JPH11290696A - Photocatalyst base material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a base material which can be easily manufactured and shows a high photocatalytic action by forming a coating film containing titanium oxide obtained by hydrolyzing a titanium compound and/or a precursor thereof. SOLUTION: Titanium oxide obtained by hydrolyzing a base material such as a resin, e.g. and acrylic resin or a polycarbonate resin, woods, a metal or the like and a titanium compound such as a titanium alkoxide or a titanium chloride or the precursor of the titanium oxide, are used. A hydrolyzed solution of a titanium alkoxide obtained by hydrolyzing it in a mixed solvent such as of water and alcohol is applied to the surface of the base material, and then is dried at a specified temperature to form a coating film. This coating film is treated in the presence of water to convert the titanium oxide which is amorphous in the coating film to anatase-type crystalline titanium oxide having an outstanding photocatalytic function. The treatment in the presence of water is to perform a water vapor treatment by holding the photocatalytic base material containing the titanium oxide or the precursor thereof in an atmosphere of a water vapor partial pressure adjusted to a specified atmospheric pressure. Thus, it is possible to easily manufacture the base material of high photocatalytic activity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to resins, woods,
The present invention relates to a photocatalyst substrate having a photocatalyst on the surface of metals, ceramics, and their painted products.

[0002]

2. Description of the Related Art A photocatalyst is a substance that exhibits a photocatalytic action when irradiated with light having a wavelength having an energy greater than its band gap. Examples of such a substance include titanium oxide, zinc oxide, tungsten oxide, and iron oxide. And metal compound semiconductor powders such as strontium titanate, cadmium sulfide, and cadmium selenide. When these substances are irradiated with light having a wavelength having energy equal to or greater than the band gap, photoexcitation generates electrons in the conduction band and holes in the valence band. These electrons generated by light irradiation
Among the hole pairs, the high reducing power of the electrons and the high oxidizing power of the holes are used for decomposing organic substances and decomposing water. In order to use these properties for environmental purification such as decomposition and removal of harmful substances and odorous substances, it is necessary to immobilize the photocatalyst powder on the surface of the substrate, and various studies have been made. Among the above photocatalysts, titanium oxide has been studied most widely because it is excellent in transparency and durability and is harmless. Usually, titanium oxide containing an anatase crystal is used as the titanium oxide used for the photocatalytic reaction.

[0003] Various studies have been made to immobilize titanium oxide containing anatase-type crystals on the surface of a substrate. For example, Japanese Patent Application Laid-Open No. Hei 7-100378 discloses that after coating a titania sol on a substrate such as glass or ceramic,
A method has been proposed in which a temperature is gradually raised from room temperature to a final temperature of 600 to 700 ° C., followed by firing to produce a titanium oxide thin film photocatalyst of anatase type crystal. JP-A-7-171
No. 408 proposes a photocatalyst in which photocatalyst particles such as titanium oxide or titanium oxide subjected to hydrothermal treatment at 100 ° C. or higher are adhered to a substrate via a hardly decomposable binder. JP-A-8-164334 proposes a titanium oxide film-forming composition comprising a hydrolyzate of a titanium oxide and a silicon compound and a solvent. JP-A-8-299
No. 789 discloses an anatase-type titanium oxide photocatalyst obtained by forming a layer of a solution containing a titanium alkoxide in an anhydrous organic solvent on a substrate surface, forming a hydrous titanium oxide layer by hydrolysis, and then calcining the layer. Manufacturing methods have been proposed. Japanese Patent Application Laid-Open No. 9-920 proposes a highly light-transmissive titanium oxide photocatalyst comprising a titanium oxide film in which an organic titanium compound is sprayed on a heated base material and thermally decomposed to align the crystal orientation. . Also, Japanese Patent Application Laid-Open No. 9-2484
No. 67 proposes a photocatalyst in which a composition containing a titanium oxide sol and a stabilized titanium alkoxide is applied to the surface of a heat-resistant substrate.

On the other hand, as for the photocatalytic titanium oxide treated with water, for example, Japanese Patent Application Laid-Open No. 6-293519 discloses that titanium oxide fine particles are subjected to hydrothermal treatment at a temperature of 100 ° C. or more to crystally grow the fine particles. There has been proposed a method for producing a titanium oxide film in which titanium particles are applied to a support and fired to fix the particles on the support.

[0005]

However, Japanese Patent Application Laid-Open Nos. Hei 7-100378, Hei 8-299789, Hei 9-920, and Hei 9-2484
Both the photocatalyst and the photocatalyst proposed in Japanese Patent Publication No. 67 are fired at a temperature of several hundred degrees to obtain anatase type titanium oxide. Therefore, when baking is performed after being applied to the base material, the base material cannot be applied to a resin such as an acrylic resin or a polycarbonate resin, and the efficiency is not good because a high temperature is required. Also, Japanese Patent Application Laid-Open No. 7-171
The photocatalyst proposed in JP-A-408 and JP-A-8-164334 is a method in which crystallized titanium oxide having photocatalytic performance is used in advance, and the photocatalyst particles are used for immobilizing the photocatalyst particles on a substrate. Must be dispersed in a solvent or the like, and the method is complicated.

The hydrothermal treatment proposed in Japanese Patent Application Laid-Open No. 6-293519 is a method in which a titanium oxide fine particle suspension is subjected to hydrothermal treatment at a temperature of 100 ° C. or more to grow crystals. In order to do so, it is necessary to apply the fine particles on a support, bake and fix them, which is very complicated and cannot be applied to a resin substrate or the like depending on the baking temperature.

In view of such circumstances, the present inventors have made intensive studies on a photocatalytic substrate which can be easily produced and has a high photocatalytic action. As a result, the titanium compound is hydrolyzed to contain titanium oxide and / or a precursor thereof. In the case of applying a hydrolysis solution of titanium alkoxide on a photocatalyst substrate having a film to be formed, particularly a substrate, drying and forming a film containing titanium oxide and / or a precursor thereof, and then performing a steam treatment. Have found that a photocatalytic substrate having high photocatalytic activity can be easily obtained without firing the film at a high temperature, and have completed the present invention.

[0008]

That is, the present invention provides a photocatalyst substrate obtained by forming a film containing titanium oxide and / or a precursor thereof by hydrolyzing a titanium compound on the substrate. is there. The present invention further provides a titanium oxide formed by hydrolyzing a titanium compound formed on a substrate and / or
Another object of the present invention is to provide a photocatalyst substrate obtained by treating a film containing the precursor with water. Another object of the present invention is to provide a method for producing a photocatalyst substrate, which is obtained by applying a hydrolysis solution of a titanium compound onto a substrate and drying to form a film. In addition, the present invention provides a method for producing a photocatalyst substrate, which comprises applying a hydrolysis solution of a titanium compound on a substrate, forming a film by drying, and treating the film in the presence of water. .

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The substrate in the present invention is not particularly limited, and may be a resin, wood, metal, or the like.
And ceramics. Resins such as acrylic resin and polycarbonate resin are preferably used from the viewpoint of easiness of processing, transparency and the like.

As the titanium oxide or its precursor in the present invention, those obtained by hydrolyzing a titanium compound (hereinafter referred to as titanium alkoxide) such as titanium alkoxide, titanium chloride, titanium sulfate and titanium nitrate can be mentioned. In the present invention, titanium oxide or a precursor thereof obtained by hydrolyzing a titanium alkoxide is preferably used. As titanium alkoxide,
Titanium tetramethoxide, titanium tetraethoxide, titanium tetraisopropoxide, titanium tetrabutoxide, titanium diethoxydiisopropoxide, titanium dimethoxydibutoxide, titanium tetrakis (2-ethylhexyl oxide), titanium tetrastearyl oxide, and the like. .

The hydrolysis of titanium alkoxide and the like is carried out by adding water to one or more of the above compounds. The hydrolysis may be performed under acidic or basic conditions, and depending on the conditions, anatase-crystallized titanium oxide or its precursor is obtained. For the purpose of increasing the strength of the obtained film, a mixture with another metal alkoxide may be hydrolyzed at the same time, if necessary. Furthermore, silica sol and other metal oxides are used to improve the strength of the film, and metals and metal compounds such as vanadium, copper, palladium, silver, platinum and gold are used to improve the photocatalytic function. Adsorbent,
Repels adsorbents such as zeolite-based adsorbents, molecular sieves, metal oxide-based adsorbents, chelating resins,
For the purpose of preventing pinholes, various additives such as a surfactant may be mixed and contained in the film. These may be added at the time of hydrolysis or may be added after hydrolysis.

The hydrolysis of titanium alkoxide and the like is performed, for example, in a mixed solvent such as water and alcohol. Alternatively, hydrolysis may be performed by dissolving titanium alkoxide or the like in an organic solvent capable of dissolving, and then dropwise adding water under heating and reflux. The hydrolysis method may be any method and is not particularly limited.

As a solvent for dissolving titanium alkoxide and the like, a solvent which is easily mixed with water is usually preferably used, for example, alcohols such as methanol, ethanol, isopropanol and n-butanol, ethers such as tetrahydrofuran and dioxane, and acetone. And ketones such as methyl ethyl ketone. These solvents may be used alone or in combination of two or more. The concentration of titanium alkoxide and the like in the solution is not particularly limited, but is about 0.1 to 85% by weight.

The mixing ratio of water and titanium alkoxide is not particularly limited as long as it is within a range in which hydrolysis occurs. Usually, the molar ratio of water / titanium alkoxide is 0.5 to 3 or so. When the amount of water to be added is large, for example, when an alcohol solvent is used, the generated polymer may be precipitated. In this case, the precipitated polymer can be dissolved in a highly soluble solvent such as tetrahydrofuran.

For the purpose of increasing the solubility of the hydrolyzate having a high degree of polymerization in a solvent, an organic compound capable of forming a chelate compound with titanium ions during hydrolysis may be added. Examples of the organic compound include acetylacetone, benzoylacetone, acetoacetic acid, propionylacetic acid and their lower alkyl esters such as methyl, ethyl and propyl, glycolic acid, lactic acid and their methyl, ethyl,
Examples thereof include lower alkyl esters such as propyl, alcohol amines such as diethanolamine and triethanolamine, and these may be used alone or as a mixture of two or more.

The thus obtained hydrolyzed solution of titanium alkoxide or the like can be used as it is as a solution for forming a coating film, but it may be concentrated or may be further diluted by adding a solvent. I don't care. Examples of the solvent include alcohols, ketones, esters, cellosolves, ethers, halides, carboxylic acids, and aromatic compounds. The solvent is used singly or as a mixture of two or more types, mainly in consideration of the solubility of the hydrolyzate, the type of base material used, the evaporation rate, and the like. The amount of the solvent to be used is appropriately determined depending on the required thickness of the coating film, coating method and the like.

The thus obtained hydrolysis solution such as titanium alkoxide is applied on a substrate and dried to form a film. The hydrolysis solution is applied to the substrate by a commonly used method such as spray coating, dip coating, roll coating and the like. Drying is performed at room temperature or at an elevated temperature to remove the solvent. Drying temperature is about 15
It may be carried out at 0 ° C. or lower, usually at about 100 ° C. or lower.
The thickness of the coating film to be formed is not particularly limited also changes depending on the viscosity and solid content concentration of the hydrolysis solution,
The thickness is preferably about 0.01 to 100 μm. If the thickness is too small, the photocatalyst performance such as antifouling performance and deodorization performance of the finally obtained photocatalyst substrate becomes insufficient. If the thickness is too large, there is a fear of cracking of the coating film, which is not preferable. The coating film thus formed is usually amorphous, but may be crystallized by anatase depending on hydrolysis conditions, and when crystallized, it can be used as it is as a photocatalytic substrate.

Usually, after the formation of the film, the treatment is performed in the presence of water. By performing the treatment in the presence of water, the titanium oxide in the amorphous film is converted into effective titanium oxide of an anatase type crystal by a photocatalytic function, and the photocatalyst has an excellent photocatalytic function. Also, the treatment in the presence of water,
Crystallization may be further promoted under acidic or basic conditions. The treatment in the presence of water is preferably a steam treatment, and the steam treatment is performed by holding the photocatalyst substrate containing titanium oxide or its precursor in an atmosphere having a partial pressure of steam of 0.1 atm or more. If the partial pressure of steam is less than 0.1 atm, crystallization by steam treatment does not proceed sufficiently. The temperature condition of the water treatment is selected in consideration of the heat resistance of the substrate to be used. For example, when a glass substrate is used as the substrate, water treatment may be performed at a high temperature, but when the substrate is a resin substrate, it depends on the heat resistance of the substrate.
Water treatment conditions at temperatures below 0 ° C. are selected. The holding time is determined by the processing temperature, the state of film formation, etc.
Usually, it is several hours to several tens of hours.

Usually, the water treatment (hydrothermal treatment) is carried out under a high temperature condition of 100 ° C. or more. In the present invention, the water treatment may be carried out at a partial pressure of steam of 0.1 atm or more.
It can be performed at a temperature of 00 ° C. or less, and is suitable for a resin base material.

The thus obtained photocatalyst substrate of the present invention decomposes dirt substances adhered to the surface of the photocatalyst substrate when irradiated with light having a wavelength greater than the band gap of titanium oxide as a photocatalyst. It is also possible to remove contaminants such as odorous substances and nitrogen oxides near the photocatalyst by oxidation or decomposition. As the light source, for example, sunlight, a fluorescent lamp, a black light, a mercury lamp, or the like can be used.

The photocatalyst substrate of the present invention includes a light cover, a soundproof plate, a vending machine front panel, a signboard, a sanitary substrate such as a bathtub and a wash basin, a water tank, various signs and signs, window glass,
It can be applied to various uses such as windshields, various ornaments, display cases, building materials, building interior and exterior, film materials, solar cell covers, lighting dome, sunroof, and the like.

[0022]

According to the present invention, a photocatalyst substrate having high catalytic activity can be easily obtained. The photocatalyst substrate of the present invention is particularly suitable for a photocatalyst substrate using a resin substrate, and is applicable to various uses.

[0023]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the present invention. Example 1 (1) Preparation of hydrolysis solution Titanium isopropoxide (Nippon Soda Co., Ltd., A-1)
6000 g and 1099 g of ethyl acetoacetate (manufactured by Daicel Chemical Industries, Ltd.) are dissolved in 1473 g of isopropyl alcohol (reagent grade, Wako Pure Chemical Industries, Ltd.), refluxed under a nitrogen atmosphere for 1 hour, and the alcohol solution of the raw material is dissolved. Was prepared. At this time, the molar ratio of ethyl acetoacetate to titanium isopropoxide is 0.40.
720 g of pure water was mixed with 6480 g of isopropyl alcohol to prepare an alcohol solution having a water concentration of 10% by weight.
This water content is 1.9 per mole of titanium alkoxide.
It is a molar amount. The alcohol solution as a raw material was heated in a nitrogen atmosphere and refluxed under boiling. At the same time, an alcohol solution having a water concentration of 10% by weight was added with stirring while distilling off the alcohol. The distillation rate of the alcohol and the addition rate were adjusted to be substantially equal, and the addition time was adjusted to be 135 minutes. When the entire amount of the alcohol solution having a water concentration of 10% by weight is added, a complete slurry state is obtained,
After refluxing the slurry for one hour, the alcohol was distilled off by heating as it was, and the alcohol was partially concentrated to obtain 6112 g of a hydrolyzed slurry. The amount of water contained in the alcohol distilled out of the system by the addition and partial concentration of water was 0.13 mol per 1 mol of titanium alkoxide. Therefore, the difference between the amount of water added and the amount of water discharged out of the system together with alcohol or the like (1.9-0.
13) is 1.7 moles to 1 mole of titanium alkoxide.
The amount was 7 mol. To this hydrolyzed slurry was added 7050 g of tetrahydrofuran (Wako Pure Chemicals, special grade of reagent),
Reflux for 1 hour to dissolve, and in terms of titanium oxide,
A 12.8% by weight hydrolysis solution was prepared.

(2) Preparation of Photocatalyst Substrate The hydrolysis solution was applied to a 3 mm thick, 100 cm ² acrylic plate using a bar coater # 3. The applied film thickness was about 0.4 μm. After application, after drying at 80 ° C for about 1 day, water vapor partial pressure 0.542 atm (85 ° C, 95% RH)
For 8 hours to obtain a photocatalyst substrate.

(3) Evaluation of Photocatalyst Substrate This photocatalyst substrate was placed in a glass container having a diameter of about 15 cm and a height of about 3 cm, and NOx gas adjusted to a concentration of 1 ppm (prepared by mixing 90 ppm NO and clean air. ) Was continuously supplied into the vessel at a flow rate of about 1.5 liter / min, and the concentration of NOx (NO + NO ₂ ) in the gas coming out of the vessel was evaluated. For evaluation, after mounting the sample, NOx gas was allowed to flow for 30 minutes without irradiating light, then light was applied and NOx gas was allowed to flow for 1 hour, and after stopping light irradiation, NOx gas was allowed to flow for 10 minutes. And the degree of NOx reduction during irradiation was examined. A black light was used as the light source, and the ultraviolet intensity on the sample surface was about 0.4 mW / cm.
Irradiation was performed so as to be ² . The NOx removal rate at the time of irradiation with respect to the time of non-irradiation was 28% on average.

Example 2 The hydrolyzed solution prepared in Example 1 was 3 mm thick, 100 c
It was applied to an m ² acrylic plate using a bar coater # 3. The applied film thickness was about 0.4 μm. After application, 80
After drying for about 1 day at a temperature of
(95% RH) for 15 hours to obtain a photocatalyst substrate. The photocatalyst substrate was placed in a glass container having a diameter of about 15 cm and a height of about 3 cm, and evaluated in the same manner as in Example 1. The NOx removal rate at the time of irradiation with respect to the time of non-irradiation was 43% on average.

Claims (11)

[Claims] 1. A photocatalyst substrate comprising a substrate and a film containing titanium oxide and / or a precursor thereof obtained by hydrolyzing a titanium compound. 2. A photocatalytic substrate obtained by subjecting a film containing titanium oxide and / or a precursor thereof obtained by hydrolyzing a titanium compound formed on the substrate to a water treatment. 3. The photocatalyst substrate according to claim 1, wherein the film is made of anatase-type titanium oxide formed by heat treatment at a temperature of 150 ° C. or less. 4. The photocatalyst substrate according to claim 1, wherein the substrate is made of a resin. 5. The photocatalyst substrate according to claim 1, wherein the titanium compound is a titanium alkoxide. 6. A method for producing a photocatalyst substrate, comprising applying a hydrolysis solution of a titanium compound onto a substrate and drying to form a film. 7. A method for producing a photocatalytic substrate, comprising applying a hydrolysis solution of a titanium compound onto a substrate, forming a film by drying, and treating the film in the presence of water. 8. The method for producing a photocatalyst substrate according to claim 7, wherein the treatment in the presence of water is a steam treatment. 9. A steam partial pressure of 0.1 in steam treatment.
9. The method for producing a photocatalyst substrate according to claim 7, wherein the pressure is equal to or higher than the atmospheric pressure. 10. The method for producing a photocatalyst substrate according to claim 6, wherein the drying temperature is 150 ° C. or lower. 11. The method according to claim 6, wherein the titanium compound is a titanium alkoxide.