JP2010280859A - Photocatalytic coating composition for high temperature firing, and method for producing photocatalytic material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photocatalytic coating composition for high temperature firing, capable of forming coatings excellent in photocatalytic gas degradation activity by coating onto a heat resistant base material requiring abrasion resistance, and a method for producing a photocatalytic material. <P>SOLUTION: The photocatalytic coating composition for high temperature firing comprises photocatalyst particles, an alkyl silicate and a solvent. In the composition, the content of a solid component is <5 wt.% based on the whole composition, the main ingredient of the solvent is water and the solvent contains an alcohol as an optional component in 0 wt.% to less than 50 wt.%. The composition is able to form a coated film excellent in the photocatalytic gas degradation activity by applying the composition onto the heat resistant base material and firing at a high temperature. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a photocatalyst coating composition for high-temperature firing, which is capable of forming a film excellent in photocatalytic gas decomposition activity by applying to a heat-resistant substrate and firing at high temperature.

  In recent years, photocatalysts such as titanium oxide have been used in many applications such as exterior building materials and interior building materials for buildings. For exterior applications, by applying a photocatalyst to the substrate surface, it is possible to impart a decomposition function of harmful substances such as NOx and SOx using light energy.

  Conventionally, NOx decomposition using a photocatalyst is conventionally performed by (1) a method of blending photocatalyst particles into a porous membrane (JP-A-8-99041, etc.), (2) mixing photocatalyst particles and an alkyl silicate, and having a temperature of 300 ° C. There are known methods for hydrolyzing and polycondensing alkyl silicates at a temperature (Japanese Patent Laid-Open Nos. 4-174679 and 8-164334).

JP-A-8-99041 JP-A-4-174679 JP-A-8-164334 WO00 / 006300 Publication

However, as a method for adding a NOx decomposition function to a heat resistant substrate, the method of blending the photocatalyst particles into the porous film reduces wear resistance due to the porosity. The features cannot be fully utilized.
In addition, as a method for adding a NOx decomposition function to a heat-resistant substrate, when using a method in which photocatalyst particles and alkyl silicate are mixed and the alkyl silicate is hydrolyzed and polycondensed at a temperature of 300 ° C. or lower, the wear resistance is also reduced. The characteristics are not sufficient, and the characteristics cannot be fully utilized when fixing to a heat-resistant substrate.

  In the present invention, in view of the above circumstances, a photocatalyst coating composition for high-temperature firing, which is capable of forming a film that is excellent in photocatalytic gas decomposition activity by applying to a heat-resistant substrate and firing at high temperature, which requires abrasion resistance, and It aims at providing the photocatalyst material using the same.

  That is, in the present invention, a photocatalyst coating composition for high-temperature firing comprising photocatalyst particles, an alkyl silicate, and a solvent, wherein the solid content concentration in the entire composition is less than 5% by weight, and the solvent is a main component Is a water, and further contains an alcohol as an optional component in an amount of 0 wt% to less than 50 wt%, and can be formed on a heat-resistant substrate and baked at a high temperature to form a film excellent in photocatalytic gas decomposition activity The photocatalyst coating composition for high temperature firing.

Photocatalyst coating composition for high-temperature firing A photocatalyst coating composition for high-temperature firing according to the present invention is a photocatalyst coating composition for high-temperature firing containing photocatalyst particles, an alkyl silicate, and a solvent, and a solid content concentration in the total composition Is less than 5% by weight, the solvent is mainly composed of water, and further contains alcohol as an optional component in an amount of 0% by weight to less than 50% by weight. Is a photocatalyst coating composition for high-temperature firing, which can form a film excellent in photocatalytic gas decomposition activity.
According to paragraph No. (0018) line 5 and below of JP-A-8-164334, a coating film from a coating solution containing photocatalyst particles and alkyl silicate is described as follows. “Preferable solid content concentration is 5 to 20%, and if it is 5% or less, the adhesion to the substrate becomes strong, but the coating thickness, that is, the amount of titanium dioxide is insufficient, and the coating can sufficiently exhibit the photocatalytic function. Can't form. "
Further, according to paragraph number (0023) of JP-A-8-164334, a coating film from a coating liquid containing photocatalyst particles and alkyl silicate is described as follows. “Due to drying at 100 ° C., it is possible to form a fairly strong coating film that does not easily peel off when rubbed with a nail, but silica binder can form a stronger coating film by drying at a temperature of 100 ° C. or higher. Depending on the temperature, it may be dried or calcined at a low temperature of 100 to 300 ° C. However, the catalytic activity of ultrafine particulate titanium dioxide begins to gradually decrease after drying at 150 ° C. or higher, and may rapidly decrease when the temperature exceeds 400 ° C. Therefore, it is necessary to appropriately select the drying temperature according to the necessity of the coating film strength. "
However, the heat-resistant substrate is required to have a high degree of wear resistance as an original application, and generally sufficient wear resistance cannot be obtained by firing at 300 ° C. or lower.
However, this time, the photocatalyst for high-temperature firing that can realize high wear resistance without reducing the gas decomposition activity of the photocatalyst even when firing at a temperature exceeding 300 ° C, more preferably above 400 ° C. A new coating composition has been found.
It is a photocatalyst coating composition for high-temperature firing containing photocatalyst particles, alkyl silicate, and a solvent, and the solid content concentration in the whole composition is less than 5% by weight, and the solvent is mainly composed of water. In addition, it is possible to form a film excellent in photocatalytic gas decomposition activity by coating on a heat-resistant substrate and baking at a high temperature, characterized by containing an alcohol as an optional component in an amount of 0 to 50% by weight. It is a photocatalyst coating composition for use.
Even when this coating composition is baked at a temperature exceeding 300 ° C., more preferably above 400 ° C., it is possible to realize high wear resistance without reducing the gas decomposition activity of the photocatalyst. Probably, it can be explained as follows. That is, since the solid content concentration in the whole composition is less than 5% by weight and the solvent is mainly water, the storage stability is stable for about one month, but the hydrolysis / condensation polymerization of alkyl silicate. Goes to some extent at room temperature. It becomes a steric hindrance structure, and polymerization occurs to the extent that abrasion resistance can be satisfied when it is fired at a high temperature above 300 ° C., more preferably above 400 ° C., but the resin density per unit volume increases so much. Therefore, it is considered that the active sites of the photocatalyst were not covered so much and the photocatalytic activity was not rapidly reduced.

In a preferred embodiment of the present invention, the alkyl silicate is a lower alkyl silicate condensation represented by the general formula Si _n O _n-1 (OR) _{2n + 2} (where n is 2-6 and R is a C1-4 alkyl group). A product obtained by further hydrolyzing the product so that the hydrolysis rate is 50 to 1500% is used.
By using such a lower alkyl silicate, the above phenomenon is likely to occur, and the gas decomposition activity of the photocatalyst is reduced even when the firing temperature is higher than 300 ° C., more preferably higher than 400 ° C. Therefore, it is considered that high wear resistance can be easily realized.

In the present invention, the photocatalytic particle is a particle of a photocatalytic metal oxide having photoconductivity, and more specifically, an energy larger than the energy gap between the conduction band and the valence band of the crystal (that is, When irradiated with light (excitation light) of a short wavelength, it means a metal oxide particle capable of generating conduction electrons and holes due to excitation (photoexcitation) of electrons in the valence band. According to such photocatalyst particles, an extremely high degree of hydrophilicity is exhibited by decomposing an organic compound by a so-called redox reaction or by adsorbing water molecules in the atmosphere. According to a preferred embodiment of the present invention, the photocatalyst particles are preferably crystalline TiO ₂ such as anatase type titanium oxide, rutile type titanium oxide, brookite type titanium oxide, ZnO, SnO ₂ , SrTiO ₃ , WO ₃ , Bi _2. Particles selected from the group consisting of O ₃ , Fe ₂ O ₃ , CeO ₂ and V ₂ O ₅ .

  According to a preferred embodiment of the present invention, the photocatalyst particles preferably have an average particle size of 10 nm or more and less than 100 nm, more preferably 10 nm or more and 60 nm or less. The average particle diameter is calculated as a number average value obtained by measuring the length of any 100 particles that enter a 200,000-fold field of view with a scanning electron microscope.

  According to a preferred embodiment of the present invention, the photocatalyst particles preferably have an average crystallite diameter of 3 nm or more and less than 30 nm, more preferably 5 nm or more and 20 nm or less. The average particle diameter is calculated by the Scherrer equation from the integral width of the three strong lines of the X-ray profile obtained by the powder X-ray diffraction method.

  According to a preferred embodiment of the present invention, the photocatalytic coating composition comprises a metal and / or metal oxide, such as Cu, Ag, Ni, Fe, Zn, Pt, Au, Rh, V, Cr, Co, Mn, W , Nb, Sb, and platinum group metals and at least one metal or metal oxide selected from oxides thereof. Preferred examples of the metal and metal oxide include at least one metal particle selected from the group consisting of Cu, Ag, Pt, Co, Fe, Ni, Cu2O, Ag2O, Au, Zn, Cr, Mn, and Mo. is there. When these metals or metal oxides are added, the formed film can kill bacteria and sputum attached to the surface even in the dark. In addition, platinum group metals or oxides such as Pt, Pd, Ru, Rh, Ir, and Os enhance the redox activity of the photocatalyst, and as a result, improve the degradability of organic contaminants and the decomposability of harmful gases and odors. Addition is preferable because it can be made to occur.

As the alkyl silicate, for example, methyl silicate, ethyl silicate, propyl silicate, and butyl silicate can be suitably used.
The hydrolysis rate of the lower alkyl silicate condensate represented by the general formula Si _n O _n-1 (OR) _{2n + 2} (where n is 2-6 and R is a C1-4 alkyl group) is 50-1500%. The hydrolyzate hydrolyzed as described above can be particularly preferably used.

  The mass ratio of the photocatalyst particles in the photocatalyst coating liquid to the alkyl silicate is preferably 30 to 95% by mass, more preferably 50 to 90% by mass with respect to the total mass of the two components.

  According to a preferred embodiment of the invention, the solids concentration in the total composition is less than 5% by weight. The content is preferably 0.01% by weight to 5% by weight, and more preferably 0.1% by weight to 1% by weight. By being in the above range, it is possible to form a film excellent in photocatalytic gas decomposition activity by applying to a heat resistant substrate and baking at a high temperature.

According to a preferred embodiment of the present invention, the solvent contains water as a main component, and further contains 0 to 50% by weight of alcohol as an optional component.
In order to form a film excellent in photocatalytic gas decomposition activity by applying to a heat-resistant substrate and baking at a high temperature, the alcohol content is preferably as small as possible, and preferably 0 to 30% by weight.
However, when the alcohol is contained, the storage stability period of the coating liquid becomes longer. Therefore, the amount of alcohol is preferably determined within the above range in view of the balance.

  Furthermore, according to the preferable aspect of this invention, it is preferable that a photocatalyst coating liquid contains surfactant. By adding the surfactant, the photocatalytic coating composition can be uniformly applied to the surface of the substrate.

Furthermore, according to the preferable aspect of this invention, the inorganic oxide particle may be further added to the photocatalyst coating liquid.
Examples of inorganic oxide particles include single oxides such as silica, alumina, zirconia, ceria, yttria, boronia, magnesia, calcia, ferrite, amorphous titania, and hafnia, as well as barium titanate, calcium silicate, and aluminosilicate. Examples include complex oxides such as acid salts and calcium phosphate.

  The particle size of the inorganic oxide particle is not particularly limited, but when it is in the form of an aqueous colloid or organosol, the particle size of about 5 to 50 nm is the final photocatalytic hydrophilic coating gloss, turbidity, cloudiness, transparency, etc. From the viewpoint of

 Furthermore, according to a preferred embodiment of the present invention, the photocatalyst coating liquid contains, in addition to the above components, a polymerization curing catalyst, a hydrolysis catalyst, a leveling agent, an antibacterial metal, a pH adjuster, a fragrance, a storage stabilizer, an organic antifungal agent and the like. Can comprise.

  Here, as a polymerization catalyst, aluminum compounds such as aluminum chelate, aluminum acetylacetonate, aluminum perchlorate, aluminum chloride, aluminum isobutoxide, and aluminum isopropoxide; titanium compounds such as tetraisopropyl titanate and tetrabutoxy titanate Basic compounds such as sodium hydroxide, lithium hydroxide, potassium hydroxide, sodium methylate, sodium acetate, sodium formate, potassium acetate, potassium formate, potassium propionate, tetramethylammonium hydroxide; n-hexylamine , Tributylamine, diazabicycloundecene, ethylenediamine, hexanediamine, diethylenetriamine, tetraethylenebentamine, triethylenetetramine Ethanolamines, γ-aminopropyltrimethoxysilane, γ-aminopropylmethyldimethoxysilane, γ- (2-aminomethyl) -aminopropyltrimethoxysilane, γ- (2-aminomethyl) -aminopropylmethyldimethoxysilane Amine compounds; tin compounds such as tin acetylacetonate and dibutyltin octylate; metal compounds such as cobalt octylate, cobalt acetylacetonate and iron acetylacetonate; phosphoric acid, nitric acid, phthalic acid, p-toluene Examples include acidic compounds such as sulfonic acid and trichloroacetic acid.

  Hydrolysis catalysts include nitric acid, hydrochloric acid, acetic acid, sulfuric acid, sulfonic acid, maleic acid, propionic acid, adipic acid, fumaric acid, phthalic acid, valeric acid, lactic acid, butyric acid, citric acid, malic acid, and picrine. Acid, formic acid, carbonic acid, phenol and the like can be suitably used.

  Leveling agents include diacetone alcohol, ethylene glycol monomethyl ether, 4-hydroxy-4-methyl-2-pentanone, dipropylene glycol, tripropylene glycol, 1-ethoxy-2-propanol, 1-butoxy-2-propanol, Propylene glycol monomethyl ether, 1-propoxy-2-propanol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, tripropylene glycol monoethyl ether and the like can be suitably used.

  The photocatalyst layer preferably has a thickness of 0.1 μm to 5.0 μm, more preferably 0.2 μm to 3.0 μm, and most preferably 0.1 μm to 1.0 μm. is there. Within such a range, the photocatalyst particles having a lower content ratio than the inorganic oxide particles can be increased in the film thickness direction, so that the harmful gas decomposability is improved. Further, excellent characteristics can be obtained in the transparency of the photocatalyst layer.

Method for producing photocatalyst material A photocatalyst coating composition for high-temperature firing comprising photocatalyst particles, an alkyl silicate, and a solvent, wherein the solid content concentration in the whole composition is less than 5% by weight, and the solvent has a main component. It is water, and further contains an alcohol as an optional component in an amount of 0% by weight or more and less than 50% by weight. A coating excellent in photocatalytic gas decomposition activity can be formed by coating on a heat-resistant substrate and baking at a high temperature. A photocatalyst layer is formed by applying a photocatalyst coating composition for high-temperature firing to a surface of a heat-resistant substrate and firing at a temperature exceeding 300 ° C., more preferably exceeding 400 ° C. It is a manufacturing method.
By the method for producing the photocatalyst material, high wear resistance can be realized without reducing the gas decomposition activity of the photocatalyst.

However, the photocatalyst layer is preferably formed by curing the photocatalyst particles and the alkyl silicate at less than 600 ° C., more preferably less than 550 ° C.
This is because when the temperature is excessively high, the fluidity of silica produced by the curing reaction of the alkyl silicate is increased, and it is considered that the active point of the photocatalyst starts to be covered.

  In the method according to the present invention, the above-described photocatalytic coating composition is applied to a heat-resistant substrate. As a coating method, a spray coating method, a dip coating method, a flow coating method, a spin coating method, a roll coating method, a brush coating method, a sponge coating method, or the like can be suitably used. According to a preferred embodiment of the present invention, the photocatalytic coating composition is preferably applied by spraying.

  Furthermore, according to a preferred embodiment of the present invention, it is preferred that the substrate surface is preheated before application of the photocatalytic coating composition. Preheating is performed by heating the surface of the substrate to 40 ° C to 200 ° C. The photocatalytic coating composition applied to the heated substrate surface is advantageous because it spreads uniformly and provides a uniform coating.

  Furthermore, according to a preferred embodiment of the present invention, the substrate surface to which the photocatalytic coating composition is applied may be dried before rapid heating. A large amount of heat is applied to the base material by rapid heating described later. If excessive moisture or solvent components are present on the substrate, the smoothness of the substrate surface may be lost due to rapid evaporation of water or solvent components due to a rapid temperature change. Thus, it may be desirable to remove excess water or solvent components beforehand by drying. Drying may be performed by blowing or heating.

  Firing is carried out in a roller hearth kiln, an electric furnace, etc. at a temperature exceeding 300 ° C. or more, more preferably 400 ° C., more preferably exceeding 300 ° C. or more and less than 600 ° C., most preferably exceeding 300 ° C. or more and less than 550 ° C. You may make it harden | cure with a rapid heating apparatus described in WO00 / 006300.

  In the case of using a rapid heating apparatus, the coating surface of the coating solution on the heat-resistant substrate on which the curing reaction occurs has a maximum temperature exceeding 300 ° C. or more, more preferably 400 ° C., more preferably 300 ° C. or more and 600 ° C. Less than, most preferably more than 300 degreeC and less than 550 degreeC, and you may set atmospheric temperature to 400 degreeC-1200 degreeC, More preferably, about 500 degreeC-1000 degreeC.

  The “heat resistant substrate” to which the method according to the present invention can be applied is a substrate having a heat resistance exceeding 300 ° C., more preferably a heat resistance exceeding 400 ° C. Examples thereof include metals, inorganic materials, and composites thereof. Specifically, tiles, sanitary ware, tableware, wash basin, calcium silicate plates, semiconductors and other new ceramics, insulators, glass, mirrors, aluminum plates, steel plates, faucets, copper alloys, stainless steel plates Etc.

Example 1:
An anatase-type titanium oxide sol having an average crystallite size of 7 nm and an average particle size of 50 nm, an alkyl silicate, and a solvent are blended so that the mass ratio of the titanium oxide particles to the alkyl silicate is 65:35, and the solid content concentration is 0.6. A photocatalyst coating solution (A1) by weight was prepared. Here, a mixed solvent of water and alcohol was used as the solvent, and the amount ratio was 90:10. Further, the alkyl silicate is a lower alkyl silicate condensate represented by the general formula Si _n O _n-1 (OR) _{2n + 2} (where n is 2 to 6 and R is a C1 to 4 alkyl group), and further has a hydrolysis rate of 50. The hydrolyzate hydrolyzed to ˜1500% was used.
This photocatalyst coating liquid (A1) was apply | coated by the spray coating method on the glazed tile (T1) pre-heated to 80-150 degreeC previously (B1).
Next, the tile (B1) is baked for 1 hour in an electric furnace set at a maximum temperature of 450 ° C.,
A photocatalytic tile (C1) in which a photocatalytic layer having a film thickness of about 0.5 μm was formed on the tile surface was obtained.
About the obtained sample (C1), it confirmed about the NOx decomposition | disassembly function by photocatalyst, and abrasion resistance.
The NOx decomposition function by the photocatalyst was performed by a test method of JIS R1701-1 “Testing method for air purification performance of photocatalytic material—Part 1: Nitrogen oxide removal performance”. As a result, ΔNOx was 0.79 μmol, indicating a good result.
With regard to abrasion resistance, a silver nitrate color test was conducted to confirm that the photocatalytic function was maintained after sliding 1200 times with a nylon brush, that is, a 1% by weight aqueous silver nitrate solution was applied on the photocatalyst layer, and a BLB lamp Is irradiated for 20 minutes at an illuminance of ² mW / cm ² , the excess silver nitrate is washed with tap water and dried, and the color value (L *, a *, b *) of the photocatalyst layer surface and before application of the aqueous silver nitrate solution This was confirmed by a test for measuring a color difference change ΔE with the color value (L *, a *, b *) of the surface of the photocatalyst layer. As a result, ΔE = 10 and good results were shown.
In addition, after sliding 1200 times with a nylon brush, the NOx decomposition function by the photocatalyst was tested in accordance with the test method of JIS R1701-1 “Testing method for air purification performance of photocatalytic materials—Part 1: Removal performance of nitrogen oxides”. As a result, ΔNOx was 0.6 μmol, and good results were maintained.

Example 2:
Anatase-type titanium oxide sol having an average crystallite diameter of 7 nm and an average particle diameter of 50 nm, an alkyl silicate, and a solvent are blended so that the mass ratio of the titanium oxide particles to the alkyl silicate is 65:35, and the solid content concentration is 1.0. A photocatalyst coating solution (A1) by weight was prepared. Here, a mixed solvent of water and alcohol was used as the solvent, and the amount ratio thereof was 70:30. Further, the alkyl silicate is a lower alkyl silicate condensate represented by the general formula Si _n O _n-1 (OR) _{2n + 2} (where n is 2 to 6 and R is a C1 to 4 alkyl group), and further has a hydrolysis rate of 50. The hydrolyzate hydrolyzed to ˜1500% was used.
This photocatalyst coating liquid (A1) was apply | coated by the spray coating method on the glazed tile (T1) pre-heated to 80-150 degreeC previously (B1).
Next, the tile (B1) is baked for 1 hour in an electric furnace set at a maximum temperature of 450 ° C.,
A photocatalytic tile (C1) in which a photocatalytic layer having a film thickness of about 0.5 μm was formed on the tile surface was obtained.
About the obtained sample (C1), it confirmed about the NOx decomposition | disassembly function by photocatalyst, and abrasion resistance.
The NOx decomposition function by the photocatalyst was performed by a test method of JIS R1701-1 “Testing method for air purification performance of photocatalytic material—Part 1: Nitrogen oxide removal performance”. As a result, ΔNOx was 0.71 μmol, indicating a good result.
With regard to abrasion resistance, a silver nitrate color test was conducted to confirm that the photocatalytic function was maintained after sliding 1200 times with a nylon brush, that is, a 1% by weight aqueous silver nitrate solution was applied on the photocatalyst layer, and a BLB lamp Is irradiated for 20 minutes at an illuminance of ² mW / cm ² , the excess silver nitrate is washed with tap water and dried, and the color value (L *, a *, b *) of the photocatalyst layer surface and before application of the aqueous silver nitrate solution This was confirmed by a test for measuring a color difference change ΔE with the color value (L *, a *, b *) of the surface of the photocatalyst layer. As a result, ΔE = 10 and good results were shown.
In addition, after sliding 1200 times with a nylon brush, the NOx decomposition function by the photocatalyst was tested by the test method of JIS R1701-1 “Testing method for air purification performance of photocatalytic materials—Part 1: Nitrogen oxide removal performance”. As a result, ΔNOx was 0.59 μmol, and good results were maintained.

Example 3:
An anatase-type titanium oxide sol having an average crystallite size of 7 nm and an average particle size of 50 nm, an alkyl silicate, and a solvent are blended so that the mass ratio of the titanium oxide particles to the alkyl silicate is 65:35, and the solid content concentration is 0.6. A photocatalyst coating solution (A1) by weight was prepared. Here, a mixed solvent of water and alcohol was used as the solvent, and the amount ratio was 90:10. The alkyl silicate is a lower alkyl silicate condensate represented by the general formula Si _n O _n-1 (OR) _{2n + 2} (where n is 2 to 6 and R is a C1 to 4 alkyl group), and the hydrolysis rate is further 50. The hydrolyzate hydrolyzed to ˜1500% was used.
This photocatalyst coating liquid (A1) was apply | coated by the spray coating method on the glazed tile (T1) pre-heated to 80-150 degreeC previously (B1).
Next, the tile (B1) is heated in a furnace atmosphere temperature of 800 to 1000 ° C. (a thermocouple is installed at a position where no direct flame is applied in the vicinity of the burner), and heating is 1000 MJ / m ² · h per unit area. A heating element was used, and the distance from the heating element to the surface on which the coating liquid was applied was set in the range of 5 mm to 300 mm, and baked for 10 to 20 seconds. As a result, a photocatalyst (C2) in which a photocatalyst layer having a film thickness of about 0.5 μm was formed on the tile surface was produced. The surface temperature of the photocatalyst (C2) immediately after being carried out of the furnace in this sample was 400 to 450 ° C.
About the obtained sample (C2), it confirmed about the NOx decomposition | disassembly function by a photocatalyst, and abrasion resistance.
The NOx decomposition function by the photocatalyst was performed by a test method of JIS R1701-1 “Testing method for air purification performance of photocatalytic material—Part 1: Nitrogen oxide removal performance”. As a result, ΔNOx was 0.96 μmol, indicating a good result.
With regard to abrasion resistance, a silver nitrate color test was conducted to confirm that the photocatalytic function was maintained after sliding 1200 times with a nylon brush, that is, a 1% by weight aqueous silver nitrate solution was applied on the photocatalyst layer, and a BLB lamp Is irradiated for 20 minutes at an illuminance of ² mW / cm ² , the excess silver nitrate is washed with tap water and dried, and the color value (L *, a *, b *) of the photocatalyst layer surface and before application of the aqueous silver nitrate solution This was confirmed by a test for measuring a color difference change ΔE with the color value (L *, a *, b *) of the surface of the photocatalyst layer. As a result, ΔE = 14 and a good result were shown.
In addition, after sliding 1200 times with a nylon brush, the NOx decomposition function by the photocatalyst was tested in accordance with the test method of JIS R1701-1 “Testing method for air purification performance of photocatalytic materials—Part 1: Removal performance of nitrogen oxides”. As a result, ΔNOx was 0.7 μmol, and good results were maintained.

Example 4:
Anatase-type titanium oxide sol having an average crystallite diameter of 7 nm and an average particle diameter of 50 nm, an alkyl silicate, and a solvent are blended so that the mass ratio of the titanium oxide particles to the alkyl silicate is 65:35, and the solid content concentration is 1.0. A photocatalyst coating solution (A1) by weight was prepared. Here, a mixed solvent of water and alcohol was used as the solvent, and the amount ratio thereof was set to 60:40. Also.
Further, the alkyl silicate is a lower alkyl silicate condensate represented by the general formula Si _n O _n-1 (OR) _{2n + 2} (where n is 2 to 6 and R is a C1 to 4 alkyl group), and further has a hydrolysis rate of 50. The hydrolyzate hydrolyzed to ˜1500% was used.
This photocatalyst coating liquid (A1) was apply | coated by the spray coating method on the glazed tile (T1) pre-heated to 80-150 degreeC previously (B1).
Next, the tile (B1) is heated at an atmosphere temperature in the furnace of 800 to 1100 ° C. (the thermocouple is installed in a position near the burner where no direct flame hits), and the heating value is 1000 MJ / m ² · h per unit area. A heating element was used, and the distance from the heating element to the surface on which the coating liquid was applied was set in the range of 5 mm to 300 mm, and baked for 10 to 20 seconds. As a result, a photocatalyst (C2) in which a photocatalyst layer having a film thickness of about 0.5 μm was formed on the tile surface was produced. The surface temperature of the photocatalyst (C2) immediately after being carried out of the furnace in this sample was 400 to 450 ° C.
About the obtained sample (C2), it confirmed about the NOx decomposition | disassembly function by a photocatalyst, and abrasion resistance.
The NOx decomposition function by the photocatalyst was performed by a test method of JIS R1701-1 “Testing method for air purification performance of photocatalytic material—Part 1: Nitrogen oxide removal performance”. As a result, ΔNOx was 0.80 μmol, indicating a good result.
With regard to abrasion resistance, a silver nitrate color test was conducted to confirm that the photocatalytic function was maintained after sliding 1200 times with a nylon brush, that is, a 1% by weight aqueous silver nitrate solution was applied on the photocatalyst layer, and a BLB lamp Is irradiated for 20 minutes at an illuminance of ² mW / cm ² , the excess silver nitrate is washed with tap water and dried, and the color value (L *, a *, b *) of the photocatalyst layer surface and before application of the aqueous silver nitrate solution This was confirmed by a test for measuring a color difference change ΔE with the color value (L *, a *, b *) of the surface of the photocatalyst layer. As a result, ΔE = 12, a good result was shown.
In addition, after sliding 1200 times with a nylon brush, the NOx decomposition function by the photocatalyst was tested by the test method of JIS R1701-1 “Testing method for air purification performance of photocatalytic materials—Part 1: Nitrogen oxide removal performance”. As a result, ΔNOx was 0.67 μmol, and good results were maintained.

Claims (3)

A photocatalyst coating composition for high-temperature firing comprising photocatalyst particles, an alkyl silicate, and a solvent,
The solids concentration in the total composition is less than 5% by weight;
The solvent is mainly composed of water,
Furthermore, it contains 0 wt% or more and less than 50 wt% of alcohol as an optional component,
A photocatalyst coating composition for high-temperature firing, which is capable of forming a film excellent in photocatalytic gas decomposition activity by applying to a heat-resistant substrate and firing at a high temperature. The alkyl silicate is a lower alkyl silicate condensate represented by the general formula Si _n O _n-1 (OR) _{2n + 2} (where n is 2-6 and R is a C1-4 alkyl group), and the hydrolysis rate is further 50 The photocatalyst coating composition for high-temperature firing according to claim 1, which is a hydrolyzate hydrolyzed to ˜1500%. The photocatalyst coating composition for high temperature firing according to any one of claims 1 and 2,
A method for producing a photocatalyst material, characterized in that a photocatalyst layer is formed by coating on the surface of a substrate and firing at a temperature exceeding 300 ° C.