JPH07286282A - Silicon steel sheet having electrically insulated film excellent in oilless punching property - Google Patents

Abstract

PURPOSE:To produce a silicon steel sheet having an electrically insulated film excellent in electrical insulating properties, adhesion, punching properties and corrosion resistance. CONSTITUTION:This is a silicon steel sheet having an electrically insulated film on the surface. The surface of a silicon steel sheet is coated with a treating soln. contg. a soln. with primary organic resin as solid content, an aq. soln. of chromate contg. at least on kind of bivalent metals and an organic reducing agent, and baking is executed. It is coated with a soln. with secondary organic resin as solid content in the process of cooling the silicon steel sheet. After the coating, it is furthermore cooled to concentrate the resin on the surface of the insulated film, by which the silicon steel sheet having an electrically insulated film excellent in oilless punching properties can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrical insulating coating containing an organic resin as an insulating coating of an electromagnetic steel sheet, and particularly as an environmentally friendly product which has been attracting attention in recent years, an electromagnetic steel sheet excellent in punching property without using punching oil. Regarding the product.

[0002]

2. Description of the Related Art The properties required for an insulating coating of an electromagnetic steel sheet include a large number of properties such as electric insulation, adhesion, punchability, weldability and corrosion resistance. Many studies have been conducted in order to satisfy these requirements, and many techniques have been proposed for a method of forming an insulating coating on the surface of an electromagnetic steel sheet and an insulating coating composition.

In particular, a laminated coating or composite coating of chromate-based and organic resin can significantly improve the punchability of the steel sheet as compared with the conventional phosphate-based and chromate-based inorganic coatings. It is used a lot. For example, Japanese Patent Publication 6
No. 0-36476 discloses a dichromate-based aqueous solution containing at least one divalent metal and Cr in the aqueous solution.
O ₃ : Vinyl acetate / as an organic resin with respect to 100 parts by weight
Applying a treatment liquid in which a resin emulsion having a Veova ratio of 90/10 to 40/60 at a resin solid content of 5 to 120 parts by weight and an organic reducing agent at a ratio of 10 to 60 parts by weight is applied to the surface of a base iron plate. However, a method for forming an insulating coating on an electromagnetic steel sheet is disclosed, which is obtained through a baking process according to a conventional method.

Further, JP-A-62-100561 discloses an aqueous emulsion having a pH of 2 to 8 and an acrylonitrile obtained by emulsifying and dispersing an organic film-forming resin composed of one or both of an acrylic resin and an acrylic-styrene resin. An aqueous dispersion having a pH of 6 to 8 containing substantially no emulsifying dispersant in which the system resin is dispersed is mixed so that the non-volatile matter of the latter is 10 to 90 wt% with respect to the total amount of the non-volatile matter of both. The obtained mixed resin solution was added to an aqueous solution of an inorganic film-forming substance containing chromate as a third component, and the non-volatile content of the mixed resin solution was 100 parts by weight of the chromate in the aqueous solution in terms of CrO _3. The composition is added and mixed so as to be 15 to 120 parts by weight, and the composition for forming an electrical steel sheet insulating coating thus obtained is applied to an electrical steel sheet, and the temperature is 300 ° C to 5 ° C.
Heat at a temperature of 00 ° C to form an insulating coating of 0.4 to 2.0 g /
Disclosed is a method for forming an insulating coating on a magnetic steel sheet, which is characterized in that it is formed in the range of m ² .

[0005]

As organic resins to be blended with the above-mentioned chromic acid-based agents, vinyl acetate resins, Veova (abbreviation of Versatec acid vinyl ester) resins, acrylic resins, polystyrene resins, acrylonitrile resins have been used. Thermoplastic resins such as polyester resin and polyethylene resin are used. The thermal decomposition reaction of these thermoplastic resins starts at a relatively low temperature in the baking process, so the amount of resin remaining in the film decreases due to decomposition gas, and the punchability of the electrical steel sheet with an insulating film does not improve. It was. Further, when the compounding amount of the resin is increased, the resins are fused to each other at the time of baking the film and the film after baking shows good corrosion resistance. However, when strain relief annealing is performed in a nitrogen atmosphere of 750 ° C. × 2 Hr. There is a defect that the resin mass is carbonized and decomposed to lower the strength of the coating and reduce the adhesion of the coating. In order to solve these problems, use of a thermosetting organic resin having a crosslinked structure and having a high temperature at which a thermal decomposition reaction starts can be considered. However, most uncrosslinked thermosetting resins contain a large number of reactive groups such as hydroxyl groups and epoxy groups in the molecule. Therefore, when this is mixed with a chromate drug, a reaction occurs, resulting in gelation. To do. That is,
This causes another serious problem in industrial practice that the storage stability of the coating solution before forming the electrically insulating coating is deteriorated. Moreover, it is difficult to disperse the resin in the aqueous medium as fine particles, and it has not been put to practical use that the resin which has been subjected to a thermosetting reaction in advance is used.

Therefore, the present inventors have found a thermosetting resin that does not cause gelation even if it is mixed with a chromate-based drug,
The inventors have invented an electromagnetic steel sheet having a resin as a coating and having good weldability, and filed an application for it. However, since an electromagnetic steel sheet having good weldability does not always have good punchability, oil is applied to the surface of the steel sheet to perform punching to improve punchability when punching and forming. However, the applied oil must be dissolved and removed in a solvent or the like before it is made into a product after punching, and the drainage of these causes environmental pollution.

[0007]

In order to solve the above problems, the inventors of the present invention have invented a magnetic steel sheet having a high punching property and no environmental pollution problem even if oil is not applied to the surface of the steel sheet.

That is, the present invention is a method for producing an electromagnetic steel sheet having an electrically insulating coating on its surface, which comprises a liquid containing a first organic resin as a solid content and chromic acid containing at least one divalent metal. A treatment solution containing a salt-based aqueous solution and an organic reducing agent is applied to the surface of the electromagnetic steel sheet, baked, and a solution having a second organic resin as a solid content is applied during the cooling step of the electromagnetic steel sheet,
(EN) Provided is an electromagnetic steel sheet having an electric insulating coating excellent in oilless punching property, which is characterized by further cooling after coating.

The first or second organic resin is vinyl acetate resin, Veova resin, acrylic resin, polyethylene resin, acrylonitrile resin, polyester resin, polystyrene resin, epoxy resin, phenoxy resin, polyamide-imide resin, urethane resin, It is preferable that the organic resin is one or two or more selected from the group consisting of a phenol resin and a cresol resin, or an organic resin which is a copolymer of two or more selected from the group.

It is preferable that the first or second organic resin is an emulsion composed of resin particles capable of forming a crosslinked structure in which an outer layer is formed by coating with a resin having a chromic acid resistance.

It is preferable that the first organic resin is an emulsion composed of thermosetting resin particles whose outer layer is formed by coating with a resin having chromium acid resistance.

The amount of the liquid containing the second organic resin as the solid content applied to the surface of the magnetic steel sheet is preferably 0.2 to 1.0 g / m ² as the solid content.

In the step of applying the liquid containing the second organic resin as a solid content on the surface of the electromagnetic steel plate, the plate temperature of the steel plate is 60 to
It is preferable that the step of applying is performed at 300 ° C.

The electromagnetic steel sheet of the present invention has a first coating film applied and baked on the surface of the steel sheet and a second coating film after the first coating film baking step.
Is further formed on the first coating during the cooling step of the first baking, and is characterized by having two different or identical coatings. By using such a two-layer coating, the surface characteristics of the electrical steel sheet are further improved without impairing the adhesion and weldability of the coating and without reducing the effective thickness of iron when laminated as an electrical steel sheet. Can be made. Therefore, it is possible to obtain a magnetic steel sheet having an electric insulating coating excellent in oilless punching property, which has a good punching property without using punching oil.

The magnetic steel sheet of the present invention is characterized by having two layers as a surface coating, and is manufactured as follows. First, a liquid having a first organic resin as a solid content,
A treatment liquid containing an aqueous chromate solution containing at least one kind of divalent metal and an organic reducing agent is applied to the surface of the magnetic steel sheet. As for the coating, as is usually done after continuously coating the surface of the magnetic steel sheet uniformly with a roll coater,
By baking and curing for a short time at a drying oven atmosphere temperature of 300 to 700 ° C., a desired good electric insulating coating is formed. At this time, the coating amount after baking is 0.2 to 4
g / m ² , but more preferably 0.3 to 3 g / m ^2.
Is. This is because if it is less than 0.2 g / m ² , the coverage of the insulating coating decreases, and if it exceeds 4 g / m ² , the adhesion of the insulating coating deteriorates.

Next, the treatment liquid for the electric insulating coating is applied to a base steel sheet.
It is applied to the surface and baked by a conventional method,
The second organic resin while the plate temperature of the treated steel plate is 300 to 60 ° C.
Is applied as a solid content. The method of application is particularly limited
Not sprayed, electrostatically coated, powder coated, dipped
Although there are coatings, spray coating is preferred. Above 300 ° C
If so, the resin particles will be granulated immediately before they spread on the surface of the steel sheet.
The adhesiveness is reduced and it becomes easier to generate dust, and
Due to the tension pad powder adhering when slitting, dirt is generated
It causes raw defects. When the temperature is lower than 60 ° C, the resin fine particles are
Inadequate drying on the surface of the steel sheet causes sticky trouble
It The steel plate is coated with a second organic resin solid solution
After that, further cool to room temperature. The amount applied is solid
0.2 to 1.0 g / m in terms of minutes²And 0.2 g / m
²If it is less than 1, the oilless punching performance cannot be exhibited.
0 g / m²If it exceeds the limit, baking at the lower limit of plate temperature will be insufficient.
Cause stickiness.

The insulating coating thus obtained is not only excellent in oilless punching property, but also has other properties required for the coating, such as adhesion, electrical insulation, corrosion resistance,
It has also been confirmed that it is sufficiently satisfactory in terms of heat resistance and chemical resistance. The following treatment liquid is used for the first coating film applied and baked on the surface of the steel sheet of the present invention: (a) A liquid containing the first organic resin as a solid content (b) At least one divalent metal Chromic acid aqueous solution (c) Contains an organic reducing agent. As its specific composition, the ratio of the component (a) and the component (b) is preferably Cr in the chromate drug.
The liquid containing the first organic resin as a solid content is added to 100 parts by weight of O ₃ in an amount of 5 to 120 parts by weight, more preferably 20 to 80 parts by weight, as a resin solid content. The addition amount of the component (c) is preferably Cr in the chromic acid-based drug.
10 to 60 parts by weight, more preferably 20 to 50 parts by weight, based on 100 parts by weight of O ₃ .

The first organic resin may be any one, but it is preferable that the first organic resin contains a thermosetting resin capable of forming a crosslinked structure and has chromium acid resistance. Such a resin may form fine particles with a uniform single layer, but may also have a multilayer structure to form fine particles.

In order to control the thermal decomposability of the resin, a crosslinked structure may be formed inside the fine particles. Therefore, a thermosetting resin may be used, but a thermosetting resin capable of forming a crosslinked structure usually has a large amount of functional groups such as a hydroxyl group and an epoxy group in the molecule in a non-crosslinked state, and has a chromic acid resistance. Since it is inferior and gels easily with chromic acid, a resin layer having chromic acid resistance may be present on the surface in contact with chromic acid.

Such resin fine particles are preferably composed of an inner layer (core) made of a thermosetting resin capable of forming a crosslinked structure and an outer layer (shell) made of a resin having a chromic acid resistance.

That is, as the thermosetting resin forming the inner layer (core), phenol resin (phenol / formaldehyde resin, xylenol / formaldehyde resin, cresol / formaldehyde resin, resorcin / formaldehyde resin, etc.), epoxy resin (bisphenol type epoxy resin, Alicyclic epoxy resin, novolac type epoxy resin, aliphatic epoxy resin, epoxidized urethane resin, etc.), furfural resin, urethane resin, unsaturated polyester resin, amino resin, polyimide resin, polyamideimide resin, etc. Other than the above resins, those having a crosslinked structure can be used.

Further, it is essential that the resin having chromium acid resistance that covers the outside of the core is integrated with the thermosetting resin of the core to form an emulsion. A resin formed from an ethylenically unsaturated carboxylic acid and a monomer copolymerizable therewith corresponds to satisfying this condition. Examples of the ethylenically unsaturated carboxylic acid employed here include ethylenically unsaturated monobasic carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid, ethylenic unsaturated dicarboxylic acids such as itaconic acid, maleic acid and fumaric acid. As the basic carboxylic acid and the ethylenically unsaturated monomer, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate,
(Meth) acrylic acid such as 2-ethylhexyl alkyl ester of acrylic acid or methacrylic acid, and other monomer having an ethylenically unsaturated bond which can be copolymerized therewith, for example, styrene, α-methylstyrene, vinyltoluene,
There are t-butyl styrene, ethylene, propylene, vinyl acetate, vinyl chloride, vinyl propionate, acrylonitrile, methacrylonitrile, dimethylaminoethyl (meth) acrylate, vinyl pyridine, acrylamide, etc., and two or more kinds of these monomers. You may use.

The preferred method for producing a core / shell type aqueous emulsion of resin fine particles used in the present invention is described below in JP-A-64-4662 and JP-B-2-12964.
The manufacturing method thereof is disclosed in detail below. Emulsion polymerization is at least two stages of first-stage emulsion polymerization for forming the core resin particles and second-stage polymerization for forming the shell copolymer coating on the surface of the formed core resin particles. The multistage emulsion polymerization of is used. First, in the first emulsion polymerization of the first stage, the core portion is formed. That is, the thermosetting resin used as the microparticles constituting the core portion is easily prepared by dissolving the water-insoluble thermosetting resin in the ethylenically unsaturated monomer used for emulsion polymerization and then emulsion-polymerizing it by a known method. Can be obtained. As another method, a water-insoluble thermosetting resin may be added to and dispersed in an aqueous phase containing an emulsifier, and then emulsion polymerization may be performed while adding an ethylenically unsaturated monomer. As the water-insoluble thermosetting resin, a commercially available phenolic resin, epoxy resin, furfural resin, urethane resin, unsaturated polyester resin, amino resin, polyimide resin, or polyamide-imide resin is selected which is insoluble or sparingly soluble in water. do it.

Next, in the emulsion polymerization of the second stage, the shell portion that covers the core portion is formed. In order to make the resulting resin particles have a two-layer structure, in the second-stage emulsion polymerization, a new emulsifier is not added at all, or a small amount is used so that new resin particles are not formed even if the emulsifier is added. The polymerization is allowed to substantially proceed on the surface of the resin particles formed in the first stage emulsion polymerization. Since it is essential that the shell portion formed by the second-stage emulsion polymerization is hydrophilic, an amino group-containing ethylenically unsaturated monomer is preferable as the ethylenically unsaturated monomer, and N-methylamino Having ethyl acrylate or methacrylate, monopyridines such as vinyl pyridine, vinyl ethers having an alkylamino group such as dimethylaminoethyl vinyl ether, and having an alkylamino group such as N- (2-dimethylaminoethyl) acrylamide or methacrylamide. Unsaturated amides are preferably used. These amino group-containing ethylenically unsaturated monomers can be used as homopolymers, but copolymers with other ethylenically unsaturated monomers are most useful.

In the second-stage emulsion polymerization, ethylenically unsaturated carboxylic acid may be used as a part of the ethylenically unsaturated monomer. That is, as the ethylenically unsaturated carboxylic acid, an ethylenically unsaturated monobasic carboxylic acid such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, an ethylenically unsaturated dibasic acid such as fumaric acid. There are carboxylic acids, one or two of these
More than one seed is used.

Then, the emulsion polymer obtained in the above-mentioned first step is added to the aqueous phase, and the ethylenically unsaturated monomer mixture and the radical-forming initiator are added in the same manner to carry out emulsion polymerization by a known method. Thus, an aqueous emulsion of the resin fine particles of the present invention is produced. At this time, an emulsifier may be added to prevent the formation of aggregates or to stabilize the polymerization reaction. As the emulsifier used in the present invention, those used in ordinary emulsion polymerization such as anionic emulsifiers such as sodium alkylbenzene sulfonate and nonionic emulsifiers such as polyoxyethylene alkyl ether can be used. Also,
As a radical generation initiator used in emulsion polymerization, potassium persulfate, ammonium persulfate, azobisisobutyronitrile, etc. are used. In addition, the concentration at the time of emulsion polymerization is generally 2% for the resin in the final aqueous emulsion.
It is preferable to have a solid content concentration of 5 to 65% by weight. The temperature at the time of emulsion polymerization may be within the range of the known method, and the pressure is usually atmospheric pressure. As described above, by using the thermosetting resin as the resin for the first layer, the resin is uniformly dispersed in the coating film, so that the uniform coating film can be retained even after the resin is decomposed after the strain relief annealing.

The amount of the thermosetting resin in the core portion and the resin having chrome acid resistance in the shell portion forming the aqueous emulsion of resin fine particles is such that the resin having chrome acid resistance in 100 parts by weight of the thermosetting resin. 2 to 100 parts by weight is preferable. That is, when the amount of the resin having chromic acid resistance is 2 parts by weight or less, it is impossible to completely cover the thermosetting resin of the core part, and therefore gelation occurs when compounded with the chromic acid-based agent. Further, if the compounding amount of the resin having chrome acid resistance is 100 parts by weight or more, the curing becomes insufficient.

The component (b) of the treatment liquid used in the present invention is preferably a chromate containing at least one divalent metal, and at least one of chromic anhydride, chromate and dichromate. Is an aqueous solution containing as a main ingredient. As chromate, salts of sodium, potassium, magnesium, calcium, manganese, molybdenum, zinc, aluminum and the like can be used. For example, MgO, CaO, ZnO or the like is used as the divalent metal oxide to be dissolved, and Mg (OH) ₂ , Ca is used as the hydroxide.
(OH) with a _2, Zn (OH) _2. Examples of the carbonate may be used MgCO _3, CaCO _3, ZnCO _3, and the like. These are dissolved in an aqueous solution containing at least one of chromic anhydride, chromate and dichromate as a main component to obtain a desired chromate-based aqueous solution.

As the component (c), an organic reducing agent for making the coating film insoluble is used in the treatment liquid. As the organic reducing agent, polyhydric alcohols such as glycerin, ethyl glycol and sucrose are preferable as reducing agents for hexavalent chromium. At this time, the amount of these organic reducing agents added is CrO ₃ 10
The amount is preferably 10 to 60 parts by weight with respect to 0 parts by weight, but is not particularly limited. If the compounding amount of the organic reducing agent is less than 10 parts by weight, the water resistance of the coating is deteriorated, while if it is more than 60 parts by weight, the reduction reaction proceeds in the treatment liquid.
This is because the treatment liquid has a disadvantage of gelling. In order to further improve the heat resistance of the coating, boric acid, phosphate, etc. may be added, or colloidal substances such as colloidal silica and inorganic fine particles such as silica powder may be added to improve the interlayer resistance after strain relief annealing. It may be mixed.

The resin used in the liquid containing the second organic resin as a solid content is not particularly limited as long as it achieves the intended purpose. For example, vinyl acetate resin, Veova resin,
Acrylic resin, polyethylene resin, acrylonitrile resin, polyester resin, polystyrene resin, epoxy resin, phenokinshi resin, polyamide-imide resin, uretare resin, phenol resin or cresol resin, and a mixture thereof or a copolymer resin of these resins. It may be. As the resin solution, those obtained by dissolving these resins in a general-purpose solvent such as thinner or toluene, those obtained by making the resins water-soluble or those obtained by emulsifying with a surfactant, and dispersion can be used. The type and formulation of the solution are not particularly limited as long as it can be sprayed.

In the above description, the liquid containing the first organic resin as the solid content and the liquid containing the second organic resin as the solid content are described as suitable examples, but the liquids are not limited thereto. Alternatively, the same first organic resin and second organic resin may be used, or any combination thereof may be used. In particular, if a thermosetting resin coated with a (meth) acrylic copolymer, an example of which is a liquid containing the first organic resin as a solid content, is used as the second organic resin, the second organic resin has high heat resistance. A coating can be obtained.

[0032]

EXAMPLES The present invention will be specifically described below based on examples, but the present invention is not limited to these examples. Reference Example 1 Resin emulsion (E1) used in the present invention
Was produced by the following raw material and production method. 1.5 with stirrer, reflux condenser, dropping funnel and thermometer
The following raw materials were charged and dissolved in an L reaction vessel. Deionized water 3240 parts Emulgen 031 (Kao Co., Ltd. nonionic emulsifier) 10.0 parts Neogen R (Daiichi Kogyo Seiyaku Co., Ltd. anion emulsifier) 4.0 parts Next, the following mixture was used as the first stage emulsion polymerization. It was placed in a dropping funnel. Bisphenol type epoxy resin 100 parts Butyl acrylate 200 parts Methyl methacrylate 100 parts Acrylic acid 8.0 parts While flowing nitrogen gas, the temperature in the reactor was raised to 60 ° C. under stirring to deionized water. 40 parts of a dissolved 2% aqueous potassium persulfate solution was added, and then 20% of a mixture of the epoxy resin and butyl acrylate, methyl methacrylate and acrylic acid monomers placed in a dropping funnel was added. The temperature rise due to the heat of polymerization is controlled by a water bath, and while maintaining the internal temperature at 80 ° C, the epoxy resin
The rest of the monomer mixture and 80 parts of a 2% aqueous solution of potassium persulfate were added dropwise over 2 hours for polymerization. After further holding at 80 ° C. for 2 hours, it was cooled to room temperature, filtered through a 200-mesh filter cloth, and taken out to obtain an emulsion polymer as seed particles. This had a nonvolatile concentration of 50.3 wt% and a pH of 2.8. The same 1.5 L reactor was charged with 452 parts of the emulsion polymer obtained above and 125 parts of water. Next, as the second-stage emulsion polymerization, the following ethylenically unsaturated monomers were prepared and placed in a dropping funnel. Ethyl acrylate 60 parts Methyl methacrylate 30 parts Dimethylaminoethyl methacrylate 2.0 parts Acrylic acid 1.0 parts While stirring nitrogen gas, the internal temperature of the reactor is set to 7
The temperature was raised to 0 ° C., and 60 parts of a 2% potassium persulfate aqueous solution prepared above and the above monomer mixture solution were added dropwise to another dropping funnel to carry out polymerization. These drops were carried out for 2 hours while maintaining the internal temperature at 70 ° C. Further, the mixture was kept at the same temperature for 2 hours, cooled to room temperature and filtered with a 200 mesh filter cloth to obtain a polymer emulsion used in the present invention. The resin solid content of the obtained polymer emulsion was 48 wt%.

Reference Example 2 A resin emulsion (E2) used in the present invention was produced by the following raw materials and production method. The following mixture was used in the first stage. Bisphenol type epoxy resin 100 parts Ethyl acrylate 300 parts Methyl methacrylate 100 parts Methacrylic acid 8.0 parts The following mixture was used in the second stage. Ethyl acrylate 50 parts Methyl methacrylate 30 parts Methacrylic acid 2.0 parts Butyl acrylate 2.0 parts Other manufacturing methods were the same as in Reference Example 1. The resin solid content of the obtained emulsion was 52 wt%.

Reference Example 3 A resin emulsion (E3) used in the present invention was produced by the following raw materials and production method. Same as Reference Example 1 except that the following mixture was used in the first step. Resol type phenol formaldehyde resin 100 parts Ethyl acrylate 200 parts Methyl methacrylate 100 parts Methacrylic acid 8.0 parts

Reference Example 4 A resin emulsion (E4) used in the present invention was manufactured by the following raw materials and manufacturing method. The following mixture was used in the second stage. The resin solid content of the obtained emulsion was 46 wt%. Ethyl acrylate 50 parts Methyl methacrylate 30 parts Vinyl pyridine 1.0 part Acrylic acid 1.0 part Other manufacturing methods were the same as in Reference Example 1.

Reference Example 5 A resin emulsion (E5) used in the present invention was produced by the following raw materials and production method. The following mixture was used in the second stage. The resin solid content of the obtained emulsion was 46 wt%. Ethyl acrylate 50 parts Methyl methacrylate 30 parts Acrylamide 1.0 part Acrylic acid 1.0 part Other manufacturing methods were the same as in Reference Example 1.

(Examples and Comparative Examples) After applying treatment liquids containing various components shown in Table 1 to the surface of an electromagnetic steel sheet having a thickness of 0.5 mm, the steel sheet surface was baked for 80 seconds in a hot air oven at 450 ° C. An insulating film was formed on the. After that, when the temperature of the steel sheet was cooled to 120 ° C., the post-applied resin liquid shown in Table 1 was sprayed as the resin solid content at the application amount shown in Table 1. Comparative Example 1
3 and Comparative Example 6 were not post-coated. The coating workability at this time was extremely good with the resins used in the examples, and the desired target film was obtained.

Then, a test material having a width of 25 mm was sampled from the obtained magnetic steel sheet with an insulating coating, and the number of oilless punchings was performed in a 15 mmφ steel die until the burr height reached 50 μm without punching oil. It was measured.
The larger the number of punches until the burr height reaches 50 μm, the better the punchability. The results of Example 1 are shown in FIG. 1 together with Comparative Example 2.

(1) Interlayer resistance It was measured by the JIS second method. The larger the interlayer resistance value, the better the electric insulation. (2) Adhesion property Before annealing: The diameter (cm) at which the coating was not bent and peeled off was measured. After annealing: The presence or absence of tape peeling of the coating film in the planographic printing plate was observed. The less the peeling, the better the adhesion. (3) Corrosion resistance (3-1) Corrosion resistance of product plate The salt rusting test and the rusting rate of the surface after 7 hours are shown in%.
The lower the rust rate, the better the corrosion resistance. (3-2) Corrosion resistance after strain relief annealing A constant temperature and humidity test (wetting rate 80%, 50 ° C, 14 days) after annealing was performed in 750 ° C x 2 hr N ₂ and the rust rate was shown in%. (4) Refrigerant resistance 80 ° C x 1 in a mixture of Freon 22: Refrigerating machine oil = 9: 1
The sample was left for 0 days and the weight loss was measured. The smaller the weight loss, the better the refrigerant resistance. (5) Oil resistance It was immersed in No. 1 insulating oil at 120 ° C. for 72 hours, and the weight reduction amount was measured. The smaller the weight loss, the better the oil resistance. (6) Heat resistance In differential thermogravimetry, the sample is 2 per minute in an inert atmosphere.
The sample is heated at 0 ° C., the weight loss of the sample with respect to temperature is measured, and the peak temperature Dp at which the weight change dG / dt shows a maximum
I asked. The higher Dp, the higher the heat resistance.

[0040] * Amount of resin solid content converted to 100 parts by weight of chromic anhydride ** Amount based on 100 parts by weight of chromic anhydride *** Amount of solid content converted to 100 parts by weight of chromic anhydride

[0041]

[0042] * Amount of resin solid content converted to 100 parts by weight of chromic anhydride ** Amount based on 100 parts by weight of chromic anhydride *** Amount of solid content converted to 100 parts by weight of chromic anhydride

[0043]

[0044] * Amount of resin solid content converted to 100 parts by weight of chromic anhydride ** Amount based on 100 parts by weight of chromic anhydride *** Amount of solid content converted to 100 parts by weight of chromic anhydride

[0045]

[0046]

[Table 1]

Comparative Example Resin used R1 Bisphenol type epoxy resin aqueous emulsion (solid resin amount 40 wt%) R2 Vinyl acetate resin aqueous emulsion (solid resin amount 4
5 wt%) R3 Resol type phenol resin aqueous emulsion (solid resin amount 53 wt%) R4 Polyester resin aqueous emulsion (solid resin amount 55 wt%) R5 Acrylic resin aqueous emulsion (solid resin amount 47
wt%) 50 parts by weight of methyl acrylate and 3 parts of butyl acrylate
0 parts by weight of copolymer

[0048] * Amount of resin solid content converted to 100 parts by weight of chromic anhydride ** Amount based on 100 parts by weight of chromic anhydride *** Amount of solid content converted to 100 parts by weight of chromic anhydride

[0049] * Amount of resin solid content converted to 100 parts by weight of chromic anhydride ** Amount based on 100 parts by weight of chromic anhydride *** Amount of solid content converted to 100 parts by weight of chromic anhydride

[0050]

[0051]

[Table 2]

[0052]

According to the present invention, a treatment liquid consisting of a liquid containing the first organic resin as a solid content, a chromate-based aqueous solution and an organic reducing agent is applied to the surface and baked, and the second organic resin is further applied thereon. A magnetic steel sheet having an electrically insulating film coated with,
Excellent electrical insulation, adhesion, oilless punching and corrosion resistance. Moreover, since the second coating is formed during the baking and cooling step of the first coating, the step of baking and forming two layers of coating can be performed in one step.

[Brief description of drawings]

FIG. 1 is a graph comparing the results of Example 1 and Comparative Example 2.

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Claims (6)

[Claims] 1. A method for producing an electromagnetic steel sheet having an electrically insulating coating on its surface, comprising a liquid containing a first organic resin as a solid content and a chromate-based aqueous solution containing at least one divalent metal. And a treatment liquid containing an organic reducing agent are applied to the surface of the electromagnetic steel sheet, baked, and a solution containing the second organic resin as a solid content is applied during the cooling step of the electromagnetic steel sheet, and further cooled after the application. An electrical steel sheet having an electric insulating coating excellent in oilless punching characteristics, which is characterized in that 2. The first or second organic resin is vinyl acetate resin, Veova resin, acrylic resin, polyethylene resin, acrylonitrile resin, polyester resin, polystyrene resin, epoxy resin, phenoxy resin, polyamide-imide resin, urethane. The oilless punching according to claim 1, which is an organic resin selected from the group consisting of a resin, a phenol resin and a cresol resin, or an organic resin which is a copolymer of two or more selected from the group. Electrical steel sheet with an electrically insulating coating with excellent properties. 3. The oilless punching according to claim 1, wherein the first or second organic resin is an emulsion comprising resin particles capable of forming a crosslinked structure in which an outer layer is coated with a resin having resistance to chrome acid. Electrical steel sheet with an electrically insulating coating with excellent properties. 4. The oilless punching according to claim 1, wherein the first organic resin is an emulsion comprising thermosetting resin particles whose outer layer is formed by coating a resin having chromium acid resistance. Electrical steel sheet with an electrically insulating coating with excellent properties. 5. The amount of the liquid containing the second organic resin as a solid content applied to the surface of the magnetic steel sheet is 0.2 to 1.0 g / m ² as a solid content. An electrical steel sheet having an electric insulating coating excellent in oilless punchability as described in 1. 6. The step of applying a liquid containing the second organic resin as a solid content to the surface of an electromagnetic steel plate, the plate temperature of the steel plate is 60 to 60.
The electrical steel sheet having an electrical insulating coating excellent in oilless punching property according to any one of claims 1 to 5, which is a step of applying at 300 ° C.