JP2006182791A - Coating material for forming photocatalyst film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating material for forming a photocatalyst film, which is capable of forming the photocatalyst film showing an excellent photocatalytic activity under light irradiation, wherein the film is not brittle even though it contains a photocatalyst at a high concentration. <P>SOLUTION: The coating material contains (A) an aqueous peroxotitanic acid solution obtained by mixing a hydrogen peroxide solution with a titanium hydroxide compound, a hydrolyzable titanium compound and/or a low condensate thereof and (B) a photocatalyst powder, wherein a portion of (A) the aqueous peroxotitanic acid solution is previously mixed with (B) the photocatalytic powder in a weight ratio of from 1/200 to 10/100 on a solid basis and heated to form reactive hydroxytitanium groups on the surface of the photocatalyst powder. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a coating agent for forming a photocatalyst film that can form a photocatalyst film exhibiting an excellent photocatalytic action when irradiated with light, even if it contains a high concentration photocatalyst, and the film does not become brittle.
[0002]
[Prior art]
When a semiconductor is irradiated with ultraviolet rays, electrons having a strong reducing action and holes having a strong oxidizing action are generated, and molecular species in contact with the semiconductor are decomposed by the redox action. Such an action is called a photocatalytic action, and various measures for utilizing this photocatalytic action have been proposed in recent years. Specifically, decomposition of NOx in the atmosphere, prevention of contamination, decomposition and removal of malodorous substances and molds in living spaces and work spaces, or decomposition and removal of environmental pollutants such as organic solvents, pesticides and surfactants in water It is an application to. Titanium oxide attracts attention as a substance having such a photocatalytic action, and a photocatalyst made of titanium oxide is commercially available. In recent years, various studies have been made on not only a photocatalyst utilizing an ultraviolet region but also a photocatalyst exhibiting a high photocatalytic action when irradiated with visible light.
[0003]
Since such a photocatalytic action is obtained on the contact surface with the photocatalyst body, when the photocatalytic film is formed on the substrate surface, it is very high in the binder component in order to maximize its function. Although it is necessary to contain the photocatalyst at a concentration, the physical properties of the film become insufficient, such as the film becoming brittle with a normal organic binder component, and long-term durability could not be obtained. Therefore, the present applicant has proposed to use peroxotitanic acid having light resistance as a binder component (see, for example, Patent Document 1).
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-144543
[Problems to be solved by the invention]
When peroxotitanic acid or the like is used as a binder component, it is excellent in long-term light resistance, but it cannot be said that the film properties and the storage stability of the coating solution are sufficient.
[0006]
The object of the present invention is to form a photocatalyst film that solves the above-mentioned problems and can form a photocatalyst film exhibiting an excellent photocatalytic action when irradiated with light without the film becoming brittle even if a high concentration photocatalyst is included. It is to provide a coating agent.
[0007]
[Means for Solving the Problems]
That is, the present invention
1. (A) A peroxotitanic acid aqueous solution obtained by mixing a titanium hydroxide compound or a hydrolyzable titanium compound and / or a low condensate thereof with hydrogen peroxide, and (B) a photocatalyst powder, B) mixes a part of the peroxotitanic acid aqueous solution (A) with the photocatalyst powder (B) at a solid content weight ratio of 1/200 to 10/100, and heats to react reactive hydroxy on the surface of the photocatalyst powder. A coating agent for forming a photocatalyst film, wherein a titanic acid group is previously formed;
2. The peroxotitanic acid aqueous solution (A) contains a titanium hydroxide compound or a hydrolyzable titanium compound and / or a low condensate thereof and a hydrogen peroxide solution, and the latter is 1 in terms of hydrogen peroxide with respect to 100 parts by weight of the former. The coating agent for forming a photocatalyst film according to claim 1, wherein the coating agent is mixed at a ratio of 1 to 10,000 parts by weight.
3. 2. The coating agent for forming a photocatalyst film according to 1, which contains the aqueous peroxotitanic acid solution (A) and the photocatalyst powder (B) at a solid content weight ratio of 100/10 to 100/500,
4). 5. The photocatalyst film-forming coating agent according to any one of 1 to 4 is applied to the substrate surface and dried to react at least part of the particle surface of the peroxotitanic acid as a binder and the photocatalyst powder (B). A method for forming an integrated photocatalytic film,
5. Articles formed by forming the photocatalyst film according to item 4 on the substrate surface,
About.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the peroxotitanic acid aqueous solution (A) is obtained by mixing a titanium hydroxide compound or a hydrolyzable titanium compound and / or a low condensate thereof with a hydrogen peroxide solution.
As the hydrolyzable titanium compound, in particular, the general formula (I)
Ti (OR) ₄ (I)
(Wherein, R is the same or different and represents an alkyl group having 1 to 5 carbon atoms). Moreover, as a low-condensate of a titanium hydroxide compound or a hydrolyzable titanium compound, a thing with a condensation degree of about 2-30 is preferable.
[0009]
In the peroxotitanic acid aqueous solution (A), the titanium hydroxide compound or the hydrolyzable titanium compound and / or the low condensate thereof and the hydrogen peroxide solution consist of 100 parts by weight of the former and hydrogen peroxide of the latter. It is suitable to mix in the ratio of 1 to 1,000 parts by weight, preferably 10 to 200 parts by weight. If the latter is less than 1 part by weight in terms of hydrogen peroxide, a stable and uniform aqueous solution cannot be obtained, and long-term storage becomes difficult. On the other hand, if it exceeds 1,000 parts by weight, the oxygen partial pressure becomes high and the foamability is strong. Since it becomes unstable storage, it is not preferable.
[0010]
The hydrogen peroxide concentration of the hydrogen peroxide solution is not particularly limited, but is preferably in the range of 3 to 30% by weight from the viewpoint of ease of handling.
[0011]
The mixing of the titanium hydroxide compound or hydrolyzable titanium compound and / or the low condensate thereof with hydrogen peroxide is usually preferably performed at about 1 to 70 ° C. with stirring for about 10 minutes to 20 hours. When mixing, a water-soluble organic solvent such as, for example, alcohols such as methanol, ethanol, n-propanol, iso-isopropanol; alcohol ethers such as ethylene glycol monobutyl ether and propylene glycol monomethyl ether may be used. It can also be used.
[0012]
The aqueous peroxotitanic acid solution (A) is obtained by mixing a titanium hydroxide compound or a hydrolyzable titanium compound and / or a low condensate thereof with hydrogen peroxide solution, whereby the former is hydrolyzed with water and hydroxyl group-containing titanium. It is presumed that this is obtained by forming a compound and then immediately coordinating hydrogen peroxide to this hydroxyl group-containing titanium compound to form peroxotitanic acid. This aqueous solution of peroxotitanic acid (A) is highly stable at room temperature and can withstand long-term storage.
[0013]
If necessary, at least one compound selected from acetanilide, phenacetin, and oxyquinoline may be added to the aqueous peroxotitanic acid solution (A) to improve storage stability. The addition amount of the compound is preferably in the range of 0.01 to 20 parts by weight, particularly 0.2 to 2.0 parts by weight with respect to 100 parts by weight of the solid content of (A).
[0014]
As the photocatalyst powder (B) in the present invention, any conventionally known photocatalyst powder can be used without particular limitation as long as it can absorb ultraviolet light and / or visible light to express a photocatalytic action. For example, titanium oxide, Examples of the oxide semiconductor include tungsten oxide, zinc oxide, hafnium oxide, zirconium oxide, strontium titanate, titanium oxide-zirconium oxide composite oxide, and silicon oxide-titanium oxide composite oxide. Vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), ruthenium (Ru), rhodium (Rh), Rhenium (Re), osmium (Os), palladium (Pd), platinum (Pt), iridium (Ir), niobium (Nb), molybdenum At least one metal compound of the emissions (Mo) is also mentioned those carried, they can be used alone or in combination with, the powder is preferable to particularly mainly of titanium oxide.
[0015]
The powder mainly composed of titanium oxide is any one of anatase type, rutile type, brookite type, and Cr, Ru, V, Nb, Fe, Ni, Cu, Mg, Ag on the surface as required. , Titanium oxide carrying or containing at least one metal fine particle selected from the group consisting of Mn, Pd and Pt; titanium oxide carrying or containing a platinum halide compound such as a platinum chloride compound on the surface; or stable oxygen A main signal having a g value of 2.004 to 2.007 in a measurement with an electron spin resonance spectrum (measured under light irradiation in a wavelength region of 420 nm or more), and g of 1.985. ˜1.986, and titanium oxide in which two side signals having a g value of 2.024 are observed.
[0016]
In the present invention, the photocatalyst powder (B) comprises a part of the aqueous peroxotitanic acid solution (A) and the photocatalyst powder (B) in a solid content weight ratio of 1/200 to 10/100, preferably 1/100. It is essential that a reactive hydroxytitanium group is previously formed on the surface of the photocatalyst powder by mixing and heating at a ratio of ˜5 / 100. As heating conditions, it is desirable to carry out at 40 to 250 ° C. for about 24 to 1 hour. As a result, after the film is formed, the condensation reaction of the reactive hydroxytitanium group on the surface of the photocatalyst powder and the peroxotitanic acid of the binder proceeds by drying, thereby producing an effect that a strong integrated film can be formed. Further, since the surface of the photocatalyst powder has a hydrophilic and sterically hindered functional group called a peroxo group, the reactive hydroxytitanium group can be protected and the storage stability can be dramatically improved in the coating solution.
[0017]
In the present invention, the peroxotitanic acid aqueous solution (A) and the photocatalyst powder (B) treated as described above are in a ratio of 100/10 to 100/500, preferably 100/50 to 100/300 in terms of solid content by weight. It is suitable to contain. If the amount of the component (A) is small outside this range (the component (B) is large), the resulting coating is brittle, the photocatalyst powder (B) tends to deviate, and eventually the long-term photocatalytic performance cannot be maintained. ) If the component is large (the component (B) is small), the photocatalytic reaction that occurs on the powder surface is inhibited, which is not preferable.
[0018]
The mixing of the peroxotitanic acid aqueous solution (A) and the photocatalyst powder (B) may be performed by performing a dispersion treatment so that the dispersed particle diameter of the component (B) is about 10 nm to 10 μm, preferably about 10 nm to 1 μm. It is desirable from the viewpoint of securing.
[0019]
The photocatalyst film-forming coating agent of the present invention contains the above components (A) and (B), and can further contain various additives as necessary. For example, an organic acid and / or a salt thereof May be added from the viewpoint of storage stability. Examples of the organic acid include organic carboxylic acids such as acetic acid, oxalic acid, glycolic acid, lactic acid, malic acid, citric acid, tartaric acid, and gluconic acid; organic sulfonic acids such as methanesulfonic acid, ethanesulfonic acid, and p-benzenesulfonic acid. Acid; organic sulfinic acid such as 2-amino-ethanesulfinic acid and p-toluenesulfinic acid; organic nitro compounds such as nitromethane, nitroethane, nitropropionic acid, nitrocatechol, 2-nitroresorcinol, nitrobenzoic acid; phenol, catechol , Resorcinol, hydroquinone, pyrogallol, salicylic acid, gallic acid, benzoic acid, thiophenol, 2-aminothiophenol, 4-ethylthiophenol and other phenols; 1-hydroxymethane-1, 1-diphosphonic acid, 1-hydroxyethane -1, 1 Diphosphonic acid, 1-hydroxypropane-1, 1-diphosphonic acid, nitrilo (amino) trimethylenephosphonic acid, nitrilo (amino) triethylenephosphonic acid, nitrilo (amino) tripropylenephosphonic acid, ethylenediaminetetramethylenephosphonic acid, ethylenediaminetetra Hydrolyzate of ethylenephosphonic acid, ethylenediaminetetrapropylenephosphonic acid, N, N-bis (2-phosphoethyl) hydroxyamine, N, N-bis (2-phosphomethyl) hydroxyamine, 2-hydroxyethylphosphonic acid dimethyl ether, 2- And organic phosphoric acid compounds such as hydroxyphosphonoacetic acid and 2-phosphonobutane-1,2,4-tricarboxylic acid.
[0020]
Moreover, as an organic acid salt, the salt of the organic acid formed by adding an alkali compound to the said organic acid can be used. Examples of the alkali compound include organic or inorganic alkali compounds containing lithium, sodium, potassium, ammonium and the like.
[0021]
As the organic acid or the organic acid salt, it is preferable to use those that are soluble in water. In particular, hydroxycarboxylic acids such as glycolic acid, lactic acid, malic acid, citric acid, tartaric acid, and gluconic acid; 1-hydroxymethane -1,1-diphosphonic acid, 1-hydroxyethane-1,1-diphosphonic acid, 1-hydroxypropane-1, hydroxyphosphorus-containing organic phosphorous acid such as 1-diphosphonic acid; 2-hydroxyphosphonoacetic acid, 2- Use of at least one compound selected from the group consisting of carboxyl group-containing organic phosphorous acid such as phosphonobutane-1,2,4-tricarboxylic acid and salts thereof, and the effect excellent in storage stability of the coating agent Is preferable.
[0022]
The amount of the organic acid and / or organic acid salt added to the coating agent of the present invention is usually in the range of about 1 to 400 parts by weight, particularly 10 parts per 100 parts by weight of the solid content of (A). The range is preferably about 200 parts by weight.
[0023]
The coating agent of the present invention may further contain a basic neutralizing agent such as ammonia, an organic basic compound, an alkali metal hydroxide, or an alkaline earth metal hydroxide, if necessary. Examples of the organic basic compound include dimethylethanolamine, 2-amino-2-methyl-1-propanol, triethylamine, and morpholine. Examples of the alkali metal hydroxide include lithium hydroxide and sodium hydroxide. And potassium hydroxide.
[0024]
In the coating agent of the present invention, if necessary, for example, a thickener, an organic solvent, a surfactant, a fungicide, a rust inhibitor, a lubricant, an antifoaming agent, a leveling agent, a coloring pigment, an extender pigment, An antirust pigment etc. can be mentioned. Examples of the color pigment include Bengala and colored glass frit powder, and examples of the extender pigment include mica, talc, silica, fine silica, barita, and clay.
[0025]
The coating agent for forming a photocatalyst film of the present invention is a photocatalyst film in which peroxotitanic acid as a binder and at least part of the particle surface of the photocatalyst powder (B) react and are integrated by applying and drying on a substrate surface. Can be formed. In particular, in order to integrate both components, it is desirable to heat, for example, drying at 40 ° C. to 250 ° C., preferably 80 to 200 ° C., microwave heating, microwave induction heating and the like are desirable.
[0026]
Although the film thickness of the photocatalyst film | membrane formed is not specifically limited, Usually, it is preferable that it is about 0.001-20 micrometers, and it is more preferable that it is the range of 0.1-15 micrometers. Also, a uniform and dense titanium oxide porous film having a thickness of 1 μm or more, which is excellent in adhesion and hardly peeled off, can be formed usually by a single application. Of course, you may apply | coat several times as needed.
[0027]
Application to the substrate surface is not particularly limited, and may be a known coating method. As the coating method, for example, various coating methods such as printing coating, knife coater coating, doctor blade coating, immersion coating, shower coating, spray coating, roll coating, and electrodeposition coating can be employed. Moreover, it is good also as an impregnation to the base-material surface.
[0028]
As said base material, the thing of all materials, such as a metal, ceramics, plastics, a fiber, glass, concrete, can be used, for example. For materials such as plastics and fibers that are decomposable by photocatalysis, do not apply to the surface of the material in advance using an insulating treatment film from photocatalysis, such as silicates such as silicates or peroxotitanic acid. These films can be formed by impregnation treatment. Also, the shape of the substrate may be any shape such as a plate shape, a spherical shape, a rectangular parallelepiped shape, and a cylindrical shape. Furthermore, it is also possible to use a porous body, powder, or the like as the base material to perform internal treatment or surface treatment of the porous body, or surface treatment of the powder. Examples of the porous body include a foam, a honeycomb structure, a corrugated structure, and the like. Examples of the powder include extender pigments such as mica, talc, silica, barium sulfate, and clay, and colored pigments such as petals, cobalt blue, and colored glass frit pigments intended for coloring.
Specific examples of the substrate surface include interior and exterior surfaces of buildings, window glass surfaces, curtains, road protection walls and tunnel inner walls, vehicle interior surfaces, window glasses, and mirror surfaces.
[0029]
【Example】
Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. “Parts” and “%” are both based on weight.
[0030]
Preparation of peroxotitanic acid aqueous solution (A) Preparation Example 1
A mixture of 10 parts of tetraiso-propoxytitanium and 10 parts of iso-propanol was dropped into a mixture of 10 parts of 30% hydrogen peroxide and 100 parts of deionized water at 20 ° C. over 1 hour with ultrasonic stirring. Thereafter, aging was carried out at 25 ° C. for 2 hours to obtain a yellow transparent slightly viscous peroxotitanic acid aqueous solution. This was diluted with water to obtain a peroxotitanic acid aqueous solution (1) having a solid concentration of 3%.
[0031]
Creation example 2
A mixture of 10 parts of tetra-n-butoxytitanium and 10 parts of iso-propanol was dropped into a mixture of 20 parts of 30% hydrogen peroxide and 100 parts of deionized water at 20 ° C. over 1 hour with ultrasonic stirring. . Thereafter, aging was carried out at 25 ° C. for 2 hours to obtain a yellow transparent slightly viscous peroxotitanic acid aqueous solution. This was diluted with water to obtain a peroxotitanic acid aqueous solution (2) having a solid concentration of 1%.
[0032]
Creation example 3
A mixture of 10 parts of tetraethoxytitanium and 15 parts of methoxyethanol was dropped into a mixture of 20 parts of 30% aqueous hydrogen peroxide and 100 parts of deionized water at 20 ° C. over 1 hour with ultrasonic stirring. Thereafter, aging was carried out at 25 ° C. for 2 hours to obtain a yellow transparent slightly viscous peroxotitanic acid aqueous solution. This was diluted with water to obtain a peroxotitanic acid aqueous solution (3) having a solid content concentration of 2%.
[0033]
Preparation and evaluation of coating agent for photocatalyst film formation Example 1
To 20 parts of the peroxotitanic acid aqueous solution (1) having a solid content concentration of 3% obtained in Preparation Example 1 above, 7 parts of “MPT-621” (manufactured by Ishihara Sangyo Co., Ltd., visible light responsive photocatalytic titanium oxide) and alumina beads The mixture was shaken and dispersed for 2 hours, and then heat-treated at 150 ° C. for 30 minutes.
[0034]
Next, 80 parts of a peroxotitanic acid aqueous solution (1) having a solid content concentration of 3% was added thereto, and after shaking for 15 minutes, the solution and beads were separated and discharged to obtain a photocatalyst film-forming coating agent (I). It was.
[0035]
The coating liquid (I) was applied to an aluminum substrate (49.5 mm * 100 mm * 3.0 mm) by an air spray method so that the dry film thickness was 2 μm, and was heated and dried at 170 ° C. for 30 minutes to form a film. . The pencil hardness of this coating was 5H.
[0036]
Further, after the film formation, the NOx decomposition rate was measured. The NOx decomposition rate was evaluated using an NOx gas (NO gas concentration of 1 ppm) calibrated with a standard gas having a NO concentration of 2 ppm using an environmental tester “nitrogen oxide meter CLAD-1000 for atmospheric measurement” manufactured by Shimadzu Corporation. ) At a flow rate of 2 L / min, and the decomposition rate of NOx gas was evaluated while irradiating an AM1.5 halogen 100 W artificial solar lamp. As a result, an NOx decomposition rate of 81% was obtained.
Similarly, when the coating liquid (I) was formed into a film using foam aluminum as a base material and the decomposition rate of NOx gas was evaluated, the NOx decomposition rate of 98% or more could be achieved due to the effect of increasing the apparent surface area. It was.
Example 2
100 parts of “NTB-200” (made by Showa Denko KK, brookite-type photocatalytic titanium oxide, 2.5% water dispersion sol) is added to 25 parts of the peroxotitanic acid aqueous solution (2) having a solid content concentration of 1% obtained in Preparation Example 2. And shaken, and then heat-treated at 80 ° C. for 4 hours. Next, 75 parts of a peroxotitanic acid aqueous solution (2) having a solid content concentration of 1% and 0.001 part of acetanilide were added and shaken for 30 minutes to obtain a coating agent (II) for forming a photocatalyst film.
[0037]
This coating solution (II) was applied to an ITO transparent conductive glass substrate (50 * 100 mm * 2 mm) by an air spray method so that the dry film thickness was 0.1 μm, and dried by heating at 150 ° C. for 30 minutes. After film formation, 1% methylene blue aqueous solution was impregnated for 10 minutes to adsorb methylene blue. The remaining dye was absorbed by filter paper and removed to obtain an evaluation substrate contaminated in blue. The photodegradability of methylene blue was evaluated while irradiating a 27 W fluorescent lamp stand (distance 30 cm). As a result, methylene blue was decomposed in 30 hours.
This photocatalyst coating film had a light transmittance of 95% and was transparent, and a 32 dB shield characteristic was obtained by electromagnetic wave reflection of the ITO conductive film. As a result, it is possible to control the transmission / reception of the mobile phone.
[0038]
Similarly, when the above coating liquid (II) was applied using a double-sided ITO sputtered conductive glass as a base material and formed into a film, a shield characteristic of 45 dB was obtained. As a result, information leakage of the wireless LAN can be prevented.
Example 3
To 20 parts of the peroxotitanic acid aqueous solution (3) having a solid content concentration of 2% obtained in Preparation Example 3 above, 3 parts of “Nanopure DR35PT30” (Daiken Chemical Co., Ltd., nanoparticle platinum-supported rutile titanium oxide photocatalyst), talc 0.5 parts, 0.1 part of red petite, and alumina beads were added and shake-dispersed for 2 hours, followed by heat treatment at 90 ° C. for 6 hours.
[0039]
Next, 80 parts of the above-mentioned aqueous solution of peroxotitanic acid (3) having a solid content concentration of 1%, 10 parts of 10% hydrogen peroxide solution and 0.2 parts of butyl cellosolve were added, and the mixture was shaken for 15 minutes. Were separated and discharged to obtain a photocatalyst film-forming coating agent (III).
[0040]
On the surface of a PET film (50 mm * 50 mm * 0.1 mm) that has been subjected to surface hydrophilization treatment by plasma treatment in advance, the above-mentioned aqueous solution of peroxotitanic acid (2) having a solid content of 1% is dried to a thickness of 0.2 μm. And then dried by heating at 120 ° C. for 10 minutes, and then the coating liquid (III) obtained above is applied thereon by a roll coater method so that the dry film thickness becomes 1 μm. The porous visible light photocatalyst film was obtained by heating and drying at 1 ° C. for 1 minute. Put this film in a 500ml glass container, irradiate it with a 27W fluorescent lamp stand (distance 30cm), circulate air containing 300ppm of acetaldehyde, extract gas every 10 minutes, and measure the aldehyde concentration by gas chromatography. did. As a result, the acetaldehyde concentration became 1 ppm or less in 12 hours, and the optical resolution of the aldehyde could be confirmed.
Example 4
7 parts of “AMT-600” (manufactured by Teika, anatase-type titanium oxide) and alumina beads were added to 20 parts of the peroxotitanic acid aqueous solution (1) having a solid content concentration of 3% obtained in Preparation Example 1 for 2 hours. After shaking and dispersing, heat treatment was performed at 150 ° C. for 30 minutes.
[0041]
Next, 80 parts of the above-mentioned peroxotitanic acid aqueous solution having a solid content concentration of 3% was added thereto, and after shaking for 15 minutes, the solution and beads were separated and discharged to obtain a coating solution (IV) for forming a photocatalyst film.
[0042]
This coating liquid (VI) was applied to an aluminum substrate (49.5 mm * 100 mm * 3.0 mm) by an air spray method so that the dry film thickness was 2 μm, and was heated and dried at 170 ° C. for 30 minutes to form a film. . This film had a pencil height of 5H. In addition, a wear test was repeatedly performed 20 times with a load of 200 g using a gag type wear tester, and it was confirmed that there was no abnormality.
Further, after the film formation, the NOx resolution was measured. For the evaluation of NOx decomposition rate, an environmental tester manufactured by Shimadzu Corporation was used, a NOx gas calibrated with a standard gas having a NO concentration of 2 ppm (NO gas concentration of 1 ppm) was flowed at 2 L / min, and an ultraviolet intensity was 0.8 mW / cm. The decomposition rate of NOx gas was evaluated while irradiating ultraviolet light with a black light of No. ² . As a result, the NOx decomposition rate was 87%.
[0043]
Comparative Example 1
To 20 parts of an anatase-type titanium oxide sol aqueous solution having a solid content concentration of 3%, 7 parts of “MPT-621” (manufactured by Ishihara Sangyo Co., Ltd., visible light responsive photocatalytic titanium oxide) and alumina beads are added and shaken for 2 hours. Further, 80 parts of an anatase-type titanium oxide sol aqueous solution with a solid content concentration of 3% was added, and after shaking for 15 minutes, the solution and beads were separated and discharged to obtain a photocatalyst film-forming coating liquid (V). .
[0044]
This coating liquid (V) was applied to an aluminum substrate (49.5 mm * 100 mm * 3.0 mm) by an air spray method so that the dry film thickness was 2 μm, and dried by heating at 170 ° C. for 30 minutes. The film was fragile, and when the vibration or the substrate was tilted, the film peeled off and could not be evaluated.
Comparative Example 2
7 parts of “AMT-600” (manufactured by Teika Co., Ltd., anatase type titanium oxide) and alumina beads were added to 100 parts of an aqueous solution of peroxotitanic acid having a solid content concentration of 3% obtained in Preparation Example 1 for 2 hours. After shaking and dispersing, the solution and beads were separated and discharged to obtain a photocatalyst film-forming coating liquid (VI).
[0045]
This coating liquid (VI) was applied to an aluminum substrate (49.5 mm * 100 mm * 3.0 mm) by an air spray method so that the dry film thickness was 2 μm, and was heated and dried at 170 ° C. for 30 minutes to form a film. . This film had a pencil height of 2B. Moreover, when the abrasion test was repeatedly performed 20 times with a load of 200 g using a galvan type abrasion tester, the aluminum surface was exposed. Further, after the film formation, the NOx resolution was measured. For the evaluation of NOx decomposition rate, an environmental tester manufactured by Shimadzu Corporation was used, a NOx gas calibrated with a standard gas having a NO concentration of 2 ppm (NO gas concentration of 1 ppm) was flowed at 2 L / min, and an ultraviolet intensity was 0.8 mW / cm. ^{When the} ultraviolet light was irradiated with the black light of No. ² , the NOx decomposition rate was 87%.
[0046]
【The invention's effect】
In the present invention, since the aqueous solution of peroxotitanic acid, which is a binder, contains titanium and oxygen as main components, particularly when it is formed into a film by heating or the like, it can form an inorganic film having a high purity and rigidity. Further, this film has an advantage that it is not adversely affected by photodegradation or the like by radicals generated by the photocatalytic reaction. Furthermore, in order to form a hydroxytitanic acid layer with a peroxotitanic acid aqueous solution that is a binder in advance with respect to the photocatalyst powder, the surface of the photocatalyst powder reacts with the peroxotitanic acid that is the binder during heating and drying after coating, It is presumed to be an integrated strong inorganic composite film.
[0047]
In particular, in the present invention, even if the content of the photocatalytic titanium oxide powder exceeds a critical concentration CPVC (Critical Pigment Volume Concentration), a solid film can be formed by the integration of the binder and the powder. The resulting coating has a light resistance that is higher than the photocatalytic action because the binding energy of titanium and oxygen is larger than the photocatalytic reaction energy, and has excellent light resistance.

Claims (5)

A coating agent containing (A) a peroxotitanic acid aqueous solution obtained by mixing a titanium hydroxide compound or a hydrolyzable titanium compound and / or a low condensate thereof with hydrogen peroxide, and (B) a photocatalyst powder. The photocatalyst powder (B) is prepared by mixing a part of the peroxotitanic acid aqueous solution (A) and the photocatalyst powder (B) at a solid content weight ratio of 1/200 to 10/100, and heating the mixture. A coating agent for forming a photocatalyst film, wherein a reactive hydroxytitanium group is previously formed on the surface. The peroxotitanic acid aqueous solution (A) contains a titanium hydroxide compound or a hydrolyzable titanium compound and / or a low condensate thereof and a hydrogen peroxide solution, and the latter is 1 in terms of hydrogen peroxide with respect to 100 parts by weight of the former. The coating agent for forming a photocatalyst film according to claim 1, wherein the coating agent is mixed at a ratio of 1 to 10,000 parts by weight. The coating agent for photocatalyst film formation of Claim 1 which contains peroxotitanic acid aqueous solution (A) and photocatalyst powder (B) in the ratio of 100/10-100/500 by solid content weight ratio. 4. The photocatalyst film-forming coating agent according to any one of claims 1 to 3 is applied to a substrate surface and dried, so that at least a part of the particle surface of peroxotitanic acid as a binder and photocatalyst powder (B) is coated. A method of forming a photocatalyst film integrated by reaction. An article formed by forming the photocatalyst film according to claim 4 on a substrate surface.