Curable epoxy composition

Abstract

Provided is a curable epoxy composition that can be cured in a short time in the presence of oxygen and has excellent filling properties. The curable epoxy composition contains an epoxy compound having an epoxy group in a molecule, contains a photocationic polymerization initiator, and is for use in rotary electric machines and / or semiconductors. The curable epoxy composition is preferably essentially free from curing agents other than the photocationic polymerization initiator. The curable epoxy composition may contain a polyol.

Description

Curable epoxy composition

[0001] The present disclosure relates to a curable epoxy composition for use in rotating electrical machines and / or semiconductors. More particularly, 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 electrical machine. This application claims priority from Japanese Patent Application No. 2023-139154, filed August 29, 2023, the contents of which are incorporated herein by reference.

[0002] Radically polymerizable compounds and epoxy resins are used as resins for molded coils in which coils such as ignition coils are impregnated and cast, and as resins for rotating electrical machines (for example, insulating materials, adhesive resins for fixing permanent magnets, gap fillers, etc.) (see, for example, Patent Documents 1 to 3).

[0003] For example, Patent Document 1 discloses a resin composition containing a base unsaturated polyester resin and / or a base vinyl ester resin, a radically polymerizable monomer, and a photoradical polymerization initiator as a resin composition for coating an insulating-coated copper wire. Patent Document 2 discloses an epoxy resin composition for use in rotating electrical machines containing an epoxy resin and a sulfonium salt cationic polymerization initiator. Patent Document 3 discloses a powder coating containing an epoxy resin and an acid anhydride-based curing agent as a resin composition for filling gaps between copper wires in coils.

[0004] JP 2015-19457 A JP 2005-245143 A JP 2020-157183 A

[0005] However, resin compositions containing radically polymerizable monomers such as those described in Patent Document 1 must be cured in an oxygen-blocking state in order to undergo radical polymerization. When coating and curing components with complex structures, such as rotating electrical machines, methods of curing in an oxygen-blocking state are cumbersome. Furthermore, when using a thermal cationic polymerization initiator as described in Patent Document 2, the curing time is long. If the curing process is complicated or the curing time is long, dripping occurs while coating and curing the component, resulting in poor handling. Furthermore, powder coatings such as those described in Patent Document 3 are poor at filling gaps.

[0006] Therefore, an object of the present disclosure is to provide a curable epoxy composition that can be cured in the presence of oxygen in a short time and has excellent filling properties.

[0007] As a result of intensive research to achieve the above object, the inventors of the present disclosure have found that a curable epoxy composition containing an epoxy compound having an epoxy group in the molecule and a cationic photopolymerization initiator can be cured in a short time in the presence of oxygen and has excellent filling properties. The present disclosure relates to a product that has been completed based on these findings.

[0008] The present disclosure provides a curable epoxy composition that includes an epoxy compound having an epoxy group in the molecule and a cationic photopolymerization initiator, and that is suitable for use in rotating electrical machines and / or semiconductors.

[0009] The curable epoxy composition preferably does not substantially contain any curing agent other than the cationic photopolymerization initiator.

[0010] The curable epoxy composition preferably contains a polyol.

[0011] The content of the epoxy compound relative to the total amount of the cationically curable compounds is preferably 90 mass % or more.

[0012] The curable epoxy composition preferably contains substantially no radically polymerizable compounds.

[0013] The curable epoxy composition preferably contains an inorganic filler.

[0014] The curable epoxy composition is preferably liquid at 25°C.

[0015] The curable epoxy composition is preferably used for impregnating the stator coil of the rotating electric machine, or for fixing a magnet inserted into a hole formed in the rotor core of the rotating electric machine to the inner wall of the hole.

[0016] The present disclosure also provides a cured product of the curable epoxy composition.

[0017] The present disclosure also provides a stator for a rotating electric machine formed so as to cover a stator coil.

[0018] The present disclosure also provides a stator for a rotating electric machine, comprising the above-described cured product covering a rotor winding.

[0019] The curable epoxy composition of the present disclosure can be cured in a short time in the presence of oxygen and has excellent filling properties. Therefore, when a component having a complex structure is coated with the curable epoxy composition, dripping during curing is less likely to occur, and stickiness of the resin surface is quickly reduced, resulting in excellent handleability. Furthermore, the ability to cure in a short time leads to reduced CO2 emissions and a reduced environmental impact.

[0020] [Curable Epoxy Composition] The curable epoxy composition of the present disclosure is a composition that contains at least an epoxy compound having an epoxy group in the molecule and a cationic photopolymerization initiator, and has both photocurable and thermosetting properties.

[0021] (Epoxy Compound) The epoxy compound is a compound having one or more epoxy groups (oxiranyl groups) in the molecule. Among them, the epoxy compound is preferably a compound having two or more epoxy groups (preferably 2 to 6, more preferably 2 to 4) in the molecule. Only one type of epoxy compound may be used, or two or more types may be used.

[0022] The epoxy compound may be any known or commonly used epoxy compound, and is not particularly limited. Examples of the epoxy compound include alicyclic epoxy compounds (alicyclic epoxy resins); aliphatic epoxy compounds (aliphatic epoxy resins) such as aliphatic polyglycidyl ethers; aromatic epoxy compounds (aromatic epoxy resins) such as bisphenol A epoxy compounds; and heterocyclic epoxy compounds (heterocyclic epoxy resins).

[0023] The alicyclic epoxy compound is a compound having at least an alicyclic (aliphatic hydrocarbon ring) structure and an epoxy group in the molecule. As the alicyclic epoxy compound, a known or conventional alicyclic epoxy compound can be used, and is not particularly limited, but examples thereof include (I) a compound having an epoxy group (referred to as an "alicyclic epoxy group") composed of two adjacent carbon atoms and an oxygen atom constituting an alicyclic ring in the molecule; (II) a compound in which an epoxy group is directly bonded to an alicyclic ring by a single bond; (III) a compound having an alicyclic ring and a glycidyl ether group in the molecule (glycidyl ether type epoxy compound), etc.

[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] Furthermore, the above-mentioned (1) compound having an alicyclic epoxy group in the molecule includes an epoxy-modified siloxane. Examples of the epoxy-modified siloxane include linear or cyclic polyorganosiloxanes having a structural unit represented by the following formula (i'):

[0030] In the above formula (i'), R 3represents a substituent containing a group represented by the following formula (1a) or a substituent containing a group represented by the following formula (1b), and R 4 represents an alkyl group or an alkoxy group.

[0031] In formula (1a) and formula (1b), R 1a , R 1b are the same or different and represent a linear or branched alkylene group, and examples thereof include linear or branched alkylene groups having 1 to 10 carbon atoms such as a methylene group, a methylmethylene group, a dimethylmethylene group, an ethylene group, a propylene group, a trimethylene group, a tetramethylene group, a pentamethylene group, a hexamethylene group, and a decamethylene group.

[0032] The epoxy equivalent of the epoxy-modified siloxane (according to JIS K7236) is, for example, 100 to 400, preferably 150 to 300.

[0033] As the epoxy-modified siloxane, for example, a commercially available product such as the compound represented by the following formula (i'-1) (trade name "X-40-2670", manufactured by Shin-Etsu Chemical Co., Ltd.) can be used.

[0034] 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):

[0035] 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. pExamples 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)].

[0036] Examples of the compound (III) having an alicyclic ring and a glycidyl ether group in the molecule include, for example, glycidyl ethers of alicyclic alcohols (particularly, alicyclic polyhydric alcohols). More specifically, for example, compounds obtained by hydrogenating bisphenol A type epoxy compounds (hydrogenated 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; 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-(2,3-epoxypropoxy)cyclohexyl]methane; Examples of such epoxy compounds include hydrogenated compounds of bisphenol F epoxy compounds such as [(2,3-epoxypropoxy)cyclohexyl]methane (hydrogenated bisphenol F epoxy compounds); hydrogenated biphenol epoxy compounds; hydrogenated phenol novolac epoxy compounds; hydrogenated cresol novolac epoxy compounds; hydrogenated cresol novolac epoxy compounds of bisphenol A; hydrogenated naphthalene epoxy compounds; hydrogenated epoxy compounds of epoxy compounds obtained from trisphenolmethane; and hydrogenated epoxy compounds of other epoxy compounds having an aromatic ring.

[0037] Examples of the aromatic epoxy compounds include epibis-type glycidyl ether epoxy resins obtained by a condensation reaction between bisphenols [e.g., bisphenol A, bisphenol F, bisphenol S, fluorene bisphenol, etc.] and 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, resorcinol, catechol, bisphenol A, bisphenol F]; and bisphenol S] with an aldehyde [for example, formaldehyde, acetaldehyde, benzaldehyde, hydroxybenzaldehyde, salicylaldehyde], and then subjecting the resulting polyhydric alcohol to a condensation reaction with epihalohydrin. Examples of such epoxy compounds include novolak alkyl type glycidyl ether epoxy resins obtained by further subjecting the resulting polyhydric alcohol to a condensation reaction 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.

[0038] 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, or a polyolefin polyol.

[0039] Examples of the heterocyclic epoxy compound include epoxy compounds having an epoxy group and a heterocycle other than the epoxy group in the molecule (e.g., a tetrahydrofuran ring, a tetrahydropyran ring, a morpholine ring, a chroman ring, an isochroman ring, a tetrahydrothiophene ring, a tetrahydrothiopyran ring, an aziridine ring, a pyrrolidine ring, a piperidine ring, a piperazine ring, an indoline ring, a 2,6-dioxabicyclo[3.3.0]octane ring, a 1,3,5-triazacyclohexane ring, a 1,3,5-triazacyclohexa-2,4,6-trione ring (an isocyanuric ring), a dihydroimidazo[4,5-d]imidazole-2,5-dione ring (a glycoluril ring), and the like; and aromatic heterocycles such as a thiophene ring, a pyrrole ring, a furan ring, and a pyridine ring). Among these, heterocyclic epoxy compounds composed of carbon, hydrogen, oxygen, and nitrogen atoms are preferred.

[0040] Examples of the heterocyclic epoxy compound include an epoxy compound having an isocyanuric ring (an isocyanuric ring-containing epoxy compound) and an epoxy compound having a glycoluril ring (a glycoluril ring-containing epoxy compound). The number of epoxy groups contained in the molecule of the isocyanuric ring-containing epoxy compound is not particularly limited, but is preferably 1 to 6, and more preferably 1 to 3. The number of epoxy groups contained in the molecule of the glycoluril ring-containing epoxy compound is not particularly limited, but is preferably 1 to 6, and more preferably 2 to 4.

[0041] Examples of the isocyanuric ring-containing epoxy compound include compounds represented by the following formula (iii).

[0042] In formula (iii), R 4 ~R 6 are the same or different and represent a hydrogen atom or a monovalent organic group. 4 ~R 6At least one of the groups is a monovalent organic group containing an epoxy group. Examples of the monovalent organic group include monovalent aliphatic hydrocarbon groups (e.g., alkyl groups, alkenyl groups, etc.); monovalent aromatic hydrocarbon groups (e.g., aryl groups, etc.); monovalent heterocyclic groups; and monovalent groups formed by the bonding of two or more aliphatic hydrocarbon groups, alicyclic hydrocarbon groups, and aromatic hydrocarbon groups. The monovalent organic group may have a substituent (e.g., a hydroxy group, a carboxy group, a halogen atom, etc.). Examples of the monovalent organic group containing an epoxy group include monovalent organic groups containing an epoxy group, such as an epoxy group, a glycidyl group, a 2-methylepoxypropyl group, and a cyclohexene oxide group, which will be described later.

[0043] In particular, R in formula (iii) 4 ~R 6 are the same or different and are a group having a group represented by the following formula (iiia) or a group having a group represented by the following formula (iiib), 4 ~R 6 It is preferable that at least one of the groups has a group represented by formula (iiia).

[0044] R in the above formula (iiia) and formula (iiib) 7 and R 8 are the same or different and represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. Examples of the alkyl group having 1 to 8 carbon atoms include linear or branched alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, s-butyl, pentyl, hexyl, heptyl, and octyl groups. Among these, linear or branched alkyl groups having 1 to 3 carbon atoms such as methyl, ethyl, propyl, and isopropyl groups are preferred. R in formula (iiia) and formula (iiib) 7 and R 8 is particularly preferably a hydrogen atom.

[0045] X in the above formula (iiia) and formula (iiib) 1 and X 2are the same or different and represent a divalent organic group. The divalent organic group may be a divalent hydrocarbon group, or may be a group in which two or more divalent hydrocarbon groups are bonded via a linking group such as an ester bond or an ether bond.

[0046] R in formula (iii) 4 ~R 6 may be the same or different and may have only one group having a group represented by the above formula (iiia) and / or one group having a group represented by the above formula (iiib), or may have two or more groups. 4 ~R 6 The number of groups having a group represented by the above formula (iiia) and / or groups having a group represented by the above formula (iiib) that each of the groups has is preferably 1 to 3, and more preferably 1 or 2.

[0047] More specifically, examples of the isocyanuric ring-containing epoxy compound include a compound represented by the following formula (iii-1), a compound represented by the following formula (iii-2), and a compound represented by the following formula (iii-3).

[0048] In the above formulas (iii-1) to (iii-3), R 7 , R 8 , X 1 , and X 2 are the same or different and are the same as those in formula (iiia) and formula (iiib).

[0049] Representative examples of the compound represented by the formula (iii-1) include monoallyl diglycidyl isocyanurate, 1-allyl-3,5-bis(2-methylepoxypropyl)isocyanurate, 1-(2-methylpropenyl)-3,5-diglycidyl isocyanurate, and 1-(2-methylpropenyl)-3,5-bis(2-methylepoxypropyl)isocyanurate.

[0050] Representative examples of the compound represented by the above formula (iii-2) include diallyl monoglycidyl isocyanurate, 1,3-diallyl-5-(2-methylepoxypropyl) isocyanurate, 1,3-bis(2-methylpropenyl)-5-glycidyl isocyanurate, and 1,3-bis(2-methylpropenyl)-5-(2-methylepoxypropyl) isocyanurate.

[0051] Representative examples of the compound represented by the above formula (iii-3) include triglycidyl isocyanurate and tris(2-methylepoxypropyl) isocyanurate.

[0052] Commercially available products of the isocyanuric ring-containing epoxy compound include the TEPIC series (TEPIC-G, TEPIC-S, TEPIC-SS, TEPIC-HP, TEPIC-L, TEPIC-PAS, TEPIC-VL, TEPIC-UC) manufactured by Nissan Chemical Industries, Ltd.

[0053] The isocyanuric ring-containing epoxy compound can also be used after being modified in advance by adding a compound that reacts with an epoxy group, such as an alcohol or an acid anhydride.

[0054] Examples of the glycoluril ring-containing epoxy compound include compounds represented by the following formula (iv):

[0055] In formula (iv), R 9 ~R 12 are the same or different and represent a hydrogen atom or a monovalent organic group. 9 ~R 12 At least one of the R is a monovalent organic group containing an epoxy group. Examples of the monovalent organic group include the same as the monovalent organic group in the isocyanuric ring-containing epoxy compound described above. The monovalent organic group may have a substituent. Among the monovalent organic groups, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, and a monovalent organic group containing an epoxy group are preferred. Therefore, the R 9 ~R 12are preferably the same or different and are monovalent organic groups containing a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkenyl group, or an epoxy group.

[0056] The monovalent organic group containing an epoxy group is an organic group containing at least one epoxy group (oxirane ring), and examples thereof include a group in which at least one double bond of a linear or branched aliphatic hydrocarbon group having a carbon-carbon double bond, such as an alkenyl group, has been epoxidized, and a group in which at least one double bond of a cyclic aliphatic hydrocarbon group having a carbon-carbon double bond (e.g., a cycloalkenyl group; a cycloalkenylalkyl group such as a cyclohexenylethyl group, etc.) has been epoxidized. More specific examples thereof include a 1,2-epoxyethyl group (epoxy group), a 1,2-epoxypropyl group, a 2,3-epoxypropyl group (glycidyl group), a 2,3-epoxy-2-methylpropyl group (methylglycidyl group), a 3,4-epoxybutyl group, a 3-glycidyloxypropyl group, a 3,4-epoxycyclohexylmethyl group, and a 2-(3,4-epoxycyclohexyl)ethyl group.

[0057] Examples of the alkenyl group include substituted or unsubstituted alkenyl groups such as vinyl, allyl, butenyl, pentenyl, and hexenyl. Examples of the substituent include a halogen atom, a hydroxy group, and a carboxy group. Among these, an ω-alkenyl group (an alkenyl group having a terminal carbon-carbon unsaturated double bond) is preferred, more preferably an ω-alkenyl group having 2 to 6 carbon atoms, and even more preferably an allyl group.

[0058] In formula (iv), R 13 and R 14 are the same or different and represent a hydrogen atom or a monovalent organic group. Examples of the monovalent organic group include the same monovalent organic groups as those in the isocyanuric ring-containing epoxy compound described above.

[0059] In particular, R in formula (iv) 9 ~R 12are the same or different and are a group having a group represented by the following formula (iva) or a group having a group represented by the following formula (ivb), 9 ~R 12 It is preferable that at least one of the groups has a group represented by formula (iva).

[0060] R in the above formula (iva) and formula (ivb) 15 and R 16 are the same or different and represent a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. Examples of the alkyl group having 1 to 8 carbon atoms include a straight-chain or branched-chain alkyl group such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a s-butyl group, a pentyl group, a hexyl group, a heptyl group, and an octyl group. Among these, a straight-chain or branched-chain alkyl group having 1 to 3 carbon atoms such as a methyl group, an ethyl group, a propyl group, and an isopropyl group is preferred. R in formula (iva) and formula (ivb) 15 and R 16 is particularly preferably a hydrogen atom.

[0061] X in the above formula (iva) and formula (ivb) 3 and X 4 are the same or different and represent a divalent organic group. The divalent organic group may be a divalent hydrocarbon group, or may be a group in which two or more divalent hydrocarbon groups are bonded via a linking group such as an ester bond or an ether bond.

[0062] R in formula (iv) 9 ~R 12 may be the same or different and may have only one group having a group represented by the above formula (iva) and / or one group having a group represented by the above formula (ivb), or may have two or more groups. 9 ~R 12 The number of groups having a group represented by the above formula (iva) and / or groups having a group represented by the above formula (ivb) that each of the groups has is preferably 1 to 3, and more preferably 1 or 2.

[0063] More specifically, examples of the glycoluril ring-containing epoxy compound include a compound represented by the following formula (iv-1), a compound represented by the following formula (iv-2), a compound represented by the following formula (iv-3), a compound represented by the following formula (iv-4), a compound represented by the following formula (iv-5), and a compound represented by the following formula (iv-6).

[0064] In the above formulas (iv-1) to (iv-6), R 15 , R 16 , X 3 , and X 4 are the same or different and are the same as those in formula (iva) and formula (ivb).

[0065] Representative examples of the compound represented by the above formula (iv-1) include 1,3,4,6-tetraglycidyl glycoluril, tetrakis(2-methylepoxypropyl) glycoluril, and the like.

[0066] Representative examples of the compound represented by formula (iv-2) above include 1-allyl-3,4,6-triglycidyl glycoluril, 1-allyl-3,4,6-tris(2-methylepoxypropyl) glycoluril, 1-(2-methylpropenyl)-3,4,6-triglycidyl glycoluril, and 1-(2-methylpropenyl)-3,4,6-tris(2-methylepoxypropyl) glycoluril.

[0067] Representative examples of the compound represented by formula (iv-3) above include 1,4-diallyl-3,6-diglycidyl glycoluril, 1,4-diallyl-3,6-bis(2-methylepoxypropyl) glycoluril, 1,4-bis(2-methylpropenyl)-3,6-diglycidyl glycoluril, and 1,4-bis(2-methylpropenyl)-3,6-bis(2-methylepoxypropyl) glycoluril.

[0068] Representative examples of the compound represented by formula (iv-4) include 1,3-diallyl-4,6-diglycidyl glycoluril, 1,3-diallyl-4,6-bis(2-methylepoxypropyl) glycoluril, 1,3-bis(2-methylpropenyl)-4,6-diglycidyl glycoluril, and 1,3-bis(2-methylpropenyl)-4,6-bis(2-methylepoxypropyl) glycoluril.

[0069] Representative examples of the compound represented by formula (iv-5) include 1,6-diallyl-3,4-diglycidyl glycoluril, 1,6-diallyl-3,4-bis(2-methylepoxypropyl) glycoluril, 1,6-bis(2-methylpropenyl)-3,4-diglycidyl glycoluril, and 1,6-bis(2-methylpropenyl)-3,4-bis(2-methylepoxypropyl) glycoluril.

[0070] Representative examples of the compound represented by formula (iv-6) include 1,3,4-triallyl-6-glycidylglycoluril, 1,3,4-triallyl-6-(2-methylepoxypropyl)glycoluril, 1,3,4-tris(2-methylpropenyl)-6-glycidylglycoluril, and 1,3,4-tris(2-methylpropenyl)-6-(2-methylepoxypropyl)glycoluril.

[0071] The glycoluril ring-containing epoxy compound can also be used after being modified in advance by adding a compound that reacts with an epoxy group, such as an alcohol or an acid anhydride.

[0072] The content of the epoxy compound 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 (e.g., when no inorganic filler is contained), the content of the epoxy compound is more preferably 60 to 99.5% by mass, even more preferably 70 to 99% by mass, and even more preferably 75 to 98.5% by mass. In another embodiment of the curable epoxy composition (e.g., when an inorganic filler is contained), the content of the epoxy compound is more preferably 10 to 50% by mass, even more preferably 15 to 40% by mass, and even more preferably 18 to 30% by mass.

[0073] In this specification, the content of each component (e.g., epoxy compound, photocationic polymerization initiator, 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.

[0074] (Photocationic Polymerization Initiator) Examples of the photocationic polymerization initiator include hexafluoroantimonate salt, pentafluorohydroxyantimonate salt, hexafluorophosphate salt, hexafluoroarsenate salt, tetrakis(pentafluorophenyl)borate salt, pentafluoroethylphosphate salt, etc. One or more of the photocationic polymerization initiators may be used.

[0075] Examples of the photocationic polymerization initiator include sulfonium salts (particularly triarylsulfonium salts) such as triarylsulfonium hexafluorophosphate (for example, p-phenylthiophenyldiphenylsulfonium hexafluorophosphate) and triarylsulfonium hexafluoroantimonate; iodonium salts such as diaryliodonium hexafluorophosphate, diaryliodonium hexafluoroantimonate, bis(dodecylphenyl)iodonium tetrakis(pentafluorophenyl)borate and iodonium [4-(4-methylphenyl-2-methylpropyl)phenyl]hexafluorophosphate; phosphonium salts such as tetrafluorophosphonium hexafluorophosphate; and pyridinium salts such as N-hexylpyridinium tetrafluoroborate.

[0076] Specific examples of the photocationic polymerization initiator include (4-hydroxyphenyl)methylbenzylsulfonium tetrakis(pentafluorophenyl)borate, 4-(4-biphenylylthio)phenyl-4-biphenylylphenylsulfonium tetrakis(pentafluorophenyl)borate, 4-(phenylthio)phenyldiphenylsulfonium phenyltris(pentafluorophenyl)borate, [4-(4-biphenylylthio)phenyl]-4-biphenylylphenylsulfonium phenyltris(pentafluorophenyl)borate, and diphenyl[4-(phenylthio)phenyl]sulfonium Examples of such sulfonyl groups include tris(pentafluoroethyl)trifluorophosphate, diphenyl[4-(phenylthio)phenyl]sulfonium tetrakis(pentafluorophenyl)borate, diphenyl[4-(phenylthio)phenyl]sulfonium hexafluorophosphate, 4-(4-biphenylylthio)phenyl-4-biphenylylphenylsulfonium tris(pentafluoroethyl)trifluorophosphate, bis[4-(diphenylsulfonio)phenyl]sulfidophenyltris(pentafluorophenyl)borate, [4-(2-thioxanthonylthio)phenyl]phenyl-2-thioxanthonylsulfonium phenyltris(pentafluorophenyl)borate, and 4-(phenylthio)phenyldiphenylsulfonium hexafluoroantimonate.

[0077] The photocationic polymerization initiator may be a commercially available product. Examples of the commercially available product include trade names "Cyracure UVI-6970", "Cyracure UVI-6974", "Cyracure UVI-6990", and "Cyracure UVI-950" (all manufactured by Union Carbide Corporation, USA), "Omnirad 250", "Omnirad 261", "Omnirad 264", and "CG-24-61" (all manufactured by IGM). Resins Co., Ltd.), "OPTOMER SP-150", "OPTOMER SP-151", "OPTOMER SP-170", "OPTOMER SP-171" (all manufactured by ADEKA Corporation), "DAICATII" (manufactured by Daicel Corporation), "UVAC1590", "UVAC1591" (all manufactured by Daicel-Allnex Co., Ltd.), "CI-2064", "CI-2639", "CI-2624", "CI-2481", "CI-2734", "CI-2855", "CI-2823", "CI-2758", "CIT-1682" (all manufactured by Nippon Soda Co., Ltd.), "PI-2074" (tetrakis(pentafluorophenyl)borate tolylcumyl iodonium salt, manufactured by Rhodia), "FFC509" (manufactured by 3M), "BBI-102", "BBI-101", "BBI-103", "MPI-103", "TPS-103", "MDS-103", "DTS-103", "NAT-103", "NDS-103" (all manufactured by Midori Chemical Industry Co., Ltd.), "CD-1010", "CD-1011", "CD-1012" (all manufactured by Sartomer, USA), "CPI-100P", "CPI-101A" (all manufactured by San-Apro Ltd.), and the like.

[0078] The content of the cationic photopolymerization initiator is preferably 0.01 to 10 parts by mass, more preferably 0.1 to 7 parts by mass, and even more preferably 0.5 to 4 parts by mass, relative to the total amount (100 parts by mass) of the cationic curable compounds in the curable epoxy composition. When the content is 0.01 parts by mass or more, photocuring proceeds more easily and photocationic polymerization proceeds in a short period of time. When the content is 10 parts by mass or less, storage stability is improved.

[0079] (Polyol) The curable epoxy composition may contain a polyol. By incorporating a polyol, the cured product obtained by curing the curable epoxy composition can have a high glass transition temperature and high flexibility. This improves the heat resistance of the cured product of the curable epoxy composition. Furthermore, by incorporating a polyol, the reaction can proceed slowly. Only one type of polyol may be used, or two or more types may be used.

[0080] The polyol is a compound having two or more hydroxy groups in the molecule. Examples of the polyol include aliphatic polyols, alicyclic polyols, aromatic polyols, polyether polyols, polyester polyols, polycarbonate polyols, and polyolefin polyols. Among these, polyester polyols are preferred as the polyols, from the viewpoint of increasing the glass transition temperature and flexibility of the cured product.

[0081] The polyester polyols include compounds having two or more hydroxy groups and two or more ester bonds in the molecule, such as polylactone polyols (e.g., polycaprolactone polyols), aliphatic polyester polyols, aromatic polyester polyols, and alicyclic polyester polyols.

[0082] The polyester polyol 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, and from the same viewpoint, the polyester polyol preferably contains a polyester diol and / or a polyester triol.

[0083] The molecular weight of the polyol (particularly, polyester polyol) 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 flexibility 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 polyol means the number average molecular weight in terms of standard polystyrene, measured by gel permeation chromatography (GPC).

[0084] The hydroxyl value of the polyol (particularly, polyester polyol) 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 epoxy compound polymerization 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.

[0085] When the curable epoxy composition contains a polyol, the content of the polyol in the curable epoxy composition is not particularly limited, but is preferably 1 to 40 mass%, more preferably 3 to 30 mass%, and even more preferably 5 to 20 mass%, relative to the total amount (100 mass%) of the curable epoxy composition. When the content is within the above range, the cured product exhibits excellent heat resistance and flexibility. In particular, it is preferable that the content of the polyester polyol is within the above range.

[0086] (Inorganic Filler) The curable epoxy composition may contain an inorganic filler. The incorporation of an inorganic filler can impart thixotropy to the composition, thereby suppressing the settling of powder that may be contained in the composition, and can also impart low linear expansion to the cured product. Only one type of the inorganic filler may be used, or two or more types may be used.

[0087] The inorganic filler may be any known or conventional inorganic filler, and may include, but is 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, or molded products thereof (e.g., spherical beads). The inorganic filler may or may not be surface-treated. Examples of the surface-treated inorganic filler include the above-mentioned inorganic fillers that have been subjected to a known or conventional surface treatment. Among these, silica, alumina, and aluminum nitride are preferred as the inorganic filler, 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.

[0088] 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.

[0089] Examples of silica include hydrophilic silica and hydrophobic silica, but 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, thereby improving dispersibility, and it also imparts thixotropy to the curable epoxy composition, thereby improving workability such as impregnation and pourability.

[0090] 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, or an autoclave method.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] When the curable epoxy composition contains an inorganic filler, the content (blending amount) of the inorganic filler in the curable epoxy composition is not particularly limited, but is preferably 0.5 to 500 parts by mass, more preferably 10 to 400 parts by mass, even more preferably 30 to 350 parts by mass, and particularly preferably 50 to 320 parts by mass, relative to 100 parts by mass of the total amount of the cationic curable compounds contained in the curable epoxy composition. When the content is within the above range, the viscosity of the curable epoxy composition increases appropriately, and workability such as impregnation property and castability is improved.

[0095] When the curable epoxy composition contains an inorganic filler, the content of the inorganic filler in the curable epoxy composition is not particularly limited, but is preferably 0.5 to 95 mass %, more preferably 30 to 90 mass %, even more preferably 40 to 85 mass %, and particularly preferably 45 to 80 mass %, relative to the total amount (100 mass %) of the curable epoxy composition.

[0096] The curable epoxy composition may contain a cationic curable compound other than an epoxy compound. The content of the epoxy compound in the cationic curable compound in the curable epoxy composition is preferably 50% by mass or more, more preferably 60% by mass or more, still more preferably 70% by mass or more, still more preferably 80% by mass or more, still 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.

[0097] Furthermore, it is preferable that the curable epoxy compound is substantially free of curable compounds other than the cationically polymerizable compound (other curable compounds). In this specification, "substantially free" means that the other curable compounds are not actively added, excluding cases where the other curable compounds are unavoidably present. The proportion of the other curable compounds in the curable epoxy composition is preferably less than 1% by mass, more preferably less than 0.5% by mass, and even more preferably less than 0.1% by mass, relative to the total amount (100% by mass) of the curable compounds contained in the curable epoxy composition. By being substantially free of other curable compounds, the composition is less susceptible to curing inhibition by oxygen during photocuring, allowing for more thorough curing.

[0098] Examples of the other curable compounds include anionically polymerizable compounds, radically polymerizable compounds, etc. Examples of the radically polymerizable compounds include compounds having a radiation-active carbon-carbon double bond, such as compounds having a (meth)acryloyl group (an acryloyl group and / or a methacryloyl group).

[0099] The content of the polyol in the curable epoxy composition is preferably 5 to 45 parts by mass, more preferably 10 to 35 parts by mass, and even more preferably 15 to 30 parts by mass, relative to the total amount (100 parts by mass) of the curable compounds contained in the curable epoxy composition. When the content is within the above range, the cured product will have excellent heat resistance and flexibility.

[0100] The curable epoxy composition may contain other components in addition to the above-mentioned components. Examples of other components that can be used, within the scope of not impairing viscosity or transparency, include conventional additives such as silicone-based or fluorine-based antifoaming agents, leveling agents, coupling agents such as silane coupling agents such as γ-glycidoxypropyltrimethoxysilane or 3-mercaptopropyltrimethoxysilane, surfactants, flame retardants, colorants, antioxidants, ultraviolet absorbers, ion adsorbents, colorants, phosphors (e.g., YAG-based phosphor fine particles, inorganic phosphor fine particles such as silicate-based phosphor fine particles), release agents, thickeners, dispersants, rust inhibitors, corrosion inhibitors, freezing point depressants, and anti-wear additives. Only one of each of the above other components may be used, or two or more may be used.

[0101] The curable epoxy composition preferably does not substantially contain any curing agent (other curing agent) other than the cationic photopolymerization initiator. The content of the other curing agent is preferably less than 0.01 parts by mass, more preferably less than 0.005 parts by mass, relative to the total amount (100 parts by mass) of the cationically curable compounds in the curable epoxy composition. By substantially not containing any other curing agent, the storage stability of the curable epoxy composition is excellent.

[0102] Examples of the other curing agents include a thermal cationic polymerization initiator, an anionic polymerization initiator, a radical polymerization initiator, a curing accelerator, and a curing catalyst.

[0103] The curable epoxy composition is preferably liquid at 25°C. When the curable epoxy composition is liquid at 25°C, it exhibits excellent workability, such as impregnation, casting, and filling. The viscosity of the curable epoxy composition at 25°C is not particularly limited, but is preferably 330 mPa·s or higher (e.g., 330 to 100,000 mPa·s). When the viscosity is 330 mPa·s or higher, the composition does not drip after impregnation, and workability during impregnation and casting tends to be improved. When the viscosity is 100,000 mPa·s or lower, impregnation and workability during casting tend to be improved, and defects due to poor casting tend to be less likely to occur in the cured product. The viscosity of the curable epoxy composition at 25°C can be measured, for example, using a digital viscometer (model number "DVU-EII" manufactured by Tokimec Inc.) under the following conditions: rotor: standard 1°34' x R24, temperature: 25°C, and rotation speed: 0.5 to 10 rpm.

[0104] In one embodiment of the curable epoxy composition (e.g., when an inorganic filler is not included), the viscosity of the curable epoxy composition at 25°C is more preferably 400 mPa·s or more (e.g., 400 to 10,000 mPa·s), and even more preferably 450 mPa·s or more (e.g., 450 to 1,000 mPa·s). In another embodiment of the curable epoxy composition (e.g., when an inorganic filler is included), the viscosity of the curable epoxy composition at 25°C is more preferably 2,000 mPa·s or more (e.g., 2,000 to 100,000 mPa·s), 8,000 mPa·s or more (e.g., 8,000 to 80,000 mPa·s), and even more preferably 10,000 mPa·s or more (e.g., 10,000 to 70,000 mPa·s).

[0105] 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.

[0106] The curable epoxy composition of the present disclosure can be cured in a short time in the presence of oxygen and has excellent filling properties. Therefore, when a component having a complex structure is coated with the curable epoxy composition, dripping during curing is less likely to occur, and stickiness of the resin surface is quickly reduced, resulting in excellent handleability. Furthermore, the ability to cure in a short time leads to reduced CO2 emissions and a reduced environmental impact.

[0107] [Cured Product] A cured product can be obtained by curing the curable epoxy composition. Since the curable composition has photocurability and thermosetting properties, it is preferable to perform photocuring and thermosetting in this order. By first performing photocuring, dripping and stickiness (tackiness) after application of the curable epoxy composition are suppressed, resulting in excellent handleability, and by subsequently performing thermosetting, thermosetting can be performed in a short time.

[0108] The curable epoxy composition can be applied by a known or conventional method. When the curable epoxy composition is applied to an adherend, such as a component included in a rotating electrical machine having a complex shape, such as a coil, or a semiconductor, the adherend to be applied may be impregnated with the curable epoxy composition. After impregnation, the adherend is removed from the curable epoxy composition and photocured by irradiating it with active energy rays.

[0109] Examples of the active energy rays include ionizing radiation such as α rays, β rays, γ rays, neutron rays, and electron beams, as well as ultraviolet rays. The conditions for active energy ray irradiation are appropriately set depending on the type of active energy ray, but for example, an illuminance of 5 to 300 mW / cm 2 , irradiation amount 50-18000mJ / cm 2 The irradiation time is preferably from 10 seconds to 5 minutes, more preferably from 20 seconds to 1 minute.

[0110] Following the photocuring, thermal curing is performed. The temperature for thermal curing (curing temperature) is not particularly limited, but is preferably 45 to 200°C, more preferably 50 to 190°C, and even more preferably 55 to 180°C. The heating time for curing (curing time) is also not particularly limited, but is preferably 5 to 60 minutes, more preferably 10 to 45 minutes. By performing thermal curing after photocuring, the curable epoxy composition can shorten the thermal curing time, and a cured product with a high degree of cure can be obtained even within the above curing time. Furthermore, each curing can be performed in a single stage, or in multiple stages of two or more stages.

[0111] The glass transition temperature (Tg-DMA) of the cured product is preferably at least 78° C., more preferably at least 80° C., and even more preferably at least 100° C. When the glass transition temperature is at least 78° C., the heat resistance is excellent.

[0112] The glass transition temperature (Tg-TMA) of the cured product is preferably 40° C. or higher, more preferably 50° C. or higher, and even more preferably 60° C. or higher. When the glass transition temperature is 40° C. or higher, the heat resistance is excellent.

[0113] In one embodiment (e.g., when no inorganic filler is contained), the elastic modulus of the cured product at 25°C is preferably 1.0 to 10.0 GPa, more preferably 2.0 to 6.0 GPa, and even more preferably 3.0 to 5.0 GPa. In another embodiment (e.g., when an inorganic filler is contained), the elastic modulus of the cured product at 25°C is preferably 12.0 to 30.0 GPa, more preferably 14.0 to 28.0 GPa, and even more preferably 16.0 to 26.0 GPa. When the elastic modulus is equal to or greater than the lower limit, the product easily follows the movement of an adherend such as a rotating electrical machine or a semiconductor, and exhibits superior adhesion to the adherend. When the elastic modulus is equal to or less than the upper limit, the internal stress is more appropriate. The elastic modulus can be measured by viscoelasticity measurement.

[0114] In one embodiment (e.g., when an inorganic filler is not included), the linear expansion coefficient (α1) of the cured product in the temperature range lower than the Tg is preferably 90 ppm / °C or less (e.g., 20 to 90 ppm / °C), more preferably 80 ppm / °C or less (e.g., 30 to 80 ppm / °C), and even more preferably 70 ppm / °C or less (e.g., 40 to 70 ppm / °C). In another embodiment (e.g., when an inorganic filler is included), the linear expansion coefficient (α1) is preferably 200 ppm / °C or less (e.g., 5 to 200 ppm / °C), more preferably 100 ppm / °C or less (e.g., 7 to 100 ppm / °C), and even more preferably 30 ppm / °C or less (e.g., 10 to 30 ppm / °C). When the linear expansion coefficient (α1) is below the upper limit, the product is less likely to deform due to temperature changes and has excellent coating properties on the adherend.

[0115] In one embodiment (e.g., when an inorganic filler is not included), the linear expansion coefficient (α2) in the temperature range higher than the Tg of the cured product is preferably 220 ppm / °C or less (e.g., 60 to 220 ppm / °C), more preferably 200 ppm / °C or less (e.g., 70 to 200 ppm / °C), and even more preferably 180 ppm / °C or less (e.g., 100 to 180 ppm / °C). In another embodiment (e.g., when an inorganic filler is included), the linear expansion coefficient (α2) is preferably 90 ppm / °C or less (e.g., 20 to 90 ppm / °C), more preferably 85 ppm / °C or less (e.g., 30 to 85 ppm / °C), and even more preferably 80 ppm / °C or less (e.g., 40 to 80 ppm / °C). When the linear expansion coefficient (α2) is below the upper limit, the product is less likely to deform due to temperature changes and has excellent coating properties on the adherend.

[0116] The curable epoxy composition and the cured product are used in components included in rotating electrical machines (rotating electrical machine applications) and / or semiconductor applications. Because the cured product has excellent heat resistance, it can be preferably used in components used in high-heat environments, particularly automotive components (such as EV motor applications). Specific uses of the cured product include insulating materials, coating materials, adhesives, etc. The curable epoxy composition has excellent wettability, impregnation, and filling properties for the object to be coated. Therefore, the curable epoxy composition can be preferably used in processes such as atmospheric pressure impregnation, reduced-pressure impregnation, pressure impregnation, and dipping.

[0117] 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.

[0118] The curable epoxy composition and the cured product are preferably used for coil impregnation, such as impregnation and casting of coils (wires, windings) in stators and rotors of rotating electrical machines.

[0119] 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 coils; 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.

[0120] Examples of the semiconductor applications include semiconductor encapsulation and semiconductor underfill. By using the cured product in the semiconductor application, the curable epoxy composition can be cured in a short time in the presence of oxygen, thereby suppressing thermal damage to the semiconductor. Furthermore, it is particularly preferable that the semiconductor is a power semiconductor. Power semiconductors require higher insulating properties than ordinary semiconductors, and the curable epoxy composition is less likely to drip, so that thick films can be easily formed even when recoated to provide sufficient insulating properties.

[0121] 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.

[0122] Hereinafter, one embodiment of the present disclosure will be described in more detail based on examples.

[0123] Example 1 (Preparation of curable composition) An alicyclic epoxy compound (trade name "Celloxide 2021P", manufactured by Daicel Corporation), a polyester polyol (trade name "Placcel 220", manufactured by Daicel Corporation), and diphenyl[4-(phenylthio)phenyl]sulfonium tris(pentafluoroethyl)trifluorophosphate (curing agent A) as a UV cationic polymerization initiator were charged into an ointment container in the blending ratios (unit: parts by mass) shown in Table 1, and the mixture was mixed uniformly using a planetary stirring device (trade name "Awatori Rentaro AR-250", manufactured by Thinky Corporation), followed by degassing to prepare a curable composition that was liquid at 25°C.

[0124] (Preparation of cured product) The curable composition obtained above was filled into a mold, sandwiched between glass plates, and the illuminance was adjusted with an illuminance meter (product name "Ultraviolet Illuminance Meter UIT-201", manufactured by Ushio Inc.). After that, the surface was irradiated with ultraviolet light in the atmosphere using a UV irradiator (product name "San Ace 120", manufactured by Sanyo Denki Co., Ltd.), followed by thermal curing in an oven to prepare a cured product. The irradiation conditions are as shown in Table 2.

[0125] Examples 2 to 8, Comparative Example 1 (Preparation of Curable Compositions) Curable compositions that were liquid at 25°C were prepared in the same manner as in Example 1, except that the composition of the curable epoxy composition was changed to the composition shown in Table 1.

[0126] (Preparation of cured product) The curable composition obtained above was filled into a mold, sandwiched between glass plates, and the illuminance was adjusted with an illuminance meter (product name "Ultraviolet Illuminance Meter UIT-201", manufactured by Ushio Inc.). After that, the surface was irradiated with ultraviolet light in the atmosphere using a UV irradiator (product name "San Ace 120", manufactured by Sanyo Denki Co., Ltd.), followed by thermal curing in an oven to prepare a cured product. The irradiation conditions are as shown in Table 2 or 3.

[0127]

[0128] The components used in the examples and comparative examples are as follows: (Epoxy compounds) CELLOXIDE 2021P: Trade name "CELLOXIDE 2021P", manufactured by Daicel Corporation, 3,4-epoxycyclohexylmethyl (3,4-epoxy) cyclohexanecarboxylate TEPIC-FL: Trade name "TEPIC-FL", manufactured by Nissan Chemical Industries, Ltd., triepoxy isocyanurate type compound TEPIC-UC: Trade name "TEPIC-UC", manufactured by Nissan Chemical Industries, Ltd., hexaepoxy isocyanurate type compound YX8000: Trade name "YX8000", manufactured by Mitsubishi Chemical Corporation, hydrogenated bisphenol type diglycidyl compound jER 806: Trade name "jER 806", manufactured by Mitsubishi Chemical Corporation, bisphenol F type epoxy resin YD128: Trade name "YD-128", manufactured by Nippon Steel Chemical & Material Co., Ltd., bisphenol A diglycidyl ether (Polyol) PCL: Trade name "Placcel" 220", manufactured by Daicel Corporation, aliphatic polyester diol, molecular weight 2000, hydroxyl value 56.8 KOHmg / g (acrylic monomer) Viscoat #230: trade name "Viscoat #230", manufactured by Osaka Organic Chemical Industry Ltd., 1,6-hexanediol diacrylate (additive) Silica filler: manufactured by Denka Co., Ltd., non-surface treated, median particle size approximately 0.1 to 100 μm, spherical shape (UV cationic polymerization initiator) Curing agent A: diphenyl[4-(phenylthio)phenyl]sulfonium tris(pentafluoroethyl)trifluorophosphate Curing agent B: triarylsulfonium salt (radical polymerization initiator) Omnirad 184: trade name "Omnirad 184", manufactured by IGM Resins, 1-hydroxycyclohexyl phenyl ketone

[0129] <Evaluation> The following evaluation tests were carried out on the curable compositions and cured products obtained in the examples and comparative examples. Note that the physical properties of the cured product in Comparative Example 1 were evaluated using a cured product prepared by irradiating with ultraviolet light under a nitrogen gas flow instead of under air.

[0130] (Viscoelasticity Measurement) The cured product was subjected to viscoelasticity measurement using a solid viscoelasticity measuring device (trade name "DMA 7100", manufactured by Hitachi High-Tech Science Corporation) under conditions of a nitrogen gas flow, a temperature rise rate of 5°C / min, a measurement temperature range of -50 to 300°C, a deformation mode of tension, and a frequency of 1 Hz, to measure the elastic modulus at 25°C. The inflection point of the obtained temperature thermal history change curve was then taken as the glass transition temperature (Tg-DMA).

[0131] (Thermomechanical analysis) The cured product was subjected to thermomechanical analysis using a thermomechanical analyzer (trade name "TMA 6100", manufactured by Hitachi High-Tech Science Corporation) under conditions of a nitrogen gas flow, a heating rate of 5°C / min, and a measurement temperature of 30 to 300°C. The inflection point of the obtained temperature thermal history change curve was designated as the glass transition temperature (Tg-TMA), and the linear expansion coefficients (α1, α2) were calculated from the change curve before and after the glass transition temperature.

[0132] (Differential Scanning Calorimetry) For the curable compositions of Examples 6 to 8, ultraviolet light was irradiated under nitrogen flow using a differential scanning calorimeter (trade name "DSC 6200", manufactured by Seiko Instruments Inc.) equipped with a UV irradiator (trade name "San Ace 120", manufactured by Sanyo Denki Co., Ltd.) at a temperature of 30°C and an irradiation intensity of 200 mW x 10 sec. Differential scanning calorimetry was performed on the samples after ultraviolet light irradiation under nitrogen flow at a temperature rise rate of 10°C / min and a measurement temperature range of 30 to 300°C. The heat generated between the inflection point (glass transition temperature) and 300°C of the obtained temperature thermal history change curve was taken as the residual heat, and the degree of cure was calculated.

[0133] (Curability (i)) After irradiation with ultraviolet light in the atmosphere, which was carried out to prepare a cured product, the case where there was no curing failure was evaluated as "good", and the case where there was curing failure was evaluated as "poor".

[0134] (Curability (ii)) After heat curing in the preparation of the cured product, the cured product was evaluated as "good" if there was no curing defect, and as "poor" if there was curing defect.

[0135] (Handling properties) After UV irradiation in the atmosphere, which was carried out to prepare a cured product, if no dripping or tackiness occurred, the product was evaluated as "Good", and if dripping or tackiness occurred, the product was evaluated as "Poor".

[0136]

[0137]

[0138] As can be seen from Table 2, the curable compositions of Examples 1 to 5 could be cured by UV irradiation under atmospheric conditions and had excellent handleability. Furthermore, heat curing could be performed in a short time of 30 minutes, and the curability after heat curing was excellent. On the other hand, the curable composition of Comparative Example 1 was insufficiently cured by UV irradiation under atmospheric conditions and had poor handleability. Furthermore, in Comparative Example 1, curing did not proceed sufficiently by UV irradiation under atmospheric conditions, and therefore, curing was insufficient with a heat curing time of 30 minutes.

[0139] The curable compositions of Examples 6 to 8 contain an inorganic filler, but as can be seen from Table 3, they could be cured by ultraviolet irradiation in the atmosphere and had excellent handleability. Furthermore, they could be thermally cured in a short time of 15 minutes, and had excellent curability after thermal curing. Furthermore, the curable compositions of the Examples were liquid at 25°C and had excellent filling and impregnation properties.

[0140] Variations of the invention according to the present disclosure are described below. [Appendix 1] A curable epoxy composition comprising an epoxy compound having an epoxy group in the molecule and a photocationic polymerization initiator, and suitable for use in rotating electrical machines and / or semiconductors. [Appendix 2] The curable epoxy composition according to Appendices 1, comprising an alicyclic epoxy compound as the epoxy compound. [Appendix 3] The curable epoxy composition according to Appendices 1 or 2, comprising an aromatic epoxy compound as the epoxy compound. [Appendix 4] The curable epoxy composition according to any one of Appendices 1 to 3, comprising an aliphatic epoxy compound as the epoxy compound. [Appendix 5] The curable epoxy composition according to any one of Appendices 1 to 4, comprising a heterocyclic epoxy compound as the epoxy compound. [Appendix 6] The curable epoxy composition according to Appendices 5, comprising an epoxy compound having an isocyanuric ring as the heterocyclic epoxy compound. [Appendix 7] The curable epoxy composition according to Appendices 6, comprising a compound represented by the following formula (iii) as the epoxy compound having an isocyanuric ring: (In formula (iii), R 4 ~R 6 are the same or different and represent a hydrogen atom or a monovalent organic group. 4 ~R 6 at least one of which is a monovalent organic group containing an epoxy group.) [Appendix 8] The curable epoxy composition according to any one of Appendices 5 to 7, which contains an epoxy compound having a glycoluril ring as the heterocyclic epoxy compound. [Appendix 9] The curable epoxy composition according to Appendices 8, which contains a compound represented by the following formula (iv) as the epoxy compound having a glycoluril ring: (In formula (iv), R 9 ~R 12 are the same or different and represent a hydrogen atom or a monovalent organic group. 9 ~R 12 At least one of R is a monovalent organic group containing an epoxy group. 13 and R 14are the same or different and represent a hydrogen atom or a monovalent organic group.) [Appendix 10] The curable epoxy composition according to any one of Appendices 1 to 9, wherein the content of the epoxy compound is 60 to 99.5 mass%, based on the total amount (100 mass%) of the curable epoxy composition. [Appendix 11] The curable epoxy composition according to any one of Appendices 1 to 10, which is substantially free of a curing agent other than the cationic photopolymerization initiator. [Appendix 12] The curable epoxy composition according to any one of Appendices 1 to 11, which comprises a polyol. [Appendix 13] The curable epoxy composition according to Appendices 12, which comprises a polyester polyol as the polyol. [Appendix 14] The curable epoxy composition according to Appendices 12 or 13, wherein the molecular weight of the polyol is 600 or more and 50,000 or less. [Appendix 15] The curable epoxy composition according to any one of Appendices 12 to 14, wherein the acid group value of the polyol is 600 KOHmg / g or less. [Appendix 16] The curable epoxy composition according to any one of Appendices 12 to 15, wherein the content of the polyol is 1 to 40% by mass, relative to the total amount (100% by mass) of the curable epoxy composition. [Appendix 17] The curable epoxy composition according to any one of Appendices 1 to 16, wherein the content of the epoxy compound relative to the total amount of cationic curable compounds is 90% by mass or more. [Appendix 18] The curable epoxy composition according to any one of Appendices 1 to 17, which is substantially free of a radically polymerizable compound. [Appendix 19] The curable epoxy composition according to any one of Appendices 1 to 18, which contains an inorganic filler. [Appendix 20] The curable epoxy composition according to Appendice 19, which contains silica as the inorganic filler. [Appendix 21] The curable epoxy composition according to any one of Appendices 1 to 18, wherein the specific surface area of ​​the silica is 10 m 2 / g or more. [Appendix 22] The curable epoxy composition according to Appendices 20 or 21, wherein the silica has a median particle size of 3 nm or more and 200 nm or less. [Appendix 23] The curable epoxy composition according to Appendices 20 or 21, wherein the silica has a median particle size of 0.1 to 30 μm. [Appendix 24] The curable epoxy composition according to any one of Appendices 20 to 23, wherein the content of the inorganic filler is 0.5 to 500 parts by mass per 100 parts by mass of the total amount of cationic curable compounds contained in the curable epoxy composition. [Appendix 25] The curable epoxy composition according to any one of Appendices 1 to 24, which is liquid at 25°C. [Appendix 26] The curable epoxy composition according to any one of Appendices 1 to 25, which is used for impregnating a stator coil of the rotating electric machine, or for fixing a magnet inserted into a hole provided in a rotor core of the rotating electric machine to the inner wall of the hole. [Appendix 27] A cured product of the curable epoxy composition according to any one of Appendices 1 to 26. [Appendix 28] A stator for a rotating electric machine, comprising the cured product according to Appendices 27 formed so as to cover a stator coil. [Appendix 29] A rotor for a rotating electric machine, comprising the cured product according to Appendices 27 covering a rotor winding.

Claims

1. A curable epoxy composition comprising an epoxy compound having an epoxy group in the molecule and a photocationic polymerization initiator, the curable epoxy composition being intended for use in rotating electrical machines and / or semiconductors.

2. The curable epoxy composition according to claim 1, which is substantially free of any curing agent other than the photocationic polymerization initiator.

3. The curable epoxy composition according to claim 1 or 2, which comprises a polyol.

4. The curable epoxy composition according to claim 1 or 2, wherein the content of the epoxy compound relative to the total amount of the cationic curable compound is 90 mass% or more.

5. The curable epoxy composition according to claim 1 or 2, which is substantially free of radically polymerizable compounds.

6. A curable epoxy composition according to claim 1 or 2, which contains an inorganic filler.

7. A curable epoxy composition according to claim 1 or 2, which is liquid at 25°C.

8. A curable epoxy composition according to claim 1 or 2, which is used for impregnating a stator coil of the rotating electric machine, or for fixing a magnet inserted into a hole provided in a rotor core of the rotating electric machine to the inner wall of the hole.

9. A cured product of the curable epoxy composition according to claim 1 or 2.

10. A stator for a rotating electric machine comprising the hardened material according to claim 9 formed so as to cover a stator coil.

11. A rotor for a rotating electric machine, comprising the cured material according to claim 9 coating a winding of the rotor.

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