WO2022045959A1 - Procédé de purification de lactide - Google Patents

Procédé de purification de lactide Download PDF

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Publication number
WO2022045959A1
WO2022045959A1 PCT/SG2020/050492 SG2020050492W WO2022045959A1 WO 2022045959 A1 WO2022045959 A1 WO 2022045959A1 SG 2020050492 W SG2020050492 W SG 2020050492W WO 2022045959 A1 WO2022045959 A1 WO 2022045959A1
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Prior art keywords
lactide
divided wall
lactic acid
product stream
zone
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PCT/SG2020/050492
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English (en)
Inventor
Jianjun SUI
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Sui Jianjun
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Priority to PCT/SG2020/050492 priority Critical patent/WO2022045959A1/fr
Publication of WO2022045959A1 publication Critical patent/WO2022045959A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • 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

Definitions

  • This invention relates to a process for the purification of lactide from a crude lactide vapor product stream, wherein said crude lactide prepared by means of depolymerization of low molecular weight polylactic acid, is purified by means of distillation. More specifically, the invention relates to an improved process for the separation of lactide from said crude lactide composed of at least water, lactic acid, lactide and lactic acid oligomers by at least two distillation stages, wherein a divided wall column is used as one of the distillation stages to obtain substantially pure liquid lactide.
  • Lactides are cyclic dimers of lactic acid and can be used as intermediates in the production of high molecular weight polylactic acid. These polymers may be useful in the biomedical industry and other applications e.g. as a decomposable packaging material due to their ability to be degraded biologically and hydrolytically while forming environmentally acceptable degradation products.
  • Examples of known methods for synthesizing lactide comprise a step of prepolymerization and a step of depolymerization.
  • First, lactic acid as a raw material is prepolymerized in a prepolymer reactor to generate low molecular weight polylactic acid by condensation of said lactic acid.
  • Second the thus obtained low molecular weight polylactic acid depolymerize to lactide in a lactide reactor under heating and reduced pressure in the presence of a catalyst, which lactide is recovered as a vapor product stream.
  • Methods for performing said prepolymerization and depolymerization are known in the art, see e.g. U.S. Pat. No. 5,053,522.
  • lactic acid includes two optical isomers, i.e. the ( A“ )-l act ic acid and (S)-lactic acid.
  • formation of lactide from the enantiomers of lactic acid gives rise to three stereoisomers with different geometric structures distinguished as ( A”, A“ )-l actide (or D-lactide), (S,S)-lactide (or L-lactide) and (7?,S)-lactide (or meso-lactide).
  • the concentration of these stereoisomers in the produced lactide differ, and is essentially based on the type and optical purity of the lactic acid and various process conditions applied in the lactide manufacturing process.
  • a crude lactic acid feed to the reactor system contains one of the two lactic acid selected from (S)-lactic acid and (7?)-lactic acid as a major component. Therefore, the crude lactide vapor product stream that is produced by depolymerization contains a major portion of an optically pure lactide (L-lactide or D-lactide), a minor portion of meso-lactide and the remaining third lactide in an even much smaller amount.
  • the said crude lactide not only comprises lactide but also other impurities, such as residual lactic acid, water, lactic acid oligomers and other reaction byproducts.
  • the molecular weight of polylactic acid is controlled by the amount of hydroxy lie impurities in lactide.
  • the crude lactide vapor product stream from depolymerization may, without condensation be fed directly to a conventional distillation system for purification.
  • U.S. Pat. No. 8,053,584 describes a process, wherein a crude lactide vapor product stream formed through depolymerization is transferred to a distillation column, which column is mounted onto a lactide reactor.
  • the liquid lactide containing condensate fraction removed from the top of the top-mounted distillation column comprises a major portion of lactide and is fed to the second distillation column, wherein the purified vapor lactide is obtained as a sidedraw stream located between the feed inlet and the lower end of the second distillation column.
  • the purified vapor lactide is subjected to condensation by means of a condenser as lactide in liquid form is more easily fed to an additional purification system such as melt crystallization or to a polymerization system.
  • a condenser as lactide in liquid form is more easily fed to an additional purification system such as melt crystallization or to a polymerization system.
  • One disadvantage of the process is that during distillation a stable control of flow rate of the purified vapor lactide stream fed to the subsequent condenser is complicated.
  • the pipes, valves and flanges connecting the outlet of the sidedraw with the subsequent condenser, and the condenser itself may be very large in size under the condition of deep vacuum applied in the distillation column, which will hold especially true for a high throughput of the purified vapor lactide stream.
  • U.S. Pat. No. 10,023,553 describes a process, wherein the crude lactide prepared by means of depolymerization of low molecular weight polylactic acid is maintained for a period of at least 5 hours in a reaction vessel at a temperature between 97° C and 200° C prior to a distillation column, in a purpose of decreasing the lactic acid content and increasing the lactic acid oligomers concentration, so that the resulting crude lactide can be more efficiently purified in the subsequent distillation column.
  • the purified vapor lactide is removed as the sidedraw from the distillation column and fed to a condenser for further processing.
  • the purified lactide in liquid form can be obtained directly as the sidedraw of the divided wall column, which purified lactide has a higher purity and is almost free of lactic acid and lactic acid oligomers in comparison with the purified lactide in gaseous form as the sidedraw of a conventional distillation column.
  • the above-mentioned equipment such as e.g. the condenser for condensing the purified vapor lactide stream and the reaction vessel for decreasing the lactic acid content in the lactide are saved.
  • FIG. 1 is a schematic diagram of a preferred lactide production system utilizing a divided wall column as one of the distillation stages to obtain the purified liquid lactide.
  • a typical prepolymerization reaction is conducted to generate low molecular weight polylactic acid in a prepolymer reactor at a pressure of about 10-20 mbar and at a temperature ranging from 120 to 250° C.
  • the said prepolymerization is a condensation reaction, by which lactic acid polymerizes to form low molecular weight polylactic acid.
  • the condensation reaction byproducts such as water is removed by evaporation or other means to cause the prepolymerization up to a molecular weight ranging from 150 to 10,000, preferably ranging from 250 to 5,000, and more preferably ranging from 400 to 2500.
  • a depolymerization reaction in the presence of a catalyst such as stannous octoate, is carried out in a depolymerization reactor at a pressure of about 20-50 mbar and at a temperature about 180-250° C.
  • Low molecular weight polylactic acid is depolymerized to generate crude lactide in gaseous form, which crude lactide comprises at least lactide, lactic acid, water and lactic acid oligomers.
  • the said crude lactide may additionally comprise other possible reaction by-products such as e.g. lactyl lactate and pyruvic acid.
  • the composition of the crude lactide depends largely on the molecular weight of the introduced low molecular weight polylactic acid, the type and amount of catalyst used and the reaction conditions such as the reaction temperature and pressure.
  • the said crude lactide can contain, for example, 60 to 99% by weight of lactide, 0 to 15% by weight of meso-lactide, 0 to 10% by weight of lactic acid, 0 to 12% by weight of lactic acid oligomers and 0 to 3% by weight of water.
  • the crude lactide vapor product stream is directly fed to the bottom of a distillation column as the first distillation stage, in which column the said crude lactide is fractionated based on volatility differences between components.
  • the relative order of decreasing volatility of the principal components of the said crude lactide is water, lactic acid, meso-lactide, optically pure lactide and lactic acid oligomers.
  • the less volatile components such as lactic acid oligomers, having a higher-boiling point than optically pure lactide, are concentrated at the bottom of the column, removed as bottoms product stream and refluxed to the lactic acid prepolymer reactor.
  • the other components such as water, lactic acid and lactide, having a lower-boiling point than lactic acid oligomers, are evaporated more easily than lactic acid oligomers, and thus concentrated at the top of the column.
  • the overhead vapor stream at the top of the column is condensed by means of a condenser to obtain a rectified liquid lactide stream. Vapors that have not been condensed in the condenser may be fed to an additional condenser for further condensation.
  • a portion of the rectified liquid lactide is preferably refluxed into the column.
  • the rectified liquid lactide stream comprises at least 90% by weight of lactide and 0-10% by weight of lactic acid, more preferably at least 96% by weight of lactide and 0-4% by weight of lactic acid.
  • the divided wall column preferably comprises: a divided wall provided vertically inside the column shell, defining a divided wall section between an upper undivided section as a rectifying zone for concentrating more volatile components such as water, lactic acid and meso-lactide of having a lower-boiling point than optically pure lactide and a lower undivided section as a stripping zone for concentrating less volatile components such as lactic acid oligomers of having a higher-boiling point than optically pure lactide; a divided wall section located between the rectifying zone and the stripping zone having a vertical dividing wall dividing the inner space of the divided wall section into a pre-fractionation zone at one side of the divided wall and a main fractionation zone at the other side of the divided wall; an inlet for the feed containing at least lactide and lactic acid in the pre-fractionation zone, a sidedraw outlet for the purified liquid lactide product stream in the main fractionation
  • the distillation in the divided wall column is preferably carried out at low temperatures and reduced pressures. Lower temperatures minimize the possible occurrence of side -reactions between lactic acid and lactide that can lead to product loss and contamination of the purified liquid lactide product stream as the sidedraw of the divided wall column.
  • the pressure and temperature at the top of the divided wall column are preferably in the ranges of 3 to 25 mbar and of 100 to 140° C, and more preferably of 5 to 15 mbar and of 105 to 130° C.
  • the pressure and temperature at the bottom of the divided wall column are preferably in the ranges of 10 to 35 mbar and of 140 to 175° C, more preferably of 12 to 25 mbar and of 145 to 160° C.
  • the present invention is not particularly limited with regard to the type of mass transfer elements installed in the divided wall column. Good results are obtained by using suitable mass transfer elements selected from the group consisting of random packings, structured packings and any combinations thereof. It is however, structured packings are particularly suitable as mass transfer elements with the advantages of reducing the liquid hold-up in the column and resulting in a lower pressure drop over the column. It is preferred that the structured packings have a specific surface area in the range of 125 to 750 m 2 /m 3 , and more preferably in the range of 250 to 350 m 2 /m 3 .
  • the length of the divided wall in the divided wall section depends on the process conditions and on the mass transfer elements used.
  • the length of the divided wall is approximately 2/3 of the total length of the mass transfer elements portion installed in the divided wall column. It is preferred that the total mass transfer elements portion of the divided wall column has a length between 4,000 and 20,000 mm, and more preferably between 6,000 and 15,000 mm.
  • the optimum length of the mass transfer elements portion depends particularly on the type of mass transfer elements selected, for example when a structured packing having a specific surface area of 250 m 2 /m 3 is used, the total length of mass transfer elements portion of the divided wall column is approximately in the range of 8,000 to 10,000 mm.
  • the divided wall section is partitioned by the divided wall into a pre-fractionation zone and a main fractionation zone, which each has a different volume, i.e. a different cross-sectional area for each zone.
  • Different processes may be optimized by appropriate selection of the partial cross-sections of the two zones.
  • Vapor flow from the stripping zone is divided in the pre-fractionation zone and the main fractionation zone in accordance with the cross-sectional area of each zone.
  • the partial cross- sectional areas are set in such a manner that the pressures at the inlet and outlet regions of the pre-fractionation zone are respectively identical with those at the inlet and outlet regions of the main fractionation zone, which means the total pressure drop of the packings within the pre- fractionation zone is the same as that for the packings within the main fractionation zone.
  • the divided wall column is equipped with at least one reboiler to generate the energy required for the evaporation and at least one condenser to condense the overhead vapor stream.
  • the reboiler can be of any of the types commonly found in the chemical industry, including, but not limited to, falling-film evaporators, forced circulation evaporators, thermosiphon evaporators and etc. However, due to its particularly reduced liquid hold-up, a falling film evaporator is preferred to minimize the residence time of lactide and lactic acid oligomers in the reboiler and therefore reduce any unfavorable side-reactions.
  • the condenser can be of any of the types commonly used in the chemical industry including cocurrent and counter-current condensers.
  • the overhead product stream of the divided wall contains a major portion of meso-lactide and a minor portion of mixture of lactic acid and optically pure lactide.
  • the bottoms product stream of the divided wall column comprises a major portion of lactic acid oligomers and a minor portion of lactide.
  • the purified liquid lactide product stream as the sidedraw is withdrawn from the main fractionation zone of the divided wall column, consisting essentially solely of lactide.
  • the overhead vapor stream at the top of the divided wall column is condensed by means of a condenser to obtain a condensate stream enriched in meso-lactide. Vapors that have not been condensed in the condenser may be fed to an additional condenser for further condensation. In order to efficiently remove other components from meso-lactide, a portion of the said condensate stream is preferably refluxed into the column. The other portion of the said condensate stream may be fed to an additional purification system such as a distillation, a crystallization or a combination thereof to obtain pure meso-lactide.
  • the liquid bottom stream concentrated in the stripping zone is drawn off from the bottom of the divided wall column and subsequently divided into a bottoms product stream, which stream is preferably refluxed to the lactic acid prepolymer reactor, and a recirculation stream, which stream is reboiled in the falling film evaporator.
  • the increase of the amount of lactic acid oligomers in the bottoms product stream is observed due to the side -reactions occurring under the distillation conditions of a relatively high temperature at the bottom of the divided wall column, which is also the case for an above-mentioned conventional distillation column with a vapor sidedraw for the purified vapor lactide product stream.
  • the purified liquid lactide product stream as the sidedraw of the divided wall column comprises lactide in substantially pure form (in excess of 99.9% by weight of lactide). It is stressed that the lactide present in the said purified liquid lactide stream may be composed of three stereoisomers, i.e. L-lactide, meso-lactide and D-lactide. The concentration of these stereoisomers in the said purified liquid lactide stream differ, and is essentially based on the type and optical purity of the lactic acid.
  • the said purified liquid lactide stream will comprise a major portion of L-lactide or D-lactide, a minor portion of mesolactide and the remaining third lactide in an even much smaller amount.
  • the said purified liquid lactide stream is almost free of lactic acid and lactic acid oligomers and may directly, without further purification, be polymerized to high molecular weight polylactic acid.
  • certain specific cases such as to obtain the optically pure lactide, e.g.
  • the said purified liquid lactide stream may be subsequently fed to a further purification step, which step comprises at least one melt crystallization.
  • the melt crystallization is preferably performed by a suspension melt crystallization, a static crystallization, a falling film crystallization or a combination thereof.
  • FIG. 1 schematically shows a preferred lactide production system in accordance with the present invention, which production system comprises a lactic acid prepolymer reactor 2, a depolymerization reactor 4, a conventional distillation column 6, a condenser 8, a condensate drum 11, a column shell 15, a condenser 17, a condensate drum 20, a circulation pump 25, a falling film evaporator 27, a substantially fluid tight divided wall 30 extending vertically through the middle part of the column shell 15.
  • the inner space of the column shell 15 is divided by the divided wall 30 into four distinct zones, i.e.
  • the vapors generated at the bottom of the divided wall column flow upwards through the stripping zone 34 and divide into the pre-fractionation zone 31 and the main fractionation zone 33, counter-currently contacting the liquids flowing downwards from rectifying zone 32, effective for a mass transfer.
  • the overhead product stream 14 of the distillation column 6 is then separated by the mass transfer within the four operating zones into three product streams, i.e. an overhead product stream 22, a bottoms product stream 29 and a liquid sidedraw product stream 23.
  • a crude lactic acid feed is continuously fed through stream 1 to the prepolymer reactor 2.
  • the low molecular weight polylactic acid from the prepolymer reactor 2 is fed through stream 3 to the depolymerization reactor 4.
  • the crude vapor lactide generated from the depolymerization reactor 4 is fed directly to the conventional distillation column 6 through stream 5.
  • the overhead vapors are drawn off through stream 7, which is subsequently condensed in the condenser 8.
  • the condensates flow to the condensate drum 11 through stream 10 and then divide into an overhead product stream 14 distilled out from the top and into a reflux stream 12, which is fed back to the top of the conventional distillation column 6.
  • the uncondensed vapors are removed through stream 9.
  • the bottoms product is removed through stream 13 and refluxed to the prepolymer reactor 2.
  • the overhead product of the conventional distillation column 6 is fed through stream 14 to the pre-fractionation zone 31 of the divided wall column.
  • the overhead vapors are enriched in meso-lactide during the distillation in the rectifying zone 32 of the divided wall column, and are drawn off through stream 16, which is subsequently condensed in the condenser 17.
  • the condensates flow to the condensate drum 20 through stream 19 and then divide into an overhead product stream 22 distilled out from the top of the divided wall column and into a reflux stream 21, which is fed back to the rectifying zone 32.
  • the uncondensed vapors are removed through stream 18.
  • the lactic acid oligomers are concentrated in the stripping zone 34 and drawn off as a bottom stream 24.
  • the bottom stream 24 is subsequently divided into a bottoms product stream 29, which stream is withdrawn from the bottom of the divided wall column and refluxed to the prepolymer reactor 2, and a recirculation stream 26, which stream is reboiled in the falling film evaporator 27 and then fed back to the stripping zone 34 through stream 28.
  • the said purified liquid lactide product as the sidedraw of the divided wall column is withdrawn through stream 23 from the main fractionation zone 33.
  • the use of a divided-wall column as the second distillation stage to obtain the purified liquid lactide product stream as the sidedraw of the divided wall column makes it possible to obviate one or more disadvantages and drawbacks occurring for a conventional distillation column with a vapor sidedraw.
  • the said purified liquid lactide stream is almost free of lactic acid and lactic acid oligomers and may directly, without further purification, be polymerized to high molecular weight polylactic acid.
  • a distillation stage of a divided wall column according to an embodiment of the invention as shown in FIG. 1 was performed. Structured packings with a specific surface area of 250 m 2 /m 3 were used as mass exchange elements in the divided wall column. 35% by weight of the liquid from the rectifying zone 32 was introduced to the pre-fractionating zone 31 and 65 % by weight of the liquid from the rectifying zone 32 to the main fractionating zone 33.
  • the rectifying zone 32 had 4 theoretical stages and the stripping zone 34 had 1 theoretical stage.
  • the prefractionation zone 31 had 2 theoretical stages above and 9 theoretical stages below the feeding point for the overhead product stream 14 into the pre-fractionation zone 31.
  • the main fractionation zone 33 had 9 theoretical stages above and 2 theoretical stages below the withdrawal point of the sidedraw product stream 23 in the main fractionating zone 33.
  • the overhead pressure was 9 mbar.
  • the reflux ratio at the withdrawal point of the overhead product stream 22 was 9:1.
  • the pressure and temperature at the bottom of the divided wall column were 17 mbar and 149° C, respectively.
  • the overhead product stream 14 from the distillation column 6 with a mass flow rate of 5670 kg/h was continuously fed to the pre-fractionation zone 31 of the divided wall column.
  • meso-lactide was concentrated and might be fed to an additional purification system (not shown in FIG.l).
  • the bottoms product stream 29 containing a major portion of lactic acid oligomers was refluxed to the prepolymer reactor 2.
  • the liquid sidedraw product stream 23 is composed of substantially pure lactide that is almost free of lactic acid and lactic acid oligomers.
  • the liquid sidedraw product stream 23 could directly, without further purification, be polymerized to high molecular weight polylactic acid, or fed to a melt crystallization (not shown in FIG.l).
  • the energy consumption was as low as 1.8 MW for the divided wall column.
  • the compositions of different streams were tabulated in the following table.
  • a distillation stage of a conventional distillation column with a vapor sidedraw for purified lactide was performed. Structured packings with a specific surface area of 250 m 2 /m 3 were used as mass exchange elements in the column.
  • the column has the same number of theoretical stages as the divided wall column mentioned in Example 1, i.e. a total of 16 theoretical stages for each column.
  • the overhead product stream 14 with a mass flow rate of 5670 kg/h was continuously fed to the conventional distillation column with the feed inlet located at the point of theoretical stage 6.
  • the overhead product stream contained a major portion of meso-lactide and the bottoms product stream contained a major portion of lactic acid oligomers.
  • the withdrawal outlet of the vapor sidedraw product stream for purified lactide was at the point of theoretical stage 15.
  • the overhead pressure of the conventional distillation column was 9 mbar.
  • the pressure and temperature at the bottom of the conventional distillation column were 17 mbar and 149° C, respectively.
  • the energy consumption was 2.0 MW for the conventional distillation column.
  • the compositions of different streams were tabulated in the following table.
  • a distillation stage of a divided wall column according to an embodiment of the invention as shown in FIG. 1 was performed. Structured packings with a specific surface area of 250 m 2 /m 3 were used as mass exchange elements in the divided wall column. 53% by weight of the liquid from the rectifying zone 32 was introduced to the pre-fractionating zone 31 and 47% by weight of the liquid from the rectifying zone 32 to the main fractionating zone 33.
  • the rectifying zone 32 had 4 theoretical stages and the stripping zone 34 had 1 theoretical stage.
  • the prefractionation zone 31 had 2 theoretical stages above and 9 theoretical stages below the feeding point for the overhead product stream 14 into the pre-fractionation zone 31.
  • the main fractionation zone 33 had 9 theoretical stages above and 2 theoretical stages below the withdrawal point of the sidedraw product stream 23 in the main fractionating zone 33.
  • the overhead pressure was 8 mbar.
  • the reflux ratio at the withdrawal point of the overhead product stream 22 was 7.3:1.
  • the pressure and temperature at the bottom of the divided wall column were 16 mbar and 150° C, respectively.
  • the overhead product stream 14 from the distillation column 6 with a mass flow rate of 5665 kg/h was continuously fed to the pre-fractionation zone 31 of the divided wall column.
  • meso-lactide was concentrated and might be fed to an additional purification system (not shown in FIG.l).
  • the bottoms product stream 29 containing a major portion of lactic acid oligomers was refluxed to the prepolymer reactor 2.
  • the liquid sidedraw product stream 23 is composed of substantially pure lactide that is almost free of lactic acid and lactic acid oligomers.
  • the liquid sidedraw product stream 23 could directly, without further purification, be polymerized to high molecular weight polylactic acid, or fed to a melt crystallization (not shown in FIG.l).
  • the energy consumption was as low as 1.9 MW for the divided wall column.
  • the compositions of different streams were tabulated in the following table.
  • Lactic acid wt. % 3.85 20.61 0 0
  • a distillation stage of a conventional distillation column with a vapor sidedraw for purified lactide was performed. Structured packings with a specific surface area of 250 m 2 /m 3 were used as mass exchange elements in the column.
  • the column has the same number of theoretical stages as the divided wall column mentioned in Example 2, i.e. a total of 16 theoretical stages for each column.
  • the overhead product stream 14 with a mass flow rate of 5665 kg/h was continuously fed to the conventional distillation column with the feed inlet located at the point of theoretical stage 6.
  • the overhead product stream contained a major portion of meso-lactide and the bottoms product stream contained a major portion of lactic acid oligomers.
  • the withdrawal outlet of the vapor sidedraw product stream for purified lactide was at the point of theoretical stage 15.
  • the overhead pressure of the conventional distillation column was 8 mbar.
  • the pressure and temperature at the bottom of the conventional distillation column were 16 mbar and 150° C, respectively.
  • the energy consumption was 2.1 MW for the conventional distillation column.
  • the compositions of different streams were tabulated in the following table.
  • Lactic acid wt. % 3.85 20.57 0 0.01
  • the purified lactide obtained by the divided wall column of the present invention has a higher purity and is almost free of lactic acid and lactic acid oligomers, compared with that obtained by means of the conventional distillation column with a vapor sidedraw in the comparative examples.
  • the energy consumption for the divided wall column of the present invention is about 10% less than that for the comparative conventional distillation column with a vapor sidedraw. Consequently, the process for purification of the lactide of the present invention is useful as an industrially advantageous method for purified lactide to be polymerized to high molecular weight polylactic acid without further condensation.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Heterocyclic Compounds That Contain Two Or More Ring Oxygen Atoms (AREA)

Abstract

La présente invention concerne un procédé mettant en œuvre une distillation pour la purification de lactide à partir d'un flux de produit de vapeur de lactide brut, ledit lactide brut étant produit par dépolymérisation d'acide polylactique à faible poids moléculaire et étant composé d'au moins de l'eau, d'acide lactique, d'oligomères de lactide et d'acide lactique, une colonne à paroi divisée étant utilisée comme un des étages de distillation pour obtenir un flux de produit de lactide liquide purifié en tant que soutirage latéral de ladite colonne à paroi divisée.
PCT/SG2020/050492 2020-08-22 2020-08-22 Procédé de purification de lactide WO2022045959A1 (fr)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114653086A (zh) * 2022-03-11 2022-06-24 孝感市易生新材料有限公司 一种制备高纯度l-丙交酯的装置及方法
CN115010695A (zh) * 2022-05-31 2022-09-06 江苏景宏新材料科技有限公司 一种利用回收聚乳酸制备高纯度丙交酯的方法

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20100249364A1 (en) * 2007-09-03 2010-09-30 Uhde Inventa-Fischer Gmbh Cleaning device for separating dilactide from mixtures, polymerisation device, method for separating dilactide from mixtures and use thereof

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20100249364A1 (en) * 2007-09-03 2010-09-30 Uhde Inventa-Fischer Gmbh Cleaning device for separating dilactide from mixtures, polymerisation device, method for separating dilactide from mixtures and use thereof

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114653086A (zh) * 2022-03-11 2022-06-24 孝感市易生新材料有限公司 一种制备高纯度l-丙交酯的装置及方法
CN115010695A (zh) * 2022-05-31 2022-09-06 江苏景宏新材料科技有限公司 一种利用回收聚乳酸制备高纯度丙交酯的方法

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