JP3200462B2 - Paint composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method of coating a thermosetting paint containing a pigment on a surface to be coated and then applying a clear paint on the paint to simultaneously cure two uncured coating films. The present invention relates to a two-coat, one-bake finish clear coating composition which provides a coating film excellent in acid resistance and scratch resistance.

[0002]

2. Description of the Related Art In the fields of automobiles, heavy vehicles, industrial equipment, household appliances and the like, color finishing by baking of a thermosetting paint containing a pigment is widely practiced. Thus, as the baking finish method, a base paint containing a pigment was applied to improve sharpness and long-term outdoor weather resistance, and then a top clear paint was continuously applied without being cured. After that, a so-called two-coat one-bake method in which both the coating films are simultaneously cured by heating is often used.

[0003] The two-coat one-bake method is widely used especially in the field of automobiles which require formation of a coating film having excellent finished appearance such as smoothness, gloss and sharpness because of its excellent finished appearance. Have been.

[0004] However, the gloss retention, water resistance, stain resistance, scratch resistance, etc. of the coating film when exposed to the outdoors such as automobiles, heavy vehicles, buildings, etc., which are coated and finished by the two-coat one-bake method, are as follows. It is greatly affected by the composition of the paint for forming the film, particularly the composition of the top clear paint.

At present, as a top clear coating material, a coating material containing a hydroxyl group-containing acrylic resin and an amino resin as main components is often used, and a coating film excellent in finished appearance, weather resistance, physical function, and the like can be obtained. . However, this coating film has a disadvantage that its surface is easily deteriorated by acid rain (pH 4 or less), which has recently become a social problem.

[0006] Particularly, in paints for automobiles, adhesion of dust and generation of scratches due to car washing have recently become a serious problem.

Under these circumstances, there has been a strong demand in recent years for the development of a two-coat, one-bake finish clear top coating which forms a coating film having excellent acid resistance and scratch resistance.

[0008]

Means for Solving the Problems The present inventors have formed a coating film whose acid resistance and abrasion resistance are dramatically improved without impairing the finished appearance, weather resistance and physical performance of the coating film. Intensive research was conducted for the purpose of developing a top clear paint for finishing two coats and one bake.

As a result, an acrylic polymer containing a specific alkoxysilane group-containing monomer, a specific low molecular weight polyol, a non-aqueous dispersion type acrylic resin and a coating mainly composed of an amino resin are used as top clear coatings. As a result, the inventors have found that the acid resistance and scratch resistance of the coating film are significantly improved, and have completed the present invention.

That is, the present invention relates to a two-coating method in which a thermosetting paint containing a pigment is applied to the surface to be coated, and two uncured coating films obtained by applying a clear paint on the paint are heated and cured simultaneously. 1. A top clear paint used for a bake finish, wherein (A) a general formula (I)

Embedded image [Wherein A is an ester bond, or a phenylene bond, R ₁
Is a hydrogen atom or a methyl group, R ₂ is a divalent aliphatic saturated hydrocarbon group having 1 to 6 carbon atoms, R ₃ and R ₄ are the same or different and are a phenyl group, an alkyl group having 1 to 6 carbon atoms or R ₅ represents an alkoxy group having 1 to 10 carbon atoms, and R ₅ represents an alkyl group having 1 to 10 carbon atoms. n shows the integer of 1-100. 5 to 40% by weight of an alkoxysilane group-containing vinyl monomer, 5 to 50% by weight of a hydroxyl group-containing vinyl monomer, and 10 to 90% by weight of another copolymerizable vinyl monomer. % (B) a weight-average molecular weight of 400 to less than 2,000, and a ratio Mw between the weight-average molecular weight (Mw) and the number-average molecular weight (Mn). / Mn has a molecular weight distribution of 1.6 or less and a hydroxyl value of 150 to 40.
A non-aqueous dispersion-type acrylic resin obtained by dispersion-polymerizing at least one vinyl monomer in the presence of a low-molecular-weight polyol of 0 mgKOH / g, (C) a polymer dispersion stabilizer and an organic solvent; Resin as a main component, based on the total weight of the above components (A) to (D),
The component (A) is 20 to 80% by weight, and the component (B) is 5 to 30% by weight.
The present invention relates to a top clear coating composition for two-coat / one-bake finishing, wherein the component (C) is 5 to 50% by weight and the component (D) is 10 to 50% by weight.

The present inventors have proposed a glass transition temperature (Tg point) of an acrylic resin, which is a base resin of a conventional amino resin-cured top clear paint, in order to improve the acid resistance of a coating film in a two-coat one-bake method. Research on molecular weight, styrene content, etc., could be slightly improved, but there was no significant difference from the conventional one, considering various situations where outdoor painted articles such as automobiles are actually placed, The fundamental solution has not been reached.

Therefore, as a result of further study, it has been found that acid-induced deterioration of a conventional amino resin cured coating film is caused by a crosslinking reaction between a methylol group directly bonded to an N atom in an amino resin and a hydroxyl group in an acrylic resin. Presumed that the basic cause is that the ether bond is susceptible to hydrolysis,
-SiOSi-, a chemical bond that is not easily hydrolyzed
It has been found that by introducing SiOR- as a crosslinking point, a large improvement in acid resistance can be realized. The present invention has been completed based on such new findings.

Hereinafter, the top clear coating composition of the present invention will be described in detail.

(A) Acrylic copolymer This is represented by the general formula (I)

Embedded image [Wherein A represents an ester bond or a phenylene bond represented by R ₁
Is a hydrogen atom or a methyl group, R ₂ is a divalent aliphatic saturated hydrocarbon group having 1 to 6 carbon atoms, R ₃ and R ₄ are the same or different and are a phenyl group, an alkyl group having 1 to 6 carbon atoms or R ₅ represents an alkoxy group having 1 to 10 carbon atoms, and R ₅ represents an alkyl group having 1 to 10 carbon atoms. n shows the integer of 1-100. 5 to 40% by weight of an alkoxysilane group-containing vinyl monomer, 5 to 50% by weight of a hydroxyl group-containing vinyl monomer, and 10 to 90% by weight of another copolymerizable vinyl monomer. % Is an acrylic copolymer obtained by polymerizing a monomer component containing 0.1%.

In the compound of the formula (I), which is an essential monomer in the acrylic copolymer, n is preferably 1 to 10.

In the general formula (I), as the divalent saturated aliphatic hydrocarbon group having 1 to 6 carbon atoms represented by R ₂ , a linear or branched alkylene group such as methylene, ethylene, propylene, , 2-butylene, 1,3-butylene, 2,3-butylene, tetramethylene, ethylethylene, pentamethylene, hexamethylene group and the like. As the alkyl group having 1 to 6 carbon atoms represented by R ₃ and R ₄ , a linear or branched alkyl group such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert -Butyl, n-
Pentyl, isopentyl, neopentyl, n- hexyl, isohexyl group and the like can be exemplified, further n- heptyl In addition to these as an alkyl group having 1 to 10 carbon atoms represented by R _5, 1-methylpentyl, 2- Methylhexyl, n-octyl, n-nonyl, n-decyl and the like can be mentioned. 1 to ₃ carbon atoms represented by R ₃ and R ₄
Examples of the 10 alkoxy groups include linear or branched alkoxy groups such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, tert-butoxy, n-pentoxy, isopentoxy, n- Hexyloxy, isohexyloxy, n-
Octyloxy and the like can be mentioned. In the general formula (I), when n is 2 or more, R ₃ and R ₄
Comrades may be the same or different.

Among the compounds of the general formula (I) in the present invention, those in which A is an ester bond include, for example, γ-
(Meth) acryloxyethyltrimethoxysilane, γ-
(Meth) acryloxypropyltrimethoxysilane, γ
-(Meth) acryloxypropyltriethoxysilane,
γ- (meth) acryloxypropyltripropoxysilane, γ- (meth) acryloxypropylmethyldimethoxysilane, γ- (meth) acryloxypropylmethyldiethoxysilane, γ- (meth) acryloxypropylmethyldipropoxysilane, γ- (meth) acryloxybutylphenyldimethoxysilane, γ- (meth) acryloxybutylphenyldiethoxysilane, γ- (meth) acryloxybutylphenyldipropoxysilane, γ-
(Meth) acryloxypropyldimethylmethoxysilane, γ- (meth) acryloxypropyldimethylethoxysilane, γ- (meth) acryloxypropylphenylmethylmethoxysilane, γ- (meth) acryloxypropylphenylmethylethoxysilane,

[0018]

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[0019]

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[0020]

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[0021]

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[0022]

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[0023]

Embedded image And the like.

Further, among the compounds of the general formula (I), those in which A is a phenylene bond include, for example,

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[0025]

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[0026]

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[0027]

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[0028]

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[0029]

Embedded image And the like.

Among these compounds of the general formula (I), in particular, acryloxypropyltrimethoxysilane, methacryloxypropyltriethoxysilane, methacryloxypropyltri-n-butoxysilane, acryloxypropylmethyldimethoxysilane, methacryloxy Propylmethyldimethoxysilane, methacryloxypropylmethyldi-n-butoxysilane and the like are preferred.

In the polymer, a hydroxyl group-containing vinyl monomer which is another essential component is, for example, acrylic acid 2
-Hydroxyethyl, 2-hydroxyethyl methacrylate, hydroxypropyl (meth) acrylate, butanediol monoacrylate, "Placcel FM-1",
"Placcel FM-2", "Placcel FM-3",
"Placcel FA-1", "Placcel FA-2",
"Placcel FA-3" (all from Daicel Chemical Co., Ltd.)
Made, trade name, caprolactone-modified (meth) acrylic acid 2
-Hydroxyethyls) and the like, but are not limited thereto.

Examples of the vinyl monomer copolymerizable with the above-mentioned alkoxysilane group-containing vinyl monomer and hydroxyl group-containing vinyl monomer include methyl acrylate, methyl methacrylate,
Ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, lauryl acrylate,
Esters of acrylic acid or methacrylic acid such as lauryl methacrylate, stearyl acrylate, stearyl methacrylate and monohydric alcohol having 1 to 22 carbon atoms; carboxyl group-containing vinyl monomers such as acrylic acid, methacrylic acid and maleic anhydride; acrylic Glycidyl group-containing vinyl monomers such as glycidyl acrylate and glycidyl methacrylate; amide vinyl monomers such as acrylamide, methacrylamide, N-methylolacrylamide, and N-methylol methacrylamide; Amine vinyl monomers such as -butylaminoethyl; styrene, vinyltoluene, acrylonitrile, methacrylonitrile, α-methylstyrene, vinyl acetate and the like; Vinyl monomers; compounds having one polymerizable unsaturated bond per molecule, and the like.

The copolymerization amount of the alkoxysilane group-containing vinyl monomer is 5 to 40% by weight, preferably 5 to 30% by weight. If it is less than 5% by weight, the acid resistance decreases and 4%
If the amount is more than 0% by weight, problems such as deterioration of the storage stability of the paint arise. The copolymerization amount of the hydroxyl group-containing vinyl monomer is 5 to 50% by weight, preferably 10 to 40% by weight.
It is. When the content is 5% by weight or less, the reaction between the amino resin and the alkoxysilane group and the hydroxyl group does not sufficiently proceed, and the curability and acid resistance are reduced. When the content is 50% by weight or more, the water resistance is impaired. .

The copolymerization reaction of an alkoxysilane group-containing vinyl monomer with a hydroxyl group-containing vinyl monomer and other vinyl monomers can be carried out in the same manner as in a conventional method for synthesizing an acrylic resin or a vinyl resin. For example, it can be carried out by dissolving or dispersing the two components in an organic solvent and heating with stirring at a temperature of about 60 to 180 ° C. in the presence of a radical polymerization initiator. The reaction time may be generally about 1 to 10 hours.

As the organic solvent, heptane,
Hydrocarbon solvents such as toluene, xylene, octane, and mineral spirits; ester solvents such as ethyl acetate, n-butyl acetate, isobutyl acetate, methyl cellosolve acetate, and butyl carbitol acetate; methyl ethyl ketone, methyl isobutyl ketone, and diisobutyl ketone Ketone solvent, ethanol, isopropanol, n
-Butanol, sec-butanol, alcohol solvents such as isobutanol, n-butyl ether, dioxane,
Ether solvents such as ethylene glycol monomethyl ether and ethylene glycol monoethyl ether can be used. Among these, when a hydrocarbon solvent is used, it is preferable to use another solvent in combination from the viewpoint of solubility.

As the radical initiator, any of those generally used can be used. Examples thereof include benzoyl peroxide and t-butylperoxy-2-yl.
Examples thereof include peroxides such as ethylhexanoate, and azo compounds such as azoisobutyronitrile and azobisdimethylvaleronitrile. The number average molecular weight of the acrylic polymer is usually about 3,000 to 500,000, preferably about 5,000 to 100,000.

As described above, the acrylic polymer as the component (A) in the present invention is a compound represented by the general formula (I) containing an alkoxysilane group-containing vinyl monomer and a hydroxyl group-containing vinyl monomer, It is obtained by copolymerizing another vinyl monomer, and an alkoxysilane group and a hydroxyl group are bonded as side chains to the acrylic polymer. Therefore, compared with the acrylic resin which is the base resin of the conventional amino resin cured top clear paint, the acrylic polymer is a chemical bond that is less susceptible to hydrolysis.
Since the acrylic polymer has an alkoxysilane group capable of introducing-, -SiOR- at a crosslinking point, when the acrylic polymer is used as a base resin for an amino resin-cured top clear coating, the cured coating film has an extremely excellent surface. Properties (acid resistance, water repellency, scratch resistance, water resistance, chemical resistance, weather resistance, heat resistance),
Above all, it gives particularly excellent acid resistance.

(B) Low molecular weight polyol The component (B) has a weight average molecular weight of 400 to less than 2,000, and has a weight average molecular weight (Mw) and a number average molecular weight (Mw).
This is a low-molecular-weight polyol component having a molecular weight distribution in which the ratio Mw / Mn to n) is 1.6 or less and having a hydroxyl value of 150 to 400 mgKOH / g.

Here, the weight-average molecular weight (Mw), number-average molecular weight (Mn) and Mw / Mn are measured by gel permeation chromatography (GPC) using a polystyrene as a standard substance and preparing a calibration curve. .

The component (B) has a weight average molecular weight of 400 to 400.
It is important that it is less than 2,000, preferably in the range of 1,000 to 1,800. Weight average molecular weight 400
If the diameter is smaller, the coating properties such as weather resistance are reduced, and the rate of evaporation at the time of baking is increased. Conversely, if the weight average molecular weight is 2,000 or more, the crosslinking density of the coating film becomes insufficient, and it becomes difficult to obtain a coating film having excellent scratch resistance.

The component (B) must have a narrow molecular weight distribution, and Mw / Mn is 1.6 or less, preferably 1.4 or less. If Mw / Mn exceeds 1.6, the resulting coating film is unfavorably deteriorated in scratch resistance.
It is considered that the scratch resistance is lowered because the molecular weight distribution between cross-linking points becomes non-uniform, and micro elastic deformation required for the scratch resistance is not exhibited.

A suitable low molecular weight polyol component having such a molecular weight distribution is a copolymer of a hydroxyl group-containing monomer and a monomer copolymerizable therewith, and an acrylic polyol having a molecular weight and a molecular weight distribution within the above ranges. .

Examples of the hydroxyl group-containing monomer include ordinary hydroxyl group-containing monomers such as hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, and caprolactone-modified hydroxyethyl (meth) acrylate. In particular, "Placcel F" which is a caprolactone-modified hydroxyethyl (meth) acrylate
M-1 "," Placcel FM-2 "," Placcel FM "
-3 "," Placcel FA-1 "," Placcel FA-
"Placcel FA-3" (trade names, manufactured by Daicel Chemical Industries, Ltd.) and the like, when acrylic polyol is copolymerized with another acrylate ester or the like to form an acrylic polyol, the primary functional group Since the hydroxyl group is located at the end of the flexible polycaprolactone side chain far away from the main chain skeleton, the reactivity with the curing agent such as melamine is large, and the crosslinking reaction of the obtained coating film proceeds sufficiently, so that the solvent resistance is high. It is characterized by providing a tough coating film with excellent properties and water resistance.

As the monomer copolymerizable with the hydroxyl group-containing monomer, monomers generally used for the synthesis of acrylic resins for coatings can be widely used, for example, acrylic acid or methacrylic acid ester of C _1-18 monohydric alcohol, styrene , Acrylonitrile, acrylamide, methacrylamide, N-methylolacrylamide butyl ether and the like.

The above-mentioned acrylic polyol can be obtained, for example, by purifying a radical polymerization product obtained by copolymerizing the above-mentioned monomer by heating under reduced pressure or fractional precipitation.

Further, according to the present invention, the hydroxyl value of the whole component (B) is preferably from 150 to 400 mgKOH / g, more preferably from 180 to 300 mgKOH / g.
It is preferable to adjust to H / g. Hydroxyl value is 150
If it is less than mgKOH / g, the number of crosslinking and curing reaction points with the component (C) becomes insufficient, and the improvement in scratch resistance becomes insufficient.
If it is more than 00 mgKOH / g, adverse effects such as a decrease in water resistance, a decrease in repelling resistance at the time of coating, and a decrease in finished appearance appear.

(C) Non-aqueous dispersion type acrylic resin The component (C) is a non-aqueous dispersion type acrylic resin obtained by dispersion-polymerizing at least one vinyl monomer in the presence of a polymer dispersion stabilizer and an organic solvent. Resin.

The polymer dispersion stabilizer used in the production of the component (C) is generally a polymer obtained by copolymerizing a long-chain vinyl monomer with another polymerizable monomer as required.

The long-chain vinyl monomer used in the polymer can be appropriately selected according to the performance required for the coating film, but can be preferably used from the viewpoints of copolymerizability, solubility in organic liquid, and the like. The following can be exemplified as the long-chain vinyl monomer.

For example, n-butyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, n
-Alkyl or cycloalkyl esters of (meth) acrylic acid having 4 to 18 carbon atoms, such as octyl (meth) acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate; Alkoxyalkyl esters of (meth) acrylic acid such as methoxybutyl (meth) acrylate, methoxyethyl (meth) acrylate and ethoxybutyl (meth) acrylate; and aromatic alcohols such as benzyl (meth) acrylate with (meth) acrylic acid Esters; adducts of hydroxyalkyl esters of glycidyl (meth) acrylate or (meth) acrylic acid with monocarboxylic compounds such as capric acid, lauric acid, linoleic acid, oleic acid, and the like, (meth)
Adducts of acrylic acid with monoepoxy compounds such as "Cardiura E10"; vinyl aromatic compounds such as styrene, α-methylstyrene, vinyltoluene, p-chlorostyrene, p-tert-butylstyrene; itaconic acid, itaconic anhydride Acid, crotonic acid, maleic acid, maleic anhydride, fumaric acid, α, β-unsaturated carboxylic acids other than (meth) acrylic acid such as citraconic acid and butyl alcohol, pentyl alcohol, heptyl alcohol, octyl alcohol, stearyl alcohol, etc. Mono- or diesters with a monoalcohol having 4 to 18 carbon atoms;
F "," VISCOAT 8FM "," VISCOAT 3F ",
"Viscort 3FM" (all manufactured by Osaka Organic Chemical Co., Ltd.
Trade names, (meth) acrylates having a fluorine atom in a side chain), fluorine-containing compounds such as perfluorocyclohexyl (meth) acrylate, and perfluorohexylethylene.

The polymerization for producing the dispersion stabilizer resin is usually carried out using a radical polymerization initiator. Examples of usable radical polymerization initiators include, for example, 2,2′-
Azo initiators such as azobisisobutyronitrile and 2,2'-azobis (2,4-dimethylvaleronitrile); benzoyl peroxide, lauryl peroxide, tert-butyl peroctoate, tert-butyl peroxy- Peroxide initiators such as 2-ethylhexanoate and the like, and these polymerization initiators are generally about 0.2 to 10 parts by weight per 100 parts by weight of monomers used for polymerization,
Preferably, it can be used in the range of 0.5 to 5 parts by weight. It is appropriate to use a reaction temperature in the polymerization generally in the range of about 60 to 160 ° C, and the reaction is usually completed in about 1 to 15 hours.

The molecular weight of the copolymer used as the dispersion stabilizer resin is usually about 5,000 to 1 in terms of weight average molecular weight.
About 000 (about 1,000 to 6 in number average molecular weight)
5,000), preferably about 5,000 to 50,000.
It is preferable to be in the range of about 00. When the molecular weight is less than about 5,000, the dispersion particles are insufficiently stabilized, and tend to cause aggregation and sedimentation.
If it exceeds 000, the viscosity becomes extremely high and handling becomes difficult, which is not preferable.

The dispersion stabilizer resin used in the production of the component (C) may be used alone, or may be used in combination of two or more resins having different copolymer compositions and molecular weights. And a small amount of a dispersion stabilizer such as butyl etherified melamine-formaldehyde resin and alkyd resin.

In the production of the component (C), at least one radically polymerizable unsaturated monomer (vinyl monomer) is polymerized in an organic liquid in the presence of the above-mentioned dispersion stabilizer resin. A non-aqueous dispersion of insoluble polymer particles is prepared.

The organic liquid used in the above polymerization includes:
The dispersed polymer particles formed by the polymerization are not substantially dissolved, but include an organic liquid which is a good solvent for the stabilizer resin and the radically polymerizable unsaturated monomer. Specific examples of such an organic liquid include hexane, heptane,
Aliphatic hydrocarbons such as octane; aromatic hydrocarbons such as benzene, toluene and xylene; alcohols such as methyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol and octyl alcohol; cellosolve, butyl cellosolve, diethylene glycol monobutyl ether and the like Ethers; ketones such as methyl isobutyl ketone, diisobutyl ketone, methyl ethyl ketone, methylhexyl ketone, ethyl butyl ketone;
Esters such as ethyl acetate, isobutyl acetate, amyl acetate and 2-ethylhexyl acetate can be exemplified. These organic liquids may be used alone or in combination of two or more. However, in general, aliphatic liquids are mainly used, and aromatic hydrocarbons, alcohols, and ethers are appropriately added thereto. , Ketones or esters are preferably used.

The radically polymerizable unsaturated monomer used in the above polymerization is excellent in polymerizability and has a smaller carbon number than that of the monomer used as a monomer component of the dispersion stabilizer resin. It is preferable to use one from the viewpoint that it is easily formed as dispersed polymer particles.

Examples of such radical polymerizable unsaturated monomers include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate Tert-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, n-octyl (meth)
C1-C18 alkyl or cycloalkyl esters of (meth) acrylic acid such as acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, and stearyl (meth) acrylate; methoxybutyl (meth) acrylate, methoxyethyl (meth) ) (Meth) such as acrylate, ethoxybutyl (meth) acrylate
Alkoxyalkyl esters of acrylic acid; (meth) of aromatic alcohols such as benzyl (meth) acrylate
Esters of acrylic acid; adducts of glycidyl (meth) acrylate with monocarboxylic acid compounds having 2 to 18 carbon atoms such as acetic acid, propionic acid, oleic acid, p-tert-butylbenzoic acid; and (meth) acrylic acid "Cardiura E1
Adduct with a monoepoxy compound such as "0"; styrene, α
-Vinyl aromatic compounds such as methylstyrene, vinyltoluene, p-chlorostyrene, p-tert-butylstyrene; itaconic acid, itaconic anhydride, crotonic acid, maleic acid, maleic anhydride, fumaric acid, citraconic acid, etc. Mono- or diesters of α, β-unsaturated carboxylic acids other than meth) acrylic acid and mono-alcohols having 1 to 18 carbon atoms such as methyl alcohol, butyl alcohol, hexyl alcohol, stearyl alcohol;
F "," VISCOAT 8FM "," VISCOAT 3F ",
"Viscort 3FM" (all manufactured by Osaka Organic Chemical Co., Ltd.
Trade names, (meth) acrylates having a fluorine atom in the side chain), fluorine atom-containing compounds such as perfluorocyclohexyl (meth) acrylate and perfluorohexylethylene; cyano group-containing unsaturated compounds such as (meth) acrylonitrile; acetic acid Vinyl esters such as vinyl, vinyl benzoate, and “VEOVA” (manufactured by Shell Co.); vinyl ethers such as n-butyl vinyl ether, ethyl vinyl ether, and methyl vinyl ether;
Polyvinyl compounds such as di (meth) acrylate of 6-hexanediol, tri (meth) acrylate of trimethylolpropane, and divinylbenzene; α-olefin compounds such as ethylene, propylene, vinyl chloride, and vinylidene chloride; .

As described above, the monomer component forming the polymer particles stably forms the particle component by combining those having a carbon number smaller than that of the monomer component of the dispersion stabilizer resin. Particularly preferred from this viewpoint are (meth) acrylates having 8 or less carbon atoms, preferably 4 or less carbon atoms, vinyl aromatic compounds, (meth) acrylonitrile, and the like. These radically polymerizable unsaturated monomers can be used alone or in combination of two or more.

The radically polymerizable unsaturated monomer is usually polymerized using a radical polymerization initiator. Examples of usable radical polymerization initiators include, for example, 2,2′-
Azo initiators such as azobisisobutyronitrile and 2,2'-azobis (2,4-dimethylvaleronitrile); benzoyl peroxide, lauryl peroxide, tert-butyl peroctoate, tert-butyl peroxy- Peroxide initiators such as 2-ethylhexanoate and the like, and these polymerization initiators are generally about 0.2 to 10 parts by weight per 100 parts by weight of monomers used for polymerization,
Preferably, it can be used in the range of 0.5 to 5 parts by weight.

The proportion of the dispersion stabilizer resin to be used in the above polymerization can be selected from a wide range depending on the type of the resin and the like. The amount of the saturated monomer is suitably about 3 to 240 parts by weight, preferably 5 to 82 parts by weight. Further, the total concentration of the dispersion stabilizer resin and the radical polymerizable unsaturated monomer in the organic liquid is generally about 30 to 70% by weight, preferably 30 to 60% by weight.

The polymerization can be carried out by a method known per se, and the reaction temperature during the polymerization is usually from 60 to 160 ° C.
The reaction is suitably within the range, and the reaction is usually completed in about 1 to 15 hours.

Thus, the non-aqueous dispersion type acryl in which the liquid phase is a liquid in which the dispersion stabilizer resin is dissolved in the organic liquid, and the solid phase is polymer particles obtained by polymerizing a radical polymerizable unsaturated monomer (vinyl monomer). A stable non-aqueous dispersion of the resin is obtained. The particle size of the polymer particles is usually about 0.1 to 1.
The range is 0 μm. When the particle size is smaller than this range, the viscosity of the varnish increases, while when the particle size is larger than this range, the particles swell or aggregate during storage, which is not preferable.

In the production of the component (C), the storage stability and mechanical properties of the non-aqueous dispersion are further improved by bonding the dispersion stabilizer resin and the polymer particles in the non-aqueous dispersion. be able to. Even when the particles are bonded, there is almost no change in the dispersion state in appearance, and the particle size of the polymer particles is also within the above range.

As a method for bonding the dispersion stabilizer resin and the polymer particles, for example, a hydroxyl group, an acid group, an acid anhydride group, an epoxy group,
A methylol group, an isocyanate group, an amide group, a monomer component having a functional group such as an amino group is partially copolymerized, and a hydroxyl group that reacts with the above functional group as a monomer component forming a polymer particle, Acid groups, acid anhydride groups, epoxy groups,
It can be carried out by using a monomer having a functional group such as a methylol group, an isocyanate group, an amide group, or an amino group. Examples of these combinations include an isocyanate group and a hydroxyl group, an isocyanate group and a methylol group, an epoxy group and an acid (anhydrous) group, an epoxy group and an amino group, an isocyanate group and an amide group, and an acid (anhydrous) group and a hydroxyl group. .

Examples of such a monomer having a functional group include (meth) acrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, itaconic anhydride,
Α, β-ethylenically unsaturated carboxylic acids such as fumaric acid and citraconic acid; glycidyl group-containing compounds such as glycidyl (meth) acrylate, vinyl glycidyl ether, allyl glycidyl ether; (meth) acrylamide;
Carboxamide compounds such as N-dimethyl (meth) acrylamide, N-alkoxymethylated (meth) acrylamide, diacetone acrylamide, N-methylol (meth) acrylamide; p-styrenesulfonamide, N-methyl-p-styrene Sulfonamide, N, N
-Sulfonamide group-containing compounds such as -dimethyl-p-styrenesulfonamide; amino-group-containing compounds such as tert-butylaminoethyl (meth) acrylate; 2-hydroxyethyl (meth) acrylate and phosphoric acid or phosphoric acid ester -Containing compounds, such as condensates with glycidyl groups, glycidyl (meth) acrylates and other compounds having a glycidyl group, and phosphoric acid or phosphoric acid esters added to the glycidyl group; 2-acrylamido-2-methyl- Sulfonic acid group-containing compounds such as propane sulfonic acid; m-isopropenyl-α, α-dimethylbenzyl isocyanate;
Examples thereof include an equimolar adduct of isophorone diisocyanate or tolylene diisocyanate with hydroxy (meth) acrylate, and an isocyanate group-containing compound such as isocyanoethyl methacrylate.

Another method for bonding the dispersion stabilizer resin and the polymer particles is to polymerize a radical polymerizable unsaturated monomer in the presence of a dispersion stabilizer resin having a polymerizable double bond. Can do it.

The polymerizable double bond is introduced into the dispersion stabilizer resin by, for example, using an acid group-containing monomer such as carboxylic acid, phosphoric acid or sulfonic acid as a copolymerization component of the resin, The reaction can be carried out by reacting a glycidyl group-containing unsaturated monomer such as glycidyl (meth) acrylate or allyl glycidyl ether. However, it is needless to say that a glycidyl group is contained in the resin and an acid group-containing compound is not added thereto. It can also be carried out by reacting a saturated monomer. These reactions can be performed under conventionally known conditions.

Further, as another method for bonding the dispersion stabilizer resin and the polymer particles, a non-aqueous dispersion in which functional groups which do not react with each other are introduced into the dispersion stabilizer resin and the polymer particles is prepared. It can also be carried out by blending a binding agent that binds the two with this.

Specifically, for example, a hydroxyl group-containing unsaturated monomer alone or in the form of a mixture with another unsaturated monomer is polymerized in the presence of a hydroxyl group-containing dispersion stabilizer resin and an organic liquid, and both of the hydroxyl group-containing unsaturated monomers are polymerized. After the production of a non-aqueous dispersion containing
At about -100 ° C, the reaction can be carried out for about 1-5 hours.

As the polyisocyanate compound, any compounds having one or more isocyanate groups in the molecule can be used. For example, aromatic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate, and 4,4'-diphenylmethane diisocyanate can be used. Or hydrides thereof; aliphatic diisocyanates such as hexamethylene diisocyanate, lysine diisocyanate and dimer acid (dimer of tall oil fatty acid) diisocyanate; and alicyclic diisocyanates such as isophorone diisocyanate.

In addition to the above combinations, the combination of a dispersion stabilizer resin and a polymer particle containing an acid group with a polyepoxide, a dispersion stabilizer resin and a polymer particle containing an epoxy group and a polycarboxylic acid , A dispersion stabilizer resin containing an epoxy group or an isocyanate group and a combination of polymer particles and a polysulfide compound.

Examples of the polyepoxide include bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolak type epoxy resin, epoxy group-containing acrylic resin and the like. Examples of polycarboxylic acids include adipic acid, sebacic acid, azelaic acid, and isophthalic acid. Acids and the like; Examples of polysulfide include pentamethylene disulfide, hexamethylene disulfide, poly (ethylene disulfide) and the like.

As described above, the dispersion stabilizer resin and the polymer particles can be chemically bonded. At this time, various functional groups and polymerizable double bonds are added to the dispersion stabilizer resin and / or the polymerizable double bond. It is sufficient that the amount introduced into the conductive particles is at least 0.1 on average in one molecule of the resin and / or the particles.

The non-aqueous dispersion thus obtained has excellent storage stability because the dispersion stabilizer resin and the polymer particles are chemically bonded, and the formed coating film is chemically and Shows excellent mechanical properties.

(D) Amino Resin There are known partially or completely methylolated amino resins obtained by reacting an aldehyde with an amino component such as melamine, urea, benzoguanamine, acetoguanamine, steroganamin, spiroguanamine and dicyandiamide. Aldehydes include formaldehyde, paraformaldehyde, acetaldehyde, benzaldehyde and the like. Further, those obtained by etherifying the methylolated amino resin with an appropriate alcohol can also be used. Examples of the alcohol used for the etherification include methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, and n-butyl alcohol. , I-butyl alcohol, 2-ethylbutanol, 2-ethylhexanol and the like.

[0076] In the present invention, it is particularly preferable to use etherified melamine resin obtained by substituting a part or all of hexamethoxymethylmelamine and its methoxy group at C ₄ or higher alcohols. In this case, it is preferable to add a usual curing catalyst such as paratoluenesulfonic acid and dodecylbenzenesulfonic acid.

In the present invention, as the component (D), trade names such as Cymel 303 (full methoxylated melamine resin, manufactured by Mitsui Cyanamid) and Uban 20SE-60 (butylated melamine resin, manufactured by Mitsui Toatsu) are used. A commercially available amino resin can be used.

The top clear coating composition of the present invention contains the above components (A) to (D) as main components, and the mixing ratio of the components can be arbitrarily selected according to the purpose. The range is 20 to 80% by weight of the component (A), based on the total solid content of the components (A) to (C), and (B)
The component is 5 to 30% by weight, the component (C) is 5 to 50% by weight, and the component (D) is 10 to 50% by weight.

The top clear coating composition of the present invention includes:
Further, it is preferable to use a curing acceleration catalyst for an alkoxysilane group as needed. For example, p-toluenesulfonic acid, dodecylbenzenesulfonic acid, trichloroacetic acid,
Phosphoric acid, mono-n-propyl phosphoric acid, monoisopropyl phosphoric acid, mono-n-butyl phosphoric acid, monoisobutyl phosphoric acid, mono-tert-butyl phosphoric acid, monooctyl phosphoric acid, monoalkyl phosphoric acid such as monodecyl phosphoric acid, di-n-propyl phosphoric acid, Dialkyl phosphoric acid such as diisopropyl phosphoric acid, di-n-butyl phosphoric acid, diisobutyl phosphoric acid, di-tert-butyl phosphoric acid, dioctyl phosphoric acid, and didecyl phosphoric acid; β-hydroxyethyl (meth) acrylate phosphoric acid ester; mono-n-propyl phosphorous acid; Monoalkyl phosphite such as monoisopropyl phosphite, mono-n-butyl phosphite, monoisobutyl phosphite, mono-tert-butyl phosphite, monooctyl phosphite, monodecyl phosphite, di-n-propyl phosphite, diisopropyl Phosphorous acid, di-n-butylphosphorous acid, diisobutylphosphorous acid, di-tert-butylphosphorous acid, Octyl phosphite, acidic compounds dialkyl phosphite such as didecyl phosphite; tetraisopropyl titanate, tetrabutyl titanate,
Tin-containing compounds such as tin octylate, dibutyltin diacetate, dibutyltin dioctoate, dibutyltin dilaurate, dibutyltin dimaleate; butylamine, tert-butylamine, dibutylamine, hexylamine, ethylenediamine, triethylamine, isophoronediamine, imidazole, lithium hydroxide And basic compounds such as sodium hydroxide, potassium hydroxide, and sodium methylate, and at least one of them is used.

[0080] For the curing catalyst, but it is of particular interest, the amino resin, etherified melamine resin a part or all of hexamethoxymethylmelamine and its methoxy group substituted with C ₄ or higher alcohol (D) When used, a strong acid catalyst such as paratoluenesulfonic acid, dodecylbenzenesulfonic acid or the like is generally used as a curing catalyst with a hydroxyl group, and the strong acid catalyst is triethylamine, diethanolamine, 2-amino-2-amine, or the like.
By neutralizing (blocking) with an amine compound such as methylpropanol, storage stability as a one-pack coating is imparted and used. This neutralizing (blocking) strong acid catalyst is used as a curing catalyst for alkoxysilane groups. Also. That is, at a baking temperature of 100 ° C. or higher, the neutralized (blocked) strong acid catalyst becomes a common catalyst for the reaction of the resin and the reaction of the alkoxysilane. What is more interesting is that this neutralized (blocked) strong acid catalyst does not function as a curing catalyst for alkoxysilanes at room temperature, so that one-pack storage under release, which is generally not possible in alkoxysilane curing systems. Also enable.

The coating composition of the present invention may contain, if necessary, an organic and / or inorganic thixotropy-imparting agent; a silicon-based surface modifier; an ultraviolet absorber; a light stabilizer and the like. .

As the solvent for dilution, all the solvents used in conventional acrylic resin / melamine resin paints can be used, for example, organic solvents such as toluene, xylene, methyl ethyl ketone, ethyl acetate, dioxane, butanol and the like. Water and the like can be mentioned. These solvents can be used alone or in a suitable mixture.

The base coating material used in the present invention may be any coating material containing a resin which is curable and crosslinked by heating as a main component, and a base coating material using an acrylic thermosetting resin is easy to apply. And weather resistance. The base coating material is mainly composed of a thermosetting resin, but may be used in combination with a resin that does not cure and crosslink, for example, a cellulose acetate butyrate resin. As a pigment to be incorporated into the base paint, a usual paint pigment can be used.

The coating finish by the two-coat one-bake method in the present invention is performed in exactly the same manner as the conventional coating method using a solution type paint as the top coat. That is, first, the viscosity of the base paint was adjusted with a diluting solvent for 10 to 30 seconds (Ford Cup No. 4/20 ° C.), and the base paint was formed directly or on a substrate to be coated (mainly a metal substrate) by a primer coating. Thereafter, the dried coating film is applied so as to have a thickness of about 10 to 30 μm. The coating method is performed using an air spray, an airless spray, a rotary atomizing coater, an electrostatic coater or the like. Then, after standing at room temperature for several minutes, the top clear coating material whose viscosity has been adjusted with a diluting solvent for 20 to 40 seconds (Ford Cup No. 4/20 ° C.) is applied in the same manner as the base coating material so as to have a dry film thickness of 20 to 50 μm. Paint. Then left for several minutes at room temperature and then heated at 120-160 ° C for 10-30 minutes,
The base paint and top clear paint are cured at the same time.

[0085]

According to the present invention, the top clear coating composition of the present invention
Coat 1 The coating film formed by the baking finish method has excellent acid resistance, scratch resistance, stain resistance, water resistance and weather resistance without impairing the appearance of the coating film, and their effects are maintained for a long time. Coating film can be obtained.

[0086]

The present invention will be specifically described below with reference to examples. In the examples, all parts and percentages are based on weight.

1. Preparation of base paint 50% acrylic resin liquid (Note 1) 110 parts 88% Cymel 370 (Note 2) 28 parts 20% CAB solution (Note 3) 100 parts Aluminum paste (Note 4) 20 parts Dibutyl acid phosphate 0.3 parts The above mixture was mixed with 30 parts of toluene, 20 parts of isobutyl alcohol, 30 parts of cellosolve acetate and 20 parts of "Swazol 1000" (manufactured by Cosmo Oil Co.) to a viscosity of 13 seconds (Ford Cup No. 4/20 ° C). It was adjusted. (Note 1) 50 acrylic resin liquid: methyl methacrylate 3
0 parts, 59 parts of ethyl acrylate, 10 parts of hydroxyethyl acrylate and 1 part of acrylic acid were added to the polymerization initiator α,
Xylene / α-azobisisobutyronitrile
Polymerization in a mixed solvent of n-butanol = 70/30, weight average molecular weight 25,000, resin solid content 50%
Acrylic resin liquid. (Note 2) 88% “Cymel 370”: trade name of melamine resin manufactured by Mitsui Sianamide, Inc. (Note 3) 20% CAB solution: mixed solvent solution of cellulose acetate butyrate in toluene / n-butyl acetate. (Note 4) Aluminum paste: manufactured by Toyo Aluminum Co., Ltd., trade name is “Alpaste # 55.519”.

2. Preparation of Top Clear Coating (A) Production of Acrylic Copolymer (A-1) Styrene 100 parts n-butyl acrylate 450 parts 2-ethylhexyl methacrylate 200 parts 2-hydroxyethyl methacrylate 150 parts γ-methacryloxypropyl trimethoxysilane A mixture consisting of 100 parts of azobisisobutyronitrile and 20 parts of azobisisobutyronitrile is mixed with 11 parts of xylene in the same amount as the mixture.
The solution was added dropwise at 0 ° C. over 3 hours and aged at the same temperature for 2 hours. The number average molecular weight by GPC of the obtained transparent polymer was 20,000.

(A-2) A mixture consisting of 150 parts of methyl methacrylate, 500 parts of n-butyl methacrylate, 200 parts of 1,4-butanediol monoacrylate, 150 parts of γ-methacryloxypropyl trimethoxysilane and 20 parts of azobisisobutyronitrile. Xylene 500 parts, n-butanol 5
After dripping into 00 parts of the mixed solvent at 120 ° C. over 3 hours, the mixture was aged at the same temperature for 2 hours. The number average molecular weight of the obtained transparent polymer was 18,000.

(A-3) A mixture of 200 parts of styrene, 600 parts of n-butyl methacrylate, 200 parts of 2-hydroxyethyl methacrylate, and 20 parts of azobisisobutyronitrile was dropped into the same amount of xylene at 120 ° C. over 3 hours. And aged at the same temperature for 2 hours. The number average molecular weight of the obtained transparent polymer was 18,000.

(B) Production of Low-Molecular-Weight Polyol (B-1) 70 parts of Swazol 1000 (an aromatic petroleum solvent manufactured by Cosmo Oil Co., Ltd.) was charged into a flask and heated to 150 ° C. There, 25 parts of n-butyl methacrylate, 25 parts of n-butyl acrylate, 35 parts of 2-hydroxyacrylate, 15 parts of Praxel FM-1 (a product of Daicel Chemical Co., Ltd., trade name), 15 parts of azobisisobutyronitrile (A
A mixture of 4 parts of (IBN) and 3 parts of n-dodecyl mercaptan was added dropwise over 3 hours. Next, AIBN powder 1
The portion was divided into 12 and added every 5 minutes. After the last AIBN was added, the mixture was kept at 150 ° C. for 30 minutes and then cooled.
This was diluted with xylene to a solid concentration of 40%. At 80 ° C, methanol as a poor solvent was added, and the mixture was allowed to cool to 20 ° C as it was. Discard the lower layer separated by two layers,
The upper layer was reprecipitated in petroleum etal and purified. After heating and cooling the precipitated resin, xylene / n-butanol = 90
/ 10 mixed solvent. The acrylic resin solution finally obtained has a solid content of 60% and a hydroxyl value (solid content).
203, Mw was 1,800, and Mw / Mn was 1.40.

(B-2) 25 parts of n-butyl methacrylate, 25 parts of n-butyl acrylate,
40 parts of 2-hydroxyethyl methacrylate, Praxel FM-2 (product of Daicel Chemical Industries, Ltd., trade name) 10
Parts, a mixture of 4 parts of azobisisobutyronitrile (AIBN) and 3 parts of n-dodecyl mercaptan,
An acrylic resin solution having a solid content concentration of 60%, a hydroxyl value (solid content) of 188, Mw of 1,800, and Mw / Mn of 1.40 was obtained in exactly the same manner as (B-1).

(C) Production of Non-Aqueous Dispersion Type Acrylic Resin Synthesis of Dispersion Stabilizing Resin (C) 40 parts of isobutyl acetate and 40 parts of toluene were heated to reflux, and the following monomers and a polymerization initiator were added in 3 hours. The mixture was added dropwise and aged for 2 hours after the addition. Styrene 10 parts Isobutyl methacrylate 49 parts 2-Ethylhexyl methacrylate 30 parts 2-Hydroxyethyl methacrylate 11 parts Azobisisobutyronitrile 2 parts The obtained acrylic resin has a nonvolatile content of 55% and a viscosity (Gardner, 25 ° C., the same applies hereinafter). G and weight average molecular weight 1
6,000.

Preparation of Non-Aqueous Dispersion (C-1) 93 parts of heptane, 55% dispersion stabilizer resin varnish (C) 9
Eight parts were charged into a flask and heated to reflux, and the following monomers and a polymerization initiator were added dropwise over 3 hours, followed by aging for 2 hours. Styrene 15 parts Methyl methacrylate 40 parts Acrylonitrile 30 parts 2-hydroxyethyl methacrylate 15 parts t-butylperoxy-2-ethylhexanoate 1.5 parts The obtained non-aqueous dispersion has a nonvolatile content of 53%, a viscosity B, Particle size of polymer particles (measured by electron microscope, the same applies hereinafter)
It was a milky white stable low-viscosity polymer dispersion of 2 to 0.3 μm. No precipitate or coarse particles were generated even after standing at room temperature for 3 months.

Example 1 (A-1) Solution 90 parts (B-1) Solution 30 parts (C-1) Dispersion liquid 18.8 parts Cymel 303 (Note 1) 30 parts Nacure 5225 (Note 2) 1.5 parts Surface conditioner (BYK-300 solution manufactured by BYK Chemi Co., Ltd.) 0.1 part UV absorber (Tinuvin 900, manufactured by Ciba Geigy Co., Ltd.) 1.0 part The above mixture was diluted with Swarsol 1000, and the viscosity (Ford Cup No. 4, 20) ℃) 25 seconds to prepare a top clear paint. The paint solids was 51%. (Note 1) Cymel 303: Fully methoxylated melamine resin manufactured by Mitsui Cyanamid. (Note 2) Nacure 5225: manufactured by King Industries, a neutralized product of dodecylbenzenesulfonic acid in dimethyloxazolidine.

Example 2 (A-2) Solution 90 parts (B-1) Solution 40 parts (C-1) Dispersion liquid 18.8 parts Cymel 303 20 parts Nacure 5225 2 parts Surface conditioner 0.1 part UV absorber 1.0 part The above mixture was adjusted in the same manner as in Example 1 to prepare a top clear paint. The paint solids was 52%.

Example 3 (A-1) 70 parts of solution (B-2) 40 parts of solution (C-1) 18.8 parts of dispersion liquid 50 parts of 60% Uban 20SE (butylated melamine manufactured by Mitsui Toatsu Co.) dibutyl Tin dilaurate 0.5 part Surface conditioner 0.1 part Ultraviolet absorber 1.0 part Using the above mixture, adjustment was carried out in the same manner as in Example 1 to prepare a top clear paint. The paint solids were 50%.

Comparative Example 1 (A-3) Solution 90 parts (B-1) Solution 30 parts (C-1) Dispersion liquid 18.8 parts Cymel 303 30 parts Nacure 5225 2 parts Surface conditioner 0.1 part UV absorber 1.0 part The above mixture was adjusted in the same manner as in Example 1 to prepare a top clear paint. The paint solids was 51%.

Comparative Example 2 (A-1) Solution 35 parts (B-1) Solution 30 parts (C-1) Dispersion liquid 18.8 parts Cymel 303 55 parts Nacure 5225 2 parts Surface conditioner 0.1 part UV absorber 1.0 part The above mixture was adjusted in the same manner as in Example 1 to prepare a top clear paint. The paint solids was 53%.

Comparative Example 3 (A-1) Solution 40 parts (B-1) Solution 50 parts Cymer 303 50 parts Nacure 5225 1.5 parts Surface conditioner 0.1 parts UV absorber 1.0 part Using the above mixture Adjustment was performed in the same manner as in Example 1 to produce a top clear coating. The paint solids was 45%.

3. Performance test An epoxy-based cationic electrodeposition paint is electrodeposited on a 0.8 mm thick dull steel plate that has been subjected to a chemical conversion treatment with zinc phosphate to a dry coating of about 20 μm, and baked at 170 ° C. for 20 minutes.
Sharpened with 400 sandpaper, wiped with petroleum benzene, degreased, then air-sprayed with an automotive midcoat surfacer to a dry coating of about 25μ, 140 ° C
After baking for 30 minutes, sanded with # 400 sandpaper, drained and dried, and then degreased with petroleum benzene to prepare a test material.

Then, the above-mentioned metallic base paint was applied on the material to a cured film thickness of 20 μm, left at room temperature for 5 minutes, and the coated surface was coated with the top clear paint of Examples 1-3 and Comparative Examples 1-3. Was applied to a cured film thickness of 40 μm, and heated at 140 ° C. for 30 minutes to cure both coating films. Table 1 shows the performance test results of the obtained coating films.

[0103]

[Table 1]

4. Test Method Coating Appearance: The finished appearance of the coating film was evaluated based on the following criteria from the glossiness and the feeling of holding. ◎: Very good ○: Good ×: Poor

Scratch resistance: After the automobile having the test coated plate attached to the roof was washed 15 times with a car washer, the coated surface of the coated plate was observed. The car washer was manufactured by Yasui Sangyo
FWRC "was used. The evaluation criteria are as follows. ：: Almost no scratches were found by visual observation, and the test passed. ：: Slight scratches were found, but the degree was extremely slight. X: Scratch was conspicuous by visual observation, and was rejected.

Acid resistance: 1% of test coated plate in 40% sulfuric acid solution
/ 2 immersion, left at 50 ° C. for 5 hours, washed with water, observed the coated surface, and evaluated according to the following criteria. ◎: No change at all. ：: There is no abnormality in the coated surface, but a slight step is recognized at the boundary between the immersed part and the non-immersed part. X: The coating surface was whitened.

Water resistance: After being immersed in warm water of 40 ° C. for 240 hours, it was washed with water, the coated surface was observed, and evaluated according to the following criteria. ◎: No change at all. ○: Slightly glossy. X: The coating surface was whitened.

Gasoline wiping resistance: Nisseki silver gasoline was moistened with gauze, and a 10 cm length of the coated surface was strongly rubbed back and forth for 8 times, and then the coated surface was observed. A: No scratches and no gloss on the painted surface. ：: Almost no scratches and no gloss on the painted surface. X: Scratch scratches and shiny blur are conspicuous.

Claims (1)

(57) [Claims] 1. A two-coat, one-bake coating method in which a two-layer uncured coating film obtained by applying a pigment-containing thermosetting coating material on a surface to be coated and then applying a clear coating material thereon is heated and cured simultaneously. A top clear paint used for finishing, comprising: (A) a general formula (I) [Wherein A is an ester bond, or a phenylene bond, R ₁
Is a hydrogen atom or a methyl group, R ₂ is a divalent aliphatic saturated hydrocarbon group having 1 to 6 carbon atoms, R ₃ and R ₄ are the same or different and are a phenyl group, an alkyl group having 1 to 6 carbon atoms or R ₅ represents an alkoxy group having 1 to 10 carbon atoms, and R ₅ represents an alkyl group having 1 to 10 carbon atoms. n shows the integer of 1-100. 5 to 40% by weight of an alkoxysilane group-containing vinyl monomer, 5 to 50% by weight of a hydroxyl group-containing vinyl monomer, and 10 to 90% by weight of another copolymerizable vinyl monomer. (B) a weight average molecular weight of 400 to less than 2,000, and a ratio Mw between the weight average molecular weight (Mw) and the number average molecular weight (Mn). / Mn has a molecular weight distribution of 1.6 or less,
A low-molecular-weight polyol having a hydroxyl value of 150 to 400 mgKOH / g; and (C) a non-aqueous dispersion-type acrylic resin obtained by dispersion-polymerizing at least one vinyl monomer in the presence of a polymer dispersion stabilizer and an organic solvent. And (D) hexamethoxymethylmelamine and / or its method.
Replacing part or all of the butoxy group C ₄ or higher alcohol
An amino resin consisting of an etherified melamine resin is used as a main component. Based on the total weight of the components (A) to (D), the component (A) is 20 to 80% by weight, and the component (B) is
30% by weight, 5 to 50% by weight of component (C) and 10 to 50% by weight of component (D) .
A top clear coating composition for finishing two coats and one bake coating, characterized by using acids neutralized with the compound.