Epoxy resin composition containing dicarboxylic anhydride and cured product thereof

Abstract

To provide an epoxy resin composition having superior storage stability, which exhibits a small change in properties when comparing a cured product of the epoxy resin composition before storage with the cured product after storage.SOLUTION: An epoxy resin composition comprises an epoxy resin and a curing agent, wherein the curing agent comprises a dicarboxylic anhydride represented by formula (1) and / or a dicarboxylic anhydride represented by formula (2) [wherein R1 to R10 are each independently hydrogen or an alkyl group having 1 to 4 carbon atoms, where at least one of R3 and R4 is an alkyl group having 1 to 4 carbon atoms, and at least one of R7 to R10 is an alkyl group having 1 to 4 carbon atoms].SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an epoxy resin composition containing a specific dicarboxylic acid anhydride, and a cured product thereof. [Background technology]

[0002] Epoxy resins have been widely used in the fields of adhesives, paints, semiconductors, composite materials, etc., because their cured products have excellent heat resistance and electrical insulation. Amines and acid anhydrides are generally used as curing agents for epoxy resins, but amine-based curing agents are highly toxic or irritating to the skin, and epoxy resin compositions containing amine-based curing agents have problems with storage stability. Acid anhydride-based curing agents are preferably used because they are less toxic or irritating to the skin than amine-based curing agents. For example, Patent Document 1 discloses that an epoxy resin composition having excellent fluidity and adhesiveness can be provided by using an acid anhydride such as 2,4-dialkylglutaric anhydride as a curing agent. From the viewpoint of workability of the epoxy resin composition, in order to provide an epoxy resin composition having a low viscosity, methylhexahydroxyphthalic anhydride, methyltetrahydroxyphthalic anhydride, or the like, which is liquid at room temperature, is used as a curing agent. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2004-131623 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, storage stability is not considered in Patent Document 1. Furthermore, according to the studies by the present inventors, the epoxy resin composition containing the above-mentioned acid anhydride does not necessarily have sufficient storage stability. An object of the present invention is to provide an epoxy resin composition which has excellent storage stability and shows little change in properties when a cured product of the epoxy resin composition before storage is compared with a cured product of the epoxy resin composition after storage. [Means for solving the problem]

[0005] As a result of extensive investigations, the present inventors have found that the above problems can be solved by causing an epoxy resin composition to contain a specific dicarboxylic acid anhydride as a curing agent. That is, the present invention includes the following preferred embodiments. [1] An epoxy resin composition comprising an epoxy resin and a curing agent, the curing agent being a dicarboxylic acid anhydride represented by formula (1) and / or a dicarboxylic acid anhydride represented by formula (2): TIFF2025080087000001.tif22102[where, R 1 ~R 10 are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, provided that R 3 and R 4 At least one of R is an alkyl group having 1 to 4 carbon atoms; 7 ~R 10 At least one of the groups is an alkyl group having 1 to 4 carbon atoms. 1. An epoxy resin composition comprising: [2] R 3 is an alkyl group having 1 to 4 carbon atoms, and R 1 ~R 2 and R 4 ~R 6 [1] The epoxy resin composition according to [1], wherein [3] R 8 is an alkyl group having 1 to 4 carbon atoms, and R 7 and R 9 ~R 10 The epoxy resin composition according to [1] or [2], wherein [4] The epoxy resin composition according to any one of [1] to [3], wherein the alkyl group having 1 to 4 carbon atoms is a methyl group or an ethyl group. [5] The epoxy resin composition according to any one of [1] to [4], wherein the dicarboxylic acid anhydride represented by the formula (1) is selected from the group consisting of 3-methylglutaric anhydride, 3-ethylglutaric anhydride, 3-propylglutaric anhydride, 3-isopropylglutaric anhydride, 3-n-butylglutaric anhydride, 3-sec-butylglutaric anhydride, 3-tert-butylglutaric anhydride and 3-isobutylglutaric anhydride. [6] The epoxy resin composition according to any one of [1] to [5], wherein the dicarboxylic acid anhydride represented by the formula (2) is selected from the group consisting of 2-methylsuccinic anhydride, 2-ethylsuccinic anhydride, 2-propylsuccinic anhydride, 2-isopropylsuccinic anhydride, 2-n-butylsuccinic anhydride, 2-sec-butylsuccinic anhydride, 2-tert-butylsuccinic anhydride, and 2-isobutylsuccinic anhydride. [7] The epoxy resin composition according to any one of [1] to [6], wherein a molar ratio of the total amount of the dicarboxylic anhydride represented by the formula (1) and the dicarboxylic anhydride represented by the formula (2) to the amount of epoxy groups in the epoxy resin is 0.05 to 10. [8] The epoxy resin composition according to any one of [1] to [7], further comprising an acid anhydride other than the dicarboxylic acid anhydride represented by the formula (1) and the dicarboxylic acid anhydride represented by the formula (2). [9] The epoxy resin composition according to [8], wherein the molar ratio of the amount of the acid anhydride other than the dicarboxylic acid anhydride represented by the formula (1) and the dicarboxylic acid anhydride represented by the formula (2) to the total amount of the dicarboxylic acid anhydride represented by the formula (1) and the dicarboxylic acid anhydride represented by the formula (2) is 0.01 to 50.

[10] A cured product of the epoxy resin composition according to any one of [1] to [9]. Effect of the Invention

[0006] According to the present invention, it is possible to provide an epoxy resin composition which has excellent storage stability and shows only small changes in properties when a cured product of the epoxy resin composition before storage is compared with a cured product of the epoxy resin composition after storage. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0007] Hereinafter, embodiments of the present invention will be described in detail. However, there is no intention to limit the present invention to the following embodiments.

[0008] [Epoxy resin composition] <Epoxy resin> The epoxy resin is not particularly limited as long as it can be cured by a curing agent. For example, an epoxy resin containing at least two epoxy groups in one molecule can be suitably used. Specifically, biphenyl type epoxy resin, naphthalene type epoxy resin, diphenyl ether type epoxy resin, diphenyl thioether type epoxy resin, hydroquinone type epoxy resin, biphenyl novolac type epoxy resin, cresol novolac type epoxy resin, phenol novolac type epoxy resin, bisphenol A novolac type epoxy resin, trisphenol type epoxy resin, tetraphenylolethane type epoxy resin, dicyclopentadiene type epoxy resin, cyclohexane type epoxy resin, triazine type epoxy resin, bisphenol A type epoxy resin, and bisphenol F type epoxy resin can be mentioned. One of these epoxy resins may be used alone, or two or more types may be used in combination. These epoxy resins are commercially available. From the viewpoint of easily achieving the effects of the present invention and from the viewpoint of handleability, the epoxy resin is preferably a liquid epoxy resin, more preferably a liquid cyclohexane type epoxy resin, a liquid triazine type epoxy resin, a liquid bisphenol A type epoxy resin, or a liquid bisphenol F type epoxy resin, and particularly preferably a liquid bisphenol A type epoxy resin or a liquid bisphenol F type epoxy resin.

[0009] <Hardening agent> The curing agent is at least one dicarboxylic acid anhydride represented by formula (1) and / or at least one dicarboxylic acid anhydride represented by formula (2): TIFF2025080087000002.tif22102[where, R 1 ~R 10 are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, provided that R3 and R 4 At least one of R is an alkyl group having 1 to 4 carbon atoms; 7 ~R 10 at least one of which is an alkyl group having 1 to 4 carbon atoms.

[0010] The present inventors have unexpectedly found that when an epoxy resin composition contains a dicarboxylic anhydride represented by formula (1) and / or a dicarboxylic anhydride represented by formula (2), the epoxy resin composition can achieve improved storage stability, and the change in properties can be reduced when comparing a cured product of the epoxy resin composition before storage with a cured product of the epoxy resin composition after storage. The reason for this is presumed to be the following mechanism of action (reason), although it is not intended to be limiting. The curing agent contained in the epoxy resin composition of the present invention is glutaric anhydride or succinic anhydride having an aliphatic group with a relatively short chain length. This aliphatic group with a relatively short chain length possessed by glutaric anhydride or succinic anhydride reduces the intermolecular interaction between the curing agent and the epoxy resin in a temperature range around room temperature, so that the epoxy resin composition has improved storage stability, and it is considered that the change in properties is small when comparing the cured product of the epoxy resin composition before storage with the cured product of the epoxy resin composition after storage. It was unexpected that the epoxy resin composition had excellent storage stability when the dicarboxylic anhydride represented by formula (1) was 3-alkyl substituted. The reason is unclear and is not intended to be limiting, but it is believed that the presence of an alkyl substituent at the 3-position reduces the interaction between the curing agent and the epoxy resin, and further reduces the reactivity in a temperature range around room temperature. It was also unexpected that the epoxy resin composition had excellent storage stability when the acid anhydride had an aliphatic group with a relatively short chain length as a substituent, rather than a long-chain aliphatic group. The reason is unclear and is not intended to be limiting, but it is believed that the interaction between the alkyl substituents of the curing agent and each other is suppressed in addition to the interaction with the epoxy resin. It was also unexpectedly found that the epoxy resin composition had excellent storage stability when the acid anhydride had an aliphatic group with a relatively short chain length as a substituent, rather than a non-substituted acid anhydride. Furthermore, the cured product of the present invention can have good flexibility. This is presumably because the epoxy resin composition contains the dicarboxylic anhydride represented by the formula (1) and / or the dicarboxylic anhydride represented by the formula (2), and the cured product of the epoxy resin composition contains an aliphatic chain in its crosslinked structure. The above effect in the present invention is related to the interaction between the dicarboxylic anhydride represented by the formula (1) and / or the dicarboxylic anhydride represented by the formula (2) and the epoxy group. Therefore, any epoxy resin that can be cured by a curing agent can exhibit the same effect.

[0011] In a preferred embodiment of the present invention, R 3 is an alkyl group preferably having 1 to 4 carbon atoms, more preferably 1 to 3 carbon atoms, and particularly preferably 1 or 2 carbon atoms. At this time, R 1 ~R 2 and R 4 ~R 6 are hydrogen. In this embodiment, the alkyl group of the dicarboxylic anhydride represented by the formula (1) is one and is 3-alkyl-substituted. In a particularly preferred embodiment, R 3 is a methyl group or an ethyl group, and R 1 ~R 2 and R 4 ~R 6 are hydrogen. In a preferred embodiment of the present invention, R 8 is an alkyl group preferably having 1 to 4 carbon atoms, more preferably 1 to 3 carbon atoms, and particularly preferably 1 or 2 carbon atoms. At this time, R 7 and R 9 ~R 10 are hydrogen. In this embodiment, the alkyl group of the dicarboxylic anhydride represented by the formula (2) is one and is 2-alkyl-substituted. In a particularly preferred embodiment, R 8 is a methyl group or an ethyl group, R 7 and R 9 ~R 10 are hydrogen. The reason why these two embodiments are preferred is unclear, and although it is not intended to be limiting, the following mechanism of action (reason) is presumed. It is believed that a dicarboxylic acid anhydride having only one alkyl substituent can reduce interactions between dicarboxylic acid anhydrides and between an epoxy resin and a dicarboxylic acid anhydride over time compared to other curing agents such as dicarboxylic acid anhydrides having multiple alkyl substituents, and as a result, the storage stability of the epoxy resin composition is improved.

[0012] The dicarboxylic acid anhydride represented by the formula (1) is preferably selected from the group consisting of 3-methylglutaric anhydride, 3-ethylglutaric anhydride, 3-propylglutaric anhydride, 3-isopropylglutaric anhydride, 3-n-butylglutaric anhydride, 3-sec-butylglutaric anhydride, 3-tert-butylglutaric anhydride and 3-isobutylglutaric anhydride, more preferably from the group consisting of 3-methylglutaric anhydride, 3-ethylglutaric anhydride, 3-propylglutaric anhydride and 3-n-butylglutaric anhydride, particularly preferably from the group consisting of 3-methylglutaric anhydride, 3-ethylglutaric anhydride and 3-propylglutaric anhydride, and more particularly preferably from the group consisting of 3-methylglutaric anhydride and 3-ethylglutaric anhydride.

[0013] The dicarboxylic acid anhydride represented by the formula (2) is preferably selected from the group consisting of 2-methylsuccinic anhydride, 2-ethylsuccinic anhydride, 2-propylsuccinic anhydride, 2-isopropylsuccinic anhydride, 2-n-butylsuccinic anhydride, 2-sec-butylsuccinic anhydride, 2-tert-butylsuccinic anhydride and 2-isobutylsuccinic anhydride, more preferably from the group consisting of 2-methylsuccinic anhydride, 2-ethylsuccinic anhydride, 2-propylsuccinic anhydride and 2-n-butylsuccinic anhydride, particularly preferably from the group consisting of 2-methylsuccinic anhydride, 2-ethylsuccinic anhydride and 2-propylsuccinic anhydride, and more particularly preferably from the group consisting of 2-methylsuccinic anhydride and 2-ethylsuccinic anhydride.

[0014] In the epoxy resin composition, the molar ratio of the total amount of the dicarboxylic anhydride represented by formula (1) and the dicarboxylic anhydride represented by formula (2) to the amount of epoxy groups in the epoxy resin [(total amount of the dicarboxylic anhydride represented by formula (1) and the dicarboxylic anhydride represented by formula (2)) / (amount of epoxy groups in the epoxy resin)] is preferably 0.05 to 10, more preferably 0.1 to 3. When the molar ratio is within the above range, the storage stability of the epoxy resin composition can be improved (e.g., a small rate of change in viscosity before and after storage), and the change in properties (e.g., bending strain or degree of cure) can be smaller when comparing a cured product of the epoxy resin composition before storage with a cured product of the epoxy resin composition after storage.

[0015] In one embodiment of the present invention, the epoxy resin composition may further contain an acid anhydride other than the dicarboxylic acid anhydride represented by formula (1) and the dicarboxylic acid anhydride represented by formula (2). Examples of such further acid anhydrides include glutaric anhydrides other than the dicarboxylic anhydrides represented by formula (1), succinic anhydrides other than the dicarboxylic anhydrides represented by formula (2), adipic anhydride, pimelic anhydride, suberic anhydride, azelaic anhydride, sebacic anhydride, brassylic anhydride, dodecanedioic anhydride, eicosane diacid anhydride, hexahydroxyphthalic anhydride, 3-methylhexahydroxyphthalic anhydride, 4-methylhexahydroxyphthalic anhydride, methyltetrahydroxyphthalic anhydride, dodecenyl Examples of the acid anhydride include, but are not limited to, succinic anhydride, methylnadic anhydride, 5-(2,5-dioxotetrahydro-3-furanyl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, glycerol trisanhydrotrimellitate, pyromellitic anhydride, benzophenonetetracarboxylic anhydride, and methylcyclohexenetetracarboxylic anhydride, 1,2,3,6-tetrahydro-6-isobutenyl-3,4-dimethylphthalic anhydride, and 1,2,4-cyclohexanetricarboxylic anhydride. The additional acid anhydride can be used alone or in combination of two or more. From the viewpoint of handling, the additional acid anhydride is preferably one or more selected from the group consisting of liquid acid anhydrides, more preferably one or more selected from the group consisting of 3-methylhexahydroxyphthalic anhydride, 4-methylhexahydroxyphthalic anhydride, methyltetrahydroxyphthalic anhydride, and methylnadic anhydride.

[0016] When the epoxy resin composition contains an acid anhydride other than the dicarboxylic anhydride represented by formula (1) and the dicarboxylic anhydride represented by formula (2), the molar ratio of the amount of the dicarboxylic anhydride represented by formula (1) and the acid anhydride other than the dicarboxylic anhydride represented by formula (2) to the total amount of the dicarboxylic anhydride represented by formula (1) and the dicarboxylic anhydride represented by formula (2) [(amount of the dicarboxylic anhydride represented by formula (1) and the acid anhydride other than the dicarboxylic anhydride represented by formula (2)) / (total amount of the dicarboxylic anhydride represented by formula (1) and the dicarboxylic anhydride represented by formula (2)] is preferably 0.01 to 50, more preferably 0.1 to 25, and particularly preferably 0.4 to 10. When the molar ratio is within the above range, the storage stability of the epoxy resin composition can be further improved, and the change in properties can be smaller when comparing the cured product of the epoxy resin composition before storage with the cured product of the epoxy resin composition after storage.

[0017] The dicarboxylic anhydride represented by formula (1), the dicarboxylic anhydride represented by formula (2), and other acid anhydrides can be prepared by subjecting the corresponding dicarboxylic acid to a known treatment such as vacuum distillation. The dicarboxylic anhydride represented by formula (1), the dicarboxylic anhydride represented by formula (2), and acid anhydrides other than the dicarboxylic anhydride represented by formula (1) and the dicarboxylic anhydride represented by formula (2) are also available as commercial products.

[0018] <Optional ingredients> The epoxy resin composition of the present invention may further contain one or more optional components as long as the components do not impair the object and effect of the present invention. Examples of such components include a curing accelerator, an inorganic filler, a reactive diluent, a non-reactive diluent, a plasticizer, a silane coupling agent, a pigment, carbon black, a reinforcing fiber, a wax, a thickener, a thixotropic agent, an antioxidant, a light stabilizer, an ultraviolet absorber, a flame retardant, and an antifoaming agent.

[0019] Examples of the curing accelerator include phosphines such as triphenylphosphine, tris(dimethoxyphenyl)phosphine, and dibutylphenylphosphine; phosphonium salts such as tetraphenylphosphonium bromide; amines such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and 2,4,6-tris(dimethylaminomethyl)phenol; quaternary ammonium salts such as trimethylammonium chloride; imidazoles such as 2-ethyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 2-methylimidazole, and 1-methylimidazole; ureas such as 3-(p-chlorophenyl)-1,1-dimethylurea; complex compounds of boron trifluoride and amines; and complex compounds of boron trifluoride and ether compounds. One of these curing accelerators may be used alone, or two or more may be used in combination. When a curing accelerator is used, the amount is not particularly limited, and may be appropriately set according to the application of the epoxy resin composition. When a curing accelerator is used, the amount is usually 0.05 to 5 parts by mass based on 100 parts by mass of the epoxy resin contained in the epoxy resin composition.

[0020] Examples of inorganic fillers include fused silica, crystalline silica, glass, alumina, silicon nitride, boron nitride, calcium carbonate, magnesium hydroxide, talc, and combinations of two or more of these. By using these inorganic fillers, the moisture absorption, thermal conductivity, and / or mechanical strength of the epoxy resin composition of the present invention can be improved. In addition, by using inorganic fillers, the linear expansion coefficient of the cured epoxy resin can be reduced, and cracks or peeling due to temperature changes during molding, for example, when used for semiconductor sealing, can be reduced. When inorganic fillers are used, the amount is not particularly limited and may be appropriately set depending on the application of the epoxy resin composition. When inorganic fillers are used, the amount is usually 10 to 200 parts by mass with respect to 100 parts by mass of the epoxy resin composition.

[0021] As the pigment, either an inorganic pigment or an organic pigment may be used. Examples of inorganic pigments include titanium oxide, zinc oxide, zinc sulfide, white lead, calcium carbonate, precipitated barium sulfate, white carbon, alumina white, kaolin clay, talc, bentonite, black iron oxide, cadmium red, red iron oxide, molybdenum red, molybdate orange, chrome vermilion, yellow lead, cadmium yellow, yellow iron oxide, titanium yellow, chromium oxide, viridian, titanium cobalt green, cobalt green, cobalt chrome green, Victoria green, ultramarine, Prussian blue, cobalt blue, cerulean blue, cobalt silica blue, cobalt zinc silica blue, manganese violet, and cobalt violet. Examples of organic pigments include azo pigments, phthalocyanine pigments, anthraquinone pigments, quinacridone pigments, isoindolinone pigments, quinophthalone pigments, dye lake pigments, fluorescent pigments, and the like. When a pigment is used, one kind of pigment may be used, or two or more kinds of pigments may be used in combination. When a pigment is used, the amount of the pigment may be appropriately set depending on the application of the epoxy resin composition, and is usually 0.01 to 30 parts by mass relative to 100 parts by mass of the epoxy resin composition.

[0022] Examples of carbon black include channel black, acetylene black, thermal black, furnace black, ketjen black, and combinations of two or more of these. When carbon black is used, the amount thereof may be appropriately set depending on the application of the epoxy resin composition, and is usually 0.01 to 10 parts by mass per 100 parts by mass of the epoxy resin composition.

[0023] Examples of reinforcing fibers include polyacrylonitrile carbon fibers, pitch carbon fibers, rayon carbon fibers, glass fibers, aramid fibers, boron fibers, alumina fibers, silicon carbide fibers, and combinations of two or more of these. When reinforcing fibers are used, the amount thereof may be appropriately set depending on the application of the epoxy resin composition, and is usually 50 to 600 parts by mass per 100 parts by mass of the epoxy resin composition.

[0024] Examples of the antioxidant include phenol-based antioxidants, sulfur-based antioxidants, phosphorus-based antioxidants, and amine-based antioxidants. When an antioxidant is used, one type of antioxidant may be used, or two or more types of antioxidants may be used in combination. When an antioxidant is used, the amount thereof may be appropriately set depending on the application of the epoxy resin composition, and is usually 0.01 to 10 parts by mass relative to 100 parts by mass of the epoxy resin composition.

[0025] Examples of reactive diluents include alkyl glycidyl ethers such as phenyl glycidyl ether and butyl glycidyl ether, Versatic acid glycidyl ester, α-olefin epoxide, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, trimethylolpropane triglycidyl ether, methylphenol glycidyl ether, ethylphenol glycidyl ether, propylphenol glycidyl ether and other alkylphenol glycidyl ethers. When using a reactive diluent, one type of reactive diluent may be used, or two or more types of reactive diluents may be used in combination. When using a reactive diluent, the amount of the reactive diluent may be appropriately set depending on the application of the epoxy resin composition, and is usually 1 to 25 parts by mass relative to 100 parts by mass of the epoxy resin composition.

[0026] Examples of non-reactive diluents include organic solvents such as toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, and butyl acetate. When using a non-reactive diluent, one type of non-reactive diluent may be used, or two or more types of non-reactive diluents may be used in combination. When using a non-reactive diluent, the amount may be appropriately set depending on the application of the epoxy resin composition, and is usually 10 to 400 parts by mass relative to 100 parts by mass of the epoxy resin composition.

[0027] [Method for preparing epoxy resin composition] The epoxy resin composition of the present invention may be prepared by any method that can uniformly disperse and mix the epoxy resin, the curing agent containing the dicarboxylic anhydride represented by formula (1) and / or the dicarboxylic anhydride represented by formula (2), and any other optional components as required. For dispersing and mixing, a general device such as a mixer, a mixing roll, or an extruder can be used.

[0028] The epoxy resin composition of the present invention has excellent storage stability. The storage stability of the epoxy resin composition can be evaluated, for example, by comparing the change in viscosity of a liquid epoxy resin composition before and after storage, or by comparing the quantitative change in epoxy groups of the epoxy resin contained in the epoxy resin composition before and after storage using a Fourier transform infrared spectrophotometer or the like.

[0029] [Cured product] The present invention also covers a cured product of the epoxy resin composition. The epoxy resin composition of the present invention is superior in storage stability to an epoxy resin composition that does not contain a dicarboxylic anhydride represented by formula (1) or a dicarboxylic anhydride represented by formula (2) and contains a curing agent other than these (e.g., an acid anhydride other than these). That is, the change in the properties of the epoxy resin composition before and after storage is small. Therefore, the change in properties is also small when comparing the cured product of the epoxy resin composition before storage with the cured product of the epoxy resin composition after storage.

[0030] The cured product of the present invention contains an aliphatic chain in the crosslinked structure due to the epoxy resin composition containing the dicarboxylic anhydride represented by formula (1) and / or the dicarboxylic anhydride represented by formula (2), which allows the cured product of the present invention to have good flexibility.

[0031] [Method of manufacturing the cured product] The cured product of the present invention can be produced by heating the epoxy resin composition of the present invention. As a molding method for producing a cured molded product from an epoxy resin composition, a transfer molding method is generally used, but an injection molding method, a compression molding method, etc. may also be used. Heating conditions may be appropriately determined depending on the composition of the epoxy resin composition. Heating is preferably performed at a temperature of 50 to 250°C, more preferably 80 to 200°C, for 30 minutes to 12 hours, more preferably 1 to 6 hours. Heating may be performed in one step or in two or more steps within the above temperature range and time. For example, when heating in two steps, heating may be performed at 60 to 120°C for 30 minutes to 2 hours, and then at 120 to 200°C for 1 to 6 hours. EXAMPLES

[0032] The present invention will be specifically described below with reference to examples, but the scope of the present invention is not limited to these examples. Note that the methods for measuring the physical properties of the epoxy resin composition and its cured product are described below, but the physical properties and measurements (or physical property values ​​and measured values) described in this specification, including the examples, are based on values ​​obtained by the following methods.

[0033] <Viscosity change rate> Using a digital viscometer (DV-II+Pro manufactured by Brookfield), the viscosity of the epoxy resin composition immediately after preparation (initial viscosity) at 25°C and the viscosity of the epoxy resin composition after standing at room temperature (23°C±1°C) for 24 hours (hereinafter abbreviated as "24 hours later") (viscosity after 24 hours) were measured at 25°C. The viscosity after 24 hours was measured after the epoxy resin composition after standing for 24 hours was allowed to stand until it reached 25°C. The viscosity change rate of the epoxy resin composition was calculated using the following formula. Viscosity change rate [%] = {(viscosity after 24 hours - initial viscosity) / (initial viscosity)} x 100

[0034] <Rate of change in bending strain> The cured product (cured product 1) obtained by curing the epoxy resin composition immediately after preparation, and the cured product (cured product 2) obtained by curing the epoxy resin composition after 24 hours were cut into a length of 80 mm, a width of 10 mm, and a thickness of 4 mm to obtain test pieces. A universal testing machine (Instron 5966) was used to measure the bending strain of test pieces of cured material 1 and cured material 2 in a three-point bending test. A load was applied until the test pieces broke at a test speed of 2 mm / min, a support distance of 64 mm, and a test temperature of 23°C. The rate of change in bending strain of the cured material was calculated using the following formula. Change in bending strain [%] = {(Bending strain of cured material 2 - Bending strain of cured material 1) / (Bending strain of cured material 1)} x 100

[0035] <Change in degree of hardening> Using a Fourier transform infrared spectrophotometer (Nicolet is10 manufactured by Thermo Fisher Scientific), the peak intensity of the epoxy group of the epoxy resin composition immediately after preparation, the epoxy resin composition after 24 hours, the cured product 1, and the cured product 2 were each measured. The degree of cure of each resin composition was determined from the peak intensity of the epoxy group. Then, the rate of change in the degree of cure was calculated using the following formula. Curing degree change rate [%] = {(degree of cure of cured material 2 - degree of cure of cured material 1) / (degree of cure of cured material 1)} x 100

[0036] In the examples and comparative examples, the following materials were used. Epoxy resin: Mitsubishi Chemical Corporation jER-828 (epoxy equivalent: 185) Hardener: 3-methylglutaric anhydride manufactured by Tokyo Chemical Industry Co., Ltd. Hardener: 2-Methylsuccinic anhydride manufactured by Sigma-Aldrich Co. LLC Hardener: 4-methylhexahydroxyphthalic anhydride manufactured by Tokyo Chemical Industry Co., Ltd. Hardener: Methyltetrahydroxyphthalic anhydride from Sigma-Aldrich Co. LLC Curing accelerator: 2,4,6-tris(dimethylaminomethyl)phenol manufactured by Tokyo Chemical Industry Co., Ltd.

[0037] [Examples 1 to 9 and Comparative Examples 1 to 3] <Preparation of Epoxy Resin Composition> According to the composition (unit: parts by mass) shown in Table 1 below, an epoxy resin, an acid anhydride, and a curing accelerator were placed in a polypropylene container and stirred uniformly to obtain an epoxy resin composition. <Production of cured product> The epoxy resin composition was poured into a mold made of a glass substrate so as to obtain dimensions appropriate for the evaluation items, and then heated at 80°C for 1 hour and then at 150°C for 2 hours to obtain a cured product. The obtained epoxy resin compositions and cured products were each evaluated, and the results are shown in Table 1.

[0038] [Table 1] [Industrial Applicability]

[0039] The epoxy resin composition of the present invention has excellent storage stability, and the change in properties is small when comparing the cured product of the epoxy resin composition of the present invention before storage with the cured product of the epoxy resin composition after storage. Therefore, the epoxy resin composition of the present invention can be suitably used in various fields in which epoxy resin compositions and their cured products are utilized, for example, adhesives (e.g., transparent adhesives, structural adhesives), paints (e.g., repair materials, anticorrosive materials, flooring materials, architectural paints), electrical insulating materials (e.g., printed circuit boards, transistors, solder masks, semiconductor encapsulants, underfills), matrixes for fiber (e.g., carbon fiber, glass fiber) reinforced plastics, molded products (e.g., desks, fiber-reinforced molded products), etc.

Claims

1. An epoxy resin composition comprising an epoxy resin and a curing agent, the curing agent being a dicarboxylic acid anhydride represented by formula (1) and / or a dicarboxylic acid anhydride represented by formula (2): [In the formula, R １ ~R １０ are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, provided that R ３ and R ４ At least one of R is an alkyl group having 1 to 4 carbon atoms; ７ ~R １０ at least one of the groups is an alkyl group having 1 to 4 carbon atoms.

1. An epoxy resin composition comprising:

2. R ３ is an alkyl group having 1 to 4 carbon atoms, R １ ~R ２ and R ４ ~R ６ The epoxy resin composition according to claim 1 , wherein is hydrogen.

3. R ８ is an alkyl group having 1 to 4 carbon atoms, R ７ and R ９ ~R １０ The epoxy resin composition according to claim 1 , wherein is hydrogen.

4. 2. The epoxy resin composition according to claim 1, wherein the alkyl group having 1 to 4 carbon atoms is a methyl group or an ethyl group.

5. 2. The epoxy resin composition according to claim 1, wherein the dicarboxylic acid anhydride represented by the formula (1) is selected from the group consisting of 3-methylglutaric anhydride, 3-ethylglutaric anhydride, 3-propylglutaric anhydride, 3-isopropylglutaric anhydride, 3-n-butylglutaric anhydride, 3-sec-butylglutaric anhydride, 3-tert-butylglutaric anhydride and 3-isobutylglutaric anhydride.

6. The epoxy resin composition according to claim 1, wherein the dicarboxylic acid anhydride represented by the formula (2) is selected from the group consisting of 2-methylsuccinic anhydride, 2-ethylsuccinic anhydride, 2-propylsuccinic anhydride, 2-isopropylsuccinic anhydride, 2-n-butylsuccinic anhydride, 2-sec-butylsuccinic anhydride, 2-tert-butylsuccinic anhydride and 2-isobutylsuccinic anhydride.

7. 2. The epoxy resin composition according to claim 1, wherein a molar ratio of the total amount of the dicarboxylic anhydride represented by the formula (1) and the dicarboxylic anhydride represented by the formula (2) to the amount of epoxy groups in the epoxy resin is 0.05 to 10.

8. 2. The epoxy resin composition according to claim 1, further comprising an acid anhydride other than the dicarboxylic acid anhydride represented by formula (1) and the dicarboxylic acid anhydride represented by formula (2).

9. 9. The epoxy resin composition according to claim 8, wherein a molar ratio of the amount of the acid anhydride other than the dicarboxylic acid anhydride represented by the formula (1) and the dicarboxylic acid anhydride represented by the formula (2) to the total amount of the dicarboxylic acid anhydride represented by the formula (1) and the dicarboxylic acid anhydride represented by the formula (2) is 0.01 to 50.

10. A cured product of the epoxy resin composition according to any one of claims 1 to 9.

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