Specification
Title of invention: Painted metal plate and method for producing painted metal plate
Technical field
[0001]
　The present invention relates to a coated metal plate and a method for manufacturing a coated metal plate.
　The present application claims priority based on Japanese Patent Application No. 2017-209460 filed in Japan on October 30, 2017, the contents of which are incorporated herein by reference.
Background technology
[0002]
　Instead of conventional coated products that are painted after processing, coated metal plates coated with coatings are used for automobiles, home appliances, building materials, civil engineering, machinery, furniture, containers, etc. Is starting to appear. Such a coated metal plate is generally cut and press-molded after the paint is applied to the metal plate.
[0003]
　Since the coated metal plate is mainly used as an exterior material and exposed to various solvents and chemicals, it often has solvent resistance and chemical resistance. Since it is an exterior material, there are usually many painted metal plates that are colored and painted, and due to the concealability for color tone, the film thickness of such a coating film is relatively large. On the other hand, in the case of a metal-coated metal plate in which the appearance of the metal plate that is the base material is the same as that of the design, it is necessary to perform clear coating that does not contain a coloring pigment. In such a case, by making the film thickness of the clear coating film thin, the coated metal plate has an excellent metal appearance. Also, from the viewpoint of productivity and commerciality, the thinner the clear coating film is, the better.
[0004]
　Generally, it is required that the coating film is not deteriorated or discolored by chemicals as the chemical resistance. However, when the coating film is thin, the problem is that the chemical penetrates to the plating interface and dissolves the plating, rather than the deterioration of the coating film by the chemical. In the case of colored coating, even if the metal discolors due to chemicals, the appearance does not become abnormal, the dissolution of the metal progresses and a corrosion product is generated, and the generated corrosion product causes the coating film to swell. , The appearance is abnormal. On the other hand, in the case of clear coating, it is considered that the appearance is abnormal when the metal discolors. In other words, clear coating requires that the chemical components do not reach the metal. Such a property is called chemical penetration resistance.
[0005]
　Several examples of coated metal sheets having excellent chemical resistance have been reported so far.
　For example, Patent Document 1 below discloses a technique for coating a metal plate, which coats a paint containing a solvent-soluble fluororesin as a main component.
[0006]
　Further, in Patent Document 2 below, a coating film using a polyester resin having a high glass transition point temperature, a polyester resin having a low glass transition point temperature, and an aminoformaldehyde resin provides workability, stain resistance, and scratch resistance. A technique of a coated metal plate having excellent properties and chemical resistance is disclosed.
[0007]
　Further, the following Patent Document 3 discloses a technique of a pre-coated metal which is excellent in stain resistance, chemical resistance, weather resistance and workability by coating a polyacrylic resin on the upper layer and a polyester resin on the lower layer. Has been done.
[0008]
　Further, Patent Document 4 below discloses a technique of a coated metal plate which is excellent in workability, corrosion resistance (especially end face corrosion resistance), chemical resistance, etc. by a coating film obtained by mixing a specific polyurethane resin and polyester resin. Has been done.
[0009]
　Further, Patent Document 5 below discloses a technique of a metal plate having excellent bending workability by a coating film in which melamine resin particles having a particle diameter of 50 nm or less are dispersed.
[0010]
　Further, in Patent Document 6 below, in a coating film using an aminoblast resin such as a melamine resin, a technique of thickening the aminoblast resin in the surface layer of the coating film is disclosed.
Prior art documents
Patent literature
[0011]
Patent Document 1: Japanese Unexamined Patent Publication No. 5-111675
Patent Document 2: Japanese Unexamined Patent Publication No. 7-331167
Patent Document 3: Japanese Unexamined Patent Publication No. 7-313929
Patent Document 4: Japanese Unexamined Patent Publication 2013-213281 JP
Patent Document 5: Japanese Patent 2005-53002 JP
Patent Document 6: Japanese Patent 2006-175815 JP
Summary of the invention
Problems to be Solved by the Invention
[0012]
　However, the fluororesin used in the technique of Patent Document 1 is expensive and is not preferable industrially.
[0013]
　In some cases, as described in Patent Document 2 above, it is suggested to utilize the self-condensation reaction of a melamine resin, which is a cross-linking agent, in forming a coating film using a solvent-based paint. However, what is disclosed therein does not consider the conditions for surface concentration necessary for forming a barrier layer. It is also disclosed that an amine compound is added to thicken the surface, but the effect is such that it affects the distribution density of the generated melamine self-condensed particles. Therefore, the structure of the coating film obtained under these conditions is such that coarse self-condensate particles of about 50 to 100 μm are dispersed in the coating film, and surface concentration as the distribution density of the particles is recognized. The effect of improving the chemical penetration resistance of the coating film was limited.
[0014]
　The polyacrylic resin used in the technique of Patent Document 3 is inferior in processability, and when the coating film disclosed in Patent Document 3 is a clear coating film, the barrier property is not sufficient. Furthermore, the chemical penetration resistance is poor.
[0015]
　The coating film disclosed in Patent Document 4 has insufficient barrier properties and further has poor chemical permeation resistance.
[0016]
　When the melamine resin particles are dispersed in the coating film as in the technique of Patent Document 5, the coating film has poor solvent resistance.
[0017]
　In the technique disclosed in Patent Document 6 described above, the particle size of the melamine resin particles in the coating film is large, the barrier property is not sufficient, and further the chemical penetration resistance is poor.
[0018]
　As described above, Patent Documents 1 to 6 do not disclose a technique for obtaining a coated metal plate having excellent metal appearance, chemical permeation resistance, and solvent resistance while suppressing manufacturing costs.
[0019]
　Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to suppress the manufacturing cost, a metal appearance, a chemical resistance to chemical penetration and a coated metal plate excellent in solvent resistance. A method of manufacturing such a coated metal plate is provided.
Means for solving the problem
[0020]
　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 appropriately controlling the glass transition temperature of such a resin coating film and the state of existence of the second portion in the resin coating film, while suppressing the manufacturing cost, the metal appearance, chemical permeation resistance and solvent resistance can be improved. It was conceived that an excellent coated metal plate can be manufactured.
　The gist of the present invention completed based on such knowledge is as follows.
[0021]
(1) A coated metal plate according to an aspect of the present invention includes a metal plate and a first coating film that is located on at least one surface of the metal plate and contains a resin, and the first coating film is It has a first part having a urethane bond skeleton and a second part having a triazine ring skeleton. The glass transition temperature of the first coating film is 85° C. or higher and 170° C. or lower. When the second portion is dyed with osmium oxide and observed with a transmission electron microscope at a magnification of 100,000 times, the dispersion-type second portion in which particles having a number average particle diameter of 5 to 20 nm are dispersed, A thickened type second portion 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 is observed.
(2) The coated metal plate according to the above (1), wherein the N concentration N1 at a depth position of 0.2 μm from the surface of the first coating film, the interface between the first coating film and the metal plate, N1/N2, which is the ratio to N concentration N2 at a depth of 0.2 μm on the first coating film side, may be 1.2 or more.
(3) In the coated metal plate according to (1) or (2), the first coating film may have a plurality of the concentration-type 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 lower 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 may be 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 film is 5° C. or more higher than the glass transition temperature of the second coating film. Good.
(10) In the coated metal plate according to any one of the above (4) to (9), the 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 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.
[0022]
(15) A method for producing a coated metal plate according to another aspect of the present invention is a method for producing a coated metal plate having a predetermined first coating film on at least one surface of the metal plate, wherein at least the metal plate is A first containing a polyurethane resin (a) containing an anionic functional group and having a glass transition temperature of 75° C. or higher and 160° C. or lower, a triazine ring-containing water-soluble curing agent (b), and an aqueous solvent on one surface. The first coating film is formed by applying a paint and heating the metal plate coated with the first paint.
(16) In the method for producing a coated metal plate according to (15) above, the triazine ring-containing water-soluble curing agent (b) may be a melamine resin containing an imino group.
(17) In the method for producing a coated metal plate according to the above (15) or (16), the first coating material has a content (Wa) of the polyurethane resin (a) with respect to the total solid content and a 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 content based on the total solid content is 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. Formula (II) may be satisfied.
　　90% by mass≦(Wa)+(Wb)≦100% by 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), wherein the coated metal further has a predetermined second coating film between the metal plate and the first coating film. A method for producing a plate, comprising a polyurethane resin (c) having a glass transition temperature equal to or lower than the glass transition temperature of the polyurethane resin (a), an epoxy resin (d), and a silane coupling prior to coating the first paint. Agent (e), and at least one of rust preventive agent (f) containing any one or more elements selected from the group consisting of P, V, Ti, Si and Zr, and an aqueous solvent The second coating film may be formed by coating the second coating material on at least one surface of the metal plate and heating the metal plate coated with the second coating material.
(19) In the method for producing a coated metal plate as described in (18) above, the glass transition temperature of the polyurethane resin (c) may be lower than the glass transition temperature of the polyurethane resin (a) by 5° C. or more.
(20) In the method for producing a coated metal plate according to any one of the above (15) to (19), when the first coating film is formed, heating of the metal plate coated with the first coating material is started. To the maximum reached temperature is 1 second or more and 30 seconds or less, the metal plate coated with the first coating material is heated, and the cooling time from the maximum reached temperature to 30° C. is 0.1 second. The metal plate coated with the first paint may be cooled so as to be 5 seconds or less.
(21) In the method for producing a coated metal plate according to the above (20), in the heating, the temperature is maintained at 40 to 100° C. for 1 to 20 seconds, and then the heating time is set to 1 to 10 seconds until the temperature exceeds 200° C. You may heat.
Effect of the invention
[0023]
　As described above, according to the present invention, it is possible to obtain a coated metal plate that is excellent in metal appearance, chemical permeation resistance, and solvent resistance while suppressing manufacturing costs.
Brief description of the drawings
[0024]
FIG. 1A is an explanatory diagram schematically showing an example of the structure of a coated metal plate according to an embodiment of the present invention.
FIG. 1B is an explanatory diagram schematically showing an example of the structure of the coated metal plate according to the embodiment.
FIG. 2A is an explanatory view schematically showing another example of the structure of the coated metal plate according to the same embodiment.
FIG. 2B is an explanatory view schematically showing another example of the structure of the coated metal plate according to the same embodiment.
FIG. 3 is an explanatory diagram for explaining an upper layer coating film of a coated metal plate according to the same embodiment.
FIG. 4 is a flowchart for explaining an example of the flow of the method for manufacturing a coated metal plate according to the same embodiment.
FIG. 5A is a microscope image of the upper coating film of Test Example 3 observed with a transmission electron microscope.
FIG. 5B is an elemental mapping image of osmium when the upper coating film of Test Example 3 is observed with a transmission electron microscope.
FIG. 5C is a microscope image of the upper coating film of Test Example 3 observed with a transmission electron microscope.
FIG. 5D is a microscope image of the upper coating film of Test Example 3 observed with a transmission electron microscope.
FIG. 6 is an explanatory diagram for explaining an upper layer coating film when a plurality of concentrated portions are formed.
MODE FOR CARRYING OUT THE INVENTION
[0025]
　Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and the drawings, constituent elements having substantially the same functional configuration are designated by the same reference numerals, and a duplicate description will be omitted.
[0026]
(Overall Configuration of Painted Metal Plate and Outline thereof)
　First, the overall configuration of a coated metal plate according to an embodiment of the present invention will be described with reference to FIGS. 1A to 3. 1A and 1B are explanatory views schematically showing an example of the structure of the coated metal plate according to the present embodiment, and FIGS. 2A and 2B show other structures of the coated metal plate according to the present embodiment. It is explanatory drawing which showed an example typically. FIG. 3 is an explanatory diagram for explaining the upper layer coating film of the coated metal plate according to the present embodiment.
[0027]
　As shown schematically in FIG. 1A, the coated metal plate 1 according to the present embodiment has an upper coating film 13 as a first coating film on one surface of a metal plate 11 as a base material. Further, as schematically shown in FIG. 1B, a lower layer coating film 15 may be provided as a second coating film between the metal plate 11 and the upper layer coating film 13.
[0028]
　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 may be formed. The lower coating film 13 and the lower coating film 15 may be provided on both surfaces of the metal plate 11.
[0029]
　The structure of the coated metal plate 1 according to the present embodiment is not limited to the structure shown in FIGS. 1A to 2B. A configuration in which 15 is provided and the upper coating film 13 or the lower coating film 15 is provided on the other surface of the metal plate 11 is also feasible.
[0030]
　The upper 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 a resin coating film containing. The glass transition temperature of the upper coating film 13 is 80° C. or higher and 170° C. or lower.
　Further, as schematically shown in FIG. 3, the second site having a triazine ring skeleton was stained with osmium oxide and observed with a transmission electron microscope at a magnification of 100,000 times to find that the number average particle size was 5 nm. Particles having a number average particle diameter of 5 nm or more are not observed, which are present in the dispersion-type second portion (reference numeral 101 in FIG. 3) in which the above particles are dispersed and at a position from the surface of the upper coating film 13 to a depth of 15 nm. Both the concentrated second region (reference numeral 103 in FIG. 3) is present.
[0031]
　The coated metal plate 1 according to the present embodiment is a coated metal plate excellent in metal appearance, chemical permeation resistance, and solvent resistance without using an expensive resin such as a fluororesin due to the above-described configuration. .. The reason for this is presumed as follows.
[0032]
　First, in order to set the glass transition temperature of the upper coating film 13 to 80° C. or higher and 170° C. or lower, the urethane portion needs to have a considerably high glass transition temperature. Since the urethane part has a high glass transition temperature, a high cohesive force is generated in the urethane part when the upper coating film 13 is formed. As a result, the triazine site is not condensed alone, the triazine site is dispersed in the urethane site, and the urethane site and the triazine site are easily bonded preferentially. The triazine moiety having high solvent resistance is bonded to the urethane moiety to form a three-dimensional network structure. As a result, the upper coating film 13 has improved barrier properties (that is, chemical penetration resistance). In order to obtain such characteristics, in this embodiment, the glass transition temperature of the upper coating film 13 is set to 80° C. or higher and 170° C. or lower.
[0033]
　Further, the triazine moiety forms a domain in the upper layer coating film 13 and is dispersed in a granular form (reference numeral 101 in FIG. 3), and at the same time, is concentrated on the surface layer of the upper layer coating film 13 to form a thickened portion 103, The solvent resistance of the upper coating film 13 is enhanced by the triazine moiety having high solvent resistance. Moreover, as described above, when a high cohesive force is generated in the urethane part when forming the upper coating film 13, the urethane part and the triazine part are likely to be bonded preferentially, as shown schematically in FIG. In addition, the atomized granular triazine site (hereinafter, also referred to as “triazine granular material 101”) is concentrated on the surface layer of the upper coating film 13. From this point as well, the solvent resistance of the upper coating film 13 is further improved.
[0034]
　When the finely divided granular triazine moiety (triazine granules 101) is concentrated on the surface layer of the upper coating film 13, light scattering by the triazine moiety is suppressed, and as a result, the transparency of the upper coating film 13 is improved. However, the glossy feeling of the underlying metal plate 11 is easily visible from the outside. Thereby, in the coated metal plate 1 according to the present embodiment, the metallic appearance is also improved.
[0035]
　As described above, the coated metal plate 1 according to the present embodiment has the above-described configuration, without using an expensive resin such as a fluororesin, and has a metal appearance, chemical penetration resistance, and solvent resistance. It is presumed that it is excellent in sex.
[0036]
　Hereinafter, each component of the coated metal plate 1 according to the present embodiment will be described in detail.
[0037]
In the
　coated metal plate 1 according to the present embodiment, as the metal plate 11, various publicly known metal plates can be used. Specifically, examples of the metal plate 11 include various metal plates and alloy plates such as a steel plate, a stainless steel plate, an aluminum plate, an aluminum alloy plate, a titanium plate, and a copper plate. In the coated metal plate 1 according to this embodiment, various kinds of plating (not shown) may be applied to the surface of the metal plate 11. The type of plating is not particularly limited, but examples thereof include zinc plating, aluminum plating, copper plating, nickel plating, alloy plating of these, and the like.
[0038]
　In particular, when the metal plate 11 is a plated steel plate, it tends to be inferior in chemical penetration resistance, so that the effect of improving chemical penetration resistance by providing the upper coating film 13 becomes more effective.
[0039]
　The galvanized steel sheet used as the metal plate 11 is not particularly limited, and hot-dip galvanized steel sheet, electrogalvanized steel sheet, zinc-nickel alloy plated steel sheet, hot-dip galvannealed steel sheet, aluminized steel sheet, aluminium-zinc. Various generally known plated steel plates such as alloyed plated steel plates and stainless steel plates can be applied. In particular, the use of a zinc-based plated steel plate as the metal plate 11 is more suitable because the corrosion resistance is further improved. Here, the zinc-based plated steel sheet means zinc, such as zinc-plated zinc-coated steel sheet, zinc-nickel alloy-plated steel sheet, hot-dip galvanized steel sheet, and aluminum-zinc alloy-plated steel sheet, or zinc and other zinc It refers to a plated steel sheet in which an alloy with a metal is plated on the surface of the steel sheet. The galvanized steel sheet may be any of hot dip galvanized steel sheet, electrogalvanized steel sheet and the like.
[0040]
　Further, on the surface of the metal plate 11, in order to further improve the designability of the coated metal plate 1 according to the present embodiment, satin, roughening, creases (hairline), cloth (satin), hammer (hammer), etc. Various textures may be formed. In the coated metal plate 1 according to the present embodiment, since the transparency of the upper coating film 13 is improved by the above-mentioned configuration, it is possible to form the texture as described above on the surface of the metal plate 11. However, the metallic feeling evoked by such a texture is easily visible from the outside.
[0041]

　The upper layer coating 13 of the coated metal plate 1 according to the present embodiment has a urethane portion (first portion having a urethane bond skeleton) and a triazine portion (triazine ring skeleton) as previously mentioned. And a second portion) having a.
[0042]
　Each part included in the upper coating film 13 will be described below.
　The urethane bond skeleton of the urethane moiety in the upper coating film 13 can be confirmed by analyzing the upper coating film 13 by Fourier transform infrared spectroscopy and detecting a vibration peak attributed to the urethane bond. ..
[0043]
　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 site is a site derived from the triazine ring contained in the melamine resin.
[0044]
　As mentioned above with reference to FIG. 3, the triazine site is a particle having a number average particle size of 5 to 20 nm when the triazine site is stained with osmium oxide and observed with a transmission electron microscope at a magnification of 100,000. Observed: a dispersion-type second part in which is dispersed, and a concentration-type second part which is present at a position from the surface of the upper coating film 13 to a depth of 15 nm and in which particles having a number average particle size of 5 nm or more are not observed. To be done.
[0045]
　Here, as shown schematically in FIG. 3, the concentrated portion 103 according to the present embodiment has a range of positions from the surface layer of the upper coating film 13 toward the metal plate 11 side to the depth d (15 nm). Exists within.
　It should be noted that "the triazine moiety is concentrated on the surface layer of the upper coating film 13" means that a granular triazine moiety (that is, triazine particles on the surface side of the upper coating film 13 on the side opposite to the interface with the metal plate 11). Object 101) is unevenly distributed in layers. That is, the region of the granular triazine site unevenly distributed in the layer form constitutes the surface layer of the upper coating film 13.
　Here, "the triazine sites are unevenly distributed in a layered manner to form the concentrated portion 103" means that the average concentration (average content) of the triazine sites in the region in which the triazine sites are unevenly distributed is other than the unevenly distributed parts. It means that the average concentration of the triazine site in the region is 1.2 times or more.
[0046]
　Here, the triazine moiety according to the present embodiment is dispersed in the upper coating film 13 in the form of particles having a number average particle size of 5 nm or more and 20 nm (in other words, the number average particle size of the triazine particles 101 is 5 nm or more and 20 nm or less). And the surface layer of the upper coating film 13 has a depth of 15 nm or less (in other words, the depth d in FIG. 3 is 15 nm or less).
[0047]
　Here, the fact that the triazine moiety is concentrated in the surface layer within a depth of 15 nm from the surface of the upper coating film 13 means that the triazine moiety is unevenly distributed in layers on the surface side of the upper coating film 13 opposite to the interface with the metal plate 11. It is shown that the region of the granular triazine site exists within a depth of 15 nm from the surface of the upper coating film 13. That is, it is shown that the region of the granular triazine site unevenly distributed in the layer form the surface layer of the upper coating film 13 and has a thickness of 15 nm or less.
[0048]
　When the number average particle diameter of the granular triazine moiety (that is, the triazine granular material 101) is less than 5 nm, the chemical penetration resistance may decrease. On the other hand, when the number average particle diameter of the triazine portion dispersed in a granular form exceeds 20 nm, the metal appearance and chemical permeation resistance of the coated metal plate 1 are deteriorated, or the metal appearance, chemical permeation resistance and processability are deteriorated. There is something to do. Here, when the workability of the coated metal plate 1 is lowered, the upper coating film 13 is cracked and the chemical penetration resistance and solvent resistance are also lowered. The number average particle diameter of the triazine moiety (triazine granules 101) dispersed in a granular form is more preferably 5 nm or more and 15 nm or less from the viewpoint of metal appearance, chemical penetration resistance and solvent resistance.
[0049]
　Further, when the granular triazine site is not concentrated in the surface layer of the upper coating film 13 (that is, when the concentrated portion 103 does not exist), the metal appearance and solvent resistance may be deteriorated. Furthermore, in the case where the granular triazine portion is concentrated from the surface of the upper coating film 13 to a depth of more than 15 nm (that is, the depth at which the concentrated portion 103 is present exceeds 15 nm from the surface of the upper coating film 13). In the case of), the workability may decrease. When the workability of the coated metal plate 1 is lowered, the upper coating film 13 is cracked and the chemical permeation resistance and solvent resistance are also lowered.
[0050]
　As shown in FIG. 6, it is preferable that a plurality of concentrated portions 103 be formed in the upper coating film 13. By forming a plurality of thickened portions 103, the barrier property is further improved, and suitable chemical resistance can be obtained. In order to form the thickened portion 103, a heating method in an upper layer coating film forming step described later is important. This point will be described later.
[0051]
　Here, in the upper layer coating film 13 according to the present embodiment, the N concentration N1 at a depth of 0.2 μm from the surface of the upper layer coating film 13 and the upper layer coating film 13 from the interface between the upper layer coating film 13 and the metal plate 11. N1/N2, which is the ratio with the N concentration N2 at a depth of 0.2 μm on the side, is 1.2 or more.
　By setting N1/N2 to 1.2 or more, it becomes possible to more reliably improve the metal appearance and the solvent resistance. N1/N2 is more preferably 1.5 or more and 10 or less.
[0052]
　Next, various analysis methods for the triazine site in the upper coating film 13 will be described.
　First, the upper coating film 13 to be analyzed is dyed with osmium oxide. As a result, the triazine site in the upper coating film 13 is selectively dyed. Next, using a microtome, a focused ion beam processing device or the like, the coating film dyed with osmium oxide is cut along the film thickness direction to prepare a coating film sample whose cross section can be observed. Then, the thin film sample is observed with a transmission electron microscope at a magnification of 100,000 times. 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.
[0053]
　By the above-mentioned analysis method, the triazine site in the upper coating film 13 can be confirmed. The triazine moiety in the upper coating film 13 is analyzed by energy dispersive X-ray spectroscopy or Fourier transform infrared spectroscopy to detect nitrogen and osmium, and is assigned to the triazine ring. It can also be confirmed by detecting the vibration peak.
[0054]
　The thickness of the region where the granular triazine site is concentrated (that is, the thickness of the concentrated portion (concentrated second region) 103, which is the region of the granular triazine site that is unevenly distributed in layers) is measured by the following method. Is a value. As described above, the thin film sample is observed with a transmission electron microscope at a magnification of 100,000 times to obtain a STEM-BF (bright field) image. The obtained STEM-BF (bright field) image is binarized with a threshold value 120, for example. Then, in the obtained binarized image, the thickness of the layered region observed in black from the surface of the upper coating film 13 was measured at arbitrary 20 points, and the average value was measured for the region where the granular triazine site was concentrated. Calculate as thickness. Further, regarding the position where the thickened portion 103 exists, pay attention to the position of the lower end (interface on the metal plate 11 side) of the thickness of the thickened portion 103 obtained as described above in the binarized image. Can be specified. When a layered black region is observed from the surface of the upper coating film 13, it is considered that the granular triazine site is concentrated on the surface layer of the upper coating film 13.
[0055]
　The number average particle size of the granular triazine moiety (the number average particle size of the triazine particles 101) is a value measured by the following method. As described above, the STEM-BF (bright field) image is obtained by observing the thin film sample with a transmission electron microscope at a magnification of 500,000 times. The obtained STEM-BF (bright field) image is binarized with a threshold value 120, for example. Then, in the obtained binarized image, the equivalent circle diameter of the granular region observed in black is calculated by the formula: equivalent circle diameter=2 (area/π) 0.5. The "area" in this equation indicates the area of ​​the granular region observed as black. Then, the calculation of the equivalent circle diameter is performed at 20 arbitrarily selected granular regions, and the average value thereof is obtained as the number average particle size of the granular triazine site.
[0056]
　The average concentration of the triazine moiety concentrated on the surface layer side of the upper coating film 13 can be measured as follows. That is, the distribution of the N element concentration in the depth direction from the surface layer side of the upper coating film 13 to the metal plate direction was measured, and the N element concentration N1 at a position at a distance of 0.2 μm from the outermost layer and the metal plate or the lower layer N1/N2, which is the ratio of the N element concentration and N2 at the position of 0.2 μm on the surface side from the boundary with the coating film, is determined.
　The elemental analysis in the depth direction can be carried out by a known method, for example, by using high-frequency glow discharge spectroscopy (GD-OES), Auger electron spectroscopy (AES), or the like. It is feasible.
[0057]
　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 higher and 170 or lower. When the glass transition temperature of the upper coating film 13 is lower than 85° C., the chemical permeation resistance of the coated metal plate 1 is lowered. On the other hand, when the glass transition point temperature of the upper coating film 13 exceeds 170° C., the workability of the coated metal plate 1 deteriorates. When the workability of the coated metal plate 1 is lowered, the upper coating film 13 is cracked and the chemical penetration resistance and solvent resistance are also lowered. The glass transition temperature of the upper coating film 13 is preferably 100° C. or higher and 170° C. or lower, and more preferably 110° C. or higher, from the viewpoint of chemical penetration resistance and solvent resistance (particularly chemical penetration resistance). It is 165°C or lower.
[0058]
　When the coated metal plate 1 according to the present embodiment has the lower layer coating film 15, the glass transition temperature of the upper layer coating film 13 is preferably equal to or higher than the glass transition temperature of the lower layer coating film 15. When the glass transition temperature of the upper coating film 13 is lower 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 permeation resistance is reduced. There is.
[0059]
　On the other hand, the glass transition temperature of the upper coating film 13 is preferably higher than the glass transition temperature of the lower coating film 15 by 5° C. or more. When the difference between the glass transition temperature of the upper coating film 13 and the glass transition temperature of the lower coating film 15 is 5° C. or more, the adhesion between the upper coating film 13 and the lower coating film 15 is further improved, and chemical permeation resistance is improved. The property is further improved.
[0060]
　Further, the glass transition temperature of the upper coating film 13 is more preferably higher than the glass transition temperature of the lower coating film 15 in the range of 10° C. or higher and 50° C. or lower. 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 10 by 10° C. or more, the chemical permeation resistance is easily increased. On the other hand, when the glass transition temperature of the upper coating film 13 is higher than the glass transition temperature of the lower coating film 15 in the range of 50° C. or less, the decrease in coating hardness is easily suppressed.
[0061]
　Here, the glass transition temperature (Tg) is a value measured by the following method. First, the coating film to be measured is peeled or scraped off to prepare a measurement sample. Then, using the measurement sample, the glass transition temperature is determined according to the differential scanning calorimetry (DSC method) of the plastic transition temperature measuring method (JIS K7121 1987).
[0062]
　The upper coating film 13 preferably does not contain silica. This is because if the upper coating film 13 contains silica, the chemical resistance of the upper coating film 13 deteriorates.
　For the same reason, the upper coating film 13 preferably does not contain at least one metal complex compound selected from zinc, aluminum and titanium. Here, the at least one metal complex compound selected from zinc, aluminum and titanium includes, for example, zinc stearate, zinc gluconate, zinc picolinate, zinc citrate, zinc acetylacetonate, aluminum acetate, aluminum stearate. , Aluminum ethylate, aluminum isopropylate, aluminum triisopropyloxide, aluminum ethylacetoacetate diisopropylate, aluminum trisethylacetoacetate, aluminum tris(acetylacetate), aluminum oxide isopropyloxide trimer, titanium tetraisopropoxide, Titanium tetra-normal butoxide, titanium butoxide dimer, titanium tetra-2-ethylhexoxide, titanium diisopropoxybis(acetylacetonate), titanium tetraacetylacetonate, titanium dioctyloxybis(octylene glycolate), titanium diisopropoxy Examples thereof include bis(ethylacetoacetate), titanium diisopropoxybis(triethanolaminate), titanium lactate ammonium salt, titanium lactate, and polyhydroxytitanium stearate.
[0063]
In the
　coated metal plate 1 according to the present embodiment, the lower-layer coating film 15 is not particularly limited, and includes polyurethane resin, epoxy resin, acrylic resin, polyester resin, phenol resin, and polyolefin. A well-known resin coating film such as a system resin, an alkyd resin, a melamine resin, and a silicone resin can be applied. Moreover, when forming such a resin coating film, it is also possible to use a known additive such as a silane coupling agent.
[0064]
　Among these resin coating films, the lower coating film 15 has at least a first portion having a urethane bond skeleton (hereinafter also referred to as “urethane portion”) from the viewpoint of metal appearance, chemical penetration resistance, and solvent resistance. It preferably further contains a site having at least one of an epoxy group and a siloxane bond skeleton (hereinafter, a site having an epoxy group is also referred to as an “epoxy site” and a site having a siloxane bond skeleton is also referred to as a “siloxane site”). Such a resin coating film is preferable. Further, the lower coating film 15 preferably contains a compound having any one or more elements selected from the group consisting of P, V, Ti, Si and Zr in addition to the urethane portion as described above. .
[0065]
　Here, since the urethane moiety further has an anionic functional group, the dispersibility of the urethane moiety in the water-based medium (water-based paint) is improved, and the film-forming property of the lower layer coating film 15 is increased, so that the lower layer coating film 15 and Adhesion with the metal plate 11 is improved, and the barrier property (that is, chemical penetration resistance) of the lower coating film 15 is improved.
[0066]
　Moreover, the chemical permeation resistance of the lower layer coating film 15 is also improved by including the urethane portion and at least one of the epoxy group and the siloxane bond skeleton. Further, by forming the lower layer coating film 15 as a resin coating film having at least a urethane portion, the transparency of the lower layer coating film 15 is improved and the metallic appearance becomes good.
[0067]
　Further, the compound having any one or more elements selected from the group consisting of P, V, Ti, Si and Zr generally functions as a rust preventive agent in many cases, but in the lower coating film 15, You may include such a compound. By including such a compound in the lower layer coating film 15, it becomes possible to further improve the corrosion resistance of the coated metal plate 1.
[0068]
　Next, each part included in the lower coating film 15 will be described.
　Examples of anionic functional groups that the urethane moiety preferably has include a carboxylic acid group (carboxy group) and a sulfonic acid group (sulfo group). On the other hand, the urethane bond skeleton of the urethane moiety is a skeleton derived from a polyurethane resin. That is, it can be said that the urethane moiety is a moiety derived from the polyurethane resin and may further have an anionic functional group.
[0069]
　The epoxy moiety having an epoxy group is a moiety derived from an epoxy resin. That is, the epoxy group of the epoxy moiety is an epoxy group residue that has not reacted with the urethane moiety derived from the polyurethane resin. 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.
[0070]
　The urethane bond skeleton of the urethane part, the epoxy group of the epoxy part, and the siloxane bond skeleton of the siloxane part in the lower layer coating film 15 are coated in the lower layer by energy dispersive X-ray spectroscopy or Fourier transform infrared spectroscopy. This can be confirmed by analyzing the film 15 and detecting the element constituting the corresponding bond or functional group, or by detecting the vibration peak attributed to the corresponding bond or functional group. In addition, the presence of a compound having any one or more elements selected from the group consisting of P, V, Ti, Si and Zr in the lower layer coating film 15 causes such a compound to be present by energy dispersive X-ray spectroscopy. It can be confirmed by whether or not the contained element is detected.
[0071]
　Next, 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 lower 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 higher and 170 or lower, and is the glass transition temperature of the upper coating film 13 or lower. If the glass transition temperature of the lower coating film 15 is lower than 80° C., the chemical penetration resistance may decrease. On the other hand, when the glass transition point temperature of the lower layer coating film 15 exceeds 170° C., the workability may decrease. If the workability is lowered, the lower coating film 15 may be cracked, and the chemical penetration resistance and the solvent resistance may be lowered. The glass transition temperature of the lower coating film 15 is more preferably not higher than the glass transition temperature of the upper coating film 13 from the viewpoint of chemical penetration resistance and solvent resistance (particularly from the viewpoint of chemical penetration resistance), and 100 It is in the range of ℃ to 170 ℃.
[0072]
In the
　coated metal plate 1 according to the present embodiment , the film thickness of the upper coating film 13 as described above is preferably 0.5 μm or more and 15 μm or less. .. When the film thickness of the upper coating film 13 is less than 0.5 μm, the chemical permeation resistance of the coated metal plate 1 may decrease. On the other hand, when the film thickness of the upper coating film 13 exceeds 15 μm, the transparency of the upper coating film 13 may be deteriorated and the metallic appearance may be deteriorated. The film thickness of the upper coating film 13 is more preferably 1 μm or more and 10 μm or less from the viewpoint of metal appearance and chemical penetration resistance.
[0073]
　Further, in the coated metal plate 1 according to the present embodiment, when the lower layer coating film 15 is provided in addition to the upper layer coating film 13, the film thickness of the lower layer coating film 15 is preferably 0.5 μm or more and 15 μm or less. .. By setting the film thickness of the lower coating film 15 to 0.5 μm or more and 15 μm or less, it becomes possible to further improve the chemical permeation resistance while maintaining the metallic appearance. From the viewpoint of chemical penetration resistance, the thickness of the lower coating film 15 is more preferably more than 1.0 μm and 15 μm or less.
[0074]
In the
　coated metal plate 1 according to the present embodiment, the upper coating 13 and/or the lower coating 15 as described above contains a coloring agent. You may. By including a colorant in the upper coating film 13 and/or the lower coating film 15, the color tone of the product can be adjusted, and the product can be applied to various uses.
[0075]
　Here, when the color pigment is a black pigment, it is preferably dispersed in the lower coating film 15. This is because if the black pigment is dispersed in the upper coating film 13, the chemical resistance may decrease. It is considered that such a decrease in chemical resistance is because the black pigment in the upper coating film 13 facilitates the permeation 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. .. When the concentration of the black pigment 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 layer coating film 15 exceeds 20% by mass, the chemical resistance and the corrosion resistance may decrease.
[0076]
In the
　coated metal plate 1 according to the present embodiment, the upper coat 13 has a glass transition temperature of 75° C. or higher and 160° C. or lower. A resin coating film obtained by curing an upper coating material containing a certain polyurethane resin (a), a water-soluble melamine resin (b) which is a triazine ring-containing water-soluble curing agent, and an aqueous solvent (for example, polyurethane resin and water-soluble melamine). A resin coating film containing a crosslinked product with a resin is preferable. The glass coating temperature of the resin coating film formed from the upper coating material is 85° C. or higher and 170° C. or lower as a whole. At this time, the water-soluble melamine resin (b) is dispersed in the upper coating film 13 in a granular form and is concentrated on the surface side of the upper coating film 13. Further, 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 polyurethane resin (a) is as follows. It is preferably at least the glass transition temperature of (c).
[0077]
　When a polyester resin is used in place 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 coating film in order to obtain equivalent chemical resistance. .. If the film thickness of the upper coating film is too thick, a desired metallic appearance cannot be obtained when a clear coating film is formed, which is not preferable.
[0078]
　Further, when the lower layer coating film 15 is provided on the coated metal plate 1 according to the present embodiment, the lower layer coating film 15 specifically has a glass transition temperature of the glass transition of the polyurethane resin (a) of the upper layer coating film 13. Polyurethane resin (c) at a temperature or lower, epoxy resin (d), silane coupling agent (e), and any one or more elements selected from the group consisting of P, V, Ti, Si and Zr A resin coating film obtained by curing a lower layer coating material containing at least one of the rust preventive agent (f) containing a water-based solvent (for example, a resin coating film containing a cross-linked product of a polyurethane resin (c) and an epoxy resin (d)). A resin coating film containing a cross-linked 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) The resin coating film containing the crosslinked product of 1. and the rust preventive agent (f), the resin coating film containing the crosslinked product of the polyurethane resin (c) and the silane coupling agent (e), the polyurethane resin (c) and the silane coupling agent ( (e) a resin coating film containing the crosslinked product and the rust preventive agent (f), a resin coating film containing the polyurethane resin (c) and the rust preventive agent (f), etc.). ..
[0079]
　The coated metal plate 1 according to the present embodiment has been described above 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, machinery, furniture, containers, and the like.
[0080]
(Regarding Manufacturing Method of Painted Metal Plate)
　Next , the manufacturing method of the painted metal plate according to the present embodiment will be described in detail with reference to FIG. FIG. 4 is a flow chart showing an example of the flow of the method for manufacturing a coated metal plate according to this embodiment.
[0081]
　The method for producing a coated metal plate according to this embodiment is a method for producing
a coated metal plate 1 having at least an upper coating film 13 on at least one surface of a predetermined metal plate 11 . As shown in FIG. 4, an example of the method for producing a coated metal plate is as follows. A lower layer coating film forming step (step S103) of forming the lower layer coating film 15 on 11 and an upper layer coating film forming step (step S105) of forming the upper layer coating film 13 on the metal plate 11 or the lower layer coating film 15. Have.
[0082]
　Here, the texture forming step and the lower layer coating film forming step may be carried out as necessary. For example, the coated metal plate 1 in which the upper layer coating film 13 is formed on the metal plate 11 having no texture or the like is used. In manufacturing, only step S105 is performed among the three steps shown in FIG.
[0083]
　In the method for manufacturing a coated metal plate shown in FIG. 4, the most important step is the upper layer coating film forming step (step S105). In the upper layer coating film forming step, a polyurethane resin (a) containing an anionic functional group and having a glass transition temperature of 75° C. or higher and 160° C. or lower, and a water-soluble melamine resin (b) which is a triazine ring-containing water-soluble curing agent. And an aqueous solvent, an upper layer coating material (such an upper layer coating material is an example of the first coating material) on the metal plate 11 (when the lower layer coating film 15 is formed on the metal plate 11). , The lower coating film 15) and heating and cooling the metal plate coated with the upper coating material to form the upper coating film 13.
[0084]
　The method for producing a coated metal plate according to the present embodiment is a coated metal plate according to the present embodiment (that is, a coated metal plate excellent in metal appearance, chemical penetration resistance, and solvent resistance) by the above-described method. Can be manufactured while suppressing the cost. The reason is presumed as follows.
[0085]
　First, generally, when forming a coating film with a coating material containing a polyurethane resin and a water-soluble melamine resin, the melamine resin is difficult to coexist with the polyurethane resin because of poor compatibility with the polyurethane resin, As the self-condensed particles become large, the melamine resin thickens in the surface layer of the coating film.
[0086]
　On the other hand, in the method for producing a coated metal plate 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 compound are contained in the aqueous medium. The water-soluble melamine resin (b), which is a water-soluble curing agent, is uniformly mixed and coexists. When the upper layer coating material in such a state is formed on the metal plate 11 (or the lower layer coating film 15) and heated, self-shrinkage of the water-soluble melamine resin (b) is suppressed, and the water-soluble melamine resin (b) and The reaction with the polyurethane resin (a) occurs preferentially. Further, when vaporization (drying) of the aqueous solvent progresses by heating, the polyurethane resin (a) becomes in a molten state. When the polyurethane resin (a) is in a molten state, the glass transition temperature is as high as 75° C. or higher and 160° C. or lower, so that the viscosity increases, resulting in a high cohesive force and a slow diffusion rate of the melamine resin (b). 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) occurs preferentially.
[0087]
　As described above, the melamine resin (b), which has a low compatibility with the polyurethane resin (a), suppresses the self-shrinkage of the water-soluble melamine resin (b) while being concentrated on the surface layer of the coating film, and the polyurethane resin (a ) And react preferentially. 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 coating film 13. And the reaction product resulting from the self-shrinking of the water-soluble melamine resin (b) coexist. As a result, the portion derived from the water-soluble melamine resin (b) is present in the upper coating film 13 in a granular form and in the surface layer of the upper coating film 13 concentrated. Moreover, as described above, when the upper coating film 13 is formed, a high cohesive force is generated in the polyurethane resin (a), so that the reaction between the water-soluble melamine resin (b) and the polyurethane resin (a) is caused. It occurs preferentially. Therefore, the finely divided granular water-soluble melamine resin (b) is concentrated on the surface layer of the upper coating film 13 to form the concentrated portion 103 as shown in FIG. The non-thickened, micronized particulate water-soluble melamine resin (b) forms triazine granules 101 as shown in FIG.
[0088]
　Further, when the lower layer coating film 15 is provided, the lower layer coating film is formed by using the polyurethane resin (c) having a glass transition temperature of 80° C. or higher and 160° C. or lower and a glass transition temperature lower than that of the polyurethane resin (a). By forming 15, high adhesion between the upper layer coating film 13 and the lower layer coating film 15 can be realized. Further, by adopting the polyurethane resin (a) containing an anionic functional group, the dispersibility of the urethane moiety in the water-based medium (water-based paint) is improved, and as a result, the film-forming property of the upper-layer coating film 13 is increased and the upper-layer coating film 13 is formed. High adhesion between the coating film 13 and the lower coating film 15 is realized.
[0089]
　As described above, 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 having excellent metal appearance, chemical penetration resistance, and solvent resistance). ) Is presumed to be able to be manufactured while suppressing the cost.
[0090]
　Hereinafter, the method for manufacturing a coated metal plate according to this embodiment will be described in detail.
[0091]
Although
　the flow is the reverse of that shown in FIG. 4, the upper layer coating film forming step will first be described in detail below.
　In the upper layer coating film forming step, first, an upper layer coating material, which is an example of the first coating material, is prepared. The upper layer coating material contains a polyurethane resin (a), a water-soluble melamine resin (b) which is a water-soluble curing agent containing a triazine ring, and an aqueous solvent.
[0092]
[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 higher and 160°C or lower. Further, in the coated metal plate according to the present embodiment, when not only the upper layer coating film 13 but also the lower layer coating film 15 is formed, the glass transition temperature of the polyurethane resin (a) is the polyurethane resin used for the lower layer coating film 15. It is preferably at least the glass transition temperature of (c).
[0093]
　In order to obtain the high glass transition point temperature (85° C. or higher and 170° C. or lower) in the upper coating film 13 as mentioned above, it is suitable to use a polyurethane resin having a urethane bond. A point temperature polyester resin is difficult to manufacture. Further, since a polyurethane resin having a high glass transition temperature has a very high melt viscosity, it is difficult to apply a coating (form a coating film) unless a coating material dispersed in an aqueous medium is used. Therefore, by imparting an anionic functional group to the polyurethane resin, it becomes possible to disperse it in an aqueous medium together with the water-soluble melamine resin.
[0094]
　The polyurethane resin (a) is, for example, a multivalent compound such as ethylene glycol, propylene glycol, diethylene glycol, 1,6-hexanediol, neopentyl glycol, triethylene glycol, bisphenol hydroxypropyl ether, glycerin, trimethylolethane and trimethylolpropane. Obtaining by reacting alcohols with a diisocyanate compound such as hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, and further chain-extending with diamine or the like, and water-dispersing You can
[0095]
　Examples of the polyurethane resin (a) include 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) and the like are preferable. A coating film using these polyurethane resins is likely to have improved chemical penetration resistance and solvent resistance.
[0096]
　The polyether polyurethane resin, polyester polyurethane resin, and polyether polyester polyurethane resin can be obtained by using at least one of polyether polyol and polyester polyol as the polyhydric alcohol.
　Examples of the polyether polyol include polyethylene glycol, polyoxyethylene glycol, polyoxypropylene glycol, polytetramethylene glycol and copolymers thereof.
　The polyester polyol is, for example, a dibasic acid or a dialkyl ester of a dibasic acid such as terephthalic acid, isophthalic acid, adipic acid, azelaic acid, sebacic acid, ethylene glycol, propylene glycol, diethylene glycol, butylene glycol, neopentyl glycol. , 1,6-hexane glycol, 3-methyl-1,5-pentanediol, 3,3′-dimethylolheptane, polyoxyethylene glycol, polyoxypropylene glycol, polytetramethylene ether glycol, and other glycols, It can be obtained by reacting.
　The polyester polyol can be obtained by ring-opening polymerization of lactones such as polycaprolactone, polyvalerolactone, poly(β-methyl-γ-valerolactone).
[0097]
　The glass transition temperature of the polyurethane resin (a) is 75° C. or higher and 160° C. or lower. When the glass transition temperature of the polyurethane resin (a) is lower than 75°C, the chemical penetration resistance is lowered. On the other hand, when the glass transition temperature of the polyurethane resin (a) exceeds 160°C, the workability is lowered. When the workability is lowered, the upper coating film 13 is cracked and the chemical penetration resistance and the solvent resistance are also lowered. The glass transition temperature of the polyurethane resin (a) is preferably 100° C. or higher and 160° C. or lower from the viewpoint of chemical penetration resistance and solvent resistance (particularly chemical penetration resistance).
[0098]
　Here, the glass transition temperature of various resins including the polyester resin can be measured according to the differential scanning calorimetry (DSC method) of the transition temperature measuring method of plastics (JIS K7121 1987).
[0099]
[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, complete alkyl ether) are used. Melamine resin) can be used. Examples of commercially available water-soluble melamine resins include water-soluble melamine resins manufactured by Nippon Carbide Co., Ornex Co., DIC Co., etc.
[0100]
　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 the melamine resin containing an imino group, the granular water-soluble melamine resin is likely to be concentrated in the surface layer of the upper coating film 13, so that the solvent resistance is further improved.
[0101]
　The term “water-soluble” means that the amount of the target substance dissolved in 100 parts by mass of water at 25° C. is 5 parts by mass or more (preferably 10 parts by mass or more).
[0102]
[Regarding Colorant]
　The colorant dispersed in the upper layer coating material containing the above components is not particularly limited, and known ones can be appropriately used. Examples of such colorants include various inorganic pigments such as titanium oxide, zinc oxide, calcium carbonate, aluminum oxide, barium sulfate, aluminum, iron oxide, copper/chromium complex oxide, carbon black, cyanine, quinacridone, etc. Various organic pigments and various dyes can be used.
[0103]
　When the colorant used is a black pigment such as carbon black or a metal oxide exhibiting a black color, the chemical resistance may decrease, so the concentration in the upper layer paint is limited or dispersed in the lower layer paint. Preferably, it is more preferably dispersed in the lower layer paint.
[0104]
　The type of carbon black dispersed in the upper coating material is not particularly limited, and known carbon blacks such as furnace black, Ketjen black, acetylene black, and channel black can be used.
[0105]
　The particle size of carbon black to be used is not particularly limited as long as there is no problem in dispersibility in paint, coating quality and paintability, but primary particle size of about 10 to 120 nm should be used. Cheap. In particular, when chemical resistance or corrosion resistance is required, it is preferable to use one having a primary particle size of 10 to 50 nm. It is generally difficult to disperse these carbon blacks with their primary particle diameters because agglomeration occurs in the process of being dispersed in the paint. That is, actually, they are present in the coating material in the form of secondary particles having a particle size larger than the primary particle size. The same form is present in such an upper layer paint.
[0106]
　The type of the metal oxide exhibiting a black color is not particularly limited, but known black pigments such as triiron tetroxide and copper-chromium composite oxide can be used.
[0107]
[Aqueous solvent]
　Examples of the aqueous solvent include water, a mixed solution of water and a lower alcohol, and the like. Such an aqueous solvent may contain water in an amount of 50% by mass or more (preferably 80% by mass or more).
　It is not preferable to use a solvent represented by an organic solvent as the solvent, because the melamine particles are dispersed in the coating film and the surface is not thickened. As described above, in order to concentrate the melamine in the coating layer formed by using the solvent-based paint, it is necessary that the solvent-based paint contains an amine compound. Therefore, it is possible to concentrate the melamine particles on the surface without using an amine compound.
[0108]
　Examples of water include distilled water, ion-exchanged water, ultrapure water, and ultrafiltered water. Examples of the lower alcohol include alcohols having 1 to 4 carbon atoms such as methanol, ethanol, butanol, isopropyl alcohol and the like.
[0109]
[Regarding Content] In
　the upper layer coating material containing the above components, the content (Wa, unit:% by mass) of the polyurethane resin (a) with respect to the total solid content, and the water-soluble melamine resin (b) with respect to the total solid content. Content (Wb, unit:% by mass) and total content (Wa)+(Wb) satisfy the following formula (11), and the content (Wa) of the polyurethane resin (a): And the content (Wb) of the water-soluble melamine resin (b), the ratio (Wb)/(Wa) preferably satisfies the following formula (13).
　　90% by mass≦(Wa)+(Wb)≦100% by mass Formula (11)
　　0<(Wb)/(Wa)≦1 Formula (13)
[0110]
　Here, in the above formula (11), when the total content (Wa)+(Wb) is less than 90% by mass, the metal appearance, the chemical permeation resistance and the solvent resistance of the coated metal plate 1 are deteriorated. Sometimes. Further, in the above formula (13), when the ratio (Wb)/(Wa) exceeds 1, the water-soluble melamine resin (b) becomes excessive, and the workability of the coated metal plate 1 may deteriorate. When the workability is lowered, the upper coating film 13 is cracked and the chemical penetration resistance and the solvent resistance are also lowered.
[0111]
　From the viewpoint of metal appearance, chemical permeation resistance and solvent resistance, the total content (Wa)+(Wb) satisfies the following formula (15), and the ratio (Wb)/(Wa) is It is more preferable to satisfy the expression (17).
　　95 mass%≦(Wa)+(Wb)≦100 mass% Formula (15)
　　0.1≦(Wb)/(Wa)≦0.3 Formula (17)
[0112]
　The upper coating material preferably does not contain silica. This is because when the upper coating material contains silica, the upper coating film 13 contains silica, and as a result, the chemical resistance of the upper coating film 13 deteriorates.
　For the same reason, it is preferable that the upper coating material does not contain at least one metal complex compound selected from zinc, aluminum and titanium. Here, the at least one metal complex compound selected from zinc, aluminum and titanium includes, for example, zinc stearate, zinc gluconate, zinc picolinate, zinc citrate, zinc acetylacetonate, aluminum acetate, aluminum stearate. , Aluminum ethylate, aluminum isopropylate, aluminum triisopropyloxide, aluminum ethylacetoacetate diisopropylate, aluminum trisethylacetoacetate, aluminum tris(acetylacetate), aluminum oxide isopropyloxide trimer, titanium tetraisopropoxide, Titanium tetra-normal butoxide, titanium butoxide dimer, titanium tetra-2-ethylhexoxide, titanium diisopropoxybis(acetylacetonate), titanium tetraacetylacetonate, titanium dioctyloxybis(octylene glycolate), titanium diisopropoxy Examples thereof include bis(ethylacetoacetate), titanium diisopropoxybis(triethanolaminate), titanium lactate ammonium salt, titanium lactate, and polyhydroxytitanium stearate.
[0113]
[Film Forming Method (Coating Method)] The method of forming (coating) the
　upper layer coating film on the metal plate 11 or the lower layer coating film 15 in the upper layer coating film forming step is not particularly limited, and may be, for example, a roll. Well-known film forming methods (coating methods) such as a coating method, a Ringer roll coating method, an air spray method, an airless spray method, and a dipping method can be used. Also, if film formation is carried out on a continuous coating line called a coil coating line or sheet coating line that is equipped with a film forming device (coating device) that implements these well-known film forming methods (coating methods), the coating work efficiency will be high and a large amount of material will be produced. It is more preferable because it can be produced.
[0114]
[About heating method (baking method) and cooling method] In the
　upper layer coating film forming step, after the upper layer coating film is formed (applied) on the metal plate 11 or the lower layer coating film 15, the method of heating the upper layer coating film is Although not particularly limited, generally known devices such as a hot-air oven, a direct-fired oven, a far-infrared oven, and an induction heating oven can be used. By heating the film of the upper coating material, the aqueous solvent present in the film of the upper coating material is dried, and then the polyurethane resin (a) and the water-soluble melamine resin (b) react with each other to form the upper coating film 13. It is formed.
[0115]
　On the other hand, the method of cooling the upper coating film 13 after heating is not particularly limited, but for example, well-known methods such as water cooling (spraying, submersion, etc.), air cooling (spraying with nitrogen gas, etc.) are used. can do.
[0116]
　In the upper layer coating film forming step, in particular, after the upper layer coating film is formed, heating is performed under conditions such that the heating time from the start of heating to the maximum reached temperature is 1 second or more and 30 seconds or less. It is preferable to form the upper coating film 13 by cooling under conditions such 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.
[0117]
　When the heating is performed for a short time of 1 second or more and 30 seconds or less after the formation of the upper coating material, the self-shrinkage of the water-soluble melamine resin (b) is further suppressed, and the above-mentioned 0.1% When the cooling is performed for a short time of 5 seconds or more and 5 seconds or less, diffusion of the water-soluble melamine resin (b) is suppressed. As a result, the water-soluble melamine resin (b) that has reacted with the polyurethane resin (a) forms domains, is dispersed in the upper coating film 13 in the form of particles having a number average particle diameter of 5 nm or more and 20 nm, and the upper coating film 13 is formed. It tends to be in a concentrated state on the surface layer within a depth of 15 nm from the surface. Therefore, in the manufactured coated metal plate 1, the metal appearance, chemical penetration resistance, and solvent resistance are likely to be further improved.
[0118]
　Here, when the heating time is less than 1 second, the reaction between the polyurethane resin (a) and the water-soluble melamine resin (b) becomes insufficient, and the chemical penetration resistance and the solvent resistance may decrease. .. On the other hand, when the heating time exceeds 30 seconds, the water-soluble melamine resin (b) is easily self-condensed, the self-condensed particles become large, and a phenomenon occurs in which the surface layer of the coating film is thickened, and the manufactured film is produced. In the coated metal plate 1, the metal appearance and chemical penetration resistance may decrease.
[0119]
　If the cooling time is less than 0.1 seconds, the upper 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 penetration resistance of the manufactured coated metal plate 1 may deteriorate.
[0120]
　From the viewpoint of metal appearance, chemical penetration resistance and solvent resistance, the heating time is preferably 1 second or more and 20 seconds or less. From the same viewpoint, the cooling time is preferably 0.1 second or more and 2 seconds or less.
[0121]
　The maximum temperature and its holding time are not particularly limited, and depending on the aqueous solvent used, after appropriately setting the maximum temperature that is equal to or higher than the boiling point of the aqueous solvent, for example, 0.1 It suffices to set a holding time of not less than 2 seconds and not more than 5 seconds.
[0122]
　When forming a plurality of concentrated portions 103 in the upper 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, it cools. By forming the upper coating film 13 in this manner, in addition to the concentrated portion 103 on the surface layer, the concentrated portion 103 is formed at a depth position other than the surface layer.
[0123]
　Heretofore, the upper coating film forming step according to the present embodiment has been described in detail.
[0124]

　Next, the lower layer coating film forming step in the method for producing a coated metal sheet according to the present embodiment will be described.
　In the method for producing a coated metal sheet according to the present embodiment, the lower layer coating film forming step is not particularly limited, and a well-known lower layer coating material is used as an example of the second coating material to form the lower layer coating film 15 by a well-known method. Can be formed.
[0125]
　Among known methods, from the viewpoint of metal appearance, chemical permeation resistance and solvent resistance, the lower layer coating film forming step includes an anionic functional group and has a glass transition temperature of not more than the glass transition temperature of the polyurethane resin (a). It contains a certain polyurethane resin (c), an epoxy resin (d), a silane coupling agent (e), and any one or more elements selected from the group consisting of P, V, Ti, Si and Zr. In the step of forming a lower layer coating film 15 by forming a lower layer coating material containing at least one of the rust preventive agent (f) and an aqueous solvent on at least one surface of the metal plate 11 and heating and then cooling. Preferably.
[0126]
[Polyurethane Resin (c)] As
　mentioned above, the glass transition temperature of the polyurethane resin (c) is preferably equal to or lower than the glass transition temperature of the polyurethane resin (a). When the glass transition temperature of the polyurethane resin (c) is not higher than the glass transition temperature of the polyurethane resin (a), the adhesion between the lower layer coating film 15 and the upper layer coating film 13 is improved, and the chemical permeation resistance is further improved. It will be easier.
[0127]
　The glass transition temperature of the polyurethane resin (c) is a value within the range of 80° C. or higher and 160° C. or lower, and is equal to or lower than the glass transition temperature of the polyurethane resin (a) (preferably, the glass transition temperature of the polyurethane resin (a). 5° C. or more lower than that) is more preferable. When the glass transition temperature of the polyurethane resin (c) is lower than 80° C., the chemical penetration resistance may decrease. On the other hand, when the glass transition temperature of the polyurethane resin (c) exceeds 160° C., the processability may decrease. When the workability is lowered, the lower coating film 15 is cracked and the chemical penetration 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 higher and 160° C. or lower from the viewpoint of chemical penetration resistance and solvent resistance (particularly chemical penetration resistance).
[0128]
　The polyurethane resin (c) may be a polyurethane resin containing a polyurethane resin having a glass transition temperature of 80°C or higher and 160°C or lower and a polyurethane resin having a glass transition temperature of 20°C or higher and 60°C or lower. By using a polyurethane resin having a different glass transition temperature and adjusting the glass transition temperature of the polyurethane resin (c), the chemical permeation resistance is further improved.
[0129]
　Specific examples of the polyurethane resin (c) include various polyurethane resins exemplified as the polyurethane resin (a).
[0130]
[Regarding Epoxy Resin (d)]
　Examples of the epoxy resin (d) include bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolac type epoxy resin, and aliphatic type epoxy resin. Among these resins, the aliphatic type epoxy resin is not easily discolored by baking, so that it is particularly preferable to use it as the epoxy resin (d).
[0131]
　The specific type of the epoxy resin (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 compound by itself and use it appropriately.
[0132]
[About silane coupling agent (e)] The
　silane coupling agent (e) is not particularly limited, and various known silane coupling agents can be used. Examples of such silane coupling agents include 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-glyc Sidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane and the like can be mentioned. By including such a silane coupling agent in the lower layer coating material, the chemical penetration resistance of the lower layer coating film 15 can be further improved.
[0133]
[About rust preventive agent (f)] In the
　lower coating film forming step according to the present embodiment, as the rust preventive agent (f), any one or more selected from the group consisting of P, V, Ti, Si and Zr. It is possible to use a rust preventive agent containing the element. By including such a rust preventive agent (f) in the lower layer coating material, the corrosion resistance of the lower layer coating film 15 can be improved.
[0134]
　Examples of the P-containing compound that functions as the rust preventive agent (f) include phosphoric acids such as orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, triphosphoric acid, tetraphosphoric acid and salts thereof, and aminotri(methylenephosphonic acid). ), 1-hydroxyethylidene-1,1-diphosphonic acid, ethylenediaminetetra(methylenephosphonic acid), diethylenetriaminepenta(methylenephosphonic acid), and their salts, and organic phosphoric acids such as phytic acid, and their salts Etc. can be mentioned.
[0135]
　Examples of the compound containing V that functions as a rust preventive agent (f) include vanadium pentoxide, metavanadate, ammonium metavanadate, sodium metavanadate, vanadium oxytrichloride, vanadium trioxide, vanadium dioxide, vanadium oxysulfate, and the like. Examples thereof include vanadium oxyacetylacetonate, vanadium acetylacetonate, vanadium trichloride, phosphovanadomolybdic acid and the like. Further, a pentavalent vanadium compound is 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. Salt of oxovanadium cation reduced with tetravalent to divalent by an inorganic acid anion such as hydrochloric acid, nitric acid, phosphoric acid and sulfuric acid or organic acid anion such as formic acid, acetic acid, propionic acid, butyric acid and oxalic acid Alternatively, a chelate of an organic acid and a vanadyl compound such as vanadyl glycolate and vanadyl dehydroascorbate can be used.
[0136]
　Examples of the Ti-containing compound that functions as a rust preventive agent (f) include titanium potassium oxalate, titanyl sulfate, titanium chloride, titanium lactate, titanium isopropoxide, isopropyl titanate, titanium ethoxide, and titanium 2-ethyl. Examples thereof include -1-hexanolate, tetraisopropyl titanate, tetra-n-butyl titanate, titania sol, titanium hydrofluoric acid and salts thereof.
[0137]
　Examples of the Si-containing compound that functions as a rust preventive agent (f) include Snowtex C, Snowtex O, Snowtex N, Snowtex S, Snowtex UP, Snowtex PS-M, Snowtex PS-L. , Snowtex 20, Snowtex 30, Snowtex 40 (all manufactured by Nissan Chemical Industries, Ltd.), Adelite AT-20N, Adelite AT-20A, Adelite AT-20Q (all manufactured by Asahi Denka Co., Ltd.) , Aerosil 50, Aerosil 130, Aerosil 200, Aerosil 300, Aerosil 380, Aerosil TT600, Aerosil MOX80, Aerosil MOX170 (all manufactured by Nippon Aerosil Co., Ltd.) and the like.
[0138]
　Examples of the Zr-containing compound that functions as the rust preventive agent (f) include zirconyl nitrate, zirconyl acetate, zirconyl sulfate, ammonium zirconium carbonate, potassium zirconium carbonate, sodium zirconium carbonate, zirconium acetate, zirconium hydrofluoric acid or the like. Examples thereof include salt.
[0139]
[Coloring Agent]
　The coloring agent dispersed in the lower layer coating material containing the above-mentioned components is not particularly limited, as in the upper layer coating material, and known ones can be appropriately used. As such a colorant, for example, titanium oxide, zinc oxide, calcium carbonate, aluminum oxide, barium sulfate, aluminum, iron oxide, various inorganic pigments such as carbon black, cyanine, various organic pigments such as quinacridone, Various dyes and the like can be used.
[0140]
[Regarding Aqueous Solvent] As the
　aqueous solvent, it is possible to use water, a mixed solution of water and a lower alcohol, or the like, as in the above upper layer coating material. The aqueous solvent preferably contains water in an amount of 50% by mass or more (preferably 80% by mass or more).
[0141]
　Examples of water include distilled water, ion-exchanged water, ultrapure water, and ultrafiltered water. Examples of the lower alcohol include alcohols having 1 to 4 carbon atoms such as methanol, ethanol, butanol, isopropyl alcohol and the like.
[0142]
[Regarding Content] The content
　of the polyurethane resin (c), the epoxy resin (d), the silane coupling agent (e) and the rust preventive agent (f) as described above is not particularly limited. The content of each component may be appropriately determined according to the characteristics required for the lower coating film 15. 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 in the range of, for example, 10 to 40% by mass, and the content of the rust preventive agent (f) is in the range of, for example, 1 to 15% by mass. It can be within. The content of each component from the above range is adjusted so that the total content of the polyurethane resin (c), the epoxy resin (d), the silane coupling agent (e) and the rust preventive agent (f) is 100% by mass. It may be determined appropriately.
[0143]
[Regarding film forming method (coating method), heating method (baking method) and cooling method] In the
　lower layer coating film forming step, regarding the method of forming and heating the lower layer coating material on at least one surface of the metal plate 11 and then cooling it, There is no particular limitation, and for example, various film forming methods (coating methods), heating methods, and cooling methods as described in the upper layer coating film forming step can be used. The maximum temperature, heating time, holding time and cooling time of the metal plate 11 coated with the lower layer coating material are not particularly limited and may be set appropriately.
[0144]
In the
　method for producing a coated metal plate according to the present embodiment, well-known additions such as wax, leveling agent, defoaming agent, thickener, dispersant, etc. to the upper layer coating material and the lower layer coating material. An agent may be included. That is, in the coated metal plate according to this embodiment, both the upper layer coating film 11 and the lower layer coating film 15 may contain these well-known additives.
[0145]
In the
　method for manufacturing a coated metal plate according to the present embodiment, the surface of the metal plate 11 to which the above-described upper layer coating material is applied is, as necessary, satin, roughening, streaks (hairlines), and texture. Various textures such as (satin) and mallet (hammer) may be formed. By forming the above texture on the surface of the metal plate 11 in advance, it is possible to further improve the designability of the coated metal plate according to the present embodiment.
[0146]
　Here, the method and the apparatus used for forming the various textures as described above are not particularly limited, and various known ones can be appropriately used.
[0147]
　The method for manufacturing a coated metal plate according to this embodiment has been described above in detail.
Example
[0148]
　Hereinafter, the coated metal plate and the method for producing a coated metal plate according to the present invention will be described more specifically with reference to Examples and Comparative Examples. The examples shown below are merely examples of the method for producing a coated metal plate and a coated metal sheet according to the present invention, and the method for producing a coated metal sheet and a coated metal sheet according to the present invention is limited to the following examples. Not something that will be done.
[0149]
(Test Example 1)
　Nippon Steel & Sumitomo Metal Corporation's hot dip galvanized steel sheet "NS Silver Zinc (registered trademark)" (hereinafter referred to as "GI"), Nippon Steel & Sumitomo Metal Corporation Electrogalvanized steel sheet "NS Zinccoat (registered trademark)" (hereinafter referred to as "EG"), Nippon Steel & Sumitomo Metal Corporation zinc-nickel alloy plated steel sheet "NS Zinclite (registered trademark)" (hereinafter , "ZL"), zinc-iron alloy plating "NS Silver Alloy (registered trademark)" (hereinafter referred to as "GA"), aluminum plate "JIS3004" (hereinafter referred to as "Al"), stainless steel. Steel plate "SUS430" (hereinafter referred to as "SUS"), zinc-aluminum-magnesium-silicon alloy plated steel sheet "Super Daimer (registered trademark)" (hereinafter referred to as "SD") manufactured by Nippon Steel & Sumitomo Metal Corporation. A zinc-aluminum-magnesium alloy plated steel sheet "ZAM (registered trademark)" (hereinafter referred to as "ZAM") manufactured by Nisshin Steel Co., Ltd. was used as a metal plate (original plate). The plate thickness of each metal plate was 0.6 mm.
[0150]
　The coating amount of ZL was 20 g/m 2 per side , and the amount of nickel in the plating layer was 12% by mass. In addition, the amount of GI, SD, GL, and ZAM deposited on each surface was 60 g/m 2 . The coating weight of GA was 45 g/m 2 per side . The coating weight of EG was 20 g/m 2 per side .
[0151]
In
　this test example, a one-layer structure as shown in FIG. 1A having only the upper layer coating, or the lower layer coating and the upper layer coating are provided on one surface of the metal plate (original plate) as described above. A coated metal plate having a two-layer structure as shown in FIG. 1B was produced. The polyurethane resins used for preparing the upper layer coating material and the lower layer coating material are shown in Table 1 below. Similarly, the polyester resin, the water-soluble melamine resin, the silane coupling agent, the rust preventive, and the colorant used for preparing the lower layer coating material are shown in Tables 2 to 7 below.
[0152]
[table 1]

[0153]
[Table 2]

[0154]
[Table 3]

[0155]
[Table 4]

[0156]
[Table 5]

[0157]
[Table 6]

[0158]
[Table 7]

[0159]
[Original Polyurethane Resin A]
　145 g of 1,3-bis(isocyanatomethyl)cyclohexane, 20 g of dimethylolpropionic acid, 15 g of neopentyl glycol, 75 g of polycarbonate diol having a molecular weight of 1000, and 64 g of acetonitrile as a solvent were added, and the mixture was heated to 75° C. under a nitrogen atmosphere. The temperature was raised and the mixture was stirred for 3 hours. After confirming that a 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 35.6 g of ethylenediaminehydrazine monohydrate was added as a chain extender to carry out a chain extension reaction. Subsequently, the reaction liquid was distilled off at 50° C. under a reduced pressure of 150 mmHg to remove acetonitrile used in the synthesis of the polyurethane prepolymer, thereby obtaining a self-made polyurethane resin A.
　The triethylamine used as a raw material was removed in the resin refining process.
[0160]
[Original Polyurethane Resin B]
　145 g of 1,3-bis(isocyanatomethyl)cyclohexane, 20 g of dimethylolpropionic acid, 15 g of neopentyl glycol, 75 g of polycarbonate diol having a molecular weight of 1000, and 64 g of acetonitrile as a solvent were added, and the mixture was heated to 75° C. under a nitrogen atmosphere. The temperature was raised and the mixture was stirred for 3 hours. After confirming that the predetermined amine equivalent was reached, the reaction solution was cooled to 40° C., and then 20.00 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 700.00 g of water using a homodisper to form an emulsion, the solution was kept at 40° C., 21 g of γ-(2-aminoethyl)aminopropyltrimethoxysilane as a chain extender, and ethylenediaminehydrazine. A chain extension reaction was carried out by adding 18 g of monohydrate. Subsequently, the reaction liquid was distilled off at 50° C. under a reduced pressure of 150 mmHg to remove acetonitrile used in the synthesis of the polyurethane prepolymer, thereby obtaining a self-made polyurethane resin B.
　The triethylamine used as a raw material was removed in the resin refining process.
[0161]
　By using the raw materials shown in Tables 1 to 7 and mixing the respective raw materials in a predetermined amount in water as described in Tables 8 and 9, an upper layer coating material and a lower layer coating material were produced.
[0162]
[Table 8]

[0163]
[Table 9]

[0164]
　In Table 9, the lower coating materials 9, 10 and 11 were prepared by mixing 15 parts by mass of the main resin-2 with 100 parts by mass of the main resin-1.
[0165]

　Various metal plates are degreased by immersing them in an aqueous solution containing 2% by mass of FC-4336 (manufactured by Nippon Parkerizing) at a temperature of 60°C for 10 seconds, washed with water, and dried. Let
[0166]
　Next, the lower layer coating material produced as described above was applied by a roll coater so as to have a predetermined dry film thickness. In an induction heating furnace in which hot air was blown, the film of the lower layer paint was heated (dried) under the conditions that the maximum temperature of the metal plate reached 150°C and the heating time from the start of heating to the maximum temperature reached was 10 seconds. Hardened). One second after reaching the maximum temperature, the coated metal plate was wiped with water by spraying, and water cooling was performed under the condition that the cooling time from the maximum temperature to 30°C was 1 second. The holding time of the highest temperature reached during heating was 1 second.
[0167]
　Next, the upper layer coating material produced as described above was applied by a roll coater so as to have a predetermined dry film thickness. In an induction heating furnace in which hot air is blown, the maximum temperature of the metal plate reaches 230°C, and the upper coating film is heated (dry hardening) under the condition that the heating time from the start of heating to the maximum temperature reaches 10 seconds. did. 1 second after reaching the highest temperature, wipe the coated metal plate with water with a spray, and 1 second after reaching the highest temperature with a water spray on the coated metal plate, Water cooling was performed under the condition that the cooling time from the highest temperature to 30° C. was 1 second. The holding time of the highest temperature reached during heating was 1 second.
[0168]
The
　composition of the upper coating film and the lower coating film was analyzed for each sample of the coated metal plate produced.
　Specifically, the constituent parts of the upper coating film and the lower coating film (urethane bond skeleton (UB), triazine ring skeleton (TR), epoxy group (EP), presence or absence of siloxane bond (silane) derived from silane coupling agent) The coating film was analyzed using a Fourier transform infrared spectrophotometer (FT-IR, Frontier manufactured by PerkinElmer) and judged based on whether the following vibration peaks were observed. If it is, and as "Yes" in the table.
　　urethane bond backbone (UB): 1540 cm -1 observed in the vicinity of the N-H vibrational peak of bending vibration, and, 1730 cm -1 is observed in the vicinity C = O stretching vibration of the vibration peak
　　triazine ring skeleton (TR): 1550,1450,815Cm -1 vibration peak derived from triazine ring observed in the vicinity of
　　the epoxy group (EP): 910 cm -1 derived from epoxy groups observed in the vicinity Vibration peak of
　　Siloxane bond: Vibration peak of Si—O—Si stretching vibration observed near 1050 cm −1
[0169]
　In addition, according to the method described above, in the upper coating film, the thickness (concentration depth) of the concentrated portion existing in the surface layer, and the number average particle diameter (particle diameter of the triazine moiety (water-soluble melamine resin)) of the granular triazine portion (particle diameter) ) Was measured respectively. Further, N concentration N1 at a depth position of 0.2 μm from the surface of the first coating film and N concentration N2 at a depth position of 0.2 μm from the interface between the first coating film and the metal plate to the first coating film side. N1/N2 (concentration ratio), which is the ratio of and, was measured according to the method described above. Further, the glass transition temperature (Tg) of each coating film was measured for each manufactured sample of the coated metal plate according to the method described above.
　In addition, when the surface layer concentrated portion is stained with osmium oxide and observed with a transmission electron microscope at a magnification of 100,000 times, whether or not melamine particles of 5 nm or more are observed, and a plurality of concentrated portions are formed. It was determined according to the method described above.
[0170]

　Each manufactured coated metal plate was evaluated according to the following criteria.
[0171]
[Metal Appearance] For
　each of the manufactured coated metal plates, the C*LAB (JISZ8729) L*, a*, b* color system was used with the Konica Minolta CR-400 spectrophotometer (light source 10°D65, SCI method). And evaluated in four grades of (excellent) A, B, C, and D (inferior).
　　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
[0172]
[Chemical Penetration Resistance Test]
　Each of the manufactured coated metal plates was cut into a width of 5 cm, and the end surface of each sample was protected with Nitoflon (registered trademark) tape. It was dipped for 24 hours, and the degree of discoloration was evaluated in four grades of (excellent) A, B, C and D (poor).
　　A: No discoloration AB
　　: Very slight discoloration
　　B: Slight discoloration
　　C: Many discolorations
　　D: Many discolorations and peeling of coating film
[0173]
[
　Workability test] Each of the manufactured coated metal plates was cut into a width of 5 cm, and subjected to 2T 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 inside, and the surface on which the upper layer coating film and the lower layer coating film were formed was set to the outer side, and 180 degree contact bending was performed. The cracks in the coating film were evaluated in four grades of (excellent) A, B, C and D (poor).
　　A: No cracks
　　B: Slight cracks
　　C: Many cracks
　　D: Many cracks and peeling of coating film
[0174]
[Contamination resistance test]
　Red ink was applied to each of the manufactured coated metal plates (Teranishikagaku Kogyo Co., Ltd.) and wiped off with ethanol after 24 hours. It was evaluated in four grades of C and D (poor). In addition, for those with remarkable marks, a commercially available spectrocolorimeter (light source 10°D65, SCI method) was used to measure the a* value representing CIELAB (JIS Z8729) redness before and after the test, and the difference (Δa*) was evaluated as follows.
　　A: No trace
　　B: Slight trace
　　C: Δa*≦3
　　D: Δa*>3
[0175]
　Table 10 shows the levels and evaluation results of the manufactured coated metal plates. The abbreviations in Table 10 are as follows. The same applies to other tables regarding abbreviations and the like.
　　UB: Urethane bond skeleton
　　TR: Triazine ring skeleton
　　EP: Epoxy group
　　silane: Siloxane bond
　　Rust inhibitor: Rust inhibitor (f)
　　Concentration depth: Concentrated portion formed in the surface layer (referred to as surface layer concentrated portion) In some cases) thickness
　　particle size: number average particle size of triazine granules (water-soluble melamine resin)
　　Tg: glass transition temperature
　　Tg difference of each coating film : difference in glass transition temperature between upper coating film and lower coating film (Glass transition temperature of upper layer coating-glass transition temperature of lower layer coating)
[0176]
[Table 10-1]

[0177]
[Table 10-2]

[0178]
　As is clear from Tables 10-1 and 10-2, the coated metal plates corresponding to the examples of the present invention are excellent in metal appearance, chemical penetration resistance, solvent resistance and workability. ..
[0179]
　On the other hand, as is clear from Table 10-2, when the concentrated layer is not formed on the surface layer of the upper 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 When observed) (Comparative Example 105), the chemical permeation resistance is clearly inferior to the Examples. It can be seen that when the upper coating film 13 does not have a urethane bond skeleton (Comparative Example 104), the chemical permeation resistance is clearly inferior to that in the Examples. It can be seen that when the triazine ring skeleton is not present and the granular triazine moiety is not concentrated on the surface layer of the upper coating film (Comparative Example 103), the chemical resistance and the solvent resistance are clearly inferior to those of the Examples. .. It can be seen that when the glass transition temperature of the upper coating film 13 is lower than 80° C. (Comparative Example 101), the chemical resistance and penetrability are clearly inferior to those of the examples. When the glass transition temperature of the upper coating film 13 is higher than 170° C. (Comparative Example 102), the workability is obviously inferior, and when processed, the chemical resistance and the solvent resistance are lowered. ..
[0180]
　Further, as is clear from Table 10-2, when the upper layer coating material contained silica (Comparative Example 106), the chemical penetration resistance and stain resistance were inferior to those of the Examples.
　When the upper coating material contained the metal complex compound (Comparative Examples 107, 108, 109), the chemical permeation resistance was inferior to that of the Examples.
[0181]
　Further, in the upper coating film 13, when the granular triazine site is concentrated at a position exceeding 15 nm from the surface layer (Example 143), the processability was lower than that of the other Examples, and the processing was not performed. It can be seen that the chemical resistance, the permeation resistance and the solvent resistance are lowered when the above is done. Moreover, when the glass transition temperature of the lower layer coating film 15 is higher than the glass transition temperature of the upper layer coating film 13 (Example 146), it turns out that chemical penetration resistance is inferior compared with other Examples.
[0182]
(Test Example 2) An
　electrogalvanized steel sheet "NS Zincoat (registered trademark)" (hereinafter, referred to as "EG") manufactured by Nippon Steel & Sumitomo Metal Corporation is used as a metal plate (original plate). used. The coating weight of EG was 20 g/m 2 per side .
[0183]
In
　this test example, a one-layer structure as shown in FIG. 1A having only the upper layer coating, or the lower layer coating and the upper layer coating are provided on one surface of the metal plate (original plate) as described above. A coated metal plate having a two-layer structure as shown in FIG. 1B was produced.
[0184]
　Commercially available resins, silane coupling agents and rust preventives used for forming the upper coating film and the lower coating film are as follows.
　　Polyurethane resin for upper coating film: Polyurethane resin 4 in Test Example 1 Polyurethane resin
　　for lower coating film: 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 Antirust agent
　　: Antirust agent 2 in Test Example 1 Wax: Chemipearl S100 (manufactured by Mitsui Chemicals, Inc.)
[0185]
　The upper layer coating material was prepared by mixing the polyurethane resin, the melamine resin and the wax in predetermined amounts in a composition according to Table 11. Similarly, the lower layer paint was prepared by mixing the polyurethane resin, the epoxy resin, the silane coupling agent, the rust preventive agent, and the coloring agent in a predetermined amount in a composition according to Table 11.
[0186]

　Various metal plates are degreased by immersing them in an aqueous solution containing 2% by mass of FC-4336 (manufactured by Nippon Parkerizing) at a temperature of 60°C for 10 seconds, washed with water, and dried. Let
[0187]
　Next, the lower layer coating material produced as described above was applied by a roll coater to a dry film thickness of 0.5 μm. In an induction heating furnace in which hot air is blown, the film of the lower layer paint is heated (dried) under the conditions that the maximum temperature of the metal plate reaches 150°C and the heating time from the start of heating to the maximum temperature reaches 5 seconds. Hardened). One second after reaching the maximum temperature, the coated metal plate was wiped with water by spraying, and water cooling was performed under the condition that the cooling time from the maximum temperature to 30°C was 1 second. The holding time of the highest temperature reached during heating was 1 second.
[0188]
　Next, the upper layer coating material produced as described above was applied by a roll coater to a dry film thickness of 10 μm. In an induction heating furnace in which hot air is blown, the maximum temperature of the metal plate reaches 230°C, and the upper coating film is heated (dry hardening) under the condition that the heating time from the start of heating to the maximum temperature reaches 10 seconds. did. 1 second after reaching the highest temperature, wipe the coated metal plate with water with a spray, and 1 second after reaching the highest temperature with a water spray on the coated metal plate, Water cooling was performed under the condition that the cooling time from the highest temperature to 30° C. was 1 second. The holding time of the highest temperature reached during heating was 1 second.
[0189]
For
　each sample of each coated metal plate produced, according to the method described above, the position (concentration depth) of the region where the granular triazine moiety (water-soluble melamine resin) is concentrated in the upper coating film, The number average particle size (particle size) of the granular triazine moiety (water-soluble melamine resin) was measured. In addition, the degree of concentration of the triazine site present in the region where the granular triazine site (water-soluble melamine resin) is concentrated was measured according to the method described above. Further, the glass transition temperature (Tg) of each coating film was measured for each manufactured sample of the coated metal plate according to the method described above.
　In addition, when the surface layer concentrated portion is stained with osmium oxide and observed with a transmission electron microscope at a magnification of 100,000 times, whether or not melamine particles of 5 nm or more are observed, and a plurality of concentrated portions are formed. It was determined according to the method described above.
[0190]
For
　each manufactured coated metal plate, the same evaluation as in Test Example 1 was performed for the metal appearance, chemical permeation resistance test, and stain resistance test. The workability test and the corrosion resistance of the processed part were evaluated as follows.
[0191]
[
　Workability Test] Each of the manufactured coated metal plates was cut into a width of 5 cm, and 6T bending was performed in an atmosphere of 20° C. by a test method according to JIS G3312. Specifically, six sheets of the same coated plate as the test piece were sandwiched on the inner side, and 180 degree contact bending was performed with the surface on which the upper layer coating film and the lower layer coating film were formed as the outer side. The cracks in the coating film were evaluated in four grades of (excellent) A, B, C and D (poor).
　　A: No cracks
　　B: Slight cracks
　　C: Many cracks
　　D: Many cracks and peeling of coating film
[0192]
[Processed part corrosion resistance test]
　Each of the manufactured coated metal plates was cut into a width of 5 cm and extruded. The extrusion height was 7 mm. Then, a salt spray test according to JIS Z 2371 was carried out for 240 hours. After the test, the white rust generation area ratio in the entire area of ​​the processed part was obtained by visual observation and evaluated as follows. The white rust occurrence area ratio is the percentage of the area of ​​the white rust occurrence area to the area of ​​the observed area.
　　A: White rust occurrence area ratio less than 10%
　　B: White rust occurrence area ratio 10% to less than 25%
　　C: White rust occurrence area ratio 25% to less than 50%
　　D: White rust occurrence area ratio of 50% to less than 75%
　　E : White rust occurrence area ratio 75% or more
[0193]
　Table 11 shows the levels and evaluation results of the manufactured coated metal plates. The abbreviations in Table 11 are the same as those in Table 10.
　However, (Wa)+(Wb) and (Wb)/(Wa) are as follows.
　　(Wa)+(Wb): Content of polyurethane resin (a) (Wa: unit, mass%) with respect to total solids, and content of water-soluble melamine resin (b) (Wb: unit, mass) with respect to total solids %), and the total content
　　(Wb)/(Wa): the content (Wa) of the polyurethane resin (a) with respect to the total solids, and the content (Wb) of the water-soluble melamine resin (b) with respect to the total solids. And the ratio of
[0194]
[Table 11]

[0195]
　As is clear from Table 11, the total content (Wa)+(Wb) of the polyurethane resin (a) and the water-soluble melamine resin (b) used in the upper coating film 13 is 90% by mass or more and 100% by mass or more. It can be seen that when the ratio (Wb)/(Wa) is 0% or more and 0 is more than 0 and 1 or less, the chemical permeation resistance of the manufactured coated metal sheet is further improved.
[0196]
(Test Example 3) An
　electrogalvanized steel sheet "NS Zincoat (registered trademark)" (hereinafter, referred to as "EG") manufactured by Nippon Steel & Sumitomo Metal Corporation was used as a metal plate (original plate) used. The coating weight of EG was 20 g/m 2 per side .
[0197]
In
　this test example, a one-layer structure as shown in FIG. 1A having only the upper layer coating, or the lower layer coating and the upper layer coating are provided on one surface of the metal plate (original plate) as described above. A coated metal plate having a two-layer structure as shown in FIG. 1B was produced.
[0198]
　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.
[0199]

　Various metal plates are degreased by immersing them in an aqueous solution containing 2% by mass of FC-4336 (manufactured by Nippon Parkerizing) at a temperature of 60°C for 10 seconds, washed with water, and dried. Let
[0200]
　Next, the lower layer coating material produced as described above was applied by a roll coater to a dry film thickness of 1.0 μm. In an induction heating furnace in which hot air is blown, the film of the lower layer paint is heated (dried) under the conditions that the maximum temperature of the metal plate reaches 150°C and the heating time from the start of heating to the maximum temperature reaches 5 seconds. Hardened). One second after reaching the maximum temperature, the coated metal plate was wiped with water by spraying, and water cooling was performed under the condition that the cooling time from the maximum temperature to 30°C was 1 second. The holding time of the highest temperature reached during heating was 1 second.
[0201]
　Next, the upper layer coating material produced as described above was applied by a roll coater to a dry film thickness of 8 μm. In the induction heating furnace in which hot air is blown, the uppermost layer temperature of the metal plate, the heating time from the start of heating to the highest temperature and the holding time at 40 to 100° C. are the upper layers so that the conditions are as shown in Table 12. The paint film was heated (dry cured). One second after the maximum temperature was reached, the coated metal plate was wiped with water by spraying, and water cooling was performed under the condition that the cooling time from the maximum temperature to 30° C. was the time shown in Table 12. The holding time of the highest temperature reached during heating was 1 second.
[0202]
For
　each sample of the coated metal plate produced, according to the method described above, in the upper coating film, the thickness of the surface concentrated portion (concentration depth) and the granular triazine portion (water-soluble melamine resin) The number average particle size (particle size) was measured. Further, N concentration N1 at a depth position of 0.2 μm from the surface of the first coating film and N concentration N2 at a depth position of 0.2 μm from the interface between the first coating film and the metal plate to the first coating film side. The ratio of N1/N2 was measured according to the method described above. Further, the glass transition temperature (Tg) of each coating film was measured for each manufactured sample of the coated metal plate according to the method described above.
　In addition, when the surface layer concentrated portion is stained with osmium oxide and observed with a transmission electron microscope at a magnification of 100,000 times, whether or not melamine particles of 5 nm or more are observed, and a plurality of concentrated portions are formed. It was determined according to the method described above.
[0203]
For
　each manufactured coated metal plate, the same evaluation as in Test Example 1 was performed.
[0204]
　Table 12 shows the levels and the evaluation results of the manufactured coated metal plates. The abbreviations in Table 12 are the same as those in Table 10.
[0205]
[Table 12]

[0206]
　As is clear from Table 12, after the upper layer coating is formed, the heating time from the start of heating to the maximum reached temperature is heated under the condition of 1 second or more and 30 seconds or less, and the cooling time from the maximum reached temperature to 30° C. When the upper coating film 13 is formed by cooling under conditions of 0.1 second or more and 5 seconds or less, the obtained coated metal plate has excellent metal appearance, chemical penetration resistance, workability, solvent resistance, and particularly, It had excellent chemical penetration resistance.
　Further, in the first coating film produced by a method of holding at a temperature of 40 to 100° C. for 1 to 20 seconds, then heating to over 200° C. for 1 to 10 seconds, and then cooling, a plurality of concentrated layers are formed. Formed (Examples 315, 316, 317). When a plurality of concentrated layers were formed on the first coating film, the metal appearance, chemical penetration resistance, workability and solvent resistance were all excellent.
[0207]
　When the maximum reached plate temperature was 160° C. (Comparative Example 301), the chemical penetration resistance and solvent resistance were poor.
[0208]
　Here, after the cross section of the upper coating film 13 of Example 303 was dyed with osmium oxide, it was 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 to 5D. 5A, 5C and 5D are sectional TEM images of the upper coating film 13 of Example 303, and FIG. 5B is a TEM image of the upper coating film 13 of Example 303 stained with osmium oxide. It is an element mapping image of osmium when observed by EDX.
[0209]
　As is clear from FIG. 5A, in the cross-sectional TEM image of the upper coating film 13 of Example 303, it can be seen that a black linear region appears on the surface side. Looking at the osmium element mapping image shown in FIG. 5B, the osmium element that selectively stains the triazine site is linearly distributed in the portion corresponding to the black linear region in FIG. 5A. From these results, it can be seen that the black linear region in FIG. 5A corresponds to the thickened portion 103.
[0210]
　5C is an enlarged view of the 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 are reflected in the cross-sectional TEM image. FIG. 5D is an enlarged view of one of the black particles. When the regions corresponding to FIGS. 5C and 5D are confirmed in FIG. 5B, it can be seen that the element of osmium is dispersed in these regions. Therefore, it is understood that these dispersed osmium portions correspond to the triazine granular material 101. That is, it can be seen that the black granular material in FIGS. 5C and 5D is the triazine granular material 101.
[0211]
　The preferred embodiments of the present invention have been described above in detail with reference to the accompanying drawings, but the present invention is not limited to these examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.
Explanation of symbols
[0212]
　DESCRIPTION OF SYMBOLS 　　　1 Coated metal plate
　　11 Metal plate
　　13 Upper layer coating film (first coating film)
　　15 Lower layer coating film (second coating film)
　101 Triazine granules (dispersion type second part)
103 Concentrated part (concentration type second part)
The scope of the claims
[Claim 1]
　A metal plate;
　a first coating film which is located on at least one side of the metal plate and contains a resin;
and
　the first coating film has:
　　a first portion having a urethane bond skeleton; and a
　　triazine ring skeleton. a second portion;
has,
　the glass transition temperature of the first coating is at 85 ° C. or higher 170 ° C. or less,
　the second portion was stained with osmium oxide, 100,000 times using a transmission electron microscope When viewed magnification:
　　number average particle diameter 5 and the second portion distributed particles of ~ 20 nm are dispersed;
　　present at the position of depth 15nm from the surface of the first coating film, the number average particle diameter 5nm A coated metal plate, characterized in that : the above-mentioned particles and the thickened second part where the above particles are not observed
are observed
.
[Claim 2]
　N concentration N1 at a depth position of 0.2 μm from the surface of the first coating film, N at a depth position of 0.2 μm from the interface between the first coating film and the metal plate to the first coating film side.
The coated metal plate according to claim 1, wherein N1/N2, which is a ratio to the concentration N2, is 1.2 or more .
[Claim 3]

The coated metal plate according to claim 1, 　wherein the first coating film has a plurality of the concentration-type second portions .
[Claim 4]
　A second coating film is further provided between the first coating film and the metal plate,
　wherein the glass transition temperature of the second coating film is equal to or lower than the glass transition temperature of the first coating film
. The coated metal plate according to any one of claims 1 to 3.
[Claim 5]

The coated metal plate according to claim 4, 　wherein the second coating film contains a resin and has a urethane bond skeleton .
[Claim 6]
　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.
[Claim 7]

The coated metal plate according to any one of claims 4 to 6, 　wherein the second coating film contains a resin and has a siloxane bond .
[Claim 8]
　Wherein the second coating film, P, V, Ti, include any one or more elements selected from the group consisting of Si and Zr
, characterized in that, any one of claims 4-7 The painted metal plate described in.
[Claim 9]

The coated metal plate according to any one of claims 4 to 8 　, wherein the glass transition temperature of the first coating film is higher than the glass transition temperature of the second coating film by 5°C or more .
[Claim 10]

The coated metal plate according to any one of claims 4 to 9, 　wherein the thickness of the second coating film is 0.5 μm or more and 15 μm or less .
[Claim 11]

The coated metal plate according to any one of claims 1 to 10, 　wherein the film thickness of the first coating film is 0.5 μm or more and 15 μm or less .
[Claim 12]

The coated metal plate 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 .
[Claim 13]

The coated metal plate according to any one of claims 4 to 12, 　wherein the second coating film contains a black pigment as a colorant .
[Claim 14]

The coated metal plate according to any one of claims 1 to 13, characterized 　in that a texture is formed on at least one surface of the metal plate.
[Claim 15]
　A method for producing a coated metal plate having a predetermined first coating film
　on at least one surface of a metal plate, the glass transition temperature of which includes an anionic functional group on at least one surface of the metal plate and is 75°C or higher and 160°C or lower. Coating a first paint containing a polyurethane resin (a), a triazine ring-containing water-soluble curing agent (b), and an aqueous solvent, and heating the metal plate coated with the first paint. The
method for producing a coated metal plate , wherein the first coating film is formed by .
[Claim 16]
　The
method for producing a coated metal plate according to claim 15, wherein the triazine ring-containing water-soluble curing agent (b) is a melamine resin containing an imino group .
[Claim 17]
　The first coating
　composition contains a total content (Wa) of the polyurethane resin (a) based on the total solid content and a content (Wb) of the triazine ring-containing water-soluble curing agent (b) based on the total solid content. The amount (Wa)+(Wb) satisfies the following formula (I), and
　the content (Wa) of the polyurethane resin (a) based on the total solid content and the triazine ring content based on the total solid content.
The coating according to claim 15 or 16, characterized in that the ratio (Wb)/(Wa) of the content (Wb) of the water-soluble curing agent (b) satisfies the following formula (II). Manufacturing method of metal plate.
　　90% by mass≦(Wa)+(Wb)≦100% by mass Formula (I)
　　0<(Wb)/(Wa)≦1 Formula (II)
[Claim 18]
　A method for producing a coated metal plate further having a predetermined second coating film between the metal plate and the first coating film,
　wherein the glass transition temperature of the polyurethane resin (a 1) selected from the group consisting of a polyurethane resin (c) having a glass transition temperature of 5) or less, an epoxy resin (d), a silane coupling agent (e), and P, V, Ti, Si, and Zr. A second coating material containing at least one of the rust preventive agent (f) containing one or more elements and an aqueous solvent is applied on at least one surface of the metal plate, and the second coating material is applied. The
method for producing a coated metal plate according to any one of claims 15 to 17 , wherein the second coating film is formed by heating a metal plate.
[Claim 19]
　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 .
[Claim 20]
　When the first coating film is formed,
　the first coating material is applied so that the heating time from the start of heating the metal plate coated with the first coating material to the maximum temperature reaches 1 second or more and 30 seconds or less. metal plate is heated and
　the like cooling time from the peak temperature to 30 ° C. is 5 seconds or less than 0.1 seconds, cooling the coated metal plate of the first coating material
and wherein the The method for producing a coated metal plate according to any one of claims 15 to 19, which comprises:
[Claim 21]

The coated metal sheet according to claim 20, characterized in that, 　in the heating, the temperature is kept at 40 to 100°C for 1 to 20 seconds, and then the temperature is raised to more than 200°C for the heating time of 1 to 10 seconds . Production method.