JP2020186415A - Electromagnetic steel sheet with organic insulation film - Google Patents

Abstract

To provide an electromagnetic steel sheet with an insulation film coated with an insulation film that is excellent in adhesion, punching quality and flaw resistance and does not diminish a volume ratio of the electromagnetic steel sheet in a laminate iron core.SOLUTION: An electromagnetic steel sheet with an organic insulation film is coated with an organic insulation film having a Martens hardness of 300 N/mm2 or more and less than 600 N/mm2 and an arithmetic average roughness Ra of 0.3 μm or less.SELECTED DRAWING: None

Description

The present invention is an electromagnetic steel sheet with an insulating coating suitable as a material for a laminated iron core, which is excellent in insulation, punching and scratch resistance, and is an organic insulation that does not impair the space factor of the electromagnetic steel sheet in the laminated iron core. The present invention relates to an electromagnetic steel sheet with an organic insulating film on which a film is formed.

Since electromagnetic steel sheets have high conversion efficiency between electrical energy and magnetic energy, they are widely used as materials for iron cores of electrical equipment such as generators, transformers, and motors for home appliances. These iron cores are usually formed by laminating a large number of electromagnetic steel sheets punched into a desired shape by press forming. An iron core formed by laminating electromagnetic steel sheets in this way is called a laminated iron core.

In order to improve the energy conversion efficiency, it is important to reduce the iron loss of the laminated iron core. In a laminated iron core, when the laminated steel plates are short-circuited, a local eddy current is generated and iron loss increases. Therefore, an insulating film is usually formed on the surface of an electromagnetic steel sheet that is a material for a laminated iron core. By using such an electromagnetic steel sheet with an insulating coating, the interlayer resistance when the steel sheets are laminated is improved, short circuits between the laminated steel sheets are suppressed, local eddy currents are reduced, and the iron core is extended. Iron loss is reduced.

Laminated iron cores using electrical steel sheets with an insulating coating have been used in a wide variety of fields to date. In recent years, application to large-scale generators and wind power generators has been actively promoted. However, in order to apply a laminated iron core using an electromagnetic steel sheet with an insulating coating to a large-scale generator and a wind power generator, the insulating coating is required to satisfy some characteristics.

First, large generators and wind power generators need to handle high voltages. Therefore, the electromagnetic steel sheets used as the material for these iron cores have a larger insulating property (interlayer resistance) than the insulation (interlayer resistance value) required for the electromagnetic steel sheets used as the material for the iron cores of small motors of home appliances. Value) is required. Specifically, the interlayer resistance values required for the electromagnetic steel sheets constituting the iron cores of large generators and wind power generators are measured in accordance with JIS C 2550 (2000) "9. Interlayer resistance test" (method A). The value is about 50Ω · cm ² / sheet or more.

Further, when manufacturing a large iron core used for a large generator and a wind power generator, in many cases, an electromagnetic steel plate as a material is manually laminated. During this manual laminating, the end face of the electrical steel sheet and the insulating coating may come into contact with each other, resulting in defects in the insulating coating. Since the flaws generated in the insulating coating are a factor of lowering the interlayer resistance, the insulating coating is required to have excellent flaw resistance so as to be able to suppress the flaws during manual work.

Various technologies have been proposed to meet these demands. For example, Patent Document 1 states that (A) an aqueous carboxyl group-containing resin: 100 parts by mass in terms of solid content and (B) Al-containing oxide: solid in 100 parts by mass in terms of solid content of (A) above. More than 40 parts by mass and less than 150 parts by mass in terms of minutes, (C) one or more cross-linking agents selected from melamine, isocyanate and oxazoline: equivalent to 100 parts by mass in terms of solid content in (A) above. Disclosed is a method for producing an electromagnetic steel plate with an insulating coating using a coating agent for forming an insulating coating containing more than 20 parts by mass and less than 100 parts by mass.

Further, in Patent Document 2, the solvent contains (A) an aqueous carboxyl group-containing resin: 100 parts by mass in terms of solid content, and (B) an aluminum-containing oxide: 100 parts by mass in terms of solid content in (A) above. More than 40 parts by mass and less than 300 parts by mass in terms of solid content, and at least one cross-linking agent selected from the group consisting of (C) melamine, isocyanate and oxide: solid with respect to 100 parts by mass of solid content in (A) above A method for producing an electromagnetic steel plate with an insulating coating using a coating agent for forming an insulating coating containing 100 parts by mass or more and less than 300 parts by mass in terms of minutes is disclosed.

Further, if the insulating coating does not easily damage the die during punching by press molding, the number of times the die is replaced or polished can be reduced, and the iron core can be efficiently produced. Therefore, in addition to the above-mentioned characteristics. There is a demand for an electromagnetic steel sheet with an insulating coating, which has an insulating coating having excellent punching properties.

Japanese Unexamined Patent Publication No. 2013-209739 JP-A-2018-21120

According to the conventional technique as described above, it is possible to form an insulating film having excellent various properties such as insulating properties. However, the present inventors have newly found that there is room for improvement in the flaw resistance of the coating film and the space factor of the electromagnetic steel sheet in the laminated iron core in the above-mentioned conventional technique.

That is, the present invention advantageously solves the problems of the prior art, and forms an insulating film which is excellent in insulating property, punching property, and scratch resistance and does not impair the space factor of the electromagnetic steel sheet in the laminated iron core. Another object of the present invention is to provide an electromagnetic steel sheet with an insulating coating.

In order to solve the above problems, the present inventors have made extensive studies to form an insulating film having excellent insulating properties, punching properties, and scratch resistance, and which does not impair the space factor of the electrical steel sheet in the laminated iron core. For this purpose, we have obtained new findings that it is effective to appropriately define the Martens hardness and surface roughness of the coating film and to make the coating film an organic coating.

That is, the present inventors have found that an insulating film having excellent punching property and scratch resistance can be obtained by appropriately defining the Martens hardness of the insulating film.

Further, as described in Patent Documents 1 and 2, the present inventors manufacture an electromagnetic steel plate with an insulating coating by using the coating agent in a coating agent containing a large amount of inorganic pigments such as aluminum-containing oxides. It was found that the voids generated between the steel plates of the laminated core lead to a decrease in the space factor due to the unevenness of the film surface due to the presence of the inorganic pigment. Therefore, it was newly discovered that by using an organic coating as the coating and appropriately defining the surface roughness, it is possible to prevent the space factor from being lowered due to the voids generated between the steel plates of the laminated core due to the unevenness of the coating surface. ..

The present invention has been completed based on the above findings, and its gist structure is as follows.
[1] An electromagnetic steel sheet with an organic insulating coating having an organic insulating coating having a Martens hardness of 300 N / mm ² or more and less than 600 N / mm ² and an arithmetic mean roughness Ra of 0.3 μm or less.
[2] The electromagnetic steel sheet with an organic insulating coating according to the above [1], wherein the amount of adhesion of the organic insulating coating on one side is 0.9 g / m ² or more and 20 g / m ² or less.

According to the present invention, there is provided an electromagnetic steel sheet with an organic insulating film, which is excellent in insulating property, punching property, and scratch resistance, and has an organic insulating film formed in which the space factor of the electromagnetic steel sheet in the laminated iron core is not impaired. can do.

Hereinafter, the present invention will be specifically described.

The "organic insulating film" according to the present invention is an insulating film mainly composed of an organic resin, but may contain other components as long as it is 5% by mass or less. Other components include pigments, surfactants, rust inhibitors, lubricants, defoamers, antioxidants and the like. The content of other components contained in the organic insulating coating is preferably 4% by mass or less, and more preferably 2% by mass or less.

The electromagnetic steel sheet with an organic insulating film of the present invention has an organic insulating film having a Martens hardness of 300 N / mm ² or more and less than 600 N / mm ² and an arithmetic mean roughness Ra of 0.3 μm or less.

The Martens hardness of the organic insulating film shall be 300 N / mm ² or more and less than 600 N / mm ² . As described above, the present inventors have newly found that a coating film having excellent adhesion, punching property, and scratch resistance can be obtained by appropriately defining the maltensity hardness of the coating film. However, the present invention has been completed. If the Martens hardness of the organic insulating film is less than 300, the hardness is insufficient and the flaw resistance is inferior. Therefore, by setting the Martens hardness to 300 or more, it is possible to secure a hardness capable of suppressing defects during handling. On the other hand, when the Martens hardness is 600 or more, the organic insulating film is remarkably hardened and the punching property is deteriorated. In addition, the adhesion between the organic insulating film and the steel sheet deteriorates. The Martens hardness is preferably 320 N / mm ² or more, more preferably 340 N / mm ² or more. Moreover, Martens hardness is preferably 550 N / mm ² or less, more preferably 510N / mm ² or less.

The arithmetic average roughness (surface roughness) Ra of the organic insulating film shall be 0.3 μm or less. As described above, the present inventors have newly discovered that the voids generated between the steel plates of the laminated core due to the unevenness of the coating surface reduce the space factor, and appropriately define the surface roughness of the organic insulating coating. This has led to the completion of the present invention. When the arithmetic mean roughness Ra exceeds 0.3 μm, the space factor of the electromagnetic steel sheet in the laminated iron core is lowered because the voids generated between the steel sheets of the laminated core are lowered due to the unevenness of the film surface. Is. The arithmetic average roughness Ra of the organic insulating film is preferably 0.2 μm or less, more preferably 0.1 μm or less. The lower limit of the arithmetic mean roughness Ra of the organic insulating film is not particularly limited and may be 0 μm.

The organic insulating film is formed on at least one surface of the electromagnetic steel sheet, but it is preferably formed on both surfaces. Depending on the purpose, the organic insulating film according to the present invention may be formed only on one surface of the electromagnetic steel sheet, and another known insulating film may be formed on the other surface.

In the present invention, the amount of the organic insulating coating adhered to one side is preferably 0.9 g / m ² or more and 20 g / m ² or less. By setting the adhesion amount of the organic insulating film to 0.9 g / m ² or more, it is possible to provide an electromagnetic steel sheet with an organic insulating film having excellent insulating properties and punching properties. More preferably, the amount of the organic insulating film adhered is 5.0 g / m ² or more. Also, when the amount of deposition of the organic insulating film is more than 20 g / m ^2, adhesion degradation, reduction in space factor at core, and since the cost is increased, the adhesion amount of the organic insulating film is 20 g / m ² or less Is preferable.

Next, a suitable manufacturing method of the electromagnetic steel sheet with an organic insulating film according to the present invention will be described. The electromagnetic steel sheet with an organic insulating coating according to the present invention can be produced by applying a coating agent for an insulating coating to the electrical steel sheet and baking it. First, a coating agent for an insulating coating used for manufacturing an electromagnetic steel sheet with an organic insulating coating will be described.

The insulating coating coating agent used for manufacturing an electromagnetic steel sheet with an organic insulating coating has a period reduction start temperature of 120 ° C. or higher and 200 ° C. or lower in a rigid pendulum test. The period in the rigid pendulum test is measured by the rigid pendulum test specified in ISO12013-1 and ISO12013-1 and 2. The temperature at which the cycle starts to decrease in the rigid pendulum test is one of the indexes showing the curing behavior. When the lowering start temperature is 120 ° C. or higher, the coating agent sufficiently cures during baking. Therefore, an organic insulating coating having a coating hardness capable of suppressing defects during handling and having excellent flaw resistance can be obtained. Can be formed. On the other hand, if the period does not decrease even if it exceeds 200 ° C., the coating agent cannot be sufficiently cured, and therefore the flaw resistance of the organic insulating coating formed by using the coating agent is inferior. The cycle lowering start temperature in the rigid pendulum test is preferably 125 ° C. or higher, more preferably 130 ° C. or higher. The temperature at which the cycle starts to decrease in the rigid pendulum test is preferably 195 ° C. or lower, more preferably 180 ° C. or lower.

The coating agent for an insulating coating of the present invention may satisfy the above-mentioned characteristics, and is not limited to any other requirements. Examples of the coating agent satisfying the above characteristics include a coating agent in which (A) an aqueous carboxyl group-containing resin and (B) one or more cross-linking agents selected from melamine, isocyanate and oxazoline are blended. Will be done. Further, the type of the aqueous carboxyl group-containing resin (A) is not limited at all, and any aqueous resin containing a carboxyl group can be applied, for example, epoxy resin (a1) and amines (a1). An example is a reaction product obtained by polymerizing a modified epoxy resin obtained by reacting a2) with a vinyl monomer component containing a carboxyl group-containing vinyl monomer (a3).

In one example, the coating agent for forming an insulating film is
A coating agent for forming an insulating film containing the following components (A) and (B) in a solvent.
The coating agent for forming an insulating film may have a total amount of the following components (A) and (B) in terms of solid content with respect to the total solid content contained in the coating agent, which accounts for 95% by mass or more and 100% by mass or less.
(A) Aqueous carboxyl group-containing resin: 100 parts by mass in terms of solid content,
(B) One or more cross-linking agents selected from the group consisting of melamine, isocyanate and oxazoline: 30 parts by mass or more and 300 parts by mass or less in terms of solid content with respect to 100 parts by mass in terms of solid content in (A) above.

Hereinafter, an example of each component contained in the coating agent for forming an insulating film will be described.

(A) Water-based carboxyl group-containing resin In one embodiment, the coating agent for forming an insulating film contains a water-based carboxyl group-containing resin. In the present specification, the water-based resin is a general term for a water-dispersible resin and a water-soluble resin. In the present embodiment, by using an aqueous resin, the amount of volatile organic solvent generated during the formation of the insulating film can be reduced as much as possible.

The type of the aqueous carboxyl group-containing resin (A) is not particularly limited, and any aqueous resin containing a carboxyl group can be applied. Since the water-based carboxyl group-containing resin (A) has a carboxyl group, a crosslink is preferably formed between the water-based carboxyl group-containing resin (A) and the cross-linking agent (B) to improve the flaw resistance of the insulating coating. It can be enhanced, and the adhesion between the insulating coating and the electromagnetic steel plate can be enhanced. The aqueous carboxyl group-containing resin (A) contains, for example, a carboxyl group-containing vinyl monomer (a3) with respect to an aqueous modified epoxy resin obtained by reacting an epoxy resin (a1) with amines (a2). The reaction product obtained by polymerizing the vinyl monomer component to be used is preferably applied.

The modified epoxy resin obtained by modifying the epoxy resin (a1) with amines (a2) is an aqueous system in which a part of the epoxy group of the epoxy resin (a1) undergoes a ring-opening addition reaction with the amino group of the amines (a2). It becomes the resin of. When the epoxy resin (a1) is modified with amines (a2) to obtain a water-based modified epoxy resin, the compounding ratio of the epoxy resin (a1) and the amines (a2) is 100 parts by mass of the epoxy resin (a1). ), It is preferable that the amines (a2) are 3 parts by mass or more and 30 parts by mass or less. By setting the amount of amines to 3 parts by mass or more, a sufficient amount of polar groups can be secured, so that the adhesion of the coating film is improved. Further, by setting the amount of amines to 30 parts by mass or less, it is possible to provide a film having excellent water resistance and organic solvent resistance.

The epoxy resin (a1) is not particularly limited, and various known epoxy resins can be used. Specifically, as the epoxy resin (a1), a bisphenol type epoxy resin, a novolak type epoxy resin, a polyhydric alcohol glycidyl ether, or the like can be used.

Examples of the bisphenol type epoxy resin include reaction products of bisphenols and haloepoxides.

Examples of the bisphenols include reaction products of phenol or 2,6-dihalophenol and aldehydes such as formaldehyde and acetaldehyde; phenol or 2,6-dihalophenol, acetone, acetophenone, cyclohexanone, benzophenone and the like. Reaction products with ketones; peroxides of dihydroxyphenylsulfide; and etherification reactions between hydroquinones and the like.

Examples of the haloepoxides include epichlorohydrin and β-methylepichlorohydrin.

As the bisphenol type epoxy resin, specifically, a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, and the like can be preferably used.

Examples of the novolak type epoxy resin include reaction products of novolak type phenol resin and epichlorohydrin. The novolak type phenol resin can be synthesized from phenol, cresol and the like.

Examples of the polyhydric alcohol glycidyl ethers include 1,4-butanediol, 1,6-hexanediol, trimethylolpropane, cyclohexanedimethanol, and hydrogenated bisphenol (type A and type F). ), And those using polyalkylene glycols and the like. Examples of polyalkylene glycols include polyethylene glycol, polypropylene glycol, polybutylene glycol and the like.

Further, as the epoxy resin (a1), in addition to the above, a known epoxy resin such as polybutadiene diglycidyl ether can also be applied. Further, various known epoxidized oils, dimer acid glycidyl ester and the like can be used in order to impart flexibility to the film.

As the epoxy resin (a1), any one of the above can be used alone, or two or more of them can be used in combination. The epoxy resin (a1) is preferably a bisphenol type epoxy resin. If the epoxy resin (a1) is a bisphenol type epoxy resin, it is possible to provide a film having particularly excellent adhesion to an electromagnetic steel sheet.

The epoxy equivalent of the epoxy resin (a1) is preferably 100 or more and 3000 or less, although it depends on the molecular weight of the finally obtained aqueous carboxyl group-containing resin (A). When the epoxy equivalent of the epoxy resin (a1) is 100 or more, the cross-linking reaction with the cross-linking agent (B) does not become extremely fast, so that the workability when applying the coating agent is good. On the other hand, when the epoxy equivalent of the epoxy resin (a1) is 3000 or less, the workability in producing the water-based carboxyl group-containing resin (A) is good, and the water-based carboxyl group-containing resin (A) gels. It doesn't get easier.

As the amines (a2), various known amines can be applied. Examples thereof include alkanolamines, aliphatic amines, aromatic amines, alicyclic amines, and aromatic nucleus-substituted aliphatic amines. Any one of these amines can be used alone, or two or more of these amines can be used in combination.

Examples of the alkanolamines include ethanolamine, diethanolamine, diisopropanolamine, di-2-hydroxybutylamine, N-methylethanolamine, N-ethylethanolamine, N-benzylethanolamine and the like.

Examples of the aliphatic amines include ethylamine, propylamine, butylamine, hexylamine, octylamine, laurylamine, stearylamine, palmitylamine, oleylamine, and elcilamine.

Examples of the aromatic amines include toluidine, xylidine, kumidin (isopropylaniline), hexylaniline, nonylaniline, dodecylaniline and the like.

Examples of the alicyclic amines include cyclopentylamine, cyclohexylamine, norbornylamine and the like.

Examples of the aromatic nucleus-substituted aliphatic amines include benzylamine and phenethylamine.

Among the above-mentioned amines, alkanolamines are particularly preferable from the viewpoint of contributing to the hydrophilicity of the resin.

As described above, the vinyl monomer component containing the carboxyl group-containing vinyl monomer (a3) is polymerized with the water-based modified epoxy resin obtained by modifying the epoxy resin (a1) with amines (a2). Therefore, the aqueous carboxyl group-containing resin (A) is obtained. That is, among the water-based modified epoxy resins, a part of the epoxy group that has not reacted with the amino group reacts with a part of the carboxyl group of the vinyl monomer component to obtain the water-based carboxyl group-containing resin. In addition, in the polymerization, a known polymerization initiator such as an azo compound can be used.

The carboxyl group-containing vinyl monomer (a3) is not particularly limited as long as it is a monomer having a carboxyl group as a functional group and having a polymerizable vinyl group, and known ones are applied. Can be done. Specific examples thereof include carboxyl group-containing vinyl monomers such as (meth) acrylic acid, maleic acid, maleic anhydride, fumaric acid, and itaconic acid.

The vinyl monomer component containing the carboxyl group-containing vinyl monomer (a3) may contain various vinyl monomer components in addition to the above-mentioned carboxyl group-containing vinyl monomer (a3). For example, a styrene-based monomer may be contained as a vinyl monomer component other than the carboxyl group-containing vinyl monomer (a3). By containing the styrene-based monomer, the stability of the vinyl monomer component containing the carboxyl group-containing vinyl monomer (a3) during production and storage can be improved. The content of the carboxyl group-containing vinyl monomer is preferably 0% by mass or more and 10% by mass or less with respect to the entire vinyl monomer component containing the carboxyl group-containing vinyl monomer (a3).

When polymerizing a vinyl monomer component containing a carboxyl group-containing vinyl monomer (a3) to the above water-based modified epoxy resin to obtain an aqueous carboxyl group-containing resin, the epoxy resin (a1) and the carboxyl group-containing vinyl simple substance are used. The compounding ratio of the weight component (a3) is such that the vinyl monomer is 5 parts by mass or more and 100 parts by mass or less in terms of solid content with respect to 100 parts by mass of the epoxy resin (a1) in terms of solid content. It is preferable to do so. This is because when the blending amount of the vinyl monomer is 5 parts by mass or more, the wettability of the coating film is good, and when it is 100 parts by mass or less, the water resistance and the organic solvent resistance of the coating film are preferable.

The method for producing the aqueous carboxyl group-containing resin (A) is not particularly limited, but the following procedure is preferable. After dissolving the epoxy resin (a1) at a high temperature, amines (a2) are added and reacted to obtain an aqueous modified epoxy resin. Next, a carboxyl group-containing vinyl monomer (a3) is added to the obtained aqueous modified epoxy resin to keep it warm. Then, it is cooled, and a neutralizing agent and water are sequentially added and mixed to obtain an aqueous carboxyl group-containing resin (A).

As the solvent used in the preparation of the water-based carboxyl group-containing resin (A), water is preferably used from the viewpoint of making the finally obtained water-based carboxyl group-containing resin water-based. Further, a small amount of a hydrophilic solvent can be mixed with water before use. Specific examples of the hydrophilic solvent include propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono n-butyl ether, propylene glycol mono t-butyl ether, dipropylene glycol monomethyl ether, methyl cellosolve, ethyl cellosolve, and n-. Glycol ethers such as butyl cellosolve and t-butyl cellosolve; and alcohols such as isopropyl alcohol and butyl alcohol. Any one of these hydrophilic solvents can be used alone, or two or more of them can be used in combination. The hydrophilic solvent is preferably 5% by mass or more and 20% by mass or less with respect to the entire coating agent. When the amount of the hydrophilic solvent is within the above range, the storage stability of the coating agent is good.

At the time of producing the aqueous carboxyl group-containing resin (A), various known amines can be applied as a neutralizing agent. Examples of the neutralizing agent include alkanolamines, aliphatic amines, aromatic amines, alicyclic amines, aromatic nucleus-substituted aliphatic amines and the like. One of these neutralizers can be used alone, or two or more of these neutralizers can be used in combination. Among the above neutralizers, monoethanolamine, diethanolamine, monoisopropanolamine, diisopropanolamine, N-methylethanolamine, N-ethylethanolamine, etc. are particularly good because of their good stability after hydration. Alkanolamines are preferred. Further, it is preferable to adjust the pH of the aqueous carboxyl group-containing resin (A) solution to 6 to 9 by adding a neutralizing agent.

(B) One or more cross-linking agents selected from melamine, isocyanate and oxazoline The cross-linking agent cross-links the aqueous carboxyl group-containing resin (A) to enhance the flaw resistance of the insulating coating, and also serves as the insulating coating. It is contained in the coating agent for the purpose of improving the adhesion with the electromagnetic steel plate. As the cross-linking agent, one or more cross-linking agents selected from melamine, isocyanate and oxazoline, which react with the carboxyl group and the epoxy group of the aqueous carboxyl group-containing resin (A) to cause a cross-linking reaction, are used. As the melamine, for example, methylated melamine, butylated melamine and the like can be used. As the isocyanate, hexamethylene diisocyanate, isocyanate type polyisocyanate derived from hexamethylene diisocyanate and the like can be used. The oxazoline is not particularly limited as long as it is a compound having an oxazoline ring.

The coating agent according to the present embodiment is obtained by adding one or more cross-linking agents (B) selected from melamine, isocyanate and oxazoline to 100 parts by mass of the solid content of the aqueous carboxyl group-containing resin (A). It is contained in the range of 30 parts by mass or more and 300 parts by mass or less in terms of minutes. When the amount of the cross-linking agent (B) is less than 30 parts by mass with respect to 100 parts by mass of the solid content of the water-based carboxyl group-containing resin (A), the scratch resistance of the formed insulating film is lowered. On the other hand, when the amount of the cross-linking agent (B) is more than 300 parts by mass with respect to 100 parts by mass of the solid content of the water-based carboxyl group-containing resin (A), the insulating film is remarkably cured due to the increase in the cross-linking density. Punchability and adhesion are reduced. Therefore, the amount of the cross-linking agent (B) is 30 parts by mass or more and 300 parts by mass or less with respect to 100 parts by mass of the solid content of the aqueous carboxyl group-containing resin (A). The amount of the cross-linking agent (B) with respect to 100 parts by mass of the solid content of the aqueous carboxyl group-containing resin (A) is preferably 50 parts by mass or more and 150 parts by mass or less, more preferably 80 parts by mass or more and 100 parts by mass in terms of solid content. It is as follows.

Since isocyanate has low stability in water, when isocyanate is used as a cross-linking agent, it is preferable to mix the isocyanate immediately before using the coating agent for forming an insulating film.

Solvent In this embodiment, the above components (A) and (B) are contained in the solvent. The solvent preferably used as the solvent is water, a hydrophilic solvent, and a mixture of water and a hydrophilic solvent. Specific examples of the hydrophilic solvent include propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono n-butyl ether, propylene glycol mono t-butyl ether, dipropylene glycol monomethyl ether, methyl cellosolve, ethyl cellosolve, and n-. Glycol ethers such as butyl cellosolve and t-butyl cellosolve; and alcohols such as isopropyl alcohol and butyl alcohol. A small amount of the solvent used for preparing the resin can be mixed with the solvent. The content of the solvent in the coating agent for forming an insulating film is not particularly limited, but is preferably 40% by mass or more and 90% by mass or less. That is, the amount of the solid content in the coating agent is preferably 10% by mass or more and 60% by mass or less. When the amount of solvent and solid content in the coating agent is within the above range, the storage stability of the coating agent and the workability when applying the coating agent to the steel sheet are good.

Other Components The coating agent for forming an insulating film according to the present embodiment contains components other than the above components (A) and (B) in an amount of 5% by mass or less in terms of solid content with respect to the total solid content of the coating agent. You may. That is, the total amount of the above components (A) and (B) in terms of solid content with respect to the total solid content contained in the coating agent accounts for 95% by mass or more and 100% by mass or less. As described above, in a coating agent containing a large amount of an inorganic pigment such as an aluminum-containing oxide, when an electromagnetic steel sheet with an insulating coating is manufactured using the coating agent, the coating surface unevenness due to the presence of the inorganic pigment It was found that the voids generated between the steel plates of the laminated core lead to a decrease in the space factor. On the other hand, in the present invention, the coating agent in which the total amount of the above components (A) and (B) in terms of solid content with respect to the total solid content contained in the coating agent accounts for 95% by mass or more and 100% by mass or less, that is, By using the coating agent whose solid content is substantially composed of the above components (A) and (B), the coating surface unevenness due to the presence of the inorganic pigment does not appear. Therefore, according to the coating agent of the present invention, the insulating film can be formed without impairing the space factor of the electromagnetic steel sheet in the laminated iron core. The total amount of the above components (A) and (B) in terms of solid content with respect to the total solid content contained in the coating agent is preferably 96% by mass or more, and more preferably 98% by mass or more.

Other components that can be contained in the coating agent for forming an insulating coating include, for example, surfactants, rust preventives, lubricants, defoaming agents, which are added to further improve the performance and uniformity of the insulating coating. And antioxidants and the like. In addition, known coloring pigments and extender pigments can also be contained in a solid content of 5% by mass or less and within a range that does not deteriorate the performance of the insulating coating.

Method for Producing Coating Agent The method for producing the coating agent according to the present embodiment is not particularly limited, but the following procedure is preferable. A part of the aqueous carboxyl group-containing resin (A) is charged in the disperser, and water and, if necessary, a hydrophilic solvent are added to uniformly disperse the resin. Then, the remainder of the aqueous carboxyl group-containing resin (A) and the cross-linking agent (B) are added and dispersed. If necessary, a leveling agent, a neutralizing agent, water, and an antifoaming agent are added to the obtained dispersion to obtain a coating agent.

Electromagnetic steel sheet The type of electromagnetic steel sheet to which the coating agent is applied is not particularly limited. For example, so-called soft iron plates (electric iron plates) with high magnetic flux density, general cold-rolled steel sheets such as SPCC, non-oriented electrical steel sheets containing Si or Al to increase specific resistance, and grain-oriented electrical steel sheets are used. be able to.

The thickness of the electromagnetic steel sheet is also not particularly limited. If the steel sheet is made thin, the iron loss is reduced, but if it is too thin, the shape stability is lowered and the manufacturing cost of the steel sheet is increased. Therefore, the thickness of the steel sheet is preferably 50 μm or more. As the plate thickness increases, the iron loss increases accordingly. Further, by reducing the plate thickness, it is possible to integrate the steel plate by caulking or welding without applying the adhesive film. Therefore, the plate thickness is preferably 1 mm or less, and more preferably 0.5 mm or less.

The pretreatment of the electrical steel sheet before applying the coating agent is not particularly limited. A coating agent can be applied to the untreated electromagnetic steel plate, but preferably, the electromagnetic steel plate is subjected to a degreasing treatment such as alkaline degreasing or a pickling treatment using an acid such as hydrochloric acid, sulfuric acid or phosphoric acid. Then apply the coating agent.

As a method of applying the coating agent, various methods such as roll coating, flow coating, knife coating, bar coating, and spray can be used.

The amount of the coating agent applied to the electromagnetic steel sheet is preferably 0.9 g / m ² or more, and more preferably 5.0 g / m ² or more in terms of the amount of the insulating film adhered after baking. The cost of the coating material increases as the coating amount of the insulating coating increases, and the space factor of the electromagnetic steel sheet in the laminated iron core decreases due to the thick coating. From the above viewpoint, the amount of the coating agent applied to the electrical steel sheet is preferably 100 g / m ² or less, more preferably 50 g / m ² or less, still more preferably 20 g / m ² or less in terms of the amount of the insulating film adhered after baking. It shall be m ² or less.

The amount of the insulating film adhered after baking can be measured from the change in the weight of the electromagnetic steel sheet before and after the insulating film is melted by dissolving only the insulating film from the electromagnetic steel sheet with the insulating film with thermal alkali or the like (weight method). ).

The baking method after applying the coating agent to the electromagnetic steel sheet is also not particularly limited, and a baking method such as a hot air method, an infrared heating method, or an induction heating method, which is usually performed, can be applied.

The baking temperature can be in a generally practiced temperature range, for example, the maximum temperature of the steel sheet can be 150 ° C. or higher and 350 ° C. or lower. In order to avoid thermal decomposition of the coating agent, it is preferable that the maximum temperature of the steel sheet reached is 150 ° C. or higher and 300 ° C. or lower. Further, the baking time in the baking step, that is, the time from the start of heating to reaching the maximum temperature of the steel sheet is not particularly limited, but is preferably about 10 to 60 seconds. After reaching the maximum temperature of the steel sheet, it is preferable to cool it to room temperature without particular limitation.

[Manufacturing of water-based carboxyl group-containing resin]
The aqueous carboxyl group-containing resin (A) was prepared by the following procedure. A bisphenol A type epoxy resin (epoxy resin (a1)) was dissolved at 100 ° C., diethanolamine (amines (a2)) was added, and the mixture was reacted for 5 hours to prepare an aqueous modified epoxy resin. Next, acrylic acid (carboxyl group-containing vinyl monomer (a3)) or styrene (vinyl monomer other than (a3)) is added to the obtained aqueous modified epoxy resin, and then the mixture is kept warm at 130 ° C. for 4 hours. did. Then, the mixture was cooled to 80 ° C., and a neutralizing agent (diethanolamine) and water were sequentially added and mixed to obtain an aqueous carboxyl group-containing resin (A). The vinyl monomers other than the amines (a2), the carboxyl group-containing vinyl monomer (a3), and (a3) have a solid content equivalent to 100 parts by mass of the epoxy resin (a1) in terms of solid content. The reaction was carried out in parts by mass shown in Table 1.

[Manufacturing of coating agent for insulating coating]
For the various aqueous carboxyl group-containing resins (A) and cross-linking agents (B) obtained above, and for Invention Example 19 and Comparative Example 8, further kaolinite (kaolin manufactured by Takehara Chemical Industry Co., Ltd .; Al-containing oxide) was added below. A coating agent having the composition (solid content equivalent) shown in Table 1 was prepared by mixing according to the procedure of.

For Invention Examples 1 to 18 and Comparative Examples 3 to 7 and 9, first, an aqueous carboxyl group-containing resin (A), water, and a hydrophilic solvent (butyl cellosolve) which is 10% by mass of the whole coating agent are charged and uniformly charged. It was mixed until it became. Then, methylated melamine (Simel 303LF manufactured by Ornex Co., Ltd., cross-linking agent (B)) was added and dispersed. Then, diethanolamine was added as a neutralizing agent, and water was added to adjust the solid content concentration in the coating agent.

For Comparative Examples 1 and 2, after methylated melamine was added and dispersed, water sol D-720 (manufactured by DIC Corporation) was added and dispersed as an acrylic resin before adding diethanolamine as a neutralizing agent. A coating agent was prepared in the same manner as in Examples 1 to 18 of the above invention and Comparative Examples 3 to 7 and 9 except for the above.

In Invention Example 19 and Comparative Example 8, first, a part of the aqueous carboxyl group-containing resin (A) is charged, and kaolinite (Al-containing oxide), water, and a hydrophilic solvent which is 10% by mass of the whole coating agent are prepared. (Butyl cellosolve) was placed in a disperser and uniformly dispersed, and the particle size of kaolinite (Al-containing oxide) measured with a tube gauge was reduced to 20 μm or less. Then, the remainder of the aqueous carboxyl group-containing resin (A) and methylated melamine (Simel 303LF manufactured by Ornex Co., Ltd., cross-linking agent (B)) were added and dispersed to obtain a dispersion. Then, diethanolamine was added as a neutralizing agent, and water was added to adjust the solid content concentration in the coating agent.

The solid content concentration of each coating agent was adjusted to 50% by mass, and the pH was adjusted to 8.5.

Table 1 shows the compounding ratios of the aqueous carboxyl group-containing resin (A), the cross-linking agent (B), and the Al-containing oxide in the coating agent. In Table 1, the parts by mass of the cross-linking agent (B) and the Al-containing oxide are shown as parts by mass (in terms of solid content) with respect to 100 parts by mass of the aqueous carboxy group-containing resin (A). Further, in Table 1, the solid content-equivalent contents of the aqueous carboxyl group-containing resin (A), the cross-linking agent (B), and the Al-containing oxide with respect to the total solid content contained in the coating agent are each in mass%. Shown.

In Comparative Example 10, a resole-type phenol resin (PC-1, manufactured by Sumitomo Bakelite Co., Ltd.), titanium oxide (Titania TTO-55 (D), manufactured by Ishihara Sangyo Co., Ltd.) and an antifoaming agent (KM-made by Shinetsu Silicone Co., Ltd.) 7750) was added and dispersed. Then, diethanolamine was added as a neutralizing agent, and the pH was adjusted to 8.5. Then, water was added to adjust the solid content concentration in the coating agent to 50% by mass to obtain a coating agent. Table 1 shows the compounding ratios of the resole-type phenol resin, titanium oxide, and the antifoaming agent. In Table 1, the contents of the resole-type phenol resin, titanium oxide, and the defoaming agent in terms of solid content with respect to the total solid content contained in the coating agent are shown in mass%, respectively.

[Manufacturing of electrical steel sheets with organic insulating film]
A steel sheet having a width of 150 mm and a length of 300 mm was cut out from a non-oriented electrical steel sheet having a thickness of 0.5 mm and used as a test material. The electromagnetic steel sheet was immersed in an aqueous sodium orthosilicate aqueous solution (concentration 0.8% by mass) at room temperature for 30 seconds, then washed with water and dried. The surface (both sides) of the test material subjected to this pretreatment is coated with various insulating coating coating agents manufactured as described above with a roll coater, baked in a hot air baking furnace, and then allowed to cool at room temperature. An electromagnetic steel sheet with an organic insulating film was obtained. Table 1 shows the maximum temperature of the steel sheet reached during baking and the amount of the organic insulating film adhered after baking.

The characteristics of the insulating coating of the electromagnetic steel sheet with an organic insulating coating and the laminated electromagnetic steel sheet manufactured as described above were evaluated as follows. The evaluation results are shown in Table 1.

<Temperature at which the cycle starts to decrease in the rigid pendulum test>
According to ISO12013-1 and ISO12013-1, a rigid pendulum type physical property tester RPT-3000W manufactured by A & D Co., Ltd. was used, and the decrease start temperature of the cycle was measured using a coating agent for an insulating coating as a sample. The rate of temperature rise during the measurement was 12.5 ° C./min. A cylinder edge was used as the edge of the pendulum.

<Martens hardness>
The Martens hardness of the surface of the insulating film was measured using an ultrafine hardness tester HM2000 manufactured by Fisher Instruments. The measurement was performed at room temperature (25 ° C.) using a diamond quadrangular pyramid type Vickers indenter having a facing angle of 136 degrees. Martens hardness was calculated from the slope of the load-dent depth curve.

<Insulation (interlayer resistance test)>
The interlayer resistance value of the insulating coated steel sheet was measured in accordance with the interlayer resistance test (method A) specified in JIS C 2550 (2000). The evaluation criteria are as follows. If it was ◎, ○, or △, it was accepted.
(Criteria)
⊚: Interlayer resistance value 200 [Ω ・ cm ² / sheet] or more ○: Interlayer resistance value 100 [Ω ・ cm ² / sheet] or more, less than 200 [Ω ・ cm ² / sheet] Δ: Interlayer resistance value 50 [Ω ・ ・cm ² / sheet or more, less than 100 [Ω · cm ² / sheet] ×: Interlayer resistance value less than 50 [Ω · cm ² / sheet]

<Adhesion>
A cellophane adhesive tape is attached to the surface of the steel sheet with an insulating film to be tested, and the steel sheet is bent 180 ° using a round bar having a diameter of 5 mm with the surface to be tested as the compression side, and then the cellophane adhesive tape is peeled off. The film peeling area was calculated and evaluated. The evaluation criteria are as follows. If ○ or △, it was accepted.
(Criteria)
〇: Film peeling area <5%
Δ: Slight film peeling: 5% ≤ film peeling area <10%
X: Film peeling area ≥ 10%

<Punchability>
Using a 15 mmφ steel die, the steel sheet with an insulating coating was repeatedly punched, and the number of punches until the burr height reached 50 μm was measured. The evaluation criteria are as follows. If it was ◎, ○, or △, it was accepted.
(Criteria)
⊚: Number of punches 2 million or more ○: Number of punches 1 million or more and less than 2 million Δ: Number of punches 500,000 or more and less than 1 million ×: Number of punches less than 500,000

<Scratch resistance>
Two types of electromagnetic steel sheets with an insulating coating adjusted to a size of width: 100 mm and length: 200 mm were prepared. One side of each of the two electrical steel sheets with an insulating coating is used as a test surface, and the test surfaces are overlapped with each other and slid at a pressure of 2 kg / cm ² and a relative speed of 2 cm / s for 10 seconds to visually check the surface defects on the test surface. Observed by. The evaluation criteria are as follows. If it was ◎, ○, or △, it was accepted.
(Evaluation criteria)
⊚: Almost no scratches are observed ○: Some scratches are observed △: Scratches are clearly observed ×: Scratches are observed to the extent that the ground iron is exposed

<Space factor>
The space factor was measured according to JIS 2550-5 (2011).
That is, a laminated test piece having a thickness of 6 mm or more by stacking Epstein test pieces (width 30 mm, length 290 mm) from which shear burrs have been removed is placed between the rams of the compressor. The surface area of the ram shall be an area that can completely cover the laminated body of the test pieces. A pressure of (1.00 ± 0.05) MPa was applied to the laminated body of the test pieces, and the lengths of the four sides of the laminated body were measured.
The space factor was calculated using the formula shown below.
Space factor (%) = 100 x total mass of test pieces (kg) / density of test pieces (kg / m ³ ) x average width of test pieces (m) x average length of test pieces (m) x distance between rams Distance (m)
If the space factor is 96% or more, it is considered as acceptable.

<Surface roughness Ra>
The surface roughness (arithmetic mean roughness) Ra was measured in the width direction of the steel sheet using a stylus type surface roughness meter in accordance with JIS B 0601.
If the surface roughness Ra was 0.3 μm or less, it was judged as acceptable.

As shown in Table 1, in the electromagnetic steel sheet with an organic insulating film according to the present invention and the laminated electromagnetic steel sheet prepared by using the electromagnetic steel sheet, good results were obtained in all the evaluation items. In the insulating coating and the laminated electromagnetic steel sheet of the comparative example, the adhesion, punching property, scratch resistance, or space factor of the insulating coating was inferior to that of the example of the present invention. Regarding the temperature at which the cycle starts to decrease in the rigid pendulum test in Table 1, "does not decrease" means that the cycle in the rigid pendulum test did not decrease even if the temperature was changed.

Claims (2)

An electromagnetic steel sheet with an organic insulating coating having an organic insulating coating having a Martens hardness of 300 N / mm ² or more and less than 600 N / mm ² and an arithmetic mean roughness Ra of 0.3 μm or less. The electromagnetic steel sheet with an organic insulating coating according to claim 1, wherein the amount of adhesion of the organic insulating coating on one side is 0.9 g / m ² or more and 20 g / m ² or less.