Curing agent and epoxy resin composition using the same

Abstract

To provide a curing agent allowing easy decoupling (easy separation) while maintaining high adhesive strength between two adherends.SOLUTION: The invention provides compounds having the structure of the general formula 1 in the figure, where n is an integer equal to or greater than 2, and R1 and R2 are each independently an organic group without any phenol group.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a curing agent and an epoxy resin composition using the same. More specifically, the present invention relates to a curing agent that has high adhesive strength between two adherends and is simultaneously easily dismantled, and an epoxy resin composition using the curing agent. [Background technology]

[0002] Epoxy resins are used in a variety of applications, including adhesives, paints, electrical insulating materials, composite materials, and civil engineering and construction materials. Epoxy resins are difficult to decompose. For example, adhesives using epoxy resins are difficult to remove and disassemble once bonded. However, in recent years, from the perspectives of environmental protection and resource recycling, there has been a growing demand for curing agents that provide sufficient adhesive strength during use but allow for easy removal and disassembly.

[0003] For example, a method for producing poly(diacylhydrazine) is described in Patent Document 1. The poly(diacylhydrazine) described in this document is easily decomposed by an oxidizing agent such as sodium hypochlorite. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-52075 Summary of the Invention [Problem to be solved by the invention]

[0005] However, although the polymer described in Patent Document 1 is a high molecular weight substance and therefore suitable for use in moldings, it is unable to develop adhesive strength.

[0006] As mentioned above, conventionally, the properties of cured materials are high adhesive strength, but it has been difficult to make the bonded material easy to peel off or dismantle.

[0007] Therefore, the present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a curing agent that is easy to dismantle (easy to peel) while maintaining high adhesive strength between two adherends. [Means for solving the problem]

[0008] The present inventors have conducted extensive research to achieve the above object, and as a result have found that compounds having specific structures can solve the above problems, thereby completing the present invention.

[0009] That is, the present invention includes the following aspects and modes. 1. A compound having the structure of general formula 1 below:

[0010] [ka]

[0011] In the above general formula 1, n is an integer of 1 or more, R 1 and R 2 are each independently an organic group that does not have a phenol group. 2. The compound according to 1 above, wherein in the general formula 1, n is an integer of 2 or 3. 3. In the general formula 1, R 2 The compound according to 1 or 2 above, wherein the total number of carbon atoms in 4. In the general formula 1, R 2 The compound according to any one of the above 1 to 3, wherein contains an ester group. 5. In the general formula 1, R 1 The compound according to any one of the above 1 to 4, wherein is a group containing a benzene ring. 6. A curing agent containing the compound according to any one of 1. to 5. above. 7. An epoxy resin composition containing the following components (A) and (B), and not containing a solvent: (A) component: epoxy resin, Component (B): the compound described in any one of 1. to 5. or the curing agent described in 6. 8. The epoxy resin composition according to 7 above, further comprising a curing catalyst as component (C). 9. The epoxy resin composition according to 8 above, wherein the component (C) contains a phosphorus-based curing catalyst. 10. The epoxy resin composition according to any one of items 7 to 9 above, wherein the component (A) comprises a water-insoluble epoxy resin and a water-soluble epoxy resin. 11. The epoxy resin composition according to claim 10, wherein the water-soluble epoxy resin comprises at least one epoxy resin selected from the group consisting of epoxy resins having an alkylene oxide skeleton, epoxy resins having a glycerol skeleton, epoxy resins having a hydroxyl group in the molecule, and epoxy resins having a carboxyl group in the molecule. 12. A cured product obtained by curing the epoxy resin composition according to any one of items 7 to 11 above by heating. 13. A method for decomposing the cured product described in 12 above by oxidative decomposition. 14. The method according to claim 13, wherein the oxidative decomposition is carried out using an aqueous solution of sodium hypochlorite. [Effects of the Invention]

[0012] The compound according to the present invention can provide a curing agent that is easy to dismantle (easy to peel) while maintaining high adhesive strength between two adherends. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments.

[0014] In this specification, the range "X to Y" includes X and Y and means "X or more and Y or less." Unless otherwise specified, operations and measurements of physical properties are carried out at room temperature (20 to 25°C) and a relative humidity of 40 to 50% RH.

[0015] [Compound] The compound of the present disclosure has the structure of the following general formula 1. The compound of the present disclosure can provide a curing agent that maintains high adhesive strength between two adherends while exhibiting easy dismantling (easy peeling). Specifically, by using the compound of the present disclosure as a curing agent, the initial adhesive strength of the cured product is high, but even for surface-bonded structures that are difficult to decompose during peeling or dismantling, the adhesive strength can be reduced by appropriate treatment (e.g., oxidative decomposition), making peeling and dismantling easier (exhibiting easy peeling and dismantling). Therefore, dismantling and subsequent recycling are easy when discarding the product. The above effect is particularly pronounced when the object to be cured is an epoxy resin. In this specification, easy peeling and easy dismantling are also collectively referred to as "easy peeling and dismantling."

[0016] [ka]

[0017] In the following, R 1 The following structure bonded to is also referred to as "substituent X".

[0018] [ka]

[0019] In the above general formula 1, n is an integer of 1 or more. From the viewpoint of further improving the adhesive strength (initial adhesive strength) during adhesion, ease of peeling and dismantling, and the balance thereof, n is preferably 2 or 3, and more preferably 3.

[0020] In the above general formula 1, R 1 and R 2 each independently represents an organic group that does not have a phenol group. 1 and R 2 may be the same or different. 1 and R 2 In the above, the term "phenol group" refers to a group derived from phenol which may have a substituent.1 and R 2 each independently represents an organic group having no phenol group" means that R 1 and R 2 means that it is not a group derived from phenol which may have a substituent, and does not have a group derived from phenol which may have a substituent.

[0021] R 1 and R 2 The organic group as R is not particularly limited, but examples thereof include linear or branched alkyl groups, linear or branched alkenyl groups, linear or branched alkynyl groups, cycloalkyl groups, aromatic hydrocarbon groups, aromatic heterocyclic groups, ester groups, and combinations thereof. 1 and R 2 The organic group as may be unsubstituted or may have a substituent.

[0022] Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a tert-pentyl group, a neopentyl group, a 1,2-dimethylpropyl group, an n-hexyl group, an isohexyl group, a 1,3-dimethylbutyl group, a 1-isopropylpropyl group, a 1,2-dimethylbutyl group, an n-heptyl group, a 1,4-dimethylpentyl group, a 3-ethylpentyl group, and a 2-methyl-1-isopropylpropyl group. Examples of such alkyl groups include butyl, 1-ethyl-3-methylbutyl, n-octyl, 2-ethylhexyl, 3-methyl-1-isopropylbutyl, 2-methyl-1-isopropyl, 1-tert-butyl-2-methylpropyl, n-nonyl, 3,5,5-trimethylhexyl, n-decyl, isodecyl, n-undecyl, 1-methyldecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, and n-octadecyl groups.

[0023] Examples of the alkenyl group include a vinyl group, an allyl group, a 1-propenyl group, a 2-butenyl group, a 1,3-butadienyl group, a 2-pentenyl group, and an isopropenyl group.

[0024] Examples of the alkynyl group include an ethynyl group and a propargyl group.

[0025] Examples of the cycloalkyl group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and a cyclohexyl group.

[0026] Examples of aromatic hydrocarbon groups include groups derived from aromatic hydrocarbons such as benzene (benzene ring), pentalene, indene, naphthalene, anthracene, azulene, acenaphthene, phenalene, fluorene, phenanthroline, biphenyl, terphenyl, quaterphenyl, pyrene, 9,9-diphenylfluorene, 9,9'-spirobi[fluorene], and 9,9-dialkylfluorene.

[0027] Examples of the aromatic heterocyclic group include pyridine, pyrazine, pyridazine, pyrimidine, triazine, quinoline, isoquinoline, quinoxaline, quinazoline, naphthyridine, acridine, phenazine, benzoquinoline, benzoisoquinoline, phenanthridine, phenanthroline, benzoquinone, coumarin, fluorenone, furan, thiophene, benzofuran, benzothiophene, dibenzofuran, dibenzothiophene, pyrrole, indole, carbazole, imidazole, benzimidazole, and pyrazoline. Examples of heterocyclic aromatic compounds include groups derived from heterocyclic aromatic compounds such as benzol, indazole, oxazole, isoxazole, benzoxazole, benzisoxazole, thiazole, isothiazole, benzothiazole, benzisothiazole, imidazolinone, benzimidazolinone, imidazopyridine, imidazopyrimidine, azadibenzofuran, azacarbazole, azadibenzothiophene, diazadibenzofuran, diazacarbazole, diazadibenzothiophene, xanthone, and thioxanthone.

[0028] The ester group is a group represented by the formula: -COOR. In this case, R is a linear or branched alkyl group having 1 to 18 carbon atoms. From the viewpoint of further improving the adhesive strength (initial adhesive strength) during adhesion, ease of peeling and dismantling, and the balance between these, R is preferably a linear or branched alkyl group having 3 to 15 carbon atoms, more preferably a linear or branched alkyl group having 5 to 10 carbon atoms, and particularly preferably a linear alkyl group having 7 to 9 carbon atoms (n-heptyl group, n-octyl group, n-nonyl group).

[0029] R 1 and R 2 When the organic group as R has a substituent, examples of the substituent include, but are not limited to, an alkyl group, an alkoxy group, a halogen atom (which may be a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom), an amino group, and an acyl group. 1 or R 2 When has two or more substituents, they may be the same or different.

[0030] Among these, R is selected from the viewpoints of adhesive strength (initial adhesive strength), ease of peeling and dismantling, and the balance between these. 1 is more preferably a substituted or unsubstituted group containing a benzene ring, and particularly preferably a group derived from a benzene ring.

[0031] In addition, from the viewpoints of adhesive strength (initial adhesive strength), ease of peeling and dismantling, and the balance between these, R 2 The total number of carbon atoms in R is preferably 3 or more, more preferably 5 to 15, and particularly preferably 8 to 10. Instead of or in addition to the above, from the viewpoints of adhesive strength during adhesion (initial adhesive strength), ease of peeling and dismantling, and the balance thereof, it is preferable to select R 2More preferably, contains a substituted or unsubstituted ester group, and is further preferably an unsubstituted ester group (a group represented by the formula: -COOR, where R=n-heptyl group, n-octyl group, or n-nonyl group), and -COOCH 17 It is even more preferred that:

[0032] R of the substituent X 1 The bonding position to R is not particularly limited and can be appropriately selected depending on the desired effect (e.g., adhesive strength at the time of bonding (initial adhesive strength), ease of peeling and dismantling, and the balance thereof). 1 is a group derived from a benzene ring and n is 2, the substituent X may be at any of the o-, m-, or p-positions of the benzene ring. 1 is a group derived from a benzene ring and n is 3, the substituent X may be at any of the 1,2,3-positions, 1,2,4-positions, 1,2,5-positions, 1,3,4-positions, or 1,3,5-positions of the benzene ring, but is preferably at the 1,3,5-positions from the viewpoints of adhesive strength during adhesion (initial adhesive strength), ease of peeling and dismantling, and the balance between these.

[0033] Specifically, in a more preferred embodiment of the present disclosure, in the above general formula 1, n is 3 and R 1 is a group derived from a benzene ring, and R 2 Ga-COOC8H 17 That is, compounds of the present disclosure have the following structure:

[0034] [ka]

[0035] In a more preferred form of the disclosure, the compounds of the disclosure have the structure:

[0036] [ka]

[0037] The compounds of the present disclosure can be produced by known methods, for example, by referring to the methods in the following examples. Specifically, a benzene compound having two carboxyl groups and one hydroxyl group (e.g., 5-hydroxyisophthalic acid) is reacted with an alkanol (R 2 OH) to convert the carboxyl group to -COOR 2 This intermediate A is reacted with, for example, hydrazine to give a compound (intermediate A) converted to -COOR 2 is converted to -CONHNH to obtain a compound (intermediate B). A method can be used in which intermediate A is reacted with a benzene compound having a reactive group (for example, -C(=O)Cl) (for example, trimesoyl chloride).

[0038] [Hardening agent] When the compound of the present disclosure is applied between two adherends and cured, it exhibits sufficient adhesive strength (initial adhesive strength), but can be easily peeled and disassembled (has easy peelability and disassembly properties) by appropriate treatment (e.g., oxidative decomposition). Therefore, the compound of the present disclosure can be suitably used as a curing agent. Accordingly, the present invention also provides a curing agent containing the compound of the present disclosure; and the use of the compound of the present disclosure as a curing agent.

[0039] The curing agent of the present disclosure may contain other components in addition to the compound of the present disclosure, but is preferably composed substantially of the compound of the present disclosure, and more preferably composed solely of the compound of the present disclosure. In this specification, the phrase "the curing agent of the present disclosure is composed substantially of the compound of the present disclosure" means that the content of the compound of the present disclosure contained in the curing agent of the present disclosure exceeds 90% by mass, and preferably exceeds 95% by mass (upper limit: 100% by mass).

[0040] [Epoxy resin composition] The curing agent of the present disclosure can be suitably used as a curing agent for epoxy resins in particular. Accordingly, the present invention also provides an epoxy resin composition containing the following components (A) and (B), and containing no solvent: (A) component: epoxy resin, (B) Component: a curing agent of the present disclosure.

[0041] The epoxy resin composition of the present disclosure contains an epoxy resin, and therefore, the epoxy resin composition of the present disclosure can be suitably used as an adhesive.

[0042] Furthermore, the epoxy resin composition of the present disclosure does not contain a solvent. Conventionally, solvents such as N-methylpyrrolidone have been used in epoxy resin compositions for adhesives. However, the presence of a solvent can trap the solvent inside the adhesive surface during heat curing, potentially leading to instability or a decrease in adhesive strength. In contrast, the epoxy resin composition of the present disclosure does not contain a solvent. This prevents instability or a decrease in adhesive strength after heat curing. Furthermore, no solvent is released into the atmosphere during heat curing of the epoxy resin. Therefore, the use of the epoxy resin composition of the present disclosure is preferable from the standpoints of environmental and safety. As used herein, the phrase "the epoxy resin composition does not contain a solvent" means that no solvent is intentionally added to the epoxy resin composition, although trace amounts of solvent may be present in the composition. Specifically, the solvent content in the epoxy resin composition is intended to be less than 3% by mass, preferably less than 1% by mass (lower limit: 0% by mass).

[0043] The epoxy resin composition of the present disclosure will be described below.

[0044] (Component (A)) In the present disclosure, component (A) is an epoxy resin. Epoxy resins are classified into water-soluble epoxy resins and water-insoluble epoxy resins. It is preferable to use only a water-soluble epoxy resin or to use both a water-soluble epoxy resin and a water-insoluble epoxy resin in combination, and more preferable to use both a water-soluble epoxy resin and a water-insoluble epoxy resin in combination. As described in detail below, the combined use of a water-soluble epoxy resin and a water-insoluble epoxy resin allows the decomposition liquid (e.g., aqueous sodium hypochlorite solution) used to decompose the cured product of the epoxy resin composition to penetrate deep into the resin (further improving peelability and dismantling properties). Furthermore, the presence of a water-soluble epoxy resin (water-soluble unit) allows the resin decomposition products after decomposition (particularly oxidative decomposition) to dissolve in water. Meanwhile, the presence of a water-insoluble epoxy resin can enhance adhesive strength in high-humidity environments. That is, in a preferred embodiment of the present disclosure, component (A) contains only a water-soluble epoxy resin, or contains both a water-soluble epoxy resin and a water-insoluble epoxy resin. In a more preferred embodiment of the present disclosure, component (A) contains both a water-soluble epoxy resin and a water-insoluble epoxy resin.

[0045] The water-soluble epoxy resin is not particularly limited as long as it is a water-soluble epoxy resin having at least one epoxy group, and can be appropriately selected from commonly used epoxy resins. Here, "water-soluble" means that when 10 parts by mass of the epoxy resin is added and mixed with 100 parts by mass of ion-exchanged water at room temperature (25°C), the mixture becomes transparent. The water-soluble epoxy resin may be used alone or in combination of two or more types.

[0046] Water-soluble epoxy resins include epoxy resins with a polyether or polyester backbone. Specifically, they include epoxy resins with an alkylene oxide backbone, a glycerol backbone, or a backbone containing water-miscible functional groups, such as hydroxyl groups or carboxyl groups, on the polymer side chains within the molecule. The water-soluble epoxy resins may be used alone or in combination. That is, in one embodiment of the present disclosure, the water-soluble epoxy resin includes at least one epoxy resin selected from the group consisting of epoxy resins with an alkylene oxide backbone, epoxy resins with a glycerol backbone, epoxy resins with hydroxyl groups within the molecule, and epoxy resins with carboxyl groups within the molecule. In one embodiment of the present disclosure, the water-soluble epoxy resin is at least one epoxy resin selected from the group consisting of epoxy resins with an alkylene oxide backbone, epoxy resins with a glycerol backbone, epoxy resins with hydroxyl groups within the molecule, and epoxy resins with carboxyl groups within the molecule.

[0047] The water-soluble epoxy resin may be synthesized or may be a commercially available product. Examples of commercially available products include 1,4-butanediol diglycidyl ether, polypropylene glycol #400 diglycidyl ether (Epolite 400E, viscosity = 60 to 110 (mPa·s / 25°C), epoxy equivalent = 264 to 290 (g / eq), average number of moles of ethylene oxide added = about 9, manufactured by Kyoeisha Chemical Co., Ltd.), glycerol polyglycidyl ether (Denacol EX-313, manufactured by Nagase ChemteX Corporation), trimethylolpropane diglycidyl ether (Denacol EX-313, manufactured by Nagase ChemteX Corporation), and trimethylolpropane diglycidyl ether (Denacol EX-313, manufactured by Nagase ChemteX Corporation). Examples include the Denacol series (manufactured by Nagase ChemteX Corporation) such as panpolyglycidyl ether (Denacol EX-321, viscosity = 130 (mPa·s), epoxy equivalent = 140 (g / eq), Nagase ChemteX Corporation), and the Epolite E series (manufactured by Kyoeisha Chemical Co., Ltd.) such as ethylene glycol diglycidyl ether (Epolite 40E, viscosity = 400 to 800 (mPa·s / 25°C), Kyoeisha Chemical Co., Ltd.).

[0048] The water-insoluble epoxy resin can be appropriately selected from epoxy resins containing aromatic rings. Here, "water-insoluble" means that the resulting mixture does not become transparent when 10 parts by mass of the epoxy resin is added to 100 parts by mass of ion-exchanged water at room temperature (25°C) and mixed. The water-insoluble epoxy resin may be used alone or in combination of two or more types.

[0049] Specific examples of the water-insoluble epoxy resin include epoxy resins having a bisphenol skeleton, epoxy resins having a phenol novolac skeleton, urethane-modified epoxy resins, and rubber-modified epoxy resins.

[0050] The water-insoluble epoxy resin may be synthetically obtained or commercially available. Commercially available products include bisphenol A epoxy resin (EPICLON®). EPICLON (registered trademark) series (manufactured by DIC Corporation) such as EXA-850CRP, epoxy equivalent = 168 to 178 (g / eq), viscosity = 3500 to 5500 (mPa·s / 25°C), manufactured by DIC Corporation), bisphenol A type epoxy resin (jER828, viscosity = 120 to 150 (P / 25°C), epoxy equivalent (number of grams of resin containing 1 gram equivalent of epoxy groups (g / eq)) = 184 to 194, specific gravity = 1.17, molecular weight (Mw) = approximately 370, manufactured by Mitsubishi Chemical Corporation), bisphenol A type epoxy resin (jER834, viscosity = P to U(4) (Gardner-Holt), epoxy equivalent (number of grams of resin containing 1 gram equivalent of epoxy groups (g / eq)) = 230 to 270, specific gravity = 1.18, molecular weight (Mw) = approximately 370, manufactured by Mitsubishi Chemical Corporation), Examples of epoxy resins include the jER series (manufactured by Mitsubishi Chemical Corporation), such as polyfunctional phenol novolac epoxy resin (jER152, viscosity = 14-18 / 52°C, epoxy equivalent (number of grams of resin containing 1 gram equivalent of epoxy groups (g / eq)) = 176-178, manufactured by Mitsubishi Chemical Corporation), and the Epolite P series (manufactured by Kyoeisha Chemical Co., Ltd.), such as propylene glycol diglycidyl ether (Epolite 70P, viscosity = 1000-1400 (mPa·s / 25°C), manufactured by Kyoeisha Chemical Co., Ltd.) and tripropylene glycol diglycidyl ether (Epolite 200P, viscosity = 600-900 (mPa·s / 25°C), manufactured by Kyoeisha Chemical Co., Ltd.).

[0051] When a water-soluble epoxy resin and a water-insoluble epoxy resin are used in combination as component (A), the mixing ratio of the water-soluble epoxy resin and the water-insoluble epoxy resin is not particularly limited and can be appropriately selected depending on the desired properties. The mixing ratio of the water-soluble epoxy resin and the water-insoluble epoxy resin (mass ratio of water-soluble epoxy resin to water-insoluble epoxy resin) is, for example, 0.5 to 10:1, preferably 0.7 to 5.0:1, more preferably 1.0 to 4.5:1, and particularly preferably 1.5 to 3.5:1. Cured products of epoxy resin compositions are generally weak in high-humidity environments, and strength in tensile shear tests may decrease under high-humidity conditions. However, by mixing the water-soluble epoxy resin and the water-insoluble epoxy resin at the above-mentioned mixing ratio, strength under high-humidity environments can be increased.

[0052] ((B) component) In the present disclosure, the component (B) is a compound according to the present disclosure or a curing agent according to the present disclosure. The compound according to the present disclosure or the curing agent according to the present disclosure is the same as described above, and therefore a description thereof will be omitted here. The curing agent may be used alone or in combination of two or more types.

[0053] The blend amount of the component (B) is, for example, 50 to 250 parts by mass, preferably 60 to 210 parts by mass, and more preferably 75 to 145 parts by mass per 100 parts by mass of the component (A).

[0054] ((C) component) The epoxy resin composition of the present disclosure essentially contains components (A) and (B), but preferably also contains a curing catalyst (component (C)) in addition to these. This further accelerates curing. That is, in a preferred embodiment of the present invention, the epoxy resin composition further contains a curing catalyst as component (C).

[0055] Component (C) may be any curing catalyst that promotes polymerization between the epoxy resin (A) and the curing agent (B), and can be appropriately selected from known curing catalysts depending on the type of epoxy resin and curing agent. From the viewpoint of further promoting the reaction between components (A) and (B), component (C) is preferably a phosphorus-based curing catalyst. Specific examples of phosphorus-based curing catalysts include alkylphosphines (alkylphosphines), arylphosphines (arylphosphines) such as triphenylphosphine (triphenylphosphine), phosphine oxides (phosphine oxides), and phosphonium salts. The curing catalysts may be used alone or in combination of two or more.

[0056] When the epoxy resin composition contains the component (C), the amount of the component (C) blended is, for example, 0.2 to 10 parts by mass, preferably 2 to 8 parts by mass, and more preferably 3 to 6 parts by mass, per 100 parts by mass of the component (A).

[0057] Alternatively or additionally, when the epoxy resin composition contains the component (C), the amount of the component (C) blended is, for example, 2 to 10 parts by mass, preferably 3 to 6 parts by mass, and more preferably 3.5 to 5.0 parts by mass, per 100 parts by mass of the component (B).

[0058] (Other ingredients) The epoxy resin composition of the present disclosure contains components (A) and (B), and, if necessary, component (C). However, it may further contain components other than components (A) to (C) (hereinafter, "other components") as long as the properties of the present disclosure are not impaired. Examples of such other components include colorants such as pigments and dyes, curing accelerators, inorganic fillers, organic fillers such as polystyrene fillers, polyurethane fillers, poly(meth)acrylic fillers, and rubber fillers, thermoplastic resins, rubbers, elastomers, plasticizers, anti-foaming agents, flame retardants, antioxidants, polymerization inhibitors, defoamers, coupling agents, leveling agents, and rheology control agents. Among these, inorganic fillers, thermoplastic resins, rubbers, elastomers, anti-foaming agents, and coupling agents are preferred. Each of the above other components may be used alone, or two or more may be used in combination. Furthermore, one or more of the above other components may be used in combination. The addition of these other components results in compositions and cured products with excellent resin strength, adhesive strength, workability, and shelf life. The contents of the above components are not particularly limited, and can be appropriately determined by a person skilled in the art within a range that does not impair the characteristics of the present invention.

[0059] Examples of inorganic fillers that can be used include amorphous silica, silica, hydrophobic fumed silica, hydrophilic fumed silica, metal powder, calcium carbonate, talc, alumina, aluminum hydroxide, soda-lime glass, and glass beads. Among these, amorphous silica, hydrophobic fumed silica, hydrophilic fumed silica, soda-lime glass, and glass beads are preferred, hydrophobic fumed silica, hydrophilic fumed silica, soda-lime glass, and glass beads are more preferred, and hydrophobic fumed silica is particularly preferred. Combining these fillers with components (A) and (B), and optionally component (C), can further improve and achieve both adhesive strength (initial adhesive strength) and ease of peeling and dismantling. This can also contribute to achieving and stabilizing both low viscosity and a high structural viscosity ratio. The inorganic fillers may be used alone or in combination.

[0060] The size of the inorganic filler is not particularly limited, but for example, the average primary particle diameter is 1 nm to 300 μm, preferably 5 nm to 50 μm, and more preferably 10 to 50 nm. In the case of amorphous silica, the average primary particle diameter is 1 to 100 nm, and the specific surface area by the BET method is 10 to 300 μm. 2 / g. In this specification, the average primary particle diameter is a value measured using image analysis software or the like from a scanning electron microscope image of the object to be measured. Specifically, a statistically reliable number of particles (for example, 100 particles x 10 or more per field of view, totaling 1000 or more) are observed, particle images are extracted using analysis software, and the particle diameter (average) is calculated.

[0061] The inorganic filler may be either a commercially available product or a synthetic product. Specific examples of commercially available products include, but are not limited to, hydrophobic fumed silica surface-treated with silicone oil (AEROSIL RY-200, manufactured by EVONIK, particle size = 12 nm), hydrophilic fumed silica (AEROSIL 200, manufactured by EVONIK, particle size = 12 nm), soda-lime glass particles (Unibeads SPL-200, manufactured by Unitika Ltd., average particle size = 200 μm), microglass beads (EMB-20, manufactured by Potters-Barotini Co., Ltd., average particle size = 20 μm), and EVONIK's AEROSIL (registered trademark) series OX50, 50, 90G, 130, 150, 200, 300, and 380.

[0062] When the epoxy resin composition of the present disclosure contains an inorganic filler, the amount of the inorganic filler to be added is not particularly limited, but is, for example, 0.5 to 10 parts by mass, preferably 1 to 7 parts by mass, and more preferably more than 3 parts by mass and less than 6 parts by mass, per 100 parts by mass of component (A).

[0063] Thermoplastic resins, rubbers, and elastomers are non-reactive and are liquid or solid at 25°C. If they are liquid at 25°C, they can be used by being compatible with or dispersed in component (A). If they are solid at 25°C, they can be used by being dissolved in component (A). Specific examples include polyester polyol resins, polyester elastomers, polystyrene elastomers, poly(meth)acrylate elastomers, polybutadiene, hydrogenated polybutadiene, polyisoprene, hydrogenated polybutadiene, polybutene, polyisobutylene, copolymers of these monomers, diblock polymers thereof, and triblock polymers thereof, as well as rubber-based elastomers. The thermoplastic resins, rubbers, and elastomers may be used alone or in combination of two or more.

[0064] The thermoplastic resin may be either a commercially available product or a synthetic product. Specific examples of commercially available products include, but are not limited to, the Polylite series (manufactured by DIC Corporation) such as polyester polyol resin (Polylite BC40, manufactured by DIC Corporation).

[0065] When the epoxy resin composition of the present disclosure contains a thermoplastic resin, rubber, or elastomer, the amount of the thermoplastic resin, rubber, or elastomer is not particularly limited, but is, for example, 1 to 40 parts by mass, preferably 9 to 30 parts by mass, and more preferably more than 10 parts by mass and less than 25 parts by mass, per 100 parts by mass of component (A).

[0066] Examples of the anti-foaming agent include calcium oxide, aluminum oxide, calcium chloride, etc. The anti-foaming agents may be used alone or in combination of two or more.

[0067] When the epoxy resin composition of the present disclosure contains an antifoaming agent, the amount of the antifoaming agent to be added is not particularly limited, but is preferably 1 to 10 parts by mass, more preferably 3 to 8 parts by mass, per 100 parts by mass of component (A). With such an amount, the resulting cured product can exhibit sufficient strength.

[0068] As the coupling agent, in particular, silane coupling agent.Specific examples thereof include glycidyl group-containing silane coupling agents such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, vinyl group-containing silane coupling agents such as vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane, vinyltrimethoxysilane, (meth)acryloyl group-containing silane coupling agents such as γ-methacryloxypropyltrimethoxysilane, amino group-containing silane coupling agents such as N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, and others such as γ-mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, etc. The coupling agents may be used alone or in combination of two or more. Among these, a silane coupling agent containing an epoxy group or a (meth)acryloyl group is preferably used from the viewpoint that further improvement in adhesion can be expected.

[0069] When the epoxy resin composition of the present disclosure contains a coupling agent, the amount of the coupling agent to be added is not particularly limited, but is, for example, preferably 0.5 to 20 parts by mass, more preferably 1 to 10 parts by mass, and even more preferably 1 to 7 parts by mass, per 100 parts by mass of component (A).

[0070] The method for producing the epoxy resin composition of the present disclosure is not particularly limited. For example, when the epoxy resin composition of the present disclosure contains component (A), component (B), component (C), and other components, first, component (A) and component (B) are weighed and mixed, and then heated and stirred at a temperature of, for example, 25 to 120°C, preferably 60 to 100°C, for, for example, 5 to 60 minutes, preferably 5 to 30 minutes, to obtain a mixture. Next, component (C) and other components are weighed and added to the mixture with stirring to disperse them. This yields the epoxy resin composition of the present disclosure.

[0071] [Cured product] The epoxy resin composition of the present disclosure is cured by heating. Accordingly, the present invention also provides a cured product obtained by curing the epoxy resin composition of the present disclosure by heating, or a method for producing a cured product, which comprises curing the epoxy resin composition of the present disclosure by heating.

[0072] Here, the curing conditions are not particularly limited, but the curing temperature is, for example, more than 80°C and not more than 200°C, or 100°C or more and 180°C or less. The curing time is, for example, more than 30 minutes and not more than 7 hours, or 1 to 5 hours. Under these conditions, the epoxy resin composition of the present disclosure is sufficiently cured.

[0073] [Decomposition of the cured product] The cured product of the present disclosure can be easily decomposed by an appropriate treatment such as oxidative decomposition, etc. Therefore, the present invention also provides a method for decomposing the cured product of the present disclosure by oxidative decomposition.

[0074] The decomposing agent usable for the oxidative decomposition according to the present disclosure is not particularly limited and can be appropriately selected depending on the composition of the epoxy resin composition. Specific examples include sodium hypochlorite and potassium permanganate. Of these, sodium hypochlorite is preferably used from the viewpoints of the availability and price of the reagent itself, and the safety of the reagent itself. Here, the decomposing agent may be used as is or as an aqueous solution. However, from the viewpoints of ease of mixing (and therefore ease of decomposition), it is preferably used in the form of an aqueous solution, and it is more preferable to decompose the cured product by immersing it in an aqueous solution containing the decomposing agent. That is, in a preferred embodiment of the present invention, the oxidative decomposition is carried out using sodium hypochlorite. In a more preferred embodiment of the present invention, the oxidative decomposition is carried out using an aqueous sodium hypochlorite solution. In a particularly preferred embodiment of the present invention, the oxidative decomposition is carried out by immersing the cured product in an aqueous sodium hypochlorite solution.

[0075] When an aqueous sodium hypochlorite solution is used for oxidative decomposition, the concentration of the aqueous sodium hypochlorite solution is not particularly limited and is, for example, 1 to 12% by mass, preferably 3 to 10% by mass.

[0076] The oxidative decomposition conditions are not particularly limited and can be appropriately selected depending on the composition of the epoxy resin composition. The oxidative decomposition temperature is, for example, 25 to 80°C, and preferably 40 to 60°C. The oxidative decomposition time is, for example, 1 to 72 hours, and preferably 12 to 48 hours. Under these conditions, the cured product of the present disclosure can be sufficiently decomposed. [Example]

[0077] The effects of the present invention will be explained using the following examples and comparative examples. However, the technical scope of the present invention is not limited to the following examples. In the following examples, unless otherwise specified, operations were performed at room temperature (25°C). Furthermore, unless otherwise specified, "%" and "parts" mean "% by mass" and "parts by mass," respectively. Hereinafter, the epoxy resin composition will also be simply referred to as the "composition."

[0078] [Synthesis Example 1: Synthesis of Compound 1] According to the following scheme 1, compound 1 of the following formula 2 was synthesized.

[0079] [ka]

[0080] [ka]

[0081] (Process 1) 12.5 g (68.7 mmol) of 5-hydroxyisophthalic acid (reagent), 1.97 g (10.4 mmol) of p-toluenesulfonic acid monohydrate (reagent), 23.0 ml (251 mol) of octanol (reagent), and 40 ml of toluene were all added to a recovery flask. A Dean-Stark apparatus was then attached and the mixture was refluxed at 110 °C for 15 hours. During reflux, water generated by the reaction was removed from the reaction system using the Dean-Stark apparatus. The octanol and toluene were then removed using an evaporator. The residue was dissolved in 100 ml of ethyl acetate, transferred to a separatory funnel, and washed three times with saturated aqueous sodium bicarbonate. The solution was dehydrated using magnesium sulfate, filtered, and the ethyl acetate was removed using an evaporator. As a result, 26.7 g (yield: 96% by mass) of 1-hydroxy-3,5-octyl ester-benzene was obtained as a white solid as intermediate 1.

[0082] (Process 2) 112 g (276 mmol) of the intermediate 1 obtained above was added to a recovery flask, and 300 ml of ethanol was added to dissolve the intermediate 1. Then, 26.8 ml (552 mmol) of hydrazine monohydrate (reagent) was added to obtain a mixture. This mixture was stirred at 40°C for 48 hours, and the ethanol was removed using an evaporator to obtain a solid. The obtained solid was transferred to a Soxhlet extractor, and dimethoxyethane was circulated to remove the by-products using filter paper, obtaining intermediate 2 dissolved in dimethoxyethane. The dimethoxyethane was removed from this solution using an evaporator. As a result, 78.8 g (yield: 92% by mass) of 3-hydroxy-5-octyl ester benzene monohydrazide was obtained as a white solid as intermediate 2.

[0083] (Step 3) 41.2 g (134 mmol) of the intermediate 2 obtained above and 400 ml of tetrahydrofuran were added to a recovery flask and dissolved. 11.5 g (43.2 mmol) of trimesoyl chloride (reagent) was then added and stirred at 0°C for 3 hours. Aqueous sodium hydroxide solution was added to the recovery flask to neutralize the mixture, and the mixture was poured into a beaker containing 1 L of water to precipitate compound 1. Compound 1 was recovered by suction filtration and then washed with water, yielding 40.5 g of compound 1 (yield: 94% by mass).

[0084] [Synthesis Example 2: Synthesis of Compound 2] According to the following scheme 2, compound 2 of the following formula 4 was synthesized.

[0085] [ka]

[0086] [ka]

[0087] (Step 4) 50.0 g (275 mmol) of 5-hydroxyisophthalic acid (reagent), 10.4 g (54.7 mmol) of p-toluenesulfonic acid monohydrate (reagent), and 800 ml of ethanol were added to a recovery flask. A Dean-Stark apparatus was attached and the mixture was refluxed at 80°C for 48 hours. After removing the ethanol using an evaporator, the residue was dissolved in ethyl acetate, transferred to a separatory funnel, and washed with saturated aqueous sodium bicarbonate. The solution was dehydrated using magnesium sulfate, filtered, and the ethyl acetate was removed using an evaporator. 60.5 g (94% yield) of 1-hydroxy-3,5-ethyl ester-benzene was obtained as a white solid as intermediate 3.

[0088] (Step 5) 23.8 g (102 mmol) of the intermediate 3 obtained above was added to a recovery flask, and 120 ml of ethanol was added to dissolve the intermediate 3. Then, 10.1 ml (204 mmol) of hydrazine monohydrate (reagent) was added to obtain a mixture. This mixture was stirred at 40°C for 72 hours, and water was then added to precipitate intermediate 4. Intermediate 4 was collected by suction filtration and washed with water and ethyl acetate. As a result, 21.0 g (yield: 92% by mass) of 3-hydroxy-5-ethyl ester benzene monohydrazide was obtained as a white solid as intermediate 4.

[0089] (Step 6) 19.6 g (87.2 mmol) of the intermediate 5 obtained above, 50 ml of N-methylpyrrolidone, 50 ml of acetonitrile, and 50 ml of water were placed in a recovery flask. 60.2 g (97.9 mmol) of potassium peroxymonosulfate (Oxone, Merck) was then added and stirred at room temperature for 72 hours. The resulting solution was transferred to a beaker containing 500 ml of water, and Compound 2 was precipitated. Compound 2 was collected by suction filtration and washed with water, yielding 19.8 g (yield: 78% by mass) of white solid Compound 2.

[0090] [Synthesis Example 3: Synthesis of Compound 3] According to the following scheme 3, compound 3 of the following formula 6 was synthesized.

[0091] [ka]

[0092] [ka]

[0093] Intermediate 2 was synthesized in the same manner as in Steps 1 and 2 of Synthesis Example 1. 29.8 g (96.9 mmol) of the obtained intermediate 2, 80 ml of N-methylpyrrolidone, 80 ml of acetonitrile, and 70 ml of water were placed in a recovery flask. 66.1 g (107 mmol) of potassium peroxymonosulfate (Oxone, manufactured by Merck) was then added and stirred at 40°C for 72 hours. The resulting solution was transferred to a beaker containing 600 ml of water, and Compound 3 was precipitated. Compound 3 was recovered by suction filtration and then washed with water. As a result, 22.5 g (yield: 80% by mass) of Compound 3 was obtained as a white solid.

[0094] [Examples 1 to 19, Comparative Examples 1 to 9] The following ingredients were prepared to prepare the composition:

[0095] (A) Component: Epoxy resin (non-water-soluble epoxy resin) Bisphenol A epoxy resin (EPICLONEXA-850CRP manufactured by DIC Corporation) Bisphenol A epoxy resin (jER828, manufactured by Mitsubishi Chemical Corporation) Bisphenol A epoxy resin (jER834, manufactured by Mitsubishi Chemical Corporation) Multifunctional phenol novolac epoxy resin (jER152, manufactured by Mitsubishi Chemical Corporation) Propylene glycol diglycidyl ether (Epolite 70P, manufactured by Kyoeisha Chemical Co., Ltd.) Tripropylene glycol diglycidyl ether (Epolite 200P, manufactured by Kyoeisha Chemical Co., Ltd.) It was confirmed that all of the above-mentioned (A) component: epoxy resin (water-insoluble epoxy resin) did not become transparent when 10 parts by mass of the epoxy resin was added to 100 parts by mass of ion-exchanged water and mixed at room temperature (25°C).

[0096] (A) Component: Epoxy resin (water-soluble epoxy resin) 1,4-Butanediol diglycidyl ether (reagent) (hereinafter abbreviated as BDG) Polypropylene glycol #400 diglycidyl ether (Epolite 400E, manufactured by Kyoeisha Chemical Co., Ltd.) Glycerol polyglycidyl ether (Denacol EX-313, Nagase ChemteX Corporation) Ethylene glycol diglycidyl ether (Epolite 40E, manufactured by Kyoeisha Chemical Co., Ltd.) Trimethylolpropane polyglycidyl ether (Denacol EX-321, Nagase ChemteX Corporation) It was confirmed that all of the above-mentioned component (A): epoxy resin (water-soluble epoxy resin) became transparent when 10 parts by mass of the epoxy resin was added to 100 parts by mass of ion-exchanged water and mixed at room temperature (25°C).

[0097] (B) Component: Specific compound Compound 1 (in general formula 1, n: 3, R 1 : benzene ring, R 2 :-COOC8H 17 ) Component (B'): a compound other than component (B) ·Composite 2 ·Composite 3 Hydroquinone (reagent) (C) Component: Curing catalyst Triphenylphosphine (reagent) Curing accelerator Imidazole (reagent) thermoplastic resin Polyester polyol resin (Polylite BC40 manufactured by DIC Corporation) Coupling Agent 3-Glycidoxypropyltrimethoxysilane (KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.) Anti-foaming agent Calcium oxide (CML#35 manufactured by Omi Chemical Industry Co., Ltd.) Filler Hydrophobic fumed silica (AEROSIL RY-200 EVONIK) surface-treated with silicone oil with a particle size of 12 nm Hydrophilic fumed silica with a particle size of 12 nm (AEROSIL 200 manufactured by EVONIK) Soda-lime glass particles with an average particle size of 200 μm (Unibeads SPL-200, manufactured by Unitika Ltd.) Micro glass beads with an average particle size of 20 μm (EMB-20, manufactured by Potters-Barotini Co., Ltd.) solvent ·N-methylpyrrolidone (reagent).

[0098] The components (A) and (B) (or (B')) (thermoplastic resin and solvent in the comparative examples) were weighed out so as to obtain the composition shown in Table 1 below, and the components were heated and stirred at 80°C for 10 minutes to homogenize the components. The mixture was then cooled to room temperature (25°C). The components (C) (curing accelerator in the comparative examples), filler, and remaining components were added so as to obtain the composition shown in Table 1 below, and the mixture was stirred for 1 hour, followed by dispersion using a three-roll mill to prepare each composition. Detailed amounts prepared are shown in Table 1, and all values ​​are expressed in parts by mass.

[0099] [Table 1-1]

[0100] [Table 1-2]

[0101] [Table 1-3]

[0102] The tensile shear bond strength was measured according to the following method for Examples 1 to 19 and Comparative Examples 1 to 9. The results are summarized in Table 2.

[0103] [Lasting shear adhesive strength measurement] Two aluminum (JISH4000 A1061P) plates measuring 100 mm long, 25 mm wide, and 2.0 mm thick were prepared. 0.5 g of each composition was applied to two plates, and the coated surfaces were bonded together over an area measuring 10 mm long and 25 mm wide, and then secured in place with a jig. Any excess composition was wiped off. The plates were then placed in a hot air oven set at 150°C for three hours to cure the composition. After the specified time, the plates were removed from the oven and allowed to cool to room temperature to prepare test pieces. Then, using a TENSILON RTF-2350 manufactured by A&D Co., Ltd., both ends of the test piece were secured with chucks and pulled in the tensile direction at a tensile speed of 10 mm / min, measuring the maximum strength. The "adhesive strength (MPa)" was calculated from the adhesive area. This adhesive strength was designated the "initial adhesive strength (MPa)." Furthermore, the "condition" of the adhesive surface after pulling is visually confirmed according to the following evaluation criteria, and evaluated based on the following (evaluation criteria), which is designated as the "initial condition." The initial adhesive strength is preferably 2.0 MPa or more, more preferably 2.4 MPa or more, even more preferably 3.0 MPa or more, and particularly preferably 5.0 MPa or more.

[0104] (Evaluation criteria) CF (cohesive failure of adhesive) AF (interfacial fracture at the adherend interface) CF / AF (mottled interfacial failure at the adherend interface and cohesive failure of the adhesive).

[0105] Test pieces were prepared in the same manner as above. Each test piece was immersed in a 6% by mass aqueous solution of sodium hypochlorite (Kitchen Haiter, manufactured by Kao Corporation) at 50°C for 24 hours. The test pieces were then removed, the aqueous solution was wiped off, and the pieces were left to stand for 30 minutes. The adhesive strength was then measured and the condition was confirmed in the same manner as in the test method described above, and these were recorded as "adhesive strength after immersion (MPa)" and "condition after immersion," respectively. The "percent change (%)" was calculated using the following formula 1 and used as an index of peelability. The percent change (%) is preferably between -10% and -100%, and more preferably between -50% and -90%. However, if the test piece decomposed during immersion, it was recorded as "detached" and the percent change was not calculated. The adhesive strength after immersion is preferably 0.1 MPa or more, more preferably between 0.3 MPa and 6.0 MPa, and particularly preferably between 2.0 MPa and less than 5.0 MPa.

[0106]

number

[0107] [Table 2]

[0108] In Examples 1 to 19, the initial adhesive strength was 2.0 MPa or higher, indicating the initial adhesive strength. The negative values ​​for the rate of change after immersion indicate a decrease in adhesive strength and easy peeling. Comparative Example 1 also had an initial adhesive strength of 2.0 MPa or higher, but the rate of change was negative. This is likely due to the large amount of N-methylpyrrolidone contained in the composition as a solvent, which reduces the rate of change to a negative value. It is expected that a large adhesive area will trap the solvent inside the adhesive surface during heat curing, resulting in unstable adhesive strength. Furthermore, when the amount of solvent (N-methylpyrrolidone) was reduced to the same level as in Comparative Examples 2 and 3, the adhesive strength after immersion did not decrease. This is presumably because the small amount of solvent prevented the curing agent (Compound 2) from dispersing uniformly. Therefore, the curing promoter (imidazole) independently initiated a curing reaction with the epoxy resin, and the curing agent was not incorporated into the main chain of the cured product to a large extent, preventing strength loss due to oxidative decomposition of the resin. Looking at Comparative Examples 2 to 9, it can be seen that the rate of change is positive or the film falls off after immersion, so it is not easy to peel off. [Industrial Applicability]

[0109] When the product is discarded, it can be easily disassembled to facilitate recycling.

Claims

1. A curing agent comprising a compound having the structure of general formula 1: 【Chemistry 1】 In the above general formula 1, n is an integer of 1 or more, R １ and R ２ each independently represents an organic group that does not have a phenol group.

2. The curing agent according to claim 1 , wherein in said general formula 1, n is 2 or 3.

3. In the general formula 1, R ２ The curing agent according to claim 1 or 2, wherein the total number of carbon atoms in

4. In the general formula 1, R ２ The curing agent according to any one of claims 1 to 3, wherein comprises an ester group.

5. In the general formula 1, R １ The curing agent according to any one of claims 1 to 4, wherein is a group containing a benzene ring.

6. An epoxy resin composition containing the following components (A) and (B), and not containing a solvent: Component (A): epoxy resin, Component (B): the curing agent according to any one of claims 1 to 5.

7. The epoxy resin composition according to claim 6, further comprising a curing catalyst as component (C).

8. 8. The epoxy resin composition according to claim 7, wherein the component (C) comprises a phosphorus-based curing catalyst.

9. 9. The epoxy resin composition according to claim 6, wherein the component (A) comprises a water-insoluble epoxy resin and a water-soluble epoxy resin.

10. 10. The epoxy resin composition according to claim 9, wherein the water-soluble epoxy resin comprises at least one epoxy resin selected from the group consisting of epoxy resins having an alkylene oxide skeleton, epoxy resins having a glycerol skeleton, epoxy resins having a hydroxyl group in the molecule, and epoxy resins having a carboxyl group in the molecule.

11. A cured product obtained by curing the epoxy resin composition according to any one of claims 6 to 10 by heating.

12. A method for decomposing the cured product according to claim 11 by oxidative decomposition.

13. 13. The method of claim 12, wherein the oxidative decomposition is carried out using an aqueous sodium hypochlorite solution.

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