JPH11114492A - Coating method for metallic plate and coated metallic plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coated metallic plate excellent in coating film performance and external appearance of the coating film by a coating method wherein cost required for the equipment is small and a coating film comprised of three layers can be formed. SOLUTION: In a method for forming a laminated coating film comprised of a primer coating film, a top coating colored base film, and a top coating clear coating film on a metallic plate by forming and baking the primer coating film and the top coating colored base film to be overlapped with each other on the continuously moving long metallic plate, and thereafter by coating and baking a top coating clear coating material on the metallic plate, the top coating colored base film is formed on the primer coating film with wet-on-wet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for coating a continuously moving long metal plate, comprising applying a top-coating colored base coating on a primer coating film in a wet-on-wet manner to simultaneously coat both coating layers. The present invention relates to a method of coating a metal plate by a three-coat two-bake method in which baking is performed, and then a top clear paint is applied and baked, and a coated metal plate.

[0002]

2. Description of the Related Art In the field of precoated metal sheets, a one-coat, one-bake method in which a topcoat is applied to a continuously moving long metal sheet and baked is used. A two-coat two-bake method is generally used in which a primer paint is applied and baked, and then a top-coat paint is applied and baked on the primer coating film. Among them, the two-coat two-bake method occupies a large part. I have. In addition, a part is painted with a primer paint on a metal plate and baked, then an intermediate coat is applied on the primer coat and baked, and then a top coat is applied and baked.
The coat 3 baking method is performed.

[0003] By forming three coating films, it is possible to achieve a coating film performance and a coating appearance that cannot be achieved with one or two layers as a total coating film. The number of times of coating and the number of times of baking of the coating film are each one more than those of the two-coat baking method, and there is a problem in that the burden on equipment is increased.

Accordingly, the present inventors have proposed a coating method capable of forming a three-layer coating film on a long metal plate that moves continuously and with a small load on equipment. As a result of intensive research on the method of coating a metal plate that can provide a comprehensive coating film with excellent film appearance, a primer coating and a top coating colored base coating are applied on a metal plate by wet-on-wet and baked. Then, it has been found that the above object can be achieved by applying a topcoat clear paint on the topcoat colored base coating film and baking it, thereby completing the present invention.

[0005]

That is, according to the present invention, a primer coating film and a top coating base coating film are formed on a continuously moving long metal plate and baked.
A method of applying a topcoat clear paint on the topcoat base coating and baking to form a laminated coating of a primer coating, a topcoat basecoat and a topcoat clearcoat on a metal plate,
The top-coating base paint film is provided on a primer paint film in a wet-on-wet manner.

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

[0007]

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 precoated steel sheet, and examples of the material include cold-rolled steel sheet, zinc-based plated steel sheet, aluminum sheet, stainless steel sheet and the like. 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.

[0009] In the primer coating method of the present invention, on the metal plate of the long continuously moving, coating film of the primer coating is formed. 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.

As the primer coating, a primer coating conventionally known in the field of precoat coating can be used without any particular limitation. Among them, primer paints are epoxy resin-based, polyester resin-based, and polyester-modified epoxy resin-based paints, and include rust preventive pigments (for example, chromic acid such as strontium chromate, calcium chromate, zinc chromate, and barium chromate). A salt-containing rust-preventive pigment; a non-chromium-based rust-preventive pigment such as zinc phosphate) is preferred.

[0011] In the topcoat colored base coating process of the present invention, on the coating film of the primer coating, topcoat colored base coating paint film is formed by wet-on-wet.

The base resin of the film-forming resin of the top-colored base paint used in the method of the present invention is not particularly limited, and one or two or more of polyester resin, silicone polyester resin, acrylic resin, fluororesin, etc. Mixtures of more than one species 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 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, an oil-free polyester resin is preferable. 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 coating base paint may contain a cross-linking agent which reacts with the base resin and cross-links. Representative 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.

Examples of the polyisocyanate compound before blocking include aliphatic diisocyanates such as hexamethylene diisocyanate or trimethylhexamethylene diisocyanate; cycloaliphatic diisocyanates such as hydrogenated xylylene diisocyanate or isophorone diisocyanate; tolylene 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; 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 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 usually contains a solvent in addition to the base resin and, if necessary, a cross-linking agent. For the purpose, organic resin fine particles (C), coloring pigment (D)
It contains.

The organic resin fine particles (C) have an average particle size of from 5 to 8 which is not completely melted by baking during the formation of a coating film.
Organic resin fine particles having a thickness of 0 μm, preferably 15 to 60 μm, and the resin fine particles may contain a color pigment. When a coloring pigment is contained, the coating film can be colored with organic resin fine particles. Organic resin particles are
When the average particle diameter is less than 5 μm, it becomes difficult to form a design-like unevenness on the surface of the top-coating colored base coating film.
If it exceeds 80 μm, the design properties will deteriorate, and the coating workability will also decrease.

As the resin type of the organic resin fine particles (C),
For example, fluorine resins such as polyvinylidene fluoride and polytetrafluoroethylene, polyamides, acrylic resins,
Examples include polyurethane, phenolic resin, silicone resin, polypropylene, and polyamide such as nylon 11 and nylon 12.

As the coloring pigment which may be contained in the organic resin fine particles, any coloring pigment used in the field of paints can be used without any limitation. For example, titanium white, red iron,
Examples thereof include carbon black, titanium yellow, cyanine blue, cyanine green, organic red pigment, and organic yellow pigment.

The amount of the organic resin fine particles in the top coating base paint is usually 1 to 40 parts by weight, preferably 2 to 15 parts by weight, based on 100 parts by weight of the total film-forming resin component of the base resin and the crosslinking agent. By weight, the design,
It is suitable from the viewpoints of workability and adhesion of the coating film.

The above-mentioned coloring pigment (D) to be added to the top coating base paint is a coloring pigment usually used in the field of paints, for example, a white pigment such as titanium white or zinc white; a cyanine blue or an induslen blue or the like. Blue pigments; green pigments such as cyanine green and patina; organic red pigments such as azo-based and quinacridone-based; red pigments such as redwood;
Organic yellow pigments such as benzimidazolones, isoindolinones, isoindolines and quinophthalones; yellow pigments such as titanium yellow and graphite; carbon black;
Black pigments such as graphite and pine smoke; and glittering pigments such as aluminum powder, copper powder, nickel powder, mica powder coated with titanium oxide, mica powder coated with iron oxide, and glittering 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.

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 coating base paint includes a base resin, a crosslinking agent optionally blended, organic resin fine particles, a color pigment,
A solvent, but if necessary, a curing catalyst; extender pigments such as talc, clay, silica, mica, and alumina; strontium chromate, calcium chromate, zinc chromate, barium chromate, Rust-preventive pigments such as zinc phosphate; and may contain additives known per se for paints, such as antifoaming agents and coating surface conditioners.

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
The organic resin fine particles (C) are based on 100 parts by weight of a total solid content of 5 parts by weight and 5 to 40 parts by weight of at least one crosslinking agent (B) selected from the melamine resin and the blocked polyisocyanate compound. It contains 1 to 30 parts by weight and further contains the coloring pigment (D).

Top clear paint The top clear paint used in the method of the present invention is a paint which is applied on the above-mentioned top colored base coat which has been baked, and which forms the uppermost clear coat layer. It is.

The top clear paint is a thermosetting top clear paint containing a base resin and a crosslinking agent as essential components. The base resin is not particularly limited, and examples thereof include one or a mixture of two or more of polyester resin, silicone polyester resin, acrylic resin, and fluororesin. 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.

As the cross-linking agent in the top clear paint, for example, a melamine resin cross-linking agent (F) which is a melamine resin described as a representative example of the cross-linking agent in the above-mentioned top color base paint is preferably used. When a coating film having excellent smoothness is to be formed, it is advantageous to use a butyl etherified melamine resin from the viewpoint of thermal fluidity.
The blending amount of the crosslinking agent is not particularly limited, but is usually 10 to 50 parts by weight in 100 parts by weight of the film-forming resin component which is the total solid content of the base resin and the crosslinking agent in the top clear paint. It is preferably in the range of parts by weight.

In the clear top coating, a melamine resin cross-linking agent containing at least 80% by weight of a melamine resin cross-linked with methyl ether or mixed ether of methyl ether and butyl ether is used as the melamine resin cross-linking agent (F). The sulfonic acid compound or a neutralized sulfonic acid compound as a curing catalyst (G) is used in an amount of 0.1 to 2 in terms of the amount of the sulfonic acid compound per 100 parts by weight of the coating film-forming resin component of the paint. 0.0 parts by weight and (H) boiling point 3
Secondary or tertiary amine compound at 0 to 250 ° C 0.1 to 10
By including the parts by weight, a uniform shrinkage pattern can be formed on the surface of the clear top coat at the time of baking and curing.

As the melamine resin crosslinking agent (F),
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
As described above, preferably, the melamine resin containing 90% by weight or more, that is, a methyl etherified melamine resin and a mixed etherified melamine resin of methyl ether and butyl ether in a total of 80% by weight in the melamine resin crosslinking agent (F).
As described above, the melamine resin preferably contains 90% by weight or more, and among them, it is preferable that the melamine resin is composed of a methyl etherified melamine resin.

In the melamine resin crosslinking agent (F),
The melamine resin other than the methyl etherified melamine resin and the mixed etherified melamine resin of methyl ether and butyl ether, which may be contained in an amount of 20% by weight or less, preferably 10% by weight or less, includes methyl ether. A non-esterified melamine resin is exemplified, and a representative example is a butyl etherified melamine resin.

Specific examples of the melamine resin include Cymel 300, 303, 325, 327, 350, 730, 736, and 738 (all of which are manufactured by Mitsui Cytec Co., Ltd.), and melan. 522, 523
[These are all manufactured by Hitachi Chemical Co., Ltd.], Nicaraq MS
001, MX430, and MX650 (all manufactured by Sanwa Chemical Co., Ltd.), Sumimar M-55, and M-M
100 and M-40S [all of which are Sumitomo Chemical Co., Ltd.]
Melamine resins such as Resin 740 and 747 [all of which are manufactured by Monsanto]; Cymel 232, 266, XV-514, 1130.
[The above are all manufactured by Mitsui Cytec Co., Ltd.], Nikarac MX500, MX600, MS35, MS95
[These are all manufactured by Sanwa Chemical Co., Ltd.], Regimin 7
Mixed etherified melamine resin of methyl ether and butyl ether such as 53, 755 [all, manufactured by Monsanto Co., Ltd.] and Sumimar M-66B [Sumitomo Chemical Co., Ltd.]; Uban 20SE, 225 [all, all] Mitsui Toatsu Co., Ltd.], Super Beckamine J820-6
0, L-117-60, L-109-65, 47
-508-60, L-118-60, G821-6
And a butyl etherified melamine resin such as 0 [all manufactured by Dainippon Ink and Chemicals, Inc.].

The above-mentioned curing catalyst (G) is blended for accelerating the crosslinking reaction between the base resin and the melamine resin crosslinking agent (F). And the amine-neutralized sulfonic acid compound described above.
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. 0.1 to 2.0 parts by weight, preferably 0.2
１．５1.5 parts by weight.

The above-mentioned 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 contains a base resin and a crosslinking agent as essential components and, if necessary, a curing catalyst and an amine compound.
It may contain a solvent, a glitter powder, a lubricity-imparting agent, an ultraviolet absorber, an ultraviolet stabilizer, an antifoaming agent, a coating surface adjusting agent, and an inorganic fine powder such as a silica fine powder.

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

Examples of the glittering powder to be added to the top clear paint as required include aluminum powder, copper powder, nickel powder, mica powder coated with titanium oxide, mica powder coated with iron oxide, and glittering 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.

Coating method of the present invention In the coating method of the present invention, the primer coating film and the top coating base coating film are formed on the continuously moving long metal plate and baked, and then the top coating clear is applied. The paint is applied and baked to form a topcoat clear coat on the topcoat base coat. The topcoat base paint film is formed wet-on-wet on the primer paint film.

In the method of the present invention, the uncured primer coating film and the uncured topcoat colored base coating film are applied to a metal plate in a wet-on-wet manner, and then both coatings are simultaneously baked. Let it cure.

As a method of applying the primer paint film and the top coat color base paint film so as to be in contact with each other in a wet-on-wet manner, there is a method such as a roll coater or a curtain coater on a long metal plate which moves continuously. On the uncured primer coating film formed by the coating machine, a coating method in which a roller coating machine or a slit type curtain coating machine is used to form a top coating coloring base coating in a curtain shape,
A coating method by a die coating method in which a primer coating layer and a top coating base coating layer are superposed in two layers and discharged from a die to simultaneously form two layers of a primer coating layer and a top coating base coating layer on an object to be coated. Can be mentioned.

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. 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-4-1570 can be mentioned. FIG. 1 shows a conceptual cross-sectional view of a typical 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, and are usually 5 to 500 μm, preferably 10 to 12 μm.
Within the range of 0 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 merge smoothly to form a layer of overlapping paint. 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 onto 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 substantially perpendicular to the object 15, that is, substantially 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 primer coating film to be formed is not particularly limited.
Usually, the thickness is preferably in the range of 1 to 15 μm in dry film thickness. The thickness of the formed top-coating base coating film is not particularly limited, but is generally preferably in the range of 5 to 25 μm in dry film thickness.

In the coating method in which the top coating base paint is applied in the form of a curtain on the primer coating film, the viscosity is 40 to 150 seconds (Ford Cup # 4, 25).
It is preferable to apply a top-coating base paint having a viscosity of 40 to 150 seconds on the primer coating film having a viscosity of 40 to 150 seconds.

In the coating method using the die coater, a primer coating layer having a viscosity of 40 to 250 seconds and a viscosity of 50
It is preferable to discharge from the die by superimposing the top coating base paint layer for ~ 250 seconds.

The conditions for curing the two paint layers, the primer paint film and the top-colored base paint film, can be appropriately selected from the baking conditions under which the two paints are cured. Maximum temperature reached (PMT) 160-250
C. in the range of 15 to 180 seconds, especially PMT 180 to 23
Conditions within the range of 20 to 120 seconds at 0 ° C. are preferred.

In the coating method of the present invention, the above-mentioned clear top coating is applied on the baked top-colored base coating film obtained as described above. The coating method is not particularly limited, and the coating can be performed by a roll coater, a curtain coating machine, a spray coating machine, or the like. The thickness of the formed clear top coating film is not particularly limited, but is generally preferably in the range of 5 to 25 μm in dry film thickness. The curing conditions for the top clear coating film can be appropriately selected from among the baking conditions under which the top clear coating film cures, and usually, the maximum material temperature (PMT) is 160 to 250 ° C. for 15 to 180 seconds. Conditions within the range, particularly within the range of 20 to 120 seconds at a PMT of 180 to 230 ° C, are suitable.

[0072]

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

Production of Coating Base Paints Production Examples 1 to 11 Coatings were prepared according to the composition shown in Table 1 below to obtain each coating 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 was converted to the amount of the sulfonic acid compound, and for the organotin-based curing catalyst, the amount was converted to the amount of the organic tin compound, and the weight was expressed. In addition, when making the top-colored base paint in the production example,
After dispersing -95 (Ishihara Sangyo Co., Ltd., titanium white pigment), carbon black and red red iron oxide, the mixture was mixed with the remaining components and uniformly stirred to form a coating. In addition, cyclohexanone / solvesso 150 ("solvesso 150")
Is an aromatic petroleum-based high-boiling solvent manufactured by Esso Oil Co., Ltd.)
A mixed solvent of 40/60 (weight ratio) was used for adjusting the viscosity of the paint and the like, and the viscosity of the top coating base paint was adjusted to 90 seconds (Ford Cup # 4, 25 ° C.).

[0075]

[Table 1]

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

The polyester resins indicated by (* 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.

[0078]

[Table 2]

(* 6) Cymel 303: manufactured by Mitsui Cytec Co., Ltd., having a low molecular weight methyl etherified melamine resin and 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 dodecylbenzenesulfonic acid secondary amine equimolar neutralization solution, 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) Olgasol 2002ES-
3: trade name, manufactured by Ato Simmy, France, resin fine particles of nylon 12, average particle diameter of about 30 μm. (* 12) TEXTURE-ULTRAFINE: Texture-Ultrafine, manufactured by Shamrock Chemical Co., Ltd., trade name, polypropylene resin fine particles, average particle diameter of about 18 μm. (* 13) Tuftic A-20: manufactured by Toyobo Co., Ltd., trade name, fine particles of polyacrylonitrile resin, average particle diameter of about 26 μm.

(* 14) Tospearl 2000B: trade name, manufactured by Toshiba Silicone Co., Ltd., silicone resin fine particles, average particle diameter of about 6 μm. (* 15) 020 (IWA) Black: trade name “Labcolor 020 (IWA) Black” manufactured by Dainichi Seika Kogyo Co., Ltd., acrylic resin fine particles containing a black pigment, average particle diameter of about 38 μm. (* 16) 040 (F) Red: 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. (* 17) 060 (F) Blue: Dainichi Seika Kogyo 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. (* 18) Art Pearl C400 Green: Negami Industry Co., Ltd.
Made, trade name, true spherical urethane resin fine particles containing a green pigment, average particle diameter of about 15 μm.

Production of Top Coated Clear Coatings Production Examples 12 to 23 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 cross-linking 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.

[0085]

[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 44 Preparation of Painted Metal Plate Method of preparing coated metal plate (1): Examples 1 to 22 Kansai Paint Co., Ltd. was placed on a 0.5 mm thick hot-dip galvanized steel plate that had been subjected to chromate treatment. ), KP color 8630 primer (polyester modified epoxy resin primer for pre-coated steel sheet, contains chromate rust preventive pigment, Tg of coating film
(The point is 52 ° C.) so as to have a dry film thickness of about 5 μm.
Each of the overcoated colored base paints obtained in Nos. 1 to 11 was applied by a roller curtain coating method so that the dry film thickness became about 14 μm. Then, set the maximum temperature to reach 220 ° C.
Baking was carried out for 0 second to obtain each top-coated colored base-coated steel sheet. The viscosity (measured at a measuring temperature of 25 ° C. in a Ford cup # 4 at a measuring temperature of 25 ° C., the viscosity is measured in the same manner as described below) of the primer coating film immediately before the top coating base paint is applied is 100 seconds, and each top coating color is applied. The coating viscosity of the base paint was 100 seconds.

Then, the top clear coating composition obtained in the above Preparation Examples 12 to 23 was adjusted to a viscosity of 60 seconds on the top coating base coating film of each baked coated plate, and the dried film thickness was determined by a roll coater. The coated metal plate was coated to a thickness of about 7 μm and baked for 50 seconds so that the maximum temperature of the material reached 235 ° C. to obtain each coated metal plate. Table 4 shows combinations of the top-coating colored base coating type and the top-coat clear coating type in each example. Various tests were performed on each of the obtained coated metal plates. The test results are shown in Table 4 below.

Preparation Method of Painted Metal Plate (2): Embodiment 23
-44 KP color 863, manufactured by Kansai Paint Co., Ltd., on a 0.5 mm thick hot-dip galvanized steel sheet subjected to chromate treatment.
No. 0 primer and each of the top coating base paints obtained in Production Examples 1 to 11 were overlaid in two layers by a die coating method, extruded from a die, and coated on a galvanized steel sheet so that the primer coating film faced.

The coating thickness of each paint was about 5 μm in dry film thickness of the primer paint film, and about 14 μm in dry film thickness of the top coating base paint layer. The viscosity of the paint extruded from the die was 90 seconds for the primer paint and 1 for the top-colored base paint.
00 seconds. After the coating, each material was baked for 70 seconds so that the maximum temperature of the material reached 220 ° C. to obtain each overcoated base coated steel sheet.

Then, the top clear coating composition obtained in the above Preparation Examples 12 to 23 was adjusted to a viscosity of 60 seconds on the top coated base coating film of each baked coated plate, and the dried film thickness was adjusted by a roll coater. The coated metal plate was coated to a thickness of about 7 μm and baked for 50 seconds so that the maximum temperature of the material reached 235 ° C. to obtain each coated metal plate. Table 5 shows combinations of the top-coating colored base coating type and the top-coat clear coating type in each example. Various tests were performed on each of the obtained coated metal plates. The test results are shown in Table 5 below.

[0095]

[Table 4]

[0096]

[Table 5]

The tests in Tables 4 and 5 were performed 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. ：: Not remarkable but has the unevenness, and the design is good.-: 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 all over-: No glittering shine is recognized. Shrinkage of coated surface: The coated surface was observed with a magnifying glass of 30 times, and the degree of shrinking pattern 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.-: 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 was applied and reciprocated for a length of about 5 cm, and the number of reciprocations until the primer coating film was visible was recorded.
Those in which the primer coating film was not visible after 50 reciprocations were indicated as 50 <. 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 ×: The coating film peeled off, and the number of remaining squares was less than 50.

[0105]

According to the coating method of the present invention, a primer coating film and a top coating base coating film are formed on a continuously moving long object by wet-on-wet, and then both coating films are formed. Simultaneous baking and curing, and then applying and baking a clear top coating, the conventional 3 coating film is formed.
The number of baking can be reduced by one time as compared with the coat 3 baking method. In the coating method of the present invention, since a top clear coating film is formed on the uppermost layer, a coating film having excellent aesthetics can be formed.

Further, a three-dimensional design can be imparted by blending the organic resin fine particles with the top-coating colored base paint, and a glitter can be imparted by blending the glitter powder with the top-coat clear paint. By shrinking the coating film, a matte coating film having uniform shrinkage 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 diagram showing an example of a positional relationship between a die coating machine and a workpiece when a coating material 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: 32)

Claims (9)

[Claims] Claims: 1. A primer coating film and a top coating base paint film are formed on a continuously moving long metal plate and baked, and then a top coating clear paint is applied on the top coating base film. Painted and baked, primer coating on a metal plate,
A method for forming a laminated coating film of a top-coating colored base coating film and a top-coating clear coating film, wherein the top-coating colored base coating film is formed on a primer coating film in a wet-on-wet manner. Painting method. 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.
60 to 95 parts by weight of a hydroxyl group-containing polyester resin having a hydroxyl value of 3 to 100 mg KOH / g and 5 to 40 parts by weight of at least one crosslinking agent selected from (B) a melamine resin and a blocked polyisocyanate compound. The coating method according to claim 1, wherein the coating method is a film-forming resin component. 3. An organic resin fine particle having an average particle diameter of 5 to 80 μm, which is not completely melted by baking at the time of forming a coating film, based on 100 parts by weight of the coating film forming resin component. The coating method according to claim 1 or 2, further comprising (D) a color pigment, if necessary, in an amount of from 40 to 40 parts by weight. 4. The overcoat clear coating composition according to claim 1, wherein the (E) has a number average molecular weight of 1,500 to 25,000 and a glass transition temperature of 0 to 70.
C., 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 (F) 10 to 50 parts by weight of a melamine resin crosslinking agent. The coating method according to claim 1. 5. The melamine resin cross-linking agent (F) in the top clear paint is a methyl etherified or mixed etherified melamine resin of methyl ether and butyl ether.
A melamine resin crosslinking agent containing at least 100% by weight, based on 100 parts by weight of a film-forming resin component of a top clear paint.
(G) As a curing catalyst, 0.1 to 2.0 parts by weight of a sulfonic acid compound or a neutralized sulfonic acid compound in terms of the amount of the sulfonic acid compound, and (H) a boiling point of 30 to 250.
The coating method according to claim 4, wherein the coating composition contains 0.1 to 10 parts by weight of a secondary or tertiary amine compound at a temperature of 0 ° C. 6. An overcoat clear paint is used in an amount of (I) a glitter powder of 0.005 to 100 parts by weight of a film-forming resin component.
The coating method according to claim 1, wherein the coating method contains 30 parts by weight. 7. The coating method according to claim 1, wherein the primer coating layer and the top coating base coating layer are extruded and coated in two layers from a die of a die coater. 8. An uncured primer coating layer coated on a continuously moving long metal plate, wherein a top coating base coating is applied in a curtain shape by a curtain coating method. The coating method according to claim 1. 9. A coated metal plate coated by the coating method according to claim 1.