JP5915293B2 - Surface-treated steel sheet - Google Patents

Description

  The present invention is a surface-treated steel sheet that is most suitable for use in automobiles, home appliances, and building materials, and does not contain chromium in the surface treatment composition for forming a film and the surface treatment film, and is used in automobiles, home appliances, building materials, and the like. The present invention relates to a surface-treated steel sheet having excellent corrosion resistance capable of omitting pretreatment and after-coating for imparting corrosion resistance.

Conventionally, chromate treatment and phosphate treatment have been widely performed in order to improve the corrosion resistance of metal surfaces. However, the toxicity of chromium and the sludge resulting from phosphate treatment have become social problems, and various chromate-free treated steel sheets have been developed.
In order to improve the corrosion resistance of chromate-free treated steel sheets, surface treatment compositions using hydrazine derivatives as shown in Patent Documents 1 to 3 have been developed. However, even if it is a method using a high molecular weight epoxy resin like patent documents 1-3, when severe processing was added to a steel plate, fully satisfactory coating film performance was not obtained. In addition, a new resin in which a polymer having a neutralized acid group and a polysiloxane segment are combined as in Patent Document 4 has been proposed, but only corrosion resistance as primary rust prevention can be obtained, and the steel plate is severely processed. In addition, there is a problem that the film damage is large, and only insufficient corrosion resistance less than Patent Documents 1 to 3 can be obtained.

JP 2001-49450 A JP 2003-34713 A JP 2008-80465 A JP 2008-106228 A

  Accordingly, an object of the present invention is a surface-treated steel sheet that can be obtained without performing treatment with chromium or phosphate, and has high corrosion resistance and workability, and is suitable for pretreatment and after-coating for the purpose of imparting corrosion resistance. The object is to provide a highly corrosion-resistant surface-treated steel sheet that can be omitted.

  As a result of repeated studies to solve the above problems, the present inventors have identified a specific compound for a resin in which a polymer having a neutralized acid group and a polysiloxane segment are combined as shown in Patent Document 4. An epoxy resin is compounded and compounded, and a non-chromium rust preventive additive is added to the surface treatment composition. By forming a surface treatment film with this surface treatment composition, extremely excellent corrosion resistance and It was found that processability was obtained, and that a high degree of anticorrosion effect was obtained even after processing.

The present invention has been made on the basis of such findings and has the following gist.
[1] Polymer segment that contains the following components (α), (β) and (γ) on the surface of a zinc-based plated steel plate or an aluminum-based plated steel plate, and constitutes a composite resin (ABC) in the component (α) ( It is formed by a surface treatment composition in which the mass ratio (A) / [(B) + (C)] of the solid content of A) and the polysiloxane segments (B) and (C) is 40/60 to 20/80. A surface-treated steel sheet having a surface-treated film having a thickness of 3.0 to 15 μm.
Component (α): a polysiloxane segment (B) of a composite resin (AB) in which a polymer segment (A) having a neutralized acid group and a polysiloxane segment (B) are chemically bonded, and an alkyl group A composite resin (ABC) in which the polysiloxane segment (C) derived from the condensate (c) of trialkoxysilane having 1 to 3 carbon atoms is bonded through a silicon-oxygen bond or dissolved in an aqueous medium Component (β): Aqueous epoxy ester resin having a functional group that reacts with a hydroxyl group Component (γ): Non-chromium rust preventive additive [2] Surface of [1] above In the treated steel sheet, the mass ratio (α) / (β) of the solid content of the component (α) and the component (β) in the surface treatment composition is 70/30 to 40/60. .
[3] The surface-treated steel sheet according to [1] or [2], wherein the component (β) in the surface-treated composition is a dispersion-type aqueous epoxy ester resin.

[4] In the surface-treated steel sheet according to any one of the above [1] to [3], the surface treatment composition contains 1 to 50 masses of the component (γ) as a solid content with respect to 100 mass parts of the solid content of the resin composition. A surface-treated steel sheet characterized by containing a part.
[5] In the surface-treated steel sheet according to any one of the above [1] to [4], the surface treatment composition is one or more prevention materials selected from the following (γ1) to (γ5) as the component (γ): A surface-treated steel sheet characterized by containing a rust additive.
(Γ1) Silicon oxide (γ2) Calcium and / or calcium compound (γ3) Slightly soluble phosphate compound (γ4) Molybdate compound (γ5) Triazoles, thiols, thiadiazoles, thiazoles, thiurams One or more organic compounds containing S atoms [6] The surface-treated steel sheet according to any one of [1] to [5] above, wherein the surface treatment composition further contains a solid lubricant. Surface treated steel sheet.
[7] On the surface of the zinc-based plated steel sheet or the aluminum-based plated steel sheet, as a first layer, an organic film, an inorganic film or an organic-inorganic composite film having a film thickness not containing chromium of 0.01 to 2 μm is formed. A surface-treated steel sheet in which the surface-treated film according to any one of [1] to [6] is formed as a second layer on the upper layer.

  The surface-treated steel sheet of the present invention has very excellent corrosion resistance and workability, and a high degree of anticorrosion effect is obtained even after processing. For this reason, it is also possible to omit pretreatment and after-coating for the purpose of imparting corrosion resistance.

SEM image of the surface of the surface-treated steel sheet on which the surface-treated film is formed only with the composite resin (ABC). SEM image of the surface of the steel sheet that has been surface-treated with a resin composition in which a composite resin (ABC) and an epoxy ester resin are combined, and the surface of the film after press working is observed.

The surface-treated steel sheet of the present invention has a surface-treated film formed by a surface-treating composition containing the following components (α), (β) and (γ) on the surface of a zinc-based plated steel sheet or an aluminum-based plated steel sheet. Is. This surface treatment film is formed by applying the surface treatment composition to the surface of the plated steel sheet and drying it.
Component (α): a polysiloxane segment (B) of a composite resin (AB) in which a polymer segment (A) having a neutralized acid group and a polysiloxane segment (B) are chemically bonded, and an alkyl group A composite resin (ABC) in which the polysiloxane segment (C) derived from the condensate (c) of trialkoxysilane having 1 to 3 carbon atoms is bonded through a silicon-oxygen bond or dissolved in an aqueous medium Component (β): Aqueous epoxy ester resin having a functional group that reacts with a hydroxyl group Component (γ): Non-chromium rust preventive additive

Examples of the galvanized steel sheet used as the base of the surface-treated steel sheet of the present invention include a galvanized steel sheet, a Zn—Ni alloy plated steel sheet, a Zn—Fe alloy plated steel sheet (electroplated steel sheet, galvannealed steel sheet), Zn -Cr alloy plated steel sheet, Zn-Mn alloy plated steel sheet, Zn-Co alloy plated steel sheet, Zn-Co-Cr alloy plated steel sheet, Zn-Cr-Ni alloy plated steel sheet, Zn-Cr-Fe alloy plated steel sheet, Zn-Al Alloy-plated steel sheet (for example, Zn-5% Al alloy-plated steel sheet, Zn-55% Al alloy-plated steel sheet), Zn-Mg alloy-plated steel sheet, Zn-Al-Mg alloy-plated steel sheet (for example, Zn-6% Al-3) % Mg alloy-plated steel sheet, Zn-11% Al-3% Mg alloy-plated steel sheet), and metal oxides and polymers in the plating film of these plated steel sheets. Or the like can be used dispersed zinc composite-plated steel sheet (for example, Zn-SiO ₂ dispersion plating steel plate).

In addition, among the above-described plating, a multi-layer plated steel sheet in which two or more layers of the same type or different types are plated can also be used.
Moreover, as an aluminum system plated steel plate used as the base of the surface treatment steel plate of this invention, an aluminum plating steel plate, an Al-Si alloy plating steel plate, etc. can be used, for example.
Moreover, as a plated steel plate, the steel plate surface may be previously plated with lightness such as Ni, and various plating as described above may be performed thereon.
As a plating method, any feasible method among an electrolytic method (electrolysis in an aqueous solution or electrolysis in a nonaqueous solvent), a melting method, and a vapor phase method can be adopted.
Furthermore, for the purpose of preventing blackening of the plating, about 1 to 2000 ppm of trace elements of Ni, Co, and Fe are deposited in the plating film, or an alkaline aqueous solution or acid solution containing Ni, Co, Fe on the surface of the plating film. You may make it surface-treat with an aqueous solution and precipitate these elements.

Next, the surface treatment film formed on the surface of the zinc-based plated steel sheet or the aluminum-based plated steel sheet and the surface treatment composition for forming the film will be described.
First, an aqueous product (resin solution) of a composite resin (ABC) that is a component (α) constituting the surface treatment composition will be described.
The composite resin (ABC) used in the present invention is a polysiloxane segment of a composite resin (AB) in which a polymer segment (A) having a neutralized acid group and a polysiloxane segment (B) are chemically bonded. A composite resin in which (B) and a polysiloxane segment (C) derived from a condensate (c) of an alkyltrialkoxysilane having 1 to 3 carbon atoms of an alkyl group are bonded via a silicon-oxygen bond For example, a composite resin having a graft structure in which a polysiloxane segment (B) is chemically bonded to a side chain of a polymer segment (A) having a neutralized acid group, or a polymer segment (A) The polysiloxane segment (B) of the composite resin having a block structure in which the polysiloxane segment (B) is chemically bonded to the terminal, and an alkyl group having 1 to 3 carbon atoms. Condensates quilt trialkoxysilane (c) derived from a polysiloxane segment (C) and silicon - composite resins having a chemically bonded structure through an oxygen bond.
The chemical bond between the polymer segment (A) and the polysiloxane segment (B) included in the composite resin (ABC) is not particularly limited. For example, the following structural formula (S-1) or the following structural formula Examples include (S-2) bonding mode, among others, use of a composite resin having the bonding mode of structural formula (S-1) can form a coating film excellent in rust prevention and weather resistance. To preferred.

[However, the carbon atom in the structural formula (S-1) constitutes a part of the polymer segment (A), and the silicon atom and the oxygen atom constitute a part of the polysiloxane segment (B). ]

[However, the carbon atom in the structural formula (S-2) constitutes a part of the polymer segment (A), and the silicon atom constitutes a part of the polysiloxane segment (B). ]

  The polymer segment (A) constituting the composite resin (ABC) is essential to be a polymer segment having a neutralized acid group in order to disperse or dissolve the composite resin (ABC) in an aqueous medium. In particular, the polysiloxane segment (B) and the synthesis raw material thereof have a hydroxyl group bonded to a silicon atom or a hydrolyzable group bonded to a silicon atom, which is easily hydrolytically condensed and bonded to the structural formula (S-1). Since it is chemically bonded in a manner, a hydroxyl group bonded to a silicon atom and / or a hydrolyzable group bonded to a silicon atom together with an acid group (hereinafter referred to as “hydroxyl group and / or hydrolyzable group of silicon atom bond” for convenience of explanation) It is preferable that the polymer segment is derived from the polymer (a ′) having the above) or the polymer (a) which is a neutralized product thereof. The polymer (a ′) and the polymer (a) may be any polymer other than polysiloxane having an acid group or a neutralized acid group. Examples of the polymer include an acrylic polymer, a fluoroolefin polymer, and the like. Examples thereof include vinyl polymers such as polymers, vinyl ester polymers, aromatic vinyl polymers, polyolefin polymers, polyurethane polymers, polyester polymers, polyether polymers, among others, vinyl polymers and polyurethanes. Polymers are preferred, and acrylic polymers are more preferred.

Examples of the acid group in the polymer (a ′) include a carboxyl group, a phosphoric acid group, an acidic phosphoric acid ester group, a phosphorous acid group, a sulfonic acid group, and a sulfinic acid group. Among them, a composite resin (ABC) A carboxyl group is preferable because it can be easily introduced into the skeleton.
Examples of the basic compound used for neutralizing the acid group include organic amines such as methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, 2-aminoethanol, and 2-dimethylaminoethanol. Inorganic inorganic compounds such as ammonia, sodium hydroxide and potassium hydroxide; quaternary ammonium hydroxides such as tetramethylammonium hydroxide, tetra-n-butylammonium hydroxide and trimethylbenzylammonium hydroxide can be used. Of these, organic amines and ammonia (ammonia water may be used) are preferable.

The neutralized acid group in the polymer (a) is a composite resin from the viewpoint of maintaining good storage stability of an aqueous dispersion or aqueous solution in which the composite resin (ABC) is dispersed or dissolved in an aqueous medium. (ABC) It is preferable that it exists in the ratio of 0.1-20 mass% with respect to 100 mass%, and it is more preferable that it exists especially in the ratio of 0.2-10 mass%.
The hydrolyzable group bonded to the silicon atom in the polymer (a ′) may be any functional group that can generate a hydroxyl group (silanol group) bonded to the silicon atom by hydrolysis. Well, for example, halogen atom bonded to silicon atom, alkoxy group bonded to silicon atom, acyloxy group bonded to silicon atom, phenoxy group bonded to silicon atom, mercapto group bonded to silicon atom, amino bonded to silicon atom Groups, amide groups bonded to silicon atoms, aminooxy groups bonded to silicon atoms, iminooxy groups bonded to silicon atoms, alkenyloxy groups bonded to silicon atoms, etc. In addition, an alkoxy group bonded to a silicon atom is preferable because a by-product after the reaction can be easily removed.

  The polymer segment (A) has other functional groups other than neutralized acid groups, hydroxyl groups bonded to silicon atoms, and hydrolyzable groups bonded to silicon atoms, as long as the effects of the present invention are not impaired. You may do it. Such other functional groups include, for example, unneutralized carboxyl groups, blocked carboxyl groups, carboxylic anhydride groups, hydroxyl groups, blocked hydroxyl groups, cyclocarbonate groups, epoxy groups, carbonyl groups, primary grades. Examples include an amide group, a secondary amide group, a carbamate group, a polyethylene glycol group, a polypropylene glycol group, and a group represented by the following structural formula (S-3).

Examples of the polysiloxane segment (B) constituting the composite resin (ABC) include a segment derived from a polysiloxane having a silicon atom-bonded hydroxyl group and / or a hydrolyzable group. In addition, as a hydrolysable group couple | bonded with this silicon atom, the thing similar to the hydrolyzable group couple | bonded with the silicon atom described in the polymer segment (A) is mentioned, A preferable thing is also the same.
As the polysiloxane segment (B), those having a structure represented by the following general formulas (S-4) and (S-5) are particularly preferable. Since the polysiloxane segment (B) having the structure represented by the following general formula (S-4) or (S-5) has a three-dimensional network-like polysiloxane structure, the resulting coating film has solvent resistance, Excellent weather resistance.

[In the general formulas (S-4) and (S-5), R ¹ is an organic group having 4 to 12 carbon atoms bonded to a silicon atom, and R ² and R ³ are each independently a silicon atom. A bonded methyl group or an ethyl group bonded to a silicon atom. In particular, R ¹ is preferably a hydrocarbon group having 4 to 12 carbon atoms bonded to a silicon atom, and more preferably a phenyl group or an alkyl group having 4 carbon atoms. R ² and R ³ are each preferably a methyl group bonded to a silicon atom or an ethyl group bonded to a silicon atom, and more preferably a methyl group bonded to a silicon atom. ]

  As the polysiloxane segment having the structure represented by the general formula (S-4) or (S-5), an organoalkoxysilane, preferably an organic group having 4 to 12 carbon atoms bonded to a silicon atom (hereinafter, described) For convenience, a monoorganotrialkoxysilane having “an organic group having 4 to 12 carbon atoms bonded to a silicon atom”) and / or a methyl group bonded to a silicon atom and / or an ethyl group bonded to a silicon atom (hereinafter, For convenience of explanation, a segment derived from polysiloxane obtained by hydrolytic condensation of a diorganodialkoxysilane having two of “a silicon atom-bonded methyl group and / or ethyl group”) may be mentioned. These polysiloxane segments consist of two organic atom-bonded organic groups having 4 to 12 carbon atoms, silicon atom-bonded hydroxyl groups and / or hydrolyzable groups, and / or silicon atom-bonded methyl groups and / or ethyl groups. And a silicon atom-bonded hydroxyl group and / or hydrolyzable group, and may have any structure of linear, branched, and cyclic.

Examples of the organic group having 4 to 12 carbon atoms bonded to a silicon atom include an alkyl group, a cycloalkyl group, an aryl group, and an aralkyl group each having 4 to 12 carbon atoms bonded to a silicon atom. In addition, these organic groups may have a substituent.
As such an organic group having 4 to 12 carbon atoms bonded to a silicon atom, a hydrocarbon group bonded to a silicon atom is preferable. For example, an n-butyl group, an iso-butyl group, or an n-bonded group bonded to a silicon atom. -Alkyl groups such as hexyl group, n-octyl group, n-dodecyl group and cyclohexylmethyl group; cycloalkyl groups such as cyclohexyl group and 4-methylcyclohexyl group; aryl groups such as phenyl group and 4-methylphenyl group; benzyl And an aralkyl group such as a group. Among them, a phenyl group bonded to a silicon atom or an alkyl group having 4 carbon atoms bonded to a silicon atom is more preferable.

The polysiloxane segment (C) constituting the composite resin (ABC) is a segment derived from a condensate (c) of an alkyltrialkoxysilane having an alkyl group having 1 to 3 carbon atoms, and the carbon of the alkyl group used here The condensate (c) of the alkyltrialkoxysilane having 1 to 3 has a hydroxyl group bonded to a silicon atom and / or an alkoxy group bonded to a silicon atom.
The alkyltrialkoxysilane condensate (c) preferably has a structure represented by the following general formula (S-6). Since the polysiloxane segment derived from the alkyltrialkoxysilane condensate having the structure represented by the following general formula (S-6) has a three-dimensional network-like polysiloxane structure, the resulting coating film is solvent resistant. In addition, the weather resistance is excellent.

[However, R ⁴ in the general formula (S-6) is an alkyl group having 1 to 3 carbon atoms. ]

Since the composite resin (ABC) is excellent in corrosion resistance after processing + alkali degreasing, the mass ratio (A) / [(B) + of the solid content of the polymer segment (A) and the polysiloxane segments (B), (C) (C)] is set to 40/60 to 20/80. If the mass ratio (A) / [(B) + (C)] exceeds 40/60, corrosion resistance deteriorates, which is not preferable. On the other hand, the mass ratio (A) / [(B) + (C)] is 20/80. If it is less than 1, the film becomes hard, so that many film damages and cracks are caused by press processing, and the corrosion resistance after processing deteriorates.
In addition, since the composite resin (ABC) has excellent adhesive compatibility, the mass ratio of the solid content of the polysiloxane segment (C), the polymer segment (A), and the polysiloxane segments (B) and (C) (C ) / [(A) + (B) + (C)] is preferably 40/100 to 60/100.

The composite resin (ABC) can be produced by various methods, and in particular, it is preferably produced by a method comprising the following production steps (I) and (II).
(I) A polymer (a ′) having both an acid group and a silicon atom-bonded hydroxyl group and / or hydrolyzable group, and an organoalkoxysilane (b) and / or a hydrolysis condensate thereof (b-1). Composite resin (A'B) formed by chemical condensation of polymer segment (A ') derived from polymer (a') and polysiloxane segment (B) derived from organoalkoxysilane (b) by hydrolytic condensation The process of obtaining

(II) Next, the resulting composite resin (A′B) and the alkyltrialkoxysilane condensate (c) having 1 to 3 carbon atoms in the alkyl group are hydrolytically condensed to give the composite resin (A′B). The polysiloxane segment (B) and the polysiloxane segment (C) derived from the condensate (c) of alkyltrialkoxysilane having 1 to 3 carbon atoms in the alkyl group are bonded via a silicon-oxygen bond. A step of obtaining a composite resin (ABC) by neutralizing acid groups in the composite resin (A'BC) with a basic compound after the composite resin (A'BC) is obtained, or the obtained composite resin (A'BC) After the acid group in ′ B) is neutralized with a basic compound to form a composite resin (AB), the condensation product (c) of alkyltrialkoxysilane having 1 to 3 carbon atoms in the alkyl group is hydrolyzed and condensed. Polysiloxane segment of composite resin (AB) Composite resin (B) and a polysiloxane segment (C) derived from a condensate (c) of alkyltrialkoxysilane having 1 to 3 carbon atoms of an alkyl group bonded via a silicon-oxygen bond ( Step of obtaining ABC)

The hydrolysis-condensation reaction in the production process can be progressed by various methods, but a method in which the reaction is advanced by supplying water and a catalyst during the production process is simple and preferable.
The hydrolysis condensation reaction refers to a condensation reaction in which a part of the hydrolyzable group is hydrolyzed under the influence of water or the like to form a hydroxyl group, and then proceeds between the hydroxyl group or the hydrolyzable group. Say.

The polymer (a ′) is a polymer having both an acid group and a silicon atom-bonded hydroxyl group and / or a hydrolyzable group, and the neutralized acid group except that the acid group is not neutralized. And a polymer (a) having both a silicon atom-bonded hydroxyl group and / or hydrolyzable group.
When a vinyl polymer is used as the polymer (a ′), the vinyl polymer may be, for example, an acid group-containing vinyl monomer, a hydroxyl group-containing vinyl monomer bonded to a silicon atom, and / or a silicon atom. It can be produced by polymerizing the combined hydrolyzable group-containing vinyl monomer and, if necessary, other vinyl monomers.
Examples of the acid group-containing vinyl monomer include various vinyl monomers containing an acid group such as a carboxyl group, a phosphoric acid group, an acidic phosphoric ester group, a phosphorous acid group, a sulfonic acid group, and a sulfinic acid group. Among them, a vinyl monomer containing a carboxyl group (which may be a carboxylic anhydride group) is preferable.

  Examples of the carboxyl group-containing vinyl monomer include (meth) acrylic acid, 2-carboxyethyl (meth) acrylate, crotonic acid, itaconic acid, maleic acid, fumaric acid and other unsaturated carboxylic acids; maleic anhydride, Unsaturated polycarboxylic acid anhydrides such as itaconic anhydride; unsaturated monocarboxylic acid anhydrides such as acrylic acid anhydride and methacrylic anhydride; unsaturated carboxylic acid such as acrylic acid and methacrylic acid; acetic acid and propion Acid, mixed acid anhydride with saturated carboxylic acid such as benzoic acid; monomethyl itaconate, mono-n-butyl itaconate, monomethyl maleate, mono-n-butyl maleate, monomethyl fumarate, mono-n-fumarate Various monoesters (half-esters) of saturated dicarboxylic acids such as butyl and saturated monohydric alcohols; Monovinyl esters of saturated dicarboxylic acids such as monovinyl dipinate and monovinyl succinate; bonded to carbon atoms with anhydrides of saturated polycarboxylic acids such as succinic anhydride, glutaric anhydride, phthalic anhydride and trimellitic anhydride Addition reaction products with vinyl monomers containing hydroxyl groups; and various monomers obtained by addition reaction of the carboxyl group-containing monomers with lactones, among others. The unsaturated carboxylic acids such as (meth) acrylic acid are preferred because they can be easily introduced into the vinyl polymer.

  The carboxyl group may be blocked, and examples of the vinyl monomer having such a blocked carboxyl group include trimethylsilyl (meth) acrylate, dimethyl-tert-butylsilyl (meth) acrylate, Silyl ester group-containing vinyl monomers such as trimethylsilyl crotonate; hemiacetals such as 1-ethoxyethyl (meth) acrylate, 2-methoxy-2- (meth) acryloyloxypropane, 2- (meth) acryloyloxytetrahydrofuran Ester group or hemiketal ester group-containing monomers; tert-butyl ester group-containing monomers such as tert-butyl (meth) acrylate and tert-butyl crotonate.

Examples of the hydroxyl group-containing vinyl monomer bonded to the silicon atom include trihydroxyvinylsilane, ethoxydihydroxyvinylsilane, diethoxyhydroxyvinylsilane, dichlorohydroxyvinylsilane, 3- (meth) acryloyloxypropyltrihydroxysilane, 3 -(Meth) acryloyloxypropylmethyldihydroxysilane and the like.
As the hydrolyzable group-containing vinyl monomer bonded to the silicon atom, for example, a vinyl monomer having a hydrolyzable group represented by the following general formula (S-7) can be used.

[In the general formula (S-7), R ⁵ is a monovalent organic group such as an alkyl group, an aryl group, and an aralkyl group, and R ⁶ is a halogen atom, an alkoxy group, an acyloxy group, a phenoxy group, an aryloxy group, Mercapto group, amino group, amide group, aminooxy group, iminooxy group or alkenyloxy group. Moreover, b is an integer of 0-2. ]

  Examples of the vinyl monomer having a hydrolyzable group represented by formula (S-7) include vinyltrimethoxysilane, vinyltriethoxysilane, vinylmethyldimethoxysilane, vinyltri (2-methoxyethoxy) silane, and vinyltrimethoxysilane. Acetoxysilane, vinyltrichlorosilane, 2-trimethoxysilylethyl vinyl ether, 3- (meth) acryloyloxypropyltrimethoxysilane, 3- (meth) acryloyloxypropyltriethoxysilane, 3- (meth) acryloyloxypropylmethyldimethoxysilane , 3- (meth) acryloyloxypropyltrichlorosilane and the like, and among them, the hydrolysis reaction can easily proceed, and the by-product after the reaction can be easily removed. , 3- ( Data) acryloyloxypropyltrimethoxysilane are preferred.

  Examples of the other vinyl monomers include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, tert- Alkyl (meth) acrylates having an alkyl group having 1 to 22 carbon atoms such as butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate; benzyl (meth) acrylate, 2-phenylethyl (meta ) Aralkyl (meth) acrylates such as acrylate; Cycloalkyl (meth) acrylates such as cyclohexyl (meth) acrylate and isobornyl (meth) acrylate; 2-methoxyethyl (meth) acrylate, 4-methoxybutyl (meth) acrylic Ω-alkoxyalkyl (meth) acrylates such as carbonates; aromatic vinyl monomers such as styrene, p-tert-butylstyrene, α-methylstyrene, vinyltoluene; vinyl acetate, vinyl propionate, pivalic acid Carboxylic acid vinyl esters such as vinyl and vinyl benzoate; alkyl esters of crotonic acid such as methyl crotonate and ethyl crotonate; Unsaturation such as dimethyl malate, di-n-butyl malate, dimethyl fumarate and dimethyl itaconate Dialkyl esters of dibasic acids; α-olefins such as ethylene and propylene; fluoroolefins such as vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene and chlorotrifluoroethylene; alkyls such as ethyl vinyl ether and n-butyl vinyl ether Nyl ethers; Cycloalkyl vinyl ethers such as cyclopentyl vinyl ether and cyclohexyl vinyl ether; Tertiary amides such as N, N-dimethyl (meth) acrylamide, N- (meth) acryloylmorpholine, N- (meth) acryloylpyrrolidine and N-vinylpyrrolidone Group-containing monomers;

Hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate; hydroxyl groups such as 2-hydroxyethyl vinyl ether and 4-hydroxybutyl vinyl ether -Containing vinyl ethers; hydroxyl group-containing allyl ethers such as 2-hydroxyethyl allyl ether and 2-hydroxybutyl allyl ether; vinyl monomers containing hydroxyl groups bonded to these carbon atoms and lactones such as ε-caprolactone; Addition reaction product of

2-dimethylaminoethyl (meth) acrylate, 2-diethylaminoethyl (meth) acrylate, 2-di-n-propylaminoethyl (meth) acrylate, 3-dimethylaminopropyl (meth) acrylate, 4-dimethylaminobutyl (meth) ) Tertiary amino group-containing (meth) acrylic acid esters such as acrylate and N- [2- (meth) acryloyloxy] ethylmorpholine; tertiary amino group-containing vinylpyridine, N-vinylcarbazole, N-vinylquinoline, etc. Aromatic vinyl monomers: N- (2-dimethylamino) ethyl (meth) acrylamide, N- (2-diethylamino) ethyl (meth) acrylamide, N- (2-di-n-propylamino) ethyl ( Tertiary amino group-containing (meth) acrylamides such as (meth) acrylamide; Tertiary amino group-containing crotonic acid amides such as-(2-dimethylamino) ethylcrotonic acid amide, N- (4-dimethylamino) butylcrotonic acid amide; 2-dimethylaminoethyl vinyl ether, 2-diethylaminoethyl vinyl ether, 4 -Tertiary amino group-containing vinyl ethers such as dimethylaminobutyl vinyl ether.

The type and amount of the other vinyl monomer can be appropriately selected within a range that does not impair the effects of the present invention, depending on the properties imparted to the surface treatment composition used in the present invention.
The polymer (a ′) is at least one selected from the group consisting of an anionic group, a cationic group and a nonionic group for the purpose of improving the solubility or dispersibility of the composite resin (ABC) in an aqueous medium. Those having a kind of hydrophilic group can be used.

  Examples of the vinyl polymer usable as the polymer (a ′) include an acid group-containing vinyl monomer, a hydroxyl group-containing vinyl monomer bonded to a silicon atom, and / or a hydrolyzable group bonded to a silicon atom. It can be produced by polymerizing the containing vinyl monomer and, if necessary, other vinyl monomers by a polymerization method such as a bulk radical polymerization method, a solution radical polymerization method or a non-aqueous dispersion radical polymerization method. Especially, since it is easy to manufacture, it is preferable to apply a so-called solution radical polymerization method in which a vinyl polymer is manufactured by radical polymerization of the vinyl monomer in an organic solvent.

  When the vinyl monomer is polymerized by the radical polymerization method, a polymerization initiator can be used as necessary. Examples of such polymerization initiators include 2,2'-azobis (isobutyronitrile), 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (2-methylbutyronitrile). Azo compounds such as nitrile); tert-butyl peroxypivalate, tert-butyl peroxybenzoate, tert-butyl peroxy-2-ethylhexanoate, di-tert-butyl peroxide, cumene hydroperoxide, diisopropyl And peroxides such as peroxycarbonate.

  Examples of the organic solvent include aliphatic or alicyclic hydrocarbons such as n-hexane, n-heptane, n-octane, cyclohexane, and cyclopentane; aromatic hydrocarbons such as toluene, xylene, and ethylbenzene. Alcohols such as methanol, ethanol, n-butanol, ethylene glycol monomethyl ether, propylene glycol monomethyl ether; ethyl acetate, n-butyl acetate, n-amyl acetate, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether acetate Esters such as acetone; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl n-amyl ketone, cyclohexanone; diethylene glycol dimethyl ether, diethylene glycol dibutyl ether Such as polyalkylene glycol dialkyl ethers; ethers such as 1,2-dimethoxyethane, tetrahydrofuran, dioxane; N-methylpyrrolidone, dimethylformamide, dimethylacetamide, ethylene carbonate, etc., and one or more of these Can be used.

  The polymer (a ') preferably has a number average molecular weight in the range of 500 to 200,000, more preferably in the range of 700 to 100,000, and in the range of 1,000 to 50,000. What has is especially preferable. By using the polymer (a ′) having a number average molecular weight within such a range, it is possible to prevent thickening and gelation during the production of the composite resin (ABC) and to have excellent durability. Can be formed.

Next, the organoalkoxysilane (b) and / or its hydrolysis condensate (b-1) used for constituting the polysiloxane segment (B) in the production step (I) will be described.
The organoalkoxysilane (b) is not particularly limited, but in particular, a composite resin (ABC) excellent in dispersion stability can be produced, and a coating film excellent in durability can be formed. A monoorganotrialkoxysilane having an organic group having 4 to 12 carbon atoms and a diorganodialkoxysilane having two methyl groups and / or ethyl groups are preferred.
The hydrolyzed condensate (b-1) of the organoalkoxysilane (b) is not particularly limited as long as it is a hydrolyzed condensate of the organoalkoxysilane (b). A monoorganotrialkoxysilane having 12 organic groups and / or a diorganodialkoxysilane having two silicon atom-bonded methyl and / or ethyl groups hydrolyzed and condensed are preferred.

Examples of the monoorganotrialkoxysilane having a silicon atom-bonded organic group having 4 to 12 carbon atoms include iso-butyltrimethoxysilane, cyclohexyltrimethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, 3- ( And (meth) acryloyloxypropyltrimethoxysilane, 3- (meth) acryloyloxypropyltriethoxysilane, and the like.
Examples of the diorganodialkoxysilane having two silicon atom-bonded methyl groups and / or ethyl groups include dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldi-n-butoxysilane, dimethyldiacetoxysilane, and diethyldimethoxy. Silane, diethyl diacetoxysilane, etc. are mentioned.

Among these organoalkoxysilanes (b), the hydrolysis reaction can easily proceed and the by-products after the reaction can be easily removed. Therefore, iso-butyltrimethoxysilane, phenyltrimethoxysilane, and dimethyldimethoxysilane are used. preferable. Moreover, 1 type (s) or 2 or more types can be used for these organoalkoxysilane (b).
In addition, in the said manufacturing process (I), although it is also possible to use the hydrolysis-condensation product (b-1) of organoalkoxysilane (b) independently, of composite resin (A'B) by hydrolysis condensation is sufficient. Since it is easy to produce, it is preferable to use an organoalkoxysilane (b) alone or a combination of an organoalkoxysilane (b) and its hydrolysis condensate (b-1), and use an organoalkoxysilane (b) alone. Is particularly preferred. Here, the single use of the organoalkoxysilane (b) is to use only the organoalkoxysilane (b), and includes the case where two or more organoalkoxysilanes (b) are used in combination.

The hydrolysis condensation reaction in the production step (I) can proceed by various methods, but there is a method in which the reaction is advanced by supplying water and a catalyst during the production step (I). Simple and preferable.
Examples of the catalyst include inorganic acids such as hydrochloric acid, sulfuric acid and phosphoric acid; organic acids such as p-toluenesulfonic acid, monoisopropyl phosphate and acetic acid; inorganic bases such as sodium hydroxide and potassium hydroxide; tetraisopropyl titanate; Titanate esters such as tetrabutyl titanate; 1,8-diazabicyclo [5.4.0] undecene-7 (DBU), 1,5-diazabicyclo [4.3.0] nonene-5 (DBN), 1, Compounds containing basic nitrogen atoms such as 4-diazabicyclo [2.2.2] octane (DABCO), tri-n-butylamine, dimethylbenzylamine, monoethanolamine, imidazole, 1-methylimidazole; tetramethylammonium Quaternary compounds such as salt, tetrabutylammonium salt, dilauryldimethylammonium salt, etc. Quaternary ammonium salts having chloride, bromide, carboxylate, hydroxide, etc. as counter anions; dibutyltin diacetate, dibutyltin dioctoate, dibutyltin dilaurate, dibutyltin diacetylacetonate, tin octylate, Examples thereof include tin carboxylates such as tin stearate, and one or more of these can be used.

The catalyst is preferably used in the range of 0.0001 to 10 parts by mass with respect to 100 parts by mass of the organoalkoxysilane (b) and / or its hydrolysis condensate (b-1). It is more preferable to use in the range of ˜3 parts by mass, and it is particularly preferable to use in the range of 0.001 to 1 part by mass.
The water used when the hydrolysis condensation reaction proceeds is based on 1 mol of the hydrolyzable group and hydroxyl group of the organoalkoxysilane (b) and / or the hydrolysis condensate (b-1) thereof. 0.05 mol or more is appropriate, preferably 0.1 mol or more, particularly preferably 0.5 to 3.0 mol.
The catalyst and water may be supplied all at once or sequentially, or a catalyst and water mixed in advance may be supplied.

The reaction temperature of the hydrolysis condensation reaction is suitably in the range of 0 to 150 ° C, and preferably in the range of 20 to 100 ° C. The reaction can be carried out under normal conditions, under pressure or under reduced pressure.
Alcohol and water, which are by-products that can be generated in the hydrolysis-condensation reaction, may be removed by a method such as distillation, in order to reduce the stability of the surface treatment composition to be obtained.

Next, the alkyltrialkoxysilane condensate (c) having 1 to 3 carbon atoms in the alkyl group used for constituting the polysiloxane segment (C) in the production step (II) will be described.
Examples of the alkyltrialkoxysilane having 1 to 3 carbon atoms in the alkyl group include, for example, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, and iso-propyl. Examples include trimethoxysilane, and among these, methyltrimethoxysilane and ethyltrimethoxysilane are preferable because the hydrolysis reaction can easily proceed and by-products after the reaction can be easily removed. These alkyltrialkoxysilanes can be used alone or in combination of two or more.

There are no particular limitations on the method for obtaining the condensate (c) from the alkyltrialkoxysilane, and various methods can be mentioned, but a method of proceeding the hydrolysis condensation reaction by supplying water and a catalyst is simple. preferable.
About the water and catalyst used in that case, it can be used on the same conditions as the hydrolysis-condensation reaction in the said manufacturing process (I).
Moreover, in the said manufacturing process (II), in addition to the condensate (c) of alkyl trialkoxysilane whose alkyl group has 1 to 3 carbon atoms, other silane compounds and hydrolysis condensates thereof may be used in combination. it can.

Examples of the other silane compounds include tetrafunctional alkoxysilane compounds such as tetramethoxysilane, tetraethoxysilane, and tetra n-propoxysilane; hydrolysis condensates of the tetrafunctional alkoxysilane compounds, and the like. These can be used in combination as long as the effects of the present invention are not impaired.
When the tetrafunctional alkoxysilane compound or a hydrolysis condensate thereof is used in combination, the tetrafunctional alkoxy is used with respect to 100 mol% of all silicon atoms constituting the polysiloxane segment (B) and the polysiloxane segment (C). It is preferable to use together in the range which the silicon atom which a silane compound and its hydrolysis condensate does not exceed 20 mol%.

  Examples of the aqueous medium used in the present invention include water, an organic solvent miscible with water, and a mixture thereof. Examples of the organic solvent miscible with water include alcohols such as methanol, ethanol, n- and isopropanol; ketones such as acetone and methyl ethyl ketone; polyalkylene glycols such as ethylene glycol, diethylene glycol and propylene glycol; Alkyl ethers; lactams such as N-methyl-2-pyrrolidone, and the like. In the present invention, only water may be used, or a mixture of water and an organic solvent miscible with water may be used, or only an organic solvent miscible with water may be used. From the viewpoint of safety and load on the environment, water alone or a mixture of water and an organic solvent miscible with water is preferable, and only water is particularly preferable.

Next, an aqueous epoxy ester resin having a functional group that reacts with a hydroxyl group, which is a component (β) constituting the surface treatment composition, will be described.
Aqueous epoxy ester resin is esterified by reacting a hydroxyl group in the epoxy resin molecule with a monobasic acid such as fatty acid or rosin or a dibasic acid such as phthalic anhydride. It is a resin dispersed in water by ionization by neutralization of the carboxyl group.

When the above epoxy ester resin and composite resin (ABC) are combined with other resins (vinyl resin, polyester resin, epoxy resin, polyurethane resin, acrylic resin, ethylene resin, etc.) In addition, it was found that the composite effect that the corrosion resistance after processing is remarkably improved can be obtained as compared with the case where the composite resin (ABC) and the curing agent (such as isocyanate) are combined. The mechanism by which such a remarkable compounding effect can be obtained is not always clear, but the epoxy resin is superior in oxygen permeation suppression of the resin film compared to other resins, and the oxygen reduction reaction that is the starting point of the corrosion reaction (O ₂ + 2H ₂ O → 4OH ⁻ + e−) is suppressed, and the carboxyl group (—COOH) at the end of the ester resin modified with the epoxy resin is dehydrated and condensed with the hydroxyl group (—OH) of the composite resin (ABC). As a result, the epoxy ester resin and the composite resin (ABC) are firmly bonded to form a dense composite resin film, and the oxygen permeation suppressive and the oxygen permeation of the epoxy resin are excellent due to the polysiloxane segment of the composite resin (ABC). It is considered that the inhibitory property exerted a synergistic effect.

On the other hand, when the composite resin (ABC) is used alone or when the composite resin (ABC) is cured with a curing agent or the like, the film becomes hard, so that the occurrence of film damage or cracks is remarkable when subjected to press working. And the corrosion resistance deteriorates after processing. FIG. 1 is an SEM image of the surface of a surface-treated steel sheet formed with a composite resin (ABC) only, and the surface of the film after press working is observed. Cracks are remarkably generated on the surface of the film. On the other hand, when the epoxy ester resin and the composite resin (ABC) are combined, the occurrence of film damage and cracks is effectively suppressed. FIG. 2 is an SEM image obtained by observing the film surface after press working on a surface-treated steel sheet in which a surface-treated film is formed with a resin composition obtained by combining a composite resin (ABC) and an epoxy ester resin. In comparison, there are very few cracks on the coating surface.
And it is thought that the especially outstanding corrosion resistance after a process is acquired by suppression of such film | membrane damage.

  Examples of the aqueous epoxy ester resin include Watersol BM-1000P, EFD-5501P, EFD-5530, EFD-5560, EFD-5580 (all trade names) manufactured by DIC Corporation, and Nippon Shokubai Co., Ltd. Examples include Alloron 5, 7, and 27 (all are trade names) and Modelix 301, 302, and 304 (all are trade names) manufactured by Arakawa Chemical Industries, Ltd. These are all water-based types called dispersions, and are superior in water resistance compared to water-soluble resins. In addition, since the resin particle size is smaller than that of the emulsion resin, it becomes a dense film when it is combined with the composite resin (ABC), so that it is excellent in oxygen permeation suppression and workability. is there.

The ratio of the composite of the composite resin (ABC), which is the component (α), and the aqueous epoxy ester resin, which is the component (β), is 70/30 to the solid mass ratio (α) / (β). It is preferable that it is 40/60. When the mass ratio (α) / (β) is more than 70/30, the coating becomes hard, so that coating damage or cracks are likely to occur when subjected to press working, and the post-processing corrosion resistance tends to decrease. On the other hand, if mass ratio ((alpha)) / ((beta)) is less than 40/60, the oxygen-permeation suppression property by a polysiloxane segment will fall easily, and there exists a tendency for corrosion resistance to deteriorate.
Thus, the curing agent is not required in the surface treatment composition of the present invention by complexing the aqueous product of the composite resin (ABC) as the component (α) and the aqueous epoxy ester resin as the component (β). .

Next, the non-chromium rust preventive additive which is the component (γ) constituting the surface treatment composition will be described.
This non-chromium-based rust preventive additive is blended in the surface treatment composition for the purpose of improving the corrosion resistance, whereby a particularly excellent anticorrosion performance (self-repairability) can be obtained.
As the non-chromium rust preventive additive, it is particularly preferable to use one or more selected from the following (γ1) to (γ5).
(Γ1) silicon oxide (γ2) calcium and / or calcium compound (γ3) poorly soluble phosphate compound (γ4) molybdate compound (γ5) selected from triazoles, thiols, thiadiazoles, thiazoles, thiurams One or more organic compounds containing S atoms The details and anticorrosion mechanisms of these non-chromium rust preventive additives (γ1) to (γ5) are as follows.

  First, as the component (γ1), colloidal silica or dry silica, which is fine particle silica, can be used. From the viewpoint of corrosion resistance when there is no processing, it is particularly desirable to use calcium ion exchange silica in which calcium is bound to the surface. However, when processed, calcium ion exchange silica having a large particle size (average particle size) 3 μm) is more preferable for fine particle silica because it has a larger film damage due to processing and is inferior in corrosion resistance after processing than colloidal silica and dry silica (average particle size of 4 to 20 nm) having a small particle size. In particular, those having a particle diameter of 14 nm or less, and more preferably those having a particle diameter of 8 nm or less are preferred from the viewpoints of corrosion resistance and post-processing corrosion resistance.

As colloidal silica, for example, Snowtex S, OS, NS, XS, NXS (all trade names) manufactured by Nissan Chemical Co., Ltd. can be used. As fumed silica, AEROSIL130, 200, 300, 300CF (all trade names) manufactured by Nippon Aerosil Co., Ltd. can be used. As calcium ion exchange silica, WRGrace & Co. SHIELDEX C303, SHIELDEX made
AC3, SHIELDEX AC5 (all are trade names), SHIELDEX, SHIELDEX SY710 (all are trade names) manufactured by Fuji Silysia Chemical Co., Ltd., and the like can be used. These silicas contribute to the production of dense and stable zinc corrosion products in a corrosive environment, and the corrosion products are formed densely on the plating surface, thereby suppressing the promotion of corrosion.

In addition, the above components (γ2) and (γ3) exhibit particularly excellent anticorrosion performance (self-repairing property) due to precipitation.
The calcium compound as the component (γ2) may be any of calcium oxide, calcium hydroxide, and calcium salt, and one or more of these can be used. In addition, there are no particular restrictions on the type of calcium salt. In addition to simple salts containing only calcium as a cation such as calcium silicate, calcium carbonate, and calcium phosphate, calcium and calcium such as calcium phosphate / zinc, calcium phosphate / magnesium, etc. Double salts containing other cations may be used. This (γ2) component preferentially dissolves base calcium over the plating metals zinc and aluminum in a corrosive environment, which seals the defective part as a dense and sparingly soluble product with OH ⁻ produced by the cathode reaction. And suppress the corrosion reaction. Moreover, when it mix | blends with the above silicas, a calcium ion adsorb | sucks to the surface and neutralizes a surface charge electrically and aggregates. As a result, a dense and sparingly soluble protective film is formed to block the corrosion and suppress the corrosion reaction.

  Moreover, as a poorly soluble phosphoric acid compound which is said ((gamma) 3), a poorly soluble phosphate can be used. This sparingly soluble phosphate includes all types of salts such as single salts and double salts. Moreover, there is no limitation in the metal cation which comprises it, and any metal cation, such as poorly soluble zinc phosphate, magnesium phosphate, calcium phosphate, aluminum phosphate, may be sufficient. Further, there is no limitation on the skeleton or the degree of condensation of phosphate ions, and any of normal salt, dihydrogen salt, monohydrogen salt or phosphite may be used. In addition, orthophosphate may be polyphosphate other than orthophosphate. Includes all condensed phosphates such as salts. This hardly soluble phosphorus compound is a metal plating zinc or aluminum eluted by corrosion, and forms a dense and hardly soluble protective film by complexing reaction with phosphate ions dissociated by hydrolysis, thereby blocking the origin of corrosion. Inhibits corrosion reactions.

  In addition, as the molybdate compound (γ4), for example, molybdate can be used. The molybdate is not limited in its skeleton and degree of condensation, and examples thereof include orthomolybdate, paramolybdate, and metamolybdate. Moreover, all salts, such as a single salt and a double salt, are included, and phosphoric acid molybdate etc. are mentioned as a double salt. Molybdate compounds exhibit self-repairing properties due to the passivating effect. That is, by forming a dense oxide on the plating film surface together with dissolved oxygen in a corrosive environment, the corrosion starting point is blocked and the corrosion reaction is suppressed.

  Examples of the organic compound (γ5) include the following. That is, as triazoles, 1,2,4-triazole, 3-amino-1,2,4-triazole, 3-mercapto-1,2,4-triazole, 5-amino-3-mercapto-1,2 1,4-triazole, 1H-benzotriazole, etc., and as thiols, 1,3,5-triazine-2,4,6-trithiol, 2-mercaptobenzimidazole, etc., and as thiadiazoles, 5- Amino-2-mercapto-1,3,4-thiadiazole, 2,5-dimercapto-1,3,4-thiadiazole and the like, and as thiazoles, 2-N, N-diethylthiobenzothiazole, 2-mercapto Examples include benzothiazoles, and examples of thiurams include tetraethylthiuram disulfide. It is. These organic compounds exhibit self-repairing properties due to the adsorption effect. That is, zinc and aluminum eluted by corrosion are adsorbed on polar groups containing sulfur contained in these organic compounds to form an inert film, thereby blocking the corrosion starting point and suppressing the corrosion reaction.

The compounding amount of the non-chromium-based rust preventive additive is 1 to 50 parts by mass, preferably 5 to 30 parts by mass, based on 100 parts by mass of the total solids of the component (α) and the component (β). The part is appropriate. If the blending amount of this non-chromium rust preventive additive is less than 1 part by mass, the effect of improving the corrosion resistance after alkali degreasing cannot be sufficiently obtained. On the other hand, if it exceeds 50 parts by mass, only the paintability and workability are lowered. Moreover, since corrosion resistance also falls, it is not preferable.
Two or more rust preventive additives (γ1) to (γ5) may be added in combination.
Further, in the surface treatment film (and surface treatment composition), other oxide fine particles (for example, aluminum oxide, zirconium oxide, titanium oxide, cerium oxide, antimony oxide, etc.), phosphomolybdate as corrosion inhibitors. One or more of an organic inhibitor (for example, hydrazine and derivatives thereof, a thiol compound, a thiocarbamate, and the like) can be added.

If necessary, a solid lubricant can be blended in the surface treatment film for the purpose of improving the workability of the film.
Examples of the solid lubricant that can be applied to the present invention include the following, and one or more of these can be used.
(1) Polyolefin wax, paraffin wax: For example, polyethylene wax, synthetic paraffin, natural paraffin, micro wax, chlorinated hydrocarbon, etc. (2) Fluororesin fine particles: For example, polyfluoroethylene resin (polytetrafluoroethylene resin, etc.) In addition to these, fatty acid amide compounds (for example, stearic acid amide, palmitic acid amide, methylene bisstearamide, ethylene bisstearamide, oleic acid amide, esyl) Acid amides, alkylene bis-fatty acid amides), metal soaps (eg, calcium stearate, lead stearate, calcium laurate, calcium palmitate), metal sulfides (eg, molybdenum disulfide, tungsten disulfide, etc.) Etc.), graphite, fluorinated graphite, boron nitride, polyalkylene glycols, may be used one or more, such as alkali metal sulfates.

Examples of the solid lubricant suitable for the present invention include the following polyethylene and polytetrafluoroethylene resins, which can be used in combination.
As the polyethylene, for example, Chemipearl W-100, Chemipearl W-200, Chemipearl W-500, Chemipearl W-800, Chemipearl W-950 (all trade names) manufactured by Mitsui Petrochemical Co., Ltd. can be used. .
Examples of polytetrafluoroethylene include KD-100CS and KD-120AS (both trade names) manufactured by Kitamura Co., Ltd., Lubron LDW-40 (trade name) manufactured by Daikin Industries, Ltd., and Mitsui DuPont. Teflon 30J and 120J (all trade names) manufactured by Co., Ltd., and Fullon AD-1, AD-639, AD-660, and AD-938L (all trade names) manufactured by Asahi Glass Co., Ltd. are preferable.

In the present invention, it is preferable to add these polyethylene and polytetrafluoroethylene in a specific ratio. By adding these in a composite manner, excellent processability can be obtained as compared with the case of adding them individually. The mixing ratio of polyethylene and polytetrafluoroethylene is preferably 5/5 to 1/9 in terms of the mass ratio of polyethylene / polytetrafluoroethylene. Outside this range, a sufficient combined effect on processability cannot be obtained, and there is almost no change from the case of addition alone.
The blending amount of the solid lubricant in the surface treatment film is 10 to 30 parts by mass (solid content), preferably 15 to 100 parts by mass (solid content) of the component (α) and the component (β). It is preferable to set it as 30 mass parts (solid content). If the blending amount of the solid lubricant is less than 10 parts by mass, the effect of improving the workability is poor. On the other hand, if the blending amount exceeds 30 parts by mass, the paintability is undesirably reduced.

If necessary, the surface-treated film of the surface-treated steel sheet of the present invention may further include an organic color pigment (for example, a condensed polycyclic organic pigment, a phthalocyanine-based organic pigment), a color dye (for example, organic) as an additive. Solvent-soluble azo dyes, water-soluble azo metal dyes, etc.), inorganic pigments (eg, titanium oxide), chelating agents (eg, thiols), conductive pigments (eg, metal powders such as zinc, aluminum, nickel, etc.) 1 type, or 2 or more types, such as an iron phosphide and antimony dope-type tin oxide), a coupling agent (for example, a silane coupling agent, a titanium coupling agent, etc.), a melamine cyanuric acid adduct, etc. can be added. .
The dry film thickness of the surface treatment film is 3.0 to 15 μm, preferably 5.0 to 10 μm. When the film thickness is less than 3.0 μm, the corrosion resistance is insufficient. On the other hand, when the film thickness exceeds 15 μm, adhesive bondability and top coatability are deteriorated.

The highly corrosion-resistant surface-treated steel sheet of the present invention is an organic film, inorganic film or organic film having a film thickness of 0.01 to 2 μm not containing chromium as the first layer on the surface of a zinc-based plated steel sheet or an aluminum-based plated steel sheet. An inorganic composite film may be formed, and the above-described surface treatment film may be formed as a second layer thereon.
Hereinafter, the first layer coating and the surface treatment composition for forming the coating will be described.
The function of the first layer film is to impart strong adhesion to the zinc-based plating and to suppress corrosion of the plated metal at the first layer film-plating interface. Corrosion resistance even better than in the case of a single layer is achieved by forming the first layer film (preferably a first layer film having a reaction layer) and the surface treatment film (second layer film) described above. Can be realized.
The first layer film preferably contains an amorphous phosphate compound for the purpose of forming a reaction layer with zinc-based plating. The amorphous phosphoric acid compound is not only advantageous for ensuring adhesion with zinc, but also has an effect of suppressing the generation of white rust by the soluble phosphoric acid in the film capturing the zinc.

  A colloidal inorganic oxide (fine particles) can be blended with such an amorphous phosphate compound. The oxide fine particles are preferably silicon dioxide, colloidal silica such as SNOWTEX O, OS, OXS, OUP, AK, O40, OL, OZL (above acidic solution), SNOWTEX XS manufactured by Nissan Chemical Co., Ltd. , S, NXS, NS, N, QAS-25, LSS-35, LSS-45, LSS-75 (alkaline solution) and the like can be applied. Also, Cataloid S, SI-350, SI-40, SA (alkaline solution), Cataloid SN (acid solution), Adelite AT-20-50 manufactured by Asahi Denka Kogyo Co., Ltd. AT-20N, AT-300, AT-300S (above alkaline solution), Adelite AT20Q (acidic solution) and the like can be applied. Of these, particles having a particle diameter of 14 nm or less, and particularly fine particles of 8 nm or less are preferred from the viewpoint of corrosion resistance. Alternatively, dry silica fine particles dispersed in a coating composition solution may be used. As this dry silica, AEROSIL200, 300, 300CF, 380 manufactured by Nippon Aerosil Co., Ltd. can be used, and those having a particle diameter of 12 nm or less, preferably 7 nm or less are preferable.

In addition to the above, colloidal solutions and fine powders such as aluminum oxide, zirconium oxide, titanium oxide, cerium oxide, and antimony oxide can be used as the oxide fine particles.
In addition, the conventional phosphating (crystallinity) is not preferable because workability and weldability are inferior.
In addition, the first layer film may be any of an inorganic film, an organic film, and an organic-inorganic composite film. However, in consideration of severe press working as a steel sheet for automobiles, it is desirable to incorporate an organic resin. An organic film or an organic-inorganic composite film is preferred. As the organic resin, an epoxy resin, a modified epoxy resin, a polyhydroxy polyether resin, a polyalkylene glycol-modified epoxy resin, and a resin obtained by further modifying these are preferable.

  Furthermore, by adding a silane coupling agent or the like to these, the corrosion resistance can be further improved. Examples of the silane coupling agent include vinyl methoxy silane, vinyl ethoxy silane, vinyl trichloro silane, vinyl trimethoxy silane, vinyl triethoxy silane, β- (3,4 epoxy cyclohexyl) ethyl trimethoxy silane, and γ-glycid. Xylpropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltriethoxysilane, N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane, N-β (aminoethyl) γ -Aminopropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-me Tacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-mercaptopropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane, p-styryltrimethoxysilane, γ -Acryloxypropyltrimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-ureidopropyltriethoxysilane, γ-chloropropyltrimethoxysilane, bis (triethoxysilylpropyl) tetrasulfide, γ-isocyanatopropyl Triethoxysilane, γ-triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine, N- (vinylbenzylamine) -β-aminoethyl-γ-aminopropyltri Etc. can be mentioned Tokishishiran can use these alone or in combination of two or more kinds. The reason why the film containing these silane coupling agents is excellent in corrosion resistance is that silanol groups (Si-OH) generated by hydrolysis of the silane coupling agent in the aqueous solution hydrogen bond with the surface of the plating film. This is considered to be due to imparting excellent adhesion by the dehydration condensation reaction.

The dry film thickness of the first layer film (organic film, inorganic film or organic-inorganic composite film) is 0.01 to 2 μm, preferably 0.1 to 1.0 μm. When the film thickness is less than 0.01 μm, the corrosion resistance is insufficient. On the other hand, when the film thickness exceeds 2 μm, the workability and adhesive bondability are lowered.
The film thickness of the surface treatment film to be the second layer is set to 3.0 to 15 μm, preferably 5 to 10 μm, for the reason described above.

Next, the manufacturing method of the surface treatment steel plate of this invention is demonstrated.
In order to form the above-mentioned surface treatment film on the surface of a zinc-based plated steel sheet or an aluminum-based plated steel sheet, the surface-treated composition (treatment liquid) having the above-described composition is plated steel sheet surface so that the dry film thickness is in the above range. It is preferable to apply to and heat dry without washing with water.
The method for coating the surface treatment composition on the surface of the plated steel sheet may be any of an application method, a dipping method, and a spray method. As a coating method, any method such as a roll coater (3-roll method, 2-roll method, etc.), a squeeze coater, or a die coater may be used. In addition, after the coating process or dipping process using a squeeze coater or the like, or the spray process, the coating amount can be adjusted, the appearance can be made uniform, and the film thickness can be made uniform by an air knife method or a roll drawing method.

  After coating the surface treatment composition, drying is performed without washing with water. As the heating and drying means, a dryer, a hot air furnace, a high frequency induction heating furnace, an infrared furnace or the like can be used. Heat drying is preferably performed in the range of 30 to 150 ° C., preferably 40 to 140 ° C., at the ultimate plate temperature. If the heating and drying temperature is less than 30 ° C., a large amount of moisture remains in the film, and the corrosion resistance tends to be insufficient. In addition, when the heating and drying temperature exceeds 150 ° C., not only is it uneconomical, but defects are generated in the film, and the corrosion resistance tends to be lowered. Moreover, since it becomes impossible to apply to a BH steel plate when heat drying temperature exceeds 150 degreeC, it is unpreferable.

  Moreover, it has an organic film, an inorganic film, or an organic-inorganic composite film as a first layer on the surface of a zinc-based plated steel sheet or an aluminum-based plated steel sheet, and has the above-described surface treatment film as a second layer thereon. When producing a surface-treated steel sheet, the surface treatment composition (treatment liquid) for forming the first layer is applied to the surface of the plated steel sheet so that the dry film thickness is in the above range, and is heated and dried without being washed with water. The method of coating the surface treatment composition on the surface of the plated steel plate and the method of heat drying are the same as described above. It is desirable that the heat drying is carried out in the range of 30 to 160 ° C., preferably 50 to 140 ° C., at the ultimate plate temperature. When the heating and drying temperature is less than 30 ° C., a large amount of moisture remains in the surface treatment film, and the corrosion resistance tends to be insufficient. On the other hand, if it exceeds 160 ° C., not only is it uneconomical, but it is not preferable because it cannot be applied to BH steel sheets. Next, a surface treatment film as the second layer is formed by the same method as described above.

<Preparation of surface treatment composition for first layer formation>
As shown in Table 2, a water-dispersible epoxy resin is used as the organic resin, and a silane coupling agent, phosphoric acid, etc. are appropriately blended therein, and the mixture is stirred for a predetermined time using a paint disperser (sand grinder). A surface treatment composition for single layer formation was prepared.
<Preparation of surface treatment composition for forming second layer>
As the resin composition, an aqueous dispersion of composite resins (ABC-1) to (ABC-6) prepared in the synthesis examples shown below (corresponding to the component (α) in the present invention example) and the organics shown in Table 5 A resin (corresponding to the component (β) in the present invention example) was blended, and the non-chromium anticorrosive additive shown in Table 6 (corresponding to the component (γ) in the present invention example), and a solid lubricant shown in Table 7 Were appropriately mixed and stirred for a predetermined time using a disperser for coating (sand grinder) to prepare a surface treatment composition for forming a second layer. The contents of Synthesis Examples 1 to 6 shown below are shown in Tables 3 and 4.

Synthesis Example 1 [Preparation of methyltrimethoxysilane condensate (c-1)]
A reaction vessel equipped with a stirrer, thermometer, dropping funnel, condenser and nitrogen gas inlet is charged with 1,421 parts (part by mass) of methyltrimethoxysilane (MTMS) and heated to 60 ° C. did. Next, a mixture of 0.17 part of “A-3” (iso-propyl acid phosphate manufactured by Sakai Chemical Co., Ltd.) and 207 parts of deionized water was added dropwise over 5 minutes. After completion of the dropwise addition, the temperature in the reaction vessel was raised to 80 ° C. and stirred for 4 hours to conduct a hydrolysis condensation reaction. Then, the obtained condensate is reduced under a reduced pressure of 300 to 10 mmHg (reduced pressure conditions at the start of methanol distillation are 300 mmHg and finally reduced to 10 mmHg; hereinafter the same), 40 to 60 Distilled within a temperature range of 0 ° C. for 2 hours to remove the generated methanol and water, and a methyltrimethoxysilane condensate having a number average molecular weight of 1,000 and an active ingredient in the reaction solution of 70% by mass (C-1) 1,000 parts were obtained. The active ingredient in the reaction solution is the theoretical yield (parts by mass) when all methoxy groups of silane monomers such as MTMS and ethyltrimethoxysilane (ETMS) undergo a condensation reaction. Part)) [theoretical yield when all methoxy groups of the silane monomer have undergone condensation reaction (mass part) / actual yield after condensation reaction (mass part)] (hereinafter the same).

Synthesis Example 2 [Preparation of condensate (c-2) of ethyltrimethoxysilane]
In the same reaction vessel as in Synthesis Example 1, 1,296 parts of ethyltrimethoxysilane (ETMS) was charged, and the temperature was raised to 60 ° C. Next, a mixture of 0.14 part of “A-3” and 171 parts of deionized water was added dropwise over 5 minutes. After completion of the dropwise addition, the temperature in the reaction vessel was raised to 80 ° C. and stirred for 4 hours to conduct a hydrolysis condensation reaction. Next, the obtained condensate was distilled for 2 hours in a temperature range of 40 to 60 ° C. under a reduced pressure of 300 to 10 mmHg to remove the generated methanol and water, and the number average molecular weight was 1,100. Then, 1,000 parts of an ethyltrimethoxysilane condensate (c-2) having an active ingredient content of 70% by mass in the reaction solution was obtained.

Synthesis Example 3 [Preparation of aqueous dispersion of composite resin (ABC-1)]
In the same reaction vessel as in Synthesis Example 1, 126 parts of propylene glycol monopropyl ether (PnP), 59 parts of phenyltrimethoxysilane (PTMS) and 62 parts of dimethyldimethoxysilane (DMDMS) were charged, and the temperature was raised to 80 ° C. Next, at the same temperature, 21 parts of methyl methacrylate (MMA), 20 parts of butyl methacrylate (BMA), 14 parts of butyl acrylate (BA), 13 parts of acrylic acid (AA), 2 parts of 3-methacryloxypropyltrimethoxysilane (MPTS) A mixture containing 3.5 parts of PnP and 3.5 parts of tert-butylperoxy-2-ethylhexanoate (TBPEH) was dropped into the reaction vessel over 4 hours. To obtain a polymer (a′-1) having a number average molecular weight of 14,000 having both a carboxyl group and a hydrolyzable group bonded to a silicon atom, and then 0.016 part of “A-3”. A mixture of water and 45 parts of deionized water is added dropwise over 5 minutes, and the mixture is further stirred for 1 hour at the same temperature to carry out a hydrolytic condensation reaction to bond to a carboxyl group and a silicon atom. It was to obtain a hydrolyzable group and having both polymer segments and PTMS and DMDMS from polysiloxane segments consisting of composite resin (A'B-1). Next, 290 parts of a condensate (c-1) of methyltrimethoxysilane was added, 59 parts of deionized water was further added, and the mixture was stirred at the same temperature for 16 hours to conduct hydrolysis condensation reaction, and the composite resin A reaction solution containing a composite resin (A'BC-1) in which a polysiloxane segment (C-1) derived from a condensate (c-1) of (A'B-1) and methyltrimethoxysilane was bonded was obtained. .

  Next, the obtained reaction liquid was distilled under reduced pressure of 300 to 10 mmHg for 2 hours at 40 to 60 ° C. to remove generated methanol and water, and then 15 parts of triethylamine (TEA) was added. The carboxyl group in the composite resin (A'BC-1) is neutralized to form a composite resin (ABC-1), and then dispersed in an aqueous medium by adding 497 parts of deionized water, and the non-volatile content Obtained 1,000 parts of an aqueous dispersion of 35% by mass of composite resin (ABC-1).

Synthesis Examples 4 to 8 [Preparation of aqueous dispersions of composite resins (ABC-2) to (ABC-6)]
In the same manner as in Synthesis Example 3, the ratio of each compound was changed as shown in Table 4, so that the mass ratio of the solid content of the polymer segment (A) and the polysiloxane segments (B) and (C) (A) / Composite resins (ABC-2) to (ABC-6) having different [(B) + (C)] were synthesized. In Synthesis Example 5 and Synthesis Example 6, instead of the methyltrimethoxysilane condensate (c-1) used in Synthesis Example 3, ethyltrimethoxysilane condensate (c-2) was similarly converted to butyl acrylate ( Instead of BA), 2-ethylhexyl methacrylate (2-EHMA) was used.
These composite resins (ABC-2) to (ABC-6) are dispersed in an aqueous medium by adding deionized water, and the non-volatile composite resins (ABC-2) to (ABC-) shown in Table 4 are used. 1,000 parts by weight of the aqueous dispersion 6) was obtained.

<Manufacture of surface-treated steel sheets>
The plated steel sheet shown in Table 1, which is a plated steel sheet for home appliances, building materials, and automobile parts based on cold-rolled steel sheets, was used as a processing original sheet. In addition, the thing of predetermined | prescribed board thickness was employ | adopted for the board thickness of the steel plate according to the objective of evaluation. After the surface of this plated steel sheet was subjected to alkaline degreasing treatment, washed with water and dried, the surface treatment composition for forming the first layer was applied by a roll coater and dried by heating at 110 ° C. Next, the surface treatment composition for forming the second layer was applied by a roll coater and dried by heating at 140 ° C. The film thickness of the film was adjusted by the solid content (heating residue) of the surface treatment composition or coating conditions (rolling force of the roll, rotation speed, etc.).

<Evaluation of quality performance of surface-treated steel sheet>
Tables 8 to 10 show the results of evaluating the coating composition and quality performance (corrosion resistance, post-processing corrosion resistance, adhesive bondability, top coatability) of the obtained surface-treated steel sheet. The quality performance was evaluated as follows.
(1) Corrosion resistance About each sample, the composite cycle test (CCT) based on SAE-J2334 was given, and the white rust generation | occurrence | production area ratio and red rust generation | occurrence | production area ratio after progress of 120 cycles were evaluated.
[Monday to Friday]
Wet (50 ° C,> 95% RH): 6 hours ↓
Salt water immersion (25 ° C): 15 minutes ↓
Drying (60 ° C, 50% RH): 17 hours 45 minutes [Saturday, Sunday]
Drying (60 ° C., 50% RH): all day The evaluation criteria are as follows.
◎: No white rust occurrence area rate ○: White rust occurrence area rate less than 10% ○-: White rust occurrence area rate of 10% to less than 50% No red rust occurrence △: White rust occurrence area rate of 50% or more ×: Red rust generated

(2) Corrosion resistance after processing For each sample, deformation and sliding were added with a draw bead under the following conditions, and this sample was used at 45 ° C. for 2 minutes using “FC-4460” manufactured by Nihon Parkerizing Co., Ltd. After degreasing under the conditions, the CCT performed in “(1) Corrosion resistance” was performed, and the white rust generation area ratio and the red rust generation area ratio after 120 cycles were evaluated.
Pressing load: 800kgf
Drawing speed: 1000mm / min
Bead shoulder R: Male side 2mmR, Female side 3mmR
Pushing depth: 7mm
Oil used: “Preton R-352L” manufactured by Sugimura Chemical Co., Ltd.
The evaluation criteria are as follows.
◎: White rust generation area rate less than 10% ○: White rust generation area rate of 10% or more and less than 30% ○-: White rust generation area rate of 30% or more and less than 50%, no red rust △: White rust generation area rate No red rust generated ×: Red rust generated

(3) Adhesive bondability Each sample was sheared to 25 × 200 mm, and 1 g / m ² of cleaning oil (“Preton 303P” manufactured by Sugimura Chemical Industry Co., Ltd.) was applied to the surface. “Felco 5010” manufactured by Aisin Chemical Co., Ltd.) was applied to a range of 25 × 100 mm of the sample, two 0.15 mm piano wires were put, the other sample was overlapped, and fixed with a clip. After the baking treatment was performed under the conditions of 180 ° C. × 20 minutes, the sample was left again for one day to prepare a sample. A shear peeling test was conducted by pulling both ends of the portion where the adhesive was not applied under a condition of 5 mm / min with a tensile tester, and the shear strength at that time was measured.
The evaluation criteria are as follows.
◎: 25 MPa or more ○: 24 MPa or more, less than 25 MPa Δ: 22 MPa or more, less than 24 MPa ×: less than 22 MPa

(4) Top coat coating properties Each sample was degreased using “FC-E2001” manufactured by Nihon Parkerizing Co., Ltd. under conditions of 40 ° C. × 2 minutes, and then an intermediate coating for automobiles (“TP manufactured by Kansai Paint Co., Ltd.) −65-P gray ”) was applied to a film thickness of 40 μm, and then a baking process of 140 ° C. × 18 minutes was performed. Further, an automotive top coating (“Neoamylac 6000-4” manufactured by Kansai Paint Co., Ltd.) was applied to the surface so as to have a film thickness of 40 μm, and then subjected to a baking treatment at 140 ° C. for 30 minutes. The coated sample is immersed in pure water at 40 ° C. for 500 hours, immediately cut into grids (10 × 10, 2 mm intervals), and attached and peeled off with adhesive tape. It was measured.
The evaluation criteria are as follows.
◎: No peeling ○: Peeling area ratio less than 5% △: Peeling area ratio of 5% or more and less than 20% ×: Peeling area ratio of 20% or more

In addition, each component of Table 3 and Table 4 is as follows.
“MTMS”: methyltrimethoxysilane “ETMS”: ethyltrimethoxysilane “PnP”: propylene glycol monopropyl ether “PTMS”: phenyltrimethoxysilane “DMDMS”: dimethyldimethoxysilane “MMA”: methylmethacrylate “BMA”: Butyl methacrylate “2-EHMA”: 2-ethylhexyl methacrylate “BA”: Butyl acrylate “AA”: Acrylic acid “MPTS”: 3-Methacryloyloxypropyltrimethoxysilane “TBPEH”: tert-butylperoxy-2-ethylhexa Noate "TEA": Triethylamine

In addition, * 1 to * 6 described in Tables 8 to 10 indicate the following contents.
* 1: Plated steel plate No. in Table 1 1-9
* 2: Surface treatment composition No. 1 for film formation for the first layer described in Table 2 1-3
* 3: Aqueous dispersions (ABC-1) to (ABC-6) of composite resins (ABC) described in Table 4
* 4: Resin No. described in Table 5 1-10
* 5: Rust preventive additive No. described in Table 6 1-7
* 6: Solid lubricant Nos. Listed in Table 7 1-7
* 7: Mass parts

Claims (7)

A polymer segment (A) containing the following components (α), (β) and (γ) on the surface of a zinc-based plated steel plate or an aluminum-based plated steel plate, and constituting the composite resin (ABC) in the component (α): The film thickness formed by the surface treatment composition in which the mass ratio (A) / [(B) + (C)] of the solid content of the polysiloxane segments (B) and (C) is 40/60 to 20/80. A surface-treated steel sheet having a surface-treated film of 3.0 to 15 μm.
Component (α): a polysiloxane segment (B) of a composite resin (AB) in which a polymer segment (A) having a neutralized acid group and a polysiloxane segment (B) are chemically bonded, and an alkyl group A composite resin (ABC) in which the polysiloxane segment (C) derived from the condensate (c) of trialkoxysilane having 1 to 3 carbon atoms is bonded through a silicon-oxygen bond or dissolved in an aqueous medium Component (β): Aqueous epoxy ester resin having a functional group that reacts with a hydroxyl group Component (γ): Non-chromium rust preventive additive   2. The surface according to claim 1, wherein the mass ratio (α) / (β) of the solid content of the component (α) and the component (β) in the surface treatment composition is 70/30 to 40/60. Treated steel sheet.   The surface-treated steel sheet according to claim 1 or 2, wherein the component (β) in the surface treatment composition is a dispersion type aqueous epoxy ester resin.   The surface treatment composition contains 1 to 50 parts by mass of the component (γ) in a ratio of the solid content to the total solid content of 100 parts by mass of the component (α) and the component (β). The surface-treated steel sheet according to any one of 3 above. The surface treatment composition contains one or more rust preventive additives selected from the following (γ1) to (γ5) as the component (γ). The surface-treated steel sheet described.
(Γ1) Silicon oxide (γ2) Calcium and / or calcium compound (γ3) Slightly soluble phosphate compound (γ4) Molybdate compound (γ5) Triazoles, thiols, thiadiazoles, thiazoles, thiurams One or more organic compounds containing S atoms   The surface-treated steel sheet according to any one of claims 1 to 5, wherein the surface treatment composition further contains a solid lubricant.   On the surface of the zinc-based plated steel sheet or aluminum-based plated steel sheet, an organic film, inorganic film or organic-inorganic composite film having a film thickness of 0.01 to 2 μm not containing chromium is formed as the first layer, and the upper layer is formed thereon. A surface-treated steel sheet, wherein the surface-treated film according to any one of claims 1 to 6 is formed as a second layer.