JPH05146739A - Formation of coating film - Google Patents

Abstract

PURPOSE:To form a coating film having excellent finishing and precoating properties, etc., by using a coating material compsn. contg. respectively specific essential components as a coating material compsn. for forming a colored base coat and clear top coat. CONSTITUTION:The coating material compsn. contg. a hydroxyl group-contg. polyester resin, amino resin, polyorgano-siloxane having >=2 pieces of silanol groups and/or alkoxysilane groups in average in one molecule and having >=1000 number average mol. wt., metallic flake powder and/or mica powder as well as org. solvent as essential components is used as the coating material compsn. for forming the colored base coat. The coating material compsn. contg. a resin contg. at least one kind of the group selected from a silanol group and hydrolyzable group directly bonded to a silicon atom and a hydroxyl group as essential function groups, amino resin and org. solvent as essential components is used as the coating material compsn. for forming the clear top coat.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel coating film forming method, and more particularly to a coating film forming method having a particularly excellent finished appearance.

[0002]

2. Description of the Related Art Conventionally, there has been a demand for improving finish appearance, coating film performance and the like in top coating films, particularly for automobile exterior panels. In addition, there is a strong demand for the development of a low temperature curable coating film for the purpose of reducing the energy cost and enabling the integral coating of the same coating material on the outer panel of an automobile in which a steel sheet substrate and a plastic substrate are integrated. is there.

Currently, the mainstream paints for automobile topcoats are thermosetting acrylic resin / melamine resin-based paints,
Thermosetting polyester resin / melamine resin-based paints and the like are close to the limit in high smoothness, and there is room for improvement in various coating film performances. There is also a problem that the low temperature curability is not sufficient. Further, there are still problems such as a coating film being cracked by a condensate (formalin, etc.) generated during baking and environmental pollution.

The applicant of the present invention has proposed a coating composition for automobiles in Japanese Patent Application Laid-Open No. 2-160879 as a coating excellent in low temperature curability. The coating composition is a silicone coating composition prepared by blending a metal chelate compound with a copolymer having a silanol group- and / or alkoxysilane group-containing polysiloxane macromonomer and an oxirane group-containing vinyl monomer as monomer components. This product is applied to both metallic base coat (aluminum flake pigment is mixed with paint) / clear top coat, and the finish with 2 coat / 1 bake method is the metallic base coat affected by the clear top coat. There is a drawback that the orientation of the aluminum flake pigment is changed and a coating film having an aluminum luster (having a feeling of gleaming and white) cannot be obtained. Further, in the case where a thermosetting polyester resin / melamine resin-based material is used as the metallic base coat, the clear top coat starts to cure before the metallic base coat begins to cure, and as a result, the coating film has defects such as cracks and stripes. There was a drawback that it caused.

When a defect occurs in the finish coating film, a metallic base coat and a clear top coat of the same kind are usually recoated in order to repair the defect.
In the case of using the above silicone-based coating composition, there is also a problem that the adhesion between coating films (top clear coat and metallic base coat to be recoated) is not sufficient.

[0006]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned drawbacks, the present inventors have found that a specific colored base coat and a specific clear top coat are combined to form a finished product. The inventors have found that a coating film having excellent recoatability can be provided, and completed the present invention.

That is, the present invention provides a coating composition for forming a colored base coat in a topcoat coating method in which a colored base coat and a clear top coat are sequentially formed on a material and finished by a two-coat one-bake system. (2) Amino resin (3) Polyorganosiloxane having an average number of two or more silanol groups and / or alkoxysilane groups in one molecule and a number average molecular weight of 1,000 or more (4) Metal flake powder and / or mica powder, and ( 5) Using a coating composition containing an organic solvent as an essential component, as a coating composition for forming a clear top coat, (1) at least one selected from a silanol group and a hydrolyzable group directly bonded to a silicon atom. A resin containing a group and a hydroxyl group as an essential functional group, (2) an amino resin, According to a coating film forming method which comprises using a (3) coating composition containing an organic solvent as an essential component in the beauty.

Next, the method of the present invention will be specifically described.

Colored Base Coat The colored base coat comprises (1) a hydroxyl group-containing polyester resin, (2) an amino resin, and (3) a number average molecular weight of 1,000 or more having at least two silanol groups and / or alkoxysilane groups in one molecule. Polyorganosiloxane (hereinafter sometimes simply referred to as “polyorganosiloxane”), (4) Metal flake powder and / or mica powder (hereinafter sometimes simply referred to as “metal flake”).
And (5) a base coat coating composition containing an organic solvent as an essential component.

The hydroxyl group-containing polyester resin has a hydroxyl group in the molecule and preferably has a hydroxyl value of about 20 to 20.
Those in the range of 0, more preferably about 50 to 150 can be used. If the hydroxyl value is less than 20, the curing speed of the base coat coating will be slower than that of the top coat coating, and the top coat coating will be cured before the base coating coating is cured. And the finished appearance of the coating film deteriorates. Also,
Since the curing is not sufficient, the coating film performance (water resistance, impact resistance, etc.) may be deteriorated, which is not preferable. On the other hand, when the hydroxyl value exceeds about 200, a large amount of unreacted hydroxyl groups remain in the coating film and the coating film performance (water resistance, weather resistance, etc.) is deteriorated, which is not preferable.

As the hydroxyl group-containing polyester resin, one containing a carboxyl group in the molecule can be used. In particular, the carboxyl group increases the reaction rate such as the reaction between the hydroxyl group and the amino group, the reaction between the hydroxyl group and the silanol group and / or the alkoxysilane group, the reaction between the silanol group and / or the alkoxysilane group, and the coating finish is good. Has the effect of The carboxyl group has a resin acid value of about 0 to 50, preferably about 5 to 20.

The hydroxyl group-containing polyester resin may be an oil-free alkyd resin obtained by reacting a polybasic acid, a polyhydric alcohol and, if necessary, an aromatic monobasic acid, or a polybasic acid, a polyhydric alcohol, and if necessary. An alkyd resin obtained by reacting an aliphatic monobasic acid in addition to an aromatic monobasic acid is mentioned.

Polybasic acids, polyhydric alcohols, aromatic or aliphatic monobasic acids used in the production of the above (oil-free) alkyd resin will be described below.

Examples of polybasic acids include phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, tetrahydroterephthalic acid, hexahydrophthalic acid, hexahydroisophthalic acid, hexahydroterephthalic acid, het acid, trimellitic acid and hexa. Hydrotrimellitic acid,
Pyromellitic acid, cyclohexanetetracarboxylic acid, methyltetrahydrophthalic acid, methylhexahydrophthalic acid, endomethylenehexahydrophthalic acid, methylendomethylenetetrahydrophthalic acid, maleic acid, fumaric acid, itaconic acid, succinic acid, glutaric acid, adipine acid,
Azelaic acid, sebacic acid, decanedicarboxylic acid, suberic acid, pimelic acid, dimer acid (dimer of tall oil fatty acid), tetrachlorophthalic acid, naphthalenedicarboxylic acid, 4,4′-diphenylmethanedicarboxylic acid, 4,
Examples thereof include 4'-dicarboxybiphenyl and the like, their acid anhydrides and dialkyl esters, especially dimethyl ester.

Examples of the polyhydric alcohol include ethylene glycol, propylene glycol, 1,4-butanediol, 1,3-butanediol, 2,3-butanediol, 1,2-butanediol and 1,5-pentanediol. 1,4-pentanediol, 2,4-pentanediol, 2,3-dimethyltrimethylene glycol, 3,
-Methyl-pentane-1,5-diol, 3-methyl-
4,5-pentanediol, 2,2,4-trimethyl-
1,3-pentanediol, 1,6-hexanediol, 1,5-hexanediol, 1,4-hexanediol, 2,5-hexanediol, 1,4-cyclohexanedimethanol, diethylene glycol, dipropylene glycol, tri Ethylene glycol, neopentyl glycol, hydroxypivalic acid neopentyl glycol ester, polyalkylene oxide, bishydroxyethyl terephthalate, (hydrogenated) bisphenol A alkylene oxide adduct, glycerin, trimethylolpropane, trimethylolethane, diglycerin, penta Examples thereof include erythritol, dipentaerythritol and sorbitol. Kajura E1
Monoepoxy compounds such as 0 (manufactured by Shell Chemical Co.), α-olefin epoxide and butylene oxide can also be used as a kind of glycol.

Compounds having both carboxylic acid and hydroxyl group in the molecule can also be used. Examples of such compounds include dimethylolpropionic acid, pivalic acid, and 1
2-hydroxystearic acid, ricinoleic acid, etc. are mentioned. Lactones such as ε-caprolactone and γ-valerolactone are also cyclic ester compounds, and thus belong to the category of the above compounds.

Examples of the aromatic monobasic acid include benzoic acid and p-tert-butylbenzoic acid.

Examples of the aliphatic monobasic acid include caproic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, isononanoic acid, coconut oil (fatty acid) and the like.

The above-mentioned (oil-free) alkyd resin can be produced by a conventionally known method, for example, an esterification catalyst (for example, dibutyltin dilaurate, etc.) from a mixture of the above polybasic acid, polyhydric alcohol and, if necessary, a monobasic acid. Can be carried out by carrying out an esterification reaction or a transesterification reaction in the presence of The mixing ratio of the polybasic acid and the polyhydric alcohol is about 0.7 to 0.99 mol, preferably about 0.8 to 0.98, based on 1 mol of the polyhydric alcohol component.
It is desirable to set it in the molar range. In addition, the esterification catalyst is a total measurement of polyhydric alcohol and polybasic acid components 100
It is desirable that the amount is about 0.1 to 1.0 part by weight, preferably about 0.2 to 0.5 part by weight.
The reaction conditions are usually in the range of about 160 to 280 ° C., preferably about 180 to 260 ° C. for about 5 to 12 hours, preferably about 6 to 8 hours.

Besides the above (oil-free) alkyd resin, for example, vinyl-modified alkyd resin can be used.
Examples of the vinyl-modified alkyd resin include a reaction product of a hydroxyl group-containing (oil-free) alkyd resin and a carboxyl group- or isocyanate group-containing vinyl resin, a hydroxyl group- and carboxyl group-containing (oil-free) alkyd resin, and an epoxy group-containing vinyl resin. Reaction product, alkyd resin having (radical polymerizable unsaturated group) (oil-free) (for example, alkyd resin having drying oil as an essential component, alkyd resin containing hydroxyl group and carboxyl group (oil-free), reacted with glycidyl (meth) acrylate Radical polymerization reaction of vinyl monomer (for example, polymerizable unsaturated monomer (b) described below) in the presence of alkyd resin, etc., (oil-free) alkyd resin, vinyl-modified alkyd resin, etc. dispersed. As a stabilizer, in the presence of the dispersion stabilizer, vinyl monomer (for example, Serial polymerizable unsaturated monomer (b), etc.)
It is possible to use those obtained by carrying out the polymerization reaction by adding to an organic solvent in which the monomer and the dispersion stabilizer are dissolved but the polymer particles obtained from the monomer are not dissolved.

The molecular weight of the hydroxyl group-containing polyester resin is a number average molecular weight, for example, in the range of about 500 to 10000 for (oil-free) alkyd resin and in the range of about 2000 to 80,000 for vinyl-modified alkyd resin. When the molecular weight is less than the above range, the melt viscosity of the base coat is reduced during baking, and it is difficult to obtain a coating having a metallic feeling by changing the orientation of the metal flakes, while when it exceeds the above molecular weight range, the coating workability is generally deteriorated. It is not preferable because

The amino resin is used as a cross-linking agent, and examples thereof include a methylolated amino resin obtained by reacting an amino component such as melamine, urea, benzoguanamine, acetoguanamine, steroguanamine, spiroguanamine and dicyandiamide with an aldehyde. .. Examples of the aldehyde include formaldehyde, paraformaldehyde, acetaldehyde, benzaldehyde and the like.
In addition, it is also possible to use a product obtained by etherifying this methylolated amino resin with a suitable alcohol. As an example of the alcohol used for the etherification, methyl alcohol,
Examples thereof include ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol, i-butyl alcohol, 2-ethylbutanol, 2-ethylhexanol and the like. As the amino resin, melamine having a high degree of etherification, that is, melamine which has an average of 3 or more methyl ethers per triazine nucleus and melamine resin in which a part of its methoxy group is substituted with an alcohol having 2 or more carbon atoms is used. it can. Among them, the average degree of condensation is about 2 or less and the ratio of mononuclear body is about 50 from the viewpoint of high solidification.
A low molecular weight melamine of not less than wt% is preferred, and when this is used it is preferred to add a conventional curing catalyst such as paratoluene sulfonic acid.

The polyorganosiloxane is used together with the amino resin as a cross-linking agent for the hydroxyl group-containing polyester resin and as a resin that self-crosslinks by itself. The average number of polyorganosiloxanes is 2 or more, preferably 2 to 10 per molecule.
Number average molecular weight of 1,000 or more, preferably 1000 to 5 having one silanol group and / or alkoxysilane group.
0000 polyorganosiloxanes are suitable. This polyorganosiloxane preferably has a ladder structure portion, and can be obtained, for example, by hydrolyzing and condensing a silane compound containing a trifunctional silane represented by the following general formula (I) as an essential component.

R _x Si (OR ') _4-x (I) (In the formula, R and R'may be the same or different and each represents a hydrocarbon group having 1 to 13 carbon atoms, and x is 1 Examples of R and R'include, for example, a methyl group, an ethyl group, a propyl group, a butyl group, and a phenyl group.

The above silane compound to be hydrolyzed and condensed may be only the trifunctional silane of the formula (I), but if necessary, in addition to the trifunctional silane, x of the formula (I) may be used. It may contain a bifunctional or monofunctional silane having a value of 2 or 3, and in the silane compound,
The silane of the formula (I) is preferably contained in an amount of 30% by weight or more, more preferably 80% by weight or more.

Typical examples of the silane of the formula (I) are methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, isobutyltrimethoxysilane, isobutyltriethoxysilane, ethyltrimethoxysilane and the like. Is mentioned. Examples of the bifunctional or monofunctional silane which may be used as a mixture with the silane of the formula (I) include dimethyldimethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, diisobutyldimethoxysilane, diisobutyldipropoxysilane and trimethylmethoxysilane. Is mentioned.

Hydrolytic condensation of the silane compound is carried out by mixing the silane compound with a water-soluble solvent (eg alcohol solvent, cellosolve solvent, etc.) as necessary, and then adding hydrochloric acid, sulfuric acid,
20 ° C. to 100 ° C., preferably in the presence of mineral acids such as phosphoric acid or organic acids such as formic acid and acetic acid, and water, preferably at pH 6 or lower.
It is carried out by allowing the hydrolysis and condensation reaction to proceed with stirring for about 30 minutes to 20 hours.

The molecular weight of the polyorganosiloxane can be appropriately adjusted depending on the amount of water used, the type and amount of catalyst, the reaction temperature, the reaction time and the like.

In the above polyorganosiloxane resin, when the number of silanol groups and / or alkoxysilane groups is less than 2 on average in one molecule, the curing speed of the base coat film becomes slower than that of the top coat film. ,
Since the topcoat coating film begins to cure before the basecoat coating film cures, the topcoat cured coating film suffers from defects such as blemishes and the finished appearance of the coating film deteriorates.

Further, in the polyorganosiloxane resin, when the number average molecular weight is less than 1000, the melt viscosity of the base coat is lowered during baking, the orientation of the metal flakes is changed, and a coating film having a metallic feel cannot be obtained. There is.

The metal flake powder gives a metallic feeling to the coating film, and examples of the metal flake include aluminum flakes, nickel flakes, copper flakes, brass flakes and chrome flakes. Examples include pearl mica and colored pearl mica. In the coating composition for a colored base coat, the compounding amount of the metal flake powder and / or the mica powder may be about 1 to 20 parts by weight with respect to 100 parts by weight of the resin solid content.

Examples of the organic solvent include aromatic hydrocarbon solvents such as xylene and toluene; ester solvents such as ethyl acetate, propyl acetate and butyl acetate; ketone solvents such as acetone and methyl ethyl ketone; ethylene glycol, cellosolve, butyl cellosolve and cellosolve acetate. Examples of such solvents include ether solvents. The organic solvent may be used alone or in combination of two or more. Further, from the viewpoint of finishability, a boiling point of about 150 ° C. or lower is preferable, but the boiling point is not limited to this.

In the coating composition for base coat, the proportion of the hydroxyl group-containing resin serving as the binder, the amino resin and the polyorganosiloxane is based on the total amount of the three components (resin solid content) of 100 parts by weight and the hydroxyl group-containing resin of 5 to 5. 9
0 parts by weight, preferably 30 to 60 parts by weight, amino resin 5
-50 parts by weight, preferably 10-40 parts by weight, polyorganosiloxane 1-40 parts by weight, preferably 5-30 parts by weight, more preferably 5-20 parts by weight.

When the compounding amount of the hydroxyl group-containing resin is less than 5 parts by weight, the adhesion to the base is lowered, while when it exceeds 90 parts by weight, the finish appearance of the coating film and the coating film performance (water resistance, processability, etc.) Is reduced. When the blending ratio of the amino resin is less than 5 parts by weight, the crosslink density of the hydroxyl group-containing resin is low, the water resistance,
The impact resistance is remarkably impaired, and when the amount is more than 50 parts by weight, problems such as deterioration in mechanical properties and adhesion to the base occur. Further, if the mixing ratio of the polyorganosiloxane is less than 1 part by weight, the effect of accelerating the curing speed of the base coat coating is small and the finished appearance of the coating cannot be improved. Adhesion decreases.

In the base coat coating composition, in addition to the above-mentioned components, if necessary, an organic pigment, an inorganic pigment, a pigment dispersant, polymer fine particles, an ultraviolet absorber, a coating surface adjusting agent, a curing catalyst, a cellulose acetate ( And their derivatives),
Other paint additives and the like may be added.

The pigment which may be incorporated in the paint is
For example, organic pigments (for example, quinacridone type such as quinacridone red, azo type such as pigment red, phthalocyanine type such as phthalocyanine blue, phthalocyanine green, etc.), inorganic pigments (for example, titanium oxide, barium sulfate,
Calcium carbonate, barita, clay, silica, etc.), carbon-based pigments (carbon black), and the like.

The base coat coating composition used in the present invention may have a resin solid content of about 10 to 50% by weight.

Clear Top Coat The clear top coat is a resin containing a hydrolyzable group directly bonded to a silanol group and / or a silicon atom (hereinafter referred to as "hydrolyzable silyl group") and a hydroxyl group ( Hereinafter, abbreviated as "base resin for top coat"),
It is formed of a clear coating composition containing an amino resin and an organic solvent as essential components.

The hydrolyzable group contained in the base resin for a top coat is a residue which is hydrolyzed in the presence of water to form a silanol group, for example, a C _1-5 alkoxy group; a phenoxy group, a tolyloxy group. Aryloxy groups such as paramethoxyphenoxy group, paranitrophenoxy group, and benzyloxy group; acyloxy groups such as acetoxy group, propionyloxy group, butanoyloxy group, benzoyloxy group, phenylacetoxy group, and formyloxy group;
_{^{-N (R 1) 2, -ON}} (R 1) 2, -ON = C (R 1) 2,
—NR ² COR ¹ (in the formula, R ¹ is the same or different and represents a C _1-8 alkyl group, an aryl group or an aralkyl group, and R ² represents H or a C _1-8 alkyl group). There are residues represented.

The base resin for topcoat used in the present invention is a single resin containing at least one group selected from a silanol group and a hydrolyzable silyl group and a hydroxyl group in the same molecule as an essential functional group component (hereinafter, referred to as This is sometimes abbreviated as "resin (A)." And a resin having at least one group selected from a silanol group and a hydrolyzable silyl group (hereinafter, this resin is referred to as "resin (or polymer)".
It may be abbreviated as "B". And a resin having a hydroxyl group (hereinafter, this may be abbreviated as “resin (or polymer) C”). Examples of the resin include vinyl polymers, polyester resins, and polyether polyester resins. The number average molecular weight of these resins is about 2000 to 100,000, preferably about 4000 to 80 in the case of a vinyl polymer.
000, and in the case of polyester type and polyether polyester type, it is in the range of about 500 to 20,000, preferably about 1,000 to 5,000. When the number average molecular weight is less than the lower limit, defects such as stripes are likely to occur on the coating film surface, while when the number average molecular weight exceeds the upper limit, the coating workability is poor, and defects on the coating film surface are easily generated. It is not preferable because it has the drawback that

As the base resin for the top coat used in the present invention, it is preferable to use a vinyl polymer having excellent weather resistance, acid resistance and scratch resistance among the above resins. The vinyl polymer will be described below.

The resin A of the vinyl polymer is, for example, a silanol group- and / or hydrolyzable silyl group-containing vinyl monomer (a), a hydroxyl group-containing vinyl monomer (b) and, if necessary, other A vinyl-based copolymer obtained by a copolymerization reaction of the vinyl monomer (c) and a vinyl-based polymer having a functional group are produced in advance, and then the functional group of the polymer is complementarily obtained. A polymer obtained by reacting a silane compound having a reactive group with a silanol and / or a hydrolyzable silyl group (which may be a group which reacts complementarily) [eg (meth) acryl) A copolymer obtained by reacting γ-aminopropyltrimethoxysilane with a copolymer of glycidyl acid salt, a hydroxyl group-containing vinyl monomer (b) and another vinyl monomer (c), (meth) acrylic acid and a hydroxyl group-containing group. Vinyl monomer (b) and the copolymer in the γ- glycidoxypropyltrimethoxysilane those reacted etc.] or the like with other vinyl monomer (c).

The vinyl polymer preferably has an average of one or more silanol groups and / or hydrolyzable silyl groups in one molecule. When the number of the silanol groups and / or hydrolyzable silyl groups is less than 1 on average in one molecule,
It is not preferable because the curability is lowered and a coating film excellent in weather resistance, acid resistance, scratch resistance and the like cannot be formed. The vinyl polymer has a hydroxyl value of about 30 to 300,
It is desirable to have it in the range of preferably about 50 to 200. When the hydroxyl value is less than about 30, the curability is lowered, and it is difficult to form a coating film having excellent weather resistance, acid resistance, scratch resistance, etc. On the other hand, when the hydroxyl value is greater than about 300, unreacted hydroxyl groups remain. A large amount remains in the coating film and the water resistance of the coating film decreases, which is not preferable.

As a mixed resin of vinyl resin,
For example, a vinyl-based polymer obtained by (co) polymerizing a silanol group- and / or hydrolyzable silyl group-containing vinyl monomer (a) and, if necessary, other vinyl monomer (c), A vinyl-based polymer having a functional group is produced in advance, and then a group that reacts complementarily with the functional group of the polymer and a silanol and / or hydrolyzable silyl group (a group that the group reacts complementarily to A polymer obtained by reacting a silane compound having γ-aminopropyl (for example, a copolymer of glycidyl (meth) acrylate and another vinyl monomer (c), Such as those obtained by reacting trimethoxysilane or those obtained by reacting γ-glycidoxypropyltrimethoxysilane with a copolymer of (meth) acrylic acid and other vinyl monomer (c)]. Polymer B and the same polymer obtained by polymerizing, for example, a hydroxyl group-containing vinyl monomer (b), a copolymerization reaction of the vinyl monomer (b) with another vinyl monomer (c) Examples thereof include vinyl polymers C such as copolymers obtained by

The vinyl polymer B has an average of 1 in one molecule.
It is desirable to have one or more silanol groups and / or hydrolyzable silyl groups. When the number of silanol groups and / or hydrolyzable silyl groups is less than 1 on average in one molecule, curability is lowered and a coating film excellent in weather resistance, acid resistance, scratch resistance and the like cannot be formed, which is not preferable.

The vinyl polymer C preferably has a hydroxyl value of about 30 or more. When the hydroxyl value is less than about 30, the curability is deteriorated and it is difficult to form a coating film excellent in weather resistance, acid resistance, scratch resistance and the like. Further, when the hydroxyl value becomes too large, a large amount of unreacted hydroxyl groups remain in the coating film, and the water resistance of the coating film decreases, so the hydroxyl value is preferably about 300 or less.

The blending ratio of the vinyl polymers B and C is
The polymer B: polymer C weight ratio is 90:10 to 10: 9.
The range of 0, preferably 80:20 to 20:80 is preferable.

Among the above-mentioned single resin A and the mixed resin of resin B and resin C, it is preferable to use the resin A which can be uniformly cured and can easily form a coating film excellent in finished appearance and performance.

Examples of the vinyl monomer (a) include 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, Acrylic silane compounds such as γ- (meth) acryloxypropyltriacetoxysilane; vinylsilane compounds such as vinyltrimethoxysilane and vinyltriethoxysilane; allylsilane compounds such as allyltriethoxysilane;
Examples thereof include styrylsilane compounds such as 2-styrylethyltrimethoxysilane. In addition, a radically polymerizable unsaturated group, a siloxane bond, a silanol and / or a hydrolyzable group in a molecule obtained by reacting these monomers with, for example, a silane compound (eg, trimethoxysilane, triethoxysilane, etc.) Those having a silyl group are also included.

As the hydroxyl group-containing vinyl monomer (b),
For example, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl (meth) acrylate, butanediol monoacrylate, "Plaxel FM-1", "Plaxel FM-2", "Plaxel FM-3", " Praxel FA-1 "," Plaxel FA-2 "," Plaxel FA-3 "(all manufactured by Daicel Chemical Industries Ltd., trade name, caprolactone modified (meta)
2-hydroxyethyl acrylates) and the like.

Examples of other vinyl monomers (c) include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, Acrylic acid such as 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, lauryl acrylate, lauryl methacrylate, stearyl acrylate, stearyl methacrylate, or an ester of methacrylic acid and a monohydric alcohol having 1 to 22 carbon atoms; acrylic acid Carboxyl group-containing vinyl monomers such as methacrylic acid and (anhydrous) maleic acid; amide vinyl monomers such as acrylamide, methacrylamide, N-methylol acrylamide and N-methylol methacrylamide; dimethylaminoethyl Amino vinyl monomers such as methacrylate, 2-diethylamine ethyl methacrylate and tert-butylaminoethyl methacrylate; aromatic vinyl monomers such as styrene and vinyltoluene; (meth) acrylonitrile monomers such as acrylonitrile and methacrylonitrile; perfluorobutylethyl (Meta)
Acrylate, perfluoroisononylethyl (meth)
Perfluoroalkyl vinyl monomers such as acrylate and perfluorooctylethyl (meth) acrylate,
Fluoroolefins such as chlorotrifluoroethylene; cyclohexyl or alkyl vinyl ethers; aryl ethers; vinyl esters; olefins:
And a compound having one polymerizable unsaturated bond in one molecule.

In the base resin for a top coat used in the present invention, a resin having a carboxyl group introduced therein can also be used. As a method of introducing a carboxyl group into the resin, for example, in the production of a vinyl polymer, a carboxyl group-containing vinyl monomer may be used as the other vinyl monomer (c) component. When this monomer component is used, the monomer component can be used in the range of about 5 to 50% by weight, preferably about 10 to 40% by weight, based on the vinyl polymer.

The amino resin used in combination with the base resin for the top coat is a methylolated amino resin similar to that described in the coating composition for a colored base coat or an etherified amino resin obtained by etherifying the amino resin with an alcohol. Resin etc. can be used. The blending amount of the amino resin is preferably about 2 to 100 parts by weight with respect to 100 parts by weight of the base resin. If the blending amount is less than 2 parts by weight, the water resistance decreases, and if it exceeds 100 parts by weight, the weather resistance decreases, which is not preferable.

Examples of the organic solvent include hydrocarbon solvents such as heptane, toluene, xylene, octane and mineral spirit, ethyl acetate, n-butyl acetate,
Ester-based solvents such as isobutyl acetate, methyl cellosolve acetate and butyl carbitol acetate, ketone-based solvents such as methyl ethyl ketone, methyl isobutyl ketone and diisobutyl ketone, alcohol-based solvents such as ethanol, isopropanol, n-butanol, sec-butanol and isobutanol. , N-butyl ether, dioxane, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether and the like can be used.

In the present invention, a clear coating composition for forming a clear topcoat can be obtained by dissolving or dispersing the above basecoat base resin and amino resin in an organic solvent. It can also be used as a non-aqueous dispersion type coating composition using this as a dispersion stabilizer.

In addition to the above-mentioned base resin and organic solvent, a curing catalyst for silanol groups and / or hydrolyzable silyl groups may be added to the clear coating composition as required.

Examples of the curing catalyst include p-toluenesulfonic acid, dodecylbenzenesulfonic acid, trichloroacetic acid, phosphoric acid, mono-n-propylphosphoric acid, monoisopropylphosphoric acid, mono-n-butylphosphoric acid, monoisobutylphosphoric acid and monoisobutylphosphoric acid. -Tert-butyl phosphoric acid, monooctyl phosphoric acid,
Monoalkyl phosphoric acid such as monodecyl phosphoric acid, di-n-propyl phosphoric acid, diisopropyl phosphoric acid, di-n-butyl phosphoric acid, diisobutyl phosphoric acid, di-tert-butyl phosphoric acid, dioctyl phosphoric acid, didecyl phosphoric acid and the like, β-hydroxyethyl ( Phosphoric acid ester of (meth) acrylate, mono-n-propylphosphorous acid, monoisopropylphosphorous acid, mono-n-butylphosphorous acid, monoisobutylphosphorous acid, mono-t
ert-Butyl phosphite, monooctyl phosphite, monodecyl phosphite and other monoalkyl phosphites, di-n-propyl phosphite, diisopropyl phosphite, di-n-butyl phosphite,
Acid compounds such as dialkyl phosphites such as diisobutyl phosphite, di-tert-butyl phosphite, dioctyl phosphite, didecyl phosphite; tetraisopropyl titanate, tetrabutyl titanate, tin octylate, dibutyltin diacetate, dibutyltin dioctoate, Tin-containing compounds such as dibutyltin dilaurate and dibutyltin dimaleate; butylamine, tert-butylamine, dibutylamine, hexylamine, ethylenediamine, triethylamine,
Isophorone diamine, imidazole, lithium hydroxide,
Basic compounds such as sodium hydroxide, potassium hydroxide and sodium methylate can be mentioned, and at least one of them is used.

These curing catalysts are usually added in an amount of about 0.05 to 20 parts by weight, preferably about 0.1 to 10 parts by weight, based on 100 parts by weight of the base resin for topcoat.

When an etherified melamine resin in which hexamethoxymethylmelamine or a part or all of its methoxy groups is substituted with an alcohol having a C4 or more is used as an amino resin, paratoluenesulfonic acid or dodecyl is used as a curing catalyst for hydroxyl groups. It is common to use a strong acid catalyst such as benzenesulfonic acid, and the strong acid catalyst is
Triethylamine, diethanolamine, 2-amino-
It is used by imparting storage stability as a one-pack paint by neutralizing (blocking) it with an amine compound such as 2-methylpropanol. This neutralizing (blocking) strong acid catalyst cures the alkoxysilane group. It also serves as a catalyst. 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.

Further, the clear coating composition may contain, if necessary, an ultraviolet absorber, an antioxidant, a light stabilizer, polymer fine particles, and other additives for various coatings.

The clear coating composition used in the present invention may usually have a resin solid content of about 35 to 70% by weight.

In the method of the present invention, for example, a chemically treated steel plate is coated with an electrodeposition paint, and an intermediate coating paint (may be omitted).
Coating, a primer suitable for various plastic materials, a coating composition coated with an intermediate coating (which may be omitted), a colored base coating composition, and then a top clear coating. It can be carried out by coating the composition. The above-mentioned electrodeposition paint and intermediate paint are different depending on the type of paint, but are usually 140 to 190.
Bake at 30 ° C for 90-90 minutes. Coating of the colored base and top clear coating compositions can be carried out using conventional coating methods, for example electrostatic coating or non-electrostatic coating machines. The thickness of the colored base coat is preferably about 10 to 50 μm (after curing). After coating the coating composition, the coating composition is left at room temperature for several minutes or forcedly dried at about 50 to 80 ° C. for several minutes, and then coated with the clear coating composition. Clear coating thickness is 20
˜100 μm (after curing) is preferred. Then, the article to be coated can be heated and cured at about 120 to 180 ° C. for about 30 to 90 minutes.

[0063]

In the method of the present invention, the coating for the colored base coat, which is finished by the two-coat one-bake method, is
Containing a polyorganosiloxane having two or more silanol groups and / or alkoxysilane groups in one molecule as a binder component, the reaction of silanol groups (or silanol groups produced by hydrolysis of alkoxysilane groups) by heating The reaction between the silanol group and the silanol group and the hydroxyl group in the hydroxyl group-containing resin is rapidly performed at a relatively low temperature.
Since the reaction is carried out faster than the curing reaction of the clear coat paint, the viscosity of the base coat paint increases faster than that of the clear coat paint in the early stage of baking.
For this reason, it is considered that a base coating film that can withstand the shrinkage force of the clear coating film due to the volume change due to the curing of the clear coat coating material and the volatilization of the solvent is formed, and as a result, the finished appearance of the coating film is improved. Further, when the colored base coat paint was applied to a clear top coat cured coating film and re-coated, improvement in adhesion between both coating films was also recognized.

[0064]

The present invention will be described in more detail with reference to the following examples.

In the following, "parts" and "%" mean "parts by weight" and "% by weight", respectively.

[0066]

[Production Example 1] 0.29 mol of isophthalic acid and 0.
23 mol, hexahydrophthalic acid 0.43 mol, trimethylolpropane 0.4 mol, neopentyl glycol 0.6 mol, and coconut oil fatty acid 0.1 mol are added to a reaction vessel and the acid value is obtained by condensation polymerization at 200 to 230 ° C. 8, hydroxyl value 7
A coconut oil-modified polyester resin No. 2 was obtained. 43 parts of xylene was added to 100 parts of the polyester resin to prepare a 60% by weight varnish (a-1). The viscosity was Y (25 ° C., Gardner bubble viscosity).

[0067]

[Production Example 2] Phenyltrimethoxysilane 198 parts Deionized water 54 parts 98% sulfuric acid 0.002 parts were mixed and reacted at 60 ° C. for 5 hours, then methanol was removed by reduced pressure, and xylol was added to obtain a solid content of 50. %, Gardner viscosity AB polyorganosiloxane liquid (low
1) was obtained. The resulting polyorganosiloxane is GPC
According to the number average molecular weight (hereinafter, the same) is about 5,000,
It had an average of 6 silanol groups per molecule.

[0068]

[Production Example 3] Methyltrimethoxysilane 136 parts Diphenyldimethoxysilane 182 parts Deionized water 90 parts 60% Phosphoric acid 1 part After mixing and reacting at 60 ° C for 10 hours, methanol was removed by reduced pressure and butyl acetate was added. And solid content 50%,
Gardner viscosity D polyorganosiloxane liquid (low
2) was obtained. The obtained polyorganosiloxane had a number average molecular weight of about 15,000 and had an average of 10 silanol groups per molecule.

Colored base coat paint composition Base coat paint-1 100 parts of resin solution (a-1) obtained in Production Example 1 (60 parts by solid content), 33.3 parts of Uban 20SE (Note 1) (solid) 20 parts by weight), the resin solution obtained in Production Example 2 (b-1)
Stir a mixture of 40 parts (20 parts by solids), 20 parts aluminum paste and 1 part Raybo # 3 (note 2), then Swazol 1000 (note 3) / ethyl acetate = 30
The paint viscosity was adjusted to 15 seconds (Ford cup # 4/20 ° C.) by adding a mixed solvent of 70 / (weight ratio), and the mixture was subjected to the test.

(Note 1) U-Van 20SE ... Mitsui Toatsu Chemical Co., Ltd., butyl etherified melamine resin solution with a solid content of about 60%, trade name.

(Note 2) Raybo # 3: manufactured by Raybo Chemical Co., Ltd., a silicon-based surface conditioner liquid containing about 1% of active ingredient,
Product name.

(Note 3) Swazol 1000 ... Petrochemical aromatic solvent, trade name, manufactured by Cosmo Oil Co., Ltd.

Base coat paint-2 In the base coat paint-1, the resin solution (b-1)
The same formulation as in Paint-1 was used except that the resin solution (B-2) was used in place of the above to obtain Base Paint-2.

Base coat paint-3 In the base coat paint-1, the resin solution (b-1)
A base coat paint-3 was obtained in the same manner as in paint-1, except that the above was not used.

[0075]

[Production Example 4] Styrene 100 parts n-butyl acrylate 450 parts 2-ethylhexyl methacrylate 200 parts 2-hydroxyethyl methacrylate 150 parts γ-methacryloxypropyltrimethoxysilane 100 parts Azobisisobutyronitrile 40 parts 11 in the same amount of xylene as the mixture
The solution was added dropwise at 0 ° C. over 3 hours and aged at the same temperature for 2 hours to obtain a polymer solution. The number average molecular weight of the obtained transparent polymer by GPC was 6000.

[0076]

[Production Example 5] A mixture of styrene 150 parts n-butyl methacrylate 500 parts 1,4-butanediol monoacrylate 200 parts γ-methacryloxypropyltrimethoxysilane 150 parts azobisisobutyronitrile 40 parts, In a mixed solvent of 500 parts of xylene and 500 parts of n-butanol, the solution was added dropwise at 120 ° C. for 3 hours and aged for 2 hours at the same temperature to obtain a polymer solution. The number average molecular weight of the obtained transparent polymer was 6000.

Clear Top Coat Coating Composition Clear Top Coat Coating-1 Production Example 4 Solution (solid content 50%) 140 parts Cymel 303 (Note 4) 30 parts Nacure 5225 (Note 5) 1.5 parts Surface conditioner 0.1 part (manufactured by Big Chem Co., BYK-300 solution, having the same meaning below) UV absorber 1.0 part (Tinubin 900, manufactured by Ciba-Geigy, having similar meanings below) Swallow the above mixture It was diluted with # 1000 and the viscosity (Ford cup # 4, 20 ° C.) was adjusted to 25 seconds.

(Note 4) Cymel 303: full-methoxylated melamine resin manufactured by Mitsui Cyanamide Co., Ltd. (Note 5) Nacure 5225: KING INDUS
TRIES, dimethyloxazolidine neutralized product of dodecylbenzene sulfonic acid clear topcoat paint-2 Production Example 5 solution (solid content 50%) 160 parts Cymel 303 20 parts Nacure 5225 2 parts Surface conditioner 0.1 part UV absorption Agent 1.0 part Coating composition for clear top coat-1 using the above mixture
Adjusted as in.

Clear Top Coat Paint-3 Production Example 5 Solution (solid content 50%) 140 parts 60% Uban 20SE 50 parts Dibutyltin dilaurate 0.5 part Surface conditioner 0.1 part UV absorber 1.0 part Above Clear topcoat paint using the mixture of -1
Adjusted as in.

[0080]

Examples 1 to 6 and Comparative Examples 1 to 3 Preparation of Coated Plate A dull steel plate (chemical conversion treatment) was coated with an epoxy resin-based cationic electrodeposition coating (25 μm) and cured by heating at 170 ° C. for 30 minutes, and then as an intermediate coating. Lugabak AM (trade name, manufactured by Kansai Paint Co., Ltd., polyester resin / melamine resin-based automotive paint) was applied to a dry film thickness of 30 μm and baked at 140 ° C. for 30 minutes. Next, the coated surface was water-polished with # 400 sandpaper, drained and dried, and the coated surface was wiped with petroleum benzine as a material.

After the paint for coloring base coat was applied by air spray coating, the paint for clear top coat was applied immediately after standing for 3 minutes. The film thickness is a dry film thickness of 15 to 2 each.
It was set to 0 μm and 35 to 45 μm. Then, it was left at room temperature for 10 minutes and baked at 140 ° C. for 30 minutes. However, in the recoatability test, the first baking was performed at 160 ° C. for 30 minutes, and the second baking was performed at 120 ° C. for 30 minutes. The coating film performance and appearance are shown in Table 1.

[0082]

[Table 1]

Test method (* 1) Appearance: The coating film was examined for cracks and spots. ◎ No abnormality, ○ Slightly recognized, × Many recognized.

(* 2) Image clarity: image clarity measuring device (IMAGE CL
It was measured with ARITY METER, manufactured by Suga Test Instruments Co., Ltd. The numbers in the table are ICM values in the range of 0 to 100%. The larger the number, the better the sharpness (image clarity), and the ICM value is 7.
If it is 5 or more, the image clarity is extremely excellent.

(* 3) Metallic feeling: The metallic feeling and whiteness viewed from the front were visually evaluated. ◎ There is a feeling of gleaming, white thing, △ There is no feeling of gleaming, and it is inferior in whiteness,
× There is no glitter and no whiteness.

(* 4) Water resistance: The sample coated plate was immersed in warm water of 40 ° C. for 240 hours, and the blistering state of the coated surface was visually evaluated. ◎ No abnormality, △ Slightly observed, × markedly observed.

(* 5) Recoatability: The same base paint and clear paint as those in Examples and Comparative Examples were applied on the surface of the coating film and baked at 120 ° C. for 30 minutes to obtain a coating film. Cross-cut the obtained coating film with a cutter knife and stick cellophane tape on the coated surface, and peel it off rapidly, and the adhesion between the first and second coating films (clear coating / base coating) Was evaluated. ◎ No peeling was observed, △ Slight peeling was observed, × Marked peeling was observed.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location B05D 7/24 B 8616-4D C09D 5/38 PRF 7211-4J 161/20 PHK 8215-4J 167 / 00 PLB 8933-4J 183/06 PMS 8319-4J

Claims (1)

[Claims] 1. A coating composition for forming a colored base coat in a topcoat coating method in which a colored base coat and a clear top coat are sequentially formed on a material and finished by a two-coat one-bake system, (1) Hydroxyl group-containing polyester resin (2) Amino resin (3) Polyorganosiloxane having an average number of two or more silanol groups and / or alkoxysilane groups in one molecule and a number average molecular weight of 1,000 or more (4) Metal flake powder and / or mica powder, and (5) Organic As a coating composition for forming a clear top coat, a coating composition containing a solvent as an essential component is used. (1) At least one group selected from a silanol group and a hydrolyzable group directly bonded to a silicon atom, and a hydroxyl group. Containing as an essential functional group, (2) amino resin, and (3) A coating film-forming method which comprises using a coating composition containing a solvent as an essential component.