WO2003091238A1 - Process for producing lactide - Google Patents

Process for producing lactide Download PDF

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Publication number
WO2003091238A1
WO2003091238A1 PCT/JP2003/005244 JP0305244W WO03091238A1 WO 2003091238 A1 WO2003091238 A1 WO 2003091238A1 JP 0305244 W JP0305244 W JP 0305244W WO 03091238 A1 WO03091238 A1 WO 03091238A1
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WO
WIPO (PCT)
Prior art keywords
lactide
lactic acid
acid polymer
magnesium
pyrolysis
Prior art date
Application number
PCT/JP2003/005244
Other languages
French (fr)
Japanese (ja)
Inventor
Haruo Nishida
Yujiang Fan
Yoshihito Shirai
Original Assignee
Haruo Nishida
Yujiang Fan
Yoshihito Shirai
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Publication date
Application filed by Haruo Nishida, Yujiang Fan, Yoshihito Shirai filed Critical Haruo Nishida
Priority to AU2003231482A priority Critical patent/AU2003231482A1/en
Priority to JP2004501944A priority patent/JP4458422B2/en
Publication of WO2003091238A1 publication Critical patent/WO2003091238A1/en

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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
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J11/00—Recovery or working-up of waste materials
    • C08J11/04—Recovery or working-up of waste materials of polymers
    • C08J11/10—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation
    • C08J11/12—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation by dry-heat treatment only
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J11/00—Recovery or working-up of waste materials
    • C08J11/04—Recovery or working-up of waste materials of polymers
    • C08J11/10—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation
    • C08J11/16—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation by treatment with inorganic material
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J2367/00—Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
    • C08J2367/04—Polyesters derived from hydroxy carboxylic acids, e.g. lactones
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/62—Plastics recycling; Rubber recycling

Definitions

  • the present invention relates to a method for producing lactide, which is a cyclic dimer of lactic acid, by depolymerizing a lactic acid polymer, and can be used not only for production but also as a chemical recycling technique.
  • lactic acid polymers With the increasing awareness of environmental issues in recent years, the development of biorecyclable and chemically recyclable lactic acid polymers has been actively developed.
  • a method for producing a lactic acid polymer a technique for synthesizing lactide from a lactic acid oligomer by thermal decomposition and then polymerizing the lactide to produce a lactic acid polymer has been well known. In this manufacturing process, maintaining optical purity is important. Because practical lactic acid polymers are transparent, high-strength polymers with a melting point of about 175 ° C, produced by ring-opening polymerization of optically active L-lactide, and a slight decrease in optical activity. This causes a remarkable decrease in the melting point and loses its practicality.
  • the optical purity of lactide is significantly affected not only by the optical purity of lactic acid as a raw material but also by the racemization during the depolymerization of lactic acid oligomers.
  • Noda and Okuyama studied a thermal decomposition catalyst for lactate oligosaccharide under a temperature of 190 to 230 ° C and a reduced pressure of 4 to 5 mmHg.
  • the order of the catalytic activities was Sn>Zn>Ti> Al, and almost the same tendency was reported for the retention of optical purity (Chemical Pharmaceutical. Bulletin, 47, 467 (1999)).
  • 11-209370 discloses a technique for obtaining high-purity lactide by heating to 120 to 230 ° C. in the presence of monobutyltin.
  • Japanese Patent Application Laid-Open No. 11-292,871 discloses a method in which copper chloride is added to a lactic acid oligomer having a molecular weight of 400 to 300, and the mixture is heated to 130 to 260 ° C. And that the racemization of lactide produced by the method is suppressed.
  • Japanese Patent Application Laid-Open No. Hei 10-30691 discloses that steam is blown into a depolymerization reaction system of lactic acid oligomer using a catalyst of Group IA, IIIA, IVA, IIB, and VA. It discloses that racemization is suppressed by heating to 130 to 260 ° C while mixing.
  • tin compounds are both good catalysts in terms of catalytic activity for thermal decomposition and ability to maintain optical purity.
  • it In consideration of chemical recycling, it must generally be applied to higher molecular weight lactic acid polymers, and similar properties are desired in high-temperature and long-time thermal decomposition.
  • the racemization proceeds and the optical purity of the resulting lactide decreases (for example, Polymer Degradation and Stability, 53, 329-342). (1996) and Journal of Applied Polymer Science, 78, 2369-2378 (2000)).
  • Several techniques have been disclosed as methods for suppressing racemization during the depolymerization of this high-molecular-weight lactic acid polymer.
  • Japanese Patent Application Laid-Open No. 9-214141 discloses a method in which a high-boiling alcohol is added in addition to tin as a pyrolysis catalyst, followed by depolymerization after alcohol decomposition. .
  • Japanese Patent Application Laid-Open No. HEI 8-111969 discloses a method for synthesizing lactide from a lactic acid oligomer using ferrous oxide as a catalyst. Furthermore, a method for thermally decomposing a lactic acid oligomer using a hydroxide or alkoxide of an alkali metal, a salt with a carboxylic acid or the like as a catalyst (Japanese Patent Application Laid-Open No. 6-65230) is disclosed. However, all of these methods are methods of lactide synthesis from lactic acid oligomers.
  • Alkali metal compounds and alkaline earth metal compounds generally have many safe compounds and are expected to be used as depolymerization catalysts in place of tin.On the other hand, they are also used as catalysts that are prone to racemization. It is known (JP-A-11-35663). Disclosure of the invention Therefore, a method for efficiently producing lactide with high optical purity from a high-molecular-weight lactic acid polymer is currently desired.
  • An object of the present invention is to provide a catalyst and depolymerization conditions for efficiently converting a lactic acid polymer to lactide having a high optical purity, for example, for chemical recycling of a used high-molecular-weight lactic acid polymer. .
  • the present inventors have conducted intensive studies on the above problems, and as a result, added an alkaline earth metal compound to the lactic acid polymer, and set the temperature at 320 ° C or lower, preferably at 200 ° C or higher and 320 ° C or lower.
  • the inventors have found that by heating in the lower temperature range, lactide can be efficiently converted into lactide having high optical purity, and the present invention has been completed. That is, the present inventors have found the following inventions.
  • a method for producing lactide comprising adding a compound of an alkaline earth metal to a lactic acid polymer and heating the compound to a temperature of from 200 ° C to 320 ° C.
  • the lactic acid polymer may have a weight average molecular weight of 10,000 or more, preferably 30,000 or more, and more preferably 100,000 or more.
  • the alkaline earth metal is preferably calcium or magnesium.
  • the compound of the alkaline earth metal is calcium carbonate, calcium oxide, calcium hydroxide, calcium hydride, magnesium carbonate, magnesium oxide, magnesium hydroxide, and hydrogenated. It is good to be one or more kinds different from the group consisting of magnesium, especially the group consisting of calcium carbonate, calcium oxide, calcium hydroxide, magnesium carbonate, magnesium oxide and magnesium hydroxide.
  • the addition step is preferably performed so that a counter ion of an alkaline earth metal is present around the molecular terminal of the lactic acid polymer.
  • the heating is performed at a temperature of 225 to 320 ° C, preferably 225 to 300 ° C. C, more preferably at 225-250 ° C.
  • the optical purity of the lactic acid polymer is at least 80% e.e., preferably at least 90% e.e., more preferably at least 96% e.e. e.
  • the content of meso-lactide in the lactide obtained is at least It is preferably 1 mol or less, preferably 5 mol or less, and more preferably 2 mol or less.
  • a magnesium compound is added to a lactic acid polymer, and the mixture is heated to a temperature of 320 ° C or less, preferably, 200 to 320 ° C, and 250 to 300 ° C. Manufacturing method of lactide.
  • the lactic acid polymer has a weight average molecular weight of 10,000 or more, preferably 30,000 or more, and more preferably 100,000 or more.
  • the magnesium compound is preferably one or more selected from the group consisting of magnesium carbonate, magnesium oxide, and magnesium hydroxide.
  • the magnesium compound is preferably magnesium oxide.
  • the addition step may be performed by mixing a solid of lactic acid polymer and a solid of magnesium oxide.
  • the addition step is preferably performed so that the magnesium counterion exists around the molecular terminal of the lactic acid polymer.
  • the optical purity of the lactic acid polymer is at least 80% e.e., preferably at least 90% e.e., more preferably at least 96% e.e. e. or more, and the content of meso-lactide in the obtained lactide is 1 O mo 1% or less, preferably 5 mo 1% or less, more preferably 2 mo 1% or less with respect to all lactides. It is good.
  • the lactic acid polymer is a polymer having a lactic acid ester structure as a basic unit.
  • the L-lactic acid ester structure unit is 90% or more, preferably 95% or more of all the units, more preferably 98% or more of the polymer.
  • Components other than the L-lactic acid ester unit include copolymers derived from lactones, cyclic ethers, cyclic amides, and cyclic acid anhydrides that can be copolymerized with D-lactic acid ester unit lactide. It is possible for a component unit to be present.
  • Copolymer components preferably used include lactones such as hydroprolactone, phenolic lacrolactone,] 3-butyrolactone and valaxoxanone; ethylene oxide, propylene oxide, butylene oxide, styrene oxide, styrene oxide, and phenol.
  • Cyclic ethers such as diglycidyl ether, oxetane, and tetrahydrofuran; cyclic amides such as ⁇ - caprolactam; cyclic acid anhydrides such as succinic anhydride and adipic anhydride.
  • an initiator component may be included as a unit that can coexist in the lactic acid polymer.
  • the initiator component alcohols, glycols, glycerols, other polyhydric alcohols, carboxylic acids, polycarboxylic acids, phenols and the like are used.
  • Specific examples of preferred initiator components include: ethylhexyl alcohol, ethylene glycol, propylene glycol, butanediol, polyethylene glycol, polypropylene glycol, polybutyl alcohol, glycerin, and octylic acid. Lactic acid, glycolic acid and the like.
  • an alkaline earth metal is an alkaline earth metal.
  • Known compounds can be used as the alkaline earth metal compound without any particular limitation.
  • Preferably used alkaline earth metal compounds are calcium compounds and magnesium compounds.
  • Specific examples of suitably used alkaline earth metal compounds include calcium carbonate such as calcium carbonate, calcium bicarbonate, calcium oxide, calcium hydroxide, and calcium hydride.
  • Compounds; magnesium compounds such as magnesium carbonate, magnesium bicarbonate, magnesium oxide, magnesium hydroxide, and magnesium hydride; composite metal compounds of calcium and magnesium; and the above calcium compounds and magnesium compounds.
  • a composite compound containing at least 10% by weight or more can be mentioned. Furthermore, two or more of these alkaline earth metal compounds can be used in combination.
  • the method of adding the alkaline earth metal compound can be a known addition method or a mixing method, and is not particularly limited.
  • the alkaline earth metal compound is preferably added so as to be present around the molecular terminal of the lactic acid polymer.
  • a compound of alkaline earth metal or a counterion of alkaline earth metal is preferably present around the molecular terminal of the lactic acid polymer, and an addition method or a mixing method designed as such is used. Is good. More specifically, it is desirable that the alkaline earth metal or a compound thereof is uniformly dispersed in the lactic acid polymer.
  • a method using a finely ground alkaline earth metal or a compound thereof in advance, a method of mixing an alkaline earth metal or a compound thereof with a lactic acid polymer, and then mechanically and / or thermally mixing and dispersing the mixture can be used.
  • suitable addition methods or mixing methods include a melt mixing method, a solution mixing method, a powder mixing and subsequent melt dispersion method, and a master batch method using a conventionally known mixing and dispersing apparatus such as a mixer or an extruder. be able to.
  • the lactic acid polymer has a thermal decomposition mechanism as described below. Samples can be made.
  • the degree of racemization of an alkaline earth metal compound varies depending on its type. For example, comparing a hydroxide with a strong alkalinity as an alkaline earth metal compound with a carbonate that is relatively neutral, the start of thermal decomposition is slow in the case of carbonate, and the carbonate moves to a higher temperature side than the hydroxide. Cheap. As a result, in the case of carbonate, the degree of racemization tends to be higher than that of hydroxide in the temperature range of 200 to 320 ° C. In the case of an oxide of a relatively alkaline alkaline earth metal, such as magnesium oxide, the start of thermal decomposition is slightly higher than that of the hydroxide, but it is 200.
  • magnesium oxide does not promote the decomposition of polylactic acid below 200 ° C due to its low dispersibility in polylactic acid. Since it tends to promote thermal decomposition due to its luka properties, it exhibits an extremely favorable effect of promoting the conversion to lactide with high optical purity while essentially suppressing the racemization reaction at less than 200 ° C.
  • Polylactic acid is considered to have the following thermal decomposition mechanism. That is, as the ripening mechanism, reaction 1 at 200 ° C or lower, reaction 2 at 200 to 320 ° C, and reaction 3 at 320 ° C or higher are considered.
  • Reaction 1 Selective racemization and meso-lactide formation reaction of carboxylic acid anion (one RCOO-one) by asymmetric carbon attack at 200 ° C or lower. In this temperature range, carboxylate acts as the main reactive species, which attacks the asymmetric carbon with a low electron density and produces meso-lactide while causing almost selective racemization by Balden inversion.
  • Reaction 2 Selective L, L-lactide formation reaction at 200-320 ° C by attack of alkanol anion (_RO—) by carbonyl carbon. At 200-320 ° C, alcoholate anion is considered to play a leading role in the decomposition reaction and attack carbonyl carbon to produce lactide without causing racemization. Since reaction 2 is much faster than reaction 1, reaction 1 is considered to be negligible in this temperature range.
  • Reaction 3 Racemization progresses by tautomerization reaction in the polymer main chain at 320 ° C or higher (increase in the production ratio of meso and D, D-lactide). Above 320 ° C, a "keto-enol tautomerization reaction" occurs in the polymer backbone, which is believed to cause racemization with a 50% probability.
  • the addition amount of the alkaline earth metal compound is 50 pp II! ⁇ 10% by weight, more preferably ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ! It should be in the range of ⁇ 5% by weight.
  • the amount of the above addition is Applied. More specifically, the above addition amount is also applied to the case where a polymer system containing another polymer in addition to the lactic acid polymer is subjected to chemical power recycling.
  • the polyolefin component is melted and reprocessed in the thermal decomposition temperature range of the lactic acid polymer.
  • the alkaline earth metal compound is reworked as it is in the polyolefin component, and can function as a reworked polyolefin filler.
  • the amount of the alkaline earth metal compound can be sufficiently added up to 100% by weight based on the total amount of the lactic acid polymer and the other polymer. After the addition or mixing step, it is subjected to a heating step.
  • the heating step is preferably at a temperature of from 200 to 320 ° C., preferably from 25 to 320 ° C., more preferably from 25 to 300 ° C., most preferably from 22 to 25 ° C. It is better to carry out at ⁇ 250 ° C.
  • This temperature range depends on the molecular weight of the lactic acid polymer, the alkaline earth metal, and the type and shape of the compound. For example, in the case of lactic acid polymers having a low molecular weight, the degree of racemization tends to be low even at relatively low temperatures. The cause of this is not clear yet, but it is considered that the racemization reaction that proceeds at less than 200 ° C. has a lactic acid polymer molecular weight dependency.
  • the above-mentioned temperature range of the present invention can sufficiently bring about the effect of suppressing racemization during the production of lactide.
  • lactic acid polymer into a reactor set to the above-mentioned temperature range, but it is also possible to increase the temperature from a lower temperature to a higher speed. Is selectable. In this case, it is desirable to raise the temperature as quickly as possible, but it is necessary to raise the temperature by at least 30 ° C to suppress racemization.
  • any of a batch type and a continuous type can be used.
  • Extruder is a preferred reactor 1. Autoclave, fluidized bed reactor and the like.
  • the control of the thermal decomposition temperature, the thermal decomposition rate, and the rate of temperature rise are controlled according to the temperature setting of each block of the cylinder, the number of rotations of the screw, the shape of the screw, the type of single screw and twin screw, etc. It is possible to set a suitable temperature range and a temperature rising range in the invention.
  • Each of the above-mentioned reactors has an outlet for removing a gas phase component and an inlet for an inert gas such as nitrogen gas for extruding and replacing Z or the gas phase component.
  • an inert gas such as nitrogen gas for extruding and replacing Z or the gas phase component.
  • a ventro is suitably used as an outlet.
  • the lactide of the present invention can be obtained.
  • a conventionally known method can be used for the evaluation of the racemization of the obtained lactide. For example, if one lactic acid unit undergoes racemization followed by lactide unit elimination, meso-lactide is formed. If two consecutive lactate units undergo racemization and the two lactate units are eliminated as lactide, D, D-lactide is formed. Generally, when the racemization reaction proceeds randomly, meso-lactide is produced as the main reaction product. The ratio of these meso-lactide and D, D-lactide to L, relactide can be confirmed by gas chromatogram analysis.
  • the racemization evaluation is based on the meso-lactide generation rate.
  • the combination can be used as an index. Therefore, the production ratio of meso-lactide in the obtained lactide is 1 Omo 1% or less, preferably 5mo 1% or less, and more preferably 2mo 1% or less.
  • the present invention can provide a method for producing lactide having an effect of suppressing racemization, but the optical purity of lactide obtained depends on the optical purity of polylactic acid used. That is, the higher the optical purity of the polylactic acid used, the higher the optical purity of the lactide obtained. Therefore, if the optical purity of the polylactic acid is at least 80% e.e., preferably at least 90% e.e., more preferably at least 96% e.e. Purity also increases.
  • % e.e The excess amount of one enantiomer present in a mixture consisting of only a pair of enantiomers called enantiomeric excess, expressed as a percentage.
  • Example 1 Synthesis of lactide by thermal decomposition of calcium salt-terminated PLL A in a temperature range of 225 to 250 ° C
  • the pyrolyzer with sampler is the same in the following Examples, Reference Examples and Comparative Examples.
  • PLLA-Ca10 was quickly charged into a pyrolysis oven preheated to 60 ° C while passing an active gas (He). Thereafter, the temperature was raised to 250 ° C at 10 ° C / min.
  • the pyrolysis products in the temperature range of 225-250 ° C were sampled using a sampler and analyzed by gas chromatography-mass spectrometry (GCMS). As a result of analysis, the content of meso-lactide in the total product lactide was 1.3%.
  • the pyrolysis of PLLA-Ca was carried out in the same manner as in Example 1, and the pyrolysis products in a temperature range of 60 to 250 ° C. were sampled using a sampler and analyzed by GCMS. As a result of analysis, the content of meso-lactide was 34.6% of the total lactide produced.
  • the pyrolysis of PLLA-Ca was carried out in the same manner as in Example 1, and the pyrolysis products in the temperature range of 60 to 225 ° C were separated using a sampler and analyzed by GCMS. As a result of analysis, the content of meso-lactide was 92.0% of the total lactide produced.
  • Example 1 The pyrolysis of PLLA-Ca was performed in the same manner as in Example 1, and the pyrolysis products in the temperature range of 60 to 200 ° C. were separated using a sampler and analyzed by GCMS. As a result of the analysis, the content of meso-lactide was 100% of the total lactide produced. From the results of Example 1 and Comparative Examples 1 to 3 above, in the temperature range: 200 to 250 ° C, particularly at 225 to 250 ° C, racemization accompanying thermal decomposition hardly occurs. At temperatures lower than 200 ° C, it can be seen that significant racemization has progressed.
  • Example 2 Synthesis of lactide by isothermal pyrolysis of PL LA-Ca at 250 ° C
  • the content of meso-lactide after decomposition for 10 minutes was 2.3%.
  • Example 2 From the results of Example 2 and Comparative Example 1, the isothermal pyrolysis of PL LA-Ca at 250 ° C clearly showed higher optical purity lactide than when the temperature was raised from 60 ° C to 250 ° C. It can be seen that it can be obtained.
  • the activation energy of the thermal decomposition reaction was 98 kJ Zinol, and it was confirmed that the decomposition reaction proceeded by the primary reaction that selectively generates lactide. Furthermore, it was preheated to 60 ° C while passing inert gas through the above-mentioned pyrolyzer with sampler. 10 ⁇ g of the PLLA-Ca sample was quickly introduced into the pyrolyzer and the temperature was raised in 10 minutes at a heating rate of 10 to completely pyrolyze the PLLA-Ca sample. As a result of analyzing the generated pyrolysis product by GCMS, the content of meso-lactide was 13.3%.
  • the PL LA-Na sample was completely Was pyrolyzed. Analysis of the generated pyrolysis products using GCMS showed that the lactide content was 58.2%, and that the lactate ester (4.7%), 3- to 10-mer (33.2 %), Lactic acid (1.5%), and acrylic acid (0.7%). That is, it was confirmed that the thermal decomposition of PLLA-Na was a decomposition that proceeded randomly within an intermolecular molecule, and was not a reaction for selectively producing lactide.
  • He inert gas
  • the prepared PLLA-Mg 10 ig was quickly charged into a pyrolysis oven heated to 250 ° C. Pyrolysis proceeded quickly, and the pyrolysis products were analyzed by GCMS. As a result, the content of meso-lactide in the case of pyrolysis for 60 seconds was 5.0%.
  • Example 6 Synthesis of lactide by isothermal pyrolysis of P LLA-Mg at 220 ° C
  • the heating temperature of the pyrolysis oven was set to 220 ° C.
  • Isothermal pyrolysis of the prepared magnesium oxide dispersion, PL LA-Mg was performed.
  • the content of meso-lactide after pyrolysis for 60 seconds was 4.2%.
  • Example 7 Synthesis of lactide by isothermal pyrolysis of P LLA-Mg at 200 ° C
  • the heating temperature of the pyrolysis oven was set to 200 ° C. Isothermal pyrolysis of the prepared magnesium oxide-dispersed PLLA-Mg was performed.
  • the content of meso-lactide in the case of performing the pyrolysis for 60 seconds was 5.0%.
  • the pyrolysis product distilled off under reduced pressure was collected in a room temperature trap.
  • the weight of the product distilled off during heating for 4 hours was 11.93 g, and the crude recovery was 59.6%.
  • Analysis of the recovered pyrolysis products using a gas chromatograph showed that the composition of the product was 94.5% for L-lactide, 4.7% for meso-lactide, and D -The lactide content was 0.8%.

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Abstract

A catalyst and depolymerization conditions for efficiently converting a lactic acid polymer into a lactide having a high optical purity. These are used for the purpose of, e.g., subjecting a waste high-molecular lactic acid polymer to chemical recycling. Also provided is a process for producing a lactide, characterized by adding a compound of an alkaline earth metal to a lactic acid polymer and heating the mixture to 320°C or lower.

Description

. 明 細 書  . Specification
ラクチドの製造方法 技術分野  Manufacturing method of lactide
本発明は、 乳酸ポリマーを解重合して乳酸の環状二量体であるラグチドを製造 する方法に関するものであり、 単に製造のみならずケミカルリサイクル技術とし て利用可能なものである。 背景技術  The present invention relates to a method for producing lactide, which is a cyclic dimer of lactic acid, by depolymerizing a lactic acid polymer, and can be used not only for production but also as a chemical recycling technique. Background art
近年の環境間題に対する意識の高まりから、 バイオリサイクルおよびケミカル リサイクル可能な乳酸ポリマーの開発が活発に展開されている。 乳酸ポリマーの 製造方法として、 乳酸オリゴマーから熱分解によってラクチドを合成し、 さらに そのラクチドを重合することによって乳酸ポリマーを製造する技術は従来から良 く知られている。 この製造過程において、 光学純度の保持は重要である。 なぜな ら、 実用的な乳酸ポリマーは、 光学活性な Lーラクチドの開環重合によって製造 される融点約 1 7 5 °Cの透明で高強度のポリマーであり、 わずかの光学活性の低 下によつて融点の著しい低下を招き、 その実用性を失ってしまうからである。 ラクチドの光学純度は、 原料となる乳酸の光学純度のみならず乳酸オリゴマー の解重合時のラセミ化によっても著しい影響を受ける。 野田と奥山は、 乳酸オリ ゴマ一の熱分解触媒の検討を温度 1 9 0〜 2 3 0 °C、 圧力 4〜 5 mmH gの減圧 下で行った。 その結果、 触媒活性の順序は S n〉 Z n〉T i 〉A lであり、 光学 純度の保持についても、 ほぼ同じ傾向を報告した （Chemical Pharmaceutical. Bulletin, 47, 467(1999))。 特開平 1 1— 2 0 9 3 7 0号公報は、 モノブチル錫 の存在下で 1 2 0〜 2 3 0 °Cに加熱することによって高純度のラクチドを得る技 術を開示している。 また、 特開平 1 1— 2 9 2 8 7 1号公報は、 分子量 4 0 0〜 3 0 0 0の乳酸オリゴマーに塩化銅を添加して、 1 3 0〜 2 6 0 °Cに加熱するこ とによって生成するラクチドのラセミ化が抑制されることを開示している。また、 特開平 1 0— 3 0 6 0 9 1号公報は、周期律表 I A、 I I I A、 I V A、 I I B、 および V A族の触媒を用いた乳酸オリゴマーの解重合反応系内に、 水蒸気を吹き 込みながら 1 3 0〜2 6 0 °Cに加熱する事によって、 ラセミ化が抑制されること を開示している。 With the increasing awareness of environmental issues in recent years, the development of biorecyclable and chemically recyclable lactic acid polymers has been actively developed. As a method for producing a lactic acid polymer, a technique for synthesizing lactide from a lactic acid oligomer by thermal decomposition and then polymerizing the lactide to produce a lactic acid polymer has been well known. In this manufacturing process, maintaining optical purity is important. Because practical lactic acid polymers are transparent, high-strength polymers with a melting point of about 175 ° C, produced by ring-opening polymerization of optically active L-lactide, and a slight decrease in optical activity. This causes a remarkable decrease in the melting point and loses its practicality. The optical purity of lactide is significantly affected not only by the optical purity of lactic acid as a raw material but also by the racemization during the depolymerization of lactic acid oligomers. Noda and Okuyama studied a thermal decomposition catalyst for lactate oligosaccharide under a temperature of 190 to 230 ° C and a reduced pressure of 4 to 5 mmHg. As a result, the order of the catalytic activities was Sn>Zn>Ti> Al, and almost the same tendency was reported for the retention of optical purity (Chemical Pharmaceutical. Bulletin, 47, 467 (1999)). Japanese Patent Application Laid-Open No. 11-209370 discloses a technique for obtaining high-purity lactide by heating to 120 to 230 ° C. in the presence of monobutyltin. Japanese Patent Application Laid-Open No. 11-292,871 discloses a method in which copper chloride is added to a lactic acid oligomer having a molecular weight of 400 to 300, and the mixture is heated to 130 to 260 ° C. And that the racemization of lactide produced by the method is suppressed. Also, Japanese Patent Application Laid-Open No. Hei 10-30691 discloses that steam is blown into a depolymerization reaction system of lactic acid oligomer using a catalyst of Group IA, IIIA, IVA, IIB, and VA. It discloses that racemization is suppressed by heating to 130 to 260 ° C while mixing.
このように、 スズ化合物は熱分解触媒活性および光学純度保持能に関していず れも良好な触媒である。 ケミカルリサイクルを考えた場合、 一般的に、 より高分 子量の乳酸ポリマーに適用されなければならず、 高温かつ長時間での熱分解にお いても同様の特性が望まれる。 しカゝしながら、 スズ触媒であっても、 高温かつ長 時間の条件下では、 ラセミ化が進行し、 生成するラクチドの光学純度は低下する (例えば、 Polymer Degradation and Stability, 53, 329-342(1996)および Journal of Applied Polymer Science, 78, 2369-2378(2000)を参照のこと）。 この 高分子量の乳酸ポリマーの解重合時に、 ラセミ化を抑制する方法として、 従来、 幾つかの技術が開示されている。 例えば、 特開平 9 _ 2 4 1 4 1 7号公報は、 熱 分解触媒としてのスズの他に高沸点のアルコール類を添加して、 加アルコール分 解の後に解重合させる方法を開示している。  Thus, tin compounds are both good catalysts in terms of catalytic activity for thermal decomposition and ability to maintain optical purity. In consideration of chemical recycling, it must generally be applied to higher molecular weight lactic acid polymers, and similar properties are desired in high-temperature and long-time thermal decomposition. However, even with a tin catalyst, under high-temperature and long-time conditions, the racemization proceeds and the optical purity of the resulting lactide decreases (for example, Polymer Degradation and Stability, 53, 329-342). (1996) and Journal of Applied Polymer Science, 78, 2369-2378 (2000)). Several techniques have been disclosed as methods for suppressing racemization during the depolymerization of this high-molecular-weight lactic acid polymer. For example, Japanese Patent Application Laid-Open No. 9-214141 discloses a method in which a high-boiling alcohol is added in addition to tin as a pyrolysis catalyst, followed by depolymerization after alcohol decomposition. .
一方、ポリマーのケミカルリサイクルシステムとして解重合反応を考えた場合、 単純に工場内でのラクチド合成プロセスとは異なり、 スズあるいはその他のエス テル交換金属触媒の環境への悪影響が危惧されている。 高分子量の乳酸ポリマー をより低温でかつ短時間で解重合反応を行うためには、 解重合のための触媒を新 たに添加する必要があるが、 より安全なものが要求されている。  On the other hand, when the depolymerization reaction is considered as a chemical recycling system for polymers, unlike the lactide synthesis process in the factory, there is a concern that tin or other ester exchange metal catalysts may have an adverse effect on the environment. In order to carry out the depolymerization reaction of a high molecular weight lactic acid polymer at a lower temperature and in a shorter time, it is necessary to newly add a depolymerization catalyst, but a safer one is required.
このような要求を受けて、 例えば、 特開平 8 _ 1 1 9 9 6 1号公報は、 酸化第 一鉄を触媒とする乳酸オリゴマーからのラクチドの合成法を開示している。 さら に、 アルカリ金属の水酸化物やアルコキシド、 およびカルボン酸との塩などを触 媒とする乳酸オリゴマーの熱分解方法 （特開平 6— 6 5 2 3 0号公報） が開示さ れている。 しかしながらこれらの方法は、 いずれも乳酸オリゴマーからのラクチ ド合成の方法である。  In response to such a demand, for example, Japanese Patent Application Laid-Open No. HEI 8-111969 discloses a method for synthesizing lactide from a lactic acid oligomer using ferrous oxide as a catalyst. Furthermore, a method for thermally decomposing a lactic acid oligomer using a hydroxide or alkoxide of an alkali metal, a salt with a carboxylic acid or the like as a catalyst (Japanese Patent Application Laid-Open No. 6-65230) is disclosed. However, all of these methods are methods of lactide synthesis from lactic acid oligomers.
アル力リ金属化合物やアル力リ土類金属化合物は、 一般的に安全な化合物が多 く、 スズに代わる解重合触媒として期待されるが、 これらは一方で、 ラセミ化を 起こし易い触媒としても知られている （特開平 11-35663)。 発明の開示 したがって、 高分子量の乳酸ポリマーから、 高い光学純度のラクチドを効率的 に生成するための方法が現在望まれている。 Alkali metal compounds and alkaline earth metal compounds generally have many safe compounds and are expected to be used as depolymerization catalysts in place of tin.On the other hand, they are also used as catalysts that are prone to racemization. It is known (JP-A-11-35663). Disclosure of the invention Therefore, a method for efficiently producing lactide with high optical purity from a high-molecular-weight lactic acid polymer is currently desired.
本発明の目的は、 例えば使用済みの高分子量の乳酸ポリマーをケミカルリサイ クルするためなど、 乳酸ポリマーを高い光学純度のラクチドに効率的に変換する ための触媒および解重合条件を提供することにある。  An object of the present invention is to provide a catalyst and depolymerization conditions for efficiently converting a lactic acid polymer to lactide having a high optical purity, for example, for chemical recycling of a used high-molecular-weight lactic acid polymer. .
本発明者らは上記課題について鋭意検討を行った結果、 乳酸ポリマーにアル力 リ土類金属化合物を添加し、 3 2 0 °C以下、 好ましくは 2 0 0 °C以上 3 2 0 °C以 下の温度範囲で加熱することによって、 効率的にかつ高い光学純度のラクチドに 変換することができることを見出し、 本発明を完成するに至った。 即ち、 本発明 者らは、 以下の発明を見出した。  The present inventors have conducted intensive studies on the above problems, and as a result, added an alkaline earth metal compound to the lactic acid polymer, and set the temperature at 320 ° C or lower, preferably at 200 ° C or higher and 320 ° C or lower. The inventors have found that by heating in the lower temperature range, lactide can be efficiently converted into lactide having high optical purity, and the present invention has been completed. That is, the present inventors have found the following inventions.
< 1 > 乳酸ポリマーにアルカリ土類金属の化合物を添加し、 2 0 0 °C以上 3 2 0 °C以下に加熱することを特徴とするラクチドの製造方法。  <1> A method for producing lactide, comprising adding a compound of an alkaline earth metal to a lactic acid polymer and heating the compound to a temperature of from 200 ° C to 320 ° C.
< 2 > 上記 < 1 >において、乳酸ポリマーはその重量平均分子量が 1万以上、 好ましくは 3万以上、 より好ましくは 1 0万以上であるのがよい。  <2> In the above item <1>, the lactic acid polymer may have a weight average molecular weight of 10,000 or more, preferably 30,000 or more, and more preferably 100,000 or more.
< 3 > 上記く 1〉又は < 2 >において、 アルカリ土類金属は、 カルシウム又 はマグネシウムであるのがよい。  <3> In the above item <1> or <2>, the alkaline earth metal is preferably calcium or magnesium.
< 4 > 上記く 1 >〜< 3 >のいずれかにおいて、 アルカリ土類金属の化合物 は、 炭酸カルシウム、 酸化カルシウム、 水酸化カルシウム、 水素化カルシウム、 炭酸マグネシウム、 酸化マグネシウム、 水酸化マグネシウム及び水素化マグネシ ゥムからなる群、 特に炭酸カルシウム、 酸化カルシウム、 水酸化カルシウム、 炭 酸マグネシウム、 酸化マグネシウム及び水酸化マグネシウムからなる群、 から違 ばれる 1種または 2種以上であるのがよい。  <4> In any one of <1> to <3> above, the compound of the alkaline earth metal is calcium carbonate, calcium oxide, calcium hydroxide, calcium hydride, magnesium carbonate, magnesium oxide, magnesium hydroxide, and hydrogenated. It is good to be one or more kinds different from the group consisting of magnesium, especially the group consisting of calcium carbonate, calcium oxide, calcium hydroxide, magnesium carbonate, magnesium oxide and magnesium hydroxide.
< 5 > 上記く 1〉〜く 4〉のいずれかにおいて、 乳酸ポリマーの分子末端周 辺にアルカリ土類金属の対イオンが存在するように、 添加工程を行うのがよい。  <5> In any one of the above items 1) to 4), the addition step is preferably performed so that a counter ion of an alkaline earth metal is present around the molecular terminal of the lactic acid polymer.
< 6 > 上記く 1 >〜< 5 >のいずれかにおいて、加熱を、 2 2 5〜 3 2 0 °C、 好ましくは 2 2 5〜 3 0 0。C、より好ましくは 2 2 5〜 2 5 0 °Cで行うのがよい。  <6> In any one of the above items 1 to <5>, the heating is performed at a temperature of 225 to 320 ° C, preferably 225 to 300 ° C. C, more preferably at 225-250 ° C.
< 7 > 上記く 1 >〜< 6〉のいずれかにおいて、 乳酸ポリマーの光学純度が 8 0 % e . e . 以上、 好ましくは 9 0 % e . e . 以上、 より好ましくは 9 6 % e . e . 以上であって、 且つ得られるラクチド中のメソ-ラクチドの含有率が全ラクチ ドに対して 1 O m o 1 %以下、 好ましくは 5 m o 1 %以下、 より好ましくは 2 m o 1 %以下であるのがよい。 <7> In any one of the above items 1> to <6>, the optical purity of the lactic acid polymer is at least 80% e.e., preferably at least 90% e.e., more preferably at least 96% e.e. e. The content of meso-lactide in the lactide obtained is at least It is preferably 1 mol or less, preferably 5 mol or less, and more preferably 2 mol or less.
< 8 > 乳酸ポリマーにマグネシウムの化合物を添加し、 3 2 0 °C以下、 好ま しくは 2 0 0〜3 2 0 °C、 2 5 0〜 3 0 0 °Cに加熱することを特徴とするラクチ 'ドの製造方法。  <8> A magnesium compound is added to a lactic acid polymer, and the mixture is heated to a temperature of 320 ° C or less, preferably, 200 to 320 ° C, and 250 to 300 ° C. Manufacturing method of lactide.
く 9〉 < 8 >において、 乳酸ポリマーはその重量平均分子量が 1万以上、 好 ましくは 3万以上、 より好ましくは 1 0万以上であるのがよい。  <9> In <8>, the lactic acid polymer has a weight average molecular weight of 10,000 or more, preferably 30,000 or more, and more preferably 100,000 or more.
< 1 0 > < 8〉又はく 9〉において、 マグネシウムの化合物は、 炭酸マグネ. シゥム、 酸化マグネシウム及び水酸化マグネシウムからなる群から選ばれる 1種 または 2種以上であるのがよい。  In <10> or <8> or <9>, the magnesium compound is preferably one or more selected from the group consisting of magnesium carbonate, magnesium oxide, and magnesium hydroxide.
< 1 1 > < 8〉又はく 9〉において、 マグネシウムの化合物は、 酸化マグネ シゥムであるのがよい。  In <11> <8> or <9>, the magnesium compound is preferably magnesium oxide.
< 1 2 > < 1 0〉又はく 1 1 >において、 乳酸ポリマーの固体と酸化マグネ シゥムの固体とを混合することにより、 添加工程を行うのがよい。  <12> In <10> or <11>, the addition step may be performed by mixing a solid of lactic acid polymer and a solid of magnesium oxide.
< 1 3 > < 8〉〜く 1 2 >のいずれかにおいて、 乳酸ポリマーの分子末端周 辺に前記マグネシウムの対イオンが存在するように、 添加工程を行うのがよい。  In any one of <13> to <8> to <12>, the addition step is preferably performed so that the magnesium counterion exists around the molecular terminal of the lactic acid polymer.
< 1 4 > < 8 >〜< 1 3 >のいずれかにおいて、 乳酸ポリマーの光学純度が 8 0 % e . e . 以上、 好ましくは 9 0 % e . e . 以上、 より好ましくは 9 6 % e . e . 以上であって、 且つ得られるラクチド中のメソ-ラクチドの含有率が全ラクチ ドに対して 1 O m o 1 %以下、 好ましくは 5 m o 1 %以下、 より好ましくは 2 m o 1 %以下であるのがよい。 発明を実施するための最良の形態  <14> In any one of <8> to <13>, the optical purity of the lactic acid polymer is at least 80% e.e., preferably at least 90% e.e., more preferably at least 96% e.e. e. or more, and the content of meso-lactide in the obtained lactide is 1 O mo 1% or less, preferably 5 mo 1% or less, more preferably 2 mo 1% or less with respect to all lactides. It is good. BEST MODE FOR CARRYING OUT THE INVENTION
以下、 本発明をより詳細に説明する。  Hereinafter, the present invention will be described in more detail.
後述する実施例において詳述するように、 アル力リ土類金属化合物の存在下に 高分子量の乳酸ポリマ一を熱分解した場合、 乳酸ポリマーの分子鎖末端より分解 が開始し、 ラクチド単位でジッパー式に脱離する解重合反応メカニズムで熱分解 が進行することを発見するに至った。 一方、 アルカリ土類金属化合物が共存しな い場合、 複雑な分子内ノ分子間での分解反応が進行し、 ラクチド以外の様々の分 解生成物が生成することを確認した。さらに、アルカリ金属化合物の存在下でも、 同様に複雑な分子内 分子間での分解反応が進行し、 ラクチド以外の様々な分解 生成物が生成することを確認した。 即ち、 アルカリ土類金属化合物の共存は、 特 異的なラクチド単位での解重合反応を引き起こすものである。 As will be described in detail in the examples below, when a high molecular weight lactic acid polymer is thermally decomposed in the presence of an alkaline earth metal compound, decomposition starts from the molecular chain end of the lactic acid polymer, and a zipper is formed in lactide units. They have discovered that thermal decomposition proceeds by a depolymerization reaction mechanism that desorbs according to the formula. On the other hand, when the alkaline earth metal compound does not coexist, the decomposition reaction between the complex intramolecular molecules proceeds, and various components other than lactide occur. It was confirmed that a decomposition product was formed. Furthermore, it was confirmed that, even in the presence of an alkali metal compound, a similarly complicated intermolecular decomposition reaction proceeds, and various decomposition products other than lactide are generated. That is, the coexistence of the alkaline earth metal compound causes a depolymerization reaction in a specific lactide unit.
本発明において、 乳酸ポリマーとは乳酸エステル構造を基本ュニットとするポ リマーであり、 特に L-乳酸エステル構造ユニットが全ユニッ トの 9 0 %以上、 好 ましくは 9 5 %以上、 さらに好ましくは 9 8 %以上のポリマーである。 L-乳酸ェ ステル構造ュニット以外の成分としては、 D-乳酸エステルュニットゃラクチドと 共重合可能なラク トン類、 環状エーテル類、 環状アミ ド類、 環状酸無水物類など に由来する共重合成分ュニッ トが存在することが可能である。  In the present invention, the lactic acid polymer is a polymer having a lactic acid ester structure as a basic unit. In particular, the L-lactic acid ester structure unit is 90% or more, preferably 95% or more of all the units, more preferably 98% or more of the polymer. Components other than the L-lactic acid ester unit include copolymers derived from lactones, cyclic ethers, cyclic amides, and cyclic acid anhydrides that can be copolymerized with D-lactic acid ester unit lactide. It is possible for a component unit to be present.
好適に用いられる共重合成分としては、 力プロラク トン、 ノくレロラク トン、 ]3 - ブチロラク トン、 バラジオキサノンなどのラク トン類；エチレンオキサイド、 プ ロピレンオキサイ ド、 ブチレンオキサイ ド、 スチレンオキサイ ド、 フエ二ルグリ シジルエーテル、 ォキセタン、 テ トラヒ ドロフランなどの環状エーテル類 ； ε - 力プロラクタムなどの環状アミ ド類； コハク酸無水物、 アジピン酸無水物などの 環状酸無水物類などである。 Copolymer components preferably used include lactones such as hydroprolactone, phenolic lacrolactone,] 3-butyrolactone and valaxoxanone; ethylene oxide, propylene oxide, butylene oxide, styrene oxide, styrene oxide, and phenol. Cyclic ethers such as diglycidyl ether, oxetane, and tetrahydrofuran; cyclic amides such as ε- caprolactam; cyclic acid anhydrides such as succinic anhydride and adipic anhydride.
さらに、 乳酸ポリマー中に共存しうるユニットとして、 開始剤成分も含まれ得 る。 この開始剤成分として、 アルコール類、 グリコール類、 グリセロール類、 そ の他の多価アルコール類、 カルボン酸類、 多価カルボン酸類、 およびフエノール 類などが用いられる。 好適に用いられる開始剤成分を具体的に例示すれば、 ェチ ルへキシルァノレコーノレ、 エチレングリコール、 プロピレングリコール、 ブタンジ オール、 ポリエチレングリ コール、 ポリプロピレングリ コール、 ポリ ビュルアル コール、 グリセリン、 ォクチル酸、 乳酸、 グリコール酸などである。  Further, an initiator component may be included as a unit that can coexist in the lactic acid polymer. As the initiator component, alcohols, glycols, glycerols, other polyhydric alcohols, carboxylic acids, polycarboxylic acids, phenols and the like are used. Specific examples of preferred initiator components include: ethylhexyl alcohol, ethylene glycol, propylene glycol, butanediol, polyethylene glycol, polypropylene glycol, polybutyl alcohol, glycerin, and octylic acid. Lactic acid, glycolic acid and the like.
本発明において不可欠の要件は、 アルカリ土類金属の存在である。 そのために 用いられるアルカリ土類金属の化合物として、 特に制限なく公知の化合物を用い ることができる。 好適に用いられるアルカリ土類金属の化合物として、 カルシゥ ムの化合物およびマグネシゥムの化合物であるのがよい。 好適に用いられるアル カリ土類金属の化合物を具体的に例示すれば、 炭酸カルシウム、 重炭酸カルシゥ ム、 酸化カルシウム、 水酸化カルシウム、 水素化カルシウムなどのカルシウム化 合物類；炭酸マグネシウム、 重炭酸マグネシウム、 酸化マグネシウム、 水酸化マ グネシゥム、 水素化マグネシウムなどのマグネシウム化合物類；カルシウムとマ グネシゥムの複合金属化合物類；並びに上記カルシウム化合物類およびマグネシ ゥム化合物類を少なく とも 1 0重量％以上含有する複合化合物などを挙げること ができる。 さらにこれらのアル力リ土類金属化合物が 2種以上混合して用いるこ ともできる。 An essential requirement of the present invention is the presence of an alkaline earth metal. Known compounds can be used as the alkaline earth metal compound without any particular limitation. Preferably used alkaline earth metal compounds are calcium compounds and magnesium compounds. Specific examples of suitably used alkaline earth metal compounds include calcium carbonate such as calcium carbonate, calcium bicarbonate, calcium oxide, calcium hydroxide, and calcium hydride. Compounds; magnesium compounds such as magnesium carbonate, magnesium bicarbonate, magnesium oxide, magnesium hydroxide, and magnesium hydride; composite metal compounds of calcium and magnesium; and the above calcium compounds and magnesium compounds. A composite compound containing at least 10% by weight or more can be mentioned. Furthermore, two or more of these alkaline earth metal compounds can be used in combination.
アル力リ土類金属の化合物の添加方法として、 公知の添加法又は混合法を挙げ ることができ、 特に限定されない。 但し、 アルカリ土類金属の化合物は、 乳酸ポ リマーの分子末端周辺に存在するように、 添加するのがよい。 例えば、 乳酸ポリ マーの分子末端周辺にアル力リ土類金属の化合物、 又はアル力リ土類金属の対ィ オンを存在させるのがよく、 そのように設計された添加法又は混合法を用いるの がよい。 より具体的には、 アルカリ土類金属又はその化合物が乳酸ポリマー中に 均一分散することが望ましい。 例えば、 アルカリ土類金属又はその化合物を予め 微細に粉砕したものを用いる力、 アルカリ土類金属又はその化合物と乳酸ポリマ 一とを混合した後、 機械的及び/又は熱的に混合分散させる方法を用いることが できる。 好適に用いられる添加法又は混合法として、 ミキサー又はェクス トルー ダーなどの従来より公知の混合分散装置を用いる、 溶融混合法、 溶液混合法、 粉 体混合後溶融分散法、 マスターバッチ法などを挙げることができる。  The method of adding the alkaline earth metal compound can be a known addition method or a mixing method, and is not particularly limited. However, the alkaline earth metal compound is preferably added so as to be present around the molecular terminal of the lactic acid polymer. For example, a compound of alkaline earth metal or a counterion of alkaline earth metal is preferably present around the molecular terminal of the lactic acid polymer, and an addition method or a mixing method designed as such is used. Is good. More specifically, it is desirable that the alkaline earth metal or a compound thereof is uniformly dispersed in the lactic acid polymer. For example, a method using a finely ground alkaline earth metal or a compound thereof in advance, a method of mixing an alkaline earth metal or a compound thereof with a lactic acid polymer, and then mechanically and / or thermally mixing and dispersing the mixture. Can be used. Examples of suitable addition methods or mixing methods include a melt mixing method, a solution mixing method, a powder mixing and subsequent melt dispersion method, and a master batch method using a conventionally known mixing and dispersing apparatus such as a mixer or an extruder. be able to.
なお、 アルカリ土類金属の化合物として、 酸化マグネシウムを用いる場合、 後 述するような熱分解メカニズムを有するため、 乳酸ポリマーと酸化マグネシウム とを、 固体同士で混合する方法により、 乳酸ポリマーを熱分解する試料を作製す ることができる。  When magnesium oxide is used as the alkaline earth metal compound, the lactic acid polymer has a thermal decomposition mechanism as described below. Samples can be made.
アルカリ土類金属の化合物は、 その種類によってラセミ化の度合いが変化する 。 例えば、 アルカリ土類金属化合物としてアルカリ性の強い水酸化物と比較的中 性に近い炭酸塩とを比較すると、 炭酸塩の場合、 熱分解の開始進行が遅くかつ水 酸化物より高温側に移動しやすい。 その結果として、 炭酸塩の場合、 2 0 0〜3 2 0 °Cの温度域で、 ラセミ化の度合いが水酸化物よりも高い傾向になる場合があ る。 比較的アルカリ性の強いアルカリ土類金属の酸化物、 例えば酸化マグネシゥ ムの場合、 熱分解の開始が水酸化物よりも少し高温側に移動するものの、 2 0 0 〜 320°Cの温度域においてラセミ化の度合いは比較的低い傾向にある。 とりわ け、 酸化マグネシウムの場合、 ポリ乳酸中への分散性の低さから、 200°C以下 でのポリ乳酸の分解を促進せず、 一方、 200〜320°Cの温度域では、 そのァ ルカリ性によって熱分解を促進する傾向があるため、 200°C未満でのラセミ化 反応を本質的に抑制しつつ光学純度の高いラクチドへの転換を促進するという極 めて好ましい作用を示す。 The degree of racemization of an alkaline earth metal compound varies depending on its type. For example, comparing a hydroxide with a strong alkalinity as an alkaline earth metal compound with a carbonate that is relatively neutral, the start of thermal decomposition is slow in the case of carbonate, and the carbonate moves to a higher temperature side than the hydroxide. Cheap. As a result, in the case of carbonate, the degree of racemization tends to be higher than that of hydroxide in the temperature range of 200 to 320 ° C. In the case of an oxide of a relatively alkaline alkaline earth metal, such as magnesium oxide, the start of thermal decomposition is slightly higher than that of the hydroxide, but it is 200. In the temperature range of ~ 320 ° C, the degree of racemization tends to be relatively low. In particular, magnesium oxide does not promote the decomposition of polylactic acid below 200 ° C due to its low dispersibility in polylactic acid. Since it tends to promote thermal decomposition due to its luka properties, it exhibits an extremely favorable effect of promoting the conversion to lactide with high optical purity while essentially suppressing the racemization reaction at less than 200 ° C.
なお、 ポリ乳酸は、 次のような熱分解メカニズムを有しているものと考えられ る。 即ち、 熟分解メカニズムとして、 200°C以下での反応 1、 200〜320 °Cでの反応 2、 及び 320°C以上での反応 3が考えられる。  Polylactic acid is considered to have the following thermal decomposition mechanism. That is, as the ripening mechanism, reaction 1 at 200 ° C or lower, reaction 2 at 200 to 320 ° C, and reaction 3 at 320 ° C or higher are considered.
反応 1 ： 200°C以下でのカルボン酸ァニオン （一 RCOO一） の不斉炭素攻 撃による選択的ラセミ化とメソラクチド生成反応。 この温度範囲では、 カルボン 酸ァユオンが主反応活性種として作用し、 これが電子密度の低い不斉炭素を攻撃 し、 バルデン反転によってほぼ選択的にラセミ化を起こしながらメソラクチドを 生成するものと考えられる。  Reaction 1: Selective racemization and meso-lactide formation reaction of carboxylic acid anion (one RCOO-one) by asymmetric carbon attack at 200 ° C or lower. In this temperature range, carboxylate acts as the main reactive species, which attacks the asymmetric carbon with a low electron density and produces meso-lactide while causing almost selective racemization by Balden inversion.
反応 2 ： 200〜320°Cでのアルコラ一トァニオン （_RO— ) のカルボ二 ル炭素攻撃による選択的 L， Lーラクチド生成反応。 200〜320°Cでは、 ァ ルコラートァニオンが分解反応の主役となり、 カルボニル炭素を攻撃して、 ラセ ミ化を引き起こすことなくラクチドを生成するものと考えられる。 反応 2は、 反 応 1と比べて非常に速いため、 この温度範囲では、 反応 1は無視できる程度にな るものと考えられる。  Reaction 2: Selective L, L-lactide formation reaction at 200-320 ° C by attack of alkanol anion (_RO—) by carbonyl carbon. At 200-320 ° C, alcoholate anion is considered to play a leading role in the decomposition reaction and attack carbonyl carbon to produce lactide without causing racemization. Since reaction 2 is much faster than reaction 1, reaction 1 is considered to be negligible in this temperature range.
反応 3 ： 320°C以上でのポリマー主鎖での互変異性反応によるラセミ化の進 行 （メソ及び D， D—ラクチドの生成比率の増大）。 320°C以上では、 ポリマー 主鎖内で "ケト—エノール互変異性化反応" が生じ、 50%の確率でラセミ化を 引き起こすものと考えられる。  Reaction 3: Racemization progresses by tautomerization reaction in the polymer main chain at 320 ° C or higher (increase in the production ratio of meso and D, D-lactide). Above 320 ° C, a "keto-enol tautomerization reaction" occurs in the polymer backbone, which is believed to cause racemization with a 50% probability.
具体的には、 アルカリ土類金属の化合物の添加量は、 乳酸ポリマーに対して 5 0 p p II！〜 10重量％、 より好ましくは Ι Ο Ο ρ ρ π！〜 5重量％の範囲であるの がよい。 例えば、 乳酸ポリマー以外に他のポリマーを含むポリマー系に、 アル力 リ土類金属の化合物が含まれる場合、 該ポリマ一系中の乳酸ポリマーからラクチ ドを製造する場合も、 上記の添加量が適用される。 より具体的には、 乳酸ポリマー以外に他のポリマーを含むポリマー系をケミ力 ルリサイクルする場合にも、 上記添加量は適用される。 なお、 他のポリマーとし て例えばポリオレフインを含むポリマー系をケミカルリサイクルする場合、 ポリ ォレフィン成分は乳酸ポリマーの熱分解温度領域において溶融再加工される。 一 方、 アル力リ土類金属化合物はそのままポリオレフイン成分中に混合した状態で 再加工され、 再加工ポリオレフインのフイラ一として機能することができる。 こ のような場合には、 アルカリ土類金属化合物の添加量は、 乳酸ポリマーとその他 のポリマーとの総和に対して、 最大 1 0 0重量％まで十分添加可能である。 添加又は混合工程後、 加熱工程に付される。 加熱工程は、 2 0 0〜 3 2 0 °Cで あるのがよく、好ましくは 2 2 5〜 3 2 0 °C、より好ましくは 2 2 5〜 3 0 0 °C、 最も好ましくは 2 2 5〜 2 5 0 °Cで行うのがよい。 Specifically, the addition amount of the alkaline earth metal compound is 50 pp II! ~ 10% by weight, more preferably Ι Ο ρ ρ ρ π! It should be in the range of ~ 5% by weight. For example, when the polymer containing another polymer in addition to the lactic acid polymer contains an alkaline earth metal compound, or when lactide is produced from the lactic acid polymer in the polymer system, the amount of the above addition is Applied. More specifically, the above addition amount is also applied to the case where a polymer system containing another polymer in addition to the lactic acid polymer is subjected to chemical power recycling. In the case where a polymer system containing, for example, polyolefin as another polymer is chemically recycled, the polyolefin component is melted and reprocessed in the thermal decomposition temperature range of the lactic acid polymer. On the other hand, the alkaline earth metal compound is reworked as it is in the polyolefin component, and can function as a reworked polyolefin filler. In such a case, the amount of the alkaline earth metal compound can be sufficiently added up to 100% by weight based on the total amount of the lactic acid polymer and the other polymer. After the addition or mixing step, it is subjected to a heating step. The heating step is preferably at a temperature of from 200 to 320 ° C., preferably from 25 to 320 ° C., more preferably from 25 to 300 ° C., most preferably from 22 to 25 ° C. It is better to carry out at ~ 250 ° C.
この温度範囲は、 乳酸ポリマーの分子量、 アルカリ土類金属、 その化合物の種 類及び形状に依存する。 例えば、 分子量の低い乳酸ポリマーの場合、 比較的低い 温度でもラセミ化の程度は低い傾向にある。 この原因は未だ明確ではないが、 2 0 0 °c未満で進行するラセミ化反応が乳酸ポリマー分子量依存性を有しているた めと考えられる。  This temperature range depends on the molecular weight of the lactic acid polymer, the alkaline earth metal, and the type and shape of the compound. For example, in the case of lactic acid polymers having a low molecular weight, the degree of racemization tends to be low even at relatively low temperatures. The cause of this is not clear yet, but it is considered that the racemization reaction that proceeds at less than 200 ° C. has a lactic acid polymer molecular weight dependency.
一方、 乳酸ポリマーの分子量が大であると末端数の減少に伴い分解速度が低下 するため、 同程度の分解速度を保持するにはより高温が必要となり、 高温側で進 行するラセミ化が顕在化してくる。 この高温側でのラセミ化反応は、 3 2 0 °Cを 超える温度で急上昇し、分子量依存性が比較的小さいと考えられる。したがって、 本発明の上述の温度範囲によって、 ラクチド生成時のラセミ化抑制効果を十分に もたらすことができる。  On the other hand, if the molecular weight of the lactic acid polymer is large, the decomposition rate decreases with a decrease in the number of terminals, so higher temperatures are required to maintain the same decomposition rate, and racemization progressing on the higher temperature side is apparent. It will become. It is considered that the racemization reaction on the high temperature side sharply increases at a temperature exceeding 320 ° C, and the molecular weight dependence is relatively small. Therefore, the above-mentioned temperature range of the present invention can sufficiently bring about the effect of suppressing racemization during the production of lactide.
本発明において、 光学純度の高いラクチドを合成する方法として、 乳酸ポリマ 一を、 上記温度範囲に設定された反応器中に投入することが望ましいが、 より低 温から高速で昇温する方法も場合によって選択可能である。 この場合、 可能な限 り急速な昇温が望ましいが、 少なく とも 3 0 °Cノ分以上の昇温がラセミ化を抑制 するために必要である。  In the present invention, as a method for synthesizing lactide having a high optical purity, it is desirable to introduce lactic acid polymer into a reactor set to the above-mentioned temperature range, but it is also possible to increase the temperature from a lower temperature to a higher speed. Is selectable. In this case, it is desirable to raise the temperature as quickly as possible, but it is necessary to raise the temperature by at least 30 ° C to suppress racemization.
本発明において利用される熱分解のための反応器として、 バッチ式、 連続式の いずれも用いることができる。 好適に用いられる反応器として、 ェクス トルーダ 一、 オートクレープ、 流動床式反応器などを挙げることができる。 ェクストルー ダ一を用いる場合、 シリンダ一の各プロックの温度設定とスクリユーの回転数、 スクリユーの形状、 一軸ノ二軸スクリューなどの形式によって、 熱分解温度や熱 分解速度の制御および昇温速度を本発明における好適な温度範囲およぴ昇温範囲 に設定することが可能である。 As a reactor for thermal decomposition used in the present invention, any of a batch type and a continuous type can be used. Extruder is a preferred reactor 1. Autoclave, fluidized bed reactor and the like. When an extruder is used, the control of the thermal decomposition temperature, the thermal decomposition rate, and the rate of temperature rise are controlled according to the temperature setting of each block of the cylinder, the number of rotations of the screw, the shape of the screw, the type of single screw and twin screw, etc. It is possible to set a suitable temperature range and a temperature rising range in the invention.
これらの熱分解反応器を用いて乳酸ポリマーの熱分解を実施する場合、 生成し たラクチドは揮発してくるため、 気相成分を取り出すプロセスが不可欠である。 上記した各反応器は、 気相成分を取り出すための排出口および Z又は気相成分を 押出し置換するために窒素ガスなどの不活性ガスの注入口を有する。 例えば、 ェ クストルーダー反応器の場合、 ベントロが排出口として好適に用いられる。  When lactic acid polymer is thermally decomposed using these pyrolysis reactors, the generated lactide is volatilized, so a process for extracting gas phase components is indispensable. Each of the above-mentioned reactors has an outlet for removing a gas phase component and an inlet for an inert gas such as nitrogen gas for extruding and replacing Z or the gas phase component. For example, in the case of an extruder reactor, a ventro is suitably used as an outlet.
このようにして、 本発明のラクチドを得ることができる。 得られたラクチドの ラセミ化の評価は、 従来より公知の方法を用いることができる。 例えば、 1つの 乳酸単位でラセミ化が生じ、 続いてラクチド単位での脱離が生じた場合、 meso- ラクチドが生成する。 連続する 2つの乳酸単位でラセミ化が生じ、 その 2つの乳 酸単位がラクチドとして脱離した場合、 D，D-ラクチドが生成する。 一般的に、 ラ セミ化反応がランダムに進行した場合、 meso-ラクチドが主な反応生成物として 生成する。 これらの meso-ラクチド及び D，D-ラクチドの L，レラクチドに対する 割合は、 ガスクロマトグラム分析によって確認することができる。 但し、 光学分 割が不可能なカラムを利用した場合、 D，D-ラクチドと L，L-ラクチドとは、 同一フ ラクシヨンとして検知されるため、 ラセミ化の評価は、 meso-ラクチドの生成割 合が指標として利用することができる。 したがって、 meso-ラクチドの生成割合 が、 得られたラクチド中 1 O m o 1 %以下、 好ましくは 5 m o 1 %以下、 より好 ましくは 2 m o 1 %以下であるのがよい。  Thus, the lactide of the present invention can be obtained. For the evaluation of the racemization of the obtained lactide, a conventionally known method can be used. For example, if one lactic acid unit undergoes racemization followed by lactide unit elimination, meso-lactide is formed. If two consecutive lactate units undergo racemization and the two lactate units are eliminated as lactide, D, D-lactide is formed. Generally, when the racemization reaction proceeds randomly, meso-lactide is produced as the main reaction product. The ratio of these meso-lactide and D, D-lactide to L, relactide can be confirmed by gas chromatogram analysis. However, when a column that cannot be optically separated is used, D, D-lactide and L, L-lactide are detected as the same fraction. Therefore, the racemization evaluation is based on the meso-lactide generation rate. The combination can be used as an index. Therefore, the production ratio of meso-lactide in the obtained lactide is 1 Omo 1% or less, preferably 5mo 1% or less, and more preferably 2mo 1% or less.
なお、 本発明により、 ラセミ化抑制効果を奏するラクチドの製法を提供するこ とができるが、 得られるラクチドの光学純度は、 用いるポリ乳酸の光学純度に依 存する。 即ち、 用いるポリ乳酸の光学純度が高ければ高いほど得られるラクチド の光学純度も-高くなる。 したがって、 ポリ乳酸の光学純度は、 8 0 % e . e . 以 上、 好ましくは 9 0 % e . e . 以上、 より好ましくは 9 6 % e . e . 以上であれ ば、 得られるラクチドの光学純度も高くなる。 なお、 ここで 「％e . e .」 とは、 enantiomeric excess という一対の鏡像異性体だけからなる混合物中に存¾する 一方の鏡像異性体の過剰量を百分率で表したものである。 実施例 The present invention can provide a method for producing lactide having an effect of suppressing racemization, but the optical purity of lactide obtained depends on the optical purity of polylactic acid used. That is, the higher the optical purity of the polylactic acid used, the higher the optical purity of the lactide obtained. Therefore, if the optical purity of the polylactic acid is at least 80% e.e., preferably at least 90% e.e., more preferably at least 96% e.e. Purity also increases. Here, "% e.e." The excess amount of one enantiomer present in a mixture consisting of only a pair of enantiomers called enantiomeric excess, expressed as a percentage. Example
以下、 実施例により本発明を説明するが、 本発明はこれらの実施例に限定され るものではない。  Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.
(実施例 1 ： 225〜 250°Cの温度範囲でのカルシウム塩末端 P L L Aの熱分 解によるラクチドの合成）  (Example 1: Synthesis of lactide by thermal decomposition of calcium salt-terminated PLL A in a temperature range of 225 to 250 ° C)
塩酸処理によって金属を含まないポリ乳酸 （Mn= 1 38000、 Mw/Mn = 1. 8 3) 5 gをテトラヒ ドロフラン （THF) 1 5 OmLに溶かして、 水素 化カルシウム （C aH2) を 0. 5 g加えて 1時間攪拌した。 未反応の C aH2を 濾別した後、 ポリ乳酸溶液をメタノール 1 00 OmL中に滴下し末端カルシウム 塩構造を有するポリ （L一乳酸） （PL LA-C a) を沈殿させた。 これをろ過回 収後真空乾燥した。 サンプラー付き熱分解装置 （フロンティアラボ社製 PY20 20 D、 Shimadzu 製 GC— 1 7A + GCMS-QP 5050。 「サンプラー付き 熱分解装置」 は、 以下の実施例、 参考例、 比較例において同じ） に不活性ガス （H e ) を通しながら、 60°Cに予熱した熱分解オーブンの中に、 P LLA-C a 1 0 をすばやく投入した。 その後、 1 0°C/分で 250°Cまで昇温した。 225 - 250°Cの温度範囲での熱分解生成物をサンプラーを用いて分取し、 ガスクロ マトグラム—質量分析器 （GCMS) にかけて分析した。 分析の結果、 全生成ラ クチド中の meso-ラクチドの含有率は 1. 3%であった。 By dissolving polylactic acid (Mn = 1 38000, Mw / Mn = 1. 8 3) 5 g without metal by hydrochloric acid treatment in as tetrahydrofuran (THF) 1 5 OmL, calcium hydride (C aH 2) 0. 5 g was added and the mixture was stirred for 1 hour. After filtering off unreacted CaH 2 , the polylactic acid solution was dropped into 100 mL of methanol to precipitate poly (L-lactic acid) (PL LA-Ca) having a terminal calcium salt structure. This was collected by filtration and dried under vacuum. Pyrolyzer with sampler (PY20 20D manufactured by Frontier Laboratories, GC-17A + GCMS-QP 5050 manufactured by Shimadzu. "The pyrolyzer with sampler" is the same in the following Examples, Reference Examples and Comparative Examples.) PLLA-Ca10 was quickly charged into a pyrolysis oven preheated to 60 ° C while passing an active gas (He). Thereafter, the temperature was raised to 250 ° C at 10 ° C / min. The pyrolysis products in the temperature range of 225-250 ° C were sampled using a sampler and analyzed by gas chromatography-mass spectrometry (GCMS). As a result of analysis, the content of meso-lactide in the total product lactide was 1.3%.
(比較例 1 ： 60〜 250°Cの温度範囲でのカルシウム塩末端 P L L Aの熱分解 によるラクチドの合成） (Comparative Example 1: Synthesis of lactide by thermal decomposition of calcium salt-terminated PLL A in the temperature range of 60 to 250 ° C)
実施例 1と同様にして P L LA-C aの熱分解を行レ、、温度範囲 60— 250 °C での熱分解生成物をサンプラーを用いて分取し、 G CMSにかけて分析した。 分 析の結果、 meso-ラクチドの含有率は、 全生成ラクチド中、 34. 6%であった。  The pyrolysis of PLLA-Ca was carried out in the same manner as in Example 1, and the pyrolysis products in a temperature range of 60 to 250 ° C. were sampled using a sampler and analyzed by GCMS. As a result of analysis, the content of meso-lactide was 34.6% of the total lactide produced.
(比較例 2 ： 60〜 225°Cの温度範囲でのカルシウム塩末端 P L L Aの熱分解 によるラクチドの合成） (Comparative Example 2: Pyrolysis of calcium salt-terminated PLLA in the temperature range of 60 to 225 ° C Synthesis of lactide)
実施例 1と同様にして P L LA-C aの熱分解を行い、温度範囲 60〜 225 °C での熱分解生成物をサンプラーを用いて分取し、 GCMSにかけて分析した。 分 析の結果、 meso-ラクチドの含有率は、 全生成ラクチド中、 92. 0%であった。  The pyrolysis of PLLA-Ca was carried out in the same manner as in Example 1, and the pyrolysis products in the temperature range of 60 to 225 ° C were separated using a sampler and analyzed by GCMS. As a result of analysis, the content of meso-lactide was 92.0% of the total lactide produced.
(比較例 3 ： 60〜 200°Cの温度範囲でのカルシウム塩末端 P L L Aの熱分解 によるラクチドの合成） (Comparative Example 3: Synthesis of lactide by pyrolysis of calcium salt-terminated PLL A in the temperature range of 60 to 200 ° C)
実施例 1と同様にして P L LA-C aの熱分解を行い、温度範囲 60〜200°C での熱分解生成物をサンプラーを用いて分取し、 GCMSにかけて分析した。 分 析の結果、 meso-ラクチドの含有率は、 全生成ラクチド中、 1 00%であった。 以上の実施例 1、 及び比較例 1〜比較例 3の結果から、 温度範囲： 200〜 2 50°C、 特に 22 5〜 250°Cでは、 熱分解に伴うラセミ化は殆ど起こらない一 方、 200°Cより低温では、 著しいラセミ化が進行していることがわかる。  The pyrolysis of PLLA-Ca was performed in the same manner as in Example 1, and the pyrolysis products in the temperature range of 60 to 200 ° C. were separated using a sampler and analyzed by GCMS. As a result of the analysis, the content of meso-lactide was 100% of the total lactide produced. From the results of Example 1 and Comparative Examples 1 to 3 above, in the temperature range: 200 to 250 ° C, particularly at 225 to 250 ° C, racemization accompanying thermal decomposition hardly occurs. At temperatures lower than 200 ° C, it can be seen that significant racemization has progressed.
(実施例 2 ： 2 50°Cでの P L LA-C aの等温熱分解によるラクチドの合成） サンプラー付き熱分解装置に不活性ガス （He) を通しながら、 250°Cに加 熱した熱分解オーブンの中に、実施例 1で用いた; P L L A-C a 1 0 /X gをすばや く投入した。 熱分解は速やかに進行し、 熱分解生成物を GCMSにかけて分析し た。分析の結果、 10分間分解を行つた場合の meso-ラクチドの含有率は 2. 3% であった。 (Example 2: Synthesis of lactide by isothermal pyrolysis of PL LA-Ca at 250 ° C) Pyrolysis heated to 250 ° C while passing an inert gas (He) through a pyrolyzer with a sampler Used in Example 1 in the oven; PLL AC a 10 / X g was quickly charged. The pyrolysis proceeded quickly, and the pyrolysis products were analyzed by GCMS. As a result of analysis, the content of meso-lactide after decomposition for 10 minutes was 2.3%.
実施例 2および比較例 1の結果より、 P L LA-C aの 250°Cでの等温熱分解 は、 60°Cから 250°Cまで昇温した場合より、 明らかに高い光学純度のラクチ ドが得られることがわかる。  From the results of Example 2 and Comparative Example 1, the isothermal pyrolysis of PL LA-Ca at 250 ° C clearly showed higher optical purity lactide than when the temperature was raised from 60 ° C to 250 ° C. It can be seen that it can be obtained.
(参考例 1 ： P L L A-C aの熱分解メカニズムの確認） (Reference Example 1: Confirmation of thermal decomposition mechanism of PLL A-Ca)
塩酸処理によって作られた金属を含まない乳酸ポリマー 2 gを THF 50m l に溶解して、 水素化カルシウムを 0. 2 g加えて 1時間攪拌した。 未反応の水素 化カルシウムをメンブランフィルター （ポアサイズ： 1 μ) で濾別した後、 乳酸 ポリマー溶液をメタノール 1 Lに滴下して、 乳酸ポリマ一を沈殿させた。 沈殿し た乳酸ポリマーを濾取した後、 乾燥させて？ L L A-C a (Mn= 94200、 M w/Mn= 1. 9 5) を得た。 2 g of a metal-free lactic acid polymer prepared by hydrochloric acid treatment was dissolved in 50 ml of THF, 0.2 g of calcium hydride was added, and the mixture was stirred for 1 hour. Unreacted calcium hydride is filtered off with a membrane filter (pore size: 1μ), and lactic acid The polymer solution was added dropwise to 1 L of methanol to precipitate lactic acid polymer. After filtering out the precipitated lactic acid polymer and drying it? LL ACa (Mn = 94200, Mw / Mn = 1.95) was obtained.
この P L LA-C a O. 25 gをクロ口ホルム 5 m 1に溶解して、 この溶液をフ ラッ トシャーレ上に展開してキャス トフイルムを作成した。得られたフィルムを、 一回につき約 5 m gを切り出し、 S E I KO製 TGZDTA6200を用いて、 窒素雰囲気下、 室温〜 400°Cまでの温度範囲で、 1、 3、 5、 7および 9°CZ 分の昇温速度で熱分解を行った。 重量変化のデータは、 SE I KO製 E x t e r 6000データ処理システムにより取り出し、 この熱重量変化データを、 熱分解 解析のための積分法、 微分法、 ランダム解析法をそれぞれ用いて解析し、 熱分解 の動力学的パラメータを求めた。  25 g of this PLLA-CaO was dissolved in 5 ml of black-mouthed form, and this solution was spread on a flat petri dish to prepare a cast film. Approximately 5 mg of the obtained film was cut out at a time, and TGZDTA6200 manufactured by SEI KO was used under a nitrogen atmosphere in a temperature range from room temperature to 400 ° C, 1, 3, 5, 7, and 9 ° C. Was thermally decomposed at a heating rate of. The weight change data is extracted by the SEIKO Exter 6000 data processing system, and the thermogravimetric change data is analyzed using the integration method, differentiation method, and random analysis method for pyrolysis analysis, respectively, and The kinetic parameters of were determined.
その結果、 熱分解反応活性化エネルギーは 98 k J Zin o 1であり、 分解反応 は、 ラクチドを選択的に生成する 1次反応によって進行することが確認された。 さらに、 上述のサンプラー付き熱分解装置に不活性ガスを通しながら、 60°C まで予熱した。 P LLA-C aサンプル 10 μ gを熱分解装置にすばやく投入し、 昇温速度 1 0で 分で昇温して P L LA-C aサンプルを完全に熱分解させた。生 成した熱分解生成物を、 G CMSにかけて分析した結果、 meso-ラクチドの含有 率は 1 3. 3 %であった。  As a result, the activation energy of the thermal decomposition reaction was 98 kJ Zinol, and it was confirmed that the decomposition reaction proceeded by the primary reaction that selectively generates lactide. Furthermore, it was preheated to 60 ° C while passing inert gas through the above-mentioned pyrolyzer with sampler. 10 μg of the PLLA-Ca sample was quickly introduced into the pyrolyzer and the temperature was raised in 10 minutes at a heating rate of 10 to completely pyrolyze the PLLA-Ca sample. As a result of analyzing the generated pyrolysis product by GCMS, the content of meso-lactide was 13.3%.
(比較例 4 ： P L LA-Naの熱分解） (Comparative Example 4: Thermal decomposition of PLLA-Na)
参考例 1において、 水素化カルシウムの代わりに水素化ナトリゥムを用いて、 ナトリゥム塩末端構造を有する乳酸ポリマー （P L L A-N a、 Mn= 1 1 960 0、 Mw/Mn = 1. 97) を得た。  In Reference Example 1, a lactic acid polymer having a sodium salt terminal structure (PLL A-Na, Mn = 1119600, Mw / Mn = 1.97) was obtained using sodium hydride instead of calcium hydride.
この P L L A-N a 0. 2 5 gを用いて、 参考例 1と同様に、 キャストフイルム を作成し、 参考例 1と同様に、 S E I KO製 TG/DTA6 200を用いて、 熱 分解の動力学的パラメータを求めた。 その結果、 熱分解反応活性化エネルギーは 1 70 k 1 /mo 1であり、 分解反応は主にランダム反応によって進行すること が確認された。  Using 0.25 g of this PLL AN a, a cast film was prepared in the same manner as in Reference Example 1, and the kinetics of thermal decomposition was performed using TG / DTA6 200 manufactured by SEI KO in the same manner as in Reference Example 1. The parameters were determined. As a result, the activation energy of the thermal decomposition reaction was 170 k 1 / mo 1, and it was confirmed that the decomposition reaction proceeded mainly by a random reaction.
さらに、参考例 1と同様に、熱分解装置を用いて P L LA-Naサンプルを完全 に熱分解させた。 生成した熱分解生成物を GCMSを用いて分析した結果、 ラク チドの含有率は 58. 2%であり、 その他に乳酸エステル （4. 7%)、 3〜1 0 量体 （3 3. 2%)、 さらに乳酸 （1. 5%)、 アクリル酸 （0. 7%) などが確 認された。 即ち、 P LLA-Naの熱分解は、 分子間 分子内でランダムに進行す る分解であり、 ラクチドが選択的に生成する反応でないことを確認した。 Further, as in Reference Example 1, the PL LA-Na sample was completely Was pyrolyzed. Analysis of the generated pyrolysis products using GCMS showed that the lactide content was 58.2%, and that the lactate ester (4.7%), 3- to 10-mer (33.2 %), Lactic acid (1.5%), and acrylic acid (0.7%). That is, it was confirmed that the thermal decomposition of PLLA-Na was a decomposition that proceeded randomly within an intermolecular molecule, and was not a reaction for selectively producing lactide.
参考例 1及び比較例 4の結果より、カルシゥム末端乳酸ポリマー PL LA-C a は、 ラクチドを選択的に生成する連鎖的解重合反応であるのに対し、 ナトリウム 末端乳酸ポリマー P L L A-N aは、ラクチドの選択性が低いランダムな分解反応 であることが確認された。  From the results of Reference Example 1 and Comparative Example 4, the calcium-terminated lactic acid polymer PL LA-C a is a chain depolymerization reaction that selectively produces lactide, whereas the sodium-terminated lactic acid polymer PLL ANa is It was confirmed that this was a random decomposition reaction with low selectivity.
(実施例 3 : 300 - 320°Cの温度範囲での P L L A-C aの熱分解によるラク チドの合成） (Example 3: Synthesis of lactide by thermal decomposition of PLLA-Ca in the temperature range of 300 to 320 ° C)
実施例 1と同様の操作によって、 P L L A-C a (Mn = 26, 900, Mw / Mn= 2. 56) を調製した。 これをろ過回収後真空乾燥した。 サンプラー付き 熱分解装置に不活性ガス (He) を通しながら、 60°Cに予熱した熱分解オーブンの 中に、 P L L A-C a 10 μ gをすばやく投入した。その後、 1 0°C/分で 320 °C まで昇温した。 熱分解生成物を GCMSにかけて分析した結果、 全生成ラクチド 中の meso-ラクチドの含有率は 7. 9%であった。 次に、 同じ PLLA-Ca を同様 の方法で、 300°Cまで昇温し、熱分解生成物を GCMSにかけて分析した結果、 全生成ラクチド中の meso-ラクチドの含有率は 7. 8%であった。  PLL A-Ca (Mn = 26,900, Mw / Mn = 2.56) was prepared in the same manner as in Example 1. This was vacuum-dried after being collected by filtration. While passing an inert gas (He) through a pyrolyzer with a sampler, 10 μg of PLL A-Ca was quickly introduced into a pyrolysis oven preheated to 60 ° C. Thereafter, the temperature was raised to 320 ° C at 10 ° C / min. Analysis of the pyrolysis products by GCMS revealed that the content of meso-lactide in the total lactide produced was 7.9%. Next, the same PLLA-Ca was heated to 300 ° C by the same method, and the pyrolysis products were analyzed by GCMS.As a result, the content of meso-lactide in the total lactide produced was 7.8%. Was.
以上の結果から、 300〜 3 20°Cの温度範囲での P L L A-C aの熟分解にお いて、 ラセミ化が殆ど進行していないことがわかる。  From the above results, it is found that racemization hardly progresses in the ripening of PLL A-Ca in the temperature range of 300 to 320 ° C.
(比較例 5： 3 20〜 340°Cの温度範囲でのカルシウム塩末端 P L L A-C aの 熱分解によるラクチドの合成） (Comparative Example 5: Synthesis of lactide by thermal decomposition of calcium salt-terminated PLL A-Ca in a temperature range of 20 to 340 ° C)
実施例 3と同様にして P L L A-C aの熱分解を行い、 60〜 340°C温度範囲 での熱分解生成物をサンプラーを用いて分取し、 G C M Sにかけて分析した結果、 meso-ラクチドの含有率は、 全生成ラクチド中、 1 4. 2%であった。 従って、 比較例 5の結果を参照すれば、 320〜340°Cの温度範囲で、 急速なラセミ化 が進行したことが結論される。 The pyrolysis of PLL ACa was performed in the same manner as in Example 3.The pyrolysis products in the temperature range of 60 to 340 ° C were sampled using a sampler and analyzed by GCMS.As a result, the content of meso-lactide was determined. Was 14.2% of the total lactide produced. Therefore, referring to the results of Comparative Example 5, rapid racemization occurs in the temperature range of 320 to 340 ° C. It is concluded that has progressed.
(実施例 4：炭酸カルシウムを用いて調製された P L LA-C aの熱分解によるラ クチドの合成） (Example 4: Synthesis of lactide by pyrolysis of PLLA-Ca prepared using calcium carbonate)
塩酸処理によって調製した金属を含有しないポリ乳酸（Mn= 1 38, 000、 Mw/Mn = 1. 83) 500 m gをクロ口ホルム 5 m 1に溶解し、 次に炭酸力 ルシゥム 25 mgを加えた。 1 5分間攪拌して炭酸カルシウムを均一に分散させ た後、 溶媒を揮発させ、 さらに真空下で乾燥した。 これにより、 カルシウム含有 率約 2 w t %の P LLA-C aを調製した。 次に、 サンプラー付き熱分解装置に不 活性ガス (He)を通しながら、 250°Cに加熱した熱分解オーブンの中に、 調製し た P L L A-C a 1 0 μ gをすばやく投入した。 熱分解は速やかに進行し、熱分解 生成物を GCMSにかけて分析した。 分析の結果、 60秒問の熱分解を行った場 含の meso-ラクチドの含有率は 4. 9%であった。  500 mg of metal-free polylactic acid prepared by hydrochloric acid treatment (Mn = 138,000, Mw / Mn = 1.83) was dissolved in 5 ml of black-mouthed form, and 25 mg of carbonic acid was added. . After stirring for 15 minutes to uniformly disperse the calcium carbonate, the solvent was volatilized and further dried under vacuum. Thus, PLLA-Ca having a calcium content of about 2 wt% was prepared. Next, while the inert gas (He) was passed through the pyrolysis apparatus equipped with a sampler, 10 μg of the prepared PLLA-Ca was quickly charged into a pyrolysis oven heated to 250 ° C. Pyrolysis proceeded quickly and the pyrolysis products were analyzed by GCMS. As a result of analysis, the content of meso-lactide after pyrolysis for 60 seconds was 4.9%.
(比較例 6 ： 350°Cでの P L L A-C aの等温熱分解によるラクチドの合成） 熱分解オーブンの加熱温度を 35 0°Cにした以外は実施例 4と同様の方法で、 実施例 4において調製した炭酸カルシウム分散 P L LA-C aの等温熱分解を行 つた。 熱分解生成物を GCMSにかけて分析した結果、 60秒問の熱分解を行つ た場合の meso-ラクチドの含有率は 3 1. 4%であった。 (Comparative Example 6: Synthesis of lactide by isothermal pyrolysis of PLL AC a at 350 ° C) A method similar to that of Example 4 except that the heating temperature of the pyrolysis oven was 350 ° C. Isothermal pyrolysis of the prepared calcium carbonate dispersion PL LA-Ca was performed. Analysis of the pyrolysis products by GCMS revealed that the content of meso-lactide was 31.4% when pyrolysis was performed for 60 seconds.
(比較例 7 ： 1 90°Cでの P L L A-C aの等温熱分解によるラクチドの合成） 熱分解オーブンの加熱温度を 1 9 0°C、 熱分解時問を 10分問にした以外、 実 施例 4と同様の方法で、実施例 5において調製した炭酸カルシウム分散 P LLA- C aの等温熱分解を行った。 熱分解生成物を GCMSにかけて分析した結果、 meso-ラクテドの含有率は 1 1. 3%であった。 (Comparative Example 7: Synthesis of lactide by isothermal pyrolysis of PLL AC a at 190 ° C) Except that the heating temperature of the pyrolysis oven was set to 190 ° C and the thermal decomposition time was changed to 10 minutes. In the same manner as in Example 4, the calcium carbonate dispersion P LLA-Ca prepared in Example 5 was subjected to isothermal pyrolysis. As a result of analyzing the pyrolysis product by GCMS, the content of meso-lactide was 11.3%.
(実施例 5 ：酸化マグネシウムを用いて調製された P LL A— Mgの熱分解によ るラクチドの合成） (Example 5: Synthesis of lactide by pyrolysis of PLLA-Mg prepared using magnesium oxide)
塩酸処理によって調製した金属を含有しないポリ乳酸（Mn= 1 38, 000、 Mw/Mn= 1. 8 3) 500 m gをクロ口ホルム 5 m 1に溶解し、 次に酸化マ グネシゥム 1 6. 6mgを加えた。 1 5分問攪拌して酸化マグネシウムを均一に 分散させた後、 溶媒を揮発させ、 さらに真空下で乾燥した。 これにより、 マグネ シゥム含有率約 2 w t%の末端マグネシウム塩構造を有するポリ （L_乳酸） （P LLA-Mg) を調製した。 得られた P L L A— Mgの分子量は、 サイズ排除クロ マトグラフィ一によつて測定した結果、 Mn = 14 1, 000、 Mw/Mn = 1. 93であった。 次に、 サンプラー付き熱分解装置に不活性ガス（H e)を通しなが ら、 2 50°Cに加熱した熱分解オーブン中に、 調製した P LLA-Mg 1 0 i g をすばやく投入した。 熱分解は速やかに進行し、 熱分解生成物を G CMSにかけ て分析した結果、 60秒問の熱分解を行った場合の meso-ラクチドの含有率は 5. 0%であった。 Metal-free polylactic acid prepared by hydrochloric acid treatment (Mn = 138,000, Mw / Mn = 1.8 3) 500 mg was dissolved in 5 ml of black-mouthed form, and then 16.6 mg of magnesium oxide was added. After stirring for 15 minutes to uniformly disperse the magnesium oxide, the solvent was volatilized and further dried under vacuum. As a result, poly (L_lactic acid) (P LLA-Mg) having a magnesium content of about 2 wt% and having a terminal magnesium salt structure was prepared. The molecular weight of the obtained PLLA-Mg was measured by size exclusion chromatography, and as a result, Mn was 141,000 and Mw / Mn was 1.93. Next, while passing an inert gas (He) through a pyrolyzer with a sampler, the prepared PLLA-Mg 10 ig was quickly charged into a pyrolysis oven heated to 250 ° C. Pyrolysis proceeded quickly, and the pyrolysis products were analyzed by GCMS. As a result, the content of meso-lactide in the case of pyrolysis for 60 seconds was 5.0%.
(実施例 6 ： 220°Cでの P LLA— Mgの等温熱分解によるラクチドの合成） 熱分解オーブンの加熱温度を 220°Cにした以外、 実施例 5と同様の方法で、 実施例 5において調製した酸化マグネシウム分散 P L LA— Mgの等温熱分解を 行った。 熱分解生成物を GCMSにかけて分析した結果、 60秒間の熱分解を行 つた場合の meso-ラクチドの含有率は 4. 2%であった。 (Example 6: Synthesis of lactide by isothermal pyrolysis of P LLA-Mg at 220 ° C) In the same manner as in Example 5, except that the heating temperature of the pyrolysis oven was set to 220 ° C. Isothermal pyrolysis of the prepared magnesium oxide dispersion, PL LA-Mg, was performed. As a result of analyzing the pyrolysis products by GCMS, the content of meso-lactide after pyrolysis for 60 seconds was 4.2%.
(実施例 7 ： 200°Cでの P LLA— Mgの等温熱分解によるラクテドの合成） 熱分解オーブンの加熱温度を 200°Cにした以外、 実施例 5と同様の方法で、 実施例 5において調製した酸化マグネシウム分散 P L L A— Mgの等温熱分解を 行った。 (Example 7: Synthesis of lactide by isothermal pyrolysis of P LLA-Mg at 200 ° C) In the same manner as in Example 5, except that the heating temperature of the pyrolysis oven was set to 200 ° C. Isothermal pyrolysis of the prepared magnesium oxide-dispersed PLLA-Mg was performed.
熱分解生成物を G CMSにかけて分析した結果、 60秒間の熱分解を行った場 合の meso-ラクチドの含有率は 5. 0%であった。  As a result of analyzing the pyrolysis products by GCMS, the content of meso-lactide in the case of performing the pyrolysis for 60 seconds was 5.0%.
(実施例 8 ： 2 1 0°Cでの酸化マグネシウム添加 P L L Aの熱分解によるラクチ ドの合成） (Example 8: Synthesis of lactide by thermal decomposition of PLLA with addition of magnesium oxide at 210 ° C)
攪拌翼を備えた 1 00m l容量の三口フ スコ中に、 塩酸処理によって金属を 含まないポリ乳酸 （Mn = 1 33000、 Mw Mn = 1. 82) 20 gと酸化 マグネシウム （MgO) 1. 66 g (Mgとして P L L Aに対して 5重量0 /0) を 加えて、 機械的攪拌によって固体同士のまま混合した。 攪拌を停止し、 真空ボン プを用いて三口フラスコ内部を減圧にした後、 油浴中で昇温加熱した。 2 10°C まで昇温した後、 溶融した P L L Aと酸化マグネシゥム混合物を再び機械的に攪 拌しながら、 減圧下に 2 1 0°Cで 4時間保持した。 減圧下に溜去した熱分解生成 物は、 室温トラップ中に捕集した。 4時間の加熱中に溜去した生成物の重量は 1 1. 93 gであり粗回収率は 59. 6%であった。 回収された熱分解生成物をガ スクロマトグラフを用いて分析した結果、生成物の組成は、 L-ラクチドの含有率 が 94. 5%、 meso -ラクチドの含有率が 4. 7 %、 および D-ラクチドの含有率 が 0. 8%であった。 In a 100 ml three-necked fucco equipped with a stirring blade, 20 g of metal-free polylactic acid (Mn = 133000, Mw Mn = 1.82) was oxidized by hydrochloric acid treatment. By adding magnesium (MgO) 1. (5 wt 0/0 for PLLA as Mg) 66 g, they were mixed in a solid state together by mechanical agitation. The stirring was stopped, the inside of the three-necked flask was evacuated using a vacuum pump, and then heated and heated in an oil bath. After the temperature was raised to 210 ° C, the molten PLLA and magnesium oxide mixture was again kept under reduced pressure at 210 ° C for 4 hours while mechanically stirring. The pyrolysis product distilled off under reduced pressure was collected in a room temperature trap. The weight of the product distilled off during heating for 4 hours was 11.93 g, and the crude recovery was 59.6%. Analysis of the recovered pyrolysis products using a gas chromatograph showed that the composition of the product was 94.5% for L-lactide, 4.7% for meso-lactide, and D -The lactide content was 0.8%.

Claims

請 求 の 範 囲 The scope of the claims
I . 乳酸ポリマーにアル力リ土類金属の化合物を添加し、 2 0 0 °C以上 3 2 0 °C 以下に加熱することを特徴とするラクチドの製造方法。 I. A method for producing lactide, comprising adding a compound of an alkaline earth metal to a lactic acid polymer and heating the compound to a temperature of from 200 ° C to 320 ° C.
2 . 前記乳酸ポリマーはその重量平均分子量が 1万以上である請求項 1記載の 方法。  2. The method according to claim 1, wherein the lactic acid polymer has a weight average molecular weight of 10,000 or more.
3 . 前記アルカリ土類金属は、 カルシウム又はマグネシウムである請求項 1又 は 2記載の方法。  3. The method according to claim 1, wherein the alkaline earth metal is calcium or magnesium.
4 . 前記アルカリ土類金属の化合物は、 炭酸カルシウム、 酸化カルシウム、 水 酸化カルシウム、 炭酸マグネシウム、 酸化マグネシウム及び水酸化マグネシウム からなる群から選ばれる 1種または 2種以上である請求項 1 〜 3のいずれか 1項 記載の方法。  4. The compound of claim 1, wherein the alkaline earth metal compound is one or more selected from the group consisting of calcium carbonate, calcium oxide, calcium hydroxide, magnesium carbonate, magnesium oxide and magnesium hydroxide. A method according to any one of the preceding claims.
5 . 前記乳酸ポリマーの分子末端周辺に前記アル力リ土類金属の対イオンが存 在するように、 前記添加工程を行う請求項 1 〜 4のいずれか 1項記載の方法。 5. The method according to any one of claims 1 to 4, wherein the adding step is performed so that a counter ion of the alkaline earth metal is present around a molecular terminal of the lactic acid polymer.
6 . 前記乳酸ポリマーの光学純度が 8 0 % e . e . 以上であって、 且つ得られ るラクチド中のメソ-ラクチドの含有率が全ラクチドに対して 1 O m o 1 %以下 である請求項 1 〜 5のいずれか 1項記載の方法。 6. The optical purity of the lactic acid polymer is at least 80% e.e., and the content of meso-lactide in the obtained lactide is 1 Omo 1% or less with respect to all lactides. The method according to any one of claims 1 to 5.
7 . 乳酸ポリマーにマグネシウムの化合物を添加し、 3 2 0 °C以下に加熱する ことを特徴とするラクチドの製造方法。  7. A method for producing lactide, comprising adding a magnesium compound to a lactic acid polymer and heating the mixture to 320 ° C. or lower.
8 . 前記乳酸ポリマーはその重量平均分子量が 1万以上である請求項 7記載の 方法。  8. The method according to claim 7, wherein the lactic acid polymer has a weight average molecular weight of 10,000 or more.
9 . 前記マグネシウムの化合物は、 炭酸マグネシウム、 酸化マグネシウム及び 水酸化マグネシゥムからなる群から選ばれる 1種または 2種以上である請求項 7 又は 8記載の方法。  9. The method according to claim 7, wherein the magnesium compound is one or more selected from the group consisting of magnesium carbonate, magnesium oxide, and magnesium hydroxide.
1 0 . 前記マグネシウムの化合物は、 酸化マグネシウムである請求項 7又は 8 記載の方法。  10. The method according to claim 7, wherein the magnesium compound is magnesium oxide.
I I . 前記乳酸ポリマーの固体と前記酸化マグネシウムの固体とを混合するこ とにより、 前記添加工程を行う請求項 9又は 1 0記載の方法。  11. The method according to claim 9, wherein the adding step is performed by mixing the solid of the lactic acid polymer and the solid of the magnesium oxide.
1 2 . 前記乳酸ポリマーの分子末端周辺に前記マグネシウムの対イオンが存在 するように、 前記添加工程を行う請求項 7〜.l 1のいずれか 1項記載の方法。 1 3. 前記乳酸ポリマーの光学純度が 8 0% e . e . 以上であって、 且つ得ら れるラクチド中のメソ-ラクチドの含有率が全ラクチドに対して 1 O mo 1 %以 下である請求項 7〜 1 2のいずれか 1項記載の方法。 1 2. The magnesium counter ion exists around the molecular terminal of the lactic acid polymer. The method according to any one of claims 7 to .11, wherein the adding step is performed so as to perform the adding step. 1 3. The optical purity of the lactic acid polymer is 80% e.e. or more, and the content of meso-lactide in the obtained lactide is 1 Omo 1% or less based on all lactide. The method according to any one of claims 7 to 12.
PCT/JP2003/005244 2002-04-25 2003-04-24 Process for producing lactide WO2003091238A1 (en)

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JP2011507934A (en) * 2007-12-26 2011-03-10 クタントン・リミテッド Method for producing cyclic diester of α-hydroxy acid
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JPH11292871A (en) * 1998-04-08 1999-10-26 Shimadzu Corp Production of racemization-suppressed lactide
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Publication number Priority date Publication date Assignee Title
JP2008201680A (en) * 2007-02-16 2008-09-04 Teijin Fibers Ltd Method for producing lactide from polylactic acid
JP2008231048A (en) * 2007-03-22 2008-10-02 Kyushu Institute Of Technology Method for recovering lactide
JP2011507934A (en) * 2007-12-26 2011-03-10 クタントン・リミテッド Method for producing cyclic diester of α-hydroxy acid
JP2010120915A (en) * 2008-11-22 2010-06-03 Kitakyushu Foundation For The Advancement Of Industry Science & Technology Method for recovering lactide from flame-retarded lactic acid polymer composition
JP2010126491A (en) * 2008-11-28 2010-06-10 Japan Steel Works Ltd:The Lactide recovery apparatus and recovery method
JP2010168415A (en) * 2009-01-20 2010-08-05 Kitakyushu Foundation For The Advancement Of Industry Science & Technology Apparatus and method for recovering lactide
JP2011162480A (en) * 2010-02-10 2011-08-25 Kitakyushu Foundation For The Advancement Of Industry Science & Technology Method of recovering lactide
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WO2021181532A1 (en) * 2020-03-10 2021-09-16 マクセルホールディングス株式会社 Polylactic acid decomposition method
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