JP2020143192A - Epoxy resin, epoxy resin composition, epoxy resin cured product and composite material - Google Patents

Abstract

To provide an epoxy resin that can form a cured product that maintains excellent toughness and also has excellent strength, and an epoxy resin composition, and an epoxy resin cured product and a composite material obtained by using these.SOLUTION: An epoxy resin contains an epoxy compound having a mesogen structure, and an epoxy compound having an alicyclic structure and at least one of an epoxy group and an alicyclic epoxy group bound to the alicyclic structure via a single bond, a C1-3 alkylene group or a C1-3 alkylene oxy group.SELECTED DRAWING: None

Description

The present disclosure relates to epoxy resins, epoxy resin compositions, epoxy resin cured products and composite materials.

In recent years, the replacement of metals with fiber reinforced plastics (FRP) has been progressing in fields where high levels of strength and toughness are required, such as aircraft body structural materials. Epoxy resins are used for various purposes by taking advantage of their excellent heat resistance, and are also widely used as materials for FRP (see, for example, Patent Documents 1 and 2).

Japanese Unexamined Patent Publication No. 2017-82213 Special Table 2017-505844

As an epoxy resin having excellent toughness, an epoxy resin containing an epoxy compound having a mesogen structure in the molecule is known. In the epoxy resin having a mesogen structure, molecules are oriented in the curing process to form a liquid crystal structure (smetic structure or nematic structure), so that a cured product having excellent toughness can be obtained.

The cured product obtained by using an epoxy resin having a mesogen structure exhibits excellent toughness, but there is room for improvement in terms of strength. However, there is generally a trade-off relationship between the strength and toughness of the cured epoxy resin, and it is difficult to improve the strength without lowering the toughness.

In view of the above circumstances, the present disclosure provides an epoxy resin and an epoxy resin composition capable of forming a cured product having excellent strength while maintaining good toughness, and an epoxy resin cured product and a composite material obtained by using these. The task is to do.

Means for solving the above problems include the following embodiments.
<1> An epoxy compound having a mesogen structure and an epoxy group bonded to the alicyclic structure and the alicyclic structure via a single bond, an alkylene group having 1 to 3 carbon atoms or an alkyleneoxy group having 1 to 3 carbon atoms. And an epoxy resin containing an epoxy compound having at least one of an alicyclic epoxy group.
<2> The epoxy resin according to <1>, wherein the mesogen structure contains a mesogen structure represented by the following general formula (1).

In the general formula (1), X represents a single bond or a linking group having at least one divalent group selected from the following group (A). 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. .. n independently represents an integer of 0 to 4. * Represents a binding site with an adjacent atom.

In group (A), 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, and a nitro group. , Or represents an acetyl group. n 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.
<3> The epoxy resin according to <2>, wherein the structure represented by the general formula (1) includes at least one structure selected from the group consisting of the following general formulas (3) and (4). ..

In the general formula (3) and the general formula (4), R ^{3 to} R ⁶ independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. * Represents a binding site with an adjacent atom.
<4> The epoxy compound having the mesogen structure contains an epoxy compound having at least two mesogen structures and a divalent group containing an aromatic ring arranged between the mesogen structures. <1> to < The epoxy resin according to any one of 3>.
<5> An epoxy resin composition containing the epoxy resin according to any one of <1> to <4> and a curing agent.
<6> An epoxy resin cured product, which is a cured product of the epoxy resin composition according to <5>.
<7> A composite material containing the epoxy resin cured product according to <6> and a reinforcing material.
<8> The composite material according to <7>, wherein the reinforcing material contains a carbon material.

According to the present disclosure, there are provided an epoxy resin and an epoxy resin composition capable of forming a cured product having excellent strength while maintaining good toughness, and an epoxy resin cured product and a composite material obtained by using them.

Hereinafter, embodiments for carrying out the present invention will be described in detail. However, the present invention is not limited to the following embodiments. In the following embodiments, the components (including element steps and the like) are not essential unless otherwise specified. The same applies to the numerical values and their ranges, and does not limit the present invention.

In the present disclosure, the term "process" includes not only a process independent of other processes but also the process if the purpose of the process is achieved even if the process cannot be clearly distinguished from the other process. ..
The numerical range indicated by using "~" in the present disclosure includes the numerical values before and after "~" as the minimum value and the maximum value, respectively.
In the numerical range described stepwise in the present disclosure, the upper limit value or the lower limit value described in one numerical range may be replaced with the upper limit value or the lower limit value of another numerical range described stepwise. .. Further, in the numerical range described in the present disclosure, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples.
In the present disclosure, each component may contain a plurality of applicable substances. When a plurality of substances corresponding to each component are present in the composition, the content or content of each component is the total content or content of the plurality of substances present in the composition unless otherwise specified. Means quantity.
In the present disclosure, a plurality of types of particles corresponding to each component may be contained. When a plurality of particles corresponding to each component are present in the composition, the particle size of each component means a value for a mixture of the plurality of particles present in the composition unless otherwise specified.
In the present disclosure, the term "layer" is used not only when the area where the layer exists is observed, but also when the layer is formed in the entire area or only a part of the area. included.
In the present disclosure, the term "laminated" refers to stacking layers, and two or more layers may be bonded or the two or more layers may be removable.
In the present disclosure, the "epoxy compound" means a compound having an epoxy group in the molecule. The "epoxy resin" is a concept in which a plurality of epoxy compounds are regarded as an aggregate and means a state in which the compound is not cured.

≪Epoxy resin≫
The epoxy resin of the present disclosure includes an epoxy compound having a mesogen structure (hereinafter, also referred to as a mesogen-containing epoxy compound), an alicyclic structure, and a single bond to the alicyclic structure, an alkylene group having 1 to 3 carbon atoms or 1 to 1 carbon atoms. It is an epoxy resin containing an epoxy compound having at least one of an epoxy group bonded via an alkyleneoxy group of 3 and an alicyclic epoxy group (hereinafter, also referred to as an alicyclic-containing epoxy compound).

The cured product obtained by curing the epoxy resin exhibits excellent toughness and is also excellent in strength. The reason is not always clear, but it is presumed as follows.

When the mesogen-containing epoxy compound contained in the epoxy resin is cured, the molecules are oriented to form a liquid crystal structure. This imparts excellent toughness to the cured product. On the other hand, the alicyclic structure contained in the alicyclic-containing epoxy compound improves the strength of the cured product. Here, since the epoxy group contained in the alicyclic-containing epoxy compound has a lower reactivity than the epoxy group contained in the mesogen-containing epoxy compound, the curing reaction of the mesogen-containing epoxy compound tends to proceed first. Therefore, it is considered that the molecular orientation of the mesogen-containing epoxy compound is less likely to be inhibited by the curing reaction of the alicyclic-containing epoxy compound, and the decrease in toughness is suppressed.

The ratio of the mesogen-containing epoxy compound and the alicyclic-containing epoxy compound contained in the epoxy resin is not particularly limited and can be selected according to the desired cured product properties. For example, the amount of the alicyclic-containing epoxy compound may be 10 parts by mass to 80 parts by mass, 15 parts by mass to 80 parts by mass, or 20 parts by mass to 60 parts by mass with respect to 100 parts by mass of the mesogen-containing epoxy compound. It may be a department.

In the present disclosure, when a certain epoxy compound corresponds to both a mesogen-containing epoxy compound and an alicyclic-containing epoxy compound, the epoxy compound corresponds to a mesogen-containing epoxy compound.

<Mesogen-containing epoxy compound>
The mesogen structure of a mesogen-containing epoxy compound means a structure in which an epoxy resin, which is a reaction product of an epoxy compound having the mesogen-containing epoxy compound, may exhibit liquid crystallinity. Specifically, the mesogen structure includes a biphenyl structure, a phenylbenzoate structure, a cyclohexylbenzoate structure, an azobenzene structure, a stilbene structure, a terphenyl structure, an anthracene structure, derivatives thereof, and two or more of these mesogen structures via a linking group. Examples thereof include a combined structure.

The number of mesogen structures in one molecule of the mesogen-containing epoxy compound may be one or two or more. The two or more mesogen structures in an epoxy compound having two or more mesogen structures may be different or the same.

The epoxy resin containing the mesogen-containing epoxy compound can form a higher-order structure in the cured product of the epoxy resin composition containing the epoxy resin. Here, the higher-order structure means a structure including a higher-order structure in which its components 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 a higher-order structure can be determined by a polarizing microscope. That is, the presence or absence of the higher-order structure can be discriminated by observing the cross-nicol state by observing interference fringes due to depolarization. This higher-order structure usually exists in an island shape in the cured product of the 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.

Examples of the higher-order structure formed in the cured state include a nematic structure and a smectic structure. The nematic structure and the smectic structure are each a kind of liquid crystal structure. The nematic structure is a liquid crystal structure in which the major axis of the molecule is oriented in a uniform direction and only the orientation order is present. On the other hand, the smectic structure is a liquid crystal structure having a one-dimensional position order in addition to the orientation order and having a layered structure. The order is higher in the smectic structure than in the nematic structure. Therefore, from the viewpoint of toughness of the cured product, it is more preferable to form a higher-order structure having a 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 in the range of tube voltage 40 kV, tube current 20 mA, 2θ = 1 ° to 30 ° using CuKα1 wire, a diffraction peak appears in the range of 2θ = 2 ° to 10 °. In some cases, it is determined that a smectic structure is formed in the cured product.

Epoxy resins containing mesogen-containing epoxy compounds tend to form higher-order structures when cured. Therefore, the epoxy resin containing the mesogen-containing epoxy compound tends to be more tough than the epoxy resin containing no epoxy compound having a mesogen structure.

The mesogen structure of the mesogen-containing epoxy compound may be a structure represented by the following general formula (1).

In the general formula (1), X represents a single bond or a linking group having at least one divalent group selected from the following group (A). 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. .. n independently represents an integer of 0 to 4. * Represents a binding site with an adjacent atom.

In group (A), 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, and a nitro group. , Or represents an acetyl group. n 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 mesogen structure represented by the general formula (1), when X is a linking group having at least one divalent group selected from the above group (A), the linking group is the following group (Aa). It is preferably a linking group having at least one divalent group selected from the group (Aa), having a linking group having at least one divalent group selected from the group (Aa), and at least one. More preferably, it is a linking group having a cyclic structure.

In the group (Aa), 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, and a nitro group. , Or represents an acetyl group. n 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.

From the viewpoint of easily forming a higher-order structure in the cured product, the mesogen structure represented by the general formula (1) preferably contains the mesogen structure represented by the following general formula (2).

In the general formula (2), X represents a single bond or a linking group having at least one divalent group selected from the group (A). 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. .. n independently represents an integer of 0 to 4. * Represents a binding site with an adjacent atom.

A preferable example of the mesogen structure represented by the general formula (2) is a mesogen structure represented by the following general formula (3) or general formula (4).

In the general formula (3) or the general formula (4), R ^{3 to} R ⁶ independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. * Represents a binding 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 even more preferably a hydrogen atom. Further, it is preferable that 2 to 4 of R ^{3 to} R ⁶ are hydrogen atoms, more preferably 3 or 4 are hydrogen atoms, and further 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, it is preferable that at least one of R ³ and R ⁶ is an alkyl group having 1 to 3 carbon atoms.

The mesogen-containing epoxy compound may be an epoxy compound having a structure represented by the following general formula (1-m).

In the 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 the general formula (1) described above.

From the viewpoint of forming a higher-order structure in the cured product, the epoxy compound represented by the general formula (1-m) may be an epoxy compound having a structure represented by the following general formula (2-m). preferable.

In the general formula (2-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 the general formula (1-m).

The epoxy compound represented by the general formula (1-m) is more preferably an epoxy compound having a structure represented by the following general formula (3-m) or general formula (4-m).

In the general formula (3-m) and the general formula ^(4-m), definition and preferred examples of R 3 to R ⁶ are defined and preferred for ^R 3 to R ⁶ in the general formula (3) and the general formula (4) Similar to the example.

<Alicyclic-containing epoxy compound>
The type of alicyclic structure contained in the alicyclic-containing epoxy compound is not particularly limited. For example, it may be a monocyclic type (cycloalkane) or a polycyclic type (bicycloalkane, tricycloalkane, etc.). From the viewpoint of making it difficult to inhibit the molecular orientation of the mesogen-containing epoxy compound, a monocyclic alicyclic structure is preferable.

Specifically, as the alicyclic structure, cyclopropane structure, cyclobutane structure, cyclopentane structure, cyclohexane structure, cycloheptane structure, cyclooctane structure, cubane structure, norbornane structure, tetrahydrodicyclopentadiene structure, adamantane structure, diadamantane structure, Examples thereof include a spiro ring structure such as a bicyclo [2.2.2] octane structure, a decahydronaphthalene structure, and a spiro [5.5] undecane structure.

The number of alicyclic structures contained in the alicyclic-containing epoxy compound is not particularly limited. For example, the number may be 1 to 20 in one molecule, preferably 1 to 10. When the alicyclic-containing epoxy compound contains two or more alicyclic structures, these structures may be the same or different from each other.

The alicyclic-containing epoxy compound is attached to the alicyclic structure via a single bond, an alkylene group having 1 to 3 carbon atoms (preferably a methylene group) or an alkyleneoxy group having 1 to 3 carbon atoms (preferably a methyleneoxy group). It has at least one of an epoxy group and an alicyclic epoxy group.
In the present disclosure, the "alicyclic epoxy group" means an ethylene oxide structure formed by two adjacent carbon atoms and one oxygen atom among the carbon atoms constituting the alicyclic structure.

The number of epoxy groups contained in the alicyclic-containing epoxy compound is not particularly limited. For example, the number may be 1 to 20 in one molecule, preferably 2 to 10. When the alicyclic-containing epoxy compound contains two or more epoxy groups, the method of bonding to the alicyclic structure may be the same or different.

Specific examples of the alicyclic-containing epoxy compound include the following compounds (a) to (d).

<Other epoxy compounds>
If necessary, the epoxy resin may contain an epoxy compound that does not fall under any of the mesogen-containing epoxy compound and the alicyclic-containing epoxy compound. The type of such an epoxy compound is not particularly limited and can be selected from commonly used ones.

In some embodiments, the epoxy resin may include an epoxy compound having an aromatic ring as an epoxy compound that does not fall under any of the mesogen-containing epoxy compound and the alicyclic-containing epoxy compound. The epoxy compound having an aromatic ring is preferably a compound in which one or more glycidyl ether groups are bonded to the aromatic ring, and is preferably a compound in which two glycidyl ether groups are bonded to the aromatic ring. Examples of the aromatic ring include a benzene ring and a naphthalene ring.

Specific examples of the epoxy compound that does not correspond to either the mesogen-containing epoxy compound or the alicyclic-containing epoxy compound are the epoxy compound represented by the following general formula (1-a) and the following general formula (1-b). Epoxy compounds can be mentioned.

In the general formula (1-a) and the general formula (1-b), Z 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, and the like. Represents a bromine atom, an iodine atom, a cyano group, a nitro group, or an acetyl group. p represents an integer from 0 to 4. q represents an integer from 0 to 6.
p is preferably 0 to 2, and more preferably 0.
q is preferably 0 to 4, more preferably 0 to 2, and even more preferably 0.

Among the epoxy compounds represented by the general formula (1-a) and the epoxy compounds represented by the following general formula (1-b), the following general formulas (1-c) to (1-e) are used. The epoxy compound to be used is preferable.

In the general formulas (1-c) to (1-e), the definitions and preferable examples of Z, p, and q are the Z, p, of the general formulas (1-a) and the general formula (1-b). And q are similar to the definitions and preferred examples.

When the epoxy resin contains an epoxy compound that does not correspond to either the mesogen-containing epoxy compound or the alicyclic-containing epoxy compound, the total ratio of the mesogen-containing epoxy compound and the alicyclic-containing epoxy compound is 50% by mass or more of the total epoxy resin. It is preferable, it is more preferably 70% by mass or more, and further preferably 80% by mass or more.

<Specific epoxy compound>
The mesogen-containing epoxy compound may be an epoxy compound having two or more mesogen structures (hereinafter, also referred to as “specific epoxy compound”).
When at least a part of the mesogen-containing epoxy compound is in the state of a specific epoxy compound, crystallization and high viscosity of the epoxy resin before curing are suppressed, and the handleability tends to be excellent.

The specific epoxy compound is not particularly limited as long as it is an epoxy compound having two or more mesogen structures. For example, the specific epoxy compound may be a dimer containing two or more molecules of a mesogen-containing epoxy compound (mesogen epoxy monomer) as a polymerization component, or a multimer of a trimer or more. The two or more mesogen structures in the particular epoxy compound may be the same or different from each other.

The specific epoxy compound preferably has a structure in which at least two mesogen structures are linked via a divalent group containing an aromatic ring. In this case, the at least two mesogen structures and the divalent group containing the aromatic ring may be directly linked or may be linked via a linking group.

In the present disclosure, when the mesogen structure of the specific epoxy compound contains a divalent group containing an aromatic ring, the divalent group containing an aromatic ring arranged between the two mesogen structures is included in the mesogen structure. It shall be different from the divalent group containing an aromatic ring.

Examples of the divalent group containing an aromatic ring arranged between the two mesogen structures include a phenylene group, a divalent biphenyl group, and a naphthylene group. The phenylene group has a structure represented by the following general formula (5A), the divalent biphenyl group has a structure represented by the following general formula (5B), and the naphthylene group has the following general formula (5C). ) Can be mentioned.

In the general formula (5A), the general formula (5B), and the general formula (5C), * represents a bond position with an adjacent atom. Examples of adjacent atoms include oxygen atoms and nitrogen atoms. R ¹ and R ² each independently represent an alkyl group having 1 to 8 carbon atoms. Each of m independently represents an integer of 0 to 4. p represents an integer from 0 to 6.

R ¹ and R ² are each independently preferably an alkyl group having 1 to 3 carbon atoms, and more preferably a methyl group.

m is preferably an integer of 0 to 2, more preferably an integer of 0 to 1, and even more preferably 0, respectively. p is preferably an integer of 0 to 2, and more preferably an integer of 0 to 1.

Among the structures represented by the general formula (5A), the structure represented by the following general formula (5a) is preferable, and among the structures represented by the general formula (5B), the structure represented by the following general formula (5b) is preferable. The structure is preferred. Among the structures represented by the general formula (5C), the structures represented by the following general formulas (5c-1) and general formula (5c-2) are preferable. It is considered that the specific epoxy compound having such a structure has high molecular stacking property and is more likely to form a higher-order structure.

Formula (5a), in the general formula (5b), the general formula (5c-1), and the general formula ^(5c-2), defined and preferred examples of R ^{1, R} 2, m, and p have the general formula ( 5A), the general formula (5B), and is the same as the definitions and preferable examples of ^R 1, ^{R 2} and m, and p in the general formula (5C). * Represents the bond position with an adjacent atom.

The specific epoxy compound may be an epoxy compound having a structure represented by the following general formula (1-A), general formula (1-B), or general formula (1-C).

In the general formula (1-A), the general formula (1-B), and the general formula (1-C), the definitions and preferable examples of X, Y and n are the X, Y and n of the general formula (1). Similar to the definition and preferred examples. ^{Further, the} definition and preferred examples of R ^{1, R} 2, m, and p, ^{R 1, R} 2, m, and the definition of p in the general formula (5A), the general formula (5B), and the general formula (5C) And similar to the preferred example. Z independently represents -O- or -NH-. * Represents a binding site with an adjacent atom.

From the viewpoint of forming a higher-order structure in the cured product, the epoxy compound having the structure represented by the general formula (1-A) is an epoxy compound having the structure represented by the following general formula (2-A). The epoxy compound having a structure represented by the general formula (1-B) is preferably an epoxy compound having a structure represented by the following general formula (2-B), and is preferably a general formula (1). The epoxy compound having a structure represented by −C) is preferably an epoxy compound having a structure represented by the following general formula (2-C).

Formula (2-A), the general formula (2-B), and in the general formula (2-C), X, Y, n, m, p, defined and preferred examples of R 1, ^{R 2,} and Z is , The definitions and preferred examples of X, Y, n, m, p, R ¹ , R ² and Z of the general formula (1-A), the general formula (1-B), and the general formula (1-C). Is. * Represents a binding site with an adjacent atom.

The epoxy compound having a structure represented by the general formula (1-A) has at least one structure selected from the group consisting of the following general formulas (3-A-1) to (3-A-4). Epoxy compounds having.
The epoxy compound having a structure represented by the general formula (1-B) is at least one structure selected from the group consisting of the following general formulas (3-B-1) to (3-B-4). Epoxy compounds having.
The epoxy compound having a structure represented by the general formula (1-C) is at least one structure selected from the group consisting of the following general formulas (3-C-1) to (3-C-4). Epoxy compounds having.

General formulas (3-A-1) to (3-A-4), general formulas (3-B-1) to (3-B-4), and general formulas (3-C-1) to (3-) in ^C-4), definition and preferred examples of ^{R 1, R 2, m,} p, and Z are formula (1-a), the general formula (1-B), and formula (1-C) Similar to the definitions and preferred examples of R ¹ , R ² , m, p and Z. Definitions and preferred examples of R ³ to R ⁶ are the same as defined and preferred examples of ^R 3 to R ⁶ in the general formula (3) or general formula (4). * Represents a binding site with an adjacent atom.

Further, the specific epoxy compound may have at least one structure selected from the group consisting of the following general formulas (1-a') and (1-b'). When the specific epoxy compound has at least one structure selected from the group consisting of (1-a') and (1-b'), the elastic modulus tends to be improved.

In the general formula (1-a') and the general formula (1-b'), the definitions and preferable examples of Z, p, q are Z, p of the general formula (1-a) and the general formula (1-b). , Q are similar to the definitions and preferred examples. * Represents a binding site with an adjacent atom.

Among the structures represented by the general formula (1-a'), the structures represented by the general formula (1-c') and the general formula (1-d') are preferable, and the general formula (1-b') is used. Among the structures represented, the structure represented by the general formula (1-e') is preferable.

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

The specific epoxy compound may be a reaction product of a mesogen-containing epoxy compound and a compound having a functional group capable of reacting with an epoxy group. Further, the specific epoxy compound may be a reaction product of a mesogen-containing epoxy compound, an epoxy compound other than the mesogen-containing epoxy compound, and a compound having a functional group capable of reacting with the epoxy group.

[Method for synthesizing specific epoxy compounds]
The method for synthesizing the specific epoxy compound is not particularly limited. The method for synthesizing the specific epoxy compound is, for example, a compound having one mesogen structure and an epoxy group (hereinafter, also referred to as a mesogen epoxy monomer), a compound having a functional group capable of reacting with the epoxy group, and if necessary. A specific epoxy compound may be obtained by reacting with an epoxy compound other than the epoxy compound having a mesogen structure.

The structure of the mesogen epoxy monomer is not particularly limited, and may be, for example, an epoxy compound having a structure represented by the above-mentioned general formula (1-m). Epoxy compounds other than epoxy compounds having a mesogen structure are as described above.

The compound having a functional group capable of reacting with the epoxy group is not particularly limited, and is preferably an aromatic compound having a functional group capable of reacting with the epoxy group.

Examples of the functional group capable of reacting with the epoxy group include a hydroxyl group, an amino group, an isocyanate group and the like. The number of functional groups capable of reacting with the epoxy group in the aromatic compound having a functional group capable of reacting with the epoxy group may be one or two or more, and is preferably two. .. Further, the functional group may or may not be directly linked to the aromatic ring, and may be linked to the aromatic ring via an alkylene oxide chain such as an ethylene oxide chain or a propylene oxide chain, or an alkyl chain.

From the viewpoint of forming a smectic structure in the cured product, the aromatic compound having a functional group capable of reacting with an epoxy group is a dihydroxybenzene compound having a structure in which two hydroxyl groups are bonded to one benzene ring, and one benzene ring. A diaminobenzene compound having a structure in which two amino groups are bonded to each other, a dihydroxybiphenyl compound having a structure in which one hydroxyl group is bonded to each of two benzene rings forming a biphenyl structure, and two benzene rings forming a biphenyl structure, respectively. A diaminobiphenyl compound having a structure in which one amino group is bonded, 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. It is preferable that it is at least one selected from the group consisting of (hereinafter, also referred to as a specific aromatic compound).

Examples of the dihydroxybenzene compound include catechol, resorcinol, hydroquinone, and derivatives thereof.
Examples of the diaminobenzene compound include 1,2-diaminobenzene, 1,3-diaminobenzene, 1,4-diaminobenzene, and derivatives thereof.

Examples of the dihydroxybiphenyl compound include 2,2'-dihydroxybiphenyl, 2,3'-dihydroxybiphenyl, 2,4'-dihydroxybiphenyl, 3,3'-dihydroxybiphenyl, 3,4'-dihydroxybiphenyl, 4,4'. -Dihydroxybiphenyl, derivatives thereof and the like can be mentioned.

Examples of the diaminobiphenyl compound include 2,2'-diaminobiphenyl, 2,3'-diaminobiphenyl, 2,4'-diaminobiphenyl, 3,3'-diaminobiphenyl, 3,4'-diaminobiphenyl, 4,4'. − Diaminobiphenyl, derivatives thereof and the like.

Examples of the dihydroxynaphthalene compound include 1,2-dihydroxynaphthalene, 1,3-dihydroxynaphthalene, 1,4-dihydroxynaphthalene, 1,5-dihydroxynaphthalene, 1,6-dihydroxynaphthalene, 1,7-dihydroxynaphthalene, 1, Examples thereof include 8-dihydroxynaphthalene, 2,3-dihydroxynaphthalene, 2,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, and derivatives thereof.

Examples of the diaminonaphthalene compound include 1,2-diaminonaphthalene, 1,3-diaminonaphthalene, 1,4-diaminonaphthalene, 1,5-diaminonaphthalene, 1,6-diaminonaphthalene, 1,7-diaminonaphthalene, 1, Examples thereof include 8-diaminonaphthalene, 2,3-diaminonaphthalene, 2,6-diaminonaphthalene, 2,7-diaminonaphthalene, and derivatives thereof.

Examples of the derivative of the specific aromatic compound include a compound 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. As the specific aromatic compound, one kind may be used alone, or two or more kinds may be used in combination.

The functional group equivalent of a compound having a functional group capable of reacting with an epoxy group is not particularly limited. From the viewpoint of reaction efficiency, the functional group equivalent (equivalent to active hydrogen when the functional group is an amino group) of a compound having a functional group capable of reacting with an epoxy group is 65 g / eq to 200 g / eq. Is more preferable, and it is more preferably 70 g / eq to 150 g / eq, and even more preferably 75 g / eq to 100 g / eq.

The method for synthesizing a specific epoxy compound by reacting a mesogen epoxy monomer, a compound having a functional group capable of reacting with an epoxy group, and an epoxy compound other than the epoxy compound having a mesogen structure, if necessary, is not particularly limited. Specifically, for example, a mesogen epoxy monomer, a compound having a functional group capable of reacting with an epoxy group, an epoxy compound other than an epoxy compound having a mesogen structure used as needed, and a reaction catalyst used as needed. Can be synthesized in a solvent and stirred while heating to synthesize a specific epoxy compound.

Alternatively, for example, a mesogen epoxy monomer, a compound having a functional group capable of reacting with an epoxy group, an epoxy compound other than the epoxy compound having a mesogen structure used as needed, and a reaction catalyst used as needed are used as a solvent. A specific epoxy compound can be synthesized by mixing without using the above and stirring while heating.

The solvent can dissolve the mesogen epoxy monomer, a compound having a functional group capable of reacting with the epoxy group, and an epoxy compound other than the epoxy compound having a mesogen structure used as needed, and these compounds react with each other. The solvent is not particularly limited as long as it can be heated to a required temperature. Specific examples thereof 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 is such that the mesogen epoxy monomer, the compound having a functional group capable of reacting with the epoxy group, the epoxy compound other than the epoxy compound having the mesogen structure used as needed, and the reaction catalyst used as needed are reacted. The amount is not particularly limited as long as it can be melted at a temperature. Although the solubility varies depending on the type of raw material before the reaction, the type of solvent, etc., for example, when the charged solid content concentration 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 viewpoints of reaction rate, reaction temperature, storage stability and the like. Specific examples thereof include imidazole compounds, organic phosphorus compounds, tertiary amines, and quaternary ammonium salts. One type of reaction catalyst may be used alone, or two or more types 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 the organic phosphorus compound are an organic phosphine compound, a compound having an intramolecular polarization obtained by adding a compound having a π bond such as maleic anhydride, a quinone compound, a diazophenylmethane, and a phenol resin to the organic phosphine compound, and an organic compound. Examples thereof include a complex of a phosphine compound and an organic boron compound. Of these, a compound obtained by adding an organic phosphine compound and a quinone compound is preferable.

Specifically, as the organic phosphine compound, triphenylphosphine, diphenyl (p-tril) 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 Examples include phosphine.

Specifically, as the quinone compound, 1,4-benzoquinone, 2,5-turquinone, 1,4-naphthoquinone, 2,3-dimethylbenzoquinone, 2,6-dimethylbenzoquinone, 2,3-dimethoxy-5-methyl- Examples thereof include 1,4-benzoquinone, 2,3-dimethoxy-1,4-benzoquinone and phenyl-1,4-benzoquinone.

Specific examples of the organic boron compound include tetraphenyl borate, tetra-p-tolyl borate, and tetra-n-butyl borate.

The amount of the reaction catalyst is not particularly limited. From the viewpoint of reaction rate and storage stability, the total mass of the mesogen epoxy monomer, the epoxy compound other than the epoxy compound having a mesogen structure used as necessary, and the compound having a functional group capable of reacting with the epoxy group is 100 mass. The amount is preferably 0.1 parts by mass to 1.5 parts by mass, and more preferably 0.2 parts by mass to 1 part by mass.

The specific epoxy compound can be synthesized using a reaction vessel such as a flask for a small amount of scale and a synthesis pot for a large amount of scale. The specific synthesis method is as follows, for example. First, a mesogen epoxy monomer and an epoxy compound other than the epoxy compound having a mesogen structure to be used as needed are put into a reaction vessel, a solvent is added if necessary, and the mixture is heated to the reaction temperature by an oil bath or a heat medium. Dissolve epoxy compounds other than mesogen epoxy monomers and epoxy compounds having a mesogen structure used as needed. A compound having a functional group capable of reacting with an epoxy group is added thereto, and then a reaction catalyst is added as needed to initiate the reaction. Then, if necessary, the solvent is distilled off under reduced pressure to obtain a specific epoxy compound.

The reaction temperature is not particularly limited as long as the reaction proceeds between the epoxy group of the epoxy compound other than the mesogen epoxy monomer and the epoxy compound having the mesogen structure used as necessary and the functional group capable of reacting with the epoxy group. .. The reaction temperature is, for example, preferably in the range of 100 ° C. to 180 ° C., and more preferably in the range of 100 ° C. to 150 ° C. By setting the reaction temperature to 100 ° C. or higher, the time until the reaction is completed tends to be shortened. On the other hand, by setting the reaction temperature to 180 ° C. or lower, the possibility of gelation tends to be reduced.

When synthesizing a specific epoxy compound, an epoxy compound as a raw material (that is, an epoxy compound other than a mesogen epoxy monomer and an epoxy compound having a mesogen structure used as necessary) and a compound having a functional group capable of reacting with an epoxy group The compounding ratio of is not particularly limited. For example, the compounding ratio in which the ratio (A: B) of the equivalent number of epoxy groups (A) to the equivalent number of functional groups capable of reacting with the epoxy group (A: B) is in the range of 10:10 to 10: 0.01. May be. From the viewpoint of toughness and heat resistance of the cured product, a blending ratio in which A: B is in the range of 10: 5 to 10: 0.1 is preferable.

The structure of the specific epoxy compound obtained by the synthesis has, for example, a mesogen epoxy monomer used in the synthesis, an epoxy compound other than the epoxy compound having a mesogen structure used as needed, and a functional group capable of reacting with the epoxy group. To collate the molecular weight of the specific epoxy compound estimated to be obtained from the reaction with the compound with the molecular weight of the target compound determined by liquid chromatography performed using a liquid chromatograph equipped with a UV and mass spectrum detector. Can be determined with.

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

The epoxy resin preferably contains both a specific epoxy compound and a mesogen epoxy monomer. When the specific epoxy compound and the mesogen epoxy monomer are present in the epoxy resin in an appropriate ratio, the handleability before curing tends to be better. In addition, the crosslink density at the time of curing can be made higher, and a cured epoxy resin product having better heat resistance tends to be obtained. The ratio of the specific epoxy compound and the mesogen epoxy monomer present in the epoxy resin can be adjusted by the compounding ratio of the mesogen epoxy monomer and the compound having a functional group capable of reacting with the epoxy group and other reaction conditions.

The content ratio of the mesogen epoxy monomer contained in the epoxy resin is preferably 50% or less of the total epoxy resin. An epoxy resin having a mesogen epoxy monomer content of 50% or less tends to have a lower viscosity at the time of temperature rise than an epoxy resin having a mesogen epoxy monomer content of more than 50%, and tends to be excellent in handleability. The reason is not clear, but when the ratio of the mesogen epoxy monomer is 50% or less of the total epoxy resin, the temperature is lower than the melting temperature of the epoxy resin as compared with the case where the content ratio of the mesogen epoxy monomer exceeds 50%. It is presumed that this is because the precipitation of crystals is further suppressed.

In the present disclosure, the content ratio of the mesogen epoxy monomer in the epoxy resin can be calculated from, for example, a chart obtained by a liquid chromatograph.
More specifically, it is determined as the ratio (%) of the area of the peak derived from the mesogen epoxy monomer to the total area of the peaks derived from all the components constituting the epoxy resin in the chart obtained by the liquid chromatograph. Specifically, the absorbance of the epoxy resin to be measured at a wavelength of 280 nm is detected, and the total area of all the detected peaks and the area of the peak corresponding to the mesogen epoxy monomer are calculated by the following formula.

Percentage of peak area derived from mesogen epoxy monomer (%) = (area of peak derived from mesogen epoxy monomer / total area of peaks derived from all components constituting the epoxy resin) × 100

Liquid chromatography is performed with a sample concentration of 0.5% by mass, tetrahydrofuran being used as the 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 analysis device "C-R4A" manufactured by Shimadzu Corporation. As the column, for example, "G2000HXL" and "G3000HXL", which are GPC columns manufactured by Tosoh Corporation, can be used.

From the viewpoint of improving handleability, the proportion of the mesogen epoxy monomer is preferably 50% or less, more preferably 49% or less, and further preferably 48% or less of the entire epoxy resin.

From the viewpoint of reducing the intrinsic viscosity (viscosity at the time of melting), the ratio of the mesogen epoxy monomer is preferably 35% or more, more preferably 37% or more, and more preferably 40% or more of the entire epoxy resin. Is even more preferable.

<Physical properties of epoxy resin>
[Weight average molecular weight]
The weight average molecular weight (Mw) of the epoxy resin is not particularly limited. From the viewpoint of reducing the viscosity, the weight average molecular weight (Mw) of the epoxy resin is preferably 500 to 3000, more preferably 700 to 2500, and even more preferably 800 to 2000.

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

[Epoxy equivalent]
The epoxy equivalent of the epoxy resin is not particularly limited. From the viewpoints of fluidity of the epoxy resin, thermal conductivity of the cured product, compatibility between toughness and flexural modulus, etc., it is preferably 245 g / eq to 500 g / eq, and preferably 250 g / eq to 450 g / eq. More preferably, it is 260 g / eq to 400 g / eq. In the present disclosure, epoxy equivalents are measured by the perchloric acid titration method.

〔viscosity〕
The viscosity of the epoxy resin is not particularly limited and can be selected according to the application of the epoxy resin. From the viewpoint of handleability, the viscosity of the epoxy resin at 100 ° C. is preferably 200 Pa · s or less, more preferably 100 Pa · s or less, and further preferably 20 Pa · s or less.
The viscosity of the epoxy resin at 100 ° C. can be measured in vibration mode with a rheometer (MCR-301, manufactured by Anton Pearl). For example, using a parallel plate portion rate having a diameter of 12 mm, measurement can be performed under the conditions of a frequency of 1 kHz, a gap of 0.2 mm, and a strain of 2%.

≪Epoxy resin composition and cured epoxy resin≫
The epoxy resin composition of the present disclosure contains the epoxy resin of the present disclosure and a curing agent. The epoxy resin cured product of the present disclosure is a cured product of the epoxy resin composition of the present disclosure.
From the viewpoint of toughness, the epoxy resin composition is preferably capable of forming a smectic structure or a nematic structure when formed into a cured product.

<Hardener>
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 the curing agent include amine curing agents, phenol curing agents, acid anhydride curing agents, polypeptide curing agents, polyaminoamide curing agents, isocyanate curing agents, blocked isocyanate curing agents and the like. As the curing agent, one type may be used alone or two or more types may be used in combination.

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, and 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 an amino group is directly bonded to the aromatic ring is more preferable, and two amino groups directly bonded to the aromatic ring are used. The amine curing agent having the above is more preferable. Examples of the aromatic ring include a benzene ring and a naphthalene ring.

Specifically, as the amine curing agent, 3,3'-diaminodiphenylsulfone, 4,4′-diaminodiphenylsulfone, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylether, 4,4′-diamino− 3,3'-dimethoxybiphenyl, 4,4'-diaminophenylbenzoate, 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 can be mentioned.

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

Examples of the phenol curing agent include a low-molecular-weight phenol compound and a phenol novolac resin obtained by connecting low-molecular-weight phenol compounds with a methylene chain or the like to form a novolak. Examples of the low molecular weight phenol compound include monofunctional phenol compounds such as phenol, o-cresol, m-cresol and p-cresol, bifunctional phenol compounds such as catechol, resorcinol and hydroquinone, 1,2,3-trihydroxybenzene and 1 , 2,4-Trihydroxybenzene, 1,3,5-trihydroxybenzene and other trifunctional phenolic compounds and the like.

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 equivalent number of functional groups of the curing agent contained in the epoxy resin composition (active hydrogen in the case of an amine curing agent, the equivalent number of hydroxyl groups in the case of a phenol curing agent) and the epoxy resin. The ratio of the epoxy group to the equivalent number of the epoxy group (the number of equivalents of the functional group / the number of equivalents of the epoxy group) is preferably an amount of 0.3 to 3.0, and an amount of 0.5 to 2.0. More preferably.

<Other ingredients>
The epoxy resin composition may contain other components other than the epoxy resin and the curing agent, if necessary. For example, it may contain a curing catalyst, a filler and the like. Specific examples of the curing catalyst include compounds exemplified as reaction catalysts that can be used in the synthesis of specific epoxy compounds.

[Use of epoxy resin composition and cured epoxy resin]
The use of the epoxy resin composition and the cured epoxy resin is not particularly limited, and for example, it can be suitably used for producing a fiber reinforced composite material (FRP) used for aircraft, spacecraft and the like.
In addition, the epoxy resin composition of the present disclosure can also be suitably used in a production method in which steps such as localizing thermoplastic resin particles in the surface region of a prepreg are omitted in the production of a fiber-reinforced composite material.

≪Composite material≫
The composite material of the present disclosure includes the epoxy resin cured product 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 and the like. Specific examples of the reinforcing material include carbon materials, glass, aromatic polyamide-based resins (for example, 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 examples thereof include fibrous form and particulate form (filler). From the viewpoint of the strength of the composite material, the reinforcing material is preferably a carbon material, and more preferably carbon fiber. The reinforcing material contained in the composite material may be one kind or two or more kinds.

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 an epoxy resin cured product and at least one reinforcing material-containing layer containing a reinforcing material are laminated.

Next, the embodiments of the present disclosure will be specifically described with reference to Examples, but the present invention is not limited to these Examples. Details of the materials used are as follows.

Mesogen-containing epoxy compound ... (4- {4- (2,3-epoxypropoxy) phenyl} cyclohexyl = 4- (2,3-epoxypropoxy) benzoate, R ^{3 to} R ⁶ in the general formula (3-m) are all Compounds that are hydrogen atoms Specific aromatic compounds 1 ... 1,5-dihydroxynaphthalene Specific aromatic compounds 2 ... 4,4'-dihydroxybiphenyl Alicyclic-containing epoxy compound 1 ... Compound of formula (a) Alicyclic-containing epoxy compound 2 ... Compound of formula (b) Alicyclic-containing epoxy compound 3 ... Compound of formula (c) Alicyclic-containing epoxy compound 4 ... Compound of formula (d) Curing agent ... 3,3'-diaminodiphenylsulfone Naphthalene-type epoxy compound ... General formula Compound reaction catalyst in which q is 0 in (1-e) ... Tetrabutylphosphonium laurylate (TBPLA)

[Example 1]
To a 500 ml three-necked flask, 100 parts by mass of a mesogen-containing epoxy compound was added, and 160 parts by mass of a synthetic solvent (cyclohexanone) was added. A cooling tube and a nitrogen introduction tube were installed in the three-necked flask, and stirring blades were attached so as to be immersed in the synthetic solvent. The three-necked flask was immersed in an oil bath at 120 ° C., and stirring was started. After confirming that the mesogen-containing epoxy compound was dissolved to form a transparent solution, 7.6 parts by mass of the specific aromatic compound 1 and 0.5 parts by mass of the reaction catalyst were added, and the mixture was heated in an oil bath at 120 ° C. Continued. After continuing heating for 3 hours, the synthetic solvent was distilled off from the reaction solution under reduced pressure, the residue was cooled to room temperature (25 ° C.), and a part of the mesogen-containing epoxy compound was formed by reacting with the specific aromatic compound 1. An epoxy resin containing a multi-layer was obtained.

Next, the obtained epoxy resin (100 parts by mass) and the alicyclic-containing epoxy compound 1 (20 parts by mass) were weighed in a stainless steel petri dish, heated to 180 ° C. to melt, and stirred. A curing agent (27 parts by mass) was added thereto, and the mixture was stirred in a molten state. The obtained mixture was cooled to room temperature (25 ° C.) and heat-treated at 180 ° C. for 4 hours in a constant temperature bath to obtain a cured epoxy resin.

[Example 2]
An epoxy resin cured product was obtained in the same manner as in Example 1 except that the amount of the alicyclic-containing epoxy compound 1 was changed to 30 parts by mass and the amount of the curing agent was changed to 30 parts by mass.

[Example 3]
An epoxy resin cured product was obtained in the same manner as in Example 1 except that the amount of the alicyclic-containing epoxy compound 1 was changed to 50 parts by mass and the amount of the curing agent was changed to 37 parts by mass.

[Example 4]
To a 500 ml three-necked flask, 100 parts by mass of a mesogen-containing epoxy compound was added, and 160 parts by mass of a synthetic solvent (cyclohexanone) was added. A cooling tube and a nitrogen introduction tube were installed in the three-necked flask, and stirring blades were attached so as to be immersed in the synthetic solvent. The three-necked flask was immersed in an oil bath at 120 ° C., and stirring was started. After confirming that the mesogen-containing epoxy compound was dissolved to form a transparent solution, 10 parts by mass of the specific aromatic compound 2 and 0.5 parts by mass of the reaction catalyst were added, and heating was continued in an oil bath at 120 ° C. did. After continuing heating for 3 hours, the synthetic solvent was distilled off from the reaction solution under reduced pressure, the residue was cooled to room temperature (25 ° C.), and a part of the mesogen-containing epoxy compound was formed by reacting with the specific aromatic compound 2. An epoxy resin containing a multi-layer was obtained.

Next, the obtained epoxy resin (100 parts by mass) and the alicyclic-containing epoxy compound 1 (20 parts by mass) were weighed in a stainless steel petri dish, heated to 180 ° C. to melt, and stirred. A curing agent (26 parts by mass) was added thereto, and the mixture was stirred in a molten state. The obtained mixture was cooled to room temperature (25 ° C.) and heat-treated at 180 ° C. for 4 hours in a constant temperature bath to obtain a cured epoxy resin.

[Example 5]
An epoxy resin cured product was obtained in the same manner as in Example 4 except that the amount of the alicyclic-containing epoxy compound 1 was changed to 30 parts by mass and the amount of the curing agent was changed to 29 parts by mass.

[Example 6]
An epoxy resin cured product was obtained in the same manner as in Example 1 except that the alicyclic-containing epoxy compound 1 was changed to the same amount of the alicyclic-containing epoxy compound 2 and the amount of the curing agent was changed to 25 parts by mass.

[Example 7]
An epoxy resin cured product was obtained in the same manner as in Example 1 except that the alicyclic-containing epoxy compound 1 was changed to the same amount of the alicyclic-containing epoxy compound 3 and the amount of the curing agent was changed to 37 parts by mass.

[Example 8]
An epoxy resin cured product was obtained in the same manner as in Example 1 except that the alicyclic-containing epoxy compound 1 was changed to the same amount of the alicyclic-containing epoxy compound 4 and the amount of the curing agent was changed to 35 parts by mass.

[Example 9]
A mesogen-containing epoxy compound (50 parts by mass) and a naphthalene-type epoxy compound (31 parts by mass) were added to a 500 ml three-necked flask, and a synthetic solvent (cyclohexanone) was added. A cooling tube and a nitrogen introduction tube were installed in the three-necked flask, and stirring blades were attached so as to be immersed in the synthetic solvent. The three-necked flask was immersed in an oil bath at 120 ° C., and stirring was started. After confirming that the mesogen-containing epoxy compound was dissolved to form a transparent solution, 6 parts by mass of the specific aromatic compound 1 and 0.5 parts by mass of the reaction catalyst were added, and heating was continued in an oil bath at 120 ° C. did. After continuing heating for 3 hours, the synthetic solvent was distilled off from the reaction solution under reduced pressure, the residue was cooled to room temperature (25 ° C.), and a part of the mesogen-containing epoxy compound and the naphthalene-type epoxy compound became the specific aromatic compound 1. An epoxy resin containing a multimer formed by the reaction was obtained.

Next, the obtained epoxy resin (100 parts by mass) and the alicyclic-containing epoxy compound 1 (20 parts by mass) were weighed in a stainless steel petri dish, heated to 180 ° C., melted, and stirred. A curing agent (31.6 parts by mass) was added thereto, and the mixture was stirred in a molten state. The obtained mixture was cooled to room temperature (25 ° C.) and heat-treated at 180 ° C. for 4 hours in a constant temperature bath to obtain a cured epoxy resin.

[Comparative Example 1]
The alicyclic-containing epoxy compound 1 (100 parts by mass) and the curing agent (35 parts by mass) were weighed in a stainless steel petri dish, heated to 180 ° C. to melt, melted, and stirred. The obtained mixture was cooled to room temperature (25 ° C.) and heat-treated at 180 ° C. for 4 hours in a constant temperature bath to obtain a cured epoxy resin.

[Comparative Example 2]
An epoxy resin (100 parts by mass) containing a multimer formed by reacting a part of the mesogen-containing epoxy compound obtained in Example 4 with the specific aromatic compound 2 and a curing agent (19 parts by mass) are stainless steel petri dishes. Weighed each and heated to 180 ° C. to melt and stir. The obtained mixture was cooled to room temperature (25 ° C.) and heat-treated at 150 ° C. for 4 hours in a constant temperature bath to obtain a cured epoxy resin.

[Comparative Example 3]
The naphthalene-type epoxy compound (100 parts by mass) and the curing agent (44 parts by mass) were weighed in a stainless steel petri dish, heated to 180 ° C. to melt, and stirred. The obtained mixture was cooled to room temperature (25 ° C.) and heat-treated at 150 ° C. for 4 hours in a constant temperature bath to obtain a cured epoxy resin.

[Measurement of fracture toughness value]
The fracture toughness value was measured as an index of the toughness of the cured epoxy resin. The cured epoxy resin obtained in Examples and Comparative Examples was cut into a rectangular parallelepiped having a size of 3.75 mm × 7.5 mm × 33 mm to prepare a test piece for evaluating fracture toughness. Using this test piece, a three-point bending measurement was performed based on ASTM D5045 to calculate a fracture toughness value (MPa · m ^1/2 ). Instron 5948 (Instron) was used as the evaluation device.

[Measurement of bending strength and flexural modulus]
The cured epoxy resin obtained in Examples and Comparative Examples was cut into a rectangular parallelepiped having a size of 2.0 mm × 5.0 mm × 40 mm to prepare a test piece for evaluating flexural modulus and bending strength. Using this test piece, a bending test was performed with a Tensilon universal material tester (Instron 5948, Instron) under the conditions of a distance between fulcrums of 32 mm and a crosshead speed of 1 mm / min. Using the measurement results, a bending stress-displacement curve was created from the formula (A), and the maximum stress was taken as the bending strength. Further, the bending strain was calculated from the formula (B), and the flexural modulus was calculated by the formula (C) using the bending stress when the bending strain was 0.25% and the bending stress when the bending strain was 0.45%. ..

As shown in Table 1, the epoxy resin cured product of the example in which both the mesogen-containing epoxy compound and the alicyclic-containing epoxy compound were used as the epoxy resin was Comparative Example 1 in which only the alicyclic-containing epoxy compound was used as the epoxy resin. Compared with Comparative Example 2 in which only the mesogen-containing epoxy compound was used as the epoxy resin and Comparative Example 3 in which only the naphthalene type epoxy compound was used, the balance between the breaking toughness value and the bending strength was excellent.

Claims (8)

An epoxy compound having a mesogen structure and an epoxy group and an alicyclic which are bonded to the alicyclic structure and the alicyclic structure via a single bond, an alkylene group having 1 to 3 carbon atoms or an alkyleneoxy group having 1 to 3 carbon atoms. An epoxy resin containing an epoxy compound having at least one of the formula epoxy groups. The epoxy resin according to claim 1, wherein the mesogen structure contains a mesogen structure represented by the following general formula (1).

In the general formula (1), X represents a single bond or a linking group having at least one divalent group selected from the following group (A). 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. .. n independently represents an integer of 0 to 4. * Represents a binding site with an adjacent atom.

In group (A), 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, and a nitro group. , Or represents an acetyl group. n 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 epoxy resin according to claim 2, wherein the structure represented by the general formula (1) includes at least one structure selected from the group consisting of the following general formula (3) and the general formula (4).

In the general formula (3) and the general formula (4), R ^{3 to} R ⁶ independently represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. * Represents a binding site with an adjacent atom. Claims 1 to 3, wherein the epoxy compound having a mesogen structure comprises an epoxy compound having at least two mesogen structures and a divalent group containing an aromatic ring arranged between the mesogen structures. The epoxy resin according to any one item. An epoxy resin composition containing the epoxy resin according to any one of claims 1 to 4 and a curing agent. An epoxy resin cured product, which is a cured product of the epoxy resin composition according to claim 5. A composite material containing the cured epoxy resin according to claim 6 and a reinforcing material. The composite material according to claim 7, wherein the reinforcing material contains a carbon material.