WO2021181532A1 - Polylactic acid decomposition method - Google Patents

Polylactic acid decomposition method Download PDF

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Publication number
WO2021181532A1
WO2021181532A1 PCT/JP2020/010352 JP2020010352W WO2021181532A1 WO 2021181532 A1 WO2021181532 A1 WO 2021181532A1 JP 2020010352 W JP2020010352 W JP 2020010352W WO 2021181532 A1 WO2021181532 A1 WO 2021181532A1
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Prior art keywords
polylactic acid
mass
additive
water content
decomposing
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PCT/JP2020/010352
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French (fr)
Japanese (ja)
Inventor
遊佐　敦
後藤　敏晴
吟 孫
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マクセルホールディングス株式会社
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Priority to JP2022507057A priority Critical patent/JP7425181B2/en
Priority to PCT/JP2020/010352 priority patent/WO2021181532A1/en
Publication of WO2021181532A1 publication Critical patent/WO2021181532A1/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
    • 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

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  • the present invention relates to a method for decomposing polylactic acid.
  • Japanese Unexamined Patent Publication No. 6-279434 discloses a method for producing meso-containing lactides, which thermally decomposes a hydroxy acid-based oligomer using an alkali metal salt as a catalyst.
  • Japanese Unexamined Patent Publication No. 2007-210889 discloses a method for monomerizing stereocomplex-type polylactic acid in which stereocomplex-type polylactic acid is treated at a high temperature of 170 to 330 ° C. for 5 to 240 minutes.
  • polylactic acid and a depolymerization catalyst are put into an extruder that leads to a vent chamber held under reduced pressure, and the polylactic acid and the depolymerization catalyst are melt-kneaded by the extruder.
  • a lactide recovery method is disclosed in which a melt-kneaded product is supplied into a vent chamber, polylactic acid is depolymerized in the vent chamber, and the produced lactide is gasified and recovered from the vent chamber.
  • JP-A-6-279434 is a reaction in a reduced pressure environment, and has a problem that the apparatus becomes large-scale and batch processing is unavoidable. In addition, it is necessary to use a raw material having a low molecular weight of hydroxy acid.
  • Japanese Unexamined Patent Publication No. 2007-210889 proposes a method for obtaining lactic acid by decomposing polylactic acid.
  • the method of synthesizing polylactic acid directly from lactic acid has not been put into practical use due to the problem that the molecular weight does not increase.
  • in order to produce lactide it is necessary to separate polylactic acid and water. This process requires a lot of energy, which goes against the purpose of recycling biodegradable resins to reduce the environmental load.
  • JP-A-2017-132730 has low reaction reproducibility, and the molecular weight and reaction rate of the product cannot be stably controlled.
  • An object of the present invention is to provide a method for decomposing polylactic acid, which can decompose polylactic acid while suppressing energy consumption.
  • the method for decomposing polylactic acid is selected from the group consisting of polylactic acid, an alkali metal salt, an alkaline earth metal salt, an alkali metal oxide, and an alkaline earth metal oxide.
  • Moisture content mass of water in the reactor / (mass of polylactic acid + mass of additive + mass of water added from the outside)
  • the mass of water in the reactor includes the mass of water adsorbed on the polylactic acid and the additive and the mass of water added from the outside, and the mass of the polylactic acid and the mass of the additive are , The mass including the mass of water adsorbed on each.
  • polylactic acid can be decomposed while suppressing energy consumption.
  • FIG. 1 is a flow chart of a method for decomposing polylactic acid according to the first embodiment of the present invention.
  • FIG. 2 is a flow chart of a method for decomposing polylactic acid according to the second embodiment of the present invention.
  • FIG. 3 is a flow chart of a method for decomposing polylactic acid according to the third embodiment of the present invention.
  • FIG. 4 is a schematic view of an example of a polylactic acid decomposition device.
  • FIG. 5 is a schematic view of another example of the polylactic acid decomposition device.
  • FIG. 6 is a graph showing the relationship between the water content, the number average molecular weight of the decomposition products, and the energy consumption.
  • Japanese Patent Application Laid-Open No. 2007-210889 described above describes that 5 to 100 parts by mass of water coexists with 1 part by mass of polylactic acid.
  • the present inventors have found that under the condition that a predetermined additive is added, the decomposition reaction of polylactic acid proceeds even if the amount of water is very small.
  • FIG. 1 is a flow chart of a method for decomposing polylactic acid according to the first embodiment of the present invention.
  • the method for decomposing polylactic acid according to the present embodiment includes a step of preparing polylactic acid and additives (step S1), a step of adjusting the water content of polylactic acid and additives (step S2), and a reaction device using polylactic acid and additives. (Step S3), a step of holding or kneading polylactic acid and additives (step S4), and a step of taking out decomposition products (step S5) are provided.
  • step S1 prepare polylactic acid as a raw material and additives to be added to polylactic acid (step S1).
  • the polylactic acid is preferably pretreated in the form of powder or pellets.
  • a crushing device may be provided at the raw material charging port of the reaction device so that the raw material containing polylactic acid (for example, waste) is crushed at the same time as the raw material charging step (step S3) described later.
  • the additive is one kind or a mixture of two or more kinds selected from the group consisting of an alkali metal salt, an alkaline earth metal salt, an alkali metal oxide, and an alkaline earth metal oxide.
  • the additive is preferably one kind or a mixture of two or more kinds selected from the group consisting of sodium hydrogen carbonate (baking soda), sodium carbonate, potassium carbonate, and magnesium oxide, and baking soda is particularly preferable.
  • step S2 adjust the water content of polylactic acid and additives (step S2).
  • Additives are hygroscopic and may have moisture adsorbed. Polylactic acid may also have water adsorbed. Therefore, the water content of polylactic acid and the additive may be adjusted in advance before being added to the reactor.
  • step S2 The step of adjusting the water content (step S2) is an arbitrary step, and may be omitted if the water content of the added polylactic acid and the additive is stable.
  • the water content of at least one of polylactic acid and the additive may be adjusted.
  • Specific methods for adjusting the water content include drying polylactic acid and additives in a dryer, holding them in a constant temperature and humidity chamber for a predetermined time, and moistening them with a sprayer or the like.
  • the water content of polylactic acid and the additive may be adjusted by controlling the humidity of the inlet of the reactor.
  • the water content of polylactic acid and the additive is affected by the humidity of the inlet of the reactor. If you want to lower the water content of polylactic acid and additives, you can lower the humidity of the inlet of the reactor, and if you want to increase the water content of polylactic acid and additives, you can lower the humidity of the inlet of the reactor. Should be raised.
  • Examples of the device for controlling the humidity of the inlet of the reaction device include an air-conditioning device and a spray device.
  • step S3 Add polylactic acid and additives to the reactor (step S3).
  • polylactic acid is decomposed in a state where the water content in the reactor is controlled. Therefore, it is preferable that the reactor has a structure capable of sealing the inside except for the raw material inlet and outlet, the gas inlet and outlet (vent port), and the water inlet and the like.
  • the reaction apparatus is preferably made of metal, glass, or ceramic, and particularly preferably made of metal.
  • the reaction device may be an extruder as described later.
  • the amount of the additive is preferably 0.2 to 20 parts by mass with respect to 100 parts by mass of polylactic acid.
  • the mass of polylactic acid and the mass of the additive shall be the mass including the mass of water adsorbed on each.
  • additive concentration the value of (mass of additive (including mass of adsorbed water)) / (mass of polylactic acid (including mass of adsorbed water)) ⁇ 100 is referred to as “additive concentration”.
  • the lower limit of the additive concentration is more preferably 0.50 parts by mass, further preferably 1.0 part by mass, and further preferably 2.0 parts by mass. On the other hand, if the additive concentration is too high, the energy required for heating becomes large.
  • the upper limit of the additive concentration is more preferably 18 parts by mass, further preferably 15 parts by mass, and further preferably 10 parts by mass.
  • the polylactic acid and the additive are retained or kneaded (step S3).
  • the water content represented by the following formula is set to 0.15 to 3.0%.
  • Moisture content mass of water in the reactor / (mass of polylactic acid + mass of additive + mass of water added from the outside)
  • the mass of water in the reactor includes the mass of water adsorbed on the polylactic acid and the additive and the mass of the water added from the outside, and the mass of the polylactic acid and the mass of the additive are adsorbed on each.
  • the mass includes the mass of water.
  • water may be added from the outside of the reaction device to adjust the water content in the reaction device.
  • Moisture can be added from the outside, for example, by supplying water from an inlet of the reactor or an injection port provided separately from the inlet. Moisture may be supplied as a liquid or as a humidifying body. However, it is not essential to add water from the outside, and the mass of the water added from the outside may be zero. Further, the water content may be reduced by supplying a dry gas.
  • the lower limit of the water content is preferably 0.20%, more preferably 0.50%, still more preferably 1.0%.
  • the upper limit of the water content is preferably 2.8%, more preferably 2.5%, and even more preferably 2.0%.
  • This holding or kneading is preferably performed by heating the inside of the reactor.
  • the heating temperature is preferably 120 to 340 ° C. The higher the heating temperature, the easier the reaction will proceed.
  • the lower limit of the heating temperature is more preferably 160 ° C., still more preferably 180 ° C. On the other hand, if the heating temperature is too high, the bonds other than the ester bonds are broken, and the yield of the desired decomposition product decreases.
  • the upper limit of the heating temperature is more preferably 300 ° C, still more preferably 280 ° C, still more preferably 260 ° C.
  • This holding or kneading is preferably performed by pressurizing the inside of the reactor.
  • the pressure in the reactor is preferably 0.15 to 20.0 MPa.
  • the lower limit of the pressure in the reactor is more preferably 0.5 MPa, further preferably 1.0 MPa, still more preferably 3.0 MPa.
  • the upper limit of the pressure in the reactor is more preferably 15.0 MPa, further preferably 10.0 MPa, still more preferably 5.0 MPa.
  • the holding or kneading time is not particularly limited, but is preferably 1 second or longer, for example, 1 second to 12 hours.
  • the lower limit of the holding or kneading time is more preferably 30 seconds, further preferably 1 minute, still more preferably 2 minutes.
  • the upper limit of the holding or kneading time is more preferably 6 hours, further preferably 2 hours, still more preferably 30 minutes.
  • the shear rate is preferably 500 s -1 or less.
  • the decomposition product formed by decomposing polylactic acid is taken out from the reactor (step S5).
  • This decomposition product contains lactic acid oligomers, lactic acid, lactide and the like.
  • the method for decomposing polylactic acid according to the first embodiment of the present invention has been described above.
  • the method for decomposing polylactic acid according to the present embodiment includes a step of retaining or kneading the polylactic acid and the additive under the condition that the water content is 0.15 to 3.0%. According to this configuration, polylactic acid can be decomposed while suppressing the consumption of energy required for heating water. Further, according to the present embodiment, not only lactic acid oligomer and lactic acid but also lactide can be recovered.
  • FIG. 2 is a flow chart of a method for decomposing polylactic acid according to the second embodiment of the present invention.
  • the method for decomposing polylactic acid according to the present embodiment is based on the step of measuring the water content in the reactor (step S6) and the measured water content in addition to the steps of the first embodiment (FIG. 1). It further includes a step (step S7) of adjusting the water content in the reaction apparatus.
  • the water content in the reaction apparatus is measured in parallel with the step of holding or kneading the polylactic acid and the additive (step S4) (step S6).
  • the water content in the reaction device can be measured, for example, by collecting a gas component in the reaction device from a vent port provided in the reaction device and analyzing the collected gas component with a moisture meter.
  • the moisture meter is, for example, a Karl Fischer titer or an infrared moisture meter.
  • Adjust the water content in the reactor based on the measured water content (step S7). Specifically, the measured water content is compared with the preset lower limit of water content, and if the measured water content is less than the lower limit of water content, an operation of increasing the water content in the reactor is performed. Specific operations for raising the water content in the reactor include, for example, injecting liquid water into the reactor and introducing a humidifier into the reactor.
  • step S7 instead of or in addition to the above operation, the measured water content is compared with the preset water content upper limit, and the measured water content is measured. If the water content exceeds the upper limit of water content, an operation of lowering the water content in the reactor may be performed.
  • Specific operations for lowering the water content in the reactor include, for example, stopping water injection into the reactor and introducing a dry gas into the reactor.
  • a step of holding or kneading the polylactic acid and the additive (step S4), a step of measuring the water content in the reaction device (step S6), and a step of adjusting the water content in the reaction device (step S7) are performed. , Repeat until a predetermined time has elapsed. Thereby, the polylactic acid and the additive can be retained or kneaded in a state where the water content is controlled to be within a predetermined range.
  • FIG. 3 is a flow chart of a method for decomposing polylactic acid according to the third embodiment of the present invention.
  • the process from the addition of polylactic acid and additives to the removal of decomposition products is performed continuously.
  • a treatment for example, using a reaction device having an inlet and an outlet, polylactic acid and additives are charged from the inlet, and in parallel with this, the reaction product is taken out from the outlet, and polylactic acid is taken out.
  • a process of continuously decomposing for example, using a reaction device having an inlet and an outlet, polylactic acid and additives are charged from the inlet, and in parallel with this, the reaction product is taken out from the outlet, and polylactic acid is taken out.
  • the decomposition method of this embodiment is also the same as the decomposition method of the first embodiment (FIG. 1), that is, a step of preparing polylactic acid and additives (step S1), and a step of adjusting the water content of polylactic acid and additives.
  • Step S2 a step of adding polylactic acid and additives to the reactor (step S3), a step of holding or kneading the polylactic acid and additives (step S4), and a step of taking out decomposition products (step S5).
  • the process from the addition of polylactic acid and additives to the removal of decomposition products is continuously performed. Specifically, the steps from the step of preparing the polylactic acid and the additive (step S1) to the step of taking out the decomposition product (step S5) are repeated until a predetermined time elapses.
  • the decomposition method of the present embodiment also has a step of measuring the water content in the reaction device (step S6) and the inside of the reaction device based on the measured water content. Further includes a step (step S7) of adjusting the water content of the above.
  • step S7 the timing of carrying out the step of adjusting the water content in the reactor (step S7) is different from that of the second embodiment.
  • the water content in the reactor is adjusted by adjusting the water content of at least one of the polylactic acid and the additive to be charged into the reactor. That is, in the present embodiment, the step of adjusting the water content of the polylactic acid and the additive (step S2) also serves as the step of adjusting the water content in the reactor (step S7).
  • the measured water content is compared with the preset lower limit of water content, and if the measured water content is less than the lower limit of water content, the inside of the reactor is used. Perform an operation to raise the water content.
  • an operation for increasing the water content in the reactor an operation for increasing the water content of at least one of the polylactic acid and the additive to be charged into the reactor is performed. More specifically, for example, operations such as lowering the drying temperature of polylactic acid and additives, shortening the drying time, moistening with a mist, and increasing the humidity of the inlet of the reactor can be mentioned.
  • the measured moisture is compared with the preset moisture upper limit, and the measured moisture sets the moisture upper limit. If it exceeds the limit, an operation of lowering the water content in the reactor may be performed.
  • an operation of lowering the water content in the reactor an operation of lowering the water content of at least one of the polylactic acid and the additive to be charged into the reactor is performed. More specifically, for example, operations such as raising the drying temperature of polylactic acid and additives, lengthening the drying time, stopping moistening by spraying, etc., and lowering the humidity of the inlet of the reactor can be mentioned. ..
  • the water content in the reaction device may be adjusted by injecting water into the reaction device or introducing a humidifying body or a dry gas. That is, in addition to or instead of adjusting the water content in the reactor by adjusting the water content of at least one of the polylactic acid and the additive to be charged into the reactor, as in the case of the second embodiment. Similarly, the water content in the reactor may be adjusted by injecting water into the reactor or introducing a humidifier or a dry gas.
  • polylactic acid and additives can be retained or kneaded in a state where the water content is controlled to be within a predetermined range.
  • FIG. 4 is a schematic view of a decomposition device 1 which is an example of a decomposition device for polylactic acid.
  • the decomposition device 1 includes an extruder 10, a feeder 20, a moisture adjusting device 25, a gas analyzer 30, and a control device 40.
  • the polylactic acid and the additive are charged into the extruder 10 by the feeder 20, kneaded by the extruder 10, and finally taken out as a low molecular weight decomposition product from the discharge port (outlet) 11c of the extruder 10.
  • the feeder 20 feeds polylactic acid and additives into the extruder 10 in a predetermined supply amount.
  • the feeder 20 preferably has a structure capable of independently controlling the supply amounts of polylactic acid and additives.
  • the feeder 20 includes a motor 21, and the supply amount of polylactic acid and additives can be controlled by controlling the rotation speed of the motor 21. More specifically, as the feeder 20, for example, a screw feeder or a belt conveyor can be used.
  • the extruder 10 includes a cylinder wall 11 (reactor), a screw 12, a heating device 13, a seal member 14, a die 15, and the like.
  • the cylinder wall 11 has a structure in which the inside is sealed except for the openings (input port 11a, vent port 11b, discharge port 11c) described later, and functions as a reaction device for the decomposition reaction of polylactic acid.
  • the screw 12 kneads the contents of the cylinder wall 11.
  • the polylactic acid and additives charged into the cylinder wall 11 are conveyed toward the discharge port 11c while being kneaded by the screw 12.
  • the screw 12 includes a motor 121, and the shear rate can be adjusted by controlling the rotation speed of the motor 121.
  • the heating device 13 heats the cylinder wall 11 and adjusts the temperature of the cylinder wall 11.
  • the heating device 13 is divided and arranged around the three regions defined by the seal member 14, so that the temperature of each region can be controlled independently.
  • the cylinder wall 11 is provided with an input port 11a, a vent port 11b, and a discharge port 11c as openings.
  • the input port 11a is provided on the most upstream side of the cylinder wall 11 in the transport direction. Polylactic acid and additives are charged from the feeder 20 into the inlet 11a.
  • the vent port 11b is provided on the downstream side of the cylinder wall 11 in the transport direction so that only the gas component can pass through.
  • the bend port 11b is preferably provided in the vicinity of the discharge port 11c.
  • the vent port 11b is arranged in the downstream region (deaeration / cooling discharge zone) of the three regions defined by the seal member 13.
  • the vent port 11b is connected to the gas analyzer 30.
  • the discharge port 11c is provided on the most downstream side of the cylinder wall 11 in the transport direction.
  • a die 15 is arranged at the discharge port 11c.
  • the decomposition product formed by kneading in the cylinder wall 11 is molded into a predetermined shape by the die 15 and extruded from the discharge port 11c.
  • the moisture adjusting device 25 adjusts the moisture in the cylinder wall 11.
  • the moisture adjusting device 25 is, for example, a spraying device that adjusts the humidity of the inlet 11a.
  • the moisture adjusting device 25 may be a pump for injecting water into the cylinder wall 11 or a device for introducing a dry gas or a humidifying body into the cylinder wall 11.
  • the gas analyzer 30 includes a moisture meter (not shown).
  • the gas analyzer 30 analyzes the gas component collected from the vent port 11b and measures the water content in the cylinder wall 11. The measured moisture value is transmitted to the control device 40.
  • the control device 40 receives the value of the water content in the cylinder wall 11 from the gas analyzer 30, and controls the water content adjusting device 25 based on this value. This adjusts the water content in the cylinder wall 11. That is, the decomposition device 1 is configured so that the control device 40 can automatically perform the step of adjusting the water content in the cylinder wall 11.
  • the disassembling device 1 is provided with the control device 40 and the step of adjusting the water content in the cylinder wall 11 by the control device 40 is automatically performed has been described.
  • the step of adjusting the water content may be performed manually, and the decomposition device may not include the control device 40.
  • FIG. 5 is a schematic view of the decomposition device 2 which is another example of the decomposition device for polylactic acid.
  • the decomposition device 2 is provided with a reaction facility 60 in place of the extruder 10 of the decomposition device 1 (FIG. 4).
  • the reaction equipment 60 includes a reaction device 61, a screw 62, and a heating device 63.
  • the reaction device 61 includes a main body 611 and a lid 612.
  • the lid 612 is provided with a raw material input port 612a, a gas introduction port 612b, and a vent port 612c, which are connected to a feeder 20, a moisture adjusting device 25, and a gas analyzer 30, respectively.
  • the screw 62 kneads the contents of the reaction device 61.
  • the heating device 63 heats the reaction device 61.
  • the control device 40 receives the value of the water content in the reaction device 61 from the gas analyzer 30, and controls the water content adjusting device 25 based on this value. This adjusts the water content in the reactor 61. That is, the decomposition device 2 is configured so that the control device 40 can automatically perform the step of adjusting the water content in the reaction device 61. In this example as well, the step of adjusting the water content may be performed manually, and the decomposition device may not include the control device 40.
  • polylactic acid having a number average molecular weight of 78,000 was decomposed by changing the water content, pressure, type of additive, and additive concentration, and the number average of decomposition products was obtained. The molecular weight was measured. The results are shown in Tables 1 and 2.
  • the values in the "Energy consumption” column of Tables 1 and 2 are the energy required to heat 100 g of polylactic acid, additives, and water from room temperature (20 ° C) to reaction temperature (200 ° C) (polylactic acid). And the heat of fusion of the additive and the heat of vaporization of water).
  • FIG. 6 is a graph created from Example 1 and Comparative Examples 1 to 3 showing the relationship between the water content, the number average molecular weight of the decomposition products, and the energy consumption.
  • Example 1 when comparing Example 1 with Comparative Examples 2 and 3, it can be seen that the decomposition rate does not decrease so much even if the water content is reduced to about 1.5%.
  • the reaction rate of Example 1 is higher than the reaction rate of Comparative Examples 2 and 3.
  • energy consumption can be significantly reduced by reducing the water content.

Abstract

Provided is a polylactic acid decomposition method with which polylactic acid can be decomposed while suppressing energy consumption. This polylactic acid decomposition method comprises: a step for introducing, in a reaction device, polylactic acid and an additive which is a mixture of one or more types of compounds selected from the group consisting of alkali metal salts, alkaline-earth metal salts, alkali metal oxides, and alkaline-earth metal oxides (step S3); and a step for retaining or kneading said polylactic acid and said additive under a condition where the moisture content expressed by the following equation is 0.15-3.0% (step S4).　Moisture content = Mass of moisture in the reaction device/(Mass of the polylactic acid + Mass of the additive + Mass of moisture added from outside). Herein, the mass of moisture in the reaction device includes the mass of moisture adhering to the polylactic acid and the additive and also the mass of moisture added from outside, and the mass of the polylactic acid, as well as the mass of the additive, is the mass including the mass of moisture adhering thereto respectively.

Description

ポリ乳酸の分解方法Decomposition method of polylactic acid
　本発明は、ポリ乳酸の分解方法に関する。 The present invention relates to a method for decomposing polylactic acid.
　樹脂廃棄物による環境汚染が社会的な問題となる中、ポリ乳酸に代表される生分解性樹脂が注目されている。近年、生分解性樹脂を分解して再利用するケミカルリサイクルに関する技術が開発されている。 While environmental pollution caused by resin waste has become a social problem, biodegradable resins typified by polylactic acid are attracting attention. In recent years, technologies related to chemical recycling for decomposing and reusing biodegradable resins have been developed.
　特開平６－２７９４３４号公報には、アルカリ金属塩を触媒として、ヒドロキシ酸系オリゴマーの熱分解を行うメソ体含有ラクタイド類の製造方法が開示されている。特開２００７－２１０８８９号公報には、ステレオコンプレックス型ポリ乳酸を１７０～３３０℃の高温下で、５～２４０分間処理するステレオコンプレックス型ポリ乳酸のモノマー化方法が開示されている。 Japanese Unexamined Patent Publication No. 6-279434 discloses a method for producing meso-containing lactides, which thermally decomposes a hydroxy acid-based oligomer using an alkali metal salt as a catalyst. Japanese Unexamined Patent Publication No. 2007-210889 discloses a method for monomerizing stereocomplex-type polylactic acid in which stereocomplex-type polylactic acid is treated at a high temperature of 170 to 330 ° C. for 5 to 240 minutes.
　特開２０１７－１３２７３０号公報には、減圧下に保持されたベント室に通じる押出機にポリ乳酸及び解重合触媒を投入し、該押出機でポリ乳酸と解重合触媒とを溶融混練し、該溶融混練物をベント室内に供給し、該ベント室内でポリ乳酸の解重合を行い、生成したラクチドをガス化して該ベント室から回収するラクチド回収方法が開示されている。 In Japanese Patent Application Laid-Open No. 2017-132730, polylactic acid and a depolymerization catalyst are put into an extruder that leads to a vent chamber held under reduced pressure, and the polylactic acid and the depolymerization catalyst are melt-kneaded by the extruder. A lactide recovery method is disclosed in which a melt-kneaded product is supplied into a vent chamber, polylactic acid is depolymerized in the vent chamber, and the produced lactide is gasified and recovered from the vent chamber.
特開平６－２７９４３４号公報Japanese Unexamined Patent Publication No. 6-279434 特開２００７－２１０８８９号公報Japanese Unexamined Patent Publication No. 2007-210889 特開２０１７－１３２７３０号公報JP-A-2017-132730
　特開平６－２７９４３４号公報に記載の方法は、減圧環境下での反応であり、装置が大掛かりになる上にバッチ処理せざるを得ないという問題がある。また、原料にするヒドロキシ酸の分子量が低いものを用いる必要がある。 The method described in JP-A-6-279434 is a reaction in a reduced pressure environment, and has a problem that the apparatus becomes large-scale and batch processing is unavoidable. In addition, it is necessary to use a raw material having a low molecular weight of hydroxy acid.
　特開２００７－２１０８８９号公報には、ポリ乳酸を分解して乳酸を得る方法が提案されている。しかし、乳酸から直接ポリ乳酸を合成する方法は、分子量が上がらないといった問題があり実用化されていない。一方、ラクチドを生成するためには、ポリ乳酸と水とを分離する必要がある。この工程には多くのエネルギーが必要であり、環境負荷を低減するという生分解性樹脂のリサイクルの趣旨に反することになる。 Japanese Unexamined Patent Publication No. 2007-210889 proposes a method for obtaining lactic acid by decomposing polylactic acid. However, the method of synthesizing polylactic acid directly from lactic acid has not been put into practical use due to the problem that the molecular weight does not increase. On the other hand, in order to produce lactide, it is necessary to separate polylactic acid and water. This process requires a lot of energy, which goes against the purpose of recycling biodegradable resins to reduce the environmental load.
　特開２０１７－１３２７３０号公報に記載された方法は、反応の再現性が低く、生成物の分子量や反応率を安定的に制御できない。 The method described in JP-A-2017-132730 has low reaction reproducibility, and the molecular weight and reaction rate of the product cannot be stably controlled.
　本発明の目的は、エネルギー消費を抑えながらポリ乳酸を分解することができる、ポリ乳酸の分解方法を提供することである。 An object of the present invention is to provide a method for decomposing polylactic acid, which can decompose polylactic acid while suppressing energy consumption.
　本発明の一実施形態によるポリ乳酸の分解方法は、ポリ乳酸と、アルカリ金属塩、アルカリ土類金属塩、アルカリ金属の酸化物、及びアルカリ土類金属の酸化物からなる群から選択される１種、又は２種以上の混合物である添加剤とを反応装置に投入する工程と、下記の式で表される水分含有量が０．１５～３．０％となる条件で、前記ポリ乳酸及び前記添加剤を保持又は混練する工程とを備える。
　　水分含有量＝反応装置内の水分の質量／（ポリ乳酸の質量＋添加剤の質量＋外部から添加する水分の質量）
　ただし、前記反応装置内の水分の質量は、前記ポリ乳酸及び前記添加剤に吸着している水分の質量並びに外部から添加する水分の質量を含み、前記ポリ乳酸の質量及び前記添加剤の質量は、それぞれに吸着している水分の質量を含む質量とする。 The method for decomposing polylactic acid according to one embodiment of the present invention is selected from the group consisting of polylactic acid, an alkali metal salt, an alkaline earth metal salt, an alkali metal oxide, and an alkaline earth metal oxide. The polylactic acid and the polylactic acid and the above-mentioned polylactic acid and the above-mentioned polylactic acid and the condition that the water content represented by the following formula is 0.15 to 3.0% in the step of adding the seed or the additive which is a mixture of two or more kinds to the reactor. It includes a step of holding or kneading the additive.
Moisture content = mass of water in the reactor / (mass of polylactic acid + mass of additive + mass of water added from the outside)
However, the mass of water in the reactor includes the mass of water adsorbed on the polylactic acid and the additive and the mass of water added from the outside, and the mass of the polylactic acid and the mass of the additive are , The mass including the mass of water adsorbed on each.
　本発明によれば、エネルギー消費を抑えながらポリ乳酸を分解することができる。 According to the present invention, polylactic acid can be decomposed while suppressing energy consumption.
図１は、本発明の第１の実施形態によるポリ乳酸の分解方法のフロー図である。FIG. 1 is a flow chart of a method for decomposing polylactic acid according to the first embodiment of the present invention. 図２は、本発明の第２の実施形態によるポリ乳酸の分解方法のフロー図である。FIG. 2 is a flow chart of a method for decomposing polylactic acid according to the second embodiment of the present invention. 図３は、本発明の第３の実施形態によるポリ乳酸の分解方法のフロー図である。FIG. 3 is a flow chart of a method for decomposing polylactic acid according to the third embodiment of the present invention. 図４は、ポリ乳酸の分解装置の一例の模式図である。FIG. 4 is a schematic view of an example of a polylactic acid decomposition device. 図５は、ポリ乳酸の分解装置の他の例の模式図である。FIG. 5 is a schematic view of another example of the polylactic acid decomposition device. 図６は、水分含有量と分解生成物の数平均分子量及び消費エネルギーとの関係を示すグラフである。FIG. 6 is a graph showing the relationship between the water content, the number average molecular weight of the decomposition products, and the energy consumption.
　従来、ポリ乳酸の分解反応を促進するためには多量の水が必要であると考えられていた。例えば、上述した特開２００７－２１０８８９号公報には、ポリ乳酸１質量部に対して、水５～１００質量部を共存させることが記載されている。 Conventionally, it was thought that a large amount of water was required to promote the decomposition reaction of polylactic acid. For example, Japanese Patent Application Laid-Open No. 2007-210889 described above describes that 5 to 100 parts by mass of water coexists with 1 part by mass of polylactic acid.
　本発明者らは、所定の添加剤を添加した条件下においては、水を非常に少量にしても、ポリ乳酸の分解反応が進むことを見出した。 The present inventors have found that under the condition that a predetermined additive is added, the decomposition reaction of polylactic acid proceeds even if the amount of water is very small.
　本発明は、この知見に基づいて完成された。以下、図面を参照し、本発明の実施の形態を詳しく説明する。図中同一または相当部分には同一符号を付してその説明は繰り返さない。各図に示された構成部材間の寸法比は、必ずしも実際の寸法比を示すものではない。 The present invention was completed based on this finding. Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are designated by the same reference numerals, and the description thereof will not be repeated. The dimensional ratio between the constituent members shown in each figure does not necessarily indicate the actual dimensional ratio.
　［第１の実施形態］
　図１は、本発明の第１の実施形態によるポリ乳酸の分解方法のフロー図である。本実施形態によるポリ乳酸の分解方法は、ポリ乳酸及び添加剤を準備する工程（ステップＳ１）、ポリ乳酸及び添加剤の含水率を調整する工程（ステップＳ２）、ポリ乳酸及び添加剤を反応装置に投入する工程（ステップＳ３）、ポリ乳酸及び添加剤を保持又は混練する工程（ステップＳ４）、及び分解生成物を取り出す工程（ステップＳ５）を備えている。 [First Embodiment]
FIG. 1 is a flow chart of a method for decomposing polylactic acid according to the first embodiment of the present invention. The method for decomposing polylactic acid according to the present embodiment includes a step of preparing polylactic acid and additives (step S1), a step of adjusting the water content of polylactic acid and additives (step S2), and a reaction device using polylactic acid and additives. (Step S3), a step of holding or kneading polylactic acid and additives (step S4), and a step of taking out decomposition products (step S5) are provided.
　原料となるポリ乳酸、及びポリ乳酸に加える添加剤を準備する（ステップＳ１）。ポリ乳酸は、粉末状又はペレット状に前処理されたものが好ましい。あるいは、反応装置の原料投入口に粉砕装置を設けて、後述する原料投入工程（ステップＳ３）と同時にポリ乳酸を含む原料（例えば廃棄物等）が粉砕されるようにしてもよい。 Prepare polylactic acid as a raw material and additives to be added to polylactic acid (step S1). The polylactic acid is preferably pretreated in the form of powder or pellets. Alternatively, a crushing device may be provided at the raw material charging port of the reaction device so that the raw material containing polylactic acid (for example, waste) is crushed at the same time as the raw material charging step (step S3) described later.
　添加剤は、アルカリ金属塩、アルカリ土類金属塩、アルカリ金属の酸化物、及びアルカリ土類金属の酸化物からなる群から選択される１種、又は２種以上の混合物である。添加剤は、炭酸水素ナトリウム（重曹）、炭酸ナトリウム、炭酸カリウム、及び酸化マグネシウムからなる群から選択される１種、又は２種以上の混合物であることが好ましく、重曹が特に好ましい。 The additive is one kind or a mixture of two or more kinds selected from the group consisting of an alkali metal salt, an alkaline earth metal salt, an alkali metal oxide, and an alkaline earth metal oxide. The additive is preferably one kind or a mixture of two or more kinds selected from the group consisting of sodium hydrogen carbonate (baking soda), sodium carbonate, potassium carbonate, and magnesium oxide, and baking soda is particularly preferable.
　必要に応じて、ポリ乳酸及び添加剤の含水量を調整する（ステップＳ２）。添加剤は、吸湿性があり、水分が吸着している場合がある。ポリ乳酸も、水分が吸着している場合がある。そのため、ポリ乳酸及び添加剤を反応装置に投入する前に、予めこれらの含水率を調整しておいてもよい。 If necessary, adjust the water content of polylactic acid and additives (step S2). Additives are hygroscopic and may have moisture adsorbed. Polylactic acid may also have water adsorbed. Therefore, the water content of polylactic acid and the additive may be adjusted in advance before being added to the reactor.
　含水率を調整する工程（ステップＳ２）は任意の工程であり、投入されるポリ乳酸及び添加剤の含水率が安定している場合には省略してもよい。含水率を調整する場合、ポリ乳酸及び添加剤の少なくとも一方の含水率を調整すればよい。 The step of adjusting the water content (step S2) is an arbitrary step, and may be omitted if the water content of the added polylactic acid and the additive is stable. When adjusting the water content, the water content of at least one of polylactic acid and the additive may be adjusted.
　含水率を調整する具体的な方法としては、ポリ乳酸及び添加剤を乾燥機で乾燥することや、恒温恒湿槽に所定時間保持すること、霧吹き等で湿らせること等が挙げられる。 Specific methods for adjusting the water content include drying polylactic acid and additives in a dryer, holding them in a constant temperature and humidity chamber for a predetermined time, and moistening them with a sprayer or the like.
　また、反応装置の投入口の湿度を制御することで、ポリ乳酸及び添加剤の含水率を調整してもよい。上述のとおり、特に添加剤には吸湿性があるため、ポリ乳酸及び添加剤の含水率は、反応装置の投入口の湿度の影響を受ける。ポリ乳酸及び添加剤の含水率を低くしたい場合には、反応装置の投入口の湿度を低くすればよく、ポリ乳酸及び添加剤の含水率を高くしたい場合には、反応装置の投入口の湿度を高くすればよい。反応装置の投入口の湿度を制御する装置としては、空調設備のほか、噴霧装置が挙げられる。 Further, the water content of polylactic acid and the additive may be adjusted by controlling the humidity of the inlet of the reactor. As described above, since the additive is hygroscopic in particular, the water content of polylactic acid and the additive is affected by the humidity of the inlet of the reactor. If you want to lower the water content of polylactic acid and additives, you can lower the humidity of the inlet of the reactor, and if you want to increase the water content of polylactic acid and additives, you can lower the humidity of the inlet of the reactor. Should be raised. Examples of the device for controlling the humidity of the inlet of the reaction device include an air-conditioning device and a spray device.
　ポリ乳酸及び添加剤を反応装置に投入する（ステップＳ３）。本実施形態では、後述するように、反応装置内の水分を制御した状態でポリ乳酸を分解させる。そのため、反応装置は、原料の投入口や取出口、ガスの導入口や排出口（ベント口）、水分の注入口等を除いて、内部を密閉できる構造であることが好ましい。反応装置は、金属製、ガラス製、又はセラミック製であることが好ましく、金属製であることが特に好ましい。反応装置は、後述するような押出機であってもよい。 Add polylactic acid and additives to the reactor (step S3). In this embodiment, as will be described later, polylactic acid is decomposed in a state where the water content in the reactor is controlled. Therefore, it is preferable that the reactor has a structure capable of sealing the inside except for the raw material inlet and outlet, the gas inlet and outlet (vent port), and the water inlet and the like. The reaction apparatus is preferably made of metal, glass, or ceramic, and particularly preferably made of metal. The reaction device may be an extruder as described later.
　添加剤の量は、ポリ乳酸１００質量部に対して０．２～２０質量部とすることが好ましい。ただし、ポリ乳酸の質量及び添加剤の質量は、それぞれに吸着している水分の質量を含む質量とする。以下、この（添加剤の質量（吸着している水分の質量を含む））／（ポリ乳酸の質量（吸着している水分の質量を含む））×１００の値を「添加剤濃度」という。 The amount of the additive is preferably 0.2 to 20 parts by mass with respect to 100 parts by mass of polylactic acid. However, the mass of polylactic acid and the mass of the additive shall be the mass including the mass of water adsorbed on each. Hereinafter, the value of (mass of additive (including mass of adsorbed water)) / (mass of polylactic acid (including mass of adsorbed water)) × 100 is referred to as “additive concentration”.
　添加剤濃度が低すぎると、ポリ乳酸の分解速度が遅くなる。添加剤濃度の下限は、より好ましくは０．５０質量部であり、さらに好ましくは１．０質量部であり、さらに好ましくは２．０質量部である。一方、添加剤濃度が高すぎると、加熱に必要なエネルギーが大きくなる。添加剤濃度の上限は、より好ましくは１８質量部であり、さらに好ましくは１５質量部であり、さらに好ましくは１０質量部である。 If the additive concentration is too low, the decomposition rate of polylactic acid will slow down. The lower limit of the additive concentration is more preferably 0.50 parts by mass, further preferably 1.0 part by mass, and further preferably 2.0 parts by mass. On the other hand, if the additive concentration is too high, the energy required for heating becomes large. The upper limit of the additive concentration is more preferably 18 parts by mass, further preferably 15 parts by mass, and further preferably 10 parts by mass.
　ポリ乳酸及び添加剤を保持又は混練する（ステップＳ３）。この保持又は混練する工程（ステップＳ３）は、下記の式で表される水分含有量が０．１５～３．０％になるようにする。
　　水分含有量＝反応装置内の水分の質量／（ポリ乳酸の質量＋添加剤の質量＋外部から添加する水分の質量）
　ただし、反応装置内の水分の質量は、ポリ乳酸及び添加剤に吸着している水分の質量並びに外部から添加する水分の質量を含み、ポリ乳酸の質量及び添加剤の質量は、それぞれに吸着している水分の質量を含む質量とする。 The polylactic acid and the additive are retained or kneaded (step S3). In this holding or kneading step (step S3), the water content represented by the following formula is set to 0.15 to 3.0%.
Moisture content = mass of water in the reactor / (mass of polylactic acid + mass of additive + mass of water added from the outside)
However, the mass of water in the reactor includes the mass of water adsorbed on the polylactic acid and the additive and the mass of the water added from the outside, and the mass of the polylactic acid and the mass of the additive are adsorbed on each. The mass includes the mass of water.
　この保持又は混練する工程（ステップＳ３）において、反応装置の外部から水分を添加して、反応装置内の水分を調整してもよい。外部からの水分の添加は例えば、反応装置の投入口や、投入口とは別途に設けられた注入口から水分を供給することで行うことができる。水分は、液体として供給してもよいし、加湿気体として供給してもよい。もっとも、外部から水分を添加することは必須ではなく、外部から添加する水分の質量は０であってもよい。また、乾燥気体を供給することで水分を低下させてもよい。 In this holding or kneading step (step S3), water may be added from the outside of the reaction device to adjust the water content in the reaction device. Moisture can be added from the outside, for example, by supplying water from an inlet of the reactor or an injection port provided separately from the inlet. Moisture may be supplied as a liquid or as a humidifying body. However, it is not essential to add water from the outside, and the mass of the water added from the outside may be zero. Further, the water content may be reduced by supplying a dry gas.
　水分含有量が低すぎると、ポリ乳酸の分解速度が遅くなる。水分含有量の下限は、好ましくは０．２０％であり、さらに好ましくは０．５０％であり、さらに好ましくは１．０％である。一方、水分含有量が高すぎると、加熱に必要なエネルギーが大きくなる。水分含有量の上限は、好ましくは２．８％であり、さらに好ましくは２．５％であり、さらに好ましくは２．０％である。 If the water content is too low, the decomposition rate of polylactic acid will slow down. The lower limit of the water content is preferably 0.20%, more preferably 0.50%, still more preferably 1.0%. On the other hand, if the water content is too high, the energy required for heating becomes large. The upper limit of the water content is preferably 2.8%, more preferably 2.5%, and even more preferably 2.0%.
　この保持又は混練は、反応装置内を加熱して行うことが好ましい。加熱温度は、好ましくは１２０～３４０℃である。加熱温度が高い程、反応が進みやすくなる。加熱温度の下限は、より好ましくは１６０℃であり、さらに好ましくは１８０℃である。一方、加熱温度が高すぎると、エステル結合以外の部分の結合が切れ、所期の分解生成物の収率が低下する。加熱温度の上限は、より好ましくは３００℃であり、さらに好ましくは２８０℃であり、さらに好ましくは２６０℃である。 This holding or kneading is preferably performed by heating the inside of the reactor. The heating temperature is preferably 120 to 340 ° C. The higher the heating temperature, the easier the reaction will proceed. The lower limit of the heating temperature is more preferably 160 ° C., still more preferably 180 ° C. On the other hand, if the heating temperature is too high, the bonds other than the ester bonds are broken, and the yield of the desired decomposition product decreases. The upper limit of the heating temperature is more preferably 300 ° C, still more preferably 280 ° C, still more preferably 260 ° C.
　この保持又は混練は、反応装置内を加圧して行うことが好ましい。反応装置内の圧力は、好ましくは０．１５～２０．０ＭＰａである。反応装置内の圧力の下限は、より好ましくは０．５ＭＰａであり、さらに好ましくは１．０ＭＰａであり、さらに好ましくは３．０ＭＰａである。反応装置内の圧力の上限は、より好ましくは１５．０ＭＰａであり、さらに好ましくは１０．０ＭＰａであり、さらに好ましくは５．０ＭＰａである。 This holding or kneading is preferably performed by pressurizing the inside of the reactor. The pressure in the reactor is preferably 0.15 to 20.0 MPa. The lower limit of the pressure in the reactor is more preferably 0.5 MPa, further preferably 1.0 MPa, still more preferably 3.0 MPa. The upper limit of the pressure in the reactor is more preferably 15.0 MPa, further preferably 10.0 MPa, still more preferably 5.0 MPa.
　保持又は混練する時間は、特に限定されないが、好ましくは１秒間以上であり、例えば１秒間～１２時間である。保持又は混練する時間の下限は、より好ましくは３０秒間であり、さらに好ましくは１分間であり、さらに好ましくは２分間である。保持又は混練する時間の上限は、より好ましくは６時間であり、さらに好ましくは２時間であり、さらに好ましくは３０分間である。混練する場合、剪断速度を５００ｓ－１以下にすることが好ましい。 The holding or kneading time is not particularly limited, but is preferably 1 second or longer, for example, 1 second to 12 hours. The lower limit of the holding or kneading time is more preferably 30 seconds, further preferably 1 minute, still more preferably 2 minutes. The upper limit of the holding or kneading time is more preferably 6 hours, further preferably 2 hours, still more preferably 30 minutes. When kneading, the shear rate is preferably 500 s -1 or less.
　所定時間保持又は混練した後、ポリ乳酸が分解されて形成された分解生成物を反応装置から取り出す（ステップＳ５）。この分解生成物は、乳酸のオリゴマー、乳酸、ラクチド等を含む。 After holding or kneading for a predetermined time, the decomposition product formed by decomposing polylactic acid is taken out from the reactor (step S5). This decomposition product contains lactic acid oligomers, lactic acid, lactide and the like.
　以上、本発明の第１の実施形態によるポリ乳酸の分解方法を説明した。本実施形態によるポリ乳酸の分解方法は、水分含有量が０．１５～３．０％となる条件で、ポリ乳酸及び添加剤を保持又は混練する工程を含む。この構成によれば、水の加熱に必要なエネルギーの消費を抑制しつつ、ポリ乳酸を分解することができる。また、本実施形態によれば、乳酸のオリゴマー及び乳酸だけではなく、ラクチドを回収することもできる。 The method for decomposing polylactic acid according to the first embodiment of the present invention has been described above. The method for decomposing polylactic acid according to the present embodiment includes a step of retaining or kneading the polylactic acid and the additive under the condition that the water content is 0.15 to 3.0%. According to this configuration, polylactic acid can be decomposed while suppressing the consumption of energy required for heating water. Further, according to the present embodiment, not only lactic acid oligomer and lactic acid but also lactide can be recovered.
　［第２の実施形態］
　図２は、本発明の第２の実施形態によるポリ乳酸の分解方法のフロー図である。本実施形態によるポリ乳酸の分解方法は、第１の実施形態（図１）の各工程に加えて、反応装置内の水分を測定する工程（ステップＳ６）と、測定された水分に基づいて、反応装置内の水分を調整する工程（ステップＳ７）とをさらに備えている。 [Second Embodiment]
FIG. 2 is a flow chart of a method for decomposing polylactic acid according to the second embodiment of the present invention. The method for decomposing polylactic acid according to the present embodiment is based on the step of measuring the water content in the reactor (step S6) and the measured water content in addition to the steps of the first embodiment (FIG. 1). It further includes a step (step S7) of adjusting the water content in the reaction apparatus.
　本実施形態では、ポリ乳酸及び添加剤を保持又は混練する工程（ステップＳ４）と併行して、反応装置内の水分を測定する（ステップＳ６）。反応装置内の水分の測定は、例えば、反応装置に設けたベント口から反応装置内のガス成分を採取し、採取したガス成分を水分計で分析することで行うことができる。水分計は例えば、カールフィッシャー水分計や赤外水分計である。 In the present embodiment, the water content in the reaction apparatus is measured in parallel with the step of holding or kneading the polylactic acid and the additive (step S4) (step S6). The water content in the reaction device can be measured, for example, by collecting a gas component in the reaction device from a vent port provided in the reaction device and analyzing the collected gas component with a moisture meter. The moisture meter is, for example, a Karl Fischer titer or an infrared moisture meter.
　測定された水分に基づいて、反応装置内の水分を調整する（ステップＳ７）。具体的には、測定された水分と予め設定された水分下限とを比較し、測定された水分が水分下限未満である場合には、反応装置内の水分を上げる操作を行う。反応装置内の水分を上げる具体的な操作としては例えば、反応装置内に液体の水を注入したり、反応装置内に加湿気体を導入したりすることが挙げられる。 Adjust the water content in the reactor based on the measured water content (step S7). Specifically, the measured water content is compared with the preset lower limit of water content, and if the measured water content is less than the lower limit of water content, an operation of increasing the water content in the reactor is performed. Specific operations for raising the water content in the reactor include, for example, injecting liquid water into the reactor and introducing a humidifier into the reactor.
　反応装置内の水分を調整する工程（ステップＳ７）として、上記の操作に代えて、又は上記の操作に加えて、測定された水分と予め設定された水分上限とを比較し、測定された水分が水分上限を超えている場合には、反応装置内の水分を下げる操作を行ってもよい。反応装置内の水分を下げる具体的な操作としては例えば、反応装置内への注水を停止したり、反応装置内に乾燥気体を導入したりすることが挙げられる。 As a step of adjusting the water content in the reactor (step S7), instead of or in addition to the above operation, the measured water content is compared with the preset water content upper limit, and the measured water content is measured. If the water content exceeds the upper limit of water content, an operation of lowering the water content in the reactor may be performed. Specific operations for lowering the water content in the reactor include, for example, stopping water injection into the reactor and introducing a dry gas into the reactor.
　本実施形態では、ポリ乳酸及び添加剤を保持又は混練する工程（ステップＳ４）、反応装置内の水分を測定する工程（ステップＳ６）、及び反応装置内の水分を調整する工程（ステップＳ７）を、所定の時間が経過するまで繰り返す。これによって、水分含有量が所定の範囲になるように制御した状態で、ポリ乳酸及び添加剤を保持又は混練することができる。 In the present embodiment, a step of holding or kneading the polylactic acid and the additive (step S4), a step of measuring the water content in the reaction device (step S6), and a step of adjusting the water content in the reaction device (step S7) are performed. , Repeat until a predetermined time has elapsed. Thereby, the polylactic acid and the additive can be retained or kneaded in a state where the water content is controlled to be within a predetermined range.
　［第３の実施形態］
　図３は、本発明の第３の実施形態によるポリ乳酸の分解方法のフロー図である。本実施形態では、ポリ乳酸及び添加剤の投入から分解生成物の取り出しまでを連続的に行う。このような処理として例えば、投入口及び取出口を有する反応装置を用いて、投入口からポリ乳酸及び添加剤を投入しながら、これと併行して取出口から反応生成物を取り出して、ポリ乳酸を連続的に分解する処理が挙げられる。 [Third Embodiment]
FIG. 3 is a flow chart of a method for decomposing polylactic acid according to the third embodiment of the present invention. In the present embodiment, the process from the addition of polylactic acid and additives to the removal of decomposition products is performed continuously. As such a treatment, for example, using a reaction device having an inlet and an outlet, polylactic acid and additives are charged from the inlet, and in parallel with this, the reaction product is taken out from the outlet, and polylactic acid is taken out. There is a process of continuously decomposing.
　本実施形態の分解方法も、第１の実施形態（図１）の分解方法と同様に、ポリ乳酸及び添加剤を準備する工程（ステップＳ１）、ポリ乳酸及び添加剤の含水率を調整する工程（ステップＳ２）、ポリ乳酸及び添加剤を反応装置に投入する工程（ステップＳ３）、ポリ乳酸及び添加剤を保持又は混練する工程（ステップＳ４）、及び分解生成物を取り出す工程（ステップＳ５）を備えている。上述したように、本実施形態では、ポリ乳酸及び添加剤の投入から分解生成物の取り出しまでを連続的に行う。具体的には、ポリ乳酸及び添加剤を準備する工程（ステップＳ１）から分解生成物を取り出す工程（ステップＳ５）までを、所定の時間が経過するまで繰り返す。 The decomposition method of this embodiment is also the same as the decomposition method of the first embodiment (FIG. 1), that is, a step of preparing polylactic acid and additives (step S1), and a step of adjusting the water content of polylactic acid and additives. (Step S2), a step of adding polylactic acid and additives to the reactor (step S3), a step of holding or kneading the polylactic acid and additives (step S4), and a step of taking out decomposition products (step S5). I have. As described above, in the present embodiment, the process from the addition of polylactic acid and additives to the removal of decomposition products is continuously performed. Specifically, the steps from the step of preparing the polylactic acid and the additive (step S1) to the step of taking out the decomposition product (step S5) are repeated until a predetermined time elapses.
　本実施形態の分解方法も、第２の実施形態（図２）の分解方法と同様に、反応装置内の水分を測定する工程（ステップＳ６）と、測定された水分に基づいて、反応装置内の水分を調整する工程（ステップＳ７）とをさらに備えている。ただし、本実施形態の分解方法では、反応装置内の水分を調整する工程（ステップＳ７）を実施するタイミングが、第２の実施形態と異なっている。 Similar to the decomposition method of the second embodiment (FIG. 2), the decomposition method of the present embodiment also has a step of measuring the water content in the reaction device (step S6) and the inside of the reaction device based on the measured water content. Further includes a step (step S7) of adjusting the water content of the above. However, in the decomposition method of the present embodiment, the timing of carrying out the step of adjusting the water content in the reactor (step S7) is different from that of the second embodiment.
　本実施形態では、反応装置に投入するポリ乳酸及び添加剤の少なくとも一方の含水率を調整することによって、反応装置内の水分を調整する。すなわち、本実施形態では、ポリ乳酸及び添加剤の含水率を調整する工程（ステップＳ２）が、反応装置内の水分を調整する工程（ステップＳ７）を兼ねている。 In the present embodiment, the water content in the reactor is adjusted by adjusting the water content of at least one of the polylactic acid and the additive to be charged into the reactor. That is, in the present embodiment, the step of adjusting the water content of the polylactic acid and the additive (step S2) also serves as the step of adjusting the water content in the reactor (step S7).
　具体的には、第２の実施形態の場合と同様に、測定された水分と予め設定された水分下限とを比較し、測定された水分が水分下限未満である場合には、反応装置内の水分を上げる操作を行う。本実施形態では、反応装置内の水分を上げる操作として、反応装置に投入するポリ乳酸及び添加剤の少なくとも一方の含水率を上げる操作を行う。より具体的には例えば、ポリ乳酸及び添加剤の乾燥温度を低くする、乾燥時間を短くする、霧吹き等で湿らせる、反応装置の投入口の湿度を高くするといった操作が挙げられる。 Specifically, as in the case of the second embodiment, the measured water content is compared with the preset lower limit of water content, and if the measured water content is less than the lower limit of water content, the inside of the reactor is used. Perform an operation to raise the water content. In the present embodiment, as an operation for increasing the water content in the reactor, an operation for increasing the water content of at least one of the polylactic acid and the additive to be charged into the reactor is performed. More specifically, for example, operations such as lowering the drying temperature of polylactic acid and additives, shortening the drying time, moistening with a mist, and increasing the humidity of the inlet of the reactor can be mentioned.
　第２の実施形態の場合と同様に、上記の操作に代えて、又は上記の操作に加えて、測定された水分と予め設定された水分上限とを比較し、測定された水分が水分上限を超えている場合には、反応装置内の水分を下げる操作を行ってもよい。本実施形態では、反応装置内の水分を下げる操作として、反応装置に投入するポリ乳酸及び添加剤の少なくとも一方の含水率を下げる操作を行う。より具体的には例えば、ポリ乳酸及び添加剤の乾燥温度を高くする、乾燥時間を長くする、霧吹き等で湿らせることを停止する、反応装置の投入口の湿度を低くするといった操作が挙げられる。 As in the case of the second embodiment, instead of or in addition to the above operation, the measured moisture is compared with the preset moisture upper limit, and the measured moisture sets the moisture upper limit. If it exceeds the limit, an operation of lowering the water content in the reactor may be performed. In the present embodiment, as an operation of lowering the water content in the reactor, an operation of lowering the water content of at least one of the polylactic acid and the additive to be charged into the reactor is performed. More specifically, for example, operations such as raising the drying temperature of polylactic acid and additives, lengthening the drying time, stopping moistening by spraying, etc., and lowering the humidity of the inlet of the reactor can be mentioned. ..
　上記の操作に加えて、あるいは上記の操作に代えて、反応装置内への水の注入や、加湿気体又は乾燥気体の導入によって反応装置内の水分を調整するようにしてもよい。すなわち、反応装置に投入するポリ乳酸及び添加剤の少なくとも一方の含水率を調整することによって反応装置内の水分を調整することに加えて、あるいはこれに代えて、第２の実施形態の場合と同様に、反応装置内への水の注入や、加湿気体又は乾燥気体の導入によって反応装置内の水分を調整するようにしてもよい。 In addition to or in place of the above operation, the water content in the reaction device may be adjusted by injecting water into the reaction device or introducing a humidifying body or a dry gas. That is, in addition to or instead of adjusting the water content in the reactor by adjusting the water content of at least one of the polylactic acid and the additive to be charged into the reactor, as in the case of the second embodiment. Similarly, the water content in the reactor may be adjusted by injecting water into the reactor or introducing a humidifier or a dry gas.
　本実施形態によっても、水分含有量が所定の範囲になるように制御した状態で、ポリ乳酸及び添加剤を保持又は混練することができる。 Also in this embodiment, polylactic acid and additives can be retained or kneaded in a state where the water content is controlled to be within a predetermined range.
　［ポリ乳酸の分解装置の構成］
　次に、ポリ乳酸の分解装置の構成を説明する。以下に説明する分解装置はあくまでも例示であって、本実施形態によるポリ乳酸の分解方法を限定するものではない。 [Structure of polylactic acid decomposition device]
Next, the configuration of the polylactic acid decomposition device will be described. The decomposition apparatus described below is merely an example, and does not limit the method for decomposing polylactic acid according to the present embodiment.
　［構成例１］
　図４は、ポリ乳酸の分解装置の一例である分解装置１の模式図である。分解装置１は、押出機１０、フィーダ２０、水分調整装置２５、ガス分析装置３０、及び制御装置４０を備えている。ポリ乳酸及び添加剤は、フィーダ２０によって押出機１０に投入され、押出機１０によって混練されて、最終的に押出機１０の吐出口（取出口）１１ｃから低分子量の分解生成物として取り出される。 [Configuration Example 1]
FIG. 4 is a schematic view of a decomposition device 1 which is an example of a decomposition device for polylactic acid. The decomposition device 1 includes an extruder 10, a feeder 20, a moisture adjusting device 25, a gas analyzer 30, and a control device 40. The polylactic acid and the additive are charged into the extruder 10 by the feeder 20, kneaded by the extruder 10, and finally taken out as a low molecular weight decomposition product from the discharge port (outlet) 11c of the extruder 10.
　フィーダ２０は、ポリ乳酸及び添加剤を所定の供給量で押出機１０に投入する。フィーダ２０は、ポリ乳酸及び添加剤の供給量をそれぞれ独立に制御できる構造であることが好ましい。フィーダ２０は、モータ２１を備えており、モータ２１の回転数を制御することによって、ポリ乳酸及び添加剤の供給量を制御することができる。フィーダ２０として、より具体的には例えば、スクリューフィーダやベルトコンベアを用いることができる。 The feeder 20 feeds polylactic acid and additives into the extruder 10 in a predetermined supply amount. The feeder 20 preferably has a structure capable of independently controlling the supply amounts of polylactic acid and additives. The feeder 20 includes a motor 21, and the supply amount of polylactic acid and additives can be controlled by controlling the rotation speed of the motor 21. More specifically, as the feeder 20, for example, a screw feeder or a belt conveyor can be used.
　押出機１０は、シリンダ壁１１（反応装置）、スクリュー１２、加熱装置１３、シール部材１４、ダイス１５等を備えている。 The extruder 10 includes a cylinder wall 11 (reactor), a screw 12, a heating device 13, a seal member 14, a die 15, and the like.
　シリンダ壁１１は、後述する開口部（投入口１１ａ、ベント口１１ｂ、吐出口１１ｃ）を除き、内部が密閉された構造を有しており、ポリ乳酸の分解反応の反応装置として機能する。 The cylinder wall 11 has a structure in which the inside is sealed except for the openings (input port 11a, vent port 11b, discharge port 11c) described later, and functions as a reaction device for the decomposition reaction of polylactic acid.
　スクリュー１２は、シリンダ壁１１の内容物を混練する。シリンダ壁１１内に投入されたポリ乳酸及び添加剤は、スクリュー１２によって混練されながら吐出口１１ｃに向かって搬送される。スクリュー１２は、モータ１２１を備えており、モータ１２１の回転数を制御することによって、剪断速度を調整することができる。  The screw 12 kneads the contents of the cylinder wall 11. The polylactic acid and additives charged into the cylinder wall 11 are conveyed toward the discharge port 11c while being kneaded by the screw 12. The screw 12 includes a motor 121, and the shear rate can be adjusted by controlling the rotation speed of the motor 121.
　加熱装置１３は、シリンダ壁１１を加熱して、シリンダ壁１１の温度を調整する。図４の例では、シール部材１４によって画された三つの領域の周りに加熱装置１３を分割して配置し、それぞれの領域の温度を独立して制御できるようにしている。これによって例えば、搬送方向の上流側の領域を溶融遷移ゾーン、中央の領域を分解ゾーン、下流側の領域を脱気・冷却吐出ゾーンとして、分解ゾーンを最も高温にした温度分布を形成することができる。 The heating device 13 heats the cylinder wall 11 and adjusts the temperature of the cylinder wall 11. In the example of FIG. 4, the heating device 13 is divided and arranged around the three regions defined by the seal member 14, so that the temperature of each region can be controlled independently. As a result, for example, it is possible to form a temperature distribution in which the decomposition zone has the highest temperature, with the region on the upstream side in the transport direction as the melting transition zone, the region on the center as the decomposition zone, and the region on the downstream side as the degassing / cooling discharge zone. can.
　シリンダ壁１１には、開口部として、投入口１１ａ、ベント口１１ｂ、及び吐出口１１ｃが設けられている。 The cylinder wall 11 is provided with an input port 11a, a vent port 11b, and a discharge port 11c as openings.
　投入口１１ａは、シリンダ壁１１の搬送方向の最も上流側に設けられている。投入口１１ａには、フィーダ２０からポリ乳酸及び添加剤が投入される。 The input port 11a is provided on the most upstream side of the cylinder wall 11 in the transport direction. Polylactic acid and additives are charged from the feeder 20 into the inlet 11a.
　ベント口１１ｂは、シリンダ壁１１の搬送方向の下流側に、ガス成分のみが通過できるように設けられている。ベンド口１１ｂは、吐出口１１ｃの近傍に設けられていることが好ましい。図４の例では、ベント口１１ｂは、シール部材１３によって画された三つの領域のうち、下流側の領域（脱気・冷却吐出ゾーン）に配置されている。ベント口１１ｂは、ガス分析装置３０に接続されている。 The vent port 11b is provided on the downstream side of the cylinder wall 11 in the transport direction so that only the gas component can pass through. The bend port 11b is preferably provided in the vicinity of the discharge port 11c. In the example of FIG. 4, the vent port 11b is arranged in the downstream region (deaeration / cooling discharge zone) of the three regions defined by the seal member 13. The vent port 11b is connected to the gas analyzer 30.
　吐出口１１ｃは、シリンダ壁１１の搬送方向の最も下流側に設けられている。吐出口１１ｃには、ダイス１５が配置されている。シリンダ壁１１内で混練されて形成された分解生成物は、ダイス１５によって所定の形状に成型されて吐出口１１ｃから押し出される。 The discharge port 11c is provided on the most downstream side of the cylinder wall 11 in the transport direction. A die 15 is arranged at the discharge port 11c. The decomposition product formed by kneading in the cylinder wall 11 is molded into a predetermined shape by the die 15 and extruded from the discharge port 11c.
　水分調整装置２５は、シリンダ壁１１内の水分を調整する。水分調整装置２５は例えば、投入口１１ａの湿度を調整する噴霧装置である。水分調整装置２５は、シリンダ壁１１内に水を注入するポンプや、シリンダ壁１１内に乾燥気体や加湿気体を導入する装置であってもよい。 The moisture adjusting device 25 adjusts the moisture in the cylinder wall 11. The moisture adjusting device 25 is, for example, a spraying device that adjusts the humidity of the inlet 11a. The moisture adjusting device 25 may be a pump for injecting water into the cylinder wall 11 or a device for introducing a dry gas or a humidifying body into the cylinder wall 11.
　ガス分析装置３０は、図示しない水分計を含んでいる。ガス分析装置３０は、ベント口１１ｂから採取されたガス成分を分析し、シリンダ壁１１内の水分を測定する。測定された水分の値は、制御装置４０に送信される。 The gas analyzer 30 includes a moisture meter (not shown). The gas analyzer 30 analyzes the gas component collected from the vent port 11b and measures the water content in the cylinder wall 11. The measured moisture value is transmitted to the control device 40.
　制御装置４０は、ガス分析装置３０からシリンダ壁１１内の水分の値を受け取り、この値に基づいて、水分調整装置２５を制御する。これによって、シリンダ壁１１内の水分を調整する。すなわち、分解装置１は、制御装置４０によって、シリンダ壁１１内の水分を調整する工程を自動で行うことができるように構成されている。 The control device 40 receives the value of the water content in the cylinder wall 11 from the gas analyzer 30, and controls the water content adjusting device 25 based on this value. This adjusts the water content in the cylinder wall 11. That is, the decomposition device 1 is configured so that the control device 40 can automatically perform the step of adjusting the water content in the cylinder wall 11.
　上記の例では、分解装置１が制御装置４０を備え、制御装置４０によってシリンダ壁１１内の水分を調整する工程を自動で行う場合を説明した。しかし、水分を調整する工程は手動で行ってもよく、分解装置は制御装置４０を備えていなくてもよい。 In the above example, the case where the disassembling device 1 is provided with the control device 40 and the step of adjusting the water content in the cylinder wall 11 by the control device 40 is automatically performed has been described. However, the step of adjusting the water content may be performed manually, and the decomposition device may not include the control device 40.
　［構成例２］
　図５は、ポリ乳酸の分解装置の他の例である分解装置２の模式図である。分解装置２は、分解装置１（図４）の押出機１０に代えて、反応設備６０を備えている。反応設備６０は、反応装置６１、スクリュー６２、及び加熱装置６３を備えている。 [Configuration Example 2]
FIG. 5 is a schematic view of the decomposition device 2 which is another example of the decomposition device for polylactic acid. The decomposition device 2 is provided with a reaction facility 60 in place of the extruder 10 of the decomposition device 1 (FIG. 4). The reaction equipment 60 includes a reaction device 61, a screw 62, and a heating device 63.
　反応装置６１は、本体６１１と蓋６１２とを含んでいる。蓋６１２には、原料投入口６１２ａ、ガス導入口６１２ｂ、ベント口６１２ｃが設けられており、それぞれ、フィーダ２０、水分調整装置２５、及びガス分析装置３０に接続されている。 The reaction device 61 includes a main body 611 and a lid 612. The lid 612 is provided with a raw material input port 612a, a gas introduction port 612b, and a vent port 612c, which are connected to a feeder 20, a moisture adjusting device 25, and a gas analyzer 30, respectively.
　スクリュー６２は、反応装置６１の内容物を混練する。加熱装置６３は、反応装置６１を加熱する。 The screw 62 kneads the contents of the reaction device 61. The heating device 63 heats the reaction device 61.
　分解装置２においても、制御装置４０は、ガス分析装置３０から反応装置６１内の水分の値を受け取り、この値に基づいて、水分調整装置２５を制御する。これによって、反応装置６１内の水分を調整する。すなわち、分解装置２は、制御装置４０によって、反応装置６１内の水分を調整する工程を自動で行うことができるように構成されている。なお、この例においても、水分を調整する工程は手動で行ってもよく、分解装置は制御装置４０を備えていなくてもよい。 Also in the decomposition device 2, the control device 40 receives the value of the water content in the reaction device 61 from the gas analyzer 30, and controls the water content adjusting device 25 based on this value. This adjusts the water content in the reactor 61. That is, the decomposition device 2 is configured so that the control device 40 can automatically perform the step of adjusting the water content in the reaction device 61. In this example as well, the step of adjusting the water content may be performed manually, and the decomposition device may not include the control device 40.
　以下、実施例によって本発明をより具体的に説明する。本発明はこれらの実施例に限定されない。 Hereinafter, the present invention will be described in more detail with reference to Examples. The present invention is not limited to these examples.
　図４で示した装置に準じた分解装置を用いて、水分含有量、圧力、添加剤の種類、及び添加剤濃度を変えて、数平均分子量７８０００のポリ乳酸の分解を行い、分解生成物の数平均分子量を測定した。結果を表１及び表２に示す。 Using a decomposition apparatus similar to the apparatus shown in FIG. 4, polylactic acid having a number average molecular weight of 78,000 was decomposed by changing the water content, pressure, type of additive, and additive concentration, and the number average of decomposition products was obtained. The molecular weight was measured. The results are shown in Tables 1 and 2.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　表１及び表２の「消費エネルギー」の欄の値は、１００ｇのポリ乳酸、添加剤、及び水を室温（２０℃）から反応温度（２００℃）まで加熱するのに必要なエネルギー（ポリ乳酸及び添加剤の融解熱、並びに水の蒸発熱を含む）の計算値である。 The values in the "Energy consumption" column of Tables 1 and 2 are the energy required to heat 100 g of polylactic acid, additives, and water from room temperature (20 ° C) to reaction temperature (200 ° C) (polylactic acid). And the heat of fusion of the additive and the heat of vaporization of water).
　図６は、実施例１及び比較例１～３から作成した、水分含有量と分解生成物の数平均分子量及び消費エネルギーとの関係を示すグラフである。 FIG. 6 is a graph created from Example 1 and Comparative Examples 1 to 3 showing the relationship between the water content, the number average molecular weight of the decomposition products, and the energy consumption.
　表１及び表２、並びに図６に示すように、比較例１の条件では、分解生成物の数平均分子量が十分に下がらなかった。これは、水分含有量が低すぎたことにより、分解速度が著しく低下したためと考えられる。 As shown in Tables 1 and 2, and FIG. 6, under the conditions of Comparative Example 1, the number average molecular weight of the decomposition products did not decrease sufficiently. It is considered that this is because the decomposition rate was significantly reduced because the water content was too low.
　一方、実施例１と比較例２及び３とを比較すると、水分含有量を１．５％程度まで低下させても、分解速度はそれほど低下しないことが分かる。この例では、実施例１の反応速度は、比較例２及び３の反応速度よりもむしろ大きくなっている。一方、水分含有量を低下させることで、消費エネルギーを大きく削減できることが分かる。 On the other hand, when comparing Example 1 with Comparative Examples 2 and 3, it can be seen that the decomposition rate does not decrease so much even if the water content is reduced to about 1.5%. In this example, the reaction rate of Example 1 is higher than the reaction rate of Comparative Examples 2 and 3. On the other hand, it can be seen that energy consumption can be significantly reduced by reducing the water content.
　以上、本発明についての実施形態を説明したが、本発明は上述の実施形態のみに限定されず、発明の範囲内で種々の変更が可能である。 Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the invention.
１，２　ポリ乳酸の分解装置、１０　押出機、１１　シリンダ壁（反応装置）、１２　スクリュー、１３　加熱装置、１４　シール部材、１５　ダイス、２０　フィーダ、２５　水分調整装置、３０　ガス分析装置、４０　制御装置、６０　反応設備、６１　反応装置、６２　スクリュー、６３　加熱装置 1, 2, polylactic acid decomposition device, 10 extruder, 11 cylinder wall (reactor), 12 screw, 13 heating device, 14 seal member, 15 die, 20 feeder, 25 moisture regulator, 30 gas analyzer, 40 control Equipment, 60 reaction equipment, 61 reaction equipment, 62 screws, 63 heating equipment

Claims (10)

  1. 　ポリ乳酸と、アルカリ金属塩、アルカリ土類金属塩、アルカリ金属の酸化物、及びアルカリ土類金属の酸化物からなる群から選択される１種、又は２種以上の混合物である添加剤とを反応装置に投入する工程と、
    　下記の式で表される水分含有量が０．１５～３．０％となる条件で、前記ポリ乳酸及び前記添加剤を保持又は混練する工程とを備える、ポリ乳酸の分解方法。
    　　水分含有量＝反応装置内の水分の質量／（ポリ乳酸の質量＋添加剤の質量＋外部から添加する水分の質量）
    　ただし、前記反応装置内の水分の質量は、前記ポリ乳酸及び前記添加剤に吸着している水分の質量並びに外部から添加する水分の質量を含み、前記ポリ乳酸の質量及び前記添加剤の質量は、それぞれに吸着している水分の質量を含む質量とする。     Polylactic acid and an additive that is one or a mixture of two or more selected from the group consisting of alkali metal salts, alkaline earth metal salts, alkali metal oxides, and alkaline earth metal oxides. The process of charging into the reactor and
    A method for decomposing polylactic acid, which comprises a step of holding or kneading the polylactic acid and the additive under the condition that the water content represented by the following formula is 0.15 to 3.0%.
    Moisture content = mass of water in the reactor / (mass of polylactic acid + mass of additive + mass of water added from the outside)
    However, the mass of water in the reactor includes the mass of water adsorbed on the polylactic acid and the additive and the mass of water added from the outside, and the mass of the polylactic acid and the mass of the additive are , The mass including the mass of water adsorbed on each.
  2. 　請求項１に記載のポリ乳酸の分解方法であって、
    　前記ポリ乳酸及び前記添加剤を前記反応装置に投入する前に、前記ポリ乳酸及び前記添加剤の少なくとも一方の含水率を調整する工程をさらに備える、ポリ乳酸の分解方法。     The method for decomposing polylactic acid according to claim 1.
    A method for decomposing polylactic acid, further comprising a step of adjusting the water content of at least one of the polylactic acid and the additive before charging the polylactic acid and the additive into the reactor.
  3. 　請求項２に記載のポリ乳酸の分解方法であって、
    　前記反応装置の投入口の湿度を制御することによって、前記ポリ乳酸及び前記添加剤の少なくとも一方の含水率を調整する、ポリ乳酸の分解方法。     The method for decomposing polylactic acid according to claim 2.
    A method for decomposing polylactic acid, which adjusts the water content of at least one of the polylactic acid and the additive by controlling the humidity of the inlet of the reactor.
  4. 　請求項３に記載のポリ乳酸の分解方法であって、
    　前記投入口の湿度を調整する装置が噴霧装置である、ポリ乳酸の分解方法。     The method for decomposing polylactic acid according to claim 3.
    A method for decomposing polylactic acid, wherein the device for adjusting the humidity of the inlet is a spray device.
  5. 　請求項１～４のいずれか一項に記載のポリ乳酸の分解方法であって、
    　前記反応装置内の水分を測定する工程と、
    　前記測定した水分に基づいて、前記反応装置内の水分を調整する工程とをさらに備える、ポリ乳酸の分解方法。     The method for decomposing polylactic acid according to any one of claims 1 to 4.
    The step of measuring the water content in the reactor and
    A method for decomposing polylactic acid, further comprising a step of adjusting the water content in the reactor based on the measured water content.
  6. 　請求項５に記載のポリ乳酸の分解方法であって、
    　前記反応装置に投入する前記ポリ乳酸及び前記添加剤の少なくとも一方の含水率を調整することによって、前記反応装置内の水分を調整する、ポリ乳酸の分解方法。     The method for decomposing polylactic acid according to claim 5.
    A method for decomposing polylactic acid, which adjusts the water content in the reaction apparatus by adjusting the water content of at least one of the polylactic acid and the additive to be charged into the reactor.
  7. 　請求項１～６のいずれか一項に記載のポリ乳酸の分解方法であって、
    　前記添加剤は、炭酸水素ナトリウム、炭酸ナトリウム、炭酸カリウム、及び酸化マグネシウムからなる群から選択される１種、又は２種以上の混合物である、ポリ乳酸の分解方法。     The method for decomposing polylactic acid according to any one of claims 1 to 6.
    The method for decomposing polylactic acid, wherein the additive is one or a mixture of two or more selected from the group consisting of sodium hydrogen carbonate, sodium carbonate, potassium carbonate, and magnesium oxide.
  8. 　請求項７に記載のポリ乳酸の分解方法であって、
    　前記添加剤は、炭酸水素ナトリウムである、ポリ乳酸の分解方法。     The method for decomposing polylactic acid according to claim 7.
    The additive is sodium hydrogen carbonate, a method for decomposing polylactic acid.
  9. 　請求項１～８のいずれか一項に記載のポリ乳酸の分解方法であって、
    　前記添加剤の量が、前記ポリ乳酸１００質量部に対して０．２～２０質量部である、ポリ乳酸の分解方法。
    　ただし、前記ポリ乳酸の質量及び前記添加剤の質量は、それぞれに吸着している水分の質量を含む質量とする。     The method for decomposing polylactic acid according to any one of claims 1 to 8.
    A method for decomposing polylactic acid, wherein the amount of the additive is 0.2 to 20 parts by mass with respect to 100 parts by mass of the polylactic acid.
    However, the mass of the polylactic acid and the mass of the additive shall be the mass including the mass of water adsorbed on each of them.
  10. 　請求項１～９のいずれか一項に記載のポリ乳酸の分解方法であって、
    　前記保持又は混練する工程は、０．１５～２０．０ＭＰａで１秒間以上保持又は混練する工程である、ポリ乳酸の分解方法。     The method for decomposing polylactic acid according to any one of claims 1 to 9.
    The step of holding or kneading is a step of holding or kneading at 0.15 to 20.0 MPa for 1 second or longer, which is a method for decomposing polylactic acid.
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