JP2002144474A - White metallic coated metal panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a white metallic coated metal panel suppressed in its coloration caused by a rustproof pigment and holding excellent metallic appearance over a long period of time. SOLUTION: The white metallic coated metal panel is constituted by forming a white undercoat layer to which a colorless or white rustproof pigment is added and a topcoat layer in which a metallic pigment is dispersed on the surface of a substrate metal panel through a chemical forming treatment film. As the rustproof pigment, modified silica, ion exchanged silica, zinc molybdate, calcium molybdate, zinc phosphate, calcium phosphate, aluminum phosphomolybdate, aluminum pyrophosphate, aluminum dihydrogen tripolyphosphate, calcium zinc cyanamide or the like are used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-coated white metallic-coated metal sheet.

[0002]

2. Description of the Related Art Precoated metal sheets having a beautiful appearance and excellent workability and corrosion resistance are used for home appliances, automobile steel sheets, building materials and the like. The pre-coated metal sheet is obtained by forming an organic coating film on the surface of a metal sheet such as a steel sheet or a plated steel sheet which has been subjected to rust prevention treatment such as chromate treatment. When a metallic tone is imparted to a precoated metal plate, an undercoat having an arbitrary tone with a colored pigment is provided, and then only a metallic pigment containing no colored pigment is used for the top coat. However, general lead pigments, chromate pigments,
Since all rust preventive pigments such as metal powder pigments are pigments having a unique dark color, it is difficult to produce a white color tone with a coating film to which these rust preventive pigments are added. In order to counteract the color tone caused by the rust-preventive pigment and obtain a white appearance, after providing a primer layer containing the rust-preventive pigment and a white coating film with a concealing property, a metallic clear color is further applied on it. A three-layer structure provided with a coating film is employed.

[0003]

With a coating film having a three-layer structure, it is possible to prevent the occurrence of blisters and rust originating from the sheared end surface of the coated metal plate or a coating film defect introduced during processing or construction. However, corrosion and discoloration of the metallic pigment due to corrosive factors such as oxygen, moisture, water vapor, acid, and alkali penetrating from the surface of the top coat are inevitable, and the metallic feeling is impaired. Further, during a long use period, delamination may occur at the interface between the top clear and the colored layer. Furthermore, if a three-coat type coated metal plate is to be manufactured on a continuous coating line on the premise of manufacturing a two-coated metal plate, redundant line operations are required, and productivity is reduced.

[0004]

SUMMARY OF THE INVENTION The present invention has been devised to solve such a problem, and has been proposed by providing a white undercoat to which a colorless or white rust preventive pigment is added. An object of the present invention is to provide a white metallic-coated metal sheet which exhibits sufficient corrosion resistance even with a coat type and maintains an excellent metallic appearance over a long period of time.

[0005] In order to achieve the object, a white metallic coated metal plate of the present invention is a white undercoat in which a colorless or white rust-preventive pigment is added to the surface of a base metal plate via a chemical conversion coating. And a top coat in which a metallic pigment is dispersed. The rust-preventive pigment is selected from modified silica, ion-exchanged silica, zinc molybdate, calcium molybdate, zinc phosphate, calcium phosphate, aluminum phosphomolybdate, aluminum pyrophosphate, aluminum dihydrogen tripolyphosphate, and zinc zinc cyanamide. Seed or 2
More than seeds are used.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As a base metal plate (painted original plate), various metal plates such as a normal steel plate, a stainless steel plate, a plated steel plate, an aluminum plate and a copper plate are used. After degreased pickling of the paint base plate, a chemical conversion coating is formed by chromate treatment, phosphate treatment, Cr-free treatment, or the like.

[0007] The chemical conversion coating is formed with a thickness effective to prevent corrosion of the base metal plate and enhance the adhesion of the coating. For example, for a chromate film, the total Cr equivalent
~100mg / m ^2, 5~500mg the phosphate film
/ M ² , 10 to 500 mg /
m ² , 0.1 to 500 mg / m ² of fluorine adhesion for fluoroalkyd coating or 0.1 to 500 mg of total metal adhesion
By forming the chemical conversion coating so as to have a concentration of 500 mg / m ² , the adhesion of the coating between the base metal plate and the undercoat is improved.

[0008] As an environment-friendly Cr-free film, a fluoroalkyd-based film is preferable because it exhibits a film adhesion equal to or higher than that of a chromate film. H ₂ TiF ₆ , H ₂ ZrF ₆ , H ₂ HfF ₆ , H ₂
SiF ₆ , H ₂ GeF ₆ , H ₂ SnF ₆ , HBF _{4 and the} like can be mentioned, and they can be used alone or as a mixture of two or more. Among them, H ₂ TiF ₆ exhibits a good rust prevention effect.

After the formation of the chemical conversion coating, a white paint is applied to the original coating plate to form an undercoat. Epoxy-based, epoxy-modified polyester-based,
Epoxy-modified high polymer polyester, polyester,
For base resins such as polymer polyester, polyether sulfone, urethane, and urethane modified epoxy,
Paints colored white by adding titanium oxide, zinc oxide, zinc white, lithopone, calcium carbonate, barium sulfate, etc. as white pigments can be used. The white paint may be colored with a dye, a pigment or the like to such an extent that the whiteness is not impaired. Examples of usable coloring agents include a very small amount of black pigments such as carbon black, blue pigments such as cyanine blue, and red pigments. By adding the coloring agents, a high-grade light-colored design is provided.

[0010] White paints include colorless or white rust preventive pigments, specifically modified silica, ion-exchanged silica, zinc molybdate, calcium molybdate, zinc phosphate, calcium phosphate, aluminum phosphomolybdate, aluminum pyrophosphate. Rust-preventive pigments, such as aluminum dihydrogen tripolyphosphate and zinc zinc cyanamide. The modified silica is calcium, zinc, cobalt,
It is obtained by binding cations such as lead, strontium and barium to porous silica particles, and ion-exchange silica can be obtained by binding cations by ion exchange.

The colorless or white rust-preventive pigment added to the white paint preferably has an average particle size in the range of 0.1 to 1 μm. When the average particle size is less than 0.1 μm, the particles are likely to be agglomerated when dispersed in the paint, and it is difficult to uniformly disperse the rust preventive pigment. Conversely, if an rust-preventive pigment having an average particle size exceeding 10 μm is added, the intrinsic properties of the coating film will be impaired and the physical properties will be adversely affected. In addition, the rust-preventive pigment having a large particle size not only deteriorates the smoothness of the coating film, but also makes the appearance of the coating film yuzu-like, and significantly reduces the design.

The rust-preventive pigment is used in an amount of 5 parts per 100 parts by mass of the resin.
It is preferable to add at a ratio of 150 parts by mass. If the amount is less than 5 parts by mass, the corrosion resistance of the coating film is reduced. The effect of improving the corrosion resistance is saturated at an addition amount of 150 parts by mass, and even if added more, the workability and adhesion of the coating film are reduced due to excessive rust preventive pigment.

The white paint prepared to a predetermined composition is prepared by using a roll coat, which is generally used for producing a pre-coated metal sheet,
Flow coat, curtain flow, spray, etc.
It is applied to a metal plate in an application amount such that the dry film thickness is 5 to 30 μm. The applied white paint is baked at a reaching plate temperature of 200 to 280 ° C. for 30 to 120 seconds according to a conventional method.
When the dry film thickness is less than 5 μm, even if 50 parts by mass or more of titanium oxide is added as a white pigment, the underlying metal plate cannot be hidden. On the other hand, when the dry film thickness exceeds 30 μm, not only does the surface of the coating film have a yuzu-skin appearance and the appearance is deteriorated, but also fire tends to occur during baking.

After baking, a coating film is formed which can be clearly determined to be white by visual inspection. The obtained coating film is JIS
The lightness index L value defined by Z8737 (color difference display method) is 80 or more, and the white undercoat has a rust-preventive effect.

[0015] A metallic paint is applied on the undercoat. The resin used for the metallic paint is not particularly limited in the type of the resin, but polyester-based, high-molecular-weight polyester-based, fluorine-based, acrylic-based, urethane-based, epoxy-based, vinyl acetate-based, chloroprene-based and A mixture, a modified resin, a resin that forms a shrinking pattern, or the like can be used. The kind of the metallic pigment added to the metallic paint is not limited, but generally includes commercially available aluminum flakes, pearl mica, metal-coated glass flakes, metal flakes, and plate-like iron oxide.

The metallic pigment added to the metallic coating preferably has an average particle size of 10 to 300 μm. If the average particle diameter is less than 10 μm, the metallic feeling is poor. On the other hand, if the average particle diameter exceeds 300 μm, the original performance of the coating film is impaired, which may cause an adverse effect. The amount of the metallic pigment to be added is appropriately adjusted according to the required degree of metallic feeling, but is preferably in the range of 0.5 to 30% by mass. If the amount is less than 0.5% by mass, the metallic feeling is poor. If the amount exceeds 30% by mass, not only the smoothness of the coating film surface is impaired, but also the design is remarkably deteriorated, and the original performance of the coating film is adversely affected.

The metallic paint may contain dyes, pigments and the like to such an extent that the transparency is not impaired. For example, by adding a very small amount of a black pigment such as carbon black or a blue pigment such as cyanine blue or a red pigment so as not to impair the transparency, and coloring, a deeper metallic design is imparted.

The metallic paint prepared to a predetermined composition is applied by a method such as roll coating, flow coating, curtain flow, spraying or the like which is usually used for the production of a precoated metal sheet at a coating amount of a dry film thickness of 5 to 30 μm. It is applied to a metal plate. The applied metallic paint is baked at an ultimate plate temperature of 200 to 280 ° C. for 30 to 120 seconds according to a conventional method. With a dry film thickness of less than 5 μm, it is difficult to obtain a high-quality white metallic tone design with a sense of depth. Conversely 3
With a thick film having a thickness of more than 0 μm, not only does the surface of the coating film become yuzu-skinned and the appearance is deteriorated, but also burning easily occurs during baking. In this way, an undercoat is formed with a white paint containing a rust-preventive pigment, and a metallic coating film is provided on the undercoat. Excellent coated metal sheet is obtained.

[0019]

The white metallic coating metal plate according to the present invention is provided with a two-layer coating film in which a metallic top coat is formed on a white undercoat. Since the top coat in which the metallic pigment is dispersed is in contact with the undercoat containing the rust-preventive pigment, corrosion and discoloration of the metallic pigment due to corrosive factors penetrating from the top coat surface are suppressed, and the metallic pigment is produced over a long period of time. The metallic tone is maintained. In this respect, in the conventional three-layer configuration in which the white coating film for concealment is provided between the primer layer containing the rust-preventive pigment and the top coat, the anti-corrosion effect of the rust-preventive pigment of the primer layer is blocked by the white paint film, Since the effect of inhibiting the corrosion of the paint is weakened, the discoloration resistance is poor.

The presence of the rust-preventive pigment in the lower layer of the top coat in which the metallic pigment is dispersed is also effective in preventing delamination between the top coat and the undercoat. It is assumed that delamination is prevented by the following mechanism. That is, the anions that are corrosive factors such as Cl ⁻ , SO ₄ ²⁻ , and NO ₃ ⁻ penetrating from the top coat surface are reduced to calcium, zinc, cobalt, and lead contained in the rust preventive pigment in the undercoat. ,strontium,
Trapped by cations such as barium. Therefore, no corrosive factors are accumulated at the interface between the top coat and the undercoat, and as a result, delamination between the top coat and the undercoat is suppressed.

In this respect, in the conventional three-layer structure, since the concealing white coating film containing no rust-preventive pigment is provided between the primer layer and the top coat, the corrosive factor permeating from the top coat surface is reduced. Accumulate at the interface of the top coat / white coating film for concealment, and swelling of the coating film occurs therefrom, eventually leading to delamination. Furthermore, since it has a two-layer structure of an undercoat containing a rust-preventive pigment and a topcoat containing a metallic paint, the present invention is also applied to a continuous coating line assuming two conventional coats. As a result, a white painted metal plate having a metallic tone can be manufactured at low cost. In addition, non-Cr
Since a rust-preventive pigment is used, the coated metal plate is environmentally friendly.

[0022]

[Example] Plate thickness 0.5 mm, coating weight per side 60
A hot-dip galvanized steel sheet of g / m ² was used as a coating original sheet. After the steps of pickling, washing with water, surface conditioning, washing with water, and drying,
Fluoroacid-based Cr-free treatment, 100 ℃
And dried. In the Cr-free treatment, the following chemical conversion treatment solution was applied to a coating original plate using a bar coater and dried at 100 ° C. to form a chemical conversion treatment film having a fluorine adhesion amount of 30 mg / m ² .

[0023]

An epoxy-modified high-molecular polyester paint shown in Table 1 was applied to the surface of the original plate on which the chemical conversion coating was formed, and baked and dried at 220 ° C. for 50 seconds to obtain a dry film having a dry film thickness of 10 μm. An undercoat was formed. In the epoxy-modified high-molecular polyester paint according to the present invention, the whiteness was adjusted by adding 30% by mass of titanium oxide as a white pigment. Next, a high-molecular polyester-based transparent resin paint containing a metallic pigment was applied, and baked and dried at 230 ° C. for 50 seconds to form a top coat having a dry film thickness of 12 μm. For comparison, three-layer coated steel sheets (Comparative Examples 12 and 13) in which the color tone of the undercoat colored with a rust-preventive pigment was hidden by a white intermediate coating film (15 μm in thickness) were also prepared.

[0025]

A test piece was cut out from each of the obtained coated steel sheets and subjected to the following test. Appearance evaluation test The test piece was visually observed under a fluorescent lamp, and a whiteness and a metallic tone were subjected to a sensory test. When the appearance of white and metallic tone was obtained, it was evaluated as ○. When the appearance was metallic, but the whiteness was low and the color was slightly colored, the appearance was changed to metallic. The whiteness and the metallic tone were evaluated by setting the colored one to x.

Boiling water test A test piece was immersed in boiling water for 240 hours, taken out of the boiling water, and the appearance of the coating was observed. The specimens were evaluated as △, and those with remarkable coating blisters or gloss and deterioration of metallic tone were evaluated as ×. Further, the test piece after the immersion in boiling water was subjected to T processing, and a processing adhesion test was conducted in which an adhesive tape was once applied to the processed portion and then peeled off. Inspect the peeling state of the coating film after peeling the tape, and mark ○ if no abnormality was detected in the coating film, △ if some of the coating film was peeled off, and × if the whole surface was peeled. The processing adhesion was evaluated.

Corrosion / moisture resistance test After a cross cut reaching the base steel was put in a test piece, JI
Salt spraying was continued for 240 hours according to SZ2371. Further, a test piece having the same cross cut was subjected to a temperature of 5 ° C.
It was left in a constant temperature and humidity atmosphere of 0 ° C. and a humidity of 98% for 500 hours. After each test, the flat part of the test piece was observed. If no abnormality was detected, the sample was evaluated as ○. If the coating was blistered or glossy or metallic deterioration was observed, the symbol was Δ. If the coating was blistered or glossy or metallic. A sample in which the deterioration of the tone was observed was evaluated as x, and the corrosion resistance and the moisture resistance were evaluated. Also, the maximum blister width of the lower burr end face and one side of the cross cut was measured, and the maximum blister width was 1 mm or less as ◎, 1 to 3 mm as 〜, 3 to 6 mm as Δ, and 6 mm or more as ×. The corrosion resistance and moisture resistance were evaluated.

As can be seen from the investigation results in Table 2, the coated steel sheets of Test Nos. 1 to 8 according to the present invention are all excellent in boiling water resistance, corrosion resistance, and moisture resistance, and have a high design quality. It had a toned appearance. On the other hand, in Test No. 9 (Comparative Example) in which the rust-preventive pigment was not added to the undercoat, the whiteness and metallic tone immediately after production were good, but all of the boiling water resistance, corrosion resistance and moisture resistance were inferior. I was Deterioration due to corrosion and discoloration of the metallic pigment was observed in the whiteness and the metallic tone after being left for 500 hours in the same constant temperature and humidity atmosphere as in the humidity resistance test.

In Test No. 10 (Comparative Example) in which a small amount of strontium chromate was added to the undercoat, coloring due to strontium chromate was observed, and it was inferior in boiling water resistance, corrosion resistance and moisture resistance of the flat part. In Test No. 11 (Comparative Example) in which the amount of strontium chromate was increased, the coating film was markedly colored, and was poor in boiling water resistance and corrosion resistance. In Test Nos. 12 and 13 (Comparative Examples) provided with an intermediate coating film, the whiteness and the metallic tone were good immediately after coating, but the metallic pigment was left for 500 hours in the same constant temperature and humidity atmosphere as in the humidity resistance test. Corrosion of
Deterioration due to discoloration was observed. The boiling water resistance, corrosion resistance and moisture resistance were also slightly inferior to the coated steel sheets of Test Nos. 1 to 8 (Examples of the present invention).

[0031]

[0032]

As described above, the metal plate of the present invention is provided by directly providing a top coat in which a metallic pigment is dispersed on an undercoat to which a colorless or white rust preventive pigment is added. Therefore, the anticorrosion function of the rust-preventive pigment directly acts on the metallic paint, thereby suppressing corrosion and discoloration of the metallic pigment and maintaining a beautiful metallic tone for a long time. Further, since it is a two-coat type, it can be manufactured in a conventional continuous coating line, and is provided as an inexpensive coated steel sheet having excellent design properties.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroyuki Kawanobe 7-1 Takaya Shinmachi, Ichikawa City, Chiba Prefecture Nisshin Steel R & D Co., Ltd. (72) Inventor Koji Mori 7-1 Takaya Shinmachi, Ichikawa City, Chiba Prefecture Sun F-term (Reference) 4D075 CA33 DB01 DC01 DC12 DC18 DC15 EC15 4F100 AA02C AA02H AA04C AA04H AA20C AA20H AB01A AB03 AB18 AK41 AR00B BA03 BA07 CA15C CC00C EH46 EH71 EJ68B EJ86 GB02 A32 GB02 J02 GB02 J02 GB04 J03 BA10 BA20 BA21 BB04 BB16 BC02 BC09 CA11 CA16 CA53 CA62

Claims (2)

[Claims] 1. A white undercoat to which a colorless or white rust preventive pigment is added and a topcoat in which a metallic pigment is dispersed are formed on the surface of a base metal plate via a chemical conversion coating. White metallic paint metal plate. 2. One selected from the group consisting of modified silica, ion-exchanged silica, zinc molybdate, calcium molybdate, zinc phosphate, calcium phosphate, aluminum phosphomolybdate, aluminum pyrophosphate, aluminum dihydrogen tripolyphosphate, and zinc zinc cyanamide. Or 2
The white metallic-coated metal sheet according to claim 1, wherein at least one kind is used as a rust preventive pigment.