Method for recycling polyester-containing substance

Abstract

[Problem] To provide a method for recycling a polyester-containing substance by a new means. [Solution] The method for recycling a polyester-containing substance comprises a step in which the polyester-containing substance is subjected to alcoholysis in a solvent in the presence of a catalyst and an alcohol and a step in which an alcoholysis product obtained in the above-mentioned step is isolated. Specifically, the method is performed using a device including a tank for holding a polyester-containing substance therein and a tank and / or a path for isolating a product of alcoholysis of the polyester.

Description

Method for recycling polyester-containing materials

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

[0002] Completely decomposing a substance to its smallest units and purifying the decomposition products to remove impurities not only requires a great deal of energy but also takes time and effort. Therefore, the term "recycling" in the present invention refers to making the polyester-containing substance reusable as a resource. That is, the purpose is to reduce the energy consumption and labor required for recycling, and does not necessarily mean decomposing and purifying the polyester to its smallest units by chemical decomposition. However, decomposition and purification aimed at reducing energy consumption and shortening the process are not excluded. For this purpose, the alcoholysis product of the polyester-containing substance 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. Furthermore, it is useful to subject the remaining components of the composite that are not affected by alcoholysis to material recycling.

[0003] Plastics are inexpensive and durable materials. Due to their convenience, polyethylene terephthalate (PET) in particular has been widely used in textiles, films, bottles, and other applications, resulting in a rapid increase in production and consumption over the past few decades. However, despite its durability, PET is not easily biodegradable, leading to landfills worldwide and the resulting marine pollution caused by microplastics, exposing social issues of environmental destruction. Against this backdrop, the development of recycling technologies for PET and other plastic waste is highly desirable. Compared to Europe and the United States, Japan has a high rate of thermal recycling, which utilizes the heat generated during incineration. However, concerns remain about global warming due to carbon dioxide emissions. Therefore, much research has been conducted on chemical recycling of polyester products, i.e., chemically converting polyester products into monomers, recovering them, and then 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 waste multilayer film is selectively dissolved to induce layer separation, and the resulting film is separated into a PP / PE mixture layer and a PET layer based on the difference in specific gravity. Furthermore, to increase the purity of the PET separated based on 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 comprises 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 produced ethylene carbonate must be decomposed into ethylene glycol in order to reuse it as a PET raw material.

[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 involves 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 contacting with methanol and a catalyst selected from potassium carbonate, sodium carbonate, magnesium methoxide, 1,8-diazabicyclo[5.4.0]undec-7-ene, and triazabicyclodecene. The specification indicates 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 80% or higher by using a mixture of methanol and toluene in a volume ratio of 8:2 to 5:5.

[0011] Japanese Patent Application Laid-Open No. 2001-039908 Japanese Patent Application Laid-Open No. 2012-131729 Japanese Patent Application Laid-Open No. 2006-205160 Japanese Patent Application Laid-Open No. 2022-126617 Special Publication No. 2020-533395 Special Publication No. 2023-506948

[0012] 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

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

[0014] As a result of intensive research aimed at solving the above-mentioned problems, the present inventors have discovered a method for recycling a polyester-containing material, which comprises the steps of alcoholyzing a polyester-containing material 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 a polyester-containing material, which is characterized by using an apparatus having a tank for storing the polyester-containing material 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, a composite containing a polyester component, or a laminate in the form of multiple films, as described below. The present invention is applicable to various polyesters and is not particularly limited, as described below. One example is polyethylene terephthalate. The catalyst (b) is not particularly limited, as described below. Various metal salts and nitrogen-containing organic base compounds can be used, as described below. For example, at least one selected from the group consisting of alkali metal alkoxides and nitrogen-containing organic base compounds can be selected. More specifically, sodium methoxide and / or 1,5,7-triazabicyclo[4.4.0]dec-5-ene can be used. The alcohol (c) can also be selected from a variety of alcohols and is not particularly limited, as described below. However, a monohydric alcohol having 1 to 8 carbon atoms is preferred. Methanol is a simple example. The solvent (d) is also not particularly limited, as described below. However, from the perspective of recycling, those that react with the alcoholysis product in the reaction system should be 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] 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), and step (B) of separating the alcoholysis product obtained in step (A), and further includes 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 implementing the present invention, polyester-containing materials (a) can be recycled without incineration or other disposal, which can also contribute to reducing carbon dioxide emissions.

[0018] 1 is a structural diagram of an apparatus for carrying out the present invention;

[0019] The method of recycling a polyester-containing substance (a) by alcoholysis in the present invention involves a catalyst (b) and an alcohol (c) and is carried out in a solvent (d). The blending ratio of these components can be appropriately changed within a range in which the alcoholysis proceeds smoothly. 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 configuration of the present invention, and may be changed within a range that does not deviate from the spirit of the present invention.

[0020] <Polyester-Containing Substance (a)> One embodiment of the polyester-containing substance (a) of the present invention includes a polyester resin product. Typical 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] Another embodiment of the polyester-containing substance (a) of the present invention may be a composite containing a polyester component, including food trays, fibers, adhesives, pressure-sensitive adhesives, inks, and coatings. For example, in recent years, products in which PET bottles are compounded with polyamide resins to impart gas barrier properties have been adopted for wine and other beverages. The present invention can also be applied to such composites containing physically added substances. Since the present invention does not decompose amide bonds, in the above example, the polyethylene terephthalate, the raw material for PET bottles, decomposes, while the polyamide resin remains. Other examples include polyester products with a vapor-deposited layer on the surface and those containing coloring components for decorative purposes. The present invention can also be applied to any of these. Furthermore, some of the components may be chemically modified. Examples of resins that can be used in polyester-based 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 with polyisocyanates; and powder coating films formed by epoxy polyester-based powder coatings or powder coatings consisting of a combination of a carboxyl group-containing polyester resin and a β-hydroxyalkylamide.

[0022] The polyester-containing material (a) of the present invention also includes, as another embodiment, 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 non-oriented 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 deposition layer or ink layer formed thereon. Colored films may also be used. When the polyester-containing material (a) of the present invention is a laminate containing a polyester film, the polyester film is separated from the other laminate films by alcoholysis, allowing for recycling. Furthermore, even if a laminate does not contain a polyester film, if the laminate is bonded with a polyester-based adhesive, the adhesive component is alcoholyzed, thereby separating the films bonded with the adhesive, and recycling can be promoted. The above-mentioned films having ester bonds can be subject to alcoholysis in the present invention. Thus, in the present invention, it is not necessary to decompose and purify the polyester-containing substance (a) to the minimum monomer unit; it is sufficient to decompose it to the extent that the remaining components that have not been alcoholyzed 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 a general method of use as a laminating adhesive can be applied. Examples include a non-solvent lamination method in which the adhesive is heated to achieve an appropriate viscosity, and a dry lamination method 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 in a dry state is 1 to 10 g / m. ２The temperature range is generally within this range, but 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 provided. For example, aging may be provided 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, a metal salt or a nitrogen-containing organic basic compound can be used.

[0026] As the metal salt, 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 can be used. In particular, alkali metal alkoxides and alkali metal hydroxides are preferably used. 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. Among these, sodium hydroxide is particularly preferred. 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, increasing the amount of post-treatment work, which is 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 nylon film and aluminum foil, which are not involved in alcoholysis. Therefore, this advantageously acts to separate 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 per 100 parts by weight of the polyester-containing substance (a), catalyst (b), alcohol (c), and solvent (d) combined. More preferably, it is 0.03 to 5 parts by weight. The amount of catalyst (b) added can be adjusted within a range in which alcoholysis proceeds. However, if the amount added is large, not only will costs increase, but separation of the catalyst residue will become more time-consuming. Furthermore, it is likely to adversely affect components separated as substances other than the alcoholysis product, making material recycling difficult. On the other hand, if the amount added is small, the catalyst may be 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. Of 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). It is preferably 0.9 parts by weight or more and 50 parts by weight or less relative to 100 parts by weight of the total of the polyester-containing substance (a), catalyst (b), alcohol (c), and solvent (d). It is more preferably 2 parts by weight or more and 30 parts by weight or less. The amount of alcohol (c) added can be adjusted within a range in which alcoholysis proceeds. However, if the amount added is large, costs increase. Furthermore, if the amount added is small, alcoholysis does not proceed sufficiently. Note that the present invention does not require complete decomposition of the polyester-containing substance (a) down to its minimum units and purification of the decomposition products. Therefore, it is sufficient that alcoholysis proceeds to a degree sufficient for recycling. If alcoholysis does not proceed sufficiently, alcoholysis can be resumed by adding more alcohol (c).

[0034] <Solvent (d)> The solvent (d) of the present invention excludes solvents that react with the alcoholysis product in the alcoholysis reaction system. For example, if dimethyl carbonate is selected as the 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 this solvent unsuitable from the perspective of resource recycling. Furthermore, when considering the reuse of the solvent, a boiling point that is too high will require a large amount of thermal energy for the distillation operation. Therefore, 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 that can be used include toluene, acetonitrile, N,N-dimethylformamide, dimethyl sulfoxide, n-hexane, cyclohexane, dichloromethane, tetrahydrofuran, methyl ethyl ketone, and ethyl acetate. These solvents can be selected appropriately as long as they do not inhibit the alcoholysis, and may be used alone or in combination of two or more. However, the use of alcoholic solvents is excluded.

[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) to the solvent (d) is preferably 1 / 1 to 1 / 99 by weight, and more preferably 1 / 2 to 1 / 50 by weight.

[0037] <Other Components (e)> In addition to the above (a) to (d), other components such as a desiccant or a substance that does not participate in alcoholysis may be included. These do not limit the configuration 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. These desiccants may 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 not involved 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 non-oriented 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, polystyrene (PS) sheets, and the like can also be used. These films and sheets may have a vapor-deposited layer formed thereon. They may also be colored. They may be a mixture of multiple components or may be produced by coextrusion or the like. Furthermore, mineral components such as sodium chloride may be mixed in the film or sheet.

[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 be stopped and a product separation step may be carried out at an intermediate stage.

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

[0045] <Step (B)> Step (B), which separates 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. Therefore, for example, separation can be performed by a method such as concentration and recrystallization or an extraction method, but is not limited to these methods. Furthermore, water washing or a liquid separation operation may be performed as necessary. The alcoholysis product obtained by these methods can be further decomposed and purified as necessary and then subjected to chemical recycling.

[0046] <Step (C)> 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 Apparatus> Next, one embodiment of an apparatus having a tank (X) and a tank and / or a path (Y) will be described with reference to FIG. 1 , but the apparatus can be implemented in various forms.

[0048] A polyester-containing substance (a) is placed in tank 1 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 path, 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] Examples of mixing methods include stirring with a ceramic rotor, mechanical stirring with a stirring blade, and mixing by circulation. The example in Figure 1 shows an example of stirring with a stirring blade 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 a pump 9 placed along the path, and in this example, a flow rate adjusting 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 tank 1, tank 2, and / or the path, etc., can be selected appropriately as long as they do not hinder recycling.

[0050] The present invention can be embodied in the various embodiments described above, as well as in the following embodiment. A method for recycling a polyester-containing substance (a) according to this embodiment includes a step (A) of alcoholyzing the polyester-containing substance (a) in a solvent (d) in the presence of a catalyst (b) and an alcohol (c), a step (B) of separating the alcoholysis product obtained in the step (A), and a 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 per 100 parts by weight of the polyester-containing substance (a), the catalyst (b), the alcohol (c), and the solvent (d). More preferably, the amount can be 2 parts by weight or more and 30 parts by weight or less. The solvent (d) contains toluene. The blending ratio of the alcohol (c) and the solvent (d) can be varied 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. 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 respective features of the above-described embodiments can be applied. The polyester-containing substance (a) can be at least one selected from the group consisting of polyethylene terephthalate, a polyester-based adhesive for a laminate film, a polyester-based coating film, and a laminate 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 a plurality of films are bonded together via an adhesive, the catalyst (b) may be any of the above-mentioned 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 In addition to -azabicyclo[5.4.0]undec-7-ene (DBU) and 1,3-dimesitylimidazol-2-ylidene, at least one selected from the group consisting of lithium hydroxide, sodium hydroxide, and potassium hydroxide can be selected.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) may be sodium methoxide or sodium hydroxide, the alcohol (c) may be methanol, and the solvent (d) may be toluene.

[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 (a) containing polyester> PET pellets (commercially available product) Eco A-PET film (commercially available product) G-PET flakes (commercially available product) Polyester polyurethane laminating adhesive (ADOLOCK RU-77 / H-7, manufactured by Rock Paint Co., Ltd.), hereinafter abbreviated as "AD1" Polyether polyurethane laminating adhesive (ADOLOCK RN-230 / HN-230, manufactured by Rock Paint Co., Ltd.), hereinafter abbreviated as "AD2" <Catalysts (b)> Sodium methoxide (Wako Pure Chemical Industries, Fujifilm Corporation, Wako Grade 1) 1,5,7-Triazabicyclo[4.4.0]dec-5-ene (TBD, Tokyo Chemical Industry Co., Ltd.) Sodium hydroxide (Kanto Chemical Co., Ltd., Deka Grade 1) Potassium hydroxide (Kanto Chemical Co., Ltd.) Calcium hydroxide (Kanto Chemical Co., Ltd., Special Grade) <Alcohol (c)> Methanol (Fujifilm Wako Pure Chemical Industries, Ltd., ultra-dehydrated grade) Ethanol (Fujifilm Wako Pure Chemical Industries, Ltd., 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 stabilizer)) Dichloromethane (Kanto Chemical Co., Ltd., special grade) <Film> PET film (Toyobo Ester Film E5102, 12 μm, Toyobo Co., Ltd.) 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, Toyo Aluminum K.K., 20 μm) LLDPE film (RM Tocello Co., Ltd., TUX-FC-S, 60 μm) Note that, 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 adjust the amounts of catalyst (b) and alcohol (c) added appropriately depending on the film thickness. <Filter> - Mesh size 0.5 mm, made of stainless steel.

[0054] The method for producing a laminate film will be described using a PET / AD1 / OPP structure as an example. A dry coating amount of 4 g / m was applied using a bar coater. ２ After coating and drying the PET film so that the thickness was 100 μm, 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 components, the dry coating amount was adjusted to 1 to 10 g / m depending on the type of film used and the application 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): Alcoholysis rate A [%] = (1 - weight of (a) after alcoholysis / weight of (a) before alcoholysis) × 100 (Formula 1)

[0056] In the following examples, the evaluation results are shown according to the following criteria: Alcoholization rate A is 90% or more: Excellent Alcoholization rate A is 60% or more but less than 90%: Good Alcoholization rate A is 30% or more but less than 60%: Fair Alcoholization rate A is less than 30%: Poor

[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). Toluene was added so that the total amount became 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 through a filter, and the filtration residue was washed with water. No unreacted PET pellets were obtained as the filtration residue. The alcoholysis rate A was 100%.

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

[0060] Comparative Example 1: The same procedure as in Example 1 was carried out, 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 the catalyst (b), the reaction solution became a highly viscous liquid, and it was found that the conditions needed to be adjusted and investigated in order to efficiently proceed with alcoholysis.

[0061] Comparative Example 2 The same procedure as in Example 1 was carried out, 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 as in Example 1 was carried out, 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 as in Example 1 was carried out except that sodium methoxide was not added. The alcoholysis rate A was 0%.

[0064] Comparative Example 5 The same procedure as in Example 1 was carried out, except that sodium methoxide and methanol were not added. The alcoholysis rate A was 0%.

[0065]

[0066]

[0067] As shown in Tables 1 and 2, it was confirmed that PET, a polyester resin product, can be alcoholized by appropriately combining the catalyst (b), alcohol (c), and solvent (d) of the present invention. In Examples 16 to 18, it was confirmed that alcoholysis of PET pellets proceeded even when substances not involved in alcoholysis were contained. 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 procedure as in Example 1 was carried out, except that the PET pellets were replaced with white PET film (Toyobo Ester Film E-5102, manufactured by Toyobo Co., Ltd., printed with white ink). The alcoholysis rate A was 95.9%.

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

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

[0072] Example 22 The same procedure as in Example 1 was carried out, 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%. Since the polyester resin used here was dissolved in the reaction solution and could not be isolated by filtration, after completion of the reaction, 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 The same experiment was carried out under the same conditions as in Example 1, except that the PET pellets were replaced with a resin prepared by grinding and mixing an epoxy resin (35 parts by weight of jER1055K manufactured by Mitsubishi Chemical Group Corporation) and a polyester resin (65 parts by weight of CRYLCOAT1713 manufactured by Daicel-Allnex Corporation) and thermally crosslinking the mixture at 160°C for 20 minutes. These resins can be used as resins for powder coatings. For simplicity's sake, 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 procedure as in Example 1 was carried out, 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 filtration residue. The residue was analyzed by FT-IR (IRPrestige-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 through a filter, and the paper label was recovered, but no filtration residue other than the paper label 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 procedure as in Example 20 was carried out 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]

[0078] As shown in Table 3, it was confirmed that alcoholysis could be achieved even when a polyester composite was used as the polyester-containing substance (a) by appropriately combining the catalyst (b), alcohol (c), and solvent (d) of the present invention. Furthermore, even in Example 23, in which nylon-composite PET was used as the polyester-containing substance (a), the nylon component that remained without alcoholysis could be separated, as in Example 17, in which a 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) x 100 (formula 2) Separation rate B is 90% or more: Excellent Separation rate B is 60% or more but less than 90%: Good Separation rate B is 30% or more but less than 60%: Fair Separation rate B is less than 30%: Bad

[0080] [Example 27] A laminate film (6 parts by weight) composed 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 was 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 filtration 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 conditions of Example 27 were changed to those shown in Table 4, and the same procedures were carried out.

[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 so that the total was 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 filtration residue was washed with water to recover the unseparated laminate film. The separation rate B was 92.1%.

[0083]

[0084] In Examples 27 to 30, the PET film and polyester-based adhesive (AD1) underwent alcoholysis, and the OPP film, CPP film, nylon film, and aluminum foil could be separated, respectively. None of these were altered by the catalyst, alcohol, or solvent of the present invention. In Example 31, the polyester-based adhesive (AD1) underwent alcoholysis, and the nylon film and aluminum foil could be separated. None of these were altered by the catalyst, alcohol, or solvent of the present invention. In Example 32, the PET film and polyester-based adhesive (AD1) underwent alcoholysis, and the nylon film and aluminum foil could be separated. None of these were altered by the catalyst, alcohol, or solvent of the present invention. In Example 33, the PET film underwent alcoholysis, and the nylon film could be recovered. However, since the polyether-based adhesive (AD2) did not alcoholyze, residual adhesive was observed in 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 similarly separated. 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, the nylon film and aluminum foil could be separated at 65°C. On the other hand, in Comparative Example 6, a laminate film composed of components not involved in alcoholysis was used, and therefore the individual constituent films could not be separated. Thus, it was found that the individual constituent films could be efficiently separated from laminate films containing polyester components of various compositions by appropriately combining catalyst (b), alcohol (c), and solvent (d).

[0085] Examples 36 to 44, Comparative Examples 7 to 9 The conditions of Example 27 were changed to those shown in Table 5, and the same procedures were carried out.

[0086] In Examples 36 to 44, the catalyst (b) and alcohol (c) were within the specified ranges, so all of them were able to separate into their respective 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 Comparative Examples 7 to 9, in which ethylene glycol was used as the alcohol (c), none of them were able to separate into their respective constituent films at 25°C.

[0087]

[0088] Examples 45 to 53 The same procedures as in Example 27 were 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 all were separated into their respective constituent films. In Examples 48 to 50, the solvent (d) was changed from toluene to dichloromethane, as compared to Examples 45 to 47, and all were separated into their respective constituent films. In Examples 51 to 53, the catalyst (b) was changed from sodium methoxide to TBD, as compared to Examples 45 to 47, and all were separated into their respective constituent films. Furthermore, none of the separated films were altered by the catalyst, alcohol, or solvent of the present invention.

[0090]

[0091] Examples 54 to 63, Comparative Examples 10 and 11 The conditions of Example 27 were changed to those shown in Table 7, and the same procedures were carried out.

[0092] In Examples 54 to 63, the catalyst (b) and alcohol (c) were within the specified ranges, so all of them were separated into their 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, the catalyst (b) was changed from sodium hydroxide to calcium hydroxide in Examples 56 and 57, but separation of the constituent films was not possible.

[0093]

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

[0095] 1 Tank 2 Tank 3 Motor 4 Heater 5 Stirring blade 6 Valve 7 Pressure gauge 8 Filtration device 9 Pump

Claims

1. A step (A) of subjecting a polyester-containing substance (a) to alcoholysis in a solvent (d) in the presence of a catalyst (b) and an alcohol (c); A step (B) of separating the alcoholysis product obtained in the step (A); and (C) separating substances other than the alcoholysis product. A method for recycling a polyester-containing material (a), comprising the steps of: The catalyst (b) is at least one selected from the group consisting of alkali metal alkoxides and nitrogen-containing organic base compounds, The alcohol (c) is a monohydric alcohol having 1 to 8 carbon atoms, and the blending amount of the alcohol (c) is 2 to 30 parts by weight with respect 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 weight ratio of alcohol (c) / solvent (d) is 1 / 1 to 1 / 99; The alcoholysis proceeds at a temperature of 20° C. or higher and lower than 100° C. A method for recycling a polyester-containing material (a).

2. The recycling method according to claim 1, characterized in that the polyester-containing substance (a) is at least one selected from the group consisting of polyethylene terephthalate, a polyester-based adhesive for laminate films, a polyester-based coating film, and a laminate in which multiple films are bonded together via an adhesive.

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

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

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

6. A process (A) for alcoholysing a polyester-containing substance (a) in the presence of a catalyst (b) and an alcohol (c) in a solvent (d); A step (B) of separating the alcoholysis product obtained in the step (A); and (C) separating substances other than the alcoholysis product. A method for recycling a polyester-containing material (a), comprising the steps of: The polyester-containing material (a) is a laminate in which a plurality of films are bonded together via a polyester-based adhesive for laminate films, and the catalyst (b) is an alkali metal hydroxide; 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 and lower than 100° C. A method for recycling a polyester-containing material (a).

7. The recycling method according to claim 6, wherein the catalyst (b) is sodium hydroxide.

8. The recycling method according to any one of claims 1 to 7, 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 an alcoholysis product of the polyester is utilized.