COATING COMPOSITION FOR ELECTRICAL STEEL SHEET, ELECTRICAL STEEL SHEET WITH SURFACE COATING FOR ADHESION AND LAMINATED CORE

Abstract

This coating composition for an electrical steel sheet is a coating composition for an electrical steel sheet containing an epoxy resin, a high-temperature curing agent, and inorganic fine particles, wherein the content of the high-temperature curing agent with respect to 100 parts by mass of the epoxy resin is from 5 to 30 parts by mass, wherein the inorganic fine particles are one or more selected from metal hydroxides, metal oxides that react with water at 25°C to become metal hydroxides, and silicate minerals having a hydroxyl group, wherein the volume-average particle diameter of the inorganic fine particles is from 0.05 to 2.0 µm, wherein the epoxy resin content with respect to the total mass of the coating composition for an electrical steel sheet is 45% by mass or more, and wherein the inorganic fine particle content with respect to 100 parts by mass of the epoxy resin is from 1 to 100 parts by mass.

Description

COATING COMPOSITION FOR ELECTRICAL STEEL SHEET, ELECTRICAL STEEL SHEET WITH SURFACE COATING FOR ADHESION AND LAMINATED CORE Technical field of the invention [1] The present invention relates to a coating composition for an electrical steel sheet, an electrical steel sheet with a surface coating for adhesion, and a laminated core. Priority is claimed over Japanese Patent Application No. 2020-104244, filed June 17, 2020, the contents of which are incorporated herein by reference. RPfrfr Ln / Zznz / E / YIAI Background of the invention [2] In general, when assembling laminated cores for motors and transformers using electrical steel sheet, the unit iron cores are obtained by shearing or stamping, and then rolled and secured by clamping, brazing, welding, or bonding bolts to form a laminated core. In recent years, there has been a demand for further improvements in motor efficiency, and a greater reduction in core loss has been required. To reduce core loss, it is effective to reduce the thickness of the electrical steel sheet. However, when the electrical steel sheet is thin, not only is caulking or welding difficult, but the surface of the rolled end also cracks easily, and it is difficult to maintain the shape of the laminated core. [3] To address these problems, instead of integrating electrical steel sheets by fastening or welding, a technique has been proposed in which an electrical steel sheet having an adhesive insulating coating formed on its surface is thermally compressed to form a laminated core. For example, Patent Document 1 proposes a coating composition for an electrical steel sheet containing an epoxy resin, a curing agent, and nanoparticles having a specific average radius. Patent Document 2 proposes a coating composition for an electrical steel sheet containing a water-soluble epoxy resin, inorganic nanoparticles, and an inorganic additive. Patent Document 3 proposes an electrical steel sheet in which a thermosetting enamel layer containing an epoxy resin, a curing agent, and a filler is provided on a flat surface. List of appointments Patent documents [4] Patent Document 1: Published Japanese Translation PCT International Publication No. 2008-518087 Patent Document 2: Published Japanese Translation PCT International Publication No. 2016-540901 Patent Document 3: Published Japanese Translation PCT International Publication No. 2018-518591 RPfrfr Ln / Zznz / E / YIAI Summary of the invention Problems that must be solved by the invention [5] In the technologies of Patent Documents 1 to 3. An attempt is made to improve the bonding strength of the insulating coating, corrosion resistance, electrical insulation, surface quality of the electrical steel sheet, and stability of the laminated core shape. However, productivity improvement is not considered when molding the laminated core. [6] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a coating composition for an electrical steel sheet that can improve the productivity of a laminated core, an electrical steel sheet with a surface coating for adhesion, and a laminated core. Means to solve the problem [7] In order to address the above problems, the present invention proposes the following aspects. [1] A coating composition for an electrical steel sheet, comprising: an epoxy resin, a high-temperature curing agent, and inorganic fine particles, wherein the content of the high-temperature curing agent relative to 100 parts by mass of the epoxy resin is from 5 to 30 parts by mass, wherein the inorganic fine particles are one or more selected from metal hydroxides, metal oxides that react with water at 25°C to become metal hydroxides, and silicate minerals having a hydroxyl group, wherein the volume-average particle diameter of the inorganic fine particles is from 0.05 to 2.0 pm, wherein the content of the epoxy resin relative to the total mass of the coating composition for an electrical steel sheet is 45% by mass or more, and wherein the content of inorganic fine particles relative to 100 parts by mass of the epoxy resin is from 1 to 100 parts by mass. mass. [2] The coating composition for an electrical steel sheet in accordance with [1] wherein the inorganic fine particles are one or more selected from aluminum hydroxide, calcium hydroxide, magnesium hydroxide, calcium oxide, magnesium oxide, talc, mica, and kaolin. [3] The coating composition for an electrical steel sheet in accordance with [1] or [2], wherein the high-temperature curing agent is one or more selected from aromatic amines, phenolic curing agents, and dicyandiamides. [4] An electrical steel sheet with surface coating for adhesion having an insulating coating obtained by applying the coating composition for an electrical steel sheet in accordance with any of [1] to [3] on the surface. [5] A laminated core obtained by rolling two or more sheets of electrical steel with a surface coating for adhesion in accordance with [4]. Effects of the invention [8] In accordance with the coating composition for an electrical steel sheet of the present invention, it is possible to improve the productivity of the laminated core. Brief description of the drawings [9] Figure 1 is a cross-sectional view of an electric motor including a laminated core according to an embodiment of the present invention. Figure 2 is a side view of the laminated core shown in Figure 1. Figure 3 is a cross-sectional view taken along line AA of Figure 2. Figure 4 is a plan view of a material forming the laminated core shown in Figure 1. Figure 5 is a cross-sectional view taken along line BB of Figure 4. Figure 6 is an enlarged view of part C of Figure 5. Figure 7 is a side view of a production device used to produce the laminated core shown in Figure 1. Figure 8 is an example of a graph showing the correlation between treatment time and adhesive strength. RPfrfr Ln / Zznz / E / YIAI Method(s) for implementing the invention

[10] Hereafter, a laminated core (laminated core) according to an embodiment of the present invention, an electric motor including the laminated core, and a material forming the laminated core shall be described with reference to the drawings. Herein, in the present embodiment, an electric motor shall be described by way of example as an electric motor, specifically an AC electric motor, more specifically a synchronous electric motor, and even more specifically, a permanent magnetic field electric motor. This type of electric motor is suitable for, for example, an electric car.

[11] As shown in Figure 1, an electric motor includes a stator 20, a rotor 30, a housing 50, and a rotating shaft 60. The stator 20 and the rotor 30 are housed in the housing 50. The stator 20 is fixed in the housing 50. In the present embodiment, the electric motor 10 is an internal rotor type machine in which the rotor 30 is positioned inside the stator 20 in the radial direction. However, the electric motor 10 can also be an external rotor type machine in which the rotor 30 is positioned outside the stator 20. Furthermore, in the present embodiment, the electric motor 10 is a 12-pole, 18-slot three-phase AC motor. However, the number of poles, the number of slots, the number of phases, and similar characteristics can be changed accordingly. The electric motor 10 can rotate at a rotational speed of 1,000 rpm by applying, for example, an excitation current that has an effective value of 10 A and a frequency of 100 Hz to each phase.

[12] The stator 20 includes an adhesive laminated core for a stator (hereafter referred to as the stator core) 21 and a winding (not shown). The stator core 21 includes a circular back portion 22 and a plurality of toothed parts 23. Hereafter, the direction of the central axis O of the stator core 21 (or the back portion of the core 22) shall be referred to as the axial direction, the radial direction (direction orthogonal to the central axis O) of the stator core 21 (or the back portion of the core 22) shall be referred to as the radial direction, and the circumferential direction (direction around the central axis O) of the stator core 21 (or the back portion of the core 22) shall be referred to as the circumferential direction.

[13] The rear portion of the core 22 is annular in a plan view of the stator 20 viewed from the axial direction. The plurality of toothed parts 23 project from the inner periphery of the rear portion of the core 22 in a radially inward direction (toward the central axis O of the rear portion of the core 22 in the radial direction). The plurality of toothed parts 23 are arranged at equal angular intervals in the circumferential direction. In the present embodiment, 18 toothed parts 23 are provided every 20 degrees at central angles centered on the central axis O. The plurality of toothed parts 23 are formed so as to have the same shape and size. Therefore, the plurality of toothed parts 23 have the same thickness. The winding is wound around the toothed parts 23. The winding can be a concentrated winding or a distributed winding.

[14] The rotor 30 is arranged within the stator 20 (the stator core 21) in the radial direction. The rotor 30 includes a rotor core 31 and a plurality of permanent magnets 32. The rotor core 31 is circular (annular) and arranged coaxially with the stator 20. The rotating shaft 60 is arranged in the rotor core 31. The rotating shaft 60 is fixed to the rotor core 31. The plurality of permanent magnets 32 are fixed to the rotor core 31. In this embodiment, a pair of permanent magnets 32 form a magnetic pole. The plurality of permanent magnet assemblies 32 are arranged at equal angular intervals in the circumferential direction. In this embodiment, 12 assemblies (24 in total) of permanent magnets 32 are provided every 30 degrees at central angles centered on the central axis O.

[15] In the present embodiment, a built-in magnet motor is used as a permanent magnet field-type electric motor. A plurality of through-holes 33 are formed in the rotor core 31, penetrating it axially. These through-holes 33 are arranged to accommodate the arrangement of the plurality of permanent magnets 32. The permanent magnets 32, arranged in the corresponding through-holes 33, are fixed to the rotor core 31. Each permanent magnet 32 ​​can be fixed to the rotor core 31, for example, by bonding the outer surface of the permanent magnet 32 ​​to the inner surface of the through-hole 33 with an adhesive. A surface magnet motor can be used instead of a built-in magnet motor as the permanent magnet field-type electric motor.

[16] Both the stator core 21 and the rotor core 31 are laminated cores. For example, as shown in Figure 2, the stator core 21 is formed by laminating a plurality of electrical steel sheets (electrical steel sheets with a surface coating for adhesion) 40 in the axial direction. Here, the lamination thickness (total length along the central axis 0) of each of the stator cores 21 and the rotor core 31 is, for example, 50.0 mm. The outer diameter of the stator core 21 is, for example, 250.0 mm. The inner diameter of the stator core 21 is, for example, 165.0 mm. The outer diameter of the rotor core 31 is, for example, 163.0 mm. The inner diameter of the rotor core 31 is, for example, 30.0 mm. However, these values ​​are examples, and the lamination thickness, outer diameter, and inner diameter of the stator core 21, and the lamination thickness, outer diameter, and inner diameter of the rotor core 31 are not limited to these values. Here, the inside diameter of the stator core 21 is based on the tip portion of the toothed portion 23 on the stator core 21.That is, the inner diameter of the stator core 21 is the diameter of an imaginary circle inscribed in the tip part of all the toothed parts 23.

[17] Each electrical steel sheet 40 that forms the stator core 21 and the rotor core 31 is formed, for example, by stamping a material 1 as shown in Figures 4 to 6. The material 1 is a steel sheet, (electrical steel sheet) which is a basis of the electrical steel sheet 40. As material 1, for example, a strip-shaped steel sheet and a cut sheet can be illustrated. Although the description of the laminated core is ongoing, Material 1 will be described below. Here, in this specification, the strip-shaped steel sheet that is a basis for Electrical Steel Sheet 40 may be referred to as Material 1. A steel sheet having a shape used for a laminated core obtained by stamping Material 1 may be referred to as Electrical Steel Sheet 40.

[18] For example, material 1 is manipulated by winding it around a coil 1A. In the present embodiment, non-oriented electrical steel sheet is used as material 1. Non-oriented electrical steel strip in accordance with JIS C 2552:2014 may be used as the non-oriented electrical steel sheet. However, grain-oriented electrical steel sheet may be used as material 1 instead of the non-oriented electrical steel sheet. In this case, grain-oriented electrical steel strip in accordance with JIS C 2553:2019 may be used as the grain-oriented electrical steel sheet. In addition, thin non-oriented electrical steel strip or thin grain-oriented electrical steel strip in accordance with JIS C 2558:2015 may be used.

[19] The upper and lower limit values ​​of an average sheet thickness tO of material 1 are set, for example, as follows, considering a case where material 1 is used for electrical steel sheet 40. As material 1 becomes thinner, the production cost of material 1 increases. Therefore, taking into account the production cost, the lower limit value of the average sheet thickness tO of material 1 is 0.10 mm, preferably 0.15 mm and very preferably 0.18 mm. On the other hand, when material 1 is too thick, the production cost is favorable, but when material 1 is used for electrical steel sheet 40, eddy current losses increase and core loss deteriorates. Therefore, considering core loss and production cost, the upper limit for the average sheet thickness tO of material 1 is 0.65 mm, preferably 0.35 mm, and most preferably 0.30 mm. 0.20 mm can be illustrated as a value that satisfies the above interval of the average sheet thickness tO of the tO of the 40 electrical steel sheet. For example, the following measurement method is used. For instance, the rolling thickness of the rolled core is measured at four locations (i.e., every 90 degrees around the central axis O) at equal intervals in the circumferential direction. Each of the rolling thicknesses measured at four locations is divided by the number of 40 electrical steel sheets to calculate the sheet thickness per sheet. The average value of the sheet thicknesses at four locations can be established as the average sheet thickness tO of the 40 electrical steel sheet.

[22] As shown in Figure 5 and Figure 6, material 1 includes the base steel sheet 2 and the insulating coating 3. In material 1, both surfaces of the strip-shaped base steel sheet 2 are covered with the insulating coating 3. In the present embodiment, most of material 1 is formed from the base steel sheet 2, and the insulating coating 3, which is thinner than the base steel sheet 2, is laminated onto the surface of the base steel sheet 2.

[23] The chemical composition of the base steel sheet 2 includes 2.5% to 4.5% Si by mass, as shown below in mass % units. Here, when the chemical composition is within the above range, the yield strength of material 1 (the electrical steel sheet) 40) can be adjusted, for example, to 380 MPa or more and 540 MPa or less.

[24] Yes: 2.5% to 4.5% Al: 0.001% to 3.0% Mn: 0.05% to 5.0% The rest: Faith and impurities

[25] When material 1 is used for electrical steel sheet 40, the insulating coating 3 exhibits insulation performance between adjacent electrical steel sheets 40 in the axial direction. Furthermore, in the present embodiment, the insulating coating 3 has adhesive properties and adheres to adjacent electrical steel sheets 40 in the axial direction. The insulating coating 3 may have a single-layer or multi-layer structure. More specifically, for example, the insulating coating 3 may have a single-layer structure that has both insulating and adhesive properties, or it may have a multi-layer structure that includes an underlying insulating coating with excellent insulation performance and a top insulating coating with excellent adhesive performance.Here, having adhesive capability means having an adhesive strength of a predetermined value or more below a predetermined temperature condition.

[26] In the present embodiment, the insulating coating completely covers both surfaces of the gapless base steel sheet 2. However, provided the above insulation performance and adhesive capacity are ensured, the insulating coating 3 need not cover both surfaces of the gapless base steel sheet 2. In other words, the insulating coating 3 can be provided intermittently on the surface of the base steel sheet 2.For example, when insulating coating 3 has a multi-layered structure that includes an underlying insulating coating that has excellent insulation performance and a top insulating coating that has excellent adhesive performance, even if the underlying insulating coating is formed over the entire surface of the base steel sheet without gaps and the top insulating coating is provided intermittently, it is possible to achieve both insulation performance and adhesive capability.

[27] The coating composition that forms the underlying insulating coating is not particularly restricted and, for example, a general treatment agent such as a treatment agent containing chromic acid or a treatment agent containing phosphate may be used.

[28] The adhesive insulating coating is formed by applying a coating composition for electrical steel sheet, as described above, onto a base steel sheet. The adhesive insulating coating is, for example, a single-layer insulating coating that has both insulating performance and adhesive properties, or a top insulating coating applied over an underlying insulating coating. The adhesive insulating coating is in an uncured or semi-cured state (stage B) before heating and pressurization. When a laminated core is formed, a curing reaction occurs during heating and pressurization, resulting in adhesive properties.

[29] The coating composition for an electrical steel sheet of the present invention contains an epoxy resin, a high-temperature curing agent, and fine inorganic particles.

[30] Any epoxy resin having two or more epoxy groups in one molecule may be used as an epoxy resin without particular limitation. Examples of such epoxy resins include bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, triphenylmethane-type epoxy resins, phenol novolac-type epoxy resins, cresol novolac-type epoxy resins, alicyclic epoxy resins, glycidyl ester-type epoxy resins, glycidylamine-type epoxy resins, hydantoin-type epoxy resins, isocyanurate-type epoxy resins, acrylic acid-modified epoxy resins (epoxyacrylate), epoxy resins containing phosphorus and its halides (brominated epoxy resins, etc.), hydrogen additives, and the like. These epoxy resins may be used alone, or two or more of them may be used in combination.

[31] The epoxy resin content relative to the total mass of the coating composition for an electrical steel sheet is 45% by mass or more. The epoxy resin content relative to the total mass of the coating composition for an electrical steel sheet is preferably from 45% to 90% by mass, very preferably from 50% to 80% by mass, and very preferably still from 50% to 70% by mass. When the epoxy resin content is equal to or greater than the lower limit, the bond strength of the electrical steel sheet 40 is further improved. When the epoxy resin content is equal to or less than the upper limit, it is possible to further reduce the tensile strain of the electrical steel sheet 40.

[32] The high-temperature curing agent can crosslink the epoxy resin. Here, the high-temperature curing agent is a crosslinking agent in which the curing reaction does not take place at room temperature (e.g., 20°C to 30°C) and the curing temperature (reaction temperature) is 100°C or higher. The curing temperature of the mixture containing an epoxy resin and a high-temperature curing agent is preferably 150°C or higher. On the other hand, the limit The upper curing temperature for RPfrfr Ln / Zznz / E / YIAI is not particularly limited. However, when the curing temperature exceeds 200°C, the curing during coating and baking is insufficient, making coil winding impossible and potentially hindering the production of the laminated core. Therefore, the curing temperature is preferably 200°C or lower.

[33] Here, the curing temperature is the temperature at which the viscoelasticity, as measured by a rigid pendulum-type physical property testing machine, decreases as curing progresses. When a lattice structure develops as the curing reaction progresses, the pendulum's motion is restricted, and the pendulum's oscillation cycle decreases rapidly. Therefore, the curing temperature can be determined based on the change in the pendulum's oscillation cycle.

[34] Examples of high-temperature curing agents include aromatic amines, phenolic curing agents, acid anhydride-based curing agents, dicyandiamides, and blocked isocyanates. When a high-temperature curing agent is applied, over-curing of the resin during the baking process can be minimized. Therefore, when surface-coated electrical steel sheets obtained for bonding are rolled, heated, and pressurized to produce a laminated core, RPfrfr Ln / Zznz / E / YIAI since the curing reaction can continue, the high temperature adhesive strength improves even further.

[35] Examples of aromatic amines include m-xylylenediamine, m-phenylenediamine, diaminodiphenylmethane, and diaminodiphenylsulfone. Examples of phenolic curing agents include phenol novolac resins, cresol novolac resins, bisphenol novolac resins, triazine modified phenol novolac resins, phenol resol resins and cresol naphthol formaldehyde condensates. Examples of acid anhydride-based curing agents include italic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, chlorenedic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic acid anhydride, ethylene glycol bis(anhydrotrimate), methylcyclohexene tetracarboxylic acid anhydride, and polyazelaic anhydride. Dicyandiamide is also known as a latent curing agent. This agent can be mixed with an epoxy resin and stored stably at room temperature. It has the ability to rapidly cure the resin composition through heat, light, pressure, or similar means. Dicyandiamide is a colorless, orthorhombic crystal or crystal sheet with a melting point of 207°C. 210°C. Reacts with an epoxy resin at 160 to 180°C and cures in 20 to 60 minutes. Dicyandiamide is preferably used in combination with a curing accelerator. Examples of curing accelerators include tertiary amines, imidazoles, and aromatic amines. A blocked isocyanate is a compound that inhibits the reaction by masking an isocyanate group of a polyisocyanate with a blocking agent. Examples of polyisocyanate raw materials include diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI), toluene diisocyanate (TDI), and isophorone diisocyanate (IPDI). Examples of blocking agents include alcohols and phenols. To further improve the productivity of the laminated core, as a high-temperature curing agent, one or more selected aromatic amines, phenolic curing agents and dicyandiamides are preferred, and one or more selected m-xylylenediamine, m-phenylenediamine, diaminodiphenylmethane, phenol novolac resins, cresol novolac resins, phenol resol resins and dicyandiamide are more preferable. High-temperature curing agents can be used alone or in combination.

[36] The content of the high-temperature curing agent relative to 100 parts by mass of epoxy resin is 5 to 30 parts by mass, preferably 10 to 30 parts by mass, and most preferably 15 to 25 parts by mass. When the content of the high-temperature curing agent is equal to or greater than the lower limit, the productivity of the laminated core is further improved. When the content of the high-temperature curing agent is equal to or less than the upper limit, the adhesive strength of the laminated core is further improved.

[37] The inorganic fine particles are one or more selected metal hydroxides, metal oxides that react with water at 25°C to become metal hydroxides, and silicate minerals that have a hydroxyl group. The inorganic fine particles of the present embodiment contain hydroxyl groups. When hydroxyl groups are provided, they activate the high-temperature curing agent and effectively promote cross-linking curing of the epoxy resin. As a result, compared to the case where the inorganic fine particles of the present embodiment are not contained, the time required to bond the electrical steel sheets to each other can be shortened, and the productivity of the laminated core can be improved. Inorganic fine particles can be used alone or two or more of them can be used in combination.

[38] Examples of metal hydroxides include aluminum hydroxide, calcium hydroxide, magnesium hydroxide, manganese hydroxide, iron(II) hydroxide, and zinc hydroxide. Among the metal hydroxides, aluminum hydroxide, calcium hydroxide, and magnesium hydroxide are particularly preferable because they activate the curing agent at high temperatures and have a strong effect on promoting the curing of the epoxy resin. Metal hydroxides can be used alone or two or more of them can be used in combination.

[39] Examples of metal oxides that react with water at 25°C (room temperature) to become metal hydroxides include calcium oxide and magnesium oxide. Metal oxides that react with water at 25°C to become metal hydroxides can be used alone or two or more of them can be used in combination.

[40] Examples of silicate minerals that have a hydroxyl group include talc, mica, kaolin (kaolinite), montmorillonite, chlorite, and glauconite. Among the silicate minerals that have a hydroxyl group, talc, mica, and kaolin are particularly preferable because they activate the curing agent at high temperatures and have a strong effect in promoting the curing of the epoxy resin. Silicate minerals that have a hydroxyl group can be used alone or two or more of them can be used in combination.

[41] The content of inorganic fine particles relative to 100 parts by mass of the epoxy resin is from 1 to 100 parts by mass, preferably from 5 to 70 parts by mass, and most preferably from 10 to 50 parts by mass. When the content of inorganic fine particles is equal to or greater than the lower limit, the productivity of the laminated core is further improved. When the content of inorganic fine particles is equal to or less than the upper limit, the adhesive strength of the laminated core is further improved.

[42] The volume-average particle diameter of inorganic fine particles is 0.05 to 2.0 pm, preferably 0.05 to 1.5 pm, and very preferably 0.05 to 1.0 pm. The volume-average particle diameter of inorganic fine particles is very preferably even less than 0.2 pm. When the volume-average particle diameter of inorganic fine particles is equal to or less than the upper limit, the hydroxyl groups contained in the inorganic fine particles can be more uniformly dispersed. It is difficult to obtain inorganic fine particles with a volume-average particle diameter less than 0.05 pm at low cost. The volume average particle diameter of inorganic fine particles is a numerical value (d50) defined by a particle diameter corresponding to a cumulative frequency of 50% based on the volume in a distribution curve of equivalent spherical diameters obtained by a laser diffraction method in accordance with ISO13320 and JIS Z 8825: 2013.

[43] The coating composition for an electrical steel sheet of the present modality may contain a component (hereinafter referred to as the optional component) other than the epoxy resin, the high-temperature curing agent and the inorganic fine particles. Examples of optional components include a curing accelerator (curing catalyst), an antifoaming agent, and a surfactant, which are not the same as the high-temperature curing agent mentioned above. Examples of antifoaming agents include silicone oil. Examples of surfactants include alkyl polyglucosides.

[44] The coating composition for an electrical steel sheet of the present embodiment may contain a silicone resin. When it contains a silicone resin, the silicone resin content relative to the total mass of the coating composition for an electrical steel sheet is preferably 40% by mass or less. Here, the silicone resin is a resin having a siloxane (Si-O-Si) linkage. The silicone resin content is very preferably 30% by mass or less, very preferably still 20% by mass or less, and particularly preferably 10% by mass or less. Since it is not necessary that it contain a silicone resin, the lower limit is 0% by mass.

[45] When the coating composition for an electrical steel sheet of the present modality contains an optional component, the content of the optional component with respect to 100 parts by mass of the epoxy resin is preferably from 0.1 to 5 parts by mass.

[46] The coating composition for an electrical steel sheet of the present embodiment is applied to the electrical steel sheet and then dried to obtain the insulating coating 3. When the coating composition for an electrical steel sheet of the present embodiment is applied to the electrical steel sheet, baking and application (baking process) are preferred. The endpoint temperature in the baking process is, for example, preferably 120 to 220°C, very preferably 130 to 210°C, and very preferably still 140 to 200°C. When the endpoint temperature is equal to or greater than the lower limit, the coating composition for an electrical steel sheet adheres sufficiently to the sheet, and peeling is restricted. When the endpoint temperature is equal to or less than the upper limit, the curing of the epoxy resin can be minimized, and the adhesive properties of the coating composition for an electrical steel sheet can be maintained. The baking time in the baking process is, for example, preferably 5 to 60 seconds, very preferably 10 to 30 seconds, and very preferably still 10 to 20 seconds. When the baking time is equal to or greater than the lower limit, the coating composition for an electrical steel sheet adheres sufficiently to the sheet, and peeling is restricted. When the baking time is equal to or less than the upper limit, the curing of the epoxy resin can be minimized, and it is possible to maintain the adhesive capacity of the coating composition for an electrical steel sheet.

[47] The upper and lower limit values ​​of an average thickness ti of the insulating coating 3 are set, for example, as follows, considering a case in which material 1 is used for the electrical steel sheet 40. When material 1 is used for the 40 electrical steel sheet, to ensure the insulation performance between the 40 electrical steel sheets laminated together, the average thickness ti of the insulating coating 3 (the thickness per surface of the 40 electrical steel sheet (material 1)) is adjusted so that the insulation performance and adhesive capacity between the 40 electrical steel sheets laminated together can be ensured.

[48] ​​In the case of insulating coating 3 having a single-layer structure, the average thickness ti of insulating coating 3 (the thickness per surface of electrical steel sheet 40 (material 1)) can be, for example, 1.5 pm or more and 8.0 pm or less. In the case of insulating coating 3 which has a multi-layer structure, the average thickness of the underlying insulating coating can be, for example, 0.1 pm or more and 2.0 pm or less, and is preferably 0.3 pm or more and 1.5 pm or less. The average thickness of the upper insulating coating can be, for example, 1.5 pm or more and 8.0 pm or less. Here, a method for measuring the average thickness ti of the insulating coating 3 on material 1 is the same as that for the average sheet thickness tO of material 1, and the average thickness can be determined by obtaining the thickness of the insulating coating 3 at a plurality of locations and averaging these thicknesses. The thickness of the insulating coating 3 is determined, for example, by observing a cross-section of material 1 cut in the thickness direction under a scanning electron microscope (SEM).

[49] The upper and lower limit values ​​of the average thickness ti of the insulating coating 3 in material 1 can naturally be used as upper and lower limit values RPfrfr Ln / Zznz / E / YIAI lower of the average thickness ti of the insulating coating 3 on the electrical steel sheet 40. Here, one method for measuring the average thickness ti of the insulating coating 3 on the electrical steel sheet 40 is, for example, the following measurement method. For example, among the plurality of electrical steel sheets forming the laminated core, the electrical steel sheet 40 positioned on the outermost side in the axial direction is selected (the electrical steel sheet 40 whose surface is exposed in the axial direction). On the surface of the selected electrical steel sheet 40, a predetermined position is selected in the radial direction (for example, a position exactly halfway (center) between the inner peripheral edge and the outer peripheral edge of the electrical steel sheet 40).In the selected position, the thickness of the insulating coating 3 of the electrical steel sheet 40 is measured at four locations (i.e., every 90 degrees around the central axis 0) at equal intervals in the circumferential direction. The average value of the thicknesses measured at four locations can be established as the average thickness ti of the insulating coating 3. Here, the reason why the average thickness ti of the insulating coating 3 is measured on the electrical steel sheet 40 placed on the outside side in the axial direction in this way is that the insulating coating 3 is formed in such a way that the thickness of the insulating coating 3 hardly changes in the rolling position in the axial direction of the electrical steel sheet 40.

[50] Electrical steel sheet 40 is produced by stamping material 1 as described above, and the laminated core (stator core 21 and rotor core 31) is produced using electrical steel sheet 40.

[51] The description will now return to the laminated core. As shown in Figure 3, the plurality of electrical steel laminations 40 forming the stator core 21 are laminated through the insulating covering 3.

[52] The electrical steel sheets 40 adjacent to each other in the axial direction are bonded over their entire surface with the insulating coating 3. In other words, on a surface of the electrical steel sheet 40 (hereafter referred to as a first surface) facing the axial direction, there is an adhesive area 41a over its entire surface. However, the electrical steel sheets 40 adjacent to each other in the axial direction may not be bonded over their entire surface. In other words, on the first surface of the electrical steel sheet 40, the adhesive area 41a and the non-adhesive area (not shown) may be mixed.

[53] In the present embodiment, the plurality of electrical steel sheets forming the rotor core 31 are fixed together by a fixation 42 (movement) shown in Figure 1.However, the plurality of electrical steel sheets forming the rotor core 31 can also have a laminated structure fixed by the insulating coating 3 as in the stator core 21. Furthermore, the laminated core, such as the stator core 21 and the rotor core 31, can be formed by so-called gyratory stacking.

[54] The stator core 21 is produced, for example, using a production device 100 shown in Figure 7. Hereafter, in the description of the production method, the laminated core production device 100 (hereafter referred to simply as production device 100) will be described first. In production device 100, while material 1 is fed from coil 1A (loop) in the direction of arrow F, it is punched multiple times using dies arranged on the stage, gradually forming it into the shape of electrical steel sheet 40. The punched electrical steel sheets 40 are then rolled and pressurized while the temperature is raised. As a result, adjacent electrical steel sheets 40 bond to each other in the axial direction with the insulating coating 3 (i.e., a portion of the insulating coating 3 placed in the adhesive area 41a is made to exhibit adhesive properties), and bonding is completed.

[55] RPfrfr Ln / Zznz / E / YIAI As shown in Figure 7, the production device 100 includes a plurality of die-cutting station stages 110. The die-cutting station 110 may have two, three, or more stages. Each stage of the die-cutting station 110 includes a female die 111 arranged below material 1 and a male die 112 arranged above material 1.

[56] The production device 100 further includes a laminating station 140 in a downstream position of the further downstream die-cutting station 110. The laminating station 140 includes a heating device 141, an outer peripheral die-cutting female mold 142, a thermal insulation member 143, an outer peripheral die-cutting male mold 144, and a spring 145. The heating device 141, the outer peripheral die-cutting female mold 142 and the thermal insulation element 143 are arranged below material 1. On the other hand, the outer peripheral die-cutting male mold 144 and the spring 145 are arranged above material 1. Here, reference number 21 indicates a stator core.

[57] In the production device 100 having the configuration described above, first, material 1 is sequentially fed from coil 1A in the direction of arrow F in Figure 7. Then, material 1 is sequentially stamped in the plurality of stages of the stamping stations 110. According to these stamping procedures, the shape of the electrical steel sheet 40, having the back of the core 22 and the plurality of serrated parts 23 shown in Figure 3, is obtained in material 1. However, since the material is not completely stamped at this point, it continues with the next process in the direction of arrow F.

[58] Then, finally, material 1 is sent to the rolling station 140, punched by the external peripheral punching die 144, and rolled with high precision. During this rolling, the electric steel sheet 40 receives a certain pressure force from the spring 145. When the punching and rolling processes as described above are repeated sequentially, a predetermined number of electric steel sheets 40 can be stacked. Furthermore, the laminate formed by stacking the electric steel sheets 40 in this manner is heated, for example, to a temperature of 200°C, by the heating device 141 (heating process). According to this heating, the insulation coatings 3 of the adjacent electric steel sheets 40 adhere to each other. Here, the heating device 141 cannot be arranged in the outer peripheral die-cutting female mold 142. That is, it can be removed from the outer peripheral die-cutting female mold 142 before the electrical steel sheet 40, rolled with the outer peripheral die-cutting female mold 142, adheres. In this case, the outer peripheral die-cutting female mold 142 may not have the thermal insulation member 143. Furthermore, in this case, the stacked electrical steel sheets 40, before adhesion, can be sandwiched and held from both sides in the axial direction with a template (not shown) and then transported and heated. In accordance with the above processes, the stator core 21 is completed.

[59] The heating temperature in the heating process is, for example, preferably 120 to 220°C, very preferably 130 to 210°C, and very preferably still 140 to 200°C. When the heating temperature is equal to or greater than the lower limit, the insulating coating 3 cures sufficiently, and the adhesive strength of the laminated core is further improved. When the heating temperature is equal to or less than the upper limit, the deterioration of the insulating coating 3 can be reduced, and the stress deformation of the electrical steel sheet 40 can be further relaxed.

[60] When the insulating coating 3 is cured, it is preferable to pressurize the laminate. When the laminate is pressurized, the pressure is, for example, preferably from 0.1 to 20 MPa, very preferably from 0.2 to 10 MPa, and very preferably still from 0.5 to 5 MPa. If, when the laminate is pressurized, the pressure is equal to or greater than the lower limit, the insulating coating 3 cures sufficiently and the adhesive strength of the laminate core is further improved. If, when the laminate is pressurized, the pressure is equal to or less than the upper limit, the deterioration of the insulating coating 3 can be reduced and the stress in the electrical steel sheet 40 can be further relieved. The treatment time when the laminate is heated and pressurized is, for example, preferably 5 to 12 minutes, very preferably 6 to 11 minutes, and very preferably still 7 to 10 minutes. When the treatment time is equal to or greater than the lower limit, the insulating coating 3 cures sufficiently and the adhesive strength of the laminate core is further improved. When the treatment time is equal to or less than the upper limit, the productivity of the laminate core is further improved. Here, when no inorganic fine particles are present, a treatment time of 20 minutes or more is required, but in the present modality, since the coating composition for an electrical steel sheet contains a specific amount of inorganic fine particles, it is possible to produce a laminated core that has sufficient adhesive strength within a treatment time of 12 RPfrfr ίη / ΖΖΠΖ / Ε / ΥΙΛΙ minutes .

[61] One embodiment of the present invention has been described above. However, the technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, the shape of the stator core 21 is not limited to the shape shown in the previous embodiment. Specifically, the size of the outer and inner diameters of the stator core 21, the lamination thickness, the number of slots, the size ratio between the circumferential and radial directions of the toothed portion 23, the size ratio between the toothed portion 23 and the back of the core 22 in the radial direction, and the like can be arbitrarily designed according to the desired properties of the electric motor. In the rotor 30 of the prior embodiment, a pair of permanent magnets 32 form a magnetic pole, but the present invention is not limited to this form. For example, one permanent magnet 32 ​​may form a magnetic pole, or three or more permanent magnets 32 may form a magnetic pole.

[62] In the above modality, the permanent magnetic field type electric motor has been described as electric motor 10 as an example, but the structure of electric motor 10 is not limited to this as illustrated below, and several known structures not illustrated below can also be used. In the preceding embodiment, the permanent magnetic field type electric motor has been described as electric motor 10 by way of example, but the present invention is not limited to this. For example, electric motor 10 may be a reluctance type electric motor or an electromagnetic field type electric motor (wound-field type electric motor). In the previous embodiment, the synchronous electric motor has been described as an AC electric motor by way of example, but the present invention is not limited to this. For example, the electric motor 10 can be an induction electric motor. In the preceding embodiment, the AC electric motor has been described as electric motor 10 by way of example, but the present invention is not limited to this. For example, electric motor 10 may be a direct current electric motor. In the previous embodiment, the electric motor has been described as electric motor 10 by way of example, but the present invention is not limited to this. For example, electric motor 10 can be a generator.

[63] Furthermore, the constituent elements in the above embodiment can be appropriately replaced by well-known constituent elements without departing from the spirit of the present invention, and the above modified examples can be appropriately combined. Examples

[64] The present invention will now be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following examples.

[65] Example 1 A non-oriented electrical steel sheet was produced containing, by mass percent, Si: 3.0%, Mn: 0.2%, and Al: 0.5%, the remainder being Fe and impurities, and having a thickness of 0.25 mm and a width of 100 mm. The following epoxy resin composition was used as the coating composition for the electrical steel sheet. An electrical steel sheet was obtained by baking and applying the coating composition to an endpoint temperature of 200°C for 10 seconds, so that the average thickness of the insulating coating was 3 pm. Epoxy resin composition Epoxy resin (bisphenol A type epoxy resin): 100 parts by mass. High temperature curing agent (dicyandiamide): RPfrfr Ln / Zznz / E / YIAI parts in mass. Inorganic fine particles (aluminum hydroxide, volume average particle diameter of 0.5 pm): 30 parts by mass. RPfrfr Ln / Zznz / E / YIAI

[66] Measurement of adhesive strength To measure shear bond strength, a single sheet measuring 30 mm x 60 mm was cut and rolled into a 30 mm x 10 mm wrap. The rolls (samples) were produced at a steel sheet temperature of 200°C and a pressure of 2 MPa for treatment times of 4, 5, 6, 7, and 8 minutes. After these samples cooled to room temperature (25°C), the shear bond strength was measured, and the bond strength was calculated as the numerical value divided by the bonded area.

[67] Comparative Example 1 An electrical steel sheet was obtained in the same manner as in Example 1 except that an epoxy resin composition that did not contain inorganic fine particles was used as the coating composition for an electrical steel sheet. A single sheet measuring 30 mm x 60 mm was cut from the obtained electrical steel sheet and rolled to a size of 30 mm x 10 mm. A laminate (sample) was produced in the same manner as in Example 1 except that the temperature of the steel sheet was 200°C, the pressure was 2 MPa, and the treatment time was 12 minutes, 14 minutes, 16 minutes, 18 minutes, 20 minutes, and 22 minutes, and the adhesive strength at shear was measured.

[68] Figure 8 shows the measured adhesive strength results for Example 1 and Comparative Example 1. Figure 8 shows the correlation between treatment time and adhesive strength due to the difference in coating composition for an electrical steel sheet. As shown in Figure 8, in Example 1 where the present invention was applied, the adhesive strength was 2 MPa or more within a treatment time of 5 minutes, and the adhesive strength was 10 MPa within a treatment time of 8 minutes. On the other hand, in Comparative Example 1, in which an epoxy resin composition that did not contain inorganic fine particles was used, a treatment time of 14 minutes was required for the adhesive strength to be 2 MPa or more, and a treatment time of 22 minutes was required for the adhesive strength to be 10 MPa.

[69] Examples 2 to 28 and Comparative Examples 2 to 8 Electrical steel sheets were obtained in the same manner as in Example 1, except that the epoxy resin compositions containing inorganic fine particles, high-temperature curing agents, and epoxy resins shown in Tables 1 and 2 were used as the coating composition for one electrical steel sheet. A single sheet measuring 30 mm x 60 mm was cut from the obtained electrical steel sheet and rolled to create a 30 mm x 10 mm wrap. A laminate (sample) was produced in the same manner as in Example 1, except that the treatment time was 8 minutes, and the shear bond strength was measured. The results are shown in Tables 1 and 2. In Table 1, the column for inorganic fine particles in Comparative Example 2 indicates that it did not contain inorganic fine particles.The column for resin other than epoxy resin in Table 1 and Table 2 indicates that it did not contain any resin other than epoxy resin.

[70] Table 09 ID OR 00 Example | comparative Example comparative Example 2 Example 3 o E φ ID OE Φ Example 6 Example 7 00 o E ϕ Comparative Example Example 9 Example 10 I Example 11 Example 12 Comparative example o E φ EN Example 1 4 comparative o E Example 15 I Example 16 Example 17 Comparative Example Φ ω ω JZ CO φ ϕ s Force ad after minutes o oo oao CO Csl ID CO ΟΊ Csl Cs| ooo oo Csl Φ ϕ oo Csl o Csl oo Csl o Csl o Csl o OsJ o OM o OsJ a Csl O OsJ O ID o 09 o O Csl s 091 o Csl o Csl o CJ o Csl o Csl O Csl Φ Φ ϕ i_ → o σ O a Φ _Φ ca O Φ OS Φ o Φ a Φ Φ Φ Φ E Φ lami lami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iami iam ¡ciand ¡ciand ¡ciand ¡ciand ¡ciand ¡ciand ¡ciand ¡ciand ¡ciand cyand cyand cyand cyand cyand Ό C Φ u icia ndi ¡ciand ¡cyand cyand ¡ciand CT φ Φ □ OQOOOQ φOQOQOQO □ ω φ 01 of epoxy (*) 1 • 1 • Silicone resin / 35 • •resina ϕ ο υ ϕ (% en Contenido de epoxy con res| la masa total masa) 09 CO 09 00 09 CO o oo LD 09 LD ID 09 CO o CO 00 ío __ < < < < < < < < < < < < < < < < < < < < < < < 6 φ ϕ ó Φ V) ¡sfenol ¡sfenol ¡sfenol ¡sfenol ¡sfenol ¡sfenol !!!! _Q X9 inorgánicas Diametro de [ average en ' (μπι) 1 500 500 500 0.05 ID O ID O ID O ID O ID O ID O 500 I 0.05 005 LD O 005 500 ID OO Csl O o LD O Csí a ω <υ φ ω ϕ 3 Φ Cantida aditivo 1 SI id OO 09 O ID OO o L50 O 09 LLCO 09 OO o 09 O 09 o 09 O 09 O 09 o 09 Tipo Ninguno o Φ ιη Φ Ε (Λ V) ιπ < > S Ν C Ν Ν C —ι £

[71] Table Example 18 Example 19 Example 20 Example 21 Example 22 Example 23 Example 24 Example 25 Example 26 Example 27 Example 28 Adhesive strength after 8 minutes (MPa) OOOOOOOOOOO High temperature curing agent / Additive quantity (') m-Xylylenediamine / 20 Phthalic anhydride / 20 Dicyandiamide / 20 m-Xylylenediamine / 20 Phthalic anhydride / 20 Dicyandiamide / 20 m-Xylylenediamine / 20 Phthalic anhydride / 20 Dicyandiamide / 20 m-Xylylenediamine / 20 Triazine-modified novolac phenol resin / 20 Epoxy resin content relative to total mass (70 by mass) O ​​LO LO lo O* LO LO 5 lo n LO LO ío LO Epoxy resin Bisphenol A type Bisphenol F type Novolac phenol Acrylic acid-modified epoxy Bisphenol A type Bisphenol F type Phenol novolac type Acrylic acid modified epoxy Bisphenol A type Bisphenol F type Acrylic acid modified epoxy Inorganic fine particles Volume average particle diameter (μm) OOO LO OOO CM O LO OOO LO O Additive quantity (*) omo LOor LO or LO or LO or LO or LO or LO or LO Type Magnesium hydroxide Iron hydroxide Zinc hydroxide Calcium oxide Magnesium oxide Talc Mica Kaolin Montmorillonite Glauconite Aluminum hydroxide RPfrfr ίη / ΖΖΠΖ / Ε / ΥΙΛΙ

[72] As shown in Tables 1 and 2, in Examples 2 to 28 where the present invention was applied, the adhesive strength was 6 MPa or more within a treatment time of 8 minutes. On the other hand, in Comparative Example 2, using the epoxy resin composition that did not contain inorganic fine particles, the bond strength was 0 MPa within a treatment time of 8 minutes. In Comparative Example 3, where the amount of added inorganic fine particles was outside the scope of the present invention, the bond strength was 1 MPa within a treatment time of 8 minutes. In Comparative Example 4, where the amount of added inorganic fine particles was outside the scope of the present invention, the bond strength was 2 MPa within a treatment time of 8 minutes. In Comparative Example 5, where the epoxy resin content was outside the scope of the present invention, the bond strength was 2 MPa within a treatment time of 8 minutes.In Comparative Example 6, where the content of the high-temperature curing agent was outside the scope of the present invention, the bond strength was 2 MPa after a treatment time of 8 minutes. In Comparative Example 7, where the content of the high-temperature curing agent was outside the scope of the present invention, the bond strength was 2 MPa after a treatment time of 8 minutes. In Comparative Example 8, where the volume-average particle diameter of the inorganic fine particles was outside the scope of the present invention, the bond strength was 2 MPa after a treatment time of 8 minutes.

[73] Based on the above results, it was found that, according to the coating composition for an electrical steel sheet of the present invention, it was possible to shorten the treatment time required to produce the laminated core, and it was possible to improve the productivity of the laminated core. Furthermore, it was discovered that, according to the coating composition for an electrical steel sheet of the present invention, it was possible to produce a laminated core that had sufficient adhesive strength even in a short treatment time. RPfrfr Ln / Zznz / E / YIAI Brief description of the reference symbols

[74] 10 Electric motor Stator Adhesive laminated core for stator Rotor Electrical steel sheet Casing Rotating axis

Claims

CLAIMS 1. A coating composition for an electrical steel sheet, the coating composition comprising: an epoxy resin, a high-temperature curing agent, and inorganic fine particles, wherein the content of the high-temperature curing agent relative to 100 parts by mass of the epoxy resin is from 5 to 30 parts by mass, wherein the inorganic fine particles are one or more selected from metal hydroxides, metal oxides that react with water at 25°C to become metal hydroxides, and silicate minerals having a hydroxyl group, wherein the volume-average particle diameter of the inorganic fine particles is from 0.05 to 2.0 pm, wherein the content of the epoxy resin with respect to the total mass of the coating composition for an electrical steel sheet is 45% by mass or more, and wherein the content of inorganic fine particles with respect to 100 parts by mass of the epoxy resin is 1 to 100 parts by mass.

2. The coating composition for the electrical steel sheet according to claim 1, wherein the inorganic fine particles are one or more selected from aluminum hydroxide, calcium hydroxide, magnesium hydroxide, calcium oxide, magnesium oxide, talc, mica, and kaolin.

3. The coating composition for the electrical steel sheet according to claim 1 or 2, wherein the high-temperature curing agent is one or more selected from aromatic amines, phenolic curing agents, and dicyandiamides.

4. An electrical steel sheet with a surface coating for adhesion having an insulating coating obtained by applying the coating composition for an electrical steel sheet according to any of claims 1 to 3 onto the surface.

5. A laminated core obtained by rolling two or more sheets of electrical steel with a surface coating for adhesion in accordance with claim 4.