Surface-treated steel sheet for organic resin coating, method for manufacturing the same, and organic resin coated steel sheet and method for manufacturing the same

Abstract

A method for producing a surface-treated steel sheet for organic resin coating, characterized by applying a surface treatment liquid containing, in a specific ratio, a resin compound having a specific bisphenol skeleton, a cationic polyurethane resin emulsion, a silane coupling agent having a specific reactive functional group, an organic titanium chelate compound, a tetravalent vanadium compound, a molybdate compound, a fluorine compound, and water, and having a pH of 4 to 5, to a surface of a zinc-based plated steel sheet, and drying the same to form a surface treatment film having an adhering amount of 0.005 to 0.18 g / m 2 2 per one side.

Description

Technical Field

[0001] This invention relates to a surface-treated steel plate coated with organic resin and a method for manufacturing the same. Background Technology

[0002] Zinc-coated steel sheets are widely used in the automotive, home appliance, and building materials industries. Previously, to improve corrosion resistance, zinc-coated steel sheets were widely surface-treated with chromate solutions, primarily composed of chromic acid, dichromic acid, or their salts. However, considering recent environmental concerns, there is a growing demand for chromate-free zinc-coated steel sheets (hereinafter referred to as "chromate-free treated steel sheets"), and various chromate-free treated steel sheets are being developed and put into practical use.

[0003] Considering the use of chromate-free steel sheets in various applications such as automobiles, home appliances, and building materials, in addition to corrosion resistance, resistance to blackening and excellent storage stability of surface treatment solutions are also required.

[0004] Patent Document 1 describes a method for manufacturing a surface-treated steel sheet, characterized in that a surface treatment solution containing a resin compound with a specific bisphenol backbone, a cationic polyurethane resin emulsion, a silane coupling agent with specific reactive functional groups, an organotitanium chelate compound, a tetravalent vanadium compound, a molybdate compound, a fluorine compound, and water, with a pH of 4-5, is applied to the surface of a zinc-plated steel sheet and dried, resulting in an adhesion amount of 0.2-1.8 g / m² per single side. 2 The surface treatment film.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2012-67369 Summary of the Invention

[0008] The manufacturing method for surface-treated steel sheets described in Patent Document 1 can produce surface-treated steel sheets with excellent corrosion resistance and resistance to blackening, and is preferred in terms of excellent storage stability of the surface treatment solution. However, Patent Document 1 does not study the corrosion resistance when (i) an organic resin film with a thickness of 60 μm or more or an organic resin film with low elongation is formed on the surface-treated steel sheet, and (ii) the adhesion between the organic resin film and the surface-treated film and the adhesion between the surface-treated film and the coating when the above-mentioned organic resin film is formed on the surface-treated steel sheet and then subjected to rigorous processing. The main purpose of forming an organic resin film on the surface-treated steel sheet is to impart appearance and durability, and ensuring film thickness is very effective. The appropriate film thickness also depends on the type of organic resin film and the environment in which it is used, but it is mostly 60 μm or more. The inventors have conducted research and found that there is room for improvement in (i) and (ii) above in the manufacturing method for surface-treated steel sheets described in Patent Document 1.

[0009] Therefore, in view of the above-mentioned problems, the present invention aims to provide a method for manufacturing a surface-treated steel sheet coated with organic resin, which can produce a surface-treated steel sheet that does not contain chromium compounds, has excellent resistance to blackening, and (i) exhibits excellent corrosion resistance when an organic resin film with a thickness of 60 μm or more or an organic resin film with low elongation is formed on the surface-treated steel sheet, (ii) exhibits excellent adhesion between the organic resin film and the surface-treated film and excellent adhesion between the surface-treated film and the coating when the above-mentioned organic resin film is formed on the surface-treated steel sheet and then subjected to strict processing, and also exhibits excellent storage stability of the surface-treated liquid.

[0010] The inventors have conducted repeated and in-depth research, and have found that the properties of (i) and (ii) above can be improved and the above-mentioned problems can be solved by the combination of the following (A) and (B): (A) using a surface treatment solution with a specific ratio of a resin compound having a specific bisphenol backbone, a cationic polyurethane resin emulsion, a silane coupling agent having a specific reactive functional group, an organotitanium chelate compound, a tetravalent vanadium compound, a molybdate compound, a fluorine compound, and water, and a pH of 4 to 5, wherein the content of the fluorine compound is intentionally set to be relatively high in the above-mentioned specific ratio; and (B) applying the surface treatment solution to the surface of a zinc-plated steel sheet and drying it to form a surface treatment film, wherein the amount of coating per single side is set to 0.005 to 0.18 g / m 2 A small amount.

[0011] The present invention was made based on the following circumstances, and its main structure is as follows.

[0012] [1] A method for manufacturing an organic resin coated surface-treated steel sheet, characterized in that a surface treatment liquid containing (A) to (H) within the range of conditions (1) to (6) and having a pH of 4 to 5 is applied to the surface of a zinc-plated steel sheet, and then dried to form an adhesion amount of 0.005 to 0.18 g / m² per single side. 2 Surface treatment film,

[0013] A resin compound (A) having a bisphenol skeleton represented by the following general formula (I);

[0014] A cationic polyurethane resin emulsion (B) having at least one cationic functional group selected from primary amino to tertiary amino and quaternary ammonium salt groups;

[0015] A silane coupling agent (C) having at least one reactive functional group selected from amino, epoxy, mercapto and methacryloyloxy groups containing active hydrogen;

[0016] Organotitanium chelates (D);

[0017] Vanadium compounds with a valence of four (E);

[0018] molybdate compound (F);

[0019] Fluorine compounds (G); and

[0020] Water (H);

[0021] (1) The mass of solid components (B) of the above-mentioned cationic polyurethane resin emulsion (B) S The mass of solid components relative to the above resin compound (A) (A) S The solid content (B) of the above-mentioned cationic polyurethane resin emulsion (B) S ) and the mass of the solid components of the above-mentioned silane coupling agent (C) (C S The ratio of the total of (B) S ) / {(A S )+(B S )+(C S The value is 0.10 to 0.30.

[0022] (2) The mass of the solid components (C) of the above-mentioned silane coupling agent (C) S The mass of solid components relative to the above resin compound (A) (A) S The solid content (B) of the above-mentioned cationic polyurethane resin emulsion (B) S ) and the mass of the solid components of the above-mentioned silane coupling agent (C) (C S The ratio of the total of (C) S ) / {(A S )+(BS )+(C S The value is 0.60 to 0.85.

[0023] (3) The mass of the solid components (C) of the above-mentioned silane coupling agent (C) S The titanium equivalent mass (D) relative to the above-mentioned organotitanium chelate compound (D) Ti The ratio of ) to {(C) S ) / (D Ti )} is 50-70

[0024] (4) The vanadium equivalent mass (E) of the above tetravalent vanadium compound (E) V The titanium equivalent mass (D) relative to the above-mentioned organotitanium chelate compound (D) Ti The ratio of ) to {(E) V ) / (D Ti The value is 0.30 to 0.50.

[0025] (5) The molybdenum equivalent mass (F) of the above molybdate compound (F) Mo The mass of solid components relative to the above resin compound (A) (A) S The solid content (B) of the above-mentioned cationic polyurethane resin emulsion (B) S ) and the mass of the solid components of the above-mentioned silane coupling agent (C) (C S The ratio of the total of (F) Mo ) / {(A S )+(B S )+(C S The value is 0.003 to 0.030.

[0026] (6) Fluorine equivalent mass (G) of the above fluorine compound (G) F The mass of solid components relative to the above resin compound (A) (A) S The solid content (B) of the above-mentioned cationic polyurethane resin emulsion (B) S ) and the mass of the solid components of the above-mentioned silane coupling agent (C) (C S The ratio of the total of (G) F ) / {(A S )+(B S )+(C S The value is 0.101 to 0.200.

[0027]

[0028] In formula (I), Y1 and Y2, which are bonded to the benzene ring, are each independently a hydrogen atom or a Z group represented by the following general formula (II) or (III). The average number of substitutions of the Z group in each benzene ring is 0.2 to 1.0, and n represents an integer from 2 to 50.

[0029]

[0030] In formulas (II) and (III), R1, R2, R3, R4 and R5 independently represent hydrogen atoms, alkyl groups with 1 to 10 carbon atoms, or hydroxyalkyl groups with 1 to 10 carbon atoms, and A- represents hydroxide ions or acid radical ions.

[0031] [2] The method for manufacturing a surface-treated steel sheet coated with organic resin according to [1] above, wherein the surface treatment liquid is dried under conditions where the maximum plate temperature is 50 to 180°C.

[0032] [3] An organic resin coated surface-treated steel sheet is manufactured by the manufacturing method of the organic resin coated surface-treated steel sheet described in [1] or [2] above.

[0033] [4] A method for manufacturing an organic resin-coated steel sheet, comprising:

[0034] The method for manufacturing the surface-treated steel sheet coated with organic resin as described in [1] or [2] above; and

[0035] The process of forming an organic resin film on the surface-treated steel sheet coated with the aforementioned organic resin.

[0036] [5] The method for manufacturing an organic resin coated steel sheet according to [4] above, wherein the organic resin coating is formed by laminating an organic resin film onto the surface-treated coating.

[0037] [6] In the method for manufacturing an organic resin coated steel sheet according to [5] above, the organic resin film has a thickness of 60 μm or more.

[0038] [7] In the method for manufacturing an organic resin coated steel sheet according to [5] or [6] above, the organic resin film is selected from one or more of polyvinyl chloride film, polyolefin film, polyester film and fluororesin film.

[0039] [8] An organic resin coated steel sheet is manufactured by the manufacturing method of the organic resin coated steel sheet described in any one of [4] to [7] above.

[0040] The method for manufacturing surface-treated steel sheets with organic resin coating of the present invention can produce surface-treated steel sheets that do not contain chromium compounds in the surface-treated coating, have excellent resistance to blackening, and (i) have excellent corrosion resistance when an organic resin coating with a thickness of 60 μm or more or an organic resin coating with low elongation is formed on the surface-treated steel sheet, and (ii) have excellent adhesion between the organic resin coating and the surface-treated coating and excellent adhesion between the surface-treated coating and the coating when the above-mentioned organic resin coating is formed on the surface-treated steel sheet and then subjected to strict processing. In addition, the surface-treated liquid has excellent storage stability. Detailed Implementation

[0041] Zinc-coated steel sheet

[0042] The zinc-coated steel sheet used in this invention can be any type of zinc-coated steel sheet based on cold-rolled steel sheet, such as electroplated Zn steel sheet, hot-dip Zn steel sheet, Zn-Al steel sheet, Zn-Al-Mg steel sheet, Zn-Mg steel sheet, Zn-Fe steel sheet, or Zn-Ni steel sheet. The coating method can be either electroplating or hot-dip galvanizing. Furthermore, to improve the zinc-coated steel sheet's resistance to blackening, the coating can be performed by adding trace amounts of Ni, Co, or an acidic or alkaline aqueous solution containing Ni, Co, and Fe, causing these metals to precipitate on the surface of the zinc-coated steel sheet. From the viewpoint of ensuring corrosion resistance, the coating adhesion amount of the zinc-coated steel sheet is preferably 5 g / m² per single side. 2 above.

[0043] [Surface treatment liquid]

[0044] The surface treatment liquid used in this invention contains a resin compound (A) with a specific bisphenol backbone, a cationic polyurethane resin emulsion (B), a silane coupling agent (C) with specific reactive functional groups, an organotitanium chelate compound (D), a tetravalent vanadium compound (E), a molybdate compound (F), a fluorine compound (G), and water.

[0045] <Resin Compound (A)>

[0046] The resin compound (A) contained in the surface treatment liquid has a bisphenol skeleton represented by the following general formula (I).

[0047]

[0048] In formula (I), Y1 and Y2 bonded to the benzene ring are each independently hydrogen atoms or Z groups represented by the following general formula (II) or (III), the average number of substitutions of the Z groups of each benzene ring is 0.2 to 1.0, and n represents an integer from 2 to 50.

[0049] Here, the average number of substitutions of the Z groups refers to the value obtained by dividing the total number of Z groups introduced by the total number of benzene rings (i.e., 2n). In this invention, when the Z group is selected as at least one of Y1 and Y2, the resin compound (A) has at least one cationic functional group selected from secondary amino, tertiary amino, and quaternary ammonium salt groups, and therefore can dissolve more stably relative to the surface treatment liquid. When the average number of substitutions of the Z groups is less than 0.2, the stability of the surface treatment liquid decreases, and when it exceeds 1.0, the corrosion resistance shown in (i) and the adhesion (especially the adhesion after the boiling water test) shown in (ii) above deteriorate. In addition, in this invention, the average degree of polymerization n is set to 2 to 50. When n is less than 2, the corrosion resistance shown in (i) above becomes insufficient. On the other hand, if n exceeds 50, the stability of the resin compound (A) in the surface treatment liquid decreases due to the decrease in water solubility, thickening, etc., and the storage stability becomes insufficient. Preferably, n is 2 to 10.

[0050]

[0051]

[0052] In formulas (II) and (III), R1, R2, R3, R4, and R5 are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or a hydroxyalkyl group having 1 to 10 carbon atoms. If the alkyl group or hydroxyalkyl group has more than 10 carbon atoms, the resin compound (A) cannot be sufficiently dissolved in water and becomes unstable in the surface treatment solution. Specific examples of R1, R2, R3, R4, and R5 include methyl, ethyl, propyl, butyl, hydroxyethyl, 2-hydroxypropyl, and hydroxyisobutyl. - This refers to hydroxide ions or acid radical ions. Specific examples of acid radical ions include acetate ions, phosphate ions, and formate ions.

[0053] The resin compound (A) represented by general formula (I) is a bisphenol-formalin condensate. The synthesis method is not limited, and it can be obtained, for example, by reacting formalin and an amine with bisphenol A in the presence of a base catalyst.

[0054] <Catonic polyurethane resin emulsion (B)>

[0055] The cationic polyurethane resin emulsion (B) contained in the surface treatment solution is not particularly limited in terms of the polyol, isocyanate component, and polymerization method, as long as it has at least one cationic functional group selected from primary amino, secondary amino, tertiary amino, and quaternary ammonium salt groups. Examples of cationic functional groups include amino, methylamino, ethylamino, dimethylamino, diethylamino, trimethylamino, and triethylamino groups, and there are no particular limitations as long as it is a primary amino, secondary amino, tertiary amino, or quaternary ammonium salt group.

[0056] <Silane Coupling Agent (C)>

[0057] The silane coupling agent (C) contained in the surface treatment solution is not particularly limited as long as it has at least one reactive functional group selected from amino, epoxy, mercapto, and methacryloyloxy groups containing active hydrogen. Trialkoxysilanes having three alkoxy groups are particularly preferred. Specific examples include N-(2-aminoethyl)3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, and 3-mercaptopropyltrimethoxysilane.

[0058] <Organotitanium chelates (D)>

[0059] The organotitanium chelate compound (D) contained in the surface treatment solution is not particularly limited, and examples include titanium acetylacetonate, titanium octylene glycolate, titanium tetraacetylacetonate, and titanium ethylacetoacetate. Inorganic salts such as titanium nitrate, titanium sulfate, titanium acetate, titanium phosphate, and titanium carbonate are not preferred because they do not enhance the corrosion resistance shown in (i) above. It should be noted that when the organotitanium chelate compound (D) is dissolved in water, titanium dissolves as a chelate ligand; therefore, it is preferable not to add highly polar water-soluble solvents or peroxides that affect the polarity of this ligand.

[0060] <Tetravalent vanadium compounds (E)>

[0061] The tetravalent vanadium compound (E) contained in the surface treatment solution is not particularly limited, and examples include vanadium oxysulfate, vanadium oxydichloride, vanadium oxyphosphate, vanadium oxyoxalate, and vanadium acetylacetonate. From the viewpoint of achieving even higher corrosion resistance, the tetravalent vanadium compound (E) preferably produces VO₂. 2+Vanadium compounds with (vanadium oxy) ions. Vanadium compounds with a valence of 5 (e.g., ammonium metavanadate) are not used in this invention because their water solubility is too high, resulting in high leaching from the film and insufficient adhesion as described in (ii) above (especially adhesion after boiling water test).

[0062] <Molybdate compound (F)>

[0063] The molybdenum compound (F) contained in the surface treatment solution is not particularly limited, and examples include molybdic acid, ammonium molybdate, sodium molybdate, potassium molybdate, magnesium molybdate, zinc molybdate, etc. Additionally, examples include phosphomolybdic acid, ammonium phosphomolybdate, sodium phosphomolybdate, etc. In this invention, it is preferred to use one or more compounds selected from these compounds.

[0064] <Fluorine compounds (G)>

[0065] The fluorine compound (G) contained in the surface treatment solution is not particularly limited, and examples include hydrofluoric acid, fluorosilicic acid, fluoroboric acid, fluorotitanic acid, acidic ammonium fluoride, sodium fluoride, fluorozirconic acid, and their salts. In this invention, it is preferred to use one or more of these.

[0066] [(B S ) / {(A S )+(B S )+(C S ))]:0.10~0.30

[0067] In the surface treatment solution, the mass of solids component (B) of the cationic polyurethane resin emulsion (B) S The mass of solid components relative to resin compound (A) S The solid content (B) of the cationic polyurethane resin emulsion (B) S The solid composition mass (C) of the silane coupling agent (C) and the silane coupling agent (C) S The ratio of the total of (B) S ) / {(A S )+(B S )+(C SThe mass ratio must be between 0.10 and 0.30. If the mass ratio is less than 0.10, the proportion of polyurethane resin becomes too low, and the surface-treated film tends to harden. As a result, if processing is performed after forming an organic resin film on the surface-treated steel sheet, the surface-treated film is damaged, and peeling occurs from the surface-treated film to the organic resin film formed thereon, starting from that point. That is, the adhesion (especially the adhesion after the boiling water test) shown in (ii) above deteriorates. Therefore, the mass ratio is 0.10 or more, preferably 0.12 or more. On the other hand, if the mass ratio exceeds 0.30, the adhesion (especially the adhesion after the boiling water test) shown in (ii) above deteriorates. Therefore, the mass ratio is 0.30 or less, preferably 0.28 or less.

[0068] [(C S ) / {(A S )+(B S )+(C S )}]:0.60~0.85

[0069] In the surface treatment solution, the mass of solid component (C) of silane coupling agent (C) S The mass of solid components relative to resin compound (A) S The mass of solids in cationic polyurethane resin emulsion (B) S The solid composition mass (C) of the silane coupling agent (C) and the silane coupling agent (C) S The ratio of the total of (C) S ) / {(A S )+(B S )+(C S The mass ratio must be between 0.60 and 0.85. If the mass ratio is less than 0.60, the adhesion (especially the adhesion after the boiling water test) described above deteriorates. Therefore, the mass ratio is 0.60 or more, preferably 0.65 or more. On the other hand, if the mass ratio exceeds 0.85, the storage stability of the surface treatment solution decreases. Therefore, the mass ratio is 0.85 or less, preferably 0.80 or less.

[0070] {(C S ) / (D Ti )}:50~70

[0071] In the surface treatment solution, the mass of solid component (C) of silane coupling agent (C) S Titanium equivalent mass (D) relative to organotitanium chelate (D) Ti The ratio of ) to {(C) S ) / (D TiThe mass ratio must be between 50 and 70. If the mass ratio is less than 50, the corrosion resistance shown in (i) and the adhesion (especially the adhesion after the boiling water test) shown in (ii) deteriorate. Therefore, the mass ratio is 50 or more, preferably 55 or more. On the other hand, if the mass ratio exceeds 70, the solubility of the surface-treated film increases, and the adhesion (especially the adhesion after the boiling water test) shown in (ii) is poor. Therefore, the mass ratio is 70 or less, preferably 65 or less.

[0072] It should be noted that in this invention, when calculating various mass ratios, the solid component mass (C) of the silane coupling agent (C) is... S The mass of silanol (R-Si(-OR1)3) after hydrolysis refers to the mass of silanol (R-Si(-OH)3). This is because when the silane coupling agent is dissolved in water, most of it undergoes hydrolysis. The alcohol produced by hydrolysis evaporates when the surface treatment solution is coated and dried to form a surface treatment film, and does not function as an effective component.

[0073] {(E V ) / (D Ti )}:0.30~0.50

[0074] In the surface treatment solution, the vanadium equivalent mass (E) of tetravalent vanadium compounds (E) V Titanium equivalent mass (D) relative to organotitanium chelate (D) Ti The ratio of ) to {(E) V ) / (D Ti The mass ratio must be between 0.30 and 0.50. If the mass ratio is less than 0.30, the corrosion resistance shown in (i) above deteriorates. Therefore, the mass ratio is 0.30 or more, preferably 0.35 or more. On the other hand, if the mass ratio exceeds 0.50, the sealing performance shown in (ii) above (especially the sealing performance after the boiling water test) is poor. Therefore, the mass ratio is 0.50 or less, preferably 0.48 or less.

[0075] [(F Mo ) / {(A S )+(B S )+(C S )}]:0.003~0.030

[0076] In the surface treatment solution, the molybdenum equivalent mass (F) of the molybdate compound (F) Mo The mass of solid components relative to resin compound (A) S The mass of solids in cationic polyurethane resin emulsion (B) S ), and the solid composition mass (C) of the silane coupling agent (C) S The ratio of the total of (F)Mo ) / {(A S )+(B S )+(C S The mass ratio must be between 0.003 and 0.030. When the mass ratio is less than 0.003, the resistance to blackening deteriorates. Therefore, the mass ratio is 0.003 or more, preferably 0.006 or more. On the other hand, if the mass ratio exceeds 0.030, the storage stability of the surface treatment solution decreases. Therefore, the mass ratio is 0.030 or less.

[0077] [(G F ) / {(A S )+(B S )+(C S )}]:0.101~0.200

[0078] In the surface treatment solution, the fluorine equivalent mass (G) of the fluorine compound (G) F The mass of solid components relative to resin compound (A) S The mass of solids in cationic polyurethane resin emulsion (B) S The solid composition mass (C) of the silane coupling agent (C) and the silane coupling agent (C) S The ratio of the total of (G) F ) / {(A S )+(B S )+(C S The mass ratio must be between 0.101 and 0.200. If the mass ratio is less than 0.101, the adhesion (especially the adhesion after the boiling water test) shown in (ii) above is poor. Therefore, the mass ratio is 0.101 or more, preferably 0.105 or more. On the other hand, if the mass ratio exceeds 0.200, the soluble components of the surface-treated film increase, thus deteriorating the corrosion resistance shown in (i) above and the adhesion (especially the adhesion after the boiling water test) shown in (ii) above. Therefore, the mass ratio is 0.200 or less.

[0079] pH: 4-5

[0080] The pH of the surface treatment solution is 4–5. If the pH is less than 4, more zinc will dissolve from the zinc-plated steel sheet coating, resulting in a deterioration of the corrosion resistance as described in (i) above. On the other hand, if the pH exceeds 5, the storage stability of the surface treatment solution cannot be achieved.

[0081] Here, phosphoric acid (orthophosphoric acid), acetic acid, formic acid, hydrofluoric acid, and fluorides are preferred as acidic agents used to adjust the pH to 4-5. Acetic acid and formic acid are weak acids, making them suitable for pH adjustment. Furthermore, they are highly volatile, evaporating during the drying of the surface treatment solution and leaving little residue in the surface-treated film. Therefore, even if added in excess, performance degradation is minimal, making them preferred. On the other hand, in cases where the pH becomes too low, ammonia or amines with a boiling point below 100°C are preferred as alkaline agents used to adjust the pH to 4-5.

[0082] <Water>

[0083] The water contained in the surface treatment solution preferably has minimal impact on the components of the resin compound (A), the cationic polyurethane resin emulsion (B), the silane coupling agent (C), and the organotitanium chelate compound (D), as well as on the acidic or alkaline components used for pH adjustment. Impurities such as Na and Cl contained in the water can sometimes reduce corrosion resistance or coatability if they remain in the film. Therefore, the water used preferably has few impurities, for example, preferably has a conductivity of less than 100 μS / cm. More preferably, it is 50 μS / cm or less, and even more preferably, it is 10 μS / cm or less.

[0084] <Solid component concentration>

[0085] The solid content concentration of the surface treatment solution is preferably 0.05 to 5% by mass, based on the solid content concentration after drying at 110°C for 2 hours. This is because setting the solid content concentration to the range of 0.05 to 5% by mass makes it easy to ensure the adhesion of the surface treatment film described later, and also ensures the stability of the surface treatment solution.

[0086] <Other Ingredients>

[0087] Defoamers and wettability improvers can be added to the surface treatment solution as needed. There are no particular limitations on the type of defoamer; for example, silicone-based or fatty acid-based emulsion types can be used. Wetness improvers reduce the surface tension of the surface treatment solution, improving the wettability of zinc-plated steel sheets and enhancing appearance uniformity. Examples of wettability improvers include water-soluble solvents such as ethanol, tert-butanol, and butyl cellosolve, but are not limited to these. Furthermore, wettability improvers containing acetylene also have defoaming effects and are therefore suitable. To further improve resistance to blackening, nitrates such as nickel nitrate and ammonium nitrate can be added to the surface treatment solution. In the surface treatment solution, other components including these defoamers, wettability improvers, and nitrates constitute 7% by mass or less of the solid content.

[0088] [Manufacturing method for surface-treated steel sheets coated with organic resin]

[0089] The method for manufacturing the surface-treated steel sheet coated with organic resin of the present invention includes applying the above-mentioned surface treatment liquid to the surface of a zinc-plated steel sheet and drying it to form an adhesion amount of 0.005 to 0.18 g / m² per single side. 2 The process of surface treatment coating, thereby enabling the manufacture of surface-treated steel sheets with organic resin coatings that do not contain chromium compounds, are resistant to blackening, and exhibit excellent corrosion resistance as described in (i) and adhesion as described in (ii).

[0090] The method for applying a surface treatment solution to the surface of zinc-plated steel sheet can be any of the following: coating, dipping, or spraying. The coating method can be any of the following: roller coater (3-roller, 2-roller, etc.), extrusion coater, die coater, bar coater, etc. Furthermore, after applying the surface treatment solution, the coating amount, appearance uniformity, and film thickness uniformity can be achieved through air knife method or roller drawing method.

[0091] Maximum plate temperature reached: 50~180℃

[0092] After applying the surface treatment solution, it is usually dried by heating without washing. Drying methods include dryers, hot air furnaces, high-frequency induction heating furnaces, and infrared furnaces. When the surface treatment solution comes into contact with the surface of the zinc-plated steel sheet, the plating components react with fluorine compounds (G), which are reactive components in the surface treatment solution, on the surface of the zinc plating layer. This forms a reaction layer of plating components and fluorides, etc., and the surface treatment solution dries, thereby forming a surface-treated film. The inventors hypothesize that this improves the adhesion between the plating layer and the surface-treated film. However, if the amount of (G) is high, fluorine compounds not consumed by the reaction at the interface between the plating layer and the surface-treated film remain in the surface-treated film, creating areas of insufficient film formation. This leads to reduced corrosion resistance when an organic resin film is formed and decreased adhesion between the organic resin film and the surface-treated film after a boiling water test. However, the inventors hypothesize that if reactive components not consumed in the reaction at the interface between the coating and the surface treatment liquid remain in the surface treatment film as soluble components, a mixed layer can be formed at the interface between the organic resin film and the surface treatment film, thereby improving the adhesion between the organic resin film and the surface treatment film. Furthermore, it is believed that the surface treatment film also contains water-soluble solvents from wetting improvers and surfactants from resin compounds (A) or cationic polyurethane resin emulsions (B), so even if the treatment liquid forming the organic resin film is solvent-based, trace amounts of reactive components will mix into the organic resin side. To achieve the above effects, the maximum plate temperature is preferably 50°C or higher. At temperatures below 50°C, excessive reactive components remain in the surface treatment film, resulting in insufficient film formation. During processing after the organic resin film is formed, the surface treatment film is damaged, and peeling of the surface treatment film and the organic resin film formed thereon easily occurs from this point. Preferably, the temperature is 70°C or higher. On the other hand, if the temperature exceeds 180°C, the amount of reactive components remaining in the surface-treated film decreases, and an interfacial mixture layer with the organic resin film formed thereon is not formed, thus reducing the effect of improving the adhesion between the surface-treated film and the organic resin film. Therefore, the maximum plate temperature reached is preferably below 180°C, more preferably below 140°C, and even more preferably below 110°C. Furthermore, the holding time at the maximum plate temperature is preferably less than 15 seconds.

[0093] The adhesion amount of the surface-treated film per single side is 0.005~0.18g / m². 2

[0094] In this invention, the amount of surface-treated film adhering to each single side must be 0.005–0.18 g / m². 2 When the adhesion amount is less than 0.005 g / m 2In this case, the corrosion resistance shown in (i) above and the adhesion shown in (ii) above (especially the adhesion after the boiling water test) deteriorate. Therefore, the adhesion amount is 0.005 g / m 2 The above is preferably 0.010 g / m 2 That's all. On the other hand, if the adhesion amount exceeds 0.18 g / m 2 If the surface treatment film is damaged during processing after the organic resin film has formed, peeling of the surface treatment film and the organic resin film formed thereon will occur, starting from that point. In other words, the adhesion shown in (ii) above (especially the adhesion after the boiling water test) deteriorates. Therefore, the adhesion amount is 0.18 g / m 2 The preferred value is 0.14 g / m³. 2 the following.

[0095] It should be noted that the above-mentioned surface treatment coating can be applied to one side or both sides of the zinc-plated steel sheet.

[0096] [Function of the Invention]

[0097] In the surface treatment liquid used in this invention, it is presumed that each component has the following effect, but this invention is not limited by these presumptions.

[0098] In the surface treatment liquid used in this invention, resin compound (A), cationic polyurethane resin emulsion (B), and silane coupling agent (C) are the main components, and the skeleton of the surface treatment film is formed by these main components.

[0099] The resin compound (A) has bisphenol as the backbone of phenol, thus it is not easily soluble in polar solvents (conferring solvent resistance) and improves the corrosion resistance shown in (i) above.

[0100] However, the aforementioned resin compound (A) tends to harden the surface-treated film. As a result, if processing is performed after the formation of the organic resin film, the surface-treated film is damaged, and peeling of the surface-treated film and the organic resin film formed thereon occurs from this point. Therefore, in this invention, by incorporating a cationic polyurethane resin emulsion (B), the hardness of the phenolic resin can be mitigated, thus preventing damage to the surface-treated film due to processing.

[0101] While the cationic polyurethane resin emulsion (B) exhibits the aforementioned effects, the adhesion between the organic resin film and the surface-treated film, as well as the adhesion between the surface-treated film and the coating, is weak. Therefore, due to insufficient adhesion between the organic resin film and the surface-treated film during formation, and insufficient adhesion between the surface-treated film and the coating, a silane coupling agent (C) is incorporated. The silane coupling agent (C) generates active silanol groups (Si-OH) through the hydrolysis of its terminal alkoxy groups, thus bonding with the zinc-plated steel surface and contributing to improved adhesion between the surface-treated film and the coating during the formation of the organic resin film. Furthermore, the silane coupling agent possesses organic functional groups, which also contribute to improved adhesion with the organic resin film. Additionally, a portion of the silane coupling agent (C) undergoes dehydration condensation to generate siloxane bonds (Si-O-Si), which are continuously polymerized (polysiloxaneization: -Si-O-Si-O-Si-). This results in an extremely stable structure, with improved corrosion resistance as shown in (i) and improved sealing performance as shown in (ii) (especially sealing performance after boiling water test).

[0102] Therefore, it is believed that by using resin compound (A), cationic polyurethane resin emulsion (B), and silane coupling agent (C) as the main components of the surface treatment liquid in appropriate proportions, a good balance of various properties can be obtained. However, using only the above-mentioned main components, as in this invention, when the amount of surface treatment film adhering is small, the corrosion resistance after organic resin coating cannot be ensured. Therefore, in the surface treatment liquid used in this invention, in addition to the above-mentioned main components, an organotitanium chelate compound (D) is an essential component. It is presumed that the organotitanium chelate compound (D) acts as a catalyst to promote polysiloxaneization when the surface treatment liquid is dried to form a surface treatment film. Thus, even with a small amount of surface treatment film adhering, the corrosion resistance after organic resin coating is ensured.

[0103] To achieve the aforementioned effects, a predetermined amount of organotitanium chelate compound (D) is required, as described above, based on the amount of silane coupling agent (C). Insufficient (D) yields the desired effect, while excessive (D) results in an overabundance of polysiloxane, leading to a hard and brittle surface-treated film. If processing is performed after the formation of the organic resin film, the surface-treated film is damaged, and peeling from the surface-treated film to the organic resin film occurs from this point. This results in a deterioration of the adhesion (especially after the boiling water test) as described in (ii). Furthermore, while it is ideal for polysiloxane formation by organotitanium chelate compound (D) to be promoted during surface-treated film formation, since polysiloxane formation is also promoted during storage of the surface-treated solution, excessive (D) content reduces storage stability (inhibition of thickening and gelation), resulting in a quality that is not the same after storage as before storage.

[0104] Furthermore, tetravalent vanadium compounds (E) are also an essential component in the surface treatment solution of this invention. It is presumed that tetravalent vanadium compounds (E) in this invention act as corrosion inhibitors, such as zinc passivation during plating. It is particularly presumed that vanadium oxyion [VO₄⁻], which has one oxygen atom, is particularly effective. 2+ Even in humid environments, it is not easily dissolved, remains in the surface-treated film, and acts as an inhibitor. Therefore, even if the surface-treated film or the coated surface itself is scratched, the corrosion resistance of that part is prevented from deteriorating. It should be noted that the inventors speculate that this effect is achieved through the synergistic effect of Ti, which is also a cation, on the premise that the film framework with cationic functional groups is suitable.

[0105] Furthermore, molybdate compound (F) is also an essential component in the surface treatment solution used in this invention. In zinc-plated steel sheets, whether electroplated or hot-dip galvanized, blackening of the plating surface is common in corrosive environments. Particularly in zinc-plated hot-dip galvanized steel sheets, when Mg and Al are added to improve corrosion resistance or adhesion between the coating and the base steel sheet, these elements thicken at the interface between the coating and the base steel sheet, and on the surface of the coating, promoting blackening and resulting in a darker appearance compared to pure zinc-plated steel sheets. The cause of blackening in zinc-plated steel sheets is unclear. It is said that zinc oxide formed on the outermost surface of the coating loses oxygen and becomes oxygen-deficient zinc oxide, or that insufficient oxygen supply during zinc corrosion (oxidation) results in oxygen-deficient zinc oxide forming on the plating surface, both of which appear black.

[0106] In this invention, excellent resistance to blackening is achieved by introducing a molybdenum acid compound (F) into a surface-treated film. Molybdenum is a transition metal that bonds with oxygen to form molybdenum oxide (MoO2, MOO3) and molybdenum acid (MoO4). 2- It is believed that in this invention, molybdic acid (MOO4) 2- A portion of the zinc oxide, under high temperature and humidity or corrosive environments, transforms into molybdenum oxides (MoO2, MoO3), thus moderately supplying oxygen to the surface of the zinc plating layer, making it less prone to forming oxygen-deficient zinc oxide. The inventors hypothesize that this mechanism improves resistance to blackening.

[0107] In the surface treatment solution used in this invention, fluorine compound (G) is an essential component. The inventors speculate that this is because, by adding fluorine compound (G), when the surface treatment solution comes into contact with the zinc-plated steel sheet surface, a reaction layer of plating components and fluorides is formed on the surface of the zinc plating, improving the adhesion between the plating and the surface treatment film. However, if the amount of (G) is insufficient, the reaction layer cannot be uniformly formed on the plating surface, leading to peeling of the surface treatment film at the interface between the plating and the surface treatment film when an organic resin film is formed. On the other hand, if the amount of (G) is excessive, fluorine compounds not consumed in the reaction at the interface between the plating and the surface treatment film remain in the surface treatment film, reducing the corrosion resistance during the formation of the organic resin film and the adhesion between the organic resin film and the surface treatment film after the boiling water test. However, by reducing the amount of surface treatment film adhered and lowering the drying temperature (or shortening the drying time), a thin and uniform reaction layer can be formed on the plating surface, allowing an appropriate amount of unreacted fluorine compounds to remain in the surface treatment film. Therefore, the corrosion resistance shown in (i) and the sealing performance shown in (ii) above can be ensured (especially the sealing performance after the boiling water test). At this time, F is prone to occur. - Hydrofluoric acid and its salts, ammonium fluoride, sodium fluoride, especially surface treatment films and coatings, have a great effect on improving the adhesion between the film and the coating, and are easy to leave a suitable amount of soluble components in the film, so they are preferred.

[0108] [Organic resin coated steel sheet and its manufacturing method]

[0109] The organic resin coated steel sheet of the present invention forms an organic resin film on the surface-treated coating of the surface-treated steel sheet described above. The method for forming this organic resin film is arbitrary; for example, a method for applying and drying a coating composition, a method for laminating an organic resin film, etc., can be used. As the coating composition, acrylic resin, epoxy resin, polyurethane resin, phenolic resin, polyester resin, and mixtures thereof are preferred. As the organic resin film, one or more films selected from polyvinyl chloride film, polyolefin film, polyester film, and fluoropolymer film are preferred, or laminated films formed by laminating two or more of these. The thickness of the organic resin film is preferably 60 μm or more, more preferably 100 μm or more. Although no particular upper limit is defined, the thickness is preferably 600 μm or less.

[0110] Furthermore, the organic resin-coated steel sheet of the present invention exhibits excellent corrosion resistance as described in (i) above and excellent adhesion as described in (ii) above (especially adhesion after boiling water test).

[0111] It should be noted that various additives, such as non-chromium rust inhibitors, solid lubricants, and coloring pigments, can be incorporated into organic resin coatings.

[0112] Example

[0113] The surface treatment solution uses the following components: resin compound (A) as shown in Table 1 (Table 1a and Table 1b), polyurethane resin emulsion (B) as shown in Table 2, silane coupling agent (C) as shown in Table 3, titanium compound (D) as shown in Table 4, vanadium compound (E) as shown in Table 5, molybdate compound (F) as shown in Table 6, and fluorine compound (G) as shown in Table 7. Additionally, various zinc-plated steel sheets as shown in Table 8 are prepared.

[0114] The components listed in Tables 1 to 7 are mixed according to the proportions shown in Tables 9-1 and 9-2. After adjusting the pH to the value shown in Table 9-2 using acetic acid or ammonia, deionized water is added so that the solid component concentration after drying at 110°C for 2 hours is as shown in Table 10, to prepare surface treatment solutions of various levels. It should be noted that ion-exchange water with a conductivity of 10 μS / cm is used as the deionized water mentioned above. It should be noted that the mass ratios (X1) to (X6) shown in Table 9-2 refer to the mass ratios (1) to (6) specified in claim 1, respectively.

[0115] On one side of zinc-coated steel sheets of the types shown in Table 10, surface treatment solutions of various levels were applied using a roller coater. Without washing, the sheets were heated and dried to the maximum plate temperature (PMT) shown in Table 10 to produce surface-treated steel sheets of various levels. The adhesion amount of the surface treatment film on each side was adjusted to the values ​​shown in Table 10 by adjusting the coating conditions (roller pressure, rotation speed, etc.) and the solid content concentration of the surface treatment solution. It should be noted that the adhesion amount of the surface treatment film was quantified by using a fluorescence X-ray analysis device to determine the amount of Si in the silane coupling agent (C) incorporated into the surface treatment film, and the amount of Si was calculated from this Si content.

[0116] Furthermore, prepare the organic resin films or coatings shown in Table 11. In Table 11, R1 is a 200 μm thick polyvinyl chloride film with high elongation, R2 is a 100 μm thick polyester film with low elongation, and R3 is a 100 μm thick polyolefin film with low elongation. At each level, an adhesive layer is formed by applying an adhesive to the surface-treated film with a dry film thickness of 3 μm, followed by heat drying (up to a maximum plate temperature of 80°C). Next, the organic resin films of the types shown in Table 10 are hot-pressed onto the adhesive layer at 210°C to bond the films (organic resin films) together, thus producing an organic resin-coated steel sheet. Additionally, R4 is a polyolefin coating composition, which is applied to the surface-treated film and dried at 150°C for 30 minutes to produce an organic resin-coated steel sheet.

[0117] Samples taken from surface-treated steel sheets at each level were evaluated for their resistance to blackening as shown in (1) below. Additionally, samples taken from organic resin-coated steel sheets at each level were evaluated for their corrosion resistance and adhesion as shown in (2) to (6) below. Furthermore, the surface-treated liquids at each level were evaluated for their storage stability as shown in (7) below. The results are shown in Table 12.

[0118] (1) Resistance to blackening

[0119] The change in brightness (L value) of each sample after standing for 24 hours in a constant temperature and humidity chamber at 50°C and 95% relative humidity was calculated (ΔL = L value after test - L value before test). The evaluation criteria are as follows. The L value was measured using an SR2000 manufactured by Nippon Denshoku Kogyo Co., Ltd. in SCE mode (excluding positive reflection light).

[0120] ◎:-6≤ΔL

[0121] ○: -10≤ΔL<-6

[0122] △:-14≤ΔL<-10

[0123] ×:ΔL<-14

[0124] (2) Corrosion resistance of organic resin coated steel plates

[0125] A cross-cut corrosion test was performed on the surface of a 50mm × 100mm sample, and a 1000-hour salt spray test was conducted according to JIS-Z-2371-2000. The unilateral corrosion width from the cross-cut was measured. The evaluation criteria are as follows.

[0126] ◎: The average corrosion width starting from the grid section is less than 5mm.

[0127] ○: The average corrosion width starting from the grid section is more than 5mm and less than 10mm.

[0128] △: The average corrosion width starting from the grid section is more than 10mm and less than 15mm.

[0129] ×: The average corrosion width starting from the grid section is over 15mm.

[0130] (3) Adhesion of organic resin coated steel plate 1

[0131] Using a cutting tool, cuts were made on the sample surface to form a 5mm square grid (well-shaped) in the center of the Erickson processing (described later). After being suspended to 6mm using an Erickson testing machine, the peeling area of ​​the organic resin film within the 5mm square was measured.

[0132] ◎: Not stripped

[0133] ○: Less than 3% of the peeled area

[0134] △: Peeling area is 3% or more but less than 10%

[0135] ×: Peeling area of ​​10% or more

[0136] (4) Adhesion of the organic resin-coated steel plate after the boiling water test 1

[0137] Each sample was immersed in boiling water for 2 hours and then lifted out. The peeling area of ​​each sample was then determined using the same method as described in (3) above.

[0138] ◎: No peeling

[0139] ○: Less than 3% of the peeled area

[0140] △: Peeling area is 3% or more but less than 10%

[0141] ×: Peeling area of ​​10% or more

[0142] (5) Adhesion of organic resin coated steel plate 2

[0143] Using a cutting tool, a 5mm square grid (well-shaped) is formed in the center of the sample surface during the Erickson machining process (described later) to make a cut that reaches the zinc-plated steel sheet. After being suspended to 8mm using an Erickson testing machine, the peeling area of ​​the organic resin film within the 5mm square is measured.

[0144] ◎: No peeling

[0145] ○: Less than 3% of the peeled area

[0146] △: Peeling area is 3% or more but less than 10%

[0147] ×: Peeling area of ​​10% or more

[0148] (6) Adhesion of organic resin coating after boiling water test 2

[0149] Each sample was immersed in boiling water for 2 hours and then lifted out. The peeling area of ​​each sample was then measured using the same method as described in (5) above.

[0150] ◎: No stripping

[0151] ○: Less than 3% of the peeled area

[0152] △: Peeling area is 3% or more but less than 10%

[0153] ×: Peeling area of ​​10% or more

[0154] (7) Storage stability

[0155] After storing the surface treatment solutions at each level in a constant temperature bath at 40°C for 30 days, the appearance of each surface treatment solution was visually observed for investigation and evaluation. The evaluation criteria are as follows.

[0156] ◎: No change

[0157] O: I saw a very small amount of sediment.

[0158] △: You may see trace amounts of sediment or a slight increase in viscosity.

[0159] ×: Observing a large amount of precipitation or gelation

[0160]

[0161]

[0162] [Table 2]

[0163] Table 2 Polyurethane Resin (B)

[0164] No. Polyurethane resin (B) Ionicity Manufacturer B1 ADEKA BONTIGHTER HUX-670 cation ADEKA Co., Ltd. B2 Super Flex 600 cation Daiichi Kogyo Pharmaceutical Co., Ltd. B3 PERMARIN UC-20 cation Sanyo Chemical Industries, Ltd. <![CDATA[ B4 ]]> <![CDATA[ ADEKA BONTIGHTER UX-206 ]]> <![CDATA[ nonionic ]]> ADEKA Co., Ltd. <![CDATA[ B5 ]]> <![CDATA[ HYDRAN AP-10 anion ]]> <![CDATA[ anions ]]> DIC Co., Ltd.

[0165] [Table 3]

[0166] Table 3 Silane Coupling Agents (C)

[0167] No. Silane coupling agent (C) C1 3-Mercaptopropyltrimethoxysilane C2 N-(2-Aminoethyl)-3-aminopropyltrimethoxysilane C3 3-Glycidoxypropyltrimethoxysilane C4 3-Methacryloxypropyltrimethoxysilane <![CDATA[ C5 ]]> <![CDATA[ Vinyltrimethoxysilane ]]>

[0168] [Table 4]

[0169] Table 4 Titanium Compounds (D)

[0170] No. Titanium compounds (D) D1 Titanium acetylacetonate (Ti: 12.5% ​​by mass) D2 Titanium tetraacetylacetonate (Ti: 10.8% by mass) <![CDATA[ D3 ]]> <![CDATA[ Titanium nitrate (Ti: 16.2% by mass) ]]> <![CDATA[ D4 ]]> <![CDATA[ Fluorotitanic acid (Ti: 29.2% by mass) ]]>

[0171] [Table 5]

[0172] Table 5 Vanadium compounds (E)

[0173] No. Vanadium compounds (E) E1 Vanadium oxalate (V: 32.9% by mass) E2 Vanadyl acetylacetonate (V: 19.2% by mass) E3 Vanadium oxysulfate (V: 31.2% by mass) <![CDATA[ E4 ]]> <![CDATA[ Ammonium metavanadate (V: 43.5% by mass) ]]>

[0174] [Table 6]

[0175] Table 6. Molybdate Compounds (F)

[0176] No. Molybdate compound (G) F1 <![CDATA[Na2MoO4·2H2O]]> F2 <![CDATA[(NH4)6Mo7O 24 ·4H2O]]> F3 <![CDATA[(NH4)3[PMo 12 O 40 ]·3H2O]]>

[0177] [Table 7]

[0178] Table 7 Fluorine Compounds (G)

[0179] No. Fluorine compounds (G) G1 hydrofluoric acid G2 Fluorosilicic acid G3 Fluorotitanic acid G4 Acidic ammonium fluoride G5 Sodium fluoride

[0180] [Table 8]

[0181] Table 8 Zinc-coated steel sheets

[0182]

[0183] *Although the plating is applied on both sides, the above represents the amount of plating applied per single side.

[0184]

[0185]

[0186]

[0187]

[0188]

[0189]

[0190]

[0191]

[0192]

[0193] [Table 11]

[0194] Table 11 Organic Resin Coatings

[0195] No. membrane or coating Film thickness R1 Polyvinyl chloride film 200μm R2 Polyester film 100μm R3 Polyolefin membranes 100μm R4 Polyolefin coatings 60μm

[0196]

[0197]

[0198]

[0199] As shown in Table 12, in the examples of the present invention, each example has excellent resistance to blackening, corrosion resistance and adhesion after being coated with organic resin, and storage stability.

[0200] Industrial availability

[0201] The zinc-coated steel sheet with a surface-treated coating manufactured by the manufacturing method of the present invention can be widely used in the fields of automobiles, home appliances, and building materials.

Claims

1. A method of manufacturing an organic resin-coated steel sheet, comprising: A method for producing a surface-treated steel sheet for organic resin coating, and a step of forming an organic resin film on the surface treatment film of the surface-treated steel sheet for organic resin coating; The method for producing a surface-treated steel sheet coated with an organic resin is characterized by applying a surface treatment liquid containing A to H in a range satisfying the following conditions (1) to (6) and having a pH of 4 to 5 to the surface of a zinc-based plated steel sheet, and drying it to form a surface treatment film having an adhering amount of 0.005 to 0.18 g / m 2 2 per one side. a resin compound A having a bisphenol skeleton represented by the following general formula (I), a cationic polyurethane resin emulsion B having at least one cationic functional group selected from a primary amino group, a secondary amino group, a tertiary amino group, and a quaternary ammonium salt group, a silane coupling agent C having at least one reactive functional group selected from an active hydrogen-containing amino group, an epoxy group, a mercapto group, and a methacryloyloxy group, an organic titanium chelate compound D, a tetravalent vanadium compound E, a molybdate compound F, a fluorine compound G, and water H; (1) The mass of solid component B of the cationic polyurethane resin emulsion B S The mass A of the solid component relative to the resin compound A S The solid component mass B of the cationic polyurethane resin emulsion B S And the solid component mass C of the silane coupling agent C S The total ratio of B S / (A S +B S +C S The value is 0.10 to 0.

30. (2) The solid component mass C of the silane coupling agent C S The mass A of the solid component relative to the resin compound A S The solid component mass B of the cationic polyurethane resin emulsion B S And the solid component mass C of the silane coupling agent C S The total ratio of C S / (A S +B S +C S The value ranges from 0.60 to 0.

85. (3) the solid content mass C of the silane coupling agent C S the titanium conversion mass D of the organic titanium chelate compound D Ti the ratio C S / D Ti is 50 to 70, (4) the vanadium equivalent mass E of the tetravalent vanadium compound E V relative to the titanium equivalent mass D of the organic titanium chelate compound D Ti the ratio E V / D Ti is 0.30 to 0.50, (5) The molybdenum equivalent mass F of the molybdate compound F Mo The mass A of the solid component relative to the resin compound A S The solid component mass B of the cationic polyurethane resin emulsion B S And the solid component mass C of the silane coupling agent C S The total ratio of F Mo / (A S +B S +C S The value ranges from 0.003 to 0.

030. (6) the fluorine conversion mass G of the fluorine compound G F with respect to the solid component mass A of the resin compound A S , the solid component mass B of the cationic polyurethane resin emulsion B S and the solid component mass C of the silane coupling agent C S is 0.101 to 0.200 F / (A S +B S +C S ) in formula (I), Y1 and Y2 bonded to the benzene ring are each independently a hydrogen atom or a Z group represented by the following general formula (II) or (III), the average number of Z groups per 1 benzene ring is 0.2 to 1.0, and n represents an integer of 2 to 50, In formulae (II) and (III), R1, R2, R3, R4and R5each independently represent a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or a hydroxyalkyl group having 1 to 10 carbon atoms, A － represents a hydroxide ion or an acid ion.

2. The method of producing an organic resin-coated steel sheet according to claim 1, wherein the drying of the surface treatment liquid is performed at a maximum plate temperature of 50 to 180°C.

3. The method of producing an organic resin-coated steel sheet according to claim 1, wherein the organic resin film is formed by laminating an organic resin film on the surface treatment film.

4. The method of producing an organic resin-coated steel sheet according to claim 3, wherein the organic resin film has a thickness of 60 μm or more.

5. The method of producing an organic resin-coated steel sheet according to claim 3 or 4, wherein the organic resin film is one or more selected from a polyvinyl chloride film, a polyolefin-based film, a polyester-based film, and a fluororesin-based film.

6. An organic resin-coated steel sheet produced by the method for producing an organic resin-coated steel sheet according to any one of claims 1 to 5.

Images