JP7119801B2 - Epoxy resins, epoxy resin compositions, cured epoxy resins and composite materials - Google Patents

Description

TECHNICAL FIELD The present invention relates to epoxy resins, epoxy resin compositions, cured epoxy resins and composite materials.

Epoxy resins are widely used as matrix resins for fiber reinforced plastics (FRP). Recently, epoxy resins are also used as matrix resins for FRPs used in aerospace applications, which require high levels of physical properties such as fracture toughness, elasticity and heat resistance. However, thermosetting resins such as epoxy resins tend to be inferior to thermoplastic resins in terms of fracture toughness, although they are superior in heat resistance.

As a technique for improving the fracture toughness of an epoxy resin, for example, it is known to introduce a mesogenic structure into the molecule to enhance the orientation of the molecule in the cured product (see, for example, Patent Document 1).

JP 2014-122337 A

When the mesogen-containing epoxy resin described in Patent Document 1 is used to form a cured product, it is difficult to obtain high elasticity although high toughness is obtained.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an epoxy resin and an epoxy resin composition from which a cured epoxy resin having both high elasticity and high toughness can be obtained.
Another object of the present invention is to provide an epoxy resin cured product having both high elasticity and high toughness, and a composite material containing the same.

Means for solving the above problems include the following embodiments.
<1> A compound having a mesogenic structure and an epoxy group, a compound having an epoxy group and an epoxy equivalent of 160 g/eq or less, and an aromatic compound having a functional group capable of reacting with the epoxy group are reacted. Epoxy resin containing compounds.
<2> The epoxy resin according to <1>, wherein the reacted compound contains at least one of a compound represented by the following general formula (a) and a compound represented by the following general formula (b).

[In general formulas (a) and (b), R ¹ , R ² and R ³ each independently represent a monovalent group, and Z each independently represents -O- or -NH-. In general formula (a) at least one of R ¹ , R ² and R ³ has an epoxy group, and in general formula (b) at least one of R ¹ and R ² has an epoxy group. In general formula (a), at least one of R ¹ , R ² and R ³ has a structure derived from the compound having a mesogenic structure and an epoxy group, and in general formula (b) R ¹ and R ² At least one has a structure derived from a compound having a mesogenic structure and an epoxy group. In general formula (a), at least one of R ¹ , R ² and R ³ has the epoxy group and has a structure derived from a compound having an epoxy equivalent of 160 g/eq or less, and general formula (b) At least one of R ¹ and R ² has the epoxy group and has a structure derived from a compound having an epoxy equivalent of 160 g/eq or less. ]
<3> An epoxy resin containing a first epoxy compound having a mesogenic structure and a second epoxy compound having an epoxy equivalent of 160 g/eq or less.
<4> The epoxy according to <3>, wherein the first epoxy compound includes a compound obtained by reacting a compound having a mesogenic structure and an epoxy group with an aromatic compound having a functional group capable of reacting with the epoxy group. resin.
<5> The first epoxy compound includes a compound having a mesogenic structure and an epoxy group, a compound having an epoxy group and an epoxy equivalent of 160 g/eq or less, and an aromatic having a functional group capable of reacting with the epoxy group. The epoxy resin according to <3> or <4>, which contains a compound obtained by reacting with a group compound.
<6> The epoxy resin according to any one of <1> to <5>, wherein the mesogenic structure includes a structure represented by the following general formula (3).

[In general formula (3), R ³ to R ⁶ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. * represents a bonding site with an adjacent atom. ]
<7> The compounds formed by the reaction are represented by the following general formulas (3-A), (3-B), (4-A), (4-B), (5-A) and (5-B) The epoxy resin according to any one of <1>, <2>, <4> and <5>, which has at least one structure selected from the group consisting of:

[In general formulas (3-A), (3-B), (4-A), (4-B), (5-A) and (5-B), R ¹ and R ² are each independently It represents an alkyl group having 1 to 8 carbon atoms. Each m independently represents an integer of 0 to 4, and each n independently represents an integer of 0 to 6. R ³ to R ⁶ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. Each Z independently represents -O- or -NH-. * represents a bonding site with an adjacent atom. ]

<8> An epoxy resin composition further comprising the epoxy resin according to any one of <1> to <7> and a curing agent.
<9> The epoxy resin composition according to <8>, which can form a smectic structure or a nematic structure when cured.
<10> An epoxy resin cured product which is a cured product of the epoxy resin composition according to <8> or <9>.
<11> A composite material comprising the epoxy resin cured product according to <10> and a reinforcing material.

ADVANTAGE OF THE INVENTION According to this invention, the epoxy resin and epoxy resin composition which can obtain the epoxy resin hardened|cured material which balanced high elasticity and high toughness can be provided.
Further, according to the present invention, it is possible to provide an epoxy resin cured product having both high elasticity and high toughness, and a composite material containing the same.

DETAILED DESCRIPTION OF THE INVENTION Embodiments for carrying out the present invention will be described in detail below. However, the present invention is not limited to the following embodiments. In the following embodiments, the constituent elements (including element steps and the like) are not essential unless otherwise specified. The same applies to numerical values and their ranges, which do not limit the present invention.

In the present disclosure, the term "process" includes a process that is independent of other processes, and even if the purpose of the process is achieved even if it cannot be clearly distinguished from other processes. .
In the present disclosure, the numerical range indicated using "-" includes the numerical values before and after "-" as the minimum and maximum values, respectively.
In the numerical ranges described step by step in the present disclosure, the upper limit or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described step by step. . Moreover, in the numerical ranges described in the present disclosure, the upper or lower limits of the numerical ranges may be replaced with the values shown in the examples.
In the present disclosure, each component may contain multiple types of applicable substances. When there are multiple types of substances corresponding to each component in the composition, the content rate or content of each component is the total content rate or content of the multiple types of substances present in the composition unless otherwise specified. means quantity.
In the present disclosure, "epoxy compound" means a compound having an epoxy group in its molecule. "Epoxy resin" is a concept that considers a plurality of epoxy compounds as an aggregate and means an uncured state.

[First embodiment]
<Epoxy resin>
First, the epoxy resin of the first embodiment will be described. The epoxy resin of the present disclosure comprises a compound having a mesogenic structure and an epoxy group, a compound having an epoxy group and an epoxy equivalent of 160 g/eq or less, and an aromatic compound having a functional group capable of reacting with the epoxy group. A compound formed by reaction (hereinafter also referred to as "specific epoxy compound (A)") is included. By using the epoxy resin of the present disclosure, a cured epoxy resin product having both high elasticity and high toughness can be obtained. The reason for this is that the compound having a mesogenic structure and an epoxy group has excellent molecular orientation, so that the cured product has excellent toughness. It is presumed that this is because the density is improved and the cured product can be made highly elastic.

An epoxy resin containing a compound having a mesogenic structure and an epoxy group forms a higher order structure in a cured product of an epoxy resin composition containing this resin. Here, the higher-order structure means a structure including a higher-order structure in which its constituent elements are arranged to form a micro-ordered structure, and corresponds to, for example, a crystal phase and a liquid crystal phase. The presence or absence of such higher-order structures can be determined by a polarizing microscope. That is, it can be determined by observing interference fringes due to depolarization in observation in the crossed Nicols state. This higher-order structure usually exists in the form of islands in the cured epoxy resin composition to form a domain structure, and one of the islands corresponds to one higher-order structure. The components themselves of this higher-order structure are generally formed by covalent bonds.

Higher-order structures formed in a cured state include a nematic structure and a smectic structure. A nematic structure and a smectic structure are each a type of liquid crystal structure. The nematic structure is a liquid crystal structure in which the long axes of the molecules are oriented in a uniform direction, and only the alignment order is present. On the other hand, the smectic structure is a liquid crystal structure having a one-dimensional positional order and a layered structure in addition to the orientational order. Order is higher in the smectic structure than in the nematic structure. Therefore, from the viewpoint of thermal conductivity and fracture toughness of the cured product, it is more preferable to form a higher-order smectic structure.

Whether or not a smectic structure is formed in the cured product can be determined by X-ray diffraction measurement of the cured product. The X-ray diffraction measurement can be performed using, for example, an X-ray diffractometer manufactured by Rigaku Corporation. In the present disclosure, when X-ray diffraction measurement is performed using CuKα1 radiation, with a tube voltage of 40 kV, a tube current of 20 mA, and 2θ = 1° to 30°, a diffraction peak appears in the range of 2θ = 2° to 10°. In this case, it is determined that a smectic structure is formed in the cured product.

A mesogenic structure in a compound having a mesogenic structure and an epoxy group means a structure in which an epoxy resin containing an epoxy compound having the mesogenic structure may exhibit liquid crystallinity. Specifically, biphenyl structure, phenylbenzoate structure, cyclohexylbenzoate structure, azobenzene structure, stilbene structure, terphenyl structure, anthracene structure, derivatives thereof, and structures in which two or more of these mesogenic structures are bonded via a bonding group. etc.

The specific epoxy compound (A) preferably contains at least one of a compound represented by the following general formula (a) and a compound represented by the following general formula (b).

In general formulas (a) and (b), R ¹ , R ² and R ³ each independently represent a monovalent group, and Z each independently represents -O- or -NH-. In general formula (a) at least one of R ¹ , R ² and R ³ has an epoxy group, and in general formula (b) at least one of R ¹ and R ² has an epoxy group. In general formula (a), at least one of R ¹ , R ² and R ³ has a structure derived from a compound having a mesogenic structure and an epoxy group (hereinafter also referred to as structure (A)), and general formula (b ), at least one of R ¹ and R ² has a structure (structure (A)) derived from a compound having a mesogenic structure and an epoxy group. In general formula (a), at least one of R ¹ , R ² and R ³ has an epoxy group, and a structure derived from a compound having an epoxy equivalent of 160 g/eq or less (hereinafter also referred to as structure (B)) and in general formula (b), at least one of R ¹ and R ² has an epoxy group and has a structure (structure B) derived from a compound having an epoxy equivalent of 160 g/eq or less.

In general formula (a), each of R ¹ , R ² and R ³ preferably has at least one of structure (A) and structure (B). Also, in general formula (b), each of R ¹ and R ² preferably has at least one of structure (A) and structure (B).

The mesogenic structure in the compound having a mesogenic structure and an epoxy group may be a structure represented by the following general formula (1).

In general formula (1), X represents at least one linking group selected from group (I) consisting of the following divalent groups. Each Y independently represents an aliphatic hydrocarbon group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a nitro group, or an acetyl group. . Each n independently represents an integer of 0 to 4. * represents a bonding site with an adjacent atom.

In group (I), each Y is independently an aliphatic hydrocarbon group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a nitro group. , or an acetyl group. Each n independently represents an integer of 0 to 4, k represents an integer of 0 to 7, m represents an integer of 0 to 8, and l represents an integer of 0 to 12.

In the mesogenic structure represented by the general formula (1), X is preferably at least one linking group selected from the group (Ia) consisting of the following divalent groups, selected from the group (Ia) It is more preferable that the linking group is at least one linking group containing at least one cyclic structure.

In group (Ia), each Y is independently an aliphatic hydrocarbon group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a cyano group, a nitro group. , or an acetyl group. Each n independently represents an integer of 0 to 4, k represents an integer of 0 to 7, m represents an integer of 0 to 8, and l represents an integer of 0 to 12.

The mesogenic structure in the compound having a mesogenic structure and an epoxy group is preferably a mesogenic structure represented by the following general formula (2).

In general formula (2), the definitions and preferred examples of X, Y and n are the same as the definitions and preferred examples of X, Y and n in general formula (1). * represents a bonding site with an adjacent atom.

Furthermore, the mesogenic structure in the compound having a mesogenic structure and an epoxy group may be a mesogenic structure represented by the following general formula (3) or a mesogenic structure represented by the following general formula (4). Among them, a mesogenic structure represented by the following general formula (3) is preferable.

In general formulas (3) and (4), R ³ to R ⁶ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. * represents a bonding site with an adjacent atom.

R ³ to R ⁶ are each independently preferably a hydrogen atom or an alkyl group having 1 to 2 carbon atoms, more preferably a hydrogen atom or a methyl group, and still more preferably a hydrogen atom. In addition, 2 to 4 of R ³ to R ⁶ are preferably hydrogen atoms, more preferably 3 or 4 are hydrogen atoms, and more preferably all 4 are hydrogen atoms. preferable. When any one of R ³ to R ⁶ is an alkyl group having 1 to 3 carbon atoms, at least one of R ³ and R ⁶ is preferably an alkyl group having 1 to 3 carbon atoms.

The compound having a mesogenic structure and an epoxy group may contain an epoxy compound monomer having a mesogenic structure, for example, an epoxy compound represented by the following general formula (1-m).

In general formula (1-m), the definitions and preferred examples of X, Y and n are the same as the definitions and preferred examples of X, Y and n in general formula (1).

From the viewpoint of higher-order structure formation, the epoxy compound represented by general formula (1-m) is preferably an epoxy compound represented by general formula (2-m) below.

The definitions and preferred examples of X, Y and n in general formula (2-m) are the same as the definitions and preferred examples of X, Y and n in general formula (1-m).

The epoxy compound represented by general formula (1-m) is more preferably an epoxy compound represented by general formula (3-m) below.

The definitions and preferred examples of R ³ to R ⁶ in general formula (3-m) are the same as the definitions and preferred examples of R ³ to R ⁶ in general formula (3).

Also, the compound having a mesogenic structure and an epoxy group may contain an epoxy compound represented by the following general formula (4-m).

The definitions and preferred examples of R ³ to R ⁶ in general formula (4-m) are the same as the definitions and preferred examples of R ³ to R ⁶ in general formula (3).

Moreover, as a compound having a mesogenic structure and an epoxy group, one type may be used alone, or a mixture of two or more types may be used.

The compound having an epoxy group and an epoxy equivalent of 160 g/eq or less is preferably a compound having an aromatic ring, more preferably a compound having one or more glycidyl ether groups bonded to the aromatic ring. A compound in which two glycidyl ether groups are bonded to an aromatic ring is more preferable.
Aromatic rings include benzene and naphthalene rings.
As the compound having an epoxy group and an epoxy equivalent of 160 g/eq or less, one type may be used alone, or a mixture of two or more types may be used.

A compound having an epoxy group and an epoxy equivalent of 160 g/eq or less preferably has two epoxy groups. Since the number of epoxy groups is two, it tends to be possible to suitably form a cured product while suppressing gelation of the epoxy resin.

The compound having an epoxy group and an epoxy equivalent of 160 g/eq or less is an epoxy compound represented by the following general formula (1-a) and an epoxy compound represented by the following general formula (1-b). is preferred.

In general formula (1-a), each Z is independently an aliphatic hydrocarbon group having 1 to 8 carbon atoms, an alkoxy group having 1 to 7 carbon atoms, a fluorine atom, a chlorine atom, a bromine atom, a cyano group, a nitro group. , or an acetyl group. p represents an integer of 0-4.
In general formula (1-b), each Z is independently an aliphatic hydrocarbon group having 1 to 3 carbon atoms, an alkoxy group having 1 to 2 carbon atoms, a fluorine atom, a chlorine atom, a cyano group, a nitro group, or acetyl indicates a group. q represents an integer of 0 to 3;
Also, p is preferably 0 to 2, more preferably 0.
q is preferably 0 or 1, more preferably 0.

The compound having an epoxy group and an epoxy equivalent of 160 g/eq or less is more preferably at least one of epoxy compounds represented by the following general formulas (1-c) to (1-e). .

In general formulas (1-c) to (1-e), the definitions and preferred examples of Z, p, and q are Z, p, and q in general formulas (1-a) and (1-b). is the same as the definition and preferred examples of

The type of aromatic compound having a functional group capable of reacting with an epoxy group is not particularly limited. From the viewpoint of forming a smectic structure in the cured product, dihydroxybenzene compounds having a structure in which two hydroxyl groups are bonded to one benzene ring, diaminobenzene compounds having a structure in which two amino groups are bonded to one benzene ring, A dihydroxybiphenyl compound having a structure in which one hydroxyl group is bonded to each of two benzene rings forming a biphenyl structure, a diaminobiphenyl compound having a structure in which one amino group is bonded to each of two benzene rings forming a biphenyl structure, 1 At least one selected from the group consisting of a dihydroxynaphthalene compound having a structure in which two hydroxyl groups are bonded to one naphthalene ring and a diaminonaphthalene compound having a structure in which two amino groups are bonded to one naphthalene ring (hereinafter referred to as a specific aromatic Also referred to as a group compound).

Dihydroxybenzene compounds include catechol, resorcinol, hydroquinone, derivatives thereof, and the like.
Diaminobenzene compounds include 1,2-diaminobenzene, 1,3-diaminobenzene, 1,4-diaminobenzene and derivatives thereof.

Dihydroxybiphenyl compounds include 2,2'-dihydroxybiphenyl, 2,3'-dihydroxybiphenyl, 2,4'-dihydroxybiphenyl, 3,3'-dihydroxybiphenyl, 3,4'-dihydroxybiphenyl, 4,4' -dihydroxybiphenyl, derivatives thereof, and the like.
Diaminobiphenyl compounds include 2,2'-diaminobiphenyl, 2,3'-diaminobiphenyl, 2,4'-diaminobiphenyl, 3,3'-diaminobiphenyl, 3,4'-diaminobiphenyl, 4,4' -diaminobiphenyl, derivatives thereof, and the like.

Dihydroxynaphthalene compounds include 1,2-dihydroxynaphthalene, 1,3-dihydroxynaphthalene, 1,4-dihydroxynaphthalene, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 1,7-dihydroxynaphthalene, 1, 8-dihydroxynaphthalene, 2,3-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, derivatives thereof, and the like.
Diaminonaphthalene compounds include 1,2-diaminonaphthalene, 1,3-diaminonaphthalene, 1,4-diaminonaphthalene, 1,5-diaminonaphthalene, 1,6-diaminonaphthalene, 1,7-diaminonaphthalene, 1, 8-diaminonaphthalene, 2,3-diaminonaphthalene, 2,6-diaminonaphthalene, 2,7-diaminonaphthalene, derivatives thereof, and the like.

Derivatives of the specific aromatic compound include compounds in which a substituent such as an alkyl group having 1 to 8 carbon atoms is bonded to the benzene ring or naphthalene ring of the specific aromatic compound. One of the specific aromatic compounds may be used alone, or two or more thereof may be used in combination.

A method of reacting a compound having a mesogenic structure and an epoxy group, a compound having an epoxy group and an epoxy equivalent of 160 g/eq or less, and an aromatic compound having a functional group capable of reacting with the epoxy group is particularly limited. not. Specifically, for example, these compounds and a reaction catalyst to be used as necessary may be dissolved in a solvent and stirred while being heated for reaction.
Alternatively, for example, these compounds may be mixed without using a reaction catalyst and a solvent and reacted by stirring while heating.

The solvent can dissolve a compound having a mesogenic structure and an epoxy group, a compound having an epoxy group and an epoxy equivalent of 160 g/eq or less, and an aromatic compound having a functional group capable of reacting with the epoxy group, and There is no particular limitation as long as the solvent can be heated to a temperature required for these compounds to react. Specific examples include cyclohexanone, cyclopentanone, ethyl lactate, propylene glycol monomethyl ether, N-methylpyrrolidone, methyl cellosolve, ethyl cellosolve, propylene glycol monopropyl ether and the like.

The amount of the solvent includes a compound having a mesogenic structure and an epoxy group, a compound having an epoxy group and an epoxy equivalent of 160 g/eq or less, an aromatic compound having a functional group capable of reacting with the epoxy group, and, if necessary, There is no particular limitation as long as the amount is capable of dissolving the reaction catalyst to be used accordingly at the reaction temperature. Although the solubility varies depending on the type of raw material before the reaction, the type of solvent, etc., for example, if the concentration of solids charged is 20% by mass to 60% by mass, the viscosity of the solution after the reaction is in a preferable range. There is a tendency.

The type of reaction catalyst is not particularly limited, and an appropriate one can be selected from the viewpoint of reaction rate, reaction temperature, storage stability, and the like. Specific examples include imidazole compounds, organic phosphorus compounds, tertiary amines, quaternary ammonium salts and the like. One of the reaction catalysts may be used alone, or two or more thereof may be used in combination.

From the viewpoint of heat resistance of the cured product, an organic phosphorus compound is preferable as the reaction catalyst.
Preferred examples of organic phosphorus compounds include organic phosphine compounds, compounds having intramolecular polarization obtained by adding compounds having π bonds such as maleic anhydride, quinone compounds, diazophenylmethane, and phenolic resins to organic phosphine compounds, and organic phosphine compounds. A complex of a phosphine compound and an organic boron compound and the like can be mentioned.

Specific examples of organic phosphine compounds include triphenylphosphine, diphenyl(p-tolyl)phosphine, tris(alkylphenyl)phosphine, tris(alkoxyphenyl)phosphine, tris(alkylalkoxyphenyl)phosphine, tris(dialkylphenyl)phosphine, tris(trialkylphenyl)phosphine, tris(tetraalkylphenyl)phosphine, tris(dialkoxyphenyl)phosphine, tris(trialkoxyphenyl)phosphine, tris(tetraalkoxyphenyl)phosphine, trialkylphosphine, dialkylarylphosphine, alkyldiaryl phosphine and the like.

Specific examples of quinone compounds include 1,4-benzoquinone, 2,5-toluquinone, 1,4-naphthoquinone, 2,3-dimethylbenzoquinone, 2,6-dimethylbenzoquinone, 2,3-dimethoxy-5-methyl- 1,4-benzoquinone, 2,3-dimethoxy-1,4-benzoquinone, phenyl-1,4-benzoquinone and the like.

Specific examples of organic boron compounds include tetraphenylborate, tetra-p-tolylborate, tetra-n-butylborate and the like.

The amount of reaction catalyst is not particularly limited. From the viewpoint of reaction rate and storage stability, 0.1 per 100 parts by mass of the total mass of the compound having a mesogenic structure and an epoxy group and the aromatic compound having a functional group capable of reacting with the epoxy group of this compound. It is preferably from 0.2 parts by mass to 1.5 parts by mass, more preferably from 0.2 parts by mass to 1 part by mass.

When these compounds are reacted, all of the compounds having a mesogenic structure and an epoxy group may be reacted, or part of them may remain unreacted. Moreover, all the compounds having an epoxy group and an epoxy equivalent of 160 g/eq or less may be reacted, or a part of them may remain unreacted.

From the viewpoint of balancing elasticity and toughness, before reacting these compounds, the epoxy group equivalent number (Ep1) of the compound having a mesogenic structure and an epoxy group and the epoxy group having an epoxy equivalent of 160 g / eq The ratio (Ep1:Ep2) to the number of epoxy group equivalents (Ep2) of the following compounds is preferably 90:10 to 10:90, more preferably 75:25 to 25:75, and 60 :40 to 40:60 is more preferable.

When these compounds are reacted, a reaction vessel such as a flask can be used for a small scale, and a reaction vessel such as a synthesis tank can be used for a large scale. A specific synthesis method is, for example, as follows.
First, a compound having a mesogenic structure and an epoxy group and a compound having an epoxy group and an epoxy equivalent of 160 g/eq or less are put into a reaction vessel, a solvent is added as necessary, and an oil bath or heat medium is added to the reaction temperature. to dissolve these epoxy compounds. An aromatic compound having a functional group capable of reacting with an epoxy group is added thereto, and then, if necessary, a reaction catalyst is added to initiate the reaction. Then, if necessary, the epoxy resin of the present disclosure is obtained by distilling off the solvent under reduced pressure.

The reaction temperature is not particularly limited as long as the reaction of these compounds proceeds. For example, it is preferably in the range of 100.degree. C. to 180.degree. Setting the reaction temperature to 100° C. or higher tends to shorten the time until the reaction is completed. On the other hand, setting the reaction temperature to 180° C. or lower tends to reduce the possibility of gelation.

When these compounds are reacted, a compound having a mesogenic structure and an epoxy group, a compound having an epoxy group and an epoxy equivalent of 160 g/eq or less, and an aromatic having a functional group capable of reacting with the epoxy group The compounding ratio with the compound is not particularly limited. For example, the ratio (A:B) of the total number of equivalents of epoxy groups (A) to the number of equivalents (B) of functional groups capable of reacting with epoxy groups is in the range of 10:10 to 10:0.01. A ratio may be used. From the viewpoint of fracture toughness and heat resistance of the cured product, a compounding ratio of A:B in the range of 10:5 to 10:0.1 is preferable.
From the viewpoint of the handleability of the epoxy resin, the ratio (A:B) of the total number of equivalents of epoxy groups (A) and the number of equivalents (B) of functional groups capable of reacting with epoxy groups is 10:1.6 to A compounding ratio in the range of 10:3.0 is preferable, a compounding ratio in the range of 10:1.8 to 10:2.9 is more preferable, and a range of 10:2.0 to 10:2.8 is preferable. A compounding ratio is more preferable.

The structure of the specific epoxy compound (A) is, for example, the molecular weight of the compound presumed to be obtained by the reaction, and the target compound determined by liquid chromatography performed using a liquid chromatograph equipped with a UV and mass spectrum detector. can be determined by comparing the molecular weight of

For liquid chromatography, for example, "LaChrom II C18" manufactured by Hitachi, Ltd. is used as an analytical column, and a gradient method is used to set the mixing ratio (volume basis) of the eluent to acetonitrile/tetrahydrofuran/10 mmol/l ammonium acetate. Measurement is performed by continuously changing the aqueous solution from 20/5/75 to acetonitrile/tetrahydrofuran=80/20 (20 minutes from the start) to acetonitrile/tetrahydrofuran=50/50 (35 minutes from the start). Also, the flow rate is set at 1.0 ml/min. The UV spectral detector detects absorbance at a wavelength of 280 nm, and the mass spectral detector detects an ionization voltage of 2700V.

The specific epoxy compound (A) is selected from the group consisting of the following general formulas (3-A), (3-B), (4-A), (4-B), (5-A) and (5-B) It is preferred to have at least one structure selected.

In general formulas (3-A), (3-B), (4-A), (4-B), (5-A) and (5-B), R ¹ and R ² are each independently carbon represents an alkyl group of numbers 1 to 8; Each m independently represents an integer of 0 to 4, and each n independently represents an integer of 0 to 6. R ³ to R ⁶ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. Each Z independently represents -O- or -NH-. * represents a bonding site with an adjacent atom.

Further, the specific epoxy compound (A) consists of the following general formulas (6-A), (6-B), (7-A), (7-B), (8-A) and (8-B) It may have at least one structure selected from the group.

In general formulas (6-A), (6-B), (7-A), (7-B), (8-A) and (8-B), R ¹ and R ² are each independently carbon represents an alkyl group of numbers 1 to 8; Each m independently represents an integer of 0 to 4, and each n independently represents an integer of 0 to 6. R ³ to R ⁶ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. Each Z independently represents -O- or -NH-. * represents a bonding site with an adjacent atom.

Further, the specific epoxy compound (A) preferably has at least one structure selected from the group consisting of the following general formulas (1-a') and (1-b').

In general formula (1-a′) and general formula (1-b′), the definitions and preferred examples of Z, p, and q are Z, p in general formula (1-a) and general formula (1-b) , q definitions and preferred examples. * represents a bonding site with an adjacent atom.

The specific epoxy compound (A) preferably has at least one structure selected from the group consisting of the following general formulas (1-c'), (1-d') and (1-e').

In general formulas (1-c′) to general formulas (1-e′), the definitions and preferred examples of Z, p, and q are Z, p in general formulas (1-c) to general formulas (1-e) , q definitions and preferred examples. * represents a bonding site with an adjacent atom.

The weight average molecular weight of the specific epoxy compound (A) that can be contained in the epoxy resin of the present disclosure is
There are no particular restrictions. From the viewpoint of lowering the viscosity, the weight average molecular weight (Mw) of the specific epoxy compound (A) is preferably selected from the range of 500 to 5000, more preferably selected from the range of 700 to 3000. More preferably, it is selected from the range of 800-1300.

In the present disclosure, number average molecular weight (Mn) and weight average molecular weight (Mw) are values obtained by liquid chromatography.
Liquid chromatography is performed with a sample concentration of 0.5% by mass, using tetrahydrofuran as a mobile phase, and a flow rate of 1.0 ml/min. A calibration curve is prepared using a polystyrene standard sample, and using it, Mn and Mw are measured in terms of polystyrene.
The measurement can be performed using, for example, a high-performance liquid chromatograph “L6000” manufactured by Hitachi, Ltd. and a data analyzer “C-R4A” manufactured by Shimadzu Corporation. As the column, for example, GPC columns "G2000HXL" and "G3000HXL" manufactured by Tosoh Corporation can be used.

The epoxy resin may contain a specific epoxy compound (B) described later, which is a compound obtained by reacting a compound having a mesogenic structure and an epoxy group with an aromatic compound having a functional group capable of reacting with the epoxy group. good.

(Physical properties of epoxy resin)
The physical properties of the epoxy resin of the present disclosure are described below.

[Weight average molecular weight]
The weight average molecular weight (Mw) of the epoxy resin of the present disclosure is not particularly limited. From the viewpoint of lowering the viscosity, the weight average molecular weight (Mw) of the epoxy resin is preferably selected from the range of 500-5000, more preferably from the range of 700-3000.

[Epoxy equivalent]
The epoxy equivalent of the epoxy resin of the present disclosure is not particularly limited. From the viewpoint of achieving both the fluidity of the epoxy resin and the thermal conductivity of the cured product, it is preferably 245 g/eq to 360 g/eq, more preferably 250 g/eq to 355 g/eq, and more preferably 260 g/eq to More preferably 350 g/eq. When the epoxy equivalent of the epoxy resin is 245 g/eq or more, the crystallinity of the epoxy resin does not become too high, so the fluidity of the epoxy resin tends to be less likely to decrease. On the other hand, when the epoxy equivalent of the epoxy resin is 360 g/eq or less, the crosslink density of the epoxy resin is less likely to decrease, so the thermal conductivity of the cured product tends to increase.

[viscosity]
The viscosity of the epoxy resin of the present disclosure is not particularly limited and can be selected according to the application of the epoxy resin. From the viewpoint of handleability, the epoxy resin preferably has a viscosity of less than 200 Pa·s at 60°C.
The viscosity of the epoxy resin at 60°C was measured using a dynamic viscoelasticity measuring device (e.g. Anton Paar's Rheometer MCR301). is raised from 30° C. to 150° C. in this order, and the viscosity at 60° C. during the temperature raising process is taken as the viscosity of the epoxy resin at 60° C. (Pa·s). The measurement conditions are: frequency: 1 Hz, plate: φ12 mm, gap: 0.2 mm, temperature drop rate during temperature drop process: 2° C./min, temperature rise rate during temperature rise process: 2° C./min.

[GPC peak area ratio]
In the epoxy resin of the present disclosure, the total ratio of the specific epoxy compound (A) obtained by liquid chromatography and the specific epoxy compound (B) described later (hereinafter also referred to as "GPC peak area ratio") is the epoxy having a mesogenic structure. It may be 50% or more of the entire compound. As a result, the viscosity tends to decrease when the temperature rises, and the handling of the epoxy resin tends to be excellent.
The GPC peak area ratio is the total area of the peaks derived from the specific epoxy compound (A) and the specific epoxy compound (B) in the total area of the peaks derived from the epoxy compounds having a mesogenic structure in the chart obtained by liquid chromatography. is the ratio (%) of Specifically, the absorbance of the epoxy resin to be measured at a wavelength of 280 nm is detected, and the total area of the peaks corresponding to the epoxy compound having a mesogenic structure and the specific epoxy compound (A) and the specific epoxy compound (B) are detected. It is calculated by the following formula from the total area of the peaks.
Percentage (%) of total area of peaks derived from specific epoxy compound (A) and specific epoxy compound (B) = (total area of peaks derived from specific epoxy compound (A) and specific epoxy compound (B)/mesogenic structure Total area of peaks derived from epoxy compounds having) × 100

Liquid chromatography is performed with a sample concentration of 0.5% by mass, using tetrahydrofuran as a mobile phase, and a flow rate of 1.0 ml/min. The measurement can be performed using, for example, a high-performance liquid chromatograph “L6000” manufactured by Hitachi, Ltd. and a data analyzer “C-R4A” manufactured by Shimadzu Corporation. As the column, for example, GPC columns "G2000HXL" and "G3000HXL" manufactured by Tosoh Corporation can be used.

From the viewpoint of improving handleability, the GPC peak area ratio may be 51% or more, or 52% or more, of the entire epoxy compound having a mesogenic structure.

In the epoxy resin of the present disclosure, the proportion of the monomer of the epoxy compound having a mesogenic structure obtained by liquid chromatography may be 50% or less, or 49% or less, of the total epoxy compound having a mesogenic structure. may be 48% or less. This ratio can be obtained by the same method as the GPC peak area ratio described above.

[Second embodiment]
Next, the epoxy resin of the second embodiment will be described. The epoxy resin of the present disclosure includes a first epoxy compound having a mesogenic structure and a second epoxy compound having an epoxy equivalent of 160 g/eq or less. By using the epoxy resin of the present disclosure, a cured epoxy resin product having both high elasticity and high toughness can be obtained. In addition, the description is abbreviate|omitted about the matter which is common in above-mentioned 1st embodiment.

The first epoxy compound used in the second embodiment may be a compound having a mesogenic structure and an epoxy group described above, may be the specific epoxy compound (A) described above, or may be a specific epoxy compound ( B). The first epoxy compound may be a mixture of a compound having one mesogenic structure and a compound having two or more mesogenic structures. Two or more mesogenic structures in a compound having two or more mesogenic structures may be different or the same.

The second epoxy compound used in the second embodiment may be a compound having the epoxy group described above and having an epoxy equivalent of 160 g/eq or less.

The first epoxy compound is a compound obtained by reacting a compound having a mesogenic structure and an epoxy group with an aromatic compound having a functional group capable of reacting with the epoxy group (hereinafter also referred to as "specific epoxy compound (B)" ) may be included. This tends to improve the fluidity of the epoxy resin.
The compound having a mesogenic structure and an epoxy group and the aromatic compound used to synthesize the specific epoxy compound (B) are the compounds having a mesogenic structure and an epoxy group used to synthesize the specific epoxy compound (A). And since it is the same as the above-mentioned aromatic compound, the explanation thereof is omitted. Moreover, since the preferred synthesis conditions for the specific epoxy compound (B) are the same as the preferred synthesis conditions for the specific epoxy compound (A), the description thereof is omitted.
Moreover, the weight average molecular weight of the specific epoxy compound (B) is not particularly limited. From the viewpoint of lowering the viscosity, the weight average molecular weight (Mw) of the specific epoxy compound (B) is preferably selected from the range of 500 to 5000, more preferably selected from the range of 700 to 3000. More preferably, it is selected from the range of 800-1300.

When synthesizing the specific epoxy compound (B), the compounding ratio of the compound having a mesogenic structure and an epoxy group and the aromatic compound having a functional group capable of reacting with the epoxy group is not particularly limited. For example, the ratio (A':B) of the equivalent number (A') of the epoxy group and the equivalent number (B) of the functional group capable of reacting with the epoxy group is in the range of 10:10 to 10:0.01. It is good also as a compounding ratio. From the viewpoint of the fracture toughness and heat resistance of the cured product, a mixing ratio of A':B in the range of 10:5 to 10:0.1 is preferable.
From the viewpoint of the handleability of the epoxy resin, the ratio (A':B) of the number of equivalents of the epoxy group (A') to the number of equivalents (B) of the functional group capable of reacting with the epoxy group is 10:1.6. ~10:3.0 is preferred, more preferably 10:1.8 to 10:2.9, and 10:2.0 to 10:2.8. is more preferable.

From the viewpoint of balancing elasticity and toughness, the ratio (Ep3:Ep2) of the number of epoxy group equivalents (Ep3) of the first epoxy compound to the number of epoxy group equivalents (Ep2) of the second epoxy compound is 90. : 10 to 10:90, more preferably 75:25 to 25:75, even more preferably 60:40 to 40:60.

When the epoxy resin contains an epoxy compound other than the first epoxy compound and the second epoxy compound, the total content of the first epoxy compound and the second epoxy compound is not particularly limited. For example, it is preferably 70% by mass to 99% by mass, more preferably 80% by mass to 99% by mass, and even more preferably 90% by mass to 99% by mass of the total epoxy resin.

<Epoxy resin composition>
The epoxy resin composition of the present disclosure includes the epoxy resin described above and a curing agent. From the viewpoint of fracture toughness, the epoxy resin composition is preferably capable of forming a smectic structure or a nematic structure when cured.

(curing agent)
The curing agent is not particularly limited as long as it is a compound capable of causing a curing reaction with the epoxy resin. Specific examples of curing agents include amine curing agents, phenol curing agents, acid anhydride curing agents, polymercaptan curing agents, polyaminoamide curing agents, isocyanate curing agents, blocked isocyanate curing agents, and the like. Curing agents may be used alone or in combination of two or more.

From the viewpoint of forming a higher-order structure in the cured product of the epoxy resin composition, the curing agent is preferably an amine curing agent or a phenol curing agent, more preferably an amine curing agent. As the amine curing agent, an amine curing agent having an aromatic ring and an amino group is preferable, an amine curing agent in which the amino group is directly bonded to the aromatic ring is more preferable, and two or more amino groups are directly bonded to the aromatic ring. more preferred are amine curing agents. Aromatic rings include benzene and naphthalene rings.

Specific examples of amine curing agents include 3,3′-diaminodiphenyl sulfone, 4,4′-diaminodiphenyl sulfone, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenyl ether, 4,4′-diamino- 3,3'-dimethoxybiphenyl, 4,4'-diaminophenyl benzoate, 1,5-diaminonaphthalene, 1,3-diaminonaphthalene, 1,4-diaminonaphthalene, 1,8-diaminonaphthalene, 1,3-diamino Benzene, 1,4-diaminobenzene, 4,4'-diaminobenzanilide, trimethylene-bis-4-aminobenzoate and the like.

From the viewpoint of forming a smectic structure in the cured product of the epoxy resin composition, 3,3'-diaminodiphenylsulfone, 4,4'-diaminodiphenylsulfone, 1,3-diaminobenzene, 1,4-diaminobenzene, 4 ,4'-diaminobenzanilide, 1,5-diaminonaphthalene, 4,4'-diaminodiphenylmethane and trimethylene-bis-4-aminobenzoate are preferred, from the viewpoint of obtaining a cured product with low water absorption and high fracture toughness. 3,3'-diaminodiphenyl sulfone is more preferred.

Examples of the phenolic curing agent include low-molecular-weight phenolic compounds and phenolic novolac resins formed by linking low-molecular-weight phenolic compounds with methylene chains or the like to form novolacs. Examples of low-molecular-weight phenol compounds include monofunctional phenol compounds such as phenol, o-cresol, m-cresol and p-cresol; bifunctional phenol compounds such as catechol, resorcinol and hydroquinone; , 2,4-trihydroxybenzene and 1,3,5-trihydroxybenzene.

The content of the curing agent in the epoxy resin composition is not particularly limited. From the viewpoint of the efficiency of the curing reaction, the number of equivalents of the functional groups of the curing agent contained in the epoxy resin composition (the number of equivalents of active hydrogen in the case of an amine curing agent) and the number of equivalents of the epoxy groups of the epoxy resin. The amount is preferably such that the ratio (number of equivalents of functional group/number of equivalents of epoxy group) is from 0.3 to 3.0, and more preferably from 0.5 to 2.0.

(other ingredients)
The epoxy resin composition may contain components other than the epoxy resin and the curing agent, if necessary. For example, it may contain curing catalysts, fillers, and the like. Specific examples of curing catalysts include compounds exemplified as reaction catalysts that can be used for synthesis of multimers.

The epoxy resin composition preferably has a fracture toughness value of 0.8 MPa m ^1/2 or more, more preferably 0.9 MPa m ^1/2 or more, and 1.0 MPa when cured. • More preferably, m ^1/2 or more.
The fracture toughness value of the cured product is measured by the method described in Examples below.

The epoxy resin composition preferably has a flexural modulus of 2.8 GPa or more, more preferably 2.9 GPa or more, and even more preferably 3.0 GPa or more when cured.
The flexural modulus of the cured product is measured by the method described in Examples below.

The epoxy resin composition preferably has a glass transition temperature of 145° C. or higher, more preferably 150° C. or higher, and even more preferably 155° C. or higher when cured.
The glass transition temperature of the cured product can be measured, for example, as follows. Specifically, the cured product is cut into strips to prepare a test piece, and dynamic viscoelasticity measurement is performed in a tensile mode to calculate. The measurement conditions are a frequency of 10 Hz, a heating rate of 5° C./min, and a strain of 0.1%. For example, RSA-G2 (TA Instruments) can be used as the evaluation device.

(Application)
Applications of the epoxy resin composition are not particularly limited, and it can be suitably used in processing methods that require low viscosity and excellent fluidity. For example, it is also suitable for the production of FRP, which involves impregnating the voids between fibers with an epoxy resin composition while heating, and the production of sheet-like materials, which involves spreading the epoxy resin composition with a squeegee or the like while heating. can be used for

The epoxy resin composition of the present disclosure is used in processing methods where it is desired to omit or reduce the addition of a solvent for viscosity reduction from the viewpoint of suppressing the generation of voids in the cured product (for example, aircraft, spacecraft, etc.) production of FRP).

<Epoxy resin cured product and composite material>
The epoxy resin cured product of the present disclosure is a cured product obtained by curing the epoxy resin composition of the present disclosure. A composite material of the present disclosure includes the cured epoxy resin of the present disclosure and a reinforcing material.

The material of the reinforcing material contained in the composite material is not particularly limited, and can be selected according to the application of the composite material. Specific examples of reinforcing materials include carbon materials, glass, aromatic polyamide resins (eg, Kevlar (registered trademark)), ultra-high molecular weight polyethylene, alumina, boron nitride, aluminum nitride, mica, and silicon. The shape of the reinforcing material is not particularly limited, and may be fibrous, particulate (filler), or the like. From the viewpoint of the strength of the composite material, the reinforcing material is preferably a carbon material, more preferably carbon fiber. One or two or more reinforcing materials may be included in the composite material.

The form of the composite material is not particularly limited. For example, it may have a structure in which at least one cured product-containing layer containing a cured epoxy resin and at least one reinforcing material-containing layer containing a reinforcing material are laminated.

EXAMPLES The above embodiments will be described in more detail below based on examples, but the above embodiments are not limited to these. "Parts" and "%" are based on mass unless otherwise specified.

[Example 1]
(Synthesis of epoxy resin 1)
50 parts by mass of (4-{4-(2,3-epoxypropoxy)phenyl}cyclohexyl=4-(2,3-epoxypropoxy)benzoate, compound of the following structural formula (1)) was added to a 500 ml three-necked flask. and 26 parts by mass of EX201 (resorcinol-type diglycidyl ether, Nagase ChemteX Corporation, epoxy equivalent: 117 g/eq). Furthermore, 80 parts by mass of a synthetic solvent (propylene glycol monomethyl ether) was added to the three-necked flask. A cooling tube and a nitrogen inlet tube were installed in the three-necked flask, and a stirring blade was attached so that the flask was immersed in the solvent. This three-necked flask was immersed in a 120° C. oil bath and stirring was started. After confirming that the epoxy compound was dissolved to form a transparent solution, 8 parts by mass of 1,5-dihydroxynaphthalene and 0.5 parts by mass of a reaction catalyst were added, and heating was continued in an oil bath at 120°C. . After continuing heating for 3 hours, propylene glycol monomethyl ether was distilled off from the reaction solution under reduced pressure, and the residue was cooled to room temperature (25°C) to obtain epoxy resin 1.

Next, 100 parts by mass of the obtained epoxy resin 1 and 26 parts by mass of 3,3′-diaminodiphenylsulfone as a curing agent were weighed into a stainless petri dish, heated to 180° C. on a hot plate, and the epoxy in the stainless petri dish was cured. After the resin composition was melted, it was stirred with a spatula. After heating at 180° C. for 1 hour and then cooling to room temperature (25° C.), the epoxy resin composition is taken out from the stainless petri dish and heated at 230° C. for 1 hour in a constant temperature bath to complete curing. got This epoxy resin cured product was cut into a rectangular parallelepiped of 3.75 mm×7.5 mm×33 mm to prepare a test piece for evaluation of fracture toughness. Further, the epoxy resin cured product was cut into strips of 2 mm×5 mm×50 mm to prepare test pieces for evaluation of bending elastic modulus.

[Example 2]
Epoxy resin 2 was obtained in the same manner as in Example 1, except that 32 parts by mass of HP4032 (epoxy resin having a naphthalene structure, DIC Corporation, epoxy equivalent: 147 g/eq) was used instead of 26 parts by mass of EX201. rice field. Then, an epoxy resin cured product was obtained in the same manner as in Example 1 except that epoxy resin 2 was used instead of epoxy resin 1, and each test piece was produced.

[Example 3]
Epoxy resin 3 was obtained in the same manner as in Example 1, except that 10 parts by mass of 4,4-biphenol was used instead of 8 parts by mass of 1,5-dihydroxynaphthalene. Then, 100 parts by mass of the obtained epoxy resin 3, 20 parts by mass of EX201, and 34 parts by mass of 3,3′-diaminodiphenylsulfone as a curing agent were weighed into a stainless petri dish. After that, an epoxy resin cured product was obtained in the same manner as in Example 1, and each test piece was produced.

[Example 4]
100 parts by mass of epoxy resin 3 obtained in Example 3, 40 parts by mass of EX201, and 45 parts by mass of 3,3'-diaminodiphenylsulfone as a curing agent were weighed into a stainless petri dish. After that, an epoxy resin cured product was obtained in the same manner as in Example 1, and each test piece was produced.

[Example 5]
Epoxy resin 4 was obtained in the same manner as in Example 2, except that 8 parts by mass of 4,4-biphenol was used instead of 8 parts by mass of 1,5-dihydroxynaphthalene. Then, 100 parts by mass of the obtained epoxy resin 4 and 24 parts by mass of 3,3'-diaminodiphenylsulfone as a curing agent were weighed into a stainless petri dish. After that, an epoxy resin cured product was obtained in the same manner as in Example 1, and each test piece was produced.

[Example 6]
100 parts by mass of epoxy resin 4 obtained in Example 5, 20 parts by mass of HP4032, and 33 parts by mass of 3,3'-diaminodiphenylsulfone as a curing agent were weighed into a stainless petri dish. After that, an epoxy resin cured product was obtained in the same manner as in Example 1, and each test piece was produced.

[Comparative Example 1]
50 parts by mass of the compound of the above structural formula (1) was added to a 500 ml three-necked flask, and 80 parts by mass of a synthetic solvent (propylene glycol monomethyl ether) was added thereto. A cooling tube and a nitrogen inlet tube were installed in the three-necked flask, and a stirring blade was attached so that the flask was immersed in the solvent. This three-necked flask was immersed in a 120° C. oil bath and stirring was started. After confirming that the epoxy compound was dissolved to form a transparent solution, 5 parts by mass of 4,4-biphenol and 0.5 parts by mass of a reaction catalyst were added, and heating was continued in an oil bath at 120°C. After continuing heating for 3 hours, propylene glycol monomethyl ether was distilled off from the reaction solution under reduced pressure, and the residue was cooled to room temperature (25° C.) to obtain epoxy resin 5.

Next, 100 parts by mass of the obtained epoxy resin 5 and 19 parts by mass of 3,3'-diaminodiphenylsulfone as a curing agent were weighed into a stainless petri dish. After that, an epoxy resin cured product was obtained in the same manner as in Example 1, and each test piece was produced.

[Comparative Example 2]
100 parts by mass of a commercially available epoxy resin (ELM434, Sumitomo Chemical Co., Ltd., epoxy equivalent: 106 g/eq) and 59 parts by mass of 3,3'-diaminodiphenylsulfone as a curing agent were weighed into a stainless petri dish. After that, an epoxy resin cured product was obtained in the same manner as in Example 1, and each test piece was produced.

The compositions of the epoxy resins prepared in Examples 1 to 6 and Comparative Examples 1 and 2 are shown in Table 1 below. As the reaction catalyst in Table 1, "TBPLA" means tetra(n-butyl)phosphonium laurate, and "TBP2" means an adduct of tri-n-butylphosphine and p-benzoquinone.

[Measurement of fracture toughness value]
A fracture toughness value (MPa·m ^1/2 ) was used as an index of the fracture toughness of the epoxy resin cured product. The fracture toughness value of the specimen was calculated by performing a three-point bending measurement based on ASTM D5045. Instron 5948 (Instron) was used as an evaluation device.

[Measurement of flexural modulus]
A flexural modulus (GPa) at 25° C. was obtained as an index of elasticity of the epoxy resin cured product. The bending elastic modulus of the test piece was calculated by performing three-point bending measurement based on JIS K 7171 (2016). Tensilon (A&D Co., Ltd.) was used as an evaluation device.

[Presence or absence of higher-order structure]
The test pieces prepared in Examples 1 to 6 and Comparative Examples 1 and 2 were examined for the presence or absence of higher-order structures using a polarizing microscope. That is, the presence or absence of the higher-order structure was determined by whether or not interference fringes due to depolarization were observed in the crossed Nicols state.

Table 2 shows the flexural modulus, fracture toughness, and presence or absence of higher-order structures of the epoxy resin cured products of Examples 1 to 6 and Comparative Examples 1 and 2. In addition, in Comparative Example 2, the test piece was brittle and the fracture toughness value could not be measured.

As shown in Table 2, the epoxy resin cured products of Examples 1 to 6 had both high flexural modulus and fracture toughness, and both high elasticity and high toughness were achieved.

Claims (10)

Contains a compound obtained by reacting a compound having a mesogenic structure and an epoxy group, a compound having an epoxy group and an epoxy equivalent of 160 g/eq or less, and an aromatic compound having a functional group capable of reacting with the epoxy group. fruit,
The mesogenic structure includes a structure represented by the following general formula (3),
The compound having an epoxy group and an epoxy equivalent of 160 g/eq or less is at least an epoxy compound represented by the following general formula (1-a) and an epoxy compound represented by the following general formula (1-b): Epoxy resin on the one hand .

[In general formula (3), R ³ to R ⁶ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. * represents a bonding site with an adjacent atom. In general formula (1-a), each Z is independently an aliphatic hydrocarbon group having 1 to 8 carbon atoms, an alkoxy group having 1 to 7 carbon atoms, a fluorine atom, a chlorine atom, a bromine atom, a cyano group, a nitro group. , or an acetyl group. p represents an integer of 0-4. In general formula (1-b), each Z is independently an aliphatic hydrocarbon group having 1 to 3 carbon atoms, an alkoxy group having 1 to 2 carbon atoms, a fluorine atom, a chlorine atom, a cyano group, a nitro group, or acetyl indicates a group. q represents an integer of 0 to 3; ] 2. The epoxy resin according to claim 1, wherein the reacted compound includes at least one of a compound represented by the following general formula (a) and a compound represented by the following general formula (b).

[In general formulas (a) and (b), R ¹ , R ² and R ³ each independently represent a monovalent group, and Z each independently represents -O- or -NH-. In general formula (a) at least one of R ¹ , R ² and R ³ has an epoxy group, and in general formula (b) at least one of R ¹ and R ² has an epoxy group. In general formula (a), at least one of R ¹ , R ² and R ³ has a structure derived from the compound having a mesogenic structure and an epoxy group, and in general formula (b) R ¹ and R ² At least one has a structure derived from a compound having a mesogenic structure and an epoxy group. In general formula (a), at least one of R ¹ , R ² and R ³ has the epoxy group and has a structure derived from a compound having an epoxy equivalent of 160 g/eq or less, and general formula (b) At least one of R ¹ and R ² has the epoxy group and has a structure derived from a compound having an epoxy equivalent of 160 g/eq or less. ] A first epoxy compound having a mesogenic structure and a second epoxy compound having an epoxy equivalent of 160 g/eq or less ,
The mesogenic structure includes a structure represented by the following general formula (3),
The second epoxy compound is an epoxy resin that is at least one of an epoxy compound represented by the following general formula (1-a) and an epoxy compound represented by the following general formula (1-b) .

[In general formula (3), R ³ to R ⁶ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. * represents a bonding site with an adjacent atom. In general formula (1-a), each Z is independently an aliphatic hydrocarbon group having 1 to 8 carbon atoms, an alkoxy group having 1 to 7 carbon atoms, a fluorine atom, a chlorine atom, a bromine atom, a cyano group, a nitro group. , or an acetyl group. p represents an integer of 0-4. In general formula (1-b), each Z is independently an aliphatic hydrocarbon group having 1 to 3 carbon atoms, an alkoxy group having 1 to 2 carbon atoms, a fluorine atom, a chlorine atom, a cyano group, a nitro group, or acetyl indicates a group. q represents an integer of 0 to 3; ] 4. The epoxy resin according to claim 3, wherein the first epoxy compound comprises a compound obtained by reacting a compound having a mesogenic structure and an epoxy group with an aromatic compound having a functional group capable of reacting with the epoxy group. The first epoxy compound includes a compound having a mesogenic structure and an epoxy group, a compound having an epoxy group and an epoxy equivalent of 160 g/eq or less, and an aromatic compound having a functional group capable of reacting with the epoxy group. 5. The epoxy resin according to claim 3 or 4, which contains a compound formed by reacting with. The compound formed by the reaction is selected from the group consisting of the following general formulas (3-A), (3-B), (4-A), (4-B), (5-A) and (5-B) 6. The epoxy resin of any one of claims 1, 2, 4 and 5 having at least one selected structure.

[In general formulas (3-A), (3-B), (4-A), (4-B), (5-A) and (5-B), R ¹ and R ² are each independently It represents an alkyl group having 1 to 8 carbon atoms. Each m independently represents an integer of 0 to 4, and each n independently represents an integer of 0 to 6. R ³ to R ⁶ each independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. Each Z independently represents -O- or -NH-. * represents a bonding site with an adjacent atom. ] An epoxy resin composition further comprising the epoxy resin according to any one of claims 1 to 6 and a curing agent. 8. The epoxy resin composition according to claim 7 , which can form a smectic structure or a nematic structure when cured. An epoxy resin cured product which is a cured product of the epoxy resin composition according to claim 7 or 8 . A composite material comprising the epoxy resin cured product according to claim 9 and a reinforcing material.