Curable epoxy composition for dynamo-electric machines

Abstract

The purpose of the present disclosure is to provide a curable epoxy composition for dynamo-electric machines, the curable epoxy composition being able to be easily bonded to a PEEK resin, and being able to be suppressed in separation during use. An epoxy composition for dynamo-electric machines according to the present disclosure is characterized by containing an epoxy compound (A), an acid anhydride-based curing agent (B), and an amine-based curing accelerator (C), and is also characterized by being in a liquid state at 25°C, having a viscosity of 3,000 mPa∙s or less at 25°C, and having a bonding strength to a PEEK resin of 2.5 N / cm2 or more when cured. In addition, it is preferable that the viscosity increase rate is 20,000% or less before and after a storage test that is carried out at a temperature of 23 ± 5°C and a humidity of 50 ± 5% for 41 days.

Description

Curable epoxy composition for rotating electrical machines

[0001] The present disclosure relates to a curable epoxy composition for use in a rotating electric machine. More specifically, in one embodiment, the present disclosure relates to a curable epoxy composition for forming a cured product for use in a stator or rotor in a rotating electric machine. This application claims priority from Japanese Patent Application No. 2023-108870, filed on June 30, 2023, the contents of which are incorporated herein by reference.

[0002] Epoxy resins are used as resins (encapsulants) that cover optical semiconductor elements in optical semiconductor devices, resins for molded coils 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, gap fillers, etc.) (see, for example, Patent Documents 1 and 2).

[0003] In particular, polyamide-imide resin, which has high heat resistance, has traditionally been used as the insulating layer for windings in rotating electrical machines. However, as a measure to withstand high voltage (PDIV) to achieve high-speed charging, etc., there has been a trend toward replacing polyamide-imide resin with PEEK resin, which has higher voltage resistance.

[0004] Japanese Patent Application Laid-Open No. 2017-199566 Japanese Patent Application Laid-Open No. 2021-183687 Special Publication No. 2020-524190

[0005] However, due to its properties, PEEK resin has problems with its adhesiveness to epoxy resin. Patent Document 3 proposes a method for improving adhesiveness to epoxy resin by improving the composition of PEEK resin, but this method is insufficient. As a result, when exposed to motor vibrations, peeling occurs between the epoxy resin and the PEEK resin, causing the peeled epoxy resin and the windings, or the windings themselves, to repeatedly collide with each other due to motor vibrations, leading to wear of the PEEK resin that protects the windings and ultimately causing deterioration of insulation.

[0006] Therefore, an object of the present disclosure is to provide a curable epoxy composition for a rotating electrical machine that can be easily bonded to a PEEK resin and that can suppress peeling during use.

[0007] As a result of extensive research to achieve the above object, the inventors of the present disclosure have found that a curable epoxy composition for rotating electrical machines containing an epoxy compound, an acid anhydride curing agent, and an imidazole curing accelerator, which exhibits a specific viscosity and adhesive strength, can be easily bonded to PEEK resin and can suppress peeling during use. The present disclosure relates to a product completed based on these findings.

[0008] The present disclosure provides a curing agent that includes an epoxy compound (A), an acid anhydride-based curing agent (B), and an amine-based curing accelerator (C), is liquid at 25°C, has a viscosity at 25°C of 3000 mPa s or less, and when cured, has an adhesive strength to PEEK resin of 2.5 N / cm 2 The present invention provides the above curable epoxy composition for use in rotating electrical machines.

[0009] The curable epoxy composition for rotating electrical machines is liquid at 25°C, and has a viscosity of 3000 mPa·s or less at 25°C, which allows for excellent impregnation and facilitates adhesion while suppressing defects. When cured, the adhesive strength to PEEK resin is 2.5 N / cm 2 As a result, sufficient adhesive strength to the PEEK resin can be exerted.

[0010] The curable epoxy composition for a rotating electrical machine preferably exhibits a viscosity increase of 20,000% or less after a storage test conducted at a temperature of 23±5°C and a humidity of 50±5% for 41 days. The composition has excellent long-term stability and ease of handling.

[0011] The curable epoxy composition for a rotating electrical machine preferably has a glass transition temperature when cured of at least 170° C. By having the above-mentioned constitution, it becomes easy to exhibit sufficient heat resistance.

[0012] The present disclosure also provides a cured product of the above-mentioned curable epoxy composition for a rotating electric machine.

[0013] The present disclosure also provides a stator for a rotating electric machine, including the above-described cured product formed so as to cover a stator coil.

[0014] The present disclosure also provides a rotor for a rotating electric machine, comprising the above-described cured product coating a winding of the rotor.

[0015] The curable epoxy composition for a rotating electric machine according to the present disclosure can be easily bonded to PEEK resin, and peeling during use can be suppressed.

[0016] [Curable Epoxy Composition] A curable epoxy composition for a rotating electric machine according to one embodiment of the present disclosure (hereinafter, may be referred to as a "curable epoxy composition") contains at least an epoxy compound (A), an acid anhydride-based curing agent (B), and an amine-based curing accelerator (C), is liquid at 25°C, has a viscosity at 25°C of 3000 mPa·s or less, and when cured, has an adhesive strength to PEEK resin of 2.5 N / cm 2 The above is a curable (thermosetting) composition.

[0017] The curable epoxy composition preferably contains a polyester polyol (D). By incorporating the polyester polyol (D), the cured product obtained by curing the curable epoxy composition has a high glass transition temperature, excellent flexibility, and improved bending strain. This further improves the heat resistance of the cured product of the curable epoxy composition. The curable epoxy composition may also contain an inorganic filler (E). By incorporating the inorganic filler (E), thixotropy is imparted to the composition, thereby making it possible to suppress settling of powder that may be contained in the composition and also to impart low linear expansion to the cured product.

[0018] The curable epoxy composition is liquid at 25°C, which provides excellent workability, such as impregnation and casting properties. The viscosity of the curable epoxy composition at 25°C is 3000 mPa·s or less, preferably 2000 mPa·s or less, more preferably 1500 mPa·s or less, and even more preferably 1000 mPa·s or less. A viscosity of 3000 mPa·s or less provides excellent long-term stability, improves impregnation and casting workability, and reduces the occurrence of defects in the cured product due to poor casting. 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. A viscosity of 100 mPa·s or more tends to prevent the composition from dripping after impregnation, improving workability during impregnation and casting. The viscosity of the curable epoxy composition at 25°C can be measured, for example, under the conditions of a rheometer (trade name "Modular Compact Rheometer, MCR302", manufactured by Anton Paar, rotor diameter 25 mm, sample thickness 0.1 mm).

[0019] Furthermore, the curable epoxy composition preferably exhibits a viscosity increase rate at 25°C before and after a storage test conducted under conditions of a temperature of 23±5°C, a humidity of 50±5%, and for 41 days of 20,000% or less, more preferably 3,000% or less, even more preferably 5,000% or less, and particularly preferably 400% or less. By having the viscosity increase rate of 20,000% or less, the curable epoxy composition can suppress viscosity increase over a long period of time, and has excellent long-term stability and handleability. The lower limit is not particularly limited, but may be 80% or more.

[0020] The curable epoxy composition has an adhesive strength to PEEK resin of 2.5 N / cm when cured. 2 or more, preferably 2.7 N / cm 2 More preferably, 2.9 N / cm 2 The adhesive strength is 2.5 N / cm or more. 2By setting the adhesive strength to be equal to or greater than this, sufficient adhesive strength with the PEEK resin can be exhibited, and peeling from the PEEK resin can be suppressed. The upper limit is not particularly limited, but is 10 N / cm 2 or less. In the present disclosure, the adhesive strength is a value measured by a die shear test in which a bonding tester (product name "4000pxy DS100", manufactured by DAGE) is used to press a bonded portion made of a cured product of the curable epoxy composition and calculate the load [N] at break. The die shear test is performed on the cured product (bonded portion) obtained by applying the curable epoxy composition to a PEEK resin and laminating a chip thereon. The curing conditions for the cured product can be appropriately selected depending on the composition of the curable epoxy composition. For example, the die shear test is performed on a cured product cured under at least one of the following conditions: a temperature of 80 to 180°C and a time of 60 to 300 minutes. The die shear test can be performed more quickly and simply than conventional methods for evaluating adhesion, and can reduce repeatability errors even for substrates with low smoothness or low-viscosity resins.

[0021] The glass transition temperature of the curable epoxy composition when cured is preferably 170°C or higher, more preferably 174°C or higher, even more preferably 180°C or higher, and particularly preferably 200°C or higher. A glass transition temperature of 170°C or higher provides excellent heat resistance even in high temperature environments, such as the working temperature of an EV motor. The glass transition temperature of the cured product is a value measured by DSC (differential scanning calorimeter).

[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 these, alicyclic epoxy compounds are preferred as the epoxy compound (A). The epoxy compound (A) may be used alone or in combination of two or more.

[0023] The alicyclic epoxy compound may be any known or commonly used alicyclic epoxy compound, and is not particularly limited. Examples include: (I) a compound having an epoxy group composed of two adjacent carbon atoms and an oxygen atom that constitute an alicyclic ring in the molecule (referred to as an "alicyclic epoxy group"); (II) a compound in which an epoxy group is directly bonded to an alicyclic ring via a single bond; and (III) a compound having an alicyclic ring and a glycidyl ether group in the molecule (glycidyl ether type epoxy compound).

[0024] The above (I) compound having an alicyclic epoxy group in the molecule includes a compound having a cyclohexene oxide group, for example, a compound represented by the following formula (i).

[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 a divalent hydrocarbon group, an alkenylene group in which some or all of the carbon-carbon double bonds have been epoxidized, a carbonyl group, an ether bond, an ester bond, a carbonate group, an amide group, and groups in which multiple of these are linked together. Note that a substituent such as an alkyl group may be bonded to one or more of the 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 and divalent alicyclic hydrocarbon groups having 1 to 18 carbon atoms. Examples of the linear or branched alkylene groups having 1 to 18 carbon atoms include methylene, methylmethylene, dimethylmethylene, ethylene, propylene, and trimethylene. Examples of the divalent alicyclic hydrocarbon group include divalent cycloalkylene groups (including cycloalkylidene groups) such as 1,2-cyclopentylene, 1,3-cyclopentylene, cyclopentylidene, 1,2-cyclohexylene, 1,3-cyclohexylene, 1,4-cyclohexylene, and cyclohexylidene.

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

[0028] Representative examples of the alicyclic epoxy compound represented by formula (i) above include (3,4,3',4'-diepoxy)bicyclohexyl and compounds represented by formulas (i-1) to (i-10) below. In formulas (i-5) and (i-7) below, l and m each represent an integer of 1 to 30. R' in formula (i-5) below is an alkylene group having 1 to 8 carbon atoms, and among these, a linear or branched alkylene group having 1 to 3 carbon atoms, such as a methylene group, an ethylene group, a propylene group, or an isopropylene group, is preferred. In formulas (i-9) and (i-10) below, n1 to n6 each represent an integer of 1 to 30. Further, other examples of the alicyclic epoxy compound represented by the above formula (i) include 2,2-bis(3,4-epoxycyclohexyl)propane, 1,2-bis(3,4-epoxycyclohexan-1-yl)ethane, 1,2-epoxy-1,2-bis(3,4-epoxycyclohexan-1-yl)ethane, and bis(3,4-epoxycyclohexylmethyl)ether.

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

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

[0031] Examples of the compound (III) having an alicyclic ring and a glycidyl ether group in the molecule include glycidyl ethers of alicyclic alcohols (particularly alicyclic polyhydric alcohols). More specifically, examples include hydrogenated compounds of bisphenol A 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 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-

[0033] Examples of the epoxy compounds include hydrogenated compounds of bisphenol F type epoxy compounds such as [(2,3-epoxypropoxy)cyclohexyl]methane (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 an aromatic ring.

[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 a condensation reaction of bisphenols [e.g., bisphenol A, bisphenol F, bisphenol S, fluorene bisphenol, etc.] with epihalohydrin; high-molecular-weight epibis-type glycidyl ether epoxy resins obtained by further addition reaction of these epibis-type glycidyl ether epoxy resins with the above-mentioned bisphenols; phenols [e.g., phenol, cresol, xylenol, resol, Examples of suitable epoxy resins include novolak alkyl type glycidyl ether epoxy resins obtained by condensing polyhydric alcohols obtained by condensing polyhydric alcohols [e.g., rusine, catechol, bisphenol A, bisphenol F, bisphenol S, etc.] with aldehydes [e.g., formaldehyde, acetaldehyde, benzaldehyde, hydroxybenzaldehyde, salicylaldehyde, etc.] with epihalohydrin; and epoxy compounds in which two phenol skeletons are bonded to the 9-position of a fluorene ring and a glycidyl group is bonded, directly or via an alkyleneoxy group, to the oxygen atom obtained by removing the hydrogen atom from the hydroxy group of each of the phenol skeletons.

[0033] Examples of the aliphatic epoxy compound include glycidyl ethers of q-valent alcohols (q is a natural number) that do not have a cyclic structure; glycidyl esters of monovalent or polyvalent carboxylic acids [for example, acetic acid, propionic acid, butyric acid, stearic acid, adipic acid, sebacic acid, maleic acid, itaconic acid, etc.]; epoxidized products of fats and oils having double bonds, such as epoxidized linseed oil, epoxidized soybean oil, and epoxidized castor oil; and epoxidized products of polyolefins (including polyalkadiene), such as epoxidized polybutadiene. Examples of the q-valent alcohol not having a 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 trihydric or higher polyhydric alcohols such as glycerin, diglycerin, erythritol, trimethylolethane, trimethylolpropane, pentaerythritol, dipentaerythritol, and sorbitol. The q-valent alcohol may be a polyether polyol, a polyester polyol, a polycarbonate polyol, a polyolefin polyol, or the like.

[0034] The content of the epoxy compound (A) in the curable epoxy composition is preferably 10% by mass or more, based on the total amount (100% by mass) of the curable epoxy composition. In one embodiment of the curable epoxy composition (for example, when the inorganic filler (E) is not included), the content of the epoxy compound (A) is more preferably 20 to 90% by mass, even more preferably 30 to 70% by mass, and even more preferably 35 to 60% by mass. In another embodiment of the curable epoxy composition (for example, when the inorganic filler (E) is included), the content of the epoxy compound (A) is more preferably 10 to 60% by mass, even more preferably 12 to 55% by mass, and even more preferably 14 to 50% by mass.

[0035] In this specification, the content of each component (e.g., the epoxy compound (A), the acid anhydride curing agent (B), etc.) contained in the curable epoxy composition can be appropriately selected from the described ranges so that the total amount is 100 mass% or less.

[0036] (Acid anhydride curing agent (B)) The acid anhydride curing agent (B) is a compound that has the function of curing the curable epoxy composition by reacting with the epoxy compound (A). Only one type of acid anhydride curing agent (B) may be used, or two or more types may be used.

[0037] As the acid anhydride curing agent (B) (acid anhydrides), known or conventional acid anhydride curing agents can be used, and are not particularly limited. Examples thereof include methyltetrahydrophthalic anhydride (4-methyltetrahydrophthalic anhydride, 3-methyltetrahydrophthalic anhydride, etc.), methylhexahydrophthalic anhydride (4-methylhexahydrophthalic anhydride, 3-methylhexahydrophthalic anhydride, etc.), dodecenyl succinic anhydride, methyl-endomethylenetetrahydrophthalic anhydride, phthalic anhydride, maleic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, Examples of suitable carboxylic acid anhydrides include phthalic anhydride, methylcyclohexene dicarboxylic anhydride, pyromellitic anhydride, trimellitic anhydride, benzophenone tetracarboxylic anhydride, nadic anhydride, methyl nadic anhydride, hydrogenated methyl nadic anhydride, 4-(4-methyl-3-pentenyl)tetrahydrophthalic anhydride, succinic anhydride, adipic anhydride, sebacic anhydride, dodecanedioic anhydride, methylcyclohexene tetracarboxylic anhydride, vinyl ether-maleic anhydride copolymer, and alkylstyrene-maleic anhydride copolymer.

[0038] Among the acid anhydride curing agents (B), from the viewpoint of handleability, acid anhydrides that are liquid at 25° C. [e.g., methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, dodecenylsuccinic anhydride, methyl-endomethylenetetrahydrophthalic anhydride, etc.] are preferred. On the other hand, when an acid anhydride that is solid at 25° C. is dissolved in an acid anhydride that is liquid at 25° C. to form a liquid mixture, the handleability of the acid anhydride as a curing agent in the curable epoxy composition tends to be improved.

[0039] Furthermore, from the viewpoint of increasing the glass transition temperature of the cured product and further improving the heat resistance of the cured product, the acid anhydride curing agent (B) preferably contains nadic anhydride or a derivative thereof, such as nadic anhydride, methyl nadic anhydride, or hydrogenated methyl nadic anhydride, and more preferably contains methyl nadic anhydride.

[0040] The content (amount) of the acid anhydride curing agent (B) in the curable epoxy composition is not particularly limited, but 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 the epoxy compound (A) contained in the curable epoxy composition. More specifically, it is preferably used in a ratio of 0.5 to 1.5 equivalents (preferably 0.8 to 1.1 equivalents, more preferably 0.9 equivalents or more but less than 1.0 equivalent) per equivalent of epoxy groups in the epoxy compound (A) contained in the curable epoxy composition. When the content of the 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 acid anhydride curing agent (B) is 200 parts by mass or less, coloration is suppressed, and a cured product with excellent hue tends to be obtained. Furthermore, the proportion of the acid anhydride curing agent (B) in the curing agents contained in the curable epoxy composition is preferably more than 80% by mass, and may be 85% by mass or more, 90% by mass or more, 95% by mass or more, or 99% by mass or more, relative to the total amount (100% by mass) of the curing agents.

[0041] (Amine-based curing accelerator (C)) The amine-based curing accelerator (C) is a compound that has the function of accelerating the reaction rate when the epoxy compound (A) reacts with the acid anhydride-based curing agent (B). By using the amine-based curing accelerator (C) as a curing accelerator, a cured product with excellent heat resistance can be formed. Examples of the amine-based curing accelerator (C) include imidazole-based curing accelerators and strong basic compound-based curing accelerators. Only one type of amine-based curing accelerator (C) may be used, or two or more types may be used.

[0042] As the imidazole curing accelerator, known or commonly used imidazole curing accelerators can be used, and are not particularly limited to, for example, 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, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-(2-hydroxypropyl)imidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-phenylimidazole, 1-benzyl-2-methylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-(2-hydroxypropyl) ... Examples of imidazole compounds include imidazole, 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.

[0043] The imidazole curing accelerator may also be a derivative of an imidazole compound, such as an amine adduct of the imidazole compound (e.g., an amine adduct with an epoxy compound). Examples of the epoxy compound include those exemplified and explained as the epoxy compound (A). Only one type of the epoxy compound may be used, or two or more types may be used.

[0044] Among the imidazole curing accelerators, from the viewpoint of increasing the glass transition temperature of the cured product and further improving the heat resistance of the cured product, it is preferable to include at least 1-methylimidazole, 2-methylimidazole, 1-(2-hydroxypropyl)imidazole, or an amine adduct thereof (particularly, an amine adduct with an epoxy compound, more preferably, an amine adduct with a bisphenol-type epoxy compound). Among these, from the viewpoint of excellent long-term stability (shelf life) when mixed with the acid anhydride-type curing agent (B), 1-(2-hydroxypropyl)imidazole or an amine adduct (particularly, an amine adduct with an epoxy compound) is preferred, more preferably an amine adduct, even more preferably an amine adduct of 2-methylimidazole and an epoxy compound, and particularly preferably an amine adduct of 2-methylimidazole and a bisphenol-type epoxy compound.

[0045] The imidazole curing accelerator may be incorporated as a latent curing accelerator. Use of a latent curing accelerator can improve the long-term stability of the curable epoxy composition. Examples of latent curing accelerators include imidazole curing accelerators that have been microencapsulated (microencapsulated latent curing agents).

[0046] The microcapsule-type latent curing agent contains, for example, a core and a shell covering the surface of the core, the core containing an imidazole-based curing accelerator, and the shell containing an organic polymer and / or an inorganic compound. Note that when the shell is an inorganic compound, the microcapsule-type latent curing agent does not fall under the category of inorganic filler (E).

[0047] The content of the shell is preferably 0.01 to 100 parts by mass, more preferably 0.1 to 80 parts by mass, even more preferably 1 to 60 parts by mass, and particularly preferably 5 to 50 parts by mass, per 100 parts by mass of the core. When the content of the shell is within the above range, both excellent long-term stability and curability can be achieved.

[0048] Examples of the organic polymer include natural polymers such as cellulose, synthetic resins, etc. Among these, synthetic resins are preferred from the viewpoints of long-term stability, ease of destruction of the shell during curing, and uniformity of the physical properties of the cured product.

[0049] Examples of the synthetic resin include epoxy resin, acrylic resin, polyester resin, phenolic resin, polyethylene resin, nylon resin, polystyrene resin, urea resin, urethane resin, and mixtures and copolymers thereof.

[0050] Examples of the inorganic compound include boron compounds such as boron oxide and boric acid esters, silicon dioxide, calcium oxide, etc. Among these, boron oxide is preferred from the viewpoint of superior film stability and ease of destruction when heated.

[0051] As the microcapsule-type latent curing agent, known or conventional microcapsule-type latent curing agents can be used, and commercially available products such as those under the trade names "Novacure HX-3742" and "Novacure HXA-3792" (both manufactured by Asahi Kasei Corporation) and "Technicure LC-80" (manufactured by A&C Catalysts) can be used.

[0052] The strongly basic compound-based curing accelerator is preferably a curing accelerator containing a strongly basic compound having a pKa of 10 or more, more preferably a pKa of 11 or more, even more preferably a pKa of 11 to 16, and particularly preferably a pKa of 11 to 14. The pKa is the pKa in water. The strongly basic compound is preferably a nitrogen-containing cyclic compound having the above pKa. Specific examples of the strongly basic compound include 1,8-diazabicyclo[5.4.0]undecene-7 (DBU) and salts thereof (e.g., phenol salt, octylate salt, 2-ethylhexanoate, p-toluenesulfonate, formate salt, tetraphenylborate salt, etc.), 1,5-diazabicyclo[4.3.0]nonene-5 (DBN) and salts thereof (e.g., phenol salt, octylate salt, p-toluenesulfonate, formate salt, tetraphenylborate salt, etc.), tetramethylguanidine (TMG) and salts thereof, 1,4-diazabicyclo[2.2.2]octane (DABCO), 1,5,7-triazabicyclo[4.4.0]decene-5 (TBD) and salts thereof, and 7-methyl-1,5,7-triazabicyclo[4.4.0]decene-5 (MTBD) and salts thereof. Among these, DBU and its salts are more preferred as the strongly basic compound.

[0053] Furthermore, as the amine-based curing accelerator (C), commercially available products such as "Technicure LC-100" (manufactured by A&C Catalysts) can also be used.

[0054] The content (amount) of the amine-based curing accelerator (C) in the curable epoxy composition is not particularly limited, but 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 parts by mass, relative to 100 parts by mass of the total amount of curable compounds (e.g., compounds reactive with a curing agent, such as the epoxy compound (A) and the polyester polyol (D)) contained in the curable epoxy composition. When the content of the amine-based curing accelerator (C) is 0.01 parts by mass or more, heat resistance tends to be further improved and a more efficient curing acceleration effect tends to be obtained. Furthermore, when the polyester polyol (D) is contained, the heat resistance and bending strain of the cured product tend to be both excellent. When the content of the amine-based curing accelerator (C) is 5 parts by mass or less, coloration tends to be suppressed and a cured product with excellent hue tends to be obtained. When the amine-based curing accelerator (C) is blended as a latent curing accelerator, the content of the latent curing accelerator (e.g., the total content of the core and shell) is, for example, 0.6 to 10 parts by mass, and preferably 2 to 8 parts by mass, relative to 100 parts by mass of the total amount of the curable compounds contained in the curable epoxy composition. The proportion of the amine-based curing accelerator (C) in the curing accelerators contained in the curable epoxy composition is preferably 50% by mass or more, and may be 60% by mass or more, 75% by mass or more, 90% by mass or more, 95% by mass or more, or 99% by mass or more, relative to the total amount (100% by mass) of the curing accelerators.

[0055] (Polyester polyol (D)) Examples of the polyester polyol (D) include compounds having two or more hydroxy groups and two or more ester bonds in the molecule. Examples of the polyester polyol 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.

[0056] The polyester polyol (D) preferably contains a polylactone polyol and / or an aliphatic polyester polyol, from the viewpoint of maintaining a high glass transition temperature and improving flexibility of the cured product. Also, from the same viewpoint, the polyester polyol (D) preferably contains a polyester diol and / or a polyester triol.

[0057] The molecular weight of the polyester polyol (D) is not particularly limited, but is preferably 250 or more, more preferably 600 or more, even more preferably 1100 or more, and particularly preferably 1700 or more. When the molecular weight is 250 or more (particularly 600 or more), the toughness of the cured product is likely to be 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 the polyester polyol (D) means the number average molecular weight measured by gel permeation chromatography (GPC) in terms of standard polystyrene.

[0058] The hydroxyl value of the polyester polyol (D) is not particularly limited, but is preferably 600 KOHmg / g or less, more preferably 200 KOHmg / g or less, even more preferably 100 KOHmg / g or less, and particularly preferably 80 KOHmg / g or less. When the hydroxyl value is 600 KOHmg / g or less (particularly 200 KOHmg / g or less), the chain transfer reaction of the polymerization of the epoxy compound (A) is suppressed, the degree of polymerization of the epoxy main chain tends to be high, and the glass transition temperature of the cured product can be maintained high. The hydroxyl value can be measured by potentiometric titration in accordance with JIS K0070.

[0059] When the curable epoxy composition contains polyester polyol (D), the content of polyester polyol (D) in the curable epoxy composition is not particularly limited, but is preferably 1 to 30 mass%, more preferably 3 to 20 mass%, and even more preferably 5 to 15 mass%, relative to the total amount (100 mass%) of the curable epoxy composition. When the content is within the above range, the cured product will have even better heat resistance and bending strain.

[0060] (Inorganic Filler (E)) As the inorganic filler (E), known or conventional inorganic fillers can be used, and are not particularly limited. Examples of the inorganic filler (E) include, but are not limited to, silica, alumina, zircon, calcium silicate, calcium phosphate, calcium carbonate, magnesium carbonate, silicon carbide, silicon nitride, aluminum nitride, boron nitride, aluminum hydroxide, iron oxide, zinc oxide, zirconium oxide, magnesium oxide, titanium oxide, aluminum oxide, calcium sulfate, barium sulfate, fosterite, steatite, spinel, clay, kaolin, dolomite, hydroxyapatite, nepheline cyanoite, cristobalite, wollastonite, diatomaceous earth, talc, and other powders, as well as molded products thereof (e.g., spherical beads). Further examples of the inorganic filler (E) include the above-mentioned inorganic fillers subjected to known or conventional surface treatments. Only one type of inorganic filler (E) may be used, or two or more types may be used. Among these, as the inorganic filler (E), silica, alumina, and aluminum nitride are preferred, and silica (silica filler) is more preferred, from the viewpoint of reducing the linear expansion coefficient of the cured product and making the cured product less susceptible to warping.

[0061] The silica is not particularly limited, and may be any known or commonly used silica such as fused silica, crystalline silica, high-purity synthetic silica, etc. Silica that has been subjected to a known or commonly used surface treatment (for example, a surface treatment with a surface treatment agent such as a metal oxide, a silane coupling agent, a titanium coupling agent, an organic acid, a polyol, or silicone) may also be used.

[0062] Examples of silica include hydrophilic silica and hydrophobic silica, and hydrophobic silica is preferred from the viewpoints that it easily increases the viscosity of the curable epoxy composition, it inhibits the settling of solid components such as the microcapsule-type latent curing agent to improve dispersibility, and it also imparts thixotropy to the curable epoxy composition, resulting in excellent workability such as impregnation and pourability.

[0063] Above-mentioned hydrophobic silica is the silica that hydrophilic silica is subjected to hydrophobic treatment.The treating agent used for hydrophobic treatment can be, for example, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, hexamethyldisilazane, methyltrialkoxysilane, dimethyldialkoxysilane, trimethylalkoxysilane, ethyltrichlorosilane, propyltrichlorosilane, hexyltrichlorosilane, long-chain alkyltrichlorosilane, ethyltrialkoxysilane, propyltrialkoxysilane, hexyltrialkoxysilane, long-chain alkyltrialkoxysilane, methacrylsilane, fluoroalkylsilane, perfluoroalkylsilane and other organic silyl compounds; dimethylpolysiloxane (silicone oil), methylphenylpolysiloxane, methylhydrogenpolysiloxane, amino-modified silicone and other polysiloxanes and other silicone compounds.Among them, the hydrophobic treatment by polysiloxane is preferred. The hydrophobic treatment can be carried out using a known method, such as a liquid phase method, a gas phase method, an autoclave method, or the like.

[0064] The shape of the silica is not particularly limited, and examples thereof include powder, spheres, crushed particles, fibers, needles, scales, etc. Among these, from the viewpoint of dispersibility, spherical silica is preferred, and spherical silica (for example, spherical silica having an aspect ratio of 1.2 or less) is particularly preferred.

[0065] The specific surface area of ​​the silica is not particularly limited, but from the viewpoint of imparting thixotropy to the curable epoxy composition and providing excellent workability such as impregnation and casting properties, it is preferred that the specific surface area be 10 m 2 / g or more is preferable, and 40m 2 / g or more, more preferably 70m 2 / g or more.

[0066] The median particle size of the silica is not particularly limited, but from the viewpoint of imparting thixotropy to the curable epoxy composition and achieving excellent workability such as impregnation and casting properties, it is preferably 200 nm or less, more preferably 100 nm or less, and even more preferably 50 nm or less. The median particle size is, for example, 3 nm or more. Furthermore, from the viewpoint of improving the low linear expansion, strength, and crack resistance of the cured product, it is preferably 0.1 to 50 μm, more preferably 0.1 to 30 μm. The median particle size refers to the particle size (median diameter) at 50% of the integrated value in the particle size distribution measured by laser diffraction / scattering method.

[0067] When the curable epoxy composition contains an inorganic filler (E), the content (amount) of the inorganic filler (E) in the curable epoxy composition is not particularly limited, but is preferably 0.5 to 500 parts by mass per 100 parts by mass of the total amount of curable compounds contained in the curable epoxy composition. In one embodiment, the content is more preferably 0.5 to 50 parts by mass, and even more preferably 1 to 10 parts by mass. In this case, thixotropy can be easily imparted to the composition. In another embodiment, the content is more preferably 100 parts by mass or more (e.g., 100 to 500 parts by mass), and even more preferably 250 parts by mass or more (e.g., 250 to 400 parts by mass). In this case, the linear expansion of the cured product is more likely to be reduced.

[0068] When the curable epoxy composition contains an inorganic filler (E), the content of the inorganic filler (E) in the curable epoxy composition is not particularly limited, but is preferably 0.3 to 90 mass% relative to the total amount (100 mass%) of the curable epoxy composition. In one embodiment, the content is more preferably 0.3 to 8 mass%, and even more preferably 0.5 to 3 mass%. In this case, thixotropy can be easily imparted to the composition. In another embodiment, the content is more preferably 50 mass% or more (e.g., 50 to 90 mass%), and even more preferably 55 mass% or more (e.g., 55 to 80 mass%). In this case, the linear expansion of the cured product is more likely to be reduced.

[0069] The curable epoxy composition may contain a curable compound other than the epoxy compound (A) and the polyester polyol (D) (a compound that can react with a curing agent such as an acid anhydride curing agent (B)). The total content of the epoxy compound (A) and the polyester polyol (D) in the curable compounds in the curable epoxy composition is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more, relative to the total amount (100% by mass) of all the curable compounds in the curable epoxy composition. Note that when the curable epoxy composition does not contain the polyester polyol (D), the above content is the content of the epoxy compound (A).

[0070] The proportion of the epoxy compound (A) in the curable epoxy composition is preferably 50% by mass or more, and may be 60% by mass or more, 70% by mass or more, or even 75% by mass or more, based on the total amount (100% by mass) of the curable compounds contained in the curable epoxy composition. The proportion of the polyester polyol (D) in the curable epoxy composition is preferably 5 to 45% by mass, more preferably 10 to 35% by mass, and even more preferably 15 to 30% by mass, based on the total amount (100% by mass) of the curable compounds contained in the curable epoxy composition. When the proportion is within the above range, the cured product exhibits even better heat resistance and bending strain.

[0071] The curable epoxy composition may contain components other than those described above. For example, the addition of a compound having a hydroxy group, such as ethylene glycol, diethylene glycol, propylene glycol, or glycerin (particularly a polyhydric alcohol other than the polyester polyol (D)), allows the reaction to proceed more slowly. In addition, within the range that does not impair viscosity or transparency, conventional additives such as silicone-based or fluorine-based defoamers, leveling agents, coupling agents such as silane coupling agents such as γ-glycidoxypropyltrimethoxysilane and 3-mercaptopropyltrimethoxysilane, surfactants, flame retardants, colorants, antioxidants, ultraviolet absorbers, ion adsorbents, colorants, phosphors (e.g., inorganic phosphor particles such as YAG-based phosphor fine particles and silicate-based phosphor fine particles), release agents, thickeners, dispersants, rust inhibitors, corrosion inhibitors, freezing point depressants, anti-wear additives, and wettability modifiers may be used. In particular, when 1-methylimidazole is used as the amine curing accelerator (C), it is preferable to use an antifoaming agent or a leveling agent from the viewpoint of reducing the viscosity and improving the impregnation property. The above-mentioned other components may each be used singly or in combination of two or more.

[0072] By including the antioxidant, it is possible to form a cured product having even more excellent heat resistance (particularly, yellowing resistance). As the antioxidant, a known or commonly used antioxidant can be used, and examples thereof include, but are not limited to, phenol-based antioxidants (phenol-based compounds), hindered amine-based antioxidants (hindered amine-based compounds), phosphorus-based antioxidants (phosphorus-based compounds), sulfur-based antioxidants (sulfur-based compounds), and the like.

[0073] Examples of phenolic antioxidants include monophenols such as 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-p-ethylphenol, and stearyl-β-(3,5-di-t-butyl-4-hydroxyphenyl)propionate; 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 4,4'-thiobis(3-methyl-6-t-butylphenol), 4,4'-butylidenebis(3-methyl-6-t-butylphenol), and 3,9-bis[1,1-dimethyl-2-{β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy}ethyl]2,4,8,1 bisphenols such as 0-tetraoxaspiro[5.5]undecane; and polymeric phenols such as 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, bis[3,3'-bis-(4'-hydroxy-3'-t-butylphenyl)butyric acid]glycol ester, 1,3,5-tris(3',5'-di-t-butyl-4'-hydroxybenzyl)-s-triazine-2,4,6-(1H,3H,5H)trione, and tocophenol.

[0074] Examples of the hindered amine antioxidant include bis(1,2,2,6,6-pentamethyl-4-piperidyl)[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butyl malonate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate, methyl-1,2,2,6,6-pentamethyl-4-piperidylsebacate, and 4-benzoyloxy-2,2,6,6-tetramethylpiperidine.

[0075] Examples of phosphorus-based antioxidants include triphenyl phosphite, diphenyl isodecyl phosphite, phenyl diisodecyl phosphite, tris(nonylphenyl) phosphite, diisodecyl pentaerythritol phosphite, tris(2,4-di-t-butylphenyl) phosphite, cyclic neopentane tetrayl bis(octadecyl) phosphite, cyclic neopentane tetrayl bis(2,4-di-t-butylphenyl) phosphite, cyclic neopentane tetrayl bis(2,4-di-t-butylphenyl) phosphite, phosphites (phosphite antioxidants) such as bis[2-t-butyl-4-methylphenyl]phosphite and bis[2-t-butyl-6-methyl-4-{2-(octadecyloxycarbonyl)ethyl}phenyl]hydrogenphosphite; and oxaphosphaphenanthrene oxides such as 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 10-(3,5-di-t-butyl-4-hydroxybenzyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide.

[0076] Examples of sulfur-based antioxidants include dodecanethiol, dilauryl-3,3'-thiodipropionate, dimyristyl-3,3'-thiodipropionate, and distearyl-3,3'-thiodipropionate.

[0077] Among these, the antioxidant preferably contains a phosphorus-based antioxidant, and more preferably contains a phosphite-based antioxidant, from the viewpoint of further improving the heat resistance of the cured product.

[0078] When the curable epoxy composition contains an antioxidant, the content (blending amount) of the antioxidant in the curable epoxy composition is not particularly limited, but is preferably 0.1 to 5 parts by mass, and more preferably 0.5 to 3 parts by mass, per 100 parts by mass of the total amount of epoxy compound (A) contained in the curable epoxy composition. When the content of the antioxidant is 0.1 part by mass or more, oxidation of the cured product is efficiently prevented, and heat resistance and yellowing resistance tend to be further improved. When the content of the antioxidant is 5 parts by mass or less, coloration is suppressed, and a cured product with a better hue tends to be obtained.

[0079] As the wettability modifier, known or commonly used wettability modifiers can be used, and commercially available products such as those under the trade names "BYK-327," "BYK-302," "BYK-310," "BYK-320," and "BYK-330" (all manufactured by BYK Corporation) can be used.

[0080] The curable epoxy composition can be prepared by stirring and mixing the above-mentioned components, while heating them as needed, without any particular limitations. The curable epoxy composition can be used as a one-component composition in which the components are premixed and used as is, or as a multi-component (e.g., two-component) composition in which two or more components stored separately are mixed before use. The stirring and mixing method is not particularly limited, and known or conventional stirring and mixing means can be used, such as various mixers such as dissolvers and homogenizers, kneaders, rolls, bead mills, and planetary stirring devices. After stirring and mixing, the mixture may be degassed under vacuum.

[0081] [Cured Product] By curing the curable epoxy composition, a cured product with excellent heat resistance can be obtained. Known or conventional methods, such as heat treatment, can be used as the curing method. The temperature (curing temperature) during curing by heating 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 (curing time) during curing is also not particularly limited, but is preferably 30 to 600 minutes, more preferably 45 to 540 minutes, and even more preferably 60 to 480 minutes. A curing temperature and curing time of 45°C or higher ensures sufficient curing, while a temperature of 220°C or lower can suppress decomposition of the resin components. Curing conditions vary depending on various factors, but can be appropriately adjusted, for example, by shortening the curing time when the curing temperature is increased and lengthening the curing time when the curing temperature is decreased. Curing can be carried out in a single stage or in multiple stages (two or more stages).

[0082] The bending strain of the cured product at 23°C is preferably 2.0% or more, more preferably 3.0% or more, even more preferably 4.0% or more, and particularly preferably 4.3% or more. When the bending strain is 2.0% or more (particularly 4.0% or more), flexibility in a room temperature environment is improved and toughness is excellent. The bending strain at 23°C can be measured in accordance with JIS K7171 (2008).

[0083] The curable epoxy composition and the cured product are used in components included in rotating electrical machines (rotating electrical machine applications). Because the cured product has excellent adhesion to PEEK resin, it can be preferably used in components for which PEEK resin is preferably used, particularly automotive components (such as for automotive EV motors). Specific uses of the cured product include insulating materials, coating materials, adhesives, and the like. Furthermore, a curing agent composition containing an acid anhydride-based curing agent (B) and an amine-based curing accelerator (C) has a long shelf life and is less likely to thicken during storage. Therefore, the curable epoxy composition obtained by mixing the curing agent composition with an epoxy compound (A) has excellent wettability and impregnation properties for the coated object. Therefore, the curable epoxy composition can be preferably used in processes such as atmospheric pressure impregnation, reduced pressure impregnation, pressure impregnation, and dipping.

[0084] Examples of the above-mentioned rotating electric machine applications include applications for protecting rotor wires (such as winding coating applications and winding tip coating applications), impregnation and casting applications for stator coils, applications for impregnation and casting applications to cover the entire stator, magnet fixing applications for fixing magnets inserted into holes provided in the rotor core or stator core to the inner walls of the holes in the rotor and / or stator, and applications for filling gaps between the holes and the magnets.

[0085] The curable epoxy composition and the cured product are preferably used for impregnating coils, such as impregnating and casting coils (wires and windings) in the stators and rotors of rotating electrical machines.

[0086] By using the cured product in the above-mentioned rotating electric machine application, it is possible to obtain a rotating electric machine comprising the cured product, such as: a rotor for a rotating electric machine comprising the cured product covering the rotor windings; a stator for a rotating electric machine comprising the cured product formed so as to cover the stator coil; a stator for a rotating electric machine comprising the cured product covering the entire stator; a rotor or stator for a rotating electric machine comprising a rotor core or stator core having a hole, a magnet inserted into the hole, and the cured product bonding the magnet to the inner wall of the hole; or a rotor or stator for a rotating electric machine comprising a rotor core or stator core having a hole, a magnet inserted into the hole, and the cured product filling the gap between the magnet and the inner wall of the hole.

[0087] Each aspect disclosed in this specification can be combined with any other feature disclosed in this specification. Each configuration and combination thereof in each embodiment is an example, and addition, omission, substitution, and other modifications of configurations are possible as appropriate within the scope of the present disclosure. Furthermore, each invention according to this disclosure is not limited by the embodiments or the following examples, but is limited only by the scope of the claims.

[0088] Hereinafter, one embodiment of the present disclosure will be described in more detail based on examples.

[0089] Example 1 (Preparation of Curable Epoxy Composition) The epoxy compound (A) and polyester polyol (D) were uniformly mixed and degassed using a planetary stirring device (trade name "Thinner Mixer AR-250", manufactured by Thinky Corporation) in the blending ratio (unit: parts by mass) shown in Table 1. Next, the acid anhydride curing agent (B) and amine curing accelerator (C) were added in the blending ratio (unit: parts by mass) shown in Table 1, and the mixture was uniformly mixed using a planetary stirring device (trade name "Thinner Mixer AR-250", manufactured by Thinky Corporation) and further degassed to prepare a curable epoxy composition.

[0090] (Preparation of Cured Product) The curable epoxy composition obtained above was filled into a mold and heated in an oven at 80°C for 1 hour, at 130°C for 1 hour, and at 180°C for 1 hour successively to prepare a cured product of Example 1.

[0091] Examples 2 to 6 and Comparative Examples 1 and 2 (Preparation of Curable Epoxy Compositions) The curable epoxy compositions of Examples 2 to 6 and Comparative Examples 1 and 2 were prepared in the same manner as in Example 1, except that the formulation of the curable epoxy composition was changed to the formulation shown in Table 1.

[0092] (Preparation of cured product) The curable epoxy compositions obtained above were filled into a mold and cured using an oven by successively heating at 80°C for 1 hour, at 130°C for 1 hour, and at 180°C for 1 hour for the curable epoxy compositions of Examples 2 to 6 and Comparative Example 2, by successively heating at 130°C for 2 hours and at 150°C for 1 hour for the curable epoxy composition of Comparative Example 1, and by successively heating at 100°C for 1 hour, at 150°C for 1 hour, and at 180°C for 3 hours for the curable epoxy composition of Comparative Example 3, to prepare cured products of Examples 2 to 6 and Comparative Examples 1 to 3.

[0093] <Evaluation> The curable epoxy compositions and cured products obtained in the examples and comparative examples were subjected to the following evaluation tests.

[0094] (1) Adhesion Strength: The curable epoxy composition was applied evenly to a glass plate with a constant film thickness (40 μm), and the curable epoxy composition was transferred to a Si chip (1.25 mm square). The Si chips were evenly arranged on a PEEK resin base (2.5 × 1.5 cm) using tweezers and thermally cured under the same conditions as for preparing the cured product. A test specimen was prepared in which the cured product of the curable epoxy compound and the Si chip were laminated on the PEEK resin in this order. The test specimen was attached to a bonding tester (product name "4000pxy DS100", manufactured by DAGE Corporation). A tool attached to the load sensor of the bonding tester was moved to a set height (150 μm) above the PEEK resin base, pressed against the Si chip, and the load [N] at which the bond of the cured product broke was measured as the adhesive strength to the PEEK resin.

[0095] (2) Glass Transition Temperature The glass transition temperature of the cured product was measured using a differential scanning calorimeter (product name "Q2000", manufactured by T.A. Instruments) under conditions of a temperature rise rate of 10°C / min and a measurement temperature range of 30 to 250°C under a nitrogen gas flow after pre-treatment (heating from 30°C to 250°C at a heating rate of 10°C / min, followed by cooling from 250°C to 30°C at a heating rate of -10°C / min). The inflection point of the obtained temperature thermal history change curve was then taken as the glass transition temperature.

[0096] (3) Bending Strain The bending strain of the cured product was measured in accordance with JIS K7171 (2008).

[0097] (4) Viscosity at 25°C and Viscosity Increase Rate The viscosity of the curable epoxy composition at 25°C was measured using a rheometer (trade name "Modular Compact Rheometer MCR302", manufactured by Anton Paar, rotor diameter 25 mm, sample thickness 0.1 mm).

[0098] Furthermore, the curable epoxy composition was subjected to a storage test under conditions of a temperature of 23±5° C. and a humidity of 50±5% for 41 days, and the viscosity at 25° C. after the storage test was similarly measured.

[0099] Furthermore, the viscosity at 25°C before and after the storage test was compared, and the viscosity increase rate (%) before and after the storage test was calculated. Note that examples in which gelation occurred after the storage test and viscosity measurement was not possible are indicated by "-".

[0100]

[0101] As can be seen from Table 1, Examples 1 to 6 contain an epoxy compound, an acid anhydride curing agent, and an amine curing accelerator, have a viscosity of 3000 mPa·s or less at 25°C, and have an adhesive strength of 2.5 N / cm to PEEK after curing. 2 The above-described curable epoxy compositions for rotating electric machines can be easily bonded to PEEK resin, and are expected to be able to suppress peeling from the PEEK resin during use and maintain insulating properties. On the other hand, the curable epoxy composition for rotating electric machines of Comparative Example 1 had poor adhesive strength. Furthermore, the curable epoxy composition for rotating electric machines of Comparative Example 2 had sufficient adhesive strength after curing, but had high viscosity, making it difficult to bond to PEEK resin, and was poor in handleability and long-term stability.

[0102] The components used in the examples and comparative examples are as follows: (Epoxy compounds (A)) CELLOXIDE 2021P: Trade name "CELLOXIDE 2021P" (3,4-epoxycyclohexylmethyl (3,4-epoxy) cyclohexanecarboxylate), manufactured by Daicel Corporation. YD128: Trade name "YD-128" (Poly[2-(chloromethyl)oxirane-alt-4,4'-(propane-2,2-diyl)diphenol)], manufactured by Nippon Steel Chemical & Material Co., Ltd. E530: Trade name "Epiform E-530", manufactured by Somar Corporation (Polyimide compounds) Voltatex 4200: Trade name "Voltatex 4200", manufactured by Axalta. (Acid anhydride curing agent (B)) NMA: Trade name "NMA", methyl nadic anhydride, manufactured by POLYNT. MTHPA: Trade name "MTHPA", methyl tetrahydrophthalic anhydride, manufactured by RESONAC. (Amine-based curing accelerators (C)) 1B2MZ: 1-benzyl-2-methylimidazole HPI: 1-(2-hydroxypropyl)imidazole U-CAT SA-102: Trade name "U-CAT SA-102", manufactured by San-Apro Ltd., 2-ethylhexane salt of 1,8-diazabicyclo[5.4.0]undecene-7 U-CAT SA-1: Trade name "U-CAT SA-1", manufactured by San-Apro Ltd., phenol salt of 1,8-diazabicyclo[5.4.0]undecene-7 LC-80: Trade name "Technicure LC-80", amine adduct of 2-methylimidazole and bisphenol A type epoxy compound, latent curing accelerator, manufactured by A&C Catalysts LC-100: Trade name "Technicure LC-100" manufactured by A&C Catalysts (Polyester polyol (D)) Polyol A: Aliphatic polyester diol, molecular weight 2000, hydroxyl value 56.8 KOH mg / g

[0103] Variations of the present disclosure are described below. [Appendix 1] An epoxy compound (A), an acid anhydride curing agent (B), and an amine curing accelerator (C), which is liquid at 25°C, has a viscosity of 3000 mPa·s or less at 25°C, and has an adhesive strength to PEEK resin when cured of 2.5 N / cm 2[Appendix 2] The curable epoxy composition for a rotating electric machine according to Appendix 1, which has a viscosity increase rate of 20,000% or less before and after a storage test carried out under conditions of a temperature of 23±5°C, a humidity of 50±5%, and 41 days. [Appendix 3] The curable epoxy composition for a rotating electric machine according to Appendix 1, which has an adhesive strength to PEEK resin of 2.5 N / cm when cured. 2The curable epoxy composition for a rotating electric machine according to any one of Appendices 1 to 2, wherein the epoxy compound (A) is an alicyclic epoxy compound. [Appendix 6] The curable epoxy composition for a rotating electric machine according to any one of Appendices 1 to 5, wherein the epoxy compound (A) is contained in an amount of 10 mass% or more relative to the total amount (100 mass%) of the curable epoxy composition. [Appendix 7] The curable epoxy composition for a rotating electric machine according to any one of Appendices 1 to 6, wherein the acid anhydride-based curing agent (B) is an acid anhydride that is liquid at 25°C. [Appendix 8] The curable epoxy composition for a rotating electric machine according to any one of Appendices 1 to 7, wherein the acid anhydride-based curing agent (B) contains nadic anhydride or a derivative thereof. [Appendix 9] The curable epoxy composition for a rotating electric machine according to any one of Appendices 1 to 8, wherein the amine-based curing accelerator (C) comprises an imidazole-based curing accelerator. [Appendix 10] The curable epoxy composition for a rotating electric machine according to any one of Appendices 1 to 9, wherein the content of the amine-based curing accelerator (C) is 0.01 to 5 parts by mass per 100 parts by mass of the total amount of curable compounds contained in the curable epoxy composition. [Appendix 11] The curable epoxy composition for a rotating electric machine according to any one of Appendices 1 to 10, further comprising a polyester polyol (D). [Appendix 12] The curable epoxy composition for a rotating electric machine according to Appendices 11, wherein the polyester polyol (D) has a molecular weight of 250 to 100,000. [Appendix 13] The curable epoxy composition for a rotating electric machine according to Appendices 11 or 12, wherein the polyester polyol (D) has a hydroxyl value of 600 KOHmg / g or less. [Appendix 14] The curable epoxy composition for a rotating electric machine according to any one of Appendices 1 to 13, further comprising an inorganic filler (E). [Appendix 15] The curable epoxy composition for a rotating electric machine according to Appendices 14, comprising silica as the inorganic filler (E). [Appendix 16] A cured product of the curable epoxy composition for a rotating electric machine according to any one of Appendices 1 to 15. [Appendix 17] A stator for a rotating electric machine, comprising the cured product according to Appendices 16 formed so as to cover a stator coil.[Appendix 18] A stator for a rotating electric machine, comprising the cured product according to appendix 16 covering a winding of a rotor.

Claims

1. Contains an epoxy compound (A), an acid anhydride curing agent (B), and an amine curing accelerator (C), is liquid at 25°C, has a viscosity of 3000 mPa·s or less at 25°C, and has an adhesive strength to PEEK resin of 2.5 N / cm when cured. 2 The above curable epoxy composition for use in a rotating electrical machine.

2. A curable epoxy composition for rotating electrical machines according to claim 1, which has a viscosity increase rate of 20,000% or less before and after a storage test carried out under conditions of a temperature of 23±5°C and a humidity of 50±5% for 41 days.

3. A curable epoxy composition for use in rotating electrical machines according to claim 1 or 2, which has a glass transition temperature of 170° C. or higher when cured.

4. A cured product of the curable epoxy composition for rotating electrical machines according to claim 1 or 2.

5. A stator for a rotating electric machine comprising the hardened material according to claim 4 formed so as to cover a stator coil.

6. A rotor for a rotating electric machine, comprising the cured material according to claim 4 coating the windings of the rotor.

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