JPH06145584A - Top coating method - Google Patents

Abstract

(57) [Summary] [Structure] On the object on which the coating film of the undercoat paint is formed,
Fluorine-containing vinyl monomers represented by vinyl fluoride, tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropylene, or perfluoroalkyl / trifluorovinyl ethers having an alkyl group of C _{1 to} C ₁₈ , and the like, By copolymerizing monomers containing 2-oxo-1,3-dioxolane group-containing vinyl-based monomers and other copolymerizable vinyl-based monomers as essential monomer components With the resulting fluorine-containing vinyl copolymers,
A topcoat coating method comprising applying a topcoat paint containing a specific fluorine-containing resin composition as an essential component, which contains a compound having at least two carboxyl groups in one molecule. [Effect] Particularly, it gives a very useful film excellent in weather resistance and chemical resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel and useful top coating method. More specifically, the present invention copolymerizes monomers comprising a fluorine-containing vinyl monomer, a 2-oxo-1,3-dioxolane group-containing vinyl monomer and another copolymerizable vinyl monomer. At the very least,
Specific fluorine-containing vinyl copolymer (A) and compound (B) having at least two carboxyl groups in one molecule
The present invention relates to a topcoating method, which is particularly excellent in weather resistance and chemical resistance, and which comprises applying a topcoating paint containing a resin composition containing as a main component as an essential component.

In addition, the above-mentioned top coating method of the present invention is mainly used mainly for the fluororesin / melamine resin coating or the acrylic resin / melamine resin as in the case of coating metals such as car bodies. It is used in the fields where the paints were used.

[0003]

2. Description of the Related Art Heretofore, as a top coating method for automobile bodies and the like, a top coating method using a melamine / alkyd resin and a melamine / acrylic resin as a top coating has been used. However, the coating film obtained by coating these top-coat paints, when used for a long period of time, has reduced gloss and discoloration.

As a solution to these problems, there has been proposed a method of using a fluororesin as the top coating material. (JP-A-61-197074 or 63-264175)

According to this method, a coating film excellent in weather resistance for an extremely long period of time can be obtained, but it cannot be said that the acid resistance is still sufficient. In recent years, damage to the coating film due to acid rain, which is thought to be due to sulfur oxides and nitrogen oxides released into the atmosphere, has become a problem in recent years, and it is now time to improve acid resistance. , Strong, there is no demand for it.

However, in order to solve the problem of maintaining the appearance of the coating film, such as the deterioration of the appearance due to acid rain, a topcoat using a paint that combines the existing fluororesin or acrylic resin with a curing agent of melamine resin. With the painting method, it is no longer possible to satisfy these required performances.

In these movements, a combination of a polyol type resin and an isocyanate prepolymer, a combination of a silanol group-containing resin and an epoxy group containing resin, a moisture curing by a trialkoxysilyl group, a hydroxyl group containing resin and an acid are used. Overcoating methods using various paints such as a curing system in combination with an anhydride group-containing resin are gradually being developed and studied.

However, among the above-mentioned top coating methods, the method using the polyol type resin / isocyanate prepolymer type coating has a short pot life and has a major drawback in terms of workability.

Further, in the case of using a curable coating of a silanol group-containing resin and an epoxy group-containing resin, or a moisture-curing coating of a trialkoxysilyl group, there is a difference in curability depending on coating and baking conditions, and the appearance is also different. Not satisfactory. In addition, such a coating system causes scratches on the coating film during car washing, and significantly impairs the appearance of the coating film.

[0010]

Further, in addition to such long-term storage stability and coating appearance, it is possible to obtain a coating resistant to acid rain mainly in the automobile industry.
The current situation is that there is a strong demand for urgent development of extremely useful top coating methods.

[0011] Therefore, the inventors of the present invention tried to solve or solve various drawbacks or problems in the prior art as described above, and in addition, earnestly began research in order to meet the above-mentioned demand.

[0012] Therefore, the problem to be solved by the present invention is to use a resin composition for a one-pack type coating which is excellent in storage stability and is also extremely useful because it is excellent in acid resistance and weather resistance. It is to provide a top coating method.

[0013]

Therefore, the present inventors have
Mainly, as a result of intensive studies in accordance with the problems to be solved by the invention as described above, as a result, a fluorine-containing vinyl monomer, 2-oxo-1,3 as an essential monomer component has been obtained.
A fluorine-containing vinyl-based copolymer (A) obtained by copolymerizing monomers comprising a dioxolane group-containing vinyl monomer and another copolymerizable vinyl monomer, and at least one in one molecule. A topcoat paint containing a resin composition containing, as a main component, a compound (B) having two carboxyl groups as an essential component is applied onto a coating film on which a coating film of the undercoat paint is formed. The present invention has been completed by finding an extremely practical topcoating method consisting of the following.

That is, according to the present invention, the fluorine-containing vinyl monomer (a) and the general formula are provided on the coating film on which the coating film of the undercoat paint is formed, respectively.

[0015]

[Chemical 2]

[Wherein R ₁ represents an alkyl group, a substituted alkyl group, a cycloalkyl group, a substituted dicycloalkyl group or an aromatic residue, and R ₂ and R ₃ are the same. May represent a hydrogen atom or an alkyl group, a substituted alkyl group, a cycloalkyl group, a substituted dicycloalkyl group or an aromatic residue, which may be different from each other, and n is an integer of 0 or 1. To do. ] 2-oxo-1,3-dioxolane group-containing vinyl monomer (b) represented by

And a fluorine-containing vinyl-based copolymer (A) obtained by copolymerizing monomers having other vinyl monomer (c) which is copolymerizable as an essential component, in one molecule. It comprises applying a top-coat paint containing a resin composition containing as a main component a compound (B) having at least two carboxyl groups as a main component, and in particular, is excellent in weather resistance and chemical resistance. ,
The present invention intends to provide an extremely practical topcoating method.

Here, first, the above-mentioned undercoat paint is an organic solvent type, non-aqueous dispersion mainly composed of a resin composition as described below and, if necessary, a scaly metal powder and / or a coloring pigment. Type, water-soluble type or water-dispersed type paint is a generic term, and it goes without saying that it may include a solvent, an additive and a modifier.

As the resin composition, only representative ones are listed, and various resins such as acrylic resin, alkyd resin, polyester resin, epoxy resin, cellulose resin (fibrous resin) or vinyl resin can be used. Thermosetting or room temperature curable ones composed of a main agent and various curing agents such as amino resins or polyisocyanate compounds.

Of course, a so-called thermoplastic resin composition which does not use a curing agent can be used, but it is preferable to use any one of the curable resin compositions from the viewpoint of long-term weather resistance.

Next, the above-mentioned top coating material will be described. As the fluorine-containing vinyl monomer (a) used in the present invention, any known and commonly used fluorine-containing monomer can be used, but of these, only typical ones can be used. Vinyl, vinylidene fluoride,
Various fluorine-containing α-olefins such as trifluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene, bromotrifluoroethylene, pentafluoropropylene or hexafluoropropylene;

Alternatively, perfluoroalkyl perfluorovinyl ethers having an alkyl group of C _{1 to} C ₁₈ , such as trifluoromethyl trifluorovinyl ether, pentafluoroethyl trifluorovinyl ether or heptafluoropropyl trifluorovinyl ether, and an alkyl group having C Examples thereof include various fluorine atom-containing vinyl ethers such as _{1 to} C ₁₈ perfluoroalkyl vinyl ether. Among them, vinyl fluoride, tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropylene, or an alkyl group is C ₁ ~ C ₁₈
It is preferable to use the following perfluoroalkyl trifluorovinyl ether.

These fluorine-containing vinyl monomers listed above are
It goes without saying that they may be used alone or in combination of two or more.

The general formula

[0025]

[Chemical 3]

[Wherein R ₁ represents an alkyl group, a substituted alkyl group, a cycloalkyl group, a substituted dicycloalkyl group or an aromatic residue, and R ₂ and R ₃
Are hydrogen atoms, alkyl groups, substituted alkyl groups, cycloalkyl groups, substituted dicycloalkyl groups or aromatic residues, which may be the same or different, and n is 0 or It shall be an integer of 1. ] As a 2-oxo-1,3-dioxolane group-containing vinyl monomer (b) represented by

4-vinyloxycarbonylmethyl-2-
Oxo-1,3-dioxolane, 4-methyl-4-vinyloxycarbonylmethyl-2-oxo-1,3-dioxolane, 4- (1-propenyl) oxycarbonylmethyl-2-oxo-1,3-dioxolane, 4 -Methyl-
4- (1-propenyl) oxycarbonylmethyl-2-
Oxo-1,3-dioxolane, 4-vinyloxymethyl-2-oxo-1,3-dioxolane, 4-methyl-
4-Vinyloxymethyl-2-oxo-1,3-dioxolane, 4- (1-propenyl) oxymethyl-2-oxo-1,3-dioxolane or 4-methyl-4-
(1-Propenyl) oxymethyl-2-oxo-1,3
-Dioxolane and the like.

Of course, these vinyl monomers containing a 2-oxo-1,3-dioxolane group may be used alone or in combination of two or more kinds.

In preparation of the above-mentioned fluorine-containing vinyl copolymer (A) used in the present invention, in addition to the various main monomer components described above, they are copolymerized with each of these monomer components. Other possible monomers can also be used.

As such other copolymerizable monomers (c), of course, any one having copolymerizability may be used, but among them, only typical ones may be used. For example, 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, 2-hydroxypropyl vinyl ether,
Various hydroxyl group-containing vinyl ethers such as 4-hydroxybutyl vinyl ether, 3-hydroxybutyl vinyl ether, 2-hydroxy-2-methylpropyl vinyl ether, 5-hydroxypentyl vinyl ether or 6-hydroxyhexyl vinyl ether;

Various vinyl ethers listed above,
Addition reaction product with ε-caprolactone; or 2-hydroxyethyl (meth) allyl ether, 3-hydroxypropyl (meth) allyl ether, 2-hydroxypropyl (meth) allyl ether, 4-hydroxybutyl (meth) allyl ether , 3-hydroxybutyl (meth) allyl ether, 2-hydroxy-2-methylpropyl (meth) allyl ether, 5-hydroxypentyl (meth) allyl ether or 6-hydroxyhexyl (meth) allyl ether Addition reaction product of the contained allyl ether and ε-caprolactone;

Methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, tert-butyl butynyl ether, n-
Various alkyl vinyl ethers or substituted alkyl vinyl ethers such as pentyl vinyl ether, n-hexyl vinyl ether, n-octyl vinyl ether, 2-ethylhexyl vinyl ether, chloromethyl vinyl ether, chloroethyl vinyl ether, benzyl vinyl ether or phenylethyl vinyl ether;

Various cycloalkyl vinyl ethers such as cyclopentyl vinyl ether, cyclohexyl vinyl ether or methyl cyclohexyl vinyl ether; vinyl-2,2-dimethylpropanoate, vinyl-2,2-dimethylbutanoate, vinyl-2,
2-dimethylpentanoate, vinyl-2,2-dimethylhexanoate, vinyl-2-ethyl-2-methylbutanoate, vinyl-2-ethyl-2-methylpentanoate, vinyl-3-chloro- 2,2-Dimethylpropanoate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl laurate, C ₉ branched aliphatic vinyl carboxylate, C Various aliphatic vinyl carboxylates such as branched aliphatic vinyl carboxylate _{10 and} branched aliphatic vinyl carboxylate C ₁₁ or vinyl stearate;

Vinyl esters of various carboxylic acids having a cyclic structure, such as vinyl cyclohexanecarboxylate, vinyl methylcyclohexanecarboxylate, vinyl benzoate or vinyl p-tert-butylbenzoate; methyl acrylate, ethyl acrylate, butyl acrylate. Or various acrylic acid esters such as cyclohexyl acrylate; various methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate or benzyl methacrylate;

Ethylene, propylene or butene-1
, Various α-olefins; vinyl chloride or vinylidene chloride, various halogenated olefins other than fluoroolefins; styrene, α-methylstyrene, vinyltoluene, various aliphatic vinyl compounds, vinyl Trimethoxysilane, vinyltriethoxysilane, vinyltripropoxysilane, vinylmethyldiethoxysilane, vinyltris (β-methoxyethoxy) silane, allyltrimethoxysilane, trimethoxysilylethyl vinyl ether, triethoxysilylethyl vinyl ether, methyldimethoxysilylethyl Vinyl ether, trimethoxysilylpropyl vinyl ether, triethoxysilylpropyl vinyl ether,
Methyldiethoxysilylpropyl vinyl ether, γ-
Various hydrolyzable silyl group-containing monomers such as (meth) acryloyloxypropyltrimethoxysilane, γ- (meth) acryloyloxypropyltriethoxysilane or γ- (meth) acryloyloxypropylmethyldimethoxysilane;

Various amino group-containing amide systems such as N-dimethylaminoethyl (meth) acrylamide, N-diethylaminoethyl (meth) acrylamide, N-dimethylaminopropyl (meth) acrylamide or N-diethylaminopropyl (meth) acrylamide. Unsaturated monomers; various dialkylaminoalkyl (meth) acrylates such as dimethylaminoethyl (meth) acrylate or diethylaminoethyl (meth) acrylate; tert-butylaminoethyl (meth) acrylate, tert-bitylamino Propyl (meta)
Various amino group-containing monomers such as acrylate, aziridinylethyl (meth) acrylate, pyrrolidinylethyl (meth) acrylate or piperidinylethyl (meth) acrylate; or (meth) acrylic acid, crotonic acid , Various carboxyl group-containing monomers such as itaconic acid, maleic acid or fumaric acid.

In particular, from the viewpoint of increasing the polymerization yield of the fluorine-containing vinyl copolymer (A) itself, alkyl vinyl ethers, cycloalkyl vinyl ethers, hydroxyl group-containing vinyl ethers or carboxylic acid vinyl esters. Use of is preferred.

To prepare the fluorine-containing vinyl copolymer (A), a known and conventional radical polymerization initiator is used,
Such as emulsion polymerization, suspension polymerization, bulk polymerization or solution polymerization,
It suffices to carry out the polymerization reaction by making use of known and commonly used means, and if only typical examples of the above radical polymerization initiator are exemplified, various diacyl peroxides such as acetyl peroxide or benzoyl peroxide can be used. Oxides;

Various ketone peroxides such as methyl ethyl ketone peroxide or cyclohexanone peroxide; various hydroperoxides such as hydrogen peroxide, tert-butyl hydroperoxide or cumene hydroperoxide; di-
various dialkyl peroxides such as tert-butyl peroxide or dicumyl peroxide;

Such as tert-butyl peroxyacetate or tert-butyl peroxypivalate,
Various alkyl peroxyesters; various azo compounds such as azobisisobutyronitrile or azobisisovaleronitrile; and various persulfates such as potassium persulfate or ammonium persulfate.

The polymerization reaction method is as described above.
Although there are various known and commonly used methods, among them, it is desirable to use bulk polymerization or solution polymerization. Furthermore, the obtained copolymer is used as it is, for example, in a resin composition for solution type coating. From the standpoint that it can be used as, the solution polymerization method is particularly desirable.

The organic solvents used in the preparation of the fluorine-containing vinyl copolymer (A) by the solution polymerization method are only typical ones. For example, benzene, toluene or Various aromatic hydrocarbons such as xylene; various aliphatic hydrocarbons such as n-pentane, n-hexane or n-octane;

Such as cyclopentane, cyclohexane, methylcyclohexane or ethylcyclohexane,
Various alicyclic hydrocarbons; such as mineral spirits,
Various mixed hydrocarbons;

Methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butanol, n-pentanol, isopentanol, n-hexanol, n-octanol, 2
Various alcohols such as ethylhexanol, cyclohexanol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether or propylene glycol monoethyl ether;

Dimethoxyethane, tetrahydrofuran,
Dioxane, diisopropyl ether or di-n-
Various ethers such as butyl ether; acetone,
Various ketones such as methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, methyl amyl ketone, cyclohexanone or isophorone;

Methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, amyl acetate, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate or ethylene. Various esters such as glycol monobutyl ether acetate;

In addition to various chlorinated hydrocarbons such as chloroform, methylene chloride, carbon tetrachloride, trichloroethane or tetrachloroethane, N-methylpyrrolidone, dimethylformamide, dimethylacetamide or ethylene carbonate, etc. Is. Such organic solvents can be used alone or 2
Of course, a combination of two or more kinds may be used.

From the various monomer components described above, the fluorine-containing vinyl copolymer (A) is prepared by a solution polymerization method.
In order to prepare the above, all monomers, polymerization initiators and solvents are charged in a reaction vessel at a time and polymerized, or a reaction vessel in which fluorine-containing vinyl monomers (a) and solvents are charged. In addition, each of the monomers other than the fluorine-containing vinyl monomers (a) and the polymerization initiator are continuously added or dividedly added to perform polymerization, and further, It is possible to apply various methods such as adding all the monomers and the polymerization initiator to the reaction vessel charged with only the solvents continuously, or by adding them in a divided manner for polymerization. I can.

In the above description, a solvent-soluble type fluorine-containing vinyl polymer has been mainly described, but of course, the polymer is a so-called non-aqueous dispersion form in which it is dispersed in a solvent. However, it may also contain partially gelled particles.

Then, at least 2 in one molecule described above.
As the compound (B) having one or more carboxyl groups, at least one compound selected from the group consisting of vinyl copolymers having a carboxyl group, polyester resins and polyester low molecular weight compounds, and the like,
This is a typical example.

That is, first, as the above-mentioned carboxyl group-containing vinyl copolymer, for example, various carboxyl group-containing monomers as described below and other copolymerizable monomers as described above may be used. Such as various carboxyl group-containing monomers, each of which is capable of being copolymerized with the above-mentioned hydroxyl group-containing monomer, respectively. And the like, which can be obtained by copolymerization with the above monomers.

As only specific examples of such carboxyl group-containing monomers, various α, β-ethylenes such as (meth) acrylic acid, maleic acid, fumaric acid or itaconic acid are listed. Sex unsaturated monomer
Or dicarboxylic acids; esterified products of various α, β-ethylenically unsaturated dicarboxylic acids such as malein diethyl, dibutyl maleate, dibutyl fumarate or diethyl itaconate with monohydric alcohols having 1 to 4 carbon atoms Or a compound obtained by adding various acid anhydrides such as phthalic anhydride to various hydroxyl group-containing vinyl monomers such as 2-hydroxyethyl (meth) acrylate.

Further, only specific examples of the acid anhydrides or the acid anhydride group-containing monomers are exemplified, and the acid anhydride groups represented by maleic anhydride, itaconic anhydride, etc. It is like having an unsaturated bond together.

Further, the above-mentioned carboxyl group-containing polyester resin is one obtained by excessively reacting an acid component with a polyhydric alcohol component (polyol component), or a hydroxyl group in a hydroxyl group-containing polyester resin. On the other hand, there are those obtained by reacting an acid anhydride group.

The polyester resin mentioned here is by no means special, and various polyvalent carboxylic acids such as phthalic acid, isophthalic acid, adipic acid, maleic acid or dimer acid, ethylene glycol, propylene glycol, It refers to various compounds and the like which can be obtained by condensing various polyols such as neopentyl glycol or trimethylolpropane by a known and commonly used method.

More specifically, various acid anhydride group-containing compounds such as trimellitic acid are added to hydroxyl group-terminated polyesters obtained by reacting under conditions such that the polyol component is in excess. Examples thereof include carboxyl group-terminated polyester resins and the like in the form of a compound obtained by the above, or a compound obtained by reacting the polycarboxylic acid from the beginning under a condition in which the polyvalent carboxylic acid is excessive.

Further, the hydroxyl group can be introduced by adding an epoxy compound,
Of course.

Examples of the carboxyl group-containing low molecular weight compounds as one of the carboxyl group-containing compounds (B) include adipic acid, phthalic acid, isophthalic acid and dimer acid.

Of course, various oxycarboxylic acids such as p-oxybenzoic acid (parahydroxybenzoic acid) are also used as the carboxyl group-containing low molecular weight compounds as one of the carboxyl group-containing compounds (B). You can

It is desirable to use a curing catalyst when preparing a topcoat paint using the resin composition thus obtained in the present invention. As only such typical curing catalysts, only tetramethylammonium bromide, trimethylbenzylammonium hydroxide, 2-hydroxypyridine, trimethylbenzylammonium methoxide, phenyltrimethylammonium chloride, phenyltrimethylammonium bromide can be given. , Phenyltrimethylammonium hydroxide, phenyltrimethylammonium iodide, phenyltrimethylammonium tribromide or phosphocholine chloride sodium salt,

Alternatively, stearyl ammonium bromide, tetra-n-amyl ammonium iodide, tetra-n-butyl ammonium bromide, tetra-n-
Butyl ammonium hydroxide, tetra-n-
Butylammonium phosphate, tetra-n-decylammonium trichloride, tetraethylammonium hydroxide, tetraethylammonium tetrafluoroborate, acetylcholine bromide, alkyldimethylbenzylammonium chloride, benzylcholine bromide, benzyl-n-butylammonium bromide, betaine, butyryl chloride. , Bis (tetra-n-butylammonium) dichromate or trimethylvinylammonium bromide,
Various quaternary ammonium salts;

Allyltriphenylphosphonium chloride, n-amyltriphenylphosphonium bromide,
Benzyltriphenylphosphonium chloride, bromomethyltriphenylphosphonium bromide, 2-dimethylaminoethyltriphenylphosphonium bromide, ethoxycarbonylphosphonium bromide, n-
Various phosphonium salts such as heptyltriphenylphosphonium bromide, methyltriphenylphosphonium bromide, tetrakis (hydroxymethyl) phosphonium sulfate or tetraphenylphosphonium bromide; various acid catalysts such as phosphoric acid, p-toluenesulfonic acid or dimethylsulfate Or various carbonates such as calcium carbonate.

The appropriate amount of the curing catalysts used is 0.01 to 5 parts by weight based on 100 parts by weight of the solid content of the fluorine-containing vinyl copolymer (A). Further, the resin composition used in the present invention contains various curing agents capable of reacting with a hydroxyl group, such as other amino resins (aminoplasts), polyisocyanate compounds or blocked polyisocyanate compounds. It is also possible to use together.

The top coating composition of the present invention can be used as it is,
Although it can be used as a clear paint, it can also be used by adding coloring pigments and / or metal powders. Further, if necessary, for the top coating composition of the present invention, various resins and solvents, flow regulators,
It goes without saying that various well-known and commonly used additives such as color separation inhibitors, antioxidants, ultraviolet absorbers, light stabilizers or silane coupling agents can be added. is there.

Examples of such color pigments include dyes,
Examples thereof include organic pigments, inorganic pigments, metal pigments, and the like. Examples of the above-mentioned resins include acrylic resins and fluorine-containing vinyl resins other than the fluorine-containing vinyl copolymer (A) used in the present invention. , Various cellulose resins such as nitrocellulose or cellulose acetate butyrate, vinyl chloride / vinyl acetate copolymer resins, petroleum resins, ketone resins, silicone resins, oil-free alkyd resins or epoxy resins And so on.

Further, as various additive components, flow regulators, color separation inhibitors, antioxidants, ultraviolet absorbers,
Various known and conventional compounds such as light stabilizers or silane coupling agents can be used.

Further, as the above-mentioned solvents, the same various solvents as mentioned above, which are the same as those used for preparing the above-mentioned fluorine-containing vinyl copolymer (A), and a mixture thereof can be used.

The coating for carrying out the method of the present invention is carried out in the same manner as in the prior art, using the undercoat paint and the above-mentioned topcoat paint. That is, a surface treatment is applied, or if necessary, a primer or a surfacer is applied in advance on an object to be coated, an undercoat paint is adjusted to a desired viscosity, and a dried film is applied to the object. The thickness may be 5 to 40 microns (μm).

Then, the topcoat paint may be adjusted to a desired viscosity so that the dry film thickness is 5 to 60 μm. As a method for coating the undercoat paint and the topcoat paint, any ordinary method such as roll coater, air spray, airless spray, or electrostatic coating may be used.

In the method of the present invention, this topcoat paint may be applied while the undercoat paint is in an uncured state, or may be applied in a cured state. After coating, a cured coating film can be obtained by drying at room temperature for 3 days or at a temperature of 60 to 300 ° C. for several seconds to 60 minutes.

The topcoat coating method of the present invention obtained as described above is mainly used in the past, as in the case of coating various metals such as car bodies.
It is used in various fields where fluororesin / melamine resin-based paints, acrylic resin / melamine resin-based paints and the like have been used.

[0072]

EXAMPLES Next, the present invention will be described more specifically with reference to Reference Examples, Examples and Comparative Examples. In the following, all parts and% are based on weight unless otherwise specified. To do.

Reference Example 1 [Preparation Example of Fluorine-Containing Vinyl Copolymer (A)] 85 parts of ethyl vinyl ether was added to a 1 liter stainless steel autoclave sufficiently replaced with nitrogen gas.
4- (1-propenyl) oxymethyl-2-oxo-
100 parts of 1,3-dioxolane, 50 parts of 4-hydroxybutyl vinyl ether, 20 parts of methyl ethyl ketone
0 part, 5 of tert-butyl peroxyoctoate
Part, 5 parts of azobisisovaleronitrile and 1,
1.5 parts of 2,2,6,6-pentamethylpiperidine were charged.

Then, 265 parts of the liquefied and collected chlorotrifluoroethylene was injected under pressure, and the temperature was raised to 60.degree. Then, the mixture was maintained at 60 ° C. for 15 hours, 300 parts of methyl ethyl ketone was added, and the reaction was continued at the same temperature for 2 hours to obtain a solution of the target copolymer. Hereinafter, this is abbreviated as A-1.

Reference Examples 2 to 4 (same as above) A solution of the target copolymer was obtained in the same manner as in Reference Example 1 except that the monomers to be used were changed as shown in Table 1. .

[0076]

[Table 1]

<< Footnote in Table 1 >> * 1) Chlorotrifluoroethylene * 2) Hexafluoropropylene

* 3) 4- (1-propenyl) oxymethyl-2-oxo-1,3-dioxolane * 4) 4-vinyloxymethyl-2-oxo-1,3
-Dioxolane * 5) 4- (1-propenyl) oxycarbonylmethyl-2-oxo-1,3-dioxolane

* 6) Ethyl vinyl ether * 7) Butyl vinyl ether * 8) 4-Hydroxybutyl vinyl ether

[0080] * 9) "VeoVa 9" (manufactured by The Netherlands Shell, having C ₈ comprising alkyl groups, branched carboxylic acid vinyl esters) * 10) crotonate

Reference Example 5 (Preparation Example of Compound Having Carboxylic Acid Group in Molecule) 500 parts of xylene and n-butanol were placed in a four-necked flask equipped with a thermometer, a stirrer, a cooling tube and a nitrogen gas introducing tube. Then, 300 parts of acrylic acid was charged to 300 parts of acrylic acid as monomers.
Part, 100 parts of methyl methacrylate and 600 parts of n-butyl methacrylate, and azobisisobutyronitrile (A
15 parts of IBN) and tert-butylperoxy 2-
A mixture with 70 parts of ethylhexanoate was added dropwise at the same temperature over 5 hours, and after completion of the addition, the temperature was kept at the same temperature for 7 hours to allow the reaction to continue.
A target curing agent having a nonvolatile content of 50.2%, that is, a solution of a carboxyl group-containing vinyl copolymer was obtained. Hereinafter, this is abbreviated as a curing agent (B-1).

Reference Example 6 (Preparation Example of Compound Having Carboxylic Anhydride Group in Molecule) 500 parts of xylene and butyl acetate were placed in a four-necked flask equipped with a thermometer, a stirrer, a cooling tube and a nitrogen gas introducing tube. Then, 300 parts of itaconic acid as a monomer were added to 300 parts of it, which was heated to 120 ° C.
Parts, 100 parts of methyl methacrylate and 600 parts of n-butyl methacrylate, and 15 parts of AIBN, respectively, as initiators, and tert-
A mixture of 70 parts of butylperoxy 2-ethylhexanoate and 70 parts of butylperoxy was added dropwise at the same temperature over 5 hours, and after completion of the addition, the reaction was continued by maintaining the same temperature for 7 hours. Thus, a solution of a target curing agent having a nonvolatile content of 50.3%, that is, a vinyl carboxylic acid group-containing vinyl copolymer was obtained. Hereinafter, this is abbreviated as a curing agent (B-2).

(Preparation Example of Top Coat) Using various fluorine-containing vinyl copolymers and curing agents obtained in Reference Examples 1 to 4 and Reference Examples 5 and 6, the results are shown in Table 2. Various resin compositions were obtained by blending as shown in the blending ratio.

For comparison, a conventional commercial product "Acridic 52-748" [acrylic resin manufactured by Dainippon Ink and Chemicals, Inc.] and "Super Beckamine" were used.
L-117-60 "(melamine resin manufactured by the same company),
A control acrylic resin / melamine resin-based resin composition was prepared in such a form that it was compounded at a compounding composition ratio of 70/30 (solid content weight ratio).

Regarding the resin compositions used in the present invention and the control acrylic resin / melamine resin-based resin compositions thus obtained, xylene / “Solvesso 100” (petroleum-based solvent manufactured by Exxon, USA) /
n-butyl alcohol / cellosolve acetate = 20 /
40/20/20 (weight mixing ratio) mixed solvent, Ford Cup No. 4 was diluted to 23 seconds and used as the topcoat paint.

(Preparation Example of Undercoat Paint) Next, a mixture prepared by a conventional paint manufacturing method so as to have the following ratio was diluted with a solvent for Ford Cup No. In step 4, the viscosity was adjusted to 13 to 14 seconds to prepare an undercoat paint.

“Acridic 47-712” (hydroxyl group-containing acrylic resin manufactured by Dainippon Ink and Chemicals, Inc. 160 parts industry; nonvolatile content = 50%) “Super-Beckamine L-117-60” 33 parts “ Alpaste 1860YL "[23 parts aluminum paste from Toyo Aluminum Co., Ltd .; nonvolatile content = 65%]" First Gen Blue NK "[Cyanine blue manufactured by Dainippon Ink and Chemicals, Inc. 2 parts] ─── ──────────────────────────────── 218 copies

Examples 1 to 4 and Comparative Example 1 Then, a mild steel sheet was coated with a cationic electrodeposition coating film and a polyester / melamine-based surfacer, and the undercoat paint was dried by air spray to form a dry film. 20 thickness
It was painted so as to have a thickness of μm.

After that, setting was carried out for 5 minutes, and then the top coating composition obtained by using the above-mentioned resin composition of the present invention was air sprayed to give a dry film thickness of 35.
The coating was repeated so that the thickness became μm.

Leave at room temperature for 20 minutes and then 1
It was baked and dried at 50 ° C. for 30 minutes.

Each of the sample coating films thus obtained was evaluated for acid resistance and weather resistance. In addition, the acrylic resin / melamine resin-based top coating composition for control was also evaluated and examined in the same manner. The results are
Collectively shown in Table 2.

[0092]

[Table 2]

<Footnotes in Table 2> All the formulations are represented by non-volatile components.

* 1) "Super Beckamine L
-117-60 "* 2) Trimethylbenzylammonium hydroxide * 3)" Tinuvin 900 "(product of Ciba-Geigy, Switzerland) is used * 4)" Tinuvin 292 "(same as above) is used

* 5) In a 1% aqueous sulfuric acid solution at 60 ° C.,
The state of the coated surface after the sample was immersed for 24 hours was visually determined. * 6) With a sunshine weather ometer,
The change in gloss of the coated surface after exposure for 000 hours, that is, the gloss retention rate was compared and examined.

[0096]

[Table 3]

[0097]

According to the top coating method of the present invention, it is possible to obtain a coating film which is particularly excellent in weather resistance and chemical resistance.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location C09D 131/02 PFR 6904-4J 201/08 PDH 7415-4J

Claims (2)

[Claims] 1. A fluorine-containing vinyl monomer (a) having the general formula: [Wherein R ₁ is an alkyl group, a substituted alkyl group,
Represents a cycloalkyl group, a substituted dicycloalkyl group or an aromatic residue, and R ₂ and R ₃ are respectively
The same or different hydrogen atom, alkyl group, substituted alkyl group, cycloalkyl group, substituted dicycloalkyl group or aromatic residue, which may be the same or different, and n is an integer of 0 or 1. There is. ] The 2-oxo-1,3-dioxolane group-containing vinyl monomer (b) and the other copolymerizable vinyl monomer (c) as essential components are copolymerized. Fluorine-containing vinyl copolymer (A) obtained by
And a topcoat paint containing a resin composition containing as a main component a compound (B) having at least two carboxyl groups in one molecule, as an essential constituent. 2. The above-mentioned fluorine-containing vinyl monomer (a)
However, vinyl fluoride, vinylidene fluoride, trifluoroethylene, tetrafluoroethylene, hexafluoropropylene, chlorotrifluoroethylene, pentafluoropropylene and a (per) fluoroalkyl group having 1 to 18 carbon atoms (per) fluoroalkyl The topcoat coating method according to claim 1, which is at least one compound selected from the group consisting of vinyl ethers.