JP3468413B2 - Method for forming photocatalyst-containing coating film - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for forming a photocatalyst-containing coating film containing an inorganic oxygen-containing titanium compound, and more specifically, it is excellent in transparency, smoothness, adhesion, weather resistance and stain removability. The present invention relates to a method for forming a photocatalyst-containing coating film.

[0002]

2. Description of the Related Art Titanium oxide is itself a semiconductor,
When light having energy higher than the band gap, for example, ultraviolet rays is irradiated, electrons are accumulated in the conduction band and holes are generated in the valence band. Since organic substances in the atmosphere can be decomposed by the redox action based on the electron transfer generated by the accumulated electrons and holes, various attempts have been made to industrially utilize this activating action (photocatalytic action). For example, various attempts have been made to purify air pollution and waste water by utilizing the photocatalytic action of titanium oxide.
However, it is difficult to form a titanium dioxide layer having high photocatalytic activity on the surface of the base material. As one of the conventional methods, there is a method of forming a titanium dioxide film by air-oxidizing or anodizing the surface of a pure titanium plate, but a good function can be obtained although the oxidation method is difficult. Hateful. As another method, a method of depositing titanium dioxide on the surface of a substrate by a CVD method and a method of performing plasma spraying (Japanese Patent Laid-Open No. 6-210170) are also known.
Both methods are costly and have the drawback that they cannot be applied (in terms of heat resistance, chemical reactivity, etc.) depending on the type of substrate. Furthermore, attempts have been made to attach titanium dioxide powder to the base material via an adhesive called a binder, but the photocatalytic action of titanium dioxide causes the binder to be oxidatively decomposed and fall off from the base material after a few months. It could not stand the intended use.

[0003]

As described above, all of the conventional methods for forming or adhering titanium dioxide on the surface of a substrate have problems, and a definitive method has not yet been found. The current situation is not. An object of the present invention is to apply a clear coat containing an inorganic oxygen-containing titanium compound which functions as a photocatalyst on the surface of a substrate to be coated.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies in order to achieve the above-mentioned objects, and as a result, applied a clear coating agent containing a specific alkoxysilane compound on the surface of a base material to be coated, Applying and drying a clear coating agent containing a specific alkoxysilane compound as a binder and an inorganic oxygen-containing titanium compound with a specific particle size as a photocatalyst until it reaches a semi-cured dry state. As a result, they have found that the above problems can be solved, and completed the present invention.

That is, the method for forming a photocatalyst-containing coating film of the present invention is as follows: (1) The surface of a substrate to be coated is represented by the general formula R ¹ Si (OR ² ) ₃ [wherein R ¹ is a group having 1 to 8 carbon atoms]. An organic group, R ² is an alkyl group having 1 to 5 carbon atoms], and at least one compound selected from the group consisting of alkoxysilanes and partial hydrolysis-condensation products thereof is contained in the coating agent. Of 50
Clear coating agent (A) contained in an amount of not less than wt%
At a solid coating amount of 5 to 100 g / m ² , and (2) until the coating film formed by the clear coating agent (A) reaches a semi-cured dry state, on the surface of the coating film, As a binder, a compound represented by the general formula (R ¹ ) _n Si (OR ² ) _4-n [wherein
R ¹ is an organic group having 1 to 8 carbon atoms, and R ² is 1 to 1 carbon atoms.
Which is an alkyl group of 5 and n is an integer of 0 to 3] and which contains at least one compound selected from the group consisting of alkoxysilanes and partial hydrolysis-condensation products thereof, and has an average particle size as a photocatalyst. Clear coat containing an inorganic oxygen-containing titanium compound having a maximum particle diameter of 0.001 to 0.1 μm and 0.5 μm or less in an amount of 30% by weight or more of the total solids in the coating agent in terms of TiO _2. The agent (B) is applied at a solid content of 0.1 to 10 g / m ² , and (3) the coating film formed by the clear coating agent (A) and the clear coating agent (B) is dried. And

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below. Examples of the substrate to be coated used in the present invention include, but are not limited to, a metal plate, an inorganic plate, a wood plate and a plastic substrate. It should be noted that these base materials can be used with or without a surface pre-treated, and if necessary, the surface is pre-treated before use.

Examples of the metal plate include various metal plates such as a steel plate, an aluminum plate, a stainless plate and a titanium plate. Among these, examples of the steel sheet include cold-rolled steel sheet, hot-rolled steel sheet, galvanized steel sheet, zinc alloy-plated steel sheet, zinc-iron alloy-plated steel sheet, zinc-aluminum alloy-plated steel sheet, aluminum-plated steel sheet, chrome-plated steel sheet, tin-plated steel sheet. Examples include steel plates. As the base treatment of those metal plates, water-washing, hot-water washing, pickling, alkaline degreasing, polishing, chromate treatment, a composite oxide film treatment or the like is used alone or in combination to perform a pre-coating treatment, and if necessary, a polyester-based, Epoxy type,
Roll coater, curtain flow coater, roller coater, electrostatic coater, blade coater, die coater, etc. are coated with urethane type primer and then left at room temperature, or hot air oven, induction heating oven, induction heating and hot air combination oven , Near-infrared furnace, far-infrared furnace, active energy ray irradiation furnace, etc.
Apply a film thickness of about m.

Examples of the inorganic boards include slate boards used for outer wall materials and interior materials, wood chip cement boards, pulp cement boards, asbestos cement boards, lightweight aggregate-containing cement boards,
Examples thereof include calcium silicate plate, calcium carbonate plate, and other water-curable plate materials. Examples of the surface treatment of these inorganic plates include applying a urethane-based, epoxy-based or vinyl-based sealer. As for the wood board, examples of the base treatment include joint fixing treatment, polishing treatment, wood sealer coating and the like. As for the base material for the plastic base material, various primer coatings for plastics and the like can be mentioned as the base treatment. Further, a pre-patterned one such as a decorative plate patterned by printing, transfer, ink jet printing, sputter coating or the like, or a melamine decorative plate on which a printing sheet is pressure-bonded can also be used.

In the present invention, the clear coating agent (A) is intended to form a coating film having weather resistance, and it is necessary to form a relatively thick coating film. Therefore, in the clear coating agent (A), the general formula (1) R ¹ Si (OR ² ) ₃ (1) [In the formula, R ¹ is an organic group having 1 to 8 carbon atoms, and R ² is 1 to 5 carbon atoms. Which is an alkyl group of] and at least one compound selected from the group consisting of alkoxysilanes and partial hydrolysis-condensation products thereof. R ¹ in the general formula (1) is an organic group having 1 to 8 carbon atoms, and examples thereof include alkyl groups such as methyl group, ethyl group, n-propyl group and i-propyl group, and others. Γ-chloropropyl group, vinyl group, 3,3,3-trifluoropropyl group, γ-glycidoxypropyl group, γ-methacryloxypropyl group, γ-mercaptopropyl group, phenyl group, 3,4-epoxy Cyclohexylethyl group, γ
-Aminopropyl group and the like.

On the other hand, R ² in the general formula (1) is an alkyl group having 1 to 5 carbon atoms, examples of which are, for example,
Methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, s-butyl group, t-butyl group, i-
A butyl group and the like can be mentioned. Specific examples of the alkoxysilane represented by the general formula (1) include methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, and n-propyltriethoxysilane. , I-propyltrimethoxysilane, i-propyltriethoxysilane, γ-chloropropyltrimethoxysilane, γ-chloropropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 3,
3,3-trifluoropropyltrimethoxysilane, 3,
3,3-trifluoropropyltriethoxysilane, γ-
Glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxy Examples include silane, phenyltrimethoxysilane, phenyltriethoxysilane, γ-aminopropyltrimethoxysilane, 3,4-epoxycyclohexylethyltrimethoxysilane, and 3,4-epoxycyclohexylethyltriethoxysilane, but preferably,
Examples thereof include methyltrimethoxysilane and methyltriethoxysilane. These alkoxysilanes may be used alone or in combination of two or more.

The compound used in the clear coat agent (A) in the present invention may be a partial hydrolysis-condensation product of the above-mentioned alkoxysilane. The polystyrene reduced weight average molecular weight of the partially hydrolyzed condensate is preferably 300 to
It is suitable that it is 5,000, more preferably 500 to 3,000. By using a partial hydrolysis-condensation product having such a molecular weight, a coating having good adhesion without deteriorating storage stability. Can be formed.

In the present invention, the clear coating agent (A) is intended to form a coating film having weather resistance, and it is necessary to form a relatively thick coating film. Therefore, the above compound used in the clear coating agent (A) is 50% by weight or more, preferably 60% by weight or less of the total solid content in the clear coating agent (A).
It is necessary to occupy more than weight%. When the content of the above-mentioned compound is less than 50% by weight of the total solid content, accompanying this, when the content of the inorganic component other than the above-mentioned compound becomes larger than that of the above-mentioned compound, film-forming property and crack resistance of the coating film When the content of the organic component is increased, the above-mentioned compound is oxidatively decomposed by the photocatalytic action of the inorganic oxygen-containing titanium compound, and the inorganic oxygen-containing titanium compound falls off from the substrate, resulting in a coating film. Is not preferable because it does not exhibit its function as.
Within the range that does not impair the performance of the coating film formed by the clear coating agent (A), the alkoxysilane represented by the following general formula (2) and / or its partial hydrolysis-condensation product and n value other than 1 Those described above can also be included in the clear coating agent (A). Further, the clear coat agent (A) may be blended with a film forming aid, a surface conditioner, a thickener and the like as additives.

In the present invention, a compound used as a binder in the clear coating agent (B), represented by the general formula (2) (R ¹ ) _n Si (OR ² ) _4-n (2) [wherein R ¹ has 1 to ¹ carbon atoms] 8 is an organic group, R ² is charcoal
Is an alkyl group having a prime number of 1 to 5 , and n is an integer of 0 to 3], and is at least one compound selected from the group consisting of an alkoxysilane and a partial hydrolysis-condensation product thereof. Specific examples of the alkoxysilane represented by the general formula (2) include methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, and n-propyltriethoxysilane. , I-propyltrimethoxysilane, i-propyltriethoxysilane,
γ-chloropropyltrimethoxysilane, γ-chloropropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 3,3,3-trifluoropropyltrimethoxysilane, 3,3,3-trifluoropropyltriethoxy Silane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, γ- Mercaptopropyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, γ-aminopropyltrimethoxysilane, 3,4-
Epoxycyclohexylethyltrimethoxysilane,
3,4-epoxycyclohexylethyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, dimethoxymethylphenylsilane, dimethyldipropoxysilane and the like. However, methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane and the like are preferable.
These alkoxysilanes may be used alone or in combination of two or more.

In the present invention, the compound used as the binder in the clear coat agent (B) may be a partial hydrolysis-condensation product of the alkoxysilane represented by the above general formula (2). The polystyrene reduced weight average molecular weight of the partially hydrolyzed condensate is preferably 300 to 5,000, more preferably 500 to 3,000, and a partially hydrolyzed condensate having such a molecular weight is used. By doing so, a coating film having good adhesion can be formed without deteriorating the storage stability.

In the present invention, the clear coating agent (B) is intended to stably support the photocatalyst. Therefore, as long as the photocatalyst can be stably supported, it is represented by the above general formula (2) in the clear coating agent (B). The content of at least one compound selected from the group consisting of alkoxysilane and its partial hydrolysis-condensation product is not particularly limited. In the present invention, the inorganic oxygen-containing titanium compound (hereinafter, simply referred to as “oxygen-containing titanium compound”) used as a photocatalyst in the clear coating agent (B) is a redox reaction of an organic substance when irradiated with light having a specific energy. It shows a catalytic action against, for example, in addition to pure titanium oxide, hydrous titanium oxide, hydrated titanium oxide, metatitanic acid,
Examples include orthotitanic acid and titanium hydroxide. Preferably, titanium dioxide or one having a lower oxidation state than titanium dioxide is used. The titanium dioxide may be either anatase type or rutile type crystal system, or a mixture thereof.

These oxygen-containing titanium compounds have an average particle size of 0.001 to 0.1 μm and a maximum particle size of 0.5 μm.
m or less in powder form, having an average particle size of 0.005
It is preferably about 0.05 μm. When the average particle size of the oxygen-containing titanium compound is larger than 0.1 μm or the maximum particle size is larger than 0.5 μm, the transparency of the coating film is lost and the original purpose of clear coating can be achieved. Disappear. Further, when the average particle size is less than 0.001 μm, handling is difficult due to reaggregation and the like, which is industrially disadvantageous. The oxygen-containing titanium compound is contained in an amount of 30% by weight or more, preferably 40% by weight or more, based on the total solid content in the clear coat (B) in terms of TiO ₂ . When the content of the oxygen-containing titanium compound is less than 30% by weight, the effect of the photocatalyst, which is the original purpose, is lowered, which is not preferable.

Clear coating agent (B) used in the present invention
Is a method of condensing an alkoxysilane in the presence of a powder or an oxygen-containing titanium compound previously dispersed with water, alcohol, acid or the like, or mixing the powder or the oxygen-containing titanium compound as a dispersion with a binder. It can be prepared by a method of dispersing. The clear coat agent (B) can also contain a film forming aid, a surface conditioner, a thickener, etc. as additives. Method of forming a photocatalyst-containing coating film of the present invention, the coated substrate surface, clear coating agent (A) to 5 to 100 g / m ² of the, preferably coated with a solid content coating amount of 10 to 50 g / m ² Then, 0.1 to 10 g / m of the clear coating agent (B) is applied to the surface of the coating film until the coating film formed by the clear coating agent (A) reaches a semi-cured dry state. ² , preferably 0.5 to 5 g / m ² of solid content coating amount, and the coating film formed by the clear coating agent (A) and the clear coating agent (B) is dried.

The amount of the clear coating agent (A) applied is 5 g /
When it is less than m ^2, it is difficult to obtain a continuous and uniform coating by a usual coating method, and the film forming property and smoothness of the coating become poor, which is not preferable. On the other hand, when it exceeds 100 g / m ² , cracks and peeling may occur in the coating film, and it is not preferable from the economical viewpoint. On the other hand, when the coating amount of the clear coating agent (B) is less than 0.1 g / m ² , the effect of the photocatalyst, which is the original purpose, is lowered, which is not preferable. On the contrary, if it exceeds 10 g / m ² , cracks and peeling may occur in the coating film, and it is not preferable from the economical viewpoint. In the present invention, "during reaching a semi-cured dry state" means from immediately after the application of the clear coat (A) to a partially cured state,
Also, "drying" after applying the clear coat (B)
In addition to general baking and drying, drying by leaving at room temperature is included.

[0019]

EXAMPLES The present invention will be described in more detail below with reference to Examples and Comparative Examples. In the examples and comparative examples, "part"
And "%" are shown on a weight basis unless otherwise specified. Examples 1 to 7 and Comparative Examples 1 to 7 Preparation of clear coating agent (A) and clear coating agent (B) used in each example and comparative example, preparation of raw materials used for the preparation, and formation of coating film The coating film evaluation method is as follows.

<Preparation of vinyl resin solution containing silyl group> To a reactor equipped with a reflux condenser and a stirrer, 50 parts of xylene and 50 parts of isobutanol were added, and mixed with stirring 8
Warmed to 5 ° C. Next, isobutyl methacrylate 50
Part, 2-ethylhexyl methacrylate 35 parts, γ-methacryloxypropyltrimethoxysilane 15 parts and azobisisovaleronitrile 1.5 parts were added dropwise at 85 ° C. over 3 hours, and then the temperature was raised to 90 ° C. Warmed and maintained for 2 hours to complete the reaction. The resulting silyl group-containing vinyl resin solution had a solid content concentration of 50%, the resin had a number average molecular weight of 14,000, and had an average of 7 silyl groups per polymer molecule.

<Preparation of Clear Coat Agent A-1> To a reactor equipped with a reflux condenser and a stirrer, 100 parts of methyltriethoxysilane and 10 parts of ion-exchanged water were added, and tris (acetylacetonato) aluminum was further added. Two parts were added, and the mixture was reacted at 60 ° C. for 3 hours to obtain a solution of a hydrolytic condensate having an average hexamer content. Then, 20 parts of methyltrimethoxysilane and 9.5 parts of ion-exchanged water were added to the obtained solution of the hydrolyzed condensate, and 0.1N hydrochloric acid was further added so that the pH of the resulting mixture was 4. Reaction was carried out at 60 ° C. for 3 hours to obtain a polysiloxane solution. Isopropanol was added to this solution to prepare a clear coating agent A-1 having a solid content of 27%.

<Preparation of clear coat agent A-2> A partial hydrolysis condensate of methyltrimethoxysilane (SR2402 manufactured by Toray Dow Corning Co., Ltd .; solid content 100%) was placed in a reactor equipped with a reflux condenser and a stirrer. ) 40 parts, 50 parts of methyltrimethoxysilane, 10 parts of dimethyldimethoxysilane, 1 part of trimethylmethoxysilane and 20 parts of isopropanol are added and mixed, then 20 parts of ion-exchanged water is added with stirring, and then colloidal silica. 30 parts (isopropanol silica sol manufactured by NISSAN CHEMICAL INDUSTRIES, LTD .; solid content 30%) was added and reacted at 60 ° C. for 3 hours, and then isopropanol was added to bring the solid content to 32%, followed by cooling to room temperature to give a clear coating agent. A-2 was prepared.

<Preparation of clear coat agent A-3> A partial hydrolysis condensate of methyltrimethoxysilane (SR2402 manufactured by Toray Dow Corning Co., Ltd .; solid content 100%) was placed in a reactor equipped with a reflux condenser and a stirrer. ) 40 parts, methyltrimethoxysilane 50 parts, dimethyldimethoxysilane 10 parts, trimethylmethoxysilane 1 part, silyl group-containing vinyl resin solution 25 parts prepared by the above method, diisopropoxyaluminum ethylacetoacetate 1.5.
Parts and 20 parts of isopropanol are added and mixed, then, 20 parts of ion-exchanged water is added with stirring and reacted at 60 ° C. for 3 hours, and then isopropanol is added to adjust the solid content to 34%, and cooled to room temperature. A clear coat agent A-3 was prepared.

<Preparation of clear coat agent A-4> A partial hydrolysis condensate of methyltrimethoxysilane (SR2402 manufactured by Toray Dow Corning Co., Ltd .; solid content 100%) was placed in a reactor equipped with a reflux condenser and a stirrer. ) 20 parts, methyltrimethoxysilane 25 parts, dimethyldimethoxysilane 5 parts, trimethylmethoxysilane 1 part, silyl group-containing vinyl resin solution 100 parts prepared by the above method, diisopropoxyaluminum ethylacetoacetate 1.5
Parts and 20 parts of isopropanol are added and mixed, then, 20 parts of ion-exchanged water is added with stirring and reacted at 60 ° C. for 3 hours, and then isopropanol is added to adjust the solid content to 34%, and cooled to room temperature. A clear coat agent A-4 was prepared.

<Preparation of Hydrolysis Condensate Solution of Tetraethoxysilane> In a reactor equipped with a reflux condenser and a stirrer,
204 parts of methyl alcohol and tetraethoxysilane (ethyl silicate 40; product name of Nippon Colcoat Co., Ltd.)
Add 30 parts and stir-mix at 40 ° C, then add 60 parts to it.
% Was added a mixed solution of nitric acid 1.5 parts of ion-exchanged water 4.5 parts, and further stirred for 4 hours at 40 ° C., SiO ₂ concentration of 5
% Hydrolyzed condensate solution of tetraethoxysilane was obtained.

<Preparation of Hydrolysis Condensate Solution of Methyltriethoxysilane> 177.5 parts of methyl alcohol and 20 parts of methyltriethoxysilane are added to a reactor equipped with a reflux condenser and a stirrer, and the mixture is stirred and mixed at 40 ° C. Then, a mixed solution of 1.5 parts of 60% nitric acid and 3 parts of ion-exchanged water was added thereto, and the mixture was stirred at 40 ° C. for an additional 4 hours to hydrolyze and condense methyltriethoxysilane having a SiO ₂ concentration of 5%. A product solution was obtained.

<Preparation of clear coat agent B-1> To a reactor equipped with a reflux condenser and a stirrer, 60 parts of isopropyl alcohol and 10 parts of the hydrolyzed condensate solution of tetratriethoxysilane were added and homogenized at 40 ° C. And mixed with stirring. A predetermined amount of an aqueous TiO ₂ dispersion having an average particle size of 5 nm was added to this mixed solution so that the content of TiO ₂ became 80% by weight of the total solid content in the coating agent, and the mixture was further stirred and mixed at 40 ° C. for 1 hour. Then, isopropyl alcohol was added to prepare a clear coating agent B-1 having a solid content of 10%.

<Preparation of Clear Coating Agent B-2> TiO
A clear coating agent B- having a solid content of 10% was prepared in the same manner as in the preparation of the clear coating agent B-1 except that the content of ₂ was 50% by weight of the total solid content in the coating agent. 2 was prepared.

<Preparation of clear coat agent B-3> To a reactor equipped with a reflux condenser and a stirrer, 60 parts of isopropyl alcohol and 10 parts of a solution of the above hydrolyzed condensate of alkoxysilane were added and stirred uniformly at 40 ° C. Mixed. A predetermined amount of TiO ₂ aqueous dispersion having an average particle size of 5 nm was added to this mixed solution so that the content of TiO ₂ became 60% by weight of the total solid content in the coating agent, and the mixture was further stirred and mixed at 40 ° C. for 1 hour. ,
After that, isopropyl alcohol is added to make the solid content 1
0% of clear coat agent B-3 was prepared.

<Preparation of Clear Coating Agent B-4> TiO
_A clear coating agent B-having a solid content of 10% was prepared in the same manner as in the preparation of the clear coating agent B-3 except that the content of ₂ was 20% by weight of the total solid content in the coating agent. 4 was prepared. <Preparation of clear coat agent B-5> T having an average particle size of 5 nm
A clear coating agent B-5 having a solid content of 10% was prepared in the same manner as in the preparation of the clear coating agent B-1 except that TiO ₂ having an average particle size of 500 nm was used instead of iO ₂ .

<Formation of coating film> A large number of aluminum plates which have been preliminarily subjected to a base treatment and coated with an intermediate coating material are prepared, and each of the aluminum plates is first coated with a clear coating agent (A) of the type shown in Table 1.
Comparative example 1 was spray-coated so as to have the coating amount shown in the table.
Other than the above, in Comparative Example 1, the coating film of the clear coating agent (A) was heated to 120 ° C. for 3 minutes until the coating film formed by the clear coating agent (A) reached a semi-cured dry state.
After drying for 0 minutes, a clear coating agent (B) of the type shown in Table 1 was spray-coated so as to have a coating amount shown in Table 1, and baked and dried at 150 ° C. for 30 minutes. The obtained coating film was evaluated according to the following evaluation methods. The results are as shown in Table 1.

<Transparency> The surface of the coating film was visually observed, and the clear film had no cloudiness and had high transparency, and the transparency was 5, and the one with extremely cloudy and almost no visible background color was 1.
The difference in the degree was evaluated by the 5-point method. <Smoothness> The surface of the coating film is visually observed, and a clear film having almost no irregularities on the surface is 5 and a surface having irregularities on the surface is 1 and the difference in degree is 5
It was evaluated by the point method.

<Adhesiveness> Gobangme (100 pieces at 1 mm intervals) was put into the sample with a cutter knife, cellophane tape was peeled off, and the adhered state of the coating film after peeling was visually observed, and the remaining number of 100 pieces was determined. I counted. <Weather resistance> Visually observe the degree of choking of the coating film after irradiation for 1000 hours with a sunshine weather meter.
The difference in the degree was evaluated by the 5-point method.

<Decontamination property> The test piece was allowed to stand in a closed container filled with the smoke of two cigarettes to adhere the cigarette tar to the test piece, and then using a black light (manufactured by Toshiba), It was exposed to ultraviolet rays of 1 mW / cm ² for 12 hours, and the residual state of the tobacco tar was visually observed. The one completely free of tar was set to 5, and the tar that remained almost unchanged from before irradiation was set to 1. The difference in degree was evaluated by the 5-point method.

[0035]

[Table 1]

As is clear from the data in Table 1, in the case of Examples 1 to 7 which are the method for forming a coating film of the present invention, the transparency, smoothness, adhesion, weather resistance and stain removability are excellent. Everything was good. On the other hand, clear coat agent (A)
In the case of Comparative Example 1 in which the clear coat agent (B) was applied after curing and drying, the adhesiveness, transparency, smoothness, and weather resistance were poor. In the case of Comparative Example 2 in which the content of the partial hydrolyzate of the alkoxysilane was less than 50% of the total solid content in the clear coating agent (A), the weather resistance was poor. In the case of Comparative Example 3 using the clear coating agent (B) in which the content of the oxygen-containing titanium compound was less than 30% by weight of the total solid content in the coating agent in terms of TiO ₂ , the stain removability was poor. there were. In the case of Comparative Example 4 in which the clear coating agent (B) using an oxygen-containing titanium compound having an average particle size of more than 0.1 μm was used, the transparency and smoothness were poor. In the case of Comparative Example 5 in which the coating amount of the clear coating agent (B) was more than 10 g / m ² , the transparency, smoothness and adhesion were poor, and cracks were formed in the coating film. In the case of Comparative Example 6 using the acrylic urethane resin coating, the weather resistance was poor. In the case of Comparative Example 7 in which the clear coat agent (A) was not applied at all, the transparency, smoothness, adhesion and weather resistance were poor.

[0037]

According to the method for forming a photocatalyst-containing coating film of the present invention, a photocatalyst-containing coating film excellent in transparency, smoothness, adhesion, weather resistance and stain removability can be formed.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 10-296185 (JP, A) JP 9-24335 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C09D 1/00-10/00 C09D 101/00-201/00 B05D 7/24

Claims (2)

(57) [Claims] 1. A general formula R ¹ Si is applied to a surface of a substrate to be coated.
(OR ² ) ₃ [wherein, R ¹ is an organic group having 1 to 8 carbon atoms, and R ² is an alkyl group having 1 to 5 carbon atoms] and an alkoxysilane and its partially hydrolyzed condensate. A clear coating agent (A) containing at least one compound selected from the group consisting of 50% by weight or more of the total solid content of the coating agent is applied at a solid coating amount of 5 to 100 g / m ^2. (2) Before the coating film formed by the clear coating agent (A) reaches a semi-cured dry state, a general formula (R ¹ ) _n Si (OR ² ) _{4 is} added as a binder on the surface of the coating film. _-n [wherein
R ¹ is an organic group having 1 to 8 carbon atoms, and R ² is 1 to 1 carbon atoms.
Which is an alkyl group of 5 and n is an integer of 0 to 3] and which contains at least one compound selected from the group consisting of alkoxysilanes and partial hydrolysis-condensation products thereof, and has an average particle size as a photocatalyst. Clear coat containing an inorganic oxygen-containing titanium compound having a maximum particle diameter of 0.001 to 0.1 μm and 0.5 μm or less in an amount of 30% by weight or more of the total solids in the coating agent in terms of TiO _2. The agent (B) is applied at a solid content of 0.1 to 10 g / m ² , and (3) the coating film formed by the clear coating agent (A) and the clear coating agent (B) is dried. A method for forming a photocatalyst-containing coating film. 2. An inorganic oxygen-containing titanium compound as titanium oxide, hydrous titanium oxide, hydrated titanium oxide, metatitanic acid,
The method for forming a photocatalyst-containing coating film according to claim 1, wherein orthotitanic acid or titanium hydroxide is used.