JP2004196985A - Photocatalyst coating - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photocatalyst coating increasing water resistance of a coated film by fusing a hydrophobic substance without inhibiting catalytic reaction of normal temperature-curable photocatalyst coating and hard film formation and forming a colorless and transparent coated film not producing interference fringe of light thereby. <P>SOLUTION: The photocatalyst coating is a normal temperature-curable type containing titanium dioxide, silicon dioxide and methylmethoxysiloxane. The coated film obtained by applying the photocatalyst coating to the surface of a building or a building material including glass and drying the surface is colorless, transparent and water-resistant and does not produce interference fringe to visible light. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a photocatalytic paint for forming a colorless and transparent water-resistant coating film for protecting the surface of a building or a building material, for example, a translucent glass, and using it for antibacterial and antifouling purposes.
[0002]
[Prior art]
Conventional cold-curable photocatalytic paints have the drawback that they do not have water resistance and, when exposed to water for a long time, hydrolyze and peel off the coating film. When ultraviolet light having a wavelength of 400 nm or less is applied to the surface coated with the photocatalytic paint, a photocatalytic reaction occurs, and hydrophobic molecules that stabilize the water adsorbed on the surface are decomposed by the oxidation-reduction action, so that a hydrophilic coating film is formed. . A hydrophilic coating film is easily hydrolyzed and easily hydrolyzed because of its large contact area. Therefore, if the object coated with the conventional photocatalytic paint is immersed in water for 24 hours or more, the hydrolysis of the coating film proceeds, the hardness decreases, and the film becomes cloudy and loses transparency. When the hardness of the coating film is reduced to a pencil hardness B or less, the coating surface is peeled off only by rubbing with a finger. From a practical viewpoint, a room temperature-curable photocatalytic coating material could not be used in a portion in contact with water. In addition, it has been a fact that iridescent interference fringes are generated on the coated surface of the conventional photocatalytic coating formed on the glass surface, which impairs the aesthetic appearance.
[0003]
Prior art related to the present invention is as follows. (1) Japanese Patent Application Laid-Open No. 60-187322, entitled "Waste Purification Method". (2) JP-A-4-174679, entitled "Photoreactive harmful substance remover and harmful substance removal method using the same". (3) Japanese Patent Application Laid-Open No. 6-278241, entitled "Building Material". (5) Japanese Patent Application Laid-Open No. 7-51646, entitled "Method of Purifying Soil on Solid Surface". (6) Japanese Patent Application No. 11-76285, entitled "Super Water Resistant Photocatalytic Paint".
[0004]
[Problems to be solved by the invention]
The biggest cause of deterioration of the coating film of the photocatalytic paint of the room temperature curing type is due to hydrolysis. According to the present invention, a photocatalytic coating material that cures at room temperature is mixed with a hydrophobic substance to prevent the coating film from becoming compatible with water, thereby preventing hydrolysis. The present invention increases the water resistance by fusing a hydrophobic substance without hindering the catalytic reaction and hardening of a cold-curable photocatalytic coating, thereby forming a colorless and transparent coating film without light interference fringes. It is an object of the present invention to provide a lasting photocatalytic paint.
[0005]
[Means for Solving the Problems]
The present invention is a cold curing type photocatalytic paint containing titanium dioxide, silicon dioxide and methylmethoxysiloxane. This photocatalytic paint is applied to the surface of a building or a building material containing glass and dried, and the coating film is colorless and transparent, has water resistance, and does not generate interference fringes of light with respect to visible light.
[0006]
The photocatalytic paint of the present invention is excellent in water resistance, and the coated film after drying for 48 hours or more exhibits a pencil hardness of 9H, and water droplets adhered to the coated surface even when irradiated with sunlight for 5 hours. Since the contact angle with the surface is maintained at 28 to 42 °, it does not exhibit superhydrophilicity, and the pencil hardness of the coating film is maintained at 7H even after immersion in water for 1000 hours.
[0007]
The composition of the photocatalytic paint of the present invention is 0.4 to 1.0% by weight of titanium dioxide (hereinafter simply referred to as%), 0.5 to 1.0% of silicon dioxide, and 0.1% of methylmethoxysiloxane. 6 to 4.0%.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
The photocatalytic paint of the present invention is constituted by blending ethyl silicate, a silane coupling agent, and methylmethoxysiloxane in a liquid in which titanium dioxide and silicon dioxide are dispersed and supported in a mixed alcohol. Even if the photocatalyst paint of the present invention is applied to translucent glass, the coating film formed by drying hardens at room temperature and does not generate light interference fringes. In addition, since this coating film forms a large contact angle with water droplets attached to the surface, it is understood that the coating film has excellent water resistance.
[0009]
In particular, when the primer (G) is applied to the surface of the raster tile and the photocatalytic paint of the present invention is applied thereon, no interference fringes are generated.
[0010]
Further, by changing the mixing ratio of titanium dioxide and methylmethoxysiloxane, it is possible to freely control the hardness of the coating film of the photocatalytic coating material, the strength of the photocatalytic reaction, and the contact angle between the coating film and water droplets.
[0011]
With the following composition, the photocatalyst paint of the present invention can be obtained.
Tatin dioxide 0.4-1.0%
Silicon dioxide 0.5-1.0%
Methanol 20-40%
Methylmethoxysiloxane 0.6-4.0%
Nitric acid 0.01-0.3%
Pure water 2.0-4.0%
Ethanol residue [0012]
Hereinafter, the present invention will be further described with reference to Examples.
Embodiment 1
A photocatalytic paint was prepared in which methanol, nitric acid, ethanol and pure water were mixed in addition to 0.5% of tin dioxide, 0.5% of silicon dioxide and 0.6% of methylmethoxysiloxane according to the above.
[0013]
The photocatalyst paint prepared as described above was applied to a glass surface and dried at room temperature for 48 hours to obtain a sample. The coating film was cured by drying at room temperature for 48 hours, and exhibited a pencil hardness of 9H according to the hardness measurement according to JIS K5404. Further, no interference fringes due to the respective reflected light on the sample surface, that is, at the interface between the glass and the coating film and on the coating film surface are observed. Water was dropped on the sample according to this example, and the contact angle between the sample surface and the water droplet was measured. The contact angle was measured using a Kyowa contact angle meter CA-A (manufactured by Kyowa Interface Science Co., Ltd.), and a measurement method based on a three-point average value was adopted. As a result, the contact angle was 48 to 76 °. Next, water was dropped on the sample after irradiation with sunlight for 5 hours, and the contact angle between the glass surface and the water droplet was measured in the same manner. The result was 28 to 42 °. From this result, it can be seen that the surface of the sample at the time when the photocatalytic paint according to the present example was applied was hydrophobic, but changed to hydrophilic as a result of irradiation with sunlight for 5 hours.
[0014]
Water adhering to the application surface of the photocatalytic paint of this embodiment becomes polka dots. However, the irradiation of light decomposes the hydrophobic molecules that stabilize the adsorbed water on the application surface, so that there is no factor supporting the polka dots attached to the surface of the sample, and the sample becomes unstable. As a result, the polka dot slides down from the coating film surface with a slight inclination or vibration, so that water droplets and dirt hardly adhere to the coating surface.
[0015]
Embodiment 2
Photocatalytic paint containing 0.9% of statine dioxide, 0.9% of silicon dioxide, 4.0% of methylmethoxysiloxane, 40% of methanol, 0.01% of nitric acid, 3% of pure water and ethanol (residual) Prepared.
[0016]
The photocatalytic paint according to the present example was applied to glass, and the same measurement as in Example 1 was performed. The same results as in Example 1 were obtained except that the coating film of this example had high transparency.
[0017]
Further, two sets of samples in which the photocatalytic paint according to the present example was applied to a plywood of 4 cm × 4 cm were manufactured. This sample was subjected to a mold resistance test according to JISZ2911 standard. The sample was grounded on an agar medium dispensed into a sterilized petri dish having a diameter of 15 cm, inoculated with a mixed spore dispersion of mold, and then cultured at a temperature of 24 to 26 ° C. and a humidity of 95 ± 5%. One sample was shielded from light, and the other sample was irradiated with 20 watt fluorescent lamp light (ultraviolet light intensity 1 μw) and cultured for 30 days each. As a result, a large amount of mold propagated in a week in a sample cultured in the light-shielded state.
[0018]
No mold propagates on the sample cultured under light irradiation even after 30 days. In addition, a stop zone is formed around the sample with a width of 1 to 1.5 cm in which the inoculated bacteria cannot propagate. The antibacterial effect of the OH radical generated by the photocatalytic reaction is acting around the sample. Even when the physical properties of the coating film were made hydrophobic, the bactericidal activity by the reaction did not decrease, and the antibacterial and antifouling function was not hindered.
[0019]
In the case of a composition in which titanium dioxide is less than 0.4% or silicon dioxide is less than 0.5%, a sufficient photocatalytic effect cannot be obtained. If the composition contains more than 1.0% of titanium dioxide or more than 2.0% of silicon dioxide, the hardness of the coating film is reduced and the coating film is easily scratched and easily broken. Further, methylmethoxysiloxane contributes to the hardness of the coating film of the photocatalytic paint, the strength of the photocatalytic reaction, and the maintenance of the contact angle between the coating film and water droplets. When the composition of methylmethoxysiloxane is less than 0.6% or more than 6.0%, it is difficult to sufficiently obtain these properties.
[0020]
【The invention's effect】
As described above, the photocatalytic paint of the present invention cures at room temperature and forms a water-resistant, colorless and transparent hard film, so that it hardly peels off and prevents deterioration and damage due to wind and rain. Since the coating film is colorless and transparent, it can be applied to a building or a building material including glass. Even in such a case, light interference fringes do not occur. By maintaining the transparency of the coating film, the light irradiated on the surface can be used efficiently for photocatalytic reactions, so the effect of decomposing organic substances by the oxidation-reduction reaction is maintained, preventing the adhesion of dirt and microorganisms and purifying the environment. I do.

Claims (6)

A room temperature-curable photocatalytic paint containing titanium dioxide, silicon dioxide and methylmethoxysiloxane. 2. The photocatalyst according to claim 1, wherein the colorless and transparent coating film formed by applying to a surface of a building or a building material including glass does not generate interference fringes of visible light after drying. paint. 3. The photocatalytic coating according to claim 1, wherein the coating film after drying for 48 hours or more exhibits a pencil hardness of 9H. The contact angle formed by a water droplet attached to the coating film surface with the coating film surface is maintained at 28 to 42 degrees even when the coating film is irradiated with sunlight for 5 hours. 3. The photocatalytic paint according to any one of 3. The photocatalyst paint according to any one of claims 1 to 4, wherein the coating film after coating and drying on the surface of the glass maintains a pencil hardness of 7H even when immersed in water for 1000 hours. The photocatalytic paint has a composition of 0.4 to 1.0% by weight of titanium dioxide, 0.5 to 1.0% by weight of silicon dioxide, and 0.6 to 4.0% by weight of methylmethoxysiloxane. The photocatalytic paint according to any one of claims 1 to 5, characterized in that: