JP2012126131A - Chromate-free coating plated steel sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive chromate-free coating plated steel sheet, which does not contain hexavalent chromium high in environment load property and is remarkably excellent in designability (tinting and hiding power including a processing section), moisture resistance, corrosion resistance, processabilities, scratch resistance, chemical resistance, etc.SOLUTION: The chromate-free coating plated steel sheet includes A coated film (α) containing a film-forming component consisting of an organic resin (A) and a silica particle (B) formed on at least one surface of a Zn-based alloy plated steel sheet containing at least 0.01-1 mass% of one kind selected from Ni and Co, in the plated layer, and the organic resin (A) contains a polyester resin (A1) including a sulfonic acid group, as an essential component.

Description

  The present invention is a low-cost design that is excellent in workability, corrosion resistance, scratch resistance, etc., in which a coating film (α) that does not contain hexavalent chromium having high environmental impact is formed on at least one surface of a Zn-based alloy-plated steel sheet. It is related with a chromate-free painted steel sheet.

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

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

  The coating used for these precoated steel sheets is thick with a coating 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, these colored steel sheets are designed to ensure corrosion resistance by providing a chromate-treated film, and thus cannot meet the recent needs for non-chromation. In addition, since it 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 is relatively thin with a thickness of 10 μm or less, and is a non-chrome specification. However, a solvent-based paint is used as the paint for forming the clear coating. is required. In addition, although it is excellent in designability and workability, it has a problem that the scratch resistance is not sufficient.

  Improvement of the corrosion resistance and scratch resistance of the coated metal plate has been studied from the viewpoint of improving the plating on the metal plate of the substrate. In Patent Document 8, an organic resin film having a thickness of 0.01 to 3 μm is formed on an upper layer of a zinc-based alloy-plated steel sheet having a micro Vickers hardness of 80 or more on the surface of the plating layer in order to improve scratch resistance and corrosion resistance. A surface-treated steel sheet is disclosed. In order to achieve a Vickers hardness of 80 or more, a Zn-Ni alloy plated steel sheet containing 9 to 15 mass% of Ni in the plating layer has been proposed. However, this surface-treated steel sheet is excellent in scratch resistance and corrosion resistance, but because it is not designed in consideration of designability and workability, it is said that designability and workability are not sufficient for use in design applications. Had problems.

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 JP 2005-89848 A

  In view of the present situation, an object of the present invention is to provide an inexpensive design chromate-free coated plated steel 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 order to improve various performances such as workability, scratch resistance, corrosion resistance, etc. required for coated Zn-plated steel sheets, approaches have been made mainly from improving the performance of the coating film coated on the upper layer. . However, workability, scratch resistance, and corrosion resistance are generally technically contradictory performances, and it has been difficult to achieve both of these performances at a high level by examining only the upper coating film. Accordingly, the present inventors have also paid attention to a Zn plating layer as a base, and a Zn-based alloy containing at least one selected from Ni and Co in the Zn plating layer in a trace amount compared to the conventional addition amount. By using a plating layer, it was found that workability, scratch resistance, and corrosion resistance, which could not be achieved by studying only the upper coating film, can be achieved at a high level.

  When at least one selected from Ni and Co is contained in the underlying Zn plating layer, the hardness of the plating layer increases as the content increases, and the scratch resistance of the plating layer improves. Particularly in the region where the film thickness of the coating film of 10 μm or less is thin, it is easily affected by the hardness of the surface of the underlying plating layer, and the effect of improving the scratch resistance by increasing the hardness of the surface of the plating layer becomes remarkable. Specifically, a significant scratch resistance improvement effect can be obtained by making the underlying plating layer a Zn-based alloy plating containing 0.01% by mass or more of at least one selected from Ni and Co. understood. Although the effect of improving the scratch resistance of the plating layer itself is not significant by itself in an extremely small amount of 0.01% by mass which is the lower limit of the alloying element content, a polyester containing a sulfonic acid group in the upper layer is not significant. By providing a paint film with an organic resin as an essential component as a film-forming component, good adhesion to the underlying plating layer, appropriate lubricity, etc. are imparted, and silica particles are added to the paint film. Addition improves the scratch resistance of the paint film, and significant damage resistance is achieved by synergistic effects such as increasing the hardness of the plating layer and providing adhesion, lubricity, and improvement of the paint film's scratch resistance. It is presumed that the addictive effect was obtained.

  On the other hand, as the hardness of the underlying plating layer increases, the plating layer tends to become brittle. If the hardness of the plating layer is too high, the workability is extremely lowered. It has been found that if the content of at least one selected from Ni and Co in the underlying Zn-based alloy plating layer is suppressed to 1.0% by mass or less, workability is not greatly adversely affected. By providing an upper layer with a coating film having an organic resin as an essential component of a polyester resin having an excellent balance between elongation and strength, an effect of compensating for a decrease in workability due to cracking of the plating layer is obtained. It is estimated that the upper limit of the alloy element content can be raised to 1.0% by mass.

  In addition, at least one selected from Ni and Co contained in the underlying Zn-based alloy plating layer has an effect of improving corrosion resistance more than expected, and an extremely small amount region of 0.01% by mass which is the lower limit concentration of the content However, it was found that a significant effect of improving corrosion resistance was obtained. This is due to the fact that Zn-based alloy plating containing at least one selected from Ni and Co has a higher effect of stably holding the initial corrosion product than Zn plating, and a very small amount of Ni and Co. In addition to the Zn-based alloy plating layer to which is added, an organic resin containing a polyester resin as an essential component is used as a film-forming component, and a coating film containing silica particles is further used in a synergistic manner to cause initial corrosion. It is presumed that the retention of sex organisms has increased. In particular, in a region where the film thickness of the coating film of 10 μm or less is thin, it is easily affected by the corrosion resistance of the base plating layer, and the effect of improving the corrosion resistance by the base plating layer becomes remarkable.

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

(1) A film-forming component composed of an organic resin (A) on at least one surface of a Zn-based alloy-plated steel sheet containing 0.01 to 1% by mass of at least one selected from Ni and Co in the plating layer, and silica A chromate-free coated plated steel sheet in which a coating film (α) comprising particles (B) is formed,
The said organic resin (A) contains the polyester resin (A1) containing a sulfonic acid group as an essential component, The chromate free coating plated steel plate characterized by the above-mentioned.

  (2) The chromate-free coated plated steel sheet according to (1), wherein the coating film (α) has a thickness of 2 to 10 μm.

  (3) The chromate-free painted steel sheet according to (1) or (2), wherein the organic resin (A) is a resin cured with a curing agent (C).

  (4) The silica particles (B) contain spherical silica particles (B1) having an average particle diameter of 5 to 50 nm and spherical silica particles (B2) having an average particle diameter of 0.3 to 5 μm, The chromate-free painted steel sheet according to any one of (1) to (3).

  (5) In any one of (1) to (4), the coating film (α) further contains at least one resin particle (D) selected from an acrylic resin and a silicone resin. The chromate-free painted steel sheet described.

  (6) The chromate-free coated plated steel sheet according to (5), wherein the resin particles (D) have an average particle diameter of 1 to 5 μm.

  (7) The chromate-free coated plated steel sheet according to any one of (1) to (6), wherein the coating film (α) further contains a color pigment (E).

  (8) The chromate-free coated plated steel sheet according to (7), wherein the color pigment (E) contains carbon black (E1).

  (9) The chromate-free painted steel sheet according to (7) or (8), wherein the color pigment (E) contains titanium dioxide (E2).

(10) The chromate-free painted steel sheet according to any one of (1) to (9), wherein the polyester resin (A1) further contains a bisphenol group in the structure.
(11) The chromate-free coated plated steel sheet according to any one of (1) to (10), wherein the organic resin (A) further includes a polyurethane resin (A2) containing a urea group. .

  (12) The chromate-free coated plated steel sheet according to any one of (1) to (11), wherein the coating film (α) further contains polyethylene resin particles (F).

  (13) The chromate-free coated plated steel sheet according to (12), wherein the polyethylene resin particles (F) have an average particle diameter of 0.5 to 3 μm.

  (14) The chromate-free coated plated steel sheet according to any one of (1) to (13), wherein a base treatment layer (β) is provided below the coating film (α).

  (15) The chromate, wherein the coating film (α) according to any one of (1) to (14) is formed by coating with an aqueous solvent and drying by heating. Free painted steel sheet.

  The designable chromate-free coated steel sheet 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.

  The chromate-free coated plated steel sheet of the present invention is formed from an organic resin (A) on at least one surface of a Zn-based alloy plated steel sheet containing 0.01 to 1% by mass of at least one selected from Ni and Co in the plating layer. A coating film (α) containing the film-forming component and the silica particles (B) is formed, and the organic resin (A) contains a polyester resin (A1) containing a sulfonic acid group as an essential component. It is characterized by that.

  The chromate-free painted steel sheet of the present invention is a coated steel sheet based on a Zn-based alloy plated steel sheet. Compared to the case where Zn plating is used for the plating layer, when using a Zn-based alloy plating layer containing at least one selected from Ni and Co in an extremely small amount of 0.01 to 1% by mass, corrosion resistance and scratch resistance Is significantly improved. Regarding the improvement of scratch resistance, as described above, it is due to the effect that the hardness of the plating layer is significantly improved by containing at least one of Ni and Co in an extremely small amount of 0.01 to 1% by mass. Conceivable. In addition, regarding the improvement of corrosion resistance, even in the addition range of 0.01 to 1% by mass, Zn-based alloy plating containing at least one kind of Ni and Co holds the initial corrosion product more stably. It is thought that it contributes that the effect to do is high.

  Furthermore, an organic resin containing a polyester resin containing a sulfonic acid group as an essential component is formed on the Zn-based alloy plating layer containing a trace amount of at least one selected from Ni and Co, and includes silica particles. These effects are remarkably improved by coating with the coating film (α). As for corrosion resistance, the sulfonic acid group contained in the polyester resin is chemically bonded to the surface of the plating layer, suppressing the formation of plating corrosion products, and the initial plating corrosion generation of the aforementioned Zn-based alloy plated steel sheet In addition to the effect that the object is strongly retained (chemical retention effect) by the action of the alloying element Ni or / and Co, the permeation inhibiting effect of the corrosion factor of the coating film (α) (physical barrier) It is presumed to be due to the effect that the corrosion of the plated steel sheet is suppressed and the corrosion resistance is synergistically improved by the effect) and the effect of strongly holding the initial corrosion product. As for the scratch resistance, in addition to the effect of increasing the hardness of the plating layer surface by using a Zn-based alloy plating containing Ni or / and Co, good adhesion to the underlying plating layer by the coating film (α) It is presumed to be due to a synergistic effect such as an imparting effect and a lubricity imparting effect.

The Zn-based alloy plating layer containing a trace amount of at least one selected from Ni and Co has a lower limit of 3 g / m ² and an upper limit of 40 g / m ² , and a lower limit of 0.01% by mass and an upper limit of 1.0% by mass. % Of Ni or / and Co content in the plating. When the adhesion amount and the composition are less than the lower limit adhesion amount of 3 g / m ² and the lower limit Ni or / and Co content is less than 0.01% by mass, corrosion resistance and scratch resistance are lowered. On the other hand, if the adhesion amount and the composition exceed the upper limit adhesion amount of 40 g / m ² and the upper limit Ni or / and Co content exceeds 1.0% by mass, the workability deteriorates, which is disadvantageous economically. .

  Examples of the plating method for the steel plate of Zn-based alloy plating containing a trace amount of at least one selected from Ni and Co include electroplating method, hot dipping method, vapor deposition plating method, displacement plating, molten salt electroplating method, etc. Any method may be used as long as a predetermined plating composition and plating adhesion amount can be secured.

  It is preferable that the coating film ((alpha)) which coat | covers the Zn-type alloy plating layer of the chromate-free coating plating steel plate of this invention is formed by apply | coating as an aqueous-type coating composition using an aqueous solvent, and heat-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 invention is preferably 50% by mass. The solvent other than water contained in the aqueous solvent in the present invention may be an organic solvent, but the organic solvent-containing substance defined in the organic solvent poisoning prevention regulations of the Industrial Safety and Health Act It is more preferable that the organic solvent listed in 2) does not fall under 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.

  Although the coating-film thickness of the said coating film ((alpha)) is not specifically limited, It is preferable that it is 2-10 micrometers, More preferably, it is 3-7 micrometers. 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 when the coating film (α) is formed from a water-based coating composition, coating film defects such as armpits may occur, which is necessary as an industrial product. It may not be possible to obtain a stable appearance.

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

  Among the various measuring methods described above, 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 film-forming component of the coating film (α) is composed of an organic resin (A) containing a polyester resin (A1) containing a sulfonic acid group as an essential component.
The content of the film-forming component (the total amount of the organic resin (A) and the curing agent when it contains the curing agent (C)) is 55 to 80% by mass in the coating film (α). It is preferable. 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) contains a polyester resin containing a sulfonic acid group as an essential component. By including the polyester resin (A1) containing a sulfonic acid group, workability, corrosion resistance, and scratch resistance can be achieved at a high level. 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 the coating film (α) is very effective in achieving both workability and scratch resistance at a high level. In addition, the sulfonic acid group contained in the polyester resin also contributes to improving the adhesion with the plated steel sheet (base treatment layer if there is a base treatment), thereby improving workability and scratch resistance. It is suitable. Further, when the coating composition for forming the coating film (α) is aqueous, the sulfonic acid group has high hydrophilicity, so that the stability of the polyester resin in the aqueous coating composition is increased. It is also preferable for preventing solidification of the coating composition and generation of aggregates. In particular, when the curing agent (C) described later is used in combination, the pH fluctuation of the coating composition increases and the stability of the coating composition may decrease. However, when using a polyester resin containing a sulfonic acid group, It is difficult to be influenced by the pH fluctuation of the coating composition, and it is possible to suppress a decrease in coating 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 may be difficult to use with things. Therefore, the coating composition for forming the coating film is preferably water-based. When the coating composition for forming the coating film is water-based and contains a coloring pigment (E) described later, and the coloring pigment is a pigment having a hydrophobic surface such as carbon black (E1) described later, the pigment It is preferable to contain a sulfonic acid group also when uniformly disperse | distributing in an aqueous solvent and providing the formed coating film ((alpha)) with the outstanding designability. 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.

  It is preferable that content of the said polyester resin (A1) is 10-100 mass% in the said organic resin (A), More preferably, it is 40-100 mass%. If it is less than 10% by mass, the workability may be reduced.

  The polyester resin (A1) preferably further contains 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 (A1) is not particularly limited as long as it contains a sulfonic acid group in the structure. For example, it can be obtained by polycondensing a polyester raw material comprising a polycarboxylic acid component and a polyol component. Moreover, it can also be made water-based by dissolving or dispersing 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 anhydride can be mentioned.

  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, and examples thereof include 5-sulfoisophthalic acid, 4-sulfonaphthalene-2, 7-dicarboxylic acid, and 5 (4-sulfophenoxy) isophthalic acid. Examples include a method of using dicarboxylic acids or glycols such as 2-sulfo-1,4-butanediol and 2,5-dimethyl-3-sulfo-2,5-hexyldiol 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. In the case of neutralization, the already neutralized sulfonic acid group may be incorporated into the resin, or may be neutralized after the sulfonic acid group is incorporated into the resin. In particular, a sulfonic acid metal base neutralized with an alkali metal such as Li, Na, or K is particularly preferable for improving the adhesion to a base material or for increasing the dispersibility of a coloring pigment having a hydrophobic surface. Na base is more 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 these, 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%.

  The organic resin (A), which is a film-forming component of the coating film (α), further includes a polyurethane resin (A2) containing a urea group in addition to the polyester resin (A1), thereby providing corrosion resistance and scratch resistance. It is preferable in terms of improvement. 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 that the polyurethane resin (A2) containing a urea group having a very high cohesive energy is used in combination with the polyester resin (A1), 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 said polyurethane resin (A2) is included with the said polyester resin (A1) in the said organic resin (A), the total content of the said polyester resin (A1) and the said polyurethane resin (A2) is the said 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 (A1) / (A2) of the said polyester resin (A1) and the said polyurethane resin (A2) is 25 / 75-90 / 10, and is 50 / 50-75 / 25. More preferably it is. If it is less than 25/75, the workability may be deteriorated, and if it exceeds 90/10, the effect of improving the corrosion resistance and scratch resistance may not be obtained.

  The polyurethane resin (A2) is not particularly limited as long as it contains a urea group in the structure. For example, the polyurethane resin (A2) 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), which is a film-forming component of the coating film (α), further contains an acrylic resin in addition to the polyester resin (A1). It is preferable for improving the adhesion to the treatment layer) and scratch resistance. 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 has a hydrophobic surface such as carbon black (E1) described later. In the case of a pigment, it is preferable to contain an acrylic resin even when the pigment is uniformly dispersed in an aqueous solvent and imparts excellent design properties to the formed coating film (α).

  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. Here, the expression (meth) acryl means acryl or methacryl.

  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 effect of improving designability and scratch resistance may not be obtained, and if it exceeds 20% by mass, corrosion resistance and workability may be deteriorated.

  The coating film (α) needs to contain silica particles (B). The silica particles (B) have the effect of improving corrosion resistance and scratch resistance. The coating film (α) has spherical silica particles (B1) having an average particle diameter of 5 to 50 nm and an average particle diameter of 0. It is preferable to contain both 3-5 micrometers spherical silica particles (B2). In particular, the spherical silica particles (B1) contained as fine particles having an average particle diameter of 5 to 50 nm have a large effect of improving the corrosion resistance, and the spherical particles contained as relatively large particles having an average particle diameter of 0.3 to 5 μm. Silica particles (B2) have a great effect of improving scratch resistance. By simultaneously containing spherical particles having different characteristics and different particle diameters, the corrosion resistance and scratch resistance are synergistically improved. 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. Further, the spherical silica particles (B2) contained as relatively large particles having an average particle diameter of 0.3 to 5 μm also have the effect of degrading the gloss of the coated steel sheet, whereby the coating film (α ) Also has the advantage that it will be less noticeable even if there are some scratches. 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. Making the average particle diameter of the spherical silica particles (B1) less than 5 nm is technically difficult from the viewpoint of particle stability (problems such as particle aggregation and gelation of the coating composition). When the average particle diameter is more than 50 nm, the effect of improving the corrosion resistance is small. A more preferable range of the average particle diameter is 8 to 30 nm. If the average particle diameter of the spherical silica particles (B2) is less than 0.3 μm, the effect of improving the scratch resistance is small, and if it exceeds 5 μm, workability and corrosion resistance are lowered. Moreover, the dispersion stability in a coating composition is also inferior (precipitation etc. arise). A more preferable range of the average particle diameter is 0.5 to 3 μm.

  The type of the silica particles (B) 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) , Functional spherical silica HPS series (Toa Gosei), Nipsil series (Tosoh Silica) and the like.

  The content of the spherical silica particles (B1) is preferably 3 to 30% by mass, more preferably 5 to 20% by mass in the coating film (α). If it is less than 3% 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 (B2) 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 (B1) and the spherical silica particles (B2) (content of the silica particles (B)) is 10 to 40% by mass in the coating film (α). Preferably, it is 10-30 mass%. 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 (B1) and the spherical silica particles (B2) in the coating film is preferably 30/70 to 80/20 by mass ratio. The ratio of the number average particle diameter of the spherical silica particles (B1) and the spherical silica particles (B2) contained in the coating film (α) is preferably 1/350 to 1/16.

  The organic resin (A) that is a film-forming component of the coating film (α) is cured with a curing agent (C) that can cure the organic resin (A), thereby improving scratch resistance and corrosion resistance. This is preferable. The curing agent (C) is not particularly limited as long as it cures the organic resin (A), and examples thereof include a melamine resin and a polyisocyanate compound. The melamine resin is a resin obtained by etherifying a part or all of the methylol group of a product obtained by condensing melamine and formaldehyde with a lower alcohol such as methanol, ethanol, or butanol. It does not specifically limit as a polyisocyanate compound, For example, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, tolylene diisocyanate etc. can be mentioned. 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 (C) is 5-35 mass% with respect to 100 mass% of said organic resins (A). If it is less than 5% by mass, the bake-curing may be insufficient, and the effect of improving the corrosion resistance and scratch resistance may not be obtained. If it exceeds 35% by mass, the bake-curing will be excessive, and the corrosion resistance and workability May decrease.

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

  The coating film (α) preferably further contains at least one resin particle (D) selected from an acrylic resin and a silicone resin. The resin particles (D) 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 is not particularly limited, and examples thereof include crosslinked polymethyl methacrylate, crosslinked polybutyl methacrylate, non-crosslinked polymethyl methacrylate, non-crosslinked polybutyl methacrylate, and polyalkyl acrylate. it can. In order to achieve both high scratch resistance and workability, crosslinked polymethyl methacrylate is particularly preferable.

  The type of the silicone resin 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 (D) is not particularly limited, but the resin particles (D) are preferably dispersed as spherical particles having an average particle diameter of 1 to 5 μm in the coating film (α). When the average particle size is less than 1 μm, the effect of improving scratch resistance may not be obtained, and when the average particle size is more than 5 μm, it is difficult to ensure dispersion stability in the coating composition, In some cases, the particles settle and solidify. In addition, workability may also be reduced.

  When the average particle diameter of the resin particles (D) dispersed in the coating film (α) is c μm and the thickness of the coating film (α) is b μm, 0.3 ≦ c / b ≦ 1.2 Is preferably satisfied. If c / b is less than 0.3, the effect of improving scratch resistance may not be obtained, and if c / b is more than 1.2, corrosion resistance and workability may be deteriorated.

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

  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, metal-coated mica powder, titanium dioxide-coated mica powder, titanium dioxide Bright materials such as emission coated glass powder can be exemplified.

  When the coating film (α) is colored in a deep color, or when an excellent design is imparted with a thin film having a film thickness of 10 μm or less, the coloring pigment (E) contains carbon black (E1). It is preferable. The type of the carbon black (E1) is not particularly limited, and known carbon blacks such as furnace black, ketjen black, acetylene black, and channel black 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 dispersibility in the coating solution, coating film quality, and paintability. Specifically, a particle having a primary particle size of 10 to 120 nm may be used. 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 solution 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 solution. In order to ensure designability and corrosion resistance in the thin film, the particle diameter of the carbon black (E1) dispersed in the coating film (α) is important, and the number average particle diameter thereof is 20 to 300 nm. Is preferred.

  When the content of the carbon black (E1) in the coating film (α) is d mass% and the thickness of the coating film (α) is b μm, d ≦ 15, b ≦ 10, d × b ≧ 20. It is preferable to satisfy. 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 expressed by the product of the carbon black content (d mass%) contained in the coating film and the coating film thickness (b μm). That is, if d × b is less than 20, designability (concealment) may be deteriorated. On the other hand, if d 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 lightly, it is preferable that the colored pigment (E) contains titanium dioxide (E2). It is preferable that content in the said coating film ((alpha)) of the said titanium dioxide (E2) is 5-30 mass%. If it is less than 5% by mass, the designability (concealment) may be reduced, and if it exceeds 30% by mass, the workability and corrosion resistance may be reduced. Generally, when the coating film (α) contains the carbon black (E1) and is colored deeply, it is more scratched than when it is not colored or lightly colored. It has the feature that it is easily noticeable when. The titanium dioxide (E2) 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 (E1) and the titanium dioxide (E2). In this case, the ratio of the titanium dioxide (E2) to the carbon black (E1) is preferably contained in a mass ratio of 0.5 / 9.5 to 3/7.

  The coating film (α) of the present invention preferably further contains a lubricant. By including a lubricant, scratch resistance is improved. The lubricant is not particularly limited, and a known lubricant can be used, but it is preferable to use at least one selected from a fluororesin system and a polyolefin resin system.

  Examples of fluororesins include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polychlorotrifluoroethylene (PCTFE). ), Polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), ethylene-tetrafluoroethylene copolymer (ETFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), and the like can be used. Of these, one type may be used alone, or two or more types may be used in combination.

  The polyolefin resin is not particularly limited, and examples thereof include paraffin, microcrystalline, hydrocarbon waxes such as polyethylene, and derivatives thereof, and polyethylene resin (F) is preferable. The derivative is not particularly limited, and examples thereof include carboxylated polyolefin and chlorinated polyolefin. Of these, one type may be used alone, or two or more types may be used in combination. When using the said polyethylene resin (F), it is preferable from a viewpoint of corrosion resistance or damage resistance that it is disperse | distributed by the particle | grains with an average particle diameter of 0.5-3 micrometers in the said coating film ((alpha)).

  It is preferable that content of the said polyethylene resin is 0.5-10 mass% in the said coating film ((alpha)), More preferably, it is 1-7 mass%. If the amount is less than 0.5% by mass, the effect of improving the lubricity is small and the effect of improving the scratch resistance may not be obtained. If the amount exceeds 10% by mass, the corrosion resistance and workability may be deteriorated.

  The average particle diameter of the polyethylene resin particles (F) is not particularly limited, but is preferably spherical particles of 0.5 to 3 μm. If the average particle size is less than 0.5 μm, the effect of improving the scratch resistance may not be obtained, and if the average particle size exceeds 3 μm, the corrosion resistance may be lowered.

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

  Specifically, of the silica particles (B), the spherical silica particles (B1) having an average particle diameter of 5 to 50 nm, the carbon black (B1) and the titanium dioxide (B2) of the color pigment (B) are relatively fine. The diameter of the fine particles 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 paint. 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 diameter by the dynamic light scattering method is described in, for example, Journal of Chemical Physics, Vol. 57, No. 11 (December, 1972), page 4814.

  On the other hand, among the silica particles (B), at least one resin particle (D) selected from spherical silica particles (B2) having an average particle diameter of 0.3 to 5 μm, acrylic resin, and silicone resin, polyethylene resin particles (F The particle diameter at an integrated value of 50% in the particle size distribution measured by the laser diffraction / scattering method (microtrack method) can be adopted as the diameter of relatively large particles such as The laser diffraction / scattering method is widely used to measure particle diameters from the submicron range to several millimeters by utilizing the fact that the amount of scattered light and the pattern scattered by the particle diameter vary depending on the particle size. It has been. Also in this case, the particulate component used in the present invention is selected so that it does not significantly dissolve in the aqueous solvent of the paint and does not react with the solvent or other coating film constituents. It can employ | adopt as a particle diameter of a particulate component. For measurement by the laser diffraction / scattering method, for example, a microtrack particle size analyzer manufactured by Nikkiso Co., Ltd. can be used. In the present invention, the average value of five measurements in total is taken as the average particle diameter of the particles.

  Moreover, in the said coating film ((alpha)), at least 1 sort (s) of resin particle (D) chosen from a silica particle (B), an acrylic resin, and a silicone resin, a color pigment (E), and a polyethylene resin particle (F) When at least one kind is present as a particulate component, the colored 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 coating, curtain coating, 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 or the like may be added as necessary.

  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 150 degreeC-250 degreeC in the ultimate plate temperature of a plated steel plate, It is more preferable that it is 170 degreeC-240 degreeC, It is most preferable that it is 180 degreeC-230 degreeC. 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 bake hardening of the coating film (α) is excessive. Thus, corrosion resistance and workability may be deteriorated. The baking and drying time is preferably 1 to 60 seconds, and more preferably 3 to 20 seconds. If it is less than 1 second, the bake hardening is insufficient, and the corrosion resistance and scratch resistance may be lowered. If it exceeds 60 seconds, the productivity is lowered.

  The chromate-free coated plated steel sheet of the present invention may have a base treatment layer (β) under the coating film (α). 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 plated steel sheet, it is preferable to use at least one of polyester resin, polyurethane resin, epoxy resin, and phenol resin, and the polyester resin (α) contained in the coating film (α) ( In order to increase the compatibility with A1) 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.

The adhesion amount of the base treatment layer (β) is not particularly limited, but is preferably in the range of 10 to 1000 mg / m ² . If it is 10 mg / m ² or less, the effect of the sufficient ground treatment layer (β) cannot be obtained, and if 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. .

  Examples of the present invention will be described below. However, the present invention is not limited to these examples.

(1) Zn-based alloy-plated steel sheet A cold-rolled steel sheet having a thickness of 0.5 mm was used as the original sheet. Electroplating was performed with the plating bath composition and plating conditions shown in Table 1. Table 1 also shows the content (% by mass) of Co or / and Ni in each of the obtained Zn-based alloy plating layers.

(2) Ground treatment layer The coating agent for forming the ground treatment layer is composed of an organic resin (Table 2), a silane coupling agent (Table 3), and a polyphenol compound (Table 4) in the blending amounts shown in Table 5. It was prepared by stirring using a paint disperser. Necessary by applying the coating agent on the surface of the Zn-based alloy-plated steel sheet prepared in (1) above with a roll coater so as to have an adhesion amount of 100 mg / m ² , and drying it at a final plate temperature of 70 ° C. In accordance with the above, base treatment layers (E1 to E9) were formed.

(3) Coating Film The coating composition for forming the coating film is an organic resin (A) aqueous dispersion (the following Production Examples 1 to 5 and Table 6), a curing agent (C) (Table 7), and a color pigment. (E) (Table 8), silica particles (B) (Table 9), resin particles (E) (Table 10), polyethylene resin particles (F) (Table 11) were blended in the blending amounts shown in Table 12, and paint It was prepared by stirring using a dispersing machine. In the production examples, “part” simply means mass part, and “%” means mass%. The above coating composition is applied to the upper layer of the base treatment layer formed in (2) (or a metal plate if there is no base treatment layer) with a roll coater so as to obtain a predetermined ultimate plate temperature. And dried 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 (F1) 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, 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 through a 200 mesh nylon mesh to obtain a polyester resin aqueous dispersion (F2) having a solid content concentration of 30%.

<Organic resin production example 3>
Add 230 parts of a polyether polyol of average molecular weight 900 synthesized from tetramethylene glycol and ethylene glycol and 15 parts of 2,2-bis (hydroxymethyl) propionic acid to 100 parts of N-methyl 2-pyrrolidone and warm to 80 ° C. And dissolved. 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 (F3) having a solid content concentration of 30%.

<Organic resin production example 4>
80 parts of a polyether polyol having an average molecular weight of 900 synthesized from tetramethylene glycol and ethylene glycol, 120 parts of a 3 mol adduct of bisphenol A propylene oxide having an average molecular weight of 700, and 12 parts of 2,2-bis (hydroxymethyl) propionic acid In addition to 100 parts of N-methyl 2-pyrrolidone, it was heated to 80 ° C. and dissolved. 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 with strong stirring to obtain a polyurethane resin aqueous dispersion (F4) having a solid content concentration of 30%.

(4) Paint-plated steel sheet Table 12 shows the coating film composition, the film thickness of the paint film, and the ultimate plate temperature of the paint-plated steel sheets prepared in (1) to (3) above.

(5) Evaluation test About the coating plating steel 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 13.

(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 1.0 mm spacer in between (generally called 2T 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 the end surface of the test plate was tape-sealed, a salt spray test (SST) based on JIS Z 2371 was performed for 120 hours, 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)
In accordance with JIS K 5600-5-4, after drawing 5 lines with a pencil lead at a 45 ° angle on the coating film on the surface of the test plate and erasing the line with an eraser, the pencil hardness is not damaged more than twice. It was measured. When the pencil hardness was H or more, it was evaluated that the scratches were not noticeable, that is, the scratch resistance was good. The pencil was a uni-pencil manufactured by Mitsubishi Pencil Co., Ltd., and the test was performed under a load condition of 20 ° C. and 4.903 N (500 gf).

  The examples of the present invention exhibited excellent workability of 3 points or more, corrosion resistance, and excellent scratch resistance of pencil hardness H or higher in any evaluation test. In addition, sediment was generated in the coating compositions used in Examples 39, 44, 119, and 124. That is, the silica particles (B) using relatively large spherical silica particles having a particle diameter of 6.8 μm, and the resin particles (D) using relatively large resin particles having a particle diameter of 8 μm are silica particles or Sedimentation of the resin particles occurred, and their dispersion stability was slightly inferior to those of other coating compositions. Nevertheless, the workability, corrosion resistance, and scratch resistance of the coating films of Examples 39, 44, 119, and 124 were all good.

  On the other hand, Comparative Examples 1 and 8 using a Zn-plated steel sheet containing neither Co nor Ni alloying elements as the base were inferior in corrosion resistance and scratch resistance. Comparative Examples 2 to 4 and 9 to 11 using Zn-based alloy-plated steel sheets containing either Co or Ni in excess of 1.0 mass% were inferior in workability. The comparative examples 5 and 12 which do not contain a silica particle (B) in a coating film were inferior in corrosion resistance and scratch resistance. In Comparative Examples 6, 7, 13, and 14 in which the polyester resin containing a sulfonic acid group was not included in the film forming component of the coating film, one or more items of workability, corrosion resistance, and scratch resistance were inferior.

  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 film-forming component made of an organic resin (A) and silica particles (B) on at least one surface of a Zn-based alloy-plated steel sheet containing 0.01 to 1% by mass of at least one selected from Ni and Co in the plating layer A chromate-free painted steel sheet on which a coating film (α) comprising
The said organic resin (A) contains the polyester resin (A1) containing a sulfonic acid group as an essential component, The chromate free coating plated steel plate characterized by the above-mentioned.   The chromate-free painted steel sheet according to claim 1, wherein the coating film (α) has a thickness of 2 to 10 μm.   The chromate-free coated plated steel sheet according to claim 1 or 2, wherein the organic resin (A) is a resin cured with a curing agent (C).   The silica particles (B) contain spherical silica particles (B1) having an average particle diameter of 5 to 50 nm and spherical silica particles (B2) having an average particle diameter of 0.3 to 5 µm. The chromate-free painted steel sheet of any one of -3.   The chromate-free according to any one of claims 1 to 4, wherein the coating film (α) further contains at least one resin particle (D) selected from an acrylic resin and a silicone resin. Painted steel sheet.   The chromate-free painted steel sheet according to claim 5, wherein the resin particles (D) have an average particle diameter of 1 to 5 μm.   The chromate-free coated plated steel sheet according to any one of claims 1 to 6, wherein the coating film (α) further contains a color pigment (E).   The chromate-free painted steel sheet according to claim 7, wherein the color pigment (E) contains carbon black (E1).   The chromate-free painted steel sheet according to claim 7 or 8, wherein the color pigment (E) contains titanium dioxide (E2).   The chromate-free painted steel sheet according to any one of claims 1 to 9, wherein the polyester resin (A1) further contains a bisphenol group in the structure.   The chromate-free painted steel sheet according to any one of claims 1 to 10, wherein the organic resin (A) further includes a polyurethane resin (A2) containing a urea group.   The chromate-free painted steel sheet according to any one of claims 1 to 11, wherein the coating film (α) further contains polyethylene resin particles (F).   The chromate-free painted steel sheet according to claim 12, wherein the polyethylene resin particles (F) have an average particle diameter of 0.5 to 3 µm.   The chromate-free painted steel sheet according to any one of claims 1 to 13, further comprising a base treatment layer (β) below the coating film (α).   The said coating film ((alpha)) of any one of Claims 1-14 is formed by apply | coating using an aqueous solvent, and heat-drying, The chromate free coating plated steel plate characterized by the above-mentioned.