JP2000256880A - Non-chromium type treated zinc system platted steel sheet and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the adhesion property of a film to a substrate steel sheet and the corrosion resistance thereof by treating a non-chromium type treated zinc system plated steel sheet with an aqueous alkaline solution, then providing the surface thereof with a film prepared by incorporating specific ratios of a thiocarbonyl group-containing compound and phosphoric acid compound into an organic resin. SOLUTION: The non-chromium type treated zinc system plated steel sheet is treated with the aqueous alkaline solution of a pH >=10 and the coating film containing water and 0.1 to 50 pts.wt. thiocarbonyl group-containing compound and 0.01 to 20 pts.wt. phosphoric acid compound (as PO4) per 100 pts.wt. aqueous resin as a solid content is formed on the substrate steel sheet. Fine grain silica is incorporated at about 0.1 to 20 parts as a solid content at need into this film. Further, about 0.1 to 20 parts vanadic acid compound is otherwise incorporated therein. The formed coating film is subjected to heating and drying, and further, about 0.1 to 5 μm film is formed, by which the non-chromium type treated zinc system plated steel sheet is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to home appliances, construction materials,
The present invention relates to a non-chromium-type treated galvanized steel sheet containing no hexavalent chromium and having excellent corrosion resistance, which is used for automobiles and the like, and a method for producing the same.

[0002]

2. Description of the Related Art A galvanized steel sheet or a zinc alloy-coated steel sheet, in an atmosphere containing salt such as seawater or a high-temperature and high-humidity atmosphere, has white rust on its surface and significantly impairs its appearance.
The rust-preventive force on the base iron surface is reduced.

In order to prevent white rust, a chromate-based rust preventive agent has conventionally been used.
No. 370 describes a resin-based treating agent comprising a water-dispersible chromium compound and water-dispersible silica in an olefin-α, β-ethylenically unsaturated carboxylic acid copolymer resin dispersion.

[0004] Such a film made of a chromate-based treating agent is recognized as having the best corrosion resistance among known treating agents. Nevertheless, the film formed by the chromate treatment contains hexavalent chromium, which is known to be a harmful element, and there is an increasing demand for a surface-treated steel sheet containing no hexavalent chromium.

[0005] Non-chromium rust preventive agents containing no harmful chromium are disclosed in JP-A-8-239776 and JP-A-8-6.
No. 7834, which uses sulfide and sulfur. However, not only sulfur but also some sulfides give off a peculiar odor, and handling of these treating agents was not always easy.

[0006] A treating agent using a triazine thiol compound containing a sulfur atom but having no odor or toxicity has also been proposed. For example, Japanese Patent Application Laid-Open No. 53-37737 discloses a water-soluble agent containing a dithiol-S-triazine derivative. An anticorrosive paint is disclosed. However, this water-soluble anticorrosive paint
It is intended to prevent corrosion of mild steel, copper, brass, etc., and is particularly prepared so that the base material is more easily adhered to copper or brass. Therefore, it is not sufficient as a rust inhibitor for metal surfaces such as zinc.

[0007] JP-A-61-223062 describes a reactive emulsion of a metal obtained by mixing a thiocarbonyl group-containing compound with an organic compound which is hardly soluble or insoluble in water. However, this emulsion also
It reacts with copper, nickel, tin, cobalt, aluminum and the like and their alloys, and is still insufficient as a rust inhibitor for metal surfaces such as zinc.

The applicants of the present application have disclosed in Japanese Patent Application No. 9-2557 a triazinethiol-containing rust-preventive coating agent which is also effective for rust-prevention of galvanized steel sheets. However, triazine thiol is an expensive compound, so it would be beneficial to have a less expensive rust inhibitor.

As a surface treatment method for zinc or zinc alloy which does not contain chromium and does not use triazine thiol,
JP-A-54-71734 and JP-A-3-2265.
No. 84 is disclosed. JP-A-54-
No. 71734 discloses a treatment method in which 2 to 6 bonded phosphate esters of myo-inositol or salts thereof are mixed with 0.5% of myo-inositol.
And at least one of titanium fluoride and zirconium fluoride is 0.5 to 30 g in terms of metal.
/ L and an aqueous solution containing 1 to 50 g / l of thiourea or a derivative thereof for surface-treating zinc or a zinc alloy. This method requires titanium fluoride or zirconium fluoride to form a passivation film as a protective layer on the zinc surface. JP-A-3-226584 discloses that one or both of Ni ²⁺ and Co ²⁺ is 0.02 g / l.
A surface treatment agent that is an aqueous solution having a pH of 5 to 10 containing the above and at least one of the compounds having ammonia and a primary amine group is used. This treatment agent requires one or both of Ni ²⁺ and Co ^{2+ to} impart coating adhesion and corrosion resistance after coating by depositing cobalt or nickel. The treating agents containing these metal ions have disadvantages such as an increase in load during wastewater treatment.

[0010]

As described above, conventional rust inhibitors containing no chromium are inferior to chromium-containing rust inhibitors in terms of corrosion resistance, and have other disadvantages as described above. Was. So, instead of chromium-containing rust inhibitor,
In addition, there has been a strong demand for the development of a new rust inhibitor that does not have the above-mentioned disadvantages.

As a new technique for satisfying such a demand, the applicant of the present application has proposed a rust-proof coating containing an aqueous resin, a thiocarbonyl group-containing compound and a phosphate ion, and optionally containing fine silica (Japanese Patent Application Laid-Open (JP-A) no. Flat 10-3626
No. 4) was developed. In addition, a rust-proof coating containing an aqueous resin, a thiocarbonyl group-containing compound, and fine-particle silica and not containing phosphate ions (Japanese Patent Application No. 10-36265).
Was developed. Furthermore, a rust-preventive coating containing an aqueous resin and a vanadate compound and optionally further containing at least one of a thiocarbonyl group-containing compound, phosphate ions and fine silica particles has been developed (Japanese Patent Application No. 10-362).
No. 67).

Since these new rust-preventive coating agents do not contain chromium and have excellent corrosion resistance, they are expected to be used as rust-preventive agents for galvanized or zinc-alloy-plated steel sheets in place of conventional chromate treatment agents. Is done. In order to make these new rust preventive coating agents more practical, it is very useful to increase the adhesion of the coating formed by the coating agent to the lower layer.

In view of the above, the present invention is to provide a non-chromium treated galvanized steel sheet provided with a film made of the above-mentioned new rust-preventive coating agent and having excellent adhesion to a lower layer of the film, and a method for producing the same. That is.

[0014]

Means for Solving the Problems When forming a rust-preventive film on a galvanized steel sheet using the above-mentioned new rust-preventive coating agent which does not contain chromium, the inventors pre-processed the plated steel sheet with an alkaline aqueous solution. It has been found that the treatment improves the adhesion of the coating (film) formed from the rust preventive coating agent to the base plated steel sheet.

Accordingly, the non-chromium-type treated galvanized steel sheet of the present invention is based on a galvanized steel sheet or a zinc alloy-coated steel sheet having a surface treated with an alkaline aqueous solution having a pH of 10 or more. Is 0.1 to 5 μm
Characterized by having a coating of one of the following (A) to (D).

(A) Coating containing 0.1 to 50 parts by weight of thiocarbonyl group-containing compound and 0.01 to 20 parts by weight of phosphoric acid compound (as PO ₄ ) based on 100 parts by weight of organic resin as solids . (B) Fine silica 1 to 5 as a solid content in the above (A).
A film containing 00 parts by weight. (C) A film containing 0.1 to 50 parts by weight of a thiocarbonyl group-containing compound and 1 to 500 parts by weight of fine silica and containing no phosphoric acid compound based on 100 parts by weight of an organic resin as a solid content. (D) at least 0.1 to 20 parts by weight of a vanadate compound based on 100 parts by weight of an organic resin as a solid content, and optionally 0.1 to 50 parts by weight of a thiocarbonyl group-containing compound and 0.01 part of a phosphoric acid compound coating containing at least one of 20 (as PO ₄₎ parts by weight and fine silica 1-500 parts by weight.

The non-chromium treated galvanized steel sheet of the present invention is obtained by treating a base steel sheet, which is a galvanized steel sheet or a zinc alloy-coated steel sheet, with an aqueous alkaline solution having a pH of 10 or more,
Then, on the base steel sheet, (1) water and 0.1 to 50 parts by weight of a thiocarbonyl group-containing compound and 0.01 to 5.0 parts by weight of a phosphoric acid compound based on 100 parts by weight of an aqueous resin as a solid content.
A coating composition containing 20 parts by weight (as PO ₄ ); (2) a coating composition containing 1 to 500 parts by weight of finely divided silica as a solid component in the above (1); (3) water; (4) a coating composition containing 0.1 to 50 parts by weight of a thiocarbonyl group-containing compound and 1 to 500 parts by weight of fine silica and containing no phosphoric acid compound based on 100 parts by weight of an aqueous resin as a solid content; water and,
0.1 to 20 parts by weight of a vanadate compound per 100 parts by weight of an aqueous resin as a solid content, and optionally 0.1 to 50 parts by weight of a thiocarbonyl group-containing compound and 0.01 to 20 parts by weight of a phosphoric acid compound (As PO ₄ ) and 1 to 500 parts by weight of finely divided silica to form a coating film by applying one of the coating agent compositions, and then heating and drying the coating film Thus, it can be manufactured by a method for manufacturing a non-chromium-type treated galvanized steel sheet, characterized in that a film having a thickness of 0.1 to 5 μm is formed.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION A steel sheet having a zinc-plated or zinc-alloy-plated surface is used as a base in the present invention. Here, zinc plating and zinc alloy plating are collectively referred to as “zinc-based plating”.

In the present invention, before forming a rust-preventive coating film on a zinc-based plated steel sheet, the zinc-based plated steel sheet is subjected to pH adjustment.
Treat with 10 or more aqueous alkaline solutions. The plating surface that has undergone this treatment is roughened, thereby improving the adhesion of the rust-preventive coating film formed later to the plating surface. Further, the treatment with the alkaline aqueous solution having a pH of 10 or more has an effect of removing the oxide film on the plating surface and thereby improving the adhesion and corrosion resistance of the rust preventive coating film to the plating surface.

Examples of the substance which can be used for the alkali treatment of the base steel sheet in the present invention include a hydroxyl compound, a phosphoric acid compound,
Examples thereof include sodium, potassium, lithium and ammonium salts of a carbonate compound, a silicic acid compound and a boric acid compound. Further, nitrate, sulfate, hydrofluoric acid and the like can be added for the purpose of increasing the etching ability of the plating surface. In addition, Co, Ni, Cu, Zn, Al are used in these alkaline aqueous solutions for the purpose of promoting detergency, further improving corrosion resistance, and suppressing blackening of the plating surface.
It is also effective to add a metal ion such as the above, and it is preferable to add it as a salt, metal salt or hydroxide of the above acid.

The treatment with an alkaline aqueous solution is generally performed by immersion. However, any other method can be used.

The conditions for treatment with an alkaline aqueous solution vary depending on the method of treatment and the substance used, and specific conditions can be determined as appropriate. As an example, general processing conditions when immersion is used are as follows.

The alkaline aqueous solution used for the treatment is p
H is in the range of 10 or more. If the pH of the aqueous solution is less than 10, the effect of improving the adhesion will be diminished.

The temperature of the aqueous solution is not particularly specified, but is preferably 5 ° C. or higher, since the time required for the treatment is longer if the temperature is lower than 5 ° C. On the other hand, the use of a high-temperature treatment liquid has disadvantages such as the necessity of a heating facility. Therefore, the aqueous solution is generally preferably at a temperature of 80 ° C. or lower.

If the time for immersing the base steel sheet in the aqueous solution is too short, a sufficient effect of improving the adhesion cannot be obtained, and if the time is too long, the plating layer may be destroyed and cause corrosion. In consideration of these, when immersing the base steel sheet, the time is preferably set in the range of 0.1 to 20 seconds. Before applying the coating agent, it is preferable to dry the treated surface by air blow, or to dry after passing through a water washing and hot water washing process. In particular, when the treated steel sheet is directly brought to the coating agent application step, an alkaline liquid is mixed into the coating agent, and the coating material is likely to gel.

Next, one of the above (A) to (D) is formed on the base steel sheet after the pretreatment with the alkaline aqueous solution.

In order to form such a film, a coating composition containing predetermined components (aqueous resin as an organic resin, an inhibitor component, and other optional components) in water is prepared, and the composition of the present invention is prepared in advance. Is applied to a galvanized steel sheet that has been treated with an alkaline aqueous solution, and the coating film is heated and dried. The coating composition may be adjusted at any concentration. Generally, the solid content (components other than water) is 1 to
A coating composition containing 80 parts by weight and 20 to 99 parts by weight of water is preferred from the viewpoint of application and subsequent heating and drying. The method of applying the coating composition is not particularly limited, and generally known application methods, for example, roll coating,
Air spray, airless spray, immersion, etc. can be adopted. By heating the coating film, the resin is cured in the case of a curable resin, and the resin is crosslinked in the case of a crosslinkable resin. Heating and drying (baking) of the coating film may be performed by a known method using a hot blast stove, an induction heating furnace, a near-infrared furnace, a direct-fired furnace, or a combination thereof. Alternatively, air drying may be performed without using the forced drying, or the metal material may be preheated, and the coating composition may be air-dried after being applied thereto. In addition, depending on the type of the aqueous resin used, the resin can be cured by energy rays such as ultraviolet rays and electron beams. The heating temperature is 50-250 ° C
Is good. If the temperature is less than 50 ° C., the evaporation rate of water is too slow to obtain a sufficient film-forming property, so that the rust-preventing ability is insufficient. 250
When the temperature exceeds ℃, the organic resin is thermally decomposed and the like, so that rust prevention and water resistance are reduced, and the appearance is yellowed. 70-200 degreeC is more preferable. Cooling after heating and drying may be performed by a known method such as water cooling, air cooling, natural cooling, or a combination thereof.

The dry film thickness of the film is preferably 0.1 μm or more. If it is less than 0.1 μm, rust prevention (corrosion resistance) is insufficient. On the other hand, when the film thickness is large, further improvement in rust prevention (corrosion resistance) is not recognized so much, which is uneconomical. Therefore, it is appropriate that the upper limit of the film thickness is 5 μm. Further, in order to provide properties such as weldability, the thickness is preferably 2 μm or less.

The method for applying the coating agent composition is not particularly limited, and generally used roll coating, air spray, airless spray, immersion and the like can be employed.

The coating (rust-proof coating) used in the present invention will be described. This coating is based on an organic resin. The organic resin is obtained by applying a composition containing an aqueous resin and other components of a film in water and then drying the composition. The term "aqueous resin" used herein includes, in addition to a water-soluble resin, a resin (a water-dispersible resin) that is insoluble in nature but can be in a finely dispersed state in water, such as an emulsion or a suspension. .

Examples of the resin which can be used as the aqueous resin in the present invention include polyolefin resins, polyurethane resins, acrylic resins, polycarbonate resins, epoxy resins, polyester resins, alkyd resins, phenol resins, and others. And the like, and a cross-linkable resin is more preferable. Particularly preferred resins are polyolefin-based resins, polyurethane-based resins, and mixed resins of both. The aqueous resin may be used as a mixture of two or more kinds.

The thiocarbonyl group-containing compound used in the film is a sulfide, and is easily adsorbed on the metal surface and has excellent oxidizing power, so that the metal surface is passivated and exhibits an antirust effect. In particular, it is considered that thiol group ions in the thiocarbonyl group-containing compound are adsorbed to active sites on the surface of the steel sheet (particularly, the surface of zinc or a zinc alloy) and exhibit a rust-preventive effect.

The thiocarbonyl group-containing compound also acts as a crosslinking accelerator for the resin film, reduces the micropores in the resin film, and has the effect of efficiently blocking harmful ions such as water and chloride ions. Is also considered to contribute to the rust prevention effect.

In the present invention, the thiocarbonyl group-containing compound is a thiocarbonyl group represented by the following formula:

[0035]

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Means a compound having Typically,

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And thiourea represented by the following formulas, for example, methylthiourea, dimethylthiourea, ethylthiourea, diethylthiourea, diphenylthiourea, thiopental, thiocarbazide, thiocarbazones, thiocyanuric acids, thiohydantoin, 2-thiouramil,
Such as thiourazole,

[0038]

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A thioamide compound represented by the formula:
Is, for example, H, CH ₃ , C ₂ H ₅ , C ₆ H ₅ , C
₈ H ₅ , C ₅ H ₃ SO, etc.), for example, thioformamide, thioacetamide, thiopropionamide,
Thiobenzamide, thiocarbostyril, thiosaccharin, etc.

[0040]

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(Wherein R represents, for example, H or CH ₃ ), for example, thioformaldehyde, thioacetaldehyde, etc.

[0042]

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Carbothioic acids represented by the formula (R in the formula:
For example, CH ₃ , C ₆ H _5, etc.), for example, thioacetic acid, thiobenzoic acid, dithioacetic acid and the like,

[0044]

Embedded image

Thiocarbonates represented by the following formulas and other compounds having the structure of the formula (1), for example, thiocoumazone,
Thiocmotiazone, thionin blue J, thiopyrone, thiopyrine, thiobenzophenone and the like are exemplified.

The content of the thiocarbonyl group-containing compound is as follows:
In the films (A) to (C), the solid content is preferably 0.1 to 50 parts by weight based on 100 parts by weight of the organic resin. When the content of the thiocarbonyl group-containing compound is less than 0.1 part by weight, the above-mentioned effects become inconspicuous, and when the content is more than 50 parts by weight, an effect corresponding to an increase in cost associated therewith cannot be expected.

On the other hand, when the thiocarbonyl group-containing compound is contained in the film (D), the content is preferably 0.1 to 50 parts by weight based on 100 parts by weight of the organic resin as a solid content. When the content of the thiocarbonyl group-containing compound is 0.
If the amount is less than 1 part by weight, the above-mentioned effects are still inconspicuous. If the amount is more than 50 parts by weight, an effect corresponding to the increase in cost cannot be expected.

The coating of the present invention contains a phosphoric acid compound together with a thiocarbonyl group-containing compound, whereby the rust-preventing effect thereof is significantly improved. As described above, the thiocarbonyl group-containing compound is adsorbed on active sites on the steel sheet surface (especially, zinc or zinc alloy surface) and exerts a rust-preventive effect, but the steel sheet surface (especially, zinc or zinc alloy surface) is not absorbed. Phosphate acts on the inactive sites to form an active surface,
Since the thiocarbonyl group-containing compound is adsorbed there,
It is considered that the rust prevention effect is exerted on the entire surface of the steel sheet (particularly, the surface of zinc or zinc alloy), and the rust prevention effect is improved. Phosphoric acid compounds also act as a cross-linking accelerator for the resin film, reducing micropores in the resin film and effectively blocking harmful ions such as water and chloride ions, which also contributes to the rust prevention effect. It is thought that.

The phosphate compound may be any compound containing a phosphate ion. For example, orthophosphate (phosphate), metaphosphate, pyrophosphate, and all or some hydrogen ions of these substances Ammonium salts, sodium salts, calcium salts,
Salts such as potassium salts and magnesium salts can be used alone or as a mixture.

The content of the phosphoric acid compound is as described in the above (A),
In the film of (B), organic resin 100
It is in the range of 0.01 to 20 parts by weight as phosphate ion with respect to parts by weight. If the phosphoric acid compound is less than 0.01 part by weight, the rust-preventing effect is not sufficiently exhibited, while if it exceeds 20 parts by weight, the rust-preventing effect is rather reduced, or the resin is gelled in the state of the coating solution. May occur.

When the phosphate compound is contained in the film (D), the content is 0.01 to 20 parts by weight as a phosphate ion per 100 parts by weight of the organic resin as a solid content. If the amount of the phosphoric acid compound is less than 0.01 part by weight, the rust-preventing effect is not sufficiently exhibited, while if it exceeds 20 parts by weight, the rust-preventing effect is rather reduced, or the resin gels in the state of the coating solution. Malfunction may occur.

The coating according to the present invention can contain finely divided silica. When the coating contains silica, its rust-preventing action (corrosion resistance) is remarkably promoted. Moreover, in addition to the corrosion resistance, the drying property at the time of film formation, the abrasion resistance and adhesion of the formed film can be improved.

In the present invention, the term "fine silica" refers to a silica having such a property that when it is dispersed in water, it can maintain a stable water-dispersed state and has no permanent sedimentation when dispersed in water. It is a generic term. The finely divided silica is not particularly limited as long as it has a small amount of impurities such as sodium and is weakly alkaline. For example, "Snowtex N", "Snowtex NS", "Snowtex NXS", "Snowtex-C" (above,
Commercially available silica gel such as "Adelite AT-20N" and "Adelite AT-20A" (all manufactured by Asahi Denka Kogyo KK), or commercially available Aerosil powdered silica can be used.

When fine silica particles are contained in the film, the content of the fine particles is 1 part per 100 parts by weight of the organic resin as a solid content.
It is preferably from 500 to 500 parts by weight. If the amount is less than 1 part by weight, the effect of addition is small, and if it exceeds 500 parts by weight, the effect of improving corrosion resistance is saturated and uneconomical, and the film becomes too hard, resulting in film cracking, peeling, etc., resulting in deterioration of corrosion resistance. There is also.

The film (C) contains silica in addition to the thiocarbonyl group-containing compound and does not contain a phosphoric acid compound. The phosphoric acid compound significantly improves the rust-preventive effect by coexisting with the thiocarbonyl group-containing compound as described above, while reducing the pot life of the coating composition for forming the upper layer coating when silica coexists. Tends to lower. Therefore, the film of (C) corresponds to a film formed from a composition excluding a phosphoric acid compound in order to extend the pot life of the coating composition.

The film (D) contains the organic resin described above, and optionally contains any combination of the thiocarbonyl group-containing compound, the phosphoric acid compound and the fine silica described above. It contains a vanadate compound as an essential component.

The vanadate compound has the same rust preventive action as the chromic compound. That is, the vanadate compound forms a passive film on the metal surface when the composition for forming a film is applied, and exhibits a rust-preventive effect. Furthermore, even when a corrosion site occurs on the steel sheet surface (particularly, zinc or zinc alloy plating surface), it is considered that vanadate ions present in the film act on the corrosion site to suppress the corrosion reaction. .

Examples of the vanadate compound include vanadates such as vanadate, ammonium vanadate, sodium vanadate, potassium vanadate, strontium vanadate, sodium hydrogen vanadate, and phosphovanadate and ammonium phosphovanadate. And the like can be used.

The amount of the vanadate compound is preferably in the range of 0.1 to 20 parts by weight based on 100 parts by weight of the organic resin as a solid content. If the amount is less than 0.1 part by weight, the rust preventing effect is not sufficient, and if it is more than 20 parts by weight, the rust preventing effect is saturated and uneconomical.

When the vanadate compound is used in combination with the fine silica particles, the vanadate compound is adsorbed on the surface of the fine silica particles, and the rust-preventive effect is synergistically exhibited. In this sense, when the fine silica particles are of the ammonium adsorption type or the aluminum oxide coating type, the silica particles are easily adsorbed and the rust prevention effect is improved, which is preferable.

In the film (D), various combinations of components other than the organic resin and the vanadate compound are possible.
Preferred examples include (1) a thiocarbonyl group-containing compound, (2) a thiocarbonyl group-containing compound and finely divided silica, and (3) a thiocarbonyl group-containing compound, finely divided silica and a phosphoric acid compound. The combination of components in the film is not limited to these.

The coating in the present invention may contain components other than the above components. For example, pigments, surfactants and the like can be mentioned. Further, a silane coupling agent or a hydrolytic condensate thereof to improve the affinity between the organic resin and the silica particles, the pigment, and further improve the adhesion between the organic resin and the zinc or iron phosphate layer or the like. Both of them may be blended. Here, the “hydrolysis condensate of a silane coupling agent” refers to an oligomer of a silane coupling agent obtained by subjecting a silane coupling agent to a raw material and hydrolyzing and polymerizing the same.

Examples of such pigments include titanium oxide (TiO ₂ ), zinc oxide (ZnO), zirconium oxide (ZrO ₂ ), calcium carbide (CaCO ₃ ), barium sulfate (BaSO ₄ ), and alumina (Al ₂ O ₃ ). O ₃ ),
Kaolin clay, carbon black, iron oxide (Fe ₂ O
₃ , various pigments such as inorganic pigments such as Fe ₃ O ₄ ) and organic pigments.

The silane coupling agent which can be used in the present invention is not particularly limited, but preferred examples include the following: vinylmethoxysilane, vinyltrimethoxysilane, vinylethoxysilane, Vinyltriethoxysilane, 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, N- (1,3-dimethylbutylidene) ) -3-
(Triethoxysilyl) -1-propanamine, N,
N′-bis [3- (trimethoxysilyl) propyl] ethylenediamine, N- (β-aminoethyl) -γ-aminopropylmethyldimethoxysilane, N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane, 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.

Particularly preferred silane coupling agents are vinyltrimethoxysilane, vinylethoxysilane, 3-
Aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, N- (1,3-dimethylbutylidene)
-3- (triethoxysilyl) -1-propanamine,
N, N'-bis [3- (trimethoxysilyl) propyl] ethylenediamine. One of these silane coupling agents may be used alone, or two or more thereof may be used in combination.

In the present invention, the silane compound is used in an amount of 0.01 to 2 parts by weight based on 100 parts by weight of the organic resin as a solid content.
It is preferably 0 parts by weight. When the addition amount of the silane compound is less than 0.01 part by weight, the effect of the addition is reduced, and the effect of improving the corrosion resistance and the adhesion of the top coat is insufficient.
If the amount is more than the weight part, the resin may gel in the state of the coating solution or cause a problem.

[0067]

Next, the present invention will be further described with reference to examples.
The evaluation method used in the following examples is as follows.

A) Film Adhesion The adhesion of the film treated in the following example was 0T-18.
After being bent at 0 °, the sheet was adhered and peeled off using Cellotape (trademark), and the degree of peeling was evaluated according to the following evaluation method. 10 points: No abnormality 9 points: Peeling rate is 10% or less 8 points: 〃 20% or less 7 points: ３０ 30% or less 6 points: ４０ 40% or less 5 points: ５０ 50% or less 4 points: ６０ 60% or less 3 points: 〃 70% or less 2 points: ８０ 80% or less 1 point: ９０ 90% or less 0 points: 大 Greater than 90%

B) Corrosion resistance (salt spray test) According to JIS Z 2371, the degree of white rust after spraying for 168 hours was evaluated out of 10 points. The evaluation was performed 120 hours later on the flat portion and the 4 mmφ180 ° bent portion. The evaluation criteria were as follows. 10 points: No abnormality 9 points: White rust generation area is 10% or less 8 points: ２０ 20% or less 7 points: ３０ 30% or less 6 points: ４０ 40% or less 5 points: ５０ 50% or less 4 points: ６０ 60% Less than 3 points: ７０ 70% or less 2 points: ８０ 80% or less 1 point: を Exceeds 80% or generates red rust

C) Adhesion of top coat paint Super rack 100 (manufactured by Nippon Paint Co., Ltd.)
(Acrylic melamine paint) was applied by a bar coat so as to have a dry film thickness of 20 μm, and was baked at a plate temperature of 150 ° C. for 20 minutes to produce a top coat adhesion test plate.
The following tests were performed on these test plates.

C1) Primary adhesion test Erichsen 7 mm: A tape was applied to a portion extruded to 7 mm with Erichsen, and the tape peelability was evaluated. The evaluation criteria were as follows. 10 points: No abnormality 9 points: Peeling rate is 10% or less 8 points: 〃 20% or less 7 points: ３０ 30% or less 6 points: ４０ 40% or less 5 points: ５０ 50% or less 4 points: ６０ 60% or less 3 points: 〃 70% or less 2 points: ８０ 80% or less 1 point: ９０ 90% or less 0 points: 大 Greater than 90%

C2) Secondary adhesion test The test plate coated with the top coat was immersed in boiling water for 30 minutes, taken out, left to stand all day and night, and subjected to the same test and evaluation as the primary adhesion test.

[Examples 1 to 12, Comparative Examples 1 and 2] Hot-dip galvanized steel sheet manufactured by the Sendzimer method (coating weight: 60 g / m ² , aluminum content in plating bath: 0.21
%) In a solution shown in Table 1 for 10 seconds, washed with running water, dried by air blow, and then coated with a chromium-free anticorrosive coating agent to a dry film thickness of 1 μm. 160 ° C hot air circulation baking oven
And then cooled to room temperature by air cooling.

The anticorrosive coating agent containing no chromium is
As solids, 50 parts by weight of olefin resin manufactured by Toho Chemical Co., Ltd. (trade name: Hitech S-7024) and 50 parts by weight of urethane resin manufactured by Asahi Denka Co., Ltd. (trade name: Bontiter HUX-320) are 100 parts by weight of resin solids. Thiourea as a thiocarbonyl group-containing compound with a solid content of 2.5%
Parts by weight, 30 parts by weight as solid content of silica manufactured by Nissan Chemical Industries (trade name: Snowtex-C) as fine silica,
The solution was diluted with pure water so that ammonium phosphate was adjusted to 1.0 part by weight as PO ₄ , adjusted so that the total solid concentration became 20%, and further adjusted to pH 8.2. As is evident from the results shown in Table 1, all the cases according to the present invention exhibited excellent performance.

On the other hand, Comparative Example 1 was a comparative example in which the treatment with alkali was not performed before the rust-proof coating, but the adhesion of the film was lower than that of the example of the present invention. Also,
Comparative Example 2 was a comparative example in which the pH of the alkali treatment solution was out of the range of the present invention, but the adhesion of the coating was similarly reduced.

Examples 13 to 42 and Comparative Examples 3 to 9 In Examples 13 to 42, a hot-dip galvanized steel sheet (80 g / m ² of coating weight, an aluminum content of 0.1% in a plating bath) manufactured by the Sendzimer method was used. (15%, Pb 0.10%) was added to a 5 g / l solution of sodium phosphate with sodium hydroxide, immersed in a solution having a pH of 14 for 5 seconds, washed with running water, and dried by air blow. Thereafter, a rust-preventive coating agent containing no chromium was applied so as to have a dry film thickness of 1.3 μm, and was baked in a hot air circulating baking furnace at 400 ° C. to a plate temperature of 150 ° C., and then cooled to room temperature by air cooling. .

The rust-preventive coating agent not containing chromium is a solid content of thiourea as a thiocarbonyl group-containing compound per 100 parts by weight of an olefin resin (trade name: Hitec S-7024) manufactured by Toho Chemical Co., Ltd. 2.5 parts by weight were added, the amount of fine silica and phosphoric acid compound was changed, diluted with pure water to adjust the total solid concentration to 5%, and the pH was further adjusted to 8.5. Was used.

The names of the phosphoric acid compounds in Table 2 are as follows. Symbol A Ammonium monohydrogen phosphate Symbol B Ammonium dihydrogen phosphate Symbol C Phosphoric acid Symbol D Sodium phosphate + ammonium monohydrogen phosphate (mixing ratio 1: 1) Symbol E Ammonium pyrophosphate

The silica chemicals in Table 2 are as follows. Symbol A Snowtex-N made by Nissan Chemical Co., Ltd. Symbol B Snowtex-NS made by Nissan Chemical Co., Ltd. Snowtex-C made by Nissan Chemical Co., Ltd. Symbol D Snowtex-NXS made by Nissan Chemical Co., Ltd. Symbol F Adelite AT-20A manufactured by Asahi Denka Co., Ltd.

The higher the concentration of the phosphoric acid compound, the lower the adhesion of the secondary top coat tended to be. Also, the higher the silica concentration, the lower the adhesion of the film and the adhesion of the top coat tended to decrease. Furthermore, all the components contributed to the corrosion resistance, and although the corrosion resistance was improved by the addition, the increase in the amount of addition rather increased the solubility of the film, indicating that the corrosion resistance tended to decrease.

On the other hand, Comparative Example 3 contained 30 parts by weight of phosphoric acid and had a higher concentration than the examples of the present invention and contained no silica, but had low corrosion resistance and low adhesion to the top coat. In Comparative Examples 4 and 5, phosphoric acid concentration was higher than that of Examples of the present invention and silica was contained. In Comparative Example 4 in which silica concentration was higher than that of Examples of the present invention, all performances were deteriorated. ing. In addition, these two coating agents caused a gelling phenomenon when left for one month, but no other such phenomenon was observed. Comparative Example 6 contains both silica and a phosphoric acid compound, and has a higher silica concentration range than that of the examples of the present invention, but the adhesion of the film is reduced. Comparative Example 7 was a comparative example containing neither silica nor a phosphoric acid compound, but had very poor corrosion resistance. Comparative Example 8 contains a phosphate compound,
Comparative Example 9 is a comparative example that does not contain silica at a concentration below the range of the present invention and contains silica, but is a comparative example that contains silica but does not contain a phosphate compound at a concentration below the range of the present invention, In both cases, the corrosion resistance was inferior.

[Examples 43 to 59, Comparative Examples 10 and 11]
A hot-dip galvanized steel sheet (coated amount of 120 g / m ² , aluminum content of plating bath 0.20%, lead 0.03%) manufactured by the Sendzimer method was converted to nickel sulfate 2 g / l.
Add ammonia water and sodium hydroxide to the solution and adjust the pH.
Was immersed in an aqueous solution of 10.5 for 10 seconds, washed with running water, dried by air blow, and then coated with a chromium-free rust-preventive coating agent to a dry film thickness of 1 μm. Plate temperature 15 in hot air circulation baking furnace
It was baked at 0 ° C., then cooled with water, and dried by air blow.

As the rust-free coating agent containing no chromium, 50 parts by weight of olefin resin (trade name: Hitec S-7024) manufactured by Toho Chemical Co., Ltd. and urethane resin (trade name: Bontiter HUX-320) manufactured by Asahi Denka Co., Ltd. are used as solid components. )
The thiocarbonyl group-containing compound was variously changed with respect to 100 parts by weight of the total resin solid content of 50 parts by weight, and silica (trade name: Snowtex-
N) as a solid content of 30 parts by weight, and a silane compound of γ
-Glycidoxypropyltriethoxysilane "KBE-
403 "(manufactured by Shin-Etsu Chemical Co., Ltd.) was diluted with pure water to 1 part by weight and ammonium phosphate to 1.5 parts by weight as PO ₄ , and the total solid content was adjusted to 20%.
What adjusted H to 9.0 was used.

The thiocarbonyl group-containing compounds in Table 3 are as follows. Symbol A Thiourea Symbol B 1,3-Diethyl-2-thiourea Symbol C 1,3-Diphenyl-2-thiourea Symbol D Dibutylthiourea Symbol E Tetramethylthiuram monosulfide Symbol F Tetramethylthiuram disulfide Symbol G Thioacetamide Symbol H thioacetaldehyde

Table 3 shows the performance evaluation results. In contrast to Examples 43 to 59, Comparative Example 10 is a comparative example in which the concentration of the thiocarbonyl group-containing compound is not more than the range of the present invention, and Comparative Example 11 is a comparative example not including the thiocarbonyl group-containing compound. Also had poor corrosion resistance.

[Examples 60 to 80, Comparative Examples 12 and 13]
A hot dip galvanized steel sheet (coated amount of 60 g / m ² , aluminum content of 0.23% in the plating bath) manufactured by the Sendzimer method was added with sodium hydroxide to a sodium carbonate 3 g / l solution to adjust the pH to 12. After immersion in the prepared aqueous solution for 5 seconds, washing with running water and drying by air blow, a chromium-free rust-preventive coating agent was applied so as to have a dry film thickness of 0.7 μm. The plate was baked in a hot air circulating baking furnace to a sheet temperature of 120 ° C. and cooled to room temperature by air blow.

As chromium-free rust-preventive coating agents, 50 parts by weight of olefin resin (trade name: Hitec S-7024) manufactured by Toho Chemical Co., Ltd. and urethane resin (trade name: Bontiter HUX-320) manufactured by Asahi Denka Co., Ltd. are used as solid components. )
With respect to 100 parts by weight of the total resin solid content of 50 parts by weight, the vanadate compound was variously changed, and fine silica, a phosphoric acid compound and a thiocarbonyl group-containing compound were prepared as shown in Table 4 according to the symbols in Tables 1 to 3. And pure water, adjusted so that the total solid content concentration became 25%, and further adjusted the pH to 9.0.

The vanadate compounds in Table 4 are as follows. Symbol A Ammonium vanadate Symbol B Vanadate acid symbol C Strontium vanadate Symbol D Ammonium phosphovanadate Symbol E Potassium vanadate

Table 4 shows the results of these performance evaluations. In contrast to Examples 60 to 80, Comparative Example 12 is a comparative example in which the concentration of the vanadate compound is less than the range of the present invention and contains silica, and Comparative Example 13 is a comparative example in which the concentration of the vanadate compound is less than the range of the present invention. Although the comparative examples did not contain any of them, the corrosion resistance was inferior.

[Examples 81 to 102, Comparative Examples 14 and 1]
5] In the following examples, the following types of steel plates were used. Symbol A hot-dip galvanized steel sheet (aluminum in bath: 0.
22%) (Coating weight 140g / m ² ) Symbol B 5% Aluminum-Zinc alloy hot-dip galvanized steel sheet (Coating weight 80g / m ² ) Symbol C 55% Aluminum-Zinc alloy hot-dip galvanized steel sheet (Plating weight 60g / M ² ) Symbol D Evaporated galvanized steel sheet (coating weight 10 g / m
² ) Symbol E Electric 11% nickel-zinc alloy coated steel sheet (coating weight 20g / m ² ) Symbol F Electrogalvanized steel sheet (coating weight 20g / m
² ) Symbol G Alloyed hot-dip zinc-10% iron alloy-coated steel sheet (coating weight: 45 g / m ² )

[0091] These steel plates were treated with 2 g of sodium fluoride /
After adding sodium hydroxide to the 1 solution and spraying an aqueous solution having a pH of 14 at a spray pressure of 1.0 kg / cm ² for 10 seconds, washing with running water and drying with a hot air blow at 40 ° C., A rust-preventive coating agent containing no chromium was applied so as to have an adhesion amount shown in Table 5, and was baked in a direct-fired baking furnace at 850 ° C. to a plate temperature of 160 ° C., and cooled to room temperature by air blowing.

Examples of the rust-free coating agent containing no chromium include resins represented by the following symbols: symbol A: 50 parts by weight of an olefin resin (trade name: Hitec S-7024) manufactured by Toho Chemical Co., Ltd .; Resin mixed with 50 parts by weight of urethane resin (trade name: Bontiter HUX-320) Symbol B 100 parts by weight of olefin resin (trade name: Hitec S-7024) manufactured by Toho Chemical Co., Ltd. Symbol C Acrylic resin manufactured by Toa Gosei Co. (trade name: AP-1
058 (12)) 100 parts by weight Symbol D 100 parts by weight of epoxy resin (trade name: Polysol 8500) manufactured by Showa Polymer Co., Ltd. Symbol E 100 parts by weight of polyester resin (trade name: Pesresin A-124G) manufactured by Takamatsu Yushi Co., Ltd. As a thiocarbonyl group-containing compound, thiourea is 2.5 parts by weight as solids, Nissan Chemical Industries silica (trade name: Snowtex-N) is 30 parts by weight as solids, and ammonium phosphate is PO ₄ as fine silica. 1.0 part by weight, a compound represented by the following symbol as a silane compound A: γ-glycidoxypropyltriethoxysilane “K
BE-403 "(manufactured by Shin-Etsu Chemical Co., Ltd.) B: γ-glycidoxypropyltrimethoxysilane" K
BM-403 "(Shin-Etsu Chemical Co., Ltd.) C: Vinyltrimethoxysilane" KBM-1003 "
(Manufactured by Shin-Etsu Chemical Co., Ltd.) D: N-β (aminoethyl) γ-aminopropyltriethoxysilane “KBE-603” (manufactured by Shin-Etsu Chemical Co., Ltd.) E: γ-mercaptopropyltrimethoxysilane “KB”
M-803 "(manufactured by Shin-Etsu Chemical Co., Ltd.) was diluted with pure water so as to have the weight parts shown in Table 5, and the total solid content was adjusted to 20%, and the pH was further adjusted to 8.0. Was used.

[0093] In the case where the alloyed hot-dip zinc-10% iron alloy plated steel sheet was used as the base, white rust and red rust tended to appear when the coating amount was small, and the corrosion resistance tended to be poor, but other plating materials were good. Characteristics. Further, Comparative Example 14 in which the coating amount was not more than the range of the present invention and Comparative Example 15 having no coating of the present invention were inferior in corrosion resistance and adhesion of the top coat.

[0094]

[Table 1]

[0095]

[Table 2]

[0096]

[Table 3]

[0097]

[Table 4]

[0098]

[Table 5]

[0099]

As described above, according to the present invention,
It is possible to use a non-chromium-treated zinc-coated steel sheet that does not contain hexavalent chromium, has excellent corrosion resistance, and has excellent adhesion to the lower layer.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09D 7/12 C09D 7/12 Z 201/00 201/00 (72) Inventor Akira Takahashi Kimitsu, Kimitsu City, Chiba Prefecture 1 Nippon Steel Corporation Kimitsu Works (72) Inventor Atsushi Morishita 1 Kimitsu City, Kimitsu City, Chiba Prefecture Nippon Steel Corporation Kimitsu Works (72) Inventor Toshiaki Shimakura 4 Minamishinagawa, Shinagawa-ku, Tokyo Nippon Paint Co., Ltd. (72) Inventor Katsuyoshi Yamazoe 4-1-1, Minamishinagawa, Shinagawa-ku, Tokyo

Claims (2)

[Claims] 1. A galvanized steel sheet or a zinc alloy-plated steel sheet having a surface treated with an alkaline aqueous solution having a pH of 10 or more is used as a base, and a thickness of 0.1 to 5 μm is formed on the base steel sheet.
m, having a coating of one of the following (A) to (D). (A) A film containing 0.1 to 50 parts by weight of a thiocarbonyl group-containing compound and 0.01 to 20 parts by weight (as PO ₄ ) of a phosphoric acid compound based on 100 parts by weight of an organic resin as a solid content. Fine particles of silica 1 to 5 as solids in the above (A)
Coating containing 100 parts by weight (C) 0.1 to 50 parts by weight of a thiocarbonyl group-containing compound and 1 to 500 parts by weight of fine silica are contained with respect to 100 parts by weight of an organic resin as a solid content. Film not containing (D) at least 0.1 to 20 parts by weight of a vanadate compound per 100 parts by weight of an organic resin as a solid content, and optionally 0.1 to 50 parts by weight of a thiocarbonyl group-containing compound, a phosphoric acid compound Coating containing at least one of 0.01 to 20 parts by weight (as PO ₄ ) and 1 to 500 parts by weight of fine silica 2. A base steel sheet, which is a galvanized steel sheet or a zinc alloy-plated steel sheet, is treated with an alkaline aqueous solution having a pH of 10 or more, and then (1) water and 100 parts by weight of a water-based resin as a solid content are put on the base steel sheet. On the other hand, 0.1 to 50 parts by weight of a thiocarbonyl group-containing compound,
And a phosphoric acid compound in an amount of 0.01 to 20 parts by weight (as PO ₄ ).
(3) water and 0.1 to 50 parts by weight of a thiocarbonyl group-containing compound with respect to 100 parts by weight of an aqueous resin as a solid content;
A coating agent composition containing 1 to 500 parts by weight of fine silica and not containing a phosphoric acid compound; (4) water and 0.1 to 20 parts by weight of a vanadate compound per 100 parts by weight of an aqueous resin as a solid content. And optionally contains at least one of 0.1 to 50 parts by weight of a thiocarbonyl group-containing compound, 0.01 to 20 parts by weight of a phosphoric acid compound (as PO ₄ ) and 1 to 500 parts by weight of fine silica. One of the coating agent compositions is applied to form a coating film, and then the coating film is heated and dried to form a film having a thickness of 0.1 to 5 μm. Manufacturing method of chrome-type treated zinc-based galvanized steel sheet.