WO2012074044A1 - Colored and coated chromate-free metal sheet, and colored aqueous composition - Google Patents

Abstract

The present invention provides a colored and coated chromate-free metal sheet which has, formed on at least one surface of a metal sheet, a colored coating film (α) that comprises a film-forming component comprising a polyurethane resin (A1) containing a urea group, a urethane group and a carboxyl group, a coloring pigment (B) and spherical silica particles (C) having an average particle diameter of 5-50 nm, wherein the polyurethane resin (A1) contains structural units each derived from a polyester polyol component (a) having an aromatic ring structure and structural units each derived from an isocyanate component (b) having an aromatic ring structure, each of the structural units derived from the isocyanate component (b) contains an aromatic ring structure, and the colored coating film (α) has a thickness of 2-10 μm, and wherein the metal sheet has excellent chemical resistance.

Description

Chromate-free colored coated metal plate and aqueous colored composition

The present invention has a design property (colorability including processing parts, concealment property), moisture resistance, corrosion resistance, and workability, in which a colored coating film not containing hexavalent chromium having high environmental impact is formed on at least one surface of a metal plate. Further, the present invention relates to an inexpensive chromate-free colored painted metal plate that is extremely excellent in scratch resistance, chemical resistance, and the like.
This application claims priority on December 1, 2010 based on Japanese Patent Application No. 2010-268184 filed in Japan, the contents of which are incorporated herein by reference.

For home appliances, building materials, and automobiles, pre-coated steel sheets coated with a colored organic film have been used in place of post-painted products that have been painted after conventional molding. This pre-coated steel sheet is obtained by coating a rust-proof steel sheet or a plated steel sheet with a colored organic film, and has good workability and corrosion resistance while having a beautiful appearance.

For example, Patent Document 1 discloses a technique for obtaining a precoated steel sheet excellent in workability, contamination resistance, and hardness by defining the structure of the film. On the other hand, Patent Document 2 discloses a precoated steel sheet having improved end face corrosion resistance by using a specific chromate treatment liquid. These pre-coated steel sheets have corrosion resistance, workability, and paint adhesion due to the combined effect of the plating film, chromate-treated film, and chrome-based anti-corrosive pigment (primary coating). The purpose is to improve productivity and quality.

However, in view of the environmental load of hexavalent chromium that may be eluted from the chromate-treated film and the organic film containing the chromium-based anticorrosive pigment, recently there has been a growing demand for non-chromium anti-rust treatment and non-chromium organic film. . On the other hand, for example, Patent Document 3 and Patent Document 4 disclose non-chromium precoated steel sheets having excellent corrosion resistance, which have already been put into practical use.

The coating used for these precoated steel sheets is thick with a coating thickness of 10 μm or more. In addition, since a large amount of solvent-based paint is used, special coating equipment such as an incinerator and odor control equipment is required, and it is generally manufactured on a dedicated paint line. That is, since an extra coating process is passed in addition to the manufacturing process of the steel sheet as a coating original sheet, many costs are required in addition to the material cost required for coating. Therefore, the precoated steel sheet obtained is expensive.

However, due to diversification of user needs, there is a demand for colored steel sheets in fields where the purpose can be sufficiently achieved if they have durability under daily use conditions such as home appliances and interior building materials, and lower priced products are required. Yes. That is, conventional expensive pre-coated steel sheets alone are not sufficient to meet diversified demands.

As a colored steel plate that can be manufactured at low cost for such needs, for example, a colored steel plate provided with a colored resin layer having a thickness of 5 μm or less in Patent Document 5 has a specific roughness in Patent Document 6. A colored steel sheet having a colored film on the surface is disclosed. However, these colored steel sheets are designed to ensure corrosion resistance by providing a chromate-treated film, and thus cannot meet the recent needs for non-chromation. In addition, since it has not been designed in consideration of the concealability of the processed and stretched colored layer, it has a problem that the appearance of the processed portion is remarkably deteriorated.

Further, Patent Document 7 discloses a surface-treated metal material having improved characteristics such as alkali resistance and solvent resistance by using a polyurethane resin containing a silanol group and a bond derived from a silanol group. . However, when the polyurethane resin contains a silanol group or a bond derived from the silanol group, there is a problem that the processability and corrosion resistance cannot be sufficiently exhibited, and the chemical resistance cannot be sufficiently exhibited.

Patent Document 8 discloses an aqueous dispersion of a polyurethane resin containing a polyalkylene oxide group and a rust inhibitor obtained by a reaction between an epoxy prepolymer (I) having an amino group and a urethane prepolymer (II). An aqueous surface treatment composition containing is disclosed. However, this aqueous surface treatment composition has a problem that the adhesion to the base metal is not sufficient, and sufficient workability and chemical resistance cannot be exhibited.

In addition, when a design-coated steel sheet coated with a surface-treated coating film disclosed in Patent Documents 7 and 8 is used as a back cover material for a thin television, the back cover is made of a cleaning agent containing alcohol. When the dirt on the surface was wiped off, there was a problem that the coating film dissolved and discolored.

Japanese Laid-Open Patent Publication No. 8-168723 Japanese Unexamined Patent Publication No. 3-100180 Japanese Unexamined Patent Publication No. 2000-199075 Japanese Unexamined Patent Publication No. 2000-262967 Japanese Patent Laid-Open No. 5-16292 Japanese Unexamined Patent Publication No. 2-93093 Japanese Unexamined Patent Publication No. 2008-25023 Japanese Unexamined Patent Publication No. 2009-127061

In view of the present situation, the present invention does not include hexavalent chromium having high environmental impact, design properties (colorability including processing parts, hiding properties), moisture resistance, corrosion resistance, workability, scratch resistance, and chemical resistance. An object of the present invention is to provide an inexpensive chromate-free colored painted metal plate having excellent properties.

That is, the gist of the present invention is as follows.
(1) A first aspect of the present invention is a film-forming component comprising a polyurethane resin (A1) containing a urea group, a urethane group, and a carboxyl group; a color pigment (B); and an average particle size of 5 to 50 nm A structure derived from a polyester polyol component (a) in which the polyurethane resin (A1) has an aromatic ring structure. And a structural unit derived from an isocyanate component (b) having an aromatic ring structure, all of the structural units derived from the isocyanate component (b) have an aromatic ring structure, and the colored coating film ( This is a chromate-free colored coated metal plate having excellent chemical resistance, with a film thickness of α) of 2 to 10 μm.
(2) In the chromate-free colored coated metal plate having excellent chemical resistance described in (1) above, the aromatic ring structure contained in the isocyanate component (b) having the aromatic ring structure is the polyurethane resin (A1 ) May be contained in an amount of 5 to 20% by mass.
(3) In the chromate-free colored coated metal plate having excellent chemical resistance described in (2) above, the aromatic ring structure contained in the polyester polyol component (a) having the aromatic ring structure is the polyurethane resin ( A1) may contain 5 to 25% by mass.
(4) In the chromate-free colored coated metal plate having excellent chemical resistance described in any one of (1) to (3) above, the isocyanate component (b) may be tolylene diisocyanate.
(5) In the chromate-free colored coated metal sheet having excellent chemical resistance according to any one of (1) to (4) above, the film-forming component of the colored coating film (α) contains a sulfonic acid group. You may further contain the polyester resin (A2) to do.
(6) In the chromate-free colored coated metal plate having excellent chemical resistance according to any one of (1) to (5) above, the film-forming component of the colored coating film (α) is a curing agent (D). It may be cured with.
(7) In the chromate-free colored coated metal plate having excellent chemical resistance according to any one of (1) to (6), the colored coating film (α) further contains a lubricant (E). May be.
(8) The chromate-free colored coated metal plate having excellent chemical resistance according to any one of the above (1) to (7) has a base treatment layer (β) under the colored coating film (α). May be.
(9) According to a second aspect of the present invention, there is provided an aqueous solvent in which the colored coating film (α) according to any one of the above (1) to (8) contains a coating film component. It is a chromate-free colored painted metal plate formed by applying to at least one surface of a metal plate using heat and drying by heating.
(10) A third aspect of the present invention includes a polyurethane resin (A1) containing a urea group, a urethane group, and a carboxyl group; a colored pigment (B); and spherical silica particles (C); The polyurethane resin (A1) contains a structural unit derived from a polyester polyol component (a) having an aromatic ring structure; and a structural unit derived from an isocyanate component (b) having an aromatic ring structure, and the isocyanate component It is an aqueous coloring composition which contains an aromatic ring structure in all the structural units derived from (b).
(11) In the aqueous coloring composition described in (10) above, the aqueous coloring composition may further contain a polyester resin (A2) containing a sulfonic acid group.

The chromate-free colored coated metal plate of the present invention does not contain highly environmentally friendly hexavalent chromium, is inexpensive, has design properties (coloring and concealment including processed parts), moisture resistance, corrosion resistance, workability, and scratch resistance. Excellent in chemical and chemical resistance. In addition, the organic resin as a film-forming component does not necessarily have to be crosslinked and cured for forming a coating film, so that it is possible to suppress energy costs and improve productivity. For this reason, it is very promising as an inexpensive high-design, high-value-added environment-friendly material, and the contribution to each industrial field is very large.

As described above, colored coated metal plates mainly used for design applications are required to have various performances such as design properties, moisture resistance, corrosion resistance, workability, scratch resistance, chemical resistance, etc. . Conventionally, in order to meet these needs, an organic resin (for example, polyester / melamine resin) cross-linked and cured with a curing agent is used as a film-forming component, and a coating film in which a color pigment is dispersed therein is 10 μm or more. A coated metal plate formed on the upper layer of a metal plate with a relatively thick film thickness has been used. In order to increase the cohesive strength of the coating film and to ensure various performances, the coating film in which the color pigment is dispersed with a thick film needs to use an organic resin that has been crosslinked and cured with a curing agent as a binder component. . In order to cure the organic resin by crosslinking, a sufficient baking temperature and baking time are required, which causes an increase in energy cost and a decrease in productivity, and has become a main factor for an increase in manufacturing cost.

Accordingly, the present inventors have intensively studied a colored coating film that can ensure various performance even with a relatively thin film and without using a curing agent, and coloring an organic resin containing a specific functional group in the resin structure. It is used as a film-forming component of the film, and further contains a coloring pigment for ensuring designability, and silica particles for improving corrosion resistance and scratch resistance, thereby providing extremely excellent designability and moisture resistance. The present inventors have found that various performances such as corrosion resistance, workability, scratch resistance, and chemical resistance can be secured. In particular, workability, corrosion resistance, and chemical resistance are technically contradictory, and the performance is greatly affected by the organic resin that is a film-forming component. And have succeeded in ensuring unprecedented processability, corrosion resistance, and chemical resistance.
Specifically, the organic resin used as a film-forming component contains a structural unit derived from a polyester polyol component and a structural unit derived from an isocyanate component, which contains a urea group, a urethane group, and a carboxyl group, and further has an aromatic ring structure. And a polyurethane resin containing an aromatic ring structure in all of the structural units derived from the isocyanate component. Urea groups and urethane groups, particularly urea groups, have very high cohesive energy, and thus have the same effect of increasing the cohesive strength of the colored coating film as that obtained by crosslinking and curing using a curing agent. The carboxyl group has an effect of improving adhesion to a metal plate as a base material (a base treatment layer when there is a base treatment).
In the present invention, a urethane obtained by subjecting a polyol component containing a polyester polyol component having an aromatic ring structure and an isocyanate component having an aromatic ring structure to a urethanization reaction under the condition that the isocyanate group contained in the isocyanate component is excessive. A polyurethane resin obtained by further extending the prepolymer (with the isocyanate group remaining) with a polyamine compound is used. A urethane group is formed by the reaction of the polyol component and the isocyanate component, and a urea group is formed by further reacting with the polyamine compound, resulting in an ultrahigh molecular weight. As described above, polyurethane resins containing urethane groups and urea groups in the resin structure and having a high molecular weight are relatively excellent in balance between processability and corrosion resistance, while resins containing these functional groups are There was a problem of being easily attacked by chemicals and inferior in chemical resistance.
First, the inventors focused on the point that the urethane group and urea group produced during the reaction of the isocyanate component are most easily attacked by chemicals, and the fragrance preferentially has excellent chemical resistance in the vicinity of the urethane group and urea group. In order to arrange the aromatic ring structure, it has been devised to use an isocyanate compound containing an aromatic ring structure as the isocyanate component.
Next, the polyol component is devised to contain a polyester polyol component having an aromatic ring structure that is excellent in processability and chemical resistance, and by combining these, it is excellent in all of processability, corrosion resistance, and chemical resistance. Succeeded in finding a polyurethane resin.
The polyurethane resin used in the present invention includes (1) a structural unit derived from a polyester polyol component having an aromatic ring structure, (2) a structural unit derived from an isocyanate component, and a structural unit derived from the isocyanate component. It is an essential requirement that all of these contain an aromatic ring structure. The contribution to chemical resistance is greater in (2) than in (1), but none of these alone can provide satisfactory chemical resistance. The present invention achieves excellent chemical resistance due to the synergistic effect of the above (1) and (2). Specifically, as described above, the urethane group or urea group that is easily affected by chemicals. In the vicinity, an aromatic ring structure that is excellent in chemical resistance and can suppress the penetration of chemicals due to the steric hindrance effect is preferentially arranged, and the soft segment formed from the components derived from the polyol component has an appropriate cohesive force. The chemical resistance is maximized by arranging an ester group having an aromatic ring structure with excellent chemical resistance.
The present invention has been completed on the basis of these new findings. In particular, even in the case of a colored coating film that contains a color pigment and it is difficult to ensure the cohesive strength of the coating film, the above-described various methods are used without depending on the crosslinking effect of the curing agent. The knowledge that performance can be secured was obtained.

Hereinafter, a preferred embodiment of the present invention made based on the above-described knowledge will be described in detail.

A chromate-free colored painted metal plate according to an embodiment of the present invention has a film-forming component containing a polyurethane resin (A1) containing a urea group, a urethane group and a carboxyl group, a color pigment (B), and an average particle size of 5 to A structure derived from a polyester polyol component (a) having a colored coating film (α) containing spherical silica particles (C) of 50 nm on at least one surface of a metal plate and the polyurethane resin (A1) having an aromatic ring structure. It contains a unit and a structural unit derived from an isocyanate component (b) having an aromatic ring structure, and all the structural units derived from the isocyanate component (b) contain an aromatic ring structure.

More specifically, the chromate-free colored painted metal plate according to this embodiment contains a urea polyol, a urethane group, and a carboxyl group as a film-forming component of the colored coating film, and further has an aromatic ring structure. It contains a structural unit derived from component (a) and a structural unit derived from isocyanate component (b) having an aromatic ring structure, and all of the structural units derived from isocyanate component (b) contain an aromatic ring structure. A color pigment (B) that contains the polyurethane resin (A1) as an essential component, and further imparts design properties to the coated metal plate by coloring the coating film, and an average that contributes to improving the corrosion resistance and scratch resistance of the coated metal plate A colored coating film (α) containing spherical silica particles (C) having a particle diameter of 5 to 50 nm is formed on at least one surface of a metal plate as a substrate. Since the urea group and the urethane group contained in the polyurethane resin (A1) have high cohesive energy, a crosslinking curing reaction with a curing agent is not necessarily required. Ductility as well as homogeneous film formation can be achieved. The carboxyl group contained in the polyurethane resin (A1) has an effect of improving the adhesion with a metal plate (base treatment layer when there is a base treatment) as a base material. The polyurethane resin (A1) contains a structural unit derived from a polyester polyol component (a) having an aromatic ring structure and a structural unit derived from an isocyanate component (b) having an aromatic ring structure, and the isocyanate component By including an aromatic ring structure in all the structural units derived from (b), extremely excellent processability, corrosion resistance, chemical resistance, particularly chemical resistance can be ensured as described above. By these synergistic effects, various performances such as extremely excellent design properties, moisture resistance, corrosion resistance, workability, scratch resistance, chemical resistance and the like can be secured.

The chromate-free colored coated metal plate according to this embodiment is provided with a non-chrome coating that does not contain hexavalent chromium, which is highly environmentally friendly, and this non-chromium coating is an organic solvent system in which dedicated coating equipment is indispensable. It can be produced by forming with an aqueous coloring composition instead of a coloring composition. By making the coloring composition aqueous, the polyurethane resin (A1) used as a film-forming component can also be designed in water. Unlike polyurethane resins used in conventional organic solvent systems, water-based polyurethane resins can be designed with a very high molecular weight and do not necessarily require a crosslinking and curing reaction with a curing agent. However, it also has the advantage that sufficient coating strength and ductility, and uniform film formation can be achieved. Further, the carboxyl group contained in the structure of the polyurethane resin is a hydrophilic functional group important for making the polyurethane resin aqueous, and also for ensuring the stability of the polyurethane resin in the aqueous coloring composition. It is an essential functional group. Thus, according to the present invention, it is possible to provide an inexpensive high-design chromate-free colored coated metal plate having both moisture resistance, corrosion resistance, workability, scratch resistance, and chemical resistance.

The colored coating film (α) formed on the metal plate contains a coating film component (the polyurethane resin (A1), the colored pigment (B), and the silica particles (C)) in an aqueous solvent. Preferably, the aqueous coloring composition is applied on a metal plate and dried by heating. Here, the aqueous solvent means that water is a solvent that is a main component of the solvent. The amount of water in the solvent is preferably 50% by mass or more. Solvents other than water may be organic solvents, but those containing organic solvents as defined in the Occupational Safety and Health Act organic solvent poisoning prevention regulations (the weight of organic solvents listed in Schedule 6-2 of the Industrial Safety and Health Act Enforcement Ordinance) It is more preferable that the content does not fall under 5). The use of water-based solvents eliminates the need for extra lines for painting to use organic solvent-based paints, which can greatly reduce manufacturing costs and reduce volatile organic compounds. There are also advantages in terms of environment, such as significantly reducing (VOC) emissions.

The thickness of the colored coating (α) is 2 to 10 μm. The thickness of the colored coating film (α) is more preferably 3 to 7 μm. If it is less than 2 μm, sufficient designability (concealment) and corrosion resistance may not be obtained. If it exceeds 10 μm, it is not only economically disadvantageous, but also when a colored coating film (α) is formed from an aqueous coloring composition, coating defects such as armpits may occur. The appearance required for the painted metal plate may not be obtained stably.

The thickness of the colored coating film (α) can be measured by observing the section of the coating film or using an electromagnetic film thickness meter. In addition, the mass of the coating film adhered per unit area may be calculated by dividing by the specific gravity of the coating film or the specific gravity after drying of the coating solution. The adhesion mass of the coating is the mass difference before and after coating, the mass difference before and after peeling the coating after coating, or the presence of an element whose content in the coating is known in advance by fluorescent X-ray analysis. What is necessary is just to select appropriately from the existing methods, such as measuring quantity. Specific gravity of the coating film or specific gravity after drying of the coating solution is measured by measuring the volume and mass of the isolated coating film, measuring the volume and mass after taking an appropriate amount of the coating solution in a container and drying, or coating film. What is necessary is just to select suitably from the existing method, such as calculating from the compounding quantity of a structural component, and the known specific gravity of each component.

Among the various measuring methods described above, it is preferable to use a cross-sectional observation of a coating film because it can easily and accurately measure coating films with different specific gravity and the like.

The method for observing the cross section of the colored coating film (α) is not particularly limited, but after embedding a coated metal plate perpendicularly to the coating thickness direction in a room temperature drying type epoxy resin and mechanically polishing the embedded surface, SEM Using a method of observation with a scanning electron microscope or a FIB (focused ion beam) device, an observation sample having a thickness of 50 to 100 nm is cut out from a coated metal plate so that a vertical section of the coating can be seen. A method of observing the cross section with a TEM (transmission electron microscope) can be suitably used.

The polyurethane resin (A1) contained as an essential component in the film-forming component of the colored coating film (α) is derived from the polyester polyol component (a) containing a urea group, a urethane group and a carboxyl group, and further having an aromatic ring structure. And a structural unit derived from an isocyanate component (b) having an aromatic ring structure, and all the structural units derived from the isocyanate component (b) contain an aromatic ring structure. For example, it is obtained by subjecting a polyol compound containing a polyester polyol component having an aromatic ring structure and an isocyanate compound having an aromatic ring structure to a urethanation reaction under the condition that the isocyanate group contained in the isocyanate compound is excessive. Products obtained by further reacting a urethane prepolymer with a polyamine compound and extending the chain It can be used. By such a production method, a urethane group is generated by the reaction of the hydroxyl group contained in the polyol compound and the isocyanate group contained in the isocyanate compound, and the urea group is produced by the reaction of the amino group contained in the polyamine compound and the isocyanate group contained in the isocyanate compound. Can be produced, and an ultrahigh molecular weight polyurethane resin containing a urea group and a urethane group can be produced.

The polyol compound refers to a compound containing two or more hydroxy groups per molecule. In the present invention, a polyester polyol component (a) having an aromatic ring structure (hereinafter also referred to as an aromatic polyester polyol (a)) is used. A polyol compound contained as an essential component is used.

The aromatic polyester polyol (a) includes a constituent unit derived from an aromatic polyvalent carboxylic acid and / or an aromatic polyhydric alcohol, and a raw material containing the aromatic polyvalent carboxylic acid and / or the aromatic polyhydric alcohol. The composition can be obtained by a condensation reaction by a known method.

The aromatic polyvalent carboxylic acids include aromatic divalent carboxylic acids or trivalent or higher aromatic carboxylic acids. Examples of the aromatic divalent carboxylic acids include terephthalic acid, isophthalic acid, orthophthalic acid, 1, 4-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, naphthalic acid (naphthalene-1,8-dicarboxylic acid), biphenyldicarboxylic acid, 1,2-bis (phenoxy) ethane-P , P′-dicarboxylic acids and the like, or their anhydride or ester-forming derivatives; aromatic hydroxycarboxylic acids such as p-hydroxybenzoic acid or their ester-forming derivatives; and 5-sulfoisophthalate Aromatic dicarboxylic acids containing sulfonic acid groups such as acids or their ester-forming properties Conductor and the like. These aromatic divalent carboxylic acids may be substituted with various substituents.

Examples of the trivalent or higher aromatic carboxylic acids include aromatic polyvalent carboxylic acids such as trimellitic acid and pyromellitic acid, or acid anhydrides or ester-forming derivatives thereof. These trivalent or higher aromatic carboxylic acids may be substituted with various substituents. Aromatic polyvalent carboxylic acids may be used alone or in combination of two or more.

The aromatic polyester polyol (a) may contain a structural unit derived from a polyvalent carboxylic acid other than the aromatic polyvalent carboxylic acid. Examples of polyvalent carboxylic acids other than aromatic polycarboxylic acids include aliphatic dicarboxylic acids such as succinic acid, adipic acid, speric acid, azelaic acid, sebacic acid, dimer acid, maleic acid and fumaric acid, or acids thereof. Anhydrides or ester-forming derivatives; and alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid or acid anhydrides or ester-forming derivatives thereof. These polyvalent carboxylic acids may be substituted with various substituents. As the polyvalent carboxylic acids other than the aromatic polyvalent carboxylic acids, only one kind may be used alone, or two or more kinds may be used in combination.

Examples of the aromatic polyhydric alcohols include bisphenol A, bisphenol S, hydroxin, bishydroxyethoxybenzene, and alkylene oxide adducts thereof. These aromatic polyhydric alcohols may be substituted products substituted with various substituents. Aromatic polyhydric alcohols may be used alone or in combination of two or more.

The aromatic polyester polyol (a) may contain a structural unit derived from polyhydric alcohols other than aromatic polyhydric alcohols. Examples of polyhydric alcohols other than aromatic polyhydric alcohols include ethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, and 1,5-pentanediol. 1,6-hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, polyethylene glycol, 3-methyl-1,5-pentanediol, 2-butyl-2- Aliphatic diols such as ethyl-1,3-propanediol; alicyclic diols such as 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, hydrogenated bisphenol A; glycerin, trimethylolpropane, pentaerythris Aliphatic or alicyclic, such as tall polyhydric alcohols; and, .epsilon.-caprolactone, aliphatic polyhydric alcohol obtained by a cyclic ester such as γ- Parerorakuton by ring-opening polymerization. These polyhydric alcohols may be substituted products substituted with various substituents. Polyhydric alcohols other than aromatic polyhydric alcohols may be used alone or in combination of two or more.

Aromatic polyester polyol (a), which can constitute aromatic polyhydric carboxylic acids, polyhydric carboxylic acids other than aromatic polyhydric carboxylic acids, aromatic polyhydric alcohols, polyhydric alcohols other than aromatic polyhydric alcohols The content ratio of the structural unit derived from a class may be adjusted so that the aromatic ring structure contained in the aromatic polyester polyol (a) is contained in an amount of 5 to 25% by mass in the polyurethane resin (A1). From the viewpoint of workability and chemical resistance, it is preferably 15 to 20% by mass. If it is less than 5% by mass, chemical resistance may be lowered, and if it is more than 25% by mass, workability may be lowered.

The content of the aromatic ring structure contained in the aromatic polyester polyol (a) in the polyurethane resin (A1) is calculated by the following formula [1].
Content of aromatic ring structure (% by mass) = 100 × [{number of moles of aromatic polyvalent carboxylic acids constituting aromatic polyester polyol (a) (mol) × aromatic in one molecule of aromatic polyvalent carboxylic acids Number of aromatic ring structures (number) × molecular weight of aromatic ring portion (g / mol)} + {mol number of aromatic polyhydric alcohols constituting aromatic polyester polyol (a) × aromatic polyvalent Number of aromatic ring structures in one molecule of alcohols × molecular weight of aromatic ring portion (g / mol)}] / {solid content mass (g) of polyurethane resin (A1)} [1]

Here, the “molecular weight of the aromatic ring portion” is not the molecular weight as the aromatic ring residue of the aromatic polyester polyol (a) but the molecular weight when this residue exists as a free aromatic ring compound. In addition, the substituent (excluding the aromatic ring) possessed by the aromatic ring structure is not included in the molecular weight. For example, when “alkyl substituted terephthalic acid” is used as the aromatic polyvalent carboxylic acid, the “molecular weight of the aromatic ring portion” is a molecular weight of 78.11 of the benzene ring. When using two or more aromatic polyvalent carboxylic acids, in the above formula [1], {number of moles of aromatic polyvalent carboxylic acids constituting the aromatic polyester polyol (a) (mol) × aromatic polyvalent carboxylic acids The number of aromatic ring structures in one molecule (number) × molecular weight of aromatic ring portion (g / mol)} is the sum of those calculated for each aromatic polycarboxylic acid. The same applies when two or more aromatic polyhydric alcohols are used.

The polyol component may contain a polyol compound other than the aromatic polyester polyol (a). Examples of such polyol compounds include polyester polyols that do not contain an aromatic ring structure such as aliphatic and alicyclic polyester polyols, and macropolyols such as polycarbonate polyol, polyether polyol, polyester amide polyol, acrylic polyol, and polyurethane polyol; ethylene glycol , Propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol, tetra Ethylene glycol, dipropylene glycol, tripropylene glycol, polyethylene glycol, 3-methyl-1,5-pentanediol, 2-butyl-2-ethyl Aliphatic diols such as 1,3-propanediol; Alicyclic diols such as 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol and hydrogenated bisphenol A; Fats such as glycerin, trimethylolpropane and pentaerythritol And aliphatic polyhydric alcohols obtained by ring-opening polymerization of cyclic esters such as ε-caprolactone and γ-parerolactone, or mixtures thereof can be used. Aliphatic and alicyclic polyester polyols can be prepared using polyhydric carboxylic acids other than the above-mentioned aromatic polyhydric carboxylic acids and polyhydric alcohols other than aromatic polyhydric alcohols.

As the isocyanate compound, an isocyanate compound having an aromatic ring structure (hereinafter also referred to as aromatic isocyanate (b)) is used. Specific examples of the aromatic isocyanate (b) include, for example, 1,3- or 1,4-α, α, α ′, α′-tetramethylxylylene diisocyanate, m-xylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diene Examples thereof include isocyanate, 2,6-tolylene diisocyanate, 4,4′-toluidine diisocyanate, dianisidine diisocyanate, and 4,4′-diphenyl ether diisocyanate. These may be used alone or in combination of two or more. From the viewpoint of chemical resistance, it is preferable to use tolylene diisocyanate.

It is possible to adjust the aromatic ring structure contained in the isocyanate component (b) having an aromatic ring structure so that it is contained in the polyurethane resin (A1) in an amount of 5 to 20% by mass. From the viewpoint, it is preferably 10 to 15% by mass. If it is less than 5% by mass, the chemical resistance may decrease, and if it exceeds 20% by mass, the coating film may be cured and the processability may decrease.

The content of the aromatic ring structure contained in the aromatic isocyanate (b) in the polyurethane resin (A1) is calculated by the following formula [2].
Content of aromatic ring structure (% by mass) = 100 × {number of moles of aromatic isocyanate (b) (mol) × aromatic isocyanate (b) number of aromatic ring structures in one molecule × aromatic Molecular weight of ring part (g / mol)} / {solid content mass (g) of polyurethane resin (A1)} [2]

Here, the “molecular weight of the aromatic ring portion” is not the molecular weight of the aromatic isocyanate (b) as an aromatic ring residue, but the molecular weight when this residue exists as a free aromatic ring compound. In addition, substituents (excluding aromatic rings) possessed by the aromatic ring structure are not included in the molecular weight. For example, the “molecular weight of the aromatic ring moiety” when tolylene diisocyanate is used as the aromatic isocyanate (b) is a molecular weight of 78.11 of the benzene ring. When two or more aromatic isocyanates (b) are used, {number of moles of aromatic isocyanate (b) (mol) x number of aromatic ring structures in one molecule of aromatic isocyanate (b) in the above formula [2] (Number) × molecular weight of aromatic ring portion (g / mol)} is the sum of those calculated for each aromatic isocyanate (b). The same applies when two or more aromatic isocyanates (b) are used.

Conventionally known compounds can be used as the polyamine compound. Examples of ipolyamine compounds include metal salts of N- (2-sulfoethyl) ethylenediamine, diaminosulfonates such as 2- (β-aminoalkyl-aminopropionamide) -alkanesulfonate, and aliphatic primary diamines such as ethylenediamine. And polyamine compounds having an anionic group such as adducts of α-olefinic carboxylic acids such as (meth) acrylic acid; hydrazine and polyamines having no anionic group such as hydrazine derivatives such as adipic dihydrazide, , 2-diaminoethane, 1,2- or 1,3-diaminopropane, 1,2-, 1,3-, or 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, Piperazine, N, N′-bis- (2-aminoethyl) piperazine, 1-amino-3- Aminomethyl-3,5,5-trimethyl-cyclohexane (isophoronediamine), bis- (4-aminocyclohexyl) methane, bis- (4-amino-3-butylcyclohexyl) methane, 1,2-, 1,3- Or diamines such as 1,4-diaminocyclohexane and 1,3-diaminopropane; polyamines such as diethylenetriamine and triethylenetetramine.

It is an essential requirement that the polyurethane resin (A1) contains a carboxyl group. The method for introducing the carboxyl group into the polyurethane resin (A1) is not particularly limited. For example, 2,2-dimethylolpropionic acid, 2,2-dimethylolbutyric acid, 2,2-dimethylolvaleric acid, Carboxyl group-containing compounds such as oxymaleic acid, 2,6-dioxybenzoic acid, 3,4-diaminobenzoic acid or derivatives thereof, or polyester polyols obtained by copolymerizing these, maleic anhydride, phthalic anhydride, A carboxyl group-containing compound obtained by reacting a compound having an anhydride group with a compound having an active hydrogen group, such as succinic anhydride, trimellitic anhydride, pyromellitic anhydride, or a derivative thereof, or obtained by copolymerization thereof One or more polyester polyols are used together during the production of the urethane prepolymer. And a method such engaged.

The carboxyl group contained in the polyurethane resin (A1) has an effect of improving the adhesion with a metal plate (base treatment layer when there is a base treatment) as a base material, and the polyurethane resin (A1). ) Is aqueous, it greatly contributes to dispersibility and stability in the aqueous medium. In order to improve dispersibility and stability in an aqueous medium, the carboxyl group may be neutralized with a neutralizing agent. The neutralizing agent is not particularly limited, but examples thereof include tertiary amines such as ammonia, triethylamine, triethanolamine, triisopropanolamine, trimethylamine, dimethylethanolamine, sodium hydroxide, potassium hydroxide, calcium hydroxide, and the like. Examples include basic substances such as alkali metal and alkaline earth metal hydroxides, but the film-forming property of the colored coating film (α), and the aqueous coloring composition for forming the colored coating film (α). From the viewpoint of stability, it is preferable to use an alkanolamine having a boiling point of 150 ° C. or lower such as triethanolamine or dimethylethanolamine. These neutralizing agents may be used alone or in a mixture of two or more. As a method for adding the neutralizing agent, the neutralizing agent may be added directly to the urethane prepolymer, or may be added to the aqueous solvent when dissolved or dispersed in the aqueous solvent. The addition amount of the neutralizing agent is 0.1 to 2.0 equivalents, more preferably 0.3 to 1.3 equivalents with respect to the carboxyl group.

The content of the carboxyl group contained in the polyurethane resin (A1) is not particularly limited, but is preferably such an amount as to exhibit an acid value in the range of 0.1 to 50 mgKOH / g. If it is less than 0.1 mgKOH / g, the effect of improving the adhesion between the colored coating film (α) and the metal plate of the base material (the base treatment layer when there is a base treatment) may not be obtained. When the polyurethane resin (A1) is aqueous, the dispersibility and stability in the aqueous medium may be insufficient. If it exceeds 50 mgKOH / g, the corrosion resistance and chemical resistance of the colored coated metal plate may be lowered. Considering the balance of performance, it is more preferably in the range of 0.5 to 25 mg KOH / g.

When the polyurethane resin (A1) is aqueous, “aqueous” means “water-soluble or water-dispersible”. Water-soluble or water-dispersible means that when an attempt is made to dissolve a polymer in water at a concentration of 1% by weight, efforts were made to homogenize by heating or stirring, and then left at 25 ° C. for 24 hours. Sometimes the solution is homogeneous without causing precipitation of the polymer and without phase separation. The definition of “being aqueous” also applies to resins (details will be described later) other than the polyurethane resin (A1) used in the present invention.

In addition to the polyurethane resin (A1), the colored coating film (α) further contains a polyester resin (A2) containing a sulfonic acid group in addition to the polyurethane resin (A1) to improve workability and chemical resistance. Is preferable. As the polyester resin (A2), for example, a polyester raw material composed of a polycarboxylic acid component and a polyol component can be obtained by condensation polymerization. Moreover, when the coloring composition for forming the said colored coating film ((alpha)) is aqueous, what melt | dissolved or disperse | distributed the polyester resin obtained in that way in water, and can make it water-based can be used.

Examples of the polycarboxylic acid component include phthalic acid, phthalic anhydride, tetrahydrophthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic acid, hexahydrophthalic anhydride, methyltetraphthalic acid, methyltetrahydrophthalic anhydride, hymic anhydride, Trimellitic acid, trimellitic anhydride, pyromellitic acid, pyromellitic anhydride, isophthalic acid, terephthalic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, adipic acid, azelaic acid, sebacic acid, succinic acid, anhydrous Mention may be made of succinic acid, lactic acid, dodecenyl succinic acid, dodecenyl succinic anhydride, cyclohexane-1,4-dicarboxylic acid, and anhydrous endo acid. As the polycarboxylic acid component, one type may be used, or a plurality of types may be used.

Examples of the polyol component include ethylene glycol, diethylene glycol, 1,3-propanediol, 1,2-propanediol, triethylene glycol, 2-methyl-1,3-propanediol, and 2,2-dimethyl-1,3. -Propanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,4-butanediol, 2-methyl-1,4-butanediol, 2-methyl-3-methyl-1,4-butane Diol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,2-cyclohexanedimethanol , Hydrogenated bisphenol-A, dimer diol, trimethylol ethane, trimethylo Mention may be made of propane, glycerin, pentaerythritol and the like. As the polyol component, one kind may be used, or a plurality kinds may be used.

The polyester resin (A2) contains a sulfonic acid group in the resin structure. The sulfonic acid group enhances the adhesion between the colored coating film (α) and the metal plate of the base material (in the case where there is a base treatment, the base treatment layer (β)) and is a coating solution for a coloring pigment having a hydrophobic surface. It has the effect of increasing dispersibility. A method for introducing a sulfonic acid group into the polyester resin is not particularly limited, and examples thereof include 5-sulfoisophthalic acid, 4-sulfonaphthalene-2,7-dicarboxylic acid, and 5- (4-sulfophenoxy) isophthalic acid. And dicarboxylic acids such as 2-sulfo-1,4-butanediol and 2,5-dimethyl-3-sulfo-2,5-hexyldiol.

The sulfonic acid group refers to a functional group represented by —SO ₃ H, which may be neutralized with alkali metals, amines containing ammonia, or the like. In the case of neutralization, the already neutralized sulfonic acid group may be incorporated into the resin, or may be neutralized after the sulfonic acid group is incorporated into the resin. In particular, a sulfonic acid metal base neutralized with an alkali metal such as Li, Na, or K enhances the adhesion between the colored coating film and the metal plate of the base material, or is applied to a coating liquid for a coloring pigment having a hydrophobic surface. Is more preferable in terms of enhancing the dispersibility of the sulfonic acid, and sodium sulfonate is particularly preferable.

The amount of the dicarboxylic acid or glycol containing a sulfonic acid group used for introducing a sulfonic acid group into the polyester resin (A2) is 0.1 to 10 mol based on the total polycarboxylic acid component or the total polyol component. % Is preferred. If it is less than 0.1 mol%, the effect of improving the adhesion between the colored coating film and the metal plate of the base material may not be obtained, and when an aqueous solvent is used, the polyester resin (A2) The solubility or dispersibility of water in water may be lowered, the dispersibility of the colored pigment may be lowered, and the design of the formed colored coating film may be lowered. If it exceeds 10 mol%, the corrosion resistance of the colored coated metal plate may be lowered. Considering the balance of performance, it is more preferably in the range of 0.5 to 7 mol%.

It is preferable that a bisphenol group is contained in the resin structure of the polyester resin (A2). Since the bisphenol group has high cohesive energy and excellent water resistance, it is preferable that the polyester resin (A2) contains a bisphenol group in order to improve the scratch resistance and corrosion resistance of the colored coated metal plate. The method for introducing a bisphenol group into the polyester resin (A2) is not particularly limited. For example, bisphenol A ethylene oxide adduct, bisphenol A propylene oxide adduct, bisphenol F ethylene oxide adduct, bisphenol F The method of using glycols, such as a propylene oxide adduct, as a polyester raw material is mentioned.

The amount of glycol containing a bisphenol group as described above is preferably 1 to 40 mol% with respect to the total polyol component. If it is less than 1 mol%, the effect of improving scratch resistance and corrosion resistance of the colored coated metal sheet may not be obtained. If it exceeds 40 mol%, the workability of the colored coated metal plate may be lowered. Considering the balance of performance, it is more preferably in the range of 5 to 30 mol%.

As for the content of the polyester resin (A2), the mass ratio of the polyurethane resin (A1) / the polyester resin (A2) is preferably 10/90 to 90/10, and preferably 25/75 to 75/25. It is more preferable. If it is less than 10/90, the corrosion resistance and scratch resistance may decrease, and if it exceeds 90/10, the workability and chemical resistance may not be improved.

It is preferable that the colored coating film (α) further contains an acrylic resin (A3) in addition to the polyurethane resin (A1) as a coating film forming component. By containing the acrylic resin, the adhesion with the metal plate (base treatment layer when there is a base treatment) is improved, and the scratch resistance is improved. In addition, when the colored pigment (B) is a pigment having a hydrophobic surface such as carbon black (B1) to be described later, and the colored composition for forming the colored coating film (α) is aqueous, the pigment It is also preferable to contain the acrylic resin (A3) in order to uniformly disperse the resin in an aqueous solvent and to impart excellent design properties to the formed colored coating film (α).

The acrylic resin (A3) is not particularly limited, and examples thereof include ethylene such as methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. An unsaturated carboxylic acid alkyl ester monomer alone or a copolymer of two or more thereof, and further, an ethylenically unsaturated carboxylic acid monomer such as acrylic acid, methacrylic acid, maleic acid, itaconic acid; Ethylenically unsaturated carboxylic acid alkyl ester monomers such as methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate; ethyl maleate, malee Monoester monomer of ethylenically unsaturated dicarboxylic acid such as butyl acrylate, ethyl itaconate, butyl itaconate Reaction of 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate and ε-caprolactone Hydroxyl group-containing ethylenically unsaturated carboxylic acid alkyl ester monomers such as amino acids; ethylenically unsaturated carboxylic acids such as aminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, and butylaminoethyl (meth) acrylate Acid aminoalkyl ester monomers; ethylenically unsaturated carboxylic acid aminoalkylamide monomers such as aminoethyl (meth) acrylamide, dimethylaminomethyl (meth) acrylamide, methylaminopropyl (meth) acrylamide; acrylamide, methacrylamide, N-methylol Other amide group-containing ethylenically unsaturated carboxylic acid monomers such as acrylamide, methoxybutyl acrylamide and diacetone acrylamide; unsaturated fatty acid glycidyl ester monomers such as glycidyl acrylate and glycidyl methacrylate; (meth) acrylonitrile, α -Vinyl cyanide monomers such as chloroacrylonitrile; saturated aliphatic carboxylic acid vinyl ester monomers such as vinyl acetate and vinyl propionate; styrene monomers such as styrene, α-methylstyrene and vinyltoluene. One or a copolymer of two or more types can be used. The method for polymerizing these monomers is not particularly limited, and examples thereof include those obtained by radical polymerization of these monomers in an aqueous solution using a polymerization initiator. The polymerization initiator is not particularly limited, and for example, persulfates such as potassium persulfate and ammonium persulfate, and azo compounds such as azobiscyanovaleric acid and azobisisobutyronitrile can be used. The monomer used to synthesize the acrylic resin may be used alone or in combination of two or more components.

Content of the acrylic resin (A3) is the polyurethane resin (A1) (when the polyester resin (A2) is included in the film-forming component of the colored coating film (α), the polyurethane resin (A1) and the polyester The total amount of the resin (A2)) is preferably 0.5 to 20% by mass, more preferably 1 to 15% by mass, and particularly preferably 2 to 10% by mass with respect to 100% by mass. . If it is less than 0.5% by mass, the effect of improving the design properties (colorability, concealment) of the formed colored coating film may not be obtained. If it exceeds 20% by mass, Workability may be reduced.

The polyurethane resin (A1) (when the polyester resin (A2) or the acrylic resin (A3) is included in the film-forming component of the colored coating film (α)) is also a scratch resistance of the colored coated metal plate. In order to improve adhesion and corrosion resistance, a resin cured with a curing agent (D) is preferable. The curing agent (D) is not particularly limited as long as it cures the resin (A) as described above, and examples thereof include a melamine resin and a polyisocyanate compound. The melamine resin is a resin obtained by etherifying a part or all of the methylol group of a product obtained by condensing melamine and formaldehyde with a lower alcohol such as methanol, ethanol, or butanol. It does not specifically limit as a polyisocyanate compound, For example, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, tolylene diisocyanate etc. can be mentioned. A blocked product of a polyisocyanate compound may be used. For example, a blocked product of hexamethylene diisocyanate, a blocked product of isophorone diisocyanate, a blocked product of xylylene diisocyanate, or a blocked product of tolylene diisocyanate, which is a blocked product of the polyisocyanate compound. Etc. A hardening | curing agent (D) may be used by 1 type, and may use 2 or more types together.

The amount of the curing agent (D) used is the polyurethane resin (A1) (if the polyester resin (A2) or the acrylic resin (A3) is included in the film-forming component of the colored coating film (α), these resins are used. The total amount is preferably 5 to 35% by mass with respect to 100% by mass. If it is less than 5% by mass, the bake-hardening of the coating film is insufficient, and the corrosion resistance and scratch resistance of the colored coated metal plate may be lowered. If it exceeds 35% by mass, the bake-hardening of the coating film is excessive. Thus, the corrosion resistance and workability of the colored coated metal plate may be reduced.

From the viewpoint of scratch resistance, the curing agent (D) preferably contains a melamine resin. The content of the melamine resin is preferably 30 to 100% by mass in the curing agent (D). If it is less than 30% by mass, the effect of improving scratch resistance may not be obtained.

The colored pigment (B) contained in the colored coating (α) of the chromate-free colored coated metal sheet according to the present embodiment is a component that imparts a sufficient color and concealing property to the coating. Examples of typical colored pigments that can be used in the present invention include colored inorganic pigments such as carbon black, titanium dioxide, graphite, iron oxide, lead oxide, coal dust, talc, cadmium yellow, cadmium red, and chrome yellow; phthalocyanine Blue, phthalocyanine green, quinacridone, perylene, anthrapyrimidine, carbazole violet, anthrapyridine, azo orange, flavanthrone yellow, isoindoline yellow, azo yellow, indanthrone blue, dibromoanthanthrone red, perylene red, azo red, anthraquinone red, etc. Colored organic pigments: aluminum powder, alumina powder, bronze powder, copper powder, tin powder, zinc powder, iron phosphide powder, metal coated mica powder, titanium dioxide coated mica powder, And the like bright materials, such as titanium oxide-coated glass powder.

When carbon black is used as the color pigment (B), there is no particular limitation. For example, known carbon black such as furnace black, ketjen black, acetylene black, channel black and the like can be used. Further, carbon black subjected to known ozone treatment, plasma treatment, or liquid phase oxidation treatment can also be used. Carbon black having a primary particle size of 10 to 120 nm is preferably used in consideration of dispersibility in an aqueous coloring composition, paintability, and coating film quality. In consideration of design properties (colorability, hiding properties) and corrosion resistance of a thin film, for example, a thin film of about 10 μm or less, it is preferable to use fine carbon black having a primary particle size of 10 to 50 nm. On the other hand, since carbon black aggregates in the process of dispersion in a dispersion medium (water), it is generally difficult to disperse with the primary particle diameter. That is, carbon black actually exists in the form of secondary particles having a particle size larger than the primary particle size in the aqueous coloring composition, and also exists in the same form in the coating film formed from the composition. . In order to ensure designability (colorability, concealment) and corrosion resistance in a thin film, the particle size of carbon black dispersed in the coating film is important, and the average particle size of the secondary particles is 20 to 300 nm. Preferably there is. The average particle size of the carbon black secondary particles is more preferably 30 to 250 nm, still more preferably 50 to 200 nm.

Carbon black is a color pigment with excellent concealment. Therefore, the use of carbon black as the color pigment (B) is effective in reducing the thickness of the formed colored coating film (α).

In order to ensure the design properties (colorability and concealment) of the coating film with carbon black, it is important to ensure a certain amount or more of the carbon black contained in the colored coating film (α). The absolute amount of carbon black can be represented by the product (X × Y) of the content (X mass%) of carbon black contained in the coating film and the coating film thickness (Y μm). When X × Y is less than 20, design properties (colorability and concealment) may be deteriorated. When X is more than 15, the film-forming property of the coating film may decrease, and the corrosion resistance and workability may decrease. That is, it is preferable that the carbon black and the coating film satisfy the relationship of X × Y ≧ 20 and X ≦ 15. More preferably, X × Y ≧ 25 and X ≦ 15, and even more preferably X × Y ≧ 30 and X ≦ 12.

When a colored pigment other than carbon black is used, the colored pigment particles in the coating film have the above-mentioned 20 to 300 nm of carbon black secondary particles regardless of whether they are primary particles or secondary particles. It is preferable to have an average particle size. A more preferable average particle diameter is 30 to 250 nm, and still more preferably 50 to 200 nm.

The spherical silica particles (C) having an average particle size of 5 to 50 nm contained in the colored coating film (α) of the chromate-free colored coated metal sheet according to the present embodiment have sufficient corrosion resistance and scratch resistance to the colored coating film (α). It is an effective ingredient for imparting sex. The “spherical shape” in the present invention refers to not only a true sphere but also a shape approximate to a sphere, and includes an ellipsoid. However, in the case of an ellipsoid, the ratio of the minor axis to the major axis is preferably 0.7 or more from the viewpoint of workability, corrosion resistance, and scratch resistance, and more preferably 0.8 or more. Although it does not restrict | limit especially as said spherical silica particle (C), It is preferable to use silica microparticles, such as colloidal silica. Examples of commercially available products include Snowtex O, Snowtex N, Snowtex C (Nissan Chemical Industry Co., Ltd.), Adelite AT-20N, AT-20A (Asahi Denka Kogyo Co., Ltd.) and the like. A more preferable average particle diameter of the spherical silica particles (C) is 8 to 30 nm, and further preferably 10 to 20 nm.

The spherical silica particles (C) are preferably present in 3 to 30% by mass in the colored coating film (α). If the content of the spherical silica particles (C) in the coating film is less than 3% by mass, the corrosion resistance and scratch resistance of the coating film may be insufficient, and if it exceeds 30% by mass, the moisture resistance of the coating film , Corrosion resistance, and workability may deteriorate. A more preferable content of the spherical silica particles (C) in the coating film is 5 to 20% by mass, and further preferably 7 to 15% by mass.

The colored coating (α) of the chromate-free colored coated metal plate according to the present embodiment further contains a lubricant (E) in addition to the film-forming component, the colored pigment (B), and the silica particles (C). May be. By including the lubricant (E), the scratch resistance of the coating film (α) is improved. The lubricant (E) is not particularly limited, and a known lubricant can be used, but it is preferable to use at least one selected from a fluororesin system and a polyolefin resin system. Fluororesin lubricants include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), ethylene-tetrafluoroethylene copolymer (ETFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), and the like can be used. Of these, one type may be used alone, or two or more types may be used in combination.

The polyolefin resin-based lubricant is not particularly limited, and examples thereof include paraffin, microcrystalline, hydrocarbon waxes such as polyethylene, and derivatives thereof, but polyethylene resins are preferable. The derivative is not particularly limited, and examples thereof include carboxylated polyolefin and chlorinated polyolefin. Of these, one type may be used alone, or two or more types may be used in combination. When the polyethylene resin is used, it is preferable that it is dispersed in the colored coating film (α) with particles having an average particle diameter of 0.5 to 2 μm from the viewpoint of corrosion resistance and scratch resistance.

The content of the lubricant (E) is preferably 0.5 to 10% by mass in the colored coating film (α), more preferably 1 to 5% by mass. If it is less than 0.5% by mass, the scratch resistance may be lowered, and if it exceeds 10% by mass, the corrosion resistance and workability may be lowered.

The colored pigment (B) and the spherical silica particles (C) are present as particulate components in the colored coating (α) of the chromate-free colored coated metal plate of the present invention. If necessary, a lubricant (E) may be present in addition to them.

Generally, it is extremely difficult to specify the shape and size of particles contained in a thin coating film. However, the particulate component contained in the coating material used to form the coating film (solution or dispersion (coloring composition) containing the constituent components of the coating film) Exists in paint even after film formation, unless it undergoes physical or chemical changes (eg, binding or agglomeration of particles, significant dissolution in paint solvent, reaction with other components) It can be considered that it retains the shape and size as it was. The colored pigment (B), the spherical silica particles (C), and the lubricant (E), which are particulate components used in the present invention, are significantly used as the solvent for the colored composition used for forming the coating film of the present invention. It is selected so that it does not dissolve and does not react with the solvent or other coating components. Further, for the purpose of enhancing the retention of the existing form in the colored composition of these particulate components, if necessary, it was dispersed in an aqueous solvent with a dispersant such as a known surfactant or water-soluble resin in advance. A thing can also be used as a raw material of a coloring composition. Therefore, the particle diameters of these particulate components contained in the coating film defined in the present invention can be expressed by their particle diameters in the colored composition used for forming the coating film.

Specifically, the diameter of relatively fine particles such as the colored pigment (B) and the spherical silica particles (C) can be measured by a dynamic light scattering method (nanotrack method). According to the dynamic scattering method, the diameter of fine particles in a dispersion medium having a known temperature, viscosity, and refractive index can be easily obtained. The particulate component used in the present invention is selected so that it does not significantly dissolve in the solvent of the paint and does not react with the solvent or other coating components, so measure the particle size in a predetermined dispersion medium, It can be employed as the particle size of the particulate component in the colored composition. In the dynamic light scattering method, laser light is irradiated to fine particles that are dispersed in a dispersion medium and moving in brown, the scattered light from the particles is observed, the autocorrelation function is obtained by the photon correlation method, and the cumulant method is used. Measure the particle size. As a particle size measuring apparatus by the dynamic light scattering method, for example, FPAR-1000 manufactured by Otsuka Electronics Co., Ltd. can be used. In the present invention, a dispersion sample containing the particles to be measured is measured at 25 ° C. to determine the cumulant average particle size, and the average value of five measurements in total is taken as the average particle size of the particles. The measurement of the average particle diameter by the dynamic light scattering method is described in, for example, Journal of Chemical Physics, Vol. 57, No. 11 (December, 1972), page 4814.

On the other hand, as the diameter of relatively large particles such as the lubricant (E), the particle diameter at an integrated value of 50% in the particle size distribution measured by the laser diffraction / scattering method (microtrack method) can be adopted. . The laser diffraction / scattering method is widely used to measure particle diameters from the submicron range to several millimeters by utilizing the fact that the amount of scattered light and the pattern scattered by the particle diameter vary depending on the particle size. It has been. Also in this case, the particulate component used in the present invention is selected so that it does not significantly dissolve in the solvent of the colored composition and does not react with the solvent or other coating film constituents. It can employ | adopt as a particle diameter of the particulate component in a thing. For measurement by the laser diffraction / scattering method, for example, a microtrack particle size analyzer manufactured by Nikkiso Co., Ltd. can be used. In the present invention, the average value of five measurements in total is taken as the average particle diameter of the particles.

In addition, the particulate component in the colored coating film (α) (the color pigment (B) as an essential component, the spherical silica particles (C), and the optional component, the lubricant (E)) is a colored coating film ( It is also possible to observe α) from a cross section and directly measure its shape and particle diameter. When the particles are not spherical, the major and minor diameters of the particles are measured, and the average value can be adopted as the particle diameter. The method for observing the cross section of the colored coating film (α) is not particularly limited, but after embedding the coated metal plate perpendicularly to the thickness direction of the coating film in the room temperature drying type epoxy resin and mechanically polishing the embedded surface, SEM ( Using a scanning electron microscope) or a FIB (focused ion beam) device, a sample for observation having a thickness of 50 nm to 100 nm is cut out from the coated metal plate so that the vertical section of the coating can be seen. A method of observing the cross section with a TEM (transmission electron microscope) can be suitably used.

The colored coating film (α) of the chromate-free colored painted metal plate according to the present embodiment is a component of the polyurethane resin (A1), the colored pigment (B), and the spherical silica particles (C) as solvents. It can form by apply | coating the coloring composition comprised in at least one surface of a metal plate, and heat-drying. The coloring composition is preferably a composition in which the solvent is water, or a composition in which the main component of the solvent is water, that is, an “aqueous coloring composition” as defined above.

In addition to the polyurethane resin (A1), the color pigment (B), and the spherical silica particles (C), the components of the colored composition are the above-mentioned optional components (the polyester resin (A2), the acrylic resin ( A3) and the lubricant (E)). Further, when the film-forming resin of the colored coating film (α) (the polyurethane resin (A1) as an essential component and the polyester resin (A2) and the acrylic resin (A3) as optional components) are cured, coloring The composition contains the aforementioned curing agent (D).

The coloring composition is not limited to a specific method and can be obtained by any method. As an example, a preferable aqueous coloring composition will be described as an example. A method of adding a constituent of the colored coating film (α) to water as a dispersion medium, stirring with a disper, and dissolving or dispersing. In order to improve the solubility or dispersibility of each component, a known hydrophilic solvent, for example, alcohols such as ethanol, isopropyl alcohol, t-butyl alcohol and propylene glycol, ethylene glycol monobutyl ether, if necessary Cellosolves such as ethylene glycol monoethyl ether, esters such as ethyl acetate and butyl acetate, and ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone may be added.

The application method of the coloring composition is not particularly limited, and any known method can be used. For example, roll coating, curtain coating, spray coating, bar coating, dipping, electrostatic coating, and the like can be used.

The heat drying for forming the colored coating film (α) from the colored composition is not particularly limited and can be performed by any method. For example, the metal plate can be heated in advance before applying the coloring composition, the metal plate can be heated after application, or a combination thereof can be used for drying. There is no restriction | limiting in particular also in a heating method, A coloring composition can be dried and baked using hot air, induction heating, near infrared rays, a direct fire, etc. individually or in combination. The dry baking temperature is preferably 150 ° C. to 250 ° C. at the ultimate plate temperature, more preferably 160 ° C. to 230 ° C., and most preferably 180 ° C. to 220 ° C. If the ultimate plate temperature is less than 150 ° C., the bake hardening is insufficient, and the moisture resistance, corrosion resistance, scratch resistance, and chemical resistance of the coating film may be lowered. Excessive corrosion resistance and workability may decrease. The drying baking time (heating time) is preferably 1 to 60 seconds, and more preferably 3 to 20 seconds. If it is less than 1 second, the bake hardening is insufficient, and the moisture resistance, corrosion resistance, scratch resistance, and chemical resistance of the coating film may be lowered. If it exceeds 60 seconds, the productivity is lowered.

The chromate-free colored coated metal plate according to this embodiment can also be provided with a base treatment layer (β) below the colored coating film (α). The base treatment layer (β) is not particularly limited, and for example, a layer containing at least one selected from a silane coupling agent, an organic resin, and a polyphenol compound can be used. By providing this layer in the lower layer of the colored coating film, the adhesion between the metal plate and the colored coating film (α) can be increased, and the corrosion resistance of the coating film can be increased. By providing a base treatment layer (β) containing all of the silane coupling agent, organic resin, and polyphenol compound, the adhesion between the metal plate and the colored coating film (α) is particularly enhanced, and the corrosion resistance of the coating film is particularly enhanced. it can.

The silane coupling agent contained in the ground treatment layer (β) is not particularly limited. For example, it is sold by Shin-Etsu Chemical Co., Toray Dow Corning, Chisso, Momentive Performance Materials Japan, etc. Vinyltrimethoxysilane, vinyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropylethoxysilane, N- [2- (vinylbenzylamino) ethyl] -3-aminopropyltrimethoxysilane, γ- Methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxy Propyl Tildiethoxysilane, γ-glycidoxypropyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, N-β- (aminoethyl) γ-aminopropyltrimethoxysilane, N-β- (Aminoethyl) -γ-aminopropyltriethoxysilane, N-β- (aminoethyl) -γ-aminopropylmethyldimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane Etc. A silane coupling agent may be used independently and may use 2 or more types together.

The organic resin contained in the base treatment layer (β) is not particularly limited, and for example, a known organic resin such as a polyester resin, a polyurethane resin, an epoxy resin, a phenol resin, an acrylic resin, or a polyolefin resin can be used. In order to further improve the adhesion between the colored coating film (α) and the metal plate, it is preferable to use at least one of a polyester resin, a polyurethane resin, an epoxy resin, and a phenol resin. In the case where the colored coating film (α) contains a polyester resin, it is particularly preferable that the base treatment layer (β) contains a polyester resin in the sense that the compatibility with the colored coating film (α) is enhanced and the adhesion is enhanced.

As the polyphenol compound contained in the ground treatment layer (β), a compound having two or more phenolic hydroxyl groups bonded to a benzene ring or a condensate thereof is used. Examples of the compound having two or more phenolic hydroxyl groups bonded to the benzene ring include gallic acid, pyrogallol, catechol and the like. The condensate of the compound having two or more phenolic hydroxyl groups bonded to the benzene ring is not particularly limited, and examples thereof include polyphenol compounds that are widely distributed in the plant kingdom, usually called tannic acid.

Tannic acid is a general term for aromatic compounds having a complex structure having many phenolic hydroxyl groups widely distributed in the plant kingdom. The tannic acid used in the ground treatment layer (β) may be hydrolyzable tannic acid or condensed tannic acid. The tannic acid is not particularly limited, and examples thereof include hameli tannin, oyster tannin, chatannin, pentaploid tannin, gallic tannin, mylobarantannin, dibidi tannin, argarovira tannin, valonia tannin, catechin tannin and the like. Commercially available tannic acids such as “tannic acid extract A”, “B tannic acid”, “N tannic acid”, “industrial tannic acid”, “purified tannic acid”, “Hi tannic acid”, “F tannic acid” "Tannin tannic acid" (all manufactured by Dainippon Pharmaceutical Co., Ltd.), "Tannic acid: AL" (manufactured by Fuji Chemical Industry Co., Ltd.) and the like can also be used.

¡Polyphenol compounds may be used alone or in combination of two or more.

Although content of the component (at least 1 sort (s) chosen from a silane coupling agent, organic resin, and a polyphenol compound) contained in a base-treatment layer ((beta)) is not specifically limited, 10 mass parts in 100 mass parts of base-treatment layers. It is preferable to contain above. If the amount is less than 10 parts by mass, the effect of improving adhesion and corrosion resistance may not be obtained.

The adhesion amount of the base treatment layer (β) is not particularly limited, but is preferably in the range of 10 to 1000 mg / m ² . When the amount is less than 10 mg / m ² , the sufficient effect of the ground treatment layer (β) cannot be obtained, and when it exceeds 1000 mg / m ² , the ground treatment layer (β) tends to cohesively break down and the adhesion may be lowered. A more preferable adhesion amount range is 50 to 500 mg / m ² from the viewpoint of stable effect and economy.

There is no restriction | limiting in particular in the formation method of a base-treatment layer ((beta)), Generally it forms by apply | coating the coating agent for forming a base-treatment layer ((beta)) to the at least single side | surface of a metal plate, and heat-drying. The coating agent is preferably an aqueous coating agent using water as a medium because of excellent industrial productivity. The coating agent is not limited to a specific method and can be obtained by any method. For example, there may be mentioned a method of adding a constituent component of the base treatment layer (β) to water as a medium, stirring with a disper, and dissolving or dispersing. In order to improve the solubility or dispersibility of each component, a known hydrophilic solvent, for example, alcohols such as ethanol, isopropyl alcohol, t-butyl alcohol and propylene glycol, ethylene glycol monobutyl ether, if necessary One or more of cellosolves such as ethylene glycol monoethyl ether, esters such as ethyl acetate and butyl acetate, and ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone may be added. There is no restriction | limiting in particular in the coating method of the said coating agent, Well-known roll coat, spray coating, bar coating, immersion, electrostatic coating etc. can be used suitably. There is no restriction | limiting in particular in a heat-drying method, A metal plate can be heated previously before coating agent application | coating, a metal plate can be heated after application | coating, or drying can be performed combining these. There is no restriction | limiting in particular in a heating method, A hot air, induction heating, near infrared rays, a direct fire, etc. can be used individually or in combination. The dry baking temperature is preferably 60 ° C. to 150 ° C., more preferably 70 ° C. to 130 ° C. as the ultimate plate temperature. When the ultimate plate temperature is less than 60 ° C., the drying is insufficient, the adhesion between the colored coating film and the substrate and the corrosion resistance of the colored coating film may be lowered, and when it exceeds 150 ° C., the colored coating film The adhesion between the substrate and the substrate may be reduced.

The metal plate applicable in the present invention is not particularly limited, and examples thereof include an iron plate, an iron base alloy plate, an aluminum plate, an aluminum base alloy plate, a copper plate, and a copper base alloy plate. A plated metal plate plated on these metal plates can also be used. Among them, the most preferable ones in the application of the present invention are zinc-based plated steel sheets and aluminum-based plated steel sheets.

Zinc-based plated steel sheets include galvanized steel sheet, zinc-nickel plated steel sheet, zinc-iron plated steel sheet, zinc-chromium plated steel sheet, zinc-aluminum plated steel sheet, zinc-titanium plated steel sheet, zinc-magnesium plated steel sheet, zinc-manganese Galvanized steel sheets such as galvanized steel sheets, zinc-aluminum-magnesium-plated steel sheets, zinc-aluminum-magnesium-silicon-plated steel sheets, and cobalt, molybdenum, tungsten, nickel as small amounts of different metal elements or impurities in these plated layers Examples include those containing titanium, chromium, aluminum, manganese, iron, magnesium, lead, bismuth, antimony, tin, copper, cadmium, arsenic and the like, and those in which inorganic substances such as silica, alumina, and titania are dispersed.

Examples of the aluminum-plated steel sheet include an aluminum-plated steel sheet or a steel sheet plated with an alloy of aluminum and at least one of silicon, zinc, and magnesium, such as an aluminum-silicon-plated steel sheet, an aluminum-zinc-plated steel sheet, an aluminum- Examples thereof include silicon-magnesium plated steel sheets.

Furthermore, it is also possible to use a multi-layer plated steel plate in which the above plating and other types of plating, such as iron plating, iron-phosphorus plating, nickel plating, cobalt plating, etc., are combined.

The plating method is not particularly limited, and any known method such as an electroplating method, a hot dipping method, a vapor deposition plating method, a dispersion plating method, or a vacuum plating method may be used.

The present invention will be further described with reference to examples. However, the present invention is not limited to the following examples.

(1) Metal plate Table 1 shows the types of metal plates used. A mild steel plate having a thickness of 0.5 mm was used as the base material of the plated metal plate. For SUS plate, ferritic stainless steel plate (steel component: C: 0.008 mass%, Si: 0.07 mass%, Mn: 0.15 mass%, P: 0.011 mass%, S: 0.009 mass) %, Al: 0.067% by mass, Cr: 17.3% by mass, Mo: 1.51% by mass, N: 0.0051% by mass, Ti: 0.22% by mass, balance Fe and inevitable impurities). used. The metal plate was used after subjecting the surface to alkaline degreasing treatment, washing with water and drying.

(2) Ground treatment layer The coating agent for forming the ground treatment layer is an organic resin (Table 2), a silane coupling agent (Table 3), and a polyphenol compound (Table 4) as shown in Table 5 (mass%). ) And prepared by stirring using a dispersing machine for paint. The coating agent is applied to the surface of the metal plate prepared in the above (1) with a roll coater so as to have an adhesion amount of 100 mg / m ² , and dried under the condition of a reaching plate temperature of 70 ° C. A ground treatment layer was formed.

(3) Polyurethane resin (Preparation of polyester polyol)
<Production Example PO1: Preparation of polyester polyol PO1>
While introducing nitrogen gas into a reaction vessel equipped with a thermometer, a nitrogen gas inlet tube, and a stirrer, 443 parts by mass of terephthalic acid, 443 parts by mass of isophthalic acid, 420 parts by mass of adipic acid, 196 parts by mass of ethylene glycol, 1, 306 parts by mass of 4-butanediol, 328 parts by mass of neopentyl glycol and 0.5 parts by mass of dibutyltin oxide were charged and stirred. Next, while introducing nitrogen gas, the temperature was raised to 230 ° C., and a polycondensation reaction was carried out at the same temperature for 15 hours until the acid value became 1 or less to obtain polyester polyol PO1.

<Production Examples PO2 to PO7: Preparation of polyester polyols PO2 to PO7>
According to the raw material composition shown in Table 6, polyester polyols PO2 to PO7 were obtained in the same procedure as in Production Example PO1. In any preparation, the dibutyltin oxide was 0.5 mass part.

Table 6 also shows the number average molecular weights (polystyrene conversion values by GPC measurement) of the polyester polyols PO1 to PO7 and the content (mass%) of the aromatic ring structure in the polyester polyols PO1 to PO7 solid content. The content of the aromatic ring structure in the solid content of the polyester polyols PO1 to PO7 is the denominator {solid content mass (g) of the polyurethane resin (A1)} in the above formula [1]. It is calculated by replacing with mass (g)}.

(Preparation of aqueous dispersion of polyurethane resin)
<Production Example PU1: Preparation of Aqueous Dispersion PU1 of Polyurethane Resin>
1000 parts by weight of polyester polyol PO1 and 40 parts by weight of 2,2′-dimethylolpropionic acid were added to 900 parts by weight of methyl ethyl ketone and dissolved by heating to 80 ° C. Thereafter, 250 parts by mass of isophorone diisocyanate was added, heated to 110 ° C. and reacted for 2 hours, and neutralized by adding 60 parts by mass of triethylamine. Subsequently, this solution was dropped into an aqueous solution in which 10 parts by mass of ethylenediamine and 4000 parts by mass of deionized water were mixed under strong stirring, and chain elongation and water dispersion were completed. Subsequently, after the methyl ethyl ketone was distilled off from the aqueous dispersion at a reduced pressure of 50 ° C. and 150 mmHg, the concentration was adjusted by adding deionized water to obtain an aqueous dispersion PU1 of polyurethane resin having a resin solid content concentration of 30% by mass. Obtained.

<Production Examples PU2 to PU19: Preparation of polyurethane resin aqueous dispersions PU2 to PU19>
In accordance with the raw material composition shown in Tables 7 and 8, polyurethane resin aqueous dispersions PU2 to PU19 having a resin solid content of 30% by mass were obtained in the same procedure as in Production Example PU1.

For the obtained polyurethane resin aqueous dispersions PU1 to PU19, the content of the aromatic ring structure in the polyurethane resin solid content was calculated based on the above formula [1].

(4) Polyester resin <Production example PE1: Preparation of aqueous dispersion PE1 of polyester resin>
In a reaction vessel equipped with a stirrer, condenser and thermometer, 199 parts terephthalic acid, 232 parts isophthalic acid, 199 parts adipic acid, 27 parts 5-sodium sulfoisophthalic acid, 312 parts ethylene glycol, 2,2-dimethyl-1,3 -125 parts of propanediol, 187 parts of 1,5-pentanediol and 0.41 part of tetrabutyl titanate were charged, and the esterification reaction was carried out from 160 ° C to 230 ° C over 4 hours. Next, the pressure in the system was gradually reduced, the pressure was reduced to 5 mmHg over 20 minutes, and a polycondensation reaction was performed at 260 ° C. for 40 minutes under a vacuum of 0.3 mmHg or less. After adding 20 parts of butyl cellosolve and 42 parts of methyl ethyl ketone to 100 parts of the obtained copolyester resin, the mixture was stirred and dissolved at 80 ° C. for 2 hours, and further 213 g of ion-exchanged water was added to perform water dispersion. Then, the solvent was distilled off while heating, and the mixture was filtered through a 200 mesh nylon mesh to obtain a polyester resin aqueous dispersion PE1 having a solid content concentration of 30%.

<Production Example PE2: Preparation of Polyester Resin Water Dispersion PE2>
In a reaction vessel equipped with a stirrer, condenser and thermometer, 199 parts terephthalic acid, 266 parts isophthalic acid, 199 parts adipic acid, 312 parts ethylene glycol, 125 parts 2,2-dimethyl-1,3-propanediol, 1,5 -187 parts of pentanediol and 0.41 part of tetrabutyl titanate were charged, and the esterification reaction was carried out from 160 ° C to 230 ° C over 4 hours. Next, the pressure in the system was gradually reduced, the pressure was reduced to 5 mmHg over 20 minutes, and a polycondensation reaction was performed at 260 ° C. for 40 minutes under a vacuum of 0.3 mmHg or less. The mixture was cooled to 220 ° C. in a nitrogen stream, and 23 parts of trimellitic anhydride and 16 parts of ethylene glycol bisanhydrotrimellitate were added and reacted for 30 minutes. 100 parts of the obtained copolyester resin, 20 parts of butyl cellosolve and 42 parts of methyl ethyl ketone were added, and then stirred and dissolved at 80 ° C. for 2 hours. Then, 23 parts of isopropyl alcohol and 3.5 parts of triethylamine were added, and 213 parts of ions were added. Water dispersion was performed with exchange water. Then, the solvent was distilled off while heating, and the mixture was filtered through a 200 mesh nylon mesh to obtain a polyester resin aqueous dispersion PE2 having a solid content concentration of 30%.

<Production Example PE3: Preparation of Polyester Resin Water Dispersion PE3>
In a reaction vessel equipped with a stirrer, condenser and thermometer, 199 parts terephthalic acid, 232 parts isophthalic acid, 199 parts adipic acid, 33 parts 5-sodium sulfoisophthalic acid, 250 parts ethylene glycol, 2,2-dimethyl-1,3 -125 parts of propanediol, 187 parts of 1,5-pentanediol, 62 parts of bisphenol A ethylene oxide adduct, and 0.41 part of tetrabutyl titanate were subjected to an esterification reaction from 160 ° C to 230 ° C over 4 hours. . Next, the pressure in the system was gradually reduced, the pressure was reduced to 5 mmHg over 20 minutes, and a polycondensation reaction was performed at 260 ° C. for 40 minutes under a vacuum of 0.3 mmHg or less. After adding 20 parts of butyl cellosolve and 42 parts of methyl ethyl ketone to 100 parts of the obtained copolyester resin, the mixture was stirred and dissolved at 80 ° C. for 2 hours, and further 213 g of ion-exchanged water was added to perform water dispersion. Thereafter, the solvent was distilled off while heating, and the mixture was filtered through a 200 mesh nylon mesh to obtain a polyester resin aqueous dispersion PE3 having a solid content concentration of 30%.

(3) Colored coating film A colored composition for forming a coating film includes an aqueous dispersion of an organic resin (the above production examples PU1 to PU19, PE1 to 3, and Tables 8 and 9), a curing agent (D) ( Table 10), coloring pigment (B) (Table 11), silica particles (C) (Table 12), and lubricant (E) (Table 13) were blended in the blending amounts shown in Tables 14 to 20, and a paint disperser It was prepared by stirring using. In the production examples, “part” simply means mass part, and “%” means mass%. The colored composition is applied to the upper layer of the base treatment layer formed in (2) (or a metal plate if there is no base treatment layer) with a roll coater so as to have a predetermined film thickness, and reaches a predetermined ultimate plate temperature. And dried to form a coating film.

(4) Colored painted metal plate As described in (3) above, the coating composition of the colored coated metal plate on which the colored coating (α) is formed, the thickness of the colored coating, and the final plate baking temperature are shown in Tables 14 to 20 shows.

(5) Evaluation test About the colored coated metal plate (test plate) produced as described in (3) above, the designability, moisture resistance, corrosion resistance, and workability of the flat plate portion (designability of the processed portion, work adhesion) The scratch resistance and chemical resistance were evaluated by the following evaluation methods and evaluation criteria. The evaluation results are shown in Table 21 to Table 27.

(Design of flat plate part)
The appearance of the test plate was evaluated according to the following evaluation criteria.
5: Both coloring and surface gloss are uniform. The groundwork cannot be seen through at all.
4: Although the coloring is uniform, the surface gloss is slightly non-uniform (a level that can be confirmed by looking closely). The groundwork cannot be seen through at all.
3: Coloring and surface gloss are slightly non-uniform (levels that can be confirmed by looking closely). The groundwork cannot be seen through at all.
2: Both coloring and surface gloss are non-uniform (a level that can be easily confirmed visually). The groundwork cannot be seen through at all.
1: Both coloring and surface gloss are non-uniform (a level that can be easily confirmed visually). The groundwork is slightly transparent.

(Moisture resistance)
The appearance after the test plate was allowed to stand for 500 hours under conditions of a temperature of 40 ° C. and a humidity of 90% was evaluated according to the following evaluation criteria.
5: No change in appearance is observed.
4: The gloss of the surface slightly decreased (a level at which the test plates before the test were arranged side by side).
3: The gloss of the surface slightly decreased (a level that can be easily understood by arranging the test plates before the test side by side).
2: The gloss of the surface was lowered (a level that can be understood by looking at only the test plate).
1: The gloss of the surface was remarkably lowered (a level that can be easily seen by looking at only the test plate).

(Corrosion resistance)
After the end face of the test plate was tape-sealed, a salt spray test (SST) based on JIS Z 2371 was performed for 168 hours, the rust generation state was observed, and the following evaluation criteria were evaluated.
5: No rust generation.
4: Rust generation area is less than 1%.
3: Rust generation area is 1% or more and less than 2.5%.
2: Rust generation area is 2.5% or more and less than 5%.
1: Rust generation area is more than BR> T%.

(Machinability (designability of machined parts))
The test plate was subjected to 180 ° bending, and the outer appearance of the bent portion was evaluated according to the following evaluation criteria. The bending process was performed in an atmosphere of 20 ° C. with a 0.5 mm spacer in between (generally referred to as 1T bending).
5: The coating has no defects such as cracks and has a uniform colored appearance. No discoloration is observed.
4: Since slight cracks are observed in the coating film, a slight color fading is observed, but the appearance is almost uniform (a level that can be understood by arranging the test plates before the test side by side).
3: Slight cracking is observed because a slight crack is observed in the coating film, but the color appearance is almost uniform (a level that can be easily understood when the test plates before the test are arranged side by side).
2: Cracks are observed in the coating film, and color fading is observed (a level that can be understood by looking at only the test plate).
1: Cracks were observed in the coating film, and color fading was remarkable (a level that can be easily seen by looking at only the test plate).

(Processability (work adhesion))
The test plate was bent by 180 °, and then a tape peeling test (the tape peeling method conforming to JIS K 5600-5-6) was performed on the outside of the bent portion. The appearance of the tape peeling part was evaluated according to the following evaluation criteria. The bending process was performed in an atmosphere of 20 ° C. with a 0.5 mm spacer sandwiched therebetween (generally called 1T bending).
5: Peeling is not recognized in the coating film.
4: Peeling is observed in a very small part of the coating film (appropriately understood by observation with a loupe).
3: Peeling is observed in a part of the coating film (approximated by observation with a loupe).
2: Peeling is observed in the partial coating film (to the extent that it can be easily seen by visual inspection).
1: Peeling is recognized in most coating films (to the extent that it can be easily seen by visual inspection).

(Scratch resistance)
Five lines were drawn with a pencil lead at an angle of 45 ° on the test plate, and the pencil hardness was evaluated so as not to be damaged more than twice. As the pencil, a uni-pencil manufactured by Mitsubishi Pencil Co., Ltd. was used, tested under a load condition of 20 ° C. and 4.903 N (500 gf), and evaluated according to the following evaluation criteria. Other test conditions were in accordance with JIS K 5600-5-4.
5: Pencil hardness is 3H or more 4: Pencil hardness is 2H
3: Pencil hardness is H
2: Pencil hardness is F
1: Pencil hardness is HB or less

(chemical resistance)
After the test plate was placed on a rubbing tester, the state of the film after rubbing the absorbent cotton impregnated with ethanol with a load of 49.03 kPa (0.5 kgf / cm ² ) for 20 reciprocations and 50 reciprocations was evaluated according to the following evaluation criteria.
5: There is no trace on the rubbing surface.
4: A trace is left on the rubbing surface (a level at which the rubbing trace can be discriminated with some attention).
3: A slight mark is made on the rubbing surface (a level at which the rubbing mark can be easily discerned when the eyes are closed).
2: A clear mark is made on the rubbing surface (a level at which the rubbing mark can be discriminated instantaneously visually).
1: The coating film dissolves on the rubbing surface, and the base is exposed.

The examples of the present invention exhibited excellent flat surface designability, moisture resistance, corrosion resistance, workability, scratch resistance, and chemical resistance with a score of 3 or more in any evaluation test. On the other hand, a polyurethane resin that does not contain a structural unit derived from a polyester polyol component having an aromatic ring structure in an organic resin that is a film-forming component in a colored coating film, which is a comparative example outside the scope of the present invention (in Table 9). Comparative Examples 1, 8, 11, 18 using A12 and A19), polyurethane resins not containing an aromatic ring structure in all structural units derived from the isocyanate component (b) (A13, A14, A17 shown in Table 9) Comparative Examples 2, 3, 6, 7, 12, 13, 16, 17 using A18), Comparative Examples 4 and 14 using a polyurethane resin containing no urea group (A15 shown in Table 9), isocyanate component (b Comparative Examples 5 and 15 using a polyurethane resin (A16 shown in Table 9) that does not contain an aromatic ring and does not contain a urea group in the derived structural unit are both corrosion resistance and chemical resistance. Or either one was poor. Comparative Examples 9, 10, 19, and 20 using a polyurethane resin (A20 shown in Table 9) and a polyolefin resin (A25 shown in Table 9) that do not contain a carboxyl group and contain a cationic functional group One or more items of partial design, corrosion resistance, workability, scratch resistance, and chemical resistance were inferior. In addition, when the aqueous coloring composition used for the Example of this invention and the comparative example was left still at 40 degreeC for 1 day, and the storage stability was investigated, the aqueous coloring composition used by the comparative examples 9 and 19 was gelatinized. It was. That is, it was found that the one using the polyurethane resin A20 which does not contain a carboxyl group and contains a cationic functional group is inferior in storage stability compared to other colored compositions and is not at a practical level. Moreover, the comparative examples 21 and 22 which do not contain a silica particle (C) were inferior in corrosion resistance, process adhesiveness, and scratch resistance (comparative example 22 was also inferior in solvent resistance). The comparative example 23 in which the film thickness of the colored coating film is 1.5 μm is a flat surface design property, corrosion resistance, processed part design property, and scratch resistance, and the comparative example 24 in which the film thickness of the colored coating film is 12 μm is a coating As film defects occurred, the processed part design was inferior.
Examples 1 to 109 having both a polyester polyol component (a) having an aromatic ring structure and an isocyanate component (b) having an aromatic ring structure, and a polyester polyol component (a) having an aromatic ring structure And Comparative Examples 1 to 20 that do not have both the aromatic component and the isocyanate component (b) having an aromatic ring structure, it can be confirmed that Examples 1 to 109 have extremely excellent chemical resistance. From such a comparison, it can be seen that by having both the polyester polyol component (a) having an aromatic ring structure and the isocyanate component (b) having an aromatic ring structure, extremely excellent chemical resistance can be obtained. .
Further, in Examples 1 to 109, “the content of the aromatic ring structure contained in the isocyanate component (b) having an aromatic ring structure is within a numerical range of 5 to 20% by mass of the polyurethane resin (A1)”. Examples 6, 10, 18, 22, 31, 35 "and" polyester polyol component (a) having an aromatic ring structure content of aromatic ring structure contained in polyurethane resin ( In Examples 5, 17, 30, 107, 108, 109 "that do not fall within the numerical range of 5 to 25% by mass of A1), these Examples 5, 6, 10, 17, 18, 22, 30 , 31, 35, 107, 108, and 109 are not as excellent in chemical resistance and workability as the examples. From this point, “the content of the aromatic ring structure contained in the isocyanate component (b) having an aromatic ring structure falls within the range of 5 to 20% by mass of the polyurethane resin (A1)” and / or “By keeping the content of the aromatic ring structure contained in the polyester polyol component (a) having an aromatic ring structure within the numerical range of 5 to 25% by mass of the polyurethane resin (A1)”, a more excellent resistance It can be seen that chemical properties and processability can be exhibited.

The preferred embodiments of the present invention have been described above, but it goes without saying that the present invention is not limited to such examples. It will be apparent to those skilled in the art that various changes and modifications can be envisaged within the scope of the claims, and these are naturally within the technical scope of the invention. Is done.

According to the present invention, it does not contain highly environmentally-friendly hexavalent chromium, and has extremely high design properties (colorability and concealment including processed parts), moisture resistance, corrosion resistance, workability, scratch resistance, chemical resistance, etc. An excellent and inexpensive chromate-free colored metal sheet can be provided.

Claims (11)

1. A film-forming component comprising a polyurethane resin containing a urea group, a urethane group, and a carboxyl group;
   With colored pigments;
   Spherical silica particles having an average particle size of 5 to 50 nm;
   Having a colored coating film containing at least one side of the metal plate,
   The polyurethane resin is
   A structural unit derived from a polyester polyol component having an aromatic ring structure;
   A structural unit derived from an isocyanate component having an aromatic ring structure;
   Containing
   All of the structural units derived from the isocyanate component contain an aromatic ring structure,
   A chromate-free colored painted metal plate having excellent chemical resistance, wherein the colored coating film has a thickness of 2 to 10 μm.
2. The chromate having excellent chemical resistance according to claim 1, wherein the polyurethane resin contains 5 to 20% by mass of an aromatic ring structure contained in the isocyanate component having an aromatic ring structure. Free colored painted metal plate.
3. 3. The chemical resistance according to claim 2, wherein the aromatic ring structure contained in the polyester polyol component having an aromatic ring structure is contained in the polyurethane resin in an amount of 5 to 25% by mass. Chromate-free colored painted metal plate.
4. The chromate-free colored coated metal sheet having excellent chemical resistance according to any one of claims 1 to 3, wherein the isocyanate component is tolylene diisocyanate.
5. The chromate-free colored coating excellent in chemical resistance according to any one of claims 1 to 3, wherein the film-forming component of the colored coating film further contains a polyester resin containing a sulfonic acid group. Metal plate.
6. The chromate-free colored coated metal sheet having excellent chemical resistance according to any one of claims 1 to 3, wherein the film-forming component of the colored coating film is cured with a curing agent.
7. The chromate-free colored coated metal sheet having excellent chemical resistance according to any one of claims 1 to 3, wherein the colored coating film further contains a lubricant.
8. The chromate-free colored coated metal sheet having excellent chemical resistance according to any one of claims 1 to 3, further comprising a base treatment layer under the colored coating film.
9. The colored coating film according to any one of claims 1 to 3 is formed by applying a colored composition containing a coating film constituent component to at least one side of a metal plate using an aqueous solvent, followed by drying by heating. A chromate-free colored painted metal plate with excellent chemical resistance.
10. A polyurethane resin containing a urea group, a urethane group, and a carboxyl group;
    With colored pigments;
    Spherical silica particles;
    Containing
    The polyurethane resin is
    A structural unit derived from a polyester polyol component having an aromatic ring structure;
    A structural unit derived from an isocyanate component having an aromatic ring structure;
    Containing
    An aqueous coloring composition comprising an aromatic ring structure in all of the structural units derived from the isocyanate component.
11. The aqueous coloring composition according to claim 10, wherein the aqueous coloring composition further contains a polyester resin containing a sulfonic acid group.