JPH05161869A - Method for forming paint film - Google Patents

Abstract

PURPOSE:To provide a method for forming paint film adaptable for pollution control measure, high in economical efficiency through energy and resources conservation and space saving and capable of producing the paint film excellent in appearance, adhesion, scratch resistance, acid resistance and durability. CONSTITUTION:A method for forming paint film with a clear paint of the radical polymerization type hardenable at a glass transition temperature of 60-140 deg.C comprises the process A of applying a colored water-based paint to an object, allowing the resulting paint film to lose its fluidity and applying to this paint film an activated energy line hardenable clear paint and the process B of irradiating the unhardened clear paint film produced by undergoing the process A with an activated energy line and, as required, heating the paint film so as to harden the same.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
More specifically, it is suitable for pollution control, can form a coating with good appearance and excellent durability such as scratch resistance and acid resistance, and it is highly economical in energy saving, resource saving and space saving. Concerning the law.

[0002]

2. Description of the Related Art Conventionally, the outer coating of automobiles, motorcycles, electric appliances, etc., where cosmetic appearance is important, usually has a top coat film excellent in coating performance such as smoothness, sharpness and weather resistance. It is finished with the organic solvent-diluted thermosetting top coat that forms. As the coating method, generally, an organic solvent-diluted thermosetting enamel paint containing a color pigment and / or a metallic pigment is applied as a base coat, and after air-drying, an organic solvent-diluted thermosetting transparent clear paint is applied, and both are applied. The mainstream is a two-coat, one-bake system in which the coating film is cured simultaneously.

Further, in recent years, the demand for improving the cosmetic appearance has been further strengthened, and mainly in order to improve the smoothness of the top coating film, various rheology control agents have been added, and the intermediate coating film has been sharpened. The measures are taken. Further, since the high-solid type paint originally developed as a measure against pollution is easy to obtain a sufficient film thickness and is advantageous for improving the appearance, it may be used as a clear paint in combination with the above base coat.

[0004]

However, the above-mentioned various methods have a problem in that the number of steps by polishing and the sufficient improvement in appearance cannot be obtained. Further, a large amount of organic solvent is blended in the conventional base coat, which is not preferable from the viewpoint of resource saving and prevention of pollution. For this reason, there are cases where a highly solid paint is used as the base coat, but there is a limit to the reduction of organic solvent, and there is a problem that the light metallic finish such as silver lacks a white finish.

Further, the conventional organic solvent-diluted thermosetting transparent clear coating composition has an appearance quality such as scratches due to dust, car wash brush scratches, and stain marks on the coating film due to acid rain. There was a case where it was significantly impaired. Therefore, a clear clear paint which is not easily scratched or a clear clear paint which is excellent in acid resistance may be used as the clear paint in the above 2 coat 1 bake system, but it is possible to satisfy both scratch resistance and acid resistance at the same time. There wasn't. In addition, a method is also known in which the coating film formed by the two-coat one-bake method is further overlaid to give a necessary function and at the same time, to improve the appearance, but it is possible to save the number of man-hours in addition to a great increase in man-hours. There are many problems in terms of resources and prevention of pollution.

[0006]

Means for Solving the Problems The inventors of the present invention have earnestly studied a method of forming a coating film capable of eliminating the above-mentioned various defects in a finish coating method, and as a result, an aqueous coating material was used as a base coat and a transparent clear coating material was used. By using a specific active energy ray-curable clear coating, the above objects can be sufficiently achieved, and smoothness, image clarity, scratch resistance, and acid resistance are remarkably excellent, and adhesion, hardness, solvent resistance, and weather resistance The inventors have completed the present invention by finding that a coating film excellent in water resistance can be formed.

That is, the present invention provides a step (A) of applying a colored water-based paint to an object to be coated, and then applying an active energy ray-curable clear paint onto the paint film when the fluidity of the paint film is lost. (B) A coating film forming method comprising a step of irradiating an uncured clear coating film formed through the step (A) with an active energy ray and heating the coating film as necessary to cure the coating film, The clear coating has a glass transition temperature of 6
The present invention provides a method for forming a coating film, which is a radical polymerization type coating material that forms a cured coating film in the range of 0 to 140 ° C.

In the method of the present invention, the use of a colored aqueous paint containing little or no organic solvent as the base coat is useful for resource saving and pollution prevention.
In addition, since the clear coating contains no organic solvent or uses a specific active energy ray-curable coating with a very low organic solvent content, it has a beautifully finished appearance such as smoothness and sharpness of the coated surface. And the economical efficiency such as energy saving, resource saving, and space saving are further improved, and scratch resistance, acid resistance, etc. are also significantly improved.

The colored aqueous paint and clear paint used in the present invention will be described below. [1] Colored water-based paint A base coat paint that is pre-painted prior to the application of the clear paint described later, and is a water-soluble or water-dispersible liquid paint containing a base resin, a cross-linking agent, a coloring material and water as main components.

Each of the above components will be described. (1) Base resin: A basic constituent component of a base coat cured coating film, and examples thereof include acrylic resin, alkyd resin (polyester resin, hereinafter the same), epoxy resin, fluorine-containing resin, and the like. Used by dispersing in water. Of these, acrylic resin is preferable.

(A) Water-soluble acrylic resin An acid value obtained by copolymerizing a carboxyl group-containing vinyl monomer (M-1), a hydroxyl group-containing vinyl monomer (M-2) and another vinyl monomer (M-3). 20 to about 1
50, hydroxyl value about 20 to about 200, number average molecular weight about 3,
000 to about 100,000 neutralized acrylic resins may be mentioned.

A carboxyl group-containing vinyl monomer (M-
1) is a compound having at least one carboxyl group and one polymerizable unsaturated bond in one molecule, and examples thereof include acrylic acid, methacrylic acid, crotonic acid, maleic acid and itaconic acid.

The hydroxyl group-containing vinyl monomer (M-2) is
It is a compound having one hydroxyl group and one polymerizable unsaturated bond in one molecule, and this hydroxyl group mainly acts as a functional group that reacts with a crosslinking agent. As the monomer, specifically, a monoester product of acrylic acid or methacrylic acid and a dihydric alcohol having 2 to 10 carbon atoms is preferable, and examples thereof include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, Examples thereof include hydroxypropyl acrylate and hydroxypropyl methacrylate.

The other vinyl monomer (M-3) is a compound other than the above monomers (M-1) and (M-2) and has one polymerizable unsaturated bond in one molecule. The specific examples are listed below.

Monoester products of acrylic acid or methacrylic acid and monohydric alcohols having 1 to 20 carbon atoms: for example, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, lauryl acrylate, lauryl metalylate and the like.

Aromatic vinyl monomer: for example, styrene, α-methylstyrene, vinyltoluene and the like. Glycidyl group-containing vinyl monomer: A compound having one glycidyl group and one polymerizable unsaturated bond in one molecule, such as glycidyl acrylate and glycidyl methacrylate. Nitrogen-containing alkyl (C1 to C20) acrylate: for example, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate and the like.

Amide compound containing a polymerizable unsaturated bond:
For example, acrylic acid amide, methacrylic acid amide, dimethylacrylamide, N, N-dimethylpropylacrylamide, N-butoxymethylacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, diacetoneacrylamide and the like.

Vinyl compounds: For example, vinyl acetate, vinyl propionate, vinyl chloride and the like. Polymerizable unsaturated bond-containing nitrile compound: For example, acrylonitrile, methacrylonitrile and the like. Diene compound: For example, butadiene, isoprene and the like. These other vinyl monomers (M-3) may be used alone or in combination of two or more.

The copolymerization reaction of the vinyl monomer can be carried out by a known method, for example, azobisisobutyronitrile, benzoyl peroxide, dibutyl peroxide, ammonium persulfate, potassium persulfate, sodium pyrosulfite, t-butyl. It is carried out in an organic solvent compatible with water such as butyl cellosolve using a radical polymerization catalyst such as hydroperoxide or cumene hydroperoxide. The radical polymerization catalyst is all vinyl monomer 1
It is recommended to use about 0.1 to 10 parts by weight, preferably about 0.2 to 5 parts by weight, per 100 parts by weight. If the acid value of the resin is less than about 20, it is difficult to dissolve in water, and if it exceeds about 150, the coating performance may be deteriorated due to the effect of residual carboxyl groups.

The acrylic resin thus obtained can be made water-soluble by neutralizing it with a basic substance. The basic substance is, for example, ammonia: ethylamine,
Primary alkylamines such as propylamine, isopropylamine, butylamine and 2-ethylhexylamine: monoalkanolamines such as monoethanolamine and monobutanolamine: primary alkylamines such as dimethylamine, diethylamine, dipropylamine, diisopropylamine and dibutylamine. Secondary alkylamine: Diamine such as ethylenediamine and propylenediamine: Monoalkylmonoalkanolamine such as methylethanolamine: Dialkylmonoalkanolamine such as dimethylethanolamine and diethylethanolamine: Dialkanolamine such as diethanolamine and propanolamine: Triethylamine Tolualkylamines such as tributylamine: Trialkalamines such as triethanolamine and tributanolamine Ruamin: potassium hydroxide,
Examples thereof include alkali metal hydroxides such as sodium hydroxide. Among these, it is particularly preferable to use dialkanolamine, especially diethanolamine.

(B) Water-dispersible acrylic resin An average particle diameter of 0.05 to 1.0 μm obtained by emulsion polymerization of a vinyl monomer in the presence of a dispersion stabilizer.
This is a fine particle acrylic resin dispersed in water. The vinyl monomer to be emulsion-polymerized is a carboxyl group-containing vinyl monomer (M-
1), 1 type, or 2 or more types selected from a hydroxyl group-containing vinyl monomer (M-2) and other vinyl monomers (M-3) are preferable, and further, if necessary, a polymerizable unsaturated bond in one molecule. It is preferable to use a small amount of a polyvinyl compound (M-4) having two or more of them together because an intra-particle crosslinked water-dispersible acrylic resin is obtained and the coating film performance is further improved.

As the dispersion stabilizer, a surfactant or a water-soluble resin is used, and the surfactant may be either an anionic type or a nonionic type. Examples of the anionic type include, for example, long-chain alkyl sulfates, long-chain alkyl sulfonates and long-chain alkyl sulfonates. Chain alkyl sulfosuccinate alkali metal or ammonium salts; alkyl disulfate alkali metal salts; polyoxyethylene alkylphenyl ether sulfate alkali metal salts or ammonium salts; alkyl diphenyl ether disulfonate alkali metal salts or ammonium salts; dialkyl sulfo Examples thereof include alkali metal salts or ammonium salts of succinate, and nonionic compounds include polyoxyethylene alkylphenyl ether, polyoxyethylene alkyl ether, and polyoxyethylene alkyl ether. And oxyethylene long chain carboxylic acid esters and the like. The water-soluble resin has an acid value of 20-
An acrylic resin having about 150 and a number average molecular weight of about 5,000 to 30,000 is available. The amount of dispersion stabilizer used is
The amount is preferably 0.05 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, and particularly preferably 0.5 to 3 parts by weight, based on 100 parts by weight of all monomers.

Examples of the polyvinyl compound (M-4) having two or more polymerizable unsaturated bonds in one molecule include ethylene glycol diacrylate, ethylene glycol dimethacrylate, triethylene glycol diacrylate and tetraethylene glycol dimethacrylate. , 1,
6-hexanediol diacrylate, divinylbenzene, trimethylolpropane triacrylate and the like can be mentioned. It is preferable that the reactivity of two or more unsaturated bonds contained in each compound is not significantly different from each other. No compound is included.

As the neutralizing agent that can be used in the production of this water-dispersible acrylic resin, one or more selected from the above-mentioned basic substances are preferable, and among them, dialkanolamine and diethanolamine are most preferable. is there.

(C) Water-Dispersible Acrylic Resin This is an aqueous dispersion in which acrylic resin fine particles dispersed in water are stabilized by a stabilizer polymer, and the particles are the core part and the stabilizer polymer is the shell part. And the core /
It is a shell type emulsion.

Specifically, a vinyl monomer component containing no or almost no carboxyl group-containing vinyl monomer (M-1) is emulsion polymerized first, and then a large amount of the carboxyl group-containing vinyl monomer (M-1) is contained. It is obtained by emulsion polymerization with the addition of a vinyl monomer component, which is preferable from the viewpoint of coating workability because it thickens by neutralizing with a neutralizing agent. The neutralizing agent to be used is preferably one or more selected from the basic substances used for water-solubilizing the above-mentioned (i) water-soluble acrylic resin, and dialkanolamine, especially diethanolamine is particularly desirable. It is preferable that the core portion has undergone a crosslinking reaction.

(D) Water-dispersible acrylic resin A core in which the polymerizable particles (core portion) are crosslinked, and there is a polymer (shell portion) for stabilizing the particles, and the core portion and the shell portion are bonded to each other. / It is a shell type emulsion. The method for bonding the core part and the shell part is, in particular, to have a hydrolyzable functional group or a silanol group on the surface of the core part, and then to introduce a polymerizable unsaturated bond into these groups, and to the unsaturated bond. A product obtained by copolymerizing a vinyl monomer component containing a carboxyl group-containing vinyl monomer (M-1) (forming a shell portion) and then neutralizing the carboxyl group of the shell portion is preferable.

Since this product is thixotropic (thixotropic), the coating film hardly sags even under high humidity, and no abnormality is recognized even when an organic solvent is added.
It has features such as excellent smoothness, gloss, water resistance and adhesion. The core / shell type emulsion in which the core portion and the shell portion are bonded together is obtained, for example, by the following steps.

(A): Silane-based monomer having a hydrolyzable functional group and / or silanol group and a polymerizable unsaturated bond (hereinafter abbreviated as "silane-based monomer") (M-
5), an emulsion obtained by reacting a hydroxyl group-containing vinyl monomer (M-2) and another vinyl monomer (M-6) in an aqueous medium to three-dimensionally cross-link, and dispersing a fine particle polymer in water. To manufacture. The fine particles form the core portion.

(B): The fine particle polymer in the emulsion is reacted with a silane monomer (M-5) and / or an allyl (meth) acrylate (M-7). The silane-based monomer (M-5) reacts with a hydrolyzable functional group on the surface of the fine particle polymer, a functional group such as a silanol group or a hydroxyl group, and allyl (meth) acrylate (M-7) reacts with a (meth) acryloyl group. Utilizing the difference in reactivity of
A (meth) acryloyl group is copolymerized with an unreacted polymerizable unsaturated bond remaining in the fine particle polymer to introduce an allyl group on the surface of the fine particle polymer, and the fine particles can be obtained by any of these methods. A polymerizable unsaturated bond can be introduced into the surface of the polymer.

(C): In the emulsion after the reaction of (B) above, a carboxyl group-containing vinyl monomer (M-1)
A vinyl monomer component (M-8) containing is copolymerized, and the carboxyl group is further neutralized. The neutralized copolymer is a stabilizing polymer for stabilizing the dispersion of the fine particle polymer, and corresponds to the shell portion. In (C), the vinyl monomer component (M-8) is a silane-based monomer (M-5) on the surface of the particulate polymer after the reaction of (B) and /
Alternatively, it is copolymerized with a polymerizable unsaturated bond derived from allyl (meth) acrylate (M-7).

The silane-based monomer (M
-5) is a residue 1 having three hydrolyzable functional groups and / or silanol groups and one polymerizable unsaturated bond in one molecule.
And a general formula (R ₁ )
_3- Si-X (R ₁ is a hydrolyzable functional group and / or silanol group, X is a residue having a polymerizable unsaturated bond)
Indicated by. The silane-based monomer (M-5) mainly has a function of forming a core portion by internal crosslinking.

In this general formula, the hydrolyzable functional group for R ₁ is, for example, an alkoxy group having 1 to 12 carbon atoms, an alkoxyalkoxy group having 3 to 15 carbon atoms and 1 to 1 carbon atoms.
12 is an alkanoyloxy group or the like, and X is, for example, CH ₂ ═CH— and CH ₂ ═C (R ₂ ) —C (O) O.
— (CH ₂ ) _n — and the like, and R ₂ is H or CH ₃
-, N is an integer of 2-10.

Specific examples of the silane-based monomer (M-5) include vinyltrimethoxysilane, vinyltriethoxysilane, acryloxyethyltrimethoxysilane,
Methacryloxyethyltrimethoxysilane, acryloxypropyltrimethoxysilane, methacryloxypropyltrimethoxysilane, acryloxypropyltriethoxysilane, methacryloxypropyltriethoxysilane, vinyltris (β-methoxyethoxy) silane and the like can be mentioned. Among these, particularly preferable silane-based monomers include vinyltrimethoxysilane, γ-acryloxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, and the like.

As the hydroxyl group-containing vinyl monomer (M-2) in the step (A), those described above can be used, and the "other vinyl monomer (M-6)" is the above-mentioned monomer (M-).
1) to (M-5) from which (M-5) and (M-2) have been removed. The particle size of the fine particle polymer obtained in the step (A) varies depending on the kind and amount of the surfactant and the polymerization method, but is preferably 10 to 500 nm, particularly 30 to 300 nm.

Step (B): The fine particle polymer having a polymerizable unsaturated bond introduced therein obtained in the step (B) is abbreviated as "unsaturated fine particle polymer" hereinafter. The reaction of the silane-based monomer (M-5) is carried out by blending the silane-based monomer (M-5) in the emulsion obtained in the step (A), for example, 20
It is carried out by leaving it at -90 ° C or stirring it to introduce a polymerizable unsaturated bond to the surface of the fine particle polymer in the emulsion.

Further, comparing the polymerizability of the allyl double bond and the (meth) acryloyl double bond in the monomer (M-7), the latter is more likely to polymerize. When the monomer (M-7) is blended in the aqueous dispersion obtained in the step (A) and heated to 40 to 90 ° C, the monomer (M-7) is obtained.
(Meth) acryloyl-based double bond is polymerized with the unreacted polymerizable double bond contained in the particulate polymer in the aqueous dispersion, and as a result, the allyl-based double bond having poor polymerization reactivity is not formed. It can be presumed that it remains on the surface of the particulate polymer in the reaction state. When the monomers (M-5) and (M-7) are used in combination, the above reactions are considered to occur concurrently.

Step (C): The copolymerization reaction of the vinyl monomer component (M-8) in the step (C) is carried out by adding the vinyl monomer component (M-) to the emulsion of the unsaturated fine particle polymer obtained in the step (B). 8) can be added and the reaction can be carried out at a temperature of 50 to 90 ° C., and this reaction is preferably carried out in the presence of the radical polymerization initiator, if necessary.

Neutralization of the carboxyl group in the shell portion in the step (C) is carried out by mixing a neutralizing agent in the reaction system, and the neutralizing agent is selected from the water-soluble acrylic resin (a) mentioned above. One or more kinds selected from those exemplified as the solvating agent can be used, and dialkanolamine and diethanolamine are particularly preferable.

Core / combined core and shell
The shell type emulsion is (A), (B),
In the step (C), the vinyl monomer (M
(M-6) containing a vinyl monomer having a carboxyl group is used as -6), and the silane-based monomer (M-5) and / or allyl (meth) acrylate (M) is used in the step (B).
Instead of -7), an epoxy group-containing vinyl monomer such as glycidyl (meth) acrylate or 3,4-epoxycyclohexylmethyl (meth) acrylate is used, and a polymerizable unsaturated double bond is formed by the reaction between the carboxyl group and the epoxy group. It can also be obtained by introducing.

(E) Other base resin A water-soluble or water-dispersible alkyd resin containing a polybasic acid and a polyhydric alcohol, and optionally a fatty acid (including oil). A water-soluble or water-dispersible resin obtained by adding an α, β-unsaturated acid to an unsaturated bond portion of an unsaturated fatty acid-modified epoxy resin or obtained by esterifying a polybasic acid to a hydroxyl group of an epoxy ester compound.

The neutralizing agents used in these are the above-mentioned (a)
One or more selected from those exemplified above are preferable, and dialkanolamine and diethanolamine are particularly suitable. In the present invention, it is preferable to use a resin selected from the above (a) to (e) as the base resin of the water-based paint.

(2) Cross-linking agent A compound for reacting with the above-mentioned base resin to form a three-dimensionally cross-linked and cured base coat coating film, which is uniformly dissolved or dispersed in the base resin and has a cross-linking functional group. It has a group.

Specifically, methylol compounds of amino resins such as melamine resins, benzoguanamine resins and urea resins, alkyl ether compounds thereof, phenol formaldehyde resins, blocked polyisocyanate compounds and the like can be applied. These may be water-soluble or hydrophobic, but it is preferable to use hydrophobic ones in order to improve coating workability, storage stability, moisture resistance and the like.

For example, as the hydrophobic melamine resin, the solvent dilution ratio in a water / methanol mixed solvent (weight ratio 35/65) is 20 or less, preferably 15 or less, and its weight average molecular weight is 700 to 4,000. , Preferably 800
Those having a range of up to 3,000 are suitable. The solvent dilution rate is an index showing the solubility of the melamine resin in the hydrophilic solvent, and the lower the value, the more hydrophobic it is. The measurement method is as follows: Take 2 g of melamine resin in a 50 cc beaker, place it on the paper on which the No. 5 type is printed, then add a water / methanol mixed solvent (weight ratio 35/65) dropwise at 25 ° C and stir the type. Drop until unreadable. The drop amount (cc) at this time is divided by the amount of the melamine resin collected (cc / g).

The hydrophobic melamine resin is not particularly limited as long as the solvent dilution ratio and the molecular weight are satisfied, and various etherification products such as methyl alcohol, ethyl alcohol, isopropyl alcohol, n-
It is possible to use those modified with one or more of butyl alcohol, isobutyl alcohol, octyl alcohol, 2-ethylhexyl alcohol, benzyl alcohol and the like. Those modified with C ₄ or more alcohols, more preferably C _{4 to} C ₇ alcohols, are preferred in the present invention.

The amount of ether groups in the melamine resin is not particularly limited, but it is 5 on average per triazine ring nucleus.
It is suitable that the number is about 1 or less, preferably about 1.5 to 3. Further, regarding the amino group, the imino group, and the functional group represented by the methylol group, if the solvent dilution ratio and the molecular weight are satisfied, the kind and amount of the residual functional group are not particularly limited, but preferably the normal imino group ( The average number of amino groups) and methylol groups is 0.2 to 2.0, and more preferably 0.5 to 1.5, per triazine nucleus.

When blending the hydrophobic cross-linking agent with the water-soluble resin in advance, it is necessary to coat the surface of the hydrophobic cross-linking agent (usually in the form of fine particles) with the water-soluble resin. It is preferable for improving the properties (prevention of sagging, etc.) and storage stability.

The water-soluble resin has a hydrophilic group such as a carboxyl group (--COOH), a hydroxyl group (--OH), a methylol group (--CH ₂ OH), an amino group (--NH ₂ ), a sulfone group (--SO ₃ H). , Polyoxyethylene bond [CH ₂ CH
₂ O] _n etc. introduced resins (eg acrylic resin, alkyd resin, epoxy resin, etc.), the most common of which is the water-soluble one which has a carboxyl group introduced and neutralized to form an alkali salt. It is an acrylic resin.

The mixing ratio of the hydrophobic cross-linking agent and the water-soluble resin is usually about 20 to 100 parts by weight, preferably about 28 to 80 parts by weight, based on 100 parts by weight of the solid content. Is appropriate. The method of mixing the two is
Although it can be performed arbitrarily, for example, both components can be mixed and homogenized with a disper, a homomixer, or the like. At this time, if necessary, a small amount of a hydrophilic solvent such as an alcohol solvent or an ether solvent can be added. Next, while stirring vigorously, this is gradually added with deionized water in an amount of about 0.5 to 5 times the amount of the hydrophobic cross-linking agent and the water-soluble resin, to obtain a milky white or colored water dispersion. A cross-linking agent is obtained. The average particle size of the water dispersion is 0.
It is in the range of about 05 to 0.5 μm. The amount of the cross-linking agent to be added is 10 to 50 based on the total solid content weight with the base resin.
%, Particularly 15-40% is preferable.

(3) Colorant: It is for coloring the base coat coating film and includes metallic pigments and coloring pigments. Examples of the metallic pigment include aluminum flakes, copper bronze flakes, mica-like iron oxides, mica flakes, mica-like iron oxides coated with metal oxides, and mica flakes coated with metal oxides. As, for example, inorganic pigments such as titanium dioxide, iron oxide, chromium oxide, chromate, carbon black, phthalocyanine blue, phthalocyanine green, carbazole dioxazine violet, anthrapyrimidine yellow, isoindolinone yellow,
Organic pigments such as indanthrene blue and quinacridone red may be mentioned.

The water-based paint used in the method of the present invention can be obtained by mixing and dispersing the above-mentioned base resin, curing agent and colorant in water, and further, if necessary, an antifoaming agent, an antifungal agent and the like. May be. Also, an organic solvent can be blended.

[2] Active energy ray-curable clear coating material Next, the active energy ray-curable clear coating material used in the method of the present invention will be described. The active energy ray-curable clear coating composition applied to the colored aqueous coating composition coating surface is
There is no particular limitation as long as it is a radical polymerization type coating which can be cured by irradiation with active energy rays and forms a clear coating film having a glass transition temperature of 60 to 140 ° C., but is not limited to active energy ray curable resins and / or active energy rays. An active energy ray-curable clear coating material containing a curable vinyl monomer as a main component is suitable.

The active energy ray-curable resin includes an ethylenically unsaturated group-containing resin, and specifically, for example, a resin obtained by condensing (meth) acrylic acid with polyester, and an ethylenically unsaturated group-containing polyurethane. resin,
Ethylenically unsaturated group-containing epoxy resin, ethylenically unsaturated group-containing phosphorus-containing epoxy resin, ethylenically unsaturated group-containing acrylic resin, ethylenically unsaturated group-containing silicone resin,
Examples include ethylenically unsaturated group-containing melamine resins.

The active energy ray-curable vinyl monomer includes not only a polymerizable unsaturated monomer but also a polymerizable unsaturated oligomer. Specific examples include the following.

Examples of the polymerizable unsaturated monomer include esterified products of acrylic acid or methacrylic acid and a monohydric alcohol having 1 to 28 carbon atoms, such as methyl acrylate, methyl methacrylate and ethyl acrylate.
Ethyl methacrylate, n-butyl acrylate, n-butyl methacrylate, iso-butyl acrylate, iso-butyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, propyl acrylate, propyl methacrylate, acrylic acid Hexyl, hexyl methacrylate,
Octyl acrylate, octyl methacrylate, lauryl acrylate, lauryl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate,
Examples include stearyl acrylate and stearyl methacrylate. Examples of the monomer include vinyl aromatic compounds such as styrene, vinyltoluene, methylstyrene, chlorostyrene, and divinylbenzene: vinyl acetate, vinyl chloride, vinyl isobutyl ether, methyl vinyl ether, acrylonitrile, 2-ethylhexyl vinyl ether, and other vinyl compounds. Compounds can also be used. Further, as the monomer, carboxyl group-containing monomers such as acrylic acid and methacrylic acid: 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate,
Hydroxyl group-containing monomers such as 2-hydroxypropyl acrylate and 2-hydroxypropyl methacrylate: Addition products of isocyanate compounds such as butyl isocyanate and phenyl isocyanate with the above hydroxyl group-containing monomers: Addition products of phosphoric acid and the above hydroxyl group-containing monomers: Vinylpyrrolidone Unsaturated monomers having a nitrogen-containing heterocycle such as vinyl pyridine can also be used.

As the polymerizable unsaturated oligomer,
For example, diethylene glycol diacrylate, diethylene glycol dimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, propylene glycol diacrylate, propylene glycol dimethacrylate, 1,3-butanediol diacrylate, 1,3-butanediol dimethacrylate, 1, 4-butanediol diacrylate,
1,4-butanediol dimethacrylate, neopentyl glycol diacrylate, neopentyl glycol dimethacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate,
Trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, pentaerythritol tetraacrylate,
Di-, tree or tetravinyl compounds such as pentaerythritol tetramethacrylate, tricyclodecane dialcohol diacrylate, tricyclodecane dialcohol dimethacrylate: reacting acrylic acid and / or methacrylic acid with an adduct of polyhydric alcohol and ethylene oxide Products obtained by reacting an adduct of polyhydric alcohol and propylene oxide with acrylic acid and / or methacrylic acid: Polyhydric alcohol and ε-
The product obtained by reacting acrylic acid and / or methacrylic acid with an adduct with caprolactone: a phosphorus-containing polymerizable unsaturated oligomer and the like are included. The monomers and oligomers described above can be used alone or in combination of two or more.

The clear paint can be cured by irradiating with active energy rays such as electron rays and ultraviolet rays. If necessary, it may be heated before irradiation for the purpose of removing the solvent. In the case of curing by ultraviolet irradiation, it is necessary to add a photopolymerization initiator to the coating material in advance. As the photopolymerization initiator, a normal photopolymerization initiator of a type that is excited by irradiation of ultraviolet rays to generate a radical is used, and examples thereof include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin n-propyl ether, and benzoin isopropyl. Ether, benzoin n-butyl ether, α-hydroxyisobutylphenone, benzophenone, p-methylbenzophenone, Michler's ketone, acetophenone, 1
-Hydroxy-1-cyclohexylacetophenone, 2
-Chlorothioxanthone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholino-propanone, anthraquinone, 2-methylanthraquinone, phenyl disulfide, 2-nitrofluorene and the like can be mentioned. These photopolymerization initiators can be used alone or in admixture of two or more, and the blending amount thereof is the sum of the active energy ray-curable resin and the active energy ray-curable vinyl monomer, that is, with respect to 100 parts by weight of the binder component. 0.
The range of 1 to 10 parts by weight is preferable.

In order to accelerate the photopolymerization reaction by these photopolymerization initiators, a photosensitization accelerator may be used in combination with the photopolymerization initiator. Examples of the photosensitizer that can be used in combination include, for example, triethylamine, triethanolamine, 2-
Examples include tertiary amines such as (dimethylamino) ethanol; alkylphosphines such as triphenylphosphine; and photosensitization accelerators such as thioethers such as β-thiodiglycol. Each of these photosensitizers may be used alone or 2
It is possible to mix and use one or more species, and the blending amount thereof is preferably in the range of 0.1 to 10 parts by weight with respect to 100 parts by weight of the binder component.

On the other hand, when electron beam irradiation is used, it is not necessary to add the above-mentioned photopolymerization initiator or photosensitization accelerator to the clear paint. As the electron beam generation source in the case of curing the clear paint by irradiation of an electron beam, Cockcroft type, Cockcroft-Walton type, Van de Graaf type, resonance transformer type, transformer type, insulating core transformer type,
An electron beam generator such as a dynamitron type, a linear filament type and a high frequency type can be used. The electron beam irradiation conditions at that time vary depending on the film thickness and the like, but generally a dose within the range of 1 to 20 megarads is suitable.

As the ultraviolet ray irradiation source, a mercury lamp, a xenon lamp, a carbon arc, a metal halide lamp, sunlight or the like can be used. The irradiation conditions of ultraviolet rays are not particularly limited, but it is preferable to irradiate light rays containing ultraviolet rays within the range of 150 to 450 nm in air or in an inert gas atmosphere. The UV irradiation conditions vary depending on the film thickness and other factors, but generally 50 to 2,000 mJ / c
The dose is m ² , preferably 300 to 1,200 mJ / cm ² .

It is essential that the glass transition temperature (Tg) of the coating film formed by the above clear paint is 60 to 140 ° C, preferably 70 to 120 ° C. This Tg is 6
If it is lower than 0 ° C, a coating film having sufficient hardness, chipping resistance and durability cannot be obtained. On the other hand, if Tg is higher than 140 ° C, the adhesion and flexibility to the coating surface of the colored water-based coating are poor. It is not preferable because it will happen. The Tg of the clear coating composition can be adjusted by appropriately selecting the composition of the active energy ray-curable resin, the compounding components such as monomers and oligomers, the amount of crosslinkable functional groups, and the compounding ratio.

The glass transition temperature referred to in the present invention is DAYN
AMIC VISCOELASTOMETER MODEL VIBRON DDV-II-EA type (TO
YOBALDWIN Co. Ltd.), and the sample used for such measurement is the clear paint coated on a tin plate to a predetermined film thickness based on the dry film thickness. It is a clear film isolated from a tin plate by the mercury amalgam method after being irradiated with energy rays and cured.

The clear coating composition has a cured coating film having a molecular weight between crosslinks of 50 to 70, which is measured by the xylene swelling method.
0, preferably 70 to 300 is desirable from the viewpoint of scratch resistance. The xylene swelling method uses an isolated clear film prepared in the same manner as the sample used at the time of measuring the glass transition temperature, and as shown in, for example, JP-A No. 1-310773, the resin in the xylene swelling coating film. It is a method of obtaining the molecular weight between crosslinks from the volume fraction of minutes.

If necessary, the clear coating composition may include a surface conditioner, a leveling agent, a reactive diluent, an ultraviolet absorber, and
A light stabilizer, an anti-repellent agent, a thixotropy-imparting agent, a solvent and the like can be added, and pigments, dyes and inert organic polymers can be used as long as they do not inhibit curing or cause poor transparency.

In the method of the present invention, a coating film is formed on an object to be coated by using the above-mentioned colored aqueous coating material and active energy ray-curable coating material.

In the coating film forming method of the present invention, the outer coating of automobiles such as passenger cars, buses, trucks and motorcycles is particularly suitable as the coating object, but other coatings such as outer coating of electric products are also suitable. It is suitable for coated objects where the finished appearance is important. The material of the object to be coated is not limited to metal, but can be applied to plastics, inorganic substances and the like. For these objects to be coated, usual chemical conversion treatment, electrodeposition coating (a known cationic electrodeposition coating can be used as electrodeposition coating, but the film thickness is about 20 μm based on the cured coating in the flat part, Moreover, those which form a single-layer coating film are particularly suitable.), And intermediate coating may be applied if necessary.

First, a colored water-based paint is applied to the object to be coated. It is preferable to use an atomization type coating machine as the coating machine, for example, an air spray coating machine, an airless spray coating machine and an air atomization type or rotary electrostatic coating machine, and the like, the coating viscosity at the time of coating, 800-5,000 cps
It is preferably adjusted to about / 6 rpm (B-type viscometer), and the coating film thickness is preferably about 10 to about 50 microns, particularly about 15 to about 30 microns based on the heat-cured film.

After applying the above-mentioned colored paint, an active energy ray-curable clear paint is applied on the paint film. At this time, before applying the active energy ray-curable clear paint, it is usually necessary to set the colored water-based paint coating, and to dry it more than the touch-dry state in a state where it loses fluidity by heating and drying. is necessary. The state where the fluidity is lost includes both an uncured state and a cured state. By this drying, the content of water in the coating film of the colored aqueous paint is usually adjusted to 5% by weight or less. If an active energy ray-curable clear paint is applied while the colored water-based paint coating is in a fluid state, the colored water-based paint coating and the clear paint coating will mix significantly, resulting in a deterioration in appearance and coating performance. , Colored water-based paint The water content in the coating film may deteriorate the coatability of the clear paint.

When coating the active energy ray-curable clear coating composition, it is preferable to use an atomizing coating machine similar to the case of the colored water-based coating composition as the coating composition, and the coating composition viscosity at the coating is 15 to 25 seconds ( Ford Cup No. 4/25
The coating film thickness is preferably about 5 to about 40 microns, especially about 15 to 3 based on the dry film thickness.
0 micron is suitable. When the coated clear coating film contains a solvent, it is preferable to remove the solvent by heating, air blowing or the like, if necessary, before irradiation with active energy rays. Further, after the clear coating film is cured by irradiation with active energy rays, it can be heated if necessary. When the colored aqueous paint coating film is uncured, the colored aqueous paint coating film can be cured by this heating.

[0071]

In the present invention, since the water-based paint is used as the base coat, it can contribute to resource saving and pollution prevention, and is safe in handling and economical. In particular, when a water-dispersible acrylic resin, especially a core / shell type emulsion is used as the base resin, the coating film does not sag immediately after being applied with a high shearing force or even under high humidity. A coating film with excellent smoothness can be formed with little or no effect, and even if an organic solvent is added or brought into contact with it, sagging, smoothness, etc. do not deteriorate. Furthermore, the water resistance and chemical resistance of the coating film. , Weather resistance, metallic feeling, and physical performance are also good.

Further, in the method of the present invention, since a specific active energy ray-curable clear coating composition is applied on the base coat coating film, the following excellent effects can be obtained. The main curing reaction of the clear coating film is the radical polymerization reaction, and the generation of reaction by-products is extremely small, so the volume shrinkage during the curing process of the coating film is small, and there is no high level of fine unevenness (scratchy skin). It is possible to obtain a coating film having image clarity and smoothness. Clear paint is easy to use as a high solids paint and can contribute to resource saving and pollution prevention.

The acid resistance is extremely good, and problems such as stains, glossiness and etching due to acid rain can be solved. Has excellent scratch resistance. Since the curing of the clear coating material can be achieved in an extremely short time of several seconds to several tens of seconds, it is possible to save energy and save the equipment space for curing as compared with the case of the thermosetting clear coating material.

[0074]

EXAMPLES Next, production examples, examples and comparative examples will be given.
The present invention will be described more specifically. All parts and% are by weight. Production Example (1) Core / shell type emulsion (EM-1 to
Production of 6) Using the components shown in Table 1, production was performed according to the following steps.

Step (A): Deionized water 12 in the flask
0 part was added, it was heated to 80 to 85 ° C., and 2 parts of the first pre-emulsion in Table 1 was added dropwise with stirring.
After aging for a minute, the remaining first pre-emulsion was added dropwise at a constant rate for 3 hours at the same temperature to obtain an aqueous dispersion of a core portion obtained by three-dimensionally crosslinking reaction. Step (B): After the completion of the dropping of the first pre-emulsion, the silane-based monomer and the allyl methacrylate are quickly added dropwise and kept at 80 to 85 ° C. for 1 hour to allow the silane-based monomer and the allyl methacrylate to react with the core surface. It was

Step (C): Add 50 parts of deionized water,
The second pre-emulsion of Table 1 was added dropwise at 80 to 85 ° C. at a constant rate over 1 hour. Then, the mixture was kept at the same temperature for 1 hour and then rapidly cooled to room temperature, and deionized water was added so that the solid content was 30%. The polymer particles obtained were insoluble in organic solvents. Then, deionized water was added and the mixture was neutralized with diethanolamine and adjusted to a solid content of 20% to obtain core / shell type emulsions EM-1 to EM-6.

[0077]

[Table 1]

[0078]

[Table 2]

In Table 1, * 1 to 4 indicate the following. (* 1) Pre-emulsion: An emulsion obtained by uniformly dispersing a mixture of the components described in each with a high-speed stirrer. (* 2) Weight ratio based on the polymerizable monomer component contained in each pre-emulsion. (* 3) Diethanolamine was used for neutralization. (* 4) Measured by laser correlation spectroscopy.

(2) Manufacture of core / shell type emulsion (EM-7) 140 parts of deionized water and "Newcol 707S" were placed in a reaction vessel.
F "(manufactured by Nippon Emulsifier Co., Ltd., anionic surfactant, solid content about 30%) 2.5 parts and the following monomer mixture (1)
1 part was added, the mixture was stirred and mixed in a nitrogen stream, and 3 parts of 3% ammonium persulfate was added at 60 ° C. Then, after raising the temperature to 80 ° C., 79 parts of the following monomer mixture (1),
A monomer emulsion consisting of 2.5 parts of "Newcol 707SF", 4 parts of a 3% ammonium persulfate aqueous solution and 42 parts of deionized water was added to the reaction vessel using a metering pump over 4 hours. After completion of the addition, aging was carried out for 1 hour.

Further, the following monomer mixture (2) was prepared at 80 ° C.
20.5 parts and 4 parts of a 3% ammonium persulfate aqueous solution were simultaneously dropped into the reaction vessel in parallel over 1.5 hours. After the addition was completed, the mixture was aged for 1 hour, diluted with 30 parts of deionized water, and 30 ° C.
Filtered through a 200 mesh nylon cloth. To this filtrate, add deionized water and adjust the pH with diethanolamine.
Adjusted to 7.5, average particle size 100nm, nonvolatile content 20%
To obtain a core / shell type emulsion (EM-7).

Monomer mixture (1) Methyl methacrylate 54 parts Styrene 8 parts n-Butyl acrylate 10 parts 2-Hydroxyethyl acrylate 5 parts 1,6-hexanediol diacrylate 2 parts Methacrylic acid 1 part Monomer Mixture (2) Methyl methacrylate 5 parts N-butyl acrylate 7 parts 2-Ethylhexyl acrylate 5 parts Methacrylic acid 3 parts "Newcol 707SF" 0.5 parts

(3) Preparation of Core / Shell Type Emulsion (EM-8) The following monomer mixture (3) was used in place of the monomer mixture (1) of (EM-7), and other than that. A core / shell emulsion (EM-8) having an average particle size of 100 nm and a nonvolatile content of 20% was obtained by the same steps as in (EM-7). Monomer mixture (3) Methyl methacrylate 52.5 parts Styrene 10 parts N-butyl acrylate 9 parts 2-Hydroxyethyl acrylate 5 parts Allyl methacrylate 2.5 parts Methacrylic acid 1 part

(4) Aqueous dispersion of hydrophobic melamine resin (E
Production of M-9) Hydrophobic melamine resin (A) (details below) has a solid content of 25.
Into an agitation container so that the total amount becomes 20 parts, add 20 parts of the acrylic resin aqueous solution (B) (details below), and rotate at 1,000-
88.75 parts of deionized water was gradually added while stirring with a disperser at 1,500 rpm, and stirring was continued for another 30 minutes, whereby the hydrophobic melamine resin fine particles were coated with a water-soluble acrylic resin and dispersed in water. A crosslinking agent having an average particle size of 110 nm was obtained.

(Production of Hydrophobic Melamine Resin (A)) 126 parts of melamine and 80% paraformalin (Mitsui Toatsu Chemicals, Inc.) were placed in a 2-liter four-necked flask equipped with a thermometer, a stirrer and a reflux condenser. 225 parts and n-butanol 592 parts were added, and the pH was adjusted to 9.5 to 10% with a 10% caustic soda aqueous solution.
After adjusting to 0, the mixture was reacted at 80 ° C. for 1 hour.

Thereafter, 888 parts of n-butanol was added, and 5
% Sulfuric acid aqueous solution to adjust the pH to 5.5 to 6.0, and the reaction was carried out at 80 ° C. for 3 hours. After completion of the reaction, the solution was neutralized with a 20% aqueous sodium hydroxide solution to pH 7 to 7.5, and n-butanol was concentrated under reduced pressure at 60 to 70 ° C and filtered to obtain a hydrophobic melamine resin A. When this resin was analyzed, it had a nonvolatile content of 80% and a water / methanol mixed solvent (weight ratio 35/65).
The solvent dilution rate (hereinafter referred to simply as the solvent dilution rate) in 3.
6, the weight average molecular weight was 800.

(Production of Acrylic Resin Aqueous Solution (B)) 60 parts of butyl cellosolve and 15 parts of isobutyl alcohol are added to a reaction vessel and heated to 115 ° C. in a nitrogen stream. 11
When the temperature reached 5 ° C, 26 parts of n-butyl acrylate, 47 parts of methyl methacrylate, 10 parts of styrene, 2-methacrylate
A mixture of 10 parts of hydroxyethyl, 6 parts of acrylic acid and 1 part of azobisisobutyronitrile was added over 3 hours. After the addition was completed, the mixture was aged at 115 ° C. for 30 minutes, a mixture of 1 part of azobisisobutyronitrile and 115 parts of butyl cellosolve was added over 1 hour, and after aged for 30 minutes, the mixture was filtered through a 200 mesh nylon cloth at 50 ° C.

The acid value of the obtained reaction product was 48, the viscosity was Z ₄ (Gardner foam viscometer), and the nonvolatile content was 5%. This was neutralized with diethanolamine in an equivalent amount, and deionized water was further added to obtain a 50% acrylic resin aqueous solution (B).

(5) Aqueous dispersion of hydrophobic melamine resin (E
Production of M-10) In EM-9, instead of the above hydrophobic melamine resin A, a commercially available hydrophobic melamine resin (“Super Beckamine L-1
27-75B ", manufactured by Dainippon Ink and Chemicals, Inc., nonvolatile content 80%, solvent dilution rate 0.5, weight average molecular weight 1,4.
No. 00 to 1,800) was used in the same manner as above, except that an aqueous dispersion of a crosslinking agent having an average particle diameter of 120 nm (EM) was used.
-10) was obtained.

(6) Production of concentrated aluminum pigment liquid Aluminum paste (metal content 65
%) 23 parts and butyl cellosolve 25 parts, and the mixture was stirred for 1 hour to obtain an aluminum pigment concentrated liquid (P-1).

(7) Production of Coloring Material-Containing Aqueous Paint An aqueous coating composition for base coat was obtained using the emulsion obtained in the above Production Example, an aqueous dispersion of melamine resin, a pigment concentrate, and the like. That is, the components shown in Table 2 were uniformly mixed and dispersed, and 2.9 to 2.1 parts of "Acrysol ASE-60" (a thickener manufactured by Rohm and Haas Co.) and diethanolamine 0.27 to 0.20 parts were added to each to give an apparent viscosity of 3,000 cps / 6 rpm (B type viscometer), pH:
It was adjusted to 7.80 to obtain water-based paints Y-1 to 10. In Table 2, "Aqueous solution (B)" in the column of base resin indicates the acrylic resin aqueous solution (B) used in the production of the above aqueous dispersion (EM-9).

[0092]

[Table 3]

(8) Production of active energy ray-curable clear paint Production Example 1 Urethane resin solution containing ethylenically unsaturated group (Note-1) 95 parts

[0094]

[Chemical 1]

1,6-hexanediol diacrylate 23 parts Irgacure 651 (manufactured by Ciba Geigy, photopolymerization initiator) 5 parts The above components were mixed to prepare an unsaturated urethane clear coating L-1.
Got

(Note-1) A urethane resin solution containing an ethylenically unsaturated group was prepared as follows. Methyl methacrylate 300 parts, n-butyl acrylate 6
00 parts, 2-hydroxyethyl acrylate 100 parts, toluene 1,500 parts, azobisisobutyronitrile 50
Parts were placed in a four-necked flask and kept at 110 ° C. for 5 hours to produce an acrylic resin polyol solution. This acrylic resin polyol has a molecular weight of 5,000 and a hydroxyl equivalent of 1,160.
Met. To this acrylic resin polyol solution, 1,014 parts of a monoisocyanate compound obtained by adding 222 parts of isophorone diisocyanate and 116 parts of 2-hydroxyethyl acrylate was added and reacted at 100 ° C. for 3 hours to completely react the remaining isocyanate groups. Was confirmed and cooled to obtain an ethylenically unsaturated group-containing urethane resin solution. The solid content of the obtained resin solution was 57%.

Production Example 2

[0098]

[Chemical 2]

Ethylenically unsaturated group-containing acrylic resin (Note-2) 30 parts Trimethylolpropane triacrylate 50 parts Irgacure 651 5 parts The above components are mixed to prepare an unsaturated acrylic clear paint L-2.
Got

(Note-2) The above ethylenically unsaturated group-containing acrylic resin was produced as follows. 400 parts of styrene, 600 parts of n-butyl methacrylate,
600 parts of n-butyl acrylate, 200 parts of acrylic acid,
1,800 parts toluene, 9 azobisisobutyronitrile
0 part was placed in a four-necked flask and stirred, and the mixture was maintained at 110 ° C. for 5 hours to prepare a carboxyl group-containing acrylic resin solution. Then, 380 parts of glycidyl methacrylate and 5 parts of tetraethylammonium bromide were added thereto and kept at 110 ° C. for 2 hours while stirring, and after confirming that glycidyl methacrylate was sufficiently reacted, the pressure was reduced and the toluene was removed to cool the solvent. An ethylenically unsaturated group-containing acrylic resin (solid content 100%) was obtained.

Production Example 3

[0102]

[Chemical 3]

Polyester resin containing ethylenically unsaturated group (Note-3) 50 parts Irgacure 651 5 parts

The above components were mixed to obtain an unsaturated polyester clear paint L-3. (Note-3) The ethylenically unsaturated group-containing polyester resin was manufactured according to the following.
Put 148 parts of phthalic acid, 146 parts of adipic acid, and 354 parts of 1,6-hexanediol in a four-necked flask.
The mixture was azeotropically dehydrated with toluene at ℃ for 5 hours and then cooled to 100 ℃. After adding 144 parts of acrylic acid and 10 parts of paratoluene sulfonic acid and keeping it for 5 hours while azeotropically dehydrating with toluene at 120 ° C. while blowing a small amount of air, the toluene is removed to contain an ethylenically unsaturated group. A polyester resin (solid content 100%) was obtained.

Production Example 4 Unsaturated urethane clear coating composition L-was prepared in the same manner as in Production Example 1 except that the photopolymerization initiator Irgacure 651 was not added to the unsaturated urethane clear coating composition L-1 of Production Example 1.
Got 4.

Production Example 5 Urethane resin solution containing the ethylenically unsaturated group (Note-1) 95 parts Monomer of the above formula (I) used in Production Example 1 46 parts Irgacure 651 5 parts The above components were mixed and unsaturated. Urethane clear paint L-5
Got

Production Example 6 Ethylenically unsaturated group-containing acrylic resin (Note-2) 30 parts Trimethylolpropane triacrylate 70 parts Irgacure 651 5 parts The above components were mixed to prepare an unsaturated acrylic clear paint L-6.
Got

Examples 1 to 10 Using the colored aqueous coating material and the active energy ray-curable clear coating material obtained in the above Production Examples, coating was carried out in the following manner to prepare coated plates. As the object to be coated, "Unibond # 303
0 "(Nihon Parkerizing Co., Ltd., zinc phosphate type)
Steel plate (size 7.5 × 15 × 0.2cm)
"Electron No. 9200" (Kansai Paint Co., Ltd.)
Made by epoxy-based cationic electrodeposition paint) 20 μm,
Further, an "Amilak N-2 Sealer" (Kansai Paint Co., Ltd., aminopolyester resin-based intermediate coating material) coated thereon was used.

First, as a base coat, deionized water was added to the colored aqueous paint (Y) shown in Table 3 so that the solid content was 2%.
It was adjusted to 0%, and electrostatic spray coating was performed in an environment where the temperature was 25 ° C. and the relative humidity was 70%. The coating thickness is 15 based on the dry coating film.
˜20 μm.

Next, the colored aqueous paint film was heated under the conditions shown in Table 3. All the coating films after heating had no fluidity and were in a dry state more than finger-drying, and in Examples 3 to 10, they were cured. Then, xylene /
A clear paint whose viscosity was adjusted to about 20 seconds (Ford Cup No. 4, 25 ° C) with a mixed solvent of butyl acetate = 2/1 was applied by air spray coating to a dry film thickness of about 20 µm, and then 70 ° C. The solvent was removed by heating for 10 minutes. In Examples 4 and 5, the clear paint had a viscosity of 25 seconds (Ford cup No. 4/25 ° C.), and therefore the viscosity was not adjusted by a solvent, and the paint was directly applied and heated after the paint was applied. There wasn't.

Next, in Examples 1 to 7 and 9 and 10, the clear coating film was exposed to a high pressure mercury lamp of 180 W / cm at a dose of 700.
The clear coating film was cured by irradiating it at mJ / cm ² . In Example 1, after irradiation, the coated plate was heated at 140 ° C. for 30 minutes to be cured. In Example 2, the coated plate was 1 after the irradiation.
Cured at 40 ° C. for 20 minutes. In Examples 3 to 10, heating after irradiation was not performed. Further, in Example 8, clear paint was applied, the solvent was removed, and electron beam irradiation was then performed by an electron beam generator under the condition of a dose of 7 megarads to cure the clear coating film.

COMPARATIVE EXAMPLE 1 On the article to be coated used in Example 1, the colored aqueous coating material Y-1 was applied in the same manner as in Example 1 as a base coat, and then 120 ° C.
And dried for 10 minutes. Then, an organic solvent-based acrylic resin / melamine resin-based thermosetting clear coating L-7 is applied on top of this.
(“Magiclon Clear” manufactured by Kansai Paint Co., Ltd.) was adjusted to a viscosity of about 20 seconds (Ford cup No. 4, 25 ° C.) with a mixed solvent of xylene / butyl acetate = 2/1, and dried by air spray coating. After coating so as to have a thickness of about 20 μm, it was cured by heating at 140 ° C. for 30 minutes.

A coating film performance test was conducted on the cured coated plates obtained in Examples 1 to 10 and Comparative Example 1. The results are shown in Table 3.
Shown in. Table 3 shows the glass transition temperature (Tg point) of the clear coating film. The Tg point of the clear coating film in Table 3 and the coating film performance test were performed according to the following methods.

Tg point of clear coating film: A clear coating material was coated on a tin plate so that the dry film thickness was 20 μm, and the irradiation conditions (in Examples 1 to 7 and 9, 10 were
After irradiation with ultraviolet rays under the condition that the irradiation dose was 700 mJ / cm ^2, and irradiation with electron beam irradiation under the conditions that the irradiation dose was 7 megarads in Example 8, the cured film was isolated from the tin plate after curing. About this isolated membrane DYNAMIC VISCOELAST
Tg point was measured with OMETER MODEL VIBRONDDV-II-EA type.

Smoothness: The smoothness of the coated surface was visually evaluated. ○
Indicates good, Δ indicates inferior, and x indicates extremely inferior. Image clarity: The coated surface was measured with an image clarity measuring device (manufactured by Suga Test Instruments Co., Ltd.). The values in Table 3 are ICM values, 0 to 100%
Value in the range of, and the larger the number, the sharpness (image clarity)
And the ICM value is 80% or more, the image clarity is extremely excellent. Acid resistance: Drop 0.5 ml of 40% sulfuric acid aqueous solution on the coated surface,
After heating at 70 ° C. for 20 minutes and washing with water, the state of the coated surface was evaluated. Depending on the degree, there were no abnormalities (⊚), abnormal glossiness, swelling, and other abnormalities (x), and in order of goodness, the four grades of ⊚, ○, Δ, and × were evaluated.

Scratch resistance: A dyed product friction fastness tester (manufactured by Daiei Kagaku Seiki Seisakusho) is used. Polishing powder (Dalma Cleanser) is kneaded with water, placed on the coated surface, pressed on it with a tester terminal, and rubbed 20 reciprocations with a load of 0.5 kg. After washing with water, the degree of scratches was evaluated. ◎, in order from the best
Judgment was made in four levels of ○, △, and ×. Adhesion: According to JIS K5400 8.5.2-1990, 100 pieces of 1 mm x 1 mm squares are made on the coating film, and adhesive cellophane tape is attached to the surface, and it remains on the coated surface after it is rapidly peeled off. The number of crepe coats is shown.

[0117]

[Table 4]

Claims (2)

[Claims] 1. A colored water-based paint is applied to (A) an object to be coated,
The active energy ray is applied to the uncured clear coating film formed through the steps (B) and (A) of applying the active energy ray-curable clear coating composition on the coating film in the state where the fluidity of the coating film is lost. A coating film forming method comprising a step of curing the coating film by irradiating the coating composition and heating it as necessary, wherein the clear coating composition has a glass transition temperature of 60 to 140.
A method for forming a coating film, which is a radical polymerization type coating material that forms a cured coating film in the range of ℃. 2. The coating film forming method according to claim 1, wherein the colored aqueous coating material is a liquid coating material containing a base resin, a crosslinking agent, a colorant and water as main components, and the base resin is a core / shell type emulsion. Law.