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

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, the adhesive coating comprising a crosslinked thermoplastic A and a thermoplastic B in addition to the crosslinked thermoplastic A, wherein the adhesive coating has a hardness of 200 to 260 MPa, and after heating the adhesive coating at 200°C for 5 minutes, the hardness of the adhesive coating is 200 to 300 MPa.

Description

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

[0001] The present disclosure relates to an adhesive coated electrical steel sheet, a laminated core, and a method for manufacturing the same. This disclosure claims priority to Japanese Patent Application No. 2023-163604, 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 mixture of a dispersed 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. In other words, adhesive strength and magnetic properties are in a trade-off relationship, and it is difficult to achieve both. In particular, it is necessary to ensure the adhesive strength of the electrical steel sheet with the adhesive coating from room temperature to high temperatures.

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

[0012] An object of the present disclosure is to provide an adhesive coated electrical steel sheet that has excellent adhesive strength and magnetic properties from room temperature to high temperature, 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 according to one aspect 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, 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 hardness of 200 to 260 MPa, and a hardness of 200 to 300 MPa after heating the adhesive coating at 200°C for 5 minutes. <2> In the adhesive-coated electrical steel sheet according to <1>, the crosslinkable thermoplastic resin A may be one or more resins selected from the group consisting of (meth)acrylic resins and polyester resins. <3> A laminated core according to another aspect of the present disclosure comprises a plurality of adhesive-coated electrical steel sheets according to <1> or <2> stacked together, the electrical steel sheets being bonded to each other by a cured film of the adhesive coating. <4> The laminated core described in <3> may have a space factor of 96 to 98%. <5> A method for producing an adhesive-coated electrical steel sheet according to another aspect of the present disclosure includes a coating step of applying an adhesive-coating-forming coating liquid to at least a portion of one or both sides of an electrical steel sheet to obtain a coated steel sheet, and a coating step of heating the coated steel sheet to a drying temperature of 100 to 200°C at a temperature increase rate of 6.0°C / second or less and holding the coated steel sheet in a temperature range from the drying temperature to the drying temperature minus 10°C for 10 to 90 seconds to dry the coated steel sheet, thereby forming an adhesive coating on the surface of the electrical steel sheet. <6> The method for producing an adhesive-coated electrical steel sheet described in <5> may be such that in the coating step, the adhesive-coating-forming coating liquid contains a crosslinkable thermoplastic resin A and a thermoplastic resin B other than the crosslinkable thermoplastic resin A, and the mass ratio of the crosslinkable thermoplastic resin A to the thermoplastic resin B is 97 / 3 to 70 / 30.<7> A method for producing a laminated core according to another aspect of the present disclosure includes a coating step of applying an adhesive coating film-forming coating liquid to at least a portion of one or both sides of an electromagnetic steel sheet to obtain a coated steel sheet; a coating step of heating the coated steel sheet to a drying temperature of 100 to 200°C at a temperature increase rate of 6.0°C / second or less and holding the coated steel sheet in a temperature range from the drying temperature to the drying temperature −10°C for 10 to 90 seconds to dry the coated steel sheet, thereby forming an adhesive coating on the surface of the electromagnetic steel sheet to obtain an adhesive-coated electromagnetic steel sheet; a punching step of punching the adhesive-coated electromagnetic steel sheet to obtain a punched member; a lamination step of stacking a plurality of the punched members to obtain a laminate; and a bonding step of heating the laminate to a pressing temperature in a temperature range of 200 to 300°C and holding the laminate for 5 to 60 minutes while applying a pressure of 0.5 to 10 MPa in a range from the pressing temperature to the pressing temperature −10°C.

[0014] According to the above aspects of the present disclosure, there are provided an adhesive coated electrical steel sheet having excellent adhesive strength and magnetic properties from room temperature to high temperature, 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, when the coating liquid for forming an adhesive coating contains multiple substances corresponding to each component, the amount of each component in the coating liquid for forming an adhesive coating refers to the total amount of the multiple substances present in the coating liquid for forming an adhesive coating, unless otherwise specified.

[0020] In the present disclosure, "% by mass" and "% by weight" are synonymous, and "parts by mass" and "parts by weight" are synonymous.

[0021] [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 derived from an adhesive coating-forming coating liquid and a thermoplastic resin B other than the crosslinkable thermoplastic resin A. The adhesive coating has a hardness (coating hardness) of 200 to 260 MPa, and a hardness (coating hardness) of 200 to 300 MPa after heating at 200°C for 5 minutes. 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.

[0022] Due to the above-described configuration, the adhesive-coated electrical steel sheet of the present disclosure has excellent adhesive strength and magnetic properties from room temperature (25°C) to high temperature (150°C) (it also has excellent magnetic properties as a laminated core). The reasons for this are presumed to be as follows: The application of cross-linkable thermoplastic resin A having self-cross-linking groups improves the rigidity of the molecular chain, resulting in excellent adhesive strength from room temperature to high temperatures. Furthermore, the application of thermoplastic resin B and the hardness of the coating within the above-described range alleviates compressive stress, resulting in excellent magnetic properties.

[0023] Hereinafter, the adhesive-coated electrical steel sheet of the present disclosure will be described in detail.

[0024] (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 sheet according to JIS C 2552:2014, a directional electromagnetic steel sheet according to JIS C 2553:2019, a non-oriented thin electromagnetic steel sheet or a directional electromagnetic steel sheet according to JIS C 2558:2021 can be used.

[0025] (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 in a pattern such as a staggered arrangement on one or both sides of the electromagnetic steel sheet. However, it is preferable that the adhesive coating is provided over 60% or more, 80% or more, or 100% of the area (area ratio) of one side of the electromagnetic steel sheet.

[0026] [Coating Hardness] -Coating Hardness before Heating- The hardness of the adhesive coating (hereinafter also referred to as "pre-heating coating hardness") is 200 to 260 MPa. If the pre-heating coating hardness is less than 200 MPa, the adhesive strength decreases. If the pre-heating coating hardness exceeds 260 MPa, the adhesive strength becomes excessively high, the adhesive coating becomes too hard, and the magnetic properties deteriorate. Therefore, the pre-heating coating hardness is set to the above range. The pre-heating coating hardness is preferably 200 to 250 MPa, and more preferably 210 to 240 MPa.

[0027] - Coating hardness after heating - The hardness of the adhesive coating after heating at 200°C for 5 minutes (hereinafter also referred to as "coating hardness after heating") is 200 to 300 MPa. If the coating hardness after heating is less than 200 MPa, the adhesive strength decreases. If the coating hardness after heating exceeds 300 MPa, the adhesive strength becomes excessively high, the adhesive coating becomes too hard, and the magnetic properties deteriorate. Therefore, the coating hardness is set to the above range. The coating hardness after heating is preferably 200 to 290 MPa, and more preferably 210 to 260 MPa.

[0028] The hardness of the coating before and after heating can be adjusted by the types and the ratio of amounts of the crosslinkable thermoplastic resin A and the thermoplastic resin B. The hardness of the coating before and after heating can also be adjusted by the type and amount of the crosslinking agent and the coating formation conditions, which will be described later.

[0029] -Method for measuring pre-heating coating hardness and post-heating coating hardness- The pre-heating coating hardness and post-heating coating hardness are microhardnesses, and are measured by a nanoindentation test in accordance with ISO 14577-1:2015. Specifically, the method is as follows: ---Pre-heating coating hardness--- A test piece measuring 20 mm x 60 mm is taken from the electrical steel sheet with an adhesive coating to be measured. The hardness of the adhesive coating on the test piece is measured using a microhardness measuring device (nanoindenter) under the measurement conditions below. This operation is performed on three test pieces, and the arithmetic mean value of the obtained hardness is calculated. The obtained arithmetic mean value is called the "pre-heating coating hardness." --Method for measuring coating hardness-- Measuring device: HYSITRON "TRIBOINDER" Indenter type: triangular pyramidal Berkovich type diamond indenter with diagonal angle of 142.3° Test load: 0.25 mN Load application rate: 0.10 mN / sec Measurement temperature: 25°C Measurement points: 25 locations

[0030] ---Coating hardness after heating--- A test piece measuring 20 mm x 60 mm is taken from the electrical steel sheet with an adhesive coating to be measured. The test piece is heated at a steel sheet surface temperature of 200°C for 5 minutes. After heating, the test piece is cooled to room temperature (25°C). Then, as in the measurement of the coating hardness before heating, a nanoindentation test is performed on the adhesive coating of the test piece, and the arithmetic mean value of the hardness is determined. The obtained arithmetic mean value is defined as the "coating hardness after heating."

[0031] [Average Thickness of Adhesive Coating] The average thickness of the adhesive coating is preferably 1.0 to 6.0 μm, more preferably 1.5 to 4.0 μm, and even more preferably 2.0 to 3.0 μm. Even when the average thickness of the adhesive coating is reduced to fall within the above range, the adhesive-coated electrical steel sheet of the present disclosure has excellent adhesive strength and magnetic properties.

[0032] The average thickness of the adhesive coating is measured as follows: The adhesive coated electrical steel sheet to be measured is cut along the thickness direction to obtain a test piece with the cut surface as the observation surface. The observation surface of the test piece is observed using a scanning electron microscope (SEM), and the thickness of the adhesive coating is measured at any three locations. The thicknesses of the adhesive coating at the three locations are then arithmetically averaged to determine the average thickness of 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. In other words, the adhesive coating is an insulating coating that, when heated and pressurized, crosslinking of at least the crosslinkable thermoplastic resin A progresses, hardens, and develops adhesive properties.

[0034] -Crosslinkable Thermoplastic Resin A- Crosslinkable thermoplastic resin A is a thermoplastic resin having a crosslinkable group. In order to ensure heat resistance, crosslinkable thermoplastic resin A is preferably a water-insoluble resin. Here, 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 whose solubility in water at 25°C is less than 5 g (e.g., 1 g or less) per 100 g of water. Crosslinkable thermoplastic resin A is preferably dispersed in the form of particles in an adhesive coating having 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 that can crosslink even in the absence of a crosslinking agent (i.e., a self-crosslinking group that crosslinks by reacting with each other), or a crosslinkable group that can crosslink by reacting with a crosslinking agent. The crosslinkable group is preferably a group that can exhibit crosslinking properties by heating.

[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 polyester resins, polyurethane resins, polyamide resins, and phenoxy 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] Here, "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). Furthermore, "styrene-based resin" refers to a resin in which structural units derived from styrene-based monomers account for 50% by mass or more of all structural units. Furthermore, "(meth)acrylic acid-based monomer" refers to a monomer having a (meth)acryloyl group. Furthermore, "(meth)acrylic acid-based monomer" refers to a resin in which structural units derived from (meth)acrylic acid-based monomers account for 50% by mass or more of all structural units. "(Meth)acrylic" is a term that encompasses both "acrylic" and "methacrylic." Furthermore, "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. Furthermore, "olefin-based monomer" refers to a resin in which structural units derived from olefin-based monomers account for 50% by mass or more of all structural units.

[0039] Among these, (meth)acrylic resins and polyester resins are preferred as the crosslinkable thermoplastic resin A from the viewpoint of improving adhesive strength and magnetic properties.

[0040] —Content of Crosslinkable Thermoplastic Resin A— The content of the crosslinkable thermoplastic resin A is preferably 70% by mass to 97% by mass, more preferably 75% by mass to 95% by mass, and even more preferably 80% by mass to 93% by mass, relative to the adhesive coating.

[0041] -Thermoplastic resin B- Thermoplastic resin B is a thermoplastic resin other than crosslinkable thermoplastic resin A. From the viewpoint of ensuring coatability, 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-based thermoplastic resin or a non-vinyl-based thermoplastic resin. Examples of the non-vinyl-based thermoplastic resin include the non-vinyl-based resins exemplified as the crosslinkable thermoplastic resin A. Examples of the vinyl-based thermoplastic resin include the vinyl-based resins exemplified as the crosslinkable thermoplastic resin A. Among these, from the viewpoint of improving adhesive strength and magnetic properties, (meth)acrylic resins and polyester resins are preferred as the thermoplastic resin B.

[0043] Here, the thermoplastic resin B may be a crosslinkable thermoplastic resin or a non-crosslinkable thermoplastic resin, but a non-crosslinkable thermoplastic resin is preferable from the viewpoint of improving adhesive strength and magnetic properties. Examples of the non-crosslinkable thermoplastic resin include vinyl thermoplastic resins having no crosslinkable groups, such as those exemplified for the crosslinkable thermoplastic resin A, and non-vinyl thermoplastic resins.

[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 97 / 3 to 70 / 30 (A:B = 97:3 to 70:30), more preferably 95 / 5 to 85 / 15, and even more preferably 95 / 5 to 90 / 10. When the mass ratio of crosslinkable thermoplastic resin A to thermoplastic resin B is 97 / 3 to 70 / 30, 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 affect 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). Examples of crosslinking agents include 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] - Component Analysis - The adhesive coating in the adhesive coated magnetic steel sheet or the laminated core obtained by laminating adhesive coated magnetic steel sheets can be qualitatively analyzed for its components using infrared spectroscopy, nuclear magnetic resonance, or gas chromatography, and then the component ratios can be estimated by performing weight distribution of the fragments using TOFMS. Analysis samples of the adhesive coated magnetic steel sheet can be obtained by cutting out the coating portion with a precision cutter. Furthermore, in the case of a laminated core, several magnetic steel sheets are peeled off from the laminated core and then sampled using the above method.

[0048] (Method for manufacturing an adhesive coated electrical steel sheet) The adhesive coated electrical steel sheet of the present disclosure will exhibit its effects as long as it has the above-mentioned characteristics, regardless of the manufacturing method, but can be obtained, for example, by a manufacturing method including the following steps: (I) a coating step in which an adhesive coating-forming coating liquid is applied to at least a portion of one or both sides of an electrical steel sheet to obtain a coated steel sheet, and (II) a coating step in which the coated steel sheet is heated to a drying temperature of 100 to 200°C at a temperature increase rate of 6.0°C / second or less, and then held in a temperature range from the drying temperature to the drying temperature minus 10°C for 10 to 90 seconds to dry, thereby forming an adhesive coating on the surface of the electrical steel sheet. Each step will now be described.

[0049] - Coating Step - In the coating step, a coating liquid for forming an adhesive coating (hereinafter also referred to as "the coating liquid of the present disclosure") is applied to at least a portion of one or both sides of an electrical steel sheet to obtain a coated steel sheet.

[0050] 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. By applying this coating fluid and then drying it, an adhesive coating containing the crosslinkable thermoplastic resin A and the thermoplastic resin B is obtained. In the coating fluid of the present disclosure, the mass ratio of the crosslinkable thermoplastic resin A to the thermoplastic resin B is preferably 97 / 3 to 70 / 30. By blending in this manner, the mass ratio of the crosslinkable thermoplastic resin A to the thermoplastic resin B in the formed adhesive coating will also be 97 / 3 to 70 / 30.

[0051] Here, the type of water is not particularly limited. As water, for example, distilled water, deionized water (also called "ion-exchanged water"), and pure water are preferred from the viewpoint of having few impurities. The water content is preferably 35% by mass to 50% by mass, and more preferably 40% by mass to 45% by mass, relative to the total mass of the coating liquid.

[0052] The coating fluid of the present disclosure may contain components other than the components described above (so-called other components) as needed, within the scope that does not impair the effects of the coating fluid.

[0053] 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.

[0054] The coating liquid of the present disclosure can be obtained, for example, by mixing a dispersion of crosslinkable thermoplastic resin particles A 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.

[0055] The adhesive coating film can be formed using the coating liquid of the present disclosure by applying the coating liquid to the surface of the electrical steel sheet by a known coating method such as a roll coater method or a 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%.

[0056] -Coating Process- In the coating process, the coated electrical steel sheet (painted steel sheet) is heated to a drying temperature (maximum temperature reached by the material) of 100 to 200°C at a temperature increase rate of 6.0°C / second or less, and then held at a temperature range of 10 to 90 seconds between the drying temperature and (drying temperature -10°C), thereby drying the sheet and forming an adhesive coating on the surface of the electrical steel sheet. The drying time (the time during which the material temperature is held between the drying temperature -10°C and the drying temperature) is preferably 30 to 90 seconds. The temperature increase rate is the average rate calculated from the time it takes to reach the drying temperature from 50°C. If the drying temperature exceeds 200°C, there is a risk of resin oxidation. If the drying temperature is less than 100°C or the drying time is less than 10 seconds, the sheet will not dry sufficiently. If the drying time exceeds 90 seconds, productivity will be poor. Furthermore, if the temperature increase rate exceeds 6.0°C / second, the sheet will not be properly formed and the adhesive strength will be insufficient. Generally, slowing the temperature rise rate requires an increase in furnace length or a reduction in line speed, which is considered undesirable in terms of equipment constraints and productivity. However, in the method for producing an adhesive-coated electrical steel sheet according to this embodiment, the temperature rise rate is deliberately slowed based on the new finding that the above-mentioned effects can be obtained by slowing the temperature rise rate. The drying method is preferably a method using a copying type heating furnace, but a hot air oven or other method may also be used.

[0057] The laminated core of the present disclosure is formed by laminating a plurality of magnetic steel sheets with adhesive coatings of the present disclosure, the magnetic steel sheets being bonded to one another by a cured film of the adhesive coating. Here, the cured film of the adhesive coating is a film that has hardened due to the progress of crosslinking of the crosslinkable thermoplastic resin A in the adhesive coating, and has developed adhesive properties.

[0058] Specifically, examples of the laminated core of the present disclosure include a laminated core obtained by punching an adhesive-coated magnetic steel sheet of the present disclosure to produce a punched member, stacking the punched members, and integrating them under heat and pressure. The laminated core of the present disclosure preferably has a space factor of 96 to 98%. When manufactured using an adhesive-coated magnetic steel sheet of the present disclosure, high adhesive strength can be obtained even if the adhesive layer is thin, so the space factor can be set to be within the above range.

[0059] 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 is formed as a laminate 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.

[0060] The laminated core of the present disclosure is manufactured, for example, by a manufacturing method including the following steps: (III) a punching step of punching an adhesive-coated magnetic steel sheet of the present disclosure to obtain a punched member, (IV) a lamination step of stacking a plurality of the punched members to obtain a laminate, and (V) a bonding step of heating the laminate to a pressing temperature in the temperature range of 200 to 300°C and holding the laminate for 5 to 60 minutes while applying a pressure of 0.5 to 10 MPa in a range from the pressing temperature to the pressing temperature minus 10°C. Each step will be described below.

[0061] -Punching Step- In the punching step, the adhesive coated magnetic steel sheet is punched to obtain a member (punched member) having a predetermined shape. There are no limitations on the punching method.

[0062] -Laminating Process- In the laminating process, the punched members are laminated with adhesive coatings interposed between the magnetic steel sheets, thereby obtaining a laminate.

[0063] - Bonding Process - In the bonding process, the laminate is heated to a pressing temperature (the maximum temperature reached by the material) in the temperature range of 200 to 300°C, and maintained at a pressure of 0.5 to 10 MPa for 5 to 60 minutes within a range from the pressing temperature to the pressing temperature minus 10°C. This promotes crosslinking of the crosslinkable thermoplastic resin A in the adhesive coating, hardening the adhesive coating. As a result, the cured film of the adhesive coating exhibits adhesive properties, bonding the magnetic steel sheets together via the cured film of the adhesive coating, and a laminated core is obtained. The magnetic steel sheets with adhesive coatings may be bonded together with the cured film of the adhesive coating of each magnetic steel sheet facing each other, or may be bonded together with the cured film of the adhesive coating of one magnetic steel sheet facing the surface of the other magnetic steel sheet not bearing the adhesive coating. Pressing temperatures below 200°C result in insufficient hardening, while temperatures above 300°C result in oxidation of the resin. If the pressure is less than 0.5 MPa, non-bonded areas are likely to occur, and if it exceeds 10 MPa, the steel sheet will be distorted. If the holding time (the time during which the material temperature is held between the pressing temperature -10°C and the pressing temperature) is less than 5 minutes, curing will be insufficient, and if it exceeds 60 minutes, productivity will be poor. When a large number of sheets are stacked, the holding time is preferably 30 minutes or more to ensure uniform heating.

[0064] (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.

[0065] 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.

[0066] [Examples 1 to 8, Comparative Examples 1 to 9] 1. Preparation of Coating Liquid A coating liquid with a solids concentration of 40 mass% was prepared by mixing an aqueous dispersion of particles of crosslinkable thermoplastic resin A, an aqueous solution of thermoplastic resin B, and a crosslinking agent in the types and amounts (parts (parts by mass)) shown in Table 1. However, the amounts (parts) of crosslinkable thermoplastic resin A, thermoplastic resin B, and crosslinking agent in the coating liquid were as shown in Table 1. Furthermore, the "solids concentration" refers to the mass proportion of the total of the crosslinkable thermoplastic resin A, the aqueous solution of thermoplastic resin B, and the crosslinking agent in the coating liquid.

[0067] In Examples 1 to 4 and 8 and Comparative Examples 4 and 8, coating fluids containing no crosslinking agent were obtained. In Comparative Example 1, a coating fluid containing no thermoplastic resin B was obtained. In Comparative Examples 3, 7 and 9, coating fluids containing no crosslinkable thermoplastic resin A were obtained. In Comparative Example 5, a coating fluid containing no crosslinkable thermoplastic resin A and no crosslinking agent was obtained. In Comparative Example 6, a coating fluid containing no thermoplastic resin B and no crosslinking agent was obtained.

[0068] 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 Weight average molecular weight: 180,000 Crosslinkable acrylic resin (2): Crosslinkable group = glycidyl group Weight average molecular weight: 150,000 Crosslinkable acrylic resin (3): Crosslinkable group = carboxyl group Weight average molecular weight: 300,000 Crosslinkable acrylic resin (4): Crosslinkable group = amino group Weight average molecular weight: 80,000 Crosslinkable polyester (5): Crosslinkable group = hydroxyl group Weight average molecular weight: 30,000 Crosslinkable polyester (6): Crosslinkable group = carboxyl group Weight average molecular weight: 120,000

[0069] <Thermoplastic resin B> Acrylic resin Weight average molecular weight: 50,000 Polyester resin Weight average molecular weight: 160,000 Polyurethane resin Weight average molecular weight: 20,000 Phenoxy resin Weight average molecular weight: 100,000

[0070] <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

[0071] In Table 1, the units of the numerical values ​​shown in the columns for crosslinkable thermoplastic resin A, thermoplastic resin B, and crosslinking agent are parts by mass, and blank spaces in the columns for crosslinkable thermoplastic resin A, thermoplastic resin B, and crosslinking agent indicate that the material corresponding to that column was not used.

[0072]

[0073] 2. Preparation of Adhesive-Coated Electrical Steel Sheet A non-oriented electrical steel sheet having a thickness of 0.25 mm and a width of 100 mm was prepared, consisting of, by mass, 3.0% Si, 0.2% Mn, 0.5% Al, with the remainder being Fe and impurities. Next, the coating liquid obtained in 1. was applied to the entire surface of one side of the electrical steel sheet, and then heated and dried at the drying temperature, drying time, and heating rate shown in Table 1, to form an adhesive coating with the thickness shown in Table 1. In this way, an adhesive-coated electrical steel sheet was obtained.

[0074] [Evaluation] (Coating Hardness) The coating hardness of the adhesive coating of each example of the magnetic steel sheet with the adhesive coating before heating and after heating at 200° C. for 5 minutes were measured according to the method described above.

[0075] (Adhesive Strength) Two 30 mm × 60 mm veneer test pieces were cut out from each adhesive-coated electrical steel sheet. The 30 mm × 10 mm edges of the two veneer test pieces were overlapped with the adhesive coatings facing each other to form a laminate. The laminate was heated and pressed at a temperature of 250°C, a pressure of 2 MPa, and a holding time (heating and pressing) of 5 minutes to obtain a laminate sample for measuring adhesive strength.

[0076] The shear adhesive strength was measured as follows when the steel plate temperature was room temperature (25°C). The adhesive strength measurement sample was attached to a tensile tester, and the shear adhesive strength was measured at a tensile speed of 50 mm / min. The obtained shear adhesive strength value was then divided by the adhesive area of ​​the two single-plate test pieces to determine the room-temperature adhesive strength. An adhesive strength of 6.0 MPa or more was determined to be sufficient.

[0077] Separately, two 30 mm x 60 mm single-plate test pieces were cut from each adhesive-coated electrical steel sheet of each example, and the 30 mm x 10 mm ends were overlapped with the adhesive coatings facing each other to obtain a laminate sample. The resulting laminate sample was placed in a 150°C atmosphere, and the shear bond strength was measured under the same conditions as at room temperature, with the steel sheet temperature at 150°C. The obtained shear bond strength value was then divided by the bond area of ​​the two single-plate test pieces to determine the 150°C bond strength. An bond strength of 2.0 MPa or more was considered to be sufficient.

[0078] (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 at a temperature of 250°C, a pressure of 2 MPa, and a holding (heating and pressing) time of 5 minutes to obtain a laminate sample. The iron losses in the rolling direction and the direction perpendicular to the rolling direction of the obtained laminate sample were measured using the single sheet magnetic measurement method specified in JIS 2556:2015, and the average values ​​of the iron losses W10 / 400 in the rolling direction and the direction perpendicular to the rolling direction were calculated. A sample with an iron loss of 10.9 W / Kg or less was determined to have excellent magnetic properties.

[0079] (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. Evaluation was then performed according to the following evaluation criteria, with A and B being considered acceptable. A: No coating defects such as cracks, fissures, or peeling were observed. B: The area ratio of coating defects was 10% or less. C: The area ratio of coating defects was more than 10% but less than 30%. D: The area ratio of coating defects was 30% or more.

[0080]

[0081] From the above results, it can be seen that the present example is superior to the comparative example in appearance, adhesive strength from room temperature to high temperature, and magnetic properties.

[0082] The present disclosure provides an adhesive-coated electrical steel sheet that has excellent adhesive strength and magnetic properties from room temperature to high temperature, a laminated core using the same, and methods for manufacturing the same, which have high industrial applicability.

[0083] 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 comprising a crosslinkable thermoplastic resin A and a thermoplastic resin B other than said crosslinkable thermoplastic resin A; wherein the adhesive coating has a hardness of 200-260 MPa; and after heating said adhesive coating at 200°C for 5 minutes, the adhesive coating has a hardness of 200-300 MPa.

2. The adhesive-coated electrical steel sheet according to claim 1, wherein the crosslinkable thermoplastic resin A is one or more resins selected from the group consisting of (meth)acrylic resins and polyester resins.

3. A laminated core, comprising a plurality of laminated magnetic steel sheets with the adhesive coating according to claim 1 or 2, the magnetic steel sheets being bonded to one another by the hardened film of the adhesive coating.

4. The laminated core according to claim 3, having a space factor of 96 to 98%.

5. A method for producing an adhesive coated electromagnetic steel sheet, comprising: a coating step of applying an adhesive coating forming coating liquid to at least a portion of one or both sides of an electromagnetic steel sheet to obtain a coated steel sheet; and a coating step of heating the coated steel sheet to a drying temperature of 100 to 200°C at a temperature increase rate of 6.0°C / sec or less and holding the coated steel sheet in a temperature range from the drying temperature to the drying temperature - 10°C for 10 to 90 seconds to dry the sheet, thereby forming an adhesive coating on the surface of the electromagnetic steel sheet.

6. A method for producing an adhesive coated electrical steel sheet as described in claim 5, wherein in the coating step, the coating liquid for forming the adhesive coating contains a crosslinkable thermoplastic resin A and a thermoplastic resin B other than the crosslinkable thermoplastic resin A, and the mass ratio of the crosslinkable thermoplastic resin A to the thermoplastic resin B is 97 / 3 to 70 / 30.

7. A method for manufacturing a laminated core, comprising: a coating step of applying a coating liquid for forming an adhesive coating to at least a portion of one or both sides of an electromagnetic steel sheet to obtain a coated steel sheet; a coating formation step of heating the coated steel sheet to a drying temperature of 100 to 200°C at a temperature increase rate of 6.0°C / sec or less, and holding the coated steel sheet in a temperature range from the drying temperature to the drying temperature - 10°C for 10 to 90 seconds to dry it, thereby forming an adhesive coating on the surface of the electromagnetic steel sheet to obtain an adhesive-coated electromagnetic steel sheet; a punching step of punching out the adhesive-coated electromagnetic steel sheet to obtain a punched member; a lamination step of stacking a plurality of the punched members to obtain a laminate; and a bonding step of heating the laminate to a pressurizing temperature in the temperature range of 200 to 300°C, and holding the laminate for 5 to 60 minutes while applying a pressurizing pressure of 0.5 to 10 MPa in a range from the pressurizing temperature to the pressurizing temperature - 10°C.

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