JP2020041073A - Epoxy resin curing agent, epoxy resin, epoxy resin composition, phenolic resin and method for producing epoxy resin - Google Patents

Abstract

To provide an epoxy resin and an epoxy resin composition that can be produced from renewable resources as raw materials and have excellent heat resistance after curing.SOLUTION: The present invention relates to an epoxy resin represented by the formula (II), and an epoxy resin composition containing the epoxy resin, where, in formula (II), one of Rand Ris a CHgroup and the other one is a CH(CH)group, and one of Rand Ris a CHgroup and the other one is a CH(CH)group. Ris a hydrogen atom or CH(CH)group.SELECTED DRAWING: None

Description

  The present invention relates to a curing agent for an epoxy resin, an epoxy resin, an epoxy resin composition, a phenol resin, and a method for producing an epoxy resin.

Epoxy resins are widely used in various fields because of their excellent mechanical strength, heat resistance, chemical resistance, adhesiveness, and the like, and low curing shrinkage. Epoxy resins are often produced from petroleum-derived raw materials.
On the other hand, in recent years, since there is a concern that petroleum resources may be depleted, production of resins using renewable resources such as plants is being studied. For example, a method of epoxidizing a phenol resin obtained using eugenol or thymol and furfural to obtain an epoxy resin is known (Patent Document 1).

JP 2008-195842 A

  When a cured product obtained by curing an epoxy resin is used as an insulating material for electronic materials, it is required to have excellent heat resistance. However, it is difficult to obtain an epoxy resin having excellent heat resistance after curing by a conventional method as in Patent Document 1.

  The present invention provides a curing agent for an epoxy resin, an epoxy resin, an epoxy resin composition, a phenol resin, and a method for producing an epoxy resin, which can be produced from renewable resources as raw materials and have excellent heat resistance after curing.

The present invention has the following aspects.
<1> A curing agent for an epoxy resin represented by the following formula (I).

(However, in the above formula (I), one of R ¹¹ and R ²¹ is a CH ₃ group and the other is a CH (CH ₃ ) ₂ group, and one of R ¹² and R ²² is a CH ₃ group and the other is A CH (CH ₃ ) ₂ group, and R ³ is a hydrogen atom or a CH (CH ₃ ) ₂ group.)
<2> An epoxy resin represented by the following formula (II).

(However, in the above formula (II), one of R ¹¹ and R ²¹ is a CH ₃ group, the other is a CH (CH ₃ ) ₂ group, and one of R ¹² and R ²² is a CH ₃ group and the other is A CH (CH ₃ ) ₂ group, and R ³ is a hydrogen atom or a CH (CH ₃ ) ₂ group.)
<3> An epoxy resin composition containing the epoxy resin curing agent according to <1> and an epoxy resin.
<4> An epoxy resin composition containing the epoxy resin of the above <2> and a curing agent.
<5> An epoxy resin composition comprising the epoxy resin curing agent of <1> and the epoxy resin of <2>.
<6> As shown in the following formula (1), a compound represented by the following formula (A) is reacted with a compound represented by the following formula (B) to form a phenol represented by the following formula (I). A method for producing a phenolic resin, which obtains a resin.

(However, in the above formula, ^one of R ¹ and R ² is a CH ₃ group, the other is a CH (CH ₃ ) ₂ group, one of R ¹¹ and R ²¹ is a CH ₃ group, and the other is CH (CH 3 ₃ ) _Two groups, one of R ¹² and R ²² is a CH ₃ group, the other is a CH (CH ₃ ) ₂ group, and R ³ is a hydrogen atom or a CH (CH ₃ ) ₂ group.)
<7> An epoxy resin obtained by reacting a phenol resin represented by the following formula (I) produced by the method for producing a phenol resin of the above <6> with epihalohydrin to obtain an epoxy resin represented by the following formula (II): Method of manufacturing resin.

(However, in the above formula, X is a halogen atom.)

  The curing agent for epoxy resin, epoxy resin and epoxy resin composition of the present invention can be produced using renewable resources as raw materials and have excellent heat resistance after curing. An epoxy resin composition is provided. Further, according to the method for producing a phenolic resin and an epoxy resin of the present invention, a curing agent for an epoxy resin and an epoxy resin having excellent heat resistance after curing can be produced using a renewable resource as a raw material.

<Curing agent for epoxy resin>
The epoxy resin curing agent according to the first aspect of the present invention is an epoxy resin curing agent represented by the following formula (I) (hereinafter, also referred to as “curing agent (I)”).

However, in the formula (I), one of R ¹¹ and R ²¹ is a CH ₃ group, and the other is a CH (CH ₃ ) ₂ group. One of R ¹² and R ²² is a CH ₃ group and the other is a CH (CH ₃ ) ₂ group, similarly to R ¹¹ and R ²¹ . R ³ is a hydrogen atom or a CH (CH ₃ ) ₂ group.

In the curing agent (I), R ¹¹ and R ¹² may be the same group, and R ²¹ and R ²² may be the same group. R ¹¹ and R ²² may be the same group, and R ²¹ and R ¹² may be the same. It may be a group. Among them, it is preferable that R ¹¹ and R ¹² be the same group, and that R ²¹ and R ²² be the same group, from the viewpoint of reaction control and cost reduction.
R ³ is preferably a CH (CH ₃ ) ₂ group from the viewpoint of low water absorption.

  Examples of the curing agent (I) include epoxy resin curing agents represented by the following formulas (I-1) to (I-2).

<Production method of phenol resin>
In the method for producing a phenolic resin according to the second aspect of the present invention, as shown in the following formula (1), a compound represented by the following formula (A) (hereinafter, also referred to as “compound (A)”) and the following: By reacting with a compound represented by the formula (B) (hereinafter, also referred to as “compound (B)”), a phenol resin represented by the following formula (I) (hereinafter, also referred to as “phenol resin (I)”) This is a method for obtaining

However, in the above formula, ^one of R ¹ and R ² is a CH ₃ group, and the other is a CH (CH ₃ ) ₂ group. R ¹¹ , R ²¹ , R ¹² , R ²² and R ³ are as described above.

Examples of the compound (A) include thymol and carvacrol. As the compound (A), one type may be used alone, or two types may be used in combination.
Examples of the compound (B) include cuminaldehyde and benzaldehyde. As the compound (B), one type may be used alone, or two types may be used in combination.

For example, the phenol resin (I) is obtained by reacting the compound (A) with the compound (B) in a solvent in the presence of an acid catalyst.
Examples of the acid catalyst include hydrochloric acid, sulfuric acid, phosphoric acid, p-toluenesulfonic acid, methanesulfonic acid, trifluoromethanesulfonic acid, trifluoroacetic acid, and trichloroacetic acid. As the acid catalyst, one type may be used alone, or two or more types may be used in combination.

The solvent is not particularly limited as long as it does not inhibit the reaction, and examples thereof include water, alcohols, ketones, amides, ethers, aromatic hydrocarbons, halogenated aromatic hydrocarbons, and halogenated fats. Group hydrocarbons.
Examples of alcohols include methanol, ethanol, 2-propanol and the like. Examples of ketones include acetone, methyl ethyl ketone, methyl isobutyl ketone, and the like. Examples of the amide include N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone, and the like. Examples of the ethers include diethyl ether, diisopropyl ether, tetrahydrofuran, dimethoxyethane, dioxane, and the like. Examples of the aromatic hydrocarbons include benzene, toluene, xylene, and the like. Examples of the halogenated aromatic hydrocarbons include chlorobenzene, dichlorobenzene and the like. Examples of the halogenated aliphatic hydrocarbons include dichloromethane, chloroform and the like.
As the solvent, one type may be used alone, or two or more types may be used in combination.

The molar ratio of the compound (A) to the compound (B) in the reaction solution is preferably from 2: 1 to 10: 1, more preferably from 2: 1 to 5: 1.
The amount of the acid catalyst to be used is preferably 0.01 to 1 mol, more preferably 0.1 to 0.8 mol, per 1 mol of compound (B).

The reaction temperature of the reaction between the compound (A) and the compound (B) is preferably from 0 to 150C, more preferably from 20 to 80C.
The reaction time of the reaction between the compound (A) and the compound (B) can be appropriately set according to the reaction temperature and the like, and can be, for example, 1 to 50 hours.
The purification of the reaction product is not particularly limited, and a known method can be employed.

  The reaction product obtained by the method for producing a phenolic resin according to the second embodiment includes a phenolic resin represented by the following formula (III) (hereinafter, also referred to as “phenolic resin (III)”) in addition to the phenolic resin (I). .) May be included.

Here, in the above formula (III), n is an integer of 2 to 10. R ¹ and R ² are the same as R ¹ and R ² in the formula (A). A plurality of R ¹ in the formula (III) may be the same group or different groups. Further, a plurality of R ² in the formula (III) may be the same group or different groups.

  The phenolic resin (I) obtained by the method for producing a phenolic resin of the second embodiment can be used, for example, as the above-mentioned curing agent (I). The phenol resin (I) can also be used as a raw material in the production of an epoxy resin of a third embodiment described later.

  Further, the phenolic resin (I) obtained by the method for producing a phenolic resin according to the second embodiment may have a hydroxy group substituted with a functional group other than an epoxy group. For example, the phenolic resin (I) can be used as a raw material for a polyester resin, a polycarbonate resin, a polyformal resin, a phenoxy resin, a carbonate monomer, an epoxy acrylate, and the like.

  When the phenol resin (III) is by-produced in the production of the phenol resin (I), when the phenol resin (I) is used as a raw material for the curing agent (I) or the epoxy resin of the third embodiment, The phenol resin (III) may be used while containing it, or the phenol resin (III) may be separated and used.

<Epoxy resin>
The epoxy resin of the third aspect of the present invention is an epoxy resin represented by the following formula (II) (hereinafter, also referred to as “epoxy resin (II)”).

However, ^{R 11, R 21, R 12} , R 22 and ^{R 3} in the formula (II) is the same as ^{R 11, R 21, R 12} , R 22 and ^{R 3} in the formula (I) .

In the epoxy resin (II), R ¹¹ and R ¹² may be the same group, and R ²¹ and R ²² may be the same group. R ¹¹ and R ²² may be the same group, and R ²¹ and R ¹² may be the same. It may be a group. Among them, it is preferable that R ¹¹ and R ¹² be the same group, and that R ²¹ and R ²² be the same group, from the viewpoint of reaction control and cost reduction.
R ³ is preferably a CH (CH ₃ ) ₂ group from the viewpoint of low water absorption.

  Examples of the epoxy resin (II) include epoxy resins represented by the following formulas (II-1) to (II-2).

  The epoxy resin (II) can be produced by reacting the phenolic resin (I) produced by the above-mentioned method for producing a phenolic resin with epihalohydrin, as shown in the following formula (2).

  Here, in the above formula, X is a halogen atom. Examples of the halogen atom include a chlorine atom and a bromine atom, and a chlorine atom is preferable.

For example, an epoxy resin (II) can be obtained by reacting a phenol resin (I) with epihalohydrin in the presence of an alkali compound.
Examples of epichlorohydrin include epichlorohydrin, epibromohydrin and the like, and epichlorohydrin is preferable.

  In the reaction between the phenolic resin (I) and epihalohydrin, a solvent may be used or a solvent may not be used. For example, the reaction can be performed without using a solvent by using epihalohydrin in excess. The solvent is not particularly limited as long as it does not inhibit the reaction, and includes the same solvents as those described in the method for producing phenolic resin (I).

  Examples of the alkali compound include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and alkali metal carbonates such as sodium carbonate and potassium carbonate. As the alkali compound, one type may be used alone, or two or more types may be used in combination. The alkali compound may be added from the beginning of the reaction, or may be added after the phenol resin (I) and epihalohydrin are sufficiently reacted.

  In the reaction between the phenol resin (I) and epihalohydrin, a catalyst for accelerating the reaction may be used. As the catalyst, a known catalyst used for a reaction of epoxidizing a hydroxy group with epihalohydrin can be applied, and an ammonium salt is preferable.

  Examples of the ammonium salt include quaternary ammonium salts such as benzyltriethylammonium chloride, benzyltriethylammonium bromide, tetra-n-butylammonium fluoride and tetra-n-butylammonium bromide. As the ammonium salt, one type may be used alone, or two or more types may be used in combination.

The amount of epihalohydrin used is preferably an excess with respect to the phenol resin (I).
The amount of the alkali compound to be used is preferably 1.8 to 6 mol, more preferably 1.9 to 5 mol, per 1 mol of the phenol resin (I).
When a catalyst is used, the amount of the catalyst to be used is preferably 0.01 to 1 mol, more preferably 0.1 to 0.5 mol, per 1 mol of the phenol resin (I).

The reaction temperature of the reaction between the phenolic resin (I) and epihalohydrin is preferably from 0 to 150 ° C, more preferably from 20 to 100 ° C.
The reaction time of the reaction between the phenolic resin (I) and epihalohydrin can be appropriately set according to the reaction temperature and the like, and can be, for example, 1 to 50 hours.
The purification of the product after the reaction is not particularly limited, and a known method can be employed.

<Epoxy resin composition>
The epoxy resin composition of the fourth aspect of the present invention (hereinafter referred to as “epoxy resin composition (i)”) contains a curing agent (I) and an epoxy resin. The epoxy resin contained in the epoxy resin composition (i) is an epoxy resin other than the epoxy resin (II).

The epoxy resin composition (i) may contain a curing agent other than the curing agent (I) in addition to the curing agent (I).
The curing agent other than the curing agent (I) is not particularly limited, and includes, for example, an imidazole-based curing agent, an amine-based curing agent, an acid anhydride-based curing agent, and an amidoamine-based curing agent. As the curing agent, one type may be used alone, or two or more types may be used in combination.

  Examples of the imidazole-based curing agent include, for example, 2-methylimidazole, 2-ethylimidazole, 2-undecylimidazole, 2,4-dimethylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, and 1,2-dimethylimidazole. Diethylimidazole, 2-phenyl-4-methylimidazole, 2,4,5-triphenylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2 -Methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-benzyl-2-methylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 2-aryl-4,5-diphenylimidazole, 2,4- Diamino-6- [2 ′ Methylimidazolyl- (1) ′]-ethyl-S-triazine, 2,4-diamino-6- [2′-ethyl-4′-methylimidazolyl- (1) ′]-ethyl-S-triazine, 2,4 -Diamino-6- [2'-methylimidazolyl- (1) ']-ethyl-S-triazine isocyanuric acid adduct and 2-phenyl-4-methyl-5-hydroxymethylimidazole.

  Examples of the amine-based curing agent include ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, dipropylenetriamine, diethylaminopropylamine, N-aminoethylpiperazine, isophoronediamine, and bis (4-amino-3-methylcyclohexyl). Examples include methane, menthanediamine, 1,3-bisaminomethylcyclohexane, xylylenediamine, phenylenediamine, diaminodiphenylmethane, and diaminodiphenylsulfone.

Examples of the acid anhydride-based curing agent include phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, trimellitic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic anhydride, chlorendic anhydride, dodecynyl succinic anhydride, Examples thereof include methylhexahydrophthalic anhydride represented by methyltetrahydrophthalic anhydride, methylendomethylenetetrahydrophthalic anhydride, and 4-methylhexahydrophthalic anhydride.
Examples of the amidoamine-based curing agent include dicyandiamide.

  The epoxy resin is not particularly limited, and examples thereof include a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, a cresol novolak type epoxy resin, a phenol novolak type epoxy resin, and a biphenyl type epoxy resin. As the epoxy resin, one type may be used alone, or two or more types may be used in combination.

The epoxy resin composition (i) may include a curing catalyst.
The curing catalyst is not particularly limited. For example, 2-methyl-4-methylimidazole (2E4MZ), triarylphosphines, tetraphenylphosphonium / tetraphenylborate, 1,8-diazabicyclo (5,4,0) undecene -7 and the like. As the curing catalyst, one type may be used alone, or two or more types may be used in combination.

  The epoxy resin composition (i) may contain a photopolymerization initiator or a thermal polymerization initiator. The photopolymerization initiator and the thermal polymerization initiator are not particularly limited, and known photopolymerization initiators and thermal polymerization initiators can be applied. As the photopolymerization initiator and the thermal polymerization initiator, one type may be used alone, or two or more types may be used in combination.

  The epoxy resin composition (i) may contain a diluting solvent. The diluting solvent is not particularly limited as long as it can dissolve or disperse each component and does not inhibit the curing reaction, and examples thereof include the same ones as described in the method for producing phenolic resin (I).

  The epoxy resin composition (i) may contain various additives as long as the curing is not hindered. As additives, for example, stabilizers, lubricants, pigments, impact modifiers, processing aids, reinforcing agents, colorants, flame retardants, weather resistance modifiers, ultraviolet absorbers, antioxidants, antifungal agents, Examples include antibacterial agents, light stabilizers, antistatic agents, silicone oils, antiblocking agents, release agents, foaming agents, fragrances and the like.

  The ratio of the curing agent (I) to the total amount of the curing agent in the epoxy resin composition (i) is preferably 10% by mass or more, more preferably 20% by mass or more, still more preferably 40% by mass or more, and 100% by mass or more. Particularly preferred. When the proportion of the curing agent (I) is at least the lower limit, a cured product having low water absorption and excellent heat resistance can be easily obtained.

The content of the curing agent in the epoxy resin composition (i) is such that the number of moles of an active hydrogen group such as a hydroxy group, a carboxy group or the like contained in the curing agent is 0.5 to 1. An amount of 5 mol is preferable, and an amount of 0.8 to 1.2 mol is more preferable.
The content of the curing agent (I) in the epoxy resin composition (i) can be, for example, 10 to 100 parts by mass with respect to 100 parts by mass of the epoxy resin.

  The content of the curing catalyst in the epoxy resin composition (i) is not particularly limited, and may be, for example, 0.1 to 20 parts by mass with respect to 100 parts by mass of the epoxy resin.

  The epoxy resin composition of the fifth aspect of the present invention (hereinafter referred to as “epoxy resin composition (ii)”) contains an epoxy resin (II) and a curing agent. The curing agent contained in the epoxy resin composition (ii) is a curing agent other than the curing agent (I). Examples of the curing agent other than the curing agent (I) include the same curing agents as those described for the epoxy resin composition (i).

The epoxy resin composition (ii) may contain an epoxy resin other than the epoxy resin (II) in addition to the epoxy resin (II). Examples of the epoxy resin other than the epoxy resin (II) include the same ones as those described for the epoxy resin composition (i).
Further, the epoxy resin composition (ii) may contain a curing catalyst, a photopolymerization initiator, a thermal polymerization initiator, a diluting solvent, and various additives similarly to the epoxy resin composition (i).

  The ratio of the epoxy resin (II) to the total amount of the epoxy resin in the epoxy resin composition (ii) is preferably 10% by mass or more, more preferably 20% by mass or more, still more preferably 40% by mass or more, and 100% by mass or more. Particularly preferred. When the proportion of the epoxy resin (II) is at least the lower limit, a cured product having low water absorption and excellent heat resistance can be easily obtained.

The content of the curing agent in the epoxy resin composition (ii) is preferably such that the number of moles of active hydrogen groups contained in the curing agent is 0.5 to 1.5 mol per 1 mol of epoxy group contained in the epoxy resin. , 0.8 to 1.2 mol is more preferable.
The content of the curing agent in the epoxy resin composition (ii) can be, for example, 10 to 100 parts by mass with respect to 100 parts by mass of the epoxy resin.
The content of the curing catalyst in the epoxy resin composition (ii) is not particularly limited, and may be, for example, 0.1 to 20 parts by mass with respect to 100 parts by mass of the epoxy resin.

  The epoxy resin composition of the sixth aspect of the present invention (hereinafter referred to as “epoxy resin composition (iii)”) contains a curing agent (I) and an epoxy resin (II).

The epoxy resin composition (iii) may contain a curing agent other than the curing agent (I) in addition to the curing agent (I). Examples of the curing agent other than the curing agent (I) include the same curing agents as those described for the epoxy resin composition (i).
The epoxy resin composition (iii) may contain an epoxy resin other than the epoxy resin (II) in addition to the epoxy resin (II). Examples of the epoxy resin other than the epoxy resin (II) include the same ones as those described for the epoxy resin composition (i).
Further, the epoxy resin composition (iii) may contain a curing catalyst, a photopolymerization initiator, a thermal polymerization initiator, a diluting solvent, and various additives similarly to the epoxy resin composition (i).

  The proportion of the epoxy resin (II) to the total amount of the epoxy resin in the epoxy resin composition (iii) is preferably 10% by mass or more, more preferably 20% by mass or more, still more preferably 40% by mass or more, and 100% by mass. Particularly preferred. When the proportion of the epoxy resin (II) is at least the lower limit, a cured product having low water absorption and excellent heat resistance can be easily obtained.

  The ratio of the curing agent (I) to the total amount of the curing agent in the epoxy resin composition (iii) is preferably 10% by mass or more, more preferably 20% by mass or more, still more preferably 40% by mass or more, and 100% by mass. Particularly preferred. When the proportion of the curing agent (I) is at least the lower limit, a cured product having low water absorption and excellent heat resistance can be easily obtained.

The content of the curing agent in the epoxy resin composition (iii) is preferably such that the number of moles of active hydrogen groups contained in the curing agent is 0.5 to 1.5 mol per mol of epoxy group contained in the epoxy resin. , 0.8 to 1.2 mol is more preferable.
The content of the curing agent in the epoxy resin composition (iii) can be, for example, 10 to 100 parts by mass with respect to 100 parts by mass of the epoxy resin.
The content of the curing catalyst in the epoxy resin composition (iii) is not particularly limited, and may be, for example, 0.1 to 20 parts by mass with respect to 100 parts by mass of the epoxy resin.

  The epoxy resin composition (i) is cured by the reaction between the epoxy resin and a curing agent containing at least the curing agent (I). The epoxy resin composition (ii) is cured by reacting an epoxy resin containing at least the epoxy resin (II) with a curing agent. The epoxy resin composition (iii) is cured by a reaction between an epoxy resin containing at least the epoxy resin (II) and a curing agent containing at least the curing agent (I).

At the time of the curing reaction, heating is preferred from the viewpoint of accelerating the curing reaction. The heating method is not particularly limited.
The curing temperature is, for example, preferably from 40 to 250C, more preferably from 60 to 230C.

The glass transition temperature (Tg) of the cured product obtained by curing the epoxy resin compositions (i) to (iii) is preferably 100 ° C. or higher, and more preferably 120 ° C. or higher, from the viewpoint of heat resistance. The upper limit of the Tg of the cured product is not particularly limited, and is, for example, about 250 ° C. as a guide.
The Tg of the cured product is a temperature determined as a midpoint glass transition temperature (T _mg ) measured according to JIS K 7121: 1987 “Method of measuring transition temperature of plastic”.

  The uses of the epoxy resin compositions (i) to (iii) are not particularly limited, and include, for example, paints (coatings), adhesives, electric insulating materials, composite materials (composite materials), civil engineering building materials, tools, and 3D printers. Materials. The epoxy resin compositions (i) to (iii) are particularly useful as an electrical insulating material because a cured product having a low water absorption and a high Tg can be obtained.

  As described above, the curing agent (I) can be produced by reacting the compound (A), which is a renewable resource, with the compound (B). The epoxy resin (II) can be produced by reacting a phenolic resin (I) obtained by reacting the compound (A) with the compound (B) and epihalohydrin, which is a renewable resource. In addition, when the curing agent (I), the epoxy resin (II), and the epoxy resin compositions (i) to (iii) are used, a cured product excellent in heat resistance can be obtained. Further, the obtained cured product has low water absorption.

Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited by the following description.
[Example 1]
A phenol resin (I-1) was produced by a reaction represented by the following formula (1-1).
Specifically, 3.00 g of thymol as the compound (A), 1.48 g of cuminaldehyde as the compound (B), 0.49 g of 35% hydrochloric acid, and 3.5 g of methanol were put into a glass container and mixed. While stirring at 50 ° C. for 25 hours. After completion of the reaction, the mixture was allowed to cool to precipitate crystals. Thereafter, the crystals were neutralized with a 10% aqueous sodium hydroxide solution and then washed with water, and the crystals were separated by filtration. The crystals separated by filtration were dried under reduced pressure at room temperature to obtain 3.94 g of phenol resin (I-1).
The obtained phenol resin (I-1) was identified by measuring its ¹ H-NMR spectrum using heavy dimethyl sulfoxide (DMSO) as a heavy solvent.

[Example 2]
A phenol resin (I-2) was produced by a reaction represented by the following formula (1-2).
Specifically, the reaction was carried out in the same manner as in Example 1 except that carvacrol was used as the compound (A) instead of thymol, and the reaction time was changed to 28 hours. After completion of the reaction, the mixture was allowed to cool to precipitate crystals, which was separated by filtration and washed with a mixed solvent of methanol and water. Thereafter, the crystals were dissolved in ethyl acetate, neutralized with a 5% aqueous sodium hydrogen carbonate solution, washed with water, and dehydrated with anhydrous magnesium sulfate. After the ethyl acetate was distilled off, the residue was recrystallized from a mixed solution of methanol and water, filtered and dried to obtain 3.32 g of a phenol resin (I-2).
The obtained phenol resin (I-2) was identified by ¹ H-NMR measurement in the same manner as in Example 1.

[Example 3]
The epoxy resin (II-1) was produced by the reaction represented by the following formula (2-1).
Specifically, 1.00 g of the phenol resin (I-1) obtained in Example 1, 4.29 g of epichlorohydrin, 0.18 g of tetra-n-butylammonium bromide (TBAB) as a catalyst, and ion-exchanged water 24 mg was put into a glass container, mixed, heated to 80 ° C., and reacted for 6 hours. Thereafter, while cooling with ice, 1.0 g of a 48% by mass aqueous sodium hydroxide solution was added dropwise, and the reaction was allowed to proceed for 1 hour.
Next, after ion-exchanged water was added to dissolve the precipitated salt, ethyl acetate was added and mixed well, and the aqueous phase was separated. The obtained organic phase was washed with brine, dried over anhydrous magnesium sulfate, and ethyl acetate and remaining epichlorohydrin were distilled off under reduced pressure to give a yellow viscous epoxy resin (II-1) 1. .28 g were obtained.
The obtained epoxy resin (II-1) was identified by ¹ H-NMR measurement in the same manner as in Example 1.

[Example 4]
An epoxy resin (II-2) was produced by a reaction represented by the following formula (2-2).
A pale yellow viscous epoxy resin (II-2) in the same manner as in Example 3 except that the phenol resin (I-2) obtained in Example 2 was used instead of the phenol resin (I-1). 1.28 g were obtained.
The obtained epoxy resin (II-2) was identified by ¹ H-NMR measurement in the same manner as in Example 1.

(Evaluation)
0.83 g of the epoxy resin (II-1) obtained in Example 3 and 0.13 g of isophoronediamine were mixed in a glass container and heated in an oven at 100 ° C. × 1 h, 160 ° C. × 1 h, and 200 ° C. × 1 h. Thus, a cured product was prepared. This cured product was finely crushed, and Tg was measured by a differential scanning calorimeter (DSC). The Tg was 148 ° C., indicating good heat resistance.
0.66 g of the epoxy resin (II-2) obtained in Example 4 and 0.11 g of isophoronediamine were mixed in a glass container, and heated in an oven at 100 ° C. × 1 h, 160 ° C. × 1 h, and 200 ° C. × 1 h. Thus, a cured product was prepared. The cured product was finely crushed, and the Tg was measured by DSC. The Tg was 139 ° C., indicating good heat resistance.

  The curing agent (I), the epoxy resin (II), and the epoxy resin compositions (i) to (iii) are useful as an electric insulating material.

Claims (7)

A curing agent for an epoxy resin represented by the following formula (I).

(However, in the above formula (I), one of R ¹¹ and R ²¹ is a CH ₃ group and the other is a CH (CH ₃ ) ₂ group, and one of R ¹² and R ²² is a CH ₃ group and the other is A CH (CH ₃ ) ₂ group, and R ³ is a hydrogen atom or a CH (CH ₃ ) ₂ group.) An epoxy resin represented by the following formula (II).

(However, in the above formula (II), one of R ¹¹ and R ²¹ is a CH ₃ group, the other is a CH (CH ₃ ) ₂ group, and one of R ¹² and R ²² is a CH ₃ group and the other is A CH (CH ₃ ) ₂ group, and R ³ is a hydrogen atom or a CH (CH ₃ ) ₂ group.)   An epoxy resin composition comprising the epoxy resin curing agent according to claim 1 and an epoxy resin.   An epoxy resin composition comprising the epoxy resin according to claim 2 and a curing agent.   An epoxy resin composition comprising the epoxy resin curing agent according to claim 1 and the epoxy resin according to claim 2. As shown in the following formula (1), a compound represented by the following formula (A) is reacted with a compound represented by the following formula (B) to obtain a phenol resin represented by the following formula (I). , Phenolic resin production method.

(However, in the above formula, ^one of R ¹ and R ² is a CH ₃ group, the other is a CH (CH ₃ ) ₂ group, one of R ¹¹ and R ²¹ is a CH ₃ group, and the other is CH (CH 3 ₃ ) _Two groups, one of R ¹² and R ²² is a CH ₃ group, the other is a CH (CH ₃ ) ₂ group, and R ³ is a hydrogen atom or a CH (CH ₃ ) ₂ group.) A method for producing an epoxy resin, comprising reacting a phenol resin represented by the following formula (I) produced by the method for producing a phenol resin according to claim 6 with epihalohydrin to obtain an epoxy resin represented by the following formula (II). .

(In the above formula, X is a halogen atom.)