Method for producing recycled resin composition

Abstract

The present disclosure addresses the problem of providing a low-energy production method with which it is possible to separate a material in a polymer state from a mixture containing a plurality of materials. A method for producing a recycled resin composition according to the present disclosure comprises a separation step A of separating a resin composition A from a resin mixture containing at least the resin composition A and an article B containing a material b. The resin composition A has a glass transition temperature and / or a melting point temperature in the presence of water. The method further comprises a heat treatment step A of melting the resin composition A by bringing the resin mixture into contact with water at a temperature equal to or higher than the glass transition temperature or the melting point temperature in the presence of water of the resin composition A and at a pressure equal to or higher than a saturated water vapor pressure.

Description

Method for manufacturing recycled resin compositions

[0001] This disclosure relates to a method for producing recycled resin compositions, and to a method for recycling resin compositions and resin mixtures.

[0002] In recent years, attention has been focused on recycling waste materials from the perspective of reducing environmental impact. Plastics are indispensable resins in various industries, but their recycling rate as a material is low, and incineration and landfill disposal remain the main methods of disposal, which is a problem. For example, in the automotive industry, since the enactment of various laws, the recycling of materials has become urgently required. Generally, after end-of-life vehicles (ELVs) are collected, they are crushed and separated into residues (Automobile Shredder Residue; ASR) containing metals and other resins through physical destruction. ASR may contain polypropylene resin, polyethylene resin, polyamide resin, ABS resin, polycarbonate resin, polyurethane resin, polyethylene terephthalate resin, and polybutylene terephthalate resin. Therefore, when recycling these materials, it is necessary to separate individual materials from mixtures containing multiple materials.

[0003] As a method for recycling mixtures containing multiple materials, for example, a method for separating light plastics and heavy plastics based on their specific gravity difference is known. Specifically, a technique is known for efficiently separating mixed plastic slurries while washing them using a special stirring method (for example, Patent Document 1).

[0004] Furthermore, there is a recycling technology called chemical recycling, which is known to allow for high-purity recycling by decomposing polymers into monomers, followed by purification and repolymerization. As a method for recycling mixtures containing multiple materials using chemical recycling, considering the presence of various substances and the enormous time, energy, and cost required to separate them, a method is known for ASR (Advanced Plastic Residue) mainly composed of foamed plastic, in which a specific treatment is performed before the decomposition reaction step (for example, Patent Document 2).

[0005] Japanese Patent Publication No. 11-005218 Japanese Patent Publication No. 2001-64437

[0006] However, the method described in Patent Document 1 had the problem of poor separation accuracy due to the shape of the resin and air bubbles inside the resin. Furthermore, the types of resins to which it could be applied were limited, making it difficult to apply to the separation of mixtures consisting of various materials. The method described in Patent Document 2 solved the problems of conventional chemical recycling, but the energy required for purification and repolymerization after decomposing the resin into monomers was enormous, making it insufficient as an environmentally friendly recycling method.

[0007] This disclosure has been made in view of the above circumstances, and its purpose is to provide a low-energy recycling method that enables the separation of materials in a polymer state from a mixture containing multiple materials, and a method for producing a recycled resin composition. Preferably, the disclosure is to provide a recycling method that enables the separation of materials from a mixture containing multiple materials regardless of the shape of the materials or internal bubbles, and a method for producing a recycled resin composition.

[0008] As a result of diligent research to solve the above problems, the present inventors have found that a mixture containing at least one polymer resin composition (resin composition A) and article B containing material b can be melted and separated by contacting it with water at a temperature above the glass transition temperature or melting point temperature of resin composition A in the presence of water, and above the saturated water vapor pressure, thereby enabling the recycling of resin composition A. Furthermore, a method for recycling a resin composition or resin mixture, or a method for producing a recycled resin composition, is characterized by comprising: a heat treatment step of melting resin composition A and separating it from the resin mixture by contacting a mixture containing at least two polymer resin compositions (resin composition A and resin composition B) with water at a temperature above the glass transition temperature or melting point of resin composition A in the presence of water, and below the glass transition temperature or melting point of resin composition B in the presence of water, and at a saturated water vapor pressure above the saturated water vapor pressure, wherein the glass transition temperature or melting point of resin composition A in the presence of water is ≤ resin composition B (preferably resin composition A < resin composition B), and a recovery step of recovering the resin mixture from which at least one polymer resin composition has been removed and / or resin composition A. This disclosure was completed based on the discovery that a resin composition or resin mixture can be recycled without using chemical substances or aqueous solutions thereof, such as organic solvents or alkaline aqueous solutions, which can cause environmental burden and decomposition or degradation of polymers.

[0009] The gist of this disclosure is as follows: [Item 1] A method for producing a recycled resin composition, comprising a separation step A for separating the resin composition A from a resin mixture comprising at least a resin composition A and an article B containing material b, wherein the resin composition A has a glass transition temperature and / or a melting point temperature in the presence of water, and further comprising a heat treatment step A for melting the resin composition A by contacting the resin mixture with water at a temperature equal to or greater than the glass transition temperature or melting point temperature of the resin composition A in the presence of water and equal to or greater than the saturated water vapor pressure. [Item 2] The method for producing a recycled resin composition according to Item 1, wherein if the resin composition A has a melting point temperature in the presence of water, the melting point temperature in the presence of water is used as the reference temperature for the resin composition A, if the resin composition A does not have a melting point temperature in the presence of water, the glass transition temperature in the presence of water is used as the reference temperature for the resin composition A, the processing temperature of the heat treatment step A is equal to or greater than the reference temperature for the resin composition A, and the processing pressure of the heat treatment step A is equal to or greater than the saturated water vapor pressure at the processing temperature. [Item 3] The method for producing a recycled resin composition according to Item 1 or 2, wherein the article B is a resin composition B, and the glass transition temperature or melting point temperature of the resin composition B in the presence of water is less than the glass transition temperature or melting point temperature of the resin composition B in the presence of water, and further, the processing temperature of the heat treatment step A is less than or equal to the glass transition temperature or melting point temperature of the resin composition B in the presence of water. [Item 4] The method for producing a recycled resin composition according to Item 2, wherein the article B is a resin composition B, and if the resin composition B has a melting point temperature in the presence of water, the melting point temperature in the presence of water is used as the reference temperature for the resin composition B, and if the resin composition B does not have a melting point temperature in the presence of water, the glass transition temperature in the presence of water is used as the reference temperature for the resin composition B, and further, the reference temperature of the resin composition B is higher than the reference temperature of the resin composition A, and the processing temperature of the heat treatment step A is less than or equal to the reference temperature of the resin composition B.[Item 5] A method for producing a recycled resin composition according to Item 3 or 4, wherein the resin mixture further comprises a resin composition C, wherein the glass transition temperature or melting point temperature of the resin composition C in the presence of water is less than that of the resin composition B, and the method for producing a recycled resin composition comprises a heat treatment step B and a separation step B, wherein the resin composition B is melted and separated from the resin mixture by contacting it with water at a temperature equal to or greater than the glass transition temperature or melting point temperature of the resin composition B in the presence of water, and equal to or less than the glass transition temperature or melting point temperature of the resin composition C in the presence of water, and at or greater than the saturated water vapor pressure. [Item 6] The manufacturing method according to Item 4, wherein the resin mixture further comprises a resin composition C, a heat treatment step B for melting the resin composition B by contacting the resin mixture after the separation of the resin composition A with water, and a separation step B for separating the resin composition B from the resin mixture, wherein if the resin composition C has a melting point temperature in the presence of water, the melting point temperature in the presence of water is used as the reference temperature for the resin composition C, if the resin composition C does not have a melting point temperature in the presence of water, the glass transition temperature in the presence of water is used as the reference temperature for the resin composition C, the reference temperature of the resin composition C is higher than the reference temperature of the resin composition B, the processing temperature of the heat treatment step B is higher than or equal to the reference temperature of the resin composition C, and the processing pressure of the heat treatment step B is higher than or equal to the saturated water vapor pressure at the processing temperature. [Item 7] The manufacturing method according to any one of Items 3 to 6, wherein the resin a constituting the matrix of the resin composition A is a thermoplastic resin, and the resin b constituting the matrix of the resin composition B is a thermoplastic resin. [Clause 8] The manufacturing method according to Clause 5 or 6, wherein the resin c constituting the matrix of the resin composition C is a thermoplastic resin. [Clause 9] The manufacturing method according to any one of Clauses 1 to 8, characterized in that the heat treatment step A has a treatment temperature of 100°C or more and 250°C or less, and a treatment pressure of 0.1 MPa or more and 4.0 MPa or less. [Clause 10] The manufacturing method according to Clause 5, Clause 6, or Clause 8, characterized in that the heat treatment step B has a treatment temperature of 100°C or more and 250°C or less, and a treatment pressure of 0.1 MPa or more and 4.0 MPa or less.[Clause 11] The manufacturing method according to any one of Clauses 1 to 10, characterized in that in the separation step A, the resin composition A is separated from the resin mixture by applying an external force. [Clause 12] The manufacturing method according to any one of Clauses 1 to 11, wherein the material b is an inorganic substance and the article B does not contain resin. [Clause 13] A recycled resin composition manufactured by the manufacturing method according to any one of Clauses 1 to 12. [Clause 14] A manufacturing method for a recycled resin composition, characterized by comprising: a heat treatment step AB in which a resin mixture containing resin composition A and resin composition B, wherein the glass transition temperature or melting point temperature in the presence of water is at least ≤ resin composition A and resin composition B, is brought into contact with water at a temperature equal to or greater than the glass transition temperature or melting point temperature of resin composition B in the presence of water and at or greater than the saturated water vapor pressure, thereby melting resin composition A and resin composition B; and a separation step AB in which resin composition A or resin composition B is separated in water. [Clause 15] The manufacturing method according to Clause 14, wherein if the resin composition A has a melting point temperature in the presence of water, the melting point temperature in the presence of water is used as the reference temperature for the resin composition A; if the resin composition A does not have a melting point temperature in the presence of water, the glass transition temperature in the presence of water is used as the reference temperature for the resin composition A; if the resin composition B has a melting point temperature in the presence of water, the melting point temperature in the presence of water is used as the reference temperature for the resin composition B; if the resin composition B does not have a melting point temperature in the presence of water, the glass transition temperature in the presence of water is used as the reference temperature for the resin composition B; the reference temperature of the resin composition B is equal to or greater than the reference temperature of the resin composition A; the processing temperature of the heat treatment temperature AB is equal to or greater than the reference temperature of the resin composition B; and the processing pressure of the heat treatment temperature AB is equal to or greater than the saturated water vapor pressure at the processing temperature. [Clause 16] The manufacturing method according to Clause 14 or Clause 15, wherein the separation step AB includes separating by at least one of water flow, filtering, or difference in specific gravity of the resin compositions.

[0010] According to one aspect of this disclosure, a novel recycling method and a method for producing a recycled resin composition can be provided that allows for the separation and recovery of a material (resin composition) in polymer form from a mixture containing multiple materials. The recycling method and production method according to one aspect of this disclosure do not decompose the resin to monomers, thus reducing the energy required for purification and repolymerization, and enabling the recovery of the resin (resin composition) as a low-energy process. Preferably, according to one aspect of this disclosure, the resin (resin composition) can be separated regardless of the shape of the material or the presence or absence of internal bubbles, enabling more stable separation compared to conventional methods. Even more preferably, according to one aspect of this disclosure, a novel recycling method can be provided that does not require an alkaline aqueous solution for the separation of polymer resins. Since the recycling method and production method do not use an alkaline aqueous solution or reduce its use, damage to the polymer resin due to alkaline treatment can be suppressed, and the polymer resin can be easily recovered in a process with a low environmental impact.

[0011] DSC measurement results of nylon 66 in air and water. Example 1 of the apparatus used in this disclosure. Example 2 of the apparatus used in this disclosure. Example 3 of the apparatus used in this disclosure.

[0012] One embodiment of the present disclosure of a method for recycling a resin composition and a method for manufacturing a recycled resin composition is a method that includes a heat treatment step A in which a resin mixture containing a resin composition A having a glass transition temperature and / or melting temperature in the presence of water and an article B containing material b is brought into contact with water at a temperature equal to or greater than the glass transition temperature or melting temperature of the resin composition A in the presence of water and equal to or greater than the saturated water vapor pressure, and is applicable as both a method for recycling a resin composition and a method for recycling a resin mixture. Furthermore, one embodiment of the present disclosure of a method for recycling a resin composition or resin mixture and a method for manufacturing a recycled resin composition is a method in which, if the resin composition A has a melting temperature in the presence of water, the melting temperature in the presence of water is used as the reference temperature for the resin composition A, and if the resin composition A does not have a melting temperature in the presence of water, the glass transition temperature in the presence of water is used as the reference temperature for the resin composition A, the processing temperature of the heat treatment step A is equal to or greater than the reference temperature for the resin composition A, and the processing pressure of the heat treatment step A is equal to or greater than the saturated water vapor pressure at the processing temperature. Furthermore, one embodiment of the recycling method and manufacturing method according to the present disclosure is a method comprising: a heat treatment step A in which a resin mixture containing at least two polymer resin compositions (resin composition A, resin composition B) has a glass transition temperature or melting point temperature in the presence of water such that resin composition A ≤ resin composition B (preferably resin composition A < resin composition B), and the resin mixture is brought into contact with water at a temperature above the glass transition temperature or melting point temperature of resin composition A in the presence of water, and below the glass transition temperature or melting point temperature of resin composition B in the presence of water, and at a saturated water vapor pressure above the saturated water vapor pressure, thereby melting resin composition A and separating it from the mixture; and a recovery step in which the resin mixture from which at least one polymer resin composition has been removed and / or resin composition A is recovered.Furthermore, one embodiment of the recycling method and manufacturing method relating to this disclosure is a method wherein, if the resin composition B has a melting point temperature in the presence of water, the melting point temperature in the presence of water is used as the reference temperature for the resin composition B, and if the resin composition B does not have a melting point temperature in the presence of water, the glass transition temperature in the presence of water is used as the reference temperature for the resin composition B, the reference temperature of the resin composition B is higher than the reference temperature of the resin composition A, the processing temperature of the heat treatment step A is equal to or greater than the reference temperature of the resin composition A and equal to or less than the reference temperature of the resin composition B, and the processing pressure of the heat treatment step A is equal to or greater than the saturated water vapor pressure at the processing temperature. In this specification, "water" does not necessarily refer to liquid water, but rather to H as a compound. ２ O. In this disclosure, H is greater than or equal to the saturated water vapor pressure. ２ Depending on its temperature and pressure, O may be in a liquid state (so-called hot water), a gaseous state (water vapor), subcritical water, or supercritical water. In this specification, "in the presence of water" or "in water" means a state in which water can affect the physical properties of the resin composition, and "in the air" means a gaseous atmosphere in which water does not substantially affect the physical properties of the resin composition. Furthermore, in this specification, "having no melting point temperature" means that when measurements are taken using a differential scanning calorimeter in the temperature range of 30 to 300°C, a clear melting point peak is not detected, and therefore the melting point temperature cannot be measured.

[0013] (Resin Composition) First, let's explain resin compositions. Resin compositions are resin products used, for example, in automobile parts, electrical appliances, household goods, etc. Generally, they are resin compositions to which the following additives are added, but in this specification, resins that do not contain additives are also included as resin compositions.

[0014] Examples of additives include stabilizers such as antioxidants and heat aging inhibitors, colorants such as pigments and dyes, antistatic agents, flame retardants, blooming inhibitors, and various fillers such as glass fibers, glass particles, talc, and calcium carbonate. The resin composition may also be a polymer alloy.

[0015] In one aspect of this disclosure, a resin mixture containing a resin composition is subject to recycling. The resin mixture includes article B containing resin composition A and material b. Article B and material b are different from resin composition A. Material b can be metal, glass, ceramics, inorganic substances, or resins, and if it is a resin, it may be a thermosetting resin or a thermoplastic resin. In particular, it is preferable that material b is a resin and article B is a resin composition, and when article B is a resin composition, article B is also referred to as "resin composition B". Article B may be a solid that does not contain resin, and may be composed of inorganic substances such as metal, glass, or ceramics. The resin mixture contains multiple resin compositions, and it is preferable that the resin compositions are physically mixed with each other. A typical example is when resin parts of an automobile or the like are crushed in a shredder, and the crushed material is physically mixed without any particular sorting. The resin mixture may contain materials other than resin compositions, such as metal or glass. Also, the resin composition may be attached to metal or glass, etc. The recycling method and manufacturing method described herein preferably allow processing regardless of the shape or internal structure (for example, the presence or absence of internal bubbles) of the materials such as the resin composition contained in the resin mixture.

[0016] Resin composition A contains a matrix resin a. Resin composition B contains a matrix resin b. The resin mixture may further contain resin composition C, which contains a matrix resin c. Here, the matrix resin is the resin that forms a continuous layer in the resin composition, and is usually the largest component in terms of weight of the resin components. However, in the case of a polymer alloy, the polymer alloy is treated as a single resin (e.g., resin a), rather than the individual resins that make up the polymer alloy. The resin mixture may further contain resin composition D, and may contain yet another resin composition.

[0017] Thermoplastic resins are preferred as the resin constituting the matrix of the resin composition. Examples of thermoplastic resins include polyolefin resins (e.g., polypropylene, polyethylene, etc.), polyethylene vinyl acetate copolymer resins, polyamide resins, polyester resins, polystyrene resins, styrene copolymer resins, polycarbonate resins, polyurethane resins, acrylic resins, synthetic rubber resins, and polymer alloys.

[0018] Examples of polyamide resins include polycaproamide (nylon 6), polyhexamethylene adipamide (nylon 66), polytetramethylene adipamide (nylon 46), polyhexamethylene sebaamide (nylon 610), polyhexamethylene dodecamide (nylon 612), polylauryl lactam (nylon 12), and polyundecaneamide (nylon 11).

[0019] Examples of polyester resins include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, as well as polyester elastomers such as polybutylene terephthalate-polytetramethylene glycol, polybutylene terephthalate-polycaprolactone copolymer, and polybutylene terephthalate-polycarbonate copolymer.

[0020] Examples of styrene copolymer resins include ABS resin and AS resin. Examples of synthetic rubber resins include styrene-based, olefin-based, PVC-based, urethane-based, ester-based, and amide-based thermoplastic elastomers. ABS resin is a representative polymer alloy, but other examples of polymer alloys include combinations of ABS resin with carbonate, polybutylene terephthalate, polyamide, etc., and combinations of polystyrene with polyphenylene ether, polycarbonate, etc.

[0021] When a resin mixture obtained by mixing multiple resin compositions is considered to be 100% by weight, it is preferable that resin composition A is present in an amount of 5% or more by weight, and more preferably 10% or more by weight. The same applies to resin composition B, resin composition C, etc. In other words, in this disclosure, it is preferable that resin composition A, resin composition B, and resin composition C, etc., refer to resin compositions that constitute 5% or more by weight in the resin mixture. In this disclosure, it is also possible to separate resin compositions with a weight ratio of less than 5%, but from an economic and productivity standpoint, it may be more advantageous to recycle resin compositions with a weight ratio of less than 5% while they are mixed in with the separated resin composition (for example, resin composition A or resin composition B). Furthermore, it is preferable that resin composition A constitutes 95% by mass or less in the resin mixture, and more preferably 90% by mass or less. The same applies to resin composition B and resin composition C. Furthermore, if the resin mixture contains resin compositions D, E, F, etc., in amounts of 5% or more by weight, the preferred upper limit for each of these compositions decreases in increments of 5% by weight, starting with 85% by weight or less, then 80% by weight or less, and so on, depending on the number of resin compositions included.

[0022] When resin composition B is present in the resin mixture, it is preferable that the glass transition temperature or melting point temperature in the presence of water is less than that of resin composition B. In the above case, it is preferable that the glass transition temperature in the presence of water is less than that of resin composition B, or that the melting point temperature in the presence of water is less than that of resin composition B. If both resin composition A and resin composition B have a melting point temperature, it is preferable that the melting point temperature of resin composition A is less than that of resin composition B. Furthermore, it is preferable that the higher of the glass transition temperature or melting point temperature of resin composition A is less than the lower of the glass transition temperature or melting point temperature of resin composition B. The temperature difference in the above inequality relationship is preferably 5°C or more, and is more preferably in the order of 10°C or more, 15°C or more, 20°C or more, 25°C or more, and 30°C or more.

[0023] In one embodiment of the present disclosure, when the resin mixture includes resin composition A and resin composition B, if resin composition A has a melting point temperature in the presence of water, the melting point temperature in the presence of water is used as the reference temperature for resin composition A; if resin composition A does not have a melting point temperature in the presence of water, the glass transition temperature in the presence of water is used as the reference temperature for resin composition A; and if resin composition B has a melting point temperature in the presence of water, the melting point temperature in the presence of water is used as the reference temperature for resin composition B; if resin composition B does not have a melting point temperature in the presence of water, the glass transition temperature in the presence of water is used as the reference temperature for resin composition B, and it is preferable that the reference temperature of resin composition B is higher than the reference temperature of resin composition A. The difference between the reference temperature of resin composition A and the reference temperature of resin composition B is preferably 5°C or more, more preferably 10°C or more, even more preferably 15°C or more, even more preferably 20°C or more, even more preferably 25°C or more, and even more preferably 30°C or more, and there is no particular upper limit, but it is preferably 100°C or less.

[0024] The resin mixture may include resin composition C in addition to resin composition A and resin composition B. Resin composition C has a glass transition temperature or melting point temperature in the presence of water such that resin composition B < resin composition C. The relationship between the glass transition temperatures or melting points of resin composition B and resin composition C in the presence of water is the same as the relationship between resin composition A and resin composition B described above.

[0025] In one embodiment of the present disclosure, if the resin mixture further includes resin composition C in addition to resin composition A and resin composition B, if resin composition C has a melting point temperature in the presence of water, the melting point temperature in the presence of water is used as the reference temperature for resin composition C, and if it does not have a melting point temperature in the presence of water, the glass transition temperature in the presence of water is used as the reference temperature for resin composition C, and it is preferable that the reference temperature of resin composition C is higher than the reference temperature of resin composition B. The difference between the reference temperature of resin composition B and the reference temperature of resin composition C is preferably 5°C or more, more preferably 10°C or more, even more preferably 15°C or more, even more preferably 20°C or more, even more preferably 25°C or more, and even more preferably 30°C or more, and there is no particular upper limit, but it is preferably 100°C or less.

[0026] (Heat Treatment Process) In one embodiment of the present disclosure, a heat treatment process A is included, in which a resin mixture containing resin composition A and article B is brought into contact with water at a temperature above the glass transition temperature or melting point temperature of resin composition A in the presence of water, and at a saturated water vapor pressure above that temperature. If article B is a thermoplastic resin composition (resin composition B), the heat treatment process A brings the resin mixture containing resin composition A and resin composition B into contact with water at a temperature above the glass transition temperature or melting point temperature of resin composition A in the presence of water, and below the glass transition temperature or melting point temperature of resin composition B in the presence of water, and at a saturated water vapor pressure above that temperature. This process softens resin composition A, making it fluid and easy to separate from the resin mixture. If resin composition B is included, resin composition B does not melt or soften and maintains its shape. By taking advantage of the fact that resin composition A is fluid and resin composition B maintains its shape during and / or after heat treatment process A, it becomes easy to separate resin composition A. Therefore, regardless of the shape or internal structure of resin composition A in the resin mixture, resin composition A can be easily separated and recovered.

[0027] In one embodiment of the present disclosure, it is preferable that the heat treatment step A has a treatment temperature equal to or greater than the reference temperature of the resin composition A, and a treatment pressure equal to or greater than the saturated water vapor pressure at the treatment temperature. Furthermore, if the resin mixture includes resin composition A and resin composition B (preferably a thermoplastic resin composition), it is preferable that the heat treatment step A has a treatment temperature equal to or greater than the reference temperature of the resin composition A and less than or equal to the reference temperature of the resin composition B (preferably less than the reference temperature of the resin composition B), and a treatment pressure equal to or greater than the saturated water vapor pressure at the treatment temperature.

[0028] The heat treatment process will be explained in more detail. For example, crystalline polymers such as polypropylene and polyethylene terephthalate have a melting point temperature associated with crystalline melting, while amorphous polymers such as polycarbonate have a glass transition point (glass transition temperature) of the amorphous chain. In this heat treatment process A, if resin a constituting the matrix of resin composition A is a crystalline polymer, it is preferable to melt resin composition A at a temperature above its melting point temperature in the presence of water. By treating it at a temperature above its melting point temperature in water, resin composition A can be sufficiently melted. If resin a is an amorphous polymer, it is preferable to melt resin composition A at a temperature above its glass transition temperature in the presence of water. Furthermore, if resin composition B has a melting point temperature, it is preferable that the heat treatment temperature be below the melting point temperature of resin composition B. In particular, if resin b constituting the matrix of resin composition B is a thermoplastic resin and resin b has a melting point temperature, it is preferable that the heat treatment temperature be below the melting point temperature of resin b. If resin composition B does not have a melting point, the heat treatment temperature is preferably below the glass transition temperature of resin composition B, and more preferably below the glass transition temperature of resin b (preferably a thermoplastic resin) that constitutes the matrix of resin composition B.

[0029] One of the technical features of this disclosure is that, by utilizing the fact that a hydrated polymer resin has a lower melting point and / or glass transition temperature, and becomes fluid even at relatively low temperatures due to molten or softened state, the resin composition (polymer resin) is detached from the resin mixture by heat treatment in the hydrated state. Due to these technical features, the recycling method and manufacturing method according to this disclosure can recover the resin composition by processing at relatively low temperatures, and can maintain the polymer state while suppressing thermal decomposition and degradation of the resin composition. For this reason, the resin a constituting the matrix of resin composition A contained in the resin mixture is preferably a resin that melts with high-pressure hot water (preferably water at 0.1 MPa to 4.0 MPa and 100°C to 250°C), and for example, polyolefin resins, polyamide resins, and polyester resins are preferred. The inventors have confirmed that polyamide resins and polyester resins melt sufficiently in the presence of high-pressure hot water (water at 0.1 MPa to 4.0 MPa and 100 to 250°C (preferably 180°C to 250°C)) because their melting point temperature is lower than that in air (dry state). One of the major features of this disclosure is that this phenomenon has been applied to a method for separating resin compositions from resin mixtures and recycling the resin compositions.

[0030] Specifically, the melting point of nylon 66, a polyamide resin, was determined by measuring the heat flow rate using a differential scanning calorimeter (DSC; "DSC214Polyma" manufactured by Netch Japan Co., Ltd.). The melting point was found to be 257°C in air and 177°C in water. The DSC measurement involved placing 10 mg of nylon 66 (for measurement in air) or 10 mg of nylon 66 and 19 mg of water (for measurement in water) into a DSC pressure-resistant pan. The measurement was performed at a temperature range of 30 to 300°C and a heating rate of 10°C / min, and the temperature at the maximum endothermic peak was defined as the melting temperature (melting point). Figure 1 shows the DSC measurement data for nylon 66 in air and water. As shown in Figure 1, the melting point of nylon 66 was approximately 80°C lower in water compared to air. Similarly, when the melting points of other resins were measured using DSC, the melting points in water were approximately 228°C for polyethylene terephthalate (approximately 257°C in air), approximately 199°C for polybutylene terephthalate (approximately 225°C in air), and approximately 161°C for polypropylene (approximately 164°C in air).

[0031] By processing resins in water, where the melting point is lower than in air, resin degradation can be suppressed, and separation efficiency is improved due to the desaturation effect of the water. As mentioned above, polyamide resins and polyester resins experience a significant decrease in their melting point in water, so the degradation suppression effect from processing at low temperatures is substantial. On the other hand, polyolefin resins such as polypropylene have a low water absorption rate, and although the decrease in their melting point in water is small, hydrolysis is unlikely to occur, so there is no concern about resin degradation due to hydrolysis even when processed in water.

[0032] Similarly, when the glass transition temperature of polycarbonate, an amorphous polymer, was measured using DSC, it was found to be approximately 132°C in water (approximately 147°C in air). By utilizing the differences in the melting points and glass transition temperatures of these resins in water, resin compositions can be separated.

[0033] From the perspective of the efficiency of heat treatment, the size of each resin composition in the resin mixture to be subjected to heat treatment is 100 cm ３ or less, preferably 50 cm ３ or less, and it is preferably crushed in such a manner. The lower limit of the size to be subjected to heat treatment is not particularly limited. For example, 0.001 cm ３ or more is preferable, and 0.01 cm ３ or more is more preferable. The shape of the crushed material is not particularly limited and may be spherical, cubic, rectangular parallelepiped, rectangular, square or other quadrangular shapes, circular shapes, elliptical shapes, other polygonal shapes, or irregular shapes. From the perspective of handling properties, a cubic shape is preferable. When the fragment shape is a quadrangular shape, the length of one side is preferably within the range of 0.1 to 10 cm, and more preferably within the range of 0.1 to 1 cm.

[0034] The treatment temperature in the heat treatment is, for example, 100°C or higher, preferably 110°C or higher, more preferably 120°C or higher, and even more preferably 130°C or higher. Also, the treatment temperature is preferably 250°C or lower, more preferably 240°C or lower, even more preferably 230°C or lower, and even more preferably 220°C or lower. That is, as the treatment temperature in the heat treatment, 100 to 250°C is preferable, 110 to 240°C is more preferable, 120 to 230°C is even more preferable, and 130 to 220°C is even more preferably. If the treatment temperature is within the above range, while suppressing deterioration such as decomposition of the resin composition, a specific resin composition can be made into a state where it is easy to separate from the resin mixture.

[0035] The processing temperature in heat treatment step A is preferably higher than the glass transition temperature or melting point temperature of resin composition A in the presence of water (preferably the reference temperature of resin composition A), preferably 1°C or more higher, more preferably 3°C or more higher, even more preferably 5°C or more higher, even more preferably 10°C or more higher, even more preferably 20°C or more higher, and may be 30°C or more, 40°C or more, or 50°C or more higher. However, since a lower temperature is preferable from the standpoint of resin degradation, the temperature can be adjusted as appropriate depending on the processing conditions and the type of resin, for example, the processing temperature in heat treatment step A may not exceed 100°C above the reference temperature of resin composition A. Furthermore, if the resin mixture contains resin composition B, the processing temperature in heat treatment step A is preferably lower than the glass transition temperature or melting point temperature of resin composition B in the presence of water (preferably the reference temperature of resin composition B), preferably 1°C or more lower, more preferably 3°C or more lower, and even more preferably 5°C or more lower. Furthermore, if resin composition B does not exist (i.e., article B is a metal or the like and not a resin composition), or if resin composition B is a thermosetting resin composition, it is preferable to determine the upper limit of the processing temperature in heat treatment step A considering the degradation of resin composition A. Specifically, it is preferable to set the temperature to be 70°C or less above the glass transition temperature or melting point temperature of resin composition A in the presence of water (preferably the reference temperature of resin composition A), more preferably 60°C or less above the glass transition temperature or melting point temperature of resin composition A, and it may also be 50°C or less above the glass transition temperature or melting point temperature of resin composition A in the presence of water, or 40°C or less above the glass transition temperature or melting point temperature of resin composition A.

[0036] The treatment pressure in the heat treatment is not less than the saturated water vapor pressure at the treatment temperature. For example, it is preferably not less than 0.1 MPa, more preferably not less than 1.4 MPa, still more preferably not less than 2.0 MPa, even more preferably not less than 2.7 MPa, and preferably not more than 4.0 MPa, more preferably not more than 3.3 MPa, still more preferably not more than 2.8 MPa, and even more preferably not more than 2.3 MPa. That is, the treatment pressure in the heat treatment is preferably from 0.1 to 4.0 MPa, more preferably from 1.4 to 3.3 MPa, still more preferably from 2.0 to 2.8 MPa, and preferably from 2.7 to 3.3 MPa. If the treatment pressure is within the above range, it is possible to make the state in which a specific resin composition can be easily separated from the resin mixture while suppressing deterioration such as decomposition of the resin composition.

[0037] The state of the water brought into contact with the resin mixture may be a gas (i.e., water vapor) or a liquid (i.e., water). Specifically, it is saturated water vapor when performing heat treatment at the saturated water vapor pressure at the treatment temperature, and subcritical water (also referred to as pressurized hot water or high-pressure hot water) or supercritical water when performing heat treatment at a pressure exceeding the saturated water vapor pressure at the treatment temperature.

[0038] From the viewpoint of simplicity in controlling the temperature and pressure in the heat treatment, it is preferable to perform the treatment at the saturated water vapor pressure at the treatment temperature.

[0039] Examples of the method for performing the heat treatment include a method of supplying high-pressure steam from a boiler or the like to a pressure-resistant reaction vessel containing a sample, and a method of putting a sample and water into a pressure-resistant reaction vessel and heating it using a heater or the like.

[0040] In the recycling method and the manufacturing method according to one aspect of the present disclosure, since the resin mixture is treated with high-temperature and high-pressure water, it is possible to make the state in which a specific resin composition can be easily separated from the resin mixture while suppressing deterioration such as decomposition of the resin composition. Even if the treatment is performed at a temperature not lower than the melting point temperature of the specific resin composition in water in the atmospheric atmosphere, it is not possible to make the state in which the specific resin composition can be easily separated from the resin mixture.

[0041] The processing time in the heat treatment can be set appropriately according to the processing temperature and processing pressure, but for example, it is preferably 1 minute or more and 360 minutes or less, more preferably 3 minutes or more, even more preferably 5 minutes or more, even more preferably 10 minutes or more, and most preferably 60 minutes or more. Longer processing times are preferable because they suppress clumping of a specific resin composition (polymer resin) with other resin compositions (polymer resins) when melted, and allow for sufficient separation. It is also more preferably 240 minutes or less, even more preferably 180 minutes or less, and even more preferably 120 minutes or less. In other words, the processing time in the heat treatment is more preferably 3 to 240 minutes, even more preferably 5 to 180 minutes, and particularly preferably 10 to 120 minutes. If the processing time is within the above range, it is possible to suppress deterioration such as decomposition of the resin composition while making it easy to separate a specific resin composition from the resin mixture.

[0042] From the viewpoint of preventing deterioration of the recovered resin composition (recycled resin composition), it is preferable to raise the temperature and / or pressure to the processing temperature and / or processing pressure in a short time. For example, it is preferable to raise the pressure from 0.05 MPa to the processing pressure within 60 minutes, and more preferably within 30 minutes. Similarly, it is preferable to raise the temperature from 80°C to the processing temperature within 60 minutes, and more preferably within 30 minutes. Within the above ranges, deterioration of the recovered resin composition can be suppressed, which is preferable. After heat treatment, cooling may be performed by natural cooling or using a known cooling device.

[0043] The heat treatment may be carried out while stirring, if necessary, using a known stirring device such as a stirring blade when the water is in liquid. When the heat treatment is carried out while stirring, it is preferable to stir at a rotational speed of 10 to 3000 rpm, and more preferably at 20 to 2000 rpm. By carrying out the heat treatment while stirring, the resin composition A can be made easier to separate from the resin mixture.

[0044] When the water is in liquid form, contact between the resin mixture and water is preferably achieved by applying a water flow generated by stirring or pumping to the resin mixture, which is fixed by a filter or the like. The water flow causes the softened resin composition A to flow and become easier to separate. The water flow velocity is preferably 0.001 m / s or more, more preferably 0.01 m / s or more, and even more preferably 0.02 m / s or more. Furthermore, if the purpose is to more actively separate the resin composition A by the water flow, the flow velocity may be 0.05 m / s or more, 0.1 m / s or more, 0.2 m / s or more, or 0.5 m / s or more. From an economic standpoint, the flow velocity is preferably 10 m / s or less, more preferably 5 m / s or less, and even more preferably 2 m / s or less. In other words, the water flow velocity is preferably 0.001 to 10 m / s, more preferably 0.01 to 5 m / s, and even more preferably 0.02 to 2 m / s.

[0045] Contact between the resin mixture and water may be achieved by generating a stream of water vapor using a fan or the like and applying it to the resin mixture, if the water is a gas. The flow velocity of the stream is preferably 0.1 m / s or more, more preferably 0.5 m / s or more, and even more preferably 1 m / s or more. The flow velocity is preferably 30 m / s or less, more preferably 20 m / s or less, and even more preferably 10 m / s or less. In other words, the flow velocity of the stream of water vapor is preferably 0.1 to 30 m / s, more preferably 0.5 to 20 m / s, and even more preferably 1 to 10 m / s.

[0046] Furthermore, the heat treatment may be carried out using a holding member such as a wire mesh or filter to hold the sample, if necessary. By using a holding member (preferably a metal holding member), the resin composition (polymer resin) molten in water and the article (preferably polymer resin) that does not melt or melts poorly under heat treatment conditions can be easily separated, and the heat treatment process and the separation process described later can be carried out simultaneously. Materials such as metal, ceramics, and glass can be used as the holding member.

[0047] (Separation Step) The separation step A for separating resin composition A from the resin mixture is not particularly limited as long as it is a method that can separate resin composition A. For example, the following can be used: - A method of settling resin composition A (separation method a) - A method of making resin composition A float (separation method b) - A method using the flow of water (water flow) which is the heat treatment medium (separation method c) - A method using centrifugal force (centrifugation) (separation method d) - A method using bubbling (separation method e) These separation methods may be carried out individually, or two or more may be carried out in appropriate combination as needed. In separation step A, it is preferable that article B (preferably resin composition B) is fixed so that it does not move together with resin composition A. Examples of fixing methods include a mesh made of metal or the like.

[0048] The above method will be further explained with specific examples. The method for settling resin composition A (separation method a) involves placing the resin mixture on a mesh and performing heat treatment, causing the resin composition A to settle (drop) below the mesh. This method is suitably used for resin compositions with high specific gravity, such as polyamide and polyester.

[0049] The method for floating resin composition A (separation method b) involves placing the resin mixture in a container with a mesh lid and performing heat treatment, thereby causing resin composition A to float on the mesh. This method is suitably used for resin compositions with low specific gravity, such as polypropylene and polyethylene.

[0050] In the water flow method (separation method c), the resin mixture is placed in a container with a mesh on at least two sides, and the resin composition A can be made to flow out of the container by the flow of the medium (water). This method can be applied regardless of the specific gravity of the resin composition, and the separation efficiency can be further increased by increasing the flow velocity of the water flow.

[0051] In the centrifugal force method (separation method d), the efficiency of the sedimentation and flotation methods can be increased by utilizing centrifugal acceleration. Furthermore, by using a perforated basket, water flow can be generated by centrifugal force, etc., to separate the softened resin composition A.

[0052] The bubbling method (separation method e) generates bubbles in liquid water, and the softened resin composition A can be separated by the buoyancy of the bubbles that adhere to it. Known methods can be used without limitation to generate the bubbles. There are no restrictions on the type of gas used for bubbling, but nitrogen gas is preferred in terms of economy and because it does not easily degrade the resin composition.

[0053] Apart from these methods, the resin mixture is often in the form of crushed material, and resin composition A and article B (preferably resin composition B) have the shape of sharp crushed material. However, the fact that the corners of resin composition A become rounded by the heat treatment process A, while resin composition B retains its original shape, can be utilized. Specifically, methods include manual separation by visual inspection, taking images with a camera or the like to automatically determine the shape and blow it away with air, and picking up using a gripping mechanism, suction mechanism, etc. Furthermore, methods include passing the resin mixture through an inclined belt conveyor belt or the like to cause resin composition A to roll off.

[0054] The separation step A may be performed in conjunction with the heat treatment step A, or the separation step A may be performed after the heat treatment step A. For example, in the separation methods a to e described above, the heat treatment step A and the separation step A can be performed simultaneously by fixing the resin mixture using a filter or the like as illustrated, while performing heat treatment in a way that maintains the fixed state of article B (resin composition B). Alternatively, the resin mixture can be heat-treated without being fixed, and then the resin composition A can be separated using a filter or the like.

[0055] Furthermore, separation step A may be carried out simultaneously with or integrated with recovery step A, which recovers the resin composition A described later.

[0056] (Recovery Process) It is preferable to remove and recover the separated resin composition A (Recovery Process A). Recovery Process A is the process of removing and recovering resin composition A. As a recovery method, it is preferable to cool resin composition A after separation process A and recover it as a solid. Alternatively, a method combining separation process A and recovery process A may be used after heat treatment process A. In the method combining separation process A and recovery process A, after heat treatment process A, the resin mixture is cooled to solidify resin composition A, and then resin composition A and resin composition B are separated.

[0057] Recovery step A is a step of removing and recovering the heat-treated resin composition A from the water. In recovery step A, it is preferable to collect the resin composition A in a specific location to facilitate recovery. Methods of collection include settling, flotation, and using filters, and may also be centrifugal separation or bubbling. These methods may be performed while the resin composition A is still softened, or after it has been cooled and solidified. For example, if using a filter, it is preferable to cool and solidify the softened and fluid resin composition A. Specifically, for example, a mixture of separated resin composition A and water is cooled to solidify the resin composition A, and then the resin composition A is separated from the water and recovered using a filter or the like. Alternatively, if the water is a gas (water vapor), for example, the softened and fallen resin composition A is cooled to solidify and recovered. In these cases, if the location where separation step A is performed and the location where recovery step A is performed are different places, a mixture of only resin composition A and water, or only resin composition A or a mixture of resin composition A and water vapor can be cooled. If the location where separation step A is performed and the location where recovery step A is performed are the same, for example, in the same tank, the entire tank can be cooled and the solidified resin composition A can be removed. In the case where the resin composition A is ultimately separated from water and removed in recovery step A, it is preferable to remove it after the resin composition A has solidified. The temperature at which the resin composition A is separated from water and removed is preferably less than 100°C, more preferably 80°C or less, and even more preferably 60°C or less.

[0058] The above recovery method A is an example in the case where the resin composition A softens and flows out of the resin mixture. However, when the resin composition A does not detach from the resin mixture, the separation step A and the recovery step A may be performed simultaneously. In this case, examples of the recovery method include applying an external force such as manually peeling the resin composition A from the cooled resin mixture for separation and recovery. Also, in the heat treatment step A, when at least a part of the resin composition A (polymer resin) is separated from the article B (preferably another polymer resin such as the resin composition B), or is about to be separated, or has a different shape or color, a method of visually sorting and recovering the resin composition A separated from the resin mixture can be mentioned. Further, methods such as taking an image with a camera or the like, automatically judging its shape, and blowing it with air, or picking it up using a gripping mechanism, a suction mechanism, etc. can also be mentioned. Furthermore, a method such as passing it through an inclined belt conveyor and rolling down the resin composition A can be mentioned.

[0059] When manually peeling the resin composition A, the resin mixture after heat treatment may be peeled after applying external forces such as further kneading or rubbing. However, from the perspective of the ease of separation of the resin composition A (polymer resin), it is preferable that it can be peeled by hand without applying further external forces such as kneading or rubbing.

[0060] Also, since the shape of the resin mixture after heat treatment changes due to the melting of the resin composition A, it easily separates when external forces such as frictional force and shear force act due to stirring or crushing. Therefore, the resin mixture after heat treatment may be stirred and / or crushed to separately recover the resin composition A in the same manner as above.

[0061] When crushing the resin mixture after heat treatment to separate the resin composition A (polymer resin), using a known crusher or pulverizer, for example, it is preferable to crush it into small pieces with an area of 1 cm ２ or less, more preferably 0.5 cm ２ or less, and there is no particular lower limit, and it may be 0.001 cm ２ or more.

[0062] The recovered resin composition A may be subjected to appropriate post-treatment such as washing with a cleaning solution such as water or an organic solvent, and drying. Article B (preferably resin composition B) is also preferably recovered and recycled, and may similarly undergo post-treatment such as washing, dewatering, and drying. Dewatering and drying can be carried out using a known dewatering machine and / or dryer; for example, it is preferable to dry at 40 to 80°C for 1 to 60 minutes using a dryer such as an infrared heater, oven, or hot air dryer.

[0063] Furthermore, for example, if the resin mixture contains resin composition B, after separating resin composition A, resin composition B can also be separated by treating the resin mixture after the separation of resin composition A at a temperature equal to or higher than the glass transition temperature or melting point temperature of resin composition B in water (preferably the reference temperature of resin composition B). When the resin mixture contains substances that do not become fluid when heated, such as metals, glass, ceramics, or thermosetting resin molded products, and resin composition B is to be recovered and recycled, it is preferable to separate resin composition B by treating the resin mixture after the separation of resin composition A at a temperature equal to or higher than the glass transition temperature or melting point temperature of resin composition B in water (preferably the reference temperature of resin composition B). In this case as well, it is preferable to go through a heat treatment step, a separation step, and a recovery step, and these conditions are the same as above, with resin composition A appropriately replaced with resin composition B, etc.

[0064] The recovered resin composition A and resin composition B (recycled resin composition) do not need to have the same composition as the resin composition A and resin composition B contained in the resin mixture before heat treatment and recovery. For example, if resin composition A is FRP (Fiber Reinforced Plastics), even if the reinforcing fibers such as glass fibers have not softened and the reinforcing fibers have been removed from resin composition A, it is still within the scope of this disclosure. Also, if resin composition A contains water-soluble substances, these water-soluble substances may leach out, reducing the amount of water-soluble substances contained in the recovered resin composition A. Furthermore, if a small amount (e.g., 5% by mass or less) of resin composition x is present in the resin mixture, and the glass transition temperature or melting point temperature of resin composition x in water is close to or lower than the glass transition temperature or melting point temperature of resin composition A in water (preferably the reference temperature of resin composition A), resin composition x may be mixed into the recovered resin composition A. Moreover, even if resin composition A is a polymer alloy, it does not need to have the same composition before and after recovery. For example, in a polymer alloy made of thermoplastic resin, if the resin with a low melting point is the matrix and the resin with a high melting point is the domain, even if heat treatment and separation are performed at a temperature above the melting point of the polymer alloy, the matrix will soften while the domains will not. As a result, the domains will be stopped by filters, and the separated polymer alloy may consist only of the matrix resin, or a large proportion of the matrix resin. Thus, even if the composition of the recovered resin composition A has changed from that of the resin composition A before heat treatment, if the recovered resin composition A mainly consists of the composition derived from the resin composition A before heat treatment (for example, preferably 80% by mass or more, more preferably 90% by mass or more), it falls within the scope of this disclosure. The same applies to resin composition B.

[0065] Even if the composition of the resin composition in a resin mixture differs, if the resin constituting the matrix is ​​the same, it may be treated as the same resin composition. In this case, even if the molecular weight differs, it will be treated as the same resin. Furthermore, even if the composition of the copolymer or other components of the resin differs, if the total amount of monomer components constituting the resin is taken as 100 mol%, and the difference in composition is 10 mol% or less, preferably 5 mol% or less, that is, if 90 mol% or more is a common composition, preferably 95 mol% or more is a common composition, it may be treated as the same resin. For example, polyethylene terephthalate A (terephthalic acid component: 50 mol%, ethylene glycol component: 48.5 mol%, diethylene glycol component: 1.5 mol%) and polyethylene terephthalate B (terephthalic acid component: 49 mol%, isophthalic acid component: 1 mol%, ethylene glycol component: 49.5 mol%, diethylene glycol component: 0.5 mol%) share 98 mol%, which is the sum of the 49 mol% terephthalic acid component, the 48.5 mol% ethylene glycol component, and the 0.5 mol% diethylene glycol component. Therefore, they can be treated as the same resin. In the case of polymer alloys, if the total mass is 100% by mass, then polymer alloys can be treated as the same if the mass of the common resin among the resins constituting the polymer alloy is 80% by mass or more, preferably 90% by mass or more.

[0066] Furthermore, even if the resin constituting the matrix is ​​the same, the glass transition temperature or melting point temperature in the presence of water may not necessarily be the same due to differences in the composition of the resin composition. If the resin constituting the matrix is ​​the same, it can be treated as the same resin composition if the difference in the glass transition temperature or melting point temperature in the presence of water is 30°C or less, 20°C or less, 10°C or less, preferably 5°C or less. The same resin here is the same as described above. On the other hand, even if the resin constituting the matrix is ​​the same, if the composition of the resin composition is different and there is a difference in the melting point temperature or glass transition temperature in the presence of water, and if the two can be separated using this temperature difference, they can be treated as different resin compositions. When treating them as different resin compositions, the temperature difference is preferably 5°C or more, more preferably 10°C or more.

[0067] Resin mixtures subjected to heat treatment may undergo pretreatment separation. A preferred pretreatment separation method is one based on specific gravity difference. For example, in automobiles, polypropylene resin is often used for inner door panels, instrument panels, bumpers, etc., while polyethylene resin is often used for washer fluid tanks. On the other hand, polyamide resin, polyester resin, ABS resin, polycarbonate resin, etc., are used for engine covers, door handles, air conditioning vents, door mirrors, headlight and rear lamp housings, reflectors, extensions, etc. In the case of these resin mixtures, polypropylene resin and polyethylene resin can be removed beforehand by specific gravity separation using water.

[0068] The above has described the case in which the resin mixture includes resin composition A and article B (preferably resin composition B), but the resin mixture may further include resin composition C. Resin composition C has a glass transition temperature or melting point temperature in the presence of water such that resin composition B < resin composition C. When resin composition C is included, resin composition B can be melted (heat treatment step B) by contacting it with water at a temperature above the glass transition temperature or melting point temperature of resin composition B in the presence of water, and below the glass transition temperature or melting point temperature of resin composition C in the presence of water, and at a saturated water vapor pressure above, thereby separating it from the resin mixture (separation step B). In one embodiment of the present disclosure, it is preferable that the heat treatment step B has a treatment temperature above the reference temperature of resin composition B and below the reference temperature of resin composition C, and that the treatment pressure is above the saturated water vapor pressure at the treatment temperature.

[0069] When separating resin composition B from a resin mixture by melting it, it is preferable to have a heat treatment step B, a separation step B, and a recovery step B. These steps can be appropriately replaced with heat treatment step B, separation step B, recovery step B, etc., respectively.

[0070] Heat treatment step B is preferably performed after the heat treatment and separation treatment of resin composition A. Heat treatment step B may be performed after cooling the system after heat treatment step A and then reheating it, but it is preferable to raise the temperature further without lowering it. The temperature may be maintained at the temperature of heat treatment step A, then raised to the temperature of heat treatment step B and maintained thereafter, or the temperature may be gradually and continuously raised from near the lower limit of the temperature of heat treatment step A to near the upper limit of the heat treatment temperature B.

[0071] Alternatively, a heat treatment step (also called heat treatment step AB) may be performed to melt resin composition A and resin composition B without going through heat treatment step A, etc. In this case, after both resin composition A and resin composition B have been melted, a separation step (also called separation step AB) may be performed to separate resin composition A or resin composition B. The resin mixture subjected to heat treatment step AB preferably includes at least resin composition A and resin composition B, and it is preferable that the reference temperature of resin composition B is equal to or greater than the reference temperature of resin composition A. In heat treatment step AB, it is preferable that the treatment temperature is equal to or greater than the reference temperature of resin composition B, and the treatment pressure is equal to or greater than the saturated water vapor pressure at the treatment temperature.

[0072] In separation step AB, it is preferable to separate resin composition A and resin composition B in water. Since melting resin composition A and resin composition B preferably creates a difference in specific gravity and / or viscosity between them, it is preferable to separate them using this difference in specific gravity or viscosity. For example, if the difference in specific gravity between resin composition A and resin composition B is 0.08 g / cm³ ３ Preferably, it is 0.10 g / cm³ or more. ３ More preferably, 0.12 g / cm³ ３ The above is even more preferable, and there is no particular upper limit, but 1.00 g / cm³ is preferable. ３The following is preferable: If the difference in specific gravity between resin composition A and resin composition B is within the above range, the two can be well separated by utilizing the difference in fluidity in the molten state. Specific separation methods include using water flow from stirring or a liquid transfer pump, filtering with a filter, or buoyancy separation using the difference in specific gravity and buoyancy of the resin compositions. Alternatively, resin composition B may be separated by filtering or the like by setting the water containing both resin composition A and resin composition B to a temperature above the glass transition temperature or melting point temperature of resin composition A in the presence of water (preferably the reference temperature of resin composition A) and below the glass transition temperature or melting point temperature of resin composition B in the presence of water (preferably the reference temperature of resin composition B).

[0073] If the resin mixture contains resin composition A, resin composition B, and resin composition C, the resin mixture containing resin composition C after removing resin compositions A and B may be further heat-treated (heat treatment step C) at or above the glass transition temperature or melting point temperature of resin composition C in the presence of water (preferably the reference temperature of resin composition C). By further separating and recovering the resin composition C softened by the heat treatment, resin composition C can be recovered and recycled.

[0074] In one embodiment of the present disclosure, a resin composition D having a glass transition temperature or melting point temperature higher than that of resin composition C in the presence of water may be further included, and resin composition C can be recovered by performing a heat treatment step C, a separation step C, and a recovery step C in the same manner. Similarly, resin composition D can be recovered and recycled separately.

[0075] (Apparatus) An example of a heat treatment apparatus used in this disclosure, shown in Figure 2, will be used for explanation. The apparatus in Figure 2 is an example of an apparatus suitable for successively separating resin composition A and article B (preferably resin composition B) from a resin mixture, but the contents of this disclosure are not limited to the following description. A resin mixture 10 containing resin composition A is introduced into a heat treatment tank 1 equipped with a separation filter 2, and hot water is introduced from a hot water tank 5 using a pump 6. The flow rate can be adjusted by controlling the rotation speed of the pump 6, etc. The heat treatment tank 1 is equipped with a jacket (not shown), and a heat transfer medium for heat retention and heating may be introduced into the jacket. The hot water is heated by a heater 7 to a temperature above the glass transition temperature or melting point temperature of resin composition A in the presence of water (preferably the reference temperature of resin composition A). Resin composition A contained in the resin mixture 10 is softened and, along with the flow of hot water, passes through the separation filter 2 and is separated from the resin mixture 10. Data from a temperature sensor (not shown) installed in the heat treatment tank 1 is sent to a temperature controller (not shown) of the heater 7, and the temperature controller adjusts the heater output so that the temperature of the hot water in the heat treatment tank 1 becomes appropriate.

[0076] Hot water containing resin composition A is sent to a cooling tank 31 equipped with a recovery filter 41. The cooling tank 31 is equipped with a cooling jacket 311 into which a cooling medium is introduced and cooled to a temperature below the glass transition temperature or melting point temperature of resin composition A in the presence of water (preferably the reference temperature of resin composition A). The cooled resin composition A solidifies and is stopped by the recovery filter 41. During cooling, it is not necessary to lower the temperature of the hot water excessively; it is sufficient if the temperature is such that resin composition A solidifies and is stopped by the recovery filter. The cooling temperature is preferably 5°C or more lower than the glass transition temperature or melting point temperature of resin composition A in the presence of water (preferably the reference temperature of resin composition A), and more preferably 10°C or more lower. Furthermore, since the hot water can be circulated and reused, for economic and environmental reasons, the lower limit of the cooling temperature is preferably 50°C or more lower than the glass transition temperature or melting point temperature of resin composition A in the presence of water (preferably the reference temperature of resin composition A). In other words, the cooling temperature is preferably 5 to 50°C lower than the reference temperature of resin composition A, and more preferably 10 to 50°C lower. The hot water from which resin composition A has been removed is returned to the hot water tank 5 and circulated.

[0077] If the resin mixture 10 contains resin composition B, after resin composition A is separated, it is preferable that the hot water sent to the heat treatment tank 1 be raised to above the glass transition temperature or melting point temperature of resin composition B in the presence of water (preferably the reference temperature of resin composition B). At this time, the switching valves 81 and 82 are operated so that cooling and recovery processing is carried out using the cooling tank 32. Subsequently, the heat treatment and separation of resin composition B is carried out in the same manner as the heat treatment and separation of resin composition A described above. Meanwhile, after the cooling tank 31 has been further cooled, it is opened, and the resin composition A (recycled resin composition) on the separation filter 41 is removed and recovered. Similarly, after the separation of resin composition B, the cooling tank 32 is cooled in the same manner, and the resin composition B (recycled resin composition) on the separation filter 42 is recovered. Furthermore, if the resin mixture contains resin composition C and resin composition C (recycled resin composition) is to be recovered, the temperature can be raised and the same procedure can be carried out. In this case, the cooling tank 31 after the recovery of resin composition A can be used. Note that Figure 2 shows an example of recovery by filter, but buoyancy, centrifugal separation, or bubbling may also be used.

[0078] Figures 3 and 4 show examples of suitable apparatus for melting both resin composition A and resin composition B, and then separating either resin composition A or resin composition B. Similarly, the contents of this disclosure are not limited to those described below.

[0079] In Figure 3, the resin mixture 10 containing resin composition A and resin composition B is treated in the heat treatment tank 1 at a temperature above the glass transition temperature or melting point temperature of resin composition B in the presence of water (preferably the reference temperature of resin composition B). This softens resin composition A and resin composition B, which then pass through the separation filter 2 with the flow of hot water. The water containing resin composition A and resin composition B is sent to the cooling tank 33, where it is cooled to a temperature above the glass transition temperature or melting point temperature of resin composition A in the presence of water (preferably the reference temperature of resin composition A), and below, preferably less than, the glass transition temperature or melting point temperature of resin composition B in the presence of water (preferably the reference temperature of resin composition B). The resin composition B (recycled resin composition) that has solidified due to cooling remains on the recovery filter 43. The molten resin composition A and water pass through the recovery filter 43 and are sent to the cooling tank 34. In the cooling tank 34, the mixture of resin composition A and water is cooled to a temperature below, preferably below, the glass transition temperature or melting point temperature of resin composition A in the presence of water (preferably the reference temperature of resin composition A), and the solidified resin composition A (recycled resin composition) is stopped by the recovery filter 44.

[0080] Figure 4 shows an example of a device that separates resin compositions based on their specific gravity differences. For example, it is used when the specific gravity of resin composition A is lower than that of water and the specific gravity of resin composition B is higher than that of water. Similar to Figure 3, the water containing resin composition A and resin composition B that has passed through the separation filter 2 is sent to the cooling tank 35. The cooling tank 35 also serves as a specific gravity separation tank, in which resin composition A (recycled resin composition) floats and resin composition B (recycled resin composition) sinks. In specific gravity separation, the state of resin composition A and resin composition B is not particularly limited. For example, specific gravity separation may be performed when both resin composition A and B are softened, or after cooling, specific gravity separation may be performed when resin composition A is softened and resin composition B is solidified, or specific gravity separation may be performed when both resin composition A and B are solidified.

[0081] The recovery rate of the resin composition (recycled resin composition) is preferably as high as possible, with an upper limit of 100% by weight, preferably 1% by weight or more, more preferably 5% by weight or more, even more preferably 10% by weight or more, and even more preferably 15% by weight or more. In other words, the recovery rate of the resin composition is preferably 1 to 100% by weight, more preferably 5 to 100% by weight, even more preferably 10 to 100% by weight, and even more preferably 15 to 100% by weight. The recovery rate of the resin composition can be calculated from the following formula based on the weight of the recovered resin composition (Y parts by weight) and the weight of the resin composition contained in the resin mixture before treatment (X parts by weight): Recovery rate (%) = {Y / X} × 100 Note that the weight of the resin composition contained in the resin mixture before treatment used to calculate the recovery rate does not need to be determined from the total amount of the resin mixture, but may be determined using a sample taken after stirring the resin mixture to make it uniform, for example. The sample amount may be 2 g or more and 5000 g or less, or 100 g or more and 1000 g or less. The appropriate sample amount can be determined according to the size of the resin composition and the amount of resin mixture before treatment. The resin composition in the sample can be distinguished by its color, hardness, etc.

[0082] In one embodiment of the recycling method and manufacturing method relating to this disclosure, a specific resin composition can be separated from the resin mixture by contacting it with high-temperature, high-pressure water. Therefore, alkaline treatment is not required, deterioration of the resin composition due to alkaline treatment can be avoided, and complicated operations such as removal of alkaline aqueous solution and post-treatment of waste liquid are unnecessary, allowing for simple recycling.

[0083] Furthermore, it is preferable that the resin composition recovered by the recycling method according to one embodiment of this disclosure and the recycled resin composition produced by the manufacturing method according to one embodiment of this disclosure show suppressed changes in physical properties such as molecular weight compared to the resin composition before processing. If the changes in the physical properties of the resin composition are suppressed, it can be reused without further processing such as polymerization, thus having high recyclability. The use of the recovered resin composition (recycled resin composition) is not particularly limited, and for example, it can be reused by decomposing it into monomers and repolymerizing it (chemical recycling), but from the viewpoint of energy costs, it is preferable to reuse it by melting it and re-pelletizing it without decomposing it into monomers (material recycling).

[0084] The degree of degradation of a resin composition (recycled resin composition) can be confirmed by measuring the viscosity and molecular weight of the resin composition, and can be appropriately selected depending on the resin composition in question. When the resin composition is a polyamide resin, the relative viscosity and the molecular weight of the resin composition are proportional; therefore, the higher the relative viscosity, the larger the molecular weight of the recovered polyamide resin, meaning that it maintains its polymer state. Specifically, if the relative viscosity is 1.3 or higher (preferably 1.5 or higher, more preferably 1.7 or higher, even more preferably 1.9 or higher, even more preferably 2.1 or higher, and even more preferably 2.3 or higher), it can be said that the polyamide resin is suitable for material recycling. The relative viscosity (RV) of a polyamide resin can be calculated, for example, by dissolving 0.25 g of polyamide resin in 46 g of 96% by mass sulfuric acid, placing 10 ml of this solution in an Oswald viscosity tube, measuring the falling time at 20°C, and comparing the falling time of the sample solution with the falling time of the solvent obtained by similarly placing 10 ml of 96% by mass sulfuric acid in the same viscosity tube and measuring the falling time at 20°C, using the following formula. RV = T / T0 (RV: relative viscosity, T: time for the sample solution to fall, T0: time for the solvent to fall) Furthermore, if it is possible to measure not only the relative viscosity of the recovered polyamide resin (RV1) but also the relative viscosity of the polyamide resin before heat treatment (RV0), it is preferable that the ratio of RV1 (relative viscosity of the recovered polyamide resin) to RV0 (RV1 / RV0) is 0.4 or higher (preferably 0.5 or higher, more preferably 0.6 or higher, even more preferably 0.7 or higher, and even more preferably 0.8 or higher). If the value of RV1 / RV0 is within the above range, the polyamide resin obtained by the recovery method or manufacturing method of this disclosure has suppressed degradation and can be said to be a polyamide resin that can be suitably used for material recycling.

[0085] Furthermore, when the resin composition is polyethylene terephthalate, the intrinsic viscosity and the molecular weight of the resin composition are proportional. Therefore, the higher the intrinsic viscosity, the larger the molecular weight of the recovered polyethylene terephthalate resin, meaning that it maintains a polymer state. Specifically, if the intrinsic viscosity is 0.3 dl / g or higher (preferably 0.5 dl / g or higher, more preferably 0.7 dl / g or higher), it can be said that the polyethylene terephthalate resin is suitable for material recycling. The intrinsic viscosity (η) of polyethylene terephthalate resin can be determined, for example, by dissolving 0.1 g of polyethylene terephthalate resin in 25 mL of a mixed solvent of phenol / 1,1,2,2-tetrachloroethane (60 / 40 (weight ratio)) and measuring it using an Ostwald viscometer at 30°C. Furthermore, if it is possible to measure not only the intrinsic viscosity (η1) of the recovered polyethylene terephthalate resin but also the intrinsic viscosity (η0) of the polyethylene terephthalate resin before heat treatment, it is preferable that the ratio of η1 (intrinsic viscosity of the recovered resin) to η0 (η1 / η0) is 0.3 or higher (preferably 0.5 or higher, more preferably 0.7 or higher). If the value of η1 / η0 is within the above range, the recovered polyethylene terephthalate composition can be said to have suppressed degradation and be a polyethylene terephthalate resin that can be suitably used for material recycling.

[0086] Furthermore, the degree of degradation of the resin composition (recycled resin composition) can be confirmed by comparing the glass transition temperature and / or melting point temperature before and after recovery. Generally, in resin compositions (polymer resins), when degradation such as a decrease in molecular weight occurs, the glass transition temperature and melting point temperature tend to fluctuate. Therefore, by comparing the glass transition temperature and / or melting point temperature before and after recovery, it is possible to grasp the degree of degradation of the resin composition. The measurement of the glass transition temperature and / or melting point temperature before and after recovery may be performed in air or water, as long as the measurement conditions are unified before and after recovery. If the recovered resin composition has the same or substantially equivalent glass transition temperature or melting point temperature as the resin composition before recovery, it is evaluated that no significant degradation of the resin composition has occurred and that a polymer state suitable for material recycling has been maintained. Specifically, the difference (absolute value) between the glass transition temperature and melting point temperature before and after recovery is preferably 5°C or less, and more preferably 3°C or less.

[0087] The resin mixture may contain additives in addition to resin composition A and article B. Examples of such additives include antioxidants, heat stabilizers, smoothing agents, antistatic agents, thickeners, flame retardants, weathering agents, color inhibitors, and colorants. The resin mixture and / or the resin composition within the resin mixture may have a coating layer on its surface. The resin mixture may also be a polymer laminate or a composite formed by methods such as blending, compounding, or alloying.

[0088] A recycled resin composition, which is a resin composition recovered by a recycling method according to one embodiment of the disclosure, and a recycled resin composition manufactured by a manufacturing method according to one embodiment of the disclosure, can be used to form recycled products containing the resin composition as at least a portion of the raw materials through chemical recycling or material recycling. Examples of recycled products include pelletized resins, injection-molded products, textile products, film products, and the like.

[0089] This application claims the benefit of priority based on Japanese Patent Application No. 2025-016895, filed on February 4, 2025. The entire specification of Japanese Patent Application No. 2025-016895, filed on February 4, 2025, is incorporated herein by reference.

[0090] The contents of this disclosure will be explained in more detail below with reference to examples, but the contents of this disclosure are not limited by the examples below, and it is certainly possible to implement the disclosure with appropriate modifications to the extent that it is in line with the spirit of the preceding and following statements, and all such modifications are included within the technical scope of this disclosure.

[0091] In the following examples and comparative examples, a resin selected from the polymer resins listed below was used according to each example.

[0092] (Polyethylene terephthalate resin) The esterification reaction vessel was heated, and when it reached 200°C, a slurry consisting of 86.4 parts by mass of terephthalic acid and 64.4 parts by mass of ethylene glycol was charged in. While stirring, 0.017 parts by mass of antimony trioxide and 0.16 parts by mass of triethylamine were added as catalysts. Next, the temperature was increased under pressure to a gauge pressure of 3.5 kgf / cm². ２ The esterification reaction was carried out under pressure at 240°C. After that, the pressure in the esterification reaction vessel was returned to atmospheric pressure, and 0.071 parts by mass of magnesium acetate tetrahydrate was added, followed by 0.014 parts by mass of trimethyl phosphate. Furthermore, the temperature was raised to 260°C over 15 minutes, and 0.012 parts by mass of trimethyl phosphate was added, followed by 0.0036 parts by mass of sodium acetate. After 15 minutes, the obtained esterification reaction product was transferred to a polycondensation reaction vessel, and the temperature was gradually raised from 260°C to 285°C under reduced pressure, and the polycondensation reaction was carried out at 285°C.

[0093] After the polycondensation reaction was complete, the mixture was filtered through a Naslon filter with a 95% cut diameter of 5 μm, extruded in strand form from a nozzle, cooled and solidified using cooling water that had been pre-filtered (pore size: 1 μm or less), and then cut into pellets. The resulting polyethylene terephthalate resin had a melting point of approximately 257°C in air, a melting point of approximately 228°C in the presence of water, and an intrinsic viscosity of 0.616 dl / g. It contained virtually no inert particles or internally precipitated particles.

[0094] (Polybutylene terephthalate resin) A commercially available polybutylene terephthalate resin (NV5020, manufactured by Mitsubishi Engineering Plastics Co., Ltd.) was used. The melting point of this polybutylene terephthalate resin in air was approximately 225°C, and the melting point in the presence of water was 199°C.

[0095] (Polycarbonate resin) A commercially available polycarbonate resin (L-1225LL, manufactured by Teijin Corporation) was used. The glass transition temperature of this polycarbonate resin in air was approximately 147°C, and the glass transition temperature in the presence of water was 132°C.

[0096] (Polypropylene resin) A commercially available polypropylene resin (FS2011DG3, manufactured by Sumitomo Chemical Co., Ltd.) was used as the polypropylene resin. The melting point of this polypropylene resin in air was approximately 164°C, and the melting point in the presence of water was 161°C.

[0097] In the following examples and comparative examples, the ease of separation of the resin composition from the resin mixture was confirmed using the following procedure. Furthermore, the recovered resin was evaluated using the following procedure.

[0098] (Ease of Separation: Peel Test) After drying the heat-treated sample, the resin composition, which had become separable from the resin mixture by the heat treatment, was peeled off by hand. The ease of separation by external force was evaluated according to the following criteria: A (Excellent): The target resin composition can be peeled off without applying further external force such as friction. B (Poor): The target resin composition cannot be peeled off even when further external force such as rubbing or scrubbing is applied. (Ease of Separation: Floating Separation) The container was visually inspected after heat treatment and cooling, and the ease of separation by floating separation was evaluated according to the following criteria: A (Good): The target resin composition separated from the resin mixture by heat treatment floats to the water surface, making floating separation possible. B (Poor): The target resin composition separated from the resin mixture by heat treatment sinks into the water, making floating separation impossible.

[0099] (Recovery Rate) The weight (Y parts by weight) of the recovered resin composition was measured, and the recovery rate was calculated using the following formula based on the weight (X parts by weight) of the resin composition contained in the sample before processing: Recovery Rate (%) = {Y / X} × 100

[0100] (Melting point temperature in air) Using a differential scanning calorimeter (DSC; "DSC214Polyma" manufactured by Netch Japan Co., Ltd.), 10 mg of the sample was placed in a standard DSC measurement pan (Concavus Al), and measurements were taken at a temperature range of 30 to 300°C and a heating rate of 10°C / min. The temperature at the maximum endothermic peak was defined as the melting temperature (melting point temperature) in air.

[0101] (Melting point temperature in the presence of water) Using a differential scanning calorimeter (DSC; "DSC214Polyma" manufactured by Netch Japan Co., Ltd.), 10 mg of the sample and approximately 20 mg of pure water were placed in a high-pressure pan for DSC measurement, and measurements were taken at a temperature range of 30 to 300°C and a heating rate of 10°C / min. The temperature at the maximum endothermic peak was defined as the melting temperature (melting point temperature) in the presence of water.

[0102] (Glass transition temperature in air) Using a differential scanning calorimeter (DSC; "DSC214Polyma" manufactured by Netch Japan Co., Ltd.), 10 mg of the sample was placed in a standard DSC measurement pan (Concavus Al), and measurements were taken at a temperature range of 30 to 300°C and a heating rate of 10°C / min. From the obtained heat flow curve, tangents were drawn between the curve showing endothermic heating and the baselines before and after it, and the midpoint of the line connecting the intersections of these tangents was found. The temperature of this midpoint was defined as the glass transition temperature in air.

[0103] (Glass transition temperature in the presence of water) Using a differential scanning calorimeter (DSC; "DSC214Polyma" manufactured by Netch Japan Co., Ltd.), 10 mg of sample and approximately 20 mg of pure water were placed in a high-pressure pan for DSC measurement. Measurements were taken at a temperature range of 30 to 300°C and a heating rate of 10°C / min. From the obtained heat flow curve, tangents were drawn between the curve showing endothermic effects and the baselines before and after it. The midpoint of the line connecting the intersections of these tangents was found, and the temperature of this midpoint was defined as the glass transition temperature in the presence of water.

[0104] (Example 1) A resin mixture containing 2.0 g of polyethylene terephthalate resin and 2.0 g of polybutylene terephthalate resin was placed in a stainless steel metal cage (mesh opening 2 mm) and placed in a reaction vessel (high-pressure vessel). 300 mL of water was added to the vessel, and the pressure was set to 1.9 MPa and 210°C. The mixture was then heated for 10 minutes in a standing state. After the heat treatment and cooling to room temperature, the sample in the reaction vessel was observed. It was found that some of the polybutylene terephthalate resin had passed through the mesh of the metal cage and fallen to the bottom of the reaction vessel, while some of the polybutylene terephthalate resin was adhering to the outer wall of the metal cage. It was confirmed that these polybutylene terephthalate resins had been separated from the resin mixture. Some polybutylene terephthalate resin remained adhering to the polyethylene terephthalate resin inside the metal cage, but these could be easily separated by hand. From the above results, it was found that the manufacturing method (recycling method) disclosed herein makes it possible to separate each resin composition from a resin mixture of polyethylene terephthalate resin and polybutylene terephthalate resin. Furthermore, it was inferred that separation could be achieved with higher efficiency by using an apparatus such as that shown in Figure 2. When the ease of separation was evaluated, the peel test result was "A", indicating that polybutylene terephthalate resin could be easily manufactured (recovered) from the resin mixture. The recovered polybutylene terephthalate resin (recycled polybutylene terephthalate resin) had a melting point temperature in air substantially equivalent to that of the polybutylene terephthalate resin before heat treatment, and it was confirmed that it was in a polymer state suitable for material recycling.

[0105] (Example 2) The resin mixture used in Example 1 was further treated with 2.0 g of the polycarbonate resin, and the heat treatment conditions were changed to 1.0 MPa, 180°C, and 10 minutes, except that the treatment was carried out in the same manner as in Example 1. After heat treatment and cooling to room temperature, the sample in the reaction vessel was examined and found that the polycarbonate resin was adhering to the polyethylene terephthalate resin and polybutylene terephthalate resin in the metal cage, but the polycarbonate resin could be easily separated by hand. From these results, it was found that the manufacturing method (recycling method) of the present disclosure makes it possible to separate polycarbonate resin from the resin mixture. Furthermore, it was inferred that separation could be achieved with higher efficiency by using an apparatus such as that shown in Figure 2. When the ease of separation was evaluated, the peel test result was "A", indicating that polycarbonate resin could be easily manufactured (recovered) from the resin mixture. The recovered polycarbonate resin (recycled polycarbonate resin) had a glass transition temperature in air substantially equivalent to that of the polycarbonate resin before heat treatment, confirming that it was in a polymer state suitable for material recycling.

[0106] (Example 3) The resin mixture was changed to a resin mixture containing 2.0 g of the above-mentioned polypropylene resin and 2.0 g of the above-mentioned polybutylene terephthalate resin, and the heat treatment conditions were changed to 1.9 MPa, 210°C, and 10 minutes, except that the treatment was carried out in the same manner as in Example 1. After heat treatment and cooling to room temperature, the sample in the reaction vessel was observed to find that some of the polybutylene terephthalate resin passed through the mesh of the metal cage and fell to the bottom of the reaction vessel, some of the polybutylene terephthalate resin adhered to the outer wall of the metal cage, and all of the polypropylene resin passed through the mesh of the metal cage and floated to the surface of the water in the reaction vessel, confirming that the polypropylene resin and polybutylene terephthalate resin could be separated from the resin mixture. The specific gravity measured in accordance with ISO 1183 was 0.90 g / cm³ for the polypropylene resin. ３ The polybutylene terephthalate resin is present at 1.31 g / cm³. ３ The specific gravity difference is 0.41 g / cm³. ３The results were as follows. From the above results, it was found that, according to the manufacturing method (recycling method) of this disclosure, both the polypropylene resin and the polybutylene terephthalate resin can be melted by heat treatment, and the polypropylene resin and the polybutylene terephthalate resin can be separated from the resin mixture by the difference in specific gravity. When the ease of separation of the treated sample was evaluated, the evaluation result for buoyancy separation was "A", indicating that polypropylene resin and polybutylene terephthalate resin could be easily manufactured (recovered) from the resin mixture. The recovered polypropylene resin (recycled polypropylene resin) had a melting point temperature in air substantially equivalent to that of the polypropylene resin before heat treatment, and it was confirmed that it was in a polymer state that could be suitably used for material recycling.

[0107] (Example 4) The resin mixture used in Example 1 was further treated by adding 2.0 g of the above polypropylene resin, and the heat treatment conditions were changed to 1.0 MPa, 180°C, and 10 minutes, except that the treatment was carried out in the same manner as in Example 1. After heat treatment and cooling to room temperature, the sample in the reaction vessel was observed and it was confirmed that all of the polypropylene resin had passed through the opening of the metal cage and floated to the surface of the water in the reaction vessel, confirming that the polypropylene resin could be separated from the resin mixture. From these results, it was found that it is possible to separate polypropylene resin from a resin mixture using the manufacturing method (recycling method) of the present disclosure. Furthermore, it was inferred that separation could be achieved with higher efficiency by using an apparatus such as that shown in Figure 2. When the ease of separation was evaluated, the evaluation result of the peel test was "A", indicating that polypropylene resin could be easily produced (recovered) from the resin mixture. The recovered polypropylene resin (recycled polypropylene resin) had a melting point temperature in air substantially equivalent to that of the polypropylene resin before treatment, and it was confirmed that it was in a polymer state that could be suitably used for material recycling.

[0108] (Example 5) After performing the procedure in Example 2 above, a second heat treatment was carried out. In the second heat treatment, the sample from which the polycarbonate resin had been removed in the first treatment was placed in a stainless steel metal cage (mesh opening 2 mm) and placed in a reaction vessel (high-pressure vessel). 300 mL of water was added to the vessel, and the pressure was set to 1.9 MPa and 210°C, and the sample was heated for 10 minutes while standing. When the ease of separation of the sample after the second treatment was evaluated, the peel test result was "A", indicating that polybutylene terephthalate resin could be easily produced (recovered) from the resin mixture. The recovered polybutylene terephthalate resin (recycled polybutylene terephthalate resin) had a melting point temperature in air substantially equivalent to that of the polybutylene terephthalate resin before heat treatment, and it was confirmed that it was in a polymer state that could be suitably used for material recycling. From these results, it was found that, for example, by using an apparatus like the one shown in Figure 2, the polycarbonate resin can be removed first from a resin mixture containing polyethylene terephthalate resin, polybutylene terephthalate resin, and polycarbonate resin, and then the polybutylene terephthalate resin can be separated continuously with high efficiency.

[0109] (Example 6) After performing the procedure in Example 4 above, a second heat treatment was carried out. In the second heat treatment, the sample from which the polypropylene resin had been removed in the first treatment was placed in a stainless steel metal cage (mesh opening 2 mm) and placed in a reaction vessel (high-pressure vessel). 300 mL of water was added to the vessel, and the pressure was set to 1.9 MPa and 210°C, and the sample was heated for 10 minutes while standing. When the ease of separation of the sample after the second treatment was evaluated, the peel test result was "A", indicating that polybutylene terephthalate resin could be easily produced (recovered) from the resin mixture. The recovered polybutylene terephthalate resin (recycled polybutylene terephthalate resin) had a melting point temperature in air substantially equivalent to that of the polybutylene terephthalate resin before heat treatment, and it was confirmed that it was in a polymer state that could be suitably used for material recycling. From these results, it was found that, for example, by using an apparatus like the one shown in Figure 2, the polypropylene resin can be removed first from a resin mixture containing polyethylene terephthalate resin, polybutylene terephthalate resin, and polypropylene resin, and then the polybutylene terephthalate resin can be separated continuously with high efficiency.

[0110] (Comparative Example 1) The procedure was carried out in the same manner as in Example 1, except that the heat treatment conditions were 1.6 MPa, 195°C, and 10 minutes. There was no change in the shape of the sample after treatment, and it was not possible to separate and produce (recover) polybutylene terephthalate resin from the resin mixture using heat treatment.

[0111] (Comparative Example 2) The same procedure as in Example 1 was followed, except that the heat treatment conditions were 2.8 MPa and 230°C for 10 minutes. The specific gravity measured in accordance with ISO 1183 was 1.31 g / cm³ for the polybutylene terephthalate resin. ３ The polyethylene terephthalate resin content is 1.38 g / cm³. ３ The specific gravity difference is 0.07 g / cm³. ３The sample shape after processing showed that both the polybutylene terephthalate resin and the polyethylene terephthalate resin were affected by melting. When the ease of separation was evaluated, the peel test result was "B," indicating that it was not possible to separate and manufacture (recover) the polybutylene terephthalate resin from the resin mixture.

[0112]

[0113] In Table 1, "PET" refers to polyethylene terephthalate resin, "PBT" refers to polybutylene terephthalate resin, "PC" refers to polycarbonate resin, and "PP" refers to polypropylene resin. In Table 1, "molten material" means a form in which the resin has molten, or a form in which it is observed to have been molten, based on observation of the sample after heat treatment. In Table 1, "Tg or Tm (°C)" refers to the glass transition temperature in air of the separated and recovered polycarbonate resin, or the melting point temperature in air of the separated and recovered polybutylene terephthalate resin or polypropylene resin.

[0114] 1 Heat treatment tank 2 Separation filters 31, 32, 33, 34, 35 Cooling tanks 311, 321, 331, 341, 351 Cooling jackets 41, 42, 43, 44 Recovery filter 5 Hot water tank 6 Pump 7 Heater 81, 82 Flow path switching valve 10 Resin mixture 11, 13, 14, 151, 152 Recovery resin composition

Claims

1. A method for producing a recycled resin composition, comprising a separation step A for separating the resin composition A from a resin mixture containing at least the resin composition A and an article B containing material b, wherein the resin composition A has a glass transition temperature and / or melting temperature in the presence of water, and further comprising a heat treatment step A for melting the resin composition A by contacting the resin mixture with water at a temperature equal to or greater than the glass transition temperature or melting temperature of the resin composition A in the presence of water and equal to or greater than the saturated water vapor pressure.

2. The manufacturing method according to claim 1, wherein if the resin composition A has a melting point temperature in the presence of water, the melting point temperature in the presence of water is used as the reference temperature for the resin composition A; if the resin composition A does not have a melting point temperature in the presence of water, the glass transition temperature in the presence of water is used as the reference temperature for the resin composition A; the processing temperature of the heat treatment step A is equal to or greater than the reference temperature for the resin composition A; and the processing pressure of the heat treatment step A is equal to or greater than the saturated water vapor pressure at the processing temperature.

3. The method for producing a recycled resin composition according to claim 1, wherein the article B is a resin composition B, and the glass transition temperature or melting point temperature of resin composition A in the presence of water is less than the glass transition temperature or melting point temperature of resin composition B in the presence of water, and furthermore, the processing temperature of the heat treatment step A is less than or equal to the glass transition temperature or melting point temperature of resin composition B in the presence of water.

4. The manufacturing method according to claim 2, wherein the article B is a resin composition B, and if the resin composition B has a melting point temperature in the presence of water, the melting point temperature in the presence of water is used as the reference temperature for the resin composition B, and if the resin composition B does not have a melting point temperature in the presence of water, the glass transition temperature in the presence of water is used as the reference temperature for the resin composition B, and the reference temperature of the resin composition B is higher than the reference temperature of the resin composition A, and the processing temperature of the heat treatment step A is less than or equal to the reference temperature of the resin composition B.

5. A method for producing a recycled resin composition according to claim 3, wherein the resin mixture further comprises a resin composition C, wherein the glass transition temperature or melting point temperature of resin composition C in the presence of water is less than that of resin composition B, and the method for producing a recycled resin composition comprises a heat treatment step B and a separation step B, wherein the resin composition B is melted and separated from the resin mixture by contacting it with water at a temperature equal to or greater than the glass transition temperature or melting point temperature of resin composition B in the presence of water, and equal to or less than the glass transition temperature or melting point temperature of resin composition C in the presence of water, and at or greater than the saturated water vapor pressure.

6. The manufacturing method according to claim 4, wherein the resin mixture further comprises a resin composition C, a heat treatment step B for melting the resin composition B by contacting the resin mixture after the separation of the resin composition A with water, and a separation step B for separating the resin composition B from the resin mixture, wherein if the resin composition C has a melting point temperature in the presence of water, the melting point temperature in the presence of water is used as the reference temperature for the resin composition C, if the resin composition C does not have a melting point temperature in the presence of water, the glass transition temperature in the presence of water is used as the reference temperature for the resin composition C, the reference temperature of the resin composition C is higher than the reference temperature of the resin composition B, the processing temperature of the heat treatment step B is above the reference temperature of the resin composition B and below the reference temperature of the resin composition C, and the processing pressure of the heat treatment step B is above the saturated water vapor pressure at the processing temperature.

7. The manufacturing method according to claim 3, wherein the resin a constituting the matrix of resin composition A is a thermoplastic resin, and the resin b constituting the matrix of resin composition B is a thermoplastic resin.

8. The manufacturing method according to claim 5, wherein the resin c constituting the matrix of the resin composition C is a thermoplastic resin.

9. The manufacturing method according to claim 1, characterized in that the heat treatment step A has a treatment temperature of 100°C or more and 250°C or less, and a treatment pressure of 0.1 MPa or more and 4.0 MPa or less.

10. The manufacturing method according to claim 5, characterized in that the heat treatment step B has a treatment temperature of 100°C or more and 250°C or less, and a treatment pressure of 0.1 MPa or more and 4.0 MPa or less.

11. The manufacturing method according to claim 1, characterized in that, in the separation step A, the resin composition A is separated from the resin mixture by applying an external force.

12. The manufacturing method according to claim 1, wherein the material b is an inorganic substance and the article B does not contain resin.

13. A recycled resin composition produced by the manufacturing method described in any one of claims 1 to 12.

14. A method for producing a recycled resin composition, comprising: a heat treatment step AB in which a resin mixture containing resin composition A and resin composition B, wherein at least the glass transition temperature or melting point temperature in the presence of water is less than or equal to that of resin composition A, is brought into contact with water at a temperature equal to or greater than the glass transition temperature or melting point temperature of resin composition B in the presence of water and at or greater than the saturated water vapor pressure, thereby melting resin composition A and resin composition B; and a separation step AB in which resin composition A or resin composition B is separated in water.

15. The manufacturing method according to claim 14, wherein if the resin composition A has a melting point temperature in the presence of water, the melting point temperature in the presence of water is used as the reference temperature for the resin composition A; if the resin composition A does not have a melting point temperature in the presence of water, the glass transition temperature in the presence of water is used as the reference temperature for the resin composition A; if the resin composition B has a melting point temperature in the presence of water, the melting point temperature in the presence of water is used as the reference temperature for the resin composition B; if the resin composition B does not have a melting point temperature in the presence of water, the glass transition temperature in the presence of water is used as the reference temperature for the resin composition B; the reference temperature of the resin composition B is equal to or greater than the reference temperature of the resin composition A; the processing temperature of the heat treatment temperature AB is equal to or greater than the reference temperature of the resin composition B; and the processing pressure of the heat treatment temperature AB is equal to or greater than the saturated water vapor pressure at the processing temperature.

16. The manufacturing method according to claim 14, wherein the separation step A and B includes separation by at least one of the following: water flow, filtering, or difference in specific gravity of the resin composition.

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