JP2000119879A - Organic coated steel sheet with excellent corrosion resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic coated steel sheet which can obtain excellent corrosion resistance without containing a heavy metal such as hexavalent chromium in a film. SOLUTION: On a surface of a zinc-based or aluminum-based plated steel sheet, a film-forming organic resin (A) and an active hydrogen-containing compound (B) composed of a hydrazine derivative (C) in which some or all of the compounds have active hydrogen are used. It is characterized in that it has an organic film having a film thickness of 0.1 to 5 μm containing a reaction product. By providing a hydrazine derivative to the film-forming organic resin, the hydrazine derivative is adsorbed or reacted on the surface of the plating film, Since a dense passivation layer stably and firmly adhered to the surface is formed, and the hydrazine derivative traps zinc ions eluted during film formation to form an electrically neutral insoluble chelate compound layer, The formation of an ion conductive layer at the interface between the plating film and the organic resin layer is suppressed, thereby suppressing the progress of corrosion. It is suppressed, resulting excellent corrosion resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic coated steel sheet which is most suitable for use in automobiles, home appliances, building materials, etc. Environmentally-friendly surface treatment that does not contain any heavy metals such as chromium, lead, cadmium, and mercury that are harmful to the environment and humans during manufacturing and in products, in order to adapt to environmental issues such as volatilization and elution of harmful substances from products. It relates to a steel plate.

[0002]

2. Description of the Related Art Steel sheets for home appliances, building materials, and automobiles have been used to improve the corrosion resistance (white rust resistance, red rust resistance) on the surface of a zinc-based steel sheet or an aluminum-based steel sheet. A steel sheet which has been subjected to chromate treatment with a treatment liquid containing chromic acid, bichromic acid or salts thereof as a main component is widely used. This chromate treatment is an economical treatment method that has excellent corrosion resistance and can be performed relatively easily.

[0003] However, since chromate treatment uses hexavalent chromium, which is a pollution control substance, it is difficult for chromate salts to have an adverse effect on the human body in the treatment process, and it is difficult to dispose of chromium sludge after wastewater treatment. In addition, there are various problems, for example, that hexavalent chromium may be eluted from the product after the chromate treatment. For this reason, as the use control standards for chromic acids have become stricter, the management of chromate treatment plants, wastewater treatment, and secondary contamination by chromate treatment have become problems, and in response to this, each plant has closed drainage relations. In addition, measures are taken to minimize the emission of chromium ions to the outside.
In addition, in the process of degreasing the rust-preventive oil and press oil attached to the chromate-treated steel sheet by the user, when using an alkaline degreasing solution, the elution of chromium into the degreasing solution is considerably increased. Dechrome treatment is required.

[0004] In view of such circumstances, in order to prevent the generation of white rust on a zinc-based plated steel sheet, many pollution-free treatment techniques not based on chromate treatment have been proposed. Among them, several methods using an organic compound or an organic resin have been proposed, and for example, the following methods can be mentioned.

(1) A method using tannic acid (for example,
(2) A method of using a thermosetting paint in which an epoxy resin, an amino resin and tannic acid are mixed (for example, JP-A-63-971).
No. 0581) (3) A method using a mixed composition of an aqueous resin and a polyhydric phenol carboxylic acid (for example, JP-A-8-325760)
Using the chelating power of tannic acid, such as

(4) A surface treatment method of applying an aqueous solution of a hydrazine derivative to the surface of a tin or zinc iron plate (for example,
JP-B-53-27694, JP-B-56-10386
(5) A method using a rust inhibitor containing an amine addition salt obtained by adding an amine to a mixture of acyl sarcosine and benzotriazole (for example, JP-A-58-130284)
(6) A method using a treating agent in which a heterocyclic compound such as a benzothiazole compound and tannic acid are mixed (for example, JP-A-57-198267)

[0007]

However, these prior arts have the following problems. First, all of the above methods (1) to (4) have a problem in terms of corrosion resistance and the like. That is, the method (1) is insufficient in corrosion resistance and cannot provide a uniform appearance after the treatment. In addition, the method (2) is particularly suitable for forming a thin film (0.1 to 5 μm) directly on a zinc-based or aluminum-based plating surface.
m) is not intended to form a rust-preventive film. Therefore, even when applied in a thin film form to a zinc-based or aluminum-based plating surface, a sufficient anticorrosion effect cannot be obtained. Similarly, the method (3) is also insufficient in corrosion resistance.

Further, the method (4) is not applied to a zinc-based or aluminum-based plated steel sheet. Even if applied to a zinc-based or aluminum-based plated steel sheet, the obtained film has a network structure. It does not have sufficient barrier properties due to lack of corrosion resistance, and therefore has insufficient corrosion resistance. In addition, Japanese Patent Publication No. 53-23772
And JP-B-56-10386, in which a water-soluble polymer compound (polyvinyl alcohol, maleic acid ester copolymer, acrylic acid ester copolymer, etc.) is mixed with an aqueous solution of a hydrazine derivative in order to improve the uniformity of the film. However, a simple mixture of an aqueous hydrazine derivative solution and a water-soluble polymer compound does not provide sufficient corrosion resistance.

Further, the methods (5) and (6) are not aimed at forming a rust-preventive film on the surface of a zinc-based or aluminum-based plated steel sheet in a short time.
Even if the treating agent is applied to the surface of the plated steel sheet, excellent corrosion resistance cannot be obtained because there is no barrier to corrosion factors such as oxygen and water. As for the method (6), mixing with a resin (an epoxy resin, an acrylic resin, a urethane resin, a nitrocellulose resin, a vinyl chloride resin, etc.) as an additive is described, but a complex such as a benzothiazole compound is used. A simple mixture of a ring compound and a resin does not provide sufficient corrosion resistance.

In any of the above methods (1) to (6), practical conditions such as alkali degreasing at a pH of about 9 to 11 using a spray or the like to remove oil applied to the surface by press working or the like. However, there is a problem that the film is peeled or damaged by alkali degreasing, and the corrosion resistance cannot be maintained. Therefore, these methods are not suitable for practical use as a method for forming a rust preventive film. Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art and to provide an organic-coated steel sheet which can obtain excellent corrosion resistance without containing a heavy metal such as hexavalent chromium in a film.

[0011]

Means for Solving the Problems As a result of intensive studies by the present inventors to solve the above problems, a specific chelate-forming resin film is formed on the surface of a zinc-based steel sheet or an aluminum-based steel sheet. As a result, it has been found that an organic-coated steel sheet having no pollution and excellent corrosion resistance can be obtained without performing a chromate treatment that may adversely affect the environment and the human body. The present invention has been made based on such knowledge, and the characteristic configuration thereof is as follows.

[1] An active hydrogen-containing compound (A) comprising a film-forming organic resin (A) and a hydrazine derivative (C) in which some or all of the compounds have active hydrogen is formed on the surface of a zinc-based plated steel sheet or an aluminum-based plated steel sheet. An organic-coated steel sheet having excellent corrosion resistance, characterized by having an organic film having a thickness of 0.1 to 5 μm containing a reaction product with B). [2] The organic-coated steel sheet according to [1] above, wherein the film-forming organic resin (A) is an epoxy group-containing resin (D). [3] The organic-coated steel sheet according to the above [1] or [2], wherein the hydrazine derivative (C) having active hydrogen is a pyrazole compound having active hydrogen and / or a triazole compound having active hydrogen. Organic coated steel sheet with excellent corrosion resistance.

[4] The hydrazine derivative (C) having active hydrogen in the organic-coated steel sheet according to any one of the above [1] to [3].
Is contained in the active hydrogen-containing compound (B) in an amount of 10 to 100 mol%. [5] In the organic-coated steel sheet according to any one of the above [2] to [4],
An organic-coated steel sheet having excellent corrosion resistance, wherein the epoxy group-containing resin (D) is an epoxy resin represented by the following formula (1).

Embedded image

The feature of the organic coated steel sheet of the present invention is that a film-forming organic resin (A) is reacted with an active hydrogen-containing compound (B) comprising a hydrazine derivative (C) in which some or all of the compounds have active hydrogen. Thus, the hydrazine derivative (C) can be used as a chelate-forming group in the film-forming resin (A).
And that the chelate-forming resin as a reaction product is formed as a rust-preventive film on the surface of a zinc-based plated steel sheet or an aluminum-based plated steel sheet.

Although the mechanism of corrosion protection of the organic film by such a specific reaction product is not always clear, (1) by adding a hydrazine derivative to a film-forming organic resin instead of a low molecular weight chelating agent, The organic polymer film has the effect of blocking corrosion factors such as oxygen and chlorine ions, and (2) the hydrazine derivative is adsorbed on the surface of the plating film or reacts with the plating film surface, making it stable on the plating film surface (3) The hydrazine derivative traps zinc ions eluted during film formation and forms an electrically neutral insoluble chelate compound layer (a dense barrier having a complex structure). Layer), the formation of an ion conductive layer at the interface between the plating film and the organic resin layer is suppressed, and the progress of corrosion is suppressed. 4) Further, even in a corrosive environment, free hydrazine derivatives in the film trap zinc ions generated by the corrosion and form a stable metal complex structure, thereby suppressing the progress of corrosion.
Corrosion progress is effectively suppressed by the effects of
It is considered that excellent corrosion resistance can be obtained.

When an epoxy group-containing resin is used as the film-forming organic resin (A), a dense barrier film is formed by the reaction between the epoxy group-containing resin and the crosslinking agent. It has an excellent ability to suppress permeation of corrosion factors such as corrosion factors, and a hydroxyl group in a molecule provides an excellent bonding force with a substrate, so that particularly excellent corrosion resistance is obtained. Further, a hydrazine derivative (C) having active hydrogen
By using a pyrazole compound having active hydrogen and / or a triazole compound having active hydrogen, more excellent corrosion resistance can be obtained.

As in the prior art, a film-forming organic resin (A)
By simply mixing the hydrazine derivative (C), the effect of improving corrosion inhibition is hardly recognized. The reason is,
It is considered that the hydrazine derivative not incorporated in the molecules of the film-forming organic resin is adsorbed on the metal surface, but the adsorbed product does not form a dense barrier layer due to its low molecular weight. On the other hand, by incorporating the hydrazine derivative into the molecule of the film-forming organic resin (A) as in the present invention, a significantly excellent corrosion suppressing effect can be obtained.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention and the reasons for limiting the same will be described below. The zinc-coated steel sheet serving as a base of the organic coated steel sheet of the present invention includes a zinc-coated steel sheet, Zn-Ni
Alloy plated steel sheet, Zn-Fe alloy plated steel sheet (electroplated steel sheet and galvannealed steel sheet), Zn-Cr
Alloy plated steel sheet, Zn-Mn alloy plated steel sheet, Zn-C
o alloy plated steel sheet, Zn-Co-Cr alloy plated steel sheet,
Zn-Cr-Ni alloy plated steel sheet, Zn-Cr-Fe alloy plated steel sheet, Zn-Al alloy plated steel sheet (for example, Z
n-5% Al alloy plated steel sheet, Zn-55% Al alloy plated steel sheet), Zn-Mg alloy plated steel sheet, Zn-Al-
Mg-plated steel sheets, and zinc-based composite plated steel sheets (eg, Zn—SiO ₂ dispersed plated steel sheets) in which metal oxides, polymers, and the like are dispersed in the plating films of these plated steel sheets can be used.

Further, among the above-mentioned platings, it is also possible to use a multi-layer plated steel sheet obtained by plating two or more layers of the same type or different types. In addition, as the aluminum-plated steel sheet serving as the base of the organic-coated steel sheet of the present invention, an aluminum-plated steel sheet, an Al—Si alloy-plated steel sheet, or the like can be used. Further, the plated steel sheet may be one in which thin steel plating such as Ni is previously applied to the surface of the steel sheet and various platings as described above are applied thereon. As a plating method, any practicable method can be adopted among an electrolysis method (electrolysis in an aqueous solution or electrolysis in a non-aqueous solvent), a melting method, and a gas phase method.

Next, a specific organic film formed on the surface of the zinc-based steel sheet or the aluminum-based steel sheet will be described. In the present invention, the organic film formed on the surface of the zinc-based plated steel sheet or the aluminum-based plated steel sheet has an activity comprising a film-forming organic resin (A) and a hydrazine derivative (C) in which some or all of the compounds have active hydrogen. An organic film containing a reaction product with the hydrogen-containing compound (B) and having a thickness of 0.1 to 5 μm.

The types of the film-forming organic resin (A) include:
Some or all of the compounds react with an active hydrogen-containing compound (B) composed of a hydrazine derivative (C) having active hydrogen, and the active hydrogen-containing compound (B) is added to the film-forming organic resin by a reaction such as addition or condensation. There is no particular limitation as long as the resin can be bonded and a film can be appropriately formed. As the film-forming organic resin (A), for example, epoxy resin,
Modified epoxy resins, polyurethane resins, polyester resins, alkyd resins, acrylic copolymer resins, polybutadiene resins, phenolic resins, and adducts or condensates of these resins can be mentioned. They can be used alone or in combination of two or more.

Further, as the film-forming organic resin (A),
Those containing an epoxy group in the resin (epoxy group-containing resin) are particularly preferred from the viewpoints of reactivity, ease of reaction, corrosion resistance and the like. As the epoxy group-containing resin (D),
Some or all of the compounds react with an active hydrogen-containing compound (B) composed of a hydrazine derivative (C) having active hydrogen, and the active hydrogen-containing compound (B) is added to the film-forming organic resin by a reaction such as addition or condensation. There are no special restrictions as long as the resin can be bonded and a film can be appropriately formed.
Epoxy resins, modified epoxy resins, acrylic copolymer resins copolymerized with epoxy group-containing monomers, polybutadiene resins having epoxy groups, polyurethane resins having epoxy groups, and adducts or condensates of these resins. , One of these epoxy group-containing resins
The species can be used alone or as a mixture of two or more. Further, among these epoxy group-containing resins, a thermosetting epoxy resin and a modified epoxy resin having excellent barrier properties against corrosion factors such as oxygen are particularly preferable.

The epoxy resin may be prepared by introducing a glycidyl group by reacting a polyphenol such as bisphenol A, bisphenol F or novolac phenol with an epihalohydrin such as epichlorohydrin, or the glycidyl group-introduced reaction product. Further, aromatic epoxy resins obtained by increasing the molecular weight by reacting polyphenols, furthermore, aliphatic epoxy resins, alicyclic epoxy resins, and the like, may be used alone or in combination of two or more. Can be used.
It is preferable that these epoxy resins have a number average molecular weight of 1500 or more especially when a film-forming property at a low temperature is required.

Examples of the modified epoxy resin include resins obtained by reacting various modifiers with an epoxy group or a hydroxyl group in the epoxy resin. Examples of the modified epoxy resin include an epoxy ester resin obtained by reacting a drying oil fatty acid, acrylic acid, and acrylic acid. Examples thereof include an epoxy acrylate resin modified with a polymerizable unsaturated monomer component containing methacrylic acid and the like, and a urethane-modified epoxy resin reacted with an isocyanate compound.

As the acrylic copolymer resin copolymerized with the epoxy group-containing monomer, an unsaturated monomer having an epoxy group and a polymerizable unsaturated monomer component having an acrylic ester or a methacrylic ester as an essential component may be used as a solution. Resins synthesized by a polymerization method, an emulsion polymerization method, a suspension polymerization method, or the like can be given.

The polymerizable unsaturated monomer component includes:
For example, methyl (meth) acrylate, ethyl (meth)
Acrylate, propyl (meth) acrylate, n-,
C1-24 alkyl esters of acrylic or methacrylic acid such as iso- or tert-butyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, decyl (meth) acrylate, lauryl (meth) acrylate; Acrylic acid, methacrylic acid, styrene, vinyltoluene, acrylamide, acrylonitrile, N-methylol (meth) acrylamide, a C1-4 alkyl etherified product of N-methylol (meth) acrylamide; N, N-diethylaminoethyl methacrylate and the like. it can.

The unsaturated monomer having an epoxy group is not particularly limited as long as it has an epoxy group and a polymerizable unsaturated group, such as glycidyl methacrylate, glycidyl acrylate, and 3,4-epoxycyclohexylmethyl (meth) acrylate. There are no restrictions. The acrylic copolymer resin copolymerized with the epoxy group-containing monomer may be a resin modified with a polyester resin, an epoxy resin, a phenol resin, or the like.

Particularly preferred as the epoxy resin is a resin having a chemical structure represented by the following formula (1), which is a reaction product of bisphenol A and epihalohydrin. This epoxy resin is particularly excellent in corrosion resistance. preferable.

Embedded image Methods for producing such bisphenol A type epoxy resins are widely known in the art. In the above chemical structural formula, q is 0 to 50, preferably 1 to 40, particularly preferably 2 to 20. The film-forming organic resin (A) may be any of an organic solvent-soluble type, an organic solvent-dispersed type, a water-soluble type, and a water-dispersed type.

The present invention aims at providing a hydrazine derivative in the molecule of the film-forming organic resin (A), so that at least a part (preferably all) of the active hydrogen-containing compound (B) contains at least one active hydrogen. Hydrazine derivative (C) having the following formula:

When the film-forming organic resin (A) is an epoxy group-containing resin, examples of the active hydrogen-containing compound (B) which reacts with the epoxy group include the following compounds. You can use more than species,
Also in this case, at least a part (preferably all) of the active hydrogen-containing compound (B) needs to be a hydrazine derivative having active hydrogen.・ Hydrazine derivative having active hydrogen ・ Primary or secondary amine compound having active hydrogen ・ Organic acid such as ammonia or carboxylic acid ・ Halogen halide such as hydrogen chloride ・ Alcohols, thiols ・ Has active hydrogen Quaternary chlorinating agents which are hydrazine derivatives or mixtures of tertiary amines and acids

Examples of the hydrazine derivative (C) having an active hydrogen include the following. Carbohydrazide, propionic hydrazide, salicylic hydrazide, adipic dihydrazide, sebacic dihydrazide, dodecanoic dihydrazide, isophthalic dihydrazide, thiocarbohydrazide, 4,4'-oxybisbenzenesulfonyl hydrazide, benzophenone hydrazide, aminopolyacrylamide such as benzophenone hydrazide Compounds; pyrazole compounds such as pyrazole, 3,5-dimethylpyrazole, 3-methyl-5-pyrazolone, 3-amino-5-methylpyrazole;

1,2,4-triazole, 3-amino-1,2,4-triazole, 4-amino-1,2,2
4-triazole, 3-mercapto-1,2,4-triazole, 5-amino-3-mercapto-1,2,4-
Triazole, 2,3-dihydro-3-oxo-1,
2,4-triazole, 1H-benzotriazole, 1
-Hydroxybenzotriazole (monohydrate), 6-methyl-8-hydroxytriazolopyridazine, 6-phenyl-8-hydroxytriazolopyridazine, 5-hydroxy-7-methyl-1,3,8-triazaind Triazole compounds such as lysine;

5-phenyl-1,2,3,4-tetrazole, 5-mercapto-1-phenyl-1,2,2
Tetrazole compounds such as 3,4-tetrazole; thiadiazole compounds such as 5-amino-2-mercapto-1,3,4-thiadiazole and 2,5-dimercapto-1,3,4-thiadiazole; maleic hydrazide; Pyridazine compounds such as methyl-3-pyridazone, 4,5-dichloro-3-pyridazone, 4,5-dibromo-3-pyridazone, 6-methyl-4,5-dihydro-3-pyridazone

Of these, a five-membered ring or a six-membered ring
Pyrazole compounds and triazole compounds having a membered ring structure and having a nitrogen atom in the ring structure are particularly preferred. These hydrazine derivatives can be used alone or in combination of two or more.

Representative examples of the amine compound having active hydrogen which can be used as a part of the active hydrogen-containing compound (B) include the following. The primary amino group of an amine compound containing one secondary amino group and one or more primary amino groups such as diethylenetriamine, hydroxyethylaminoethylamine, ethylaminoethylamine, and methylaminopropylamine can be converted to ketone, aldehyde or carboxyl. Acid and eg 1
A compound denatured to aldimine, ketimine, oxazoline or imidazoline by a heating reaction at a temperature of about 00 to 230 ° C;

Diethylamine, diethanolamine, di-n- or -iso-propanolamine, N
A secondary monoamine such as methylethanolamine or N-ethylethanolamine; a secondary amine-containing compound obtained by adding a monoalkanolamine such as monoethanolamine and a dialkyl (meth) acrylamide by a Michael addition reaction. Monoethanolamine, neopentanolamine,
2-aminopropanol, 3-aminopropanol, 2
A compound in which the primary amino group of an alkanolamine such as -hydroxy-2 '(aminopropoxy) ethyl ether is modified to ketimine;

The quaternary chlorinating agents which can be used as a part of the active hydrogen-containing compound (B) include hydrazine derivatives having no active hydrogen and tertiary amines, which themselves have no reactivity with epoxy groups. Is a mixture with an acid so that it can react with an epoxy group. The quaternary chlorinating agent reacts with an epoxy group in the presence of water if necessary, to form a quaternary salt with the epoxy group-containing resin.

The acid used to obtain the quaternary chlorinating agent is
Any of organic acids such as acetic acid and lactic acid and inorganic acids such as hydrochloric acid may be used. Examples of the hydrazine derivative having no active hydrogen used to obtain a quaternary chlorinating agent include, for example, 3,
Examples of 6-dichloropyridazine and the like and tertiary amines include, for example, dimethylethanolamine, triethylamine, trimethylamine, triisopropylamine, methyldiethanolamine and the like.

The reaction product of the film-forming organic resin (A) and the active hydrogen-containing compound (B) comprising a hydrazine derivative (C) in which some or all of the compounds have active hydrogen is converted to the film-forming organic resin (A) And the active hydrogen-containing compound (B) at 10 to 300 ° C, preferably 50 to 150 ° C, for about 1 to 8
It is obtained by reacting for about an hour.

This reaction may be carried out by adding an organic solvent, and the type of the organic solvent used is not particularly limited. For example, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, dibutyl ketone and cyclohexanone; ethanol, butanol, 2-ethylhexyl alcohol, benzyl alcohol, ethylene glycol, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether Alcohols and ethers having a hydroxyl group such as propylene glycol, propylene glycol monomethyl ether, diethylene glycol, diethylene glycol monoethyl ether, and diethylene glycol monobutyl ether; esters such as ethyl acetate, butyl acetate, and ethylene glycol monobutyl ether acetate; toluene, xylene Such as aromatic hydrocarbons. It can be used one or two or more thereof. Among these, ketone-based or ether-based solvents are particularly preferable from the viewpoints of solubility with an epoxy resin, coatability, and the like.

The compounding ratio of the film-forming organic resin (A) and the active hydrogen-containing compound (B) composed of a hydrazine derivative (C) in which some or all of the compounds have active hydrogen is determined in terms of the solid content. With respect to 100 parts by weight of resin (A), 0.5 to 20 parts by weight of active hydrogen-containing compound (B),
Particularly preferably, the content is 1.0 to 10 parts by weight.

When the film-forming organic resin (A) is an epoxy group-containing resin (D), the mixing ratio of the epoxy group-containing resin (D) and the active hydrogen-containing compound (B) is The ratio of the number of active hydrogen groups in the compound (B) to the number of epoxy groups in the epoxy group-containing resin (D) [the number of active hydrogen groups / the number of epoxy groups] is 0.01 to 10, more preferably 0.1 to 8, It is more preferably 0.2 to 4 from the viewpoint of corrosion resistance and the like.

The ratio of the hydrazine derivative (C) having active hydrogen in the active hydrogen-containing compound (B) is 1%.
Suitably, it is 0 to 100 mol%, more preferably 30 to 100 mol%, further preferably 40 to 100 mol%. If the ratio of the hydrazine derivative (C) having active hydrogen is less than 10 mol%, a sufficient rust-preventing function cannot be imparted to the organic film, and the obtained rust-preventive effect is obtained by simply mixing the hydrazine derivative with the film-forming organic resin. There is no big difference from the case of using.

In the present invention, in order to form a dense barrier film, it is desirable that a curing agent is blended in the resin composition and the organic film is cured by heating. As the curing method for forming the resin composition film, (1) a curing method utilizing a urethanization reaction between an isocyanate and a hydroxyl group in the base resin, and (2) one selected from melamine, urea and benzoguanamine. At least one or more methylol compounds obtained by reacting formaldehyde with at least one of
A curing method using an etherification reaction between an alkyl etherified amino resin obtained by reacting a monohydric alcohol with a hydroxyl group in the base resin is suitable. It is particularly preferred that the urethanation reaction be the main reaction.

The polyisocyanate compound used in the curing method (1) is an aliphatic, alicyclic (including heterocyclic) or aromatic isocyanate compound having at least two isocyanate groups in one molecule, or a compound thereof. A compound obtained by partially reacting a compound with a polyhydric alcohol. Examples of such a polyisocyanate compound include the following. m- or p-phenylenediisocyanate, 2,
4- or 2,6-tolylene diisocyanate, o- or p-xylylene diisocyanate, hexamethylene diisocyanate, dimer diisocyanate, isophorone diisocyanate

The above compound alone or a mixture thereof and a polyhydric alcohol (a dihydric alcohol such as ethylene glycol and propylene glycol; a trihydric alcohol such as glycerin and trimethylolpropane; a tetrahydric alcohol such as pentaerythritol; sorbitol and dihydric alcohol) Compounds having at least two isocyanates remaining in one molecule. These polyisocyanate compounds may be used alone or in combination of two or more. Can be used.

Examples of the protecting agent (blocking agent) for the polyisocyanate compound include aliphatic monoalcohols such as methanol, ethanol, propanol, butanol and octyl alcohol. Monoethers of ethylene glycol and / or diethylene glycol, for example. Methyl, ethyl, propyl (n-, iso), butyl (n-, iso, se)
c) monoether phenols, aromatic alcohols such as cresol, acetoximes, oximes such as methyl ethyl ketone oxime, and the like. One or more of these can be reacted with the polyisocyanate compound at least at room temperature. Thus, a protected polyisocyanate compound can be obtained.

Such a polyisocyanate compound (E) is used as a curing agent with respect to the film-forming organic resin (A) with respect to (A) / (E) = 95/5 to 55/45 (weight ratio of non-volatile components); Preferably (A) / (E) = 90/10
It is appropriate to mix them in a ratio of 65/35. The polyisocyanate compound has water absorption, which is referred to as (A) /
(E) If it exceeds 55/45, the adhesion of the organic film is deteriorated. Furthermore, when an overcoat is applied on the organic film, the unreacted polyisocyanate compound moves into the coating film, and causes curing inhibition and poor adhesion of the coating film. From such a viewpoint, the blending amount of the polyisocyanate compound (E) is preferably (A) / (E) = 55/45 or less.

The film-forming organic resin (A) is sufficiently crosslinked by the addition of a crosslinking agent (curing agent) as described above.
In order to further increase the low-temperature crosslinking property, it is desirable to use a known curing acceleration catalyst. As the curing promoting catalyst, for example, N-ethylmorpholine, dibutyltin dilaurate, cobalt naphthenate, stannous chloride, zinc naphthenate, bismuth nitrate and the like can be used. For example, when an epoxy group-containing resin is used as the film-forming organic resin (A), a known acrylic, alkyd,
A resin such as polyester can be used as a mixture.

The organic film of the organic coated steel sheet of the present invention is usually an active hydrogen-containing compound (B) comprising a film-forming organic resin (A) and a hydrazine derivative (C) in which some or all of the compounds have active hydrogen. And a hardening agent (for example, polyethylene wax, a fluororesin compound) and an anticorrosive additive (for example, , Silica), organic color pigments (eg, condensed polycyclic organic pigments, phthalocyanine-based organic pigments, etc.), coloring dyes (eg, organic solvent-soluble azo-based dyes, water-soluble azo-based metal dyes, etc.), inorganic pigments (eg, Titanium oxide), chelating agent (eg, thiol, etc.), conductive pigment (eg, zinc,
Metal powders such as aluminum and nickel, iron phosphide, antimony-doped tin oxide, etc.), coupling agents (eg, silane coupling agents, titanium coupling agents, etc.), melamine / cyanuric acid adducts, etc. may be added. it can.

The coating composition for forming a film containing the above-mentioned main components and additional components usually contains a solvent (organic solvent and / or water), and if necessary, a neutralizing agent or the like is added. . The organic solvent is not particularly limited as long as it can dissolve or disperse a reaction product of the film-forming organic resin (A) and the active hydrogen-containing compound (B), and can be adjusted as a coating composition. Various organic solvents exemplified above can be used. The neutralizing agent is added as necessary to neutralize the film-forming organic resin (A) to make it aqueous, and when the film-forming organic resin (A) is a cationic resin, Acids such as acetic acid, lactic acid and formic acid can be used as neutralizing agents.

The above-mentioned organic film is formed on the surface of a zinc-based plated steel sheet or an aluminum-based plated steel sheet without a chromate treatment film. The dry film thickness of the organic film is 0.1 to 5 μm. When the thickness of the organic film is less than 0.1 μm, the corrosion resistance is insufficient. On the other hand, in general applications requiring weldability, the weldability is reduced when the thickness exceeds 5 μm. Further, a more preferred film thickness is 0.5 to
3 μm.

The organic coated steel sheet of the present invention is formed by the reaction between the above-mentioned film-forming organic resin (A) and an active hydrogen-containing compound (B) comprising a hydrazine derivative (C) in which some or all of the compounds have active hydrogen. The composition is produced by applying a coating composition containing a substance (preferably as a main component) to the surface of a zinc-based plated steel sheet or an aluminum-based plated steel sheet and drying. Before applying the coating composition, the surface of the plated steel sheet may be subjected to an alkali degreasing treatment, if necessary, and may be subjected to a pretreatment such as a surface conditioning treatment in order to improve adhesion and corrosion resistance.

As a method of applying the coating composition to the surface of a galvanized steel sheet or an aluminum-coated steel sheet, any method such as a coating method, a dipping method, and a spraying method can be adopted. As a coating method, any method such as a roll coater (three-roll system, two-roll system, etc.), a squeeze coater, a die coater, and the like may be used. In addition, after the coating, dipping, or spraying with a squeeze coater or the like, it is also possible to adjust the coating amount, uniform the appearance, and uniform the film thickness by an air knife method or a roll drawing method.

After application of the coating composition, heating and drying are usually performed without washing with water. However, since the organic coating of the present invention is bonded to the surface of the plated steel sheet as a base by chemical adsorption or reaction, a water washing step may be performed after application of the coating composition. For the heating and drying treatment, a dryer, a hot blast furnace, a high-frequency induction heating furnace, an infrared furnace, or the like can be used. The heat treatment is desirably performed at a temperature of the ultimate plate temperature of 50 to 300 ° C, preferably 80 to 250 ° C. If the heating temperature is lower than 50 ° C., a large amount of water in the film remains, and the corrosion resistance becomes insufficient. On the other hand, if the heating temperature exceeds 300 ° C., it is not only uneconomical, but also there is a possibility that a defect occurs in the film and the corrosion resistance is reduced.

The present invention includes a steel sheet having the above-described organic film on both sides or one side. Therefore, examples of the form of the steel sheet of the present invention include the following. (1) One side: Plating film-Organic film, One surface: Plating film (2) One surface: Plating film-Organic film, One surface: Known phosphate treatment film, etc. (3) Both surfaces: Plating film-Organic film

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EXAMPLES Examples of the synthesis of a resin composition for forming a film are shown below. [Synthesis Example 1] 1870 parts of EP828 (manufactured by Yuka Shell Epoxy, epoxy equivalent: 187) and bisphenol A91
Two parts, 2 parts of tetraethylammonium bromide and 300 parts of methyl isobutyl ketone were charged into a four-necked flask, heated to 140 ° C., and reacted for 4 hours to obtain an epoxy resin having an epoxy equivalent of 1,391 and a solid content of 90%. Add ethylene glycol monobutyl ether 150
After adding 0 parts, the mixture was cooled to 100 ° C., 96 parts of 3,5-dimethylpyrazole (molecular weight: 96) and 129 parts of dibutylamine (molecular weight: 129) were added, and the mixture was reacted for 6 hours until the epoxy group disappeared. While cooling, 205 parts of methyl isobutyl ketone was added to obtain a pyrazole-modified epoxy resin having a solid content of 60%. This is a resin composition (1)
And This resin composition (1) is a reaction product of a film-forming organic resin (A) and an active hydrogen-containing compound containing 50 mol% of a hydrazine derivative (C) having active hydrogen.

[Synthesis Example 2] 4000 parts of EP1007 (manufactured by Yuka Shell Epoxy Co., epoxy equivalent: 2000) and 2239 parts of ethylene glycol monobutyl ether were charged into a four-necked flask, and the temperature was raised to 120 ° C and completely completed in 1 hour. The epoxy resin was dissolved. This was cooled to 100 ° C., and 3-amino-1,2,4-triazole (molecular weight: 8
After adding 168 parts of 4) and reacting for 6 hours until the epoxy group disappeared, 540 parts of methyl isobutyl ketone was added with cooling to obtain a modified triazole epoxy resin having a solid content of 60%. This is designated as a resin composition (2). This resin composition (2) comprises a film-forming organic resin (A) and 100 mol of a hydrazine derivative (C) having active hydrogen.
% Of the active hydrogen-containing compound.

[Synthesis Example 3] 222 parts of isophorone diisocyanate (isocyanate equivalent: 111) and 34 parts of methyl isobutyl ketone were charged into a four-necked flask, and 30 to 4
Keeping at 0 ° C, methyl ethyl ketoxime (molecular weight 87) 8
After dropping 7 parts over 3 hours, the mixture was kept at 40 ° C. for 2 hours to obtain a partially blocked isocyanate having an isocyanate equivalent of 309 and a solid content of 90%. Next, 1496 parts of EP828 (manufactured by Yuka Shell Epoxy Co., Ltd., epoxy equivalent: 187), 684 parts of bisphenol A, 1 part of tetraethylammonium bromide, and 241 parts of methyl isobutyl ketone were charged into a four-necked flask, and heated to 140 ° C. for 4 hours. The reaction was performed to obtain an epoxy resin having an epoxy equivalent of 1090 and a solid content of 90%. To this, add methyl isobutyl ketone 100
After adding 0 parts, the mixture was cooled to 100 ° C., and 3-mercapto-
After adding 202 parts of 1,2,4-triazole (molecular weight 101) and reacting for 6 hours until the epoxy group disappears, 230 parts of the above partially blocked isocyanate having a solid content of 90% is added and reacted at 100 ° C. for 3 hours. It was confirmed that the isocyanate group had disappeared. Further, 461 parts of ethylene glycol monobutyl ether was added, and a solid content of 6% was added.
0% of the modified triazole epoxy resin was obtained. This is referred to as a resin composition (3). This resin composition (3) is a reaction product of a film-forming organic resin (A) and an active hydrogen-containing compound containing 100 mol% of a hydrazine derivative (C) having active hydrogen.

[Synthesis Example 4] 1870 parts of EP828 (manufactured by Yuka Shell Epoxy Co., Ltd., epoxy equivalent: 187), 912 parts of bisphenol A, 2 parts of tetraethylammonium bromide, and 300 parts of methyl isobutyl ketone were charged into a four-necked flask and heated to 140 ° C. Raise the temperature and let it react for 4 hours.
An epoxy resin having an epoxy equivalent of 1391 and a solid content of 90% was obtained. After adding 1500 parts of ethylene glycol monobutyl ether, the mixture was cooled to 100 ° C., 258 parts of dibutylamine (molecular weight: 129) was added, and the mixture was reacted for 6 hours until the epoxy group disappeared. Add 225 parts of ketone, 60% solids
Was obtained. This is referred to as a resin composition (4). This resin composition (4) is a reaction product of a film-forming organic resin (A) and an active hydrogen-containing compound that does not contain a hydrazine derivative (C) having active hydrogen.

A curing agent was added to the resin compositions (1) to (4) synthesized as described above to prepare coating compositions shown in Table 1. To obtain organic-coated steel sheets for home appliances, building materials, and automobile parts, the sheet thickness: 0.8 mm, the surface roughness Ra: 1.
Using a galvanized steel sheet shown in Table 2 obtained by subjecting a cold-rolled steel sheet having a thickness of 0 μm to various zinc-based or aluminum-based plating as a processing base plate, subjecting the surface of the plated steel sheet to alkali degreasing treatment, washing with water and drying, and a coating composition shown in Table 1 The material was applied by a roll coater and dried by heating at various temperatures to produce an organic-coated steel sheet. The thickness of the organic film was adjusted according to the solid content (heating residue) of the coating composition or the application conditions (roll rolling force, rotation speed, etc.).

The obtained organic coated steel sheets were evaluated for quality performance (coating appearance, white rust resistance, paint adhesion).
The results are shown in Tables 3 to 5 together with the film configuration of the organic film. The evaluation of the quality performance of the organic coated steel sheet was performed as follows.

(1) Appearance of Film For each sample, the uniformity of the film appearance (with or without unevenness) was visually evaluated. The evaluation criteria are as follows. ：: uniform appearance without any unevenness △: appearance with some unevenness ×: appearance with unevenness

(2) White Rust Resistance For each sample, salt spray test (JIS-Z-23)
71) was carried out, and evaluated by the area ratio of white rust occurrence after a predetermined time. The evaluation criteria are as follows. ◎: No white rust generated ○ +: White rust generation area ratio less than 5% ○: White rust generation area ratio 5% or more and less than 10% ○-: White rust generation area ratio 10% or more and less than 25% △: White rust Generated area rate 25% or more, less than 50% ×: White rust generated area rate 50% or more

(3) Adhesion of paint For each sample, a melamine baking paint (film thickness 30
μm), immersed in boiling water for 2 hours, immediately cut in a grid (10 × 10 grids at 1 mm intervals), adhered and peeled with an adhesive tape, and peeled area of the coating film Rate was evaluated. The evaluation criteria are as follows. ：: No peeling ○: Peeling area rate less than 5% △: Peeling area rate 5% or more, less than 20% ×: Peeling area rate 20% or more

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[Table 1]

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[Table 2]

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[Table 3]

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[Table 4]

[0070]

[Table 5]

[0071]

As described above, the organically coated steel sheet of the present invention contains no hexavalent chromium in the processing solution during production or in the film component of the product, and furthermore, the organic coated steel sheet for use in building materials, home appliances, automobiles, etc. It has high corrosion resistance as a steel sheet,
Excellent paint adhesion.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Satoshi Ando 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Inventor Akihiko Furuta 1-1-2 Marunouchi, Chiyoda-ku, Tokyo Sun Kanko Paint Co., Ltd. (72) Inventor Masaru Sagiyama 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Japan Co., Ltd. (72) Inventor Yasuhiko Haruta 4-171-1, Higashi-Yawata, Hiratsuka-shi, Kanagawa Paint Kansai Paint (72) Inventor Hiroyasu Matsuki 4-171-1, Higashi-Hachiman, Hiratsuka-shi, Kanagawa Paint Inside (72) Kenichi Tomita 4-171-1, Higashi-Yawata, Hiratsuka-shi, Kanagawa Paint Kansai Paint Co., Ltd. F term (reference) 4J038 DB061 JB17 JB32 JB35 NA01 NA03 NA12 PB05 PB07 PB08 PC02 4K062 BB18 BC12 BC21 CA04 FA12 FA16 GA08

Claims (5)

[Claims] An active hydrogen-containing compound (B) comprising a film-forming organic resin (A) and a hydrazine derivative (C) in which some or all of the compounds have active hydrogen on the surface of a zinc-based plated steel sheet or an aluminum-based plated steel sheet. An organic-coated steel sheet having excellent corrosion resistance, characterized by having an organic film having a thickness of 0.1 to 5 μm containing a reaction product of the above. 2. The organic coated steel sheet having excellent corrosion resistance according to claim 1, wherein the film-forming organic resin (A) is an epoxy group-containing resin (D). 3. The method of claim 1, wherein the hydrazine derivative (C) having active hydrogen is a pyrazole compound having active hydrogen and / or
The organic-coated steel sheet having excellent corrosion resistance according to claim 1 or 2, which is a triazole compound having active hydrogen. 4. An excellent corrosion resistance according to claim 1, wherein the hydrazine derivative (C) having active hydrogen is contained in the active hydrogen-containing compound (B) in an amount of 10 to 100 mol%. Organic coated steel sheet. 5. The organic coated steel sheet having excellent corrosion resistance according to claim 2, wherein the epoxy group-containing resin (D) is an epoxy resin represented by the following formula (1). Embedded image