Formation of inorganic coating film

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Industrial application field]

The present invention relates to a method for forming an inorganic paint film.

【0002】

[Conventional technology]

Antibacterial organic paints containing an antibacterial agent in an organic resin are coated due to deterioration of the resin after long-term use, especially when used outdoors, due to stains on the surface and deterioration due to ultraviolet rays. There is a drawback that the antibacterial performance of the membrane tends to deteriorate. Therefore, an inorganic paint containing an antibacterial agent in a silicate-based, phosphate-based, or zirconium-based inorganic composition is known. The inorganic paint has better durability than an organic paint, but all of them have better durability. Since it is necessary to bake at a high temperature of 200 ° C or higher, the usable range is limited, and it is not suitable for direct application to building materials and plastics. The silicate-based inorganic paint has a drawback that when used for a long period of time, the alkali elutes on the surface and easily causes an efflorescence phenomenon . Further, Japanese Patent Application Laid-Open No. 62-57470 discloses an inorganic paint containing a metal alkoxide. Although this inorganic paint cures at 200 ° C or lower, the coating film is inflexible and cracks occur. There was an easy problem. In recent years, due to the need to use paints for a wide variety of materials, there has been a demand for paints that maintain antibacterial performance even after long-term use, have no cracks, and can be baked at a temperature of 200 ° C. or lower.

【0003】

[Problems to be Solved by the Invention]

Therefore, the present inventors have proposed an antibacterial inorganic coating material containing a photocatalyst, which is a component having a photocatalytic function, as an antibacterial agent in Japanese Patent Application No. 6-205835. However, when the photocatalyst is supported on the base material, there are problems in the restrictions and adhesion of the base material, and when the photocatalyst is coated with a paint, the coating film itself is affected by the oxidizing action of the photocatalyst in the organic paint. However, when an inorganic paint is used, the photocatalyst tends to settle in the inorganic paint, making it difficult for the photocatalyst to exhibit its performance.

【0004】

The present invention has been made in view of the above facts, and an object of the present invention is to provide a method for forming an inorganic paint film having high photocatalytic performance by supporting a photocatalyst on a surface.

【0005】

[Means for solving problems]

The method for forming an inorganic paint coating film according to claim 1 of the present invention uses the following compositions (A), (B) and (C) as raw materials, and the weight average molecular weight adjusted from these raw materials is 900 or more in terms of polystyrene. It is characterized in that a mixed solution of a mixture of an inorganic paint and a powder having a photocatalytic function is applied to a base material and then treated with an acid or an alkali. (A) 20 to 200 parts by weight of a silicon compound and / or colloidal silica represented by the following general formula. Si (OR¹)₄ ------ (B) 100 parts by weight of a silicon compound represented by the following general formula, R²Si (OR¹)₃ ------ (C) 0 to 60 parts by weight of a silicon compound represented by the following general formula, R²₂Si (OR¹)₂ ------ [In the above general formula to general formula, R¹, R²Indicates a monovalent hydrocarbon group. ] In the method for forming an inorganic paint coating film according to claim 2 of the present invention, the powder having a photocatalytic function is composed of titanium oxide, zirconium oxide, zinc oxide, strontium titanate, tin oxide, tungsten oxide, iron oxide and bismuth oxide. It is characterized by being at least one species selected from the group.

【0006】

In the method for forming an inorganic paint coating film according to claim 3 of the present invention, a mixed product obtained by adding a compound having a boiling point of 100 ° C to 300 ° C to the mixed liquid is applied to a base material, and then the boiling point of the compound is increased. It is characterized by firing at a high temperature.

【0007】

The method for forming an inorganic paint film according to claim 4 of the present invention is characterized by further adding acrylic silicone to the mixed solution.

【0008】

Hereinafter, the present invention will be described in detail. The method for forming an inorganic paint coating film according to the present invention is a method for forming a coating film in which a mixed solution of an inorganic paint and a powder having a photocatalytic function is applied to a base material and then treated with an acid or an alkali. Any of methanol, acetone, ethanol, propanol, isopropyl alcohol, etc. may be used, but it is desirable to match with R in the inorganic paint in consideration of the exchange reaction of the hydrocarbon group (R) of the alkoxide in the inorganic paint to be used.

【0009】

The silicon compound is represented by the following general formula. R²_nSi (OR¹)_4-n ------ [In the above general formula, n is an integer from 0 to 3, R¹, R²Indicates a monovalent hydrocarbon group. ] R in the above general formula¹, R²Is not limited as long as it indicates a monovalent hydrocarbon group, but R²Indicates a substituted or unsubstituted hydrocarbon group having 1 to 8 carbon atoms, for example, an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group or an octyl group, or a cyclopentyl group. , Cycloalkyl group such as cyclohexyl group, aralkyl group such as 2-phenylethyl group, 3-phenylpropyl group, aryl group such as phenyl group and trill group, alkenyl group such as vinyl group and allyl group, chloromethyl group, γ -Halogen-substituted hydrocarbon groups such as chloropropyl group and 3,3,3-trifluoropropyl group, and γ-methacryloxypropyl group, γ-glycidoxypropyl group, 3,4-epoxycyclohexylethyl group and γ. -Substituted hydrocarbon groups such as mercaptopropyl groups can be mentioned. Of these, an alkyl group having 1 to 4 carbon atoms and a phenyl group are preferable because of their ease of synthesis or availability.

【0010】

R in the above general formula¹The one using an alkyl group having 1 to 4 carbon atoms as a main raw material is used. In particular, examples of the tetraalkoxysilane with n = 0 include tetramethoxysilane and tetraethoxysilane, and examples of the organotrialkoxysilane with n = 1 include methyltrimethoxysilane, methyltriethoxysilane, and methyltriisopropoxysilane. , Phenyltrimethoxysilane, phenyltriethoxysilane, 3,3,3-trifluoropropyltrimethoxysilane and the like. Further, examples of the n = 2 diorganodialkoxysilane include dimethyldimethoxysilane, dimethyldiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, and methylphenyldimethoxysilane, as n = 3 triorganoalkoxysilane. Examples thereof include trimethylmethoxysilane, trimethylethoxysilane, trimethylisopropoxysilane, and dimethylisobutylmethoxysilane.

【0011】

R in the above general formula to general formula¹, R²May be the same hydrocarbon group or different. The inorganic paint is produced, for example, by diluting a silicon compound represented by the general formula, the general formula, or the general formula with a solvent, adding water or a catalyst as a curing agent, hydrolyzing, and forming the inorganic paint. It is prepared by performing a polycondensation reaction. The weight average molecular weight (Mw) of these silicon compounds is calculated in terms of polystyrene. At the time of this preparation, the weight average molecular weight (Mw) of the inorganic paint is set to 900 or more in terms of polystyrene. When the weight average molecular weight (Mw) is less than 900 in terms of polystyrene, the curing shrinkage becomes large during the polycondensation reaction, and cracks are likely to occur in the coating film of the baked inorganic paint.

【0012】

The inorganic coating material can be used in combination with the silicon compound represented by the above general formula, or may contain colloidal silica as a component instead. The colloidal silica is an water-dispersible colloidal silica dispersed in water or an organic solvent-dispersible colloidal silica dispersed in a non-aqueous organic solvent such as alcohol. The colloidal silica contains 20 to 50% by weight of silica as a solid content. In the preparation of the inorganic paint, the water-dispersible colloidal silica can use water existing as a component outside the solid content as a curing agent. Further, the organic solvent-dispersible colloidal silica can be easily prepared by replacing the organic solvent with water. Examples of the organic solvent in which the colloidal silica is dispersed include lower aliphatic alcohols such as methanol, ethanol, isopropanol, n-butanol and isobutanol, ethylene glycol, ethylene glycol monobutyl ether, ethylene glycol monoethyl ether and the like. Examples of the ethylene glycol derivative, diethylene glycol, diethylene glycol derivative such as diethylene glycol monobutyl ether, diacetone alcohol and the like, and one or more of these are used. Further, toluene, xylene, ethyl acetate, butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, methyl ethyl ketooxime and the like can also be used in combination with a hydrophilic organic solvent. The blending amount of the colloidal silica is the weight including the dispersion medium.

【0013】

Water is widely used as a curing agent when producing an inorganic paint, and the amount of this water is preferably 45% or less, more preferably 25% or less in the inorganic paint.

【0014】

Organic solvents used in producing inorganic paints include, for example, lower aliphatic alcohols such as methanol, ethanol, isopropanol, n-butanol and isobutanol, ethylene glycol, ethylene glycol monobutyl ether, ethylene glycol monoethyl ether and the like. Examples of the ethylene glycol derivative, diethylene glycol, diethylene glycol derivative such as diethylene glycol monobutyl ether, diacetone alcohol and the like, and one or more of these are used. Further, toluene, xylene, ethyl acetate, butyl acetate, methyl ethyl ketone, methyl isobutyl ketone, methyl ethyl ketooxime and the like can also be used in combination with a hydrophilic organic solvent.

【0015】

When preparing the inorganic paint, it is desirable that the pH of the inorganic paint is 3.8 to 6. If it is within this pH range, the storage stability of the inorganic paint is good, and if it is outside this pH range, the period during which it can be applied from the preparation period is limited. The method for adjusting the pH is not limited, but for example, if the pH is less than 3.8 when the materials are mixed, a basic reagent such as ammonia may be added to adjust the pH, and if the pH exceeds 6, the pH may be adjusted. The pH may be adjusted by adding an acidic reagent such as hydrochloric acid. Further, depending on the pH, if the progress of the reaction is slowed down in a state where the molecular weight is small, the reaction may be promoted by heating, or a basic reagent is added after lowering the pH with an acidic reagent to proceed with the reaction. It may have a predetermined pH.

【0016】

As the photocatalyst, for example, it is preferable to use at least one selected from the group consisting of titanium oxide, zirconium oxide, zinc oxide, strontium titanate, tin oxide, tungsten oxide, iron oxide, and bismuth oxide. A powder having a photocatalytic function is used as the photocatalyst, and this powder is mixed with the inorganic paint to obtain a mixed solution within a range that does not impair the functional weather resistance of the inorganic paint. This mixed solution is applied to a base material to form an inorganic paint film.

【0017】

Further, a metal may be supported on the photocatalyst. As this metal, for example, at least one selected from the group consisting of gold, silver, copper, iron, zinc, nickel, cobalt, platinum, ruthenium, palladium, and rhodium is used. By supporting these metals, charge separation of the photocatalyst is promoted and the photocatalytic action is exhibited. That is, it has an oxidizing performance in the presence of light, and this oxidizing performance exerts effects such as deodorization and antibacterial. Further, a clay crosslinked body in which a photocatalyst is supported between layers may be used. By introducing these photocatalysts between layers, oxides are supported on the fine particles and the photocatalyst performance is improved.

【0018】

By treating the inorganic paint film with an acid or an alkali, only the inorganic paint is dissolved and the photocatalyst appears on the surface of the inorganic paint film, so that the catalytic effect of the photocatalyst is improved. The acid or alkali does not have to dissolve the photocatalyst or react with the photocatalyst, and examples thereof include an aqueous nitric acid solution of about 0.1 to 1% by weight and sodium hydroxide.

【0019】

A compound having a boiling point of 100 ° C to 300 ° C is also added to the mixed solution to obtain a mixed product. Examples of the compound having a boiling point of 100 ° C to 300 ° C include at least one selected from the group consisting of formamide, dimethylformamide, acetonitrile, dioxane and normal heptane. By applying the mixture to a base material, the dispersibility of the photocatalyst is enhanced, and by firing at a temperature higher than the boiling point of the compound in the drying step, a porous inorganic paint film can be obtained.

【0020】

By adding acrylic silicon to the mixed solution, a porous film having many pores is formed, so that the area where the photocatalyst comes into contact with air increases, so that an inorganic paint film that easily exhibits the photocatalyst function can be obtained. ..

【0021】

[Action]

In the method for forming an inorganic paint film according to claim 1 of the present invention, the compositions (A), (B) and (C) are used as raw materials, and the weight average molecular weight adjusted from these raw materials is 900 or more in terms of polystyrene. By applying a mixed solution of the inorganic paint and the powder having a photocatalyst function to the base material and then treating with acid or alkali, only the inorganic paint is dissolved, so that the photocatalyst is applied to the surface of the inorganic paint coating film. The number of photocatalysts exposed and in contact with air increases. That is, when the surface of the compound having a photocatalytic function is exposed, the function is easily exhibited sufficiently.

【0022】

In the method for forming an inorganic paint coating film according to claim 2 of the present invention, the powder having a photocatalytic function is composed of titanium oxide, zirconium oxide, zinc oxide, strontium titanate, tin oxide, tungsten oxide, iron oxide and bismuth oxide. Since it is at least one selected from the group, it has an excellent photocatalytic function.

【0023】

In the method for forming an inorganic coating film according to claim 3 of the present invention, a mixed product obtained by adding a compound having a boiling point of 100 ° C to 300 ° C to the mixed liquid is applied to a base material, and then the boiling point of the compound is increased. By firing at a high temperature, micropores are formed, so that the area where the photocatalyst comes into contact with air increases. That is, the photocatalyst is supported on the coating film in a state in which the photocatalyst function is likely to be exhibited.

【0024】

In the method for forming an inorganic paint film according to claim 4 of the present invention, a porous film having many pores is formed by further adding acrylic silicon to the mixed solution, so that the area where the photocatalyst comes into contact with air is formed. Therefore, the photocatalytic function is likely to be exhibited.

【0025】

[Example]

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.

【0026】

(Example 1) Tetraethoxysilane as the silicon compound represented by the above general formula, IPA organosilica sol (manufactured by JGC Catalysts and Chemicals Co., Ltd .: trade name OSCAL1432) as the colloidal silica, and methyl as the silicon compound represented by the above general formula. Trimethoxysilane, dimethyldimethoxysilane was used as the silicon compound represented by the above general formula. After mixing 10 parts of tetraethoxysilane, 90 parts of IPA organosilica sol, 30 parts of dimethyldimethoxysilane, and 100 parts of isopropyl alcohol (hereinafter referred to as IPA) in 100 parts by weight of methyltrimethoxysilane (hereinafter referred to as IPA). , 90 parts of water and TiO as a photocatalyst₂(Manufactured by Nippon Aerosil Co., Ltd .: Product name P-25) 42 parts were added and stirred. The weight average molecular weight (hereinafter referred to as Mw) was adjusted to 1500 in a constant temperature bath at 60 ° C. to obtain a photocatalyst-containing inorganic paint. The obtained inorganic paint was sprayed on an alumina substrate and then fired at a temperature of 100 ° C. for 1 hour to obtain a coating film. The obtained coating film was further immersed in a 1 wt% sodium hydroxide aqueous solution for 24 hours to obtain an inorganic paint film.

【0027】

In order to evaluate the photocatalytic action of this inorganic paint film, the acetaldehyde removal rate was measured and shown in Table 1. Here, it is shown that the larger the acetaldehyde removal rate, the greater the photocatalytic action. The acetaldehyde removal rate was measured by placing an alumina substrate on which an inorganic paint coating was formed in a container, injecting 50 ppm of acetaldehyde into the container, irradiating with 10 W black light for 30 minutes, and using gas chromatography. ..

【0028】

(Example 2) In the same manner as in Example 1 except that a 1 wt% nitric acid aqueous solution was used instead of the 1 wt% sodium hydroxide aqueous solution in Example 1, an inorganic paint coating film was obtained to remove acetaldehyde. The rates were measured and shown in Table 1.

【0029】

(Example 3) In Example 1, 90 parts of water and TiO as a photocatalyst₂(Manufactured by Nippon Aerosil Co., Ltd .: Trade name P-25) Add 30 parts of dimethylformamide having a boiling point of 153 ° C together with 42 parts, bake at a temperature of 200 ° C for 1 hour, and do not immerse in 1 wt% sodium hydroxide aqueous solution. Except for the above, an inorganic paint coating film was obtained in the same manner as in Example 1, and the acetaldehyde removal rate was measured and shown in Table 1.

【0030】

(Example 4) In Example 1, 90 parts of water and TiO as a photocatalyst₂Along with 42 parts (manufactured by Nippon Aerosil Co., Ltd .: product name P-25), 30 parts of acrylic silicon (manufactured by Kanebuchi Chemical Industry Co., Ltd .: product name Zemrack) was added, except that it was not immersed in a 1 wt% sodium hydroxide aqueous solution. , An inorganic paint coating film was obtained in the same manner as in Example 1, and the acetaldehyde removal rate was measured and shown in Table 1.

【0031】

(Example 5) TiO used as a photocatalyst in Example 1₂Inorganic paint film was obtained in the same manner as in Example 1 except that ZnO (manufactured by Sakai Chemical Co., Ltd .: trade name FINEX50) was used instead of, and the acetaldehyde removal rate was measured and shown in Table 1.

【0032】

(Example 6) TiO used as a photocatalyst in Example 1₂Inorganic paint film was obtained and the acetaldehyde removal rate was measured in the same manner as in Example 1 except that the photocatalytic functional clay interlayer crosslinked body prepared as follows was used instead of the above. .. Titanate isopropoxide was blended in a ratio of 1 part by weight with respect to 10 parts by weight of 2 normal (N) hydrochloric acid, and the titanoic acid isopropoxide was dissolved with hydrochloric acid to obtain a solution. This solution is added to a 1 wt% aqueous solution of clay mineral (manufactured by Kunimine Co., Ltd .: trade name montmorillonite) dispersed in water in advance, and reacted at 60 ° C. for 1.5 hours.₂Obtained a photocatalytic functional clay interlayer crosslinked product in an amount of 0.6 parts by weight.

【0033】

(Comparative Example 1) After mixing 10 parts of tetraethoxysilane, 90 parts of IPA organosilica sol, 30 parts of dimethyldimethoxysilane, and 100 parts of isopropyl alcohol (IPA) with 100 parts of methyltrimethoxysilane, 90 parts of water is added. It was added and stirred. The weight average molecular weight (hereinafter referred to as Mw) was prepared to 1500 in a constant temperature bath at 60 ° C, and TiO, which is a photocatalyst, was added to this solution.₂Inorganic paint was obtained by adding 20 parts (manufactured by Nippon Aerosil Co., Ltd .: trade name P-25). This inorganic paint was applied to an alumina substrate washed with acetone and dried at a temperature of 100 ° C. for 1 hour to obtain an inorganic paint coating film, and the acetaldehyde removal rate was measured and shown in Table 1.

【0034】

[table 1]

<img file="JPH08259891A_D0001.tif" />【0035】

As shown in Table 1, it was confirmed that in the examples, the acetaldehyde removal rate of the inorganic paint film was larger than that in the comparative example, the oxidation performance by the photocatalytic action was excellent, and the effects of deodorization, antibacterial, etc. were large.

【0036】

[Effect of the invention]

According to the method for forming an inorganic paint film according to claims 1 and 2 of the present invention, many photocatalysts are in a state where the photocatalyst is exposed on the surface of the inorganic paint film and is in contact with air, and its function is sufficient. Therefore, an inorganic coating film having photocatalytic performance such as high oxidation performance can be obtained.

【0037】

According to the method for forming an inorganic coating film according to claim 3 of the present invention, since the photocatalyst is supported on the coating film in a state where the photocatalyst function is likely to be exhibited, the inorganic coating material has even higher photocatalytic performance such as oxidation performance. A coating film is obtained.

【0038】

According to the method for forming an inorganic paint film according to claim 4 of the present invention, since a porous film having many pores is formed, the area where the photocatalyst comes into contact with air increases, and the photocatalyst function is more likely to be exhibited. An inorganic paint film having photocatalytic performance such as high oxidation performance can be obtained.