Method for recycling polyester-containing material

Abstract

To provide a method for recycling a polyester-containing substance by a new means.SOLUTION: The method for recycling the polyester-containing substance comprises a step of subjecting the polyester-containing substance to alcoholysis in a solvent in the presence of a catalyst and an alcohol and a step of separating the alcoholysis product obtained in the above step. Specifically, the method is carried out using an apparatus having a tank for storing a substance containing a polyester and a tank and / or a path for separating an alcoholysis product of the polyester.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for recycling polyester-containing materials.

[0002] Breaking down a substance completely to its smallest units and purifying the resulting material to remove impurities not only requires a lot of energy but is also time-consuming. Therefore, "recycling" in the present invention is intended to make the polyester-containing material reusable as a resource. In other words, the purpose is to reduce the energy consumption and labor required for recycling, and does not necessarily mean decomposing and purifying the material to its smallest units by chemical decomposition. However, decomposition and purification aimed at reducing energy consumption and shortening the process are not excluded, and for this purpose, the alcoholysis product of the polyester-containing material obtained by the present invention can be subjected to chemical recycling. The present invention is particularly useful when applied to composites containing a polyester component, and further useful when the components remaining in the composite that are not affected by alcoholysis are subjected to material recycling. [Background technology]

[0003] Plastics are inexpensive and highly durable materials. Due to their convenience, polyethylene terephthalate (PET) in particular has been widely used in a wide range of applications, including fibers, films, and bottles, and its production and consumption have skyrocketed over the past few decades. However, despite its durability, PET is not easily biodegradable, leading to the filling of landfills around the world and the resulting marine pollution caused by microplastics, which is a major social issue affecting the global environment. Given this background, there is a need for the development of recycling technologies for PET and other plastic waste. Compared to Europe and the United States, Japan has a higher proportion of thermal recycling, which utilizes the heat energy generated during incineration, but there are concerns about global warming due to carbon dioxide emissions. As a result, much research has been conducted into chemical recycling of polyester products, i.e., methods of chemically converting polyester products into monomers, recovering them, and reusing these monomers.

[0004] Patent Document 1 discloses a method for continuously producing aromatic dimethyl dicarboxylic acid and dihydric alcohol, which are monomer components of aromatic polyester such as PET, from the aromatic polyester using supercritical alcohol, but requires high temperatures of 300°C or higher.

[0005] Patent Document 2 discloses a method for producing dimethyl terephthalate by depolymerizing polyester with alkylene glycol and then transesterifying it with methanol, but the alkylene glycol must be distilled off at a temperature of 150°C or higher.

[0006] Patent Document 3 discloses a method for recycling multilayer film containing a plastic layer primarily composed of polyester (PET), polypropylene (PP), and polyethylene (PE) and an aluminum layer. In this method, aluminum in multilayer film waste is selectively dissolved to induce layer separation, and the layer is separated into a PP / PE mixture layer and a PET layer using the difference in specific gravity. Furthermore, to increase the purity of the PET separated by the difference in specific gravity, an organic solvent is used to extract the PP and PE contained in the PET layer, thereby separating the main components of the multilayer film into PET, a PP / PE mixture, and an aluminum component. However, dissolving aluminum requires energy for recycling.

[0007] Patent Document 4 discloses a catalyst composition for depolymerizing polyesters, which contains a base catalyst, a monohydric alcohol, and a carbonate diester or tetraalkoxysilane as a glycol scavenger, and a method for depolymerizing polyesters using the catalyst composition. However, because ethylene glycol, a component of PET, is stably captured, the generated ethylene carbonate must be decomposed into ethylene glycol in order to reuse it as a raw material for PET.

[0008] Patent Document 5 discloses a process for converting polyethylene terephthalate or poly(ethylene glycol-co-1,4-cyclohexanedimethanol terephthalate) into terephthalic acid esters by depolymerization. The process includes contacting the polyester with a solvent for swelling, an alcoholic solvent, and a substoichiometric amount of an alkoxide. In particular, the examples use dichloromethane or dimethyl sulfoxide as the solvent for swelling the polyester, methanol as the alcoholic solvent, and a substoichiometric amount of sodium methoxide as the alkoxide, and demonstrate that polyethylene terephthalate is converted to dimethyl terephthalate at 50 to 60°C. The specification also indicates that the ratio of the solvent for swelling the polyester to the alcoholic solvent is between about 0.5:1 and about 1:1 (w:w).

[0009] Patent Document 6 discloses a method for depolymerizing poly(C2-C4 alkylene terephthalate). In particular, the specification discloses a method comprising the step of contacting the poly(C2-C4 alkylene terephthalate) with methanol and a catalyst selected from potassium carbonate, sodium carbonate, magnesium methoxide, 1,8-diazabicyclo[5.4.0]undec-7-ene, and triazabicyclodecene. It is disclosed that the depolymerization can be carried out at a temperature of about 100°C to about 180°C and a pressure of about 1 to 15 atmospheres.

[0010] Non-Patent Document 1 discloses that dimethyl terephthalate and ethylene glycol can be obtained by methanolysis of polyethylene terephthalate (PET) in the presence of an aluminum isopropoxide catalyst. It discloses that the methanolysis is preferably carried out at 200°C, and that a mixture of methanol and toluene is preferred. It also discloses that the yield of dimethyl terephthalate and ethylene glycol can be increased to 80% or more by using a mixture in which the volume ratio of methanol to toluene is in the range of 8:2 to 5:5. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-039908 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-131729 [Patent Document 3] Japanese Patent Application Laid-Open No. 2006-205160 [Patent Document 4] Japanese Patent Publication No. 2022-126617 [Patent Document 5] Special Publication No. 2020-533395 [Patent Document 6] Special Publication No. 2023-506948 [Non-patent literature]

[0012] [Non-Patent Document 1] Kurokawa et al.,Methanolysis of polyethylene terephthalate in the presence of aluminum triisopropoxide catalyst to form dimethyl terephthalate and ethylene glycol,Polymer Degradation and Stability,2003,79,529-533 Summary of the Invention [Problem to be solved by the invention]

[0013] The present invention has been made to overcome the above-mentioned problems of the prior art, and an object of the present invention is to provide a new method for recycling polyester-containing materials. [Means for solving the problem]

[0014] As a result of intensive research to solve the above-mentioned problems, the present inventors have discovered a method for recycling a polyester-containing substance, which comprises the steps of alcoholyzing a polyester-containing substance in a solvent in the presence of a catalyst and an alcohol, and separating the alcoholysis product obtained in the above step. More specifically, the present inventors have discovered a method for recycling polyester-containing materials, which is characterized by using an apparatus having a tank for storing polyester-containing materials and a tank and / or a path for separating the alcoholysis product of the polyester, and have completed the present invention.

[0015] The polyester-containing substance (a) may be a polyester resin product, as described below, or a composite containing a polyester component, or may be in the form of a laminate in which multiple films are stacked. The present invention can be applied to various polyesters as described below, and is not particularly limited, but polyethylene terephthalate can be given as an example. The catalyst (b) is not particularly limited and may be any of various metal salts and nitrogen-containing organic base compounds, as described below, but may be, for example, at least one selected from the group consisting of alkali metal alkoxides and nitrogen-containing organic base compounds. More specifically, sodium methoxide and / or 1,5,7-triazabicyclo[4.4.0]dec-5-ene may be used as an example. As for the alcohol (c), at least one of various types can be selected as described below, and there are no particular restrictions. However, it is preferably a monohydric alcohol having 1 to 8 carbon atoms, and methanol can be given as just one specific example. As will be described later, the solvent (d) is not particularly limited, but from the viewpoint of recycling, those which react with the alcoholysis product in the reaction system are excluded. For example, at least one can be selected from the group of compounds that do not react with the alcoholysis product in the alcoholysis reaction system, and toluene can be given as a specific example.

[0016] Furthermore, the present invention is preferably practiced as a recycling method that includes step (A) of alcoholyzing a polyester-containing substance (a) in a solvent (d) in the presence of a catalyst (b) and an alcohol (c), step (B) of separating the alcoholysis product obtained in step (A), and step (C) of separating substances other than the alcoholysis product obtained in step (A).

[0017] The present invention provides a new means for recycling polyester-containing materials (a). Furthermore, by carrying out the present invention, the polyester-containing substance (a) can be recycled without being incinerated or otherwise disposed of, which can also contribute to reducing carbon dioxide emissions. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a structural diagram of an apparatus for carrying out the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0019] The method of recycling a polyester-containing substance (a) by alcoholysis in the present invention involves the use of a catalyst (b) and an alcohol (c) in a solvent (d). The blending ratio of these components can be appropriately changed within a range in which the alcoholysis proceeds satisfactorily. Each component used in the present invention will be described in detail below. Note that the raw materials exemplified in the following description do not limit the constitution of the present invention, and may be changed within the scope of the present invention.

[0020] <Substances containing polyester (a)> In one embodiment, the polyester-containing material (a) of the present invention includes a polyester resin product. Representative polyester resin products include polyethylene terephthalate (PET), amorphous polyethylene terephthalate (A-PET), glycol-modified polyethylene terephthalate (G-PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), polyarylate (PAR), polycaprolactone (PCL), polylactic acid (PLA), and polyethylene adipate (PEA). These polyester resin products may be used alone or in combination of two or more.

[0021] In another embodiment, the polyester-containing material (a) of the present invention may be a composite containing a polyester component, and includes food trays, fibers, adhesives, pressure-sensitive adhesives, inks, coating films, and the like. For example, in recent years, products in which PET bottles are compounded with polyamide resin to impart gas barrier properties have been adopted for wine and other beverages, but the present invention can be applied even to such composites that physically contain additional substances. Since the present invention cannot decompose amide bonds, in the above example, polyethylene terephthalate, the raw material of PET bottles, decomposes, while the polyamide resin remains undecomposed. Other examples include polyester products having a vapor deposition layer on the surface thereof, and polyester products having a coloring component mixed therein for the purpose of providing a design, and the present invention is applicable to any of these. In addition, some of the components may be chemically modified. Examples of resins that can be used in polyester adhesives for laminate films include polyester polyurethane, polyester polyether, and polyester polyether polyurethane. Examples of coating films formed by polyester-based paints (polyester-based coating films) include coating films formed by the oxidative polymerization of alkyd paints; polyester polyurethane coating films obtained by the reaction of polyester polyols and polyisocyanates; and powder coating films formed by epoxy polyester-based powder coatings or powder coatings consisting of a combination of carboxyl group-containing polyester resins and β-hydroxyalkylamides.

[0022] In yet another embodiment, the polyester-containing material (a) of the present invention also includes a laminate in which multiple films are laminated. There are no particular limitations on the films that can be used, but examples include polyester films such as PET; polyolefin films such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE), biaxially oriented polypropylene (OPP), and solid polypropylene (CPP); metal films such as aluminum foil (AL); nylon (NY) films; polyvinyl alcohol (PVA) films; cellulose films; acrylic films; polyphenylsulfide (PPS) films; polyimide (PI) films; vinyl chloride films; fluororesin films such as PTFE; and paper films. These films may also have a vapor-deposited layer or ink layer formed thereon. Colored films are also acceptable. When the polyester-containing substance (a) of the present invention is a laminate containing a polyester film, the polyester film is separated from other laminate films by alcoholysis, allowing for recycling. Even in laminates that do not contain polyester film, if the laminate is bonded with a polyester-based adhesive, the adhesive component is alcoholyzed, separating the films bonded by the adhesive, allowing for recycling. The films exemplified above that contain ester bonds can be subject to alcoholysis in the present invention. As described above, in the present invention, it is not necessary to decompose and purify the polyester-containing substance (a) down to the minimum monomer unit, but it is sufficient to decompose it to the extent that the components remaining without alcoholysis can be separated.

[0023] There are no particular limitations on the method of using the adhesive used in the laminate in which multiple films are laminated, and it can be used in a general manner as a laminating adhesive. For example, there are non-solvent lamination methods in which the adhesive is heated to achieve an appropriate viscosity, and dry lamination methods in which a dilution solvent or other compounded adhesive is added to adjust the coating viscosity to an appropriate level. An active energy ray curable adhesive may also be used. The coating amount is 1 to 10 g / m in dry state. 2 This range is generally used, but it may be changed as appropriate depending on the type of film and the performance requirements for the application of the laminate. An aging period may also be set. For example, aging can be set at 20°C or higher and 50°C or lower for 2 days or higher and 5 days or lower.

[0024] The polyester-containing substance (a) can take various forms depending on the embodiment. For example, it can be used in a solid state such as a lump, fiber, film, or pellet. It can also be used in a liquid state.

[0025] <Catalyst (b)> As the catalyst (b) of the present invention, metal salts and nitrogen-containing organic basic compounds can be used.

[0026] Examples of metal salts that can be used include hydroxides, carbonates, fatty acid salts, and alkoxides of alkali metals; hydroxides, carbonates, fatty acid salts, alkoxides, and oxides of alkaline earth metals; and hydroxides, carbonates, fatty acid salts, and alkoxides of transition metals. Alkali metal alkoxides and alkali metal hydroxides are particularly preferred. These catalysts can be used alone or in combination of two or more.

[0027] Examples of alkali metal alkoxides include lithium methoxide, lithium ethoxide, lithium tert-butoxide, sodium methoxide, sodium ethoxide, sodium tert-butoxide, potassium methoxide, potassium ethoxide, and potassium tert-butoxide. Of these, it is particularly preferable to use sodium methoxide.

[0028] Examples of nitrogen-containing organic base compounds include trimethylamine, triethylamine, tributylamine, pyrazole, imidazole, N-methylimidazole, benzimidazole, N-methylbenzimidazole, triazoles, benzotriazole, pyridine, quinoline, isoquinoline, triazines, 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), 1,8-azabicyclo[5.4.0]undec-7-ene (DBU), and 1,3-dimesitylimidazol-2-ylidene. Among these, TBD is particularly preferred.

[0029] Examples of alkali metal hydroxides include lithium hydroxide, sodium hydroxide, and potassium hydroxide. Of these, it is particularly preferable to use sodium hydroxide. When an alkali metal hydroxide is used as catalyst (b), the alcoholysis of the polyester component in the polyester-containing substance (a) tends to produce a large amount of by-products, such as partial decomposition products. For example, when applied to polyester resin products such as PET pellets, the reaction solution becomes a highly viscous liquid, which increases the amount of post-treatment work required, making it undesirable from the perspective of recycling. On the other hand, when applied to polyester composites such as laminate films composed of NY / polyester polyurethane adhesive / AL, the adhesive layer formed by the adhesive undergoes alcoholysis, weakening the interaction with the nylon film and aluminum foil, which are not involved in the alcoholysis. This therefore favors the separation of these constituent films, making it preferable from the perspective of recycling.

[0030] The amount of catalyst (b) added can be varied as appropriate depending on the type of polyester-containing substance (a), but is preferably 0.01 to 10 parts by weight, more preferably 0.03 to 5 parts by weight, per 100 parts by weight of the total of polyester-containing substance (a), catalyst (b), alcohol (c), and solvent (d). The amount of catalyst (b) added should be adjusted within the range in which alcoholysis proceeds. However, adding a large amount not only increases costs, but also increases the effort required to separate the catalyst residue. It also tends to have a negative effect on the components separated as substances other than the alcoholysis product, making material recycling difficult. On the other hand, adding a small amount may result in the catalyst being deactivated, preventing sufficient alcoholysis.

[0031] <Alcohol (c)> The alcohol (c) of the present invention is not particularly limited, but is preferably a monohydric alcohol having 1 to 8 carbon atoms.

[0032] Examples of monohydric alcohols include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, tert-butanol, 2-ethylhexanol, and benzyl alcohol. These may be used alone or in combination of two or more. Among these, primary alcohols are preferred, and methanol is particularly preferred.

[0033] The amount of alcohol (c) added can be varied as appropriate depending on the type of polyester-containing substance (a), but is preferably 0.9 to 50 parts by weight, more preferably 2 to 30 parts by weight, per 100 parts by weight of the total of polyester-containing substance (a), catalyst (b), alcohol (c), and solvent (d). The amount of alcohol (c) added may be adjusted within a range in which alcoholysis proceeds. However, if the amount added is too large, costs increase. If the amount added is too small, alcoholysis does not proceed sufficiently. In the present invention, it is not required to completely decompose the polyester-containing substance (a) into its smallest units and purify the decomposition products, so it is sufficient that the alcoholysis proceeds to an extent sufficient for recycling. If the alcoholysis does not proceed sufficiently, the alcoholysis can be resumed by adding more alcohol (c).

[0034] <Solvent (d)> The solvent (d) of the present invention excludes those which react with the alcoholysis product in the alcoholysis reaction system. For example, if dimethyl carbonate is selected as a solvent in the alcoholysis of polyethylene terephthalate, ethylene glycol produced by the alcoholysis of polyethylene terephthalate will react with dimethyl carbonate to form ethylene carbonate, making it unsuitable as a solvent from the viewpoint of recycling. Furthermore, when considering the reuse of the solvent, if the boiling point is too high, a large amount of heat energy will be required in the distillation operation, so the boiling point is preferably 200°C or lower, more preferably 150°C or lower, and even more preferably 120°C or lower. Examples of such solvents include toluene, acetonitrile, N,N-dimethylformamide, dimethyl sulfoxide, n-hexane, cyclohexane, dichloromethane, tetrahydrofuran, methyl ethyl ketone, and ethyl acetate. These can be selected appropriately as long as they do not inhibit alcoholysis, and may be used alone or in combination of two or more. However, this does not include the use of alcoholic solvents.

[0035] The ratio of the solvent (d) used in the present invention can be adjusted appropriately depending on the weight and shape of the polyester-containing substance (a). If a large amount is added, the reaction apparatus becomes large, resulting in a decrease in the processing capacity of the polyester-containing substance (a). If a small amount is added, the contact efficiency between the catalyst (b), the alcohol (c), and the polyester-containing substance (a) becomes poor, making it difficult for alcoholysis to proceed sufficiently.

[0036] In the present invention, the mixing ratio of the alcohol (c) and the solvent (d) is preferably 1 / 1 to 1 / 99 by weight, and more preferably 1 / 2 to 1 / 50 by weight.

[0037] <Other ingredients (e)> In addition to the above (a) to (d), other components such as a desiccant or a substance not involved in alcoholysis may be included. These do not limit the constitution of the present invention and may be added as appropriate within the scope of the present invention.

[0038] <Desiccant> Desiccants include physical desiccants and chemical desiccants, which can be used alone or in combination of two or more.

[0039] Physical desiccants include those that utilize the increased water and / or moisture transfer path due to the matrix structure inside the desiccant, and those that utilize physical interactions such as adsorption of water and / or moisture with the desiccant. Specific examples include silica gel, molecular sieves, zeolites, and activated carbon.

[0040] Chemical desiccants include those that adsorb moisture and / or humidity through chemical reactions. Specific examples include metal oxides such as calcium oxide, barium oxide, and magnesium oxide; metal salts such as sodium sulfate, calcium sulfate, magnesium sulfate, calcium chloride, magnesium chloride, sodium carbonate, and potassium carbonate; diphosphorus pentoxide; silane compounds such as vinyltrimethoxysilane, dimethyldimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, tetramethoxysilane, tetraethoxysilane, diphenyldimethoxysilane, and phenyltrimethoxysilane; and orthoester compounds such as methyl orthoformate, ethyl orthoformate, methyl orthoacetate, and ethyl orthoacetate. However, those that react with alcoholysis products are excluded from the perspective of recycling.

[0041] <Substances not involved in alcoholysis> In the present invention, a substance that does not participate in alcoholysis may be contained. Examples include polyolefin films such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE), biaxially oriented polypropylene (OPP), and unoriented polypropylene (CPP); metal films such as aluminum foil (AL); nylon (NY) films; cellulose films; polyphenylsulfide (PPS) films; polyimide (PI) films; vinyl chloride films; and fluororesin films such as PTFE. Paper films and polystyrene (PS) sheets may also be used. These films and sheets may have a vapor-deposited layer formed thereon or may be colored. They may also be produced by kneading a plurality of these components or by coextrusion. Furthermore, mineral components such as sodium chloride may be mixed in.

[0042] The alcoholysis in the present invention preferably proceeds at a temperature of 20° C. or higher but lower than 100° C., preferably 30° C. or higher but lower than 90° C., and more preferably 40° C. or higher but lower than 80° C. If the temperature is lower than 20° C., the catalytic activity is insufficient. Although alcoholysis also proceeds at a temperature of 100° C. or higher, this is not preferred from the viewpoint of energy costs.

[0043] The alcoholysis of the present invention can be carried out under normal pressure or reduced pressure, but may also be carried out under increased pressure. The reaction time may be the time required for the polyester-containing substance (a) to undergo alcoholysis, and may be, for example, 0.5 to 24 hours. The alcoholysis may not be allowed to proceed completely, and the reaction may be shifted to a product separation step at an intermediate stage.

[0044] <Process (A)> The step (A) of alcoholyzing a polyester-containing substance (a) in a solvent (d) in the presence of a catalyst (b) and an alcohol (c) in the present invention will be described in detail below using a laminate of multiple different films including a PET film as an example. The polyester-containing substance (a) can be washed and dried before use, if necessary. The polyester-containing material (a), the laminate, catalyst (b), alcohol (c), and solvent (d) are placed in a tank and heated with stirring. During this process, alcoholysis yields PET-derived terephthalic acid derivatives and ethylene glycol (hereinafter, these and catalyst residues are defined as "alcoholization products"). Meanwhile, the tank also contains PET residues that remain unalcoholized, as well as films other than PET (hereinafter, these are defined as "substances other than alcoholysis products").

[0045] <Process (B)> Step (B) of separating the alcoholysis product obtained in step (A) will now be described. When the alcoholysis product obtained in step (A) is in a solid state, it can be separated by ordinary filtration or hot filtration. The filter used for the filtration operation is not particularly limited, and the size and material can be appropriately selected depending on the target. When the alcoholysis product obtained in step (A) is in a liquid state, it cannot be separated by filtration, and therefore can be separated by, for example, a method of concentration and recrystallization or a method of extraction, but is not limited to these methods. If necessary, washing with water or liquid separation may be carried out. The alcoholysis products obtained by these methods can be further decomposed and purified as necessary, and then subjected to chemical recycling.

[0046] <Process (C)> In order to achieve the object of the present invention, it is preferable to include a step of separating substances other than the alcoholysis product in addition to the step (B). In the example of the laminate, PET residues and films other than PET are mixed in. In such cases, further separation can be performed according to previously reported methods such as separation by specific gravity or dissolution in a specific solvent. The separated constituent films can be recycled.

[0047] <Embodiment of the device> Next, referring to FIG. 1, one embodiment of an apparatus having a tank (X) and a tank and / or a path (Y) will be described, but the apparatus can be implemented in various forms.

[0048] A polyester-containing substance (a) is placed in tank 1, which is surrounded by a filter or the like that does not allow any solids to pass through, and a catalyst (b), an alcohol (c), and a solvent (d) are placed in tank 2 and / or the pathway, and (a) to (d) are mixed so that they come into contact with each other. Here, the polyester-containing substance (a) in tank 1 cannot pass through the filter surrounding tank 1, but as alcoholysis progresses, the structure is such that only the alcoholysis product dissolved in the reaction solution can pass through tank 1. A heater 4 may be placed in tank 2 as needed to adjust the reaction temperature.

[0049] Mixing methods include stirring with a ceramic rotor, mechanical stirring with impellers, and mixing by circulation. The example in Figure 1 shows an example of stirring using impellers 5 at the tip of a rotating shaft connected to a motor 3. The liquid in tank 2 and the liquid in the path connected to tank 2 are circulated by pump 9 placed along the path, and in this example, a flow rate adjustment valve 6, a pressure gauge 7, and a filtration device 8 are placed in parallel along the path. The materials of the equipment used for recycling, such as the tank 1, the tank 2 and / or the pathway, can be selected appropriately as long as they do not impede recycling.

[0050] The present invention can be implemented in the various modes described above, and can also be implemented in the following modes. The method for recycling a polyester-containing substance (a) according to this embodiment comprises step (A) of alcoholyzing the polyester-containing substance (a) in a solvent (d) in the presence of a catalyst (b) and an alcohol (c), step (B) of separating the alcoholysis product obtained in step (A), and step (C) of separating substances other than the alcoholysis product. The alcohol (c) is a monohydric alcohol having 1 to 8 carbon atoms, and the amount of the alcohol (c) added can be 0.9 parts by weight or more and 50 parts by weight or less, more preferably 2 parts by weight or more and 30 parts by weight or less, relative to 100 parts by weight in total of the polyester-containing substance (a), the catalyst (b), the alcohol (c), and the solvent (d). The solvent (d) contains toluene. The blending ratio of the alcohol (c) and the solvent (d) can be changed as appropriate, but the amount of the solvent (d) is suitably 1 part by weight or more, preferably 2 parts by weight or more, and more preferably 2.1 parts by weight or more, per 1 part by weight of the alcohol (c). The amount of the solvent (d) is suitably 99 parts by weight or less, preferably 50 parts by weight or less, and more preferably 45.9 parts by weight or less, per 1 part by weight of the alcohol (c). The alcoholysis is carried out at a temperature of 20°C or higher but lower than 100°C. Furthermore, the alcohol (c) may be methanol, or the solvent (d) may be one that does not react with the alcoholysis product in the alcoholysis reaction system.

[0051] When implementing this embodiment, the same features as those of the above-described embodiment can be applied. The polyester-containing substance (a) can be at least one selected from the group consisting of polyethylene terephthalate, polyester-based adhesives for laminate films, polyester-based coating films, and laminates in which multiple films are bonded together via an adhesive. The catalyst (b) is at least one selected from the group consisting of lithium methoxide, lithium ethoxide, lithium tert-butoxide, sodium methoxide, sodium ethoxide, sodium tert-butoxide, potassium methoxide, potassium ethoxide, potassium tert-butoxide, trimethylamine, triethylamine, tributylamine, pyrazole, imidazole, N-methylimidazole, benzimidazole, N-methylbenzimidazole, triazoles, benzotriazole, pyridine, quinoline, isoquinoline, triazines, 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), 1,8-azabicyclo[5.4.0]undec-7-ene (DBU), and 1,3-dimesitylimidazol-2-ylidene. When the polyester-containing substance (a) is a laminate in which multiple films are bonded together via an adhesive, the catalyst (b) can be at least one selected from the group consisting of lithium methoxide, lithium ethoxide, lithium tert-butoxide, sodium methoxide, sodium ethoxide, sodium tert-butoxide, potassium methoxide, potassium ethoxide, potassium tert-butoxide, trimethylamine, triethylamine, tributylamine, pyrazole, imidazole, N-methylimidazole, benzimidazole, N-methylbenzimidazole, triazoles, benzotriazole, pyridine, quinoline, isoquinoline, triazines, 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), 1,8-azabicyclo[5.4.0]undec-7-ene (DBU), and 1,3-dimesitylimidazol-2-ylidene, as well as lithium hydroxide, sodium hydroxide, and potassium hydroxide. More specifically, the polyester-containing substance (a) may contain polyethylene terephthalate, the catalyst (b) may be sodium methoxide, the alcohol (c) may be methanol, and the solvent (d) may be toluene. Alternatively, the polyester-containing substance (a) may be a laminate in which multiple films are bonded together via an adhesive, at least one of the multiple films being a PET film or a nylon film, the adhesive being a polyester-based adhesive, the catalyst (b) being sodium methoxide or sodium hydroxide, the alcohol (c) being methanol, and the solvent (d) being toluene. [Example]

[0052] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0053] In the examples shown below, the following reagents were used unless otherwise specified. <Substances containing polyester (a)> PET pellets (commercially available) Eco A-PET film (commercially available) G-PET flakes (commercially available) Polyester polyurethane laminating adhesive (Rock Paint Co., Ltd., Adlock RU-77 / H-7), hereafter abbreviated as "AD1" Polyether polyurethane laminating adhesive (manufactured by Rock Paint Co., Ltd., Adlock RN-230 / HN-230), hereafter abbreviated as "AD2" <Catalyst (b)> Sodium methoxide (Fujifilm Wako Pure Chemical Industries, Ltd., Wako First Grade) 1,5,7-Triazabicyclo[4.4.0]dec-5-ene (TBD, manufactured by Tokyo Chemical Industry Co., Ltd.) Sodium hydroxide (Kanto Chemical Co., Ltd., Grade 1) Potassium hydroxide (Kanto Chemical Co., Ltd.) Calcium hydroxide (Kanto Chemical Co., Ltd., special grade) <Alcohol (c)> Methanol (Fujifilm Wako Pure Chemical Industries, ultra-dehydrated grade) Ethanol (Fujifilm Wako Pure Chemical Industries, ultra-dehydrated grade) Benzyl alcohol (Tokyo Chemical Industry Co., Ltd.) Ethylene glycol (Fujifilm Wako Pure Chemical Industries, Ltd., dehydrated grade) <Solvent (d)> Toluene (Kanto Chemical Co., Ltd., special grade) Ethyl acetate (Kanto Chemical Co., Ltd., special grade) Acetonitrile (Fujifilm Wako Pure Chemical Industries, Ltd., special grade) Tetrahydrofuran (Fujifilm Wako Pure Chemical Industries, Ltd., ultra-dehydrated grade (contains stabilizers)) Dichloromethane (Kanto Chemical Co., Ltd., special grade) <Film> PET film (Toyobo Co., Ltd., Toyobo Ester Film E5102, 12 μm) OPP film (Toyobo Co., Ltd., Pylen Film-OT P2241, 25 μm) CPP film (Toyobo Co., Ltd., Pylen Film-CT P1146, 60 μm) Nylon (NY) film (Unitika Ltd., Emblem ONBC-RT, 15 μm) Aluminum foil (AL, manufactured by Toyo Aluminum Co., Ltd., 20 μm) LLDPE film (RM Tocello Co., Ltd., TUX-FC-S, 60 μm) In the examples relating to laminate films, the above films were used as examples, but the film thickness is not limited to these. However, it is preferable to appropriately adjust the amounts of catalyst (b) and alcohol (c) added depending on the film thickness. <filter> · 0.5mm mesh, stainless steel

[0054] The method for producing a laminate film will be explained using a PET / AD1 / OPP structure as an example. The dry coating amount is 4 g / m2 using a bar coater. 2 After applying the coating to the PET film and drying it, an OPP film was attached to the film and nipped on a hot plate at 60° C. Then, the film was aged at 40° C. for 3 days. For other compositions, the dry coating weight should be 1 to 10 g / m depending on the type of film used and the intended use of the laminate film. 2 The range was adjusted appropriately.

[0055] The progress of alcoholysis can be evaluated based on the alcoholysis rate A according to the following formula (1). Alcoholization rate A [%] = (1 - weight of (a) after alcoholization / weight of (a) before alcoholization) × 100 (Equation 1)

[0056] In the following examples, the evaluation results are shown according to the following criteria. Alcoholization rate A is 90% or more: ◎ Alcoholysis rate A is 60% or more but less than 90%: 〇 Alcoholysis rate A is 30% or more but less than 60%: △ Alcoholysis rate A is less than 30%: ×

[0057] First, as a preliminary test, in Examples 1 to 18 and Comparative Examples 1 to 5, the alcoholysis rate A was verified using PET, which is a polyester resin product, among polyester-containing substances (a).

[0058] [Example 1] Sodium methoxide (1 part by weight) and methanol (2 parts by weight) were added to a vessel containing PET pellets (6 parts by weight), and toluene was added to bring the total to 100 parts by weight, followed by stirring at 65°C for 2 hours. After the reaction was completed, the reaction solution was filtered and the residue was washed with water. No unreacted PET pellets were obtained as the residue. The alcoholysis rate A was 100%.

[0059] [Examples 2 to 18] The same procedure was carried out under the conditions of Example 1, except that the conditions were changed to those shown in Tables 1 and 2.

[0060] [Comparative Example 1] The same procedure was carried out as in Example 1, except that sodium methoxide was replaced with sodium hydroxide (1 part by weight). The alcoholysis rate A was 16.2%. However, when sodium hydroxide was used as catalyst (b), the reaction solution became a highly viscous liquid, and it was found that the conditions needed to be adjusted and examined in order to efficiently proceed with alcoholysis.

[0061] Comparative Example 2 The same procedure was carried out as in Example 1, except that methanol was replaced with ethylene glycol (4 parts by weight). The alcoholysis rate A was 0%.

[0062] Comparative Example 3 The same procedure was carried out under the conditions of Example 1, except that the amount of methanol was changed to 80 parts by weight based on the total amount. The alcoholysis rate A was 10.3%.

[0063] Comparative Example 4 The same procedure was carried out except that sodium methoxide was not added under the conditions of Example 1. The alcoholysis rate A was 0%.

[0064] Comparative Example 5 The same procedure was carried out under the conditions of Example 1, but without adding sodium methoxide and methanol. The alcoholysis rate A was 0%.

[0065] [Table 1]

[0066] [Table 2]

[0067] As shown in Tables 1 and 2, it was confirmed that by appropriately combining the catalyst (b), alcohol (c), and solvent (d) of the present invention, PET, which is a polyester resin product, can be alcoholyzed. In Examples 16 to 18, it was confirmed that alcoholysis of PET pellets proceeded even when substances not involved in alcoholysis were present. After alcoholysis was completed, OPP film, nylon film, and aluminum foil were recovered, respectively. Furthermore, these were not altered by the catalyst, alcohol, or solvent of the present invention.

[0068] Next, in Examples 19 to 26, the alcoholysis rate A was examined using polyester composites among the polyester-containing substances (a).

[0069] [Example 19] The same experiment was carried out under the conditions of Example 1, except that the PET pellets were replaced with white PET film (Toyobo Ester Film E-5102, manufactured by Toyobo Co., Ltd., with white ink printed on it). The alcoholysis rate A was 95.9%.

[0070] [Example 20] The same experiment was carried out under the conditions of Example 1, except that the PET pellets were replaced with a transparent alumina vapor-deposited PET film (Barrierox 1011SBR2, manufactured by Toray Advanced Film Co., Ltd.) The alcoholysis rate A was 100%.

[0071] [Example 21] The same experiment was carried out under the conditions of Example 1, except that the PET pellets were replaced with polyester fiber (King High Span button thread, manufactured by Fujix Co., Ltd.). The alcoholysis rate A was 90.0%.

[0072] [Example 22] The same procedure was carried out under the conditions of Example 1, except that the PET pellets were replaced with an aliphatic polyester resin (Adlock RU-10, manufactured by Rock Paint Co., Ltd.) The alcoholysis rate A was 100%. The polyester resin used here was dissolved in the reaction solution and could not be isolated by filtration. Therefore, after the reaction was completed, the reaction solution was isolated and characterized by GPC (gel permeation chromatography), and it was confirmed that no unalcoholized polyester resin was found.

[0073] [Example 23] Under the conditions of Example 1, the PET pellets were replaced with a resin prepared by grinding and mixing epoxy resin (35 parts by weight of jER1055K manufactured by Mitsubishi Chemical Group Corporation) and polyester resin (65 parts by weight of CRYLCOAT1713 manufactured by Daicel-Allnex Corporation) and thermally crosslinking the mixture at 160°C for 20 minutes, and the experiment was carried out in the same manner. These resins can be used as resins for powder coatings. For simplicity, the experiment was carried out using only the resin components without adding pigments or the like. The alcoholysis rate A was 45.8%.

[0074] [Example 24] The same experiment was carried out under the same conditions as in Example 1, except that the nylon-composite PET was prepared by combining PET pellets and Nylon-MXD6 (a crystalline polyamide obtained by the polycondensation reaction of metaxylenediamine and adipic acid, manufactured by Mitsubishi Gas Chemical Company, Inc.) in a weight ratio of 95:5. The reaction solution was filtered, and unreacted nylon-composite PET was removed from the resulting residue. The residue was analyzed by FT-IR (IR Prestige-21, manufactured by Shimadzu Corporation), and amide bonds originating from Nylon-MXD6 were detected. The alcoholysis rate A was 93.4%.

[0075] [Example 25] Under the conditions of Example 20, a PET egg carton with a paper label was used instead of the laminate film. After the reaction was completed, the reaction solution was filtered and the paper label was recovered, but no other residue was obtained. Here, the alcoholysis rate A of the PET egg carton itself, excluding the paper label, was calculated. The alcoholysis rate A was 100%.

[0076] [Example 26] The same experiment was carried out under the conditions of Example 20, except that a blended fiber of 65% polyester and 35% cotton was used instead of the laminate film. The alcoholysis rate A was 34.5%.

[0077] [Table 3]

[0078] As shown in Table 3, by appropriately combining the catalyst (b), alcohol (c), and solvent (d) of the present invention, it was confirmed that alcoholysis could occur even when a polyester composite was used as the polyester-containing substance (a). Furthermore, even in Example 23, in which nylon-composite PET was used as the polyester-containing substance (a), the nylon component that remained without being alcoholyzed could be separated, as in Example 17, in which nylon film was mixed.

[0079] Next, alcoholysis was investigated when a laminate film having the composition shown in Table 4 was used as the polyester-containing substance (a). Here, the separation rate B was evaluated based on the following formula 2. Separation rate B [%] = (1 - weight of unseparated laminate film after alcoholysis / weight of laminate film before alcoholysis) × 100 (Equation 2) Separation rate B is 90% or more: ◎ Separation rate B is 60% or more but less than 90%: 〇 Separation rate B is 30% or more but less than 60%: △ Separation rate B is less than 30%: ×

[0080] [Example 27] A laminate film (6 parts by weight) consisting of a PET film / polyester adhesive (AD1) / OPP film was placed in a tank, and sodium methoxide (1 part by weight) and methanol (2 parts by weight) were added. Toluene was added so that the total amount became 100 parts by weight, and the mixture was stirred at 25°C for 4 hours. After the reaction was completed, the reaction solution was filtered and the residue was washed with water, but no unseparated laminate film was recovered. The separation rate B was 100%.

[0081] [Examples 28 to 34, Comparative Example 6] The same procedure as in Example 27 was carried out except that the conditions were changed to those shown in Table 4.

[0082] [Example 35] A laminate film (6 parts by weight) consisting of PET film / polyester adhesive (AD1) / nylon film / polyester adhesive (AD1) / aluminum foil was placed in a tank, and sodium methoxide (0.03 parts by weight) and methanol (2 parts by weight) were added. Toluene was added to bring the total to 100 parts by weight, and the mixture was stirred at 65°C for 2 hours. After the reaction was completed, the reaction solution was filtered, and the residue was washed with water to recover the unseparated laminate film. The separation rate B was 92.1%.

[0083] [Table 4]

[0084] In Examples 27 to 30, the PET film and polyester adhesive (AD1) underwent alcoholysis, and the OPP film, CPP film, nylon film, and aluminum foil were separated, respectively. None of these films were altered by the catalyst, alcohol, or solvent of the present invention. In Example 31, the polyester adhesive (AD1) underwent alcoholysis, allowing the nylon film and aluminum foil to be separated. Neither adhesive was altered by the catalyst, alcohol, or solvent of the present invention. In Example 32, the PET film and polyester adhesive (AD1) underwent alcoholysis, allowing the nylon film and aluminum foil to be separated. Neither of these was altered by the catalyst, alcohol, or solvent of the present invention. In Example 33, the PET film underwent alcoholysis and the nylon film was recovered. However, since the polyether adhesive (AD2) did not undergo alcoholysis, residual adhesive was found on the recovered nylon film. In Example 34, the amount of catalyst was reduced to 0.3 parts by weight compared to Example 32, but the nylon film and aluminum foil could be separated in the same manner. In Example 35, the amount of catalyst was reduced to 0.03 parts by weight compared to Example 32. Even with a smaller amount of catalyst, nylon film and aluminum foil could be similarly separated under the condition of 65°C. On the other hand, in Comparative Example 6, a laminate film composed of components that are not involved in alcoholysis was used, and therefore the constituent films could not be separated. In this way, it was found that by appropriately combining catalyst (b), alcohol (c), and solvent (d), it is possible to efficiently separate each constituent film from a laminate film containing polyester components of various compositions.

[0085] [Examples 36 to 44, Comparative Examples 7 to 9] The same procedure as in Example 27 was carried out except that the conditions were changed to those shown in Table 5.

[0086] In Examples 36 to 44, the catalyst (b) and alcohol (c) were within the specified ranges, so all of them could be separated into the constituent films. Furthermore, none of the separated films were altered by the catalyst, alcohol, or solvent of the present invention. On the other hand, in the cases of Comparative Examples 7 to 9 in which ethylene glycol was used as the alcohol (c), separation into the respective constituent films was not possible at 25°C.

[0087] [Table 5]

[0088] [Examples 45 to 53] The same procedure as in Example 27 was carried out except that the conditions were changed to those shown in Table 6.

[0089] In Examples 45 to 47, the catalyst (b) and alcohol (c) were within the specified ranges, and therefore separation into the constituent films was possible in all cases. In Examples 48 to 50, the solvent (d) was changed from toluene to dichloromethane in comparison with Examples 45 to 47, and in all cases separation into the respective constituent films was possible. In Examples 51 to 53, the catalyst (b) was changed from sodium methoxide to TBD in comparison with Examples 45 to 47, but in all cases separation into the constituent films was possible. Furthermore, none of the separated films was altered by the catalyst, alcohol, or solvent of the present invention.

[0090] [Table 6]

[0091] [Examples 54 to 63, Comparative Examples 10 to 11] The same procedure as in Example 27 was carried out except that the conditions were changed to those shown in Table 7.

[0092] In Examples 54 to 63, the catalyst (b) and alcohol (c) were within the specified ranges, so all of them could be separated into the constituent films. Furthermore, none of the separated films were altered by the catalyst, alcohol, or solvent of the present invention. In Comparative Examples 10 and 11, in contrast to Examples 56 and 57, the catalyst (b) was changed from sodium hydroxide to calcium hydroxide, and the constituent films could not be separated.

[0093] [Table 7]

[0094] As shown in Tables 5 to 7, by appropriately combining the catalyst (b), alcohol (c), and solvent (d) of the present invention, it was confirmed that when a laminate film was used as the polyester-containing substance (a), alcoholysis proceeded efficiently and each constituent film could be separated. [Explanation of symbols]

[0095] 1 tank 2 tanks 3 motors 4 Heater 5 Mixing blades 6 valves 7. Pressure gauge 8. Filtration equipment 9. Pump

Claims

1. A step (A) of alcoholysing a polyester-containing substance (a) in a solvent (d) in the presence of a catalyst (b) and an alcohol (c); The method includes a step (B) of separating the alcoholysis product obtained in the step (A), A method for recycling a polyester-containing material (a), comprising: the weight ratio of alcohol (c) / solvent (d) is 1 / 1 to 1 / 99; The alcoholysis proceeds at a temperature of 20°C or higher but lower than 100°C. A method for recycling a polyester-containing material (a).

2. The recycling method described in claim 1, characterized in that the polyester-containing substance (a) is at least one selected from the group consisting of four types: polyethylene terephthalate, polyester-based adhesives for laminate films, polyester-based coating films, and laminates in which multiple films are bonded together via adhesives.

3. 2. The recycling method according to claim 1, wherein the catalyst (b) is at least one selected from the group consisting of alkali metal alkoxides and nitrogen-containing organic basic compounds.

4. 2. The recycling method according to claim 1, wherein the catalyst (b) is sodium methoxide and / or 1,5,7-triazabicyclo[4.4.0]dec-5-ene.

5. the alcohol (c) is a monohydric alcohol having 1 to 8 carbon atoms; The recycling method according to claim 1, characterized in that the amount is 2 to 30 parts by weight per 100 parts by weight of the total of the polyester-containing substance (a), the catalyst (b), the alcohol (c), and the solvent (d).

6. 2. The recycling method according to claim 1, wherein the alcohol (c) is methanol.

7. 2. The recycling method according to claim 1, wherein the solvent (d) does not react with the alcoholysis product in the alcoholysis reaction system.

8. 2. The recycling method according to claim 1, wherein the solvent (d) contains toluene.

9. The recycling method according to claim 1, characterized in that the polyester-containing substance (a) is a laminate in which multiple films are bonded together via a polyester-based adhesive for laminate films, and the catalyst (b) is an alkali metal hydroxide.

10. 10. The recycling method according to claim 9, wherein the catalyst (b) is sodium hydroxide.

11. The recycling method according to any one of claims 1 to 10, further comprising a step (C) of separating substances other than the alcoholysis product.

12. The recycling method according to claim 11, characterized in that an apparatus having a tank (X) for storing the polyester-containing substance (a) and a tank and / or a path (Y) for separating the alcoholysis product of the polyester is utilized.

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