Photocatalyst coating solution having excellent response to visible light

The present invention relates to a photocatalytic coating liquid (coating liquid). More specifically, the present invention relates to a coating liquid capable of developing a photocatalytic thin film having high adhesion to various substrates, high photocatalytic activity, and particularly visible light responsiveness, without impairing the performance of the photocatalyst body. is there.

Photocatalytic thin films made of titanium oxide or the like are formed on the surfaces of various substrates, and by utilizing the strong decomposing power and hydrophilicity obtained by the photocatalytic action of titanium oxide and the like, applications such as cleaning, deodorizing, and antibacterial of the substrate surface can be applied. It has been done. However, in the current coating liquid for forming a titanium oxide thin film, a silicone-based material is often used as a binder component for holding fine particles of a photocatalyst as a thin film (for example, Patent Documents 1 and 2). However, the particle size of the photocatalyst powder is extremely fine, and most of the powder is buried in the film during film formation, or the binder component is included around the photocatalyst particles, and the photocatalyst activity is impaired. There was a drawback.

<p><patcit num="1"><text>Japanese Unexamined Patent Publication No. 2006-116461</text></patcit><patcit num="2"><text>Japanese Unexamined Patent Publication No. 2006-272757</text></patcit></p>

<p> An object of the present invention is to solve the above problems, and by preventing a decrease in photocatalytic activity due to a binder component, it exhibits high responsiveness to both ultraviolet rays and visible rays, and is transparent. It is an object of the present invention to provide a coating liquid capable of forming a highly photocatalytic thin film.</p>

<p> The present invention provides a photocatalytic coating liquid containing a photocatalyst component and a binder component, wherein the binder component contains a water-soluble titanium compound.</p>

<p> When a photocatalytic thin film is formed using the photocatalytic coating liquid of the present invention, the decrease in the catalytic activity of the highly active photocatalytic powder due to the binder component is effectively suppressed, and the transparency is sufficient to exhibit sufficient photocatalytic activity even under weak illuminance. A high thin film is obtained.</p>

Hereinafter, the present invention will be described in detail. In the present invention, the "titanium oxide-based" material includes various titanium oxides, various titanium peroxides, and compounds with their bases or acids.

[photocatalyst] In the present invention, any conventionally known photocatalyst can be used, and examples thereof include titanium oxide-based photocatalyst, tungsten oxide-based photocatalyst, and niobium-based photocatalyst. Of these, a titanium oxide-based photocatalyst is preferable.

Examples of the titanium oxide-based photocatalyst include anatase-type crystalline titanium dioxide; crystalline titanium dioxide carrying a metal such as platinum and iron; peroxotitanium having a structural formula below (particularly peroxotitanium having an anatase-type crystalline structure). , Peroxotitanic acid; metal salts of titanate, such as strontium titanate, barium titanate, sodium titanate. These can be used in the form of powders or powder dispersions, particularly dispersions using water, ethanol or the like as a dispersion medium. As the powder, those having a fine primary particle size, that is, those having a primary particle size determined by an X-ray diffraction method in the range of 0.1 nm to 100 nm, more preferably in the range of 1 nm to 50 nm are preferably used. The particles (secondary particles) of the powder in the dispersion liquid have a 50% cumulative distribution diameter (D) based on the volume obtained by dynamic light scattering method / frequency analysis (FFT-heterodyne method).₅₀) (Hereinafter referred to as "average particle size") is preferably in the range of 0.1 nm to 200 nm, more preferably in the range of 1 nm to 100 nm, and particularly preferably in the range of 1 nm to 50 nm.

Commercially available materials for such titanium oxide-based photocatalyst powder or its dispersion are MPT-623 (trade name, visible light responsive photocatalyst, powder, crystalline titanium dioxide carrying platinum, manufactured by Ishihara Sangyo), MPT. -625 (trade name, visible light responsive photocatalyst, powder, crystalline titanium dioxide carrying iron, manufactured by Ishihara Sangyo), Sagan Coat TO sol (trade name, anatase type crystalline peroxotitanium aqueous dispersion, manufactured by Saba Corporation) ) Etc. can be mentioned.

Peroxotitanium is a compound (complex) in which a part of the Ti-O-Ti bond is converted into a Ti-OO-Ti bond as shown in the following structural formula.

<chemistry num="1"><img file="JP2010234355A_D0001.tif" /></chemistry>

[Binder component] Examples of the water-soluble titanium compound that can be used as a binder component in the coating liquid of the present invention include peroxotitanium; and water-soluble organic titanium such as water-soluble titanium alkoxide compound, water-soluble titanium acylate compound, and water-soluble titanium chelate compound. Compounds are mentioned.

The water-soluble titanium alkoxide compound has a general formula (1) :. Ti (OR¹)₄ (1) [In the formula, R independently represents the same or different alkyl groups. ] The ones represented by are mentioned.

R in general formula (1)¹Alkyl groups represented by are those having 1 to 8 carbon atoms, for example, methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, sec-butyl group, t-butyl group, n-pentyl. There are a group, an n-hexyl group, an n-heptyl group, an n-octyl group, a 2-ethylhexyl group and the like.

As specific examples of the water-soluble titanium alkoxide represented by the above general formula (1), for example, tetramethoxytitanium, tetraethoxytitanium, tetrapropoxytitanium, tetraisopropoxytitanium, tetrabutoxytitanium and the like can be used.

The water-soluble titanium acylate compound has a general formula (2) :. Ti-(-O (CO) -R²)₄ (2) [In the formula, R²Is an independently homovalent or heterologous monovalent organic group, preferably a monovalent aliphatic hydrocarbon group. ] The ones represented by are mentioned.

In general formula (2), R²Examples of the organic group represented by are an alkyl group such as methyl, ethyl, propyl and butyl, an aliphatic unsaturated hydrocarbon group such as an alkenyl group such as vinyl, allyl and 1-propenyl, an acryloyl group and a methacryloyl group. In addition to groups having an aliphatic unsaturated bond, alicyclic hydrocarbon groups such as cyclohexyl and 1-cyclohexenyl, aromatic hydrocarbon groups such as phenyl, styryl, trill and xsilyl, epoxy groups, glycidyl groups and acryloyloxy. Examples thereof include an oxygen-containing complex group such as a group and a methacryloyloxy group, a nitrogen-containing complex group such as a ureido group, an amino group, an amide group and an isocyanate group.

Examples of the water-soluble titanium acylate compound include titanium lactate, titanium lactate ammonium salt, oxotitanium bis (monoammonium oxalate) and the like, and titanium lactate, titanium lactate ammonium salt and the like are preferable.

As the water-soluble titanium chelate compound, for example, titanium diisopropoxybis (triethanolamineate), titanium tetraacetylacetonate and the like can be used.

Among these water-soluble titanium compounds, peroxotitanic acid is preferable.

Commercially available materials for such water-soluble titanium compounds include Sagancoat PTA sol (trade name, peroxotitanic acid neutral aqueous solution, solid content 0.85% by mass, manufactured by Saba Corporation), and Tioskycoat TAK-B (commodity). Name, Peroxotitanic acid aqueous solution, solid content 0.85% by mass, manufactured by Tiotechno, Inc., 80% by mass 2-propanol solution of Organix TC-400 (trade name, titanium diisopropoxybis (triethanolaminete)), titanium Content content 9.3% by mass, manufactured by Matsumoto Fine Chemical Co., Ltd., Organix TC-310 (trade name, Titanium Lactate water / 2-propanol mixed solvent solution, titanium content content 8.2% by mass, manufactured by Matsumoto Fine Chemical Co., Ltd. ) Etc. can be mentioned.

These water-soluble titanium compounds may be used alone or in combination of two or more. The coating liquid of the present invention contains 0.1 to 10% by mass of a photocatalyst component, more preferably 0.5 to 5% by mass, and 0.01 to 5% by mass, more preferably 0.25 to 2% by mass of the above water-soluble titanium compound as a binder component. It is preferable to include it.

[Hypokeimenon] The substrate on which the coating liquid of the present invention is applied is not particularly limited as long as it can form a photocatalytic thin film. Examples of the material of the substrate include an organic material, an inorganic material, and a metal material. These can have various shapes according to their respective purposes and uses.

For example, examples of organic materials include vinyl chloride resin, polyethylene, polypropylene, polycarbonate, acrylic resin, polyacetal, fluororesin, silicone resin, ethylene-vinyl acetate copolymer (EVA), acrylonitrile-butadiene rubber (NBR), and polyethylene. Synthetic resin materials such as terephthalate (PET), ethylene-vinyl alcohol copolymer (EVOH), polyimide resin, polyphenylene sulfide (PPS), acrylonitrile-butadiene-styrene (ABS) resin, melamine resin; natural, synthetic or semi-synthetic Examples include textile materials and textile products. These may be commercialized into required shapes and configurations such as films, other molded products, and laminates.

Examples of the inorganic material include glass and ceramic materials. These can be commercialized in various forms such as tiles, insulators and mirrors.

Examples of the metal material include cast iron, steel, iron, iron alloy, aluminum, aluminum alloy, nickel, nickel alloy, zinc die cast and the like, which may be plated and coated with an organic paint. Further, it may be a metal plating coating applied to the surface of an inorganic or organic material.

Especially when the substrate is made of an organic material, it is preferable to surface-activate the substrate before forming a photocatalytic thin film on the substrate. By this treatment, the wettability and coatability of the coating liquid of the present invention to the substrate are effectively improved. As the surface activation treatment, for example, corona treatment, normal pressure (or atmospheric pressure) plasma treatment, or low pressure low temperature plasma treatment can be used.

[Thin film formation] The present invention provides a method for forming a photocatalytic thin film. The above coating liquid is applied to the surface of the substrate to form a coating film, and the coating film is formed. Dry the resulting coating at a temperature of 80-150 ° C, Also provided is a method for forming a photocatalytic thin film. In order to form a photocatalytic thin film on a substrate, the coating liquid of the present invention is applied to the surface of the substrate to form a coating film, and the obtained coating film is 80 to 150 ° C., preferably 90 to 110 ° C. Dry at temperature C.

The photocatalyst coating liquid can be applied to the substrate by any conventionally known method. Specifically, the coating film is used as a substrate by using a dip coating method, a spin coating method, a spray coating method, a brush coating method, an impregnation method, a roll method, a wire bar method, a die coating method, a gravure printing method, an inkjet method, or the like. Form on top.

The temperature at which the coating film on the substrate is dried is 80 to 150 ° C, preferably 90 to 110 ° C. By heating and drying at this temperature, the water-soluble titanium compound as a binder component is converted into an amorphous titanium oxide-based material. This amorphous titanium oxide-based material is based on amorphous titanium oxide, but when a water-soluble organic titanium compound is used as the water-soluble titanium compound, an organic component may remain. When the temperature is higher than 150 ° C., the binder component in the coating liquid crystallizes and the function as a binder is lowered, and the effect of protecting the substrate is also lowered.

The thickness of the formed thin film is usually 0.01 to 10 μm, preferably 0.05 to 2 μm. If the photocatalytic thin film is too thin, the photocatalytic activity is inferior, and if it is too thick, peeling, cracking, warpage, etc. are likely to occur, and the durability of the thin film is lowered.

When a thin film having a thickness of 0.01 to 10 μm is formed using the coating liquid of the present invention, a transparent thin film having a Haze value of 5 or less, particularly 3.5 or less, and a total light transmittance of 80% or more, particularly 85% or more can be obtained. .. In addition, the thin film has a photocatalytic activity (ultraviolet light) of 10 or more and a photocatalytic activity (visible light) of 2.0 or more.

The photocatalyst thin film thus obtained is composed of a photocatalyst and a binder made of an amorphous titanium oxide-based material.

<p> Hereinafter, the present invention will be specifically described with reference to Examples. This patent is not limited by these examples.</p><p>[Examples 1 to 4 and Comparative Examples 1 to 3] The following materials were used as titanium oxide-based photocatalyst materials. -Commercially available MPT625 (trade name, iron-supported crystalline titanium dioxide fine particles, manufactured by Ishihara Sangyo). -Commercially available Sagan Coat TO sol (manufactured by Saba Corporation: anatase-type crystalline peroxotitanium aqueous dispersion, peroxotitanium solid content 0.85%).</p><p> The following binder materials were used to make these photocatalytic dispersions a coating liquid capable of forming a film. -Commercially available Sagan Coat PTA sol (trade name, neutral aqueous solution of peroxotitanic acid, solid content 0.85% by mass, manufactured by Saba Corporation). -Organics TC-310 (titanium lactate, made by Matsumoto Chemical). -KR-400 (trade name, room temperature curable silicone resin, manufactured by Shin-Etsu Chemical Co., Ltd.). -FJ-294 (trade name, general-purpose binder, made by GRANDEX).</p><p> In each Example and each Comparative Example, as shown in Table 1, the above photocatalyst material and binder material are mixed and diluted so that the respective photocatalyst components and binder components have the concentrations shown in the table, and the coating liquid is applied. Was prepared.</p><p> In each example, a coating liquid was applied onto a 50 μm-thick polyethylene terephthalate (PET) film, and the obtained coating film was heated at 100 ° C. for 30 minutes and dried to form a 100 nm-thick photocatalytic thin film. The thickness of the thin film was measured using a thin film measuring device F-20 (trade name, manufactured by FILMETRICS) and a scanning electron microscope S-3400NX (trade name, Hitachi High-Technologies Corporation).</p><p> The photocatalytic thin film thus obtained was evaluated by the following method. The results are shown in Table 1. Evaluation method of photocatalytic activity A 1.0 mmol / L aqueous solution of methylene blue was applied to a photocatalytic thin film, a sufficient amount of methylene blue was adsorbed, and the mixture was dried to prepare a test piece for evaluation. The evaluation test piece was irradiated with ultraviolet rays or visible light using a photocatalyst evaluation checker PCC-2 (trade name, manufactured by ULVAC), and the decrease in the absorbance of the blue dye was measured. The irradiation light condition is ultraviolet light 1mW / cm.², Visible light (wavelength 400nm ~ 600nm) 1mW / cm²Met. Table 1 shows the photocatalytic activity, the amount of change in methylene blue absorbance 15 minutes after the start of measurement x 10³Shown as.</p><p> Light transmittance Haze Measured with NDH-20D, a digital haze meter manufactured by Nippon Denshoku Kogyo.</p><p><tables num="1"><img file="JP2010234355A_D0002.tif" /></tables></p><p>(Note) An example of combining TO sol and KR-400 was not carried out because they are immiscible.</p>