JP5279952B2 - Chromate-free painted metal plate - Google Patents

Abstract

This chromate-free coated metal plate has a coating film (a) containing an organic resin (A), silica particles (C), and polyolefin resin particles (D) on at least one surface of a metal plate. When considering the average particle size of the polyolefin resin particles (D) to be a µm and the thickness of the coating film (a) to be b µm, the relationships 0.5 = a = 3, 2 = b = 10, and 0.1 = a/b = 0.8 are satisfied, and the silica particles (C) include both spherical silica particles (C1) having an average particle size of 5-50 nm and spherical silica particles (C2) having an average particle size of 0.3-5 µm. The result is a low-cost, aesthetic, chromate-free coated metal plate having highly superior workability, corrosion resistance, damage resistance, and the like without including hexavalent chromium, which has a high environmental impact,

Description

  The present invention is an inexpensive design chromate-free coating that is extremely excellent in workability, corrosion resistance, scratch resistance, etc., in which a coating film (α) that does not contain hexavalent chromium, which has high environmental impact, is formed on at least one surface of a metal plate. It relates to a metal plate.

  Clear pre-coating that uses the metallic feeling of pre-coated metal plates and metal surfaces coated with colored organic coatings instead of post-painted products that have been painted after conventional molding for home appliances, building materials, and automobiles. Metal plates and the like have come to be used. These designable metal plates are made by coating a colored organic film on a rust-proof steel plate or plated steel plate, or by applying a clear coating on a metal plate exhibiting a metallic luster, and have a beautiful appearance. However, it has processability and good corrosion resistance.

  For example, Patent Document 1 discloses a technique for obtaining a precoated steel sheet having excellent 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 solution. 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, considering the environmental impact of hexavalent chromium that may be eluted from the chromate-treated film and the organic film containing chromium-based rust-preventive pigments, recently there has been an increasing demand for chromate-free rust-proof treatment and chromate-free organic films. ing. On the other hand, for example, Patent Document 3 and Patent Document 4 disclose chromate-free 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 film 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 the diversification of user needs, there is a demand for design 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. ing. That is, conventional expensive pre-coated steel sheets alone are not sufficient to meet diversified demands.

  As a designable metal 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 steel sheet surface is disclosed. However, since these colored steel sheets are designed to ensure corrosion resistance by providing a chromate-treated film, they cannot meet the recent needs for chromate-free. In addition, since it is not designed to take into account the resistance to scratches that occur during handling and press molding and the concealment of the part where the colored layer is stretched, the appearance of the scratched part and the molded part There was also a problem that remarkably decreased.

  On the other hand, Patent Document 7 discloses a heat-resistant clear pre-coated metal plate having excellent design properties. The clear coating used here has a relatively thin film thickness of 10 μm or less, and is chromate-free. However, a solvent-based paint is used as the paint for forming the clear coating. Equipment is required. In addition, although it is excellent in designability and workability, it has a problem that the scratch resistance is not sufficient.

JP-A-8-168723 Japanese Patent Laid-Open No. 3-100180 JP 2000-199075 A JP 2000-262967 A Japanese Patent Laid-Open No. 5-16292 JP-A-2-93093 JP 2008-149608 A

  In view of the present situation, an object of the present invention is to provide an inexpensive design chromate-free coated metal sheet that does not contain hexavalent chromium having high environmental impact and is extremely excellent in workability, corrosion resistance, scratch resistance, and the like. Is.

In general, workability, corrosion resistance, and scratch resistance are technically conflicting performances. In order to ensure workability, it is important that the coating film covering the surface of the metal plate follows the deformation such as elongation that occurs when the metal plate is molded without cracking or peeling. is there. This is because if the coating film is cracked or peeled off, the design appearance may be remarkably impaired. In order to improve the followability of the coating film against deformation of the metal plate, it is preferable to use a relatively soft and excellent organic resin as a film-forming component of the coating film, but with only a soft organic resin, corrosion resistance and It is difficult to ensure scratch resistance.
As one of the techniques for improving the corrosion resistance and scratch resistance, there is known a technique of adding inorganic oxide particles to a coating film using an organic resin as a film-forming component. However, since the addition of inorganic oxide particles reduces the elongation characteristics of the coating film, it has been difficult to achieve both workability, corrosion resistance, and scratch resistance.
In addition, as one technique for improving the scratch resistance, a technique of adding a lubricant such as polyolefin resin particles, fluororesin particles, molybdenum disulfide particles or the like to the coating film is also known. However, it has been newly found that the corrosion resistance of a paint film that is chromate-free and relatively thin as a coated metal plate and is 10 μm or less may be significantly reduced depending on the conditions of addition of these lubricants.
Accordingly, as a result of intensive investigations to overcome these problems, the present inventors have obtained a silica film having a specific particle shape and two different particle diameter ranges on a coating film containing an organic resin as a film-forming component. It was found that by adding and dispersing the particles, the corrosion resistance and scratch resistance can be greatly improved without degrading the workability.
In addition, polyolefin resin particles are suitable as a lubricant to be added to the coating film, the average particle diameter of the polyolefin resin particles is limited, and the ratio of the coating film thickness to the average particle diameter of the polyolefin resin particles is in a specific range. It has been found that the scratch resistance can be greatly improved without reducing the corrosion resistance.
By combining these findings, we succeeded in achieving high compatibility between workability, corrosion resistance, and scratch resistance, which are chromate-free and thin film coated metal plates of 10 μm or less, which are contradictory properties.

  That is, the gist of the present invention is as follows.

[1] A chromate-free coated metal plate having a coating film (α) comprising an organic resin (A) as a film-forming component and containing silica particles (C) and polyolefin resin particles (D) on at least one surface of the metal plate. There,
When the average particle diameter of the polyolefin resin particles (D) is a μm and the thickness of the coating film (α) is b μm, 0.5 ≦ a ≦ 3, 2 ≦ b ≦ 10, 0.1 ≦ a / b ≦ 0.8 satisfied,
Chromate-free, characterized in that the silica particles (C) contain both spherical silica particles (C1) having an average particle size of 5 to 50 nm and spherical silica particles (C2) having an average particle size of 0.3 to 5 μm. Painted metal plate.

  [2] The chromate-free coated metal plate according to [1], wherein the organic resin (A) contains a polyester resin (Ae) containing a sulfonic acid group in the structure.

  [3] The chromate-free painted metal plate according to [2], wherein the organic resin (A) further contains a polyurethane resin (Au) having a urea group in its structure.

  [4] The chromate-free coated metal plate according to [1] or [2], wherein the coating film (α) further contains a color pigment (E).

  [5] The chromate-free coated metal plate according to [1] or [2], wherein the polyolefin resin particles (D) have a softening point of 125 ° C. or higher.

[6] The polyolefin resin particles (D) are high density polyethylene resin particles (D1) having a density of 950 kg / m ³ or more and a penetration hardness of 2 or less. ] Or the chromate-free painted metal plate according to [2].

  [7] The chromate-free coated metal plate according to [1] or [2], wherein the polyolefin resin particles (D) have an average molecular weight of 3000 to 6000.

  [8] The chromate-free coating according to [1] or [2], wherein the content of the polyolefin resin particles (D) in the coating film (α) is 0.5 to 10% by mass. Metal plate.

  [9] When the average particle diameter of the spherical silica particles (C2) is c μm and the thickness of the coating film (α) is b μm, 0.1 ≦ c / b ≦ 0.7 is satisfied. The chromate-free painted metal plate according to [1] or [2].

  [10] The chromate-free coated metal plate according to [1] or [2], wherein the organic resin (A) is a resin cured by a curing agent (B).

  [11] The chromate-free coated metal plate according to [10], wherein the curing agent (B) contains a melamine resin (B1).

  [12] The coating film (α) according to [1] or [2] is coated with an aqueous coating composition (X) containing a component of the coating film (α) on at least one side of a metal plate, and heated. A chromate-free painted metal plate, characterized by being formed by drying.

  [13] The temperature at the time of heating and drying of the water-based coating composition (X) is in the range of 150 to 250 ° C. as the ultimate temperature of the metal plate, and the heating and drying time is in the range of 2.5 to 20 seconds. The chromate-free painted metal plate according to [11], wherein

[14] After the water-based coating composition (X) is heated and dried, there is further a water cooling step, the softening point of the polyolefin resin particles (D) is T _S ° C, and the plate temperature of the metal plate during water cooling is T _M ° C. the water temperature of the water-cooled water when the _{T W} ° _C., and satisfies T _M> T S, the _{T W ≧ (T M -150)} / 4, chromate-free coating according to [11] Metal plate.

[15] A water-based coating composition (X) containing an organic resin (A), silica particles (C), and polyolefin resin particles (D),
The polyolefin resin particles (D) have an average particle size of 0.5 to 3 μm,
The silica paint (C) contains both spherical silica particles (C1) having an average particle diameter of 5 to 50 nm and spherical silica particles (C2) having an average particle diameter of 0.3 to 5 μm. Composition (X).

  The design chromate-free painted metal plate of the present invention does not contain hexavalent chromium having high environmental impact, is inexpensive, and is extremely excellent in workability, corrosion resistance, scratch resistance, and the like. 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.

It is a schematic cross section which shows an example of the cross-sectional structure of the chromate-free coating metal plate of this invention.

  The chromate-free coated metal plate of the present invention has, on at least one surface of the metal plate, a coating film (α) containing an organic resin (A) as a film-forming component and containing silica particles (C) and polyolefin resin particles (D). A chromate-free coated metal plate having an average particle diameter of the polyolefin resin particles (D) of a μm and a thickness of the coating film (α) of b μm, 0.5 ≦ a ≦ 3, 2 ≦ b ≦ 10, 0.1 ≦ a / b ≦ 0.8; the silica particles (C) are spherical silica particles (C1) having an average particle size of 5 to 50 nm and spherical silica having an average particle size of 0.3 to 5 μm It contains both particles (C2).

  More specifically, the chromate-free coated metal sheet of the present invention has an organic resin (A) that contributes to guaranteeing the workability and corrosion resistance (corrosion factor shielding effect) of the coating film as a film-forming component. Silica particles (C) that contribute to improvement of corrosion resistance and scratch resistance, and polyolefin resin particles (D) that act as a lubricant, improve the lubricity of the coating film, and contribute to improvement of scratch resistance The coating film (α) is formed on at least one side of a metal plate as a base material. When the average particle diameter of the polyolefin resin particles (D) is a μm and the thickness of the coating film (α) is b μm, 0.5 ≦ a ≦ 3, 2 ≦ b ≦ 10, 0.1 ≦ a / b ≦ By satisfying 0.8, the scratch resistance is greatly improved without lowering the corrosion resistance, and the silica particles (C) are spherical silica particles (C1) having an average particle diameter of 5 to 50 nm and an average particle diameter of 0. By containing both the spherical silica particles (C2) of 3 to 5 μm, the corrosion resistance and scratch resistance are greatly improved without reducing the workability. That is, workability, corrosion resistance, and scratch resistance are balanced at a high level.

  The coating film (α) is preferably formed by applying an aqueous coating composition (X) containing a constituent of the coating film (α) in an aqueous solvent to at least one surface of a metal plate and heating and drying. Here, the aqueous solvent means that water is a solvent that is a main component of the solvent. The amount of water in the aqueous solvent of the present application is preferably 50% by mass or more. Solvents other than water contained in the aqueous solvent of the present application may be organic solvents, but those containing organic solvents as defined in the Occupational Safety and Health Act organic solvent poisoning prevention regulations (Attached Table 6-2 of the Ordinance for Enforcement of the Industrial Safety and Health Act) It is more preferable that the organic solvent listed in (1) exceeds 5% by weight). By using such an aqueous solvent, it is not necessary to pass an extra coating line for using the organic solvent-based paint, so that the manufacturing cost can be greatly reduced and the volatilization can be reduced. There is also a merit in terms of the environment, such as emission of volatile organic compounds (VOC) can be greatly suppressed.

  The coating film thickness of the coating film (α) is 2 to 10 μm. The coating thickness 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 the coating film (α) is formed from an aqueous coating composition, coating film defects such as armpits may occur. The required appearance may not be obtained stably.

  The thickness of the 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 method for measuring the adhesion mass of the coating is as follows: the difference in mass before and after coating, the difference in mass before and after peeling the coated film after coating, or the content in the film in advance by fluorescent X-ray analysis of the coating What is necessary is just to select from existing methods appropriately, such as measuring the abundance of an element. The specific gravity of the coating film or the 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 What is necessary is just to select suitably from the existing method, such as calculating from the compounding quantity of a coating-film component, and the known specific gravity of each component.

  Among the various measuring methods described above, since coatings having different specific gravities and the like can be easily and accurately measured, it is preferable to use cross-sectional observation of the coating.

  The method for observing the cross section of the 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 film with a TEM (transmission electron microscope) can be suitably used.

  The organic resin (A) is a film forming component of the coating film (α). It does not specifically limit as a kind of said organic resin (A), For example, a polyester resin, a polyurethane resin, an epoxy resin, an acrylic resin, polyolefin resin, or those modified bodies etc. can be mentioned. Here, the modified product is a reactive functional group contained in the structure of these resins and reacts with “another compound” (such as a monomer or a crosslinking agent) containing a functional group capable of reacting with the functional group in the structure. It refers to the resin. The organic resin (A) may be used alone or in combination of two or more, and an organic resin obtained by modifying at least one other organic resin in the presence of at least one organic resin. You may use 1 type or in mixture of 2 or more types.

  Content of the film-forming component (when the organic resin (A) is not cured with a curing agent (B) described later, the content of only the organic resin (A), the curing agent described later with the organic resin (A) When it is cured in (B), the total amount of the organic resin (A) and the curing agent (B) is preferably 55 to 80% by mass in the coating film. If it is less than 55% by mass, the workability may decrease, and if it exceeds 80% by mass, the scratch resistance may decrease.

  The organic resin (A) preferably contains a polyester resin (Ae) containing a sulfonic acid group in the structure in order to achieve both high workability, corrosion resistance, and scratch resistance. Since the ester group contained in the structure of the polyester resin has an appropriate cohesive energy, the film physical properties (balance between elongation and strength) of the coating film can be enhanced in a high dimension. That is, applying a polyester resin as a film-forming component of a coating film is very effective in achieving both workability and scratch resistance at a high level.

  A coating film containing a polyester resin containing a sulfonic acid group in the structure as a film-forming component has high surface free energy due to the high polarity of the sulfonic acid group. On the other hand, polyolefin resin particles, which are essential components of the coating film, have relatively low polarity and low surface free energy. Therefore, by containing a polyester resin containing a sulfonic acid group as a film-forming component, the polyolefin resin particles are applied to the surface of the coating film during the formation of the coating film due to the difference in surface free energy between the coating film-forming component and the polyolefin resin particles. Has a tendency to align. Since the polyolefin resin particles act as a lubricant, orientation on the coating film surface is more effective in reducing the frictional resistance with the contacted object, and can further improve the scratch resistance.

  On the other hand, corrosion factors are likely to penetrate into the grain boundaries between the film-forming component and the polyolefin resin particles, so if the polyolefin resin particles exist so as to penetrate the entire thickness of the coating film, the grain boundaries (corrosion factor penetration path) are the base. It reaches the metal plate and causes a significant decrease in corrosion resistance. As described above, the present invention includes a polyester resin containing a sulfonic acid group as a film-forming component, so that the polyolefin resin particles are oriented on the surface of the coating film by the interaction between the film-forming component of the coating film and the polyolefin resin particles. ing. By doing so, the grain boundary is designed to stop only at the upper part of the coating, and the invasion path of the corrosion factor is designed not to reach the base metal, thereby suppressing the corrosion resistance. That is, it becomes possible to achieve both high scratch resistance and corrosion resistance.

  In addition, in this embodiment, the sulfonic acid group contained in the polyester resin also contributes to improving the adhesion with the metal plate (base treatment layer when there is a base treatment) as a base material. It is suitable for enhancing the properties. Further, when the coating composition for forming the coating film is aqueous, the sulfonic acid group has high hydrophilicity, so that the stability of the polyester resin in the aqueous coating composition is improved (coating composition). To prevent the solidification and the generation of aggregates). In particular, when a curing agent described later is used in combination, the pH fluctuation of the coating composition increases and the stability of the coating may decrease. However, when using a polyester resin containing a sulfonic acid group, the coating composition It is difficult to be affected by pH fluctuations and can suppress a decrease in paint stability. In addition, since the polyester resin containing a sulfonic acid group is difficult to dissolve in an organic solvent (is soluble only in some polar solvents), the resin is an organic solvent-based coating composition using an organic solvent as a solvent. It cannot be used practically with things. Moreover, when using a hardening | curing agent, it is common to use hardening catalysts, such as a sulfonic acid group containing compound, together, but there exists a possibility that such a hardening catalyst may reduce the corrosion resistance of a coating film. On the other hand, since the polyester resin containing a sulfonic acid group can be cured at low temperature without using a curing catalyst, it is not necessary to add a curing catalyst, and there is no concern about a decrease in corrosion resistance due to the addition of the curing catalyst. Therefore, since a polyester resin containing a sulfonic acid group cannot be applied to a paint using an organic solvent as a solvent, in the case of a coating film formed using this, the effects of the above sulfonic acid, particularly corrosion resistance and scratch resistance. We cannot expect the effect of having both sexes.

  It is preferable that content of the said polyester resin (Ae) is 60-100 mass% in the said organic resin (A), More preferably, it is 80-100 mass%. If it is less than 60% by mass, the effect of improving workability, scratch resistance and corrosion resistance may not be obtained.

  The polyester resin resin (Ae) preferably further includes a bisphenol structure in the structure. Since the bisphenol structure has high cohesive energy and excellent water resistance, it is preferable to include the bisphenol structure in order to improve scratch resistance and corrosion resistance.

  The polyester resin (Ae) is not particularly limited as long as it contains a sulfonic acid group in the structure. For example, it can be obtained by condensation polymerization of a polyester raw material comprising a polycarboxylic acid component and a polyol component. Moreover, it can also be made water-based by dissolving or dissolving the polyester resin obtained there in water.

  Examples of the polycarboxylic acid component include phthalic acid, phthalic anhydride, tetrahydrophthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic acid, hexahydrophthalic anhydride, methyltetraphthalic acid, methyltetrahydrophthalic anhydride, and 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, One or a plurality of types such as succinic anhydride, lactic acid, dodecenyl succinic acid, dodecenyl succinic anhydride, cyclohexane-1,4-dicarboxylic acid, and anhydrous endo acid can be exemplified.

  Examples of the polyol component include ethylene glycol, diethylene glycol, 1,3-propanediol, 1,2-propanediol, triethylene glycol, 2-methyl-1,3-propanediol, 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 It may be mentioned propane, glycerol, one or more of pentaerythritol.

  The method for introducing the sulfonic acid group into the polyester resin is not particularly limited. For example, 5-sulfoisophthalic acid, 4-sulfonaphthalene-2,7-dicarboxylic acid, 5 (4-sulfophenoxy) isophthalic acid And dicarboxylic acids such as 2-sulfo-1,4-butanediol, 2,5-dimethyl-3-sulfo-2,5-hexyldiol and the like as a polyester raw material.

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. When the sulfonic acid group is neutralized, 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, sulfonic acid metal bases neutralized with alkali metals such as Li, Na, and K are particularly preferable for improving adhesion to a base material and dispersibility of a coloring pigment having a hydrophobic surface. Acid Na base is most preferred.

  The amount of the dicarboxylic acid or glycol containing the sulfonic acid group is preferably 0.1 to 10 mol% based on the total polycarboxylic acid component or the total polyol component. If it is less than 0.1 mol%, the effect of improving adhesion may not be obtained. Moreover, when using an aqueous solvent, the solubility or dispersibility with respect to water falls, and also when using a colored pigment, the dispersibility of a colored pigment may fall and the designability may fall. If it exceeds 10 mol%, the corrosion resistance may decrease. Considering the balance of performance, it is more preferably in the range of 0.5 to 7 mol%.

  The method for introducing the bisphenol structure is not particularly limited. For example, an ethylene oxide adduct of bisphenol A, a propylene oxide adduct of bisphenol A, an ethylene oxide adduct of bisphenol F, a propylene oxide adduct of bisphenol F The method of using glycols, such as, as a polyester raw material is mentioned.

  It is preferable that the usage-amount of the glycol containing the said bisphenol structure contains 1-40 mol% with respect to all the polyol components. If it is less than 1 mol%, the effect of improving scratch resistance and corrosion resistance may not be obtained. If it exceeds 40 mol%, the processability may deteriorate. Considering the balance of performance, it is more preferably in the range of 5 to 30 mol%.

  In the embodiment of the present invention in which the organic resin (A) contains the polyester resin (Ae), it further includes a polyurethane resin (Au) containing a urea group in the structure, thereby improving corrosion resistance and scratch resistance. This is particularly preferable. In order to achieve both workability, scratch resistance, and corrosion resistance, both the elongation and strength of the coating film are excellent, and the adhesion to the metal plate (base treatment layer if there is a base treatment) is increased. It is important, however, that a polyurethane resin (Au) containing a urea group having a very high cohesive energy is used in combination with the polyester resin (Ae), so that both the elongation and strength are excellent. It is possible to design a coating film with excellent adhesion to the material.

  When the polyurethane resin (Au) is included in the coating film (α) together with the polyester resin (Ae), the total content of the polyester resin (Ae) and the polyurethane resin (Au) is the organic resin (A). It is preferable that it is 60-100 mass% in inside, More preferably, it is 80-100 mass%. If it is less than 60% by mass, the effect of improving workability, scratch resistance and corrosion resistance may not be obtained.

  Moreover, it is preferable that solid content mass ratio (Ae) / (Au) of the said polyester resin (Ae) and the said polyurethane resin (Au) is 50 / 50-90 / 10. If it is less than 50/50, the workability may be lowered, and if it exceeds 90/10, the effect of improving the corrosion resistance and scratch resistance may not be obtained.

  The polyurethane resin (Au) is not particularly limited as long as it contains a urea group in the structure. For example, the polyurethane resin (Au) is reacted with a polyol compound and a polyisocyanate compound and then further contains a chain extender containing an amino group. Examples thereof include those obtained by chain elongation.

  The polyol compound is not particularly limited as long as it is a compound containing two or more hydroxy groups per molecule. For example, polycarbonate polyol, polyester polyol, polyether polyol, polyesteramide polyol, acrylic polyol, polyurethane polyol, or A mixture thereof may be mentioned.

  The polyisocyanate compound is not particularly limited as long as it is a compound containing two or more isocyanate groups per molecule. For example, aliphatic isocyanate, alicyclic diisocyanate, aromatic diisocyanate, araliphatic diisocyanate, or those Of the mixture.

  The chain extender is not particularly limited as long as it is a compound containing one or more amino groups in the molecule. Ethylenediamine, propylenediamine, hexamethylenediamine, diethylenetriamine, dipropylenetriamine, triethylenetetramine, tetraethylenepenta Aliphatic polyamines such as min, aromatic polyamines such as tolylenediamine, xylylenediamine, diaminodiphenylmethane, alicyclic polyamines such as diaminocyclohexylmethane, piperazine, 2,5-dimethylpiperazine, isophoronediamine, hydrazine, Hydrazines such as succinic acid dihydrazide, adipic acid dihydrazide, phthalic acid dihydrazide, hydroxyethyldiethylenetriamine, 2-[(2-aminoethyl) amino] ethanol, 3-aminopropane Alkanolamines such as ol. These compounds can be used alone or in a mixture of two or more.

The organic resin (A) preferably further contains an acrylic resin. 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, the coating composition for forming the coating film (α) is water-based and further contains a coloring pigment (E) described later, and the coloring pigment is hydrophobic such as carbon black (E ₁ ) described later. In the case of a pigment having a surface, the effect of uniformly dispersing the pigment in the aqueous coating composition can be obtained by including an acrylic resin. For this reason, it is suitable to contain an acrylic resin also in order to disperse | distribute a color pigment uniformly to the formed said coating film ((alpha)), and to provide the outstanding designability.

  The acrylic resin is not particularly limited, and for example, ethylenic unsaturated such as methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, etc. A single carboxylic acid alkyl ester monomer 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; ethyl maleate, Monoester monomers of ethylenically unsaturated dicarboxylic acids such as butyl maleate, ethyl itaconate, butyl itaconate; (meth) acrylic acid-2-hydroxyethyl, (meth) acrylic acid-2-hydroxypropyl, (meta ) -4-hydroxybutyl acrylate, 2-hydroxyethyl (meth) acrylate and ε-caprola Hydroxyl group-containing ethylenically unsaturated carboxylic acid alkyl ester monomer such as a reaction product with Tn; ethylene such as aminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, butylaminoethyl (meth) acrylate Unsaturated carboxylic acid aminoalkyl ester monomers such as aminoethyl (meth) acrylamide, dimethylaminomethyl (meth) acrylamide, and ethylenically unsaturated carboxylic acid aminoalkylamide monomers such as methylaminopropyl (meth) acrylamide; acrylamide , Other amide group-containing ethylenically unsaturated carboxylic acid monomers such as methacrylamide, N-methylolacrylamide, methoxybutylacrylamide, diacetoneacrylamide; unsaturated fats such as glycidyl acrylate and glycidyl methacrylate Fatty acid glycidyl ester monomers; vinyl cyanide monomers such as (meth) acrylonitrile and α-chloroacrylonitrile; saturated aliphatic carboxylic acid vinyl ester monomers such as vinyl acetate and vinyl propionate; styrene, α- A styrene monomer such as methylstyrene or vinyltoluene may be used alone or in combination of two or more. The method for polymerizing these monomers is not particularly limited, and examples thereof include a method of 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.

  It is preferable that content of the said acrylic resin is 0.5-20 mass% in the said organic resin (A). If it is less than 0.5% by mass, the designability and scratch resistance may decrease, and if it exceeds 20% by mass, the corrosion resistance and workability may decrease.

The organic resin (A) is preferably a resin cured with a curing agent (B) in order to improve scratch resistance and corrosion resistance. The curing agent (B) is not particularly limited as long as it cures the organic resin (A), and examples thereof include a melamine resin (B1) and a polyisocyanate compound.
The melamine resin (B1) is a resin obtained by etherifying a part or all of methylol groups 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. Examples of the blocked product include a blocked product of hexamethylene diisocyanate, a blocked product of isophorone diisocyanate, a blocked product of xylylene diisocyanate, and a blocked product of tolylene diisocyanate, which are blocked products of the polyisocyanate compound. These curing agents may be used alone or in combination of two or more.

  It is preferable that content of the said hardening | curing agent (B) is 5-35 mass% with respect to 100 mass% of said organic resins (A). If it is less than 5% by mass, bake hardening may be insufficient, and corrosion resistance and scratch resistance may be reduced. If it exceeds 35% by mass, bake hardening will be excessive, and corrosion resistance and workability will be reduced. There is.

  From the viewpoint of scratch resistance, the curing agent (B) preferably contains a melamine resin (B1). It is preferable that content of a melamine resin (B1) is 30-100 mass% in the said hardening | curing agent (B). If it is less than 30% by mass, the effect of improving scratch resistance may not be obtained.

  When the curing agent (B) is used (especially when the curing agent (B) contains a melamine resin (B1)), a relatively high temperature of 150 ° C. or higher compared to the conventional water-based paint in order to cause a curing reaction thereof. It is necessary to heat-dry the coating film at the baking temperature to form a coating film. When the coating film is heated and dried at a baking temperature of 150 ° C. or more, the polyolefin resin particles easily flow out from the coating film, and the trace of the outflow becomes a pinhole, which may cause a decrease in corrosion resistance. In such a case, controlling the average particle diameter of the polyolefin resin particles (D) as described above, the thickness of the coating film, and the ratio thereof to a specific range suppresses a decrease in corrosion resistance. It is particularly effective.

  The coating film (α) containing the organic resin (A) as a film-forming component contains silica particles (C) and polyolefin resin particles (D), and the average particle diameter of the polyolefin resin particles (D) is determined. When a μm and the thickness of the coating film (α) are b μm, 0.5 ≦ a ≦ 3, 2 ≦ b ≦ 10, and 0.1 ≦ a / b ≦ 0.8 are satisfied, and the silica particles (C ) Contains both spherical silica particles (C1) having an average particle diameter of 5 to 50 nm and spherical silica particles (C2) having an average particle diameter of 0.3 to 5 μm is an essential requirement of the present invention. 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.

  The spherical silica particles (C1) which are fine particles having an average particle diameter of 5 to 50 nm have a large effect of improving the corrosion resistance, and the spherical silica particles (C2) which are relatively large particles having an average particle diameter of 0.3 to 5 μm are scratch resistant. Great effect to improve adhesion. When the coating film (α) contains particles having such different characteristics and different particle sizes at the same time, the corrosion resistance and scratch resistance of the coated metal plate are synergistically improved.

  The relatively large spherical silica particles (C2) having an average particle size of 0.3 to 5 μm also have the effect of degrading the gloss of the coated metal plate, so that even if the coating film (α) has some scratches, it is conspicuous. It also has the advantage of becoming difficult. In the case of a colored coating film further containing a color pigment (E) described later in the coating film (α), the effect is particularly great.

  When the average particle size of the spherical silica particles (C1) is less than 5 nm, the viewpoint of the stability of the particles in the coating composition (if lacking in stability, problems such as aggregation of particles and gelation of the coating composition) Therefore, if the average particle diameter exceeds 50 nm, the effect of improving the corrosion resistance is small. A more preferable range of the average particle diameter of the spherical silica particles (C1) is 8 to 30 nm. When the average particle diameter of the spherical silica particles (C2) is less than 0.3 μm, the effect of improving the scratch resistance of the coated metal plate is small, and when it exceeds 5 μm, workability and corrosion resistance are deteriorated. Moreover, the dispersion stability in a coating composition is also inferior (precipitation etc. arise). A more preferable range of the average particle diameter of the spherical silica particles (C2) is 0.5 to 3 μm.

  The kind of the spherical silica particles (C1) is not particularly limited, and examples thereof include silica particles such as colloidal silica and fumed silica. Examples of commercially available products include Snowtex O, Snowtex N, Snowtex C, Snowtex IPA-ST (Nissan Chemical Industry), Adelite AT-20N, AT-20A (Asahi Denka Kogyo), Aerosil 200 (Nippon Aerosil) Etc.

  The kind of the spherical silica particles (C2) is not particularly limited, and examples thereof include functional spherical silica HPS series (Toagosei), Nipsil series (Tosoh silica). Since the particle shape is spherical, scratch resistance and workability can be achieved at a high level.

  The content of the spherical silica particles (C1) is preferably 3 to 30% by mass, more preferably 5 to 20% by mass in the coating film (α). If it is less than 5% by mass, the effect of improving the corrosion resistance and scratch resistance may not be obtained, and if it exceeds 30% by mass, the corrosion resistance and workability may be deteriorated.

  The content of the spherical silica particles (C2) is preferably 3 to 20% by mass, more preferably 5 to 15% by mass in the coating film (α). If it is less than 3% by mass, the effect of improving scratch resistance may not be obtained, and if it exceeds 20% by mass, corrosion resistance and workability may be deteriorated.

  The total content of the spherical silica particles (C1) and the spherical silica particles (C2) is preferably 10 to 40% by mass, more preferably 10 to 30% by mass in the coating film (α). is there. If it is less than 10% by mass, the effect of improving the corrosion resistance and scratch resistance may not be obtained, and if it exceeds 40% by mass, the corrosion resistance and workability may be lowered. The content ratio of the spherical silica particles (C1) and the spherical silica particles (C2) in the coating film is preferably 30/70 to 80/20 in mass ratio. Moreover, it is preferable that ratio of the average particle diameter of the said spherical silica particle (C1) and the said spherical silica particle (C2) contained in the said coating film ((alpha)) is 1/350-1/16.

  When the average particle diameter of the spherical silica particles (C2) contained in the coating film (α) is c μm and the thickness of the coating film (α) is b μm, 0.1 ≦ c / b ≦ 0.7 is satisfied. It is preferable to do. If c / b is less than 0.1, the effect of improving scratch resistance may not be obtained, and if c / b is more than 0.7, corrosion resistance and workability may be deteriorated.

  The polyolefin resin particles (D) have an average particle size of 0.5 to 3 μm. When the average particle diameter is less than 0.5 μm, the effect of improving the scratch resistance may not be obtained, and when the average particle diameter is more than 3 μm, the corrosion resistance decreases.

  When the average particle diameter of the polyolefin resin particles (D) dispersed in the coating film (α) is a μm and the thickness of the coating film (α) is b μm, 0.1 ≦ a / b ≦ 0. It is necessary to satisfy 8. If a / b is less than 0.1, the effect of improving scratch resistance cannot be obtained. When a / b is more than 0.8, the corrosion resistance decreases.

  The content of the polyolefin resin particles (D) is preferably 0.5 to 15% by mass, more preferably 1 to 10% by mass in the coating film (α). If it is less than 0.5% by mass, the effect of improving scratch resistance may not be obtained, and if it exceeds 10% by mass, corrosion resistance and workability may be deteriorated.

  In the present invention, the polyolefin resin particles (D) preferably have a softening point of 125 ° C. or higher. By containing polyolefin resin particles (D) having a softening point of 125 ° C. or higher, when the coating film (α) is formed by heating and drying, the outflow of the polyolefin resin particles from the coating film becomes light. Generation of holes and outflow of polyolefin resin particles are suppressed, and corrosion resistance and scratch resistance are improved.

  As used herein, the “softening point” of polyolefin resin particles refers to the temperature at which heated polyolefin resin particles soften and begin to deform, and refers to the temperature measured by the method described in JIS K2207.

  Examples of the polyolefin resin particles (D) having a softening point of 125 ° C. or more include Chemipearl W900, W700, W300, W308, W800, W310 (above, softening point 132 ° C.), Chemipearl W100 (softening point) manufactured by Mitsui Chemicals. 128 ° C.), A-113 (softening point 126 ° C.), A-375, A-575, AB-50 (above, softening point 125 ° C.) manufactured by Gifu Seratech Manufacturing Co., Ltd., Hitech E-manufactured by Toho Chemical Industries, Ltd. Polyethylene resin particles such as 4A, E-4B, E-1000, E-6314 (softening point 138 ° C.), Chemipearl WP100 (softening point 148 ° C.) manufactured by Mitsui Chemicals, AC-35 manufactured by Gifu Seratech Manufacturing Co., Ltd. (Softening point 143 ° C), Hitec P-5043 (softening point 157 ° C), P-5300 (softening point 145 ° C) manufactured by Toho Chemical Industries, Ltd. It can be mentioned particles, not limited to these resin particles.

The polyolefin resin particles (D) are preferably high-density polyethylene resin particles (D1) having a density of 950 kg / m ³ or more and a penetration hardness of 2 or less. If the density of the polyolefin resin particles (D) is less than 950 kg / m ³ , corrosion resistance and scratch resistance may be deteriorated, which is not preferable. On the other hand, when the hardness of the polyolefin resin particles (D) exceeds 2, the corrosion resistance and scratch resistance may be lowered, which is not preferable. As used herein, the “density” of the polyolefin resin particles can be measured by the method described in JIS K6760, and the “penetration hardness” can be measured by the method described in JIS K2207.

The number average molecular weight of the polyolefin resin particles (D) is preferably in the range of 3000 to 6000. If the number average molecular weight of the polyolefin resin particles (D) is less than 3000, scratch resistance may be lowered, which is not preferable. Moreover, when the number average molecular weight of the said polyolefin resin particle (D) exceeds 6000, a scratch resistance may fall and it is unpreferable. The “number average molecular weight (Mn)” of the polyolefin resin particles used in the present specification can be measured by GPC (gel permeation chromatography). The GPC measurement apparatus uses Alliance 2000 (Waters), and TSKgel GMH ₆ -HT × 2 + TSKgel GMH ₆ -HTL × 2 (7.5 mm ID × 30 cm, Tosoh Corp., respectively) is used for the column. O-dichlorobenzene (Wako Pure Chemicals special grade reagent) was used. The measurement was performed under conditions of a column temperature of 140 ° C. and a mobile phase flow rate of 1.0 mL / min, and a differential refractometer was used for detection. Monodispersed polystyrene was used for molecular weight calibration.

  The coating film (α) preferably further contains at least one resin particle (F) selected from an acrylic resin and a silicone resin. Similar to the spherical silica particles (C2), the resin particles (F) have the effect of improving the scratch resistance and the effect of reducing the gloss of the coated metal plate and making it less noticeable even if there are some scratches.

  The type of the acrylic resin particles is not particularly limited. For example, crosslinked polymethyl methacrylate, crosslinked polybutyl methacrylate, non-crosslinked polymethyl methacrylate, non-crosslinked polybutyl methacrylate, polystyrene, polyalkyl acrylate, etc. Can be mentioned. In order to achieve both high scratch resistance and workability, crosslinked polymethyl methacrylate is particularly preferable.

  The type of the silicone resin particles is not particularly limited, and examples thereof include dimethylpolysiloxane and polyorganosilsesquioxane. Polyorganosilsesquioxane is particularly preferable for achieving both high scratch resistance and workability.

  The average particle diameter of the resin particles (F) is not particularly limited, but is preferably spherical particles having a flatness of 1 to 5 μm. When the average particle size is less than 1 μm, the effect of improving the scratch resistance of the coated metal plate may not be obtained, and when the average particle size exceeds 5 μm, the dispersion stability in the coating composition is ensured. It may be difficult to cause problems such as sedimentation and solidification of particles. In addition, workability may also be reduced.

  When the average particle diameter of the resin particles (F) contained in the coating film (α) is d μm and the thickness of the coating film (α) is b μm, 0.3 ≦ d / b ≦ 1.2 is satisfied. It is preferable. When d / b is less than 0.3, the effect of improving the scratch resistance of the coated metal sheet may not be obtained. When d / b is more than 1.2, the corrosion resistance and workability are deteriorated. There is.

  It is preferable that content of the said resin particle (F) is 0.5-15 mass% in the said coating film ((alpha)). If it is less than 0.5% by mass, the effect of improving the scratch resistance of the coated metal plate may not be obtained, and if it exceeds 15% by mass, the corrosion resistance and workability may be deteriorated. The more preferable content of the resin particles (F) is 1 to 10% by mass.

  The coating film (α) can further contain a color pigment (E). The type of the color pigment (E) is not particularly limited. Colored inorganic pigments such as titanium dioxide, carbon black, graphite, iron oxide, lead oxide, coal dust, talc, cadmium yellow, cadmium red, 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, dioxide Tan coated glass powder include a luminous material such as titanium dioxide coated alumina powder.

  When the coating film (α) is colored in a deep color or when an excellent design property is imparted with a thin film having a film thickness of 10 μm or less, it is preferable that the coloring pigment (E) contains carbon black. .

  The type of carbon black is not particularly limited, and known carbon blacks 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. The particle size of the carbon black to be used is not particularly limited as long as there is no problem in the dispersibility in the coating composition, the coating film quality, and the coating property. Is possible. Considering the design properties and corrosion resistance of the thin film, it is preferable to use fine carbon black having a primary particle diameter of 10 to 50 nm. When these carbon blacks are dispersed in an aqueous solvent, agglomeration occurs in the dispersion process, so that it is generally difficult to disperse with the primary particle size. That is, actually, it exists in the coating composition in the form of secondary particles having a particle size larger than the primary particle size, and also exists in the same form in the coating film (α) formed from the coating composition. . In order to ensure designability and corrosion resistance in the thin film, the particle size of the carbon black dispersed in the coating film (α) is important, and the average particle size is preferably 20 to 300 nm.

  When the content of the carbon black in the coating film (α) is e% by mass and the thickness of the coating film (α) is b μm, e ≦ 15, b ≦ 10, and e × b ≧ 20 are satisfied. Is preferred. In order to ensure designability (concealment), it is also important to ensure a certain amount or more of the absolute amount of carbon black contained in the coating film (α). The absolute amount of carbon black can be represented by the product of the carbon black content (e mass%) contained in the coating film and the coating film thickness (b μm). That is, when e × b is less than 20, designability (concealment) may be deteriorated. On the other hand, if e is more than 15, the film-forming property of the coating film is lowered, and the corrosion resistance and workability may be lowered.

  When the paint film (α) is colored in a pale color, it is preferable that the colored pigment (E) contains titanium dioxide. It is preferable that content in the said coating film ((alpha)) of the said titanium dioxide is 10-70 mass%. If it is less than 10% by mass, the designability (concealment) may be reduced, and if it exceeds 70% by mass, the workability and corrosion resistance may be reduced. Generally, when the coating film (α) contains the carbon black and is colored deeply, it is scratched more than when it is not colored or lightly colored. It has the feature of being easily noticeable. The titanium dioxide has the effect of raising the scratch resistance, and also has the effect of making the appearance close to light and making the scratches less noticeable. Therefore, in order to improve the scratch resistance while ensuring the design (concealment), workability, and corrosion resistance when coloring with a thin film having a film thickness of 10 μm or less, the carbon black is contained in the coating film (α). It is preferable to contain both the titanium dioxide and the titanium dioxide. In this case, the carbon black and the titanium dioxide are preferably contained in a mass ratio of 0.5 / 9.5 to 3/7.

  Generally, it may be difficult to specify the shape and size of particles contained in a thin coating film. Nonetheless, the particulate components contained in the coating composition used to form the coating film may undergo some physical or chemical change during the coating film formation process (for example, bonding or aggregation between particles, or coating solvent). As long as it does not suffer from significant dissolution of the resin, reaction with other components, etc., it can be considered that it retains its shape and size even when it is present in the paint even after the coating is formed. . At least selected from spherical silica particles (C1), spherical silica particles (C2), polyolefin resin particles (D), color pigments (E), and acrylic resins and silicone resins, which are particulate components that can be used in the present invention. One type of resin particle (F) is selected so that it does not significantly dissolve in the solvent of the coating composition used to form the coating film (β) and does not react with the solvent or other coating film components. In addition, for the purpose of enhancing the retention of the existence form of these particulate components in the coating material, a coating material obtained by dispersing the particulate component in a solvent with a known surfactant or a dispersing resin as necessary is used. It can also be used as a raw material for the composition. Therefore, the particle size of these particulate components contained in the coating film defined in the present invention is expressed by their particle size in the coating composition used for forming the coating film (α). Can do.

  Specifically, the spherical silica particles (C1), the spherical silica particles (C2), the polyolefin resin particles (D), the color pigment (E), and the acrylic resin, silicone, which are particulate components that can be used in the present invention. The particle size of at least one resin particle (F) selected from resins 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 coating 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 device 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 size by the dynamic light scattering method is described in detail, for example, in Journal of Chemical Physics (Vol. 57, No. 11 (December, 1972), page 4814. .

  In the coating film (α), at least one selected from spherical silica particles (C1), spherical silica particles (C2), polyolefin resin particles (D), color pigments (E), acrylic resins, and silicone resins. When at least one of the resin particles (F) is present as a particulate component, the coating film (α) can be observed from the cross section, and its shape and particle diameter can be directly measured. 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 coating film (α) is not particularly limited, but after embedding a coated metal plate perpendicular to the thickness direction of the coating film in a room temperature drying type epoxy resin and mechanically polishing the embedded surface, SEM (scanning) Using an electron microscope) or a FIB (focused ion beam) apparatus, cut out a sample for observation having a thickness of 50 nm to 100 nm from a painted metal plate so that the vertical cross section of the coating film can be seen, A method of observing the film with a TEM (transmission electron microscope) can be suitably used.

  It is preferable that the said coating film ((alpha)) of this invention is formed by apply | coating as an aqueous coating composition using an aqueous solvent, and heat-drying. Although there is no restriction | limiting in particular in the application | coating method of the said water-system coating composition, Well-known roll coat, spray coating, bar coating, immersion, electrostatic coating, etc. can be used suitably.

  Although the manufacturing method of the said water-system coating composition is not specifically limited, For example, the method of adding each coating-film ((alpha)) formation component in water, stirring with a disper, and melt | dissolving or disperse | distributing is mentioned. In order to improve the solubility or dispersibility of each coating film (α) forming component, a known hydrophilic solvent, for example, ethanol, isopropyl alcohol, t-butyl alcohol, propylene glycol, etc. Alcohols, cellosolves such as ethylene glycol monobutyl ether and 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.

  As described above, in the present invention, the coating film (α) comprises the organic resin (A) as a film-forming component, two specific types of spherical silica particles (C1, C2), and a polyolefin having a specific average particle size. It is characterized by containing resin particles (D).

  When the coating film (α) is flake silica (not spherical silica particles), it tends to be difficult to achieve both scratch resistance and workability.

Further, it is known that there is a term “ablation resistance” in relation to scratch resistance. The difference between "ablation resistance" and "scratch resistance" is not always clearly defined, but "ablation resistance" is generally used when a processed product is transported in a cardboard box. This refers to wear scars (scratches caused by repeated wear at a relatively low surface pressure) caused by rubbing the workpiece and cardboard with vibration. On the other hand, “scratch resistance” generally covers “all” with scratches that occur during handling, pressing, and transportation of steel sheets. Therefore, from such a viewpoint, “ablation resistance” is included in “scratch resistance”.
That is, even a coated steel sheet having “abrasion resistance” does not necessarily satisfy “scratch resistance”. For example, in the case where the above scaly silica is used, the effect of avoiding contact with the contacted object while the silica particles roll as in the case of spherical silica cannot be obtained as will be described later, and the frictional resistance is low. growing. For this reason, scaly silica is useful for ensuring abrasion resistance, but an effect on scratch resistance cannot be expected.

  According to the knowledge of the present inventors, the scratch resistance that has actually become a user-side problem is not a wear scar caused by corrugated cardboard, but a metal powder such as a burr powder generated from a steel plate, even if it occurs during transportation. Or scratches that occur when the mold surface becomes rough during pressing, and are not relatively soft materials such as corrugated cardboard, but scratches caused by rubbing against hard objects such as metal Met. Therefore, there is a need for an evaluation method that simulates “scratch resistance” under conditions that are more severe than the normally-known abrasion. Examples of such an evaluation method include steel used in the evaluation of the present application. An assessment of scratchability with wool can be used.

  In order to improve the scratch resistance as described above, it is important to avoid contact between an object to be contacted (burr powder, metal mold or the like) and the base metal, and to reduce the frictional resistance even if contacted. In particular, if the contacted object is hard, contact can be suppressed by the presence of hard particles in the coating film. However, the hard particles themselves may become an abrasive and may damage the base metal, and it is necessary to devise the shape to prevent the hard particles. Since it is spherical (silica particles), the contact can be suppressed while rolling, so that the frictional resistance with the base metal can be suppressed, which is very effective. On the other hand, in the case of scaly (silica particles), since the contact area with the coating film in the coating film is large and trapped in the coating film, it may not move easily and may act as an abrasive. It is unsuitable because it is expensive.

  In the present invention, it is also important to improve the scratch resistance while not reducing the workability, which is the opposite performance. If hard particles are added to the coating film in order to improve the scratch resistance, the coating film becomes hard and the workability may be reduced. In particular, if the particle shape is scaly, it exists in a layered manner in the coating film, so that the workability tends to be greatly reduced (when the base metal is stretched, the coating film is likely to crack). On the other hand, if the shape is spherical (silica particles), it is possible to suppress a decrease in workability to a minimum.

  In the present invention, extremely high scratch resistance can be obtained by suppressing contact with the base metal with hard and relatively large spherical particles and reducing frictional resistance with polyolefin resin particles that are soft and have low polarity. In particular, when the material to be contacted is hard, polyolefin resin particles that are soft and have a small polarity are effective.

  In the present invention, the above-described spherical silica and polyolefin resin particles are mixed to produce a remarkable effect in improving the scratch resistance. According to the knowledge of the present inventor, the combined use of spherical silica and polyolefin resin particles prevents, for example, the head of spherical silica on the coating from preventing steel wool from damaging the coating, and the polyolefin resin particles from steel wool. It is estimated that it can be slippery. Furthermore, it is conceivable that the polyolefin resin adhered to the steel wool in a small amount can easily roll the spherical silica by using the polyolefin resin particles and the spherical silica in combination. In addition, the sulfonic acid group contained in the polyester resin is also considered to promote the rolling of the spherical silica.

  In the present invention, as described above, the polyester resin that is the film forming component (matrix component) of the coating film has a relatively high polarity (for example, a mode in which a sulfonic acid group is included). The polyolefin resin particles having a low particle size tend to be oriented on the surface of the coating film in the formation stage of the coating film due to the difference in surface free energy. Orientation of the polyolefin resin on the surface of the coating film is effective in reducing the frictional resistance with the object to be contacted, and the scratch resistance can be improved.

  As described above, in order to ensure the corrosion resistance of the chromate-free coated metal plate, it is necessary to avoid the polyolefin particles from coming into contact with the surface of the base metal plate which is the base material. It is necessary that the polyolefin resin particles appear from the surface of the coating film of a mixture of the film forming component (matrix component) of the coating film and the polyethylene resin particles. For this purpose, the present inventors have found that it is preferable to “pull” the polyolefin resin particles from the base metal plate as the base material at the stage of the coating film before drying. Thus, the above-described difference in surface free energy can be suitably used as one of means for “pulling away” the polyolefin resin particles from the base metal plate as the base material.

  There is no particular limitation on the baking and drying method of the coating composition for forming the coating film (α) of the present invention. The metal plate is heated in advance, the metal plate is heated after application, or a combination thereof. Drying may be performed. 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 baking drying temperature is preferably 150 ° C. to 250 ° C., more preferably 170 ° C. to 240 ° C., and most preferably 180 ° C. to 230 ° C. as the ultimate plate temperature of the metal plate. When the ultimate temperature is less than 150 ° C., the bake hardening is insufficient, and the workability, corrosion resistance, and scratch resistance may be lowered, and when it exceeds 250 ° C., the coating film of the polyolefin resin particles (D). The outflow from (α) increases, and the corrosion resistance and scratch resistance may decrease, or the coating film (α) may be excessively baked and hardened to decrease the corrosion resistance and workability. The baking and drying time is preferably 2.5 to 20 seconds, and more preferably 3 to 15 seconds. If it is less than 2.5 seconds, the bake hardening is insufficient, and the corrosion resistance and scratch resistance may be lowered. If it exceeds 20 seconds, the productivity may be lowered. In the case of heating for a short time of 20 seconds or less, if polyolefin resin particles having a low softening point are used, the polyolefin resin particles easily flow out of the coating film when the coating film is heated and dried, resulting in a significant decrease in corrosion resistance and scratch resistance. On the other hand, when the polyolefin resin particle (D) having a softening point of 125 ° C. or higher, which is one embodiment of the present invention, is applied, the deterioration in corrosion resistance and scratch resistance is reduced even by heating for a short time.

  After the baking and drying step, a cooling step may be further continued as necessary. The cooling method is not particularly limited, but a water cooling method is preferable. When there is a cooling process, especially a rapid cooling process such as water cooling, after the baking and drying process, if polyolefin resin particles with a low softening point are used, the polyolefin resin particles will easily flow out of the coating film during cooling, resulting in corrosion resistance and scratch resistance. In contrast, when the polyolefin resin particles (D) having a softening point of 125 ° C. or higher, which is one embodiment of the present invention, is applied, the corrosion resistance and scratch resistance are improved even when there is a cooling step. The decline is reduced.

Considering the softening point of the polyolefin resin particles (D) used in the present invention, the temperature of the heat-dried metal plate and the temperature of the water-cooled water in the cooling step are set to T _S ° C. , a plate temperature of the metal plate during water cooling _{T M} ° C., the water temperature of the water-cooled water when the _{T W ℃, T M> T} S, T W ≧ (T M -150) / 4 to satisfy the Is preferred. When the plate temperature of the metal plate at the time of water cooling is higher than the softening point of the polyolefin resin particles (D), the polyolefin resin particles (D) are softened and are likely to flow out of the coating film (α). In addition, the higher the plate temperature of the metal plate and the lower the temperature of the water-cooled water (the more rapid the cooling), the easier the polyolefin resin particles (D) to flow out from the coating film (α), and the corrosion resistance and scratch resistance. Is prone to decline. That is, when the plate temperature of the metal plate is high, setting the temperature of water-cooled water accordingly can suppress the outflow of the polyolefin resin particles (D) from the coating film (α), and the corrosion resistance and It is possible to minimize a decrease in scratch resistance. More specifically, it is preferable to control the temperature of the water-cooled water so that T _W ≧ (T _M −150) / 4 is satisfied.

  In this invention, it is preferable to have a base-treatment layer ((beta)) in the lower layer of the said coating film ((alpha)). Although the said base treatment layer ((beta)) is not specifically limited, By providing the base treatment layer ((beta)) containing at least 1 sort (s) chosen from a silane coupling agent, organic resin, and a polyphenol compound, a base metal plate and The adhesion can be further improved, and the corrosion resistance can be further improved. Moreover, by providing the base treatment layer (β) containing all of the silane coupling agent, the organic resin, and the polyphenol compound, the adhesion to the base metal plate can be particularly enhanced, and the corrosion resistance can be particularly enhanced.

  The silane coupling agent contained in the base coating layer (β) is not particularly limited. For example, from 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-glycyl Sidoxypropi Methyldiethoxysilane, 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. Can be mentioned. The said silane coupling agent may be used independently and may use 2 or more types together.

The organic resin contained in the said base treatment layer ((beta)) is not specifically limited, For example, well-known organic resins, such as a polyester resin, a polyurethane resin, an epoxy resin, a phenol resin, an acrylic resin, a polyolefin resin, can be used. In order to further improve the adhesion to the base metal plate, it is preferable to use at least one of a polyester resin, a polyurethane resin, an epoxy resin, and a phenol resin, and the polyester resin contained in the black coating film (α) In order to increase the compatibility with (A ₁ ) and increase the adhesion, it is particularly preferable that the base treatment layer (β) contains a polyester resin.

  The polyphenol compound contained in the base treatment layer (β) refers to a compound having two or more phenolic hydroxyl groups bonded to a benzene ring, or a condensate thereof. 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 a large number of phenolic hydroxyl groups widely distributed in the plant kingdom. The tannic acid 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, algarobilatannin, valonia tannin, catechin tannin, and the like. . Examples of the tannic acid include commercially available ones such as “tannic acid extract A”, “B tannic acid”, “N tannic acid”, “industrial tannic acid”, “purified tannic acid”, “Hi tannic acid”, "F tannic acid", "local 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.

  The said polyphenol compound may be used by 1 type, and may use 2 or more types together.

  Although content of at least 1 sort (s) chosen from the silane coupling agent, organic resin, and polyphenol compound contained in the said base treatment layer ((beta)) is not specifically limited, It contains 10 mass% or more in 100 mass% of base treatment layers. Is preferred. If it is less than 10% by mass, the content may be small and the effect of improving adhesion and corrosion resistance may not be obtained.

Although the adhesion amount of the said base treatment layer ((beta)) is not specifically limited, It is preferable to exist in the range of 10-1000 mg / m < ² >. When the amount is 10 mg / m ² or less, the effect of the sufficient 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 adhesion may be lowered. From the stable effect and economical efficiency, a more preferable adhesion amount range is 50 to 500 mg / m ² .

  Although there is no restriction | limiting in particular in the formation method of the said base treatment layer ((beta)), The coating agent for forming a base treatment layer ((beta)) is apply | coated to at least one side of a metal plate, and it heat-drys and forms. Although 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 the baking drying method, A metal plate may be heated previously, a metal plate may be heated after application | coating, or you may dry 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. About baking baking temperature, it is preferable that it is 60 to 150 degreeC by the ultimate temperature, and it is still more preferable that it is 70 to 130 degreeC. If the ultimate temperature is less than 60 ° C, drying may be insufficient, and adhesion and corrosion resistance with the substrate may be reduced, and if it exceeds 150 ° C, adhesion with the substrate may be reduced. .

  The metal plate applicable in the present invention is not particularly limited, and examples thereof include iron, iron-base alloy, aluminum, aluminum-base alloy, copper, copper-base alloy, and the like, and optionally plated on the metal plate. A plated metal plate 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-coated steel sheets include galvanized steel sheets, zinc-nickel plated steel sheets, zinc-iron plated steel sheets, zinc-chromium plated steel sheets, zinc-aluminum plated steel sheets, zinc-titanium plated steel sheets, zinc-magnesium plated steel sheets, zinc-manganese. Galvanized steel sheets such as plated steel sheets, zinc-aluminum-magnesium plated steel sheets, zinc-aluminum-magnesium-silicon-plated steel sheets, and cobalt, molybdenum, tungsten, nickel as a small amount 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-based plated steel sheet include aluminum or an alloy composed 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, and an aluminum-silicon-magnesium plated steel sheet. .

  Furthermore, the present invention can also be applied to multilayer plating in combination with the above plating and other types of plating such as iron plating, iron-phosphorus plating, nickel plating, cobalt plating and the like. 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, and a vacuum plating method may be used.

  Examples of the present invention will be described below. However, the present invention is not limited to these 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 (solid content). (Mass%), and it adjusted by stirring using the disperser for coating materials. The coating agent is applied to the surface of the metal plate prepared in (1) above 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. Base treatment layers (β1 to β9) were formed.

(3) Coating film The coating composition for forming the coating film is composed of an organic resin (A) (the following Production Examples 1 to 5 and Table 6), a curing agent (B) (Table 7), a silica particle (C) ( Table 12), polyolefin resin particles (D) (Table 9), colored pigments (E) (Table 10), at least one resin particle (F) (Table 11) selected from acrylic resins and silicone resins It mix | blended with the compounding quantity (solid content mass%) shown in Table 22, and it adjusted by stirring using the disperser for coating materials. The coating composition is applied to the upper layer of the base treatment layer formed in (2) above (the metal plate prepared in (1) if there is no base treatment layer) with a roll coater so as to have a predetermined film thickness. The film was heated and dried at a predetermined reaching plate baking temperature to form a coating film.

<Organic resin production example 1>
In a reaction vessel equipped with a stirrer, condenser and thermometer, 199 parts of terephthalic acid, 232 parts of isophthalic acid, 199 parts of adipic acid, 33 parts of 5-sodium sulfoisophthalic acid, 312 parts of 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 performed 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, followed by filtration through a 200 mesh nylon mesh to obtain a polyester resin aqueous dispersion (A1) having a solid content concentration of 30%.

<Organic resin production example 2>
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 Water dispersion was performed with exchange water. 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 (A2) having a solid content concentration of 30%.

<Organic resin production example 3>
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 -Propanediol 125 parts, 1,5-pentanediol 187 parts, bisphenol A ethylene oxide adduct 62 parts, tetrabutyl titanate 0.41 part were charged, and esterification was performed 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, followed by filtration with a 200 mesh nylon mesh to obtain a polyester resin aqueous dispersion (A3) having a solid content concentration of 30%.

<Organic resin production example 4>
230 parts of an average molecular weight 900 polyester polyol synthesized from adipic acid having a hydroxyl group at the terminal and 1,4-butylene glycol, 15 parts of 2,2-bis (hydroxymethyl) propionic acid and 100 parts of N-methyl 2-pyrrolidone And dissolved by heating to 80 ° C. Thereafter, 100 parts of hexamethylene diisocyanate was added, heated to 110 ° C. and reacted for 2 hours, and 11 parts of triethylamine was added for neutralization. This solution was dropped into an aqueous solution in which 5 parts of ethylenediamine and 570 parts of ion-exchanged water were mixed under strong stirring to obtain a polyurethane resin aqueous dispersion (A4) having a solid content concentration of 30%.

<Organic resin production example 5>
80 parts of a polyester polyol having an average molecular weight of 900 synthesized from adipic acid having a hydroxyl group at the terminal and 1,4-butylene glycol, 120 parts of a 3-mol adduct of bisphenol A propylene oxide having an average molecular weight of 700, and 2,2-bis ( 12 parts of hydroxymethyl) propionic acid was added to 100 parts of N-methyl 2-pyrrolidone and heated to 80 ° C. to dissolve. Thereafter, 100 parts of hexamethylene diisocyanate was added, heated to 110 ° C. and reacted for 2 hours, and 11 parts of triethylamine was added for neutralization. This solution was dropped into an aqueous solution in which 5 parts of ethylenediamine and 570 parts of ion-exchanged water were mixed under strong stirring to obtain a polyurethane resin (A5) having a solid content concentration of 30%.

(4) Painted metal plate Coating film composition and coating film thickness of coating metal plate prepared in the above (1) to (3), reaching plate temperature, heating and drying time, cooling method (after heating and drying, immediately submerged in water Table 12 to Table 22 show the temperature of water-cooled water at the time of water cooling. Further, when the softening point of the polyolefin resin particles (D) is T _S ° C, the plate temperature of the metal plate during water cooling is T _M ° C, and the water temperature of the water-cooled water is T _W ° C, T _M > T _S Or whether T _W ≧ (T _M −150) / 4 is satisfied (denoted as feasibility) is also shown in Tables 12 to 22 (denoted as “good” and “x” when not satisfied). .

  The average particle size of at least one resin particle (F) selected from silica particles (C), polyolefin resin particles (D), color pigments (E), acrylic resins, and silicone resins contained in the coating film is shown in Tables 12 to 12. It shows in Table 22. These average particle diameters are for observation with a thickness of 50 to 100 nm using a FIB (focused ion beam) apparatus so that the vertical cross section of the coating film can be seen from the painted metal plate prepared in (1) to (3) above. The sample was cut out, the cross section of arbitrary 10 places of a coating film was observed with TEM (transmission electron microscope), the particle diameter of 20 places was measured arbitrarily, and it calculated | required from the average value. When observing particles of 1 μm or more, the particle size of a particle having a width of 20 μm is used. When observing particles of 100 nm or more and less than 1 μm, the particle size of a particle having a width of 5 μm is used. The particle diameter of particles entering 1 μm was measured. When the particles were not spherical, the short and long diameters of the particles were measured, and the average value was taken as the particle diameter.

  In addition, the spherical particle (C2) having an average particle size of 0.3 to 5 μm among the average particle size (a μm) of the polyolefin resin particles (D), the film thickness (b μm) of the coating film, and the silica particles (C). A / b, c / b, d determined from the average particle diameter (c μm) of the corresponding silica particles and the average particle diameter (d μm) of at least one resin particle (F) selected from the acrylic resin and silicone resin. The values of / b are also shown in Tables 12 to 22.

(5) Evaluation test About the coating metal plate (test plate) obtained by said (4), workability, corrosion resistance, and damage resistance were evaluated by the evaluation method and evaluation criteria shown below. The evaluation results are shown in Table 23 to Table 29.

(Processability)
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 film has no defects such as cracks and has a uniform appearance. When the coating film is colored, it has a uniform colored appearance and no color fading is observed.
4: Although a very slight crack is recognized in the coating film, it has a substantially uniform appearance. When the coating is colored, a slight color fading is observed, but the appearance is almost uniform. (The level that you can manage by arranging the test plates before the test side by side).
3: Since a slight crack is recognized in the coating film, it has a slightly non-uniform appearance. When the coating is colored, a slight color fading is observed, but the appearance is almost uniform. (The level that can be easily understood by arranging the test plates before the test side by side).
2: Cracks are observed in the coating film, and the appearance is uneven. When the coating is colored, 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 the appearance was uneven. When the coating is colored, the color fading is significant (a level that can be easily seen by looking at only the test plate).

(Corrosion resistance)
After tape-sealing the end face of the test plate, a salt spray test (SST) based on JIS Z2371 was performed for 120 hours, and the rust generation state was observed and evaluated according to the following evaluation criteria.
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 5% or more.

(Scratch resistance)
After the test plate was placed on a rubbing tester, the steel wool (# 0000) was rubbed 10 times with a load of 49.03 kPa (0.5 kgf / cm ² ) and 196.12 kPa (2.0 kgf / cm ² ), and the coating state Was evaluated according to the following evaluation criteria.
5: The scratched surface is not scratched at all.
4: Scratches are slightly scratched on the rubbing surface (a level at which the rubbing marks can be discriminated with some attention).
3: Scratches are slightly scratched on the rubbing surface (a level at which the rubbing marks can be easily discerned when the eyes are closed).
2: Clear scratches on the rubbing surface (a level at which rubbing traces can be identified instantaneously).
1: The base metal plate of the rubbing surface is exposed.

  The Examples of the present invention showed excellent workability, corrosion resistance, and scratch resistance with a score of 3 or more in any evaluation test. In addition, the Example which added the said resin particle (F) had the streak pattern on the appearance a little. The larger the particle size, the more noticeable the streaks. In addition, precipitates were generated in the coating compositions used in Examples 42, 144, 145, 224, and 225. That is, when the resin particles (F) are made of relatively large spherical acrylic resin particles having a particle diameter of 8 μm and 10 μm, the resin particles are settled, and the dispersion stability of the resin particles is higher than that of other coating compositions. It was inferior.

  On the other hand, Comparative Examples 1-42 which were outside the scope of the present invention had a score of 2 or less in at least one item of workability, corrosion resistance, and scratch resistance. In addition, the levels in which the spherical silica particles (C2) of Examples 7 and 105 were replaced with spherical alumina particles (SO-E3 manufactured by Admatechs Co., Ltd., particle diameter: 1 μm) were all aggregated in the coating composition, and the coating material A precipitate was generated in the composition, and the coating appearance was also a dot-like appearance, and the corrosion resistance and scratch resistance were inferior to 2 points. The organic resin (A) of Examples 7 and 105 was charged with the butyl cellosolve and methyl ethyl ketone of the organic resin production example 1 and stirred and dissolved at 80 ° C. for 2 hours (the solvent before being dispersed in water remained as an organic solvent) ), The coating composition was solidified and could not be applied.

  As mentioned above, although preferred embodiment of this invention was described, it cannot be overemphasized that this invention is not limited to this example. 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.

Claims (15)

A chromate-free coated metal plate having a coating film (α) comprising an organic resin (A) as a film-forming component, silica particles (C), and polyolefin resin particles (D) on at least one surface of the metal plate,
When the average particle diameter of the polyolefin resin particles (D) is a μm and the thickness of the coating film (α) is b μm, 0.5 ≦ a ≦ 3, 2 ≦ b ≦ 10, 0.1 ≦ a / b ≦ 0.8 satisfied,
Chromate-free, characterized in that the silica particles (C) contain both spherical silica particles (C1) having an average particle size of 5 to 50 nm and spherical silica particles (C2) having an average particle size of 0.3 to 5 μm. Painted metal plate.   The chromate-free painted metal sheet according to claim 1, wherein the organic resin (A) contains a polyester resin (Ae) containing a sulfonic acid group in the structure.   The chromate-free painted metal plate according to claim 2, wherein the organic resin (A) further contains a polyurethane resin (Au) containing a urea group in the structure.   The chromate-free painted metal sheet according to claim 1 or 2, wherein the coating film (α) further contains a color pigment (E).   The chromate-free painted metal sheet according to claim 1 or 2, wherein the polyolefin resin particles (D) have a softening point of 125 ° C or higher. The polyolefin resin particles (D) are high density polyethylene resin particles (Dl) having a density of 950 kg / m ³ or more and a penetration hardness of 2 or less. Chromate-free painted metal plate as described in 1.   The chromate-free painted metal plate according to claim 1 or 2, wherein the polyolefin resin particles (D) have an average molecular weight of 3000 to 6000.   The chromate-free painted metal sheet according to claim 1 or 2, wherein the content of the polyolefin resin particles (D) in the coating film (α) is 0.5 to 10% by mass.   When the average particle diameter of the spherical silica particles (C2) is c μm and the thickness of the coating film (α) is b μm, 0.1 ≦ c / b ≦ 0.7 is satisfied. The chromate-free painted metal plate according to 1 or 2.   The chromate-free painted metal sheet according to claim 1 or 2, wherein the organic resin (A) is a resin cured by a curing agent (B).   The chromate-free painted metal sheet according to claim 10, wherein the curing agent (B) contains a melamine resin (Bl).   The said coating film ((alpha)) of Claim 1 or 2 forms by apply | coating the water-based coating composition (X) containing the structural component of the said coating film ((alpha)) to the at least single side | surface of a metal plate, and heat-drying. This is a chromate-free painted metal plate. The temperature at the time of heating and drying of the water-based coating composition (X) is in the range of 150 to 250 ° C. as the ultimate temperature of the metal plate, and the heating and drying time is in the range of 2.5 to 20 seconds. that, chromate-free coated metal sheet according to claim 1 2. After the water-based coating composition (X) is heated and dried, there is a further water cooling step. The polyolefin resin particles (D) have a softening point T _S ° C, the metal plate temperature during water cooling is T _M ° C, and water-cooled water. the water temperature is taken as _{T W ℃, T M> T} S, and satisfies the _{T W ≧ (T M -150)} / 4, chromate-free coated metal sheet according to claim 1 2 . A water-based paint composition (X) containing an organic resin (A), silica particles (C), and polyolefin resin particles (D),
The polyolefin resin particles (D) have an average particle size of 0.5 to 3 μm,
The silica paint (C) contains both spherical silica particles (C1) having an average particle diameter of 5 to 50 nm and spherical silica particles (C2) having an average particle diameter of 0.3 to 5 μm. Composition (X).

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