JP2003170527A - Painted metal plate and method of coating metal plate - Google Patents

Abstract

(57) [Summary] A metal plate 1 that has been subjected to a surface treatment as required.
0, an undercoat layer 20, an intermediate coat layer 30 formed by applying and curing a polyester melamine-based colored paint, and at least one average particle size selected from the group consisting of colored mica, metal powder, and organic colored beads. A coated metal plate 100 formed by laminating in this order a top coat layer 40 formed by applying and curing a polyester melamine-based paint containing a filler of 0.5 mm or less. (a) a step of forming an undercoat by applying an undercoat to the surface of the metal plate subjected to surface treatment, if necessary, by a spray method or a roll coater method, (b) the surface of the undercoat film A step of forming an intermediate coating film by applying a polyester melamine-based coloring paint by a spray method or a roll coater method, and (c) a polyester melamine containing the filler described above on the surface of the intermediate coating film. A method for coating a metal plate, comprising a step of applying a base paint by a roll coater method to form a top coat. According to the present invention, there is provided such a method of coating a metal plate coated with a feeling of unevenness, a sense of quality and the like, and a metal plate.

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 and a method for coating a metal plate, and more particularly to a coated metal plate having a high-grade feeling and such a coating method for a metal plate.

[0002]

BACKGROUND OF THE INVENTION Conventionally, there has been a demand for an exterior material and an interior material for a building that have a high-class feeling and excellent design characteristics, and various proposals have been made. For example, in JP-A-8-318592, as shown in FIG. 2, an undercoat layer 2 formed by baking a resin coating on the surface of a base material 1 and imparting a design property such as metal powder or organic colored beads. Intermediate coating layer 3 made by baking clear paint of melamine-curable polyester resin containing powdered granules and UV absorber, baking paint of clear paint of melamine-curing polyester resin containing UV absorber A precoated metal plate 5 in which the overcoat layer 4 formed in this order is sequentially laminated in this order is disclosed, and it is described that the precoated metal plate has a metallic feeling and the like.

However, such a pre-coated metal sheet has room for further improvement in terms of designability such as unevenness and luxury.

[0004]

It is an object of the present invention to solve the problems associated with the prior art as described above, and to provide a coated metal plate and a metal plate having a high-class feeling and excellent design. The purpose is to provide a painting method.

[0005]

SUMMARY OF THE INVENTION A coated metal plate according to the present invention (painted metal plate) is obtained by applying an undercoat layer and a polyester melamine-based coloring paint on the surface of a metal plate which has been surface-treated as necessary. A polyester melamine-based coating material (preferably polyester melamine) containing an intermediate coating layer formed from the above and a filler having an average particle size of 0.5 mm or less selected from the group consisting of colored mica, metal powder and organic colored beads. An overcoat layer formed by applying and curing a clear clear paint) is laminated in this order.

In the present invention, it is desirable that the average particle diameter of the filler is 0.4 mm or less, preferably 0.3 mm or less. The coating method of the metal plate according to the present invention is (a)
A step of forming an undercoat coating film (layer) by applying an undercoat paint by a spray method or a roll coater method on the surface of a metal plate which has been subjected to surface treatment as necessary, (b) the surface of the undercoat coating film In, a step of forming an intermediate coating film (layer) by applying an intermediate coating paint comprising a polyester melamine-based colored coating material by a spray method or a roll coater method, and (c) on the surface of the intermediate coating film, Colored mica,
A polyester melamine-based paint, preferably a polyester melamine-based clear paint, containing at least one filler having an average particle size of 0.5 mm or less selected from the group consisting of metal powder and organic colored beads is applied by a roll coater method, The method is characterized by having a step of forming an overcoat coating film (layer).

In the present invention, it is desirable that the average particle size of the filler is 0.4 mm or less, preferably 0.3 mm or less, and particularly 0.2 mm or less. The lower limit of the average particle size of the filler is preferably 0.1 mm or more. According to the present invention as described above, there is provided a coated metal plate having a feeling of unevenness, a feeling of high quality, and the like, which is excellent in designability, and such a coating method of a metal plate.

[0008]

DETAILED DESCRIPTION OF THE INVENTION A coated metal plate (painted metal plate) and a method for coating a metal plate according to the present invention will be specifically described below with reference to the accompanying drawings. <Coated Metal Plate (Coated Metal Plate)> FIG. 1 shows a preferred embodiment of the coated metal plate according to the present invention.

This coated metal plate 100 has an undercoat coating film (layer) 20 and an intermediate coating film (layer) 30 formed by coating and curing a polyester melamine color paint on one surface of the metal plate 10.
And a top coat film (layer) 40 formed by applying and curing a polyester melamine paint containing a filler 42 such as colored mica, metal powder, organic colored beads, etc. are sequentially laminated.

In such a coated metal plate 100, the thickness of each layer is not particularly limited. For example, the metal plate 10 has a thickness of 0.1 to 2.0 mm, and the undercoat coating film (layer) 20 has a thickness of 1 to 10 μm thick, the thickness of the intermediate coating film (layer) 30 is 5 to 30 μm, and the thickness of the top coating film (layer) 40 is
Filler 4 for colored mica, metal powder, organic colored beads, etc.
The thickness of the coating surface concave portion 44 where 2 does not exist is about 5 to 30 μm. <Metal plate 10> The material of the metal plate 10 is not particularly limited, and iron, aluminum, tin-plated steel plate, galvanized steel plate, stainless plate, copper plate, aluminum-zinc alloy plated steel plate, aluminized steel plate, chrome-treated steel plate, etc. ,
A galvanized steel sheet and an aluminum zinc alloy plated steel sheet are preferably used. Moreover, the surface shape is not particularly limited, and the surface shape shown in FIG.
In addition to the flat plate shape indicated by number 10, a corrugated plate after painting,
It may be embossed or the like.

The surface of such a metal plate 10 may be subjected to surface treatment such as roughening treatment, rustproofing treatment (eg chromate treatment, etc.), degreasing and phosphate treatment in advance (not shown). ). <Undercoat film (layer) 20> The undercoat film (layer) 20 is formed, for example, by coating and curing an epoxy-based primer, a polyester-based primer, a urethane-based primer, etc. Considering this, it is preferably formed by applying and curing an epoxy primer or a polyester primer. <Intermediate coating film (layer) 30> The intermediate coating film (layer) 30 is a coating film formed by applying and curing the following polyester melamine-based coloring paint containing a colorant.

<Polyester Melamine-based Colored Coating> The polyester melamine-based colored coating (melamine-curable polyester-based colored coating) used in this intermediate coating film is a solvent containing a polyester resin, a melamine resin as a curing agent, and a coloring pigment. It is a mold or water-based paint. Such polyester melamine-based coloring paint, in addition to this, additives, for example, ultraviolet absorbers, light stabilizers, antioxidants, peroxide decomposers, organic solvents for viscosity adjustment, catalysts, thixotropic agents, A dispersant, an antifoaming agent, a leveling agent, etc. may be contained.

In the coating composition, the melamine resin, as a solid content, is usually 5 to 40 relative to 100 parts by weight of the total of the melamine resin (solid content) and the polyester resin (solid content).
It is desirable that it is contained in an amount of parts by weight, preferably 15 to 30 parts by weight. If the amount of this melamine resin is less than the above amount, curing tends to be insufficient, and if it is more than the above amount, the coating film becomes brittle, and processability, adhesion, impact resistance, etc. tend to be reduced.

In the polyester melamine-based color paint, the polyester resin (solid content) is usually 10
To 60% by weight, preferably 20 to 50% by weight, and the melamine resin (solid content) is usually 1 to 40% by weight, preferably 4 to 20% by weight. , Light stabilizers, etc.) are usually included in an amount of 0 to 15% by weight, preferably 1 to 10% by weight, and the solvent is usually included in an amount of 10 to 60% by weight, preferably 20 to 50% by weight. It is desirable that the total amount of all components be 100% by weight.

As the polyester resin, an ester reaction product of a polyhydric alcohol and a polybasic acid or an anhydride thereof, which usually has a hydroxyl group, is used. The weight average molecular weight (Mw) of the polyester resin is usually
1000-10000, preferably 2000-5000
Is desirable. Examples of the polyhydric alcohol include ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, neopentyl glycol, 1,3-butanediol, 1,6-hexanediol, ε-caprolactam, glycerin and trimethylol. Examples include propane, pentaerythritol, dipentaerythritol, and the like.

These polyhydric alcohols may be used alone or in combination.
Used in combination of two or more species. Examples of the polybasic acid or its anhydride include phthalic acid, phthalic anhydride, tetrahydrophthalic acid, tetrahydrophthalic anhydride, trimellitic acid, trimellitic anhydride, pyromellitic acid, isophthalic acid, terephthalic acid, maleic acid, maleic anhydride. Acid, fumaric acid,
Examples thereof include itaconic acid, adipic acid, succinic acid, dodecenyl succinic acid, dodecenyl succinic anhydride and the like.

These polybasic acids or their anhydrides are
They may be used alone or in combination of two or more. The hydroxyl group-containing polyester resin (polyol) may be modified with a long chain monoepoxide or the like. An alkoxymethyl melamine resin is used as the melamine resin.

The alkoxy group has 1 to 10 carbon atoms,
Preferably, a linear or branched alkoxy group of about 1 to 5 is used, for example, a methoxy group, an ethoxy group, n-
Examples thereof include butoxy group and isobutoxy group. Specific examples thereof include methoxymethyl melamine resin, ethoxymethyl melamine resin, n-butoxymethyl melamine resin, isobutoxymethyl melamine resin and the like. These melamine resins, melamine amino groups (-NH ₂₎ is completely alkoxymethyl amino group _{[-N (CH 2 OR) 2} ),
R: an alkyl group having 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms]
May be a completely alkylated melamine resin,
Some of the amino groups _{[-N (CH 2 OR) (} CH 2 OH)
Etc.] may be a partially alkylated melamine resin.

The curing mechanism of such a polyester melamine-based coloring paint depends on the type of melamine resin, the type of catalyst, the amount ratio of polyester resin and melamine resin, the amount of water in the system, the type of polyol hydroxyl group, the baking temperature, etc. Although it is not completely determined, it is believed that the self-condensation reaction of the melamine resin, the cross-linking reaction of the melamine resin and the hydroxyl group-containing polyester resin (polyol), and the like may occur and cure.

Examples of the ultraviolet absorber include benzophenone-based, benzotriazole-based, oxalic anilide-based, cyanoacrylate-based and triazine-based ultraviolet absorbers, and examples of the light stabilizer (radical scavenger) include For example, a hindered amine type is mentioned.

Examples of the organic solvent include aromatic hydrocarbons such as toluene and xylene; aliphatic hydrocarbons such as cyclohexane and ethylcyclohexane; ethyl acetate,
Esters such as butyl acetate and ethyl cyclohexane; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone and isophorone; alcohols such as methanol, ethanol, n-butanol, isobutanol and butyl cellosolve; ethers such as carbitol acetate; Etc.

These organic solvents may be used alone or in combination of two or more. Examples of the catalyst include protonic acids such as carboxylic acid and sulfonic acid. Moreover, what blocked these acids with the amine etc. may be used. <Top coat film (layer) 40> The top coat film (layer) 40 contains a filler typified by colored mica, metal powder, and organic colored beads, and is a polyester melamine-based resin similar to the above intermediate coat film. It is a coating film formed by applying and curing a polyester melamine-based coating material containing a resin.

The average particle size of the filler in the coating film is usually 0.5 mm or less, preferably 0.4 mm or less, more preferably 0.3 mm or less, and especially 0.2 mm or less. The lower limit of the average particle size of the filler is
It is preferably 0.1 mm or more. Further, it is desirable that the filler having such an average particle diameter is contained in the top coating film in an amount of usually 1 to 30% by weight, preferably 3 to 20% by weight. When the filler having the average particle diameter as described above is contained in the overcoat coating film (layer) 40 preferably in the amount as described above, colored mica, metal powder, organic colored beads are formed on the surface of the coated metal plate. A large number of fine protrusions (or irregularities) of the filler due to the filler, etc. are generated on the surface, and a coated metal plate having a high-quality calm color tone can be obtained. Further, the filler 42 having such a particle size is well transferred onto the surface of the intermediate coating film 30 together with the polyester melamine-based coating material adhered to the surface of the roll coater when the roll coater coating is performed, and the top coat excellent in design is obtained. It is preferable because the film 40 is obtained. If the average particle size of the filler such as colored mica is larger than the above range, generally, the filler such as colored mica or metal powder easily falls off from the surface of the coating film 40, impairing the high-class feeling. In addition, there is a tendency that it is difficult to be transferred from the roll coater surface to the surface of the coating object during roll coater coating, and if the average particle size of this filler is less than the above range, it will depend on the film thickness etc. High-quality tones may not appear.

The colored mica compounded in the top coat has a structure in which the mica is coated with an acrylic melamine resin containing a coloring pigment. For example, a melted or dissolved acrylic melamine resin containing a coloring pigment is used. It is obtained by adding mica in an amount of about 400 to 900 parts by weight (solid content 100 parts by weight) and coating with resin.

Examples of the metal powder include aluminum powder, copper powder and stainless powder, and aluminum powder is preferable. In the present invention, for example, any one of the preferable fillers represented by the colored mica, the metal powder and the organic colored beads may be used alone, or two or more kinds may be used in combination. .

In addition to the above, other additives such as an ultraviolet absorber, a light stabilizer, an antioxidant, a peroxide decomposing agent, an organic solvent for adjusting viscosity, a catalyst and a rocking agent are added to the polyester melamine-based top coating composition. A modifier, a dispersant, an antifoaming / leveling agent, etc. may be contained. In the polyester melamine-based top coating composition, the polyester resin (solid content) is usually 10 to 60% by weight, preferably 20 to 50% by weight, and the melamine resin (solid content) is usually 1 to 40% by weight. %, Preferably 4 to 20% by weight, the filler is
Usually, the amount is 1 to 30% by weight, preferably 3 to 20% by weight, and the additive (eg, ultraviolet absorber, light stabilizer, etc.) is usually 0 to 15% by weight, preferably 1 to 10% by weight. It is desirable that the solvent is usually contained in an amount of 10 to 60% by weight, preferably 20 to 50% by weight (however, the total amount of all components is 100% by weight).

In the coating composition, the melamine resin, as a solid content, is usually 5 to 5 parts by weight based on a total of 100 parts by weight of the melamine resin (solid content) and the polyester resin (solid content).
It is desirable that it is contained in an amount of 40 parts by weight, preferably 15 to 30 parts by weight. When the amount of this melamine resin is less than the above amount, curing tends to be insufficient and chemical resistance and the like tend to be inferior. When the amount is more than the above amount, the coating film becomes brittle and the workability, adhesion, impact resistance, etc. are reduced. Tend to do.

In the present invention, since the intermediate coating composition and the top coating composition contain the same polyester melamine resin as described above, the intermediate coating layer 30 and the upper coating layer 40 have excellent adhesion. <Method of Painting Metal Plate> Next, a method of painting the metal plate will be described with reference to FIG. <Undercoating step (a)> In the first coating method of the metal plate, the undercoat coating film 20 is formed by applying the undercoat paint onto the surface of the metal plate 10 as shown in FIG. 1 by a spray method or a roll coater method. To form. The surface of the metal plate 10 may be subjected to a surface treatment such as the above-described chromate treatment in advance, if necessary.

The drying method is not particularly limited, and examples thereof include room temperature drying, heat drying, baking and the like, of which baking is preferable. <Intermediate coating step (b)> Next, in the intermediate coating step (b), a dry film thickness of the above-mentioned intermediate coating material which is a polyester melamine-based color coating material is applied to the surface of the undercoat coating film 20 by a spray method or a roll coater method. For example, the intermediate coating film 30 is formed by coating so as to have a thickness of 5 to 30 μm and curing. More specifically, this intermediate coating composition has, for example, a weight average molecular weight (Mw) of 2500 to 35.
00 to polyester resin 32 to 48% by weight, weight average molecular weight (Mw) of 500 to 1500 melamine resin 8 to
12% by weight, 5 to 7% by weight of additives (eg UV absorber, light stabilizer, suspending agent) and 20 to 30% by weight of solvent (total 100% by weight) Is preferably used. Further, examples of the curing method of the intermediate coating include baking, heat drying, and the like. In the baking curing method preferably used, for example, the plate surface temperature is 140 to 280.
20 to 10 ° C., preferably at a temperature of 180 to 240 ° C.
It is desirable to heat for 0 seconds, preferably 30 to 80 seconds. <Overcoating step (c)> Next, in the overcoating step (c), the average particle diameter as described above, that is, the average particle diameter is 0.5 mm or less, preferably 0.4 mm or less, on the surface of the intermediate coating film 30. , More preferably 0.3 mm or less, especially 0.2 mm
And the lower limit of the average particle diameter is preferably 0.1 mm or more in any case (at least one selected from the group consisting of colored mica, metal powder and organic colored beads), preferably The same polyester melamine-based coating material (more preferably clear coating material) containing colored mica as described above was applied by a roll coater method so that the dry film thickness (film thickness of the recess) was, for example, 5 to 30 μm. Curing is performed to form the top coat film (layer) 40.

The filler having such a particle size contained in the top coating composition is applied from a roll coater surface to a surface of an article to be coated (intermediate coating layer 30 surface) by coating with a roll coater.
Is preferable, since the topcoat layer does not foam even when baked and cured after coating, and a coated metal plate having a feeling of unevenness and a sense of quality can be obtained, which is preferable. As the top coating, more specifically, for example, the weight average molecular weight (Mw) is 2500.
To 3500 polyester resin 32 to 48% by weight, weight average molecular weight (Mw) of melamine resin 500 to 1500 is 8 to 12% by weight, and average particle size is preferably 0.1 mm to
5 to 15% by weight of 0.5 mm of the above-mentioned filler, and 5 to 5% of additives (eg, ultraviolet absorber, light stabilizer, suspending agent, etc.)
A paint containing 7% by weight and a solvent in an amount of 20 to 50% by weight (total 100% by weight) is preferable.

Examples of the curing method of the overcoat paint include baking and heat drying as described above. In the baking curing method which is preferably used, for example, a plate temperature of 140 to 280 ° C.,
It is desirable to heat at a temperature of 180 to 240 ° C. for 20 to 100 seconds, preferably 30 to 80 seconds. The coated metal plate 100 thus obtained has a high-grade feeling and is suitable for use as an exterior material or interior material for buildings, partitions and the like.

[0032]

EFFECTS OF THE INVENTION According to the present invention, the shape and color tone of the above-mentioned dispersed filler appear clearly on the surface, and there is a feeling of unevenness, a feeling of luxury, etc. A method of painting a board is provided.

[0033]

EXAMPLES Hereinafter, the coated metal plate and the method for coating a metal plate according to the present invention will be described more specifically based on examples, but the present invention is not limited to these examples. The paints used in the following examples and comparative examples are as follows. (i) Epoxy-based primer (Chugoku Paint Co., Ltd., undercoat
For use) Type of colorant: titanium white, strontium chromate, etc. Amount of colorant: 15% by weight, epoxy resin (solid content) / melamine resin (solid content) (weight ratio) = 80/20 Weight average molecular weight of each resin (Mw) = epoxy resin (10
00-3000), melamine resin (500-150)
0).

Optional component and its amount: Additive, etc. (kind: precipitation inhibitor such as amide wax) (solid content) 2% by weight, solvent (xylene, Solvec 150, N-butanol, etc.)
58% by weight. (ii) Polyester melamine-based coloring paint A (A for intermediate coating)
(Chugoku Paint Co., Ltd.) Colorant type: titanium white, etc. Colorant amount: 30% by weight, polyester resin (solid content) / melamine resin (solid content)
(Weight ratio) = 80/20, weight average molecular weight (Mw) of each resin: polyester (25
00-3500), melamine resin (500-150)
0).

Optional components and their amounts; additives (precipitating agent such as amide wax, defoaming / leveling agent such as acrylic copolymer) (solid content) 5% by weight, solvent (xylene, Solvec 150, N-butanol, etc.) ) 35% by weight. (iii) Mica-blended polyester melamine-based top coating B
(Topcoat B) (Chugoku Paint Co., Ltd.) Colored mica [(color: black, average particle size 0.3 mm, content:
5% by weight, mica / polyester melamine resin (weight ratio) = 10/90] Polyester resin / melamine resin (weight ratio of solid content) =
80/20, weight average molecular weight (Mw) of each resin: polyester (25
00-3500), melamine resin (500-150)
0). (iv) Optional components and their amounts: Additives, etc. (Type: Amide wax, precipitation inhibitors, acrylic copolymers, etc., defoaming / leveling agents) 5% by weight, solvents (xylene, Solvek 15)
0, N-butanol, etc.) 45% by weight.

[0036]

[Embodiment 1] <Undercoating step> An epoxy-based primer is applied to the surface of a zinc-plated steel sheet 10 having a thickness of 0.5 mm and subjected to chromate treatment as shown in FIG. It was applied so as to have a thickness of 5 μm, heated at a plate temperature of 210 ° C. for 1 minute and dried to form an undercoat layer 20. <Intermediate coating step> Next, a polyester melamine-based color coating material A (for intermediate coating) is applied to the surface of the undercoat coating film 20 with a coating machine (roll coater) to have a dry film thickness of 15 μm.
The coating was applied to have a thick thickness, and the coated layer was heated with a heater (conveyor oven) at a plate temperature of 210 ° C. for 1 minute, baked and dried to form an intermediate coating layer 30. <Topcoating Step> Next, a polyester melamine-based clear coating material B for topcoating (B for topcoating) is applied to the surface of the intermediate coating film 30 with a roll coater so that the dry film thickness is 10 μm.
Coating was performed so as to have a thick thickness, followed by heating with a heater (conveyor oven) at a plate temperature of 210 ° C. for 1 minute and baking and drying to form an overcoat layer 40.

The coated metal sheet of the present invention thus obtained was subjected to a bending test with respect to coating film performance by (4) sandwiching four sheets having the same thickness as the base material and visually evaluating. However, no cracks occurred (workability (4T) evaluation: 3 points), (b) Immersed in 5% H ₂ SO ₄ aq at room temperature for 24 hours, then pulled up and washed with water, and visually blistered When the condition was evaluated, no blister was generated (acid resistance evaluation: 3 points), and (c) after being immersed in 5% NaOHaq at room temperature for 24 hours, pulled up and washed with water to visually check for glossiness. As a result of examination, there was no glossiness (alkali resistance evaluation: 3 points).

Further, in the coated metal sheet according to the present invention, the color tone of the coloring agent blended in the intermediate coating layer appears as a basic tone on the surface, and the colored mica contained in the upper coating layer appears on the surface. Evenly dispersed and firmly attached,
Further, the layers are firmly adhered to each other. Regarding the design of the coated metal plate, when the appearance of the coating film is visually observed, excellent unevenness (evaluation: 3 points) and excellent luxury (evaluation) are obtained. : 3 points).

Table 1 also shows coating specifications, coating film performance and designability.

[0040]

[Comparative Example 1] <Undercoating step> In Example 1, a urethane-modified epoxy primer C was applied to the surface of a chromate-treated 0.5 mm thick galvanized steel sheet as shown in FIG.
Using a roll coater coating machine to obtain a dry film thickness of 5μ
It was applied so as to have a thickness of m and heated and dried at a plate temperature of 210 ° C. for 1 minute to form an undercoat coating layer.

Urethane modified epoxy primer C (medium
Kokuni Paint Co., Ltd., undercoat paint) Colorant type: titanium white, strontium chromate, etc. Colorant amount: 20% by weight, resin type: block urethane-modified epoxy resin, resin amount (solid content): 20 % By weight, weight average molecular weight (Mw) of resin: 1000 to 3000, optional components and amounts thereof: additives, etc. (precipitating agent such as amide wax) (solid content) 2% by weight, solvent (xylene, Solvec 150, N-) Butanol) 58% by weight. <Intermediate coating step> Next, a polyester melamine-based coloring coating D (for intermediate coating) is applied to the surface of the undercoat coating film by a coating machine (roll coater) so that the dry film thickness becomes 15 μm. Then, it was heated at a plate temperature of 210 ° C. for 1 minute with a heater (conveyor oven), baked and dried to form an intermediate coating layer.

Mica-blended polyester melamine intermediate coating
Clear paint D (for intermediate coating D) (Chugoku Paint Co., Ltd.) Colored mica [(color: black, average particle size 0.3 mm, content:
5% by weight, mica / polyester melamine resin (weight ratio) = 10/90] Polyester resin / melamine resin (weight ratio of solid content) =
80/20, weight average molecular weight (Mw) of each resin: polyester (25
00-3500), melamine resin (500-150)
0).

Optional components and their amounts: Additives etc. (Amide wax as anti-settling agent, acrylic copolymers as defoaming / leveling agent, etc.) 5% by weight, solvent (xylene, Solvec 150, N-butanol, etc.) 45 weight%. <Topcoating Step> Next, a polyester melamine-based clear coating E for topcoating (E for topcoating) is formed on the surface of the intermediate coating film.
Was coated with a roll coater so that the dry film thickness would be 15 μm, and heated with a heater (conveyor oven) at a plate temperature of 210 ° C. for 1 minute to be baked and dried to form an overcoat layer.

Polyester melamine-based clear coating for top coating
Material E (E for top coating) Mica-free polyester melamine-based clear coating for top coating E (manufactured by China Paint Co., Ltd., polyester resin / melamine resin (weight ratio of solid content) = 80/20, weight average molecular weight of each resin (Mw): Polyester (25
00-3500), melamine resin (500-150)
0).

Optional component and its amount: Additive, etc. (kind: defoaming / leveling agent acrylic copolymer, etc.) 2% by weight,
Solvent (type: xylene, Solvec 150, N-butanol, etc.) 45% by weight. With respect to the coating film performance of the coated metal plate thus obtained, a bending test was conducted with (4) four plates having the same thickness as the base material and visually evaluated, and it was found that cracks occurred. None (workability (4T) rating: 3 points), (b) 5%
After immersing in H ₂ SO ₄ aq at room temperature for 24 hours, pulling up, washing with water, and visually observing the occurrence of blisters, no blisters were found (acid resistance evaluation: 3 points), and (c) 5 After immersing in% NaOHaq at room temperature for 24 hours, it was pulled up and washed with water, and the presence or absence of glossiness was visually inspected to find no glossiness (alkali resistance evaluation: 3
point).

Regarding the design, the appearance of the coating film was visually observed, and it was found that there was no unevenness, or the unevenness was inferior (evaluation: 1 point), and the high-grade appearance was slightly inferior (evaluation: 2 points). .
Table 1 also shows coating specifications, coating film performance, and designability.

[0047]

[Table 1]

The test methods and evaluation criteria are as follows. “Workability (4T)”: 4 pieces of plate with the same thickness as the base material in the tester
A bending test was conducted between the sheets and visually evaluated. <Workability evaluation criteria> 3 points: No cracks were generated.

2 points: Some cracks occurred. 1 point: A lot of cracks were generated. "Acid resistance": After immersing for 24 hours at room temperature in a 5% H ₂ SO ₄ aq, washed with water and pulled up to assess the blister occurrence visually. <Acid resistance evaluation criteria> 3 points: No blister is generated.

2 points: Some blister is generated. 1 point: A large amount of blisters occur. "Alkali resistance" After immersing in 5% NaOH aq at room temperature for 24 hours, it was pulled up and washed with water, and the presence or absence of glossiness was visually examined. <Evaluation Criteria for Alkali Resistance> 3 points: No gloss loss.

2 points: There is some luster. 1 point: There is glossiness. "High-class feeling": The appearance of the coating film was visually observed to check whether there is a high-class feeling. <Evaluation criteria for luxury> 3 points: There is a feeling of luxury.

2 points: The quality is slightly inferior. 1 point: Poor quality. "Unevenness": The appearance of the coating film was visually observed to check the presence or absence of unevenness. <Evaluation Criteria for Unevenness> 3 points: There is unevenness.

2 points: The unevenness is slightly inferior. 1 point: Inferior feeling of unevenness. Or there is no unevenness.

[0054]

Examples 2 to 5 and Comparative Examples 2 to 3 A coated metal plate was prepared in the same manner as in Example 1 except that the average particle size (mm) of the colored mica was changed as shown in Table 2. Was produced, and the transferability of the colored mica and the falling property of the colored mica were evaluated. The results are shown in Table 2.

[0055]

[Table 2]

The evaluation criteria are as follows. [Evaluation Criteria] "Transferability of colored mica": The top coating composition was applied onto the intermediate coating film with a roll coater, and the appearance of the coating film was visually evaluated. (In general, the larger the average particle diameter, the more difficult it is to transfer.) <Evaluation Criteria for Transfer> 3 Points: Good transfer efficiency of colored mica in the topcoat paint.

2 points: The transfer efficiency of the colored mica is slightly inferior. 1 point: Transfer efficiency of the colored mica is inferior or hardly transferred. "Detachability of colored mica": After coating and baking in the same manner as described above, the ease of removal of the colored mica on the coating film was evaluated. (In general, if the average particle size is large, the colored mica tends to fall off from the coating film.) <Evaluation Criteria for Dropping Property> 3 Points: The colored mica does not fall off easily.

2 points: Colored mica comes off rather easily. 1 point: Colored mica easily comes off.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a coated metal plate according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of a coated metal plate according to a conventional example.

[Explanation of symbols]

10 ... Metal plate 20: Undercoat layer (undercoat film), undercoat paint 30 ... Intermediate coating layer (intermediate coating film), intermediate coating material 40 ... Top coat layer (top coat film), top coat paint 42 ... Filling agent (colored mica, etc.) 44 ... Recessed topcoat layer 46 ... Convex portion of top coat layer 100 ... Painted metal plate

Front page continuation (51) Int.Cl. ⁷ identification code FI theme code (reference) B05D 7/24 302 B05D 7/24 302V C09D 5/00 C09D 5/00 D 161/28 161/28 167/00 167 / 00 F-term (reference) 4D075 AA01 AC21 AE03 BB73X CA04 CA13 CA33 CA44 CB06 CB11 CB27 DA06 DB02 DB04 DB05 DB06 DB07 DC02 EA07 EA43 EB32 EB33 EB35 EB38 EB45 EC04 EC07 AK41C36D36H41AB36C41D36H41AB05D36H01 AB03H18AB01H01 AB03H18AB01H01 AB03H18AB01H01AB03H18AB01H01AB03H01AB01H01AB03H18AB01H01AB03H01AB01H01AB03H18AB01H01AB03H01AB01H01AB03H01AB01H01AB03H04H01HHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHHH AK53 AT00A BA04 BA07 BA10A BA10D CA02C CA02D CA23D CC00B CC00C CC00D DE01D DE01H DE04D EH46C EH46D EH462 EH71 EJ08C EJ08D EJ64A EJ65B KA65 EJ65D HA0600DHA06D0607B00D HA07D00D J07D00D J07D04D00D H01

Claims (10)

[Claims] 1. An undercoat layer on the surface of a metal plate, an intermediate coating layer formed by coating and curing a polyester melamine-based coloring paint, and at least one selected from the group consisting of colored mica, metal powder and organic colored beads. And a topcoat layer formed by coating and curing a polyester melamine-based coating material containing a filler having an average particle diameter of 0.5 mm or less, and a laminated metal plate formed in this order. . 2. The coated metal plate according to claim 1, wherein the surface of the metal plate is surface-treated. 3. The coated metal plate according to claim 1, wherein the filler has an average particle size of 0.4 mm or less. 4. The coated metal plate according to claim 1, wherein the filler has an average particle diameter of 0.3 mm or less. 5. The coated metal sheet according to any one of claims 1 to 4, wherein the polyester melamine-based coating material for the topcoat layer is a clear coating material. 6. (a) A step of forming an undercoat coating film on the surface of a metal plate by applying an undercoat paint by a spray method or a roll coater method, (b) a polyester melamine-based resin on the surface of the undercoat coating film. A step of forming an intermediate coating film by applying a colored coating material by a spray method or a roll coater method, and (c) on the surface of the intermediate coating film, from the group consisting of colored mica, metal powder and organic colored beads. At least one chosen
A polyester melamine-based paint containing a filler having an average particle size of 0.5 mm or less is applied by a roll coater method,
A method for coating a metal plate, comprising the step of forming an overcoat coating film. 7. The method for coating a metal plate according to claim 6, wherein the surface of the metal plate has been surface-treated in advance. 8. The method for coating a metal plate according to claim 6, wherein the filler has an average particle size of 0.4 mm or less. 9. The method for coating a metal plate according to claim 6, wherein the filler has an average particle diameter of 0.3 mm or less. 10. The method for coating a metal plate according to claim 6, wherein the polyester melamine-based coating material for the top coating film is a clear coating material.