Powder coating

Abstract

To provide a powder coating that can be used to form a coil end coating with excellent high voltage resistance. [Solution] The powder coating of the present invention is a powder coating used for coating coil ends, and comprises an epoxy resin, a curing agent, a pigment having an average particle size of 0.30 μm or less, and silica having an average particle size of 1 μm or more and 40 μm or less. The pigment is preferably an organic pigment. The organic pigment is preferably at least one of an azo pigment and a phthalocyanine pigment. The content of the pigment in the powder coating is preferably 0.01% by mass or more and 5% by mass or less.

Description

Technical Field

[0001] The present invention relates to a powder coating.

Background Art

[0002] A battery that supplies electric power to electronic components and a motor of an automobile uses a rotating electric machine having a rotor (rotor) and a stator (stator). A stator of a vehicle rotating electric machine generally includes a stator core (stator core), a stator coil (stator winding) provided on the stator core, and the like. Further, the stator coil includes an inner conductor accommodated in the stator core, and a conductor exposed portion (coil end) exposed from the stator core. In recent years, rectangular copper wires are increasingly used to improve the space factor. In this case, the enamel protective film of the copper wire is peeled off at the tip of the coil end for welding connection. Therefore, insulation of the coil end is achieved by coating the coil end with the powder coating. Further, as motors are becoming smaller and have higher output, insulating coating films with higher voltage resistance are required.

[0003] Patent Document 1 describes a method of coating a coil end of a stator coil by immersing the coil end in a fine granular powder coating contained in a powder tank.

[0004] However, conventionally, it has not been possible to provide a powder coating that can be used for forming a covering portion (covering portion of a coil end) having sufficiently excellent high voltage resistance.

Prior Art Literature

Patent Literature

[0005]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0006] The object of the present invention is to provide a powder coating that can be used to form a coating portion of a coil end having excellent high voltage resistance. [Means for solving the problem]

[0007] These objectives are achieved by the present invention as described in (1) to (8) below. (1) A powder coating used to cover the coil end, A powder coating comprising epoxy resin, a hardener, a pigment with an average particle size of 0.30 μm or less, and silica with an average particle size of 1 μm or more and 40 μm or less.

[0008] (2) The powder coating according to (1) above, wherein the pigment is an organic pigment.

[0009] (3) The powder coating according to (2) above, wherein the organic pigment is at least one of azo pigments and phthalocyanine pigments.

[0010] (4) The powder coating according to any one of (1) to (3) above, wherein the pigment content is 0.01% by mass or more and 5% by mass or less.

[0011] (5) A powder coating according to any one of (1) to (4) above, where the average particle size of the pigment is DP [μm] and the average particle size of the silica is DS [μm], and the relationship 0.0025 ≤ DP / DS ≤ 0.1 is satisfied.

[0012] (6) A powder coating according to any one of (1) to (5) above, where the pigment content is XP [mass%] and the silica content is XS [mass%], and the relationship 0.000125 ≤ XP / XS ≤ 0.25 is satisfied.

[0013] (7) A powder coating according to any of (1) to (6) above, wherein the gel time determined by measurement in accordance with JIS K5600-9-1:2006 is 5 seconds or more and 30 seconds or less.

[0014] (8) The powder coating material according to any one of the above (1) to (7), wherein the content of said silica is 20.0% by mass or more and 80.0% by mass or less.

Effects of the Invention

[0015] According to the present invention, a powder coating material that can be used for forming a coating portion of a coil end having excellent high voltage resistance can be provided.

Brief Description of Drawings

[0016] [Figure 1] It is a perspective view showing a configuration example of a stator to which the powder coating material of the present invention is applied. [Figure 2] It is a plan view showing a configuration example of a coil end of a stator coil in the stator shown in Fig. 1. [Figure 3] It is a diagram illustrating an example of a coating method.

Mode for Carrying Out the Invention

[0017] Hereinafter, preferred embodiments of the present invention will be described in detail. [1] Powder coating material First, the powder coating material of the present invention will be described.

[0018] The powder coating material of the present invention is a powder coating material used for coating a coil end, and comprises an epoxy resin, a curing agent, a pigment having an average particle diameter of 0.30 µm or less, and silica having an average particle diameter of 1 µm or more and 40 µm or less.

[0019] By satisfying such conditions, a powder coating material that can be used for forming a coating portion of a coil end having excellent high voltage resistance can be provided.

[0020] More specifically, by containing a pigment having an average particle diameter of 0.30 µm or less, the high voltage resistance of a cured product of the powder coating material, more specifically, the coating portion formed from the powder coating material, can be made excellent while maintaining hiding properties by coloring.

[0021] Furthermore, by including silica with an average particle size of 1 μm to 40 μm, the cured product of the powder coating, more specifically, the coating formed by the powder coating, can be made to have excellent high voltage resistance. In addition, the fluidity of the powder coating can be improved, improving moldability, as well as improving filling properties and suppressing the occurrence of unfilled areas.

[0022] Conversely, if the above conditions are not met, the excellent effects described above cannot be obtained.

[0023] For example, even if silica with the average particle size described above is included, if no pigment is included, it will not be able to exhibit opacity through coloring. Furthermore, it will be difficult to achieve sufficiently high voltage resistance in the coated portion of the formed coil end. Moreover, if the silica content is increased to improve the high voltage resistance of the coated portion of the formed coil end, the overall fluidity and moldability will decrease significantly, making it difficult to form a coated portion with sufficiently high film thickness uniformity, and thus high voltage resistance in the coated portion cannot be achieved.

[0024] Furthermore, even if the pigment contains the average particle size described above, if silica is not included, it becomes difficult to achieve sufficiently high voltage resistance in the coated portion of the formed coil end. Also, if the pigment content is increased to improve the high voltage resistance of the coated portion of the formed coil end, the overall fluidity and moldability decrease significantly, making it difficult to form a coated portion with sufficiently uniform film thickness, and thus preventing the achievement of high voltage resistance in the coated portion.

[0025] Furthermore, even if silica with the average particle size described above is included, if the average particle size of the pigment exceeds 0.30 μm, sufficient opacity through coloring cannot be achieved, requiring an increase in the amount of pigment blended. This increases viscosity, reduces the fluidity and moldability of the powder coating, and prevents the high voltage resistance of the coated portion of the formed coil end from being sufficiently excellent.

[0026] Furthermore, even if the pigment contains pigments with the average particle size described above, if the average particle size of silica is less than 1 μm, aggregation of silica particles is likely to occur. As a result, the fluidity and moldability of the powder coating decrease, and the high voltage resistance of the coated portion of the formed coil end cannot be sufficiently excellent.

[0027] Furthermore, even if the pigment contains pigments with the average particle size described above, if the average particle size of silica exceeds 40 μm, it becomes difficult to adjust the particle size to one suitable for powder coating, and the high voltage resistance of the coated portion of the formed coil end cannot be sufficiently excellent.

[0028] In this invention, "average particle size (D50)" refers to the particle size at which the cumulative value of the volume frequency particle size distribution of the pigment or silica, measured by laser diffraction scattering, reaches 50%.

[0029] As described above, the average particle size of the pigment should be 0.30 μm or less, but it is preferably 0.05 μm or more and 0.20 μm or less, more preferably 0.08 μm or more and 0.18 μm or less, and even more preferably 0.10 μm or more and 0.15 μm or less. This makes the effects of the present invention described above even more pronounced.

[0030] Furthermore, as mentioned above, the average particle size of silica should be between 1 μm and 40 μm, but preferably between 5 μm and 37 μm, and more preferably between 10 μm and 35 μm. This makes the effects of the present invention described above even more pronounced.

[0031] [1-1]Thermosetting resin composition The powder coating comprises a thermosetting resin composition containing epoxy resin, a curing agent, a pigment, and silica.

[0032] Powder coatings have multiple particles composed of a thermosetting resin composition. These particles may be amorphous.

[0033] [1-1-1] Epoxy resin The thermosetting resin composition includes an epoxy resin.

[0034] Specific examples of epoxy resins include those having two or more epoxy groups in their molecule and being solid at room temperature. Examples of such epoxy resins include bisphenol A type, bisphenol F type, bisphenol S type, novolac type, phenol novolac type, cresol novolac type, biphenyl type, naphthalene type, biphenyl aralkyl type, and aromatic amine type epoxy resins.

[0035] The epoxy resin preferably contains one or more types selected from the group consisting of bisphenol A type epoxy resin, biphenyl aralkyl type epoxy resin, dicyclopentadiene type epoxy resin, orthocresol novolac type epoxy resin, and tetramethylbiphenyl type epoxy resin.

[0036] In particular, the epoxy resin more preferably contains bisphenol A type epoxy resin and one or more selected from the group consisting of biphenyl type epoxy resin, dicyclopentadiene type epoxy resin, biphenyl aralkyl type epoxy resin, and tetramethylbiphenyl type epoxy resin, and even more preferably contains bisphenol A type epoxy resin and novolac type epoxy resin.

[0037] This allows the coil ends to be more stably covered by the coating formed by the powder coating.

[0038] The softening point of the bisphenol A type epoxy resin is preferably between 50°C and 100°C, and more preferably between 60°C and 90°C.

[0039] This makes it possible to more effectively suppress the solidification of the powder coating in the fluidized bed, improve the adhesion of the powder to the coil end, and make the appearance of the coating formed by the powder coating more favorable.

[0040] The epoxy resin content in the thermosetting resin composition is preferably 30.0% by mass or more and 70.0% by mass or less, more preferably 31.0% by mass or more and 65.0% by mass or less, and even more preferably 32.0% by mass or more and 60.0% by mass or less.

[0041] This improves the smoothness of the surface of the cured powder coating, more specifically, the coated portion formed by the powder coating, and also improves the moldability of the coated portion. Furthermore, it allows for a sufficiently high content of pigments and silica with the above-mentioned average particle size, enabling the above-mentioned effects to be exerted more effectively.

[0042] Furthermore, since the thermal expansion coefficient (linear expansion coefficient) of epoxy resin is larger than that of silica and other inorganic fillers, the thermal expansion coefficient of the cured powder coating increases as the epoxy resin content in the thermosetting resin composition increases.

[0043] [1-1-2] Hardener A thermosetting resin composition and a curing agent are included.

[0044] Specific examples of curing agents include, for example, aromatic amines such as diaminodiphenylmethane and aniline resins, condensates of aliphatic amines and aliphatic dicarboxylic acids, dicyandiamides and their derivatives; various imidazole and imidazoline compounds; polydicarboxylic acids or acid anhydrides such as adipic acid, sebatic acid, phthalic acid, maleic acid, trimellitic acid, benzophenone dicarboxylic acid, benzophenone tetracarboxylic acid, and pyromellitic acid; phenolic resins such as novolac-type phenolic resins, biphenylaralkyl-type phenolic resins, and naphtholaralkyl-type phenolic resins; novolacs, which are condensates of dihydrazides such as adipic acid and phthalic acid, phenol, cresol, xylenol, bisphenol A, etc., with aldehydes; carboxylic acid amides; methylolated melamines; and block-type isocyanurates.

[0045] The curing agent preferably contains one or more selected from the group consisting of acid anhydrides and phenolic resins.

[0046] This makes it possible to achieve sufficient meltability during powder coating while simultaneously obtaining excellent cured material properties.

[0047] The ratio of curing agent to epoxy resin can be adjusted, for example, depending on the type of epoxy resin and curing agent used. However, it is preferable that the number of moles of functional groups of the curing agent contained in the thermosetting resin composition is 0.3 molar equivalents or more and 1.5 molar equivalents or less, more preferably 0.3 molar equivalents or more and 1.3 molar equivalents or less, and even more preferably 0.4 molar equivalents or more and 1.1 molar equivalents or less, relative to the number of moles of epoxy groups in the epoxy resin.

[0048] This makes it possible to improve the curability of the powder coating. Furthermore, it is possible to improve the flexural strength and shear tensile strength of the cured powder coating, more specifically, the coating formed by the powder coating.

[0049] In powder coatings, the content of the curing agent per 100 parts by mass of epoxy resin is preferably 7.0 parts by mass or more and 22.0 parts by mass or less, more preferably 8.0 parts by mass or more and 21.5 parts by mass or less, and even more preferably 9.0 parts by mass or more and 21.0 parts by mass or less.

[0050] This makes it possible to improve the curability of the powder coating. Furthermore, it is possible to improve the flexural strength and shear tensile strength of the cured powder coating, more specifically, the coating formed by the powder coating.

[0051] [1-1-3] Pigments The thermosetting resin composition contains a pigment having an average particle size of 0.30 μm or less.

[0052] Various inorganic and organic pigments can be used as pigments, but organic pigments are preferred. This makes the effects of the present invention described above even more pronounced.

[0053] Examples of organic pigments include azo pigments, phthalocyanine pigments, quinacridone pigments, anthraquinone pigments, berine pigments, thioindigo pigments, dioxane pigments, isoindoline pigments, imidazolon pigments, and perinone pigments, but it is preferable that at least one of azo pigments and phthalocyanine pigments is used. This makes the effects of the present invention described above even more pronounced.

[0054] Furthermore, the color of the pigment is not particularly limited; for example, it may be a chromatic pigment such as blue, yellow, or orange pigment, or it may be an achromatic pigment. Multiple types of pigments may also be used in combination.

[0055] While there are no particular limitations on the blue pigment, from the viewpoint of dehalogenation, it is preferable that the compound structure does not contain halogen atoms.

[0056] Examples of such blue pigments include copper phthalocyanine blue (CIPigment Blue 15), metal-free phthalocyanine blue (CIPigment Blue 16), titanyl phthalocyanine blue, iron phthalocyanine blue, nickel phthalocyanine blue, aluminum phthalocyanine blue, tin phthalocyanine blue, alkali blue (CIPigment Blue 1, 2, 3, 10, 14, 18, 19, 24, 56, 57, 61), sulfonated CuPc (CIPigment Blue 17), disazo (CIPigment Blue 25, 26), indanthron (CIPigment Blue 60), indigo (CIPigment Blue 63, 66), and cobalt phthalocyanine (CIPigment Blue 75).

[0057] While there are no particular limitations on the yellow pigment, from the viewpoint of dehalogenation, it is preferable that the compound structure does not contain halogen atoms.

[0058] Examples of such yellow pigments include monoazo yellow (CIPigment Yellow 1, 4, 5, 9, 65, 74), benzimidazolone yellow (CIPigment Yellow 120, 151, 175, 180, 181, 194), flavantron yellow (CIPigment Yellow 24), azomethyl yellow (CIPigment Yellow 117, 129), anthraquinone yellow (CIPigment Yellow 123, 147), isoindoline yellow (CIPigment Yellow 139, 185), disazo yellow (CIPigment Yellow 155), condensed polycyclic pigments (CIPigment Yellow 148, 182, 192), disazomethine (CIPigment Yellow 101), and azo lakes (CIPigment Yellow 61, 62, 100, 104, 133, 168, 169).

[0059] While there are no particular limitations on the orange pigment, from the viewpoint of dehalogenation, it is preferable that the compound structure does not contain halogen atoms.

[0060] Examples of such orange pigments include perinone (CIPigment Orange 43), benzimidazolon (CIPigment Orange 62), azomethine (CIPigment Orange 64), and diketopyrrolopyrrole (CIPigment Orange 71).

[0061] When the pigment is an organic pigment, the average particle size of the organic pigment is preferably 0.06 μm or more and 0.16 μm or less, and more preferably 0.09 μm or more and 0.13 μm or less. This makes the effects of the present invention described above even more pronounced.

[0062] Examples of achromatic pigments include titanium dioxide, iron oxide, zinc oxide, and carbon black.

[0063] The pigment content in the powder coating is preferably 0.01% by mass or more and 5% by mass or less, more preferably 0.05% by mass or more and 3% by mass or less, and even more preferably 0.1% by mass or more and 1% by mass or less.

[0064] This makes it possible to achieve a higher level of opacity through coloring and high voltage resistance of the cured powder coating, more specifically, the coating formed by the powder coating. In addition, the viscosity of the powder coating during melting can be made more suitable, improving its applicability to coil ends.

[0065] [1-1-4] Silica The thermosetting resin composition contains silica with an average particle size of 1 μm or more and 40 μm or less.

[0066] Examples of silica include crystalline silica, fused silica such as molten and crushed silica, spherical silica, surface-treated silica, and amorphous silica.

[0067] In particular, amorphous silica is preferred as the silica material. This allows for improved high voltage resistance of the cured powder coating, more specifically, of the coating formed by the powder coating, as well as more suitable bending strength. Furthermore, it effectively prevents the thermal expansion coefficient of the coating from becoming too large, improves the adhesion between the coil end and the coating, and more effectively prevents cracks during thermal cycling.

[0068] In powder coatings, the silica content 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 50 parts by mass or more and 220 parts by mass or less, and even more preferably 70 parts by mass or more and 200 parts by mass or less.

[0069] This makes it possible to improve the mechanical strength and high voltage resistance of the cured powder coating, or more specifically, the coating formed by the powder coating, as well as improve the smoothness of the surface of the coating.

[0070] The silica content in the powder coating is preferably 20.0% by mass or more and 80.0% by mass or less, more preferably 25.0% by mass or more and 75.0% by mass or less, and even more preferably 30.0% by mass or more and 70.0% by mass or less.

[0071] This makes it possible to improve the mechanical strength and high voltage resistance of the cured powder coating, or more specifically, the coating formed by the powder coating, as well as improve the smoothness of the surface of the coating.

[0072] In powder coatings, when the average particle size of the pigment is DP [μm] and the average particle size of the silica is DS [μm], it is preferable that the relationship 0.0025 ≤ DP / DS ≤ 0.1 is satisfied, more preferably that the relationship 0.005 ≤ DP / DS ≤ 0.080 is satisfied, and even more preferably that the relationship 0.010 ≤ DP / DS ≤ 0.060 is satisfied. This makes the effects of the present invention described above even more pronounced.

[0073] In powder coatings, when the pigment content is XP [mass%] and the silica content is XS [mass%], it is preferable that the relationship 0.000125 ≤ XP / XS ≤ 0.25 is satisfied, more preferably that 0.0025 ≤ XP / XS ≤ 0.20 is satisfied, and even more preferably that 0.005 ≤ XP / XS ≤ 0.15 is satisfied. This makes the effects of the present invention described above even more pronounced.

[0074] [1-1-5]Inorganic filler The thermosetting resin composition may further contain inorganic fillers other than silica.

[0075] Examples of such inorganic fillers include 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 fibers, glass beads, zircon, and molybdenum compounds.

[0076] However, the content of inorganic fillers other than silica 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.

[0077] [1-1-6]Curing catalyst The thermosetting resin composition may further contain a curing catalyst (curing accelerator).

[0078] This makes it possible to more effectively suppress unintended dripping of the powder coating during the formation of the coating, and also improves the filling properties of the powder coating.

[0079] Examples of curing catalysts include organophosphines such as triphenylphosphine; imidazole compounds such as 2-phenylimidazole; and amine compounds such as tertiary amines.

[0080] The content of the curing catalyst per 100 parts by mass of 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 0.9% by mass or less, and even more preferably 0.05% by mass or more and 0.8% by mass or less. This allows for better curing characteristics to be obtained.

[0081] [1-1-7]Dye The thermosetting resin composition may contain dyes.

[0082] However, the dye content in the thermosetting resin composition is preferably 4.0% by mass or less, more preferably 2.0% by mass or less, and even more preferably 1.0% by mass or less.

[0083] [1-1-8] Other ingredients The thermosetting resin composition may contain components other than those described above. Hereinafter, in this section, such components will be referred to as "other components."

[0084] Other components include, for example, thermosetting resins other than epoxy resins, leveling agents, flame retardants, coupling agents, and so on.

[0085] Examples of thermosetting resins other than epoxy resins include phenolic resins, melamine resins, unsaturated polyester resins, and polyurethane resins.

[0086] However, the content of other components in the thermosetting resin composition is preferably 5.0% by mass or less, more preferably 3.0% by mass or less, and even more preferably 2.0% by mass or less.

[0087] [1-1-9] Other conditions As described above, the thermosetting resin composition is in the form of parts in the powder coating.

[0088] The average particle size D50 of the thermosetting resin composition is not particularly limited, but is preferably 45 μm or more and 120 μm or less, more preferably 50 μm or more and 110 μm or less, and even more preferably 55 μm or more and 100 μm or less.

[0089] This improves the fluidity of the powder coating in the fluidized bed, resulting in a superior coating with fewer pinholes and less variation in film thickness. Furthermore, it improves the mechanical strength and high voltage resistance of the coating formed by the powder coating.

[0090] When the average particle size of the thermosetting resin composition is DR [μm] and the average particle size of the silica is DS [μm], it is preferable that the relationship 0.005 ≤ DS / DR ≤ 0.95 is satisfied, more preferably that 0.009 ≤ DS / DR ≤ 0.90 is satisfied, and even more preferably that 0.01 ≤ DS / DR ≤ 0.80 is satisfied. This makes it possible to further improve the fluidity of the powder coating. In addition, it is possible to improve the mechanical strength and high voltage resistance of the coating formed by the powder coating.

[0091] [1-2] Components other than thermosetting resin composition The powder coating may consist solely of a thermosetting resin composition, or it may further contain components other than the thermosetting resin composition. Examples of such components include fluidity enhancers.

[0092] Specific examples of fluidity-imparting materials include, for instance, inorganic particles such as silica and alumina.

[0093] However, the content of components other than the thermosetting resin composition in the powder coating is preferably 2.0% by mass or less, more preferably 1.5% by mass or less, and even more preferably 1.0% by mass or less.

[0094] [1-3] Other conditions The powder coating or its cured product preferably satisfies the following conditions:

[0095] For example, the gel time of powder coatings, as determined by measurement in accordance with JIS K5600-9-1:2006, is preferably 5 seconds or more and 30 seconds or less, more preferably 8 seconds or more and 28 seconds or less, and even more preferably 10 seconds or more and 25 seconds or less.

[0096] This allows for, for example, a more favorable flow of the powder coating in the fluidized bed, improving the applicability to the coil ends and more effectively suppressing coating film sagging.

[0097] Gel time refers to the time it takes for a specified volume of powder coating to become undeformable under specified conditions after it has melted.

[0098] The gel time of powder coatings is measured using the following procedure. First, 0.1g of powder coating is placed on a hot plate controlled at 200°C and kneaded with a spatula in strokes of approximately 1 per second. The time from when the powder coating melts due to heat until it hardens, in other words, the time until the powder coating hardens due to the reaction caused by heating, becomes unable to deform, and no longer stretches of string from the molten material, is measured and defined as the gel time (seconds) of the powder coating.

[0099] Furthermore, the flow rate (horizontal flow rate) of the powder coating is preferably 10% or more and 60% or less, more preferably 15% or more and 50% or less, and even more preferably 20% or more and 40% or less.

[0100] This allows for, for example, a more favorable flow of the powder coating in the fluidized bed, improving the applicability to the coil ends and more effectively suppressing coating film sagging.

[0101] The flow rate of powder coatings is measured using the following procedure. First, 0.5 g of powder coating is placed in a 10 mm diameter molding die and press-molded under 20 kgf for 10 seconds to create a cylindrical sample, and the diameter D0 of the obtained sample is measured. Next, the sample is placed on a 70 mm × 150 mm × 0.8 mm SPCC plate coated with a release agent on its surface and left to stand in a 150°C hot air dryer for 30 minutes. After standing, the diameter D1 of the sample at the contact surface with the SPCC plate is measured.

[0102] The flow rate is calculated based on the following formula (i). Flow rate (%) = {(D1-D0) / D0} × 100···(i)

[0103] Furthermore, the dielectric breakdown voltage of the cured powder coating at 25°C, measured by a method compliant with JIS C2110-1, is preferably 37 [kV / mm] or higher, more preferably 38 [kV / mm] or higher, and even more preferably 40 [kV / mm] or higher. This makes the effects of the present invention described above even more pronounced.

[0104] Furthermore, the shear tensile strength of the cured powder coating is preferably 7 MPa or higher, more preferably 10 MPa or higher, and even more preferably 12 MPa or higher.

[0105] This allows for better adhesion between the coil end and the coating formed by the powder coating, especially when the coil end is made of copper.

[0106] The shear tensile strength was measured according to the method specified in JIS K 6850.

[0107] 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.

[0108] This increases the crosslinking density of the coating formed by the powder coating, resulting in improved strength and flexibility of the coating.

[0109] It is preferable that the thermal expansion coefficient of the cured powder coating is close to that of the material constituting the coil end; in other words, it is preferable that the difference between the thermal expansion coefficient of the coil end and the thermal expansion coefficient of the cured powder coating is small. This makes it possible to suppress peeling of the coating caused by a large difference in thermal expansion coefficient between the coil end and the coating formed by the powder coating.

[0110] For example, if the coil end is made of copper, it is preferable that the thermal expansion coefficient of the cured powder coating be close to the thermal expansion coefficient of copper.

[0111] Specifically, the average thermal expansion coefficient of the cured powder coating from 40°C to 50°C is 1.0 × 10⁻⁶. -5 / K or more 5.0×10 -5 It is preferable that it is less than or equal to / K, and 1.0 × 10 -5 / K or more 3.5×10 -5 It is more preferable that the value be less than or equal to / K, and 1.5 × 10 -5 / K or more 2.5×10 -5 It is even more preferable that it is less than or equal to / K. This makes the effects described above even more pronounced.

[0112] Furthermore, the physical properties of the cured powder coatings mentioned above can be based on measurements taken from cured products obtained by curing the powder coatings at 190°C for 20 minutes.

[0113] [2] Method for manufacturing powder coatings Next, we will explain the manufacturing method of powder coatings.

[0114] The method for manufacturing powder coatings according to this embodiment includes a preparation step for preparing a thermosetting resin composition. Furthermore, if the powder coating contains components other than the thermosetting resin composition (for example, a fluidity imparter), the method for manufacturing the powder coating may further include a mixing step for mixing the thermosetting resin composition with the other components. For example, in the preparation step for a particulate thermosetting resin composition, epoxy resin, curing agent, pigment, silica, and any other component are blended in a predetermined order, mixed, and then melt-kneaded while heating to obtain a mixture of all raw materials.

[0115] Next, the mixture of all the obtained raw materials is pulverized using an impact-type pulverizer to obtain epoxy resin powder coating. Alternatively, after pulverization, the powder may be sieved to separate fine and coarse particles, thereby adjusting the particle size of the powder coating.

[0116] [3] Coil end Next, we will describe the coil end of a coil to which the powder coating of the present invention is applied. Figure 1 is a perspective view showing an example of the configuration of a stator to which the powder coating of the present invention is applied. Figure 2 is a plan view showing an example of the configuration of the coil end of the stator coil in the stator shown in Figure 1.

[0117] The coil according to the present invention has coil ends whose exposed portions are sealed with the powder coating of the present invention.

[0118] The coil end may be made of any material, but it is preferably made of copper. Copper has advantages in that it is a relatively inexpensive material with high electrical conductivity.

[0119] Specific examples of coils include motor coils, such as drive motor coils. The following provides a more detailed explanation using a motor stator coil as an example.

[0120] The stator 100 shown in Figure 1 has a stator core 101 and a stator coil 103. The stator coil 103 is arranged in a groove (slot) (not shown) provided in the inner wall of the stator core 101.

[0121] As shown in Figure 2, the coil end 105 is provided with an enamel-coated portion 107 in which the conductor portion is covered with an insulating coating, such as enamel, and an exposed portion 109 in which the conductor portion is exposed from the enamel coating. The exposed portion 109 is sealed with the powder coating of the present invention. In Figure 2, a coating portion 111 is provided extending from the exposed portion 109 to the enamel-coated portion 107. The coating portion 111 is made of a cured product of the powder coating of the present invention. As a result, the coating portion 111 has excellent high voltage resistance.

[0122] [4] Painting method Next, a painting method using the powder coating of the present invention, or in other words, a method for forming the coating portion of a coil end, will be described. Figure 3 illustrates an example of a painting method.

[0123] The coating method of this embodiment specifically includes an adhesion step (first step) 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 an exposed portion 109 is provided where the conductor portion is exposed from the insulating coating is immersed in a fluidized tank 20 in which powder coating 10 flows, and the molten powder coating 10 is attached to the outside of the exposed portion 109, and a curing step (second step) in which the powder coating 10 attached to the coil end 105 is cured.

[0124] The adhesion process may include, for example, a fluidization step in which compressed air G is introduced into a fluidized tank 20 containing the powder coating 10 to fluidize the powder coating 10, and an immersion step in which the coil end 105 is immersed in the fluidized tank 20 in which the powder coating 10 is flowing.

[0125] The fluidization process can be carried out, for example, by using a fluidized tank 20 equipped with a perforated plate 21 at the bottom, filling the top of the perforated plate 21 with powder coating 10, and then introducing compressed air G from the outside of the perforated plate 21, thereby introducing compressed air G into the fluidized tank 20 through the perforated plate 21.

[0126] In the immersion process, the stator core 101 is positioned so that the coil end 105 is located vertically downward, and the stator core 101 is lowered. Then, the coil end 105 is immersed in the powder coating 10 in the fluidized bed 20.

[0127] In the immersion process, immersing the coil end 105 in the fluidized bath 20 and adhering the molten powder coating 10 to the outside of the exposed portion 109 may be performed as a single step or as separate steps, but it is preferable to perform it as a single step. In other words, it is preferable that the adhesion of the molten powder coating 10 to the outside of the exposed portion 109 occurs while the coil end 105 is immersed in the fluidized bath 20.

[0128] The painting method of this embodiment preferably further includes a heating step of heating the coil end 105 before immersing the coil end 105 in the fluidized bed 20. This improves the sealing stability of the exposed portion 109.

[0129] At this time, by immersing the heated coil end 105 in the fluidized bed 20 in which the powder coating 10 flows, the powder coating 10 near the coil end 105 in the fluidized bed 20 adheres to the coil end 105 as a molten substance.

[0130] Alternatively, after removing the coil end 105 from the fluidized bed tank 20, the coil end 105 may be subjected to a heat treatment.

[0131] This allows the powder coating 10 adhering to the coil end 105 to be further stably molten.

[0132] The coil end 105 can be heated, for example, by a drying oven (not shown).

[0133] The heat curing conditions in the curing process can be appropriately set according to the type and size of the coil end 105, the components of the powder coating 10, etc.

[0134] The curing process may be carried out continuously with the adhesion process. More specifically, for example, if the coil end 105 was heated before being immersed in the fluidized bed 20, the residual heat of the coil end 105 after it is removed from the fluidized bed 20 may promote the curing reaction of the powder coating 10 attached to the coil end 105. Also, as described above, if the coil end 105 is subjected to a heat treatment after being removed from the fluidized bed 20, this heat treatment may be for the purpose of further stabilizing the powder coating 10 attached to the coil end 105 into a molten state and promoting the curing reaction.

[0135] Furthermore, the heat treatment may not be intended to further stabilize the powder coating 10 adhering to the coil end 105 into a molten state, but rather solely to promote the curing reaction.

[0136] The cured powder coating 10 becomes integrated with the coil end 105, forming a coating portion 111. The coating portion 111 formed in this way has excellent high voltage resistance.

[0137] Furthermore, in the coating method of this embodiment, the adhesion step and the curing step may be repeated alternately multiple times in order to increase the thickness of the coating film (covered portion).

[0138] Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto.

[0139] For example, the powder coating of the present invention may be manufactured by any method, and is not limited to the method described above. Furthermore, the coating method using the powder coating of the present invention is not limited to the method described above. [Examples]

[0140] 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, processes for which no specific temperature conditions are given were performed at room temperature, specifically 25°C. Similarly, for various measurement conditions for which no specific temperature conditions are given, the values ​​are for room temperature, specifically 25°C.

[0141] [5] Manufacturing of powder coatings (Examples 1-4, Comparative Examples 1-4) The raw materials were mixed in a mixer according to the formulations shown in Table 1, melt-kneaded under 80°C conditions, then pulverized in a pulverizer. The thermosetting resin composition was obtained as the subsieved fraction using air classification and a 90-mesh (180 μm opening) sieve. The obtained thermosetting resin composition was used as a powder coating.

[0142] The raw materials used to prepare the powder coatings in each of the above examples and comparative examples are summarized below. (A) Epoxy resin • Epoxy resin 1: Bisphenol A type epoxy resin ("YD-013", manufactured by Nippon Steel Chemical & Materials Co., Ltd., epoxy equivalent 850 g / eq) • Epoxy resin 2: Novolac-type epoxy resin ("N-670", manufactured by DIC Corporation, epoxy equivalent 210 g / eq)

[0143] (B) Hardener • Hardener 1: Novolac-type phenolic resin ("PR-53195", manufactured by Sumitomo Bakelite Co., Ltd., hydroxyl group equivalent 104 g / eq)

[0144] (C) Pigment • Pigment 1 (Yellow Pigment): Pigment Yellow 138 ("Paliotol Yellow L 0960HD", manufactured by BASF, average particle size 0.12 μm) • Pigment 2 (blue pigment): Phthalocyanine blue ("Fastogen Blue 15:3", manufactured by Toyo Ink Co., Ltd., average particle size 0.15 μm) • Pigment 3 (Red Pigment): Pigment Red 254 ("Irgazin Red D3656HD" manufactured by BASF, average particle size 0.2 μm) • Pigment 4: Pigment Blue 15:6 ("Lionol Blue E," manufactured by Toyo Ink Co., Ltd., average particle size 0.4 μm)

[0145] (D) Silica • Silica 1: Spherical silica ("HS-103", manufactured by Nippon Steel Chemical & Materials Co., Ltd., average particle size 28 μm) • Silica 2: Spherical silica ("HS-208", manufactured by Nippon Steel Chemical & Materials Co., Ltd., average particle size 20 μm) • Silica 3: Spherical silica ("SO-C1" manufactured by Admatex, average particle size 0.3 μm) • Silica 4: Spherical silica ("FB-40R" manufactured by Denka Co., Ltd., average particle size 41 μm)

[0146] (E) Curing accelerator • Curing accelerator 1: Triphenylphosphine (TPP) (manufactured by K.I. Chemicals Co., Ltd.)

[0147] (F) Leveling agent • Leveling agent 1: Acrylic oligomer ("Modaflow Powder 3," manufactured by Allnex)

[0148] (G) Inorganic fillers other than silica • Inorganic filler 1: Heavy calcium carbonate ("Whiteon P-70," manufactured by Shiraishi Calcium Co., Ltd.)

[0149] [6] Rating The powder coatings and their cured products obtained in each of the above examples and comparative examples were evaluated as follows.

[0150] [6-1] Flow rate 0.5 g of the powder coating obtained in each of the above examples and comparative examples was placed in a 10 mmφ molding die and pressure-molded at 20 kgf for 10 seconds to produce a cylindrical sample, and the diameter D0 of the obtained sample was measured. Next, the sample was placed on a 70 mm × 150 mm × 0.8 mm SPCC plate coated with a release agent on its surface and left to stand in a 150°C hot air dryer for 30 minutes. After standing, the diameter D1 of the sample at the contact surface with the SPCC plate was measured.

[0151] The flow rate [%] was calculated based on the following formula (i). Flow rate (%) = {(D1-D0) / D0} × 100···(i)

[0152] [6-2] Geltime In accordance with JIS K5600-9-1:2006, the time (in seconds) until gelation occurred was measured using a 200°C hot plate. Specifically, 0.1 g of the powder coating obtained in each of the above examples and comparative examples was placed on a hot plate controlled to 200°C and kneaded with a spatula in strokes of approximately 1 per second. The time from when the powder coating melted due to heat until it hardened, in other words, the time until long strings no longer formed from the molten material was measured and defined as the gel time (seconds). A smaller gel time indicates faster hardening.

[0153] [6-3] Dielectric breakdown voltage First, the powder coatings obtained in each of the above examples and comparative examples were melted and cured by heating at 190°C for 20 minutes to prepare test specimens (1.0 mm × 100 mm × 100 mm). The dielectric breakdown voltage of the aforementioned test specimens was measured using a method compliant with JIS C2110-1. The dielectric breakdown voltage was measured using a high-voltage breakdown device (compliant with ASTM D149) equipped with an oil bath. A higher dielectric breakdown voltage indicates superior high voltage resistance of the cured powder coating.

[0154] The evaluation results are summarized in Table 1.

[0155] [Table 1]

[0156] As is clear from Table 1, the present invention yielded a powder coating with excellent high voltage resistance. In contrast, the comparative examples did not yield satisfactory results.

[0157] Furthermore, the average particle size of the pigment was varied within the range of 0.30 μm or less, the average particle size of the silica was varied within the range of 1 μm to 40 μm, the DP / DS value when the average particle size of the pigment is DP [μm] and the average particle size of the silica is DS [μm] was varied within the range of 0.0025 to 0.1, the epoxy resin content in the thermosetting resin composition was varied within the range of 30.0% by mass to 70.0% by mass, and the curing agent content per 100 parts by mass of epoxy resin was varied within the range of 7.0 parts by mass to 22.0 parts by mass. Except for various modifications, such as changing the pigment content in the powder coating within the range of 0.01% by mass to 5% by mass, changing the silica content in the powder coating within the range of 20.0% by mass to 80.0% by mass, and changing the XP / XS value within the range of 0.000125 to 0.25 when the pigment content in the powder coating is XP [by mass%] and the silica content is XS [by mass%], a powder coating was prepared in the same manner as in the above example, and evaluated in the same manner as above, and excellent results were obtained in the same manner as above. [Explanation of Symbols]

[0158] 10: Powder coating 20: Fluidized tank 21: Perforated plate 100: Stator 101: Stator core 103: Stator coil 105: Coil End 107: Enamel coating 109:Exposed part 111: Covering part G: Compressed air

Claims

1. A powder coating used to cover the coil end, A powder coating comprising epoxy resin, a hardening agent, a pigment with an average particle size of 0.30 μm or less, and silica with an average particle size of 1 μm or more and 40 μm or less.

2. The powder coating according to claim 1, wherein the pigment is an organic pigment.

3. The powder coating according to claim 2, wherein the organic pigment is at least one of azo pigments and phthalocyanine pigments.

4. The powder coating according to claim 1 or 2, wherein the pigment content is 0.01% by mass or more and 5% by mass or less.

5. The powder coating according to claim 1 or 2, where the average particle size of the pigment is DP [μm] and the average particle size of the silica is DS [μm], and the relationship 0.0025 ≤ DP / DS ≤ 0.1 is satisfied.

6. The powder coating according to claim 1 or 2, where the pigment content is XP [mass%] and the silica content is XS [mass%], satisfying the relationship 0.000125 ≤ XP / XS ≤ 0.

25.

7. The powder coating according to claim 1 or 2, wherein the gel time determined by measurement in accordance with JIS K5600-9-1:2006 is 5 seconds or more and 30 seconds or less.

8. The powder coating according to claim 1 or 2, wherein the silica content is 20.0% by mass or more and 80.0% by mass or less.

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