Separation system, control device, separation method and program

Abstract

Properly separate the polyester from the plant fibers. [Solution] A separation system comprising: a dissolution unit that receives a monomer derived from a carboxylic acid and a polyester raw material including polyester and plant fibers to produce a solution in which polyester is dissolved in the monomer; a detection unit that detects the temperature of the solution; and a control unit that controls dissolution conditions, including a processing time which is the time since the polyester raw material and monomer were supplied to the dissolution unit and the temperature of the solution, such that the index R0 shown in the following formula (1) is 2 or more and less than 4.5.

Description

Technical Field

[0001] The present disclosure relates to a separation system, a control device, a separation method, and a program.

Background Art

[0002] For example, in order to recycle polyester, a technique for separating impurities from polyester is known. Patent Document 1 describes that polyethylene terephthalate (PET) waste is put into ethylene glycol (EG) for depolymerization to obtain bis(β-hydroxyethyl) terephthalate (BHET), and that foreign substances other than PET are removed by a filter during or after the depolymerization reaction.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Here, the object to be recycled may contain vegetable fibers in addition to polyester. In this case, in order to appropriately recycle polyester or reuse vegetable fibers, it is required to appropriately separate polyester and vegetable fibers.

[0005] The present disclosure solves the above-described problems, and an object thereof is to provide a separation system, a control device, a separation method, and a program that appropriately separate polyester and vegetable fibers.

Means for Solving the Problems

[0006] To solve the above-mentioned problems and achieve the objective, the separation system according to this disclosure includes: a dissolution unit to which monomers derived from carboxylic acids and polyester raw materials including polyester and plant fibers are supplied to produce a solution in which the polyester is dissolved in the monomers; a detection unit to detect the temperature of the solution; and a control unit to control dissolution conditions, including a processing time which is the time since the polyester raw materials and monomers were supplied to the dissolution unit and the temperature of the solution, such that the index R0 shown in the following formula (1) is 2 or more and less than 4.5. R0=Log(t·exp[(T-100) / 14.75]) ···(1) However, t refers to the processing time (min), and T refers to the temperature of the dissolving solution (°C).

[0007] To solve the above-mentioned problems and achieve the objective, the control device according to this disclosure includes an information acquisition unit that acquires the temperature of a solution in which polyester contained in a polyester raw material including polyester and plant fibers is dissolved in a monomer derived from a carboxylic acid, and a processing time which is the time since the polyester raw material and the monomer were supplied to the dissolution unit, and a system control unit that controls dissolution conditions, including the processing time and the temperature of the dissolution solution, such that the index R0 shown in the following formula (1) is 2 or more and less than 4.5. R0=Log(t·exp[(T-100) / 14.75]) ···(1) However, t refers to the processing time (min), and T refers to the temperature of the dissolving solution (°C).

[0008] To solve the above-mentioned problems and achieve the objective, the separation method according to the present disclosure includes the steps of: supplying a monomer derived from a carboxylic acid and a polyester raw material including polyester and plant fibers to a dissolution unit to produce a solution in which the polyester is dissolved in the monomer; detecting the temperature of the solution; and controlling dissolution conditions, including a processing time which is the time since the polyester raw material and the monomer were supplied to the dissolution unit and the temperature of the solution, such that the index R0 shown in the following formula (1) is 2 or more and less than 4.5. R0=Log(t·exp[(T-100) / 14.75]) ···(1) However, t refers to the processing time (min), and T refers to the temperature of the dissolving solution (°C).

[0009] To solve the above-mentioned problems and achieve the objective, the program according to this disclosure causes a computer to perform the following steps: supplying a monomer derived from a carboxylic acid and a polyester raw material including polyester and plant fibers to a dissolution unit to generate a solution in which the polyester is dissolved in the monomer; detecting the temperature of the solution; and controlling dissolution conditions, including a processing time which is the time since the polyester raw material and the monomer were supplied to the dissolution unit and the temperature of the solution, such that the index R0 shown in the following formula (1) is 2 or more and less than 4.5. R0=Log(t·exp[(T-100) / 14.75]) ···(1) However, t refers to the processing time (min), and T refers to the temperature of the dissolving solution (°C). [Effects of the Invention]

[0010] According to this disclosure, polyester and plant fibers can be appropriately separated. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a schematic diagram of the polyester recycling process in an embodiment. [Figure 2] Figure 2 is a schematic diagram of the separation system according to the embodiment. [Figure 3] Figure 3 is a schematic block diagram of the control unit. [Figure 4] Figure 4 is a flowchart illustrating the control flow of the control unit. [Modes for carrying out the invention]

[0012] Preferred embodiments of the present invention will be described in detail below with reference to the attached drawings. However, the present invention is not limited to these embodiments, and if there are multiple embodiments, they may be constructed by combining these embodiments.

[0013] (Recycling process) Figure 1 is a schematic diagram of the polyester recycling process in this embodiment. In this embodiment, the polyester raw material Pm is depolymerized to monomerize it, and the monomer is repolymerized to recycle (regenerate) the polyester raw material Pm. Specifically, as shown in Figure 1, the polyester raw material Pm is flaked (step S100), the flaked polyester raw material Pm is dissolved in monomer D derived from a carboxylic acid to produce a polyester solution (step S101), foreign matter is removed from the solution (step S102), the solution from which foreign matter has been removed is mixed with reaction solvent M and depolymerized (step S103), the monomer of the depolymerized polyester is purified (separated) to produce monomer D derived from a carboxylic acid and monomer E of an alcohol component (step S104), monomer D is hydrolyzed to separate the reaction solvent M (step S106), and monomer F produced by the hydrolysis of monomer D and monomer E are polymerized (step S108) to regenerate the polyester raw material Pm. In addition, the recycling process employing the separation system 1 of this embodiment may omit the flake formation in step S100, or it may only involve recovering monomers D and E shown in steps S102 and S104, and monomer F shown in step S106, without performing the repolymerization process as in step S108.

[0014] (Polyester raw material) In this embodiment, the polyester raw material Pm to be depolymerized is a substance containing polyester and vegetable fiber. The polyester raw material Pm is not particularly limited. For example, waste products containing polyesters such as polyethylene terephthalate (PET), polyethylene butylene terephthalate (PEBT), polybutylene terephthalate (PBT), polycyclohexane dimethyl terephthalate (PCT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), and polycarbonate (PC) as polyester components can be mentioned. The vegetable fiber contained in the polyester raw material Pm refers to a fiber derived from plants, rather than a fiber derived from fossil fuels such as polyester. The polyester raw material Pm preferably contains at least one of cotton, hemp, rayon, polynosic, cupra, acetate, triacetate, and bromix as the vegetable fiber.

[0015] The polyester raw material Pm is not limited to those containing only polyester components and vegetable fibers, and may also contain components (impurities) other than polyester components and vegetable fibers. Examples of components other than polyester contained in the polyester raw material Pm include plastics other than polyester such as polyethylene, polystyrene, polypropylene, and polyvinyl chloride, metals, dyes, pigments, and polymerization catalysts. Examples of the polyester raw material Pm also include clothes in which polyester and other components are woven into fibers. In addition, the polyester raw material Pm may also include those in which vegetable fibers other than clothes are woven (for example, towels, bedding, other wearable items, etc.).

[0016] Hereinafter, components other than polyester contained in the polyester raw material Pm are referred to as impurities R. That is, in this embodiment, the impurity R is at least a substance containing vegetable fiber. When the polyester raw material Pm contains components other than polyester components and vegetable fibers, including the vegetable fiber and those components, they are called impurity R.

[0017] (Reaction solvent) The reaction solvent M is a solvent that reacts with the polyester to depolymerize the polyester. The reaction solvent M may be, for example, at least one of methanol, ethanol, water, and ethylene glycol.

[0018] (Monomer derived from carboxylic acid) The monomer D derived from carboxylic acid is a monomer having a carboxyl group, which is generated by the depolymerization reaction of the polyester. The monomer D may be, for example, dimethyl carboxylate or diethyl carboxylate. Further, the monomer D is preferably a monomer of terephthalic acid and may be, for example, dimethyl terephthalate (DMT).

[0019] (Monomer of alcohol component) The monomer E of the alcohol component is a monomer of the alcohol component, which is generated by the depolymerization reaction of the polyester. The monomer E may be, for example, a dihydroxy compound (dihydric alcohol), and further may be ethylene glycol (EG).

[0020] Hereinafter, the case where the polyester is PET, the reaction solvent M is methanol, the monomer D is DMT, and the monomer E is EG will be described as an example.

[0021] (Separation system) Figure 2 is a schematic diagram of the separation system according to the embodiment. The separation system 1 according to the embodiment is a system that monomerizes the polyester contained in the polyester raw material Pm to generate monomers D and E. As shown in Figure 2, the separation system 1 includes a raw material storage unit 10, a dissolution unit 12, a solid-liquid separation unit 13, a storage unit 20, a removal unit 26, a reaction solvent storage unit 14, a reaction unit 16, a separation unit 18, a control unit 30, and a detection unit 60.

[0022] (Raw material storage unit) The raw material storage section 10 is a tank into which polyester raw material Pm is introduced and stored. In this embodiment, flake-formed polyester raw material Pm is stored in the raw material storage section 10, but the shape and size of the polyester raw material Pm may be arbitrary. The raw material storage section 10 is connected to the dissolution section 12 via an introduction pipe 10a. The polyester raw material Pm in the raw material storage section 10 is supplied to the dissolution section 12 through the introduction pipe 10a. The introduction pipe 10a is provided with an adjustment section 10b that adjusts the amount of polyester raw material Pm supplied from the raw material storage section 10 to the dissolution section 12. The adjustment section 10b is, for example, an on-off valve, which, when open, allows the supply of polyester raw material Pm in the raw material storage section 10 to the dissolution section 12, and when closed, stops the supply of polyester raw material Pm from the raw material storage section 10 to the dissolution section 12. However, the adjustment section 10b is not limited to an on-off valve, and may be any mechanism capable of adjusting the supply of polyester raw material Pm to the dissolution section 12. Alternatively, the polyester raw material Pm may be supplied directly to the dissolution section 12 without passing through the raw material storage section 10, the introduction pipe 10a, and the adjustment section 10b.

[0023] The raw material storage section 10 may also be equipped with a cutting machine for cutting the polyester raw material Pm. In this case, the polyester raw material Pm is introduced into the raw material storage section 10 and cut by a cutting machine (not shown) provided in the raw material storage section 10. Preferably, the cutting machine cuts the polyester raw material Pm so that the length of the cut polyester raw material Pm (e.g., clothing) is 10 cm or more. The length of the polyester raw material Pm here refers to the length of the longest part of any straight line connecting the surfaces of the cut polyester raw material Pm. That is, for example, when cutting the polyester raw material Pm into a rectangle, the length of the polyester raw material Pm may be the length of the diagonal. The cutting machine may cut the polyester raw material Pm into any shape with a length of 10 cm or more. Also, the cutting machine cuts the polyester raw material Pm so that the area of ​​1 cm² 2 It is preferable to cut it so that it is 100cm or larger. 2It is more preferable to cut the material in the manner described above. Note that the cutting machine is not limited to being located in the raw material storage section 10, but may be located at a different location from the raw material storage section 10.

[0024] (melting part) The dissolution section 12 is a tank in which the dissolving solution Pd is stored. The dissolving solution Pd is a solution produced by mixing polyester raw material Pm and monomer D. Here, the polyester contained in the polyester raw material Pm dissolves in monomer D, but impurities R, which are components other than polyester contained in the polyester raw material Pm, remain without dissolving in monomer D. Therefore, it can be said that the dissolving solution Pd contains polyester solution P, in which the polyester contained in the polyester raw material Pm is dissolved in monomer D, and impurities R contained in the polyester raw material Pm.

[0025] Monomer D and polyester raw material Pm are supplied to the dissolution section 12. Within the dissolution section 12, the polyester contained in the polyester raw material Pm dissolves in the monomer D, while the impurity R remains undissolved in the monomer D, thereby generating a polyester solution P and a dissolution solution Pd containing the impurity R. Dissolving the polyester in the monomer D in this way reduces viscosity and improves fluidity, allowing the polyester to be easily introduced to the reaction section 16. Note that the polyester solution P is not limited to a state where the entire amount of polyester is dissolved in the monomer D; at least some of the polyester may remain undissolved in the monomer D. Furthermore, if there are components other than polyester contained in the polyester raw material Pm that are soluble in the monomer D, the polyester solution P may also contain those components dissolved in the monomer D.

[0026] In this embodiment, the dissolution section 12 is provided with a heating section 12A. The heating section 12A heats the inside of the dissolution section 12, thereby heating the monomer D and polyester raw material Pm supplied to the dissolution section 12 to a predetermined temperature. The predetermined temperature is the temperature at which polyester can dissolve in monomer D. By heating to this predetermined temperature, the polyester contained in the polyester raw material Pm can be appropriately dissolved in monomer D. In other words, the heating section 12A heats the monomer D and polyester raw material Pm supplied to the dissolution section 12 to a predetermined temperature, thereby generating a dissolution solution Pd within the dissolution section 12. That is, the predetermined temperature can also be said to be the temperature of the dissolution solution Pd. The temperature of the dissolution solution Pd (predetermined temperature) is preferably 140°C to 300°C, more preferably 160°C to 280°C, and even more preferably 170°C to 200°C. Note that impurities R may include components that melt when the dissolution solution Pd is heated to the above temperature (predetermined temperature). Therefore, if the impurity R contains components that melt when heated to a predetermined temperature, a portion of it will be contained in the dissolution solution Pd in ​​a molten state. In this embodiment, the heating section 12A is provided in the dissolution section 12, but the position where the heating section 12A is provided is not limited to that and is arbitrary.

[0027] (Detection unit) The detection unit 60 is a sensor provided in the dissolution unit 12. The detection unit 60 includes, for example, a temperature sensor that detects the temperature of the dissolution solution Pd in ​​the dissolution unit 12. In this case, the detection unit 60 as a temperature sensor is provided in a position where it can detect the temperature of the monomer D in the dissolution unit 12. The detection unit 60 may also include a timer that measures time. The detection unit 60 as a timer detects, for example, the processing time, which is the time elapsed since both the polyester raw material Pm and the monomer D were supplied to the dissolution unit 12. The detection unit 60 may be implemented by a temperature sensor with a timer function, or by providing a temperature sensor and a timer separately.

[0028] (Solid-liquid separation section) The solid-liquid separation unit 13 is located in the dissolution unit 12. The solid-liquid separation unit 13 collects solid impurities R contained in the dissolution liquid Pd stored in the dissolution unit 12 and separates the solid impurities R from the dissolution liquid Pd. The solid-liquid separation unit 13 is a mesh-shaped filter through which liquid passes and which collects solids. In this embodiment, the solid-liquid separation unit 13 is a container shape with an open top and is located at a predetermined distance from the sides and bottom of the dissolution unit 12. The solid-liquid separation unit 13 is located downstream of the inlet pipe 10a and the supply pipe to which monomer D is supplied, and upstream of the inlet pipe 12a that supplies the dissolution liquid Pd from the dissolution unit 12 to the storage unit 20 downstream. The dissolution liquid Pd flowing from the dissolution unit 12 into the inlet pipe 12a passes through the solid-liquid separation unit 13. As a result, the solid-liquid separation unit 13 collects solids larger than the opening diameter of the mesh. The solid-liquid separation section 13 preferably has a mesh opening diameter of 1 mm or more and 50 mm or less.

[0029] In this embodiment, the solid-liquid separation unit 13 uses a mesh-shaped filter for filtration, but is not limited to this. The solid-liquid separation unit 13 may also separate impurities R from the dissolving solution Pd by centrifugal separation, which stirs the inside of the dissolving unit 12 around a predetermined axis and moves the impurities radially outward from the axis of rotation. The solid-liquid separation unit 13 is not limited to filtration or centrifugal separation, as long as it can separate solid impurities of a predetermined size or larger from the dissolving solution Pd.

[0030] The foreign matter recovery unit 50 recovers solid impurities collected by the solid-liquid separation unit 13. The foreign matter recovery unit 50 recovers impurities attached to the filter of the solid-liquid separation unit 13, for example. The solid-liquid separation unit 13 may also be equipped with a press device that presses impurities attached to the mesh-shaped filter against the filter and squeezes out the dissolving liquid Pd contained in the impurities. By squeezing out the dissolving liquid with the press device before the foreign matter recovery unit 50 recovers the impurities, more dissolving liquid Pd can be left in the separation system 1. When the solid-liquid separation unit 13 separates by centrifugal separation, the foreign matter recovery unit 50 recovers impurities from the area where impurities are stored by centrifugal separation.

[0031] Furthermore, the foreign matter recovery unit 50 can also supply reaction solvent M (e.g., methanol) to the dissolution unit 12 after the dissolution liquid Pd has been discharged from the dissolution unit 12, wash the remaining material (waste clothing, etc.) in the dissolution unit 12, and dissolve and recover monomer D (e.g., DMT) attached to the remaining material in reaction solvent M. Then, for example, monomer D may be recovered by distillation separation of the reaction solvent M and monomer D in the recovered monomer D solution. The material remaining in the dissolution unit 12 refers to impurities R (e.g., metal buttons, plant fibers, etc.) that were contained in the polyester raw material Pm (e.g., clothing). Of the impurities R, plant fibers may be reused. For example, washed cotton can be used as raw material for recycled cotton yarn. Other washed impurities R (e.g., metal buttons, etc.) may be disposed of appropriately or reused.

[0032] (Storage section) The storage section 20 is a tank in which the dissolving solution Pd is stored. The storage section 20 is connected to the dissolving section 12 via an inlet pipe 12a. The dissolving solution Pd in ​​the dissolving section 12 is supplied to the storage section 20 through the inlet pipe 12a. The inlet pipe 12a is provided with an adjustment section 12a1 that adjusts the amount of dissolving solution Pd supplied from the dissolving section 12 to the storage section 20. The adjustment section 12a1 is, for example, an on-off valve, which, when open, allows the dissolving solution Pd in ​​the dissolving section 12 to be supplied to the storage section 20, and when closed, stops the supply of dissolving solution Pd from the dissolving section 12 to the storage section 20. However, the adjustment section 12a1 is not limited to an on-off valve, and may be any mechanism capable of adjusting the supply of dissolving solution Pd to the storage section 20. In this embodiment, the storage unit 20 is connected to the dissolution unit 12 via the introduction pipe 12a, but a temporary storage unit for temporarily storing the dissolving solution Pd can also be provided between the dissolution unit 12 and the storage unit 20.

[0033] In the storage section 20, the dissolving solution Pd is separated by gravity into the polyester solution P and impurities R. Here, the impurities R separated in the storage section 20 are impurities that were not recovered in the solid-liquid separation section 13 and moved to the storage section 20 together with the dissolving solution Pd. In this embodiment, the dissolving solution Pd stored in the storage section 20 is allowed to stand, and is separated by gravity into the polyester solution P and impurities R.

[0034] In this embodiment, the dissolution Pd stored in the storage section 20 is separated by gravity into a layer of first impurity R1, a layer of polyester solution P, and a layer of second impurity R2. The layer of first impurity R1 is formed vertically below the layer of polyester solution P. That is, first impurity R1 is an impurity R that does not dissolve in monomer D and has a higher specific gravity than polyester solution P. First impurity R1 settles in the polyester solution P within the storage section 20 to form the layer of first impurity R1. On the other hand, the layer of second impurity R2 is formed vertically above the layer of polyester solution P. That is, second impurity R2 is an impurity R that does not dissolve in monomer D and has a lower specific gravity than polyester solution P. Second impurity R2 floats in the polyester solution P within the storage section 20 to form the layer of second impurity R2.

[0035] Furthermore, the dissolving solution Pd in ​​the storage section 20 is maintained at a predetermined temperature (the temperature at which polyester can dissolve in monomer D). The first impurity R1 and the second impurity R2 are components of impurity R that melt when heated to the predetermined temperature, and therefore exist in a molten state in the storage section 20. The first impurity R1 and the second impurity R2 are, for example, plastics other than polyester (such as polyethylene other than polyester, polystyrene, polypropylene, polyvinyl chloride, etc.).

[0036] In this embodiment, the polyester solution P layer contains a third impurity R3. The third impurity R3 is a component of impurity R that does not dissolve in monomer D and does not melt even at a predetermined temperature (the temperature at which polyester can dissolve in monomer D). That is, the third impurity R3 is not separated from the polyester solution P by gravity separation and exists in the polyester solution P in an insoluble solid state. In this embodiment, the third impurity R3 is dispersed in the polyester solution P. The third impurity R3 is, for example, a dye, a pigment, and a polymerization catalyst.

[0037] (Discharge section) The discharge section 22 is a mechanism for discharging impurities R separated from the polyester solution P in the storage section 20 to the outside of the storage section 20. The configuration of the discharge section 22 may be arbitrary, but in this embodiment, the discharge section 22 has a first discharge section 22a and second discharge sections 22b1 and 22b2.

[0038] The first discharge section 22a discharges the first impurity R1 from the storage section 20. In this embodiment, the first discharge section 22a is provided in a discharge pipe 20a connected to the storage section 20. The discharge pipe 20a is a pipe for discharging the first impurity R1, which has been separated to a lower layer from the polyester solution P, from the storage section 20. The discharge pipe 20a is connected to a position in the storage section 20 where the layer of the first impurity R1 is formed, and in this embodiment, it is connected to the bottom of the storage section 20. The discharge pipe 20a is provided with the first discharge section 22a. The first discharge section 22a is a mechanism for discharging the first impurity R1 from the storage section 20, and in this embodiment, it is a pump.

[0039] The second discharge sections 22b1 and 22b2 discharge the second impurity R2 from the storage section 20. The storage section 20 is connected to a discharge pipe 20b, which is provided with the second discharge section 22b2. The discharge pipe 20b is a pipe for discharging the second impurity R2, which has been separated to the upper layer above the polyester solution P, from the storage section 20. The discharge pipe 20b is connected to the position where the layer of second impurity R2 in the storage section 20 is formed, and is connected vertically above the discharge pipe 20a. In this embodiment, the second discharge section 22b1 is a skimmer provided at the liquid surface of the polyester solution P, which recovers (scrapes off) the second impurity R2 floating on the liquid surface of the polyester solution P. The second discharge section 22b2 is provided on the discharge pipe 20b and is a mechanism for discharging the second impurity R2 recovered in the second discharge section 22b1 via the discharge pipe 20b, and in this embodiment it is a pump. Thus, in this embodiment, second discharge sections 22b1 and 22b2 are provided as a mechanism for discharging the second impurity R2, but the configuration of the second discharge section for discharging the second impurity R2 is not limited to this and may be arbitrary.

[0040] The first impurity R1 and the second impurity R2 separated from the polyester solution P in the storage section 20 are discharged to the outside of the storage section 20 by the first discharge section 22a and the second discharge sections 22b1 and 22b2. This removes the first impurity R1 and the second impurity R2 from the polyester solution P. In the above description, the impurity R included the first impurity R1, which has a higher specific gravity than the polyester solution P, and the second impurity R2, which has a lower specific gravity than the polyester solution P. However, the impurity R is not limited to this, and may include only one of the first impurity R1 or the second impurity R2.

[0041] In the above description, the second impurity R2 is discharged from the storage section 20 by the second discharge section 22b1, which is a skimmer. However, it may also be discharged from the storage section 20 by overflow, for example. In this case, for example, the upper end surface of the wall of the tank constituting the storage section 20 constitutes the second discharge section 22b1, and when the second impurity R2 reaches a position higher than the second discharge section 22b1 (the upper end surface of the wall) due to the rise in the liquid level of the polyester solution P or the accumulation of the second impurity R2, it is discharged to the outside from the second discharge section 22b1. The second discharge section 22b1 may be lower than, for example, the upper end surface of another part of the wall of the storage section 20. As a result, the second impurity R2 is preferentially discharged from the part in which the second discharge section 22b1 is formed. If the second impurity R2 is discharged from the storage section 20 by overflow, a skimmer may not be provided. Also, the overflow is not limited to the method described above.

[0042] (Derivation part) An inlet pipe 20c is connected to the storage section 20. The inlet pipe 20c is a pipe for discharging the polyester solution P separated from impurities R from the storage section 20. The inlet pipe 20c is connected to the position where the layer of polyester solution P in the storage section 20 is formed, and in this embodiment, it is connected to a position between the discharge pipe 20a and the discharge pipe 20b in the vertical direction. An outlet section 24 is provided on the inlet pipe 20c. The outlet section 24 is a mechanism for discharging the polyester solution P in the storage section 20 from the storage section 20, and in this embodiment, it is a pump. In this embodiment, the inlet pipe 20c is provided as an inlet pipe 20c1 connecting the storage section 20 and the filter 26a described later, an inlet pipe 20c2 connecting the filter 26a and the adsorption tower 26b described later, and an inlet pipe 20c3 connecting the adsorption tower 26b and the reaction section 16.

[0043] (Removal part) The removal unit 26 is a mechanism for removing the third impurity R3 contained in the polyester solution P from the polyester solution P. The removal unit 26 is connected to the storage unit 20 and removes the third impurity R3 present in the polyester solution P discharged from the storage unit 20 from the polyester solution P. In this embodiment, the removal unit 26 is provided with a filter 26a and an adsorption tower 26b.

[0044] (Filtration machine) The filter 26a is connected to the storage section 20 via an inlet pipe 20c1. The polyester solution P discharged from the storage section 20 is introduced into the filter 26a through the inlet pipe 20c1. The filter 26a captures solid components contained in the third impurity R3 of the polyester solution P using a filter. For example, the filter 26a removes polymerization catalyst particles ranging from 0.1 μm to 1.0 μm using a filter. The filter may be made of ceramic or sintered metal.

[0045] (Adsorption tower) The adsorption tower 26b is connected to the filter 26a via an inlet pipe 20c2. The polyester solution P discharged from the filter 26a (the polyester solution P after solid components have been collected in the filter 26a) is introduced into the adsorption tower 26b through the inlet pipe 20c2. The adsorption tower 26b has a collection section for collecting the third impurity R3 contained in the polyester solution P. The collection section of the adsorption tower 26b may be an adsorbent that adsorbs the third impurity R3 contained in the polyester solution P, or it may be a filtration section that collects the third impurity by filtration. That is, the adsorption tower 26b may collect the third impurity R3 by adsorption or by filtration, or at least one of the two. It is preferable that the adsorbent contained in the adsorption tower 26b is capable of adsorbing the molecular skeleton of the third impurity R3 (e.g., quinone group, azo group, heterocycle, benzene ring). The adsorbent is preferably activated carbon, for example.

[0046] The adsorption tower 26b is connected to the reaction section 16, which will be described later, via the introduction tube 20c3. That is, the polyester solution P, from which the third impurity has been removed in the adsorption tower 26b, is introduced into the reaction section 16 through the introduction tube 20c3.

[0047] In this manner, the polyester solution P led from the storage section 20 to the inlet pipe 20c1 is introduced into the filter 26a, where at least a portion of the third impurity R3 contained in the polyester solution P is collected by the filter 26a. The third impurity R3 collected by the filter 26a is discharged to the outside through the discharge pipe 26a1 connected to the filter 26a. In the example in Figure 2, the discharge pipe 26a1 is connected to the discharge pipe 20a, but it is not necessary for it to be connected to the discharge pipe 20a. The polyester solution P from which at least a portion of the third impurity R3 has been removed by the filter 26a is led out of the filter 26a and introduced into the adsorption tower 26b. In the adsorption tower 26b, any remaining third impurity R3 in the polyester solution P is adsorbed or filtered by the adsorption tower 26b and removed from the polyester solution P. The third impurity R3 adsorbed or filtered by the adsorption tower 26b is, for example, a dye or a polymerization catalyst. The polyester solution P from which the third impurity R3 has been removed by the adsorption tower 26b is discharged from the adsorption tower 26b and introduced into the reaction section 16 through the introduction tube 20c.

[0048] Thus, in this embodiment, a filter 26a and an adsorption tower 26b are provided as a mechanism for removing the third impurity R3 from the polyester solution P. However, the configuration of the removal section 26 for discharging the third impurity R3 is not limited to this and may be arbitrary. For example, although not shown, the removal section 26 may include a temporary storage tank connected to an inlet pipe 20c3 that temporarily stores the polyester solution P from which the third impurity R3 has been removed, in an inlet pipe 20c3 connected to the adsorption tower 26b.

[0049] (Reaction solvent storage section) The reaction solvent storage section 14 is a tank into which the reaction solvent M is introduced and stored. The reaction solvent storage section 14 is connected to the reaction section 16 via an introduction pipe 14a. The reaction solvent M in the reaction solvent storage section 14 is supplied to the reaction section 16 through the introduction pipe 14a. More specifically, the introduction pipe 14a is provided with a heating and pressurizing section 14b that pressurizes and heats the reaction solvent M. The heating and pressurizing section 14b pressurizes and heats the reaction solvent M, bringing it to a supercritical or subcritical state (pressurized gas or pressurized liquid). The reaction section 16 is supplied with the reaction solvent M in a supercritical or subcritical state (pressurized gas or pressurized liquid).

[0050] (Reaction section) The reaction section 16 is a container into which the polyester solution P, separated from impurities R in the storage section 20, and the reaction solvent M are introduced to depolymerize the polyester in the polyester solution P. The reaction section 16 includes a first reaction section 16A and a second reaction section 16B. In the following, within the reaction section 16, the direction from the first reaction section 16A toward the second reaction section 16B is referred to as direction Y1, and the opposite direction to direction Y1 (the direction from the second reaction section 16B toward the first reaction section 16A) is referred to as direction Y2. In this embodiment, direction Y2 is the direction of gravity (downward vertically).

[0051] (First reaction section) The first reaction section 16A is formed within the reaction section 16. In this embodiment, the first reaction section 16A can be described as a section within the reaction section 16 that is filled with a packing material. As the packing material for the first reaction section 16A, known materials used in gas-liquid or liquid-liquid contact devices can be used, such as the same packing material used in contact devices that extract active ingredients by bringing heavy oil and water into contact. Specific examples of packing materials include pipes made of SUS, Raschig rings, Berl saddles, Terralets, balls, etc.

[0052] An inlet tube 20c is connected to the first reaction section 16A. More specifically, an inlet port 16C of the inlet tube 20c, into which the polyester solution P from the storage section 20 is introduced, is connected to the first reaction section 16A. The inlet port 16C is connected to the surface 16A1 of the first reaction section 16A on the first direction Y1 side. The inlet tube 20c is connected to the surface 16A1 such that the inlet port 16C opens facing the second direction Y2 side, opposite to the first direction Y1. Thus, in this embodiment, the inlet port 16C that opens facing the second direction Y2 side is connected to the surface 16A1 of the first reaction section 16A, but it is not limited to this. For example, the inlet port 16C does not have to be directly connected to the first reaction section 16A, and the inlet port 16C that opens facing the second direction Y2 side may be connected to the first direction Y1 side of the surface 16A1 of the first reaction section 16A within the reaction section 16.

[0053] An inlet tube 14a is connected to the reaction section 16. More specifically, an inlet port 16D of the inlet tube 14a, into which the reaction solvent M from the reaction solvent reservoir 14 is introduced, is connected to the reaction section 16. The inlet port 16D is connected to the second direction Y2 side of the surface 16A2 of the first reaction section 16A on the second direction D2 side. The inlet tube 14a is connected to the second direction Y2 side of the surface 16A2 such that the inlet port 16D opens facing the first direction Y1 side or facing from the side toward the center. Thus, in this embodiment, the inlet port 16D, which opens facing the first direction Y1 side or facing from the side toward the center, is connected to the second direction Y2 side of the surface 16A2 of the first reaction section 16A, but is not limited to this. For example, the inlet port 16D may be directly connected to the first reaction section 16A, or it may be connected to the surface 16A2 of the first reaction section 16A.

[0054] Thus, in this embodiment, the inlet 16C into which the polyester solution P is introduced opens facing the second direction Y2, and the inlet 16D into which the reaction solvent M is introduced opens facing the first direction Y1, or facing from the side toward the center. Therefore, the polyester solution P and the reaction solvent M are introduced into the first reaction section 16A in directions facing each other.

[0055] The polyester solution P introduced into the first reaction section 16A from the inlet 16C moves along the surface of the packing material in the first reaction section 16A in the second direction Y2. Meanwhile, the supercritical or subcritical (pressurized gas or pressurized liquid) reaction solvent M introduced from the inlet 16D moves within the first reaction section 16A in the first direction Y1. In the first reaction section 16A, the supercritical or subcritical (pressurized gas or pressurized liquid) reaction solvent M comes into contact with the polyester solution P. The polyester in the polyester solution P is depolymerized (reduced to a lower molecular weight) by the reaction solvent M, and the depolymerized polyester is extracted into the supercritical or subcritical (pressurized gas or pressurized liquid) reaction solvent M. Hereinafter, the polyester depolymerized in the first reaction section 16A will be referred to as the first depolymerized polyester P1, and the mixture of the first depolymerized polyester P1 and the reaction solvent M (the reaction solvent M from which the first depolymerized polyester P1 has been extracted) will be referred to as the first solvent M1. The first solvent M1 containing the first depolymerized polyester P1 proceeds through the first reaction section 16A toward the first direction Y1 and is led out toward the first direction Y1 of the first reaction section 16A.

[0056] The first depolymerized polyester P1 includes monomers D and E produced by the depolymerization of polyester in polyester solution P, monomer D which was originally mixed in polyester solution P, and oligomers produced by the depolymerization of polyester. Here, oligomers are oligomers of carboxylic acid-derived or alcohol components that have not been monomerized but have been depolymerized from polyester (oligomers of carboxylic acid-derived or alcohol components with a smaller molecular weight than polyester).

[0057] (Second reaction section) The second reaction section 16B is formed within the reaction section 16, and is located where the first solvent M1 is led out from the first reaction section 16A. In this embodiment, since the first solvent M1 is led out in the first direction Y1, the second reaction section 16B can be described as a space formed in the first direction Y1 on the side of the first reaction section 16A.

[0058] In the second reaction section 16B, the first depolymerized polyester P1 contained in the first solvent M1 is further depolymerized (reduced to a lower molecular weight) by the reaction solvent M contained in the first solvent M1. Hereinafter, the first depolymerized polyester P1 further depolymerized in the second reaction section 16B will be referred to as the second depolymerized polyester P2, and the mixture of the second depolymerized polyester P2 and the reaction solvent M (reaction solvent M in which the second depolymerized polyester P2 is dissolved) will be referred to as the second solvent M2. A discharge tube 16a is connected to the second reaction section 16B. More specifically, an outlet 16E of the discharge tube 16a, which is the opening through which the second solvent M2 from the second reaction section 16B is discharged, is connected to the second reaction section 16B. The second solvent M2 containing the second depolymerized polyester P2 in the second reaction section 16B is discharged from the outlet 16E through the discharge tube 16a to the outside of the second reaction section 16B.

[0059] Furthermore, the second depolymerized polyester P2 includes monomers D and E from the first depolymerized polyester P1, monomers D and E produced by the depolymerization of the oligomer in the first depolymerized polyester P1, and oligomers produced by the depolymerization of the first depolymerized polyester P1.

[0060] A discharge pipe 16b is connected to the bottom of the reaction section 16. More specifically, an outlet 16F of the discharge pipe 16b is connected to the bottom of the reaction section 16, which is an opening from which non-extracted substances (described later) from the reaction section 16 are discharged. Non-extracted substances, including impurities such as metal compounds that were not extracted by the reaction solvent M, and residues of undecomposed polyester that were not extracted by the reaction solvent M, are discharged from the outlet 16F. In other words, the non-extracted substances at the bottom of the reaction section 16 are discharged to the outside of the reaction section 16 through the outlet 16F and the discharge pipe 16b. The non-extracted substances discharged from the outlet 16F can be said to be components of the polyester solution P that remained in the first reaction section 16A and the second reaction section 16B without being led to the separation section 18 as the second solvent M2 (reaction solvent M in which the second depolymerized polyester P2 is dissolved).

[0061] Furthermore, the reaction section 16 may be provided with a heating section for heating the inside of the reaction section 16 and a pressurizing section for maintaining the internal pressure of the reaction section 16 above a predetermined value. The internal temperature of the reaction section 16 is preferably 250°C to 400°C, and more preferably 250°C to 350°C. The internal pressure of the reaction section 16 is preferably 1 MPa to 30 MPa, and more preferably 6 MPa to 25 MPa. The pressurizing section and the heating section may be controlled by the control unit 30.

[0062] (separation part) In the separation unit 18, a second solvent M2 containing the second depolymerized polyester P2 is introduced, and the second solvent M2 is separated into the reaction solvent M, monomer D derived from the carboxylic acid contained in the second depolymerized polyester P2, monomer E of the alcohol component contained in the second depolymerized polyester P2, and residual substances. The residual substances are components of the second solvent M2 other than the reaction solvent M, monomer D, and monomer E, and include oligomers.

[0063] In this embodiment, the separation unit 18 has a first separation unit 18A, a second separation unit 18B, and a third separation unit 18C.

[0064] The first separation section 18A is a separation column connected to the outlet tube 16a. The second solvent M2 containing the second depolymerized polyester P2 is introduced into the first separation section 18A via the outlet tube 16a. The first separation section 18A separates the second solvent M2 into a low-boiling point component and a high-boiling point component with a higher boiling point than the low-boiling point component. For example, in the first separation section 18A, the second solvent M2 may be heated to a predetermined temperature, with the gaseous component being the low-boiling point component and the liquid component being the high-boiling point component. Outlet tubes 18Aa and 18Ab are connected to the first separation section 18A. The low-boiling point component is discharged from outlet tube 18Aa, and the high-boiling point component is discharged from outlet tube 18Ab.

[0065] The second separation section 18B is a separation column connected to the first separation section 18A via a discharge tube 18Aa. Low-boiling point components are introduced into the second separation section 18B via the discharge tube 18Aa. The second separation section 18B separates the low-boiling point components into reaction solvent M and monomer E. Discharge tubes 18Ba and 18Bb are connected to the second separation section 18B. Reaction solvent M is discharged from discharge tube 18Ba, and monomer E is discharged from discharge tube 18Bb. Discharge tube 18Ba is connected to both the second separation section 18B and the reaction solvent storage section 14. Therefore, the reaction solvent M discharged from the second separation section 18B is returned to the reaction solvent storage section 14 and reused for polyester depolymerization.

[0066] The third separation section 18C is a separation column connected to the first separation section 18A via a discharge tube 18Ab. High-boiling-point components are introduced into the third separation section 18C via the discharge tube 18Ab. The third separation section 18C further separates the high-boiling-point components into residual high-boiling-point substances, low-boiling-point components containing the reaction solvent M and monomer E, and monomer D. Discharge tubes 18Ca, 18Cb, and 18Cc are connected to the third separation section 18C. Discharge tube 18Ca is connected to the second separation section 18B. The low-boiling-point components separated in the third separation section 18C are discharged to the second separation section 18B via the discharge tube 18Ca. Monomer D separated in the third separation section 18C is discharged from the discharge tube 18Cb, and residual substances separated in the third separation section 18C are discharged from the discharge tube 18Cc.

[0067] An introduction pipe 18Cd is connected to the third separation section 18C. The introduction pipe 18Cd is also connected to the dissolution section 12, and introduces monomer D, which is discharged from the third separation section 18C, into the dissolution section 12. In the example shown in Figure 2, the introduction pipe 18Cd branches off from the outlet pipe 18Cb. The introduction pipe 18Cd is provided with an adjustment section 18Ce that adjusts the amount of monomer D supplied from the third separation section 18C to the dissolution section 12. The adjustment section 18Ce is, for example, an on-off valve, which, when open, allows monomer D to be supplied to the dissolution section 12, and when closed, stops the supply of monomer D to the dissolution section 12. However, the adjustment section 18Ce is not limited to an on-off valve, and may be any mechanism capable of adjusting the supply of monomer D to the dissolution section 12. In this embodiment, the adjustment section 18Ce is provided at the branching point of the introduction pipe 18Cd from the outlet pipe 18Cb, but it is not limited to this location and may be provided at any location. Furthermore, the inlet pipe 18Cd does not have to be connected to the outlet pipe 18Cb, and may be directly connected to the third separation section 18C. Alternatively, for example, the outlet pipe 18Cb may be provided with a storage section (tank) for storing monomer D, and the inlet pipe 18Cd may be connected to the storage section.

[0068] Furthermore, by connecting the outlet tube 18Cc to the dissolution section 12, at least a portion of the residual substance may be introduced into the dissolution section 12. By introducing the residual substance into the dissolution section 12, it becomes possible to depolymerize the oligomers contained in the residual substance again in the reaction section 16, thereby improving the monomer yield.

[0069] (Control Unit) Next, the control unit 30 (control device) shown in Figure 2 will be described. Figure 3 is a schematic block diagram of the control unit. The control unit 30 is a control device that controls the separation system 1, and in this embodiment, it is a computer. As shown in Figure 3, the control unit 30 includes an input unit 32, an output unit 34, a communication unit 36, a storage unit 38, and a processing unit 40.

[0070] The input unit 32 is a device that accepts user input and may be, for example, a mouse, keyboard, or touch panel. The output unit 34 is a device that outputs information and may be, for example, a display that shows images. The input unit 32 and the output unit 34 are not required. The communication unit 36 ​​is a module that communicates with external devices and may include, for example, an antenna. In this embodiment, the communication method used by the communication unit 36 ​​is wireless communication, but the communication method may be arbitrary. The control unit 30 may be configured as a standalone device, integrated with other devices, or as a system combining various devices such as a computing unit and a data server, and is not particularly limited.

[0071] The memory unit 38 is a memory that stores various information such as the calculation contents and programs of the processing unit 40, and includes at least one of the following: RAM (Random Access Memory), main memory such as ROM (Read Only Memory), and external memory such as HDD (Hard Disk Drive). The program for the processing unit 40 stored in the memory unit 38 may be stored on a recording medium that can be read by the control unit 30.

[0072] The processing unit 40 is an arithmetic unit and includes arithmetic circuits such as a CPU (Central Processing Unit). The processing unit 40 includes a detection control unit 42, an information acquisition unit 44, a calculation unit 45, and a system control unit 46. The processing unit 40 reads a program (software) from the storage unit 38 and executes it to realize the detection control unit 42, the information acquisition unit 44, the calculation unit 45, and the system control unit 46, and executes their processes. The processing unit 40 may execute these processes with a single CPU, or it may have multiple CPUs and execute the processes with those multiple CPUs. In addition, at least a part of the detection control unit 42, the information acquisition unit 44, the calculation unit 45, and the system control unit 46 may be realized in hardware.

[0073] (Processing of the control unit) The processing details of the control unit 30 are described below.

[0074] (Control of the separation system) The system control unit 46 controls each mechanism of the separation system 1. The system control unit 46 controls the adjustment unit 10b to control the amount of polyester raw material Pm supplied from the raw material storage unit 10 to the dissolution unit 12. The system control unit 46 controls the adjustment unit 18Ce to control the amount of monomer D supplied to the dissolution unit 12. It is preferable that the system control unit 46 controls the adjustment unit 10b and the adjustment unit 18Ce to control the supply amounts such that the ratio of the supply amount of monomer D to the supply amount of polyester raw material Pm to the dissolution unit 12 exceeds 0.5 (supply amount of monomer D / supply amount of polyester raw material Pm > 0.5). It is preferable that the system control unit 46 controls the supply amounts such that the supply amount of monomer D is, for example, 0.51 times or more the supply amount of polyester raw material Pm.

[0075] Furthermore, the system control unit 46 controls the heating unit 12A to control the temperature of the dissolving solution Pd in ​​the dissolving unit 12. It is preferable that the system control unit 46 controls the temperature of the dissolving solution Pd in ​​the dissolving unit 12 so that the temperature of the dissolving solution Pd in ​​the dissolving unit 12 reaches the predetermined temperature described above. The predetermined temperature is preferably 140°C to 300°C, more preferably 160°C to 280°C, and even more preferably 170°C to 200°C. The system control unit 46 may maintain the temperature of the dissolving solution Pd at a constant level, or it may allow the temperature of the dissolving solution Pd to fluctuate within the range of the predetermined temperature described above.

[0076] Furthermore, the system control unit 46 controls the foreign matter recovery unit 50 to recover impurities collected in the solid-liquid separation unit 13. The system control unit 46 also controls the operation of the solid-liquid separation unit 13 if it includes a drive unit. The system control unit 46 controls the adjustment unit 12a1 to control the amount of dissolving solution Pd supplied from the dissolution unit 12 to the storage unit 20. The system control unit 46 controls the discharge unit 22 to discharge the impurities R separated from the polyester solution P in the storage unit 20. The system control unit 46 controls the outlet unit 24 to discharge the polyester solution P separated from the impurities R in the storage unit 20 and control the amount of polyester solution P introduced into the reaction unit 16. The system control unit 46 controls the heating and pressurizing unit 14b to bring the reaction solvent M into a supercritical or subcritical state (pressurized gas or pressurized liquid), and controls the amount of the supercritical or subcritical (pressurized gas or pressurized liquid) reaction solvent M supplied to the reaction unit 16.

[0077] Furthermore, the system control unit 46 controls the discharge unit 22 to discharge the first impurity R1 and the second impurity R2 from the storage unit 20, while controlling the outlet unit 24 to release the polyester solution P from the storage unit 20. The polyester solution P released from the storage unit 20 has the third impurity R3 removed by the removal unit 26 and is introduced into the first reaction unit 16A. The control unit 30 controls the heating and pressurizing unit 14b to supply the reaction solvent M, which is in a supercritical or subcritical state (pressurized gas or pressurized liquid), to the reaction unit 16. The system control unit 46 prefers that the reaction solvent M be at a temperature of 250°C or higher and 400°C or lower, and more preferably at 250°C or higher and 350°C or lower. The system control unit 46 prefers that the reaction solvent M be at a temperature of 1 MPa or higher and 30 MPa or lower, and more preferably at 6 MPa or higher and 25 MPa or lower.

[0078] In this manner, when the polyester solution P and the reaction solvent M are supplied to the reaction section 16, the polyester contained in the polyester solution P is depolymerized in the first reaction section 16A to produce the first depolymerized polyester P1. Then, in the second reaction section 16B, the first depolymerized polyester P1 is further depolymerized to produce the second solvent M2, which is a mixture of the second depolymerized polyester P2 and the reaction solvent M. The second solvent M2 is separated into the reaction solvent M, monomer D, monomer E, and residual substances in the first separation section 18A, the second separation section 18B, and the third separation section 18C.

[0079] However, the separation system 1 is not limited to being automatically controlled by the control unit 30; for example, at least some of the processes may be controlled by human operators.

[0080] (Regarding the separation of polyester components from plant fibers) Here, if the polyester raw material Pm contains both polyester components and plant fibers, it is necessary to appropriately separate the polyester components and plant fibers. The control unit 30 of this embodiment makes it possible to appropriately separate the polyester components and plant fibers by controlling the dissolution conditions of the polyester raw material Pm in the dissolution unit 12, as will be explained below. A detailed explanation follows.

[0081] (Detection and acquisition of dissolution conditions) The detection control unit 42 controls the detection unit 60 to cause the detection unit 60 to detect the dissolution conditions of the polyester raw material Pm in the dissolution unit 12. Specifically, the detection control unit 42 causes the detection unit 60, acting as a temperature sensor, to detect the temperature of the dissolution solution Pd in ​​the dissolution unit 12. The detection control unit 42 also causes the detection unit 60, acting as a timer, to detect the processing time since the polyester raw material Pm and monomer D were supplied to the dissolution unit 12. Note that the method for detecting the processing time is not limited to being performed by the detection unit 60 and may be arbitrary; for example, the processing time may be detected by a timer provided in the control unit 30. The information acquisition unit 44 acquires the dissolution conditions detected by the detection unit 60. Specifically, the information acquisition unit 44 acquires the detection result of the temperature of the dissolution solution Pd. The information acquisition unit 44 also acquires the detection result of the processing time. The detection control unit 42 sequentially detects the dissolution conditions, and the information acquisition unit 44 sequentially acquires the detection results of the dissolution conditions.

[0082] (Calculation of indicators) The calculation unit 45 calculates the index R0 shown in the following formula (1) based on the dissolution conditions acquired by the information acquisition unit 44.

[0083] R0=Log(t·exp[(T-100) / 14.75])···(1)

[0084] In equation (1), t is the processing time (min) after the polyester raw material Pm and monomer D are supplied to the dissolution section 12, and T is the temperature (°C) of the dissolution solution Pd.

[0085] In other words, the calculation unit 45 calculates the index R0 shown in equation (1) using the temperature detection result of the dissolving solution Pd acquired by the information acquisition unit 44 as temperature T, and the processing time acquired by the information acquisition unit 44 as processing time t.

[0086] Furthermore, the calculation unit 45 determines whether the calculated index R0 is within a predetermined range. The predetermined range for index R0 is 2 or more and less than 4.5, preferably 2 or more and 3.5 or less, and more preferably 2 or more and 2.5 or less.

[0087] The calculation unit 45 sequentially calculates the index R0 based on the latest dissolution conditions acquired by the information acquisition unit 44.

[0088] (Control of dissolution conditions) The system control unit 46 controls the dissolution conditions so that the index R0 falls within the predetermined range described above. Here, the dissolution conditions refer to the dissolution conditions of the polyester raw material Pm in the dissolution unit 12. Specifically, the dissolution conditions here include the processing time, which is the time from when the polyester raw material Pm and monomer D are supplied to the dissolution unit 12, and the temperature of the dissolved solution Pd in ​​the dissolution unit 12. That is, the system control unit 46 controls at least one (preferably both) of the processing time and the temperature of the dissolved solution Pd so that the index R0 falls within the predetermined range described above. In this embodiment, the processing time can also be said to be the time from when the polyester raw material Pm and monomer D are supplied to the dissolution unit 12 until the dissolved solution Pd is discharged from the dissolution unit 12.

[0089] For example, the system control unit 46 maintains the temperature of the dissolving solution Pd within the predetermined temperature range, and terminates the process of dissolving the polyester raw material Pm into monomer D in the dissolving unit 12 when the index R0 calculated by the calculation unit 45 reaches a predetermined range. That is, for example, when the index R0 reaches a predetermined range, the system control unit 46 controls the adjustment unit 12a1 to discharge the dissolving solution Pd from the dissolving unit 12 to the storage unit 20. As a result, the liquid component dissolving solution Pd is discharged from the dissolving unit 12, impurities R containing plant fibers remain in the dissolving unit 12, and the process of dissolving the polyester raw material Pm into monomer D is stopped.

[0090] In this way, by adjusting the dissolution conditions (in this case, the temperature of the dissolution solution and the processing time) so that the index R0 falls within a predetermined range, polyester can be properly dissolved and plant fibers and polyester can be properly separated.

[0091] (Control flow) The control flow of the control unit 30 described above will now be explained. Figure 4 is a flowchart illustrating the control flow of the control unit. As shown in Figure 4, the control unit 30 supplies polyester raw material Pm and monomer D to the dissolution unit 12 via the system control unit 46 and starts the dissolution of these materials in the dissolution unit 12 (step S10). The control unit 30 causes the detection unit 60 to detect the temperature of the dissolution solution Pd via the detection control unit 42 and detects the processing time since the polyester raw material Pm and monomer D were supplied to the dissolution unit 12 (step S12). The control unit 30 determines whether the index R0 has reached a predetermined range via the calculation unit 45 (step S14). If the calculation unit 45 determines that the index R0 has reached a predetermined range (step S14; Yes), the control unit 30 causes the system control unit 46 to stop the dissolution in the dissolution unit 12 (step S16). Specifically, the system control unit 46 discharges the dissolution solution Pd from the dissolution unit 12 to the storage unit 20. If the control unit 30 determines that the index R0 has not reached a predetermined range (step S14; No), it returns to step S12 and continues processing until the index R0 reaches a predetermined range.

[0092] (Effects of this disclosure) A separation system according to a first aspect of this disclosure includes a dissolution unit 12 to which monomer D derived from a carboxylic acid and polyester raw material Pm including polyester and plant fibers are supplied to produce a dissolution solution Pd in ​​which polyester is dissolved in monomer D; a detection unit 60 for detecting the temperature of the dissolution solution Pd; and a control unit 30 for controlling dissolution conditions, including a processing time which is the time since polyester raw material Pm and monomer D were supplied to the dissolution unit 12, and the temperature of the dissolution solution Pd, such that the index R0 shown in formula (1) above is 2 or more and less than 4.5.

[0093] According to this disclosure, polyester and plant fibers can be appropriately separated.

[0094] A separation system according to a second aspect of this disclosure is a separation system according to a first aspect, wherein the control unit 30 controls the dissolution conditions so that the index R0 is in the range of 2 to 3.5. This makes it possible to suppress the destruction of the structure of the plant fibers. In other words, according to this aspect, polyester and plant fibers can be appropriately separated, and the plant fibers can be appropriately recovered and, for example, the plant fibers can be suitably reused.

[0095] A separation system according to a third aspect of this disclosure is a separation system according to the first or second aspect, wherein the control unit 30 controls the dissolution conditions so that the temperature of the dissolution solution Pd is in the range of 140°C to 300°C. This allows for the appropriate separation of polyester and plant fibers.

[0096] The separation system according to the fourth aspect of this disclosure is a separation system according to any one of the first to third aspects, wherein the length of the polyester raw material Pm is 10 cm or more. This allows the plant fibers to be recovered in a long state, making them easier to reuse. In other words, polyester and plant fibers can be properly separated.

[0097] A separation system according to a fifth aspect of this disclosure is a separation system according to any one of the first to fourth aspects, wherein the plant fibers include at least one of cotton, linen, rayon, polynosic, cupro, acetate, triacetate, and bromix. According to this disclosure, such plant fibers can be appropriately separated from polyester.

[0098] A control device according to a sixth aspect of this disclosure includes an information acquisition unit 44 that acquires the temperature of a solution Pd in ​​which polyester contained in a polyester raw material Pm, which includes polyester and plant fibers, is dissolved in a monomer D derived from a carboxylic acid, and a processing time which is the time since the polyester raw material Pm and monomer D were supplied to the dissolution unit 12, and a system control unit 46 that controls dissolution conditions, including the processing time and the temperature of the solution Pd, so that the index R0 shown in the above formula (1) is 2 or more and less than 4.5.

[0099] According to this disclosure, polyester and plant fibers can be appropriately separated.

[0100] A separation method according to a seventh aspect of this disclosure includes the steps of: supplying a monomer D derived from a carboxylic acid and a polyester raw material Pm including polyester and plant fibers to a dissolution unit 12 to produce a dissolution solution Pd in ​​which polyester is dissolved in monomer D; detecting the temperature of the dissolution solution Pd; and controlling dissolution conditions, including a processing time which is the time since polyester raw material Pm and monomer D were supplied to the dissolution unit and the temperature of the dissolution solution Pd, such that the index R0 shown in formula (1) above is 2 or more and less than 4.5.

[0101] According to this disclosure, polyester and plant fibers can be appropriately separated.

[0102] A program according to the eighth aspect of this disclosure causes a computer to perform the following steps: supplying a monomer D derived from a carboxylic acid and a polyester raw material Pm including polyester and plant fibers to a dissolution unit 12 to generate a dissolution solution Pd in ​​which polyester is dissolved in monomer D; detecting the temperature of the dissolution solution Pd; and controlling dissolution conditions, including a processing time which is the time since polyester raw material Pm and monomer D were supplied to the dissolution unit 12 and the temperature of the dissolution solution Pd, such that the index R0 shown in formula (1) above is 2 or more and less than 4.5.

[0103] According to this disclosure, polyester and plant fibers can be appropriately separated.

[0104] (Examples) Next, we will describe the examples. Table 1 shows the processing conditions and evaluation results for each example. [Table 1]

[0105] (Example 1) In Example 1, a polyester raw material containing polyester and cotton was prepared. This polyester raw material was then added to a tank containing DMT as a monomer. The temperature of the dissolution solution in the tank was set to 160°C, and the processing time (the time from adding the polyester raw material to the tank until the dissolution solution was discharged) was set to 2 minutes. Therefore, the index R0 in Example 1 was 2.0.

[0106] (Examples 2 to Comparative Example 2) In Examples 2, 3, Comparative Example 1, and Comparative Example 2, the treatment was carried out under the same conditions as in Example 1, except that the temperature of the dissolution and the treatment time were as shown in Table 1.

[0107] (evaluation) An evaluation was conducted for each example. In the evaluation, cases where polyester and cotton (plant fiber) could not be separated, or where the cotton was damaged to the point of being unusable, were marked with ×, and cases where polyester and cotton could be separated and the cotton was not damaged to the point of being reusable were marked with ○. As shown in Table 1, in Examples 1, 2, and 3, where the index R0 was 2 or more and less than 4.5, it can be seen that the polyester dissolved appropriately, allowing for appropriate separation of polyester and cotton and suppressing damage to the cotton. On the other hand, in Comparative Example 1, where the index R0 was less than 2, the polyester did not dissolve appropriately, but the polyester and cotton could be separated appropriately, and in Comparative Example 2, where the index R0 was 4.5 or more, the cotton was damaged to the point of being unusable.

[0108] Although embodiments of the present invention have been described above, the embodiments are not limited to those described herein. Furthermore, the aforementioned components include those that can be easily conceived by those skilled in the art, those that are substantially the same, and those that fall within the so-called equivalent range. Moreover, the aforementioned components can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the components can be made without departing from the spirit of the embodiments described above. [Explanation of Symbols]

[0109] 1 Separation System 12 Melting part 13 Solid-liquid separation section 14 Reaction solvent storage section 16 Reaction section 18 Separation part 20 Storage section 22 Discharge section 26 Removal part 30 Control Unit 60 Detection unit D and E monomers M reaction solvent P polyester solution Pd solution PM polyester raw material R impurities R1 First purpurine R2 Secondary impurity R3 Third impurity

Claims

1. A dissolving unit is supplied with a monomer derived from a carboxylic acid and a polyester raw material containing polyester and plant fibers, and generates a solution in which the polyester is dissolved in the monomer. A detection unit for detecting the temperature of the aforementioned dissolving solution, The index R shown in the following equation (1) ０ The system includes a control unit that controls the dissolution conditions, including the processing time which is the time from when the polyester raw material and the monomer are supplied to the dissolution unit, and the temperature of the dissolution solution, such that the ratio is 2 or more and less than 4.

5. Separation system. R ０ =Log(t・exp[(T-100) / 14.75]) ・・・(1) however, t refers to the processing time (min), and T refers to the temperature of the dissolving solution (°C).

2. The control unit is the index R ０ The dissolution conditions are controlled so that the value is in the range of 2 to 3.

5. The separation system according to claim 1.

3. The control unit controls the dissolution conditions so that the temperature of the dissolution solution is in the range of 140°C to 300°C. The separation system according to claim 1 or claim 2.

4. The length of the aforementioned polyester raw material is 10 cm or more. The separation system according to claim 1 or claim 2.

5. The aforementioned plant fiber includes at least one of cotton, linen, rayon, polynosic, cupro, acetate, triacetate, and bromix. The separation system according to claim 1 or claim 2.

6. An information acquisition unit that acquires the temperature of a solution in which polyester contained in a polyester raw material including polyester and plant fibers is dissolved in a monomer derived from a carboxylic acid, and the processing time which is the time since the polyester raw material and the monomer were supplied to the dissolution unit. The index R shown in the following equation (1) ０ A system control unit controls the dissolution conditions, including the processing time and the temperature of the dissolution solution, such that the ratio is 2 or more and less than 4.

5. including, Control device. R ０ =Log(t・exp[(T-100) / 14.75]) ・・・(1) however, t refers to the processing time (min), and T refers to the temperature of the dissolving solution (°C).

7. A step in which a monomer derived from a carboxylic acid and a polyester raw material containing polyester and plant fibers are supplied to a dissolution section to produce a solution in which the polyester is dissolved in the monomer, The step of detecting the temperature of the dissolving solution, The index R shown in the following equation (1) ０ The process includes controlling the dissolution conditions, which include the processing time (the time from when the polyester raw material and the monomer are supplied to the dissolution section) and the temperature of the dissolution solution, such that the ratio is 2 or more and less than 4.

5. Separation method. R ０ =Log(t・exp[(T-100) / 14.75]) ・・・(1) however, t refers to the processing time (min), and T refers to the temperature of the dissolving solution (°C).

8. A step in which a monomer derived from a carboxylic acid and a polyester raw material containing polyester and plant fibers are supplied to a dissolution section to produce a solution in which the polyester is dissolved in the monomer, The step of detecting the temperature of the dissolving solution, The index R shown in the following equation (1) ０ The computer is instructed to perform a step of controlling the dissolution conditions, including the processing time which is the time since the polyester raw material and the monomer were supplied to the dissolution section, and the temperature of the dissolution solution, such that the ratio is 2 or more and less than 4.

5. program. R ０ =Log(t・exp[(T-100) / 14.75]) ・・・(1) however, t refers to the processing time (min), and T refers to the temperature of the dissolving solution (°C).

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