Reaction monitoring device, reaction monitoring method, and reaction monitoring program

Abstract

A polymerization reaction monitoring device 40 comprises: a polymerization reaction tank 400 in which a polymer is synthesized through a polymerization reaction of a depolymerized product of polyester; a polymerization reaction characteristic measurement unit for measuring a characteristic of a reaction liquid RL of the polymerization reaction containing the polymer and the depolymerized product; and a polymerization reaction progress monitoring unit 45 for monitoring the progress of the polymerization reaction on the basis of the characteristic of the reaction liquid RL measured by the polymerization reaction characteristic measurement unit. The polymerization reaction characteristic measurement unit measures a characteristic based on a chemical bond common to the depolymerized product and the polymer contained in the reaction liquid RL. The characteristic based on the common chemical bond changes according to the ratio between the depolymerized product and the polymer contained in the reaction liquid RL.

Description

Reaction monitoring device, reaction monitoring method, and reaction monitoring program

[0001] The present disclosure relates to reaction monitoring devices and the like.

[0002] Patent Document 1 discloses a method for recycling PET (polyethylene terephthalate) bottles by crushing the PET bottles to produce PET flakes, which serve as the raw material for new PET bottles. Specifically, known methods include mechanical recycling, in which crushed PET bottles are heated and melted, and then PET flakes are obtained by solid-state polymerization, and chemical recycling, in which crushed PET bottles are decomposed into intermediates such as bis(2-hydroxyethyl) terephthalate (BHET) or depolymerized polymers by a depolymerization reaction, and then PET flakes are obtained by a repolymerization reaction.

[0003] JP 2016-153176 A JP 2022-27158 A

[0004] For efficient chemical recycling of PET, it is important to monitor the progress of chemical reactions such as depolymerization and repolymerization in a timely manner. The progress of chemical reactions can be monitored by measuring reactants and / or products sampled from the reaction vessel. However, this method has some drawbacks, such as the need for special sampling equipment to sample reactants and / or products and the need to stop the chemical reaction during sampling.

[0005] The present disclosure has been made in view of these circumstances, and aims to provide a reaction monitoring device and the like that can efficiently grasp the progress of a polymerization reaction.

[0006] In order to solve the above problems, a reaction monitoring device according to one embodiment of the present disclosure includes a polymerization reaction tank in which a polyester depolymerization product is synthesized into a polymer through a polymerization reaction, a polymerization reaction characteristic measurement unit that measures the characteristics of a reaction liquid of the polymerization reaction containing the depolymerization product and the polymer, and a polymerization reaction progress monitoring unit that monitors the progress of the polymerization reaction based on the characteristics of the reaction liquid measured by the polymerization reaction characteristic measurement unit.

[0007] According to this aspect, the progress of the polymerization reaction in a polymerization reactor can be efficiently monitored by measuring the properties of the reaction solution of the polymerization reaction containing the depolymerization product as a reactant and the polymer as a product. The properties of the reaction solution of the polymerization reaction may be measured in the polymerization reactor, or in a pipe, a buffer tank, or another processing unit provided downstream of the polymerization reactor.

[0008] Another aspect of the present disclosure is also a reaction monitoring device. This device includes: a depolymerization reaction tank in which a depolymerization reaction occurs using a depolymerization agent to decompose polyester into depolymers; a depolymerization reaction characteristic measurement unit that measures the characteristics of the depolymerization agent dissolved in the depolymerization reaction tank; a depolymerization reaction progress monitoring unit that monitors the progress of the depolymerization reaction based on the characteristics of the depolymerization agent measured by the depolymerization reaction characteristic measurement unit; a polymerization reaction tank that synthesizes the depolymers into polymers through a polymerization reaction; a polymerization reaction characteristic measurement unit that measures the characteristics of a reaction solution of a polymerization reaction containing depolymers and polymers; and a polymerization reaction progress monitoring unit that monitors the progress of the polymerization reaction based on the characteristics of the reaction solution measured by the polymerization reaction characteristic measurement unit. The polymerization reaction characteristic measurement unit and the depolymerization reaction characteristic measurement unit measure different characteristics from each other.

[0009] Yet another aspect of the present disclosure is a reaction monitoring method, which includes synthesizing a depolymerization of a polyester into a polymer through a polymerization reaction in a polymerization reactor, measuring properties of a reaction solution of the polymerization reaction containing the depolymerization and the polymer, and monitoring the progress of the polymerization reaction based on the measured properties of the reaction solution.

[0010] Any combination of the above components, or any conversion of these expressions into methods, devices, systems, recording media, computer programs, etc., are also encompassed within the present disclosure.

[0011] According to the present disclosure, the progress of the polymerization reaction can be efficiently monitored.

[0012] 1 shows a schematic diagram of the configuration of a chemical recycling molding system. A schematic diagram of the polymerization reaction and depolymerization reaction of PET. A modified example of a by-product removal device is shown. A first embodiment of a depolymerization reaction monitoring device is shown. An example of monitoring the progress of a depolymerization reaction by a depolymerization reaction progress monitoring unit is shown. A second embodiment of a depolymerization reaction monitoring device is shown. An example of dilution of a depolymerization agent by a depolymerization agent dilution unit is shown. A flowchart of a specific example of a measurement procedure in the second embodiment. A third embodiment of a depolymerization reaction monitoring device is shown. A flowchart of a specific example of a measurement procedure in the third embodiment. An embodiment of a polymerization reaction monitoring device is shown. An embodiment of a polymerization reaction monitoring device is shown. A schematic diagram of chemical bonds and vibration modes common to BHET and PET contained in a reaction liquid. An example of absorbance at each wavelength measured when infrared light was irradiated onto a BHET reagent and a PET reagent, respectively. Experimental results showing that each peak area represents the progress of the polymerization reaction.

[0013] Hereinafter, with reference to the drawings, a detailed description will be given of a mode for carrying out the present disclosure (hereinafter also referred to as an embodiment). In the description and / or drawings, identical or equivalent components, members, processes, etc. are designated by the same reference numerals, and redundant description will be omitted. The scale and shape of each part shown in the drawings are set for convenience to simplify the description and should not be interpreted as limiting unless otherwise specified. The embodiment is an example and does not limit the scope of the present disclosure in any way. Not all features and their combinations presented in the embodiment are necessarily essential to the present disclosure. For convenience, the embodiment is presented broken down into components for each function and / or functional group that realizes the embodiment. However, one component in the embodiment may actually be realized by a combination of multiple separate components, or multiple components in the embodiment may actually be realized by a single integrated component.

[0014] FIG. 1 schematically illustrates the configuration of a chemical recycling molding system to which a reaction monitoring device according to an embodiment of the present disclosure can be applied. The chemical recycling molding system includes a chemical recycling apparatus 100 and an injection molding machine 1. The chemical recycling apparatus 100 includes a polymer preparation apparatus 200, a depolymerization reactor 300, a polymerization reactor 400, a by-product removal apparatus 500, and a polymer supply unit 600. The number of injection molding machines 1 (two of which are shown in FIG. 1 ), polymer preparation apparatuses 200, depolymerization reactors 300, polymerization reactors 400, by-product removal apparatuses 500, and polymer supply units 600 may be arbitrarily determined. In particular, by increasing the number of injection molding machines 1 and polymerization reactors 400, which typically have slower processing speeds or reaction rates than other processing units, processing performance can be improved to prevent these processing units from becoming serious bottlenecks.

[0015] The polymer preparation apparatus 200 prepares a polymer such as PET constituting a first molded article such as a PET bottle for the subsequent depolymerization reaction tank 300. Specifically, the polymer preparation apparatus 200 subjects the first molded article such as a PET bottle to treatments such as pulverization, heat melting, and mixing to prepare the polymer such as PET in a state (phase, shape, size, etc.) suitable for the depolymerization reaction in the depolymerization reaction tank 300. The first molded article may be any molded article other than a bottle, such as a sheet, film, or fiber. The polymer constituting the first molded article may be any polymer other than PET, such as polyester (including PET), polyamide, or polyurethane.

[0016] The depolymerization reaction tank 300 decomposes the polymer, such as PET, prepared by the polymer preparation apparatus 200 into depolymers through a depolymerization reaction. When the polymer supplied from the polymer preparation apparatus 200 is PET, the intermediate BHET is obtained as the depolymer through the depolymerization reaction in the depolymerization reaction tank 300. The depolymer obtained in the depolymerization reaction tank 300 may contain a monomer of the polymer. When the polymer is PET, examples of the monomer include ethylene glycol, terephthalic acid, dimethyl terephthalate, and ethylene terephthalate. As will be described in detail later, a depolymerization reaction monitoring device according to an embodiment of the present disclosure may be configured to include the depolymerization reaction tank 300.

[0017] As shown schematically in FIG. 2 , in the depolymerization reaction (300) of PET as a polymer, PET is decomposed by ethylene glycol (EG) as a depolymerization agent supplied from a depolymerization agent supply unit 310 ( FIG. 1 ) to the depolymerization reaction vessel 300, to obtain BHET as a depolymerized product. Instead of or in addition to the depolymerization agent supply unit 310, EG may be supplied from the polymer preparation apparatus 200. To promote this depolymerization reaction, the inside of the depolymerization reaction vessel 300 is maintained at a temperature suitable for the depolymerization reaction by a heater 320 ( FIG. 1 ) or a warmer provided next to the depolymerization reaction vessel 300. The temperature suitable for the depolymerization reaction of PET to BHET in FIG. 2 is between 180°C and 250°C, preferably between 230°C and 245°C, and more preferably between 235°C and 240°C. 2 is suitable for the depolymerization reaction of PET to BHET is between atmospheric pressure (0 MPa, G) and 0.8 MPa, G, preferably between 0.4 MPa, G and 0.6 MPa, G, and more preferably between 0.45 MPa, G and 0.55 MPa, G. The pressure unit, MPa, G, is gauge pressure. The pressure in depolymerization reaction tank 300 is adjusted by a pump (not shown) or the like that is provided in addition to depolymerization reaction tank 300.

[0018] The viscosity of the fluid in the depolymerization reaction tank 300, where BHET, which has a smaller molecular weight than PET, is produced, is lower than the viscosity of the fluid in the polymerization reaction tank 400, which will be described later, where PET, which has a larger molecular weight, is produced. Therefore, a low-viscosity agitator blade 330 is used to agitate the fluid in the depolymerization reaction tank 300 and promote the depolymerization reaction. Examples of the low-viscosity agitator blade 330 include a propeller blade, a disk turbine blade, and a paddle blade.

[0019] Installed downstream of the depolymerization reaction tank 300 are foreign matter removal devices 340, 350, and 360 that remove foreign matter from the fluid primarily composed of depolymerized BHET. The foreign resin removal device 340 removes resins other than the target resin, such as PET, and / or depolymerized resins thereof using the principles of flotation separation and sedimentation removal. The colored matter removal device 350 removes colored matter using activated carbon or the like. The metal ion removal device 360 ​​removes metal ions using the principles of ion exchange or the like. Installed downstream of the foreign matter removal devices 340, 350, and 360 is a buffer tank 370 that temporarily stores the fluid primarily composed of BHET and the like after the foreign matter has been removed before supplying it to the polymerization reaction tank 400.

[0020] The buffer tank 370 may be provided with a first preheater 371 that heats or keeps warm the depolymerized polymer (a fluid mainly composed of BHET, etc.) before it is supplied to the downstream polymerization reaction tank 400. The first preheater 371 may maintain the depolymerized polymer at a temperature (between 180°C and 250°C) similar to that of the heater 320 provided in the depolymerization reaction tank 300, or may maintain the depolymerized polymer at a temperature (between 250°C and 300°C) suitable for the polymerization reaction similar to that of the heater 410 provided in the polymerization reaction tank 400, which will be described later. In this way, by providing the buffer tank 370 equipped with a preheating mechanism (first preheater 371) as needed upstream of the polymerization reaction tank 400, the depolymerized polymer can be stored at an appropriate temperature while being fed into the polymerization reaction tank 400, which typically has a slower processing speed or reaction rate than other processing units, such as the depolymerization reaction tank 300 and the byproduct removal device 500, which will be described later. As a result, the overall capacity of the chemical recycling apparatus 100 can be increased, and the chemical recycling apparatus 100 can be operated stably and continuously (without running out of resin) while supplying appropriate amounts of reactants in a timely manner to each processing section, such as the depolymerization reaction tank 300, the polymerization reaction tank 400, the by-product removal apparatus 500, and the polymer supply section 600. Note that the preheating mechanism such as the first preheater 371 is not limited to being provided in the buffer tank 370, but may be provided in any desired location between the depolymerization reaction tank 300 and the polymerization reaction tank 400 (for example, in the foreign matter removal apparatuses 340, 350, 360) in any desired manner.

[0021] The polymerization reactor 400 polymerizes depolymerized materials such as BHET produced in the depolymerization reactor 300 and from which foreign matter has been removed by the foreign matter removal devices 340, 350, and 360 through a polymerization reaction. If the depolymerized material produced in the depolymerization reactor 300 is BHET, the polymer PET is re-obtained through a polymerization reaction in the polymerization reactor 400. As will be described in detail below, a polymerization reaction monitoring device according to an embodiment of the present disclosure may be configured to include the polymerization reactor 400.

[0022] As shown schematically in FIG. 2 , the polymerization reaction (400) of BHET as a depolymerization product produces PET as a main polymer product, as well as EG as a by-product. This EG may be recycled to the depolymerization agent supply unit 310 and used in the depolymerization reaction of PET in the depolymerization reaction tank 300. Because the EG produced in the polymerization reaction tank 400 can be reused on-site (in the depolymerization reaction tank 300) without being wasted, the operating efficiency of the chemical recycling apparatus 100 can be improved. In particular, the amount of EG purchased for the depolymerization reaction of PET in the depolymerization reaction tank 300 can be significantly reduced, leading to a reduction in the operating costs of the chemical recycling apparatus 100.

[0023] To promote the above-described polymerization reaction, the interior of the polymerization reactor 400 is maintained at a temperature suitable for the polymerization reaction by a heater 410 ( FIG. 1 ) or a warmer attached to the polymerization reactor 400 as a second heater. The temperature suitable for the polymerization reaction of BHET to PET in FIG. 2 is between 250°C and 300°C, preferably between 260°C and 290°C, and more preferably between 270°C and 280°C. The polymerization heating temperature by the heater 410 attached to the polymerization reactor 400 is higher than the depolymerization heating temperature by the heater 320 attached to the depolymerization reactor 300. The polymerization reactor 400 produces PET with a high molecular weight and a high melting point. By maintaining the temperature higher than that of the depolymerization reactor 300, which produces BHET with a low molecular weight and a low melting point, the PET, the main product of the polymerization reactor 400, remains molten. The polymerization reaction of BHET to PET in FIG. 2 is preferably carried out under vacuum. For this purpose, the polymerization reaction vessel 400 is provided with a vacuum pump or the like (not shown).

[0024] The viscosity of the fluid in the polymerization reaction tank 400, where PET with a high molecular weight is produced, is higher than the viscosity of the fluid in the depolymerization reaction tank 300, where BHET with a lower molecular weight than PET, a polymer, is produced. Therefore, a stirring blade 420 for high viscosity is used to stir the fluid in the polymerization reaction tank 400 and promote the polymerization reaction. Examples of the stirring blade 420 for high viscosity include an anchor blade and a helical ribbon blade.

[0025] The IV (intrinsic viscosity) value, or inherent viscosity, is known as a value correlated with the degree of polymerization of polymers such as PET. The IV value (dL / g) is also used as an indicator of polymer applications. For PET, an IV value of approximately 0.72 or higher is suitable for bottles, an IV value of approximately 0.65 or higher is suitable for sheets and films, and an IV value of approximately 0.58 or higher is suitable for fibers. In this embodiment, the goal is to ultimately obtain PET with an IV value suitable for bottles and sheets. As described below, the IV value is also increased in the by-product removal device 500 downstream of the polymerization reactor 400, so the IV value of the PET synthesized in the polymerization reactor 400 can be relatively low. Specifically, the IV value of the PET synthesized in the polymerization reactor 400 is between 0.2 and 0.7, preferably between 0.3 and 0.7, and more preferably between 0.3 and 0.55.

[0026] A buffer tank 430 may be provided downstream of the polymerization reaction tank 400 to temporarily store the polymer synthesized in the polymerization reaction tank 400 before supplying it to the downstream by-product removal device 500 and / or polymer supply unit 600. The buffer tank 430 may be provided with a second preheater 431 to heat or keep the polymer warm before supplying it to the downstream by-product removal device 500 and / or polymer supply unit 600. The second preheater 431 may maintain the polymer at a temperature (between 250°C and 300°C) similar to that of the heater 410 provided adjacent to the polymerization reaction tank 400, or may maintain the polymer at a temperature (between 250°C and 290°C) suitable for polymerization reaction similar to that of the heater 520 provided adjacent to the by-product removal device 500 described below, or may maintain the polymer at a temperature (between 250°C and 290°C) similar to that of the heater 620 provided adjacent to the polymer supply unit 600 described below.

[0027] In this way, by providing a buffer tank 430 equipped with a preheating mechanism (second preheater 431) as needed upstream of the by-product removal apparatus 500 and / or the polymer supply section 600, polymers waiting to be introduced into the by-product removal apparatus 500 and / or the polymer supply section 600 can be stored while being maintained at an appropriate temperature. As a result, the overall capacity of the chemical recycling apparatus 100 can be increased, and the chemical recycling apparatus 100 can be operated stably and continuously while supplying appropriate amounts of reactants to each processing section, such as the depolymerization reaction tank 300, the polymerization reaction tank 400, the by-product removal apparatus 500, and the polymer supply section 600, in a timely manner (without running out of resin). Note that a preheating mechanism such as the second preheater 431 is not limited to the buffer tank 430, but can be provided in any manner at any location between the polymerization reaction tank 400 and the by-product removal apparatus 500 and / or at any location between the by-product removal apparatus 500 and the polymer supply section 600.

[0028] A by-product removal device 500 is provided downstream of the polymerization reaction tank 400 (and upstream of the polymer supply section 600, described below), through which PET (main product) and EG (by-product) produced by the polymerization reaction in the polymerization reaction tank 400 are passed, and which removes the EG as a by-product. The by-product removal device 500 in the illustrated example includes a number of linear members 510 extending from above to below. The increased surface area provided by the number of linear members 510 promotes the volatilization of EG adhering to the surface of each linear member 510, thereby effectively separating and removing the EG from the highly viscous PET.

[0029] This EG may be recycled to the depolymerization agent supply unit 310 and used in the depolymerization reaction of PET in the depolymerization reaction tank 300. The EG separated and removed in the byproduct removal device 500 can be reused on site (in the depolymerization reaction tank 300) without being wasted, thereby improving the operating efficiency of the chemical recycling apparatus 100. In particular, the amount of EG purchased for the PET depolymerization reaction in the depolymerization reaction tank 300 can be significantly reduced, leading to a reduction in the operating costs of the chemical recycling apparatus 100.

[0030] Furthermore, PET with a relatively low degree of polymerization (i.e., IV value) and BHET that did not react in the polymerization reactor 400 also adhere to the surface of each linear member 510, allowing the large surface area to effectively promote a polymerization reaction similar to that in the polymerization reactor 400. Therefore, by passing through the by-product removal device 500, the IV value of the PET as the main product is increased. Specifically, the IV value of the PET after passing through the by-product removal device 500 is 0.7 or higher, preferably 0.8 or higher, and more preferably 0.85 or higher.

[0031] To promote this polymerization reaction, the inside of the by-product removal apparatus 500 is maintained at a temperature suitable for the polymerization reaction by a heater 520 ( FIG. 1 ) or a warmer attached to the by-product removal apparatus 500 as a second heater. Specifically, the heating temperature by the heater 520 is between 250°C and 290°C, preferably between 260°C and 280°C. The heating temperature by the heater 520 attached to the by-product removal apparatus 500 is preferably higher than the polymerization heating temperature by the heater 410 attached to the polymerization reaction tank 400. Since the polymerization reaction proceeds more rapidly in the by-product removal apparatus 500 than in the polymerization reaction tank 400, the molecular weight of the PET polymer increases and the melting point increases. Therefore, by maintaining the inside of the by-product removal apparatus 500 at a higher temperature than in the polymerization reaction tank 400, the PET product of the by-product removal apparatus 500 can be maintained in a molten state. A heater or a warmer may be provided as a second heater around the piping between the polymerization reaction tank 400 and the by-product removal apparatus 500, which heats or keeps the temperature at least to the polymerization heating temperature of the heater 410 provided next to the polymerization reaction tank 400. The polymerization reaction in the by-product removal apparatus 500 is preferably carried out in a vacuum state, similar to the polymerization reaction in the polymerization reaction tank 400. For this reason, a vacuum pump (not shown) or the like is provided next to the by-product removal apparatus 500. By creating a vacuum state (reduced pressure state) inside the by-product removal apparatus 500, the by-product EG can be efficiently removed.

[0032] The configuration of the by-product removal apparatus 500 is not limited to the "vertical" type shown in FIG. 1 . For example, a "horizontal two-axis" agitator as shown in FIG. 3 may be used as the by-product removal apparatus 500. This agitator has two rotating shafts extending perpendicular to the plane of FIG. 3 and two agitating blades that rotate around the two rotating shafts to agitate the PET and EG as the agitation targets. Agitation by the two agitating blades promotes the volatilization of EG, thereby effectively separating and removing it from the highly viscous PET. Details of the agitator shown in FIG. 3 are disclosed in Japanese Patent No. 2925599, which is incorporated herein by reference.

[0033] The polymer supply unit 600 supplies a polymer such as PET synthesized in the polymerization reaction tank 400 (or the polymerization reaction tank 400 and the by-product removal device 500) to the injection molding machine 1 that molds a second molded product such as a PET bottle. The polymer supply unit 600 is equipped with a transfer pump 610 such as a gear pump or a screw pump that is suitable for supplying the PET in a molten state, from which the by-product EG has been removed in the by-product removal device 500, to the injection molding machine 1.

[0034] The polymer supply section 600 is provided with a heater 620 or a warmer as a first heater that heats or keeps warm the polymer such as PET transferred to the injection molding machine 1 by the transfer pump 610, thereby maintaining the polymer in a molten state. Specifically, the heating temperature by the heater 620 is between 250°C and 290°C, preferably between 260°C and 280°C. Here, the heating temperature (first heating temperature) by the heater 620 (first heater) provided in the polymer supply section 600 is preferably higher than the second heating temperature by a second heater such as the heater 410 provided adjacent to the polymerization reaction tank 400, the heater 520 provided adjacent to the by-product removal device 500, or a heater (not shown) provided between the polymerization reaction tank 400 and the by-product removal device 500. The polymerization reaction initiated in the polymerization reaction tank 400 gradually progresses and is completed in the by-product removal device 500. As a result, the molecular weight of the polymer, such as PET, becomes larger and the melting point becomes higher in the polymer supply section 600 than in the polymerization reaction tank 400 and the by-product removal device 500. Therefore, by setting the first heating temperature in the polymer supply section 600 higher than the previous second heating temperature, the polymer, such as PET, which has a high viscosity (i.e., a high degree of polymerization or a high IV value) and a high melting point, can be maintained in a molten state.

[0035] A temperature gradient may be provided so that the heating temperature increases stepwise from the polymerization reaction tank 400 to the polymer supply unit 600. For example, the heating temperature by a heater (not shown) provided between the polymerization reaction tank 400 and the by-product removal device 500 may be made higher than the heating temperature by the heater 410 provided adjacent to the polymerization reaction tank 400, the heating temperature by the heater 520 provided adjacent to the by-product removal device 500 may be made higher than the heating temperature by the heater (not shown), and the heating temperature by the heater 620 provided in the polymer supply unit 600 may be made higher than the heating temperature by the heater 520. This ensures that a polymer such as PET, whose melting point increases from the polymerization reaction tank 400 to the polymer supply unit 600, can be maintained in a molten state. Note that a heater may be provided between the polymer supply unit 600 and the injection molding machine 1 to heat or keep the polymer such as PET warm and maintain it in a molten state.

[0036] The injection molding machine 1 molds a molten polymer, such as PET, produced in the chemical recycling apparatus 100 into a second molded product. The second molded product may be the same or different from the first molded product, which is subjected to processing such as pulverization in the polymer preparation apparatus 200. For example, both the first and second molded products may be PET bottles. Alternatively, one of the first and second molded products may be a PET bottle, and the other may be a molded product other than a bottle, such as a sheet, film, or fiber. Generally, in mechanical recycling, the IV value of the second molded product after recycling is lower than that of the first molded product before recycling. However, the chemical recycling apparatus 100 according to this embodiment, which is equipped with IV value-increasing mechanisms such as the foreign matter removal devices 340, 350, and 360 and the by-product removal device 500, can increase the IV value of the second molded product after recycling compared to that of the first molded product before recycling. For example, according to this embodiment, PET fiber, which serves as the first molded product with a low IV value, can be recycled into a PET bottle, which serves as the second molded product with a high IV value.

[0037] The injection molding machine 1 molds a molten resin such as PET into a second molded product. An injection molding machine using molten resin as a raw material is disclosed, for example, in Patent Document 2. This application incorporates by reference the entire contents of that document (Japanese Patent Application No. 2020-130985), filed on July 31, 2020. As shown schematically in FIG. 1 , multiple injection molding machines 1 may be arranged in parallel. Note that the molding machine to which the molten resin or the like is supplied from the chemical recycling device 100 is not limited to an injection molding machine, and may be any molding machine (e.g., a compression molding machine).

[0038] In the present embodiment described above, the polymer resynthesized in the polymerization reaction tank 400 is not made into flakes or pellets, but is supplied as is by the polymer supply unit 600 to the injection molding machine 1. Since the conventional cooling and heating processes for flakes and pellets are no longer necessary, molded products such as PET bottles can be recycled with less energy than conventional methods.

[0039] In the chemical recycling apparatus 100 according to this embodiment, the polymer resynthesized in the polymerization reaction tank 400 is directly supplied to the injection molding machine 1, so it is necessary to quickly achieve the IV value of the polymer required for the molded product (second molded product). In this embodiment, a by-product removal device 500 having the function of accelerating the polymerization reaction and increasing the IV value of the polymer is provided in addition to the polymerization reaction tank 400, so this requirement can be fully met.

[0040] In the example of Fig. 1, only one of each of the polymer adjustment apparatus 200, depolymerization reaction tank 300, polymerization reaction tank 400, by-product removal apparatus 500, polymer supply unit 600, etc. is provided, but a plurality of each may be provided. Such a plurality of treatment units can perform equivalent treatments in parallel, thereby improving the treatment performance of the treatment unit group. Furthermore, the difference in treatment speed or reaction rate between treatment units can be reduced by increasing the number of slower treatment units.

[0041] Furthermore, one or more processing units may accept external materials procured from a location or facility different from the chemical recycle molding system shown in FIG. 1 , instead of or in addition to materials from the preceding processing unit. For example, when multiple polymerization reaction tanks 400 are provided, some of them may be supplied with depolymerized polymer from the depolymerization reaction tank 300, and the remaining units may be supplied with depolymerized polymer procured from an external source. Similarly, when multiple by-product removal devices 500 and / or polymer supply units 600 are provided, some of them may be supplied with polymer from the polymerization reaction tank 400, and the remaining units may be supplied with polymer procured from an external source. In this way, by allowing the acceptance of external materials at each stage of processing in the chemical recycle molding system, the chemical recycle molding system can be operated flexibly and efficiently.

[0042] FIG. 4 shows a first embodiment of a depolymerization reaction monitoring device 30 according to the present disclosure. The depolymerization reaction monitoring device 30 includes the aforementioned depolymerization reaction tank 300. The depolymerization reaction tank 300 causes a depolymerization reaction in which a depolymerization agent decomposes polyester into depolymers. In this embodiment, similar to FIG. 2 , the polyester is polyethylene terephthalate (PET), the depolymerization agent is ethylene glycol (EG), and the depolymer is bis(2-hydroxyethyl) terephthalate (BHET).

[0043] However, the present disclosure is also applicable to other combinations of polyester, depolymerizer, and depolymerizer. For example, the polyester may be polypropylene terephthalate (PPT), the depolymerizer may be propylene glycol (PG), and the depolymerizer may be bis(2-hydroxypropyl) terephthalate (BHPT). Alternatively, the polyester may be polybutylene terephthalate (PBT), the depolymerizer may be butylene glycol (BG), and the depolymerizer may be bis(2-hydroxybutyl) terephthalate (BHBT). These combinations of polyester, depolymerizer, and depolymerizer share the common feature that the depolymerization product (BHET, BHPT, BHBT, etc.) is soluble in the depolymerizer (EG, PG, BG, etc.), which is one of the reactants or catalysts in the depolymerization reaction, while the polyester (PET, PPT, PBT, etc.), which is the other reactant in the depolymerization reaction, is insoluble in the depolymerizer (EG, PG, BG, etc.).

[0044] Furthermore, as long as similar characteristics are observed, the depolymerization reaction monitoring device 30 according to this embodiment may be used to monitor the progress of the depolymerization reaction of polymers other than polyester, such as polyamides and polyurethanes. That is, the depolymerization reaction monitoring device 30 according to this embodiment is applicable to cases where the depolymerization product is soluble in a depolymerization agent, which is one of the reactants or catalysts in the depolymerization reaction, while the polymer, which is the other reactant in the depolymerization reaction, is insoluble in the depolymerization agent.

[0045] As described above, the depolymerization reaction monitoring device 30 according to this embodiment is not limited to the depolymerization reaction tank 300 provided in the chemical recycle molding system shown in FIG. 1 , but can be applied to the depolymerization reaction tank 300 provided in any system or any standalone depolymerization reaction tank 300.

[0046] The depolymerization reaction tank 300 includes a tank body 31 in which a depolymerization reaction of polyester or polymer occurs, and a depolymerization agent circulating section 32 through which a depolymerization agent such as EG circulates between the tank body 31 and the depolymerization agent circulating section 32. The depolymerization agent circulating section 32 forms a flow path for the depolymerization agent such as EG outside the tank body 31. As shown in the figure, one end 321 and the other end 322 of the tubular depolymerization agent circulating section 32 are connected to different positions on the tank body 31. As will be described later, the depolymerization agent such as EG may flow from the one end 321 to the other end 322 of the depolymerization agent circulating section 32, or from the other end 322 of the depolymerization agent circulating section 32 to the one end 321.

[0047] The depolymerization agent flow section 32 is provided with a depolymerization reaction characteristic measuring section 33 , an intrusion prevention section 34 , a direction switching section 35 , and a cooling section 36 .

[0048] The depolymerization reaction characteristic measuring unit 33 measures the characteristics of the depolymerization agent such as EG in which depolymerized polymers such as BHET are dissolved in the depolymerization reaction tank 300. Specifically, the depolymerization reaction characteristic measuring unit 33 measures the characteristics of the depolymerization agent such as EG in the depolymerization agent flow unit 32.

[0049] In the example shown in FIG. 4 , the depolymerization reaction characteristic measuring unit 33 measures the optical characteristics of the depolymerization agent, such as EG, in the depolymerization agent flow section 32. This depolymerization reaction characteristic measuring unit 33 includes a light source 331, a light receiving unit 332, and a window 333. The light source 331 emits light of any intensity, pattern, wavenumber, wavelength, frequency, or other characteristics suitable for measuring the optical characteristics of the depolymerization agent, such as EG, in which depolymerized polymers, such as BHET, have been dissolved. The light from the light source 331 passes through the light-transmitting window 333, which constitutes part of the tubular wall of the tubular depolymerization agent flow section 32, enters the interior of the depolymerization agent flow section 32, and is irradiated onto the depolymerization agent, such as EG. This light is subject to optical effects such as reflection, refraction, absorption, scattering, diffraction, polarization, interference, and dispersion, depending on the optical characteristics of the depolymerization agent, such as EG, in which depolymerized polymers, such as BHET, have been dissolved. The light receiving unit 332 receives the light that has been subjected to such optical effects through the window 333. The light received by the light receiving unit 332 represents the optical characteristics of the depolymerization agent, such as EG, in which depolymerization polymers, such as BHET, are dissolved. Examples of optical characteristics that can be measured by the depolymerization reaction characteristic measuring unit 33 include a refractive index and a spectrum. In this embodiment, an example will be described in which the depolymerization reaction characteristic measuring unit 33 measures the refractive index of the depolymerization agent, such as EG, in which depolymerization polymers, such as BHET, are dissolved.

[0050] The refractive index measured by the depolymerization reaction characteristic measuring unit 33 is provided to a depolymerization reaction progress monitoring unit 37 configured by a computer or a processor. The depolymerization reaction progress monitoring unit 37 monitors the progress of the depolymerization reaction in the depolymerization reaction tank 300 (particularly the tank main body 31) based on the optical characteristics, such as the refractive index, of the depolymerization agent such as EG measured by the depolymerization reaction characteristic measuring unit 33 and other characteristics.

[0051] FIG. 5 shows an example of monitoring the progress of the depolymerization reaction by the depolymerization reaction progress monitor 37. As shown in FIG. 5A, a correlation, such as a proportional relationship, exists between the refractive index measured by the depolymerization reaction characteristics measurement unit 33 and the concentration of depolymerized species such as BHET in the depolymerization agent such as EG being measured (the dots (◯) in FIG. 5A are examples of measured values). As described above, in the depolymerization reaction tank 300 (particularly the tank body 31), PET is decomposed by EG as a depolymerization agent, yielding BHET as a depolymerized species. Therefore, the concentration of BHET represents the progress of the depolymerization reaction of PET. In other words, the depolymerization reaction progress monitor 37 can recognize the progress of the depolymerization reaction of polymers such as PET based on the concentration of depolymerized species such as BHET, which is determined based on the correlation shown in FIG. 5A from the refractive index measured by the depolymerization reaction characteristics measurement unit 33. For example, as shown in Fig. 5B , the depolymerization reaction progress monitoring unit 37 calculates the total amount of BHET produced in the depolymerization reaction tank 300 based on the BHET concentration recognized from Fig. 5A , and expresses this as a change over time with respect to the reaction time (the dots (○) in Fig. 5B are examples of actually measured values). The monitoring results by the depolymerization reaction progress monitoring unit 37 shown in Fig. 5A and Fig. 5B may be provided to the controllers of the chemical recycling molding system and the chemical recycling apparatus 100 in Fig. 1 for controlling these systems, or may be displayed on a management screen or an operation screen viewable by a manager or operator of these systems.

[0052] The depolymerization reaction characteristic measurement unit 33 may be one that measures non-optical characteristics of a depolymerization agent such as EG in which depolymerization polymers such as BHET are dissolved. For example, the depolymerization reaction characteristic measurement unit 33 may be one that measures electrical characteristics of a depolymerization agent such as EG in which depolymerization polymers such as BHET are dissolved in the depolymerization reaction tank 300. In this case, instead of the optical depolymerization reaction characteristic measurement unit 33 in FIG. 4 , a depolymerization reaction characteristic measurement unit including an electrode that electrically interacts (e.g., contacts) with the depolymerization agent such as EG in the depolymerization agent flow unit 32 is provided. Furthermore, the type of the depolymerization reaction characteristic measurement unit 33 is not important as long as it can measure the characteristics of the depolymerization agent such as EG without sampling it from the depolymerization agent flow unit 32 (depolymerization reaction tank 300).

[0053] Furthermore, in the case where polymers such as PET that remain in the tank body 31 without dissolving in the depolymerization agent such as EG do not interfere with the measurement, the depolymerization reaction characteristic measuring unit 33 may be provided in the tank body 31 instead of the depolymerization agent circulating unit 32. However, in the case of an optical depolymerization reaction characteristic measuring unit 33 as shown in Fig. 4, the remaining polymers such as PET have undesirable effects such as diffuse reflection on the measurement light, so the depolymerization reaction characteristic measuring unit 33 is preferably provided in the depolymerization agent circulating unit 32 outside the tank body 31, and further preferably is provided with an intrusion prevention unit 34 described below.

[0054] The intrusion prevention unit 34 includes a first filter 341 provided at one end 321 of the tubular depolymerization agent flow section 32 and a second filter 342 provided at the other end 322 of the tubular depolymerization agent flow section 32. The first filter 341 and the second filter 342 prevent insoluble matter, such as EG, from entering the depolymerization agent flow section 32 from the tank body 31. As described above, examples of insoluble matter, such as EG, that is insoluble in a depolymerization agent include polyesters, such as PET, which are reaction products of the depolymerization reaction, and polymers, as well as oligomers produced by partial depolymerization of these polyesters. In this way, the first filter 341 and / or the second filter 342 can effectively remove insoluble matter in the depolymerization agent flow section 32 that may interfere with optical measurement by the depolymerization reaction characteristic measurement unit 33.

[0055] The direction switching unit 35 is configured by a backwash pump or the like that can switch the flow direction of the depolymerization agent such as EG in the tubular depolymerization agent flow unit 32 between a first direction from one end 321 to the other end 322 and a second direction from the other end 322 to the one end 321 in order to prevent clogging of the first filter 341 and / or the second filter 342. When the direction switching unit 35 flows the depolymerization agent such as EG in the first direction, the insoluble matter captured by the second filter 342 at the other end 322 is returned to the tank body 31, thereby clearing clogging of the second filter 342. When the direction switching unit 35 flows the depolymerization agent such as EG in the second direction, the insoluble matter captured by the first filter 341 at the one end 321 is returned to the tank body 31, thereby clearing clogging of the first filter 341. In order to avoid clogging of both the first filter 341 and the second filter 342, it is preferable that the direction switching unit 35 repeatedly or periodically switches the flow direction of the depolymerization agent such as EG in the depolymerization agent flow unit 32 between the first direction and the second direction.

[0056] The backwash pump and other components of the direction switching unit 35 only need to operate before or during measurement by the depolymerization reaction characteristic measuring unit 33, and may be stopped at other times. When the backwash pump and other components of the direction switching unit 35 operate, the depolymerization agent such as EG to be measured by the depolymerization reaction characteristic measuring unit 33 is taken in from the tank body 31 at one of the one end 321 and the other end 322 of the depolymerization agent circulating unit 32. At this time, the "old" depolymerization agent originally in the depolymerization agent circulating unit 32 is discharged into the tank body 31 from the other of the one end 321 and the other end 322 of the depolymerization agent circulating unit 32, thereby clearing clogging of the other of the first filter 341 and the second filter 342 provided therein. The depolymerization reaction characteristic measuring unit 33 can then perform measurement on the "new" depolymerization agent newly taken in from the tank body 31.

[0057] The cooling unit 36 ​​cools the depolymerization agent such as EG in the tubular depolymerization agent flow section 32. Optical properties such as refractive index and other properties measurable by the depolymerization reaction characteristic measurement unit 33 depend on the temperature of the depolymerization agent such as EG being measured. Therefore, the cooling unit 36 ​​stabilizes the measurement accuracy of the depolymerization reaction characteristic measurement unit 33 by cooling the depolymerization agent such as EG to a predetermined temperature before measurement by the depolymerization reaction characteristic measurement unit 33. As described above, the depolymerization agent such as EG in the depolymerization agent flow section 32 can flow in either the first direction or the second direction by the direction switching unit 35. Therefore, the cooling unit 36 ​​preferably includes a first cooling unit 361 located on the one end 321 side of the depolymerization reaction characteristic measurement unit 33 and a second cooling unit 362 located on the other end 322 side of the depolymerization reaction characteristic measurement unit 33.

[0058] Instead of the cooling unit 36, a heating unit may be provided that heats the depolymerization agent, such as EG, to a predetermined temperature. However, since components such as sensors that constitute the depolymerization reaction characteristic measurement unit 33 generally have low operating temperatures (e.g., 150°C or below), it may be impossible to measure the depolymerization agent, such as EG, in the tank body 31 at temperatures between 180°C and 250°C, for example. For this reason, it is preferable to use the cooling unit 36 ​​to lower the depolymerization agent, such as EG, to a measurable temperature (operating temperature) of the depolymerization reaction characteristic measurement unit 33. As shown in FIG. 4 , the cooling units 36 provided before and after (or above and below) the depolymerization reaction characteristic measurement unit 33 may cool the depolymerization reaction characteristic measurement unit 33 itself. Alternatively, a temperature sensor (not shown) that measures the temperature of the depolymerization agent, such as EG, facing the depolymerization reaction characteristic measurement unit 33 may be provided, and the cooling unit 36 ​​and / or the heating unit may be controlled so that the temperature measured by the temperature sensor approaches the predetermined measurable temperature of the depolymerization reaction characteristic measurement unit 33.

[0059] According to the depolymerization reaction monitoring device 30 or the depolymerization reaction progress monitoring unit 37 of the first embodiment described above, the progress of the depolymerization reaction of polyester or polymer, in which the depolymerized product such as BHET dissolves in the depolymerization agent such as EG, which is the reactant or catalyst, can be efficiently monitored by measuring the characteristics of the depolymerization agent such as EG by the depolymerization reaction characteristic measuring unit 33 in the depolymerization reaction tank 300 (depolymerization agent flow unit 32). Because it is not necessary to sample the depolymerization agent such as EG to be measured from the depolymerization reaction tank 300 (depolymerization agent flow unit 32), the progress of the depolymerization reaction can be monitored in real time.

[0060] 1 , until the degree of progress of the depolymerization reaction in the depolymerization reaction tank 300 monitored by the depolymerization reaction progress monitoring unit 37 reaches a desired value, the supply of the depolymerized polymer decomposed in the depolymerization reaction tank 300 to the downstream foreign matter removal devices 340, 350, 360 and the polymerization reaction tank 400 may be temporarily stopped. The liquid containing the depolymerized polymer that temporarily accumulates in this manner may be retained in a pipe or buffer tank 370 provided between the depolymerization reaction tank 300 and the polymerization reaction tank 400, or may be refluxed into the depolymerization reaction tank 300 to further progress the depolymerization reaction. Furthermore, a depolymerization reaction tank 300 and a polymerization reaction tank 400 may be provided between the depolymerization reaction tank 300 and the polymerization reaction tank 400. The depolymerization reaction tank 300 may be opened to allow the supply of depolymerized polymers to the polymerization reaction tank 400 when the degree of progress of the depolymerization reaction in the depolymerization reaction tank 300 monitored by the depolymerization reaction progress monitoring unit 37 reaches a desired value, and the depolymerization reaction tank 300 may be closed to stop the supply of depolymerized polymers to the polymerization reaction tank 400 when the degree of progress of the depolymerization reaction in the depolymerization reaction tank 300 monitored by the depolymerization reaction progress monitoring unit 37 falls below the desired value.

[0061] 6 shows a second embodiment of a depolymerization reaction monitoring device 30 according to the present disclosure. The same components as those in the first embodiment shown in FIG. 4 are denoted by the same reference numerals, and redundant explanations will be omitted.

[0062] The depolymerization agent circulating section 32 is provided with a depolymerization agent dilution section 38 that dilutes the depolymerization agent such as EG by adding more depolymerization agent such as EG in the depolymerization agent circulating section 32. The depolymerization agent dilution section 38 includes a diluted depolymerization agent supply section 381 that supplies the depolymerization agent such as EG for dilution, a dilution pipe 382 that connects the diluted depolymerization agent supply section 381 to the depolymerization agent circulating section 32, a dilution valve 383 that is provided on the dilution pipe 382, ​​a first valve 384 that is provided at a connection section of the depolymerization agent circulating section 32 with the dilution pipe 382 and on the one end 321 side of the depolymerization reaction characteristic measuring section 33 and on the other end 322 side of the first cooling section 361, and a second valve 385 that is provided at a connection section of the depolymerization agent circulating section 32 with the dilution pipe 382 and on the other end 322 side of the depolymerization reaction characteristic measuring section 33 and on the one end 321 side of the second cooling section 362.

[0063] Fig. 7 shows an example of dilution of the depolymerization agent by the depolymerization agent dilution unit 38. As also shown in Fig. 5A , there is a correlation, such as a proportional relationship, between the refractive index of the depolymerization agent, such as EG, in which depolymerization agents, such as BHET, have been dissolved and the concentration of depolymerization agents, such as BHET, in the depolymerization agent, such as EG. However, as shown in Fig. 7 (before dilution), this correlation is lost when the concentration of BHET or the like exceeds a predetermined value A. For this reason, there is a possibility that the depolymerization reaction progress monitoring unit 37 will not be able to correctly determine the concentration of BHET or the like from the refractive index measured by the depolymerization reaction characteristic measurement unit 33.

[0064] Therefore, the depolymerization agent dilution unit 38 additionally supplies a depolymerization agent such as EG from the diluted depolymerization agent supply unit 381 to a solution of BHET or the like with such a high concentration that it breaks the linearity of the measurement in the depolymerization reaction characteristic measurement unit 33. As a result, the concentration of depolymerized substances such as BHET in the depolymerization agent circulation unit 32 (between the first valve 384 and the second valve 385) decreases, and as shown in Fig. 7 (after dilution), the correlation or linearity is apparently maintained even in the high-concentration region. In other words, by reducing the concentration of depolymerized substances such as BHET in the depolymerization agent circulation unit 32, the refractive index measured by the depolymerization reaction characteristic measurement unit 33 falls within the linear range in Fig. 7. The depolymerization reaction progress monitoring unit 37 can accurately determine the original (undiluted) concentration of BHET and the like in the tank body 31 (the concentration on the line "after dilution" in FIG. 7 ) based on the refractive index normally measured within the linear range by the depolymerization reaction characteristic measuring unit 33 and the amount of EG and the like used for dilution by the diluted depolymerization agent supplying unit 381 (which is adjusted by the dilution valve 383 as will be described later).

[0065] In order to improve the measurement accuracy of the depolymerization reaction characteristic measuring unit 33 when the above-described depolymerization agent diluting unit 38 is used, various valves such as a dilution valve 383, a first valve 384, and a second valve 385 are provided. The opening and closing operations of each valve will be described below in accordance with the flowchart of a specific example of the measurement procedure shown in Fig. 8. In the explanation of the flowchart, "S" denotes a step or a process.

[0066] At the start of measurement in S1, the first valve 384 and the second valve 385 are open, and the dilution valve 383 is closed. In S2, the backwash pump and other components of the direction switching unit 35 are operated, and the depolymerization agent to be measured, such as EG, is taken from the tank body 31 into the depolymerization agent flow unit 32. At this time, as described above, the first cooling unit 361 and / or the second cooling unit 362 cool the taken-in depolymerization agent, such as EG, to a predetermined measurable temperature in the depolymerization reaction characteristic measurement unit 33. As a result, the depolymerization agent, such as EG, cooled by the first cooling unit 361 and / or the second cooling unit 362 enters the space between the first valve 384 and the second valve 385, which are open in S1. In S3, the first valve 384 and the second valve 385 are switched to a closed state. As a result, a closed space is temporarily formed between the first valve 384 and the second valve 385, and the total amount of BHET and other substances in the closed space is determined.

[0067] In S4, the depolymerization reaction characteristic measuring unit 33 performs a primary measurement of the refractive index of the depolymerization agent, such as EG, in the closed space formed in S3. In S5, it is determined whether the refractive index measured in S4 exceeds the saturation threshold B shown in Fig. 7. If the determination in S5 is "No," the refractive index measured in S4 falls within a linear range below the saturation threshold B, and therefore is adopted as the measurement result by the depolymerization reaction characteristic measuring unit 33 in S6. In S7, the depolymerization reaction progress monitoring unit 37 calculates the concentration of the depolymerized agent, such as BHET, based on the refractive index measurement result obtained in S6.

[0068] If the determination in S5 is "Yes," the refractive index measured in S4 deviates from the linear range of the depolymerization reaction characteristic measurement unit 33. Therefore, proceeding to S6 and S7 would not result in a correct concentration of depolymerized materials such as BHET. Therefore, in S8, the dilution valve 383 is switched to an open state. In the following S8(2), the second valve 385 is switched to an open state to guide EG or the like for dilution to the depolymerization reaction characteristic measurement unit 33. Then, in S9, the backwash pump or the like constituting the direction switching unit 35 is operated, and EG or the like for dilution is supplied from the dilution depolymerization agent supply unit 381 through the open dilution valve 383 to the space between the first valve 384 and the second valve 385. The amount of EG or the like used for dilution in S9 is measured by a flow rate sensor (not shown) or the like provided in the dilution valve 383 or the like. In S10, the dilution valve 383 is switched to the closed state, and in S10(2), the second valve 385 is switched to the closed state, thereby forming a closed space between the first valve 384 and the second valve 385 again.

[0069] In S11, the depolymerization reaction characteristic measuring unit 33 performs a secondary measurement of the refractive index of the depolymerization agent, such as EG, in the closed space formed in S3 and S10(2), and then the process returns to S5. If the determination in S5 is "No," the refractive index after EG dilution measured in S11 falls within a linear range not exceeding the saturation threshold B, and therefore, in S6, the measured refractive index is directly adopted as the measurement result by the depolymerization reaction characteristic measuring unit 33. In S7, the depolymerization reaction progress monitoring unit 37 calculates the original (undiluted) concentration of BHET, etc. in the tank body 31 (the concentration on the "after dilution" line in FIG. 7 ) based on the secondary measurement result of the refractive index within the linear range obtained in S11 and the amount of EG, etc., used for dilution in S9. That is, as described above, the dilution valve 383, the first valve 384, and the second valve 385 can control the amounts of the depolymerization agent such as EG that enter the closed space formed in S3 (the space defined by the three valves) from the tank main body 31 and the diluted depolymerization agent supply unit 381, respectively. Therefore, the depolymerization reaction progress monitoring unit 37 can calculate the concentration of BHET, etc. in the tank main body 31 while grasping the quantitative effect of dilution by the depolymerization agent dilution unit 38.

[0070] If the determination in S5 is "Yes," the process proceeds again to S8 to S11, and the dilution in S9 and the secondary measurement in S11 are repeated until the determination in S5 is "No," that is, until the secondary measurement result of the refractive index in S11 falls within a linear range below the saturation threshold B. At the end of measurement in S7, the first valve 384, the second valve 385, and the dilution valve 383 are in a closed state.

[0071] The dilution valve 383 or the like may be used to control not only the amount of dilution EG or the like supplied by the dilution depolymerization agent supply unit 381 but also its temperature. For example, by supplying the temperature-controlled dilution EG or the like in S9 to the closed space formed in S3, the EG or the like in the closed space can be cooled to a predetermined measurable temperature of the depolymerization reaction characteristic measurement unit 33. In this way, at least part of the function of the cooling unit 36 ​​may be achieved by the dilution EG or the like supplied by the dilution depolymerization agent supply unit 381. In this case, at least part of the first cooling unit 361 and the second cooling unit 362 in FIG. 6 may not be provided.

[0072] 9 shows a third embodiment of a depolymerization reaction monitoring device 30 according to the present disclosure. Components similar to those of the first embodiment in FIG. 4 and / or the second embodiment in FIG. 6 are designated by the same reference numerals, and redundant description will be omitted.

[0073] The depolymerization agent circulating section 32 is provided with an extraction section 39 that can extract a specified amount of the depolymerization agent such as EG flowing therethrough. The extraction section 39 includes, for example, a syringe pump 391 and an extraction valve 392. The syringe pump 391 extracts, takes in, or discharges the depolymerization agent such as EG according to the position of a movable piston housed therein. The extraction valve 392 is provided between the main body of the tubular depolymerization agent circulating section 32 and the syringe pump 391.

[0074] The depolymerization reaction characteristic measuring unit 33 is provided in the syringe pump 391. Specifically, as schematically shown in the figure, the above-described optical measurement is performed through a window 333 provided in the syringe pump 391 (illustration of the light source 331 and the light receiving unit 332 is omitted). The depolymerization reaction characteristic measuring unit 33 measures the characteristics of the depolymerization agent such as EG extracted by the extracting unit 39 (syringe pump 391).

[0075] 6 , the depolymerization agent circulating section 32 is provided with a depolymerization agent diluting section 38 that dilutes the depolymerization agent such as EG extracted by the extracting section 39 (syringe pump 391) by adding more depolymerization agent such as EG. The depolymerization reaction characteristic measuring section 33 measures the characteristics of the depolymerization agent such as EG diluted by the depolymerization agent diluting section 38.

[0076] 10 is a flowchart of a specific example of the measurement procedure. Steps or processes similar to those in FIG. 8 in the second embodiment are denoted by the same reference numerals, and redundant explanations will be omitted.

[0077] At the start of measurement in S1, the extraction valve 392 is open and the dilution valve 383 is closed. In S2, the backwash pump and other components of the direction switching unit 35 are operated, and the depolymerization agent to be measured, such as EG, is taken from the tank body 31 into the depolymerization agent circulating unit 32. In S12, the extraction unit 39 extracts (primary extraction) a designated amount (first designated amount) of the depolymerization agent, such as EG, taken into the depolymerization agent circulating unit 32 in S2. In S3, the extraction valve 392 is switched to a closed state. As a result, the first designated amount of depolymerization agent, such as EG, is secured in the extraction unit 39 (syringe pump 391).

[0078] In S4, the depolymerization reaction characteristic measuring unit 33 performs a primary measurement of the refractive index of the first specified amount of depolymerization agent such as EG secured in the extraction unit 39 (syringe pump 391) in S3. In S5, it is determined whether the refractive index measured in S4 exceeds the saturation threshold B shown in FIG. 7. If the determination in S5 is "No," the refractive index measured in S4 falls within a linear range not exceeding the saturation threshold B, and therefore is adopted as the measurement result by the depolymerization reaction characteristic measuring unit 33 in S6. In S7, the depolymerization reaction progress monitoring unit 37 calculates the concentration of the depolymerized material such as BHET based on the refractive index measurement result obtained in S6.

[0079] If the determination in S5 is "Yes," the refractive index measured in S4 deviates from the linear range of the depolymerization reaction characteristic measurement unit 33. Therefore, proceeding to S6 and S7 would not yield a correct concentration of depolymerized materials such as BHET. Therefore, in S8, the dilution valve 383 is switched to an open state. In S13, the extraction unit 39 extracts (secondarily extracts) a specified amount (second specified amount) of EG for dilution from the diluted depolymerization agent supply unit 381 through the dilution valve 383 in the open state. Then, in S9, the EG for dilution extracted in S13 is used to dilute the EG in the extraction unit 39 (syringe pump 391). In S10, the dilution valve 383 is switched to a closed state. As a result, in addition to the first specified amount of depolymerization agent such as EG (in which depolymerization agents such as BHET are dissolved) extracted primarily in S12, a second specified amount of depolymerization agent such as EG (in which depolymerization agents such as BHET are not dissolved) extracted secondarily in S13 is secured in the extraction unit 39 (syringe pump 391).

[0080] In S11, the depolymerization reaction characteristic measurement unit 33 performs a second measurement of the refractive index of the depolymerization agent, such as EG, in the first specified amount and the second specified amount secured in the extraction unit 39 (syringe pump 391) in S3 and S10, and then the process returns to S5. If the determination in S5 is "No," the refractive index after EG dilution measured in S11 falls within a linear range not exceeding the saturation threshold B. Therefore, in S6, the refractive index is directly adopted as the measurement result by the depolymerization reaction characteristic measurement unit 33. In S7, the depolymerization reaction progress monitoring unit 37 calculates the original (undiluted) concentration of BHET, etc. in the tank body 31 (the concentration on the "after dilution" line in FIG. 7 ) based on the second measurement result of the refractive index within the linear range obtained in S11, the first specified amount primarily extracted in S12 (obtained from the syringe pump 391 and the extraction valve 392), and the second specified amount secondarily extracted in S13 (obtained from the syringe pump 391 and the dilution valve 383). That is, as described above, the syringe pump 391, the extraction valve 392, and the dilution valve 383 can be used to control the amounts of the depolymerization agent such as EG that enter the extraction unit 39 (syringe pump 391) from the tank main body 31 (or the depolymerization agent circulation unit 32) and the diluted depolymerization agent supply unit 381, respectively. Therefore, the depolymerization reaction progress monitoring unit 37 can calculate the concentration of BHET and the like in the tank main body 31 while grasping the quantitative effect of dilution by the depolymerization agent dilution unit 38.

[0081] If the determination in S5 is "Yes," the process proceeds again to S8 to S11, and the secondary extraction in S13, dilution in S9, and secondary measurement in S11 are repeated until the determination in S5 is "No," that is, until the secondary refractive index measurement result in S11 falls within a linear range below the saturation threshold B. At the end of measurement in S7, the extraction valve 392 and dilution valve 383 are closed.

[0082] 11 and 12 show an embodiment of a polymerization reaction monitoring device 40 according to the present disclosure. The polymerization reaction monitoring device 40 may be configured to include the polymerization reaction tank 400 described above. In the following example, a polymerization reaction characteristic measurement unit (specifically, a convex portion 41, a measurement window 42, a light emitter 43, a light receiver 44, etc., which will be described later) that is a main component of the polymerization reaction monitoring device 40 is provided integrally with the polymerization reaction tank 400. However, the polymerization reaction characteristic measurement unit may also be provided in a reaction liquid circulation unit (not shown) outside the polymerization reaction tank 400 through which the reaction liquid of the polymerization reaction flows between the polymerization reaction tank 400 and the polymerization reaction tank 400, similar to the depolymerization reaction characteristic measurement unit 33 in the depolymerization reaction monitoring device 30 shown in FIG. 4 etc. The polymerization reaction characteristic measurement unit may also be provided in a pipe, buffer tank 430 ( FIG. 1 ), or other processing unit (e.g., by-product removal device 500 or polymer supply unit 600) downstream of the polymerization reaction tank 400, where the reaction liquid (typically a liquid containing a depolymerized product such as BHET as a reactant and a polymer such as PET as a product) flows or accumulates. In this manner, the expression "provided in the polymerization reaction tank 400" in the following description is intended to encompass not only a case where the measurement unit is provided integrally with the polymerization reaction tank 400 itself, but also a case where the measurement unit is provided adjacent to the polymerization reaction tank 400 or a case where the measurement unit is provided downstream of the polymerization reaction tank 400.

[0083] Fig. 11 is a schematic side view of a polymerization reaction tank 400 in which a polymerization reaction characteristic measuring unit in a polymerization reaction monitoring device 40 is integrally provided, and Fig. 12 is a schematic front view of the polymerization reaction tank 400. Here, the side (Fig. 11) and the front (Fig. 12) are relative concepts, but in this embodiment they represent the side and front of a convex portion 41, which will be described later. That is, Fig. 11 is a view of the convex portion 41 as seen from the side, and Fig. 12 is a view of the convex portion 41 as seen from the front.

[0084] As shown in FIG. 11A , the convex portion 41 protrudes outward (to the left in FIG. 11A ) from the polymerization reaction vessel 400. A measurement window 42 (described later) is provided on the side or flank of the convex portion 41 (the front in FIG. 11A ). As shown in FIG. 11B , an enlarged cross-sectional view of the convex portion 41 in FIG. 11A , the interior of the convex portion 41 (on the right in FIG. 11B ), which constitutes the vessel wall of the polymerization reaction vessel 400, is filled with a polymerization reaction liquid RL containing a depolymerized polymer such as BHET and a polymer such as PET. As described above, the depolymerized polymer such as BHET is a reactant of the polymerization reaction occurring in the polymerization reaction vessel 400 (i.e., in the convex portion 41), and the polymer such as PET is a product of the polymerization reaction. The ratio of the depolymerized polymer such as BHET and the polymer such as PET contained in the reaction liquid RL changes dynamically depending on the progress of the polymerization reaction occurring in the polymerization reaction vessel 400 (i.e., in the convex portion 41). For example, as the polymerization reaction proceeds for a given amount of depolymerized BHET or the like, the ratio of the polymer such as PET to the depolymerized BHET or the like decreases.

[0085] In order to indirectly grasp the ratio of depolymerization and polymerization in the reaction solution RL, which changes dynamically as the polymerization reaction progresses, a light-emitting unit 43 and a light-receiving unit 44 are provided to non-invasively or non-contact optically measure the reaction solution RL in the convex portion 41. As shown in Fig. 12B, which is an enlarged cross-sectional view of the convex portion 41 in Fig. 12A, the light-emitting unit 43 is provided on one of the opposing sides of the convex portion 41 (the left side in Fig. 12B), and the light-receiving unit 44 is provided on the other opposing side of the convex portion 41 (the right side in Fig. 12B).

[0086] Corresponding to the light-emitting unit 43 and the light-receiving unit 44, the measurement window 42 includes a first measurement window 421 and a second measurement window 422. Specifically, the first measurement window 421, like the light-emitting unit 43, is provided on one of the opposing sides of the convex portion 41 (the left side in FIG. 12B ), and the second measurement window 422, like the light-receiving unit 44, is provided on the other opposing side of the convex portion 41 (the right side in FIG. 12B ). In this manner, the measurement windows 42 (the first measurement window 421 and / or the second measurement window 422) are provided on at least the opposing sides of the convex portion 41. As in the illustrated example, the light-emitting surface of the light-emitting unit 43 (the right side in FIG. 12B ) may be fixed to the surface of the first measurement window 421 (the left side in FIG. 12B ), and the light-receiving surface of the light-receiving unit 44 (the left side in FIG. 12B ) may be fixed to the surface of the second measurement window 422 (the right side in FIG. 12B ).

[0087] The number, arrangement, shape, etc. of the measurement windows 42 are arbitrary as long as they do not have a significant adverse effect on the measurement accuracy of the light-emitting unit 43 and the light-receiving unit 44. For example, the measurement windows 42 may be formed in an annular or semi-annular shape over the side surface of the convex portion 41, or the measurement windows 42 may be formed over not only the side surface but also the front surface of the convex portion 41. In these cases, the first measurement window 421 and the second measurement window 422 are connected to form a single measurement window 42.

[0088] A reflecting portion (not shown), such as a mirror, that reflects the measurement light ML, such as infrared light, may be provided on the inner and / or outer peripheral surface of the convex portion 41 (for example, the inner and / or outer peripheral surface of the upper and / or lower side of the convex portion 41 in FIG. 12B ). At least a portion of the measurement light ML emitted from the light-emitting portion 43 is reflected by this reflecting portion and enters the light-receiving portion 44. In this way, not only can the amount of light received by the light-receiving portion 44 be increased through the reflecting portion, but the distance that the measurement light ML passing through the reflecting portion travels through the reaction liquid RL is also increased, thereby improving the accuracy of measuring the characteristics of the reaction liquid RL.

[0089] The first measurement window 421 and the second measurement window 422 preferably have the following properties. First, the first measurement window 421 and the second measurement window 422 are heat-resistant, able to withstand the high temperatures of the polymerization reaction tank 400 (between 250°C and 300°C, as described above). Second, the first measurement window 421 and the second measurement window 422 are translucent, allowing at least a portion of the measurement light ML that the light emitter 43 irradiates onto the reaction liquid RL in the polymerization reaction tank 400 and that the light receiver 44 receives. As described below, when infrared light is used as the measurement light ML, sodium chloride (NaCl) and calcium fluoride (CaF2), which are translucent to infrared light, are candidates for the material of the first measurement window 421 and the second measurement window 422. Third, because the inner surfaces of the first measurement window 421 and the second measurement window 422 come into contact with the reaction liquid RL, they have low reactivity with alcohols, such as EG, contained in the reaction liquid RL. Of the candidate materials when the measurement light ML is infrared, sodium chloride and calcium fluoride, sodium chloride easily reacts with alcohol, so calcium fluoride, which does not easily react with alcohol, is suitable as the material for the first measurement window 421 and the second measurement window 422.

[0090] As described above, when infrared light is used as the measurement light ML, it is preferable that the first measurement window 421 and the second measurement window 422 contain calcium fluoride. Note that when light or electromagnetic waves other than infrared light are used as the measurement light ML, a material having the above-described first to third properties is appropriately selected as the material for the first measurement window 421 and the second measurement window 422.

[0091] In the above-described configuration, the measurement window 42 (first measurement window 421 and / or second measurement window 422) is provided in the polymerization reaction tank 400 (convex portion 41) and transmits at least a portion of the measurement light ML used to measure the optical properties of the reaction liquid RL in the polymerization reaction. The light emitter 43 irradiates the reaction liquid RL in the convex portion 41 (in the polymerization reaction tank 400) with measurement light ML, such as infrared light, through the first measurement window 421 provided on one of the opposing sides of the convex portion 41 (the left side in FIG. 12B ). The light receiver 44 receives the measurement light ML, such as infrared light, irradiated onto the reaction liquid RL in the convex portion 41 (in the polymerization reaction tank 400) through the second measurement window 422 provided on the other opposing side of the convex portion 41 (the right side in FIG. 12B ).

[0092] The convex portion 41, measurement window 42, light-emitting portion 43, and light-receiving portion 44 described above constitute a polymerization reaction characteristic measurement unit that measures the optical characteristics of the reaction liquid RL in the polymerization reaction tank 400 (in the convex portion 41). As will be described below, the polymerization reaction characteristic measurement unit measures characteristics based on chemical bonds in the depolymerization products such as BHET and the polymerization products such as PET contained in the reaction liquid RL. More specifically, the polymerization reaction characteristic measurement unit measures characteristics based on chemical bonds common to the depolymerization products such as BHET and the polymerization products such as PET contained in the reaction liquid RL.

[0093] Figure 13 schematically shows the chemical bonds and vibrational modes common to BHET as a depolymerized polymer and PET as a polymer contained in the reaction solution RL. Note that the chemical bonds and vibrational modes shown in this figure are merely examples, and other chemical bonds and vibrational modes not shown in this figure may also be considered. Figure 13 exemplifies the following six types of chemical bonds / vibrational modes: out-of-plane bending vibration of the C-H bond in the benzene ring (C-H out-of-plane bending vibration), stretching vibration of the C-H bond in the benzene ring (C-H stretching vibration), stretching vibration of the C-H bond in the alkylene group (C-H stretching vibration), stretching vibration of the O-H bond (O-H stretching vibration), stretching vibration of the C-O-C bond (C-O-C stretching vibration), and stretching vibration of the C=O bond (C=O stretching vibration). Note that only some of these chemical bonds / vibrational modes are highlighted in Figure 13 (for example, BHET has two C=O bonds, but only one is highlighted).

[0094] When a measurement light ML such as infrared light is irradiated onto molecules (BHET or PET) having the above-described various chemical bonds / vibration modes, energy at wavelengths or frequencies corresponding to the vibrations is selectively absorbed. FIG. 14 shows examples of absorbance at each wavelength measured when infrared light is irradiated onto a BHET reagent (top row) and a PET reagent (bottom row) with a predetermined degree of polymerization n (n is a sufficiently large natural number). Specifically, an infrared light was irradiated onto the BHET reagent and the PET reagent using a light-emitting element similar to the light-emitting element 43 in FIG. 12B, and the infrared light that passed through the BHET reagent and the PET reagent (i.e., the transmitted light) was detected using a light-receiving element similar to the light-receiving element 44 in FIG. 12B. Here, the intensity of the infrared light irradiated onto the BHET reagent and the PET reagent by the light-emitting element is represented by I. ０ The transmittance I / I is calculated as follows: ０ is expressed as A = -log 10 This is converted into absorbance A by "(I / I0)". Figure 14 shows the results of measuring such absorbance A while continuously changing the wavelength of the infrared light. This method is known as infrared spectroscopy.

[0095] As shown schematically in Figure 14, the absorbance measurement results for the BHET reagent and the PET reagent, which share the same chemical bond / vibration mode as described above, show peaks at the wavelengths or wavelength ranges common to the chemical bond / vibration mode. In the example of Figure 14, the following peaks appear in the wavelength range common to the BHET reagent and the PET reagent, in order from shortest wavelength to longest: O-H stretching vibration (approximately 2-4 μm), C-H stretching vibration in an alkylene group (approximately 2-5 μm), C=O stretching vibration (approximately 4-8 μm), C-H stretching vibration in a benzene ring (approximately 5-8 μm), C-O-C stretching vibration (approximately 9-14 μm), and C-H out-of-plane bending vibration in a benzene ring (approximately 12-16 μm).

[0096] However, even if the BHET and PET reagents share a common chemical bond / vibration mode, differences in the number of chemical bonds or the surrounding chemical structure will result in differences in the measured absorbance peak height or peak area (the integral of the absorbance over the wavelength range near the peak).

[0097] For example, BHET has two O-H bonds at both ends of a relatively short chemical structure, whereas PET has two O-H bonds at both ends of a relatively long chemical structure, as shown in Figure 13. As such, differences in the chemical structures surrounding the O-H bonds between BHET and PET result in significant differences in the peak height or area of ​​absorbance for the O-H stretching vibration.

[0098] As shown in Figure 13, BHET has two alkylene groups ((CH2)2), while PET has n. As such, differences between BHET and PET in the number of alkylene groups and / or the surrounding (left and right) chemical structures result in significant differences in the peak height or area of ​​absorbance for the C-H stretching vibrations in the alkylene groups.

[0099] As shown in Figure 13, BHET has two C=O bonds, while PET has 2n C=O bonds. Thus, because BHET and PET differ in the number of C=O bonds and / or the surrounding chemical structures (on both the left and right sides), significant differences appear in the peak heights or areas of absorbance for the C=O stretching vibration.

[0100] As shown in Figure 13, BHET has one benzene ring, while PET has n benzene rings. As such, BHET and PET differ in the number of benzene rings and / or the surrounding chemical structure (on both the left and right sides), which results in significant differences in the peak height or area of ​​absorbance for the C-H stretching vibration of the benzene ring.

[0101] As shown in Figure 13, BHET has two C-O-C bonds, while PET has n+1. As such, there are differences between BHET and PET in the number of C-O-C bonds and / or the chemical structure around them (on both the left and right sides), which results in significant differences in the peak height or area of ​​absorbance for the C-O-C stretching vibration.

[0102] As shown in Figure 13, BHET has one benzene ring, while PET has n benzene rings. As such, differences in the number of benzene rings and / or the surrounding (left and right) chemical structures between BHET and PET result in significant differences in the peak height or area of ​​absorbance for the C-H out-of-plane bending vibration of the benzene ring.

[0103] Here, the phenomenon of C-H out-of-plane bending vibration in each benzene ring is not easily affected by differences in the surrounding chemical structures and occurs stably. Therefore, by using the peak height or peak area of ​​absorbance for C-H out-of-plane bending vibration as a common standard for BHET and PET, the differences between BHET and PET regarding other peaks can be made apparent in a comparable manner. In other words, the polymerization reaction characteristic measurement unit according to this embodiment measures a reference characteristic based on the C-H out-of-plane bending vibration in the benzene ring and then measures a characteristic (e.g., a peak area in absorbance) based on a chemical bond / vibration mode common to the reference characteristic.

[0104] The reference characteristic is not limited to that based on the C-H out-of-plane bending vibration of the benzene ring. For example, a substance other than the reaction solution RL may be placed in the polymerization reaction vessel 400, and the peak derived from this substance may be used as the reference peak. Such a substance is preferably one that is not involved in the polymerization reaction occurring in the polymerization reaction vessel 400 and that exhibits an absorbance peak at a wavelength or wavelength range different from the peaks corresponding to the chemical bond / vibration modes of BHET and PET shown in FIG. 14 .

[0105] FIG. 14 shows the measurement results after normalization or standardization of the C-H out-of-plane bending vibration. In this figure, the absorbance peak height or peak area for the C-H out-of-plane bending vibration is adjusted to the same value (hereinafter, for example, "1") for BHET and PET. The peak areas corresponding to vibrations other than the C-H out-of-plane bending vibration (in the example of FIG. 14, the O-H stretching vibration, the C-H stretching vibration in the alkylene group, the C=O stretching vibration, the C-H stretching vibration in the benzene ring, and the C-O-C stretching vibration) are obtained as relative values ​​to the reference characteristic value of "1" for the C-H out-of-plane bending vibration. As shown in the figure, the peak areas corresponding to vibrations other than the C-H out-of-plane bending vibration are significantly different between BHET and PET.

[0106] As described above, when the peak areas corresponding to vibrations other than the C-H out-of-plane bending vibration are measured after normalization or standardization using a reference characteristic value for the C-H out-of-plane bending vibration, significant differences are obtained between BHET and PET. Based on this principle, when the peak areas corresponding to vibrations other than the C-H out-of-plane bending vibration (which is also normalized or standardized) are measured for a polymerization reaction reaction liquid RL, which is a mixture of BHET and PET, a value corresponding to the ratio of depolymerized polymer (BHET) to polymer (PET) contained in the reaction liquid RL is obtained. Since the ratio of depolymerized polymer (BHET) to polymer (PET) contained in the reaction liquid RL indicates the progress of the polymerization reaction occurring in the polymerization reactor 400, the polymerization reaction monitoring device 40 according to this embodiment can grasp the progress of the polymerization reaction in the polymerization reactor 400 by measuring at least one peak area over a predetermined wavelength range, as shown in FIG. 14 .

[0107] 12B, a light-emitting unit 43 sequentially irradiates a reaction liquid RL with measurement light ML such as infrared light while, for example, continuously changing the wavelength. A light-receiving unit 44 sequentially detects the measurement light ML irradiated onto the reaction liquid RL by the light-emitting unit 43. A polymerization reaction progress monitoring unit 45 shown in FIG. 12B detects the intensity I and transmittance I / I of the measurement light ML at each wavelength detected by the light-receiving unit 44. ０is converted to absorbance A as described above. As a result, an absorbance spectrum over a predetermined wavelength range is obtained, as shown in Fig. 14. However, since the reaction liquid RL to be measured is a mixture of a depolymerized substance such as BHET and a polymerized substance such as PET, a single spectrum is obtained in which the BHET spectrum in the upper part of Fig. 14 and the PET spectrum in the lower part of Fig. 14 are "mixed" according to their ratio (i.e., the degree of progress of the polymerization reaction).

[0108] In this spectrum, the polymerization reaction progress monitor 45 normalizes or standardizes the reference characteristic (e.g., peak area) based on the C-H out-of-plane bending vibration in the benzene ring to a reference characteristic value such as "1." As a result, each peak area corresponding to each vibration other than the C-H out-of-plane bending vibration (e.g., O-H stretching vibration, C-H stretching vibration in an alkylene group, C=O stretching vibration, C-H stretching vibration in a benzene ring, and C-O-C stretching vibration) is obtained as a relative value relative to the reference characteristic value "1" for the C-H out-of-plane bending vibration. As described above, each of these peak values ​​represents the ratio of depolymerized polymer (BHET) to polymer (PET) contained in the reaction liquid RL, and thus represents the progress of the polymerization reaction occurring in the polymerization reaction tank 400. In this way, the polymerization reaction progress monitor 45 can efficiently monitor the progress of the polymerization reaction in the polymerization reaction tank 400. In the above example, we focused on peaks corresponding to chemical bonds / vibration modes common to BHET and PET. However, if there is a chemical bond / vibration mode that exists only in one of the depolymerization products such as BHET and the polymerization product such as PET, the progress of the polymerization reaction can be similarly understood by focusing on the corresponding peak.

[0109] Figure 15 shows experimental results showing that each peak area represents the progress of the polymerization reaction. In these experiments, the polymerization reaction was carried out in the polymerization reactor 400, and the peak areas were measured using the polymerization reaction characteristic measurement unit (protrusion 41, measurement window 42, light-emitting unit 43, light-receiving unit 44, etc.). The measured peak areas are plotted along the vertical axis as a percentage (area ratio), with the initial value at the start of the polymerization reaction being "100." In this experiment, the amount of EG (see Figure 2) produced by the polymerization reaction was measured as data representing the progress of the polymerization reaction (the amount of EG was not measured when measuring the actual reaction solution RL). In Figure 15, the conversion rate to EG by the polymerization reaction or the progress of the polymerization reaction is plotted along the horizontal axis. At the start of the polymerization reaction, the conversion rate on the horizontal axis is "0%," and the area ratio on the vertical axis is "100%."

[0110] FIG. 15A shows the experimental results for the peak area corresponding to O-H stretching vibration (the area of ​​the leftmost peak in FIG. 14 ), and FIG. 15B shows the experimental results for the peak area corresponding to C-H stretching vibration in an alkylene group (the area of ​​the second peak from the left in FIG. 14 ). In both experimental results, it can be seen that the peak area ratio decreases monotonically (particularly linearly in the example of FIG. 15 ) (there is a negative correlation) from "100%" at the start of the polymerization reaction as the conversion rate increases (i.e., as the polymerization reaction progresses). As such, it was confirmed that the peak areas corresponding to O-H stretching vibration and C-H stretching vibration in an alkylene group represent the progress of the polymerization reaction. Although not shown, it was also confirmed that the peak areas corresponding to C═O stretching vibration, C-H stretching vibration in a benzene ring, and C-O-C stretching vibration similarly represent the progress of the polymerization reaction. However, as a result of experiments, it was confirmed that the peak areas corresponding to the two illustrated vibrations particularly well represent the progress of the polymerization reaction, and therefore, when it is necessary to narrow down the peak areas to be measured to a small number, it is preferable to preferentially select the peak area corresponding to either of the two illustrated vibrations.

[0111] According to the polymerization reaction monitoring device 40 or the polymerization reaction progress monitoring unit 45 of this embodiment as described above, the progress of the polymerization reaction in the polymerization reaction tank 400 can be efficiently monitored by measuring the characteristics of the reaction liquid RL (e.g., the area of ​​each peak corresponding to each chemical bond / vibration mode) using the polymerization reaction characteristic measurement unit (e.g., the convex portion 41, the measurement window 42, the light-emitting unit 43, the light-receiving unit 44, etc.). Because there is no need to sample the reaction liquid RL, which is the measurement target in the polymerization reaction tank 400, from the polymerization reaction tank 400, the progress of the polymerization reaction can be monitored continuously in real time. Furthermore, because there is no need to stop the polymerization reaction in the polymerization reaction tank 400 during measurement by the polymerization reaction characteristic measurement unit, the operating efficiency of the chemical recycling apparatus 100 can be maintained at a high level.

[0112] 1 , the supply of the polymer synthesized in the polymerization reaction tank 400 to the downstream by-product removal apparatus 500 may be temporarily stopped until the degree of progress of the polymerization reaction in the polymerization reaction tank 400 monitored by the polymerization reaction progress monitoring unit 45 reaches a desired value. The reaction liquid RL containing the polymer temporarily retained in this manner may be retained in a pipe or buffer tank 430 provided between the polymerization reaction tank 400 and the by-product removal apparatus 500, or may be refluxed into the polymerization reaction tank 400 to further progress the polymerization reaction. Furthermore, a polymer supply control valve (not shown) may be provided between the polymerization reaction tank 400 and the by-product removal apparatus 500. The valve opens to allow the supply of polymer to the by-product removal apparatus 500 when the degree of progress of the polymerization reaction in the polymerization reaction tank 400 monitored by the polymerization reaction progress monitoring unit 45 reaches a desired value, and closes to stop the supply of polymer to the by-product removal apparatus 500 when the degree of progress of the polymerization reaction in the polymerization reaction tank 400 monitored by the polymerization reaction progress monitoring unit 45 falls below the desired value.

[0113] Comparing the above-described embodiments, the depolymerization reaction characteristic measurement unit 33 described with reference to FIG. 4 and the polymerization reaction characteristic measurement unit (e.g., convex portion 41, measurement window 42, light-emitting portion 43, light-receiving portion 44) described with reference to FIG. 12 measure different characteristics using different principles and methods. In this manner, by individually selecting a principle and method suitable for monitoring the progress of the depolymerization reaction in the depolymerization reaction tank 300 and the polymerization reaction in the polymerization reaction tank 400, the efficiency of monitoring each reaction can be improved. For example, in the depolymerization reaction in the depolymerization reaction tank 300, solid components such as PET are present as shown in FIG. 4 and the like, and therefore it was necessary to provide an intrusion prevention unit 34 or the like to exclude the solid components from the measurement target. In contrast, in the polymerization reaction in the polymerization reaction tank 400, both the reactant BHET and the product PET (present as an oligomer with a relatively low degree of polymerization) are generally liquid, and therefore the intrusion prevention unit 34 or the like shown in FIG. 4 and the like is not necessary, and the reaction liquid RL in the polymerization reaction tank 400 can be directly measured as shown in FIG. 12.

[0114] The present disclosure has been described above based on the embodiments. Various modifications are possible to the combinations of the components and processes in the exemplary embodiments, and it will be obvious to those skilled in the art that such modifications are included within the scope of the present disclosure.

[0115] In the embodiment of the polymerization reaction monitoring device 40 shown in Figures 11 and 12, infrared light is primarily used as the measurement light ML, but the measurement light ML may be light or electromagnetic waves (light in a broad sense) of any wavelength, not limited to infrared light. The optical measurement method is also not limited to the infrared spectroscopy described as an example, and any method including Raman spectroscopy and ultraviolet-visible spectroscopy can be used. Furthermore, although this embodiment illustrates an optical measurement method using the measurement light ML, any measurement method based on any principle that can measure any characteristic of the reaction liquid RL of a polymerization reaction noninvasively and / or noncontactly can be used.

[0116] The configuration, operation, and function of each device and method described in the embodiments can be realized by hardware resources, software resources, or a combination of hardware and software resources. Examples of hardware resources include processors, ROM, RAM, and various integrated circuits. Examples of software resources include operating systems, applications, and other programs.

[0117] The present disclosure relates to reaction monitoring devices and the like.

[0118] REFERENCE SIGNS LIST 1 Injection molding machine, 30 Depolymerization reaction monitoring device, 40 Polymerization reaction monitoring device, 41 Convex portion, 42 Measurement window, 43 Light-emitting portion, 44 Light-receiving portion, 45 Polymerization reaction progress monitoring portion, 100 Chemical recycling device, 300 Depolymerization reaction tank, 400 Polymerization reaction tank, 421 First measurement window, 422 Second measurement window.

Claims

1. A reaction monitoring device comprising: a polymerization reaction tank for synthesizing a depolymerization product of polyester into a polymer through a polymerization reaction; a polymerization reaction characteristic measuring unit for measuring characteristics of a reaction liquid of the polymerization reaction containing the depolymerization product and the polymer; and a polymerization reaction progress monitoring unit for monitoring the progress of the polymerization reaction based on the characteristics of the reaction liquid measured by the polymerization reaction characteristic measuring unit.

2. The reaction monitoring device according to claim 1, wherein the polymerization reaction characteristic measuring section measures characteristics based on chemical bonds in the depolymerization product and the polymer contained in the reaction liquid.

3. The reaction monitoring device according to claim 2, wherein the polymerization reaction characteristic measuring section measures a characteristic based on a chemical bond common to the depolymerization product and the polymer contained in the reaction liquid.

4. The reaction monitoring device of claim 3, wherein the characteristic based on the common chemical bond varies depending on the ratio of the depolymerization and the polymerization contained in the reaction solution.

5. The reaction monitoring device according to claim 4, wherein the depolymerization product and the polymer have a benzene ring, and the polymerization reaction characteristic measurement unit measures a reference characteristic based on a C-H out-of-plane bending vibration in the benzene ring, and measures a characteristic based on the common chemical bond with respect to the reference characteristic.

6. The reaction monitoring device of claim 5, wherein the characteristic based on the common chemical bond is at least one of a characteristic based on C-H stretching vibration in a benzene ring, a characteristic based on C-H stretching vibration in an alkylene group, a characteristic based on O-H stretching vibration, a characteristic based on C-O-C stretching vibration, and a characteristic based on C=O stretching vibration.

7. A reaction monitoring device according to any one of claims 1 to 6, wherein the polymerization reaction characteristic measuring section measures optical characteristics of the reaction liquid.

8. The reaction monitoring device described in claim 7, wherein the polymerization reaction characteristic measuring unit comprises: a measurement window provided in the polymerization reaction tank for transmitting at least a portion of the measurement light used to measure the optical characteristics; a light emitting unit for irradiating the measurement light into the polymerization reaction tank through the measurement window; and a light receiving unit for receiving the measurement light irradiated to the reaction liquid in the polymerization reaction tank through the measurement window.

9. The reaction monitoring device described in claim 8, wherein the polymerization reaction tank has a convex portion protruding outward, the measurement window is provided on at least opposing sides of the convex portion, the light-emitting portion irradiates the measurement light through one of the opposing sides, and the light-receiving portion receives the measurement light through the other opposing side.

10. The reaction monitoring device of claim 9, wherein the measurement window comprises a first measurement window provided on one of the opposing sides and a second measurement window provided on the other of the opposing sides, the light emitting unit irradiates the measurement light through the first measurement window, and the light receiving unit receives the measurement light through the second measurement window.

11. The reaction monitor of claim 8, wherein said measurement window comprises calcium fluoride.

12. The reaction monitoring device according to claim 8, wherein the measurement light is infrared light.

13. The reaction monitor of any of claims 1 to 6, wherein the polyester is polyethylene terephthalate and the depolymerization product is bis(2-hydroxyethyl) terephthalate.

14. A reaction monitoring device as described in any one of claims 1 to 6, comprising: a depolymerization reaction tank in which a depolymerization reaction occurs by using a depolymerization agent to decompose polyester into the depolymerized polymer; a depolymerization reaction characteristic measuring unit in the depolymerization reaction tank that measures characteristics of the depolymerization agent in which the depolymerized polymer has been dissolved; and a depolymerization reaction progress monitoring unit that monitors the progress of the depolymerization reaction based on the characteristics of the depolymerization agent measured by the depolymerization reaction characteristic measuring unit.

15. The reaction monitoring device according to claim 14, wherein the polymerization reaction characteristic measuring section and the depolymerization reaction characteristic measuring section measure different characteristics from each other.

16. A reaction monitoring device comprising: a depolymerization reaction tank in which a depolymerization reaction occurs by using a depolymerization agent to decompose polyester into depolymers; a depolymerization reaction characteristic measuring unit that measures characteristics of the depolymerization agent in which the depolymerization agent is dissolved in the depolymerization reaction tank; a depolymerization reaction progress monitoring unit that monitors the progress of the depolymerization reaction based on the characteristics of the depolymerization agent measured by the depolymerization reaction characteristic measuring unit; a polymerization reaction tank in which the depolymerization agent is synthesized into a polymer by a polymerization reaction; a polymerization reaction characteristic measuring unit that measures characteristics of a reaction liquid of the polymerization reaction containing the depolymerization agent and the polymer; and a polymerization reaction progress monitoring unit that monitors the progress of the polymerization reaction based on the characteristics of the reaction liquid measured by the polymerization reaction characteristic measuring unit, wherein the polymerization reaction characteristic measuring unit and the depolymerization reaction characteristic measuring unit measure different characteristics from each other.

17. A reaction monitoring method comprising: synthesizing a depolymerization product of a polyester into a polymer through a polymerization reaction in a polymerization reaction tank; measuring characteristics of a reaction liquid of the polymerization reaction containing the depolymerization product and the polymer; and monitoring the progress of the polymerization reaction based on the measured characteristics of the reaction liquid.

18. A reaction monitoring program that causes a computer to execute the steps of: synthesizing a depolymerization product of a polyester into a polymer through a polymerization reaction in a polymerization reaction tank; measuring the properties of a reaction liquid of the polymerization reaction that contains the depolymerization product and the polymer; and monitoring the progress of the polymerization reaction based on the measured properties of the reaction liquid.

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