Powdered paint, coil and method for sealing coil end

Abstract

To provide a powdered paint capable of covering a coil end with improved tracking resistance.SOLUTION: A powdered paint capable of covering coil ends, includes a thermosetting resin composition, wherein the thermosetting resin composition includes (A) epoxy resin, (B) one or more curing agents selected from the group consisting of phenolic resin and anhydride, (C) one or more components selected from the group consisting of silica and calcium carbonate, and (D) titanium oxide; the total content of component (C) and component (D) is 40 mass% or more when the entire thermosetting resin composition is considered to be 100 mass%, and the content of component (D) exceeds 1.0 mass% when the entire thermosetting resin composition is considered to be 100 mass%.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a powder coating, a coil, and a method for sealing a coil end.

Background Art

[0002] As technologies related to powder coatings containing epoxy resins, there are those described in Patent Documents 1 and 2. Patent Document 1 describes a thermosetting powder coating for forming a cured product, which is composed of a fine pulverized product of a composition. The composition contains (A): a bisphenol type epoxy resin having an epoxy equivalent of 600 to 800 g / eq (excluding 800 g / eq), (C): a bisphenol type phenolic resin curing agent, and (D): a compound for activating (C), and does not contain (B): a rubber-modified epoxy resin. (D) contains (D1): an imidazole compound and (D2): an amine-epoxy adduct compound, and a powder coating in which the mass ratio of (D2) to (D1) is 1.0 or more and 3.7 or less is described. Further, in the examples, an example containing titanium oxide in addition to the above (A), (C), and (D) is described. Patent Document 1 states that according to the thermosetting powder coating, excellent workability during coating is achieved, and high flexibility is imparted even at low temperatures together with heat resistance. As a result, it is possible to provide a thermosetting powder coating capable of forming a cured product having heat resistance and crack resistance during bending.

[0003] Patent Document 2 describes an epoxy resin composition for powder coatings, which contains an epoxy resin that is solid at room temperature and a curing agent for the epoxy resin. The epoxy resin is obtained by reacting a hydrogenated epoxy resin component (A) obtained by hydrogenating an aromatic epoxy resin with a polyester oligomer component (B) having two or more terminal carboxyl groups in one molecule, which is obtained by an ester bond formation reaction of a polycarboxylic acid compound (b-1) composed of at least one selected from alicyclic polycarboxylic acids, aliphatic polycarboxylic acids, and their acid anhydrides, and a polyalcohol compound (b-2) composed of at least one selected from alicyclic polyalcohols and aliphatic polyalcohols. Patent Document 2 states that according to the epoxy resin composition for powder coatings, it has storage stability at room temperature, and its cured coating film performance is excellent in mechanical properties, and particularly can provide a coating film excellent in weather resistance.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] There is a demand for improving the tracking resistance of powder coatings. The present invention has been made in view of the above circumstances, and provides a powder coating with improved tracking resistance.

Means for Solving the Problems

[0006] The present invention provides the following powder coatings, coils, and methods for sealing coil ends.

[0007] [1] A powder coating capable of coating a coil end, containing a thermosetting resin composition, The thermosetting resin composition contains (A) an epoxy resin, and one or more curing agents selected from the group consisting of (B) a phenolic resin and an acid anhydride, and one or more selected from the group consisting of (C) silica and calcium carbonate, and (D) titanium oxide, and the total content of the component (C) and the component (D) is 40% by mass or more when the total amount of the thermosetting resin composition is 100% by mass, and the content of the component (D) exceeds 1.0% by mass when the total amount of the thermosetting resin composition is 100% by mass, a powder coating. [2] In the complex viscosity of the powder coating measured by dynamic viscoelasticity measurement under the conditions of temperature: 150 °C, frequency: 1 Hz, measuring jig: aluminum parallel plate with a diameter of 25 mmφ, and gap: 0.5 mm, the viscosity η 1 after 1 minute from the start of measurement is 5 Pa·s or more and 1000 Pa·s or less, and the ratio (η 1 of the viscosity η 2 after 2 minutes from the start of measurement to the η 2 (η 1 / η [3] The powder coating is pressed at 120 °C and 7 MPa using a hot press machine to prepare a semi-cured product, and then heated at 190 °C for 20 minutes. The tensile strength measured according to the following <Tensile Strength> of the obtained cured product is 10 N / mm 2 or more. The powder coating according to [1] or [2]. <Tensile Strength> A test piece having a width of 10 mm, a length of 80 mm, and a thickness of 1 mm is cut out from the cured product, and the obtained test piece is subjected to a tensile test using an autograph under the conditions of a temperature of 25 °C and a test speed of 5 mm / min by a method conforming to JIS K 7161:2014, and the tensile strength (N / mm 2 ) is measured. [4] The powder coating according to any one of [1] to [3], wherein the gel time at 170 ° C measured according to the following <gel time> of the powder coating is 30 seconds or more and 120 seconds or less. <gel time> Place 0.1 g of the powder coating on a hot plate controlled at 170 ° C, knead it with a spatula at a stroke of about once per second, and measure the time from when the powder coating melts due to heat until it hardens, and define it as the gel time (seconds). [5] The powder coating according to any one of [1] to [4], wherein the flexural strength measured according to the following <three-point bending test> of the cured product obtained by pressing the powder coating at 120 ° C and 7 MPa using a hot press machine to form a semi-cured product and then heating it at 190 ° C for 20 minutes is 50 N / mm 2 or more. <three-point bending test> Cut out a test piece with a width of 10 mm, a length of 100 mm, and a thickness of 2 mm from the cured product, and perform a bending test on the obtained test piece with an autograph under the conditions of a two-point distance L: 50 mm, a measurement temperature: 25 ° C, and a test speed: 5 mm / min according to the method conforming to JIS K 6911:2006 to measure the flexural strength (N / mm 2 ). [6] The powder coating according to any one of [1] to [5], wherein the flow rate X of the powder coating measured according to the following <flow rate> is 30% or more and 80% or less. <flow rate> (1) Put 0.5 g of the powder coating into a 10 mmφ molding die, press-mold it at 20 kgf for 10 seconds to produce a cylindrical sample. (2) After measuring the diameter D 0 of the sample, place the sample on an SPCC plate with a width of 70 mm, a length of 150 mm, and a thickness of 0.8 mm, and leave it standing in a hot air dryer at 150 ° C for 30 minutes. (3) Measure the diameter D 1 at the contact surface between the sample after standing and the SPCC plate. (4) Measure the D 0 and D 1 , and calculate the flow rate X of the sample before storage based on the following formula (i). X (%) = (D1 -D 0 ) / D 0 ×100 ··· (i) [7] The powder coating is pressed at 120 °C and 7 MPa using a hot press to produce a semi-cured product, and then heated at 190 °C for 20 minutes. The tracking resistance index (CTI) of the cured product measured according to the following <tracking resistance index> is 250 V or more. The powder coating according to any one of [1] to [6]. <tracking resistance index> A test piece with a size of 35 mm square and a thickness of 3 mm is cut out from the cured product, and in accordance with JIS 2161:2010, a tracking resistance characteristic test of the measurement sample is performed. In the evaluation with the number of measurements n = 5, when 50 drops of a 0.1% aqueous solution of ammonium chloride are dropped onto the measurement sample, the maximum voltage (kV / mm) at which all measurement samples do not undergo dielectric breakdown is defined as the tracking resistance index (CTI). [8] The powder coating is pressed at 120 °C and 7 MPa using a hot press to produce a semi-cured product, and then heated at 190 °C for 20 minutes. The glass transition temperature of the cured product measured according to the following <glass transition temperature> is 100 °C or more. The powder coating according to any one of [1] to [7]. <glass transition temperature> A test piece with a width of 5 mm, a length of 20 mm, and a thickness of 5 mm is cut out from the cured product, and using a thermomechanical analyzer, measurements are taken under the conditions of a measurement temperature range of 0 °C to 320 °C and a heating rate of 5 °C / min to measure the glass transition temperature (°C). [9] The powder coating is pressed at 120 °C and 7 MPa using a hot press to produce a semi-cured product, and then heated at 190 °C for 20 minutes. The coefficient of linear expansion (α 1 ) below the glass transition temperature and the coefficient of linear expansion (α 2 ) above the glass transition temperature of the cured product measured according to the following <coefficient of linear expansion>, and the ratio α 1 / α 2 is 0.10 or more and 0.50 or less. The powder coating according to any one of [1] to [8]. <coefficient of linear expansion> A test piece with a width of 5 mm, a length of 20 mm, and a thickness of 5 mm is cut out from the cured product, and measurement is performed using a thermomechanical analyzer under the conditions of a measurement temperature range of 0 °C to 320 °C and a heating rate of 5 °C / min. The linear expansion coefficient (α 1 ) at below the glass transition temperature (40 °C to 60 °C) and the linear expansion coefficient (α 2 ) at above the glass transition temperature (180 °C to 200 °C) are calculated, and α 1 (ppm / °C) and α 2 (ppm / °C) are used to calculate α 1 / α 2 .

[10] The powder coating is pressed at 120 °C and 7 MPa using a hot press to form a semi-cured product, and then heated at 190 °C for 20 minutes. The powder coating according to any one of [1] to [9], wherein the breakdown voltage measured in accordance with JIS 2161:2010 is 15 kV / mm or more according to the following <breakdown voltage>. <breakdown voltage> The cured product is cut into a 100 mm square with a thickness of 1 mm to form a test piece. The test piece is placed in insulating oil while being sandwiched between circular electrodes, and then an alternating voltage is applied using an insulation resistance tester such that the voltage rises at a rate of 2.5 kV / second between both electrodes. The voltage at which the test piece breaks is defined as the breakdown voltage (kV / mm).

[11] The powder coating according to any one of [1] to

[10] , wherein the thermosetting resin composition further contains a curing accelerator (E).

[12] The powder coating according to any one of [1] to

[11] , wherein the (A) epoxy resin contains one or more selected from the group consisting of bisphenol A type epoxy resin, cresol novolak type epoxy resin, bisphenol F type epoxy resin, phenol novolak type epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy resin, and biphenyl aralkyl type epoxy resin.

[13] The powder coating according to any one of [1] to

[12] , wherein the content of the component (A) is 10% by mass or more and 70% by mass or less based on 100% by mass of the entire thermosetting resin composition.

[14] The powder coating according to any one of [1] to

[13] , wherein the content of the component (B) is 1% by mass or more and 20% by mass or less based on 100% by mass of the entire thermosetting resin composition.

[15] The powder coating according to any one of [1] to

[14] , wherein the total content of the component (A), the component (B), the component (C), and the component (D) is 50% by mass or more and 100% by mass or less based on 100% by mass of the entire thermosetting resin composition.

[16] The coil end has an exposed portion in which the conductor portion is covered with an insulator and a part of the conductor portion is exposed from the insulator, The powder coating according to any one of [1] to

[15] , which can be used in a powder coating method including a step of immersing the coil end in a flowing tank in which the powder coating flows and attaching a melt of the powder coating to the outside of the exposed portion.

[17] The powder coating according to

[16] , which can be used in the powder coating method of attaching the melt of the powder coating to the outside of the exposed portion, and attaching the melt to the insulator from the exposed portion of the coil end.

[18] A coil including a coil end, The coil end has a conductor, an insulator for covering the conductor, and an exposed portion in which a part of the conductor portion is exposed from the insulator, A coil in which the exposed portion is sealed with a cured product of the powder coating according to any one of [1] to

[17] .

[19] Including a step of immersing the coil end of a coil having a coil end provided with an exposed portion in which the conductor portion is covered with an insulator and the conductor portion is exposed from the insulator in a flowing tank in which the powder coating flows and attaching a melt of the powder coating to the outside of the exposed portion, A method for sealing a coil end, wherein the powder coating is the powder coating according to any one of [1] to

[17] .

[0008] In addition, any combination of these respective configurations, and those obtained by converting the expression of the present invention between methods, apparatuses, etc. are also effective as aspects of the present invention. For example, according to the present invention, an article coated with the powder coating in the present invention can also be obtained.

Advantages of the Invention

[0009] According to the present invention, a powder coating, a coil end, and a coil with improved tracking resistance can be provided.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments will be described. In the present embodiment, the composition can include each component alone or in combination of two or more. In this specification, the notation "X to Y" regarding a numerical range represents X or more and Y or less unless otherwise specified. In this specification, the upper limit value and the lower limit value of the numerical range can be arbitrarily combined unless otherwise specified.

[0012] (Powder Coating) The powder coating of this embodiment is a powder coating capable of coating coil ends and includes a thermosetting resin composition. This thermosetting resin composition contains (A) an epoxy resin, (B) one or more curing agents selected from the group consisting of a phenol resin and an acid anhydride, (C) one or more selected from the group consisting of silica and calcium carbonate, and (D) titanium oxide. The total content of component (C) and component (D) is 40% by mass or more when the total amount of the thermosetting resin composition is 100% by mass, and the content of component (D) exceeds 1.0% by mass when the total amount of the thermosetting resin composition is 100% by mass.

[0013] In recent years, with the miniaturization and high power of motors, the interval between coil ends has tended to become narrower. When the interval between coil ends is narrow, there is a high possibility that a conductive path (track) is formed between the coil ends, and higher tracking resistance is required. On the other hand, in the coating of powder coatings, there is a problem that pinholes and voids are formed during coating. Even when exposed portions are formed due to pinholes and voids, there is a high possibility that a conductive path (track) is formed in the exposed portions, and higher tracking resistance is required.

[0014] In this embodiment, the thermosetting resin composition contains an epoxy resin, a specific curing agent, one or more selected from the group consisting of silica and calcium carbonate, and titanium oxide. By setting the total content of one or more selected from the group consisting of silica and calcium carbonate and the content of titanium oxide within a specific range and the content of titanium oxide being equal to or more than a predetermined value, it is possible to provide a powder coating with improved tracking resistance. The reason for this is not clear, but when the total content of one or more selected from the group consisting of silica and calcium carbonate and the content of titanium oxide in the thermosetting resin composition are within a specific range and the content of titanium oxide is not less than a predetermined value, aggregation of the fillers is suppressed, the paintability is improved, and formation of pinholes and voids in the coating film formed by the powder coating can be suppressed. As a result, it is considered that the tracking resistance is improved.

[0015] The components of the powder coating will be described. The powder coating contains a thermosetting resin composition, and the thermosetting resin composition contains (A) an epoxy resin, (B) one or more curing agents selected from the group consisting of a phenol resin and an acid anhydride, (C) one or more selected from the group consisting of silica and calcium carbonate, and (D) titanium oxide.

[0016] (A) Epoxy resin Specific examples of the (A) epoxy resin (hereinafter also simply referred to as the “(A) component”) include those having two or more epoxy groups in the molecule and being solid at room temperature. Examples of such epoxy resins include bisphenol A type, cresol novolak type, bisphenol F type, phenol novolak type, biphenyl aralkyl type, bisphenol S type, novolak type, biphenyl type, naphthalene type, and aromatic amine type epoxy resins. From the perspective of more stably coating the coil ends, (A) epoxy resin preferably contains one or more selected from the group consisting of bisphenol A type epoxy resin, cresol novolak type epoxy resin, bisphenol F type epoxy resin, phenol novolak type epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy resin, and biphenyl aralkyl type, more preferably contains one or more selected from the group consisting of bisphenol A type epoxy resin and biphenyl aralkyl type epoxy resin, and it is even more preferable to use bisphenol A type epoxy resin and biphenyl aralkyl type epoxy resin in combination. Thereby, the performance balance such as tracking resistance, fluidity, solidification property, moisture resistance, and flame retardancy can be further improved. Also, cost reduction is possible.

[0017] From the perspective of further improving the smoothness of the surface of the cured product of the powder coating, when the total amount of the thermosetting resin composition is 100% by mass, the content of the (A) component in the thermosetting resin composition is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, even more preferably 25% by mass or more, and even more preferably 30% by mass or more. Also, from the perspective of further improving the coating formability of the powder coating, when the total amount of the thermosetting resin composition is 100% by mass, the content of the epoxy resin in the thermosetting resin composition is preferably 70% by mass or less, more preferably 60% by mass or less, even more preferably 50% by mass or less, and even more preferably 40% by mass or less.

[0018] Also, the thermosetting resin composition may contain other thermosetting resins. Examples of other thermosetting resins include one or more selected from the group consisting of phenol resins (excluding one or more curing agents selected from the group consisting of (B) phenol resins and acid anhydrides described below), melamine resins, unsaturated polyester resins, and polyurethane resins.

[0019] (B) One or more curing agents selected from the group consisting of phenol resins and acid anhydrides From the perspective of further improving the tracking resistance, the thermosetting resin composition of this embodiment contains one or more curing agents (hereinafter, also simply referred to as "(B) curing agent" or "(B) component") selected from the group consisting of (B) phenol resin and acid anhydride, and preferably contains an acid anhydride as the curing agent from the perspective of further improving the tracking resistance. Specific examples of the phenol resin include novolak-type phenol resins such as phenol novolak resin, cresol novolak resin, bisphenol novolak resin, and phenol-biphenyl novolak resin; polyvinylphenol; polyfunctional phenol resins such as triphenylmethane-type phenol resin; modified phenol resins such as terpene-modified phenol resin and dicyclopentadiene-modified phenol resin; bisphenol compounds such as bisphenol A and bisphenol F (dihydroxydiphenylmethane); and compounds having a biphenylene skeleton such as 4,4'-biphenol. The phenol resin can contain one or more selected from the above specific examples, and preferably contains a phenol novolak resin.

[0020] From the perspective of obtaining good curability and cured product properties, the ratio of the phenol resin curing agent to the (A) epoxy resin is such that the number of functional groups of the phenol resin curing agent is preferably 0.3 molar equivalent or more, more preferably 0.5 molar equivalent or more, still more preferably 0.6 molar equivalent or more, and preferably 1.3 molar equivalent or less, more preferably 1.2 molar equivalent or less, still more preferably 1.1 molar equivalent or less, based on the number of epoxy groups of the (A) epoxy resin.

[0021] Examples of the acid anhydride include alicyclic acid anhydrides such as hexahydrophthalic anhydride (HHPA), tetrahydrophthalic anhydride (THPA), and maleic anhydride; and aromatic acid anhydrides such as trimellitic anhydride (TMA), pyromellitic anhydride (PMDA), benzophenone tetracarboxylic acid (BTDA), and phthalic anhydride.

[0022] The content of component (B) is preferably 1% by mass or more, more preferably 3% by mass or more, still more preferably 4% by mass or more, and even more preferably 7% by mass or more, based on 100% by mass of the entire thermosetting resin composition, from the viewpoint of making the curability and curing rate of the thermosetting resin composition fall within a more appropriate range. Further, from the viewpoint of further improving the storage stability, the content of the curing agent (B) in the thermosetting resin composition is preferably 20% by mass or less, more preferably 15% by mass or less, and still more preferably 10% by mass or less, based on 100% by mass of the entire thermosetting resin composition.

[0023] The ratio of the curing agent (B) to the epoxy resin (A) can be adjusted, for example, according to the types of the epoxy resin (A) and the curing agent (B) used. The ratio of the curing agent (B) to the epoxy resin (A) is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and still more preferably 13 parts by mass or more, and is preferably 40 parts by mass or less, more preferably 35 parts by mass or less, and still more preferably 30 parts by mass or less, per 100 parts by mass of the epoxy resin, from the viewpoint of obtaining good curability and cured product properties.

[0024] (C) One or more selected from the group consisting of silica and calcium carbonate The thermosetting resin composition of the present embodiment contains one or more selected from the group consisting of silica and calcium carbonate (C) (hereinafter, also simply referred to as “component (C)”), and preferably contains silica. Examples of the silica include crystalline silica, fused silica such as fused crushed silica, spherical silica, surface-treated silica, etc., and preferably include spherical silica. The volume-based average particle diameter D of the component (C) measured by the laser diffraction particle size distribution measurement method 50 is preferably 10 μm or more, more preferably 13 μm or more, still more preferably 15 μm or more, and is preferably 50 μm or less, more preferably 40 μm or less, and still more preferably 30 μm or less, from the viewpoint of further improving the tracking resistance.

[0025] From the viewpoint of further improving the performance balance between mechanical strength and tracking resistance, when the total amount of the thermosetting resin composition is 100% by mass, the content of component (C) is preferably 20% by mass or more, more preferably 25% by mass or more, still more preferably 30% by mass or more. From the viewpoint of further improving the smoothness of the cured product of the thermosetting resin composition, it is preferably 70% by mass or less, more preferably 65% by mass or less, still more preferably 60% by mass or less, and still more preferably 55% by mass or less.

[0026] (D) Titanium oxide The thermosetting resin composition of the present embodiment contains (D) titanium oxide (hereinafter, also simply referred to as “component (D)”). Thereby, the performance balance of the strength, adhesion, and tracking resistance of the coating film can be improved. The crystal structure of titanium oxide includes a high-temperature rutile type belonging to the tetragonal system and a low-temperature anatase type, and either one may be used, but it is preferable to use the rutile type. The volume-based average particle diameter D measured by the laser diffraction particle size distribution measurement method of titanium oxide 50 is preferably 0.15 μm or more, more preferably 0.18 μm or more, still more preferably 0.20 μm or more, and preferably 0.40 μm or less, more preferably 0.35 μm or less, still more preferably 0.30 μm or less.

[0027] When the total amount of the thermosetting resin composition is 100% by mass, the content of component (D) exceeds 1.0% by mass. Thereby, the performance balance of the strength, adhesion, and tracking resistance of the coating film can be improved. From the viewpoint of further improving the tracking resistance, when the total amount of the thermosetting resin composition is 100% by mass, the content of component (D) is preferably 2.0% by mass or more, more preferably 3.0% by mass or more, still more preferably 4.0% by mass or more, still more preferably 6.0% by mass or more, still more preferably 8.0% by mass or more, still more preferably 15.0% by mass or more, still more preferably 20.0% by mass or more. From the viewpoint of further improving the dielectric strength, it is preferably 40% by mass or less, more preferably 35% by mass or less, still more preferably 30% by mass or less.

[0028] The thermosetting resin composition may further contain (E) a curing accelerator other than (B) the curing agent. Specific examples of the (E) curing accelerator include organic phosphines such as triphenylphosphine. From the viewpoint of obtaining better curing properties, the content of the (E) curing accelerator in the thermosetting resin composition is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, still more preferably 0.1% by mass or more, and preferably 2% by mass or less, more preferably 1% by mass or less, still more preferably 0.5% by mass or less, and still more preferably 0.3% by mass or less, when the total amount of the thermosetting resin composition is 100% by mass.

[0029] In the powder coating of the present embodiment, the total content of the (C) component and the (D) component is 40% by mass or more, preferably 45% by mass or more, more preferably 50% by mass or more, still more preferably 55% by mass or more, and preferably 70% by mass or less, more preferably 65% by mass or less, when the total amount of the thermosetting resin composition is 100% by mass, from the viewpoint of improving the tracking resistance.

[0030] From the viewpoint of further improving the performance balance such as tracking resistance, coating film strength, and paintability, the total content of the (A) component, (B) component, (C) component, and (D) component is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, still more preferably 90% by mass or more, still more preferably 95% by mass or more, still more preferably 97% by mass or more, still more preferably 99% by mass or more, and may be, for example, 100% by mass or less, or 99.9% by mass or less, when the total amount of the thermosetting resin composition is 100% by mass.

[0031] The thermosetting resin composition may further contain components other than the above-described components. For example, the thermosetting resin composition may be blended with a colorant, a leveling agent, a flame retardant, a coupling agent, or the like.

[0032] As a specific example of the leveling agent, an acrylic oligomer can be mentioned. From the viewpoint of improving the smoothness of the coating film, the content of the leveling agent in the thermosetting resin composition is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, when the total amount of the thermosetting resin composition is 100% by mass, and is preferably 2.0% by mass or less, more preferably 1.5% by mass or less, still more preferably 1.0% by mass or less, and still more preferably 0.5% by mass or less.

[0033] Also, the powder coating may contain components other than the thermosetting resin composition. Specific examples of such components include fluidity-imparting materials and the like. The fluidity-imparting agent is preferably at least one selected from the group consisting of alumina and silica, and more preferably alumina.

[0034] From the viewpoint of further improving the performance balance such as tracking resistance, coating film strength, and paintability, the content of the thermosetting resin composition in the powder coating of the present embodiment is preferably 60% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, still more preferably 90% by mass or more, still more preferably 95% by mass or more, still more preferably 97% by mass or more, still more preferably 99% by mass or more, when the total amount of the powder coating is 100% by mass, and may be, for example, 100% by mass or less, or may be 99.5% by mass or less.

[0035] Next, the physical properties of the powder coating of the present embodiment will be specifically described.

[0036] In the complex viscosity of the powder coating measured by dynamic viscoelasticity measurement under the conditions of temperature: 150 °C, frequency: 1 Hz, measurement jig: aluminum parallel plate with a diameter of 25 mmφ, and gap: 0.5 mm, the viscosity η after 1 minute from the start of measurement 1is preferably 5 Pa·s or more, more preferably 8 Pa·s or more, still more preferably 10 Pa·s or more, still more preferably 15 Pa·s or more, still more preferably 20 Pa·s or more, and is preferably 1000 Pa·s or less, more preferably 800 Pa·s or less, still more preferably 700 Pa·s or less. In the complex viscosity of the powder coating measured by dynamic viscoelasticity measurement under the conditions of temperature: 150 °C, frequency: 1 Hz, measurement jig: aluminum parallel plate with a diameter of 25 mmφ, and gap: 0.5 mm, the viscosity η after 2 minutes from the start of measurement 2 is preferably 500 Pa·s or more, more preferably 550 Pa·s or more, still more preferably 600 Pa·s or more, still more preferably 800 Pa·s or more, still more preferably 1000 Pa·s or more, and is preferably 100000 Pa·s or less, more preferably 90000 Pa·s or less, still more preferably 50000 Pa·s or less, still more preferably 10000 Pa·s or less. And, η 1 The ratio of η 2 to η 2 / η 1 ) is preferably 50 or more, more preferably 51 or more, still more preferably 52 or more, still more preferably 60 or more, still more preferably 100 or more, and is preferably 150 or less, more preferably 145 or less, still more preferably 140 or less. η 1 and η 2 / η 1 are each within the above ranges, so that the performance balance between the filling property and the suppression of sagging is further improved, the generation of pinholes and voids in the cured product of the powder coating can be further suppressed, and thus the tracking resistance can be further improved.

[0037] The powder coating was pressed at 120 °C and 7 MPa using a hot press to prepare a semi-cured product, and then heated at 190 °C for 20 minutes. The tensile strength of the obtained cured product is preferably 10 N / mm 2 or more, more preferably 20 N / mm 2 or more, still more preferably 30 N / mm 2More preferably, it is 40 N / mm or more. 2 or more. There is no upper limit on the tensile strength of the cured product of the powder coating, but for example, it may be 60 N / mm or less, 2 or may be 55 N / mm or less. 2 or less. The tensile strength of the cured product of the powder coating is measured as follows. A test piece with a width of 10 mm, a length of 80 mm, and a thickness of 1 mm is cut out from the above-mentioned cured product, and the obtained test piece is subjected to a tensile test using an autograph under the conditions of a temperature of 25 °C and a test speed of 5 mm / min by a method conforming to JIS K 7161:2014, and the tensile strength (N / mm 2 ) is measured.

[0038] The shear tensile strength of the cured product obtained by curing the powder coating at 190 °C for 20 minutes is preferably 5 N / mm or more, 2 more preferably 7 N / mm or more, 2 even more preferably 9 N / mm or more, 2 and preferably 25 N / mm or less, 2 more preferably 20 N / mm or less, 2 even more preferably 15 N / mm or less 2 from the viewpoint of further improving the adhesion and preventing the peeling of the cured coating film. The shear tensile strength is measured as follows. Two copper plates (material C1100: width 15 mm × length 100 mm × thickness 1 mm) are overlapped and shifted in opposite directions in the length direction, and arranged so that the overlapping portion of the two is 10 mm in the length direction. That is, the overlapping area of the two copper plates is an area of width 15 mm × length 10 mm. 0.1 g of the powder coating is allowed to stand between the two copper plates in the overlapping area, heated at 190 °C for 20 minutes, and the powder coating is melted and cured to obtain a test piece. The two ends of this test piece, that is, the ends of each copper plate on the side opposite to the overlapping area, are clamped by an autograph and pulled until it breaks at 10 mm / min to measure the shear tensile strength (N / mm 2 ).

[0039] The gel time of the powder coating at 170°C is preferably 30 seconds or more, more preferably 35 seconds or more, still more preferably 40 seconds or more, still more preferably 50 seconds or more, still more preferably 60 seconds or more, still more preferably 67 seconds or more, from the viewpoint of further improving the filling property of the powder coating between coils. Also, from the viewpoint of further improving productivity, it is preferably 120 seconds or less, more preferably 110 seconds or less, still more preferably 100 seconds or less, still more preferably 90 seconds or less. The gel time of the powder coating is measured as follows. Place 0.1 g of the powder coating on a hot plate controlled at 170°C, knead it with a spatula at a stroke of about 1 time / second, and measure the time from when the powder coating melts due to heat until it hardens, which is taken as the gel time (seconds).

[0040] The powder coating was pressed at 120°C and 7 MPa using a hot press machine to prepare a semi-cured product, and then heated at 190°C for 20 minutes. The flexural strength of the obtained cured product is preferably 50 N / mm 2 or more, more preferably 60 N / mm 2 or more, still more preferably 70 N / mm 2 or more, still more preferably 80 N / mm 2 or more, still more preferably 90 N / mm 2 or more, from the viewpoint of further enhancing the strength of the coating. Also, from the viewpoint of further suppressing the occurrence of cracks in the coating and enhancing productivity, it is preferably 130 N / mm 2 or less, more preferably 125 N / mm 2 or less, still more preferably 120 N / mm 2 or less, still more preferably 115 N / mm 2 or less, still more preferably 110 N / mm 2 or less. The flexural strength is measured as follows. Cut out a test piece with a width of 10 mm, a length of 100 mm, and a thickness of 2 mm from the above-mentioned cured product, and perform a flexural test on the obtained test piece using an autograph under the conditions of a two-point distance L: 50 mm, a measurement temperature: 25°C, and a test speed: 5 mm / min according to the method conforming to JIS K 6911:2006, and measure the flexural strength (N / mm 2 ).

[0041] The flow rate X of the powder coating is preferably 30% or more, more preferably 35% or more, still more preferably 40% or more, still more preferably 45% or more, still more preferably 50% or more, still more preferably 55% or more, from the viewpoint of making the fluidity of the powder coating in the fluidization tank in a preferable state and further improving the coatability to the coil end. Also, from the viewpoint of further suppressing the sagging of the coating film, it is preferably 80% or less, more preferably 70% or less, still more preferably 65% or less. The flow rate is measured as follows. (1) Put 0.5 g of the powder coating into a molding die with a diameter of 10 mm, and press-mold it at 20 kgf for 10 seconds to produce a cylindrical sample. (2) After measuring the diameter D of the above sample 0 place the above sample on an SPCC plate with a width of 70 mm, a length of 150 mm, and a thickness of 0.8 mm, and leave it standing in a hot air dryer at 150 °C for 30 minutes. (3) Measure the diameter D at the contact surface between the above sample and the SPCC plate after standing 1 . (4) Measure the above D 0 and D 1 and calculate the flow rate X of the sample before storage based on the following formula (i). X (%) = (D 1 - D 0 ) / D 0 × 100 ··· (i)

[0042] After pressing the powder coating at 120 °C and 7 MPa using a hot press to prepare a semi-cured product, and then heating it at 190 °C for 20 minutes, the glass transition temperature of the obtained cured product is preferably 100 °C or higher, more preferably 110 °C or higher, still more preferably 120 °C or higher, from the viewpoint of further improving the heat resistance. And it is preferably 160 °C or lower, more preferably 150 °C or lower, still more preferably 140 °C or lower, still more preferably 130 °C or lower.

[0043] The powder coating was pressed at 120 °C and 7 MPa using a hot press to prepare a semi-cured product, and then heated at 190 °C for 20 minutes. The coefficient of linear expansion (α 1 )(ppm / °C) below the glass transition temperature and the coefficient of linear expansion (α 2 )(ppm / °C) above the glass transition temperature, and the ratio α 1 / α 2 are preferably 0.10 or more, more preferably 0.15 or more, still more preferably 0.20 or more, and even more preferably 0.26 or more, from the viewpoint of improving the adhesion to the coil, and preferably 0.50 or less, more preferably 0.45 or less, still more preferably 0.40 or less, and even more preferably 0.35 or less. The numerical range of the coefficient of linear expansion (α 1 )(ppm / °C) below the glass transition temperature is preferably 10 ppm / °C or more, more preferably 15 ppm / °C or more, still more preferably 20 ppm / °C or more, and even more preferably 25 ppm / °C or more, and preferably 50 ppm / °C or less, more preferably 45 ppm / °C or less, still more preferably 40 ppm / °C or less, and even more preferably 35 ppm / °C or less. The numerical range of the coefficient of linear expansion (α 2 ) above the glass transition temperature is preferably 80 ppm / °C or more, more preferably 85 ppm / °C or more, still more preferably 90 ppm / °C or more, and even more preferably 95 ppm / °C or more, and preferably 120 ppm / °C or less, more preferably 110 ppm / °C or less, still more preferably 105 ppm / °C or less.

[0044] The glass transition temperature and the coefficient of linear expansion are measured as follows. A test piece with a width of 5 mm, a length of 20 mm, and a thickness of 5 mm was cut out from the above-mentioned cured product, and using a thermomechanical analyzer, measurement was performed under the conditions of a measurement temperature range of 0 °C to 320 °C and a heating rate of 5 °C / min to measure the glass transition temperature (°C). Also, the coefficient of linear expansion (α 1 )(ppm / °C) below the glass transition temperature (40 °C to 60 °C) and the coefficient of linear expansion (α 2 )(ppm / °C) above the glass transition temperature (180 °C to 200 °C) were calculated, and α1 (ppm / °C) and α 2 From the value of (ppm / °C) and α 1 / α 2 calculate α / α.

[0045] The powder coating was pressed at 120°C and 7 MPa using a hot press to produce a semi-cured product, and then heated at 190°C for 20 minutes. The breakdown voltage measured in accordance with JIS 2161:2010 of the cured product obtained is preferably 15 kV / mm or more, more preferably 17 kV / mm or more, still more preferably 19 kV / mm or more, from the viewpoint of further improving the insulation resistance. There is no upper limit to the breakdown voltage of the cured product of the powder coating, but it may be, for example, 50 kV / mm or less, or 40 kV / mm or less. The breakdown voltage of the cured product of the powder coating measured in accordance with JIS 2161:2010 is measured as follows. The above cured product is cut into a 100 mm square with a thickness of 1 mm to form a test piece, and the test piece is placed in insulating oil while being sandwiched between circular electrodes. Next, using an insulation resistance tester, an alternating voltage is applied so that the voltage rises at a rate of 2.5 kV / second between both electrodes, and the voltage at which the test piece breaks is defined as the breakdown voltage (kV / mm).

[0046] The powder coating was pressed at 120°C and 7 MPa using a hot press to produce a semi-cured product, and then heated at 190°C for 20 minutes. The comparative tracking index (CTI) of the cured product measured in accordance with JIS 2161:2010 of the cured product obtained is preferably 250 V or more, more preferably 280 V or more, still more preferably 300 V or more, still more preferably 330 V or more, still more preferably 350 V or more, from the viewpoint of further improving the insulation. There is no upper limit to the comparative tracking index (CTI) of the cured product of the powder coating, but it may be, for example, 600 V or less, or 550 V or less. The comparative tracking index (CTI) of the cured product of the powder coating measured in accordance with JIS 2161:2010 is measured as follows. A test piece with a size of 35 mm square and a thickness of 3 mm is cut out from the cured product. Next, in accordance with JIS 2161:2010, a tracking resistance characteristic test of the above measurement sample is performed. In the evaluation with the measurement number n = 5, when 50 drops of 0.1% aqueous ammonium chloride solution are dropped onto the measurement sample, the maximum voltage (kV / mm) at which all measurement samples do not break down is defined as the comparative tracking index (CTI).

[0047] The powder coating in the present embodiment can be used in a powder coating method, for example, including a step of dipping a coil end having a coil end where an insulator covers a conductor part and an exposed part where a part of the conductor part is exposed from the insulator into a flow tank in which the powder coating flows, and attaching a melt of the powder coating to the outside of the exposed part. Further, the powder coating in the present embodiment is preferably used in a powder coating method of attaching a melt of the powder coating to the outside of the exposed part, covering the insulator from the exposed part of the coil end. More specifically, the powder coating in the present embodiment can stably seal the connection part, welding part, etc. of the conductor at the exposed part, thereby making it possible to improve the strength of the connection part, welding part, etc., for example.

[0048] Next, a method for manufacturing the powder coating will be described. Specifically, the method for manufacturing the powder coating includes a step of preparing a thermosetting resin composition. When the powder coating contains components other than the thermosetting resin composition, the method for manufacturing the powder coating may further include, for example, a step of mixing the thermosetting resin composition and other components. Here, the method for manufacturing the thermosetting resin composition is, for example, to appropriately select (A) the type of epoxy resin, (B) the type of one or more curing agents selected from the group consisting of phenolic resins and acid anhydrides, (C) the type of one or more selected from the group consisting of silica and calcium carbonate, and (D) the type of titanium oxide, make the total content of component (C) and the content of component (D) be a predetermined value or more, adjust the content of each component so that the content of component (D) is a predetermined value or more, and then mix all of component (A), component (B), component (C), component (D), and optional components. For mixing, for example, a V blender or the like can be used. After mixing, heat and melt-knead to obtain a kneaded product of all raw materials. Next, after sufficiently cooling the obtained kneaded product of all raw materials at room temperature, pulverize it with an impact pulverizer, and perform fine powder and coarse particle cutting by air classification and sieving to obtain a powder coating. In sieving, for example, a sieve of about 90 mesh can be used.

[0049] (Coil) The coil of this embodiment includes a coil end, and the coil end has a conductor, an insulator for coating the conductor, and an exposed portion where a part of the conductor portion is exposed from the insulator, and the exposed portion is sealed with the powder coating in this embodiment. As a specific example of the coil, a motor coil such as a drive motor coil can be mentioned. Hereinafter, the stator coil of the motor will be further specifically described as an example.

[0050] FIG. 1 is a perspective view showing a configuration example of a stator in an embodiment. The stator 100 shown in FIG. 1 has a stator core 101 and a stator coil 103. The stator coil 103 is disposed in a groove portion (slot, not shown) provided on the inner wall of the stator core 101.

[0051] FIG. 2 is a top view showing a configuration example of a coil end 105 of a stator coil 103. The coil end 105 is provided with an enamel coating portion 107 in which a 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. The exposed portion 109 is sealed with the powder paint in the present embodiment. In FIG. 2, a covering portion 111 is provided from the exposed portion 109 to the enamel coating portion 107. The covering portion 111 is composed of a cured product of the powder paint in the present embodiment.

[0052] (Powder coating method) The powder coating method is, for example, a method of sealing a coil end using the powder paint in the present embodiment. Specifically, such a method includes a step (step 1) of immersing a coil end 105 of a coil (stator coil 103) having a coil end 105 provided with an exposed portion 109 in which a conductor portion is covered with an insulator and the conductor portion is exposed from the insulator in a flow tank in which the powder paint of the present embodiment flows, and attaching a melt of the powder paint to the outside of the exposed portion.

[0053] Step 1 may include, for example, a step (step 1-1) of introducing air into a flow tank containing the powder paint to flow the powder paint, and a step (step 1-2) of immersing the coil end 105 in the flow tank in which the powder paint is flowing. Step 1-1 can be performed, for example, by filling the upper part of a flow tank provided with a perforated plate at the bottom with the powder paint and introducing air from the outside of the perforated plate to introduce air into the flow tank through the perforated plate.

[0054] In step 1-2, immersing the coil end 105 in the flow tank and attaching the melt of the powder paint to the outside of the exposed portion may be performed as a single step or stepwise. However, from the viewpoint of improving the sealing stability of the exposed portion 109, it is preferably performed as a single step. That is, the attachment of the melt of the powder paint to the outside of the exposed portion preferably occurs when the coil end 105 is immersed in the flow tank.

[0055] From the viewpoint of improving the sealing stability of the exposed portion 109, the powder coating method preferably further includes a step of heating the coil end 105 before immersing the coil end 105 in the fluidized bath. At this time, by immersing the heated coil end 105 in the fluidized bath in which the powder coating flows, the powder coating near the coil end 105 adheres to the coil end 105 as a melt in the fluidized bath. Further, from the viewpoint of making the powder coating adhered to the coil end 105 more stably into a melt, the coil end 105 may be heated after taking out the coil end 105 from the fluidized bath. The heating of the coil end 105 can be performed, for example, by a heater disposed above the fluidized bath. When further including the step of heating the coil end 105, it is preferable to heat at a temperature of 150 °C or lower. Thereby, the energy used can be further reduced and the CO2 emission amount can be further reduced.

[0056] In the present embodiment, the powder coating method may further include a step (step 2) of heating the coil end 105 to cure the powder coating after the step of attaching the melt of the powder coating to the outside of the exposed portion 109 of 105. The heat curing conditions such as temperature can be appropriately set according to the type and size of the coil end 105, the constituent components of the powder coating, and the like. Further, from the viewpoint of increasing the thickness of the coating, steps 1 and 2 may be alternately repeated a plurality of times.

[0057] As described above, the embodiments of the present invention have been described, but these are examples of the present invention, and various configurations other than the above can be adopted.

Example

[0058] The components used in the powder coating of this example are shown below.

[0059] (Raw materials of the thermosetting resin composition) (Epoxy resin) · Epoxy resin 1: Bisphenol A type epoxy resin, manufactured by Nippon Steel Chemical & Material Co., Ltd., YD-012, softening point 81 °C · Epoxy resin 2: Bisphenol A type epoxy resin, manufactured by Nippon Steel Chemical & Material Co., Ltd., YD-013, softening point 95°C · Epoxy resin 3: Biphenyl aralkyl type epoxy resin, manufactured by Nippon Kayaku Co., Ltd., NC-3000H (Hardener) · Hardener 1: Phenol novolak type hardener, manufactured by Sumitomo Bakelite Co., Ltd., PR-53195 · Hardener 2: 3,3’,4,4’-Benzophenone tetracarboxylic dianhydride (BTDA) (Silica) · Silica 1: Spherical silica, average particle size D 50 : 20μm, manufactured by Nippon Steel Chemical & Material Co., Ltd., HS-208 (Titanium oxide) · Titanium oxide 1: Titanium oxide, average particle size D 50 : 0.27μm, manufactured by Teika Co., Ltd., JR-600E (Curing accelerator) · Curing accelerator 1: Triphenylphosphine (TPP), manufactured by KAIKA KASEI CO., LTD (Leveling agent) · Leveling agent 1: Acrylic oligomer, manufactured by allnex, Modaflow Powder 3

[0060] (Manufacture of powder coating) A thermosetting resin composition was prepared with the formulation shown in Table 1 (unit: mass %), and the obtained thermosetting resin composition was mixed according to a conventional method to obtain the powder coatings of each example. Here, for the thermosetting resin composition, the raw material components were mixed with a V blender (manufactured by Tokuju Co., Ltd., V-10), melt-kneaded under the condition of 80°C, sufficiently cooled at room temperature, and then finely pulverized with a pulverizer (manufactured by Hosokawa Micron Corporation, ACM pulverizer), and the powder coatings shown in Table 1 were obtained by air classification and using a 90-mesh sieve.

[0061] (Physical properties of powder coating) The flow rate, complex viscosity, gel time, and shear tensile strength of the powder coatings obtained in each example were measured. The measurement results are shown in Table 1.

[0062] (Flow rate) The flow rate was measured according to the following method. (1) 0.5 g of the powder coating of each example was placed in a 10 mm φ molding die, and pressure molding was performed at 20 kgf for 10 seconds to produce a cylindrical sample. (2) After measuring the diameter D 0 of the above sample, the above sample was placed on an SPCC plate with a width of 70 mm, a length of 150 mm, and a thickness of 0.8 mm, and left standing in a hot air dryer at 150 °C for 30 minutes. (3) The diameter D 1 at the contact surface of the above sample with the SPCC plate after standing was measured. (4) D 0 and D 1 were measured, and based on the following formula (i), the flow rate X (%) of the sample before storage was calculated. X (%) = (D 1 - D 0 ) / D 0 × 100 ··· (i)

[0063] (Complex viscosity) Using the powder coating of each example, the complex viscosity was measured under the conditions of temperature: 150 °C, frequency: 1 Hz, measurement jig: aluminum parallel plate with a diameter of 25 mm φ, and gap: 0.5 mm by a dynamic viscoelasticity measuring device (manufactured by Anton Paar, MCR301). The viscosity η 1 (Pa·s) 1 minute after the start of measurement and the viscosity η 2 (Pa·s) 2 minutes after the start of measurement were measured, and the ratio of η 1 to η 2 (η 2 / η 1 ) was calculated.

[0064] (Gel time) 0.1 g of the powder coating of each example was placed on a hot plate controlled at 170 °C, and kneaded with a spatula at a stroke of about 1 time / second. The time from when the powder coating melted due to heat until it hardened was measured and taken as the gel time (seconds).

[0065] (Shear tensile strength) Two copper plates (material C1100: width 15 mm × length 100 mm × thickness 1 mm) were overlapped and shifted in opposite directions in the length direction so that the overlapping portion of the two plates was 10 mm in the length direction. That is, the overlapping region of the two copper plates was a region of width 15 mm × length 10 mm. 0.1 g of the powder coating of each example was placed statically between the two copper plates in the overlapping region, and heating was carried out at 190 °C for 20 minutes to melt and cure the powder coating to obtain a test piece. Both ends of this test piece, that is, the ends of each copper plate on the side opposite to the overlapping region, were clamped by an autograph and pulled at 10 mm / min until breakage, whereby the shear tensile strength (N / mm 2 ) was measured.

[0066] (Preparation of cured product) Using the powder coating of each example, a semi-cured product was prepared by pressing at 120 °C and 7 MPa using a hot press machine (SA-302 manufactured by Tester Sangyo Co., Ltd.), and then heated at 190 °C for 20 minutes to obtain a cured product. Using the obtained cured product, a bending test, tensile strength, glass transition temperature, linear expansion coefficient, dielectric breakdown voltage, and tracking resistance index were measured. The measurement results are shown in Table 1.

[0067] (Bending test) From the cured product of each example, a test piece with a width of 10 mm, a length of 100 mm, and a thickness of 2 mm was cut out, and the obtained test piece was subjected to a bending test using an autograph under the conditions of a two-point support distance L: 50 mm, a measurement temperature: 25 °C, and a test speed: 5 mm / min according to the method conforming to JIS K 6911:2006, and the bending strength (N / mm 2 ) was measured.

[0068] (Tensile strength) From the cured product of each example, a test piece with a width of 10 mm, a length of 80 mm, and a thickness of 1 mm was cut out, and the obtained test piece was subjected to a tensile test using an autograph under the conditions of a temperature of 25 °C and a test speed: 5 mm / min according to the method conforming to JIS K 7161:2014, and the tensile strength (N / mm 2 ) was measured.

[0069] (Glass transition temperature and linear expansion coefficient) Test pieces with a width of 5 mm, a length of 20 mm, and a thickness of 5 mm were cut out from the cured products of each example, and using a thermomechanical analyzer, measurements were carried out under the conditions of a measurement temperature range of 0 °C to 320 °C and a heating rate of 5 °C / min to measure the glass transition temperature (°C). Also, the linear expansion coefficient (α 1 )(ppm / °C) at temperatures below the glass transition temperature (40 °C to 60 °C) and the linear expansion coefficient (α 2 )(ppm / °C) at temperatures above the glass transition temperature (180 °C to 200 °C) were calculated, and from the values of α 1 (ppm / °C) and α 2 (ppm / °C), α 1 / α 2 was calculated.

[0070] (Dielectric breakdown voltage) In accordance with JIS 2161:2010, the dielectric breakdown voltage was measured as follows. The cured products of each example were cut into 100 mm squares with a thickness of 1 mm to form test pieces, and the test pieces were placed in insulating oil while being sandwiched between circular electrodes. Next, using an insulation resistance tester, an alternating voltage was applied such that the voltage increased at a rate of 2.5 kV / second between the two electrodes, and the voltage at which the test piece broke was taken as the dielectric breakdown voltage (kV / mm).

[0071] (Tracking resistance index) From the cured products of each example, test pieces with a size of 35 mm square and a thickness of 3 mm were cut out, and in accordance with JIS 2161:2010, the tracking resistance characteristic test of the above measurement samples was carried out. In the evaluation with the number of measurements n = 5, when 50 drops of a 0.1% aqueous solution of ammonium chloride were dropped onto the measurement samples, the maximum voltage (kV / mm) at which all the measurement samples did not break down was taken as the tracking resistance index (CTI). The measurement results are shown in Table 1.

[0072]

Table 1

Explanation of symbols

[0073] 100 Stator 101 Stator core 103 Stator coil 105 Coil end 107 Enamel coating part 109 Exposed part 111 Coating part

Claims

1. A powder coating capable of coating coil ends, comprising a thermosetting resin composition, wherein the thermosetting resin composition contains (A)an epoxy resin, (B)one or more curing agents selected from the group consisting of a phenolic resin and an acid anhydride, (C)one or more selected from the group consisting of silica and calcium carbonate, (D)titanium oxide, and the total content of the component (C) and the component (D) is 40% by mass or more based on 100% by mass of the entire thermosetting resin composition, and the content of the component (D) exceeds 1.0% by mass based on 100% by mass of the entire thermosetting resin composition. A powder coating.

2. In the complex viscosity of the powder coating measured by dynamic viscoelasticity measurement under the conditions of temperature: 150 ° C, frequency: 1 Hz, measuring jig: aluminum parallel plate with a diameter of 25 mmφ, and gap: 0.5 mm,

3. <Tensile strength> Viscosity η one minute after the start of measurement １ is 5 Pa·s or more and 1000 Pa·s or less, Said η １ The viscosity η after 2 minutes from the start of measurement with respect to ２ Ratio of (η ２ / η １ ) is 50 or more and 150 or less. The powder coating according to claim 1.

4. The powder coating was pressed at 120°C and 7 MPa using a hot press machine to produce a semi-cured product, and then heated at 190°C for 20 minutes. The tensile strength of the cured product thus obtained, measured according to the following <Tensile Strength>, is 10 N / mm ２ or more. The powder coating according to claim 1 or 2. The powder coating according to claim 1 or 2, wherein the gel time at 170 ° C measured according to the following <gel time> of the powder coating is 30 seconds or more and 120 seconds or less. A test piece with a width of 10 mm, a length of 80 mm, and a thickness of 1 mm is cut out from the cured product, and the obtained test piece is subjected to a tensile test using an autograph under the conditions of a temperature of 25°C and a test speed of 5 mm / min by a method compliant with JIS K 7161:2014, and the tensile strength (N / mm ２ 2) is measured. <Gel time> Place 0.1 g of the powder coating on a hot plate controlled at 170 ° C, knead it with a spatula at a stroke of about once per second, and measure the time from when the powder coating melts due to heat until it hardens, and define it as the gel time (seconds).

5. <Three-point bending test>

6. The powder coating was pressed at 120°C and 7 MPa using a hot press to prepare a semi-cured product, and then heated at 190°C for 20 minutes. The flexural strength of the cured product measured according to the following <Three-point bending test> is 50 N / mm ２ or more. The powder coating according to claim 1 or 2. The powder coating according to claim 1 or 2, wherein the flow rate X of the powder coating measured according to the following <flow rate> is 30% or more and 80% or less. A test piece with a width of 10 mm, a length of 100 mm, and a thickness of 2 mm is cut out from the cured product, and the obtained test piece is subjected to a bending test using an autograph under the conditions of a two-point distance L of 50 mm, a measurement temperature of 25 °C, and a test speed of 5 mm / min by a method conforming to JIS K 6911:2006, and the flexural strength (N / mm ２ 2) is measured. <Flow rate> (1)Put 0.5 g of the powder coating into a 10 mmφ molding die, press-mold it at 20 kgf for 10 seconds to prepare a cylindrical sample.

7. The powder coating according to claim 1 or 2, wherein the tracking resistance index (CTI) of the cured product obtained by pressing the powder coating at 120 ° C and 7 MPa using a hot press machine to prepare a semi-cured product and then heating it at 190 ° C for 20 minutes, measured according to the following <tracking resistance index>, is 250 V or more. (2) Diameter D of the sample ０ After measuring the diameter D of the sample, the sample is placed on an SPCC plate with a width of 70 mm, a length of 150 mm, and a thickness of 0.8 mm, and left standing in a hot air dryer at 150 °C for 30 minutes. (3)Measure the diameter D at the contact surface of the sample with the SPCC plate after standing still. １ ​ (4) Measure the aforementioned D ０ and D １ and calculate the flow rate X of the sample before storage based on the following formula (i). X(%) = (D １ - D ０ ) / D ０ × 100... (i) <Tracking resistance index> ​ ​ A test piece with a size of 35 mm square and a thickness of 3 mm is cut out from the cured product, and in accordance with JIS 2161:2010, the tracking resistance property test of the measurement sample is carried out. In the evaluation with the number of measurements n = 5, when 50 drops of 0.1% aqueous ammonium chloride solution are dropped onto the measurement sample, the maximum voltage (kV / mm) at which all measurement samples do not undergo dielectric breakdown is defined as the comparative tracking index (CTI).

8. The powder coating material according to claim 1 or 2, wherein the cured product obtained by pressing the powder coating material at 120 °C and 7 MPa using a hot press machine to form a semi-cured product and then heating it at 190 °C for 20 minutes has a glass transition temperature measured according to the following <glass transition temperature> of 100 °C or higher. <Glass transition temperature> A test piece with a width of 5 mm, a length of 20 mm, and a thickness of 5 mm is cut out from the cured product, and using a thermomechanical analyzer, measurement is carried out under the conditions of a measurement temperature range of 0 °C to 320 °C and a heating rate of 5 °C / min to measure the glass transition temperature (°C).

9. The powder coating was pressed at 120°C and 7 MPa using a hot press to produce a semi-cured product, and then heated at 190°C for 20 minutes. The coefficient of linear expansion (α １ below the glass transition temperature, measured according to the following <Coefficient of Linear Expansion>, and the coefficient of linear expansion (α ２ above the glass transition temperature), and the ratio α １ / α ２ is 0.10 or more and 0.50 or less. The powder coating according to claim 1 or 2. <Coefficient of linear expansion> A test piece with a width of 5 mm, a length of 20 mm, and a thickness of 5 mm is cut out from the cured product, and measurement is performed using a thermomechanical analyzer under the conditions of a measurement temperature range of 0 °C to 320 °C and a heating rate of 5 °C / min. The linear expansion coefficient (α １ ) and the linear expansion coefficient (α ２ ) at temperatures above the glass transition temperature (180 °C to 200 °C) are calculated, and α １ (ppm / °C) and α ２ (ppm / °C) are used to calculate α １ / α ２ .

10. The powder coating material according to claim 1 or 2, wherein the cured product obtained by pressing the powder coating material at 120 °C and 7 MPa using a hot press machine to form a semi-cured product and then heating it at 190 °C for 20 minutes has a dielectric breakdown voltage measured in accordance with the following <dielectric breakdown voltage> and in accordance with JIS 2161:2010 of 15 kV / mm or higher. <Dielectric breakdown voltage> The cured product is cut into a size of 100 mm square and a thickness of 1 mm to form a test piece. The test piece is placed in insulating oil while being sandwiched between circular electrodes. Then, using an insulation resistance tester, an alternating voltage is applied such that the voltage rises at a rate of 2.5 kV / second between the two electrodes, and the voltage at which the test piece breaks is defined as the dielectric breakdown voltage (kV / mm).

11. The powder coating material according to claim 1 or 2, wherein the thermosetting resin composition further contains a curing accelerator (E).

12. The powder coating material according to claim 1 or 2, wherein the (A) epoxy resin contains one or more selected from the group consisting of bisphenol A type epoxy resin, cresol novolak type epoxy resin, bisphenol F type epoxy resin, phenol novolak type epoxy resin, biphenyl type epoxy resin, naphthalene type epoxy resin, and biphenyl aralkyl type epoxy resin.

13. The powder coating according to claim 1 or 2, wherein the content of the component (A) is 10% by mass or more and 70% by mass or less based on 100% by mass of the entire thermosetting resin composition.

14. The powder coating according to claim 1 or 2, wherein the content of the component (B) is 1% by mass or more and 20% by mass or less based on 100% by mass of the entire thermosetting resin composition.

15. The powder coating according to claim 1 or 2, wherein the total content of the component (A), the component (B), the component (C) and the component (D) is 50% by mass or more and 100% by mass or less based on 100% by mass of the entire thermosetting resin composition.

16. The coil end has an exposed portion in which the conductor portion is covered with an insulator and a part of the conductor portion is exposed from the insulator. The powder coating can be used in a powder coating method including a step of immersing the coil end in a flowing tank in which the powder coating flows and attaching a melt of the powder coating to the outside of the exposed portion. The powder coating according to claim 1 or 2.

17. The powder coating according to claim 16, which can be used in the powder coating method of attaching the melt of the powder coating to the outside of the exposed portion, and attaching the melt to the insulator from the exposed portion of the coil end.

18. A coil having a coil end. The coil end has a conductor, an insulator for covering the conductor, and an exposed portion in which a part of the conductor portion is exposed from the insulator. A coil in which the exposed portion is sealed with a cured product of the powder coating according to claim 1 or 2.

19. Including a step of immersing the coil end of a coil having a coil end provided with an exposed portion in which the conductor portion is covered with an insulator and the conductor portion is exposed from the insulator in a flowing tank in which the powder coating flows and attaching a melt of the powder coating to the outside of the exposed portion. A method for sealing a coil end, wherein the powder coating is the powder coating according to claim 1 or 2.

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