JP2023100439A - Epoxy resin, epoxy resin composition, and cured product - Google Patents

Abstract

To provide an epoxy resin which can satisfy both of fast curability and storage stability and which has excellent handleability and workability.SOLUTION: Provided is an epoxy resin which is a reaction product of 1,2,3-trihydroxybenzene and epihalohydrin. The epoxy resin contains a cyclic compound which has a cyclic structure containing two adjacent oxygen atoms derived from 1,2,3-triglycidyloxybenzene and 1,2,3-trihydroxy benzene as constituent atoms, where a content of the cyclic compound is less than 0.040 mol per 100 g of the epoxy resin.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to an epoxy resin, an epoxy resin composition containing the same, and a cured product using the epoxy resin composition.

Carbon fiber reinforced plastic (CFRP) is a high-performance material that is lighter, stronger, and more rigid than general structural metal materials, and has excellent electrical properties and corrosion resistance.

Moreover, in recent years, the demand for CFRP as an alternative to metal materials is expanding, mainly in the mobility field such as aircraft and automobiles, where reduction of carbon dioxide emissions is required.

Even in the CFRP manufacturing process, improvement of production efficiency is being studied for the purpose of reducing the burden on the environment and reducing costs. As a reduction of , rapid curability is required.

However, when an epoxy resin composition mixed with an epoxy resin and a curing agent is used as the matrix resin, the reaction progresses during the storage period of the composition, shortening the pot life and reducing storage stability and handling. It contained gender issues. In order to solve these problems, attempts have been made to improve the storage stability by using a highly purified bisphenol A type epoxy resin as the epoxy resin (Patent Document 1).

In addition, by using a liquid epoxy resin, in order to obtain an epoxy resin with excellent handling properties, an epoxy resin containing a certain ratio of by-products generated during the synthesis of the epoxy resin or an epoxy resin containing the above epoxy resin is used. An epoxy resin composition that does this is disclosed (Patent Document 2).

JP-A-58-128757 Patent No. 6590126

However, in Patent Document 1, the rapid curability and storage stability required in recent years cannot be satisfied. Although there is a strong desire to achieve both of these properties, rapid curability and storage stability are generally in conflict with each other, and so are not currently being achieved. In addition, in Patent Document 2, an epoxy resin composition having excellent handleability was obtained by using a liquid epoxy resin. Since it was necessary to set the conditions, side reactions due to by-products proceeded, and an epoxy resin composition that satisfies storage stability was not obtained.

Accordingly, the present invention provides an epoxy resin that achieves both rapid curability and storage stability and is excellent in handleability and workability.

In order to solve the above problems, the present inventors have made intensive studies and found that an epoxy resin obtained using 1,2,3-trihydroxybenzene and a by-product contained in the epoxy resin Focusing on the amount, the present inventors have found that the above-mentioned problems can be solved by controlling the content of the by-products, and have completed the present invention.

That is, the present invention provides an epoxy resin which is a reaction product of 1,2,3-trihydroxybenzene and epihalohydrin, wherein the epoxy resin comprises 1,2,3-triglycidyloxybenzene and 1, It contains a cyclic compound having a cyclic structure containing two adjacent oxygen atoms derived from 2,3-trihydroxybenzene as constituent atoms, and the content of the cyclic compound is less than 0.040 mol per 100 g of the epoxy resin. It concerns an epoxy resin.

Preferably, the epoxy resin of the present invention further contains an oligomer, and the content of the oligomer is 10% or less in terms of area ratio in GPC measurement.

In the epoxy resin of the present invention, the content of 1,2,3-triglycidyloxybenzene is preferably 80% or more in terms of area ratio as measured by GPC.

The epoxy resin of the present invention preferably has an epoxy equivalent weight of 120 g/equivalent or less.

The present invention relates to an epoxy resin composition containing the epoxy resin and a curing agent.

The present invention relates to a cured product obtained by curing the epoxy resin composition.

By using the epoxy resin of the present invention, it is possible to achieve both rapid curing and storage stability, and it is also excellent in handleability and workability, and is useful.

1 is a GPC chart of the epoxy resin produced in Synthesis Example 1 (unpurified product). 2 is a GPC chart of the epoxy resin produced in Synthesis Example 2 (purified product). 13 is a ¹³ C-NMR chart of the epoxy resin produced in Synthesis Example 1 (unpurified product). 13 is a ¹³ C-NMR chart of the epoxy resin produced in Synthesis Example 2 (purified product).

DETAILED DESCRIPTION OF THE INVENTION Embodiments for carrying out the present invention will be described in detail below.

<Epoxy resin>
The present invention provides an epoxy resin which is a reaction product of 1,2,3-trihydroxybenzene and epihalohydrin, wherein said epoxy resin comprises 1,2,3-triglycidyloxybenzene and 1,2, Epoxy containing a cyclic compound having a cyclic structure containing two adjacent oxygen atoms derived from 3-trihydroxybenzene as constituent atoms, wherein the content of the cyclic compound is less than 0.040 mol per 100 g of the epoxy resin. Regarding resin. By using the epoxy resin, it is possible to achieve both rapid curing and storage stability. Furthermore, the epoxy resin has a low viscosity, and the cured product obtained using the epoxy resin has excellent mechanical properties. , will be useful.

The epoxy resin in the present invention is a reaction product of 1,2,3-trihydroxybenzene (hereinafter also referred to as "pyrogallol") and epihalohydrin.

When pyrogallol and epihalohydrin are reacted, generally the phenolic hydroxyl groups at the 1-, 2- and 3-positions of pyrogallol are glycidylated to give a triglycidyl ether. However, various other reactions may proceed, and as a result, the reaction product of pyrogallol and epihalohydrin may contain various epoxy compounds (by-products).

[1,2,3-trihydroxybenzene (pyrogallol)]
Pyrogallol has a structure represented by the following structural formula.

Pyrogallol is obtained by decarboxylation of gallic acid (3,4,5-trihydroxybenzoic acid) found in plants. Pyrogallol to be used is preferably biobased from the viewpoints of low environmental load and easy availability. However, an industrially synthesized one can also be used.

[Epihalohydrin]
Epihalohydrin includes, but is not limited to, epichlorohydrin, epibromohydrin, β-methylepichlorohydrin, β-methylepibromohydrin, and the like. These epihalohydrins may be used alone or in combination of two or more.

The amount of epihalohydrin used is not particularly limited, but is preferably 1.2 to 20 mol, more preferably 1.5 to 10 mol, per 1 mol of the phenolic hydroxyl group of pyrogallol. It is preferable that the amount of epihalohydrin used is 1.2 mol or more because other compounds that can be contained in the epoxy resin can be easily controlled. On the other hand, when the amount of epihalohydrin to be used is 20 mol or less, it is preferable from the viewpoint of yield because the cost is low.

The reaction between pyrogallol and epihalohydrin is not particularly limited and can be carried out by a known method. In one embodiment, the reaction comprises step (1) of reacting a mixture containing pyrogallol and epihalohydrin in the presence of a quaternary onium salt and/or a basic compound, and the reaction obtained in step (1) and step (2) of ring-closing the compound in the presence of a basic compound. The mixture may further contain a reaction solvent and the like, if necessary.

[Reaction solvent]
Examples of the reaction solvent include, but are not limited to, alcohols such as methanol, ethanol, isopropyl alcohol and butanol; ketones such as acetone and methyl ethyl ketone; ethers such as dioxane; These reaction solvents may be used alone or in combination of two or more.

When a reaction solvent is used, the amount added is preferably 5 to 150 parts by mass, more preferably 7.5 to 100 parts by mass, and more preferably 10 to 50 parts by mass with respect to 100 parts by mass of epihalohydrin. It is even more preferable to have

[Quaternary onium salt]
The quaternary onium salt has the function of promoting the reaction in step (1) described below.

Examples of the quaternary onium salt include, but are not limited to, quaternary ammonium salts and quaternary phosphonium salts.

The quaternary ammonium salt is not particularly limited, but tetramethylammonium cation, methyltriethylammonium cation, tetraethylammonium cation, tributylmethylammonium cation, tetrabutylammonium cation, phenyltrimethylammonium cation, benzyltrimethylammonium cation, phenyltriethyl ammonium cation, benzyltriethylammonium cation, chloride salt of benzyltributylammonium cation, tetramethylammonium cation, trimethylpropylammonium cation, tetraethylammonium cation, bromide salt of tetrabutylammonium cation, and the like.

The quaternary phosphonium salt is not particularly limited, but includes tetraethylphosphonium cation, tetrabutylphosphonium cation, methyltriphenylphosphonium cation, tetraphenylphosphonium cation, ethyltriphenylphosphonium cation, butyltriphenylphosphonium cation, and benzyltriphenylphosphonium cation. Bromide salts of cations are mentioned.

Of these, the quaternary onium salts are preferably tetramethylammonium cations, benzyltrimethylammonium cations, chloride salts of benzyltriethylammonium cations, and bromide salts of tetrabutylammonium cations.

In addition, the above-mentioned quaternary onium salts may be used alone or in combination of two or more.

The amount of the quaternary onium salt added is preferably 0.15 to 5% by mass, more preferably 0.18 to 3% by mass, based on the total mass of pyrogallol and epihalohydrin. It is preferable that the amount of the quaternary onium salt added is 0.15% by mass or more because the reaction in step (1) can proceed appropriately. On the other hand, when the amount of the quaternary onium salt added is 5% or less, it is preferable because the amount of residue in the resin can be reduced.

[Basic compound]
The basic compound also has the function of promoting the reaction of step (1), which will be described later, similarly to the quaternary onium salt.

Examples of basic compounds include, but are not limited to, potassium hydroxide, sodium hydroxide, barium hydroxide, magnesium hydroxide, sodium carbonate, potassium carbonate, and the like. Among these, it is preferable to use potassium hydroxide and sodium hydroxide. In addition, these basic compounds may be used independently or may be used in combination of 2 or more type.

The amount of the basic compound added is not particularly limited, but it is preferably 0.01 to 0.3 mol, and 0.02 to 0.2 mol, per 1 mol of the phenolic hydroxyl group of pyrogallol. is more preferred. It is preferable that the amount of the basic compound to be added is 0.01 mol or more, because the reaction in step (2) described below can proceed favorably. On the other hand, when the amount of the basic compound added is 0.3 mol or less, it is preferable because side reactions can be prevented or suppressed.

[Reaction of step (1)]
In the reaction of step (1), mainly the phenolic hydroxyl group of pyrogallol reacts with epihalohydrin to give the tris(3-halogeno-2-hydroxypropyl ether) intermediate shown below.

In the structural formula above, each "X" independently represents a halogen atom. Each "R" independently represents a hydrogen atom or a methyl group.

Although the reaction temperature in step (1) is not particularly limited, it is preferably 20 to 80°C, more preferably 40 to 75°C. It is preferable that the reaction temperature in step (1) is 20° C. or higher because the reaction in step (1) can proceed favorably. On the other hand, it is preferable that the reaction temperature in step (1) is 80° C. or lower because side reactions can be prevented or suppressed.

The reaction time in step (1) is not particularly limited, but is preferably 0.5 hours or more, more preferably 1 to 50 hours. A reaction time of 0.5 hours or longer in step (1) is preferable because the reaction proceeds favorably and side reactions can be prevented or suppressed.

[Step (2)]
Step (2) is a step of ring-closing the reactant obtained in step (1) in the presence of a basic compound.

[Reactant obtained in step (1)]
The reactants obtained in step (1) include the tris(3-halogeno-2-hydroxypropyl ether) intermediate obtained by the first reaction. In addition, it may contain by-products, unreacted pyrogallol, unreacted epihalohydrin, reaction solvents, impurities, and the like.

[Basic compound]
The basic compound has a function of making the reaction conditions of step (2) basic conditions and promoting the ring closure reaction.

Examples of basic compounds include, but are not limited to, potassium hydroxide, sodium hydroxide, barium hydroxide, magnesium hydroxide, sodium carbonate, potassium carbonate, and the like. Among these, it is preferable to use potassium hydroxide and sodium hydroxide. In addition, these basic compounds may be used independently or may be used in combination of 2 or more type.

The amount of the basic compound added is not particularly limited, but it is preferably 0.8 to 1.5 mol, preferably 0.9 to 1.3 mol, per 1 mol of the phenolic hydroxyl group of pyrogallol. is more preferred. It is preferable that the addition amount of the basic compound is 0.8 mol or more because the ring closure reaction in step (2) can proceed favorably. On the other hand, when the amount of the basic compound added is 1.5 mol or less, it is preferable because side reactions can be prevented or suppressed. When a basic compound is used in step (1), it is preferable to use the above-described addition amount including the amount used in step (1).

[Reaction of step (2)]
In the reaction of step (2), mainly the 3-halogeno-2-hydroxypropyl ether group of the tris(3-halogeno-2-hydroxypropyl ether) intermediate undergoes a glycidylation reaction under basic conditions. , to obtain the 1,2,3-triglycidyloxybenzene shown below.

In the above structural formulas, each "R" independently represents a hydrogen atom or a methyl group.

Although the reaction temperature in step (2) is not particularly limited, it is preferably 30 to 120°C, more preferably 25 to 80°C.

The reaction time in step (2) is not particularly limited, but is preferably 0.5 to 4 hours, more preferably 1 to 3 hours.

In addition, in order to allow the reaction in step (2) to proceed appropriately, a step of further purification may be used.

Further, after performing the step (2), the reaction product obtained can be purified, etc., if necessary.

[Reaction product]
The epoxy resin of the present invention is an epoxy resin that is a reaction product of 1,2,3-trihydroxybenzene and epihalohydrin, wherein the epoxy resin is 1,2,3-triglycidyloxybenzene (herein Also referred to as "pyrogallol triglycidyl" in the above.), and the pyrogallol triglycidyl is a crystalline compound. The epoxy resin contains a cyclic compound as a by-product together with the triglycidyl form of pyrogallol, and may further contain oligomers, other glycidyl forms, solvents, other compounds, and the like.

Since the epoxy resin (reaction product) contains a triglycidyl form of pyrogallol, the epoxy resin (pyrogallol-type epoxy resin) can have high physical properties. Specifically, since the triglycidyl form of pyrogallol has three glycidyl forms, the degree of cross-linking is increased, and a cured product having excellent heat resistance can be obtained. In addition, since three glycidyl bodies of pyrogallol triglycidyl body are adjacent to each other, the adjacent glycidyl groups are densely packed during the cross-linking reaction, and a cured product having excellent elastic modulus can be obtained.
In addition, compared with general bisphenol A type epoxy resins, pyrogallol type epoxy resins are excellent in low-temperature curability, excellent in handling and workability, and useful.

In addition, cyclic compounds and other oligomers, which are by-products contained in the epoxy resin (reaction product), are obtained as a result of side reactions of the glycidylation reaction of 1,2,3-trihydroxybenzene. The cyclic compound and by-products such as the oligomer can affect the physical properties of the epoxy resin and the physical properties of its cured product.
The cyclic compound is an intramolecular product having a primary hydroxyl group generated by an intramolecular reaction, and the oligomer is a compound having a secondary hydroxyl group, and these by-products are alcoholic hydroxyl groups and phenolic hydroxyl groups. Therefore, it acts as a cocatalyst during the curing reaction and promotes curability, but when it is contained as an epoxy resin composition, it may deteriorate the storage stability, so the content of the by-product A reduction is performed. On the other hand, the reduction of the by-products may deteriorate the curability, so it is important to achieve both storage stability and curability (rapid curability).

At this time, the side reaction can be controlled by adjusting the reaction conditions, whereby the content of not only the triglycidyl form of 1,2,3-trihydroxybenzene but also the cyclic compound, the oligomer, etc. can be controlled.

For example, step (1) yields a tris(3-halogeno-2-hydroxypropyl ether) intermediate as described above, but depending on the reaction conditions, the 3-halogeno-2-hydroxypropyl ether group may A partial ring-closing side reaction can occur to produce an intermediate having a glycidyl group and a hydroxyl group. In this case, the intramolecular reaction of the intermediates obtained by the side reaction results in the formation of a cyclic compound, and the intermolecular reaction results in the formation of an oligomer. Therefore, in step (1), controlling the side reaction that produces an intermediate having a glycidyl group and a hydroxyl group tends to control the amounts of cyclic compounds and oligomers. For example, if step (1) is carried out under high temperature conditions, the side reaction that produces glycidyl groups is promoted, and the amount of cyclic compounds and oligomers in the resulting reaction product can be high. On the other hand, when step (1) is carried out under low temperature conditions, the reaction to form glycidyl groups is relatively suppressed, and the amount of cyclic compounds and oligomers in the resulting reaction product can be low. In addition, when step (1) is performed for a short time, there are many unreacted hydroxyl groups, and the amount of cyclic compounds and oligomers in the reaction product is high due to reaction with glycidyl groups generated in step (2). can be.

The content of each component in the reaction product can be controlled by various methods. For example, the amount of 1,2,3-trihydroxybenzene (pyrogallol) added in step (1) above, the type and amount of epihalohydrin added, the quaternary onium salt, the type and amount of basic compound added, the reaction temperature, The reaction can be controlled by adjusting the reaction time or the like. Also, the reaction can be controlled by addition or removal of raw materials, products, etc. in step (1). Furthermore, the reaction can be controlled by adjusting the type and amount of the basic compound added, the reaction temperature, the reaction time, the reaction rate, etc. in the above step (2). In addition, the reaction can be controlled by adding or removing the product of step (2) or the like. As a result, the content of each component in the reaction product can be controlled.

[1,2,3-triglycidyloxybenzene (triglycidyl form of pyrogallol)]
1,2,3-triglycidyloxybenzene has the following structure.

In the above structural formulas, each "R" independently represents a hydrogen atom or a methyl group.

The epoxy resin of the present invention contains 1,2,3-triglycidyloxybenzene, and the content of the 1,2,3-triglycidyloxybenzene is 80% or more in area ratio as measured by gel permeation chromatography (GPC). is preferably 82% or more, more preferably 84% or more, particularly preferably 86% or more, most preferably 88 to 98%. If the content of 1,2,3-triglycidyloxybenzene (pyrogallol triglycidyl form) is 80% or more in terms of area ratio in GPC measurement, curability, heat resistance, mechanical properties, and even shortening of the process time, etc. can be improved, which is preferable. In addition, the content of by-products can be controlled (reduced), and both rapid curability and storage stability can be achieved, which is useful. In this specification, the term "area ratio in GPC measurement" means the ratio of the area occupied by the target compound in the GPC chart obtained by GPC measurement of the reaction product. As for a specific measuring method, the method described in Examples shall be adopted.

[Cyclic compounds]
The present invention provides an epoxy resin which is the reaction product of 1,2,3-trihydroxybenzene and epihalohydrin, wherein said epoxy resin has two adjacent oxygen atoms derived from 1,2,3-trihydroxybenzene. as constituent atoms. Since the epoxy resin contains the cyclic compound due to a side reaction, the epoxy resin becomes liquid at room temperature (25° C.) and has low viscosity and excellent handling and workability. In the case where the cyclic compound is not contained, the epoxy resin tends to crystallize, and as a liquid epoxy resin, the storage (preservation) stability is inferior, and the handleability is also inferior, which is not preferable.

Specific cyclic compounds include, but are not particularly limited to, compounds shown below and compounds obtained by further reacting the above compounds with epihalohydrin.

In the above structural formulas, each "R" independently represents a hydrogen atom or a methyl group.

The cyclic compound may be contained alone or may be contained in combination of two or more.

The content of the cyclic compound is less than 0.040 mol, preferably 0.004 to 0.035 mol, more preferably 0.006 to 0.030 mol, and still more preferably 100 g of the epoxy resin. 0.008 to 0.025 mol, particularly preferably 0.010 to 0.020 mol. When the content of the cyclic compound is less than 0.40 mol, when the epoxy resin containing the cyclic compound is used, 1,2,3-triglycidyloxybenzene is highly purified and is a by-product. It is preferable that the content of the cyclic compound is low, because it is possible to achieve both rapid curability and storage stability, although the detailed reason is not clear. In addition, in this specification, "the content of a cyclic compound" shall employ|adopt the value measured by the method as described in an Example. Moreover, when two or more kinds of cyclic compounds are included, the "content of cyclic compounds" means the total content thereof.

The content of the cyclic compound can be adjusted by controlling the reaction as described above. Adjustment of the content of such a cyclic compound can be achieved by, for example, the amount of 1,2,3-trihydroxybenzene added, the type and amount of epihalohydrin added, the quaternary onium salt, the basic compound, etc. can be carried out by appropriately adjusting the type and amount of addition, reaction temperature, reaction time, and the like. It can also be carried out by adding or removing raw materials, products, etc. in step (1). Furthermore, it can be carried out by appropriately adjusting the type and amount of the basic compound added, the reaction temperature, the reaction time, the reaction rate, etc. in the above step (2). It can also be carried out by adding or removing the product of step (2) or the like.

[Oligomer]
The epoxy resin of the present invention further contains oligomers. When the epoxy resin contains the oligomer as a by-product, controlling (adjusting) the content of the oligomer makes it easier for the epoxy resin to achieve both rapid curability and storage stability, which is preferable.
As used herein, the term "oligomer" means a compound obtained by reacting pyrogallol or a derivative thereof with each other. Therefore, an oligomer can be said to have a structure having a plurality of pyrogallol skeletons, and examples thereof include those represented by the following structures.

In the above structural formulas, each "R" independently represents a hydrogen atom or a methyl group, and "n" represents an integer of 0-5.

The oligomer is not particularly limited, but the tris(3-halogeno-2-hydroxypropyl ether) intermediate, bis(3-halogeno-2-hydroxypropyl ether) intermediate, mono (3-halogeno-2-hydroxypropyl ether) oligomers obtained by reacting one or more intermediates; bifunctional or higher functional epoxy compounds such as 1,2,3-triglycidyloxybenzene, pyrogallol, etc. and an oligomer obtained by reacting with a polyhydric phenol having a functionality of 2 or more.

The oligomer may be contained singly or in combination of two or more.

The content of the oligomer is preferably 10% or less, more preferably 8% or less, still more preferably 6% or less, and particularly 4% or less in terms of area ratio in GPC measurement. Preferably, 0.05 to 2% is most preferred. When the content of the oligomer is 10% or less, the viscosity of the epoxy resin becomes low and the handleability is improved, which is preferable. In addition, when two or more types of oligomers are included, the "oligomer content" means the total content of these.

As for the adjustment of the content of the oligomer, the amount of pyrogallol added, the type and amount of epihalohydrin added, the type of quaternary onium compound, and the basic compound in steps (1) and (2) are the same as in the case of the cyclic compound. And it can be carried out by appropriately adjusting the addition amount, reaction temperature, reaction time, and the like.

[Other glycidyl bodies]
Reaction products may include other glycidyl forms. Other glycidyl forms refer to compounds having a glycidyl group, excluding 1,2,3-triglycidyloxybenzene, cyclic compounds, and oligomers.

Examples of the other glycidyl forms include diglycidyl forms of pyrogallol represented by the following structures, monoglycidyl forms of pyrogallol, derivatives thereof, and the like. In this case, the “derivative” means a compound obtained by further reacting the glycidyl group of the pyrogallol diglycidyl derivative or the pyrogallol monoglycidyl derivative with epihalohydrin through a ring-opening addition reaction.

In the structural formula above, each "X" independently represents a halogen atom. Each "R" independently represents a hydrogen atom or a methyl group.

The other glycidyl bodies may be contained singly or in combination of two or more.

[solvent]
The solvent is not particularly limited, and includes the reaction solvents described above, as well as water and solvents that may be intentionally added in the purification process and the like.

The content of the solvent is preferably 5 parts by mass or less, more preferably 1 part by mass or less with respect to 100 parts by mass of the solid content (active ingredient) of the epoxy resin. In addition, in this specification, the "solid content of the epoxy resin" means the total mass of the components excluding the solvent in the epoxy resin. Therefore, if the epoxy resin does not contain solvent, the total weight of the epoxy resin corresponds to the solids content. Further, when the epoxy resin, epoxy resin composition, or the like contains a liquid component, the "solid content" means an "active component" that does not contain a solvent.

[Other compounds]
Other compounds include, but are not limited to, those other than products produced by the reaction of pyrogallol and epihalohydrin. Specific examples include unreacted pyrogallol, unreacted epihalohydrin, unreacted quaternary onium salts, unreacted basic compounds, and compounds derived from these. The content of other compounds tends to be low because the reaction conditions are usually controlled and purified.

The content of the other compounds is preferably 5% by mass or less, more preferably 0.05 to 5% by mass, based on the solid content (active ingredient) of the epoxy resin.

The epoxy resin of the present invention preferably has an epoxy equivalent weight of 120 g/equivalent or less, more preferably 80 to 120 g/equivalent or less, even more preferably 90 to 115 g/equivalent or less, and 100 to 110 g/equivalent. / equivalent is particularly preferred. When the epoxy equivalent of the epoxy resin is 120 g/equivalent or less, it is preferable because the heat resistance can be improved. In addition, in this specification, the value of "epoxy equivalent" shall adopt the value measured by the method described in an Example.

The components and physical properties in the epoxy resin may be adjusted by controlling the reaction, by controlling the purification process, or by adding additional components. At this time, from the viewpoint of efficiently preparing the epoxy resin, the reaction is controlled to adjust the content of the components of the epoxy resin, and the obtained epoxy resin is purified to reduce unreacted components and side effects. It is preferable to adopt a method of adjusting (reducing) the cyclic compounds and oligomers that are products.

[Method for reducing by-products]
As a method for adjusting (reducing) the content of by-products in the obtained epoxy resin, as described above, it is possible to reduce it by adjusting the raw materials used and adjusting the reaction conditions. By purifying the resin, the content of by-products can be adjusted (reduced) more easily. For example, general purification methods such as purification by column chromatography, molecular distillation, recrystallization, and reprecipitation can be employed. Among them, column chromatography and molecular distillation can obtain the target compound with high purity. It is also preferable from the point of view. By purifying the epoxy resin, high-purity 1,2,3-triglycidyloxybenzene is contained, and by-products are reduced, thereby achieving both rapid curing and storage stability of the epoxy resin. It becomes easier and preferable.

Specific methods for purification by column chromatography include silica gel column chromatography using silica gel.
As the silica gel, acidic silica gel, neutral silica gel, chemically modified silica gel, etc. can be used, and neutral silica gel is preferred.
The amount of silica gel to be used is preferably 2 to 100 times mL of the sample amount (g).
As a developing solvent, it is possible to adjust the polarity by using low-polarity solvents such as hexane, toluene, and chloroform together with high-polarity solvents such as ethyl acetate, acetone, and methanol. You can also Toluene, acetone, and methanol are preferred from the viewpoints of environmental load, safety, and economy, and it is preferred to use toluene and acetone in combination from the viewpoints of improving purity and recovery after use.

A specific method for purification by molecular distillation includes a method using a thin film distillation apparatus.
Molecular distillation is usually carried out under reduced pressure. The degree of pressure reduction is preferably 0 to 30 Torr, and the temperature is preferably 200 to 250°C.

<Epoxy resin composition>
The present invention relates to an epoxy resin composition containing the epoxy resin and a curing agent. Since the epoxy resin (pyrogallol-type epoxy resin) contains the triglycidyl form of pyrogallol, it has high reactivity with a curing agent and is excellent in rapid curability. Generally, an epoxy resin composition containing an epoxy resin, a curing agent, and the like undergoes a reaction after being compounded, resulting in thickening and handling and workability problems. However, the epoxy resin of the present invention is By using, the content ratio of the cyclic compound (etc.), which is a by-product, is controlled (adjusted), so thickening is suppressed, storage stability is excellent, and it is useful.

The epoxy resin composition may further contain, if necessary, other epoxy resins, other resins, curing accelerators, organic solvents, additives, and the like.

The content of the epoxy resin is preferably 30 to 99% by mass, more preferably 40 to 97% by mass, based on the solid content (active ingredient) of the epoxy resin composition. When the content of the epoxy resin is 30% by mass or more, it is preferable because the performance of the epoxy resin is likely to be exhibited. On the other hand, when the content of the epoxy resin is 99% by mass or less, it is preferable because the options for the curing agent are widened. In addition, in this specification, "the solid content of the resin composition" means the total mass of the components in the composition excluding the solvent described later. Therefore, if the resin composition does not contain solvent, the total weight of the composition corresponds to the solids content.

[Other epoxy resins]
Other epoxy resins include, but are not particularly limited to, bisphenol-type epoxy resins such as bisphenol A-type epoxy resin and bisphenol F-type epoxy resin; biphenyl-type epoxy resins such as biphenyl-type epoxy resin and tetramethylbiphenyl-type epoxy resin; type epoxy resin, cresol novolac type epoxy resin, bisphenol A novolac type epoxy resin, biphenyl novolac type epoxy resin; triphenylmethane type epoxy resin; tetraphenylethane type epoxy resin; dicyclopentadiene-phenol addition reaction type epoxy resin; phenol aralkyl type epoxy resin; naphthol novolak type epoxy resin, naphthol aralkyl type epoxy resin, naphthol-phenol co-condensed novolac type epoxy resin, naphthol-cresol co-condensed novolak type epoxy resin, diglycidyloxynaphthalene, phosphorus atom-containing An epoxy resin etc. are mentioned.

The other epoxy resins may be used alone or in combination of two or more.

[Other resins]
Other resins mean resins other than epoxy resins. The other resin may be a thermosetting resin or a thermoplastic resin. Specific examples of other resins include, but are not limited to, polycarbonate resins, polyphenylene ether resins, polyethylene terephthalate resins, polybutylene terephthalate resins, polyethylene resins, polypropylene resins, polyimide resins, polyamideimide resins, polyetherimide resins, and polyethers. Examples include sulfone resins, polyketone resins, polyetherketone resins, polyetheretherketone resins, and phenolic resins. These other resins may be used alone or in combination of two or more.

[Curing agent]
Examples of the curing agent include, but are not limited to, amine compounds, amide compounds, acid anhydride compounds, phenol compounds, and the like.

Examples of the amine compounds include ethylenediamine, diaminopropane, diaminobutane, diethylenetriamine, triethylenetetramine, 1,4-cyclohexanediamine, isophoronediamine, diaminodicyclohexylmethane, diaminodiphenylmethane, diaminodiphenylsulfone, phenylenediamine, imidazole, BF3. -amine complexes, dicyandiamide, guanidine derivatives and the like.

Examples of the amide compounds include polyamide resins synthesized from dimers of linolenic acid and ethylenediamine.

Examples of the acid anhydride compounds include phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, maleic anhydride, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylnadic anhydride, hexahydrophthalic anhydride, methylhexa hydrophthalic anhydride and the like.

Examples of the phenolic compound include phenol novolak resin, cresol novolak resin, aromatic hydrocarbon formaldehyde resin-modified phenol resin, dicyclopentadiene phenol addition type resin, phenol aralkyl resin, α-naphthol aralkyl resin, β-naphthol aralkyl resin, biphenyl Aralkyl resins, triphenylolmethane resins, tetraphenylolethane resins, naphthol novolac resins, naphthol-phenol co-condensed novolac resins, naphthol-cresol co-condensed novolac resins, amino group-containing triazine compounds (melamine, benzoguanamine, etc.) and phenols (phenol, cresol, etc.) and aminotriazine-modified phenol resin, which is a copolymer of formaldehyde, and the like.

Among these, it is preferable to use amine compounds and phenol compounds, such as diaminodiphenylsulfone, phenol novolak resin, cresol novolak resin, phenol aralkyl resin, α-naphthol aralkyl resin, β-naphthol aralkyl resin, biphenyl aralkyl resin, amino It is more preferable to use a triazine-modified phenolic resin.

In addition, the said hardened|cured material may be used independently, or may be used in combination of 2 or more type.

The content of the curing agent is preferably 1 to 70% by mass, more preferably 3 to 60% by mass, based on the solid content (active ingredient) of the epoxy resin composition. It is preferable that the content of the curing agent is 1% by mass or more because the options for the curing agent are widened. On the other hand, when the content of the curing agent is 70% by mass or less, the performance of the epoxy resin is likely to be exhibited, which is preferable.

[Curing accelerator]
A curing accelerator has a function of accelerating curing. As a result, the reaction time can be shortened, and the generation of unreacted epoxy compounds can be prevented or reduced.

Examples of the curing accelerator include, but are not limited to, phosphorus compounds, tertiary amines, imidazoles, organic acid metal salts, Lewis acids, amine complexes, urea derivatives, and the like. Among these, it is preferable to use imidazoles. These curing accelerators may be used alone or in combination of two or more.

The content of the curing accelerator is preferably 0.1 to 10% by mass, more preferably 0.5 to 5% by mass, based on the solid content (active ingredient) of the epoxy resin composition. . A content of the curing accelerator of 0.1% by mass or more is preferable because curing can be accelerated. On the other hand, when the content of the curing accelerator is 10% by mass or less, the pot life can be lengthened and the storage stability is excellent, which is preferable.

[Organic solvent]
The organic solvent has the function of adjusting the viscosity of the epoxy resin composition. This can improve the impregnability into the base material and the like.

The organic solvent is not particularly limited, but ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone; ethyl acetate, butyl acetate, cellosolve acetate, propylene glycol monomethyl ether acetate, carbitol acetate, ethyl diglycol acetate, propylene Acetic esters such as glycol monomethyl ether acetate; Alcohols such as isopropyl alcohol, butanol, cellosolve and butyl carbitol; Aromatic hydrocarbons such as toluene and xylene; Amides such as dimethylformamide, dimethylacetamide and N-methylpyrrolidone etc. Among these, alcohols and ketones are preferably used, and butanol and methyl ethyl ketone are more preferably used. These solvents may be used alone or in combination of two or more.

The content of the organic solvent is preferably 10 to 60 parts by mass, more preferably 20 to 50 parts by mass, based on 100 parts by mass of the solid content (active ingredient) of the epoxy resin composition. It is preferable that the content of the organic solvent is 10 parts by mass or more because the viscosity can be lowered. On the other hand, if the content of the organic solvent is 60 parts by mass or less, it is preferable because non-volatile components can be reduced.

[Additive]
Additives that can be contained in the epoxy resin composition are not particularly limited, but inorganic fillers, reinforcing fibers, flame retardants, release agents, pigments, antioxidants, ultraviolet absorbers, light stabilizers, antistatic agents, A conductivity-imparting agent and the like can be mentioned. These additives may be used alone or in combination of two or more.

[Use]
In one embodiment, the epoxy resin composition containing the epoxy resin is used for prepregs, fiber-reinforced composite materials, heat dissipation members, adhesives, paints, semiconductors, printed wiring boards, automobile members, railway vehicle members, aerospace aircraft members, It can be applied to applications such as ship members, housing equipment members, sports members, light vehicle members, construction and civil engineering members, and housings for OA equipment and the like.

<Cured product>
The present invention relates to a cured product obtained by curing the epoxy resin composition. The cured product is obtained by curing the epoxy resin composition described above. The cured product has high heat resistance and mechanical properties (high elastic modulus, etc.).

The shape of the cured product is not particularly limited, and may be a sheet shape or a shape in which the cured product is impregnated with another material (fibrous reinforcing material, etc.).

The curing temperature of the epoxy resin composition is preferably 50 to 250°C, more preferably 70 to 200°C. A curing temperature of 50° C. or higher is preferable because the curing reaction can be carried out quickly. On the other hand, if the curing temperature is 250° C. or less, it is preferable because the amount of energy required for curing can be suppressed.

EXAMPLES The present invention will be described below using examples, but the present invention is not limited to the description of the examples.

Regarding the epoxy resin, GPC, ¹³ C-NMR, epoxy equivalent, and cyclic compound content were measured under the following conditions.

<GPC measurement conditions>
GPC measurement was performed using the following measurement apparatus and measurement conditions to analyze the cyclic compounds contained in the epoxy resin obtained by the synthesis method shown below. The GPC measurement results (GPC chart) are shown for Synthesis Example 1 (Comparative Example 1) and Synthesis Example 2 (Example 1) (see FIGS. 1 and 2).
Measuring device: "HLC-8220 GPC" manufactured by Tosoh Corporation,
Column: Guard column "HXL-L" manufactured by Tosoh Corporation
+ "TSK-GEL G2000HXL" manufactured by Tosoh Corporation
+ "TSK-GEL G2000HXL" manufactured by Tosoh Corporation
+ "TSK-GEL G3000HXL" manufactured by Tosoh Corporation
+ "TSK-GEL G4000HXL" manufactured by Tosoh Corporation
Detector: RI (differential refractometer)
Data processing: "GPC-8020 model II version 4.10" manufactured by Tosoh Corporation
Measurement conditions: Column temperature 40°C
Developing solvent: tetrahydrofuran Flow rate: 1.0 ml/min Standard: The following monodisperse polystyrene having a known molecular weight was used according to the measurement manual of "GPC-8020 Model II Version 4.10".
(Polystyrene used)
"A-500" manufactured by Tosoh Corporation
"A-1000" manufactured by Tosoh Corporation
"A-2500" manufactured by Tosoh Corporation
"A-5000" manufactured by Tosoh Corporation
"F-1" manufactured by Tosoh Corporation
"F-2" manufactured by Tosoh Corporation
"F-4" manufactured by Tosoh Corporation
"F-10" manufactured by Tosoh Corporation
"F-20" manufactured by Tosoh Corporation
"F-40" manufactured by Tosoh Corporation
"F-80" manufactured by Tosoh Corporation
"F-128" manufactured by Tosoh Corporation
Sample: 50 µl of a tetrahydrofuran solution of 1.0% by mass in terms of resin filtered through a microfilter.

< ¹³ C-NMR measurement conditions>
Apparatus: JNM-ECA500 manufactured by JEOL Ltd.
Measurement mode: Decoupling with reverse gate Solvent: Deuterated dimethyl sulfoxide Pulse angle: 30° pulse Sample concentration: 30% by mass
Accumulation times: 4000 times Chemical shift standard: Peak of dimethyl sulfoxide: 39.5 ppm
From the results of ¹³ C-NMR measurement, a peak derived from the target product (epoxy resin) was confirmed, confirming that the target product was obtained in each reaction. The results of the ¹³ C-NMR measurement ( ¹³ C-NMR chart) are shown for Synthesis Example 1 (Comparative Example 1) and Synthesis Example 2 (Example 2) (see FIGS. 3 and 4). .

<Epoxy equivalent>
The epoxy equivalent (g/equivalent) of the epoxy resin obtained in Examples and Comparative Examples below was measured by the method of JIS K 7236:2009.

<Content of cyclic compound>
The content X (mol) of the cyclic compound per 100 g of the epoxy resin was measured for the epoxy resins obtained in the following examples and comparative examples. Specifically, it was calculated using the following formula.
X=(100×(A))/((B)×(C))
In the above formula, X is the cyclic compound content (mol) per 100 g of epoxy resin, (A) is the cyclic compound (mol) per 1 mol of the aromatic ring, and (B) is the epoxy group per 1 mol of the aromatic ring. (mol) and (C) is the epoxy equivalent (g/equivalent).

[Synthesis Example 1]
<Preparation of epoxy resin (E-1)>
(Step (1))
126 g (1.00 mol) of 1,2,3-trihydroxybenzene (pyrogallol) and 1388 g (15 mol) of epichlorohydrin were added to a flask equipped with a thermometer, dropping funnel, condenser, nitrogen inlet tube, and stirrer. and the temperature was raised to 50°C. Then, 11.2 g (0.06 mol) of benzyltrimethylammonium chloride was added and stirred at 50° C. for 24 hours.

(Step (2))
1000 mL of distilled water was poured into the reaction liquid obtained in the step (1), and the mixture was stirred, left to stand, and then the upper layer was removed. 318 g of a 48% sodium hydroxide aqueous solution was added dropwise over 2.5 hours, and the mixture was stirred for 1 hour.

400 mL of distilled water was poured into the resulting solution and left to stand. The lower layer of saline was removed, and epichlorohydrin was recovered by distillation at 120°C. Then, 500 g of methyl isobutyl ketone (MIBK) and 147 g of water were sequentially added and washed with water at 80°C. After removing the washing water of the lower layer, dehydration and filtration were performed, and MIBK was desolvated at 150° C. to obtain epoxy resin (E-1). The obtained epoxy resin (E-1) was visually observed to be liquid.
The content of the cyclic compound in the obtained epoxy resin (E-1) was 0.086 mol/100 g, and the area ratio of 1,2,3-triglycidyloxybenzene (triglycidyl form of pyrogallol) in GPC measurement was 77%. , the area ratio of the oligomer in GPC was 3.2%, and the epoxy equivalent was 128 g/equivalent. These results were taken as the results of Comparative Example 1.

[Synthesis Example 2]
<Preparation of epoxy resin (E-2)>
A chromatography column with a diameter of 10 cm was wet-packed with 800 mL of silica gel 60N (spherical, neutral) (manufactured by Kanto Kagaku), and then 15 g of the epoxy resin (E-1) obtained in Synthesis Example 1 was packed and adsorbed onto the silica gel. Thereafter, purification was performed by silica gel column chromatography under a gradient condition of toluene/acetone=30/1 to 10/1 to obtain epoxy resin (E-2). In addition, when the obtained epoxy resin was visually observed, it was found to be liquid.
The content of the cyclic compound in the obtained epoxy resin (E-2) was 0.012 mol/100 g, and the area ratio of 1,2,3-triglycidyloxybenzene (triglycidyl form of pyrogallol) in GPC measurement was 95%. , the area ratio of the oligomer in GPC was 0.7%, and the epoxy equivalent was 102 g/equivalent. These results are the results of Example 1.

<Preparation of epoxy resin composition>
4,4′-diaminodiphenylsulfone (4,4′-DDS) as a curing agent is added to the above epoxy resin (E-1) and epoxy resin (E-2), respectively, as an epoxy group/active Hydrogen groups were blended at a ratio of 1/1 (equivalent ratio) and uniformly dispersed at room temperature to prepare a sample composition.

<Curability evaluation of epoxy resin composition>
Regarding the above sample composition, a differential scanning calorimeter ("DSC1" manufactured by METTOLER TOLEDO Co., Ltd., sample amount 4.0 to 8.0 mg, aluminum sample pan size φ5 × 2.5 mm, heating rate 10 ° C./min, The exothermic temperature range was measured with a nitrogen flow rate of 40 ml/min and a temperature range of 20 to 350°C. The "onset temperature" is the intersection point of the tangent line passing through the baseline and the inflection point before the transition, and the "endset temperature" is the tangent line passing through the baseline and the inflection point after the transition. The intersection point, the peak temperature, and the temperature at which the heat generation is maximum were automatically calculated by STARe Software manufactured by METLLOER TOLEDO Co., Ltd., respectively.
The difference between the end-set temperature (° C.) and the on-set temperature (° C.) is preferably within 90° C., more preferably within 88° C., and within 86° C. from the viewpoint of further shortening the curing reaction time. is more preferred.

<Storage stability evaluation of epoxy resin composition>
With respect to the sample solution, the glass transition temperature (Tg) (° C.) after 0 hours (initial value) and 168 hours after the retention time is measured using the differential scanning calorimeter. The difference (ΔTg) (°C) was calculated to evaluate the storage stability of the epoxy resin composition.
The ΔTg (°C) is preferably 15°C or less, more preferably 10°C or less, and even more preferably 5°C or less from the viewpoint of maintaining handleability after storage.
(Measurement condition)
Temperature/humidity conditions: 25°C, 50% RH
Temperature range: -30 to 70°C
Heating rate: 10°C/min

Epoxy resin compositions were prepared using the epoxy resins obtained in Synthesis Example 1 (Comparative Example 1) and Synthesis Example 2 (Example 1). Examples 2 and 2) are shown in Table 1 below.

From the results in Table 1 above, it was confirmed that the epoxy resin composition (Example 2) using the epoxy resin (purified product) obtained in Example 1 could achieve both rapid curing and storage stability. . On the other hand, the epoxy resin composition (Comparative Example 2) using the epoxy resin (unrefined product) obtained in Comparative Example 1 has a larger glass transition temperature difference (ΔTg) than Example 2, and is storage stable. confirmed to be inferior.

In the present invention, the epoxy resin is excellent in rapid curing and storage stability, and is also excellent in workability and handleability. Components, adhesives, paints, semiconductors, printed wiring boards, automotive components, railway vehicle components, aerospace aircraft components, ship components, housing equipment components, sports components, light vehicle components, construction and civil engineering components, housings for OA equipment, etc. It can be suitably used for automobile parts, aerospace machine parts, etc. in particular.

Claims (6)

An epoxy resin that is the reaction product of 1,2,3-trihydroxybenzene and an epihalohydrin,
The epoxy resin comprises a cyclic compound having a cyclic structure containing two adjacent oxygen atoms derived from 1,2,3-triglycidyloxybenzene and 1,2,3-trihydroxybenzene as constituent atoms,
An epoxy resin in which the content of the cyclic compound is less than 0.040 mol per 100 g of the epoxy resin. further comprising an oligomer;
2. The epoxy resin according to claim 1, wherein the oligomer content is 10% or less in terms of area ratio as measured by GPC. 3. The epoxy resin according to claim 1, wherein the content of said 1,2,3-triglycidyloxybenzene is 80% or more in terms of area ratio as measured by GPC. The epoxy resin according to any one of claims 1 to 3, which has an epoxy equivalent weight of 120 g/equivalent or less. An epoxy resin composition comprising the epoxy resin according to any one of claims 1 to 4 and a curing agent. A cured product obtained by curing the epoxy resin composition according to claim 5 .