, and disposable discharge is female
Liquid, containing most of meso, acid, water and a small amount of pigment in mother liquor, postprocessing working procedures are sent to, are handled, again reuse；
Then, crystal sweating, for heating rate in 2 DEG C/h, sweating temperature rises to 95 DEG C, collects sweating, is sent to post-processing
Process is handled, again reuse, and meso, acid, water are contained in sweating；
Then the product that sweating effort is completed in melting crystallizer, as high-purity lactide are collected, using GB/
T9722-2006 " chemical reagent gas chromatography general rule " method is detected, mass content 99.75%；
The collection method is as follows:
The lactide crystalline solid of sweating effort will be completed in melting crystallizer, is warming up to 110 DEG C, finished product is put into after dissolution
Basin；
In postprocessing working procedures, it can be used using Hydrolyze method, second melting crystallisation, short-path distillation method etc..Oligomer is turned
It is melted into lactic acid and a part of meso oligomer is separated by the control of different degradation rates, partially utilized as common lactic acid,
Major part can be with cycling and reutilization with reuse, process sweating.
Purifying total recovery is 93%；
In the above process, the material component table of each equipment is as follows: where is weight content.
Each position material component table of crystallizer
Embodiment 2
Crude lactide to be processed includes the component of following weight percent:
Lactide 93.8%
High boiling product 3.4%
Low boilers 2.8%
Evaporation equipment is common downward film evaporator:
(1) it by the crude lactide of processing, is sent into downward film evaporator, material is at 160 DEG C of temperature, vacuum degree 100Pa
Under conditions of continuous evaporation, lactide rapid evaporation with this condition, and being distilled out of together with moisture along with meso, acid,
Lactide crude product is collected by first-stage condenser, temperature control is 90 DEG C, and the lactide crude product that first-stage condenser is collected is evaporation
The 90% of gross mass is directly entered melting crystallizer, fusion-crystallization separation；
Secondary condenser temperature is 90 DEG C, collects the 10% of evaporation total amount, is sent to postprocessing working procedures and is handled, recycling benefit
With；
It is evaporated to light component no longer to come out, remaining raffinate is about 5%, and main component is oligomer, polymeric lactic acid and color
Element and coke object.
Evaporation yield is 90%, while raffinate is sent to postprocessing working procedures and is handled, and is recycled.
Melting crystallizer is made of crystallizer, material basin, the heat-conducting oil system of similar vertical tube type condenser:
(2) the lactide crude product for collecting first-stage condenser, is squeezed into melting crystallizer with pump, at this time in melting crystallizer
Temperature be 100 DEG C；
Melting crystallizer starts decrease temperature crystalline, and for rate of temperature fall in 2 DEG C/h, crystallization temperature is down to 80 DEG C, and disposable discharge is female
Liquid, containing most of meso, acid, water and a small amount of pigment in mother liquor, postprocessing working procedures are sent to, are handled, again reuse；
Then, crystal sweating, for heating rate in 2 DEG C/h, sweating temperature rises to 98 DEG C, collects sweating, is sent to post-processing
Process is handled, again reuse, and meso, acid, water are contained in sweating；
Then the product that sweating effort is completed in melting crystallizer, as high-purity lactide are collected, using GB/
T9722-2006 " chemical reagent gas chromatography general rule " method is detected, mass content 99.87%；
The collection method is as follows:
The lactide crystalline solid of sweating effort will be completed in melting crystallizer, is warming up to 110 DEG C, finished product is put into after dissolution
Basin；
In postprocessing working procedures, it can be used using Hydrolyze method, second melting crystallisation, short-path distillation method etc..Oligomer is turned
It is melted into lactic acid and a part of meso oligomer is separated by the control of different degradation rates, partially utilized as common lactic acid,
Major part can be with cycling and reutilization with reuse, process sweating.
Purifying total recovery is 90%；
In the above process, the material component table of each equipment is as follows: where is weight content.
Each position material component table of crystallizer
Claims (9)
1. the method for the continuous preparation high-purity lactide of industrialization, which is characterized in that in turn include the following steps: (1) thick third handing over
Ester evaporation and (2) fusion-crystallization；
(1) the crude lactide evaporation includes the following steps:
Crude lactide is sent into the evaporation equipment for being equipped with the condenser that second level is connected in series, heated under vacuum evaporation, from one
The lactide intermediate products for being stripped of most of high boiling product component are collected in grade condenser；
Described (2) fusion-crystallization includes the following steps:
Product among lactide will be collected in first-stage condenser, be sent into melting crystallizer, melting crystallizer decrease temperature crystalline, discharge mother
Liquid；
Then the crystal that will be left in melting crystallizer carries out crystal sweating, then collects the high-purity lactide.
2. the method according to claim 1, wherein in (1) crude lactide evaporation process, vacuum degree 100-
1000Pa, evaporating temperature are 130-160 DEG C.
3. according to the method described in claim 2, being stripped of most of higher boiling it is characterized in that, collecting from first-stage condenser
The lactide intermediate products of object component, yield are evaporating the 90%~95% of total amount.
4. according to the method described in claim 2, it is characterized in that, the temperature of the first-stage condenser be 90-100 DEG C, two
The temperature of grade condenser is 80-90 DEG C.
5. the method according to claim 1, wherein described (2) fusion-crystallization, will collect in first-stage condenser
Product among lactide are sent into the melting crystallizer that temperature is 100-120 DEG C.
6. according to the method described in claim 5, temperature is down to 70-90 DEG C it is characterized in that, rate of temperature fall is 2-8 DEG C/h.
7. according to the method described in claim 6, it is characterized in that, the crystal sweating: including the following steps:
For heating rate in 2-8 DEG C/h, sweating temperature rises to 93-100 DEG C, and sweating is discharged, and crystal is melted, then collected by heating
The high-purity lactide.
8. being sent into the method according to claim 1, wherein collecting the evaporant of surplus in secondary condenser
Postprocessing working procedures are handled, and are evaporated remaining raffinate feeding postprocessing working procedures and are handled, (2) the fusion-crystallization discharge
Mother liquor is sent to postprocessing working procedures and is handled in mother liquor containing most of meso, acid, water and a small amount of pigment at this time, recycling benefit
With；Contain meso, acid and water in sweating, be sent to postprocessing working procedures and handled, recycles.
9. described in any item methods according to claim 1~8, which is characterized in that the crude lactide includes following quality
The component of percentage: lactide 92-94%, low boilers 2.8-4.2%, high boiling substance: 3.2-3.8%.
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| CN110498787A (en) * | 2019-09-05 | 2019-11-26 | 安徽丰原福泰来聚乳酸有限公司 | A kind of purification system and purification process of lactide |
| CN111793055A (en) * | 2020-08-13 | 2020-10-20 | 山东寿光巨能金玉米开发有限公司 | Method for preparing high-gloss pure lactide by suspension crystallization method |
| CN112812094A (en) * | 2021-02-02 | 2021-05-18 | 江苏科富恺机械设备有限公司 | Method for purifying L-lactide |
| CN115010695A (en) * | 2022-05-31 | 2022-09-06 | 江苏景宏新材料科技有限公司 | Method for preparing high-purity lactide by utilizing recovered polylactic acid |
| CN115504956A (en) * | 2021-06-22 | 2022-12-23 | 上海浦景化工技术股份有限公司 | Method for preparing refined glycolide by purifying crude glycolide |
| CN115536628A (en) * | 2021-06-29 | 2022-12-30 | 中船重工鹏力（南京）塑造科技有限公司 | Purification method of crude lactide |
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Cited By (9)
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|---|---|---|---|---|
| CN110498787A (en) * | 2019-09-05 | 2019-11-26 | 安徽丰原福泰来聚乳酸有限公司 | A kind of purification system and purification process of lactide |
| CN110498787B (en) * | 2019-09-05 | 2020-10-27 | 安徽丰原福泰来聚乳酸有限公司 | Lactide purification system and purification method |
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| CN115504956A (en) * | 2021-06-22 | 2022-12-23 | 上海浦景化工技术股份有限公司 | Method for preparing refined glycolide by purifying crude glycolide |
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| CN115536628A (en) * | 2021-06-29 | 2022-12-30 | 中船重工鹏力（南京）塑造科技有限公司 | Purification method of crude lactide |
| CN115536628B (en) * | 2021-06-29 | 2024-05-31 | 中船鹏力(南京)塑造科技有限公司 | Purification method of crude lactide |
| CN115010695A (en) * | 2022-05-31 | 2022-09-06 | 江苏景宏新材料科技有限公司 | Method for preparing high-purity lactide by utilizing recovered polylactic acid |
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