JP2005171029A - Coating composition, method of forming film having optical catalytic function, and optical catalytic member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology that can realize a film having optical catalytic functioon which never has cracks and peeling due to shrinkage by drying even being made thick, that is, which can be made a thick film, and also, which is superior in adhesion and transparency, thereby, made high in optical catatytic activity. <P>SOLUTION: The coating composition contains optical catalytic particles, an organic alkali, an anionic dispersant, and hardenable platy particles, and it is characterised in that the optical catalytic particles are selected from titania and titanic acid; the organic alkali is selected from the group consisting of an alkanolamine, a tetraalkyl ammonium, oxazine, pyperidine, and choline; the anionic dispersant is selected from the group consisting of condensed phosphoric acid, phosphoric acid, hydroxycarboxylic acid, polyhydric carboxylic acid, polycarboxylic acid; the hardenable platy particles have SiO<SB>2</SB>as their main component. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a coating composition, particularly a coating composition having a photocatalytic function (photocatalytic activity), a method for forming a film having a photocatalytic function, and a film having a photocatalytic function, such as deodorization, nitrogen oxide removal, stain prevention, hydrophilicity The present invention relates to a photocatalytic member that exhibits functions such as antibacterial properties or antibacterial properties.

  As ceramic-based paints that are superior in heat resistance and wear resistance compared to organic paints, paints such as alkali metal silicate, phosphate, silica sol, and metal oxide are known. These paints have characteristics inherent to ceramic paints such as excellent heat resistance and wear resistance, but in recent years, attempts have been made to add new functions to ceramic coatings. It is made mainly in the system.

  Among these, titanium oxide can impart an excellent photocatalytic effect, and exhibits high oxidizing power when irradiated with ultraviolet rays. And by providing titanium oxide with excellent photocatalytic activity on the surface of the object to be coated (base material) such as metal, glass, ceramic, etc., prevention of adhesion of dirt, decomposition of malodorous components, purification of water quality, rust prevention, antibacterial, It is said to be effective in preventing the growth of algae and decomposing difficult-to-decompose waste.

  For this reason, various titanium oxide paints for the purpose of forming a titanium oxide film on the surface of the material and methods for producing the same have been proposed.

  The most common method for forming a titanium oxide film is a sol-gel method in which a hydrolyzed titanium alkoxide is applied.

  As a technique similar to this, for example, a method of adding an amide or glycol to a titanium alkoxide disclosed in JP-A-4-83537, or a method of adding an alcoholamine to a titanium alkoxide disclosed in JP-A-7-100388 It has been known.

  In addition to these, as disclosed in JP-A-6-293519, a method is known in which titanium oxide fine particles crystallized by hydrothermal treatment are dispersed in an acid solution having a pH of 3 or less and applied.

  Also, as disclosed in JP-A-9-71418, a sol solution composed of hydrogen peroxide and titanium oxide and a method for producing the same are known.

  Furthermore, as disclosed in Japanese Patent No. 3238349, a titanium oxide ceramic paint containing one kind selected from orthotitanic acid and titanium (IV) ions and anatase type crystalline particles is known.

  However, in the proposed technique, when the thickness of the film having a photocatalytic function is 1 μm or more, when the film is dried, the film is cracked or severe due to shrinkage stress at the time of drying. There is a strong risk of peeling.

  For this reason, conventionally, the thickness of the film having a photocatalytic function must be a thin film of less than 1 μm, and the photocatalytic activity is inferior.

In order to solve such problems, a coating composition containing photocatalyst particles and curable plate-like particles has been proposed (Japanese Patent Laid-Open No. 2002-166175).
JP-A-4-83537 JP-A-7-1000037 JP-A-6-293519 JP-A-9-71418 Japanese Patent No. 3238349 JP 2002-166175 A

  However, it has been found that the technique proposed in Japanese Patent Laid-Open No. 2002-166175 has a problem that the transparency of the coating film is insufficient and a white opaque film is formed.

  Therefore, the problem to be solved by the present invention is that even if the thickness of the film having a photocatalytic function is increased, cracking or peeling does not occur due to drying shrinkage, that is, a thick film can be formed. It is to provide a technique that is excellent in film adhesion and excellent in transparency and that exhibits high photocatalytic activity.

By the way, the present inventors prepared a dispersion solution of titanium dioxide such as titanic acid or anatase type obtained by hydrolyzing an aqueous solution of an inorganic titanium salt such as titanium chloride or titanium sulfate at a low temperature. The solution was neutralized by adding an anionic dispersant such as polyphosphoric acid and an organic alkali, and then redispersed to obtain a highly dispersed sol of titanium oxide. On the other hand, sulfuric acid was mixed into an aqueous solution of alkali silicate and gelled. Curable plate-like particles containing SiO ₂ as a main component produced by washing and hydrothermal treatment of the particles were prepared, and the curable plate-like particles were mixed with the titanium oxide dispersion sol to produce a photocatalyst coating agent.

  Then, this prototype coating agent was applied to a glass plate so that the dry film thickness was 2 to 3 μm, and then baked at 400 ° C. to examine the adhesion, transparency, and photocatalytic activity of the photocatalytic film, Was colorless and transparent, excellent in adhesion, and was confirmed to have an excellent photocatalytic activity that has never been seen before.

The present invention has been achieved based on the above findings.
That is, the problem is that the photocatalyst particles,
Organic alkali,
An anionic dispersant;
It is solved by a coating composition characterized by comprising curable plate-like particles.

  Moreover, it solves with the photocatalyst member characterized by apply | coating said coating composition.

  In particular, it is solved by a photocatalyst member characterized in that the coating composition is applied so as to have a dry film thickness of 0.5 to 50 μm.

Also, an application step of applying the above-mentioned coating composition to a substrate,
This is solved by a method for forming a film having a photocatalytic function, comprising an organic alkali decomposition step of decomposing an organic alkali in a coating film after the coating step.

In particular, an application step of applying the coating composition to a substrate so that the dry film thickness is 0.5 to 50 μm;
This is solved by a method for forming a film having a photocatalytic function, comprising an organic alkali decomposition step of decomposing an organic alkali in a coating film after the coating step.

  Moreover, it solves by the photocatalyst member formed by the formation method of the film | membrane which has said photocatalyst function.

  In the present invention, various kinds of photocatalyst particles can be used. That is, any material that exhibits a photocatalytic function when irradiated with light having a wavelength greater than the band gap is used. For example, known metal compound semiconductors such as titanium oxide, titanic acid, zinc oxide, tungsten oxide, and iron oxide can be used alone or in combination of two or more. Among these, it is preferable when titanium oxide or titanic acid is used. That is, when titanic acid such as orthotitanic acid and peroxotitanic acid is used, or anatase type titanium dioxide (including metatitanic acid) or visible light type titanium oxide (nitrogen doped type or oxygen defect type visible light responsiveness, etc. When crystalline titanium dioxide (such as titanium dioxide) or a crystalline material having photocatalytic activity such as rutile type or brookite type was used, the transparency and photocatalytic activity of the film were further improved. Of these, amorphous titanic acid (orthotitanic acid), which becomes a crystalline titanium dioxide photocatalyst by heating and baking, and metatitanic acid or anatase type titanium dioxide having crystallinity are preferable. And the thing with the secondary particle diameter of 1-300 nm is preferable. When crystalline titanium dioxide is used, the primary crystal diameter is preferably 1 to 30 nm. The colloidal particles of titanium dioxide in the present invention are not particularly limited in particle diameter, but those having a particle diameter of 1 nm to 500 nm are preferable. In particular, the one of 3 to 120 nm is preferable.

  The titanic acid used in the present invention may be added with an alkali to a solution of an inorganic titanium compound such as titanium chloride, titanium oxychloride, titanium sulfate, titanyl sulfate in water, or treated with an anion exchange membrane or an ion exchange resin. A sol solution can be used. In this case, after removing impurity ions such as chlorine and sulfuric acid, hydrogen peroxide may be added to form a peroxotitanic acid solution. Moreover, when using an alkoxide as a raw material, a preferable titanic acid solution can be obtained by hydrolyzing a titanium alkoxide at low temperature. A large amount of crystalline titanium dioxide can be obtained by carrying out the hydrolysis at a temperature of 70 ° C. or higher, and amorphous orthotitanic acid can be mainly obtained by carrying out the hydrolysis at room temperature or lower. These acidic sols are preferably used as a raw material for the titanium oxide of the present invention. However, when the raw acidic sol contains corrosive anions such as chloride ions, sulfate ions, nitrate ions, it is filtered and washed. It is preferable to remove as much as possible by a method such as ion exchange or dialysis. Examples of the most preferable titanic acid solution include neutral amorphous titanium oxide sol disclosed in Japanese Patent No. 3238349 and peroxo titanium oxide sol disclosed in JP-A-9-71418.

  The titanium dioxide used in the present invention can be obtained by a method such as subjecting a raw material solution obtained by the same method as described above to heat hydrolysis or reacting a vaporized titanium compound with oxygen at a high temperature. Visible light-responsive titanium dioxide can be obtained by bringing anatase-type titanium dioxide into contact with ammonia at a temperature of 300 ° C. or higher, or baking titanic acid containing an ammonium salt.

In addition, in the coating film formed by apply | coating the coating composition of this invention, it is preferable that photocatalyst particles, such as titanium dioxide, are about 300-3000 mg / m < ² >. This is because if the amount of photocatalyst particles is too small, the catalytic activity effect becomes poor. The increase in photocatalyst particles is not problematic from the viewpoint of the catalytic activity effect, but is preferably 3000 mg / m ² or less from the viewpoint of cost and physical strength of the coating film.

  An anionic dispersant is used as an essential component in the coating composition of the present invention. That is, when an anionic dispersant is not used, for example, the dispersibility of photocatalyst particles such as titanium compound particles deteriorates, the dispersed particle diameter becomes excessive, and the adhesion of the coating film decreases. Thus, anionic dispersants are a very demanding factor.

  As the dispersant, those other than the anionic dispersant are known, but in the present invention, they must be anionic dispersants. For example, when a cationic dispersant is used, in the neutral to weak alkaline region, the photocatalyst particles such as titanium oxide particles are likely to aggregate due to unstable charge, and the effect of the present invention is not achieved. . In addition, when a nonionic dispersant is used, there is no effect of giving a negative charge to the photocatalyst particles such as titanium oxide particles. Therefore, the dispersion effect is poor unless a large amount of the dispersant is used. Characteristics and catalytic activity are reduced. Therefore, it is not simply said that a dispersant should be used, and an anionic dispersant must be used.

  Anionic dispersants include polyphosphoric acids such as pyrophosphoric acid and tripolyphosphoric acid that exhibit anionic properties in aqueous solution, hydroxycarboxylic acids such as phosphoric acid, lactic acid and glycolic acid, polyvalent carboxylic acids such as gluconic acid and tartaric acid, poly Preferred are those selected from the group of compounds such as carboxylic acids, ammonium salts containing them, and alkali metal salts. Other anionic dispersants such as other organic carboxylic acids, sulfate esters, phosphate esters, and organic sulfonic acids can also be used. In addition, an amphoteric surfactant can be used as an anionic dispersant as long as it is neutral and has an anionic group. Of these, preferred are dispersants including those selected from the group consisting of condensed phosphoric acid, phosphoric acid, hydroxycarboxylic acid, polyvalent carboxylic acid and polycarboxylic acid.

  In addition, it is preferable that the quantity of an anionic dispersing agent is 0.5-50 mass parts with respect to 100 mass parts of photocatalyst particles. That is, when the amount of the anionic dispersant is small, the dispersion of the photocatalyst particles becomes unstable, and the dispersibility effect is poor, the diameter of the dispersed particles is increased, and the adhesion of the coating film tends to be lowered. Because. On the other hand, if the amount is too large, the catalytic activity and the film strength tend to be adversely affected. Accordingly, the anionic dispersant is preferably 0.5 to 50 parts by mass with respect to 100 parts by mass of the photocatalyst particles. A more preferable range is 1 to 40 parts by mass, and further 3 to 20 parts by mass.

  An organic alkali is used as an essential component in the coating composition of the present invention. This is because when no organic alkali is used, the pH value is small, and the dispersion of photocatalyst particles such as titanium compound particles is insufficient. And the dispersibility of photocatalyst particles like a titanium compound particle improves by using an organic alkali.

  If the pH value is increased, an inorganic alkali can be used instead of an organic alkali. However, when an inorganic alkali is used, photocatalyst particles such as titanium dioxide particles tend to aggregate and dispersibility is lowered. Therefore, it must be organic alkali, not just alkali.

  The organic alkali is preferably selected from the group consisting of alkanolamines such as monoethanolamine, diethanolamine and triethanolamine, tetraalkylammonium such as tetramethylammonium, oxazine such as morpholine, piperidine and choline. I can list them. Of these, monoethanolamine, diethanolamine, morpholine, and tetramethylammonium hydroxide are preferable.

  In addition, it is preferable that the quantity of an organic alkali is 0.5-100 mass parts with respect to 100 mass parts of photocatalyst particles. That is, when the amount of organic alkali is small, the pH value becomes too low and the dispersibility effect of the photocatalyst particles is poor. On the other hand, if the amount is too large, the pH value tends to be too high and the corrosivity tends to become strong. Therefore, 0.5-100 mass parts of organic alkalis are preferable with respect to 100 mass parts of photocatalyst particles. A more preferable range is 2 to 80 parts by mass, and further 4 to 40 parts by mass.

  Moreover, it is preferable that the ratio (mass ratio) of an anionic dispersing agent and an organic alkali is anionic dispersing agent: organic alkali = 100: 50-500.

In the coating composition of the present invention, curable plate-like particles are used as an essential component. That is, by using curable plate-like particles, the film thickness can exceed 1 μm, for example, 2 to 50 μm. In the present invention, the curable plate-like particle means a plate-like particle having a cohesive property and curable alone. As such, for example, layered polysilicic acid such as silica-X, silica-Y, magazinite, kanemite and the like can be mentioned as preferable ones. Examples of silica-X include scaly silica described in Japanese Patent Application No. 11-351182 (Japanese Patent Laid-Open No. 2001-136613). In addition, talc, mica, glass flakes and the like can be mentioned, but curable plate-like particles mainly composed of SiO ₂ as described above are particularly preferable. Incidentally, as shown in JP-A-2001-136613, for example, after washing silica gel particles that have been gelled by mixing sulfuric acid with a water glass aqueous solution, the scaly primary particles are aggregated by further hydrothermal treatment. The curable plate-like particles obtained by forming the formed particles and pulverizing the aggregated particles are most preferable.

  The curable plate-like particles preferably have an aspect ratio of 10 to 300. In particular, an aspect ratio of 20 to 200 is preferable. This is because when the aspect ratio of the curable plate-like particles is too small, the adhesion of the coating film is lowered, and conversely, when it is too large, the transparency of the coating film tends to be lowered. Further, plate-like particles having an average grain length of 2 μm or less, particularly 0.1 to 0.8 μm are preferable.

  In addition, it is preferable that the quantity of a curable plate-shaped particle is 0.5-400 mass parts with respect to 100 mass parts of photocatalyst particles. That is, when the amount of the curable plate-like particles is small, the adhesion of the coating film tends to decrease, and it is difficult to increase the film thickness. On the contrary, if the amount is too large, the transparency of the coating film is lowered, and the photocatalytic particles in the film are relatively decreased, and the photocatalytic activity tends to be poor. Accordingly, the curable plate-like particle is preferably 0.5 to 400 parts by mass with respect to 100 parts by mass of the photocatalyst particles. A more preferable range is 5 to 200 parts by mass, and further 10 to 150 parts by mass.

  The said coating composition is apply | coated on a base material, and the film | membrane which shows a photocatalytic function is provided.

  However, it is not only that the coating composition is simply formed by applying the coating composition on a substrate and drying, but it is preferable that the organic alkali component present in the coating film is decomposed. For example, after the coating step, the organic alkali component is decomposed by heating (heating and baking) to a high temperature of 200 ° C. or higher (preferably 600 ° C. or lower) or by irradiating light (electromagnetic wave) having a wavelength of 600 nm or lower. Of course, you may use both together. That is, by decomposing the organic alkali, the photocatalytic function is further improved. In other words, the organic alkali adsorbed on the surface of the titanium dioxide particles in the coating film is decomposed by these post-treatments and the coating film is cured, and at the same time, fine voids are formed, and water, gas, organic matter, etc. are formed on the surface of the photocatalyst particles. This is because it is considered that it will be easily adsorbed and will exhibit more excellent photocatalytic activity and hydrophilicity.

  In addition, when an inorganic alkali such as sodium hydroxide is used instead of an organic alkali as an alkali component necessary for neutralization of the coating composition of the present invention, the alkali component adsorbed on the surface of the photocatalyst particles such as titanium dioxide particles is reduced. It cannot be removed, and the photocatalytic activity decreases accordingly. Therefore, the organic alkali is used in the present invention because the alkali can be easily removed by the post-treatment as described above.

  The coating composition of the present invention preferably has a pH of the liquid of the composition in the range of 4 to 10.

  In consideration of the case where it is applied to a substrate such as metal, it is preferable that the chlorine ion concentration is 0 to 20 ppm in order to prevent crevice corrosion.

  As the solvent of the coating composition of the present invention, water is most preferable. Next, a solvent compatible with water, such as ethanol, methanol, propanol or the like is preferable. A part of the water may be replaced with a water-soluble solvent such as alcohol, glycol, or ketone.

  In the present invention, the physical properties of the coating film can be improved by adding a silane derivative such as silica sol or alkyltrimethoxysilane as a binder component.

  Although it does not specifically limit as a base material used for the photocatalyst member of this invention, Resins, such as metals, such as aluminum, stainless steel, and plating steel, polycarbonate, vinyl chloride, a polyethylene terephthalate, an acryl, paper, wood, glass, ceramics, etc. are mentioned. It is done.

  The photocatalyst member of the present invention is obtained by providing a coating containing the coating composition of the present invention on the surface of a substrate by a method such as spraying, dipping, roll coating, spin coating, blade coating, brush coating, or the like, and drying it. Preferably, after that, the organic alkali in the coating film is decomposed and the coating film is cured by a method such as heat drying or electromagnetic wave irradiation.

  The coating film formed as described above is deposited in parallel on the substrate surface to form a multilayer structure in which photocatalyst particles such as titanium dioxide are sandwiched therebetween. And since the surface of the plate-like particles has many hydroxyl groups, it is chemically bonded to the adjacent plate-like particles in the process of dehydration and drying, and a porous and strong inorganic flexible film is formed. A thick film with no peeling is obtained. Furthermore, the coating film formed as described above is preferably substantially transparent. For example, those having a haze of less than 10% and a visible light transmittance of 60% or more when applied to colorless and transparent glass are preferred.

  The coating film formed by applying the coating composition according to the present invention has excellent adhesion to the base material, is highly transparent, has excellent catalytic activity, and has a highly practical photocatalytic member. can get. For example, it can be applied to various purposes such as deodorization, soil decomposition, and antibacterial, and its practical value is extremely large.

  The coating composition of the present invention contains photocatalyst particles, an organic alkali, an anionic dispersant, and curable plate-like particles.

Various kinds of photocatalyst particles are used. For example, known metal compound semiconductors such as titanium oxide, titanic acid, zinc oxide, tungsten oxide, and iron oxide can be used alone or in combination of two or more. Among these, titanium oxide and titanic acid are used. That is, when titanic acid such as orthotitanic acid and peroxotitanic acid is used, or anatase type titanium dioxide (including metatitanic acid) or visible light type titanium oxide (nitrogen doped type or oxygen defect type visible light responsiveness, etc. When crystalline titanium dioxide (such as titanium dioxide) or a crystalline material having photocatalytic activity such as rutile type or brookite type was used, the transparency and photocatalytic activity of the film were further improved. Among them, amorphous titanic acid (orthotitanic acid) that becomes a crystalline titanium dioxide photocatalyst by heating and baking, and crystalline metatitanic acid or anatase type titanium dioxide were preferred. For example, titanic acid is made into a sol solution by adding alkali to a solution obtained by dissolving an inorganic titanium compound such as titanium chloride, titanium oxychloride, titanium sulfate, titanyl sulfate in water, or by treatment with an anion exchange membrane or an ion exchange resin. Things can be used. In this case, after removing impurity ions such as chlorine and sulfuric acid, hydrogen peroxide is added to form a peroxotitanic acid solution. When alkoxide is used as a raw material, titanium alkoxide is hydrolyzed at low temperature. In addition, many crystalline titanium dioxides are obtained by performing a hydrolysis at the temperature of 70 degreeC or more. Amorphous orthotitanic acid is mainly obtained by hydrolysis at room temperature or lower. These acidic sols are used as a raw material for the titanium oxide of the present invention. In the case where a corrosive anion such as chloride ion, sulfate ion or nitrate ion is contained in the raw acid sol, it is removed as much as possible by methods such as filtration washing, ion exchange and dialysis. Examples of preferred titanic acid solutions are neutral amorphous titanium oxide sols disclosed in Japanese Patent No. 3238349 and peroxotitanium oxide sols disclosed in JP-A-9-71418. Titanium dioxide is obtained by a method such as subjecting a raw material solution obtained by the same method to heat hydrolysis or reacting a vaporized titanium compound with oxygen at a high temperature. Visible light-responsive titanium dioxide can be obtained by a method in which anatase-type titanium dioxide is brought into contact with ammonia at a temperature of 300 ° C. or higher, or titanic acid containing an ammonium salt is baked. The amount of the photocatalyst particles, such as titanium dioxide, in the coating film coating composition is made is coated photocatalyst particles 300~3000mg / ^{m 2} (in particular, 500 mg / ^{m 2} or more .2000mg / ^{m 2} or less.) And Is the amount.

  Various types of anionic dispersants are used. For example, condensed phosphoric acid such as pyrophosphoric acid and tripolyphosphoric acid that are anionic in aqueous solution, hydroxycarboxylic acid such as phosphoric acid, lactic acid and glycolic acid, polyvalent carboxylic acid such as gluconic acid and tartaric acid, polycarboxylic acid and the like It is selected from the group of compounds such as ammonium salts and alkali metal salts. Other anionic dispersants such as other organic carboxylic acids, sulfate esters, phosphate esters, and organic sulfonic acids can also be used. In addition, an amphoteric surfactant can be used as an anionic dispersant as long as it is neutral and has an anionic group. Particularly preferred are dispersants including those selected from the group of condensed phosphoric acid, phosphoric acid, hydroxycarboxylic acid, polyvalent carboxylic acid and polycarboxylic acid. The amount of the anionic dispersant is 0.5 to 50 parts by mass (particularly 1 part by mass or more, further 3 parts by mass or more, and 40 parts by mass or less, and further 20 parts by mass with respect to 100 parts by mass of the photocatalyst particles. Part or less.).

  Various organic alkalis are used. For example, alkanolamines such as monoethanolamine, diethanolamine and triethanolamine, tetraalkylammonium such as tetramethylammonium, oxazines such as morpholine, piperidine and choline can be mentioned as preferred. Of these, monoethanolamine, diethanolamine, morpholine, and tetramethylammonium hydroxide are preferable. The amount of the organic alkali is 0.5 to 100 parts by mass with respect to 100 parts by mass of the photocatalyst particles (particularly 2 parts by mass or more, further 4 parts by mass or more. And 80 parts by mass or less, further 40 parts by mass or less. .) Moreover, the ratio (mass ratio) of an anionic dispersing agent and an organic alkali is anionic dispersing agent: organic alkali = 100: 50-500.

Various kinds of curable plate-like particles are used. For example, there are layered polysilicic acids such as silica-X, silica-Y, magazinite, and kanemite. Examples of silica-X include scaly silica described in Japanese Patent Application No. 11-351182 (Japanese Patent Laid-Open No. 2001-136613). Besides, talc, mica, and glass flakes may be mentioned, curing the plate-like particles composed mainly of SiO ₂ is particularly preferred. In particular, as shown in JP-A No. 2001-136613, for example, after washing particles that have been gelled by mixing sulfuric acid with a water glass aqueous solution, the primary particles of scales aggregated by further hydrothermal treatment. A curable plate-like particle obtained by forming particles and pulverizing the aggregated particles is most preferable. The curable plate-like particles have an aspect ratio of 10 to 300, particularly 20 to 200. Further, it is a plate-like particle having an average particle diameter of 2 μm or less, particularly 0.1 to 0.8 μm. The amount of the curable plate-like particles is 0.5 to 400 parts by mass (particularly 5 parts by mass or more, more preferably 10 parts by mass or more, and 200 parts by mass or less, and further 150 parts with respect to 100 parts by mass of the photocatalyst particles. Or less).

  In the coating composition of the present invention, the pH of the liquid is 4 to 10 (particularly 4.5 or more and 9.0 or less). The chlorine ion concentration is 20 ppm or less (including 0). Water is particularly used as the solvent for the coating composition. Solvents that are compatible with water, such as ethanol, methanol, and propanol are also used. A part of the water can be replaced with a water-soluble solvent such as alcohol, glycol, or ketone.

  The coating composition of the present invention may contain a sol derivative such as silica sol or alkyltrimethoxysilane as a binder component.

  The method for forming a film having a photocatalytic function of the present invention is a method of applying the coating composition to a substrate. In particular, it is a method of coating so that the dry film thickness is 0.5 to 50 μm (particularly 1 μm or more, further 1.5 μm or more, more preferably 2 μm or more, and 40 μm or less, further 30 μm or less). As a coating method, methods such as spraying, dipping, roll coating, spin coating, blade coating, and brush coating are employed. And after apply | coating, it has the organic alkali decomposition process which decomposes | disassembles the organic alkali in a coating film. The organic alkali decomposition step is, for example, a heating step. More specifically, it is a step of heating (heating and baking) to a high temperature of 200 ° C. or higher (preferably 600 ° C. or lower). Or it is a light irradiation process. More specifically, it is a step of irradiating light (electromagnetic wave) having a wavelength of 600 nm or less. That is, by decomposing the organic alkali content in the coating film, the organic alkali adsorbed on the surface of the titanium dioxide particles in the coating film is decomposed and the coating film is cured, and at the same time, fine voids are created, photocatalyst particles Water, gas, organic matter and the like are easily adsorbed on the surface.

  Although it does not specifically limit as a base material used for the photocatalyst member of this invention, Resins, such as metals, such as aluminum, stainless steel, and plated steel, polycarbonate, vinyl chloride, PET, and acrylic, paper, wood, glass, ceramics, etc. are used. .

  The photocatalyst member of the present invention is obtained by applying the coating composition on a substrate. In particular, it is formed on a substrate by the above-described method for forming a film having a photocatalytic function. The film thickness after drying is 0.5 to 50 μm (particularly 1 μm or more, further 1.5 μm or more, more preferably 2 μm or more, and 40 μm or less, further 30 μm or less).

  Hereinafter, the present invention will be described with specific examples. However, this invention is not restrict | limited at all by an Example.

The following materials were used.
[Photocatalyst particles]
Either of the following two types (A, B) was used.
(A) Titanic acid

In Examples 1-5, Example 7, and Comparative Examples 1-8, what was prepared with the following method was used as a titanate sol.
A titanium chloride aqueous solution (Ti: 15-16%) manufactured by Toho Titanium Co., Ltd. was diluted with water, deionized with an ion exchange membrane to obtain a titanium oxychloride aqueous solution, and heated and hydrolyzed at 70 to 85 ° C. The resulting titanium dioxide sol having a pH of 1-2 was purified and used. The crystal particle diameter of titanium dioxide measured by a transmission electron microscope was 0.002 to 0.01 μm. The concentration of the titanium oxide sol particles was 5.0% by dry weight.
In Example 10, a precipitate of orthotitanic acid generated by adding ammonia to a titanium oxychloride aqueous solution was washed with water, and this was dissolved in hydrogen peroxide to obtain a 2% peroxotitanic acid solution.
(B) Titanium dioxide

In Examples 6, 8, 9 and Comparative Example 9, 5% in which titanium dioxide powder particles: ST-01 (crystal particle diameter: 0.007 μm, anatase type) manufactured by Ishihara Sangyo Co., Ltd. was dispersed in water. A dispersion was used.

[Dispersant]
The anionic dispersant was selected from gluconic acid, glycolic acid, lactic acid, polyphosphoric acid, sodium pyrophosphate, and tripolyphosphoric acid.
Benzalkonium chloride was used as the cationic dispersant.
These chemicals are grade 1 reagents manufactured by Wako Pure Chemical Industries, Ltd.

[Alkali component]
The organic alkali was selected from monoethanolamine, diethanolamine, triethanolamine, morpholine, piperidine, and choline.
Sodium hydroxide or potassium hydroxide was used as the inorganic alkali.
These chemicals are reagent grade 1 products or equivalent products.

[Curable particle]
In Examples 1 to 10 and Comparative Examples 1 to 6, Sunlably LFS-050 (aspect ratio: 50) manufactured by Dokai Chemical Industries, Ltd. was used as the plate-like particles.
In Comparative Examples 7 to 9, silica sol: Snowtex O manufactured by Nissan Chemical Co., Ltd. was used as spherical particles.

[Example 1]
A water-dispersed sol containing 100 parts by mass of photocatalyst particles was mixed and stirred with 4.3 parts by mass of monoethanolamine, 5.7 parts by mass of polyphosphoric acid, and 14.3 parts by mass of plate-like curable particles, and titanium oxide. A coating solution was prepared.

[Example 2]
Mixing and stirring 5.0 parts by weight of tetramethylammonium, 14.3 parts by weight of glycolic acid, and 35.7 parts by weight of plate-like curable particles in an aqueous dispersion sol containing 100 parts by weight of photocatalyst particles, titanium oxide A coating solution was prepared.

[Example 3]
An aqueous dispersion sol containing 100 parts by mass of photocatalyst particles is mixed and stirred with 14.3 parts by mass of choline, 28.6 parts by mass of polyphosphoric acid, and 57.1 parts by mass of plate-like curable particles, and a titanium oxide coating solution. Was made.

[Example 4]
13.3 parts by mass of diethanolamine, 10.0 parts by mass of gluconic acid, 250.0 parts by mass of plate-like curable particles are mixed and stirred in an aqueous dispersion sol containing 100 parts by mass of photocatalyst particles, and a titanium oxide coating solution Was made.

[Example 5]
Mixing and stirring 4.2 parts by weight of monoethanolamine, 1.7 parts by weight of glycolic acid, and 125.0 parts by weight of plate-like curable particles in an aqueous dispersion sol containing 100 parts by weight of photocatalyst particles, titanium oxide A coating solution was prepared.

[Example 6]
In an aqueous dispersion sol containing 100 parts by mass of photocatalyst particles, 14.3 parts by mass of morpholine, 7.1 parts by mass of lactic acid, 3.6 parts by mass of plate-like curable particles are mixed and stirred, and a titanium oxide coating solution is added. Produced.

[Example 7]
42.1 parts by mass of triethanolamine, 21.0 parts by mass of phosphoric acid, and 52.6 parts by mass of plate-like curable particles are mixed and stirred in an aqueous dispersion sol containing 100 parts by mass of photocatalyst particles, and titanium oxide is mixed. A coating solution was prepared.

[Example 8]
5.7 parts by mass of tetramethylammonium, 25.0 parts by mass of glycolic acid, and 57.1 parts by mass of plate-like curable particles were mixed and stirred in an aqueous dispersion sol containing 100 parts by mass of photocatalyst particles, and titanium oxide. A coating solution was prepared.

[Example 9]
A water-dispersed sol containing 100 parts by mass of photocatalyst particles is mixed and stirred with 2.9 parts by mass of morpholine, 17.9 parts by mass of phosphoric acid, and 1.4 parts by mass of plate-like curable particles. Was made.

[Example 10]
A water-dispersed sol containing 100 parts by mass of photocatalyst particles is mixed and stirred with 7.1 parts by mass of piperidine, 4.3 parts by mass of glycolic acid, and 39.3 parts by mass of plate-like curable particles, and a titanium oxide coating solution. Was made.

[Comparative Example 1]
An aqueous dispersion sol containing 100 parts by mass of photocatalyst particles is mixed and stirred with 4.3 parts by mass of monoethanolamine, 5.7 parts by mass of polyphosphoric acid, and 14.3 parts by mass of spherical curable particles, and coated with titanium oxide. A liquid was prepared.

[Comparative Example 2]
A water-dispersed sol containing 100 parts by mass of photocatalyst particles was mixed and stirred with 4.3 parts by mass of sodium hydroxide, 5.7 parts by mass of polyphosphoric acid, and 14.3 parts by mass of plate-like curable particles, and titanium oxide. A coating solution was prepared.

[Comparative Example 3]
In an aqueous dispersion sol containing 100 parts by mass of photocatalyst particles, 4.3 parts by mass of monoethanolamine, 5.7 parts by mass of benzalkonium chloride (cationic dispersant), and 14.3 parts by mass of plate-like curable particles. Mixing and stirring were performed to prepare a titanium oxide coating solution.

[Comparative Example 4]
5.7 parts by mass of polyphosphoric acid and 14.3 parts by mass of spherical curable particles were mixed and stirred in an aqueous dispersion sol containing 100 parts by mass of photocatalyst particles to prepare a titanium oxide coating solution.

[Comparative Example 5]
A water-dispersed sol containing 100 parts by mass of photocatalyst particles was mixed and stirred with 4.3 parts by mass of monoethanolamine and 14.3 parts by mass of spherical curable particles to prepare a titanium oxide coating solution.

[Comparative Example 6]
A water-dispersed sol containing 100 parts by mass of photocatalyst particles was mixed with 4.3 parts by mass of monoethanolamine and 5.7 parts by mass of polyphosphoric acid to prepare a titanium oxide coating solution.

[Comparative Example 7]
8.6 parts by weight of sodium hydroxide, 21.4 parts by weight of polyphosphoric acid, 35.7 parts by weight of spherical curable particles are mixed and stirred in an aqueous dispersion sol containing 100 parts by weight of photocatalyst particles, and coated with titanium oxide. A liquid was prepared.

[Comparative Example 8]
8.3 parts by mass of potassium hydroxide, 0.3 parts by mass of lactic acid, and 250.0 parts by mass of spherical curable particles are mixed and stirred in an aqueous dispersion sol containing 100 parts by mass of photocatalyst particles, and a titanium oxide coating solution Was made.

[Comparative Example 9]
55.6 parts by mass of spherical curable particles were mixed and stirred in an aqueous dispersion sol containing 100 parts by mass of photocatalyst particles to prepare a titanium oxide coating solution.

[Characteristic]
The coating solutions of the above examples were applied to the substrate with a bar coater so that the film thickness was 2.5 μm. As the substrate, an acrylic resin-coated aluminum alloy coated with SiO ₂ primer and a glass plate were used. A glass plate was used for evaluation of transparency.
And the thing of Examples 1-6, Example 10, Comparative Examples 1-7, and Comparative Example 9 performed the heat drying for 10 minutes at 300 degreeC.
Examples 7 to 9 and Comparative Example 8 were irradiated with ultraviolet rays having a wavelength of 360 nm and an intensity of ² mW / cm ² for 24 hours.

  Since the performance of the coating film thus obtained was evaluated by the following test methods and evaluation criteria, the results are shown in Table 1 below.

[transparency]
○: Visible light transmittance of glass test piece is 70% or more Δ: Visible light transmittance of glass test piece is 40% or more and less than 70% ×: Visible light transmittance of glass test piece is 40% Less than [Adhesion]
The adhesion of the coating film was determined according to the JIS-K5400 cross-cut tape method coating film adhesion test.
○: No peeling of coating film is observed Δ: Partial peeling of coating film is recognized ×: All coating film is peeled [Photocatalytic activity]

A 100 × 100 mm aluminum test piece was placed in a 3 L Pyrex glass container, sealed, and acetaldehyde gas was injected to a concentration of 300 ppm. Ultraviolet rays were irradiated for 3 hours with a 20 W black light, the aldehyde concentration after irradiation was measured with a gas detector tube, the removal rate was calculated, and the decomposability by the photocatalyst was measured.

Table-1
Transparency Adhesion Acetaldehyde removal rate (%)
Example 1 ○ ○ 95
Example 2 ○ ○ 92
Example 3 ○ ○ 92
Example 4 ○ ○ 94
Example 5 ○ ○ 91
Example 6 ○ ○ 94
Example 7 ○ ○ 89
Example 8 ○ ○ 90
Example 9 ○ ○ 94
Example 10 ○ ○ 92
Comparative Example 1 Δ × 75
Comparative Example 2 × △ 78
Comparative Example 3 Δ × 78
Comparative Example 4 Δ × 70
Comparative Example 5 Δ × 72
Comparative Example 6 Δ × 76
Comparative Example 7 Δ × 55
Comparative Example 8 Δ × 65
Comparative Example 9 △ △ 70

Patent Applicant Nippon Parkerizing Co., Ltd.
Asahi Glass Co., Ltd.
Dokai Chemical Industry Co., Ltd.
Representative Katsumi Udaka

Claims (11)

Photocatalyst particles,
Organic alkali,
An anionic dispersant;
A coating composition comprising curable plate-like particles.   2. The coating composition according to claim 1, wherein the photocatalyst particles are particles containing one selected from the group consisting of titanium oxide and titanic acid.   The coating composition according to claim 1 or 2, wherein the organic alkali is an alkali containing one selected from the group of alkanolamine, tetraalkylammonium, oxazine, piperidine and choline.   The anionic dispersant is a dispersant containing one selected from the group of condensed phosphoric acid, phosphoric acid, hydroxycarboxylic acid, polyvalent carboxylic acid and polycarboxylic acid. 3. Any one of the coating compositions. 5. The coating composition according to claim 1, wherein the curable plate-like particles are composed mainly of SiO ₂ and have an aspect ratio of 10 to 300. 6.   The organic alkali is 0.5 to 100 parts by weight, the anionic dispersant is 0.5 to 50 parts by weight, and the curable plate-like particles are 0.5 to 400 parts by weight with respect to 100 parts by weight of the photocatalyst particles. The coating composition according to claim 1, which is contained. An application step of applying the coating composition according to claim 1 to a substrate;
A method for forming a film having a photocatalytic function, comprising: an organic alkali decomposition step of decomposing an organic alkali in a coating film after the coating step.   8. The method for forming a film having a photocatalytic function according to claim 7, wherein the organic alkali decomposition step is a step by heating.   The method for forming a film having a photocatalytic function according to claim 7 or 8, wherein the organic alkali decomposition step is a step by light irradiation.   A photocatalyst member comprising the coating composition according to claim 1 applied thereto. A photocatalytic member formed by the method for forming a film having a photocatalytic function according to any one of claims 7 to 9.