WO2018123996A1 - Surface treatment agent for galvanized steel sheets - Google Patents

Abstract

Provided is a surface treatment agent for galvanized steel sheets, the surface treatment agent having excellent film formability and being capable of providing a coating film having excellent corrosion resistance, chemical resistance, and weather resistance. The surface treatment agent for galvanized steel sheets contains a zirconium compound (A), a chelating agent (B) having at least one hydroxyl group in one molecule, and an organic resin (C) having a carboxyl group (c1), wherein the content of the zirconium compound (A) in the surface treatment agent for galvanized steel sheets is in the range of 200-1000 mass ppm, the molar ratio of elemental zirconium (Zr) derived from the zirconium compound (A) to the chelating agent (B), i.e., (Zr)/(B), is in the range of 4-100, the acid value of the organic resin (C) is in the range of 10-30 mgKOH/g, and the molar ratio of the carboxyl group (c1) to the chelating agent (B), i.e., (c1)/(B), is in the range of 30-1000.

Description

Surface treatment agent for galvanized steel sheet

The present invention relates to a surface treatment agent for galvanized steel sheet.

Conventionally, zinc-based plated steel sheets that have been galvanized or zinc alloy plated have been used as steel sheets with excellent corrosion resistance. Such a zinc-based plated steel sheet is oxidized by the plating layer coming into contact with air and white rust is generated. For this reason, it is necessary to impart corrosion resistance and prevent oxidation by applying a surface treatment. Moreover, the weatherability and chemical resistance of a surface treatment layer are also requested | required depending on a use, for example, when using it outdoors as a building material. As such a surface treatment agent, a chromium-based surface treatment agent such as chromate treatment or phosphoric acid chromate treatment has been conventionally applied.

However, since chromium is toxic, chromium-free technology that does not contain chromium is being studied from the viewpoint of reducing the environmental burden and the cost of wastewater treatment. Specifically, a surface on which a coating film is formed on a zinc-based plated steel sheet by dispersing an aqueous resin or the like as an emulsion in water, applying it on an object by roll coating, etc., baking and drying, and fusing. A processing agent is mentioned.

For example, Patent Document 1 discloses one or two or more resins having a glass transition temperature of −10 ° C. or higher, colloidal silica, zirconium, and the like, selected from the group consisting of acrylic resins, polyester resins, and urethane resins. A chromium-free surface-treated steel sheet containing a compound and a triazole / tetrazole in a specific ratio is described.

Patent Document 2 discloses that an aqueous organic resin dispersion containing an anionic urethane resin (CII) contains predetermined amounts of an organic phosphate compound, colloidal silica, a vanadium compound, a zirconium carbonate compound, a silane coupling agent, and a polyolefin wax. An added chromium and fluorine compound free aqueous metal surface treatment composition is described.

Patent Document 3 discloses a water-based resin having a carboxyl group and an acid amide bond, selected from metal compounds of Al, Mg, Ca, Zn, Ni, Co, Fe, Zr, Ti, V, W, Mn, and Ce. There is described a surface treatment agent for a metal plate material which does not contain chromium, characterized by containing a seed or two or more metal compounds and a silicon compound.

JP 2013-237874 A JP 2014-055319 A JP 2003-201579 A

However, with these conventional chromium-free treatment agents, particularly when baking and drying at low temperatures and in a short time, the film forming property is insufficient, so the corrosion resistance of the coating film is not sufficient, and chemical resistance, weather resistance, When applied to various applications requiring paint adhesion, the performance was insufficient.

The present invention has been made in view of the above, and its purpose is to provide a surface treatment agent for galvanized steel sheets that is excellent in film forming properties and excellent in corrosion resistance, chemical resistance, weather resistance, and paint adhesion of the coating film. It is to provide.

The present invention is a surface treatment agent for a zinc-based plated steel sheet, comprising a zirconium compound (A), a chelating agent (B) having one or more hydroxyl groups in one molecule, and an organic resin having a carboxyl group (c1). (C), and the zirconium compound (A) is contained in the surface treatment agent for zinc-based plated steel sheet in the range of 200 to 10000 mass ppm in terms of Zr element, and is derived from the zirconium compound (A). The molar ratio of the element (Zr) to the chelating agent (B) is in the range of (Zr) / (B) = 4 to 100, and the acid value of the organic resin (C) is in the range of 10 to 30 mgKOH / g. Further, the present invention relates to a surface treatment agent for galvanized steel sheets in which the molar ratio of the carboxyl group (c1) to the chelating agent (B) is in the range of (c1) / (B) = 30 to 1000.

The organic resin (C) has a hydroxyl group (c2), and the hydroxyl value of the organic resin (C) is in the range of 10 to 30 mgKOH / g. The hydroxyl group (c2) and the chelating agent (B ) Is preferably in the range of (c2) / (B) = 30 to 1000.

The organic resin (C) is preferably at least one selected from the group consisting of acrylic resin, urethane resin, polyolefin resin and vinyl resin.

Further, it is preferable to contain the vanadium compound (D) in the range of 20 to 300 ppm by mass in terms of V element.

Further, it is preferable to contain the titanium compound (E) in the range of 50 to 1000 ppm by mass in terms of Ti element.

Further, it is preferable that the silane coupling agent (F) is contained in the range of 0.5 to 5% by mass with respect to the solid content mass of the organic resin (C).

Further, it is preferable to contain silicon oxide (G) in the range of 2.0 to 4.0% by mass in terms of SiO ₂ .

According to the present invention, it is possible to provide a surface treating agent for galvanized steel sheet that is excellent in film forming properties and excellent in corrosion resistance, chemical resistance, weather resistance, and paint adhesion of the coating film.

Hereinafter, embodiments of the present invention will be described. In addition, this invention is not limited to the following embodiment.

<Surface treatment agent for galvanized steel sheet>
The surface treating agent for galvanized steel sheet according to this embodiment includes a zirconium compound (A), a chelating agent (B), and an organic resin (C). Moreover, the surface treating agent for galvanized steel sheet according to the present embodiment includes a vanadium compound (D), a titanium compound (E), a silane coupling agent (F), silicon oxide (G), or other components (H). It is preferable to include. The surface treatment agent for galvanized steel sheet according to the present embodiment is superior in film-forming properties compared to the conventional surface treatment agent for galvanized steel sheet, and the corrosion resistance, chemical resistance, weather resistance, and coating of the coating film. Since it is excellent in adhesiveness, it is characterized in that it can be preferably used as a temporary rust preventive for galvanized steel sheets.

<Zirconium compound (A)>
Zirconium compound (A) according to this embodiment is a compound containing zirconium element (Zr), and in the surface treatment agent for zinc-based plated steel sheet in terms of Zr element with respect to the mass of the surface treatment agent for zinc-based plated steel sheet In the range of 200 to 10000 mass ppm. Thereby, a zirconium compound (A) has a function which improves the corrosion resistance of a coating film. More preferably, the zirconium compound (A) is contained in the surface treatment agent for a zinc-based plated steel sheet in terms of Zr element in a range of 335 to 7500 mass ppm, and more preferably in a range of 2000 to 3500 mass ppm. When the content of the zirconium compound (A) is less than 200 ppm by mass, sufficient corrosion resistance cannot be imparted, and when it exceeds 10000 ppm by mass, the flexibility of the coating becomes insufficient. May be inferior.

The type of the zirconium compound (A) according to the present embodiment is not particularly limited. For example, zirconium carbonate, zirconium carbonate ammonium, zirconium borate, zirconium oxalate, zirconium sulfate, zirconium nitrate, zirconyl nitrate, zirconium fluoride, zircon hydrogen fluoride Acid, ammonium zircon fluoride, ammonium oxycarbonate zirconate, zirconium hydroxide, potassium zircon fluoride, sodium zircon fluoride, dibutyl zirconium dilaurate, dibutyl zirconium dioctate, zirconium naphthenate, zirconium octylate, zirconium acetylacetone, zirconium acetylacetate NART, zirconium butoxide 1-butanol solution, zirconium n-propoxide, etc. are preferably usedIn addition, these zirconium compounds (A) may be used individually by 1 type, or may use 2 or more types together.

<Chelating agent (B)>
The chelating agent (B) according to the present embodiment has one or more hydroxyl groups in one molecule from the viewpoint of the storage stability of the surface treatment agent and the corrosion resistance of the galvanized steel sheet. Thereby, chelating agent (B) can disperse zirconium compound (A) stably in a surface treating agent, and a surface treating agent excellent in storage stability is obtained. Moreover, aggregation of a zirconium compound (A) can be suppressed and the coating film excellent in corrosion resistance can be formed.

The chelating agent (B) is not particularly limited as long as it has one or more hydroxyl groups in one molecule. For example, 1-hydroxyethane-1,1-diphosphonic acid (HEDP), triethanolamine (TEA), citric acid, gluconic acid, or a salt thereof (ammonium citrate, Na gluconate, etc.) is preferably used. In addition, these chelating agents (B) may be used individually by 1 type, or may use 2 or more types together.

<Organic resin (C)>
The organic resin (C) according to the present embodiment has a carboxyl group (c1). The acid value of the organic resin (C) is in the range of 10 to 30 mgKOH / g. When the acid value is less than 10 mg KOH / g, there are few carboxyl groups contributing to the stabilization of the resin, the stability of the surface treatment agent is lowered, and not only the thickening or gelation is promoted, but also the metal base material as the film performance. The adhesion of the will be reduced. In addition, when the acid value exceeds 30 mgKOH / g, the carboxyl group that functions as a hydrophilic group is excessively present in the film, so that the surface after the film is formed becomes hydrophilic, corrosion resistance, alkali resistance, boiling water resistance, water resistance Sexuality will decrease.

In the present embodiment, the organic resin (C) has a hydroxyl group (c2). The hydroxyl value of the organic resin (C) is 10 to 30 mgKOH / g. When the hydroxyl value is less than 10 mgKOH / g, it does not sufficiently function as an adhesion functional group with the top coating material, and the coating adhesion deteriorates. In addition, when the hydroxyl value exceeds 30 mgKOH / g, the hydroxyl group that functions as a hydrophilic group is excessively present in the film, so that the surface after the film formation becomes hydrophilic, corrosion resistance, alkali resistance, boiling water resistance, water resistance Etc. will fall.

The organic resin (C) is not particularly limited as long as it has a carboxyl group (c1). For example, an acrylic resin (CI), a urethane resin (CII), a polyolefin resin (CIII), and a vinyl resin ( Preferably, at least one selected from the group consisting of CIV). When the organic resin (C) is selected from the group consisting of these resins, the metal surface treatment composition has a good film-forming property, and a coating film having excellent barrier properties, uniformity, and low-temperature drying properties. Can be formed. Moreover, the metal surface treatment composition can form a continuous film with a thin film. These resins are also components necessary for ensuring adhesion to the metal surface.
Hereinafter, acrylic resin (CI), urethane resin (CII), olefin resin (CIII), and vinyl resin (CIV) are used as the organic resin (C), and particularly acrylic resin (CI) and urethane resin. Each case where (CII) is used in combination will be described in detail.

<Acrylic resin (CI)>
When an acrylic resin (CI) is used as the organic resin (C), the acrylic resin (CI) is a copolymer mainly composed of one or both of acrylic acid and methacrylic acid, and has an aromatic structure in the structure. It is preferable that it does not have a group structure. Since the acrylic resin (CI) does not have an aromatic structure in the structure, a chemically stable coating film can be formed. For example, since deterioration due to ultraviolet light absorption of the coating film can be suppressed, a coating film having excellent weather resistance can be formed.

Examples of the acrylic resin (CI) copolymer include derivatives thereof such as methyl acrylate, ethyl acrylate, methyl methacrylate, and ethyl methacrylate, and copolymers with other acrylic monomers. Since the structure does not have an aromatic structure, for example, a commonly used acrylic-styrene copolymer or the like is not included.

Further, the acrylic resin (CI) preferably has a core / shell structure having a multilayer structure instead of a normal uniform structure. This is because by using an acrylic resin (CI) having a structurally hard core portion and a structurally soft shell portion, it becomes easy to achieve both film forming properties and performance such as corrosion resistance of the coating film.
For example, the core / shell structure acrylic resin (CI) is manufactured by first emulsion polymerizing a polymerizable unsaturated monomer component containing no or almost no carboxyl group-containing polymerizable unsaturated monomer, and then containing a carboxyl group. It can be obtained by emulsion polymerization by adding a polymerizable unsaturated monomer component containing a large amount of a polymerizable unsaturated monomer.
The bond between the core part and the shell part is obtained by, for example, adding a polymerizable unsaturated monomer component containing a carboxyl group-containing polymerizable unsaturated monomer to a polymerizable unsaturated bond such as allyl acrylate or allyl methacrylate remaining on the surface of the core part. It can be carried out by copolymerization.

Moreover, Tg of acrylic resin (CI) is 10 ° C. or higher and 100 ° C. or lower. When Tg is less than 10 ° C., the formed coating film has insufficient water and chemical barrier properties, so that a coating film excellent in corrosion resistance and chemical resistance cannot be obtained. When the temperature exceeds 100 ° C., the resin is not sufficiently fused at the time of forming the coating film, and the film forming property is deteriorated.

When the urethane resin (CII) is used as the organic resin (C), the urethane resin (CII is preferably a saturated aliphatic urethane resin obtained by a chemical reaction of a cyclic aliphatic polyol compound and an isocyanate. (CII) can form a highly corrosion-resistant coating film and can form a chemically stable coating film because it does not contain multiple bonds, for example, it can suppress deterioration of the coating film due to absorption of ultraviolet light, and thus has excellent weather resistance. A coating film can be formed.

The cycloaliphatic polyol compound is not particularly limited, and one or a mixture of two or more commonly used polyols can be used. Specific examples of the cycloaliphatic polyol compound include, for example, 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,2-bis (hydroxymethyl) cyclohexane and hydrogenated bisphenol. A etc. are mentioned.

The isocyanate compound is not particularly limited as long as the resin skeleton of the produced urethane resin (CII) does not include a double bond, a triple bond and an aromatic ring, and diisocyanate and other polyisocyanates are used. be able to.
As diisocyanate, generally used diisocyanate can be used singly or in combination of two or more. Specific examples of the diisocyanate include alicyclic diisocyanates such as isophorone diisocyanate, dicyclohexylmethane-4,4′-diisocyanate, trans-1,4-cyclohexyl diisocyanate, norbornene diisocyanate, 1,6-hexamethylene diisocyanate, 2, Examples thereof include aliphatic diisocyanates such as 2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, and methyl 2,6-diisocyanatohexanoate.
The other polyisocyanate is preferably a polyisocyanate having three or more isocyanate groups in one molecule. Examples include trifunctional or higher functional isocyanates such as the above-mentioned diisocyanate isocyanurate trimers, burette trimers, trimethylolpropane adducts, etc. These isocyanate compounds are carbodiimide modified, isocyanurate modified, biuret modified, etc. It may be used in the form of a modified product.

The glass transition temperature (hereinafter referred to as “Tg”) of the urethane resin (CII) is preferably 90 ° C. or higher. This is because when the Tg is less than 90 ° C., the formed coating film has insufficient water and chemical barrier properties, so that a coating film excellent in corrosion resistance and chemical resistance cannot be obtained.

<Olefin resin (CIII)>
As the olefin resin of the organic resin (C), for example, a copolymer resin with an unsaturated carboxylic acid such as ethylene-acrylic acid, methacrylic acid or maleic anhydride (for example, ethylene-acrylic acid copolymer) is used as sodium hydroxide. And water-dispersed acrylic resins neutralized with alkali metal hydroxides such as potassium hydroxide, ammonia or organic amines. When the ethylene-acrylic acid copolymer resin is used, the ethylene content is preferably in the range of 70 to 90% by mass and the acrylic acid content in the range of 10 to 30% by mass.

<Vinyl resin (CIV)>
When a vinyl resin (CIV) is used as the organic resin (C), PVA such as polyvinyl alcohol (PVA) and modified PVA such as carboxyl group-modified PVA; cellulose derivatives such as hydroxyethyl cellulose and carboxymethyl cellulose; isobutylene and A copolymer of an α-olefin and an unsaturated carboxylic acid such as a copolymer with maleic anhydride or a water-soluble product of a derivative thereof can be used. Moreover, these 1 type (s) or 2 or more types are used suitably.

<Acrylic resin (CI) and urethane resin (CII)>
When the acrylic resin (CI) and the urethane resin (CII) are used in combination, the solid mass ratio of the acrylic resin (CI) and the urethane resin (CII) is (CI) / (CII) = 5/95 to 50 / A range of 50 is preferred. When the solid content mass ratio between the acrylic resin (CI) and the urethane resin (CII) is less than 5/95, the weather resistance of the coating film may not be sufficiently obtained. On the other hand, when the solid content mass ratio between the acrylic resin (CI) and the urethane resin (CII) exceeds 50/50, the cohesive force between the resins is insufficient, and the resin is not sufficiently fused when the coating film is formed. Therefore, there are cases where sufficient film forming properties cannot be obtained.

Also, the difference in Tg between the resins used together (for example, the difference between the Tg of the urethane resin (CII) and the Tg of the acrylic resin (CI)) is preferably in the range of 40 ° C to 120 ° C. Further, when the acrylic resin (CI) has a core / shell structure, the difference between the Tg of the core part in the core / shell structure and the Tg of the urethane resin (CII) is in the range of 0 ° C. to 100 ° C. / The difference between the Tg of the shell part in the shell structure and the Tg of the urethane resin (CII) is more preferably 40 ° C. or higher and 120 ° C. or lower. If the difference in Tg is outside the above range, sufficient film-forming properties cannot be obtained, and the coating film may have poor corrosion resistance and chemical resistance.

[Ratio of zirconium compound (A) / chelating agent (B) / organic resin (C)]
The molar ratio (mol ÷ mol) between the zirconium element (Zr) derived from the zirconium compound (A) contained in the surface treatment agent for galvanized steel sheet according to the present embodiment and the chelating agent (B) is (Zr) It is preferable that / (B) = 4 to 100.
Moreover, the molar ratio of the carboxyl group (c1) of the organic resin (C) and the chelating agent (B) contained in the surface treatment agent for galvanized steel sheet according to the present embodiment is (c1) / (B) = A range of 30 to 1000 is preferred.
In addition, the molar ratio of the hydroxyl group (c2) to the chelating agent (B) of the organic resin (C) contained in the surface treatment agent for galvanized steel sheet according to the present embodiment is (c2) / (B) = 30 to A range of 1000 is preferable.

If these ratios are out of the above ranges, sufficient film-forming properties cannot be obtained, and the coating film may have poor corrosion resistance, chemical resistance, weather resistance, and coating adhesion.
For example, when the zirconium compound (A) is excessive with respect to the chelating agent (B), the stability of the zirconium compound (A) is lowered and the stability of the treatment agent cannot be obtained, but also has a specific structure. The coating adhesiveness expressed as the effect of using the chelating agent (B) having a sufficient function does not function. On the contrary, if the chelating agent (B) is excessive, the chelating agent contributing to the stabilization of the zirconium compound (A) becomes excessive, so that the chelate effect is saturated and the film structure becomes easy to attract water. Due to the decrease, the corrosion resistance, alkali resistance, and boiling water resistance cannot be fully exhibited.

<Vanadium compound (D)>
By further adding the vanadium compound (D) according to the present embodiment to the surface treatment agent for a zinc-based plated steel sheet, a film with improved corrosion resistance can be formed.

Although the kind of vanadium compound (D) used in this embodiment is not particularly limited, for example, metavanadate and its salt, vanadium oxide, vanadium trichloride, vanadium oxytrichloride, vanadium acetylacetonate, vanadium oxyacetylacetonate, Vanadium sulfate, vanadium sulfate, vanadium nitrate, vanadium phosphate, vanadium acetate, vanadium biphosphate, vanadium alkoxide, vanadium oxyalkoxide, and the like are preferably used.
Among these, it is preferable to use a compound in which the oxidation number of vanadium is pentavalent. Specifically, metavanadate and its salt, vanadium oxide, vanadium oxytrichloride, vanadium alkoxide, and vanadium oxyalkoxide are preferable.

In this embodiment, the surface treatment agent for galvanized steel sheet contains the vanadium compound (D) in the range of 20 to 300 ppm by mass in terms of V element with respect to the mass of the surface treatment agent for galvanized steel sheet. It is preferable. When the surface treatment agent contains the vanadium compound (D) in the range of 20 to 300 ppm by mass, the corrosion resistance can be improved.

<Titanium compound (E)>
The performance of the coating film can be further improved by further including the titanium compound (E) according to the present embodiment in the surface treatment agent for galvanized steel sheet.

The type of the titanium compound (E) used in this embodiment is not particularly limited, but titanium (IV) (titania), titanium nitrate, zirconyl titanium sulfate (III), titanium sulfate, titanium fluoride (III), fluorine Titanium (IV) fluoride, hexafluorotitanic acid (H ₂ TiF ₆ ), ammonium hexafluorotitanate, tetraisopropyl titanate, tetra n-butyl titanate, tetraoctyl titanate, titanium acetylacetonate, titanium octylene glycolate, titanium lactate , Titanium lactate ethyl ester, titanium triethanolaminate, titanium tetraisopropoxide, titanium tetranormal butoxide, titanium tetra-2-ethylhexoxide, titanium diisopropoxybis (acetylacetonate), Titanium tetraacetylacetonate, titanium dioctyloxybis (octylene glycolate), titanium diisopropoxy (ethyl acetoacetate), titanium diisopropoxybis (triethanolaminate), titanium laurate, titanium lactate ammonium salt, di Examples thereof include isopropoxytitanium bisacetone and titanium acetylacetonate. These may be anhydrides or hydrates. These compounds may be used alone or in combination of two or more.

In the present embodiment, the surface treatment agent for galvanized steel sheet contains the titanium compound (E) in a range of 50 to 1000 ppm by mass in terms of Ti with respect to the mass of the surface treatment agent for galvanized steel sheet. It is preferable. If the titanium compound (E) is less than 50 mass ppm, the amount of titanium contained in the film is not sufficient, and it is difficult to form a barrier film due to the bond of Ti—O—Ti, so the alkali resistance and corrosion resistance are reduced. If the titanium compound (E) exceeds 1000 ppm by mass, the corrosion resistance can be sufficiently exhibited, but the stability of the treatment liquid is lowered.

<Silane coupling agent (F)>
The silane coupling agent (F) according to the present embodiment plays a role as a crosslinking agent between the organic resins (C) and exhibits a binder effect between the galvanized steel sheet and the coating film, thereby improving the adhesion of the coating film. It has the function of improving and improving the corrosion resistance.

The type of the silane coupling agent (F) used in the present embodiment is not particularly limited. For example, vinyl methoxy silane, vinyl trimethoxy silane, vinyl ethoxy silane, vinyl triethoxy silane, 3-aminopropyl trimethoxy silane, 3 -Aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, N- (1,3-dimethylbutylidene) -3- (tri Ethoxysilyl) -1-propanamine, N, N′-bis [3- (trimethoxysilyl) propyl] ethylenediamine, N- (β-aminoethyl) -γ-aminopropylmethyldimethoxysilane, N- (β-amino Ethyl) -γ-aminopropyltrime Xysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, N- [ 2- (Vinylbenzylamino) ethyl] -3-aminopropyltrimethoxysilane and the like are preferably used.

In addition, these silane coupling agents (F) may be used individually by 1 type, or may use 2 or more types together. Moreover, you may use the hydrolysis condensate of these silane coupling agents, or the mixture of a silane coupling agent and its hydrolysis condensate.

In this embodiment, the surface treating agent for galvanized steel sheet is based on the solid content mass of the organic resin (C) and the silane coupling agent (F) is based on the solid content mass of the organic resin particles (C). It is preferably contained in the range of 0.5 to 5% by mass. When the surface treatment agent contains the silane coupling agent (F) in the range of 0.5 to 5% by mass, a sufficient film-forming property can be obtained, and a coating film excellent in corrosion resistance and chemical resistance can be formed.

<Silicon oxide (G)>
By further including the silicon oxide (G) according to the present embodiment in the surface treatment agent for galvanized steel sheet, the performance of the coating film can be further improved.

The shape of the silicon oxide (G) used in the present invention is not particularly limited, but is preferably in the form of particles, the primary particles have a number average particle diameter of 5 to 50 nm, more preferably 5 to 20 nm. Such silicon oxide (G) can be appropriately selected from colloidal silica, fumed silica, and the like. Specific examples of silicon oxide (G) include Snowtex N, Snowtex C (Nissan Chemical Industries), Adelite AT-20N, AT-20A (ADEKA), Cataloid S-20L, Cataloid SA (JGC Catalyst) Kasei Co., Ltd.). These may be used alone or in combination of two or more.
In addition, the number average particle diameter of the primary particles of silicon oxide (G) can be obtained by observation with an electron microscope.
In the present embodiment, the surface treatment agent for galvanized steel sheet preferably contains silicon oxide (G) in the range of 2.0 to 4.0 mass% in terms of SiO ₂ . If silicon oxide (G) is less than 2.0 mass%, sufficient coating film performance, especially corrosion resistance and substrate adhesion cannot be obtained. Moreover, silicon oxide (G) is 4.0 mass% or less from a viewpoint of adjusting the balance with content of another component and exhibiting the effect of this invention satisfactorily.

<Other components (H)>
In addition, the surface treatment agent of the present embodiment may further contain other components (H) in a range that does not inhibit the above-described function, depending on the function to be added. For example, tannic acid or a salt thereof, phytic acid or a salt thereof, or other aqueous resin such as an epoxy resin, an ethylene acrylic copolymer, a polyester resin, a polyolefin resin, an alkyd resin, or a polycarbonate resin may be used. it can. These aqueous resins may be used alone or in combination of two or more, or may be used after copolymerization. Further, an organic solvent may be used in order to improve the film forming property and form a more uniform and smooth coating film. Further, a leveling agent, a wettability improver, or an antifoaming agent may be used.

<Zinc-based plated steel plate>
Zinc-based plated steel sheets using the surface treatment agent according to this embodiment as a temporary rust preventive are widely used as steel sheets with high corrosion resistance. Here, zinc plating and zinc alloy plating are collectively referred to as “zinc-based plating”.
The zinc-based plated steel sheet that can use the surface treatment agent of the present embodiment is not particularly limited, and examples thereof include galvanized steel sheet, zinc-nickel plated steel sheet, zinc-iron plated steel sheet, zinc-chromium plated steel sheet, zinc-aluminum. Examples thereof include zinc-based electroplating such as a plated steel plate, zinc-titanium-plated steel plate, zinc-magnesium-plated steel plate, and zinc-manganese-plated steel plate, and zinc or zinc-based alloy-plated steel plate such as hot dipped and vapor-deposited steel plate. Among them, a zinc-55 wt% aluminum alloy plated steel plate (Galbarium steel plate (registered trademark)) is preferably used because it has high corrosion resistance.

Although the manufacturing method of the surface treating agent which concerns on this embodiment is not specifically limited, For example, a zirconium compound (A) and a chelating agent (B) are mixed and stirred previously, the zirconium compound (A) is stabilized, and organic resin Zirconium compound (A) and chelating agent (B) are added to (C) while stirring, and can be obtained by diluting and preparing.

The method for applying the surface treatment agent according to the present embodiment to the zinc-based plated steel sheet is not particularly limited. For example, the method of applying the surface treatment agent to the zinc-based plated steel sheet and drying the object to be coated by heating after the application is performed. It may be. Alternatively, a method may be used in which a galvanized steel sheet is heated in advance, and then the surface treatment agent is applied and dried using residual heat.

The method for applying the surface treatment agent is not particularly limited, and can be applied by roll coating, shower coating, spraying, dipping, brush coating, or the like. In addition, although the coating method by roll coating is preferably used in a normal coil coating line, the surface treatment agent according to the present embodiment is excellent in film forming property even when coil coating is considered.
The conditions for heating and drying the surface treatment agent are such that the highest material temperature (hereinafter referred to as PMT) is preferably 20 to 250 ° C., more preferably 50 to 220 ° C. When the heating temperature is 50 ° C. or higher, the moisture evaporation rate is high and sufficient film forming properties can be secured, so that the corrosion resistance and alkali resistance are improved. On the other hand, when PMT exceeds 250 ° C., components in the coating film formed by high temperature may be decomposed, resulting in poor adhesion and corrosion resistance. Moreover, even if the PMT is under low temperature conditions around 20 ° C., a film having sufficiently excellent performance can be formed by evaporating and drying the moisture.
The amount of the surface treatment agent applied is preferably such that the thickness of the coating film is about 0.5 to 3.0 μm. If the film thickness is too thin relative to the above range, the corrosion resistance will be insufficient. On the other hand, if the film thickness is too thick, the workability and adhesion are lowered and it is uneconomical.

As described above, the surface treatment agent for a zinc-based plated steel sheet according to this embodiment includes a zirconium compound (A), a chelating agent (B) having one or more hydroxyl groups in one molecule, and a carboxyl group (c1). Zirconium compound (A) is contained in the surface treatment agent for zinc-based plated steel sheet in the range of 200 to 10000 mass ppm in terms of Zr element, and is derived from zirconium compound (A). The molar ratio of the elemental zirconium (Zr) to the chelating agent (B) is in the range of (Zr) / (B) = 4 to 100, and the acid value of the organic resin (C) is in the range of 10 to 30 mgKOH / g The molar ratio of carboxyl group (c1) to chelating agent (B) is in the range of (c1) / (B) = 30 to 1000. Thereby, a metal surface treatment composition is excellent in film forming property, and can form the coating film excellent in corrosion resistance, chemical resistance, weather resistance, and paintability on the zinc-based plated steel sheet.

The organic resin (C) has a hydroxyl group (c2), the hydroxyl value of the organic resin (C) is in the range of 10 to 30 mgKOH / g, and the molar ratio between the hydroxyl group (c2) and the chelating agent (B). The ratio is in the range of (c2) / (B) = 30 to 1000. Since the zirconium compound (A) is stabilized by an organic resin containing a hydroxyl group or a chelating agent, the coating adhesiveness is exhibited by the chelating agent (B), and further an organic resin (C) having a hydroxyl group is used. This will improve the paint adhesion. Moreover, compatibility with a chelating agent, an organic resin, and a top coat film can also be improved by using the organic resin (C) which has a hydroxyl group. The effect of the organic resin (C) having a hydroxyl group is sufficiently exhibited when the molar ratio of the hydroxyl group (c2) to the chelating agent (B) is in the range of (c2) / (B) = 30 to 1000. it can. Thereby, especially the metal surface treatment composition can form the coating film excellent in coating adhesiveness.

Further, the organic resin (C) is at least one selected from the group consisting of an acrylic resin, a urethane resin, a polyolefin resin, and a vinyl resin. Thereby, the metal surface treatment composition is excellent in film forming property, and can form a coating film excellent in barrier properties, uniformity, and low temperature drying properties. Moreover, a continuous film can be formed with a thin film.

The surface treatment agent for galvanized steel sheet contains the vanadium compound (D) in the range of 20 to 300 ppm by mass in terms of V element. The surface treating agent for galvanized steel sheet contains the titanium compound (E) in the range of 50 to 1000 ppm by mass in terms of Ti element. The surface treatment agent for galvanized steel sheet contains the silane coupling agent (F) in the range of 0.5 to 5% by mass with respect to the solid content mass of the organic resin (C). The surface treating agent for galvanized steel sheet contains silicon oxide (G) in the range of 2.0 to 4.0% by mass in terms of SiO ₂ . Thereby, especially the metal surface treatment composition can form the coating film excellent in corrosion resistance.

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

<Surface treatment agent production example, coating example>
[Examples 1 to 26]
The zirconium compound (A) and the chelating agent (B) are mixed and stirred in advance to stabilize the zirconium compound (A), and the zirconium compound (A) and the chelating agent (B) are added to the organic resin (C). The mixture was added with stirring, diluted and prepared to obtain the surface treating agent shown in Table 1.
Regarding the resin (C), in Examples 1 to 20, a single resin was used. On the other hand, in Examples 21 to 26, those obtained by mixing a plurality of resins in combinations and ratios of types shown in Table 1 were used.

Each material in Table 1 was the following material.
[Zirconium compound (A)]
A1: Zircosol AC-7
A2: Zr nitrate
A3: Zircon ammon fluoride

[Chelating agent (B)]
B1: HEDP
B2: TEA
B3: Ammon citrate B4: Na gluconate

[Organic resin (C)]
C1: An acrylic acid having an acid value of 20 mgKOH / g and a hydroxyl value of 20 mgKOH / g C2: An acrylic having an acid value of 10 mgKOH / g and a hydroxyl value of 20 mgKOH / g C3: An acid value of 30 mgKOH / g Acrylic having a hydroxyl value of 20 mgKOH / g C4: An acrylic acid having an acid value of 20 mgKOH / g and no hydroxyl group (c2) C5: An acrylic having an acid value of 20 mgKOH / g and a hydroxyl value of 30 mgKOH / g C6 : An acrylic acid having an acid value of 20 mgKOH / g and a hydroxyl value of 10 mgKOH / g C7: An acrylic having an acid value of 10 mgKOH / g and a hydroxyl value of 5 mgKOH / g C8: An acid value of 20 mgKOH / g Urethane having no hydroxyl group (c2) C9: Acid value is 25 mgKOH / g, Hydroxide (C2) an olefin having no C10: an acid value of 20 mgKOH / g, the vinyl acetate having no hydroxyl group (c2)

[Examples 27 to 54]
The zirconium compound (A) and the chelating agent (B) were mixed and stirred in advance to stabilize the zirconium compound (A).
The organic resin (C) was stirred, and in Examples 27 to 31, 47 to 50, 53, and 54, the vanadium compound (D) was added to the organic resin (C) and stirred.
In Examples 32-36 and 48-50, the titanium compound (E) was further added and stirred.
In Examples 38 to 41, 49, and 50, the silane coupling agent (F) was further added and stirred.
In Examples 42 to 46 and 50 to 52, silicon oxide (G) was further added and stirred.
A zirconium compound (A) and a chelating agent (B) were further added to the organic resin (C), and the mixture was stirred, diluted and prepared to obtain the surface treating agent described in Table 2.

Each material newly shown in Table 2 was the following material.
[Vanadium compound (D)]
D1: Ammon metavanadate (manufactured by Shinsei Chemical Industry Co., Ltd.)
D2: Sodium metavanadate (manufactured by Shinsei Chemical Industry Co., Ltd.)
D3: Vanadyl sulfate (manufactured by Shinsei Chemical Industry Co., Ltd.)
D4: vanadyl acetylacetonate (manufactured by Shinsei Chemical Industry Co., Ltd.)

[Titanium compound (E)]
E1: Titanium ammonium fluoride (Morita Chemical Industries, Ltd.)
E2: TC400 (Matsumoto Fine Chemical Co., Ltd.)
E3: T-50 (Nippon Soda Co., Ltd.)

[Silane coupling agent (F)]
F1: 3-Glycidoxyuropyrtrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.)
F2: 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane (manufactured by Shinsei Chemical Industry Co., Ltd.)
F3: N-2- (aminoethyl) -3-aminopropyltrimethylsilane (manufactured by Shinsei Chemical Industry Co., Ltd.)
F4: 3-aminopropyltrimethylsilane (manufactured by Shinsei Chemical Industry Co., Ltd.)

[Silicon oxide (G)]
G1: ST-N (Nissan Chemical Co., Ltd.)
G2: AT-20A (made by ADEKA Corporation)
G3: ST-C (manufactured by Nissan Chemical Co., Ltd.)

[Comparative Examples 1 to 16]
In Comparative Example 1, the zirconium compound (A) was added to the organic resin (C), stirred, diluted and prepared to obtain the surface treating agent described in Table 3.
In Comparative Examples 2, 3, 5 to 7, and 9 to 12, the zirconium compound (A) and the chelating agent (B) were mixed and stirred in advance to stabilize the zirconium compound (A). Zirconium compound (A) and chelating agent (B) were added to organic resin (C), stirred, diluted and prepared to obtain the surface treating agent described in Table 3.
In Comparative Examples 4 and 13 to 16, the chelating agent (B) was added to the organic resin (C), stirred, diluted and prepared to obtain the surface treating agent described in Table 3.
In Comparative Example 8, the zirconium compound (A) and the chelating agent (B) were stirred, diluted and prepared to obtain the surface treating agent described in Table 3.

Each material newly shown in Table 3 was the following material.

[Chelating agent (B)]
B5: EDTA
Note that B5 (EDTA) does not have one or more hydroxyl groups in one molecule.

[Organic resin (C)]
C11: an acrylic acid having an acid value of 5 mgKOH / g and a hydroxyl value of 20 mgKOH / g C12: an acrylic having an acid value of 40 mgKOH / g and a hydroxyl value of 20 mgKOH / g

<Storage stability>
The surface treatment agent for each zinc-based plated steel sheet of each Example and Comparative Example was allowed to stand in a constant temperature bath at 40 ° C., and the liquid state when stored for up to 3 months was evaluated according to the following criteria. The results are shown in Table 4.
1: No precipitate or thickening occurs in the treatment agent after 3 months at 40 ° C 2: 40 ° C No precipitation or thickening occurs in the treatment agent after 1 month 3: 40 ° C Sedimentation, thickening, etc. occur in the treatment agent for 1 week 4: Gelation occurs in the treatment agent within 40 minutes at 40 ° C. As shown in Table 4, in all the surface treatment agents of all examples, more than 2. High storage stability satisfying high evaluation criteria (1 or 2) was confirmed.

Using the surface treating agents described in Tables 1 to 3, test plates for each evaluation test were prepared by the following method.
Each steel material listed in Tables 1 to 3 was degreased by spray treatment at 60 ° C. for 2 minutes using a commercially available alkaline degreasing agent (manufactured by Nippon Paint Co., Ltd., “Surf Cleaner 53S”). The surface treatment agent of the comparative example was applied with a bar coater so that the film thickness after drying was 1 to 2 μm. Then, it dried at the raw material highest achieved temperature 80 degreeC, and obtained the test plate.
The steel materials listed in Tables 1 to 3 were as follows.
GL: 55% molten aluminum / galvanized steel sheet (Galbarium steel sheet (registered trademark))
GI: Galvanized steel sheet EG: Electrogalvanized steel sheet GF: Molten 5% aluminum / zinc alloy plated steel sheet ZL: Electrical Zn-10% Ni alloy plated steel sheet

<Flat surface corrosion resistance>
The edge and back surface of the test plate were tape-sealed, and a salt spray test SST (JIS-Z-2371) was performed. The occurrence of white rust after 240 hours was observed and evaluated according to the following criteria. The results are shown in Table 4.
1: No white rust generation 2: White rust generation area is less than 10% 3: White rust generation area is 10% or more and less than 30% 4: White rust generation area is 30% or more All implementation as shown in Table 4 In the example test plate, high planar portion corrosion resistance satisfying an evaluation criterion (1 or 2) higher than 2 was confirmed.

<Corrosion resistance after alkaline degreasing>
The test plate was immersed in a 2% aqueous solution (pH 12.5) at 60 ° C. with an alkaline degreasing agent (Surf Cleaner 155, Nippon Paint Co., Ltd.) for 2 minutes with stirring, and then the edges and back of the test plate were tape sealed and sprayed with salt water A test (JIS-Z-2371) was conducted. The occurrence of white rust after 96 hours was observed and evaluated according to the following criteria. The results are shown in Table 4.
1: No white rust generation 2: White rust generation area is less than 10% 3: White rust generation area is 10% or more and less than 30% 4: White rust generation area is 30% or more All implementation as shown in Table 4 High corrosion resistance after alkaline degreasing satisfying an evaluation standard (1 or 2) higher than 2 was confirmed in the test plate of the example.

<Corrosion resistance of processed parts>
The test plate was processed by extruding 7 mm with an elixir tester, the edges and back of the test plate were tape-sealed, and a salt spray test SST (JIS-Z-2371) was performed. After 120 hours, the occurrence of white rust was observed and evaluated according to the following criteria. The results are shown in Table 4.
1: No white rust generation 2: White rust generation area is less than 10% 3: White rust generation area is 10% or more and less than 30% 4: White rust generation area is 30% or more All implementation as shown in Table 4 In the test plate of the example, high processed part corrosion resistance satisfying an evaluation criterion (1 or 2) higher than 2 was confirmed.

<Alkali resistance>
The edge and back surface of the test plate were tape-sealed, and the appearance discoloration area and the color difference change before and after the test were immersed in a 20% NaOH solution at room temperature for 2 minutes were observed and evaluated according to the following criteria. The results are shown in Table 4.
1: No discoloration (ΔE (color difference) <2.0)
2: Discolored area is less than 25% (ΔE <2.0)
3: Discolored area of 25% or more and less than 50% (2.0 ≦ ΔE <3.0)
4: Full color change (ΔE ≧ 3.0)
As shown in Table 4, high alkali resistance satisfying the evaluation criteria (1 or 2) higher than 2 was confirmed in the test plates of all Examples.

<Base material adhesion>
The test plate was extruded 8 mm with an elixir tester, and then a cellophane tape (manufactured by Nichiban Co., Ltd.) was applied to the extruded portion and forcedly peeled off. The test plate was immersed in a methyl violet staining solution, the state of the film was observed and evaluated according to the following criteria. The results are shown in Table 4.
1: Almost no peeling 2: Peeling area is less than 10% 3: Peeling area is 10% or more and less than 25% 4: Peeling area is 25% or more As shown in Table 4, in all the test plates of Example 2, Also, high substrate adhesion satisfying the high evaluation criteria (1 or 2) was confirmed.

<Boiling water resistance>
The edge and back surface of the test plate were tape-sealed and the appearance discoloration area after immersion for 1 hour in boiling water and the color difference change before and after the test were observed and evaluated according to the following criteria. The results are shown in Table 4.
1: No color change on the entire surface (ΔE <1.0)
2: Discolored area is less than 25% (ΔE <1.0)
3: Discolored area of 25% or more and less than 50% (1.0 ≦ ΔE <3.0)
4: The entire surface is discolored (ΔE ≧ 3.0)
As shown in Table 4, high boiling water resistance satisfying the evaluation criteria (1 or 2) higher than 2 was confirmed in the test plates of all Examples.

<Coating adhesion>
A melamine alkyd paint (Organeo White, manufactured by Nippon Paint Co., Ltd.) was applied to the test plate surface with a bar coater so as to have a dry film thickness of 20 μm, and baked at 130 ° C. for 15 minutes to prepare a coated plate. Next, immerse the coating plate in boiling water for 30 minutes, leave it for 24 hours, extrude the coating plate 7 mm with an elixir tester, apply cellophane tape (manufactured by Nichiban Co., Ltd.) to the extruded part, and forcibly peel it off The film state was evaluated according to the following evaluation criteria. The results are shown in Table 4.
1: Almost no peeling 2: Peeling area is less than 10% 3: Peeling area is 10% or more and less than 25% 4: Peeling area is 25% or more As shown in Table 4, in all the test plates of Examples, In addition, high paint adhesion satisfying a high evaluation standard (1 or 2) was confirmed.

<Water resistance>
Tap water was dropped on the treated steel plate coated with the surface treatment agent and dried, and after 15 minutes, the water droplets were removed. Then, the water droplet traces on the treated steel plate surface were visually observed before and after the test and evaluated according to the following criteria. The results are shown in Table 4.
1: Traces of water droplets could not be confirmed at all, and ΔE <1.0
2: Some traces of water droplets can be confirmed, but ΔE <1.0
3: Some traces of water droplets can be confirmed, ΔE> 1.0
4: Traces of water droplets can be clearly confirmed, ΔE> 3.0
As shown in Table 4, high water resistance satisfying the evaluation criteria (1 or 2) higher than 2 was confirmed in the test plates of all Examples.

The surface treatment agents of Examples 1 to 3 differ in the amount of the zirconium compound (A) in the surface treatment agent in the range of 200 to 10000 mass ppm. It was confirmed that

Further, the surface treatment agents of Examples 4 to 6 differ in the molar ratio (Zr) / (B) between the zirconium element (Zr) and the chelating agent (B) in the surface treatment agent in the range of 4 to 100. Within this range, it was confirmed that high evaluation criteria were satisfied in any evaluation.

Further, the surface treating agents of Examples 7 to 9 differ in the molar ratio (c1) / (B) of the carboxyl group (c1) to the chelating agent (B) in the range of 30 to 1000. In any evaluation, it was confirmed that the high evaluation criteria were satisfied.

Further, the surface treatment agents of Examples 10 to 26 have different acid values of the organic resin (C) in the range of 10 to 30 mgKOH / g, but within this range, the high evaluation criteria are satisfied in any evaluation. Was confirmed.

The surface treating agents of Examples 27 to 54 contain a predetermined amount of at least one of the vanadium compound (D), the titanium compound (E), the silane coupling agent (F), and the silicon oxide (G). As for the surface treatment agent, it was confirmed that high evaluation criteria were satisfied in any evaluation.

Although details are omitted, it was confirmed that the test plates of each example satisfied higher evaluation standards than the test plates of the comparative examples. Based on the above results, the surface treatment agent for galvanized steel sheet according to this embodiment includes the content, ratio, organic resin (C) of the zirconium compound (A), the chelating agent (B) and the organic resin (C). It was shown that adjusting the acid value and the like not only improved the storage stability but also improved the adhesion of the top coat and the boiling water blackening.

Claims (7)

1. A surface treatment agent for galvanized steel sheet,
   A zirconium compound (A), a chelating agent (B) having one or more hydroxyl groups in one molecule, and an organic resin (C) having a carboxyl group (c1),
   The zirconium compound (A) is contained in the range of 200 to 10000 mass ppm in the surface treatment agent for galvanized steel sheet in terms of Zr element,
   The molar ratio of the zirconium element (Zr) derived from the zirconium compound (A) and the chelating agent (B) is in the range of (Zr) / (B) = 4 to 100,
   The acid value of the organic resin (C) is in the range of 10 to 30 mgKOH / g,
   A surface treating agent for a zinc-based plated steel sheet, wherein the molar ratio of the carboxyl group (c1) to the chelating agent (B) is in the range of (c1) / (B) = 30 to 1000.
2. The organic resin (C) has a hydroxyl group (c2),
   The hydroxyl value of the organic resin (C) is in the range of 10 to 30 mgKOH / g,
   The surface treating agent for galvanized steel sheet according to claim 1, wherein the molar ratio of the hydroxyl group (c2) to the chelating agent (B) is in the range of (c2) / (B) = 30 to 1000.
3. The surface treatment agent for galvanized steel sheets according to claim 1 or 2, wherein the organic resin (C) is at least one selected from the group consisting of acrylic resins, urethane resins, polyolefin resins and vinyl resins.
4. The surface treating agent for galvanized steel sheet according to any one of claims 1 to 3, comprising a vanadium compound (D) in a range of 20 to 300 ppm by mass in terms of V element.
5. The surface treating agent for galvanized steel sheets according to any one of claims 1 to 4, comprising a titanium compound (E) in a range of 50 to 1000 ppm by mass in terms of Ti element.
6. The galvanized steel sheet according to any one of claims 1 to 5, wherein the silane coupling agent (F) is contained in a range of 0.5 to 5 mass% with respect to the solid mass of the organic resin (C). Surface treatment agent.
7. Zinc-plated steel sheet for surface treatment agent according to any one of claims 1 to 6 containing silicon oxide (G) in the range of 2.0 to 4.0 mass% in terms of SiO _2.