Method for decomposing synthetic resin

Abstract

[Problem] To provide a method for decomposing a synthetic resin containing at least one of polysulfone, polyphenylsulfone, polyethersulfone, polyether ether sulfone, or polyether ether ketone. [Solution] A synthetic resin, a base, an organic solvent, and at least one of methanol, ethanol, isopropyl alcohol, tert-butyl alcohol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, 2-ethylhexanol benzyl alcohol, 2-phenylethyl alcohol, phenol, cresol, 4-tert-butylphenol, 4-methoxyphenol, hydroquinone, bisphenol A (2,2-bis(4-hydroxyphenyl)propane), or bisphenol S (bis(4-hydroxyphenyl)sulfone) are mixed.

Description

Synthetic resin decomposition method

[0001] The present invention relates to a method for decomposing a synthetic resin containing at least one of polysulfone, polyphenylsulfone, polyethersulfone, polyetherethersulfone, and polyetheretherketone.

[0002] Among the super engineering plastics widely used as stable materials, polysulfone (PSU) is a thermoplastic resin that not only excels in heat resistance, a wide range of operating temperatures, hydrolysis resistance, chemical resistance, and electrical properties, but also has ideal properties as a processable material, such as mechanical strength, transparency, moldability, and weather resistance. Because of these properties, polysulfone is used in a wide range of applications, including medical biomembrane replacements, artificial kidneys, medical instruments, food containers, cooker parts, and other medical and food processing fields, as well as electronic device parts such as connectors and printed circuit boards.

[0003] Furthermore, super engineering plastics similar to polysulfone include polyphenylsulfone (PPSU), polyethersulfone (PES), polyetherethersulfone (PEES), and polyetheretherketone (PEEK), all of which have excellent stability and properties.

[0004] As of 2019, the total production volume of polysulfone and polyphenylsulfone was 26,600 tons, and the production volume of polyether ether ketone was approximately 7,000 tons, which at first glance may seem small. However, considering the high cost of these synthetic resins, this production volume cannot be said to be small, and because they have the excellent properties described above, they will be essential materials for the future industrial society.

[0005] However, due to their high stability, disposal and recycling of these synthetic resins is difficult. These synthetic resins have a molecular structure that contains many benzene rings, making them difficult to decompose even by microorganisms. Furthermore, because these synthetic resins are used in high-priced products, disposing of them currently results in a significant economic loss.

[0006] Therefore, with regard to the chemical recycling of super engineering plastics, there have been reports on the decomposition of polysulfones into lower molecular weight compounds (Patent Document 1), examples of decomposition of polyphenylene sulfide into monomer units and oligomer units at temperatures of 150°C or higher (Patent Document 2, Non-Patent Documents 1 to 5), and the decomposition of polyethersulfone using subcritical water (Patent Document 3).

[0007] Recently, there have been reports of depolymerization of polyether ether ketone with a sulfur nucleophile at 150°C (Non-Patent Document 6), and depolymerization of polysulfone, polyether ketone, polyphenyl sulfone, polyether ether sulfone, and polyether ether ketone with an alkali hydroxide at 150°C (Non-Patent Document 7).

[0008] International Publication No. WO2008 / 004642 JP 2013-249324 A JP 2022-170457 A

[0009] Yu, ZL; Miao, GX; Chen, YR Macromol Chem Phys 1996, 197, 4061.Wang, SJ; Bian, SG; Yan, H.; Xiao, M.; Meng, YZJ App. Poly. Sci. 2008, 110, 4049.Lian, Z.; Bhawal, BN; Morandi, B. Science 2017, 356, 1059.Minami, Y.; Matsuyama, N.; Matsuo, Y.; Tamura, M.; Sato, K.; Nakajima, Y. Synthesis 2021, 53, 3351.Delcaillau, T.; Woenckhaus-Alvarez, A.; Morandi, B. Org. Lett. 2021, 23, 7018.Minami, Y.; Matsuyama, N.; Takeichi, Y.; Watanabe, R.; Mathew, S.; Nakajima, Y. Communications Chemistry, 2023, 6, 14.Minami, Y.; Inagaki, Y.; Tsuyuki, T.; Sato, K.; Nakajima, JACS Au DOI: 10.1021 / jacsau.3c00357.Shigeno, M.; Hayashi, K.; Nozawa-Kumada, K.; Kondo, Y. Org. Lett. 2019, 21, 5505.

[0010] However, as mentioned above, although several depolymerization methods for super engineering plastics have been developed, they are fragmented technologies and require relatively high temperatures (higher than 120°C). The development of chemical recycling technology for super engineering plastics has only just begun, and there is a need to develop depolymerization methods (decomposition methods) based on various ideas and to improve the value of the resulting products.

[0011] As a reaction related to the decomposition of super engineering plastics, a substitution reaction of the methoxy group of a para-methoxy-substituted benzophenone, one of the structural units of polyphenylene sulfide, with an amino group using an organic superbase catalyst t-Bu-P4 and an arylamine (Non-Patent Document 8), has been known (see, for example, "Decomposition of Polyphenylene Sulfide by Para-Methoxy Substitution of Benzophenone"), but there have been no examples of this method being applied to the depolymerization of polysulfone, polyphenylsulfone, or polyethersulfone.

[0012] In view of the above circumstances, the present invention aims to provide a method for decomposing synthetic resins containing at least one of polysulfone, polyphenylsulfone, polyethersulfone, polyetherethersulfone, and polyetheretherketone. These problems do not preclude the existence of other problems. Furthermore, each aspect of the present invention described below does not necessarily solve all of these problems (problems). Furthermore, other problems (problems) can be identified from the description of the specification, drawings, or claims.

[0013] As a result of intensive research into the above-mentioned problems, the inventors of the present invention have discovered the following revolutionary method for decomposing synthetic resins containing at least one of polysulfone, polyphenylsulfone, polyethersulfone, polyetherethersulfone, and polyetheretherketone.

[0014] A first aspect of the present invention for solving the above problems is a synthetic resin decomposition method for synthetic resins containing at least one of polysulfone, polyphenylsulfone, polyethersulfone, polyetherethersulfone, and polyetheretherketone, the synthetic resin decomposition method comprising a decomposition step of mixing the synthetic resin, a base, and at least one alcohol selected from the group consisting of methanol, ethanol, isopropyl alcohol, tert-butyl alcohol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, 2-ethylhexanol, benzyl alcohol, 2-phenylethyl alcohol, phenol, cresol, 4-tert-butylphenol, 4-methoxyphenol, hydroquinone, bisphenol A (2,2-bis(4-hydroxyphenyl)propane), and bisphenol S (bis(4-hydroxyphenyl)sulfone), and an organic solvent, to decompose the polysulfone, polyphenylsulfone, polyethersulfone, polyetherethersulfone, and polyetheretherketone contained in the synthetic resin.

[0015] According to the first aspect, synthetic resins can be decomposed at a lower reaction temperature (in the case of fatty acid alcohols) and more quickly than in conventional decomposition methods.

[0016] A second aspect of the present invention is the synthetic resin decomposition method according to the first aspect, characterized in that the base comprises at least one of sodium hydroxide, potassium hydroxide, potassium phosphate, cesium hydroxide, cesium carbonate, sodium tert-butoxide, lithium tert-butoxide, potassium tert-butoxide, lithium bis(trimethylsilyl)amide, sodium bis(trimethylsilyl)amide, and potassium bis(trimethylsilyl)amide.

[0017] According to the second aspect, the synthetic resin can be decomposed more quickly.

[0018] A third aspect of the present invention is the synthetic resin decomposition method according to the first or second aspect, characterized in that the organic solvent contains at least one of 1,3-dimethyl-2-imidazolidinone, tetramethylurea, 1,3-dimethylpropyleneurea, N-methyl-2-pyrrolidone, N,N-dimethylacetamide, dimethyl sulfoxide, and tetrahydrothiophene-1,1-dioxide.

[0019] According to the third aspect, the synthetic resin can be decomposed even more quickly.

[0020] A fourth aspect of the present invention is the synthetic resin decomposition method according to the first aspect, characterized in that the reaction temperature in the decomposition step is in the range of 25°C to 200°C.

[0021] According to the fourth aspect, the synthetic resin can be decomposed at a lower reaction temperature.

[0022] A fifth aspect of the present invention is the synthetic resin decomposition method according to the first aspect, characterized in that the reaction temperature in the decomposition step is in the range of 25°C to 120°C.

[0023] According to the fifth aspect, the synthetic resin can be decomposed at an even lower reaction temperature.

[0024] A sixth aspect of the present invention is the synthetic resin decomposition method according to the first aspect, characterized in that the synthetic resin contains at least one of polyether ether ketone, polyether ether sulfone, polysulfone, and polyether sulfone, the alcohol is at least one of hydroquinone, bisphenol A, and bisphenol S, and the reaction temperature in the reaction step is in the range of 25°C to 160°C.

[0025] According to the sixth aspect, the monomers constituting the polymer compound contained in the synthetic resin can be recovered simply by cooling the reaction solution obtained by this embodiment, adding hydrochloric acid, and washing the resulting solid with water. The reaction temperature in this aspect is preferably in the range of 140°C to 160°C, since this allows for the recovery of a larger amount of the monomers constituting the polymer compound contained in the synthetic resin. These monomers can be used to resynthesize the polymer compound contained in the synthetic resin.

[0026] For example, when the synthetic resin contains at least one of polyether ether ketone and polyether ether sulfone, hydroquinone is used as the alcohol; when the synthetic resin contains polysulfone, bisphenol A is used as the alcohol; or when the synthetic resin contains polyether sulfone, bisphenol S is used as the alcohol; and by applying the synthetic resin decomposition method of the first aspect at a reaction temperature in the reaction step in the range of 25°C to 160°C, it is possible to recover the monomers that constitute the polymer compounds contained in each synthetic resin.

[0027] Furthermore, for example, when a synthetic resin contains polysulfone, by using hydroquinone as the alcohol and setting the reaction temperature in the reaction step within the range of 25°C to 160°C and applying the synthetic resin decomposition method of the first aspect, it is possible to recover a monomer that constitutes a polymer compound different from the polymer compound contained in the synthetic resin.

[0028] The contents of Japanese Patent Application No. 2023-180795 are incorporated herein by reference as part of this specification.

[0029] FIG. 1 is a table relating to a method for recovering synthetic resin decomposition products. FIG. 2 is a chemical reaction formula for the reaction in Example 1. FIG. 3 is a table showing the reaction conditions in Example 1 and the yield of each synthetic resin decomposition product obtained. FIG. 4 is a chemical reaction formula for the reaction in Example 2. FIG. 5 is a chemical reaction formula for the reaction in Example 3. FIG. 6 is a chemical reaction formula for the reaction in Example 4. FIG. 7 is a chemical reaction formula for the reaction in Example 5. FIG. 8 is a chemical reaction formula for the reactions in Examples 6 to 8. FIG. 9 is a table showing the reaction conditions in Examples 6 to 8 and the yield of each synthetic resin decomposition product obtained. FIG. 10 is a chemical reaction formula for the reaction in Example 9. FIG. 11 is a chemical reaction formula for the reaction in Example 10. FIG. 12 is a chemical reaction formula for the reaction in Example 11. FIG. 13 is a chemical reaction formula for the reaction in Example 12. FIG. 14 is a chemical reaction formula for the reaction in Example 13. FIG. 15 is a chemical reaction formula for the product obtained in Example 13. １ 16 is a chemical reaction formula for the reaction of Example 14. FIG. 17 is a graph showing the results of analysis by H NMR. １ 1 is a graph showing the results of H NMR analysis.

[0030] Hereinafter, an embodiment of the method for decomposing synthetic resins containing at least one of polysulfone, polyphenylsulfone, polyethersulfone, polyetherethersulfone, and polyetheretherketone according to the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the following embodiment.

[0031] (Embodiment 1) <<Synthetic Resin Decomposition Method>> A synthetic resin decomposition method according to this embodiment includes a decomposition step of mixing (blending) at least one of methanol, ethanol, isopropyl alcohol, tert-butyl alcohol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, 2-ethylhexanol, benzyl alcohol, 2-phenylethyl alcohol, phenol, cresol, 4-tert-butylphenol, 4-methoxyphenol, hydroquinone, bisphenol A (2,2-bis(4-hydroxyphenyl)propane), and bisphenol S (bis(4-hydroxyphenyl)sulfone), with a synthetic resin, a base, and an organic solvent, to decompose polysulfone, polyphenylsulfone, polyethersulfone, polyetherethersulfone, or polyetheretherketone contained in the synthetic resin.

[0032] According to the synthetic resin decomposition method of this embodiment, synthetic resins can be decomposed quickly at a low reaction temperature (e.g., 25 to 120°C in the case of fatty acid alcohols, and 150 to 180°C in the case of aromatic alcohols) compared to conventional decomposition methods. <Synthetic Resins>

[0033] The synthetic resin to be decomposed by the synthetic resin decomposition method according to the present embodiment (target synthetic resin) is not particularly limited as long as it contains at least one of polysulfone, polyphenylsulfone, polyethersulfone, polyetherethersulfone, and polyetheretherketone. While the synthetic resin may contain multiple polymer compounds from these, a synthetic resin containing only one polymer compound (synthetic polymer compound) is preferred, and a polymer compound containing only one polymer compound at a high concentration (preferably 70 to 100%, more preferably 80 to 100%, and particularly preferably 90 to 100%) is more preferred. Using a synthetic resin containing only one polymer compound allows for efficient (rapid) decomposition, and as described below, allows for the recovery of only the specified bisphenol or hydroquinone in a high yield. Furthermore, using a synthetic resin containing only one polymer compound at a high concentration allows for efficient (rapid) decomposition, and as described below, allows for the recovery of only the specified bisphenol or hydroquinone in a higher yield.

[0034] Here, polysulfone is a synthetic polymer compound having the following repeating structure:

[0035] Here, n is in the range of 20 to 300, preferably in the range of 30 to 250 since it is easily decomposable, and more preferably in the range of 35 to 200 since it is particularly easily decomposable.

[0036] Polyphenylsulfone is a synthetic polymer compound having the following repeating structure:

[0037] Here, n is in the range of 25 to 140, preferably in the range of 35 to 120 since it is easily decomposable, and more preferably in the range of 40 to 110 since it is particularly easily decomposable.

[0038] Polyethersulfone is a synthetic polymer compound with the following repeating structure:

[0039] Here, n is in the range of 40 to 180, preferably in the range of 55 to 150 since it is easily decomposable, and more preferably in the range of 65 to 140 since it is particularly easily decomposable.

[0040] Polyether ether sulfone is a synthetic polymer compound with the following repeating structure:

[0041] Here, n is in the range of 10 to 300, preferably in the range of 15 to 200 since it is easily decomposable, and more preferably in the range of 20 to 150 since it is particularly easily decomposable.

[0042] Polyether ether ketone is a synthetic polymer compound with the following repeating structure:

[0043] Here, n is in the range of 25 to 100, preferably in the range of 30 to 85 since it is easily decomposable, and more preferably in the range of 38 to 73 since it is particularly easily decomposable.

[0044] The synthetic resin may contain components other than polysulfone, polyphenylsulfone, polyethersulfone, polyetherethersulfone, and polyetheretherketone. Specifically, the synthetic resin may contain polyester, polyamide, polycarbonate, polyfluorocarbon, etc. Even if these components are contained, the synthetic resin decomposition method according to the present invention can decompose the polysulfone, polyphenylsulfone, polyethersulfone, polyetherethersulfone, or polyetheretherketone contained in the synthetic resin. <Alcohol>

[0045] In the synthetic resin decomposition method according to this embodiment, the alcohol is not particularly limited as long as it contains at least one of methanol, ethanol, isopropyl alcohol, tert-butyl alcohol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, 2-ethylhexanol, benzyl alcohol, 2-phenylethyl alcohol, phenol, cresol, 4-tert-butylphenol, 4-methoxyphenol, hydroquinone, bisphenol A (2,2-bis(4-hydroxyphenyl)propane), and bisphenol S (bis(4-hydroxyphenyl)sulfone). These alcohols are believed to have sufficient nucleophilicity toward polysulfone, polyphenylsulfone, polyethersulfone, polyetherethersulfone, and polyetheretherketone when reacted with a base to form an alkoxide.

[0046] Among these alcohols, methanol is particularly preferred. The use of methanol allows for faster decomposition of synthetic resins compared to conventional decomposition methods. Among phenols, hydroquinone is preferred. The use of hydroquinone allows for the production of the above-mentioned renewable monomers in higher yields compared to other phenols.

[0047] The amount of alcohol used in the synthetic resin decomposition method according to this embodiment is not particularly limited, but it is preferable to react 2 to 16 equivalents of alcohol with respect to the synthetic resin, more preferably 4 to 14 equivalents, and particularly preferably 6 to 12 equivalents.

[0048] In the synthetic resin decomposition method according to this embodiment, the base is not particularly limited, but is preferably one that can activate the alcohol to produce an alkoxide. Specific examples of the base include sodium hydroxide, potassium hydroxide, potassium phosphate, cesium hydroxide, cesium carbonate, sodium tert-butoxide, lithium tert-butoxide, potassium tert-butoxide, lithium bis(trimethylsilyl)amide, sodium bis(trimethylsilyl)amide, and potassium bis(trimethylsilyl)amide. The use of these bases makes it possible to more easily decompose synthetic resins.

[0049] In the synthetic resin decomposition method according to this embodiment, the amount of base is not particularly limited, but it is preferable to react 2 to 4 equivalents of base with respect to the synthetic resin, more preferably 2 to 3 equivalents, and particularly preferably 2 to 2.4 equivalents. <Organic solvent>

[0050] In the synthetic resin decomposition method according to this embodiment, the organic solvent that can be used is not particularly limited, but 1,3-dimethyl-2-imidazolidinone, tetramethylurea, 1,3-dimethylpropyleneurea, N-methyl-2-pyrrolidone, N,N-dimethylacetamide, dimethyl sulfoxide, and tetrahydrothiophene-1,1-dioxide are preferred, with 1,3-dimethyl-2-imidazolidinone and 1,3-dimethylpropyleneurea being particularly preferred. These organic solvents improve the solubility of the salt produced by the reaction of the alcohol and the base through solvation, maintain the nucleophilicity of the produced alkoxide, and are less likely to react with alkoxide (1,3-dimethyl-2-imidazolidinone and 1,3-dimethylpropyleneurea are particularly stable toward alkoxides), and can be used even at high temperatures (100 to 200°C). The use of these organic solvents allows for easier decomposition of synthetic resins.

[0051] In the synthetic resin decomposition method according to the present embodiment, the amount of organic solvent used is not particularly limited, but it is preferable to react with 0.1 to 11 moles of the organic solvent relative to the moles of the monomer units of the synthetic resin, more preferably 0.3 to 4 moles, and particularly preferably 0.5 to 1 mole. <Reaction conditions for the decomposition step>

[0052] The decomposition of the synthetic resin according to this embodiment can be carried out by mixing at least one of methanol, ethanol, isopropyl alcohol, tert-butyl alcohol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, 2-ethylhexanol, benzyl alcohol, 2-phenylethyl alcohol, phenol, cresol, 4-tert-butylphenol, 4-methoxyphenol, hydroquinone, bisphenol A (2,2-bis(4-hydroxyphenyl)propane), and bisphenol S (bis(4-hydroxyphenyl)sulfone), with the synthetic resin, a base, and an organic solvent.

[0053] The order of mixing (blending) these materials (substances) is not particularly limited, but it is preferable to prepare a raw material composition that is a blend of an alcohol, a base, and an organic solvent, and then mix this raw material composition with the synthetic resin. By using such a mixing order, the decomposition of the synthetic resin can proceed at a higher rate.

[0054] The reaction temperature during synthetic resin decomposition (reaction temperature during the decomposition step) can be adjusted appropriately taking into account the synthetic polymer compounds contained in the synthetic resin. Decomposition may be carried out at room temperature (25°C) or under heated conditions. Specifically, the reaction temperature during synthetic resin decomposition can be in the range of 25 to 200°C, but a reaction temperature during synthetic resin decomposition in the range of 25 to 180°C is preferred because it allows for easy decomposition of the synthetic resin. When an aliphatic alcohol is used as the alcohol, a reaction temperature during synthetic resin decomposition in the range of 25 to 120°C is preferred because it allows for easier decomposition of the synthetic resin, and a reaction temperature during synthetic resin decomposition in the range of 60 to 100°C is even more preferred because it allows for easy and rapid decomposition of the synthetic resin. Here, in this specification, aliphatic alcohol refers to methanol, ethanol, isopropyl alcohol, tert-butyl alcohol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, 2-ethylhexanol, and benzyl alcohol.

[0055] On the other hand, when an aromatic phenol is used as the alcohol, it is preferable that the reaction temperature during decomposition of the synthetic resin be in the range of 120°C to 160°C, as this allows the synthetic resin to be decomposed more easily, and it is even more preferable that the reaction temperature during decomposition of the synthetic resin be in the range of 140°C to 160°C, as this allows the synthetic resin to be decomposed easily and quickly. Here, in this specification, aromatic phenol refers to 2-phenylethyl alcohol, phenol, cresol, 4-tert-butylphenol, 4-methoxyphenol, hydroquinone, bisphenol A (2,2-bis(4-hydroxyphenyl)propane), and bisphenol S (bis(4-hydroxyphenyl)sulfone).

[0056] The equipment used for heating is not particularly limited, and equipment such as a heater can be used.

[0057] Furthermore, the reaction time during decomposition of the synthetic resin (reaction time in the decomposition step) is preferably 1 to 40 hours, and more preferably 15 to 24 hours. If this reaction time is shorter than 1 hour, the synthetic resin cannot be sufficiently decomposed, and if it is longer than 40 hours, a side reaction that decomposes the carbon groups derived from the alcohol occurs. When decomposing the synthetic resin, it is preferable to stir the reaction mixture containing all of the above materials by known means. By stirring the reaction mixture, the synthetic resin can be quickly decomposed.

[0058] Furthermore, the decomposition of synthetic resin according to this embodiment can be carried out in an inert gas atmosphere (preferably at a concentration of 99% or more) or in air. Examples of inert gas include rare gases such as argon, and nitrogen. <<Method for recovering synthetic resin decomposition products>>

[0059] The synthetic resin decomposition products produced using the synthetic resin decomposition method according to this embodiment contain a specific bisphenol and a specific bisphenol ether. Therefore, by using this synthetic resin decomposition method, bisphenol A can be recovered from synthetic resins containing polysulfone, and 4,4'-dihydroxybiphenyl can be recovered from synthetic resins containing polyphenylsulfone or polyether ether sulfone. The specific bisphenol can ultimately be obtained from the bisphenol ether by a known hydrolysis reaction.

[0060] Furthermore, after using the synthetic resin decomposition method according to this embodiment, hydroquinone can be recovered from synthetic resins containing polyether ether sulfone or polyether ether ketone by using, for example, column chromatography.

[0061] Specifically, by using the synthetic resin decomposition method, it is possible to recover the substances shown in the right column of the table in Figure 1 from the polymer compounds shown in the left column of the table. In this synthetic resin decomposition method, methanol or hydroquinone is used as the alcohol, and sodium hydroxide is used as the base.

[0062] Next, the synthetic resin decomposition method according to this embodiment will be described in more detail using examples, but the present invention is not limited to the following examples. The present invention includes combinations of synthetic resins, bases, alcohols, and organic solvents that are not described in the following examples. However, those skilled in the art will understand from the following examples that synthetic resins can be similarly decomposed even with combinations not described in the examples, and can actually confirm this through experiments. <Example 1>

[0063] Under an argon atmosphere, a base (2.2 equivalents based on the polysulfone), each solvent (0.4 mL), and alcohol (methanol) were added sequentially to 88.5 mg of pellet-shaped polysulfone (PSU) (0.20 mmol, calculated based on the molar weight of the monomer, average Mw 35,000, average Mn 16,000, Cat. No. 428302 (Sigma-Aldrich)), and the reaction mixture was stirred while heating at room temperature (25°C) to 100°C.

[0064] The temperature of the reaction mixture was then returned to room temperature (25°C), and 1 M hydrochloric acid was added to quench the reaction. Ethyl acetate was then added, and the organic layer was extracted from the resulting two-layer solution. The organic layer was dried over magnesium sulfate and evaporated under reduced pressure to obtain a crude product.

[0065] Then, using mesitylene as an internal standard and deuterated chloroform, １ H NMR was used to measure the yields of bisphenol S dimethyl ether A (A), bisphenol A (BPA), its intermediate product B, and by-product C obtained according to the chemical reaction formula shown in Figure 2. These reaction conditions and the yields of the resulting synthetic resin decomposition products are shown in Figure 3.

[0066] In this figure, DMI stands for 1,3-dimethyl-2-imidazolidinone, TMU stands for tetramethylurea, DMPU stands for 1,3-dimethylpropyleneurea, NMP stands for N-methyl-2-pyrrolidone, DMAc stands for N,N-dimethylacetamide, and DMSO stands for dimethyl sulfoxide. N.D. stands for not detected, and rt stands for room temperature (25°C).

[0067] As shown in this figure, the decomposition reaction of polysulfone was carried out using 4 to 12 equivalents of methanol at various temperatures (Entries 1 to 5), various bases (Entries 4, 6, and 7), and organic solvents (Entries 4, 5, and 8 to 12).

[0068] As a result, it was found that the decomposition (depolymerization) of the target polymer compound proceeds with good selectivity when the reaction temperature is 80°C and a strong inorganic base such as sodium hydroxide, potassium hydroxide, or cesium hydroxide, or a urea-based solvent or an amide-based solvent such as DMI, TMU, DMPU, NMP, or DMAc is used.

[0069] In particular, it has been found that when the decomposition reaction (depolymerization) is carried out at 80°C using sodium hydroxide and DMI solvent, bisphenol S dimethyl ether A (A) and bisphenol A (BPA) can be obtained in high yields with almost no intermediate product B or by-product C produced (see Entry 4).

[0070] Furthermore, when the equivalent amount of base (Entry 13) and the amount of methanol (Entries 14 and 15) were investigated, it was found that when 2.2 equivalents of base and 12 equivalents of methanol were used, the target synthetic resin decomposition products, bisphenol S dimethyl ether A (A) and bisphenol A (BPA), were obtained in high yield and selectively (Entry 15). Example 2

[0071] The chemical reaction shown in Figure 4 was carried out as follows. Under an argon atmosphere, 1.25 mL of methanol, 226 mg (5.5 mmol) of sodium hydroxide, and 5 mL of 1,3-dimethyl-2-imidazolidinone (DMAc) were sequentially added to 1.10 g (2.49 mmol, calculated based on the molar weight of the monomer, average Mw 35,000, average Mn 16,000, Cat. No. 428302, Sigma-Aldrich) of colorless, transparent, pellet-like polysulfone (PSU), and the reaction mixture was stirred at 80°C.

[0072] After 28 hours, the yellow solution containing the white solid was returned to room temperature and then separated into the white solid and the yellow solution by filtration. The organic layer was then extracted with ethyl acetate, dried over magnesium sulfate, and evaporated under reduced pressure to obtain a crude product 1 containing bisphenol S dimethyl ether A.

[0073] Ethyl acetate and hydrochloric acid were added to the white solid obtained so far, and the layers were separated. The organic layer was extracted, dried over magnesium sulfate, and evaporated under reduced pressure to obtain a crude product containing bisphenol S dimethyl ether. NMR analysis revealed that a crude product 2 containing mainly bisphenol A (BPA) was obtained.

[0074] The crude product 1 was purified by recrystallization using methylene chloride and hexane to give 421 mg (61%) of bisphenol S dimethyl ether A. If necessary, the purity of bisphenol S dimethyl ether can be improved by silica gel column chromatography (changing the weight ratio of hexane:ethyl acetate from 95:5 to 6:4) (recovery yield: 346 mg).

[0075] The crude product 2 was subjected to base-acid extraction, specifically, ethyl acetate and a sodium hydroxide solution were added to the crude product 2 to convert bisphenol A into an anion, which was then dissolved in the aqueous layer, and hydrochloric acid and ethyl acetate were added to the separated aqueous layer to regenerate bisphenol A, which was then dissolved in the organic layer. The organic layer was then dried over magnesium sulfate, and bisphenol A was obtained by distillation under reduced pressure (380 mg, yield 66%).

[0076] The NMR measurement results of the obtained bisphenol S dimethyl ether and bisphenol A are shown below. Bisphenol A: 1 H NMR (600 MHz, acetone-d6) δ 1.58 (s, 6H, methyl), 6.72 (AA'BB', 4H, aromatic), 7.05 (AA'BB', 4H, aromatic), 8.07 (br, 2H, hydroxy). Bisphenol S dimethyl ether: 1H NMR (600 MHz, acetone-d6) δ 3.87 (s, 6H, methyl), 7.09 (AA'BB', 4H, aromatic), 7.87 (AA'BB', 4H, aromatic). 13 C NMR (151 MHz, acetone-d6) δ 56.2, 115.4, 130.3, 135.4, 164.2. Example 3

[0077] A baby bottle made of polyphenylsulfone (PPSU) (manufactured by ChuChu) was cut into 5 mm sides.

[0078] Under an argon atmosphere, 100 μL (2.4 mmol) of methanol, 17.6 mg (0.44 mmol) of sodium hydroxide, and 0.4 mL of 1,3-dimethyl-2-imidazolidinone (DMI) were added sequentially to the above pale yellow polyphenylsulfone pieces (84.8 mg; an amount corresponding to 0.2 mmol of the repeating unit in the general formula shown on the right side of the chemical reaction formula in FIG. 5 ), and the reaction mixture was stirred at 80° C.

[0079] After 17 hours, the yellow solution containing the white solid was returned to room temperature (25°C) and then separated into a white solid and a yellow solution by filtration. Ethyl acetate and hydrochloric acid were then added to the separated white solid, followed by liquid separation, and the organic layer was extracted. The organic layer was then dried over magnesium sulfate and evaporated under reduced pressure to obtain 23.9 mg (0.128 mmol, 61%) of 4,4'-dihydroxybiphenyl.

[0080] Subsequently, the yellow solution was distilled off under reduced pressure to obtain a crude product. From the obtained crude product, the target synthetic resin decomposition product, di(4-(methoxy)phenyl)sulfone (BMPS) (yield: 34.5 mg, 0.124 mmol, 59%), was obtained by preparative thin-layer silica gel chromatography (developing solvent: hexane / ethyl acetate 10 / 3).

[0081] The obtained di(4-(methoxy)phenyl)sulfone (BMPS) １ H NMR and １３ The results of the C NMR analysis were found to be similar to those in Example 2.

[0082] The obtained 4,4'-dihydroxybiphenyl １ The results of the H NMR analysis are shown below. 4,4'-Dihydroxybiphenyl: 1 H NMR (600 MHz, acetone-d6) δ 6.87 (AA'BB', 4H, aromatic), 7.38 (AA'BB', 4H, aromatic). <Example 4>

[0083] Under an argon atmosphere, 100 μL (2.4 mmol) of methanol, 18.1 mg (0.45 mmol) of sodium hydroxide, and 0.4 mL of 1,3-dimethyl-2-imidazolidinone (DMI) were added sequentially to brown pellet-shaped polyether ether sulfone (69.4 mg; an amount corresponding to 0.21 mmol of the repeating unit in the general formula on the right side of the chemical reaction formula in FIG. 6 , manufactured by Sigma-Aldrich, Cat. No. 440965), and the reaction mixture was stirred at 80° C.

[0084] After 17 hours, the yellow solution containing the white solid was returned to room temperature (25°C) and then separated into the white solid and the yellow solution by filtration. The separated white solid was treated with hydrochloric acid, and ethyl acetate was added to further extract the white solid.

[0085] Then, measurement was performed by 1H NMR using mesitylene as an internal standard and deuterated chloroform, and the results showed that hydroquinone (HQ) was produced in a yield of 34%.

[0086] Subsequently, hydrochloric acid was added to the yellow solution, and the organic layer was extracted with ethyl acetate, dried over magnesium sulfate, and evaporated under reduced pressure to obtain a crude product.

[0087] The crude product thus obtained was subjected to preparative thin-layer silica gel chromatography (developing solvent: hexane / ethyl acetate 10 / 3) to obtain the target synthetic resin decomposition product, di(4-(methoxy)phenyl)sulfone (BMPS) (yield: 18.3 mg, 0.066 mmol, 31%).

[0088] The obtained di(4-(methoxy)phenyl)sulfone (BMPS) １ H NMR and １３The results of the C NMR analysis were found to be similar to those in Example 2.

[0089] of the generated hydroquinone １ The results of the H NMR analysis are shown below. Hydroquinone (HQ): 1 H NMR (600 MHz, acetone-d6) δ 6.66 (s, 4H, aromatic). Example 5

[0090] Under an argon atmosphere, 100 μL (2.4 mmol) of methanol, 19.5 mg (0.49 mmol) of sodium hydroxide, and 0.4 mL of 1,3-dimethyl-2-imidazolidinone (DMI) were added sequentially to powdered polyether ether ketone (57.5 mg; the amount corresponds to 0.20 mmol of the repeating unit in the general formula on the right side of the chemical reaction formula in FIG. 7 , weight average molecular weight 20,800, number average molecular weight 10,300, manufactured by Sigma-Aldrich, Cat. No. 456640), and the mixture was stirred at 80° C.

[0091] After 17 hours, the yellow solution containing the white solid was returned to room temperature (25°C), and the white solid and the yellow solution were separated by filtration. The separated white solid was treated with hydrochloric acid, and ethyl acetate was added to further extract the white solid.

[0092] Then, using mesitylene as an internal standard and deuterated chloroform, the resulting mixture was analyzed by 1H NMR. The results showed that hydroquinone (HQ) was produced in a yield of 42%. Hydroquinone can be recovered by known methods such as silica gel column chromatography.

[0093] Subsequently, hydrochloric acid was added to the yellow solution, and the organic layer was extracted with ethyl acetate, dried over magnesium sulfate, and evaporated under reduced pressure to obtain a crude product.

[0094] From the obtained crude product, the target synthetic resin decomposition product, di(4-(methoxy)phenyl)ketone (BMPK) (yield: 27.7 mg, 0.114 mmol, 58% yield) was obtained by preparative thin-layer silica gel chromatography (developing solvent: hexane / ethyl acetate 10 / 3).

[0095] of the generated hydroquinone１ The results of the H NMR analysis were found to be similar to those in Example 4.

[0096] The obtained di(4-(methoxy)phenyl)ketone (BMPK) １ The results of the H NMR analysis are shown below. Di(4-(methoxy)phenyl)ketone (BMPK): 1 H NMR (600 MHz, acetone-d6) δ 3.91 (s, 6H, methyl), 7.07 (AA'BB', 4H, aromatic), 7.76 (AA'BB', 4H, aromatic). 13 C NMR (151 MHz, acetone-d6) δ 55.9, 114.4, 131.6, 132.7, 163.9, 194.0. Examples 6 to 8

[0097] In the above-described examples, methanol was used as the alcohol, but the alcohol that can be used in the synthetic resin decomposition method according to this embodiment is not limited to methanol.

[0098] In the chemical reaction formula shown in Figure 8, the reaction conditions when ethanol (Example 6), isopropyl alcohol (Example 7), and ethylene glycol (Example 8) were used as alcohols, and the yield of the resulting synthetic resin decomposition product are shown in Figure 9. The values ​​(numbers in parentheses) in the ROH column of the table in this figure indicate the equivalent weight of the alcohol used in each example. For example, "EtOH (6)" indicates that 6 equivalents of ethanol were used. Also, the BPS-R ２ The values ​​in the "yield" column indicate the yield calculated by NMR, and the values ​​in parentheses next to them indicate the yield when actually isolated. Furthermore, the "BPA" column in the table in this figure indicates the yield of bisphenol A (BPA).

[0099] As can be seen from this figure, it was found that synthetic resins can be sufficiently decomposed even when ethanol, isopropyl alcohol, and ethylene glycol are used as alcohols.

[0100] Under a nitrogen atmosphere, 488 mg (4.43 mmol) of hydroquinone, 321 mg (8.03 mmol) of sodium hydroxide, and 8.0 mL of 1,3-dimethyl-2-imidazolidinone (DMI) were added sequentially to brown pellet-shaped polyether ether sulfone (1.31 g; an amount corresponding to 4.01 mmol of the repeating unit in the general formula on the right side of the chemical reaction formula in FIG. 10 , manufactured by Sigma-Aldrich, Cat. No. 440965), and the reaction mixture was stirred at 150° C.

[0101] After 41 hours, the reaction solution was returned to room temperature (25°C), hydrochloric acid was added, and the organic layer was extracted with ethyl acetate. The organic layer was then dried over magnesium sulfate and evaporated under reduced pressure to obtain a crude product. Water was added to the crude product, which was then filtered, washed with water, and dried under reduced pressure to obtain the desired synthetic resin decomposition product, 4,4'-((sulfonylubris(4,1-phenylene))bis(oxy))diphenol (yield: 1.55 g, 3.57 mmol, 89%).

[0102] The obtained 4,4'-((sulfonylbis(4,1-phenylene))bis(oxy))diphenol １ H NMR and １３ The results of the C NMR analysis are shown below. 1 H NMR (600 MHz, acetone-d6) δ 6.91 (AA'BB', 4H, aromatic), 6.98 (AA'BB', 4H, aromatic), 7.02 (AA'BB', 4H, aromatic), 8.49 (br, 2H, OH). 13 C NMR (151 MHz, acetone-d6) δ 117.4, 117.6, 122.8, 130.6, 136.4, 148.0, 155.8, 164.0. Example 10

[0103] Under a nitrogen atmosphere, 1.61 g (14.6 mmol) of hydroquinone, 648 mg (16.2 mmol) of sodium hydroxide, and 8.0 mL of 1,3-dimethyl-2-imidazolidinone (DMI) were added sequentially to powdered polyether ether ketone (1.15 g; an amount corresponding to 4.00 mmol of the repeating unit in the general formula on the right side of the chemical reaction formula in FIG. 11 , manufactured by Sigma-Aldrich, Cat. No. 456640), and the reaction mixture was stirred at 150° C.

[0104] After 41 hours, the reaction solution was returned to room temperature (25°C), hydrochloric acid was added, and the precipitated colorless solid was filtered to obtain a crude product. The crude product was washed with water, dried over magnesium sulfate, and then dried under reduced pressure to obtain the desired synthetic resin decomposition product, bis(4-(4-hydroxyphenoxy)phenyl)methanone (yield: 1.37 g, 3.44 mmol, 86%). In other words, the synthetic resin decomposition method of this example using hydroquinone does not require an isolation procedure such as a column; bis(4-(4-hydroxyphenoxy)phenyl)methanone can be easily recovered simply by treating the crude product with hydrochloric acid and then washing the remaining solid with water.

[0105] The obtained bis(4-(4-hydroxyphenoxy)phenyl)methanone １ H NMR and １３ The results of the C NMR analysis are shown below. 1 H NMR (600 MHz, acetone-d6) δ 6.92 (AA'BB', 4H, aromatic), 7.00 (AA'BB', 4H, aromatic), 7.01 (AA'BB', 4H, aromatic), 7.78 (AA'BB', 4H, aromatic), 8.45 (br, 2H, hydroxy). 13 C NMR (151 MHz, acetone-d6) δ 116.8, 117.4, 122.7, 132.7, 132.9, 148.5, 155.6, 163.5, 193.9. Example 11

[0106] Carbon fiber-reinforced polyether ether ketone (TECAPEEK CF30, Cat. No. 3-3094-02, manufactured by Ensinger) was processed into a powder, and the content of polyether ether ketone relative to the total mass of this carbon fiber-reinforced polyether ether ketone was 70 mass%.

[0107] Under a nitrogen atmosphere, 81.2 mg (0.74 mmol) of hydroquinone, 32.1 mg (0.80 mmol) of sodium hydroxide, and 0.4 mL of 1,3-dimethyl-2-imidazolidinone (DMI) were added sequentially to this powdered carbon fiber-reinforced polyether ether ketone (82.4 mg; an amount corresponding to 0.20 mmol of the repeating unit in the general formula on the right side of the chemical reaction formula in FIG. 12 ), and the reaction mixture was stirred at 150° C.

[0108] After 41 hours, the reaction solution was returned to room temperature (25°C), hydrochloric acid was added, and the precipitated solid mixture was filtered to obtain a crude product. The crude product was washed with water and then dissolved in acetone to extract the organic components. The organic components were then dried under reduced pressure to obtain the target synthetic resin decomposition product, bis(4-(4-hydroxyphenoxy)phenyl)methanone (yield: 64.8 mg, 0.163 mmol, 81%). Meanwhile, the black solid obtained by removing the organic components from the crude product was dried, and 32.1 mg (39 wt%) of carbon fiber powder was recovered.

[0109] The obtained bis(4-(4-hydroxyphenoxy)phenyl)methanone １ The results of the H NMR analysis were found to be similar to those of Example 10. Example 12

[0110] Glass fiber-reinforced polyether ether ketone (TECAPEEK GF30, Cat. No. 3-3095-01, manufactured by Ensinger) was processed into a powder, in which the content of polyether ether ketone relative to the total mass of the glass fiber-reinforced polyether ether ketone was 70 mass%.

[0111] Under a nitrogen atmosphere, 80.7 mg (0.73 mmol) of hydroquinone, 32.0 mg (0.80 mmol) of sodium hydroxide, and 0.4 mL of 1,3-dimethyl-2-imidazolidinone (DMI) were added sequentially to this powdered glass fiber-reinforced polyether ether ketone (82.5 mg; an amount corresponding to 0.20 mmol of the repeating unit in the general formula on the right side of the chemical reaction formula in FIG. 13 ), and the reaction mixture was stirred at 150° C.

[0112] After 41 hours, the reaction solution was returned to room temperature (25°C), hydrochloric acid was added, and the precipitated solid mixture was filtered to obtain a crude product. The crude product was washed with water and then dissolved in acetone to extract the organic components. The organic components were then dried under reduced pressure to obtain the target synthetic resin decomposition product, bis(4-(4-hydroxyphenoxy)phenyl)methanone (yield: 57.2 mg, 0.144 mmol, 72%). Meanwhile, the black solid obtained by removing the organic components from the crude product was dried, and 35.0 mg (42 wt%) of a powdery residue containing glass fibers was recovered.

[0113] The obtained bis(4-(4-hydroxyphenoxy)phenyl)methanone １ The results of the H NMR analysis were found to be similar to those of Example 10.

[0114] As can be seen from the results of Examples 9 to 12, it was found that synthetic resins can be sufficiently decomposed even when hydroquinone is used as the alcohol.

[0115] The chemical reaction shown in Figure 14 was carried out as follows: Under an argon atmosphere, 55.9 mg (0.245 mmol) of bisphenol A, 16.2 mg (0.405 mmol) of sodium hydroxide, and 0.4 mL of 1,3-dimethyl-2-imidazolidinone (DMI) were sequentially added to 89.6 mg (0.203 mmol, calculated based on the molar weight of the monomer, average Mw 35,000, average Mn 16,000, Cat. No. 428302 (Sigma-Aldrich)) of colorless, transparent, pellet-like polysulfone (PSU), and the reaction mixture was stirred at 150°C.

[0116] After 17 hours, the yellow, transparent solution was returned to room temperature, and then ethyl acetate (0.4 mL) and 2 M hydrochloric acid (0.2 mL) were added. After separation, the organic layer was extracted. 5.0 μL of mesitylene, an internal standard, was added, and a small amount was taken and analyzed by NMR and GC. It was found that 0.11 mmol of the raw material bisphenol A and the target product HO-BPA-BPS-BPA-OH were produced in a yield of 53%. １ The results of the H NMR analysis are shown in Figure 15. Example 14

[0117] The chemical reaction shown in Figure 16 was carried out as follows: Under an argon atmosphere, 65.4 mg (0.261 mmol) of bisphenol S, 17.4 mg (0.436 mmol) of sodium hydroxide, and 0.4 mL of 1,3-dimethyl-2-imidazolidinone (DMI) were sequentially added to 50.8 mg (0.219 mmol, calculated based on the molar weight of the monomer, Cat. No. 428302 (Sigma-Aldrich)) of pellet-shaped polyethersulfone (PES), and the reaction mixture was stirred at 150°C.

[0118] After 17 hours, the yellow, transparent solution was returned to room temperature, and then ethyl acetate (0.4 mL) and 2 M hydrochloric acid (0.2 mL) were added and the solution was separated. The organic layer was then extracted. 5.0 μL of mesitylene, an internal standard, was added, and a small amount was taken and analyzed by NMR and GC. It was found that the raw material bisphenol S was present in an amount of 0.12 mmol, and the products HO-BPS-BPS-OH and HO-BPS-BPS-BPS-OH were present in an amount of 0.073 mmol and 0.077 mmol, respectively. １ The results of the H NMR analysis are shown in FIG.

Claims

1. A method for decomposing a synthetic resin containing at least one of polysulfone, polyphenylsulfone, polyethersulfone, polyetherethersulfone, and polyetheretherketone, comprising a decomposition step of mixing the synthetic resin, a base, and at least one alcohol selected from the group consisting of methanol, ethanol, isopropyl alcohol, tert-butyl alcohol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, 2-ethylhexanol, benzyl alcohol, 2-phenylethyl alcohol, phenol, cresol, 4-tert-butylphenol, 4-methoxyphenol, hydroquinone, bisphenol A (2,2-bis(4-hydroxyphenyl)propane), and bisphenol S (bis(4-hydroxyphenyl)sulfone), and an organic solvent, to decompose the polysulfone, polyphenylsulfone, polyethersulfone, polyetherethersulfone, and polyetheretherketone contained in the synthetic resin.

2. The synthetic resin decomposition method according to claim 1, characterized in that the base comprises at least one of sodium hydroxide, potassium hydroxide, potassium phosphate, cesium hydroxide, cesium carbonate, sodium tert-butoxide, lithium tert-butoxide, potassium tert-butoxide, lithium bis(trimethylsilyl)amide, sodium bis(trimethylsilyl)amide, and potassium bis(trimethylsilyl)amide.

3. The synthetic resin decomposition method according to claim 1 or 2, characterized in that the organic solvent contains at least one of 1,3-dimethyl-2-imidazolidinone, tetramethylurea, 1,3-dimethylpropyleneurea, N-methyl-2-pyrrolidone, N,N-dimethylacetamide, dimethylsulfoxide and tetrahydrothiophene-1,1-dioxide.

4. The synthetic resin decomposition method according to claim 1, wherein the reaction temperature in the decomposition step is in the range of 25°C to 200°C.

5. The synthetic resin decomposition method according to claim 1, wherein the reaction temperature in the decomposition step is in the range of 25°C to 120°C.

6. The synthetic resin decomposition method according to claim 1, characterized in that the synthetic resin contains at least one of polyether ether ketone, polyether ether sulfone, polysulfone and polyether sulfone, the alcohol is at least one of hydroquinone, bisphenol A and bisphenol S, and the reaction temperature in the reaction step is in the range of 25°C to 160°C.

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