KR20100078856A - Coating composition and for the improvement of compactness and smoothness of silica coating and method of forming coating - Google Patents

Abstract

PURPOSE: A coating composition and a coating method using thereof are provided to obtain a smooth silica base coating surface with the small amount of spraying for improving the scratch resistance. CONSTITUTION: A coating composition for improving the smoothness of a silica coating layer contains the following: 20~95wt% of compound including ethanol, 2-isopropanol, and 1-butanol; 2~40wt% of compound including tetraethoxysilane, vinyl triethoxysilane, and ethyltriethoxysilane; 0.1~3wt% of nitric acid; 0.5~5wt% of surfactant; 1~10wt% of polyethylene glycol; and the balance of water.

Description

Coating composition and method for forming improvement of density and smoothness of silica coating layer {Coating composition and for the improvement of compactness and smoothness of silica coating and method of forming coating}

The present invention relates to a coating composition and a coating forming method for improving the density and smoothness of the silica coating layer, and more particularly, to improve the density and smoothness of the existing silica-based coating surface, thereby providing excellent corrosion resistance and scratch resistance. A silica coating composition and a coating forming method using the coating composition.

The silica-based coating refers to a protective film that is applied to a surface of metal or plastic to improve physical and chemical durability. This protective film should have good physical and chemical bonding strength with the substrate, but at the same time, the protective film layer should be dense and the surface smooth. The denseness of the protective film is correlated with corrosion resistance, and the smoothness of the surface is closely related to the scratch resistance, which is one of physical durability, and the characteristics such as optical transparency and reflectivity. The tight protective barrier effectively blocks the entry of corrosive substances, improving corrosion resistance. The improved smoothness of the protective film shows a cleaner surface and results in improved scratch resistance.

The subject technology of the present invention belongs to the field of physico-chemical protective coating coating based on inorganic silica. That is, a solution containing a silica precursor (precursor) or the like is formed for the purpose of imparting scratch and corrosion resistance to the surface of a metal, and the like, using a dip or spray-coating technique. To form a protective film. In this technical field, the present invention aims to present a technique for obtaining a coating layer having excellent properties easily and stably compared to the conventional technology by adjusting the composition and content of the solution.

Inorganic silica is generally used as a material for scratch and corrosion resistant coatings. One of the most important characteristics for spray coating on the metal surface to produce scratch and corrosion resistance effects is the density and smoothness of the coating layer. In other words, if the density is low, corrosion can easily occur due to the corrosive material passing through the coating layer, and if the smoothness is reduced, a part of the coating layer is easily damaged by external mechanical shock, and the fragments cause secondary scratches. Greatly falls.

In the existing techniques, first, a large amount of sprayed solution is often added to completely wet the surface layer in order to simultaneously improve the density and smoothness of the surface layer. However, when the solution is applied too much, the coating layer finally obtained becomes too thick, which may then be a source of peeling phenomenon. In general, the inorganic silica coating layer coated on the metal surface has a large difference from the metal in thermal expansion rate, so even a slight thermal shock causes stress (stress) that greatly exceeds the mechanical bond strength, and such stress causes a crack in the silica coating layer. do. However, in order to avoid such a problem, when the inorganic content of the solution is lowered to form a thin coating, the coating layer tends to become porous rather than thin. In this case, it is difficult to obtain a dense coating layer from the porous coating layer with a general heat treatment at about 400-500 ° C.

Therefore, it is not efficient to obtain a dense and smooth thin film by adjusting the concentration or spraying amount of the coating solution as in the conventional art, and a new silica coating composition which can obtain a stable dense and smooth thin film in a relatively wide solution composition range is need.

The present invention has been proposed to solve the conventional problems as described above, to provide a silica coating composition excellent in corrosion resistance and scratch resistance by improving the density and smoothness of the conventional silica-based coating surface.

Another object of the present invention is to provide a method for forming a coating for improving the density and smoothness of the silica coating layer by applying the silica coating composition to a steel sheet.

According to one aspect of the invention,

20-95% by weight of a mixture of ethanol, 2-isopropanol and 1-butanol, 2-40% by weight of a mixture of tetraethoxysilane, vinyltriethoxysilane and ethyltriethoxysilane, 0.1-3% by weight nitric acid (HNO ₃ ) Provided is a coating composition for improving the density and smoothness of the silica coating layer, characterized in that it comprises a%, 0.5-5% by weight surfactant, 1-10% by weight polyethylene glycol, and the remaining amount of water.

According to another aspect of the present invention,

20-95% by weight of a mixture of ethanol, 2-isopropanol and 1-butanol, 2-40% by weight of a mixture of tetraethoxysilane, vinyltriethoxysilane and ethyltriethoxysilane, 0.1-3% by weight nitric acid (HNO ₃ ) Preparing a solution consisting of% and the remaining amount of water except the content of the following surfactant and polyethylene glycol;

Aging the solution at room temperature for 30-4 hours;

Preparing a coating composition for improving the density and smoothness of the silica coating layer by adding and mixing 0.5-5% by weight of the surfactant and 1-10% by weight of polyethylene glycol to the aged solution; And

Drying and heat-treating the coating composition on a steel sheet

Comprising, comprising a method for forming a coating for improving the density and smoothness of the silica coating layer on a steel sheet.

According to the present invention, a sufficiently compact and smooth silica-based coating surface can be obtained even with a small amount of spraying, thereby improving corrosion resistance and scratch resistance.

The present invention relates to a silica coating composition and a coating forming method capable of improving corrosion resistance and scratch resistance by improving the density and smoothness of the silica based coating surface.

Hereinafter, the invention according to the present invention will be described in more detail.

The component used as the solvent in the present invention is a mixture of ethanol, 2-isopropanol and 1-butanol. Ethanol, 2-isopropanol and 1-butanol each differ in viscosity and evaporation rate of the solution. Therefore, it was found that by adjusting the mixing ratio of these components, the thickness of the solution can be properly adjusted when applied on the metal substrate of the silica coating liquid. The mixture of ethanol, 2-isopropanol and 1-butanol is included in the coating composition at 20-95% by weight. When the amount of the mixture of the three components is lower or higher than the above range, the density and smoothness of the silica coating layer may be lowered when applied on the metal substrate. Preferably the solvent mixture is included in the coating composition at 30-90% by weight. In addition, the ratio of each component in the solvent mixture is not limited thereto, but ethanol: 2-isopropanol: 1-butanol is preferably mixed at a ratio of 20-35: 35-45: 35-45 by weight.

The component used as the silica precursor in the present invention is a silane compound which can easily hybridize with a polymer, and is tetraethoxysilane, vinyltriethoxysilane and ethyltriethoxysilane. The silane compounds are used in the form of mixtures. The mixture of tetraethoxysilane, vinyltriethoxysilane and ethyltriethoxysilane is included in the coating composition at 2-40% by weight. When the amount of the mixture of the silane compound is lower than the above range, the synthesis of the silica coating layer may not be performed. When the amount of the mixture of the silane compound is more than the above range, the amount of the silane compound is unnecessarily increased, which is uneconomical. Preferably, the mixture of silane compounds is included in the silica coating composition in 10-30% by weight. In addition, the ratio of each component in the mixture of the said silane compounds is not limited to this, but tetraethoxysilane: vinyltriethoxysilane: ethyltriethoxysilane is 25-80: 15-40: 5-35 by weight. It is preferred to mix in proportions.

In the present invention, nitric acid is a component that promotes the hydrolysis and condensation reaction of the added silane compound, which is included in the coating composition at 0.1-3% by weight. When the amount of nitric acid is lower than the above range, the rate of hydrolysis is slowed, so that hydroxide formation of desired silicon is not smooth, and gel is formed during hydroxide formation and condensation reaction, making it difficult to use as a coating solution. In addition, if the amount of nitric acid is higher than the amount of the nitric acid, the solution is too corrosive to cause the corrosion of the metal surface when subsequently applied to the metal substrate. Preferably, the nitric acid is included in the coating composition 0.3 to 3% by weight.

It is important to construct an additive mixture in which the solution is completely wetted to the surface of the metal substrate even when a small amount of solution is sprayed upon forming the silica coating. In the present invention, a specific amount of a surfactant is added to obtain a composition that optimizes these characteristics. The additive added at this time is a polymer consisting mainly of hydrocarbon chains. Useful as surfactants in the present invention is 4- (1,1,3,3-tetramethylbutyl) phenyl-polyethylene glycol. The surfactant component is included in the coating composition at 0.5-5% by weight, and if it is out of the range, the density or smoothness of the silica coating layer may be reduced. The 4- (1,1,3,3-tetramethylbutyl) phenyl-polyethylene glycol is generally referred to as Triton X-100 and is commercially available. Preferably, the surfactant is included in the coating composition at 1-3.5% by weight.

In addition, together with the surfactant component, a polymer composed of hydrocarbons is mixed together to control the viscosity of the coating solution being sprayed. The polymer for viscosity control added in the present invention is polyethylene glycol. Often, the sprayed solution does not sufficiently evaporate the solvent until it reaches the substrate, or if excessively evaporates, the smoothness of the coating film is greatly reduced. Therefore, there is a need for an additive having a function of appropriately controlling the polyethylene glycol added in the present invention, while controlling the viscosity of the solution while controlling the dispersion rate of the solvent. The polyethylene glycol is included in the coating composition in 1-10% by weight, the viscosity of the solution may be too low or too high when out of the range may be difficult to control the dispersion rate of the solvent. Preferably, the polyethylene glycol is included in the coating composition at 2-5% by weight.

In addition, water may be added to the coating composition except for the above-mentioned components, and the water content is not limited thereto, but the total coating composition is added to 100% by weight except for the contents of the components.

The process of forming the coating composition according to the invention on a steel sheet is schematically shown in FIG. Referring to Figure 1 describes a method for forming a coating by applying a coating composition according to the invention on a steel sheet as follows.

First, a mixture of ethanol, 2-isopropanol and 1-butanol is prepared as a solvent. The solvent mixture is then included in the coating composition in an amount of 20-95% by weight, as mentioned above. Then, a mixture of tetraethoxysilane, vinyltriethoxysilane and ethyltriethoxysilane is prepared as a component used as the silica precursor. The mixture of silane compounds is included in an amount of 2-40% by weight, as mentioned above. Then, an aqueous solution of nitric acid (HNO 3) is added and the mixed solution is aged at room temperature for 30-4 hours, preferably 1-2 hours. The nitric acid is added to the coating composition in an amount of 0.1-3% by weight, as mentioned above. Next, 4- (1,1,3,3-tetramethylbutyl) phenyl-polyethylene glycol as a surfactant and polyethylene glycol as a viscosity modifier are added to the aged solution and mixed to form a coating composition. The surfactant and the viscosity modifier are added in 0.5-5% by weight and 1-10% by weight, respectively. Then, the coating composition is applied to the steel sheet, followed by drying and heat treatment to form a silica coating on the steel sheet. The coating composition thus formed may be applied to a steel sheet such as a stainless steel sheet while maintaining a thin film. The thickness of the coating film during the coating is not limited thereto, but may be applied while maintaining a thin film thickness of 2-5 μm, preferably within about 5 μm.

When the coating composition of the present invention is applied to a steel sheet, the coating method is not limited thereto, but is preferably applied by a spray method. For example, using a spray gun, the air pressure is 2-3 kg / cm 2, preferably about 2.7 kg / cm 2, and the solution spray amount is carried out under the conditions of 50-150 ml / m 3, preferably about 70 ml / m 3.

The steel sheet to which the coating solution is applied is dried for about 1-5 hours, preferably for about 2 hours, in an oven maintained at an appropriate temperature (eg, about 60 ° C.). The dried coated product is then subjected to a heat treatment process and heat treated at about 350-550 ° C. for about 15-30 minutes. The heat treatment condition is preferably about 20 minutes at about 450 ℃.

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

<Examples>

Example 1 (Preparation of Coating Solution)

It was dissolved in 300 ml of a solvent mixture consisting of 75 ml of ethanol, 105 ml of 2-isopropanol and 120 ml of 1-butanol in the order of tetraethoxysilane, vinyltriethoxysilane and ethyltriethoxysilane. The concentrations for the solvent mixture of each component were 1.2M, 0.5M, and 0.5M, respectively. To this mixed solution was added 5% by weight of an aqueous nitric acid (HNO ₃ ) solution at a concentration of 0.1 M. The solution in which the nitric acid solution was mixed was subjected to aging so that the hydrolysis reaction was sufficiently performed. The aging time was 1 hour.

4- (1,1,3,3-tetramethylbutyl) phenyl-polyethylene glycol (Triton X-100) and polyethylene glycol were mixed at 1.5 wt% and 2.5 wt%, respectively, in the mature solution.

The solution thus prepared was aged by stirring for 24 hours in a sealed container at room temperature, and then stored in a refrigerator maintained at 4 ℃ until applied to the coating process. When the synthesis is complete, a clear, colorless solution is obtained as shown in FIG.

Example 2 (spray coating)

The coating solution prepared in Example 1 was applied to the surface of the stainless steel sheet using a spray gun, Pro or RA 100, which is generally used. The air pressure was 2.7 kg / cm 2 and the solution injection amount was 70 ml / m 3.

The solution coated stainless steel sheet was placed in an oven at 60 ° C. and dried for 2 hours. The dried coating product was put back into a heat treatment furnace and heat-treated at a temperature of 450 ° C. for 20 minutes. The thin film product thus obtained is as shown in FIG. 3.

Example 3 (Surface Microstructure Observation)

The coating layer obtained through the process up to Example 2 was found to be very smooth and dense as compared to the coating layer coated by the existing technology. The results of observing the surface of the coated surface with a scanning electron microscope are shown in FIG. 4 (left: before smoothing, right: after smoothing).

Example 4 (corrosion resistance evaluation)

Coin polarization tests were conducted to confirm that the coated side was densely constructed. Corrosion resistance was evaluated for the three coated specimens and the three uncoated stainless steel sheet specimens compared to FIG. 4. As a result, the products to which smoothing was applied showed excellent corrosion resistance characteristics compared to the products manufactured by the existing technology. The analysis results are shown in FIG. 5. As can be seen from Figure 5, it was confirmed that the flattening test specimen according to the present invention is improved in corrosion resistance compared to the test piece is not applied smoothing. Comparing the corrosion current (corrosion current) of the case of the coating without any coating and the sample by the conventional silica coating technology, and the solution configured in the present invention in the case of the coated specimen using the solution configured in the present invention Shows the lowest value. In other words, the solution proposed in the present invention provides a dense coating surface during coating, and therefore, the corrosion resistance is also improved.

1 is a process diagram schematically showing a method of forming a coating composition according to the present invention on a steel sheet.

Figure 2 is a photograph showing the coating solution prepared in Example 1 according to the present invention.

3 is a photograph showing a product obtained by applying the coating solution prepared in Example 1 to a stainless steel sheet.

4 is a photograph (left: before smoothing, right: after smoothing) of the surface of the coated surface of the product of FIG.

5 is a result of conducting a coin polarization test to confirm that the coating surface is formed densely.

Claims (14)

20-95% by weight of a mixture of ethanol, 2-isopropanol and 1-butanol, 2-40% by weight of a mixture of tetraethoxysilane, vinyltriethoxysilane and ethyltriethoxysilane, Nitric acid (HNO ₃ ) 0.1-3% by weight, 0.5-5% by weight surfactant, 1-10% by weight polyethylene glycol, and Remaining amount of water Characterized in that comprises a, coating composition for improving the density and smoothness of the silica coating layer. According to claim 1, wherein the mixture of ethanol, 2-isopropanol and 1-butanol is characterized in that the ethanol: 2-isopropanol: 1-butanol is mixed in a ratio of 20-35: 35-45: 35-45 by weight Coating composition for improving the density and smoothness of the silica coating layer. The method of claim 1, wherein the mixture of tetraethoxysilane, vinyltriethoxysilane and ethyltriethoxysilane is contained in parts by weight of tetraethoxysilane: vinyltriethoxysilane: ethyltriethoxysilane. Coating composition for improving the density and smoothness of the silica coating layer, characterized in that the mixture of -40: 5-35 ratio. The coating composition of claim 1, wherein the surfactant is 4- (1,1,3,3-tetramethylbutyl) phenyl-polyethylene glycol. The coating composition of claim 1, wherein the mixture of ethanol, 2-isopropanol and 1-butanol is included in the range of 30-90 wt%. The method of claim 1, wherein the mixture of tetraethoxysilane, vinyltriethoxysilane and ethyltriethoxysilane is included in the range of 10-30% by weight for improving the density and smoothness of the silica coating layer. Coating composition. The method of claim 1, wherein the nitric acid (HNO ₃ ) is a coating composition for improving the density and smoothness of the silica coating layer, characterized in that included in the range of 0.3-3% by weight. According to claim 1, wherein the surfactant is a coating composition for improving the density and smoothness of the silica coating layer, characterized in that included in the range of 1-3.5% by weight. According to claim 1, wherein the polyethylene glycol is a coating composition for improving the density and smoothness of the silica coating layer, characterized in that included in the range of 2-5% by weight. 20-95% by weight of a mixture of ethanol, 2-isopropanol and 1-butanol, 2-40% by weight of a mixture of tetraethoxysilane, vinyltriethoxysilane and ethyltriethoxysilane, 0.1-3% by weight nitric acid (HNO ₃ ) Preparing a solution consisting of% and the remaining amount of water except the content of the following surfactant and polyethylene glycol; Aging the solution at room temperature for 30-4 hours; Preparing a coating composition for improving density and smoothness of the silica coating layer by adding 0.5-5% by weight of the surfactant and 1-10% by weight of polyethylene glycol to the aged solution and mixing the mixture; And Drying and heat-treating the coating composition on a steel sheet Comprising a method for forming a coating for improving the density and smoothness of the silica coating layer on the steel sheet. The method of claim 10, wherein the mixture of ethanol, 2-isopropanol and 1-butanol is ethanol: 2-isopropanol: 1-butanol in a proportion of 20-35: 35-45: 35-45 by weight Method of forming a coating for improving the density and smoothness of the silica coating layer. 11. The mixture of tetraethoxysilane, vinyltriethoxysilane and ethyltriethoxysilane in parts by weight of tetraethoxysilane: vinyltriethoxysilane: ethyltriethoxysilane is 25-80: 15. A method for forming a coating for improving the density and smoothness of the silica coating layer, characterized in that the mixture of -40: 5-35 ratio. The method of claim 10, wherein the surfactant is 4- (1,1,3,3-tetramethylbutyl) phenyl-polyethylene glycol. 12. A method of forming a coating for improving density and smoothness of a silica coating layer according to claim 10. . The method of claim 10, wherein the aging time is 1-2 hours, characterized in that to form a coating for improving the density and smoothness of the silica coating layer.

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