JPH06277621A - Coated metal sheet - Google Patents

Abstract

PURPOSE:To improve corrosion resistance of an end face without decreasing processability and sharp image reflecting properties of a coated metal sheet. CONSTITUTION:As a metal sheet for a base material (e.g. a plated steel sheet prepd. by applying plating 2 on a raw material steel sheet 1), a steel sheet on which regularly arranged recessed parts are formed (e.g. a laser dull finished sheet) is used and these recessed parts are filled with a coating layer 3 with high pigment content of at least 30wt.% and the surface of this coating layer and the surface of the remaining parts (flat parts) are coated with a low pigment coating 4 with a pigment content of lower than 30wt.%. A top coating film 5 may be provided thereon.

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 useful for home appliances, building materials and the like. Especially for home appliances,
The present invention relates to a coated metal plate suitable for outdoor parts such as an outdoor unit of an air conditioner and a vending machine, which are used outdoors and which require corrosion resistance and workability. Further, since the coated metal plate of the present invention is excellent in sharpness, it is considered that it can be applied to automobile outer panel applications in the future.

[0002]

2. Description of the Related Art A so-called coated metal plate, which is a metal plate such as a plated steel plate, an aluminum plate, and a stainless steel plate, coated with various resin paints with a film thickness of about 10 to 200 μm, is applicable because of the user's process rationality. The part has expanded.

However, when a coated metal plate is cut and punched, it is inevitable that an unpainted end face is generated, and the corrosion resistance of the end face portion is significantly inferior to that of the flat portion. In the case of home appliances used indoors, there are currently few strict requirements for corrosion resistance because the corrosive environment is relatively mild, but home appliances for outdoor applications (e.g. air conditioner outdoor units,
When applied to vending machine outer panels, etc., it is required to have not only excellent workability but also excellent corrosion resistance equivalent to that of building materials.

[0004]

Generally, the higher the concentration of the rust preventive pigment in the coating film of the coated metal plate, the higher the corrosion resistance of the end surface, but the workability tends to decrease. Therefore,
In the past, it was necessary to achieve that balance, and it was difficult to simultaneously improve the end face corrosion resistance and workability of the coated metal sheet.

When a coated metal sheet is required to have a high degree of workability, not only a topcoat coating film but also a primer coating film can form a coating film having a high elongation rate (flexible) such as a high molecular weight polyester type coating material. Is often used. However, this type of paint is often inferior in physical properties such as corrosion resistance to coatings such as harder epoxy-based coatings. There is no choice but to balance.

On the other hand, the present inventors have found that even if the high-concentration rust-preventive pigment is scattered on the surface of the base rather than on the entire surface, the end face corrosion resistance is improved, and based on this finding, the anti-corrosion effect is improved. We proposed a coated steel sheet that features a primer coating with a high concentration of rust pigment distributed in islands (Japanese Patent Application No. 3-045063).
No.). A schematic diagram of the structure of this coated steel sheet is shown in Fig. 2 (b).
A primer coating film 3 having a high pigment concentration is scattered on the plated surface 2 of the steel sheet 1 in an island shape, and a primer coating film 4 having a low pigment concentration and, if desired, a top coat coating film 5 are further provided thereon. Has been.

In this coated steel sheet, the island-shaped primer coating film having a high pigment concentration provides excellent end face corrosion resistance, but since it is not a continuous film, the workability does not decrease, and therefore the workability and the end face corrosion resistance are not deteriorated. It can be improved at the same time. However, depending on the island-shaped distribution of the primer coating film, unevenness may be formed on the surface as shown in the figure, and the clearness of the coated metal plate may be poor.

In order to solve the above problems of the prior art, an object of the present invention is to provide a coated metal plate which is excellent in workability and end face corrosion resistance and has high sharpness.

[0009]

[Means for Solving the Problems]
As described in -045063, a coating film having a high pigment concentration was distributed in an island shape to achieve both workability and end face corrosion resistance, and a method capable of further maintaining sharpness was examined. As a result, for example, by filling a recess of a steel plate in which recesses are regularly arranged such as a laser dull steel plate with a coating layer having a high pigment concentration, end face corrosion resistance is secured, and a pigment concentration excellent in workability is obtained from above. The present invention has been accomplished by finding that by coating a coating film having a low viscosity, processability and sharpness can be secured.

Here, the gist of the present invention is a coated metal plate in which at least one side of a base material made of a metal plate is coated, and the base metal plate is regularly arranged on the entire coated surface. A coating film having recesses, the recesses being at least incompletely filled with a coating layer having a pigment concentration of 30% by weight or more, and the coating layer surface and the surface of the metal plate other than the recesses having a pigment concentration of less than 30% by weight. It is a painted metal plate characterized by being coated with.

[0011]

In the coated metal plate of the present invention, the type of the metal plate which is the base material is not particularly limited. However, in view of the purpose of use,
A metal plate having excellent corrosion resistance is preferable. Examples of suitable metal plates include various plated steel plates, aluminum plates, stainless steel plates and the like. Examples of the plating species of the plated steel sheet include hot dip galvanizing, electrogalvanizing, aluminum plating, alloy platings of these, and galvannealing.

The base metal plate may be subjected to a base treatment by a chemical conversion treatment (eg, chromate treatment or zinc phosphate treatment) by a conventional method in order to improve corrosion resistance and / or paintability. . Particularly, when the base steel sheet is a zinc-based plated steel sheet, it is preferable that chromate treatment is performed as a base treatment.

The base metal plate has recesses regularly arranged on the entire coated surface (the surface to be coated). This is because the end face corrosion resistance is ensured by embedding a paint layer having a high pigment concentration in the recesses. Since it is not possible to know in advance where the cut end will be on the coated metal plate, the recesses are regularly arranged on the entire coated surface of the metal plate. If the arrangement of the recesses is irregular, an end face having poor corrosion resistance may be formed.

The metal plate having such regular concave portions is subjected to finish rolling using a laser dull roll having a regular convex pattern formed by laser processing, as represented by a laser dull steel sheet. Obtainable. When the base metal plate is a plated steel plate, when the base laser-dull steel plate is plated, the plating film adheres with a uniform thickness, so the recessed shape of the base steel plate is retained on the plated surface even after plating. .

The specific shape of the recess is not particularly limited, but a semi-ring shape formed by a laser dull roll, or a simple bowl-shaped circular recess is preferable because the formation of the recess is easy. Maximum depth of recess
(Rmax) is preferably about 2 to 20 μm. If the recess is too shallow, the end face corrosion resistance cannot be sufficiently improved. If the recesses are too deep, when the paint embedded in the recesses is baked, cracks (foam) may occur due to evaporation of the thinner present in the paint. The more preferable range of the recess depth is Rmax5
~ 10 μm. The pitch of the recesses may be appropriately determined according to the conditions such as the required corrosion resistance level, and the higher the required level of corrosion resistance, the finer the recess pitch.
Generally, the area ratio of the recesses is preferably in the range of 0.5 to 20%.

In the coated metal plate of the present invention, the concave portion of the base metal plate is at least incompletely filled with a paint layer having a high pigment concentration of 30% by weight or more (hereinafter referred to as a high pigment paint layer). , The surface of this paint layer and the surface of the metal plate other than the recesses have a low pigment concentration of less than 30% by weight (hereinafter,
It is covered with a low pigment coating). That is, the surface of the coated metal plate of the present invention is completely covered with a continuous coating film having a low pigment concentration.

FIG. 1 is a schematic diagram showing the structure of a coated metal plate of the present invention in which the base metal plate is a plated steel plate, and a top coat coating film is further provided as the uppermost layer. The recesses provided in the plated surface 2 of the base steel sheet 1 in a regular array are filled with the high pigment paint layer 3, and the surface of the paint layer 3 and other parts
The plating surface of the (flat portion) is covered with a continuous low pigment coating film 4, and in the illustrated example, a top coat coating film 5 is further provided thereon as the uppermost layer.

The high pigment paint layer is present only on the concave portions as shown in the drawing, that is, on the base metal plate in the form of discontinuous islands. Since a coating film having a high pigment concentration has low workability, the workability of a coated metal plate is greatly deteriorated when such a paint layer exists as a continuous film. However, when the high pigment paint layer is scattered only in the concave portions in an island shape, the workability does not deteriorate. Even with such an island-shaped high pigment paint layer,
As described above, it is possible to impart excellent end face corrosion resistance to the coated metal plate.

When the pigment concentration of the high pigment paint layer is less than 30% by weight, the end face corrosion resistance of the obtained coated metal plate is insufficient.
The pigment concentration is preferably 50% by weight or more.

The high pigment paint layer may be formed only on the concave portion by any method that allows this.
First, a sufficient amount of high pigment paint (i.e.,
A paint containing 30% by weight or more of pigment based on the total solid content) is applied to the entire surface of the metal plate in a thin film as much as possible, and after baking the coating film if necessary, this coating film is applied by an appropriate means. It can be carried out by grinding with and removing the coating layer deposited on the flat part (the part other than the concave part). This removal of the paint layer on the flat area can also be accomplished by chemical means (eg, wiping the paint on the flat area with a solvent-soaked cloth or the like). After that, in order to protect the surface of the base metal plate exposed in the flat portion, the above-described base treatment can be performed again.

The amount of the high-pigment paint layer attached is an amount at which the high-pigment paint is at least incompletely filled, preferably substantially completely, in the concave portion, and therefore, it is appropriately selected depending on the depth of the concave portion and the area ratio thereof. Just select it.

In this way, after forming the high pigment paint layer only in the concave portion, a low pigment paint (paint whose pigment content is less than 30% by weight based on the total solid content) is applied to the entire surface of the metal plate,
By baking if necessary, a low pigment coating film is formed on the surface of the high pigment coating layer and the surface of the other metal plate (flat portion), and the coated metal plate of the present invention is obtained.

By forming a continuous coating film on the surface with a low pigment coating, it is possible to apply a coating having excellent image clarity to a metal plate without lowering workability. When the pigment content of this low pigment coating film is 30% by weight or more, the workability of the obtained coated metal plate is deteriorated. In general, it is preferable that the amount of the low-pigment coating film adhered is about the same as the amount of the conventional primer coated steel sheet coated with the primer coating film. Usually, this deposit is 3 to 15 g / m ²
It is a degree.

The pigments to be present in the high pigment paint layer and the low pigment coating film include rust preventive pigments such as strontium chromate and zinc chromate, titanium dioxide, calcium carbonate,
One type or two or more types of extender pigments such as silicon dioxide can be used.

The high-pigment paint layer and the low-pigment paint film may be of any paint resin type, but preferably those which have been used for primer paints in the past, such as epoxy type, epoxy modified polyester type and polyester type. Examples include those obtained by appropriately crosslinking a resin system such as a urethane system with a crosslinking agent such as an amino resin or an isocyanate if necessary.

As shown in FIG. 2 (a), the conventional coated metal sheet has a primer coating 4 (corresponding to the low pigment coating layer used in the present invention) and a top coat coating 5 on a plated steel sheet. Most of the formed two-coat / two-baked products are used, but even in the coated metal plate of the present invention, as shown in FIG. A cover coat coating film (not shown) may be provided thereon. Also,
In the coated metal plate of the present invention, the above-mentioned coating may be provided on only one side of the metal plate or on both sides.

In the coated metal plate of the present invention, as shown in FIG. 1, since the high pigment paint layer 3 is embedded in the concave portion of the base metal plate, the surface of the coated metal plate becomes flat and the coated metal plate shown in FIG. The image clarity is not impaired as shown in b). Moreover, since the end face corrosion resistance is improved while maintaining the workability by the high pigment paint layer scattered in islands in the recesses, the coated metal sheet of the present invention has any of end face corrosion resistance, workability, and sharpness. The characteristics of can also be satisfied.

[0028]

【Example】

(Example 1) A cold rolled steel sheet (sheet thickness: 0.6 mm) was finished and rolled by a laser dull roll.
Hot-dip galvanized on both sides of 50 μm, concave area ratio 10%)
(60 g / m ^{2 on} one side) was applied, and a chromate film was formed by a coating type chromate solution as a base treatment for coating (50 mg / m ² Cr on one side). The maximum depth (Rmax) of the recesses of the obtained chromate-treated hot-dip galvanized steel sheet was 2.3 μm.

This chromate-treated hot-dip galvanized steel sheet was used as a base metal sheet, and on one side thereof, the primer coating A for filling the concave portion was first applied with a bar coater in an amount of 10 g / m ²
Paint so that (average when dry), and reach the maximum plate temperature (P
The coating film was baked and dried by heating for 60 seconds so that MT) was 210 ° C.

Next, a surface grinding device (Scotch bright
^{By RT} ), the coating film on the flat portion of the steel sheet was removed, and the coated surface was ground until the plated surface of the flat portion was exposed to obtain a steel sheet in which only the concave portion was filled with the coating layer of the primer coating A. At this time, the coating weight was reduced by only about 1 to ² g / m ² .

Thereafter, the coated surface was again subjected to the coating type chromate treatment in the same manner as above, and then the primer coating material B was used for coating, baking and drying under the same conditions as those of the primer coating material A. Furthermore, a commercially available top coat paint (Nippon Paint Flex Coat 200) was applied on top of it, baked and dried (dry film thickness 35 g / m
² , baking conditions are PMT 230 ℃ 80 seconds).

The primer coatings A and B are high-molecular-weight polyester resins (TOYOBO VILON 2
9CS) 100 parts and a cross-linking agent of a melamine resin (Cymel 370 manufactured by Mitsui Toatsu Co., Ltd.) 15 parts (both in terms of solid content) in a resin solution, and the rust preventive pigment strontium chromate is shown in Table 1. It was added so that the content would be [% by weight based on the total solid content (polyester resin + melamine resin + pigment total amount)], and the pigment was dispersed with a paint conditioner.

The coated steel sheet having the coating composition shown in FIG. 1 thus obtained was tested for workability, edge corrosion resistance and sharpness as follows. The workability was evaluated by a 180 ° bending test in which the coated surface of the test piece was placed outside in a constant temperature room at 23 ° C, based on the minimum number of plate scissors that did not cause cracks in the coating film.

The end face corrosion resistance is the maximum blistering width of the coating film on the end face after 500 hours of a salt spray test using a cut test piece.
(mm) evaluated. The image clarity was evaluated by visual evaluation in 5 grades (maximum 5 → minimum 1). The test results are shown in the following Table 1 together with the content (% by weight) of the anticorrosive pigment in the primer coatings A and B.

[0035]

[Table 1]

When the primer coating material A filled in the recesses according to the present invention contains 30% by weight or more of the pigment, and the primer coating material B coated thereon has a pigment content of less than 30% by weight, the processability and the end surface corrosion resistance are improved. The image clarity was good. On the other hand, when the pigment content of the primer coating material A in the concave portion was less than 30% by weight, the end surface corrosion resistance deteriorated, and when the primer coating material B in the upper portion contained 30% by weight or more of the pigment, the processability deteriorated.

Example 2 A cold-rolled steel sheet (sheet thickness: 0.6 mm) was finish-rolled by a laser dull roll (recess diameter: about 50 μm).
In this example, the height of the convex portion formed on the laser dull roll was changed to change the depth of the concave portion of the obtained laser dull steel sheet. This steel sheet was subjected to double-sided hot dip galvanizing and coating type chromate treatment in the same manner as in Example 1. Maximum depth of recess after chromate treatment
(Rmax) is shown in Table 2.

Using this chromate-treated hot-dip galvanized steel sheet as a base metal sheet, coating was carried out in the same manner as in Example 1. The primer paint used to fill the recesses is a rust preventive pigment
The content of (strontium chromate) (% based on the total solid content) was 50% by weight, and the primer coating applied thereon had a content of rust preventive pigment of 10% by weight. The results of testing the coated steel sheet thus obtained in the same manner as in Example 1 are also shown in Table 2. Even if the depth of the recess was changed, the workability, the end surface corrosion resistance, and the sharpness could be well maintained.

[0039]

[Table 2]

[0040]

As is clear from the results of the examples, the coated metal sheet of the present invention has improved end face corrosion resistance without lowering workability and sharpness, and has excellent workability, end face corrosion resistance and sharpness. It is extremely suitable for the required applications such as outdoor home appliances and building materials. In addition, since the end face corrosion resistance and sharpness are very good, it is considered that it may be applicable to automobile outer panels in the future.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of an example of a coated metal plate of the present invention.

2 (a) and 2 (b) are schematic views showing the structures of a conventional representative coated metal plate and a coated steel plate described in Japanese Patent Application No. 3-045063, respectively.

[Explanation of symbols]

1: Cold rolled steel sheet, 2: Plating layer, 3: High pigment paint layer, 4:
Low pigment coating, 5: Topcoat coating

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiaki Shioda 4-53-3 Kitahama, Chuo-ku, Osaka Sumitomo Metal Industries Co., Ltd.

Claims (1)

[Claims] 1. A coated metal plate in which at least one surface of a base material made of a metal plate is coated, and the base metal plate has recesses arranged regularly on the entire coated surface, The recesses are at least incompletely filled with a paint layer having a pigment concentration of 30% by weight or more, and the surface of the paint layer and the surface of the metal plate other than the recesses are covered with a coating film having a pigment concentration of less than 30% by weight. A painted metal plate characterized by.