JP7229756B2 - painted metal plate - Google Patents

Description

TECHNICAL FIELD The present invention relates to a coated metal sheet in which resin beads are contained in the coating film on the non-decorative surface.

Since the coated metal plate is coiled while applying tension for storage or the like, the decorative surface of the coated metal plate is in close contact with the non-decorated surface of the coated metal plate. When the decorative surface and the non-decorated surface are in close contact with each other, the gloss of the decorative surface tends to change. Such changes in gloss are called pressure marks.

In Patent Documents 1 to 5, resin beads are contained in the non-decorated surface coating film in order to suppress the generation of pressure marks on the decorative surface of the coated metal plate. As a result, when the coated metal sheet is coiled, the resin beads are interposed between the contact surfaces of the decorative surface and the non-decorated surface, and the contact pressure between the decorative surface and the non-decorated surface can be reduced to suppress the occurrence of pressure marks. .

JP-A-9-100424 JP-A-2004-50657 JP-A-2005-28851 Japanese Patent Application Laid-Open No. 2005-313630 Patent No. 5732273

A leveler is used to improve the flatness of the coated metal sheet before it is coiled. The leveler corrects warping and bending of the coated metal plate by pressing both sides (decorative surface and non-decorative surface) of the coated metal plate with rolls.

FIG. 1 shows a state in which a coated metal plate is passing through a leveler. The coated metal plate 100 has a metal plate 110 and a coating film (non-cosmetic coating film) 120 forming a non-cosmetic surface, and the non-cosmetic coating film 120 contains resin beads 130. there is In addition, in FIG. 1, the coating film forming the decorative surface of the coated metal plate 100 is omitted. In FIG. 1, an arrow D1 indicates the conveying direction of the coated metal sheet 100, and an arrow D2 indicates the rotating direction of the roll 200 of the leveler.

If the non-cosmetic coating film 120 contains the resin beads 130, the resin beads 130 will be deformed by the pressure from the roll 200 of the leveler. If the resin beads 130 are deformed, there is a risk that the resin beads 130 will break and fall off the non-cosmetic coating film 120, or that the resin beads 130 will fall off the non-cosmetic coating film 120 without breaking. The resin beads 130 that have fallen off the non-cosmetic coating film 120 are likely to adhere to the surface of the roller 200. If the resin beads 130 remain adhered to the surface of the roller 200, the coated metal may be damaged during the flattening process using a leveler. Indentations are generated on the surface of the plate 100 .

SUMMARY OF THE INVENTION An object of the present invention is to provide a coated metal plate that can suppress the occurrence of pressure marks and the drop-off of resin beads.

The coated metal sheet of the present invention includes a decorative coating film formed on one surface of the metal plate, a non-cosmetic coating film formed on the other surface of the metal plate, and a non-cosmetic coating film , and beads formed of a polyurethane resin . The non-cosmetic coating film has an undercoat film formed on the surface of the metal plate and a topcoat film formed on the surface of the undercoat film and containing beads. The ratio of the amount of protruding beads to the thickness of the undercoat film is 2.0 or more and 8.0 or less. The protruding amount of the beads is the amount of protrusion of the beads from the surface of the topcoat film, and is represented by the difference between the film thickness of the topcoat film and the average particle size of the beads. The base resin for the undercoat and topcoat is polyester resin or epoxy resin. The topcoat containing beads is a cured product of a mixture containing beads and a coating containing polyester resin or epoxy resin. The average particle size of the beads is 10-30 μm.

ADVANTAGE OF THE INVENTION According to this invention, while being able to suppress that a pressure mark generate|occur|produces on the decorative surface of a coated metal plate, it can suppress that a bead falls off from a non-cosmetic coating film.

It is the schematic which shows the state which the coating metal plate is passing through the leveler. It is a schematic diagram showing the film configuration of the non-decorative surface of the coated metal sheet of the present embodiment.

Hereinafter, a coated metal sheet that is an embodiment of the present invention will be described.

FIG. 2 is a schematic diagram showing a cross section of the coated metal plate 1. As shown in FIG. The coated metal plate 1 has a decorative surface and a non-decorated surface. In FIG. 2, the upper surface of the coated metal plate 1 is the non-decorated surface, and the lower surface of the coated metal plate 1 is the decorative surface.

In FIG. 2, the film configuration of the decorative surface of the coated metal plate 1 is omitted. A known configuration can be appropriately employed for the film configuration of the decorative surface of the coated metal plate 1 . For example, the film structure of the decorative surface of the coated metal plate 1 can be composed of a plurality of layers of coating films (referred to as decorative coating films). Examples of materials used for the cosmetic coating film include polyester resins, polyurethane resins, acrylic resins, epoxy resins, and fluorine resins. A curing agent can be added to the polyester resin, polyurethane resin or acrylic resin. Curing agents include, for example, melamine resins, polyisocyanate resins, polyamine resins, and phenol resins.

The metal plate 10, which is the substrate of the coated metal plate 1, is not particularly limited. can be used. The surface (decorative surface side and non-decorative surface side) of the metal plate 10 is subjected to a chemical conversion treatment to form a chemical conversion film. Examples of chemical conversion treatments include inorganic treatments such as chromate treatment and phosphate treatment.

The film configuration of the non-decorated surface of the coated metal plate 1 will be described below.

A non-cosmetic coating film 12 is formed on the surface of the chemical conversion treatment film 11 of the metal plate 10 . The non-cosmetic coating film 12 is composed of an undercoat coating film 12a and a top coating film 12b. Specifically, an undercoat film 12a is formed on the surface of the chemical conversion treatment film 11, and a topcoat film 12b is formed on the surface of the undercoat film 12a.

The base resin for each of the undercoat film 12a and the topcoat film 12b is not particularly limited. can be mixed and used. Each of the undercoat film 12a and the topcoat film 12b may be a clear paint film containing no pigment, or may contain at least one of a coloring pigment and an extender pigment. At least one of the undercoat film 12a and topcoat film 12b may contain a curing agent.

The resin beads 13 are contained in the top coat film 12b. As the material of the resin beads 13, a thermoplastic resin, a thermosetting resin, or a mixture of a thermoplastic resin and a thermosetting resin can be used. Examples of thermoplastic resins include polyamide resins, polyurethane resins, and polyacrylourethane resins. Examples of thermosetting resins include acrylic resins, urethane resins, silicone resins, and phenol resins.

The film thickness T1 of the undercoat film 12a and the film thickness T2 of the topcoat film 12b can be appropriately determined. As shown in FIG. 2, the film thickness T1 of the undercoat film 12a is the distance from the surface of the chemical conversion treatment film 11 to the interface between the undercoat film 12a and the topcoat film 12b. The film thickness T2 of the topcoat film 12b is the distance from the interface between the undercoat film 12a and the topcoat film 12b to the surface of the topcoat film 12b excluding the resin beads 13 .

Each film thickness T1, T2 can be adjusted by using a known coating device such as a bar coater. The undercoat film 12a can be formed by applying the paint for the undercoat film 12a to the surface of the chemical conversion treatment film 11 using an applicator and baking and drying it. Alternatively, a coating apparatus may be used to apply a mixture of the paint for the top coat film 12b and the resin beads 13 to the surface of the undercoat coat 12a, followed by baking and drying to form the top coat film 12b containing the resin beads 13. can be done.

The average particle size D of the resin beads 13 can be determined appropriately. The average particle size D is the arithmetic mean value in the particle size distribution of the resin beads 13 . Here, the average particle diameter D is preferably larger than the film thickness T2 of the topcoat film 12b. Then, the average particle size D can be, for example, 10 to 30 μm.

In this embodiment, by forming the undercoat film 12a between the topcoat film 12b containing the resin beads 13 and the chemical conversion treatment film 11, the resin beads 13 are suppressed from falling off from the topcoat film 12b. easier to do. That is, when pressure is applied to the non-decorated surface of the coated metal plate 1 from a roll of a leveler or the like, the deformation of the resin beads 13 can be suppressed by the deformation of the undercoating film 12a. It is possible to suppress the falling off of the

When the value obtained by subtracting the film thickness T2 [μm] of the topcoat film 12b from the average particle diameter D [μm] of the resin beads 13 is defined as the head protrusion amount H of the resin beads 13, the thickness T1 of the undercoat film 12a A ratio Rht (Rht=H/T1) of the head protrusion amount H of the resin beads 13 satisfies the condition shown in the following formula (1). Each film thickness T1, T2 is measured using an electron microscope.
1.0≦Rht≦8.0 (1)

When the ratio Rht satisfies the condition shown in the above formula (1), the occurrence of pressure marks on the decorative surface of the coated metal plate 1 can be easily suppressed, and the resin beads 13 can be removed from the non-cosmetic coating film 12. becomes easier to suppress. By preventing the resin beads 13 from coming off, it is possible to prevent the resin beads 13 from adhering to the roll 200 of the leveler shown in FIG. In addition, it is possible to suppress the occurrence of impressions on the surface of the coated metal plate 1 due to the roll 200 coming into contact with the coated metal plate 1 while the resin beads 13 are still attached to the roll 200 or the like.

If the ratio Rht is lower than 1.0 [-], pressure marks are likely to occur on the decorative surface of the coated metal plate 1, and the glossiness of the decorative surface is likely to decrease. Also, if the ratio Rht is higher than 8.0 [−], the resin beads 13 are likely to fall off the non-cosmetic coating film 12 . Specifically, as described with reference to FIG. 1 , the leveler roll 200 presses the coated metal plate 1 , causing the resin beads 13 to come off the non-cosmetic coating film 12 .

In order to suppress the generation of pressure marks and the falling off of the resin beads 13, it is preferable that the ratio Rht satisfies the condition shown in the following formula (2).
2.0≦Rht≦8.0 (2)

A pressure mark test and a stain test were performed on a plurality of types of coated metal sheets 1 .

First, a plurality of types of coated metal plates 1 were prepared as test samples. As the metal plate 10, a hot-dip 55% aluminum-zinc alloy plated steel plate having a coating weight per both sides of 120 g/m ² and a plate thickness of 0.35 mm was used, and the surfaces (both sides) of which had been chemically treated. A decorative coating film was formed on one surface (the chemical conversion treatment film) of the metal plate 10, and a non-cosmetic coating film was formed on the other surface (the chemical conversion treatment film 11) of the metal plate 10.

The composition of the cosmetic coating was the same for all test samples. The decorative coating film was composed of an undercoat film formed on the surface of the metal plate 10 (chemical conversion treatment film) and a topcoat film overlaid on the undercoat film. After the etching primer paint was applied to the metal plate 10, the metal plate 10 was heated for 40 seconds so that the maximum plate temperature reached 210° C., thereby forming an undercoat film having a thickness of 5 [μm]. After forming the undercoat film, a polyester-based paint is applied to the undercoat film and heated for 40 seconds so that the maximum plate temperature reaches 250 ° C., thereby forming a topcoat film with a thickness of 25 [μm]. formed.

The configuration of the non-cosmetic coating film 12 is as shown in FIG. A polyester resin or an epoxy resin was used as the base resin for the undercoating film 12a of the non-cosmetic coating film 12 . As the material for the topcoat film 12b of the non-cosmetic coating film 12, polyester resin or epoxy resin (trade name "Precolor No. 3900, No. 7000", manufactured by Akzo Nobel Co., Ltd., beige color) is used. board. Polyurethane resin was used as the material of the resin beads 13 . After applying the paint for the undercoat film 12a to the surface of the metal plate 10 (the chemical conversion film 11), the undercoat film 12a was formed by heating for 40 seconds so that the maximum plate temperature reached 250°C. Then, the paint of the topcoat film 12b and the resin beads 13 are mixed, and after applying this mixture to the surface of the undercoat film 12a, the resin is heated for 40 seconds so that the maximum plate temperature reaches 250 ° C. A top coating film 12b containing beads 13 was formed.

Here, a plurality of test samples were prepared by varying the film thickness of the non-cosmetic coating film 12 (specifically, the film thickness T2 of the top coating film 12b) and the average particle diameter D of the resin beads 13. A plurality of test samples (painted metal plate 1) were superposed on the front side and the back side and left in an atmosphere of 60° C. for 24 hours while a pressure of 60 kg/cm ² was applied.

Table 1 below shows each test sample No. 1 to No. 10, the structure of the non-cosmetic coating film 12, the amount of protrusion H and the ratio Rht are shown. In Table 1 below, test sample No. 8, the resin beads 13 are not used, so the average particle diameter D, head protrusion amount H and ratio Rht of the resin beads are not shown.

In the pressure mark test, glossiness was measured for the decorative surface of the coated metal plate 1 before the test and the decorative surface of the coated metal plate 1 after being left for 24 hours (decorative surface after the test). Glossiness was measured in accordance with JIS Z8741, and 60-degree specular glossiness Gs (60°) was measured. In this example, a VG7000 gloss meter manufactured by Nippon Denshoku Industries Co., Ltd. was used in the measurement of glossiness.

Arbitrary five measurement points were specified on each of the decorative surfaces before and after the test, and the average glossiness at these measurement points was calculated. Then, a ratio Rg (Rg=100×Gs_ave2/Gs_ave1) of post-test glossiness Gs_ave2 to pre-test glossiness (average value) Gs_ave1 was calculated. The calculated value of the ratio Rg was rounded off to the nearest whole number. The pressure marks were evaluated based on this ratio Rg. The evaluation criteria for pressure marks are as shown in Table 2 below.

The contamination test is a test for evaluating dropout of the resin beads 13 . In the stain test, a rubbing tester (made of rubber) was pressed against the undecorated surface of each test sample (painted metal plate 1) with a load of 2 kg, and the rubbing tester was reciprocated on the undecorated surface 50 times.

Before conducting the stain test, a predetermined area (1200 μm×900 μm) of the non-decorated surface was observed with a microscope, and the total number N1 of resin beads 13 present in the predetermined area was counted. After the stain test, the predetermined area (1200 μm×900 μm) of the non-decorated surface was observed with a microscope, and the total number N2 of resin beads 13 present in the predetermined area was counted. After calculating the total number N3 of the dropped resin beads 13 by subtracting the total number N2 from the total number N1, the ratio Rn (Rn=100×N3/N1) of the total number N3 to the total number N1 was calculated. The calculated value of the ratio Rn was rounded off to the nearest whole number. Stain was evaluated based on this ratio Rn. The evaluation criteria for contamination are as shown in Table 3 below.

Test sample No. of coated metal plate 1; 1 to No. 10, the results of the pressure mark test and the smudge test are shown in Table 4 below. In Table 4 below, test sample No. 4, since the resin beads 13 are not used, the calculation of the ratio Rn and the contamination evaluation are not performed.

Test sample no. 8, it became difficult to suppress the occurrence of pressure marks, and test sample No. In Nos. 9 and 10, it became difficult to prevent the resin beads 13 from coming off. On the other hand, test sample No. 1 to No. 7, test sample no. 8 to No. Compared to No. 10, it was possible to achieve both suppression of pressure mark generation and suppression of dropout of the resin beads 13 . In particular, test sample no. In 2 to 7, it became easy to suppress the occurrence of pressure marks, and it became easy to suppress falling off of the resin beads 13 .

1,100: Painted metal plate, 10,110: Metal plate, 11: Chemical conversion coating,
12, 120: non-cosmetic coating film, 12a: undercoat coating film, 12b: topcoat coating film,
13, 130: resin beads, 200: roll

Claims (1)

a decorative coating film formed on one surface of the metal plate;
a non-cosmetic coating film formed on the other surface of the metal plate;
beads contained in the non-cosmetic coating film and formed of a polyurethane resin ;
The non-cosmetic coating film has an undercoat film formed on the surface of the metal plate and a topcoat film formed on the surface of the undercoat film and containing the beads,
When the protruding amount of the beads protruding from the topcoat film is the difference between the thickness of the topcoat film and the average particle diameter of the beads, the ratio of the protruding amount to the thickness of the undercoat film is 2.0 or more and 8.0 or less ,
The base resin of the undercoat film and the topcoat film is a polyester resin or an epoxy resin,
The topcoat film containing the beads is a cured product of a mixture containing the beads and the coating containing the polyester resin or the epoxy resin,
A coated metal plate , wherein the average particle diameter of the beads is 10 to 30 μm .

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