Insulating coating composition for electrical steel sheet, electrical steel sheet, and manufacturing method thereof

Abstract

The present invention provides an insulating coating composition for electrical steel sheets, an electrical steel sheet, and a method for producing the same, which are capable of improving functions such as surface insulation, high temperature resistance, corrosion resistance, adhesion, and recoatability by eliminating chromates, using a mixture of inorganic particles having different shapes and sizes, and using a composite metal phosphate and an organic / inorganic composite. [Solution] The insulating coating composition for electrical steel sheet of the present invention is characterized by comprising, based on 100% by weight of the total composition, 10 to 50% by weight of a first composition containing first inorganic particles and second inorganic particles, 10 to 50% by weight of a second composition containing a metal phosphate, and 20 to 60% by weight of a third composition containing an organic / inorganic composite in which inorganic nanoparticles are substituted for an organic resin.

Description

[Technical field]

[0001] The present invention relates to an insulating coating composition for electrical steel sheets, electrical steel sheets, and a manufacturing method thereof, and more particularly to an insulating coating composition for electrical steel sheets, which eliminates chromates in order to solve environmental issues and uses a mixture of inorganic particles having different shapes and sizes to improve the density of an electrical steel sheet coating layer, and which uses metal phosphates in which various metals are substituted in order to satisfy high-temperature heat resistance, and an organic / inorganic composite having excellent adhesion to an electrical steel sheet material, and which can exhibit functions such as surface insulation, high-temperature heat resistance, corrosion resistance, adhesion, and recoatability, and an electrical steel sheet and a manufacturing method thereof. [Background technology]

[0002] Generally, non-oriented electrical steel sheets are steel sheets with uniform magnetic properties in all directions on the rolled sheet, and are widely used in motors, generator cores, electric motors, small transformers, etc. In particular, there is a trend for non-oriented electrical steel sheets to be made more luxurious by reducing iron loss to reduce electrical loss in refrigerators, factory motors, etc., by increasing magnetic flux density to make motors smaller and more efficient in vacuum cleaners, and by making them extremely thin to accommodate increased frequencies for high output in office automation equipment and electric vehicle drive motors, etc.

[0003] Non-oriented electrical steel sheets, which are riding this wave of increasing sophistication, require thick insulating coatings (thick films) for high insulation in terms of efficient energy utilization. For example, non-oriented electrical steel sheets used in medium and large electric motors, generators, and transformers require insulating coatings that provide a high level of insulation to minimize interlaminar current loss when used as laminates for motor cores. Such high level of insulation requires thermal resistance and may require heat treatment such as stress-relief annealing (SRA).

[0004] In addition, high-grade non-oriented electrical steel sheets have a high silicon content, which increases the hardness of the material and causes problems with workability deterioration due to the high stress placed on the slitter and press during slitting and punching processes, requiring the formation of a thick coating. Such high-grade non-oriented electrical steel sheets are expected to lead the future of the electrical / electronics industry.

[0005] Insulation coating agents for non-oriented electrical steel sheets are broadly divided into three types: inorganic, organic, and organic / inorganic composite coating solutions. Research is also being conducted on a method of first applying an inorganic coating solution and then applying an organic coating solution. In the manufacture of insulation coating agents, various combinations of compositions are being considered to improve the insulation of non-oriented electrical steel sheets, and currently, most insulation coating agents commercialized by major manufacturers are based on phosphate and chromate. Phosphates and chromates play a role in greatly improving the heat resistance, insulation, and corrosion resistance of base metals. However, chromium oxide contained in the coating solution may have adverse effects on the human body and cause environmental problems. Due to this problem, environmental regulations such as the Restriction of the use of Hazardous Substances (RoHS) between EU member states regarding the use of heavy metal substances including hexavalent chromium have been strengthened, and the use of insulation coating agents containing chromate is currently limited. Therefore, although there has been active progress in recent years in the use of chromium-free coating agents for electrical steel sheets, there is a need for research into new insulating coating agents to compensate for the weakening of corrosion resistance and adhesion that occurs when chromates are not used. Summary of the Invention [Problem to be solved by the invention]

[0006] The object of the present invention has been made to solve the above problems, and is to provide an insulating coating composition for electrical steel sheet, an electrical steel sheet, and a manufacturing method thereof, which are capable of improving functions such as surface insulation, high temperature resistance, corrosion resistance, adhesion, and recoatability by eliminating chromates and using a mixture of inorganic particles having different shapes and sizes, and by using a composite metal phosphate and an organic / inorganic composite, in order to solve the environmental problems. [Means for solving the problem]

[0007] The insulating coating composition for electrical steel sheet of the present invention is characterized by comprising, based on 100% by weight of the total composition, 10 to 50% by weight of a first composition containing first inorganic particles and second inorganic particles, 10 to 50% by weight of a second composition containing a metal phosphate, and 20 to 60% by weight of a third composition containing an organic / inorganic composite in which inorganic nanoparticles are substituted for an organic resin.

[0008] The first inorganic particles and the second inorganic particles are different types and are preferably selected from the group consisting of barium sulfate (Ba2SO4), titanium dioxide (TiO2), calcium carbonate (CaCO3), clay (Al2Si2O5(OH)4) and silicon dioxide (SiO2). The metal phosphate may include one or more metals selected from the group consisting of Al, Co, Ca, Zn, Mn, Mg, Zr and Fe. When the metal phosphate comprises a composite metal phosphate of a first metal phosphate and a second metal phosphate, the first metal phosphate can be an Al phosphate, and the second metal phosphate can comprise a metal selected from the group consisting of Co, Ca, Zn, Mn, Mg, Zr, and Fe.

[0009] Based on 100% by weight of the second composition, the first metal phosphate may be contained in an amount of 60 to 80% by weight, and the second metal phosphate may be contained in an amount of 20 to 40% by weight. The organic resin is preferably at least one selected from the group consisting of epoxy resins, ester resins, acrylic resins, styrene resins, urethane resins, and ethylene resins. The inorganic nanoparticles are preferably one or more selected from the group consisting of SiO2, Al2O3, TiO2, MgO, ZnO and ZrO2.

[0010] The organic / inorganic composite may be one or more selected from the group consisting of epoxy / SiO2, epoxy / Al2O3, epoxy / TiO2, ester / SiO2, ester / ZnO, acrylic / SiO2, acrylic / Al2O3, acrylic / ZnO, acrylic / ZrO2, styrene / SiO2, styrene / TiO2, styrene / MgO, urethane / SiO2, urethane / Al2O3, urethane / ZnO, ethylene / SiO2, ethylene / Al2O3, and ethylene / ZnO. In the organic / inorganic composite, the substitution rate of the inorganic nanoparticles with the organic resin can be 1 to 50%. The average particle size of the inorganic nanoparticles is preferably 1 to 100 nm.

[0011] The electrical steel sheet of the present invention includes an electrical steel sheet substrate and an insulating coating located on the surface of the electrical steel sheet substrate, and the insulating coating may include, based on 100% by weight of the total composition, 10 to 50% by weight of a first composition including first inorganic particles and second inorganic particles, 10 to 50% by weight of a second composition including a metal phosphate, and 20 to 60% by weight of a third composition including an organic / inorganic composite in which inorganic nanoparticles are substituted for an organic resin. The insulating coating preferably has a thickness of 1 to 10 μm.

[0012] The method for producing an electrical steel sheet of the present invention is characterized by comprising the steps of preparing an electrical steel sheet substrate, applying an insulating coating composition according to any one of claims 1 to 10 to a surface of the electrical steel sheet substrate, and heat treating the electrical steel sheet substrate to which the insulating coating composition has been applied. Effect of the Invention

[0013] According to one embodiment of the present invention, an insulating coating composition for electrical steel sheets of the present invention can provide an insulating coating composition for electrical steel sheets that has excellent corrosion resistance and adhesion even without containing chromium. Furthermore, according to an embodiment of the present invention, a highly functional surface having excellent insulation properties, high temperature resistance, corrosion resistance, adhesion, and recoatability can be obtained. [Brief description of the drawings]

[0014] [Figure 1] 1 is a schematic diagram of a cross section of an electrical steel sheet according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Terms such as first, second and third are used to describe various parts, components, regions, layers and / or sections, but are not limited thereto. These terms are used only to distinguish one part, component, region, layer or section from another part, component, region, layer or section. Thus, a first part, component, region, layer or section described below may be referred to as a second part, component, region, layer or section without departing from the scope of the present invention. The terminology used herein is merely for the purpose of referring to particular embodiments and is not intended to limit the present invention. As used herein, the singular form includes the plural form unless the text clearly indicates otherwise. The term "comprising" as used in the specification embodies certain features, regions, integers, steps, operations, elements and / or components and does not exclude the presence or addition of other features, regions, integers, steps, operations, elements and / or components.

[0016] When an element is referred to as being "on" another element, it means that it is directly on top of the other element, or there may be other elements between them. In contrast, when an element is referred to as being "directly on" another element, there are no other elements between them. Unless otherwise defined, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by a person of ordinary skill in the art to which the present invention belongs. Terms defined in commonly used dictionaries are additionally interpreted to have a meaning consistent with the relevant technical literature and the presently disclosed content, and are not interpreted in an ideal or very formal sense unless defined. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to exemplary embodiments thereof, so that those skilled in the art can easily practice the present invention. However, the present invention may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein.

[0017] An insulating coating composition for electrical steel sheet according to one embodiment of the present invention may include, based on 100 wt% of the total composition, 10 to 50 wt% of a first composition including first inorganic particles and second inorganic particles, 10 to 50 wt% of a second composition including a metal phosphate, and 20 to 60 wt% of a third composition including an organic / inorganic composite in which inorganic nanoparticles are substituted for an organic resin. The insulating coating composition for electrical steel sheets according to an embodiment of the present invention can improve insulation properties, high temperature resistance, corrosion resistance, adhesion, and recoatability by adjusting the components and component ratios in the composition. The components of the insulating coating composition for electrical steel sheets according to one embodiment of the present invention will be described in detail below.

[0018] An insulating coating composition for electrical steel sheets according to an embodiment of the present invention may contain 10-50 wt% of a first composition including first inorganic particles and second inorganic particles, based on 100 wt% of the total composition. The first composition acts as a weighting agent and improves heat resistance and insulation resistance. If the content of the first composition is too low, there is a risk of problems such as deterioration of heat resistance and insulation resistance properties. Conversely, if the content of the first composition is too high, there is a risk of problems such as deterioration of coating workability and corrosion resistance. The first inorganic particles and the second inorganic particles are different in type and may be selected from the group consisting of barium sulfate (Ba2SO4), titanium dioxide (TiO2), calcium carbonate (CaCO3), clay (Al2Si2O5(OH)4) and silicon dioxide (SiO2). The inorganic particles may have different shapes and particle sizes depending on the type. For example, in the case of barium sulfate, a rod shape with an average particle size of 1 to 3 μm, in the case of titanium dioxide, a spherical shape with an average particle size of 50 to 100 nm, in the case of calcium carbonate, an amorphous shape with an average particle size of 2 to 5 μm, in the case of silicon dioxide, an amorphous shape with an average particle size of 2 to 4 μm, and in the case of clay, a plate-like crystal shape with an average particle size of 0.2 to 5.0 μm can be used. By using different types of inorganic particles with different shapes and particle sizes as the first inorganic particles and the second inorganic particles, it is possible to obtain an inorganic filling content adjustment and inorganic dispersion effect in the coating layer.

[0019] The insulating coating composition for electrical steel sheet of the present invention may contain 10 to 50% by weight of a second composition containing a metal phosphate, based on 100% by weight of the entire composition. The metal phosphate serves to improve corrosion resistance and insulation properties. The metal phosphate may include one or more metals selected from the group consisting of Al, Co, Ca, Zn, Mn, Mg, Zr, and Fe. Specifically, the phosphate may include one or more metals selected from the group consisting of Al, Co, Ca, Zn, Mn, and Mg. For example, the phosphate containing Al may be monoaluminum phosphate (Al(H3PO4)3), the phosphate containing Co may be monocobalt phosphate (Co(H3PO4)2), the phosphate containing Ca may be monocalcium phosphate (Ca(H3PO4)2), the phosphate containing Zn may be monozinc phosphate (Zn(H3PO4)2), the phosphate containing Mn may be monomanganese phosphate (Mn(H2PO4)2), and the phosphate containing Mg may be monomagnesium phosphate (Mg(H3PO4)2).

[0020] When the metal phosphate includes a composite metal phosphate of a first metal phosphate and a second metal phosphate, the first metal phosphate is preferably an Al phosphate, and the second metal phosphate is preferably a metal selected from the group consisting of Co, Ca, Zn, Mn, Mg, Zr, and Fe. Specifically, the second metal phosphate is preferably a metal selected from the group consisting of Co, Ca, Zn, Mn, and Mg. In this case, based on 100% by weight of the second composition, the first metal phosphate may include 60 to 80% by weight of Al phosphate, and the second metal phosphate may include 20 to 40% by weight. Specifically, the first metal phosphate may include 65 to 75% by weight of Al phosphate, and the second metal phosphate may include 25 to 35% by weight. If the content of Al phosphate in the first metal phosphate is too low, a problem of deterioration in corrosion resistance may occur, and if the content of Al phosphate is too high, a problem of deterioration in weather resistance may occur. If the content of the second metal phosphate is too low, there is a risk of a problem of deterioration in adhesion, whereas if the content of the second metal phosphate is too high, there is a risk of a problem of deterioration in weather resistance. Metal phosphates can be produced by reacting a metal hydroxide (Mx(OH)y, where M is a metal) or a metal oxide (MxO, where M is a metal) with phosphoric acid (H3PO4). For example, when a metal hydroxide (Mx(OH)y) or a metal oxide (MxO) is added to 100 parts by weight of an aqueous phosphoric acid solution containing 85% by weight of free phosphorus phosphate (H3PO4) and reacted at 80 to 90°C for 6 to 10 hours, the respective metal phosphates can be obtained.

[0021] The insulating coating composition for electrical steel sheet of the present invention may contain 20 to 60 wt % of a third composition including an organic / inorganic composite in which inorganic nanoparticles are substituted for an organic resin, based on 100 wt % of the total composition. The organic / inorganic composite is composed of an organic resin and inorganic nanoparticles, and can exist in a composition in a state in which the inorganic nanoparticles are bonded to the organic resin by substituting some or all of the functional groups of the organic resin. If the inorganic nanoparticles are added alone without being bonded to the resin, the inorganic nanoparticles will aggregate with each other and become difficult to disperse. The resin in the organic / inorganic composite provides insulating properties to the insulating coating and adhesion between the insulating coating and the steel sheet substrate, while the inorganic nanoparticles prevent the precipitation and agglomeration of metal phosphates and contribute to improving the surface characteristics after stress relief annealing.

[0022] The organic / inorganic composite may contain 20 to 60% by weight of the insulating coating composition, based on 100% by weight of the total composition. Specifically, the third composition may be contained in an amount of 30 to 50% by weight, and more specifically, 35 to 45% by weight. If the organic / inorganic composite is contained in an excessively small amount, it is difficult to ensure the above-mentioned insulation properties and adhesion. Conversely, if the organic / inorganic composite is contained in an excessively large amount, the addition of metal phosphate is relatively reduced, and it may be difficult to ensure high temperature resistance. In the organic / inorganic composite, the substitution rate of inorganic nanoparticles substituted with organic resin is preferably 1 to 50%. Specifically, the substitution rate of inorganic nanoparticles is preferably 10 to 30%. If the substitution rate of inorganic nanoparticles is too small, there is a risk of a problem of deterioration of insulation resistance characteristics. Conversely, if the substitution rate of inorganic nanoparticles is too large, there is a risk of a problem of deterioration of corrosion resistance and processability (punchability). The organic resin means an organic polymer compound, and is a concept that is contrasted with a monomer. Specifically, the organic resin may be one or more selected from the group consisting of an epoxy resin, an ester resin, a melamine resin, a siloxane resin, an acrylic resin, a phenolic resin, a styrene resin, a vinyl resin, a urethane resin, and an ethylene resin. More specifically, the organic resin may be one or more selected from the group consisting of an epoxy resin, an ester resin, an acrylic resin, a styrene resin, a urethane resin, and an ethylene resin. Here, the epoxy system means, for example, one in which an epoxy group or a group derived from an epoxy group exists in the main chain.

[0023] The inorganic nanoparticles prevent the precipitation and agglomeration of the insulating coating composition and contribute to improving the properties after stress relief annealing. The inorganic nanoparticles may be one or more selected from the group consisting of SiO2, Al2O3, TiO2, MgO, ZnO, and ZrO2. Specifically, the inorganic nanoparticles may be one or more selected from the group consisting of SiO2, Al2O3, TiO2, and ZnO. The average particle size of the inorganic nanoparticles is preferably 1 to 100 nm. If the average particle size of the inorganic nanoparticles is too small, there is a risk of a problem that the dispersibility of the nanoparticles in the coating solution is deteriorated. On the other hand, if the average particle size of the inorganic nanoparticles is too large, there is a risk of a problem that the workability of the coating is deteriorated.

[0024] Specifically, the organic / inorganic composite may be one or more selected from the group consisting of epoxy / SiO2, epoxy / Al2O3, epoxy / TiO2, ester / SiO2, ester / ZnO, acrylic / SiO2, acrylic / Al2O3, acrylic / ZnO, acrylic / ZrO2, styrene / SiO2, styrene / TiO2, styrene / MgO, urethane / SiO2, urethane / Al2O3, urethane / ZnO, ethylene / SiO2, ethylene / Al2O3, and ethylene / ZnO. More specifically, the organic / inorganic composite may be one or more selected from the group consisting of epoxy / SiO2, ester / SiO2, acrylic / ZnO, styrene / TiO2, urethane / Al2O3, and ethylene / Al2O3. In addition to the above-mentioned components, the insulating coating composition may contain a solvent to facilitate application and uniformly disperse the components. The amount of the solvent is not particularly limited, but may be 50 to 1000 parts by weight per 100 parts by weight of the total solid content of the insulating coating composition. In one embodiment of the present invention, the term "parts by weight" refers to the relative ratio between the weights of the components. The solid content refers to the weight of the remaining components in the insulating coating composition excluding volatile components such as the solvent.

[0025] An electrical steel sheet 100 according to one embodiment of the present invention includes an electrical steel sheet substrate 10 and an insulating coating 20 located on the electrical steel sheet substrate 10 . A general non-oriented or oriented electrical steel sheet can be used without any restrictions as the electrical steel sheet substrate 10. In one embodiment of the present invention, the main component is forming an insulating coating 20 of a special composition on the electrical steel sheet substrate 10, so a detailed description of the electrical steel sheet substrate 10 will be omitted. The thickness of the insulating coating 20 may be 1 to 10 μm. If the insulating coating 20 is too thin, it is difficult to ensure appropriate insulation. If the insulating coating 20 is too thick, the space factor decreases. In one embodiment of the present invention, appropriate insulation can be ensured even when the insulating coating 20 is formed to be thin. More specifically, the thickness of the insulating coating 20 may be 4 to 8 μm.

[0026] The components and content ratios in the insulating coating composition described above can be maintained in the insulating coating 20. Specifically, the insulating coating 20 can contain, based on a total of 100% by weight, 10 to 50% by weight of a first composition containing first inorganic particles and second inorganic particles, 10 to 50% by weight of a second composition containing a metal phosphate, and 20 to 60% by weight of a third composition containing an organic / inorganic composite in which inorganic nanoparticles are substituted for an organic resin. Furthermore, the configuration of the insulating coating 20 has been described in detail in relation to the insulating coating composition, so a duplicated description will be omitted.

[0027] The method for producing an electrical steel sheet of the present invention includes the steps of preparing an electrical steel sheet substrate, applying an insulating coating composition to a surface of the electrical steel sheet substrate, and heat treating the electrical steel sheet substrate to which the insulating coating composition has been applied. First, an electromagnetic steel sheet substrate is prepared. A general non-oriented or oriented electromagnetic steel sheet can be used as the electromagnetic steel sheet substrate 10 without any restrictions. In one embodiment of the present invention, the main configuration is to form an insulating coating 20 having a special composition on the electromagnetic steel sheet substrate 10, so a detailed description of the manufacturing method of the electromagnetic steel sheet substrate 10 will be omitted. Next, an insulating coating composition is applied to the surface of the electrical steel sheet substrate. Since the insulating coating composition has been described above, a detailed description thereof will be omitted. Next, the electrical steel sheet substrate coated with the insulating coating composition is heat-treated. The heat treatment temperature is preferably 200 to 400°C. If the temperature is too low, it takes a long time to form the coating, and whitening occurs. If the temperature is too high, there is a risk of cracking, which may result in a decrease in corrosion resistance, heat resistance, insulation resistance, and bluing resistance.

[0028] Hereinafter, preferred examples of the present invention, comparative examples for comparison, and evaluation examples thereof will be described. However, the following examples are merely examples of the present invention, and the present invention is not limited to the following examples. Experimental Example 1 First, an experiment was carried out to evaluate the compatibility of a mixed solution of inorganic particles constituting the first composition and metal phosphate constituting the second composition, and to determine the type of inorganic particles and metal phosphate to be used. The compatibility of inorganic particles and metal phosphate was evaluated by first mixing 30-70% by weight of metal phosphate and 30-70% by weight of inorganic particles, blending them with a high speed agitator (1000-3000RPM) for 1 hour, and then maintaining them at room temperature for 24 hours, and evaluating the compatibility of the solution based on the degree of gelation and phase separation of the solution.

[0029] In the compatibility evaluation, the following inorganic particles were used: barium sulfate (Ba2SO4), titanium dioxide (TiO2), clay (Al2Si2O5(OH)4), calcium carbonate (CaCO3), silica (SiO2), and talc (3MgO.4SiO2.H2O). The shape and basic physical properties of each inorganic particle are shown in Table 1 below.

[0030] [Table 1] In the compatibility evaluation, aluminum phosphate, zinc phosphate, magnesium phosphate, cobalt phosphate, manganese phosphate, and calcium phosphate were used as metal phosphates in which phosphoric acid was substituted with various metals (Al, Mg, Mn, Ca, Zn, Co). The basic physical properties of each metal phosphate are shown in Table 2 below.

[0031] [Table 2]

[0032] The solution compatibility evaluation results for the mixtures of inorganic particles and metal phosphates in Tables 1 and 2 are shown in Table 3 below. The solution compatibility evaluation was classified as ◎ very good, ○ good, △ poor, and X very poor.

[0033] [Table 3]

[0034] As can be seen from the evaluation results in Table 3, all types of metal phosphates showed good compatibility with barium sulfate, titanium dioxide, calcium carbonate, clay and silicon dioxide, and the compatibility of metal phosphates with barium sulfate and clay was particularly excellent. However, in the case of talc, it was confirmed that the compatibility was deteriorated when mixed with all types of metal phosphates, so talc was excluded from the preparation of the insulating coating composition.

[0035] Experimental Example 2 In the next experiment, the organic / inorganic composite was mixed with the mixture composition of inorganic particles and metal phosphate selected in Experimental Example 1 to evaluate the solution compatibility and coating workability. The mixture ratio of the metal phosphate to the inorganic particles was 1:1, and the mixture weight percentage of the mixture of the metal phosphate and inorganic particles obtained in Table 3 and the organic / inorganic composite was determined to be 30 to 70% by weight. As can be seen from Table 3, in the present invention, the combination of the metal phosphate and talc had poor solution compatibility, and was therefore excluded from the evaluation of compatibility with the organic / inorganic composite. The compatibility of the solution was evaluated by blending the organic / inorganic composite with the mixture of the metal phosphate and inorganic particles dispersed by a high-speed disperser using a stirrer (100 to 300 RPM) for 0.5 hours, maintaining the mixture at room temperature for 6 hours, and then evaluating the compatibility of the solution based on the degree of gelation and phase separation of the solution.

[0036] In addition, the coating workability was evaluated by adjusting the specific gravity of each solution to 1.1-1.4, applying a coating thickness of 5-7 μm to the prepared test piece (50PN400) using a bar coater, and curing at 200-350 °C for 20-60 seconds, and then evaluating the surface condition. Here, the 50PN400 used as the test piece contains 2.5 wt% Si, 0.5 wt% Al, and 0.2 wt% Mn as resistivity element components, the plate thickness is 0.5 mm, and the test piece size is 300 mm x 80 mm. In order to sufficiently cure the coating surface, the curing temperature and curing time were optimized for each solution. As shown in Table 4, the inorganic substitution ratio of the organic / inorganic composite is fixed at 20%, and the types of inorganic nanoparticles substituted by the organic polymer resin are SiO2, Al2O3, TiO2, ZnO, ZrO2, and MgO, and the inorganic nanoparticle size is 1-100 nm for each type. The solution compatibility and coating workability were evaluated as follows: ◎ very good, ○ good, △ insufficient, and X very insufficient.

[0037] [Table 4]

[0038] As can be seen from the evaluation results of solution compatibility and coating workability of the mixed solutions of metal phosphate, inorganic particles, and organic / inorganic composites in Table 4, calcium carbonate and silicon dioxide, which have relatively large inorganic particle sizes, were relatively inferior in solution compatibility and coating workability compared to barium sulfate, titanium dioxide, and clay, which have small particle sizes.

[0039] Experimental Example 3 Table 5 below shows the composition ratios of the mixed inorganic particles of the first composition, the mixed metal phosphate of the second composition, and the mixed solution composed of the organic / inorganic composite of the third composition, which are examples of the present invention, and the comparative examples. In the examples of the present invention, two types of inorganic particles, the first inorganic particles and the second inorganic particles, were mixed and used as the first composition, and the first inorganic particles and the second inorganic particles were mixed in a ratio of 7:3. In addition, the composite metal phosphate used as the second composition uses at least one type of phosphate, and in this example, the first metal phosphate and the second metal phosphate were mixed in a ratio of 7:3 using two types of metal phosphates. The coating solution used the first composition, the second composition, and the third composition in amounts of 10 to 50% by weight, 10 to 50% by weight, and 20 to 60% by weight, respectively, based on 100% by weight of the coating solution. In addition, the substitution rate of the inorganic nanoparticles substituted with the organic resin in the organic / inorganic composite used in Table 5 was fixed at 20% as shown in Table 4. In contrast, in Comparative Examples 1 and 2, no metal phosphate was added, and only inorganic particles and polymer resin were mixed, while in Comparative Examples 3 and 4, no inorganic particles were added, and only metallic phosphate and polymer resin were mixed to prepare coating solutions. In Comparative Example 5, a coating solution was prepared with the same composition ratio as in the Examples, except that one type of inorganic particles was used.

[0040] [Table 5] TIFF2025501520000007.tif177167

[0041] Table 6 below shows the results of evaluating the surface condition, insulation, corrosion resistance, high temperature resistance, and recoatability after coating the coating solutions mixed according to the composition ratios in Table 5 using a bar coater and curing at 200-400°C for 30-40 seconds. The curing temperature and curing time were optimized for each solution to fully cure the coating surface. To obtain a consistent coating thickness for each coating solution, the solid content of the coating solution was adjusted to around 30%, and the coating was applied to a consistent thickness of about 6μm using different bar cutter numbers. The coating thickness was measured using a delta scope. The methods for measuring the above-mentioned properties are as follows. Surface condition: After coating and curing, the surface was evaluated based on the degree of streaks and defects. In this experiment, if the surface area was 5% or less, it was marked as ◎ (excellent), if it was 20% or less, it was marked as ○ (good), if it was 30% or less, it was marked as △ (average), and if it was 50% or more, it was marked as X (poor).

[0042] Insulation: Insulation was measured using a Franklin Insulation Tester, which is a single plate test device that measures the surface insulation resistance of electrical steel sheets under a constant pressure and voltage. The current range is 0 to 1,000 Amp. The insulation measurement method involves placing one test piece on a plate so that all electrode contacts are in contact, and then applying pressure of 300 psi (20.4 atm) using a pressure device. When the test pressure is reached, the slip resistor is adjusted and the ammeter scale is read under a voltage of 0.5 V, which is evaluated as the interlayer insulation value. Five pieces were evaluated for each test solution. In this experiment, measurements were made using an insulation resistance meter (ASTM A717-1), and the insulation resistance value was 100 Ω·cm 2 / lamination or more: ◎ (excellent), 60Ω·cm 2 / lamination or more: ○ (good), 40Ω·cm 2 / lamination or more: △ (normal), 20Ω·cm 2 If it is more than / lamination, it is displayed as X (bad). Corrosion resistance: Corrosion resistance was evaluated by exposing the specimen to a 5% sodium chloride (NaCl) solution at 35°C for 8 hours, and then evaluating whether or not rust had developed on the specimen. In this experiment, if the rusted area was 5% or less, it was marked as ◎ (excellent), if it was 10% or less, it was marked as ○ (good), if it was 20% or less, it was marked as △ (average), and if it was 50% or more, it was marked as X (poor).

[0043] High temperature resistance: High temperature resistance was evaluated using the IEC60404-12 continuous rating (180+30℃, 2500h) and the insulation resistance, adhesion (cylindrical mandrel bending) and change in space factor were evaluated before and after the high temperature resistance evaluation. After the continuous rating evaluation, if the degree of change in insulation resistance, adhesion and space factor was less than 5%, it was marked as ◎ (excellent), if it was less than 10%, it was marked as ○ (excellent), if it was less than 30%, it was marked as △ (good), and if it was 30% or more, it was marked as X (deteriorated). Adhesion: Adhesion is expressed as the minimum arc diameter at which the coating does not peel off when the test specimen is bent 180° in contact with an arc of 5, 10, 20, 30, or 40 mmΦ. Here, if the minimum arc diameter is 5 mmΦ or less, it is indicated as ◎ (excellent), if it is 10 mmΦ or less, it is indicated as ○ (excellent), if it is 20 mmΦ or less, it is indicated as △ (average), and if it exceeds 20 mmΦ, it is indicated as X (poor). Recoatability: Recoatability was evaluated by applying the coating solution of Comparative Example 1 as a secondary coating solution on the coating layer of the specimen coated with the coating solution, drying it, and then evaluating the surface condition of the secondary coating layer and the adhesion to the primary coating layer using the method described above. In this experiment, the adhesion to the secondary coating layer was measured using a Mandrel Bend Tester (ISO1519) and was indicated as ◎ (excellent) for 5mmΦ or less, ○ (good) for 10mmΦ or less, △ (average) for 20mmΦ or less, and Χ (poor) for 20mmΦ or more.

[0044] [Table 6]

[0045] As can be seen from the evaluation results in Table 6, the surface condition, insulating property, corrosion resistance, high temperature resistance, adhesion and recoating property of the solution of the embodiment were all superior to those of the comparative example. In the solution of the embodiment, although there were some differences in properties depending on the type of organic / inorganic composite, all properties were generally excellent. In contrast, it was confirmed that some properties of the surface condition, insulating property, corrosion resistance, high temperature resistance, adhesion and recoating property were deteriorated in Comparative Example 1 to Comparative Example 4, which did not contain a mixed composition of two types of mixed inorganic particles, metal phosphate and organic / inorganic composite, and Comparative Example 5, which contained a mixed composition of inorganic particles, metal phosphate and organic / inorganic composite but only one type of inorganic particles.

[0046] The present invention is not limited to the above-mentioned embodiments, and can be manufactured in various different forms, and a person skilled in the art to which the present invention pertains will understand that the present invention can be embodied in other specific forms without changing the technical idea or essential features of the present invention. Therefore, it should be understood that the above-described embodiments are illustrative in all respects and are not limiting.

Claims

1. Based on 100% by weight of the total composition, a first composition including first inorganic particles and second inorganic particles in an amount of 10 to 50% by weight; 10 to 50 wt. % of a second composition comprising a metal phosphate; and An insulating coating composition for electrical steel sheets, comprising 20 to 60% by weight of a third composition including an organic / inorganic composite in which inorganic nanoparticles are substituted for an organic resin.

2. The first inorganic particles and the second inorganic particles are different in type, Barium sulfate (Ba ２ SO ４ ), titanium dioxide (TiO ２ ), calcium carbonate (CaCO ３ ), Clay (Al ２ S ２ O ５ (OH) ４ ) and silicon dioxide (SiO ２ 2. The insulating coating composition for electrical steel sheet according to claim 1, wherein the insulating coating composition is selected from the group consisting of:

3. The metal phosphate is 2. The insulating coating composition for electrical steel sheet according to claim 1, further comprising one or more metals selected from the group consisting of Al, Co, Ca, Zn, Mn, Mg, Zr and Fe.

4. When the metal phosphate includes a composite metal phosphate of a first metal phosphate and a second metal phosphate, 2. The insulating coating composition for electrical steel sheet according to claim 1, wherein the first metal phosphate is an Al phosphate, and the second metal phosphate contains a metal selected from the group consisting of Co, Ca, Zn, Mn, Mg, Zr, and Fe.

5. 5. The insulating coating composition for electrical steel sheet according to claim 4, wherein the first metal phosphate is contained in an amount of 60 to 80 wt % and the second metal phosphate is contained in an amount of 20 to 40 wt % based on 100 wt % of the second composition.

6. 2. The insulating coating composition for electrical steel sheet according to claim 1, wherein the organic resin is at least one selected from the group consisting of epoxy-based resins, ester-based resins, acrylic-based resins, styrene-based resins, urethane-based resins, and ethylene-based resins.

7. The inorganic nanoparticles are SiO ２ , Al ２ O ３ , TiO ２ , MgO, ZnO and ZrO ２ 2. The insulating coating composition for electrical steel sheets according to claim 1, characterized in that the composition is one or more selected from the group consisting of:

8. The organic / inorganic composite is Epoxy / SiO ２ , epoxy / Al ２ O ３ , epoxy / TiO ２ , Ester / SiO ２ , Ester / ZnO, Acrylic / SiO ２ , Acrylic / Aluminum ２ O ３ , Acrylic / ZnO, Acrylic / ZrO ２ , styrene / SiO ２ , styrene / TiO ２ , styrene / MgO, urethane / SiO ２ , urethane / Al ２ O ３ , Urethane / ZnO, Ethylene / SiO ２ , ethylene / Al ２ O ３ 2. The insulating coating composition for electrical steel sheets according to claim 1, characterized in that the composition is one or more selected from the group consisting of ethylene / ZnO.

9. 2. The insulating coating composition for electrical steel sheets according to claim 1, wherein in the organic / inorganic composite, a substitution rate of inorganic nanoparticles substituted with an organic resin is 1 to 50%.

10. The insulating coating composition for electrical steel sheets according to claim 1, wherein the inorganic nanoparticles have an average particle size of 1 to 100 nm.

11. An electromagnetic steel sheet substrate; an insulating coating located on a surface of the electrical steel sheet substrate, The insulating coating is based on 100% by weight of the total composition. An electrical steel sheet comprising: 10 to 50% by weight of a first composition including first inorganic particles and second inorganic particles; 10 to 50% by weight of a second composition including a metal phosphate; and 20 to 60% by weight of a third composition including an organic / inorganic composite in which inorganic nanoparticles are substituted for an organic resin.

12. The electrical steel sheet according to claim 11, wherein the insulating coating has a thickness of 1 to 10 μm.

13. Providing an electromagnetic steel sheet substrate; applying an insulating coating composition according to any one of claims 1 to 10 to a surface of the electrical steel sheet substrate; and heat treating the electrical steel sheet substrate to which the insulating coating composition has been applied.

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