Insulating material for stator, stator, and method for manufacturing a stator

Abstract

The present invention provides an insulating material for stators that exhibits excellent fracture elongation and copper adhesion strength of the cured product, as well as a stator having a coil insulated by the stator insulating material and a method for manufacturing the same. [Solution] A stator insulating material comprising an epoxy resin containing an alicyclic structure and a biphenyl-type epoxy resin, a curing agent, and an inorganic filler, used for insulating between coils of a stator, and a stator having coils insulated by the stator insulating material and a method for manufacturing the same.

Description

[Technical Field]

[0001] The present disclosure relates to an insulating material for a stator, a stator, and a method for manufacturing a stator. [Background Art]

[0002] Conventionally, a method using varnish has generally been used for fixing a stator coil in a motor. On the other hand, since varnish has low strength and low resistance to motor vibration and the like, a technique for fixing a coil by resin molding has been developed. For example, Patent Document 1 proposes an insulating material for a stator containing an epoxy resin, a curing agent, and a spherical inorganic filler.

[0003] Various other materials have been proposed as materials for insulating electrical and electronic components. For example, Patent Document 2 describes a urethane resin composition containing a polyol compound, a polyisocyanate compound, a plasticizer, an inorganic filler, and an antioxidant. Patent Document 3 describes a heat-dissipating resin composition containing, at a specific ratio, at least one thermosetting resin selected from the group consisting of unsaturated polyester resins, epoxy resins, urethane resins, and silicone resins, a specific thermally conductive filler, and a crosslinking agent. Patent Document 4 proposes a resin composition for a rotor containing a thermosetting resin including an epoxy resin, a curing agent, and an inorganic filler in a specific proportion. [Prior Art Documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2022 / 030252 [Patent Document 2] Japanese Unexamined Patent Application Publication No. 2008-120998 [Patent Document 3] Japanese Unexamined Patent Application Publication No. 2017-137410 [Patent Document 4] International Publication No. 2012 / 029278 [Summary of the Invention] [Problems that the invention aims to solve]

[0005] When using resin molds made of insulating materials, it is desirable that the cured product has high elongation at break and excellent copper adhesion strength, in order to ensure excellent insulation even under high-temperature conditions in an engine compartment during the summer. In view of these circumstances, this disclosure relates to an insulating material for stators that has excellent elongation at break and copper adhesion strength in the cured product, as well as a stator having a coil insulated by the stator insulating material and a method for manufacturing the same. [Means for solving the problem]

[0006] The means for solving the above problems include the following embodiments. <1> An insulating material for stators, comprising an epoxy resin containing an alicyclic structure and a biphenyl-type epoxy resin, a curing agent, and an inorganic filler, used for insulating between coils of a stator. <2> The alicyclic structure-containing epoxy resin includes a dicyclopentadiene-modified epoxy resin which is a glycidyl ether of a dicyclopentadiene-modified phenol resin. <1> The stator insulating material described above. <3> The content of the alicyclic structure-containing epoxy resin relative to the total amount of the epoxy resin is 10% by mass to 70% by mass. <1> or <2> The stator insulating material described above. <4> The curing agent includes a phenol curing agent. <1> ~ <3> Stator insulating material as described in any one of the items. <5> The inorganic filler comprises at least one selected from the group consisting of silica, alumina, and magnesium oxide. <1> ~ <4> Stator insulating material as described in any one of the items. <6> The inorganic filler content relative to the total amount of the stator insulating material is 50% by mass or more. <1> ~ <5> Stator insulating material as described in any one of the items. <7> The maximum particle size of the inorganic filler is 150 μm or less. <1> ~ <6> Stator insulating material as described in any one of the items. <8> Furthermore, it contains a curing accelerator, <1> ~ <7> Stator insulating material as described in any one of the items. <9> When the stator insulating material is molded using a spiral flow measurement mold conforming to EMMI-1-66 under the conditions of a mold temperature of 175°C, a molding pressure of 6.9 MPa, and a curing time of 90 seconds, the flow distance is 100 cm or more. <1> ~ <8> Stator insulating material as described in any one of the items. <10> The stator insulating material is molded using a transfer molding machine under the conditions of a mold temperature of 175°C, a molding pressure of 6.9 MPa, and a curing time of 90 seconds. The cured product, after curing at 175°C for 5 hours, has a bending modulus of elasticity at 260°C of 600 MPa or less in a bending test. <1> ~ <9> Stator insulating material as described in any one of the items. <11> The stator insulating material was molded using a transfer molding machine under the conditions of a mold temperature of 175°C, a molding pressure of 6.9 MPa, and a curing time of 90 seconds. The cured product, after curing at 175°C for 5 hours, exhibited a fracture elongation of 1.5% or more at 260°C in a bending test. <1> ~ <10> Stator insulating material as described in any one of the items. <12> The stator insulating material is molded using a transfer molding machine under the conditions of a mold temperature of 175°C, a molding pressure of 6.9 MPa, and a curing time of 120 seconds. The cured product, after curing at 175°C for 5 hours, has a copper adhesion strength of 1.3 MPa or more at 260°C. <1> ~ <11> Stator insulating material as described in any one of the items. <13> <1> ~ <12> A stator having coils insulated with the stator insulating material described in any one of the items. <14> <1> ~ <12> A method for manufacturing a stator, comprising insulating the coils with an insulating material for stators as described in any one of the items. <15> The insulation between the coils is performed by transfer molding. <14> A method for manufacturing a stator as described above. [Effects of the Invention]

[0007] This disclosure provides an insulating material for stators that exhibits excellent fracture elongation and copper adhesion strength of the cured product, as well as a stator having a coil insulated by the stator insulating material and a method for manufacturing the same. [Modes for carrying out the invention]

[0008] The embodiments for carrying out the present invention will be described in detail below. However, the present invention is not limited to the following embodiments. In the following embodiments, the components (including elemental steps, etc.) are not essential unless otherwise specified. The same applies to numerical values ​​and their ranges, and they do not limit the present invention.

[0009] In this disclosure, the term "process" includes not only processes that are independent of other processes, but also processes that cannot be clearly distinguished from other processes, provided that the purpose of such process is achieved. In this disclosure, the numerical range indicated using "~" includes the numbers before and after "~" as the minimum and maximum values, respectively. In numerical ranges described in stages within this disclosure, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in numerical ranges described within this disclosure, the upper or lower limit of that range may be replaced with the values ​​shown in the examples. In this disclosure, each component may contain multiple types of the corresponding substance. If multiple types of the substance corresponding to each component are present in the composition, the content or amount of each component means the total content or amount of the multiple types of substances present in the composition, unless otherwise specified. In this disclosure, each component may contain multiple types of particles. If multiple types of particles corresponding to each component are present in the composition, the particle size of each component refers to the value for a mixture of such multiple types of particles present in the composition, unless otherwise specified. In this disclosure, unless otherwise specified, the content or percentage of each component in a composition refers to the content or percentage based on the amount excluding volatile components such as solvents, if such volatile components are present in the composition. "Volatile component" means a component that volatilizes when heated at 150°C for 1 hour. In this disclosure, for convenience, the components of the composition excluding inorganic fillers (and volatile components, if present) may be referred to as "resin components."

[0010] <<Insulating material for stator>> The stator insulating material of this disclosure comprises an epoxy resin containing an alicyclic structure and a biphenyl-type epoxy resin, a curing agent, and an inorganic filler, and is used for insulating between coils of a stator. The stator insulating material of this disclosure exhibits excellent elongation at break and copper adhesion strength of the cured product. The reason for this is not entirely clear, but it is presumed to be as follows: The alicyclic structure-containing epoxy resin has a flexible and stretchable skeleton of alicyclic structure, and the biphenyl-type skeleton is also a skeleton in which molecular chain displacement is less likely to occur and crystallization is easily performed, so it is thought that the cured product exhibits excellent elongation at break. In addition, since the alicyclic structure-containing epoxy resin has a highly mobile skeleton, it is thought to interact easily with copper atoms, so it is thought that the copper adhesion strength is also improved. Furthermore, the stator insulating material disclosed herein tends to exhibit excellent fluidity during melting. Since alicyclic structure-containing epoxy resins are less prone to molecular stacking, their viscosity during melting is thought to be less likely to increase. Similarly, biphenyl-type epoxy resins also have relatively low melt viscosity; therefore, insulating materials containing both alicyclic structure-containing epoxy resins and biphenyl-type epoxy resins are thought to have low melt viscosity and high fluidity. It has also been found that using alicyclic structure-containing epoxy resins can yield cured products with low flexural modulus, which is also thought to contribute to improved strength. However, the stator insulating material disclosed herein is not limited in any way by the above-described presumed mechanism.

[0011] <Epoxy resin> The insulating material for a stator contains an epoxy resin including an alicyclic structure-containing epoxy resin and a biphenyl-type epoxy resin. The insulating material for a stator may or may not contain an epoxy resin other than the alicyclic structure-containing epoxy resin and the biphenyl-type epoxy resin. The total content of the alicyclic structure-containing epoxy resin and the biphenyl-type epoxy resin relative to the total amount of epoxy resin in the insulating material for a stator is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 90% by mass or more, and may be 100% by mass. The epoxy resin may be solid or liquid at 25°C and atmospheric pressure, and is preferably solid.

[0012] The alicyclic structure-containing epoxy resin is not particularly limited as long as it is an epoxy resin containing an alicyclic structure, and may or may not contain an aromatic ring. Examples of the alicyclic structure-containing epoxy resin include alicyclic epoxy resins such as vinylcyclohexene diepoxide obtained by epoxidizing an olefin bond in a molecule, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, and 2-(3,4-epoxy)cyclohexyl-5,5-spiro(3,4-epoxy)cyclohexane-m-dioxane; dicyclopentadiene-modified epoxy resin which is a glycidyl ether of dicyclopentadiene-modified phenol resin (hereinafter simply referred to as "dicyclopentadiene-modified epoxy resin"); and cyclopentadiene-modified epoxy resin which is a glycidyl ether of cyclopentadiene-modified phenol resin. Among these, dicyclopentadiene-modified epoxy resin is preferable.

[0013] From the viewpoint of favorably exhibiting the above properties, the content of the alicyclic structure-containing epoxy resin relative to the total amount of epoxy resins is preferably 10% by mass or more, more preferably 20% by mass or more, and still more preferably 30% by mass or more. From the viewpoint of favorably exhibiting the properties of other epoxy resins, the content of the alicyclic structure-containing epoxy resin relative to the total amount of epoxy resins is preferably 70% by mass or less, more preferably 60% by mass or less, and still more preferably 50% by mass or less. From this standpoint, the content of the alicyclic structure-containing epoxy resin relative to the total amount of epoxy resins is preferably 10% by mass to 70% by mass, more preferably 20% by mass to 60% by mass, and still more preferably 30% by mass to 50% by mass. When the epoxy resin contains dicyclopentadiene-modified epoxy resin, the content of the dicyclopentadiene-modified epoxy resin relative to the total amount of epoxy resins is preferably within the above range.

[0014] Biphenyl-type epoxy resin is diglycidyl ether of alkyl-substituted or unsubstituted biphenol. The use of biphenyl-type epoxy resin tends to improve the fluidity of the insulating material for stators. In addition, when the insulating material for stators contains a release agent, the bleeding out of the release agent is improved, and the release property tends to be enhanced. When the epoxy resin contains biphenyl-type epoxy resin, from the viewpoint of favorably exhibiting the above properties, the content of the biphenyl-type epoxy resin relative to the total amount of epoxy resins is preferably 30% by mass or more, more preferably 40% by mass or more, and still more preferably 50% by mass or more. From the viewpoint of favorably exhibiting the properties of other epoxy resins, the content of the biphenyl-type epoxy resin relative to the total amount of epoxy resins is preferably 90% by mass or less, more preferably 80% by mass or less, and still more preferably 70% by mass or less. From this standpoint, the content of the biphenyl-type epoxy resin relative to the total amount of epoxy resins is preferably 30% by mass to 90% by mass, more preferably 40% by mass to 80% by mass, and still more preferably 50% by mass to 70% by mass.

[0015] From the viewpoint of exhibiting the properties of the alicyclic structure-containing epoxy resin well, the content of the alicyclic structure-containing epoxy resin relative to the total amount of the alicyclic structure-containing epoxy resin and the biphenyl-type epoxy resin is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more. From the viewpoint of exhibiting the properties of the biphenyl-type epoxy resin well, the content is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less. From this viewpoint, the content is preferably 10% by mass to 90% by mass, more preferably 20% by mass to 80% by mass, and even more preferably 30% by mass to 70% by mass.

[0016] Epoxy resins other than alicyclic structure-containing epoxy resins and biphenyl-type epoxy resins include novolac resins obtained by condensing or co-condensing at least one phenolic compound selected from the group consisting of phenolic compounds such as phenol, cresol, xylenol, resorcinol, catechol, bisphenol A, and bisphenol F, and naphthol compounds such as α-naphthol, β-naphthol, and dihydroxynaphthalene, with an aliphatic aldehyde compound such as formaldehyde, acetaldehyde, or propionaldehyde under an acidic catalyst, and then epoxidizing the novolac resin. Novolac-type epoxy resins (phenol novolac-type epoxy resins, orthocresol novolac-type epoxy resins, etc.); triphenylmethane-type epoxy resins obtained by condensing or co-condensing the above-mentioned phenolic compound with an aromatic aldehyde compound such as benzaldehyde or salicylaldehyde under an acidic catalyst, and then epoxidizing the triphenylmethane-type phenolic resin; copolymer-type epoxy resins obtained by co-condensing the above-mentioned phenolic compound and naphthol compound with an aldehyde compound, and then epoxidizing the novolac resin obtained under an acidic catalyst. Resins; Diphenylmethane-type epoxy resins, which are diglycidyl ethers of bisphenol A, bisphenol F, etc.; Stilbene-type epoxy resins, which are diglycidyl ethers of stilbene-based phenol compounds; Sulfur atom-containing epoxy resins, which are diglycidyl ethers of bisphenol S, etc.; Epoxy resins, which are glycidyl ethers of alcohols such as butanediol, polyethylene glycol, and polypropylene glycol; Glycidyl ester-type epoxy resins, which are glycidyl esters of polycarboxylic acid compounds such as phthalic acid, isophthalic acid, and tetrahydrophthalic acid; Glycidylamine-type epoxy resins, in which the active hydrogen bonded to the nitrogen atom of aniline, diaminodiphenylmethane, isocyanuric acid, etc., is replaced by a glycidyl group; Paraxylylene-modified epoxy resins, which are glycidyl ethers of paraxylylene-modified phenol resins; Metaxylylene-modified epoxy resins, which are glycidyl ethers of metaxylylene-modified phenol resins; Terpene-modified epoxy resins, which are glycidyl ethers of terpene-modified phenol resins; Polycyclic aromatic ring-modified epoxy resins, which are glycidyl ethers of polycyclic aromatic ring-modified phenol resins;Examples of epoxy resins include naphthalene-type epoxy resins, which are glycidyl ethers of naphthalene ring-containing phenolic resins; halogenated phenol novolac-type epoxy resins; hydroquinone-type epoxy resins; trimethylolpropane-type epoxy resins; linear aliphatic epoxy resins obtained by oxidizing olefin bonds with peracids such as peracetic acid; and aralkyl-type epoxy resins, which are epoxidized aralkyl-type phenolic resins such as phenol aralkyl resins and naphthol aralkyl resins. Furthermore, epoxides of silicone resins and acrylic resins can also be cited as epoxy resins. Note that examples of epoxy resins other than the above-mentioned alicyclic structure-containing epoxy resins and biphenyl-type epoxy resins do not possess an alicyclic structure. Epoxy resins may be used individually or in combination of two or more types.

[0017] The epoxy equivalent (molecular weight / number of epoxy groups) of the epoxy resin is not particularly limited. From the viewpoint of mechanical strength, the epoxy equivalent of the epoxy resin is preferably 100 g / eq to 1000 g / eq, more preferably 150 g / eq to 500 g / eq, and even more preferably 150 g / eq to 300 g / eq. The epoxy equivalent of the alicyclic structure-containing epoxy resin is preferably 150 g / eq to 500 g / eq, and more preferably 150 g / eq to 300 g / eq. The epoxy equivalent of the biphenyl-type epoxy resin is preferably 140 g / eq to 250 g / eq, and more preferably 150 g / eq to 200 g / eq. The epoxy equivalent of the epoxy resin shall be the value measured according to the method conforming to JIS K 7236:2009.

[0018] When the epoxy resin is solid, its softening point or melting point is not particularly limited. From the viewpoint of moldability, the softening point or melting point of the epoxy resin is preferably 40°C to 180°C, more preferably 50°C to 130°C, and even more preferably 50°C to 100°C, from the viewpoint of ease of handling when preparing the insulating material for the stator. The softening point or melting point of the alicyclic structure-containing epoxy resin is preferably 40°C to 180°C, more preferably 50°C to 130°C, and even more preferably 50°C to 100°C, from the viewpoint of ease of handling when preparing the insulating material for the stator. The softening or melting point of the biphenyl-type epoxy resin is preferably 40°C to 180°C, more preferably 60°C to 130°C, and even more preferably 80°C to 110°C, from the viewpoint of ease of handling when preparing the insulating material for the stator. The melting point of the epoxy resin shall be the value measured by differential scanning calorimetry (DSC), and the softening point of the epoxy resin shall be the value measured by the method (ring-ball method) in accordance with JIS K 7234:1986.

[0019] The epoxy resin content relative to the total amount of stator insulating material is not particularly limited. From the viewpoint of fluidity, fillability, etc., the epoxy resin content is preferably 5% by mass or more, and more preferably 6% by mass or more, relative to the total amount of stator insulating material. Furthermore, from the viewpoint of mechanical strength, etc., the epoxy resin content is preferably 20% by mass or less, and more preferably 15% by mass or less, relative to the total amount of stator insulating material. From this viewpoint, the epoxy resin content is preferably 5% to 20% by mass, and more preferably 6% to 15% by mass, relative to the total amount of stator insulating material.

[0020] <Hardening agent> The stator insulating material includes a curing agent. The curing agent is not particularly limited as long as it can react with the epoxy groups of the epoxy resin to cure the epoxy resin. Examples of curing agents include phenol curing agents (compounds having phenolic hydroxyl groups in their molecules), amine curing agents, acid anhydride curing agents, polymer captan curing agents, polyaminoamide curing agents, isocyanate curing agents, and blocked isocyanate curing agents. From the viewpoint of heat resistance, high strength, and filling properties, a phenol curing agent is preferred as the curing agent. The curing agent may be solid or liquid at 25°C and atmospheric pressure, but it is preferably solid. When the curing agent contains a phenol curing agent, the content of the phenol curing agent relative to the total amount of the curing agent is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and may be 100% by mass.

[0021] The phenol curing agent is a polyhydric phenol compound such as resorcinol, catechol, bisphenol A, bisphenol F, or substituted or unsubstituted biphenols; at least one phenolic compound selected from the group consisting of phenol compounds such as phenol, cresol, xylenol, resorcinol, catechol, bisphenol A, bisphenol F, phenylphenol, aminophenol, and naphthol compounds such as α-naphthol, β-naphthol, and dihydroxynaphthalene, and an aldehyde compound such as formaldehyde, acetaldehyde, propionaldehyde, benzaldehyde, or salicylaldehyde, obtained by condensation or co-condensation under an acidic catalyst; the above phenolic compound and dimethoxyparaxylene, bis(methoxymethyl)biphen Examples include aralkyl-type phenolic resins such as phenol aralkyl resins and naphthol aralkyl resins synthesized from the above phenolic compound; paraxylylene and / or metaxylylene-modified phenolic resins; melamine-modified phenolic resins; terpene-modified phenolic resins; dicyclopentadiene-type phenolic resins and dicyclopentadiene-type naphthol resins synthesized by copolymerization of the above phenolic compound and dicyclopentadiene; cyclopentadiene-modified phenolic resins; polycyclic aromatic ring-modified phenolic resins; biphenyl-type phenolic resins; triphenylmethane-type phenolic resins obtained by condensation or co-condensation of the above phenolic compound and aromatic aldehyde compounds such as benzaldehyde and salicylaldehyde under an acidic catalyst; and phenolic resins obtained by copolymerizing two or more of these. The phenolic curing agent may be used alone or in combination of two or more.

[0022] From the viewpoint of curability and mechanical strength, novolac-type phenolic resins are preferred. In particular, when the inorganic filler contains alumina, the curability of the resin material tends to decrease compared to when silica is used. However, when the curing agent contains novolac-type phenolic resin, the crosslinking density improves, and the hardness of the cured product tends to improve. When the curing agent contains a novolac-type phenolic resin, the content of the novolac-type phenolic resin relative to the total amount of the curing agent is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and may be 100% by mass.

[0023] The functional group equivalent of the curing agent (hydroxyl group equivalent in the case of a phenol curing agent, and active hydrogen equivalent in the case of an amine curing agent) is not particularly limited. From the viewpoint of mechanical strength, the functional group equivalent of the curing agent is preferably 70 g / eq to 1000 g / eq, more preferably 80 g / eq to 500 g / eq, even more preferably 80 g / eq to 150 g / eq, and particularly preferably 80 g / eq to 110 g / eq. When the curing agent contains a novolac-type phenolic resin, the hydroxyl group equivalent of the novolac-type phenolic resin is preferably 70 g / eq to 120 g / eq, and more preferably 80 g / eq to 110 g / eq. In the case of phenol curing agents, the hydroxyl group equivalent refers to the value calculated based on the hydroxyl value measured in accordance with JIS K0070:1992. In the case of amine curing agents, the active hydrogen equivalent refers to the value calculated based on the amine value measured in accordance with JIS K7237:1995.

[0024] If the curing agent is solid, its softening point or melting point is not particularly limited. From the viewpoint of moldability, the softening point or melting point of the curing agent is preferably 40°C to 180°C, and from the viewpoint of handlingability of the stator insulating material, it is more preferably 50°C to 130°C. When the curing agent contains a novolac-type phenolic resin, its softening point or melting point is preferably 40°C to 180°C from the viewpoint of moldability, more preferably 50°C to 130°C, and even more preferably 60°C to 100°C, from the viewpoint of ease of handling of the insulating material for the stator. The melting point or softening point of the curing agent shall be a value measured in the same manner as the melting point or softening point of the epoxy resin.

[0025] The equivalent ratio of epoxy resin to curing agent, i.e., the ratio of the number of functional groups in the curing agent to the number of epoxy groups in the epoxy resin (number of functional groups in curing agent / number of epoxy groups in epoxy resin), is not particularly limited. From the viewpoint of minimizing unreacted components, the equivalent ratio of epoxy resin to curing agent is preferably set in the range of 0.5 to 2.0, and more preferably in the range of 0.6 to 1.3. From the viewpoint of moldability, it is even more preferable that the equivalent ratio of epoxy resin to curing agent is set in the range of 0.8 to 1.2.

[0026] <Inorganic filler> The stator insulating material includes an inorganic filler. The type of inorganic filler is not particularly limited and includes silica such as fused silica and crystalline silica, glass, alumina, calcium carbonate, zirconium silicate, calcium silicate, silicon nitride, aluminum nitride, boron nitride, magnesium oxide, beryllia, zirconia, zircon, fossilite, steatite, spinel, mullite, titania, talc, clay, mica, and other fine powders, or beads made by shaping these into spheres. An inorganic filler with flame retardant properties may also be used. Examples of inorganic fillers with flame retardant properties include aluminum hydroxide, magnesium hydroxide, composite metal hydroxides such as magnesium and zinc hydroxide, and zinc borate.

[0027] In particular, from the viewpoint of moldability, it is preferable that the inorganic filler includes at least one selected from the group consisting of silica, alumina, and magnesium oxide. When the inorganic filler includes at least one selected from the group consisting of silica, alumina, and magnesium oxide, the total amount of the at least one selected from the group consisting of silica, alumina, and magnesium oxide is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, based on the total amount of the inorganic filler.

[0028] In one embodiment, the inorganic filler preferably contains alumina and silica. When the inorganic filler contains alumina and silica, from the viewpoint of improving thermal conductivity, the alumina content relative to the total amount of alumina and silica is preferably 20% by mass or more, and more preferably 30% by mass or more. From the viewpoint of improving the curability, fluidity, etc., of the resin material, the alumina content relative to the total amount of alumina and silica is preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less. From this viewpoint, the alumina content relative to the total amount of alumina and silica is preferably 20% by mass to 80% by mass, more preferably 30% by mass to 70% by mass, and even more preferably 30% by mass to 60% by mass.

[0029] The average particle size of the inorganic filler is not particularly limited. From the viewpoint of filling into narrow gaps, the average particle size of the inorganic filler is preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 20 μm or less. Furthermore, from the viewpoint of the mechanical strength of the cured product, the average particle size of the inorganic filler is preferably 5 μm or more, and more preferably 10 μm or more. From this viewpoint, the average particle size of the inorganic filler is preferably 5 μm to 50 μm, more preferably 10 μm to 30 μm, and even more preferably 10 μm to 20 μm. The average particle size of inorganic fillers can be measured as the particle size (D50) at which the cumulative amount from the smaller diameter side reaches 50% in the volume-based particle size distribution measured by a laser scattering diffraction particle size distribution analyzer. In one embodiment, when the inorganic filler contains alumina, it is preferable that the average particle size of the alumina is within the above range. In one embodiment, when the inorganic filler contains silica, it is preferable that the average particle size of the silica is within the above range.

[0030] From the viewpoint of filling narrow gaps and the resulting mechanical strength of the cured product, the maximum particle size of the inorganic filler is preferably 150 μm or less, more preferably 100 μm or less, even more preferably 80 μm or less, and may also be 60 μm or less, or 50 μm or less. The maximum particle diameter can be measured as the particle diameter (D99) at which the cumulative total from the smaller diameter side reaches 99% in the volume-based particle size distribution measured by a laser scattering diffraction particle size distribution analyzer. In one embodiment, when the inorganic filler contains alumina, it is preferable that the maximum particle size of the alumina is within the above range. In one embodiment, when the inorganic filler contains silica, it is preferable that the maximum particle size of the silica is within the above range.

[0031] The circularity of the inorganic filler is not particularly limited. From the viewpoint of improving the fluidity of the stator insulating material, the average circularity of the inorganic filler observed by scanning electron microscopy (SEM) is preferably 0.8 to 1.0, and more preferably 0.9 to 1.0. In this disclosure, the "circularity" of the inorganic filler is the value obtained by the following formula. The closer the circularity is to 1, the closer the particle shape is to a perfect circle. Roundness = 4π × (area) ÷ (perimeter) 2 Furthermore, the "average circularity" is defined as the arithmetic mean of the circularity of 100 particles arbitrarily selected from the SEM image. The circularity of the inorganic filler can be calculated using known image analysis methods as needed. In one embodiment, when the inorganic filler contains alumina, it is preferable that the average circularity of the alumina is within the above range. In one embodiment, when the inorganic filler contains silica, it is preferable that the average circularity of the silica is within the above range.

[0032] The aspect ratio of the inorganic filler is not particularly limited. From the viewpoint of improving the fluidity of the stator insulating material, the average aspect ratio of the inorganic filler in SEM observation is preferably 0.8 to 1.0, and more preferably 0.9 to 1.0. In this disclosure, the "aspect ratio" of the inorganic filler refers to the value obtained by dividing the length of the short axis of the particle by the length of the long axis (short axis / long axis). The average aspect ratio of the inorganic filler is the arithmetic mean of the aspect ratios of 100 particles randomly selected from the SEM image of the inorganic filler. The aspect ratio of the inorganic filler can be calculated from the image of the inorganic filler using known image analysis means as needed. In one embodiment, when the inorganic filler contains alumina, it is preferable that the average aspect ratio of the alumina is within the above range. In one embodiment, when the inorganic filler contains silica, it is preferable that the average aspect ratio of the silica is within the above range.

[0033] The content of the inorganic filler is not particularly limited, but is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, and particularly preferably 80% by mass or more, relative to the total amount of the stator insulating material. When the inorganic filler content is 50% by mass or more relative to the total amount of the stator insulating material, the insulation between coils tends to be further improved. It also tends to reduce water absorption and improve chemical resistance. From the viewpoint of ensuring fluidity during molding and improving void filling, the inorganic filler content is preferably 95% by mass or less, and more preferably 90% by mass or less, relative to the total amount of the stator insulating material. From this viewpoint, the inorganic filler content is preferably 50% to 95% by mass, more preferably 60% to 90% by mass, even more preferably 70% to 90% by mass, and particularly preferably 80% to 90% by mass, relative to the total amount of the stator insulating material.

[0034] The volume-based content of the inorganic filler is not particularly limited, but is preferably 40% by volume or more, more preferably 50% by volume or more, even more preferably 60% by volume or more, and particularly preferably 70% by volume or more, relative to the total amount of the stator insulating material. When the inorganic filler content is 40% by volume or more relative to the total amount of the stator insulating material, the insulation between coils tends to be further improved. It also tends to reduce water absorption and improve chemical resistance. From the viewpoint of ensuring fluidity during molding and improving void filling, the inorganic filler content is preferably 85% by volume or less, and more preferably 80% by volume or less, relative to the total amount of the stator insulating material. From this viewpoint, the inorganic filler content is preferably 40% to 85% by volume, more preferably 50% to 80% by volume, even more preferably 60% to 80% by volume, and particularly preferably 70% to 80% by volume, relative to the total amount of the stator insulating material.

[0035] When the insulating material for the stator is cured, the inorganic filler content in the cured material can be measured as follows. First, the total mass of the cured material is measured, and the thermosetting material is fired at 400°C for 1 hour, then at 700°C for 1 hour to decompose the resin components, and the mass of the remaining inorganic filler is measured. The ratio of the mass of the inorganic filler to the total mass of the cured material is obtained and is taken as the inorganic filler content. Furthermore, the volume-based inorganic filler content is determined by dividing the mass-based content by the specific gravity of the inorganic filler. The specific gravity of the inorganic filler can be measured using the method using a balance as shown in JIS K0061:2022. Since a solid in a liquid is subjected to buoyancy equivalent to the mass of the same volume of liquid, the sample is weighed in air and in water of known density, and its density is determined.

[0036] <Other ingredients> The stator insulating material may include epoxy resin, a curing agent, and an inorganic filler, as well as various additives. Examples of additives include curing accelerators, coupling agents, ion exchangers, mold release agents, flame retardants, colorants, stress relievers, and adhesion promoters.

[0037] (Curing accelerator) The stator insulating material may contain a curing accelerator. The type of curing accelerator is not particularly limited and may include diazabicycloalkenes such as 1,5-diazabicyclo[4.3.0]nonene-5 (DBN) and 1,8-diazabicyclo[5.4.0]undecene-7 (DBU), cyclic amidine compounds such as 2-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, and 2-heptadecylimidazole; derivatives of the cyclic amidine compounds; phenol novolac salts of the cyclic amidine compounds or their derivatives; and quinone compounds such as maleic anhydride, 1,4-benzoquinone, 2,5-tholquinone, 1,4-naphthoquinone, 2,3-dimethylbenzoquinone, 2,6-dimethylbenzoquinone, 2,3-dimethoxy-5-methyl-1,4-benzoquinone, 2,3-dimethoxy-1,4-benzoquinone, and phenyl-1,4-benzoquinone. Compounds having intramolecular polarization formed by adding compounds with π bonds, such as diazophenylmethane; cyclic amidinium compounds such as tetraphenylborate salt of DBU, tetraphenylborate salt of DBN, tetraphenylborate salt of 2-ethyl-4-methylimidazole, and tetraphenylborate salt of N-methylmorpholine; tertiary amine compounds such as pyridine, triethylamine, triethylenediamine, benzyldimethylamine, triethanolamine, dimethylaminoethanol, and tris(dimethylaminomethyl)phenol; derivatives of the above tertiary amine compounds; ammonium salt compounds such as tetra-n-butylammonium acetate, tetra-n-butylammonium phosphate, tetraethylammonium acetate, tetra-n-hexylammonium benzoate, and tetrapropylammonium hydroxide;Organic phosphines such as primary phosphines like ethylphosphine and phenylphosphine, secondary phosphines like dimethylphosphine and diphenylphosphine, triphenylphosphine, diphenyl(p-tolyl)phosphine, tris(alkylphenyl)phosphine, tris(alkoxyphenyl)phosphine, tris(alkylalkoxyphenyl)phosphine, tris(dialkylphenyl)phosphine, tris(trialkylphenyl)phosphine, tris(tetraalkylphenyl)phosphine, tris(dialkoxyphenyl)phosphine, tris(trialkoxyphenyl)phosphine, tris(tetraalkoxyphenyl)phosphine, trialkylphosphine, dialkylarylphosphine, alkyldiarylphosphine, trinaphthylphosphine, tris(benzyl)phosphine, and other tertiary phosphines; phosphine compounds such as complexes of the above organic phosphines with organoborons; and the above organic phosphines or the above phosphine compounds with maleic anhydride, 1,4-benzoquinone, 2,5-tholquinone, 1,4-naphthoquinone, 2,3-dimethylbenzoquinone Compounds having intramolecular polarization obtained by adding compounds having π bonds, such as quinone compounds like 2,6-dimethylbenzoquinone, 2,3-dimethoxy-5-methyl-1,4-benzoquinone, 2,3-dimethoxy-1,4-benzoquinone, phenyl-1,4-benzoquinone, anthraquinone, and diazophenylmethane; and the aforementioned organophosphine or phosphine compound with 4-bromophenol, 3-bromophenol, 2-bromophenol, 4-chlorophenol, 3-chlorophenol, 2-chlorophenol, and 4-iodide pheno Compounds having intramolecular polarization obtained by reacting halogenated phenol compounds such as 3-iodidephenol, 2-iodidephenol, 4-bromo-2-methylphenol, 4-bromo-3-methylphenol, 4-bromo-2,6-dimethylphenol, 4-bromo-3,5-dimethylphenol, 4-bromo-2,6-di-t-butylphenol, 4-chloro-1-naphthol, 1-bromo-2-naphthol, 6-bromo-2-naphthol, and 4-bromo-4'-hydroxybiphenyl, followed by a dehalogenation step;Examples include tetrasubstituted phosphonium compounds such as tetraphenylphosphonium, tetraphenylborate salts of tetrasubstituted phosphoniums such as tetraphenylphosphonium tetra-p-tolylborate, and salts of tetrasubstituted phosphonium with phenolic compounds; phosphobetaine compounds; and adducts of phosphonium compounds with silane compounds. Among these, triphenylphosphine and adducts of triphenylphosphine with quinone compounds are preferred from the viewpoint of ensuring good fluidity of the stator insulating material. The curing accelerator may be used alone or in combination of two or more types.

[0038] When the stator insulating material contains a curing accelerator, the content of the curing accelerator is preferably 0.1 parts by mass or more, and more preferably 1 part by mass or more, per 100 parts by mass of the resin component, from the viewpoint of easily curing well in a short time. From the viewpoint of obtaining a good molded product without the curing speed being too fast, the content of the curing accelerator is preferably 30 parts by mass or less, and more preferably 15 parts by mass or less, per 100 parts by mass of the resin component. From this viewpoint, the content of the curing accelerator is preferably 0.1 parts by mass to 30 parts by mass, and more preferably 1 part by mass to 15 parts by mass, per 100 parts by mass of the resin component.

[0039] (Coupling agent) The stator insulating material may contain a coupling agent to improve the compatibility between the resin component and the inorganic filler, and to improve adhesion to the substrate. Examples of coupling agents include silane compounds such as epoxysilane, phenylsilane, mercaptosilane, aminosilane, phenylaminosilane, alkylsilane, ureidosilane, and vinylsilane, as well as titanium compounds, aluminum chelate compounds, and aluminum / zirconium compounds. The coupling agent may be used alone or in combination of two or more types.

[0040] If the stator insulating material contains a coupling agent, the amount of the coupling agent is preferably 0.05 to 5 parts by mass, and more preferably 0.1 to 2.5 parts by mass, per 100 parts by mass of the inorganic filler.

[0041] (Ion exchanger) The stator insulating material may include an ion exchanger to improve moisture resistance, heat resistance, and other properties. The type of ion exchanger is not particularly limited and includes hydrotalcite compounds and hydrated oxides of at least one element selected from the group consisting of magnesium, aluminum, titanium, zirconium, and bismuth. One type of ion exchanger may be used alone, or two or more types may be used in combination.

[0042] If the stator insulating material contains an ion exchanger, its content is not particularly limited. For example, the ion exchanger content is preferably 0.1 to 30 parts by mass, and more preferably 1 to 15 parts by mass, per 100 parts by mass of the resin component.

[0043] (Release agent) The insulating material for the stator may contain a release agent to obtain good release properties from the mold during molding. The type of release agent is not particularly limited and includes carnauba wax, higher fatty acids such as montanic acid and stearic acid, higher fatty acid metal salts, ester waxes such as montanic acid esters, and polyolefin waxes such as oxidized polyethylene and non-oxidized polyethylene. The release agent may be used alone or in combination of two or more types.

[0044] If the insulating material for the stator contains a release agent, its content is not particularly limited. For example, the content of the release agent is preferably 0.01 to 15 parts by mass, more preferably 0.1 to 10 parts by mass, and may be 0.1 to 5 parts by mass, or 0.1 to 3 parts by mass, per 100 parts by mass of the resin component. When the amount of release agent is 0.01 parts by mass or more per 100 parts by mass of the resin component, sufficient release properties tend to be obtained. When the amount of release agent is 15 parts by mass or less per 100 parts by mass of the resin component, better adhesion tends to be obtained.

[0045] (Flame retardant) The stator insulating material may contain a flame retardant. The type of flame retardant is not particularly limited and includes organic or inorganic compounds containing halogen atoms, antimony atoms, nitrogen atoms, or phosphorus atoms, metal hydroxides, etc. One type of flame retardant may be used alone, or two or more types may be used in combination.

[0046] If the stator insulating material contains a flame retardant, its content is not particularly limited. For example, the flame retardant content is preferably 1 to 300 parts by mass, and more preferably 2 to 150 parts by mass, per 100 parts by mass of the resin component.

[0047] (Coloring agent) The stator insulating material may contain a coloring agent. The type of coloring agent is not particularly limited and examples include carbon black, organic dyes, organic pigments, titanium dioxide, red lead, and red iron oxide. One coloring agent may be used alone, or two or more may be used in combination. The amount of coloring agent may be appropriately selected depending on the purpose.

[0048] (Stress reliever) The stator insulating material may contain a stress reliever. The type of stress reliever is not particularly limited and includes thermoplastic elastomers such as silicone, styrene, olefin, urethane, polyester, polyether, polyamide, and polybutadiene; rubber particles such as NR (natural rubber), NBR (acrylonitrile-butadiene rubber), acrylic rubber, urethane rubber, and silicone powder; and rubber particles having a core-shell structure such as methyl methacrylate-styrene-butadiene copolymer (MBS), methyl methacrylate-silicone copolymer, and methyl methacrylate-butyl acrylate copolymer. The stress reliever may be used alone or in combination of two or more types. The content of the stress reliever may be appropriately selected depending on the purpose.

[0049] (Adhesion-enhancing agent) The stator insulating material may contain an adhesion promoter to improve adhesion to the metal and to improve insulation properties. The type of adhesion promoter is not particularly limited, and examples include compounds having carboxyl groups, hydroxyl groups, amino groups, etc. The adhesion promoter may be used alone or in combination of two or more types.

[0050] If the stator insulating material contains an adhesion promoter, its content is not particularly limited, but is preferably 0.01 to 20.0 parts by mass, and more preferably 5.0 to 10.0 parts by mass, per 100 parts by mass of the resin component.

[0051] (solvent) The insulating material for the stator is preferably solvent-free in order to have a composition suitable for, for example, transfer molding. The amount of solvent relative to the total amount of the insulating material for the stator (or the total amount including the solvent if one is included) is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less.

[0052] [Method for preparing stator insulating material] The method for preparing the insulating material for the stator is not particularly limited. For example, one method is to thoroughly mix each component using a mixer, then melt-knead it using a mixing roll, extruder, etc., cool it, and pulverize it. More specifically, one method is to mix and stir each component, knead it using a preheated kneader, roll, extruder, etc., cool it, and pulverize it.

[0053] [Characteristics of stator insulating materials] (Properties) The stator insulating material may be solid or liquid at 25°C and atmospheric pressure, but it is preferable to be solid from the viewpoint of the mechanical strength of the cured product. When the stator insulating material is solid, there are no particular restrictions on its shape, and examples include powder, granules, and tablets. When the stator insulating material is in tablet form, it is preferable from the viewpoint of handling that its dimensions and mass are such that they are suitable for the molding conditions.

[0054] (viscosity) The viscosity of the stator insulating material is not particularly limited. From the viewpoint of filling narrow gaps, the viscosity of the stator insulating material is preferably 1000 Pa·s or less, more preferably 500 Pa·s or less, and even more preferably 200 Pa·s or less at 175°C. From the viewpoint of suppressing the occurrence of flow marks during molding due to excessively low viscosity, the viscosity of the stator insulating material is preferably 0.1 Pa·s or more, more preferably 0.5 Pa·s or more, and even more preferably 1 Pa·s or more at 175°C. From this viewpoint, the viscosity of the stator insulating material is preferably 0.1 Pa·s to 1000 Pa·s, more preferably 0.5 Pa·s to 500 Pa·s, and even more preferably 1 Pa·s to 200 Pa·s at 175°C. The viscosity of the stator insulating material can be measured using a high-efficiency flow tester (for example, one manufactured by Shimadzu Corporation).

[0055] (Liquidity) When stator insulating material is molded using a spiral flow measurement mold conforming to EMMI-1-66 in a transfer molding machine under the conditions of a mold temperature of 175°C, a molding pressure of 6.9 MPa, and a curing time of 90 seconds, the flow distance is preferably 100 cm or more, more preferably 110 cm or more, even more preferably 120 cm or more, and particularly preferably 123 cm or more. High fluidity during melting suppresses the occurrence of unfilled areas during molding. The upper limit of the flow distance is not particularly limited, but the flow distance may be 200 cm or less. Therefore, the flow distance may be between 100 cm and 200 cm.

[0056] (Flexural strength of hardened material) The bending strength of the cured stator insulating material at 260°C, measured by the following method, is preferably 5.0 MPa or higher, more preferably 7.0 MPa or higher, and even more preferably 9.0 MPa or higher. The bending strength of the cured material may be 10.0 MPa or lower, or 9.0 MPa or lower. After the insulating material has hardened, a rectangular parallelepiped measuring 2.0 mm × 5.0 mm × 40 mm is cut out to prepare a test specimen for evaluating bending strength. Using this test specimen, a bending test is performed on a Tensilon universal material testing machine (Instron 5948, Instron Corporation) under the conditions of a support distance of 32 mm and a crosshead speed of 1 mm / min. Using the measured results, a bending stress-displacement curve is created from equation (A), and the maximum stress is defined as the bending strength. σ = 3FL / 2bh 2 ··· Formula (A) σ: Bending stress (MPa) F: Bending load (N) L: Distance between fulcrums (mm) b: Specimen width (mm) h: Test specimen thickness (mm) In one embodiment, it is preferable that the stator insulating material is molded in a transfer molding machine under the conditions of a mold temperature of 175°C, a molding pressure of 6.9 MPa, and a curing time of 90 seconds, and that the bending strength of the cured product after curing at 175°C for 5 hours is within the above range.

[0057] (Flexural modulus of hardened material) The flexural modulus of the cured stator insulating material, measured by the following method, is preferably 600 MPa or less, more preferably 500 MPa or less, and even more preferably 450 MPa or less, from the viewpoint of improving the strength of the cured material. The flexural modulus of the hardened material is measured by the bending test described above and calculated from the linear function of stress and fracture elongation between 0% and 0.5% of the bending stress-displacement curve. In one embodiment, it is preferable that the stator insulating material is molded in a transfer molding machine under the conditions of a mold temperature of 175°C, a molding pressure of 6.9 MPa, and a curing time of 90 seconds, and that the flexural modulus of the cured product after curing at 175°C for 5 hours is within the above range.

[0058] (Elongation at break of hardened material) The elongation at break of the cured stator insulating material at 260°C is preferably 1.5% or more, more preferably 1.6% or more, and even more preferably 1.7% or more. The upper limit of the elongation at break is not particularly limited, and the elongation at break may be 3.0% or less. The fracture elongation of the hardened material is measured by the bending test described above and is obtained as the displacement from the test start point to the maximum stress. In one embodiment, it is preferable that the stator insulating material is molded in a transfer molding machine under the conditions of a mold temperature of 175°C, a molding pressure of 6.9 MPa, and a curing time of 90 seconds, and that the elongation at break of the cured product after curing at 175°C for 5 hours is within the above range.

[0059] [Copper bond strength] The copper adhesion strength of the cured stator insulating material at 260°C is preferably 1.0 MPa or higher, more preferably 1.1 MPa or higher, even more preferably 1.2 MPa or higher, and particularly preferably 1.3 MPa or higher. The upper limit of the copper adhesion strength is not particularly limited and may be, for example, 2.0 MPa. Therefore, the copper adhesion strength may be between 1.0 MPa and 2.0 MPa. The copper bonding strength is measured using a bond tester (for example, Nordson's 4000 Optima) by performing a shear strength test in which the device's tool is applied to the cured material. In one embodiment, it is preferable that the copper adhesive strength of the stator insulating material, when molded in a transfer molding machine under the conditions of a mold temperature of 175°C, a molding pressure of 6.9 MPa, and a curing time of 120 seconds, is within the above range after curing at 175°C for 5 hours.

[0060] [Insulation Method] The method for insulating the coils using stator insulating material is not particularly limited, and methods such as transfer molding, injection molding, and compression molding can be used to seal the coils. In particular, transfer molding, by sealing the coils under pressurized and heated conditions, tends to suppress void entrapment and enable a tight seal, thereby improving insulation performance. The temperature and time of transfer molding can be appropriately selected depending on the type of stator insulating material. For example, molding may be performed under conditions of a mold temperature of 170°C to 180°C, a molding pressure of 5 MPa to 150 MPa, and a molding time of 1 to 3 minutes.

[0061] In one embodiment, the entire stator, including the coil portion, may be sealed together with the stator insulating material of this disclosure by transfer molding. Alternatively, each component of the stator may be sealed individually.

[0062] [Applications of stator insulating materials] The stator insulating material of this disclosure is used for insulating between coils of a stator. In this disclosure, insulation means electrical insulation.

[0063] ≪Stata≫ The stator of this disclosure has a coil insulated with the aforementioned stator insulating material. The coil may be wound in any way, such as distributed winding or concentrated winding.

[0064] The material of the coil is not particularly limited. For example, conductors such as copper, aluminum, silver, and alloys thereof can be used as coil materials. A coil in which the conductor is covered with an insulating layer such as resin may also be used.

[0065] The stator of this disclosure can be applied to various motors, such as motors for hybrid vehicles, electric vehicles, hybrid diesel locomotives, electric motorcycles, elevators, and construction machinery. In particular, because the stator of this disclosure has excellent insulation properties between coils, it can be suitably applied even to motors for vehicles that have been made more powerful or smaller.

[0066] ≪Method of manufacturing a stator≫ The method for manufacturing a stator according to this disclosure includes insulating the coils with a stator insulating material. The insulation between coils may be performed by transfer molding. Details of the stator insulating material, the insulation method, and the stator are as described above. [Examples]

[0067] The embodiments of this disclosure will now be described in detail with reference to examples, but the embodiments of this disclosure are not limited to these examples.

[0068] <Fabrication of insulating materials> First, the following components were prepared. Epoxy resin 1 is an epoxy resin containing an alicyclic structure, while epoxy resins 2-4 are epoxy resins that do not have an alicyclic structure. • Epoxy resin 1: Polyfunctional epoxy resin containing an alicyclic structure with an epoxy equivalent of 240 g / eq to 290 g / eq and a softening point of 52°C to 90°C (dicyclopentadiene-modified epoxy resin, which is a glycidyl ether of dicyclopentadiene-modified phenolic resin). • Epoxy resin 2: Biphenyl aralkyl type epoxy resin with epoxy equivalent weight of 268 g / eq to 283 g / eq and a softening point of 55°C to 64°C. • Epoxy resin 3: A polyfunctional epoxy resin with an o-cresol novolac skeleton, epoxy equivalent weight of 233 g / eq to 244 g / eq, and a softening point of 50°C to 60°C. • Epoxy resin 4: Triphenylmethane-type epoxy resin with epoxy equivalent weight of 243 g / eq to 254 g / eq and a softening point of 53°C to 62°C. • Epoxy resin 5: Biphenyl-type epoxy resin with epoxy equivalent weight of 180 g / eq to 192 g / eq and a melting point of 105°C. • Hardener: Novolac-type phenolic resin with a hydroxyl group equivalent of 106 g / eq and a softening point of 68°C to 74°C. • Curing accelerator: 1,4-benzoquinone adduct of triphenylphosphine • Inorganic filler 1: D50 consists of fused silica particles with a maximum particle diameter of 75 μm or less (average circularity is in the range of 0.8 to 1.0, and average aspect ratio is in the range of 0.9 to 1.0). • Inorganic filler 2: D50 is 30 μm (catalog value), alumina particles with a maximum particle diameter of 75 μm or less (average circularity is in the range of 0.8 to 1.0, and average aspect ratio is in the range of 0.9 to 1.0).

[0069] Each component shown in Table 1 was blended in the amounts shown in the table and thoroughly mixed in a mixer. Then, the mixture was melt-kneaded at a temperature of 70°C to 100°C using a twin-screw kneader. Next, after the molten material was cooled, the resulting solid was pulverized into a powder to prepare the desired powdered insulating material.

[0070] <Rating> The fabricated insulating materials were evaluated by the following tests. Unless otherwise specified, the insulating materials were molded using a transfer molding machine under the following conditions: mold temperature 175°C, molding pressure 6.9 MPa, and curing time 90 seconds. Post-curing was also performed at 175°C for 5 hours as needed.

[0071] [Spiral Flow] Using a spiral flow measurement mold conforming to EMMI-1-66, the stator insulating material was molded under the above conditions, and the flow distance was determined.

[0072] [Flexural modulus, flexural strength, and elongation at break] After post-curing of the insulating material, the cured material was cut into a rectangular parallelepiped measuring 2.0 mm × 5.0 mm × 40 mm to prepare test specimens for evaluating bending strength. Using these test specimens, the specimens were tested on a Tensilon universal material testing machine (Instron 5948, Instron Corporation) under the conditions of a support distance of 32 mm and a crosshead speed of 1 mm / min. After being left in an oven heated to 260°C for 5 minutes, the test was performed at 260°C. Using the measured results, a bending stress-displacement curve was created from equation (A), the maximum stress was defined as the bending strength, the elongation at fracture was defined as the displacement from the start of the test to the maximum stress, and the modulus of elasticity was calculated from the linear function of the stress and elongation at fracture between 0% and 0.5% of the bending stress-displacement curve. σ = 3FL / 2bh 2 ··· Formula (A) σ: Bending stress (MPa) F: Bending load (N) L: Distance between fulcrums (mm) b: Specimen width (mm) h: Test specimen thickness (mm)

[0073] [Copper bond strength] For measuring copper adhesion strength, a curable resin composition was molded onto a copper substrate using a transfer mold. The molded material was prepared under conditions of 175°C, a molding pressure of 6.9 MPa, and a molding time of 120 seconds, followed by post-curing at 175°C for 5 hours. The cured sample was cylindrical with an area of ​​10 mm². 2 The sample had a shape with a height of 2 mm or more. The copper bonding strength of this sample was measured by performing a shear strength test using a bond tester (Nordson, product name 4000 Optima) at 260°C, in which the tool of the device was applied to the cured material.

[0074] [Presence or absence of flow marks] A mold with a 0.3 mm gap (L=100 mm) was prepared, and transfer molding was performed under the above conditions. The presence or absence of unfilled areas in the 0.3 mm gap was visually inspected and evaluated according to the following criteria. A: No unfilled areas B: Flow marks are observed, but there are no unfilled areas.

[0075] The formulations and evaluation results for each example are shown in the table below. In the table, the flow distance (cm) in the spiral flow test is a converted value.

[0076] [Table 1]

[0077] Example 1 showed greater elongation at break and superior copper bonding strength compared to Comparative Examples 1-3. Furthermore, in Example 1, the insulating material exhibited excellent fluidity, resulting in superior filling without any unfilled areas. Because the insulating material in Example 1 has excellent fluidity, it is believed that a highly reliable stator can be provided even if the stator size changes. On the other hand, flow marks were observed in Comparative Examples 1-3. While it is difficult to definitively determine the cause, it is thought to be related to the degree of fluidity. Additionally, the compatibility of the epoxy resin with the mold or curing agent is considered a contributing factor; such problems are less likely to occur if the fluidity of the mixed resin is uniform between the center and the mold interface. Furthermore, the flexural modulus of the cured product in Example 1 was the lowest, which is thought to contribute to the strength of the cured product.

Claims

1. An insulating material for stators, comprising an epoxy resin containing an alicyclic structure and a biphenyl-type epoxy resin, a curing agent, and an inorganic filler, used for insulating between coils of a stator.

2. The stator insulating material according to claim 1, wherein the alicyclic structure-containing epoxy resin comprises a dicyclopentadiene-modified epoxy resin which is a glycidyl ether of a dicyclopentadiene-modified phenol resin.

3. The stator insulating material according to claim 1, wherein the content of the alicyclic structure-containing epoxy resin relative to the total amount of the epoxy resin is 10% by mass to 70% by mass.

4. The stator insulating material according to claim 1, wherein the curing agent comprises a phenol curing agent.

5. The stator insulating material according to claim 1, wherein the inorganic filler comprises at least one selected from the group consisting of silica, alumina, and magnesium oxide.

6. The stator insulating material according to claim 1, wherein the content of the inorganic filler relative to the total amount of the stator insulating material is 50% by mass or more.

7. The stator insulating material according to claim 1, wherein the maximum particle size of the inorganic filler is 150 μm or less.

8. The stator insulating material according to claim 1, further comprising a curing accelerator.

9. The stator insulating material according to claim 1, wherein when the stator insulating material is molded using a spiral flow measurement mold conforming to EMMI-1-66 under the conditions of a mold temperature of 175°C, a molding pressure of 6.9 MPa, and a curing time of 90 seconds, the flow distance is 100 cm or more.

10. The stator insulating material according to claim 1, wherein the stator insulating material is molded by a transfer molding machine under the conditions of a mold temperature of 175°C, a molding pressure of 6.9 MPa, and a curing time of 90 seconds, and the cured product, after curing at 175°C for 5 hours, has a bending modulus of elasticity at 260°C of 600 MPa or less in a bending test.

11. The stator insulating material according to claim 1, wherein the stator insulating material is molded by a transfer molding machine under the conditions of a mold temperature of 175°C, a molding pressure of 6.9 MPa, and a curing time of 90 seconds, and the cured product, after curing at 175°C for 5 hours, exhibits a fracture elongation at 260°C in a bending test of 1.5% or more.

12. The stator insulating material according to claim 1, wherein the stator insulating material is molded by a transfer molding machine under the conditions of a mold temperature of 175°C, a molding pressure of 6.9 MPa, and a curing time of 120 seconds, and the copper adhesive strength of the cured product at 260°C after curing at 175°C for 5 hours is 1.3 MPa or more.

13. A stator having coils insulated with the stator insulating material described in any one of claims 1 to 12.

14. A method for manufacturing a stator, comprising insulating the coils with an insulating material for a stator as described in any one of claims 1 to 12.

15. The method for manufacturing a stator according to claim 14, wherein insulation between the coils is performed by transfer molding.

Images