JP7362224B2 - Titanium oxide particles, a dispersion thereof, a photocatalyst thin film, a member having a photocatalyst thin film on the surface, and a method for producing a titanium oxide particle dispersion - Google Patents

Description

The present invention relates to titanium oxide particles, a dispersion thereof, a photocatalytic thin film formed using the dispersion, a member having a photocatalytic thin film on the surface, and a method for producing a titanium oxide particle dispersion. The present invention relates to photocatalytic titanium oxide particles and the like that can easily produce a photocatalytic thin film with high properties.

Photocatalysts are widely used for purposes such as cleaning, deodorizing, and antibacterial purposes on substrate surfaces. A photocatalytic reaction is a reaction caused by excited electrons and holes generated when a photocatalyst absorbs light. The decomposition of organic substances by photocatalysts is thought to occur mainly through the following mechanisms [1] and [2].
[1] The generated excited electrons and holes undergo a redox reaction with oxygen and water adsorbed on the photocatalyst surface, and active species generated by the redox reaction decompose organic matter.
[2] The generated holes directly oxidize and decompose the organic matter adsorbed on the photocatalyst surface.

Recently, the application of photocatalysis as described above is not limited to outdoor use where ultraviolet rays (wavelength 10 to 400 nm) can be used, but also to light in the visible region (wavelength 400 to 800 nm) such as fluorescent lamps. Studies have been conducted to make it usable even in indoor spaces illuminated by light sources, and for example, a tungsten oxide photocatalyst (Japanese Unexamined Patent Publication No. 2009-148700: Patent Document 1) has been developed as a visible light-responsive photocatalyst.

As a method for improving the visible light activity of a photocatalyst using titanium oxide, a method of supporting iron or copper on the surface of titanium oxide fine particles or metal-doped titanium oxide fine particles (for example, Japanese Patent Laid-Open No. 2012-210632: Patent Document 2, JP 2010-104913: Patent Document 3, JP 2011-240247: Patent Document 4, JP 7-303835: Patent Document 5), solidifying tin and a transition metal that increases visible light activity. A method in which dissolved (doped) titanium oxide fine particles and titanium oxide fine particles containing copper as a solid solution are prepared and mixed together (International Publication No. 2014/045861: Patent Document 6), which improves tin and visible light responsiveness. A method is known in which titanium oxide fine particles containing a transition metal as a solid solution and titanium oxide fine particles containing an iron group element as a solid solution are prepared and then mixed together (International Publication No. 2016/152487: Patent Document 7). .

A visible light-responsive photocatalytic titanium oxide obtained by preparing and mixing titanium oxide fine particles containing tin and a transition metal that enhances visible light activity and titanium oxide fine particles containing an iron group element as a solid solution, respectively, as disclosed in Patent Document 7. When a photocatalytic film formed using a fine particle dispersion is used, high decomposition activity can be obtained under conditions of only light in the visible region. Furthermore, when using a photocatalytic film formed using a titanium oxide fine particle dispersion in which iron components are adsorbed (=supported) on the surface of titanium oxide fine particles containing tin and a transition metal that increases visible light activity as a solid solution, It has been shown that it is possible to decompose acetaldehyde gas under conditions of only light in the visible light range, but it cannot be added because the quality of the photocatalytic film obtained by coagulation and precipitation of titanium oxide fine particles due to the iron component is impaired. The amount of iron component was limited, and the photocatalytic activity obtained was low.

As mentioned above, although many studies are being carried out to increase photocatalytic activity, in actual environments it is important that harmful substances are decomposed and removed as quickly as possible, so further improvement of photocatalytic activity is necessary. It has been demanded.

Japanese Patent Application Publication No. 2009-148700 Japanese Patent Application Publication No. 2012-210632 Japanese Patent Application Publication No. 2010-104913 Japanese Patent Application Publication No. 2011-240247 Japanese Patent Application Publication No. 7-303835 International Publication No. 2014/045861 International Publication No. 2016/152487

Therefore, the present invention provides titanium oxide particles that can obtain even higher photocatalytic activity than conventional methods, a dispersion thereof, a photocatalytic thin film formed using the dispersion, a member having a photocatalytic thin film on the surface, and the production of a titanium oxide particle dispersion. The purpose is to provide a method.

In order to achieve the above object, the present inventors conducted detailed studies on combinations of photocatalysts (titanium oxide) and various materials, their quantitative ratios, etc., and found that by mixing iron and silicon components with titanium oxide particles, The present invention was completed based on the discovery that the photocatalytic activity of the resulting titanium oxide particles having iron and silicon components attached to their surfaces was dramatically improved.

Therefore, the present invention provides the following titanium oxide particles, a dispersion thereof, a photocatalytic thin film formed using the dispersion, a member having the photocatalytic thin film on its surface, and a method for producing the titanium oxide particle dispersion. .
[1]
Titanium oxide particles with iron and silicon components attached to their surfaces.
[2]
The oxidation according to [1], wherein the molar ratio of the iron component to titanium (Ti/Fe) is 10 to 10,000, and the molar ratio of the silicon component to titanium (Ti/Si) is 1 to 10,000. titanium particles.
[3]
The titanium oxide particles according to [1] or [2], further comprising at least one metal component selected from molybdenum, tungsten, and vanadium components attached to the surface.
[4]
A titanium oxide particle dispersion liquid in which the titanium oxide particles according to any one of [1] to [3] are dispersed in an aqueous dispersion medium.
[5]
The titanium oxide particle dispersion according to [4], further containing a binder.
[6]
The titanium oxide particle dispersion according to [5], wherein the binder is a silicon compound binder.
[7]
A photocatalytic thin film containing the titanium oxide particles according to any one of [1] to [3].
[8]
The photocatalytic thin film according to [7], further containing a binder.
[9]
A member in which the photocatalytic thin film of [7] or [8] is formed on the surface of a base material.
[10]
A method for producing a titanium oxide particle dispersion comprising the following steps (1) to (4).
(1) Step of producing peroxotitanic acid solution from raw material titanium compound, basic substance, hydrogen peroxide and aqueous dispersion medium. (2) Step of producing peroxotitanic acid solution produced in step (1) above under pressure control. , a step of heating at 80 to 250°C to obtain a titanium oxide particle dispersion (3) A step of producing a solution or dispersion of an iron component and a silicon component from an iron compound, a silicon compound, and an aqueous dispersion medium (4) The above ( A step of mixing the titanium oxide particle dispersion produced in step 2) and the solution or dispersion of iron components and silicon components produced in step (3) to obtain a dispersion.

The titanium oxide particles of the present invention have higher photocatalytic activity than conventional ones. Furthermore, a highly transparent photocatalytic thin film can be easily produced from the titanium oxide particle dispersion. Therefore, the titanium oxide particles of the present invention are useful for members used in actual environments where rapid decomposition and removal of harmful substances is required.

The present invention will be explained in detail below.
<Titanium oxide particle dispersion>
The titanium oxide particle dispersion of the present invention contains titanium oxide particles, an iron component, and a silicon component in an aqueous dispersion medium. The iron component and silicon component contained in the titanium oxide particle dispersion are attached to the surface of the titanium oxide particles, but the iron component and silicon component may be free in the titanium oxide particle dispersion.

As the aqueous dispersion medium, it is preferable to use water, but a mixed solvent of water and a hydrophilic organic solvent that can be mixed with water in any proportion may also be used. As water, for example, purified water such as filtered water, deionized water, distilled water, pure water, etc. is preferable. Examples of hydrophilic organic solvents include alcohols such as methanol, ethanol, and isopropanol, glycols such as ethylene glycol, and glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, and propylene glycol-n-propyl ether. Preferably. When using a mixed solvent, the proportion of the hydrophilic organic solvent in the mixed solvent is preferably more than 0% by mass and 50% by mass or less, more preferably 20% by mass or less, and still more preferably 10% by mass or less. It is.

The titanium oxide particles themselves contained in the titanium oxide particle dispersion are not particularly limited, and titanium oxide used as a photocatalyst can be used. The supported titanium oxide particles may be any of titanium oxide particles in which nitrogen, carbon, sulfur, and a metal component are dissolved in solid solution. Among them, it is preferable to use titanium oxide particles; titanium oxide particles in which a metal component is dissolved in solid solution.
The metal component to be dissolved in titanium oxide is not particularly limited, and examples include a tin component and a transition metal component.

Three crystal phases of titanium oxide particles are generally known: rutile type, anatase type, and brookite type, but the titanium oxide particles of the present invention are preferably mainly anatase type or rutile type. Note that the term "mainly" as used herein means that titanium oxide particles in the crystalline phase are contained in an amount of 50% by mass or more, preferably 70% by mass or more, and more preferably 90% by mass of all titanium oxide particles. or more, and may be 100% by mass.

Here, in this specification, a solid solution is a phase in which an atom at a lattice point of a certain crystal phase is substituted with another atom, or another atom enters a lattice gap, that is, a certain crystal phase is replaced by another atom. It refers to a substance that has a mixed phase that is considered to have dissolved substances, and a crystalline phase that is a homogeneous phase. A solid solution in which solvent atoms at lattice points are substituted with solute atoms is called a substitutional solid solution, and a solid solution in which solute atoms are present in lattice gaps is called an interstitial solid solution. In this specification, both of these are referred to.

The titanium oxide particles contained in the titanium oxide particle dispersion may form a solid solution with tin atoms and/or transition metal atoms. The solid solution may be a substitutional type or an interstitial type. A substitutional solid solution of titanium oxide is formed when the titanium sites of a titanium oxide crystal are replaced by various metal atoms, and an interstitial solid solution of titanium oxide is formed when various metal atoms enter the lattice gaps of a titanium oxide crystal. It is something that is formed. When various metal atoms are dissolved in titanium oxide, when the crystal phase is measured by X-ray diffraction, only the peak of the crystal phase of titanium oxide is observed, and the peaks of compounds derived from the various metal atoms added are not observed. .

Methods for dissolving dissimilar metals in metal oxide crystals are not particularly limited, but include gas phase methods (CVD method, PVD method, etc.), liquid phase methods (hydrothermal method, sol-gel method, etc.), and solid solution methods. Examples include phase methods (high temperature firing method, etc.).

When a tin component is solid-dissolved in titanium oxide particles, the tin component may be derived from a tin compound, such as an elemental metal of tin (Sn), an oxide (SnO, SnO ₂ ), a hydroxide, Chlorides (SnCl ₂ , SnCl ₄ ), nitrates (Sn(NO ₃ ) ₂ ), sulfates (SnSO ₄ ), halides (Br, I), oxoacids (Na ₂ SnO ₃ , K ₂ SnO ₃ ), Examples include complex compounds, and one or a combination of two or more of these may be used. Among these, it is preferable to use oxides (SnO, SnO ₂ ), chlorides (SnCl ₂ , SnCl ₄ ), sulfates (SnSO ₄ ), and oxoacid salts (Na ₂ SnO ₃ , K ₂ SnO ₃ ).

The amount of the tin component dissolved in the titanium oxide particles is 1 or more, preferably 5 or more in molar ratio (Ti/Sn) to titanium. This is because when the molar ratio is less than 1, the content of titanium oxide decreases and the photocatalytic effect is not sufficiently exhibited.

The transition metal dissolved in the titanium oxide particles is one or more elements selected from Groups 3 to 11 of the periodic table, such as vanadium, chromium, manganese, niobium, molybdenum, rhodium, It can be selected from tungsten, cerium, etc., among which molybdenum, tungsten and vanadium are preferred.

The transition metal component dissolved in the titanium oxide particles may be one derived from the transition metal compound, and may include metals, oxides, hydroxides, chlorides, nitrates, sulfates, and halogens (Br, I). compounds, oxoacid salts, various complex compounds, etc., and one or more of these may be used.

The amount of the transition metal component dissolved in the titanium oxide particles can be appropriately selected depending on the type of the transition metal component, but it is preferable that the molar ratio with titanium (Ti/transition metal) is 1 or more.

When molybdenum is dissolved in titanium oxide particles as a solid solution, the molybdenum component may be derived from a molybdenum compound, such as molybdenum elemental metal (Mo), oxides (MoO ₂ , MoO ₃ ), hydroxides, Chlorides (MoCl ₃ , MoCl ₅ ), nitrates, sulfates, halides (Br, I), molybdic acid and oxoacid salts (H ₂ MoO ₄ , Na ₂ MoO ₄ , K ₂ MoO ₄ ), complex compounds, etc. These may be used alone or in combination of two or more. Among them, it is preferable to use oxides (MoO ₂ , MoO ₃ ), chlorides (MoCl ₃ , MoCl ₅ ), and oxoacid salts (H ₂ MoO ₄ , Na ₂ MoO ₄ , K ₂ MoO ₄ ).

The amount of the molybdenum component dissolved in the titanium oxide particles is 1 or more, preferably 5 or more, and more preferably 20 or more in terms of molar ratio (Ti/Mo) to titanium. This is because if the molar ratio is less than 1, the content of titanium oxide may decrease and the photocatalytic effect may not be sufficiently exhibited.

When solid-dissolving tungsten in titanium oxide particles, the tungsten component may be derived from a tungsten compound. For example, tungsten elemental metal (W), oxide (WO ₃ ), hydroxide, chloride ( WCl ₄ , WCl ₆ ), nitrates, sulfates, halides (Br, I), tungstic acid and oxoacid salts (H ₂ WO ₄ , Na ₂ WO ₄ , K ₂ WO ₄ ), complex compounds, etc. One or a combination of two or more of these may be used. Among these, it is preferable to use oxides (WO ₃ ), chlorides (WCl ₄ , WCl ₆ ), and oxoacid salts (Na ₂ WO ₄ , K ₂ WO ₄ ).

The amount of the tungsten component dissolved in the titanium oxide particles is 1 or more, preferably 5 or more, and more preferably 20 or more in molar ratio (Ti/W) to titanium. This is because when the molar ratio is less than 1, the content of titanium oxide decreases and the photocatalytic effect is not sufficiently exhibited.

When vanadium is solid-dissolved in titanium oxide particles, the vanadium component may be derived from a vanadium compound, such as vanadium elemental metal (V), oxides (VO, V ₂ O ₃ , VO ₂ , V ₂ O ₅ ), hydroxide, chloride (VCl ₅ ), oxychloride (VOCl ₃ ), nitrate, sulfate, oxysulfate (VOSO ₄ ), halide (Br, I), oxoacid (Na ₃ VO ₄ , K ₃ VO ₄ , KVO ₃ ), complex compounds, and the like, and one or a combination of two or more of these may be used. Among them, oxides (V ₂ O ₃ , V ₂ O ₅ ), chlorides (VCl ₅ ), oxychlorides (VOCl ₃ ), oxysulfates (VOSO ₄ ), oxoacid salts (Na ₃ VO ₄ , K ₃ VO ₄ , KVO ₃ ) is preferably used.

The amount of the vanadium component solid-dissolved in the titanium oxide particles is 1 or more, preferably 10 or more, and more preferably 100 or more in molar ratio with titanium (Ti/V). This is because when the molar ratio is less than 1, the content of titanium oxide decreases and the photocatalytic effect is not sufficiently exhibited.

As the transition metal component dissolved in the titanium oxide particles, a plurality of molybdenum, tungsten, and vanadium may be selected, and the amount of each component can be selected from the above range. However, the molar ratio [Ti/(Mo+W+V)] between the total amount of each component and titanium is 1 or more.

One type of titanium oxide particles may be used, or two or more types may be used in combination. When two or more types having different photoresponsiveness are combined, the effect of increasing photocatalytic activity may be obtained.

The iron and silicon components contained in the titanium oxide particle dispersion and attached to the surface of the titanium oxide particles increase the photocatalytic activity of the photocatalytic thin film. In addition, at least one metal component selected from molybdenum, tungsten, and vanadium components, which are also transition metal components that may be solid-dissolved in the titanium oxide particles, may be contained as a component to further enhance photocatalytic activity.

The iron component contained in the titanium oxide particle dispersion is intended to enhance the photocatalytic activity of the photocatalytic thin film, but it may be derived from iron compounds, such as elemental iron metal (Fe), oxides, etc. (Fe ₂ O ₃ , Fe ₃ O ₄ ), hydroxide (Fe(OH) ₂ , Fe(OH) ₃ ), oxyhydroxide (FeO(OH)), chloride (FeCl ₂ , FeCl ₃ ), Examples include nitrates (Fe(NO) ₃ ), sulfates (FeSO ₄ , Fe ₂ (SO ₄ ) ₃ ), halides (Br, I), complex compounds, etc., and these may be used alone or in combination of two or more. May be used.

The content of the iron component contained in the titanium oxide particle dispersion is 10 to 10,000, preferably 20 to 5,000, more preferably 50 to 2,000 in molar ratio with titanium (Ti/Fe). . This is because if the molar ratio is less than 10, the quality of the photocatalytic thin film obtained by agglomeration and precipitation of titanium oxide may deteriorate and the photocatalytic effect may not be sufficiently exhibited, and if the molar ratio exceeds 10,000, the photocatalytic activity is insufficient. This is because it may become.

The silicon component contained in the titanium oxide particle dispersion suppresses agglomeration and precipitation of titanium oxide and iron components when iron components are added, thereby preventing deterioration in the quality of the photocatalytic thin film and suppressing the deterioration of the photocatalytic effect. , may be derived from silicon compounds, such as elemental silicon metal (Si), oxides (SiO, SiO ₂ ), alkoxides (Si(OCH ₃ ) ₄ , Si(OC ₂ H ₅ ) ₄ , Examples include Si(OCH(CH ₃ ) ₂ ) ₄ ), silicates (sodium salts, potassium salts), and activated silicic acids obtained by removing at least a portion of ions such as sodium and potassium from these silicates. You may use 1 type or a combination of 2 or more types. Among these, it is preferable to use silicates (sodium silicate) and active silicic acid, especially active silicic acid.

The content of the silicon component contained in the titanium oxide particle dispersion is 1 to 10,000, preferably 2 to 5,000, more preferably 5 to 2,000 in molar ratio with titanium (Ti/Si). . If the molar ratio is less than 1, the content of titanium oxide may decrease and the photocatalytic effect may not be sufficiently exhibited, and if it exceeds 10,000, the effect of suppressing agglomeration and precipitation of titanium oxide will be insufficient. This is because there are certain things.

In order to further increase the photocatalytic activity of the photocatalytic thin film, when a transition metal component (molybdenum, tungsten, vanadium) is further added to the titanium oxide particle dispersion, the content of the transition metal component contained in the titanium oxide particle dispersion is Although it can be appropriately selected depending on the type of metal component, the molar ratio with titanium (Ti/transition metal) is preferably 10 to 10,000.

When molybdenum is selected as the transition metal component contained in the titanium oxide particle dispersion, the molybdenum component may be derived from the same molybdenum compound as that used in solid solution in the titanium oxide particles.

The content of the molybdenum component contained in the titanium oxide particle dispersion is 10 to 10,000, preferably 50 to 5,000, more preferably 100 to 3,000 in molar ratio with titanium (Ti/Mo). . This is because if the molar ratio is less than 10, the content of titanium oxide may decrease and the photocatalytic effect may not be sufficiently exhibited, and if it exceeds 10,000, the photocatalytic activity may be insufficient.

When selecting tungsten as the transition metal component contained in the titanium oxide particle dispersion, the tungsten component may be one derived from the same tungsten compound as that used in solid solution in the titanium oxide particles.

The content of the tungsten component contained in the titanium oxide particle dispersion is 10 to 10,000, preferably 50 to 5,000, more preferably 100 to 3,000 in molar ratio with titanium (Ti/W). . This is because if the molar ratio is less than 10, the content of titanium oxide may decrease and the photocatalytic effect may not be sufficiently exhibited, and if it exceeds 10,000, the photocatalytic activity may be insufficient.

When vanadium is selected as the transition metal component contained in the titanium oxide particle dispersion, the vanadium component may be derived from the same vanadium compound as that used in solid solution in the titanium oxide particles.

The content of the vanadium component contained in the titanium oxide particle dispersion is 10 to 10,000, preferably 50 to 5,000, more preferably 100 to 3,000 in terms of molar ratio to titanium (Ti/V). . This is because if the molar ratio is less than 10, the content of titanium oxide may decrease and the photocatalytic effect may not be sufficiently exhibited, and if it exceeds 10,000, the photocatalytic activity may be insufficient.

As the transition metal component contained in the titanium oxide particle dispersion, a plurality of molybdenum, tungsten, and vanadium can be selected, and the amount of each component can be selected from the above range. However, the molar ratio [Ti/(Mo+W+V)] between the total amount of each component and titanium is 10 or more and less than 10,000.

The titanium oxide particles in the titanium oxide particle dispersion containing an iron component and a silicon component have a volume-based 50% cumulative distribution diameter (hereinafter referred to as D _{50 )} measured by a dynamic light scattering method using laser light. ) is preferably 3 to 50 nm, more preferably 3 to 40 nm, even more preferably 3 to 30 nm. If D ₅₀ is less than 3 nm, the photocatalytic activity may become insufficient, and if it exceeds 50 nm, the dispersion may become opaque.

Further, the volume-based 90% cumulative distribution diameter (hereinafter sometimes referred to as D ₉₀ ) is preferably 5 to 100 nm, more preferably 5 to 80 nm. If D ₉₀ is less than 5 nm, the photocatalytic activity may become insufficient, and if it exceeds 100 nm, the dispersion may become opaque.
It is preferable that the titanium oxide particles of the present invention have D ₅₀ and D ₉₀ within the above-mentioned ranges, since this results in a dispersion having high photocatalytic activity and high transparency.
The devices for measuring the D ₅₀ and D ₉₀ of the titanium oxide particles in the titanium oxide particle dispersion include, for example, ELSZ-2000ZS (manufactured by Otsuka Electronics Co., Ltd.) and Nanotrack UPA-EX150 (manufactured by Nikkiso Co., Ltd.). (manufactured by Horiba, Ltd.), LA-910 (manufactured by Horiba, Ltd.), etc. can be used.

The concentration of titanium oxide particles in the titanium oxide particle dispersion is preferably 0.01 to 20% by mass, particularly preferably 0.5 to 10% by mass, from the viewpoint of ease of producing a photocatalytic thin film with a required thickness. .

Further, a binder may be added to the titanium oxide particle dispersion for the purpose of making it easier to apply the dispersion to the surfaces of various members described later and to make it easier to adhere the particles. Examples of the binder include metal compound binders containing silicon, aluminum, titanium, zirconium, etc., and organic resin binders containing fluorine resins, acrylic resins, urethane resins, and the like.

The mass ratio of the binder and titanium oxide [titanium oxide/binder] should be added in the range of 99 to 0.01, more preferably 9 to 0.1, and still more preferably 2.5 to 0.4. is preferred. This is because if the mass ratio exceeds 99, adhesion of the titanium oxide particles to the surfaces of various members may be insufficient, and if it is less than 0.01, the photocatalytic activity may become insufficient.

Among these, in order to obtain an excellent photocatalytic thin film with high photocatalytic activity and transparency, the silicon compound binder should be used at a mass ratio (titanium oxide/silicon compound binder) of 99 to 0.01, more preferably 9 to 0.1. , more preferably in the range of 2.5 to 0.4. Here, the silicon compound binder is a colloidal dispersion, solution, or emulsion of a silicon compound containing a solid or liquid silicon compound in an aqueous dispersion medium, and specifically, a silicon compound binder is a colloidal dispersion, solution, or emulsion of a silicon compound containing a solid or liquid silicon compound in an aqueous dispersion medium. (preferred particle size 1 to 150 nm); solutions of silicates such as silicates; emulsions of silane and siloxane hydrolysates; silicone resin emulsions; silicone resins such as silicone-acrylic resin copolymers, silicone-urethane resin copolymers, etc. Examples include emulsions of copolymers with resins.

<Method for producing titanium oxide particle dispersion>
The method for producing a titanium oxide particle dispersion of the present invention includes producing a titanium oxide particle dispersion and a solution or dispersion of an iron component and a silicon component, respectively, and manufacturing a titanium oxide particle dispersion and a solution or dispersion of an iron component and a silicon component. It is prepared by mixing with liquid.

As a method for producing a titanium oxide particle dispersion containing an iron component and a silicon component, specifically, a production method having the following steps (1) to (4) can be mentioned.
(1) A step of producing a peroxotitanic acid solution from a raw material titanium compound, a basic substance, hydrogen peroxide, and an aqueous dispersion medium.(2) A step of producing a peroxotitanic acid solution produced in step (1) above under pressure control. (3) Step of producing a solution or dispersion of iron components and silicon components from an iron compound, a silicon compound, and an aqueous dispersion medium (4) The above ( A step of mixing the titanium oxide particle dispersion produced in step 2) and the solution or dispersion of iron components and silicon components produced in step (3) to obtain a dispersion.

In addition, when dissolving a tin component and/or a transition metal component in titanium oxide particles, the tin component is added in the same manner except that the tin compound and/or transition metal compound is added to the raw material titanium compound in step (1) above. and/or a titanium oxide particle dispersion containing an iron component and a silicon component in which a transition metal component is dissolved can be obtained.
In addition, in order to further enhance the photocatalytic activity of the photocatalytic thin film, if the titanium oxide particle dispersion contains a transition metal component, the iron component, A titanium oxide particle dispersion containing a silicon component and a transition metal component can be obtained.

Steps (1) and (2) are steps for obtaining a titanium oxide particle dispersion, step (3) is a step for obtaining a solution or dispersion of an iron component and a silicon component, and step (4) is a step for obtaining a titanium oxide particle dispersion. and a step of obtaining a dispersion containing titanium oxide particles having silicon components attached to their surfaces.

・Process (1):
In step (1), a peroxotitanic acid solution is produced by reacting a raw material titanium compound, a basic substance, and hydrogen peroxide in an aqueous dispersion medium.
More specifically, a basic substance is added to the raw material titanium compound in an aqueous dispersion medium to form titanium hydroxide, impurity ions other than the contained metal ions are removed, and hydrogen peroxide is added to form a peroxotitanic acid solution. get.

When the tin component and/or the transition metal component are dissolved in solid solution, the tin compound and/or the transition metal compound are added in step (1).
The reaction method at this time may be any of the following methods i) to iii).

i) Add and dissolve a tin compound and a transition metal compound to the raw material titanium compound and basic substance in an aqueous dispersion medium, and then form titanium hydroxide containing a tin component and a transition metal component, excluding the metal ions contained. A method of removing impurity ions and adding hydrogen peroxide to obtain peroxotitanic acid containing a tin component and a transition metal component.

ii) A basic substance is added to the raw material titanium compound in an aqueous dispersion medium to form titanium hydroxide, and after removing impurity ions other than the contained metal ions, a tin compound and a transition metal compound are added, and then hydrogen peroxide is added. A method of producing peroxotitanic acid containing a tin component and a transition metal component by adding

iii) A basic substance is added to the raw material titanium compound in an aqueous dispersion medium to form titanium hydroxide, impurity ions other than the contained metal ions are removed, hydrogen peroxide is added to form peroxotitanic acid, and then a tin compound is formed. and a method of adding a transition metal compound to obtain peroxotitanic acid containing a tin component and a transition metal component.

In addition, in the first step of method i), "the raw material titanium compound and the basic substance in the aqueous dispersion medium" are replaced with "the aqueous dispersion medium in which the raw material titanium compound is dispersed" and "the aqueous dispersion medium in which the basic substance is dispersed". '', and dissolve each compound in either or both of the two liquids according to the solubility of each compound of the tin compound and the transition metal compound in the two liquids. After that, both may be mixed.

Here, raw material titanium compounds include, for example, inorganic acid salts of titanium such as chloride, nitrate, and sulfate; organic acid salts such as formic acid, citric acid, oxalic acid, lactic acid, and glycolic acid; and alkali added to an aqueous solution of these. Examples include titanium hydroxide precipitated by hydrolysis, and these may be used alone or in combination of two or more. Among these, it is preferable to use titanium chloride (TiCl ₃ , TiCl ₄ ).

As the tin compound, transition metal compound, and aqueous dispersion medium, those mentioned above are used so as to have the above-mentioned formulation. The concentration of the raw material titanium compound aqueous solution formed from the raw material titanium compound and the aqueous dispersion medium is preferably 60% by mass or less, particularly 30% by mass or less. Although the lower limit of the concentration is appropriately selected, it is usually preferably 1% by mass or more.

Basic substances are used to smoothly convert raw material titanium compounds into titanium hydroxide, such as alkali metal or alkaline earth metal hydroxides such as sodium hydroxide and potassium hydroxide, ammonia, alkanolamines, and alkyl hydroxides. Examples include amine compounds such as amines, among which it is particularly preferable to use ammonia, which is added in an amount such that the pH of the raw material titanium compound aqueous solution becomes 7 or more, particularly pH 7 to 10. Note that the basic substance may be used in an aqueous solution of an appropriate concentration together with the aqueous dispersion medium.

Hydrogen peroxide is used to convert the raw material titanium compound or titanium hydroxide into peroxotitanium, that is, a titanium oxide compound containing a Ti-O-O-Ti bond, and is usually used in the form of aqueous hydrogen peroxide. be done. The amount of hydrogen peroxide added is preferably 1.5 to 20 times the mole amount of Ti or the total amount of Ti, transition metals, and Sn. In addition, in the reaction of adding hydrogen peroxide to convert the raw material titanium compound or titanium hydroxide into peroxotitanic acid, the reaction temperature is preferably 5 to 80°C, and the reaction time is preferably 30 minutes to 24 hours. preferable.

The peroxotitanic acid solution obtained in this way may contain an alkaline substance or an acidic substance for pH adjustment and the like. Examples of alkaline substances include ammonia, sodium hydroxide, calcium hydroxide, alkyl amines, etc., and examples of acidic substances include sulfuric acid, nitric acid, hydrochloric acid, carbonic acid, phosphoric acid, hydrogen peroxide, etc. and organic acids such as formic acid, citric acid, oxalic acid, lactic acid, and glycolic acid. In this case, the pH of the obtained peroxotitanic acid solution is preferably 1 to 9, particularly 4 to 7, from the viewpoint of handling safety.

・Process (2):
In step (2), the peroxotitanic acid solution obtained in step (1) above is subjected to a hydrothermal reaction at a temperature of 80 to 250°C, preferably 100 to 250°C, for 0.01 to 24 hours under pressure control. provide A suitable reaction temperature is 80 to 250° C. from the viewpoint of reaction efficiency and controllability of the reaction, and as a result, peroxotitanic acid is converted into titanium oxide particles. Note that under pressure control here means that when the reaction temperature exceeds the boiling point of the dispersion medium, pressure is applied appropriately to maintain the reaction temperature. This includes cases in which the temperature is controlled at atmospheric pressure when the temperature is below the boiling point. The pressure used here is usually about 0.12 to 4.5 MPa, preferably about 0.15 to 4.5 MPa, and more preferably about 0.20 to 4.5 MPa. The reaction time is preferably 1 minute to 24 hours. Through this step (2), a titanium oxide particle dispersion is obtained.
The pH of the titanium oxide particle dispersion obtained in step (2) is preferably 8 to 14, more preferably 10 to 14. The titanium oxide particle dispersion obtained in this step (2) may contain an alkaline substance or an acidic substance in order to adjust the pH to the above-mentioned pH. is the same as the peroxotitanic acid solution obtained in step (1) above.

The particle diameters (D ₅₀ and D ₉₀ ) of the titanium oxide particles obtained here are preferably within the ranges described above, and the particle diameter can be controlled by adjusting the reaction conditions, for example, The particle size can be reduced by shortening the reaction time and temperature rise time.

・Process (3):
In step (3), separately from the above steps (1) and (2), a solution or dispersion of the iron component and silicon component is prepared by dissolving or dispersing the raw material iron compound and the raw material silicon compound in an aqueous dispersion medium. Manufacture.

The raw material iron compounds include the above-mentioned iron compounds, such as elemental iron metal (Fe), oxides (Fe ₂ O ₃ , Fe ₃ O ₄ ), and hydroxides (Fe(OH) ₂ , Fe(OH) _{3 )} . ), oxyhydroxides (FeO(OH)), chlorides (FeCl ₂ , FeCl ₃ ), nitrates (Fe(NO) ₃ ), sulfates (FeSO ₄ , Fe ₂ (SO ₄ ) ₃ ), halogens (Br , I) compounds, complex compounds, etc., and these may be used alone or in combination of two or more. Among them, oxides (Fe ₂ O ₃ , Fe ₃ O ₄ ), oxyhydroxides (FeO(OH)), chlorides (FeCl ₂ , FeCl ₃ ), nitrates (Fe(NO) ₃ ), sulfates ( It is preferable to use FeSO ₄ , Fe ₂ (SO ₄ ) ₃ ).
As the raw material silicon compound, the above-mentioned silicon compounds, such as metal elemental silicon (Si), oxide (SiO, SiO ₂ ), alkoxide (Si(OCH ₃ ) ₄ , Si(OC ₂ H ₅ ) ₄ , Si( OCH (CH ₃ ) ₂ ) ₄ ), silicates (sodium salts, potassium salts), and activated silicic acid obtained by removing ions such as sodium and potassium from these silicates, and one or two of these. The above may be used in combination. Among these, it is preferable to use silicates (sodium silicate) and activated silicic acid. Active silicic acid can be obtained, for example, by adding a cation exchange resin to an aqueous sodium silicate solution in which sodium silicate is dissolved in pure water to remove at least a portion of the sodium ions, and the resulting activated silicic acid solution It is preferable to add the cation exchange resin so that the pH is 2 to 10, preferably 2 to 7.

The iron component and silicon component-containing solution or dispersion obtained in this way may also contain an alkaline substance or an acidic substance for pH adjustment, etc. The alkaline substance, acidic substance, and pH adjustment mentioned here are the same as described above. can be handled.
The pH of the iron component and silicon component-containing solution or dispersion is preferably 1 to 7, more preferably 1 to 5.

The raw material iron compound concentration in the solution or dispersion of the iron component and silicon component produced in step (3) is preferably 0.001 to 10% by mass, more preferably 0.01 to 5% by mass, and the raw material silicon compound concentration is It is preferably 0.001 to 10% by weight, more preferably 0.01 to 5% by weight.

The solution or dispersion of the iron component and silicon component may further have a transition metal component (molybdenum, tungsten, vanadium) dissolved or dispersed therein.
Examples of the transition metal component include molybdenum, tungsten, and vanadium, and examples of the raw material compounds include those mentioned above.
When a transition metal component (molybdenum, tungsten, vanadium) is further dissolved or dispersed in the solution or dispersion of the iron component and silicon component produced in step (3), the amount added is appropriately selected depending on the type of the transition metal component. However, the molar ratio with titanium (Ti/transition metal) is preferably 10 to 10,000.
As the transition metal component added to the titanium oxide particles, a plurality of molybdenum, tungsten, and vanadium can be selected from among molybdenum, tungsten, and vanadium, and the amount of each component can be selected from the above range. However, the molar ratio [Ti/(Mo+W+V)] between the total amount of each component and titanium is 10 or more and less than 10,000.

・Process (4):
In step (4), the titanium oxide particle dispersion obtained in step (2) and the solution or dispersion of iron and silicon components obtained in step (3) are mixed. The mixing method is not particularly limited, and may be a method of stirring with a stirrer or a method of dispersing with an ultrasonic disperser. The temperature during mixing is 20 to 100°C, preferably 20 to 80°C, more preferably 20 to 40°C, and the time is preferably 1 minute to 3 hours. Regarding the mixing ratio, the molar ratios of Ti, Fe, and Si in the titanium oxide particle dispersion may be as described above.

The titanium oxide particle dispersion obtained in the above steps (1) to (4) may contain an alkaline substance or an acidic substance for pH adjustment, etc., and the above-mentioned ones may be used as the pH adjuster. can be used. Further, ion exchange treatment or filtration cleaning treatment may be performed to adjust the ionic component concentration, or solvent replacement treatment may be performed to change the solvent component.
The pH of the titanium oxide particle dispersion is preferably 7 to 14, more preferably 8 to 12.

The mass of the titanium oxide particles contained in the titanium oxide particle dispersion can be calculated from the mass and concentration of the titanium oxide particle dispersion. The concentration of the titanium oxide particle dispersion was measured by sampling a part of the titanium oxide particle dispersion, heating it at 105°C for 1 hour to volatilize the solvent, and then measuring the mass of the nonvolatile content (titanium oxide particles). From the mass of the sampled titanium oxide particle dispersion liquid, it can be calculated according to the following formula.
Concentration of titanium oxide particle dispersion (%) = [Non-volatile mass (g)/mass of titanium oxide particle dispersion (g)] x 100

As mentioned above, the total concentration of the iron component, the silicon component, and the titanium oxide particles in the titanium oxide particle dispersion prepared in this manner is 0.01 to 0.01 to facilitate the production of a photocatalytic thin film of the required thickness. 20% by weight is preferred, particularly 0.5-10% by weight. Regarding concentration adjustment, if the concentration is higher than the desired concentration, the concentration can be lowered by adding an aqueous solvent to dilute it, and if it is lower than the desired concentration, the aqueous solvent is evaporated or filtered. This can increase the concentration. Note that the concentration can be calculated as described above.

In addition, when adding the above-mentioned binder that improves film-forming properties, titanium oxide whose concentration has been adjusted as described above so that the desired concentration is obtained after mixing the above-mentioned binder solution (aqueous binder solution). It is preferable to add it to the particle dispersion.
The silicon component contained in the titanium oxide particle dispersion suppresses aggregation and precipitation of the titanium oxide particles and iron component, and suppresses the decline in photocatalytic activity. It is added. On the other hand, the binder improves the film-forming properties of the titanium oxide particle dispersion, and is added after the titanium oxide particle dispersion is prepared and before coating, and the two are different.

<Titanium oxide particles>
The titanium oxide particles of the present invention are characterized in that an iron component and a silicon component are attached to the surface. The iron component and the silicon component need only be attached to at least a portion of the surface of the titanium oxide particles, and may be attached to the entire surface. Furthermore, in addition to the iron component and the silicon component, the titanium oxide particles of the present invention may have at least one metal component selected from molybdenum, tungsten, and vanadium components adhered to the surface.

The method of adhering the iron component and silicon component to the surface of titanium oxide particles is not particularly limited, but methods include mixing in a solid state (mixing titanium oxide particle powder and powder consisting of iron and silicon components), liquid method. (mixing a titanium oxide particle dispersion with a solution or dispersion of an iron component and a silicon component); a method of mixing a solid and a liquid (a solution or dispersion of a titanium oxide particle powder with an iron component and a silicon component); Examples include mixing a liquid, or mixing a titanium oxide particle dispersion with a powder consisting of an iron component and a silicon component. Since the silicon component plays a role in suppressing agglomeration of the iron component, it is preferable to mix the iron component and the silicon component in advance and then mix them with the titanium oxide particles.
Among these, a method of mixing in a liquid state is preferred, and a method of steps (1) to (4) as in the above-mentioned method for producing a titanium oxide particle dispersion is more preferred.

At least a portion of the mixed iron component and silicon component may adhere to the surface of the titanium oxide particles, or all of the mixed iron component and silicon component may adhere to the surface of the titanium oxide particles. Furthermore, it is preferable that the iron component and the silicon component each directly adhere to the surface of the titanium oxide particles.

As a method for producing titanium oxide particles of the present invention, it is preferable to produce them from the above-mentioned titanium oxide particle dispersion.

<Photocatalytic thin film containing titanium oxide particles/member having a photocatalytic thin film on the surface>
The titanium oxide particle dispersion of the present invention can be used to form a photocatalytic film on the surfaces of various members. Here, the various members are not particularly limited, but examples of the material of the members include organic materials and inorganic materials. These can have various shapes depending on their respective purposes and uses.

Examples of organic materials include vinyl chloride resin (PVC), polyethylene (PE), polypropylene (PP), polycarbonate (PC), acrylic resin, polyacetal, fluororesin, silicone resin, and ethylene-vinyl acetate copolymer (EVA). , acrylonitrile-butadiene rubber (NBR), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyvinyl butyral (PVB), ethylene-vinyl alcohol copolymer (EVOH), polyimide resin, polyphenylene sulfide (PPS), polyether Synthetic resin materials such as imide (PEI), polyether ether imide (PEEI), polyether ether ketone (PEEK), melamine resin, phenol resin, acrylonitrile-butadiene-styrene (ABS) resin, natural materials such as natural rubber, or Semi-synthetic materials of the above-mentioned synthetic resin materials and natural materials can be mentioned. These may be manufactured into desired shapes and configurations such as films, sheets, fiber materials, textile products, other molded products, and laminates.

Examples of the inorganic material include non-metallic inorganic materials and metallic inorganic materials. Examples of nonmetallic inorganic materials include glass, ceramics, and stone. These may be manufactured into various shapes such as tiles, glass, mirrors, walls, and decorative materials. Examples of the metal inorganic material include cast iron, steel, iron, iron alloy, aluminum, aluminum alloy, nickel, nickel alloy, zinc die casting, and the like. These may be plated with the above metal inorganic material, may be coated with the above organic material, or may be plated on the surface of the above organic material or non-metal inorganic material.

The titanium oxide particle dispersion of the present invention is particularly useful among the above-mentioned various members for producing a transparent photocatalyst thin film on a polymer film such as PET.

As a method for forming photocatalytic thin films on the surfaces of various members, for example, a titanium oxide particle dispersion is applied to the surfaces of the above members by a known coating method such as spray coating or dip coating, and then far-infrared drying, IH drying, It may be dried by a known drying method such as hot air drying, and the thickness of the photocatalyst thin film can be selected from various values, but is usually preferably in the range of 10 nm to 10 μm.
As a result, the above-mentioned coating of titanium oxide particles is formed. In this case, if the dispersion liquid contains the binder in the amount described above, a film containing titanium oxide particles and the binder is formed.

The photocatalytic thin film formed in this way is transparent and exhibits good photocatalytic action, especially in light in the ultraviolet region (wavelength 10 to 400 nm), and various members on which the photocatalytic thin film is formed are free from oxidation. Since the photocatalytic action of titanium more quickly decomposes organic matter adsorbed on the surface, it can exhibit effects such as cleaning, deodorizing, and antibacterial effects on the surface of the member.

EXAMPLES Below, the present invention will be specifically explained with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples. Various measurements in the present invention were performed as follows.

(1) 50% and 90% cumulative distribution diameters (D ₅₀ and D ₉₀ ) of titanium oxide particles in the dispersion
The D ₅₀ and D ₉₀ of the titanium oxide particles in the dispersion were measured by a dynamic light scattering method using laser light using a particle size distribution analyzer (ELSZ-2000ZS (manufactured by Otsuka Electronics Co., Ltd.)). It was calculated as the 50% and 90% cumulative distribution diameter based on the volume.

(2) Acetaldehyde gas decomposition performance test of photocatalytic thin film The activity of the photocatalytic thin film produced by coating and drying a dispersion was evaluated by a decomposition reaction of acetaldehyde gas. The evaluation was performed using a batch-type gas decomposition performance evaluation method.
Each titanium oxide particle dispersion prepared in the examples or comparative examples was coated on one side of an A4 size (210 mm x 297 mm) PET film using a #7 wire bar coater so that the dry mass of titanium oxide particles was about 20 mg. A sample for evaluation was prepared by spreading it and dried in an oven set at 80° C. for 1 hour to obtain a sample for evaluation of acetaldehyde gas decomposition performance.
Using this evaluation sample, the photocatalytic activity of the titanium oxide particles was evaluated by a decomposition reaction of acetaldehyde gas. The evaluation was performed using a batch-type gas decomposition performance evaluation method.
Specifically, after placing an evaluation sample in a stainless steel cell with a quartz glass window and a volume of 5 L, the cell was filled with acetaldehyde gas at an initial concentration of 50% humidity, and a light source was placed above the cell. irradiated with light. When acetaldehyde gas is decomposed by the photocatalytic action of titanium oxide, the acetaldehyde gas concentration in the cell decreases. Therefore, the strength of photocatalytic activity can be confirmed by measuring the change in concentration. The photocatalytic activity was evaluated by measuring the time from the start of light irradiation until the acetaldehyde gas concentration became 1 ppm or less using a photoacoustic multi-gas monitor (trade name "INNOVA1412", manufactured by LumaSense). The shorter the time, the higher the photocatalytic activity, and the longer the time, the lower the photocatalytic activity.

In the photocatalytic activity evaluation under ultraviolet irradiation, a UV fluorescent lamp (product model number "FL10 BLB", Toshiba Lighting & Technology Co., Ltd.) was used as the light source, and ultraviolet rays were irradiated at an irradiance of 0.1 mW/ ^cm2 . . At this time, the initial concentration of acetaldehyde in the cell was 20 ppm.

(3) Identification of the crystalline phase of titanium oxide particles The crystalline phase of titanium oxide particles can be determined by powder X-ray diffraction analysis (product It was identified by measurement using a desktop X-ray diffractometer D2 PHASER (Bruker AXS, Inc.).

(4) Preparation of titanium oxide particle dispersion [Preparation Example 1-1]
<Preparation of titanium oxide particle dispersion>
After diluting a 36% by mass titanium (IV) chloride aqueous solution 10 times with pure water, a precipitate of titanium hydroxide was obtained by gradually adding 10% by mass ammonia water to neutralize and hydrolyze it. Ta. The pH at this time was 8.5. The obtained precipitate was deionized by repeating the addition of pure water and decantation. After this deionization treatment, 35% by mass hydrogen peroxide solution was added to the titanium hydroxide precipitate so that the H ₂ O ₂ /Ti (molar ratio) was 8, and then stirred at 60°C for 2 hours to thoroughly dissolve the titanium hydroxide precipitate. A transparent orange peroxotitanic acid solution (1a) was obtained.

400 mL of peroxotitanic acid solution (1a) was charged into an autoclave with a volume of 500 mL, and this was hydrothermally treated at 130° C. for 90 minutes. Thereafter, pure water was added to adjust the concentration to form titanium oxide particles ( 1A) was obtained (titanium oxide concentration: 1.2% by mass, pH: 11). When the titanium oxide particles (1A) were subjected to powder X-ray diffraction measurement, the only peak observed was that of anatase-type titanium oxide.

[Preparation example 1-2]
<Preparation of titanium oxide particle dispersion containing tin as a solid solution>
Tin (IV) chloride was added and dissolved in a 36% by mass titanium (IV) chloride aqueous solution so that the Ti/Sn (molar ratio) was 20, and after diluting this 10 times with pure water, 10% by mass was added. By gradually adding aqueous ammonia to neutralize and hydrolyze, a precipitate of titanium hydroxide containing tin was obtained. The pH at this time was 8. The obtained precipitate was deionized by repeating the addition of pure water and decantation. 35% by mass hydrogen peroxide was added so that the H ₂ O ₂ /(Ti+Sn) (molar ratio) was 10, and then stirred at 60°C for 2 hours to allow a sufficient reaction, resulting in an orange transparent tin-containing peroxotitanium. An acid solution (1b) was obtained.

Into an autoclave with a volume of 500 mL, 400 mL of tin-containing peroxotitanic acid solution (1b) was charged, and this was hydrothermally treated at 150°C for 90 minutes, and then pure water was added to adjust the concentration. A dispersion (titanium oxide concentration: 1.2% by mass, pH 10) of solid-dissolved titanium oxide particles (1B) was obtained. When the titanium oxide particles (1B) were subjected to powder X-ray diffraction measurement, the observed peak was only that of rutile-type titanium oxide, indicating that tin was solidly dissolved in titanium oxide.

[Preparation example 1-3]
<Preparation of titanium oxide particle dispersion containing molybdenum as a solid solution>
After diluting a 36% by mass titanium (IV) chloride aqueous solution 10 times with pure water, a precipitate of titanium hydroxide was obtained by gradually adding 10% by mass ammonia water to neutralize and hydrolyze it. Ta. The pH at this time was 8. The obtained precipitate was deionized by repeating the addition of pure water and decantation. Sodium molybdate (VI) was added to the deionized titanium hydroxide precipitate so that the Ti/Mo (molar ratio) was 250 with respect to the Ti component in the titanium (IV) chloride aqueous solution. 35% by mass hydrogen peroxide solution was added so that the H ₂ O ₂ /(Ti+Mo) (molar ratio) was 10, and then stirred at 60°C for 2 hours to fully react, resulting in orange transparent molybdenum-containing peroxotitanium. An acid solution (1c) was obtained.

Charge 400 mL of molybdenum-containing peroxotitanic acid solution (1c) into an autoclave with a volume of 500 mL, hydrothermally treat this at 150°C for 90 minutes, and then add pure water to adjust the concentration to remove molybdenum. A dispersion of solid-dissolved titanium oxide particles (1C) (titanium oxide concentration 1.2% by mass, pH 11) was obtained. When the titanium oxide particles (1C) were subjected to powder X-ray diffraction measurement, the only peak observed was that of anatase-type titanium oxide, indicating that molybdenum was dissolved in titanium oxide.

[Preparation example 1-4]
<Preparation of titanium oxide particle dispersion in which iron and silicon are dissolved>
Iron (III) chloride was added to a 36% by mass titanium (IV) chloride aqueous solution so that the Ti/Fe (molar ratio) was 20, and this was diluted 10 times with pure water. Neutralize by gradually adding 10% by mass ammonia water in which sodium silicate is added and dissolved so that the Ti/Si (molar ratio) is 7.5 with respect to the Ti component in the titanium (IV) chloride aqueous solution. , a precipitate of titanium hydroxide containing iron and silicon was obtained by hydrolysis. The pH at this time was 8. The obtained precipitate was deionized by repeating the addition of pure water and decantation. To this deionized titanium hydroxide precipitate containing iron and silicon, 35% by mass hydrogen peroxide solution was added so that H ₂ O ₂ /(Ti+Fe+Si) (molar ratio) was 15, and then 50% by mass was added. The mixture was stirred at .degree. C. for 2 hours to allow a sufficient reaction, and a transparent orange peroxotitanic acid solution (1d) containing iron and silicon was obtained.

Into an autoclave with a volume of 500 mL, 400 mL of iron and silicon-containing peroxotitanic acid solution (1d) was charged, and this was hydrothermally treated at 130 ° C. for 120 minutes, and then pure water was added to adjust the concentration. A dispersion of titanium oxide particles (1D) in which iron and silicon were dissolved (titanium oxide concentration 1.2% by mass, pH 11) was obtained. When the titanium oxide particles (1D) were subjected to powder X-ray diffraction measurement, the observed peaks were only those of anatase-type titanium oxide, indicating that iron and silicon were dissolved in titanium oxide.

Table 1 summarizes the raw material ratio, hydrothermal treatment conditions, and dispersed particle diameters (D ₅₀ , D ₉₀ ) of the titanium oxide particles prepared in each preparation example. The dispersed particle diameter was measured by a dynamic light scattering method using laser light (ELSZ-2000ZS (manufactured by Otsuka Electronics Co., Ltd.).

(5) Preparation of solution or dispersion of iron component and silicon component [Preparation Example 2-1]
<Preparation of aqueous solution of iron sulfate and activated silicic acid>
A strongly acidic cation exchange resin (Amber Jet 1024H, manufactured by Organo Co., Ltd.) was added to a sodium silicate aqueous solution obtained by dissolving 0.34 g of JIS No. 3 sodium silicate (29.1% by mass in terms of SiO ₂ ) in 100 g of pure water. After stirring, the ion exchange resin was filtered off to obtain an active silicic acid aqueous solution. By adding 0.13 g of ferric sulfate to this activated silicic acid aqueous solution, an aqueous solution (2A) of iron sulfate and activated silicic acid having a pH of 2.6 was obtained.

[Preparation example 2-2]
<Preparation of aqueous solution of iron sulfate and activated silicic acid>
After adding a strongly acidic cation exchange resin (Amber Jet 1024H, manufactured by Organo Co., Ltd.) to a sodium silicate aqueous solution obtained by dissolving 3.43 g of JIS No. 3 sodium silicate (SiO ₂ equivalent) in 100 g of pure water and stirring, An activated silicic acid aqueous solution was obtained by filtering off the ion exchange resin. By adding 0.50 g of ferric sulfate to this activated silicic acid aqueous solution, an aqueous solution (2B) of iron sulfate and activated silicic acid having a pH of 1.9 was obtained.

[Preparation example 2-3]
<Preparation of aqueous solution of iron sulfate and activated silicic acid>
After adding a strongly acidic cation exchange resin (Amber Jet 1024H, manufactured by Organo Co., Ltd.) to a sodium silicate aqueous solution obtained by dissolving 0.034 g of JIS No. 3 sodium silicate (SiO ₂ equivalent) in 100 g of pure water and stirring, An activated silicic acid aqueous solution was obtained by filtering off the ion exchange resin. By adding 0.025 g of ferric sulfate to this activated silicic acid aqueous solution, an aqueous solution (2C) of iron sulfate and activated silicic acid having a pH of 3.1 was obtained.

[Preparation example 2-4]
<Preparation of aqueous solution of iron sulfate, activated silicic acid, and molybdic acid>
By adding 0.34 g of sodium molybdate (VI) dihydrate to the aqueous solution of iron sulfate and activated silicic acid obtained in Preparation Example 2-1, an aqueous solution of iron sulfate, activated silicic acid, and molybdic acid with a pH of 2.5 is prepared. (2D) was obtained.

[Preparation example 2-5]
<Preparation of aqueous solution of iron sulfate, activated silicic acid, and tungstic acid>
By adding 0.071 g of sodium tungstate (VI) dihydrate to the aqueous solution of iron sulfate and activated silicic acid obtained in Preparation Example 2-1, an aqueous solution of iron sulfate, activated silicic acid, and tungstic acid with a pH of 2.6 is prepared. (2E) was obtained.

[Preparation example 2-6]
<Preparation of aqueous solution of iron sulfate, activated silicic acid, and vanadate>
By adding 0.020 g of sodium vanadate (V) to the aqueous solution of iron sulfate and activated silicic acid obtained in Preparation Example 2-1, an aqueous solution (2F) of iron sulfate, activated silicic acid, and vanadate with a pH of 2.6 was prepared. Obtained.

[Preparation example 2-7]
<Preparation of iron sulfate aqueous solution>
By adding 0.50 g of ferric sulfate to 100 g of pure water, an aqueous iron sulfate solution (2G) with a pH of 1.8 was obtained.

[Preparation example 2-8]
<Preparation of activated silicic acid aqueous solution>
An activated silicic acid aqueous solution (2H) having a pH of 3.8 was obtained in the same manner as in Preparation Example 2-1 except that the iron sulfate aqueous solution was not added.

(7) Preparation of titanium oxide particle dispersion [Example 1]
A dispersion of titanium oxide particles (1A) is mixed with an aqueous solution of iron sulfate and activated silicic acid (2A) using a stirrer at 25°C for 10 minutes so that the Ti/Fe ratio is 200 and the Ti/Si ratio is 75. The concentration was adjusted to 1% by mass with pure water to obtain a titanium oxide particle dispersion (E-1) with a pH of 10.

[Example 2]
An aqueous solution (2D) of iron sulfate, activated silicic acid, and molybdic acid was added to a dispersion of titanium oxide particles (1A) at 25°C for 10 minutes so that Ti/Fe was 200, Ti/Si was 75, and Ti/Mo was 90. After mixing with a stirrer, the solid content concentration was adjusted to 1% by mass with pure water to obtain a titanium oxide particle dispersion (E-2) with a pH of 10.

[Example 3]
An aqueous solution (2E) of iron sulfate, activated silicic acid, and tungstic acid was added to a dispersion of titanium oxide particles (1A) at 30°C for 10 minutes so that Ti/Fe was 200, Ti/Si was 75, and Ti/W was 360. After mixing with a stirrer, the solid content concentration was adjusted to 1% by mass with pure water to obtain a titanium oxide particle dispersion (E-3).

[Example 4]
An aqueous solution (2F) of iron sulfate, activated silicic acid, and vanadate was added to a dispersion of titanium oxide particles (1A) at 20°C so that Ti/Fe was 200, Ti/Si was 75, and Ti/V was 1,802. After mixing with a stirrer for 10 minutes, the solid content concentration was adjusted to 1% by mass with pure water to obtain a titanium oxide particle dispersion (E-4).

[Example 5]
After mixing a dispersion of titanium oxide particles (1B) with an aqueous solution of iron sulfate and activated silicic acid (2B) at 25°C for 10 minutes so that the Ti/Fe ratio is 50 and the Ti/Si ratio is 8 using a stirrer, a solid The concentration was adjusted to 1% by mass with pure water to obtain a titanium oxide particle dispersion (E-5).

[Example 6]
After mixing a dispersion of titanium oxide particles (1C) with an aqueous solution of iron sulfate and activated silicic acid (2C) using a stirrer at 25°C for 10 minutes so that Ti/Fe is 1,000 and Ti/Si is 752. The solid content concentration was adjusted to 1% by mass with pure water to obtain a titanium oxide particle dispersion (E-6).

[Example 7]
A silicon compound-based (silica-based) binder (colloidal silica, trade name: Snowtex 20, manufactured by Nissan Chemical Industries, Ltd.) was added to the titanium oxide particle dispersion (E-1) so that the TiO ₂ /SiO ₂ (mass ratio) was 1.5 and mixed with a stirrer at 25° C. for 10 minutes to obtain a titanium oxide particle dispersion (E-7) containing a binder.

[Comparative example 1]
The solid content concentration of the titanium oxide particle dispersion (1A) was adjusted to 1% by mass with pure water to obtain a titanium oxide particle dispersion (C-1).

[Comparative example 2]
The solid concentration of the titanium oxide particle dispersion (1B) was adjusted to 1% by mass with pure water to obtain a titanium oxide particle dispersion (C-2).

[Comparative example 3]
The solid concentration of the titanium oxide particle dispersion (1C) was adjusted to 1% by mass with pure water to obtain a titanium oxide particle dispersion (C-3).

[Comparative example 4]
After mixing an aqueous iron sulfate solution (2G) with a dispersion of titanium oxide particles (1A) so that the Ti/Fe ratio is 200, the solid content concentration is adjusted to 1% by mass with pure water to prepare a titanium oxide particle dispersion. (C-4) was obtained. The titanium oxide particles coagulated and precipitated by the addition of iron sulfate. In addition, when the titanium oxide particle dispersion (C-4) was filtered through a PP filter with a pore size of 1 μm, a brown iron component was filtered out on the filter, indicating that the iron component was also aggregated. .

[Comparative example 5]
After mixing an activated silicic acid aqueous solution (2H) into a dispersion of titanium oxide particles (1A) so that the Ti/Si ratio is 75, the solid content concentration is adjusted to 1% by mass with pure water to obtain a titanium oxide particle dispersion. (C-5) was obtained.

[Comparative example 6]
After mixing a dispersion of titanium oxide particles (1D) in which iron and silicon components are dissolved in a dispersion of titanium oxide particles (1A) so that Ti/Fe is 200 and Ti/Si is 75, the solid content is The concentration was adjusted to 1% by mass with pure water to obtain a titanium oxide particle dispersion (C-6).

[Comparative Example 7]
A silicon compound-based (silica-based) binder (colloidal silica, trade name: Snowtex 20, manufactured by Nissan Chemical Industries, Ltd.) was added to the titanium oxide particle dispersion (C-1) at TiO ₂ /SiO ₂ (mass ratio). By adding and mixing so that the ratio was 1.5, a titanium oxide particle dispersion (C-7) containing a binder was obtained.

(8) Preparation of a sample member having a photocatalyst thin film Each titanium oxide particle dispersion prepared in the above Examples or Comparative Examples was coated on an A4 size PET film using a #7 wire bar coater. It was coated to form a thin film (about 80 nm thick) and dried in an oven set at 80° C. for 1 hour to obtain a sample member for evaluating acetaldehyde gas decomposition performance.

[Photocatalyst performance test under UV irradiation]
An acetaldehyde decomposition test was conducted on sample members having photocatalytic thin films of Examples and Comparative Examples under UV fluorescent lamp irradiation. Evaluation was made based on the time required to reduce the initial concentration of acetaldehyde from 20 ppm to 1 ppm.

Table 2 summarizes the types of titanium oxide particles and added metals, the molar ratio of the metal in the added metal component to Ti in titanium oxide, the dispersed particle diameter (D ₅₀ , D ₉₀ ), and the results of an acetaldehyde gas decomposition test. The dispersed particle diameter was measured by a dynamic light scattering method using laser light (ELSZ-2000ZS (manufactured by Otsuka Electronics Co., Ltd.).

As can be seen from the results of Examples 1, 5, and 6 and Comparative Examples 1, 2, and 3, titanium oxide particles were produced from a dispersion of titanium oxide particles containing an iron component and a silicon component, and the oxide particles had the iron component and silicon component attached to the surface. It was found that titanium particles have improved photocatalytic activity compared to the photocatalytic activity of titanium oxide particles alone.
Similarly, from the results of Example 7 and Comparative Example 7, it was found that the photocatalyst thin film containing a binder was also produced from a dispersion of titanium oxide particles containing iron and silicon components, and the oxidation film with the iron and silicon components attached to the surface It was found that titanium particles have improved photocatalytic activity compared to the photocatalytic activity of titanium oxide particles alone.

As can be seen from the results of Example 1 and Comparative Example 4, when adding the iron component to the dispersion of titanium oxide particles (1A), adding it together with the silicon component suppresses aggregation and precipitation of the titanium oxide particles and iron component. I found out that it can be done.

As can be seen from the results of Example 1 and Comparative Examples 1 and 5, by adding both an iron component and a silicon component to the titanium oxide particles (1A), it is possible to improve It was found that the photocatalytic activity was high.

As can be seen from the results of Example 1 and Comparative Example 6, by using titanium oxide particles (1A) with iron components and silicon components (2A) attached to the surface, oxidation with solid solution of iron components and silicon components It was found that the photocatalytic activity was higher than when titanium particles (1D) were mixed with titanium oxide particles (1A).

The titanium oxide particle dispersion of the present invention is useful for producing photocatalytic thin films by applying it to various substrates made of inorganic substances such as glass and metals, and organic substances such as resins. It is useful for producing transparent photocatalytic thin films on materials.

Claims (8)

A titanium oxide particle dispersion liquid in which titanium oxide particles having an iron component and a silicon component attached to the surface are dispersed in an aqueous dispersion medium,
The titanium oxide particles have a volume-based 50% cumulative distribution diameter D ₅₀ of 3 to 50 nm, as measured by a dynamic light scattering method using laser light;
The titanium oxide particles further have at least one metal component selected from molybdenum, tungsten, and vanadium components attached to the surface,
The titanium oxide particles do not contain nitrogen.
Titanium oxide particle dispersion . The oxidation according to claim 1, wherein the molar ratio of the iron component to titanium (Ti/Fe) is 10 to 10,000, and the molar ratio of the silicon component to titanium (Ti/Si) is 1 to 10,000. Titanium particle dispersion liquid . The titanium oxide particle dispersion according to claim 1 or 2, wherein the molar ratio (Ti/metal) of at least one metal component selected from molybdenum, tungsten, and vanadium components to titanium is 10 to 10,000. The titanium oxide particle dispersion according to any one of claims 1 to 3, further comprising a binder. The titanium oxide particle dispersion according to claim 4 , wherein the binder is a silicon compound-based binder. A photocatalytic thin film formed from the titanium oxide particle dispersion according to any one of claims 1 to 5 . A member having the photocatalytic thin film according to claim 6 formed on the surface of a base material. The method for producing a titanium oxide particle dispersion according to any one of claims 1 to 3, comprising the following steps (1) to (4).
(1) Step of producing peroxotitanic acid solution from raw material titanium compound, basic substance, hydrogen peroxide and aqueous dispersion medium. (2) Step of producing peroxotitanic acid solution produced in step (1) above under pressure control. , heating at 80 to 250° C. to obtain a titanium oxide particle dispersion (3) At least one metal component selected from iron compounds, silicon compounds, molybdenum, tungsten, and vanadium components and an aqueous dispersion medium, an iron component , A step of producing a solution or dispersion of a silicon component and at least one metal component selected from molybdenum, tungsten, and vanadium components. (4) The titanium oxide particle dispersion produced in step (2) above, and the step of (3). A step of mixing a solution or dispersion of an iron component , a silicon component , and at least one metal component selected from molybdenum, tungsten, and vanadium components produced in the process to obtain a dispersion.