JP6105998B2 - Method for producing photocatalyst composition and method for producing photocatalyst - Google Patents

Description

  The present invention relates to a method for producing a photocatalyst composition containing a photocatalyst that is photoexcited by irradiation with light having a predetermined wavelength, and a method for producing a photocatalyst.

  A photocatalyst such as titania (titanium oxide) is photoexcited when irradiated with light of a predetermined wavelength, and thereby, nitrogen oxide (NOx), sulfur oxide (SOx), and volatile organic compounds (Volatile Organic Compounds), It is known to have a decomposition function for decomposing harmful substances such as abbreviation VOC) and a superhydrophilic function for highly hydrophilizing the surface of a substrate (see Patent Documents 1 and 2).

  Such a photocatalyst is formed and formed in a layered manner on the surface of a substrate as a substance that imparts a decomposition function and a superhydrophilization function to a member constituting a building, a vehicle, an article, or the like.

  When a photocatalyst body in which a photocatalyst layer containing a photocatalyst is formed on the surface of a substrate is used as an outdoor member such as a building exterior material, the photocatalyst is photoexcited by irradiating the photocatalyst with sunlight. Self-purification (self-cleaning) function that exhibits a decomposing function for decomposing toxic substances such as NOx and SOx, and a super-hydrophilic function, so that dirt attached to the surface of the photocatalyst is washed away by rain Is demonstrated.

  In addition, when the photocatalyst is used as an indoor member such as a glass member provided indoors in a building, the photocatalyst is photoexcited by irradiating the photocatalyst with light from an artificial light source such as a fluorescent lamp, and VOC or the like. The function of decomposing toxic substances is demonstrated, and the function of superhydrophilicity is also demonstrated. Even if water droplets dewed from moisture or steam in the air adhere to the surface of the photocatalyst, the water droplets are quickly removed. A uniform water film is provided, and the function of preventing the formation of discrete and annoying water droplets is exhibited.

Japanese Patent No. 3786366 JP 2010-280545 A

  However, the prior art photocatalyst has a problem that it takes a long time after the light having a predetermined wavelength is irradiated until the superhydrophilic function is exhibited.

  An object of the present invention is to produce a photocatalyst composition capable of producing a photocatalyst that exhibits a superhydrophilization function within a short time when irradiated with light of a predetermined wavelength, and the production method It is providing the manufacturing method of the photocatalyst body using the photocatalyst composition obtained by this.

In the present invention, titanium alkoxide is added to a liquid carboxylic acid with stirring, titanium alkoxide is hydrolyzed to produce titanium hydroxide, and the titanium hydroxide is polycondensed to produce an amorphous having a titanoxane bond. An amorphous titania dispersion producing step of obtaining an amorphous titania dispersion in which the amorphous titania is dispersed in a carboxylic acid by producing the titania of
The amorphous titania dispersion and a silica sol in which amorphous silica is dispersed in carboxylic acid are added to a solvent with stirring, and a mixture of amorphous titania and amorphous silica is added to the solvent. A mixture dispersion producing step for obtaining a mixture dispersion dispersed in
The mixture dispersion is stirred at a temperature of 70 to 80 ° C. to change the amorphous titania in the mixture dispersion into titania having an anatase type crystal structure. A photocatalyst composition producing step comprising producing a photocatalyst composition in which the photocatalyst is dispersed in a solvent by producing a composite photocatalyst loaded with fine silica. Is the method.

Further, in the method for producing a photocatalyst composition of the present invention, in the amorphous titania dispersion production step, an amorphous titania dispersion containing irregularly shaped titania particles is produced,
In the mixture dispersion generating step, a silica sol containing irregularly shaped silica particles is used as the silica sol.

In addition, the present invention adds a titanium alkoxide and an acid catalyst to an alcohol with stirring, hydrolyzes the titanium alkoxide to produce titanium hydroxide, and polycondenses the titanium hydroxide to produce an amorphous having a titanoxane bond. Producing an amorphous titania dispersion in which the amorphous titania is dispersed in alcohol by producing a quality titania,
The amorphous titania dispersion and a silica sol in which amorphous silica is dispersed in alcohol are added to an alkaline aqueous solution with stirring, and the amorphous titania supports the amorphous silica. A precipitation step of precipitating the photocatalyst in an aqueous alkaline solution by producing a photocatalyst of a type;
A separation step of separating the photocatalyst from the alkaline aqueous solution in which the photocatalyst is precipitated;
A photocatalyst composition producing step, wherein the photocatalyst separated in the separation step is added to a solvent under stirring to obtain a photocatalyst composition in which the photocatalyst is dispersed in the solvent. Is the method.

Further, in the method for producing a photocatalyst composition of the present invention, in the amorphous titania dispersion production step, an amorphous titania dispersion containing irregularly shaped titania particles is produced,
In the precipitation step, a silica sol containing irregularly shaped silica particles is used as the silica sol.

The present invention also includes an application step of applying the photocatalyst composition obtained by the above production method to the surface of the substrate;
A method for producing a photocatalyst, comprising: calcining a substrate coated with the photocatalyst composition to form a photocatalyst layer on the surface of the substrate to obtain a photocatalyst.

  According to the present invention, the method for producing a photocatalyst composition includes an amorphous titania dispersion production step, a mixture dispersion production step, and a photocatalyst composition production step. In the amorphous titania dispersion production step, titanium alkoxide is added to the liquid carboxylic acid with stirring to hydrolyze the titanium alkoxide to produce titanium hydroxide and to polycondense the titanium hydroxide. Amorphous titania having a titanoxane bond is produced. In this way, an amorphous titania dispersion in which amorphous titania is dispersed in carboxylic acid is obtained. In the mixture dispersion forming step, the amorphous titania dispersion and a silica sol in which amorphous silica is dispersed in a carboxylic acid are added to a solvent under stirring to form amorphous titania and amorphous To produce a silica mixture. In this way, a mixture dispersion in which the mixture is dispersed in the solvent is obtained.

  In the photocatalyst composition generation step, the mixture dispersion is stirred at a temperature of 70 to 80 ° C., and amorphous titania in the mixture dispersion is transformed into titania having an anatase type crystal structure. A composite photocatalyst in which amorphous silica is supported on crystalline titania is produced. Thus, the photocatalyst composition in which the photocatalyst is dispersed in the solvent is obtained.

  A conventional photocatalyst (with a photocatalyst layer containing a photocatalyst formed on the surface of a base material), for example, is applied to the surface of the base material with a coating solution in which tetraethoxysilane and anatase-type titania sol are mixed in a solvent. Then, by maintaining the temperature at about 150 ° C., the tetraethoxysilane is subjected to hydrolysis and dehydration condensation polymerization, and a photocatalytic layer in which anatase-type titania particles are bound with a silica binder is formed on the surface of the substrate. Manufactured. In such a conventional photocatalyst, a photocatalyst layer in which anatase-type titania particles having a photocatalytic function are bound with a silica binder is formed on the surface of a substrate. Such a photocatalyst requires a long time of about 60 hours after the light having a predetermined wavelength is irradiated until the superhydrophilic function is exhibited. The reason for this is considered to be that the ultraviolet light (light) transmission is inhibited by the binder component of silica and the light does not uniformly reach the surface of the titania particles.

  In contrast, in the method for producing a photocatalyst composition of the present invention, an amorphous titania dispersion containing amorphous titania that has been subjected to hydrolysis and polycondensation in the amorphous titania dispersion production step is produced. In the photocatalyst composition generation step, amorphous titania is transformed into titania having an anatase type crystal structure to generate a composite type photocatalyst in which amorphous silica is supported on crystalline titania, The photocatalyst composition in which the produced photocatalyst is dispersed in a solvent is obtained. When a photocatalyst body is produced using such a photocatalyst composition obtained by the method for producing a photocatalyst composition of the present invention, silica constituting the photocatalyst does not function as a binder and inhibits ultraviolet (light) transmission. It is prevented. As a result, a photocatalyst having a high photocatalytic activity excellent in ultraviolet (light) transmittance is obtained. Therefore, the method for producing a photocatalyst composition of the present invention provides a photocatalyst composition capable of producing a photocatalyst that exhibits a superhydrophilic function in a short time when irradiated with light of a predetermined wavelength. Can be obtained.

  According to the present invention, in the amorphous titania dispersion generation step, an amorphous titania dispersion containing irregularly shaped titania particles is generated. Further, in the mixture dispersion generation step, a silica sol containing irregularly shaped silica particles is used as the silica sol. Thus, a photocatalyst composition including a composite photocatalyst in which amorphous silica is supported on amorphous titania can be produced. Since the irregularly shaped particles have a lower degree of formation of aggregated particles than spherical particles, they can be suppressed from acting as one large aggregated particle, and light scattering can be suppressed. Therefore, when the titania and silica constituting the photocatalyst are particles having an irregular shape, white turbidity due to light scattering of the photocatalyst can be prevented, and the photocatalyst can be made substantially transparent. Thereby, since the amount of light incident on the photocatalyst can be increased, a photocatalyst composition capable of producing a photocatalyst body that exhibits a superhydrophilic function within a short time is obtained.

  In addition, since the irregularly shaped particles have a larger specific surface area than the spherical particles, when the photocatalyst is produced using the photocatalyst composition, it is possible to improve the adhesion wear property of the photocatalyst to the substrate surface. Therefore, when the titania and the silica constituting the photocatalyst are particles having an indefinite shape, the photocatalyst composition is capable of suppressing the photocatalyst from being peeled off from the substrate surface.

  According to the invention, the method for producing a photocatalyst composition includes an amorphous titania dispersion production step, a precipitation step, a separation step, and a photocatalyst composition production step. In the amorphous titania dispersion production step, titanium alkoxide and an acid catalyst are added to alcohol under stirring to hydrolyze the titanium alkoxide to produce titanium hydroxide, and to polycondense the titanium hydroxide. Amorphous titania having a titanoxane bond is produced. In this way, an amorphous titania dispersion in which amorphous titania is dispersed in alcohol is obtained. In the precipitation step, the amorphous titania dispersion and a silica sol in which amorphous silica is dispersed in alcohol are added to an alkaline aqueous solution with stirring, and the amorphous titania is transformed into amorphous silica. A supported composite photocatalyst is produced, and the photocatalyst is precipitated in an alkaline aqueous solution. In the separation step, the photocatalyst is separated from the alkaline aqueous solution in which the photocatalyst is precipitated. In the photocatalyst composition generation step, the photocatalyst separated in the separation step is added to the solvent under stirring to obtain a photocatalyst composition in which the photocatalyst is dispersed in the solvent.

  In the method for producing a photocatalyst composition of the present invention, an amorphous titania dispersion containing amorphous titania that has been hydrolyzed and polycondensed is produced in the amorphous titania dispersion production step, and the photocatalyst is further produced. In the composition generation step, the photocatalyst composition is produced by dispersing the photocatalyst once separated as a solid content in the separation step in the solvent, so that the photocatalyst composition in which the highly purified photocatalyst is dispersed in the solvent is obtained. be able to. When a photocatalyst is produced using such a photocatalyst composition obtained by the method for producing a photocatalyst composition of the present invention, a photocatalyst having a high photocatalytic activity excellent in ultraviolet (light) transmittance is obtained. Therefore, the method for producing a photocatalyst composition of the present invention provides a photocatalyst composition capable of producing a photocatalyst that exhibits a superhydrophilic function in a short time when irradiated with light of a predetermined wavelength. Can be obtained.

  According to the present invention, in the amorphous titania dispersion generation step, an amorphous titania dispersion containing irregularly shaped titania particles is generated. In the precipitation step, a silica sol containing silica particles having an irregular shape is used as the silica sol. Thus, a photocatalyst composition including a composite photocatalyst in which amorphous silica is supported on amorphous titania can be produced. Since the titania and silica constituting the photocatalyst contained in the photocatalyst composition are particles having an indefinite shape, the photocatalyst composition containing such a photocatalyst can be used in a short time. It becomes a photocatalyst composition which can manufacture the photocatalyst body which expresses a superhydrophilization function.

  Moreover, according to this invention, the manufacturing method of a photocatalyst body includes a coating process and a baking process. In the application step, the photocatalyst composition obtained by the method for producing a photocatalyst composition according to the present invention is applied to the surface of the substrate. And in a baking process, a photocatalyst layer is formed on the surface of a base material by baking the base material with which the photocatalyst composition was apply | coated, and a photocatalyst body is obtained. Since a photocatalyst body is produced using the photocatalyst composition according to the present invention, the obtained photocatalyst body is exposed to light of a predetermined wavelength, so that a superhydrophilic function is exhibited in a short time.

It is process drawing which shows the manufacturing method of the photocatalyst composition which concerns on 1st Embodiment of this invention. It is the TEM photograph which observed the particle shape of the photocatalyst. It is the SEM photograph which observed the particle shape of the photocatalyst. It is process drawing which shows the manufacturing method of the photocatalyst composition which concerns on 2nd Embodiment of this invention. It is process drawing which shows the manufacturing method of the photocatalyst body which concerns on one Embodiment of this invention. It is a figure which shows typically the structure of the photocatalyst body obtained by the manufacturing method of the photocatalyst body of this invention. It is a graph which shows the time change of the contact angle with water accompanying the light irradiation of a photocatalyst body. It is a graph which shows the relationship between the transmittance | permeability of a photocatalyst, and the fall rate of a contact angle. It is a graph which shows a time-dependent change of the acetaldehyde gas concentration accompanying the light irradiation of a photocatalyst body. It is a graph which shows the relationship between the molar ratio of the silica in a photocatalyst, and the transmittance | permeability of a photocatalyst. It is a graph which shows the relationship between the frequency | count of abrasion in a photocatalyst body, and a contact angle. It is a graph which shows the adhesion abrasion property in a photocatalyst body.

(Method for producing photocatalyst composition)
The method for producing a photocatalyst composition according to the present invention is a method for producing a photocatalyst composition containing a photocatalyst. The photocatalyst composition is used when producing a photocatalyst in which a photocatalyst layer composed of a photocatalyst is formed on the surface of a substrate, and specifically, used when forming the photocatalyst layer.

<First Embodiment>
FIG. 1 is a process diagram showing a method for producing a photocatalyst composition according to the first embodiment of the present invention. The method for producing a photocatalyst composition of the present embodiment includes an amorphous titania dispersion generation step s1, a mixture dispersion generation step s2, and a photocatalyst composition generation step s3.

  In the amorphous titania dispersion production step s1, titanium alkoxide (alcohol solution) having a solid concentration of 30% is added to a liquid carboxylic acid having a concentration of 99% and mixed with stirring. Thereby, the titanium alkoxide is hydrolyzed to produce titanium hydroxide, and the titanium hydroxide is polycondensed to form a titanoxane bond to produce amorphous titania. In this way, an amorphous titania dispersion in which amorphous titania is dispersed in carboxylic acid is produced.

  In the amorphous titania dispersion production step s1, the temperature condition at the time of stirring and mixing may be set according to the types of titanium alkoxide and carboxylic acid, and is set to a temperature range of 25 to 50 ° C., for example. The mixing ratio of the titanium alkoxide having a solid content concentration of 30% and the carboxylic acid having a concentration of 99% is set to (titanium alkoxide) :( carboxylic acid) = 3: 90 to 27:10 by weight ratio.

  Examples of titanium alkoxides include tetraethoxy titanium, tetraisopropoxy titanium, tetra n-propoxy titanium, tetrabutoxy titanium, and tetramethoxy titanium. Among these, carboxylic acid is efficiently bonded to the titanium component (arrangement). Tetraisopropoxy titanium is preferred because it can be

  Examples of the carboxylic acid include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, and caproic acid. Among these, more carboxylic acid can be bound (coordinated) to the titanium component. For this reason, it is preferable to use acetic acid.

  In the mixture dispersion generation step s2, the amorphous titania dispersion generated in the amorphous titania dispersion generation step s1 and a silica sol in which amorphous silica is dispersed in a carboxylic acid are added to a solvent. And mix. Thereby, a mixture dispersion in which a mixture of amorphous titania and amorphous silica is dispersed in a solvent is obtained.

  The silica sol used in the mixture dispersion generation step s2 includes colloidal silica in which spherical, needle-like, and chain-like (particles in which spherical particles are combined in a chain) are in a colloidal state, silane alkoxide, Alkyl silicate can be produced by hydrolysis reaction in the presence of alcohol and acid.

  As the colloidal silica, commercially available ones can be used, for example, Snow Tech C, Snow Tech UP, Snow Tech PS-S, etc. manufactured by Nissan Chemical Industries, Ltd. can be used. Examples of the silane alkoxide include tetraethoxysilane and tetramethoxysilane. Examples of the alkyl silicate include propyl silicate and butyl silicate. In this embodiment, tetraethoxysilane is used. Examples of the alcohol include ethanol, isopropyl alcohol, and methanol. In the present embodiment, ethanol is used. Furthermore, examples of the acid include sulfuric acid, hydrochloric acid, nitric acid, formic acid, and acetic acid. In this embodiment, acetic acid is used.

  In the mixture dispersion generating step s2, the temperature condition at the time of stirring and mixing may be set according to the type of solvent to be used, and is set to a temperature range of 30 to 40 ° C., for example. The amount of silica sol added is such that the ratio of the molar amount of silica to the total molar amount of titania contained in the amorphous titania dispersion and silica contained in the silica sol is 0.58 to 4.1 mol%. Is set as follows. The mixing ratio of the amorphous titania dispersion having a solid concentration of about 14%, the silica sol having a solid concentration of about 16%, and the solvent (water) is expressed by weight ratio (titania in the amorphous titania dispersion). : (Silica in silica sol): (Solvent) = 1.4: 0.1: 98.5-50: 0.7: 45.

  Examples of the solvent used in the mixture dispersion generation step s2 include water, ethanol, isopropyl alcohol, methanol, and the like. Among these, water is used because the hydrolysis reaction can be efficiently promoted. Is preferred. Further, as the carboxylic acid contained in the silica sol, the same carboxylic acid used in the amorphous titania dispersion generation step s1 is used.

  In the photocatalyst composition generation step s3, the mixture dispersion generated in the mixture dispersion generation step s2 is stirred and mixed at a temperature of 70 to 80 ° C. As a result, amorphous titania in the mixture dispersion can be crystallized, and a composite photocatalyst in which amorphous silica is supported on titania having an anatase type crystal structure can be generated. A photocatalyst composition in which the produced photocatalyst is dispersed in a solvent can be obtained.

  In addition, you may make it add isopropylamine, a trimethylamine, ammonia, etc. to the photocatalyst composition produced | generated in photocatalyst composition production | generation process s3. The isopropylamine or the like is added to improve the dispersibility of the photocatalyst composition and to make the pH alkaline. In order to improve the dispersibility of the photocatalyst in the photocatalyst composition with respect to the solvent, ultrasonic vibration may be applied to the photocatalyst composition using an ultrasonic generator.

  In the method for producing the photocatalyst composition of the present embodiment, in the amorphous titania dispersion production step s1, an amorphous titania dispersion containing amorphous titania that has been hydrolyzed and polycondensated is produced, and the photocatalyst is produced. In the composition production step s3, amorphous titania is crystallized to produce a composite photocatalyst in which amorphous silica is supported on crystalline titania, and the produced photocatalyst is dispersed in the solvent. The obtained photocatalyst composition is obtained. When a photocatalyst is produced using the photocatalyst composition obtained by the method for producing a photocatalyst composition of the present embodiment, silica constituting the photocatalyst does not function as a binder and inhibits ultraviolet (light) transmission. Is prevented. As a result, a photocatalyst having a high photocatalytic activity excellent in ultraviolet (light) transmittance is obtained. Therefore, the method for producing the photocatalyst composition of the present embodiment is capable of producing a photocatalyst body that exhibits a superhydrophilic function in a short time when irradiated with light of a predetermined wavelength. Can be obtained.

  In the present embodiment, in the amorphous titania dispersion generation step s1, an amorphous titania dispersion including irregularly shaped titania particles is generated by binding (coordinating) a carboxylic acid to the titanium component. can do. Then, in the mixture dispersion generation step s2, a photocatalyst composition including a composite photocatalyst in which amorphous silica is supported on amorphous titania by using silica sol containing amorphous silica particles as silica sol. Can be manufactured. Here, the irregularly shaped particles are particles having a shape such as a needle shape, a fiber shape, a rod shape, a scale shape, and a film shape, which are not spherical.

  The particle shape of the photocatalyst can be confirmed with a transmission electron microscope (abbreviated as TEM) or a scanning electron microscope (abbreviated as SEM). FIG. 2A is a TEM photograph observing the particle shape of the photocatalyst. 2A (a) is a TEM photograph magnified 100,000 times, FIG. 2A (b) is a TEM photograph magnified 400,000 times, and FIG. 2A (c) is a TEM photograph shown in FIG. 2A (b). A boundary line indicating the boundary of each part is added so that each part of titania and silica can be clearly distinguished. FIG. 2B is an SEM photograph in which the particle shape of the photocatalyst is observed. The TEM photograph and SEM photograph shown in FIGS. 2A and 2B are observations of the particle shape of a composite photocatalyst in which amorphous silica is supported on amorphous titania. In the TEM photographs shown in FIGS. 2A (b) and 2A (c), the particle shape of one particle of the photocatalyst is observed, and the portion observed in a lattice shape (fingerprint shape) is an irregularly shaped titania. The portion observed in the shape of a cloud present in the vicinity thereof shows an amorphous silica.

  Since the irregularly shaped particles have a lower degree of formation of aggregated particles than spherical particles, they can be suppressed from acting as one large aggregated particle, and light scattering can be suppressed. Therefore, when the titania and silica constituting the photocatalyst are particles having an irregular shape, white turbidity due to light scattering of the photocatalyst can be prevented, and the photocatalyst can be made substantially transparent. Thereby, since the amount of light incident on the photocatalyst can be increased, a photocatalyst composition capable of producing a photocatalyst body that exhibits a superhydrophilic function within a short time is obtained. In addition, since the irregularly shaped particles have a larger specific surface area than the spherical particles, when the photocatalyst is produced using the photocatalyst composition, the adhesion of the photocatalyst to the substrate surface can be improved. Therefore, when the titania and the silica constituting the photocatalyst are particles having an indefinite shape, the photocatalyst composition is capable of suppressing the photocatalyst from being peeled off from the substrate surface.

  Furthermore, in this embodiment, in the mixture dispersion generating step s2, at least selected from aluminum (Al), transition metal elements (vanadium (V), niobium (Nb), chromium (Cr), manganese (Mn), etc.). One kind of compound may be added. Thereby, a photocatalyst composition containing a photocatalyst obtained by doping titania with at least one dopant selected from Al, V, Nb, Cr, and Mn can be produced. When a photocatalyst is produced using such a photocatalyst composition, the organic matter decomposition function and the superhydrophilic function of the photocatalyst can be further enhanced. In the present invention, the photocatalyst doped with a dopant has the same definition as “doping” in the semiconductor field, and the dopant is substituted with one of the crystal lattice of titania. It does not indicate that a foreign substance is adsorbed on the Ti—OH bond part, or that a foreign substance is simply mixed in titania.

Second Embodiment
FIG. 3 is a process diagram showing a method for producing a photocatalyst composition according to a second embodiment of the present invention. The method for producing a photocatalyst composition of the present embodiment includes an amorphous titania dispersion generation step a1, a precipitation step a2, a separation step a3, and a photocatalyst composition generation step a4.

  In the amorphous titania dispersion production step a1, a titanium alkoxide and an acid catalyst are added to alcohol and mixed with stirring. Thereby, the titanium alkoxide is hydrolyzed to produce titanium hydroxide, and the titanium hydroxide is polycondensed to form a titanoxane bond to produce amorphous titania. In this way, an amorphous titania dispersion in which amorphous titania is dispersed in alcohol is produced.

  In the amorphous titania dispersion production step a1, the temperature condition at the time of stirring and mixing may be set according to the types of titanium alkoxide, alcohol and acid catalyst, and is set to a temperature range of 20 to 40 ° C., for example. The mixing ratio of the titanium alkoxide having a solid content concentration of 30%, the acid catalyst having a concentration of about 34% and the alcohol is (titanium alkoxide) :( acid catalyst) :( alcohol) = 1: 7: 92˜ 40:12:53.

  Examples of the titanium alkoxide include tetraethoxy titanium, tetraisopropoxy titanium, tetra n-propoxy titanium, tetrabutoxy titanium, and tetramethoxy titanium as in the first embodiment described above. Tetraisopropoxy titanium is preferably used because of the element.

  Examples of the acid catalyst include hydrochloric acid, sulfuric acid, formic acid, nitric acid, acetic acid and the like. Among these, hydrochloric acid is preferably used because the hydrolysis reaction can be promoted with a small amount.

  Examples of the alcohol include ethanol, propanol, isopropyl alcohol, methanol, and the like. Among these, ethanol is preferably used because the ethyl group becomes a stable element with the acid.

  In the precipitation step a2, the amorphous titania dispersion produced in the amorphous titania dispersion production step a1 and the silica sol in which amorphous silica is dispersed in alcohol are added to an alkaline aqueous solution and mixed with stirring. . As a result, amorphous titania and amorphous silica come into contact with each other in an alkaline aqueous solution, and a composite photocatalyst in which amorphous silica is supported on amorphous titania is generated. The produced photocatalyst is precipitated in an alkaline aqueous solution.

  In the precipitation step a2, the temperature condition at the time of stirring and mixing is set to a temperature range of 5 to 50 ° C., for example. Further, the amount of silica sol added is such that the ratio of the molar amount of silica to the total molar amount of titania contained in the amorphous titania dispersion and silica contained in the silica sol is 3.0 to 4.1 mol%. It is set as follows. The mixing ratio of the amorphous titania dispersion having a solid concentration of about 14%, the silica sol having a solid concentration of about 27%, and the alkaline aqueous solution having a concentration of 30% is expressed by weight ratio (in the amorphous titania dispersion). Titania) :( silica in silica sol) :( alkaline aqueous solution) = 8.4: 0.27: 27.2 to 12: 8.1: 24.

  The alkaline aqueous solution is a solution in which an alkaline substance is dissolved in water, and examples of the alkaline substance include ammonia and urea. Among these, the control of the precipitation rate is excellent, and the cost is advantageous. It is preferable to use ammonia. As the alcohol contained in the silica sol, the same alcohol used in the amorphous titania dispersion generation step a1 is used.

  In the separation step a3, the photocatalyst is separated from the alkaline aqueous solution in which the photocatalyst is precipitated using a centrifuge or the like. The photocatalyst thus separated as a solid content used a cleaning liquid such as pure water in order to remove the acid catalyst used in the amorphous titania dispersion production step a1 and the alkaline aqueous solution used in the precipitation step a2. Cleaning is performed by repeating the cleaning operation.

  In the photocatalyst composition generation step a4, the photocatalyst separated as a solid content in the separation step a3 is added to a solvent and mixed with stirring. Thereby, a photocatalyst composition in which a photocatalyst is dispersed in a solvent can be obtained.

  As the solvent used in the photocatalyst composition generation step a4, it is preferable to use water because it has few impurities and is excellent in chlorine removability.

  In addition, you may make it add isopropylamine, a triethylamine, ammonia, etc. to the photocatalyst composition produced | generated in the photocatalyst composition production | generation process a4. This isopropylamine or the like is added to improve the transparency and dispersibility of the photocatalyst composition. Moreover, you may make it add nitric acid, a sulfuric acid, etc. to a photocatalyst composition. The nitric acid and the like are added to improve the dispersibility of the photocatalyst composition.

  In the method for producing a photocatalyst composition of the present embodiment, in the amorphous titania dispersion production step a1, an amorphous titania dispersion containing amorphous titania that has been hydrolyzed and polycondensated is produced. In the photocatalyst composition production step a4, the photocatalyst composition is produced by dispersing the photocatalyst once separated as a solid content in the separation step a3 in the solvent, so that the photocatalyst in which the high-purity photocatalyst is dispersed in the solvent is produced. A composition can be obtained. When a photocatalyst is produced using such a photocatalyst composition obtained by the method for producing a photocatalyst composition of the present embodiment, a photocatalyst having a high photocatalytic activity excellent in ultraviolet (light) transmittance is obtained. Therefore, the method for producing the photocatalyst composition of the present embodiment is capable of producing a photocatalyst body that exhibits a superhydrophilic function in a short time when irradiated with light of a predetermined wavelength. Can be obtained.

  Further, in the present embodiment, in the amorphous titania dispersion generation step a1, an amorphous titania dispersion containing amorphous titania particles can be generated by hydrolyzing titanium alkoxide. Then, in the precipitation step a2, by using a silica sol containing amorphous silica particles as the silica sol, a photocatalyst composition containing a composite photocatalyst in which the amorphous silica is supported on the amorphous titania is manufactured. can do. Since the titania and silica constituting the photocatalyst contained in the photocatalyst composition are particles having an indefinite shape, the photocatalyst composition containing such a photocatalyst can be used in a short time. It becomes a photocatalyst composition which can manufacture the photocatalyst body which expresses a superhydrophilization function.

  Furthermore, in this embodiment, in the amorphous titania dispersion generation step a1, from aluminum (Al), a transition metal element (vanadium (V), niobium (Nb), chromium (Cr), manganese (Mn), etc.). At least one selected compound may be added. Thereby, a photocatalyst composition containing a photocatalyst obtained by doping titania with at least one dopant selected from Al, V, Nb, Cr, and Mn can be produced. When a photocatalyst is produced using such a photocatalyst composition, the organic matter decomposition function and the superhydrophilic function of the photocatalyst can be further enhanced.

(Method for producing photocatalyst)
FIG. 4 is a process diagram showing a method for producing a photocatalyst body according to an embodiment of the present invention. The manufacturing method of the photocatalyst body of this embodiment is a method of manufacturing a photocatalyst body using the photocatalyst composition manufactured by the manufacturing method of the photocatalyst composition which concerns on 1st Embodiment or 2nd Embodiment mentioned above. The photocatalyst body 1 shown in FIG. 5 can be manufactured by this photocatalyst body manufacturing method. FIG. 5 is a diagram schematically showing the configuration of the photocatalyst obtained by the method for producing a photocatalyst of the present invention.

  A photocatalyst body 1 manufactured by the method for manufacturing a photocatalyst body of the present embodiment includes a base material 2 and a photocatalyst layer 3 formed so as to cover the surface of the base material 2. And a photocatalytic function for use as a member constituting an article or the like.

  The manufacturing method of the photocatalyst body of this embodiment includes a preheating step c1, a coating step c2, and a firing step c3.

  In the preheating step c1, the base material 2 before being coated with the photocatalyst composition is heated using an electric furnace, a gas furnace, a radiant heating furnace, etc., so that the base material 2 is heated to a predetermined temperature (a coating process described later). When the photocatalyst composition is applied in c2, the temperature is maintained at a temperature at which the liquid component in the photocatalyst composition is evaporated. What is necessary is just to set the heating temperature conditions in the preheating process c1 according to the kind of liquid component in a photocatalyst composition, for example, it sets to the temperature range of 50-200 degreeC.

  In the application step c2, the photocatalyst composition produced by the photocatalyst composition production method according to the first embodiment or the second embodiment described above is applied to the surface of the substrate 2 heated to a predetermined temperature. Examples of the coating method include spray coating, ultrasonic spray coating, rotary atomization coating, roll coating, dipping, slit coater, and spin coating. The liquid component in the photocatalyst composition is evaporated and dried by applying the photocatalyst composition to the surface of the substrate 2 heated to a predetermined temperature in the preheating step c1.

  Moreover, as a material of the base material 2, a metal, ceramics, glass, plastics, wood, stone, cement, concrete etc. are mentioned, for example. Specifically, as the base material 2, outdoor or indoor parts of buildings such as glazed tiles, window frames, window glass, bathroom or toilet mirrors on which glaze layers are formed, automobiles, railway vehicles , Members such as aircraft, ships, submersibles and other vehicle windows, eyeglass lenses, optical lenses, endoscope lenses, illumination lenses, dental teeth mirrors, road mirrors, etc. .

  In the firing step c3, the base material 2 after the photocatalyst composition is applied is fired using a firing furnace such as an electric furnace, a roller hearth kiln or a shuttle kiln, a radiant heating furnace, or the like. The photocatalyst layer 3 is formed on the surface to obtain the photocatalyst body 1.

  The firing temperature condition set in the firing step c3 varies depending on the type of photocatalyst composition used in the coating step c2. The firing temperature condition is 200 to 200 when the photocatalyst composition produced by the method for producing the photocatalyst composition according to the first embodiment described above (hereinafter sometimes referred to as “first photocatalyst composition”) is used. In the case of using a photocatalyst composition set in a temperature range of 600 ° C. and manufactured by the photocatalyst composition manufacturing method according to the second embodiment (hereinafter sometimes referred to as “second photocatalyst composition”), The temperature range is set to 600 to 800 ° C.

  When the case where the first photocatalyst composition is used is compared with the case where the second photocatalyst composition is used, the firing temperature can be lowered by using the first photocatalyst composition. This is because the titania constituting the photocatalyst contained in the first photocatalyst composition has an anatase type crystal structure and does not need to be crystallized by firing. On the other hand, since the titania constituting the photocatalyst contained in the second photocatalyst composition is amorphous titania, the titania having an anatase type crystal structure is obtained by firing in the firing step c3.

  The photocatalyst body 1 in which the photocatalyst layer 3 is formed on the surface of the substrate 2 can be manufactured by the preheating step c1, the coating step c2, and the firing step c3 as described above. In the produced photocatalyst 1, the photocatalyst 31 included in the photocatalyst layer 3 is a composite type in which amorphous silica 312 is supported on titania 311 having an anatase type crystal structure (hereinafter, “titania-silica composite type”). Photocatalyst.

  In the titania-silica composite type photocatalyst 31, the titania 311 is photoexcited when irradiated with light (ultraviolet rays) having a predetermined wavelength. When the titania 311 is photoexcited by light of a predetermined wavelength, water is chemically adsorbed on the surface in the form of hydroxyl groups, and as a result, the superhydrophilic function of the photocatalyst body 1 is considered to develop. Here, the term “superhydrophilic” means hydrophilicity (water wettability) of 10 ° or less, preferably 5 ° or less in terms of a contact angle with water. Further, in the titania-silica composite type photocatalyst 31, the silica 312 has a function of assisting the superhydrophilic function of the photocatalyst body 1 and a function of adjusting the transmittance of the photocatalyst 31.

  In the photocatalyst body 1, the photocatalyst 31 constituting the photocatalyst layer 3 preferably has a transmittance of 68 to 89%. Here, the transmittance of the photocatalyst 31 represents the light transmittance when the photocatalyst 31 is irradiated with light, and the higher the transmittance, the higher the light transmittance. The transmittance of the photocatalyst 31 shows a different value depending on the wavelength of light irradiated on the photocatalyst body 1, but in the present invention, the transmittance of the photocatalyst 31 is a value when light having a wavelength of 351 nm is irradiated. Further, the transmittance of the photocatalyst 31 is specifically measured according to JIS R 3106, and a transmittance measuring device (self-spectrophotometer) is used for a sample in which a photocatalyst layer is formed on quartz glass using a photocatalyst composition. (Total, U-4000, manufactured by Hitachi, Ltd.). In addition, the transmittance | permeability of quartz glass itself before photocatalyst layer formation is 93%.

  The present invention will be described in more detail with reference to examples below, but the present invention is not limited to these examples.

[Production of photocatalyst compositions containing photocatalysts having different transmittances]
(Production of photocatalyst composition A1)
As titanium alkoxide, tetraisopropoxy titanium (titanium isopropoxide) is mixed with acetic acid at a weight ratio of about 1: 1, and stirred and mixed at room temperature or 20-30 ° C. for about 1 hour to form amorphous titania having an irregular shape. An amorphous titania dispersion in which is dispersed in acetic acid was prepared. Next, an amorphous titania dispersion having a solid content concentration of 14%, a silica sol having a solid content concentration of 16% (a dispersion in which amorphous silica having an irregular shape is dispersed in acetic acid), a solvent (water), Are mixed in a weight ratio of (titania in amorphous titania dispersion) :( silica in silica sol) :( water) = 29: 0.4: 70.6 to obtain amorphous titania. And a mixture dispersion in which a mixture of amorphous silica was dispersed in a solvent (water) was obtained. In this case, the ratio of the molar amount of silica to the total molar amount of titania contained in the amorphous titania dispersion and silica contained in the silica sol is 2.32 mol%. Next, the mixture dispersion is stirred and mixed at a temperature of 70 to 80 ° C. for about 2 to 3 hours to transform amorphous titania in the mixture dispersion into titania having anatase type crystal structure. A composite photocatalyst in which amorphous silica is supported on crystalline titania (titania-silica composite photocatalyst) is produced, and the produced photocatalyst is dispersed in a solvent (water). Obtained. Further, to this photocatalyst composition, isopropylamine was added and the mixture was stirred and mixed at a temperature of 20 to 50 ° C. for 1 to 2 hours to alkalinize the pH, and the photocatalyst composition containing a titania-silica composite photocatalyst A1 was obtained. The transmittance of the photocatalyst contained in this photocatalyst composition A1 was 68% when irradiated with light having a wavelength of 351 nm.

(Production of photocatalyst composition A2)
A weight ratio of an amorphous titania dispersion having a solid content concentration of 14%, a silica sol having a solid content concentration of 16%, and a solvent (water): (titania in the amorphous titania dispersion): (in the silica sol (Silica): (Water) = 29: 0.2: 70.8 Photocatalyst composition containing a titania-silica composite photocatalyst in the same manner as the photocatalyst composition A1, except that the mixture was mixed to be 70.8. A2 was obtained. In this case, the ratio of the molar amount of silica to the total molar amount of titania contained in the amorphous titania dispersion and silica contained in the silica sol is 1.16 mol%. The transmittance of the photocatalyst contained in the photocatalyst composition A2 was 89% when irradiated with light having a wavelength of 351 nm.

(Production of photocatalyst composition A3)
A weight ratio of an amorphous titania dispersion having a solid content concentration of 14%, a silica sol having a solid content concentration of 16%, and a solvent (water): (titania in the amorphous titania dispersion): (in the silica sol (Silica): (Water) = 29: 0.3: Photocatalyst composition containing a titania-silica composite photocatalyst in the same manner as the photocatalyst composition A1 except that the mixture was mixed to 70.7. A3 was obtained. In this case, the ratio of the molar amount of silica to the total molar amount of titania contained in the amorphous titania dispersion and silica contained in the silica sol is 1.74 mol%. The transmittance of the photocatalyst contained in the photocatalyst composition A3 was 78% between 68% and 89% when irradiated with light having a wavelength of 351 nm.

(Production of photocatalyst composition A4)
A weight ratio of an amorphous titania dispersion having a solid content concentration of 14%, a silica sol having a solid content concentration of 16%, and a solvent (water): (titania in the amorphous titania dispersion): (in the silica sol (Silica): (Water) = 29: 0.7: A photocatalyst composition containing a titania-silica composite photocatalyst in the same manner as the photocatalyst composition A1 except that the mixture was mixed to be 70.3. A4 was obtained. In this case, the ratio of the molar amount of silica to the total molar amount of titania contained in the amorphous titania dispersion and silica contained in the silica sol is 4.1 mol%. The transmittance of the photocatalyst contained in the photocatalyst composition A4 was 66%, which is a value smaller than 68% when irradiated with light having a wavelength of 351 nm.

(Production of photocatalyst composition A5)
A weight ratio of an amorphous titania dispersion having a solid content concentration of 14%, a silica sol having a solid content concentration of 16%, and a solvent (water): (titania in the amorphous titania dispersion): (in the silica sol Silica): (Water) = 29: 0.1: A photocatalyst composition containing a titania-silica composite photocatalyst in the same manner as the photocatalyst composition A1 except that the mixture was mixed so that the ratio was 70.9. A5 was obtained. In this case, the ratio of the molar amount of silica to the total molar amount of titania contained in the amorphous titania dispersion and silica contained in the silica sol is 0.58 mol%. The transmittance of the photocatalyst contained in the photocatalyst composition A5 was 91%, which is a value greater than 89% when irradiated with light having a wavelength of 351 nm.

(Production of photocatalyst composition A6)
Using tetraethoxysilane (manufactured by Wako Pure Chemical Industries, Ltd.) and anatase type titania sol (K03, manufactured by Ishihara Sangyo Co., Ltd.), a coating solution was prepared so that the molar ratio of silica was about 40%. The photocatalyst composition A6 containing the conventional photocatalyst was obtained. The transmittance of the photocatalyst contained in this photocatalyst composition A6 was 62% when irradiated with light having a wavelength of 351 nm.

[Manufacture of photocatalyst]
The photocatalyst body was manufactured using said photocatalyst composition A1-A6 using the glazed tile in which the glaze layer was formed as a base material.

Example 1
After preheating the glazed tile substrate so that the surface temperature becomes 100 ° C., the photocatalyst composition A1 is applied by an ultrasonic spray coating method, and then baked at 500 ° C. for 15 minutes, whereby a photocatalyst having a transmittance of 68% is obtained. The photocatalyst body AA1 in which the photocatalyst layer comprised by this was formed was obtained.

(Example 2)
After preheating the glazed tile substrate so that the surface temperature becomes 100 ° C., the photocatalyst composition A2 is applied by an ultrasonic spray coating method, and then baked at 500 ° C. for 1 hour, whereby a photocatalyst having a transmittance of 89% The photocatalyst body AA2 in which the photocatalyst layer comprised by this was formed was obtained.

(Example 3)
After preheating the glazed tile substrate so that the surface temperature becomes 100 ° C., the photocatalyst composition A3 is applied by an ultrasonic spray coating method, and then baked at 500 ° C. for 1 hour, whereby the transmittance is 68%. A photocatalyst AA3 in which a photocatalyst layer constituted by 78% of the photocatalyst between 89% was formed was obtained.

(Reference Example 1)
After preheating the glazed tile base material so that the surface temperature becomes 100 ° C., the photocatalyst composition A4 is applied by an ultrasonic spray coating method, and then baked at 500 ° C. for 1 hour. A photocatalyst AA4 having a photocatalyst layer composed of 66% of the photocatalyst having a smaller value was obtained.

(Reference Example 2)
After preheating the glazed tile substrate so that the surface temperature becomes 100 ° C., the photocatalyst composition A5 is applied by an ultrasonic spray coating method, and then baked at 500 ° C. for 1 hour, whereby the transmittance is 89% or more. A photocatalyst AA5 in which a photocatalyst layer composed of a photocatalyst of 91% having a larger value was formed was obtained.

(Comparative Example 1)
After preheating the glazed tile substrate so that the surface temperature becomes 100 ° C., the photocatalyst composition A6 is applied by an ultrasonic spray coating method, and then baked at 500 ° C. for 1 hour, whereby the transmittance is 62%. Photocatalyst body AA6 in which the photocatalyst layer comprised with the photocatalyst was formed was obtained.

[Experimental result]
The six types of photocatalysts AA1 to AA6 produced as described above were tested according to JIS-R17013-1, "Fine ceramics-Test method for evaluating self-cleaning performance of photocatalyst materials-Part 1: Measurement of water contact angle" The contact angle with water after light irradiation was measured. In addition, the contact angle with water of each photocatalyst body AA1-AA6 was measured using the contact angle measuring device (DM500 type | mold, Kyowa Interface Science company make). As a specific measurement procedure of the contact angle, after measuring the contact angle of each photocatalyst AA1 to AA6 with water before light irradiation, a photocatalyst of each photocatalyst AA1 to AA6 using a black light blue fluorescent lamp as a light source The surface on the layer side was irradiated with light at an illuminance of ² mW / cm ² , and the temporal change in the contact angle with water was measured every 8 hours.

  The measurement results are shown in FIG. FIG. 6 is a graph showing temporal changes in contact angle with water accompanying light irradiation of the photocatalyst. In the graph of FIG. 6, the horizontal axis indicates the light irradiation time (Hr), and the vertical axis indicates the contact angle (°) with water. In the graph of FIG. 6, the plot of “white circle” indicates the measurement result of the photocatalyst AA1, the plot of “black circle” indicates the measurement result of the photocatalyst AA2, and the plot of “white square” indicates the measurement of the photocatalyst AA3. The result shows a measurement result of the photocatalyst AA4, a plot of “black triangle” shows a measurement result of the photocatalyst AA5, and a plot of “X” shows a measurement result of the photocatalyst AA6. .

  As is apparent from the graph of FIG. 6, photocatalysts AA1 to AA3 produced using photocatalyst compositions A1 to A3 containing photocatalysts having transmittances of 68%, 78%, and 89% (Examples 1 to 3). Compared with the photocatalyst AA6 (Comparative Example 1) produced using the photocatalyst composition A6 containing a photocatalyst having a transmittance of 62%, the contact angle with water is greatly reduced in the initial stage of light irradiation. I understand.

  FIG. 7 shows the rate of decrease in the contact angle with water based on the experimental results of FIG. FIG. 7 is a graph showing the relationship between the transmittance of the photocatalyst and the decrease rate of the contact angle. In the graph of FIG. 7, the horizontal axis indicates the transmittance (%) of the photocatalyst, and the vertical axis indicates the rate of decrease in the contact angle with water (° / Hr). In addition, the rate of decrease in the contact angle is determined from the contact angle with water before light irradiation to the required light irradiation time until the contact angle with water becomes 10 °, which is a reference for the expression of the superhydrophilization function of the photocatalyst. Based on (contact angle before light irradiation−10) [°] / required light irradiation time [Hr].

  From the experimental results of FIGS. 6 and 7, the photocatalyst AA6 (Comparative Example 1) produced using the photocatalyst composition A6 containing the photocatalyst of the prior art has a decrease rate of the contact angle of water from 0 immediately after light irradiation. .74 [° / Hr], and it can be seen that it takes a long time of about 64 hours from the time of light irradiation until the superhydrophilization function (the contact angle with water becomes 10 ° or less). The reason for this is considered to be that the ultraviolet light (light) transmission is inhibited by the binder component of silica and the light does not uniformly reach the surface of the titania particles.

  In contrast, the photocatalyst AA1 (Example 1) produced using the photocatalyst composition A1 containing a photocatalyst having a transmittance of 68% has a rate of decrease in the contact angle of water immediately after light irradiation of 1. 08 [° / Hr], and the time required from the time of light irradiation until the superhydrophilic function is developed is about 39 hours, which is shorter than 64 hours of the photocatalyst AA6. In addition, the photocatalyst AA2 (Example 2) produced using the photocatalyst composition A2 containing a photocatalyst having a transmittance of 89% has a rate of decrease in the contact angle of water of 1.51 [° immediately after light irradiation. / Hr], and the time required from the time of light irradiation until the superhydrophilic function is manifested is about 30 hours, which is shorter than 64 hours of the photocatalyst AA6. In addition, the photocatalyst AA3 (Example 3) produced using the photocatalyst composition A3 containing a photocatalyst having a transmittance of 78% has a rate of decrease in the contact angle of water of 1.38 [° immediately after light irradiation. / Hr], and the time required from the time of light irradiation to the development of the superhydrophilic function is about 32 hours, which is shorter than 64 hours of the photocatalyst AA6. In addition, the photocatalyst AA4 (Reference Example 1) produced using the photocatalyst composition A4 containing a photocatalyst having a transmittance of 66% has a rate of decrease in the contact angle of water of 0.82 [° immediately after light irradiation. / Hr], and the time required from immediately after light irradiation until the superhydrophilization function is exhibited is about 56 hours, which is shorter than 64 hours of the photocatalyst AA6. In addition, the photocatalyst AA5 (Reference Example 2) produced using the photocatalyst composition A5 containing a photocatalyst having a transmittance of 91% has a rate of decrease in the contact angle of water of 0.92 [° immediately after light irradiation. / Hr], and the time required from the time of light irradiation to the development of the superhydrophilic function is about 50 hours, which is shorter than 64 hours of the photocatalyst AA6.

  In particular, as apparent from the experimental results of the photocatalysts AA1 to AA3 (Examples 1 to 3) produced using the photocatalyst compositions A1 to A3 containing the photocatalyst having a transmittance of 68 to 89%, the transmittance is 68. The photocatalyst produced using a photocatalyst composition containing ˜89% of the photocatalyst has a rate of decrease in the contact angle of water from 1.08 to 1.60 [° / Hr] immediately after light irradiation, preferably 1 0.08 to 1.51 [° / Hr], and the superhydrophilic function is exhibited within a short time. The reason for this is considered to be that when the transmittance of the photocatalyst is 68 to 89%, the light uniformly reaches the surface of the titania particles, and the photocatalytic activity is quickly expressed.

Moreover, the acetaldehyde gas decomposition | disassembly performance was measured about photocatalyst bodies AA1-AA6. The acetaldehyde gas decomposition performance was determined by filling a test gas whose acetaldehyde gas concentration was adjusted to 45 to 65 ppm into a tedlar back so that the volume ratio of the photocatalyst to the photocatalyst coating test surface was 10.6 m ² / m ³ , Continuous irradiation was performed with a light blue fluorescent lamp at an illuminance of ² mW / cm ² , and the change with time in the acetaldehyde gas concentration was measured. The acetaldehyde gas concentration was measured at intervals of 5 minutes with a photoacoustic gas monitor (1412-5 type, manufactured by INNIVA). The measurement result of the acetaldehyde gas decomposition performance is shown in FIG.

  FIG. 8 is a graph showing a change with time of the acetaldehyde gas concentration accompanying light irradiation of the photocatalyst. In the graph of FIG. 8, the horizontal axis indicates the light irradiation time (minutes), and the vertical axis indicates the acetaldehyde gas concentration (ppm). In the graph of FIG. 8, the “white circle” plot indicates the measurement result of the photocatalyst AA1, the “black circle” plot indicates the measurement result of the photocatalyst AA2, and the “white square” plot indicates the measurement of the photocatalyst AA3. The result shows a measurement result of the photocatalyst AA4, a plot of “black triangle” shows a measurement result of the photocatalyst AA5, and a plot of “X” shows a measurement result of the photocatalyst AA6. .

  From the experimental results of FIG. 8, the transmittance is 66 to 91% as compared with the photocatalyst AA6 (Comparative Example 1) manufactured using the photocatalyst composition A6 containing the conventional photocatalyst having a transmittance of 62%. The photocatalysts AA1 to AA5 (Examples 1 to 3 and Reference Examples 1 and 2) produced using the photocatalyst compositions A1 to A5 containing the photocatalyst are maintained in a state in which the acetaldehyde gas decomposition performance accompanying light irradiation is high. I understand that. In particular, the photocatalysts AA1 to AA3 (Examples 1 to 3) produced using the photocatalyst compositions A1 to A3 containing a photocatalyst having a transmittance of 68 to 89% have higher acetaldehyde gas decomposition performance due to light irradiation. It can be seen that the state is maintained.

  Moreover, about the photocatalyst bodies AA1-AA6, the influence which it has on the transmittance | permeability of the molar ratio of the silica in a photocatalyst was examined. The examination results are shown in FIG. FIG. 9 is a graph showing the relationship between the molar ratio of silica in the photocatalyst and the transmittance of the photocatalyst. In the graph of FIG. 9, the horizontal axis indicates the molar ratio (mol%) of silica in the photocatalyst, and the vertical axis indicates the transmittance (%) of the photocatalyst.

  From the results shown in FIG. 9, it can be seen that as the molar ratio of silica in the photocatalyst decreases, the transmittance of the photocatalyst increases. That is, in the titania-silica composite type photocatalyst, it is understood that silica has a function of assisting the superhydrophilic function of the photocatalyst and a function of adjusting the transmittance of the photocatalyst.

Moreover, about the photocatalyst bodies AA1-AA6, the influence which the molar ratio of the silica in a photocatalyst exerts on the adhesion wear property was examined. The evaluation of adhesion wear was performed according to the cleaning resistance test method of JIS-K-5663 “Synthetic resin emulsion paint and sealer”. Specifically, after the surface of the photocatalyst was rubbed (worn) with a pig hair brush, the surface was washed with water, and then ² mW / cm ² was applied to the surface of the photocatalyst using a black light blue fluorescent lamp. After irradiating light with illuminance for 192 hours to further clean and activate the surface, the contact angle with water was measured. The examination result about adhesion wear property is shown in FIG. 10 and FIG.

  FIG. 10 is a graph showing the relationship between the number of wear and the contact angle in the photocatalyst. In the graph of FIG. 10, the horizontal axis indicates the number of contact wear (times) with respect to the photocatalyst, and the vertical axis indicates the contact angle (°) with water. In the graph of FIG. 10, the plot of “black circle” indicates the measurement result of the photocatalyst AA2, and the plot of “X” indicates the measurement result of the photocatalyst AA6.

  From the results shown in FIG. 10, the photocatalyst AA6 (Comparative Example 1) produced using the photocatalyst composition A6 containing the photocatalyst of the prior art has a larger contact angle with water as the number of wear increases. That is, in the photocatalyst AA6, as the number of wear increases, the photocatalyst layer is worn and peeled, and the superhydrophilic function is lost. This shows that the photocatalyst AA6 does not have excellent adhesion wear properties.

  On the other hand, the photocatalyst AA2 (Example 2) hardly changes the contact angle with water even when the number of wear increases. That is, in the photocatalyst body AA2, even if the number of wears increases, the photocatalyst layer does not wear and peel, and the superhydrophilic function is maintained. From this, it can be seen that the photocatalyst AA2 has excellent adhesion wear properties.

  FIG. 11 is a graph showing adhesion wear resistance in the photocatalyst body. In the graph of FIG. 11, the horizontal axis indicates the type of photocatalyst, and the vertical axis indicates the contact angle (°) with water. In addition, in FIG. 11, the experimental result about photocatalyst SS1 is also shown other than the experimental result of photocatalyst AA1-AA6. This photocatalyst SS1 is manufactured as follows.

  In producing the photocatalyst SS1, first, a photocatalyst composed of amorphous titania having an anatase type crystal structure is used in the same manner as the photocatalyst composition A1 except that silica sol is not mixed with the amorphous titania dispersion. A photocatalytic composition S1 in which was dispersed in a solvent (water) was obtained. The photocatalyst contained in the photocatalyst composition S1 thus obtained does not carry silica, and the molar ratio of silica in the photocatalyst is “0 mol%”.

  Next, after pre-heating the glazed tile base material so that the surface temperature becomes 100 ° C., the photocatalyst composition S1 is applied by an ultrasonic spray coating method, and then baked at 500 ° C. for 1 hour, whereby the photocatalyst SS1 Can be obtained.

  From the results shown in FIG. 11, the photocatalyst AA6 (Comparative Example 1) produced using the photocatalyst composition A6 containing the photocatalyst of the prior art (silica molar ratio = 40 mol%) is in an initial state of “no wear”. The contact angle with water after light irradiation is 4.58 °, whereas the contact angle with water after light irradiation is “37.8 °” after “1200 times wear”. It can be seen that they are lost and do not have excellent adhesion wear.

  In contrast, the photocatalyst AA1 (Example 1) manufactured using the photocatalyst composition A1 (molar ratio of silica in the photocatalyst = 2.32 mol%) was irradiated with light in the initial state of “no wear”. The contact angle with water after that is 4.1 °, whereas the contact angle with water after light irradiation in “after 1200 wear” is 8.7 °, and the superhydrophilic function is maintained. It can be seen that it has excellent adhesion wear properties. In addition, the photocatalyst AA2 (Example 2) produced using the photocatalyst composition A2 (molar ratio of silica in the photocatalyst = 1.16 mol%) is water after irradiation with light in the initial state of “no wear”. The contact angle with water after light irradiation is 9.4 ° “after 1200 times wear”, and the superhydrophilic function is maintained and excellent adhesion. It turns out that it has abrasion. In addition, the photocatalyst AA3 (Example 3) produced using the photocatalyst composition A3 (molar ratio of silica in the photocatalyst = 1.74 mol%) is water after light irradiation in the initial state of “no wear”. The contact angle with water after irradiation with light after irradiating 1200 times is 8.3 °, and the superhydrophilic function is maintained and excellent adhesion. It turns out that it has abrasion.

  In addition, the photocatalyst AA4 (Reference Example 1) produced using the photocatalyst composition A4 (silica molar ratio in photocatalyst = 4.1 mol%) is water after light irradiation in the initial state of “no wear”. The contact angle with water after irradiation with light after 7.2 times wear is 7.2 °, and the superhydrophilic function is maintained and excellent adhesion. It turns out that it has abrasion. In addition, the photocatalyst AA5 (Reference Example 2) produced using the photocatalyst composition A5 (silica molar ratio in the photocatalyst = 0.58 mol%) is water after light irradiation in the initial state of “no wear”. The contact angle with water after light irradiation is 9.1 ° after “lightening 1200 times”, and the superhydrophilic function is maintained and excellent adhesion. It turns out that it has abrasion. Furthermore, the photocatalyst SS1 produced using the photocatalyst composition S1 (silica molar ratio in the photocatalyst = 0 mol%) has a contact angle with water after light irradiation of 4 in the initial state of “no wear”. Whereas the contact angle with water after light irradiation is 8.9 °, after “1200 times wear”, the superhydrophilic function is maintained, and the adhesive wear resistance is excellent. I understand that.

  The photocatalysts AA1 to AA5 and SS1 have excellent adhesion wear properties although the molar ratio of silica in the photocatalyst is very small compared to the photocatalyst AA6. From this, in the photocatalysts AA1 to AA5, SS1, it is presumed that silica does not function as a binder to be bound to the base material.

  It is considered that the photocatalysts AA1 to AA5 and SS1 have excellent adhesion wear properties because the photocatalyst in the photocatalysts AA1 to AA5 and SS1 is composed of titania and silica having an irregular shape. That is, it is considered that the irregularly shaped particles have a larger specific surface area than the spherical particles, so that the adhesion wear property of the photocatalyst to the substrate surface can be improved.

DESCRIPTION OF SYMBOLS 1 Photocatalyst body 2 Base material 3 Photocatalyst layer 31 Photocatalyst 311 Titania 312 Silica

Claims (5)

Titanium alkoxide is added to liquid carboxylic acid under stirring, titanium alkoxide is hydrolyzed to produce titanium hydroxide, and the titanium hydroxide is polycondensed to produce amorphous titania having a titanoxane bond. An amorphous titania dispersion producing step for obtaining an amorphous titania dispersion in which the amorphous titania is dispersed in a carboxylic acid,
The amorphous titania dispersion and a silica sol in which amorphous silica is dispersed in carboxylic acid are added to a solvent with stirring, and a mixture of amorphous titania and amorphous silica is added to the solvent. A mixture dispersion producing step for obtaining a mixture dispersion dispersed in
The mixture dispersion is stirred at a temperature of 70 to 80 ° C. to change the amorphous titania in the mixture dispersion into titania having an anatase type crystal structure. A photocatalyst composition producing step comprising producing a photocatalyst composition in which the photocatalyst is dispersed in a solvent by producing a composite photocatalyst loaded with fine silica. Method. In the amorphous titania dispersion production step, an amorphous titania dispersion containing irregularly shaped titania particles is produced,
2. The method for producing a photocatalyst composition according to claim 1, wherein in the mixture dispersion generation step, a silica sol containing particles of amorphous silica is used as the silica sol. Titanium alkoxide and acid catalyst are added to the alcohol under stirring, and the titanium alkoxide is hydrolyzed to produce titanium hydroxide, and the titanium hydroxide is polycondensed to produce amorphous titania having a titanoxane bond. An amorphous titania dispersion producing step for obtaining an amorphous titania dispersion in which the amorphous titania is dispersed in alcohol;
The amorphous titania dispersion and a silica sol in which amorphous silica is dispersed in alcohol are added to an alkaline aqueous solution with stirring, and the amorphous titania supports the amorphous silica. A precipitation step of precipitating the photocatalyst in an aqueous alkaline solution by producing a photocatalyst of a type;
A separation step of separating the photocatalyst from the alkaline aqueous solution in which the photocatalyst is precipitated;
A photocatalyst composition producing step, wherein the photocatalyst separated in the separation step is added to a solvent under stirring to obtain a photocatalyst composition in which the photocatalyst is dispersed in the solvent. Method. In the amorphous titania dispersion production step, an amorphous titania dispersion containing irregularly shaped titania particles is produced,
The method for producing a photocatalyst composition according to claim 3, wherein in the precipitation step, a silica sol containing amorphous silica particles is used as the silica sol. An application step of applying the photocatalyst composition obtained by the production method according to any one of claims 1 to 4 to the surface of a substrate;
A method for producing a photocatalyst, comprising: calcining a substrate coated with the photocatalyst composition to form a photocatalyst layer on the surface of the substrate to obtain a photocatalyst.