JP2002121470A - Water-based coating composition and coated article coated with the coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-based coating composition which can form coating films having excellent corrosion resistance on various kinds of metal substrates such as steel plates, galvanized steel plates, and aluminum-plated steel plates without containing a heavy metal. SOLUTION: This water-based coating composition characterized by comprising 100 pts.wt. of a mixture comprising (A) 50 to 95 pts.wt. of at least one kind of water-borne resin selected from water-borne alkyd resins and water- based epoxy ester resins and (B) 5 to 50 pts.wt. of a water-based melamine resin, (C) 0.3 to 15 pts.wt. of a triazole compound, and (D) 3 to 30 pts.wt. of aluminum pigment subjected to a surface treatment for inactivating the pigment against water, and the coated article prepared by coating a metal substrate with the water-based coating composition and then curing the applied coating to form the coating film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel aqueous coating composition capable of forming a coating film having excellent corrosion resistance without containing heavy metals, and a coated article obtained by applying the coating composition to a metal substrate. About.

[0002]

2. Description of the Related Art In recent years, various water-based paints and organic materials have been developed for the purpose of improving the corrosion resistance of metal substrates such as steel sheets, galvanized steel sheets, and zinc alloy-plated steel sheets used for automobile parts, light electrical appliances, general-purpose equipment, and the like. Although a solvent type paint is applied, it is difficult to obtain sufficient corrosion resistance, and there is a strong demand for a paint capable of forming a coating film having excellent corrosion resistance.

[0003] In response to the above-mentioned demands, for example, aqueous paints containing a large amount of a chromium-based rust inhibitor or a lead-based rust inhibitor in a resin component such as an epoxy resin, an alkyd resin or a melamine resin;
Attempts have been made to use organic solvent-based paints.

On the other hand, a lead / tin alloyed plated steel sheet (turn sheet) has been conventionally used as a material for gasoline tanks of automobiles.
However, from the viewpoint of global environmental protection, changing the material from a turn sheet to an aluminum-plated steel sheet such as an aluminum-plated steel sheet or an aluminum alloy-plated steel sheet has been studied. In this case, it is necessary to consider a paint applied to the aluminum-plated steel sheet.

[0005] The paint for turn sheets currently used is usually an organic solvent-based paint or a water-soluble paint containing a chromium-based rust inhibitor in the same resin component as the above-mentioned paint for a metal substrate. However, when applied to an aluminum-plated steel sheet with the composition as it is, there is a problem that the corrosion resistance is significantly inferior to that when applied to a turn sheet.

[0006] In general, organic solvent type paints are CO ₂
It is not preferable from the viewpoint of gas discharge and the like.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a water-based paint composition capable of forming a coating film having excellent corrosion resistance on various metal base materials such as steel plates, galvanized steel plates, and aluminum-plated steel plates without containing heavy metals. To provide things.

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies to obtain an aqueous coating composition which can achieve the above-mentioned object. As a result, a specific aqueous resin and an aqueous melamine resin were added with triazole as a rust preventive. It has been found that the above object can be achieved by a water-based paint prepared by combining a compound and a surface-treated aluminum pigment which is inactivated with respect to water, and the present invention has been completed based on this.

That is, the present invention provides a total of 100 to 50 parts by weight of (A) at least one aqueous resin selected from aqueous alkyd resins and aqueous epoxy ester resins and (B) 5 to 50 parts by weight of an aqueous melamine resin. For parts by weight,
An aqueous coating composition comprising (C) 0.3 to 15 parts by weight of a triazole compound and (D) 3 to 30 parts by weight of a surface-treated aluminum pigment inactivated with water. According to.

[0010] The present invention also relates to a coated article in which a coating film formed by applying and curing the above aqueous coating composition on a metal substrate is formed.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the aqueous coating composition of the present invention will be described.

The aqueous coating composition of the present invention comprises the following aqueous resin (A), aqueous melamine resin (B), triazole compound (C) and a surface-treated aluminum pigment (D) which is inactivated with respect to water. As an essential component. Here, in the present invention, “aqueous” means water-soluble or water-dispersible.

Aqueous Resin (A) The aqueous resin as the component (A) of the composition of the present invention is at least one resin selected from aqueous alkyd resins and aqueous epoxy ester resins.

The aqueous alkyd resin comprises a polybasic acid component,
The resin in which the polyhydric alcohol component and the oil fatty acid are esterified is not particularly limited as long as it is aqueous and has a film forming ability.

The polybasic acid component is selected from, for example, phthalic anhydride, isophthalic acid, terephthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, succinic acid, fumaric acid, adipic acid, sebacic acid, maleic anhydride and the like. One or more dibasic acids and lower alkyl esterified products of these acids are mainly used, and if necessary, tribasic or higher polybasic acids such as trimellitic anhydride, methylcyclohexentricarboxylic acid, and pyromellitic anhydride, etc. Are used together. Further, as the acid component, a monobasic acid such as benzoic acid, crotonic acid, pt-butylbenzoic acid and the like can be used in combination for the purpose of adjusting the molecular weight and the like.

Examples of the polyhydric alcohol component include ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, 3-methylpentanediol, 1,4-hexanediol, and 1,6-hexanediol. Such dihydric alcohols are mainly used, and further, if necessary, glycerin, trimethylolethane, trimethylolpropane,
A trihydric or higher polyhydric alcohol such as pentaerythritol can be used in combination. These polyhydric alcohols can be used alone or in combination of two or more.

Further, a part of the above-mentioned acid component and alcohol component is converted to oxyacid components such as dimethylolpropionic acid, oxypivalic acid, and paraoxybenzoic acid; lower alkyl esters of these acids; and lactones such as ε-caprolactone. It can be replaced.

Examples of the above oil fatty acids include coconut oil fatty acids, soybean oil fatty acids, linseed oil fatty acids, safflower oil fatty acids, tall oil fatty acids, dehydrated castor oil fatty acids, and tung oil fatty acids. The oil length of alkyd resin is 30
% Or less, particularly about 5 to 20%.

The esterification reaction (including the transesterification reaction) of these components can be carried out by a method known per se.

The present invention also includes an epoxy-modified alkyd resin obtained by partially esterifying an epoxy compound with an epoxy compound as a part of an alcohol component, and a vinyl-modified alkyd resin obtained by graft-polymerizing a vinyl monomer such as styrene onto an alkyd resin. Of alkyd resins.

In order to make the alkyd resin aqueous, for example, a method in which the alkyd resin has a high acid value and is neutralized with a basic compound such as an amine compound to make the alkyd resin aqueous, a polyoxyethylene group is contained in the alkyd resin. And the like, a method of self-emulsifying in water by the action of the hydrophilic group, a method of forcibly stirring an alkyd resin in water in the presence of an emulsifier, and a method of dispersing in water, and a method of using these in combination. be able to.

The molecular weight and hydroxyl value of the resin of the aqueous alkyd resin are not particularly limited, but usually, the number average molecular weight is 2,000 to 10,000, and the hydroxyl value is 20 to
It is suitable from the viewpoint of the curability, corrosion resistance, physical properties of the obtained coating film, and the like, when it is within the range of 200 mgKOH / g.

The aqueous epoxy ester resin which can be used as the component (A) in the composition of the present invention is a resin in which an epoxy resin and an acid component are ester-bonded and are stably dissolved or dispersed in water.

As the aqueous epoxy ester resin, for example, a carboxyl group excess reactant obtained by subjecting a carboxyl group-containing polymer such as an acrylic resin to an esterification reaction with an epoxy resin is converted into an aqueous medium in the presence of ammonia or an amine. What is dispersed (for example,
No. 75460, JP-A-55-3481 and JP-A-55-3482); an epoxy resin is partially esterified with a carboxyl group-containing polymerizable unsaturated compound such as (meth) acrylic acid. Copolymerized with an adduct having a polymerizable unsaturated double bond in the molecule obtained and a monomer mixture containing (meth) acrylic acid, and neutralizing the carboxyl group in the obtained copolymer with a basic compound (See, for example, JP-A-57-1010)
No. 5418, JP-A-58-198513); a dibasic acid such as succinic acid, adipic acid, pimelic acid, azelaic acid, sebacic acid, dodecane diacid, hexahydrophthalic acid, etc. is reacted with an epoxy resin. And a resin obtained by neutralizing the carboxyl group of the resulting resin with a basic compound and dispersing the resin in an aqueous medium.

Examples of the epoxy resin used for producing the above-mentioned aqueous epoxy ester resin include a bisphenol type epoxy resin and a novolak type epoxy resin. Bisphenol-type epoxy resin, for example, a resin obtained by condensing epichlorohydrin and bisphenol to a high molecular weight in the presence of a catalyst such as an alkali catalyst, if necessary, epichlorohydrin and bisphenol,
If necessary, a low molecular weight epoxy resin is condensed in the presence of a catalyst such as an alkali catalyst, and any of the resins obtained by subjecting this low molecular weight epoxy resin and bisphenol to a polyaddition reaction to obtain a high molecular weight. It may be.

As the above bisphenol, bis (4-
Hydroxyphenyl) methane [common name: bisphenol F], 1,1-bis (4-hydroxyphenyl) ethane, 2,2-bis (4-hydroxyphenyl) propane [common name: bisphenol A], 2,2-bis (4-hydroxyphenyl) butane [common name: bisphenol B], bis (4-hydroxyphenyl) -1,1-isobutane, bis (4-hydroxy-tert-butyl-phenyl) -2,2-propane, p- (4-hydroxyphenyl) phenol, oxybis (4-hydroxyphenyl), sulfonylbis (4-hydroxyphenyl),
4,4'-dihydroxybenzophenone, bis (2-hydroxynaphthyl) methane and the like can be mentioned. Among them, bisphenol A and bisphenol F are preferably used. The above bisphenols can be used alone or as a mixture of two or more.

Examples of the novolak type epoxy resin usable as the epoxy resin include various types such as phenol novolak type epoxy resin, cresol novolak type epoxy resin, and phenol glyoxal type epoxy resin having a large number of epoxy groups in the molecule. Novolak type epoxy resins can be mentioned.

In the composition of the present invention, the number-average molecular weight and hydroxyl value of the aqueous epoxy ester resin which can be used as the component (A) are not particularly limited.
Number average molecular weight 2,000 to 10,000, hydroxyl value 20
It is preferable that it is in the range of 200 mgKOH / g from the viewpoints of curability, corrosion resistance, physical properties of the coating film and the like of the obtained coating film.

As the aqueous resin (A), it is particularly preferable to use a mixture of a water-soluble alkyd resin and a water-dispersible epoxy ester resin from the viewpoints of paintability, curability, coating film properties and the like. The mixing ratio of the water-soluble alkyd resin and the water-dispersible epoxy ester resin is, based on the total solid content of both, 90/10 to 2 in terms of the former / the latter solid content weight ratio.
It is preferably in the range of 0/80, particularly 80/20 to 40/60.

Aqueous Melamine Resin (B) The aqueous melamine resin which is the component (B) of the composition of the present invention comprises:
A methylolated melamine resin and a methylolated melamine, which act as a curing agent that reacts with the aqueous resin (A) and can be dissolved or dispersed in the composition of the present invention, and are obtained by reacting melamine with an aldehyde. Among etherified melamine resins obtained by etherifying a resin with an appropriate alcohol, those having water solubility or water dispersibility can be mentioned. Examples of the aldehyde used in the above reaction include formaldehyde, paraformaldehyde, acetaldehyde, benzaldehyde and the like. Examples of the alcohol used for the etherification include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, etc. Among them, methyl alcohol is preferably used. These melamine resins can be used alone or in combination of two or more.

In the composition of the present invention, the mixing ratio of the aqueous resin (A) and the aqueous melamine resin (B) is as follows:
In 100 parts by weight of the total solid content of (A) and (B), the aqueous resin (A) is 50 to 95 parts by weight, preferably 65 to 90 parts by weight, the aqueous melamine resin (B) is 5 to 50 parts by weight, It is preferably in the range of 10 to 35 parts by weight from the viewpoint of curability, corrosion resistance and the like.

Triazole Compound (C) In the composition of the present invention, the triazole compound as the component (C) is used in a metal substrate, especially an aluminum-plated steel plate and an aluminum alloy-plated steel plate, in a general portion and an edge portion which is an end surface. It is an effective component for improving water resistance.

As the triazole compound (C), for example, 1,2,4-triazole, 3-amino-1,2,2,
4-triazole, 4-amino-1,2,4-triazole, 3-mercapto-1,2,4-triazole,
-Amino-3-mercapto-1,2,4-triazole, 1H-benzotriazole, 1-hydroxybenzotriazole and the like.

Surface treated to be inactive against water
Aluminum pigment (D) used as the component (D) in the composition of the present invention;
BACKGROUND ART A surface-treated aluminum pigment which is inactivated with respect to water (hereinafter, may be abbreviated as "surface-treated aluminum pigment (D)") reacts with water in a dispersion medium in an aqueous coating composition. The surface of the aluminum pigment is subjected to a surface treatment in order to suppress the water content, and the surface of the aluminum pigment is inactivated with respect to water, whereby the aluminum pigment is stabilized with respect to water.

Examples of the surface treating agent used for the surface treatment of the aluminum pigment surface include a phosphoric acid group-containing polymerizable unsaturated monomer, a hydroxyl group-containing polymerizable unsaturated monomer, and other polymerizable copolymerizable with these monomers. A phosphoric acid group-containing copolymer obtained by copolymerizing an unsaturated monomer can be suitably used, and the copolymer is usually preferably used as an organic solvent solution.

The phosphoric acid group-containing polymerizable unsaturated monomers include (2-acryloyloxyethyl) acid phosphate, (2-acryloyloxypropyl) acid phosphate, (2-methacryloyloxyethyl) acid phosphate, and (2-methacryloyl). (Oxypropyl) acid phosphate and the like. The hydroxyl group-containing polymerizable unsaturated monomer is used for the purpose of introducing a hydroxyl group capable of reacting with the aqueous melamine resin contained in the aqueous coating composition and the like. Examples of the monomer include 2-hydroxyethyl acrylate, Examples thereof include -hydroxypropyl acrylate, 2-hydroxybutyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, and 2-hydroxybutyl methacrylate. Other polymerizable unsaturated monomers copolymerizable with these monomers include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, and 2-ethylhexyl. (Meth) acrylic acid alkyl esters such as methacrylate; carboxyl group-containing unsaturated monomers such as acrylic acid, methacrylic acid, propylacrylic acid, isopropylacrylic acid, crotonic acid, maleic anhydride and fumaric acid; styrene, acrylonitrile, etc. it can.

The copolymer of these polymerizable unsaturated monomers can be prepared by a usual polymerization method using a known polymerization initiator. Examples of the polymerization initiator include azo-based initiators such as azobisisobutyronitrile, 2,2′-azobis (methylvaleronitrile) and azocumene, and peroxides such as cyclohexanone peroxide, cumene hydroperoxide and lauroyl peroxide. Examples include a system polymerization initiator. The acid value of the obtained phosphate group-containing copolymer is
It is preferably about 20 to 200 mgKOH / g,
Of these acid values, the acid value based on the phosphoric acid group-containing polymerizable unsaturated monomer is desirably about 10 to 150 mgKOH / g. Further, the hydroxyl value of the copolymer is from 20 to 2
It is preferably about 00 mg KOH / g, and the number average molecular weight is preferably about 2,000 to 30,000.

When the above-mentioned phosphoric acid group-containing copolymer is used as a surface treating agent, it is usually prepared as a solution of a hydrophilic organic solvent such as an ester, alcohol or ketone.
It is preferred to use. As these organic solvents,
Usually, what is used at the time of preparing the copolymer may be used as it is, but may be added as needed after preparing the copolymer. Examples of the organic solvent include ester organic solvents such as ethylene glycol monoethyl ether acetate, ethylene glycol monoisobutyl ether acetate, methoxypropyl acetate, and ethyl acetate, ethyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, and ethylene. Alcohol-based organic solvents such as glycol, propylene glycol and hexylene glycol; ether-alcohols such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monopropyl ether and 3-methoxy-3-methylbutanol Organic solvents, ketones such as methyl ethyl ketone, methyl isobutyl ketone, and diacetone alcohol It can be exemplified machine solvent, etc., but appropriately xylene, and toluene may be used.

Further, since the coating composition of the present invention is aqueous, the above-mentioned phosphoric acid group-containing copolymer is, for example, ammonia; triethylamine, ethanolamine, N, N-dimethylethanolamine, dimethylamine, dimethylethanolamine, The neutralization treatment is preferably performed using an organic amine such as diisopropylamine and dipropylamine. The neutralization treatment can be performed simultaneously with or before or after the surface treatment of the aluminum pigment. Of course, it may be carried out immediately after preparing the copolymer.

The surface treatment of the aluminum pigment using the above-mentioned surface treating agent can be performed, for example, by adding the aluminum pigment to an organic solvent solution of the phosphoric acid group-containing copolymer with stirring and uniformly mixing. Thereby, the surface of the aluminum pigment can be surface-treated by adsorbing and coating the surface of the pigment with the copolymer by the action of the phosphoric acid group in the copolymer.

As the aluminum pigment to be surface-treated, any known aluminum pigment used in the field of paints can be used without particular limitation. The shape of the aluminum pigment is preferably scaly, and the particle size is not particularly limited, but is usually preferably 100 μm or less.

By blending the surface-treated aluminum pigment (D) in the composition of the present invention, the aluminum pigment is densely arranged in a coating film formed from the composition of the present invention, and the water content and the like in the coating film are reduced. Permeation of corrosive substances can be suppressed and corrosion resistance can be improved.

The compounding amount of the triazole compound (C) and the surface-treated aluminum pigment (D) in the composition of the present invention is based on 100 parts by weight of the total solid content of the aqueous resin (A) and the aqueous melamine resin (B). Within the following range, it is appropriate from the viewpoint of the corrosion resistance of the general portion and the edge portion of the obtained coated metal substrate, the water resistance of the coating film, and the like.

Triazole compound (C): 0.3 to 15
Parts by weight, preferably 1 to 10 parts by weight, surface-treated aluminum pigment (D): 3 to 30 parts by weight, preferably 5 to 20 parts by weight.

The composition of the present invention is characterized in that the cured coating film formed from the composition of the present invention has a molecular weight between crosslinks of 500 to 2,000.
0, preferably in the range of 650 to 1,500 is suitable from the viewpoint of the corrosion resistance and impact resistance of the obtained coating film.

The coating composition of the present invention can be substantially composed of the aqueous resin (A), the aqueous melamine resin (B), the triazole compound (C), the surface-treated aluminum pigment (D) and water. If necessary, the above (C)
Non-chromium rust preventive pigments other than the component and the component (D), organic solvents, curing catalysts, coloring pigments, extender pigments, neutralizing agents, defoamers,
It may contain various additives known per se for coatings such as a coating surface adjuster, a thickener, and an antisettling agent.

The chromium-free rust preventive pigments which may be contained as required include, for example, zinc oxide, zinc phosphate,
Zinc phosphorus silicate, zinc aluminum phosphate, calcium zinc phosphate, zinc zinc calcium, mixed with zinc compounds, heat-treated aluminum polyphosphate, zinc calcium molybdate, zinc molybdate, zinc phosphomolybdate, aluminum phosphomolybdate, etc. Can be mentioned. When the non-chromium rust preventive pigment is blended, the blending amount is within a range of 50 parts by weight or less based on 100 parts by weight of the total solid content of the aqueous resin (A) and the aqueous melamine resin (B). Is appropriate.

The above-mentioned organic solvent which may be contained as necessary is blended as necessary for improving the coating property of the composition of the present invention, and the above-mentioned aqueous resin (A) and aqueous melamine are used. A hydrophilic organic solvent capable of dissolving or dispersing the resin (B) in water is suitably used. Specifically, for example,
Examples thereof include ether solvents such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether and diethylene glycol monobutyl ether, alcohol solvents such as methanol, ethanol, isopropanol and butanol, and acetone. These may be used alone or in combination of two or more. Can be used in combination.

The curing catalyst is optionally blended to accelerate the curing of the resin component such as the reaction between the aqueous resin (A) and the aqueous melamine resin (B). An amine-neutralized acid compound is suitably used. Representative examples of the sulfonic acid compound include p-
Examples thereof include toluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, and dinonylnaphthalenedisulfonic acid. As the amine in the amine neutralized product of the sulfonic acid compound, primary amine, 2
Any of a tertiary amine and a tertiary amine may be used. Among these, an amine neutralized product of p-toluenesulfonic acid and / or an amine neutralized product of dodecylbenzenesulfonic acid are preferred from the viewpoints of paint stability, reaction promoting effect, and physical properties of the obtained coating film. is there. When the aqueous resin (A) is an aqueous alkyd resin and the oil fatty acid constituting the resin is a drying oil fatty acid or a semi-dry oil fatty acid, a naphthene is used as a curing catalyst to promote oxidative polymerization. Metallic desiccants such as zinc acid and cobalt naphthenate can also be used.

When a curing catalyst is blended, the aqueous resin (A)
Usually, it is preferable to mix within a range of 0.1 to 2.0 parts by weight based on 100 parts by weight of the total solid content of the melamine resin and the aqueous melamine resin (B).

Examples of the coloring pigments which may be contained as required include those which are known per se in the field of paints. Examples of the extender which may be contained as necessary include barium sulfate. , Calcium carbonate, a mixed crystal of calcium carbonate and magnesium carbonate, and the like can be suitably used from the viewpoint of coating film hardness, coating film properties, coating film adhesion, and the like. The blending amount of the extender pigment is not particularly limited, but is usually 200 parts by weight or less, preferably 30 to 150 parts by weight based on 100 parts by weight of the total amount of the film-forming resin component.
Used in parts by weight.

Next, a method for applying the coating composition of the present invention will be described.

The coating composition of the present invention can be applied to, for example, metal, mortar, cement, plastics, glass, etc., and can be suitably applied to a metal substrate, especially a steel plate. Cold-rolled steel sheet,
Hot dip galvanized steel sheet, electro galvanized steel sheet, zinc alloy coated steel sheet, aluminum plated steel sheet, aluminum alloy plated steel sheet, stainless steel sheet, copper plated steel sheet, tin plated steel sheet, lead-tin alloy plated steel sheet (turn sheet), etc. Examples of the steel sheet include a steel sheet which has been subjected to a chemical conversion treatment such as a phosphate treatment or a chromate treatment and / or an organic film treatment. As the steel sheet subjected to the chemical conversion treatment and / or the organic coating treatment, the above steel sheet was subjected to a chemical conversion treatment, an organic coating treatment, and an organic coating treatment after a chemical conversion treatment such as a chromate treatment. And the like. Acrylic emulsion,
Film formation using a film-forming agent containing a resin such as a phenoxy resin or an epoxy resin as a main component, and the like can be given. The thickness of the organic film in the organic film treatment is not particularly limited, but is usually about 0.3 to 3 μm.

Among the substrates to be coated, chemical conversion treatment and / or
Alternatively, an aluminum-plated steel sheet or an aluminum alloy-plated steel sheet which may be subjected to an organic coating treatment can be particularly preferably used. These steel sheets may be in the form of a sheet before being processed or may be formed.

The paint composition of the present invention is suitably used as an undercoat paint or a one-coat finish paint, and is applied onto a steel plate or the like to be coated by a shower coating method, a roll coating method, a spray method, a brush coating method, a dipping method. Can be applied by a known method such as

The coating composition of the present invention has a solid concentration of about 20 to 50% by weight, preferably about 30 to 40% by weight, especially when applied by a shower coat method. Brookfield viscometer (6)
rpm) is 100-1500 mP
about a · s, preferably 300 to 1,000 mPa · s
The degree is appropriate.

The thickness of the coating film obtained from the composition of the present invention is
Although not particularly limited, when used as an undercoat, as a cured coating, usually about 2 to 40 μm,
It is preferably in the range of 5 to 30 μm, and when used as a one-coat finish paint, it is usually about 8 to 50 μm,
Preferably it is in the range of 10 to 40 μm. The curing of the coating film of the composition of the present invention is usually performed when the material coated by a coil coating method or the like is continuously baked.
The condition is 0 to 230 ° C. for about 15 to 60 seconds, and when baking in a batch mode, it is usually 80 to 16 seconds.
It can be performed by baking at about 0 ° C. for about 10 to 30 minutes.

[0058]

EXAMPLES Hereinafter, Production Examples, Examples and Comparative Examples will be given,
The present invention will be described more specifically. In each example,
“Parts” and “%” are in principle based on weight.

Production Example 1 Preparation of Alkyd Resin Oil length 4 modified with tall oil fatty acid and linseed oil fatty acid
2%, an alkyd resin having an acid value of 40 mgKOH / g is neutralized with triethylamine in an equivalent amount, and the non-volatile content is 68
%, And then ethylene glycol monobutyl ether was added to obtain an aqueous alkyd resin solution having a nonvolatile content of 50%.

Production Example 2 Preparation of surface-treated aluminum pigment In a stirred vessel, "Aluminum Paste 0780M" (trade name, manufactured by Toyo Aluminum Co., Ltd., flake aluminum having a sieve with a 44 μm opening and a sieve residue of 0.5% or less) Powder 64-6
40 parts of ethylene glycol monobutyl ether was added to 30 parts of 7%, 30-35% of mineral spirits and 30 parts of aluminum pigment paste comprising a small amount of stearic acid as a leafing aid, and sufficiently stirred. To this, 25 parts (12.5 parts in solid content) of a 50% ethylene glycol monobutyl ether solution of the following acrylic resin, which is a phosphoric acid group-containing copolymer, was added, and triethylamine 2.6 was further added.
Of the surface-treated aluminum pigment solution (D-1). The obtained surface-treated aluminum pigment solution (D-1) had a nonvolatile content of about 34% and an aluminum pigment content of about 21%.

The acrylic resin, which is a phosphoric acid group-containing copolymer, has a monomer component of (2-acryloyloxyethyl) acid phosphate 20 parts, 2-hydroxyethyl methacrylate 20 parts, styrene 38 parts, n-
20 parts of butyl acrylate and 2 parts of methacrylic acid and an acid value of 115 mgKOH / g (of which the acid value based on a phosphoric acid group-containing polymerizable unsaturated monomer is 100 m
gKOH / g), and the hydroxyl value is 86 mgKOH / g.
g, and the number average molecular weight is 4,800.

Production Example 3 Preparation of Surface-treated Aluminum Pigment In Production Example 1, "Aluminum paste 0780M" 30
Part, "Aluminum paste 4-621" (trade name,
Asahi Kasei Metals Co., Ltd., 66% scaly aluminum powder having a sieve residue of 3% or less with 44 μm aperture, 33% mineral spirits, and stearic acid 1 as a leafing aid.
% Aluminum pigment paste), except that 30 parts were used, to obtain a surface-treated aluminum pigment solution (D-2). The obtained surface-treated aluminum pigment solution (D-2) had a nonvolatile content of about 34% and an aluminum pigment content of about 21%.

EXAMPLES 1 TO 8 AND COMPARATIVE EXAMPLES 1 TO 6 Preparation of aqueous coating compositions Using the aqueous alkyd resin solution having a nonvolatile content of 50% obtained in Production Example 1, the pigments shown in Table 1 (including surface-treated aluminum pigments) ) And the triazole compound were mixed and dispersed in the amounts shown in Table 1 (indicated by the nonvolatile content), and then
The remaining components were added to the obtained dispersion so as to have the composition shown in Table 1, and deionized water was further added to obtain a viscosity of about 500 mP.
Each of the aqueous coating compositions of the present invention and comparative samples having a · s (millipascal-second) [measured by a Brookfield viscometer (6 rpm) at 20 ° C.] was obtained.

[0064]

[Table 1]

In Table 1, (* 1) to (* 5) have the following meanings.

(* 1) Aqueous epoxy ester resin: an epoxy ester emulsion having a non-volatile content of 40%, manufactured by "CD540" (trade name, manufactured by Dainippon Ink and Chemicals, Inc.).

(* 2) Aqueous melamine resin: methyl etherified melamine resin.

(* 3) Triazole compound E: 3-amino-1,2,4-triazole.

(* 4) Triazole compound F: 3-mercapto-1,2,4-triazole.

(* 5) Triazole compound G: 3-mercapto-5-amino-1,2,4-triazole.

Next, the measurement of the molecular weight between crosslinks of the cured coating films of the aqueous coating compositions of Examples 1 to 8 and Comparative Examples 1 to 6 and the coating film performance tests of adhesion, corrosion resistance and water adhesion were carried out as follows. I went.

Measurement of molecular weight between crosslinks Each of the coating compositions obtained in Examples 1 to 8 and Comparative Examples 1 to 6 was applied to a Teflon sheet so as to have a cured film thickness of about 30 μm, and baked at 130 ° C. for 20 minutes. Thus, a cured coating film was obtained.
Next, the cured coating film was peeled off from the Teflon sheet to obtain a free coating film. This free coating film was cut into a width of 5 mm, and two pieces were stacked to a thickness of 60 μm to obtain a sample. The length of a measurement portion of the sample was set to 10 mm.
MV4 "(manufactured by UBM Co., Ltd.), and heated at a rate of 4 ° C./min from 30 ° C. to 200 ° C. under the conditions of a frequency of 110 Hz, a static load of 10 g, and an amplitude of 2.0 μm. Viscoelasticity was measured and the molecular weight between crosslinks was determined from the results.

Coating Performance Test The aqueous coating compositions obtained in Examples 1 to 8 and Comparative Examples 1 to 6 were coated on a 1.0 mm- thick aluminum-plated steel sheet (trade name: ULSTER, manufactured by Nissin Steel Co., Ltd.). ) Was applied by a dip coating method and baked at 130 ° C. for 20 minutes to prepare a test coated plate. Each of the cured film thicknesses was about 25 μm.
Various coating film performance tests were performed on the obtained test coated plates based on the following test methods.

Adhesion: JIS K-5400 8.5.
2 (1990) In accordance with the grid-tape method, 11 parallel vertical and horizontal lines are drawn at 1 mm intervals on the surface of the coating film of the test coating plate so as to reach the substrate with a cutter knife at 1 mm intervals. 100 × 1 mm squares were created. A cellophane adhesive tape was adhered to the surface, and the degree of peeling of the squares when the tape was abruptly peeled was observed and evaluated according to the following criteria.

：: No peeling of the coating film was observed at all. Δ: The coating film was slightly peeled, but 90 or more squares remained. ×: The coating film was significantly peeled, and the number of remaining squares was less than 90. .

Corrosion resistance: The test coated plate was cut into a size of 75 × 150 mm, and subjected to a salt spray test for 840 hours in accordance with JIS Z-2371, and the coated plate after the test was visually inspected for the degree of rusting in the general part. Edge rust width (mm), which is evaluated according to the following criteria and is the maximum rust width from the edge
Was measured.

(A degree of rusting and rusting in the general part) 錆: No rust is generated in the general part, Δ: Slight rust is generated in the general part, ×: Many rusts are generated in the general part Occurrence is observed.

Water resistance: The test coated plate was placed in warm water of 40 ° C. for 1 hour.
After immersion for 20 hours, JIS K-5400 8.5.2.
(1990) In accordance with the crosscut-tape method, 11 parallel vertical and horizontal straight lines were drawn at 1 mm intervals on the surface of the coating film of the test coating plate so as to reach the substrate with a cutter knife at 1 mm intervals. 100 1 mm squares were created. A cellophane adhesive tape was brought into close contact with the surface, and the degree of peeling of the squares when the tape was abruptly peeled was observed and evaluated according to the same criteria as in the above-mentioned adhesion test.

The measurement results of the molecular weight between crosslinks, the adhesion,
Table 2 shows the results of the corrosion resistance and water resistance coating film performance test results.

[0080]

[Table 2]

[0081]

The coating composition of the present invention is aqueous,
Since it does not need to contain heavy metals, it is advantageous from the viewpoint of pollution prevention.

The aqueous coating composition of the present invention can form a coating film having excellent anticorrosion properties without containing heavy metals. Particularly, a coated steel sheet prepared by coating the aqueous coating composition of the present invention on an aluminum-based plated steel sheet Shows extremely good corrosion resistance even in the general part and the edge part, and also has good water adhesion resistance. Therefore, it is possible to replace a turnsheet coated plate containing harmful lead with an aluminum-plated steel plate coated plate by using the aqueous coating composition of the present invention, which is advantageous from the viewpoint of global environmental protection.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) C09D 161/28 C09D 167/00 167/00 167/08 167/08 C23C 28/00 C C23C 28/00 B60K 15/02 A (72) Inventor Shoji Ogiwara 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Hideki Hara 1 Toyota Town Toyota City, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation (72) Inventor Tsutomu Ito Daihantsu Industry Co., Ltd., 2-1-1, Taoyuan, Ikeda-shi, Osaka (72) Inventor Akira Tanahashi 2-1-1 Taoyuan, Ikeda-shi, Osaka, Japan Inside Daihatsu Industry Co., Ltd. (72) Inventor, Satomi Shiiba Kanagawa Kansai Paint Co., Ltd., 4-171-1, Higashi-Hachiman, Hiratsuka-shi (72) Inventor Kazuto Yamamoto 4-17-1, Higashi-Hachiman, Hiratsuka-shi, Kanagawa Pref. Kansai Paint Co., Ltd. (72) Inventor Yoshitaka Kato 4-17-1, Yawata Kansai Paint Co., Ltd. F term (reference 3D038 CA06 CB01 CC19 4D075 CA33 DA23 DB02 DB07 DC13 EA06 EB36 EB52 EC10 EC15 4J038 DA162 DB371 DD001 DD121 DD231 HA066 HA156 JB35 KA08 KA14 MA08 MA10 MA14 NA03 PA07 PB06 PB07 PB09 PC02 4K044 AA02 AB02 BA10 BA15 BA17 BA21 BB04 BC02 BC04 CA11 CA16 CA53

Claims (6)

[Claims] (A) at least one aqueous resin selected from the group consisting of an aqueous alkyd resin and an aqueous epoxy ester resin;
0 to 95 parts by weight and (B) 5 to 50 parts by weight of the aqueous melamine resin, for a total of 100 parts by weight, 0.3 to 15 parts by weight of the (C) triazole compound and (D) inactivated against water. An aqueous coating composition comprising 3 to 30 parts by weight of a surface-treated aluminum pigment. 2. The aqueous coating composition according to claim 1, wherein the molecular weight between crosslinks of the cured coating film obtained from the coating composition is in the range of 500 to 2,000. 3. The aqueous coating composition according to claim 1, wherein the aqueous resin (A) is a mixture of a water-soluble alkyd resin and a water-dispersible epoxy ester resin. 4. A coated article having a coating formed by coating and curing the aqueous coating composition according to claim 1 on a metal substrate. 5. The coated article according to claim 4, wherein the metal substrate is an aluminum-plated steel sheet or an aluminum alloy-plated steel sheet which may be subjected to a chemical conversion treatment and / or an organic coating treatment. 6. The coated article according to claim 4, wherein the metal base is processed into an automobile gasoline tank.