JP2000129455A - Nonoriented silicon steel sheet excellent in coating film characteristics - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a silicon steel sheet with an insulating film coping with an environmental problem, further having a higher occupying volume rate and excellent in punchability, corrosion resistance, adhesion and slidability after stress relieving annealing and to provide a method for producing the insulating film. SOLUTION: This nonoriented silicon steel sheet extremely excellent in coating film characteristics is the one in which the surface of a nonoriented silicon steel sheet is provided with an insulating film obtd. by applying a treating soln. contg. phosporic metallic salt and an organic resin emulsion having 5 to 40 mgKOH/g hydroxyl group value, and in which the content of the organic resin emulsion is 5 to 100 pts.wt. (expressed in terms of the solid content) to phosphoric metallic salt of 100 pts.wt. (expressed in terms of the solid content) and executing drying.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention has a high space factor,
The present invention relates to a non-oriented electrical steel sheet which has excellent punching properties and adhesiveness, and further has an insulating coating having excellent slip properties, adhesiveness, and corrosion resistance after strain relief annealing.

[0002]

2. Description of the Related Art When manufacturing laminated iron cores for motors, transformers, etc. using non-oriented electrical steel sheets, usually, electromagnetic steel sheets are unitized by shearing or punching, then laminated, and then bolted. It is fixed by caulking, welding, bonding or the like. After being fixed, the laminated iron core is subjected to processes such as a winding coil assembling process, and finally a motor and a transformer are assembled.

[0003] In general, an insulating coating is applied to the surface of a non-oriented electrical steel sheet. The properties of the insulating coating greatly affect the properties of the steel sheet, such as weldability, punching properties, and corrosion resistance. It is important to provide not only insulating properties but also excellent film properties. Conventionally, as an insulating coating of a non-oriented electrical steel sheet, inorganic, organic, and inorganic-organic mixed insulating coatings are known.
Punching properties are inferior compared to inorganic-organic mixed systems. Inorganic insulating coatings are inferior in adhesion and corrosion resistance after strain relief annealing to inorganic and inorganic-organic mixed systems, and cannot withstand use. .

[0004] The inorganic-organic mixed insulating film is composed of these inorganic,
Intensive research has been conducted to solve the problems of the organic insulating coating. Japanese Patent Publication No. 50-15013 discloses that dichromate and an organic resin emulsion such as vinyl acetate, butadiene-styrene copolymer, and acrylic resin are used. There has been proposed a method for forming an insulating film in which a film property such as a high space factor, excellent adhesiveness, and punching property can be obtained by forming an insulating film using a treatment liquid as a main component.

However, in a conventional inorganic-organic mixed insulating coating of a non-oriented electrical steel sheet, a chromate compound is used as a coating component as seen in the use of dichromate. For this reason, at present, there is a demand for development of an insulating coating treatment technology that does not contain a chromic acid compound, because of the severe environmental problems in the manufacturing process of magnetic steel sheets or consumers of magnetic steel sheets. Therefore, Japanese Patent Application Laid-Open No. Hei 5-78855 describes that
An aqueous solution of 350 g / l of aluminum dihydrogen phosphate (in terms of P ₂ O ₅ ) and an aqueous emulsion of a synthetic resin having a pH of 1 to 3 were prepared by adding an organic resin non-volatile material to a non-volatile product of both aluminum dihydrogen phosphate and an aqueous synthetic resin aqueous emulsion. There is disclosed a technique for providing a composition for forming an insulating film having a long pot life without containing harmful substances by adjusting the content to 40% by weight. Japanese Patent Application Laid-Open No. 6-330338 discloses that a phosphate having a specific composition and an organic resin emulsion having a specific particle size are mixed in a specific ratio, and the mixture is applied to a steel plate and baked. There is disclosed a treatment method having film properties equivalent to those of an insulating film containing, and maintaining excellent slip properties after strain relief annealing.

On the other hand, there is a tendency to simplify or recycle the packaging of the coil from the viewpoint of reducing industrial waste, which is also attracting attention as one of the environmental problems. It has been demanded.

[0007]

However, when compared with an insulating film using a chromic acid compound, an insulating film using a phosphate has a poor corrosion resistance under severe conditions. That is, in the technology using these phosphates and organic resin emulsions, although the process does not proceed until gelation, the organic resin emulsion often agglomerates during the treatment solution or the coating and baking process, and as a result, the formed insulating coating film It has been found that there is a problem that the organic resin is unevenly distributed, or the corrosion resistance is deteriorated because there is no chemical reaction as seen between the chromic acid compound and the organic resin. When the organic resin particles are in an agglomerated state in the processing solution or agglomerated during the baking process to form an insulating film, a water path is formed in the agglomerated portion of the organic resin, and the water resistance of the insulating film is reduced. is there.

The present inventors have conducted intensive studies to improve the corrosion resistance of an insulating coating using phosphate, and as a result, the functional group present on the surface of the organic resin has a very large effect on the miscibility with phosphate. And found that the miscibility of the organic resin emulsion and the phosphate solution is greatly affected by the presence of hydroxyl groups and sulfonic acid groups among the functional groups,
The present invention has been completed.

[0009]

SUMMARY OF THE INVENTION The present invention is to solve the above-mentioned problems, and the gist thereof is as follows. (1) On the surface of non-oriented electrical steel sheet, metal phosphate
An organic resin emulsion having a hydroxyl value of 5 to 40 mg KOH / g and a particle size of 0.01 μm to 0.5 μm, wherein the organic resin emulsion comprises metal phosphate 1
A non-directional coating film characterized by having an insulating coating obtained by applying and drying a processing liquid in an amount of 5 to 100 parts by weight (solid content) with respect to 00 parts by weight (solid content). Electrical steel sheet. (2) The organic resin emulsion contains 5 to 30 parts by weight of a hydroxyl group-containing monomer and 0 to 5 parts by weight of a sulfonic acid group-containing monomer.
The non-oriented electrical steel sheet according to the above (1), which is obtained by containing 30 parts by weight as a copolymer component. 3) The organic resin emulsion obtained by emulsion polymerization in the presence of a reactive emulsifier having a radically polymerizable unsaturated group in a molecule is obtained by the above-mentioned (1). Excellent non-oriented electrical steel sheet. (4) The electrical insulation for an electrical steel sheet having excellent coating properties according to the above (1), (2) or (3), wherein the adhesion amount of the insulating coating is 0.3 to 5.0 g / m ^2. Coating method. (5) The treatment liquid comprises a water-soluble low-molecular-weight organic compound containing a metal phosphate and an organic resin emulsion as main components and further containing a non-dissociable hydroxyl group, an ether group and an ester group.
1 to 100 parts by weight of metal phosphate (solid content)
The above (1), which contains 15 parts by weight,
A non-oriented electrical steel sheet having extremely excellent coating properties according to (2) or (3).

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments for carrying out the present invention will be described. The inorganic compound used in the present invention will be described. As the metal phosphate used in the present invention, aluminum phosphate, calcium phosphate, zinc phosphate, magnesium phosphate and the like can be used. When a metal phosphate is used, the metal phosphate may be used directly as an aqueous solution, or the metal may be dissolved in the phosphoric acid solution in the form of an oxide, a hydroxide, or a carbonate. For example, MgO, CaO, ZnO or the like is used as the oxide of the metal to be dissolved, and Mg (OH) ₂ , Ca (OH) ₂ , Zn (O
H) ₂ , and carbonates such as MgCO ₃ , CaCO ₃ and Zn
CO _{3 and the} like.

In the present invention, one or two of colloidal silica, alumina sol, boric acid, and borate may be used as other inorganic components, if necessary. By adding these, a film improving effect such as densification of the film and improvement of heat resistance can be obtained.

Next, the organic resin used in the present invention will be described. The organic resin used in the present invention is characterized by having a hydroxyl value of 5 to 40. The hydroxyl value in the present invention is based on the hydroxyl value defined in K0070 of JIS standard, and is required for neutralizing acetic acid bonded to the hydroxyl group when 1 g of a sample is acetylated. It is indicated in mg of potassium hydroxide. In the case of using in the present invention, not only a case where the measurement is actually performed according to the JIS standard but also a value obtained by a theoretical calculation may be used.
The present inventors have found that the hydroxyl value of the organic resin has a great effect on the stability of the organic resin emulsion in the phosphate solution, and the miscibility is very good when the hydroxyl value is 5 to 40, more preferably 10 to 25. Accordingly, it has been found that the organic resin in the insulating film after the coating and baking is excellent in dispersibility and that excellent film characteristics can be obtained. When an organic resin emulsion having a hydroxyl value of 5 to 40 is used, the mechanism by which it functions is not yet clear in detail, but when the hydroxyl value is measured using an organic resin emulsion as a sample, the emulsion The hydroxyl group present on the particle surface is measured, and it is presumed that the electric double layer on the emulsion particle surface can maintain an extremely stable state even in a phosphate solution in the range of the present invention. It is also presumed that the mechanism by which the hydroxyl groups on the surface of the emulsion particles interact with metal ions in the phosphate solution to form a uniform composition film without agglomeration during film formation.

The organic resin used in the present invention has only to have a hydroxyl value in the range of 5 to 40, and is therefore an organic resin having a hydroxyl group on the surface. Any of these organic resins may be used. For example, one or two of polymers obtained by polymerizing an α, β monoethylenically unsaturated monomer and a monomer containing a hydroxyl group as main components are used.
A mixture of more than one species. More specifically, examples of the α, β monoethylenically unsaturated monomer to be polymerized include acrylates (eg, methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, and 2-ethyl acrylate). Xyl, decyl acrylate,
Isooctyl acrylate, 2-ethylbutyl acrylate,
Octyl acrylate, methoxyethyl acrylate, ethoxyethyl acrylate, 3-ethoxypropyl acrylate, etc.), methacrylates (methyl methacrylate,
Ethyl methacrylate, isopropyl methacrylate, butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, lauryl methacrylate, decyl octyl methacrylate, stearyl methacrylate, 2-methylhexyl methacrylate, 3-methoxybutyl methacrylate), Acrylonitrile, methacrylonitrile, vinyl acetate, vinyl chloride, vinyl ketone, vinyl toluene and styrene. As a monomer containing a hydroxyl group,
Hydroxypropyl acrylate, 2-hydroxyethyl acrylate, 3-hydroxybutyl acrylate, 2,2-bis (hydroxymethyl) ethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, 3-hydroxybutyl methacrylate, 2,2-methacrylic acid 3-dihydroxypropyl, N-methylolacrylamide and the like. If the value of the hydroxyl value is less than 5, the miscibility found in the present invention is not sufficiently exhibited, and if it exceeds 40, the corrosion resistance after film formation tends to be slightly inferior.

In the resin emulsion used in the present invention,
By introducing a sulfonic acid group as well as a hydroxyl group, remarkable resin dispersibility can be obtained. Specific methods for introducing a sulfonic acid group include, for example, when polymerizing an unsaturated sulfonic acid salt such as sodium styrenesulfonate with the α, β monoethylenically unsaturated monomer and a monomer containing a hydroxyl group. Can be achieved simultaneously or sequentially. In addition, although not particularly limited, when synthesizing an organic resin emulsion using an emulsion polymerization method, a sulfonic acid group is introduced on the particle surface even when a water-soluble persulfate is used as a polymerization initiator. It is possible. In this case, strictly speaking, a sulfuric acid ester group is introduced instead of a sulfonic acid group. However, in consideration of the object of the present invention, it functions as a sulfonic acid group and is treated as a sulfonic acid group. Examples of such water-soluble persulfates include, for example, sodium persulfate, potassium persulfate, ammonium persulfate, and the like.

In general, when it is intended to increase the stability of a resin emulsion, a surfactant having a high hydration power is used,
As a method for strengthening the protective layer on the surface of emulsion particles by means of adsorption of a water-soluble polymer or for improving the emulsion resin itself, carboxylation modification by copolymerization of an unsaturated carboxylic acid monomer is generally used. The present inventors have found that when an organic resin emulsion is added to an aqueous solution containing a metal phosphate as a main component, the hydroxyl groups and sulfonic acid groups present on the surface of the emulsion particles have a very large effect particularly on the stability of the emulsion. Things. Anionic, cationic, nonionic functional groups are known as hydrophilic groups introduced to enhance the stability of the resin emulsion, carboxyl groups, sulfonic acid groups are anionic, amino groups are cationic, Hydroxyl group,
Ether groups, amide groups and the like are known as nonionic. The mechanism by which the hydroxyl group and the sulfonic acid group are particularly good when an aqueous solution containing a metal phosphate as a main component is not clear in detail. However, since the carboxyl group has a small acid dissociation constant, it binds to a metal ion. Therefore, the hydrophilicity decreases, and the cationic hydrophilic group such as an amino group reacts with a phosphate ion to decrease the hydrophilicity. It is estimated that the effect on the stability of the emulsion was very small because it was too weak.

The proportions of the monomers constituting the organic resin emulsion are such that the hydroxyl group-containing monomer is 5 to 30% by weight and the sulfonic acid group-containing monomer is 0 to 30% by weight. When the amount of the hydroxyl group-containing monomer is less than 5% by weight, the stability of the emulsion tends to deteriorate. When the amount exceeds 30% by weight, the corrosion resistance is insufficient. When the amount of the sulfonic acid group-containing monomer exceeds 30% by weight, the corrosion resistance is insufficient. Tend to be. Further, when the sulfonic acid group-containing monomer is not blended,
It is preferable to add a water-soluble persulfate salt more than usual to increase the amount of sulfate group introduced. The content of the sulfonic acid group-containing monomer is more preferably 0.1 to 30% by weight, and further preferably 2 to 25% by weight.

In the present invention, in order to improve scratch resistance,
Organic resin emulsion particles may be used as the internal gelling polymer. In order to make the inside of the emulsion particles a gelled polymer, a part of α, β monoethylenically unsaturated monomer is
This can be achieved by substituting a polyfunctional monomer having two or more radically polymerizable ethylenically unsaturated groups in the molecule. Examples of such polyfunctional monomers include polymerizable unsaturated monocarboxylic acid esters of polyhydric alcohols, polymerizable unsaturated alcohol esters of polybasic acids, and aromatic compounds substituted with two or more vinyl groups. And so on. Such examples include ethylene glycol diacrylate, ethylene glycol dimethacrylate,
Triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, 1,3 butylene glycol dimethacrylate, trimethylolpropane triacrylate, glycerol diacrylate, 1,1,
1, trishydroxymethylethane diacrylate, diallyl terephthalate, divinylbenzene and the like.

Various hydroxyl group-containing organic resins can be obtained by using a monomer in which a hydroxyl group-containing monomer is introduced in addition to the above-mentioned polymers. For example, the organic resin used in the present invention can be obtained by introducing a hydroxyl group-containing monomer into an epoxy resin. More specifically, for example, epoxy resins include bisphenol A, F, B types, alicyclic type, glycidyl ether type, glycidyl ester type, biphenyl type, naphthalene type, phenol novolak type, orthocresol novolak type, and tetraphenylolethane And trishydroxynphenylmethane type, and these monomers are combined with the above-mentioned hydroxyl-containing monomers such as hydroxypropyl acrylate, 2-hydroxyethyl acrylate, and 3-hydroxybutyl acrylate. Can be obtained.

The organic resin emulsion usable in the present invention is characterized by a hydroxyl group and a sulfonic acid group on the surface of the emulsion particles. Therefore, a so-called hybrid resin in which different kinds of particles are contained in the particles or a hydroxyl group is introduced only into the surface. An emulsion may be used. The term "hybrid emulsion" as used herein refers to one in which two or more polymers having different properties are combined in emulsion particles, and various types of emulsions have been put into practical use by an emulsion polymerization method or the like. Typical examples include a core-shell type, a power feed type, a sandwich type, and a particle composite type.

By introducing a hydroxyl group and a sulfonic acid group onto the surface of the emulsion resin particles as described above, one selected from the above-mentioned acrylic, polystyrene, vinyl acetate, epoxy, polyurethane, polyamide, phenol, melamine, silicone, polypropylene, polyethylene, etc. One or more of the organic resins used can be used in the present invention.

The organic resin emulsion used in the present invention basically does not require an emulsifier. This is because the hydroxyl groups and sulfonic acid groups present on the surface of the emulsion particles enhance the stability of the electric double layer of the emulsion particles.
However, there is no problem even if a small amount of an emulsifier is added to further improve the dispersibility.

The particle size of the organic resin emulsion is from 0.01 to
It must be in the range of 0.5 μm. Particle size is 0.
When the particle size is less than 01 μm, the adhesion tends to deteriorate, and when the particle size exceeds 0.5 μm, the corrosion resistance becomes insufficient. A more desirable particle size range is 0.1 μm to 0.5 μm.
Range. This is because even if the emulsions have the same hydroxyl value, the amount of hydroxyl group per emulsion particle changes if the particle size is different. Is done.

The mixing ratio of the phosphate and the organic resin is such that the organic resin component is 5 to 100 parts by weight with respect to 100 parts by weight of the phosphate.
Parts by weight are preferred. If the organic resin content is less than 5 parts by weight, the coating is white and has no gloss, and if it exceeds 100 parts by weight, the coating may be peeled off after strain relief annealing.

The amount of the insulating film is 0.3 to 5.0 g / m
^{Assume 2} . If it is less than 0.3 g / m ² , it is difficult to secure sufficient withstand voltage, and if it is 5.0 g / m ² or more, the adhesion of the coating tends to be poor.

The baking conditions are not particularly limited, but are usually at 300 to 800 ° C.
Plate temperature in a short time in a drying oven set at
℃ is good.

The water-soluble low-molecular-weight organic compound having a non-dissociable hydroxyl group, ether group or ester group used in the present invention includes water-soluble organic substances such as alcohols, esters, ketones, ethers, carboxylic acids and sugars. A non-dissociable hydroxyl group,
It has an ether group and an ester group and does not have a polymerized state by polymerization or the like like an organic resin, and preferably has a molecular weight of 1,000 or less. In addition, the term water-soluble according to the present invention means that it is infinitely soluble in water,
Those having a relatively high solubility are sufficient, and specific compounds include alcohols such as butanol and propanol, propylene glycol, glycerin, ethylene glycol, polyols such as triethylene glycol, sucrose, sugars such as fructose, Cellosolves such as methyl cellosolve and butyl cellosolve, carbitols such as diethylene glycol monomethyl ether and diethylene glycol diethyl ether, ethers such as tetraethylene glycol dimethyl ether and 1,4-dioxane, and esters such as ethylene glycol monomethyl ether acetate can be used. However, particularly preferred are polyols such as ethylene glycol.

The water-soluble low molecular weight organic compound containing a non-dissociable hydroxyl group, ether group or ester group used in the present invention needs to remain in the film after coating and baking. In the case of a solid, the sublimation point needs to be higher than 100 ° C., which is the boiling point of water. Usually, the boiling point or the sublimation point is desirably 200 ° C. or higher.

The reason why the mixing ratio of the water-soluble low-molecular-weight organic compound used in the present invention is limited to 1 to 15 parts by weight with respect to 100 parts by weight of the phosphate, is that less than 1 part by weight of the water-soluble low-molecular-weight organic compound. This is because the effect cannot be obtained, and when the amount is 15 parts by weight or more, the film becomes cloudy and a glossy film surface cannot be obtained. By adding a water-soluble low molecular weight organic compound to the mixture of the metal phosphate and the organic resin emulsion used in the present invention, it is expected that the stability of the emulsion particles will be further improved.

[0029]

EXAMPLES Using the organic resin compositions shown in Table 1, 30% by weight of organic resin emulsions were prepared. Using these emulsions, treatment solutions shown in Table ² were prepared.
As the organic resin emulsion used in the present invention, for example, Nicazole manufactured by Nippon Carbide Co., Ltd. is suitable. Next, a treatment liquid containing an organic resin emulsion shown in Table 2 was applied to a coil of a non-oriented electrical steel sheet (plate thickness: 0.5 mm) after finish annealing, which was treated by a known method, using a rubber roll coating apparatus. Thereafter, a baking treatment was performed at a plate temperature of 200 ° C. so that the coating amount of the insulating film was 1.0 g / m ² . A sample was cut out from this coil, and the slip property was evaluated after performing strain relief annealing in a nitrogen stream at 750 ° C. for 2 hours. Table 3 shows the results.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

[Table 3]

[Slipperiness test method] A commercially available surface lubricity tester was used for the measurement of slipperiness. The measurement was performed at a moving speed of 20 mm / s using a steel ball with a load of 100 gf and a diameter of 10 mm. The sample was evaluated as acceptable if the surface did not have flaws or peeling after 10 reciprocal rubs, and failed if the surface had flaws or a ball was caught.

As is clear from Table 3, according to this example, an electrical insulating film having a high space factor, excellent punching properties, corrosion resistance, adhesion, and slip properties was obtained.

[0035]

According to the present invention, by forming an insulating film in which a specific organic resin emulsion and an inorganic component are blended in a specific ratio, it is possible to cope with environmental problems because it does not contain a chromium compound, thereby achieving high space occupation. Rate, excellent punchability, corrosion resistance,
An electromagnetic steel sheet having an electrical insulating film having adhesion and sliding properties is obtained.

Claims (5)

[Claims] 1. A non-oriented electrical steel sheet comprising, on the surface thereof, a metal phosphate and an organic resin emulsion having a hydroxyl value of 5 to 40 mg KOH / g and a particle size of 0.01 to 0.5 μm, The organic resin emulsion has an insulating film formed by applying a processing solution in an amount of 5 to 100 parts by weight (solid content) with respect to 100 parts by weight (solid content) of the metal phosphate and drying. Non-oriented electrical steel sheet with extremely excellent coating properties. 2. An organic resin emulsion obtained by containing 5 to 30 parts by weight of a hydroxyl group-containing monomer and 0 to 30 parts by weight of a sulfonic acid group-containing monomer as a copolymer component. The non-oriented electrical steel sheet according to claim 1, which has extremely excellent coating properties. 3. The film characteristic according to claim 1, wherein the organic resin emulsion is obtained by emulsion polymerization in the presence of a reactive emulsifier having a radically polymerizable unsaturated group in a molecule. Excellent non-oriented electrical steel sheet. 4. The method according to claim 1, wherein the adhesion amount of the insulating film is 0.3 to 5.0 g /
excellent electrical insulating film forming method for an electromagnetic steel sheet coating properties according to claim 1, 2 or 3, wherein the a m ^2. 5. A treatment liquid comprising a metal phosphate and an organic resin emulsion as main components, and a water-soluble low-molecular-weight organic compound containing a non-dissociable hydroxyl group, an ether group and an ester group. 3. The composition according to claim 1, wherein the content is 1 to 15 parts by weight based on parts by weight (in terms of solid content).
Or a non-oriented electrical steel sheet having extremely excellent coating properties according to 3.