KR20090073627A - Nano inorganic coating composition for plated steel and method of forming the coating layer using the same - Google Patents

Abstract

A nano inorganic coating composition for a plated steel is provided to be harmful to an operator by not including chrome, to form a film with excellent corrosion resistance, wet-proof property, and heat resistance, and to improve the quality of a galvanized sheet. A nano inorganic coating composition for a plated steel comprises colloidal nanosilica 12-30 weight%, a silane compound 2-5 weight%, an acidity regulator 0.1-1 weight%, aqueous solvent 1-10 weight%, a metal rust inhibitor 0.3-3.0 weight% containing a titanium compound, additives 0.1-0.5 weight% including an antifoaming agent, a levelling agent and silicone wax, and extra water.

Description

Nano Inorganic Coating Composition For Plated Steel And Method Of Forming The Coating Layer Using The Same}

The present invention relates to a nano-inorganic coating composition for a coated steel sheet and a coating film forming method using the same, and more particularly to a nano-inorganic coating composition for a coated steel sheet and a coating film forming method using the same, which is not harmful to the worker, and can improve the physical properties of the coating film. It is about.

Conventional galvanized steel sheet is widely used to coat with a product containing an organic polymer alone or inorganic particles in order to give corrosion resistance and fingerprint resistance. However, coating products containing organic polymers on galvanized steel sheet improves corrosion resistance and processability, but discoloration due to heat occurs in electronic products such as car engine rooms, ovens, and kitchen interiors. The situation is supplied by chromate treatment.

As a solution to the above problems, a method of simple oiling or chromate treatment of a galvanized steel sheet has been widely performed. However, in the case of simple oiling, it has to go through the process of degreasing to remove the oiled components, and after degreasing, corrosion resistance and chemical resistance are inferior, and chromate is harmful to the environment and human body, and it is restricted in use due to international regulations. There has been a demand for inorganic coating products which are resistant to heat and which do not use chromium for corrosion resistance.

The conventional surface treatment technology related to the present invention discloses a method of applying to a chromate-zinc-nickel steel sheet using nano silicate and epoxy silane in Korean Patent Publication No. 10-2005-0069304. This method is hazardous because it is chromate by pretreatment and uses zinc-nickel steel sheet, which is expensive compared to general plated steel sheet. In addition, Korean Patent Publication No. (10-2004-0026022) discloses a method of adding a silicone resin, colloidal silica, nanosilicate, and silicon leveling agent to improve workability and applying it to a chromated zinc-based alloy plated steel sheet. . However, this technique is also harmful because it is characterized by the coating on the chromated steel sheet and there is a problem in terms of energy efficiency because the temperature of the drying operation is too high above 200 ℃. In addition, the Republic of Korea Patent Publication No. (10-2004-0016893) is a surface treatment steel sheet to form a composite oxide film containing oxide fine particles and phosphoric acid or phosphoric acid compound on the surface of the zinc-based plated steel sheet and then to form a straight silicone resin film on the film Is disclosed. In this technique, since the complex oxide film is formed without using chromate, there may be no problem in environmental hazards, but since the double coating is required, the production cost increases.

Therefore, an object of the present invention for solving the above problems is to provide a nano-inorganic coating composition for a coated steel sheet applied to form a coating film having excellent physical properties, including colloidal nano-silica and silane compound.

In addition, another object of the present invention to provide a coating film forming method using the nano-inorganic coating composition for plated steel sheet.

Nano inorganic coating composition for a coated steel sheet according to the present invention for achieving the above object is 12 to 30% by weight of the nano-silica in the form of colloidal, 2 to 5% by weight of the silane compound, 0.1 to 1% by weight of acidity regulator, water-soluble solvent 1 To 10% by weight, 0.3 to 3.0% by weight of a metal rust inhibitor comprising a titanium compound, 0.1 to 0.5% by weight of an additive comprising an antifoaming agent, a leveling agent and a silicone wax and a composition comprising excess water.

Method of forming a coating film using the nano-inorganic coating composition for a coated steel sheet according to an embodiment of the present invention for achieving the above-described other objects are as follows. First, 12 to 30% by weight of the nano-silica in the colloidal form, 2 to 5% by weight of the silane compound, 0.1 to 1% by weight of the acidity regulator, 1 to 10% by weight of the water-soluble solvent, 0.3 to 3.0% by weight of the metal rust inhibitor containing a titanium compound A nano inorganic coating composition for a coated steel sheet comprising 0.1 to 0.5 wt% of an additive including%, an antifoaming agent, a leveling agent and a silicone wax, and excess water is prepared. Subsequently, the nano inorganic coating composition for plated steel sheet is coated on the surface of the plated steel sheet. Subsequently, the plated steel sheet coated with the nano-inorganic coating composition for plated steel sheet for plating steel sheet is dried. As a result, a coating film having excellent physical properties is formed on the plated steel sheet.

Examples of the metal rust inhibitors applied to the nano-inorganic coating composition for plated steel sheets include titanium tetra isopropyl oxide, titanium tetra butoxide, titanium di-triethanolamine, titanium di-acetylacetonate, or alkoxide, alkanolamine, and acetylacetonate. The substance which exists in a combined form, etc. are mentioned.

As mentioned, the nano-inorganic coating composition for coated steel sheet of the present invention does not contain chromium, which is not harmful to the human body, and is not harmful to the worker. By forming an excellent coating film, it is possible to improve the quality of the plated steel sheet and increase the utilization.

Hereinafter, a nano inorganic coating composition and a coating film forming method for a coated steel sheet according to various aspects of the present invention will be described in detail. However, the present invention is not limited to the following embodiments and may be implemented in other forms. The embodiments introduced herein are provided to make the disclosure more complete and to fully convey the spirit and features of the invention to those skilled in the art.

Nano Inorganic Coating Composition for Plated Steel Sheet

Nano inorganic coating composition for a coated steel sheet according to an embodiment of the present invention 12 to 30% by weight of the nano-silica in the form of colloidal, 2 to 5% by weight of the silane compound, 0.1 to 1% by weight of acidity regulator, 1 to 10% by weight of the water-soluble solvent, 0.3 to 3.0 weight percent of a metal rust inhibitor comprising a titanium compound, 0.1 to 0.5 weight percent of an additive comprising an antifoaming agent, a leveling agent and a silicone wax and excess water.

The nano-silica is atomized into a colloidal form is stabilized in water, the diameter of the fine particles of 5 to 20nm and the main action is used to lower the basic corrosion resistance of the coating film and the adhesion after drying of the silane.

When the content of the nanosilica is less than 12% by weight in the nano-inorganic coating composition for the coated steel sheet, there is a problem in that physical properties such as corrosion resistance and water resistance are degraded in the coating film formed. On the other hand, if the content exceeds 30% by weight, it is difficult to form a coating film due to the increase in viscosity, resulting in a problem that the adhesion to the steel sheet is lowered. Therefore, the nano inorganic coating composition for the coated steel sheet includes 12 to 30% by weight of the nanosilica, and preferably about 15 to 20% by weight.

The silane compound is used to improve the corrosion resistance by improving the hardness and water resistance of the coating film in the process of curing the coating film has a reactivity with nano-silica in the formation of the coating film. It is preferable to use the silane compound which can be easily hydrolyzed by water and has three or more alkoxy groups. Examples of the silane compound that can be used include vinyl trimethoxysilane, vinyl triethoxysilane, 3-methacryloxy trimethoxysilane, 2-glycidyloxypropyl trimethoxysilane, 2-aminopropyl triethoxysilane, 2-ureidoalkyl triethoxysilane etc. are mentioned. These may each be used alone or in combination of two or more.

If the content of the silica compound in the nano-inorganic coating composition for the coated steel sheet is 2% by weight or less, a bond with nanosilica is not formed, resulting in a difficulty in forming a coating film. On the other hand, if the content exceeds 5% by weight, there is a concern that the organic gas due to pyrolysis in the subsequent process is discharged, the silanol remains, causing a problem that the water resistance of the coating film is lowered. Therefore, the nano inorganic coating composition for the coated steel sheet includes 2 to 5% by weight of the silica compound, and preferably about 3 to 4% by weight.

The acidity regulator is used as a catalyst in the hydrolysis process of the silane compound to determine the hydrolysis molecular weight and hydrolysis structure of the silane compound, and improve the product storage stability of the silane and nanosilica after hydrolysis. That is, the acidity regulator helps to hydrolyze the silane compound while minimizing corrosion of the steel sheet and improves the storage stability of the hydrolyzed silane compound. Examples of the acidity regulator include organic acids such as acetic acid, formic acid, lactic acid, glyconic acid, and inorganic acids such as phosphoric acid. These may be used alone or in combination of two or more.

When the content of the acidity regulator is less than 0.1% by weight in the nano-inorganic coating composition for a coated steel sheet, the hydrolysis time of the silane compound increases, resulting in a long manufacturing time and a problem of inferior stability of the hydrolyzed silane compound. On the other hand, if the content exceeds 1% by weight, corrosion of the steel sheet by acid may occur, and the hydrolysis rate of the silane is excessively increased, resulting in difficulty in controlling the reaction. Therefore, the nano-inorganic coating composition for the coated steel sheet contains 0.1 to 1% by weight of the acidity regulator, preferably about 0.2 to 0.6% by weight.

The water-soluble solvents affect the molecular weight and structure of the hydrolyzed silane by improving the compatibility of the silane with water during the hydrolysis of the silane, and in the product to improve the wettability of the coating composition and the anti-foaming of the solution It works. That is, the water-soluble solvent serves to improve the compatibility and hydrolyzability of the silane to water, the wettability of the steel sheet of the treatment agent, and to speed up the drying rate of the coating film. As an example of the said water-soluble solvent, methanol, ethanol, 2-propanol, 2-methoxypropanol, 2-butoxyethanol, etc. are mentioned. These may be used alone or in combination of two or more, respectively.

When the content of the water-soluble solvent in the nano-inorganic coating composition for the coated steel sheet is less than 1% by weight, a problem in that the compatibility of the silane with water may be lowered, which may slow the hydrolysis reaction of the silane. On the other hand, if the content exceeds 10% by weight, fire and explosion may be caused by the increase of volatile components. Therefore, the nano-inorganic coating composition for the coated steel sheet contains 1 to 10% by weight of the water-soluble solvent, preferably about 3 to 7% by weight.

The metal rust inhibitor may improve the corrosion resistance of the coating film, it is preferable to use a metal rust inhibitor containing a titanium compound that inhibits the corrosion of metal cations and promotes the curing of silane and silica. The titanium-containing compound ionically bonds with the metal cations of the alloy-coated steel sheet in a corrosive environment to prevent oxidation of zinc and iron components, and promotes condensation reaction during drying of silane and silica, so that the barrier of the coating layer against corrosive factors (Barrier) Increase the effect to improve the corrosion resistance. Examples of the metal rust inhibitor containing the titanium compound are titanium tetra isopropyl oxide, titanium tetra butoxide, titanium di-triethanolamine, titanium di-acetylacetonate, or a hetero linkage of alkoxide and alkanolamine, acetylacetonate. The substance to mention etc. are mentioned. These may be used alone or in combination of two or more, respectively.

Corrosion resistance of the coating film formed when the content of the metal rust inhibitor containing the titanium compound in the nano-inorganic coating composition for the coated steel sheet is less than 0.3% by weight, when the content exceeds 3.0% by weight by the compound contained in the metal It is not economical because discoloration occurs in the heat resistance process or the price becomes expensive. Therefore, the nano-inorganic coating composition for the coated steel sheet contains 0.3 to 3% by weight of the metal rust preventive agent containing the titanium compound, preferably about 0.5 to 2% by weight.

The additive is used to improve the state of the composition and the coating performance for forming the coating film, and includes an antifoaming agent, a leveling agent, a silicone wax, and the like, and about 0.1 to 0.5% by weight is used. Specifically, the antifoaming agent included in the additive is used to prevent bubbles from occurring in the process of forming the coating film, the content is preferably 0.01 to 0.1% by weight based on the total coating composition. The leveling agent is used to help uniform formation of the coating film, the content is preferably 0.04 to 0.2% by weight based on the total coating composition. The silicone wax is used to improve the lubricity of the coating composition and to prevent adhesion between coatings, and the content thereof is preferably about 0.05 to about 0.2% by weight based on the total coating composition.

In the present embodiment, the additives are used to impart an optimal coating state and coating performance according to the type thereof, and the additives are mixed in an appropriate ratio because their types and amounts are different, and the amount of each additive is used to limit the present invention. Is not

Water, which is a solvent included in the nano-inorganic coating composition for a coated steel sheet, is used to dissolve the aforementioned components while ensuring workability of a coating for forming the nano-inorganic coating film for a coated steel sheet. When the amount of water applied to the composition is small, the viscosity of the composition is high, the coating workability is poor, and when the amount of water applied to the composition is large, the thickness of the coating film is thin, which makes it difficult to finish in one operation.

Hereinafter, a method of forming a coating film on a plated steel sheet using the nano inorganic coating composition will be described. Detailed description of the nano-inorganic coating composition is omitted because it is as described above.

In order to form a nano-inorganic coating film on the coated steel sheet, first, 12 to 30% by weight of the nano-silica in the colloidal form, 2 to 5% by weight of the silane compound, 0.1 to 1% by weight of acidity regulator, 1 to 10% by weight of water-soluble solvent, titanium A nano inorganic coating composition for a coated steel sheet comprising 0.3 to 3.0 wt% of a metal rust preventive agent comprising a compound, 0.1 to 0.5 wt% of an additive including an antifoaming agent, a leveling agent, and a silicone wax, and excess water is prepared.

Subsequently, the nano inorganic coating composition for plated steel sheet is coated on the surface of the plated steel sheet. The coating can be carried out by spray coating, roller painting or brush painting.

Subsequently, the plated steel sheet coated with the nano-inorganic coating composition for plated steel sheet for plating steel sheet is dried. At this time, the nano-inorganic coating composition occurs axial polymerization and dehydration reaction of the silane and the nano-silica present therein. Accordingly, the nano-inorganic coating film is formed on the surface of the metal steel sheet as shown in Figure 1 having an excellent bonding strength and excellent water resistance and corrosion resistance.

Since the divided inorganic coating film formed by the method according to an embodiment of the present invention is excellent in corrosion resistance, moisture resistance, heat resistance, etc., it is possible to improve the quality of the coated steel sheet and increase its utilization.

Hereinafter, the nano-inorganic coating composition for galvanized steel sheet according to an embodiment of the present invention will be described through specific examples, comparative examples, and experimental examples.

Nano Inorganic Coating Composition for Plated Steel Sheet

To prepare a nano-inorganic coating composition for the coated steel sheet of Examples 1 to 3 and Comparative Examples 1 to 2 according to the composition of Table 1 below.

[Table 1] (Unit: weight%)

In Table 1, KBM1003, KBM403 and KBM 503 (product name; Shin-Etsu Co., Japan) are silane compounds, respectively, and Noruthane 5001 (product name; Noro Paint, South Korea) is a water dispersion polyurethane resin. SNOWTEX-OUP (product name; Nissan Chemical, Japan), LUDOX SK and LUDOX SM (product name; Grace, USA) are nanosilica. Tyzor AA75 and Tyzor TEA (product name; DUPONT, USA) are titanium compounds and BYK-333, BYK-024 and BYK-331 (product name: BYK, Germany) are antifoams, levelers, and silicone waxes, respectively.

Evaluation of Properties of Coating Film

The nano-inorganic coating composition for galvanized steel sheet obtained in Examples 1 to 3 and Comparative Examples 1 and 2, respectively, was applied to the hot dip galvanized steel sheet using a bar coating so that the dry coating amount was 500 mg / m 2 and the temperature of the coated steel sheet was 100. It dried so that it may become C and a coating film was formed. Subsequently, the corrosion resistance, moisture resistance, and heat resistance of each formed coating film were measured and evaluated, and the results are reported in Table 2 below.

TABLE 2

The corrosion resistance, moisture resistance, and heat resistance of each coating film were evaluated according to the following criteria.

Corrosion resistance: The treated specimens were evaluated as being good when the 5% NaCl solution was continuously sprayed at 35 ° C. for 72 hours and less than 5% based on the area of rust (white blue, black blue, red blue), and poor at 5% or more.

Moisture resistance: Measure the color difference of the surface using a colorimeter after keeping the treated specimens in contact with the treated surface and holding it at 50 ℃ and 95% humidity for 120 hours under pressure under the condition of 10 ~ 50kgfcm. It was evaluated that ΔE ≦ 2 was good and ΔE> 2 was poor.

Heat resistance: The color difference standard after heating the treated specimens at 300-400 ° C. within 5 minutes in an electric furnace is the same as the moisture resistance standard, and if there is no crack in the appearance change of the surface, it is evaluated as poor. Evaluation method (◎: good, X: bad)

Referring to Table 2, in the case of the coating film formed using the nano-inorganic coating composition for galvanized steel sheets of Examples 1 to 3, the corrosion resistance, moisture resistance and heat resistance were higher than those of the coating film formed using the coating compositions for general plated steel sheets of Comparative Examples 1 and 2. It can be seen that excellent.

According to the present invention, the nano-inorganic coating composition for galvanized steel sheet is not harmful to the operator by not containing chromium, and also improve the quality of the galvanized steel sheet by forming a coating film excellent in corrosion resistance, moisture resistance, heat resistance and the like. And can increase the utilization.

In the detailed description of the present invention described above with reference to a preferred embodiment of the present invention, those skilled in the art or those skilled in the art having ordinary knowledge in the scope of the invention described in the claims to be described later It will be understood that various modifications and variations can be made in the present invention without departing from the scope of the present invention.

1 is a conceptual diagram showing a combination of a plated steel sheet and a nano inorganic coating composition for a coated steel sheet according to an embodiment of the present invention.

Claims (7)

12 to 30 weight percent of the nanosilica in colloidal form; 2 to 5 weight percent of silane compound; 0.1 to 1 weight percent acidity regulator; 1 to 10% by weight of a water-soluble solvent; 0.3 to 3.0 wt% of a metal rust inhibitor comprising a titanium compound; 0.1 to 0.5% by weight of an additive including an antifoam, a leveling agent and a silicone wax; And Nano inorganic coating composition for plated steel sheet containing excess water. The nano-inorganic coating composition for a coated steel sheet according to claim 1, wherein the nanosilica is atomized into a colloidal form and stabilized in water, and the diameter of the fine particles is 5 to 20 nm. The method of claim 1, wherein the silane compound is a vinyl trimethoxysilane, vinyl triethoxysilane, 3-methacryloxy trimethoxysilane, 2-glycidyloxypropyl trimethoxysilane, 2-aminopropyl tri Nano inorganic coating composition for galvanized steel sheet, characterized in that it comprises at least one selected from the group consisting of oxysilane and 2-ureidoalkyl triethoxysilane. The method of claim 1, wherein the acidity regulator comprises at least one selected from the group consisting of acetic acid, formic acid, lactic acid, glyconic acid and phosphoric acid, the water-soluble solvent is methanol, ethanol, 2-propanol, 2-methoxy propanol and Nano inorganic coating composition for a coated steel sheet, characterized in that it comprises at least one selected from the group consisting of 2-butoxy ethanol. The method of claim 1, wherein the metal rust inhibitor is present in the form of titanium tetra isopropyl oxide, titanium tetra butoxide, titanium di-triethanolamine, titanium di-acetylacetonate, or a heterogeneous bond of alkoxide and alkanolamine, acetylacetonate Nano inorganic coating composition for a coated steel sheet, characterized in that it comprises at least one selected from the group consisting of a material. According to claim 1, wherein the content of the antifoaming agent contained in the additive is 0.01 to 0.1% by weight based on the total coating composition, the content of the leveling agent is 0.04 to 0.2% by weight relative to the total coating composition, The content is a nano inorganic coating composition for coated steel sheet, characterized in that 0.05 to 0.2% by weight based on the total coating composition. 12 to 30 wt% of colloidal nanosilica, 2 to 5 wt% of silane compound, 0.1 to 1 wt% of acidity regulator, 1 to 10 wt% of water-soluble solvent, 0.3 to 3.0 wt% of metal rust inhibitor including titanium compound, Preparing a nano-inorganic coating composition for a coated steel sheet comprising 0.1 to 0.5% by weight of an additive including an antifoaming agent, a leveling agent and a silicone wax and excess water; Coating the nano-inorganic coating composition for a coated steel sheet on a surface of the coated steel sheet; And Coating film forming method comprising the step of drying the coated steel sheet coated with the inorganic coating composition for plating steel sheet for plating steel sheet.

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