JP2001240978A - Surface treatment method for zinc system plated steel products and aqueous surface treating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-polluting aqueous surface treating composition by which zinc system plated steel having excellent corrosion resistance may be obtained and which does not contain hazardous heavy metals, such as lead, chromium and cadmium. SOLUTION: This aqueous surface treating composition contains an inorganic rust preventive pigment (B) which contains none of the lead, chromium and cadmium at 5 to 80 pts.wt. by solid content and a hydrazine derivative (C) at 0.5 to 20 pts.wt. by solid content per 100 pts.wt. solid content of a copolymer resin dispersion (A) of α-olefin and α,β-ethylenic unsaturated carboxylic acid and the surface treatment method for galvanized steel characterized in that the aqueous surface treating composition described above is applied to the surfaces of the zinc system plated steel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an aqueous surface treatment composition, particularly to a surface treatment composition suitable for surface treatment of galvanized steel, and a method for surface treatment of galvanized steel using the composition.

[0002]

[Prior art and its problems] In recent years, surface treatment materials with particularly excellent corrosion resistance have been strongly demanded for electrogalvanizing used for applications such as automobile parts, light electrical appliances, and general-purpose equipment. It tends to be stronger. Conventionally, zinc plating is generally used as metal plating for improving the corrosion resistance of steel materials. In order to further improve the corrosion resistance, Zn-Ni, Zn-Ni-C
Various alloyed zinc platings such as o, Zn-Fe, Zn-Al are also applied. These zinc-based coatings suppress the corrosion of steel by sacrificial corrosion protection of zinc.In order to achieve high corrosion resistance, the amount of zinc must be increased, but workability, weldability, and productivity Problems such as reduction occur.

[0003] Further, after zinc-based plating, a chemical conversion treatment such as a chromate treatment is performed to enhance corrosion resistance and paint base. By subjecting the zinc-based plating surface to chromate treatment, a passivation film can be formed and the dissolution of zinc can be suppressed, so that the corrosion resistance can be greatly improved.However, when this is used outdoors, White rust and red rust easily occur due to the effects of water, salt water in the coastal region, acid rain, factory smoke, exhaust gas in urban areas, etc., which are sufficient to satisfy the demands of customers. Not really.

[0004] Further, after a chromate treatment for the purpose of improving the corrosion resistance of the galvanized steel material, a paint mainly composed of a water-soluble resin of an ordinary temperature type or an emulsion type resin is applied and dried at room temperature or low temperature. A method of forming a film having a thickness of 20 to 40 μm by applying a baking paint (for example, acrylic melamine resin, alkyd melamine resin, epoxy resin, etc.) and drying at a high temperature of 120 ° C. or more is performed. . However, cold-drying paints are inferior in corrosion resistance and water resistance,
On the other hand, in the case of baking paint, high-temperature treatment is required when forming a film, and if such high-temperature treatment is performed, the chromate film will crack, and hexavalent chromium will be insolubilized by high temperature, so chromate treatment Problems such as a decrease in the self-healing action inherent to the film and a significant decrease in corrosion resistance occur.

[0005] In addition, a chromium-based rust-preventive pigment (for example, strontium chromate, barium chromate, lead chromate, basic zinc chromate, etc.) is added to a paint mainly composed of a room temperature drying type resin or a baking drying type resin. Attempts have been made to improve the corrosion resistance by using a paint contained therein or a surface treatment agent obtained by combining a water-soluble resin and a water-soluble chromium compound. Although these methods are thought to be effective in improving corrosion resistance, there are many problems in terms of safety and health and environmental protection, such as adverse effects on human bodies due to harmful heavy metals and water pollution.

[0006]

Means for Solving the Problems The present inventors can solve the above-mentioned problems and can obtain a galvanized steel material having excellent corrosion resistance, and furthermore, have no pollution by using no harmful heavy metals such as lead, chromium and cadmium. As a result of intensive studies for the purpose of providing a suitable surface treatment composition, the present invention has been completed.

[0007] Thus, according to the present invention, lead, chromium and 100 parts by weight of the solid content of the copolymer resin dispersion (A) of α-olefin and α, β-ethylenically unsaturated carboxylic acid are used. The inorganic rust preventive pigment (B), which does not contain any element of cadmium (B), has a solid content of 5 to 80 parts by weight, and the hydrazine derivative (C) has a solid content of 0.5 to 80 parts by weight.
An aqueous surface treatment composition containing 20 parts by weight is provided.

Further, according to the present invention, there is provided a surface treatment method for a galvanized steel material, which comprises applying the aqueous surface treatment composition to the surface of a galvanized steel material.
Hereinafter, the present invention will be described in detail.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the aqueous surface treatment composition of the present invention will be described in detail. The aqueous surface treatment composition of the present invention is an aqueous surface treatment composition containing the following copolymer resin dispersion (A), inorganic rust preventive pigment (B) and hydrazine derivative (C) as essential components.

Copolymer Resin Dispersion (A) The copolymer resin dispersion as the component (A) in the composition of the present invention is a copolymer of an α-olefin and an α, β-ethylenically unsaturated carboxylic acid. This is a resin dispersion. Examples of the α-olefin include ethylene,
Examples thereof include propylene, butylene, and isobutylene. Examples of the α, β-ethylenically unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid and the like. The amount of α, β-ethylenically unsaturated carboxylic acid in the copolymer resin may be an amount of the carboxyl group necessary for dispersing in water and not deteriorating the water resistance, and usually, It is suitable that the amount is 5 to 40% by weight, preferably 5 to 20% by weight, based on the amount of the monomer before constituting the copolymer resin. The copolymer is dispersed in water by dispersing the carboxylic acid group introduced into the resin skeleton into an amine compound (for example, aliphatic amines represented by monoethylamine, alkanolamines represented by diethanolamine, morpholine, pyridine and the like). Of cyclic amines), ammonia water and the like and dispersing in an aqueous medium.

The copolymer resin dispersion (A) may be an ionomer (ionic copolymer) in which a carboxyl group in the resin is ion-bonded with a metal ion, for example, Na ion.

Inorganic rust preventive pigment (B) The inorganic rust preventive pigment which is the component (B) in the composition of the present invention is an inorganic rust preventive pigment containing no harmful heavy metals such as lead, chromium and cadmium, Specific examples include zinc diphosphate, aluminum dihydrogen tripolyphosphate treated with a calcium compound or a magnesium compound; zinc phosphate,
Phosphate-based rust preventive pigments such as magnesium phosphate, calcium phosphate, calcium phosphomolybdate, aluminum phosphomolybdate; zinc phosphite, zinc phosphite, calcium phosphite, and phosphorous acid modified with a calcium compound or a strontium compound Phosphite-based rust-preventive pigments such as aluminum; calcium ion-exchanged amorphous silica can be suitably used. The compounding amount of the inorganic rust preventive pigment (B) is in the range of 5 to 80 parts by weight, preferably 10 to 50 parts by weight based on 100 parts by weight of the solid content of the copolymer resin dispersion (A). Is appropriate.

Hydrazine Derivative (C) The hydrazine derivative which is the component (C) in the composition of the present invention is hydrazine hydrate; hydrazine salt compounds such as hydrazine phosphate, hydrazine carbonate, hydrazine hydrochloride, hydrazine sulfate and hydrazine hydrobromide. Carbohydrazide, propionic hydrazide, salicylic hydrazide,
Hydrazide compounds such as adipic hydrazide and sebacic hydrazide; pyrazole compounds such as pyrazole, 3-amino-5-methylpyrazole and 3,5-dimethylpyrazole; 1,2,4-triazole and 3-amino-
1,2,4-triazole, 4-amino-1,2,4-
Triazoles such as triazole, 3-mercapto-1,2,4-triazole, 3-mercapto-5-amino-1,2,4-triazole, benzotriazole and 1-hydroxybenzotriazole; 5-phenyl-
1,2,3,4-tetrazole, 5-mercapto-1-
Tetrazole compounds such as phenyl-1,2,3,4-tetrazole; 5-amino-2-mercapto-1,3;
4-thiadiazole, 2,5-dimercapto-1,3,
Examples include thiadiazole compounds such as 4-thiadiazole; pyridazine compounds such as maleic hydrazide and 4,5-dichloro-3-pyridazone; among them, triazole compounds are preferable. Hydrazine derivative (C)
Of the copolymer resin dispersion (A)
The amount is suitably in the range of 0.5 to 20 parts by weight, preferably 2 to 10 parts by weight, based on 100 parts by weight of the solid content.

The composition of the present invention comprises the above-mentioned copolymer resin dispersion (A), inorganic rust preventive pigment (B) and hydrazine derivative (C) as essential components. Water-dispersible silica, water-soluble organic solvent,
Water, pigments such as extender pigments and color pigments, and the like can be contained.

The water-dispersible silica, which is optionally added to the composition of the present invention, is incorporated for the purpose of improving the adhesion of the treated coating film to the surface of the zinc-based plated steel material, and is referred to as so-called silica. Colloidal silica having an average particle diameter of preferably from 7 to 100 nm, particularly preferably from 10 to 80 nm, is preferably used, and a known one usually supplied as an aqueous dispersion can be used as it is. The amount of the water-dispersible silica is 5 to 100 parts by weight of the copolymer resin.
100 parts by weight. The following knowledge has been obtained regarding the particle size and the proper blending amount of the water-dispersible silica. For those having an average particle size of 10 to 30 nm, the appropriate compounding amount is 5 to 50 parts by weight, and the average particle size is 30 to 80 parts by weight.
With respect to those having a thickness of nm, a blending amount of 50 to 80 parts by weight is preferable.

The water-soluble organic solvent to be added as required in the composition of the present invention includes ethanol, n-propanol, isopropanol, n-butanol, ethylene glycol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol. Alcohol organic solvents such as monoethyl ether and propylene glycol monotyl ether; organic solvents such as ethyl acetate, propyl acetate, and butyl acetate; and acetone; The water-soluble organic solvent is blended for various purposes such as defoaming, improvement in wettability to the object to be coated, reduction in freezing temperature, and viscosity adjustment.
The amount of the water-soluble organic solvent added is 15 in the surface treatment composition.
% By weight or less is preferable. If added in excess, the stability of the copolymer resin dispersion or the water-dispersible silica is impaired, and the viscosity may increase or agglomerate. ,Caution must be taken.

Next, the surface treatment method of the present invention will be described in detail. The surface treatment method of the present invention is characterized in that the above-mentioned aqueous surface treatment composition of the present invention is applied to the surface of a galvanized steel material.

The zinc-based plated steel to which the surface treatment method of the present invention is applied includes galvanized steel; nickel-zinc (Ni-Zn) plated, nickel-zinc-cobalt (N
i-Zn-Co) plating, zinc-aluminum (Zn-
Al) -plated, zinc-alloy-plated steel with zinc alloy plating such as iron-zinc (Fe-Zn) plating; chemical treatment such as phosphate treatment or chromate treatment on the surface of the above-mentioned galvanized steel or zinc alloy-plated steel Examples include those subjected to treatment. Among them, a zinc-based plated steel material whose surface is subjected to chromate treatment is preferable.

In the method of the present invention, the method of applying the aqueous surface treatment composition of the present invention to the surface of the galvanized steel material is not particularly limited, and examples thereof include dip coating, spray coating, brush coating, and showering. When applying a large amount of small zinc-based plated steel materials such as screw parts such as bolts and nuts, you can use a coating method such as a coat, etc. Is efficient. Drying of the applied aqueous surface treatment composition film may be performed under conditions in which the treated film is dried. However, from the viewpoint of energy saving and not deteriorating the chemical conversion treatment film, the steel material temperature is usually 100 ° C. or less, preferably 60 ° C. It is achieved by drying at １００100 ° C. for 15 seconds to 25 minutes. By drying at a relatively low temperature of 100 ° C. or less, even when the surface of the galvanized steel is chromate-treated, deterioration of the corrosion resistance of the galvanized steel can be eliminated.

According to the method of the present invention, a surface-treated galvanized steel material having a treated coating film formed from the aqueous surface treatment composition can exhibit excellent corrosion resistance. The reason for this is that the formed film is based on the copolymer resin dispersion (A) and thus has a low moisture permeability and has a barrier function against corrosion-forming substances. This is considered to be due to a synergistic effect with the insolubilizing effect on the zinc-based plating layer due to the chelating ability of the derivative. When the aqueous surface treatment composition further contains water-dispersible silica, the adhesion of the treated coating film can be improved, and the corrosion resistance can be further improved based on this.

[0021]

EXAMPLES The present invention will be described below in detail with reference to examples, but the present invention is not limited to the following examples. Hereinafter, “parts” and “%” are based on weight, respectively.

Example 1 Calcium-modified tripolyline was added to 15 parts of a mixed solvent A of ethylene glycol monobutyl ether / n-butanol = 50/50 (weight ratio) based on 100 parts of solid content of an ethylene-acrylic acid copolymer resin dispersion. 15 parts of aluminum dihydrogen oxide was mixed and dispersed in advance to 30 parts (15 parts in solid content) of a calcium-modified aluminum trihydrogen tripolyphosphate having a solid content of 50% and dispersed to a particle diameter of 10 μm or less, and 3 parts in 4 parts of the mixed solvent A. -4 parts of mercapto-1,2,4-triazole are blended to obtain a particle diameter of 10 µm.
The aqueous surface treatment composition was obtained by mixing 8 parts (4 parts by solid content) of 3-mercapto-1,2,4-triazole dispersion having a solid content of 50% which had been dispersed in advance until the dispersion reached m or less.

Examples 2 to 8 and Comparative Examples 1 to 4 Examples 1 to 4 were carried out in the same manner as in Example 1 except that the composition was as shown in Table 1 below to obtain each aqueous surface treatment composition. In each example, the rust-preventive pigment and the hydrazine derivative were used in the same amount of the mixed solvent A, respectively, and used as a dispersion having a solid content of 50% which was dispersed in advance until the particle diameter became 10 μm or less.

All of the amounts in Table 1 are expressed in terms of parts by weight of solids. (Note) in Table 1 has the following meaning. (* 1) Colloidal silica aqueous dispersion a: average particle diameter 10
Aqueous dispersion of colloidal silica having a solid content of 50 to 30 nm
%. (* 2) Colloidal silica aqueous dispersion b: average particle diameter 30
Aqueous dispersion of colloidal silica having a solid content of 50 to 80 nm
%.

[0025]

[Table 1]

[0026]

[Table 2]

Comparative Example 5 In Example 5, an aqueous resin solution containing an epoxy-modified alkyd resin and a melamine resin as a resin component instead of the ethylene-acrylic acid copolymer resin dispersion to give a solid content of 100 parts. An aqueous surface treatment composition was obtained in the same manner as in Example 5, except for using the composition.

Comparative Example 6 Zinc-treated aluminum tripolyphosphate 2 was added to 25 parts of the mixed solvent A per 100 parts of the solid content of an aqueous resin solution containing an epoxy-modified alkyd resin and a melamine resin as resin components.
5 parts of the mixture were mixed with 50 parts of a zinc-treated aluminum tripolyphosphate dispersion having a solid content of 50% (25 parts by solid content), which was previously dispersed until the particle diameter became 10 μm or less, to obtain an aqueous surface treatment composition.

Using the aqueous surface treatment compositions of Examples 1 to 8 and Comparative Examples 1 to 6, surface-treated steel sheets were prepared.

Example 9 Preparation of surface-treated steel sheet Example 9 A steel sheet having a zinc adhesion amount of 20 g / m ² (one side) obtained by subjecting a surface of a galvanized steel sheet to a chromate treatment (manufactured by Nippon Steel Corporation, trade name: “Jincoat EG- C)) on the surface of the aqueous surface treatment composition obtained in Example 1 having a dry film thickness of about 4 μm.
And dried at 80 ° C. for 20 minutes to obtain a surface-treated steel sheet.

Examples 10 to 16 and Comparative Examples 7 to 10 The same procedures as in Example 1 were carried out except that the type of the surface treatment composition used was as shown in Table 2 below. I got

Comparative Example 11 In Example 9, the aqueous surface treating composition obtained in Comparative Example 5 was used in place of the aqueous surface treating composition obtained in Example 1, and the drying conditions were 80 ° C. for 20 minutes. 140 from condition
A surface-treated steel sheet was obtained in the same manner as in Example 9, except that the conditions were changed to 30 ° C. for 30 minutes.

Comparative Example 12 In Example 9, the aqueous surface treatment composition obtained in Comparative Example 6 was used in place of the aqueous surface treatment composition obtained in Example 1, and the dried film thickness was adjusted to about 30 μm. Coating and drying were performed in the same manner as in Example 9 except that the conditions for drying at 80 ° C. for 20 minutes were changed to the conditions for 140 ° C. for 30 minutes to obtain a surface-treated steel sheet.

Each of the surface-treated steel sheets obtained in Examples 9 to 16 and Comparative Examples 7 to 12 and “Gincoat EG-C” itself as Comparative Example 13 was cut into a size of 70 × 150 mm, and the edge portion was cut. Using a steel plate sealed with a rust preventive paint as a test plate, tests of salt spray resistance and water resistance were performed based on the following test methods. The test results are shown in Table 2 below.

Test Method Salt Sprayability: A salt spray test was performed on a test plate according to the salt spray test method specified in JIS Z2371 and the test time was 2 hours.
The rust generation area ratio (%) of white rust and red rust on the test plate surface at 50 hours and 500 hours was determined.

Water resistance: After the test plate was immersed in deionized water at 40 ° C. for 240 hours, the test plate was pulled up, and the coated surface of the treated coating film was visually evaluated according to the following criteria. ：: No abnormality Δ: Swelling or rust was observed, but an abnormal occurrence area ratio was less than 30%. X: Swelling or rust was observed, and an abnormal occurrence area ratio was 30% or more.

Adhesion after water resistance test: After the test plate subjected to the water resistance test was left to stand at room temperature for 1 hour and dried, parallel cuts at 2 mm intervals reaching the substrate were vertically and horizontally eleven knives each. And put a grid of 2 × 2mm in a total of 10
0 pieces were prepared, and a cellophane adhesive tape was closely adhered to the cross-cut portion, and the cross-cut peeling state at the time of instantaneous peeling was evaluated according to the following criteria. ：: No peeling was observed. Δ: Peeling was observed, but the peeling area at the cross section was 50.
%: The peeling area of the cross section is 50% or more.

[0038]

[Table 3]

[0039]

The aqueous surface treatment composition of the present invention can form a treated coating film having excellent corrosion resistance to galvanized steel. Further, the surface treatment composition of the present invention does not contain heavy metals harmful to the human body and the environment, and is a coating anhydrous washing type composition, so there is no problem such as drainage and generation of sludge, and the treatment process is simplified. And labor saving can be achieved.

Further, the coating film from the surface treatment composition of the present invention can be dried at a low temperature of 100 ° C. or less, which is energy-saving, and is the case where the surface of a zinc-based plated steel material is treated with chromate. This also has the effect of preventing deterioration of the chromate treatment due to heat in such cases.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C23C 22/12 C23C 22/12 28/00 28/00 CZ (72) Inventor Yoshitaka Kato Higashika, Kanagawa Prefecture 4-171-1 Yawata Kansai Paint Co., Ltd. F term (reference) 4J038 CB001 CG011 GA06 HA426 HA446 JB17 JB35 KA05 KA14 MA08 NA03 PB05 PB07 PB09 PC02 4K026 AA02 AA11 BA06 BB08 4K044 AA02 BA10 BA15 BB04 BC02

Claims (8)

[Claims] 1. A copolymer resin dispersion of an α-olefin and an α, β-ethylenically unsaturated carboxylic acid (A)
5 to 80 parts by weight of an inorganic rust preventive pigment (B) containing no element of lead, chromium and cadmium and 100 parts by weight of a hydrazine derivative (C), An aqueous surface treatment composition containing 0.5 to 20 parts by weight. 2. The inorganic rust-preventive pigment (B) is aluminum dihydrogen tripolyphosphate that has not been treated or has been subjected to a surface treatment with any one of a zinc compound, a calcium compound and a magnesium compound. The surface treatment composition as described in the above. 3. The surface treatment composition according to claim 1, wherein the inorganic rust preventive pigment (B) is a phosphate or phosphite rust preventive pigment. 4. The surface treatment composition according to claim 1, wherein the inorganic rust preventive pigment (B) is a calcium ion-exchanged amorphous silica. 5. The surface treatment composition according to claim 1, wherein the hydrazine derivative (C) is a triazole compound. 6. The composition according to claim 1, wherein the water-dispersible silica is contained in an amount of 5 to 100 parts by weight based on 100 parts by weight of the solid content of the copolymer resin dispersion (A).
The surface treatment composition according to any one of claims 5 to 10. 7. The method according to claim 1, wherein the surface of the galvanized steel material is
A method for surface treating a galvanized steel material, comprising applying the aqueous surface treatment composition according to any one of claims 6 to 13. 8. The surface treatment method according to claim 7, wherein the zinc-based plated steel material has a surface subjected to chromate treatment.