KR20090069983A - Coating solution for forming insulating film, method for forming insulating film of non-oriented electrical steel sheet and non-oriented electrical steel sheet by using it - Google Patents

Abstract

A coating composition for forming an insulation film, a method for forming the insulation film of a non-oriented electric steel sheet, and the non-oriented electric steel sheet are provided to improve the insulating property of the surface gloss by prevent the surface gloss degradation after the thick film coating. A coating composition for forming an insulation film comprises: a phosphate solution that first aluminum phosphate(Al(H2PO4)3) and first zinc phosphate(Zn(H2PO4)2) are mixed to 1:1; a cobalt hydroxide and strontium hydroxide; polyester emulsion resin; aluminum silicate; and chelate additive of the Ti system. The molecular weight of the polyester emulsion resin is 2,000~15,000 and the Tg is 40~50°C. The solidity ratio of the polyester emulsion resin is 15~25%, the viscosity is 100~500cp, and the pH is 4~5.

Description

COATING SOLUTION FOR FORMING INSULATING FILM, METHOD FOR FORMING INSULATING FILM OF NON-ORIENTED ELECTRICAL STEEL SHEET AND NON-ORIENTED ELECTRICAL STEEL SHEET BY USING IT}

The present invention relates to a coating composition for forming an insulating coating, and more particularly to a coating composition for forming an insulating coating of a non-oriented electrical steel sheet. In the non-oriented electrical steel coating material, the composition does not contain Cr and prevents the surface gloss decrease due to the application of the thick film, thereby providing excellent surface gloss and insulation properties, and a non-directional insulation coating method having excellent corrosion resistance and film adhesion. . More specifically, after forming the non-oriented electrical steel sheet coating, the coating composition for forming an insulating coating having excellent insulation and excellent surface gloss and corrosion resistance, and excellent stress film adhesion after stress relief annealing (SRA), and using the same The present invention relates to a method for forming an insulating coating of a non-oriented electrical steel sheet.

Since electrical steel sheet is used for various uses, development of various insulating films is performed according to the use. Among electrical steel sheets, non-oriented electrical steel sheets are materials used for iron cores of electric motors and generators. Coatings, which correspond to the final manufacturing process of the product, provide not only the interlaminar resistance, but also the punching, shear and bending properties required for work forming. As described above, continuous punching workability that suppresses abrasion of a mold is required when stacking a plurality of punchings into a predetermined shape to form an iron core. In addition, after the SRA process of removing the work stress of the steel sheet to restore the magnetic properties, it requires a sticky resistance that does not adhere between the steel core steel sheet.

As described above, the non-directional insulating film is intended for the interlayer insulation between the iron plates to be laminated. However, as the use of small electric equipment has been expanded, the film performance, which is more favorable for workability, weldability and corrosion resistance than insulation, has been evaluated as the main physical property.In recent years, the quality of the steel plate surface also affects the use characteristics, requiring an electric steel sheet with excellent surface quality. Was done.

Recently, due to the emergence of high-quality products due to the improvement of the magnetic properties of non-oriented electrical steel sheet has been used for large wind turbines or thermal power generators, high insulation between steel sheets is required accordingly. As a result, in order to reinforce the heat resistance and insulation of the non-directional insulating coating, an organic inorganic composite coating agent was developed to compensate for the shortcomings of inorganic systems such as phosphate and chromate.

However, the existing coating liquid composition is required to contain chromium oxide, and thus the situation is limited to the use in view of the reality that environmental regulations are being strengthened. Recently, the chromium-free coating of electrical steel coatings is actively progressing, and it can be divided into a method of introducing phosphate and a method of inducing a barrier effect through the introduction of colloidal silica to reinforce corrosion and adhesion weakening due to the lack of chromate. The former improved the adhesiveness and corrosion resistance by using the phosphate which mixed Al phosphate, Ca phosphate, and Zn phosphate appropriately. However, when metal phosphate is used, free phosphoric acid present in the metal phosphate may cause sticky property of the film. In order to prevent sticky property of free phosphoric acid, a technique of adding an organic acid has been proposed.

On the other hand, in order to increase the barrier effect by adding colloidal silica, colloidal silica, alumina sol, zirconium oxide, one or two or more kinds of inorganic materials are used to secure corrosion resistance, adhesion and smoothness after SRA, and a silane coupling agent. The technique which improved adhesiveness and solvent resistance by adding etc. was proposed. In addition, when the ratio of the surface area of the resin and the silica is appropriate, it is possible to form a fine dispersion film structure to improve the adhesion and corrosion resistance. However, the Cr-free coatings mainly based on phosphate or colloidal silica described above have limitations on stickyness of phosphate and corrosion resistance improvement of colloidal silica, respectively. Commercialization of the technology is still difficult.

In addition, in terms of insulation resistance, which is an important property mentioned above, most of the conventionally proposed non-directional coatings have a thickness of a thin film type, and thus the insulation resistance properties cannot be satisfied because the basic insulation resistance is about 900 mA. Conventional methods for increasing insulation resistance include one of chromic anhydride (CrO ₃ ), magnesium oxide (MgO) and calcium oxide (CaO), ionized water, acryl-based resins or acryl-styrene 1) Copolymer resin, and characterized in that consisting of butyl carbitol (Butyl Carbitol) as a reducing agent, improve the coating solution stability and coating workability at room temperature and high temperature, and improve the corrosion resistance and insulation of non-oriented electrical steel sheet do.

Korean Patent Application No. 1997-0051755 (Publication No. 1996-056917) synthesizes one of chromic anhydride (CrO3), and metal oxides of calcium oxide (CaO) and magnesium oxide (MgO) to synthesize magnesium dichromate and calcium dichromate. Was prepared. In the patent, a surfactant, an antifoaming agent, and the like were added as additives to improve solution stability during continuous coating, and ultrafine mica powder was added to improve electrical insulation.

However, in the case of Cr-type coatings, it is difficult to actively cope with stringent environmental regulations, as discussed above. Especially, since the dichromate solution used in most of the coatings described above has a strong acidity of 1 or less, And the addition of an organic reducing agent to the dichromate solution has the drawback that the gelation reaction occurs in a short time.

Accordingly, there is a need for development of a Cr-free coating agent for a thick film, which is excellent in surface gloss and insulation while simultaneously eliminating Cr and allowing thick film coating.

SUMMARY OF THE INVENTION An object of the present invention is to provide a coating composition for forming an insulating film without chromium, a method for forming an insulating film of an non-oriented electrical steel sheet, and a non-oriented electrical steel sheet.

The coating composition for forming the insulating film is cobalt hydride in a phosphate solution in which first aluminum phosphate (Al (H ₂ PO ₄ ) ₃ ) and first zinc phosphate (Zn (H ₂ PO ₄ ) ₂ ) are mixed in a 1: 1 ratio. Cobalt hydroxide and strontium hydroxide, polyester emulsion resin, aluminum silicate, and Ti-based chelate additives are added, wherein the polyester emulsion resin has a molecular weight of 2,000 to 15,000.

The polyester emulsion resin has a Tg (glass transition temperature) of 40 to 50 ° C, a solid content of 15 to 25%, a viscosity of 100 to 500cp, and a pH of 4 to 5.

The first zinc phosphate has a solid content of 2.75M, 52.5%, the mixed phosphate solution has a solid content of 55 to 60% by weight and a viscosity of 30 to 70cp.

For 100 g of the mixed phosphate solution, 0.5-5 g of cobalt hydroxide and strontium hydroxide are added at a ratio of 1: 1, 150-300 g of the polyester emulsion resin is added, and the aluminum silicate is 3-10 g is added, and 0.1-6.0 g of the chelating additive of the Ti system is added.

The chelating additives of the Ti system include Triethanolamine titanate, Titanium 2,2,2-nitrilotrisethanolate (2-2-2 titanium nitrilotricetanolate), Mixture organic titanate and inorganic phophrous compounds (organic titanate) Porous composition).

In the method of forming an insulating film of the non-oriented electrical steel sheet, a coating composition for forming an insulating film is coated on a steel sheet with 2.0 to 6.0 g / m 2 per one side, and heated at a temperature of 350 to 700 ° C. for 10 to 50 seconds to insulate the insulating film. It characterized in that to form.

According to the embodiment of the present invention, the coating of the non-oriented electrical steel sheet excellent in insulation and corrosion resistance is implemented by controlling the physical properties of the coating agent to enable the thick film coating while excluding Cr. To this end, phosphates in the form of cobalt hydroxide and strontium hydroxide added aluminum monophosphate (Al (H ₂ PO ₄ ) ₃ ) and first zinc phosphate (Zn (H ₂ PO ₄ ) ₂ ) mixed with an ester resin In the case of aluminum silicate and Ti system, chromium-free non-oriented electrical steel sheet having excellent surface gloss and insulation property and excellent corrosion resistance and film adhesion after SRA when the non-oriented electrical steel sheet is formed using a coating agent based on chelate additive. An insulating film can be formed.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art may easily implement the technical idea of the present invention. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosed contents may be thorough and complete, and the technical spirit of the present invention may be sufficiently delivered to those skilled in the art.

The present invention provides a coating agent that does not contain a chromium compound in the production of non-oriented electrical steel sheet, and at the same time, the film formed even at a film thickness of 2 μm or more has excellent gloss and excellent processing properties such as high insulation and punchability, adhesion, and droplets. It relates to a non-oriented electrical steel sheet product and coating agent having an insulating coating agent and an insulating coating method using the same.

In the case where non-oriented electrical steel sheet is used for iron core of motor or transformer, the product is punched to the standard and then piled up a certain number of sheets to be iron core by welding or bonding. In these operations, SRA is performed on a case-by-case basis, and therefore, the adhesion, insulation, corrosion resistance, etc., after annealing become particularly important when an SRA process is involved. The non-oriented electrical steel film contains chromium, and in this case, it helps to improve the film properties after SRA. On the other hand, in the case of a coating agent containing no chromium, phosphate is introduced as a substitute for chromium. At this time, there may be a problem of hygroscopicity due to the trace amount of free phosphoric acid remaining in the coating or adhesion during annealing (see Equation 1). Furthermore, since the effect, such as the compactness by the unique film filling effect by a chromium compound, cannot be seen, there exists a limit in preventing a film physical property fall.

CrO ₃ + 2H ₃ PO ₄ → Cr (PO ₄ ) ₂ + 6 H ₂ O ------ (1)

As a cause of the corrosion resistance of the coating agent mentioned above and the adhesion decrease after SRA, the phosphate present in the film exists as free phosphoric acid after drying the film, and this free phosphoric acid absorbs moisture after forming the film, thereby lowering the corrosion resistance. In addition, the cause of the decrease in film adhesion after SRA is the degree of compatibility between the emulsion organic resin, which is the main component of the coating agent, and the metal phosphate. The degree of compatibility is solved through the relationship between the rheological viscoelasticity according to the molecular weight of the emulsion resin and the surface gloss after application.

Therefore, in the present invention, in order to overcome corrosion and adhesion that may occur when chromium is excluded from the coating agent and to improve film adhesion after SRA, first monophosphate (Al (H ₂ PO ₄ ) ₃ ) and first zinc phosphate (Zn) (H ₂ PO ₄ ) ₂ ) Add cobalt hydroxide and strontium hydroxide to the mixed phosphate. Solid content at this time is 55 ~ 60wt% relative to the total weight of phosphate. 100 g of phosphoric acid, the weight average molecular weight of 2,000 ~ 15,000 and the solid content of 20 ~ 25wt% polyester emulsion resin 150 ~ 300g, aluminum silicate 3 ~ 10g, and Ti system 0.5 ~ 6.0 g of chelate additive By addition a coating is prepared. The composition thus prepared is coated so as to be in a range of 2.0 to 6.0 g / m ² per one side, and then heat treated for 10 to 30 seconds at a temperature range of 350 to 700 ° C. to form an insulating coating.

Through the following method, the surface gloss reduction and the film adhesion after SRA are improved as the coating amount is increased.

Phosphates in the form of a mixture of aluminum phosphate (Al (H ₂ PO ₄ ) ₃ ) and zinc phosphate (Zn (H ₂ PO ₄ ) ₂ ) with cobalt hydroxide and strontium hydroxide By adding a polyester emulsion resin having a weight average molecular weight of 2,000 to 15,000 and a solid content weight of 15 to 25 wt%, glossiness was secured during thick film application. When the metal phosphate is introduced as a component of the coating agent, the metal phosphate plays an important role as a film forming agent having excellent heat resistance as well as improving adhesion of the coating agent by acting as a binder between the coating agent composed of an organic-inorganic composite component and the base steel sheet.

The phosphate salt is a hydrogen phosphate salt in the form of a mixture of aluminum phosphate (Al (H ₂ PO ₄ ) ₃ ) and zinc phosphate (Zn (H ₂ PO ₄ ) ₂ ). These phosphate solutions have 2.75 M, 52.5% solids for mono zinc phosphate (Zn (H ₂ PO ₄ ) ₂ ). In addition, the manufacturing method of the first aluminum phosphate (Al (H ₂ PO ₄ ) ₃ ) is not limited, but the mixing ratio between them is very closely related to the viscosity related to adhesion, and the solution viscosity according to the mixing ratio is described in Table 1 below. As seen from

The emulsion resin is a polyester emulsion resin having a weight average molecular weight of 2,000 to 15,000 and a solid weight of 20 to 25 wt%. A polymer having a molecular weight of 1,000 or more is commonly referred to as a polymer or an organic resin, and it has been found that the surface gloss degradation in thick film application is closely related to its own properties and compatibility with metal phosphate, that is, compatibility. In other words, by mixing the emulsion resin and the metal phosphate at a specific molecular weight it was possible to prevent the degradation of the gloss when applying the thick film, it was possible to prepare a Cr-free thick film coating with excellent appearance.

In addition, the compatibility of the metal phosphate and the emulsion resin is related to the film adhesion after the SRA, if the compatibility between the two components is not good may cause a fine phase separation phenomenon or the entanglement between the two components that are not observed immediately after the coating preparation. . After forming the film using the coating agent prepared as described above, the SRA process at about 750 ° C. for 2 hours can be observed that foreign substances such as black ash remain on the surface of the specimen. When the motor or compressor is manufactured using the final product where this phenomenon is found, it may not only block the water supply line of the cooling oil but also have a fatal effect on the life of the product. In the present invention, in order to solve this problem, the compatibility of the main components of the coating agent with the organic resin and the metal phosphate of the coating agent and the coating agent by using the Ti-based chelate additive with the improvement of compatibility with the metal phosphate by controlling the molecular weight of the emulsion resin mentioned above Adhesion between materials is improved.

Hereinafter, the present invention will be described in detail.

Corrosion resistance is the most typical property as a requirement for insulating coating for non-oriented electrical steel sheet, which usually contains chromium oxide as an insulating coating treatment agent for imparting the required characteristics of the coating. However, there is a concern about the adverse effects on the human body due to skin contact, etc. during the production of insulating coating liquids and the application of chromium on the line, and the environmental problems when the waste water is discharged. Since shortening occurs, it is ideal to exclude the use from the beginning of the production of insulating coating liquid.

In order to prevent corrosion and film denseness due to the exclusion of chromium oxide, the present invention requires the introduction of metal phosphate, but the first monophosphate (Al (H ₂ PO ₄ ) ₃ ) and the first zinc phosphate (Zn (H ₂ PO _{4) 2} ) Mixed hydrogen phosphate salts were used. These phosphate solutions have 2.75 M, 52.5% solids in the case of the first zinc phosphate (Zn (H ₂ PO ₄ ) ₂ ), in addition to the production method of the first aluminum phosphate (Al (H ₂ PO ₄ ) ₃ ) is limited However, the blending ratio between them is very closely related to the viscosity related to corrosion resistance and adhesion, so that the proper viscosity is maintained after preparation. In the present invention, various metal phosphates, that is, mono aluminum phosphate (Al (H ₂ PO ₄ ) ₃ ) and mono zinc phosphate (Zn (H ₂ PO ₄ ) ₂ ), and mono magnesium phosphate (Mg (H ₂ PO ₄ )) ₂ ) Various combinations of various metal phosphates, etc. were prepared and mixed with the resin of the ester system, and tested for corrosion resistance. The results were as follows: monobasic aluminum phosphate (Al (H ₂ PO ₄ ) ₃ and zinc phosphate (Zn (H ₂ PO)). _{4) 2)} 50 the solid mixture while the ratio of 60wt%, exhibited the best characteristics in corrosion resistance, when a viscosity of 30 ~ 70 cp (Table 1). the first aluminum phosphate (Al (H ₂ PO _{4 3) 3)} it can not maintain an appropriate viscosity when the high also showed a sticky properties after drying the first zinc phosphate _{(Zn (H 2 PO 4)} 2) the higher the ratio gets the decrease in corrosion resistance to achieve the expected object of the Therefore, the optimum mixing ratio of the metal phosphate was monophosphate (Al (H ₂ PO ₄ ) ₃ and mono zinc phosphate (Zn (H ₂ PO _{4). 2} ) 50/50 mixed solution with solid content of 60wt%, viscosity 30 ~ 70 cp, especially 50 cp.

However, when phosphate is used in the coating agent, as mentioned above, surface sticky or powdery precipitation by free phosphoric acid is a problem. Therefore, in the present invention, cobalt hydoroxide and strontium hydroxide replace chromium oxide by applying a wide range of metal oxides or hydroxides to solve such problems and to find a substance which substitutes chromium oxide and free phosphoric acid as shown in Equation (1). It is confirmed to improve the precipitation of free phosphoric acid and the film density. In particular, when cobalt hydoroxide and strontium hydroxide are properly mixed, surface sticky, powder precipitation prevention and corrosion resistance can be improved.

On the other hand, in recent years, due to the emergence of high-quality products in accordance with the improvement of the magnetic properties of non-oriented electrical steel sheet has been used for large wind turbines or thermal power generators, high insulation between the steel sheets is required accordingly. However, as described above, not only the surface gloss is significantly lowered when the thick film of the coating agent is applied, but the coated product may cause serious surface defects when it is accompanied by a customer processing and an SRA treatment process. As a cause of this phenomenon, the present inventors paid attention to the compatibility of the metal phosphate and the emulsion resin. In other words, compatibility between the two components is closely related to the film adhesion after SRA. Phenomenologically, if the compatibility between the two components is not good, a fine phase separation phenomenon or a entanglement between the two components that may not be observed with the naked eye immediately after the coating preparation may occur. In addition, when the film is formed with the coating agent prepared as described above, most of the thin film of 1 μm or less can obtain the same level of product in surface gloss as compared to the general non-directional coating agent. The film adhesion after the SRA is very poor.

The fundamental influencer of this phenomenon can be understood as the molecular weight of the emulsion resin. In general, polymer solutions containing emulsion resins exhibit viscoelastic (non-Newtonian) behavior unlike viscous (Newtonian) fluids such as water. The viscoelastic behavior of fluids is a property of the flow and deformation of the material. As the molecular weight of the emulsion resin increases, the fluid elasticity increases. The viscoelastic properties of the materials are measured by rheometers, and the elastic properties according to the molecular weight of the emulsion resin can be seen by the G '(storage modulus) value that is displayed from the measuring device. Figure 1 shows the storage modulus of the emulsion resin according to the molecular weight and shows the phenomenon that the storage modulus increases in the A region, that is, low frequency region of Figure 1 as the molecular weight increases, this phenomenon is theoretically the Prediction is also possible with emulsion models that simulate behavior.

Through the above experiments, the elastic properties of the fluid increased with the increase of the molecular weight of the emulsion resin, and thus the compatibility with the metal phosphate, another main component of the coating agent, was inhibited. Described. Therefore, in the present invention, the compatibility with the metal phosphate was improved by using a polyester resin in a range in which elasticity was not increased (weight average molecular weight 2,000 to 15,000), and as a result, excellent surface gloss and thick film adhesion after SRA were applied in thick film coating. Can be improved.

In addition, in order to prevent black ash from occurring on the surface after SRA of the thick film coating product, the Ti system introduced a chelate additive. The Ti-based chelate additive used may be any one of Triethanolamine titanate, Titanium 2,2,2-nitrilotrisethanolate, Mixture organic titanate and inorganic phophrous compounds.

Therefore, in order to overcome corrosion and adhesion that may occur when chromium is excluded and to improve film adhesion after SRA, first aluminum phosphate (Al (H ₂ PO ₄ ) ₃ ) and first zinc phosphate (Zn (H ₂ PO _{4) 2} ) Cobalt hydroxide and strontium hydroxide were added to the mixed phosphate, and the solid secretion was 55 ~ 60wt% of the total phosphate weight. The polyester emulsion resin 150 ~ 300g and the aluminum silicate 3 ~ 10g, and the Ti system is not strong elasticity to exhibit excellent surface gloss and insulation properties that could not be implemented in the conventional thin film Cr-free coating agent to 100 g of phosphoric acid A coating agent containing 0.5 to 6.0 g of a chelate additive was prepared, and the composition thus prepared was applied so as to be in a range of 2.0 to 6.0 g / m 2 per one side, and then heat-treated for 10 to 30 seconds at a temperature range of 350 to 700 ° C. To form an insulating coating.

   At this time, the polyester resin used in the emulsion state, the weight average molecular weight of the weight average molecular weight 2,000 ~ 15,000, Tg is 40 ~ 50 ℃, and the solid fraction is used a material of 20%. When the molecular weight of the polyester resin is 2,000 or less, the viscosity is too low, so that it is difficult to apply a thick film when the coating agent is prepared. On the contrary, when the molecular weight is 15,000 or more, the elasticity of the emulsion resin is strong and phase separation may occur when mixed with the metal phosphate. It is confirmed that the gloss of the prototype can be reduced. In addition, when an emulsion resin having a molecular weight of 2,000 to 15,000 is used, when the weight of the solid is less than 30 g, the fraction is relatively increased with phosphate, which is advantageous for corrosion resistance, but there is a risk of stickyness and powder precipitation, whereas 100 g is used. In this case, it is confirmed that the corrosion resistance and compatibility are significantly reduced.

For silica, aqueous alumina colloidal silica was used and the solid fraction was 20%. When the amount used for the coating agent was 3 to 10 g in solid weight, the film formation and the corrosion resistance of the coating were lowered, whereas the phase separation of the coating agent was accelerated by more than 10 g to decrease the adhesion between before and after SRA.

In the present invention, the non-oriented electrical steel sheet is heat treated for 10 ~ 30 seconds in the temperature range of 350 ~ 700 ℃ in the range of 2.0 ~ 6.0 g / m2 per side, dry film thickness on the surface of the grain-oriented electrical steel sheet configured as described above Insulation coating excellent in adhesion and corrosion resistance which the insulation coating agent should have is formed.

(Example)

It contains 0.1% of Si by weight, and a 0.50 mm non-oriented electrical steel sheet (120 * 60 mm) was used as a test material, and various treatment liquids were applied thereon in a range of 2.0 to 6.0 g / m ² using a coating bar. . In addition, the applied specimen is dried for several seconds at 650 ℃ and air-cooled.

The evaluation method is as follows.

SRA was annealed at 750 ℃ for 2 hours in a dry 100% N2 gas atmosphere. Insulation was expressed as the received current value when the input was 0.5V, 1.0A at 300PSI pressure. Adhesion is shown by the minimum arc diameter without film peeling when the specimen is bent 180 ^° by contacting an arc of 10, 20, 30 to 100 mmΦ before and after SRA. The appearance of the film was evaluated by visual observation of the presence of streaks and luster. Corrosion resistance is assessed for 5 hours at 35 ℃ and NaCl solution for 8 hours. In this test, it is excellent at less than 5% rust area, good at less than 20%, and slightly poor at 20 to 50%. More than 50% was marked as bad. In addition, the film strength after SRA was quantified (%) by the image processing technique to determine the adhesion of the film peeling powder and the degree of contamination of the tape when the adhesive tape of a certain size was attached to the film after the SRA. For example, 0 means that there is no film peeling off from the film surface after SRA, and 100 means that the entire tape area is contaminated with film peeling off. Therefore, the higher this number, the better the film strength.

Table 1 shows the corrosion resistance of the metal phosphate components and metal oxides. Once the weight ratio of the metal phosphate and the emulsion resin (molecular weight 14,000) that can be thick film coating was obtained through a preliminary test, the results confirmed that the ratio of the metal phosphate / emulsion resin is about 1/2. Subsequently, in order to prepare the chromium-free coating agent, corrosion resistance and adhesion must be secured through an effective combination of metal phosphate, and the metal oxide added in place of chromium should be able to suppress sticky and development of phosphate. The metal phosphate used in the present invention is adjusted to the molar ratio of aluminum or zinc oxide and phosphoric acid. When the metal phosphates prepared in this way are mixed with each other, metal phosphate combinations having different viscosities can be made according to the component ratios.

As shown in Table 1, the aluminum metal phosphate (Al (H ₂ PO ₄ ) ₃ ) and the first zinc phosphate (Zn (H ₂ PO ₄ ) ₂ ) were mixed to confirm corrosion resistance. When 2 g of cobalt hydoroxide and strontium hydroxide are added to 100 g of a solution having a solid phosphate content of 60wt%, a viscosity of 30 to 70 cp, especially 50 cp, and a 50/50 mixed solid in a solid weight ratio It can be seen that the phosphate improves surface sticky, prevention of powder precipitation and corrosion resistance (Test Material 15 in Table 1).

  number   division  Phosphate type (parts by weight 100g)  Phosphate Viscosity (cp)  Ester Resin (g)   oxide   Corrosion resistance   sticky sex  Kinds Solid weight   One   Test article   Al + Zn (10/0)   112   200  cobalt hydroxide   2   △   △   2   Test article   Al + Zn (7/3)   100   200  cobalt hydroxide   2   ▽   ×   3   Test article   Al + Zn (5/5)   50   200  cobalt hydroxide   2   △   △   4   Test article   Al + Zn (3/7)   40   200  cobalt hydroxide   2   ×   ▽   5   Test article   Al + Zn (10/0)   112   200  strontium hydroxide   2   ×   △   6   Test article   Al + Zn (7/3)   100   200  strontium hydroxide   2   ×   ×   7   Test article   Al + Zn (5/5)   50   200  strontium hydroxide   2   ▽   △   8   Test article   Al + Zn (3/7)   40   200  strontium hydroxide   2   ×   ▽   9   Test article   Al + Zn (10/0)   112   200 cobalt hydroxide + strontium hydroxide (7/3)   2   △   △   10   Test article   Al + Zn (7/3)   100   200 cobalt hydroxide + strontium hydroxide (7/3)   2   ▽   ×   11   Test article   Al + Zn (5/5)   50   200 cobalt hydroxide + strontium hydroxide (7/3)   2   ▽   O   12   Test article   Al + Zn (3/7)   40   200 cobalt hydroxide + strontium hydroxide (7/3)   2   ▽   △   13   Test article   Al + Zn (10/0)   112   200 cobalt hydroxide + strontium hydroxide (5/5)   2   △   △   14   Test article   Al + Zn (7/3)   100   200 cobalt hydroxide + strontium hydroxide (5/5)   2   ▽   △   15   Test article   Al + Zn (5/5)   50   200 cobalt hydroxide + strontium hydroxide (5/5)   2   O   O   16   Test article   Al + Zn (3/7)   40   200 cobalt hydroxide + strontium hydroxide (5/5)   2   ×   ▽   17 Test article   Al + Zn (10/0)   112   200 cobalt hydroxide + strontium hydroxide (3/7)   2   O   △   18   Test article   Al + Zn (7/3)   100   200 cobalt hydroxide + strontium hydroxide (3/7)   2   ▽   ×   19   Test article   Al + Zn (5/5)   50   200 cobalt hydroxide + strontium hydroxide (3/7)   2   ▽   △   20   Test article   Al + Zn (3/7)   40   200 cobalt hydroxide + strontium hydroxide (3/7)   2   ×   △  21  Comparative material  Cr type coating  -  -  -  -  ◎  ◎

(Physical Determination-Excellent: ◎, Good: O, Normal: △, Slightly defective: ▽, Poor: ×)

200 g of emulsion resins having different molecular weights in 100 g of solid phosphate (60 wt%) of mixed aluminum phosphate (Al (H ₂ PO ₄ ) ₃ ) and zinc phosphate (Zn (H ₂ PO ₄ ) ₂ ) derived from Table 1 Table 2 shows the results of surface gloss and film adhesion after SRA when a coating agent was prepared by mixing with a thick film to form a thick film (2.5 μm).

 number  division Phosphate type (parts by weight 100g)  Phosphate Viscosity (cp) Ester resin (solid weight)  Molecular Weight  Surface gloss  Adhesion after SRA  Thick film workability 15-1 Test article Al + Zn (5/5) 50 200 1,500 O O × 15-2 Test article Al + Zn (5/5) 50 200 2,300 O O O 15-3 Test article Al + Zn (5/5) 50 200 5,100 ◎ O O 15-4 Test article Al + Zn (5/5) 50 200 14,800 O O O 15-5 Test article Al + Zn (5/5) 50 200 25,000 △ △ O 15-6 Test article Al + Zn (5/5) 50 200 52,700 △ ▽ O 15-7 Test article Al + Zn (5/5) 50 200 110,000 ▽ × ▽ 15-8 Test article Al + Zn (5/5) 50 200 220,000 ▽ × ×

(Physical Determination-Excellent: ◎, Good: O, Normal: △, Slightly defective: ▽, Poor: ×)

As shown in Table 2, when the molecular weight of the emulsion resin is about 1,500, the surface gloss and the adhesion after SRA showed good results, but the viscosity of the resin is so low that it may be difficult to apply a thick film to be used as a mass production coating in the future. Emulsion resins of 15,000 or less did not degrade the surface gloss even at the time of thick film coating, and a relatively good adhesion after SRA was obtained. In particular, the emulsion molecular weight of 5,100 was able to obtain a film with the best surface gloss. On the other hand, in coatings prepared using emulsion resins of 15,000 or more, a product having opaque and very poor surface gloss was obtained at the time of thick film application as the molecular weight was increased, and as described above, in the emulsion resin of 15,000 or more, the elasticity was increased as the molecular weight was increased. With this increase (area A in Fig. 1), it is thought to inhibit the compatibility with the metal phosphate and cause phase separation in the coating. In this case, when the thick film coating is performed with the coating having lower compatibility, the surface gloss as well as the adhesion after the SRA are very poor.

However, in order to show the physical properties equivalent to Cr-type as shown in Table 1, it was finally necessary to improve the film adhesion after SRA. Thus, as shown in Table 2, the introduction of Ti chelate additive and colloidal silica solved this problem. . Table 3 shows the molecular weight of cobalt hydroxide and strontium hydroxide added to 100 g of phosphate mixed with aluminum monophosphate (Al (H ₂ PO ₄ ) ₃ ) and primary zinc phosphate (Zn (H ₂ PO ₄ ) ₂ ) 50/50. A coating agent was prepared by varying the amount of aluminum silicate and Ti-based chelate additive in 200 g of 5,100 polyester emulsion resin, and Table 4 shows the characteristics of the coating films coated with a thick film (2.5 μm) using the coating agent thus prepared.

  number   division  Phosphate type (parts by weight 100g)  Molecular weight 5,100 Ester resin (g)   oxide  Ti chelate   Al-Si Kinds Solid weight  15-3-1  Test article  Al + Zn (5/5)  200 cobalt hydroxide + strontium hydroxide (5/5)  2  0.05  -  15-3-2  Test article  Al + Zn (5/5)  200 cobalt hydroxide + strontium hydroxide (5/5)  2  0.1  -  15-3-3  Test article  Al + Zn (5/5)  200 cobalt hydroxide + strontium hydroxide (5/5)  2  0.5  -  15-3-4  Test article  Al + Zn (5/5)  200 cobalt hydroxide + strontium hydroxide (5/5)  2  One  -  15-3-5  Test article  Al + Zn (5/5)  200 cobalt hydroxide + strontium hydroxide (5/5)  2  5  -  15-3-6  Test article  Al + Zn (5/5)  200 cobalt hydroxide + strontium hydroxide (5/5)  2  8  -  15-3-7  Test article  Al + Zn (5/5)  200 cobalt hydroxide + strontium hydroxide (5/5)  2  0.05  0.5  15-3-8  Test article  Al + Zn (5/5)  200 cobalt hydroxide + strontium hydroxide (5/5)  2  0.1  One  15-3-9  Test article  Al + Zn (5/5)  200 cobalt hydroxide + strontium hydroxide (5/5)  2  0.5  3  15-3-10  Test article  Al + Zn (5/5)  200 cobalt hydroxide + strontium hydroxide (5/5)  2  One  5

 number  division  Corrosion resistance Water drop test  Adhesiveness (mmΦ)  Film Strength (%)  Insulation (mmA) Before SRA After SRA 15-3-1 Test article O O 20 40 35 435 15-3-2 Test article O O 20 30 29 470 15-3-3 Test article O O 20 30 28 465 15-3-4 Test article O O 20 30 25 451 15-3-5 Test article O O 20 30 19 410 15-3-6 Test article O O 20 30 16 427 15-3-7 Test article O O 20 30 10 470 15-3-8 Test article ◎ O 20 20 4 395 15-3-9 Test article ◎ O 20 20 2 401 15-3-10 Test article O O 30 40 22 450 16 Test article ◎ O 20 30 15 950

(Physical Determination-Excellent: ◎, Good: O, Normal: △, Slightly defective: ▽, Poor: ×)

As shown in Table 4, cobalt hydroxide and strontium hydroxide added monobasic aluminum phosphate (Al (H ₂ PO ₄ ) ₃ ) and primary zinc phosphate (as test samples 15-3-8 and 15-3-9). It was confirmed that corrosion resistance and film adhesion were improved when 1.0-3.0 g of aluminum silicate was added to 100 g of Zn (H ₂ PO ₄ ) ₂ ) mixed phosphate and 0.1-0.5 g of chelate additive. This is estimated to be equivalent to or higher than that of conventional chromium type coatings.

1 is a graph showing an increase in storage modulus (G ′) according to molecular weight in the low frequency region (A).

Claims (7)

In a phosphate solution in which first aluminum phosphate (Al (H ₂ PO ₄ ) ₃ ) and first zinc phosphate (Zn (H ₂ PO ₄ ) ₂ ) are mixed in a 1: 1 ratio, Cobalt hydroxide and strontium hydroxide; Polyester emulsion resins; Aluminum silicate; And Add the chelate additive of the Ti system, The polyester emulsion resin is a coating composition for forming an insulating film having a molecular weight of 2,000 ~ 15,000. The method according to claim 1, The polyester emulsion resin has a Tg (glass transition temperature) of 40 to 50 ℃, solid content of 15 to 25%, viscosity of 100 to 500cp, pH is 4 to 5 coating composition for forming an insulating film, characterized in that . The method according to claim 1, The first zinc phosphate has a solid content of 2.75M, 52.5%, the mixed phosphate solution has a solid content of 55 to 60% by weight, the coating composition for forming an insulating film, characterized in that the viscosity is 30 ~ 70cp. The method according to claim 1, For 100 g of the mixed phosphate solution, The cobalt hydroxide and strontium hydroxide is added 0.5 ~ 5g in the ratio of 1: 1, The polyester emulsion resin is added 150 ~ 300g, The aluminum silicate is added in 3 ~ 10g, The coating composition for forming an insulation film, characterized in that the chelating additive of the Ti system is added 0.1 ~ 6.0g. The method according to claim 4, The chelating additives of the Ti system include Triethanolamine titanate, Titanium 2,2,2-nitrilotrisethanolate (2-2-2 titanium nitrilotricetanolate), Mixture organic titanate and inorganic phophrous compounds (organic titanate) Porous composition), wherein the coating composition for insulating film formation, characterized in that any one selected from. The coating composition for forming an insulating film of claims 1 to 5 is coated on a steel plate with 2.0 to 6.0 g / m 2 per one side, and heated at a temperature of 350 to 700 ° C. for 10 to 50 seconds to form an insulating film. Method for forming an insulating film of non-oriented electrical steel sheet. Non-oriented electrical steel sheet produced by the method of claim 6.

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