JP2023119510A - Powder coating - Google Patents

Abstract

To provide powder coating which achieves both excellent filling property and suppression of sag.SOLUTION: Powder coating used for coating a coil end contains a particulate thermosetting resin composition, wherein the thermosetting resin composition contains an epoxy resin, a curing agent, and an inorganic filler, in complex viscosity of the powder coating measured at 150°C and 1 Hz by dynamic viscoelasticity measurement, viscosity η1 after 1 min from the start of measurement is 40 Pa s or more and 1,000 Pa s or less, and a ratio (η2/η1) of viscosity η2 after 2 min from the start of measurement to η1 is 6.0 or more and 100 or less.SELECTED DRAWING: None

Description

The present invention relates to powder coatings.

Patent Documents 1 to 3 describe techniques related to powder coatings containing epoxy resins.
In Patent Document 1 (Japanese Patent Laid-Open No. 6-039344), a resin powder coating with high melt fluidity containing a crystalline thermosetting resin is attached to the lower surface of a preheated object to be processed, and then the coating is Describes a powder coating method in which the object to be treated is turned upside down, the powder coating is heated to its curing temperature in this state, and the resin powder coating adhering to the object to be treated flows down in a molten state while the curing reaction is performed. (Claim 1). In addition, the document describes that a crystalline epoxy resin is used as the crystalline thermosetting resin (paragraph 0005), that the object to be treated may be a coil (claim 2), that the melt viscosity of the powder coating is may be 1000 cp or less (claim 3).

Patent Document 2 (Japanese Patent Application Laid-Open No. 2001-238419) describes that an insulating resin is coated so as to cover the top surface of the coil end of the stator coil (claim 1), and It is described that, as the insulating resin, a resin based on an epoxy resin having a predetermined viscosity that does not permeate and adhere from the top of the coil end to the portion of the wire other than the top during drying and curing can be used. (Claim 9).

Patent Document 3 (Japanese Unexamined Patent Application Publication No. 2000-278901) discloses a stator winding having joints and an insulating resin covering the joints. It describes an insulating structure for a stator of a rotary electric machine in which the upper limit value is set to a value smaller than the upper limit value at which peeling occurs, and the upper limit value is changed according to the film thickness of the insulating resin (claim 1). In addition, in the same document, the film thickness of the insulating resin is set to a maximum value of approximately 0.5 mm, the stator windings are formed of copper, and the insulating resin is epoxy (claim 4). It is described that the viscosity of the previous insulating resin must be at least 50 a·s or less (paragraph 0031).

JP-A-6-039344 JP-A-2001-238419 JP-A-2000-278901

However, when the present inventor examined the technique described in the above document, it was found that there is room for improvement in terms of achieving both excellent filling properties and suppression of sagging.

According to the invention,
A powder coating used to coat coil ends,
Containing a particulate thermosetting resin composition,
The thermosetting resin composition is
epoxy resin;
a curing agent;
an inorganic filler;
including
The complex viscosity of the powder coating measured by dynamic viscoelasticity measurement under the conditions of 150 ° C., 1 Hz, 25 mmφ, aluminum parallel plate, 0.5 mm gap,
Viscosity η1 one minute after the start of measurement is 40 Pa s or more and 1000 Pa s or less,
There is provided a powder coating material, wherein the ratio (η2/η1) of viscosity η2 two minutes after the start of measurement to η1 is 6.0 or more and 100 or less.

According to the present invention, there is provided a coil having the coil end in which the exposed portion is sealed with the powder coating of the present invention.

According to the invention,
immersing the coil end of a coil having a conductor portion covered with an insulating coating and having a coil end provided with an exposed portion where the conductor portion is exposed from the insulating coating in a fluidized bath in which the powder coating flows; Adhering the melt of the powder coating to the outside of the exposed portion,
There is provided a coil end sealing method, wherein the powder coating is the powder coating of the present invention.

It should be noted that arbitrary combinations of these configurations and conversion of expressions of the present invention between methods, apparatuses, and the like are also effective as aspects of the present invention.
For example, according to the present invention, an article coated with the powder coating of the present invention can be obtained.

According to the present invention, it is possible to provide a powder coating that achieves both excellent filling properties and suppression of dripping.

It is a perspective view which shows the structural example of the stator in embodiment. 2 is a plan view showing a configuration example of coil ends of stator coils in the stator shown in FIG. 1. FIG.

Embodiments will be described below. In this embodiment, the composition can contain each component alone or in combination of two or more.

(powder paint)
In this embodiment, the powder coating is used to coat the coil ends and contains a particulate thermosetting resin composition. A thermosetting resin composition includes an epoxy resin, a curing agent, and an inorganic filler. Then, by dynamic viscoelasticity measurement, the complex viscosity of the powder coating measured under the conditions of 150 ° C., 1 Hz, 25 mmφ, aluminum parallel plate, 0.5 mm gap, viscosity η1 after 1 minute from the start of measurement is 40 Pa · s or more and 1000 Pa·s or less, and the ratio (η2/η1) of the viscosity η2 two minutes after the start of measurement to the above η1 is 6.0 or more and 100 or less.

In the present embodiment, the particulate thermosetting resin composition contained in the powder coating contains specific components and has a viscosity η1 and a viscosity ratio (η2/η1) within specific ranges. Therefore, it is possible to obtain a powder coating that satisfies both excellent filling properties and suppression of dripping.

Here, the inventor of the present invention stably coats the coil ends with powder coating to obtain excellent insulation, so that even when the interval between adjacent coil ends becomes smaller due to the miniaturization of the coil, , while suppressing sagging during coating, the inventors investigated to improve the filling performance of narrow portions represented by welded portions of conductors such as copper wires. As a result, focusing on the flow behavior of the powder coating, by controlling the viscosity η1 at 150°C and the viscosity ratio (η2/η1) as indicators, it was possible to achieve both excellent filling between conductors and suppression of sagging. I discovered something new. The reason for this is thought to be that it is important to control the curing behavior of the powder coating so as to be optimal in order to achieve both of these.

By using the powder coating according to the present embodiment, for example, the conductor connection part, welding part, etc. in the exposed part can be stably sealed, thereby improving the insulation and strength of the connection part and welding part, for example. can also be improved.
According to this embodiment, it is possible to obtain a powder coating suitable for coating the coil ends. It is also possible to provide a powder coating suitable for coating the coil ends of a coil having coil ends.

Further, the powder coating in the present embodiment is, for example, a coil end of a coil having a coil end having a conductor portion covered with an insulating coating and having an exposed portion where the conductor portion is exposed from the insulating coating. It can be used in a powder coating method including a step of immersing in a fluidized bath in which the paint flows and depositing the molten powder coating on the outside of the exposed portion. A melt of powder coating can be applied from the part to the insulation coating.
Hereinafter, the composition of the powder coating will be described more specifically.

The ratio (η2/η1) of the viscosity η2 after 2 minutes from the start of measurement to the viscosity η1 after 1 minute after the start of measurement is 6.0 or more, preferably 10 or more, from the viewpoint of suppressing sagging of the coating film and improving curability. , more preferably 20 or more, and still more preferably 30 or more.
In addition, from the viewpoint of improving filling properties, the viscosity ratio (η2/η1) is 100 or less, preferably 80 or less, more preferably 60 or less, and even more preferably 50 or less.

The viscosity η1 of the powder coating is 40 Pa·s or more, preferably 80 Pa·s or more, more preferably 100 Pa·s or more, from the viewpoint of sagging suppression.
In addition, from the viewpoint of improving filling properties, the viscosity η1 of the powder coating is 1000 Pa·s or less, preferably 600 Pa·s or less, more preferably 400 Pa·s or less, and still more preferably 200 Pa·s or less.

The viscosity η2 of the powder coating may be, for example, 300 Pa·s or more, preferably 1000 Pa·s or more, more preferably 2000 Pa·s or more, still more preferably 3000 Pa·s or more, from the viewpoint of suppressing the sagging tendency. is.
In addition, from the viewpoint of improving filling properties, the viscosity η2 of the powder coating is preferably 10000 Pa·s or less, more preferably 9000 Pa·s or less, and still more preferably 8000 Pa·s or less.

In the complex viscosity of the powder coating, the ratio of the viscosity η3 1.5 minutes after the start of measurement to the viscosity η1 (η3/η1) is preferably greater than 1, more preferably more than 1, from the viewpoint of suppressing dripping and improving curability. It is 1.5 or more, more preferably 2.0 or more.
In addition, from the viewpoint of improving filling properties, the viscosity ratio (η3/η1) is preferably 10 or less, more preferably 8.0 or less, and even more preferably 5.0 or less.

In the complex viscosity of the powder coating, the viscosity η4 10 seconds after the start of measurement is preferably 20 Pa s or more, more preferably 22 Pa s or more, and still more preferably 24 Pa s or more, from the viewpoint of sagging suppression. .
Further, from the viewpoint of improving the filling property, the viscosity η4 of the powder coating is preferably 40 Pa·s or less, more preferably 35 Pa·s or less, and still more preferably 30 Pa·s or less.

Here, the complex viscosity of the powder coating is measured under the conditions described above. Measured under the conditions of parallel plates and a gap of 0.5 mm. The viscosities 1 minute, 2 minutes, 1.5 minutes and 10 seconds after the start of measurement are defined as η1, η2, η3 and η4, respectively.

Next, the particle size characteristics of the thermosetting resin composition in the powder coating will be explained.
The particle diameter d ₉₀ of the thermosetting resin composition is preferably 50 μm or more, more preferably 70 μm or more, and still more preferably 70 μm or more, from the viewpoint of allowing the powder coating to preferably flow in the fluidizing tank when coating the coil ends. is 100 μm or more.
In addition, from the viewpoint of preventing coarse particles from accumulating on the bottom surface of the fluidization tank and more stably coating, the particle size _d90 of the thermosetting resin composition is preferably 200 μm or less, more preferably 180 μm or less, and further preferably 180 μm or less. It is preferably 150 μm or less.

Here, the particle size characteristics of the thermosetting resin composition and the particle size characteristics of the inorganic particles, which will be described later, are measured by a laser diffraction method. SALD-2300) can be used to measure the particle size distribution of particles on a volume basis.

Next, the constituent components of the powder coating will be described.
A powder coating comprises a thermosetting resin composition, which comprises an epoxy resin, a curing agent and an inorganic filler.

Specific examples of epoxy resins include those that have two or more epoxy groups in the molecule and are solid at room temperature. Examples of such epoxy resins include bisphenol A type, bisphenol F type, bisphenol S type, novolak type, phenol novolak type, cresol novolak type, biphenyl type, naphthalene type, biphenylaralkyl type, and aromatic amine type epoxy resins. be done.

From the viewpoint of coating the coil ends more stably, the epoxy resin is preferably a bisphenol A type epoxy resin, a biphenyl type epoxy resin such as a biphenyl aralkyl type epoxy resin, a dicyclopentadiene type epoxy resin, an orthocresol novolak type epoxy resin, or a containing one or more selected from the group consisting of tetramethylbiphenyl-type epoxy resins;
More preferably, it 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. :
More preferably, it contains a bisphenol A type epoxy resin and a biphenyl alkyl type epoxy resin.
At this time, the softening point of the bisphenol A type epoxy resin is, for example, 65 to It is 150°C or less, preferably 70 to 120°C or less.

The content of the epoxy resin in the thermosetting resin composition is preferably 20% by mass or more with respect to the entire thermosetting resin composition, from the viewpoint of improving the smoothness of the surface of the cured product of the powder coating. , more preferably 25% by mass or more, and still more preferably 30% by mass or more.
In addition, from the viewpoint of improving the coating moldability of the powder coating, the content of the epoxy resin in the thermosetting resin composition is preferably 70% by mass or less with respect to the entire thermosetting resin composition. Yes, more preferably 60% by mass or less, still more preferably 50% by mass or less, and even more preferably 40% by mass or less.

Moreover, the thermosetting resin composition may contain other thermosetting resins. Other thermosetting resins include one or more selected from the group consisting of phenol resins, melamine resins, unsaturated polyester resins, and polyurethane resins.
The thermosetting resin may also contain a resin curing agent such as a phenolic resin curing agent, which will be described later.

The content of the thermosetting resin in the thermosetting resin composition is preferably 20% by mass or more with respect to the entire thermosetting resin composition from the viewpoint of improving the smoothness of the surface of the cured product of the powder coating. , more preferably 25% by mass or more, and still more preferably 30% by mass or more.
Further, from the viewpoint of improving the coating moldability of the powder coating, the content of the thermosetting resin in the thermosetting resin composition is preferably 70% by mass with respect to the entire thermosetting resin composition. or less, more preferably 60% by mass or less, still more preferably 50% by mass or less, even more preferably 45% by mass or less, and even more preferably 40% by mass or less.

Specific examples of curing agents include aromatic amines such as diaminodiphenylmethane and aniline resins, condensates of aliphatic amines and aliphatic dicarboxylic acids, amines such as dicyandiamide and derivatives thereof;
Various imidazole and imidazoline compounds;
Polydicarboxylic acids such as adipic acid, sebacic acid, phthalic acid, maleic acid, trimellitic acid, benzophenonedicarboxylic acid, pyromellitic acid or their acid anhydrides;
Phenolic resins such as novolac-type phenolic resins, biphenylaralkyl-type phenolic resins, and naphtholaralkyl-type phenolic resins;
Novolaks which are condensates of aldehydes with dihydrazides such as adipic acid and phthalic acid, phenol, cresol, xylenol, bisphenol A;
carboxylic acid amide;
methylolated melamines; and blocked isocyanurates.
The curing agent preferably contains one or more selected from the group consisting of acid anhydrides and phenolic resins, from the viewpoint of suppressing dripping of the powder coating and improving the filling properties of the powder coating.

The ratio of curing agent to epoxy resin can be adjusted, for example, by the type of epoxy resin and curing agent used.
From the viewpoint of obtaining good curability and cured product properties, the ratio of the curing agent to the epoxy resin is preferably such that the functional group (number) of the curing agent is 0.1 mol with respect to the epoxy group (number) of the epoxy resin. equivalent or more, more preferably 0.2 molar equivalents or more, still more preferably 0.3 molar equivalents or more, and preferably 1.2 molar equivalents or less, more preferably 1.1 molar equivalents or less, More preferably, it is 0.9 molar equivalents or less.

Specific examples of inorganic fillers include crystalline silica, fused silica such as fused crushed silica, spherical silica, silica such as surface-treated silica; calcium carbonate, calcium sulfate and other calcium compounds; barium sulfate, aluminum oxide (specifically alumina), aluminum hydroxide, magnesium hydroxide, talc, kaolin, clay, mica, dolomite, wollastonite, glass fiber, glass beads, zircon, and molybdenum compounds.
From the viewpoint of availability, the inorganic filler preferably contains one or more selected from the group consisting of silica, alumina and calcium carbonate, more preferably from the group consisting of silica, alumina and calcium carbonate. One or two or more selected, more preferably silica.

When the inorganic filler is silica, the average particle diameter _d50 of silica is preferably 50 µm or less, more preferably 30 µm or less, and still more preferably 25 µm or less, from the viewpoint of improving narrow space filling properties of the powder coating. and may be, for example, 1 μm or more.

From the viewpoint of improving the mechanical strength of the thermosetting resin composition, the content of the inorganic filler in the thermosetting resin composition is preferably 30% by mass or more with respect to the entire thermosetting resin composition. Yes, more preferably 40% by mass or more, still more preferably 50% by mass or more. Further, from the viewpoint of improving the smoothness of the cured product of the thermosetting resin composition, the content of the inorganic filler in the thermosetting resin composition is preferably 80 mass with respect to the entire thermosetting resin composition. %, more preferably 70% by mass or less, and even more preferably 65% by mass or less.

The thermosetting resin composition may contain components other than those mentioned above. For example, the thermosetting resin composition may contain curing accelerators, coloring agents, leveling agents, flame retardants, coupling agents, and the like.

For example, the thermosetting resin composition preferably further contains a curing accelerator from the viewpoint of suppressing dripping of the powder coating material and improving the filling properties of the powder coating material.

Specific examples of curing accelerators include organic phosphines such as triphenylphosphine; imidazole compounds such as 2-phenylimidazole; and amine compounds such as tertiary amines.
In addition, from the viewpoint of further improving the balance between the effects of suppressing dripping and improving filling properties, the thermosetting resin composition contains a bisphenol A type epoxy resin and a biphenyl type epoxy resin such as a biphenyl aralkyl type epoxy resin. , it is also preferable to further contain a curing accelerator.

From the viewpoint of obtaining good curing properties, the content of the curing accelerator in the thermosetting resin composition is preferably 0.01% by mass or more, more preferably 0.03, based on the entire thermosetting resin composition. % by mass or more, preferably 2% by mass or less, more preferably 1% by mass or less, even more preferably 0.5% by mass or less, and even more preferably 0.3% by mass or less.

The thermosetting resin composition may further contain a coloring agent such as a pigment.
Specific examples of pigments include one or more selected from the group consisting of titanium oxide, iron oxide, zinc oxide, carbon black and cyanine blue.
From the viewpoint of obtaining preferable coloring properties, the content of the pigment in the powder coating is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and still more preferably It is 1% by mass or more, preferably 5% by mass or less, more preferably 3% by mass or less, and still more preferably 2% by mass or less.

Moreover, the powder coating may be composed of a particulate thermosetting resin composition, and may further contain other components. Specific examples of other components include fluidity imparting agents. Specific examples of fluidity imparting materials include inorganic particles such as silica and alumina.

Next, a method for producing a powder coating will be described. A method for producing a powder coating specifically includes a step of preparing a thermosetting resin composition. Further, when the powder coating contains components other than the thermosetting resin composition (for example, inorganic particles), the method for producing the powder coating includes, for example, a step of mixing the thermosetting resin composition and other components. It may contain further. For example, in a particulate thermosetting resin composition, an epoxy resin, an inorganic filler, a curing agent, and optional components are blended in a predetermined order, mixed, and then melt-kneaded while heating to knead all raw materials. get things Next, the resulting kneaded material is pulverized by an impact pulverizer to obtain an epoxy resin powder coating. Further, after pulverization, fine particles and coarse particles may be cut by sieving to adjust the particle size of the powder coating material.

Here, in order to obtain a powder coating having the above-mentioned viscosity characteristics within a specific range, for example, the components and composition contained in the thermosetting resin composition, such as the type and amount of epoxy resin, are appropriately selected. This is very important. Moreover, it is also preferable to further mix, for example, a curing accelerator.

(coil)
The coil has coil ends whose exposed portions are sealed with the powder coating of this embodiment.
Specific examples of coils include motor coils such as drive motor coils. In the following, a more specific description will be given by taking a stator coil of a motor as an example.

FIG. 1 is a perspective view showing a configuration example of a stator according to the embodiment. A stator 100 shown in FIG. 1 has a stator core 101 and a stator coil 103 . The stator coils 103 are arranged in grooves (slots, not shown) provided in the inner wall of the stator core 101 .

FIG. 2 is a plan view showing a configuration example of the coil end 105 of the stator coil 103. As shown in FIG. The coil end 105 is provided with an enamel-coated portion 107 in which the conductor is covered with an insulating coating such as enamel, and an exposed portion 109 in which the conductor is exposed from the enamel coating. It is sealed with the powder coating in this embodiment. In FIG. 2 , a covering portion 111 is provided from the exposed portion 109 to the enamel covering portion 107 . The covering portion 111 is composed of a cured powder coating material according to the present embodiment.

(Powder coating method)
The powder coating method is, for example, a method of sealing the coil ends using the powder coating of this embodiment. Specifically, such a method is a coil end of a coil (stator coil 103) having a coil end 105 having a conductor portion covered with an insulating coating and provided with an exposed portion 109 where the conductor portion is exposed from the insulating coating. 105 is immersed in a fluidized bath in which the powder coating flows to adhere the molten powder coating to the outside of the exposed portion (step 1).

Step 1 includes, for example, a step of introducing air into a fluidizing tank in which the powder coating is contained to flow the powder coating (step 1-1); and a step of immersing (step 1-2).
In step 1-1, for example, a fluidization tank having a perforated plate at the bottom is used to fill the upper part of the perforated plate with the powder coating material, and air is introduced from the outside of the perforated plate to can be carried out by introducing air into the fluidization tank.

In step 1-2, immersing the coil end 105 in the fluidized bath and applying the molten powder coating 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, adhesion of the powder coating melt to the outside of the exposed portion preferably occurs while the coil end 105 is immersed in the fluidized bath.

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 ends 105 before the coil ends 105 are immersed in the fluid bath. At this time, by immersing the heated coil end 105 in a fluidized bath in which the powder coating flows, the powder coating in the vicinity of the coil end 105 adheres to the coil end 105 as a molten material in the fluidized bath. Further, from the viewpoint of making the powder coating adhering to the coil ends 105 more stably melted, the coil ends 105 may be heated after the coil ends 105 are removed from the fluidized bath.
The coil end 105 can be heated, for example, by a heater arranged above the fluidized bath.

In the present embodiment, the powder coating method includes a step of applying the melted powder coating to the outside of the exposed portion 109 of the coil end 105, followed by a step of heating the coil end 105 to harden the powder coating (step 2). may further include The heat curing conditions can be appropriately set according to the type and size of the coil end 105, the components of the powder coating, and the like.
Also, in the powder coating method, step 1 and step 2 may be alternately repeated multiple times from the viewpoint of increasing the thickness of the coating.

In the present embodiment, by using a powder coating containing a thermosetting resin composition having specific components and particle size characteristics, it is possible to prevent the coil end 105 from sagging when stably sealing the exposed portion. It is possible to improve the fillability of the connecting portion and the welding portion in 109 and form the covering portion 111 having excellent insulating properties.

Although the embodiments of the present invention have been described above, these are examples of the present invention, and various configurations other than those described above can be adopted.

(Examples 1 to 4, Comparative Examples 1 to 4)
In this example, a powder coating composed of a thermosetting resin composition was produced and evaluated. The components used in the powder coating are shown below.

(Raw material for thermosetting resin composition)
(Epoxy resin)
Epoxy resin 1: bisphenol A type epoxy resin, JER1001, manufactured by Mitsubishi Chemical Corporation, softening point 64°C
Epoxy resin 2: Bisphenol A type epoxy resin, JER1002, manufactured by Mitsubishi Chemical Corporation, softening point 78°C
Epoxy resin 3: Bisphenol A type epoxy resin, JER1003F, manufactured by Mitsubishi Chemical Corporation, softening point 89°C
Epoxy resin 4: Biphenyl aralkyl type epoxy resin, NC-3000H, manufactured by Nippon Kayaku Co., Ltd. Epoxy resin 5: Dicyclopentadiene type epoxy resin, XD-1000, manufactured by Nippon Kayaku Co., Ltd. Epoxy resin 6: Tetramethylbiphenyl type epoxy resin, YX4000 manufactured by Mitsubishi Chemical Corporation
(Inorganic filler)
Inorganic filler 1: Spherical silica, HS-208 manufactured by Nippon Steel Chemical & Materials, d ₅₀ = 20 µm
(curing agent)
Curing agent 1: 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA)
Curing agent 2: novolac type phenolic resin, PR-51470, manufactured by Sumitomo Bakelite (curing accelerator)
Curing accelerator 1: triphenylphosphine (TPP), manufactured by Kei Kasei Co., Ltd. (pigment)
Pigment 1: Titanium oxide, manufactured by Ishihara Sangyo Co., Ltd., CR-500

(Manufacturing of powder coating)
A powder coating of each example was obtained by preparing a thermosetting resin composition according to the formulation shown in Table 1 and mixing the obtained thermosetting resin composition and other components in a conventional manner.
Here, for the thermosetting resin composition, the raw material components are mixed with a mixer, melted and kneaded at 80 ° C., pulverized with a pulverizer, and air classified and sieved to determine the particle size shown in Table 1. A thermosetting resin composition having properties was obtained.

(Physical properties and evaluation of powder coating)
The particle size distribution and viscosity characteristics of the thermosetting resin composition obtained in each example were measured by the following methods.
Also, the thermosetting resin composition was used as a powder coating, and the coefficient of linear expansion, fillability and sagging were measured by the following methods. The measurement results are also shown in Table 1.

(complex viscosity)
Using a dynamic viscoelasticity measuring device (MCR301 manufactured by Anton Paar), the temperature of 150 ° C., frequency of 1 Hz, 25 mmφ aluminum parallel plates, gap of 0.5 mm, the complex of the thermosetting resin composition obtained in each example The viscosity was measured, and the viscosities 1 minute, 2 minutes, 1.5 minutes and 10 seconds after the start of measurement were defined as η1, η2, η3 and η4, respectively.

(Particle size distribution of thermosetting resin composition)
The particle size distribution of the particles was measured on a volume basis using a laser diffraction particle size distribution analyzer (Partica LA-950V2 manufactured by HORIBA).

(linear expansion coefficient)
The powder coating obtained in each example was melt-hardened at 190° C. for 20 minutes to obtain a molding. The obtained molding was cut into a size of 5 mm×5 mm×20 mm and used as a measurement sample.
Using TMA SS6000 manufactured by Seiko Instruments Inc., the coefficient of linear expansion was measured at a heating rate of 5°C/min and a load of 10 g, and the average coefficient of linear expansion from 40°C to 50°C was calculated.

(Fillability)
A copper plate having a length of 50 mm, a width of 3 mm, and a thickness of 1 mm was wrapped with a heat-resistant tape having a thickness of 500 μm at the lower end of the copper plate at a distance of 50 μm and a distance of 10 mm from the lower end. A test piece (TP) having a V-shaped gap was prepared by pasting together copper plates of the same size without tape.
The test piece was preheated at 170° C. and coated by a fluidization dipping method to a height that filled the gap.
Polishing was performed after curing at 170° C., and the size of the unfilled portion generated in the gap of 50 μm was compared.
An unfilled portion of less than 500 μm was evaluated as ◯, 500 μm or more and less than 1000 μm as Δ, and 1000 μm or more as x.

(drip)
A copper plate having a length of 50 mm, a width of 5 mm, and a thickness of 3 mm was heated to 170°C and dipped twice for 1 second by fluidized dip coating, followed by heat curing at 170°C. The depth of immersion of the copper plate was 20 mm from the end of the copper plate. The film thickness of the side portion 40 mm from the end of the uncoated portion (10 mm from the coated end) and the film thickness of the coated bottom portion were compared.
When the ratio (bottom film thickness/side film thickness) was less than 2 times, ◯ was given, 2 times or more and less than 3 times was given Δ, and 3 times or more or the coating film dripped was given x. Those with ○ and △ were regarded as acceptable.

As can be seen from Table 1, the powder coatings obtained in each example had an excellent balance between the effects of filling properties and suppression of dripping. The powder coating in each example can be preferably used to coat the exposed portions of the coil ends.

100 Stator 101 Stator core 103 Stator coil 105 Coil end 107 Enamel coated portion 109 Exposed portion 111 Coated portion

Claims (11)

A powder coating used to coat coil ends,
Containing a particulate thermosetting resin composition,
The thermosetting resin composition is
epoxy resin;
a curing agent;
an inorganic filler;
including
The complex viscosity of the powder coating measured by dynamic viscoelasticity measurement under the conditions of 150 ° C., 1 Hz, 25 mmφ, aluminum parallel plate, 0.5 mm gap,
Viscosity η1 one minute after the start of measurement is 40 Pa s or more and 1000 Pa s or less,
A powder coating, wherein the ratio (η2/η1) of viscosity η2 after 2 minutes from the start of measurement to η1 is 6.0 or more and 100 or less. The powder coating according to claim 1, wherein said η2 is 300 Pa·s or more and 10000 Pa·s or less. 3. The powder coating material according to claim 1, wherein, in said complex viscosity, a ratio (η3/η1) of viscosity η3 after 1.5 minutes from the start of measurement to said η1 is more than 1 and 10 or less. 4. The powder coating according to any one of claims 1 to 3, wherein the complex viscosity has a viscosity η4 of 20 Pa·s or more and 40 Pa·s or less 10 seconds after the start of measurement. The epoxy resin is
a bisphenol A type epoxy resin;
one or more selected from the group consisting of biphenyl-type epoxy resins, dicyclopentadiene-type epoxy resins, biphenylaralkyl-type epoxy resins and tetramethylbiphenyl-type epoxy resins;
The powder coating according to any one of claims 1 to 4, comprising 6. The powder coating material according to any one of claims 1 to 5, wherein said curing agent contains one or more selected from the group consisting of acid anhydrides and phenolic resins. 7. The powder coating according to any one of claims 1 to 6, wherein the particle size _d90 of the thermosetting resin composition measured by a laser diffraction method is 50 µm or more and 200 µm or less. 8. The powder coating according to any one of claims 1 to 7, wherein said thermosetting resin composition further comprises a curing accelerator. 9. The powder coating according to any one of claims 1 to 8, wherein said powder coating is used in a powder coating method in which a melt of said powder coating is adhered from an exposed portion of said coil end to an insulating coating. A coil having the coil end with the exposed portion sealed with the powder coating according to any one of claims 1 to 9. immersing the coil end of a coil having a conductor portion covered with an insulating coating and having a coil end provided with an exposed portion where the conductor portion is exposed from the insulating coating in a fluidized bath in which the powder coating flows; Adhering the melt of the powder coating to the outside of the exposed portion,
A method for sealing coil ends, wherein the powder coating is the powder coating according to any one of claims 1 to 9.

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