JP2002121469A - Water-based coating composition and coated article coated with the 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) 5 to 50 pts.wt. of a phosphate-based or phosphite-based rustproof pigment modified with a calcium compound, 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, water-based paints and organic solvent-type paints in which a chromium-based rust inhibitor containing a heavy metal or a lead-based rust inhibitor is blended in a large amount with resin components such as epoxy resin, alkyd resin and melamine resin. Attempts have been made to use 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 an aqueous coating composition in which a phosphate-based or phosphite-based rust preventive pigment modified with a compound and a calcium compound is combined, and based on this, the present invention is completed. Reached.

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,
(C) 0.3 to 15 parts by weight of a triazole compound and (D) 5 to 50 parts by weight of a phosphate-based or phosphite-based rust preventive pigment modified with a calcium compound. And a water-based coating composition.

[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 is a phosphate or phosphite modified with the following aqueous resin (A), aqueous melamine resin (B), triazole compound (C) and calcium compound. It contains a rust preventive pigment (D) 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.

Phosphate modified with a calcium compound
-Based or phosphite-based rust-preventive pigment (D) In the composition of the present invention, the rust-preventive pigment used as the component (D) (hereinafter may be abbreviated as “rust-proof pigment (D)”) is And at least one pigment selected from phosphate-based rust-proof pigments and phosphite-based rust-proof pigments modified with a calcium compound. Here, "modified" means that a calcium compound and a phosphate or phosphite are mixed and then heat-treated to cause a partial chemical bond between a calcium atom and a phosphorus atom. .

The phosphate-based rust-preventive pigment modified with the calcium compound (hereinafter sometimes abbreviated as “modified phosphate pigment”) comprises a condensed phosphate which is hardly soluble in water and a calcium compound. It is a rust preventive pigment or a rust preventive pigment comprising a phosphoric acid-based layered compound and a calcium compound. The phosphite-based rust-preventive pigment modified with the calcium compound (hereinafter sometimes abbreviated as “modified phosphite pigment”) is a rust-preventive pigment composed of a phosphite and a calcium compound It is. Both the modified phosphate pigment and the modified phosphite pigment are pollution-free rust-proof pigments containing no harmful metals, and are effective components for improving corrosion resistance and the like.

The water-insoluble condensed phosphate which can constitute the modified phosphate pigment is usually a condensed phosphate used as a rust preventive pigment and has a water solubility of phosphorus ( It is preferable that the amount of P) is 10 g / liter water or less in terms of P ₂ O ₅ . Representative examples of the water-insoluble condensed phosphates include, for example, aluminum pyrophosphate, calcium pyrophosphate, tin pyrophosphate, cerium pyrophosphate, copper pyrophosphate, iron pyrophosphate, titanium pyrophosphate, magnesium pyrophosphate, and pyrophosphate Pyrophosphates such as manganese phosphate; tripolyphosphates such as aluminum dihydrogen triphosphate and iron tripolyphosphate; aluminum metaphosphate, iron metaphosphate, calcium metaphosphate, tin metaphosphate, cerium metaphosphate, manganese metaphosphate, molybdenum metaphosphate, Examples thereof include a metaphosphate such as silver metaphosphate, and aluminum dihydrogen triphosphate and aluminum metaphosphate are particularly preferable from the viewpoint of corrosion resistance and the like. Here, condensed phosphates which are easily soluble in water are not preferred because the long-term maintenance of the corrosion resistance of the cured coating film and the like are reduced.

The phosphoric acid-based layered compound capable of forming the modified phosphate pigment includes M (HPO ₄ ) ₂ .XH ₂ O [herein, a tetravalent metal layered phosphate] M is a tetravalent metal such as Ce, Ti, Zr, and Sn, and X is a number from 0 to 2]. Representative examples of the phosphoric acid-based layered compound include layered cerium phosphate, layered titanium phosphate, layered zirconium phosphate, and layered tin phosphate.

Examples of the calcium compound which can form a modified phosphate pigment by modifying the above-mentioned condensed phosphate which is hardly soluble in water or the above-mentioned phosphoric acid-based layered compound include, for example,
Inorganic calcium salts such as calcium oxide, hydrous calcium hydroxide, calcium carbonate, basic calcium carbonate, calcium phosphate, calcium borate, calcium metaborate and calcium silicate; and organic calcium salts such as calcium stearate and organic calcium sulfonate. it can.

The mixing ratio of the water-insoluble condensed phosphate or the phosphoric acid-based layered compound to the calcium compound in the modified phosphate pigment is 10/10 by weight ratio of the former / the latter.
It is preferable that it is in the range of 1/10/10 from the viewpoint of the corrosion resistance, the effect of improving the paint stability by neutralizing the pH, and the like. The modified phosphate pigment is obtained by mixing the above-mentioned condensed phosphate insoluble in water or the above-mentioned phosphoric acid-based layered compound with a calcium compound and modifying the mixture. Any of mixing may be used.

Examples of the phosphite that can constitute the modified phosphite pigment include metal phosphites such as zinc phosphite, barium phosphite, and manganese phosphite. Among them, zinc phosphite is preferred from the viewpoint of corrosion resistance.

As the calcium compound that can constitute the modified phosphite pigment, those similar to the calcium compound that constitutes the modified phosphate pigment can be used.

The modified phosphite pigment is obtained by modifying the above phosphite by mixing with a calcium compound. In preparing the modified phosphite, the mixing thereof may be either dry mixing or wet mixing. . At this time, the mixing ratio of the phosphite and the calcium compound is 10/1 by weight ratio of the former / the latter.
It is preferable that it is in the range of 〜１０ to 10/10 from the viewpoint of the corrosion resistance, the effect of improving the paint stability by neutralizing the pH, and the like.

Also, one of the modified phosphite pigments,
The zinc phosphite pigment modified with a calcium compound can also be obtained by mixing and reacting a zinc compound, a phosphite compound and a calcium compound. Examples of the zinc compound include zinc oxide, zinc hydroxide, and zinc carbonate. Examples of the phosphorous acid compound include phosphorous acid, zinc hydrogen phosphite, and calcium hydrogen phosphite. Examples thereof include those similar to the calcium compound constituting the modified phosphate pigment.

The amount of the phosphate or phosphite rust preventive pigment (D) modified with the triazole compound (C) and the calcium compound in the composition of the present invention is the same as that of the aqueous resin (A) and the aqueous resin (A). With respect to 100 parts by weight of the total solid content of the aqueous melamine resin (B), it is within the following range from the viewpoint of corrosion resistance of the general part and the edge part of the obtained coated metal base material, water resistance of the coating film, and the like. Appropriate.

Triazole compound (C): 0.3 to 15
Parts by weight, preferably 1 to 10 parts by weight, rust preventive pigment (D): 5 to 50 parts by weight, preferably 10 to 3 parts by weight
0 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 rust preventive pigment (D), and water. Depending on the above, non-chromium rust preventive pigments other than the above components (C) and (D), organic solvents, curing catalysts, coloring pigments, extender pigments, neutralizing agents, defoamers, coating surface conditioners, thickeners, It may contain various additives known per se for coatings such as anti-settling agents.

The chromium-free rust preventive pigments which may be contained as necessary 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 organic solvent, which may be contained as required, is added as necessary to improve the coating properties of the composition of the present invention. 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 pigment 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 and the like, 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 coating 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 content 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.

[0059]

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 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%.

Examples 1 to 8 and Comparative Examples 1 to 6 Production of water-based coating compositions Using the aqueous alkyd resin solution having a non-volatile content of 50% obtained in Production Example 1, the pigments shown in Table 1 (including rust preventive pigments) And the triazole compound were mixed and dispersed in the amounts shown in Table 1 (indicated by non-volatile components), and then the remaining components were added to the obtained dispersion so as to have the composition shown in Table 1, and the mixture was further removed. Ionized water was added to obtain a water-based coating composition of the present invention having a viscosity of about 500 mPa · s (millipascal-second) [measured by a Brookfield viscometer (6 rpm) at 20 ° C] and a comparative example.

[0062]

[Table 1]

In Table 1, (* 1) to (* 8) 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) Rust prevention pigment E: calcium compound-modified aluminum dihydrogen tripolyphosphate mixed with a calcium compound and heat-treated.

(* 4) Rust preventive pigment F: calcium compound-modified zinc phosphite mixed with a calcium compound and heat-treated.

(* 5) Rust preventive pigment G: zinc phosphate.

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

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

(* 8) Triazole compound J: 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 that the cured film thickness was about 30 μm, and was applied at 130 ° C. for 20 minutes. Baking gave a cured coating. Next, the cured coating film was peeled off from the Teflon sheet to obtain a free coating film. This free coating is cut to a width of 5 mm,
A two-layered sample having a thickness of 60 μm was set as a sample, and the length of a measurement portion of the sample was set to 10 mm. The sample was set on a dynamic viscoelasticity measuring machine “UBM-V4” (manufactured by UBM Corporation), and the frequency was measured. 110Hz, static load 10g, amplitude 2.0μm
Under the conditions described above, the temperature was raised from 30 ° C. to 200 ° C. at a rate of 4 ° C./min, dynamic viscoelasticity was measured, and the molecular weight between crosslinks was determined from the results.

Film Performance Test Aqueous coating compositions obtained in Examples 1 to 8 and Comparative Examples 1 to 6 were coated with 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: A 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. 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) な い: No rust was observed in the general part, Δ: Slight rust was observed in the general part, ×: Many rusts were found in the general part Occurrence is observed.

Water Adhesion 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.

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

[0081]

[Table 2]

[0082]

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 water-based coating composition of the present invention can form a coating film having excellent anticorrosion properties without containing heavy metals. Particularly, a coated steel sheet obtained by coating the water-based 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.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int. Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09D 161/28 C09D 167/00 167/00 167/08 167/08 167/08 C23C 28/00 C C23C 28/00 B60K 15/02 Z (72) Inventor Shoji Ogihara 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Hideki Hara 1 Toyota Town Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Invention The person in charge Ito Takeshi 2-1-1 Taoyuan, Ikeda-shi, Osaka Daihatsu Industry Co., Ltd. (72) Inventor Akira Tanahashi 2-1-1 Taoyuan, Ikeda-shi, Osaka Daihatsu Industry Co., Ltd. (72) The inventor Shiiba Satomi 4-17-1, Higashi-Hachiman, Hiratsuka-shi, Kanagawa Pref. Kansai Paint Co., Ltd. (72) Inventor Kazuto Yamamoto 4-171-1, Higashi-Hachiman, Hiratsuka-shi, Kanagawa Kansai-pe Into Co., Ltd. (72) Inventor Yoshitaka Kato 4-171-1, Higashi-Hachiman, Hiratsuka-shi, Kanagawa F Kansai Paint Co., Ltd. F-term (reference) 3D038 CA06 CB01 4D075 CA33 DA23 DB02 DB07 DC13 EB36 EC01 EC15 4J038 DA162 DB371 DD001 DD121 DD231 HA416 JB35 KA05 KA08 KA14 MA08 MA10 MA14 NA03 PA07 PB06 PB07 PB09 PC02 4K044 AA02 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;
A total of 100 parts by weight of 0 to 95 parts by weight and (B) 5 to 50 parts by weight of the aqueous melamine resin was modified with 0.3 to 15 parts by weight of (C) a triazole compound and (D) a calcium compound. An aqueous coating composition comprising 5 to 50 parts by weight of a phosphate or phosphite rust preventive 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.