CN110498787A - A kind of purification system and purification process of lactide - Google Patents
A kind of purification system and purification process of lactide Download PDFInfo
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- CN110498787A CN110498787A CN201910838696.8A CN201910838696A CN110498787A CN 110498787 A CN110498787 A CN 110498787A CN 201910838696 A CN201910838696 A CN 201910838696A CN 110498787 A CN110498787 A CN 110498787A
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- C07D319/00—Heterocyclic compounds containing six-membered rings having two oxygen atoms as the only ring hetero atoms
- C07D319/10—1,4-Dioxanes; Hydrogenated 1,4-dioxanes
- C07D319/12—1,4-Dioxanes; Hydrogenated 1,4-dioxanes not condensed with other rings
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- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
- C08G63/02—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
- C08G63/06—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds derived from hydroxycarboxylic acids
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Abstract
The invention belongs to polylactic acid production technical fields, specifically disclose a kind of purification system of lactide, while also disclosing a kind of purification process of lactide.The purification process includes rectification step, fusion-crystallization step and re-crystallization step, and crude lactide rectifying first purifies to obtain lactide gas, obtains middle pure C lactide through condensation；Middle pure C lactide enters falling-film crystallizer and carries out fusion-crystallization, isolated not lime set body and pure C lactide product；Recrystallization processing is carried out to obtained not lime set body, according to the difference for recrystallizing isolated product purity, respectively enters different recycle.Purification process lactide provided by the invention purifies high income, and purifies the purity is high of obtained lactide product.
Description
Technical field
The present invention relates to polylactic acid production technical fields, relate to more particularly to a kind of purification system of lactide, while also
And a kind of purification process of lactide.
Background technique
Polylactic acid (referred to as " PLA ") is further polymerized by the lactic acid of starch or sugared fermenting and producing, and polylactic acid is not with stone
Oil is raw material, has environmentally friendly, nontoxic, antibacterial, fire-retardant, good biocompatibility and the characteristics such as biodegradable, is considered
It is the following new material for being most hopeful to shake petroleum-based plastics and chemical fibre tradition status.The production technology of polylactic acid mainly has at present
" one-step method " and " two-step method ".Make lactic acid Direct Dehydration polycondensation using solvent under " one-step method " i.e. vacuum condition, using this method
Polylactic acid is produced, polycondensation reaction, which occurs, between polymerization process lactic acid molecules can generate by-product water (20%), due to being difficult to will react
Free water small molecule in system is efficiently separated from highly viscous condensate, so the polymer molecular weight that " one-step method " obtains
It is often lower, it is only tens of thousands of.Cyclic dimer lactide first is made with lactic acid in " two-step method ", is then handed over again with the third of high-purity
As intermediate product ring-opening polymerization, synthesizing polylactic acid, since lactide will not be generated in ring-opening polymerization occur for ester
By-product water, therefore can accurately control the polylactic acid of the molecular weight synthesis high molecular weight of polymerization reaction." two-step method " synthesis is poly-
Lactic acid is the polylactic acid production technology of current mainstream, but in the lactide crude product made of lactic acid often containing a small amount of lactic acid,
The impurity such as water and catabolite, it is necessary to by purification, the preparation of polylactic acid could be used for.Poly-lactic acid in high molecular weight is obtained, it is single
Body must have high-purity.The molecular weight and molecualr weight distribution of the polylactic acid of the split cyclopolymerization preparation of the purity of lactide has significantly
Influence, it may be said that the purity of lactide determine polylactic acid synthesis quality.In addition, if polylactic acid article is for built in human body
The control of material, impurity is more stringent.Therefore polylactic acid monomer purity is generally required to reach 99.00% or more, moisture is less than
0.15%.
Polylactic acid production scale in China's is generally smaller at present, builds up there is no large-scale production line, usually several hundred tons
Or a few kiloton, current lactide purifying is primarily due in China and still belongs to problem, and there is no mature lactide purification techniques, raw
Lactide needed for producing polylactic acid relies primarily on import, on the one hand leads to that the production cost increases, and another aspect technology is under one's control,
Eventually leading to China's polylactic acid production scale can not expand.The purification process of common lactide is broadly divided into following three kinds.
First, evaporation method of air aided, the principle of this method is to vaporize lactide by heating, as the steam component in air-flow
It is separated with its impurity phase, and increases the operation that can recycle lactide from steam flow in downstream.This method separation process is complicated, and
And yield is not generally high.
Second, Hydrolyze method, the purpose of this method is to remove Study of Meso-Lactide from crude lactide to obtain optical voidness
Spend the method for higher lactide, concrete operations mode be added into the crude lactide containing Study of Meso-Lactide it is a certain amount of
Water hydrolyzes Study of Meso-Lactide.Because hydrolysis can also occur for lactide, it is added using this method purifying lactide
The requirement of polymerization is also not achieved in the purity for the lactide that the amount and hydrolysis time of water are difficult to control, and obtain, it is also necessary into
The purifying of one step.
Third, recrystallization method, this method is a kind of most methods studied in current lactide purification technique, and is had
The period of common method in machine object purification process, this method purifying is long, and repeatedly purifying is needed to can be only achieved polymerization reaction
It is required that purity, the problem is that purifying by repeated recrystallize, the gross production rate of lactide is lower, and needs using a large amount of
The organic solvent of alcohols or lipid, is related to solvent recovery problem, can bring environmental pollution.
The importance of monomer of the lactide as synthesizing polylactic acid, yield and purity is self-evident.Although many researchs
Person is dedicated to the research of this respect, and achieves comparable progress, if but investment batch production, continuity, production in production
Still there are many work to do in rate, the rate of recovery and cost.In order to make it possible the industrialized production of lactide, it is necessary to third
The purifying process of lactide monomers improves.
Summary of the invention
The invention mainly solves the technical problem of providing a kind of purification systems of lactide, and provide a kind of pure using this
Change system carries out the lactide purification process of lactide purifying, and the lactide product purity which obtains is high, reaches poly-
It closes and requires, and lactide purifies high income.
In order to solve the above technical problems, the technical solution adopted by the present invention is that: a kind of purification system of lactide, the purifying
System includes rectifying column, and crude lactide feed pipe is provided on the rectifying column, and the bottom discharge port of the rectifying column is connected with
Reboiler is provided with feed inlet, gas phase discharge port, the bottom of the feed inlet of the reboiler and the rectifying column on the reboiler
The connection of portion's discharge port, the gas phase discharge port of the reboiler are connected to the bottom of the rectifying column by conveyance conduit；
Lactide gas vent is provided in the middle part of the rectifying column, the lactide gas vent is condensed by lactide
Device is connect with middle pure C lactide tank；
The discharge port of middle pure C lactide tank is successively concatenated with the first crystallization head tank, falling-film crystallizer, the film-falling crystallization
Device bottom also connects with the first crystallization head tank, the second crystallization head tank, high-purity lactide storage tank, crude lactide feed pipe respectively
It connects, the second crystallization head tank discharge port is connected to the material inlet of the falling-film crystallizer.
As a preferred embodiment, concatenating First Heat Exchanger on the crude lactide feed pipe.Crude lactide warp
First Heat Exchanger is heated to enter back into rectifying column after certain temperature, it is ensured that rectifying separating effect.
As a preferred embodiment, the discharge port of the middle pure C lactide tank and it is described first crystallization head tank it
Between concatenate the second heat exchanger.Middle pure C lactide enters the first crystallization head tank after the second heat exchanger is preheating to certain temperature, so
After be sent into falling-film crystallizer, it is ensured that film-falling crystallization effect obtains high-purity lactide product to keep separating effect more preferable.
As a preferred embodiment, T-type condenser is provided at the top of the rectifying column, the T-type condenser
Condensate outlet connect with light phase tank, the outlet of the condensable gas of the T-type condenser is connect by cold-trap with light phase tank.Setting
T-type condenser, cooperation cold-trap effect, the light phase that rectifying generates can be collected completely.
As a preferred embodiment, the condensable gas outlet of the lactide condenser passes through cold-trap and light phase tank
Connection, the condensable gas that lactide condenser comes out also enter light phase tank after cold-trap is cooling and collect.
As a preferred embodiment, recycle feed mouth and circulation discharge port are provided on the falling-film crystallizer,
It is provided with circulating line between the recycle feed mouth and circulation discharge port of the falling-film crystallizer, concatenates object on the circulating line
Material conveying pump.Material in falling-film crystallizer is constantly recycled, it is ensured that film-falling crystallization effect, to make separating effect
More preferably, high-purity lactide product is obtained.
As a preferred embodiment, the bottom of the reboiler is provided with heavy phase discharge port.It is generated in reboiler
Heavy phase from bottom heavy phase discharge port export after be collected.
The present invention also provides a kind of purification process of lactide, carry out third using above-described lactide purification system
The purifying of lactide, including rectification step, fusion-crystallization step, re-crystallization step.
Wherein, the rectification step includes: by crude lactide pre-heating temperature elevation to feeding rectifying column after 110~130 DEG C, slightly
Lactide flows from up to down in rectifying column, subsequently into reboiler, in the reboiler temperature be 135~155 DEG C, thick third
Lactide is heated through reboiler, and the crude lactide gas based on lactide heated enters rectifying column from rectifier bottoms,
Crude lactide gas inversely contacts in rectifying column with the crude lactide and carries out rectifying purifying, and rectifying column internal temperature is 115
~145 DEG C, top of tower pressure is 300~1000Pa, and tower bottom pressure is 1000~3000Pa, the lactide that rectifying purifies
Gas obtains middle pure C lactide through condensation；
The fusion-crystallization step includes: by middle pure C lactide pre-heating temperature elevation to the first crystallization of feeding after 115~125 DEG C
Then head tank enters back into falling-film crystallizer, first carry out decrease temperature crystalline to the middle pure C lactide in the falling-film crystallizer
Processing, obtain crystalline solid and non-lime set body, not lime set body import second crystallize head tank, then the falling-film crystallizer again into
Row heating melt process, the sweating to heat up import the first crystallization head tank, mix recycling with the middle pure C lactide,
The obtained lysate that heats up is pure C lactide product；
The re-crystallization step includes；The not lime set body second crystallized in head tank is sent into falling-film crystallizer, described
Decrease temperature crystalline processing first is carried out to the not lime set body in falling-film crystallizer, obtains recrystallization crystalline solid and recrystallization not lime set
Body, lime set body mix with crude lactide and enters back into rectification step recrystallization, and then the falling-film crystallizer carries out heating up again and melt
Melt processing, the recrystallization sweating to heat up imports the second crystallization head tank and recycles, the recrystalizing solvent liquid to heat up
The first crystallization head tank is imported, mixes recycling with the middle pure C lactide.
Preferably, the cooling rate of the decrease temperature crystalline processing is 1~3 DEG C/min.
Preferably, the heating rate of the heating melt process is 1~3 DEG C/min.
The purifying of lactide, including rectification step, fusion-crystallization are carried out using lactide purification system provided by the invention
Step and re-crystallization step, i.e., the method being coupled using rectifying, fusion-crystallization and recrystallization three.Crude lactide, wherein third
The mass percentage content of lactide is generally 80~95%, and crude lactide is first in rectification step, by setting suitable rectifying
Condition, rectifying purify to obtain lactide gas, and lactide gas obtains middle pure C lactide through condensation, wherein the quality of lactide
Degree reaches 92~96%；Middle pure C lactide enters back into falling-film crystallizer, fusion-crystallization is carried out, in falling-film crystallizer
First centering pure C lactide carries out control decrease temperature crystalline processing, and the orderly decrease temperature crystalline of middle pure C lactide is precipitated, obtains crystalline solid
Not lime set body, lime set body does not import the second crystallization head tank, and falling-film crystallizer carries out heating melt process again later, heats up
The sweating arrived imports the first crystallization head tank, mixes recycling with middle pure C lactide, the lysate to heat up is pure C
Lactide product, wherein the mass percentage content of lactide is greater than 99.5%, reaches the purity requirement of polymerization reaction；Hereafter again into
Row re-crystallization step, the process object of re-crystallization step is the not lime set body imported in the second crystallization head tank, by the not lime set
Body is sent into falling-film crystallizer, makees decrease temperature crystalline processing, obtains recrystallization crystalline solid and recrystallization not lime set body, and recrystallization does not coagulate
Liquid is sent to be mixed with crude lactide, and the rectification step for entering back into purification process is recycled, and then falling-film crystallizer remakes liter
Warm melt process, the recrystallization sweating to heat up import the second crystallization head tank, can enter next recrystallization operation, rise
The recrystalizing solvent liquid that temperature obtains imports the first crystallization head tank, and fusion-crystallization processing is carried out after mixing with middle pure C lactide.
The beneficial effects of the present invention are: carrying out the purifying of lactide using lactide purification system provided by the invention, obtain
The lactide product purity arrived is greater than 99.5%, can reach the purity of polymerization reaction requirement；Due to increasing re-crystallization step,
The processing of one step recrystallization is carried out again to the not lime set body that fusion-crystallization obtains, not according to the isolated product purity of recrystallization
Together, it respectively enters different lower steps to recycle, can effectively improve the yield of lactide product in this way, and save processing energy
Consumption, purification process yield of the present invention can reach 83.88% or more.Purification process provided by the invention is suitable pure by controlling
Change condition, side reaction does not occur in purification process, and lactide purifies high income；It is not lime set body reuse using fusion-crystallization substrate
Method, make lactide purify yield further increase；Purify the purity is high of obtained lactide product；Energy consumption has been saved,
And be solvent-free purifying, any solvent is not added in purification process, has saved cost；The light phase and heavy phase that purification process generates
It is effectively collected, generation environment does not pollute, and can be used as byproduct recycling；Purification process provided by the invention is suitable for
The industrialized production of lactide.
Detailed description of the invention
Fig. 1 is a kind of schematic diagram of lactide purification system provided by the invention；
In figure, 1- first material delivery pump, 2- First Heat Exchanger, 3- rectifying column, 4-T type condenser, 5- reboiler, 6-
Two material-handling pumps, 7- third material-handling pump, 8- cold-trap, 9- light phase tank, 10- lactide condenser, pure C lactide in 11-
Tank, 12- 4 materials delivery pump, the second heat exchanger of 13-, 14- first crystallize head tank, and 15- second crystallizes head tank, 16- the
Five material-handling pumps, 17- falling-film crystallizer, the 6th material-handling pump of 18-, the high-purity lactide storage tank of 19-, the 7th material of 20- are defeated
Send pump.
Specific embodiment
Technical solution of the present invention is described in detail with reference to the accompanying drawing.
As shown in Figure 1, being a kind of purification system of lactide provided by the invention, including rectifying column 3, set on rectifying column 3
It is equipped with crude lactide feed pipe, the bottom discharge port of rectifying column 3 is connected with reboiler 5, feed inlet, gas are provided on reboiler 5
The feed inlet of phase discharge port, reboiler 5 is connect with the bottom discharge port of rectifying column 3, and the gas phase discharge port of reboiler 5 passes through conveying
Pipeline is connected to the bottom of rectifying column 3；
The middle part of rectifying column 3 is provided with lactide gas vent, lactide gas vent by lactide condenser 10 with
Middle pure C lactide tank 11 connects；
The discharge port of middle pure C lactide tank 11 is successively concatenated with the first crystallization head tank 14, falling-film crystallizer 17, falling liquid film knot
Brilliant 17 bottom of device also crystallizes head tank 15, high-purity lactide storage tank 19, crude lactide with the first crystallization head tank 14, second respectively
Feed pipe connection, the second crystallization 15 discharge port of head tank are connected to the material inlet of falling-film crystallizer 17.
Further, First Heat Exchanger 2 is concatenated on crude lactide feed pipe.
The second heat exchanger 13 is concatenated between the discharge port of middle pure C lactide tank 11 and the first crystallization head tank 14.
The top of rectifying column 3 is provided with T-type condenser 4, and the condensate outlet of T-type condenser 4 is connect with light phase tank 9, T-type
The condensable gas outlet of condenser 4 is connect by cold-trap 8 with light phase tank 9.
The condensable gas outlet of lactide condenser 10 is connect by cold-trap 8 with light phase tank 9.
It is provided with recycle feed mouth and circulation discharge port on falling-film crystallizer 17, the recycle feed mouth of falling-film crystallizer and follows
It is provided with circulating line between ring discharge port, concatenates the 6th material-handling pump 18 on circulating line.
The bottom of reboiler 5 is provided with heavy phase discharge port, and heavy phase discharge nozzle, heavy phase discharge nozzle are equipped on heavy phase discharge port
Upper concatenation third material-handling pump 7.
The workflow of the lactide purification system are as follows: crude lactide passes through First Heat Exchanger 2 by first material delivery pump 1
Rectifying column 3 is pumped into after pre-heating temperature elevation, liquid is moved inside rectifying column 3 from up to down by gravity, defeated by second material
Pump 6 is sent to be transported to reboiler 5, material vaporizes after the heating of reboiler 5, enters rectifying by 3 bottom of rectifying column in gaseous form
Tower 3, vaporized gas in the bottom-up movement in the inside of rectifying column 3, under the action of 3 inner stuffing of rectifying column with feed liquid material
Carry out mass exchange is come into full contact with, 5 bottoms of reboiler is discharged by third material-handling pump 7, and effluent is in crude lactide
Heavy component.Light component is laggard through 4 condensation liquefaction of T-type condenser by entering T-type condenser 4 at the top of rectifying column 3 in vaporized gas
Enter light phase tank 9, not solidifying gas enters 8 time condensation of cold-trap in T-type condenser 4, and light phase also enters light phase tank 9 after liquefaction.Product
Lactide enters lactide condenser 10 in the middle part of rectifying column 3 in gaseous form, laggard through 10 condensation liquefaction of lactide condenser
Enter middle pure C lactide tank 11, not solidifying gas enters 8 time condensation of cold-trap in lactide condenser 10, and light phase tank 9 is entered after liquefaction.
Crude lactide material obtains middle pure C lactide after rectification working process is handled, and middle pure C lactide is by 4 materials delivery pump 12 through second
Heat exchanger 13 heat up after enter first crystallization head tank 14, then by first crystallization head tank 14 through the 5th material-handling pump 16 into
Enter 17 bottom stock chest of falling-film crystallizer, under the action of the 6th material-handling pump 18, middle pure C lactide is in falling-film crystallizer 17
Middle circulation gradually decreases middle pure C lactide temperature of charge by the heat tracing substance HTM of falling-film crystallizer 17 in cyclic process,
Make the pure C lactide gradually solidification and crystallization on the crystallizer of falling-film crystallizer 17, lime set body does not flow under gravity
Two crystallization head tanks 15, crystallisation by cooling begins through falling-film crystallizer 17 heat tracing substance HTM after terminating gradually rise falling liquid film
The temperature of crystallizer 17 melts middle pure C lactide crystallization and freezing material slowly, first melts part and is known as sweating, sweating liquid stream
Enter pure C lactide in the first crystallization head tank 14 and lower batch and enter falling-film crystallizer 17 together and crystallize again, sweating flows into
After first crystallization head tank 14, the material of redissolution enters high-purity lactide storage tank 19.In in second crystallization head tank 2 15
Lime set body is not recrystallized through the 5th material-handling pump 16 into falling-film crystallizer 17 pure C lactide, repeats above-mentioned crystallization step
Suddenly, resulting recrystallization not feed inlet progress reuse of the lime set body by the 7th material-handling pump 20 return rectifying column 3, recrystallization
Sweating is flowed into the second crystallization head tank 15 by gravity, and recrystalizing solvent liquid flows under the influence of gravity into the first crystallization charging
Pure C lactide enters falling-film crystallizer 17 together and crystallizes again in tank 14 and lower batch.
Using the above lactide purification system carry out lactide purifying method, including rectification step, fusion-crystallization step,
Re-crystallization step；
Rectification step: by crude lactide pre-heating temperature elevation to feeding rectifying column after 110~130 DEG C, crude lactide is in rectifying
It is flowed from up to down in tower, subsequently into reboiler, temperature is 135~155 DEG C in reboiler, and crude lactide adds through reboiler
Heat, the crude lactide gas based on lactide heated enter rectifying column from rectifier bottoms, crude lactide gas with
Inversely contact carries out rectifying purifying to crude lactide in rectifying column, and rectifying column internal temperature is 115~145 DEG C, top of tower pressure
For 300~1000Pa, tower bottom pressure is 1000~3000Pa, the lactide gas that rectifying purifies through condensation obtain in it is pure
Lactide；
Fusion-crystallization step: crystallizing head tank for middle pure C lactide pre-heating temperature elevation to feeding first after 115~125 DEG C,
Then falling-film crystallizer is entered back into, decrease temperature crystalline processing first is carried out to middle pure C lactide in falling-film crystallizer, it is solid to obtain crystallization
Body and non-lime set body, lime set body does not import the second crystallization head tank, and then falling-film crystallizer carries out heating melt process again, heating
Obtained sweating imports the first crystallization head tank, mixes recycling with middle pure C lactide, the lysate to heat up is as pure
Lactide product；
Re-crystallization step；The not lime set body second crystallized in head tank is sent into falling-film crystallizer, in falling-film crystallizer
Decrease temperature crystalline processing first is carried out to not lime set body, recrystallization crystalline solid and recrystallization not lime set body is obtained, recrystallizes not lime set
Body is mixed with crude lactide enters back into rectification step, and then falling-film crystallizer carries out heating melt process again, the weight to heat up
It crystallizing sweating and imports the second crystallization head tank recycling, the recrystalizing solvent liquid to heat up imports the first crystallization head tank,
Recycling is mixed with middle pure C lactide.
Wherein, the cooling rate of decrease temperature crystalline processing is 1~3 DEG C/min.
The heating rate for the melt process that heats up is 1~3 DEG C/min.
It is illustrated below by specific embodiment.
Embodiment 1
The crude lactide content of the present embodiment processing is 89%, moisture content 0.01%, and Meso- lactide content is
4%, lactic acid content 2.25%, remaining impurity content is 4.5%；
Crude lactide enters rectifying column 3, crude lactide warp by first material delivery pump 1 after the preheating of First Heat Exchanger 2
Temperature after crossing preheating is 115 DEG C；
3 head temperature of rectifying column is 120 DEG C in the present embodiment, and top of tower pressure is 600Pa, and column bottom temperature is 140 DEG C,
Tower bottom pressure is 2000Pa；
After crude lactide enters rectifying column 3 in the present embodiment, by gravity, move from up to down, by second material
Delivery pump 6 enters reboiler 5 by the top of reboiler 5, and the temperature of 5 inside crude lactide of reboiler is 142 DEG C, and crude lactide exists
After 5 inside of reboiler is heated, the small molecules such as lactide enter rectifying column 3 from 3 bottom of rectifying column with crude lactide gas form,
Heavy phase is discharged by 5 bottom of reboiler by third material-handling pump 7 in crude lactide, and heavy phase is that crude lactide mid-boiling point is higher than third
The substance of lactide；
Crude lactide gas is vaporization substance of the crude lactide after the heating of reboiler 5, crude lactide gas in the present embodiment
After body enters rectifying column 3, the bottom-up movement in rectifying column 3, with the crude lactide liquid moved from up to down by gravity
Body carries out mass exchange under the action of 3 inner stuffing of rectifying column, and it is cold that light phase enters T-type at the top of rectifying column 3 in gaseous form
Condenser 4, light phase are the substance that crude lactide mid-boiling point is lower than lactide；T-type condenser 4 is located at 3 top of rectifying column, is shell and tube
Condenser, using 70 DEG C of water as refrigerant；
Light phase is after 4 condensation liquefaction of T-type condenser in the present embodiment, enters light phase tank 9 in liquid form, on-condensible gas into
Enter 8 time condensation of cold-trap, cold-trap 8 is using 30 DEG C of water as refrigerant；
The lactide gas that 3 rectifying of rectifying column obtains in the present embodiment enters lactide condenser 10 in the middle part of rectifying column 3,
Lactide condenser 10 is using 90 DEG C of hot water as refrigerant, and the lactide in lactide gas is after 10 condensation liquefaction of lactide condenser
Liquid be known as in pure C lactide, the pure C lactide tank 11 in, on-condensible gas enters 8 time condensation of cold-trap, middle pure C lactide
Purity be 95%；
In the present embodiment middle pure C lactide by 4 materials delivery pump 12 by the second heat exchanger 13 enter first crystallize into
Batch can 14, temperature of the middle pure C lactide after the preheating of the second heat exchanger 13 is 115 DEG C；
Middle pure C lactide enters falling liquid film knot by the 5th material-handling pump 16 by the first crystallization head tank 14 in the present embodiment
Brilliant device 17 carries out fusion-crystallization, recycles inside falling-film crystallizer 17 under the action of the 6th material-handling pump 18, passes through simultaneously
HTM carries out slow cooling to lactide, crystallizes lactide slowly in 17 solidified inside of falling-film crystallizer；In the present embodiment slowly
The speed of cooling is 2 DEG C/min；
Middle pure C lactide is by after 17 decrease temperature crystalline of falling-film crystallizer in the present embodiment, not lime set body by gravity into
Enter the second crystallization head tank 15, then slowly heated up by HTM to coagulated substance in falling-film crystallizer 17, sweating flows into first
Pure C lactide crystallizes again together in crystallization head tank 14 and lower batch, and lysate is pure C lactide, stores up into high-purity lactide
Tank 19；The speed slowly to heat up in the present embodiment is 2 DEG C/min；Lime set body is not that middle pure C lactide passes through falling liquid film in the present embodiment
After 17 crystallization and freezing of crystallizer, be unable to the liquid of solidification and crystallization, by gravity enter second crystallization head tank 15 after in case
Recrystallization；Sweating is middle pure C lactide by 17 crystallization and freezing of falling-film crystallizer and after slow heating is melted in the present embodiment
Preceding 5min trickle；Lysate is that middle pure C lactide passes through 17 crystallization and freezing of falling-film crystallizer, and slowly rises in the present embodiment
Trickle after 5min after temperature is melted, is pure C lactide；The pure lactide content that the present embodiment obtains is 99.6%, can be reached
Polymerization reaction requirement；
It is recrystallized, is recrystallized to replace the first crystallization head tank 14 as charging using the second crystallization head tank 15 later
Tank repeats above-mentioned fusion-crystallization process, and lime set body does not return the recrystallization that recrystallization process obtains by the 7th material-handling pump 20
Process carries out rectifying before returning, and the recrystallization sweating of recrystallization process enters the second crystallization head tank 15, the weight of recrystallization process
It crystallizes lysate and enters the first crystallization head tank 14.
The yield that the present embodiment purification process purifies lactide is 84.32%.
Method referring to embodiment 1 is carried out example 2 and embodiment 3 is tested, parameter and test result such as following table.
Table 1
By above embodiments, the purification process of lactide provided by the invention is tied using rectifying and fusion-crystallization and again
The Methods For Purification lactide of crystal phase coupling, first uses rectification process, using boiling point substance difference, first carries out to crude lactide preliminary
Purification, obtains middle pure C lactide, then different using melting point substance, is further mentioned by fusion-crystallization technique centering pure C lactide
It is pure, pure C lactide is obtained, is coupled and is purified by two steps, obtained lactide purity can reach 99.5% or more, meet polymerization
Reaction requires；By the suitable purification condition of selection, side reaction does not occur in purification process, the recrystallization processing after combining,
Purifying yield is improved, purifying yield can reach 83.88% or more.
The above description is only an embodiment of the present invention, is not intended to limit the scope of the invention.
Claims (10)
1. a kind of purification system of lactide, which is characterized in that including rectifying column, be provided on the rectifying column crude lactide into
Expects pipe, the bottom discharge port of the rectifying column are connected with reboiler, and feed inlet, gas phase discharge port are provided on the reboiler,
The feed inlet of the reboiler is connect with the bottom discharge port of the rectifying column, and the gas phase discharge port of the reboiler passes through conveying
Pipeline is connected to the bottom of the rectifying column；
Be provided with lactide gas vent in the middle part of the rectifying column, the lactide gas vent by lactide condenser with
Middle pure C lactide tank connection；
The discharge port of middle pure C lactide tank is successively concatenated with the first crystallization head tank, falling-film crystallizer, the falling-film crystallizer bottom
Portion is also connect with the first crystallization head tank, the second crystallization head tank, high-purity lactide storage tank, crude lactide feed pipe respectively, institute
State the material inlet that the second crystallization head tank discharge port is connected to the falling-film crystallizer.
2. the purification system of lactide according to claim 1, which is characterized in that concatenated on the crude lactide feed pipe
First Heat Exchanger.
3. the purification system of lactide according to claim 1, which is characterized in that the discharge port of the middle pure C lactide tank
The second heat exchanger is concatenated between the first crystallization head tank.
4. the purification system of lactide according to claim 1, which is characterized in that be provided with T at the top of the rectifying column
The condensate outlet of type condenser, the T-type condenser is connect with light phase tank, and the condensable gas outlet of the T-type condenser is logical
Cold-trap is crossed to connect with light phase tank.
5. the purification system of lactide according to claim 4, which is characterized in that the condensated gas of the lactide condenser
Body outlet is connect by cold-trap with light phase tank.
6. the purification system of lactide according to claim 1, which is characterized in that be provided with and follow on the falling-film crystallizer
Ring feed inlet and circulation discharge port are provided with circulation pipe between the recycle feed mouth and circulation discharge port of the falling-film crystallizer
Road concatenates material-handling pump on the circulating line.
7. the purification system of lactide according to claim 1, which is characterized in that the bottom of the reboiler is provided with weight
Phase discharge port.
8. a kind of method for carrying out lactide purifying using purification system described in claim 1~7 any one, feature exist
In, including rectification step, fusion-crystallization step, re-crystallization step.
9. according to the method described in claim 8, it is characterized in that, the rectification step includes: by crude lactide pre-heating temperature elevation
Rectifying column is sent into after to 110~130 DEG C, crude lactide flows from up to down in rectifying column, described subsequently into reboiler
Temperature is 135~155 DEG C in reboiler, and crude lactide is heated through reboiler, and thick third based on lactide heated is handed over
Ester gas enters rectifying column from rectifier bottoms, and crude lactide gas inversely contacts progress with the crude lactide in rectifying column
Rectifying purifying, rectifying column internal temperature are 115~145 DEG C, and top of tower pressure is 300~1000Pa, and tower bottom pressure is 1000
~3000Pa, the lactide gas that rectifying purifies obtain middle pure C lactide through condensation；
The fusion-crystallization step includes: by middle pure C lactide pre-heating temperature elevation to the first crystallization of feeding charging after 115~125 DEG C
Then tank enters back into falling-film crystallizer, first carry out decrease temperature crystalline processing to the middle pure C lactide in the falling-film crystallizer,
Crystalline solid and non-lime set body are obtained, lime set body does not import the second crystallization head tank, and then the falling-film crystallizer is risen again
Warm melt process, the sweating to heat up import the first crystallization head tank, mix recycling with the middle pure C lactide, heat up
Obtained lysate is pure C lactide product；
The re-crystallization step includes；The not lime set body second crystallized in head tank is sent into falling-film crystallizer, in the falling liquid film
Decrease temperature crystalline processing first is carried out to the not lime set body in crystallizer, obtains recrystallization crystalline solid and recrystallization not lime set body,
Lime set body does not mix with crude lactide and enters back into rectification step recrystallization, and then the falling-film crystallizer carries out heating up again at melting
Reason, the recrystallization sweating to heat up import the second crystallization head tank and recycle, and the recrystalizing solvent liquid to heat up imports
First crystallization head tank, mixes recycling with the middle pure C lactide.
10. according to the method described in claim 9, it is characterized in that, the decrease temperature crystalline processing cooling rate be 1~3 DEG C/
min；The heating rate of the heating melt process is 1~3 DEG C/min.
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| CN112500389A (en) * | 2020-11-28 | 2021-03-16 | 万华化学(四川)有限公司 | Method for separating and purifying lactide |
| 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 |
| CN113336739A (en) * | 2021-06-25 | 2021-09-03 | 上海东庚化工技术有限公司 | Method for preparing high-purity glycolide |
| CN113387920A (en) * | 2021-05-28 | 2021-09-14 | 深圳市思尚科技有限公司 | Continuous production method and device from lactic acid oligomer to high optical purity polymer grade lactide |
| CN114377422A (en) * | 2022-01-12 | 2022-04-22 | 德艾柯工业技术(江苏)有限公司 | Purification process and equipment for polymer grade epsilon-caprolactone |
| CN114405040A (en) * | 2022-02-18 | 2022-04-29 | 华陆工程科技有限责任公司 | High-purity lactide extraction device and method capable of continuously operating |
| CN114471438A (en) * | 2022-02-18 | 2022-05-13 | 华陆工程科技有限责任公司 | Reaction device and method for industrial preparation of lactide |
| CN114478471A (en) * | 2022-02-10 | 2022-05-13 | 普立思生物科技有限公司 | Lactide purification system and purification process |
| CN114653086A (en) * | 2022-03-11 | 2022-06-24 | 孝感市易生新材料有限公司 | Device and method for preparing high-purity 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 |
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| CN112500389A (en) * | 2020-11-28 | 2021-03-16 | 万华化学(四川)有限公司 | Method for separating and purifying lactide |
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| CN114471438A (en) * | 2022-02-18 | 2022-05-13 | 华陆工程科技有限责任公司 | Reaction device and method for industrial preparation of lactide |
| CN114471438B (en) * | 2022-02-18 | 2023-08-25 | 华陆工程科技有限责任公司 | Reaction device and method for industrially preparing lactide |
| CN114405040A (en) * | 2022-02-18 | 2022-04-29 | 华陆工程科技有限责任公司 | High-purity lactide extraction device and method capable of continuously operating |
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| CN114653086A (en) * | 2022-03-11 | 2022-06-24 | 孝感市易生新材料有限公司 | Device and method for preparing high-purity L-lactide |
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| CN115010696B (en) * | 2022-07-26 | 2023-10-27 | 浙江海正生物材料股份有限公司 | Method for continuously preparing and purifying lactide |
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