CN111278648B - Coated metal plate and method for producing coated metal plate - Google Patents

Coated metal plate and method for producing coated metal plate Download PDF

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Publication number
CN111278648B
CN111278648B CN201880070229.9A CN201880070229A CN111278648B CN 111278648 B CN111278648 B CN 111278648B CN 201880070229 A CN201880070229 A CN 201880070229A CN 111278648 B CN111278648 B CN 111278648B
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China
Prior art keywords
coating film
metal sheet
coated metal
resin
glass transition
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CN201880070229.9A
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CN111278648A (en
Inventor
柴尾史生
东新邦彦
二叶敬士
小林亚畅
石冢清和
冈田克己
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Nippon Steel Corp
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Nippon Steel and Sumitomo Metal Corp
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
    • B05D7/14—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials to metal, e.g. car bodies
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
    • B05D7/24—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials for applying particular liquids or other fluent materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
    • B05D7/50—Multilayers
    • B05D7/52—Two layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B15/00—Layered products comprising a layer of metal
    • B32B15/04—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B15/08—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
    • B32B15/095—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin comprising polyurethanes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B15/00—Layered products comprising a layer of metal
    • B32B15/04—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B15/08—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
    • B32B15/098—Layered products comprising a layer of metal comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin comprising condensation resins of aldehydes, e.g. with phenols, ureas or melamines
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
    • B32B27/20—Layered products comprising a layer of synthetic resin characterised by the use of special additives using fillers, pigments, thixotroping agents
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/38—Layered products comprising a layer of synthetic resin comprising epoxy resins
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/40—Layered products comprising a layer of synthetic resin comprising polyurethanes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/42—Layered products comprising a layer of synthetic resin comprising condensation resins of aldehydes, e.g. with phenols, ureas or melamines
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/02—Physical, chemical or physicochemical properties
    • B32B7/027—Thermal properties
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D161/00—Coating compositions based on condensation polymers of aldehydes or ketones; Coating compositions based on derivatives of such polymers
    • C09D161/20—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen
    • C09D161/26—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen of aldehydes with heterocyclic compounds
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D175/00—Coating compositions based on polyureas or polyurethanes; Coating compositions based on derivatives of such polymers
    • C09D175/04—Polyurethanes
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D7/00—Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
    • C09D7/40—Additives

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  • Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Laminated Bodies (AREA)
  • Application Of Or Painting With Fluid Materials (AREA)
  • Paints Or Removers (AREA)
  • Coating With Molten Metal (AREA)

Abstract

A coated metal plate comprising a metal plate and a first coating film which is provided on at least one surface of the metal plate and contains a resin, wherein the first coating film has a first site and a second site, the first site has a urethane bond skeleton, the second site has a triazine ring skeleton, the first coating film has a glass transition temperature of 85 ℃ to 170 ℃, and when the second site is dyed with osmium oxide and observed with a transmission electron microscope at a magnification of 10 ten thousand times, a dispersed second site in which particles having a number average particle diameter of 5nm or more are dispersed and an enriched second site in which the particles having a number average particle diameter of 5nm or more are not observed are observed.

Description

Coated metal plate and method for producing coated metal plate
Technical Field
The present invention relates to a coated metal sheet and a method for manufacturing a coated metal sheet.
This application claims priority based on japanese patent application No. 2017-209460, filed in japan at 30.10.2017, the contents of which are incorporated herein by reference.
Background
Coated metal sheets coated with a coating film are used for automobiles, home appliances, building materials, civil engineering, machinery, furniture, containers, and the like, instead of conventional coated products which are coated after processing. Such a coated metal sheet is generally cut after coating the metal sheet with a paint, and then press-formed.
Coated metal sheets are used mainly as exterior materials and exposed to various solvents and chemicals, and therefore, often have solvent resistance and chemical resistance. Since it is an exterior material, a coated metal sheet usually subjected to color coating is often used, and the coating film has a large thickness for the purpose of color shading. On the other hand, in the case of a coated metal sheet in which the appearance of the metal sheet as a base is directly designed to have a metallic color tone, it is necessary to perform clear coating without containing a coloring pigment. In such a case, the film thickness of the transparent coating film is reduced, whereby the metal appearance of the coated metal sheet is excellent. In addition, from the viewpoint of productivity and commercial properties, a transparent coating film having a small thickness is more excellent.
Generally, as chemical resistance, it is required that a coating film is not deteriorated or discolored by chemicals. However, when the film thickness of the coating film is thin, the chemical penetrates into the interface of the plating layer to dissolve the plating layer, which is a problem compared to the case where the coating film is deteriorated by the chemical. In the case of color coating, even if the metal is discolored by chemicals, the appearance is not abnormal, but the metal is dissolved to generate corrosion products, and the generated corrosion products cause the coating film to swell, resulting in the appearance being abnormal. On the other hand, in the case of clear coating, the appearance is considered to be abnormal at the time of discoloration of the metal. That is, in the clear coating, it is necessary to prevent the chemical components from reaching the metal. Such a property is called chemical resistance to permeability.
Several examples of coated metal sheets having excellent chemical resistance have been reported.
For example, patent document 1 below discloses a technique of a method for coating a metal plate with a coating material containing a solvent-soluble fluororesin as a main component.
Patent document 2 below discloses a technique for coating a metal plate with a coating film using a polyester resin having a high glass transition temperature, a polyester resin having a low glass transition temperature, and an amino-formaldehyde resin, thereby achieving excellent workability, stain resistance, scratch resistance, and chemical resistance.
Patent document 3 below discloses a technique for precoated metal that is excellent in stain resistance, chemical resistance, weather resistance, and workability by coating an upper layer with a polyacrylic resin and a lower layer with a polyester resin.
Patent document 4 below discloses a technique for coating a metal plate with a coating film obtained by mixing a specific polyurethane resin and a specific polyester resin, thereby achieving excellent workability, corrosion resistance (particularly, edge surface corrosion resistance), chemical resistance, and the like.
Patent document 5 below discloses a technique for forming a metal plate having excellent bending workability by dispersing a coating film of melamine resin particles having a particle size of 50nm or less.
Patent document 6 below discloses a technique of enriching an aminoplast resin (aminoplast resin) in a surface layer of a coating film using an aminoplast resin such as a melamine resin.
Prior art documents
Patent document
Patent document 1: japanese unexamined patent publication Hei 5-111675
Patent document 2: japanese unexamined patent publication Hei 7-331167
Patent document 3: japanese unexamined patent publication Hei 7-313929
Patent document 4: japanese laid-open patent application No. 2013-213281
Patent document 5: japanese laid-open patent publication No. 2005-53002
Patent document 6: japanese unexamined patent publication No. 2006-175815
Disclosure of Invention
However, the fluororesin used in the technique of patent document 1 is expensive and is not industrially preferable.
As in patent document 2, it is also suggested that the self-condensation reaction of a melamine resin as a crosslinking agent is utilized in the formation of a coating film using a solvent-based coating material. However, in this disclosure, the conditions of surface enrichment required to form the barrier layer are also not considered. It is also disclosed that an amine compound is added for surface enrichment, but the effect is to such an extent that the distribution density of the generated melamine self-condensed particles is influenced. Therefore, the coating film obtained under these conditions has a structure in which coarse self-condensed product particles of about 50 to 100 μm are dispersed in the coating film and the surface concentration is confirmed as the distribution density of the particles, and the effect of improving the chemical resistance permeability of the coating film is limited.
The polyacrylic resin used in the technique of patent document 3 has poor processability, and when the coating film disclosed in patent document 3 is a transparent coating film, the barrier property is insufficient and the chemical resistance is poor.
The coating film disclosed in patent document 4 has insufficient barrier properties and is poor in chemical resistance.
When the melamine resin particles are dispersed in the coating film as in the technique of patent document 5, the solvent resistance of the coating film is poor.
In the technique disclosed in patent document 6, the melamine resin particles in the coating film have a large particle size, insufficient barrier properties, and poor chemical resistance.
As described above, the above patent documents 1 to 6 do not disclose a technique for obtaining a coated metal sheet having excellent metal appearance, chemical permeation resistance, and solvent resistance while suppressing the production cost.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a coated metal sheet which is excellent in metal appearance, chemical permeation resistance and solvent resistance while suppressing the production cost, and a method for producing such a coated metal sheet.
The present inventors have conducted intensive studies on the above problems, and as a result, have conceived the following: a coated metal sheet which is excellent in metallic appearance, chemical resistance and solvent resistance while suppressing the production cost can be produced by forming a resin coating film containing a first site having a urethane skeleton and a second site having a triazine ring skeleton on at least one surface of a metal sheet and appropriately controlling the glass transition temperature of such a resin coating film and the presence state of the second site in the resin coating film.
The gist of the present invention completed based on such an insight is as follows.
(1) A coated metal sheet according to one aspect of the present invention includes a metal sheet and a first coating film containing a resin and located on at least one surface of the metal sheet, the first coating film including: a first site having a urethane bond skeleton; and a second site having a triazine ring skeleton. The first coating film has a glass transition temperature of 85 ℃ to 170 ℃. When the second site was stained with osmium oxide and observed at a magnification of 10 ten thousand times using a transmission electron microscope, it was observed that: a second dispersing part in which particles having a number average particle diameter of 5 to 20nm are dispersed; and an enrichment-type second site which is present at a position from the surface of the first coating film to a depth of 15nm and in which particles having a number average particle diameter of 5nm or more are not observed.
(2) The coated metal sheet described in the above (1), may be: N1/N2, which is the ratio of N1 at a depth position of 0.2 [ mu ] m from the surface of the first coating film to N2 at a depth position of 0.2 [ mu ] m from the interface between the first coating film and the metal plate toward the first coating film side, is 1.2 or more.
(3) The coated metal sheet according to the above (1) or (2), wherein: the first coating film has a plurality of the enrichment-type second sites.
(4) The coated metal sheet according to any one of (1) to (3) above may be: and a second coating film having a glass transition temperature not higher than that of the first coating film, the second coating film being provided between the first coating film and the metal plate.
(5) The coated metal sheet described in the above (4), may be: the second coating film contains a resin and has a urethane bond skeleton.
(6) The coated metal sheet according to the above (4) or (5), wherein: the second coating film contains a resin and has an epoxy group.
(7) The coated metal sheet according to any one of (4) to (6) above may be: the second coating film contains a resin and has a siloxane bond.
(8) The coated metal sheet according to any one of (4) to (7) above may be: the second coating film contains one or more elements selected from the group consisting of P, V, Ti, Si, and Zr.
(9) The coated metal sheet according to any one of (4) to (8) above may be: the glass transition temperature of the first coating film is higher than the glass transition temperature of the second coating film by 5 ℃ or more.
(10) The coated metal sheet according to any one of (4) to (9) above may be: the second coating film has a film thickness of 0.5 to 15 [ mu ] m.
(11) The coated metal sheet according to any one of (1) to (10) above may be: the first coating film has a film thickness of 0.5 to 15 [ mu ] m.
(12) The coated metal sheet according to any one of (4) to (11) above may be: at least one of the first coating film and the second coating film contains a colorant.
(13) The coated metal sheet according to any one of (4) to (12) above may be: the second coating film contains a black pigment as a colorant.
(14) The coated metal sheet according to any one of (1) to (13) above may be: the metal plate has a texture formed on at least one surface thereof.
(15) A method for producing a coated metal sheet according to another aspect of the present invention is a method for producing a coated metal sheet having a predetermined first coating film on at least one surface of a metal sheet, the method comprising coating a first coating material containing a polyurethane resin (a) that contains an anionic functional group and has a glass transition temperature of 75 ℃ to 160 ℃ on at least one surface of the metal sheet, a triazine ring-containing water-soluble curing agent (b), and an aqueous solvent, and heating the metal sheet coated with the first coating material to form the first coating film.
(16) The method for producing a coated metal sheet described in (15) above, may further include: the triazine ring-containing water-soluble curing agent (b) is a melamine resin containing an imino group.
(17) The method for producing a coated metal sheet according to item (15) or (16) above, wherein: in the first coating material, a total content (Wa) + (Wb) of the content (Wa) of the polyurethane resin (a) with respect to a total solid content and the content (Wb) of the triazine ring-containing water-soluble curing agent (b) with respect to a total solid content satisfies the following formula (I), and a ratio (Wb)/(Wa) of the content (Wa) of the polyurethane resin (a) with respect to the total solid content to the content (Wb) of the triazine ring-containing water-soluble curing agent (b) with respect to the total solid content satisfies the following formula (II).
90 mass% or more of (Wa) + (Wb) or less of 100 mass% of (I)
0 < (Wb)/(Wa) ≦ 1. type (II)
(18) The method for producing a coated metal sheet according to any one of the above (15) to (17), may include: the method for producing a coated metal sheet further having a predetermined second coating film between the metal sheet and the first coating film, wherein the second coating film is formed by applying a second paint on at least one surface of the metal sheet before applying the first paint, and heating the metal sheet on which the second paint is applied, the second paint containing: a urethane resin (c) having a glass transition temperature of the urethane resin (a) or lower; at least one of an epoxy resin (d), a silane coupling agent (e), and a rust inhibitor (f); and an aqueous solvent, wherein the rust inhibitor (f) contains one or more elements selected from the group consisting of P, V, Ti, Si and Zr.
(19) The method for producing a coated metal sheet according to item (18) above, wherein: the glass transition temperature of the polyurethane resin (c) is lower than the glass transition temperature of the polyurethane resin (a) by 5 ℃ or more.
(20) The method for producing a coated metal sheet according to any one of (15) to (19) above, may include: in the formation of the first coating film, the metal plate coated with the first coating material is heated so that a heating time from the start of heating of the metal plate coated with the first coating material to a maximum reaching temperature is 1 second or more and 30 seconds or less, and the metal plate coated with the first coating material is cooled so that a cooling time from the maximum reaching temperature to 30 ℃ is 0.1 second or more and 5 seconds or less.
(21) The method for producing a coated metal sheet according to item (20) above, wherein: in the heating, the temperature is kept at 40-100 ℃ for 1-20 seconds, and then the heating is carried out for 1-10 seconds until the temperature is higher than 200 ℃.
As described above, according to the present invention, a coated metal sheet having excellent metal appearance, chemical permeation resistance, and solvent resistance can be obtained while suppressing the production cost.
Drawings
Fig. 1A is an explanatory view 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 view 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 embodiment.
Fig. 2B is an explanatory view schematically showing another example of the structure of the coated metal plate according to the embodiment.
Fig. 3 is an explanatory view for explaining the upper layer coating film of the coated metal sheet according to the embodiment.
Fig. 4 is a flowchart for explaining an example of the flow of the method for manufacturing a coated metal sheet according to the embodiment.
Fig. 5A is a microscopic image of the upper layer coating film of test example 3 observed with a transmission electron microscope.
Fig. 5B is an osmium elemental map image when the upper layer coating film of test example 3 was observed with a transmission electron microscope.
Fig. 5C is a microscope image of the upper layer coating film of test example 3 observed with a transmission electron microscope.
Fig. 5D is a microscopic image of the upper layer coating film of test example 3 observed with a transmission electron microscope.
Fig. 6 is an explanatory view for explaining a case where a plurality of rich portions are formed in the upper layer coating film.
Detailed Description
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, the same reference numerals are given to the constituent elements having substantially the same functional configuration, and redundant description is omitted.
(Overall Structure of coated Metal plate and outline thereof)
First, the overall structure of a coated metal sheet according to an embodiment of the present invention will be described with reference to fig. 1A to 3. Fig. 1A and 1B are explanatory views schematically showing an example of the structure of the coated metal plate according to the present embodiment, and fig. 2A and 2B are explanatory views schematically showing another example of the structure of the coated metal plate according to the present embodiment. Fig. 3 is an explanatory view for explaining the upper layer coating film of the coated metal sheet according to the present embodiment.
As schematically shown in fig. 1A, the coated metal sheet 1 according to the present embodiment has an upper coating film 13 as a first coating film on one surface of a metal sheet 11 serving as a base material. Further, as schematically shown in fig. 1B, a lower coating film 15 as a second coating film may be provided between the metal plate 11 and the upper coating film 13.
As schematically shown in fig. 2A and 2B, in the coated metal sheet 1 according to the present embodiment, the upper coating film 13 may be provided on both surfaces of the metal sheet 11, or the upper coating film 13 and the lower coating film 15 may be provided on both surfaces of the metal sheet 11.
The structure of the coated metal sheet 1 according to the present embodiment is not limited to the structure shown in fig. 1A to 2B, and can be realized by providing an upper layer coating film 13 and a lower layer coating film 15 on one surface of the metal sheet 11, and providing the upper layer coating film 13 or the lower layer coating film 15 on the other surface of the metal sheet 11, for example.
The upper layer coating film 13 as an example of the first coating film is a resin coating film including a first site having a urethane bond skeleton (hereinafter, also referred to as a "urethane site") and a second site having a triazine ring skeleton (hereinafter, also referred to as a "triazine site"). The glass transition temperature of the upper layer coating film 13 is 80 ℃ to 170 ℃.
As schematically shown in fig. 3, when the second portion having a triazine ring skeleton is stained with osmium oxide and observed at a magnification of 10 ten thousand times using a transmission electron microscope, both a dispersed second portion (reference numeral 101 in fig. 3) in which particles having a number average particle diameter of 5nm or more are dispersed and an enriched second portion (reference numeral 103 in fig. 3) in which particles having a number average particle diameter of 5nm or more are not observed at a position from the surface of the upper layer coating film 13 to a depth of 15 nm.
The coated metal sheet 1 according to the present embodiment has the above-described structure, and thus has excellent metal appearance, chemical resistance, and solvent resistance without using expensive resins such as fluorine resin. The reason for this is presumed to be as follows.
First, in order to set the glass transition temperature of the upper layer coating film 13 to 80 ℃ or higher and 170 ℃ or lower, the urethane moiety needs to have a relatively high glass transition temperature. By providing the urethane moiety with a high glass transition temperature, a high cohesive force is generated at the urethane moiety when the upper layer coating film 13 is formed. The result is: the triazine sites are not condensed individually, but the triazine sites are dispersed into the urethane sites, and the urethane sites and triazine sites are easily preferentially bonded. The three-dimensional network structure is formed by bonding a triazine moiety having high solvent resistance to a urethane moiety. As a result, the barrier property (i.e., chemical resistance to permeation) of the upper coating film 13 is improved. In order to obtain such characteristics, in the present embodiment, the glass transition temperature of the upper layer coating film 13 is set to 80 ℃ or higher and 170 ℃ or lower.
In addition, the triazine sites form domains (domains) in the upper coating film 13, are dispersed in a granular form (reference numeral 101 in fig. 3), and are concentrated on the surface layer of the upper coating film 13 to form concentrated portions 103, whereby the solvent resistance of the upper coating film 13 is improved by the triazine sites having high solvent resistance. When a high cohesive force is generated at the urethane site during the formation of the upper coating film 13 as described above, the urethane site and the triazine site are easily preferentially bonded, and as schematically shown in fig. 3, the fine particulate triazine site (hereinafter also referred to as "triazine particulate matter 101") is concentrated on the surface layer of the upper coating film 13. From this point of view, the solvent resistance of the upper coating film 13 is further improved.
Further, if the fine particulate triazine sites (triazine particulate matter 101) are concentrated on the surface layer of the upper coating film 13, light scattering by the triazine sites is suppressed, and as a result, the transparency of the upper coating film 13 is improved, and the gloss of the underlying metal plate 11 is easily visually confirmed from the outside. As a result, the coated metal sheet 1 according to the present embodiment also has an improved metallic appearance.
As described roughly above, it is presumed that: with the coated metal sheet 1 according to the present embodiment, it is possible to obtain a metal sheet having excellent appearance, chemical resistance, and solvent resistance without using an expensive resin such as a fluororesin.
Hereinafter, each configuration of the coated metal sheet 1 according to the present embodiment will be described in detail.
< about the metal plate 11 >
In the coated metal sheet 1 according to the present embodiment, various generally known metal sheets can be used as the metal sheet 11. 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 alloy plate, a titanium plate, and a copper plate. In the coated metal plate 1 according to the present 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, and examples thereof include zinc plating, aluminum plating, copper plating, nickel plating, and alloy plating thereof.
In particular, when the metal plate 11 is a plated steel plate, the chemical resistance tends to be poor, and therefore the effect of improving the chemical resistance by providing the upper coating film 13 is more effective.
The plated steel sheet used as the metal sheet 11 is not particularly limited, and various kinds of generally known plated steel sheets such as a hot-dip galvanized steel sheet, an electrogalvanized steel sheet, a zinc-nickel alloy plated steel sheet, a hot-dip alloyed zinc plated steel sheet, an aluminum-zinc alloy plated steel sheet, and a stainless steel sheet can be used. In particular, if a zinc-based plated steel sheet is used as the metal sheet 11, the corrosion resistance is further improved, which is more preferable. Here, the zinc-based plated steel sheet refers to a plated steel sheet plated with zinc or an alloy of zinc and another metal on the surface of a steel sheet, such as a zinc-plated steel sheet plated with zinc, a zinc-nickel alloy plated steel sheet, a melt-alloyed zinc plated steel sheet, or an aluminum-zinc alloy plated steel sheet. The zinc-based plated steel sheet may be any of a hot-dip zinc-plated steel sheet, an electrogalvanized steel sheet, and the like.
In order to further improve the design of the coated metal plate 1 according to the present embodiment, various textures such as pearskin, roughness, craze (hair), cloth (satin), and hammer (hammer) may be formed on the surface of the metal plate 11. In the coated metal sheet 1 according to the present embodiment, the transparency of the upper coating film 13 is improved by the structure as described above, and therefore, even when the surface of the metal sheet 11 is textured as described above, the metallic feeling due to such texture is easily visually recognized from the outside.
< about the upper coating film 13 >
The upper layer coating film 13 of the coated metal sheet 1 according to the present embodiment is a resin coating film including a urethane moiety (a first moiety having a urethane bond skeleton) and a triazine moiety (a second moiety having a triazine ring skeleton), as mentioned above.
Hereinafter, each part included in the upper layer coating film 13 will be described.
The urethane bond skeleton of the urethane moiety in the upper layer coating film 13 can be confirmed by analyzing the upper layer coating film 13 by fourier transform infrared spectroscopy and detecting a vibrational peak attributed to the urethane bond.
The triazine ring skeleton of the triazine moiety is derived from a triazine ring contained in the melamine resin. That is, the triazine moiety is a moiety derived from a triazine ring contained in the melamine resin.
As mentioned above with reference to fig. 3, when the triazine moiety is stained with osmium oxide and observed at a magnification of 10 ten thousand times using a transmission electron microscope, the triazine moiety is observed: a second dispersing part in which particles having a number average particle diameter of 5 to 20nm are dispersed; and an enrichment-type second site which is present at a position from the surface of the upper coating film 13 to a depth of 15nm and in which particles having a number average particle diameter of 5nm or more are not observed.
Here, as schematically shown in fig. 3, the rich part 103 according to the present embodiment is present in a range from the surface layer of the upper coating film 13 to a position of a depth d (15nm) toward the metal plate 11 side.
The phrase "the triazine moiety is concentrated in the surface layer of the upper coating film 13" means that the particulate triazine moiety (i.e., the triazine particulate matter 101) is unevenly distributed in a layer on the surface side of the upper coating film 13 opposite to the interface with the metal plate 11. That is, the surface layer of the upper layer coating film 13 is constituted by a region representing a granular triazine site unevenly layered.
Here, the phrase "the triazine sites are unevenly distributed in a layered form to form the enriched portions 103" means that the average concentration (average content) of the triazine sites in the areas where the triazine sites are unevenly distributed is 1.2 times or more the average concentration of the triazine sites in the areas other than the unevenly distributed portions.
Here, the triazine sites according to the present embodiment are dispersed in the upper coating film 13 in the form of particles having a number average particle diameter of 5nm or more and 20nm or less (in other words, the number average particle diameter of the triazine particles 101 is 5nm or more and 20nm or less), and are concentrated in the surface layer having a depth of 15nm or less from the surface of the upper coating film 13 (in other words, the depth d in fig. 3 is 15nm or less).
Here, the phrase "triazine moiety is concentrated in a surface layer having a depth of 15nm or less from the surface of the upper coating film 13" means that a granular triazine moiety partially collected in a layer form on the surface side of the upper coating film 13 on the side opposite to the interface with the metal plate 11 is present in a depth of 15nm or less from the surface of the upper coating film 13. That is, the surface layer of the upper layer coating film 13 is constituted by a region of lamellar unevenly-aggregated granular triazine sites, and the thickness is 15nm or less.
When the number average particle diameter of the granular triazine moiety (that is, the triazine granules 101) is less than 5nm, the chemical resistance permeability may be lowered. On the other hand, when the number average particle diameter of the triazine moieties dispersed in the form of particles is larger than 20nm, the metal appearance and chemical resistance permeability of the coated metal sheet 1 may be reduced or the metal appearance, chemical resistance permeability, and workability may be reduced. Here, when the workability of the coated metal sheet 1 is lowered, cracks or the like occur in the upper coating film 13, and the chemical resistance and solvent resistance are also lowered. The number average particle diameter of the triazine sites dispersed in the form of particles (triazine particles 101) is more preferably 5nm to 15nm from the viewpoint of metal appearance, chemical permeation resistance, and solvent resistance.
In addition, in the case where the granular triazine sites are not concentrated on the surface layer of the upper coating film 13 (that is, in the case where the concentrated portion 103 is not present), the metallic appearance and the solvent resistance may be lowered. In addition, when the depth of the particulate triazine moiety from the surface of the upper layer coating film 13 is more than 15nm (that is, when the depth of the enriched portion 103 from the surface of the upper layer coating film 13 is more than 15nm), the workability may be deteriorated. When the workability of the coated metal sheet 1 is lowered, cracks or the like occur in the upper coating film 13, and the chemical resistance and solvent resistance are also lowered.
As shown in fig. 6, a plurality of rich portions 103 are preferably formed in the upper layer coating film 13. By forming a plurality of the enrichment parts 103, the barrier property can be further improved, and a preferable chemical resistance can be obtained. In order to form the concentrated part 103, a heating method in an upper layer coating film forming step described later is important. This will be described later.
Here, in the upper layer coating film 13 according to the present embodiment, N1/N2, which is a ratio of N1 at a depth position of 0.2 μm from the surface of the upper layer coating film 13 to N2 at a depth position of 0.2 μm from the interface between the upper layer coating film 13 and the metal plate 11 toward the upper layer coating film 13, is 1.2 or more.
By setting N1/N2 to 1.2 or more, the metallic appearance and solvent resistance can be more reliably improved. N1/N2 is more preferably 1.5 to 10 inclusive.
Next, various methods for analyzing the triazine moiety in the upper coating film 13 will be described.
First, the upper coating film 13 to be analyzed is dyed with osmium oxide. Thereby, the triazine sites in the upper coating film 13 are selectively dyed. Next, the coating film dyed with osmium oxide is cut in the film thickness direction by a microtome, a focused ion beam processing apparatus, or the like, to prepare a coating film sample with which a cross section can be observed. Next, the film sample was observed at a magnification of 10 ten thousand times using a transmission electron microscope. In this observation, the triazine moiety in the thin film sample was observed as black in a STEM-BF (bright field) image and white in a STEM-HAADF (dark field) image.
The triazine sites in the upper coating film 13 can be confirmed by the analysis method described above. The triazine moiety in the upper coating film 13 can also be confirmed by analyzing the coating film by energy dispersive X-ray spectroscopy or fourier transform infrared spectroscopy to detect nitrogen and osmium or a vibrational peak attributed to a triazine ring.
The thickness of the granular triazine moiety-enriched region (i.e., the thickness of the enriched portion (enriched second site) 103 which is a region of granular triazine moieties unevenly distributed in a layer shape) is a value measured by the following method. As described above, the thin film sample was observed with a transmission electron microscope at a magnification of 10 ten thousand times to obtain a STEM-BF (bright field) image. The obtained STEM-BF (bright field) image is subjected to 2-valued conversion using, for example, a threshold value 120. Then, in the obtained 2-valued image, the thickness of a black layer-like region observed from the surface of the upper layer coating film 13 was measured at arbitrary 20 sites, and the average value thereof was calculated as the thickness of a granular triazine site-rich region. The position where the enrichment part 103 exists can be determined by focusing on the position of the lower end (the interface on the metal plate 11 side) of the thickness of the enrichment part 103 obtained as described above in the 2-valued image. When a black layered region is observed from the surface of the upper layer coating film 13, it is considered that the granular triazine sites are concentrated on the surface layer of the upper layer coating film 13.
The number average particle diameter of the granular triazine moiety (the number average particle diameter of the triazine granules 101) is a value measured by the following method. As described above, the thin film sample was observed with a transmission electron microscope at a magnification of 50 ten thousand times to obtain a STEM-BF (bright field) image. The obtained STEM-BF (bright field) image is subjected to 2-valued conversion using, for example, a threshold value 120. Then, in the obtained 2-valued image, according to the formula: the circle equivalent (equivalent) diameter was 2 (area/. pi.) 0.5, and the circle equivalent diameter of the black granular region was calculated. The "area" in the formula indicates the area of the region where black particles are observed. Then, the circle equivalent diameter was calculated at 20 sites of the arbitrarily selected granular region, and the average value thereof was determined as the number average particle diameter of the granular triazine sites.
In addition, the average concentration of the triazine sites concentrated on the surface layer side of the upper coating film 13 can be measured in the following manner. That is, the distribution of the N element concentration in the depth direction in the direction of the metal plate from the surface layer side of the upper layer coating film 13 was measured, and the ratio of the N element concentration N1 at the position at a distance of 0.2 μm from the outermost layer to the N element concentration N2 at the position at 0.2 μm from the boundary with the metal plate or the lower layer coating film toward the surface layer side, that is, N1/N2 was determined.
The depth-direction elemental analysis can be examined by a known method, and can be carried out by, for example, a high-frequency Glow Discharge Spectroscopy (GD-OES), an Auger Electron Spectroscopy (AES), or the like.
Next, the glass transition temperature (Tg) of the upper layer coating film 13 will be described.
The glass transition temperature of the upper layer coating film 13 is 85 ℃ to 170 ℃. In the case where the glass transition temperature of the upper coating film 13 is less than 85 ℃, the chemical resistance permeability of the coated metal sheet 1 decreases. On the other hand, when the glass transition temperature of the upper layer coating film 13 is more than 170 ℃, the workability of the coated metal sheet 1 is lowered. If the workability of the coated metal sheet 1 is lowered, cracks or the like are generated in the upper coating film 13, and the chemical resistance permeability and the solvent resistance are also lowered. The glass transition temperature of the upper coating film 13 is preferably 100 ℃ or higher and 170 ℃ or lower, and more preferably 110 ℃ or higher and 165 ℃ or lower, from the viewpoint of chemical resistance and solvent resistance (particularly, from the viewpoint of chemical resistance).
In the case where the coated metal sheet 1 according to the present embodiment has the lower coating film 15, the glass transition temperature of the upper coating film 13 is preferably equal to or higher than the glass transition temperature of the lower 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 resistance may be reduced.
On the other hand, the glass transition temperature of the upper layer coating film 13 is preferably higher than that of the lower layer coating film 15 by 5 ℃ 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 ℃ or more, the adhesion between the upper coating film 13 and the lower coating film 15 becomes better, and the chemical resistance is easily further improved.
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 by 10 ℃ to 50 ℃. Chemical resistance to permeation is easily improved by making the glass transition temperature of the upper layer coating film 13 higher by 10 ℃ or more than the glass transition temperature of the lower layer coating film 15. On the other hand, by setting the glass transition temperature of the upper layer coating film 13 to be higher than the glass transition temperature of the lower layer coating film 15 by 50 ℃ or less, the decrease in coating film hardness is easily suppressed.
Here, the glass transition temperature (Tg) is a value measured by the method shown below. First, a coating film to be measured is obtained by peeling or cutting, and a measurement sample is prepared. Then, using the measurement sample, the glass transition temperature was determined by differential scanning calorimetry (DSC method) according to the plastic transition temperature measurement method (JIS K71211987).
The upper layer coating film 13 preferably does not contain silica. This is due to: if the upper coating film 13 has silica, the chemical resistance of the upper coating film 13 deteriorates.
For the same reason, the upper layer coating film 13 preferably does not contain at least one metal complex selected from zinc, aluminum, and titanium. Examples of the at least one metal complex selected from zinc, aluminum and titanium include zinc stearate, zinc gluconate, zinc picolinate, zinc citrate, zinc acetylacetonate, aluminum acetate, aluminum stearate, aluminum ethoxide, aluminum isopropoxide, aluminum triisopropoxide, ethyl acetoacetate diisopropyl aluminate, tris (ethylacetoacetato) aluminum, tris (acetoacetato) aluminum, isopropoxy alumina trimer, tetraisopropoxy titanium, tetra-n-butoxy titanium, butyl titanate dimer, tetrakis (2-ethylhexanol) titanium, diisopropoxybis (acetylacetonato) titanium, titanium tetraacetoacetone, dioctyloxybis (octyleneglycolate) titanium, diisopropyl bis (ethylacetoacetate) titanate, bis (triethanolamine) diisotitanate, titanium ammonium lactate, titanium polyhydroxystearate, and the like.
< about the lower coating film 15 >
In the coated metal sheet 1 according to the present embodiment, the lower layer coating film 15 is not particularly limited, and a known resin coating film such as a polyurethane-based resin, an epoxy-based resin, an acrylic-based resin, a polyester-based resin, a phenolic resin, a polyolefin-based resin, an alkyd-based resin, a melamine resin, or a silicone resin may be used. In addition, a known additive such as a silane coupling agent may be used for forming such a resin coating film.
Of these resin coating films, the lower layer coating film 15 is preferably a resin coating film as follows from the viewpoint of metallic appearance, chemical permeation resistance, and solvent resistance: the silicone resin composition preferably further comprises at least a first site having a urethane bond skeleton (hereinafter, also referred to as a "urethane site"), and preferably a site having at least one of an epoxy group and a siloxane bond skeleton (hereinafter, also referred to as an "epoxy site" and a site having a siloxane bond skeleton as a "siloxane site"). The lower layer coating film 15 preferably contains a compound of one or more elements selected from P, V, Ti, Si, and Zr in addition to the urethane moiety as described above.
Here, by further providing the urethane moiety with an anionic functional group, the dispersibility of the urethane moiety in an aqueous medium (aqueous coating material) is improved, and the film forming property of the lower coating film 15 is improved, whereby the adhesion between the lower coating film 15 and the metal plate 11 is improved, and the barrier property (i.e., chemical resistance) of the lower coating film 15 is improved.
In addition, the chemical resistance permeability of the lower layer coating film 15 is also improved by including a urethane moiety and at least one of an epoxy group and a siloxane bond skeleton. In addition, when the lower layer coating film 15 is a resin coating film having at least urethane portions, the transparency of the lower layer coating film 15 is improved, and the metallic appearance is also improved.
In addition, a compound having one or more elements selected from P, V, Ti, Si, and Zr generally functions as a rust inhibitor in many cases, and such a compound may be included in the lower coating film 15. By containing such a compound in the lower layer coating film 15, the corrosion resistance of the coated metal sheet 1 can be further improved.
Next, each part included in the lower coating film 15 will be explained.
Examples of the preferable anionic functional group of the urethane moiety include a carboxylic acid group (carboxyl group) and a sulfonic acid group (sulfo group). On the other hand, the urethane bond skeleton of the urethane moiety is derived from a urethane resin. That is, the urethane moiety is a moiety derived from a urethane resin, and can be said to have an anionic functional group.
The epoxy site having an epoxy group is a site derived from an epoxy resin. That is, the epoxy group of the epoxy site is an epoxy residue that does not react with the urethane site derived from the polyurethane resin. Further, 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 generating a siloxane bond.
The urethane bond skeleton at the urethane site, the epoxy group at the epoxy site, and the siloxane bond skeleton at the siloxane site in the lower coating film 15 can be confirmed by detecting elements constituting the corresponding bond or functional group or detecting a vibrational peak attributed to the corresponding bond or functional group by analyzing the lower coating film 15 by energy dispersive X-ray spectroscopy or fourier transform infrared spectroscopy. The presence of a compound having one or more elements selected from P, V, Ti, Si, and Zr in the lower coating film 15 can be confirmed by detecting the elements contained in such a compound by energy dispersive X-ray spectroscopy.
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 ℃ to 170 ℃ and is not higher than the glass transition temperature of the upper coating film 13. In the case where the glass transition temperature of the lower coating film 15 is less than 80 ℃, the chemical resistance permeability is sometimes reduced. On the other hand, when the glass transition temperature of the undercoat film 15 is higher than 170 ℃, the processability may be lowered. If the workability is lowered, cracks or the like are generated in the lower coating film 15, and the chemical resistance permeability and the solvent resistance may be lowered. From the viewpoint of chemical resistance to permeability and solvent resistance (particularly, from the viewpoint of chemical resistance to permeability), the glass transition temperature of the lower coating film 15 is more preferably equal to or lower than the glass transition temperature of the upper coating film 13 and is in the range of 100 ℃ to 170 ℃.
< film thickness of the upper layer coating film 13 and the lower layer coating film 15 >
In the coated metal sheet 1 according to the present embodiment, the thickness of the upper coating film 13 as described above is preferably 0.5 μm or more and 15 μm or less. When the thickness of the upper layer coating film 13 is less than 0.5 μm, the chemical resistance of the coated metal sheet 1 may decrease. On the other hand, when the thickness of the upper layer coating film 13 is larger than 15 μm, the transparency of the upper layer coating film 13 is lowered, and the metallic appearance may be lowered. 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 metallic appearance and chemical resistance.
In the coated metal sheet 1 according to the present embodiment, when the lower coating film 15 is provided in addition to the upper coating film 13, the film thickness of the lower coating film 15 is preferably 0.5 μm or more and 15 μm or less. By setting the film thickness of the lower layer coating film 15 to 0.5 μm or more and 15 μm or less, the chemical resistance permeability can be further improved while maintaining the metallic appearance. The film thickness of the lower coating film 15 is more preferably more than 1.0 μm and 15 μm or less from the viewpoint of chemical resistance.
< As to the coloring agent in the upper coating film 13 and/or the lower coating film 15 >
In the coated metal sheet 1 according to the present embodiment, the upper coating film 13 and/or the lower coating film 15 as described above may contain a colorant. By containing a colorant in the upper layer coating film 13 and/or the lower layer coating film 15, the color tone of the product can be adjusted, and the composition can be applied to various applications.
Here, when the color pigment is a black pigment, it is preferably dispersed in the lower coating film 15. This is due to: if the black pigment is dispersed in the upper coating film 13, chemical resistance may be reduced. It is considered that the reason for such a decrease in chemical resistance is that the black pigment in the upper coating film 13 easily penetrates into the chemicals. The black pigment concentration in the lower coating film 15 is not particularly limited, and is preferably 0.5 mass% or more and 20 mass% or less with respect to the total solid content of the lower coating film 15, for example. When the black pigment concentration in the lower coating film 15 is less than 0.5% by mass, coloring may be insufficient. On the other hand, when the black pigment concentration in the undercoat film 15 is more than 20% by mass, the chemical resistance and the corrosion resistance may be reduced.
< concrete constitution of the upper layer coating film 13 and the lower layer coating film 15 >
In the coated metal sheet 1 according to the present embodiment, the upper coating film 13 may be specifically a resin coating film (for example, a resin coating film containing a crosslinked product of a urethane resin and a water-soluble melamine resin) obtained by curing an upper coating material containing a urethane resin (a) having a glass transition temperature of 75 to 160 ℃, a water-soluble melamine resin (b) as a water-soluble triazine ring-containing curing agent, and an aqueous solvent. The resin coating film formed from the topcoat material has a glass transition temperature of 85 ℃ to 170 ℃ in the whole. At this time, the water-soluble melamine resin (b) exists as a water-soluble melamine resin dispersed in the upper coating film 13 in a granular form and as a water-soluble melamine resin concentrated on the surface side of the upper coating film 13. When the lower coating film 15 is further provided between the upper coating film 13 and the metal plate 11, the glass transition temperature of the urethane resin (a) is preferably equal to or higher than the glass transition temperature of the urethane resin (c) contained in the lower coating film 15, as described below.
When a polyester resin is used instead of a polyurethane resin, the polyester resin has lower chemical resistance than the polyurethane resin, and the thickness of the upper coating film needs to be increased to obtain the same chemical resistance. If the thickness of the upper coating film is increased, a desired metallic appearance cannot be obtained when a transparent coating film is formed, which is not preferable.
In addition, when the lower coating film 15 is provided on the coated metal sheet 1 according to the present embodiment, the lower coating film 15 may be specifically composed of a resin coating film obtained by curing a lower coating material containing: a urethane resin (c) having a glass transition temperature of not more than that of the urethane resin (a) of the upper coating film 13; at least one of an epoxy resin (d), a silane coupling agent (e), and a rust inhibitor (f) containing one or more elements selected from the group consisting of P, V, Ti, Si, and Zr; and an aqueous solvent. The resin film is, for example: a resin coating film comprising a crosslinked product of a polyurethane resin (c) and an epoxy resin (d); a resin coating film comprising a crosslinked product of a polyurethane resin (c), an epoxy resin (d), and a silane coupling agent (e); a resin coating film containing a rust inhibitor (f) and a crosslinked product of a urethane resin (c), an epoxy resin (d), and a silane coupling agent (e); a resin coating film comprising a crosslinked product of a polyurethane resin (c) and a silane coupling agent (e); a resin coating film containing a rust inhibitor (f) and a crosslinked product of a urethane resin (c) and a silane coupling agent (e); and a resin coating film containing a polyurethane resin (c) and a rust preventive (f).
The coated metal sheet 1 according to the present embodiment is explained in detail above.
As described above, the coated metal sheet 1 according to the embodiment can be used for automobiles, household electrical appliances, building materials, civil engineering, machinery, furniture, containers, and the like.
(method for producing coated Metal sheet)
Next, a method for manufacturing a coated metal sheet according to the present embodiment will be described in detail with reference to fig. 4. Fig. 4 is a flowchart illustrating an example of the flow of the method for manufacturing a coated metal sheet according to the present embodiment.
The method for manufacturing a coated metal sheet according to the present embodiment is a method for manufacturing a coated metal sheet 1 having at least an upper coating film 13 on at least one surface of a predetermined metal sheet 11. As shown in fig. 4 as an example, the method for producing a coated metal sheet includes a texture forming step (step S101) of forming a predetermined texture on the surface of the metal sheet 11 as necessary, a lower coating film forming step (step S103) of forming a lower coating film 15 on the metal sheet 11 as necessary, and an upper coating film forming step (step S105) of forming an upper coating film 13 on the metal sheet 11 or the lower coating film 15.
Here, the texture forming step and the lower layer coating film forming step may be performed as needed, and for example, in the case of manufacturing the coated metal sheet 1 in which the upper layer coating film 13 is formed on the metal sheet 11 having no texture or the like, only step S105 among 3 steps shown in fig. 4 is performed.
In the method for manufacturing a coated metal sheet shown in fig. 4, the most important step is the upper layer coating film forming step (step S105). Such an upper layer coating film forming step is a step of: an upper coating material (such an upper coating material is an example of a first coating material) containing a polyurethane resin (a) having an anionic functional group and a glass transition temperature of 75 to 160 ℃, a water-soluble melamine resin (b) as a water-soluble triazine ring-containing curing agent, and an aqueous solvent is applied to the metal sheet 11 (to the lower coating film 15 in the case of forming the lower coating film 15 on the metal sheet 11), and the metal sheet coated with such an upper coating material is heated and cooled, thereby forming the upper coating film 13.
The method for producing a coated metal sheet according to the present embodiment can suppress local production of the coated metal sheet according to the present embodiment (i.e., a coated metal sheet having excellent metal appearance, chemical resistance and solvent resistance) by the above-described method. The reason is presumed as follows.
First, in general, when a coating film is formed using a coating material containing a polyurethane resin and a water-soluble melamine resin, the melamine resin is less compatible with the polyurethane resin and is less likely to coexist with the polyurethane resin, and self-condensation particles of the melamine resin become larger, and the melamine resin is concentrated in the surface layer of the coating film.
In contrast, in the method for producing a coated metal sheet according to the present embodiment, the polyurethane resin (a) containing an anionic functional group and the water-soluble melamine resin (b) as a triazine ring-containing water-soluble curing agent are mixed uniformly in an aqueous medium to be brought into a state of coexisting with each other. When the upper layer coating material in such a state is formed on the metal plate 11 (or on the lower layer coating film 15) and heated, the self-shrinkage of the water-soluble melamine resin (b) is suppressed, and the reaction of the water-soluble melamine resin (b) and the polyurethane resin (a) occurs preferentially. Further, if the aqueous solvent is vaporized (dried) by heating, the urethane resin (a) is in a molten state. When the urethane resin (a) is in a molten state, the glass transition temperature is as high as 75 ℃ or higher and 160 ℃ or lower, and therefore the viscosity increases, resulting in high coagulation and a decrease in the diffusion rate of the melamine resin (b). Thereby, self-shrinkage of the water-soluble melamine resin (b) is suppressed, and the reaction of the water-soluble melamine resin (b) with the polyurethane resin (a) occurs preferentially.
In this way, the melamine resin (b) having low compatibility with the polyurethane resin (a) concentrates on the surface layer of the coating film, and the self-shrinkage of the water-soluble melamine resin (b) is suppressed, and preferentially reacts with the polyurethane resin (a). However, since the self-shrinkage of the water-soluble melamine resin (b) is not completely suppressed, a reaction product of the water-soluble melamine resin (b) obtained by the reaction with the urethane resin (a) and a reaction product generated as a result of the self-shrinkage of the water-soluble melamine resin (b) coexist in the upper coating film 13. As a result, the sites derived from the water-soluble melamine resin (b) are present as dispersed in the upper coating film 13 in a granular form and as concentrated on the surface layer of the upper coating film 13. When the upper coating film 13 is formed as described above, a high cohesive force is generated in the urethane resin (a), and thus the reaction between the water-soluble melamine resin (b) and the urethane resin (a) occurs preferentially. Thus, the water-soluble melamine resin (b) in the form of fine particles is concentrated on the surface layer of the upper coating film 13 to form a concentrated portion 103 as shown in fig. 3, and the water-soluble melamine resin (b) in the form of fine particles which is not concentrated on the surface layer of the upper coating film 13 forms a triazine particulate matter 101 as shown in fig. 3.
In addition, when the lower coating film 15 is provided, by forming the lower coating film 15 using the urethane resin (c) having a glass transition temperature of 80 ℃ or more and 160 ℃ or less and a glass transition temperature lower than that of the urethane resin (a), high adhesion between the upper coating film 13 and the lower coating film 15 can be achieved. Further, by using the polyurethane resin (a) containing an anionic functional group, the dispersibility of the urethane moiety in an aqueous medium (aqueous coating material) is also improved, and as a result, the film-forming property of the upper coating film 13 is improved, and high adhesion between the upper coating film 13 and the lower coating film 15 is achieved.
As described above, it is assumed that: the method for producing a coated metal sheet according to the present embodiment can suppress the local production of the coated metal sheet according to the present embodiment (i.e., a coated metal sheet excellent in metal appearance, chemical resistance and solvent resistance).
The method for producing a coated metal sheet according to the present embodiment will be described in detail below.
< Process for Forming Upper coating film >
In contrast to the flow shown in fig. 4, the upper layer coating film forming step will be described in detail below.
In the upper coating film forming step, first, an upper coating material as an example of the first coating material is prepared. The topcoat material contains a polyurethane resin (a), a water-soluble melamine resin (b) as a triazine ring-containing water-soluble curing agent, and an aqueous solvent.
[ polyurethane resin (a) ]
The polyurethane resin (a) contains an anionic functional group and has a glass transition temperature of 75 ℃ to 160 ℃. In the coated metal sheet according to the present embodiment, when not only the upper-layer coating film 13 but also the lower-layer coating film 15 are formed, the glass transition temperature of the urethane resin (a) is preferably equal to or higher than the glass transition temperature of the urethane resin (c) used in the lower-layer coating film 15.
In order to obtain a high glass transition temperature (85 ℃ to 170 ℃) in the upper coating film 13 as mentioned above, it is difficult to produce a polyurethane resin having a urethane bond, for example, a polyester resin having a high glass transition temperature. Further, since the polyurethane resin having a high glass transition temperature has a very high melt viscosity, it is difficult to apply (form a coating film) a coating material dispersed in an aqueous medium. Therefore, by providing the polyurethane resin with an anionic functional group, the polyurethane resin can be dispersed in an aqueous medium together with the water-soluble melamine resin.
The polyurethane resin (a) can be obtained by, for example, reacting a polyol such as ethylene glycol, propylene glycol, diethylene glycol, 1, 6-hexanediol, neopentyl glycol, triethylene glycol, bisphenol hydroxypropyl ether, glycerin, trimethylolethane, or trimethylolpropane with a diisocyanate compound such as hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, toluene diisocyanate, or diphenylmethane diisocyanate, and then chain-extending with a diamine or the like to disperse water.
As such a polyurethane resin (a), for example, a polyether polyurethane resin (a polyurethane resin having a polyether skeleton), a polyester polyurethane resin (a polyurethane resin having a polyester skeleton), a polyether polyester polyurethane resin (a polyurethane resin having a polyether skeleton and a polyester skeleton), and the like are preferable. The chemical resistance permeability and solvent resistance of a coating film using these urethane resins are easily improved.
The polyether polyurethane resin, the polyester polyurethane resin, and the polyether polyester polyurethane resin can be obtained by using at least one of polyether polyol and polyester polyol as the polyol.
Polyether polyols include, for example, polyethylene glycol, polyoxyethylene glycol, polyoxypropylene glycol, polytetramethylene glycol, and copolymers thereof.
The polyester polyol can be obtained by reacting a dibasic acid such as terephthalic acid, isophthalic acid, adipic acid, azelaic acid, or sebacic acid, or a dialkyl ester of the dibasic acid with a diol such as ethylene glycol, propylene glycol, diethylene glycol, butanediol, neopentyl glycol, 1, 6-hexanediol, 3-methyl-1, 5-pentanediol, 3' -dimethylolheptane, polyoxyethylene glycol, polyoxypropylene glycol, or polytetramethylene ether glycol.
The polyester polyol can be obtained by ring-opening polymerization of lactones such as polycaprolactone, polypentanolide, and poly (. beta. -methyl-. gamma. -valerolactone).
The glass transition temperature of the polyurethane resin (a) is 75 ℃ or higher and 160 ℃ or lower. In the case where the glass transition temperature of the polyurethane resin (a) is less than 75 ℃, the chemical resistance permeability is reduced. On the other hand, in the case where the glass transition temperature of the urethane resin (a) is more than 160 ℃, the processability is lowered. If the workability is lowered, cracks or the like are generated in the upper coating film 13, and the chemical permeation resistance and the solvent resistance are also lowered. The glass transition temperature of the polyurethane resin (a) is preferably 100 ℃ or higher and 160 ℃ or lower from the viewpoint of chemical resistance to permeation and solvent resistance (particularly, from the viewpoint of chemical resistance to permeation).
Here, the glass transition temperature of various resins including the above polyester resins can be measured by differential scanning calorimetry (DSC method) according to a plastic transition temperature measurement method (JIS K71211987).
[ Water-soluble Melamine resin (b) ]
As the water-soluble melamine resin (b) as the triazine ring-containing water-soluble curing agent, a generally known water-soluble melamine resin (an imino-type melamine resin, a methylol-type melamine resin, a fully alkyl etherified melamine resin, or the like) can be used. Examples of commercially available water-soluble melamine resins include water-soluble melamine resins manufactured by カーバイド, オルネクス, and DIC, for example.
As the water-soluble melamine resin (b) as described above, a melamine resin containing an imino group (imino-type melamine resin) is particularly preferably used. By using the melamine resin containing an imino group, the water-soluble melamine resin in a granular form is likely to be concentrated on the surface layer of the upper coating film 13, and thus the solvent resistance is likely to be further improved.
The term "water-soluble" means that the amount of the target substance dissolved in water at 25 ℃ is 5 parts by mass or more (preferably 10 parts by mass or more) per 100 parts by mass of water.
[ with regard to the coloring agent ]
The colorant to be dispersed in the upper layer coating material containing the above-mentioned components is not particularly limited, and a known colorant can be suitably used. Examples of the colorant include various inorganic pigments such as titanium oxide, zinc oxide, calcium carbonate, aluminum oxide, barium sulfate, aluminum, acidified iron, copper-chromium composite oxide, and carbon black, various organic pigments such as cyanine and quinacridone, and various dyes.
In the case where the colorant used is a black pigment such as carbon black or a metal oxide exhibiting black color, since there is a possibility that chemical resistance may be lowered, it is preferable to limit the concentration in the upper layer coating material or to disperse the colorant in the lower layer coating material, and it is more preferable to disperse the colorant in the lower layer coating material.
The type of carbon black dispersed in the upper layer coating material is not particularly limited, and known carbon black such as furnace black, ketjen black, acetylene black, and channel black can be used.
The particle size of the carbon black to be used is not particularly limited as long as it does not pose a problem in dispersibility in a coating material, coating film quality, and coatability, and carbon black having a primary particle size of about 10 to 120nm is easily used. Particularly, when chemical resistance and corrosion resistance are required, carbon black having a primary particle diameter of 10 to 50nm is preferably used. Since these carbon blacks aggregate during dispersion in a coating material, they are generally not easily dispersed in a state of a primary particle diameter. That is, in practice, the coating material exists in the form of secondary particles having a larger particle diameter than the primary particle diameter. The same applies to such a topcoat material.
The type of the metal oxide exhibiting black color is not particularly limited, and a known black pigment such as ferroferric oxide or a copper-chromium composite oxide can be used.
[ aqueous solvent ]
Examples of the aqueous solvent include water and a mixed solution of water and a lower alcohol. Such an aqueous solvent may contain 50 mass% or more (preferably 80 mass% or more) of water.
When a solvent such as an organic solvent is used as the solvent, only the melamine particles are dispersed in the coating film, and surface enrichment is not caused, which is not preferable. As described above, in order to enrich the surface layer of melamine in the coating film formed using the solvent-based coating material, it is necessary to include an amine compound in the solvent-based coating material, but since an aqueous solvent is used in the present embodiment, the surface layer of melamine particles can be enriched without using an amine compound.
Examples of the water include distilled water, ion-exchanged water, ultrapure water, and ultrafiltrated water. Examples of the lower alcohol include alcohols having 1 to 4 carbon atoms such as methanol, ethanol, butanol, and isopropanol.
[ As to contents ]
In the topcoat coating material containing the components as described above, it is preferable that: the total content (Wa) + (Wb) of the content (Wa, unit: mass%) of the polyurethane resin (a) with respect to the total solid content and the content (Wb, unit: mass%) of the water-soluble melamine resin (b) with respect to the total solid content satisfies the following formula (11), and the ratio (Wb)/(Wa) of the content (Wa) of the polyurethane resin (a) to the content (Wb) of the water-soluble melamine resin (b) satisfies the following formula (13).
90 mass% or more of (Wa) + (Wb) or less of 100 mass% of (11)
0 < (Wb)/(Wa) ≦ 1. cndot. formula (13)
When the total content (Wa) + (Wb) in the above formula (11) is less than 90% by mass, the metal appearance, chemical resistance and solvent resistance of the coated metal sheet 1 may be reduced. In addition, when the ratio (Wb)/(Wa) in the above formula (13) is greater than 1, the water-soluble melamine resin (b) becomes excessive, and the workability of the coated metal sheet 1 may be reduced. If the workability is lowered, cracks or the like are generated in the upper coating film 13, and the chemical permeation resistance and the solvent resistance are also lowered.
From the viewpoint of metal appearance, chemical permeation resistance and solvent resistance, more preferable are: the total content (Wa) + (Wb) satisfies the following formula (15), and the ratio (Wb)/(Wa) satisfies the following formula (17).
95% by mass or more of (Wa) + (Wb) or less of 100% by mass of (15)
0.1 ≦ (Wb)/(Wa) ≦ 0.3. cndot. formula (17)
The topcoat preferably has no silica. This is because if the upper coating material has silica, silica is contained in the upper coating film 13, and as a result, the chemical resistance of the upper coating film 13 is deteriorated.
For the same reason, the topcoat material preferably does not have a metal complex of at least one metal selected from zinc, aluminum and titanium. Examples of the metal complex of at least one metal selected from zinc, aluminum and titanium include zinc stearate, zinc gluconate, zinc picolinate, zinc citrate, zinc acetylacetonate, aluminum acetate, aluminum stearate, aluminum ethoxide, aluminum isopropoxide, aluminum triisopropoxide, ethyl acetoacetate diisopropyl aluminate, aluminum tris (ethylacetoacetato), aluminum tris (acetoacetate), aluminum isopropoxy oxide trimer, titanium tetraisopropoxide, titanium tetra-n-butoxide, butyl titanate dimer, titanium tetrakis (2-ethylhexanol), titanium diisopropoxybis (acetylacetonate), titanium tetraacetonate, titanium dioctyloxybis (octyleneglycolate), diisopropyl bis (ethylacetoacetate) titanate, diiso bis (triethanolamine) titanate, titanium ammonium lactate, titanium lactate and titanium polyhydroxystearate.
[ film Forming method (coating method) ]
In the upper coating film forming step, a method of forming (coating) the upper coating material on the metal plate 11 or the lower coating film 15 is not particularly limited, and a known film forming method (coating method) such as a roll coating method, a ring roll coating method, an air spray method, an airless spray method, a dipping method, or the like can be used. Further, if film formation is performed in a continuous coating line called a coil continuous coating line or a sheet continuous coating line, which is completed with a film forming apparatus (coating apparatus) for performing the known film forming method (coating method), the coating operation efficiency can be improved and mass production can be performed, which is more preferable.
[ heating method (baking method) and Cooling method ]
In the upper coating film forming step, a method of forming (applying) an upper coating film on the metal plate 11 or the lower coating film 15 and then heating the upper coating film is not particularly limited, and a generally known apparatus such as a hot air oven, a direct fire oven, a far infrared oven, or an induction heating oven can be used. The film of the upper layer coating material is heated to dry the aqueous solvent present in the film of the upper layer coating material, and then the urethane resin (a) and the water-soluble melamine resin (b) are reacted to form the upper layer coating film 13.
On the other hand, the method for cooling the upper layer coating film 13 after heating is not particularly limited, and known methods such as water cooling (spraying, dipping, etc.) and air cooling (blowing of nitrogen gas, etc.) can be used.
In the upper coating film forming step, it is particularly preferable that: after the upper layer coating material is formed, the upper layer coating film 13 is formed by heating the coating material under a condition that the heating time from the start of heating to the maximum reaching temperature is 1 second or more and 30 seconds or less, and cooling the coating material under a condition that the cooling time from the maximum reaching temperature to 30 ℃ is 0.1 second or more and 5 seconds or less. Here, the heating time and the cooling time were measured by detecting the temperature of the metal plate with a thermocouple.
If the coating material is heated for a short time of 1 to 30 seconds as described above after the film formation of the topcoat material, the self-shrinkage of the water-soluble melamine resin (b) is further suppressed, and if the coating material is cooled for a short time of 0.1 to 5 seconds as described above, the diffusion of the water-soluble melamine resin (b) is suppressed. As a result, the water-soluble melamine resin (b) reacted with the urethane resin (a) forms domains, and is dispersed in the upper coating film 13 in the form of particles having a number average particle diameter of 5nm or more and 20nm, and is likely to be concentrated in the surface layer having a depth of 15nm or less from the surface of the upper coating film 13. Therefore, in the produced coated metal sheet 1, the metallic appearance, chemical permeation resistance, and solvent resistance are likely to be further improved.
Here, when the heating time is less than 1 second, the reaction between the urethane resin (a) and the water-soluble melamine resin (b) becomes insufficient, and the chemical resistance permeability and the solvent resistance may be reduced. On the other hand, when the heating time is longer than 30 seconds, the water-soluble melamine resin (b) tends to undergo self-condensation, and self-condensation particles become large, and a phenomenon of concentration to the surface layer of the coating film occurs, and in the coated metal sheet 1 to be produced, the metal appearance and the chemical resistance permeability may be lowered.
If the cooling time is less than 0.1 second, cracks may develop in the upper coating film 13 as a result of rapid cooling. On the other hand, when the cooling time is longer than 5 seconds, the water-soluble melamine resin (b) diffuses, and the metal appearance and chemical resistance permeability may be reduced in the coated metal sheet 1 to be produced.
The heating time is preferably 1 second or more and 20 seconds or less from the viewpoint of the appearance of the metal, the chemical permeation resistance, and the solvent resistance. From the same viewpoint, the cooling time is preferably 0.1 to 2 seconds.
The maximum reaching temperature and the holding time thereof are not particularly limited, and the maximum reaching temperature is appropriately set to be not lower than the boiling point of the aqueous solvent according to the aqueous solvent to be used, and then the holding time may be set to be, for example, about 0.1 to 5 seconds.
In addition, when the plurality of enrichment parts 103 are formed in the upper layer coating film 13, first, the heating is performed to a temperature of 40 to 100 ℃ for 1 to 20 seconds. Then, heating to more than 200 ℃ for 1-10 seconds. Thereafter, cooling is performed. By forming the upper layer coating film 13 in this way, the enriched portions 103 are formed at the depth positions other than the surface layer in addition to the enriched portions 103 of the surface layer.
The upper layer coating film forming step according to the present embodiment is explained in detail above.
< Process for Forming lower layer coating film >
Next, a lower layer coating film forming step in the method for manufacturing 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 known lower layer coating material may be used as an example of the second coating material to form the lower layer coating film 15 by a known method.
In the known method, the lower layer coating film forming step is also preferably the following step from the viewpoint of metallic appearance, chemical resistance and solvent resistance: a lower layer coating material is formed on at least one surface of a metal plate (11), and is heated and then cooled to form a lower layer coating film (15), wherein the lower layer coating material contains: a polyurethane resin (c) which contains an anionic functional group and has a glass transition temperature of not more than the glass transition temperature of the polyurethane resin (a); at least one of an epoxy resin (d), a silane coupling agent (e), and a rust inhibitor (f) containing one or more elements selected from the group consisting of P, V, Ti, Si, and Zr; and an aqueous solvent.
[ polyurethane resin (c) ]
As mentioned previously, the glass transition temperature of the urethane resin (c) is preferably equal to or lower than the glass transition temperature of the urethane resin (a). If the glass transition temperature of the urethane resin (c) is not higher than the glass transition temperature of the urethane resin (a), the adhesion between the lower coating film 15 and the upper coating film 13 is improved, and the chemical resistance permeability is likely to be further improved.
The glass transition temperature of the urethane resin (c) is more preferably a value in the range of 80 ℃ to 160 ℃ inclusive and is equal to or lower than the glass transition temperature of the urethane resin (a) (preferably 5 ℃ or higher lower than the glass transition temperature of the urethane resin (a)). In the case where the glass transition temperature of the urethane resin (c) is less than 80 ℃, the chemical permeation resistance is sometimes reduced. On the other hand, when the glass transition temperature of the urethane resin (c) is more than 160 ℃, the processability may be lowered. If the workability is lowered, cracks or the like are generated in the lower coating film 15, and the chemical permeation resistance and the solvent resistance are also lowered. The glass transition temperature of the urethane resin (c) is preferably in the range of 100 ℃ or more and 160 ℃ or less from the viewpoint of chemical resistance to permeation and solvent resistance (particularly, from the viewpoint of chemical resistance to permeation).
The urethane resin (c) may be a urethane resin containing a urethane resin having a glass transition temperature of 80 ℃ to 160 ℃ inclusive and a urethane resin having a glass transition temperature of 20 ℃ to 60 ℃ inclusive. By using urethane resins having different glass transition temperatures and adjusting the glass transition temperature of the urethane resin (c), the chemical resistance permeability can be easily further improved.
Specific examples of the urethane resin (c) include various urethane resins exemplified for the urethane resin (a).
[ regarding the epoxy resin (d) ]
Examples of the epoxy resin (d) include bisphenol a type epoxy resins, bisphenol F type epoxy resins, phenol novolac type epoxy resins, and aliphatic type epoxy resins. Among these resins, an aliphatic epoxy resin is particularly preferably used as the epoxy resin (d) because it is difficult to discolor by baking.
Specific types of the epoxy resin (d) are not particularly limited, and various commercially available epoxy resins (d) can be used, and an epoxy resin having a glass transition temperature within the above range can be synthesized by itself and used as appropriate.
[ 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- (aminoethyl) -3-aminopropyltriethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, bis (trimethoxysilylpropyl) amine, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane and 3-glycidoxypropylmethyldiethoxysilane. By including such a silane coupling agent in the lower layer coating material, the chemical resistance permeability of the lower layer coating film 15 can be further improved.
[ anti-rust agent (f) ]
In the lower coating film forming step according to the present embodiment, as the rust inhibitor (f), a rust inhibitor containing one or more elements selected from P, V, Ti, Si, and Zr can be used. By including such a rust inhibitor (f) in the lower coating material, the corrosion resistance of the lower coating film 15 can be improved.
Examples of the compound containing P which functions as the rust inhibitor (f) include: phosphoric acids such as orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, triphosphoric acid and tetraphosphoric acid, and salts thereof; phosphonic acids such as aminotri (methylenephosphonic acid), 1-hydroxyethylidene-1, 1-diphosphonic acid, ethylenediaminetetra (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic acid), and salts thereof; organic phosphoric acids such as phytic acid and salts thereof.
Examples of the V-containing compound functioning as the rust inhibitor (f) include vanadium pentoxide, metavanadate, ammonium metavanadate, sodium metavanadate, vanadyl trichloride, vanadium trioxide, vanadium dioxide, vanadyl sulfate, vanadyl acetylacetonate, vanadium trichloride, vanadomolybdic acid, and the like. In addition, it is possible to use: reducing a vanadium compound having a valence of 5 to a vanadium compound having a valence of 4 to 2 by using 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 amino group, a secondary amino group, a tertiary amino group, an amide group, a phosphoric acid group and a phosphonic acid group; salts of vanadyl cation with anions of inorganic acids such as hydrochloric acid, nitric acid, phosphoric acid, and sulfuric acid, or anions of organic acids such as formic acid, acetic acid, propionic acid, butyric acid, and oxalic acid; chelates of organic acids and vanadyl compounds, such as vanadyl glycolate and vanadyl dehydroascorbate.
Examples of the Ti-containing compound that functions as the rust inhibitor (f) include titanium potassium oxalate, titanyl sulfate, titanium chloride, titanium lactate, titanium isopropoxide, isopropyl titanate, titanium ethoxide, titanium 2-ethyl-1-hexanoate, tetraisopropyl titanate, tetra-n-butyl titanate, titanium oxide sol, fluotitanic acid, and salts thereof.
Examples of the Si-containing compound that functions as the rust inhibitor (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, Inc.); colloidal silica such as Adelite AT-20N, Adelite AT-20A and 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 Aerosil corporation, japan), and the like.
Examples of the Zr-containing compound that functions as the rust inhibitor (f) include zirconyl nitrate, zirconyl acetate, zirconyl sulfate, ammonium zirconium carbonate, potassium zirconium carbonate, sodium zirconium carbonate, zirconium acetate, and fluorozirconic acid, and salts thereof.
[ with regard to the coloring agent ]
The colorant dispersed in the lower layer coating material containing the above-mentioned components is not particularly limited as in the upper layer coating material, and a known colorant is suitably used in the sectional view. As such a colorant, for example: various inorganic pigments such as titanium oxide, zinc oxide, calcium carbonate, aluminum oxide, barium sulfate, aluminum, iron oxide, and carbon black; various organic pigments such as cyanine and quinacridone; various dyes, and the like.
[ aqueous solvent ]
As the aqueous solvent, water, a mixed solution of water and a lower alcohol, or the like can be used as in the above-described upper layer coating material. Such an aqueous solvent preferably contains 50 mass% or more (preferably 80 mass% or more) of water.
Examples of the water include distilled water, ion-exchanged water, ultrapure water, and ultrafiltrated water. Examples of the lower alcohol include alcohols having 1 to 4 carbon atoms such as methanol, ethanol, butanol, and isopropanol.
[ As to contents ]
The contents of the urethane resin (c), the epoxy resin (d), the silane coupling agent (e), and the rust preventive (f) as described above are not particularly limited, and the contents of the respective components may be appropriately determined according to the characteristics obtained in the lower coating film 15. For example, the content of the urethane resin (c) may be in the range of 30 to 95 mass%, and the content of the epoxy resin (d) may be in the range of 1 to 5 mass%. The content of the silane coupling agent (e) may be, for example, 10 to 40 mass%, and the content of the rust inhibitor (f) may be, for example, 1 to 15 mass%. The content of each component may be appropriately determined from the above range so that the total content of the urethane resin (c), the epoxy resin (d), the silane coupling agent (e), and the rust preventive (f) is 100 mass%.
[ film formation method (coating method), heating method (baking method), and Cooling method ]
In the undercoat film forming step, the method of forming a film on at least one surface of the metal plate 11, heating the undercoat, and then cooling the undercoat is not particularly limited, and various film forming methods (coating methods), heating methods, and cooling methods as described in the undercoat film forming step can be used. The maximum reaching temperature, heating time, holding time, and cooling time of the metal plate 11 coated with the under-layer coating material are also not particularly limited, and may be appropriately set.
< with respect to other ingredients >
In the method for producing a coated metal sheet according to the present embodiment, the upper layer coating material and the lower layer coating material may contain known additives such as wax, a leveling agent, an antifoaming agent, a thickener, and a dispersant. That is, in the coated metal sheet according to the present embodiment, both the upper coating film 11 and the lower coating film 15 may contain these known additives.
< Process for Forming texture >
In the method for manufacturing a coated metal plate according to the present embodiment, various textures such as pearskin, roughness, craze (hair), cloth (satin), and hammer (hammer) may be formed on the surface of the metal plate 11 to which the above-described top coat is applied, as necessary. By forming the above-described texture on the surface of the metal plate 11 in advance, the design of the coated metal plate according to the present embodiment can be further improved.
Here, the method and the apparatus used for forming the various textures as described above are not particularly limited, and various known methods and apparatuses can be appropriately used.
The method for producing a coated metal sheet according to the present embodiment is described in detail above.
Examples
Hereinafter, a coated metal sheet and a method for producing a coated metal sheet according to the present invention will be described in more detail with reference to examples and comparative examples. The following examples are merely examples of the coated metal plate and the method for producing the coated metal plate according to the present invention, and the coated metal plate and the method for producing the coated metal plate according to the present invention are not limited to the following examples.
(test example 1) < Metal plate (original plate) >
A molten zinc-plated steel sheet "NS シルバージンク (registered trademark)" (hereinafter referred to as "GI"), an electrogalvanized steel sheet "NS ジンコート (registered trademark)" (hereinafter referred to as "EG") manufactured by Nikkaido Kabushiki Kaisha, a zinc-nickel alloy-plated steel sheet "NS ジンクライト (registered trademark)" (hereinafter referred to as "ZL"), a zinc-iron alloy-plated steel sheet "NS シルバーアロイ (registered trademark)" (hereinafter referred to as "GA"), an aluminum sheet "JIS 3004" (hereinafter referred to as "Al"), a stainless steel sheet "SUS 430" (hereinafter referred to as "SUS"), a zinc-aluminum-magnesium-silicon alloy-plated steel sheet "スーパーダイマ (registered trademark)" (hereinafter referred to as "SD") (hereinafter referred to as "SD") Zinc-aluminum-magnesium alloy-plated steel sheet "ZAM (registered trademark)" (hereinafter referred to as "ZAM") manufactured by japan steel-making corporation was used as a metal sheet (original sheet). The plate thicknesses of the metal plates were 0.6mm, respectively.
ZL coating adhesion amount is 20g/m per surface2The amount of nickel in the plating layer was 12 mass%. Further, the plating adhesion amounts of GI, SD, GL, ZAM were 60g/m per one surface, respectively2. The coating adhesion amount of GA was 45g/m per one surface2. EG coating adhesion was 20g/m per surface2。
< coating >
In this test example, a 1-layer structure shown in fig. 1A having only an upper-layer coating film on one surface of the metal plate (original plate) as described above, or a coated metal plate having a 2-layer structure shown in fig. 1B having a lower-layer coating film and an upper-layer coating film was produced. Here, the urethane 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 inhibitor and the colorant used for preparing the lower layer coating material are shown in tables 2 to 7 below.
TABLE 1
Polyurethane resin Name of commodity Glass transition temperature Company name
Polyurethane resin
1 Super flex870 78 First Industrial pharmaceutical Co Ltd
Polyurethane resin 2 Takelac WS5000 65 Manufactured by Mitsui chemical Co Ltd
Polyurethane resin 3 Super flex170 75 First Industrial pharmaceutical Co Ltd
Urethane resin 4 Takelac WS5030 80 Manufactured by Mitsui chemical Co Ltd
Polyurethane resin
5 Takelac WS6010 90 Manufactured by Mitsui chemical Co Ltd
Polyurethane resin 6 Super flex130 101 First Industrial pharmaceutical Co Ltd
Polyurethane resin 7 Adeka Bontiter HUX-522 150 Manufactured by ADEKA Inc
Polyurethane resin 8 Self-made polyurethane resin A 158 Self-made
Polyurethane resin 9 Self-made polyurethane resin B 195 Self-made
Polyurethane resin 10 Super flex150 32 First Industrial pharmaceutical Co Ltd
Polyurethane resin
11 Super flex620 43 First Industrial pharmaceutical Co Ltd
Polyurethane resin 12 Hydran HW174 60 Manufactured by DIC Inc
Polyurethane resin
13 Super flex130 modified 101 First Industrial pharmaceutical Co Ltd
In addition, the Super flex130 is changed into a cationic functional group instead of the Super flex 130.
TABLE 2
Polyester resin Name of commodity Glass transition temperature (. degree. C.) Company name
Polyester resin
1 バイロナールMD-1500 77 Manufactured by Toyo Boseki Ltd
TABLE 3
Water-soluble melamine resin Name of commodity Company name
Water-soluble melamine resin 1 Cymel 303 オルネクス manufactured by Inc
Water-soluble melamine resin 2 Cymel 327 (containing imino group) オルネクス manufactured by Inc
TABLE 4
Epoxy resin Name of commodity Company name
Epoxy resin
1 Denacol EX614B Changli chemical products
Epoxy resin 2 Epicote 801 (bisphenol type) Mitsubishi chemical corporation
TABLE 5
Silane coupling agent Name of Compound Remarks for note
Silane coupling agent 1 3-aminopropyltrimethoxysilane General reagents
Silane coupling agent 2 3-aminopropyltrimethoxysilane 3-glycidoxypropyltriethoxysilane 1:1 General reagents
TABLE 6
Rust inhibitor Containing elements Name of Compound Remarks for note
Rust inhibitor 1 P Phosphoric acid General reagents
Rust preventive 2 P、V Phosphoric acid vanadyl sulfate (mass ratio 1:1) General reagents
Rust preventive 3 Ti Fluotitanic acid General reagents
Rust preventive 4 Zr Ammonium zirconium carbonate General reagents
Rust preventive 5 Si Snowtex O Chemical industry of daily products
TABLE 7
Coloring agent Colour(s) Species of Model number Manufacturer of the product
Colorant
1 Black colour Carbon black #850 Mitsubishi chemical
Colorant 2 Blue (B) Blue flower AF BlueE-2B Large day refining industry
[ self-made polyurethane resin A ]
145g of 1, 3-bis (isocyanatomethyl) cyclohexane, 20g of dimethylolpropionic acid, 15g of neopentyl glycol, 75g of polycarbonate diol having a molecular weight of 1000 and 64g of acetonitrile as a solvent were added thereto, and the mixture was stirred for 3 hours while the temperature was raised to 75 ℃ under a nitrogen atmosphere. After confirming that the reaction solution reached a predetermined amine equivalent and the temperature of the reaction solution was reduced to 40 ℃, 30g of triethylamine (boiling point: 89 ℃) was added to obtain an acetonitrile solution of the polyurethane prepolymer. This solution (300 g) was dispersed in water (700 g) using a homodisperser to form an emulsion, and 35.6g of ethylenediamine hydrazine monohydrate as a chain extender was added while the solution was kept at 40 ℃. Subsequently, the reaction solution was distilled off under reduced pressure of 150mmHg at 50 ℃ 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 purification step of the resin.
[ self-made polyurethane resin B ]
145g of 1, 3-bis (isocyanatomethyl) cyclohexane, 20g of dimethylolpropionic acid, 15g of neopentyl glycol, 75g of polycarbonate diol having a molecular weight of 1000 and 64g of acetonitrile as a solvent were added thereto, and the mixture was stirred for 3 hours while the temperature was raised to 75 ℃ in a nitrogen atmosphere. After confirming that the reaction solution reached a predetermined amine equivalent and the temperature of the reaction solution was reduced to 40 ℃, 20.00g of triethylamine (boiling point: 89 ℃) was added to the reaction solution to obtain an acetonitrile solution of a polyurethane prepolymer. This solution (300 g) was dispersed in water (700.00 g) using a homodisperser to form an emulsion, and the solution was maintained at 40 ℃ and subjected to a chain extension reaction by adding gamma- (2-aminoethyl) aminopropyltrimethoxysilane (21 g) and ethylenediamine hydrazine monohydrate (18 g) as chain extenders. Next, the reaction solution was distilled off under reduced pressure of 150mmHg at 50 ℃ 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 purification step of the resin.
Using the raw materials shown in tables 1 to 7, a predetermined amount of each raw material was mixed in water as shown in tables 8 and 9, thereby producing an upper layer coating material and a lower layer coating material.
Figure BDA0002469815180000361
Figure BDA0002469815180000371
In Table 9, main resin-2 was blended in an amount of 15 parts by mass per 100 parts by mass of main resin-1 in the lower layer coating materials 9, 10 and 11.
< production of coated Metal sheet >
Various metal sheets were immersed in an aqueous solution containing 2 mass% of FC-4336 (manufactured by Japan パーカライジング) at a temperature of 60 ℃ for 10 seconds to degrease, washed with water, and dried.
Next, the respective undercoats produced as described above were coated with a roll coater so as to have a predetermined thickness in terms of dry film thickness. The film of the under layer coating was heated (dried and cured) in an induction heating furnace in which hot air was blown, under conditions in which the maximum arrival plate temperature of the metal plate was 150 ℃ and the heating time from the start of heating to the maximum arrival temperature was 10 seconds. After 1 second from the time of reaching the maximum reaching temperature, water was sprayed to the coated metal plate with a sprayer, and water cooling was performed under the condition that the cooling time from the maximum reaching temperature to 30 ℃ was 1 second. The holding time for the maximum reaching temperature during heating was set to 1 second.
Next, the topcoat paints prepared as described above were applied to the respective substrates by a roll coater so that the dry film thickness became a predetermined film thickness. The film of the topcoat material was heated (dried and cured) in an induction heating furnace into which hot air was blown, under conditions in which the maximum arrival temperature of the metal plate was 230 ℃ and the heating time from the start of heating to the maximum arrival temperature was 10 seconds. After 1 second from the maximum reaching temperature, water was sprayed to the coated metal plate by a sprayer, and water cooling was performed under the condition that the cooling time from the maximum reaching temperature to 30 ℃ was 1 second. The holding time for the maximum reaching temperature during heating was set to 1 second.
< level >
The composition of the upper layer coating film and the lower layer coating film was analyzed for each sample of the produced coated metal sheet.
Specifically, the presence or absence of the constituent sites (urethane bond skeleton (UB), triazine ring skeleton (TR), epoxy group (EP), siloxane bond (silane) derived from a silane coupling agent) of the upper layer coating film and the lower layer coating film was analyzed by a fourier transform infrared spectrophotometer (FT-IR, Frontier, manufactured by PerkinElmer) and judged based on whether or not the following vibration peaks were observed.
Urethane bond backbone (UB): at 1540cm-1The sum of vibration peaks of N-H deformation vibration observed nearby is 1730cm-1Vibration peak of C ═ O stretching vibration observed nearby
Triazine ring skeleton (TR): at 1550, 1450, 815cm-1Nearby observed vibration peak from triazine ring
Epoxy group (EP): at 910cm-1Nearby observed vibration peak from epoxy group
Siloxane bond: at 1050cm-1Vibration peak of Si-O-Si stretching vibration observed nearby
In addition, the thickness (depth of enrichment) of the enriched part present in the top coating film at the surface layer and the number average particle diameter (particle diameter) of the granular triazine moiety (water-soluble melamine resin) were measured according to the methods described above. The N1/N2 (concentration ratio) which is the ratio of the N concentration N1 at the depth position of 0.2 μm from the surface of the first coating film to the N concentration N2 at the depth position of 0.2 μm from the interface between the first coating film and the metal plate toward the first coating film side was measured by the above-described method. Then, with respect to each sample of the produced coated metal sheet, the glass transition temperature (Tg) of each coating film was measured in accordance with the method already described.
Further, according to the above-described method, it was determined whether melamine particles of 5nm or more were observed and whether a plurality of enriched portions were formed when the surface enriched portion was stained with osmium oxide and observed at a magnification of 10 ten thousand times using a transmission electron microscope.
< evaluation method >
Each of the produced coated metal sheets was evaluated according to the following criteria.
[ metallic appearance ]
Each of the coated metal sheets produced was evaluated on a color scale of L, a, b of CIELAB (JISZ8729) by a CR-400 spectrophotometer (light source 10 ° D65, SCI method) manufactured by コニカミノルタ on four (excellent) A, B, C, D (inferior) scales.
A: l is more than 60, and | a | < 1
B: l is less than 60, and | a | < 1
C: l is less than 60 and | a | ≧ 1
D: l is less than 60, | a | ≧ 1, and | b | ≧ 6
[ chemical resistance Permeability test ]
Each of the coated metal sheets thus produced was cut into a width of 5cm, and a sample whose end face was entirely protected with ニトフロン (registered trademark) tape was immersed in 5% sulfuric acid water and 5% sodium hydroxide water at 20 ℃ for 24 hours, and the degree of discoloration was evaluated on four scales (excellent) A, B, C, D (inferior).
A: no color change
A-B: has extremely slight color change
B: slightly discolored
C: has a plurality of color changes
D: has much discoloration and peeling of the coating
[ workability test ]
Each of the coated metal sheets thus produced was cut into a width of 5cm, and subjected to 2T bending in an atmosphere of 20 ℃ by a test method in accordance with JIS G3312. Specifically, 2 coated sheets similar to the test piece were sandwiched inside, and the surfaces on which the upper and lower coated films were formed were bent in close contact with each other by 180 degrees so that the surfaces were outside. The cracking of the coating film was evaluated on four grades (excellent) A, B, C, D (inferior).
A: without cracking
B: there is a slight cracking of the steel sheet,
c: has much cracks
D: has much cracks and has coating film peeling
[ stain resistance test ]
Each of the coated metal sheets produced was coated with a universal Ink (Magic Ink) (temple, western chemical industries, ltd.) in red, wiped off with ethanol after 24 hours, and evaluated for Ink residue on four grades (excellent) A, B, C, D (inferior). When the remaining traces were noticeable, the value a indicating the redness of CIELAB (JISZ8729) was measured before and after the test using a commercially available spectrophotometer (light source 10 ° D65, SCI method), and the following evaluation was performed using the difference (Δ a).
A: no residual trace
B: slight residual mark
C：Δa*≤3
D：Δa*＞3
The levels and evaluation results of the respective coated metal sheets produced are summarized in table 10. Note that, the abbreviations and the like in table 10 are as follows. The same applies to other tables, for example, abbreviation.
UB: urethane bond skeleton
TR: triazine ring skeleton
EP: epoxy group
Silane: siloxane bond
Antirust agent: rust inhibitor (f)
And (3) enrichment depth: the thickness of the concentrated part formed on the surface layer (sometimes referred to as "surface layer concentrated part")/the surface layer is not limited to the above-described thickness
Particle size: number average particle diameter of triazine particles (water-soluble melamine resin)
Tg: glass transition temperature of each coating film
Tg difference: difference in glass transition temperature between upper and lower coating films (glass transition temperature of upper coating film-glass transition temperature of lower coating film)
Figure BDA0002469815180000421
Figure BDA0002469815180000431
As is clear from tables 10-1 and 10-2, the coated metal sheets pertaining to the examples of the present invention are excellent in metallic appearance, chemical resistance to permeation, solvent resistance and processability.
On the other hand, as is clear from the above table 10-2, in the case where no concentrated layer was formed on the surface layer of the upper coating film 13 (in the case where melamine particles having a number average particle diameter of 5nm or more were observed when the surface layer was observed at a magnification of 10 ten thousand) (comparative example 105), the chemical resistance permeability was remarkably deteriorated as compared with the examples. It is found that in the case where the urethane bond skeleton is not present in the upper coating film 13 (comparative example 104), the chemical resistance permeability is significantly deteriorated as compared with the examples. It is found that when the granular triazine sites are not concentrated on the surface layer of the upper coating film having no triazine ring skeleton (comparative example 103), chemical resistance permeability and solvent resistance are remarkably deteriorated as compared with the examples. It is found that in the case where the glass transition temperature of the upper coating film 13 is less than 80 ℃ (comparative example 101), the chemical resistance permeability is significantly deteriorated as compared with the examples. It is found that when the glass transition temperature of the upper layer coating film 13 is higher than 170 ℃ (comparative example 102), the workability is remarkably deteriorated, and the chemical resistance permeability and the solvent resistance are lowered when the processing is performed.
Further, as is clear from table 10-2, in the case where the upper layer coating material contains silica (comparative example 106), chemical resistance permeability and stain resistance are deteriorated as compared with the examples.
In the case where the upper layer paint contained the metal complex (comparative example 107,108,109), the chemical permeation resistance was inferior to that of the examples.
In addition, it is found that when the granular triazine moiety is concentrated at a position more than 15nm from the surface layer in the upper coating film 13 (example 143), the workability is lowered as compared with other examples, and the chemical resistance permeability and the solvent resistance are lowered when the coating is processed. In addition, it is found that in the case where the glass transition temperature of the lower coating film 15 is higher than that of the upper coating film 13 (example 146), chemical resistance permeability is deteriorated as compared with other examples.
(test example 2) < Metal plate (original plate) >
As the metal plate (original plate), an electrogalvanized steel plate "NS ジンコート (registered trademark)" (hereinafter referred to as "EG") manufactured by seikagaku corporation was used. EG coating adhesion was 20g/m per surface2。
< coating >
In this test example, a 1-layer structure shown in fig. 1A having only an upper-layer coating film on one surface of the metal plate (original plate) as described above, or a coated metal plate having a 2-layer structure shown in fig. 1B having a lower-layer coating film and an upper-layer coating film was produced.
The commercially available resin, silane coupling agent and rust preventive agent used for forming the upper layer coating film and the lower layer coating film are as follows.
Urethane resin for upper layer coating film: polyurethane resin 4 in test example 1
Urethane resin for lower layer coating film: polyurethane resin 3 in test example 1
Water-soluble melamine resin: melamine resin 2 in Experimental example 1
Epoxy resin: epoxy resin 1 in test example 1
Silane coupling agent: silane coupling agent 1 in test example 1
Antirust agent: rust preventive 2 in test example 1
Wax: ケミパール S100 (manufactured by Mitsui chemical Co., Ltd.)
The topcoat material was prepared by mixing predetermined amounts of the above-mentioned urethane resin, melamine resin, and wax according to the formulation shown in table 11. Similarly, the lower layer paint was prepared by mixing predetermined amounts of the above-described urethane resin, epoxy resin, silane coupling agent, rust preventive agent and colorant according to the formulation of table 11.
< production of coated Metal sheet >
Various metal sheets were immersed in an aqueous solution containing 2 mass% of FC-4336 (manufactured by Japan パーカライジング) at a temperature of 60 ℃ for 10 seconds to degrease, washed with water, and dried.
Next, the respective under-layer paints prepared as described above were applied by a roll coater so as to have a film thickness of 0.5 μm in terms of dry film thickness. The film of the under layer coating was heated (dried and cured) in an induction heating furnace in which hot air was blown, under conditions in which the maximum arrival plate temperature of the metal plate was 150 ℃ and the heating time from the start of heating to the maximum arrival temperature was 5 seconds. After 1 second from the time of reaching the maximum reaching temperature, water was sprayed to the coated metal plate with a sprayer, and water cooling was performed under the condition that the cooling time from the maximum reaching temperature to 30 ℃ was 1 second. The holding time for the maximum reaching temperature during heating was set to 1 second.
Then, the topcoat paints prepared as described above were applied by a roll coater so as to have a film thickness of 10 μm in terms of dry film thickness. The film of the topcoat material was heated (dried and cured) in an induction heating furnace into which hot air was blown, under conditions in which the maximum arrival temperature of the metal plate was 230 ℃ and the heating time from the start of heating to the maximum arrival temperature was 10 seconds. After 1 second from the maximum reaching temperature, water was sprayed to the coated metal plate by a sprayer, and water cooling was performed under the condition that the cooling time from the maximum reaching temperature to 30 ℃ was 1 second. The holding time for the maximum reaching temperature during heating was set to 1 second.
< level >
For each of the produced samples of the coated metal sheets, the position (concentration depth) of the region where the granular triazine moiety (water-soluble melamine resin) is concentrated in the upper coating film and the number average particle diameter (particle diameter) of the granular triazine moiety (water-soluble melamine resin) were measured in accordance with the methods described above. The concentration degree of the triazine moiety present in the granular triazine moiety (water-soluble melamine resin) -rich region was measured by the method described above. Then, for each sample of the produced coated metal sheet, the glass transition temperature (Tg) of each coating film was measured in accordance with the method already described.
Further, according to the above-described method, it was determined whether melamine particles of 5nm or more were observed and whether a plurality of enriched portions were formed when the surface enriched portion was stained with osmium oxide and observed at a magnification of 10 ten thousand times using a transmission electron microscope.
< evaluation method >
The respective coated metal sheets produced were evaluated for metal appearance, chemical resistance and stain resistance in the same manner as in test example 1. The workability test and the corrosion resistance of the worked portion were evaluated as follows.
[ workability test ]
Each of the coated metal sheets thus produced was cut into a width of 5cm, and subjected to 6T bending in an atmosphere of 20 ℃ by a test method in accordance with JIS G3312. Specifically, 6 coated sheets similar to the test piece were sandwiched inside, and the surfaces on which the upper and lower coating films were formed were bent in close contact with each other by 180 degrees so that the surfaces were outside. The cracking of the coating film was evaluated on four grades (excellent) A, B, C, D (inferior).
A: without cracking
B: there is a slight cracking of the steel sheet,
c: has much cracks
D: has much cracks and has coating film peeling
[ Corrosion resistance test of worked parts ]
Each of the coated metal sheets thus produced was cut into a width of 5cm, and subjected to extrusion processing. The extrusion height was set to 7 mm. Thereafter, a salt spray test was performed for 240 hours in accordance with JIS Z2371. After the test, the area ratio of white rust generation in the entire area of the processed portion was determined by visual observation, and the following evaluation was performed. The white rust occurrence area ratio is a percentage of the area of the white rust occurrence portion to the area of the observation portion.
A: the area ratio of white rust generation is less than 10 percent
B: the white rust generation area ratio is more than 10% and less than 25%
C: the white rust generation area ratio is more than 25% and less than 50%
D: the white rust generation area ratio is more than 50 percent and less than 75 percent
E: the white rust generation area ratio is more than 75%
The levels and evaluation results of the produced coated metal sheets are summarized in table 11. Note that abbreviations and the like in table 11 are the same as those in table 10.
However, (Wa) + (Wb), (Wb)/(Wa) are as follows.
(Wa) + (Wb): the total content of the polyurethane resin (a) relative to the total solid content (Wa: unit, mass%) and the content of the water-soluble melamine resin (b) relative to the total solid content (Wb: unit, mass%)
(Wb)/(Wa): the ratio of the content (Wa) of the polyurethane resin (a) to the total solid content to the content (Wb) of the water-soluble melamine resin (b) to the total solid content
Figure BDA0002469815180000481
As is clear from table 11 above, the total content (Wa) + (Wb) of the urethane resin (a) and the water-soluble melamine resin (b) used in the upper coating film 13 is 90 mass% or more and 100 mass% or less, and the ratio (Wb)/(Wa) is more than 0 and 1 or less, whereby the chemical resistance permeability of the coated metal sheet produced is further improved.
(test example 3) < Metal plate (original plate) >
As the metal plate (original plate), an electrogalvanized steel plate "NS ジンコート (registered trademark)" (hereinafter referred to as "EG") manufactured by seikagaku corporation was used. EG coating adhesion was 20g/m per surface2。
< coating >
In this test example, a 1-layer structure shown in fig. 1A having only an upper-layer coating film on one surface of the metal plate (original plate) as described above, or a coated metal plate having a 2-layer structure shown in fig. 1B having a lower-layer coating film and an upper-layer coating film was produced.
The upper layer coating material-3 of test example 1 was used as the upper layer coating material, and the lower layer coating material-8 of test example 1 was used as the lower layer coating material.
< production of coated Metal sheet >
Various metal sheets were immersed in an aqueous solution containing 2 mass% of FC-4336 (manufactured by Japan パーカライジング) at a temperature of 60 ℃ for 10 seconds to degrease, washed with water, and dried.
Next, the respective under-layer paints prepared as described above were applied by a roll coater so as to have a film thickness of 1.0 μm in terms of dry film thickness. The film of the under layer coating was heated (dried and cured) in an induction heating furnace in which hot air was blown, under conditions in which the maximum arrival plate temperature of the metal plate was 150 ℃ and the heating time from the start of heating to the maximum arrival temperature was 5 seconds. After 1 second from the time of reaching the maximum reaching temperature, water was sprayed to the coated metal plate with a sprayer, and water cooling was performed under the condition that the cooling time from the maximum reaching temperature to 30 ℃ was 1 second. The holding time for the maximum reaching temperature during heating was set to 1 second.
Then, the topcoat paints prepared as described above were applied by a roll coater so as to have a dry film thickness of 8 μm. The film of the topcoat material was heated (dried and cured) in an induction heating furnace into which hot air was blown so that the maximum arrival temperature of the metal sheet, the heating time from the start of heating to the maximum arrival temperature, and the holding time at 40 to 100 ℃ were set to the conditions shown in table 12. After 1 second from the time of reaching the maximum reaching temperature, water was sprayed to the coated metal plate by a sprayer, and water cooling was performed under the conditions that the cooling time from the maximum reaching temperature to 30 ℃ was the time shown in table 12. The holding time for the maximum reaching temperature during heating was set to 1 second.
< level >
The thickness (depth of enrichment) of the surface layer enrichment part and the number average particle diameter (particle diameter) of the granular triazine site (water-soluble melamine resin) in the upper coating film were measured for each sample of the produced coated metal sheet by the methods described above. Further, N1/N2, which is the ratio of N1 at a depth position of 0.2 μm from the surface of the first coating film to N2 at a depth position of 0.2 μm from the interface between the first coating film and the metal plate toward the first coating film, was measured by the above-described method. Then, for each sample of the produced coated metal sheet, the glass transition temperature (Tg) of each coating film was measured in accordance with the method already described.
Further, according to the above-described method, it was determined whether melamine particles of 5nm or more were observed and whether a plurality of enriched portions were formed when the surface enriched portion was stained with osmium oxide and observed at a magnification of 10 ten thousand times using a transmission electron microscope.
< evaluation method >
The respective coated metal sheets thus produced were evaluated in the same manner as in test example 1.
The levels and evaluation results of the respective coated metal sheets produced are summarized in table 12. Note that the abbreviations and the like in table 12 are the same as those in table 10.
Figure BDA0002469815180000511
As is clear from table 12 above, if the upper coating film 13 is formed by heating under the condition that the heating time from the start of heating to the maximum reaching temperature is 1 second or more and 30 seconds or less and cooling under the condition that the cooling time from the maximum reaching temperature to 30 ℃ is 0.1 second or more and 5 seconds or less after the film formation of the upper coating, the obtained coated metal sheet is excellent in metal appearance, chemical resistance, processability, and solvent resistance, and particularly chemical resistance.
In addition, a plurality of concentrated layers were formed in the first coating film obtained by a method of holding at 40 to 100 ℃ for 1 to 20 seconds, then heating to a temperature of more than 200 ℃ for 1 to 10 seconds, and then cooling (examples 315, 316, 317). If a plurality of concentrated layers are formed in the first coating film, the metallic appearance, chemical resistance to permeation, processability, and solvent resistance are all excellent.
In the case where the maximum reached plate temperature was 160 ℃ (comparative example 301), chemical resistance permeability and solvent resistance were deteriorated.
Here, the cross section of the upper layer coating film 13 of example 303 was dyed with osmium oxide, and then observed with a Transmission Electron Microscope (TEM), and the distribution state of osmium was observed with a TEM-EDX. The obtained various microscope images are shown in fig. 5A to 5D. Fig. 5A, 5C, and 5D are cross-sectional TEM images of the upper layer coating film 13 of example 303, and fig. 5B is a drawing showing an osmium element map image obtained by observing the upper layer coating film 13 of example 303 dyed with osmium oxide by TEM-EDX.
As is clear from fig. 5A, in the upper layer coating film 13 of example 303, a black line-shaped region is shown on the surface layer side in the cross-sectional TEM image. When the osmium element mapping image shown in fig. 5B is observed, the osmium elements that selectively stain the triazine sites are linearly distributed in the portions corresponding to the black linear regions in fig. 5A. From these results, the black line-shaped region in fig. 5A corresponds to the enriched portion 103.
Fig. 5C is an enlarged view of the central portion of the upper layer coating film 13 in the cross-sectional TEM image in fig. 5A. Referring to fig. 5C, it is seen that black particles are reflected in the cross-sectional TEM image. Fig. 5D is an enlarged view of one of the black particles. It is understood that if regions corresponding to fig. 5C and 5D are confirmed by fig. 5B, the osmium element is dispersed in such regions. Therefore, it was found that these dispersed osmium portions corresponded to the triazine pellets 101. That is, it is known that the black particles in fig. 5C and 5D are triazine particles 101.
The preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can conceive various modifications and alterations within the scope of the technical idea described in the claims, and it is needless to say that these modifications and alterations also fall within the protective scope of the present invention
Description of the reference numerals
1 coating a metal plate
11 metal plate
13 Upper coating film (first coating film)
15 lower layer coating film (second coating film)
101 triazine particle (second part of dispersion type)
103 enrichment part (enrichment type second part)

Claims (20)

1. A coated metal sheet is characterized by comprising:
a metal plate; and
a first coating film containing a resin and located on at least one surface of the metal plate,
the first coating film has:
a first site having a urethane bond skeleton; and
a second site having a triazine ring backbone,
the first coating film has a glass transition temperature of 85 ℃ to 170 ℃,
when the second site was stained with osmium oxide and observed at a magnification of 10 ten thousand times using a transmission electron microscope, it was observed that:
a second dispersing part in which particles having a number average particle diameter of 5 to 20nm are dispersed; and
and an enrichment-type second site which is present at a position from the surface of the first coating film to a depth of 15nm and in which particles having a number average particle diameter of 5nm or more are not observed.
2. The coated metal sheet according to claim 1, wherein a ratio of N concentration N1 at a depth position of 0.2 μm from the surface of the first coating film to N concentration N2 at a depth position of 0.2 μm from the interface between the first coating film and the metal sheet to the first coating film side, i.e., N1/N2, is 1.2 or more.
3. The coated metal sheet according to claim 1 or 2, wherein the first coating film has a plurality of the enrichment-type second sites.
4. The coated metal sheet according to claim 1, further comprising a second coating film between the first coating film and the metal sheet,
the second coating film has a glass transition temperature not higher than that of the first coating film.
5. The coated metal sheet according to claim 4, wherein the second coating film contains a resin and has a urethane bond skeleton.
6. The coated metal sheet according to claim 4 or 5, wherein the second coating film contains a resin and has an epoxy group.
7. The coated metal sheet according to claim 4 or 5, wherein the second coating film contains a resin and has a siloxane bond.
8. The coated metal sheet according to claim 4 or 5, wherein one or more elements selected from the group consisting of P, V, Ti, Si and Zr are contained in the second coating film.
9. The coated metal sheet according to claim 4 or 5, wherein the glass transition temperature of the first coating film is higher than the glass transition temperature of the second coating film by 5 ℃ or more.
10. The coated metal sheet according to claim 4 or 5, wherein the film thickness of the second coating film is 0.5 μm or more and 15 μm or less.
11. The coated metal sheet according to any one of claims 1 to 2 and 4 to 5, wherein the film thickness of the first coating film is 0.5 μm or more and 15 μm or less.
12. The coated metal sheet according to claim 4 or 5, wherein at least one of the first coating film and the second coating film contains a colorant.
13. The coated metal sheet according to claim 4 or 5, wherein the second coating film contains a black pigment as a colorant.
14. A coated metal sheet according to any one of claims 1 to 2 and 4 to 5, wherein a texture is formed on at least one surface of the metal sheet.
15. A method for producing a coated metal sheet having a predetermined first coating film on at least one surface of a metal sheet,
forming the first coating film by applying a first coating material containing a urethane resin (a), a triazine ring-containing water-soluble curing agent (b), and an aqueous solvent to at least one surface of the metal plate, and heating the metal plate coated with the first coating material, wherein the urethane resin (a) contains an anionic functional group and has a glass transition temperature of 75 ℃ or more and 160 ℃ or less,
at the time of forming the first coating film,
heating the metal plate coated with the first paint so that a heating time from a start of heating of the metal plate coated with the first paint to a maximum reaching temperature is 1 second or more and 30 seconds or less,
cooling the metal plate coated with the first paint so that a cooling time from the maximum reaching temperature to 30 ℃ is 0.1 seconds or more and 5 seconds or less.
16. A coated metal sheet manufacturing method according to claim 15, wherein the triazine ring-containing water-soluble curing agent (b) is a melamine resin containing an imino group.
17. The method for producing a coated metal sheet according to claim 15 or 16, wherein in the first dope,
the total content (Wa) + (Wb) of the content (Wa) of the polyurethane resin (a) relative to the total solid content and the content (Wb) of the triazine ring-containing water-soluble curing agent (b) relative to the total solid content satisfy the following formula (I), and
a ratio (Wb)/(Wa) of a content (Wa) of the polyurethane resin (a) with respect to the total solid content to a content (Wb) of the triazine ring-containing water-soluble curing agent (b) with respect to the total solid content satisfies the following formula (II),
90 percent by mass or more of (Wa) + (Wb) or less of 100 percent by mass of the formula (I),
0 < (Wb)/(Wa) < 1. cndot. II).
18. The method for producing a coated metal sheet according to claim 15 or 16, further comprising a step of forming a predetermined second coating film between the metal sheet and the first coating film,
forming the second coating film by applying a second paint on at least one surface of the metal plate before applying the first paint and heating the metal plate applied with the second paint,
the second coating contains:
a urethane resin (c) having a glass transition temperature of the urethane resin (a) or lower;
at least one of an epoxy resin (d), a silane coupling agent (e), and a rust inhibitor (f); and
an aqueous solvent, a solvent,
the rust inhibitor (f) contains one or more elements selected from the group consisting of P, V, Ti, Si and Zr.
19. A coated metal sheet manufacturing method according to claim 18, wherein the glass transition temperature of the urethane resin (c) is lower than the glass transition temperature of the urethane resin (a) by 5 ℃ or more.
20. A coated metal sheet manufacturing method according to claim 15 or 16, wherein the heating is performed for 1 to 20 seconds at a temperature of 40 to 100 ℃ and then for 1 to 10 seconds until the temperature is higher than 200 ℃.
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