Surface-coated electrical steel sheets, multi-layer cores, and methods of manufacturing them.

Abstract

The invention relates to an electrical steel plate with an adhesive coating comprising an electrical steel plate; and an adhesive coating arranged on at least part of one or both surfaces of the electrical steel plate, wherein the adhesive coating contains: a crosslinked thermoplastic A and a thermoplastic B in addition to the crosslinked thermoplastic A, and having a glass transition temperature of 45 to 80°C and a melt flow rate of 1 to 25 g / 10 min at 100°C.

Description

Adhesive coated electrical steel sheet and laminated core, and manufacturing method thereof

[0001] This disclosure relates to an adhesive-coated electrical steel sheet and laminated core, and to a method for manufacturing the same. This application claims priority to Japanese Patent Application No. 2023-163609, filed on September 26, 2023, the contents of which are incorporated herein by reference.

[0002] Conventionally, cores (i.e., iron cores) used in rotating electrical machines and the like are "laminated cores" in which multiple electromagnetic steel sheets are stacked on top of each other. The multiple electromagnetic steel sheets are fixed by methods such as welding, crimping, bolting, and adhesive bonding. However, fixing multiple electromagnetic steel sheets by welding, crimping, and bolting is prone to mechanical stress, thermal stress, interlayer short circuits, and the like during processing. This deteriorates the magnetic properties of the electromagnetic steel sheets, making it difficult for the laminated core to fully demonstrate its performance.

[0003] On the other hand, when fixing multiple electromagnetic steel sheets by adhesive bonding, electromagnetic steel sheets with an adhesive coating are used, and the adhesive coating is hardened by heating and pressure to develop adhesive properties, thereby bonding the multiple electromagnetic steel sheets together. When fixing multiple electromagnetic steel sheets using adhesive-coated electromagnetic steel sheets, mechanical stress, thermal stress, interlayer short circuits, etc. are less likely to occur during processing. Therefore, the magnetic properties of the electromagnetic steel sheets are less likely to deteriorate, and the performance of the laminated core is more likely to be fully demonstrated. Due to these advantages, various technologies for fixing multiple electromagnetic steel sheets by adhesive bonding have been investigated.

[0004] For example, Patent Document 1 discloses "an adhesive surface-coated electrical steel sheet having on its surface an insulating coating that exhibits adhesive properties when heated and / or pressed, wherein the coating is a dispersed mixture of an epoxy resin or modified epoxy resin having a glass transition point (Tg) of 80°C to 150°C, an epoxy resin curing agent, and a particulate polymer having a particle size of 0.01 μm to 0.5 μm."

[0005] Furthermore, Patent Document 2 discloses "an electromagnetic steel sheet laminate comprising a plurality of electromagnetic steel sheets and a fusion layer located between the plurality of electromagnetic steel sheets, the fusion layer comprising polyethylene acrylate including a repeating unit represented by the following chemical formula 1 and a repeating unit represented by the following chemical formula 2, the polyethylene acrylate containing 65 to 90% by weight of the repeating unit represented by the following chemical formula 1 and 10 to 35% by weight of the repeating unit represented by the following chemical formula 2."

[0006] Furthermore, Patent Document 3 discloses "an electromagnetic steel sheet for lamination, the electromagnetic steel sheet comprising an electromagnetic steel sheet and an adhesive insulating coating having a Martens hardness (HM) of 50 or more and less than 500, the adhesive insulating coating being provided on at least one surface of the electromagnetic steel sheet."

[0007] Furthermore, Patent Document 4 discloses "an electromagnetic steel strip or sheet having at least one thermosetting baked enamel layer, which contains an epoxy resin as a main component, at least one curing agent, and at least one filler, provided on one of its flat surfaces, wherein the filler in the baked enamel layer contains a metal carbonate, a metal sulfate, a metal sulfide, a metal silicate, or a metal phosphate, or any mixture of two or more of these."

[0008] Furthermore, Patent Document 5 discloses "an insulating coated electrical steel sheet having a heat-resistant adhesive insulating coating on one or both sides of the electrical steel sheet, the heat-resistant adhesive insulating coating containing 10 mass % or more of a polycarbonate urethane resin having a softening point of 20 to 200°C, and 10 to 1,000 mass parts of a phenol resin per 100 mass parts of the polycarbonate urethane resin."

[0009] International Publication No. 2004 / 070080 Japanese Patent Publication No. 2023-508140 International Publication No. 2016 / 017132 Japanese Patent Publication No. 2018-518591 Japanese Patent Publication No. 2017-179233

[0010] However, in conventional techniques, including those described in Patent Documents 1 to 5, increasing the adhesive strength of the adhesive coating results in a phenomenon in which the magnetic properties of the electrical steel sheet are reduced. Therefore, the adhesive strength of the adhesive coating and the magnetic properties of the electrical steel sheet are in a trade-off relationship, making it difficult to achieve both. It is particularly necessary to ensure the adhesive strength of the electrical steel sheet with the adhesive coating at room temperature and at high temperatures.

[0011] Therefore, further improvements in adhesive strength at room temperature and at high temperatures, as well as magnetic properties, are desired for adhesive coated electrical steel sheets.

[0012] An object of the present disclosure is to provide an adhesive coated electrical steel sheet having excellent adhesive strength at room temperature and at high temperatures and excellent magnetic properties, a laminated core using the same, and methods for manufacturing the same.

[0013] Specific means for solving the problems include the following aspects. [1] An adhesive-coated electrical steel sheet comprising an electrical steel sheet and an adhesive coating provided on at least a portion of one or both sides of the electrical steel sheet, the adhesive coating comprising a crosslinkable thermoplastic resin A and a thermoplastic resin B other than the crosslinkable thermoplastic resin A, the adhesive coating having a glass transition temperature of 45 to 80°C and a melt flow rate at 100°C of 1.0 to 25 g / 10 min. [2] The adhesive-coated electrical steel sheet according to the above item [1], wherein the crosslinkable thermoplastic resin A is one or more of a (meth)acrylic resin and a polyester resin. [3] The adhesive-coated electrical steel sheet according to the above item [1], wherein a mass ratio of the crosslinkable thermoplastic resin A to the thermoplastic resin B is 97 / 3 to 70 / 30. [4] A laminated core comprising a plurality of adhesive-coated electrical steel sheets according to any one of the above items [1] to [3], laminated together, the electrical steel sheets being bonded to each other by a cured film of the adhesive coating. [5] A method for producing an adhesive coated electrical steel sheet according to any one of [1] to [4] above, comprising applying a coating liquid to at least a portion of one or both sides of an electrical steel sheet, the coating liquid containing particles of the crosslinkable thermoplastic resin A and a thermoplastic resin B other than the crosslinkable thermoplastic resin A, wherein the mass ratio of the crosslinkable thermoplastic resin A to the thermoplastic resin B is 60 / 40 to 97 / 3, to form a coating film, and drying the coating film to form the adhesive coating. [6] A method for producing a laminated core according to [4] above, comprising stacking the adhesive coated electrical steel sheets to form a laminate with the adhesive coating interposed between the electrical steel sheets to form a laminate, and heating and pressurizing the laminate to harden the adhesive coating and form the hardened film.

[0014] According to the present disclosure, there are provided an adhesive coated electrical steel sheet having excellent adhesive strength at room temperature and at high temperatures and excellent magnetic properties, a laminated core using the same, and methods for manufacturing the same.

[0015] 1 is a schematic diagram showing an example of an adhesive coated electrical steel sheet according to the present disclosure; 2 is a schematic diagram showing an example of a laminated core according to the present disclosure;

[0016] The present disclosure will be described below. The following description of the requirements may be based on representative embodiments of the present disclosure, but the present disclosure is not limited to such embodiments and can be implemented by making appropriate modifications within the scope of the purpose of the present disclosure.

[0017] In the present disclosure, a numerical range indicated using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits, respectively. In the numerical ranges described in stages in the present disclosure, the upper or lower limit described in a certain numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in the numerical ranges described in the present disclosure, the upper or lower limit described in a certain numerical range may be replaced with a value shown in the examples.

[0018] In the present disclosure, a combination of two or more preferred aspects is a more preferred aspect.

[0019] In the present disclosure, "% by mass" and "% by weight" are synonymous, and "parts by mass" and "parts by weight" are synonymous.

[0020] [Adhesive-Coated Electrical Steel Sheet] The adhesive-coated electrical steel sheet of the present disclosure comprises an electrical steel sheet and an adhesive coating provided on at least a portion of one or both sides of the electrical steel sheet (see FIG. 1). The adhesive coating contains a crosslinkable thermoplastic resin A and a thermoplastic resin B other than the crosslinkable thermoplastic resin A. Furthermore, the adhesive coating has a glass transition temperature of 45 to 80°C and a melt flow rate at 100°C of 1.0 to 25 g / 10 min. In FIG. 1, 10 denotes the adhesive-coated electrical steel sheet, 10A denotes the electrical steel sheet, and 10B and 10C denote the adhesive coatings.

[0021] The adhesive-coated electrical steel sheet of the present disclosure, due to the above-described configuration, exhibits excellent adhesive strength and magnetic properties at both room temperature and high temperatures. The reason for this is presumably as follows: When electrical steel sheets are bonded together with an adhesive coating to form a laminated core, stress is applied to the electrical steel sheets due to the volumetric shrinkage of the organic resin. This stress deteriorates the iron loss of the electrical steel sheets. However, when an electric motor incorporating the laminated core is driven, the electrical steel sheets generate heat, reducing the stress and reducing (improving) iron loss. Therefore, an organic resin that exhibits fluidity with increasing temperature can improve the magnetic properties of the laminated core. However, if the fluidity becomes too great with increasing temperature, the adhesive strength at high temperatures decreases. This can weaken the bonding strength between the laminated electrical steel sheets, potentially resulting in vibration and noise. Furthermore, in severe cases, the steel sheets may become misaligned, causing the rotor to come into contact with the stator. Therefore, by including a specific organic resin in the adhesive coating and specifying the melt flow rate, which is an indicator of fluidity at 100°C, it is possible to ensure appropriate fluidity and achieve both magnetic properties and adhesive strength at room temperature and high temperatures.

[0022] Hereinafter, the adhesive-coated electrical steel sheet of the present disclosure will be described in detail.

[0023] (Electromagnetic steel sheet) The electromagnetic steel sheet is a steel sheet on which an adhesive coating is formed, and is not particularly limited. The electromagnetic steel sheet may be a non-oriented electromagnetic steel sheet or a directional electromagnetic steel sheet. Specifically, as the electromagnetic steel sheet, for example, a non-oriented electromagnetic steel strip according to JIS C 2552:2014, a directional electromagnetic steel strip according to JIS C 2553:2019, a non-oriented thin electromagnetic steel strip or a directional thin electromagnetic steel strip according to JIS C 2558:2021 cut to a predetermined length can be used.

[0024] (Adhesive Coating) The adhesive coating is provided on at least a portion of one or both sides of the electromagnetic steel sheet (see FIG. 1 ). That is, the adhesive coating may be provided, for example, on the entire surface of one or both sides of the electromagnetic steel sheet, or may be provided on one or both sides of the electromagnetic steel sheet in a pattern such as a staggered arrangement (an arrangement in which the layers are alternately shifted up, down, left, and right). However, it is preferable that the adhesive coating be provided over 60% or more, 80% or more, or 100% of the area of ​​one side of the electromagnetic steel sheet.

[0025] [Glass transition temperature] The glass transition temperature of the adhesive coating is 45 to 80°C. If the glass transition temperature of the adhesive coating is less than 45°C, the adhesive strength at room temperature and / or high temperatures will decrease. If the glass transition temperature of the adhesive coating is more than 80°C, the fusibility of the organic resin used will decrease, resulting in poor application properties. As a result, the adhesive strength at room temperature will decrease or the magnetic properties will deteriorate. Therefore, the glass transition temperature of the adhesive coating is set to the above range. The glass transition temperature of the adhesive coating is preferably 50°C or higher. Furthermore, the glass transition temperature of the adhesive coating is preferably 75°C or lower, and more preferably 70°C or lower.

[0026] The glass transition temperature of the adhesive coating can be adjusted by the types and mass ratios of crosslinkable thermoplastic resin A and thermoplastic resin B. The glass transition temperature of the adhesive coating can also be adjusted by the type and amount of the crosslinking agent described below.

[0027] The glass transition temperature of an adhesive coating is measured by the following method. The adhesive coating is mechanically scraped off from the adhesive-coated electrical steel sheet to be measured using a cutter knife or the like. The scraped-off adhesive coating is dehydrated and pelletized to obtain a measurement sample. The glass transition temperature of the measurement sample is measured using a differential scanning calorimeter (DSC) in accordance with JIS K 7121:1987 under the following measurement conditions: measurement temperature range: -90 to 100°C, heating rate: 10°C / min, and standard: empty sample pan. The glass transition temperature of the adhesive coating is obtained by measuring the temperature at the intersection of a straight line extending the low-temperature baseline toward the high-temperature side of the DSC curve obtained by the differential scanning calorimeter and a tangent drawn at the point where the gradient of the stepwise change in the glass transition curve is maximum.

[0028] [Melt Flow Rate] The melt flow rate of the adhesive coating at 100°C is 1.0 to 25 g / 10 min. If the melt flow rate of the adhesive coating at 100°C is less than 1.0 g / 10 min, the adhesive strength will be excessively high, the adhesive coating will be too hard, and the magnetic properties will deteriorate. If the melt flow rate of the adhesive coating at 100°C is more than 25 g / 10 min, the adhesive strength will decrease. Furthermore, the magnetic properties will deteriorate. Therefore, the melt flow rate of the adhesive coating at 100°C is set to the above range. The melt flow rate of the adhesive coating at 100°C is preferably 3.0 g / 10 min or more, and more preferably 5.0 g / 10 min or more. Furthermore, the melt flow rate of the adhesive coating at 100°C is preferably 20 g / 10 min or less, and more preferably 15 g / 10 min or less.

[0029] The melt flow rate of the adhesive coating at 100°C can be adjusted by the types and mass ratios of crosslinkable thermoplastic resin A and thermoplastic resin B. The melt flow rate of the adhesive coating can also be adjusted by the type and amount of the crosslinking agent described below.

[0030] The melt flow rate of an adhesive coating at 100°C is measured by the following method. The adhesive coating is mechanically scraped off from the adhesive-coated electrical steel sheet to be measured using a cutter knife or the like. The scraped-off adhesive coating is dehydrated and pelletized to obtain a measurement sample. Using an MFR measuring device, a sample is extruded from a die with a diameter of 1 mm for 10 minutes in accordance with JIS K 7210-1:2014 under conditions of a load of 1 kg and a measurement temperature of 100°C, and the sample is cut out and weighed. This gives the melt flow rate of the adhesive coating at 100°C.

[0031] [Average Thickness of Adhesive Coating] The average thickness of the adhesive coating is preferably 1.0 to 6.0 μm. The average thickness of the adhesive coating is more preferably 1.5 μm or more, or 2.0 μm or more. The average thickness of the adhesive coating is more preferably 4.0 μm or less, or 3.0 μm or less. In the adhesive-coated electrical steel sheet according to the present disclosure, even when the average thickness of the adhesive coating is reduced to 1.0 to 6.0 μm, the adhesive strength at room temperature and at high temperatures and the magnetic properties are both excellent.

[0032] The method for measuring the average thickness of the adhesive coating is as follows: The adhesive coated electrical steel sheet to be measured is cut along the thickness direction to obtain a test specimen with the cut surface as the observation surface. The observation surface of the test specimen is observed using a scanning electron microscope (SEM), and the thickness of the adhesive coating at any three locations is measured. The thicknesses of the adhesive coating at the three locations are then arithmetically averaged to obtain the average thickness of the adhesive coating. Note that the adhesive coating and the electrical steel sheet can be easily distinguished by the difference in brightness, and the layer present in the center in the thickness direction is considered to be the electrical steel sheet, and the layers present on the surface and back side in the thickness direction are considered to be the adhesive coating.

[0033] [Components of Adhesive Coating] The adhesive coating contains a crosslinkable thermoplastic resin A and a thermoplastic resin B other than the crosslinkable thermoplastic resin A. The adhesive coating is an insulating coating that exhibits adhesive properties when heated and pressurized, as crosslinking of at least the crosslinkable thermoplastic resin A progresses and the adhesive coating hardens.

[0034] -Crosslinkable Thermoplastic Resin A- Crosslinkable thermoplastic resin A is a thermoplastic resin having a crosslinkable group. Crosslinkable thermoplastic resin A is preferably a water-insoluble resin. A water-insoluble resin is a resin that does not dissolve in water or has low solubility in water. Specifically, a water-insoluble resin is a resin that has a solubility in water at 25°C of 1 g or less per 100 g of water. The crosslinkable thermoplastic resin A is preferably dispersed in the form of particles in an adhesive coating that uses thermoplastic resin B as a matrix resin. The adhesive coating may contain only one type of crosslinkable thermoplastic resin A, or may contain two or more types.

[0035] In the crosslinkable thermoplastic resin A, the crosslinkable group may be a crosslinkable group capable of crosslinking even in the absence of a crosslinking agent (i.e., a self-crosslinking group in which crosslinking occurs when crosslinking groups react with each other), or a crosslinkable group capable of crosslinking when reacted with a crosslinking agent. The crosslinkable group is preferably a group capable of exhibiting crosslinkability when heated.

[0036] Specific examples of the crosslinkable group include an N-methylol group, an N-butyrol group, a glycidyl group, an alkoxymethylamide group, an alkoxysilyl group, a hydroxyl group, a phenolic hydroxyl group, a carboxyl group, a thiol group, and an amino group.

[0037] The crosslinkable thermoplastic resin A may be either a vinyl thermoplastic resin or a non-vinyl thermoplastic resin. Examples of non-vinyl thermoplastic resins include non-vinyl resins such as polyester resins, polyurethane resins, polyamide resins, and phenoxy resins, as well as styrene resins, (meth)acrylic resins, and polyolefin resins. Examples of vinyl thermoplastic resins include homopolymers of monomers such as styrene monomers (e.g., styrene, parachlorostyrene, α-methylstyrene, etc.), (meth)acrylic acid monomers (e.g., (meth)acrylic acid, (meth)acrylic acid alkyl esters, etc.), and olefin monomers (e.g., ethylene, propylene, butadiene, etc.), or copolymers of two or more of these monomers.

[0038] "Styrene-based monomer" refers to a monomer having a styrene skeleton (a structure in which one of the six hydrogen atoms in benzene is substituted with a vinyl group). "Styrene-based resin" refers to a resin in which structural units derived from styrene-based monomers account for 50% or more by mass of all structural units. "(Meth)acrylic acid-based monomer" refers to a monomer having a (meth)acryloyl group. "(Meth)acrylic acid-based monomer" refers to a resin in which structural units derived from (meth)acrylic acid-based monomers account for 50% or more by mass of all structural units. "(Meth)acrylic" is a term that encompasses both "acrylic" and "methacrylic." "Olefin-based monomer" refers to a monomer having an olefin skeleton consisting of at least three carbon atoms and having a carbon-carbon double bond. "Olefin-based monomer" refers to a resin in which structural units derived from olefin-based monomers account for 50% or more by mass of all structural units.

[0039] Among these, from the viewpoint of improving adhesive strength and magnetic properties, the crosslinkable thermoplastic resin A is preferably one or more of a (meth)acrylic resin and a polyester resin.

[0040] —Content of Crosslinkable Thermoplastic Resin A— The content of the crosslinkable thermoplastic resin A is preferably 60% by mass to 95% by mass, more preferably 65% ​​by mass to 90% by mass, and even more preferably 75% by mass to 90% by mass, relative to the adhesive coating.

[0041] -Thermoplastic resin B- Thermoplastic resin B is a thermoplastic resin other than crosslinkable thermoplastic resin A. Thermoplastic resin B is preferably a water-soluble resin. Here, a water-soluble resin is a resin whose solubility in water at 25°C is 5 g or more per 100 g of water. The adhesive coating may contain only one type of thermoplastic resin B, or may contain two or more types.

[0042] The thermoplastic resin B may be either a vinyl thermoplastic resin or a non-vinyl thermoplastic resin. Examples of the non-vinyl thermoplastic resin include the non-vinyl resins exemplified as the crosslinkable thermoplastic resin A. Examples of the vinyl thermoplastic resin include the vinyl resins exemplified as the crosslinkable thermoplastic resin A. Among these, from the viewpoint of improving adhesive strength and magnetic properties, the thermoplastic resin B is preferably one or more of a (meth)acrylic resin and a polyester resin.

[0043] Here, the thermoplastic resin B may be a crosslinkable thermoplastic resin or a non-crosslinkable thermoplastic resin, but from the viewpoint of improving magnetic properties, a non-crosslinkable thermoplastic resin is preferable. Examples of the non-crosslinkable thermoplastic resin include those that do not contain the crosslinkable groups of the resins exemplified as the crosslinkable thermoplastic resin A.

[0044] -Content of Thermoplastic Resin B- The adhesive coating preferably contains a predetermined amount of thermoplastic resin B relative to the crosslinkable thermoplastic resin A. Specifically, the mass ratio of crosslinkable thermoplastic resin A to thermoplastic resin B (content of crosslinkable thermoplastic resin A / content of thermoplastic resin B) is preferably 95 / 5 to 85 / 15, and more preferably 95 / 5 to 90 / 10. When the mass ratio of crosslinkable thermoplastic resin A to thermoplastic resin B is 95 / 5 to 85 / 15, both the adhesive strength and magnetic properties are superior.

[0045] - Other Components - The adhesive coating may contain components other than those already described (so-called other components) as needed, provided that the effects of the adhesive coating are not impaired.

[0046] In particular, the adhesive coating may contain a crosslinking agent. Crosslinking agents are particularly preferred components because they have a favorable effect on both adhesive strength and magnetic properties. Examples of crosslinking agents include thermosetting resins, specifically polymeric crosslinking agents such as epoxy resins, phenolic resins, and amino resins (e.g., melamine resins and guanamine resins), as well as low-molecular-weight crosslinking agents composed of monomers or oligomers such as isocyanate compounds, polyol compounds, epoxy compounds, phenolic compounds, and amino compounds (e.g., melamine compounds and guanamine compounds). The content of the crosslinking agent is preferably 1 to 20% by mass, more preferably 1 to 10% by mass, of the adhesive coating. The adhesive coating may contain only one type of crosslinking agent, or two or more types.

[0047] The components of the adhesive coating are identified by measuring the weight average molecular weight by GPC and further analyzing the functional groups by FT-IR.

[0048] The weight average molecular weight of the components of the adhesive coating is measured by Gel Permeation Chromatography (GPC). The components of the adhesive coating are identified from the molecular weight distribution obtained by GPC. The measurement conditions are as follows: Measuring device: High-speed GPC (HLC-8220GPC, manufactured by Tosoh Corporation) Detector: Differential refractive index detector (RI) (built into HLC-8220, manufactured by Tosoh Corporation) Column: Four TSK-gel GMHXL (manufactured by Tosoh Corporation) Column temperature: 40°C Eluent: Tetrahydrofuran Sample solution injection volume: 100 μL Flow rate: 0.8 mL / min

[0049] The functional groups of the components of the adhesive coating are analyzed by FT-IR (Fourier transform infrared spectrometer). The obtained spectrum is converted into a form similar to a normal absorbance spectrum by Kramers-Kronig analysis. The functional groups are identified from the obtained absorbance spectrum. The measurement conditions are as follows: Measurement device: Spotlight 400 (manufactured by Perkin Elmer) Measurement method: Specular reflection method (background: gold plating) Resolution: 2 cm －１ Scan: 16 times

[0050] For example, when a (meth)acrylic resin is included as a component of the adhesive coating as crosslinkable thermoplastic resin A, the weight-average molecular weight is 80,000 to 300,000, and N-methylol groups, glycidyl groups, carboxyl groups, or amino groups are detected. When a polyester resin is included as crosslinkable thermoplastic resin A, the weight-average molecular weight is 30,000 to 120,000, and hydroxyl groups or carboxyl groups are detected. When thermoplastic resin B is included, the weight-average molecular weight is 10,000 to 100,000, and functional groups such as carboxyl groups and hydroxyl groups are detected.

[0051] (Method for manufacturing an adhesive coating-coated electrical steel sheet) (Method for forming an adhesive coating) The adhesive coating is formed by applying an adhesive coating-forming coating fluid (hereinafter also referred to as "the coating fluid of the present disclosure") to at least a portion of one or both sides of an electrical steel sheet and drying the coating. In this disclosure, when the adhesive coating-forming coating fluid contains multiple substances corresponding to each component, the amount of each component in the adhesive coating-forming coating fluid means the total amount of the multiple substances present in the adhesive coating-forming coating fluid, unless otherwise specified.

[0052] The coating fluid of the present disclosure contains, for example, particles of crosslinkable thermoplastic resin A (hereinafter also referred to as "crosslinkable thermoplastic resin particles A"), thermoplastic resin B, and a medium containing water. In the coating fluid of the present disclosure, the crosslinkable thermoplastic resin particles A are present in a dispersed state in the medium containing water. Furthermore, the thermoplastic resin B is present in a dissolved state in the medium containing water. In the coating fluid, the mass ratio of the crosslinkable thermoplastic resin A to the thermoplastic resin B is 60 / 40 to 97 / 3. By using a coating fluid containing the crosslinkable thermoplastic resin A and the thermoplastic resin B in this mass ratio, the above-mentioned adhesive coating can be formed.

[0053] The type of water is not particularly limited. For example, distilled water, deionized water (also called "ion-exchanged water"), and pure water are preferred because they contain fewer impurities. The water content is preferably 35 to 50% by mass, and more preferably 40 to 45% by mass, based on the total mass of the coating liquid.

[0054] The coating fluid of the present disclosure may contain components other than the components described above (so-called other components) as needed, within the range that does not impair the effects of the coating fluid.

[0055] Examples of other components include aqueous media other than water. Examples of aqueous media other than water include water-miscible organic solvents. Examples of water-miscible organic solvents include monohydric alcohol compounds such as methanol and ethanol; polyhydric alcohol compounds such as glycerin, ethylene glycol, and propylene glycol; and glycol derivatives such as ethylene glycol monoethyl ether and propylene glycol monobutyl ether. Examples of other components include various additives such as chain preservatives, wetting agents, and antifoaming agents.

[0056] The coating liquid of the present disclosure can be obtained, for example, by mixing a dispersion of crosslinkable thermoplastic resin particles A in water with an aqueous solution of thermoplastic resin B. Examples of the mixing method include a method of mixing by stirring. A general stirring tool or stirring device can be used for stirring. The stirring temperature is not particularly limited, but is preferably, for example, 20°C to 30°C.

[0057] Formation of an adhesive coating using the coating liquid of the present disclosure can be achieved by applying the coating liquid to the surface of an electrical steel sheet using a known coating method such as a roll coater or spray method, and then drying the coating film. The solids concentration of the coating liquid is preferably 5 to 40 mass%, more preferably 10 to 25 mass%. The drying temperature is preferably 100 to 200°C, and the drying time is preferably 10 to 90 seconds. The drying method is preferably a method using a copying oven, but may also be a hot air oven or other method.

[0058] (Laminated Core) The laminated core of the present disclosure comprises a plurality of laminated adhesive-coated magnetic steel sheets, each of which is bonded to the other by a cured adhesive coating. The cured adhesive coating refers to a film that develops adhesive properties when the laminated adhesive-coated magnetic steel sheets are heated and pressurized, resulting in crosslinking of the crosslinkable thermoplastic resin A in the adhesive coating, which hardens and develops adhesive properties. The curing of the adhesive coating can be determined by the following method: Two 30 mm x 60 mm single-plate test pieces are cut from the adhesive-coated magnetic steel sheet. The 30 mm x 10 mm ends of the two single-plate test pieces are overlapped, with the adhesive coatings facing each other. The overlapped body is heated and pressurized under the following conditions: steel sheet temperature: 250°C, pressure: 2 MPa, heating and pressing time: 1 minute, to obtain a sample for measuring adhesive strength. The tensile shear adhesive strength is measured when the steel sheet temperature is at room temperature (25°C). The adhesive strength measurement sample is attached to a tensile tester, and the tensile shear adhesive strength is measured at a tensile speed of 50 mm / min. The obtained tensile shear adhesive strength value is divided by the adhesive area of ​​the two veneer test pieces to determine the room temperature adhesive strength. If the room temperature adhesive strength is 5.0 MPa or more, it can be determined that the adhesive strength is sufficient at room temperature, and that the adhesive coating has cured.

[0059] Specifically, examples of the laminated core of the present disclosure include a laminated core obtained by punching out an adhesive-coated electromagnetic steel sheet of the present disclosure to produce punched members, stacking the punched members, and then heating and pressurizing them to form an integrated core.

[0060] FIG. 2 is a schematic diagram illustrating an example of a laminated core according to the present disclosure. As shown in FIG. 2 , the laminated core 100 (stator 100) is formed as a lamination body 13 in which eight punched members 11 made of adhesive-coated electromagnetic steel sheets are connected in an annular shape and the annularly connected punched members 11 are stacked into eight layers. The punched members 11 made of adhesive-coated electromagnetic steel sheets are punched out of the adhesive-coated electromagnetic steel sheets, and include a circular arc-shaped yoke portion 17 and teeth portions 15 protruding radially inward from the inner peripheral surface of the yoke portion 17. The shape, number, and number of laminations of the punched members 11 forming the laminated core 100 shown in FIG. 2 are not limited, and the laminated core 100 may be designed according to the purpose.

[0061] (Method for Manufacturing Laminated Core) The laminated core of the present disclosure is manufactured, for example, by the following method. First, the adhesive-coated magnetic steel sheets of the present disclosure are stacked with the adhesive coating interposed between them. The laminate of adhesive-coated magnetic steel sheets is heated and pressurized to promote crosslinking of the crosslinkable thermoplastic resin A in the adhesive coating and harden the adhesive coating. This allows the cured film of the adhesive coating to exhibit adhesive properties, and the magnetic steel sheets are bonded to each other by the cured film of the adhesive coating. These operations result in the laminated core of the present disclosure. Note that the adhesive-coated magnetic steel sheets may be bonded to each other with the cured film of the adhesive coating of each magnetic steel sheet facing each other, or may be bonded to each other with the cured film of the adhesive coating of one magnetic steel sheet facing the surface of the other magnetic steel sheet not having the adhesive coating. The heating temperature is preferably 200 to 300°C, the pressure is preferably 0.5 to 10 MPa, and the heating and pressing time is preferably 30 to 60 minutes.

[0062] (Applications of Laminated Core) The laminated core of the present disclosure can be used as a core (i.e., iron core) used in a rotating electric machine or the like.

[0063] The coating liquid of the present disclosure will be described in more detail below with reference to examples. The present disclosure is not limited to the following examples as long as it does not deviate from the gist of the disclosure.

[0064] [Examples 1 to 8, Comparative Examples 1 to 11] 1. Preparation of Coating Fluid A coating fluid with a solids concentration of 40% by mass was prepared by mixing an aqueous dispersion of crosslinkable thermoplastic resin particles A, an aqueous solution of thermoplastic resin B, and a crosslinking agent in the types and amounts (parts by mass) shown in Tables 1A and 1B. However, the amounts (parts by mass) of crosslinkable thermoplastic resin particles A, thermoplastic resin B, and crosslinking agent in the coating fluid were as shown in Tables 1A and 1B. Blank spaces in the tables indicate that the material corresponding to that space was not used. Also, underlines in the tables indicate that the material is outside the scope of the present disclosure. Furthermore, the "solids concentration" refers to the total mass percentage of the crosslinkable thermoplastic resin particles A, the aqueous solution of thermoplastic resin B, and the crosslinking agent in the coating fluid.

[0065] In Examples 1 to 4 and 8 and Comparative Examples 3 to 4 and 7 to 10, coating liquids containing no crosslinking agent were obtained. In Comparative Example 1, a coating liquid containing no thermoplastic resin B and no crosslinking agent was obtained. In Comparative Example 5, a coating liquid containing no crosslinkable thermoplastic resin particles A and no crosslinking agent was obtained. In Comparative Example 6, a coating liquid containing no thermoplastic resin B was obtained. In Comparative Example 11, a coating liquid containing no crosslinkable thermoplastic resin particles A was obtained.

[0066] 2. Preparation of Adhesive-Coated Electrical Steel Sheet First, a non-oriented electrical steel sheet was prepared, consisting of, by mass, 3.0% Si, 0.2% Mn, 0.5% Al, with the remainder being Fe and impurities, and having a thickness of 0.25 mm and a width of 100 mm. Next, the resulting coating liquid was applied to the entire surface of one side of the electrical steel sheet, and then heated at the drying temperature and for the drying time shown in Tables 1A and 1B to dry the coating film, forming an adhesive coating with the average thickness shown in Tables 1A and 1B. In this way, an adhesive-coated electrical steel sheet was obtained.

[0067] [Evaluation] (Glass Transition Temperature, Melt Flow Rate) The glass transition temperature (Tg) and melt flow rate (MFR) at 100° C. of the adhesive coating of each example of the adhesive coated electrical steel sheet were measured according to the methods previously described.

[0068] (Adhesion Strength) Two 30 mm × 60 mm single-plate test pieces were cut out from each adhesive-coated electrical steel sheet. The 30 mm × 10 mm ends of the two single-plate test pieces were overlapped with the adhesive coatings facing each other. The overlapped body was heated and pressed under the following conditions: steel sheet temperature: 250°C, pressure: 2 MPa, heating and pressing time: 1 minute, to obtain a sample for measuring adhesive strength.

[0069] The tensile shear bond strength was measured as follows when the steel plate temperature was room temperature (25°C). The sample for adhesive strength measurement was attached to a tensile tester, and the tensile shear bond strength was measured at a tensile speed of 50 mm / min. The obtained tensile shear bond strength value was then divided by the adhesive area of ​​the two single-plate test pieces to obtain the room-temperature adhesive strength.

[0070] Furthermore, a sample for measuring adhesive strength was placed in an atmosphere at 150° C., and the tensile shear adhesive strength was measured in the same manner as above, with the steel plate temperature at 150° C. The tensile shear adhesive strength thus obtained was divided by the adhesive area of ​​the two single-plate test pieces to obtain the 150° C. adhesive strength.

[0071] When the room temperature adhesive strength was more than 5.0 MPa and the 150°C adhesive strength was more than 0.5 MPa, the adhesive strength was judged to be excellent at room temperature and at high temperature, and the test was judged as pass. On the other hand, when either one of them was not satisfied, the adhesive strength at room temperature and at high temperature was judged to be poor, and the test was judged as fail.

[0072] (Magnetic Properties) A ​​single sheet test piece measuring 55 mm x 55 mm was cut from each adhesive-coated electrical steel sheet. Two single sheet test pieces were then stacked with their adhesive coatings facing each other. The stack was heated and pressed under the following conditions: steel sheet temperature: 250°C, pressure: 2 MPa, and heating and pressing time: 1 minute to obtain a laminate sample. The iron loss in the rolling direction and the direction perpendicular to the rolling direction of the obtained laminate sample was measured using the single sheet magnetic measurement method specified in JIS C2556:2015, and the average iron loss in the rolling direction and the direction perpendicular to the rolling direction was calculated. If the average iron loss value obtained was 11.0 W / kg or less, the sample was judged to have excellent magnetic properties and was judged to have passed. On the other hand, if the average iron loss value obtained was more than 11.0 W / kg, the sample was judged to have poor magnetic properties and was judged to have failed.

[0073] (Appearance) Three 5 mm square test pieces were cut out from each adhesive coated electrical steel sheet to obtain test pieces. The adhesive coating surface of each test piece was observed at three locations using a scanning electron microscope at 100x magnification. A total of nine fields of view were observed. The test pieces were evaluated according to the following evaluation criteria, with S and A being considered acceptable. S: No coating defects such as cracks, fissures, or peeling were observed. A: The area ratio of coating defects was 10% or less. B: The area ratio of coating defects was more than 10% but less than 30%. C: The area ratio of coating defects was 30% or more.

[0074] Details of the materials used and listed in Table 1 are as follows. <Crosslinkable thermoplastic resin A> Crosslinkable acrylic resin (1): Crosslinkable group = N-methylol group, Tg = 70°C, weight average molecular weight = 200,000 Crosslinkable acrylic resin (2): Crosslinkable group = glycidyl group, Tg = 50°C, weight average molecular weight = 150,000 Crosslinkable acrylic resin (3): Crosslinkable group = carboxyl group, Tg = 55°C, weight average molecular weight = 120,000 Crosslinkable acrylic resin (4): Crosslinkable group = amino group, Tg = 85°C, weight average molecular weight = 80,000 Crosslinkable polyester resin (5): Crosslinkable group = hydroxyl group, Tg = 60°C, weight average molecular weight = 50,000 Crosslinkable polyester resin (6): Crosslinkable group = carboxyl group, Tg = 85°C, weight average molecular weight = 30,000 Crosslinkable acrylic resin (7): Crosslinkable group = glycidyl group, Tg = 30°C, weight average molecular weight = 300,000 Crosslinkable polyester resin (8): Crosslinkable group = carboxyl group, Tg = 100°C, weight average molecular weight = 20,000

[0075] <Thermoplastic resin B> Acrylic resin (1): Tg = 60°C, weight average molecular weight = 180,000 Acrylic resin (2): Tg = 0°C, weight average molecular weight = 250,000 Polyester resin: Tg = 70°C, weight average molecular weight = 80,000 Polyurethane resin: Tg = 75°C, weight average molecular weight = 20,000 Phenoxy resin (1): Tg = 80°C, weight average molecular weight = 400,000 Phenoxy resin (2): Tg = 10°C, weight average molecular weight = 280,000

[0076] <Crosslinking agent> Epoxy resin: bisphenol A type, weight average molecular weight = 1000 to 4000 Phenol resin: novolac type, weight average molecular weight = 3000 to 5000 Amino resin: methylated benzoguanamine, weight average molecular weight = 5000 to 8000

[0077]

[0078]

[0079]

[0080] From the above results, it can be seen that the present example is superior to the comparative example in adhesive strength at room temperature and high temperature, and in magnetic properties.

[0081] According to the present disclosure, there are provided an adhesive coated electrical steel sheet having excellent adhesive strength at room temperature and at high temperatures and excellent magnetic properties, a laminated core using the same, and methods for manufacturing the same.

[0082] 10: Adhesive coated electromagnetic steel sheet 10A: Electromagnetic steel sheet 10B: Adhesive coating 10C: Adhesive coating 11: Punched member of adhesive coated electromagnetic steel sheet 100: Laminated core

Claims

1. An adhesive-coated magnetic steel sheet comprising: an electromagnetic steel sheet; and an adhesive coating provided on at least a portion of one or both sides of said electromagnetic steel sheet, said adhesive coating containing a crosslinkable thermoplastic resin A and a thermoplastic resin B other than said crosslinkable thermoplastic resin A, said adhesive-coated magnetic steel sheet having a glass transition temperature of 45 to 80°C and a melt flow rate at 100°C of 1.0 to 25 g / 10 min.

2. An adhesive-coated electrical steel sheet according to claim 1, wherein the crosslinkable thermoplastic resin A is at least one of a (meth)acrylic resin and a polyester resin.

3. An adhesive-coated electrical steel sheet as described in claim 1, wherein the mass ratio of said cross-linkable thermoplastic resin A to said thermoplastic resin B is 97 / 3 to 70 / 30.

4. A laminated core in which a plurality of magnetic steel sheets with an adhesive coating according to any one of claims 1 to 3 are laminated together, the magnetic steel sheets being bonded to one another by the hardened film of the adhesive coating.

5. A method for producing an adhesive coated electrical steel sheet according to any one of claims 1 to 4, comprising the steps of: applying a coating liquid to at least a portion of one or both sides of an electrical steel sheet, the coating liquid containing particles of crosslinkable thermoplastic resin A and a thermoplastic resin B other than crosslinkable thermoplastic resin A, the mass ratio of crosslinkable thermoplastic resin A to thermoplastic resin B being 60 / 40 to 97 / 3, to form a coating film; and drying the coating film to form the adhesive coating.

6. A method for manufacturing a laminated core as described in claim 4, comprising stacking the adhesive-coated magnetic steel sheets with the magnetic steel sheets interposing the adhesive coating between each other to form a laminate, and heating and pressurizing the laminate to harden the adhesive coating and form the hardened film.

Images