WO2015112098A1 - Process for manufacturing lactide from plastics having polylactic acid - Google Patents

Process for manufacturing lactide from plastics having polylactic acid Download PDF

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Publication number
WO2015112098A1
WO2015112098A1 PCT/TH2014/000013 TH2014000013W WO2015112098A1 WO 2015112098 A1 WO2015112098 A1 WO 2015112098A1 TH 2014000013 W TH2014000013 W TH 2014000013W WO 2015112098 A1 WO2015112098 A1 WO 2015112098A1
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WIPO (PCT)
Prior art keywords
process according
lactide
pla
polylactic acid
plastic
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PCT/TH2014/000013
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French (fr)
Inventor
Vivan THAMMONGKOL
Narin KAABBUATHONG
Jirawut JUNKASEM
Tuspon THANPITCHA
Parkpoom LORJAI
Chaiyapruk KATEPETCH
Original Assignee
Ptt Public Company Limited
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Priority claimed from TH1401000401A external-priority patent/TH1401000401B/en
Application filed by Ptt Public Company Limited filed Critical Ptt Public Company Limited
Publication of WO2015112098A1 publication Critical patent/WO2015112098A1/en

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    • 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
    • C08J11/14—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 steam or water
    • 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
    • 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
    • C08J11/18—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 organic material
    • C08J11/22—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 organic material by treatment with organic oxygen-containing compounds
    • C08J11/24—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 organic material by treatment with organic oxygen-containing compounds containing hydroxyl groups
    • 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

  • This invention relates to a process for manufacturing lactide from plastics having polylactic acid (PLA-based plastics).
  • U.S. Pub. No. 2013/0023674 Al discloses a method for producing lactide, which can be used for polylactic acid (PLA) production or other bioproducts, comprising melting the PLA feedstock in a heater to produce PLA liquid, heating the PLA liquid with a catalyst to depolymerize the PLA liquid and produce lactide vapour under vacuum atmosphere, and condensing the lactide vapour to produce liquid lactide.
  • PLA polylactic acid
  • U.S. Pub. No. 2012/0142958 Al discloses a process for recycling a polymer blend having polylactic acid (PLA), comprising grinding, compacting, dissolving in a solvent of PLA, removing the undissolved having polymers, alcoholysis depolymerization reaction and purification steps.
  • PLA polylactic acid
  • U.S. Patent No. 5,142,023 discloses a process for the continuous production of polylactide polymers from lactic acid which incorporates removal of water or a solvent carrier to concentrate the lactic acid feed followed by polymerization to a low-molecular- weight prepolymer.
  • This prepolymer is fed to a reactor in which a catalyst is added to facilitate generation of lactide, the depolymerization product of polylactic acid.
  • the lactide generated is continuously fed to a distillation system as a liquid or vapor wherein water and other impurities are removed.
  • the resultant purified liquid lactide is fed directly to a polymerization process.
  • This invention relates to a process for manufacturing lactide from plastics having polylactic acid (PLA-based plastics) comprises preparing PLA-based plastics, accelerating decomposition of polylactic acid in the plastics to provide low molecular weight polylactic acid, and thermal decomposing the low molecular weight polylactic acid to provide lactide. Also, the process further comprises minimizing size of the PLA-based plastics after the step of preparing PLA-based plastics, and purifying lactide after thermal decomposing low molecular weight polylactic acid to provide lactide.
  • PLA-based plastics comprises preparing PLA-based plastics, accelerating decomposition of polylactic acid in the plastics to provide low molecular weight polylactic acid, and thermal decomposing the low molecular weight polylactic acid to provide lactide.
  • An objective of this invention is to provide a process for manufacturing lactide from PLA-based plastics providing benefits in term of technique as follows:
  • condition applied in the step of decomposing polylactic acid in plastic according to this invention is not severe (mild condition).
  • Figure 1 shows a life cycle of PLA-based plastic.
  • Figure 2 shows a continuous process for manufacturing lactide from PLA-based plastic.
  • Figure 3 shows a mechanism for accelerating chemical decomposition of polylactic acid in plastic by alcoholysis reaction.
  • Figure 4 shows 1H-NMR spectrum of purified lactide obtained from the process according to this invention.
  • Figure 5 shows GC-MS spectrum verifying structure and optical purity of the purified lactide obtained from the process according to this invention.
  • This invention relates to a process for manufacturing lactide from PLA-based plastics or recycling process of PLA-based plastics to produce lactide.
  • Said process converts polylactic acid in plastic to lactide, which is a precursor or monomer in a process for manufacturing polylactic acid and its derivative by accelerating chemical decomposition of polylactic acid in the plastic by alcoholysis reaction or hydrolysis reaction.
  • This provides lower molecular weight polylactic acid, which is suitable for thermal decomposition for converting to lactide (Fig. 1).
  • Figure 1 also shows the recycling process of polylactic acid, which requires polylactic acid decomposition to provide lactic acid, and dehydration and polycondensation step to achieve low molecular weight polylactic acid, then thermal decomposition to produce lactide.
  • the process according to this invention can be performed continuously and more efficiently by adjusting the condition in each step to provide process optimization, e.g. an input rate of reactants equivalent to an output rate of products in each stage (Fig. 2).
  • a process for manufacturing lactide from PLA-based plastic according to this invention comprising the steps of:
  • the process for manufacturing lactide from PLA-based plastic according to this invention further comprises minimizing size of said PLA-based plastic after the PLA-based plastic preparation step.
  • said plastic has a dimension in a range from 0.1 to 10 mm, preferably no larger than 5 mm. This dimension makes it easy for feeding into the depolymerization reactor, and also increases the surface area. Hence, it can be molten easier, and shortens the melting time.
  • said dimension varies with the type and size of the depolymerization reactor.
  • the rninirnizing size is performed by at least one method selected from shearing, impacting, cutting into small pieces, and grinding. The grinding can be performed in either dry or wet condition, preferably by the grinder in the dry condition.
  • the process for manufacturing PLA-based plastic according to the invention further comprises a step of purifying lactide after the step of thermal decomposition of low molecular weight polylactic acid to provide lactide
  • the PLA-based plastic has a ratio of polylactic acid from 1 to 100% by weight of total plastics, preferably a ratio of polylactic acid greater than 50% by weight of total plastics.
  • the preparation of PLA-based plastic comprising the steps of:
  • the preparation of PLA-based plastic further comprises a step of filtering said plastics after the washing step.
  • the filtering step is performed using filter device under atmospheric condition or vacuum condition.
  • said plastic in the preparation step, is dried at a temperature of 50-80°C, preferably at a temperature of 55-70°C until all water completely evaporates.
  • the plastic is dried using either conventional oven or vacuum oven.
  • the accelerating decomposition of polylactic acid in plastic is performed by an alcoholysis reaction or a hydrolysis reaction. This is to accelerate decomposition of high molecular weight polylactic acid to low molecular weight polylactic acid, which is in a suitable range for thermal decomposition of low molecular weight polylactic acid to provide lactide in the lactide reactor.
  • the accelerating decomposition of polylactic acid in plastic by the alcoholysis reaction is performed by a reaction between PLA-based plastic and alcohol as shown in Fig. 3.
  • a mechanism of said accelerating decomposition of polylactic acid in plastics is possible to begin with ester-bond breaking in the polylactic acid molecular chain allowing nucleophilic substitution.
  • the nucleophile may include alcohol, organic acid, organic alkali, inorganic alkali, water, etc.
  • the accelerating decomposition of polylactic acid in the plastic by the alcoholysis reaction comprising the steps of:
  • said alcohol is used in an amount from 0.1-10% by weight of the PLA-based plastic, preferably 2-7% by weight of the PLA-based plastic.
  • Said alcohol is selected from the group consisting of an alcohol having 1 to 10 carbon atoms (CI -CI O) and having 1 to 10 hydroxyl groups, preferably glycerol (C 3 H 8 O 3 ) or sorbitol (C 6 Hi 4 06). Since said alcohol has a higher boiling point and large quantity of hydroxyl groups, resulting in rapid chemical decomposition of polylactic acid. Besides, it facilitates a lactide recovery from the alcohol.
  • the catalyst is used in an amount of 0-5% by weight of the PLA-based plastic, preferably 0.1-0.5%) by weight of the PLA-based plastic.
  • Said catalyst is selected from the group consisting of metal oxides, preferably antimony trioxide (Sb 2 0 3 ).
  • Said catalyst is further selected from the group consisting of organometallic compounds having 1 to 20 carbon atoms (C1-C20), preferably organometallic compounds of tin, namely Sn (II); or titanium, namely Ti (II).
  • the preparation of a mixture of alcohol and catalyst is performed by mixing said catalyst with alcohol, and then stirring for good distribution and compatibility.
  • the accelerating decomposition of polylactic acid in plastic is performed under vacuum or under pressure of at least 1 bar, preferably 1 -10 bars; at a temperature of 170-250°C, preferably at a temperature of 190-210°C.
  • the mixture obtained from (i) with the PLA-based plastic can be mixed before feeding into a depolymerization reactor, or mixed all together in the depolymerization reactor.
  • the depolymerization reactor includes a batch reactor, or a continuous reactor including single screw extruder or twin screw extruder to allow continuous chemical decomposition of polylactic acid occurrence.
  • the accelerating decomposition of polylactic acid in plastic by the alcoholysis reaction provides polylactic acid having a number average molecular weight in a range of 500 to 30,000 g/mol, preferably in a range of 2,000-12,000 g/mol.
  • the accelerating decomposition of polylactic acid in plastic by hydrolysis reaction further comprises a step of mixing reactant with the PLA-based plastic.
  • Said reactant is selected from the group consisting of organic acid, inorganic acid, organic alkali, inorganic alkali, or water, preferably organic acids, namely lactic acid.
  • Advantages of using lactic acid as reactant are no impurities in the reaction, and the lactic acid being used as a precursor in the lactide production.
  • lactic acid as a reactant may not require other additional catalysts, e.g. metal oxides or organometallic compound. This is because the acid will act as an autocatalyst for polyester decomposition, such as polylactic acid. However, the use of acid as reactant may cause corrosion in the metal parts of the equipments. Therefore, precaution must be taken.
  • the hydrolysis reaction is performed under vacuum or under pressure of at least 1 bar, preferably 1-10 bars; at a temperature of 170-250°C, preferably at a temperature of 190-210°C.
  • the hydrolysis reaction is performed in the depolymerization reactor including batch reactor, or a continuous reactor namely single screw extruder or twin screw extruder.
  • the thermal decomposition of low molecular weight polylactic acid to provide lactide comprising the steps of:
  • the low molecular weight PLA-based plastic is fed to lactide reactor by batch feed or continuous feed.
  • the catalyst fed in the reactor is used in an amount of 0-2% by weight of the PLA-based plastic, preferably 0.1 -1 .0% by weight of the PLA-based plastic.
  • Said catalyst is selected from the group consisting of metal oxide or organometallic compounds having 1 to 20 carbon atoms (C1-C20), preferably organometallic compounds of tin, namely Sn (II); or titanium, namely Ti (II).
  • the organometallic compounds are not limited to those listed above.
  • the thermal decomposition of polylactic acid to provide lactide is performed at a temperature of 190-250°C, preferably at a temperature of 200-220°C under vacuum or inert gas pressure, preferably under vacuum with a pressure of 0.001 to 0.1 bar.
  • the condensation of lactide by cooling down to provide lactide solid is preferably performed at a temperatures below 25°C.
  • the condensation of lactide by cooling down to provide lactide liquid is preferably performed at a temperature 100-110°C. This provides lactide, which is ready for further purification. While alcohol, various catalysts, and/or other substances in PLA-based plastic remain in the bottom section of the lactide reactor, and will be removed or reused again as the lactide reactor's maintenance.
  • the lactide is purified by distillation or recrystallization.
  • the distillation is performed under vacuum or under inert gas pressure of at least 1 bar, preferably 1- 10 bars; at a temperature of 120-180°C, preferably at a temperature of 120-150°C.
  • the recrystallization in a lactide purification step comprising the steps of:
  • the recrystallization is performed using a solvent selected from acetone, isopropanol, toluene, benzene, diethyl ether, or ethyl acetate, preferably ethyl acetate or toluene.
  • Said recrystallization may be repeated 2-3 times to provide high purity lactide as shown in Table 1.
  • the purified lactide from a step of lactide purification can be reacted to further synthesize PLA-based plastic as shown in Figure 2.

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  • Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Separation, Recovery Or Treatment Of Waste Materials Containing Plastics (AREA)

Abstract

A process for manufacturing lactide from plastics having polylactic acid (PLA-based plastics) comprises preparing PLA-based plastics, accelerating decomposition of polylactic acid in the plastics to provide low molecular weight polylactic acid, and thermal decomposing the low molecular weight polylactic acid to provide lactide. Also, the process further comprises minimizing size of the PLA-based plastics after the PLA-based plastics preparation step, and purifying lactide after thermal decomposing low molecular weight polylactic acid to provide lactide.

Description

PROCESS FOR MANUFACTURING LACTIDE FROM PLASTICS
HAVING POLYLACTIC ACID
FIELD OF THE INVENTION
This invention relates to a process for manufacturing lactide from plastics having polylactic acid (PLA-based plastics).
BACKGROUND OF THE INVENTION
Presently, there are various approaches to minimize plastic wastes, e.g. lessening usage of plastic articles, using biodegradable plastics (e.g. plastics having polylactic acid (PLA-based plastics)), and disposing of such plastic wastes by landfill, incineration, recycling process, etc. The recycling process has received much attention since this process appears to be the most environmental-friendly approach. As cited above, however, the solution to the plastic waste's problem can be addressed either directly (e.g. lessening usage and disposal) or indirectly (e.g. using biodegradable materials). A process for manufacturing lactide and recycling process of PLA-based plastics have been disclosed in some prior arts, particularly patents.
U.S. Pub. No. 2013/0023674 Al discloses a method for producing lactide, which can be used for polylactic acid (PLA) production or other bioproducts, comprising melting the PLA feedstock in a heater to produce PLA liquid, heating the PLA liquid with a catalyst to depolymerize the PLA liquid and produce lactide vapour under vacuum atmosphere, and condensing the lactide vapour to produce liquid lactide.
U.S. Pub. No. 2012/0142958 Al discloses a process for recycling a polymer blend having polylactic acid (PLA), comprising grinding, compacting, dissolving in a solvent of PLA, removing the undissolved having polymers, alcoholysis depolymerization reaction and purification steps.
U.S. Patent No. 5,142,023 discloses a process for the continuous production of polylactide polymers from lactic acid which incorporates removal of water or a solvent carrier to concentrate the lactic acid feed followed by polymerization to a low-molecular- weight prepolymer. This prepolymer is fed to a reactor in which a catalyst is added to facilitate generation of lactide, the depolymerization product of polylactic acid. The lactide generated is continuously fed to a distillation system as a liquid or vapor wherein water and other impurities are removed. The resultant purified liquid lactide is fed directly to a polymerization process. SUMMARY OF THE INVENTION
This invention relates to a process for manufacturing lactide from plastics having polylactic acid (PLA-based plastics) comprises preparing PLA-based plastics, accelerating decomposition of polylactic acid in the plastics to provide low molecular weight polylactic acid, and thermal decomposing the low molecular weight polylactic acid to provide lactide. Also, the process further comprises minimizing size of the PLA-based plastics after the step of preparing PLA-based plastics, and purifying lactide after thermal decomposing low molecular weight polylactic acid to provide lactide.
An objective of this invention is to provide a process for manufacturing lactide from PLA-based plastics providing benefits in term of technique as follows:
- Can reduce time and energy consumption for decomposing polylactic acid in plastic. This is because said process only causes a partially chemical decomposition of polylactic acid. This differs from any existing processes for manufacturing lactide from PLA-based plastic, which, generally, decomposes completely until getting lactic acid. Moreover, applying the alcoholysis reaction in the process according to this invention provides faster chemical decomposition of polylactic acid in the plastic than using thermal decomposition as disclosed in U.S. Pub. No. 2013/0023674 Al . This results in a faster and more effective process for manufacturing lactide from PLA-based plastics.
- Can reduce steps in the process for manufacturing lactide from PLA-based plastics, which is normally conducted via polylactic acid decomposition to provide lactic acid, such as a lactic acid purification step, dehydration step, and polycondensation step to provide low molecular weight polylactic acid. The process for manufacturing lactide from PLA-based plastic according to this invention does not chemically decompose polylactic acid until obtaining lactic acid.
- Provide high purity lactide and low side reaction. Moreover, the condition applied in the step of decomposing polylactic acid in plastic according to this invention is not severe (mild condition).
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 shows a life cycle of PLA-based plastic.
Figure 2 shows a continuous process for manufacturing lactide from PLA-based plastic. Figure 3 shows a mechanism for accelerating chemical decomposition of polylactic acid in plastic by alcoholysis reaction. Figure 4 shows 1H-NMR spectrum of purified lactide obtained from the process according to this invention.
Figure 5 shows GC-MS spectrum verifying structure and optical purity of the purified lactide obtained from the process according to this invention. DETAILED DESCRIPTION OF THE EMBODIMENTS
A more detailed description about this invention will be explained as follows:
This invention relates to a process for manufacturing lactide from PLA-based plastics or recycling process of PLA-based plastics to produce lactide. Said process converts polylactic acid in plastic to lactide, which is a precursor or monomer in a process for manufacturing polylactic acid and its derivative by accelerating chemical decomposition of polylactic acid in the plastic by alcoholysis reaction or hydrolysis reaction. This provides lower molecular weight polylactic acid, which is suitable for thermal decomposition for converting to lactide (Fig. 1). Figure 1 also shows the recycling process of polylactic acid, which requires polylactic acid decomposition to provide lactic acid, and dehydration and polycondensation step to achieve low molecular weight polylactic acid, then thermal decomposition to produce lactide. The process according to this invention can be performed continuously and more efficiently by adjusting the condition in each step to provide process optimization, e.g. an input rate of reactants equivalent to an output rate of products in each stage (Fig. 2).
A process for manufacturing lactide from PLA-based plastic according to this invention comprising the steps of:
(i) preparing PLA-based plastic;
(ii) accelerating decomposition of the polylactic acid in plastic to provide low molecular weight polylactic acid; and
(iii) thermal decomposing the low molecular weight polylactic acid to provide lactide. The process for manufacturing lactide from PLA-based plastic according to this invention further comprises minimizing size of said PLA-based plastic after the PLA-based plastic preparation step. After minimizing size, said plastic has a dimension in a range from 0.1 to 10 mm, preferably no larger than 5 mm. This dimension makes it easy for feeding into the depolymerization reactor, and also increases the surface area. Hence, it can be molten easier, and shortens the melting time. However, said dimension varies with the type and size of the depolymerization reactor. According to this invention, the rninirnizing size is performed by at least one method selected from shearing, impacting, cutting into small pieces, and grinding. The grinding can be performed in either dry or wet condition, preferably by the grinder in the dry condition.
Moreover, the process for manufacturing PLA-based plastic according to the invention further comprises a step of purifying lactide after the step of thermal decomposition of low molecular weight polylactic acid to provide lactide
According to this invention, the PLA-based plastic has a ratio of polylactic acid from 1 to 100% by weight of total plastics, preferably a ratio of polylactic acid greater than 50% by weight of total plastics.
According to this invention, the preparation of PLA-based plastic comprising the steps of:
(i) washing said plastic with water, or washing with water and detergent or soap to remove any impurities in said plastic. These impurities may affect properties and purity of the products from the process, or the reaction conditions in each steps. and,
(ii) drying said plastic.
According to this invention, the preparation of PLA-based plastic further comprises a step of filtering said plastics after the washing step. The filtering step is performed using filter device under atmospheric condition or vacuum condition.
According to this invention, in the preparation step, said plastic is dried at a temperature of 50-80°C, preferably at a temperature of 55-70°C until all water completely evaporates.
The plastic is dried using either conventional oven or vacuum oven.
According to this invention, the accelerating decomposition of polylactic acid in plastic is performed by an alcoholysis reaction or a hydrolysis reaction. This is to accelerate decomposition of high molecular weight polylactic acid to low molecular weight polylactic acid, which is in a suitable range for thermal decomposition of low molecular weight polylactic acid to provide lactide in the lactide reactor.
According to this invention, the accelerating decomposition of polylactic acid in plastic by the alcoholysis reaction is performed by a reaction between PLA-based plastic and alcohol as shown in Fig. 3. A mechanism of said accelerating decomposition of polylactic acid in plastics is possible to begin with ester-bond breaking in the polylactic acid molecular chain allowing nucleophilic substitution. The nucleophile may include alcohol, organic acid, organic alkali, inorganic alkali, water, etc.
According to this invention, the accelerating decomposition of polylactic acid in the plastic by the alcoholysis reaction comprising the steps of:
(i) preparing a mixture of alcohol and catalyst; and
(ii) mixing the mixture obtained from (i) with the PLA-based plastic.
According to this invention, said alcohol is used in an amount from 0.1-10% by weight of the PLA-based plastic, preferably 2-7% by weight of the PLA-based plastic. Said alcohol is selected from the group consisting of an alcohol having 1 to 10 carbon atoms (CI -CI O) and having 1 to 10 hydroxyl groups, preferably glycerol (C3H8O3) or sorbitol (C6Hi406). Since said alcohol has a higher boiling point and large quantity of hydroxyl groups, resulting in rapid chemical decomposition of polylactic acid. Besides, it facilitates a lactide recovery from the alcohol.
Moreover, according to the invention, the catalyst is used in an amount of 0-5% by weight of the PLA-based plastic, preferably 0.1-0.5%) by weight of the PLA-based plastic. Said catalyst is selected from the group consisting of metal oxides, preferably antimony trioxide (Sb203). Said catalyst is further selected from the group consisting of organometallic compounds having 1 to 20 carbon atoms (C1-C20), preferably organometallic compounds of tin, namely Sn (II); or titanium, namely Ti (II).
According to this invention, the preparation of a mixture of alcohol and catalyst is performed by mixing said catalyst with alcohol, and then stirring for good distribution and compatibility.
According to this invention, the accelerating decomposition of polylactic acid in plastic is performed under vacuum or under pressure of at least 1 bar, preferably 1 -10 bars; at a temperature of 170-250°C, preferably at a temperature of 190-210°C. The mixture obtained from (i) with the PLA-based plastic can be mixed before feeding into a depolymerization reactor, or mixed all together in the depolymerization reactor. The depolymerization reactor includes a batch reactor, or a continuous reactor including single screw extruder or twin screw extruder to allow continuous chemical decomposition of polylactic acid occurrence.
According to this invention, the accelerating decomposition of polylactic acid in plastic by the alcoholysis reaction provides polylactic acid having a number average molecular weight in a range of 500 to 30,000 g/mol, preferably in a range of 2,000-12,000 g/mol. According to this invention, the accelerating decomposition of polylactic acid in plastic by hydrolysis reaction further comprises a step of mixing reactant with the PLA-based plastic. Said reactant is selected from the group consisting of organic acid, inorganic acid, organic alkali, inorganic alkali, or water, preferably organic acids, namely lactic acid. Advantages of using lactic acid as reactant are no impurities in the reaction, and the lactic acid being used as a precursor in the lactide production. Moreover, the use of lactic acid as a reactant may not require other additional catalysts, e.g. metal oxides or organometallic compound. This is because the acid will act as an autocatalyst for polyester decomposition, such as polylactic acid. However, the use of acid as reactant may cause corrosion in the metal parts of the equipments. Therefore, precaution must be taken.
According to this invention, the hydrolysis reaction is performed under vacuum or under pressure of at least 1 bar, preferably 1-10 bars; at a temperature of 170-250°C, preferably at a temperature of 190-210°C. The hydrolysis reaction is performed in the depolymerization reactor including batch reactor, or a continuous reactor namely single screw extruder or twin screw extruder.
According to this invention, the thermal decomposition of low molecular weight polylactic acid to provide lactide comprising the steps of:
(i) feeding low molecular weight PLA-based plastic to the lactide reactor;
(ii) adding the catalyst to lactide reactor;
(iii) thermal decomposing polylactic acid to provide lactide; and
(iv) condensing lactide by cooling down to provide lactide solid or lactide liquid.
According to this invention, the low molecular weight PLA-based plastic is fed to lactide reactor by batch feed or continuous feed.
According to this invention, the catalyst fed in the reactor is used in an amount of 0-2% by weight of the PLA-based plastic, preferably 0.1 -1 .0% by weight of the PLA-based plastic. Said catalyst is selected from the group consisting of metal oxide or organometallic compounds having 1 to 20 carbon atoms (C1-C20), preferably organometallic compounds of tin, namely Sn (II); or titanium, namely Ti (II). However, the organometallic compounds are not limited to those listed above.
According to this invention, the thermal decomposition of polylactic acid to provide lactide is performed at a temperature of 190-250°C, preferably at a temperature of 200-220°C under vacuum or inert gas pressure, preferably under vacuum with a pressure of 0.001 to 0.1 bar. According to this invention, the condensation of lactide by cooling down to provide lactide solid is preferably performed at a temperatures below 25°C. The condensation of lactide by cooling down to provide lactide liquid is preferably performed at a temperature 100-110°C. This provides lactide, which is ready for further purification. While alcohol, various catalysts, and/or other substances in PLA-based plastic remain in the bottom section of the lactide reactor, and will be removed or reused again as the lactide reactor's maintenance.
According to this invention, the lactide is purified by distillation or recrystallization. The distillation is performed under vacuum or under inert gas pressure of at least 1 bar, preferably 1- 10 bars; at a temperature of 120-180°C, preferably at a temperature of 120-150°C.
According to this invention, the recrystallization in a lactide purification step comprising the steps of:
(i) dissolving lactide by solvent at a temperature of 50-70°C;
(ii) recrystallizing lactide at room temperature;
(iii) filtering crystalline lactide; and
(iv) drying crystalline lactide at a temperature of 50-70°C under vacuum.
According to this invention, the recrystallization is performed using a solvent selected from acetone, isopropanol, toluene, benzene, diethyl ether, or ethyl acetate, preferably ethyl acetate or toluene.
Said recrystallization may be repeated 2-3 times to provide high purity lactide as shown in Table 1.
Table 1 Purity of lactide from the process according to this invention compared with lactide produced by lactic acid in the laboratory, and commercial lactide.
Figure imgf000008_0001
* Purity of sample characterized by DSC technique Table 1 shows that the lactide from the process according to this invention has a high purity up to 99.8%, which is equivalent to the purity of lactide produced by lactic acid in the laboratory and the commercial lactide. Also, it has almost 100% optical purity as shown in Figure 5. From Ή-NMR and GC-MS techniques (as shown in Figs. 4 and 5), it reveals that the lactide from the process according to this invention has L-lactide structure, which is same structure as PLA-based plastic used as precursor in the process.
According to this invention, the purified lactide from a step of lactide purification can be reacted to further synthesize PLA-based plastic as shown in Figure 2.
The process for manufacturing lactide from PLA-based plastic according to the invention is not only limited to the procedures and details as stated above. But, it also includes any modification or any other equivalent approaches, which is still within the scope of this invention as defined in the claims.

Claims

Claims
1. A process for manufacturing lactide from PLA-based plastic comprising the steps of:
(i) preparing PLA-based plastic;
(ii) accelerating decomposition of the polylactic acid in plastic to provide low molecular weight polylactic acid; and
(iii) thermal decomposing the low molecular weight polylactic acid to provide lactide.
2. The process according to claim 1 , wherein said PLA-based plastic has a ratio of polylactic acid from 1 to 100% by weight of total plastic, preferably a ratio of polylactic acid greater than 50% by weight of total plastic.
3. The process according to claim 1 further comprising the steps of:
(i) washing said plastic with water, or washing with water and detergent or soap; and
(ii) drying said plastic.
4. The process according to claim 3, wherein said plastic is dried at a temperature of 50-80°C, preferably at a temperature of 55-70°C.
5. The process according to claim 3 or 4, wherein said plastic is dried using conventional oven or vacuum oven.
6. The process according to claim 3, wherein the PLA-based plastic preparation further comprises a step of filtering said plastics after the washing step.
7. The process according to claim 6, wherein said filtering step is performed using filter device under atmospheric condition or vacuum condition.
8. The process according to claim 1 further comprising a step of minimizing size said PLA-based plastic after the preparation step.
9. The process according to claim 8, wherein the step of rninirnizing size is performed by at least one method selected from shearing, impacting, cutting into small pieces, and grinding.
10. The process according to claim 9, wherein the preferred method for iriinimizing size is grinding by a grinder.
1 1. The process according to claim 8, wherein said plastic after minimizing size has a dimension in a range from 0.1 to 10 mm, preferably no larger than 5 mm.
12. The process according to claim 1 , wherein the step of accelerating decomposition is performed by an alcoho lysis reaction or a hydrolysis reaction.
13. The process according to claim 12, wherein the accelerating decomposition by the alcoho lysis reaction comprising the steps of:
(i) preparing a mixture of alcohol and catalyst; and
(ii) mixing the mixture obtained from (i) with the PLA-based plastic.
14. The process according to claim 13, wherein said alcohol is used in an amount from 0.1-10% by weight of the PLA-based plastic, preferably 2-7% by weight of the PLA-based plastic.
15. The process according to claim 13, wherein the catalyst is used in an amount of 0-5% by weight of the PLA-based plastic, preferably 0.1 -0.5% by weight of the PLA-based plastic.
16. The process according to claim 13 or 14, wherein said alcohol is selected from the group consisting of an alcohol having 1 to 10 carbon atoms (C1-C10) and having 1 to 10 hydroxyl groups, preferably glycerol (C3H8O3) or sorbitol (C6Hi406).
17. The process according to claim 13 or 15, wherein said catalyst is selected from the group consisting of metal oxides, preferably antimony trioxide (Sb203).
18. The process according to claim 13 or 15, wherein said catalyst is further selected from the group consisting of organometallic compounds having 1 to 20 carbon atoms (C1-C20), preferably organometallic compounds of tin, namely Sn (II); or titanium, namely Ti (II).
19. The process according to claim 13, wherein the accelerating decomposition by the alcoholysis reaction is performed under vacuum or under pressure of at least 1 bar, preferably 1 -10 bars; at a temperature of 170-250°C, preferably at a temperature of 190-210°C.
20. The process according to claim 13, wherein the mixture obtained from (i) with the PLA-based plastic can be mixed before feeding into a depolymerization reactor, or mixed all together in the depolymerization reactor.
21. The process according to claim 20, wherein the depolymerization reactor includes a batch reactor, or a continuous reactor including single screw extruder or twin screw extruder.
22. The process according to claim 13, wherein polylactic acid obtained from said alcoholysis reaction has a number average molecular weight in a range of 500 to 30,000 g/mol, preferably in a range of 2,000-12,000 g/mol.
23. The process according to claim 12, wherein the accelerating decomposition by the hydrolysis reaction further comprising a step of mixing reactant with the PLA-based plastic.
24. The process according to claim 23, wherein said reactant is selected from the group consisting of organic acid, inorganic acid, organic alkali, inorganic alkali, or water, preferably organic acids, namely lactic acid.
25. The process according to claim 23, wherein the hydrolysis reaction is performed under vacuum or under pressure of at least 1 bar, preferably 1 -10 bars; at a temperature of 170- 250°C, preferably at a temperature of 190-210°C.
26. The process according to claim 23 or 25, wherein the hydrolysis reaction is performed in the depolymerization reactor including batch reactor, or a continuous reactor namely single screw extruder or twin screw extruder.
27. The process according to claim 1 , wherein the thermal decomposition of low molecular weight polylactic acid to provide lactide comprising the steps of:
(i) feeding low molecular weight PLA-based plastic to the lactide reactor;
(ii) adding the catalyst to lactide reactor;
(iii) thermal decomposing polylactic acid to provide lactide; and
(iv) condensing lactide by cooling down to provide lactide solid or lactide liquid.
28. The process according to claim 27, wherein the low molecular weight PLA-based plastic is fed to lactide reactor by batch feed or continuous feed.
29. The process according to claim 27, wherein the catalyst is used in an amount of 0-2% by weight of the PLA-based plastic, preferably 0.1-1.0% by weight of the PLA-based plastic.
30. The process according to claim 27 or 29, wherein the catalyst is selected from the group consisting of metal oxide or organometallic compounds having 1 to 20 carbon atoms (Cl -
C20), preferably organometallic compounds of tin, namely Sn (II); or titanium, namely Ti (II).
31. The process according to claim 27, wherein the thermal decomposition of polylactic acid to provide lactide is performed at a temperature of 190-250°C, preferably at a temperature of 200-220°C.
32. The process according to claim 27, wherein the thermal decomposition of polylactic acid to provide lactide is performed under vacuum or under inert gas pressure, preferably under vacuum with a pressure of 0.001 bar to 0.1 bar.
33. The process according to claim 27, wherein the condensation of lactide by cooling down to provide lactide solid is preferably performed at a temperatures below 25°C.
34. The process according to claim 27, wherein the condensation of lactide by cooling down to provide lactide liquid is preferably performed at a temperature 100-1 10°C.
35. The process according to claim 1 , further comprising a step of purifying lactide after the step of thermal decomposition of polylactic acid to provide lactide.
36. The process according to claim 35, wherein the lactide is purified by a distillation or a recrystallization.
37. The process according to claim 36, wherein the distillation is performed under vacuum or under inert gas pressure of at least 1 bar, preferably 1 -10 bars; at a temperature of 120-180°C, preferably at a temperature of 120-150°C.
38. The process according to claim 36, wherein the recrystallization comprising the steps of:
(i) dissolving lactide by solvent at a temperature of 50-70°C;
(ii) recrystallizing lactide at room temperature;
(iii) filtering crystalline lactide; and
(iv) drying crystalline lactide at a temperature of 50-70°C under vacuum.
39. The process according to claim 38, wherein the recrystallization is performed using a solvent selected from acetone, isopropanol, toluene, benzene, diethyl ether, or ethyl acetate, preferably ethyl acetate or toluene.
PCT/TH2014/000013 2014-01-23 2014-03-28 Process for manufacturing lactide from plastics having polylactic acid WO2015112098A1 (en)

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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109438411A (en) * 2018-10-24 2019-03-08 深圳光华伟业股份有限公司 Glycolide process units and production method
US10259768B2 (en) 2017-05-24 2019-04-16 Board Of Trustees Of Michigan State University Method of recycling a polyester
RU2699801C1 (en) * 2018-11-20 2019-09-11 Федеральное государственное автономное образовательное учреждение высшего образования "Национальный исследовательский Томский государственный университет" (ТГУ, НИ ТГУ) Lactide purification method
CN110760357A (en) * 2019-11-21 2020-02-07 陕西东鑫垣化工有限责任公司 Preparation method and treatment device of heating furnace fuel
WO2020263201A1 (en) 2019-06-26 2020-12-30 Orta Doğu Tekni̇k Üni̇versi̇tesi̇ High yield, eco-friendly recycling method of polylactic acid using supercritical or dense gas carbon dioxide
CN115403554A (en) * 2022-09-15 2022-11-29 扬州惠通生物新材料有限公司 Method for directly recovering lactide from polylactic acid waste
NL2028900B1 (en) * 2021-08-02 2023-02-17 Arapaha B V A method of closed loop recycling of polylactic acid
WO2023027394A1 (en) * 2021-08-25 2023-03-02 (주)코레쉬텍 Pla modifying method using saccharide or carboxylic group substituent of saccharide, and pla modified thereby

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5142023A (en) 1992-01-24 1992-08-25 Cargill, Incorporated Continuous process for manufacture of lactide polymers with controlled optical purity
WO1996006092A1 (en) * 1994-08-18 1996-02-29 Ecological Chemical Products Company Integrated process for the manufacture of lactide
KR20120009879A (en) * 2010-07-22 2012-02-02 한국화학연구원 Process for preparing lactide and polylactide from Lactic acid fermentation
US20120142958A1 (en) 2009-04-14 2012-06-07 Galactic S.A. Chemical recycling of pla by hydrolysis
US20130023674A1 (en) 2011-03-15 2013-01-24 Ramani Narayan Lactide Production from Thermal Depolymerization of PLA with applications to Production of PLA or other bioproducts
EP2559725A1 (en) * 2011-08-19 2013-02-20 Uhde Inventa-Fischer GmbH Method and device for recovery of lactide from polylactide and glycolide from polyglycolide

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5142023A (en) 1992-01-24 1992-08-25 Cargill, Incorporated Continuous process for manufacture of lactide polymers with controlled optical purity
WO1996006092A1 (en) * 1994-08-18 1996-02-29 Ecological Chemical Products Company Integrated process for the manufacture of lactide
US20120142958A1 (en) 2009-04-14 2012-06-07 Galactic S.A. Chemical recycling of pla by hydrolysis
KR20120009879A (en) * 2010-07-22 2012-02-02 한국화학연구원 Process for preparing lactide and polylactide from Lactic acid fermentation
US20130023674A1 (en) 2011-03-15 2013-01-24 Ramani Narayan Lactide Production from Thermal Depolymerization of PLA with applications to Production of PLA or other bioproducts
EP2559725A1 (en) * 2011-08-19 2013-02-20 Uhde Inventa-Fischer GmbH Method and device for recovery of lactide from polylactide and glycolide from polyglycolide

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10259768B2 (en) 2017-05-24 2019-04-16 Board Of Trustees Of Michigan State University Method of recycling a polyester
CN109438411A (en) * 2018-10-24 2019-03-08 深圳光华伟业股份有限公司 Glycolide process units and production method
RU2699801C1 (en) * 2018-11-20 2019-09-11 Федеральное государственное автономное образовательное учреждение высшего образования "Национальный исследовательский Томский государственный университет" (ТГУ, НИ ТГУ) Lactide purification method
WO2020263201A1 (en) 2019-06-26 2020-12-30 Orta Doğu Tekni̇k Üni̇versi̇tesi̇ High yield, eco-friendly recycling method of polylactic acid using supercritical or dense gas carbon dioxide
CN110760357A (en) * 2019-11-21 2020-02-07 陕西东鑫垣化工有限责任公司 Preparation method and treatment device of heating furnace fuel
CN110760357B (en) * 2019-11-21 2021-06-25 陕西东鑫垣化工有限责任公司 Preparation method and treatment device of heating furnace fuel
NL2028900B1 (en) * 2021-08-02 2023-02-17 Arapaha B V A method of closed loop recycling of polylactic acid
WO2023012142A3 (en) * 2021-08-02 2023-04-06 Arapaha B.V. A process for chemically recycling polylactic acid (pla)
WO2023027394A1 (en) * 2021-08-25 2023-03-02 (주)코레쉬텍 Pla modifying method using saccharide or carboxylic group substituent of saccharide, and pla modified thereby
CN115403554A (en) * 2022-09-15 2022-11-29 扬州惠通生物新材料有限公司 Method for directly recovering lactide from polylactic acid waste
CN115403554B (en) * 2022-09-15 2024-04-16 扬州惠通生物新材料有限公司 Method for directly recycling lactide from polylactic acid waste

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