Separation system, controller, separation method, and program

Abstract

The present invention properly separates a polyester and plant fibers from each other. This separation system comprises: a dissolution part to which a carboxylic-acid-derived monomer and a raw polyester material comprising both a polyester and plant fibers are supplied and in which a solution of the polyester in the monomer is yielded; a detection part which detects the temperature of the solution; and a control unit which controls dissolution conditions, including the solution temperature and the treatment time, so that the index R0 shown by equation (1) is 2 or greater but less than 4.5, wherein the treatment time is the time elapsed since the raw polyester material and the monomer were supplied to the dissolution part.

Description

Separation system, control device, separation method and program

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

[0002] For example, techniques are known for separating impurities from polyester in order to recycle polyester. Patent document 1 describes a method of depolymerizing polyethylene terephthalate (PET) waste by adding it to ethylene glycol (EG) 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.

[0003] Patent No. 4065659

[0004] In this case, the materials to be recycled may include plant fibers in addition to polyester. In this situation, proper separation of polyester and plant fibers is required in order to properly recycle the polyester and reuse the plant fibers.

[0005] This disclosure aims to solve the aforementioned problems and to provide a separation system, control device, separation method, and program for appropriately separating polyester and plant fibers.

[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 an index R shown in the following formula (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. ０ =Log(t・exp[(T-100) / 14.75]) ... (1) where 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 an index R shown in the following formula (1) ０ The system includes a system control unit that controls the dissolution conditions, including the processing time and the temperature of the dissolution solution, such that R is 2 or more and less than 4.5. ０ =Log(t・exp[(T-100) / 14.75]) ... (1) where 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 this disclosure comprises the steps of supplying a monomer derived from a carboxylic acid and a polyester raw material including polyester and plant fibers to a dissolution section to generate a dissolution solution in which the polyester is dissolved in the monomer; detecting the temperature of the dissolution solution; and using an index R shown in the following formula (1). ０ The process includes a step of controlling dissolution conditions, including a processing time which is 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. ０ =Log(t・exp[(T-100) / 14.75]) ... (1) where 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 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 section to generate a solution in which the polyester is dissolved in the monomer; detecting the temperature of the solution; and using an index R shown in the following formula (1). ０The computer is instructed to perform a step of controlling the dissolution conditions, including the processing time (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. ０ =Log(t・exp[(T-100) / 14.75]) ... (1) where t refers to the processing time (min) and T refers to the temperature of the dissolving solution (°C).

[0010] According to this disclosure, polyester and plant fibers can be appropriately separated.

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

[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 flakened (step S100), the flakened polyester raw material Pm is dissolved in monomer D derived from 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 carboxylic acid and monomer E of the 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 the recovery of 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 plant fibers. The polyester raw material Pm is not particularly limited, but examples include waste materials containing polyethylene terephthalate (PET), polyethylene butylene terephthalate (PEBT), polybutylene terephthalate (PBT), polycyclohexanedimethyl terephthalate (PCT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), polycarbonate (PC), etc., as polyester components. Furthermore, the plant fibers contained in the polyester raw material Pm refer to fibers derived from plants, not fibers derived from fossil fuels such as polyester. Preferably, the polyester raw material Pm contains at least one of cotton, linen, rayon, polynosic, cupro, acetate, triacetate, and bromix as plant fibers.

[0015] Polyester raw material Pm is not limited to containing only polyester components and plant fibers, but may also contain components other than polyester components and plant fibers (impurities). Examples of components other than polyester contained in polyester raw material Pm include plastics other than polyester such as polyethylene, polystyrene, polypropylene, and polyvinyl chloride, metals, dyes, pigments, and polymerization catalysts. Clothing in which polyester and other components are woven into fibers can also be cited as an example of polyester raw material Pm. Furthermore, polyester raw material Pm may also include items other than clothing that are woven with plant fibers (e.g., towels, bedding, other wearable items, etc.).

[0016] Hereinafter, components other than polyester contained in the polyester raw material Pm will be referred to as impurities R. In other words, in this embodiment, impurities R include at least plant fibers. If the polyester raw material Pm contains components other than polyester and plant fibers, the plant fibers and their components together will be referred to as impurities R.

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

[0018] (Carboxylic acid-derived monomer) Monomer D derived from a carboxylic acid is a monomer having a carboxyl group, produced by the depolymerization reaction of a polyester. Monomer D may be, for example, dimethyl carboxylate or diethyl carboxylate. More specifically, monomer D is preferably a monomer of terephthalic acid, for example, dimethyl terephthalate (DMT).

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

[0020] In the following explanation, we will use the case where the polyester is PET, the reaction solvent M is methanol, the monomer D is DMT, and the monomer E is EG 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 polyester contained in the polyester raw material Pm to produce monomers D and E. As shown in Figure 2, the separation system 1 has a raw material storage section 10, a dissolution section 12, a solid-liquid separation section 13, a storage section 20, a removal section 26, a reaction solvent storage section 14, a reaction section 16, a separation section 18, a control section 30, and a detection section 60.

[0022] (Raw material storage section) The raw material storage section 10 is a tank into which the polyester raw material Pm is introduced and stored. In the present embodiment, the flaked 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 melting section 12 via the introduction pipe 10a. The polyester raw material Pm in the raw material storage section 10 is supplied to the melting section 12 through the introduction pipe 10a. The introduction pipe 10a is provided with an adjustment section 10b for adjusting the amount of the polyester raw material Pm supplied from the raw material storage section 10 to the melting section 12. The adjustment section 10b is, for example, an on-off valve. In the open state, the polyester raw material Pm in the raw material storage section 10 is supplied to the melting section 12, and in the closed state, the supply of the polyester raw material Pm in the raw material storage section 10 to the melting section 12 is stopped. However, the adjustment section 10b is not limited to an on-off valve and may be any mechanism capable of adjusting the supply of the polyester raw material Pm to the melting section 12. Further, the polyester raw material Pm may be directly supplied to the melting section 12 without passing through the raw material storage section 10, the introduction pipe 10a, and the adjustment section 10b.

[0023] Note that a cutting machine for cutting the polyester raw material Pm may be provided in the raw material storage section 10. 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. Further, it is preferable that the cutting machine cuts the polyester raw material Pm so that the length of the cut polyester raw material Pm (for example, a piece of clothing) is 10 cm or more. Here, the length of the polyester raw material Pm refers to the length of the longest portion among any straight lines connecting the surfaces of the cut polyester raw material Pm. That is, for example, when the polyester raw material Pm is cut into a square shape, 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 an arbitrary shape with a length of 10 cm or more. Further, it is preferable that the cutting machine cuts the polyester raw material Pm so that the area of the polyester raw material Pm is 1 cm ２ or more, and 100 cm 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 in a different position from the raw material storage section 10.

[0024] (Dissolution section) The dissolution section 12 is a tank in which the dissolution solution Pd is stored. The dissolution 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 dissolution 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. By dissolving the polyester in the monomer D in this way, the viscosity can be reduced and the fluidity can be improved, allowing the polyester to be easily introduced into the reaction section 16. Note that the polyester solution P is not limited to the entire amount of polyester 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, a heating unit 12A is provided in the dissolution unit 12. By heating the inside of the dissolution unit 12, the heating unit 12A heats the monomer D and the polyester raw material Pm supplied to the dissolution unit 12 to a predetermined temperature. The predetermined temperature is a temperature at which the polyester can be dissolved in the monomer D. By heating at such a predetermined temperature, the polyester contained in the polyester raw material Pm can be appropriately dissolved in the monomer D. In other words, it can be said that the heating unit 12A generates the dissolution liquid Pd in the dissolution unit 12 by heating the monomer D and the polyester raw material Pm supplied to the dissolution unit 12 to the predetermined temperature. That is, the predetermined temperature can also be said to be the temperature of the dissolution liquid Pd. The temperature (predetermined temperature) of the dissolution liquid Pd is preferably 140°C or higher and 300°C or lower, more preferably 160°C or higher and 280°C or lower, and even more preferably 170°C or higher and 200°C or lower. Note that the impurity R may contain a component that melts when the dissolution liquid Pd is heated to the above temperature (predetermined temperature). Therefore, when the impurity R contains a component that melts when heated to the predetermined temperature, a part of it is in a molten state and is contained in the dissolution liquid Pd. In this embodiment, the heating unit 12A is provided in the dissolution unit 12, but the position where the heating unit 12A is provided is not limited to this 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 liquid Pd in the dissolution unit 12. In this case, the detection unit 60 as the temperature sensor is provided at a position where the temperature of the monomer D in the dissolution unit 12 can be detected. Further, the detection unit 60 may include a timer that measures time. The detection unit 60 as the timer detects, for example, the processing time, which is the time from when both the polyester raw material Pm and the monomer D are supplied to the dissolution unit 12. Note that the detection unit 60 may be realized by a temperature sensor having a timer function, or may be realized by providing a temperature sensor and a timer respectively.

[0028] (Solid-Liquid Separation Section) The solid-liquid separation section 13 is located in the dissolution section 12. The solid-liquid separation section 13 collects solid impurities R contained in the dissolution liquid Pd stored in the dissolution section 12 and separates the solid impurities R from the dissolution liquid Pd. The solid-liquid separation section 13 is a mesh-shaped filter through which liquid passes and which collects solids. In this embodiment, the solid-liquid separation section 13 is a container shape with an open top and is located at a predetermined distance from the sides and bottom of the dissolution section 12. The solid-liquid separation section 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 section 12 to the storage section 20 downstream. The dissolution liquid Pd flowing from the dissolution section 12 into the inlet pipe 12a passes through the solid-liquid separation section 13. As a result, the solid-liquid separation section 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 only needs to be able to separate solid impurities of a predetermined size or larger from the dissolving solution Pd, and is not limited to filtration or centrifugal separation.

[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 a 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 region where impurities are stored by centrifugal separation.

[0031] Incidentally, after discharging the dissolution liquid Pd from the dissolution section 12, the foreign matter recovery section 50 supplies the reaction solvent M (for example, methanol) to the dissolution section 12, washes the substances (such as waste clothing) remaining in the dissolution section 12, and dissolves the monomer D (for example, DMT) adhering to the remaining substances in the reaction solvent M for recovery. For example, the monomer D may be recovered by distilling and separating the reaction solvent M and the monomer D from the recovered liquid of the monomer D. The substances remaining in the dissolution section 12 refer to the impurities R (such as metal buttons and vegetable fibers) contained in the polyester raw material Pm (such as clothes). Among the impurities R, the vegetable fibers may be reused. For example, the washed cotton becomes the raw material for recycled cotton yarn. Also, the washed other impurities R (such as metal buttons) may be appropriately disposed of or reused.

[0032] (Storage section) The storage section 20 is a tank in which the dissolution liquid Pd is stored. The storage section 20 is connected to the dissolution section 12 via the introduction pipe 12a. The dissolution liquid Pd in the dissolution section 12 is supplied to the storage section 20 through the introduction pipe 12a. The introduction pipe 12a is provided with an adjustment section 12a1 for adjusting the amount of the dissolution liquid Pd supplied from the dissolution section 12 to the storage section 20. The adjustment section 12a1 is, for example, an on-off valve. In the open state, the dissolution liquid Pd in the dissolution section 12 is supplied to the storage section 20, and in the closed state, the supply of the dissolution liquid Pd in the dissolution section 12 to the storage section 20 is stopped. However, the adjustment section 12a1 is not limited to being an on-off valve and may be any mechanism capable of adjusting the supply of the dissolution liquid Pd to the storage section 20. In the present embodiment, the storage section 20 is connected to the dissolution section 12 via the introduction pipe 12a, but a temporary storage section for temporarily storing the dissolution liquid Pd may be provided between the dissolution section 12 and the storage section 20.

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

[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 specific gravity greater than that of 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 specific gravity less than that of 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 (a 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 on 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 the 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] (Outlet section) 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 a position in the storage section 20 where a layer of polyester solution P 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 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 section) The removal section 26 is a mechanism for removing the third impurity R3 contained in the polyester solution P from the polyester solution P. The removal section 26 is connected to the storage section 20 and removes the third impurity R3 present in the polyester solution P discharged from the storage section 20 from the polyester solution P. In this embodiment, the removal section 26 is provided with a filter 26a and an adsorption tower 26b.

[0044] (Filter) 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 collects 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 introduction 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 of 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, thereby bringing the reaction solvent M 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, and for example, materials similar to those used in contact devices that extract active ingredients by bringing heavy oil and water into contact can be used. Specific examples of packing materials include pipes made of SUS, etc., Raschig rings, Berl saddles, Terralets, balls, etc.

[0052] An introduction tube 20c is connected to the first reaction section 16A. More specifically, an inlet 16C of the introduction tube 20c, which is an opening into which the polyester solution P from the storage section 20 is introduced, is connected to the first reaction section 16A. The inlet 16C is connected to the surface 16A1 of the first reaction section 16A on the first direction Y1 side. The introduction tube 20c is connected to the surface 16A1 such that the inlet 16C opens facing the second direction Y2 side, opposite to the first direction Y1. Thus, in this embodiment, the inlet 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 16C does not have to be directly connected to the first reaction section 16A, and the inlet 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 storage section 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 reaction solvent M in a supercritical or subcritical state (pressurized gas or pressurized liquid) introduced from the inlet 16D moves within the first reaction section 16A in the first direction Y1. In the first reaction section 16A, the reaction solvent M in a supercritical or subcritical state (pressurized gas or pressurized liquid) 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 reaction solvent M in a supercritical or subcritical state (pressurized gas or pressurized liquid). 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 was 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 discharged from the first reaction section 16A. In this embodiment, since the first solvent M1 is discharged 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 (the 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 an opening from 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] 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 section) In the separation section 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 tower connected to the outlet pipe 16a. The second solvent M2 containing the second depolymerized polyester P2 is introduced into the first separation section 18A via the outlet pipe 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 pipes 18Aa and 18Ab are connected to the first separation section 18A. The low-boiling point component is discharged from outlet pipe 18Aa, and the high-boiling point component is discharged from outlet pipe 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 a reaction solvent M and monomer E. Discharge tubes 18Ba and 18Bb are connected to the second separation section 18B. The 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. The monomer D separated in the third separation section 18C is discharged from the discharge tube 18Cb, and the 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 the monomer D 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 the supply of monomer D 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 that position 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: a main memory device such as RAM (Random Access Memory) and ROM (Read Only Memory), and an external memory device such as an 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 processing. The processing unit 40 may execute these processing using one CPU, or it may have multiple CPUs and execute the processing using 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 for the system control unit 46 to control 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 for the system control unit 46 to control 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. Also, if the solid-liquid separation unit 13 is equipped with a drive unit, the system control unit 46 controls the operation of the solid-liquid separation unit 13. The system control unit 46 controls the adjustment unit 12a1 to control the amount of dissolving solution Pd supplied from the dissolving 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 from the storage unit 20. The system control unit 46 controls the discharge unit 24 to discharge the polyester solution P separated from the impurities R in the storage unit 20 from 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 lead-out unit 24 to lead out the polyester solution P from the storage unit 20. The polyester solution P led out 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 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 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 and plant fibers) Here, when the polyester raw material Pm contains both polyester components and plant fibers, it is required 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 the index) Based on the dissolution conditions acquired by the information acquisition unit 44, the calculation unit 45 calculates the index R shown in the following formula (1). ０ Calculate.

[0083] R ０ =Log(t・exp[(T-100) / 14.75])...(1)

[0084] In formula (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 uses 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, and calculates the index R shown in equation (1). ０ Calculate.

[0086] Furthermore, the calculation unit 45 calculates the index R ０ Determine whether it is within a predetermined range. Index R ０ The predetermined range 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 calculates the index R based on the latest dissolution conditions obtained by the information acquisition unit 44. ０ The results are calculated sequentially.

[0088] (Control of dissolution conditions) The system control unit 46 controls the index R ０ The dissolution conditions are controlled so that the index R 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 section 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 section 12, and the temperature of the dissolved solution Pd in ​​the dissolution section 12. That is, the system control unit 46 controls the index R ０ The processing time and the temperature of the dissolving solution Pd are controlled to fall within the predetermined range described above.

[0089] For example, the system control unit 46 maintains the temperature of the dissolving solution Pd within the predetermined temperature range, while the index R calculated by the calculation unit 45 ０ When the index R reaches a predetermined range, the dissolution process in the dissolution section 12 is terminated. That is, for example, the system control unit 46 determines the index R ０ When the temperature reaches a predetermined range, the adjustment unit 12a1 is controlled 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] Thus, the index R ０ By adjusting the dissolution conditions (in this case, the temperature of the dissolution solution and the processing time) so that the results fall 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 the polyester raw material Pm and monomer D to the dissolution unit 12 via the system control unit 46 and starts the dissolution of these 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 calculates the index R via the calculation unit 45. ０ The calculation unit 45 determines whether the index R has reached a predetermined range (step S14). ０ If it is determined that the index R has reached a predetermined range (step S14; Yes), the control unit 30 causes the system control unit 46 to stop dissolving in the dissolving section 12 (step S16). Specifically, the system control unit 46 discharges the dissolving solution Pd from the dissolving section 12 to the storage section 20. The control unit 30 then determines that the index R ０ If it is determined that the index R has not reached the predetermined range (step S14; No), the process returns to step S12, and index R ０ Processing continues until the value reaches a predetermined range.

[0092] (Effects of the Disclosure) The separation system according to the first aspect of the 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 solution Pd in ​​which polyester is dissolved in monomer D, a detection unit 60 for detecting the temperature of the solution Pd, and an index R shown in formula (1) above. ０ The system includes a control unit 30 that controls the dissolution conditions, including 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 dissolution solution Pd, such that the ratio 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 is index R ０The dissolution conditions are controlled so that the ratio is in the range of 2 to 3.5. This suppresses the destruction of the plant fiber structure. In other words, according to this embodiment, the polyester and plant fiber can be appropriately separated, and the plant fiber can be appropriately recovered and reused, for example.

[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 appropriately 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] The control device according to the sixth aspect of this disclosure includes an information acquisition unit 44 that acquires the temperature of a solution Pd obtained 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 an index R shown in the above formula (1) ０ The system includes a system control unit 46 that controls dissolution conditions, including processing time and temperature of the dissolving solution Pd, such that the ratio is between 2 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 containing polyester and plant fibers to a dissolution unit 12 to produce a dissolution Pd in ​​which polyester is dissolved in monomer D; detecting the temperature of the dissolution Pd; and using an index R shown in formula (1) above. ０ The process includes a step of controlling dissolution conditions, which includes a processing time (the time from when the polyester raw material Pm and monomer D are supplied to the dissolution section) and the temperature of the dissolution solution Pd, such that the ratio 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 includes the steps of supplying a monomer D derived from a carboxylic acid and a polyester raw material Pm containing polyester and plant fibers to a dissolution unit 12 to produce a dissolution Pd in ​​which polyester is dissolved in monomer D; detecting the temperature of the dissolution Pd; and the index R shown in formula (1) above. ０ The computer is instructed to perform a step of controlling the dissolution conditions, including the processing time (the time elapsed since the 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 ratio is between 2 and less than 4.5.

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

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

[0105] (Example 1) In Example 1, a material containing polyester and cotton was prepared as the polyester raw material. This polyester raw material was then added to a tank containing DMT as a monomer. At that time, the temperature of the dissolution solution in the tank was set to 160°C, and the processing time (the time from when the polyester raw material was added to the tank until the dissolution solution was discharged) was set to 2 minutes. Therefore, the index R in Example 1 ０ The value became 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 dissolving solution 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 where it could not be reused, were marked with ×, and cases where polyester and cotton could be separated and the cotton was not damaged to the point where it could be reused were marked with ○. As shown in Table 1, the index R ０ In Examples 1, 2, and 3, where the ratio is 2 or more and less than 4.5, it can be seen that the polyester dissolves appropriately, allowing for proper separation of polyester and cotton, and suppressing damage to the cotton. On the other hand, the index R ０ In Comparative Example 1, where the index R is less than 2, the polyester does not dissolve properly, and the polyester and cotton can be properly separated. ０ In Comparative Example 2, where the score is 4.5 or higher, it can be seen that the cotton is damaged to the point where it cannot be reused.

[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.

[0109] 1 Separation system 12 Dissolution section 13 Solid-liquid separation section 14 Reaction solvent storage section 16 Reaction section 18 Separation section 20 Storage section 22 Discharge section 26 Removal section 30 Control section 60 Detection section D, E Monomer M Reaction solvent P Polyester solution Pd Dissolving solution Pm Polyester raw material R Impurities R1 First impurity R2 Second impurity R3 Third impurity

Claims

1. A dissolution unit that receives monomers derived from carboxylic acids and polyester raw materials including polyester and plant fibers to produce a solution in which the polyester is dissolved in the monomer; a detection unit that detects the temperature of the solution; and an index R shown in the following formula (1). ０ A separation system comprising: a control unit for controlling dissolution conditions, including a 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. ０ =Log(t・exp[(T-100) / 14.75]) ... (1) where t refers to the processing time (min) and T refers to the temperature of the dissolving solution (°C).

2. The control unit controls the index R ０ The separation system according to claim 1, wherein the dissolution conditions are controlled so that the ratio is in the range of 2 or more and 3.5 or less.

3. The separation system according to claim 1 or 2, wherein 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.

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

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

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, and an index R shown in the following formula (1) ０ A control device including a system control unit that controls dissolution conditions, including the processing time and the temperature of the dissolution solution, such that R is 2 or more and less than 4.

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

7. A step of supplying a monomer derived from a carboxylic acid and a polyester raw material containing polyester and plant fibers to a dissolution section to produce a solution in which the polyester is dissolved in the monomer; a step of detecting the temperature of the solution; and an index R shown in the following formula (1) ０ A separation method comprising the step of controlling dissolution conditions, including a 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. ０ =Log(t・exp[(T-100) / 14.75]) ... (1) where t refers to the processing time (min) and T refers to the temperature of the dissolving solution (°C).

8. A step of supplying a monomer derived from a carboxylic acid and a polyester raw material containing a polyester and a vegetable fiber to a dissolution part to generate a solution in which the polyester is dissolved in the monomer; a step of detecting the temperature of the solution; an index R shown in the following formula (1) ０ A program for causing a computer to execute a step of controlling dissolution conditions including a treatment time, which is the time after the polyester raw material and the monomer are supplied to the dissolution part, and the temperature of the solution, so that is 2 or more and less than 4.

5. R ０ = Log(t · exp[(T - 100) / 14.75])... (1) However, t indicates the treatment time (min), and T indicates the temperature (°C) of the solution.

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