JP3860535B2 - Photocatalyst paint - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a photocatalyst coating that forms a colorless and transparent water-resistant coating film that protects the surface of a building or a building material such as translucent glass and is used for antibacterial and antifouling purposes.
[0002]
[Prior art]
Conventional room temperature curing photocatalyst paints have no water resistance and have a drawback that the coating film hydrolyzes and peels off when exposed to water for a long time. Photocatalytic reaction occurs when UV light with a wavelength of 400 nanometers or less hits the photocatalyst coating surface, and the hydrophobic molecules that stabilize the water adsorbed on the surface are decomposed by the oxidation-reduction action, resulting in a hydrophilic coating film. . Hydrophilic coatings are easily adapted to water and have a large contact area, so hydrolysis tends to occur. For this reason, when an object coated with a conventional photocatalyst paint is immersed in water for 24 hours or more, hydrolysis of the coating progresses and hardness decreases and becomes cloudy and loses transparency. When the hardness of the coating film falls below the pencil hardness B, the coated surface is peeled off simply by rubbing with a finger. Therefore, from a practical point of view, a room temperature curing type photocatalyst coating could not be used in a portion in contact with water. In addition, the actual situation is that rainbow-colored interference fringes are generated on the coated surface of the conventional photocatalyst paint formed on the glass surface, and the appearance is impaired.
[0003]
Prior arts related to the present invention are as follows. (1) The name of the invention “Japanese Industrial Waste Sho 60-187322”. (2) Japanese Patent Application Laid-Open No. 4-174679 “Name of Photoreactive Hazardous Substance Removing Agent and Hazardous Substance Removal Method Using This” (3) The name “building material” of the invention of JP-A-6-278241. (5) Name of the invention "Method for purifying dirt on solid surface" of Japanese Patent Laid-Open No. 7-51646. (6) Japanese Patent Application No. 11-76285 The title of the invention “Super water-resistant photocatalyst paint”.
[0004]
[Problems to be solved by the invention]
The biggest cause of the deterioration of the coating film of the room temperature curing type photocatalytic coating is hydrolysis. This invention mix | blends a hydrophobic substance with the photocatalyst coating material hardened | cured at normal temperature, and prevents hydrolysis by making a coating film hard to adapt to water. The present invention combines a hydrophobic substance to increase water resistance without hindering the catalytic reaction and dura film formation of a room temperature curing photocatalyst paint, thereby forming a colorless and transparent coating film free from light interference fringes. An object is to provide a photocatalytic coating that lasts.
[0005]
[Means for Solving the Problems]
The present invention is a room temperature curing photocatalyst paint containing titanium dioxide, silicon dioxide and methylmethoxysiloxane. A coating film obtained by applying this photocatalyst paint to the surface of a building or a building material containing glass and drying it is colorless and transparent and water-resistant, and no interference fringes of light occur with respect to visible light.
[0006]
The photocatalyst paint of the present invention is excellent in water resistance, the coating film after drying for 48 hours or more exhibits a pencil hardness of 9H, and water droplets adhering to the coating film 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 super hydrophilicity, and the pencil hardness of the coating film is maintained at 7H even when immersed in water for 1000 hours.
[0007]
The composition of the photocatalyst coating material of the present invention is 0.4 to 0.6 % by weight of titanium dioxide (hereinafter simply referred to as%), 0.5 to 0.8 % of silicon dioxide, and 0.1% of methylmethoxysiloxane. 6 is 2.0%.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The photocatalyst coating material 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 when the photocatalyst coating material of the present invention is applied to translucent glass, the coating film formed by drying is cured at room temperature and does not cause light interference fringes. In addition, this coating film forms a large contact angle with water droplets adhering to the surface, indicating that it has excellent water resistance.
[0009]
In particular, when the primer (G) is applied to the surface of the raster tile and the photocatalyst paint of the present invention is applied thereon, no interference fringes are generated.
[0010]
Furthermore, by changing the blending ratio of titanium dioxide and methylmethoxysiloxane, it is possible to freely control the hardness of the coating film of the photocatalytic coating, the strength of the photocatalytic reaction, and the contact angle between the coating film and water droplets.
[0011]
The photocatalyst coating material of the present invention can be obtained by the following formulation.
Tachin dioxide 0.4-0.6%
Silicon dioxide 0.5-0.8%
Methanol 20-40%
Methyl methoxysiloxane 0.6-2.0%
Nitric acid 0.01-0.3%
Pure water 2.0-4.0%
Ethanol residue [0012]
The present invention will be further described below with reference to examples.
[Example 1]
In addition to 0.5% titanium dioxide, 0.5% silicon dioxide, and 0.6% methylmethoxysiloxane, a photocatalyst coating material containing methanol, nitric acid, ethanol, and pure water was prepared as described above.
[0013]
The photocatalyst paint prepared as described above was applied to the glass surface and dried at room temperature for 48 hours to prepare 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 of JIS K5404 standard. Further, no interference fringes are observed by the reflected light on the sample surface, that is, the glass-coating interface and the coating surface. 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 type (manufactured by Kyowa Interface Science Co., Ltd.), and a measurement method using a three-point measurement average value was adopted. As a result, the contact angle was 48 to 76 °. Next, water was dropped on the sample after being irradiated with sunlight for 5 hours. Similarly, the contact angle between the glass surface and the water droplet was measured to be 28 to 42 °. From this result, it can be seen that the sample surface at the time when the photocatalyst paint according to this example was applied was hydrophobic, but changed to hydrophilic as a result of irradiation with sunlight for 5 hours.
[0014]
The water adhering to the application surface of the photocatalyst coating material of this embodiment becomes polka dots. However, since the hydrophobic molecules that stabilize the adsorbed water on the coated surface are decomposed by the light irradiation, there is no factor to support the polka dots attached to the surface of the sample, which makes it unstable. As a result, the polka dots slide down from the surface of the coating film with a slight inclination or vibration, so that water droplets and dirt are less likely to adhere to the coated surface.
[0015]
[Example 2]
Photocatalyst paint containing 0.9% titanium dioxide, 0.9% silicon dioxide, 4.0% methylmethoxysiloxane, 40% methanol, 0.01% nitric acid, 3% pure water and ethanol (residue) Prepared.
[0016]
The photocatalyst paint according to this example was applied to glass, and the same measurement as in Example 1 was performed. The coating film of this example obtained the same results as in Example 1 except that the transparency was high.
[0017]
Further, two sets of samples in which the photocatalyst paint according to this example was applied to a 4 cm × 4 cm plywood were produced. This sample was subjected to a JISZ2911 standard fungus resistance test. The sample was grounded on an agar medium dispensed in a sterilized petri dish with a diameter of 15 cm and inoculated with a mixed spore dispersion, and then cultured under conditions of a temperature of 24-26 ° C. and a humidity of 95 ± 5%. One sample was shielded from light, and the other sample was irradiated with light from a 20-watt fluorescent lamp (ultraviolet intensity of 1 μw) and cultured for 30 days. As a result, a large amount of mold propagated in one week on the sample cultured in the dark.
[0018]
Molds do not propagate at all after 30 days on the sample cultured with light irradiation. In addition, a blocking zone is formed around the sample where the inoculated bacteria with a width of 1 to 1.5 cm cannot propagate. The antibacterial power due to the OH radical generated by the photocatalytic reaction is acting around the sample. It was proved that even if the physical properties of the coating film were made hydrophobic, the bactericidal power due to the reaction was not lowered, and the antibacterial and antifouling function was not inhibited and was acting.
[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% titanium dioxide or more than 2.0% silicon dioxide, the hardness of the coating film is lowered and easily damaged and easily broken. Further, methylmethoxysiloxane contributes to the hardness of the coating film of the photocatalytic coating, 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 exceeds 6.0%, it is difficult to obtain these characteristics sufficiently.
[0020]
【The invention's effect】
As described above, the photocatalyst paint of the present invention cures at room temperature and forms a water-resistant colorless and transparent hard film, so that it is difficult to peel 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 this case, no light interference fringes 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 oxidation-reduction reactions lasts, preventing the adhesion of dirt and microorganisms and purifying the environment. To do.

Claims (1)

A photocatalytic coating comprising 0.4 to 0.6% by weight of titanium dioxide, 0.5 to 0.8% by weight of silicon dioxide, and 0.6 to 2.0% by weight of methylmethoxysiloxane .