HK1081217B - Photocatalyst coating liquid, photocatalyst film and photocatalyst member - Google Patents

Description

Photocatalyst coating liquid, photocatalyst film, and photocatalyst member

Technical Field

The present invention relates to a photocatalyst coating liquid, a photocatalyst film and a photocatalyst member. More specifically, the present invention relates to a photocatalyst coating liquid having excellent stability and capable of forming a photocatalyst film having excellent durability and retaining super-hydrophilicity in a dark place while maintaining the above functions for a long period of time on an organic substrate, a photocatalyst film having the above characteristics formed by using the coating liquid, and a photocatalyst member such as an antifouling film having the photocatalyst film on the surface.

Background

It is known that when a photocatalyst active material (hereinafter, simply referred to as a photocatalyst) is irradiated with light having an energy equal to or greater than a band gap, electrons are generated in an excited conduction band, and holes are generated in a valence band. And, the generated electrons can reduce surface oxygen to generate superoxide anion (. O)^2-) The holes oxidize the surface hydroxyl groups to generate hydroxyl radicals (. OH), and these reactive active oxygen species exert a strong oxidative decomposition function to efficiently decompose the organic substances adhered to the photocatalyst surface.

The application of such functions as deodorization, antifouling, antibacterial, sterilization, and decomposition, removal of various substances having environmental pollution problems in waste water or exhaust gas, which are functions of a photocatalyst, is being studied.

Further, as another function of the photocatalyst, it is known that when the photocatalyst is excited by light, the surface of the photocatalyst is made superhydrophilic and the contact angle with water becomes 10 degrees or less (see, for example, international patent publication No. 96/29375). The use of the super-hydrophilic function of the photocatalyst has been studied for the prevention of the contamination of sound-insulating walls of highways, illumination in tunnels, street lamps, etc. with coal contained in automobile exhaust gas, and for the use of photocatalyst films for automobile body top coats, rear-view mirror films, antifogging properties, self-cleaning window glasses, etc.

As the above-mentioned photocatalyst, various compounds having semiconductor characteristics, such as metal oxides of titanium dioxide, iron oxide, tungsten oxide, zinc oxide, and the like, metal sulfides of cadmium sulfide, zinc sulfide, and the like, have been known so far, and among them, titanium dioxide, particularly anatase-type titanium dioxide, is useful as a practical photocatalyst. The titanium dioxide exhibits excellent photocatalytic activity by absorbing light of a specific wavelength in the ultraviolet range contained in daily light such as sunlight.

When a photocatalyst layer is provided on an organic substrate such as plastic, if the photocatalyst is directly coated, a problem of deterioration of the organic substrate in a short time due to a photocatalytic action inevitably arises. Therefore, for example, in a photocatalyst film having a photocatalyst layer on a plastic film, an intermediate layer is usually provided in order to prevent deterioration of the base film due to photocatalytic action and to improve adhesion to the base film. As the intermediate layer, a material having a thickness of about several μm, which is made of an organic silicone resin, an acrylic-modified organic silicone resin, or the like, is generally used.

However, the above-mentioned intermediate layer has a problem that the durability of the action of preventing the deterioration of the organic substrate is poor, and the organic substrate is easily deteriorated in a short time due to the photocatalytic action.

On the other hand, the present inventors have proposed an organic-inorganic composite gradient (graded) material having a continuously changing composition in the thickness direction, which is useful as a novel functional material for various applications such as a coating film, an adhesive between an organic material and an inorganic or metallic material, an interlayer provided between an organic substrate and a photocatalyst coating film for preventing deterioration of the organic substrate, an interlayer for improving adhesion between an organic material and an inorganic or metallic material, and the like (for example, refer to japanese unexamined patent application publication No. 2000-336281).

The organic-inorganic composite gradient material is an organic-inorganic composite material containing a chemical combination of an organic polymer compound and a metal compound, has a composition gradient structure in which the content of the metal compound continuously changes in the thickness direction of the material, and is a novel material that can be used for the above-described various applications.

Examples of a method for forming the photocatalyst layer on the base material include a PVD method (physical vapor deposition method) such as a vacuum deposition method or a sputtering method, a dry method such as a metal melt spraying method, and a wet method using a coating liquid. When the substrate is an organic substrate, it is often not preferable to form the photocatalyst layer by a dry method in view of heat resistance thereof, and a wet method using a coating liquid is generally employed.

In the wet method using a coating liquid, a method of preparing a coating liquid composed of a dispersion liquid containing a photocatalytically active material and a photocatalyst promoter or an inorganic binder used as necessary in an appropriate solvent, coating the coating liquid on a substrate, and forming a photocatalyst layer by drying treatment is generally used.

As the binder used in the coating liquid, for example, a hydrolysate of a hydrolyzable silicon compound such as alkoxysilane is disclosed (see, for example, JP-A-2000-86938 and JP-A-2002-146283). However, the photocatalyst layer using such a binder has problems such as poor water resistance, elution of silica as a binder with water, and easy falling-off of titanium oxide particles as a photocatalyst, which results in lowering of the photocatalytic function.

Further, there is disclosed a method in which a coating liquid containing an unreacted titanium oxide sol formed by hydrolysis and condensation of a hydrolyzable titanium compound and an oxide fine particle whose reaction has been completed, such as a titanium oxide fine particle or colloidal silica, is applied to the surface of a substrate to form a film, and then the film is sintered at 250 to 850 ℃ to form a photocatalyst film (see, for example, japanese patent No. 3317668). However, in this method, in order to burn nitrocellulose used as a thickening component, a high sintering temperature must be used, and there arises a problem that it is difficult to form a photocatalyst film on an organic substrate. For example, when a coating film is heat-treated at a temperature of 200 ℃ or lower to form a photocatalyst layer on an organic substrate, a large amount of a thickening component remains in the photocatalyst film, and a dry film cannot be obtained.

Further, a photocatalyst structure having a photocatalyst film obtained from a coating liquid containing a titanium oxide sol and a stabilized titanium alkoxide on the surface of a heat-resistant base material has been disclosed (for example, see Japanese patent application laid-open No. 9-248467). In this case, since the photocatalyst film is composed of only a titanium compound, there arises a problem that the photocatalyst film hardly exhibits super-hydrophilic performance required as a self-cleaning material when stored in a dark place, and since a chelate ring-forming diol or β -diketone is used as a stabilizer for a titanium alkoxide, the photocatalyst film is formed and then sintered at a temperature of 350 to 750 ℃. When a photocatalyst film is formed on an organic substrate, if the coating film is heat-treated at a temperature not higher than the heat-resistant temperature of the substrate (for example, not higher than 200 ℃), the above-mentioned stabilizer remains in the photocatalyst film, which causes a problem of adversely affecting the function and other characteristics of the photocatalyst film.

JP-A10-237353 discloses a hydrophilic coating agent comprising amorphous titanium oxide, silicon oxide and a photocatalyst. The amorphous titanium oxide is substantially amorphous titanium peroxide TiO₃And is susceptible to becoming crystallized anatase titanium oxide at relatively low temperatures of about 100 c.

In addition, when the hydrophilic coating agent sol is dispersed in an organic solvent to form a photocatalyst film on various organic substrates and the like, the sol is immediately aggregated, and therefore, even when the film is formed, a uniform and smooth film cannot be obtained. Therefore, the dispersant of the hydrophilic coating agent must be aqueous in nature. However, since the surface energy of the coating liquid itself is high, the material of the substrate to be coated is limited, and particularly, a pretreatment step is required for a substrate having relatively low surface energy such as various organic substrates, and therefore, it is expected that the versatility is poor.

Disclosure of Invention

Under such circumstances, an object of the present invention is to provide a photocatalyst coating liquid which has excellent stability and can form a photocatalyst film having excellent durability and capable of maintaining the functions for a long period of time on an organic substrate while having an excellent photocatalytic function such as maintaining super-hydrophilicity in a dark place, a photocatalyst film having the above-mentioned properties formed by using the coating liquid, and a photocatalyst member having the photocatalyst film on the surface.

The present inventors have conducted extensive studies to achieve the above object, and as a result, have found that a coating liquid having a specific composition can achieve the above object by providing a photocatalyst film having the above properties and excellent stability even when the coating liquid is kept at 200 ℃ or lower after film formation, and have completed the present invention based on the finding.

Namely, the present invention provides:

(1) a photocatalyst coating liquid which comprises (A) titanium oxide fine particles containing anatase type crystals as the main component, (B) colloidal silica and (C) a binder comprising a hydrolysis/condensation product of a titanium alkoxide, wherein the content of the component (A) is 5 to 50% by mass, the content of the component (B) is 25 to 75% by mass in terms of solid content, and the content of the component (C) is converted to TiO, based on the total solid content₂The solid content is 10 to 55 mass%.

(2) The photocatalyst coating liquid according to the above (1), which contains ethylene glycol monoalkyl ethers or a mixture of ethylene glycol monoalkyl ethers and a monohydric alcohol having 4 or 4 carbon atoms or less as a solvent.

(3) The photocatalyst coating liquid described in the above (2), which contains ethylene glycol monoalkyl ethers and monohydric alcohols having 4 or less carbon atoms as a solvent in a mass ratio of 10: 0 to 4: 6.

(4) A photocatalyst film, characterized by being formed with the photocatalyst coating liquid as described in any 1 of the above-mentioned items (1) to (3).

(5) The photocatalyst film described in (4) above is obtained by treating a coating film formed on an organic substrate by using a photocatalyst coating liquid, while maintaining the temperature at 200 ℃ or lower.

(6) The photocatalyst film as described in the above (5) formed on an organic substrate through an interlayer film.

(7) The photocatalyst film as described in the above (6), wherein the intermediate film is an organic-inorganic composite gradient film. And

(8) a photocatalyst member characterized by having a surface with a photocatalyst film as described in any 1 of the above (4) to (7).

The present invention provides a photocatalyst coating liquid which has a particularly super-hydrophilic property and has an excellent photocatalytic function such as maintaining super-hydrophilic property in a dark place, and which can form a photocatalyst film having such a function and excellent durability on an organic substrate for a long period of time, and which is excellent in stability, a photocatalyst film having the above-mentioned properties formed therefrom, and a photocatalyst member having the photocatalyst film on the surface thereof.

Detailed Description

The photocatalyst coating liquid of the present invention is a coating liquid containing (A) titanium oxide fine particles containing anatase crystals as a main component, (B) colloidal silica, and (C) a binder composed of a hydrolysis/condensation product of a titanium alkoxide.

The fine titanium oxide particles containing anatase type crystals as the main component (hereinafter referred to as anatase type crystal titanium oxide particles) of the component (a) are photocatalyst particles, and a small amount of rutile type crystals may be mixed and present, and visible light responsive photocatalyst particles containing a part of titanium nitride, titanium suboxide, or the like may also be used. In order to achieve an excellent photocatalytic function, the average particle diameter of the anatase crystalline titanium oxide particles is preferably in the range of 1 to 500nm, more preferably in the range of 1 to 100nm, and most preferably in the range of 1 to 50 nm. The average particle diameter is measured by a laser light scattering method.

When the titanium oxide particles contain at least 1 metal and/or metal compound selected from the group consisting of V, Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, Ag, Pt and Au as the second component in the inside and/or on the surface thereof, the titanium oxide particles preferably have a higher photocatalytic function. Examples of the metal compound include metal oxides, hydroxides, oxyhydroxides, sulfates, halides, nitrates, and metal ions. The content of the second component is appropriately selected according to the kind of the substance.

The anatase crystalline titanium oxide particles can be produced by a conventionally known method, and are advantageously used in the form of a titanium oxide sol for uniform dispersion in a coating liquid. In the preparation of the above-mentioned titania sol, for example, powdered anatase crystalline titania may be deflocculated in the presence of an acid or alkali, the particle diameter thereof may be controlled by pulverization, and the crystal diameter or particle diameter may be controlled by physical or chemical means with respect to hydrous titania obtained by thermally decomposing or neutralizing titanium sulfate or titanium chloride. Further, in order to impart dispersion stability in the sol solution, a dispersion stabilizer may be used.

In the photocatalyst coating liquid of the present invention, colloidal silica used as the component (B) has an effect of maintaining the superhydrophilic performance of the photocatalyst film even when stored in a dark place.

The photocatalyst is found to have a property of decomposing organic substances on its surface or to be super-hydrophilic by irradiation with light such as ultraviolet rays, but generally does not have such a photocatalytic function in a dark place. However, the present invention exerts the property of maintaining super-hydrophilicity also in a dark place by including colloidal silica in the photocatalyst film.

The colloidal silica is composed of high purity Silica (SiO)₂) The product dispersed in the aqueous medium is colloidal, and the average particle diameter is usually in the range of 1 to 200nm, preferably in the range of 5 to 50 nm. The hydrolysis/condensation product of silica sol or silicon alkoxide is easily eluted with water because the reaction is not terminated, and the photocatalyst film containing these substances is inferior in water resistance. On the other hand, colloidal silica is a reaction-terminated fine particle, and therefore is difficult to elute with water, and a photocatalyst film containing colloidal silica is excellent in water resistance.

In the photocatalyst coating liquid of the present invention, the hydrolysis/condensation product of a titanium alkoxide used as the component (C) functions as a water-resistant binder.

The titanium alkoxide is preferably a titanium tetraalkoxide having 1 to 4 carbon atoms as an alkoxy group. In the titanium tetraalkoxide, the four alkoxy groups may be the same or different, and the same is preferably used from the viewpoint of easy availability. Examples of the titanium tetraalkoxides include titanium tetramethoxide, titanium tetraethoxyxide, titanium tetra-n-propoxide, titanium tetraisopropoxide, titanium tetra-n-butoxide, titanium tetraisopropoxide, titanium tetra-sec-butoxide, titanium tetra-tert-butoxide and the like. These can be used alone in 1, also can be combined with 2 or more than 2.

In the present invention, the hydrolysis and condensation reaction of the titanium alkoxide to form the binder is carried out in an organic solvent described later, for example, preferably 0.5 to 4 times by mol, more preferably 1 to 3 times by mol of water with respect to the titanium tetraalkoxide, in the presence of an inorganic acid such as hydrochloric acid, sulfuric acid, or nitric acid, usually at a temperature in the range of 0 to 70 ℃, preferably 20 to 50 ℃.

The binder of the present invention comprises a binder comprising a hydrolysis/condensation product of a titanium alkoxide and TiO having a large number of unreacted organic groups_xC_nH_mThe structure is difficult to crystallize at a temperature lower than the combustion temperature of the organic substrate. That is, the amorphous form is maintained at 200 ℃ or lower, and brittleness and the like of the coating film accompanying crystallization do not occur, and is substantially different from amorphous titanium oxide composed of titanium peroxide, for example.

In the photocatalyst coating liquid of the present invention, it is preferable that the solvent contains ethylene glycol monoalkyl ethers or a mixture of ethylene glycol monoalkyl ethers and monohydric alcohols having 4 or 4 carbon atoms or less, from the viewpoint of stability of the coating liquid such as dispersion stability of each particle in the coating liquid.

Examples of the ethylene glycol monoalkyl ethers include glycol ether solvents such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, and ethylene glycol monobutyl ether. These solvents may be used alone in 1 kind, or may be used in combination of 2 or more than 2 kinds.

Examples of the monohydric alcohol having 4 or less carbon atoms which can be used in combination with the ethylene glycol monoalkyl ether include methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, and tert-butanol. These alcohols may be used alone in 1 kind, or in combination of 2 or more than 2 kinds.

The mixture of the ethylene glycol monoalkyl ether and the monohydric alcohol having 4 or 4 carbon atoms or less as the dispersion solvent is excellent in wettability to various organic substrates, particularly, a substrate, and is easy to form a film.

The coating liquid is preferably such that the mass ratio of the ethylene glycol monoalkyl ether to the monohydric alcohol is 10: 0 to 4: 6, because gelation or formation of precipitates easily occurs and there is a problem in stability, and also, when the coating liquid is formed into a film, blushing or loss of transparency may occur.

In the photocatalyst coating liquid of the present invention, in order to prevent aggregation of added particles and stabilize the coating liquid and obtain a homogeneous and smooth coating film, it is preferable that the following relational expression is satisfied, assuming that the water concentration in the photocatalyst coating liquid is X mol/liter and the hydrogen atom concentration of the inorganic acid is Y mol/liter,

D＞Y＞E (a)

0.019＜Y＜0.3(b)

1＜X＜14(c)

(wherein,

D＝1.46×10^-2X²-4.06×10^-2X+3.93×10^-2

E＝-0.04×10^-2X²+1.66×10^-2X-2.88×10^-2。)

when X.gtoreq.14, it is difficult to obtain a homogeneous and smooth film, and when X < 14, the above relational expressions (a) to (b) are not satisfied, the stability of the coating liquid is poor.

The method for preparing the photocatalyst coating liquid of the present invention is not particularly limited, and the photocatalyst coating liquid can be prepared as follows.

First, a binder obtained by adding 0.5 to 4 times, preferably 1 to 3 times, moles of water and a predetermined amount of inorganic acid to a predetermined amount of titanium alkoxide in an organic solvent composed of ethylene glycol monoalkyl ether or a mixture of ethylene glycol monoalkyl ether and a monohydric alcohol having 4 or less carbon atoms, and hydrolyzing and condensing the titanium alkoxide at a temperature of about 0 to 70 ℃ and preferably at a temperature of 20 to 50 ℃ is added, and then a predetermined amount of anatase crystalline titanium oxide sol or colloidal silica is added to uniformly disperse the titanium alkoxide sol or colloidal silica, thereby preparing the photocatalyst coating liquid of the present invention.

The photocatalyst coating liquid thus prepared is coated by a known method such as dip coating, spin coating, spray coating, bar coating, air knife coating, roll coating, blade coating, die coating (dip coating), gravure coating, etc. to form a film, and then dried by natural drying or heat drying to obtain the photocatalyst film of the present invention. The temperature of the drying by heating may be 200 ℃ or lower. After the film formation, the photocatalyst film formed by the low-temperature holding treatment can exhibit a sufficient photocatalytic function, and is suitable for substrates such as inorganic substrates having good heat resistance, e.g., ceramics, glass, metals, alloys, etc., and other organic substrates having poor heat resistance.

Examples of the organic substrate include substrates composed of acrylic resins such as polymethyl methacrylate, styrene resins such as polystyrene and ABS resins, olefin resins such as polyethylene and polypropylene, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, polyamide resins such as 6-nylon and 6, 6-nylon, polyvinyl chloride resins, polycarbonate resins, polyphenylene sulfide resins, polyphenylene ether resins, polyimide resins, cellulose resins such as cellulose acetate, and the like.

The organic substrate of the present invention includes a substrate made of a material other than an organic material, for example, a metal material, a glass or ceramic material, or various other inorganic materials, and having an organic coating film on the surface thereof.

When a photocatalyst film is directly formed on such an organic substrate, the organic substrate is deteriorated in a short time by the photocatalytic action of the photocatalyst film, and therefore an intermediate film for suppressing the deterioration of the organic substrate is usually interposed between the organic substrate and the photocatalyst film. Various intermediate films have been known as such an intermediate film, for example, a silicone resin film, an acrylic-modified silicone resin film, an organic-inorganic composite gradient film, and the like, and in the present invention, an organic-inorganic composite gradient film is preferably used from the viewpoint of adhesion between an organic substrate and a photocatalyst film, prevention of deterioration of an organic substrate, and the like.

The organic-inorganic composite gradient film is a composite material containing a complex of an organic polymer compound having a metal-containing group capable of binding to a metal oxide by hydrolysis (hereinafter referred to as a hydrolyzable metal-containing group) in the molecule and a metal oxide capable of forming a metal oxide by hydrolysis, and a metal oxide, and has a structure in which the content of a metal component continuously changes in the film thickness direction.

The organic polymer compound having a hydrolyzable metal group of the component (X) can be obtained, for example, by copolymerizing (a) an ethylenically unsaturated monomer having a hydrolyzable metal group and (b) an ethylenically unsaturated monomer containing no metal.

Examples of the ethylenically unsaturated monomer having a hydrolyzable metal group as the component (X) or (a) include a group represented by the general formula (I):

(in the formula, R¹Is a hydrogen atom or a methyl group, A is an alkylene group, preferably an alkylene group having 1 to 4 carbon atoms, R²Is a hydrolyzable group or a non-hydrolyzable group, at least 1 of which is necessarily a hydrolyzable group capable of chemically bonding to the component (Y) by hydrolysis, and R²When there are plural, each R²May be the same or different from each other, M¹Is a metal atom of silicon, titanium, zirconium, indium, tin, aluminum, or the like, and K is a metal atom M¹The valence number).

In the above general formula (I), as R²In (3), the hydrolyzable group which can be chemically bonded to the component (Y) by hydrolysis includes a halogen atom such as an alkoxy group, an isocyanate group, a chlorine atom, an oxyhalogen group, an acetoacetate group, a hydroxyl group and the like, while the non-hydrolyzable group which is not chemically bonded to the component (Y) is preferably a lower alcohol and the like.

As M in the general formula (I)¹R² _k-1Examples of the metal-containing group include trimethoxysilyl, triethoxysilyl, tri-n-propoxysilyl, triisopropoxysilyl, tri-n-butoxysilyl, triisobutoxysilyl, tri-sec-butoxysilyl, tri-tert-butoxysilyl, trichlorosilyl, dimethylmethoxysilyl, methyldimethoxysilyl, dimethylchlorosilyl, methyldichlorosilyl, triisocyanatosilyl, methyldiisocyanosilyl and the like, trimethoxytitanium base, triethoxytitanium base, tri-n-propoxytitanium base, triisopropoxytitanium base, tri-n-butoxytitanium base, triisobutoxytitanium base, tri-sec-butoxytitanium base, tri-tert-butoxytitanium base and trichlorotitanium base, and further, trimethoxyzirconium base, triethoxyzirconium base, tri-n-propoxytrianyl, triisopropoxytriazinyl, tri-n-butoxyzirconium, triisobutoxyzirconium, tri-sec-butoxyzirconium, tri-tert-butoxyzirconium and trichlorozirconium, and dimethoxy aluminum, diethoxy aluminum, di-n-propoxyl aluminum, diisopropoxyl aluminum, di-n-butoxyaluminum, di-isobutoxyaluminum, di-sec-butyl aluminumOxyaluminum based, di-t-butoxyaluminum based, and trichloroaluminum based, and the like.

The ethylenically unsaturated monomer of the component (a) may be used in 1 kind, or 2 or more kinds may be used in combination.

On the other hand, examples of the metal-free ethylenically unsaturated monomer as the component (b) include ethylenically unsaturated monomers represented by the general formula (II),

(in the formula, R³Is a hydrogen atom or a methyl group, and X is a monovalent organic group. ) The ethylenically unsaturated monomer represented by the general formula (II-a) is preferable

(in the formula, R³As above, R⁴Represents a hydrocarbon group),

or a mixture of an ethylenically unsaturated monomer represented by the general formula (II-a) and an ethylenically unsaturated monomer represented by the general formula (II-b) added as an adhesion improver as required

(in the formula, R⁵Is a hydrogen atom or a methyl group, R⁶Represents a hydrocarbon group having an epoxy group, a halogen atom or an ether bond).

R in the ethylenically unsaturated monomer represented by the above general formula (II-a)⁴The hydrocarbon group preferably includes a C1-10 linear or branched alkyl group, a C3-10 cycloalkyl group, and a C6-10 aryl groupAnd an aralkyl group having 7 to 10 carbon atoms. Examples of the alkyl group having 1 to 10 carbon atoms include methyl, ethyl, n-propyl, isopropyl, and various butyl, pentyl, hexyl, octyl, and decyl groups. Examples of the cycloalkyl group having 3 to 10 carbon atoms include cyclopentyl, cyclohexyl, methylcyclohexyl, cyclooctyl, and the like; examples of the aryl group having 6 to 10 carbon atoms include a phenyl group, a tolyl group, a xylyl group, a naphthyl group, a methylnaphthyl group, and the like; examples of the aralkyl group having 7 to 10 carbon atoms include a benzyl group, a methylbenzyl group, a phenethyl group, a naphthylmethyl group and the like.

Examples of the ethylenically unsaturated monomer represented by the general formula (II-a) include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, phenyl (meth) acrylate, and benzyl (meth) acrylate, and 1 kind of the ethylenically unsaturated monomer may be used, and 2 or more kinds may be used in combination.

R in the ethylenically unsaturated monomer represented by the general formula (II-b)⁵The hydrocarbon group having an epoxy group, a halogen atom or an ether bond preferably includes a linear or branched alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms and an aralkyl group having 7 to 10 carbon atoms. The halogen atom as the above-mentioned substituent may be a chlorine atom or a bromine atom. Specific examples of the hydrocarbon group include those represented by R in the general formula (II-a)⁴The same groups as exemplified in the description of (a).

Examples of the ethylenically unsaturated monomer represented by the above general formula (II-b) include glycidyl (meth) acrylate, 3-glycidoxy (meth) acrylate, 2- (3, 4-epoxycyclohexyl) ethyl (meth) acrylate, 2-chloroethyl (meth) acrylate, and 2-bromoethyl (meth) acrylate.

Further, as the ethylenically unsaturated monomer represented by the general formula (II), in addition to these, styrene, α -toluylene, α -acetoxystyrene, m-, o-, or p-bromostyrene, m-, o-, or p-chlorostyrene, m-, o-, or p-vinylphenol, 1-or 2-vinylnaphthalene and the like can be used, and further, a stabilizer for a polymerizable polymer having an ethylenically unsaturated group, for example, an antioxidant, an ultraviolet absorber, a light stabilizer and the like having an ethylenically unsaturated group can be used. These can be used alone, also can be combined with 2 or more than 2.

When the ethylenically unsaturated monomer represented by the general formula (II-a) and the ethylenically unsaturated monomer represented by the general formula (II-b) are used in combination, the proportion of the latter ethylenically unsaturated monomer is preferably 1 to 100 mol% based on the former ethylenically unsaturated monomer.

The organic polymer compound having a hydrolyzable metal-containing group as the component (X) is obtained by radical copolymerization of the above-mentioned ethylenically unsaturated monomer having a hydrolyzable metal-containing group as the component (a) and the ethylenically unsaturated monomer containing no metal as the component (b) in the presence of a radical polymerization initiator.

On the other hand, as the metal-containing compound (hydrolyzable metal-containing compound) capable of forming a metal oxide by hydrolysis of the component (Y), a compound represented by the general formula (III) or a condensation oligomer thereof is used.

R⁷ _m-nM²R⁸n …(III)

(in the formula, R⁷Represents a non-hydrolyzable group, R⁸Represents a hydrolyzable group, M²Represents a metal atom, M is a metal atom M²N is an integer satisfying the relationship 0 < n.ltoreq.m. ).

In the above general formula (III), when R is⁷When there are plural, plural R⁷May be the same or different, R⁸When there are plural, plural R⁸May be the same or different. As R⁷The non-hydrolyzable group preferably includes alkyl, aryl and alkenyl groups, R⁸Examples of the hydrolyzable group include a hydroxyl group, an alkoxy group, a halogen atom such as an isocyanate group or a chlorine atom, an oxyhalogen group and an acetoacetateAnd the like. Furthermore, M²Examples of the metal atom include silicon, titanium, zirconium, indium, tin, and aluminum.

Examples of the compound represented by the above general formula (III) or a condensation oligomer thereof include tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetraisopropoxysilane, tetra-n-butoxysilane, tetraisobutoxysilane, tetra-sec-butoxysilane, tetra-tert-butoxysilane, and corresponding titanium tetraalkoxide and zirconium tetraalkoxide, as well as metal alkoxides and metal alkoxide oligomers such as trimethoxyaluminum, triethoxyaluminum, tri-n-propoxyaluminum, triisopropoxyaluminum, tri-n-butoxyaluminum, triisobutoxyaluminum, tri-sec-butoxyaluminum, and tri-tert-butoxyaluminum, and metal alkoxide oligomers such as commercially available alkoxysilane oligomers such as "Methyl Slate 51" Ethyl Silicate 40 "(trade name manufactured by Colcoat corporation)," MS-51 "and" MS-56 "(trade name manufactured by Mitsubishi chemical corporation), and tetraisocyanatosilane, Methyl triisocyanatosilane, tetrachlorosilane, methyltrichlorosilane, and the like. A metal alkoxide is preferable as the component (Y).

In the present invention, the hydrolyzable metal-containing compound may be used alone in 1 kind, or may be used in a mixture of 2 or more kinds.

In the present invention, a mixture of the organic polymer compound of the component (X) and at least one hydrolyzable metal-containing compound as the component (Y) is hydrolyzed in an appropriate polar solvent such as alcohol, ketone, ether or the like at a temperature of usually 0 to 100 ℃, preferably 20 to 60 ℃ using an acid such as hydrochloric acid, sulfuric acid, nitric acid or a cation exchange resin as a solid acid, and when a solid acid is used, the solid acid is removed, and then the solvent is distilled off or added as necessary to adjust the viscosity of the coating liquid to a suitable viscosity for coating, thereby preparing a coating material containing the coating liquid. When the above temperature is too low, hydrolysis does not proceed, whereas when it is too high, hydrolysis and polymerization reaction proceed too fast to be controlled, and as a result, the gradient coating film obtained has a reduced tilt property.

The inorganic component may be slowly hydrolyzed and polycondensed after preparation of the coating solution depending on its kind, thereby changing the coating conditions, and the storage time can be prevented from being shortened by adding an insoluble solid dehydrating agent such as anhydrous magnesium sulfate to the coating solution. In this case, the coating liquid is used for coating after removing the dehydrating agent.

Then, a coating film agent composed of the coating liquid thus obtained is formed into a coating film on the surface of an organic substrate by a known method such as a dip coating method, a spin coating method, a spray coating method, a bar coating method, an air knife coating method, a roll coating method, a blade method, a die coating method, a gravure coating method, etc., with an average thickness ranging from 40 to 300nm after drying, and a desired organic-inorganic composite gradient film is formed by a known drying treatment, for example, a heat drying treatment at a temperature of about 40 to 150 ℃.

When the average thickness of the composite gradient film is less than 40nm, the function as an intermediate film cannot be sufficiently exhibited. If the particle diameter exceeds 300nm, problems such as cracks may occur.

In the thus formed organic-inorganic composite gradient film, the content of the metal component of the composite film in the surface layer is almost 100%, and gradually decreases toward the substrate to almost 0% near the substrate. That is, the organic-inorganic composite gradient film is substantially composed of only the organic polymer compound component on the surface in contact with the organic substrate, and only the metal oxide compound on the other open surface.

In the present invention, a photocatalyst film can be formed by applying the photocatalyst coating liquid of the present invention to the thus-formed organic-inorganic composite gradient film to form a film and then maintaining the film at a temperature of 200 ℃ or lower. The thickness of the photocatalyst film is usually selected in the range of 10nm to 5 μm. When the thickness is less than 10nm, the photocatalyst function cannot be sufficiently exhibited. The thickness exceeding 5 μm is not only not observed to improve the photocatalytic function, but also causes the occurrence of cracks. The thickness is preferably 30nm to 3 μm, and particularly preferably 30nm to 1 μm.

The photocatalyst film of the present invention thus formed has excellent photocatalytic functions such as super-hydrophilicity and the ability to maintain super-hydrophilicity in a dark place, and also has excellent water resistance and mechanical strength, and has excellent durability capable of continuously maintaining the above functions for a long period of time.

The present invention also provides a photocatalyst member having the above photocatalyst film on the surface thereof. The shape of the photocatalyst member is not particularly limited, and various structures such as a film, a sheet, a plate, and others may be used. The photocatalyst member is suitably used in various applications such as an antifouling member.

When the photocatalyst member of the present invention is in the form of a film, it is attached to a body, a window glass or a mirror of various transportation means such as an automobile, a train, a ship, a house, a building, an apartment, or other buildings, a window (including a skylight and a bright window) for various purposes, a display window of a shop, various protective glasses such as a vending machine, a surveillance camera, a solar battery, a road lighting, an air traffic light, a transparent wall, a color glass window, a road guide sign or a price list, a transportation facility boarding place guide sign or a timetable, various meeting place or facility guide signs, an interior illumination type traffic sign, an LED guide sign, various signs such as an interior illumination type shop sign, an interior illumination type moving shop sign, various building advertising boards, various self-standing signs such as a station, a roadside, and the like, an EL light emitting display type sign, In the interior of various decorative boards, freezing and refrigerating showcases, greenhouses, etc., various decorative boards, adhesion-preventing objects, adhesion-preventing water droplets, visibility enhancing, snow slipperiness imparting, decomposition of trace amounts of harmful substances in the interior space, and prevention of scattering when glass is damaged are exhibited.

Further, the antibacterial function can be utilized for a packaging film for food packaging, an inner surface of a drinking water storage plastic container, or the like.

(examples)

The present invention will be described in more detail below with reference to examples, which are not intended to limit the scope of the present invention.

Among them, the photocatalyst films obtained in the respective examples were evaluated according to the following methods.

(1) Stability of coating liquid

After 1 week from the preparation of the photocatalyst coating liquid, the appearance of the coating liquid was visually observed, and the following evaluation was made.

O: has transparency. X: gelling or precipitation, marked whitening and clouding.

(2) Film forming property

The film forming property of the photocatalyst film thus formed was visually observed, and the following evaluation was made.

O: the transparency was kept good. X: whitish and turbid.

(3) Hydrophilic property confirmation test for maintaining contact angle less than 10 degrees in dark

A sample showing sufficient super-hydrophilicity by irradiation with ultraviolet rays was stored in a dark place, taken out at a predetermined time, and measured with a water contact angle meter [ water contact angle measuring instrument "G-1-1000" manufactured by ERMA sales corporation, temperature: 25 ℃ and humidity 50% ]. When the contact angle is less than 10 degrees, the time for maintaining the super-hydrophilicity is represented, and the number of days required for exceeding 10 degrees is defined as the number of days for maintaining the super-hydrophilicity

(4) Determination of the hydrophilization Rate

After the test of (3), the contact angle of the sample exceeding 20 ℃ was measured with 1mW/cm²The ultraviolet irradiation time and the reciprocal (1/deg) of the contact angle at the corresponding time point are plotted, and the hydrophilization rate is calculated by using the slope as the constant of the hydrophilization rate.

(5) Pencil hardness test

A pencil scratch test was carried out according to JIS K5400 with a load of 100 g. When the total of five times tested, 3 times or more, the hardness of 1 grade lower than the pencil hardness was taken as the hardness of the coating film.

(6) Durability of coating film

A300-hour accelerated test (cycle: 1 cycle for 2 hours, irradiation for 102 minutes, irradiation + rainfall for 18 minutes, black screen temperature: 63. + -. 3 ℃ C., relative humidity: 55. + -. 5%) was carried out in accordance with JIS K7350 using a carbon arc type solar climate tester (tester: sunshine weather meter "S300" manufactured by SUGA tester Co., Ltd.), the amounts of titanium and silicon atoms in the coating film before and after the weather resistance test were measured by fluorescent X-ray measurement (Rigaku ZSx100e, X-ray tube Rh, tube voltage 500Kv, tube current 60Ma) to obtain respective strength values, and the amount of decrease in each atom was calculated from the amount of change in the strength values to evaluate the durability of the coating film. That is, the lower the reduction rate, the higher the durability of the coating film.

Production example 1

Making films with organic-inorganic composite gradient membranes

After 0.1g of 2, 2' -azobisisobutyronitrile was dissolved in a mixed solution of 10.9g of methyl methacrylate and 1.36g of γ -methacryloxypropyltrimethoxysilane, the resulting solution was reacted at 75 ℃ for 3 hours while stirring to obtain a copolymer having a weight average molecular weight of about 7 million in terms of polystyrene obtained by Gel Permeation Chromatography (GPC). This copolymer (1.0 g) was dissolved in methyl isobutyl ketone (100 ml) to obtain an organic component solution having a concentration of 10 g/l.

After 10.0g (0.036 mol) of titanium tetraisopropoxide was dissolved in 19.9g (0.221 mol) of ethylene glycol ethyl ether to prepare a solution, a mixed solution of 1.68g (0.016 mol) of a 60 mass% nitric acid aqueous solution, 0.61g (0.034 mol) of water and 7.8g (0.087 mol) of ethylene glycol ethyl ether was gradually added dropwise with stirring, and then the solution was stirred at 30 ℃ for 4 hours to prepare an inorganic component solution.

After 5ml of the organic component solution was added to 20ml of methyl isobutyl ketone, 16.7ml of ethylene glycol ethyl ether and 8.8ml of the organic component solution were successively added to prepare a component gradient film coating liquid. The coating liquid bar was coated on a 50 μm-thick polyethylene terephthalate (PET) Film (Teijin-Du Pont Film Corp., "Tetlon HB-3" hair) with a Mayer bar to obtain a Film with an organic-inorganic composite gradient Film having a thickness of 100 nm.

Production example 2

Preparation of adhesive solution

After 10.00g (0.035 mol) of titanium tetraisopropoxide was dissolved in 19.9g (0.221 mol) of ethylene glycol ethyl ether to prepare a solution, a mixed solution of 1.68g (0.016 mol) of a 60 mass% nitric acid aqueous solution, 0.61g (0.034 mol) of water and 7.80g (0.087 mol) of ethylene glycol ethyl ether was gradually added dropwise with stirring, and then the mixture was stirred at 30 ℃ for 4 hours. Thereafter, 77.60g (0.863 mol) of ethylene glycol ethyl ether was added to prepare a solution of TiO₂A binder solution having a reduced solid content of 2.38% by mass.

Here, the water in the binder solution includes water contained in a 60 mass% nitric acid aqueous solution

(0.67g) and added water (0.61g), the total amount was 1.28g, and the nitric acid content in the 60 mass% nitric acid aqueous solution was 1.01 g.

Example 1

A mixture of 94.11g of ethylene glycol ethyl ether and 133.59g of n-propanol was stirred while 44.12g of a binder solution was added thereto, and then a mixed solution of 0.81g of a 60 mass% nitric acid aqueous solution and 20.40g of water was slowly dropped. Then, an anatase-type crystalline titanium oxide particle dispersion solution [ PC-201 agent manufactured by titanium industries (Ltd.): 77.2% of water, 2.1% of nitric acid, 20.7 parts by mass of a solid content concentration, 1.45g of an average particle diameter of 20 to 40nm, colloidal silica [ snowtex IPA-ST "manufactured by Nissan chemical industries, Ltd.," solvent: 69.999 mass% of isopropyl alcohol, 0.001 mass% of nitric acid, a solid content concentration of 30 mass%, and an average particle diameter of 10 to 20nm of 5.50g, thereby preparing a photocatalyst coating liquid.

Here, water contained in the photocatalyst coating liquid was 0.48g in the binder solution and 0.32g in a 60 mass% nitric acid aqueous solution, and added20.40g of (2) and 1.12g of the anatase crystalline titanium oxide particle dispersion, and 22.32g and 1.24 mol in total. Further, the amounts of nitric acid were 0.38g in the binder solution, 0.50g in the 60 mass% nitric acid aqueous solution added, 0.03g in the anatase-type crystalline titanium oxide particle dispersion liquid, and 5.50X 10 in the colloidal silica dispersion liquid^-5g, total of 0.90g and 1.43X 10^-2And (3) mol. 300g of the photocatalyst coating liquid prepared above, had a specific gravity of 0.86, a water concentration of 3.6 mol/liter, and a hydrogen atom concentration of nitric acid of 4.1X 10^-2Mol/l.

Next, on the gradient film of the thin film with an organic-inorganic composite gradient film obtained in production example 1, the coating solution was applied by a Mayer rod to form a film, and the solvent was evaporated to form a photocatalyst film having a thickness of 45nm, thereby producing a photocatalyst film.

The performance of the obtained photocatalyst film was measured by pencil hardness test, hydrophilic performance confirmation test for maintaining a contact angle of less than 10 degrees in a dark place, measurement of hydrophilization speed, and film fluorescence X-ray analysis after 300 hours from carbon arc type solar climate measurement test to calculate the reduction rate of Ti atoms and Si atoms. The composition ratio of each component in the coating liquid is shown in Table 1, and the properties are shown in Table 2. The coating film has good durability, and the composition after the weather resistance test is unchanged.

Examples 2 to 6

A coating solution was prepared and a photocatalyst film was formed in the same manner as in example 1, except that the content ratio of each component in the coating solution was changed to the state shown in table 1.

The composition ratios of the respective coating liquids are shown in table 1, and the photocatalyst film performances are shown in table 2.

The durability of the coating film is good, and the composition after the weather resistance test is almost unchanged.

Examples 7 to 9

A coating solution was prepared and a photocatalyst film was formed in the same manner as in example 1, except that the amounts of water and acid added were changed to change the concentrations of water and acid in the coating solution to the states shown in table 1.

The composition of each coating liquid is shown in table 1, and the properties of the photocatalyst film are shown in table 2.

The coating liquid has good stability and film forming property, and the performance of the photocatalyst film is not changed.

Comparative examples 1 to 3

A coating solution was prepared and a photocatalyst film was formed in the same manner as in example 1, except that the content ratio of each component in the coating solution was changed to the state shown in table 1.

The properties of each coating liquid are shown in table 1, and the photocatalytic film performance is shown in table 2.

Comparative example 4

A coating solution was prepared and a photocatalyst film was formed in the same manner as in example 1 except that tetraethoxysilane was used instead of tetraisopropanolate in example 1. The properties of each coating liquid are shown in table 1, and the photocatalytic film performance is shown in table 2.

The durability of the coating film is NG, the silicon dioxide is reduced after the weather resistance test, and the composition is changed.

Comparative example 5

A coating solution was prepared and a photocatalyst film was formed in the same manner as in example 1 except that the partially hydrolyzed condensate of tetraalkoxysilane used in comparative example 4 was used in place of the colloidal silica in example 4. The properties of the coating liquid are shown in Table 1, and the photocatalytic film performance is shown in Table 2.

The durability of the coating film is NG, the silicon dioxide is reduced after the weather resistance test, and the composition is changed.

Comparative examples 6 to 9

A coating solution was prepared and a photocatalyst film was formed in the same manner as in example 1, except that the amounts of water and acid added were changed to change the concentrations of water and acid in the coating solution to the states shown in table 1.

The composition of each coating liquid is shown in table 1, and the properties of the photocatalyst film are shown in table 2.

The stability or film-forming property of the coating liquid was NG, and the photocatalyst film property was not worth evaluation.

TABLE 1

TABLE 2

Industrial applicability

The photocatalyst coating liquid of the present invention is particularly excellent in photocatalytic functions such as super-hydrophilicity and maintenance of super-hydrophilicity in a dark place, and can give a photocatalyst film having good durability and is suitable for a photocatalyst member such as an antifouling film.

Claims (8)

1. A photocatalyst coating liquid which comprises (A) fine titanium oxide particles containing anatase type crystals as the main component, (B) colloidal silica and (C) a binder comprising a hydrolysis/condensation product of a titanium alkoxide, wherein the content of the component (A) is 5 to 50% by mass, the content of the component (B) is 25 to 75% by mass in terms of solid content, and the content of the component (C) is 25 to 75% by mass in terms of TiO, based on the total solid content₂The solid content of (b) is 10 to 55 mass%.

2. The photocatalyst coating liquid according to claim 1, wherein the solvent contains ethylene glycol monoalkyl ethers or a mixture of ethylene glycol monoalkyl ethers and a monohydric alcohol having 4 or 4 carbon atoms or less.

3. The photocatalyst coating liquid according to claim 2, wherein the solvent contains ethylene glycol monoalkyl ethers and monohydric alcohols having 4 or 4 carbon atoms or less in a mass ratio of 10: 0 to 4: 6.

4. A photocatalyst film formed using the photocatalyst coating liquid described in any 1 of claims 1 to 3.

5. The photocatalyst film according to claim 4, which is formed by treating an organic substrate with a coating film formed by using a photocatalyst coating liquid at a temperature of 200 ℃ or lower.

6. The photocatalyst film according to claim 4, which is formed by treating an intermediate film provided on an organic substrate with a coating film formed by using a photocatalyst coating liquid at a temperature of 200 ℃ or lower.

7. The photocatalyst film of claim 6, wherein the intermediate film is an organic-inorganic composite gradient film.

8. A photocatalyst member characterized in that the surface has a photocatalyst film as claimed in any 1 of claims 4 to 7.