JPH1119585A - Method for coating metal plate and coated metal plate using this method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for coating a metal plate which moves continuously by which it is possible to form a coat with a three-dimensional design appearance, crape-like pattern and beautifully decorative properties without increasing the frequency of baking process. SOLUTION: A top colored base coating and a top clear coating are applied by wet-on-wet coating on a long-size metal plate which moves continuously and these coatings are baked to form the top clear coat on the top colored base coat. In this coating method, the top colored base coating is a coating which contains fine colored organic resin particles with an average particle diameter of 5-80 μm and the top clear coating is a coating which generates a uniformly crepe-like pattern on the surface of the coating at the time of curing the coat.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for coating a continuously moving long metal plate having a metallic appearance and capable of forming a coating film having excellent aesthetics, and a coated metal plate.

[0002]

2. Description of the Related Art In recent years,
In the field of pre-coated metal sheets for building materials and container processing, coated metal sheets with excellent aesthetics are also required, and large amounts of top coatings and inorganic fine particles containing organic resin fine particles with a large particle diameter are required. There is a marketed on the market, such as a finished topcoat, or a matte-coated metal plate coated with a topcoat paint that mixes an amine compound and forms shrinkage by utilizing the difference in curing speed between the surface of the coating and the inside of the coating. In addition, a metallic coated metal plate coated with a top coat in which aluminum powder or glittering mica powder is mixed into the top coat is also on the market.

[0003] These matte-painted metal sheets and metallic coated metal sheets are popular in the market, but on the other hand, coated metal sheets having even better aesthetics are required.

[0004] The above-mentioned matte-painted metal plate and metallic-coated metal plate are formed by coating a primer and the above-mentioned top coat with two coats and two bake on a metal plate such as a galvanized steel plate. There is naturally a limit to improving cosmetics by using this method.

Until now, in the field of pre-coated metal sheets, paint has been applied on a metal sheet or a cured coating layer, so that two paint layers are in contact with each other in a wet-on-wet manner. Painting has not been put to practical use.

[0006] In the field of pre-coated metal sheets, the present inventors have made it possible to form a two-layer top coat and make a wet-on-wet contact between the two top coats without deteriorating the coating performance. On the formation of a coating film with excellent aesthetics by painting on the surface. As a result, it has been found that a topcoat two-layer coating film having excellent aesthetics can be formed by incorporating colored organic resin fine particles containing a color pigment in the topcoat colored base paint, and the present invention has been completed. .

[0007]

That is, the present invention provides a method for applying a top-coating colored base coating and a top-coating clear coating on a continuously moving long metal plate with or without a primer-cured coating film. And baking to form a topcoat clear coating on the topcoat basecoat, wherein the topcoat clearcoat is formed wet-on-wet on the topcoat basecoat and the topcoat The base paint is a paint containing colored organic resin fine particles having an average particle diameter of 5 to 80 μm which does not completely melt by baking at the time of forming a coating film and contains a coloring pigment. An object of the present invention is to provide a method for coating a metal plate, which is a paint that generates a uniform shrinkage pattern on the surface of a coating film.

[0008] The present invention also provides a coated metal plate coated by the above coating method.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the method of the present invention will be described in more detail.

The object to be coated in the method of the present invention is a long metal plate used in the field of a precoated steel sheet, and examples of the material include a cold-rolled steel sheet, a galvanized steel sheet, an aluminum sheet and a stainless steel sheet. Can be. Examples of the galvanized steel sheet include hot-dip galvanized steel sheet, electro-galvanized steel sheet, iron-zinc alloy-plated steel sheet, nickel-zinc alloy-plated steel sheet, and aluminum-zinc alloy-plated steel sheet (for example, trade names such as “Galvalume” and “Galphan”). Plated steel sheet). These metal plates may be those whose surfaces have been subjected to a chemical conversion treatment such as a phosphate treatment, a composite oxide film treatment, and a chromate treatment.

In the method of the present invention, a top-coating colored base coating and a top-coating clear coating may be applied directly or via a primer-cured coating on the long metal plate.

The formation of the primer-cured coating film can be carried out, for example, by applying a primer on a metal plate by a roll coater or the like so that the dry film thickness is about 1 to 15 μm, and baking and drying. The primer coating film is formed for the purpose of improving the corrosion resistance of the resulting coated metal plate, improving the adhesion of the coating film, and the like. Examples of the primer include polyester primers and epoxy primers.These primers contain rust preventive pigments such as strontium chromate, calcium chromate, zinc chromate, barium chromate, and zinc phosphate. You may.

[0013] topcoat colored base coating process of this invention the base resin of topcoat colored base coating film-forming resin used in, the present invention is not particularly limited, polyester resin, silicone polyester resin, acrylic resin, such as fluororesin One or a mixture of two or more thereof can be mentioned.

Among the above-mentioned base resins, a polyester resin can be suitably used. The polyester resin preferably contains a hydroxyl group, and includes an oil-free polyester resin, an oil-modified alkyd resin, and modified products of these resins, for example, a urethane-modified polyester resin, a urethane-modified alkyd resin, an epoxy-modified polyester resin, and an acrylic-modified resin. A polyester resin is exemplified.

The above-mentioned oil-free polyester resin comprises an esterified product of a polybasic acid component and a polyhydric alcohol component. As the polybasic acid component, for example, one or more selected from phthalic anhydride, isophthalic acid, terephthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, succinic acid, fumaric acid, adipic acid, sebacic acid, maleic anhydride, and the like Dibasic acids and lower alkyl esterified products of these acids are mainly used, and if necessary, monobasic acids such as benzoic acid, crotonic acid, pt-butylbenzoic acid, trimellitic anhydride, methylcyclohexenetricarboxylic acid And tribasic or higher polybasic acids such as pyromellitic anhydride. Examples of the polyhydric alcohol component include ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol,
Dihydric alcohols such as neopentyl glycol, 3-methylpentanediol, 1,4-hexanediol, and 1,6-hexanediol are mainly used, and if necessary, glycerin, trimethylolethane, trimethylolpropane, and pentane. A trihydric or higher polyhydric alcohol such as erythritol can be used in combination. These polyhydric alcohols can be used alone or in combination of two or more. The esterification or transesterification of both components can be carried out by a method known per se. As the acid component, isophthalic acid, terephthalic acid,
And lower alkyl esters of these acids are particularly preferred.

The alkyd resin is obtained by reacting an oil fatty acid by a method known per se in addition to the acid component and the alcohol component of the above-mentioned oil-free polyester resin. Soybean oil fatty acids, linseed oil fatty acids, safflower oil fatty acids, tall oil fatty acids, dehydrated castor oil fatty acids, kiri oil fatty acids and the like can be mentioned. The oil length of the alkyd resin is preferably 30% or less, particularly preferably about 5 to 20%.

As the urethane-modified polyester resin,
The oil-free polyester resin, or a low-molecular-weight oil-free polyester resin obtained by reacting an acid component and an alcohol component used in the production of the oil-free polyester resin, reacts with a polyisocyanate compound by a method known per se. Examples include: Further, the urethane-modified alkyd resin, the alkyd resin, or a low molecular weight alkyd resin obtained by reacting each component used in the production of the alkyd resin was reacted with a polyisocyanate compound by a method known per se. Things are included. Examples of polyisocyanate compounds that can be used when producing urethane-modified polyester resin and urethane-modified alkyd resin include hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate,
4,4'-methylenebis (cyclohexyl isocyanate), 2,4,6-triisocyanatotoluene, and the like. In general, as the urethane-modified resin, those having a modification degree in which the amount of the polyisocyanate compound forming the urethane-modified resin is 30% by weight or less based on the urethane-modified resin can be suitably used.

As the epoxy-modified polyester resin,
Using a polyester resin produced from each component used in the production of the above polyester resin, a reaction product of a carboxyl group of this resin and an epoxy group-containing resin, and a hydroxyl group in the polyester resin and a hydroxyl group in the epoxy resin are polyisocyanate. Reaction products such as addition, condensation, and grafting of a polyester resin and an epoxy resin, such as a product bonded via a compound, can be given.
In general, the degree of modification in such an epoxy-modified polyester resin is preferably such that the amount of the epoxy resin is 0.1 to 30% by weight based on the epoxy-modified polyester resin.

As the acrylic-modified polyester resin,
Using a polyester resin produced from each component used in the production of the polyester resin, a group having a reactivity with these groups to a carboxyl group or a hydroxyl group of the resin, such as an acrylic resin containing a carboxyl group, a hydroxyl group or an epoxy group. And a reaction product obtained by graft polymerization of (meth) acrylic acid or (meth) acrylic ester on a polyester resin using a peroxide-based polymerization initiator. The degree of modification in such an acrylic-modified polyester resin is generally
It is preferable that the amount of the acrylic resin is 0.1 to 50% by weight based on the acrylic-modified polyester resin.

Among the polyester resins described above, a preferable one is an oil-free polyester resin. Among the polyester resins, the following polyester resin (A) is preferable from the viewpoint of processability, curability, and the like.

The polyester resin (A) has a number average molecular weight of 1,500 to 35,000, preferably 3,000 to 2
5,000, glass transition temperature (Tg point) -30 to 60
° C, preferably -20 ° C to 35 ° C, hydroxyl value 3 to 100
It is a polyester resin having a mgKOH / g, preferably 8 to 70 mgKOH / g.

In the present invention, the glass transition temperature (Tg)
Is measured by differential thermal analysis (DTA), and the number average molecular weight is measured by gel permeation chromatography (GPC) using a standard polystyrene calibration curve.

The above-mentioned top-colored base paint may contain a cross-linking agent which reacts with the base resin to cross-link, and typical examples of the cross-linking agent include a melamine resin and a blocked polyisocyanate compound.

Examples of the melamine resin include a methylolated amino resin obtained by reacting melamine with an aldehyde. Examples of the aldehyde used in the above reaction include formaldehyde, paraformaldehyde, acetaldehyde, benzaldehyde and the like. Further, those obtained by etherifying the above methylolated amino resin with an appropriate alcohol can also be used as the melamine resin. Examples of alcohols used for etherification include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, 2-ethylbutanol,
2-ethylhexanol and the like.

The blocked polyisocyanate compound is a compound obtained by blocking free isocyanate groups of a polyisocyanate compound with a blocking agent.

The polyisocyanate compound before blocking is, for example, an aliphatic diisocyanate such as hexamethylene diisocyanate or trimethylhexamethylene diisocyanate; a cycloaliphatic diisocyanate such as hydrogenated xylylene diisocyanate or isophorone diisocyanate; Or an organic diisocyanate itself such as an aromatic diisocyanate such as 4,4'-diphenylmethane diisocyanate, or an adduct of each of these organic diisocyanates with a polyhydric alcohol, a low molecular weight polyester resin or water, or each organic diisocyanate described above. Cyclic polymers among diisocyanates, and isocyanate / biuret compounds are also included.

Examples of the blocking agent for blocking the isocyanate group include phenols such as phenol, cresol and xylenol; ε-caprolactam;
Lactams such as valerolactam, γ-butyrolactam, β-propiolactam; methanol, ethanol, n-
Or i-propyl alcohol, n-, i- or t-butyl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether,
Alcohols such as benzyl alcohol; oximes such as formamidoxime, acetoaldoxime, acetoxime, methyl ethyl ketoxime, diacetyl monooxime, benzophenone oxime, cyclohexane oxime; dimethyl malonate, diethyl malonate, ethyl acetoacetate, ethyl acetoacetate, methyl acetoacetate, acetylacetone A blocking agent such as an active methylene type can be suitably used.

The free isocyanate group of the polyisocyanate compound can be easily blocked by mixing the polyisocyanate compound with the blocking agent.

The crosslinking agent may be composed of one kind of crosslinking agent, or may be a mixture of two or more kinds of crosslinking agents. The amount of the crosslinking agent is not particularly limited, but is usually preferably in the range of 5 to 40 parts by weight based on 100 parts by weight of the total solid content of the base resin and the crosslinking agent. is there.

The top coating base paint contains colored organic resin fine particles as an essential component in addition to the base resin and the crosslinking agent used as necessary, and usually further contains a solvent.

The above-mentioned colored organic resin fine particles are blended for the purpose of coloring the top coat base paint and forming unevenness of the top coat base coat. The colored organic resin fine particles to be blended in the top coating base paint have an average particle diameter of 5 to 80 μm, preferably 15 to 60 μm, and the fine particles contain a color pigment. It is necessary that the baking does not completely melt.

Examples of the resin forming the colored organic resin fine particles include fluorine resin such as polyvinylidene fluoride and polytetrafluoroethylene, polyamide, acrylic resin, polyurethane, phenol resin, silicone resin, polypropylene, nylon 11 and nylon 12 And the like. When the average particle diameter of the organic resin fine particles is less than 5 μm, it is difficult to form a design-like unevenness on the surface of the top-coating colored base coating film. I do. As the coloring pigment contained in the coloring organic resin fine particles, coloring pigments used in the field of coatings, for example, titanium white, red iron, carbon black, titanium yellow, cyanine blue, cyanine green, organic red pigment, organic yellow pigment and the like Can be mentioned.

The compounding amount of the colored organic resin fine particles in the top coating base paint is usually 1 to 40 parts by weight, preferably 2 to 40 parts by weight, based on 100 parts by weight of the total film-forming resin component of the base resin and the crosslinking agent. The amount of 15 parts by weight is appropriate in terms of design properties, workability of a coating film, adhesion and the like.

[0034] The solvent blended in the top-colored base paint is
It is blended as needed to improve the paintability, etc., and can use those capable of dissolving or dispersing the above film-forming resin component. Specifically, for example, toluene, xylene, high-boiling petroleum-based carbon Hydrocarbon-based solvents such as hydrogen, ketone-based solvents such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, and isophorone; ester-based solvents such as ethyl acetate, butyl acetate, ethylene glycol monoethyl ether acetate and diethylene glycol monoethyl ether acetate; methanol and ethanol Alcohol solvents such as butanol, ether glycol solvents such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether and diethylene glycol monobutyl ether, and water. It may be used alone or in combination of two or more.

The top-colored base paint may be substantially composed of a film-forming resin component comprising a base resin and a crosslinking agent optionally blended, colored organic resin fine particles, and a solvent optionally blended. Coloring pigments can be used, if necessary, and extenders such as talc, clay, silica, mica, and alumina; rust-preventive pigments such as strontium chromate, calcium chromate, zinc chromate, barium chromate, and zinc phosphate; Curing catalyst; may contain additives known per se for coatings, such as antifoaming agents and coating surface conditioners.

Examples of the above-mentioned coloring pigments include coloring pigments usually used in the field of coatings, for example, white pigments such as titanium white and zinc white; blue pigments such as cyanine blue and induslen blue; and green pigments such as cyanine green and patina. Pigments;
Organic red pigments such as azo-based and quinacridone-based, red pigments such as bengalara; organic yellow pigments such as benzimidazolone-based, isoindolinone-based, isoindoline-based, and quinophthalone-based; yellow pigments such as titanium yellow and graphite; carbon Black pigments such as black, graphite, and pine smoke; glitter pigments such as aluminum powder, copper powder, nickel powder, mica powder coated with titanium oxide, mica powder coated with iron oxide, and glitter graphite; The compounding amount of the color pigment is not particularly limited as long as it is in a range in which good cosmetics can be exhibited, and is usually based on 100 parts by weight of the total film-forming resin component of the base resin and the crosslinking agent. It is used in the range of 1 to 120 parts by weight. By blending the color pigment, it is possible to form a top coat base coating film having a unique feeling in which the color of the colored organic resin fine particles is present in the colors of the color pigment.

The above-mentioned curing catalyst is blended as needed to promote the curing reaction between the base resin and the crosslinking agent, and can be appropriately selected and used according to the type of the crosslinking agent.

When the crosslinking agent is a melamine resin, especially a low molecular weight melamine resin of methyl etherification or a mixed etherification of methyl ether and butyl ether, the curing catalyst may be an acid catalyst such as a sulfonic acid compound or sulfonic acid. An amine neutralized product of the compound is preferably used. Representative examples of the sulfonic acid compound include p-toluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, and dinonylnaphthalenedisulfonic acid. The amine in the amine-neutralized sulfonic acid compound may be any of a primary amine, a secondary amine and a tertiary amine. Among them, an amine neutralized product of p-toluenesulfonic acid and / or an amine neutralized product of dodecylbenzenesulfonic acid are preferable from the viewpoint of the stability of the coating material, the effect of accelerating the reaction, and the properties of the obtained coating film.

When the crosslinking agent is a blocked polyisocyanate compound, a curing catalyst which promotes the dissociation of the blocking agent of the blocked polyisocyanate compound as the crosslinking agent is suitable. As a suitable curing catalyst, for example, Tin octylate, dibutyltin di (2-ethylhexanoate), dioctyltin di (2-ethylhexanoate),
Examples thereof include organometallic catalysts such as dibutyltin dilaurate, dibutyltin oxide, dioctyltin oxide, and lead 2-ethylhexanoate.

In the method of the present invention, particularly preferred top-colored base paint is the above-mentioned polyester resin (A) 60 to 9
(C) the colored organic resin fine particles with respect to 100 parts by weight of a total solid content of 5 parts by weight and (B) 5 to 40 parts by weight of at least one kind of a crosslinking agent selected from the melamine resin and the blocked polyisocyanate compound. It contains 1 to 30 parts by weight and further contains a color pigment.

The topcoat clear coating to be used in the topcoat clear coating method of this invention are coating the paint film is formed by wet-on-wet onto the topcoat colored base coating paint film, the top layer clear coating having a shrinkage pattern It forms a film layer. The top clear coating composition may contain a base resin, a melamine resin crosslinking agent (F), a curing catalyst (G), an amine compound (H), and a glitter powder (I) as essential components.

The base resin is not particularly limited.
One type or a mixture of two or more types such as a polyester resin, a silicone polyester resin, an acrylic resin, and a fluororesin can be used. Among the above-mentioned base resins, a polyester resin can be suitably used. Examples of the polyester resin include the polyester resins described as one of the base resins of the top-colored base paint. Among the polyester resins, preferred are oil-free polyester resins. Among the polyester resins, the following polyester resin (E) is preferable from the viewpoint of processability, curability, and the like.

The polyester resin (E) has a number average molecular weight of 1,500 to 25,000, preferably 5,000 to 2
000, glass transition temperature (Tg point) 0 to 70 ° C, preferably 10 ° C to 60 ° C, hydroxyl value 8 to 100 mg KO
It is a polyester resin having H / g, preferably 15 to 60 mgKOH / g.

The melamine resin crosslinking agent (F) comprises at least 80% by weight of a total of at least one melamine resin selected from a methyl etherified melamine resin and a mixed etherified melamine resin of methyl ether and butyl ether.
Preferably, the melamine resin contains 90% by weight or more. The melamine resin crosslinking agent (F) is preferably composed of a methyl etherified melamine resin.

The methyl etherified melamine resin and the mixed etherified melamine resin of methyl ether and butyl ether, which may be contained in the melamine resin crosslinking agent (F) in an amount of 20% by weight or less, preferably 10% by weight or less. Other melamine resins include melamine resins that are not methyl etherified, and representative examples include butyl etherified melamine resins.

Specific examples of the melamine resin that can be used as at least a part of the melamine resin crosslinking agent (F) include Cymel 300, 303, 325, and 3
27, 350, 730, 736, 738 [all of which are manufactured by Mitsui Cytec Co., Ltd.], Melan 52
2, 523 [all, manufactured by Hitachi Chemical Co., Ltd.], Nicaraq MS001, MX430, MX650 [all, manufactured by Sanwa Chemical Co., Ltd.], Sumimar M-
55, M-100, M-40S [all, manufactured by Sumitomo Chemical Co., Ltd.], Regin 740, 747 [all,
All are manufactured by Monsanto Co.] and methyl etherified melamine resins; Cymel 232, 266, and XV-51.
4, 1130 [Mitsui Cytec Co., Ltd.
Manufacture], Nikarac MX500, MX600, MS3
5. MS95 [all above, all of which are Sanwa Chemical Co., Ltd.]
Manufactured by Sumitomo Chemical Co., Ltd.], Resimin 753, 755 [all, manufactured by Monsanto Co., Ltd.], Sumimar M-66B [Sumitomo Chemical Co., Ltd.]
Etherified melamine resin of methyl ether and butyl ether; Uban 20SE, 225
[All are manufactured by Mitsui Toatsu Co., Ltd.], Super Beckamine J820-60, L-117-60, L-10
9-65, 47-508-60, L-118-6
And butyletherified melamine resins such as G821-60 [all, manufactured by Dainippon Ink and Chemicals, Incorporated].

The amount of the melamine resin crosslinking agent (F) is not particularly limited.
The amount is preferably in the range of 10 to 50 parts by weight of 0 parts by weight.

The curing catalyst (G) is compounded to promote a crosslinking reaction between the base resin and the melamine resin crosslinking agent (F). An amine neutralized product of an acid compound or a sulfonic acid compound can be mentioned. The amount of the curing catalyst was converted into the amount of the acid in the curing catalyst, for example, in the case of an amine neutralized sulfonic acid compound, the amount of the sulfonic acid compound with respect to 100 parts by weight of the film-forming resin component. The value is 0.1 to 2.0 parts by weight, preferably 0.2 to 1.5 parts by weight.

The above amine compound (H) is compounded to cause shrinkage on the surface of the clear top coat,
Secondary or tertiary amines having a boiling point of 30 to 250 ° C. are preferably used. Representative examples of the amine compound (H) include diethylamine, diisopropylamine, di-n-propylamine, diallylamine, diamylamine, di-n-butylamine, diisobleamine, disec-butylamine, N
-Ethyl-1,2-dimethylpropylamine, N-methylhexylamine, di-n-octylamine, piperidine, 2-pipecoline, 3-pipecoline, 4-pipecoline, 2,4-, 2,6- or 3,5 -Lupetidine, 3-
Secondary amines such as piperidine methanol; triethylamine, tributylamine, triallylamine, N-methyldiallylamine, N-methylmorpholine, N, N,
N ′, N′-tetramethyl-1,2-diaminoethane,
Tertiary amines such as N-methylpiperidine, pyridine and 4-ethylpyridine; secondary amines such as N-methylpiperazine
One or two such as amines having primary and tertiary amino groups
Mixtures of more than one species. Of these, dialkylamines, particularly diisopropylamine, di-n-propylamine, di-n-butylamine, diisobleamine, and the like are preferable because of their low odor and their ability to form beautiful uniform shrinkage.

The amount of the amine compound (H) is 0.1 to 10 parts by weight, preferably 0.3 to 5 parts by weight, based on 100 parts by weight of the film-forming resin component. In particular, when the amine compound (H) is a tertiary amine, the amine used for neutralizing the acid in the curing catalyst is reacted with the amine compound (H) per mole of the acid in the curing catalyst. It is preferred that the total amount of the amine is in the range of 1.1 to 30 mol,
When the amine compound (H) is a secondary amine, the amine of the amine compound (H) and the amine used for neutralization of the acid in the curing catalyst are used per mole of the acid in the curing catalyst. It is preferred that the total amount is in the range from 1.5 to 30 mol.

The top clear coating composition may contain, as essential components, a film-forming resin component comprising a base resin and a melamine resin crosslinking agent (F), a curing catalyst (G) and an amine compound (H). , And, if necessary, a solvent,
It may contain a brilliant powder, a lubricity-imparting agent, an ultraviolet absorber, an ultraviolet stabilizer, an antifoaming agent, a coating surface adjuster, and inorganic fine powder such as silica fine powder.

As the solvent, those capable of dissolving or dispersing paint components such as a base resin and a cross-linking agent can be used. For example, the same solvents as described in the above-mentioned top coating base paint can be used.

The glittering powder to be added to the top clear paint as required includes aluminum powder, copper powder, nickel powder,
Examples thereof include titanium oxide-coated mica powder, iron oxide-coated mica powder, and brilliant graphite. By adding a glitter powder, a glitter can be imparted to the coating film. When the glittering powder is blended, the blending amount may be any amount that gives the glittering appearance to the coated surface and is within the range in which the topcoating colored base coating film can be seen through the topcoating clear coating film. The amount is preferably in the range of 0.005 to 30 parts by weight, more preferably in the range of 0.4 to 10 parts by weight, based on 100 parts by weight of the film-forming resin component in the paint.

As the lubricity imparting agent, those which can impart lubricity to the surface of the clear top coat without deteriorating the appearance of the coated surface can be used. For example, polyethylene wax, silicone oil, modified silicone oil, paraffin wax,
Examples include petroleum waxes, montan waxes, lanolin waxes, fatty acid sucrose ester waxes, and fatty acid ester waxes such as esters of polyglycerin and fatty acids. The amount of the lubricity-imparting agent to be blended is usually preferably within the range of 0.1 to 10 parts by weight based on 100 parts by weight of the film-forming resin component in the top clear paint.

Examples of the ultraviolet absorber include benzophenones such as 2,4-dihydroxybenzophenone and 2-hydroxy-4-methoxybenzophenone; 2- (2 ′
Examples thereof include benzotriazole-based ultraviolet absorbers such as -hydroxy-5-methylphenyl) benzotriazole. Examples of the ultraviolet stabilizer include a hindered amine-based ultraviolet stabilizer. It is generally preferable that the blending amount of the ultraviolet absorber and the ultraviolet stabilizer is usually 5 parts by weight or less based on 100 parts by weight of the film-forming resin component in the top clear coating composition.

In the coating method of the present invention, in the coating method of the present invention, the top-coating colored base paint and the top-coat clear paint are applied to the continuously moving long metal plate with or without a primer-cured coating film. Painting and baking to form a topcoat colored basecoat and topcoat clearcoat.

In the method of the present invention, baking is performed after the top-coating colored base coating film and the top-coat clear coating film are applied so as to be in contact with each other on a wet-on-wet basis. As a method in which the top-coating colored base coating film and the top-coating clear coating film can be applied so as to be in contact with each other on a wet-on-wet basis, there is a method of coating a top-coating colored base coating film formed on a workpiece by a coating machine such as a roll coater or a roller curtain. A coating method in which a top coat clear paint is formed into a curtain shape by roller curtain coating or slit type curtain coating, a top coat colored base paint layer and a top coat clear paint layer are superposed in two layers, and discharged from a die. An example of the coating method is a die coating method in which two layers, a top coating base coating layer and a top coating clear coating layer, are simultaneously formed on the coating.

Here, the coating method by roller curtain coating is a method in which a coating film formed on a rotating roll is scraped off by a doctor, and the coating film is dropped on a moving object to be coated in a curtain shape to perform coating. It is. As the roller curtain coating machine, for example, the coating machines described in JP-A-6-7724 and JP-A-6-134385 can be used.

The coating method using the slit type curtain coating is a method in which the coating material is dropped from an elongated slit onto a moving object to be coated in a curtain shape to perform coating.

As a die coater that can be used in the above-mentioned die coat method, for example, a die coater described in JP-A-4-100570 can be mentioned. FIG. 1 is a conceptual sectional view of a representative example of a die in a die coating machine.
In FIG. 1, a die 1 is composed of three blades in which an upper blade 2, a middle blade 3 and a lower blade 4 are superimposed, and side plates (not shown) on both sides. The upper blade 2 and the lower blade 4 are provided with paint holding parts 5 and 6, respectively, and paint supply ports 7 and 8 for supplying paint to the paint holding parts. The gap between the upper blade 2 and the middle blade 3 and the gap between the lower blade 4 and the middle blade 3 form slots 9 and 10, respectively. The upper and lower intervals of each slot define the thickness of the paint passing through the slot,
Usually, in the range of 5 to 500 µm, preferably 10 to 120 µm, the paint is set so that the pressure loss of the paint in the slot does not become too large and the paint flows at a uniform flow rate over the entire width of the slot.

The intersection angle a between the slots 9 and 10 is an acute angle, usually 30 degrees or less, so that the upper layer paint flowing through the slot 9 and the lower layer paint flowing through the slot 10 smoothly merge to form an overlapping paint layer. In particular, it is preferable to be within the range of 5 to 25 degrees. The tip of the middle blade 3 does not need to be a knife edge.

The slots 9 and 10 are preferably merged inside the die as shown in FIG. 1 to form a single slot 11, but they may be independently opened to the outside. The die is provided with a mechanism for supporting the die 1 and adjusting the positions of the lips 12 and 13 of the die, a mechanism for supplying a constant amount of paint to the die, and the like, which are shown in FIG. Absent.

In the die coating method, the paint discharged from the die may be applied directly to the object to be coated, or may be once received by a rotating roll and then applied to the object from the rotating roll. FIG. 2 shows an example of an apparatus in a case where the paint discharged from the die is directly applied to the object to be coated in FIG. 2, in which the object to be coated 15 is supported by a rotating support roll 14, The slit of the die is arranged perpendicular to the object 15, that is, toward the center of the support roll 14.

When coating is performed using the apparatus shown in FIG.
The lower layer paint is supplied from the paint supply port 8 and the upper layer paint is supplied from the paint supply port 7 to the die by the metering pump according to the application amount while the article 15 is traveling in the direction of the arrow. The paint flows into the paint holding units 5 and 6, flows through the slots 9 and 10, merges in a layer at the slots 11, and is discharged. The paint discharged in two layers adheres uniformly to the object 15 while maintaining the layered state, and forms a coating film having a predetermined thickness.

In the method of the present invention, the thickness of the top-colored base coating film formed is not particularly limited, but is usually preferably in the range of 5 to 25 μm in dry film thickness. The thickness of the overcoating clear paint film to be formed is not particularly limited, but is usually preferably in the range of 5 to 25 μm in dry film thickness.

In the coating method in which the top clear paint is formed into a curtain on the top colored base paint film, the viscosity is 40 to 150 seconds (Ford Cup # 4, 2).
(Measurement at 5 ° C., viscosity is measured in the same manner as described below.) It is preferable to apply a topcoat clear paint having a viscosity of 50 to 250 seconds on the topcoat base paint film.

In the above-mentioned coating method using a die coater, it is preferable that a top coating base coating film having a viscosity of 40 to 250 seconds and a top coating clear coating film having a viscosity of 50 to 250 are superposed and discharged from the die.

The curing conditions for the two paint layers, the top paint base paint layer and the top clear paint layer, can be appropriately selected from the baking conditions under which the two paints are cured. Maximum temperature (PMT) 1 at 160-250 ° C
Conditions within the range of 5 to 180 seconds, particularly within the range of 20 to 120 seconds at a PMT of 180 to 230 ° C are suitable.

[0069]

The present invention will be described more specifically with reference to the following examples. Hereinafter, “parts” and “%” are based on weight.

Manufacturing Examples 1 to 12 of Top-Coated Base Coatings Coatings were prepared according to the composition shown in Table 1 below to obtain each top-coated base paint.

The amounts of the polyester resin and the cross-linking agent in Table 1 are indicated by the weight of the solid content.
For the sulfonic acid-based curing catalyst, the amount converted to the amount of the sulfonic acid compound was used, and for the organotin-based curing catalyst, the amount converted to the amount of the organic tin compound was indicated by weight. In addition, in the case of using a coloring pigment when forming a top-coating colored base coating material in the production example, Taipaque CR-95 (Ishihara Sangyo Co., Ltd.)
Was dispersed in advance, mixed with the remaining components such as colored organic resin fine particles, and uniformly stirred to form a coating. Also,
Cyclohexanone / Solvesso 150 ("Solvesso 1
50 "is a mixed solvent of an aromatic petroleum-based high-boiling solvent (manufactured by Esso Oil Co., Ltd.) = 40/60 (weight ratio) used for adjusting the viscosity of the paint and the like.
Adjusted to seconds (Ford Cup # 4, 25 ° C.). The top-colored base paints obtained in Production Examples 11 and 12 are comparative paints.

[0072]

[Table 1]

(Note) in Table 1 has the following meanings, respectively.

The polyester resins (* 1) to (* 5) in Table 1 are all polyester resins manufactured by Toyobo Co., Ltd., and have the property values shown in Table 2 below.

[0075]

[Table 2]

(* 6) Cymel 303: low molecular weight methyl etherified melamine resin, manufactured by Mitsui Cytec Co., Ltd., having a content of hexakis (methoxymethyl) melamine of 60% by weight or more. (* 7) Super Beckamine J-820-60: n-butyl etherified melamine resin solution manufactured by Dainippon Ink and Chemicals, Inc. (* 8) Desmodur BL-3175: a blocked polyisocyanate compound manufactured by Sumitomo Bayer Urethane Co., Ltd.

(* 9) Nailure 5225: a solution of equimolar neutralized secondary amine of dodecylbenzenesulfonic acid, manufactured by King Industries, USA, curing catalyst. (* 10) Formate TK-1: Takeda Pharmaceutical Company Limited
Catalyst, dissociation catalyst for blocked polyisocyanate compounds, which is an organic tin solution manufactured by Aztec.

(* 11) 020 (IWA) Black: manufactured by Dainichi Seika Kogyo Co., Ltd., trade name "Love Color 020 (IWA)
WA) black ", fine particles of an acrylic resin containing a black pigment, average particle size of about 38 μm. (* 12) 020 (F) Black: Dainichi Seika Industry Co., Ltd.
Brand name "Love Color 020 (F) Black", fine particles of acrylic resin containing black pigment, average particle size of about 2
0 μm. (* 13) 040 (F) Black: Dainichi Seika Industry Co., Ltd.
Trade name “Love Color 040 (F) Red”, acrylic resin fine particles containing a red pigment, average particle size of about 20
μm. (* 14) 060 (F) Blue: Dainichi Seika Industry Co., Ltd.
Manufactured by Rabcolor 060 (F) Blue, trade name, acrylic resin fine particles containing a blue pigment, average particle size of about 20
μm. (* 15) 080 (F) Green: Dainichi Seika Industry Co., Ltd.
A brand name “Love Color 080 (F) Green”, acrylic resin fine particles containing a green pigment, average particle size of about 2
0 μm.

(* 16) Art Pearl C400 Green: Negami Kogyo Co., Ltd., trade name, true spherical urethane resin fine particles containing a green pigment, average particle size of about 15 μm. (* 17) Art Pearl A400 Yellow: Negami Industry Co., Ltd.
Made, trade name, spherical acrylic resin fine particles containing a yellow pigment, average particle diameter about 15 μm.

(* 18) 2002D White5: manufactured by Ato Shimmy, France, trade name "Orgasol 2002"
D White 5 ”, white nylon 12 resin fine particles containing a titanium oxide pigment, average particle size of about 17 μm.

Production Examples 13 to 24 of Top Coating Clear Coatings Coatings were prepared according to the composition shown in Table 3 below to obtain each top clear coating.

In Table 3, the amounts of the base resin and the crosslinking agent are indicated by the weight of the solid content, and the amount of the curing catalyst is expressed by weight in terms of the amount of the sulfonic acid compound for the sulfonic acid-based curing catalyst. Cyclohexanone / Solvesso 1
50 ("Solvesso 150" is manufactured by Esso Oil Co., Ltd.)
A mixed solvent of aromatic petroleum-based high-boiling point solvent = 40/60 (weight ratio) is used for adjusting the viscosity of the paint, etc., and the viscosity of the clear top paint is 110 seconds (Ford Cup # 4, 25 ° C.)
Was adjusted.

[0083]

[Table 3]

In (Note) in Table 3, (* 1), (*
3), (* 6), (* 7) and (* 9) have the same meanings as above. Other (Note) in Table 3
Has the following meanings, respectively.

(* 19) Byron KS-1830V: a polyester resin manufactured by Toyobo Co., Ltd., trade name, having a number average molecular weight of 14,000, a Tg point of 45 ° C., and a hydroxyl value of 12 mg KOH / g. (* 20) Byron KS-1720V: Toyobo Co., Ltd.
Polyester resin, trade name, this resin has a number average molecular weight of 13,000, a Tg point of 68 ° C., a hydroxyl value of 9 mg KO
H / g.

(* 21) Resimin 755: a mixed etherified melamine resin of methyl ether and butyl ether, trade name, manufactured by Monsanto Co., Ltd.

(* 22) Aluminum paste MR-900
0: Asahi Kasei Metals Corporation, trade name “Asahi Kasei Aluminum Paste MR-9000”, brilliant aluminum fine powder having an average particle diameter of about 10 μm. (* 23) Aluminum paste MC-666: manufactured by Asahi Kasei Metals Corporation, trade name "Asahi Kasei Aluminum Paste MC-66"
6 ", a brilliant aluminum fine powder having an average particle size of about 20 µm. (* 24) Iriodin 225R: manufactured by Merck Japan, rutile-type titanium oxide-coated mica fine powder, particle size about 1
0-40 μm, nacreous blue. (* 25) Iriodin 103R: manufactured by Merck Japan Ltd., rutile-type titanium oxide-coated mica fine powder, particle size: about 1
0-40 μm, silver white.

Examples 1 to 38 and Comparative Examples 1 to 10 Preparation of Test Coated Plates Method of preparing test coated plates (1): Examples 1 to 19 and Comparative Examples 1 to 5 Chromate-treated 0.5 mm thick melt KP color 863 manufactured by Kansai Paint Co., Ltd. on galvanized steel sheet
0 primer (epoxy-modified polyester primer for pre-coated steel sheet, Tg point of the coating film is 52 ° C.) so that the dry film thickness is about 4 μm,
C. for 30 seconds to obtain a primer-coated steel sheet. On this primer-coated steel sheet, each of the overcoated colored base paints obtained in the above Production Examples 1 to 12 was applied so as to have a dry film thickness of about 14 μm, and on the uncured coating film of these overcoated colored base paints, The top clear paints obtained in the above Production Examples 13 to 24 were applied to the combinations shown in Tables 4 and 6 by a roller curtain coating method so that the dry film thickness became about 10 μm. Subsequently, each of the steel sheets was baked for 70 seconds so that the maximum temperature of the material reached 235 ° C. to obtain each overcoated steel sheet. The viscosity (measured at a measuring temperature of 25 ° C. in a Ford cup # 4 at a measuring temperature of 25 ° C. and the viscosity is measured in the same manner as described above) of the top-coating colored base coating layer immediately before the top-coat clear coating is applied is 100 seconds, and the top-coat clear coating is applied. Had a viscosity of 110 seconds.

In Example 18, the coating was performed using the above-described hot-dip galvanized steel sheet having no primer, instead of the primer-coated steel sheet. In Example 19, the top clear paint was applied by a slit curtain coating method instead of the roller curtain coating method.

Preparation of Test Coated Plate (2): Examples 20 to
38 and Comparative Examples 6 to 10 On the same primer-coated steel sheet as used in the method (1) for preparing a test coated plate, the overcoated colored base paints obtained in the above Production Examples 1 to 12 and the above-mentioned Production Examples 13 to 24 The resulting clear top paint was applied in a combination shown in Tables 5 and 6 below by a die coat coating method and extruded from a die in two layers so that the primer coating film faced the top coat base paint film.

The coating thickness of each paint was such that the dry color base paint layer had a dry film thickness of about 14 μm and the clear paint layer had a dry film thickness of about 7 μm. The viscosity of the paint extruded from the die was 90 seconds for the top colored base paint and 110 seconds for the top clear paint. After the coating, each of the coated steel sheets was baked for 70 seconds so that the maximum temperature of the material reached 220 ° C.

Various tests were carried out on the obtained coated steel sheet. The test results are shown in Tables 4, 5, and 6 below.

[0093]

[Table 4]

[0094]

[Table 5]

[0095]

[Table 6]

The tests in Tables 4, 5 and 6 were conducted according to the following test methods.

Test Method Three-dimensional appearance of painted surface: The three-dimensional appearance of the painted surface was visually evaluated.

◎: The unevenness is remarkable, and the design is excellent. ：: Although not remarkable, there is an unevenness and the design is good. X: The unevenness is not recognized.

Glitter of the coated surface: The coated surface was observed at an angle of regular reflection under direct sunlight, and the glitter was evaluated according to the following criteria. ◎: Glittering and uniform shining throughout-: Glittering shine is not recognized.

The shrinkage of the painted surface: The painted surface was observed with a magnifying glass of 30 times, and the degree of shrinkage was evaluated. A: A uniform and clear shrinkage pattern is observed on the coated surface. O: A uniform shrinkage pattern is observed on the coated surface, but the shrinkage pattern is not remarkable. X: No shrinkage pattern is observed on the coated surface.

Pencil hardness: JIS
A pencil scratch test specified in K-5400 8.4.2 (1990) was performed, and evaluation by tearing of the coating film was performed.

Bending workability: In a room at 20 ° C., the test plate was bent at 180 ° with the coated surface outside, and the T number at which no crack was generated in the bent portion was visually evaluated and indicated. The T number is 1 without anything inside the bend.
The case where 80 ° bending was performed was set to 0T, the case where one plate having the same thickness as the test plate was sandwiched was bent to 1T, the case of two sheets was set to 2T, and the case of three sheets was set to 3T.

Solvent resistance: In a room at 20 ° C., about 1 kg was applied to the painted surface with gauze impregnated with methyl ethyl ketone.
/ Cm ^{2 with} a load of about 5 cm. The number of round trips until the primer coating was visible was recorded. If the primer coating is not visible after 50 round trips, 50
<Is indicated. The greater the number, the better the curability of the coating film.

Adhesion: JIS K-5400 8.5.
2 (1990) According to the crosscut-tape method, 11 parallel vertical and horizontal straight lines are drawn at 1 mm intervals on the surface of the coating film of the test plate so as to reach the substrate with a cutter knife, and the distance is 1 mm. 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. ○: The coating film was slightly peeled, but 90 or more squares remained. Δ: The coating film was peeled, and the number of remaining squares was 50 or more and 90.
Less than pieces.

×: The coating film was peeled off, and the number of remaining squares was 50.
Less than pieces.

[0106]

According to the coating method of the present invention, a top coating base coating film and a top coating clear coating film are formed on a long object to be moved continuously by wet-on-wet, and then both coating films are simultaneously formed. Because of baking and hardening, a larger number of coating layers can be formed without increasing the number of times of baking as compared with the related art. In the coating method of the present invention, the base paint contains colored resin fine particles, and a coating film having a three-dimensional design feeling and a shrinking pattern and excellent in cosmetics can be formed.

[Brief description of the drawings]

FIG. 1 is a conceptual sectional view showing an example of a die of a die coating machine used in the present invention.

FIG. 2 is a view showing an example of a positional relationship between a die of a die coating machine and an object to be coated when a coating is applied in two layers in the method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Die 2 Upper blade of die 3 Middle blade of die 4 Lower blade of die 5, 6 Paint holding part of die 7, 8 Paint supply port to die 9, 10, 11 Slot of die 12, 13 Lip of die 14 Support Roll 15 substrate

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C09D 175/06 C09D 175/06 // (C09D 167/00 161: 28)

Claims (7)

[Claims] 1. A top-coating colored base coat and a top-coating clear base paint are applied to a continuously moving long metal plate with or without a primer-cured coating film and baked. A method of forming a topcoat clear coating film on top, wherein the topcoat clear coating film is formed on the topcoat base coating film in a wet-on-wet manner, and the topcoat base coating film is formed at the time of coating formation. A coating containing colored organic resin particles having an average particle diameter of 5 to 80 μm that does not completely melt by baking and contains a coloring pigment, and the clear top coating has a uniform shrinkage pattern on the coating film surface when the coating film is cured. A method for painting a metal plate, wherein the paint is generated. 2. The overcoated colored base coating composition comprises (A) a number average molecular weight of 1,500 to 35,000 and a glass transition temperature of -30.
A total of 60 to 95 parts by weight of a hydroxyl group-containing polyester resin having a hydroxyl value of 3 to 100 mgKOH / g and at least 5 to 40 parts by weight of at least one crosslinking agent selected from (B) a melamine resin and a blocked polyisocyanate compound. (C) 1 to 40 parts by weight of colored organic resin fine particles having an average particle diameter of 5 to 80 μm and not completely melted by baking at the time of forming a coating film and containing a color pigment, based on 100 parts by weight of solid content The coating method according to claim 1, wherein: 3. The top clear coating composition according to claim 1, wherein (D) the number average molecular weight is from 1,500 to 25,000 and the glass transition temperature is from 0 to 70.
Melamine resin crosslinking agent 10 containing 50 to 90 parts by weight of a hydroxyl group-containing polyester resin having a hydroxyl value of 8 to 100 mg KOH / g and (E) methyletherified or a mixed etherified methylether and butylether melamine resin at 50% by weight or more. (F) As a curing catalyst, a value obtained by converting a sulfonic acid compound or a neutralized product of the sulfonic acid compound into the amount of the sulfonic acid compound, relative to 100 parts by weight of the film-forming resin component comprising 50 to 50 parts by weight. 3. The composition according to claim 1, further comprising 0.1 to 2.0 parts by weight, and (G) 0.1 to 10 parts by weight of a secondary or tertiary amine compound having a boiling point of 30 to 250 [deg.] C. The painting method described. 4. The overcoat clear coating composition further comprises (F) glitter powder 0.0100 parts by weight based on 100 parts by weight of the film-forming resin component.
The coating method according to any one of claims 1 to 3, wherein the coating method contains 0.5 to 30 parts by weight. 5. The coating method according to claim 1, wherein the top coating color base coating and the top coating clear coating are applied by being extruded in two layers from a die of a die coater. 6. A top coat clear paint is applied on an uncured top coat coloring base paint layer which has been coated on a continuously moving long metal plate, with or without a primer-cured coating film. The coating method according to any one of claims 1 to 3, wherein the coating is performed in a curtain shape by a curtain coating method. 7. A coated metal plate coated by the coating method according to claim 1.