Resin composition for encapsulating motor stators and motor stators

Abstract

The present invention provides a resin composition for the mass sealing of motor stators, which has high thermal conductivity and can form a tough sealing material, making it suitable for the mass sealing of stators, and a motor stator using the same. [Solution] A resin composition comprising (A) epoxy resin, (B) phenolic resin curing agent, (C) alumina, and (D) silica, wherein the content of (C) alumina is 70 to 85% by mass, and a test piece of the cured product obtained by heating the resin composition at 175°C for 8 hours is subjected to a three-point bending test in accordance with the bending test method specified in JIS K 6911:2006 5.17.1, and the displacement of the pressure wedge when the test piece breaks is defined as the fracture point displacement, wherein the fracture point displacement is 1.0 mm or more, a resin composition for encapsulating motor stators.

Description

[Technical Field]

[0001] This disclosure relates to a resin composition for encapsulating a motor stator, and a motor stator using the same. [Background technology]

[0002] Motors are used in products in various fields, including home appliances, office automation equipment, audio-visual equipment, industrial machinery, and automobiles. A method of sealing the stator, which is located outside the rotor of a motor, with an epoxy resin composition is known for its insulating protection.

[0003] For example, Patent Document 1 describes that a stator obtained by batch encapsulation molding with an epoxy resin composition that yields a cured product having a predetermined flexural modulus exhibits good adhesion and waterproofing. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2023 / 189996 [Overview of the project] [Problems that the invention aims to solve]

[0005] Incidentally, in addition to insulation, the stator needs to be robust depending on the operating environment, from the standpoint of motor durability. For this reason, it is desirable that the sealing material be strong so that the motor does not break when it is dropped or hit.

[0006] In Patent Document 1, while the thermal conductivity of an epoxy resin composition can be improved when alumina is used as an inorganic filler, it could not necessarily be said that the toughness of the molded product, which is the cured product, could be ensured by a high content of inorganic filler.

[0007] This disclosure has been made in view of the above circumstances, and aims to provide a resin composition for the mass sealing of motor stators that has high thermal conductivity, can form a tough sealing material, and is suitable for the mass sealing of stators, and a motor stator using the same. [Means for solving the problem]

[0008] This disclosure is based on the discovery that a resin composition in which the composition of the inorganic filler is controlled and predetermined bending properties can constitute a sealing material with high thermal conductivity and toughness, and is suitable for stator-wide sealing.

[0009] In other words, this disclosure relates to the following: [1] A resin composition comprising (A) epoxy resin, (B) phenolic resin curing agent, (C) alumina, and (D) silica, wherein the content of (C) alumina is 70 to 85% by mass, and a test specimen of the cured product obtained by heating the resin composition at 175°C for 8 hours is subjected to a three-point bending test in accordance with the bending test method specified in JIS K 6911:2006 5.17.1, and the displacement of the pressure wedge when the test specimen breaks is defined as the fracture point displacement, wherein the fracture point displacement is 1.0 mm or more, a resin composition for encapsulating motor stators. [2](C) The alumina is a resin composition for encapsulating motor stators as in [1], comprising (C1) alumina with a cumulative volume 50% particle size (D50) of 0.1 μm or more and less than 1.0 μm, (C2) alumina with a cumulative volume 50% particle size (D50) of 1.0 μm or more and less than 20 μm, and (C3) alumina with a cumulative volume 50% particle size (D50) of 20 μm or more and less than 50 μm. [3] The motor stator encapsulation resin composition of [2], wherein the proportion of alumina (C1) is 4 to 25% by mass, the proportion of alumina (C2) is 15 to 65% by mass, and the proportion of alumina (C3) is 30 to 75% by mass of the total amount of alumina (C). [4](D) Silica has a (D1) cumulative volume 50% particle size (D50) of 0.1 μm or more and less than 1.0 μm, and a BET specific surface area of ​​1 to 10 m². 2Silica content per gram, (D2) cumulative volume 50% particle size (D50) of 1.0 μm or more and less than 20 μm, and BET specific surface area of ​​1 to 10 m². 2 A resin composition for encapsulating motor stators, comprising [1] to [3] of silica per g. [5] The resin composition for encapsulating a motor stator according to [4], wherein the silica content of (D1) in the resin composition is 1 to 5% by mass and the silica content of (D2) is 3 to 20% by mass. [6](D)Silica has a specific surface area of ​​100-300 m² (D3)BET. 2 A resin composition for encapsulating motor stators, comprising one of the following [1] to [5], containing silica at a concentration of / g. [7] The resin composition for encapsulating a motor stator, wherein the silica content of (D3) in the resin composition is 0.1 to 3% by mass. [8](A) A resin composition for encapsulating motor stators according to any of [1] to [7], wherein the epoxy resin comprises at least one epoxy resin selected from biphenyl type, biphenyl aralkyl type, and Zyloc type. [9](B) A resin composition for motor stator encapsulation, any of [1] to [8], comprising at least one phenol resin curing agent selected from biphenyl aralkyl type and Zyloc type.

[10] Furthermore, a resin composition for motor stator encapsulation according to any of [1] to [9], comprising (E) a curing accelerator.

[11] The resin composition for encapsulating a motor stator, wherein the content of (E) curing accelerator in the resin composition is 0.05 to 5% by mass.

[12] (E) A resin composition for motor stator encapsulation according to

[10] or

[11] , wherein the curing accelerator comprises a latent imidazole-based curing accelerator. A motor stator that is encapsulated in a cured product of any of the motor stator encapsulation resin compositions

[13] to

[12] . [Effects of the Invention]

[0010] The resin composition for collectively encapsulating a motor stator of the present disclosure has high thermal conductivity and can constitute a tough encapsulant, and can be suitably applied to the collective encapsulation of stators. In addition, by using the resin composition for collectively encapsulating a motor stator of the present disclosure, a motor stator with high strength and low breakage susceptibility can be provided.

Embodiments for Carrying out the Invention

[0011] Hereinafter, the present disclosure will be described in detail with reference to one embodiment. The definitions and meanings of terms and notations in the present disclosure are shown below. The notation "X to Y" (X and Y are numerical values) means a numerical range with X as the lower limit value and Y as the upper limit value. In a numerical range (for example, a range such as content), the stepwise-described lower limit value and upper limit value may be combined independently. The lower limit value and upper limit value of the numerical range may be replaced with the numerical values described in the examples. The epoxy equivalent is a value measured in accordance with the potentiometric titration method defined in JIS K 7236:2001. The hydroxyl equivalent is a value obtained from the hydroxyl value measured in accordance with the potentiometric titration method defined in JIS K 0070:1992. The cumulative volume 50% particle diameter (D50) is the particle diameter when the cumulative volume from the small particle diameter side reaches 50% in the volume-based particle size distribution measured by a laser diffraction scattering type particle size distribution measuring device, unless otherwise specified. The specific surface area is a value measured by the BET one-point method by nitrogen adsorption using a specific surface area measuring device, and specifically can be measured by the method described in the examples.

[0012] [Resin Composition for Collectively Encapsulating a Motor Stator] The resin composition for collectively encapsulating a motor stator of the present disclosure (hereinafter, also simply referred to as the resin composition) is a resin composition containing (A) an epoxy resin, (B) a phenolic resin curing agent, (C) alumina, and (D) silica, wherein the content of (C) alumina is 70 to 85% by mass, and for a test piece of the cured product obtained by heating the resin composition at 175°C for 8 hours, in a three-point bending test conforming to the bending test method defined in 5.17.1 of JIS K 6911:2006, the displacement amount of the pressing wedge when the test piece breaks is defined as the breaking point displacement amount, and the breaking point displacement amount is 1.0 mm or more. The resin composition of the present disclosure contains a predetermined amount of (C) alumina, which is an inorganic filler, and has predetermined bending properties, so that it has high thermal conductivity and toughness, and can constitute a sealing material suitable for collectively encapsulating a stator.

[0013] For a test piece of the cured product obtained by heating the resin composition of the present disclosure at 175°C for 8 hours, in a three-point bending test conforming to the bending test method defined in 5.17.1 of JIS K 6911:2006, the displacement amount of the pressing wedge when the test piece breaks is defined as the breaking point displacement amount, and the breaking point displacement amount is 1.0 mm or more. The breaking point displacement amount may be 1.1 to 2.0 mm, or may be 1.2 to 1.6 mm. Since the breaking point displacement amount of the test piece cured under the predetermined conditions as described above is 1.0 mm or more, the stator collectively encapsulated using this resin composition has a tough sealing material, and is less likely to suffer damage such as cracking and chipping even against impacts such as dropping and collision, and has high strength.

[0014] When the epoxy equivalent of the (A) epoxy resin and the hydroxyl equivalent of the (B) phenolic resin curing agent in the resin composition are large, the breaking point displacement amount tends to be large. Furthermore, a lower content of inorganic filler in the resin composition tends to result in a larger fracture point displacement. Between the inorganic fillers (C) alumina and (D) silica, (D) silica generally has a higher amount of hydroxyl groups on its surface and is more likely to form chemical bonds with the resin components of (A) epoxy resin and (B) phenolic resin curing agent. For this reason, (D) silica tends to produce a larger fracture point displacement in the resulting sealant, while having a higher thermal conductivity than (C) alumina. Therefore, the content of (C) alumina and (D) silica may be determined by considering both the fracture point displacement and thermal conductivity.

[0015] The toughness of a sealing material is correlated with its bending strength and strain, and it is considered particularly effective for a large strain to be tough for a sealing material used to enclose a stator. In this disclosure, the fracture displacement is used as a direct and simple indicator corresponding to this strain for resin compositions. The fracture point displacement is specifically determined by the method described in the examples.

[0016] ((A) Epoxy resin) The epoxy resin (A) used in the resin composition of this disclosure may be any compound having two or more epoxy groups in one molecule, and its molecular weight and molecular structure are not particularly limited. The epoxy resin (A) may be in liquid or solid form, and may be crystalline or amorphous.

[0017] (A) Examples of epoxy resins include biphenyl type, biphenyl aralkyl type, Xylylene type, cresol novolac type, phenol novolac type, bisphenol A type, bisphenol F type, bisphenol S type, dicyclopentadiene modified phenol type, trisphenolmethane type, triazine nucleus-containing type and other heterocyclic types, stilbene type, naphthalene type, condensed ring aromatic hydrocarbon modified type, and alicyclic type epoxy resins. These may be used individually or in combination of two or more types.

[0018] (A) The epoxy resin may have a structure with a tough molecular skeleton from the viewpoint of the toughness of the encapsulant, and may contain at least one epoxy resin selected from biphenyl type, biphenyl aralkyl type, and Zyloc type, or may contain a biphenyl type epoxy resin.

[0019] (A) The proportion of biphenyl-type epoxy resin in the total amount of epoxy resin may be 50 to 100% by mass, 60 to 100% by mass, or 70 to 100% by mass, from the viewpoint of the toughness of the encapsulant.

[0020] (A) From the viewpoint of the toughness of the encapsulant, the epoxy resin may have an epoxy equivalent of 120 to 350 g / eq, 150 to 300 g / eq, or 160 to 250 g / eq.

[0021] The content of (A) epoxy resin in the resin composition may be 0.5 to 15% by mass, 1 to 10% by mass, or 2 to 8% by mass, from the viewpoint of good fluidity and good curability of the resin composition.

[0022] ((B) Phenolic resin curing agent) The (B) phenolic resin curing agent used in the resin composition of this disclosure is a compound having a phenolic hydroxyl group that can cure the (A) epoxy resin by reacting with the epoxy group of the (A) epoxy resin. The (B) phenolic resin curing agent may be a compound having two or more phenolic hydroxyl groups in one molecule that can react with epoxy groups, and its molecular weight and molecular structure are not particularly limited.

[0023] (B) Examples of phenol resin curing agents include novolac-type phenol resins such as phenol novolac-type and cresol novolac-type, which are obtained by reacting phenols such as phenol and alkylphenol with formaldehyde or paraformaldehyde. Other examples include modified phenol resins such as dicyclopentadiene-modified and paraxylene-modified phenol resins, phenol aralkyl-type phenol resins, biphenyl aralkyl-type phenol resins, trisphenolmethane-type phenol resins, and Zyloc-type phenol resins. These may be used individually or in combination of two or more.

[0024] (B) The phenol resin curing agent may have a structure with a tough molecular skeleton, or a structure with a molecular skeleton similar to that of (A) the epoxy resin, from the viewpoint of compatibility with (A) the epoxy resin and toughness of the encapsulant. (B) The phenol resin curing agent may contain at least one phenol resin curing agent selected from biphenyl aralkyl type and Zylok type, or it may contain a Zylok type epoxy resin.

[0025] The content of (B) phenol resin curing agent in the resin composition may be 0.5 to 15% by mass, 1 to 10% by mass, or 2 to 8% by mass, from the viewpoint of good fluidity and good curability of the resin composition.

[0026] (B) The phenol resin curing agent may have a hydroxyl group equivalent of 120 to 350 g / eq, 150 to 300 g / eq, or 160 to 250 g / eq, in view of its reactivity with (A) the epoxy resin and the appropriate curability of the resin composition.

[0027] (B) The content of the phenol resin curing agent may be such that, from the viewpoint of appropriate curability of the resin composition and toughness of the sealant, the amount of hydroxyl groups of (B) the phenol resin curing agent is 0.3 to 1.5 moles, 0.4 to 1.3 moles, or 0.5 to 1.2 moles per mole of epoxy groups of (A) the epoxy resin.

[0028] ((C) Alumina) The resin composition of this disclosure contains (C) alumina as an inorganic filler. The inclusion of (C) alumina can enhance the thermal conductivity of the encapsulant. (C) Alumina may be in the form of a spherical powder, from the viewpoint of good fluidity of the resin composition and high thermal conductivity of the encapsulant.

[0029] The content of (C) alumina in the resin composition is 70 to 85% by mass, may be 72 to 84% by mass, or 75 to 80% by mass. If the alumina content is 70% by mass or more, a sealing material with sufficiently high thermal conductivity is easily obtained. Also, if the alumina content is 85% by mass or less, a tough sealing material is easily obtained.

[0030] (C) Alumina may include (C1) alumina with a D50 of 0.1 μm or more and less than 1.0 μm, (C2) alumina with a D50 of 1.0 μm or more and less than 20 μm, and (C3) alumina with a D50 of 20 μm or more and less than 50 μm. By using alumina with different particle size distributions in combination, the packing density of (C) alumina in the sealing material tends to increase, and the high content of (C) alumina makes it easier to ensure high thermal conductivity and toughness. The alumina of (C1), (C2), and (C3) may be a single type or two or more types.

[0031] When (C) alumina contains (C1), (C2), and (C3) alumina, from the viewpoint of good fluidity of the resin composition, high thermal conductivity of the encapsulant, and toughness, the proportion of (C1) alumina may be 4 to 25% by mass, the proportion of (C2) alumina may be 15 to 65% by mass, and the proportion of (C3) alumina may be 30 to 75% by mass of the total amount of (C) alumina. The proportion of alumina in (C1) may be 5 to 22% by mass, or may be 6 to 20% by mass. The proportion of alumina in (C2) may be 18 to 60% by mass, or may be 20 to 54% by mass. The proportion of alumina in (C3) may be 35 to 70% by mass, or may be 40 to 60% by mass. (C) From the viewpoint of the toughness of the encapsulant, the maximum particle diameter of alumina may be 85 μm or less, may be 80 μm or less, or may be 75 μm or less.

[0032] ((D) silica) The resin composition of the present disclosure also contains (D) silica as an inorganic filler. By using (D) silica in combination with (C) alumina, the fluidity of the resin composition becomes good, and the encapsulant becomes tough. Specific examples of (D) silica include fused silica, crystalline silica, crushed silica, synthetic silica, etc. (D) silica may be spherical powder from the viewpoint of the good fluidity of the resin composition and the toughness of the encapsulant.

[0033] (D) silica is (D1) silica having a D50 of 0.1 μm or more and less than 1.0 μm and a BET specific surface area of 1 to 10 m 2 / g, and (D2) silica having a D50 of 1.0 μm or more and less than 20 μm and a BET specific surface area of 1 to 10 m 2 / g. The BET specific surface area of the silica of (D1) may be 3 to 9 m 2 / g, or may be 5 to 8 m 2 / g. The BET specific surface area of the silica of (D2) may be 1 to 6 m 2 / g, or may be 2 to 5 m 2 / g. By using such silicas having different particle size distributions in combination, the packing density of (D) silica in the encapsulant tends to increase, the fluidity of the resin composition tends to be good, and a tough encapsulant is easily obtained. (D1) and (D2) silica may each be a single type or two or more types.

[0034] (D) When silica contains silica of (D1) and (D2), from the viewpoint of good fluidity of the resin composition and toughness of the sealant, the content of silica of (D1) in the resin composition may be 1 to 5% by mass and the content of silica of (D2) may be 3 to 20% by mass. The silica content of (D1) may be 1.5 to 4% by mass, or 2 to 3% by mass. The silica content of (D2) may be 5 to 18% by mass, or 7 to 15% by mass.

[0035] The smaller the diameter of the silica particles, the more likely they are to aggregate, and these aggregated points can easily cause cracks and chips in the sealing material. For this reason, from the viewpoint of the toughness of the sealing material, (D) silica may include silica that has undergone surface modification treatment (for example, surface treatment with a silicone compound) to reduce aggregation. The silica in (D1) has a particularly narrow particle size distribution and a BET specific surface area of ​​4 m². 2 If the amount exceeds / g, it is prone to aggregation, so a surface modification treatment to deactivate the hydroxyl groups on the surface may be applied.

[0036] The content of (D) silica in the resin composition may be 5 to 30% by mass, 6 to 25% by mass, or 8 to 20% by mass, from the viewpoint of good fluidity of the resin composition and toughness of the sealant.

[0037] (D) Silica has a specific surface area of ​​100-300 m² (D3) BET. 2 It may contain silica at a concentration of / g. The BET specific surface area of ​​silica (D3) is 150-250 m². 2 It may also be / g, 180-220m 2 / g is also acceptable. By including silica with a larger BET specific surface area than (D1) and (D2), the contact area between the resin components of (A) epoxy resin and (B) phenolic resin curing agent and (D) silica is increased, making it easier to obtain a tough sealant. Examples of silica in (D3) include fumed silica. Each of the silicas in (D3) may be a single type or two or more types.

[0038] The silica content of (D3) in the resin composition may be such that (D) silica does not aggregate, and may be 0.1 to 3% by mass, 0.2 to 2% by mass, or 0.3 to 1.5% by mass.

[0039] ((E) Curing accelerator) The resin composition of this disclosure may further contain (E) a curing accelerator to moderately accelerate the reaction rate between (A) the epoxy resin and (B) the phenolic resin curing agent. (E) The curing accelerator may contain a latent curing accelerator, or a latent imidazole-based curing accelerator, in order to ensure even and uniform curing even when the sealant is thick.

[0040] (E) Examples of curing accelerators include 2-methylimidazole, 2-ethylimidazole, 2-isopropylimidazole, 2-undecylimidazole, 1,2-dimethylimidazole, 2,4-dimethylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 4-methylimidazole, 4-ethylimidazole, 2-phenyl-4-hydroxymethylimidazole, 2-ethyl-4-methylimidazole, 2- Imidazole compounds such as phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole, and 1-cyanoethyl-2-phenylimidazole; 1,8 Examples include diazabicyclo compounds and their salts such as -diazabicyclo[5.4.0]undecene-7 (DBU), 1,5-diazabicyclo[4.3.0]nonene, and 5,6-dibutylamino-1,8-diazabicyclo[5.4.0]undecene-7; tertiary amines such as triethylamine, triethylenediamine, benzyldimethylamine, α-methylbenzyldimethylamine, triethanolamine, dimethylaminoethanol, and tris(dimethylaminomethyl)phenol; and organic phosphine compounds such as trimethylphosphine, triethylphosphine, tributylphosphine, diphenylphosphine, triphenylphosphine, tri(p-methylphenyl)phosphine, tri(nonylphenyl)phosphine, methyldiphenylphosphine, dibutylphenylphosphine, tricyclohexylphosphine, bis(diphenylphosphino)methane, and 1,2-bis(diphenylphosphino)ethane. Examples of latent curing accelerators include the above-mentioned compounds in microencapsulated or inclusion form. Latent imidazole-based curing accelerators may also be the above-mentioned imidazole compounds in microencapsulated or inclusion form. (E) The curing accelerator may be used alone or in combination of two or more types.

[0041] The content of (E) curing accelerator in the resin composition may be 0.05 to 5% by mass, 0.1 to 4% by mass, or 0.15 to 3% by mass, from the viewpoint of achieving an appropriate curing acceleration effect for the resin composition.

[0042] (Other ingredients) In addition to the components described above, the resin composition of this disclosure may contain, as appropriate, additives such as: inorganic fillers such as silicon nitride and aluminum nitride; coupling agents such as epoxysilanes, aminosilanes, ureidosilanes, vinylsilanes, alkylsilanes, organic titanates, and aluminum alcoholates; colorants such as carbon black and cobalt blue; stress-reducing agents such as silicone oil and liquid rubber; flexibility-imparting agents such as thermoplastic elastomers; ion-scavenging agents such as hydrotalcite; and mold release agents such as synthetic waxes, natural waxes, higher fatty acids, and their metal salts. The additives may be used individually or in combination of two or more.

[0043] The total amount of additives in the resin composition may be as long as it does not impede the high thermal conductivity and toughness of the encapsulant, and may be 0 to 3% by mass, 0 to 2% by mass, or 0 to 1% by mass.

[0044] (Manufacturing method) The resin composition of this disclosure is obtained by mixing each of the components (A) to (D), as well as optional additives, which include (E) and other components. For example, it can be obtained by blending each component and thoroughly mixing them in a mixer, then melt-kneading them in a kneading device such as a hot roll or kneader, and finally cooling them. If necessary, it may be ground in a grinder such as a cutting mill, ball mill, cyclone mill, hammer mill, vibratory mill, cutter mill, or grinder mill.

[0045] [Motor Stator] The motor stator of this disclosure is encapsulated in a cured product of the resin composition of this disclosure described above. A motor stator, which is enclosed in a single unit, has multiple windings arranged such that a magnetic field is generated when current flows through it, and may be a distributed winding stator or a concentrated winding stator. The motor stator of this disclosure can be manufactured by, for example, encapsulating it in a single unit by transfer molding, in which molten resin composition of this disclosure is injected into a mold containing windings or a stator core equipped therewith.

[0046] The molding conditions for transfer molding may be, for example, a mold temperature of 150-200°C, a pressure of 0.1-12.0 MPa, and a duration of 20-300 seconds. After molding, the product may be heated at 150-200°C for 2-12 hours for post-curing.

[0047] The motor stator obtained as described above is sealed in a highly thermally conductive and robust sealing material, making it resistant to damage even when subjected to impacts such as drops or collisions, and thus possessing high strength. [Examples]

[0048] Next, the present disclosure will be specifically described by examples. The present disclosure is not limited in any way by these examples.

[0049] [Examples 1-10 and Comparative Examples 1-5] The raw materials for each of the examples and comparative examples shown in Table 1 were mixed at room temperature (20°C), and then kneaded in a twin-screw kneader at 100°C to obtain the resin composition.

[0050] Details of the raw materials used in the examples and comparative examples are shown below. <(A) Epoxy resin> a1: "NC-3000", manufactured by Nippon Kayaku Co., Ltd.; epoxy equivalent 277 g / eq, biphenyl aralkyl type a2: "NC-2000-L", manufactured by Nippon Kayaku Co., Ltd.; epoxy equivalent 277 g / eq, Zylok type a3: "jER(registered trademark) YX4000", manufactured by Mitsubishi Chemical Corporation; epoxy equivalent 195g / eq, biphenyl type

[0051] <(B) Phenolic resin curing agent> • b1: "MEHC-7800SS", manufactured by UBE Corporation; hydroxyl group equivalent 170 g / eq, Zylock type • b2: "HE200C-10", manufactured by Air Water Performance Chemicals Inc.; hydroxyl group equivalent 204 g / eq, biphenyl aralkyl type • b3: "HE610C-07", manufactured by Air Water Performance Chemicals Inc.; hydroxyl group equivalent 183g / eq, biphenyl aralkyl type

[0052] <(C) Alumina> • c1: "AO-502", manufactured by Admatex Co., Ltd.; spherical alumina, D50 = 0.2 μm • c2-1: "DAW-05", manufactured by Denka Co., Ltd.; spherical alumina, D50=5μm • c2-2: "DAW-10", manufactured by Denka Co., Ltd.; spherical alumina, D50 = 10 μm • c3: "DAW-45", manufactured by Denka Co., Ltd.; spherical alumina, D50 = 35 μm

[0053] <(D) Silica> • d1: "AdmaFine (registered trademark) SC2500-SQ", manufactured by Admatex Co., Ltd.; spherical silica, D50 = 0.5 μm, BET specific surface area 6.0 m² 2 / g, surface modified product ·d2: "KYKLOS (registered trademark) MSR-8030", manufactured by Ryumori Co., Ltd.; spherical silica, D50=12μm, BET specific surface area 2.9m 2 / g • d3: "LeoroSeal (registered trademark) QS-102", manufactured by Tokuyama Corporation; fumed silica, D50 < 0.1 μm, BET specific surface area 200 m² 2 / g • d4: "AdmaFine (registered trademark) SO-C1", manufactured by Admatex Co., Ltd.; spherical silica, D50 = 0.3 μm, BET specific surface area 15 m² 2 / g d5: "FB-950", manufactured by Denka Co., Ltd.; spherical silica, D50 = 24 μm, BET specific surface area 1.5 m² 2 / g • d6: "FB-40R", manufactured by Denka Co., Ltd.; spherical silica, D50 = 41 μm, BET specific surface area 0.5 m² 2 / g

[0054] <(E) Curing accelerator> • e1: "NISSOCURE(registered trademark) TIC-188", manufactured by Nippon Soda Co., Ltd.; 1,1,2,2-tetrakis(4-hydroxyphenyl)ethane inclusion 2-phenyl-4-methyl-5-hydroxymethylimidazole, latent imidazole-based curing accelerator e2: "2P4MHZ-PW", manufactured by Shikoku Chemicals Co., Ltd.; 2-phenyl-4-methyl-5-hydroxymethylimidazole

[0055] <Other ingredients> • Release agent: "Carnauba wax No. 1 powder," manufactured by Toyo Chem Co., Ltd. • Coloring agent: "Mitsubishi (registered trademark) Carbon Black MA100", manufactured by Mitsubishi Chemical Corporation • Stress-reducing agent: "Ricon 657E", manufactured by Clay Valley Corporation; epoxy-modified liquid polybutadiene, liquid rubber

[0056] The D50 values ​​for (C) alumina and (D) silica were measured using a laser diffraction / scattering particle size distribution analyzer ("LA-920", manufactured by Horiba, Ltd.). The BET specific surface area of ​​(D) silica was measured using a single-point BET method with nitrogen adsorption on a specific surface area analyzer ("Macsorb® HM Model-1220", manufactured by Mountec Co., Ltd.) after degassing the sample at 60°C for 10 minutes.

[0057] [evaluation] The resin compositions obtained in each of the above examples and comparative examples were evaluated as follows. The evaluation results are shown in Table 1.

[0058] (Spiral Flow) Using a spiral flow measurement mold conforming to ASTM D3123-09 (2017), a resin composition was injected (mold temperature 175°C, injection pressure 9.8 MPa, molding time 120 seconds), and the length of the resin composition to the flowing tip (spiral flow) was measured. If the spiral flow is 35-100 cm, the resin composition has appropriate fluidity and can be said to have good filling properties and handling properties for molds, etc. The spiral flow may also be 40-95 cm or 45-90 cm.

[0059] (Flow viscosity) The flow viscosity of the resin composition was measured using a high-efficiency flow tester ("CFT-500C", manufactured by Shimadzu Corporation; measurement conditions: nozzle length 1.0 mm, nozzle diameter 0.5 mm, temperature 175°C, pressure 0.98 MPa). If the flow viscosity is 10 to 50 Pa·s or less, the resin composition has adequate fluidity and can be said to have good fillability in molds and other applications, as well as good handling properties. The flow viscosity may also be 15 to 45 Pa·s or 17 to 40 Pa·s.

[0060] (Geltime) The gel time of the resin composition was measured using a method in accordance with the gelation time method A specified in JIS C 2161:2010, 7.5.1. A 1g sample of the resin composition was quickly spread in a circle approximately 50mm in diameter on a 175°C hot plate using a stirring rod. The sample was then stirred in a circular motion at a speed of approximately two circles every three seconds, and the time until the sample became gel-like and could no longer be stirred was measured. If the gel time is 20 seconds or longer, the resin composition can be said to have a sufficient pot life (working time). Furthermore, if the gel time is 45 seconds or less, the resin composition can be said to have a moderate pot life. The gel time may also be between 23 and 40 seconds, or between 25 and 35 seconds.

[0061] (Thermal conductivity) A test specimen (100 mm in diameter, 2.0 mm thick) was prepared by transfer molding the resin composition at a mold temperature of 175°C for 120 seconds, followed by curing by heating at 175°C for 8 hours. The thermal conductivity of the test specimens was measured using a hot disk method thermophysical property measurement device ("TPS500S", manufactured by Kyoto Electronics Manufacturing Co., Ltd.). If the thermal conductivity is 2.5 W / (m·K) or higher, it can be said that a molded product with high thermal conductivity can be obtained. The thermal conductivity may also be 2.6 to 6.0 W / (m·K), or 3.0 to 5.0 W / (m·K).

[0062] (3-point bending test) The resin composition was transfer-molded at a mold temperature of 175°C for 120 seconds, and then cured by heating at 175°C for 8 hours to produce a test specimen (length 80 mm, height (thickness) 4 mm, width 10 mm). The test specimens were subjected to a three-point bending test (conformed to the bending test method specified in JIS K 6911:2006, 5.17.1) at room temperature (20°C) using a precision universal testing machine ("Autograph AG-X", manufactured by Shimadzu Corporation; measurement conditions: distance between supports 64 mm, load speed 1 mm / min). The displacement of the pressure wedge at the time of fracture was measured and defined as the fracture point displacement. The bending strength was calculated from the load at the time of fracture. If the fracture displacement is 1.0 mm or more, the resin composition can be said to exhibit high toughness for single-piece sealing. The fracture displacement may be 1.1 to 2.0 mm, or 1.2 to 1.6 mm. Furthermore, if the bending strength is 110 MPa or higher, the resin composition is more likely to exhibit high toughness suitable for bulk sealing. The bending strength may also be 120 MPa or higher, or even 130 MPa or higher.

[0063] (Drop test) A test specimen of a simulated motor was prepared by sealing a dummy bobbin with a fiber-reinforced plastic (FRP) plug in a cylindrical molded product with an outer diameter of 35 mm, an inner diameter of 15 mm, and a height of 30 mm. A resin composition was injected into the cylindrical mold, and the specimen was obtained by transfer molding at a mold temperature of 175°C, a pressure of 5.0 MPa, and 150 seconds, followed by post-curing by heating at 175°C for 8 hours. The test specimens were dropped naturally from a height of 50 cm onto a stainless steel floor with the plug facing upwards. The presence or absence of cracks and chips was checked, and they were evaluated according to the following criteria. <Judgment criteria> A: No cracks or chips. B: There is a tiny chip less than 0.3 mm in length. C: Has chips or cracks of 0.3 mm or more in length.

[0064] [Table 1]

[0065] Furthermore, some aggregation occurred in the resin composition of Comparative Example 3. In addition, the resin composition of Comparative Example 5 cured too quickly, making it impossible to prepare test specimens for evaluating thermal conductivity and three-point bending tests, as well as test specimens for drop tests.

[0066] As can be seen from the evaluation results shown in Table 1, the resin composition of this disclosure was confirmed to have moderate fluidity, be easy to handle, and produce a cured product with high thermal conductivity and toughness. Furthermore, a motor stator sealed using the resin composition of this disclosure is less susceptible to damage from impacts such as drops and can be said to have high strength.

Claims

1. A resin composition comprising (A) epoxy resin, (B) phenolic resin curing agent, (C) alumina, and (D) silica, (C) The alumina content is 70 to 85% by mass, A resin composition for encapsulating motor stators, wherein a test specimen of the cured product obtained by heating the resin composition at 175°C for 8 hours is subjected to a three-point bending test in accordance with the bending test method specified in JIS K 6911:2006, 5.17.1, and the displacement of the pressure wedge when the test specimen breaks is defined as the fracture point displacement, and the fracture point displacement is 1.0 mm or more.

2. (C) The alumina comprises (C1) alumina with a cumulative volume 50% particle size (D50) of 0.1 μm or more and less than 1.0 μm, (C2) alumina with a cumulative volume 50% particle size (D50) of 1.0 μm or more and less than 20 μm, and (C3) alumina with a cumulative volume 50% particle size (D50) of 20 μm or more and less than 50 μm, as described in claim 1.

3. The resin composition for encapsulating a motor stator according to claim 2, wherein the proportion of alumina (C1) is 4 to 25% by mass, the proportion of alumina (C2) is 15 to 65% by mass, and the proportion of alumina (C3) is 30 to 75% by mass of the total amount of alumina (C).

4. (D) Silica has a cumulative volume 50% particle size (D50) of 0.1 μm or more and less than 1.0 μm, and a BET specific surface area of ​​1 to 10 m². ２ Silica per gram, with a (D2) cumulative volume 50% particle size (D50) of 1.0 μm or more and less than 20 μm, and a BET specific surface area of ​​1 to 10 m². ２ A resin composition for encapsulating motor stators according to claim 1, comprising silica at a concentration of / g.

5. The resin composition for encapsulating a motor stator according to claim 4, wherein the content of silica of (D1) in the resin composition is 1 to 5% by mass, and the content of silica of (D2) is 3 to 20% by mass.

6. (D) Silica has a BET specific surface area of ​​100-300 m² (D3). ２ A resin composition for encapsulating motor stators according to claim 1, comprising silica at a concentration of / g.

7. The resin composition for encapsulating a motor stator according to claim 6, wherein the silica content of (D3) in the resin composition is 0.1 to 3% by mass.

8. (A) The resin composition for encapsulating a motor stator according to claim 1, wherein the epoxy resin comprises at least one epoxy resin selected from biphenyl type, biphenyl aralkyl type, and Zylok type.

9. (B) The resin composition for encapsulating a motor stator according to claim 1, wherein the phenolic resin curing agent comprises at least one phenolic resin curing agent selected from biphenyl aralkyl type and Zyloc type.

10. Furthermore, the resin composition for encapsulating a motor stator according to claim 1, further comprising (E) a curing accelerator.

11. The resin composition for encapsulating a motor stator according to claim 10, wherein the content of (E) curing accelerator in the resin composition is 0.05 to 5% by mass.

12. (E) The resin composition for motor stator encapsulation according to claim 10, wherein the curing accelerator comprises a latent imidazole-based curing accelerator.

13. A motor stator that is collectively sealed with a cured product of the motor stator collective sealing resin composition according to any one of claims 1 to 12.

Images