WO2005044929A1

WO2005044929A1 - Paste type waterbased paint composition containing metal powder and coating method of metal film using the same

Info

Publication number: WO2005044929A1
Application number: PCT/KR2003/002389
Authority: WO
Inventors: Seung Joon Lee
Original assignee: Seung Joon Lee
Priority date: 2003-11-07
Filing date: 2003-11-07
Publication date: 2005-05-19
Also published as: CN1326955C; CN1692146A; AU2003277711A1

Abstract

The present invention relates to a paste type water-based paint composition containing metal powder, which maximizes the effect of unique color and texture of metals upon reduced cost and which may be coated on low price materials that do not have high endurance against heat, does little harm to the body, and does not cause environmental pollution. The present invention provides a paste type water-based paint composition containing metal powder comprising: 100 to 500 parts by weight of metal powder with the size of 0-1~100µm, and 1 to 100 parts by weight of aqueous binder with the viscosity of 6000cps or under, wherein metal powder is selected from the group consisting of copper, brass, bronze, nickel, aluminum, iron, tin, gold and silver, and said aqueous binder comprises aqueous polyurethane resin, N,N-dimethyl formamide, acetone, silica, and water.

Description

PASTE TYPE WATERBASED PAINT COMPOSITION CONTAINING METAL POWDER AND COATING METHOD OF METAL FILM USING THE SAME

TECHNICAL FIELD The present invention relates to a water-based paint composition containing metal powders and, more particularly to a paste type metal-containing water-based paint composition comprising a binder and metal powders having a weight of at least twice that of the binder.

BACKGROUND ART In order to provide various objects with metallic luster and texture, a method of applying a metal-containing paint or a metallic coating has been typically carried out. The metal-containing paint and the metallic coating are widely used for interior decorations, architectures, industrial arts and general paintings. There are paints exhibiting metallic colors among some metal-containing paints, because they contain pigments exhibiting metallic colors. However, these paints exhibit only metallic colors, and do not offer any metallic luster or texture at short distance. Paints containing metal particles have been used to strongly exhibit metallic luster or texture. However, since the content of metal was very low in conventional most of the metal-containing paints, peculiar metallic texture was not fully exhibited. In the method of applying a metallic coating, a thermo spray type metal painting and a plasma method in which the metal is melted at high temperature are employed. In this method, since the metal is melted and coated, the metallic texture is exhibited as it stands. Accordingly, the method has an advantage of improving decorative effects. However, there is a possibility of danger due to the high temperature process. There is also a cost problem due to the expensive equipment. In addition, this method cannot be applied to materials that do not have endurance against heat since it coats a high-temperature metal. Accordingly, there has been a need of a metal- containing paint, which maximizes the effects of unique color and texture of metal with reduced cost and which can be applied to low price materials that do not have high endurance against heat. Meanwhile, the prior metal-containing paint using polyester and epoxy resins is easy to use compared to the above-mentioned methods. However, the paint is two- parts type paint containing curing agents harmful to the human body. Recently, the environmental pollution, such as destruction of the ozone layer, global warming and acid rain due to the air pollution, has been spread to the entire globe. That is, an organic solvent, which is one factor causing the environmental pollution, is spread in the air. Advanced nations enact the regulation laws to regulate the organic solvent emission. Accordingly, the concept of environmental coexistence type- products, such as products with no solvent and water-based products is beginning to make its appearance on the protection of environment, the safety of labor and the sanitation levels. Accordingly, it is required to develop a novel metal-containing paint composition that has no environmental pollution problems and is harmless to the human body.

DISCLOSURE OF THE INVENTION Accordingly, the present invention has been made to solve the above- mentioned problems occurring in the prior art. The object of the present invention is to maximize the effects of unique luster and texture of metals with reduced cost by increasing the content of metal powders of the metal-containing paint, thereby causing the content to be at least twice the weight of the binder. In addition, the object of the invention is to provide a paint composition applicable to low price materials that do not have high endurance against heat, such as urethane foam. Further, the object of the invention is to provide a metal-containing water- based paint composition, which is easy to handle, harmless to the human body and environment-friendly, by making use of an aqueous, one-part type binder that is nearly harmless to the human body and does not cause the environmental pollution problem, and a method for forming a metallic coating using the paint composition. In order to accomplish these objects, according to one embodiment of the invention, there is provided a paste type metal-containing water-based paint composition comprising 100 to 500 parts by weight of metal powders with the size of

0.1 ~ 100 micron and 1 to 100 parts by weight of aqueous binder with the viscosity of 6000 cps (centipoise) or less. According to the invention, the metal is selected from the group consisting of copper, brass, bronze, nickel, aluminum, iron, tin, gold and silver. In addition, according to the invention, the paint composition further comprises non-metals, such as graphite. Further, according to the invention, the aqueous binder comprises aqueous polyurethane resin, N,N-dimethyl formamide, acetone, silica and water. Further, according to the invention, the aqueous binder is an emulsion obtained by dissolving styrene into acrylic acid and amine, and mixing the combination with water and silica. Further, according to the invention, the aqueous binder may comprise other additives as needed. According to another embodiment of the invention, there is provided a method for forming a metallic coating to provide various objects with metallic luster and texture, comprising using the above paste type metal-containing water-based paint composition. Metals, which are incorporated into a paint composition according to the invention, are selected from the desired metals depending on the uses thereof. Metal powders can be produced by spraying, rolling, melting, or reducing-mixing methods. The diameter of metal powder should be 0.1 ~ 100 micron, because this size is suitable for producing the paste type paint. The main raw material of binder is aqueous polyurethane that can be obtained by reacting isocyanate with polyamine. The binder comprises by weight, about 25-32% of aqueous polyurethane (aqueous polyurethane dispersion resin; Aliphatic) produced by reacting isocyanate with polyamine, 7-12% of N,N-dimethyl formamide, 1-3% of acetone, 48-60% of water and other additives, and 0.1-5% of silica (SiO₂), based on the total weight of the binder. When the content of aqueous polyurethane is less than 25 weight%, the binding force between the metal particles can be lowered. Meanwhile, it is effective that the binder is filled to a height of the lower hemisphere of the metal powder. When the content of aqueous polyurethane is over 32weight%, since the binder is filled over the height of the lower hemisphere of the metal powder and set, the set surface is comprised of only the binder rather than the desired metallic surface. In this case, because the surface formed of the set paint composition cannot have the metal properties, a post process required for the metal process cannot be carried out, and the surface cannot have the metallic luster. Silica and other additives cause the metal powder having specific gravity higher than that of water not to be settled and to be uniformly distributed, and make it possible to maintain such uniform water-based metal paste state for a long time. In addition to the aqueous polyurethane, aqueous acrylic-based resin can be used as the binder. The binder is an emulsion obtained by dissolving 20-35 weight % of styrene (alpha methyl styrene) into 8-12 weight% of acrylic acid and 6-9 weight % of amine (monoethylamine) as neutralizer, and mixing the combination with 50-80 weight % of water and silica, and 0.1-5 weight% of silica (SiO₂). In this case, in the same way as the binder comprising aqueous polyurethane as the main agent, the remaining resin component in which water has evaporated holds on the metal particles. The compositional range of the aqueous acrylic-based binder is selected to be within a certain range capable of providing a binding force and metallic properties. In the above compositional range, when the spraying is used, it is possible to optimize a spraying state while maintaining the uniform state. In this case, silica and other additives still cause the metal powder having specific gravity higher than that of water not to be settled and to be uniformly distributed, and make it possible to maintain such uniform water-based metal paste state for a long time. A half or more of the binder consists of water, and the urethane or acrylic- based resin component which is present in the emulsion-type binder in which most of water has evaporated at room or high temperatures is set, thereby forming a strong coating or film and contriving a bonding between the metal particles. Specifically, 50 weight% or more of water present in the binder is evaporated at room or high temperatures, and thus only minimum binder remains in the metallic coating after having been set, thereby causing the properties of the metallic coating to be same as the metal at least 90% and the coating to have the physical properties and the partial chemical properties of the metal when after-treatment on the surface thereof is carried out. Accordingly, when a coating is applied by making use of the metal-containing water-based paint composition according to the invention, most of the metallic properties such as the luster and oxidative of metal can be maintained. In addition, the thermal and heat conductivities can be maintained depending on the selected binders. The binder should have a viscosity of 6000 cps or less for the purpose of maintaining the uniformly mixed metal powders and maximizing the effect of texture of the metallic coating. The content of metal powders in the metal-containing water-based paint composition according to the invention is much higher than that of the prior art. The content of metal powders contained in the prior paint is very low, and does not exceed to the content of the binder. Accordingly, the luster of the prior paint was determined depending on the content of the binder, which is the main component of the paint. However, contrary to the prior paint, according to the invention, the content of the metal powders is at least twice that of the binder. The most preferred content of the metal powders is at least twice that of the binder. Accordingly, the paint composition according to the invention can have the luster and surface properties of metal itself as it stands. Since the content of the metal powders is very high in the paint according to the invention, the paint is a paste-type paint. According to the invention, for the purpose of decreasing of the high viscosity of the paste-type paint, only the binder having a viscosity of 6000 cps or less is used, and water is blended to lower the viscosity. In the paste-type paint composition according to the invention, a distance between the metal powders in the coating becomes close by decreasing the content of the binder and increasing the content of the metal powders, thereby causing the bonding between the metal powders to be strengthened and the inherent properties of metals to be maintained to the utmost. In addition, when the polarity of the binder is high, the binder and free electrons in the surface of the metal powder are attracted each other, and thus the bonding between the metal particles is further induced. Accordingly, the bonding between the metal particles can be controlled by adjusting the polarity of the binder. The polarity can be maximized by using a binder having a high polarity or adding additives. Also, the resultant can be applied to plastics, wood, foam and metals etc.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the present invention will be described. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. A mechanism of forming a metallic coating of the invention is as follows. When a paint composition according to the invention is applied to a surface of a medium density fiber (MDF) by a spray gun or a brush, a solvent such as water and acetone included in a binder evaporates and only a polymer having a strong adhesivity remains. Meanwhile, since a metal powder is a sphere type having a predetermined diameter, the polymer flows down and fills a gap between the metal powders before being set, and thus a bonding between the metal powders is formed as the polymer is set. Specifically, since the polymer is positioned and set at the lower hemisphere of the metal powder, most of the extreme outer side applied with the paint has the only metal powders. Accordingly, when applying an electric current to the surface at which a coating is formed by the metal-containing water-based paint composition, a small amount of electric current flows at the surface. When applying the paint composition to architectures, interior decorations, and industrial arts and products, a roller or a paintbrush can be used. A spray can also be used. An initial setting is achieved within 4 to 8 hours at room temperature and the setting is completed in 24 hours. When a drying machine is used, the setting can be achieved within a short time, for example one hour. After the setting, a luster can be controlled by an after-treatment that uses a sandpaper, a grinder, a brush or a wool paper. In addition, a state of corrosion can be controlled by using an acidic liquid for controlling a state of corrosion of the metal surface such as a patina™. <Example 1> lOOg of binder was mixed with 26g of aqueous polyurethane, lOg of N,N- dimethyl formamide, 2g of acetone, 50g of water, lOg of additives and 2g of silica. A paste type metal-containing water-based paint composition was prepared by mixing the mixture with 300g of copper (pure copper) having a diameter of 5 micron. The prepared paste type paint composition was applied to a wooden interior ornament by using a gravity spray. After then, the ornament was put into a drying machine at 70°C or more and then completely set in 2 hours. In this example, although the drying machine was used to accelerate the setting at 70°C or more, a metallic coating can be formed even at room temperature with the paste type metal-containing water-based paint composition according to the invention. After completing the setting, the after-treatment was carried out by using a wool paper, a sandpaper, and a grinder, etc. A weak hydrochloric acid was applied to the surface, thereby forming blue verdigris on the surface.

INDUSTRIAL APPLICABILITY In the paste type metal-containing water-based paint composition according to the invention, the content of the metal powders is at least twice that of the binder, thereby causing the paint composition to have similar metallic properties after set. As a result of that, a paste type paint can be provided with low costs, which shows the luster and surface properties of metal itself as it stands. According to the invention, since a heating process is not employed at all, the paint composition can be applied to even objects that do not have high endurance against heat. In particular, according to the invention, a paint and a method for forming a metallic coating capable of applying to even low price materials such as urethane foam and MDF, etc. are provided In addition, since the aqueous binder is used, it is possible to reduce an environmental pollution, and to provide a paint that does little harm to the human body. Also, unlike plating, there is little difference in the process or price depending on the amount, and anybody can use the paint composition.

Claims

WHAT IS CLAIMED IS:

1. A paste type metal-containing water-based paint composition comprising 100 to 500 parts by weight of metal powders with the size of 0.1 - 100 micron, and 1 to 100 parts by weight of aqueous binder with the viscosity of 6000 cps or less.

2. The paint composition according to claim 1, wherein the metal is selected from the group consisting of copper, brass, bronze, nickel, aluminum, iron, tin, gold and silver.

3. The paint composition according to claim 1 , wherein the binder comprises aqueous polyurethane resin, N,N-dimethyl formamide, acetone, silica, and water.

4. The paint composition according to claim 1, wherein the binder is an emulsion obtained by dissolving styrene into acrylic acid and amine, and mixing the combination with water and silica.

5. A method for forming a metallic coating to provide various objects with metallic luster and texture, comprising using the paste type metal-containing water- based paint composition according to claim 1.

6. A method for forming a metallic coating to provide various objects with metallic luster and texture, comprising using the paste type metal-containing water- based paint composition according to claim 2.

7. A method for forming a metallic coating to provide various objects with metallic luster and texture, comprising using the paste type metal-containing water- based paint composition according to claim 3.

8. A method for forming a metallic coating to provide various objects with metallic luster and texture, comprising using the paste type metal-containing water- based paint composition according to claim 4.