Metatitanic acid particles and method for producing the same, composition for forming photocatalyst, photocatalyst and structure

0001The present invention relates to metatitanic acid particles and a method for producing the same, a composition for forming a photocatalyst, a photocatalyst, and a structure.

0002Titanium oxide particles are known to be used as a photocatalyst. For example, Patent Document 1 states, "In the infrared absorption spectrum, 650 to 990 cm.^-1A decomposition method for decomposing an object by a titanium-silicon chemical bond composite oxide having an absorption peak of, containing titanium, silicon and oxygen and chemically bonding these is disclosed.

0003Further, Patent Document 2 discloses "a nitrogen-introduced silica-modified titania photocatalyst in which nitrogen is further introduced into silica-modified titania in which Si is inserted into a tetrahedral hole in a titania crystal lattice having an anatas-type crystal structure". ing.

0004Further, Patent Document 3 discloses "a composite photocatalyst in which amorphous silica is supported on crystalline titanium". Further, in Patent Document 4, "Titanium butoxyto is mixed in an aqueous solution of an organic solvent, heated to 150 to 220 ° C. to hydrolyze the titanium butoxyto, and this is dried to obtain an intermediate product. A method for producing a photocatalyst including one step, a second step of calcining the intermediate product at 150 to 300 ° C. "is disclosed.

0005Further, Patent Documents 5 to 9 disclose "a method of coating titanium oxide with silica or the like". Further, Patent Document 10 states that "titanium oxide fine particles are dispersed in an alkaline aqueous solution, and trialkoxysilane is added to the dispersion at a ratio of 1 to 1000 parts by weight per 100 parts by weight of titanium oxide fine particles for hydrolysis. A method for producing hydrophobic titanium oxide fine particles for forming a film of a trialkoxysilane hydrolysis-condensation product on the surface of titanium oxide fine particles is disclosed.

<p num="0006"><patcit num="1"><text>Japanese Unexamined Patent Publication No. 2008-212841</text></patcit><patcit num="2"><text>Japanese Unexamined Patent Publication No. 2006-21112</text></patcit><patcit num="3"><text>Japanese Unexamined Patent Publication No. 2014-188417</text></patcit><patcit num="4"><text>Japanese Unexamined Patent Publication No. 2014-128768</text></patcit><patcit num="5"><text>Japanese Unexamined Patent Publication No. 2013-249229</text></patcit><patcit num="6"><text>Japanese Unexamined Patent Publication No. 2004-115541</text></patcit><patcit num="7"><text>Japanese Unexamined Patent Publication No. 2001-269573</text></patcit><patcit num="8"><text>JP-A-2007-16111</text></patcit><patcit num="9"><text>Japanese Unexamined Patent Publication No. 2010-6629</text></patcit><patcit num="10"><text>Japanese Patent Application Laid-Open No. 5-221640</text></patcit></p>

<p num="0007"> The problem to be solved by the present invention is that the elemental ratio C / Ti of carbon C to titanium on the surface of metatitanium particles surface-treated with a metal-containing compound having a hydrocarbon group is less than 0.3 or more than 1.2, and metatitanium acid. Wave diameter 352 nm with respect to the surface of the particle, irradiation intensity 1.3 mW / cm²Compared to the case where the amount of decrease in C / Ti on the surface of metatitanic acid particles before and after irradiation with ultraviolet rays of 20 hours is less than 0.1 or more than 0.9, the particle dispersibility is excellent and the high photocatalytic function is exhibited even in the visible light region. It is to provide metatitanic acid particles.</p>

<p num="0008"> The above problem is solved by the following means.</p><p num="0009"> The invention according to claim 1 is Surface treated with a metal-containing compound having a hydrocarbon group, Has absorption at wavelengths of 450 nm and 750 nm The elemental ratio C / Ti of carbon C and titanium Ti on the surface is 0.3 or more and 1.2 or less. Wavelength 352 nm and irradiation intensity 1.3 mW / cm for metatitanic acid particles²The amount of decrease in C / Ti on the surface of the metatitanium acid particles when irradiated with the ultraviolet rays of the above for 20 hours is 0.1 or more and 0.9 or less. Metatitanic acid particles. The invention according to claim 2 is The metatitanic acid particles according to claim 1, which have absorption in the entire range of wavelengths of 400 nm or more and 800 nm or less in the visible absorption spectrum.</p><p num="0010"> The invention according to claim 3 is The metatitanic acid particles according to claim 1 or 2, wherein the metal of the metal-containing compound is silicon.</p><p num="0011"> The invention according to claim 4 is The metal-containing compound having a hydrocarbon group has a general formula: R.¹_nMR²_m(R¹Indicates a saturated or unsaturated aliphatic hydrocarbon group or aromatic hydrocarbon group having 1 to 20 carbon atoms, and R²Indicates a halogen atom or an alkoxy group, n indicates an integer of 1 or more and 3 or less, and m indicates an integer of 1 or more and 3 or less. However, n + m = 4. Also, if n indicates an integer of 2 or 3, then multiple Rs¹May indicate the same group or may indicate different groups. Multiple Rs if m represents an integer of 2 or 3²May indicate the same group or may indicate different groups. ) Is the metatitanic acid particle according to any one of claims 1 to 3.</p><p num="0012"> The invention according to claim 5 The metatitanic acid particles according to any one of claims 1 to 4, wherein the hydrocarbon group is a saturated aliphatic hydrocarbon group.</p><p num="0013"> The invention according to claim 6 is The metatitanic acid particles according to claim 5, wherein the saturated aliphatic hydrocarbon group has 4 or more and 10 or less carbon atoms.</p><p num="0014"> The invention according to claim 7 The metatitanic acid particles according to any one of claims 1 to 6, wherein the volume average particle diameter of the metatitanic acid particles is 10 nm or more and 1 μm or less.</p><p num="0015"> The invention according to claim 8 is It includes a step of surface-treating untreated metatitanic acid particles with a metal-containing compound having a hydrocarbon group, and a step of heat-treating the meta-titanic acid particles during or after the step of surface-treating the untreated metatitanic acid particles. The method for producing metatitanic acid particles according to any one of claims 1 to 7.</p><p num="0016"> The invention according to claim 9 is A composition for forming a photocatalyst, which comprises the metatitanic acid particles according to any one of claims 1 to 7, and at least one compound selected from the group consisting of a dispersion medium and a binder.</p><p num="0017"> The invention according to claim 10 A photocatalyst containing or comprising the metatitanic acid particles according to any one of claims 1 to 7.</p><p num="0018"> The invention according to claim 11 The structure having the metatitanic acid particles according to any one of claims 1 to 7.</p>

<p num="0019"> According to the invention of claim 1 or 2, the C / Ti on the surface of the metatitanic acid particles surface-treated with the metal-containing compound having a hydrocarbon group is less than 0.3 or more than 1.2, the wavelength to the surface is 352 nm, and the irradiation intensity is 1.3. mW / cm²Compared to the case where the decrease in the C / Ti element ratio on the surface of the metatitanic acid particles before and after irradiation with ultraviolet rays for 20 hours is less than 0.1 or more than 0.9, the particle dispersibility is excellent and the photocatalytic function is high even in the visible light region. The metatitanic acid particles to be expressed are provided. According to the third aspect of the present invention, there is provided metatitanic acid particles which are excellent in particle dispersibility and exhibit high photocatalytic function even in the visible light region as compared with the case where the metal of the metal-containing compound is other than silicon. According to the invention of claim 4, there is provided metatitanic acid particles which are excellent in particle dispersibility and exhibit higher photocatalytic function even in the visible light region as compared with the case where the metal-containing compound is hexamethyldisilazane. .. According to the invention of claim 5, there is provided metatitanic acid particles which are excellent in particle dispersibility and exhibit higher photocatalytic function even in the visible light region as compared with the case where the hydrocarbon group is an aromatic hydrocarbon group. To. According to the invention of claim 6, the particle dispersibility is excellent and the photocatalyst is higher even in the visible light region as compared with the case where the metal-containing compound has a saturated aliphatic hydrocarbon group having 3 or less or 11 or more carbon atoms. Metatitanic acid particles that exhibit their function are provided. According to the invention of claim 7, the metatitanic acid particles exhibit excellent particle dispersibility and higher photocatalytic function even in the visible light region as compared with the case where the volume average particle size of the metatitanic acid particles is less than 10 nm or more than 1 μm. Is provided.</p><p num="0020"> According to the invention of claim 8, the C / Ti on the surface of the metatitanic acid particles surface-treated with the metal-containing compound having a hydrocarbon group is less than 0.3 or more than 1.2, the wavelength to the surface is 352 nm, and the irradiation intensity is 1.3 mW /. cm²Compared to the case where the amount of decrease in the C / Ti element ratio on the surface of the metatitanium acid particles before and after irradiation with ultraviolet rays for 20 hours is less than 0.1 or more than 0.9, the particle dispersibility is excellent and the photocatalytic function is high even in the visible light region. A method for producing the expressed metatitanic acid particles is provided. According to the invention of claim 9, 10 or 11, the C / Ti on the surface of the metatitanic acid particles surface-treated with the metal-containing compound having a hydrocarbon group is less than 0.3 or more than 1.2, and the surface is irradiated with a wavelength of 352 nm. Strength 1.3mW / cm²Compared to the case where the amount of decrease in C / Ti on the surface of metatitanic particles before and after irradiation with ultraviolet rays for 20 hours is less than 0.1 or more than 0.9, the particle dispersibility is excellent and a high photocatalytic function is exhibited even in the visible light region. A composition for forming a photocatalyst, a photocatalyst, or a structure is provided.</p>

0021Hereinafter, embodiments that are an example of the present invention will be described.

0022&lt;Metatitanic acid particles&gt; The metatitanium acid particles according to the present embodiment are surface-treated with a metal-containing compound having a hydrocarbon group, have absorption at wavelengths of 450 nm and 750 nm, and have an element ratio C / Ti of carbon C and titanium Ti on the surface of 0.3 or more and 1.2. The wavelength is 352 nm and the irradiation intensity is 1.3 mW / cm for the hydrocarbon particles.²The amount of decrease in C / Ti on the surface of the metatitanium acid particles when irradiated with the ultraviolet rays of the above for 20 hours is 0.1 or more and 0.9 or less. The metatitanic acid particles according to this embodiment are preferably used as a photocatalyst.

0023The metatitanic acid particles according to the present embodiment exhibit a high photocatalytic function even in the visible light region due to the above configuration. The reason for this is presumed as follows.

0024First, usually, untreated titanium oxide particles as a photocatalyst exert a photocatalytic function (photocatalytic activity) by absorbing ultraviolet light. For this reason, the untreated titanium oxide particles exhibit a photocatalytic function during the daytime on a sunny day when sufficient ultraviolet light can be secured, but cannot exhibit a sufficient function at night or in the shade. For example, when untreated titanium oxide particles are used as the outer wall material, the stain resistance performance tends to decrease in the sun and shade. Further, when untreated titanium oxide particles are used in an air purifier or a water purifier, an installation space may be required such as installing a black light or the like as a light source of ultraviolet rays inside the equipment.

0025In recent years, titanium oxide particles that exhibit a photocatalytic function (photocatalytic activity) by absorbing visible light are also known. For example, such visible light absorption type titanium oxide particles include titanium oxide particles in which dissimilar metals (iron, copper, tungsten, etc.) are adhered to titanium oxide, titanium oxide particles doped with nitrogen element, sulfur element, etc. It has been known. On the other hand, when the photocatalyst function is enhanced, there are problems such as decomposition of a binder such as an organic resin for immobilizing the photocatalyst material on the surface of the base material and deterioration of the base material itself.

0026Moreover, since most of the titanium oxide-based photocatalytic materials known so far are hydrophilic, they tend to have a low affinity with the organic / inorganic binder used for immobilizing the material, and the particles agglomerate. It was easy to do, and problems such as deterioration of photocatalytic performance and desorption from the binder were likely to occur. To solve this problem, there is a method of treating the surface of the material with a surface treatment agent or the like. Although this method improves particle agglutination and dispersibility in the binder, the surface treatment agent covers the surface of the photocatalytic material to provide photocatalytic performance. Was sometimes reduced. Therefore, there is a demand for metatitanic acid particles that exhibit a high photocatalytic function even in the visible light region, have low particle cohesiveness, and have good dispersibility in a binder.

0027On the other hand, metatitanic particles were surface-treated with a metal-containing compound having a hydrocarbon group, and these metatitanic particles had absorption at wavelengths of 450 nm and 750 nm in the visible absorption spectrum, and the element ratio C of carbon and titanium on the surface was C. / Ti is 0.3 or more and 1.2 or less, the wavelength is 352 nm, and the irradiation intensity is 1.3 mW / cm with respect to the metatitanic acid particles.²The amount of decrease in C / Ti on the surface of the metatitanium acid particles before and after the irradiation with the ultraviolet rays is 0.1 or more and 0.9 or less when the ultraviolet rays are irradiated for 20 hours.

0028The metatitanic acid particles satisfying the above numerical range of C / Ti on the particle surface have an appropriate C / Ti as compared with ordinary metatitanic acid particles surface-treated with a metal-containing compound having a hydrocarbon group or untreated metatitanic acid particles. Is shown. When the C / Ti on the surface of the metatitanic acid particles is 0.3 or more and 1.2 or less, the amount of carbon such as hydrocarbon groups on the surface of the metatitanic acid particles is appropriate, and it has sufficient absorption at wavelengths of 450 nm and 750 nm, and is in the visible light region. High photocatalytic function is exhibited in. Further, due to the appropriate amount of carbon such as hydrocarbon groups on the surface of the metatitanic acid particles, the particle cohesiveness is small and the dispersibility in the binder is improved. If the C / Ti is less than 0.3, the amount of carbon on the surface of the metatitanium acid particles is small, so that sufficient absorption cannot be obtained at wavelengths of 450 nm and 750 nm, the photocatalytic function in the visible light region is inferior, and particle cohesiveness and binder are used. Poor dispersibility in. Further, when the C / Ti element ratio exceeds 1.2, the amount of hydrocarbon groups on the surface of the metatitanic acid particles is large, so that the amount of exposure of the active portion of metatitanic acid on the surface of the metatitanic acid particles is reduced, and the photocatalyst in the visible light region is reduced. Inferior in function.

0029The metatitanic acid particles satisfying the amount of decrease in C / Ti before and after irradiation with ultraviolet rays have a decrease in C / Ti as compared with ordinary metatitanic acid particles surface-treated with a metal-containing compound having a hydrocarbon group or untreated metatitanium acid particles. The amount shows a large value. Wavelength 352 nm and irradiation intensity 1.3 mW / cm for metatitanic acid particles²When the amount of decrease in C / Ti on the surface of the metatitanic acid particles before and after the irradiation with the ultraviolet rays is 0.1 or more and 0.9 or less, carbon such as hydrocarbon groups on the surface of the metatitanic acid particles is obtained. The amount and the amount of carbon carbonized by hydrocarbons (carbon) are appropriate, and it has sufficient absorption at wavelengths of 450 nm and 750 nm, and exhibits a high photocatalytic function in the visible light region. Further, the hydrocarbon groups on the surface of the metatitanic acid particles are appropriately decomposed by the photocatalytic activity of the metatitanic acid particles to suppress the deterioration of the binder and the base material. When the amount of decrease in C / Ti exceeds 0.9, carbon such as hydrocarbon groups on the surface of metatitanic particles and carbon carbonized by hydrocarbons are decomposed by photocatalytic activity and easily separated from metatitanic particles, so that they are visible. The photocatalytic function in the optical region tends to deteriorate. Further, when the amount of decrease in C / Ti is less than 0.1, the amount of carbon on the surface of the metatitanium acid particles is small, so that sufficient absorption cannot be obtained at wavelengths of 450 nm and 750 nm, and the photocatalytic function in the visible light region is inferior. In addition, since the decomposition of hydrocarbon groups and the like on the surface of the metatitanic acid particles is small, the function of suppressing deterioration of the binder and the base material is reduced.

0030Further, the metatitanic acid particles satisfying the above numerical range of the amount of decrease in C / Ti and C / Ti before and after irradiation with ultraviolet rays on the surface of the particles are, for example, metatitanic acid particles surface-treated with a metal-containing compound having a hydrocarbon group. It is produced by oxidatively decomposing some hydrocarbon groups by treatment such as heating. In such metatitanic acid particles, hydrocarbons and carbon in which hydrocarbons are carbonized are present inside the pores of the metatitanic acid particles, that is, hydrocarbons and hydrocarbons are carbonized from the surface layer to the inside of the metatitanic acid particles. It is considered that carbon is incorporated. On the other hand, the incorporated carbon has light absorption of visible light together with ultraviolet light, and is considered to function as a charge separating substance and a co-catalyst.

0031That is, the carbon existing inside the pores of the metatitanic acid particles promotes the excitation of electrons on the surface of the metatitanic acid particles by absorbing visible light together with ultraviolet light, and the probability that the excited electrons and holes are recombined. Is lowered, and it is considered that the photocatalytic function is improved.

0032Further, in general, untreated metatitanic acid particles have a low degree of freedom in controlling the particle size, particle size distribution, and particle shape, and tend to have high particle cohesiveness. For this reason, the dispersibility of the metatitanic acid particles in the resin and the liquid is poor, 1) it is difficult to exert the photocatalytic function, 2) the transparency of the film and the like, and the uniformity of the coating film of the coating liquid tend to decrease. There is. However, since the metatitanic acid particles according to the present embodiment have a hydrocarbon group derived from a metal-containing compound on the surface, the dispersibility of the primary particles in the coating film is also ensured. Therefore, a nearly uniform coating film can be formed, the metatitanic acid particles are efficiently exposed to light, and the photocatalytic function is easily exhibited. In addition, the transparency of the film and the like and the uniformity of the coating film of the coating liquid are enhanced, and the design is maintained. As a result, for example, when a paint containing metatitanic acid particles is applied to the surface of an outer wall material, a plate, a pipe, or a non-woven fabric (nonwoven fabric such as ceramic), aggregation of metatitanic acid particles and coating defects are suppressed, and for a long period of time. The photocatalytic function is easily exhibited.

0033From the above, it is presumed that the metatitanic acid particles according to the present embodiment have excellent particle dispersibility and exhibit a high photocatalytic function even in the visible light region due to the above configuration.

0034Hereinafter, the details of the metatitanic acid particles according to the present embodiment will be described.

0035(Untreated metatitanic acid particles) The untreated metatitanate particles (metatitanate particles to be surface-treated) are titanium acid hydrate TiO.₂. NH₂Of O, the particles of titanium acid with n = 1. Needless to say, the untreated metatitanic acid particles in the present embodiment are metatitanic acid particles that have not been surface-treated with a metal-containing compound having a hydrocarbon group, and do not exclude other surface treatments. The metatitanic acid particles according to the embodiment are preferably metatitanic acid particles surface-treated only with a metal-containing compound having a hydrocarbon group.

0036The method for producing the untreated metatitanic acid particles is not particularly limited, and examples thereof include a chlorine method (gas phase method) and a sulfuric acid method (liquid phase method).

0037An example of the chlorine method (gas phase method) is as follows. First, rutile ore, which is a raw material, is reacted with coke and chlorine to form gaseous titanium tetrachloride, and then cooled to obtain liquid titanium tetrachloride. Next, by dissolving titanium tetrachloride in water and hydrolyzing it while adding a strong base, untreated metatitanium acid [titanium oxyhydroxide (TiO (OH))₂)] Particles are obtained. An example of the sulfuric acid method (liquid phase method) is as follows. First, the raw material ilmenite ore (FeTiO)₃) Or titanium slag is dissolved in concentrated sulfuric acid, and the iron component, which is an impurity, is iron sulfate (FeSO).₄), And once, titanium oxysulfate (TiOSO)₄) (Titanyl sulfate solution). Next, titanium oxysulfate (TiOSO₄) Is hydrolyzed to untreated metatitanium acid [titanium oxyhydroxide (TiO (OH)).₂)] Particles are obtained.

0038(Metal-containing compound) The metal-containing compound in this embodiment has a hydrocarbon group. The hydrocarbon group contained in the metal-containing compound is saturated or saturated with 1 or more and 20 or less carbon atoms (preferably 1 or more and 18 or less carbon atoms, more preferably 4 or more and 12 or less carbon atoms, and further preferably 4 or more and 10 or less carbon atoms). Examples thereof include unsaturated aliphatic hydrocarbon groups and aromatic hydrocarbon groups. Further, the hydrocarbon group may or may not be directly bonded to the metal in the metal-containing compound, but is directly bonded from the viewpoint of exhibiting a high photocatalytic function and improving dispersibility. Is preferable.

0039The metal atom of the metal-containing compound having a hydrocarbon group is preferably a metal atom selected from the group consisting of Si, Ti and Al, and Si is particularly preferable. That is, as the metal-containing compound having a hydrocarbon group, a silane compound having a hydrocarbon group is particularly preferable. Examples of the silane compound include chlorosilane compounds, alkoxysilane compounds, and silazane compounds (hexamethyldisilazane and the like).

0040Among these, the general formula: R is used as a silane compound from the viewpoint of exhibiting a high photocatalytic function and improving dispersibility.¹_nSiR²_mThe compound represented by is preferable. General formula: R¹_nSiR²_mIn R¹Indicates a saturated or unsaturated aliphatic hydrocarbon group or aromatic hydrocarbon group having 1 to 20 carbon atoms, and R²Indicates a halogen atom or an alkoxy group, n indicates an integer of 1 or more and 3 or less, and m indicates an integer of 1 or more and 3 or less. However, n + m = 4. Also, if n indicates an integer of 2 or 3, then multiple Rs¹May indicate the same group or may indicate different groups. Multiple Rs if m represents an integer of 2 or 3²May indicate the same group or may indicate different groups.

0041R¹The aliphatic hydrocarbon group indicated by may be linear, branched chain or cyclic, but from the viewpoint of dispersibility, linear or branched chain is preferable, and linear is more preferable. The carbon number of the aliphatic hydrocarbon group is preferably 1 or more and 18 or less, more preferably 4 or more and 12 or less, and 4 or more and 10 or less carbons, from the viewpoint of expressing a high photocatalytic function and improving dispersibility. More preferred. The aliphatic hydrocarbon group may be either saturated or unsaturated aliphatic hydrocarbon group, but from the viewpoint of exhibiting high photocatalytic function and improving dispersibility, saturated aliphatic hydrocarbon group is preferable, and alkyl group is more preferable. preferable.

0042Saturated aliphatic hydrocarbon groups include linear alkyl groups (methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, dodecyl group and hexadecyl group. , Icosyl group, etc.), branched alkyl group (isopropyl group, isobutyl group, isopentyl group, neopentyl group, 2-ethylhexyl group, tertiary butyl group, tertiary pentyl group, isopentadecyl group, etc.), cyclic alkyl group ( Cyclopropyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group, tricyclodecyl group, norbornyl group, adamantyl group, etc.) and the like. As the unsaturated aliphatic hydrocarbon group, an alkenyl group (vinyl group (ethenyl group), 1-propenyl group, 2-propenyl group, 2-butenyl group, 1-butenyl group, 1-hexenyl group, 2-dodecenyl group, (Pentenyl group, etc.), alkynyl group (ethynyl group, 1-propynyl group, 2-propynyl group, 1-butynyl group, 3-hexynyl group, 2-dodecynyl group, etc.) and the like. Aliphatic hydrocarbon groups also include substituted aliphatic hydrocarbon groups. Examples of the substituent that can be substituted with the aliphatic hydrocarbon group include an epoxy group, a mercapto group, a methacryloyl group, an acryloyl group and the like.

0043R¹Examples of the aromatic hydrocarbon group shown in the above include aromatic hydrocarbon groups having 6 or more and 27 or less carbon atoms (preferably 6 or more and 18 or less). Examples of the aromatic hydrocarbon group include a phenylene group, a biphenylene group, a terphenylene group, a naphthalene group, an anthracene group and the like. Aromatic hydrocarbon groups also include substituted aromatic hydrocarbon groups. Examples of the substituent that can be substituted with the aromatic hydrocarbon group include an epoxy group, a glycidyl group, a mercapto group, a methacryloyl group, an acryloyl group and the like.

0044R²Examples of the halogen atom indicated by are fluorine atom, chlorine atom, bromine atom, iodine atom and the like. Among these, as the halogen atom, a chlorine atom, a bromine atom, or an iodine atom is preferable.

0045R²Examples of the alkoxy group indicated by the above include alkoxy groups having 1 or more and 10 or less carbon atoms (preferably 1 or more and 8 or less, more preferably 3 or more and 8 or less). Examples of the alkoxy group include a methoxy group, an ethoxy group, an isopropoxy group, a t-butoxy group, an n-butoxy group, an n-hexyloxy group, a 2-ethylhexyloxy group, a 3,5,5-trimethylhexyloxy group and the like. Be done. Alkoxy groups also include substituted alkoxy groups. Examples of the substituent that can be substituted with the alkoxy group include a halogen atom, a hydroxyl group, an amino group, an alkoxy group, an amide group, and a carbonyl group.

0046General formula: R¹_nSiR²_mThe compound represented by R is R from the viewpoint of expressing high photocatalytic function and improving dispersibility.¹A compound showing a saturated hydrocarbon group is preferable. In particular, the general formula: R¹_nSiR²_mThe compound represented by is R¹Indicates a saturated aliphatic hydrocarbon group having 1 to 20 carbon atoms, and R²Indicates a halogen atom or an alkoxy group, n indicates an integer of 1 or more and 3 or less, and m indicates an integer of 1 or more and 3 or less (where n + m = 4).

0047General formula: R¹_nSiR²_mSpecifically, as the compound represented by, for example, vinyl trimethoxysilane, propyltrimethoxysilane, i-butyltrimethoxysilane, n-butyltrimethoxysilane, n-hexyltrimethoxysilane, n-octyltrimethoxy Silane, n-dodecyltriethoxysilane, phenyltrimethoxysilane, 3-glycoxypropyltrimethoxysilane, tetramethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, diphenyldimethoxysilane, o-methylphenyltrimethoxysilane, p- Methylphenyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, tetraethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, i-butyltriethoxysilane, decyltriethoxy Silane, vinyl triethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-glycidyloxypropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ -Aminopropyltriethoxysilane, γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ- (2-aminoethyl) aminopropylmethyldimethoxysilane and the like can be mentioned. The silane compound may be used alone or in combination of two or more.

0048Among these, the hydrocarbon group in the silane compound is preferably an aliphatic hydrocarbon group, and more preferably a saturated aliphatic hydrocarbon group, from the viewpoint of expressing a high photocatalytic function and improving dispersibility. It is preferably an alkyl group, especially preferably an alkyl group. Further, the hydrocarbon group in the silane compound preferably has 1 or more and 18 or less carbon atoms, and more preferably 4 or more and 12 or less carbon atoms, from the viewpoint of exhibiting a high photocatalytic function and improving dispersibility. , It is particularly preferable that the number of carbon atoms is 4 or more and 10 or less.

0049Examples of the titanium compound having a hydrocarbon group in which the metal atom of the metal-containing compound is Ti include isopropyltriisostearoyl titanate, tetraoctylbis (ditridecylphosphite) titanate, and bis (dioctylpyrophosphate) oxyacetate. Titanium coupling agents such as titanium, di-i-propoxybis (ethylacetacetate) titanium, di-i-propoxybis (acetylacetonate) titanium, di-i-propoxybis (triethanolaminet) titanium, di- Examples thereof include titanium chelate such as i-propoxytitanium diacetate and di-i-propoxytitanium dipropionate.

0050Examples of the aluminum compound having a hydrocarbon group in which the metal atom of the metal-containing compound is Al include alkylaluminates such as triethoxyaluminum, tri-i-propoxyaluminum, and tri-sec-butoxyaluminum, and di-i-. Examples thereof include aluminum chelates such as propoxy-mono-sec-butoxyaluminum and di-i-propoxyaluminum / ethylacetacetate, and aluminum coupling agents such as acetalkoxyaluminum diisopropyrate.

0051(Characteristics of metatitanic acid particles) The metatitanic acid particles according to the present embodiment have absorption at wavelengths of 450 nm and 750 nm in the ultraviolet-visible absorption spectrum. From the viewpoint of exhibiting a high photocatalytic function even in the visible light region, the metatitanic acid particles according to the present embodiment preferably have absorption at wavelengths of 450 nm, 600 nm and 750 nm in the visible absorption spectrum, and have wavelengths of 450 nm or more and 750 nm in the visible absorption spectrum. It is more preferable to have absorption in the entire range below, and it is particularly preferable to have absorption in the entire range of wavelengths of 400 nm or more and 800 nm or less in the visible absorption spectrum. In addition, from the viewpoint of exhibiting a high photocatalytic function even in the visible light region, the metatitanic acid particles have an absorbance of 0.02 or more (preferably 0.1 or more) at a wavelength of 450 nm when the absorbance at a wavelength of 350 nm is 1 in the ultraviolet-visible absorption spectrum. The absorbance at a wavelength of 450 nm is 0.2 or more (preferably 0.3 or more), and the absorbance at a wavelength of 750 nm is 0.02 or more (preferably 0.1 or more).

0052The ultraviolet-visible absorption spectrum is measured by the following method. First, for the metatitanic acid particles to be measured, a spectrophotometer (manufactured by Hitachi High-Technologies Corporation: U-4100) [Measurement conditions; scan speed: 600 nm, slit width: 2 nm, sampling interval: 1 nm] Measure the wavelength range from 200 nm to 900 nm to obtain an ultraviolet-visible absorption spectrum. In addition, this measurement may be performed on a thin-film sample in which particles are molded.

0053The metatitanic acid particles according to the present embodiment have a C / Ti of 0.3 or more and 1.2 or less on the surface, have a wavelength of 352 nm and an irradiation intensity of 1.3 mW / cm with respect to the metatitanium acid particles.²The amount of decrease in C / Ti on the surface of the metatitanium acid particles before and after the irradiation with the ultraviolet rays is 0.1 or more and 0.9 or less when the ultraviolet rays are irradiated for 20 hours. Further, from the viewpoint of exhibiting a high photocatalytic function even in the visible light region, the metatitanium acid particles according to the present embodiment preferably have a C / Ti on the surface of 0.4 or more and 1.1 or less, and 0.5 or more and 1.0 or less. Is more preferable, and 0.6 or more and 0.9 or less is particularly preferable. Further, the amount of decrease in C / Ti on the particle surface before and after irradiation with ultraviolet rays is preferably 0.2 or more and 0.85 or less, and more preferably 0.25 or more and 0.8 or less.

0054The C / Ti on the surface of the metatitanium acid particles is measured by the following method. First, for the metatitanic acid particles to be measured, an X-ray photoelectron spectroscopy (XPS) analyzer (JPS-9000MX manufactured by JEOL Ltd. is used, MgKα rays are used as the X-ray source, and the acceleration voltage is 10 kV. Emission current is set to 20mA and measured, and C / Ti is calculated from the peak intensity of each element. Irradiation of ultraviolet rays to the surface of metatitanic acid particles has a wavelength of 352 nm and an irradiation intensity of 1.3 mW / cm.²It shall be irradiated with the ultraviolet rays of. The temperature of the metatitanic acid particles at the start of ultraviolet irradiation shall be 15 ° C or higher and 30 ° C or lower, and the irradiation time shall be 20 hours. After the irradiation with the ultraviolet rays, C / Ti is measured by the above method, and the amount of decrease in C / Ti before and after the irradiation with the ultraviolet rays is calculated.

0055The volume average particle diameter of the metatitanic acid particles according to the present embodiment is preferably 10 nm or more and 1 μm or less, more preferably 10 nm or more and 200 nm or less, and further preferably 15 nm or more and 200 nm or less. When the volume average particle size of the metatitanic acid particles is 10 nm or more, the metatitanic acid particles are less likely to aggregate and the photocatalytic function is likely to be enhanced. When the volume average particle size of the metatitanic acid particles is 1 μm or less, the ratio of the specific surface area to the amount becomes large, and the photocatalytic function tends to be enhanced. Therefore, when the volume average particle size of the metatitanic acid particles is set in the above range, a high photocatalytic function can be easily exhibited in the visible light region.

0056The volume average particle size of the metatitanic acid particles is measured using Nanotrack UPA-ST (Dynamic Light Scattering Particle Size Measuring Device manufactured by Microtrac Bell). The measurement conditions are that the sample concentration is 20% and the measurement time is 300 seconds. This device measures the particle size by utilizing the Brownian motion of the dispersoid, and measures the particle size by irradiating the solution with laser light and detecting the scattered light. Then, based on the particle size distribution measured by the dynamic light scattering type particle size measuring device, the cumulative distribution of the volume of each particle is drawn from the small diameter side for each divided particle size range (channel), and the cumulative total is 50. The particle size to be% is calculated as the volume average particle size.

0057&lt;Manufacturing method of metatitanic acid particles&gt; The method for producing the metatitanic acid particles according to the present embodiment is not particularly limited, but is a step of surface-treating the untreated metatitanic acid particles with a silane compound having a hydrocarbon group, and surface-treating the untreated metatitanic acid particles. It is preferable to include a step of heat-treating the metatitanic acid particles during or after the step of treating.

0058First, the surface treatment of untreated metatitanic acid particles using a metal-containing compound will be described. The method of surface-treating the untreated metatitanic acid particles from the metal-containing compound is not particularly limited. For example, a method of directly contacting the metal-containing compound itself with the untreated metatitanic acid particles, or a metal-containing compound in the solvent. Examples thereof include a method in which the treatment liquid in which the compound is dissolved is brought into contact with untreated metatitanic acid particles. Specifically, for example, a method of adding the metal-containing compound itself or the treatment liquid to a dispersion liquid in which untreated metatitanic acid particles are dispersed in a solvent, a state of flowing by stirring with a Henschel mixer or the like. Examples thereof include a method of adding (dropping, spraying, etc.) to the untreated metatitanic acid particles. By these methods, the reactive group (for example, hydrolyzable group) in the metal-containing compound reacts with the hydrolyzable group (hydroxyl group, halogeno group, alkoxy group, etc.) existing on the surface of the untreated metatitanic acid particles. , The surface of untreated metatitanic acid particles is treated with a metal-containing compound.

0059Here, as the solvent for dissolving the metal-containing compound, an organic solvent (for example, a hydrocarbon solvent, an ester solvent, an ether solvent, a halogen solvent, an alcohol solvent, etc.), water, a mixed solvent thereof, etc. Can be mentioned. Examples of the hydrocarbon solvent include toluene, benzene, xylene, hexane, octane, hexadecane, cyclohexane and the like. Examples of the ester solvent include methyl acetate, ethyl acetate, isopropyl acetate, amyl acetate and the like. Examples of the ether solvent include dibutyl ether and dibenzyl ether. Examples of the halogen-based solvent include 1,1-dichloro-1-fluoroethane, 1,1-dichloro-2,2,2-trifluoroethane, and 1,1-dichloro-2,2,3,3,3. -Pentafluoropropane, chloroform, dichloroethane, carbon tetrachloride and the like. Examples of the alcohol solvent include methanol, ethanol, i-propyl alcohol and the like. Examples of water include tap water, distilled water, pure water and the like. In addition to these, solvents such as dimethylformamide, dimethylacetamide, dimethyl sulfoxide, acetic acid, and sulfuric acid may be used as the solvent.

0060In the treatment liquid in which the metal-containing compound is dissolved in the solvent, the concentration of the metal-containing compound is preferably 0.05 mol / L or more and 500 mol / L or less, and more preferably 0.5 mol / L or more and 10 mol / L or less with respect to the solvent.

0061The conditions for surface treatment of the metatitanic acid particles with the metal-containing compound are as follows from the viewpoint of exhibiting a high photocatalytic function and improving dispersibility. Untreated with a metal-containing compound of 10% by mass or more and 100% by mass or less (preferably 20% by mass or more and 75% by mass or less, more preferably 25% by mass or more and 50% by mass or less) with respect to the untreated metatitanic acid particles. It is preferable to surface-treat the metatitanic acid particles of. When the treatment amount of the metal-containing compound is 10% by mass or more, a high photocatalytic function is more likely to be exhibited even in the visible light region. In addition, the dispersibility is likely to increase. When the treatment amount of the metal-containing compound is 100% by mass or less, the amount of silicon (Si) relative to the surface (Ti-O-) of the metatitanium acid particles is suppressed from becoming excessive, and the photocatalytic function of the excess silicon (Si) is suppressed. The decrease is likely to be suppressed.

0062The surface treatment temperature of the untreated metatitanic acid particles with the metal-containing compound is preferably 15 ° C or higher and 150 ° C or lower, and more preferably 20 ° C or higher and 100 ° C or lower. The surface treatment time is preferably 10 minutes or more and 120 minutes or less, and more preferably 30 minutes or more and 90 minutes or less.

0063After the surface treatment of the untreated metatitanic acid particles with the metal-containing compound, it is preferable to carry out a drying treatment. The method of drying treatment is not particularly limited, and for example, a well-known drying method such as a vacuum drying method or a spray drying method is used. The drying temperature is preferably 20 ° C or higher and 150 ° C or lower.

0064Next, the heat treatment will be described.

0065The heat treatment is carried out during the step of surface-treating the untreated metatitanic acid particles or after the step of surface-treating the untreated metatitanic acid particles. Specifically, the heat treatment can be carried out separately when surface-treating the metatitanic acid particles untreated from the silane compound, when performing the drying treatment after the surface treatment, or separately after the drying treatment, but the heat treatment is performed. Since it is necessary to sufficiently react the metatitanic acid particles with the silane compound before, it is preferable to carry out the drying treatment after the surface treatment or separately after the drying treatment, and the surface treatment and drying of the metatitanic acid particles are properly performed. In carrying out, it is more preferable to carry out separately after the drying treatment.

0066The temperature of the heat treatment is preferably 180 ° C or more and 500 ° C or less, more preferably 200 ° C or more and 450 ° C or less, and 250 ° C or more and 400 ° C from the viewpoint of developing a high photocatalytic function and improving dispersibility. The following is more preferable. When the heat treatment is performed during the surface treatment step of the untreated metatitanic acid particles, the silane compound is first sufficiently reacted at the surface treatment temperature, and then the heat treatment is performed at the heat treatment temperature. When the heat treatment is performed in the drying treatment after the surface treatment, the temperature of the drying treatment is set as the heat treatment temperature. The heat treatment time is preferably 10 minutes or more and 300 minutes or less, and more preferably 30 minutes or more and 120 minutes or less, from the viewpoint of developing a high photocatalytic function and improving dispersibility.

0067The method of heat treatment is not particularly limited, and for example, heating by an air furnace, a firing furnace (roller harsher kiln, shuttle kiln, etc.), a radiant heating furnace, etc., heating by laser light, infrared rays, UV, microwaves, etc. Use a well-known heating method.

0068Through the above steps, the metatitanic acid particles according to the present embodiment are preferably obtained.

0069&lt;Composition for photocatalyst formation&gt; The photocatalyst-forming composition according to the present embodiment contains the metatitanic acid particles according to the present embodiment and at least one compound selected from the group consisting of a dispersion medium and a binder. Examples of the photocatalyst-forming composition according to the present embodiment include the metatitanic acid particles according to the present embodiment, a dispersion liquid containing a dispersion medium, the metatitanic acid particles according to the present embodiment, and an organic / inorganic binder. Aspects such as a composition containing the above can be mentioned. The dispersion liquid may be in the form of a paste having a high viscosity.

0070As the dispersion medium, water, an organic solvent and the like are preferably used. Examples of water include tap water, distilled water, pure water and the like. The organic solvent is not particularly limited, and examples thereof include a hydrocarbon solvent, an ester solvent, an ether solvent, a halogen solvent, and an alcohol solvent. Further, the dispersion liquid preferably contains at least one compound selected from the group consisting of a dispersant and a surfactant from the viewpoint of dispersion stability and storage stability. Known dispersants and surfactants are used.

0071The binder used in the composition is not particularly limited, but is a fluororesin, a silicone resin, a polyester resin, an acrylic resin, a styrene resin, an acrylonitrile / styrene copolymer resin, an acrylonitrile / butadiene / styrene copolymer (ABS) resin, and the like. Epoxy resin, polycarbonate resin, polyamide resin, polyamine resin, polyurethane resin, polyether resin, polysulfide resin, polyphenol resin, their composites, organic binders such as silicone-modified or halogen-modified resins, glass, ceramics, etc. Examples thereof include inorganic binders such as metal powder. Further, the dispersion liquid may contain the binder as an emulsion.

0072The photocatalyst-forming composition according to the present embodiment may contain other components other than the above. As other components, known additives are used, and examples thereof include cocatalysts, colorants, fillers, preservatives, defoamers, adhesion improvers, and thickeners.

0073The photocatalyst-forming composition according to the present embodiment may contain one type of metatitanic acid particles according to the present embodiment alone, or may contain two or more types. The content of the metatitanic acid particles according to the present embodiment in the photocatalyst forming composition according to the present embodiment is not particularly limited, and depends on various aspects such as a dispersion liquid and a resin composition, a desired photocatalyst amount, and the like. , May be selected as appropriate.

0074The method for producing a photocatalyst or a structure having a photocatalyst using the photocatalyst-forming composition according to the present embodiment is not particularly limited, and a known application method is used. Examples of the method for applying the photocatalyst forming composition according to the present embodiment include a spin coating method, a dip coating method, a flow coating method, a spray coating method, a roll coating method, a brush coating method, a sponge coating method, and a screen printing method. Inkjet printing method and the like can be mentioned.

0075&lt;Photocatalyst and structure&gt; The photocatalyst according to the present embodiment contains or consists of metatitanic acid particles according to the present embodiment. In addition, the structure according to the present embodiment has the metatitanic acid particles according to the present embodiment.

0076The photocatalyst according to the present embodiment may be a photocatalyst composed of only the metatitanic acid particles according to the present embodiment, or may be a photocatalyst obtained by mixing an auxiliary catalyst with the metatitanic acid particles according to the present embodiment. It may be a photocatalyst in which the metatitanic acid particles according to the above are solidified into a desired shape by an adhesive or a pressure-sensitive adhesive.

0077From the viewpoint of photocatalytic activity, the structure according to the present embodiment preferably has at least the metatitanic acid particles according to the present embodiment on the surface. Further, the structure according to the present embodiment preferably has the metatitanic acid particles according to the present embodiment as a photocatalyst. The structure according to the present embodiment is preferably a structure having at least the metatitanic acid particles according to the present embodiment on at least a part of the surface of the base material, and the photocatalyst according to the present embodiment is on at least a part of the surface of the base material. It is preferable that the structure is formed by applying the forming composition. In the structure, the amount of the photocatalyst-forming composition according to the present embodiment is not particularly limited and may be selected as desired. Further, in the structure according to the present embodiment, the metatitanic acid particles according to the present embodiment may be attached to the surface of the base material or may be immobilized, but from the viewpoint of the durability of the photocatalyst, the structure may be immobilized. It is preferably fixed. The immobilization method is not particularly limited, and a known immobilization method is used.

0078Examples of the base material used in the present embodiment include various materials regardless of whether they are inorganic materials or organic materials, and their shapes are not limited. Preferred examples of substrates are metals, ceramics, glass, plastics, rubber, stones, cement, concrete, fibers, fabrics, wood, paper, combinations thereof, laminates thereof, and at least one layer of coating on their surfaces. Some have. Preferred examples of base materials from the viewpoint of application are building materials, exterior materials, window frames, windowpanes, mirrors, tables, tableware, curtains, lenses, prisms, exteriors and coatings of vehicles, exteriors of machinery and articles, and dustproof. Covers and paints, traffic signs, various display devices, advertising towers, road sound insulation walls, railway sound insulation walls, bridges, guard rail exteriors and paints, tunnel interiors and paints, glass, solar cell covers, solar water heater heat collector covers, polymer films , Polymer sheets, filters, indoor signboards, outdoor signboards, vehicle lighting covers, outdoor lighting fixtures, air purifiers, water purifiers, medical appliances, nursing care products, etc.

<p num="0079"> Hereinafter, the present invention will be described in more detail with reference to examples. However, each of these examples does not limit the present invention. In addition, "part" and "%" are based on mass unless otherwise specified.</p><p num="0080">&lt;Example 1&gt; -Preparation of metatitanic acid slurry- TiO₂Concentration is 260g / L, Ti³⁺Concentration is TiO₂Anatase seeds prepared separately were added to a 6.0 g / L titanyl sulfate solution in conversion to TiO in the titanyl sulfate solution.₂Against TiO₂In terms of conversion, 8% by mass was added. The solution is then heated above the boiling point to titanyl sulfate (TiOSO).₄) Was hydrolyzed to produce granular metatitanic acid. Next, the metatitanic acid particles were filtered and washed, then slurried and neutralized and washed at pH 7. In this way, a metatitanic acid slurry having a volume average particle diameter of 40 nm was obtained.</p><p num="0081">-Preparation of metatitanic acid particles- A 5N sodium hydroxide aqueous solution was added to the metatitanic acid slurry having a volume average particle size of 40 nm while stirring, and the mixture was kept stirred at pH 8.5 for 2 hours, neutralized to pH 5.8 with 6N hydrochloric acid, filtered and washed with water. After washing, water was further added to make a slurry again, and 6N hydrochloric acid was added while stirring to adjust the pH to 1.3, and the mixture was kept stirred for 3 hours. 100 parts of metatitanic acid is separated from this slurry, heated and maintained at 60 ° C, 40 parts of isobutyltrimethoxysilane is added while stirring, and after stirring and holding for 30 minutes, a 7N sodium hydroxide aqueous solution is added. It was neutralized to pH 7, filtered and washed with water. The filtered and washed residue was spray-dried with an air flow dryer at an outlet temperature of 150 ° C. to obtain a dry powder. Then, the obtained dry powder was heat-treated in an electric furnace at 400 ° C. for 1 hour to obtain metatitanic acid particles 1.</p><p num="0082">&lt;Example 2&gt; Metatitanic acid particles 2 were obtained in the same manner as in Example 1 except that isobutyltrimethoxysilane was used as hexyltrimethoxysilane in Example 1.</p><p num="0083">&lt;Example 3&gt; Metatitanic acid particles 3 were obtained in the same manner as in Example 1 except that isobutyltrimethoxysilane was used as decyltrimethoxysilane in Example 1.</p><p num="0084">&lt;Example 4&gt; Metatitanic acid particles 4 were obtained in the same manner as in Example 2 except that the amount of hexyltrimethoxysilane added was changed from 40 parts to 50 parts in Example 2.</p><p num="0085">&lt;Example 5&gt; Metatitanic acid particles 5 were obtained in the same manner as in Example 2 except that the temperature in the electric furnace when the dried powder particles were heat-treated was changed from 400 ° C to 250 ° C in Example 2. ..</p><p num="0086">&lt;Example 6&gt; Metatitanic acid particles 6 were obtained in the same manner as in Example 1 except that the temperature in the electric furnace for heat-treating the dried powder particles was changed from 400 ° C to 500 ° C. ..</p><p num="0087">&lt;Example 7&gt; Metatitanic acid particles 7 were obtained in the same manner as in Example 2 except that the amount of hexyltrimethoxysilane added was changed from 40 parts to 25 parts in Example 2.</p><p num="0088">&lt;Example 8&gt; Metatitanic acid particles 8 were obtained in the same manner as in Example 2 except that the amount of hexyltrimethoxysilane added was changed from 40 parts to 75 parts in Example 2.</p><p num="0089">&lt;Example 9&gt; Metatitanic acid particles 9 were obtained in the same manner as in Example 1 except that 40 parts of isobutyltrimethoxysilane was changed to 35 parts of octyltrimethoxysilane.</p><p num="0090">&lt;Example 10&gt; Metatitanic acid particles 10 were obtained in the same manner as in Example 1 except that isobutyltrimethoxysilane was changed to methyltrimethoxysilane in Example 1.</p><p num="0091">&lt;Example 11&gt; Metatitanic acid granules 11 were obtained in the same manner as in Example 1 except that isobutyltrimethoxysilane was changed to hexamethyldisilazane.</p><p num="0092">&lt;Example 12&gt; Metatitanic acid particles 12 were obtained in the same manner as in Example 1 except that 40 parts of isobutyltrimethoxysilane was changed to 30 parts of dodecyltrimethoxysilane.</p><p num="0093">&lt;Example 13&gt; Metatitanic acid particles 13 were obtained in the same manner as in Example 1 except that isobutyltrimethoxysilane was changed to phenyltrimethoxysilane in Example 1.</p><p num="0094">&lt;Example 14&gt; Metatitanic acid particles 14 were obtained in the same manner as in Example 1 except that the amount of isobutyltrimethoxysilane added was changed from 40 parts to 10 parts.</p><p num="0095">&lt;Example 15&gt; In Example 2, metatitanic acid particles 15 were obtained in the same manner as in Example 2 except that the temperature in the electric furnace for heat-treating the dried powder particles was changed from 400 ° C to 180 ° C. ..</p><p num="0096">&lt;Example 16&gt; Metatitanic acid particles 16 were obtained in the same manner as in Example 2 except that the volume average particle size of the metatitanic acid slurry was changed from 40 nm to 15 nm in Example 2.</p><p num="0097">&lt;Example 17&gt; Metatitanic acid particles 17 were obtained in the same manner as in Example 2 except that the volume average particle size of the metatitanic acid slurry was changed from 40 nm to 980 nm in Example 2.</p><p num="0098">&lt;Example 18&gt; Metatitanic acid particles 18 were obtained in the same manner as in Example 2 except that the volume average particle size of the metatitanic acid slurry was changed from 40 nm to 10 nm in Example 2.</p><p num="0099">&lt;Example 19&gt; Metatitanic acid particles 19 were obtained in the same manner as in Example 2 except that the volume average particle size of the metatitanic acid slurry was changed from 40 nm to 1100 nm in Example 2.</p><p num="0100">&lt;Example 20&gt; Metatitanic acid particles 20 were obtained in the same manner as in Example 1 except that isobutyltrimethoxysilane was isopropyltriisostearoyl titanate (TTS, manufactured by Ajinomoto Co., Inc.).</p><p num="0101">&lt;Example 21&gt; In Example 1, the isobutyltrimethoxysilane was acetoalkoxyaluminum diisopropyrate (AL-M, manufactured by Ajinomoto Co., Inc., and the alkoxy group of acetoalkoxy was an oxadecyloxy group). Metatitanic acid particles 21 were obtained in the same manner as in Example 1.</p><p num="0102">&lt;Comparison example 1&gt; Commercially available anatase-type titanium oxide particles ("SSP-20 (manufactured by Sakai Chemical Industry Co., Ltd.)" volume average particle size 12 nm)) were used as they were as titanium oxide particles C1.</p><p num="0103">&lt;Comparative example 2&gt; Commercially available rutile-type titanium oxide particles ("STR-100N (manufactured by Sakai Chemical Industry Co., Ltd.)", volume average particle size 16 nm)) were used as they were as titanium oxide particles C2.</p><p num="0104">&lt;Comparative example 3&gt; Commercially available anatase-type titanium oxide particles ("SSP-20 (manufactured by Sakai Chemical Industry Co., Ltd.)", volume average particle size 12 nm)) are heat-treated in an electric furnace at 400 ° C. for 1 hour to produce titanium oxide. Particle C3 was obtained.</p><p num="0105">&lt;Comparative example 4&gt; Commercially available rutile-type titanium oxide particles ("STR-100N (manufactured by Sakai Chemical Industry Co., Ltd.)", volume average particle size 16 nm)) are heat-treated in an electric furnace at 400 ° C. for 1 hour to produce titanium oxide. Particle C4 was obtained.</p><p num="0106">&lt;Comparative example 5&gt; Metatitanic acid particles C5 were obtained in the same manner as in Example 1 except that the amount of isobutyltrimethoxysilane added was changed from 40 parts to 5 parts.</p><p num="0107">&lt;Comparative example 6&gt; Metatitanic acid particles C6 were obtained in the same manner as in Example 1 except that the amount of isobutyltrimethoxysilane added was changed from 40 parts to 120 parts.</p><p num="0108">&lt;Comparative example 7&gt; Metatitanic acid particles C7 were obtained in the same manner as in Example 1 except that the temperature in the electric furnace for heat-treating the dried powder particles was changed from 400 ° C to 600 ° C. ..</p><p num="0109">&lt;Comparative example 8&gt; Metatitanic acid particles C8 were obtained in the same manner as in Example 1 except that the temperature in the electric furnace for heat-treating the dried powder particles was changed from 400 ° C to 160 ° C. ..</p><p num="0110">&lt;Comparative example 9&gt; Metatitanic acid particles C9 were obtained in the same manner as in Example 1 except that the powder particles after drying were not heat-treated in Example 1.</p><p num="0111">&lt;Comparative example 10&gt; Metatitanic acid particles C10 were obtained in the same manner as in Example 1 except that the volume average particle size of the metatitanic acid slurry was changed from 40 nm to 6 nm in Example 1.</p><p num="0112">&lt;Measurement&gt; The visible absorption spectral characteristics of the particles obtained in each example were confirmed, and the particles of Examples 1 to 21 and Comparative Examples 5 to 7 had absorption in the wavelength range of 400 nm or more and 800 nm or less. (Indicated as "UV-Vis characteristics" in Tables 1 and 2: When the absorbance at a wavelength of 350 nm is 1, the absorbance at a wavelength of 450 nm, the absorbance at a wavelength of 600 nm, and the absorbance at 750 nm), the C / Ti element ratio on the particle surface by XPS. , And the volume average particle size (denoted as "D50v" in the table) was measured according to the method described above. In addition, on the particle surface obtained in each example, the wavelength was 352 nm and the irradiation intensity was 1.3 mW / cm.²After irradiating with the ultraviolet rays at 25 ° C for 20 hours at the start of irradiation, the C / Ti element ratio on the particle surface by XPS was measured according to the method described above, and the amount of decrease in the C / Ti element ratio before and after the irradiation of the ultraviolet rays was measured. Calculated.</p><p num="0113">&lt;Evaluation&gt; (Degradability (photocatalytic activity)) Degradability was evaluated as a photocatalytic property in the visible light region. Then, the degradability was evaluated by the degradability (variation in chromaticity) of methylene blue. Specifically, the particles obtained in each example were dispersed in pure water containing 4 parts by weight of methanol so as to have a solid content concentration of 2 parts by weight, and then the dispersion was applied to filter paper (5 cm square: manufactured by Advantech). : No.5A) is spray-applied and dried to evenly attach the sample particles to the filter paper surface. Subsequently, a methylene blue diluted solution prepared by diluting a 2 mass% methylene blue aqueous solution 5 times with methanol was spray-coated and dried on the surface to prepare a test piece. Using a light emitting diode (LED) that does not have the absorption wavelength region of methylene blue (wavelength 400 nm or more and 800 nm or less) and irradiates visible light with a wavelength of 400 nm or more and 550 nm or less, visible light (10,000LX) is used for the test piece immediately after the test piece is prepared. (Lux)) was continuously irradiated for 2 hours. At that time, a 5-yen coin was placed in the center of the irradiation surface of the test piece to form a shielding portion for irradiation.</p><p num="0114"> Immediately after the test piece was prepared, the hue of the test piece after irradiation with visible light for 2 hours was measured with a spectroscopic color difference meter "RM200QC (manufactured by X-Rite)", and ΔE1 and ΔE2 calculated by the following formulas were obtained. The chromaticity E is E = ((L)^*)²+ (a^*)²+ (b^*)²)^0.5It is a value calculated by, and each L^*, A^*, B^*Is L^*a^*b b^*It is a value based on the color system. -Formula: ΔE1 = chromaticity of the irradiated surface after continuous irradiation of visible light for 2 hours-chromaticity of the test piece immediately after preparation of the test piece -Formula: ΔE2 = chromaticity of the irradiation shielding surface after continuous irradiation of visible light for 2 hours-chromaticity of the test piece surface immediately after preparation of the test piece Then, the decomposability was evaluated based on the decolorization variation value ΔE = ΔE1-ΔE2. The evaluation criteria are as follows.</p><p num="0115">-Evaluation criteria for degradability- A (): 15% ΔE B (): 5% ΔE &lt;15% C (×): ΔE &lt;5%</p><p num="0116">(Dispersibility (particle agglutination)) The dispersibility was evaluated as follows. Place 0.05 g of the particles obtained in each example in a beaker, add 40 g of methyl ethyl ketone, and then disperse the particles with an ultrasonic disperser for 10 minutes. It was measured by a light scattering type particle size measuring device) and evaluated by the distribution form of the volume particle size distribution. The evaluation criteria are as follows.</p><p num="0117">-Evaluation criteria for dispersibility- A (): The peak value of the volume particle size distribution is one mountain, and the dispersibility is good. B (): The volume particle size distribution is bifurcated, but the main peak value is 10 times or more the other peak values, and there is no problem in practical dispersibility. C (×): Volume particle size distribution has three or more peak values and is poorly dispersed.</p><p num="0118">(Dispersibility (dispersion in binder)) The dispersibility was evaluated as follows. Put 0.05 g of the particles obtained in each example in a beaker, add 1 g of a methyl ethyl ketone solution in which acrylic resin (Mw = 10,000) is dissolved at a concentration of 1.8 mass%, and after the particles are fully blended, add 40 g of methyl ethyl ketone. Subsequently, the particle size distribution after dispersion with an ultrasonic disperser for 10 minutes was measured by Nanotrack UPA-ST (Dynamic Light Scattering Particle Size Measuring Device manufactured by Microtrack Bell), and evaluated by the distribution form of the volume particle size distribution. .. The evaluation criteria are as follows.</p><p num="0119">-Evaluation criteria for dispersibility- A (): The peak value of the volume particle size distribution is one mountain, and the dispersibility is good. B (): The volume particle size distribution is bifurcated, but the main peak value is 10 times or more the other peak values, and there is no problem in practical dispersibility. C (×): Volume particle size distribution has three or more peak values and is poorly dispersed.</p><p num="0120">(Binder decomposition inhibitory property) The decomposition inhibitory property of the binder was evaluated as follows. Put 0.5 g of the particles obtained in each example into a beaker, add 2 g of a methyl ethyl ketone solution in which acrylic resin (Mw = 10,000) is dissolved at a concentration of 13% by mass, stir, and then take 1 ml with a glass pipette and glass. After spreading on a plate (50 mm × 50 mm), it was sufficiently dried to prepare a test piece. Two test pieces were prepared. Next, using a light emitting diode (LED) that irradiates visible light with a wavelength of 400 nm or more and 800 nm or less, one of the test pieces was continuously irradiated with visible light (30,000 LX (lux)) for 30 hours. The other test piece was stored in a dark place. For the surface coating film on each of these test pieces after storage in a dark place and irradiation with visible light for 30 hours, an infrared spectrophotometer FTIR-410 (manufactured by JASCO Corporation) was used, and carbonyl in an acrylic polymer (binder). The infrared spectroscopic peak intensity of the group (C = O) was measured, and ΔT calculated by the following formula was obtained. . Equation: ΔT = Infrared spectroscopic peak intensity of carbonyl group (C = O) of sample after irradiation with visible light for 30 hours / Infrared spectroscopic peak intensity of carbonyl group (C = O) of sample stored in dark place Then, the decomposition inhibitory property of the binder polymer was evaluated based on the value of the infrared peak intensity ratio ΔT of the carbonyl group (C = O). The evaluation criteria are as follows.</p><p num="0121">-Evaluation criteria for binder degradation inhibitory- A (): 0.8 ΔT B (): 0.6 ΔT &lt;0.8 C (×): ΔT &lt;0.6</p><p num="0122"> Details of each example and evaluation results are listed in Tables 1 and 2.</p><p num="0123"><tables num="1"><img id="000002" he="221" wi="126" file="JP2018095498A_D0001.tif" img-format="tif" img-content="drawing" /></tables></p><p num="0124"><tables num="2"><img id="000003" he="221" wi="92" file="JP2018095498A_D0001.tif" img-format="tif" img-content="drawing" /></tables></p><p num="0125"> From the above results, it can be seen that this example has better degradability than the comparative example. From this, it can be seen that this example exhibits a higher photocatalytic function even in the visible light region as compared with the comparative example. Further, it can be seen that in this example, dispersibility and decomposition inhibitory property of the binder are also ensured.</p>