JP2862208B1 - Painted metal plate with excellent scratch resistance - Google Patents

Abstract

An object of the present invention is to improve the scratch resistance of the surface of a coating film without impairing the workability required for a coated metal plate such as a post-coated metal plate. SOLUTION: The surface of a metal plate is coated with a coating film containing substantially spherical organic particles, and the ratio of the projecting area (S:
%) Is 80% or less in plan view, and the average height (H: μm) of the protruding organic particles from the surface of the coating film surrounding each protruding organic particle is 50% with respect to the average diameter of the organic particles used. % Or less, and furthermore, the protruding area ratio (S:
%) And the average height of protrusion (H: μm) (S × H) is 18
Disclosed is a coated metal sheet having excellent scratch resistance of 0 (% · μm) or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated metal sheet having excellent scratch resistance and exhibiting excellent properties when used as an outer panel material for home appliances, indoor / outdoor equipment, and even a building material. It is.

[0002]

2. Description of the Related Art Metal plates used for the above-mentioned applications are:
After metal plates are manufactured by pressing and other processes, the final products are painted (generally called post-coating) to enhance the design and then commercialized. As the need for elimination is increased, the transition from post-coating to “pre-coating”, in which metal sheet manufacturers apply painting in advance, has been taking place.

[0003] Regardless of whether post-coating or pre-coating is performed, the resulting coated metal sheet is required to have excellent scratch resistance so that scratches are minimized during handling. . Especially for post-coated metal sheets,
Since it goes through many processes including packing, transportation, processing, etc. until it is processed into the final product, the surface is scratched during that time, and the yield as a post-coated metal plate until the final product is considerably reduced Will come.

[0004] Therefore, in order to suppress the decrease in the yield due to such surface flaws, studies have been made to improve the flaw resistance of the coating film. A suitable amount of powdered aggregate having a thickness of 1/2 times and a maximum particle size of not more than twice the thickness of the coating film is contained in the coating film, and the powdered aggregate improves the scratch resistance. A method is disclosed.

However, in this method, although the scratch resistance can be improved to some extent, it cannot be said that the reliability is always satisfactory.
It has also been experienced that the surface of the coated metal sheet is relatively easily flawed depending on the degree of the scratching factor, and the quality of the post-coated metal sheet cannot be maintained.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to reduce the workability required for painted metal plates such as the above-mentioned post-coated metal plates. It is an object of the present invention to establish a technology capable of securing a higher degree of scratch resistance without harm.

[0007]

According to the present invention, which is able to solve the above-mentioned problems, a coated metal plate having excellent scratch resistance is coated with a coating film containing substantially spherical organic particles on the surface of the metal plate. The ratio of the projected area (S:%) of the organic particles projecting on the surface of the coating film to the surface area of the coating film (S:%) is 80% or less in plan view, and the ratio from the surface of the coating film surrounding each protruding organic particle is Average protrusion height of the organic particles (H: μ
m) is 50% or less with respect to the average diameter of the organic particles used, and the product (S × H) of the above-mentioned projection area ratio (S:%) and the average projection height (H: μm) is 180. (% ・ Μ
m) or more.

In order to more effectively increase the scratch resistance provided by the present invention, the glass transition point (Tg _B : ° C.) of the base resin constituting the coating film and the glass transition point (Tg _A : ° C.) to satisfy the relationship of Tg _A −Tg _B ≧ 10 (° C.) so that the effect of preventing scratches given by the organic particles protruding on the surface can be more effectively exhibited. desirable.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, according to the present invention, organic particles are contained in a coating film and the particles are made to protrude from the surface of the coating film. (S:%) and the value of the average height of protrusion (H: μm) with respect to the diameter of each organic particle from the coating film surface, and further, the above-described ratio of protrusion area (S:%) and the average of protrusion height (H: μm) )) To improve the flaw resistance while securing excellent workability as a whole of the coating film. The reason for setting the above numerical values in the present invention is as follows. To clarify.

First, in the present invention, it is necessary to suppress the ratio (S:%) of the projected area of the organic particles projected on the surface of the coating film to the surface area of the coating film to be 80% or less in plan view. If the ratio exceeds 80%, the content of the organic particles as the whole coating film becomes too large, and the content ratio of the base resin constituting the coating film becomes small, so that satisfactory workability cannot be obtained. A more preferable projection area ratio for securing excellent workability is 75% or less, and further preferably 70% or less.

Next, the average height (H: μm) of protrusion of each organic particle from the coating film surface must be suppressed to 50% or less of the average diameter of the organic particles used.
Exceeding the above, the organic particles not only fall off from the surface of the coating film when subjected to sliding friction during processing and deteriorate the appearance of the coating film, but also the organic particles that have fallen off during continuous press molding etc. Adheres and accumulates on the inner surface of the substrate, which causes a defect such as a press flaw on the surface. In order to more reliably prevent such obstacles, it is desirable to suppress the protrusion height ratio to 45% or less, and more preferably to 40% or less.

As described above, in the present invention, excellent molding workability and the like are secured as the first requirement by defining the upper limit of the projection area ratio and the projection height ratio of the organic particles to the coating film surface. However, in order to secure the scratch resistance, which is the greatest object of the present invention, the product (S:%) of the protruding area ratio (S:%) of the organic particles and the average protruding height (H: μm) is obtained.
× H) is at least 180 (% · μm), more preferably 24
It is essential to appropriately control each value so as to be 0 or more, more preferably 300 or more. In other words, the scratch resistance provided by the organic particles protruding from the coating film surface is such that the ratio of the protruding area (S) and the average protruding height (H) of the organic particles are effectively exhibited in relation to each other. According to the results of various studies conducted by the present inventors, it has been confirmed that when the product (S × H) is less than 180, the effect of improving the scratch resistance by the protruding particles cannot be effectively exhibited.

That is, the scratch resistance of the whole coating film is exhibited by the sliding action given by the organic particles protruding on the surface of the coating film, and the larger the surface protruding area ratio (S) of the organic particles, the larger the ratio. Also, the higher the average protrusion height (H), the higher the improvement. Therefore, the scratch resistance of the coating film as a whole increases in proportion to the product of the ratio of the protrusion area (S) and the average protrusion height (H). Then, in order to secure the level of scratch resistance intended in the present invention, the product (S × H) must be 180 or more.

Accordingly, from the viewpoint of the scratch resistance, the lower limits of S and H are not particularly limited. However, in order to more reliably and stably improve the scratch resistance, S should be 10% or more.
It is more desirable that the H content be 20% or more, and that H be 4 μm or more, more preferably 6 μm or more.

In the present invention, the flaw resistance is enhanced by utilizing the sliding action of the organic particles protruding from the surface of the coating film as described above. However, when the glass transition point of the organic particles is lower than the glass transition point of the base resin, the sliding action of the organic particles projected on the surface is not sufficient. Sufficiently, it is difficult to obtain a satisfactory effect of improving scratch resistance. In order to more effectively exhibit the effect of improving scratch resistance provided by the organic particles, the glass transition point (T
g _B) and the difference between the glass transition point of the organic particles (Tg _A), i.e., "Tg _A -Tg _B" is 10 (° C.) or higher, more preferably 20 (° C.) as the above, the base used in combination resin It is desirable to select a material for the organic particles.

In order for the organic particles to protrude on the surface of the coating film so as to satisfy the above-mentioned average height of protrusion (H) and the ratio of the height of protrusion, the organic particles are applied to the surface of the coating film in the coating, drying and baking steps. It is desired to select and use organic particles having a specific gravity slightly lower than that of the base coating component so as to float about 10 to 50% of the coating thickness from below the coating.

The particle size of the organic particles is not particularly limited, and various particles having various particle sizes can be used according to the required surface properties. There is a tendency that the sticking property improving effect tends to be hardly exhibited effectively. On the other hand, if the particle size is too large, the surface roughness of the coating film becomes large. It is desired.

The type of the resin constituting the organic particles exhibiting the effect of improving the scratch resistance is not particularly limited, but is preferably a polyamide resin such as nylon, an acrylic resin, a urethane resin, an epoxy resin, or Examples thereof include various modified resins.

The type of the base resin is not particularly limited.
Polyester-based resins, acrylic resins, urethane-based resins, epoxy-based resins, fluorine-based resins and the like, or various modified resins thereof can be used, but polyester resins are particularly preferred in the present invention for metal plates. .

In the base resin, if necessary, a coloring agent such as a pigment, a lubricant such as a wax, an ultraviolet absorber, an antistatic agent, a plasticizer, etc., which can be contained in a usual addition which can be contained in the coating film. It is possible to mix an appropriate amount of the agent. It is also possible to add an appropriate amount of a curing agent as long as performance such as processability is not impaired.

There are no particular restrictions on the type of metal plate to be coated.
Cold rolled steel sheet, hot-dip galvanized steel sheet, electro-galvanized steel sheet,
This includes steel sheets such as galvannealed steel sheets, copper-plated steel sheets, tin-plated steel sheets, and stainless steel sheets, as well as non-metallic metal sheets such as aluminum sheets and copper sheets, and various alloy sheets.

When an organic particle-containing coating film as described above is formed on the metal plate to be coated, the coating may be carried out as long as no contaminants such as oils which impair the adhesion of the coating film adhere to the surface. It is recommended as a preferred embodiment that the surface of the metal plate to be coated is previously subjected to a known surface treatment, for example, a phosphate treatment or a chromate treatment to enhance the coating film adhesion.

[0023]

EXAMPLES Next, examples of the present invention will be described. However, the present invention is not limited by the following examples, and the present invention should be practiced with appropriate modifications within a range that can be adapted to the gist of the preceding and the following. Of course, these are also possible, and all of them are included in the technical scope of the present invention.

Example 1 As a metal plate to be coated, a thickness of 0.5 mm and a zinc adhesion amount of 20
30mg of chromium on electrogalvanized steel sheet of g / m ²
/ M ² chromate-treated surface-treated steel sheet, and a polyester resin paint having a thickness of 5 μm is applied as an undercoat to the polyester-based top paint (Tg: 30 ° C.) as a base resin. A top coat containing organic particles of different types and resin types (each having a Tg of about 60 ° C.) was applied to a thickness of about 20 μm and baked to obtain a test material. For each test material, the surface protruding area ratio (S) and the surface protruding height (H) of the organic particles were measured by the following method, and the scratch resistance and workability of each were examined. The results are shown in Table 1 below. The result was obtained. As the organic particles, nylon-based, acrylic-based, and urethane-based particles were used.

[Surface Protruding Area Ratio of Organic Particles] Surface S
The protruding area ratio of the organic particles on the coating film surface was calculated by EM photograph observation.

[Protrusion height of organic particles] SE of cross section of coating film
From the M photograph, the average value of the protruding height of the organic particles was determined using the base coating surface (the coating film surface surrounding the organic particles) as the origin.

[Scratch resistance] The surface of the coating film of each test material was coated with a sandpaper 1500-CW under a load of 200 g to obtain 1
It was rubbed 0 times and evaluated from the change in appearance of the coating film surface according to the following criteria. ◎: good (no scratches observed) ○: slight scratches observed △: considerable scratches observed ×: scratches noticeably observed

[Workability] For each test material, JIS K
In accordance with 5400, tight bending was performed, and the appearance was changed after taping. ◎: good (no cracks and no peeling of the coating film) ○: small cracks are observed △: large cracks are observed ×: peeling of the coating film occurs

[0029]

[Table 1]

From Table 1, the following can be considered. N
o. 1 to 3, 8 to 11, 14, 15, 17 to 21 are examples satisfying the requirements of the present invention, and excellent results are obtained in both workability and scratch resistance. . On the other hand, No. 4 to 6, 12, 16
Does not satisfy the “S × H” value defined in the present invention, so that the workability is good but the scratch resistance is poor. No. 7 shows that the ratio of the organic particles projected to the coating film surface is 50.
%, The flaw resistance is good, but the workability is poor and lacks practicality. No. Sample No. 13 also has poor processability because the ratio of the area of protrusion of the organic particles to the surface of the coating film exceeds 80%.

Example 2 Nylon resin particles having different glass transition points (Tg _A ) were used as the organic particles, and polyester resins having different glass transition points (Tg _B ) were used as the coating film base resin. _A coating film performance test was performed in the same manner as in Example 1 except that the value of “Tg _A −Tg _B ” was changed in various combinations. Table 2 shows the results.

[0032]

[Table 2]

As is clear from Table 2, “Tg _A −
No. Tg _B > 10 ° C. Nos. 22 to 24 are good in both workability and scratch resistance, but the values of No. 22 to 24 are less than 10C. In 25 and 26,
The effect of improving the scratch resistance provided by the organic particles is somewhat insufficient.

[0034]

The present invention is constituted as described above, and the ratio of the area of protrusion of the organic particles to the surface of the coating film in the coating film containing the organic particles, and the ratio of the protrusion of the organic particles from the surface of the coating film By defining the height ratio and defining the product (S × H) of the ratio (S) of the projected area of the organic particles from the coating film surface and the average projected height (H), the workability is not impaired. The scratch resistance of the surface of the coated metal plate can be remarkably improved, and the commercial value as a post-coated metal plate or the like can be significantly increased.

Furthermore, if the relationship between the glass transition point of the base resin and the organic particles constituting the coating film is properly controlled, the flaw resistance can be more reliably improved and the quality stability can be sufficiently satisfied. it can.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-4-2779 (JP, A) JP-A-7-221488 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B05D 7/14 B05D 5/00 B05D 7/24 303 B32B 15/08

Claims (2)

(57) [Claims] 1. A surface of a metal plate is coated with a coating film containing substantially spherical organic particles, and the ratio of the projecting area (S:
%) Is 80% or less in plan view, and the average height (H: μm) of the protruding organic particles from the surface of the coating film surrounding each protruding organic particle is 50% with respect to the average diameter of the organic particles used. % Or less, and furthermore, the protruding area ratio (S:
%) And the average height of protrusion (H: μm) (S × H) is 18
A coated metal sheet having excellent scratch resistance, characterized in that it is 0 (% · μm) or more. 2. The glass transition point (Tg _B : ° C.) of the base resin constituting the coating film and the glass transition point (Tg _A : ° C.) of the organic particles are as follows: Tg _A −Tg _B ≧ 10 (° C.) The coated metal plate according to claim 1, which satisfies the following relationship.