JPH09323066A - Magnetic steel sheet with an insulating coating that can be annealed and has excellent corrosion resistance and solvent resistance, and method for forming the insulating coating - Google Patents

Abstract

(57) [Abstract] (Corrected) [Problem] Manufactured by low temperature baking, strain relief annealing is possible, excellent corrosion resistance and solvent resistance are exhibited without using chromate, and other Magnetic steel sheet with insulating coating that also satisfies coating performance. SOLUTION: (a) Ethylene-unsaturated carboxylic acid copolymer, (b) epoxy resin, (c) silane coupling agent, (d) silica. Above (a), (b), (c),
Containing (d), (a) / (b) / (c) / (d) = 5
Insulating coating composed of a ratio of ˜95 / 5 to 95 / 0.1 to 50/20 to 500 [(a) + (b) = 100 parts by weight] is 0.05 to 4 g / m in dry weight. A magnetic steel sheet with an insulating coating that is capable of strain relief annealing and has excellent corrosion resistance and solvent resistance that is coated on the surface of a magnetic steel sheet with an adhesion amount of ² .

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention does not contain a harmful compound such as hexavalent chromium, can be manufactured by low temperature baking, can be subjected to strain relief annealing, and has excellent film performance such as corrosion resistance and solvent resistance. TECHNICAL FIELD The present invention relates to a magnetic steel sheet with an insulating coating and a method for forming the insulating coating.

[0002]

2. Description of the Related Art Insulating coatings for electrical steel sheets not only have interlayer resistance, but also punchability, TIG weldability, coating adhesion, corrosion resistance,
Various properties such as solvent resistance, heat resistance, blocking resistance, tension pad resistance, corrosion resistance after strain relief annealing and seizure resistance are required, and various insulating coatings have been developed according to the application. There is. Further, the electromagnetic steel sheet is often subjected to strain relief annealing at about 750 to 850 ° C. in order to improve the magnetic properties after punching. The insulating coating is (1) an inorganic coating that emphasizes weldability and heat resistance, (2) an organic resin-containing semi-organic coating that aims to achieve both punchability and weldability, (3)
It is roughly classified into three types of organic coatings for special applications, but it is the coating containing inorganic substances of (1) and (2) that withstands strain relief annealing, and in particular, organic resin is applicable as (2). The contained chromate-based insulating coating can be produced by one coat and one bake, and can be significantly improved in punching property as compared with the inorganic insulating coating, and is widely used.

For example, Japanese Patent Publication No. 60-36476 discloses that
An electromagnetic wave obtained by applying a treatment liquid prepared by mixing a vinyl chromate / veova resin emulsion and an organic reducing agent into a dichromate-based aqueous solution containing at least one divalent metal on the surface of a dough iron plate and performing a baking process by a conventional method. A method for forming an insulating film on a steel sheet is disclosed. This electrical steel sheet with an insulating coating satisfies various performances such as corrosion resistance and solvent resistance. However, the chromate-based coating needs to be baked at a relatively high temperature in order to reduce hexavalent chromium to trivalent and insolubilize it. Further, since hexavalent chromium is highly toxic, there is a concern about environmental pollution, and exhaust treatment and waste liquid treatment are costly.

Further, baking at a high temperature leads to an increase in cost from the viewpoint of an increase in energy consumption during manufacturing and a decrease in insulating film processing speed. Further, in the case of a semi-organic coating, the resin is thermally deteriorated during baking, which may impair the original performance of the resin.

As a technique using an inorganic substance other than chromic acid, a semi-organic insulating coating containing a phosphate is also under study. However, it is necessary to bake the phosphate at a higher temperature after coating in order to promote the dehydration reaction and make it insoluble.

As a semi-organic insulating film which can be baked at a relatively low temperature and does not contain chromic acid, Japanese Patent Application Laid-Open No. 54-3 is available.
No. 1598, a treatment liquid comprising silica hydrosol and an organic substance is applied to the surface of a steel sheet and heated at a temperature of 100 to 350 ° C. to have heat resistance having a coating film containing silica as a main component containing an organic substance, An electromagnetic steel sheet having a seizure resistant coating and a surface treatment method thereof are disclosed.
In addition, Japanese Examined Patent Publication No. 59-21927 uses heat generated during continuous annealing, and then an aqueous solution containing an inorganic colloidal substance as a main component and a water-soluble or emulsion-type resin is applied, and the tempering is performed as it is. A method of applying a strain relief annealing anti-seizure coating to an electromagnetic steel sheet by rolling is disclosed.

[0007]

[Problems to be Solved by the Invention]
No. 8 and Japanese Patent Publication No. 59-21927,
Its main purpose is to prevent seizure after annealing. JP 5
The silica hydrosol described in 4-31598 and the inorganic colloidal material described in JP-B-59-21927 are
Certainly, it can be baked at a lower temperature than chromate-based and phosphate-based coatings. That is, in order to prevent stickiness, the chromate-based and the phosphate-based require that the film-forming reaction from water-soluble to water-insoluble be advanced by high-temperature heating, but the inorganic colloidal substance is not required.
However, both are simply due to the combination of silica hydrosol or inorganic colloidal substance and resin, there is no regulation regarding the resin, such as corrosion resistance and solvent resistance, poor performance other than seizure resistance after annealing, Was limited.

Specifically, in JP-A-54-31598, as is clear from the examples, the comparative examples containing chromate do not cause rust in the wetting test, but the invention. In each of the examples, spot rust occurs. In Japanese Examined Patent Publication No. 59-21927, there is no description about corrosion resistance and the like, so that the vinegar beer used only in Examples is used.
As a result of investigating the performance of the electrical steel sheet with an insulating coating made of an acrylic copolymer resin and various inorganic colloidal substances, the performance such as corrosion resistance and solvent resistance was insufficient.

The present invention has been made to solve the above-mentioned problems, and can be manufactured by low temperature baking, strain relief annealing is possible, and excellent corrosion resistance and solvent resistance are exhibited without using chromate. In addition, the present invention provides a magnetic steel sheet with an insulating coating and a method for forming the insulating coating, which satisfies other coating performances.

[0010]

Means for Solving the Problems As a result of investigations aimed at solving the above problems, the inventors have found that a crosslinked resin obtained by a crosslinking reaction between an ethylene resin containing a carboxy group in the molecule and an epoxy resin. It is possible to manufacture by low temperature baking by increasing the interaction of these by mixing silane coupling agent and silane coupling agent, strain relief annealing is possible, and various performances such as corrosion resistance and solvent resistance. The present invention has been achieved by finding that an excellent magnetic steel sheet with an insulating coating can be obtained.

According to the present invention, (a) an ethylene-unsaturated carboxylic acid copolymer (b) an epoxy resin (c) a silane coupling agent (d) silica The above (a), (b), (c), Containing (d), (a)
/ (B) / (c) / (d) = 5 to 95/5 to 95/0.
1 to 50/20 to 500 [(a) + (b) = 10
0 parts by weight] is applied to the surface of the electrical steel sheet in an amount of 0.05 to 4 g / m ² in terms of dry weight to enable stress relief annealing and corrosion resistance. Provided is an electrical steel sheet with an insulating coating, which has excellent properties and solvent resistance.

According to another aspect of the present invention, (a)
Self-emulsifying aqueous dispersion of ethylene-unsaturated carboxylic acid copolymer, (b) epoxy resin aqueous solution or epoxy resin emulsion (c) silane coupling agent (d) colloidal silica or alkali silicate aqueous solution (a) , (B), (c), and (d) are converted into undiluted components (a) / (b) / (c) / (d) = 5 to 95/5 to 9
5 / 0.1-50 / 20-500 [(a) +
(B) = 100 parts by weight], the aqueous composition is applied to the surface of the magnetic steel sheet so that the amount of adhesion after drying is 0.05 to 4 g / m ^2, and the ultimate temperature of the steel sheet is 80 to 250 ° C.
A method for forming an insulating coating on a magnetic steel sheet, which is capable of strain relief annealing and is excellent in corrosion resistance and solvent resistance, is provided which is characterized in that an aqueous medium is dried with.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below. The steel plate used in the present invention is an electromagnetic steel plate (electric iron plate,
Electromagnetic steel sheet). The shape of the steel plate is not limited, and may be plate-shaped, sheet-shaped, or coil-shaped.

The resin forming the insulating coating of the present invention is
It is a crosslinked resin in which (a) an ethylene-unsaturated carboxylic acid copolymer and (b) an epoxy resin form a crosslink. When these resins are mixed and applied to the surface of the electromagnetic steel sheet, it is preferable to use each resin as an aqueous solution, an aqueous dispersion or an emulsion.

Examples of the (a) ethylene-unsaturated carboxylic acid copolymer include a random copolymer, a copolymer obtained by grafting an unsaturated carboxylic acid onto polyethylene, or a terpolymer obtained by adding a third component. Is mentioned. Examples of the unsaturated carboxylic acids include unsaturated carboxylic acids having usually 6 or less carbon atoms such as acrylic acid, methacrylic acid, crotonic acid, and isocrotonic acid, and dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid. Are exemplified.

(A) In order to disperse the ethylene-unsaturated carboxylic acid copolymer in water, it is necessary to neutralize a part of the unsaturated carboxylic acid with a basic substance. Bases used for this neutralization include alkali metals such as sodium hydroxide, lithium hydroxide and potassium hydroxide, zincs such as zinc hydroxide, zinc acetate and zinc oxide, ammonia, morpholine, triethylamine and amino alcohol. Are generally used.

The epoxy resin (b) is a liquid or solid resin containing two or more epoxy groups in one molecule at room temperature and can be used in the state of emulsion or aqueous solution. Specifically, it is obtained by reacting polyhydric alcohol or polyhydric phenol with halohydrin, and includes bisphenol A type, halogenated bisphenol A type, novolac type, polyglycol type, bisphenol F type, epoxidized oil, etc. Can be mentioned. As a method for emulsifying the epoxy resin (b), it can be produced by an ordinary forced emulsification method in the presence of an emulsifier. The emulsifier used may be a polyoxyethylene alkylphenol ether nonionic surfactant, a polyoxyethylene polyoxypropylene block polyether, or an adduct of these with a diisocyanate compound, alone or in a blend.
It is also effective to substitute the hydrophilic group for the molecular end of the epoxy resin to make it water-soluble.

In the present invention, it is preferred to use a mixture of (a) an ethylene-unsaturated carboxylic acid copolymer aqueous dispersion and (b) an epoxy resin aqueous solution or emulsion. The aqueous composition in which these are mixed is applied to a magnetic steel sheet and dried to form a cross-linkage bond by heating during drying. The mixing ratio of these resins is in the range of (a) / (b) = 5 to 95/95 to 5 parts by weight [where (a) + (b) = 100 parts by weight] in terms of solid content. preferable. If it is out of this range, the formation of cross-linking becomes insufficient and the effect of improving the corrosion resistance and the solvent resistance, which is the main object of the present invention, becomes small. A particularly preferable mixing ratio is (a) / (b) = 30 to 90/70 to 10 parts by weight.

The (a) ethylene-unsaturated carboxylic acid copolymer and (b) epoxy resin used in the present invention include:
From the viewpoint of improving the performance of the insulating coating, improving the workability of coating, improving the film-forming property, and reducing the cost, other monomers can be copolymerized within a range that does not impair the effects of the present invention. Further, a crosslinking agent such as an isocyanate compound, a dihydrazide compound, an aziridine compound, and an epoxy compound, and other aqueous resins can be mixed. Further, a reaction catalyst such as an amino compound may be added.

As the (c) silane coupling agent constituting the insulating coating of the present invention, (a) an ethylene-unsaturated carboxylic acid copolymer or (b) an epoxy resin, a chemical bond, an interaction such as compatibilization, etc. A reactive group having an alkoxysilyl group is selected. As a reactive group,
Vinyl group, hexenyl group, mercapto group such as γ-mercaptopropyl, epoxy group such as γ-glycidoxypropyl, methacryl group such as γ-methacryloxypropyl, γ-aminopropyl, N-β (aminoethyl) γ-
Amino groups such as aminopropyl and N-β (N-vinylbenzylaminoethyl) -γ-aminopropyl are exemplified. Examples of the alkoxysilyl group include trimethoxysilane, triethoxysilane, methyldimethoxysilane and the like.

When the silane coupling agent is added to the aqueous composition, it is usually added after being dissolved or dispersed in water. In particular, it is preferable to completely dissolve it in water, and it is also effective to add alcohol or acetic acid to dissolve it.

The silica (d) in the insulating coating of the present invention is obtained by applying silica dispersed in water to a magnetic steel sheet and drying. Any form of silica may be used as long as it can be dispersed in water, colloidal silica or an aqueous solution of alkali silicate can be used, and various types such as colloidal silica, gas phase silica, and aggregated silica are applied. It is possible. These may be surface-treated with aluminum or the like. The aqueous solution of alkali silicate is called water glass, and as an alkali species, L
i, Na, K and the like. Any of these may be used in combination.

The insulating coating of the present invention comprises (a) an ethylene-unsaturated carboxylic acid copolymer, (b) an epoxy resin, (c) a silane coupling agent and (d) silica,
Each of (a) an aqueous dispersion of an ethylene-unsaturated carboxylic acid copolymer, (b) an epoxy resin aqueous solution, (c) a silane coupling agent, and (d) a colloidal silica or alkali silicate aqueous solution in an aqueous medium. It is formed by mixing on the surface of a magnetic steel sheet and drying.
The mixing ratio of these is (a) / (b) /
(C) / (d) = 5 to 95/5 to 95 / 0.1 to 50 /
20 to 500 [(a) + (b) = 100 parts by weight]
Within the range.

The solid content weight ratio of (d) silica is 20 relative to 100 parts by weight of the solid content of the cross-linking resin (a) ethylene-unsaturated carboxylic acid copolymer and (b) epoxy resin.
If it is less than the weight part, seizure resistance during annealing and interlayer resistance may be poor. If it exceeds 500 parts by weight, the punchability may be poor. When the undiluted weight ratio of the silane coupling agent (c) is less than 0.1 part by weight, the effect of improving various performances such as corrosion resistance is small.
If it exceeds 50 parts by weight, stability may be impaired by causing aggregation of the aqueous composition.

As a method for applying the aqueous composition to the surface of the magnetic steel sheet, various methods such as a roll coater, a flow coater, a spray coating and a knife coater generally used in industry can be applied. As a drying method, a hot air method, an infrared method, an induction heating method or the like which is usually carried out can be used and is not particularly limited. The drying temperature is preferably in the range of 80 to 250 ° C. at the steel plate reaching temperature. 80
If the temperature is lower than ° C, the aqueous medium may be insufficiently removed by drying. If it exceeds 250 ° C., the resin is thermally deteriorated, the original performance of the resin may be impaired, and the silane coupling agent may evaporate, which is not preferable. The drying temperature is appropriately set according to the minimum film forming temperature of the resin and the coating amount.

The adhesion amount of the insulating coating after drying is 0.05 to 4
g / m ^2, preferably set at 0.2 to 1.5 g / m ^2. Adhesion amount seizing resistance is less than 0.05 g / m ^2, interlayer resistance, inferior and corrosion resistance, weldability is 4g / m ^2, greater than the blocking resistance, sometimes such adhesion is inferior.

The aqueous composition used in the present invention or the finally obtained electromagnetic steel sheet with an insulating coating is a known additive for the purpose of improving various properties of the insulating coating and coating workability. Agents, rust inhibitors, lubricants, defoamers, dispersants, repellants, anti-scratch agents, inorganic pigments, organic pigments, dyes, surfactants, water repellents, thickeners, film forming aids, antiseptic Agents and the like can be added.

[0028]

EXAMPLES The effects of the present invention will be specifically described below based on examples, but the present invention is not limited to these examples. (Invention Example 1) The aqueous composition shown below was applied to the surface of a magnetic steel sheet having a plate thickness of 0.5 mm using a roll coater, and hot-air drying was performed at a steel sheet arrival temperature of 180 ° C and a heating time of 10 seconds. The amount of the insulating coating attached after drying was 0.5 g / m ² . Various tests were performed after the obtained electromagnetic steel sheet with an insulating coating was allowed to cool. The adhesion, corrosion resistance, and interlayer resistance were evaluated for the product plate after being left to cool and the annealed plate after strain relief annealing at 750 ° C. for 2 hours in a nitrogen atmosphere.

[Aqueous Composition] (a) Dispersion of Ethylene-Unsaturated Carboxylic Acid Copolymer Self-Emulsifying Aqueous Dispersion: Ethylene-Methacrylic Acid-Na Methacrylic Acid Copolymer Minimum Film Forming Temperature 90 ° C. ( b) Epoxy resin emulsion: Forced emulsion of bisphenol A type epoxy resin Minimum film forming temperature 100 ° C. (c) N-β (N-vinylbenzylaminoethyl) γ-
Aminopropyltrimethoxysilane (d) Colloidal silica having an average particle diameter of 53 nm (a), (b), (c), and (d) in solid content (undiluted content)
(A) / (b) / (c) / (d) = 70/30 /
The mixture was mixed at a ratio of 10/100 parts by weight to obtain an aqueous composition having a solid content concentration of 10% by weight. The details of various performance evaluation methods are as follows. Table 2 shows the results of various performance evaluations.

(Corrosion resistance [salt spray test]) 35 ° C., 5%
The evaluation was performed from the time when the area ratio of red rust generation was 10% or more under the condition of the NaCl solution. ◎: 15 hours or more ○: 7 to less than 15 hours △: 3 to less than 7 hours ×: less than 3 hours

(Corrosion Resistance [Boiling Steam Exposure Test]) Ion-exchanged water in a beaker was boiled, an electromagnetic steel sheet with an insulating coating was placed thereon, and the state of the coating after 30 minutes was evaluated. ◎: No change ○: Part of the coating is discolored △: Almost the entire surface of the coating is discolored ×: Rust is generated

(Corrosion resistance [wet test]) Evaluation was made from the area ratio of red rust after exposure for 48 hours under a high temperature and high humidity condition of 50 ° C. and a relative humidity of 98%. ◎: No rusting ○: Less than 20% △: 20-50% ×: More than 50%

(Solvent resistance [Scratch resistance]) The surface of the insulating coating was rubbed 10 times with a cotton swab soaked in hexane, xylene, methanol, ethanol and acetone, and the dissolution of the coating and the presence of scratches were evaluated. ⊚: No change in all solvents ○: Scratches occurred in any one solvent Δ: Scratches occurred in multiple solvents ×: Film dissolved in any solvent

(Solvent resistance [Xylene solubility]) 140
Magnetic steel sheet coated in xylene heated to ℃ 6
After soaking for a time, the weight loss rate of the insulating coating was evaluated. ◎: Weight reduction rate less than 0.1% ○: Weight reduction rate 0.1 to less than 0.2% △: Weight reduction rate 0.2 to less than 0.4% ×: Weight reduction rate more than 0.5%

(Adhesion) The adhesion was evaluated from the film peeling rate after the 180 ° bending back test at 20 mmφ. ⊚: No change ◯: Peeling less than 20% △: Peeling 20 to 40% ×: Peeling 40% to full peeling

(TIG Weldability) Welding was carried out under the following conditions and evaluated from the maximum welding speed at which blowholes were not generated. Electrode: Th-W 2.6 mmφ Applied pressure: 100 kg / cm ² Current: 120 A Shield gas: Ar 6 L / min ◎: 600 mm / min ○: 400 to 600 mm / min Δ: 300 to 400 mm / min ×: Less than 300 mm / min

(Interlayer Resistance) The interlayer resistance value was measured according to JIS method 2. ○: 5Ωcm ² / sheet than △: 3~5Ωcm ² / sheet ×: 3Ωcm less than ² / sheet

(Punching property) In a 15 mmφ steel die, evaluation was made from the number of punches until the burr height reached 50 μm. ◎: more than 500,000 times ○: 300,000 to 500,000 times △: 100,000 to 300,000 times ×: less than 100,000 times

(Blocking resistance) Magnetic steel with insulating coating
2 cm for 2 plates^Two200kg / c, pasted in the area of
m ^TwoUnder a load of 80 ° C for 48 hours
Then, it was left to cool and evaluated by measuring the shear adhesive strength. ◎: No sticking at all ○: Shear adhesive strength 10 kg / cm^TwoLess than Δ: Shear adhesive strength 10 to 30 kg / cm^Two X: Shear adhesive strength 30 kg / cm^TwoSuper

(Seizure resistance) Ten sheets of 50 mm square steel sheets were stacked and annealed at 750 ° C. for 2 hours in a nitrogen atmosphere while applying a load (200 g / cm ² ) and then a weight of 500 g was dropped on the steel sheet. The drop height when dividing was investigated. ◎: 10 cm or less ○: 10 to less than 20 cm △: 20 to 40 cm ×: more than 40 cm

(Invention Examples 2 to 4, Comparative Examples 1 to 10) Inventive Examples except that the constituents of the aqueous composition, their mixing ratio, the amount of the insulating coating, the baking temperature, etc. were changed as shown in Table 1. In the same manner as in 1, produce an electrical steel sheet with an insulating coating,
Various evaluations were made. Table 2 shows the evaluation results. As is clear from Table 2, the insulating coated electromagnetic steel sheets according to the examples of the present invention all exhibit excellent corrosion resistance and solvent resistance, and have good adhesion, weldability, interlayer resistance, punchability, blocking resistance, It also has excellent seizure resistance.

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

[Table 3]

[0045]

[Table 4]

[0046]

[Table 5]

[0047]

EFFECTS OF THE INVENTION Since the present invention is constituted as described above, it can be manufactured by low temperature baking, can be strain-relieved and has an excellent corrosion resistance and solvent resistance. Since it has the required performance, it can be widely used as a magnetic steel sheet for applications such as motors and transformers.

Claims (2)

[Claims] 1. An ethylene-unsaturated carboxylic acid copolymer (a) an epoxy resin (b) a silane coupling agent (d) silica (a), (b), (c), (d) Contains, (a)
/ (B) / (c) / (d) = 5 to 95/5 to 95/0.
1 to 50/20 to 500 [(a) + (b) = 10
0 parts by weight] is applied to the surface of the electrical steel sheet in an amount of 0.05 to 4 g / m ² in terms of dry weight to enable stress relief annealing and corrosion resistance. Magnetic steel sheet with an insulating coating that excels in resistance and solvent resistance. 2. A self-emulsifying aqueous dispersion of ethylene-unsaturated carboxylic acid copolymer, (b) epoxy resin aqueous solution or epoxy resin emulsion, (c) silane coupling agent, (d) colloidal silica or alkali. Aqueous silicate solution The above (a), (b), (c) and (d) are (a) / (b) / (c) / (d) = 5 to 95/5 to 9 in terms of undiluted content.
5 / 0.1-50 / 20-500 [(a) +
(B) = 100 parts by weight], the aqueous composition is applied to the surface of the magnetic steel sheet so that the amount of adhesion after drying is 0.05 to 4 g / m ^2, and the ultimate temperature of the steel sheet is 80 to 250 ° C.
A method of forming an insulating coating on a magnetic steel sheet, which is capable of performing strain relief annealing and is excellent in corrosion resistance and solvent resistance, which is characterized by drying an aqueous medium with.