Powdered paint

Abstract

To provide a powdered paint that can be used for forming a coating part of a coil end having excellent anti ATF property.SOLUTION: Powdered paint of the present invention is used for coating a coil end, and contains a particulate thermosetting resin composition, and the thermosetting resin composition contains epoxy resin, curative and inorganic filler. In the bending strength of a cured product of the powdered paint at 25°C which is measured according to JIS K 6911(2006), when 1000 hours of immersion treatment into 150°C of automatic transmission fluid is performed to the cured product, and the bending strength before the immersion treatment is X1[MPa] and the bending strength after the immersion treatment is X2[MPa], the X1 is 40[MPa] or more, and a ratio (X2 / X1) of X2 to the X1 is 0.95 or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to powder coatings. [Background technology]

[0002] Batteries that supply power to automotive electronic components and motors use rotating electric machines that have a rotor and a stator. The stator of a vehicle rotating electric machine typically includes a stator core, a stator coil (stator winding) attached to the stator core, and the like. The stator coil also includes an internal conductor housed within the stator core and an exposed conductor portion (coil end) that is exposed from the stator core. Because the coil end is exposed from the stator core, the coil end is insulated by painting it with powder paint.

[0003] Patent Document 1 describes a method of painting the coil ends of a stator coil by immersing the coil ends in a powder coating material in the form of very small particles contained in a powder tank.

[0004] In a rotating electric machine for a vehicle, a refrigerant such as automatic transmission fluid (ATF) is supplied to the stator and rotor to cool them. In particular, to cool the coil of the rotating electric machine, the refrigerant is supplied from the rotor to the coil ends of the coil.

[0005] Because the painted coil end portion is in direct contact with ATF, the coating film, i.e., the coated portion of the coil end formed from powder paint, is particularly required to have ATF resistance. Here, ATF resistance refers to the property that prevents a decrease in the performance of the coated portion, which is the cured product of the paint, even when it comes into direct contact with ATF, such as its strength and insulating properties.

[0006] However, it has not been possible to provide a powder coating material that can be used to form a coating portion (coil end coating portion) having sufficiently excellent ATF resistance. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-095980 Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a powder coating that can be used to form a coating portion of a coil end that has excellent ATF resistance. [Means for solving the problem]

[0009] These objects can be achieved by the present invention as set forth in (1) to (4) below. (1) Powder coating used to coat coil ends, a particulate thermosetting resin composition, the thermosetting resin composition comprises an epoxy resin, a curing agent, and an inorganic filler; The bending strength of the cured product of the powder coating at 25°C measured according to JIS K 6911 (2006) is: The cured product was immersed in automatic transmission fluid at 150°C for 1000 hours, and the bending strength before the immersion treatment was defined as X1 [MPa] and the bending strength after the immersion treatment was defined as X2 [MPa]. The X1 is 40 [MPa] or more, The powder coating has a ratio of X2 to X1 (X2 / X1) of 0.95 or more.

[0010] (2) The powder coating material according to (1), wherein the content of the curing agent per 100 parts by mass of the epoxy resin is 7 parts by mass or more and 15 parts by mass or less.

[0011] (3) The dielectric breakdown voltage of the cured product of the powder coating at 25°C measured by a method in accordance with JIS C2110-1. When the breakdown voltage before the immersion treatment is V1 [kV / mm] and the breakdown voltage after the immersion treatment is V2 [kV / mm], The V1 is 37 [kV / mm] or more, The powder coating material according to (1) or (2) above, wherein the ratio of V2 to V1 (V2 / V1) is 0.90 or more.

[0012] (4) The powder coating material according to any one of (1) to (3) above, wherein the coil end is made of copper. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a powder coating material that can be used to form a coating portion of a coil end that has excellent ATF resistance. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a perspective view showing an example of the configuration of a stator to which the powder coating material of the present invention is applied. [Figure 2] 2 is a plan view showing an example of the configuration of a coil end of a stator coil in the stator shown in FIG. 1. [Figure 3] FIG. 1 is a diagram illustrating an example of a coating method. DETAILED DESCRIPTION OF THE INVENTION

[0015] Preferred embodiments of the present invention will be described in detail below. [1] Powder paint First, the powder coating material of the present invention will be described.

[0016] The powder coating material of the present invention is a powder coating material used to coat coil ends, and contains a particulate thermosetting resin composition, which contains an epoxy resin, a curing agent, and an inorganic filler.

[0017] Furthermore, the powder coating of the present invention has a flexural strength at 25°C of a cured product measured by a method in accordance with JIS K 6911 (2006), where the cured product is immersed in automatic transmission fluid (ATF) at 150°C for 1,000 hours, and the flexural strength before the immersion is X1 [MPa] and the flexural strength after the immersion is X2 [MPa], X1 is 40 [MPa] or more and the ratio of X2 to X1 (X2 / X1) is 0.95 or more.

[0018] By satisfying these conditions, it is possible to provide a powder coating that can be used to form a coating portion of a coil end that has excellent ATF resistance.

[0019] More specifically, if the bending strength X1 before the immersion treatment is 40 [MPa] or more, the initial bending strength of the coated portion of the coil end formed by the powder paint can be made sufficiently excellent.

[0020] Furthermore, by setting the ratio (X2 / X1) of the bending strength X2 after the immersion treatment to X1 to be 0.95 or more, the coated portion of the coil end formed by the powder paint will have high bending strength even after being immersed in ATF for a long period of time, and will have excellent ATF resistance.

[0021] On the other hand, if the above conditions are not met, the above excellent effects cannot be obtained.

[0022] For example, if the bending strength X1 before the immersion treatment is less than 40 [MPa], the initial bending strength of the coated portion of the coil end formed by the powder paint cannot be made sufficiently excellent.

[0023] Furthermore, if X2 / X1 is less than 0.95, the coated portion of the coil end formed by the powder coating will have significantly low bending strength after being immersed in ATF for a relatively long period of time, and will not have sufficiently excellent ATF resistance.

[0024] The cured product used to measure bending strength (the same applies to the cured product used to measure the breakdown voltage, shear tensile strength, glass transition temperature, and thermal expansion coefficient described below) can be obtained by melting and curing the powder coating material in question by heating it at 190°C for 20 minutes.

[0025] In addition, in the immersion treatment, i.e., the treatment of immersing the cured product in automatic transmission fluid at 150°C for 1000 hours, Autofluid WS (manufactured by Toyota Motor Corporation) can be used as the automatic transmission fluid.

[0026] As described above, the bending strength X1 before the immersion treatment may be 40 MPa or more, preferably 80 MPa or more, and more preferably 100 MPa or more. This makes it possible to make the above-mentioned effects of the present invention more pronounced.

[0027] The upper limit of the bending strength X1 before the immersion treatment does not need to be set, but it is preferably set to 200 MPa or less.

[0028] As mentioned above, X2 / X1 may be 0.95 or more, but is preferably 1.00 or more, and more preferably 1.05 or more. This makes it possible to make the above-mentioned effects of the present invention more pronounced.

[0029] The upper limit of X2 / X1 does not need to be set, but it is preferable to set it to 1.20 or less.

[0030] [1-1] Thermosetting resin composition The thermosetting resin composition includes an epoxy resin, a curing agent, and an inorganic filler.

[0031] [1-1-1] Epoxy resin The thermosetting resin composition includes an epoxy resin.

[0032] Specific examples of epoxy resins include those having two or more epoxy groups in the molecule and being solid at room temperature, such as bisphenol A, bisphenol F, bisphenol S, novolac, phenol novolac, cresol novolac, biphenyl, naphthalene, biphenyl aralkyl, and aromatic amine epoxy resins.

[0033] The epoxy resin preferably contains one or more selected from the group consisting of bisphenol A epoxy resins, biphenyl epoxy resins such as biphenyl aralkyl epoxy resins, dicyclopentadiene epoxy resins, orthocresol novolac epoxy resins, and tetramethylbiphenyl epoxy resins.

[0034] Among these, the epoxy resin preferably contains a bisphenol A type epoxy resin and one or more selected from the group consisting of biphenyl type epoxy resins, dicyclopentadiene type epoxy resins, biphenyl aralkyl type epoxy resins, and tetramethylbiphenyl type epoxy resins, and more preferably contains a bisphenol A type epoxy resin and a biphenyl aralkyl type epoxy resin.

[0035] This allows the coil end to be more stably covered with the covering portion formed by the powder paint.

[0036] The softening point of the bisphenol A type epoxy resin is preferably 50°C or higher and 100°C or lower, and more preferably 60°C or higher and 90°C or lower.

[0037] This makes it possible to more effectively prevent the powder paint from caking in the fluidized bed, and also makes it possible to improve the appearance of the coating formed by the powder paint.

[0038] The content of the epoxy resin in the thermosetting resin composition is preferably 30.0 mass% or more and 70.0 mass% or less, more preferably 35.0 mass% or more and 67.5 mass% or less, and even more preferably 36.5 mass% or more and 65.0 mass% or less.

[0039] This makes it possible to improve the smoothness of the surface of the cured powder coating, i.e., the coated portion formed by the powder coating, and also to improve the formability of the coated portion by the powder coating.

[0040] In addition, since the thermal expansion coefficient (linear expansion coefficient) of epoxy resin is larger than that of inorganic fillers, as the content of epoxy resin in the thermosetting resin composition increases, the thermal expansion coefficient of the cured powder coating also increases.

[0041] [1-1-2] Hardener The thermosetting resin composition contains a curing agent.

[0042] Specific examples of the curing agent include amines such as aromatic amines such as diaminodiphenylmethane and aniline resin, condensates of aliphatic amines and aliphatic dicarboxylic acids, and dicyandiamide and its derivatives; various imidazole and imidazoline compounds; polydicarboxylic acids such as adipic acid, sebacic acid, phthalic acid, maleic acid, trimellitic acid, benzophenone dicarboxylic acid, benzophenone tetracarboxylic acid, and pyromellitic acid, or acid anhydrides thereof; phenolic resins such as novolac-type phenolic resins, biphenyl aralkyl-type phenolic resins, and naphthol aralkyl-type phenolic resins; novolacs which are condensates of dihydrazides such as adipic acid and phthalic acid, phenol, cresol, xylenol, bisphenol A, or the like with aldehydes; carboxylic acid amides; methylolated melamines; and block isocyanurates.

[0043] The curing agent preferably contains one or more selected from the group consisting of acid anhydrides and phenolic resins.

[0044] This makes it possible to more effectively prevent the powder paint from dripping unintentionally when forming the coating portion, and also improves the filling properties of the powder paint.

[0045] The ratio of curing agent to epoxy resin can be adjusted, for example, depending on the types of epoxy resin and curing agent used. However, the number of moles (number) of functional groups of the curing agent contained in the thermosetting resin composition relative to the number of moles (number) of epoxy groups of the epoxy resin is preferably 0.3 molar equivalents or more and 2.0 molar equivalents or less, more preferably 0.3 molar equivalents or more and 1.8 molar equivalents or less, and even more preferably 0.4 molar equivalents or more and 1.7 molar equivalents or less.

[0046] This makes it possible to improve the curing properties of the powder coating material, and also to improve the bending strength and shear tensile strength of the cured product of the powder coating material, i.e., the coated portion formed by the powder coating material.

[0047] In the powder coating, the content of the curing agent per 100 parts by mass of the epoxy resin is preferably 7 parts by mass or more and 15 parts by mass or less, more preferably 8 parts by mass or more and 14 parts by mass or less, and even more preferably 9 parts by mass or more and 13 parts by mass or less.

[0048] This makes it possible to improve the curing properties of the powder coating material, and also to improve the bending strength and shear tensile strength of the cured product of the powder coating material, i.e., the coated portion formed by the powder coating material.

[0049] [1-1-3] Inorganic filler The thermosetting resin composition contains an inorganic filler.

[0050] Examples of inorganic fillers include silica such as crystalline silica, fused silica such as crushed fused silica, spherical silica, surface-treated silica, and amorphous silica; calcium compounds such as calcium carbonate and calcium sulfate; barium sulfate, aluminum oxide (specifically alumina), aluminum hydroxide, magnesium hydroxide, talc, kaolin, clay, mica, dolomite, wollastonite, glass fiber, glass beads, zircon, and molybdenum compounds.

[0051] Among these, it is preferable to use amorphous silica as the inorganic filler. This makes it possible to improve the bending strength and insulating properties of the cured powder coating, i.e., the coating portion formed by the powder coating. It also makes it possible to prevent the thermal expansion coefficient of the coating portion from becoming too large, thereby improving the adhesion between the coil end and the coating portion.

[0052] When the inorganic filler is amorphous silica, the average particle size D50 of the amorphous silica is preferably 1 μm or more and 50 μm or less, more preferably 1 μm or more and 30 μm or less, and even more preferably 5 μm or more and 25 μm or less.

[0053] In this specification, D50 is the particle size at which the cumulative value is 50% in the volume frequency particle size distribution of the inorganic filler measured by laser diffraction scattering method.

[0054] In the powder coating, the content of inorganic filler per 100 parts by mass of epoxy resin is preferably 40 parts by mass or more and 230 parts by mass or less, more preferably 45 parts by mass or more and 180 parts by mass or less, and even more preferably 50 parts by mass or more and 170 parts by mass or less.

[0055] This improves the mechanical strength of the cured powder coating, i.e., the coated portion formed by the powder coating, and also makes it possible to further improve the smoothness of the surface of the coated portion.

[0056] The content of the inorganic filler in the thermosetting resin composition is preferably 25.0 mass% or more and 70.0 mass% or less, more preferably 28.0 mass% or more and 66.0 mass% or less, and even more preferably 31.0 mass% or more and 62.0 mass% or less.

[0057] This improves the mechanical strength of the cured powder coating, i.e., the coated portion formed by the powder coating, and also makes it possible to further improve the smoothness of the surface of the coated portion.

[0058] [1-1-4]Curing catalyst The thermosetting resin composition may further contain a curing catalyst (curing accelerator).

[0059] This makes it possible to more effectively prevent the powder paint from dripping unintentionally when forming the coating portion, and also improves the filling properties of the powder paint.

[0060] Examples of the curing catalyst include organic phosphines such as triphenylphosphine; imidazole compounds such as 2-phenylimidazole; and amine compounds such as tertiary amines.

[0061] The content of the curing catalyst relative to 100 parts by mass of the epoxy resin is preferably 0.01% by mass or more and 1.0% by mass or less, more preferably 0.03% by mass or more and 0.5% by mass or less, and even more preferably 0.05% by mass or more and 0.3% by mass or less. This allows for better curing properties to be obtained.

[0062] [1-1-5] Colorants The thermosetting resin composition may further contain a colorant such as a pigment.

[0063] As the pigment, for example, known pigments can be used, but it is preferable to use one or a combination of two or more selected from the group consisting of titanium oxide, iron oxide, zinc oxide, carbon black, and cyanine blue.

[0064] The content of the pigment in the thermosetting resin composition is preferably 0.01% by mass or more and 5.0% by mass or less, more preferably 0.1% by mass or more and 3.0% by mass or less, and even more preferably 0.1% by mass or more and 2.0% by mass or less. This makes it possible to obtain better coloring properties.

[0065] [1-1-6] Other ingredients The thermosetting resin composition may contain components other than the components described above. Hereinafter, in this section, such components will be referred to as "other components."

[0066] Examples of other components include thermosetting resins other than epoxy resins, leveling agents, flame retardants, coupling agents, and the like.

[0067] Examples of thermosetting resins other than epoxy resins include phenolic resins, melamine resins, unsaturated polyester resins, and polyurethane resins.

[0068] However, the content of other components in the thermosetting resin composition is preferably 10.0% by mass or less, more preferably 7.0% by mass or less, and even more preferably 5.0% by mass or less.

[0069] [1-1-7] Other conditions The thermosetting resin composition is in the form of particles.

[0070] The average particle size D50 of the thermosetting resin composition is preferably 20 μm or more and 100 μm or less, more preferably 40 μm or more and 80 μm or less, and even more preferably 50 μm or more and 70 μm or less. This allows the powder coating to have better filling properties in narrow spaces.

[0071] [1-2] Components other than the granular thermosetting resin composition The powder coating may be composed of a particulate thermosetting resin composition, or may further contain components other than the particulate thermosetting resin composition. Such components include, for example, fluidity imparting agents.

[0072] Specific examples of the fluidity imparting agent include inorganic particles such as silica and alumina.

[0073] However, the content of components other than the thermosetting resin composition in the powder coating is preferably 2.0 mass % or less, more preferably 1.5 mass % or less, and even more preferably 1.0 mass % or less.

[0074] [1-3] Other conditions The cured powder coating preferably satisfies the following conditions:

[0075] For example, in the breakdown voltage of the cured powder coating at 25°C measured by a method conforming to JIS C2110-1, when the breakdown voltage before the immersion treatment is V1 [kV / mm] and the breakdown voltage after the immersion treatment is V2 [kV / mm], it is preferable that V1 is 37 [kV / mm] or more and the ratio of V2 to V1 (V2 / V1) is 0.90 or more.

[0076] This makes it possible to improve the ATF resistance of the coated portion of the coil end formed by the powder paint.

[0077] As described above, the breakdown voltage V1 before the immersion treatment is preferably 37 kV / mm or more, more preferably 38 kV / mm or more, and even more preferably 40 kV / mm or more. This makes it possible to make the above-mentioned effects more pronounced.

[0078] As mentioned above, V2 / V1 is preferably 0.90 or more, more preferably 0.95 or more, and even more preferably 1.00 or more. This makes it possible to make the above-mentioned effects more pronounced.

[0079] Furthermore, the shear tensile strength of the cured powder coating is preferably 7 MPa or more, more preferably 10 MPa or more, and even more preferably 12 MPa or more.

[0080] This makes it possible to improve the adhesion between the coil end and the coating formed by the powder paint when the coil end is made of copper.

[0081] The shear tensile strength is a value measured by a method in accordance with JIS K 6850.

[0082] The glass transition temperature of the cured powder coating is preferably 90°C or higher, more preferably 110°C or higher, and even more preferably 130°C or higher.

[0083] This increases the crosslink density of the coating portion formed by the powder coating, thereby making it possible to improve the strength and flexibility of the coating portion.

[0084] It is preferable that the thermal expansion coefficient of the cured powder paint be close to that of the material that makes up the coil end, in other words, that there is a small difference between the thermal expansion coefficient of the coil end and that of the cured powder paint. This makes it possible to prevent peeling of the coating, which would otherwise be caused by a large difference between the thermal expansion coefficients of the coil end and the coating formed by the powder paint.

[0085] For example, if the coil end is made of copper, it is preferable that the thermal expansion coefficient of the cured powder coating material is close to the thermal expansion coefficient of copper.

[0086] Specifically, the average thermal expansion coefficient of the cured powder coating from 40 to 50°C is 1.0 x 10 ―5 / K or more 5.0×10 ―5 / K or less, and preferably 1.0 × 10 ―5 / K or more 3.5×10 ―5 / K or less is more preferable, and 1.5×10 ―5 / K or more 2.5×10 ―5 It is more preferable that the temperature is not more than 1000 K / K. This makes it possible to make the above-mentioned effects more pronounced.

[0087] [2] Powder coating manufacturing method Next, a method for producing the powder coating will be described.

[0088] The method for producing a powder coating according to this embodiment includes a preparation step of preparing a thermosetting resin composition. Furthermore, when the powder coating contains components other than the thermosetting resin composition (e.g., a fluidity imparting agent), the method for producing a powder coating may further include, for example, a mixing step of mixing the thermosetting resin composition with the other components. For example, in the preparation step of a particulate thermosetting resin composition, an epoxy resin, an inorganic filler, a curing agent, and optional components are blended and mixed in a predetermined order, and then the mixture is melt-kneaded while being heated to obtain a mixture of all raw materials.

[0089] Next, the resulting mixture of all raw materials is pulverized in an impact pulverizer to obtain an epoxy resin powder coating. After pulverization, the powder coating may be sieved to separate fine particles and remove coarse particles, thereby adjusting the particle size of the powder coating.

[0090] [3] Coil end Next, the coil end of the coil to which the powder coating of the present invention is applied will be described. Fig. 1 is a perspective view showing an example of the configuration of a stator to which the powder coating material of the present invention is applied, and Fig. 2 is a plan view showing an example of the configuration of a coil end of a stator coil in the stator shown in Fig. 1.

[0091] The coil according to the present invention has coil ends whose exposed portions are sealed with the powder coating material of the present invention.

[0092] The coil ends may be constructed of any material, but are preferably constructed of copper. Copper is advantageous in that it is a relatively inexpensive material with high electrical conductivity.

[0093] A specific example of the coil is a motor coil such as a drive motor coil, etc. Hereinafter, a more specific explanation will be given using a stator coil of a motor as an example.

[0094] 1 includes a stator core 101 and a stator coil 103. The stator coil 103 is disposed in a groove (slot) (not shown) provided on the inner wall of the stator core 101.

[0095] As shown in Fig. 2, coil end 105 is provided with an enamel coating portion 107 in which the conductor portion is covered with an insulating coating, for example, enamel, and an exposed portion 109 in which the conductor portion is exposed from the enamel coating, and exposed portion 109 is sealed with the powder coating of the present invention. In Fig. 2, a coating portion 111 is provided from exposed portion 109 to enamel coating portion 107. Coating portion 111 is made of a cured product of the powder coating of the present invention.

[0096] [4] Painting method Next, a coating method using the powder coating material of the present invention, in other words, a method for forming a coated portion on a coil end, will be described. FIG. 3 is a diagram illustrating an example of a coating method.

[0097] Specifically, the painting method of this embodiment includes an adhesion process (first process) in which the coil end 105 of a coil (stator coil 103) having a coil end 105 in which the conductor portion is covered with an insulating coating and has an exposed portion 109 where the conductor portion is exposed from the insulating coating is immersed in a fluidization tank 20 in which powder paint 10 flows, and the molten powder paint 10 is adhered to the outside of the exposed portion 109, and a curing process (second process) in which the powder paint 10 adhered to the coil end 105 is cured.

[0098] The adhesion process may include, for example, a flow process in which gas G is introduced into a fluidization tank 20 containing the powder coating material 10 to cause the powder coating material 10 to flow, and an immersion process in which the coil end 105 is immersed in the fluidization tank 20 in which the powder coating material 10 is flowing.

[0099] The fluidization step can be carried out, for example, by using a fluidization tank 20 having a perforated plate 21 at the bottom, filling the powder coating material 10 above the perforated plate 21, and introducing gas G from outside the perforated plate 21 into the fluidization tank 20 through the perforated plate 21.

[0100] In the dipping process, the stator core 101 is positioned so that the coil ends 105 are positioned vertically downward, and the stator core 101 is lowered. Then, the coil ends 105 are dipped into the powder coating material 10 in the fluidization tank 20.

[0101] In the immersion step, immersing the coil ends 105 in the fluidizing bath 20 and adhering the molten powder coating material 10 to the outside of the exposed portions 109 may be performed as a single step or may be performed in stages as separate steps, but it is preferable to perform these steps as a single step. In other words, it is preferable that the adhesion of the molten powder coating material 10 to the outside of the exposed portions 109 occurs while the coil ends 105 are immersed in the fluidizing bath 20.

[0102] The coating method of this embodiment preferably further includes a heating step of heating the coil ends 105 before immersing the coil ends 105 in the fluidization bath 20 . This improves the sealing stability of exposed portion 109.

[0103] At this time, by immersing the heated coil end 105 in the fluidization tank 20 in which the powder paint 10 flows, the powder paint 10 near the coil end 105 adheres to the coil end 105 as a molten material in the fluidization tank 20.

[0104] Furthermore, after the coil ends 105 are removed from the fluidization bath 20, the coil ends 105 may be subjected to a heat treatment for heating.

[0105] This allows the powder coating material 10 adhering to the coil end 105 to be melted more stably.

[0106] The coil ends 105 can be heated by, for example, a heater 22 disposed above the fluidization tank 20 .

[0107] The heat curing conditions in the curing step can be set appropriately depending on the type and size of the coil end 105, the constituent components of the powder coating material 10, and the like.

[0108] The curing step may be carried out consecutively with the application step. More specifically, for example, if the coil ends 105 are heated before being immersed in the fluidizing bath 20, the residual heat of the coil ends 105 after they are removed from the fluidizing bath 20 may be used to promote the curing reaction of the powder coating material 10 applied to the coil ends 105. Furthermore, as described above, if the coil ends 105 are subjected to a heat treatment after being removed from the fluidizing bath 20, the heat treatment may be intended to further stably melt the powder coating material 10 applied to the coil ends 105 and promote the curing reaction.

[0109] In addition, the heat treatment may be performed, for example, only to promote the curing reaction, without the purpose of making the powder coating material 10 adhered to the coil end 105 more stable and molten.

[0110] The hardened powder coating material 10 is integrated with the coil end 105 to form a coating portion 111 .

[0111] In the coating method of this embodiment, the application step and the curing step may be alternately repeated multiple times to increase the thickness of the coating film (coated portion).

[0112] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these.

[0113] For example, the powder coating of the present invention may be produced by any method, and is not limited to those produced by the methods described above. Furthermore, for example, the coating method using the powder coating material of the present invention is not limited to the above-mentioned method. [Example]

[0114] The present invention will be described in more detail below with reference to specific examples, but the present invention is not limited to these examples. In the following description, treatments for which no temperature conditions are specified were performed at room temperature, specifically 25°C. Furthermore, various measurement conditions for which no temperature conditions are specified are values at room temperature, specifically 25°C.

[0115] [5] Powder coating manufacturing Example 1 The epoxy resin was 35.2% by mass of bisphenol A solid epoxy resin, the inorganic filler was 60.6% by mass of spherical amorphous silica with an average particle size D50 of 20 μm, the curing agent was 3.5% by mass of 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), and the other ingredients were triphenylphosphine as a curing catalyst, acrylic polymer as a leveling agent, ultrafine alumina as a fluidity imparting agent, and 0.7% by mass of titanium dioxide and carbon black as pigments. All raw materials except the fluidity imparting agent were mixed and heated to melt. The molten composition was cooled and pulverized, and the fluidity imparting agent was added to produce a powder coating.

[0116] In the powder coating of this example, the ratio of curing agent to 100 parts by mass of epoxy resin was 10.0 [phr]. The resin content of all components excluding the curing agent was 36.5%. The average particle size D50 of the granular thermosetting resin composition constituting the powder coating of this example was 60 μm.

[0117] Example 2 A powder coating was produced in the same manner as in Example 1, except that the ratio of the curing agent to 100 parts by mass of the epoxy resin was changed to 5.0 [phr].

[0118] Example 3 A powder coating was produced in the same manner as in Example 1, except that the epoxy resin blending ratio was changed so that the resin content of all components excluding the curing agent was 70.0 mass%, and the ratio of curing agent to 100 mass parts of epoxy resin was changed to 17.5 [phr].

[0119] Example 4 A powder coating was produced in the same manner as in Example 1, except that calcium carbonate was used instead of amorphous silica as the inorganic filler and the ratio of curing agent to 100 parts by mass of epoxy resin was changed to 17.5 [phr].

[0120] (Comparative Example 1) A powder coating was produced in the same manner as in Example 1, except that aluminum hydroxide was used instead of amorphous silica as the inorganic filler and the ratio of curing agent to 100 parts by mass of epoxy resin was changed to 17.5 phr.

[0121] [6] Evaluation The resulting powder coatings were evaluated as follows.

[0122] First, the powder coatings obtained in the above-mentioned examples and comparative examples were melted and cured by heat treatment at 190°C for 20 minutes to prepare a plurality of test pieces for each of the following evaluation items.

[0123] [6-1] ATF resistance The obtained test specimens were immersed in automatic transmission fluid (Autofluid WS, manufactured by Toyota Motor Corporation) at 150°C for 1000 hours. The bending strength, shear tensile strength and breakdown voltage of the test specimens were measured before and after the immersion treatment.

[0124] [6-1-1] Bending strength The bending strength of each test piece (2 mm×10 mm×100 mm) of each of the examples and comparative examples was measured at 25° C. by a method in accordance with JIS K 6911 (2006).

[0125] In addition, X2 / X1 was calculated by taking the bending strength before the immersion treatment as X1 [MPa] and the bending strength after the immersion treatment as X2 [MPa].

[0126] [6-1-2] Shear tensile strength The shear tensile strength of each copper test piece (1.0 mm×15 mm×100 mm) of each of the examples and comparative examples was measured by a method in accordance with JIS K 6850. In addition, F2 / F1 was calculated by taking the shear tensile strength before the immersion treatment as F1 [MPa] and the shear tensile strength after the immersion treatment as F2 [MPa].

[0127] [6-1-3] Breakdown voltage The breakdown voltage of each test piece (1.0 mm × 100 mm × 100 mm) of each of the examples and comparative examples was measured by a method conforming to JIS C2110-1 using a high-voltage breakdown device (conforming to ASTM D149) equipped with an oil bath.

[0128] In addition, V2 / V1 was calculated by taking the breakdown voltage before the immersion treatment as V1 [kV / mm] and the breakdown voltage after the immersion treatment as V2 [kV / mm].

[0129] [6-2] Thermal expansion coefficient, glass transition temperature (Tg) The test pieces (5 mm × 5 mm × 20 mm) of each of the examples and comparative examples were measured using a TMA SS6000 manufactured by Seiko Instruments Inc. at a heating rate of 5°C / min and a load of 10 g. The inflection point of the thermal expansion curve was taken as the glass transition temperature (Tg), and the average slope from 40°C to 50°C was calculated as the thermal expansion coefficient. The evaluation results are summarized in Table 1. The "resin content" value shown in Table 1 indicates the resin content in all components excluding the curing agent.

[0130] [Table 1]

[0131] As is clear from Table 1, the powder coating material obtained in the present invention had excellent ATF resistance. In contrast, the comparative examples did not provide satisfactory results. [Explanation of symbols]

[0132] 10: Powder coating 20: Fluidized tank 21: Perforated plate 22: Heater 100: Stator 101: Stator core 103: Stator coil 105: Coil end 107: Enamel coated part 109:Exposed part 111: Covering part G: Air

Claims

1. A powder coating used to coat coil ends, a particulate thermosetting resin composition, the thermosetting resin composition comprises an epoxy resin, a curing agent, and an inorganic filler; The bending strength of the cured product of the powder coating at 25°C measured according to JIS K 6911 (2006) is: The cured product was immersed in automatic transmission fluid at 150°C for 1000 hours, and the bending strength before the immersion treatment was defined as X1 [MPa] and the bending strength after the immersion treatment was defined as X2 [MPa]. The X1 is 40 [MPa] or more, A powder coating material in which the ratio of X2 to X1 (X2 / X1) is 0.95 or more.

2. 2. The powder coating according to claim 1, wherein the content of the curing agent per 100 parts by mass of the epoxy resin is 7 parts by mass or more and 15 parts by mass or less.

3. The dielectric breakdown voltage of the cured product of the powder coating at 25°C measured according to a method in accordance with JIS C2110-1 is: When the breakdown voltage before the immersion treatment is V1 [kV / mm] and the breakdown voltage after the immersion treatment is V2 [kV / mm], The V1 is 37 [kV / mm] or more, 3. The powder coating material according to claim 1, wherein the ratio of V2 to V1 (V2 / V1) is 0.90 or more.

4. 3. The powder coating material according to claim 1, wherein the coil end is made of copper.

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