KR100411279B1 - A coating solution for making insulation film on non-oriented electrical steel sheet and a method for making the insulation film on non-oriented electrical steel sheet by using it - Google Patents

Abstract

The present invention relates to a phosphate resin-based coating composition for forming an insulating coating of a non-oriented electrical steel sheet, a coating composition that can improve the appearance characteristics and insulation after stress relief annealing, and a method for forming an insulating coating of a non-oriented electrical steel sheet using the coating composition The purpose is to provide.

In order to achieve the above object, the present invention, 40.2 to 102.5g of the acid-soluble emulsion-acryl-styrene copolymer resin based on the weight of solid content with respect to 100g of phosphoric acid in the monobasic acid phosphate aluminum salt solution. , Zinc nitrate: 9.3 ~ 19.7g, Talc: 3.2 ~ 15.8g and acidic colloidal silica is added 0.6 ~ 12.4g by weight of solids, with respect to 100g of the solid content of the acrylic-styrene copolymer emulsion resin Crosslinking resin additive: 2.2 ~ 21.5g, and ethylene glycol: 14.2 ~ 77.2g, the coating composition for forming an insulating film to adjust the concentration with water and a method of forming an insulating film on the surface of the non-oriented electrical steel sheet using the same Let that point be about.

Description

Coating composition for forming insulating coating of non-oriented electrical steel sheet and method for forming insulating coating of non-oriented electrical steel sheet using the same ELECTRICAL STEEL SHEET BY USING IT}

The present invention relates to a coating composition for forming an insulating coating applied to a surface of an electrical steel sheet, and a method for forming an insulating coating of a non-oriented electrical steel sheet using the same, and more specifically, an inorganic coating material such as phosphorus and talc and a resin. The present invention relates to a phosphate-resin coating composition which can improve the insulation and appearance properties after stress relief annealing by securing a bonding force with and a method of forming an insulating coating of an non-oriented electrical steel sheet using the coating composition.

Non-oriented electrical steel sheets used as iron cores for electric machines such as small electric motors and transformers are provided to the demand after forming an insulating film on the surface thereof to suppress eddy currents and minimize power loss. The coil-oriented non-oriented electrical steel sheet provided to the demand includes slitting (cutting the steel plate in a predetermined width direction for use as an iron core), punching (machining to a predetermined shape by a mold), and high temperature heat treatment. (For the purpose of stress relief annealing) and automatic core formation such as automatic lamination. Therefore, the insulating film should not be peeled off during the high temperature heat treatment for stress removal in order to improve the work productivity, and have a heat resistance characteristic that can maintain the intrinsic electrical insulation. In addition, the coating process for forming the insulating film is a finishing process of the electrical steel sheet product, since it is directly provided to the demand price, the beautiful appearance is required. In addition to this, excellent adhesion, corrosion resistance, coating workability and the like are required as coating properties, but such performance must be achieved by an extremely thin coating film.

There are three kinds of coating compositions for forming an insulating coating having the above-mentioned properties, which are largely organic, inorganic or organic-inorganic. Among these, the organic-inorganic mixed composition has both the advantages of the inorganic coating composition and the advantages of the organic coating composition. However, the conventional organic-inorganic mixed coating composition contains chromic acid for coating properties such as corrosion resistance and adhesion, and thus adversely affects the human body when it comes into contact with the skin during the preparation of the insulating coating liquid and the coating treatment in the seal line, and also discharges wastewater. This is a problem because it causes environmental problems. In addition, due to the hexavalent chromium remaining in the steel sheet coating, the die may be abnormally worn and the life may be shortened during punching.

Research on the coating composition for forming an insulating coating having excellent coating properties such as corrosion resistance and adhesion without containing chromium has been conducted in the past, and as a result, a coating composition for a phosphate-acrylic resin-based insulating coating is applied. No. 97-49228. However, the coating composition according to the patent application No. 97-49228 has the property of having excellent corrosion resistance without containing chromium chemical, but when the continuous coating treatment is stained on the surface of the coil, the appearance is poor, and the insulating property after stress removal There is a problem of deterioration.

Accordingly, the present invention is composed of an organic and inorganic composite system containing no chromium composed of inorganic materials such as aluminum phosphate, talc, silica, zinc nitrate, acryl-styrene, and merbin resin, so that the appearance is good and the insulation after stress relief annealing It is an object to provide a coating composition for forming an insulating coating having excellent insulating coating properties such as continuous coating workability, adhesion, and corrosion resistance as well as improved properties.

Furthermore, the present invention provides a method for forming an insulating film of a non-oriented electrical steel sheet having a good appearance and excellent insulating properties by coating the coating on the electrical steel sheet and controlling the annealing time while controlling the coating thickness of the coating composition. have.

The inventors of the present invention, through the research and experiments to improve the appearance and insulation properties of the conventional coating composition described above, the components and contents of inorganic, organic insulating film-forming treatment liquid containing talc, ethylene gridium, etc. It was confirmed that the object can be achieved by adjusting and controlling the insulating film accordingly, and came to propose this invention.

The present invention for achieving the above object, based on the weight of the acid-soluble emulsion-acryl-styrene copolymer resin in the solid aluminum phosphate salt solution with respect to 100 g of phosphoric acid in the monobasic phosphate salt solution 40.2. ˜102.5 g, zinc nitrate: 9.3 to 19.7 g, talc: 3.2 to 15.8 g, and acidic colloidal silica are added in an amount of 0.6 to 12.4 g based on the weight of solids, and the solid content of the acrylic-styrene copolymer emulsion resin is 100 g. The crosslinking resin additive: 2.2-21.5g, and ethylene glycol: 14.2-77.2g are added, and it is related with the coating composition for insulating coatings characterized by adjusting the density | concentration with water.

In addition, the present invention for achieving the above another object, when the coating composition is applied to the surface of the non-oriented electrical steel sheet is applied while controlling so that the dry film thickness is in the range of 0.5 ~ 2.9㎛ per side, then 550 ~ 750 ℃ It relates to a method for forming an insulating coating of an non-oriented electrical steel sheet, characterized in that the annealing for 14 to 45 seconds in the heating furnace set to.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

[Coating composition for insulating film formation]

The inventors of the present invention, in the conventional coating composition (97-49228), considered the cause of the stain phenomenon appearing on the surface of the steel sheet during continuous roll coating for a long time as a local quick drying, and the insulation property after stress relief annealing is deteriorated Presumably due to a lack of resin deterioration compensation material.

Therefore, various kinds of additive elements of the phosphate-resin-based solution were examined to derive the basic composition of the coating composition having good external appearance, excellent insulation properties after stress relief annealing, and other characteristics, which will be described in theory next.

First, the reason why the phenomenon appears on the surface of the steel sheet when applying a continuous roll at high speed for a long time.

When heat annealing at a relatively high temperature of 550-750 ° C. for a short time, a volatilization rate difference occurs between the water component having a boiling point of 100 ° C. and other coating raw materials. That is, when the continuous roll is applied for a long time, the temperature rise due to the compression between the pressing rolls is caused to partially volatilize the water in the treatment liquid, so that the phosphoric acid and the resin component are quickly dried to become solid in the liquid phase. They do not re-solubilize and show stickiness, which causes surface staining. Therefore, in order to prevent the staining, by adding an appropriate amount of ethylene glycol higher than the boiling point water to enable a stable operation for a long time without staining, and also by delaying (adjusting) the volatilization speed uniformity without spots throughout the material Get an appearance.

Next, after the high temperature heat treatment for stress relief annealing performed at around 800 ° C. for 1 hour or more, in order to prevent loss of insulation effect due to deterioration of the resin component remaining in the film, fine powdery talc (talc) is pretreated. It was added directly to the treatment liquid without omission. In this case, however, the effect of improving the insulating properties can be obtained, but since the talc mixed with the air in the form of a lump deteriorates the appearance of the film after the treatment, the value as a commodity is lost. In addition, in order to directly add a small amount of fine powdery talc directly to a large amount of the processing liquid and to uniformly prepare it at high speed, energy and time required to uniformly disperse and stir the talc close to lipophilic properties are practically uneconomical. There is a problem. Therefore, in the present invention, instead of directly putting powdery talc in contact with air into the treatment liquid, talc is mixed in a small amount of the dispersion medium containing ethylene glycol and subjected to high speed stirring in order to eliminate air mixing as much as possible. After making it into a state, it inject | pours into a process liquid and homogenizes, so that the improved appearance characteristic may appear after a coating process. As a dispersion medium for the talc, it is preferable to add ethylene glycol rather than water alone, because talc dispersion is much easier and more economical.

In addition, in the present invention, by adding a combination of talc and colloidal silica to the coating composition to have an improved insulation properties after high temperature heat treatment for stress relief annealing. It is thought that this is because the spherical colloidal silica component penetrates through the stacked layers of talc and forms a dense insoluble coating, thereby compensating for the deterioration in insulation due to resin deterioration during stress relief annealing.

Hereinafter, the role and action of each component will be described, the reason for numerical limitation thereof will be described in detail, and the method of forming an insulating film on the non-oriented electrical steel sheet using the coating composition as described above will be described in detail.

[Role and Action of Each Component]

Phosphate in the present invention is added to impart heat resistance and corrosion resistance to the film, and it is preferable to add and dissolve aluminum hydroxide, which is a trivalent metal compound, to 85% phosphoric acid up to a composition ratio that becomes a solution of monobasic aluminum phosphate. However, the manufacturing method of the monophosphoric-acid phosphate solution, and the compounding ratio between them are not specifically limited in this invention, It is made to use the monobasic aluminum phosphate solution conventionally used generally. In addition, although the said phosphoric acid was 85% of concentration, this invention is not limited to this, The phosphoric acid conventionally used generally can be used.

The acryl-styrene copolymer resin is added in order to increase the adhesiveness of the material and to impart the flexibility of the film, but it is preferable to use an emulsion type resin rather than a water-soluble resin in view of compatibility and stability with an aqueous phosphate solution. In addition, the acrylic-styrene copolymer resin is preferably acid soluble in order to improve the coating stability in the acidic mixture and coating uniformity of the low viscosity emulsion. It is preferable to use an acid-soluble emulsion (average particle diameter: 0.2 mu m) type acrylic-styrene copolymer resin having a pH of 3 or less.

The amount of the acid-soluble emulsion-acryl-styrene copolymer resin to be added is 40.2 to 102.5 g by weight of the resin solid content with respect to 100 g of phosphoric acid in the monobasic aluminum phosphate solution. The reason is that if the amount of the acid-soluble emulsion-acryl-styrene resin is less than 40.2 g, sufficient film adhesion and good film appearance cannot be obtained, so that the effect of the addition of the organic resin is ineffective. This is because there is no practical use.

The zinc nitrate is added to give the coating corrosion resistance and light greenish yellow color. When the added amount is less than 9.3 g in solid content with respect to 100 g of the phosphoric acid, sufficient corrosion resistance and good film color cannot be obtained, and when it exceeds 19.7 g, it is difficult to prepare a uniform treatment solution, resulting in poor appearance and uneven insulation after coating. Therefore, since the practicality is lost, the addition amount is preferably limited to 9.3 to 19.7 g.

The talc and colloidal silica are added to give an insulating property to the film after the stress relief annealing, it is preferable to add in the sludge dispersed homogeneously with ethylene glycol, the colloidal silica is compatible with the acid treatment liquid Preference is given to using the acidic colloidal silicas considered. At this time, if the talc is less than 3.2g by weight of solid content with respect to 100g of phosphoric acid, colloidal silica is less than 0.6g, sufficient insulation properties are not obtained after stress relief annealing, talc is more than 15.8g, If the colloidal silica is added in an amount exceeding 12.4 g, an uneven coating appearance will appear during the coating treatment. Therefore, talc should be 3.2 to 15.8 g by weight of solids and 0.6 to 12.4 g by weight of solids. . In this way, satisfactory insulating effect after stress relief annealing, which cannot be obtained alone, can be obtained.

The crosslinking resin additive is added to improve the appearance properties such as surface gloss and fingerprints, for example, melanin-formaldehyde resin [CYTEC (USA): trade name Cymel-327] Can be. It is preferable that the addition amount of such a water-soluble crosslinking type resin additive is 2.2-21.5g with respect to 100g of acryl-styrene-type copolymer emulsion resin solids. The reason is that if it is added less than 2.2g, the effect of addition does not appear, and if the amount exceeds 21.5g, it becomes gel in a few hours, resulting in loss of coating processability, and because it is expensive, it is disadvantageous in terms of economy. to be.

The ethylene glycol has a role of imparting uniform appearance characteristics such as preventing staining of the coil surface. When the amount of the ethylene glycol is less than 14.2 g with respect to 100 g of the acrylic-styrene copolymer emulsion resin, the appearance characteristics are insufficient. In the case of exceeding 21.5 g, corrosion resistance and water resistance deteriorate due to hydroxyl groups remaining in some films without volatilization after drying, so that the amount of addition is preferably 14.2 to 77.2 g. The addition amount of the said ethylene glycol is the addition amount as said talc dispersion auxiliary role.

[Method for Forming Insulating Film of Non-oriented Electrical Steel Sheet]

In the present invention, when the coating composition configured as described above is applied to the surface of the non-oriented electrical steel sheet, the dry film thickness is applied so as to be 0.5 to 2.9 µm per one side, and annealing for 14 to 45 seconds in a heating furnace set at 550 to 750 ° C. . As described above, according to the present invention, it is possible to obtain an insulating film having excellent roll coating coating workability, appearance, adhesion, corrosion resistance, etc., as well as insulating properties, which are essential requirements to be provided as an inorganic-organic mixed film.

One of the factors that determine the appearance characteristics of the film is the relationship between the annealing temperature and time. If the temperature of the furnace is maintained at 750 ° C., which is the maximum temperature, and is kept at less than 14 seconds, the film formation is insufficient due to micro annealing and hygroscopicity remains. On the other hand, if it is maintained for more than 45 seconds at 550 degreeC which is the minimum allowable temperature, the coating agent chemically bonded to the oxide layer is oxidized, and the coating color becomes blackish brown to black, which is poor.

On the other hand, if the temperature of the furnace is kept below 550 ° C, annealing becomes insufficient and hygroscopicity is left or a film is formed, which requires a long time. In fact, industrial use causes a problem of low productivity, and exceeds 750 ° C. In this case, it is difficult to control the annealing temperature, so that uneven film formation is maintained, thereby making it difficult to control the surface quality such as appearance defects, which makes it difficult to work industrially stably.

On the other hand, in the present invention, the film thickness of the electrical steel sheet was controlled to 0.5 ~ 2.9㎛. If the film thickness is less than 0.5㎛, even if the film is formed while satisfying the annealing conditions after applying with a roll (roll), etc., the required insulating properties can not be obtained, while if it exceeds 2.9㎛ weldability and spot ratio Degrades.

Hereinafter, the present invention will be described in more detail with reference to Examples.

(Example)

As shown in Table 1 below, after coating compositions of various compositions were prepared, and after 7 days, the surface of the non-oriented electrical steel sheet (containing 1.0% Si) having a sheet thickness of 0.5 mm was uniformly coated with a synthetic rubber roll, and then The insulating films were formed under various annealing conditions to prepare specimens of the present invention and the comparative examples. The coating properties of each insulating film were evaluated, and the results are shown in Table 2 below. In addition, the insulating film specimens were heat-treated for 780 ° C. × 2 hours in a dry 100% N ₂ gas atmosphere for stress relief annealing, and the film properties after stress relief annealing were evaluated and the results are shown in Table 2 below.

division Cover composition Annealing Condition Film thickness (single side μm) Jeil Aluminum Solution Talc Emulsion Acrylic-Styrene Resin ^① Acid type colloidal silica ^② Ethylene Glycol Water-soluble crosslinking resin additive ^③ Zinc nitrate water Temperature (℃) Time in seconds Phosphoric Acid Aluminum hydroxide Inventive Example a 100 27.4 8.7 71 4.0 21 1.9 14 93 550 30 1.7 b 28.1 9.6 75 4.1 20 2.5 15 99 31 1.9 Comparative example One 27.8 － 128 － 45 3.1 11 83 29 1.5 2 27.3 7.5 11 4.2 18 2.2 One 102 32 0.2 3 28.0 8.4 85 4.7 24 2.7 10 94 9 － 4 29.1 9.5 84 6.7 2.5 2.9 13 98 72 － 5 38.8 3.6 44 25 23 30 12 131 － － 6 25.9 8.8 77 3.3 － － 13 99 Continuous application is not possible ① is trade name PA-P40, and the amount is based on solid content ② is Snowtex-O, and is manufactured by Japan Forest Chemical Co., Ltd. ③ is Cymel-327 and is manufactured by Cytex, USA In Comparative Example 6, staining was observed on the surface of the non-oriented electrical steel sheet for 2 hours in a practical application, and it was judged that the roll coating workability was lost and no further coating treatment was performed.

division Film characteristics Before stress relief annealing After stress relief Outer appearance Insulation (Amp.) Adhesiveness (mmΦ) Corrosion resistance (rusting phenomenon:%) Anti-fingerprint Peeling phenomenon Adhesiveness (mmΦ) Insulation (Amp.) Inventive Example a Good 0.10 10 Good (0) Good none 10 0.10 b Good 0.07 10 Good (0) Good none 10 0.08 Comparative example One Good 0.32 10 Medium (30) Bad Some 40 0.92 2 Bad 0.96 40 Poor (85) 〃 〃 20 0.98 3 〃 Not measurable Not measurable 4 〃 〃 〃 5 〃 〃 〃

In Table 2, the surface appearance is evaluated by visually observing stains, streaks, gloss and color, and it is determined that there is no stains and streaks, the gloss is good, and a light greenish yellow color appears to be good. The appearance is less gloss and the surface color becomes grayish white similar to that of the small support plate.

The insulation was evaluated by the storage current value (Amps.) When a current of 0.5 V x 1.0 A was passed under a 300 PSI input.

The adhesiveness (mm) was evaluated as the minimum arc diameter without film peeling when the specimen was bent 180 ° after being contacted with an arc of 10, 20, 30 to 100 mm after annealing.

The corrosion resistance was evaluated by visually observing the presence of rust on the surface of the coating after 24 hours of salt spray test (5% NaCl, 35 ℃).

The anti-fingerprint of the steel sheet was evaluated by the color difference (ΔE) before and after the application of petroleum jelly using the coated specimen as a standard specimen, and was good when the ΔE value was 2.0 or less and poor when it was 2.0 or more.

The film peeling was indicated by the presence or absence of adhesion of the film peeling powder which appeared when the adhesive tape (polypropylene) was poured on the film after the stress relief annealing.

As can be seen from Table 1 and Table 2, Examples (a) and (b) of the invention satisfying the conditions of the present invention showed excellent characteristics required as a coating, such as insulation properties and appearance after stress relief annealing. At this time, the appearance of gloss and beautiful appearance is presumably because it reacts with the excess free phosphoric acid remaining in the treatment liquid during annealing of the added silica and the crosslinking resin additive Cymel-327. In addition, despite the expected degradation of the insulation properties due to the oxidation of the resin component due to the oxidation of the resin component, it is hardly actually lowered after the high temperature heat treatment for stress relief annealing, the newly formed inorganic material by the added talc, silica, etc. It is assumed that this is because the degradation in insulation characteristics due to the resin component is canceled out.

On the other hand, in the case of Comparative Examples (1) to (5) in which the addition range of the coating composition was improper or improperly applied and annealed, the characteristics required as a coating such as insulation and appearance after stress relief annealing were invented (a), ( fell compared to b). That is, in Comparative Example (1) in which the resin content was excessively added and the talc and colloidal silica were treated with the unadded coating composition, the insulation characteristics were poor after the stress relief annealing. In addition, Comparative Example (2) treated with a coating composition having a low content of an emulsion-type acrylic-styrene copolymer resin and zinc nitrate had poor appearance, adhesion, insulation, and corrosion resistance. In addition, in Comparative Example (3), the annealing treatment conditions were insufficient, and thus film formation was difficult. In Comparative Example (4), the carbon annealing was performed by the annealing treatment. In Comparative Example (5), when aluminum hydroxide, talc, colloidal silica, and crosslinking resin additives were added in excess, layer separation and gelation occurred during stagnation. This becomes extremely bad.

According to the present invention as described above, it is possible to obtain a coating composition for forming an insulating film having improved insulation characteristics and appearance after stress relief annealing as well as the general properties required as a coating, and coating treatment by using this coating composition. It can prevent environmental problems that occur during

Claims (2)

40.2-102.5 g of zinc nitrate based on the weight of an acid-soluble emulsion-type acrylic-styrene copolymer resin as a solid content with respect to 100 g of phosphoric acid in the said aluminum phosphate salt, in a monobasic phosphate solution: 9.3-19.7 g, Talc: 3.2 to 15.8 g, and 0.6 to 12.4 g of acidic colloidal silica were added based on the weight of solids, and the crosslinking resin additive was added to 2.2 g of the solids of the acrylic-styrene copolymer emulsion resin. ~ 21.5g, and ethylene glycol: 14.2 ~ 77.2g is added, and the coating composition for forming an insulating film of the non-oriented electrical steel sheet, characterized in that the concentration is adjusted by water. When the coating composition of claim 1 is applied to the surface of the non-oriented electrical steel sheet, it is applied while controlling the dry film thickness to be in the range of 0.5 to 2.9 μm per one side, and then annealing for 14 to 45 seconds in a heating furnace set at 550 to 750 ° C. Method for forming an insulating film of an non-oriented electrical steel sheet, characterized in that.