WO2019088123A1

WO2019088123A1 - Coated metallic sheet and manufacturing method for coated metallic sheet

Info

Publication number: WO2019088123A1
Application number: PCT/JP2018/040384
Authority: WO
Inventors: 史生柴尾; 邦彦東新; 敬士二葉; 亜暢小林; 石塚　清和; 岡田　克己
Original assignee: 新日鐵住金株式会社
Priority date: 2017-10-30
Filing date: 2018-10-30
Publication date: 2019-05-09
Also published as: JPWO2019088123A1; CN111278648B; CN111278648A; KR20200069343A; KR102425956B1; JP6624346B2; MX2020004253A

Abstract

The coated metallic sheet according to the present invention has a metallic sheet and a fat-containing first coating film which is disposed at least on one surface of the metallic sheet, wherein: the first coating film has a first region having a urethane linkage backbone and a second region having a triazine ring backbone; the first coating film has a glass transition temperature of 85-170°C; and when the second region is stained with osmium oxide and observed with a transmission-type electron microscope in a magnification ratio of 100,000, a dispersive second region in which particles having a number average particle diameter not less than 5 nm are dispersed and a concentrated second region in which such particles having a number average particle diameter not less than 5 nm are not found, are observed.

Description

Painted metal plate and method of manufacturing painted metal plate

The present invention relates to a coated metal sheet and a method of manufacturing the coated metal sheet.
Priority is claimed on Japanese Patent Application No. 2017-209460, filed Oct. 30, 2017, the content of which is incorporated herein by reference.

A coated metal plate coated with a coating film is used for automobiles, home appliances, building materials, civil engineering, machines, furniture, containers, etc., instead of conventional painted products to which painting is applied after processing. It has become like that. Such a coated metal sheet is generally cut and applied after the paint is applied to the metal sheet.

Since a coated metal sheet is mainly used as an exterior material, it is often exposed to various solvents and chemicals, and thus often has solvent resistance and chemical resistance. Because they are exterior materials, they are usually colored and painted, and there are many coated metal plates, and the film thickness of such a coating is relatively thick because of the hiding property for color tone. On the other hand, in the case of a metal-coated metal plate in which the appearance of the metal plate as the substrate is designed as it is, it is necessary to apply a clear coating containing no color pigment. In such a case, by reducing the film thickness of the clear coating film, the coated metal plate becomes excellent in metal appearance. Also, from the viewpoints of productivity and commerce, the thinner the film thickness of the clear coating film, the better.

In general, chemical resistance is required to prevent the coating from being deteriorated or discolored by chemicals. However, when the film thickness of the coating film is thin, it is more problematic that the chemical penetrates to the plating interface to dissolve the plating than the coating film is deteriorated by the chemical. In the case of a colored coating, even if the metal is discolored by chemicals, the appearance does not become abnormal, the dissolution of the metal proceeds and a corrosion product is formed, and the coating is expanded by the generated corrosion product. , Looks abnormal. On the other hand, in the case of clear coating, the appearance is considered abnormal when the metal is discolored. That is, in clear coating, it is necessary that the chemical component does not reach the metal. Such property is called chemical resistance.

Several examples of coated metal plates having excellent chemical resistance have been reported.
For example, Patent Document 1 below discloses a coating method technology of a metal plate for coating a paint containing a solvent-soluble fluorine resin as a main component.

Further, in Patent Document 2 below, the processability, the stain resistance, and the scratch resistance are obtained by the coating film using the polyester resin having a high glass transition temperature, the polyester resin having a low glass transition temperature, and the aminoformaldehyde resin. The art of a coated metal plate excellent in resistance and chemical resistance is disclosed.

In addition, in the following Patent Document 3, a polyacrylic resin is applied to the upper layer, and a polyester resin is applied to the lower layer, and a technique of precoated metal excellent in stain resistance, chemical resistance, weather resistance and processability is disclosed. It is done.

In addition, Patent Document 4 below discloses the technology of a coated metal plate which is excellent in processability, corrosion resistance (especially end face corrosion resistance), chemical resistance, etc. by a coating film obtained by mixing a specific polyurethane resin and a polyester resin. It is done.

Moreover, the technique of the metal plate which is excellent in bending workability is disclosed by the following patent document 5 by the coating film which the melamine resin particle which is 50 nm or less in particle diameter disperse | distributed.

Further, Patent Document 6 below discloses, in a coating film using an aminoblast resin such as melamine resin, a technology for concentrating the aminoblast resin on the surface layer of the coating film.

Japanese Patent Application Laid-Open No. 5-111675 Japanese Patent Application Laid-Open No. 7-331167 Japanese Patent Application Laid-Open No. 7-313929 Japan JP 2013-213281 Japanese Patent Application Laid-Open No. 2005-53002 Japanese Patent Application Laid-Open No. 2006-175815

However, the fluorine resin used by the technique of the said patent document 1 is expensive, and industrially unpreferable.

There are some which are suggested to utilize the self condensation reaction of the melamine resin which is a crosslinking agent in the coat formation using a solvent system paint like the above-mentioned patent documents 2. However, what is disclosed therein does not take into consideration the conditions for surface thickening necessary for barrier layer formation. Moreover, although addition of an amine compound for surface concentration is also disclosed, the effect is a grade which affects the distribution density of the generated melamine self-condensing particles. Therefore, the coating film structure obtained from these conditions is such that coarse self-condensing particles of about 50 to 100 μm are dispersed in the coating film, and the surface concentration as the distribution density of the particles is observed. The chemical resistance improvement effect of the coating film is limited.

The polyacrylic resin used by the technique of the said patent document 3 is inferior to workability, and when the coating film currently disclosed by the said patent document 3 is made into a clear coating film, barrier property is enough. Furthermore, it has poor chemical resistance.

The coating film disclosed in Patent Document 4 has insufficient barrier properties and is further inferior in chemical resistance.

When the melamine resin particles are dispersed in the coating film as in the technique of Patent Document 5, the coating film is inferior in solvent resistance.

In the technique disclosed in Patent Document 6, the particle size of the melamine resin particles in the coating is large, the barrier property is not sufficient, and furthermore, the chemical permeation resistance is inferior.

As described above, Patent Documents 1 to 6 do not disclose a technique for obtaining a coated metal plate excellent in metal appearance, chemical resistance and solvent resistance while suppressing the manufacturing cost.

Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to provide a coated metal sheet which is excellent in metal appearance, chemical resistance and solvent resistance, which is suppressed in manufacturing cost. And providing a method for producing such a coated metal sheet.

As a result of intensive studies on the above problems, the present inventors formed a resin coating film including a first portion having a urethane bond skeleton and a second portion having a triazine ring skeleton on at least one surface of a metal plate. By controlling the glass transition temperature of the resin coating film and the existence state of the second portion in the resin coating film appropriately, the production cost can be suppressed, and the metal appearance, the chemical permeability and the solvent resistance can be suppressed. It was conceived to be able to manufacture an excellent coated metal sheet.
The summary of the present invention completed based on such findings is as follows.

(1) A coated metal plate according to an aspect of the present invention comprises a metal plate and a first coating film located on at least one side of the metal plate and containing a resin, the first coating film comprising It has a first site having a urethane bond skeleton and a second site having a triazine ring skeleton. The glass transition temperature of the first coating is 85 ° C. or more and 170 ° C. or less. When the second site is stained with osmium oxide and observed at a magnification of 100,000 using a transmission electron microscope, the second site is a dispersed second site in which particles having a number average particle diameter of 5 to 20 nm are dispersed, and A concentrated second portion is observed which is present at a depth of 15 nm from the surface of one coating film and in which particles having a number average particle diameter of 5 nm or more are not observed.
(2) The coated metal plate according to the above (1) is characterized in that the N concentration N1 at a depth position of 0.2 μm from the surface of the first coating film from the interface between the first coating film and the metal plate The ratio N1 / N2 to the N concentration N2 at the depth position of 0.2 μm on the first coating film side may be 1.2 or more.
(3) In the coated metal sheet according to (1) or (2), the first coating film may have a plurality of the concentrated second portions.
(4) The coated metal plate according to any one of the above (1) to (3) further comprises a second coating film between the first coating film and the metal plate; The glass transition temperature may be equal to or less than the glass transition temperature of the first coating film.
(5) In the coated metal plate according to (4), the second coating film may contain a resin and have a urethane bond skeleton.
(6) In the coated metal plate according to (4) or (5), the second coating film may contain a resin and may have an epoxy group.
(7) In the coated metal plate according to any one of the above (4) to (6), the second coating film may contain a resin and have a siloxane bond.
(8) In the coated metal plate according to any one of the above (4) to (7), the second coating film is any one selected from the group consisting of P, V, Ti, Si and Zr. The above elements may be included.
(9) In the coated metal plate according to any one of the above (4) to (8), the glass transition temperature of the first coating is higher by at least 5 ° C. than the glass transition temperature of the second coating. It is also good.
(10) In the coated metal plate according to any one of the above (4) to (9), the film thickness of the second coating film may be 0.5 μm or more and 15 μm or less.
(11) In the coated metal plate according to any one of the above (1) to (10), the film thickness of the first coating film may be 0.5 μm or more and 15 μm or less.
(12) In the coated metal plate according to any one of the above (4) to (11), at least one of the first coating film and the second coating film may contain a colorant.
(13) In the coated metal plate according to any one of the above (4) to (12), the second coating film may contain a black pigment as a colorant.
(14) In the coated metal plate according to any one of the above (1) to (13), a texture may be formed on at least one surface of the metal plate.

(15) A method of producing a coated metal sheet according to another aspect of the present invention is a method of producing a coated metal sheet having a predetermined first coating on at least one surface of a metal sheet, the method comprising the steps of First, a polyurethane resin (a) containing an anionic functional group and having a glass transition temperature of 75 ° C. to 160 ° C. on one side, a triazine ring-containing water-soluble curing agent (b), and an aqueous solvent A paint is applied, and the first paint film is formed by heating the metal plate to which the first paint is applied.
(16) In the method for producing a coated metal sheet according to (15), the triazine ring-containing water-soluble curing agent (b) may be a melamine resin containing an imino group.
(17) In the method of producing a coated metal sheet according to (15) or (16), the first paint contains the content (Wa) of the polyurethane resin (a) with respect to the total solid content and the total solid content. The total content (Wa) + (Wb) of the content (Wb) of the triazine ring-containing water-soluble curing agent (b) satisfies the following formula (I), and the above with respect to the total solid content The ratio (Wb) / (Wa) of the content (Wa) of the polyurethane resin (a) and the content (Wb) of the triazine ring-containing water soluble curing agent (b) to the total solid content is as follows: You may satisfy Formula (II).
90 mass% ≦ (Wa) + (Wb) ≦ 100 mass% Formula (I)
0 <(Wb) / (Wa) ≦ 1 formula (II)
(18) The method for producing a coated metal plate according to any one of the above (15) to (17), further comprising a coated metal further having a predetermined second coating film between the metal plate and the first coating film. It is a manufacturing method of board, Comprising: Prior to coating of said 1st paint, polyurethane resin (c) whose glass transition temperature is below the glass transition temperature of said polyurethane resin (a), epoxy resin (d), silane coupling Agent (e), and at least one of a rust inhibitor (f) containing at least one element selected from the group consisting of P, V, Ti, Si and Zr, and an aqueous solvent The second paint may be applied on at least one side of the metal plate, and the second paint film may be formed by heating the metal plate coated with the second paint.
(19) In the method of producing a coated metal sheet according to (18), the glass transition temperature of the polyurethane resin (c) may be 5 ° C. or more lower than the glass transition temperature of the polyurethane resin (a).
(20) In the method of producing a coated metal sheet according to any one of the above (15) to (19), when the first coating film is formed, the heating start of the metal sheet to which the first paint is applied The metal plate to which the first paint is applied is heated so that the heating time from the temperature to the maximum reaching temperature is 1 second to 30 seconds, and the cooling time from the maximum reaching temperature to 30 ° C. is 0.1 seconds The metal plate coated with the first paint may be cooled so as to be 5 seconds or less.
(21) In the method of producing a coated metal sheet according to (20), after holding at a temperature of 40 to 100 ° C. for 1 to 20 seconds in the heating, to 200 ° C. or more in the heating time of 1 to 10 seconds. It may be heated.

As described above, according to the present invention, it is possible to obtain a coated metal sheet which is excellent in metal appearance, chemical resistance and solvent resistance, of which the manufacturing cost is suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing which showed typically an example of the structure of the coating metal plate which concerns on embodiment of this invention. It is explanatory drawing which showed typically an example of the structure of the coating metal plate which concerns on the embodiment. It is explanatory drawing which showed typically another example of the structure of the coating metal plate which concerns on the embodiment. It is explanatory drawing which showed typically another example of the structure of the coating metal plate which concerns on the embodiment. It is explanatory drawing for demonstrating the upper-layer coating film of the coating metal plate which concerns on the embodiment. It is a flowchart for demonstrating an example of the flow of the manufacturing method of the coated metal plate which concerns on the embodiment. It is a microscope image at the time of observing the upper layer coating film of Experiment 3 with a transmission electron microscope. It is an elemental mapping image of osmium at the time of observing the upper layer coating film of Experiment 3 with a transmission electron microscope. It is a microscope image at the time of observing the upper layer coating film of Experiment 3 with a transmission electron microscope. It is a microscope image at the time of observing the upper layer coating film of Experiment 3 with a transmission electron microscope. It is explanatory drawing for demonstrating the upper-layer coating film in case multiple concentration parts are formed.

The present invention will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. In the present specification and the drawings, components having substantially the same functional configuration will be assigned the same reference numerals and redundant description will be omitted.

(About the whole constitution and the outline of the painted metal plate)
First, referring to FIGS. 1A to 3, the overall configuration of a coated metal plate according to an embodiment of the present invention will be described. 1A and 1B are explanatory views schematically showing an example of the structure of a coated metal plate according to the present embodiment, and FIGS. 2A and 2B are other views of the structure of the coated metal plate according to the present embodiment It is an explanatory view showing an example typically. FIG. 3 is an explanatory view for explaining an upper-layer coating film of the coated metal sheet according to the present embodiment.

The coated metal plate 1 which concerns on this embodiment has the upper-layer coating film 13 as a 1st coating film on the single side | surface of the metal plate 11 used as a base material, as typically shown to FIG. 1A. Further, as schematically shown in FIG. 1B, a lower coating film 15 may be provided between the metal plate 11 and the upper coating film 13 as a second coating film.

Further, as schematically shown in FIGS. 2A and 2B, in the coated metal plate 1 according to the present embodiment, the upper layer coating film 13 may be provided on both sides of the metal plate 11, or the upper layer coating film 13 and the lower layer coating 15 may be provided on both sides of the metal plate 11.

In addition, the structure of the coated metal plate 1 which concerns on this embodiment is not limited to the structure shown to FIG. 1A-FIG. 2B, For example, the upper-layer coating film 13 and the lower-layer coating film on one side of the metal plate 11 A configuration in which the upper coating 13 or the lower coating 15 is provided on the other surface of the metal plate 11 is also feasible.

The upper layer coating film 13 which is an example of the first coating film has a first portion having a urethane bond skeleton (hereinafter also referred to as "urethane portion") and a second portion having a triazine ring skeleton (hereinafter also referred to as "triazine portion") And the resin coating film containing. Moreover, the glass transition temperature of the upper-layer coating film 13 is 80 degreeC or more and 170 degrees C or less.
Furthermore, as schematically shown in FIG. 3, the second part having a triazine ring skeleton is stained with osmium oxide and observed with a transmission electron microscope at a magnification of 100,000 times, the number average particle diameter is 5 nm. The dispersed second portion (symbol 101 in FIG. 3) in which the above particles are dispersed, and a position from the surface of the upper layer coating film 13 to a depth of 15 nm, particles with a number average particle diameter of 5 nm or more are not observed Both of the concentrated second part (symbol 103 in FIG. 3) are present.

The coated metal plate 1 according to the present embodiment can be a coated metal plate having excellent metal appearance, chemical resistance and solvent resistance, without using an expensive resin such as a fluorocarbon resin, etc., by the above configuration. . The reason is presumed as follows.

First, in order to set the glass transition temperature of the upper layer coating film 13 to 80 ° C. or more and 170 ° C. or less, the urethane portion needs to have a relatively high glass transition temperature. When the upper layer coating film 13 is formed, a high cohesive force is generated in the urethane portion because the urethane portion has a high glass transition temperature. As a result, the triazine moiety is not condensed alone, the triazine moiety is dispersed in the urethane moiety, and the urethane moiety and the triazine moiety are more easily bound. A three-dimensional network structure is formed by bonding the highly solvent resistant triazine moiety to the urethane moiety. As a result, the upper layer coating 13 has an increased barrier property (i.e., chemical resistance). In order to obtain such characteristics, in the present embodiment, the glass transition temperature of the upper coating film 13 is set to 80 ° C. or more and 170 ° C. or less.

In addition, the triazine moiety forms a domain in the upper layer coating 13 and disperses in a granular form (reference numeral 101 in FIG. 3), and by thickening the surface layer of the upper layer coating 13 to form a concentrated portion 103, The triazine moiety having high solvent resistance enhances the solvent resistance of the upper coating film 13. Moreover, as described above, when a high cohesive force is generated in the urethane portion when forming the upper layer coating film 13, the urethane portion and the triazine portion are likely to be preferentially bonded, as schematically shown in FIG. Then, the finely divided particulate triazine portion (hereinafter, also referred to as “triazine particulate matter 101”) is in a state of being concentrated in the surface layer of the upper layer coating film 13. From this point as well, the solvent resistance of the upper coating 13 is further improved.

Then, when the micronized particulate triazine moiety (triazine particulate matter 101) is concentrated in the surface layer of the upper layer coating film 13, light scattering by the triazine moiety is suppressed, and as a result, the transparency of the upper layer coating film 13 is improved. The gloss of the underlying metal plate 11 is easily visible from the outside. Thereby, in the coated metal plate 1 which concerns on this embodiment, a metal external appearance also improves.

As described above, the coated metal plate 1 according to the present embodiment has the above-described configuration, and without using an expensive resin such as a fluorine resin, it has a metal appearance, chemical resistance, and solvent resistance. It is estimated that it is excellent in sex.

Hereinafter, each structure of the coating metal plate 1 which concerns on this embodiment is demonstrated in detail.

<About metal plate 11>
In the coated metal plate 1 according to the present embodiment, various generally known metal plates can be used as the metal plate 11. Specifically, as the metal plate 11, for example, various metal plates and alloy plates such as steel plate, stainless steel plate, aluminum plate, aluminum alloy plate, titanium plate, copper plate and the like can be mentioned. In the coated metal plate 1 according to the present embodiment, various types of plating (not shown) may be applied to the surface of the metal plate 11. The type of plating is not particularly limited, and examples thereof include zinc plating, aluminum plating, copper plating, nickel plating, alloy plating of these, and the like.

In particular, in the case where the metal plate 11 is a plated steel sheet, there is a tendency to be inferior in chemical resistance, so the effect of improving the chemical resistance by providing the upper coating 13 becomes more effective.

The plated steel plate used as the metal plate 11 is not particularly limited, and a galvanized steel plate, an electrogalvanized steel plate, a zinc-nickel alloy plated steel plate, a molten alloyed galvanized steel plate, an aluminum plated steel plate, an aluminum-zinc Generally known various plated steel plates such as alloyed plated steel plates and stainless steel plates can be applied. In particular, using a zinc-based plated steel sheet as the metal plate 11 is more preferable because the corrosion resistance is further improved. Here, the zinc-based plated steel sheet refers to zinc, such as zinc-plated galvanized steel sheet, zinc-nickel alloy plated steel sheet, hot-dip galvanized galvanized steel sheet, aluminum-zinc alloy coated steel sheet, etc. It refers to a plated steel plate in which an alloy with a metal is plated on the surface of the steel plate. The galvanized steel sheet may be any of a galvanized steel sheet, an electrogalvanized steel sheet, and the like.

Moreover, in order to improve the designability of the coated metal plate 1 according to the present embodiment, the surface of the metal plate 11 is textured, roughened, streaked (hairline), woven (satin), squared (hammer), etc. , And various textures may be formed. In the coated metal plate 1 according to the present embodiment, since the transparency of the upper layer coating film 13 is improved by the above-described configuration, the texture as described above is formed on the surface of the metal plate 11 Also, the metallic feeling recalled by such texture is easily visible from the outside.

<About the upper layer coating film 13>
The upper layer coating film 13 of the coated metal plate 1 according to the present embodiment has, as mentioned earlier, a urethane portion (a first portion having a urethane bond skeleton) and a triazine portion (a second portion having a triazine ring skeleton) And a resin coating film containing

Below, each site | part contained in the upper layer coating film 13 is demonstrated.
The urethane bond frame which the urethane part in the upper layer coating film 13 has can be confirmed by analyzing the upper layer coating film 13 by Fourier transform infrared spectroscopy and detecting the vibration peak attributed to the urethane bond. .

The triazine ring skeleton of the triazine moiety is a skeleton derived from the triazine ring contained in the melamine resin. That is, the triazine moiety is a moiety derived from the triazine ring contained in the melamine resin.

The triazine moiety was stained with osmium oxide as described earlier with reference to FIG. 3 and observed with a transmission electron microscope at a magnification of 100,000 to find particles with a number average particle diameter of 5 to 20 nm. The second part of the dispersion type in which the particles are dispersed and the second part of the concentrated type which is present at a depth of 15 nm from the surface of the upper layer coating 13 and in which particles with a number average particle diameter of 5 nm or more are not observed Be done.

Here, as schematically shown in FIG. 3, the concentration portion 103 according to the present embodiment has a range of positions from the surface layer of the upper layer coating film 13 to the depth d (15 nm) toward the metal plate 11 side. It exists inside.
The phrase “the triazine moiety is concentrated in the surface layer of the upper layer coating film 13” means a particulate triazine moiety (ie, triazine particles on the surface side of the upper layer coating film 13 opposite to the interface with the metal plate 11). It is shown that the object 101) is unevenly distributed in layers. That is, it is indicated that the region of the granular triazine site which is unevenly distributed in the layer constitutes the surface layer of the upper coating film 13.
Here, "the triazine moiety is unevenly distributed in a layer form the concentrated portion 103" means that the average concentration (average content) of the triazine moiety in the region where the triazine moiety is unevenly distributed is other than the uneven distribution portion. It means that it is 1.2 times or more of the average concentration of the triazine site in the region.

Here, the triazine moiety according to the present embodiment is dispersed in particles of a number average particle diameter of 5 nm to 20 nm in the upper layer coating film 13 (in other words, the number average particle diameter of triazine particles 101 is 5 nm to 20 nm) And the surface layer within a depth of 15 nm from the surface of the upper layer coating film 13 (in other words, the depth d in FIG. 3 is 15 nm or less).

Here, that the triazine moiety is concentrated in the surface layer within a depth of 15 nm from the surface of the upper layer coating film 13 is unevenly distributed in a layer on the surface side of the upper layer coating film 13 opposite to the interface with the metal plate 11 It shows that the region of the particulate triazine site is present within 15 nm in depth from the surface of the upper layer coating 13. That is, it is shown that the region of the granular triazine site which is unevenly distributed in the layer constitutes the surface layer of the upper layer coating film 13 and has a thickness of 15 nm or less.

If the number average particle size of the particulate triazine moiety (i.e., triazine particulates 101) is less than 5 nm, chemical resistance may decrease. On the other hand, when the number average particle size of the triazine site dispersed in the granular form exceeds 20 nm, the metallic appearance and the chemical resistance penetration of the coated metal plate 1 are lowered, or the metallic appearance, the chemical penetration and the processability are lowered. There is something to do. Here, when the processability of the coated metal sheet 1 is lowered, a crack or the like occurs in the upper layer coating film 13 and the chemical resistance and the solvent resistance are also lowered. The number average particle diameter of the triazine moiety (triazine particle 101) dispersed in the particles is more preferably 5 nm or more and 15 nm or less from the viewpoint of metal appearance, chemical permeability and solvent resistance.

In addition, when the granular triazine moiety is not concentrated in the surface layer of the upper layer coating film 13 (that is, when the concentrated portion 103 is not present), the metal appearance and the solvent resistance may be lowered. Furthermore, when the particulate triazine portion is concentrated from the surface of the upper layer coating 13 to a depth of more than 15 nm (that is, the depth where the concentrated portion 103 is present is more than 15 nm from the surface of the upper layer coating 13) In the case of (1), the processability may be reduced. In the case where the processability of the coated metal sheet 1 is lowered, a crack or the like occurs in the upper layer coating film 13 and the chemical resistance and the solvent resistance are also lowered.

As shown in FIG. 6, it is preferable that a plurality of thickening portions 103 be formed in the upper layer coating film 13. By forming a plurality of concentrated portions 103, the barrier property is further improved, and suitable chemical resistance can be obtained. In order to form the thickened portion 103, the heating method in the upper layer coating film forming process described later is important. This point will be described later.

Here, in the upper layer coating 13 according to the present embodiment, the N concentration N1 at a depth position of 0.2 μm from the surface of the upper layer coating 13 and the upper layer coating 13 from the interface between the upper layer coating 13 and the metal plate 11 N1 / N2 which is a ratio to the N concentration N2 at a depth position of 0.2 μm on the side is 1.2 or more.
By setting N1 / N2 to 1.2 or more, the metal appearance and the solvent resistance can be more reliably improved. More preferably, N1 / N2 is 1.5 or more and 10 or less.

Then, the various analysis methods of the triazine site | part in the upper layer coating film 13 are demonstrated.
First, the upper coating 13 to be analyzed is dyed with osmium oxide. Thereby, the triazine site | part in the upper layer coating film 13 is selectively dyed. Next, a coating film dyed with osmium oxide is cut along a film thickness direction using a microtome, a focused ion beam processing apparatus or the like to prepare a coating film sample whose cross section can be observed. Subsequently, the thin film sample is observed at 100,000 × magnification using a transmission electron microscope. In this observation, the triazine site in the thin film sample is observed black in the STEM-BF (bright field) image and white in the STEM-HAADF (dark field) image.

The triazine site | part in the upper layer coating film 13 can be confirmed by the above analysis methods. The triazine moiety in the upper coating film 13 is subjected to analysis of the coating film by energy dispersive X-ray spectroscopy or Fourier transform infrared spectroscopy to detect nitrogen and osmium, or to be attributed to a triazine ring It can also be confirmed by detecting a vibration peak.

The thickness of the region in which the particulate triazine moiety is concentrated (that is, the thickness of the concentrated portion (thickened second region) 103 which is the region of the particulate triazine moiety unevenly distributed in the layer) is measured by the following method Value. As described above, a thin film sample is observed at a magnification of 100,000 times by a transmission electron microscope to obtain a STEM-BF (bright field) image. The obtained STEM-BF (bright field) image is binarized with, for example, the threshold 120. Then, in the obtained binarized image, the thickness of a layered region observed black from the surface of the upper layer coating film 13 is measured at any 20 locations, and the average value thereof is measured in the region where the triazine moiety is concentrated. Calculated as thickness. In addition, the position where the thickening portion 103 exists is to focus on the position of the lower end (the interface on the metal plate 11 side) of the thickness of the thickening portion 103 obtained as described above in the binarized image. Can be identified. In addition, when the area | region observed in black in layer form is confirmed from the surface of the upper-layer coating film 13, it is considered that the granular triazine site | part is concentrated in the surface layer of the upper-layer coating film 13.

Further, the number average particle diameter of the particulate triazine portion (the number average particle diameter of the triazine particles 101) is a value measured by the following method. As described above, the thin film sample is observed at 500,000 × magnification by a transmission electron microscope to obtain a STEM-BF (bright field) image. The obtained STEM-BF (bright field) image is binarized with, for example, the threshold 120. Then, in the obtained binarized image, the equivalent circle diameter of the granular region observed black is calculated by the equation: equivalent circle diameter = 2 (area / π) 0.5. Note that “area” in the formula indicates the area of a granular region observed black. Then, calculation of the equivalent circle diameter is performed at 20 arbitrarily selected granular regions, and the average value thereof is determined as the number average particle diameter of the granular triazine portion.

Further, the average concentration of the triazine moiety concentrated on the surface side of the upper layer coating 13 can be measured as follows. That is, the distribution in the depth direction of the N element concentration from the surface layer side to the metal plate direction of the upper layer coating film 13 is measured, and the N element concentration N1 at a position of 0.2 μm from the outermost layer, the metal plate or the lower layer The ratio N1 / N2 of the concentration of the N element to N2 at a position 0.2 μm on the surface side from the boundary with the coating film is determined.
Elemental analysis in the direction of depth can be examined by a known method, for example, using Glow Discharge Optical Emission Spectroscopy (GD-OES), Auger Electron Spectroscopy (AES), etc. It is possible.

Next, the glass transition temperature (Tg) of the upper coating film 13 will be described.
The glass transition temperature of the upper coating film 13 is 85 ° C. or more and 170 or less. When the glass transition temperature of the upper layer coating 13 is less than 85 ° C., the chemical resistance of the coated metal sheet 1 is reduced. On the other hand, when the glass transition temperature of the upper layer coating film 13 exceeds 170 ° C., the processability of the coated metal sheet 1 is reduced. When the processability of the coated metal sheet 1 is reduced, cracking or the like occurs in the upper layer coating film 13 and the chemical resistance and the solvent resistance are also reduced. The glass transition temperature of the upper layer coating film 13 is preferably 100 ° C. or more and 170 ° C. or less, more preferably 110 ° C. or more, from the viewpoint of chemical resistance and solvent resistance (particularly, chemical resistance penetration). It is 165 ° C. or less.

Moreover, when the coated metal plate 1 which concerns on this embodiment has the lower layer coating film 15, it is preferable that the glass transition temperature of the upper layer coating film 13 is more than the glass transition temperature of the lower layer coating film 15. When the glass transition temperature of the upper coating film 13 is less than the glass transition temperature of the lower coating film 15, the adhesion between the upper coating film 13 and the lower coating film 15 is reduced, and the chemical resistance is lowered. There is.

On the other hand, it is preferable that the glass transition temperature of the upper layer coating film 13 is higher than the glass transition temperature of the lower layer coating film 15 by 5 ° C. or more. When the difference between the glass transition temperature of the upper layer coating film 13 and the lower layer coating film 15 and the glass transition temperature is 5 ° C. or more, the adhesion between the upper layer coating film 13 and the lower layer coating film 15 is further improved. It becomes easier to improve the quality.

Further, the glass transition temperature of the upper layer coating film 13 is more preferably higher than the glass transition temperature of the lower layer coating film 15 in the range of 10 ° C. to 50 ° C. When the glass transition temperature of the upper coating film 13 is higher by 10 ° C. or more than the glass transition temperature of the lower coating film 15, chemical resistance can be easily enhanced. On the other hand, when the glass transition temperature of the upper layer coating film 13 is higher than the glass transition temperature of the lower layer coating film 15 in the range of 50 ° C. or less, the decrease in the coating film hardness is easily suppressed.

Here, the glass transition temperature (Tg) is a value measured by the following method. First, the coating film to be measured is peeled off or scraped to prepare a measurement sample. And a glass transition point temperature is calculated | required according to the differential scanning calorimetry (DSC method) of the transition temperature measurement method (JISK7121 1987) of plastics using a measurement sample.

It is preferable that the upper-layer coating film 13 does not have a silica. When the upper coating film 13 has silica, the chemical resistance of the upper coating film 13 is deteriorated.
For the same reason, it is preferable that the upper layer coating film 13 does not have at least one metal complex compound selected from zinc, aluminum and titanium. Here, as at least one metal complex compound selected from zinc, aluminum and titanium, for example, zinc stearate, zinc gluconate, zinc picolinate, zinc citrate, zinc acetylacetonate, aluminum acetate, aluminum stearate , Aluminum ethylate, aluminum isopropylate, aluminum triisopoloxide, aluminum ethylacetoacetate diisopropiolate, aluminum trisethylacetoacetate, aluminum tris (acetylacetate), aluminum oxide isopropoxide trimer, titanium tetraisopropoxide, Titanium tetranormal butoxide, titanium butoxide dimer, titanium tetra-2-ethylhexoxide, titanium diisopropoxy bis (acetyl Cetonate), titanium tetraacetylacetonate, titanium dioctyloxybis (octylene glycolate), titanium diisopropoxy bis (ethyl acetoacetate), titanium diisopropoxy bis (triethanol aminate), titanium lactate ammonium salt, titanium Lactate, polyhydroxy titanium stearate and the like can be mentioned.

<About the lower layer film 15>
In the coated metal plate 1 according to the present embodiment, the lower layer coating film 15 is not particularly limited, and polyurethane resin, epoxy resin, acrylic resin, polyester resin, phenol resin, polyolefin resin, alkyd resin, Well-known resin coating films, such as melamine resin and silicone resin, can be applied. In addition, when forming such a resin coating film, it is also possible to use known additives such as a silane coupling agent.

Among these resin coating films, the lower layer coating film 15 has at least a first portion (hereinafter also referred to as a "urethane portion") having a urethane bond skeleton from the viewpoint of metal appearance, chemical resistance and solvent resistance. Preferably, it further comprises a moiety having at least one of an epoxy group and a siloxane bond skeleton (hereinafter, the moiety having an epoxy group is also referred to as “epoxy moiety” and the moiety having a siloxane bond skeleton is also referred to as “siloxane moiety”). It is preferable that it is such a resin coating film. The lower coating film 15 preferably contains a compound having at least one element selected from the group consisting of P, V, Ti, Si and Zr in addition to the above urethane site. .

Here, when the urethane portion further has an anionic functional group, the dispersibility of the urethane portion in the aqueous medium (water-based paint) is improved, and the film forming property of the lower layer coating 15 is enhanced. The adhesion to the metal plate 11 is improved, and the barrier property (that is, chemical resistance) of the lower coating film 15 is enhanced.

The chemical resistance of the lower coating film 15 is also improved by including a urethane portion and at least one of an epoxy group and a siloxane bond skeleton. In addition, by forming the lower coating film 15 as a resin coating film having at least a urethane portion, the transparency of the lower coating film 15 is improved, and the metal appearance also becomes good.

In addition, compounds having at least one element selected from the group consisting of P, V, Ti, Si and Zr generally function as a rust inhibitor in general, but Such compounds may be contained. By including such a compound in the lower coating film 15, the corrosion resistance of the coated metal sheet 1 can be further improved.

Next, each part contained in the lower layer coating film 15 will be described.
As a preferable anionic functional group which a urethane site has, a carboxylic acid group (carboxy group), a sulfonic acid group (sulfo group), etc. can be mentioned, for example. On the other hand, the urethane bond skeleton of the urethane moiety is a skeleton derived from a polyurethane resin. That is, the urethane moiety is a moiety derived from a polyurethane resin, and can be further referred to as a moiety which may have an anionic functional group.

The epoxy moiety having an epoxy group is a moiety derived from an epoxy resin. That is, the epoxy group of the epoxy site is an epoxy group residue which did not react with the urethane site derived from the polyurethane resin. In addition, the siloxane bond skeleton of the siloxane moiety is a skeleton derived from a silicone resin having a siloxane bond or a silane coupling agent capable of forming a siloxane bond.

The urethane bond skeleton of the urethane moiety in the lower coating film 15, the epoxy group of the epoxy moiety, and the siloxane bond skeleton of the siloxane moiety are coated with the lower layer by energy dispersive X-ray spectroscopy or Fourier transform infrared spectroscopy. The film 15 can be analyzed to confirm the element constituting the corresponding bond or functional group or the vibration peak attributed to the corresponding bond or functional group. Further, the presence of a compound having at least one element selected from the group consisting of P, V, Ti, Si and Zr in the lower coating film 15 causes such a compound to be obtained by energy dispersive X-ray spectroscopy. It can be confirmed by whether or not the contained element is detected.

Subsequently, the glass transition temperature of the lower coating film 15 will be described.
The glass transition temperature of the lower coating film 15 is preferably equal to or less than the glass transition temperature of the upper coating film 13. The glass transition temperature of the lower coating film 15 is more preferably in the range of 80 ° C. or more and 170 or less and not more than the glass transition temperature of the upper coating film 13. When the glass transition temperature of the lower coating film 15 is less than 80 ° C., the chemical resistance may decrease. On the other hand, when the glass transition temperature of the lower coating film 15 exceeds 170 ° C., the processability may be lowered. When the processability is lowered, the lower coating film 15 may be cracked and the like, and the chemical resistance and the solvent resistance may also be lowered. The glass transition temperature of the lower coating film 15 is more preferably equal to or less than the glass transition temperature of the upper coating film 13 from the viewpoints of chemical resistance and solvent resistance (in particular, chemical resistance penetration). It is in the range of ° C to 170 ° C.

<About the film thickness of the upper coating 13 and the lower coating 15>
In the coated metal plate 1 which concerns on this embodiment, it is preferable that the film thickness of the above upper layer coating film 13 is 0.5 micrometer or more and 15 micrometers or less. When the film thickness of the upper layer coating film 13 is less than 0.5 μm, the chemical resistance of the coated metal plate 1 may decrease. On the other hand, when the film thickness of the upper layer coating film 13 exceeds 15 μm, the transparency of the upper layer coating film 13 may be reduced and the metal appearance may be reduced. The film thickness of the upper layer coating film 13 is more preferably 1 μm or more and 10 μm or less from the viewpoint of metal appearance and chemical resistance permeability.

In addition, in the coated metal plate 1 according to the present embodiment, when the lower coating film 15 is provided in addition to the upper coating film 13, the film thickness of the lower coating film 15 is preferably 0.5 μm to 15 μm. . By setting the film thickness of the lower coating film 15 to 0.5 μm or more and 15 μm or less, it is possible to further improve the chemical resistance while maintaining the metal appearance. From the viewpoint of chemical resistance, the film thickness of the lower coating film 15 is more preferably more than 1.0 μm and 15 μm or less.

Regarding Colorant in Upper Coating 13 and / or Lower Coating 15
In the coated metal plate 1 according to the present embodiment, the upper coating film 13 and / or the lower coating film 15 as described above may contain a colorant. By incorporating a coloring agent into the upper coating 13 and / or the lower coating 15, the color tone of the product can be adjusted, and it becomes possible to apply to various applications.

Here, when the color pigment is a black pigment, it is preferable to be dispersed in the lower coating film 15. When the black pigment is dispersed in the upper coating film 13, the chemical resistance may be lowered. Such a decrease in chemical resistance is considered to be due to the fact that the black pigment in the upper layer coating film 13 facilitates the penetration of chemicals. The black pigment concentration in the lower coating film 15 is not particularly limited, but is preferably 0.5% by mass or more and 20% by mass or less based on the total solid content of the lower coating film 15, for example. . When the black pigment concentration in the lower coating film 15 is less than 0.5% by mass, coloring may be insufficient. On the other hand, when the black pigment concentration in the lower coating film 15 exceeds 20% by mass, chemical resistance and corrosion resistance may be reduced.

Regarding Specific Configurations of Upper Coating 13 and Lower Coating 15
Specifically, in the coated metal plate 1 according to the present embodiment, the upper layer coating film 13 is a polyurethane resin (a) having a glass transition temperature of 75 ° C. or more and 160 ° C. or less and a triazine ring-containing water soluble curing agent It is preferable that it is a resin coating film (For example, the resin coating film containing the crosslinked material of a polyurethane resin and a water-soluble melamine resin) which hardened the upper layer coating material containing water-soluble melamine resin (b) and an aqueous solvent. The resin coating film formed from the upper layer paint has a glass transition temperature of 85 ° C. or more and 170 ° C. or less as a whole. At this time, the water-soluble melamine resin (b) is in the form of particles dispersed in the upper layer coating film 13 and those in which the water-soluble melamine resin (b) is concentrated on the surface side of the upper layer coating film 13. Moreover, when the lower layer coating film 15 is further provided between the upper layer coating film 13 and the metal plate 11, the glass transition temperature of the said polyurethane resin (a) is the polyurethane resin which the lower layer coating film 15 as follows contains. It is preferable that it is more than the glass transition temperature of (c).

When a polyester resin is used instead of the polyurethane resin, the polyester resin is inferior in chemical resistance to the polyurethane resin, so it is necessary to increase the film thickness of the upper layer coating film in order to obtain the same chemical resistance. . When the film thickness of the upper layer coating film is increased, it is not preferable because a desired metal appearance can not be obtained in the case of forming a clear coating film.

Moreover, when providing the lower layer coating film 15 with respect to the coated metal plate 1 which concerns on this embodiment, the lower layer coating film 15 is specifically a glass transition of the polyurethane resin (a) of the upper layer coating film 13 in glass transition temperature. Any one or more elements selected from the group consisting of a polyurethane resin (c) having a temperature or less, an epoxy resin (d), a silane coupling agent (e), and P, V, Ti, Si and Zr A resin coating film obtained by curing a lower layer coating containing at least one of a rust inhibitor (f) containing an aqueous solvent and an aqueous solvent (for example, a resin coating film containing a crosslinked product of a polyurethane resin (c) and an epoxy resin (d) A resin coating film containing a crosslinked product of a polyurethane resin (c), an epoxy resin (d) and a silane coupling agent (e), a polyurethane resin (c), an epoxy resin (d) and a silane coupling agent (e) of Resin coating film containing a bridge and rust inhibitor (f), resin coating film containing a crosslinked product of polyurethane resin (c) and silane coupling agent (e), polyurethane resin (c) and silane coupling agent (e) And the like, and a resin coating film containing the cross-linked product of (1) and the rust inhibitor (f), a resin coating film containing the polyurethane resin (c) and the rust inhibitor (f), and the like.

In the above, the coated metal plate 1 which concerns on this embodiment was demonstrated in detail.
The coated metal plate 1 according to the embodiment as described above can be used for automobiles, home appliances, building materials, civil engineering, machines, furniture, containers, and the like.

(About the manufacturing method of the painted metal plate)
Then, the manufacturing method of the coated metal plate which concerns on this embodiment is demonstrated in detail, referring FIG. FIG. 4 is a flow chart showing an example of the flow of the method of producing a coated metal sheet according to the present embodiment.

In the method of manufacturing a coated metal plate according to the present embodiment, on at least one side of a predetermined metal plate 11,
This is a method of producing a coated metal sheet 1 having at least the upper coating film 13. The method of manufacturing the coated metal plate includes a texture forming step (step S101) of forming a predetermined texture on the surface of the metal plate 11 as necessary, as shown in FIG. 4 as an example, and a metal plate as necessary. A lower coating film forming step (step S103) for forming the lower coating film 15 on the upper layer 11 and an upper coating film forming step (step S105) for forming the upper coating film 13 on the metal plate 11 or the lower coating film 15; Have.

Here, the texture forming step and the lower layer coating forming step may be carried out as required. For example, the coated metal plate 1 in which the upper layer coating 13 is formed on the metal plate 11 having no texture etc. When manufacturing, only step S105 is implemented among the three steps shown in FIG.

In the method of producing a coated metal sheet shown in FIG. 4, the most important step is the upper layer film forming step (step S105). The upper layer coating film forming step includes a polyurethane resin (a) having an anionic functional group and having a glass transition temperature of 75 ° C. or more and 160 ° C. or less, and a water soluble melamine resin (b) which is a triazine ring-containing water soluble curing agent In the case where the lower layer coating film 15 is formed on the metal plate 11 (upper layer coating material is an example of the first coating material. The upper coating film 13 is formed by coating the lower coating film 15) and heating and cooling the metal plate coated with the upper coating material.

The method for producing a coated metal sheet according to the present embodiment is the coated metal sheet according to the present embodiment (that is, a coated metal sheet excellent in metal appearance, chemical resistance, and solvent resistance) by the above-described method. Can be manufactured while suppressing costs. The reason is guessed as follows.

First, in general, when forming a coating film with a paint containing a polyurethane resin and a water-soluble melamine resin, the melamine resin is less compatible with the polyurethane resin and thus hardly coexists with the polyurethane resin. As the self-condensed particles become larger, a phenomenon occurs in which the melamine resin is concentrated on the surface layer of the coating film.

On the other hand, in the method for producing a coated metal sheet according to the present embodiment, by employing the polyurethane resin (a) containing an anionic functional group, the polyurethane resin (a) and the triazine ring-containing in an aqueous medium The water-soluble melamine resin (b), which is a water-soluble curing agent, is uniformly mixed and coexistent. When the upper layer paint in such a state is formed on the metal plate 11 (or on the lower layer coating film 15) and heated, the self-shrinkage of the water-soluble melamine resin (b) is suppressed, and the water-soluble melamine resin (b) The reaction with the polyurethane resin (a) will occur preferentially. Furthermore, when vaporization (drying) of the aqueous solvent proceeds by heating, the polyurethane resin (a) is in a molten state. When the polyurethane resin (a) is in a molten state, the viscosity is increased because the glass transition temperature is as high as 75 ° C. or more and 160 ° C. or less. As a result, high cohesion is generated and the diffusion speed of the melamine resin (b) is decreased. Thereby, the self-shrinkage of the water-soluble melamine resin (b) is suppressed, and the reaction between the water-soluble melamine resin (b) and the polyurethane resin (a) is preferentially generated.

Thus, while the melamine resin (b) having low compatibility with the polyurethane resin (a) is concentrated to the surface layer of the coating film, the self-shrinkage of the water-soluble melamine resin (b) is suppressed, and the polyurethane resin (a) React preferentially with However, since the self-shrinkage of the water-soluble melamine resin (b) is not completely suppressed, the reaction product of the water-soluble melamine resin (b) reacted with the polyurethane resin (a) in the upper layer coating film 13 And the reaction product resulting from the self-shrinkage of the water-soluble melamine resin (b) coexist. As a result, in the region derived from the water-soluble melamine resin (b), the upper layer coating 13 is dispersed in the form of particles and the upper layer coating 13 is concentrated in the surface layer. Moreover, as described above, when the upper layer coating film 13 is formed, the polyurethane resin (a) has a high cohesive force, so that the reaction between the water-soluble melamine resin (b) and the polyurethane resin (a) It occurs preferentially. Therefore, the micronized particulate water-soluble melamine resin (b) is concentrated in the surface layer of the upper layer coating film 13 to form a concentrated portion 103 as shown in FIG. The micronized particulate water-soluble melamine resin (b), which was not concentrated, forms the triazine particulates 101 as shown in FIG.

When the lower coating film 15 is provided, the lower coating film is formed using a polyurethane resin (c) having a glass transition temperature of 80 ° C. to 160 ° C. and a glass transition temperature lower than that of the polyurethane resin (a). By forming 15, the high adhesion between the upper coating 13 and the lower coating 15 can be realized. Furthermore, by adopting the polyurethane resin (a) containing an anionic functional group, the dispersibility of the urethane portion in the aqueous medium (water-based paint) is improved, and as a result, the film forming property of the upper coating 13 is enhanced. High adhesion between the coating 13 and the lower coating 15 is realized.

As described above, as described in outline, the method of producing a coated metal sheet according to the present embodiment is a coated metal sheet according to the present embodiment (that is, a coated metal sheet excellent in metal appearance, chemical resistance and solvent resistance) Can be manufactured at low cost.

Hereinafter, the manufacturing method of the coated metal plate which concerns on this embodiment is demonstrated in detail.

<About the upper layer film formation process>
Although it is the reverse of the flow shown in FIG. 4, the upper layer coating film forming step will be described in detail below.
In the upper coating film forming step, first, an upper coating, which is an example of the first coating, is prepared. The upper layer paint contains a polyurethane resin (a), a water soluble melamine resin (b) which is a triazine ring-containing water soluble curing agent, and an aqueous solvent.

[Polyurethane resin (a)]
The polyurethane resin (a) is a polyurethane resin containing an anionic functional group and having a glass transition temperature of 75 ° C. or more and 160 ° C. or less. In addition, in the coated metal sheet according to the present embodiment, when not only the upper coating film 13 but also the lower coating film 15 is formed, the glass transition temperature of the polyurethane resin (a) is the polyurethane resin used for the lower coating film 15 It is preferable that it is more than the glass transition temperature of (c).

In order to obtain a high glass transition temperature (85 ° C. or more and 170 ° C. or less) in the upper coating film 13 as mentioned above, it is suitable to use a polyurethane resin having a urethane bond, for example, a high glass transition Point temperature polyester resins are difficult to manufacture. In addition, since a polyurethane resin having a high glass transition temperature has a very high melt viscosity, it is difficult to coat (form a coated film) unless a paint dispersed in an aqueous medium is used. For this reason, by providing the anionic functional group to the polyurethane resin, it becomes possible to disperse in the aqueous medium together with the water-soluble melamine resin.

The polyurethane resin (a) is, for example, polyvalent such as ethylene glycol, propylene glycol, diethylene glycol, 1,6-hexanediol, neopentyl glycol, triethylene glycol, bisphenol hydroxypropyl ether, glycerin, trimethylolethane, trimethylolpropane and the like. It is obtained by reacting an alcohol with a diisocyanate compound such as hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate and the like, and further chain extension with a diamine or the like to achieve water dispersion or the like. Can.

As such polyurethane resin (a), for example, polyether polyurethane resin (polyurethane resin having a polyether skeleton), polyester polyurethane resin (polyurethane resin having a polyester skeleton), polyether polyester polyurethane resin (polyether skeleton and polyester skeleton) Polyurethane resin etc. is preferable. Coatings using these polyurethane resins are likely to have improved chemical resistance and solvent resistance.

The polyether polyurethane resin, the polyester polyurethane resin, and the polyether polyester polyurethane resin can be obtained by using at least one of a polyether polyol and a polyester polyol as polyhydric alcohols.
The polyether polyols are, for example, polyethylene glycol, polyoxyethylene glycol, polyoxypropylene glycol, polytetramethylene glycol and copolymers thereof.
Also, polyester polyols include, for example, dibasic acids such as terephthalic acid, isophthalic acid, adipic acid, azelaic acid, sebacic acid or dialkyl esters of dibasic acids, ethylene glycol, propylene glycol, diethylene glycol, butylene glycol, neopentyl glycol Glycols such as 1,6-hexane glycol, 3-methyl-1,5-pentanediol, 3,3'-dimethyl alcohol heptane, polyoxyethylene glycol, polyoxypropylene glycol, polytetramethylene ether glycol and the like It can be obtained by reaction.
The polyester polyol can be obtained, for example, by ring-opening polymerization of lactones such as polycaprolactone, polyvalerolactone, poly (β-methyl-γ-valerolactone) and the like.

The glass transition temperature of the polyurethane resin (a) is 75 ° C. or more and 160 ° C. or less. If the glass transition temperature of the polyurethane resin (a) is less than 75 ° C., the chemical resistance will decrease. On the other hand, when the glass transition temperature of the polyurethane resin (a) exceeds 160 ° C., the processability is lowered. When the processability is lowered, the upper coating film 13 is cracked and the like, and the chemical resistance and the solvent resistance are also lowered. The glass transition temperature of the polyurethane resin (a) is preferably 100 ° C. or more and 160 ° C. or less from the viewpoints of chemical resistance and solvent resistance (particularly, chemical resistance permeability).

Here, the glass transition temperature of various resins including the above-mentioned polyester resin can be measured according to the differential scanning calorimetry (DSC method) of the plastic transition temperature measurement method (JIS K 7121 1987).

[About water soluble melamine resin (b)]
As the water-soluble melamine resin (b) which is a triazine ring-containing water-soluble curing agent, generally known water-soluble melamine resins (imino-type melamine resin, methylol-type melamine resin, completely alkyl etherified melamine resin, etc.) may be used it can. Examples of commercially available water-soluble melamine resins include water-soluble melamine resins such as those manufactured by Nippon Carbide, Ornex, and DIC.

As the water-soluble melamine resin (b) as described above, it is particularly preferable to use a melamine resin containing an imino group (imino-type melamine resin). By using a melamine resin containing an imino group, the particulate water-soluble melamine resin is easily concentrated in the surface layer of the upper layer coating film 13, so that the solvent resistance can be more easily improved.

In addition, "water solubility" shows that the dissolution amount of the object substance with respect to 100 mass parts of water of 25 degreeC is 5 mass parts or more (preferably 10 mass parts or more).

[About coloring agent]
The colorant to be dispersed in the upper layer paint containing the components as described above is not particularly limited, and known colorants can be appropriately used. As such a colorant, for example, various inorganic pigments such as titanium oxide, zinc oxide, calcium carbonate, aluminum oxide, barium sulfate, aluminum, iron oxide, copper-chromium composite oxide, carbon black, cyanine, quinacridone, etc. Various organic pigments of the above, various dyes and the like can be used.

If the colorant to be used is a black pigment such as carbon black or a metal oxide exhibiting black color, the chemical resistance may decrease, so the concentration in the upper layer paint is limited or dispersed in the lower layer paint. It is preferable to disperse in the lower layer paint.

The type of carbon black dispersed in the upper layer paint is not particularly limited, and for example, known carbon blacks such as furnace black, ketjen black, acetylene black, channel black and the like can be used.

The particle size of the carbon black used is not particularly limited as long as there is no problem in the dispersibility in the paint, the quality of the coating film, and the paintability, but the primary particle size of about 10 to 120 nm is used Cheap. In particular, when chemical resistance or corrosion resistance is required, it is preferable to use one having a primary particle diameter of 10 to 50 nm. It is generally difficult to disperse these carbon blacks as they are the primary particle size, because aggregation occurs in the process of dispersing in a paint. That is, in practice, it is present in the paint in the form of secondary particles having a particle size larger than the primary particle size. The same form exists in such upper layer paint.

The type of metal oxide exhibiting black color is not particularly limited, and, for example, known black pigments such as triiron tetraoxide and copper-chromium composite oxide can be used.

[About aqueous solvent]
Examples of the aqueous solvent include water or a mixed solution of water and a lower alcohol. Such an aqueous solvent may contain 50% by mass or more (preferably 80% by mass or more) of water.
When a solvent typified by an organic solvent is used as the solvent, it is not preferable because the melamine particles are dispersed and present in the coating film and the surface is not concentrated. As described above, in order to concentrate the surface layer of melamine in a coating film formed using a solvent-based paint, it is necessary that the solvent-based paint contain an amine compound, but in the present embodiment, an aqueous solvent is used. It is possible to concentrate melamine particles on the surface without using an amine compound.

As water, distilled water, ion exchange water, ultrapure water, ultrafiltered water, etc. can be mentioned. Moreover, as a lower alcohol, C1-C4 alcohol, such as methanol, ethanol, butanol, isopropyl alcohol etc., can be mentioned.

[About the content]
In the upper layer paint containing the components as described above, the content (Wa, unit: mass%) of the polyurethane resin (a) to the total solid content and the content (Wb) of the water-soluble melamine resin (b) to the total solid content The total content (Wa) + (Wb) of (unit: mass%) satisfies the following formula (11), and the content (Wa) of the polyurethane resin (a) and the water solubility The ratio (Wb) / (Wa) of the content (Wb) of the melamine resin (b) preferably satisfies the following formula (13).
90 mass% ≦ (Wa) + (Wb) ≦ 100 mass% formula (11)
0 <(Wb) / (Wa) ≦ 1 formula (13)

Here, in the above formula (11), when the total content (Wa) + (Wb) is less than 90% by mass, the metal appearance, the chemical resistance and the solvent resistance of the coated metal sheet 1 are lowered. Sometimes. Moreover, in said Formula (13), when ratio (Wb) / (Wa) exceeds 1, water-soluble melamine resin (b) may become excess and the workability of the coating metal plate 1 may fall. When the processability is lowered, the upper coating film 13 is cracked and the like, and the chemical resistance and the solvent resistance are also lowered.

From the viewpoint of metal appearance, chemical permeability and solvent resistance, the total content (Wa) + (Wb) satisfies the following formula (15), and the ratio (Wb) / (Wa) is as follows: It is more preferable to satisfy the equation (17) of
95 mass% ≦ (Wa) + (Wb) ≦ 100 mass% formula (15)
0.1 ≦ (Wb) / (Wa) ≦ 0.3 formula (17)

The upper layer paint preferably does not have silica. When the upper layer coating material contains silica, the upper layer coating film 13 contains silica, and as a result, the chemical resistance of the upper layer coating film 13 is deteriorated.
For the same reason, the upper layer paint preferably does not have at least one metal complex compound selected from zinc, aluminum and titanium. Here, as at least one metal complex compound selected from zinc, aluminum and titanium, for example, zinc stearate, zinc gluconate, zinc picolinate, zinc citrate, zinc acetylacetonate, aluminum acetate, aluminum stearate , Aluminum ethylate, aluminum isopropylate, aluminum triisopoloxide, aluminum ethylacetoacetate diisopropiolate, aluminum trisethylacetoacetate, aluminum tris (acetylacetate), aluminum oxide isopropoxide trimer, titanium tetraisopropoxide, Titanium tetranormal butoxide, titanium butoxide dimer, titanium tetra-2-ethylhexoxide, titanium diisopropoxy bis (acetyl Cetonate), titanium tetraacetylacetonate, titanium dioctyloxybis (octylene glycolate), titanium diisopropoxy bis (ethyl acetoacetate), titanium diisopropoxy bis (triethanol aminate), titanium lactate ammonium salt, titanium Lactate, polyhydroxy titanium stearate and the like can be mentioned.

[About the film forming method (coating method)]
The method of forming (coating) the upper layer coating on the metal plate 11 or the lower layer coating 15 in the upper layer coating forming step is not particularly limited, and, for example, a roll coating method, a ringer roll coating method, an air spray Well-known film-forming methods (coating method), such as a method, an airless spray method, an immersion method, can be utilized. In addition, if film formation is performed in a continuous coating line called a coil coating line or sheet coating line, complete with a film forming apparatus (coating apparatus) for performing these known film forming methods (coating methods), the coating operation efficiency is good and a large amount It is more preferable because production is possible.

[About heating method (baking method) and cooling method]
There is no particular limitation on the method of heating the film of the upper layer coating after the upper layer coating is formed (coated) on the metal plate 11 or the lower layer coating 15 in the upper layer coating film forming step, for example, hot air Generally known devices such as ovens, open flame ovens, far infrared ovens, induction heating ovens and the like can be used. By heating the film of the upper layer paint, the aqueous solvent present in the film of the upper layer paint is dried, and then the polyurethane resin (a) and the water-soluble melamine resin (b) react to form the upper layer coating film 13 It is formed.

On the other hand, the method for cooling the upper layer coating film 13 after heating is not particularly limited, but for example, a known method such as water cooling (spray, submersion, etc.), air cooling (spray of nitrogen gas, etc.), etc. can do.

In the upper layer coating film forming step, in particular, after film formation of the upper layer paint, heating is performed under the condition that the heating time from the heating start to the highest reaching temperature is 1 second to 30 seconds, and from the highest reaching temperature to 30 ° C. It is preferable to form the upper coating film 13 by cooling under the condition that the cooling time is 0.1 seconds or more and 5 seconds or less. Here, the heating time and the cooling time are measured by detecting the temperature of the metal plate with a thermocouple.

If heating is performed in a short time such as 1 second to 30 seconds as described above after the film formation of the upper layer paint, the self-shrinkage of the water-soluble melamine resin (b) is further suppressed, and 0.1 as described above When the cooling is performed in a short time of 2 seconds to 5 seconds, the diffusion of the water-soluble melamine resin (b) is suppressed. As a result, the water-soluble melamine resin (b) reacted with the polyurethane resin (a) forms a domain, and is dispersed in the upper layer coating 13 in particles having a number average particle diameter of 5 nm to 20 nm. It tends to be in the state of being concentrated in the surface layer within 15 nm in depth from the surface of. For this reason, in the coated metal plate 1 manufactured, the metal appearance, the chemical resistance and the solvent resistance can be further easily improved.

Here, if the heating time is less than 1 second, the reaction between the polyurethane resin (a) and the water-soluble melamine resin (b) may be insufficient and the chemical resistance and the solvent resistance may be lowered. . On the other hand, when the heating time exceeds 30 seconds, the water-soluble melamine resin (b) tends to be self-condensed, the self-condensed particles become large, and the phenomenon occurs that the film is concentrated to the surface layer. In the coated metal plate 1, the metal appearance and the chemical resistance may decrease.

In addition, when the cooling time is less than 0.1 seconds, the upper layer coating film 13 may be cracked as a result of rapid cooling. On the other hand, when the cooling time exceeds 5 seconds, diffusion of the water-soluble melamine resin (b) occurs, and the metal appearance and chemical resistance permeability may decrease in the manufactured coated metal plate 1.

The heating time is preferably 1 second or more and 20 seconds or less from the viewpoint of metal appearance, chemical resistance, and solvent resistance. Moreover, it is preferable that cooling time is 0.1 second or more and 2 seconds or less from the same viewpoint.

In addition, the maximum reaching temperature and the holding time thereof are not particularly limited, and may be, for example, 0.1, after appropriately setting the maximum reaching temperature to be the boiling point or more of the aqueous solvent according to the aqueous solvent used. The holding time may be set in the range of seconds to 5 seconds.

Further, in the case of forming a plurality of concentrated portions 103 with the upper layer coating film 13, first, heating is performed to a temperature of 40 to 100 ° C. for 1 to 20 seconds. Next, it is heated to over 200 ° C. in 1 to 10 seconds. Then cool. By forming the upper-layer coating film 13 in this manner, in addition to the concentrated portion 103 of the surface layer, the concentrated portion 103 is also formed at depth positions other than the surface layer.

The upper layer coating film forming process according to the present embodiment has been described above in detail.

<About the lower layer film formation process>
Then, the lower layer coating-film formation process in the manufacturing method of the coated metal plate which concerns on this embodiment is demonstrated.
In the method of producing a coated metal sheet according to the present embodiment, the lower coating film forming step is not particularly limited, and a known lower coating is used as an example of the second coating, and the lower coating 15 is formed by a known method. It can be formed.

Among the well-known methods, from the viewpoint of metal appearance, chemical resistance and solvent resistance, the lower coating film forming step contains an anionic functional group, and the glass transition temperature is not higher than the glass transition temperature of the polyurethane resin (a) A certain polyurethane resin (c), an epoxy resin (d), a silane coupling agent (e), and at least one element selected from the group consisting of P, V, Ti, Si and Zr The lower layer paint containing at least one of the rust preventive agent (f) and the aqueous solvent is formed into a film and heated on at least one surface of the metal plate 11 and then cooled to form the lower layer coating film 15 Is preferred.

[Polyurethane resin (c)]
As mentioned earlier, the glass transition temperature of the polyurethane resin (c) is preferably equal to or less than the glass transition temperature of the polyurethane resin (a). When the glass transition temperature of the polyurethane resin (c) is equal to or lower than the glass transition temperature of the polyurethane resin (a), the adhesion between the lower coating 15 and the upper coating 13 is improved, and the chemical resistance is further improved. It will be easier.

The glass transition temperature of the polyurethane resin (c) is a value within the range of 80 ° C. or more and 160 ° C. or less, and less than or equal to the glass transition temperature of the polyurethane resin (a) (preferably, the glass transition temperature of the polyurethane resin (a) It is more preferable that the temperature is lower than 5 ° C.). If the glass transition temperature of the polyurethane resin (c) is less than 80 ° C., the chemical resistance may decrease. On the other hand, when the glass transition temperature of the polyurethane resin (c) exceeds 160 ° C., the processability may be lowered. When the processability is lowered, the lower coating film 15 is cracked and the like, and the chemical resistance and the solvent resistance are also lowered. The glass transition temperature of the polyurethane resin (c) is preferably in the range of 100 ° C. or more and 160 ° C. or less from the viewpoints of chemical resistance and solvent resistance (in particular, in terms of chemical resistance).

The polyurethane resin (c) may be a polyurethane resin containing a polyurethane resin having a glass transition temperature of 80 ° C. to 160 ° C. and a polyurethane resin having a glass transition temperature of 20 ° C. to 60 ° C. By using a polyurethane resin having a different glass transition temperature and adjusting the glass transition temperature of the polyurethane resin (c), chemical resistance can be further improved.

In addition, as a specific kind of polyurethane resin (c), the various polyurethane resin illustrated by the polyurethane resin (a) can be mentioned.

[Epoxy resin (d)]
Examples of the epoxy resin (d) include bisphenol A epoxy resin, bisphenol F epoxy resin, novolac epoxy resin, aliphatic epoxy resin and the like. Among these resins, since the aliphatic epoxy resin is hardly discolored by baking, it is particularly preferable to use as the epoxy resin (d).

The specific type of these epoxy resins (d) is not particularly limited, and various commercially available epoxy resins (d) can be used, and the glass transition temperature is within the above range. It is possible to synthesize such a thing by itself and use it appropriately.

[Silane Coupling Agent (e)]
The silane coupling agent (e) is not particularly limited, and various known silane coupling agents can be used. As such a silane coupling agent, for example, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, N-2- (amino) Ethyl) -3-aminopropyltriethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, bis (trimethoxysilylpropyl) amine, 3-glycidoxypropyltrimethoxysilane, 3-glylic Examples thereof include cidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane and the like. By containing such a silane coupling agent in the lower layer paint, it is possible to further improve the chemical resistance of the lower layer coating film 15.

[About the rust inhibitor (f)]
In the lower coating film forming step according to this embodiment, a rust inhibitor containing at least one element selected from the group consisting of P, V, Ti, Si and Zr as a rust inhibitor (f) is used. It is possible to use. The corrosion resistance of the lower coating film 15 can be improved by incorporating the rust inhibitor (f) in the lower coating material.

Examples of P-containing compounds that function as antirust agents (f) include phosphoric acids such as orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, triphosphoric acid, tetraphosphoric acid and the like, salts thereof, and aminotri (methylene phosphonic acid ), Phosphonic acids such as 1-hydroxyethylidene-1,1-diphosphonic acid, ethylenediaminetetra (methylene phosphonic acid), diethylene triamine penta (methylene phosphonic acid) and salts thereof, organic phosphoric acids such as phytic acid, and salts thereof Etc. can be mentioned.

As a compound containing V which functions as a rust inhibitor (f), for example, vanadium pentoxide, metavanadic acid, ammonium metavanadate, sodium metavanadate, vanadium oxytrichloride, vanadium trioxide, vanadium dioxide, vanadium oxysulfate, Examples thereof include vanadium oxyacetylacetonate, vanadium acetylacetonate, vanadium trichloride, phosphorus vanadomolybdic acid and the like. In addition, an organic compound having at least one functional group selected from the group consisting of a hydroxyl group, a carbonyl group, a carboxyl group, a primary to tertiary amino group, an amide group, a phosphoric acid group and a phosphonic acid group in a pentavalent vanadium compound , A salt of oxovanadium cation and an inorganic acid anion such as hydrochloric acid, nitric acid, phosphoric acid or sulfuric acid, or an organic acid anion such as formic acid, acetic acid, propionic acid, butyric acid or oxalic acid And chelates of vanadyl compounds with organic acids such as vanadyl glycolate and vanadyl dehydroascorbate can be used.

Examples of the Ti-containing compound which functions as a rust inhibitor (f) include, for example, titanium oxalate potassium, titanyl sulfate, titanium chloride, titanium lactate, titanium isopropoxide, isopropyl titanate, titanium ethoxide, titanium 2-ethyl oxide -1-Hexanolate, tetraisopropyl titanate, tetra-n-butyl titanate, titania sol, titanium hydrofluoric acid or salts thereof and the like can be mentioned.

Examples of compounds containing Si that function as antirust agents (f) include Snowtex C, Snowtex O, Snowtex N, Snowtex S, Snowtex UP, Snowtex PS-M, and Snowtex PS-L. Colloidal silica such as Snowtex 20, Snowtex 30, Snowtex 40 (all manufactured by Nissan Chemical Industries, Ltd.), Adelite AT-20N, Adelite AT-20A, Adelight AT-20Q (both manufactured by Asahi Denka Kogyo Co., Ltd.) And aerosols such as Aerosil 50, Aerosil 130, Aerosil 200, Aerosil 300, Aerosil 380, Aerosil TT600, Aerosil MOX 80, Aerosil MOX 170 (all manufactured by Nippon Aerosil Co., Ltd.) and the like.

As a compound containing Zr which functions as an antirust agent (f), for example, zirconyl nitrate, zirconyl acetate, zirconyl sulfate, ammonium zirconium carbonate, potassium zirconium carbonate, sodium zirconium carbonate, zirconium acetate, zirconium hydrofluoric acid or the same Salt etc. can be mentioned.

[About coloring agent]
The colorant to be dispersed in the lower layer paint containing the components as described above is not particularly limited as in the case of the upper layer paint, and known materials can be suitably used. As such a coloring agent, for example, various inorganic pigments such as titanium oxide, zinc oxide, calcium carbonate, aluminum oxide, barium sulfate, aluminum, iron oxide, carbon black and the like, various organic pigments such as cyanine and quinacridone, Various dyes and the like can be used.

[About aqueous solvent]
As the aqueous solvent, water, a mixed solution of water and a lower alcohol, or the like can be used as in the above-mentioned upper layer paint. The aqueous solvent preferably contains 50% by mass or more (preferably 80% by mass or more) of water.

[About the content]
The content of the polyurethane resin (c), the epoxy resin (d), the silane coupling agent (e) and the rust inhibitor (f) as described above is not particularly limited, and the lower coating film 15 The content of each component may be appropriately determined in accordance with the characteristics to be obtained. For example, the content of the polyurethane resin (c) can be in the range of 30 to 95% by mass, and the content of the epoxy resin (d) can be in the range of 1 to 5% by mass It is possible. Further, the content of the silane coupling agent (e) can be, for example, in the range of 10 to 40% by mass, and the content of the antirust agent (f) is, for example, in the range of 1 to 15% by mass It is possible to do inside. The content of each component is within the above range so that the total content of these polyurethane resin (c), epoxy resin (d), silane coupling agent (e) and rust inhibitor (f) is 100% by mass. It may be determined appropriately.

[About a film forming method (coating method), a heating method (baking method) and a cooling method]
There is no particular limitation on the method of forming and heating the lower layer coating on at least one side of the metal plate 11 in the lower layer coating forming step, and there is no particular limitation. For example, various methods as described in the upper layer coating forming step A film forming method (coating method), a heating method and a cooling method can be used. In addition, the maximum attainable temperature, the heating time, the holding time, and the cooling time of the metal plate 11 coated with the lower layer paint are not particularly limited, and may be set as appropriate.

<About other ingredients>
In the method of producing a coated metal sheet according to the present embodiment, the upper layer paint and the lower layer paint may contain known additives such as a wax, a leveling agent, an antifoamer, a thickener, a dispersant, etc. Good. That is, in the coated metal sheet according to the present embodiment, the upper coating film 11 and the lower coating film 15 may contain any of these known additives.

<About the texture formation process>
In the method of producing a coated metal sheet according to the present embodiment, the surface of the metal sheet 11 to which the upper layer paint as described above is applied is, as required, textured, roughened, streaks (hair lines), weaves (satins), squares Various textures such as (hammer) may be formed. By previously forming the texture as described above on the surface of the metal plate 11, it is possible to further improve the design of the coated metal plate according to the present embodiment.

Here, the method and apparatus for forming the various textures as described above are not particularly limited, and various known ones can be appropriately used.

As mentioned above, the manufacturing method of the paint metal plate concerning this embodiment was explained in detail.

Below, the manufacturing method of a coated metal plate and a coated metal plate concerning the present invention is explained more concretely, showing an example and a comparative example. In addition, the Example shown below is only an example of the manufacturing method of the coating metal plate which concerns on this invention, and a coating metal plate only, and the manufacturing method of the coating metal plate which concerns on this invention, and a coating metal plate is limited to the following example. It is not something to be done.

(Test Example 1) <Metal plate (original plate)>
Hot-dip galvanized steel sheet "NS Silver Zinc (registered trademark)" manufactured by Nippon Steel & Sumikin Co., Ltd. (hereinafter referred to as "GI"), electrogalvanized steel sheet "NS Gin Coat (registered trademark) manufactured by Nippon Steel & Sumikin Co., Ltd. (Hereinafter referred to as “EG”), zinc-nickel alloy plated steel sheet “NS zincite (registered trademark)” (hereinafter referred to as “ZL”) manufactured by Nippon Steel & Sumikin Co., Ltd., zinc-iron Alloy plating "NS Silver Alloy (registered trademark)" (hereinafter referred to as "GA"), aluminum plate "JIS 3004" (hereinafter referred to as "Al"), stainless steel plate "SUS430" (hereinafter referred to as "SUS" ), Zinc-Aluminum-Magnesium-Silicon Alloy Plated Steel Sheet “Super Dima (registered trademark)” (hereinafter referred to as “SD”) manufactured by Nippon Steel & Sumikin Co., Ltd., Nisshin Steelmaking Co., Ltd. Zinc made Formula Company - aluminum - magnesium alloy plated steel sheet "ZAM (registered trademark)" (. Hereinafter referred to as "ZAM") was used as the metal plate (original plate). The thickness of each of the metal plates was 0.6 mm.

The plating adhesion amount of ZL was 20 g / m ² per one side, and the amount of nickel in the plating layer was 12% by mass. Moreover, the plating adhesion amount of GI, SD, GL, and ZAM was 60 g / m ² per one side, respectively. The plating adhesion amount of GA was 45 g / m ² per one side. The plating adhesion amount of EG was 20 g / m ² per one side.

<Paint>
In this test example, the single-layer structure as shown in FIG. 1A having only the upper coating film, or the FIG. 1B having the lower coating film and the upper coating film on one surface of the metal plate (original plate) as described above. The coated metal plate of the two-layer structure as shown was produced. Here, polyurethane resins used for preparation of the upper layer paint and the lower layer paint are shown in Table 1 below. Similarly, polyester resins, water-soluble melamine resins, silane coupling agents, rust inhibitors, and colorants used for the preparation of the lower layer paint are shown in Tables 2 to 7 below, respectively.

[Self-made polyurethane resin A]
Add 145 g of 1,3-bis (isocyanate methyl) cyclohexane, 20 g of dimethylol propionic acid, 15 g of neopentyl glycol, 75 g of polycarbonate diol having a molecular weight of 1000, 64 g of acetonitrile as a solvent, raise the temperature to 75 ° C under a nitrogen atmosphere, Stir for hours. After confirming that the predetermined amine equivalent was reached, the reaction solution was cooled to 40 ° C., and then 30 g of triethylamine (boiling point 89 ° C.) was added to obtain an acetonitrile solution of polyurethane prepolymer. 300 g of this solution was dispersed in 700 g of water using a homodisper to form an emulsion, the solution was kept at 40 ° C., and chain extension reaction was carried out by adding 35.6 g of ethylenediaminehydrazine monohydrate as a chain extender. Then, the self-made polyurethane resin A was obtained by distilling away the acetonitrile used at the time of 50 degreeC and a pressure reduction of 150 mmHg for polyurethane prepolymer synthesis at the reduced pressure.
In addition, the triethylamine used as a raw material is removed at the refinement | purification process of resin.

[Self-made polyurethane resin B]
Add 145 g of 1,3-bis (isocyanate methyl) cyclohexane, 20 g of dimethylol propionic acid, 15 g of neopentyl glycol, 75 g of polycarbonate diol having a molecular weight of 1000, 64 g of acetonitrile as a solvent, raise the temperature to 75 ° C under a nitrogen atmosphere, Stir for hours. After confirming that the predetermined amine equivalent was reached, the reaction liquid was cooled to 40 ° C., and then 20.00 g of triethylamine (boiling point 89 ° C.) was added to obtain an acetonitrile solution of a polyurethane prepolymer. 300 g of this solution is dispersed in 70. 00 g of water using a homodisper to form an emulsion, the solution is kept at 40 ° C., 21 g of γ- (2-aminoethyl) aminopropyltrimethoxysilane as a chain extender, and ethylenediaminehydrazine The chain extension reaction was carried out by adding 18 g of monohydrate. Subsequently, the acetonitrile used at the time of polyurethane prepolymer synthesis was distilled off at 50 ° C. under a reduced pressure of 150 mmHg to obtain a self-made polyurethane resin B.
In addition, the triethylamine used as a raw material is removed at the refinement | purification process of resin.

The upper layer paint and the lower layer paint were respectively manufactured by using the materials shown in Tables 1 to 7 and mixing predetermined amounts of each material with water according to the description of Table 8 and Table 9.

In Table 9, in the lower layer paints 9, 10 and 11, the main resin-2 was blended at a ratio of 15 parts by mass with respect to 100 parts by mass of the main resin-1.

<Manufacturing of painted metal sheets>
Various metal plates were degreased by immersion for 10 seconds in an aqueous solution at 60 ° C. temperature containing 2% by mass of FC-4336 (manufactured by Nippon Parkerizing Co., Ltd.), washed with water and dried.

Next, the lower layer paint manufactured as mentioned above was each coated with a roll coater so as to obtain a predetermined film thickness with a dry film thickness. In the induction heating furnace blown with hot air, the film of the lower layer paint is heated (dried) under the condition that the maximum temperature of the metal plate reaches 150 ° C and the heating time from the start of heating to the maximum temperature is 10 seconds Cured). One second after reaching the maximum reaching temperature, the coated metal plate was sprayed with water by a spray, and water cooling was performed under the condition that the cooling time from the maximum reaching temperature to 30 ° C. was 1 second. In addition, the holding time of the highest reach | attainment temperature at the time of a heating was 1 second.

Next, the upper layer paint manufactured as mentioned above was each coated with a roll coater so as to have a predetermined film thickness with a dry film thickness. In the induction heating furnace blown with hot air, the film temperature of the upper layer paint is heated (dry-cured) under the condition that the maximum temperature of the metal plate reaches 230 ° C and the heating time from the start of heating to the maximum temperature is 10 seconds. did. One second after reaching the highest reaching temperature, spray the water onto the painted metal plate with a spray, and one second after reaching the highest reaching temperature, wipe the water onto the painted metal plate with a spray. Water cooling was performed under the condition that the cooling time from the highest temperature to 30 ° C. was 1 second. In addition, the holding time of the highest reach | attainment temperature at the time of a heating was 1 second.

<Level>
The composition of the upper-layer coating film and the lower-layer coating film was analyzed about the sample of each manufactured coated metal plate.
Specifically, the upper coating film and the lower coating film constituting site (urethane bond skeleton (UB), triazine ring skeleton (TR), epoxy group (EP), presence of siloxane bond (silane) derived from silane coupling agent) The coating film was analyzed using a Fourier transform infrared spectrophotometer (FT-IR, PerkinElmer Frontier), and it was judged based on whether or not the vibration peak shown below was observed. When it was done, it described in the table as "presence".
Urethane bond backbone (UB): 1540cm ^-1 are observed in the vicinity of the N-H vibrational peak of bending vibration, and the vibration peak triazine ring skeleton of C = O stretching vibration is observed near 1730cm ^-1 (TR): 1550,1450,815Cm ^-1 vibrational peak epoxy group derived from triazine ring observed in the vicinity (EP): 910cm ^-1 from epoxy groups observed in the vicinity of the vibration peak siloxane bond: 1050 cm ^-1 Si observed in the vicinity Peak of -O-Si stretching vibration

Further, according to the method described above, in the upper layer coating film, the thickness (depth of concentration) of the concentrated portion present in the surface layer, and the number average particle diameter (particle diameter) of the particulate triazine portion (water soluble melamine resin) ) Were each measured. Also, an N concentration N1 at a depth of 0.2 μm from the surface of the first coating and an N concentration N2 at a depth of 0.2 μm from the interface between the first coating and the metal plate on the first coating side The ratio of N1 / N2 (concentration factor) was measured according to the method described above. Furthermore, the glass transition temperature (Tg) of each coating film was measured according to the method described above for each of the manufactured coated metal sheet samples.
In addition, whether the surface concentrated part is stained with osmium oxide and observed at a magnification of 100,000 times using a transmission electron microscope, whether or not melamine particles of 5 nm or more are observed, and a plurality of concentrated parts are formed It was determined according to the method described above whether or not it was.

<Evaluation method>
Each of the manufactured coated metal sheets was evaluated based on the criteria shown below.

[Metal appearance]
The L *, a *, b * color system of CIELAB (JIS Z8729) was measured for each of the manufactured coated metal plates with a CR-400 spectrocolorimeter (light source 10 ° D 65, SCI method) manufactured by Konica Minolta, (Excellent) A, B, C, D (Degraded) rated in four steps.
A: L * is 60 or more, and | a * | ≦ 1
B: L * is less than 60 and | a * | ≦ 1
C: L * is less than 60 and | a * || 1
D: L * is less than 60, | a * | ≧ 1, and | b * | ≧ 6

[Chemical resistance penetration test]
Each coated metal plate manufactured is cut into a width of 5 cm, and all the end faces are protected with Nitoflon (registered trademark) tape, the sample is dipped in 5% sulfuric acid water and 5% sodium hydroxide water at 20 ° C for 24 hours to change color The degree of was evaluated in four grades of (excellent) A, B, C, D (inferior).
A: No color change A-B: Very slight color change B: Slight color change C: Many color change D: Many color change and film peeling

[Processability test]
Each coated metal plate manufactured was cut into a width of 5 cm, and 2 T bending was performed in an atmosphere of 20 ° C. by a test method according to JIS G3312. Specifically, two coated plates identical to the test piece were sandwiched inside, and the surface on which the upper coating film and the lower coating film were formed was placed outside, and the contact bending was performed 180 degrees. The cracks of the coating film were evaluated in four grades of (excellent) A, B, C and D (inferior).
A: no cracks B: slight cracks C: many cracks D: many cracks and peeling of coating

[Stain resistance test]
To each of the manufactured coated metal plates, apply Magic Ink (Teranishi Chemical Industry Co., Ltd.) red color, wipe it off with ethanol after 24 hours, and mark the traces of ink (excellent) A, B, C, D (inferior) It was evaluated in four stages. In addition, about the thing whose mark residue is remarkable, using a commercially available spectrocolorimeter (light source 10 ° D 65, SCI method), measure the a * value representing the redness of CIELAB (JIS Z8729) before and after the test, and the difference It was evaluated as follows by (Δa *).
A: No mark remaining B: Mark left slightly C: Δa * ≦ 3
D: Δa *> 3

The level of each coated metal plate manufactured and the evaluation results are listed in Table 10 and listed. The abbreviations and the like in Table 10 are as follows. The same applies to the other tables for abbreviations and the like.
UB: Urethane bond frame TR: Triazine ring frame EP: Epoxy group Silane: Siloxane bond Antirust agent: Antirust agent (f)
Thickening depth: Thickness of thickened portion (sometimes referred to as surface thickened portion) formed on surface layer Particle diameter: Number average particle diameter of triazine particles (water-soluble melamine resin) Tg: Each coating Glass transition temperature of the film Tg difference: difference in glass transition temperature between upper and lower coating films (glass transition temperature of upper coating film-glass transition temperature of lower coating film)

As apparent from the above Table 10-1 and Table 10-2, it can be understood that the coated metal sheet corresponding to the example of the present invention is excellent in metal appearance, chemical resistance, solvent resistance and processability. .

On the other hand, as apparent from the above Table 10-2, when a concentrated layer is not formed on the surface layer of the upper layer coating film 13 (when the surface layer is observed at 100,000 times, melamine particles having a number average particle diameter of 5 nm or more are In the case where it is observed (Comparative Example 105), it can be seen that the chemical resistance is clearly inferior to that of the example. In the case where the upper layer coating film 13 does not have a urethane bond skeleton (Comparative Example 104), it can be seen that the chemical resistance penetration is clearly inferior to that of the example. In the case where there is no triazine ring skeleton and the granular triazine portion is not concentrated also on the surface layer of the upper layer coating film (Comparative Example 103), it can be seen that the chemical resistance permeability and the solvent resistance are clearly inferior to those of Examples. . In the case where the glass transition temperature of the upper coating film 13 is less than 80 ° C. (Comparative Example 101), it can be seen that the chemical resistance permeability is clearly inferior to that of the example. In the case where the glass transition temperature of the upper coating film 13 is higher than 170 ° C. (Comparative Example 102), the processability is clearly inferior, and it can be seen that the chemical resistance permeability and the solvent resistance decrease when processing is performed. .

Further, as is clear from Table 10-2, when the upper layer paint contains silica (Comparative Example 106), the chemical resistance and the stain resistance are inferior to those of Examples.
When the upper layer paint contained a metal complex (Comparative Examples 107, 108, 109), the chemical resistance was inferior to that of Examples.

Moreover, in the upper layer coating film 13, when the granular triazine portion is concentrated to a position beyond 15 nm from the surface layer (Example 143), the processability is lowered compared to the other examples, and the processing is performed. It can be seen that the chemical resistance and the solvent resistance decrease when the In addition, when the glass transition temperature of the lower coating film 15 is higher than the glass transition temperature of the upper coating film 13 (Example 146), it can be seen that the chemical resistance is inferior to that of the other examples.

(Test Example 2) <Metal plate (original plate)>
An electrogalvanized steel sheet "NS Gin Coat (registered trademark)" (hereinafter referred to as "EG") manufactured by Nippon Steel & Sumikin Co., Ltd. was used as a metal sheet (original sheet). The plating adhesion amount of EG was 20 g / m ² per one side.

<Paint>
In this test example, the single-layer structure as shown in FIG. 1A having only the upper coating film, or the FIG. 1B having the lower coating film and the upper coating film on one surface of the metal plate (original plate) as described above. The coated metal plate of the two-layer structure as shown was produced.

The commercially available resin, silane coupling agent and rust inhibitor used to form the upper layer coating film and the lower layer coating film are as follows.
Polyurethane resin for upper layer coating film: Polyurethane resin 4 in Test Example 1
Polyurethane resin for lower layer coating: Polyurethane resin 3 in Test Example 1
Water-soluble melamine resin: Melamine resin 2 in Test Example 1
Epoxy resin: Epoxy resin 1 in Test Example 1
Silane Coupling Agent: Silane Coupling Agent 1 in Test Example 1
Rust inhibitor: Rust inhibitor 2 in Test Example 1
Wax: Chemipearl S100 (Mitsui Chemical Co., Ltd.)

The upper layer paint was prepared by mixing predetermined amounts of the above-mentioned polyurethane resin, melamine resin and wax in the composition according to Table 11, respectively. Similarly, the lower layer paint was prepared by mixing predetermined amounts of the above-mentioned polyurethane resin, epoxy resin, silane coupling agent, rust inhibitor and coloring agent in the composition according to Table 11, respectively.

Next, the lower layer paint produced as described above was coated by a roll coater to a dry film thickness of 0.5 μm. In the induction heating furnace blown with hot air, the film of the lower layer paint is heated (dried) under the condition that the maximum reached plate temperature of the metal plate is 150 ° C and the heating time from the start of heating to the maximum reached temperature is 5 seconds Cured). One second after reaching the maximum reaching temperature, the coated metal plate was sprayed with water by a spray, and water cooling was performed under the condition that the cooling time from the maximum reaching temperature to 30 ° C. was 1 second. In addition, the holding time of the highest reach | attainment temperature at the time of a heating was 1 second.

Next, the upper layer paint produced as described above was coated by a roll coater to a dry film thickness of 10 μm. In the induction heating furnace blown with hot air, the film temperature of the upper layer paint is heated (dry-cured) under the condition that the maximum temperature of the metal plate reaches 230 ° C and the heating time from the start of heating to the maximum temperature is 10 seconds. did. One second after reaching the highest reaching temperature, spray the water onto the painted metal plate with a spray, and one second after reaching the highest reaching temperature, wipe the water onto the painted metal plate with a spray. Water cooling was performed under the condition that the cooling time from the highest temperature to 30 ° C. was 1 second. In addition, the holding time of the highest reach | attainment temperature at the time of a heating was 1 second.

<Level>
About the sample of each coated metal plate manufactured, according to the method as stated above, the position (thickening depth) of the area | region where the granular triazine site | part (water-soluble melamine resin) is concentrated in the upper-layer coating film, The number average particle size (particle size) of the triazine moiety (water-soluble melamine resin) was measured. Further, the degree of concentration of the triazine moiety present in the region where the particulate triazine moiety (water-soluble melamine resin) is concentrated was measured according to the method described above. Furthermore, the glass transition temperature (Tg) of each coating film was measured according to the method described above for each of the manufactured coated metal sheet samples.
In addition, whether the surface concentrated part is stained with osmium oxide and observed at a magnification of 100,000 times using a transmission electron microscope, whether or not melamine particles of 5 nm or more are observed, and a plurality of concentrated parts are formed It was determined according to the method described above whether or not it was.

<Evaluation method>
The metal appearance, the chemical resistance test, and the stain resistance test were evaluated in the same manner as in Test Example 1 for each of the manufactured coated metal sheets. The workability test and the corrosion resistance of the machined part were evaluated as follows.

[Processability test]
Each coated metal plate manufactured was cut into a width of 5 cm, and subjected to 6 T bending in an atmosphere of 20 ° C. by a test method according to JIS G3312. Specifically, the same coated plate as the test piece was sandwiched on the inner side of six sheets, and the surface on which the upper layer coating film and the lower layer coating film were formed was turned to the outside, and 180-degree contact bending was performed. The cracks of the coating film were evaluated in four grades of (excellent) A, B, C and D (inferior).
A: no cracks B: slight cracks C: many cracks D: many cracks and peeling of coating

[Corrosion test on processed parts]
Each manufactured coated metal plate was cut into a width of 5 cm and subjected to extrusion processing. The extrusion height was 7 mm. Thereafter, a salt spray test according to JIS Z 2371 was performed for 240 hours. After the test, the white rusting area ratio in the entire area of the processed portion was determined by visual observation and evaluated as follows. The white rusting area ratio is a percentage of the area of the white rusting site to the area of the observation site.
A: White rust occurrence area rate less than 10%
B: White rust occurrence area rate 10% or more and less than 25% C: White rust occurrence area rate 25% or more and less than 50% D: White rust occurrence area rate 50% or more and less than 75% E: White rust occurrence area rate 75% or more

The level and evaluation result of each coated metal plate manufactured are listed in Table 11 and listed. The abbreviations and the like in Table 11 are the same as in Table 10.
However, (Wa) + (Wb) and (Wb) / (Wa) are as follows.
(Wa) + (Wb): Content of polyurethane resin (a) to total solid content (Wa: unit, mass%) and content of water-soluble melamine resin (b) to total solid content (Wb: unit, mass) %) And the total content (Wb) / (Wa): the content (Wa) of the polyurethane resin (a) to the total solid content, and the content (Wb) of the water-soluble melamine resin (b) to the total solid content And the ratio of

As apparent from Table 11 above, the total content (Wa) + (Wb) of the polyurethane resin (a) and the water-soluble melamine resin (b) used in the upper layer coating film 13 is 90 mass% or more and 100 mass It turns out that the chemical-resistance permeability of the manufactured coated metal plate improves more because it becomes% or less and ratio (Wb) / (Wa) becomes more than 0 and 1 or less.

(Test Example 3) <Metal plate (original plate)>
An electrogalvanized steel sheet "NS Gin Coat (registered trademark)" (hereinafter referred to as "EG") manufactured by Nippon Steel & Sumikin Co., Ltd. was used as a metal sheet (original sheet). The plating adhesion amount of EG was 20 g / m ² per one side.

The upper layer paint 3 in Test Example 1 was used as the upper layer paint, and the lower layer paint 8 in Test Example 1 was used as the lower layer paint.

Next, the lower layer paint produced as described above was coated by a roll coater to a dry film thickness of 1.0 μm. In the induction heating furnace blown with hot air, the film of the lower layer paint is heated (dried) under the condition that the maximum reached plate temperature of the metal plate is 150 ° C and the heating time from the start of heating to the maximum reached temperature is 5 seconds Cured). One second after reaching the maximum reaching temperature, the coated metal plate was sprayed with water by a spray, and water cooling was performed under the condition that the cooling time from the maximum reaching temperature to 30 ° C. was 1 second. In addition, the holding time of the highest reach | attainment temperature at the time of a heating was 1 second.

Next, the upper layer paint produced as described above was coated with a roll coater to a dry film thickness of 8 μm. In the induction heating furnace blown with hot air, the upper layer of the metal plate so that the heating time from the start of heating to the maximum reaching temperature and the holding time at 40 to 100 ° C become the conditions shown in Table 12 The paint film was heated (dried and cured). One second after reaching the maximum reaching temperature, the coated metal plate was sprayed with water by spraying, and water cooling was carried out under the condition that the cooling time from the maximum reaching temperature to 30 ° C. was the time shown in Table 12. In addition, the holding time of the highest reach | attainment temperature at the time of a heating was 1 second.

<Level>
About the sample of each coated metal plate manufactured, in the upper layer coating film, according to the method described above, the thickness (depth of thickening) of the surface layer concentrated portion and the number of particulate triazine sites (water soluble melamine resin) The average particle size (particle size) was measured. Also, the N concentration N1 at a depth of 0.2 μm from the surface of the first coating and the N concentration N2 at a depth of 0.2 μm from the interface between the first coating and the metal plate on the first coating side The ratio of N1 / N2 was measured according to the method described above. Furthermore, the glass transition temperature (Tg) of each coating film was measured according to the method described above for each of the manufactured coated metal sheet samples.
In addition, whether the surface concentrated part is stained with osmium oxide and observed at a magnification of 100,000 times using a transmission electron microscope, whether or not melamine particles of 5 nm or more are observed, and a plurality of concentrated parts are formed It was determined according to the method described above whether or not it was.

<Evaluation method>
Evaluation similar to Experiment 1 was performed about each manufactured coated metal plate.

The level and evaluation result of each coated metal plate manufactured are listed in Table 12 and listed. The abbreviations and the like in Table 12 are the same as in Table 10.

As is apparent from Table 12 above, after film formation of the upper layer paint, the heating time from the heating start to the highest reaching temperature is heated under the condition of 1 second to 30 seconds, and the cooling time from the highest reaching temperature to 30 ° C. When the upper coating film 13 is formed by cooling under the conditions of 0.1 seconds to 5 seconds, the obtained coated metal sheet is excellent in metal appearance, chemical resistance, processability and solvent resistance, in particular, It was excellent in chemical resistance.
In addition, in the first coating film produced by the method of holding at a temperature of 40 to 100 ° C. for 1 to 20 seconds, and then heating to 200 ° C. for 1 to 10 seconds, and then cooling, a plurality of concentrated layers are provided. It was formed (Examples 315, 316, 317). When a plurality of concentrated layers were formed on the first coating, all of the metal appearance, chemical resistance, processability and solvent resistance were excellent.

When the highest achieved board temperature was 160 ° C. (Comparative Example 301), chemical resistance and solvent resistance were inferior.

Here, a cross section of the upper layer coating film 13 of the above Example 303 was stained with osmium oxide, and then observed with a transmission electron microscope (TEM), and the distribution state of osmium was observed with TEM-EDX. The various microscope images obtained are shown in FIGS. 5A-5D. FIGS. 5A, 5 C and 5 D show cross-sectional TEM images of the upper coating film 13 of Example 303, and FIG. 5 B shows the upper coating film 13 of Example 303 stained with osmium oxide as a TEM- It shows an elemental mapping image of osmium when observed by EDX.

As apparent from FIG. 5A, in the upper layer coating film 13 of Example 303, it can be seen that in the cross-sectional TEM image, a black linear region appears on the surface layer side. As seen from the elemental mapping image of osmium shown in FIG. 5B, in the portion corresponding to the black linear region in FIG. 5A, the osmium element that selectively stains the triazine site is distributed linearly. From these results, it can be seen that the black linear region in FIG. 5A corresponds to the darkened portion 103.

FIG. 5C is an enlarged view of a central portion of the upper coating film 13 in the cross-sectional TEM image in FIG. 5A. Referring to FIG. 5C, it can be seen that black particles appear in the cross-sectional TEM image. FIG. 5D is an enlarged view of one such black granular material. When the regions corresponding to FIGS. 5C and 5D are confirmed in FIG. 5B, it can be seen that the elements of osmium are dispersed in such regions. Therefore, it can be understood that the portion of the dispersed osmium corresponds to the triazine particles 101. That is, it can be seen that the black particles in FIGS. 5C and 5D are triazine particles 101.

Although the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to such examples. It is obvious that those skilled in the art to which the present invention belongs can conceive of various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also fall within the technical scope of the present invention.

1 Painted metal plate 11 Metal plate 13 Upper layer coating (first coating)
Lower layer coating (second coating)
101 triazine particulate matter (dispersion type second part)
103 Thickened part (thickened second part)

Claims

With metal plates;
A first coating film located on at least one side of the metal plate and containing a resin;
Equipped with
The first coating is:
A first site having a urethane linkage;
A second moiety having a triazine ring skeleton;
Have
The glass transition temperature of the first coating is 85 ° C. or more and 170 ° C. or less,
When the second site is stained with osmium oxide and observed with a transmission electron microscope at a magnification of 100,000:
A dispersed second part in which particles having a number average particle size of 5 to 20 nm are dispersed;
A concentrated second portion which is present at a depth of 15 nm from the surface of the first coating film and in which particles having a number average particle diameter of 5 nm or more are not observed:
A painted metal plate, characterized in that it is observed.
N concentration N1 at a depth of 0.2 μm from the surface of the first coating, N at a depth of 0.2 μm from the interface between the first coating and the metal plate to the first coating The coated metal sheet according to claim 1, wherein N1 / N2 which is a ratio to the concentration N2 is 1.2 or more.
The coated metal sheet according to claim 1, wherein the first coating film has a plurality of the concentrated second portions.
A second coating is further provided between the first coating and the metal plate,
The coated metal sheet according to any one of claims 1 to 3, wherein a glass transition temperature of the second coating film is equal to or less than a glass transition temperature of the first coating film.
The coated metal sheet according to claim 4, wherein the second coating film contains a resin and has a urethane bond skeleton.
The said 2nd coating film contains resin, and has an epoxy group, The coated metal plate of Claim 4 or 5 characterized by the above-mentioned.
The coated metal sheet according to any one of claims 4 to 6, wherein the second coating film contains a resin and has a siloxane bond.
The second coating film according to any one of claims 4 to 7, wherein any one or more elements selected from the group consisting of P, V, Ti, Si and Zr are contained. The painted metal plate described in.
The coated metal sheet according to any one of claims 4 to 8, wherein a glass transition temperature of the first coating is higher than a glass transition temperature of the second coating by 5 ° C or more.
The coated metal sheet according to any one of claims 4 to 9, wherein the film thickness of the second coating film is 0.5 μm or more and 15 μm or less.
The coated metal sheet according to any one of claims 1 to 10, wherein a film thickness of the first coating film is 0.5 μm or more and 15 μm or less.
The coated metal sheet according to any one of claims 4 to 11, wherein at least one of the first coating film and the second coating film contains a colorant.
The coated metal sheet according to any one of claims 4 to 12, wherein the second coating film contains a black pigment as a colorant.
The coated metal sheet according to any one of claims 1 to 13, wherein a texture is formed on at least one surface of the metal sheet.
A method for producing a coated metal plate having a predetermined first coating film on at least one side of a metal plate,
A polyurethane resin (a) containing an anionic functional group and having a glass transition temperature of 75 ° C. or more and 160 ° C. or less on at least one surface of the metal plate, a triazine ring-containing water soluble curing agent (b), and an aqueous solvent A method of producing a coated metal sheet, comprising: applying a first paint containing the mixture; and heating the metal plate to which the first paint has been applied to form the first coating film.
The method for producing a coated metal sheet according to claim 15, wherein the triazine ring-containing water-soluble curing agent (b) is a melamine resin containing an imino group.
The first paint is
Total content (Wa) + (content of the polyurethane resin (a) to total solids (Wa) and content of the triazine ring-containing water soluble curing agent (b) (wb) to total solids (Wa) Wb) satisfies the following formula (I), and
The ratio (Wb) of the content (Wa) of the polyurethane resin (a) to the total solid content and the content (Wb) of the triazine ring-containing water-soluble curing agent (b) to the total solid content (Wb) The method for producing a coated metal sheet according to claim 15 or 16, characterized in that Wa) satisfies the following formula (II).
90 mass% ≦ (Wa) + (Wb) ≦ 100 mass% Formula (I)
0 <(Wb) / (Wa) ≦ 1 formula (II)
A method for producing a coated metal sheet, further comprising a predetermined second coating film between the metal sheet and the first coating film, wherein
Prior to the application of the first paint, a polyurethane resin (c) having a glass transition temperature not higher than the glass transition temperature of the polyurethane resin (a), an epoxy resin (d), a silane coupling agent (e), and P A second paint containing at least one of an anticorrosion agent (f) containing at least one element selected from the group consisting of V, Ti, Si and Zr, and an aqueous solvent; 18. The method according to any one of claims 15 to 17, characterized in that the second paint film is formed by coating on at least one surface of a plate and heating the metal plate to which the second paint is applied. The manufacturing method of the coated metal plate as described.
The method for producing a coated metal sheet according to claim 18, wherein the glass transition temperature of the polyurethane resin (c) is lower than the glass transition temperature of the polyurethane resin (a) by 5 ° C or more.
When forming the first coating,
The metal plate coated with the first paint is heated such that the heating time from the heating start of the metal plate coated with the first paint to the highest reaching temperature is 1 second or more and 30 seconds or less,
20. The metal plate coated with the first paint is cooled such that the cooling time from the highest temperature to 30 ° C. is 0.1 seconds or more and 5 seconds or less. The manufacturing method of the coated metal plate as described in any one.
21. The coated metal sheet according to claim 20, wherein the heating is carried out by holding at a temperature of 40 to 100 ° C. for 1 to 20 seconds and then heating to over 200 ° C. for 1 to 10 seconds. Production method.