Two-component thermosetting epoxy resin composition and cured product

Abstract

This disclosure provides a two-component thermosetting epoxy resin composition that is easy to prepare and has a curing agent with excellent storage stability. [Solution] The two-component thermosetting epoxy resin composition of this disclosure comprises a first liquid which is a main component containing epoxy compound (A), The invention comprises a second liquid which is a curing agent containing an alicyclic acid anhydride curing agent (B) and a curing accelerator (C) which is an imidazole curing accelerator and / or a thermobasic generating agent, Except for certain combinations, the curing agent (B), which is an alicyclic acid anhydride-based curing agent, and / or a curing accelerator (C), which is an imidazole-based curing accelerator and / or a thermobasic generating agent, are liquid at 25°C.

Description

Technical Field

[0001] The present disclosure relates to a thermosetting epoxy resin composition and a cured product thereof.

Background Art

[0002] Epoxy resins are used as resins (sealing materials) for coating optical semiconductor elements in optical semiconductor devices, resins for mold coil applications in which coils such as ignition coils are impregnated and cast, resins for fiber reinforcement, resins for rotating electrical machines (for example, insulating materials, adhesive resins for fixing permanent magnets, fillers for gaps, etc.), and the like.

[0003] When an epoxy resin is used for such impregnation applications, low viscosity is required, and when a one-component varnish is used, refrigerated storage is necessary. On the other hand, in the case of a two-component varnish, the main agent and the curing agent can be stored separately and can be stored at normal temperature, but especially for the curing agent, storage stability may pose a problem in some cases.

[0004] As a composition with improved storage stability of the curing agent in such a two-component varnish, for example, the curable composition of Patent Document 1 is known.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, the curable composition of Patent Document 1 requires a step of high-temperature aging at 80°C to prepare the curing agent. In addition, although an improvement in the storage stability of the produced curing agent is observed, it is still insufficient, and further improvement is demanded.

[0007] Therefore, the object of this disclosure is to provide a two-component thermosetting epoxy resin composition that is easy to prepare and has a curing agent with excellent storage stability. [Means for solving the problem]

[0008] The inventors of this disclosure, after diligent research to achieve the above objectives, have found that a two-component thermosetting epoxy resin composition comprising a first liquid, which is a main component containing an epoxy compound (A), and a second liquid, which is a curing agent containing an alicyclic acid anhydride curing agent (B) and a curing accelerator (C), which is an imidazole-based curing accelerator and / or a thermobasic generating agent, is liquid at 25°C except for a specific combination of the alicyclic acid anhydride curing agent (B) and the curing accelerator (C), which is an imidazole-based curing accelerator and / or a thermobasic generating agent, allows for easy preparation of the curing agent and exhibits excellent storage stability. This disclosure relates to a product completed based on these findings.

[0009] In other words, the present disclosure comprises a first liquid, which is a main component containing an epoxy compound (A), and a second liquid, which is a curing agent containing an alicyclic acid anhydride curing agent (B) and a curing accelerator (C), which is an imidazole curing accelerator and / or a thermobasic generating agent. The combination of the alicyclic acid anhydride curing agent (B) and the curing accelerator (C), which is an imidazole curing accelerator and / or a thermobasic generating agent, includes methyl-5-norbornene-2,3-dicarboxylic acid anhydride and 1-methylimidazole, 1-(2-hydroxypropyl)imidazole, or 1-benzyl-2-phenylimidazole The present invention provides a two-component thermosetting epoxy resin composition that is liquid at 25°C, excluding combinations with zole, a mixture of 4-methylhexahydrophthalic anhydride and hexahydrophthalic anhydride, and combinations with 1-(2-hydroxypropyl)imidazole, 1-benzyl-2-methylimidazole, the phenol salt of 1,8-diazabicyclo[5.4.0]undecene-7, or the 2-ethylhexane salt of 1,8-diazabicyclo[5.4.0]undecene-7, and combinations of 3-methyltetrahydrophthalic anhydride and 1-methylimidazole.

[0010] It is preferable that the content of the curing accelerator (C), which is an imidazole-based curing accelerator and / or a thermobasic generating agent, is 0.5 to 5 parts by mass per 100 parts by mass of the alicyclic acid anhydride-based curing agent (B) in the second liquid described above.

[0011] Preferably, the viscosity increase rate of the second liquid described above is 1.2 times or less compared to the viscosity measured at 25°C before the start of the storage test, when measured at 25°C after a storage test where it is stored at 40°C for one month, and no precipitates are formed after the storage test.

[0012] Furthermore, this disclosure provides a cured product of the above-mentioned two-component thermosetting epoxy resin composition.

[0013] The above-mentioned cured product preferably has a glass transition temperature of 140°C or higher.

[0014] The cured product is preferably an insulating material.

[0015] The cured product described above is preferably an adhesive.

[0016] The cured product is preferably a sealant. [Effects of the Invention]

[0017] The two-component thermosetting epoxy resin composition of this disclosure allows for easy preparation of the curing agent and also exhibits excellent storage stability. [Modes for carrying out the invention]

[0018] [Two-component thermosetting epoxy resin composition] A two-component thermosetting epoxy resin composition according to one embodiment of the present disclosure comprises a first liquid, which is a main component containing an epoxy compound (A), and a second liquid, which is a curing agent containing an alicyclic acid anhydride curing agent (B) and a curing accelerator (C), which is an imidazole curing accelerator and / or a thermobasic generating agent. The following combinations of alicyclic acid anhydride curing agents (B) and curing accelerators (C), which are imidazole-based curing accelerators and / or thermobasic generating agents, are excluded: combinations of methyl-5-norbornene-2,3-dicarboxylic acid anhydride with 1-methylimidazole, 1-(2-hydroxypropyl)imidazole, or 1-benzyl-2-phenylimidazole; a mixture of 4-methylhexahydrophthalic anhydride and hexahydrophthalic anhydride with 1-(2-hydroxypropyl)imidazole, 1-benzyl-2-methylimidazole, the phenol salt of 1,8-diazabicyclo[5.4.0]undecene-7, or the 2-ethylhexane salt of 1,8-diazabicyclo[5.4.0]undecene-7; and combinations of 3-methyltetrahydrophthalic anhydride with 1-methylimidazole. Furthermore, the above thermosetting epoxy resin composition is liquid at 25°C. The second component, the curing agent, can be easily manufactured by containing an alicyclic acid anhydride curing agent (B) other than the specific combinations described above, and a curing accelerator (C) which is an imidazole-based curing accelerator and / or a thermobasic generating agent, and exhibits excellent long-term storage stability. Hereafter, the above two-component thermosetting epoxy resin composition may be referred to as "the two-component thermosetting epoxy resin composition of this disclosure."

[0019] The two-component thermosetting epoxy resin composition of this disclosure is liquid at 25°C, which provides excellent workability such as impregnation and casting properties. Furthermore, the viscosity of the two-component thermosetting epoxy resin composition of this disclosure at 25°C is preferably 3000 mPa·s or less, more preferably 2000 mPa·s or less, even more preferably 1500 mPa·s or less, and particularly preferably 1000 mPa·s or less. When the viscosity is 3000 mPa·s or less, impregnation and workability during casting are improved, and defects due to poor casting are less likely to occur in the cured product. Furthermore, the lower limit is preferably 100 mPa·s or more, more preferably 200 mPa·s or more, and even more preferably 300 mPa·s or more. When the viscosity is 100 mPa·s or more, the composition does not drip after impregnation, and workability during impregnation and casting tends to improve. The viscosity of the two-component thermosetting epoxy resin composition of this disclosure at 25°C can be measured, for example, using a rheometer (product name "Modular Compact Rheometer, MCR302", manufactured by Anton Paar, rotor diameter 25 mm, sample thickness 0.1 mm).

[0020] (1st liquid) The first liquid described above is the main component in the two-component thermosetting epoxy resin composition of this disclosure and contains epoxy compound (A). The first liquid may also contain other components besides epoxy compound (A), and more preferably contains polyester polyol (D), and may further contain a silane coupling agent, an antifoaming agent, and an inorganic filler. Furthermore, the first liquid may be used alone or in combination of two or more types.

[0021] The viscosity of the first liquid at 25°C is preferably 2000 mPa·s or less, more preferably 1500 mPa·s or less, even more preferably 1000 mPa·s or less, and particularly preferably 500 mPa·s or less. When the viscosity is 2000 mPa·s or less, the two-part thermosetting epoxy resin composition of the present disclosure has improved impregnation properties and workability during casting, and can hardly cause defects in the cured product derived from poor casting. In addition, the lower limit is preferably 30 mPa·s or more, more preferably 50 mPa·s or more, and even more preferably 100 mPa·s or more. When the viscosity is 30 mPa·s or more, the composition as the two-part thermosetting epoxy resin composition of the present disclosure does not drip after impregnation, and the workability during impregnation or casting tends to be improved.

[0022] <Epoxy Compound (A)> The epoxy compound (A) is a compound having one or more epoxy groups (oxirane rings). Examples of the epoxy compound (A) include alicyclic epoxy compounds (alicyclic epoxy resins), aromatic epoxy compounds (aromatic epoxy resins), and aliphatic epoxy compounds (aliphatic epoxy resins). Among them, an alicyclic epoxy compound is preferred as the epoxy compound (A). As the epoxy compound (A), only one type may be used, or two or more types may be used.

[0023] As the alicyclic epoxy compound, any known or commonly used alicyclic epoxy compound can be used, with no particular limitation. Examples include: (I) compounds having an epoxy group (referred to as "alicyclic epoxy group") composed of two adjacent carbon atoms forming an alicyclic ring in the molecule and an oxygen atom; (II) compounds in which an epoxy group is directly bonded to the alicyclic ring via a single bond; (III) compounds having an alicyclic ring and a glycidyl ether group in the molecule (glycidyl ether type epoxy compounds), and the like.

[0024] Examples of the compound (I) having an alicyclic epoxy group in the molecule include compounds having a cyclohexene oxide group, for example, a compound represented by the following formula (i).

Chemical Formula

[0025] In the above formula (i), Y represents a single bond or a linking group (a divalent group having one or more atoms). Examples of the linking group include divalent hydrocarbon groups, alkenylene groups in which part or all of the carbon-carbon double bonds are epoxidized, carbonyl groups, ether bonds, ester bonds, carbonate groups, amide groups, groups in which a plurality of these are linked, and the like. A substituent such as an alkyl group may be bonded to one or more carbon atoms constituting the cyclohexane ring (cyclohexene oxide group) in formula (i).

[0026] Examples of the divalent hydrocarbon group include linear or branched alkylene groups having 1 to 18 carbon atoms, divalent alicyclic hydrocarbon groups, and the like. Examples of the linear or branched alkylene group having 1 to 18 carbon atoms include methylene group, methylmethylene group, dimethylmethylene group, ethylene group, propylene group, trimethylene group, and the like. Examples of the divalent alicyclic hydrocarbon group include divalent cycloalkylene groups (including cycloalkylidene groups) such as 1,2-cyclopentylene group, 1,3-cyclopentylene group, cyclopentylidene group, 1,2-cyclohexylene group, 1,3-cyclohexylene group, 1,4-cyclohexylene group, cyclohexylidene group, and the like.

[0027] Examples of the alkenylene group in the alkenylene group in which part or all of the carbon-carbon double bonds are epoxidized (sometimes referred to as "epoxidized alkenylene group") include linear or branched alkenylene groups having 2 to 8 carbon atoms such as vinylene group, propenylene group, 1-butenylene group, 2-butenylene group, butadienylene group, pentenylene group, hexenylene group, heptenylene group, octenylene group, and the like. In particular, the epoxidized alkenylene group is preferably an alkenylene group in which all carbon-carbon double bonds are epoxidized, more preferably an alkenylene group having 2 to 4 carbon atoms in which all carbon-carbon double bonds are epoxidized.

[0028] Typical examples of alicyclic epoxy compounds represented by formula (i) above include (3,4,3',4'-diepoxy)bicyclohexyl and compounds represented by the following formulas (i-1) to (i-10). In formulas (i-5) and (i-7) below, l and m represent integers from 1 to 30, respectively. In formula (i-5) below, R' is an alkylene group having 1 to 8 carbon atoms, and among these, linear or branched alkylene groups having 1 to 3 carbon atoms, such as methylene, ethylene, propylene, and isopropylene groups, are preferred. In formulas (i-9) and (i-10) below, n1 to n6 represent integers from 1 to 30, respectively. Other examples of alicyclic epoxy compounds represented by formula (i) above include 2,2-bis(3,4-epoxycyclohexyl)propane, 1,2-bis(3,4-epoxycyclohexane-1-yl)ethane, 1,2-epoxy-1,2-bis(3,4-epoxycyclohexane-1-yl)ethane, and bis(3,4-epoxycyclohexylmethyl)ether. [ka] [ka]

[0029] Examples of compounds in which an epoxy group is directly bonded to the alicyclic ring (II) as described above by a single bond include the compound represented by the following formula (ii). [ka]

[0030] In formula (ii), R'' is the group obtained by removing p hydroxyl groups (-OH) from the structural formula of a p-valent alcohol (a p-valent organic group), and p and n are natural numbers. p-valent alcohol [R''(OH) pExamples of ] include polyhydric alcohols such as 2,2-bis(hydroxymethyl)-1-butanol (alcohols with 1 to 15 carbon atoms, etc.). p is preferably 1 to 6, and n is preferably 1 to 30. When p is 2 or more, the n in each group in parentheses (in the outer brackets) may be the same or different. Specific examples of compounds represented by the above formula (ii) include the 1,2-epoxy-4-(2-oxyranyl)cyclohexane adduct of 2,2-bis(hydroxymethyl)-1-butanol [for example, trade name "EHPE3150" (manufactured by Daicel Corporation), etc.].

[0031] Examples of compounds having an alicyclic ring and a glycidyl ether group in the molecule (III) above include glycidyl ethers of alicyclic alcohols (especially alicyclic polyhydric alcohols). More specifically, examples include hydrogenated compounds of bisphenol A type epoxy compounds such as 2,2-bis[4-(2,3-epoxypropoxy)cyclohexyl]propane and 2,2-bis[3,5-dimethyl-4-(2,3-epoxypropoxy)cyclohexyl]propane (hydrogenated bisphenol A type epoxy compounds); bis[o,o-(2,3-epoxypropoxy)cyclohexyl]methane, bis[o,p-(2,3-epoxypropoxy)cyclohexyl]methane, bis[p,p-(2,3-epoxypropoxy)cyclohexyl]methane, bis[3,5-dimethyl-4- Examples include hydrogenated compounds of bisphenol F type epoxy compounds such as (2,3-epoxypropoxy)cyclohexylmethane (hydrogenated bisphenol F type epoxy compounds); hydrogenated biphenol type epoxy compounds; hydrogenated phenol novolac type epoxy compounds; hydrogenated cresol novolac type epoxy compounds; hydrogenated cresol novolac type epoxy compounds of bisphenol A; hydrogenated naphthalene type epoxy compounds; hydrogenated epoxy compounds of epoxy compounds obtained from trisphenolmethane; and hydrogenated epoxy compounds of other epoxy compounds having aromatic rings.

[0032] Examples of the aromatic epoxy compounds include epibis-type glycidyl ether epoxy resins (bisphenol-type epoxy compounds such as bisphenol A type epoxy compounds and bisphenol F type epoxy compounds) obtained by the condensation reaction of bisphenols [e.g., bisphenol A, bisphenol F, bisphenol S, fluorenebisphenol, etc.] with epihalohydrins; high molecular weight epibis-type glycidyl ether epoxy resins obtained by further addition reactions of these epibis-type glycidyl ether epoxy resins with the above bisphenols; and phenols [e.g., phenol, cresol, xylenol, resol]. Examples include novolac alkyl-type glycidyl ether epoxy resins obtained by condensing polyhydric alcohols obtained by condensing rusin, catechol, bisphenol A, bisphenol F, bisphenol S, etc. with aldehydes [e.g., formaldehyde, acetaldehyde, benzaldehyde, hydroxybenzaldehyde, salicylaldehyde, etc.] with epihalohydrins; and epoxy compounds in which two phenol skeletons are bonded to the 9th position of a fluorene ring, and glycidyl groups are bonded directly or via alkylene oxy groups to the oxygen atoms obtained by removing hydrogen atoms from the hydroxyl groups of these phenol skeletons.

[0033] Examples of the above-mentioned aliphatic epoxy compounds include glycidyl ethers of alcohols (where q is a natural number) that do not have a cyclic structure with a q-valence; glycidyl esters of monovalent or polyvalent carboxylic acids [e.g., acetic acid, propionic acid, butyric acid, stearic acid, adipic acid, sebacic acid, maleic acid, itaconic acid, etc.]; epoxides of oils and fats having double bonds, such as epoxides of linseed oil, epoxides of soybean oil, and epoxides of castor oil; and epoxides of polyolefins (including polyalkadienes), such as epoxides of polybutadiene. Examples of alcohols that do not have the q-valent cyclic structure include monohydric alcohols such as methanol, ethanol, 1-propyl alcohol, isopropyl alcohol, and 1-butanol; dihydric alcohols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, polyethylene glycol, and polypropylene glycol; and polyhydric alcohols of trihydric or higher valencies such as glycerin, diglycerin, erythritol, trimethylolethane, trimethylolpropane, pentaerythritol, dipentaerythritol, and sorbitol. The q-valent alcohol may also be polyether polyol, polyester polyol, polycarbonate polyol, or polyolefin polyol.

[0034] The content of epoxy compound (A) in the first liquid is preferably 10% by mass or more, based on 100% by mass of the total amount of the first liquid. In one embodiment of the first liquid (for example, without inorganic fillers), the content of epoxy compound (A) is more preferably 20 to 90% by mass, and even more preferably 30 to 70% by mass. In another embodiment of the first liquid (for example, with inorganic fillers), the content of epoxy compound (A) is more preferably 10 to 60% by mass, and even more preferably 12 to 55% by mass.

[0035] (Polyester polyol (D)) The two-component thermosetting epoxy resin composition of this disclosure preferably further contains a polyester polyol (D) to improve the strength upon curing. Examples of polyester polyol (D) include compounds having two or more hydroxyl groups and two or more ester bonds in the molecule. Examples of polyester polyol (D) include polylactone polyols such as polycaprolactone polyol, aliphatic polyester polyols, aromatic polyester polyols, and alicyclic polyester polyols. Only one type of polyester polyol (D) may be used, or two or more types may be used.

[0036] Among the polyester polyols (D), it is preferable to include polylactone polyols and / or aliphatic polyester polyols, from the viewpoint of maintaining a high glass transition temperature of the cured product while providing superior flexibility. Similarly, from the same viewpoint, it is preferable to include polyester diols and / or polyester triols as polyester polyols (D).

[0037] The molecular weight of polyester polyol (D) is preferably 250 or higher, more preferably 600 or higher, even more preferably 1100 or higher, and particularly preferably 1700 or higher. When the molecular weight is 250 or higher (particularly 600 or higher), the toughness of the cured product is easily improved, and the bending strain is further improved. The molecular weight may be, for example, 100,000 or less, 50,000 or less, 10,000 or less, or 4,000 or less. The molecular weight of polyester polyol (D) refers to the number-average molecular weight on a standard polystyrene basis, measured by gel permeation chromatography (GPC).

[0038] The hydroxyl value of the polyester polyol (D) is preferably 600 KOH mg / g or less, more preferably 200 KOH mg / g or less, even more preferably 100 KOH mg / g or less, and particularly preferably 80 KOH mg / g or less. When the above hydroxyl value is 600 KOH mg / g or less (particularly 200 KOH mg / g or less), the chain transfer reaction of polymerization of the epoxy compound (A) is suppressed, the degree of polymerization of the epoxy main chain tends to increase, and the glass transition temperature of the cured product can be maintained at a high level. The above hydroxyl value can be measured by potentiometric titration in accordance with JIS K0070.

[0039] When the two-component thermosetting epoxy resin composition of this disclosure contains polyester polyol (D), the content of polyester polyol (D) in the first liquid is preferably 1 to 30% by mass, more preferably 3 to 20% by mass, and even more preferably 5 to 15% by mass, based on 100% by mass of the total amount of the first liquid. When the content is within the above range, the heat resistance and strength of the cured product are both further improved.

[0040] The first liquid described above may contain other curable compounds besides epoxy compound (A) and polyester polyol (D). Examples of other curable compounds include oxetane compounds, vinyl ether compounds, acrylic compounds, and silicone compounds. The total content of epoxy compound (A) and polyester polyol (D) is preferably 70% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, particularly preferably 99% by mass or more, and may be 100% by mass, based on 100% by mass of the total amount of curable compounds contained in the first liquid. In other words, the first liquid does not have to contain other curable compounds besides epoxy compound (A), and does not have to contain other curable compounds besides epoxy compound (A) and polyester polyol (D).

[0041] If the first liquid contains a silane coupling agent, its content is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 7 parts by mass, and even more preferably 1 to 4 parts by mass, based on 100 parts by mass of the total amount of epoxy compound (A).

[0042] If the first liquid contains an antifoaming agent, its content is preferably 0.001 to 1% by mass, and more preferably 0.01 to 0.1% by mass, based on 100% by mass of the total amount of the first liquid. A defoaming agent content of 0.001% by mass or more prevents the generation and retention of foam in the first liquid, thereby improving durability after curing.

[0043] If the first liquid contains an inorganic filler, its content is preferably 0.3 to 90% by mass relative to 100% by mass of the total amount of the first liquid. In one embodiment, the content is more preferably 0.3 to 8% by mass, and even more preferably 0.5 to 3% by mass. In this case, thixotropy can be easily imparted to the two-component thermosetting epoxy resin composition of this disclosure. In another embodiment, the content is more preferably 50% by mass or more (for example, 50 to 90% by mass), and even more preferably 55% by mass or more (for example, 55 to 80% by mass). In this case, the linear expansion properties of the cured product are more easily reduced. Furthermore, from the viewpoint of suppressing an increase in the viscosity of the first liquid, the content is preferably 5% by mass or less, more preferably 1% by mass or less, even more preferably 0.1% by mass or less, and may even be 0% by mass. That is, the first liquid does not have to contain an inorganic filler.

[0044] The first liquid described above may contain other components in addition to those described above. Examples of these other components include conventional additives such as flame retardants, colorants, antioxidants, ultraviolet absorbers, ion adsorbents, colorants, phosphors, mold release agents, thickeners, dispersants, rust inhibitors, corrosion inhibitors, freezing point depressants, wear-resistant additives, and wettability modifiers. Each of these other components may be used individually or in combination of two or more. Furthermore, the content of these other components is preferably 5% by mass or less, more preferably 1% by mass or less, and may even be 0% by mass, based on 100% by mass of the total amount of the first liquid.

[0045] (2nd liquid) The second liquid described above is a curing agent in the two-component thermosetting epoxy resin composition of this disclosure, and contains an alicyclic acid anhydride curing agent (B) and a curing accelerator (C) which is an imidazole-based curing accelerator and / or a thermobasic generating agent. By using an alicyclic acid anhydride curing agent (B) and a curing accelerator (C) which is an imidazole-based curing accelerator and / or a thermobasic generating agent, it is possible to produce a product that is easy to manufacture while having excellent long-term stability. Furthermore, the second liquid may contain other components other than the alicyclic acid anhydride curing agent (B) and the curing accelerator (C) which is an imidazole-based curing accelerator and / or a thermobasic generating agent, specifically, it may contain an antifoaming agent and an inorganic filler. Furthermore, the second liquid may be used alone or two or more types may be used.

[0046] Furthermore, the above-mentioned second liquid excludes the following combinations of alicyclic acid anhydride curing agent (B) and curing accelerator (C), which is an imidazole-based curing accelerator and / or thermobasic generating agent: combinations of methyl-5-norbornene-2,3-dicarboxylic acid anhydride with 1-methylimidazole, 1-(2-hydroxypropyl)imidazole, or 1-benzyl-2-phenylimidazole; a mixture of 4-methylhexahydrophthalic anhydride and hexahydrophthalic anhydride with 1-(2-hydroxypropyl)imidazole, 1-benzyl-2-methylimidazole, the phenol salt of 1,8-diazabicyclo[5.4.0]undecene-7, or the 2-ethylhexane salt of 1,8-diazabicyclo[5.4.0]undecene-7; and combinations of 3-methyltetrahydrophthalic anhydride with 1-methylimidazole. By using a cycloaliphatic acid anhydride-based curing agent (B) other than the above combination, and a curing accelerator (C) which is an imidazole-based curing accelerator and / or a thermobasic generating agent, the above second liquid can be easily manufactured and made to have excellent long-term storage stability.

[0047] The viscosity of the second liquid at 25°C is preferably 2000 mPa·s or less, more preferably 1500 mPa·s or less, even more preferably 1000 mPa·s or less, and particularly preferably 500 mPa·s or less. When the viscosity is 2000 mPa·s or less, the impregnation properties and workability during casting of the two-component thermosetting epoxy resin composition of this disclosure are improved, and defects due to poor casting are less likely to occur in the cured product. Furthermore, the lower limit is preferably 30 mPa·s or more, more preferably 50 mPa·s or more, and even more preferably 100 mPa·s or more. When the viscosity is 30 mPa·s or more, the two-component thermosetting epoxy resin composition of this disclosure does not drip after impregnation, and workability during impregnation and casting tends to be improved.

[0048] The viscosity of the second liquid described above, measured at 25°C after a storage test in which it was stored at 40°C for one month, is preferably 2400 mPa·s or less, more preferably 1800 mPa·s or less, even more preferably 1200 mPa·s or less, and particularly preferably 600 mPa·s or less. When the viscosity is 2400 mPa·s or less, the viscosity increase is small even after the storage test, and it exhibits excellent long-term storage stability. Furthermore, as a two-component thermosetting epoxy resin composition of this disclosure, the impregnation properties and workability during casting are improved, and defects caused by poor casting are less likely to occur in the cured product. The lower limit is preferably 30 mPa·s or more, more preferably 50 mPa·s or more, and even more preferably 100 mPa·s or more. When the viscosity is 30 mPa·s or more, as a two-component thermosetting epoxy resin composition of this disclosure, the composition does not drip after impregnation, and workability during impregnation and casting tends to improve.

[0049] The second liquid described above preferably has a viscosity increase rate [viscosity after storage test / viscosity before storage test] of 1.2 times or less compared to the viscosity before the storage test, measured at 25°C, more preferably 1.1 times or less, and even more preferably 1.0 times. By satisfying the above range, it is possible to maintain handling ease and exhibit storage stability over a long period of time.

[0050] Furthermore, it is preferable that the second liquid does not show any precipitate after being stored at 40°C for one month. Having the above configuration ensures that the components do not denature during storage and that the product exhibits storage stability.

[0051] <Alicyclic acid anhydride-based curing agent (B)> The alicyclic acid anhydride curing agent (B) is a compound that, by reacting with the epoxy compound (A), cures the two-component thermosetting epoxy resin composition of this disclosure. The alicyclic acid anhydride curing agent (B) may be used alone or in combination of two or more types.

[0052] As the alicyclic acid anhydride curing agent (B), known or conventional alicyclic acid anhydride curing agents can be used, for example, methyltetrahydrophthalic anhydride (4-methyltetrahydrophthalic anhydride, 3-methyltetrahydrophthalic anhydride, etc.), methylhexahydrophthalic anhydride (4-methylhexahydrophthalic anhydride, 3-methylhexahydrophthalic anhydride, etc.), dodecenyl succinic anhydride, methylendomethylenetetrahydrophthalic anhydride, phthalic anhydride, maleic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, etc. Examples include phthalic anhydride, methylcyclohexenedicarboxylic acid anhydride, nadic anhydride, methylnadic anhydride (methyl-5-norbornene-2,3-dicarboxylic acid anhydride), hydrogenated methylnadic anhydride, 4-(4-methyl-3-pentenyl)tetrahydrophthalic anhydride, succinic anhydride, adipic anhydride, sebacic anhydride, dodecanedioic anhydride, methylcyclohexenetetracarboxylic anhydride, vinyl ether-maleic anhydride copolymer, alkylstyrene-maleic anhydride copolymer, and the like.

[0053] Among the alicyclic acid anhydride curing agents (B), acid anhydrides that are liquid at 25°C are preferred from the viewpoint of ease of handling. On the other hand, for acid anhydrides that are solid at 25°C, for example, dissolving them in acid anhydrides that are liquid at 25°C to form a liquid mixture tends to improve the handling of the second liquid described above.

[0054] Furthermore, the alicyclic acid anhydride curing agent (B) is preferably methylnadic anhydride (methyl-5-norbornene-2,3-dicarboxylic acid anhydride), 4-methylhexahydrophthalic anhydride, hexahydrophthalic anhydride, or 3-methyltetrahydrophthalic anhydride, from the viewpoint of exhibiting storage stability when combined with the curing accelerator (C), which is an imidazole-based curing accelerator and / or a thermobasic generating agent.

[0055] The content of the alicyclic acid anhydride curing agent (B) in the second liquid is preferably 10% by mass or more, based on 100% by mass of the total amount of the second liquid. In one embodiment of the second liquid (for example, without inorganic fillers), the content of the alicyclic acid anhydride curing agent (B) is more preferably 20 to 90% by mass, and even more preferably 30 to 70% by mass. In another embodiment of the second liquid (for example, with inorganic fillers), the content of the alicyclic acid anhydride curing agent (B) is more preferably 10 to 60% by mass, and even more preferably 12 to 55% by mass.

[0056] (Curing accelerator (C) which is an imidazole-based curing accelerator and / or a thermobasic generating agent) The curing accelerator (C), which is an imidazole-based curing accelerator and / or a thermobasic generating agent, is a compound that has the function of accelerating the reaction rate when the epoxy compound (A) reacts with the alicyclic acid anhydride curing agent (B). Hereafter, the above-mentioned imidazole-based curing accelerator and / or thermobasic generating agent curing accelerator (C) may be simply referred to as "curing accelerator (C)". By using a curing accelerator (C) as a curing accelerator, the storage stability of the curing agent can be improved. Only one type of curing accelerator (C) may be used, or two or more types may be used.

[0057] As the above-mentioned imidazole-based curing accelerator, known or conventional imidazole-based curing accelerators can be used, including 1-methylimidazole, 2-methylimidazole, 2-ethyl-4-methylimidazole, 1-(2-hydroxypropyl)imidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-phenylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, and 1-cyanoethyl-2-ethyl-4-methylimidazole. Examples include imidazole compounds such as 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-undecylimidazolium trimellitate, 1-cyanoethyl-2-phenylimidazolium trimellitate, 2-methylimidazolium isocyanurate, 2-phenylimidazolium isocyanurate, 2,4-diamino-6-[2-methylimidazolyl-(1)]-ethyl-s-triazine, and 2,4-diamino-6-[2-ethyl-4-methylimidazolyl-(1)]-ethyl-s-triazine.

[0058] Furthermore, the imidazole-based curing accelerator may be a derivative of the imidazole compound, such as an amine adduct of the imidazole compound (for example, an amine adduct with an epoxy compound). Examples of the epoxy compound include those exemplified and described as epoxy compound (A). Only one epoxy compound may be used, or two or more may be used.

[0059] Among the above imidazole-based curing accelerators, it is preferable that they contain at least 1-methylimidazole, 2-methylimidazole, 1-(2-hydroxypropyl)imidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, or amine adducts thereof (particularly amine adducts with epoxy compounds, more preferably amine adducts with bisphenol-type epoxy compounds) in combination with alicyclic acid anhydride-based curing agents (B), from the viewpoint of further improving long-term storage stability.

[0060] The above-mentioned imidazole-based curing accelerator may also be included as a latent curing accelerator. Using a latent curing accelerator can improve the long-term stability of the curing agent.

[0061] The above-mentioned thermobasic generating agent is preferably a curing accelerator containing a strongly basic compound with a pKa of 10 or higher, more preferably with a pKa of 11 or higher, even more preferably with a pKa of 11 to 16, and particularly preferably with a pKa of 11 to 14. Note that the above pKa is the pKa in water. The above-mentioned strongly basic compound is preferably a nitrogen-containing cyclic compound having the above-mentioned pKa. Examples of the above strongly basic compounds include 1,8-diazabicyclo[5.4.0]undecene-7 (DBU) and its salts (e.g., phenol salt, octyl salt, 2-ethylhexanoate, p-toluenesulfonate, formate, tetraphenylborate salt, etc.), 1,5-diazabicyclo[4.3.0]nonene-5 (DBN) and its salts (e.g., phenol salt, octyl salt, p-toluenesulfonate, formate, tetraphenylborate salt, etc.), tetramethylguanidine (TMG) and its salts, 1,4-diazabicyclo[2.2.2]octane (DABCO), 1,5,7-triazabicyclo[4.4.0]decene-5 (TBD) and its salts, and 7-methyl-1,5,7-triazabicyclo[4.4.0]decene-5 (MTBD) and its salts. In particular, the above strongly basic compounds are preferably 1,8-diazabicyclo[5.4.0]undecene-7(DBU) and its salts, 1,5-diazabicyclo[4.3.0]nonene-5(DBN) and its salts, and more preferably phenolic salts of 1,8-diazabicyclo[5.4.0]undecene-7(DBU), 2-ethylhexanoate of 1,8-diazabicyclo[5.4.0]undecene-7(DBU), and 2-ethylhexanoate of 1,5-diazabicyclo[4.3.0]nonene-5(DBN).

[0062] The content (amount) of the curing accelerator (C) in the second liquid described above is preferably 0.3 to 5 parts by mass, and more preferably 0.5 to 4 parts by mass, based on 100 parts by mass of the total amount of the alicyclic acid anhydride curing agent (B). By having the curing accelerator (C) content within the above range, long-term storage stability can be achieved with a simple mixing process.

[0063] Furthermore, as combinations of alicyclic acid anhydride curing agents (B) and curing accelerators (C), specifically, combinations of methyl-5-norbornene-2,3-dicarboxylic acid anhydride and 1-benzyl-2-methylimidazole, phenol salt of 1,8-diazabicyclo[5.4.0]undecene-7(DBU), 2-ethylhexanoate of 1,8-diazabicyclo[5.4.0]undecene-7(DBU), or 2-ethylhexanoate of 1,5-diazabicyclo[4.3.0]nonene-5(DBN), and 4-methylhexahydrophthalic anhydride and hexahydrophthalic anhydride Preferred combinations include 1-benzyl-2-phenylimidazole or 2-ethylhexanoate of 1,5-diazabicyclo[4.3.0]nonen-5(DBN), and 3-methyltetrahydrophthalic anhydride combined with 1-(2-hydroxypropyl)imidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 2-ethylhexanoate of 1,8-diazabicyclo[5.4.0]undecene-7(DBU), or 2-ethylhexanoate of 1,5-diazabicyclo[4.3.0]nonen-5(DBN).

[0064] If the second liquid contains an antifoaming agent, its content is preferably 0.001 to 1% by mass, and more preferably 0.01 to 0.1% by mass, based on 100% by mass of the total amount of the second liquid. A defoaming agent content of 0.001% by mass or more prevents the generation and retention of foam in the second liquid, thereby improving durability after curing.

[0065] If the second liquid contains an inorganic filler, its content is preferably 0.3 to 90% by mass relative to 100% by mass of the total amount of the second liquid. In one embodiment, the content is more preferably 0.3 to 8% by mass, and even more preferably 0.5 to 3% by mass. In this case, thixotropy can be easily imparted to the two-component thermosetting epoxy resin composition of this disclosure. In another embodiment, the content is more preferably 50% by mass or more (for example, 50 to 90% by mass), and even more preferably 55% by mass or more (for example, 55 to 80% by mass). In this case, the linear expansion properties of the cured product are more easily reduced. Furthermore, from the viewpoint of suppressing an increase in the viscosity of the second liquid, the content is preferably 5% by mass or less, more preferably 1% by mass or less, even more preferably 0.1% by mass or less, and may even be 0% by mass. That is, the second liquid does not have to contain an inorganic filler.

[0066] The second liquid described above may contain other components in addition to the components described above. Examples of these other components include those described for the first liquid. Only one of these other components may be used, or two or more may be used. Furthermore, the content of these other components is preferably 5% by mass or less, more preferably 1% by mass or less, and may even be 0% by mass, based on 100% by mass of the total amount of the second liquid.

[0067] The content of epoxy compound (A) in the two-component thermosetting epoxy resin composition of this disclosure is preferably 50% by mass or more, more preferably 60 to 95% by mass, and even more preferably 70 to 90% by mass, based on 100% by mass of the total amount of curable compounds contained in the two-component thermosetting epoxy resin composition of this disclosure.

[0068] The content of the alicyclic acid anhydride curing agent (B) in the two-component thermosetting epoxy resin composition of this disclosure is preferably 50 to 200 parts by mass, more preferably 80 to 150 parts by mass, per 100 parts by mass of the total amount of epoxy compound (A). More specifically, it is preferable to use the alicyclic acid anhydride curing agent (B) in a ratio of 0.5 to 1.5 equivalents (preferably 0.8 to 1.1 equivalents, more preferably 0.9 equivalents or more and less than 1.0 equivalent) per equivalent of epoxy groups in the epoxy compound (A) contained in the two-component thermosetting epoxy resin composition of this disclosure. When the content of the alicyclic acid anhydride curing agent (B) is 50 parts by mass or more, curing can proceed sufficiently, and the heat resistance and toughness of the cured product tend to be further improved. When the content of the alicyclic acid anhydride curing agent (B) is 200 parts by mass or less, discoloration is suppressed, and a cured product with excellent hue tends to be obtained.

[0069] The content of the curing accelerator (C) in the two-component thermosetting epoxy resin composition of this disclosure is preferably 0.01 to 5 parts by mass, more preferably 0.03 to 3 parts by mass, and even more preferably 0.1 to 2.5 parts by mass, based on 100 parts by mass of the total amount of curable compounds contained in the two-component thermosetting epoxy resin composition of this disclosure. When the content of curing accelerator (C) is 0.01 parts by mass or more, heat resistance is further improved and a more efficient curing acceleration effect tends to be obtained. When the content of curing accelerator (C) is 5 parts by mass or less, discoloration is suppressed and a cured product with excellent hue tends to be obtained.

[0070] Furthermore, when the curing accelerator (C) is incorporated as a latent curing accelerator, the amount of the latent curing accelerator is, for example, 0.5 to 10 parts by mass, preferably 1 to 8 parts by mass, based on 100 parts by mass of the total amount of curable compounds contained in the two-component thermosetting epoxy resin composition of this disclosure.

[0071] The first liquid and the second liquid described above can be prepared by stirring and mixing the aforementioned components while heating them as needed. In this disclosure, it is preferable that the second liquid can be prepared without heating. Furthermore, the two-component thermosetting epoxy resin composition of this disclosure can be prepared by stirring and mixing the first liquid and the second liquid, which have been stored separately, while heating them as needed. The stirring and mixing method is not particularly limited, and known or conventional stirring and mixing means such as various mixers such as dissolvers and homogenizers, kneaders, rolls, bead mills, and self-rotating stirring devices can be used. In addition, degassing may be performed under vacuum after stirring and mixing.

[0072] [Cured product] By curing the two-component thermosetting epoxy resin composition of this disclosure, a cured product with excellent heat resistance can be obtained. Known or conventional means such as heat treatment can be used as curing methods. The temperature at which curing is performed by heating (curing temperature) is not particularly limited, but is preferably 45 to 220°C, more preferably 50 to 200°C, and even more preferably 55 to 190°C. The heating time during curing (curing time) is not particularly limited, but is preferably 30 to 600 minutes, more preferably 45 to 540 minutes, and even more preferably 60 to 480 minutes. If the curing temperature is 45°C or higher, curing is sufficient, and if it is 220°C or lower, the decomposition of the resin components can be suppressed. The curing conditions depend on various factors, but can be appropriately adjusted, for example, by shortening the curing time when the curing temperature is high, and lengthening the curing time when the curing temperature is low. Furthermore, curing can be performed in one stage or in two or more stages.

[0073] The glass transition temperature of the above-mentioned cured product is preferably 140°C or higher, more preferably 150°C or higher, even more preferably 180°C or higher, and particularly preferably 200°C or higher. A glass transition temperature of 140°C or higher provides excellent heat resistance even in high-temperature environments, such as the working environment temperature of an EV motor. The upper limit may be 230°C or lower. The glass transition temperature of the above-mentioned cured product can be measured by DMA (dynamic viscoelasticity measurement).

[0074] The two-component thermosetting epoxy resin composition and the cured product of this disclosure are preferably used in components included in rotating electric machines (for rotating electric machine applications). The cured product is particularly preferably used in automotive parts (for applications such as EV motors in automobiles). Specific uses of the cured product include insulating materials, coating materials, adhesives, and sealants. Furthermore, the curing agent containing the alicyclic acid anhydride curing agent (B) and curing accelerator (C) has a long shelf life and is less prone to thickening during storage. Therefore, the two-component thermosetting epoxy resin composition of this disclosure obtained by mixing the curing agent with the epoxy compound (A) maintains low viscosity and exhibits excellent wettability and impregnation properties to the object to be coated. For this reason, the two-component thermosetting epoxy resin composition of this disclosure can be preferably used in processes such as atmospheric pressure impregnation, reduced pressure impregnation, pressure impregnation, and dipping.

[0075] Examples of the above-mentioned applications for rotating electric machines include protection of rotor wires (winding coating, winding end coating, etc.), impregnation and casting of stator coils, impregnation and casting to cover the entire stator, magnet fixing applications in which magnets inserted into holes provided in the rotor core or stator core are fixed to the inner wall of the holes, and applications to fill the gap between the holes and the magnets.

[0076] The two-component thermosetting epoxy resin composition and the cured product of this disclosure are preferably used for coil impregnation applications, such as impregnation and casting of coils (wires, windings) in the stators and rotors of rotating electric machines.

[0077] By using the above-mentioned cured material for the above-mentioned rotating electric machine applications, a rotating electric machine equipped with the above-mentioned cured material can be obtained, for example: a rotor for a rotating electric machine equipped with the above-mentioned cured material covering the rotor windings; a stator for a rotating electric machine equipped with the above-mentioned cured material formed to cover the stator coils; a stator for a rotating electric machine equipped with the above-mentioned cured material covering the entire stator; a rotor or stator for a rotating electric machine equipped with the above-mentioned cured material, comprising a rotor core or stator core having a hole, a magnet inserted into the hole, and the above-mentioned cured material bonding the magnet to the inner wall of the hole; a rotor or stator for a rotating electric machine equipped with the above-mentioned cured material, comprising a rotor core or stator core having a hole, a magnet inserted into the hole, and the above-mentioned cured material filling the gap between the magnet and the inner wall of the hole.

[0078] Each embodiment disclosed herein can be combined with any other features disclosed herein. Each configuration and combination thereof in each embodiment is an example, and can be added, omitted, replaced, and otherwise modified as appropriate without departing from the spirit of this disclosure. Furthermore, each invention relating to this disclosure is not limited by the embodiments or the following examples, but is limited only by the claims. [Examples]

[0079] An embodiment of this disclosure will be described in more detail below based on examples.

[0080] Example 1 (Preparation of the main component) The epoxy compound (A) and polyester polyol (D) were added in the proportions shown in Table 1 (unit: parts by mass), and the mixture was uniformly mixed using a variable-speed mixer (product name "MAZERUSTAR KK-400W", manufactured by Kurabo Industries Ltd.). The mixture was then degassed to prepare the main component of the thermosetting epoxy resin composition of Example 1.

[0081] (Preparation of hardening agent) The curing agent for the thermosetting epoxy resin composition of Example 1 was prepared by adding an imidazole-based curing accelerator and / or a thermobasic generating agent (C) to an alicyclic acid anhydride curing agent (B) in the proportions shown in Table 1 (unit: parts by mass), uniformly mixing them using a variable-speed mixer (product name "MAZERUSTAR KK-400W", manufactured by Kurabo Industries Ltd.), and then degassing.

[0082] (Preparation of hardened material) The above main component and the above curing agent were mixed by hand in a mass ratio of 100:105 to prepare a thermosetting epoxy resin composition. The thermosetting epoxy resin composition was then filled into a mold and heated in an oven at 80°C for 1 hour, 130°C for 1 hour, and 180°C for 1 hour to produce the cured product of Example 1.

[0083] Examples 2-14, Comparative Examples 1-8 (Preparation of the main component) The main components of the thermosetting epoxy resin compositions for Examples 2-14 and Comparative Examples 1-8 were prepared in the same manner as in Example 1, except that the composition was changed as shown in Table 1.

[0084] (Preparation of hardening agent) Curing agents for the thermosetting epoxy resin compositions of Examples 2-14 and Comparative Examples 1-8 were prepared in the same manner as in Example 1, except that the composition was changed as shown in Table 1.

[0085] (Preparation of hardened material) Except for changing the mixing ratio shown in Table 1, the thermosetting epoxy resin compositions were prepared in the same manner as in Example 1, and then cured by heat treatment to produce the cured products of Examples 2-14 and Comparative Examples 1-8.

[0086] <Rating> The following evaluation tests were performed on the curing agents and cured products of the thermosetting epoxy resin compositions obtained in the examples and comparative examples.

[0087] (1) Glass transition temperature The glass transition temperature of the above-mentioned cured material was measured using a differential scanning calorimetry system (product name "DMA7100", manufactured by Hitachi High-Tech Science Corporation) under the following conditions: measurement temperature: 20~300°C (5°C / min), measurement atmosphere: N2 purge, measurement frequency: 1 Hz, mode: tension. The point at which the loss tangent (tanδ) changed was defined as the glass transition temperature.

[0088] (2) Viscosity and viscosity increase rate of the hardening agent The viscosity of the curing agents in the examples and comparative examples at 25°C was measured using an E-type viscometer (product name "VISCOMETER TV-25 type-H", manufactured by Toki Sangyo Co., Ltd., fixture: rotor standard 1°34'×R24).

[0089] Furthermore, the above-mentioned curing agent was subjected to a storage test under conditions of 40°C for one month, and its viscosity at 25°C after the storage test was similarly measured.

[0090] Furthermore, the viscosity at 25°C before and after the above storage test was compared, and the viscosity increase rate after the storage test [viscosity after storage test / viscosity before storage test] was calculated relative to the viscosity before the start of the storage test.

[0091] (3) Appearance after storage test Furthermore, the appearance of the hardening agent after the above storage test was visually evaluated, with ○ indicating no change in appearance and × indicating the presence of precipitates.

[0092] [Table 1]

[0093] The components used in the examples and comparative examples are as follows. (Epoxy compound (A)) A-1: Product name "Celoxide 2021P" (3,4-epoxycyclohexylmethyl(3,4-epoxy)cyclohexanecarboxylate), manufactured by Daicel Corporation. A-2: Product name "YD-128" (Poly[2-(chloromethyl)oxirane-alt-4,4'-(propane-2,2-diyl)diphenol]), manufactured by Nippon Steel Chemical & Material Co., Ltd. (Polyester polyol (D)) D-1: Aliphatic polyester diol, molecular weight 2000 (Alicyclic acid anhydride-based curing agent (B)) B-1: Product name "NMA", Methylnadic anhydride (methyl-5-norbornene-2,3-dicarboxylic acid anhydride), manufactured by POLYNT. B-2: Product name "Ricazide MH-700", a mixture of 4-methylhexahydrophthalic anhydride and hexahydrophthalic anhydride, manufactured by Shin Nippon Rika Co., Ltd. B-3: Product name "HN-2200", 3-methyltetrahydrophthalic anhydride, manufactured by RESONAC. (Curing accelerator (C)) C-1:1-methylimidazole C-2: 1-(2-hydroxypropyl)imidazole C-3: 1-benzyl-2-methylimidazole C-4: 1-benzyl-2-phenylimidazole C-5: Product name "U-CAT SA-1", manufactured by Sunapro Co., Ltd., phenolic salt of 1,8-diazabicyclo[5.4.0]undecene-7 C-6: Product name "U-CAT SA-102", manufactured by Sunapro Co., Ltd., 2-ethylhexanoate of 1,8-diazabicyclo[5.4.0]undecene-7 C-7: Product name "U-CAT UC1102", manufactured by Sunapro Co., Ltd., 2-ethylhexanoate of 1,5-diazabicyclo[4.3.0]nonene-5

[0094] As can be seen from Table 1, the curing agent in the example can be prepared by a simple mixing process using a specific combination of alicyclic acid anhydride curing agent (B) and curing accelerator (C), which is an imidazole-based curing accelerator and / or a thermobasic generating agent, and exhibits excellent long-term storage stability. On the other hand, when methyl-5-norbornene-2,3-dicarboxylic acid anhydride was combined with 1-methylimidazole, 1-(2-hydroxypropyl)imidazole, or 1-benzyl-2-phenylimidazole, precipitates were observed after the storage test (Comparative Examples 1-3). When a mixture of 4-methylhexahydrophthalic anhydride and hexahydrophthalic anhydride was combined with 1-(2-hydroxypropyl)imidazole or 1-benzyl-2-methylimidazole, the viscosity increase rate was high, and precipitates were sometimes observed after the storage test (Comparative Examples 4-7). When 3-methyltetrahydrophthalic anhydride was combined with 1-methylimidazole, the viscosity increase could not be suppressed (Comparative Example 8).

[0095] Variations of this disclosure are listed below. [Note 1] The first liquid is the main component containing epoxy compound (A), The invention comprises a second liquid which is a curing agent containing an alicyclic acid anhydride curing agent (B) and a curing accelerator (C) which is an imidazole curing accelerator and / or a thermobasic generating agent, Excluding the combinations of alicyclic acid anhydride curing agents (B) and curing accelerators (C) which are imidazole-based curing accelerators and / or thermobasic generating agents, the following combinations are permitted: a combination of methyl-5-norbornene-2,3-dicarboxylic acid anhydride with 1-methylimidazole, 1-(2-hydroxypropyl)imidazole, or 1-benzyl-2-phenylimidazole; a mixture of 4-methylhexahydrophthalic anhydride and hexahydrophthalic anhydride with 1-(2-hydroxypropyl)imidazole, 1-benzyl-2-methylimidazole, the phenol salt of 1,8-diazabicyclo[5.4.0]undecene-7, or the 2-ethylhexane salt of 1,8-diazabicyclo[5.4.0]undecene-7; and a combination of 3-methyltetrahydrophthalic anhydride with 1-methylimidazole. A two-component thermosetting epoxy resin composition that is liquid at 25°C. [Note 2] The two-component thermosetting epoxy resin composition as described in Appendix 1, wherein the content of a curing accelerator (C), which is an imidazole-based curing accelerator and / or a thermobasic generating agent, is 0.5 to 5 parts by mass per 100 parts by mass of an alicyclic acid anhydride-based curing agent (B) in the second liquid. [Note 3] The viscosity increase of the second liquid, measured at 25°C after a storage test of 1 month at 40°C, compared to the viscosity measured at 25°C before the start of the storage test, is 1.2 times or less. A two-component thermosetting epoxy resin composition as described in Appendix 1 or 2, which does not produce precipitates after the aforementioned storage test. [Note 4] A cured product of a two-component thermosetting epoxy resin composition as described in any one of the appendices 1 to 3. [Note 5] A cured product as described in Appendix 4, having a glass transition temperature of 140°C or higher. [Note 6] A cured product as described in Appendix 4 or 5, which is an insulating material. [Note 7] The cured product described in Appendix 4 or 5, which is an adhesive. [Note 8] A cured product as described in Appendix 4 or 5, which is a sealant.

Claims

1. The first liquid is the main component containing epoxy compound (A), The invention comprises a second liquid which is a curing agent containing an alicyclic acid anhydride curing agent (B) and a curing accelerator (C) which is an imidazole curing accelerator and / or a thermobasic generating agent, Excluding the combination of alicyclic acid anhydride curing agent (B) and curing accelerator (C) which is an imidazole-based curing accelerator and / or thermobasic generating agent, the following combinations of methyl-5-norbornene-2,3-dicarboxylic acid anhydride and 1-methylimidazole, 1-(2-hydroxypropyl)imidazole, or 1-benzyl-2-phenylimidazole, the combination of a mixture of 4-methylhexahydrophthalic anhydride and hexahydrophthalic anhydride and 1-(2-hydroxypropyl)imidazole, 1-benzyl-2-methylimidazole, the phenol salt of 1,8-diazabicyclo[5.4.0]undecene-7, or the 2-ethylhexane salt of 1,8-diazabicyclo[5.4.0]undecene-7, and the combination of 3-methyltetrahydrophthalic anhydride and 1-methylimidazole, A two-component thermosetting epoxy resin composition that is liquid at 25°C.

2. The two-component thermosetting epoxy resin composition according to claim 1, wherein the content of a curing accelerator (C), which is an imidazole-based curing accelerator and / or a thermobasic generating agent, is 0.5 to 5 parts by mass per 100 parts by mass of an alicyclic acid anhydride-based curing agent (B) in the second liquid.

3. The viscosity increase of the second liquid, measured at 25°C after a storage test at 40°C for one month, compared to the viscosity measured at 25°C before the start of the storage test, is 1.2 times or less. A two-component thermosetting epoxy resin composition according to claim 1 or 2, wherein no precipitate is formed after the storage test.

4. A cured product of the two-component thermosetting epoxy resin composition according to claim 1 or 2.

5. The cured product according to claim 4, wherein the glass transition temperature is 140°C or higher.

6. The cured product according to claim 4, which is an insulating material.

7. The cured product according to claim 4, which is an adhesive.

8. A cured product according to claim 4, which is a sealant.

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