Epoxy resin composition, epoxy resin cured product, decomposable epoxy resin composition, recycled cured product, method for decomposing and recycling epoxy resin cured product, monomer compound, dimer compound, trimer compound and cured product thereof

Abstract

To provide an epoxy resin composition which enables decomposition and recycling (re-curing) of an epoxy resin cured product.SOLUTION: An epoxy resin composition contains an epoxy resin monomer (A1) having epoxy groups at both terminals and a disulfide bond (-S-S-), and a curing agent (B) linkable with the epoxy group.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an epoxy resin composition, a cured epoxy resin product, a decomposable epoxy resin composition, a recycled cured product, a method for decomposing and recycling a cured epoxy resin product, a monomer compound, a dimer compound, a trimer compound, and cured products thereof. [Background technology]

[0002] Epoxy resins are one of the most common polymeric materials and are used in a wide range of applications, including coatings, paints, primers, adhesives, and composite materials. While epoxy resins generally exhibit excellent heat resistance, mechanical properties, and chemical resistance due to their cross-linked polymer network structure, they often exhibit thermosetting properties, resulting in poor recyclability and reworkability. Therefore, epoxy resins and their composites are typically disposed of by landfilling or incineration, causing significant adverse effects on the ecosystem. In particular, epoxy resins used in daily life are considered one of the sources of microplastics. Therefore, there is a strong demand for the development of degradable and reusable thermosetting epoxy resins.

[0003] For example, as a technique for decomposing a cured epoxy resin material, Patent Document 1 describes a method of immersing a substrate coated with a cured epoxy resin material in a cleaving agent solution containing a biomolecule such as glutathione. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-535552 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the method of Patent Document 1 is aimed simply at decomposing a cured epoxy resin product, and due to the composition of the epoxy resin composition, it is difficult to recycle the decomposed product. In other words, in response to the demand for establishing an environmentally friendly recycling system as described above, it is required that the epoxy resin composition not only be capable of decomposing the cured product, but also be capable of producing a recycled cured product in which a network structure is reconstructed from the decomposed product.

[0006] The present invention has been made in view of the above circumstances, and aims to provide an epoxy resin composition that allows decomposition and recycling (re-curing) of a cured epoxy resin product. It also aims to provide a cured product of this epoxy resin composition, a decomposable epoxy resin composition, a recycled cured product, a method for decomposing and recycling a cured epoxy resin product, a monomer compound, a dimer compound, a trimer compound, and cured products thereof. [Means for solving the problem]

[0007] In order to solve the above problems, the epoxy resin composition of the present invention has the following features.

[0008] [1] An epoxy resin monomer (A1) having epoxy groups at both ends and a disulfide bond (-SS-), a curing agent (B) capable of bonding with an epoxy group; Includes.

[0009] [2] The epoxy resin monomer (A1) includes a compound represented by the following formula:

[0010] [ka] (X is a disulfide bond (SS), R 1 and R 2 are the same or different and represent an aromatic carbocycle, an aromatic carbocyclic alkyl chain, an aliphatic carbocycle, an aliphatic carbocyclic alkyl chain, or an aliphatic carbon chain)

[0011] [3] The curing agent has a disulfide bond (—SS—).

[0012] [4] The curing agent includes a curing agent (B1) represented by the following formula:

[0013] [ka] (R 3 and R 4 are the same or different and represent an aromatic carbocycle, an aromatic carbocyclic alkyl chain, an aliphatic carbocycle, an aliphatic carbocyclic alkyl chain, or an aliphatic carbon chain; R 5 and R 6 are the same or different and represent primary, secondary or tertiary amines, imidazoles, acid anhydrides, and organic acid hydrazides.

[0014] [5] the molar ratio (A1 / A2) of the epoxy resin monomer (A1) to the epoxy resin monomer (A2) not having a disulfide bond (—SS—) is 100 / 0 to 25 / 75; The curing agent is a curing agent (B1) represented by the following formula:

[0015] [ka] (R 3 and R 4 are the same or different and represent an aromatic carbocycle, an aromatic carbocyclic alkyl chain, an aliphatic carbocycle, an aliphatic carbocyclic alkyl chain, or an aliphatic carbon chain; R 5 and R 6 are the same or different and represent primary, secondary or tertiary amines, imidazoles, acid anhydrides, and organic acid hydrazides. and, The curing agent (B2) does not have a disulfide bond (—SS—), The molar ratio (B1 / B2) of the curing agent (B1) to the curing agent (B2) is 100 / 0 to 0 / 100.

[0016] [6] The content of the curing agent (B1) in the curing agent (B) is such that the molar ratio (B1 / B2) exceeds 75 / 25, the molar ratio (A1 / A2) is 100 / 0 to 25 / 75, and the molar ratio (A1:B1) of the epoxy resin monomer (A1) to the curing agent (B1) is 2:1 to 0.5:1.

[0017] [7] The content of the curing agent (B1) in the curing agent (B) is 75 / 25 to 50 / 50 in the molar ratio (B1 / B2), the molar ratio (A1 / A2) is 100 / 0 to 50 / 50, and the molar ratio (A1:B1) of the epoxy resin monomer (A1) to the curing agent (B1) is 2:0.5 to 1:0.5.

[0018] [8] The content of the curing agent (B1) in the curing agent (B) is from less than 50 / 50 to 25 / 75 in the molar ratio (B1 / B2), the molar ratio (A1 / A2) is from 100 / 0 to 75 / 25, and the molar ratio (A1:B1) of the epoxy resin monomer (A1) to the curing agent (B1) is from 2:0.25 to 1.5:0.25.

[0019] [9] The content of the curing agent (B1) in the curing agent (B) is less than 25 / 75 in the molar ratio (B1 / B2), the molar ratio (A1 / A2) is 100 / 0 to 75 / 25, and the molar ratio (A1:B1) of the epoxy resin monomer (A1) to the curing agent (B1) is 2:0.01 to 1.5:0.25 or 1:0.

[0020] The cured epoxy resin material of the present invention has the following characteristics.

[0021]

[10] A cured product of the epoxy resin composition according to any one of [1] to [9].

[0022]

[11] The proportion of disulfide bonds (-SS-) is 1 equivalent or more relative to the repeating units of the epoxy resin.

[0023]

[12] The composition contains a repeating unit in which 2 equivalents of the epoxy resin monomer are bonded to 1 equivalent of the curing agent.

[0024] The epoxy resin decomposable composition of the present invention has the following characteristics.

[0025]

[13] A cured epoxy resin material according to any one of

[10] to

[12] above, Water-soluble biomolecular compounds with thiol groups (-SH) Includes.

[0026] The epoxy resin decomposition composition of the present invention has the following characteristics.

[0027]

[14] The epoxy resin decomposable composition according to

[13] contains a hydroxy thiol compound having a hydroxy group (—OH) and a thiol group (—SH), which is a decomposition reaction product of the epoxy resin decomposable composition according to

[13] .

[0028] The recycled cured product of the present invention has the following characteristics.

[0029]

[15] A recycled cured product of the epoxy resin decomposition composition according to

[14] , The composition contains the hydroxy thiol compound and has an epoxy resin network structure.

[0030]

[16] FT-NIR detects unreacted thiol groups (-SH) that are not disulfonated.

[0031]

[17] A cured product of the epoxy resin composition of [1], Unreacted thiol groups (-SH) that have not been disulfonated are detected by FT-NIR.

[0032] The method for decomposing a cured epoxy resin material of the present invention has the following features.

[0033]

[18] In a two-phase solvent system consisting of an aqueous phase and an organic phase, the cured epoxy resin material according to any one of

[10] to

[12] is contacted with a water-soluble biomolecular compound having a thiol group (-SH), to produce a hydroxythiol compound having a hydroxy group (-OH) and a thiol group (-SH) as a decomposition product in the organic phase; Includes.

[0034] The method for recycling a cured epoxy resin material of the present invention has the following features.

[0035]

[19] the steps of: In a two-phase solvent system consisting of an aqueous phase and an organic phase, the cured epoxy resin material of any one of claims 10 to 12 is contacted with a water-soluble biomolecular compound having a thiol group (-SH), to produce a hydroxythiol compound having a hydroxy group (-OH) and a thiol group (-SH) in the organic phase as a decomposition product; and The liquid containing the hydroxy thiol compound is heated and cured to obtain a cured product having an epoxy resin network structure containing disulfide bonds (-SS-). Includes.

[0036] The monomer compound of the present invention is characterized as follows.

[0037]

[20] It has the unit structure represented by the following formula:

[0038] [ka] (R 7 and R 8 are the same or different and represent an aromatic carbocycle, an aromatic carbocyclic alkyl chain, an aliphatic carbocycle, an aliphatic carbocyclic alkyl chain, or an aliphatic carbon chain; R 9 represents an aromatic carbocycle, an aromatic carbocyclic alkyl chain, an aliphatic carbocycle, an aliphatic carbocyclic alkyl chain, or an aliphatic carbon chain; Z 1 indicates a nitrogen atom, benzene, or phenol, Y1 indicates a thiol group (-SH)

[0039] The dimeric compounds of the present invention are characterized as follows:

[0040]

[21] The unit structure is represented by the following formula:

[0041] [ka] (R 7 and R 8 are the same or different and represent an aromatic carbocycle, an aromatic carbocyclic alkyl chain, an aliphatic carbocycle, an aliphatic carbocyclic alkyl chain, or an aliphatic carbon chain; R 9 represents an aromatic carbocycle, an aromatic carbocyclic alkyl chain, an aliphatic carbocycle, an aliphatic carbocyclic alkyl chain, or an aliphatic carbon chain; Z 1 indicates a nitrogen atom, benzene, or phenol, Three Ys at the ends 2 Two of these are thiol groups (-SH) and the other is a sulfide (-S-). Contains two The two unit structures are bonded to each other via a disulfide bond (-SS-) linked by the sulfides (-S-).

[0042] The trimer compound of the present invention is characterized as follows.

[0043]

[22] The unit structure is represented by the following formula:

[0044] [ka] (R 7 and R 8 are the same or different and represent an aromatic carbocycle, an aromatic carbocyclic alkyl chain, an aliphatic carbocycle, an aliphatic carbocyclic alkyl chain, or an aliphatic carbon chain; R 9represents an aromatic carbocycle, an aromatic carbocyclic alkyl chain, an aliphatic carbocycle, an aliphatic carbocyclic alkyl chain, or an aliphatic carbon chain; Z 1 indicates a nitrogen atom, benzene, or phenol.) Contains three One of the three unit structures has three terminal Y 3 One of them is a thiol group (-SH) and the other two are sulfides (-S-), The other two of the three unit structures have three terminal Y 3 Two of these are thiol groups (-SH) and the other is a sulfide (-S-), The sulfides (-S-) of the three unit structures are bonded to each other via disulfide bonds (-SS-).

[0045] The cured product of the present invention has the following characteristics.

[0046]

[23] A cured product of a composition containing any one of the compounds

[20] to

[22] . [Effects of the Invention]

[0047] The epoxy resin composition of the present invention can be decomposed and recycled into a cured epoxy resin product, which has the same mechanical strength as the cured product before recycling.

[0048] The cured epoxy resin composition and decomposable epoxy resin composition of the present invention allow the cured epoxy resin composition to be decomposed and recycled, and the recycled cured product has the same mechanical strength as the cured product before recycling.

[0049] The recycled cured product of the present invention can be disassembled and recycled, and has the same mechanical strength as the cured product before recycling.

[0050] The method for decomposing and recycling a cured epoxy resin material of the present invention makes it possible to decompose and recycle a cured epoxy resin material. [Brief explanation of the drawings]

[0051] [Figure 1] FIG. 1 is a diagram illustrating a scheme for obtaining a cured epoxy resin material by mixing two equivalents of epoxy resin monomers (A1, A2) and one equivalent of curing agent (B1, B2). [Figure 2] FIG. 1 illustrates a scheme for obtaining an epoxy resin decomposition composition by acting glutathione (a water-soluble biomolecular compound) on the cured epoxy resin shown in FIG. 1 and cleaving disulfide bonds (-SS-), and a scheme for recycling the epoxy resin decomposition composition. [Figure 3] FIG. 1 shows the results of Fourier transform near-infrared spectroscopy (FT-NIR) performed on uncured and cured ERDs having the combination (C1) shown in Table 1. [Figure 4] FIG. 1 shows the results of quantitative evaluation of the reaction mixture by 1H-NMR spectroscopy in the decomposition of ERD using glutathione (GSH). [Figure 5] FIG. 1 shows the results of quantitative evaluation of the reaction mixture by 1H-NMR spectroscopy in the decomposition of ERD using glutathione (GSH). [Figure 6] This shows the chemical reaction balance between the CDCl3 phase and the D2O phase. [Figure 7] This figure summarizes the decomposition results of ERD based on the composition ratio of epoxy resin monomer (A1 or A2) and diamine curing agent (B1 or B2). [Figure 8] FIG. 1 illustrates the structure of a cured epoxy resin material containing an epoxy resin monomer (BGPDS or DGEBA) and an amine curing agent (DTDA or DDM), and the structure of the cured epoxy resin material after decomposition. [Figure 9] FIG. 1 shows the 1H-NMR spectrum of the CDCl3 phase after removal of tributylphosphine (TBP). [Figure 10]FIG. 1 shows the FT-IR spectrum of the decomposed soluble portion of ERD-C1 in the CHCl3 phase. [Figure 11] FIG. 1 shows the UV-vis spectrum of the CHCl3 phase measured at 254 nm over time. [Figure 12] FIG. 10 is a diagram showing the results of a swelling test of ERD before and after recycling. [Figure 13] FIG. 2 is a graph showing normalized stress relaxation of a cured epoxy resin material before and after recycling. [Figure 14] FIG. 1 is a diagram showing the disassembly and recycling of a CFRP structure using the ERD matrix of Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0052] Hereinafter, one embodiment of the epoxy resin composition, the cured epoxy resin, the decomposable epoxy resin composition, the recycled cured product, and the method for decomposing and recycling the cured epoxy resin of the present invention will be described.

[0053] In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits.

[0054] Furthermore, in the description of groups (atomic groups) in this specification, when a notation that does not specify whether they are substituted or unsubstituted is used, it encompasses both those that have no substituents and those that have substituents, as long as the effects of the present invention are not impaired.

[0055] (Epoxy resin composition) The epoxy resin composition of the present invention contains an epoxy resin monomer (A1) having epoxy groups at both ends and a disulfide bond (-SS-), and a curing agent (B) capable of bonding with the epoxy groups.

[0056] The epoxy resin composition of the present invention may contain, as epoxy resin monomers, an epoxy resin monomer (A2) not having a disulfide bond (--S--) together with an epoxy resin monomer (A1) having a disulfide bond (--S--) (hereinafter, these may be simply referred to as "epoxy resin monomer (A1)" and "epoxy resin monomer (A2)"). The specific structures of the epoxy resin monomer (A1) and the epoxy resin monomer (A2) are not particularly limited, but examples thereof include glycidyl ether types (bisphenol A type, bisphenol F type, novolak type, alcohol type, etc.), glycidyl ester types (hydrophthalic acid type, dimer acid type, etc.), glycidyl amine types (aromatic amine type, aminophenol type, etc.), and oxidation types (alicyclic type, etc.).

[0057] Among these, the epoxy resin monomer (A1) is preferably a compound represented by the following chemical formula (1).

[0058] [ka] In the epoxy resin monomer (A1), X in the chemical formula (1) is a disulfide bond (SS), and R 1 and R 2 are the same or different and are an aromatic carbocycle, an aromatic carbocyclic alkyl chain, an aliphatic carbocycle, an aliphatic carbocyclic alkyl chain, or an aliphatic carbon chain.

[0059] Specifically, examples of the epoxy resin monomer (A1) include bis(4-glycidyloxyphenyl)disulfide (BGPDS), 1,2-bis((oxiran-2-ylmethoxy)methyl)disulfane, 1,2-bis(4-(oxiran-2-ylmethoxy)cyclohexyl)disulfane is more preferred.

[0060] In addition, the epoxy resin monomer (A2) does not have the symbol X representing a disulfide bond (SS) in the above chemical formula (1), and has R 1 and R 2 In the same manner as in the epoxy resin monomer (A1), the moiety may be an aromatic carbon ring, an aromatic carbon ring alkyl chain, an aliphatic carbon ring, an aliphatic carbon ring alkyl chain, or an aliphatic carbon chain.

[0061] More specifically, the epoxy resin monomer (A2) is preferably diglycidyl ether of bisphenol A (DGEBA), ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, or hydrogenated bisphenol A diglycidyl ether.

[0062] The molar ratio (A1 / A2) of the epoxy resin monomer (A1) to the epoxy resin monomer (A2) is preferably 100 / 0 to 25 / 75, more preferably 100 / 0 to 50 / 50, and even more preferably 100 / 0 to 75 / 25. When the molar ratio (A1 / A2) is in this range, the resulting epoxy resin composition can be decomposed and reused as a cured epoxy resin.

[0063] Furthermore, the epoxy resin composition may use, as the curing agent (B), one or more of a curing agent (B1) having a disulfide bond (-SS-) and a curing agent (B2) not having a disulfide bond (-SS-) (hereinafter, these may be simply referred to as "curing agent (B1)" and "curing agent (B2)"). The curing agent (B1) and the curing agent (B2) are not particularly limited as long as they can bond with an epoxy group, and examples thereof include polyamines (including diamines), modified polyamines, acid anhydrides, hydrazine derivatives, and polyphenols.

[0064] For example, polyamine-based curing agents include aliphatic polyamines, alicyclic polyamines, and aromatic polyamines. Examples of aliphatic polyamines include diethylenetriamine, triethylenetetramine, tetraethylenepentamine, m-xylenediamine, trimethylhexamethylenediamine, 2-methylpentamethylenediamine, and diethylaminopropylamine. Examples of alicyclic polyamines include isophoronediamine, 1,3-bisaminomethylcyclohexane, bis(4-aminocyclohexyl)methane, norbornenediamine, 1,2-diaminocyclohexane, and laromine. Examples of aromatic polyamines include diaminodiphenylmethane, metaphenylenediamine, and diaminodiphenylsulfone. Examples of acid anhydrides include hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, hydrogenated methylnadic anhydride, trialkyltetrahydrophthalic anhydride, methylcyclohexenetetracarboxylic dianhydride, trimellitic anhydride, pyromellitic anhydride-free, benzophenonetetracarboxylic dianhydride, aliphatic dibasic acid polyanhydrides, etc. Examples of polyphenol-based curing agents include phenol novolac, xylene novolac, bis A novolac, triphenylmethane novolac, biphenyl novolac, dicyclopentadiene phenol novolac, terpene phenol novolac, etc.

[0065] Among these, the curing agent (B1) is preferably a compound represented by the following chemical formula:

[0066] [ka] Here, in the curing agent (B1), R 3 and R 4 are the same or different and represent an aromatic carbocycle, an aromatic carbocyclic alkyl chain, an aliphatic carbocycle, an aliphatic carbocyclic alkyl chain, or an aliphatic carbon chain. 5 and R 6are the same or different and represent primary, secondary, or tertiary amine, imidazole, acid anhydride, or organic acid hydrazide.

[0067] Among these, diamine curing agents are more preferred, and 4,4'-dithiodianiline (DTDA), cystamine, cystine dimethyl ester, and cystine diethyl ester are particularly preferred.

[0068] The curing agent (B2) is also preferably a diamine curing agent, which may be one in which the disulfide bond (-SS-) in the above chemical formula (2) is substituted with an aromatic group, a (poly)ether group, an alkyl group, etc. Specifically, the curing agent (B2) is more preferably diaminodiphenylmethane (DDM), ethylenedimine, diethylenetriamine, triethylenetetramine, or norbornanediamine.

[0069] The molar ratio (B1 / B2) between the curing agent (B1) and the curing agent (B2) is 100 / 0 to 0 / 100. That is, the composition may contain at least one of the curing agent (B1) and the curing agent (B2), and the ratio between the curing agent (B1) and the curing agent (B2) can be appropriately set depending on the ratio between the epoxy resin monomer (A1) and the epoxy resin monomer (A2), etc. In particular, the molar ratio (B1 / B2) is preferably 100 / 0 to 25 / 75, more preferably 100 / 0 to 50 / 50, and even more preferably 100 / 0 to 75 / 25.

[0070] In one preferred embodiment of the epoxy resin composition of the present invention, the molar ratio (A1 / A2) of the epoxy resin monomer (A1) to the epoxy resin monomer (A2) is 100 / 0 to 25 / 75, and the molar ratio (B1 / B2) of the curing agent (B1) to the curing agent (B2) is 100 / 0 to 0 / 100.

[0071] More specifically, when the content of the curing agent (B1) in the curing agent (B) exceeds 75 / 25 in terms of the molar ratio (B1 / B2), it is preferable that the molar ratio (A1 / A2) is 100 / 0 to 25 / 75, and the molar ratio (A1:B1) of the epoxy resin monomer (A1) to the curing agent (B1) is 2:1 to 0.5:1.

[0072] When the content of the curing agent (B1) in the curing agent (B) is in a molar ratio (B1 / B2) of 75 / 25 to 50 / 50, it is preferable that the molar ratio (A1 / A2) is 100 / 0 to 50 / 50 and the molar ratio (A1:B1) is 2:0.5 to 1:0.5.

[0073] When the content of the curing agent (B1) in the curing agent (B) is less than 50 / 50 and 25 / 75 in terms of the molar ratio (B1 / B2), it is preferable that the molar ratio (A1 / A2) is 100 / 0 to 75 / 25 and the molar ratio (A1:B1) is 2:0.25 to 1.5:0.25.

[0074] When the content of the curing agent (B1) in the curing agent (B) is less than 25 / 75 in terms of the molar ratio (B1 / B2), it is preferable that the molar ratio (A1 / A2) is 100 / 0 to 75 / 25 and the molar ratio (A1:B1) is 2:0.01 to 1.5:0.25 or 1:0.

[0075] The epoxy resin composition of the present invention can be cured to form a cured epoxy resin product, which can be decomposed and reused, thereby enabling the construction of an environmentally friendly recycling system.

[0076] (cured epoxy resin) The cured epoxy resin material of the present invention is a cured product of the above-mentioned epoxy resin composition of the present invention. Hereinafter, the cured epoxy resin material having a disulfide bond may be referred to as "ERD."

[0077] The curing method and conditions for obtaining a cured epoxy resin product are not particularly limited, and known methods and conditions can be appropriately adopted. Specifically, for example, an example of a method is to mix an epoxy resin monomer and a curing agent in a predetermined ratio, and heat the mixture at 90 to 200°C while stirring as necessary to cause curing.

[0078] The structure of the cured epoxy resin material of the present invention is not specifically limited, but the proportion of disulfide bonds (-SS-) relative to the repeating units of the epoxy resin is preferably 1 equivalent or more, more preferably 2 equivalents or more.

[0079] It is also preferable that the composition contains a repeating unit in which two equivalents of epoxy resin monomer are bonded to one equivalent of curing agent.

[0080] FIG. 1 is a diagram illustrating a scheme for obtaining a cured epoxy resin material by mixing two equivalents of epoxy resin monomers (A1, A2) and one equivalent of curing agent (B1, B2).

[0081] For example, as shown in Figure 1, when diglycidyl ether of bisphenol A (DGEBA) is used as A1 and 4,4'-dithiodianiline (DTDA) is used as B1, a cured epoxy resin (ERD) containing a repeating unit formed by bonding two equivalents of epoxy resin monomer (A1) to one equivalent of curing agent (B1) can be obtained. Furthermore, in this cured epoxy resin (ERD), the proportion of disulfide bonds (-SS-) is three equivalents relative to the repeating units of the epoxy resin (X=SS, Y=SS).

[0082] The cured epoxy resin product of the present invention contains disulfide bonds (-SS-) at a predetermined ratio in the repeating units of the epoxy resin, and therefore can be decomposed and reused, allowing the construction of an environmentally friendly recycling system.

[0083] (Epoxy resin decomposition composition, method for decomposing epoxy resin cured material, and epoxy resin decomposition composition) The epoxy resin decomposable composition of the present invention contains the above-mentioned cured epoxy resin of the present invention and a water-soluble biomolecular compound having a thiol group (—SH).

[0084] Examples of water-soluble biomolecular compounds having a thiol group (-SH) include one or more of glutathione, thioredoxin, peroxiredoxin, dithiothreitol (DTT), etc. Among these, glutathione is preferred from the viewpoints of decomposability of epoxy resins and water solubility.

[0085] The epoxy resin decomposable composition of the present invention can contain an epoxy resin cured material (ERD) and a water-soluble biomolecular compound having a thiol group (-SH) in a two-phase solvent system consisting of an aqueous phase and an organic phase.

[0086] The organic solvent constituting the organic phase may be a known material, and examples thereof include aromatic hydrocarbons such as benzene, tert-butylbenzene, and chlorobenzene, or substituted derivatives thereof; aliphatic hydrocarbons such as cyclohexane, n-hexane, n-pentane, and n-octane; and chlorinated aliphatic hydrocarbons such as carbon tetrachloride, chloroform, dichloromethyl, and dichloroethane.

[0087] The epoxy resin decomposing composition of the present invention can reliably decompose the cured epoxy resin (ERD) because the disulfide bond (-SS-) in the cured epoxy resin (ERD) is cleaved by the action of the thiol group (-SH) of the water-soluble biomolecular compound.

[0088] The method for decomposing a cured epoxy resin material of the present invention includes the steps of contacting the cured epoxy resin material (ERD) of the present invention with a water-soluble biomolecular compound having a thiol group (-SH) in a two-phase solvent system consisting of an aqueous phase and an organic phase, and producing a hydroxythiol compound having a hydroxy group (-OH) and a thiol group (-SH) in the organic phase as a decomposition product.

[0089] As mentioned above, the organic solvent that constitutes the organic phase may be a known material.

[0090] In a two-phase solvent system consisting of an aqueous phase and an organic phase, a cured epoxy resin (ERD) is contacted with a water-soluble biomolecular compound containing a thiol (-SH) group. This cleaves the dynamic disulfide bonds in the epoxy resin through a thiol-disulfide exchange reaction, which then exchanges them with SH bonds of a water-soluble biomolecule such as glutathione. This allows the decomposed epoxy resin (epoxy resin decomposition composition) residue to dissolve in the organic phase. Meanwhile, the exchange product with glutathione, for example, can be dissolved in the aqueous phase due to the presence of hydrophilic groups.

[0091] Therefore, the epoxy resin decomposition composition of the present invention contains a hydroxy thiol compound having a hydroxy group (—OH) and a thiol group (—SH), which is a decomposition reaction product of the epoxy resin decomposition composition.

[0092] Specifically, for example, when the epoxy resin monomer of the above-mentioned chemical formula (1) and the curing agent of the chemical formula (2) are used, a compound (e.g., a monomer compound, a dimer compound, or a trimer compound) containing a unit structure represented by the following chemical formula (3) can be obtained as the epoxy resin decomposition composition.

[0093] [ka] In chemical formula (3), R 7 and R 8 are the same or different and represent an aromatic carbocyclic ring, an aromatic carbocyclic alkyl chain, an aliphatic carbocyclic ring, an aliphatic carbocyclic alkyl chain, or an aliphatic carbon chain. 9 represents an aromatic carbocycle, an aromatic carbocyclic alkyl chain, an aliphatic carbocycle, an aliphatic carbocyclic alkyl chain, or an aliphatic carbon chain. Z 1 represents a nitrogen atom, benzene, phenol, etc. Y represents a thiol group (-SH) or sulfide (-S-).

[0094] When the epoxy resin decomposition composition is a monomer compound,

[0095] [ka] In chemical formula (4), the three Y 1 are all thiol groups (-SH).

[0096] When the epoxy resin decomposition composition is a dimer compound,

[0097] [ka] In chemical formula (5), the three Ys at the terminals 2 Two of these are thiol groups (-SH) and the other is a sulfide (-S-). The sulfides (-S-) of the two unit structures represented by chemical formula (5) are linked to each other via a disulfide bond (-SS-).

[0098] When the epoxy resin decomposition composition is a trimer compound, one of the three unit structures constituting the trimer compound is

[0099] [ka] In chemical formula (6), the three Y 3 One of the units is a thiol group (-SH) and the other two are sulfides (-S-). The other two unit structures that make up the trimer compound are the three Y units located at the ends of the chemical formula (6). 3 Two of the units are thiol groups (-SH) and the other is a sulfide (-S-). The trimeric compound is bonded to each other via a disulfide bond (-SS-) that connects the sulfides (-S-) of the three units.

[0100] Fig. 2 illustrates a scheme for obtaining an epoxy resin decomposition composition by treating the cured epoxy resin shown in Fig. 1 with glutathione (a water-soluble biomolecular compound) to cleave disulfide bonds (-SS-), and a scheme for recycling the epoxy resin decomposition composition. In this embodiment, an epoxy resin decomposition composition represented by the following chemical formula (7) is obtained.

[0101] [ka] In chemical formula (7), similarly to chemical formula (3), the terminal Y represents a thiol group (-SH) or a sulfide (-S-).

[0102] For example, such monomeric compounds, dimeric compounds, and trimeric compounds have excellent solubility in an organic phase, and compositions containing such monomeric compounds, dimeric compounds, and trimeric compounds can be cured by heat treatment to obtain a cured product.

[0103] The epoxy resin decomposition composition of the present invention can be reused as a cured product by curing it, which allows the construction of an environmentally friendly recycling system. Furthermore, the cured product (recycled cured product) has mechanical strength substantially equivalent to that of the initial epoxy resin cured product.

[0104] (Recycling method and recycled hardened product) The recycling method of the present invention includes the following steps.

[0105] In a two-phase solvent system consisting of an aqueous phase and an organic phase, the cured epoxy resin of the present invention is brought into contact with a water-soluble biomolecular compound having a thiol group (-SH), to produce a hydroxythiol compound having a hydroxy group (-OH) and a thiol group (-SH) in the organic phase as a decomposition product (first step).

[0106] The liquid containing the hydroxythiol compound is heated and cured to obtain a cured product having an epoxy resin network structure containing disulfide bonds (-SS-) (second step).

[0107] The first step is common to the above-mentioned method for decomposing a cured epoxy resin material of the present invention, and therefore a description thereof will be omitted.

[0108] The heating method and conditions in the second step are not particularly limited, and known methods and conditions can be appropriately adopted. Specifically, for example, a method can be exemplified in which the decomposed epoxy resin residue (a liquid containing a hydroxythiol compound) is poured into a desired mold and heated at about 90°C to 250°C for about 30 minutes to 10 hours.

[0109] According to the recycling method of the present invention, a recycled cured product of the epoxy resin decomposition composition is obtained that contains a hydroxy thiol compound and has an epoxy resin network structure.

[0110] The recycled cured product of the present invention has an epoxy resin network structure common to that of the cured epoxy resin before recycling, but contains unreacted thiol groups (-SH) that were not disulfidized during recycling. Specifically, for example, by Fourier transform infrared spectroscopy (FT-NIR), -1 An absorption band derived from a thiol group (-SH) is detected nearby.

[0111] The recycled cured product of the present invention has mechanical strength substantially equivalent to that of the cured epoxy resin product before recycling, and can therefore be used in a variety of applications.

[0112] The epoxy resin composition, the cured product of the epoxy resin composition, the decomposable epoxy resin composition, the recycled cured product, and the method for decomposing and recycling the cured epoxy resin product of the present invention are not limited to the above-described embodiments.

[0113] For example, the epoxy resin composition may contain, as a compound other than the above-mentioned compounds, a known curing accelerator, etc. Furthermore, for example, the cured product of the epoxy resin composition or the recycled cured product may be in the form of a carbon fiber reinforced plastic (CFRP) containing carbon fiber. [Example]

[0114] The epoxy resin composition, the cured epoxy resin, the decomposable epoxy resin composition, the recycled cured product, and the method for decomposing and recycling the cured epoxy resin product of the present invention will be described below with reference to examples, but the present invention is not limited to the following examples.

[0115] Example 1: Synthesis of epoxy resin cured material (ERD) A cured epoxy resin (ERD) was prepared using bis(4-glycidyloxyphenyl) disulfide (BGPDS, A1) as the epoxy resin monomer and 4,4'-dithiodianiline (DTDA, B1) as the curing agent (diamine curing agent) (Figure 1).

[0116] Specifically, to clarify the thiol-disulfide exchange reaction, we employed the diglycidyl ether of bisphenol A (DGEBA, A2) and diaminodiphenylmethane (DDM, B2), which lack disulfide bonds (-SS-), as analogs of BGPDS and DTDA, respectively. We assumed that the chemical reactivities of the aromatic disulfides in the epoxy resin monomer and diamine curing agent were nearly identical. ERDs were prepared by combining epoxy resin monomer (either A1 or A2) with diamine curing agents (either B1 or B2).

[0117] Table 1 shows the detailed combinations of epoxy resin monomer (A1 or A2) and diamine curing agent (B1 or B2).

[0118] [Table 1]

[0119] As a pretreatment, a mixture of epoxy resin monomer and diamine curing agent was stirred at 90°C for 30 minutes in a stoichiometric molar ratio (2:1). The pre-cured mixture was transferred to a polytetrafluoroethylene mold and cured sequentially at 120°C, 140°C, and 160°C for 2 hours each. After cooling, ERD was obtained as a brown solid. Note that C25 in Table 1 was used as a control for a form that does not contain disulfide bonds.

[0120] To monitor the curing process, Fourier transform near-infrared spectroscopy (FT-NIR) was performed. Figure 3 shows an example of uncured and cured ERD with the combination (C1) shown in Table 1. 7200-4000 cm -1 In the nIR region from 1000, the bands related to epoxy resin monomers and primary amines are the combination band of the CH stretching vibration and the second overtone of the epoxy ring stretching vibration (approximately 4530 cm). -1 ) and a combination band of NH stretching and bending vibrations (approximately 5000-5100 cm -1 ) was observed.

[0121] Thus, the epoxy resin monomer is reduced during the curing process, and as a result, the CH stretching vibration band is at approximately 4530 cm -1 The weak overtone of the terminal CH2 is at about 6060 cm -1 Decreased from 5000 cm -1 The primary amine bond band at 7000 cm also decreased. -1 The OH overtone band increased at 7000 cm -1 The O-H overtone band of OH increased as a result of the oxirane ring-opening reaction.

[0122] Example 2: Degradation of ERD using glutathione (GSH) Prior to demonstrating the degradation of ERD using glutathione (GSH), we performed degradation experiments using disulfide-containing small molecules in an aqueous-organic binary system. Here, we selected DTDA as a model disulfide-containing molecule. DTDA and GSH were dissolved in deuterated chloroform (CDCl) (250 mM) and deuterated water (DO) (250 mM), respectively. The solutions were mixed 1:1 (v / v) and stored in the dark, covered with aluminum foil, to avoid unexpected photoinduced reactions.

[0123] The reaction mixture was quantitatively evaluated by 1H-NMR spectroscopy (Figures 4 and 5). 1H-NMR spectroscopy was measured at 25°C and 400 MHz using a JEOL ECS-400 spectrometer.

[0124] Figures 4(a) and (b) show the time-dependent changes in the 1H-NMR spectra of the CDCl3 and DO phases, respectively. In the CDCl3 phase, 1H-NMR signals from the aromatic rings of DTDA (a) and (b) appeared at 6.55 ppm and 7.22 ppm, respectively. The 1H-NMR signal at 7.12 ppm was identified as the aromatic ring (b') of 4-aminobenzenethiol (4-ABT), which is presumed to be the reducing agent for DTDA (Figure 4(a)). Furthermore, no peaks were observed in the 2-3 ppm range, suggesting that neither GSH nor its reaction products were present in the CDCl3 phase.

[0125] On the other hand, in the DO phase, a new 1H-NMR signal (e') appeared at 3.12 ppm, suggesting the formation of an SS bond between GSH and 4-ABT (Fig. 4(b)).

[0126] Furthermore, the H-NMR peaks (c) and (d) appeared at 7.15 ppm and 7.5 ppm, respectively, and increased in intensity simultaneously with peak (e'), suggesting the exchange reaction between DTDA and GSH to form the water-soluble product GSH-ABT. Furthermore, the lack of significant change in peak intensity between 7.25 ppm and 7.5 ppm suggested that a small amount of DTDA was dissolved in the aqueous phase. Compared to diphenyl disulfide (Figure 5), the solubility of DTDA in water was improved, confirming the promotion of the exchange reaction between the thiol bond of GSH and the disulfide bond of DTDA.

[0127] Next, we further evaluated the time evolution of the composition in CDCl3 / D2O. Figure 4(c) shows the rate of change of DTDA and 4-aminobenzenethiol calculated from the peak areas of the 1H-NMR signals (b) and (b') in CDCl3, respectively.

[0128] As a result, DTDA decreased rapidly with time and reached equilibrium at 60 min. Correspondingly, 4-ABT began to be produced immediately after stirring and reached equilibrium at 60 min, in contrast to DTDA.

[0129] Similarly, Figure 4(d) shows the time evolution of the decrease in GSH and the increase in the water-soluble reactants of GSH and 4-ABT in the DO phase. Similar to the CDCl phase, the increase in GSH and the decrease in the water-soluble reactants of GSH / 4-ABT tended to change symmetrically and reached equilibrium at approximately 60 min.

[0130] Furthermore, the molar ratios of the increasing and decreasing compositions in both the CDCl3 and D2O phases were kept at 30 mol%.

[0131] From these results, the chemical reaction balance between the CDCl3 phase and the D2O phase is shown in Figure 6. A thiol-disulfide exchange reaction between DTDA and GSH occurred at the interface between CDCl3 and D2O, producing a water-soluble reaction product of GSH and 4-ABT (GSH-ABT), while unreacted 4-ABT remained dissolved in CDCl3.

[0132] Since it was confirmed that the thiol-disulfide exchange reaction proceeds in a CHCl3 / water binary system via GSH, we performed a degradation test of ERD under the same binary system conditions.

[0133] First, ERD was ground by ball milling at a frequency of 25 Hz for 1 hour. The resulting ERD powder was suspended in CHCl3, and a 20 mM aqueous solution of GSH was added. Here, tributylphosphine (TBP) (10 mol%) was used to promote the thiol-disulfide exchange reaction. The 1H-NMR spectrum of the small molecule model with TBP added, shown in Figure 5, indicated that the product produced by the thiol-disulfide exchange reaction was the same as that without TBP addition.

[0134] The binary solution was then vigorously stirred at room temperature. After a certain period of time, the ERD completely dissolved in the CHCl3 phase, forming a yellow solution, and the solution was separated into two parts, one in which a precipitate formed and the other in which a yellow solution formed.

[0135] Figure 7 shows the results of ERD decomposition in terms of the composition ratio of epoxy resin monomer (A1 or A2) and diamine curing agent (B1 or B2). Figure 7 also shows the molar equivalents of disulfide bonds in each repeating unit of ERDs with various combinations of BGPDS / DGEBA (A1 / A2) and DTDA / DDM (B1 / B2).

[0136] As shown in Figure 7, complete dissolution of ERD was confirmed in C1-C13 and C16. Furthermore, the amine curing agent (DTDA or DDM) could react with two equivalents of the epoxy resin monomer (BGPDS or DGEBA), suggesting that disulfide bonds could be introduced up to three equivalents of the ERD repeat unit, as shown in the structural formula in Figure 8. After removing the CHCl3 solvent under vacuum from the completely dissolved portion, a viscous yellow liquid was obtained.

[0137] To identify the chemical structure of these residues, 1H-NMR and FT-nIR spectroscopy of ERD-C1 were performed, respectively.

[0138] FIG. 9 shows the 1H-NMR spectrum of the CDCl3 phase after removal of tributylphosphine (TBP), indicating pure resolved ERD-C1.

[0139] In this spectrum, the aromatic ring signals of the decomposed ERD were detected in the range of 6.5–7.5 ppm. The peaks at 3.0–4.0 ppm were associated with alkyl protons generated by the ring-opening reaction of the epoxy groups. Furthermore, no peaks were detected in the range of 2.0–3.0 ppm, proving the absence of GSH and exchange products in the CDCl3 phase. Furthermore, no signals were detected in the range of 1.0–1.5 ppm, indicating that tributylphosphine had been completely removed. These results demonstrate that although ERD decomposed into soluble oligomers, the epoxy structure remained intact, as shown in Figure 2.

[0140] Furthermore, Figure 10 shows the FT-IR spectrum of the decomposed soluble portion of ERD-C1 in the CHCl3 phase. As shown in Figure 10(a), the spectrum of this residue ranges from 4000 cm to 7500 cm -1 The spectrum was almost identical to that of ERD in the NIR region up to 2550 cm. This indicates that the liquid residue retains the epoxy structure of ERD. -1 A new absorption band due to thiol appeared at 1000 kJ / mol (Fig. 10(b)). This indicates that this fragment contains a thiol group due to reduction of the disulfide group of the ERD by GSH.

[0141] Here, the solubility of ERD can be discussed in terms of the stoichiometric ratio of disulfide groups to ERD repeat units (Figure 7). When the disulfide groups were 1.5 equivalents or more relative to the ERD repeat units, ERD was completely dissolved in CHCl3, and ERD was decomposed into dimers or monomers. On the other hand, when the stoichiometric ratio of disulfide groups was less than 1.5 equivalents, most of the repeat units were trimers or higher, and precipitates were observed.

[0142] Furthermore, to investigate the decomposition tendency of ERD, the UV-vis spectrum of the CHCl3 phase was measured at 254 nm over time (Fig. 11).

[0143] When a suspension of ERD-C1 in CHCl3 was mixed with a GSH / water solution, the UV absorbance at 245 nm immediately increased and followed a saturation curve. After 4 h, it reached a plateau region with a constant value, suggesting that ERD-C1 was completely dissolved in the CHCl3 phase. The resolution of ERD was clearly correlated with the number of disulfide bonds in the epoxy resin.

[0144] <Example 3> Rework test Generally, amine-cured epoxy resins are thought to have a network structure with amine bonds as crosslinking points, but ERD can also be thought of as a dynamic covalent network polymer with disulfide bonds as repeating units. Therefore, even if ERD is decomposed and regenerated by forming disulfide bonds, it is thought that the structure and physical properties of the original amine-cured epoxy resin ERD will not change.

[0145] The decomposed epoxy resin residue (epoxy resin decomposition composition) was poured into a polytetrafluoroethylene mold and heated at 180°C for 6 hours. As a result, the liquid residue became a dark brown solid. FT-NIR measurements revealed that the recycled ERD had hardened through the formation of disulfide bonds. This indicated that the decomposed yellow liquid contained thiol groups, and after hardening (after recycling), the 2550 cm corresponding to the thiol groups was observed. -1 Although the peak of thiol group almost disappeared (Fig. 10b), the presence of thiol group was confirmed slightly in the ERD after recycling by FT-NIR measurement.

[0146] Furthermore, dynamic mechanical analysis (DMA) was performed to evaluate the thermal and mechanical properties of the disulfide-containing epoxy resin before and after recycling. The results are shown in Table 2.

[0147] [Table 2]

[0148] Regarding mechanical properties, the storage modulus of the original ERD before recycling was 1.8 GPa, which was confirmed to be equivalent to that of conventional epoxy resins without disulfide bonds (1.88 GPa). It was confirmed that the storage modulus of the recycled ERD maintained approximately 90% of its initial value at room temperature.

[0149] The glass transition temperature (Tg) decreased from 131°C to 82°C due to partial incomplete reconnection of the network.

[0150] In addition, to evaluate the crosslink density before and after recycling, we conducted a swelling test on the ERD before and after recycling. The results are shown in Figure 12.

[0151] As shown in Figure 12, the swelling ratio after immersion in toluene at room temperature for 72 hours was approximately 3% for the initially cured material, while it was 13-16% for the recycled cured material. This result indicates that the crosslink density of the recycled ERD did not completely return to its original structure, causing a decrease in the glass transition temperature and mechanical strength at room temperature (from 1.8 GPa to 1.6 GPa), while also causing an increase in the rubber-like storage modulus (from 14.3 MPa to 49.9 MPa).

[0152] Figure 13 shows the normalized stress relaxation curves for cured epoxy resin before and after recycling at 130°C. The stress relaxation time was defined as the time required to release 63% of the initial stress based on the Maxwell model. The stress relaxation time for the cured recycled epoxy resin at 130°C was 152 seconds, confirming that the time required for the cured recycled epoxy resin to release 63% of the initial stress was shorter. The regenerated network of the cured recycled epoxy resin exhibited stress relaxation above its Tg, a typical dynamic network due to the reformation of dynamic disulfide bonds. Furthermore, because the cured recycled epoxy resin has a relatively low Tg, segmental chain motion occurs at low temperatures, accelerating the exchange reaction and resulting in stress relaxation.

[0153] Example 4: Recycling of CFRP Carbon fiber reinforced plastics (CFRP) are a structural material that has attracted attention in fields such as aircraft and automobiles, where lightweight construction and creep resistance are required. Generally, thermosetting resins such as epoxy are used as the matrix resin in CFRP structures, making rework and recycling difficult and raising the issue of waste disposal.

[0154] Therefore, a recycling system for CFRP structures using the ERD matrix of Example 1 was investigated.

[0155] The carbon fiber reinforced plastic (CFRP) structure was fabricated using the following procedure.

[0156] First, carbon fiber fabric was placed on an aluminum plate covered with polytetrafluoroethylene tape. An epoxy resin monomer (BGPDS) and a diamine curing agent (DTDA) were mixed in a glass vial at a molecular ratio of 2:1 at 90°C for 30 minutes. After mixing, the mixture was poured onto the aluminum plate covered with the fiber fabric and surrounded by another aluminum plate covered with polytetrafluoroethylene tape. The resulting sample and mold were cured in an oven at 120°C for 2 hours, 140°C for 2 hours, and 160°C for 2 hours, and then cooled to room temperature in the oven.

[0157] The cured CFRP structure was then fixed with clips in two liquids: an aqueous phase and an organic phase (CHCl3 phase) (Figures 14(a) and 14(b)). After 24 hours of vigorously stirring under atmospheric pressure, the ERD, which was the matrix of the CFRP structure, was decomposed into the CHCl3 phase (Figure 14(c)). After the matrix was dissolved, the carbon fibers were completely recovered by washing with water and acetone and drying at 100°C (Figure 14(d)). Meanwhile, the decomposed epoxy residue (epoxy resin decomposition composition) dissolved in the chloroform solution was obtained by evaporating the solvent (Figure 14(e)). This epoxy residue could easily be transferred to the epoxy resin network by forming disulfide bonds (Figure 14(f)). [Industrial Applicability]

[0158] As described above, we have proposed a reworking and recycling system for epoxy resins containing disulfide bonds. First, by introducing dynamic disulfide bonds, we obtained recyclable and reworkable cured epoxy resins containing disulfide bonds. Next, by cleaving the dynamic disulfide bonds in the epoxy resin through a thiol-disulfide exchange reaction and exchanging them with SH bonds of water-soluble biomolecules such as glutathione, the decomposed epoxy resin residue (decomposition composition) could be dissolved in chloroform. The exchange product was confirmed to distribute in the aqueous phase due to the presence of hydrophilic peptide groups in glutathione. Finally, by heating the epoxy residues containing SH bonds, we obtained recycled cured epoxy resins with a disulfide-containing epoxy resin network structure. The recycled cured epoxy resins obtained in this way retain approximately 90% of the mechanical strength of the original epoxy resin, making them potentially applicable to a variety of applications. Furthermore, this method has the potential to be applied to carbon fiber-reinforced composites, potentially expanding the scope of reuse of both embedded materials and matrix resins.

Claims

1. a cured epoxy resin material which is a cured product of an epoxy resin composition containing an epoxy resin monomer (A1) having epoxy groups at both ends and a disulfide bond (-S-S-) and a diamine curing agent (B); a water-soluble biomolecular compound having a thiol group (-SH); a recycled cured product of an epoxy resin decomposition composition containing a hydroxy thiol compound having a hydroxy group (—OH) and a thiol group (—SH), which is a decomposition reaction product of an epoxy resin decomposition composition containing the water-soluble biomolecular compound is at least one selected from the group consisting of glutathione, thioredoxin, peroxiredoxin, and dithiothreitol (DTT); A recycled cured product comprising the hydroxy thiol compound and having an epoxy resin network structure.

2. 2. The recycled cured product according to claim 1, wherein unreacted thiol groups (-SH) that have not been disulfonated are detected by FT-NIR.

3. The recycled hardened material of claim 1, characterized in that the diamine hardener (B) is at least one selected from the group consisting of 4,4'-dithiodianiline (DTDA), cystamine, cystine dimethyl ester, and cystine diethyl ester.

4. In a two-phase solvent system consisting of an aqueous phase and an organic phase, a cured epoxy resin material, which is a cured product of an epoxy resin composition comprising an epoxy resin monomer (A1) having epoxy groups at both ends and a disulfide bond (-S-S-) and a diamine curing agent (B), is brought into contact with a water-soluble biomolecular compound having a thiol group (-SH), to produce a hydroxythiol compound having a hydroxy group (-OH) and a thiol group (-SH) as a decomposition product in the organic phase; Including, A method for decomposing a cured epoxy resin material, wherein the water-soluble biomolecular compound is at least one selected from the group consisting of glutathione, thioredoxin, peroxiredoxin, and dithiothreitol (DTT).

5. A method for decomposing a cured epoxy resin material according to claim 4, characterized in that the diamine curing agent (B) is at least one selected from the group consisting of 4,4'-dithiodianiline (DTDA), cystamine, cystine dimethyl ester, and cystine diethyl ester.

6. The following steps: In a two-phase solvent system consisting of an aqueous phase and an organic phase, a cured epoxy resin material, which is a cured product of an epoxy resin composition comprising an epoxy resin monomer (A1) having epoxy groups at both ends and a disulfide bond (-S-S-) and a diamine curing agent (B), is contacted with a water-soluble biomolecular compound having a thiol group (-SH), to produce a hydroxythiol compound having a hydroxy group (-OH) and a thiol group (-SH) as a decomposition product in the organic phase; and The liquid containing the hydroxy thiol compound is heated and cured to obtain a cured product having an epoxy resin network structure containing disulfide bonds (-S-S-). Including, A method for recycling a cured epoxy resin material, wherein the water-soluble biomolecular compound is at least one selected from the group consisting of glutathione, thioredoxin, peroxiredoxin, and dithiothreitol (DTT).

7. A method for recycling epoxy resin cured materials as described in claim 6, characterized in that the diamine curing agent (B) is at least one selected from the group consisting of 4,4'-dithiodianiline (DTDA), cystamine, cystine dimethyl ester, and cystine diethyl ester.

8. A monomer compound having a unit structure represented by the following formula: 【Chemistry 1】 (R ７ and R ８ are the same or different and represent an aromatic carbocycle, an aromatic carbocyclic alkyl chain, an aliphatic carbocycle, an aliphatic carbocyclic alkyl chain, or an aliphatic carbon chain; R ９ is an aromatic carbocycle, an aromatic carbocycle alkyl chain, an aliphatic carbocycle, an aliphatic carbocycle alkyl chain. represents an aryl or aliphatic carbon chain, Z １ represents a nitrogen atom, Y １ indicates a thiol group (-SH) and, The unit structure represented by the following formula: 【Chemistry 2】 (R ７ and R ８ are the same or different and represent an aromatic carbocycle, an aromatic carbocyclic alkyl chain, an aliphatic carbocycle, an aliphatic carbocyclic alkyl chain, or an aliphatic carbon chain; R ９ represents an aromatic carbocycle, an aromatic carbocyclic alkyl chain, an aliphatic carbocycle, an aliphatic carbocyclic alkyl chain, or an aliphatic carbon chain; Z １ represents a nitrogen atom, Three Ys at the ends ２ Two of these are thiol groups (-SH) and the other is a sulfide (-S-). Contains two A dimeric compound in which two of the unit structures are bonded to each other via a disulfide bond (-S-S-) linked by the sulfides (-S-). and, A unit structure represented by the following formula: 【Transformation 3】 (R ７ and R ８ are the same or different and represent an aromatic carbocycle, an aromatic carbocyclic alkyl chain, an aliphatic carbocycle, an aliphatic carbocyclic alkyl chain, or an aliphatic carbon chain; R ９ represents an aromatic carbocycle, an aromatic carbocyclic alkyl chain, an aliphatic carbocycle, an aliphatic carbocyclic alkyl chain, or an aliphatic carbon chain; Z １ represents a nitrogen atom.) Includes three One of the three unit structures has three terminal Y ３ one of which is a thiol group (-SH) and the other two are sulfides (-S-), The other two of the three unit structures have three terminal Y ３ Among these, two are thiol groups (-SH) and the other is sulfide (-S-), A trimeric compound in which the sulfides (-S-) of three of the unit structures are bonded to each other via disulfide bonds (-S-S-). and, A water-soluble biomolecular compound having a thiol group (-SH), which is at least one selected from the group consisting of glutathione, thioredoxin, peroxiredoxin, and dithiothreitol (DTT). and, A cured product characterized by being a cured product of a composition comprising:

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