JP2003328150A - Coated metallic sheet having excellent workability, hiding property and photocatalytic activity and production method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coated metallic sheet which can be subjected to postworking, and has excellent hiding properties and photocatalytic activity by compositely adding flaky powder to an inorganic coating film containing photocatalytic grains. <P>SOLUTION: In the coated metallic sheet, a silica or alumina based top layer in which photocatalytic grains and flaky powder are dispersed is formed on the surface of a base material via a silica or alumina based primer layer in which flaky powder is dispersed. The top layer contains the photocatalytic grains, preferably, in ≥5 mass% by an individually blended quantity, and in 10 to 80 mass% by a blended quantity in total with the flaky powder. The primer layer contains the flaky powder, preferably, in ≥5 mass% by an individually blended quantity, and in 10 to 80 mass% by a blended quantity in total with an inorganic pigment. One or more kinds selected from Al flakes, stainless steel flakes and pearl mica are used as the flaky powder. One or more kinds selected from TiO<SB>2</SB>, ZnO, WO<SB>3</SB>, FeTiO<SB>3</SB>and SrTiO<SB>3</SB>are used as the photocatalytic grains. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated metal plate which has long-term durability even when used outdoors, is easy to post-process, and has excellent concealing properties and photocatalytic activity, and a method for producing the same.

[0002]

PRIOR ART TiO₂Photocatalysts such as
Activated by irradiation, organic matter, NO_x, SO _xWork to disassemble etc.
Present a purpose. Anatase-type TiO that acts as a photocatalyst₂
By providing a coating film containing powder on the steel plate surface,
It is considered to impart catalytic activity to coated steel sheets.
This type of coated steel sheet uses organic matter for the base coating.
Then, the O generated by the photocatalytic reaction₂ ^-, OH radical activity
The organic film is decomposed by the basic oxygen and may cause peeling of the film.
The walking phenomenon occurs. Therefore, the inorganic materials should be
It is usually used for resin to form an inorganic coating film
(JP-A-7-113272, JP-A-8-164334, W
O96 / 29375).

Although an organic coating film may be decomposed by a photocatalytic reaction, it is superior in processability to an inorganic coating film. Since the decomposition of the organic coating film can be suppressed by using a relatively stable fluororesin as the base, a coating film in which anatase type TiO ₂ particles are dispersed in the fluororesin base (JP-A-7-171408) or anatase type Photocatalyst precoated steel sheet having an organic-inorganic composite coating film formed from a silica-organosilane-based coating material containing TiO ₂ particles (Patent Document 1)
No. 0-225658) is also known.

[0004]

The inorganic coating film to which photocatalytic activity is added by adding TiO ₂ is inferior in workability,
Cracks are generated during drawing and the coating film is easily peeled off from the steel sheet surface. Therefore, in applications such as building materials and home appliances that are commercialized by bending and drawing, it is unavoidable to impart photocatalytic activity by the post-coating method of painting after processing. Considering the drawbacks of post coats, which have low productivity and increase product cost, there is a demand for post coats that are advantageous in reducing manufacturing costs. However, no inorganic precoated steel sheet has been developed that fully satisfies the workability required for applications such as building materials and home appliances.

[0005] Organic coated steel sheets using fluorocarbon resin are light
High resistance to decomposition by active oxygen generated by catalytic reaction
Despite showing resistance, required for building materials and external home appliances
The weather resistance has not been fully satisfied. For photocatalysis
Decomposition of organic matter by TiO ₂Other minerals around the particles
Coated with TiO₂Direct contact between particles and organic coating
How to avoid touch and TiO₂Paint with a reduced amount of particles
Can be suppressed by the use of₂
The photocatalytic activity of the particles is reduced. Organic with photocatalytic activity
The coated steel sheet with the inorganic composite coating film is the same as the inorganic coated steel sheet.
Like, it is inferior in workability. For example, reduce the film thickness to about 1 μm.
Even if it is a coated film, it is 10T in the T-bending tape peeling test.
6T or less required for photocatalyst precoated steel sheet that cannot be reared
The bending properties below are not obtained.

[0006]

The present invention has been devised to solve such a problem, and by dispersing a scaly powder in an inorganic primer layer and a top layer,
It is an object of the present invention to provide a coated metal plate which is easily post-processed and has excellent hiding power and photocatalytic activity. In order to achieve the object, the coated metal plate of the present invention has a silica or alumina-based top layer in which photocatalyst particles and scale-like powder are dispersed through a silica or alumina-based primer layer in which the flaky powder is dispersed. It is characterized in that it is formed on the material surface. The primer layer optionally contains an inorganic pigment.

The top layer preferably contains photocatalyst particles in an amount of 5% by mass or more in a single compounding amount and 10 to 80% by mass in a total compounding amount with the flaky powder. The primer layer is preferably 5% by mass or more in a single compounding amount, and 10% in a total compounding amount with the inorganic pigment.
-80% by mass of scaly powder. Al for scaly powder
One or more of flakes, stainless steel flakes, and pearl mica are used, and TiO ₂ , Z is used as the photocatalyst particles.
One or two of nO, WO ₃ , FeTiO ₃ , and SrTiO _3.
More than one seed is used. Inorganic pigments include rutile type TiO ₂ , TiO ₂ —Sb treated with SiO ₂ and / or Al ₂ O _{3.
2 O 5 -Cr 2 O 3,} Fe 2 O 3, CoAl 2 O 4, Cu (C
r, Mn) ₃ O ₄ , TiO ₂ —NiO—Sb ₂ O _{5 and the} like.
A silica sol and / or an alumina sol containing an inorganic pigment and a flaky powder is applied to a substrate / metal plate to form SiO ₂ and / or
Alternatively, it is produced by applying a heat treatment for forming a primer layer made of an Al ₂ O ₃ precursor, applying silica sol and / or alumina sol containing photocatalytic activity and scale-like powder, and then performing a heat treatment for forming a top layer. It

[0008]

When the photocatalyst particles such as TiO ₂ are irradiated with ultraviolet light,
A photocatalytic reaction that decomposes organic substances, NO _x , SO _x, etc. occurs. In the photocatalytic decomposition reaction, electrons in the valence band of titanium oxide are absorbed by ultraviolet light to be excited in the conduction band, and the very strong oxidizing power of the holes generated in the valence band causes an organic substance, NO _x , It is considered that SO _{x and the} like are decomposed. The decomposition reaction extends not only to organic substances, NO _x , SO _x, etc., but also to organic substances forming the coating film. Therefore, in a coating film in which an organic substance is introduced for the purpose of improving processability, the organic substance in the coating film is decomposed due to photocatalytic activity to cause a choking phenomenon, and it is difficult to achieve both durability and processability.

The inventors of the present invention, in the process of studying a method for forming a coating film which is free from chalking due to photocatalytic activity, is excellent in processability and hiding power, and does not deteriorate in photocatalytic activity, is a scaly powder in the inorganic primer layer. It has been found that when the above is dispersed and the photocatalyst particles and the scaly powder are compositely dispersed in the top layer, post-processing is easy even in an inorganic coating film, and excellent photocatalytic activity is exhibited. The effects of the dispersion of the flaky powder on the processability and photocatalytic activity are presumed as follows.

Since the inorganic coating film to be the primer layer has no elongation itself, when it is bent or drawn, cracks occur and it is peeled off from the base material / metal plate. On the other hand, when flaky powders such as Al flakes, stainless steel flakes, and pearl mica are dispersed in the coating film, the tensile stress and compressive stress applied to the coating film are relaxed by the flaky powder,
The spread of cracks reaching the metal plate is prevented by the flaky powder. Moreover, since the flaky powder itself is soft, the processability of the coating film is also improved. Furthermore, since the flaky powder is oriented in the plane direction of the substrate / metal plate during the process of forming the coating film, it has excellent concealing properties even with a thin coating film. Working at an advantage.

The scale-like powder dispersed in the top layer also improves the workability of the top layer for the same reason as the primer layer. Since the flaky powder such as Al flakes, stainless steel flakes, and pearl mica diffusely reflects the light incident on the coating film on the surface of the flakes to lengthen the optical path, the light irradiation efficiency for the photocatalyst particles is improved. As a result, even if the blending amount of the photocatalyst particles is reduced, higher photocatalytic activity is exhibited as compared with the coating film without the flaky powder. Further, when pearl mica having the mica surface coated with TiO ₂ having a rutile or anatase structure is dispersed in the top layer, photocatalytic activity is imparted to the mica surface in addition to diffuse reflection of light, and the photocatalytic reaction proceeds more efficiently.

[0012]

[Embodiment] [Base material / metal plate] Ordinary steel plate, plated steel plate, stainless steel plate, aluminum plate, aluminum alloy plate, copper plate, copper alloy plate and the like are used. The plated steel sheet includes Zn-plated steel sheet, Zn-Al alloy-plated steel sheet, Zn
-Al-Mg alloy plated steel sheet, Al plated steel sheet, Al-
There are Si-plated steel plates and the like. The base material / metal plate is subjected to pre-painting treatment such as alkali degreasing, chromate treatment, phosphate treatment, and chromium-free chemical conversion treatment, if necessary.

[Primer layer] When an organosilica sol and / or an alumina sol mixed with an inorganic pigment or a scaly powder is applied to a substrate / metal plate and heat-treated, SiO ₂ having a concealing property is obtained.
And / or a primer layer of Al ₂ O ₃ precursor is formed. As the organosilica sol, R ¹ Si (OR ² ) ₃
An organosilicate having a structure of (R ¹ , R ² : alkyl group) dissolved in an organic solvent or water is used.
The alkyl group preferably has a smaller number of carbon atoms in order to reduce the amount of organic components remaining after the heat treatment, and the methyl group is particularly preferable. As the alumina sol, a dispersion product of aluminum alkoxide hydrolysis products and fine particles having a boehmite structure is used.

For the paint for the primer layer, a single blending amount of 5
10% to 80% by mass (preferably 20% to 50% by mass) of scaly powder is blended in a total amount of at least mass% and the inorganic pigment. As the flaky powder, one or more selected from Al flakes, stainless steel flakes, and pearl mica are used. The diameter of the flaky powder is increased in order to enhance the hiding power of the primer layer by orienting in the plane direction of the base material / metal plate. Flakes having a thickness ratio of 10 or more are preferred. When the hiding property of the primer layer is insufficient due to the dispersion of the flaky powder, SiO ₂ and / or Al ₂ O ₃ -treated rutile TiO ₂ , TiO ₂ —Sb ₂ O ₅ —Cr ₂
O ₃ , Fe ₂ O ₃ , CoAl ₂ O ₄ , Cu (Cr, Mn)
An inorganic pigment such as ₃ O ₄ or TiO ₂ —NiO—Sb ₂ O ₅ is used together. If the amount of the flaky powder alone is less than 5% by mass, sufficient processability and hiding power cannot be obtained, and if the total amount of the inorganic pigments is more than 80% by mass, the adhesion of the primer layer to the base material / metal plate is high. Is reduced.

The primer layer is formed by heat-treating the coating material applied to the base material / metal plate. The heat treatment temperature at the time of forming the primer layer is preferably selected in the range of 60 to 350 ° C. At a heat treatment temperature that does not reach 60 ° C., the coating material is insufficiently dried, and unevenness easily occurs in the top layer formed in the subsequent step. On the contrary, at the heat treatment temperature exceeding 350 ° C,
A crack is generated in the primer layer, and the primer layer is easily separated from the base material / metal plate.

[Top Layer] A top layer excellent in processability and photocatalytic activity is formed by applying organosilica sol and / or alumina sol containing photocatalyst particles and flaky powder on the primer layer and heat-treating the same. The same sol as the primer layer is used for the organosilica sol and alumina sol for the top layer. Organosilica sol and / or alumina sol is 5% by mass or more in a single compounding amount,
It contains 10 to 80% by mass (preferably 20 to 50% by mass) of photocatalyst particles in the total blending amount with the scaly powder. If the amount of the photocatalyst particles alone is less than 5% by mass, the photocatalytic activity is insufficient. If the total amount of the photocatalyst particles is more than 80% by mass, the adhesion of the top layer is deteriorated.

The photocatalyst particles dispersed in the top layer include T
iO₂, ZnO, WO₃, FeTiO ₃, SrTiO₃From
One or more selected types are used. Above all,
That it is possible to obtain economically stable and inexpensive fine particles.
From the anatase type TiO₂Is preferred. Scale powder
At the end, Al flakes similar to the primer layer, stainless steel
Steel flakes and pearl mica are used. Pearl Mai
When using mosquito, it has a rutile or anatase type structure
TiO₂Mica coated with is preferred. Photocatalyst particles, scales
Organosilica sol and / or a mixture of flaky powder
Luminasol is applied to the substrate / metal plate and then applied to the primer.
A temperature higher than the heat treatment temperature during layer formation (preferably 15
Heat treatment is performed at 0 to 400 ° C. Silica by heat treatment
-Based or alumina-based polycondensation progresses, and it is
Layer is formed. In order to proceed the polycondensation efficiently,
Preferably, the heat treatment temperature is set to 150 ° C. or higher. Only
However, if heated to a temperature higher than 400 ° C, the top layer will be cracked.
The rack can be easily inserted.

The heat treatment temperature for forming the top layer is preferably selected in relation to the heat treatment temperature for forming the primer layer. Specifically, in order to accelerate the drying of the coating film, the heat treatment temperature for forming the primer layer is selected in the range of 80 to 250 ° C, and the heat treatment temperature for forming the top layer is selected in the range of 150 to 400 ° C. By setting this temperature, a strong bond is obtained between the primer layer and the top layer, and the heat treatment during the formation of the top layer improves the adhesion of the top layer to the primer layer. The formed top layer exhibits a self-cleaning action of decomposing organic components such as dirt and oil adhering to the coating film by the photocatalytic reaction of the dispersed photocatalytic particles. The photocatalyst particles also exhibit an air purifying action of decomposing NO _x , SO _{x and the} like. The coated metal plate obtained in this way is used for exterior building materials and exterior home appliances that are placed outdoors by utilizing its excellent pollution resistance and air purification effect, and has a beautiful appearance over a long period of time. A product that is maintained is provided.

[0019]

EXAMPLES [Manufacturing method 1: Example of the present invention] S having a plate thickness of 1.0 mm
A base material / metal plate was prepared by alkaline degreasing, pickling, washing with water and drying a US304 stainless steel plate. An organosilica sol in which rutile titanium oxide (white pigment) surface-treated with zirconia and flaky powder was dispersed was applied to a substrate / metal plate and baked at 200 ° C. for 1 minute to form a primer layer. Further, an organosilica sol containing 20 nm particle size anatase type TiO ₂ and flaky powder was applied onto the primer layer, and the top layer was formed by baking at 230 ° C. for 1 minute.

[Production Method 2: Inventive Example] Zn-Al-Mg
The primer layer and the top layer were formed under the same conditions as in Production Method 1, except that the alloy-plated steel plate was used as the base material / metal plate and the anatase-type TiO ₂ particles having a particle size of 7 nm were used as the photocatalyst particles.

[Manufacturing Method 3: Comparative Example] A primer layer and a top layer were formed under the same conditions as in Manufacturing Method 1, except that a top layer coating material containing no scale-like powder was used. [Manufacturing Method 4: Comparative Example] The primer layer and the top layer were formed under the same conditions as in Manufacturing Method 2, except that the top layer coating material containing no scale-like powder was used. Table 1 shows the coating film composition of each of the obtained coated metal plates.

[0022]

Test pieces were cut out from each coated metal plate and subjected to the following stain resistance test, NO _x decomposition test, processing test, and hiding test. [Contamination resistance test] A coated metal plate with a corrugated plate was placed at a right angle to the ground so that rain streaks could hang down on the coated metal plate, and exposed to the atmosphere for 3 months. Immediately after the installation and after the exposure test, the lightness of the test piece was measured, and the stain resistance was evaluated by setting the lightness difference ΔL within ± 1 to ◯, and the lightness difference ΔL exceeding ± 1 to x.

[NO _x decomposition test] 50 mm × 100 mm
Put the two test pieces in the glass container into a black light (U
V intensity: 1.0 mW / cm ² ) while irradiating the test piece,
High-purity air containing NO gas having a concentration of 1 ppm and adjusted to a humidity of 50% RH was continuously fed into a glass container at a flow rate of 3.0 liter / min. On the outlet side of the glass container, the NO concentration and NO ₂ concentration were measured using a NO _x meter. The measured value was substituted into the following equation to calculate the NO _x removal rate. NO _x removal rate (%) = [A ₁ − (A ₂ + B ₂ )] / A ₁ × 10
0 where A ₁ : initial NO concentration A ₂ : NO concentration after decomposition B ₂ : NO ₂ concentration after decomposition

[Processing Test] A 25 mm × 50 mm test piece was subjected to 6T bending, an adhesive tape was attached to the outside of the bent portion, and after peeling off, the peeled state of the coating film was visually observed.
The workability of the coating film was evaluated by setting the coating film in which peeling was detected as x and the coating film in which peeling did not occur as o. [Hiding property test] A 50 mm x 50 mm test piece was subjected to color difference measurement, and the hiding property was evaluated by setting the lightness L value of 85 or more to ◯ and less than 85 to x.

As can be seen from the survey results in Table 2, Test Nos. 1 to 1 in which flaky powder was dispersed in the primer layer and the top layer
Each of the coated metal plates of No. 12 had good workability and hiding power. Among them, the coated metal plates of test numbers 7 to 12 using the Zn-Al-Mg alloy plated steel plate as the base material / metal plate are 1
It showed a high NO _x removal rate of 3% or more. Further, although the primer layer was thinned, the hiding property was equivalent to that of the coated metal plates of test numbers 14 and 16 in which the primer layer having a film thickness of 20 μm was formed.

On the other hand, the coated metal plates of Test Nos. 13 to 16 in which the scale-like powder was not dispersed in the primer layer and the top layer were inferior in workability and concealing property and had lower NO _x than the examples of the present invention. It was the removal rate. As is clear from this comparison, by dispersing the flaky powder in the primer layer and the top layer, the processability, hiding power, and photocatalytic activity are improved, and even if the coated metal plate has an inorganic coating film, the product shape It is confirmed that it can be processed into.

[0028]

[0029]

As described above, the coated metal sheet of the present invention has a high concealing property because the flaky powder is dispersed in the primer layer and the top layer, and it is an inorganic coating film and is easy to be post-processed. It becomes a pre-coated metal plate. Moreover, since the diffuse reflection of incident light is promoted by the scale-like powder dispersed in the top layer, the photocatalytic activity of the photocatalyst particles is enhanced, and the self-cleaning action and the air purifying ability are also enhanced. Therefore, it is used as an exterior building material that maintains a beautiful appearance for a long time, a housing for external home appliances, and the like.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiroshige Nakamura             7-1 Takaya Shinmachi, Ichikawa City, Chiba Prefecture Nisshin Steel             Technical Research Institute Co., Ltd. F-term (reference) 4F100 AA19A AA19B AA20A AA20B                       AA21B AA23B AA25B AA33B                       AB01C AB04A AB04B AC05A                       AC05B AT00C BA03 BA07                       BA10B BA10C DE01B DE02A                       DE02B JL00 JL01 JL08B                       JL11A JN02 JN24A JN24B                 4G069 AA03 AA08 BA04B BA17                       BA48A BB06A BC12A BC35A                       BC50A BC60A BC66A DA06                       EA08                 4K044 AA02 AA03 AA06 AB02 BA06                       BA10 BA12 BA21 BB03 BC05                       CA16 CA53 CA62

Claims (4)

[Claims] 1. A silica or alumina-based top layer in which photocatalyst particles and flaky powder are dispersed is formed on the surface of a substrate through a silica or alumina-based primer layer in which flaky powder is dispersed. A coated metal plate with excellent processability, hiding power, and photocatalytic activity. 2. The coated metal plate according to claim 1, wherein the flaky powder is one kind or two or more kinds of Al flakes, stainless steel flakes, and pearl mica. 3. The photocatalyst particles are TiO ₂ , ZnO, WO ₃ ,
The coated metal plate according to claim 1, which is one or more of FeTiO ₃ and SrTiO ₃ . 4. A photocatalyst after applying silica sol and / or alumina sol containing flaky powder to a substrate / metal plate and subjecting it to a heat treatment for forming a primer layer comprising a SiO ₂ and / or Al ₂ O ₃ precursor. Processability, concealing property, characterized by applying silica sol and / or alumina sol mixed with active and scaly powder, and performing heat treatment to form a top layer,
A method for producing a coated metal plate having excellent photocatalytic activity.