JPH05263035A - Coating composition - Google Patents

Abstract

PURPOSE:To provide a coating compsn. capable of forming a coating film excellent in resistance to acid and scratch by compounding a specific acrylic copolymer, a low-mol.-wt. polyol, an acrylic resin of a nonaq. dispersion type, and an amino resin. CONSTITUTION:A clear topcoating compsn. for a 2-coat 1-bake finish coating mainly comprises an acrylic copolymer prepd. by copolymerizing 5-40wt.% vinyl monomer having an alkoxysilane group of the formula (wherein A is an ester or phenylene linkage; R2 is a 1-6C divalent aliph. satd. hydrocarbon group; R3 and R4 are each phenyl. 1-6C alkyl, or 1-10C alkoxy; R5 is 1-10C alkyl; and (n) is 1-100), 5-50wt.% hydroxylated vinyl monomer, and 10-90wt.% other vinyl monomers, a low-mol.-wt. polyol having a mol.wt. of 400-2,000, a mol.wt.distribution (Mw/Mn) of 1.6 or lower, and a hydroxyl value of 150-400 mgK0H/g, an acrylic resin of a nonaq. dispersion type, and an amino resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a two-layer uncured coating film obtained by coating a thermosetting coating material containing a pigment on the surface to be coated and then applying a clear coating material on the coating material at the same time by heat curing. At least, it relates to a two-coat one-bake top clear coating composition for finishing a coating film having excellent acid resistance and scratch resistance.

[0002]

2. Description of the Related Art In the fields of automobiles, heavy vehicles, industrial equipment, household electric appliances and the like, color finishing by baking coating of thermosetting paints containing pigments is widely practiced. As the baking finish method, a base paint containing a pigment was applied to improve image clarity and long-term weather resistance outdoors, and then top clear paint was continuously applied without curing the base paint. After that, a so-called two-coat one-bake system in which both the coating films are heated and cured at the same time is often adopted.

The two-coat, one-bake method is widely adopted in the field of automobiles, in particular, because it is required to form a coating film having an excellent finished appearance such as smoothness, gloss and sharpness because it has an excellent finished appearance. Has been done.

However, the gloss retention, water resistance, stain resistance, scratch resistance and the like of the coating film when exposed outdoors to automobiles, heavy vehicles, buildings and the like, which are painted and finished by the 2-coat 1-bake method, are It is greatly influenced by the composition of the coating material forming the film, especially the composition of the top clear coating material.

Currently, as the top clear paint, a paint mainly containing a hydroxyl group-containing acrylic resin and an amino resin 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 drawback that its surface is easily deteriorated by acid rain (pH 4 or less), which has recently become a social problem.

[0006] In addition, particularly in automobile paints, the adhesion of dust and the generation of scratches due to car washing have become a serious problem recently.

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

[0008]

Means for Solving the Problems The present inventors form a coating film having dramatically improved acid resistance and scratch resistance without impairing the finished appearance, weather resistance, physical performance, etc. of the coating film. We conducted intensive research to develop a top clear paint for 2 coat 1 bake painting finish.

As a result, a paint mainly containing an acrylic polymer containing a specific alkoxysilane group-containing monomer, a specific low molecular weight polyol, a non-aqueous dispersion type acrylic resin and an amino resin is used as a top clear coating. As a result, they 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 is a two-coating method in which a thermosetting coating material containing a pigment is applied to the surface to be coated, and then a clear coating material is applied over the coating material to simultaneously heat-cure two uncured coating films. (1) A top clear paint used for bake painting finishing, which comprises (A) general formula (I)

[Chemical 2] [Wherein A represents 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 1 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, which is a compound represented by % Of an acrylic copolymer obtained by polymerizing a monomer component contained therein, (B) having a weight average molecular weight of 400 to less than 2,000, and having a ratio Mw of 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
Non-aqueous dispersion type acrylic resin obtained by dispersion polymerization of at least one vinyl monomer in the presence of 0 mgKOH / g of low molecular weight polyol, (C) polymer dispersion stabilizer and organic solvent, and (D) amino. Based on the total weight of the above components (A) to (D) with a resin as the main component,
(A) component is 20 to 80% by weight, (B) component is 5 to 30
% Of component (C), 5 to 50% by weight of component (D), and 10 to 50% by weight of component (D).

In order to improve the acid resistance of the coating film in the two-coat one-bake system, the present inventors have investigated the glass transition temperature (Tg point) of the acrylic resin, which is the base resin of the conventional amino resin curing top clear coating composition, Although the molecular weight and the amount of styrene were studied and some improvements could be made, a significant difference from the conventional one was not recognized, and considering various situations where outdoor coated articles such as automobiles are actually placed, A fundamental solution has not been reached.

Then, as a result of further research, deterioration of the conventional amino resin-curing coating film due to acid 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. Presuming that the basic cause is that the ether bond is susceptible to hydrolysis,
-SiOSi-, which is a chemical bond that is difficult to undergo hydrolysis
It was found that introduction of SiOR- as a cross-linking point can realize a great improvement in acid resistance. The present invention has been completed based on such new findings.

The top clear coating composition of the present invention will be described in detail below.

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

[Chemical 3] [In the formula, A is an ester bond or a phenylene bond and is 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 An alkoxy group having 1 to 10 carbon atoms and R ₅ each represent 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, which is a compound represented by % Is an acrylic copolymer obtained by polymerizing a contained monomer component.

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

In the general formula (I), the divalent saturated aliphatic hydrocarbon group having 1 to 6 carbon atoms represented by R ₂ is a linear or branched alkylene group such as methylene, ethylene, propylene, 1 , 2-butylene, 1,3-butylene, 2,3-butylene, tetramethylene, ethylethylene, pentamethylene, hexamethylene group and the like. Examples of the alkyl group having 1 to 6 carbon atoms represented by R ₃ and R ₄ include linear or branched alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl and tert. -Butyl, n-
Examples thereof include pentyl, isopentyl, neopentyl, n-hexyl and isohexyl groups, and examples of the alkyl group having 1 to 10 carbon atoms represented by R ₅ include n-heptyl, 1-methylpentyl and 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 alkoxy group 10 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. Further, in the general formula (I), when n is 2 or more, R ₃ and R ₄
The comrades may be the same or different.

Among the compounds of 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]

[Chemical 4]

[0019]

[Chemical 5]

[0020]

[Chemical 6]

[0021]

[Chemical 7]

[0022]

[Chemical 8]

[0023]

[Chemical 9] Etc. can be mentioned.

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

[Chemical 10]

[0025]

[Chemical 11]

[0026]

[Chemical 12]

[0027]

[Chemical 13]

[0028]

[Chemical 14]

[0029]

[Chemical 15] Etc. can be mentioned.

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

In the polymer, the other 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, "Plaxel FM-1",
"Plaxel FM-2", "Plaxel FM-3",
"Plaxel FA-1", "Plaxel FA-2",
"Plaxel FA-3" (both are Daicel Chemical Industries, Ltd.)
Made, product name, caprolactone-modified (meth) acrylic acid 2
-Hydroxyethyls) and the like, but are not limited to these.

As the vinyl monomer copolymerizable with the above-mentioned vinyl monomer containing alkoxysilane group and vinyl monomer containing hydroxyl group, 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 and stearyl methacrylate with monohydric alcohols 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 acidate and glycidyl methacrylate; amide vinyl monomers such as acrylamide, methacrylamide, N-methylol acrylamide, and N-methylol methacrylamide; dimethylaminoethyl methacrylate, 2-diethylaminoethyl methacrylate, and tert-methacrylic acid. -Amine vinyl monomers such as butylaminoethyl; those of styrene, vinyltoluene, acrylonitrile, methacrylonitrile, α-methylstyrene, vinyl acetate, etc. 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 is lowered and
If it is more than 0% by weight, problems such as deterioration in storage stability of the coating material occur. The copolymerization amount of the hydroxyl group-containing vinyl monomer is 5 to 50% by weight, preferably 10 to 40% by weight.
Is. If it is 5% by weight or less, the reaction between the amino resin, the alkoxysilane group and the hydroxyl group does not proceed sufficiently and the curability and acid resistance are lowered, and if it is 50% by weight or more, water resistance is impaired. ..

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

The organic solvent may be heptane,
Hydrocarbon solvents such as toluene, xylene, octane, mineral spirits, ester solvents such as ethyl acetate, n-butyl acetate, isobutyl acetate, methyl cellosolve acetate, butyl carbitol acetate, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, etc. Ketone solvent, ethanol, isopropanol, n
-Alcoholic solvents such as butanol, sec-butanol, isobutanol, n-butyl ether, dioxane,
An ether solvent such as ethylene glycol monomethyl ether or ethylene glycol monoethyl ether can be used. Of 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 usually used can be used, and examples thereof include benzoyl peroxide and t-butylperoxy-2-.
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.

The acrylic polymer which is the component (A) in the present invention is, as described above, an alkoxysilane group-containing vinyl monomer and a hydroxyl group-containing vinyl monomer which are compounds represented by the general formula (I). It is obtained by copolymerizing another vinyl monomer, and an alkoxysilane group and a hydroxyl group are bonded to the acrylic polymer as a side chain. Therefore, as compared with the acrylic resin which is the base resin of the conventional amino resin curing type top clear paint, the acrylic polymer has a chemical bond that is less susceptible to hydrolysis, -SiOsi.
Since the acrylic polymer has an alkoxysilane group capable of introducing-, -SiOR- at the cross-linking point, when the acrylic polymer is used as a base resin for an amino resin curing top clear coating composition, the cured coating film has an extremely excellent surface. Characteristics (acid resistance, water repellency, scratch resistance, water resistance, chemical resistance, weather resistance, heat resistance),
Above all, it provides 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 also has a weight average molecular weight (Mw) and a number average molecular weight (M
It is a low molecular weight polyol component having a molecular weight distribution with a ratio Mw / Mn of n) of 1.6 or less and 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 polystyrene as a standard substance to prepare a calibration curve. ..

The component (B) has a weight average molecular weight of 400 to
It is important that it is less than 2,000, preferably in the range of 1,000 to 1,800. Weight average molecular weight is 400
When it is smaller, the coating performance such as weather resistance is deteriorated, and the ratio of evaporation during baking is increased, which causes a problem in equipment maintenance, which is not preferable. On the other hand, when the weight average molecular weight is 2,000 or more, the cross-linking density of the coating becomes insufficient and it becomes difficult to obtain a coating having excellent scratch resistance, which is not preferable.

The component (B) is required to have a narrow molecular weight distribution, and the Mw / Mn is 1.6 or less, preferably 1.4 or less. When Mw / Mn exceeds 1.6, the scratch resistance of the resulting coating film decreases, which is not preferable.
It is considered that the scratch resistance decreases because the molecular weight distribution between cross-linking points becomes non-uniform and the microscopic elastic deformation required for 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 range. ..

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. Particularly, "Praxel F which is caprolactone-modified hydroxyethyl (meth) acrylates
"M-1", "Plaxel FM-2", "Plaxel FM"
-3 "," Plaxel FA-1 "," Plaxel FA-
2 ”,“ Plaxel FA-3 ”(both manufactured by Daicel Chemical Industries, Ltd., trade names) and the like, when they are copolymerized with other acrylic acid ester or the like into an acrylic polyol, their functional groups are primary groups. 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 cross-linking reaction of the resulting coating film proceeds sufficiently, so that the solvent resistance It is characterized by giving a tough coating film with excellent properties and water resistance.

As the monomer copolymerizable with the hydroxyl group-containing monomer, the monomers generally used in the synthesis of acrylic resins for paints can be widely used. For example, acrylic acid or methacrylic acid ester of C _1-18 monohydric alcohol, styrene. , Acrylonitrile, acrylamide, methacrylamide, N-methylol acrylamide 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 by fractional precipitation.

Further, in the present invention, the hydroxyl value of the whole component (B) is 150 to 400 mgKOH / g, especially 180 to 300 mgKO.
It is preferable to adjust to H / g. Hydroxyl value is 150
If it is less than mgKOH / g, the cross-linking curing reaction points with the component (C) will be insufficient, and the scratch resistance will be insufficiently improved.
When it is more than 00 mgKOH / g, adverse effects such as a decrease in water resistance, a decrease in cissing resistance at the time of coating, a decrease in finished appearance and the like appear, and therefore, both are not preferable.

(C) Non-Aqueous Dispersion Type Acrylic Resin The (C) component 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. It is a 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, if necessary.

The long-chain vinyl monomer used in the polymer can be appropriately selected according to the performance required for the coating film, but it is preferably used from the viewpoint of copolymerizability, solubility in organic liquids and the like. The following may be mentioned as examples of long-chain vinyl monomers.

For example, n-butyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, n
-C4-18 alkyl or cycloalkyl esters of (meth) acrylic acid 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; with aromatic alcohol (meth) acrylic acid such as benzyl (meth) acrylate Ester; Addition product of hydroxyalkyl ester of glycidyl (meth) acrylate or (meth) acrylic acid with a monocarboxylic acid compound such as capric acid, lauric acid, linoleic acid and oleic acid, (meth)
Addition products of acrylic acid with monoepoxy compounds such as "Cardura E10"; vinyl aromatic compounds such as styrene, α-methylstyrene, vinyltoluene, p-chlorostyrene, p-tert-butylstyrene; itaconic acid, itacone anhydride Α, β-Unsaturated carboxylic acids other than (meth) acrylic acid such as acids, crotonic acid, maleic acid, maleic anhydride, fumaric acid, citraconic acid, and butyl alcohol, pentyl alcohol, heptyl alcohol, octyl alcohol, stearyl alcohol, etc. A mono- or diester with a C 4-18 monoalcohol;
"F", "Viscoat 8FM", "Viscoat 3F",
"Viscoat 3FM" (all manufactured by Osaka Organic Chemical Co.,
Examples thereof include trade names, (meth) acrylates having a fluorine atom in a side chain, perfluorocyclohexyl (meth) acrylate, and fluorine atom-containing compounds such as perfluorohexylethylene.

Polymerization for producing the above dispersion stabilizer resin is usually carried out using a radical polymerization initiator. Examples of usable radical polymerization initiators include 2,2′-
Azo initiators such as azobisisobutyronitrile and 2,2′-azobis (2,4-dimethylvaleronitrile); benzoyl peroxide, lauryl peroxide, tert-butyl peroctoate, tert-butyl peroxy- Examples thereof include peroxide-based initiators such as 2-ethylhexanoate. These polymerization initiators are generally used in an amount of about 0.2 to 10 parts by weight per 100 parts by weight of the monomers used for the polymerization.
Preferably, it can be used within the range of 0.5 to 5 parts by weight. It is suitable to use a temperature in the range of about 60 to 160 ° C. during the polymerization, 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.
Approximately 100,000 (about 1,000 to 6 in number average molecular weight)
50,000), preferably about 5,000 to 50,000.
It is preferable to set it within the range of about 00. When the molecular weight is less than about 5,000, the dispersion particles are insufficiently stabilized and tend to aggregate and settle, while the molecular weight is about 1
If it exceeds 0,000, the viscosity becomes so high that handling becomes difficult, which is not preferable.

The dispersion stabilizer resin used in the production of the component (C) may be used alone or in combination of two or more having different copolymerization compositions and molecular weights, and if necessary, other resins may be used. It is also possible to use it together with a small amount of a dispersion stabilizer such as butyl etherified melamine-formaldehyde resin or 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 dispersion stabilizer resin to give the organic liquid. A non-aqueous dispersion of insoluble polymer particles is prepared.

The organic liquid used for the above polymerization is
The dispersion polymer particles produced 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 the organic liquid include hexane, heptane,
Aliphatic hydrocarbons such as octane; Aromatic hydrocarbons such as benzene, toluene, xylene; Alcohols such as methyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, octyl alcohol; Cellosolve, butyl cellosolve, diethylene glycol monobutyl ether, etc. Ethers; ketones such as methyl isobutyl ketone, diisobutyl ketone, methyl ethyl ketone, methyl hexyl ketone, ethyl butyl ketone;
Examples thereof include esters such as ethyl acetate, isobutyl acetate, amyl acetate, 2-ethylhexyl acetate and the like. These organic liquids may be used alone or in admixture of two or more, but generally, they are mainly composed of aliphatic hydrocarbons, and aromatic hydrocarbons, alcohols and ethers are appropriately added. A combination of compounds, ketones or esters is preferably used.

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

Examples of such radically polymerizable unsaturated monomers include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate and 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, stearyl (meth) acrylate; methoxybutyl (meth) acrylate, methoxyethyl (meth ) (Meth) such as acrylate and ethoxybutyl (meth) acrylate
Alkoxyalkyl ester of acrylic acid; (meth) of aromatic alcohol such as benzyl (meth) acrylate
Ester with acrylic acid; Addition product of glycidyl (meth) acrylate with monocarboxylic acid compound having 2 to 18 carbon atoms such as acetic acid, propionic acid, oleic acid, p-tert-butylbenzoic acid; (meth) acrylic acid "Card Yura E1
0 "and other adducts with monoepoxy compounds; 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 with monoalcohols having 1 to 18 carbon atoms such as methyl alcohol, butyl alcohol, hexyl alcohol, and stearyl alcohol;
"F", "Viscoat 8FM", "Viscoat 3F",
"Viscoat 3FM" (all manufactured by Osaka Organic Chemical Co.,
Trade names, (meth) acrylates having a fluorine atom in the side chain, perfluorocyclohexyl (meth) acrylate, perfluorohexylethylene and other fluorine atom-containing compounds; (meth) acrylonitrile and other cyano group-containing unsaturated compounds; acetic acid Vinyl, vinyl benzoate, vinyl esters such as "VEOVA" (manufactured by Shell Co.); vinyl ethers such as n-butyl vinyl ether, ethyl vinyl ether and methyl vinyl ether; 1,
Examples include 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 is stably formed by combining those having a carbon number smaller than that of the monomer component of the dispersion stabilizer resin. However, particularly preferable from this viewpoint are (meth) acrylic acid esters having 8 or less and 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 an appropriate combination of two or more.

Polymerization of the radically polymerizable unsaturated monomer is usually carried out using a radical polymerization initiator. Examples of usable radical polymerization initiators include 2,2′-
Azo initiators such as azobisisobutyronitrile and 2,2′-azobis (2,4-dimethylvaleronitrile); benzoyl peroxide, lauryl peroxide, tert-butyl peroctoate, tert-butyl peroxy- Examples thereof include peroxide-based initiators such as 2-ethylhexanoate. These polymerization initiators are generally used in an amount of about 0.2 to 10 parts by weight per 100 parts by weight of the monomers used for the polymerization.
Preferably, it can be used within the range of 0.5 to 5 parts by weight.

The ratio of the dispersion stabilizer resin to be used in the above polymerization can be selected from a wide range according to the kind of the resin, etc. The amount of the saturated monomer is 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 radically 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 60 to 160 ° C.
It is suitable to set it within the range of about 1 to 15 hours, and the reaction is usually completed in about 1 to 15 hours.

Thus, a non-aqueous dispersion type acrylic in which the liquid phase is a dispersion stabilizer resin dissolved in an organic liquid, and the solid phase is polymer particles obtained by polymerizing a radically polymerizable unsaturated monomer (vinyl monomer). A stable non-aqueous dispersion of resin is obtained. The particle size of the polymer particles is usually about 0.1-1.
It is in the range of 0 μm. If the particle size is smaller than this range, the viscosity of the varnish will be high, while if the particle size is larger than this range, the particles will 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 binding the dispersion stabilizer resin in the non-aqueous dispersion and the polymer particles. be able to. Even when they are bonded, there is almost no change in the dispersed state in appearance, and the particle size of the polymer particles is within the above range.

As a method for binding the dispersion stabilizer resin and the polymer particles, for example, a hydroxyl group, acid group, acid anhydride group, epoxy group,
Methylol group, isocyanate group, amide group, partially copolymerized monomer components having functional groups such as amino groups, further hydroxyl groups that react with the functional groups as monomer components to form polymer particles, Acid group, acid anhydride group, epoxy group,
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 isocyanate groups and hydroxyl groups, isocyanate groups and methylol groups, epoxy groups and acid (anhydrous) groups, epoxy groups and amino groups, isocyanate groups and amide groups, acid (anhydrous) groups and hydroxyl groups. ..

Examples of the monomer having such 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 and allyl glycidyl ether; (meth) acrylamide, N,
Carboxamide compounds such as N-dimethyl (meth) acrylamide, N-alkoxymethylated (meth) acrylamide, diacetone acrylamide, N-methylol (meth) acrylamide; p-styrene sulfonamide, N-methyl-p-styrene Sulfonamide, N, N
-Sulfonamide group-containing compounds such as dimethyl-p-styrene sulfonamide; (meth) acrylic acid-amino group-containing compounds such as tert-butylaminoethyl; 2-hydroxyethyl (meth) acrylate and phosphoric acid or phosphate ester Group-containing compounds, such as those obtained by adding phosphoric acid or phosphoric acid esters to the glycidyl group of a compound having a glycidyl group such as a condensate with glycidyl (meth) acrylate; 2-acrylamido-2-methyl- Sulfonic acid group-containing compounds such as propanesulfonic acid; m-isopropenyl-α, α-dimethylbenzyl isocyanate,
Examples thereof include equimolar adducts of isophorone diisocyanate or tolylene diisocyanate with hydroxy (meth) acrylate, and isocyanate group-containing compounds such as isocyanoethyl methacrylate.

As another method for binding the dispersion stabilizer resin and the polymer particles, a radically polymerizable unsaturated monomer is polymerized in the presence of the dispersion stabilizer resin having a polymerizable double bond. Can be done.

The introduction of the polymerizable double bond into the dispersion stabilizer resin is carried out, for example, by using an acid group-containing monomer such as carboxylic acid, phosphoric acid or sulfonic acid as a copolymerization component of the resin, This can be carried out by reacting a glycidyl group-containing unsaturated monomer such as glycidyl (meth) acrylate or allyl glycidyl ether, but of course, conversely, the glycidyl group is contained in the resin and the acid group-containing unsaturated monomer is added. It can also be carried out by reacting a saturated monomer. These reactions can follow conventionally known conditions.

As another method for binding the dispersion stabilizer resin and the polymer particles, after producing a non-aqueous dispersion liquid in which functional groups that do not react with each other are introduced into the dispersion stabilizer resin and the polymer particles. It can also be carried out by blending this with a binder that binds both.

Specifically, for example, in the presence of a hydroxyl group-containing dispersion stabilizer resin and an organic liquid, a hydroxyl group-containing unsaturated monomer alone or a mixture with another unsaturated monomer is polymerized to form hydroxyl groups on both of them. After producing a non-aqueous dispersion containing the above, a polyisocyanate compound or the like was added, and the mixture was mixed at room temperature for 60 days.
The reaction can be carried out at about 100 ° C for about 1 to 5 hours.

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

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

Examples of the polyepoxide include bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolac type epoxy resin, epoxy group-containing acrylic resin and the like; examples of polycarboxylic acid include adipic acid, sebacic acid, azelaic acid and isophthalic acid. Acid, etc .; Examples of polysulfides 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 polymerization. It is sufficient that the amount introduced into the functional particles is at least 0.1 on average in one molecule of the resin and / or 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 coating film formed is chemically and chemically stable. It has excellent mechanical properties.

(D) Amino Resins Known examples of partially or completely methylolated amino resins obtained by the reaction of an aldehyde with an amino component such as melamine, urea, benzoguanamine, acetoguanamine, steroganamin, spiroguanamine, dicyandiamide. Examples of the aldehyde include formaldehyde, paraformaldehyde, acetaldehyde, benzaldehyde and the like. Further, the methylolated amino resin which is etherified with a suitable alcohol can also be used, and 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.

In the present invention, it is particularly preferable to use hexamethoxymethylmelamine or an etherified melamine resin obtained by substituting a part or all of its methoxy group with an alcohol having a C ₄ or more. In this case, it is preferable to add a usual curing catalyst such as paratoluenesulfonic acid or dodecylbenzenesulfonic acid.

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

The top clear coating composition of the present invention contains the above-mentioned components (A) to (D) as main components, and the blending ratio of the components can be arbitrarily selected according to the purpose, but the blending ratio of each component is The range is 20 to 80% by weight of the component (A), (B) based on the total weight of the solid content of the components (A) to (C).
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 comprises
Further, it is preferable to use a curing acceleration catalyst for the alkoxysilane group, if necessary. 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, monodecyl phosphoric acid, and other monoalkyl phosphoric acids, 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, phosphoric acid ester of β-hydroxyethyl (meth) acrylate, mono-n-propyl phosphorous acid, Monoisopropyl phosphorous acid such as monoisopropyl phosphorous acid, mono-n-butyl phosphorous acid, monoisobutyl phosphorous acid, mono-tert-butyl phosphorous acid, monooctyl phosphorous acid, monodecyl phosphorous acid, di-n-propyl phosphorous acid, diisopropyl Phosphorous acid, di-n-butyl phosphorous acid, diisobutyl phosphorous acid, di-tert-butyl phosphorous 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. , Basic compounds such as sodium hydroxide, potassium hydroxide, and sodium methylate, and at least one of them is used.

Regarding this curing catalyst, it is of particular interest that the amino resin (D) is an etherified melamine resin in which hexamethoxymethylmelamine or a part or all of its methoxy group is substituted with an alcohol having a C ₄ or more. When used, a strong acid catalyst such as paratoluene sulfonic acid or dodecylbenzene sulfonic acid is generally used as a curing catalyst with a hydroxyl group, and the strong acid catalyst is triethylamine, diethanolamine or 2-amino-2-
It is used by imparting storage stability as a one-pack paint by neutralizing (blocking) it with an amine compound such as methyl propanol. This strong acid catalyst (neutralizing block) is used as a curing catalyst for alkoxysilane groups. Also becomes. That is, the neutralizing (blocking) strong acid catalyst becomes a common catalyst for the reaction of the resin and the reaction of the alkoxysilane at a baking temperature of 100 ° C. or higher. More interestingly, this neutralizing (blocking) strong acid catalyst does not function as a curing catalyst for alkoxysilanes at room temperature, so that it can be stored as a one-liquid storable solution under release, which is generally impossible in an alkoxysilane curing system. Also enables.

The coating composition of the present invention may contain an organic and / or inorganic thixotropic agent, a surface modifier such as silicon, an ultraviolet absorber, a light stabilizer and the like, if necessary. ..

As the diluting solvent, all the solvents used in the conventional acrylic resin / melamine resin-based paint can be used. For example, organic solvents such as toluene, xylene, methyl ethyl ketone, ethyl acetate, dioxane and butanol, Water etc. can be mentioned. These solvents can be used alone or in an appropriate mixture.

The base coating material used in the present invention may be any coating material having a resin which is known and hardened and crosslinked by heating as a main component, but a base coating material using an acrylic thermosetting resin is easy to apply. And from the viewpoint of weather resistance. Further, the base coating material contains a thermosetting resin as a main component, but a resin that does not cure and crosslink, such as a cellulose acetate butyrate resin, may be used together. As a pigment to be added to 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 carried out in exactly the same manner as the conventional coating method using the solution type coating as the top coat. That is, first, the viscosity of the base paint was adjusted to 10 to 30 seconds (Ford cup No. 4/20 ° C.) with a diluting solvent, and this was applied directly to the article to be coated (mainly a metal substrate) or to form a primer coating film. After that, it is applied so that the dry coating film has a thickness of about 10 to 30 μm. The coating method is air spray, airless spray, rotary atomizer, electrostatic coater, etc. Then, after leaving at room temperature for several minutes, the top clear paint whose viscosity was adjusted to 20 to 40 seconds (Ford cup No. 4/20 ° C.) with a diluting solvent was dried in the same manner as the base paint so that the dry film thickness was 20 to 50 μm. To paint. Then leave it at room temperature for a few minutes, then heat at 120-160 ° C for 10-30 minutes,
The base paint and top clear paint are cured simultaneously.

[0085]

EFFECT OF THE INVENTION Using the top clear paint of the present invention
The coating film formed by the coat 1 bake coating finishing method has excellent acid resistance, scratch resistance, stain resistance, water resistance and weather resistance without impairing the appearance of the coating film, and these effects are maintained for a long time. A coating film can be obtained.

[0086]

EXAMPLES The present invention will be specifically described below with reference to examples. All parts and percentages in the examples are by 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., Ltd.) to obtain a viscosity of 13 seconds (Ford cup No. 4/20 ° C). It was adjusted. (Note 1) 50 acrylic resin liquid: methyl methacrylate 3
0 part, 59 parts of ethyl acrylate, 10 parts of hydroxyethyl acrylate and 1 part of acrylic acid were added as a polymerization initiator α,
xylene with 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 Cyanamide Co., Ltd., (Note 3) 20% CAB solution: toluene / n-butyl acetate mixed solvent solution of cellulose acetate butyrate. (Note 4) Aluminum paste: Toyo Aluminum Co., Ltd., trade name is "Alpaste # 55/519".

2. Preparation of Top Clear Paint (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 of 100 parts azobisisobutyronitrile 20 parts was mixed with 11 parts of xylene in the same amount as the mixture.
The mixture was added dropwise at 0 ° C. over 3 hours and aged at the same temperature for 2 hours. The number average molecular weight of the obtained transparent polymer by GPC was 20,000.

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

(A-3) Styrene 200 parts n-Butylmethacrylate 600 parts 2-Hydroxyethylmethacrylate 200 parts Azobisisobutyronitrile 20 parts A mixture of the same amount of xylene was added dropwise at 120 ° C. over 3 hours. Then, it was 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 (manufactured by Cosmo Oil Co., Ltd., aromatic petroleum solvent) was charged in a flask and heated to 150 ° C. 25 parts of n-butyl methacrylate, 25 parts of n-butyl acrylate, 35 parts of 2-hydroxy acrylate, 15 parts of Praxel FM-1 (product of Daicel Chemical Industries Ltd., trade name), azobisisobutyronitrile (A
A mixture of 4 parts of IBN) and 3 parts of n-dodecyl mercaptan was added dropwise over 3 hours. Then AIBN powder 1
Parts were divided into 12 and added every 5 minutes. After the last addition of AIBN was completed, the mixture was kept at 150 ° C. for 30 minutes and then cooled.
Xylene was added to this product to dilute it to a solid content concentration of 40%. Methanol, which is a poor solvent, was added at 80 ° C, and the mixture was allowed to cool to 20 ° C as it was. Discard the lower layer separated into two layers,
The upper layer was reprecipitated in petroleum etal and purified. After heating and cooling the precipitated resin, xylene / n-butanol = 90
It was dissolved in a mixed solvent of / 10. The finally obtained acrylic resin solution had a solid content concentration 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 and 25 parts of n-butyl acrylate were added to the monomer mixture added dropwise to the flask.
40 parts of 2-hydroxyethyl methacrylate, Praxel FM-2 (product of Daicel Chemical Co., Ltd., trade name) 10
Parts, azobisisobutyronitrile (AIBN) 4 parts, and n-dodecyl mercaptan 3 parts as a mixture,
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 in (B-1).

(C) Manufacture of Non-Aqueous Dispersion Acrylic Resin Synthesis of Dispersion Stabilizer Resin (C) 40 parts of isobutyl acetate and 40 parts of toluene are heated under reflux, and the following monomers and polymerization initiator are added in 3 hours. After dropping, the mixture was aged for 2 hours. Styrene 10 parts Isobutylmethacrylate 49 parts 2-Ethylhexylmethacrylate 30 parts 2-Hydroxyethylmethacrylate 11 parts Azobisisobutyronitrile 2 parts The acrylic resin obtained has a nonvolatile content of 55% and a viscosity (Gardner, 25 ° C., the same below). G, and weight average molecular weight 1
It was 6,000.

Preparation of non-aqueous dispersion liquid (C-1) 93 parts of heptane, 55% dispersion stabilizer resin varnish (C) 9
8 parts were placed in a flask and heated to reflux, the following monomer and polymerization initiator were added dropwise over 3 hours, and the mixture was aged 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 resulting 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) 0.
It was a milky white stable low-viscosity polymer dispersion of 2 to 0.3 μm. No precipitate or coarse particles were observed even after standing at room temperature for 3 months.

Example 1 (A-1) Solution 90 parts (B-1) Solution 30 parts (C-1) Dispersion 18.8 parts Cymel 303 (Note 1) 30 parts Nacure 5225 (Note 2) 1.5 parts Surface conditioner (BYK-300 solution manufactured by BYK Chem Co., Ltd.) 0.1 part Ultraviolet absorber (Tinubin 900 manufactured by Ciba-Geigy Co., Ltd.) 1.0 part The above mixture was diluted with Swazol 1000 to obtain a viscosity (Ford Cup No. 4, 20). C) 25 seconds to prepare a top clear paint. The coating solid content was 51%. (Note 1) Cymel 303: full-methoxylated melamine resin manufactured by Mitsui Cyanamid. (Note 2) Nacure 5225: a dimethyloxazolidine neutralized product of dodecylbenzene sulfonic acid manufactured by King Industries.

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

Example 3 Solution (A-1) 70 parts (B-2) Solution 40 parts (C-1) Dispersion 18.8 parts 60% Uban 20SE 50 parts (Muthi Toatsu Co. Butylated Melamine) Dibutyl Tin dilaurate 0.5 part Surface conditioner 0.1 part UV absorber 1.0 part Using the above mixture, preparation was performed in the same manner as in Example 1 to prepare a top clear paint. The coating solid content was 50%.

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

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

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

3. Performance test Epoxy-based cationic electrodeposition coating was electrodeposited on a 0.8 mm thick dull steel sheet that had been subjected to zinc phosphate chemical conversion treatment to a dry coating film thickness of approximately 20μ, and baked at 170 ° C for 20 minutes.
Sharpen with 400 sandpaper, wipe with petroleum benzine to degrease, and then air-spray an intermediate coating surfacer for automobiles to a dry coating film of about 25μ, 140 ° C.
After baking for 30 minutes, it was ground with # 400 sandpaper, drained and dried, and then degreased with petroleum benzine to prepare a test material.

Then, the above metallic base paint was applied on this material in a cured film thickness of 20 μm and left at room temperature for 5 minutes, and the top clear paints of Examples 1 to 3 and Comparative Examples 1 to 3 were applied to the coated surface. Was coated 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 Appearance of the coating film: The finished appearance of the coating film was evaluated according to the following criteria from the feeling of luster and the feeling of holding. ◎: Very good ○: Good ×: Poor

Scratch resistance: An automobile having a test coated plate adhered to the roof was washed 15 times with a car washing machine, and the coated surface state of the coated plate was observed. Car wash machine is "PO20
FWRC "was used. The evaluation criteria are as follows. ⊚: Almost no scratches were found by visual observation and passed. ○: Some scratches are found, but the degree is extremely slight. X: Scratch was noticeable by visual observation and failed.

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

Water resistance: After being immersed in warm water of 40 ° C. for 240 hours, it was washed with water and the coated surface was observed and evaluated according to the following criteria. A: No change at all. ◯: Slightly glossy. X: The coated 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 8 reciprocations, and then the coated surface was observed. ⊚: No scratches and no blur on the coated surface. ◯: Almost no scratches and no blur on the coated surface. X: Conspicuous scratches and glossiness are noticeable.

Claims (2)

[Claims] 1. A two-coat, one-bake coating in which a thermosetting paint containing a pigment is applied to the surface to be coated, and then a clear paint is applied on top of the paint to heat-harden simultaneously two layers of uncured coating film. A top clear paint used for finishing, comprising: (A) General formula (I) [Wherein A represents 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 1 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, which is a compound represented by %, An acrylic copolymer obtained by polymerizing the contained monomer components, (B) the weight average molecular weight is 400 to less than 2,000, and the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn).
A low molecular weight polyol having a molecular weight distribution of Mw / Mn of 1.6 or less and a hydroxyl value of 150 to 400 mgKOH / g, (C) at least one in the presence of a polymer dispersion stabilizer and an organic solvent. Based on the total weight of the components (A) to (D), the component (A) contains 20 parts by weight of the non-aqueous dispersion type acrylic resin obtained by dispersion-polymerizing the vinyl monomer and the component (D) amino resin. -80 wt%, (B) component 5-30 wt%, (C) component 5-50 wt% and (D) component 10-50 wt%, 2 coat 1 bake coating finish Top clear coating composition for use. 2. An amino resin wherein hexamethoxymethylmelamine and / or a part or all of its methoxy group is C ₄
2. The top clear coating composition for 2-coat 1-bake coating finish according to claim 1, which is an etherified melamine resin substituted with the above alcohols, wherein an acid neutralized with an amine compound is used as a curing catalyst.