Depolymerization method and depolymerization apparatus

Abstract

The depolymerization method for depolymerizing a synthetic resin into raw material monomers comprises: a step for setting a target temperature inside a flow reactor (13e) and a target residence time of a synthetic resin and a solvent having a weight ratio of 1.5 times or more to the synthetic resin in the flow reactor (13e) so that the yield of the raw material monomers is 70% or more; and a step for supplying the synthetic resin and the solvent to the flow reactor (13e) so that the temperature inside the flow reactor (13e) becomes the target temperature, the residence time of the synthetic resin and the solvent in the flow reactor (13e) becomes the target residence time, and the pressure inside the flow reactor (13e) becomes 10 MPa or more.

Description

Depolymerization method and depolymerization apparatus

[0001] The present invention relates to a depolymerization method and apparatus for depolymerizing synthetic resin into raw material monomers.

[0002] As an effort to reduce waste, research and development into the recycling of waste has been conducted. A conventionally known technique of this type is a method for depolymerizing nylon 6, a synthetic resin (polymer), into ε-caprolactam, a raw material monomer (see, for example, Patent Document 1). In the method described in Patent Document 1, 15 parts by weight or less of an acidic substance is added to 100 parts by weight of nylon 6 (poly-ε-caprolactam) in the waste, followed by heat treatment at 220 to 400°C to reduce the viscosity of the solution, separating any unmelted material, and then depolymerizing the poly-ε-caprolactam.

[0003] Japanese Patent Application Laid-Open No. 2001-294571

[0004] However, in the method of adding an acidic substance as described in Patent Document 1, it takes a long time for chemical decomposition, making it difficult to carry out depolymerization quickly.

[0005] One aspect of the present invention is a depolymerization method for depolymerizing a synthetic resin into raw material monomers, comprising the steps of: setting a target temperature inside a flow reactor and a target residence time in the flow reactor of the synthetic resin and the solvent in a weight ratio relative to the synthetic resin of 1.5 or more, so that the yield of the raw material monomers is 70% or more; and supplying the synthetic resin and the solvent to the flow reactor so that the temperature inside the flow reactor becomes the target temperature, the residence time of the synthetic resin and the solvent in the flow reactor becomes the target residence time, and the pressure inside the flow reactor is 10 MPa or more.

[0006] Another aspect of the present invention is a depolymerization apparatus for depolymerizing a synthetic resin into raw material monomers, comprising: a flow reactor; a supply unit that supplies the synthetic resin and the solvent to the flow reactor so that the internal temperature of the flow reactor reaches a predetermined target temperature, the residence time in the flow reactor of the synthetic resin and the solvent in a weight ratio of 1.5 times or more to the synthetic resin reaches a predetermined target residence time, and the internal pressure of the flow reactor is 10 MPa or more; and a back pressure valve that is provided downstream of the flow reactor and set to a set pressure of 10 MPa or more. The target temperature and target residence time are predetermined so that the yield of the raw material monomers is 70% or more.

[0007] According to the present invention, depolymerization can be carried out quickly.

[0008] 1 is a diagram illustrating an example of the overall configuration of a depolymerization apparatus according to an embodiment of the present invention. It is a diagram for explaining the relationship between reaction time and yield when a depolymerization reaction from PA6 to ε-caprolactam is carried out using subcritical water. It is a diagram for explaining appropriate reaction conditions when a depolymerization reaction from PA6 to ε-caprolactam is carried out using the depolymerization apparatus of FIG.

[0009] Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 to 3. In the depolymerization method and depolymerization apparatus according to the embodiment of the present invention, a synthetic resin (polymer) is depolymerized into raw material monomers. Examples of synthetic resins include PA (polyamide) 6 (nylon 6), PA66 (nylon 66), PA12, PA11, PET (polyethylene terephthalate), PBT (polybutylene terephthalate), POM (polyacetal), and urethane resin. Below, an example will be described in which PA6, which is a synthetic resin, is depolymerized into ε-caprolactam, which is a raw material monomer.

[0010] When depolymerizing synthetic resins such as PA6 into raw material monomers for the purpose of industrial reuse, it is preferable to carry out the depolymerization quickly from an industrial viewpoint. Therefore, in this embodiment, a subcritical solvent is used to quickly carry out the depolymerization reaction from the synthetic resin to the raw material monomers, and the depolymerization method and depolymerization apparatus are configured as follows.

[0011] Fig. 1 is a diagram schematically illustrating an example of the overall configuration of a depolymerization apparatus 10 according to an embodiment of the present invention. As shown in Fig. 1 , the depolymerization apparatus 10 mainly includes a hopper 11 into which pulverized PA6 material is introduced, a tank 12 in which water as a solvent is stored, and an extruder 13.

[0012] The hopper 11 is configured as a weighing hopper of a volumetric type, a weight loss control type, etc. The hopper 11 is connected to the upstream side of the extruder 13 and continuously supplies a fixed amount of pulverized PA6 material into the extruder 13 according to a preset rotation speed or vibration frequency.

[0013] The tank 12 is connected to the extruder 13 via a pipe 14 downstream of the hopper 11. The pipe 14 is provided with a pump 15 that pumps water at a preset flow rate and a heater 16 that heats the water to a preset temperature (e.g., 240°C or higher). The set flow rate of the pump 15 is set so that the weight of the water supplied to the extruder 13 is 1.5 times or more, preferably 4 times or more, the weight of the PA6 supplied to the extruder 13. A nozzle 14a is provided at the tip of the pipe 14 on the extruder 13 side. The water stored in the tank 12 is pumped by the pump 15 via the pipe 14, heated by the heater 16, and injected into the extruder 13 via the nozzle 14a in a high-temperature, high-pressure state.

[0014] The extruder 13 is configured as a single-screw or multi-screw extruder and has a steel cylinder 13a and a steel screw 13b inserted into the cylinder 13a. The ground PA6 material from the hopper 11 and water from the tank 12 are supplied to a space 13c between the cylinder 13a and the screw 13b. A heater (not shown) is wound around the cylinder 13a, and the cylinder 13a is heated by the heater as needed to maintain a preset reaction temperature. The inner diameter of the cylinder 13a is set to a predetermined value or less so that the temperature of the PA6 and water supplied to the space 13c is uniform. A motor M is connected to the upstream end of the screw 13b, and the screw 13b is driven by the motor M to rotate at a preset rotational speed. A pipe 17 is connected to the downstream end of the cylinder 13a, and a back pressure valve 18 is provided in the pipe 17.

[0015] When the screw 13b rotates, the pulverized PA6 material supplied to the space 13c is extruded toward the downstream side of the extruder 13. At this time, the pulverized PA6 material supplied from the hopper 11 is compressed and sheared by the screw 13b, generating heat, and is quickly melted and plasticized using shear heat as the main heat source while being extruded. The space 13c from the hopper 11 to the nozzle 14a, where the pulverized PA6 material is melted, is sometimes referred to as the "melting section 13d." The volume of the melting section 13d is set to the volume required to melt and plasticize the pulverized PA6 material.

[0016] In space 13c, water is injected from nozzle 14a at the downstream end of melting zone 13d. The plasticized PA6 is stirred and mixed (kneaded) with the water injected from nozzle 14a by the rotation of screw 13b, and is extruded further downstream of extruder 13. The water injected from nozzle 14a is heated by heater 16 to a sufficiently high temperature, thereby preventing the plasticized PA6 from re-solidifying.

[0017] The space 13c downstream of the melting zone 13d forms a reaction field in which PA6 and water are continuously supplied and the depolymerization reaction proceeds. The space 13c downstream of the melting zone 13d where the depolymerization reaction occurs is sometimes referred to as the "flow reactor 13e." The hopper 11, screw 13b, and motor M that supply PA6 to the flow reactor 13e, and the pump 15 that supply water to the flow reactor 13e are sometimes referred to as the "supply section." The pressure (reaction pressure) within the flow reactor 13e (reaction pressure) is increased to the set pressure of the backpressure valve 18 by the rotation of the screw 13b, as the upstream side of the flow reactor 13e is blocked by plasticized PA6.

[0018] The reaction pressure in the flow reactor 13e is maintained at a pressure slightly higher than the saturated vapor pressure of water. The temperature (reaction temperature) and reaction pressure in the flow reactor 13e are maintained at subcritical conditions, slightly lower than the critical point (374°C, 22.1 MPa) at which water changes state between liquid and gas. From this perspective, the set pressure of the backpressure valve 18 is set to 10 MPa or higher, preferably 13 MPa or higher. The set pressure of the backpressure valve 18 is set to an upper limit pressure (e.g., approximately 20 MPa) or lower depending on the pressure resistance of the apparatus. This maintains the water in the flow reactor 13e in a subcritical state, i.e., in the form of liquid subcritical water. Subcritical water can hydrolyze synthetic resins such as PA6, PA66, PA12, PA11, PET, PBT, POM, and urethane resin, rapidly promoting the depolymerization reaction.

[0019] The plasticized PA6 is agitated by the rotation of the screw 13b and mixed with and contacted with the subcritical water, rapidly depolymerizing to produce ε-caprolactam. The volume of the flow reactor 13e is set to a volume necessary for the PA6 and subcritical water to be sufficiently mixed and contacted, and for the depolymerization reaction to proceed. As long as the PA6 and subcritical water are sufficiently mixed in the flow reactor 13e, the screw 13b does not necessarily need to be disposed to the downstream end of the flow reactor 13e. Actively agitating and mixing the PA6 and subcritical water reduces the amount of subcritical water required, allowing the overall system to be more compact. Furthermore, by melting and plasticizing the pulverized PA6 material supplied from the hopper 11 in the melting section 13d before supplying it to the flow reactor 13e, the time required to mix the PA6 and subcritical water can be shortened (by approximately 15 minutes) compared to supplying the pulverized material directly to the flow reactor 13e.

[0020] When the reaction pressure in the flow reactor 13e exceeds the set pressure of the back-pressure valve 18, the back-pressure valve 18 is opened, and a depolymerization liquid containing ε-caprolactam produced by the depolymerization reaction, unreacted PA6, and water is discharged to the outside via the pipe 17. The back-pressure valve 18 closes immediately when the reaction pressure in the flow reactor 13e drops to the set pressure of the back-pressure valve 18. However, at this time, the reaction pressure in the flow reactor 13e may temporarily fall below the set pressure of the back-pressure valve 18. If the reaction pressure in the flow reactor 13e deviates from the subcritical condition for water, water will vaporize, resulting in a shortage of subcritical water required for the depolymerization reaction. Therefore, it is preferable to set the set pressure of the back-pressure valve 18 higher than the desired reaction pressure by a predetermined pressure or more (for example, 0.5 MPa or more). In this case, in order to maintain the reaction pressure in the flow reactor 13e at 10 MPa or more, preferably 13 MPa or more, the set pressure of the back pressure valve 18 is set to 10.5 MPa or more, preferably 13.5 MPa or more.

[0021] A recovery device is provided downstream of the depolymerization device 10 to recover ε-caprolactam from the depolymerization liquid. The depolymerization liquid discharged from the depolymerization device 10 through a pipe 17 into an atmospheric pressure environment is separated into a solid component and a gas component. That is, water in the depolymerization liquid is vaporized by removing the subcritical conditions. In the recovery device, the solid component mainly containing ε-caprolactam and unreacted PA6 is recovered as is, and the gas component (water) containing a trace amount of ε-caprolactam is captured, cooled, and recovered. The high-temperature solid component recovered in the recovery device is kept warm for a predetermined period, whereby the unreacted PA6 is decomposed into ε-caprolactam by residual heat. The water recovered in the recovery device is returned to the tank 12 of the depolymerization device 10 and reused as a solvent for the depolymerization reaction.

[0022] FIG. 2 is a diagram illustrating the relationship between reaction time and yield when a depolymerization reaction from PA6 to ε-caprolactam is carried out using subcritical water, and shows test results for yield per reaction time when the reaction temperature T is changed in the range from 270°C to 370°C. As shown in FIG. 2, the higher the reaction temperature T, the shorter the reaction time required to maximize the yield. When the reaction temperature T is 270°C or higher, the maximum yield can be achieved within 2 hours. When the reaction temperature T is 350°C or higher, the maximum yield can be achieved within 20 minutes.

[0023] FIG. 3 is a diagram illustrating appropriate reaction conditions when a depolymerization reaction from PA6 to ε-caprolactam is carried out using the depolymerization apparatus 10 of FIG. 1 . From an industrial perspective, in the depolymerization apparatus 10 that continuously carries out the depolymerization reaction, it is preferable to limit the reaction time of the depolymerization reaction, i.e., the residence time τ of PA6 and subcritical water in the flow reactor 13e, to no more than 2 hours, preferably no more than 20 minutes. Therefore, as shown in FIGS. 2 and 3 , the target temperature T0 in the flow reactor 13e is set to 270°C or higher, preferably about 350°C. Furthermore, the target temperature T0 in the flow reactor 13e is set to no more than an upper limit temperature (e.g., about 365°C) appropriate for the heat resistance of the apparatus.

[0024] The target residence time τ0 of the PA6 and subcritical water in the flow reactor 13e is set so that the yield of ε-caprolactam is 70% or more and the maximum yield or less, depending on the target temperature T0 in the flow reactor 13e. If the residence time τ is too short, the yield of ε-caprolactam will be insufficient. However, if the residence time τ is too long, the ε-caprolactam will be further over-cracked and converted into lower molecular weight compounds, thereby reducing the yield. In consideration of this, the target temperature T0 in the flow reactor 13e and the target residence time τ0 of the PA6 and subcritical water in the flow reactor 13e are set so as to satisfy the following formulas (i) and (ii). That is, the target temperature T0 and the target residence time τ0 are set so as to be within the range defined by formulas (i) and (ii), with formula (i) as the lower limit and formula (ii) as the upper limit. τ0≧43200e^(-0.0244T0) (i) τ0≦31800e^(-0.0211T0) (ii)

[0025] Formula (i) is an approximation based on test results of the reaction time at which the ε-caprolactam yield is 70% when the reaction temperature T is varied in the range from 270°C to 365°C. By setting the target temperature T0 and the target residence time τ0 so as to satisfy formula (i), the ε-caprolactam yield can be increased to 70% or more. Similarly, formula (ii) is an approximation based on test results of the reaction time at which the ε-caprolactam yield is maximized when the reaction temperature T is varied in the range from 270°C to 365°C. By setting the target temperature T0 and the target residence time τ0 so as to satisfy formula (ii), the ε-caprolactam yield can be maximized. Note that under the condition of τ0 > 31800 e^(-0.0211 T0), the yield actually decreases due to over-cracking of ε-caprolactam. When the target temperature T0 is set to about 350° C., the target residence time τ0 that satisfies the formulas (i) and (ii) is about 10 to 20 minutes.

[0026] The reaction temperature T in the flow reactor 13e can be adjusted via the set temperature of the heater that heats the cylinder 13a, the rotational speed (or vibration frequency) of the hopper 11, and the rotational speed of the motor M that drives the screw 13b. Like the melting zone 13d, the PA6 in the flow reactor 13e also generates heat by being compressed and sheared by the rotation of the screw 13b, and is heated by shear heat as part of the heat source. Therefore, the reaction temperature T in the flow reactor 13e can be adjusted not only via the set temperature of the heater that heats the cylinder 13a, but also via the rotational speed of the hopper 11, which determines the supply amount of PA6, and the rotational speed of the motor M, which determines the shear rate of PA6 by the screw 13b.

[0027] The residence time τ of PA6 and subcritical water in the flow reactor 13e can be adjusted by adjusting the rotation speed of the hopper 11 and the rotation speed of the motor M that drives the screw 13b. Alternatively, the residence time τ may be adjusted by adjusting the length of the flow reactor 13e by adjusting the length of the extruder 13 (cylinder 13a).

[0028] The reaction pressure in the flow reactor 13e can be adjusted not only by the set pressure of the back pressure valve 18 but also by the set temperature of the heater that heats the cylinder 13a, the rotation speed of the hopper 11, and the rotation speed of the motor M that drives the screw 13b.

[0029] The hopper 11, screw 13b, and motor M, which are supply units that supply PA6 to the flow reactor 13e, are set and adjusted so that the reaction temperature T in the flow reactor 13e is a target temperature T0, the residence time τ is a target residence time τ0, and the reaction pressure is 10 MPa or more, preferably 13 MPa or more. The set flow rate of the pump 15, which is a supply unit that supplies water to the flow reactor 13e, is set according to the rotation speed of the hopper 11, which determines the supply amount of PA6, so that the weight of water supplied to the flow reactor 13e is 1.5 times or more, preferably 4 times or more, the weight of PA6.

[0030] According to this embodiment, the following advantageous effects can be achieved. (1) A depolymerization method for depolymerizing PA6 into ε-caprolactam includes the steps of: setting a target temperature T0 in the flow reactor 13e and a target residence time τ0 of PA6 and subcritical water in the flow reactor 13e, the weight ratio of which to PA6 being 1.5 times or more, so that the yield of ε-caprolactam is 70% or more; and supplying PA6 and water to the flow reactor 13e so that the reaction temperature T in the flow reactor 13e becomes the target temperature T0, the residence time τ of the PA6 and subcritical water in the flow reactor 13e becomes the target residence time τ0, and the reaction pressure in the flow reactor 13e becomes 10 MPa or more. By continuously performing depolymerization, which requires high temperature and high pressure, using the flow reactor 13e, the time required for heating and cooling the reactor can be reduced, allowing depolymerization to be performed quickly. Furthermore, the amount of energy consumed for increasing and decreasing the temperature of the reactor can be reduced, and depolymerization can be carried out efficiently.

[0031] (2) In the setting step, the target temperature T0 and the target residence time τ0 are set so as to fall within the ranges defined by the formulas (i) and (ii). By setting the target temperature T0 and the target residence time τ0 so as to satisfy the formula (i), the yield of ε-caprolactam can be increased to 70% or more. Furthermore, by setting the target temperature T0 and the target residence time τ0 so as to satisfy the formula (ii), the yield of ε-caprolactam can be maximized.

[0032] (3) In the setting step, the target temperature T0 is set to about 350°C, and the target residence time τ0 is set to a time in the range of 10 minutes to 20 minutes. In this case, depolymerization can be carried out quickly within the heat-resistant temperature range of the apparatus.

[0033] In the (4) supplying step, PA6 and water are supplied to the flow reactor 13e so that the water in the flow reactor 13e is maintained in a subcritical state. That is, PA6 and water are supplied to the flow reactor 13e so that the temperature and pressure are maintained in a subcritical state slightly lower than the critical point, which is the limit value when water changes state from liquid to gas. Maintaining water in a subcritical state increases the reaction rate of the depolymerization reaction, enabling depolymerization to be carried out quickly.

[0034] (5) A depolymerization apparatus 10 for depolymerizing PA6 into ε-caprolactam includes a flow reactor 13e, a supply unit (hopper 11, screw 13b, motor M, pump 15) for supplying PA6 and water to the flow reactor 13e so that the reaction temperature T in the flow reactor 13e reaches a predetermined target temperature T, the residence time τ of PA6 and subcritical water in the flow reactor 13e at a weight ratio of 1.5 times or more to PA6 reaches a predetermined target residence time τ, and the reaction pressure in the flow reactor 13e is 10 MPa or higher ( FIG. 1 ), and a backpressure valve 18 provided downstream of the flow reactor 13e and set to a pressure of 10 MPa or higher. The target temperature T and the target residence time τ are preset so that the yield of ε-caprolactam is 70% or higher. This allows depolymerization, which requires high temperature and high pressure, to be carried out continuously, thereby reducing the time required for heating and cooling the reactor, enabling rapid depolymerization. Furthermore, the amount of energy consumed for heating and cooling the reactor can be reduced, allowing efficient depolymerization.

[0035] (6) The depolymerization apparatus 10 further includes a melting section 13d (FIG. 1) that is provided upstream of the flow reactor 13e and melts and extrudes PA6 into the flow reactor 13e. This allows PA6 to be supplied in a molten state to the flow reactor 13e, enabling rapid depolymerization in the flow reactor 13e.

[0036] (7) The depolymerization apparatus 10 further includes a screw 13b that stirs the PA6 and subcritical water supplied from the supply unit to the flow reactor 13e ( FIG. 1 ). By actively stirring and mixing the PA6 and subcritical water, the amount of subcritical water required can be reduced, and the entire apparatus can be made smaller.

[0037] (8) The depolymerization apparatus 10 further includes an extruder 13 that melts PA6 and extrudes it into the flow reactor 13e, and that agitates the PA6 extruded into the flow reactor 13e with subcritical water ( FIG. 1 ). That is, the single extruder 13 can melt PA6, supply the PA6 to the flow reactor 13e, agitate and mix the PA6 with the subcritical water, and discharge the ε-caprolactam obtained by depolymerization, thereby simplifying the configuration of the entire apparatus.

[0038] In the above embodiment, an example has been described in which the pulverized PA6 material is melted and plasticized in the melting section 13d before being supplied to the flow reactor 13e, but the synthetic resin supplied to the flow reactor is not limited to being melted and plasticized. Furthermore, even when a molten and plasticized synthetic resin is supplied to the flow reactor, it is not limited to melting and plasticizing the synthetic resin in the extruder 13 as in the above embodiment, and a device for melting and plasticizing the synthetic resin may be provided upstream of the extruder 13. In this case, waste such as glass fiber reinforced plastic may be melted and plasticized, and glass fibers and other foreign matter may be removed before being supplied to the flow reactor.

[0039] In the above embodiment, an example of depolymerizing PA6 as a synthetic resin has been described, but the present invention can also be applied to hydrolyzable synthetic resins such as PA66, PA12, PA11, PET, PBT, POM, urethane resin, etc. Furthermore, in the above embodiment, an example of using subcritical water as a solvent has been described, but subcritical methanol or the like may also be used.

[0040] In the above embodiment, an example in which a single-screw screw extruder 13 is used has been described with reference to Fig. 1 etc., but the flow reactor in which the depolymerization reaction takes place is not limited to the space 13c between the cylinder 13a and the screw 13b of the screw extruder 13. Furthermore, an example in which the synthetic resin and the solvent are stirred using the screw 13b has been described, but the stirring blade is not limited to this.

[0041] The above description is merely an example, and the present invention is not limited to the above-described embodiment and modifications as long as the features of the present invention are not impaired. One or more of the above-described embodiment and modifications can be arbitrarily combined, and modifications can also be combined with each other.

[0042] 10 Depolymerization device, 11 Hopper, 12 Tank, 13 Extruder, 13a Cylinder, 13b Screw, 13c Space, 13d Melting section, 13e Flow reactor, 14 Piping, 14a Nozzle, 15 Pump, 16 Heater, 17 Piping, 18 Back pressure valve, M Motor

Claims

1. A method for depolymerizing a synthetic resin into raw monomers, comprising the steps of: setting a target temperature inside a flow reactor and a target residence time in the flow reactor of the synthetic resin and a solvent having a weight ratio of 1.5 times or more to the synthetic resin, such that a yield of the raw monomers is 70% or more; and supplying the synthetic resin and the solvent to the flow reactor such that the temperature inside the flow reactor becomes the target temperature, the residence time of the synthetic resin and the solvent in the flow reactor becomes the target residence time, and the pressure inside the flow reactor is 10 MPa or more.

2. The depolymerization method according to claim 1, wherein the synthetic resin is nylon 6, the raw material monomer is ε-caprolactam, and, in the setting step, the target temperature and the target residence time are set so as to be within the ranges defined by the following two formulas, where T is the target temperature and τ is the target residence time: τ≧43200e^(-0.0244T) τ≦31800e^(-0.0211T) 3. The method for depolymerization according to claim 2, wherein in the setting step, the target temperature is set to 350°C.

4. The depolymerization method according to claim 2, wherein in the setting step, the target residence time is set to a time within a range of 10 minutes or more and 20 minutes or less.

5. A method for depolymerization according to claim 1, characterized in that in the supplying step, the synthetic resin and the solvent are supplied to the flow reactor so that the solvent in the flow reactor is maintained in a subcritical state.

6. A depolymerization apparatus for depolymerizing a synthetic resin into raw material monomers, comprising: a flow reactor; a supply section for supplying the synthetic resin and the solvent to the flow reactor so that an internal temperature of the flow reactor becomes a predetermined target temperature, the residence time in the flow reactor of the synthetic resin and a solvent having a weight ratio of 1.5 or more to the synthetic resin becomes a predetermined target residence time, and the internal pressure of the flow reactor becomes 10 MPa or more; and a back pressure valve provided downstream of the flow reactor and set to a set pressure of 10 MPa or more, wherein the target temperature and the target residence time are preset so that the yield of the raw material monomers is 70% or more.

7. The depolymerization apparatus according to claim 6, further comprising a melting section provided upstream of said flow reactor for melting said synthetic resin and extruding it into said flow reactor.

8. The depolymerization apparatus according to claim 6, further comprising an agitator for agitating the synthetic resin and the solvent supplied to the flow reactor by the supply unit.

9. The depolymerization apparatus according to claim 6, further comprising a screw extruder which melts the synthetic resin and extrudes it into the flow reactor, and which agitates the synthetic resin and the solvent extruded into the flow reactor.

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