JP2022168750A - Epoxy resin composition, epoxy resin cured product, epoxy resin decomposable composition, recycled cured product, decomposition method of epoxy resin cured product, recycling method, monomer compound, dimer compound and trimer compound and cured product thereof - Google Patents

Abstract

An object of the present invention is to provide an epoxy resin composition whose cured epoxy resin can be decomposed and recycled (recured).
An epoxy resin comprising an epoxy resin monomer (A1) having epoxy groups at both ends and having a disulfide bond (--S--S--) and a curing agent (B) capable of bonding with the epoxy groups. A composition.
[Selection drawing] Fig. 1

Description

The present invention provides an epoxy resin composition, an epoxy resin cured product, an epoxy resin decomposable composition, a recycled cured product, a method for decomposing the cured epoxy resin product, a recycling method, a monomer compound, a dimer compound and a trimer compound. and its cured product.

Epoxy resins are one of the most common polymeric materials and are used in a wide variety of applications such as coatings, paints, primers, adhesives, and composites. In general, epoxy resins exhibit excellent heat resistance, mechanical properties, and chemical resistance due to their crosslinked polymer network structure, but they often have thermosetting properties, and their recyclability and reworkability are low. Therefore, epoxy resins and their composites are usually discarded by methods such as landfilling or incineration, which has a great adverse effect on the entire ecosystem. In particular, epoxy resins used in daily life are considered to be one of the sources of microplastics. Therefore, the development of a thermosetting epoxy resin that is decomposable and reusable is strongly desired.

For example, as a technique for decomposing epoxy resin cured products, Patent Document 1 describes a method of immersing a substrate coated with epoxy resin cured products in a cleaving agent solution containing biomolecules such as glutathione. .

JP 2013-535552 A

However, the method of Patent Literature 1 simply aims at decomposing the epoxy resin cured product, and the composition of the epoxy resin composition makes it difficult to recycle the decomposed product. That is, from the demand for the construction of an environment-friendly recycling system as described above, the epoxy resin composition not only allows the decomposition of the cured product, but also the recycled cured product in which the network structure is rebuilt from the decomposition product. It is required to be able to produce

The present invention has been made in view of the circumstances as described above, and an object of the present invention is to provide an epoxy resin composition that can be decomposed and recycled (re-cured) as a cured epoxy resin. In addition, the cured product of this epoxy resin composition, the epoxy resin decomposable composition, the recycled cured product, the decomposition method of the epoxy resin cured product, the recycling method, the monomer compound, the dimer compound and the trimer compound and their curing. The task is to provide goods.

In order to solve the above problems, the epoxy resin composition of the present invention is characterized by the following.

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

[2] The epoxy resin monomer (A1) contains a compound represented by the following formula.

（Ｘは、ジスルフィド結合（Ｓ－Ｓ）であり、Ｒ^１およびＲ^２は、同一または別異であって、芳香族炭素環、芳香族炭素環アルキル鎖、脂肪族炭素環、脂肪族炭素環アルキル鎖、または脂肪族炭素鎖を示す）

(X is a disulfide bond (S—S), R ¹ and R ² are the same or different and are aromatic carbocyclic ring, aromatic carbocyclic alkyl chain, aliphatic carbocyclic ring, aliphatic carbocyclic ring an alkyl chain, or an aliphatic carbon chain)

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

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

（Ｒ^３およびＲ^４は、同一または別異であって、芳香族炭素環、芳香族炭素環アルキル鎖、脂肪族炭素環、脂肪族炭素環アルキル鎖または脂肪族炭素鎖を示し、Ｒ^５およびＲ^６は、同一または別異であって、１級、２級または３級アミン、イミダゾール、酸無水物、有機酸ヒドラジドを示す）

(R ³ and R ⁴ 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, and R ⁵ and R ⁶ is the same or different and represents a primary, secondary or tertiary amine, imidazole, acid anhydride, organic acid hydrazide)

[5] The molar ratio (A1/A2) between the epoxy resin monomer (A1) and the epoxy resin monomer (A2) having no disulfide bond (-SS-) is 100/0 to 25/75. and
The curing agent is a curing agent (B1) represented by the following formula

（Ｒ^３およびＲ^４は、同一または別異であって、芳香族炭素環、芳香族炭素環アルキル鎖、脂肪族炭素環、脂肪族炭素環アルキル鎖または脂肪族炭素鎖を示し、Ｒ^５およびＲ^６は、同一または別異であって、１級、２級または３級アミン、イミダゾール、酸無水物、有機酸ヒドラジドを示す）
と、
ジスルフィド結合（－Ｓ－Ｓ－）を有していない前記硬化剤（Ｂ２）とを含み、
前記硬化剤（Ｂ１）と前記硬化剤（Ｂ２）のモル比（Ｂ１／Ｂ２）が、１００／０～０／１００である。

(R ³ and R ⁴ 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, and R ⁵ and R ⁶ is the same or different and represents a primary, secondary or tertiary amine, imidazole, acid anhydride, organic acid hydrazide)
When,
and the curing agent (B2) that does not have a disulfide bond (-SS-),
The molar ratio (B1/B2) of the curing agent (B1) and the curing agent (B2) is 100/0 to 0/100.

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

[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), and the molar ratio (A1/A2) is 100/0 to 50/50, and the molar ratio (A1:B1) of the epoxy resin monomer (A1) and the curing agent (B1) is 2:0.5 to 1:0.5.

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

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

The epoxy resin cured product of the present invention is characterized by the following.

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

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

[12] A repeating unit in which 2 equivalents of the epoxy resin monomer are combined with 1 equivalent of the curing agent.

The epoxy resin decomposable composition of the present invention is characterized by the following.

[13] The epoxy resin cured product of any one of [10] to [12];
and a water-soluble biomolecular compound having a thiol group (—SH).

The epoxy resin decomposition composition of the present invention is characterized by the following.

[14] Contains a hydroxythiol compound having a hydroxy group (-OH) and a thiol group (-SH), which is a decomposition reaction product of the epoxy resin decomposable composition of [13].

The recycled cured product of the present invention is characterized by the following.

[15] A recycled cured product of the epoxy resin decomposition composition of [14],
It contains the hydroxythiol compound and has an epoxy resin network structure.

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

[17] A cured product of the epoxy resin composition of [1],
FT-NIR detects unreacted thiol groups (-SH) that are not disulfonated.

The method for decomposing a cured epoxy resin product of the present invention is characterized by the following.

[18] The epoxy resin cured product of any one of [10] to [12] is brought into contact with a water-soluble biomolecular compound having a thiol group (-SH) in a two-phase solvent consisting of an aqueous phase and an organic phase. , producing a hydroxy thiol compound having a hydroxy group (-OH) and a thiol group (-SH) as a decomposition product in the organic phase;
including.

The method for recycling a cured epoxy resin material of the present invention is characterized by the following.

[19] the following steps:
The epoxy resin cured product of any one of claims 10 to 12 is brought into contact with a water-soluble biomolecular compound having a thiol group (—SH) in a two-phase solvent of an aqueous phase and an organic phase, and in the organic phase, Producing a hydroxy thiol compound having a hydroxy group (-OH) and a thiol group (-SH) as a decomposition product; -) including obtaining a cured product having an epoxy resin network structure containing.

The monomer compound of the present invention is characterized by the following.

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

（Ｒ^７およびＲ^８は、同一または別異であって、芳香族炭素環、芳香族炭素環アルキル鎖、脂肪族炭素環、脂肪族炭素環アルキル鎖、または脂肪族炭素鎖を示し、
Ｒ^９は、芳香族炭素環、芳香族炭素環アルキル鎖、脂肪族炭素環、脂肪族炭素環アルキル鎖または脂肪族炭素鎖を示し、
Ｚ^１は、窒素原子、ベンゼン、フェノールを示し、
Ｙ^１は、チオール基（－ＳＨ）を示す）

(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,
R ⁹ represents an aromatic carbocyclic ring, an aromatic carbocyclic alkyl chain, an aliphatic carbocyclic ring, an aliphatic carbocyclic alkyl chain or an aliphatic carbon chain;
Z ¹ represents a nitrogen atom, benzene, phenol,
Y ¹ represents a thiol group (-SH))

The dimeric compound of the present invention is characterized by the following.

[21] a unit structure represented by the following formula;

（Ｒ^７およびＲ^８は、同一または別異であって、芳香族炭素環、芳香族炭素環アルキル鎖、脂肪族炭素環、脂肪族炭素環アルキル鎖、または脂肪族炭素鎖を示し、
Ｒ^９は、芳香族炭素環、芳香族炭素環アルキル鎖、脂肪族炭素環、脂肪族炭素環アルキル鎖または脂肪族炭素鎖を示し、
Ｚ^１は、窒素原子、ベンゼン、フェノールを示し、
末端に位置する３つのＹ^２のうち、２つがチオール基（－ＳＨ）であり、他の１つがスルフィド（－Ｓ－）である）
を２つ含み、
２つの前記単位構造が、前記スルフィド（－Ｓ－）が連結したジスルフィド結合（－Ｓ－Ｓ－）を介して互いに結合している。

(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,
R ⁹ represents an aromatic carbocyclic ring, an aromatic carbocyclic alkyl chain, an aliphatic carbocyclic ring, an aliphatic carbocyclic alkyl chain or an aliphatic carbon chain;
Z ¹ represents a nitrogen atom, benzene, phenol,
Of the three Y2s located at the terminal, ^two are thiol groups (-SH) and the other is a sulfide (-S-))
contains two
The two unit structures are linked to each other via a disulfide bond (-SS-) linked by the sulfides (-S-).

The trimeric compound of the present invention is characterized by the following.

[22] a unit structure represented by the following formula;

（Ｒ^７およびＲ^８は、同一または別異であって、芳香族炭素環、芳香族炭素環アルキル鎖、脂肪族炭素環、脂肪族炭素環アルキル鎖、または脂肪族炭素鎖を示し、
Ｒ^９は、芳香族炭素環、芳香族炭素環アルキル鎖、脂肪族炭素環、脂肪族炭素環アルキル鎖または脂肪族炭素鎖を示し、
Ｚ^１は、窒素原子、ベンゼン、フェノールを示す。）
を３つ含み、
３つの前記単位構造のうちの一つは、末端に位置する３つのＹ^３のうち、１つがチオール基（－ＳＨ）であり、他の２つがスルフィド（－Ｓ－）であり、
３つの前記単位構造のうちの他の二つは、末端に位置する３つのＹ^３のうち、２つがチオール基（－ＳＨ）であり、他の１つがスルフィド（－Ｓ－）であり、
３つの前記単位構造の前記スルフィド（－Ｓ－）が連結したジスルフィド結合（－Ｓ－Ｓ－）を介して互いに結合している。

(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,
R ⁹ represents an aromatic carbocyclic ring, an aromatic carbocyclic alkyl chain, an aliphatic carbocyclic ring, an aliphatic carbocyclic alkyl chain or an aliphatic carbon chain;
Z1 represents ^a nitrogen atom, benzene, or phenol. )
contains three
One of the three unit structures has three terminally positioned 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 are, of the three Y ^3s located at the ends, two of which are thiol groups (—SH) and the other one is a sulfide (—S—),
The sulfides (--S--) of the three unit structures are linked to each other via a disulfide bond (--S--S--).

The cured product of the present invention is characterized by the following.

[23] A cured product of a composition containing the compound according to any one of [20] to [22].

The cured epoxy resin composition of the present invention can be decomposed and recycled. The cured product after recycling has the same mechanical strength as the cured product before recycling.

The cured epoxy resin composition and the decomposable epoxy resin composition of the present invention can be decomposed and recycled. It has strength.

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

The decomposition method and recycling method of the cured epoxy resin material of the present invention can decompose and recycle the cured epoxy resin material.

FIG. 2 is a diagram illustrating a scheme of mixing 2 equivalents of epoxy resin monomers (A1, A2) and 1 equivalent of curing agents (B1, B2) to obtain a cured epoxy resin. A scheme for obtaining an epoxy resin decomposition composition by reacting glutathione (a water-soluble biomolecular compound) on an epoxy resin cured product illustrated in FIG. FIG. 2 illustrates a scheme for recycling the . FIG. 1 shows the results of Fourier transform near-infrared spectroscopy (FT-NIR) on uncured and cured ERDs with combination (C1) shown in Table 1. FIG. FIG. 2 shows the results of quantitative evaluation of the reaction mixture by 1H-NMR spectroscopy in the degradation of ERD using glutathione (GSH). FIG. 2 shows the results of quantitative evaluation of the reaction mixture by 1H-NMR spectroscopy in the degradation of ERD using glutathione (GSH). FIG. 4 is a diagram showing the chemical reaction balance of CDCl ₃ phase and D ₂ O phase, respectively. It is the figure which put together the decomposition|disassembly result of ERD by the composition ratio of an epoxy resin monomer (A1 or A2) and a diamine hardening|curing agent (B1 or B2). FIG. 2 illustrates the structure of a cured epoxy resin product containing an epoxy resin monomer (BGPDS or DGEBA) and an amine curing agent (DTDA or DDM), and the structure of the cured epoxy resin product after decomposition. FIG. 1 shows the 1H-NMR spectrum of CDCl ₃ phase after removal of tributylphosphine (TBP). FIG. 4 shows the FT-IR spectrum of the decomposed soluble portion of ERD-C1 in CHCl ₃ phase. FIG. 4 shows the results of UV-vis spectra of CHCl ₃ phase measured at 254 nm over time. It is a figure which shows the result of having done the swelling test of ERD before recycling and ERD after recycling. FIG. 4 is a diagram showing normalized stress relaxation of a cured epoxy resin material before recycling and a cured epoxy resin material after recycling. FIG. 2 is a diagram showing how the CFRP structure using the ERD matrix of Example 1 is disassembled and recycled.

Hereinafter, one embodiment of the epoxy resin composition, the epoxy resin cured product, the epoxy resin decomposable composition, the recycled cured product, the decomposition method of the epoxy resin cured product, and the recycling method of the present invention will be described.

In this specification, a numerical range represented by "-" means a range including the numerical values before and after "-" as lower and upper limits.

In addition, in the notation of a group (atom group) in the present specification, the notation that does not describe substituted or unsubstituted refers to those not having a substituent and those having a substituent within a range that does not impair the effects of the present invention. also includes

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

The epoxy resin composition of the present invention includes, as epoxy resin monomers, an epoxy resin monomer (A1) having a disulfide bond (-S-S-) and an epoxy resin having no disulfide bond (-S-S-). Monomer (A2) can be included (hereinafter, sometimes simply referred to as "epoxy resin monomer (A1)" and "epoxy resin monomer (A2)").
Specific structures of the epoxy resin monomer (A1) and the epoxy resin monomer (A2) are not particularly limited, but examples include glycidyl ether type (bisphenol A type, bisphenol F type, novolac type, alcohol type, etc.), glycidyl ester type ( Examples include hydrophthalic acid type, dimer acid type, etc.), glycidylamine type (aromatic amine type, aminophenol type, etc.), oxidized type (alicyclic type, etc.), and the like.

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

ここで、エポキシ樹脂モノマー（Ａ１）において、化学式（１）中のＸは、ジスルフィド結合（Ｓ－Ｓ）であり、Ｒ^１およびＲ^２は、同一または別異であって、芳香族炭素環、芳香族炭素環アルキル鎖、脂肪族炭素環、脂肪族炭素環アルキル鎖、または脂肪族炭素鎖である。

Here, in the epoxy resin monomer (A1), X in the chemical formula (1) is a disulfide bond (S—S), R ¹ and R ² are the same or different, and are aromatic carbocyclic rings, It is an aromatic carbocyclic alkyl chain, an aliphatic carbocyclic ring, an aliphatic carbocyclic alkyl chain, or an aliphatic carbon chain.

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.

Further, the epoxy resin monomer (A2) does not have the symbol X indicating the disulfide bond (S—S) in the above chemical formula (1), and the R ¹ and R ² sites are the same as the epoxy resin monomer (A1). may be an aromatic carbocyclic ring, an aromatic carbocyclic alkyl chain, an aliphatic carbocyclic ring, an aliphatic carbocyclic alkyl chain, or an aliphatic carbon chain.

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

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. More preferably, it is 100/0 to 75/25. When the molar ratio (A1/A2) is within this range, the cured epoxy resin composition can be decomposed and recycled.

In addition, the epoxy resin composition includes, as the curing agent (B), a curing agent (B1) having a disulfide bond (-S—S—) and a curing agent (B2) having no disulfide bond (—S—S—). One or two or more of these can be used (hereinafter sometimes simply referred to as "curing agent (B1)" and "curing agent (B2)").
The curing agent (B1) and curing agent (B2) are not particularly limited as long as they can bond with epoxy groups, and examples include polyamines (including diamines), modified polyamines, acid anhydrides, hydrazine derivatives, polyphenols, and the like. be able to.

For example, as polyamine-based curing agents, aliphatic polyamines, alicyclic polyamines, aromatic polyamines, and the like can be exemplified. Examples of aliphatic polyamines include diethylenetriamine, triethylenetetramine, tetraethylenepentamine, m-xylenediamine, trimethylhexamethylenediamine, 2-methylpentamethylenediamine, and diethylaminopropylamine. Examples of alicyclic polyamines include isophorone diamine, 1,3-bisaminomethylcyclohexane, bis(4-aminocyclohexyl)methane, norbornene diamine, 1,2-diaminocyclohexane, and lalomine. Examples of aromatic polyamines include diaminodiphenylmethane, metaphenylenediamine, diaminodiphenylsulfone, and the like. Acid anhydrides include hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, hydrogenated methylnadic anhydride, trialkyltetrahydrophthalic anhydride, and methylcyclohexenetetracarboxylic acid. Examples include dianhydride, trimellitic anhydride, pyromellitic anhydride, benzophenonetetracarboxylic dianhydride, and aliphatic dibasic acid polyanhydride. Examples of polyphenol-based curing agents include phenol novolak, xylene novolak, bis A novolak, triphenylmethane novolak, biphenyl novolak, dicyclopentadienephenol novolak, and terpenephenol novolak.

Among them, the curing agent (B1) is preferably a compound represented by the following chemical formula.

ここで、硬化剤（Ｂ１）において、Ｒ^３およびＲ^４は、同一または別異であって、芳香族炭素環、芳香族炭素環アルキル鎖、脂肪族炭素環、脂肪族炭素環アルキル鎖または脂肪族炭素鎖を示す。また、Ｒ^５およびＲ^６は、同一または別異であって、１級、２級、３級アミン、イミダゾール、酸無水物、有機酸ヒドラジドを示す。

Here, in the curing agent (B1), R ³ and R ⁴ are the same or different and are aromatic carbocyclic rings, aromatic carbocyclic alkyl chains, aliphatic carbocyclic rings, aliphatic carbocyclic alkyl chains or aliphatic indicates a group carbon chain. R5 and ^R6 are the ^same or different and represent primary, secondary or tertiary amine, imidazole, acid anhydride or organic acid hydrazide.

Among them, diamine curing agents are more preferable, and 4,4'-dithiodianiline (DTDA), cystamine, cystine dimethyl ester, and cystine diethyl ester are particularly preferable.

More preferably, the curing agent (B2) is also a diamine curing agent. can be anything. Specifically, the curing agent (B2) is more preferably diaminodiphenylmethane (DDM), ethylenedimine, diethylenetriamine, triethylenetetramine, norbornanediamine.

Further, the molar ratio (B1/B2) of the curing agent (B1) and the curing agent (B2) is 100/0 to 0/100. That is, it may be a form containing at least one of the curing agent (B1) and the curing agent (B2), and the ratio of the curing agent (B1) and the curing agent (B2) is the epoxy resin monomer (A1) and the epoxy It can be appropriately set according to the ratio of the resin monomer (A2). Among them, the molar ratio (B1/B2) is preferably 100/0 to 25/75, more preferably 100/0 to 50/50, and 100/0 to 75/25. More preferred.

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

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

When 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) is preferably 2:0.5 to 1:0.5.

When the content of the curing agent (B1) in the curing agent (B) is less than 50/50 to 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) is preferably 2:0.25 to 1.5:0.25.

When 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 preferably the molar ratio (A1:B1) is 2:0.01 to 1.5:0.25 or 1:0.

INDUSTRIAL APPLICABILITY The cured epoxy resin composition of the present invention can be decomposed and reused, and an environmentally friendly recycling system can be constructed.

(Epoxy resin cured product)
The epoxy resin cured product of the present invention is a cured product of the epoxy resin composition of the present invention described above. Moreover, below, the epoxy resin hardened|cured material which has a disulfide bond may be described as "ERD."

The curing method and conditions for obtaining the epoxy resin cured product are not particularly limited, and known methods and conditions can be appropriately employed. Specifically, for example, an epoxy resin monomer and a curing agent are mixed in a predetermined ratio, and the mixture is cured by heating at 90 to 200° C. while stirring or the like as necessary.

The structure of the cured epoxy resin product of the present invention is not specifically limited, but the proportion of disulfide bonds (-S-S-) is preferably 1 equivalent or more with respect to the repeating units of the epoxy resin. It is more preferable that it is equivalent or more.

Moreover, it is preferable to include a repeating unit in which 2 equivalents of an epoxy resin monomer are bonded to 1 equivalent of a curing agent.

FIG. 1 is a diagram illustrating a scheme for mixing 2 equivalents of epoxy resin monomers (A1, A2) and 1 equivalent of curing agents (B1, B2) to obtain a cured epoxy resin.

For example, as illustrated in FIG. 1, when using diglycidyl ether of bisphenol A (DGEBA) as A1 and 4,4'-dithiodianiline (DTDA) as B1, curing agent (B1) 1 It is possible to obtain an epoxy resin cured product (ERD) containing repeating units in which 2 equivalents of the epoxy resin monomer (A1) are combined with respect to the equivalent weight. In addition, in this epoxy resin cured product (ERD), the ratio of disulfide bonds (-S-S-) is 3 equivalents with respect to the repeating unit of the epoxy resin (X=S-S, Y=S-S). .

Since the epoxy resin cured product of the present invention contains a disulfide bond (-S-S-) in a predetermined proportion in the repeating unit of the epoxy resin, it can be decomposed and reused, and an environmentally friendly recycling system can be constructed. be able to.

(Epoxy resin decomposing composition, method for decomposing epoxy resin cured product, and epoxy resin decomposing composition)
The epoxy resin-degradable composition of the present invention contains the cured epoxy resin of the present invention and a water-soluble biomolecular compound having a thiol group (--SH).

Examples of water-soluble biomolecular compounds having a thiol group (-SH) include one or more of glutathione, thioredoxin, peroxiredoxin, dithiothreitol (DTT) and the like. Among them, glutathione is preferable from the viewpoint of the decomposability and water solubility of the epoxy resin.

The epoxy resin-degradable composition of the present invention may contain a cured epoxy resin (ERD) and a water-soluble biomolecular compound having a thiol group (—SH) in a two-phase solvent consisting of an aqueous phase and an organic phase. can.

The organic solvent constituting the organic phase may be a known material, for example, aromatic hydrocarbons such as benzene, tert-butylbenzene, chlorobenzene, or substituted products thereof, cyclohexane, n-hexane, n-pentane, n Examples include aliphatic hydrocarbons such as -octane, and chlorinated aliphatic hydrocarbons such as carbon tetrachloride, chloroform, dichloromethyl, and dichloroethane.

In the epoxy resin-degradable composition of the present invention, the disulfide bond (-S-S-) of the cured epoxy resin (ERD) is cleaved by the action of the thiol group (-SH) of the water-soluble biomolecular compound. The cured epoxy resin can be reliably decomposed.

In the method for decomposing the cured epoxy resin product of the present invention, the cured epoxy resin product (ERD) of the present invention is treated with a water-soluble biomolecular compound having a thiol group (—SH) in a two-phase solvent consisting of an aqueous phase and an organic phase. to produce a hydroxythiol compound having a hydroxy group (--OH) and a thiol group (--SH) as a decomposition product in the organic phase.

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

In a two-phase solvent of an aqueous phase and an organic phase, by contacting the epoxy resin cured product (ERD) with a water-soluble biomolecular compound having a thiol group (-SH), a thiol-disulfide exchange reaction occurs in the epoxy resin. dynamic disulfide bonds are cleaved and exchanged with SH bonds of water-soluble biomolecules such as glutathione. Thereby, the decomposed epoxy resin (epoxy resin decomposition composition) residue can be dissolved in the organic phase. On the other hand, exchange products such as glutathione, for example, can be dissolved in the aqueous phase due to the presence of hydrophilic groups.

Therefore, the epoxy resin-decomposing composition of the present invention contains a hydroxythiol compound having a hydroxy group (--OH) and a thiol group (--SH), which is a decomposition reaction product of the epoxy resin-decomposing composition.

Specifically, for example, when the epoxy resin monomer of the chemical formula (1) and the curing agent of the chemical formula (2) are used, the epoxy resin decomposition composition has a unit structure represented by the following chemical formula (3): A compound (eg, a monomeric compound, a dimeric compound, a trimeric compound) containing can be obtained.

化学式（３）において、Ｒ^７およびＲ^８は、同一または別異であって、芳香族炭素環、芳香族炭素環アルキル鎖、脂肪族炭素環、脂肪族炭素環アルキル鎖、または脂肪族炭素鎖を示す。Ｒ^９は、芳香族炭素環、芳香族炭素環アルキル鎖、脂肪族炭素環、脂肪族炭素環アルキル鎖または脂肪族炭素鎖を示している。Ｚ^１は、窒素原子、ベンゼン、フェノールなどを示している。Ｙは、チオール基（－ＳＨ）またはスルフィド（－Ｓ－）を示している。

In chemical formula (3), R ⁷ and R ⁸ are the same or different and are an aromatic carbocyclic ring, an aromatic carbocyclic alkyl chain, an aliphatic carbocyclic ring, an aliphatic carbocyclic alkyl chain, or an aliphatic carbon chain. indicates R ⁹ represents an aromatic carbocyclic ring, an aromatic carbocyclic alkyl chain, an aliphatic carbocyclic ring, an aliphatic carbocyclic alkyl chain or an aliphatic carbon chain. Z1 represents ^a nitrogen atom, benzene, phenol, or the like. Y represents a thiol group (--SH) or a sulfide (--S--).

When the epoxy resin decomposition composition is a monomer compound,

化学式（４）において末端に位置する３つのＹ^１は、全てがチオール基（－ＳＨ）である。

All of the three Y ^1s located at the ends in chemical formula (4) are thiol groups (--SH).

When the epoxy resin decomposition composition is a dimer compound,

化学式（５）において末端に位置する３つのＹ^２のうち、２つがチオール基（－ＳＨ）であり、他の１つがスルフィド（－Ｓ－）であり、この化学式（５）で示される２つの単位構造の前記スルフィド（－Ｓ－）が連結したジスルフィド結合（－Ｓ－Ｓ－）を介して互いに結合している。

Of the three Y ^2s located at the ends in chemical formula (5), two are thiol groups (-SH) and the other is sulfide (-S-), and the two The sulfides (--S--) of the unit structure are linked to each other via disulfide bonds (--S--S--).

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

化学式（６）において末端に位置する３つのＹ^３のうち、１つがチオール基（－ＳＨ）であり、他の２つがスルフィド（－Ｓ－）である。また、三量体化合物を構成する他の２つの単位構造は、化学式（６）において末端に位置する３つのＹ^３のうち、２つがチオール基（－ＳＨ）であり、他の１つがスルフィド（－Ｓ－）である。三量体化合物は、これら３つの単位構造の前記スルフィド（－Ｓ－）が連結したジスルフィド結合（－Ｓ－Ｓ－）を介して互いに結合している。

Of the three Y ^3s located at the ends in chemical formula (6), one is a thiol group (--SH) and the other two are sulfides (--S--). In addition, the other two unit structures constituting the trimer compound are, of the three Y ^3s located at the ends in the chemical formula (6), two are thiol groups (—SH) and the other one is a sulfide ( -S-). The trimeric compound is linked to each other via a disulfide bond (-S-S-) connecting the sulfides (-S-) of these three unit structures.

FIG. 2 shows a scheme for obtaining an epoxy resin decomposition composition by reacting glutathione (a water-soluble biomolecular compound) on the epoxy resin cured product illustrated in FIG. 1 to cleave disulfide bonds (—S—S—) and its epoxy It is the figure which illustrated the scheme which recycles a resin decomposition composition. In this embodiment, an epoxy resin decomposition composition represented by the following chemical formula (7) is obtained.

化学式（７）においては、化学式（３）と同様に、末端のＹは、チオール基（－ＳＨ）または、スルフィド（－Ｓ－）を示している。

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

For example, such monomeric, dimeric and trimeric compounds have good solubility in organic phases. A composition containing such a monomer compound, a dimer compound and a trimer compound can be cured by heat treatment to obtain a cured product.

The epoxy resin-decomposing composition of the present invention can be cured to be reused as a cured product, and an environment-friendly recycling system can be constructed. In addition, the cured product (recycled cured product) has mechanical strength substantially equal to that of the initial epoxy resin cured product.

(Recycling method and recycled hardened material)
The recycling method of the present invention includes the following steps.

The epoxy resin cured product of the present invention is brought into contact with a water-soluble biomolecular compound having a thiol group (—SH) in a two-phase solvent of an aqueous phase and an organic phase, and a hydroxy group is added as a decomposition product in the organic phase. Producing a hydroxythiol compound having (--OH) and a thiol group (--SH) (first step).

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

The first step is the same as the method for decomposing the epoxy resin cured product of the present invention described above, so the explanation is omitted.

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

According to the recycling method of the present invention, a recycled cured product of an epoxy resin decomposition composition containing a hydroxythiol compound and having an epoxy resin network structure is obtained.

The recycled cured product of the present invention has an epoxy resin network structure common to that of the epoxy resin cured product before recycling, but contains unreacted thiol groups (—SH) that were not disulfonated during recycling. Specifically, for example, Fourier transform infrared spectroscopy (FT-NIR) detects an absorption band derived from a thiol group (--SH) near 2500 cm.sup. ^-1 .

Since the recycled cured product of the present invention has substantially the same mechanical strength as the epoxy resin cured product before recycling, it can be applied to various uses.

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

For example, the epoxy resin composition can contain known curing accelerators and the like as compounds other than the above compounds. Further, for example, the epoxy resin composition cured product and the recycled cured product may be in the form of carbon fiber reinforced plastic (CFRP) containing carbon fiber.

The epoxy resin composition, the cured epoxy resin, the decomposable epoxy resin composition, the cured cured product for recycling, the method for decomposing the cured epoxy resin, and the recycling method of the present invention will be described below together with examples. is not limited to the examples.

<Example 1> Synthesis of epoxy resin cured product (ERD) Bis (4-glycidyloxyphenyl) disulfide (BGPDS, A1) as an epoxy resin monomer, 4,4'-dithiodianiline (BGPDS, A1) as a curing agent (diamine curing agent) DTDA, B1) was used to prepare an epoxy resin cured product (ERD) (Fig. 1).

Specifically, to demonstrate the thiol-disulfide exchange reaction, diglycidyl ether of bisphenol A (DGEBA, A2) and diamino Diphenylmethane (DDM, B2) was employed respectively. It was assumed that the chemical reactivities of the aromatic disulfides in the epoxy resin monomer and the diamine curing agent were almost the same. ERDs were prepared by combining an epoxy resin monomer (either A1 or A2) with a diamine curing agent (either B1 or B2).

Detailed combinations of epoxy resin monomer (A1 or A2) and diamine curing agent (B1 or B2) are shown in Table 1.

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 precured mixture was transferred to a polytetrafluoroethylene mold and cured at 120° C., 140° C., and 160° C. for 2 hours in sequence. After cooling, ERD was obtained as a brown solid. In addition, C25 in Table 1 is used as a control in the form containing no disulfide bond.

Fourier transform near-infrared spectroscopy (FT-NIR) was performed to monitor the curing process. FIG. 3 shows examples of uncured and cured ERDs with the combination (C1) shown in Table 1. In the nIR region from 7200−4000 cm ⁻¹ , the bands associated with epoxy resin monomers and primary amines are the combination band of the C–H stretching vibration and the double overtone of the epoxy ring stretching vibration (about 4530 cm ⁻¹ ) and the NH stretching band. It was observed as a combination band of vibration and bending (approximately 5000-5100 cm ^-1 ).

Thus, the epoxy resin monomer was reduced during the curing process, resulting in a decrease in the C—H stretching vibrational band from about 4530 cm ⁻¹ and a decrease in the terminal CH ₂ weak overtone from about 6060 cm ⁻¹ . The primary amine binding band at 5000 cm ^-1 also decreased. On the other hand, the OH overtone band at 7000 cm ^-1 increased. The OH overtone band at 7000 cm ^-1 increased as a result of the oxirane ring-opening reaction.

Example 2 Degradation of ERD with Glutathione (GSH) Prior to demonstrating the degradation of ERD with glutathione (GSH), degradation experiments were performed using small molecules containing disulfides in a water-organic binary system. gone. DTDA was chosen here as a model for disulfide-containing molecules. DTDA and GSH were dissolved in deuterated chloroform (CDCl ₃ ) (250 mM) and deuterated water (D ₂ O) (250 mM), respectively. The solutions were mixed 1:1 (v/v) and stored in the dark covered with aluminum foil to avoid unintended light-induced reactions.

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

Figures 4(a) and (b) showed the time course of 1H-NMR spectra of the CDCl ₃ phase and D ₂ O phase, respectively. In the CDCl ₃ phase, the 1H-NMR signals of the aromatic rings of DTDA (a) and (b) appear at 6.55 ppm and 7.22 ppm, and the 1H-NMR signal at 7.12 ppm is presumed to be the reducing agent of DTDA. It was identified as the aromatic ring (b') of 4-aminobenzenethiol (4-ABT) (Fig. 4(a)). Also, no peaks were observed in the 2-3 ppm range, suggesting the absence of GSH and reactants with GSH in the CDCl ₃ phase.

On the other hand, in the D ₂ O phase, a new 1H-NMR signal (e′) appeared at 3.12 ppm, suggesting the formation of an S—S bond between GSH and 4-ABT (Fig. 4(b)).

In addition, the 1H-NMR peaks (c) and (d) appear at 7.15 ppm and 7.5 ppm, and the intensity increases at the same time as the peak (e'). It was suggested that the product GSH-ABT was produced. Also, there was no significant change in peak intensity between 7.25 ppm and 7.5 ppm, suggesting that a small amount of DTDA was dissolved in the aqueous phase. It was confirmed that the solubility of DTDA in water was improved compared to the diphenyl disulfide shown in FIG. 5, and the exchange reaction between the thiol bond of GSH and the disulfide bond of DTDA was promoted.

Next, the time evolution of composition in CDCl ₃ /D ₂ O was further evaluated. FIG. 4(c) shows the conversion rates of DTDA and 4-aminobenzenethiol calculated from the peak areas of 1H-NMR signal (b) and signal (b′) in CDCl ₃ , respectively.

As a result, DTDA decreased immediately with time and reached equilibrium at 60 minutes. Correspondingly, 4-ABT started to form soon after stirring and reached equilibrium after 60 minutes, in contrast to DTDA.

Similarly, FIG. 4(d) shows the time evolution of the decrease of GSH and the increase of water-soluble reactants of GSH and 4-ABT in the D ₂ O phase. Similar to the CDCl ₃ phase, the increase in GSH and decrease in the water-soluble reactants of GSH/4-ABT tended to change symmetrically, reaching equilibrium at approximately 60 minutes.

In addition, the molar ratio of increase and decrease in composition was kept at 30 mol% for both CDCl ₃ phase and D ₂ O phase.

Based on these results, the chemical reaction balance between the CDCl ₃ phase and the D ₂ O phase is shown in FIG. A thiol disulfide exchange reaction between DTDA and GSH occurs at the interface of CDCl ₃ and D ₂ O to form a water-soluble reactant of GSH and 4-ABT (GSH-ABT), and unreacted 4-ABT dissolves in CDCl ₃ remained.

Since it was confirmed that the thiol-disulfide exchange reaction proceeds in the CHCl ₃ /water binary system mediated by GSH, ERD degradation tests were performed under the same binary system conditions.

First, the ERD was pulverized by a ball milling method at a frequency of 25 Hz for 1 hour. The obtained ERD powder was suspended in CHCl ₃ and GSH aqueous solution (20 mM) was added. Here, tributylphosphine (TBP) (10 mol%) was used to facilitate the thiol-disulfide exchange reaction. The 1H-NMR spectrum of the TBP-added low-molecular-weight model shown in FIG. 5 indicated that the product produced by the thiol-disulfide exchange reaction was the same as when TBP was not added.

The binary solution was then vigorously stirred at room temperature. After a certain period of time, the ERD was completely dissolved in the CHCl ₃ phase and separated into a yellow solution and a precipitate.

FIG. 7 is a diagram summarizing the ERD decomposition results by the composition ratio of the epoxy resin monomer (A1 or A2) and the diamine curing agent (B1 or B2). Also, in FIG. 7, molar equivalents of disulfide bonds in each repeating unit of ERD by various combinations of BGPDS/DGEBA (A1/A2) and DTDA/DDM (B1/B2) are summarized.

As shown in FIG. 7, it was confirmed that ERD was completely dissolved in C1-C13 and C16. Alternatively, an amine curing agent (DTDA or DDM) can be reacted with two equivalents of an epoxy resin monomer (BGPDS or DGEBA), which, as shown in the structural formula of FIG. It was suggested that up to 3 equivalents of units could be introduced. And from the completely dissolved part, a viscous yellow liquid was obtained after removing the _CHCl3 solvent under vacuum.

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

FIG. 9 shows the 1H-NMR spectrum of the CDCl ₃ phase after removal of tributylphosphine (TBP), showing purely cleaved ERD-C1.

In this spectrum, the signal of the aromatic ring of the degraded ERD was detected in the range of 6.5-7.5 ppm. Also, the peak at 3.0 to 4.0 ppm was associated with alkyl protons generated by the ring-opening reaction of the epoxy group. Also, no peaks were detected in the range of 2.0-3.0 ppm, demonstrating the absence of GSH and exchange products in the CDCl ₃ phase. Moreover, no signal was confirmed in the range of 1.0 to 1.5 ppm, and tributylphosphine was completely removed. From this, as shown in FIG. 2, ERD was decomposed into soluble oligomers, but it became clear that the epoxy structure was maintained.

Furthermore, FIG. 10 shows the FT-IR spectrum of the decomposed soluble portion of ERD-C1 in CHCl ₃ phase. As shown in FIG. The NIR region up to ~7500 cm ^-1 was almost the same as the ERD spectrum. This indicates that this liquid residue retains the epoxy structure of ERD. On the other hand, a new thiol-derived absorption band appeared at 2550 cm ^-1 (Fig. 10(b)). This indicates that this fragment contains a thiol group due to reduction of the ERD disulfide group by GSH.

Here, ERD solubility can be discussed in terms of the stoichiometric ratio of disulfide groups and ERD repeat units (FIG. 7). When the disulfide groups were more than 1.5 equivalents to the repeat units of ERD _, ERD was completely dissolved in CHCl3 and ERD was decomposed into dimer units or monomer units. On the other hand, it was confirmed that when the stoichiometric ratio of disulfide groups is less than 1.5 equivalents, most of the repeating units are trimers or higher, and precipitates are generated.

Furthermore, to investigate the degradation tendency of ERD, the UV-vis spectrum of CHCl ₃ phase was measured at 254 nm over time (Fig. 11).

When a suspension of ERD-C1 in CHCl ₃ was mixed with GSH/water solution, the UV absorption at 245 nm increased immediately and followed a saturation curve. A plateau region with a constant value was reached after 4 hours, suggesting that ERD-C1 was completely dissolved in the CHCl ₃ phase. ERD resolution was positively correlated with the number of disulfide bonds in the epoxy resin.

<Example 3> Rework test In general, amine-curable epoxy resins are considered to have a network structure with amine bonds as cross-linking points. can also be considered. Therefore, it was thought that even if ERD was decomposed and regenerated by forming disulfide bonds, the structure and physical properties of ERD as the original amine-curable epoxy resin would not change.

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. As a result of FT-NIR measurement, it became clear that the recycled ERD was cured by forming disulfide bonds. From this, the decomposed yellow liquid contained thiol groups, and after curing (after recycling), the 2550 cm ^-1 peak corresponding to the thiol groups almost disappeared (Fig. 10b). It was possible to confirm the presence of a slight thiol group in the recycled ERD by FT-NIR measurement.

Furthermore, dynamic mechanical analysis (DMA) was performed to evaluate the thermal and mechanical properties of the disulfide-containing epoxy resins before and after recycling. Table 2 shows the results.

Regarding mechanical properties, it was confirmed that the storage modulus of the original ERD before recycling was 1.8 GPa, which is equivalent to the conventional epoxy resin (1.88 GPa) without disulfide bonds. . It was confirmed that the storage modulus of ERD after recycling was maintained at about 90% of the initial value at room temperature.

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

In addition, in order to evaluate the crosslink density before and after recycling, a swelling test was performed on the ERD before and after recycling. The results are shown in FIG.

As shown in FIG. 12, the swelling rate after immersion in toluene at room temperature for 72 hours was about 3% for the initially cured product, while it was 13 to 16% for the recycled cured product. This result indicates that the cross-linking density of ERD after recycling does not completely return to the original structure, causing a decrease in glass transition temperature and mechanical strength at room temperature (from 1.8 GPa to 1.6 GPa). , causing an increase in rubbery storage modulus (from 14.3 MPa to 49.9 MPa).

FIG. 13 shows the normalized stress relaxation at 130° C. of the cured epoxy resin before recycling and the cured epoxy resin after recycling. Stress relaxation time was defined as the time required to release 63% of the initial stress based on the Maxwell model equation. As a result, the stress relaxation time at 130° C. of the recycled epoxy resin cured product was 152 seconds, and it was confirmed that the recycled epoxy resin cured product required a shorter time to relax 63% of the initial stress. As a result, it was confirmed that the regenerated network of the recycled epoxy resin cured product exhibits stress relaxation equal to or higher than Tg as a general dynamic network resulting from reformation of dynamic disulfide bonds. In addition, it was confirmed that since the recycled epoxy resin cured product has a relatively low Tg, segment chain motion occurs at low temperatures, the exchange reaction speeds up, and stress relaxation occurs.

<Example 4> Recycling of CFRP Carbon fiber reinforced plastic (CFRP) is a structural material that is attracting attention in fields where weight reduction and creep resistance are required, such as aircraft and automobiles. In general, a thermosetting resin such as epoxy is used as the matrix resin of the CFRP structure, which makes rework and recycling difficult, and the problem of waste disposal has become apparent.

Therefore, a recycling system for CFRP structures using the ERD matrix of Example 1 was examined.

A carbon fiber reinforced structure (CFRP) was produced by the following procedure.

First, place a carbon fiber cloth on an aluminum plate with polytetrafluoroethylene tape, and prepare epoxy resin monomer (BGPDS) and diamine curing agent (DTDA) in a glass vial so that the molecular ratio is 2:1. and mixed for 30 minutes at 90°C. After mixing, the mixture was poured onto a cloth-covered aluminum plate and surrounded by another aluminum plate covered with polytetrafluoroethylene tape. The resulting samples and molds were cured in an oven at 120° C. for 2 hours, 140° C. for 2 hours, 160° C. for 2 hours and finally cooled in the oven to room temperature.

Then, the cured CFRP structure was fixed with a clip in two liquids, an aqueous phase and an organic phase (CHCl ₃ phase) (FIGS. 14(a) and 14(b)). The ERD, which is the matrix of the CFRP structure, was decomposed into the CHCl ₃ phase by vigorously stirring for 24 hours under atmosphere (Fig. 14(c)). After dissolving the matrix, the carbon fibers were completely recovered by washing with water and acetone and drying at 100° C. (FIG. 14(d)). On the other hand, a decomposed epoxy residue dissolved in a chloroform solution (decomposed epoxy resin composition) was obtained by evaporation of the solvent (FIG. 14(e)). This epoxy residue could be easily transferred to the epoxy resin network by forming a disulfide bond (FIG. 14(f)).

As described above, we proposed a rework/recycle system for epoxy resins with disulfide bonds. First, by introducing a dynamic S—S bond, an epoxy resin cured material having recyclable and reworkable disulfide bonds was obtained. Next, by thiol-disulfide exchange reaction, dynamic disulfide bonds in the epoxy resin are cleaved and exchanged with SH bonds of water-soluble biomolecules such as glutathione, resulting in decomposed epoxy resin (decomposed composition) residues. could be dissolved in chloroform, and the exchange product was confirmed to be distributed in the aqueous phase due to the presence of hydrophilic peptide groups on glutathione. Finally, the epoxy residue having SH bonds was heated to obtain a recycled epoxy resin cured material having an epoxy resin network structure containing disulfide. The recycled epoxy resin cured product obtained in this way maintains about 90% of the mechanical strength of the original epoxy resin, and therefore has the potential to be applied to various uses. In addition, this method has the potential to be applied to carbon fiber reinforced composite materials, which may expand the range of reuse of both implants and matrix resins.

Claims (23)

an epoxy resin monomer (A1) having an epoxy group at both ends and having a disulfide bond (-S-S-);
a curing agent (B) capable of bonding with an epoxy group;
An epoxy resin composition comprising: 2. The epoxy resin composition according to claim 1, wherein the epoxy resin monomer (A1) contains a compound represented by the following formula.

(X is a disulfide bond (S—S), R ¹ and R ² are the same or different and are aromatic carbocyclic ring, aromatic carbocyclic alkyl chain, aliphatic carbocyclic ring, aliphatic carbocyclic ring an alkyl chain, or an aliphatic carbon chain) 3. The epoxy resin composition according to claim 1, wherein the curing agent has a disulfide bond (--S--S--). 4. The epoxy resin composition according to claim 3, wherein the curing agent contains a curing agent (B1) represented by the following formula.

(R ³ and R ⁴ 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, and R ⁵ and R ⁶ is the same or different and represents a primary, secondary or tertiary amine, imidazole, acid anhydride, organic acid hydrazide) The molar ratio (A1/A2) between the epoxy resin monomer (A1) and the epoxy resin monomer (A2) having no disulfide bond (-SS-) is 100/0 to 25/75,
The curing agent is a curing agent (B1) represented by the following formula

(R ³ and R ⁴ 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, and R ⁵ and R ⁶ is the same or different and represents a primary, secondary or tertiary amine, imidazole, acid anhydride, organic acid hydrazide)
When,
and the curing agent (B2) that does not have a disulfide bond (-SS-),
The molar ratio (B1/B2) of the curing agent (B1) and the curing agent (B2) is 100/0 to 0/100.
3. The epoxy resin composition according to claim 1 or 2, characterized by: The content of the curing agent (B1) in the curing agent (B) exceeds 75/25 in the molar ratio (B1/B2), and the molar ratio (A1/A2) is 100/0 to 25/75. and the molar ratio (A1:B1) of the epoxy resin monomer (A1) and the curing agent (B1) is 2:1 to 0.5:1. Resin composition. The content of the curing agent (B1) in the curing agent (B) is 75/25 to 50/50 in the molar ratio (B1/B2), and the molar ratio (A1/A2) is 100/0. to 50/50, and the molar ratio (A1:B1) of the epoxy resin monomer (A1) and the curing agent (B1) is 2:0.5 to 1:0.5. The epoxy resin composition of claim 5. The content of the curing agent (B1) in the curing agent (B) is less than 50/50 to 25/75 in the molar ratio (B1/B2), and the molar ratio (A1/A2) is 100/ 0 to 75/25, and the molar ratio (A1:B1) of the epoxy resin monomer (A1) and the curing agent (B1) is 2:0.25 to 1.5:0.25. The epoxy resin composition of claim 5, characterized by: The content of the curing agent (B1) in the curing agent (B) is less than 25/75 in the molar ratio (B1/B2), and the molar ratio (A1/A2) is 100/0 to 75/ 25, and the molar ratio (A1:B1) of the epoxy resin monomer (A1) and the curing agent (B1) is 2:0.01 to 1.5:0.25 or 1:0 The epoxy resin composition of claim 5, characterized by: A cured epoxy resin product, which is a cured product of the epoxy resin composition according to any one of claims 1 to 9. 11. The epoxy resin cured product according to claim 10, wherein the proportion of disulfide bonds (-S-S-) is 1 equivalent or more with respect to the repeating units of the epoxy resin. 12. The epoxy resin cured product according to claim 10 or 11, comprising a repeating unit in which 2 equivalents of said epoxy resin monomer are combined with 1 equivalent of said curing agent. The epoxy resin cured product according to any one of claims 10 to 12,
and a water-soluble biomolecular compound having a thiol group (--SH). 14. An epoxy resin-decomposing composition comprising a hydroxythiol compound having a hydroxy group (--OH) and a thiol group (--SH), which is a decomposition reaction product of the epoxy resin-decomposing composition according to claim 13. A recycled cured product of the epoxy resin decomposition composition of claim 14,
A recycled cured product comprising the hydroxy thiol compound and having an epoxy resin network structure. 16. The recycled cured product of claim 15, wherein FT-NIR detects unreacted thiol groups (--SH) that are not disulfonated. A cured product of the epoxy resin composition of claim 1,
A cured product characterized in that unreacted thiol groups (—SH) that are not disulfonated are detected by FT-NIR. The epoxy resin cured product of any one of claims 10 to 12 is brought into contact with a water-soluble biomolecular compound having a thiol group (—SH) in a two-phase solvent of an aqueous phase and an organic phase, and in the organic phase, Producing a hydroxythiol compound having a hydroxy group (--OH) and a thiol group (--SH) as a decomposition product;
A method for decomposing an epoxy resin cured product, comprising: The following steps:
The epoxy resin cured product of any one of claims 10 to 12 is brought into contact with a water-soluble biomolecular compound having a thiol group (—SH) in a two-phase solvent of an aqueous phase and an organic phase, and in the organic phase, Producing a hydroxy thiol compound having a hydroxy group (-OH) and a thiol group (-SH) as a decomposition product; A method for recycling an epoxy resin cured product, comprising obtaining a cured product having an epoxy resin network structure containing -). A monomer compound having a unit structure represented by the following formula.

(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,
R ⁹ represents an aromatic carbocyclic ring, an aromatic carbocyclic alkyl chain, an aliphatic carbocyclic ring, an aliphatic carbocyclic alkyl chain or an aliphatic carbon chain;
Z ¹ represents a nitrogen atom, benzene, phenol,
Y ¹ represents a thiol group (-SH)) Unit structure represented by the following formula;

(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,
R ⁹ represents an aromatic carbocyclic ring, an aromatic carbocyclic alkyl chain, an aliphatic carbocyclic ring, an aliphatic carbocyclic alkyl chain or an aliphatic carbon chain;
Z ¹ represents a nitrogen atom, benzene, phenol,
Of the three Y2s located at the terminal, ^two are thiol groups (-SH) and the other is a sulfide (-S-))
contains two
A dimer compound characterized in that the two unit structures are linked to each other via a disulfide bond (-SS-) in which the sulfides (-S-) are linked. Unit structure represented by the following formula;

(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,
R ⁹ represents an aromatic carbocyclic ring, an aromatic carbocyclic alkyl chain, an aliphatic carbocyclic ring, an aliphatic carbocyclic alkyl chain or an aliphatic carbon chain;
Z1 represents ^a nitrogen atom, benzene, or phenol. )
contains three
One of the three unit structures has three terminally positioned 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 are, of the three Y ^3s located at the ends, two of which are thiol groups (—SH) and the other one is a sulfide (—S—),
A trimeric compound, wherein the sulfides (--S--) of the three unit structures are linked to each other via a disulfide bond (--S--S--). A cured product, which is a cured product of a composition containing the compound according to any one of claims 20 to 22.

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