JP2017221880A - Photocatalytic coating liquid, photocatalyst structure and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for easily forming a photocatalyst layer excellent in strength and exhibiting sufficient photocatalyst activity by coating a substrate which is heated in advance without a calcination process especially, and a photocatalyst structure obtained by the method.SOLUTION: There is provided a photocatalyst coating liquid containing a hydrolysis degradation product which is manufactured by acid of a hydrolyzable silane compound represented by the formula (1) (R)Si(OR)(1), where Rrepresents an alkyl group which may have a substituent and has 1 to 4 carbon atoms, Rrepresents an alkyl group having 1 to 4 carbon atoms and n represents an integer of 0 or 1 and has polymerization degree of 8 or less, a photocatalyst material particle and a hydrophilic solvent.SELECTED DRAWING: None

Description

  The present invention relates to a photocatalyst structure and a method for producing the structure.

Photocatalysts are used for facilitating the removal of dirt in exterior materials and water-related products of buildings by supporting them on the surface of various materials, and preventing fogging of glass products and the like due to hydrophilicity.
When a heat-resistant material such as ceramic is used as a base material and a photocatalyst layer is supported on the surface, the photocatalyst is often supported by firing at a high temperature of about 500 ° C. in a form incorporated in the manufacturing process of the material. . However, for that purpose, it was necessary to provide a baking step for forming the photocatalyst layer. Further, when the firing temperature is low or the firing time is short, the strength of the photocatalyst film may be inferior.
Patent Document 1 describes a photocatalyst obtained by mixing a composition obtained by hydrolyzing a tetraalkoxysilane and a photocatalytic titanium oxide, applying the mixture to a substrate, and drying or heating. It has been shown that photocatalytic activity is improved by increasing the degree of condensation.
Patent Document 2 describes a film-forming composition containing photocatalytic titanium oxide particles, a hydrolyzate of a hydrolyzable silicon compound, and a solvent.
It has been shown that it is preferable to use an alkoxysilane hydrolyzate in combination with a specific photocatalytic material. For example, Patent Document 3 describes that a coating material composition containing photocatalytic titanium dioxide coated with silica and an acid partial hydrolyzate of tetraalkoxysilane in a specific ratio is suitable for an organic substrate. Yes.
Patent Document 4 discloses an antifouling emulsion containing an acid partial hydrolyzate of an organosiloxane such as tetraethoxysilane having a weight average molecular weight of 600 to 5000, a photo semiconductor, and a nonionic or anionic surfactant. A coating material composition is described.
Patent Document 5 describes a coating material composition containing a partially hydrolyzed condensate of tetrafunctional alkoxysilane, a trifunctional or bifunctional alkoxysilane, and a filler such as a photocatalyst.

JP-A-10-176140 Japanese Patent Laid-Open No. 08-164334 JP 2002-121481 A JP-A-10-316937 JP 2001-64585 A

  The present invention relates to a method for easily forming a photocatalyst layer having excellent strength and exhibiting sufficient photocatalytic activity by coating on a preheated substrate without any firing step, and a photocatalyst obtained thereby An object is to provide a structure.

  The present inventors applied a photocatalyst coating solution containing a partial hydrolysis product of an acid of tetraalkoxysilane onto a heated substrate immediately after production, thereby providing a photocatalyst-supporting structure that has solved the above problems. As a result, the present invention was completed.

That is, this invention relates to the invention which has the following aspects.
(1) Formula (1)
(R ¹ ) _n Si (OR ² ) _4-n (1)
(In the formula, R ¹ represents an optionally substituted alkyl group having 1 to 4 carbon atoms, R ² represents an alkyl group having 1 to 4 carbon atoms, and n represents an integer of 0 or 1. The photocatalyst coating liquid containing the hydrolysis product by the acid of the hydrolyzable silane compound shown by the following formula, the hydrolysis product having a polymerization degree of 8 or less, photocatalyst material particles, and a hydrophilic solvent.
(2) A method for producing a photocatalyst coating liquid,
Formula (1)
(R ¹ ) _n Si (OR ² ) _4-n (1)
(In the formula, R ¹ represents an optionally substituted alkyl group having 1 to 4 carbon atoms, R ² represents an alkyl group having 1 to 4 carbon atoms, and n represents an integer of 0 or 1. The molar ratio (water / hydrolyzable group) of the hydrolyzable group of the hydrolyzable silane compound and the total amount of water added in the photocatalyst coating liquid is 0.2 to 1. .3, a method for producing a photocatalyst coating liquid, comprising a step of hydrolyzing or hydrolytic condensation with an acid, and a step of mixing the hydrolysis product and photocatalyst material particles after the step.
(3) The method for producing a photocatalyst coating liquid according to (2), wherein the hydrolysis with the acid is performed at 30 ° C. or lower.
(4) The method for producing a photocatalyst coating liquid according to (2) or (3), wherein the degree of polymerization of the hydrolysis product of the hydrolyzable silane compound represented by the formula (1) is 8 or less.
(5) Hydrolyzate or hydrolysis condensate of the hydrolyzable silane compound with an acid (its (R ¹ ) _n SiO _{(2-n / 2)} (R ¹ and n are the same as those in the formula (1), respectively) The mass ratio A: B of the converted mass to A) and the photocatalyst material particles (its mass is B) is 1: 5 to 10: 1 (2) to (4 ). The method for producing a photocatalyst coating liquid according to any one of
(6) The manufacturing method of the photocatalyst coating liquid in any one of (2)-(5) whose n is 0 in said Formula (1).
(7) The method for producing a photocatalyst coating liquid according to any one of (2) to (6), wherein the photocatalyst material contains crystalline titanium dioxide.
(8) A method for producing a photocatalyst structure in which a photocatalyst layer is supported on a substrate,
The manufacturing method of a photocatalyst structure including the process of apply | coating the photocatalyst coating liquid as described in (1) to the surface of the preheated base material, and forming a photocatalyst layer.
(9) A method for producing a photocatalyst structure in which a photocatalyst layer is supported on a substrate,
The manufacturing method of a photocatalyst structure including the process of apply | coating the photocatalyst coating liquid manufactured by the method in any one of (2)-(7) on the surface of the preheated base material, and forming a photocatalyst layer.
(10) The manufacturing method of the photocatalyst structure as described in (8) or (9) whose film thickness of the said photocatalyst layer is 0.1-5 micrometers.
(11) The method for producing a photocatalytic structure according to (10), wherein the base material is any one of metal, glass, ceramics, stone, concrete, cement, or a composite material composed of two or more of the above materials. .
(12) A photocatalyst structure produced by the method according to any one of (8) to (11).

  When the method for producing a photocatalyst structure of the present invention is used, a photocatalyst structure excellent in strength and exhibiting sufficient photocatalytic activity can be obtained.

  The manufacturing method of the photocatalyst structure of this invention is a method including the process of apply | coating the following photocatalyst coating liquid to the surface of the preheated base material, and forming a photocatalyst layer.

  The substrate is not particularly limited, but is preferably any one of heat-resistant metal, glass, ceramics, stone, concrete, cement, or a composite material composed of two or more of the above materials. In particular, ceramic products such as ceramics and pots are preferable, and specific applications include tiles, tiles, and the like, and most preferable tiles are used as exterior wall materials for buildings.

The preheating is to heat a material to be applied before application, and to set the temperature of the material surface during application to a certain temperature or higher. The temperature of the material surface at the time of application is preferably 50 ° C. or higher, more preferably 100 ° C. or higher. By this preheating, the photocatalyst coating liquid is quickly dried and cured. Further, when the temperature of the material surface at the time of application is too high, the coating film may become excessively non-uniform at the time of application, so it is preferably 300 ° C. or lower.
In particular, when a ceramic product is used as a base material, there is a step of firing at a high temperature as a production process of the product. Therefore, by providing the photocatalyst layer forming step of the present invention immediately after the step, a new firing step is performed. Without providing, a ceramic product carrying a photocatalyst can be manufactured.

The photocatalyst coating liquid used in the method for producing a photocatalyst structure of the present invention has the formula (1)
(R ¹ ) _n Si (OR ² ) _4-n (1)
(In the formula, R ¹ represents an optionally substituted alkyl group having 1 to 4 carbon atoms, R ² represents an alkyl group having 1 to 4 carbon atoms, and n represents 0 or 1. Each R. ² may be the same as or different from each other. Hydrolyzate or hydrolysis condensate of one or more acids of the hydrolyzable silane compound represented by the formula (hereinafter referred to as “hydrolysis product”) A hydrolyzable group of the hydrolyzable silane compound, which is a starting material for the hydrolysis product, and the total amount of water added in the photocatalyst coating liquid. The molar ratio (water / hydrolyzable group) is in the range of 0.2 to 1.3, and the hydrolysis product and the photocatalytic material particles are mixed after the hydrolysis step of the hydrolyzable silane compound with an acid. This is a photocatalyst coating solution.

As a hydrolysable silane compound represented by Formula (1), any at least 1 type should just contain. Moreover, when the hydrolyzable silane compound is two or more kinds, the hydrolysis product of the hydrolyzable silane compound represented by the formula (1) by the acid coexists with two or more hydrolyzable silane compounds. A composition hydrolyzed or further condensed with an acid may be used, or a composition obtained by further hydrolyzing or further condensing one or more hydrolyzable silane compounds with an acid, or a composition obtained by further mixing two or more kinds. Good.
Further, it is preferable that at least the compound in which n is 0, that is, a tetrafunctional silane compound is contained. Of the total mass of the hydrolyzable silane compound represented by formula (1), the mass ratio of the tetrafunctional silane compound is preferably 50% or more, more preferably 80% or more, and 100%. More preferably.

  Examples of the tetrafunctional silane represented by the formula (1) include tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, and tetraisopropoxysilane.

The compound represented by formula (1) wherein n is 1, that is, the trifunctional silane compound is an alkyl group having 1 to 4 carbon atoms which may be directly bonded to a silicon atom and may have a substituent. with a R ^1. Examples of these substituents include chloro group, fluoro group, epoxy group, glycidoxy group, vinyl group, (meth) acryloxy group, amino group, and C3-6 cycloalkyl which may further have the above group as a substituent. Group or phenyl group. Specific examples of the trifunctional silane compound include methyltrimethoxysilane, methyltriethoxysilane, methyltriisopropoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, 2- Chloroethyltriethoxysilane, 3,3,3-trifluoropropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, allyltriethoxysilane, 3 -Methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, 4-aminobutyltriethoxysilane, 3-aminopropyltriethoxysilane, 3 Aminopropyltrimethoxysilane, and benzyl triethoxysilane and the like. Among the above compounds, those having a reactive substituent such as an epoxy group, a vinyl group, and an amino group can be used as a silane coupling agent. In this case, there is a possibility that the strength of the coating film can be further increased by using a compound that reacts with the silane coupling agent to crosslink.

  The hydrolyzable silane compound represented by the formula (1) is hydrolyzed when water is present, and this hydrolyzate is dehydrated to be converted into a condensate. In order to accelerate this hydrolysis, a catalyst such as heating or an acid or an alkali is generally used. The hydrolysis and condensation reactions are affected by the amount of water present in the reaction system and the type and amount of catalyst. For example, when a large excess of water is present and the reaction rate is sufficiently high, a high molecular weight condensate is formed. On the other hand, when the amount of water is limited, a partial hydrolyzate and a low molecular weight condensate derived therefrom are produced. Some hydrolyzable silane compounds have a halogeno group instead of an alkoxy group as a hydrolyzable group, but such a compound is highly reactive and a stable partial hydrolysis product cannot be obtained. It is not suitable for use in the present invention.

In the present invention, the molar ratio (water / hydrolyzable group) between the hydrolyzable group of the hydrolyzable silane compound, which is the starting material of the hydrolysis product, and the total amount of water added in the photocatalyst coating solution is 0. It is limited to the range of 2 to 1.3, and a partial hydrolyzate and a condensate derived therefrom are produced. The molar ratio between the hydrolyzable group of the hydrolyzable silane compound and the amount of water added in the hydrolysis step is preferably in the same range. The hydrolysis-condensation product has a low molecular weight and preferably has a polymerization degree of 8 or less. In particular, when only a tetrafunctional silane compound is used as the hydrolyzable silane compound, the weight average molecular weight (Mw) is preferably 100 to 600 and 150 to 580 in terms of polystyrene by gel permeation chromatography. More preferred.
In addition, in order to limit the hydrolysis condensate to a low degree of polymerization as described above, it is also effective to reduce the concentration of the hydrolyzable silane compound in the hydrolysis step. At the start, the concentration of the hydrolyzable silane compound is 30% by mass or less, more preferably 20% by mass or less, or the hydrolyzable silane compound (R ¹ ) _n SiO _{(2-n / 2)} (R ¹ and n Each represents the same thing as said Formula (1).) It is preferable that the conversion density | concentration is 10 mass% or less, More preferably, it is 8 mass% or less. For this reason, it is preferable that the hydrolyzable silane compound is diluted to the above concentration with a hydrophilic solvent described in detail below at the start of hydrolysis.

An acid is used as the hydrolysis catalyst. If alkali is used as the hydrolysis catalyst, condensation tends to proceed further after hydrolysis, which increases the viscosity of the coating solution or gels easily, so that the coating solution will not withstand long-term storage and become unstable. In this case, it is difficult to handle, and particularly, application by spraying becomes difficult. By using an acid, these problems are avoided.
As acids, soluble inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid, etc., organic acids such as acetic acid, or acidic silica sols can be used, but they volatilize quickly after the coating is formed and do not affect the strength or photocatalytic activity. From the viewpoint, hydrochloric acid or nitric acid is preferable.
The amount of acid used for hydrolysis of the hydrolyzable silane compound is in the range of 0.0001 to 0.01 in the ratio of the number of equivalents of acid to the number of moles of hydrolyzable silane compound, or in the hydrolysis step It is preferable that pH is 2-5.
In the hydrolysis step, the reaction can be promoted by further heating, but in the present invention, in order to moderately suppress the condensation reaction, it is prevented at room temperature or the temperature from becoming high (for example, (Adjusting to 30 ° C. or lower) is preferably performed while cooling.
In the hydrolysis step, stirring is performed for a certain time under the above conditions. Although this time is not particularly limited, it is preferably 10 minutes or longer, and even if it is a long time, a particular effect cannot be obtained.

The photocatalyst material fine particles used in the photocatalyst-containing coating solution of the present invention are fine particles made of an inorganic material containing a metal oxide having photocatalytic activity.
The main components of the photocatalytic material are titanium oxide, zinc oxide, tin oxide, zirconium oxide, tungsten oxide, chromium oxide, molybdenum oxide, iron oxide, nickel oxide, ruthenium oxide, vanadium oxide, niobium oxide, tantalum oxide, rhodium oxide, Examples include rhenium oxide. Among these, titanium oxide, tungsten oxide and the like, particularly anatase type or rutile type titanium oxide are preferable.

Moreover, what added metals, such as Pt, Rh, Ru, Nb, Cu, Sn, Ni, Fe, Ag, or these oxides, can also be used for these.
In particular, rutile titanium oxide carrying CuO is preferable because it exhibits a photocatalytic function in response to not only ultraviolet rays but also visible light.

The average particle diameter of the photocatalyst material fine particles is not necessarily limited, but is preferably 200 nm or less, and more preferably 1 to 20 nm so that the photocatalyst layer is not excessively nonuniform.
The fine particles of the photocatalyst material may be in a powder state, but in order to facilitate mixing with the hydrolyzate of the hydrolyzable silane compound described below, it should be in the state of a suspension or sol dispersed in a solvent. Is preferred.

When the hydrolyzable silane compound is completely hydrolyzed and dehydrated, the composition formula of the product is (R ¹ ) _n SiO _{(2-n / 2)} (where R ¹ and n are the same as those in the formula (1)). It represents the same thing.) The amount of hydrolysis product of the hydrolyzable silane compound by the acid is represented by (R ¹ ) _n SiO _{(2-n / 2)} converted mass A, and the mass of the photocatalytic material particles is B, and the mass ratio A : B is preferably 1: 5 to 10: 1. When there are more photocatalyst material particles than this, the strength of the coating film is insufficient, and when it is less, the photocatalytic activity is insufficient. The mass ratio A: B is more preferably 1: 3 to 5: 1, and particularly preferably 1: 2 to 2: 1.

In the production method of the present invention, the hydrolysis step of the hydrolyzable silane compound described above is performed in advance, and then the hydrolyzate and photocatalyst fine particles are mixed.
The method for mixing the two components is not particularly limited, and may be mixed at once or may be mixed while gradually adding one to the other. However, when the photocatalyst fine particles are a suspension or sol containing water, if the method of gradually adding the hydrolysis product to the suspension or sol of the photocatalyst is used, condensation may proceed excessively. It is not preferable. Therefore, a method of adding and mixing the photocatalyst fine particles to the hydrolysis product of the hydrolyzable silane compound is preferable.
On the other hand, when the hydrolyzable silane compound is mixed with the photocatalyst fine particles and this mixture is applied to the base material, the base material is hot, so that the hydrolyzable silane compound is easily volatilized before being hydrolyzed and condensed. It is not suitable for the purpose. If a hydrolysis step is provided after mixing the hydrolyzable silane compound with the photocatalyst fine particles, the photocatalyst fine particles are likely to be covered with the hydrolysis product of the silane compound, and the photocatalytic activity may be reduced.

In the present invention, the step of applying the photocatalyst coating solution is not particularly limited, and a known method such as a dipping method, a spray method, a spin coating method, a bar coating method, a curtain coating method, a roll coating method, or a brush coating method is used. Can do. Of these, the spray coating method is preferred because it is suitable for introduction into the production process of ceramic products, and a uniform photocatalyst layer having excellent strength can be obtained because the temperature of the base material does not drop rapidly.
Moreover, the film thickness after hardening of a photocatalyst layer is although it does not specifically limit, It is 0.2-5 micrometers normally at the point which exhibits the outstanding photocatalytic activity and intensity | strength, More preferably, it is 0.5-3 micrometers.

  In the present invention, since it is preheated, heating after the coating step is unnecessary, and it is preferable not to carry out the heating step in order to prevent a decrease in photocatalytic activity due to carbonization of organic matter. However, a heating step may be added if necessary to accelerate the curing of the photocatalyst layer. In this heating step, the temperature is preferably 600 ° C. or less and the heating time is preferably 5 minutes or less.

The photocatalyst coating liquid of the present invention contains a hydrophilic solvent. As the hydrophilic solvent, an organic solvent having a solubility in water (20 ° C.) of 50 g / L or more is preferable. Moreover, you may contain water further as a solvent. However, the molar ratio (water / hydrolyzable group) of the hydrolyzable group of the hydrolyzable silane compound which is the starting material of the hydrolysis product to the total amount of water added in the photocatalyst coating liquid is 0.2. It must be in the range of -1.3.
Further, a solvent in which the liquid phase in the photocatalyst coating liquid is uniform (that is, it does not separate into two phases and is not an emulsion) and the photocatalyst fine particles are suspended in the liquid phase to form a photocatalyst coating liquid is preferable. For this reason, it is preferable not to contain a hydrophobic surfactant.
As the solvent, an organic solvent that is miscible with water and easily volatile is more preferable. Examples of the organic solvent include lower aliphatic alcohols such as methanol, ethanol, n-propyl alcohol, and isopropyl alcohol; ketones such as acetone, or a mixture of a plurality of these. Of these, lower aliphatic alcohols are particularly preferred.

  The photocatalyst coating liquid of the present invention may further contain auxiliary components such as a metal coupling agent and a surfactant.

The metal coupling agent is a metal compound having a hydrolyzable group and thereby undergoing a crosslinking reaction (however, silicon is not included as a metal element). Specifically, any of a metal complex in which a ligand is coordinated to a metal element and a metal alcoholate in which an alkoxy group is bonded to the metal element (including compounds classified into both) is included. There is a possibility that the strength of the coating film can be further increased by the combined use of the metal coupling agent.
Specifically, titanium alkoxides such as tetraisopropyl titanate, tetra-n-butyl titanate, tetrakis (2-ethylhexyloxy) titanium, titanium-i-propoxyoctylene glycolate as titanium coupling agents; titanium acetylacetonate , Titanium tetraacetylacetonate, di-i-propoxy bis (acetylacetonato) titanium, di-n-propoxy bis (acetylacetonato) titanium, di-n-butoxy bis (acetylacetonato) titanium, diethoxy・ Titanium complexes such as bis (acetylacetonato) titanium and propanedioxytitanium bis (ethylacetoacetate);
As aluminate coupling agents, aluminum alcoholates such as aluminum isopropylate, mono-sec-butoxyaluminum diisopropylate, aluminum ethylate; ethyl acetoacetate aluminum diisopropylate, aluminum bisethylacetoacetate monoacetylacetonate, Aluminum tris (ethylacetoacetate), aluminum tris (acetylacetonate), diethoxymono (acetylacetonato) aluminum, di-i-propoxymono (acetylacetonato) aluminum, di-n-propoxymono (acetylacetonato) aluminum, Di-n-butoxymono (acetylacetonato) aluminum, ethoxybis (acetylacetonato) aluminum, i- Ropokishibisu (acetylacetonate) aluminum, n- Puropokishibisu (acetylacetonate) aluminum, n- butoxy bis aluminum complexes such as (acetylacetonate) aluminum; cyclic aluminum oligomer;
Zirconate coupling agents include zirconium tetrakis (acetylacetonate), di-n-butoxybis (acetylacetonato) zirconium, zirconium tetrakis (ethylacetoacetate), diethoxybisacetylacetonatozirconium, di-i-propoxybis ( Acetylacetonato) zirconium, di-n-propoxybis (acetylacetonato) zirconium, tri-n-butoxymonoethylacetoacetate zirconium, tri-n-butoxymonoacetylacetonatozirconium;
Etc.

The film-forming auxiliary agent is not particularly limited as long as it dissolves in the photocatalyst coating liquid of the present invention and improves the film-forming property, and specifically, the general formula: HO— (CH ₂ CH ₂ O) (poly) ethylene glycol represented by _m— R ³ (wherein R ³ is a hydrogen atom or a linear or branched alkyl group having 1 to 10 carbon atoms, and m is an integer of 1 to 5). Or (poly) ethylene glycol monoalkyl ether, general formula: R ⁵ CO—O— (CH ₂ CH ₂ O) _q —R ⁴ (wherein R ⁴ is a hydrogen atom or a straight chain having 1 to 10 carbon atoms, or (Poly) ethylene glycol ester or (poly) represented by a branched alkyl group, q is an integer of 1 to 5, and R ⁵ is a linear or branched alkyl group having 1 to 10 carbon atoms) Ethylene glycol ether ester, general formula _{HO- (C 3 H 6 O)} r -R 6 ( wherein, ^{R 6} is a hydrogen atom or a linear or branched alkyl group having 1 to 10 carbon atoms, r is an integer of 1 to 5) (Poly) propylene glycol or (poly) propylene glycol monoalkyl ether represented by the general formula: R ⁸ CO—O— (C ₃ H ₆ O) _s —R ⁷ (wherein R ⁷ is a hydrogen atom or carbon) A linear or branched alkyl group having 1 to 10 carbon atoms, s is an integer of 1 to 5, and R ⁸ is a linear or branched alkyl group having 1 to 10 carbon atoms). Preferred examples include (poly) propylene glycol ester or (poly) propylene glycol ether ester. More specifically, cellosolves such as methyl cellosolve, ethyl cellosolve, butyl cellosolve; diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, propylene glycol monoisobutyl ether, diethylene glycol Propylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monobutyl ether, dipropylene glycol monoisobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monobutyl ether, tripropylene glycol monoi Ethers such as butyl ether; ethyl cellosolve acetate, butyl cellosolve acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, dipropylene glycol monomethyl ether acetate, dipropylene glycol monoethyl ether acetate, dipropylene glycol monobutyl ether acetate, tripropylene glycol mono Ether esters such as ethyl ether acetate, tripropylene glycol monobutyl ether acetate, tripropylene glycol monoisobutyl ether acetate, propylene glycol phenyl ether, propylene glycol diacetate, 2,2,4-trimethylpentanediol-1,3-monoiso It can be exemplified Chireto like. These film forming aids can be used alone or in admixture of two or more. The amount of the film forming aid used is preferably in the range of 20% by mass or less in the photocatalyst coating solution. In particular, the range of 2 to 15% by mass is more preferable, and the transparency of the photocatalyst layer can be increased within this range.

Examples of the surfactant include known nonionic surfactants, anionic surfactants, and cationic surfactants.
By these surfactants, the stability of the photocatalyst coating liquid, specifically, the dispersibility, viscosity, leveling property, etc. of the photocatalyst material particles can be appropriately maintained. However, the photocatalyst coating solution used in the present invention preferably selects a solvent so that the liquid phase is uniform, and does not require a surfactant (emulsifier) for forming an emulsion.

  Hereinafter, the present invention will be described specifically by way of examples. However, the present invention is not limited by these examples.

(Preparation Example 1)
As a hydrolyzable silane compound, while stirring 17.36 g of tetraethoxysilane (TEOS) at room temperature, 6 g of 0.05 N nitric acid aqueous solution and 76.64 g of ethanol were added, and the mixture was stirred at room temperature for 15 minutes, acid hydrolysis. The product was obtained. The content of this acid hydrolysis product in terms of SiO ₂ is 5% by mass.
The tile was preheated to 150 to 200 ° C., and the TEOS acid hydrolysis product was spray coated on the surface at a coating amount of 20 g / m ² . As a result, there was no problem in appearance, and there was no problem such as peeling even when rubbed with a finger.
Even if this TEOS acid hydrolysis product was allowed to stand at room temperature, there was no problem of precipitation or solidification.

(Example)
Anatase-type photocatalytic titanium dioxide (IV) (manufactured by Wako Pure Chemical Industries, Ltd.) was pulverized with a bead mill under acidity of nitric acid until the particle size became 10 nm or less to obtain a 30 mass% aqueous dispersion of titanium dioxide. It was.
The photocatalytic titanium dioxide aqueous dispersion was added to the TEOS acid hydrolysis product and stirred at room temperature for 5 minutes to obtain a photocatalyst coating solution.
The amounts of the TEOS acid hydrolysis product and STS-01 are shown in Table 1.

The tile was preheated to 150 to 200 ° C., and each photocatalyst coating solution of Examples 1 to 3 was spray coated on the surface at a coating amount of 20 g / m ² . As a result, in all cases, there was no problem in appearance, and there was no problem such as peeling even when rubbing with fingers and nails.

About the photocatalyst layer obtained by the said method using Examples 1-3, the limit contact angle with respect to the water of a catalyst layer surface and a methylene blue decomposition activity were measured.
The limit contact angle with respect to water is the contact angle (limit contact angle) when the light is irradiated with black light at 1.0 mW / cm ^{2 to make} it most hydrophilic. The measuring method of the limit contact angle was based on JIS R 1703-1 (Fine ceramics-Self-cleaning performance evaluation method of photocatalyst material, Part 1: Measurement of water contact angle).
The methylene blue decomposition activity was tested in accordance with JIS R 1703-2 (Fine ceramics-photocatalytic material self-cleaning performance evaluation method, Part 2: wet decomposition performance), and the decomposition activity index (nmol / L / min) Was calculated.
The results are as shown in Table 2. It was shown that the photocatalyst has excellent hydrophilicity and self-cleaning property.

(Comparative Example 1)
A TEOS aqueous solution was obtained in the same manner as in Preparation Example 1 except that 6 g of pure water was used instead of 6 g of 0.05 N nitric acid aqueous solution.
As a result of using this TEOS aqueous solution instead of the photocatalyst coating solution in the above example and applying it to the tile in the same manner, no film was formed. This is presumably because the applied component was evaporated.

(Comparative Example 2)
A TEOS aqueous solution was obtained in the same manner as in Preparation Example 1, except that 30 g of pure water was used instead of 6 g of 0.05 N nitric acid aqueous solution and 52.64 g was used instead of 76.64 g of ethanol.
As a result of using this TEOS aqueous solution instead of the photocatalyst coating solution in the above example and applying it to the tile in the same manner, no film was formed. This is presumably because the applied component was evaporated.
When this TEOS aqueous solution was allowed to stand at room temperature, it gelled.

(Comparative Example 3)
A TEOS alkaline hydrolysis product was obtained in the same manner as in Preparation Example 1, except that 6 g of 29% by mass ammonia water was used instead of 6 g of 0.05 N nitric acid aqueous solution.
This TEOS alkaline hydrolysis product was used in place of the photocatalyst coating solution in the above examples and was applied to the tile by the same method. As a result, no film was formed. This is presumably because the applied component was evaporated.
When this TEOS alkaline hydrolysis product was allowed to stand at room temperature, a precipitate and a gel-like product were formed.

Claims (12)

Formula (1)
(R ¹ ) _n Si (OR ² ) _4-n (1)
(In the formula, R ¹ represents an optionally substituted alkyl group having 1 to 4 carbon atoms, R ² represents an alkyl group having 1 to 4 carbon atoms, and n represents an integer of 0 or 1. The photocatalyst coating liquid containing the hydrolysis product by the acid of the hydrolyzable silane compound shown by the following formula, the hydrolysis product having a polymerization degree of 8 or less, photocatalyst material particles, and a hydrophilic solvent. A method for producing a photocatalyst coating liquid,
Formula (1)
(R ¹ ) _n Si (OR ² ) _4-n (1)
(In the formula, R ¹ represents an optionally substituted alkyl group having 1 to 4 carbon atoms, R ² represents an alkyl group having 1 to 4 carbon atoms, and n represents an integer of 0 or 1. The molar ratio (water / hydrolyzable group) of the hydrolyzable group of the hydrolyzable silane compound and the total amount of water added in the photocatalyst coating liquid is 0.2 to 1. .3, a method for producing a photocatalyst coating liquid, comprising a step of hydrolyzing or hydrolytic condensation with an acid, and a step of mixing the hydrolysis product and photocatalyst material particles after the step. The method for producing a photocatalyst coating liquid according to claim 2, wherein the hydrolysis with the acid is performed at 30 ° C. or lower. The manufacturing method of the photocatalyst coating liquid of Claim 2 or 3 whose polymerization degree of the hydrolysis product by the acid of the hydrolysable silane compound shown by said Formula (1) is 8 or less. Hydrolyzate or hydrolyzed condensate of the hydrolyzable silane compound (its (R ¹ ) _n SiO _{(2-n / 2)} (wherein R ¹ and n each represent the same formula (1)). The mass ratio A: B of the converted mass to A) and the photocatalyst material particles (its mass is assumed to be B) is 1: 5 to 10: 1. The manufacturing method of the photocatalyst coating liquid of description. The manufacturing method of the photocatalyst coating liquid in any one of Claims 2-5 whose n is 0 in said Formula (1). The manufacturing method of the photocatalyst coating liquid in any one of Claims 2-6 whose photocatalyst material contains crystalline titanium dioxide. A method for producing a photocatalyst structure in which a photocatalyst layer is supported on a substrate,
The manufacturing method of a photocatalyst structure including the process of apply | coating the photocatalyst coating liquid of Claim 1 to the surface of the preheated base material, and forming a photocatalyst layer. A method for producing a photocatalyst structure in which a photocatalyst layer is supported on a substrate,
The manufacturing method of a photocatalyst structure including the process of apply | coating the photocatalyst coating liquid manufactured by the method in any one of Claims 2-7 on the surface of the preheated base material, and forming a photocatalyst layer. The manufacturing method of the photocatalyst structure of Claim 8 or 9 whose film thickness of the said photocatalyst layer is 0.1-5 micrometers. The photocatalyst structure according to any one of claims 8 to 10, wherein the substrate is any one of metal, glass, ceramics, stone, concrete, cement, or a composite material composed of two or more of the above materials. Production method. The photocatalyst structure manufactured by the method in any one of Claims 8-11.