TW202202656A - Coated plated steel sheet - Google Patents

Abstract

The present disclosure provides a coated plated steel sheet which includes a plating layer containing prescribed quantities of aluminum, silicon, zinc and magnesium, which exhibits excellent performance in terms of corrosion resistance, blackening resistance, weather resistance, and the like, and which has an excellent appearance. In the present disclosure, the plating layer of the coated plated steel sheet contains prescribed proportions of aluminum, silicon, zinc and magnesium. A protective layer is formed on the plating layer by coating an aqueous surface treatment agent on the surface of the plating layer and then drying the same The aqueous surface treatment agent contains an aqueous anionic urethane resin (A) having a polyester polyol residue, zirconia (B), a molybdenum oxoate (C), a hindered amine (D) and water. These components are blended at prescribed proportions in the aqueous surface treatment agent.

Description

Coated plated steel sheet

The present disclosure relates to a coated plated steel sheet obtained by forming a protective layer on a plated steel sheet having a plated layer containing aluminum, silicon, zinc, and magnesium.

Patent Document 1 cites a chromium-free surface-treated plated steel sheet, which is prepared by a treatment composition containing a specific titanium-containing aqueous solution, a nickel compound and/or a cobalt compound, a fluorine-containing compound and an aqueous organic resin in a predetermined ratio. The molten Zn-Al alloy coating layer is obtained by forming a protective film on the surface of the molten Zn-Al alloy-coated steel sheet, the molten Zn-Al alloy coating layer contains 1.0 to 10% of Al, 0.2 to 1.0% of Mg, 0.005 to 0.1% Ni. This document describes that it is excellent in corrosion resistance, blackening resistance, coating adhesion, and coating appearance. [Prior Art Literature] (patent literature)

Patent Document 1: Japanese Patent Laid-Open No. 2009-132952

The problem of the present disclosure is to provide a coated plated steel sheet having a coating layer containing predetermined amounts of aluminum, silicon, zinc, and magnesium, and excellent in performance and appearance such as corrosion resistance, blackening resistance, and weather resistance. [Technical means to solve the problem]

According to one aspect of the present disclosure, the plated steel sheet includes a steel sheet, a plated layer, and a protective layer that are laminated in this order. The aforementioned plating layer contains aluminum, silicon, zinc, and magnesium. In the plating layer, the ratio of aluminum is in the range of 50.0 mass % or more and 60.0 mass % or less, the ratio of silicon is in the range of 1.0 mass % or more and 3.0 mass % or less, and the ratio of magnesium is 0.5 mass %. % or more and 3.0 mass % or less, and the total ratio of the aluminum, the silicon, and the zinc is 95 mass % or more. The said protective layer is formed by apply|coating an aqueous surface treatment agent on the surface of the said plating layer, and drying it. The water-based surface treatment agent contains the aqueous anionic urethane resin (A) having a polyester polyol residue, zirconia (B), molybdenum oxo acid salt (C), hindered amines (D), and water. The mass ratio of the water-based anionic urethane resin (A) to the zirconium in the zirconium oxide (B) is 50:1 to 200:1. The mass ratio of molybdenum in the aforementioned aqueous anionic urethane resin (A) and the aforementioned molybdenum oxo acid salt (C) is 500:1 to 1000:1. The mass ratio of the aforementioned aqueous anionic urethane resin (A) to the aforementioned hindered amines (D) is 50:1 to 200:1.

First, the outline of the development of the plated steel sheet according to the present disclosure will be described. For the purpose of improving long-term corrosion resistance of steel sheets, etc., plating has been performed in the past. As a representative composition of the plated layer in such a plated steel sheet, for example, an alloy in which aluminum is 1 to 75 mass %, the remainder is mostly zinc, and further contains trace amounts of silicon (Si) and magnesium (Mg) can be cited. , cerium (Ce)-lanthanum (La) and other third components.

However, according to the investigation of the inventors, although the conventional plated steel sheet has excellent corrosion resistance, this means that the time until red rust occurs due to the corrosion of the base iron is long, and if the plated surface is not subjected to some kind of coating treatment , the white rust will turn black in a short time, which will damage the beautiful appearance of the plated steel sheet. In particular, when a plated steel sheet is applied to a building member, the surface of the plated layer tends to be discolored with time due to the influence of acid rain in recent years.

Therefore, a technique related to surface treatment for suppressing blackening of a plated steel sheet has been proposed in the past. In particular, there are many techniques for chromium-free that do not use hexavalent chromium in surface treatment agents, and many of these techniques have been disclosed.

For example, Patent Document 1 (Japanese Patent Laid-Open No. 2009-132952) lists a chromium-free surface-treated plated steel sheet, which is prepared by containing a specific titanium-containing aqueous solution, a nickel compound and/or a cobalt compound, a The treatment composition of fluorine compound and water-based organic resin is obtained by forming a protective film on the surface of a molten Zn-Al alloy-coated steel sheet having a molten Zn-Al alloy coating layer containing 1.0 ~10% Al, 0.2~1.0% Mg, 0.005~0.1% Ni. This document describes that it is excellent in corrosion resistance, blackening resistance, coating adhesion, and coating appearance.

However, according to the inventor's investigation, even the technology disclosed in Patent Document 1 is not practically satisfactory in terms of performance and appearance such as corrosion resistance, blackening resistance, and weather resistance in consideration of recent environmental conditions. Therefore, there has been demanded a plated plated steel sheet which is excellent in properties such as corrosion resistance, blackening resistance, weather resistance, and the like, and in appearance. In particular, with regard to a plated steel sheet having a plated layer containing predetermined amounts of aluminum, silicon, zinc, and magnesium, a plated plated steel sheet having excellent properties and appearance is sought. In view of the above-mentioned circumstances, the inventors have provided a plated-coated steel sheet having a coating layer containing predetermined amounts of aluminum, silicon, zinc, and magnesium, and having excellent properties and appearance such as corrosion resistance, blackening resistance, and weather resistance, As a result of the progress of research and development by the inventors, the coated plated steel sheet according to the present disclosure is completed.

Hereinafter, one embodiment of the present disclosure will be described.

According to the coated-coated steel sheet of the present embodiment, the steel sheet, the plated layer, and the protective layer are provided in order to be laminated. The coating layer contains aluminum, silicon, zinc and magnesium. In the plating layer, the ratio of aluminum is in the range of 50.0 mass % or more and 60.0 mass % or less, the ratio of silicon is in the range of 1.0 mass % or more and 3.0 mass % or less, and the ratio of magnesium is in the range of 0.5 mass % or more and 3.0 mass %. Within the range of % by mass or less, the total ratio of aluminum, silicon, and zinc is 95% by mass or more. The protective layer is made of a water-based surface treatment agent. The water-based surface treatment agent contains the aqueous anionic urethane resin (A) having a polyester polyol residue, zirconia (B), molybdenum oxo acid salt (C), hindered amines (D), and water. The mass ratio of the zirconium in the aqueous anionic urethane resin (A) and the zirconium oxide (B) is 50:1 to 200:1. The mass ratio of the aqueous anionic urethane resin (A) to the molybdenum in the molybdenum oxo acid salt (C) is 500:1 to 1000:1. The mass ratio of the aqueous anionic urethane resin (A) to the hindered amines (D) is 50:1 to 200:1.

According to the present embodiment, by forming a protective layer on a steel sheet having a predetermined coating layer, a coated steel sheet having excellent properties such as blackening resistance, corrosion resistance, and weather resistance and appearance can be provided.

Therefore, according to the present embodiment, even if the coated plated steel sheet is not coated with paint, the coated coated steel sheet is excellent in properties such as blackening resistance, corrosion resistance, and weather resistance, and its appearance.

The protective layer can be directly overlapped on the plated layer, or a functional layer can be interposed between the protective layer and the plated layer. In addition, the functional layer is a layer for surface modification of a plating layer, for example, a chemical conversion treatment layer. In addition, the functional layer may or may not be overlapped on the protective layer. However, in the present embodiment, even when the functional layer is not interposed between the protective layer and the plating layer, and when the functional layer is not overlapped on the protective layer, the effects of the present embodiment can be achieved.

The coated steel sheet will be described in more detail.

The above-mentioned plating layer will be described. As described above, the ratio of magnesium in the plating layer is in the range of 0.5 mass % or more and 3.0 mass % or less. If this ratio is less than 0.5 mass %, the corrosion resistance of the plating layer cannot be sufficiently secured. If this ratio exceeds 3 mass %, not only the effect of improving corrosion resistance is saturated, but also wrinkles are easily formed on the surface of the plating layer due to the influence of the magnesium oxide film, and the appearance is not good. During coating, dross easily occurs in the molten coating bath.

The plating layer may further contain one or more elements selected from Ni, Ce, Cr, Fe, Ca, Sr, rare earths, and the like. In particular, it is preferable that the plating layer contains at least one of Ni and Cr. When the plating layer contains Ni, the ratio of Ni in the plating layer is preferably in the range of more than 0 mass % and 1 mass % or less. It is more preferable that this ratio is 0.01 mass % or more and 0.5 mass % or less. When the plating layer contains Cr, the ratio of Cr in the plating layer is preferably in the range of more than 0 mass % and 1 mass % or less. It is more preferable that this ratio is 0.01 mass % or more and 0.5 mass % or less. In these cases, the coated steel sheet has excellent corrosion resistance.

It is also preferable that the plating layer contains at least one of Ca, Sr, Y, La, and Ce. When the plating layer contains Ca, the ratio of Ca in the plating layer is preferably in the range of more than 0 mass % and 0.5 mass % or less. It is more preferable that this ratio is 0.001 mass % or more and 0.1 mass % or less. When the plating layer contains Sr, the ratio of Sr in the plating layer is preferably in the range of more than 0 mass % and 0.5 mass % or less. It is more preferable that this ratio is 0.001 mass % or more and 0.1 mass % or less. When the plating layer contains Y, the ratio of Y in the plating layer is preferably in the range of more than 0 mass % and 0.5 mass % or less. It is more preferable that this ratio is 0.001 mass % or more and 0.1 mass % or less. When the plating layer contains La, the ratio of La in the plating layer is preferably in the range of more than 0 mass % and 0.5 mass % or less. It is more preferable that this ratio is 0.001 mass % or more and 0.1 mass % or less. When the plating layer contains Ce, the ratio of Ce in the plating layer is preferably in the range of more than 0 mass % and 0.5 mass % or less. It is more preferable that this ratio is 0.001 mass % or more and 0.1 mass % or less.

The plated steel sheet is, for example, a molten 55% aluminum-zinc alloy plated steel sheet specified in Japanese Industrial Standards (JIS) G3321:2019, and the plated layer contains 0.5 mass % or more and 3.0 mass % or less of magnesium.

Of course, the plating layer may contain elements other than the above, which are inevitably mixed.

The protective layer is formed by applying the water-based surface treatment agent on the surface of the plating layer, and then drying the applied water-based surface treatment agent. The water-based surface treatment agent contains the aqueous anionic urethane resin (A) having a polyester polyol residue, zirconia (B), molybdenum oxo acid salt (C), hindered amines (D), and water.

The water-based anionic urethane resin (A) is a urethane resin capable of dissolving at least 0.1 g in 1000 g of water at 25° C. and having an anionic functional group. As described above, the aqueous anionic urethane resin resin (A) has a polyester polyol residue. Here, the polyester polyol residue means a partial structure other than the structure of the chemical bond generated in the chemical structure of the polyester polyol at the time of synthesis of the aqueous anionic urethane resin (A). In addition, the water-based anionic urethane resin (A) has water and anionic properties by having an acidic group such as a carboxyl group. The acid value of the aqueous anionic urethane resin (A) is, for example, 10 mgKOH/g or more and 50 mgKOH/g or less.

The aqueous anionic urethane resin (A) having a polyester polyol residue can be synthesized, for example, by the following method. Furthermore, the synthesis method is not limited to the following method.

First, by polycondensing a polyol and a polyisocyanate, a urethane prepolymer having isocyanate groups at both ends is obtained. A carboxylic acid having two or more hydroxyl groups or a hydrolyzable ester compound is reacted with the urethane prepolymer to obtain a derivative having isocyanate groups at both ends. After adding triethanolamine or the like to this derivative to form an ionic polymer (triethanolamine salt), water is added to the ionic polymer to obtain an emulsified solution or a dispersed solution. Further, if necessary, a diamine is added to this solution to carry out chain extension. Thereby, the aqueous anionic urethane resin (A) can be obtained.

The above-mentioned polyol contains at least polyester polyol. Therefore, the aqueous anionic urethane resin (A) has a polyester polyol residue. Polyester polyols are, for example, polyethylene glycol and/or polypropylene glycol. The above-mentioned polyisocyanates include, for example, at least one of aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic polyisocyanates, and the like.

The above-mentioned carboxylic acid contains, for example, at least one selected from the group consisting of dimethylolpropionic acid, dimethylolbutyric acid, dimethylolvaleric acid, and dimethylolalkanoic acid such as dimethylolhexanoic acid. A sort of. The above-mentioned hydrolyzable ester compound is, for example, acid anhydrides of various carboxylic acids.

In order to disperse|distribute a zirconia (B) at the time of preparing an aqueous surface treatment agent, it is preferable to use what sol-formed the zirconia (B).

The mass ratio of the zirconium in the aqueous anionic urethane resin (A) and the zirconium oxide (B) is 50:1 to 200:1. This quality ratio is better if it is 75:1 to 175:1, and even better if it is 100:1 to 150:1.

The median particle diameter of zirconia (B) is not particularly limited, but is preferably, for example, 5 nm or more and 150 nm or less. In addition, this median particle diameter is prescribed|regulated based on the value measured by the dynamic light scattering method.

The molybdenum oxo acid salt (C) contains, for example, at least one selected from the group consisting of ammonium molybdate, sodium molybdate, potassium molybdate, and the like.

The mass ratio of the aqueous anionic urethane resin (A) to the molybdenum in the molybdenum oxo acid salt (C) is 500:1 to 1000:1. This quality ratio is better if it is 550:1 to 900:1, and even better if it is 600:1 to 800:1.

The hindered amines (D) are compounds having a structure in which a carbon atom is bonded directly or via an oxygen atom to the nitrogen atom of the piperidine ring.

The hindered amines (D) contain, for example, at least one selected from the group consisting of: 2,2,6,6-tetramethyl-4-piperidine, 1,2,3,4-butanetetra (1,2,2,6,6-Pentamethyl-4-piperidinyl) formate, tetra(2,2,6,6-tetramethyl-1,2,3,4-butanetetracarboxylate) 4-Piperidinyl) ester, tridecyl 1,2,3,4-butanetetracarboxylate, bis(1-octyloxy-2,2,6,6-tetramethyl-4-sebacic acid) piperidinyl) ester, bis(N-methyl-2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis(2,2,6,6-tetradecanoate) Methyl-4-piperidinyl) ester, bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, 2-(3,5-di-tertiary butane) yl-4-hydroxybenzyl)-2-n-butylmalonic acid (1,2,2,6,6-pentamethyl-4-piperidinyl) ester, poly[{6-(1,1 ,3,3-Tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl}{(2,2,6,6-tetramethyl-4-piperidinyl) Imino}hexamethyl{(2,2,6,6-tetramethyl-4-piperidinyl)imino}], dimethyl succinate-1-(2-hydroxyethyl)-4 -Hydroxy-2,2,6,6-tetramethylpiperidine polycondensate, and poly[N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1 , 6-hexanediamine-co-2,4-dichloro-6-(N-morpholinyl)-1,3,5-triazine] and the like.

The mass ratio of the aqueous anionic urethane resin (A) to the hindered amines (D) is 50:1 to 200:1. This quality ratio is better if it is 75:1 to 175:1, and even better if it is 100:1 to 150:1.

It is also preferable that the water-based surface treatment agent contains a titanium oxide-based white pigment (E). The titanium oxide-based white pigment (E) is, for example, titanium dioxide.

The median particle diameter (D50) calculated from the particle size distribution measured by the laser diffraction scattering method of the titanium oxide-based white pigment (E) is preferably 0.3 μm or more and 1.0 μm or less. The median particle size is more preferably 0.4 or more and 0.9 or less, and more preferably 0.5 or more and 0.8 or less.

The ratio of the titanium oxide-based white pigment (E) is preferably 0.5% by mass or more and 3.0% by mass or less with respect to the protective layer. The ratio of the titanium oxide-based white pigment (E) is more preferably 1.0 mass % or more and 2.5 mass % or less, and more preferably 1.5 mass % or more and 2.0 mass % or less.

The water-based surface treatment agent may contain additives other than those described above. The additive contains, for example, at least one selected from the group consisting of a defoamer, a pigment dispersant, an anti-sag agent, a leveling agent, and an extender pigment.

The extender pigment contains, for example, at least one selected from the group consisting of silica (G), alumina, talc, and calcium carbonate.

In particular, the water-based surface treatment agent preferably contains silica (G). When silicon dioxide (G) is contained, as the ratio of silicon dioxide (G), it is preferable that the mass ratio of silicon contained in the silicon dioxide (G) to the water-based anionic urethane resin (A) is 10:1 to 80:1, better if it is 15:1 to 70:1, and even better if it is 20:1 to 50:1.

The water-based surface treatment agent may contain vinylsilane (F). The vinylsilane (F) contains, for example, at least one selected from the group consisting of vinylmethyldimethoxysilane, vinylmethyldiethoxysilane, vinyltriethoxysilane, Vinyltrimethoxysilane, vinyltriacetoxysilane, vinyltrichlorosilane, and vinylparaffin (2-methoxyethoxysilane).

When the water-based surface treatment agent contains vinylsilane (F), the mass ratio of molybdenum oxo acid salt (C) to vinylsilane (F) is preferably 0.7:1 to 2.0:1.

In addition, the water-based surface treatment agent may contain a silane coupling agent other than vinylsilane (F). Examples of silane coupling agents other than vinylsilane (F) include γ-glycidoxypropyltrimethoxysilane, β-3,4-epoxycyclohexylethyltrimethoxysilane, etc. Oxygen-based silane coupling agents; and mercapto-containing silane coupling agents such as γ-mercaptopropyltrimethoxysilane, etc.

The water-based surface treatment agent can be produced by blending in water an aqueous anionic urethane resin (A) having a polyester polyol residue, zirconia (B), molybdenum oxo acid salt (C), and Hindered amines (D), or if necessary, a titanium oxide-based white pigment (E) is further blended. In addition, the water-based surface treatment agent can also be produced by treating the water-based anionic urethane resin (A), zirconia (B), and molybdenum oxo acid salt (C) containing a polyester polyol residue. , a composition of hindered amines (D) and water (hereinafter referred to as "composition A"), or an aqueous anionic urethane resin (A) containing polyester polyol residues, zirconia (B), molybdenum A composition of oxo acid salt (C), hindered amines (D), titanium oxide-based white pigment (E) and water (hereinafter referred to as "composition B") is further blended with a silane such as vinylsilane (F) mixture. In addition, the water-based surface treatment agent may be produced by adding a silane coupling agent to Composition A, Composition B, Composition A (hereinafter referred to as "Composition C"), or A composition obtained by adding a silane coupling agent to composition B (hereinafter referred to as "composition D") is mixed with an extender pigment such as silica (G).

The water-based surface treatment agent and the protective layer may contain at least one of chromium and a chromium compound, and preferably do not contain either chromium or a chromium compound. When the water-based surface treatment agent contains at least one of chromium and a chromium compound, it is preferable to contain only as an unavoidable impurity.

A method for producing a plated steel sheet will be described.

The coated plated steel sheet is produced by subjecting the steel sheet to a plating treatment in accordance with JIS G3321:2019 to form a plated layer, and further to form a protective layer on the plated layer.

The plating treatment is, for example, fusion plating treatment. In this case, for example, after preheating the steel sheet in a non-oxidizing furnace, reduction annealing is performed in a reduction furnace, and then the steel sheet is immersed in a molten coating bath, and then pulled. Moreover, as another method of carrying out a hot-dip coating process to a steel sheet, the method of using a total reduction furnace, for example, can also be mentioned. In either method, a plated layer can be formed on a steel sheet by adhering molten plated metal to the steel sheet, adjusting the amount of molten plated metal by gas wiping, and then performing cool down. These steps can be performed continuously.

Before forming a protective layer on the plating layer, as a base treatment for the surface of the plating layer, cleaning can be performed with pure water or various organic solvent solutions, or an aqueous solution optionally containing acid, alkali or various etchants can be used. Or cleaning with various organic solvent solutions. If the surface of the plated layer is cleaned in this way, even if a small amount of Mg-based oxide protective film exists on the surface layer of the plated layer, inorganic contamination and organic contamination adhere to the surface of the plated layer. , it is possible to remove these Mg-based oxide protective films and contaminants from the plated layer, thereby improving the adhesion between the plated layer and the protective layer.

The protective layer can be produced by a known coating method such as a roll coating method and a spray method using the above-mentioned water-based surface treatment agent. After the application of the water-based surface treatment agent, the following steps can be further added as necessary: leaving at room temperature, drying and baking with heating devices such as a hot air furnace, an electric furnace, and an induction heating furnace. The temperature and drying time at the time of drying can be appropriately determined according to the type of the water-based surface treatment agent to be used, the required productivity, and the like. The protective layer formed in this way can be a continuous protective layer or a discontinuous protective layer on the plating layer. The thickness and adhesion amount of the protective layer can be appropriately determined according to the type of treatment, required performance, and the like. For example, the adhesion amount of the protective layer is 1.0 g/m ² or more and 3.0 g/m ² . [Example]

Hereinafter, specific examples of the present embodiment will be shown. In addition, this embodiment is not limited only to the following Example.

1. Prepare the plated steel sheet The molten 55% aluminum-zinc alloy plated steel sheet specified in JIS G3321:2019 of Nos. 1 to 3 shown in Table 1 was prepared. Moreover, the plated steel sheets of Nos. 4 to 6 shown in Table 1 were also prepared. Table 1 shows the composition of the plated layer in each plated steel sheet. The numerical value in this table is a mass percentage (mass %) to express the ratio of the element in the plated layer with respect to the whole plated layer. In addition, in the Example, each slender plated steel sheet with a thickness of 0.35 mm and a width of 220 mm was used.

[Table 1]

2. Preparation of water-based surface treatment agent Water-based surface treatment agents having the compositions shown in Tables 2 to 13 were prepared. In addition, the manufacture and details of each component described in the "composition" column of Tables 2 to 13 are as follows. In addition, the composition of Comparative Example 3 corresponds to the composition after excluding the urethane resin from Example 1.

In addition, in Tables 2 to 13, "(A)/(B)" represents the value of "mass of urethane resin (A)/mass of zirconium in zirconia (B)", "(A)/( C)" represents the value of "mass of urethane resin (A)/mass of molybdenum in molybdenum oxo acid salt (C)", and "(A)/(D)" represents "mass of urethane resin (A)" /mass of hindered amine (D)", "(C)/(F)" represents the value of "mass of molybdenum oxo-acid salt (C)/mass of vinylsilane (F)", "(A) /(G)" represents the value of "mass of urethane resin (A)/mass of silicon contained in silica (G)".

<Production of urethane resin (A)> The urethane resins (A-1) to (A-5) were obtained by the synthesis method shown below.

(1) Polyester polyol urethane resin (A-1) 100 parts by mass of a polyester polyol having a number average molecular weight of 3,000 obtained from 1,6-hexanediol and adipic acid, and 5 parts by mass of 2,2-dimethyl-1,3-propanediol were added to the reactor. , 30 parts by mass of 2,2-dimethylolpropionic acid, 100 parts by mass of 4,4-dicyclohexylmethane diisocyanate, and 100 parts by mass of N-methyl-2-pyrrolidone were reacted to obtain relative A urethane prepolymer with a free isocyanate group content of 5% in non-volatile components. Then, 16 parts by mass of tetramethylene diamine and 10 parts by mass of triethylamine were added to 300 parts by mass of deionized water, and while stirring with a homomixer for 4 hours, the above-mentioned urethane prepolymer was added to emulsify and disperse. , and finally deionized water was added to obtain an aqueous anionic urethane resin with a nonvolatile content of 35% by mass and an acid value of 18 mgKOH/g.

(2) Polyester polyol urethane resin (A-2) 100 parts by mass of a polyester polyol having a number average molecular weight of 3,000 obtained from 1,4-cyclohexanediol and adipic acid, and 5 parts by mass of 2,2-dimethyl-1,3- Propylene glycol, 30 parts by mass of 2,2-dimethylolpropionic acid, 100 parts by mass of 4,4-dicyclohexylmethane diisocyanate, and 100 parts by mass of N-methyl-2-pyrrolidone were reacted to obtain A urethane prepolymer with a free isocyanate group content of 5% relative to the nonvolatile content. Then, 16 parts by mass of tetramethylene diamine and 10 parts by mass of triethylamine were added to 300 parts by mass of deionized water, and while stirring with a homomixer for 4 hours, the above-mentioned urethane prepolymer was added to emulsify and disperse. , and finally deionized water was added to obtain an aqueous anionic urethane resin with a nonvolatile content of 35% by mass and an acid value of 18 mgKOH/g.

(3) Polyester polyol urethane resin (A-3) 100 parts by mass of polyester polyol having a number average molecular weight of 3,000 obtained from 1,4-cyclohexanediol, neopentyl glycol and adipic acid, and 5 parts by mass of 2,2-dimethylene were added to the reactor. 1,3-propanediol, 30 parts by mass of 2,2-dimethylolpropionic acid, 100 parts by mass of 4,4-dicyclohexylmethane diisocyanate, 100 parts by mass of N-methyl-2-pyrrolidone, It was made to react, and the urethane prepolymer whose content of the free isocyanate group with respect to a nonvolatile component was 5% was obtained. Then, 16 parts by mass of tetramethylene diamine and 10 parts by mass of triethylamine were added to 300 parts by mass of deionized water, and while stirring with a homomixer for 4 hours, the above-mentioned urethane prepolymer was added to emulsify and disperse. , and finally deionized water was added to obtain an aqueous anionic urethane resin with a nonvolatile content of 35% by mass and an acid value of 18 mgKOH/g.

(4) Polycarbonate polyol urethane resin (A-4) 100 parts by mass of a polycarbonate polyol having a number average molecular weight of 3,000 obtained from 1,6-hexanediol and dimethyl carbonate, and 5 parts by mass of 2,2-dimethyl-1,3 were added to the reactor. - Propylene glycol, 30 parts by mass of 2,2-dimethylolpropionic acid, 100 parts by mass of 4,4-dicyclohexylmethane diisocyanate, 100 parts by mass of N-methyl-2-pyrrolidone were reacted, and A urethane prepolymer was obtained with a free isocyanate group content of 5% relative to the nonvolatile components. Then, 16 parts by mass of tetramethylene diamine and 10 parts by mass of triethylamine were added to 300 parts by mass of deionized water, and while stirring with a homomixer for 4 hours, the above-mentioned urethane prepolymer was added to emulsify and disperse. , and finally deionized water was added to obtain an aqueous anionic urethane resin with a nonvolatile content of 35% by mass and an acid value of 18 mgKOH/g.

(5) Polyether polyol urethane resin (A-5) 100 parts by mass of a polyether polyol having a number average molecular weight of 3,000 obtained from ethylene glycol and 1,4-cyclohexanediol, and 5 parts by mass of 2,2-dimethyl-1,3- Propylene glycol, 30 parts by mass of 2,2-dimethylolpropionic acid, 100 parts by mass of 4,4-dicyclohexylmethane diisocyanate, and 100 parts by mass of N-methyl-2-pyrrolidone were reacted to obtain A urethane prepolymer with a free isocyanate group content of 5% relative to the nonvolatile content. Then, 16 parts by mass of tetramethylene diamine and 10 parts by mass of triethylamine were added to 300 parts by mass of deionized water, and while stirring with a homomixer for 4 hours, the above-mentioned urethane prepolymer was added to emulsify and disperse. , and finally deionized water was added to obtain an aqueous anionic urethane resin with a nonvolatile content of 35% by mass and an acid value of 18 mgKOH/g.

<Zirconium oxide (B)> B-1: Zirconia sol, the median particle size is 90 nm. B-2: Ammonium zirconium carbonate.

<Molybdenum oxo salt (C)> C: Ammonium molybdate.

<Hindered amines (D)> D-1: bis(2,2,6,6-tetramethyl-4-piperidinyl)sebacate D-2: bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidinyl)sebacate D-3: Poly[N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine-co-2,4-dichloro-6 -(N-morpholinyl)-1,3,5-triazine] D-4: Bis(1,2,2,6,6-pentamethyl-4-piperidinyl)sebacate.

<Titanium oxide based white pigment (E)> E-1: The median particle diameter was 0.3 μm. E-2: The median particle diameter was 0.7 μm. E-3: The median particle diameter was 1.0 μm.

＜Vinylsilane (F)＞ F: 3-vinyltrimethoxysilane.

＜Silicon dioxide (G)＞ G: Colloidal silica, the median particle size by dynamic light scattering method is 50 nm.

3. Manufacture of coated plated steel sheet The protective layer was produced by applying the water-based surface treatment agent on the plated layer in the plated steel sheet by a roll coater, and then heating at a maximum temperature of 90° C. for 5 seconds. The adhesion amount of the protective layer is shown in the column "Amount of adhesion" in Tables 2 to 13.

4. Evaluation test (1) Blackening resistance (40℃) 0.1cc (100μl) of pure water was dropped on the surface of the protective layer of the plated steel sheet (hereinafter also referred to as "treated plate"), the protective layer was superimposed on the protective layer of another treated plate, and a weight of 6 kg was evenly distributed. A load is placed on the overlapped processing plate. After placing the stacked treatment plate in a constant temperature bath at 40° C. for 120 hours with a heavy object placed, the discoloration of the portion where the pure water was dropped was visually observed and evaluated according to the following evaluation criteria. The evaluation results are shown in Tables 2 to 13. In addition, 4 points or more were made good, and the case of 3 points or less was judged to be unpractical. <Evaluation Criteria> 5 points: no discoloration 4 points: Extremely slight discoloration confirmed 3 points: Slight discoloration confirmed 2 points: A clear discoloration is confirmed 1 point: Clear blackening or discoloration and unevenness were observed.

(2) Blackening resistance (20℃) Except having changed the temperature of the thermostatic chamber to 20 degreeC, the same test as the above-mentioned "(1) blackening resistance (40 degreeC)" was implemented. The discoloration state of the part where the pure water was dripped was visually observed, and it evaluated according to the following evaluation criteria. The evaluation results are shown in Tables 2 to 13. In addition, 4 points or more were made good, and the case of 3 points or less was judged to be unpractical. <Evaluation Criteria> 5 points: no discoloration 4 points: Extremely slight discoloration confirmed 3 points: Slight discoloration confirmed 2 points: A clear discoloration is confirmed 1 point: Clear blackening or discoloration and unevenness were observed.

(3) Concealment of coating wrinkles The appearance of the processing plate was visually observed and evaluated according to the following evaluation criteria. The evaluation results are shown in Table 2. If it is "3" or "2", it is a good appearance. In the case of "1", although the appearance is slightly impaired, there is no practical problem. <Evaluation Criteria> 3: No unevenness 2: Extremely slight discoloration due to unevenness is confirmed 1: Slight discoloration due to unevenness is recognized.

(4) Weather resistance A 24-week outdoor exposure test of the treated boards was carried out from autumn (around September) to spring (around March), and a color difference meter (trade name ColorMeterZE2000, manufactured by Nippon Denshoku Kogyo Co., Ltd.) was used before and after the test to measure the content of the treated boards. The color difference of the protective layer surface. The difference in L value and the difference in b value before and after the test were obtained from the measurement results, and the evaluation was performed according to the following evaluation criteria. The evaluation results are shown in Tables 2 to 13. In addition, regarding the evaluation results of Tables 2 to 13, any lower points among the difference in the L value and the difference in the b value are shown preferentially. In addition, when the evaluation result is determined to be "3" or more, it is determined to be a practical level. <Evaluation Criteria> (difference in L value) 4: More than 0 but less than 2. 3: 2 or more but less than 4. 2: Above 4 but less than 7. 1:7 or more. (difference in b value) 4: More than 0 but less than 1. 3:1 or more but less than 4. 2: Above 4 but less than 7. 1:7 or more.

(5) Corrosion resistance (SST) According to the salt spray test method JIS-Z-2371, the protective layer of the treated plate was sprayed with neutral salt water for 240 hours, and then the ratio (%) of the area where white rust occurred in the treated plate was visually determined, and the following evaluation was performed Benchmarks for evaluation. The evaluation results are shown in Tables 2 to 13. In addition, when the evaluation result is judged to be "3" or more, it is judged to be a practical level. <Evaluation Criteria: White Rust Occurrence Area Rate> 5: The area where white rust occurs is less than 1%. 4: The white rust occurrence area is 1% or more but less than 3%. 3: The white rust occurrence area is 3% or more but less than 10%. 2: The white rust occurrence area is 10% or more but less than 30%. 1: The white rust occurrence area is 30% or more.

(6) Corrosion resistance (end face red rust) According to the salt spray test method JIS-Z-2371, after the protective layer of the treated plate was sprayed with neutral salt water for 1500 hours, it was confirmed whether or not red rust had occurred on the end surface of the treated plate, and the evaluation was performed according to the following evaluation criteria. The evaluation results are shown in Tables 2 to 13. If it is "2", it is good; if it is "1", it is poor. <Evaluation Criteria> 2: No red rust occurs 1: Red rust occurs

[Table 2]

[table 3]

[Table 4]

[table 5]

[Table 6]

[Table 7]

[Table 8]

[Table 9]

[Table 10]

[Table 11]

[Table 12]

[Table 13]

without

without

Domestic storage information (please note in the order of storage institution, date and number) without Foreign deposit information (please note in the order of deposit country, institution, date and number) without

Claims (2)

A coated plated steel sheet comprising a steel sheet, a plated layer, and a protective layer in a sequential lamination manner, wherein, The aforementioned coating layer contains aluminum, silicon, zinc and magnesium, In the plating layer, the ratio of aluminum is in the range of 50.0 mass % or more and 60.0 mass % or less, the ratio of silicon is in the range of 1.0 mass % or more and 3.0 mass % or less, and the ratio of magnesium is 0.5 mass %. % or more and 3.0 mass % or less, and the total ratio of the aluminum, the silicon, and the zinc is 95 mass % or more, The above-mentioned protective layer is formed by the following method: after the water-based surface treatment agent is coated on the surface of the above-mentioned plating layer, it is dried; The aforementioned water-based surface treatment agent contains: Aqueous anionic urethane resin (A) with polyester polyol residue, Zirconia (B), Molybdenum oxoate (C), Hindered amines (D), and water; The mass ratio of the water-based anionic urethane resin (A) to the zirconium in the zirconium oxide (B) is 50:1 to 200:1, The mass ratio of molybdenum in the aforementioned aqueous anionic urethane resin (A) and the aforementioned molybdenum oxo acid salt (C) is 500:1 to 1000:1, The mass ratio of the aforementioned aqueous anionic urethane resin (A) to the aforementioned hindered amines (D) is 50:1 to 200:1. The coated steel sheet according to claim 1, wherein the water-based surface treatment agent further contains a titanium oxide-based white pigment (E).