JPH10174883A - Aluminum material having photocatalytic function and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an aluminum material having a photocatalytic function excellent in weather resistance by forming a porous aluminum oxide film on the surface of the aluminum material and fixing a semiconductor composition provided with the photocatalytic function on the film. SOLUTION: At the time of producing the aluminum material having the photocatalytic function, after forming an anodically oxidized film on the surface of the aluminum material by subjecting the aluminum material to an anodically oxidizing treatment in an acid soln. such as sulfuric acid, oxalic acid and phosphoric acid, the material is washed and immersed in a soln. in which titanium oxide particles are suspended to adsorb the titanium oxide on the porous anodically oxidized film. At this time, after forming the anodically oxidized film, the anodically oxidized film is colored by an electrolytic coloring method or dyeing method, then the titanium oxide may be adsorbed in order to increase a designing property of the aluminum material. As for the other semiconductor composition other than the titanium oxide, the soln. in which these composition are suspended is formed, and the aluminum material on which the porous anodically oxidized film is formed may be immersed in this soln..

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum material having a photocatalytic function (including an aluminum alloy material; the same applies hereinafter), more specifically, a semiconductor composition having a photocatalytic action on its surface, in particular, fixing (coating) titanium oxide. Further, the present invention relates to an aluminum material having a photocatalytic function for removing harmful and polluting substances in the air environment or water by utilizing the photocatalytic action of these compositions, and a method for producing the same.

[0002]

2. Description of the Related Art Semiconductors such as titanium oxide have a thickness of 400 nm.
It is known that when irradiated with ultraviolet rays having the following wavelengths, it has a photocatalytic action and exhibits functions such as sterilization, deodorization, and decomposition of contaminants. To explain the prior art using titanium oxide as an example, a number of methods have been proposed for fixing titanium oxide to a base material in order to form a photocatalytic film made of titanium oxide and provide it for various uses. When applied, both methods have problems.

[0003] For example, there is a method of fixing powdered titanium oxide to a base material using an inorganic binder or an organic binder.
(Japanese Unexamined Patent Publication No. Hei 5-535544, Japanese Unexamined Patent Publication No. 7-60132, Japanese Unexamined Patent Publication No. 7-171408, Japanese Unexamined Patent Publication No. 7-265714, Japanese Unexamined Patent Publication No. 7-31
However, in the method of fixing with an inorganic binder, most of the inorganic binder is used in a state of being dissolved or suspended in water,
It cannot be applied to a substrate that repels water, and depending on the type of the substrate, the adhesiveness of the binder itself is remarkably poor, so that it does not serve as a binder.

In the method using an organic binder, when ultraviolet rays having a wavelength of 400 nm are irradiated, the organic binder in contact with the titanium oxide in an excited state is decomposed and loses its function as a binder in a short period of time. There are difficulties.

[0005] A method of spraying titanium oxide on the surface of a substrate (JP-A-3-8448, JP-A-6-210170), a method in which a suspension of titanium oxide particles (titanium oxide sol) is applied to the substrate and fired. Method (Japanese Patent Laid-Open No. 6-293519,
6-205977, JP-A-7-155598) have also been proposed, but it is difficult to form a thin film of 1 μm or less by the thermal spraying method, and depending on the type of the substrate, the design of the substrate surface is impaired. In some cases.

In the method using titanium oxide sol,
The thickness of the titanium oxide tends to be large, and the adhesion durability to the substrate tends to be poor, and the design of the substrate is also impaired. In particular, when the firing temperature is low, the adhesion to the substrate is poor,
When the firing temperature is high, it is difficult to apply to a material that softens at a relatively low temperature, such as an aluminum material.

[0007] Methods of fixing titanium oxide by a gas phase method such as a CVD method, a sputtering method, and an electron beam evaporation method have also been proposed. However, in these methods, the equipment becomes large-scale, so that the manufacturing cost increases. In addition, there is a problem that titanium oxide can be used only for a substrate having a simple shape due to poor rotation.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems when a semiconductor composition having a photocatalytic action, particularly titanium oxide, is coated on an aluminum substrate. An object of the present invention is to provide an aluminum material in which titanium oxide is fixed on an aluminum substrate with good adhesion and has a photocatalytic function excellent in weather resistance and a method for producing the same.

[0009]

The aluminum material having a photocatalytic function according to the present invention for achieving the above object has a porous aluminum oxide film formed on the surface thereof, and the porous aluminum oxide film has a photocatalytic action. And a porous aluminum oxide film is formed on the surface thereof, and titanium oxide is fixed on the porous aluminum oxide film. The third and fourth features are that the aluminum film is a porous anodic oxide film and that the thickness of the porous anodic oxide film is 0.1 to 50 μm.

Fifth and sixth characteristics are that the porous aluminum oxide film is a porous boehmite film and that the thickness of the porous boehmite film is 0.1 to 5 μm.

According to the method for producing an aluminum material having a photocatalytic function according to the present invention, a porous aluminum oxide film is formed on the surface of an aluminum material, and a semiconductor composition having a photocatalytic action is adsorbed on the porous aluminum oxide film. And a porous aluminum oxide film is formed on the surface of the aluminum material, and titanium oxide sol is chemically adsorbed on the porous aluminum oxide film.

In the present invention, the porous aluminum oxide film on the surface of the aluminum material is preferably formed by subjecting the surface of the aluminum material to anodizing treatment or boehmite treatment. The amount of semiconductor composition adsorbed can be increased. For fixing titanium oxide or the like, the thickness of the porous anodic oxide film is preferably in the range of 0.1 to 50 μm, and the thickness of the porous boehmite film is preferably in the range of 0.1 to 5 μm.

When the thickness of the porous anodic oxide film is less than 0.1 μm, the corrosion resistance is poor, and the porous anodic oxide film is not sufficiently porous, so that the adsorption amount of the photocatalyst tends to be insufficient. If it exceeds 50 μm, cracks tend to occur in the film, and the photocatalytic activity reaches saturation. In addition, the processing time is undesirably long. A more preferable thickness range of the porous anodic oxide film is 3 to 20 μm.

The thickness of the porous boehmite film is 0.1 μm
If it is less than 1, the corrosion resistance is inferior and the photocatalytic ability tends to be insufficient because it is not sufficiently porous. When the thickness of the film exceeds 5 μm, the film is easily peeled, and the photocatalytic function reaches saturation. In addition, the processing time is undesirably long. A more preferable thickness range of the porous boehmite film is 0.1 to 3 μm.
m.

In the present invention, any semiconductor composition having a photocatalytic action can be used. For example, known SrTiO ₃ , ZnO, and CdS as disclosed in JP-A-6-170360 can be used. , SnO ₂ , RuO ₂ ,
Cs ₃ Sb, InAs, InSb, GaAs or TiO ₂
Among them, TiO ₂ is particularly preferably used. The particle size of the semiconductor particles used is 1 to 100.
nm, preferably 5 to 20 nm. Particle size is 1
If it is less than nm, the band gap becomes large due to the quantum size effect, and there is a problem that a photocatalytic function cannot be obtained unless the light is short-wavelength light. On the other hand, if the particle size is too small, handling becomes difficult and the dispersibility decreases. From the viewpoint of handleability, those having a particle size of 5 nm or more are preferable. On the other hand, if it exceeds 100 nm, the adsorbability to the porous aluminum oxide film becomes poor and the adhesiveness also decreases.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION In a preferred embodiment of the method for producing an aluminum material having a photocatalytic function according to the present invention, an aluminum material is mixed with sulfuric acid, oxalic acid, phosphoric acid or an acid solution in which two or more of these acids are mixed. After anodizing to form an anodized film on the surface of the aluminum material, wash it thoroughly with water, immerse it in a solution (titanium oxide sol) in which titanium oxide particles are suspended, and oxidize it to a porous anodized film. Adsorb titanium. In order to enhance the design of the aluminum material, after forming the anodized film, the anodized film may be colored by an electrolytic coloring method or a dyeing method, and then titanium oxide may be adsorbed. Also for the above-mentioned semiconductor compositions other than titanium oxide, these compositions are made into a suspended solution, and an aluminum material having a porous anodic oxide film formed thereon is immersed in this solution.

Another preferred embodiment is a method in which a boehmite film is formed on an aluminum material and then immersed in a solution in which titanium oxide is suspended to adsorb the titanium oxide on the boehmite film. The boehmite film is made of scale-like or needle-like crystals, and increases the surface area of the aluminum material to increase the adsorption amount of titanium oxide.

The boehmite film is formed on the aluminum material by a method such as immersion in high-temperature deionized water, immersion in deionized water to which an amine represented by triethanolamine is added, or exposure to heated steam. Will be According to the present invention, it is presumed that a sol of a semiconductor composition such as a titanium oxide sol is chemically adsorbed on the surface of the porous aluminum oxide in a thickness of a single molecule or several molecular layers, and excellent adhesion is provided.

[0019]

Hereinafter, examples of the present invention will be described in comparison with comparative examples. Example: Dimension 100 mm from extruded aluminum alloy A6063
A test material having a size of 100 mm × 1 mm thick was collected,
After being immersed in a 0% aqueous sodium hydroxide solution for 3 minutes to perform an etching treatment, the substrate was washed with water. Then, the mixture was immersed in a 10% nitric acid solution at 20 ° C. for 3 minutes for neutralization treatment, washed with water and dried. Each test material was processed by the following method after performing the above pretreatment.

EXAMPLE 1 DC electrolysis was carried out at 20 ° C. in a 15% aqueous sulfuric acid solution at a current density of 1.5 A / dm ² for 30 minutes using a test material as an anode, and an approximately 12 μm anodic oxide film was formed on the surface of the test material. Was formed. Next, the test material subjected to the anodizing treatment was placed in an acidic titanium oxide suspension (STS-01 manufactured by Ishihara Sangyo Co., Ltd.) at 20 ° C.
Immersion for 3 minutes, rinse with deionized water,
It was dried by heating at a temperature of ° C.

Comparative Example 1 Anodizing treatment was performed under the same conditions as in Example 1 to form an anodized film on the surface of the test material.

Comparative Example 2 Anodizing treatment was performed under the same conditions as in Example 1 to form an anodic oxide film on the surface of the test material, and then the titanium oxide suspension of Example 1 was applied by dip coating at 150 ° C. By heating and drying in the above, a product to which titanium oxide was fixed was produced.

EXAMPLE 2 DC electrolysis was performed at 20 ° C. in a 15% aqueous sulfuric acid solution at a current density of 1.5 A / dm ² for 30 minutes using a test material as an anode, and an approximately 12 μm anodic oxide film was formed on the surface of the test material. Was formed. Next, the anodized test material was replaced with nickel sulfate
It was immersed in an aqueous solution of 50 g / l of hexahydrate and 30 g / l of boric acid at 25 ° C., and subjected to alternating current electrolysis (60 Hz, 14 V (effective voltage) for 7 minutes) to be colored bronze. It was immersed in an alkaline titanium oxide suspension (TAINOK A-6 manufactured by Taki Kagaku Co., Ltd.) at 20 ° C. for 1 minute, washed with ion-exchanged water, and dried by heating at 100 ° C.

Example 3 DC electrolysis was performed at 20 V for 35 minutes at 90 V in an 18% phosphoric acid aqueous solution at 20 ° C. in an 18% phosphoric acid aqueous solution to form an anodized film of about 7 μm on the surface of the test material. Next, the anodized test material was immersed in a weakly alkaline titanium oxide suspension (TO sol manufactured by Tanaka Transfer Co., Ltd.) at 20 ° C. for 1 minute, washed with ion-exchanged water, and then washed at a temperature of 250 ° C. And dried by heating.

Comparative Example 3 A test material subjected to only the pretreatment was placed in an acidic titanium oxide suspension (STS-01 manufactured by Ishihara Sangyo Co., Ltd.) at 20 ° C.
Immersion for 3 minutes, rinse with deionized water,
It was dried by heating at a temperature of ° C.

COMPARATIVE EXAMPLE 4 In a 15% aqueous sulfuric acid solution at 20 ° C., DC electrolysis was performed at 20 V for 3 minutes using a test material as an anode to obtain a solution of
An anodic oxide film having a thickness was formed. Next, the test material subjected to the anodization treatment was immersed in a weakly alkaline titanium oxide suspension (Tainock A-6, manufactured by Taki Kagaku Co., Ltd.) at 20 ° C. for 1 minute, washed with ion-exchanged water, It was dried by heating at a temperature of 100 ° C.

Comparative Example 5 DC electrolysis was carried out at 20 V for 3 minutes in an 18% phosphoric acid aqueous solution at 20 ° C. using a test material as an anode to obtain about 0.05 μm
An anodic oxide film having a thickness was formed. Next, the anodized test material was immersed in a weakly alkaline titanium oxide suspension (TO sol manufactured by Tanaka Transfer Co., Ltd.) at 20 ° C. for 1 minute, washed with ion-exchanged water, and then washed at 250 ° C. And dried by heating.

The test materials prepared in Examples 1 to 3 and Comparative Examples 1 to 5 were placed in a container having a capacity of 8 l, and 4 l of air was degassed by a vacuum pump. Injected. (Note: The concentration of nitric oxide in the container is 40
ppm) Next, the UV intensity on the surface of each test material was 1 mW / cm ²
After irradiation with a black light blue fluorescent lamp for 30 minutes, the concentration of nitric oxide in each container was measured with a detector tube (11 L, manufactured by Gastech). Further, Examples 1 to
3. With respect to the test materials of Comparative Examples 2 to 5, each test material was irradiated for 250 hours in a sunshine carbon arc type weathering tester, and then the concentration of nitric oxide was measured in the same manner as described above. Table 1 shows the results.

[0029]

[Table 1] << Table Note >> Note 1: Extremely poor weather resistance (durability), not practical

As shown in Table 1, all of the test materials prepared in Examples 1 to 3 according to the present invention have a great effect of oxidizing and removing nitric oxide. On the other hand, the test material of Comparative Example 1 in which titanium oxide was not adsorbed had almost no effect of removing nitric oxide, and the test material of Comparative Example 2 in which titanium oxide was applied and calcined was extremely inferior in durability. The test material of Comparative Example 3, which was determined to be impossible and did not form an anodic oxide film only by the pretreatment, had a small adsorption amount of titanium oxide, and therefore had a small effect of removing nitrogen monoxide and was inferior in durability. The test materials of Comparative Examples 4 and 5 have poor corrosion resistance because the thickness of the porous anodic oxide film is too thin, and have a small effect of removing nitrogen monoxide because the amount of titanium oxide adsorbed is small.

Example 4 Dimensions of 100 mm from extruded aluminum alloy A6063
A test material having a size of 100 mm × 1 mm thick was collected,
After being immersed in a 0% aqueous sodium hydroxide solution for 3 minutes to perform an etching treatment, the substrate was washed with water. Then, the mixture was immersed in a 10% nitric acid solution at 20 ° C. for 3 minutes for neutralization treatment, washed with water and dried. Each test material was processed by the following method after performing the above pretreatment.

Immersed in 98 ° C. deionized water for 10 minutes,
A boehmite film of about 2 μm was formed. The boehmite-treated test material was then placed in a weakly alkaline titanium oxide suspension (TAINOK A-6 manufactured by Taki Kagaku Co., Ltd.) at 20 ° C.
After immersing for 1 minute and washing with ion exchange water,
It was dried by heating at a temperature of ° C.

Example 5 A test material which had been subjected to the same pretreatment as in Example 4 was immersed in a 0.5% aqueous solution of triethanolamine at 95 ° C. for 15 minutes to form a boehmite film having a thickness of about 3 μm. Then, the boehmite-treated test material was placed in a weakly alkaline titanium oxide suspension (TO sol manufactured by Tanaka Transfer Co., Ltd.) at 20 ° C.
After immersing for 1 minute, washing with ion-exchanged water, and drying by heating at a temperature of 250 ° C.

With respect to the test materials produced in Examples 4 and 5, the effect of removing nitric oxide was evaluated in the same manner as in Example 1. As a result, the detected nitric oxide concentration was 5 ppm for the test material of Example 4 and 10 ppm for the test material of Example 5, all of which had excellent nitric oxide oxidation and removal effects. . The effect of oxidizing and removing nitric oxide after the weathering test hardly decreased.

[0035]

According to the present invention, there is provided an aluminum material having a photocatalytic function having excellent durability. The aluminum material is useful as a purifying material useful for removing pollutants such as nitrogen oxides and sulfur oxides in the air environment and organic chlorine compounds in water. Since the base for fixing titanium oxide according to the present invention is an anodic oxide film or a boehmite film usually formed on an aluminum material, it can be dealt with by slightly modifying the existing surface treatment equipment.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C02F 1/58 C02F 1/72 101 1/72 101 C23C 28/04 C23C 28/04 C25D 11/04 302 C25D 11/04 302 11 / 18 308 11/18 308 B01D 53/36 J

Claims (8)

[Claims] 1. An aluminum material having a photocatalytic function, wherein a porous aluminum oxide film is formed on a surface, and a semiconductor composition having a photocatalytic action is fixed to the porous aluminum oxide film. 2. An aluminum material having a photocatalytic function, wherein a porous aluminum oxide film is formed on the surface, and titanium oxide is fixed on the porous aluminum oxide film. 3. The aluminum material having a photocatalytic function according to claim 1, wherein the porous aluminum oxide film is a porous anodic oxide film. 4. The porous anodic oxide film having a thickness of 0.1 to 5
The aluminum material having a photocatalytic function according to claim 3, wherein the thickness is 0 µm. 5. The aluminum material having a photocatalytic function according to claim 1, wherein the porous aluminum oxide film is a porous boehmite film. 6. The porous boehmite film having a thickness of 0.1 to 0.1.
6. The aluminum material having a photocatalytic function according to claim 5, wherein the thickness is 5 μm. 7. A method for producing an aluminum material having a photocatalytic function, wherein a porous aluminum oxide film is formed on a surface of an aluminum material, and a semiconductor composition having a photocatalytic action is adsorbed on the porous aluminum oxide film. Method. 8. A method for producing an aluminum material having a photocatalytic function, comprising forming a porous aluminum oxide film on the surface of an aluminum material and chemically adsorbing titanium oxide sol on the porous aluminum oxide film.