Composition for decomposing polyester, method for producing decomposed polyester products, and method for producing polyester

Abstract

To provide a polyester decomposition composition that shortens the reaction time for decomposition and yields high yields, and a method for producing polyester decomposition products, and further, a method for producing polyester using the decomposition products (monomers) obtained by this polyester decomposition method. [Solution] A polyester decomposition composition comprising a base, a monohydric alcohol, a carbonate ester, and at least one compound from a group represented by a predetermined chemical formula.

Description

Technical Field

[0001] The present invention relates to a composition for polyester decomposition, a method for producing a polyester decomposition product, and a method for producing a polyester.

Background Art

[0002] As methods for decomposing polyester, there are disclosed a method using water or supercritical alcohol (see Patent Documents 1 and 2), a method using a base catalyst and alcohol in a halogenated solvent (see Non-Patent Document 1 and Patent Document 3), a method using a basic catalyst and tetraalkoxysilane in an alcohol solvent (see Patent Document 4), and a method using a base catalyst in a mixed solvent of dimethyl carbonate and alcohol (see Patent Document 5).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Non-Patent Documents

[0004]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] As a method for decomposing polyester, for example, the methods shown in Patent Documents 4 and 5 can selectively decompose polyester contained in various polyester-containing materials in a low-temperature process below 100°C, and furthermore, the resulting decomposition products can be easily isolated with high purity. However, for industrial implementation, further reduction of reaction time and improvement of yield are required.

[0006] The present invention has been made in view of the above problems, and aims to provide a polyester decomposition composition for decomposition that shortens the reaction time for decomposition and yields high yield, as well as a method for producing polyester decomposition products, and further, a method for producing polyester using decomposition products (monomers) obtained by this polyester decomposition method. [Means for solving the problem]

[0007] The inventors diligently studied to solve the above problems. As a result, they found that by using a polyester decomposition composition containing at least one compound from the group represented by formulas (1) to (4) above, it is possible to provide a polyester decomposition composition that shortens the reaction time and enables high-yield decomposition, as well as a method for producing polyester decomposition products, and thus completed the present invention. That is, the present invention is as follows. [1] A base, a monohydric alcohol, a carbonate ester, and at least one compound from the group represented by the following formulas (1) to (4), A composition for decomposing polyester. [ka] (In formula (1), R1 is a monovalent alkyl group having 1 to 5 carbon atoms, R2 is a divalent organic group having 1 to 5 carbon atoms, and R3 is a monovalent organic group having 1 to 5 carbon atoms.) [ka] (In formula (2), R4 and R7 are each independently monovalent organic groups having 1 to 5 carbon atoms.) R5 and R6 are each independently a divalent organic group having 1 to 5 carbon atoms. [Chemical formula] (In formula (3), R8 and R 10 are each independently a monovalent organic group having 1 to 5 carbon atoms, and R9 is a divalent organic group having 1 to 5 carbon atoms.) [Chemical formula] (In formula (4), n is 1 or 2, and R 11 , R 12 , R 13 , and R 14 are each independently a monovalent organic group having 1 to 5 carbon atoms or a hydrogen atom.) [2] The polyester decomposition composition contains the compound represented by the formula (1), The polyester decomposition composition according to [1]. [3] The polyester decomposition composition contains the compound represented by the formula (2), The polyester decomposition composition according to [1] or [2]. [4] The polyester decomposition composition contains the compound represented by the formula (3), The compound represented by the formula (3) contains at least any one of the compounds represented by the following formulas (5) to (8), The polyester decomposition composition according to any one of [1] to [3]. [Chemical formula] (In formula (5), R 15 and R 18 are each independently a monovalent alkyl group having 1 to 5 carbon atoms, and R 16 and R 17 are each independently a divalent alkyl group having 1 to 5 carbon atoms.) [Chemical formula] (In formula (6), R 19 , R 20 , R 21 , and R 22 Each of these is independently a monovalent alkyl group having 1 to 5 carbon atoms. [ka] (In formula (7), R 23 , R 24 , and R 25 Each of these is independently a monovalent alkyl group having 1 to 5 carbon atoms. [ka] (In formula (8), R 26 , and R 29 Each of these is independently a monovalent alkyl group having 1 to 5 carbon atoms, and R 27 and R 28 Each of these is independently a monovalent alkyl group having 1 to 5 carbon atoms or a hydrogen atom. [5] The polyester decomposition composition contains the compound represented by formula (4), The compound represented by formula (4) contains at least one of the compounds represented by the following formulas (9) and (10): A polyester decomposition composition as described in any of [1] to [4]. [ka] (In formula (9), R 30 , R 31 , and R 32 Each of these is independently a monovalent alkyl group having 1 to 5 carbon atoms or a hydrogen atom. [ka] (In formula (10), R 33 , R 34 , R 35 , and R 36 Each of these is independently a monovalent alkyl group having 1 to 5 carbon atoms or a hydrogen atom. [6] The base contains at least one selected from the group consisting of alkali metal carbonates, alkali metal hydroxides, and alkali metal alkoxides. A polyester decomposition composition according to any one of [1] to [5]. [7] The aforementioned monohydric alcohol includes monohydric alcohols having 1 to 5 carbon atoms. A polyester decomposition composition according to any one of [1] to [6]. [8] The carbonate ester includes a carbonate ester represented by the following formula (11): A polyester decomposition composition according to any one of [1] to [7]. [ka] (In formula (11), R 37 and R 38 Each of these is independently an alkyl group or aryl group having 1 to 5 carbon atoms. [9] The ratio (a / b) of the total moles (a) of the compound represented by formulas (1) to (4) to the total moles (b) of the base is between 0.0001 and 1. A polyester decomposition composition as described in any of [1] to [8].

[10] The polyester comprises at least one selected from the group consisting of polyalkylene terephthalate, polyalkylene naphthalate, and polyalkylene furnate. A polyester decomposition composition as described in any of [1] to [9].

[11] The method comprises a decomposition step of bringing a polyester decomposition composition described in any of [1] to

[10] into contact with a polyester-containing material to decompose the polyester in the polyester-containing material and obtain a polyester decomposition product. A method for producing polyester decomposition products.

[12] The polyester decomposition product contains at least one compound represented by the following formulas (12) to (14): A method for producing polyester decomposition products as described in

[11] . [ka] (In formula (12), R 39 and R 40 These are, independently, monovalent organic groups with 1 to 5 carbon atoms. [ka] (In formula (13), R 41 and R 42 These are, independently, monovalent organic groups with 1 to 5 carbon atoms. [ka] (In formula (14), R 43 and R 44 These are, independently, monovalent organic groups with 1 to 5 carbon atoms.

[13] The process includes purifying the polyester decomposition product, which is dissolved in the polyester decomposition composition and / or suspended in the polyester decomposition composition, by distillation. A method for producing polyester decomposition products as described in

[11] or

[12] .

[14] The process includes a polymerization step in which a polyester decomposition product obtained by any of the methods in

[11] to

[13] is used as a monomer for polymerization. A method for manufacturing polyester. [Effects of the Invention]

[0008] According to the present invention, a polyester decomposition composition for shortening reaction time and achieving high yield, and a method for producing polyester decomposition products are provided, and furthermore, a method for producing polyester using decomposition products obtained by the method for producing polyester decomposition products is also provided. [Modes for carrying out the invention]

[0009] The following describes in detail an embodiment for carrying out the present invention (hereinafter referred to as "this embodiment"). This embodiment is an example for explaining the present invention, and the present invention is not limited to this embodiment. The present invention can be appropriately modified and implemented within the scope of its gist.

[0010] <Polyester decomposition composition> The polyester decomposition composition of this embodiment comprises a base, a monohydric alcohol, a carbonate ester, and at least one compound from the group represented by the following formulas (1) to (4), and may optionally contain other components. The target material for decomposition and each component of the polyester decomposition composition will be described in detail below.

[0011] <Objects to be decomposed> In this embodiment, polyester is decomposed by contacting a polyester-decomposing composition, which contains a base, a monohydric alcohol, a carbonate ester, and at least one compound from the group represented by the following formulas (1) to (4), with the polyester in the polyester-containing material. The polyester-containing material is not limited to polyester alone, but is a concept that includes materials containing polyester and materials other than polyester. Therefore, any material containing polyester is not particularly limited as a target for decomposition.

[0012] The polyester-containing material in this embodiment is not particularly limited, but examples include materials with an extremely high polyester content and a form suitable for decomposition reactions, such as pure polyester or polyethylene terephthalate (PET) film; and materials with a low polyester content or that are not suitable for decomposition reactions. The material that is not suitable for the decomposition reaction is not particularly limited, but examples include materials in which the surface of the polyester is coated with another substance, preventing physical contact between the polyester decomposition composition and the polyester. In other words, a wide range of materials can be used as the polyester-containing material in this embodiment.

[0013] More specifically, the polyester-containing material of this embodiment is not particularly limited, but examples include a material containing polyester fibers, a film containing polyester and components other than polyester, and a mass containing polyester and components other than polyester.

[0014] Materials containing polyester fibers are not particularly limited, but examples include polyester fibers (fibers that do not contain components other than polyester), polyester fiber fabrics, mixtures containing polyester fibers and components other than polyester fibers, and fabrics of such mixtures.

[0015] The mixture containing polyester fibers and components other than polyester fibers is not particularly limited, but examples include mixed fibers of polyester fibers and fibers other than polyester fibers and fabrics of the mixed fibers, composite mixtures containing polyester fibers and non-resin components (for example, colored fibers containing polyester fibers and colorants) and fabrics of the composite mixture, and composite mixed fibers containing polyester fibers, fibers other than polyester fibers and non-resin components (for example, colored mixed fibers containing mixed fibers and colorants) and fabrics of the composite mixture. Here, in this embodiment, "non-resin component" means a component that does not fall under either polyester or resins other than polyester.

[0016] Furthermore, while there are no particular limitations on the films containing polyester and other components, examples include single-layer films containing polyester and other components, and laminated films which are laminates of a polyester film and a film containing other components.

[0017] The single-layer film containing polyester and non-polyester components is not particularly limited, but examples include a single-layer film containing both polyester and non-polyester resins and no non-resin components, a single-layer film containing both polyester and non-resin components and no non-polyester resins, and a single-layer film containing polyester, non-polyester resins, and non-resin components.

[0018] Laminated films, which are laminates of a polyester film and a film containing components other than polyester, are not particularly limited, but examples include: a laminated film made of a polyester film and a film containing a resin other than polyester and not containing either polyester or non-resin components; a laminated film made of a polyester film and a film containing both a resin other than polyester and polyester and not containing any non-resin components; a laminated film made of a polyester film and a film containing both a resin other than polyester and non-resin components and not containing polyester; a laminated film made of a polyester film and a film containing both polyester and non-resin components and not containing any resin other than polyester; a laminated film made of a polyester film and a film containing polyester, a resin other than polyester, and non-resin components; a multilayer film made of one or more of the above laminated films and one or more of the above single-layer films; a multilayer film made of two or more of the above laminated films; and a multilayer film made of two or more of the above single-layer films.

[0019] The bulk material containing polyester and non-polyester components is not particularly limited, but examples include bulk material containing both polyester and non-polyester resins and no non-resin components; bulk material containing both polyester and non-resin components and no non-polyester resins; and bulk material containing polyester, non-polyester resins, and non-resin components.

[0020] Resins other than polyester can be arbitrarily selected depending on the purpose and are not particularly limited. Examples of resins other than polyester that are highly versatile and have high applicability to the present invention include polyolefins such as polyethylene and polypropylene; polyamides such as cellulose and nylon; polyurethane; and acrylic resins. These resins are not particularly limited, but may be in the form of films (resin films) or fibers (resin fibers).

[0021] Other fibers besides polyester include fibers made from resins other than polyester, cotton, rayon, polyurethane, nylon, and olefins.

[0022] Furthermore, the non-resin components can be arbitrarily selected depending on the purpose and are not particularly limited. While the non-resin components are not particularly limited, examples of highly versatile and valuable applications of the present invention include inorganic components (inorganic compounds) such as aluminum, colorants such as dyes and pigments, stabilizers, antistatic agents, flame retardants, desiccants, and gas barrier agents.

[0023] In materials containing polyester fibers, the fiber diameters of the polyester fibers and the fibers other than polyester fibers are not particularly limited, but may be, for example, 0.1 μm to 200 μm or 1 μm to 50 μm.

[0024] The thickness of the film containing polyester and other components is not particularly limited, but may be, for example, 0.5 μm to 1000 μm, or 1 μm to 500 μm. Here, if the film is the laminated film described above, the film thickness refers to the total thickness of the laminated film.

[0025] More specifically, materials containing polyester fibers include, but are not limited to, fabrics for various garments, fibers that are the material for fabrics, etc. The fabric is not limited to, but may be, for example, small pieces such as cut pieces generated during the manufacture of various garments, or cut pieces of various garments after use. The fibers that are the material for fabrics are not limited to, but may be, for example, small pieces such as cut pieces generated during the manufacture of fabrics, or cut pieces generated from used fabrics.

[0026] More specifically, films containing polyester and other components, without any particular limitations, include packaging films, small pieces such as cut materials generated during the manufacture of packaging films, and small pieces such as cut materials of used packaging films.

[0027] More specifically, the aggregate containing polyester and non-polyester components can include, but are not limited to, pellets, flakes, scraps generated during PET bottle manufacturing, and crushed recycled PET bottles containing polyester and non-polyester components. The maximum diameter of the aggregate is not particularly limited, but may be, for example, 0.01 mm to 10 mm. Here, "maximum diameter of the aggregate" means the maximum length of the line segment connecting two different points on the surface of the aggregate. Specifically, for example, commercially available PET powder with a particle size of 106 μm or less can be used.

[0028] The polyester-containing material of this embodiment may be used alone or in combination of two or more types. When two or more types are used in combination, their combination and ratio can be arbitrarily selected according to the purpose. That is, the polyester-containing material of this embodiment is one or more types selected from the group consisting of materials containing polyester fibers, films containing polyester and non-polyester components, and lumps containing polyester and non-polyester components.

[0029] In this embodiment, if the polyester-containing material is a material containing polyester fibers, it is preferable that the material containing polyester fibers is one or more selected from the group consisting of polyester fibers, fabrics of polyester fibers, mixtures containing polyester fibers and components other than polyester fibers, and fabrics of the mixture.

[0030] In this embodiment, if the polyester-containing material is a film containing polyester and components other than polyester, it is preferable that the film containing polyester and components other than polyester is either a single-layer film containing polyester and components other than polyester, or a laminated film which is a laminate of a film made of polyester and a film containing components other than polyester, or both.

[0031] In the polyester-containing material of this embodiment, the ratio of the polyester content (parts by mass) to the total mass (parts by mass) of the polyester-containing material ([polyester content (parts by mass) in the polyester-containing material] / [total mass (parts by mass) of the polyester-containing material] × 100) (polyester content ratio) can be arbitrarily selected according to the purpose and is not particularly limited. Among these, the polyester content ratio is preferably 20% by mass or more and 100% by mass or less, more preferably 40% by mass or more and 100% by mass or less, even more preferably 55% by mass or more and 100% by mass or less, and most preferably 70% by mass or more and 100% by mass or less. The higher the polyester content ratio, the greater the amount of monomer (dicarboxylic acid diester described later) produced from the polyester-containing material per unit mass due to the decomposition of polyester tends to be.

[0032] <Polyester> In this embodiment, the polyester to be decomposed can be any conventionally known polyester, and is not particularly limited as long as it is an oligomer or polymer that produces glycol and dicarboxylic acid upon decomposition. The polyester used for decomposition may be used alone or in combination of two or more types. When using two or more types in combination, the combination and ratio can be arbitrarily selected according to the purpose and are not particularly limited.

[0033] The polyester in this embodiment may be an aromatic polyester or an aliphatic polyester. An aromatic polyester refers to a polymer consisting of any combination of an aromatic dicarboxylic acid and an aliphatic diol, an aliphatic dicarboxylic acid and an aromatic diol, or an aromatic dicarboxylic acid and an aromatic diol. An aliphatic polyester refers to a polymer consisting of an aliphatic dicarboxylic acid and an aliphatic diol. The aromatic groups in the aromatic polyester may be divalent aromatic hydrocarbon groups (arylene groups), divalent aromatic heterocyclic groups (heteroarylene groups), or may be composed of both divalent aromatic hydrocarbon groups and divalent aromatic heterocyclic groups. The heteroatoms in the above aromatic heterocyclic groups are not particularly limited, but examples include oxygen atoms and nitrogen atoms.

[0034] The reactivity of polyester depolymerization can be improved by altering the structures of the carboxylic acid side and the alcohol side. As will be discussed later, considering that polyesters having aromatic rings such as benzene rings or naphthalene rings as the carboxylic acid side structure (e.g., polyethylene terephthalate, polybutylene terephthalate), it can be seen that polyesters having other aromatic structures such as furan can be similarly decomposed. Similarly, considering that polyesters having ethylene glycol (e.g., polyethylene terephthalate) or 1,4-butanediol (e.g., polybutylene terephthalate) as the alcohol side structure can be similarly decomposed, it can be seen that polyesters having other dihydric alcohol structures such as 1,3-propanediol can also be similarly decomposed.

[0035] From the viewpoint of shortening the reaction time for decomposition, the polyester of this embodiment preferably contains aromatic polyesters, more preferably contains at least one selected from the group consisting of polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), and polyethylene furanoate (PEF, also known as polyethylene furanoate), and even more preferably contains at least one selected from the group consisting of polyalkylene terephthalate, polyalkylene naphthalate, and polyalkylene furanate.

[0036] <Compounds represented by formulas (1) to (4)> The polyester decomposition composition of this embodiment contains at least one compound from the group represented by the following formulas (1) to (4). [ka] (In formula (1), R1 is a monovalent alkyl group having 1 to 5 carbon atoms, R2 is a divalent organic group having 1 to 5 carbon atoms, and R3 is a monovalent organic group having 1 to 5 carbon atoms.) [ka] (In formula (2), R4 and R7 are each independently monovalent organic groups having 1 to 5 carbon atoms.) R5 and R6 are independently divalent organic groups with 1 to 5 carbon atoms. [ka] (In equation (3), R8 and R 10 These are, independently, monovalent organic groups having 1 to 5 carbon atoms. R9 is a divalent organic group with 1 to 5 carbon atoms. [ka] (In equation (4), n is either 1 or 2, R 11 , R 12 , R 13, and R 14 Each of these is independently a monovalent organic group having 1 to 5 carbon atoms or a hydrogen atom.

[0037] [Compound represented by formula (1)] The polyester decomposition composition of this embodiment preferably contains a compound represented by formula (1). Formula (1) is a type of carbonate ester having an alkoxyalkyl group. In formula (1), R1 to R3 are preferably saturated or unsaturated linear or branched alkyl groups having 1 to 5 carbon atoms, and more preferably linear alkyl groups having 1 to 3 carbon atoms. Specific examples of formula (1) are not particularly limited, but include the following compounds. [ka]

[0038] [The compound represented by formula (2)] The polyester decomposition composition of this embodiment preferably contains a compound represented by formula (2). Formula (2) is a type of carbonate ester having an alkoxyalkyl group. In formula (2), R4 to R7 are preferably saturated or unsaturated linear or branched alkyl groups having 1 to 5 carbon atoms, and more preferably linear alkyl groups having 1 to 3 carbon atoms. Specific examples of formula (2) below are not particularly limited, but include the following compounds. [ka]

[0039] [The compound represented by formula (3)] The polyester decomposition composition of this embodiment contains the compound represented by formula (3), The compound represented by formula (3) preferably contains at least one of the compounds represented by the following formulas (5) to (8). nothing. [ka] (In formula (5), R 15 and R 18 Each of these is independently a monovalent alkyl group having 1 to 5 carbon atoms, and R 16 and R 17 Each of these is independently a divalent alkyl group having 1 to 5 carbon atoms. [ka] (In formula (6), R 19 , R 20 , R 21 , and R 22 Each of these is independently a monovalent alkyl group having 1 to 5 carbon atoms. [ka] (In formula (7), R 23 , R 24 , and R 25 Each of these is independently a monovalent alkyl group having 1 to 5 carbon atoms. [ka] (In formula (8), R 26 , and R 29 Each of these is independently a monovalent alkyl group having 1 to 5 carbon atoms, and R 27 and R 28 Each of these is independently a monovalent alkyl group having 1 to 5 carbon atoms or a hydrogen atom.

[0040] In equation (5) above, R 15 ~R 18 It is preferably a saturated or unsaturated linear alkyl group having 1 to 5 carbon atoms, and more preferably a linear alkyl group having 1 to 3 carbon atoms. Specific examples of the above formula (5) are not particularly limited, but include the following compounds. [ka]

[0041] In the above equation (6), R 19 ~R 22It is preferably a saturated or unsaturated linear or branched alkyl group having 1 to 5 carbon atoms, and more preferably a linear alkyl group having 1 to 3 carbon atoms. Specific examples of the above formula (6) are not particularly limited, but include the following compounds. [ka]

[0042] In equation (7) above, R 23 ~R 25 The alkyl group is preferably a saturated or unsaturated linear or branched alkyl group having 1 to 5 carbon atoms, and more preferably a linear alkyl group having 1 to 3 carbon atoms. Specific examples of the above formula (7) are not particularly limited, but include the following compounds. [ka]

[0043] In equation (8) above, R 26 and R 29 R is preferably a saturated or unsaturated linear or branched alkyl group having 1 to 5 carbon atoms, and more preferably a linear alkyl group having 1 to 3 carbon atoms. In the above formula (8), R 26 and R 29 The atoms are preferably saturated or unsaturated linear or branched alkyl groups or hydrogen atoms having 1 to 5 carbon atoms, and more preferably linear alkyl groups or hydrogen atoms having 1 to 3 carbon atoms. Specific examples of the above formula (8) are not particularly limited, but include, for example, the following compounds. [ka]

[0044] [The compound represented by formula (4)] The polyester decomposition composition of this embodiment contains a compound represented by formula (4), and preferably the compound represented by formula (4) contains at least one of the compounds represented by the following formulas (9) and (10). [ka] (In formula (9), R 30 , R 31 , and R 32 Each of these is independently a monovalent alkyl group having 1 to 5 carbon atoms or a hydrogen atom. [ka] (In formula (10), R 33 , R 34 , R 35 , and R 36 Each of these is independently a monovalent alkyl group having 1 to 5 carbon atoms or a hydrogen atom.

[0045] In equation (9) above, R 30 ~R 32 The atoms are preferably a saturated or unsaturated linear alkyl group having 1 to 5 carbon atoms or a hydrogen atom, and more preferably a linear alkyl group having 1 to 3 carbon atoms or a hydrogen atom. Specific examples of the above formula (9) are not particularly limited, but include the following compounds. [ka]

[0046] In the above equation (10), R 33 ~R 36 The atoms are preferably a saturated or unsaturated linear alkyl group having 1 to 5 carbon atoms or a hydrogen atom, and more preferably a linear alkyl group having 1 to 3 carbon atoms or a hydrogen atom. Specific examples of the above formula (10) are not particularly limited, but include, for example, the following compounds. [ka]

[0047] The compounds represented by formulas (1) to (4) may be used individually or in combination of two or more. When using two or more compounds represented by formulas (1) to (4), the combination and ratio of these compounds are not particularly limited and can be arbitrarily selected according to the purpose.

[0048] In the polyester decomposition composition, the ratio (a / b) of the total moles (a) of the compounds represented by formulas (1) to (4) to the total moles (b) of the base is preferably 0.0001 to 1, more preferably 0.0003 to 0.7, and even more preferably 0.005 to 0.6. A ratio (a / b) of 0.0001 or higher to the total moles (b) of the compounds represented by formulas (1) to (4) tends to shorten the reaction time for polyester decomposition. Furthermore, from the viewpoint of not inhibiting the polyester decomposition reaction, the ratio (a / b) is preferably 1 or lower. In other words, during polyester decomposition, it is preferable that the amount of compounds represented by formulas (1) to (4) used is equivalent to the amount of catalyst.

[0049] The detailed reaction mechanism is not clear and is not particularly limited, but it is thought that the compounds represented by formulas (1) to (4) improve the effect of the base catalyst on the decomposition of polyester by forming a complex through the interaction of oxygen atoms in the compound with the base catalyst described later.

[0050] <base> The base used in this embodiment is not particularly limited, but conventionally known bases can be used. The base may be either an inorganic base or an organic base, and alkali metal carbonates, alkali metal hydroxides, or alkali metal alkoxides that react with monohydric alcohols (described later) to produce alkali metal alkoxides are preferred.

[0051] Generally, in transesterification reactions, an alkoxy anion acting as a nucleophile attacks the carbonyl carbon of the ester, and after passing through a quaternary carbon intermediate, the reaction proceeds by liberating the alkoxy anion derived from the original structure that formed the ester bond. Since alkoxy anions are generated by the reaction of an alcohol with a base, the base in this embodiment is not particularly limited as long as it can deprotonate the alcohol.

[0052] Inorganic bases are not particularly limited, but examples include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; alkali metal oxides such as lithium oxide, sodium oxide, and potassium oxide; alkaline earth metal hydroxides such as calcium hydroxide and magnesium hydroxide; and alkaline earth metal oxides such as calcium oxide and magnesium oxide.

[0053] The organic bases are not particularly limited, but examples include alkali metal alkoxides such as lithium methoxide, lithium ethoxide, lithium tert-butoxide, sodium methoxide, sodium ethoxide, sodium tert-butoxide, potassium methoxide, potassium ethoxide, potassium tert-butoxide; calcium dimethoxide, calcium diethoxide, calcium ditert-butoxide, magnesium dimethoxide, magnesium diethoxide, magnesium Examples include alkaline earth metal alkoxides such as nesium ditert-butoxide; and nitrogen-containing organic bases (organic bases having a nitrogen atom) such as trimethylamine, triethylamine, tributylamine, trioctylamine, 1,5,7-triazabicyclo[4.4.0]deca-5-ene (TBD), 1,8-diazabicyclo[5.4.0]undeca-7-ene (DBU), 1,3-dimethylymidazole-2-ylidene, and 1,3-dicyclohexylimidazole-2-ylidene.

[0054] From the viewpoint of shortening the reaction time for decomposition of polyester, the alkali metal alkoxide is preferably an alkali metal alkoxide, more preferably lithium methoxide, sodium methoxide, or potassium methoxide, and particularly preferably sodium methoxide.

[0055] From the viewpoint of shortening the reaction time for polyester decomposition, the nitrogen-containing organic base is preferably 1,5,7-triazabicyclo[4.4.0]deca-5-ene.

[0056] The bases of this embodiment may be used individually or in combination of two or more. When using two or more bases, their combinations and ratios are not particularly limited and can be arbitrarily selected according to the purpose.

[0057] In this embodiment, the amount of base used is preferably 0.1 to 10 parts by mass, and more preferably 0.5 to 6 parts by mass, per 100 parts by mass of polyester in the polyester-containing material. Using 0.1 parts by mass or more of base per 100 parts by mass of polyester in the polyester-containing material tends to shorten the reaction time for decomposition of polyester. Using 10 parts by mass or less of base per 100 parts by mass of polyester in the polyester-containing material tends to prevent excessive use of base and is more economical. In other words, in the decomposition of polyester, it is preferable that the amount of base used is equivalent to the amount of catalyst.

[0058] <1K alcohol> During decomposition, monohydric alcohols undergo transesterification reactions with polyester in polyester-containing materials. Specifically, during the decomposition of polyester, the reaction between polyester and monohydric alcohol produces glycols corresponding to one monomer and dicarboxylic acid diesters corresponding to the other monomer or its derivative, which are among the raw materials used in polyester production.

[0059] The monohydric alcohol is not particularly limited, but conventionally known alcohols can be used. The reaction efficiency of the decomposition reaction in this embodiment is controlled by the capture of the liberated dihydric alcohol by the excess carbonate ester. Therefore, any monohydric alcohol and dialkyl carbonate can be used in combination, and it can be understood that the transesterification reaction proceeds efficiently regardless of the type of monohydric alcohol.

[0060] The monohydric alcohol is not particularly limited, but may be either an aliphatic alcohol or an aromatic alcohol. From the viewpoint of shortening the reaction time for decomposition of the polyester, it is preferable to use an aliphatic alcohol (saturated aliphatic alcohol or unsaturated aliphatic alcohol), and more preferably a saturated aliphatic alcohol.

[0061] The saturated aliphatic alcohol is not particularly limited, but examples include methanol, ethanol, 1-propanol (n-propyl alcohol), 2-propanol (isopropyl alcohol), 1-butanol (n-butyl alcohol), 2-methyl-1-propanol (isobutyl alcohol), 2-butanol (sec-butyl alcohol), 2-methyl-2-propanol (tert-butyl alcohol), 1-pentanol (n-pentanol), 2-pentanol, 3-pentanol, 2-methyl-1-butanol, 3-methyl-1-butanol (isoamyl alcohol), 2-methyl-2-butanol, 3-methyl-2-butanol, and 2,2-dimethyl-1-propanol, which are C1 to C5 alcohols. Here, from the viewpoint of shortening the reaction time for decomposition, it is preferable that the monohydric alcohol in this embodiment includes a C1 to C5 monohydric alcohol.

[0062] The monohydric alcohol used for decomposing polyester may be used alone or in combination of two or more types. When using two or more types in combination, the combination and ratio are not particularly limited and can be arbitrarily selected according to the purpose. From the viewpoint of shortening the reaction time for decomposing polyester, methanol is particularly preferred as the monohydric alcohol.

[0063] The amount of monohydric alcohol used during the decomposition of polyester varies depending on the structure of the polyester. Specifically, although not particularly limited, for example, if the polyester is polyethylene terephthalate (PET), 30 to 200 parts by mass, and more preferably 50 to 160 parts by mass, are used per 100 parts by mass of PET in the polyester-containing material. If the polyester is polybutylene terephthalate (PBT), 10 to 180 parts by mass, and more preferably 20 to 140 parts by mass, are used per 100 parts by mass of PBT in the polyester-containing material.

[0064] Using 30 parts by mass or more of monohydric alcohol per 100 parts by mass of PET in the polyester-containing material tends to shorten the reaction time for decomposition of polyester. On the other hand, using 200 parts by mass or less of monohydric alcohol per 100 parts by mass of PET in the polyester-containing material tends to be more economical as it suppresses the excessive use of monohydric alcohol.

[0065] <Carbonate ester> In this embodiment, the carbonate ester is a diester of carbonic acid, having a structure in which both hydrogen atoms of carbonic acid are replaced by organic groups. During the decomposition of polyester, the carbonate ester reacts with glycol produced from the polyester to generate cyclic or chain-like compounds, shifting the equilibrium between the depolymerization and polymerization reactions of the polyester so that the depolymerization reaction is dominant, thereby improving the production rate of the target monomer, which is a polyester decomposition product. Furthermore, the carbonate ester functions as a glycol scavenger.

[0066] The reaction products of carbonate esters and glycols can include cyclic compounds formed from the reaction of one molecule of carbonate ester with one molecule of glycol, chain compounds formed from the reaction of one molecule of carbonate ester with one molecule of glycol, and chain compounds formed from the reaction of one molecule of carbonate ester with two molecules of glycol. Which of these cyclic or chain compounds is formed is mainly determined by the type of glycol used. Specifically, although not particularly limited, for example, the reaction product of carbonate esters and ethylene glycol is mainly a cyclic compound formed from the reaction of one molecule of carbonate ester with one molecule of ethylene glycol.

[0067] Examples of carbonate esters include dialkyl carbonates and diaryl carbonates. The two alkyl or aryl groups bonded to the oxygen atom in a dialkyl carbonate or diaryl carbonate may be the same or different.

[0068] The alkyl group in the dialkyl carbonate is not particularly limited, but may be linear, branched, or cyclic, for example, and if cyclic, it may be monocyclic or polycyclic.

[0069] In dialkyl carbonates, the number of carbon atoms in the linear or branched alkyl group is preferably 1 to 5. Examples of such alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, and tert-pentyl groups.

[0070] In terms of specific structure, it is preferable that the carbonate ester includes a carbonate ester represented by the following formula (11). [ka] (In formula (11), R 37 and R 38 Each of these is independently an alkyl group or aryl group having 1 to 5 carbon atoms. Among these, the number of carbon atoms in the alkyl group is more preferably 1 to 4, and even more preferably 1 to 3.

[0071] The aryl group in diaryl carbonate may be monocyclic or polycyclic. The number of carbon atoms in the aryl group in diaryl carbonate is preferably 6 to 10, and such aryl groups are not particularly limited, but examples include phenyl group, 1-naphthyl group, 2-naphthyl group, o-tolyl group, m-tolyl group, p-tolyl group, 2,3-xylyl group (2,3-dimethylphenyl group), 2,4-xylyl group (2,4-dimethylphenyl group), 2,5-xylyl group (2,5-dimethylphenyl group), 2,6-xylyl group (2,6-dimethylphenyl group), 3,4-xylyl group (3,4-dimethylphenyl group), and 3,5-xylyl group (3,5-dimethylphenyl group). Among these, diphenyl carbonate is preferred from the viewpoint of shortening the reaction time in the decomposition of polyester.

[0072] The carbonate ester used for decomposing polyester may be used alone or in combination of two or more types. When using two or more carbonate esters in combination, the combination and ratio are not particularly limited and can be arbitrarily selected according to the purpose.

[0073] From the viewpoint of improving the decomposition rate of polyester, it is more preferable that the carbonate ester is one or more selected from the group consisting of dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, and diphenyl carbonate, and dimethyl carbonate is particularly preferred.

[0074] When decomposing polyester, the amount of carbonate ester used is preferably 100 to 5000 parts by mass, more preferably 100 to 1000 parts by mass, and even more preferably 100 to 500 parts by mass, per 100 parts by mass of polyester in the polyester-containing material. Using 100 parts by mass or more of carbonate ester per 100 parts by mass of polyester in the polyester-containing material tends to shorten the reaction time in decomposing polyester. Using 5000 parts by mass or less of carbonate ester per 100 parts by mass of polyester in the polyester-containing material tends to suppress the overuse of carbonate ester and is more economical.

[0075] <Solvent> When decomposing polyester, a solvent other than the compounds represented by formulas (1) to (4), a base, a monohydric alcohol, or a carbonate ester may be used, as long as it does not hinder the effects of the present invention. In this embodiment, even without using a solvent, the decomposition of polyester can be carried out efficiently. However, by using a solvent as needed, the handling of the raw material mixture, such as the reaction solution, tends to be improved, and the reaction time in the decomposition of polyester can be shortened.

[0076] In this specification, the term "solvent" is a concept that encompasses both a component that is liquid at room temperature and used to dissolve a solute, and a component that is liquid at room temperature and functions as a dispersion medium for dispersing a dispersed phase. In this embodiment, "room temperature" means the temperature under normal conditions without cooling or heating, i.e., the normal temperature, such as 15 to 25°C.

[0077] When a polyester decomposition composition contains a solvent, the solvent is preferably an organic solvent. While not particularly limited, examples of organic solvents include aromatic hydrocarbons such as toluene, ethers such as tetrahydrofuran, alkanes such as n-hexane, halogenated hydrocarbons such as chloroform and dichloromethane, amides such as dimethylformamide, and sulfoxides such as dimethyl sulfoxide.

[0078] The solvent may be used alone or in combination of two or more. When using two or more solvents, their combination and ratio can be arbitrarily selected according to the purpose.

[0079] When a solvent is used, the amount of solvent used during the decomposition of polyester is preferably 1 to 100,000 parts by mass, and more preferably 1 to 10,000 parts by mass, per 100 parts by mass of polyester-containing material. While it is preferable not to use a solvent in that it eliminates the need for a solvent removal step during the purification of the target product, if using a solvent has the effect of allowing the reaction to proceed in a homogeneous system, it is preferable that the amount of solvent used be 1 part by mass or more per 100 parts by mass of polyester-containing material. From the viewpoint of reducing the burden of the solvent removal step, it is preferable that the amount used be 100,000 parts by mass or less per 100 parts by mass of polyester-containing material.

[0080] <Other ingredients> During the decomposition of polyester, other components that do not fall under any of the following categories may be used, as long as they do not impair the effects of the present invention: polyester-containing material, compounds represented by formulas (1) to (4), bases, monohydric alcohols, carbonate esters, and solvents.

[0081] Other components can be arbitrarily selected according to the purpose and are not particularly limited. In this embodiment, the other components may be used alone or in combination of two or more. When two or more are used in combination, the combination and ratio are not particularly limited and can be arbitrarily selected according to the purpose.

[0082] During the decomposition of polyester, the ratio of the total amount (parts by mass) of polyester-containing material, compounds represented by formulas (1) to (4), bases, monohydric alcohols, and carbonate esters to the total amount (parts by mass) of components other than the solvent (([Amount of polyester-containing material (parts by mass)] + [Amount of compounds represented by formulas (1) to (4) (parts by mass)] + [Amount of base (parts by mass)] + [Amount of monohydric alcohol (parts by mass)] + [Amount of carbonate ester (parts by mass)]) / [Total amount of components other than the solvent (parts by mass)] × 100) is preferably 80% to 100% by mass, more preferably 95% to 100% by mass, and even more preferably 97% to 100% by mass. By having the above ratio above the lower limit, polyester can be decomposed more efficiently.

[0083] Here, the total amount (parts by mass) of components other than the solvent used during the decomposition of polyester refers to the total amount (parts by mass) of the polyester-containing material, the compounds represented by formulas (1) to (4) above, the base, the monohydric alcohol, the carbonate ester, and other components used during the decomposition.

[0084] <Method for producing polyester decomposition products> The method for producing polyester decomposition products according to this embodiment includes a decomposition step of contacting the polyester decomposition composition of this embodiment with a polyester-containing material to decompose the polyester in the polyester-containing material and obtain polyester decomposition products, and may include other steps as needed. Here, the polyester decomposition product in this embodiment refers to a monomer obtained by depolymerizing polyester. The definition of polyester-containing material is as described above.

[0085] <Degraded products> In the decomposition step of this embodiment, the depolymerization of polyester produces a dicarboxylic acid diester composed of polyester and a monohydric alcohol as a monomer from the polyester.

[0086] Polyester decomposition products are not particularly limited, but for example, if the polyester is derived from terephthalic acid, terephthalic acid diester is produced. If the polyester is derived from naphthalenedicarboxylic acid, naphthalenedicarboxylic acid diester is produced. If the polyester is derived from franguocarboxylic acid, franguocarboxylic acid diester is produced.

[0087] Among these, the polyester decomposition product is preferably one of the compounds represented by the following formulas (12) to (14), from the viewpoint of versatility in the production of polyester from the decomposition product as described later. [ka] (In formula (12), R 39 and R 40 These are, independently, monovalent organic groups with 1 to 5 carbon atoms. [ka] (In formula (13), R 41 and R 42 These are, independently, monovalent organic groups with 1 to 5 carbon atoms. [ka] (In formula (14), R 43 and R 44 These are, independently, monovalent organic groups with 1 to 5 carbon atoms.

[0088] When methanol is used as the monohydric alcohol, dimethyl dicarboxylate is produced as the dicarboxylic acid diester. When ethanol is used as the dihydric alcohol, diethyl dicarboxylate is produced as the dicarboxylic acid diester.

[0089] <Reaction conditions for the decomposition process> The decomposition step involves contacting a polyester-decomposing composition containing a base, a monohydric alcohol, a carbonate ester, and at least one compound from the group represented by the following formulas (1) to (4) with a polyester-containing material to decompose the polyester in the polyester-containing material and obtain a polyester decomposition product.

[0090] The method for bringing the polyester decomposition composition into contact with polyester is not particularly limited, but for example, from the viewpoint of ensuring a contact area, it is preferable to add fibrous, granular, or powdered polyester to the mixture and stir it.

[0091] The mixing order of these materials is not particularly limited, but it is preferable to prepare a mixture of a base, a monohydric alcohol, the compound represented by formulas (1) to (4), a carbonate ester, a solvent if necessary, and other components if necessary (for example, a mixture of all raw materials except the polyester-containing material), and then mix this mixture with the polyester-containing material. By using this mixing order, the compound represented by formulas (1) to (4) can be added to the state in which the basic catalyst is dissolved in alcohol, forming a catalyst before the polyester is added, and the decomposition of the polyester tends to proceed at a higher rate.

[0092] The reaction temperature in the decomposition process can be adjusted as appropriate, taking into account the type of materials used, and the decomposition may be carried out at room temperature or under heated conditions. The equipment used for heating is not particularly limited, and equipment such as heaters can be used.

[0093] The reaction temperature for the decomposition step is preferably 20°C to 150°C, more preferably 30°C to 130°C, and even more preferably 40°C to 110°C.

[0094] According to this embodiment, compared to conventional polyester decomposition methods that react polyester in a system that does not contain the compounds shown in formulas (1) to (4), polyester contained in polyester-containing materials can be decomposed in a short time of several hours and with a high decomposition rate, even at the same reaction temperature. Because polyester can be decomposed with a high decomposition rate, the amount of oligomers and other by-products generated during the decomposition reaction can be reduced.

[0095] The decomposition process may be carried out under normal pressure, reduced pressure, or increased pressure, and may be carried out under air or an inert gas atmosphere.

[0096] Furthermore, the reaction time in the decomposition process can be adjusted as appropriate considering other reaction conditions such as the reaction temperature, and is not particularly limited. The reaction time for the decomposition of polyester is not particularly limited as long as it is between 0.5 and 24 hours, but is preferably between 0.5 and 12 hours, and more preferably between 1 and 8 hours.

[0097] In this embodiment, the decomposition rate of polyester in the decomposition process can be determined by the decomposition rate after 0.5 to 1 hour. Furthermore, the final decomposition rate of polyester can be determined by the decomposition rate after 2 to 8 hours.

[0098] Immediately after mixing the materials, the unreacted polyester-containing material remains insoluble in the polyester decomposition composition. During the decomposition of polyester, typically, both the unreacted polyester-containing material and the polyester-containing material during or after the reaction remain insoluble in the other liquid components. On the other hand, the polyester decomposition products, glycols and dicarboxylic acid diesters, are typically dissolved in the liquid components.

[0099] In the disassembly process, stirring can be carried out by known methods, such as stirring by rotating a magnetic stirring bar or stirring blade, or stirring using a ball mill.

[0100] [Post-processing conditions, removal conditions] After the above decomposition process, post-treatment can be performed using conventionally known methods to extract one of the main decomposition products, dicarboxylic acid diester, in high purity.

[0101] The method for extracting the decomposition products is not particularly limited, but for example, after the decomposition of polyester, the obtained reaction product can be filtered, distilled off (concentrated) to remove volatile components, etc., and the obtained solid can be washed with methanol and water to obtain a high-purity dicarboxylic acid diester. The obtained dicarboxylic acid diester may be further purified by crystallization, distillation, etc., as needed. Furthermore, from the viewpoint of improving the yield, the method for producing polyester decomposition products in this embodiment preferably includes a step of purifying the polyester decomposition products, which are dissolved in the polyester decomposition composition and / or suspended in the polyester decomposition composition, by distillation.

[0102] The reaction products of glycols and carbonate esters, which are the main decomposition products other than dicarboxylic acid diesters, can also be isolated in the same way as dicarboxylic acid diesters by adjusting the post-treatment and isolation conditions as appropriate.

[0103] According to this embodiment, as described above, the polyester contained in the polyester-containing material can be decomposed with a high decomposition rate, thus reducing the amount of oligomers and other by-products generated during the decomposition reaction compared to conventional methods. Therefore, without adding complicated steps, a highly pure dicarboxylic acid diester (monomer) with suppressed coloring can be obtained through the simplified process of washing with methanol and water as described above. Furthermore, even if the polyester-containing material originally contains a coloring agent, the coloring of the dicarboxylic acid diester (monomer) derived from this coloring agent can also be reduced through the simplified process of washing with methanol and water as described above.

[0104] <Method for manufacturing polyester> The polyester manufacturing method of this embodiment includes a polymerization step in which the polyester decomposition product obtained by the above-described method for manufacturing polyester decomposition products is polymerized using the polyester decomposition product as a monomer, and may include other steps as needed.

[0105] Of the polyester decomposition products obtained by the polyester decomposition product manufacturing method of this embodiment, the dicarboxylic acid diester can be reused in the production of polyester by conventionally known methods. Furthermore, the dialkyl terephthalate obtained above can be converted to a polyester precursor such as bis-(2-hydroxyethyl) terephthalate (hereinafter referred to as "BHET") or terephthalic acid (hereinafter referred to as "TPA") by conventionally known methods and reused in the production of polyester.

[0106] The reaction product of glycol and carbonate ester among the polyester decomposition products obtained by the polyester decomposition product manufacturing method of this embodiment can be converted back to glycol and carbonate ester by reaction with alcohol. This regenerated carbonate ester can be reused for polyester decomposition, and the regenerated glycol can be reused for polyester production. For example, when a polyester having a structure that can be considered to be derived from ethylene glycol is decomposed, ethylene carbonate is produced as a reaction product of ethylene glycol and carbonate ester. Japanese Patent No. 4236208 discloses the conversion of ethylene carbonate to ethylene glycol and carbonate ester by reaction with alcohol.

[0107] Therefore, by using the polyester decomposition product method and polyester method of this embodiment, polyester can be continuously produced through three chemical reactions: decomposition of polyester, regeneration of glycol carbonate from the reaction product of glycol and carbonate ester, and production of polyester precursors such as dicarboxylic acid diester or BHET synthesized from the obtained dicarboxylic acid diester, or polyester by reaction of TPA with glycol.

[0108] In other words, the method for producing polyester according to this embodiment includes a step of producing polyester using polyester decomposition products (dicarboxylic acid diesters, glycols, etc.) obtained by the polyester decomposition method according to this embodiment described above. [Examples]

[0109] Next, the present invention will be specifically described based on examples, but the present invention is not particularly limited by the following examples.

[0110] <Decomposition of polyester fibers> [Example 1] A polyester decomposition composition was prepared by adding 0.58 g of sodium methoxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 1.0 mg of 2-Methoxyethyl methyl carbonate (hereinafter referred to as "compound A") to a 300 mL round-bottom flask, and then adding 13 mL of methanol (manufactured by Kishida Chemical Co., Ltd.) and 100 mL of dimethyl carbonate (hereinafter referred to as "DMC") to uniformly dissolve these components. Several 1 cm square pieces (20 g) of 100% PET white fibers were added to the polyester decomposition composition obtained above.

[0111] Next, using a magnetic stirrer and an oil bath, the mixture of the polyester decomposition composition and PET fibers was stirred at 50°C for 30 minutes by rotating the stirring bar in the round-bottom flask to depolymerize the PET fibers and obtain the reaction product. Subsequently, dimethyl carbonate (30 mL) was added to the reaction product in the round-bottom flask to dissolve the precipitated target product, and the contents of the round-bottom flask were filtered while still hot at 50°C without cooling. The filtrate was concentrated to recover dimethyl carbonate and methanol, and the residue was washed with methanol (50 mL) and water (50 mL) and dried to obtain 14.2 g of dimethyl terephthalate (yield: 70.2%).

[0112] Analysis of the dimethyl terephthalate obtained above using 1H NMR (instrument: Bruker Avance III (600 MHz) manufactured by BRUKER) revealed that dimethyl terephthalate with a purity of 99% by mass or higher was obtained.

[0113] [Examples 2-8] In Example 1, the PET fibers were decomposed using the same procedure as in Example 1, except that the reaction time and the amount of compound A added were as shown in Table 1, to obtain dimethyl terephthalate with a purity of 99% by mass or higher. The yields of dimethyl terephthalate in Examples 1 to 8 are shown in Table 1. [Table 1]

[0114] [Examples 9-12] In Examples 5-6, the PET fibers were decomposed using the same procedure as in Examples 5-6, except that DMC was changed to DMC containing ethylmethyl carbonate (hereinafter referred to as "EMC") (EMC concentration in DMC: 0.01-0.1%). The yields of dimethyl terephthalate in Examples 9-12 are shown in Table 1.

[0115] [Comparative Examples 1-2] In Examples 1 and 2, the PET fibers were decomposed using the same procedure as in Examples 1 and 2, except that compound A was not added. The yields of dimethyl terephthalate in Comparative Examples 1 and 2 are shown in Table 1.

[0116] [Comparative Example 3] In Example 8, the PET fibers were decomposed using the same procedure as in Example 8, except that sodium methoxide was not added. The yield of dimethyl terephthalate in Comparative Example 3 is shown in Table 1.

[0117] [Comparative Example 4] In Example 8, the PET fibers were decomposed using the same procedure as in Example 8, except that methanol was not added. The yield and yield of dimethyl terephthalate in Comparative Example 4 are shown in Table 1.

[0118] [Comparative Example 5] In Example 8, the PET fibers were decomposed using the same procedure as in Example 8, except that dimethyl carbonate was not added and the amount of methanol was increased to 100 mL. The yield of dimethyl terephthalate in Comparative Example 5 is shown in Table 1.

[0119] As shown in Table 1, the yield of dimethyl terephthalate in Examples 1, 3, 5, 7, 9, and 11 was higher than the yield of dimethyl terephthalate in Comparative Example 1, demonstrating that the addition of compound A allows for a faster decomposition rate. Furthermore, the yield of dimethyl terephthalate in Examples 2, 4, 6, 8, 10, and 12 was higher than the yield of dimethyl terephthalate in Comparative Example 2, demonstrating that the addition of compound A allows for a higher decomposition rate at which the reaction can be completed.

[0120] [Examples 13-58] In Examples 5-6, Compound A was replaced with Methyl 3-methoxypropyl carbonate (hereinafter referred to as "Compound B"), Carbonic acid, 2-ethoxyethyl ethyl ester (hereinafter referred to as "Compound C"), 3-Ethoxypropyl ethyl carbonate (hereinafter referred to as "Compound D"), Bis(2-methoxyethyl) carbonate (hereinafter referred to as "Compound E"), Bis(3-methoxypropyl) carbonate (hereinafter referred to as "Compound F"), Bis(3-ethoxypropyl) carbonate (hereinafter referred to as "Compound G"), Diglyme (hereinafter referred to as "Compound H"), and Diethylene glycol diethyl ether (hereinafter referred to as "compound I"), 2,2-Dimethoxypropane (hereinafter referred to as "compound J"), 2,2-Diethoxypropane (hereinafter referred to as "compound K"), 3,3-Dimethoxypentane (hereinafter referred to as "compound L"), 1,1-Dimethoxyethane (hereinafter referred to as "compound M"), 1,1-Dimethoxypropane (hereinafter referred to as "compound O"), 1-Ethoxy-1-methoxypropane (hereinafter referred to as "compound P"), 1,2-Dimethoxypropane (hereinafter referred to as "compound Q"), 2,3-Dimethoxybutane (hereinafter referred to as "compound R"), 2-Methoxy-3-ethoxy Except for the substitution of butane (hereinafter referred to as "compound S"), 2-Ethyl-1,3-dioxolane (hereinafter referred to as "compound T"), 2-Ethyl-4-methyl-1,3-dioxolane (hereinafter referred to as "compound U"), 2-Ethyl-4,5-dimethyl-1,3-dioxolane (hereinafter referred to as "compound V"), 1,4-Dioxane (hereinafter referred to as "compound W"), 2-Methyl-1,4-dioxane (hereinafter referred to as "compound X"), and Dimethyldioxane (hereinafter referred to as "compound Y"), PET fibers were decomposed in the same manner as in Examples 5-6 to obtain dimethyl terephthalate with a purity of 99% by mass or higher.Table 2 shows the yields of dimethyl terephthalate in Examples 13 to 58. [Table 2]

[0121] As shown in Table 2, the yield of dimethyl terephthalate in Examples 13-58 was higher than that in Comparative Examples 1-2, given the same reaction time. This clearly demonstrates that adding compounds B-Y allows for a faster decomposition rate and, furthermore, enables the reaction to be completed with a higher decomposition rate.

[0122] [Examples 59-70] In Examples 5-6, PET fibers were decomposed using the same procedure as in Examples 5-6, except that the base was changed to lithium methoxide, potassium methoxide, lithium tert butoxide, sodium tert butoxide, sodium hydroxide, and potassium hydroxide, yielding dimethyl terephthalate with a purity of 99% by mass or higher. The yields of dimethyl terephthalate in Examples 59-70 are shown in Table 3. [Table 3]

[0123] [Comparative Examples 6-17] In Examples 59-70, the PET fibers were decomposed using the same procedure as in Examples 59-74, except that compound A was not added. The yields of dimethyl terephthalate in Comparative Examples 6-17 are shown in Table 3.

[0124] As shown in Table 3, the yield of dimethyl terephthalate in Examples 59-70 was higher than that of dimethyl terephthalate in Comparative Examples 6-17, given the same reaction time. This clearly demonstrates that compound A improves the degradation rate and degradation percentage even when using bases other than sodium methoxide to decompose PET fibers.

[0125] [Examples 71-72] In Examples 15-16, PET fibers were decomposed using the same procedure as in Examples 15-16, except that sodium methoxide was replaced with sodium ethoxide, methanol with ethanol, and dimethyl carbonate with diethyl carbonate, yielding diethyl terephthalate with a purity of 99% by mass or higher. The yields of diethyl terephthalate in Examples 71-72 are shown in Table 4. [Table 4]

[0126] [Comparative Examples 18-19] In Examples 71-72, the PET fibers were decomposed using the same procedure as in Examples 18-19, except that compound C was not added. The yields of diethyl terephthalate in Comparative Examples 18-19 are shown in Table 4.

[0127] As shown in Table 4, the yield of diethyl terephthalate in Examples 71-72 was higher than that of diethyl terephthalate in Comparative Examples 18-19, given the same reaction time. This clearly demonstrates that compound C improves the decomposition rate and decomposition percentage even when decomposing PET fibers using methods other than methanol and dimethyl carbonate.

[0128] [Examples 73-84] In Examples 5-6, the PET fibers were decomposed using the same procedure as in Examples 5-6, except that 1cm square 100% PET white fibers were replaced with 1cm square 100% PET film, 100% PET powder, 1cm square PET fibers containing a coloring agent, 1cm square 65% PET (35% cotton) fibers, 1cm square 75% PET (25% polyurethane (hereinafter referred to as "PU")) fibers, and 1cm square 38% PET (38% cotton, 24% rayon) fibers, respectively, to obtain dimethyl terephthalate with a purity of 99% by mass or higher. The yields of dimethyl terephthalate in Examples 73-84 are shown in Table 5. [Table 5]

[0129] [Comparative Examples 20-31] In Examples 73-84, the PET fibers were decomposed using the same procedure as in Examples 73-84, except that compound A was not added. The yields of diethyl terephthalate in Comparative Examples 20-31 are shown in Table 5.

[0130] As shown in Table 5, the yield of dimethyl terephthalate in Examples 73-84 was higher than that of dimethyl terephthalate in Comparative Examples 20-31 when the reaction time was the same. This clearly demonstrates that compound A improves the decomposition rate and decomposition percentage even in the decomposition of PET-containing materials other than 1 cm square PET 100% white fibers.

[0131] [Examples 85-88] In Examples 5 and 6, the polyester powder was decomposed using the same procedure as in Examples 5 and 6, except that 1 cm square 100% PET white fibers were replaced with 100% PBT powder and 100% PEN powder, respectively, to obtain diethyl terephthalate and dimethyl 2,6-naphthalenedicarboxylate. The yields of diethyl terephthalate in Examples 85 and 86 are shown in Table 6, and the yields of dimethyl 2,6-naphthalenedicarboxylate in Examples 87 and 88 are shown in Table 7. [Table 6]

[0132] [Table 7]

[0133] [Comparative Examples 32-35] In Examples 85-88, the decomposition of the polyester powder was carried out using the same procedure as in Examples 85-88, except that compound A was not added. The yields of diethyl terephthalate in Comparative Examples 32-33 are shown in Table 6, and the yields of dimethyl 2,6-naphthalenedicarboxylate in Comparative Examples 34-35 are shown in Table 7.

[0134] As shown in Tables 6 and 7, the yield of decomposition products in Examples 85-88 was higher than that in Comparative Examples 32-35, given the same reaction time. This clearly demonstrates that compound A improves the decomposition rate and percentage even in the decomposition of polyesters other than PET.

[0135] <Post-processing conditions, removal conditions> As described above, after the polyester decomposition process is complete, post-treatment can be performed to extract dialkyl terephthalate and dialkyl 2,6-naphthalenedicarboxylate. The obtained dialkyl terephthalate and dialkyl 2,6-naphthalenedicarboxylate may be purified by crystallization, distillation, or other methods as needed.

[0136] The other main decomposition product, the reaction product of glycol and diester carbonate, can also be extracted by adjusting the post-treatment and extraction conditions as appropriate.

[0137] It goes without saying that polyester can be manufactured using the decomposition products of polyester obtained by the polyester decomposition method according to this embodiment.

[0138] From these results, it was found that the polyester decomposition method of the present invention can decompose polyester in polyester-containing materials in a short time and with a high decomposition rate. [Industrial applicability]

[0139] The polyester decomposition composition of the present invention has industrial applicability because the resulting polyester decomposition product can be used in the production of new polyesters.

Claims

1. A base, a monohydric alcohol, a carbonate ester, and at least one compound from the group represented by the following formulas (1) to (4), A composition for decomposing polyester. 【Chemistry 1】 (In formula (1), R 1 R is a monovalent alkyl group having 1 to 5 carbon atoms. 2 R is a divalent organic group having 1 to 5 carbon atoms. 3 (It is a monovalent organic group with 1 to 5 carbon atoms.) 【Chemistry 2】 (In formula (2), R 4 and R 7 Each of these is independently a monovalent organic group having 1 to 5 carbon atoms. R 5 and R 6 Each of these is independently a divalent organic group having 1 to 5 carbon atoms. 【Transformation 3】 (In formula (3), R 8 and R 10 are each independently a monovalent organic group having 1 to 5 carbon atoms, R 9 (It is a divalent organic group with 1 to 5 carbon atoms.) 【Chemistry 4】 (In equation (4), n is 1 or 2, R 11 , R 12 , R 13 , and R 14 Each of these is independently a monovalent organic group having 1 to 5 carbon atoms or a hydrogen atom.

2. The polyester decomposition composition contains the compound represented by formula (1). The polyester decomposition composition according to claim 1.

3. The polyester decomposition composition contains the compound represented by formula (2). The polyester decomposition composition according to claim 1.

4. The polyester decomposition composition contains the compound represented by formula (3), The compound represented by formula (3) contains at least one of the compounds represented by the following formulas (5) to (8): The polyester decomposition composition according to claim 1. 【Transformation 5】 (In formula (5), R 15 and R 18 Each of these is independently a monovalent alkyl group having 1 to 5 carbon atoms, and R 16 and R 17 Each of these is independently a divalent alkyl group having 1 to 5 carbon atoms. 【Transformation 6】 (In formula (6), R 19 , R 20 , R 21 , and R 22 Each of these is independently a monovalent alkyl group having 1 to 5 carbon atoms. 【Transformation 7】 (In formula (7), R 23 , R 24 , and R 25 Each of these is independently a monovalent alkyl group having 1 to 5 carbon atoms. 【Transformation 8】 (In formula (8), R 26 , and R 29 Each of these is independently a monovalent alkyl group having 1 to 5 carbon atoms, and R 27 and R 28 Each of these is independently a monovalent alkyl group having 1 to 5 carbon atoms or a hydrogen atom.

5. The polyester decomposition composition contains the compound represented by formula (4), The compound represented by formula (4) contains at least one of the compounds represented by the following formulas (9) and (10): The polyester decomposition composition according to claim 1. 【Chemistry 9】 (In formula (9), R 30 , R 31 , and R 32 Each of these is independently a monovalent alkyl group having 1 to 5 carbon atoms or a hydrogen atom. 【Chemistry 10】 (In formula (10), R 33 , R 34 , R 35 , and R 36 Each of these is independently a monovalent alkyl group having 1 to 5 carbon atoms or a hydrogen atom.

6. The base contains at least one selected from the group consisting of alkali metal carbonates, alkali metal hydroxides, and alkali metal alkoxides. The polyester decomposition composition according to claim 1.

7. The aforementioned monohydric alcohol includes monohydric alcohols having 1 to 5 carbon atoms. The polyester decomposition composition according to claim 1.

8. The carbonate ester includes a carbonate ester represented by the following formula (11): The polyester decomposition composition according to claim 1. 【Chemistry 11】 (In formula (11), R 37 and R 38 Each of these is independently an alkyl group or aryl group having 1 to 5 carbon atoms.

9. The ratio (a / b) of the total amount of the compound represented by formulas (1) to (4) to the total amount of the base (b) is 0.0001 to 1. The polyester decomposition composition according to claim 1.

10. The polyester comprises at least one selected from the group consisting of polyalkylene terephthalate, polyalkylene naphthalate, and polyalkylene furnate. The polyester decomposition composition according to claim 1.

11. The method comprises a decomposition step of bringing a polyester decomposition composition according to any one of claims 1 to 10 into contact with a polyester-containing material, and decomposing the polyester in the polyester-containing material to obtain a polyester decomposition product. A method for producing polyester decomposition products.

12. The polyester decomposition product contains at least one compound represented by the following formulas (12) to (14): A method for producing a polyester decomposition product according to claim 11. 【Chemistry 12】 (In formula (12), R 39 and R 40 These are, independently, monovalent organic groups with 1 to 5 carbon atoms. 【Chemistry 13】 (In formula (13), R 41 and R 42 These are, independently, monovalent organic groups with 1 to 5 carbon atoms. 【Chemistry 14】 (In formula (14), R 43 and R 44 These are, independently, monovalent organic groups with 1 to 5 carbon atoms.

13. The process includes purifying the polyester decomposition product, which is dissolved in the polyester decomposition composition and / or suspended in the polyester decomposition composition, by distillation. A method for producing a polyester decomposition product according to claim 11.

14. The method described in claim 11 includes a polymerization step in which a polyester decomposition product obtained by the method described in claim 11 is used as a monomer for polymerization. A method for manufacturing polyester.

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