JPH0724412A - Formation of double layered coated film - Google Patents

Abstract

PURPOSE:To provide a method for forming a double layered coated film improved in particularly curing characteristics, acid resistance, scratch resistance, finished appearance or the like of a clear coated film and furthermore adhesion between both coated films, storage stability of a clear coating material itself in the method for forming the double layered coated film composed of a colored coated film and the clear coated film. CONSTITUTION:The method for forming a double layered coated film adopts a two coat one bake process by applying a water-based color coating material, next, applying an organic solvent based clear coating material composed mainly of an acrylic resin, containing alkoxysilane group and hydroxide group, and an amino resin on the coated surface and simultaneously curing both coated films by heating, and a catalyst for hydrolyzing alkoxysilane group is added into the water-based color coating material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a multilayer coating film comprising a colored coating film and a clear coating film, and in particular, the clear coating film has improved curability, acid resistance, scratch resistance and finished appearance. Further, the present invention relates to a method for forming a multilayer coating film in which the adhesion between the coating films and the storage stability of the clear coating itself are improved.

[0002]

2. Description of the Related Art An aqueous solvent-based paint is applied, and an organic solvent-based clear paint that forms a transparent paint film is applied on the coated surface without curing, and then both paints are cured by heating. A method of forming a multilayer coating film by a two-coat one-bake method is already known (for example, Japanese Patent Laid-Open No. 4-103).
680). As the organic solvent-based clear paint in such a system, paints containing acrylic resin, melamine resin, acid catalyst and the like as main components are often used.

However, the multi-layer coating film formed by such a method has a defect that it is easily deteriorated by acid rain, which has become a social problem recently, and the finished appearance and scratch resistance are not sufficient.

[0004]

The present invention provides the above-mentioned 2 coat 1
An object of the invention is to eliminate the above-mentioned defects in the method for forming a multilayer coating film by a baking method, which is characterized in that an organic resin mainly containing an acrylic resin containing an alkoxysilane group and a hydroxyl group and an amino resin as a clear coating material. A solvent-based clear paint is used, and a catalyst for hydrolysis of the alkoxysilane group is added to the water-based colored paint.

That is, according to the present invention, an aqueous colored coating material is applied, and then an organic solvent-based clear coating material containing an acrylic resin having an alkoxysilane group and a hydroxyl group and an amino resin as a main component is applied to the coated surface. A method for forming a multilayer coating film by a two-coat one-bake system in which both coating films are simultaneously cured by heating, wherein the water-based coating composition contains a catalyst for hydrolysis of the alkoxysilane group. And a method for forming a multilayer coating film.

First, the water-based colored paint and clear paint used in the present invention will be described. The water-based coloring paint,
A paint which is applied to the surface to be coated prior to the above clear paint, which comprises a resin composition, a coloring pigment and water as main components, and further contains a catalyst for hydrolysis of an alkoxysilane group.

The resin composition in the water-based coloring paint contains a base resin and a cross-linking agent as main components and is a coloring film forming component. The base resin in the resin composition has a functional group (for example, a hydroxyl group) capable of undergoing a cross-linking reaction with the cross-linking agent, and can be one known per se which is soluble or dispersible in water. Examples are shown in (a) to (e).

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

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

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

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

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

Aromatic vinyl monomers: for example, styrene, α-methylstyrene, vinyltoluene and the like.

Glycidyl group-containing vinyl monomer: One glycidyl group and one polymerizable unsaturated bond are contained in each molecule.
A compound having an individual, such as glycidyl acrylate or glycidyl methacrylate.

Nitrogen-containing alkyl (C1-20) acrylates such as dimethylaminoethyl acrylate,
Dimethylaminoethyl methacrylate, etc.

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

Vinyl compounds: For example, vinyl acetate, vinyl propionate, vinyl chloride and the like.

Polymerizable unsaturated bond-containing nitrile compound: for example, acrylonitrile, methacrylonitrile and the like.

Diene compounds: For example, butadiene, isoprene and the like.

These other vinyl monomers (M-
3) can use 1 type (s) or 2 or more types.

The copolymerization reaction of the above vinyl monomer can be carried out by a known method. If the acid value is less than about 20, it is difficult to dissolve in water, and if it exceeds about 150, the coating performance is affected by residual carboxyl groups. May decrease.

The acrylic resin thus obtained is described in No. 1 below.
It can be rendered water-soluble by neutralizing with a secondary and / or secondary monoamine.

(B) Water-dispersible acrylic resin-1 Fine particle acrylic having an average particle diameter of 0.05 to 1.0 μ obtained by emulsion-polymerizing a vinyl monomer in the presence of a dispersion stabilizer such as a surfactant. It is a resin that is dispersed in water.

The vinyl monomer to be emulsion-polymerized is preferably one selected from the above-mentioned monomer (M-1), monomer (M-2) and monomer (M-3), and further has a polymerizable unsaturated bond of 1 if necessary. It is preferable to use a small amount of a multi-vinyl compound (M-4) having two or more molecules in the molecule, because an intra-particle crosslinked water-dispersible acrylic resin is obtained and the coating film performance is further improved.

Examples of the polyvinyl compound (M-4) include ethylene glycol diacrylate, ethylene glycol dimethacrylate, triethylene glycol diacrylate, tetraethylene glycol dimethacrylate, 1,6-hexanediol diacrylate and divinylbenzene. , Trimethylolpropane triacrylate and the like, and it is preferable that the reactivity of two or more unsaturated bonds contained in each compound is not significantly different, and the diene compound is not included here.

The water-dispersible acrylic resin produced here is also preferably neutralized with a primary and / or secondary monoamine described below.

(C) Water-dispersible acrylic resin-2 This is an aqueous dispersion in which fine acrylic resin particles dispersed in water are stabilized by a stabilizer polymer.
This is a core / shell type emulsion in which the particles are the core part and the stabilizer polymer is the shell part.

Specifically, a vinyl monomer component containing no or almost no carboxyl group-containing vinyl monomer (M-1) is emulsion polymerized first, and then a large amount of the carboxyl group-containing vinyl monomer (M-1) is contained. It is obtained by emulsion polymerization with the addition of a vinyl monomer component, which is preferable from the viewpoint of coating workability because it thickens by neutralizing with a primary and / or secondary monoamine described below. is there.

(D) Water-dispersible acrylic resin-3 The polymer particles (core portion) are crosslinked, and there is a polymer (shell portion) for stabilizing the polymer particles, and the core portion and the shell portion are chemically It is a core / shell type emulsion formed by binding.

The method for connecting the core part and the shell part is, in particular, to have a hydrolyzable functional group and / or a silanol group on the surface of the core part, and then to introduce a polymerizable unsaturated bond into these groups, and A product obtained by copolymerizing a vinyl monomer component containing a carboxyl group-containing vinyl monomer (M-1) in an unsaturated bond (forming a shell portion) and then neutralizing the carboxyl group of the shell portion is preferable. .

Since this product is thixotropic (thixotropic), the coating film hardly sags even under high humidity. No abnormalities are observed even if an organic solvent is added,
It has features such as excellent smoothness, gloss, water resistance and adhesion.

This core / shell type emulsion is obtained by the following steps (I) to (III).

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

(II): The fine particle polymer in the emulsion is reacted with a silane monomer (M-5) and / or an allyl (meth) acrylate (M-7).

In (II), the silane-based monomer (M-
It is considered that 5) undergoes a condensation reaction with a functional group on the surface of the fine particle polymer, and that allyl (meth) acrylate (M-7) copolymerizes with the unreacted polymerizable unsaturated bond remaining in the fine particle polymer. By any of these methods, a polymerizable unsaturated bond can be introduced on the surface of the fine particle polymer.

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

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

In this general formula, the hydrolyzable functional group for R ₁ is, for example, an alkoxy group having 1 to 12 carbon atoms, an alkoxyalkoxy group having 3 to 15 carbon atoms, or 1 to 1 carbon atoms.
12 alkanoyloxy groups and the like can be represented by X as, for example,
CH ₂ = CH- and

[Chemical 1] And the like, R ₂ is H or CH ₃ —, and n is 2
It is an integer of -10.

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

As the hydroxyl group-containing vinyl monomer (M-2) in the step (I), those described above can be used, and the "other vinyl monomer (M-6)" is the above monomer (M-
1) to (M-5) from which (M-5) and (M-2) have been removed.

The silane-based monomer (M
-5), a hydroxyl group-containing vinyl monomer (M-2) and a vinyl monomer (M-6) other than this are copolymerized in an aqueous medium to obtain a fine particle polymer obtained by three-dimensionally crosslinking reaction, for example, The emulsion polymerization methods (i) to (iii) listed below, which are known per se, can be used.

(I) Copolymerization is carried out at a predetermined temperature while gradually dropping the mixture of the above-mentioned monomers into an aqueous medium with stirring in which water is mixed with a surfactant under an inert gas atmosphere.

(Ii) The mixture of the above monomers is emulsified in an aqueous medium in advance, and the mixture is copolymerized at a predetermined temperature while gradually dropping into water under stirring.

(Iii) In any of the above, a small amount of a monomer (a mixture or a single monomer may be used) is preliminarily subjected to seed polymerization, and then emulsion polymerization is carried out according to the above methods (i) and (ii). You may.

Of these, (iii) can reduce the particle size,
It is preferable from the viewpoint of improving sag resistance, smoothness and the like.
All of these emulsion polymerizations are preferably carried out in the presence of a radical polymerization initiator.

Here, the constituent ratios of various monomers used in the steps (I) and (III) will be described. The composition ratio of the total monomer of step (I) and the total monomer of step (III) is 30 to 95% by weight, particularly 60 to 90% by weight, based on the total weight of both monomers. However, the total amount of the monomers in step (III) is 70 to 5% by weight, especially 40 to 10%.
Weight percentages are preferred in each case.

All the monomers in step (I) are silane-based monomers (M-5) and hydroxyl group-containing vinyl monomers (M-).
2) and a vinyl monomer (M-6) other than this, based on the total weight of these monomers, the silane-based monomer (M-5) is 0.5 to 20% by weight, especially 1
10 to 10% by weight, hydroxyl group-containing vinyl monomer (M-2) is 1 to 30% by weight, particularly 2 to 20% by weight, and other vinyl monomer (M-6) is 98.5 to 50% by weight, especially 9
It is preferably 7 to 70% by weight.

Further, all the monomers in the step (III) are composed of a vinyl monomer component (M-8) containing a carboxyl group-containing vinyl monomer (M-1), and the monomer (M-
1) is preferably 1 to 50% by weight, more preferably 3 to 30% by weight in the monomer component (M-8). Monomer component (M-8)
Are exemplified as the hydroxyl group-containing vinyl monomer (M-2) and the monomer (M-3) in the monomer (M-1).
One or more kinds selected from the above monomers are used in combination. Among them, the content of the monomer (M-2) is 30% by weight or less, particularly 1 to 25% by weight in the monomer component (M-8).
Is preferred.

Further, the monomer component (M-8) may be used in combination with a silane-based monomer (M-5) or a polyvinyl compound (M-4), and the amount thereof used is the monomer component (M-).
10% by weight or less is suitable for 8).

The fine particle polymer of the emulsion obtained by the step (I) is mainly composed of both a carbon-carbon bond due to a polymerizable unsaturated bond and a -Si-O-Si- bond due to a silane monomer (M-5). It is presumed that the three-dimensional crosslinking reaction occurs. It is considered that the surface of this fine particle polymer has a hydrolyzable functional group and / or silanol group based on the silane monomer (M-5) bonded in an unreacted state. Furthermore, hydroxyl groups based on the monomer (M-2) are also present on the surface.
The particle size of the fine particle polymer obtained in the step (I) varies depending on the kind and amount of the surfactant and the like and the polymerization method.
.About.500 nm, particularly 30 to 300 nm is preferred.

The step (II) is for introducing a polymerizable unsaturated bond into the surface of the particulate polymer. The fine particle polymer into which the polymerizable unsaturated bond is introduced obtained in the step (II) is abbreviated as "unsaturated fine particle polymer" hereinafter.

The ratio of the fine particle polymer to the silane monomer (M-5) in step (II) is not particularly limited, but the silane-based monomer (M-5) 1 used in step (I) is used.
The silane-based monomer used in the step (II) (M-
The range of 5) is preferably 0.5 to 2 mol (usually 50 to 200 parts by weight per 100 parts by weight of the former).

Monomer (M-5) and Monomer (M-7)
It is preferable to use in combination with, and the above-mentioned constitution ratios can be applied to the composition ratios of these fine particle polymers.

The step (III) is a vinyl monomer component (M containing the vinyl monomer (M-1) having a carboxyl group in the unsaturated fine particle polymer obtained in the step (II).
-8) is copolymerized, and then the carboxyl group is neutralized to form a shell part.

In this step, a vinyl monomer component (M-) is added to the unsaturated fine particle polymer (corresponding to the core portion) of the step (II).
It is mainly for chemically bonding the linear copolymerized polymer (corresponding to the shell portion) according to 8).

In step (III), a vinyl monomer component is copolymerized with the unsaturated fine particle polymer to form a shell portion,
Furthermore, neutralizing the carboxyl group in the shell part is also included. As the neutralizing agent, it is preferable to use a primary or secondary amine described below.

(E) Urethane Resin Emulsion This comprises (a) an aliphatic and / or alicyclic polyisocyanate, (b) a polymeric polyol, (c) an α, α-dimethylol monocarboxylic acid, and, if necessary, (D) A polyurethane resin aqueous dispersion obtained by reacting a chain extender and / or a polymerization terminator, and then neutralizing a carboxyl group with (e) a primary and / or secondary monoamine.

The (a) aliphatic and / or alicyclic polyisocyanate is a compound having two or more isocyanate groups and an aliphatic carbon group or an alicyclic carbon group in one molecule. Specifically, an aliphatic diisocyanate having 2 to 12 carbon atoms such as hexamethylene diisocyanate (HD
I), 2,2,4-trimethylhexane diisocyanate, lysine diisocyanate and the like; alicyclic diisocyanates having 4 to 18 carbon atoms, such as 1,4-cyclohexane diisocyanate (CDI), isophorone diisocyanate (IPDI), 4,4'- Dicyclohexylmethane diisocyanate (hydrogenated MDI), methylcyclohexane diisocyanate, isopropylidene dicyclohexyl-4,4'-diisocyanate, 1,3-diisocyanatomethylcyclohexane (hydrogenated XDI), etc .; Aliphatic diisocyanates having aromatic rings, such as xylyl Diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI) and the like; modified products of these diisocyanates (carbodiimide, uretdione, uretoimine, burette) And / or isocyanurate modified products); and mixtures of two or more thereof. Preferred among these are HDI, IPDI, hydrogenated MD
I and TMXDI.

The use of an aromatic polyisocyanate as the component (a) is not preferable because the coating film tends to turn yellow during baking and curing, and the coating film tends to change color under the influence of ultraviolet rays.

(B) Polymer polyols include polyether polyols such as alkylene oxides (ethylene oxide, propylene oxide, butylene oxide, etc.)
And / or heterocyclic ether (tetrahydrofuran etc.)
Obtained by polymerizing or copolymerizing, for example, polyethylene glycol, polypropylene glycol, polyethylene-polypropylene (block or random) glycol, polyethylene-tetramethylene glycol (block or random), polytetramethylene ether glycol, polyhexamethylene ether glycol Etc .; polyester polyols such as aliphatic dicarboxylic acids (succinic acid, adipic acid, sebacic acid, glutaric acid, azelaic acid, etc.) and / or aromatic dicarboxylic acids (isophthalic acid, terephthalic acid, etc.) and low-molecular glycols (ethylene glycol, Propylene glycol, 1,4-butanediol, 1,6-hexanediol, 3-methyl-1,5
-Pentanediol, neopentyl glycol, 1,4
-Dihydroxymethylcyclohexane etc.) such as polyethylene adipate diol, polybutylene adipate diol, polyhexamethylene adipate diol, polyneopentyl adipate diol, polyethylene / butylene adipate diol, poly-3-methylpentane adipate diol , Polybutylene isophthalate diol, etc .; polylactone polyols, such as polycaprolactone diol or triol, poly-3-methylvalerolactone diol, etc .; polycarbonate diols, such as polyhexamethylene carbonate diol; polyolefin polyols, such as polybutadiene glycol or hydrides thereof. And a mixture of two or more thereof. Among these polymeric polyols, preferred are polyester polyols, polylactone polyols, polycarbonate polyols and mixtures thereof, or mixtures of these with polyether polyols. The molecular weight of the polymer polyol is usually 500 to 5,000, preferably 1,000 to
It is 3,000.

(C) α, α-Dimethylolmonocarboxylic acid is a component used for introducing an anionic hydrophilic group for stably dispersing a polyurethane resin in water, and specific examples include α, α-dimethylol acetic acid, α,
Examples thereof include α-dimethylolpropionic acid and α, α-dimethylolbutyric acid, and the preferable one is α, α-dimethylolpropionic acid. The amount of α, α-dimethylolmonocarboxylic acid is 0.3 to 0.3 in the urethane resin formed by reacting (a) to (c) as a carboxyl group (—COOH).
5% by weight, preferably 0.5 to 3% by weight is desirable.
If it is less than 0.3% by weight, it is difficult to obtain a stable emulsion,
When it exceeds 5% by weight, the hydrophilicity of the polymer becomes high,
The emulsion may have a high viscosity and the water resistance of the coating film may decrease.

In producing the component (e), a chain extender and / or a polymerization terminator (d) may be used if necessary. Chain extenders include low molecular weight polyols and polyamines. Examples of the low molecular weight polyol include glycols and their alkylene oxide low molar adducts (molecular weight 50
Low molecular weight addition product of alkylene oxide of bisphenol (molecular weight less than 500); trihydric alcohol such as glycerin, trimethylolethane, trimethylolpropane and its low molecular weight addition product of alkylene oxide (molecular weight less than 500); Mixtures of two or more may be mentioned. Examples of the polyamine include aliphatic polyamines such as ethylenediamine, N-hydroxyethylethylenediamine, tetramethylenediamine, hexamethylenediamine, diethylenetriamine and the like; alicyclic polyamines,
For example, 4,4'-diaminodicyclohexylmethane,
1,4-diaminocyclohexane, isophoronediamine, etc .; aliphatic polyamines having an aromatic ring, such as xylylenediamine, tetramethylxylylenediamine, etc .; aromatic polyamines, such as 4,4'-diaminodiphenylmethane, tolylenediamine, benzidine, Phenylenediamine and the like; and mixtures of two or more thereof.
The amount of the chain extender is usually 0.3 to 30% by weight, preferably 0.5 to 20% by weight, based on the polymer polyol (b).

As the polymerization terminator, low molecular weight monoalcohols (methanol, butanol, cyclohexanol, etc.), monovalent alkylamines (mono- and di-ethylamine, mono- and di-butylamine, etc.), alkanolamines (mono-) are used. And di-ethanolamine etc.) and the like.

Used to neutralize carboxyl groups (e)
As primary and secondary monoamines, ammonia; lower alkyl amines such as methylamine, ethylamine, isopropylamine, n-butylamine, dimethylamine, diethylamine, diisopropylamine, di-
alicyclic amines such as cyclohexylamine; heterocyclic amines such as morpholine and pyridine; alkanolamines such as monoethanolamine, diethanolamine, monoisopropanolamine, diisopropanolamine, methylethanolamine and methylisopropanol. Amines and the like; or a mixture of two or more thereof. Of these, preferred are secondary alkanolamines. The amount of monoamine used is usually 0.5 per 1.0 equivalent of carboxyl group.
~ 1.5 equivalents, preferably 0.7-1.3 equivalents.

The equivalent ratio of the component (a) to the components (b), (c) and (d) in the polyurethane reaction is usually 0.7.
Is about 1.3, preferably 0.8 to 1.2.

The urethane resin type emulsion (e) is prepared in the presence or absence of an organic solvent as described in the above (a), (b),
(C) If necessary, (d) is reacted by a one-shot method or a multi-step method to form a carboxyl group-containing polyurethane resin, and after or neutralized in (e), mixed with water to form a dispersion. It is an aqueous dispersion of a self-emulsifying polyurethane resin having an average particle diameter of about 0.001 to 1.0 μm, which is prepared by distilling off a solvent if necessary. The polyurethane-forming reaction is usually carried out at a temperature of 20 to 150 ° C., preferably 50 to 120 ° C. (however, in the case of reacting an amine, it is usually carried out at a temperature of 80 ° C. or lower, preferably 0 to 70 ° C.). In order to accelerate the reaction, an amine-based catalyst or a tin-based catalyst that is commonly used in urethanization reaction may be used. When a solvent is used, it is particularly preferably water-soluble and has a boiling point not higher than that of water.

The (e) primary and secondary monoamines are also useful as a neutralizing agent for the resins (a) to (d) for water-based paints.

As the base resin in the resin composition of the water-based colored coating composition, one or more selected from the above (a) to (e) can be used, and particularly selected from (a) to (d). It is preferable to use one or more kinds in combination with (e). The ratio when using both of these is (a)-
Based on the total amount of at least one selected from (d) and (e), the former is 90 to 5% by weight, particularly 80 to 15% by weight, the latter is 10 to 95% by weight, and particularly 20 to 85% by weight. % Is suitable.

The cross-linking agent in the resin composition is for reacting with the base resin to cross-link and cure, and a melamine resin for coating and a phenol-formaldehyde resin are suitable. These may be water-soluble or hydrophobic, but it is preferable to use hydrophobic ones in order to improve coating workability, storage stability, moisture resistance and the like.

For example, the hydrophobic melamine resin has a solvent dilution rate of 20 or less, preferably 15 or less and a weight average molecular weight of 800 to 4,000, preferably 1,000 to 3,000. Things are suitable. The solvent dilution rate is an index showing the solubility of the melamine resin in a hydrophilic solvent, and the lower this is, the more hydrophobic it is.
The measuring method is 2g of melamine resin in a 50cc beaker.
And put it on the paper on which the No. 5 type was printed, and then at 25 ℃
At this time, a mixed solvent of water / methanol (weight ratio 35/65) is added dropwise, and the mixture is added with stirring until the characters cannot be read. The drop amount (cc) at this time is divided by the amount of the melamine resin collected and displayed as a value (cc / g).

The melamine resin is not particularly limited as long as the solvent dilution ratio and the molecular weight are satisfied, and various etherification products such as methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butyl alcohol and isobutyl alcohol are used. , Octyl alcohol, 2-ethylhexyl alcohol, benzyl alcohol and the like, which have been modified with one kind or two or more kinds can be used. Those modified with a C ₄ or higher alcohol, more preferably a C _{4 to} C ₇ alcohol, are preferred in the present invention. The amount of ether groups in the melamine resin is not particularly limited, but is appropriately about 5 mol or less, preferably about 1.5 to 3 mol, per one nucleus of the triazine ring. Further, regarding the functional group represented by amino group, imino group, and methylol group, if the solvent dilution rate and the molecular weight are satisfied, the type and amount of the residual functional group are not particularly limited, but preferably the normal imino group ( Amino group is included) and methylol group are each 0.2 to 2.0 mol, more preferably 0.5 to 1.
It is in the range of 5 mol.

The hydrophobic cross-linking agent is preferably mixed with a water-soluble resin in advance before being mixed with the base resin.

The water-soluble resin has a hydrophilic group such as a carboxyl group (--COOH), a hydroxyl group (--OH), a methylol group (--CH ₂ OH), an amino group (--NH ₂ ), a sulfone group (--SO ₃ H). , Polyoxyethylene bond

[Chemical 2] And the like (for example, acrylic resin, alkyd resin, epoxy resin, etc.), of which the most common one is a carboxyl group introduced and neutralized to make it water soluble as an alkali salt.

The mixing ratio of the hydrophobic crosslinking agent and the water-soluble resin is usually in the range of about 20 to 100 parts by weight, preferably about 28 to 80 parts by weight, based on 100 parts by weight of the solid content of the latter. Is appropriate. The mixing method of both is
Although it can be carried out arbitrarily, for example, both components may be mixed and homogenized by a Teisper, a homomixer, a ball mill, a sand mill or the like, and at this time, a coloring pigment, an extender pigment or the like may be kneaded in if necessary. At this time, if necessary, a small amount of a hydrophilic solvent such as an alcohol solvent or an ether solvent can be added. Next, while stirring this strongly, the amount of the hydrophobic melamine resin and the water-soluble resin is 0.5 to
By gradually adding about 5 times the weight of deionized water,
A cross-linking agent is obtained, which is an aqueous dispersion of milk-white or colored hydrophobic melamine resin particles whose surface is coated with a water-soluble resin. The average particle size of the aqueous dispersion without the pigment is in the range of about 0.05 to 0.5 μ.

The constituent ratio of the base resin and the cross-linking agent in the water-based coloring paint can be arbitrarily selected according to the purpose, but the base resin is 50 to 95% by weight based on the total amount of both components.
Particularly suitable is 60 to 85% by weight, and 50 to 5% by weight, particularly 40 to 15% by weight, is suitable for the cross-linking agent.

The color pigments used in the aqueous color paint of the present invention also include metallic pigments, and examples of the metallic pigments include aluminum flakes, copper bronze flakes, mica-like iron oxide, mica flakes, and mica coated with metal oxides. Iron oxide, mica flakes coated with metal oxides, and the like, and examples of the coloring pigment include titanium dioxide, iron oxide, chromium oxide, lead chromate, inorganic pigments such as carbon black, phthalocyanine blue, Organic pigments such as phthalocyanine green, carbazole violet, anthrapyrimidine yellow, flavanthrone yellow, isoindoline yellow, indanthrone blue, quinacridone violet and the like can be mentioned.

Further, the water-based coloring paint used in the present invention includes
It is necessary to add a catalyst for hydrolysis of alkoxysilane groups.

Examples of such catalysts include organic sulfonic acids such as p-toluenesulfonic acid and dodecylbenzenesulfonic acid; trichloroacetic acid; phosphoric acid; mono-n-propylphosphoric acid, monoisopropylphosphoric acid, mono-n-butylphosphoric acid, mono-n-butylphosphoric acid, and mono-n-butylphosphoric acid. Monoalkyl phosphoric acid such as isobutyl phosphoric acid, mono-tert-butyl phosphoric acid, monooctyl phosphoric acid, monodecyl phosphoric acid; di-n-propyl phosphoric acid, diisopropyl phosphoric acid, di-
Dialkyl phosphoric acid such as n-butyl phosphoric acid, diisobutyl phosphoric acid, di-tert-butyl phosphoric acid, dioctyl phosphoric acid, didecyl phosphoric acid; phosphoric acid ester of β-hydroxyethyl (meth) acrylate; mono-n-propyl phosphorous acid, monoisopropyl phosphorous acid, Mono-alkyl phosphites such as mono-n-butyl phosphite, monoisobutyl phosphite, mono-tert-butyl phosphite, monooctyl phosphite and monodecyl phosphite; di-n
Acid compounds such as -propyl phosphite, diisopropyl phosphite, di-n-butyl phosphite, diisobutyl phosphite, di-tert-butyl phosphite, dioctyl phosphite and didecyl phosphite; acidic compounds such as tetraisopropyl titanate , Titanium-containing compounds such as 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.

The water-based colored coating material used in the present invention is a coating material containing the above resin composition, color pigment, hydrolysis catalyst and water as main components. Of these, the amount of the hydrolysis catalyst to be blended is 0. 0 per 100 parts by weight of the solid content of the resin composition.
1 to 10 parts by weight, particularly 0.5 to 3 parts by weight are preferred.

If necessary, an ultraviolet absorber, a surface conditioner or the like can be added to the aqueous colored coating composition.

The organic solvent-based clear coating material used in the present invention is applied on the uncured coating surface of the above-mentioned aqueous colored coating material coating film, and comprises an acrylic resin (A) having an alkoxysilane group and a hydroxyl group and an amino resin ( B) is an organic solvent-based paint containing as a main component, or a colored transparent coating film is formed.

The acrylic resin (A) having an alkoxysilane group and a hydroxyl group in the clear paint is

General formula

[Chemical 3]

[Wherein A is

[Chemical 4] , R ₁ is a hydrogen atom or a methyl group, and R ₂ is a carbon atom of 1 to
6 is a divalent saturated aliphatic hydrocarbon group, R ₃ and R ₄ are the same or different phenyl groups, C 1-6 alkyl groups or C 1-10 alkoxy groups, and R ₅ is An alkyl group having 1 to 10 carbon atoms is shown. n is 1 to 1
Indicates an integer of 00. ]

The alkoxysilane group-containing vinyl monomer (A-1) which is a compound represented by 5 to 40% by weight, the hydroxyl group-containing vinyl monomer (A-2) to 5 to 50% by weight, and other 10 vinyl copolymerizable monomers (A-3)
It is obtained by polymerizing a monomer component consisting of ˜90% by weight.

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

In the general formula (I), the divalent aliphatic saturated hydrocarbon group having 1 to 6 carbon atoms represented by R _{2 is represented} by a linear or branched alkylene group, R ₃ and R _4. Examples of the alkyl group having 1 to 6 carbon atoms include a linear or branched alkyl group, and examples of the alkyl group having 1 to 10 carbon atoms represented by R ₅ include R ₃ and R ₄ . Further, n-heptyl, 1-methylpentyl, 2-methylhexyl, n-octyl, n-nonyl, n-decyl and the like can be mentioned. 1 to ₃ carbon atoms represented by R ₃ and R ₄
As the alkoxy group of 10, a linear or branched alkoxy group 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 R ₄ may be the same or different.

In the compound (A-1) of the above general formula (I), A is

[Chemical 5] Are, for example, γ- (meth) acryloxyethyltrimethoxysilane, γ- (meth) acryloxypropyltrimethoxysilane, γ- (meth) acryloxypropyltriethoxysilane, γ- (meth) acryloxy. Propyltripropoxysilane, 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,

[Chemical 6]

The following may be mentioned.

In the compound (A-1) of the general formula (I), A is

[Chemical 7] Is, for example,

[0091]

[Chemical 8] Etc. can be mentioned.

These compounds of the general formula (I) (A-1)
Of these, especially acryloxypropyltrimethoxysilane, methacryloxypropyltriethoxysilane, methacryloxypropyltri-n-butoxysilane, acryloxypropylmethyldimethoxysilane, methacryloxypropylmethyldimethoxysilane, methacryloxypropylmethyldi-n. -Butoxysilane and the like are preferred.

In the preparation of the acrylic resin (A),
Hydroxyl group-containing vinyl monomer (A
-2) is a compound having a hydroxyl group and a polymerizable double bond in one molecule, such as 2-hydroxyethyl acrylate, 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 "(all manufactured by Daicel Chemical Industries, Ltd., trade name, 2-hydroxyethyl caprolactone-modified (meth) acrylic acid), and the like, but are not limited to these.

The vinyl monomer (A-3) copolymerizable with the above-mentioned vinyl monomer (A-1) containing an alkoxysilane group and vinyl monomer (A-2) containing a hydroxyl group is used in one molecule. A compound having a polymerizable double bond and containing no alkoxysilane group or hydroxyl group, for example, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, acrylic acid. Butyl, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, lauryl acrylate, lauryl methacrylate, stearyl acrylate, stearyl methacrylate, etc. Acrylic acid or methacrylic acid and monohydric alcohol having 1 to 22 carbon atoms Esters with; acrylic acid, methacrylic acid, maleic anhydride, etc. Carboxyl group-containing vinyl monomer,
Glycidyl group-containing vinyl monomers such as glycidyl acrylate and glycidyl methacrylate; amide vinyl monomers such as acrylamide, methacrylamide, N-methylol acrylamide, and N-methylol methacrylamide; dimethylaminoethyl methacrylate, 2-diethylaminoethyl methacrylate, methacrylic acid Amine-based vinyl monomers such as tert-butylaminoethyl; other vinyl monomers such as styrene, vinyltoluene, acrylonitrile, methacrylonitrile, α-methylstyrene, vinyl acetate; etc. 1 polymerizable unsaturation per molecule The compound which has a bond is mentioned.

The constituent ratio of the above monomers (A-1) to (A-3) for preparing the acrylic resin (A) is (A-
1), based on the total amount of (A-2) and (A-3), for example, an alkoxysilane group-containing vinyl monomer (A
-1) is 5 to 40% by weight, preferably 5 to 30% by weight,
The hydroxyl group-containing vinyl monomer (A-2) is 5 to 50% by weight, preferably 10 to 40% by weight. The other monomer (A-3) is the rest of the above.

The above vinyl monomers (A-1) and (A-2)
The copolymerization reaction of (A-3) and (A-3) can be carried out in the same manner as a usual method for synthesizing an acrylic resin, a vinyl resin or the like. For example, the both components are dissolved or dispersed in an organic solvent, and a radical polymerization initiator In the presence of 60-1
It can be carried out by heating with stirring at a temperature of about 80 ° C. The reaction time may be usually about 1 to 10 hours.

As the radical initiator, any of those usually used can be used, and examples thereof include benzoyl peroxide, peroxides such as tert-butylperoxy-2-ethylhexanoate, and azoisosulfate. Examples thereof include azo compounds such as butyronitrile and azobisdimethylvaleronitrile.

The number average molecular weight of the acrylic resin (A) is
Usually about 3,000 to 500,000, preferably 5,0
It is about 100 to 100,000.

Acrylic resin (A) in clear paint
Has an alkoxysilane group and a hydroxyl group bonded as a side chain in one molecule thereof. Therefore, as compared with the conventional acrylic resin having only a hydroxyl group as a crosslinkable functional group which is a base resin of amino resin curing system, the acrylic resin (A) is
-SiOSi-, which is a chemical bond that is difficult to undergo hydrolysis
When the acrylic resin (A) is used as a base resin of an amino resin curing system to form SiOR-crosslinking points, the cured coating film has extremely excellent surface properties (acid resistance, water repellency, (Abrasion resistance, water resistance, chemical resistance, weather resistance, heat resistance), and particularly excellent acid resistance.

In the clear coating composition, the acrylic resin (A) may be used in combination with another hydroxyl group-containing resin such as an acrylic polyol or polyester polyol and / or another alkoxysilane group-containing resin.

Amino resin (B) in the clear paint
Examples thereof include known 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, and 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, isopropyl alcohol, n-butyl alcohol and isobutyl. Alcohol, 2
-Ethylbutanol, 2-ethylhexanol and the like can be mentioned. Among these, it is particularly preferable to use hexamethoxymethylmelamine or an etherified melamine resin in which a part or all of the methoxy group thereof is substituted with an alcohol having C ₄ or more. In this case, it is preferable to add a usual curing catalyst such as paratoluenesulfonic acid or dodecylbenzenesulfonic acid.

As the melamine resin (B) in the clear paint, Cymel 303 (full methoxylated melamine resin, manufactured by Mitsui Cyanamide Co., Ltd.), Uban 20SE
An amino resin commercially available under the trade name such as -60 (butylated melamine resin, manufactured by Mitsui Toatsu Co., Ltd.) can be used.

The clear coating composition used in the present invention contains the above-mentioned components (A) and (B) as main components, and the blending ratio of the components can be arbitrarily selected according to the purpose.
And based on the total resin solid content of the component (B),
The component (A) is 50 to 95% by weight, preferably 55 to 90%.
Wt%, more preferably 60-80 wt%, (B)
5 to 50% by weight, preferably 10 to 45% by weight,
More preferably, about 20 to 40% by weight is suitable.

In the clear coating composition, in addition to the above-mentioned (A) acrylic resin and (B) amino resin which are the main components, a specific alkoxysilane group-containing polymer is used as a dispersion stabilizer resin to obtain a non-aqueous dispersion polymerization. The resulting non-aqueous polymer particles (C) can be further blended. By blending the component (C), it is possible to achieve low viscosity and high solidification of the clear coating, remarkably improve the coating workability, and further improve the acid resistance and impact resistance of the cured coating film. It turned out that the desired effect was obtained.

The non-aqueous polymer particles (C) are copolymers obtained by using the compound (A-1) represented by the general formula (I) and a hydroxyl group-containing unsaturated monomer as essential monomer components. Is a non-aqueous polymer particle insoluble in the organic liquid obtained by polymerizing a radically polymerizable unsaturated monomer in the organic liquid in the presence of the resin.

In the production of the non-aqueous polymer particles (C),
The copolymer used as the dispersion stabilizer resin is a copolymer obtained by using the vinyl monomer (A-1) and the hydroxyl group-containing unsaturated monomer as essential monomer components. The use ratio of these essential monomers can be selected from a wide range, but usually, the monomer (A-1) is about 1 to 99% by weight, preferably about 5 to 30% by weight, and a hydroxyl group-containing content in the used monomers. The unsaturated monomer is used in an amount of about 1 to 99% by weight, preferably about 3 to 30% by weight, based on the monomers used.

The hydroxyl group-containing unsaturated monomer used for preparing the dispersion stabilizer resin in the production of the non-aqueous polymer particles (C) is derived from (A-1) by enhancing the hydrophilicity of the dispersion stabilizer. It promotes hydrolysis of the alkoxysilane group and also acts as a functional group that reacts with the above-mentioned amino resin which is a curing agent for crosslinking reaction.

Preferred examples of the hydroxyl group-containing unsaturated monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate and hydroxybutyl (meth). ) C2-C8 hydroxyalkyl ester of (meth) acrylic acid such as acrylate;
Polyethylene glycol, polypropylene glycol,
Monoesters of polyether polyols such as polybutylene glycol and unsaturated carboxylic acids such as (meth) acrylic acid; monoethers of hydroxyalkyl esters of the above (meth) acrylic acid having 2 to 8 carbon atoms and the above polyether polyols. The number of carbon atoms of the (meth) acrylic acid is 2 to
Adduct of hydroxyalkyl ester of 8 with lactones such as ε-caprolactone and γ-valerolactone;
Α, β-Unsaturated carboxylic acids such as (meth) acrylic acid and "CARDURA E10" (trade name, manufactured by Shell Petrochemical Co., Ltd., composition of glycidyl ester of versatic acid)
And adducts with monoepoxy compounds such as α-olefin epoxides such as ethylene oxide, propylene oxide and butylene oxide; glycidyl (meth) acrylate and acetic acid, propionic acid, p-tert-butylbenzoic acid, lauric acid, stearic acid Adducts with monobasic acids such as fatty acids; unsaturated compounds containing an acid anhydride group such as maleic anhydride and itaconic anhydride, and glycols such as ethylene glycol, 1,6-hexanediol, neopentyl glycol And monoesters or diesters thereof; hydroxyalkyl vinyl ethers such as hydroxyethyl vinyl ether; and those containing chlorine such as 3-chloro-2-hydroxypropyl (meth) acrylate.

Further, in the preparation of the copolymer used as the dispersion stabilizer, another polymerizable monomer may be used if necessary. As such a monomer, a long-chain vinyl-based monomer is preferable from the viewpoint of copolymerizability, solubility in an organic liquid, and the like. Other polymerizable monomers that can be preferably used include, for example, (meth) acrylic acid having 4 carbon atoms.
~ 18 alkyl or cycloalkyl ester; alkoxyalkyl ester of (meth) acrylic acid; ester of aromatic alcohol such as benzyl (meth) acrylate with (meth) acrylic acid; glycidyl (meth) acrylate or (meth) acrylic acid Of hydroxyalkyl ester of carboxylic acid with monocarboxylic acid compounds such as capric acid, lauric acid, linoleic acid and oleic acid, (meth)
Addition products of acrylic acid and monoepoxy compounds such as “Curdra E10”; itaconic acid, itaconic anhydride, crotonic acid, maleic acid, maleic anhydride, fumaric acid, citraconic acid, and other α, other than (meth) acrylic acid, Mono- or diesters of β-unsaturated carboxylic acid and butyl alcohol, pentyl alcohol, heptyl alcohol, octyl alcohol, stearyl alcohol and the like having 4 to 18 carbon atoms; "biscoat 8F", "biscoat 8FM", "biscoat" 3F "," Viscoat 3FM "
(All are manufactured by Osaka Organic Chemical Co., Ltd., trade name, (meth) acrylates having a fluorine atom in the side chain), perfluorocyclohexyl (meth) acrylate, perfluorohexylethylene and other fluorine atom-containing compounds. You can

The copolymerization for producing the dispersion stabilizer resin used in the production of the non-aqueous polymer particles is usually carried out using a radical polymerization initiator, and the molecular weight thereof is usually about 5,000 in terms of weight average molecular weight. It is suitable to be in the range of about 100,000 to about 100,000 (about 1,000 to 60,000 in number average molecular weight), preferably about 5,000 to 50,000.

The dispersion stabilizer resin may be any other dispersion stabilizer such as butyl etherified melamine-formaldehyde resin,
It is also possible to use together with a small amount of an alkyd resin or a general acrylic resin which does not contain the compound of the general formula (I) as a copolymer component.

The component (C) is obtained by polymerizing a radically polymerizable unsaturated monomer in an organic liquid in the presence of the above dispersion stabilizer resin to prepare a non-aqueous dispersion liquid of polymer particles insoluble in the organic liquid. Obtained by preparing.

As the organic liquid used in the above polymerization,
Although the dispersion polymer particles produced by the polymerization are not substantially dissolved, an organic liquid that is a good solvent for the stabilizer resin and the radically polymerizable unsaturated monomer is included. Specific examples of such an 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 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 monomer include, for example, alkyl or cycloalkyl esters of (meth) acrylic acid having 1 to 18 carbon atoms; methoxybutyl (meth) acrylate, methoxyethyl (meth) acrylate, ethoxybutyl. Alkoxyalkyl esters of (meth) acrylic acid such as (meth) acrylate; Esters of aromatic alcohols such as benzyl (meth) acrylate with (meth) acrylic acid;
Addition product of glycidyl (meth) acrylate and monocarboxylic acid compound having 2 to 18 carbon atoms such as acetic acid, propionic acid, oleic acid, p-tert-butylbenzoic acid; (meth)
Addition products of acrylic acid and monoepoxy compounds such as "Curdra 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, and citraconic acid, and carbon number of methyl alcohol, butyl alcohol, hexyl alcohol, stearyl alcohol, etc. Monoesters or diesters with 1 to 18 monoalcohols; "Viscoat 8F", "Viscoat 8F"
"M", "Biscoat 3F", "Biscoat 3FM" (all manufactured by Osaka Organic Chemical Co., Ltd., trade name, (meth) acrylates having a fluorine atom in the side chain), perfluorocyclohexyl (meth) acrylate, perfluoro Fluorine atom-containing compounds such as hexyl ethylene; cyano group-containing unsaturated compounds such as (meth) acrylonitrile; vinyl acetates, vinyl benzoate, vinyl esters such as "VEOVA" (manufactured by Shell Co.); n -Vinyl ethers such as butyl vinyl ether, ethyl vinyl ether, and methyl vinyl ether; polyvinyl compounds such as di (meth) acrylate of 1,6-hexanediol, tri (meth) acrylate of trimethylolpropane, and divinylbenzene; ethylene, propylene, vinyl chloride. ,
Examples thereof include α-olefin compounds such as vinylidene chloride. As described above, the monomer component forming the polymer particles can stably form the particle component by combining those having a carbon number smaller than that of the monomer component of the dispersion stabilizer resin. However, from this viewpoint, particularly preferable ones are those having 8 or less carbon atoms and desirably 4 or less (meta).
Acrylic esters, vinyl aromatic compounds, (meth)
Acrylonitrile and the like.

These radically polymerizable unsaturated monomers are
They can be used alone or in an appropriate combination of two or more.

Polymerization of the above radically polymerizable unsaturated monomer is usually carried out using a radical polymerization initiator. The proportion of the dispersion stabilizer resin used during the polymerization can be selected from a wide range depending on the type of the resin, etc., but in general, the radical polymerizable unsaturated monomer is added to 100 parts by weight of the dispersion stabilizer resin. About 3 to 240 parts by weight of the body, preferably 5 to
82 parts by weight is suitable. 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 stable non-aqueous dispersion liquid 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 is obtained. The particle size of the polymer particles is usually about 0.1 to 1.0.
It is in the μm range. If the particle size is smaller than this range, the viscosity of the varnish will be high, while if it is larger than this range, the particles will swell or aggregate during storage, which is not preferable.

In the production of non-aqueous polymer particles, the storage stability and mechanical properties can be further improved by binding the dispersion stabilizer resin in the non-aqueous dispersion liquid and the polymer particles. 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.

Examples of the method for binding the dispersion stabilizer resin and the polymer particles include, for example, hydroxyl group, acid group, acid anhydride group, epoxy group,
Methylol group, an isocyanate group, an amide group, a monomer component having a functional group such as an amino group is partially copolymerized, further hydroxyl group that reacts with the functional group as a monomer component 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-styrenesulfonamide; (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 ester 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.

Another method for binding the dispersion stabilizer resin and the polymer particles is to polymerize a radically polymerizable unsaturated monomer in the presence of a 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, and adding glycidyl (meta ) It can be carried out by reacting a glycidyl group-containing unsaturated monomer such as acrylate or allyl glycidyl ether, but of course, conversely, a glycidyl group is contained in the resin and an acid group-containing unsaturated monomer is added thereto. It can also be done by reacting the body. These reactions can follow conventionally known conditions.

As another method of binding the dispersion stabilizer resin and the polymer particles, after producing a non-aqueous dispersion liquid in which functional groups which 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, by polymerizing a hydroxyl group-containing unsaturated monomer alone or a mixture with another unsaturated monomer in the presence of a hydroxyl group-containing dispersion stabilizer resin and an organic liquid, both groups contain a hydroxyl group. After producing a non-aqueous dispersion, a polyisocyanate compound or the like is added, and the mixture is mixed at room temperature for several days and at 60 to 100 ° C. for 1 day.
It can be carried out by reacting for about 5 hours. As the polyisocyanate compound, any one having at least one isocyanate group in the molecule can be used, and examples thereof include aromatic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate, 4,4′-diphenylmethane diisocyanate, and the like. Hydrides; aliphatic diisocyanates such as hexamethylene diisocyanate, lysine diisocyanate, dimer acid (a dimer of tall oil fatty acid) diisocyanate; alicyclic diisocyanates such as isophorone diisocyanate. In addition to the above combination of combinations,
Dispersion stabilizer resin containing acid groups and polymer particles in combination with polyepoxide, dispersion stabilizer resin containing epoxy groups and polymer particles in combination with polycarboxylic acid, dispersion stability containing epoxy groups or isocyanate groups It can be carried out by combining the agent resin and the polymer particles with the polysulfide compound. Examples of the polyepoxide include bisphenol A type epoxy resin and bisphenol F
Type epoxy resin, novolac type epoxy resin, epoxy group-containing acrylic resin, etc .; polycarboxylic acids such as adipic acid, sebacic acid, azelaic acid, isophthalic acid; polysulfides such as pentamethylene disulfide, hexamethylene disulfide, Examples thereof include poly (ethylene disulfide).

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 stabilizer. 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 amount of the hydroxyl group-containing unsaturated monomer in the dispersion stabilizer resin used in the production of the component (C) is as described above.
It is about 1 to 99% by weight in the used monomers, but when the hydroxyl group is reacted with the polymer particles, the hydroxyl group-containing unsaturated monomer component in the resin after the reaction is in the range of 1 to 99% by weight. The amount of use should be adjusted so that

When the polymer particles thus obtained as a non-aqueous dispersion liquid are used in the clear paint, the compounding ratio can also be arbitrarily selected according to the purpose, but it is based on the total amount of resin solids in the clear paint. The polymer particles are 5 to 25% by weight, preferably 5 to 20% by weight, more preferably 10% by weight.
A range of up to 20% by weight is suitable.

The clear paint may further contain, if necessary, an organic and / or inorganic thixotropic agent, a surface modifier such as silicon, an ultraviolet absorber, a light stabilizer and the like. .

As the solvent, all of the solvents used in conventional acrylic resin / melamine resin coatings can be used. For example, toluene, xylene, methyl ethyl ketone,
Examples thereof include organic solvents such as ethyl acetate, dioxane, butanol and the like. These solvents can be used alone or in an appropriate mixture.

Next, the method of the present invention (hereinafter referred to as "the present method") for forming a multilayer coating film by using the above water-based colored coating material and clear coating material will be described.

As the article to be coated, outer panels of automobiles such as passenger cars, buses, trucks and motorcycles are particularly suitable, but there is no reason to be limited only to these. Further, the object to be coated may be either metal or plastic. Then, prior to the coating of the above-mentioned water-based coloring paint and clear paint, these objects to be coated are subjected to appropriate surface treatment, and then an undercoat paint or an intermediate paint is applied according to the purpose and the coating film is cured. It is preferable to keep it to a minimum.

In the present method, the water-based colored coating material usually has a solid content of about 10 to 50% by weight and a viscosity of about 800 to about 5.
It is preferably adjusted to 000 cps / 6 rpm / 25 ° C. (B-type viscometer).

The water-based colored coating material corresponds to the base coating material in the two-coat one-bake system coating, and is air sprayed on the surface of the above-mentioned article to a film thickness of 10 to 50 μm based on the cured coating film. The coating is applied by airless spraying or electrostatic coating, and dried by air drying or warm air drying so that the water content in the colored coating film is 1 to 30% by weight, particularly preferably 5 to 15% by weight. At this point, no or almost no crosslinking reaction has occurred in the colored coating film.

Then, an organic solvent-based clear paint is applied to the surface of the uncured colored coating film by air spray, airless spray, electrostatic coating or the like so as to have a film thickness of 15 to 70 μm based on the cured coating film. After performing the usual setting, by heating at 120 to 200 ° C. for 10 to 40 minutes, both of the above coating films are cured to obtain the multilayer coating film intended by the present invention.

The technical effects of this method are as follows.

1. The cross-linking reaction of the clear coating film is a chemical bond that is not only susceptible to the reaction between the hydroxyl group in the acrylic resin and the amino resin, but is also less susceptible to hydrolysis by the alkoxysilane group -Si-O-Si, -Si-O-R-. Crosslinking points are also introduced, so acid resistance, water repellency, scratch resistance, water resistance, chemical resistance, stain resistance, weather resistance and heat resistance are better than those of conventional amino resin / acrylic resin type clear paints. The sexuality has been greatly improved.

2. Acrylic resin containing an alkoxysilane group and a hydroxyl group, and a clear coating containing an amino resin as a main component, and a non-aqueous polymer particle obtained by non-aqueous dispersion polymerization using an alkoxysilane group-containing polymer as a dispersion stabilizer. By blending it, it becomes possible to lower the viscosity and make it high solid, the coating workability is improved, and the acid resistance and impact resistance of the cured coating film are further improved.

3. Since the clear paint does not contain a catalyst for hydrolyzing the alkoxysilane group, its storage stability is excellent.

4. Various effects were obtained by applying a clear coating on the surface of an uncured aqueous coating film containing water. That is, the hydrolysis reaction of the alkoxysilane group largely contributes to the curing of the clear coating film, and conventionally, the water content for this hydrolysis reaction often depends on the supply from the atmosphere. However, since the moisture content in the atmosphere depends on the humidity and temperature, the curability of the coating film tends to become non-uniform, and the curing reaction proceeds only in the surface layer of the coating film, and Although the curability was not sufficient in some cases, by coating a clear coating on the uncured water-based coating surface containing water as in this method, the supply of water for the hydrolysis reaction was controlled to the temperature and humidity of the atmosphere. The curing reaction of the clear coating film is carried out uniformly and promptly because the curing reaction in the deep portion of the coating film is sufficiently advanced without being affected.

5. Since the aqueous coloring paint contains a catalyst for hydrolyzing the alkoxysilane group, the storage stability of the clear coating is improved, and the catalyst contained in the aqueous coloring paint migrates into the clear coating film. In addition to promoting the hydrolysis reaction, the interlayer adhesion between the two coating films was improved, and the smoothness of the coated surface was improved due to the curing reaction from the deep portion of the coating films.

[0140]

EXAMPLES Next, production examples, examples and comparative examples will be given.
The present invention will be described more specifically. All parts and% are by weight.

1. Production Example 1) Acrylic resin emulsion (M-1) for water-based coloring paint In a reaction vessel, 140 parts of deionized water and 39% "Newcol 70"
2.5 parts of 7SF "(surfactant, manufactured by Nippon Emulsifier Co., Ltd.) and 1 part of the following monomer mixture (a) were added and mixed by stirring in a nitrogen stream, and 3 parts of 3% ammonium persulfate aqueous solution was added at 60 ° C. Then, after raising the temperature to 80 ° C., 79 parts of the following monomer mixture (a), 30% "Newcol 707SF"
A monomer emulsion consisting of 2.5 parts, 4 parts of 3% ammonium persulfate aqueous solution and 42 parts of deionized water is added to the reaction vessel using a metering pump over 4 hours. After completion of the addition, aging is carried out for 1 hour.

Further, at 80 ° C., the following monomer mixture (b) was added.
20.5 parts and 4 parts of a 3% ammonium persulfate aqueous solution are simultaneously dropped into the reaction vessel in parallel over 1.5 hours. After dripping, aging for 1 hour, diluting with 30 parts of deionized water, and 30 ° C
Filtered through 200 mesh nylon cloth. Deionized water was added to this filtrate and the pH was adjusted to 7.5 with dimethylaminoethanolamine to obtain a core / shell type acrylic emulsion (M-1) having an average particle size of 0.1 μm and a nonvolatile content of 20%. It was

Monomer mixture (a) Methyl methacrylate 55 parts Styrene 8 parts n-Butyl acrylate 9 parts 2-Hydroxyethyl acrylate 5 parts 1,6-hexanediol diacrylate 2 parts Methacrylic acid 1 part

Monomer mixture (b) Methyl methacrylate 5 parts n-Butyl acrylate 7 parts 2-Ethylhexyl acrylate 5 parts Methacrylic acid 1 part 30% "Newcol 707SF" 0.5 parts

Acrylic resin emulsion (M-2, M
-3, M-4) Core / shell type emulsion (M-2) -using the components shown in Table 1 according to the following steps (I)-(III).
(M-4) was produced.

Step (I): Deionized water 12 in the flask
0 part was added, and it was heated to 80 to 85 ° C., 2 parts of the first pre-emulsion shown in Table 1 was added dropwise with stirring, and the mixture was aged for 20 minutes.
An aqueous dispersion of the core portion obtained by three-dimensionally crosslinking reaction was obtained by dropping over time.

Step (II): Immediately after the completion of the dropping of the first pre-emulsion, the silane-based monomer and the allyl methacrylate are dropped, and the temperature is maintained at 80 to 85 ° C. for 1 hour to allow the silane-based monomer and the allyl methacrylate to be applied to the surface of the core. Methacrylate was reacted.

Step (III): Add 50 parts of deionized water,
The second pre-emulsion was added dropwise at 80 to 85 ° C. at a constant rate over 1 hour. Then, the mixture was kept at the same temperature for 1 hour and then rapidly cooled to room temperature, and deionized water was added so that the solid content was 30%. The polymer particles obtained are insoluble in organic solvents. Then, deionized water was added and the mixture was neutralized with diethanolamine and adjusted to a solid content of 20% to obtain core / shell type emulsions (M-2) to (M-4).

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

[0150]

[Table 1]

Acrylic resin aqueous solution (M-5) 60 parts of butyl cellosolve and 15 parts of isobutyl alcohol are added to a reaction vessel and heated to 115 ° C. in a nitrogen stream.
When the temperature reached 115 ° C, a mixture of 26 parts of n-butyl acrylate, 40 parts of methyl methacrylate, 17 parts of styrene, 10 parts of 2-hydroxyethyl methacrylate, 6 parts of acrylic acid and 1 part of azoisobutyronitrile was used for 3 hours. Add After completion of the addition, the mixture is aged at 115 ° C. for 30 minutes, a mixture of 1 part of azobisisobutyronitrile and 115 parts of butyl cellosolve is added over 1 hour, and the mixture is aged for 30 minutes and filtered through a 200 mesh nylon cloth at 50 ° C. The acid value of the obtained reaction product was 48, the viscosity was Z ₄ (Gardner foam viscometer), the nonvolatile content was 55%, and the Tg was 45 ° C. This was neutralized with dimethylaminoethanolamine in an equivalent amount, and deionized water was further added to obtain a 50% acrylic resin aqueous solution (M-5).

Urethane resin emulsion (U-1) Polybutylene adipate 11 having a number average molecular weight of 2,000
5.5 parts, polycaprolactone diol having a number average molecular weight of 2,000 115.5 parts, dimethylolpropionic acid 2
3.2 parts, 1,4-butanediol 6.5 parts and 1-
Isocyanato-3-isocyanatomethyl-3,5,5-
120 parts of trimethylcyclohexane (IPDI) was charged into a polymerization vessel and reacted with stirring at 85 ° C. for 7 hours under a nitrogen gas atmosphere to obtain a terminal NCO having an NCO content of 4.0%.
A base prepolymer was obtained. Next, the prepolymer was cooled to 50 ° C., 165 parts of acetone was added and uniformly dissolved, and then 15.7 parts of triethylamine was added with stirring.
While maintaining the temperature below 50 ° C, add 600 parts of deionized water,
The obtained water dispersion was kept at 50 ° C for 2 hours to complete the water elongation reaction, and then acetone was distilled off under reduced pressure at 70 ° C or lower to give a urethane resin emulsion (U-1 having a solid content of 42%). ) Got.

Urethane resin emulsion (U-2) Polyethylene isophthalate diol (molecular weight 2,000
0) 66.1 parts, neopentyl adipate diol (molecular weight 2,000) 66.1 parts, trimethylol propane 2.5 parts, bisphenol A ethylene oxide 2 mol adduct 38.8 parts, dimethylol propionic acid 8. Two
Parts, hydrogenated MDI 102.0 parts and acetone 120 parts in a prepolymer solution (NCO% 2.72) to aminoethylethanolamine 7.9 parts, isopropanol 30.
Parts and 120 parts of acetone were added, and the mixture was reacted at 30 ° C. for 1 hour, neutralized with 14.3 parts of diethanolamine and then mixed with 700 parts of ion-exchanged water. Thereafter, in the same manner as in Production Example 1, solid content 30.3%, viscosity 150 cps / 25 ° C., pH
9.2 Urethane Resin Emulsion (U-2) 990
I got a part.

Crosslinking agent (K-1) As a hydrophobic melamine resin, "Uban 28" (manufactured by Mitsui Toatsu Chemicals, Inc., solid content 60%, solvent dilution ratio 0.
4) 41.7 parts was put in a container, and an acrylic resin aqueous solution (M
-5) was added to 20 parts, and the rotation speed was 1,000 to 1,500.
After 80 parts of deionized water was gradually added while stirring with a disperser (minute), the stirring was continued for another 30 minutes to disperse the hydrophobic melamine resin in water to an average particle size of 0.11 μ (K-1 ) Component was obtained.

Aluminum Pigment Paste (P-1) An aluminum paste (metal content: 65) was added to the stirred mixed solution.
%) 23 parts and butyl cellosolve 25 parts, and after stirring, 65% Lubrizol 2062 (manufactured by Lubrizol Co.,
1 part of a trade name, an aluminum treating agent) was added and stirred for 1 hour to obtain an aluminum pigment concentrated liquid (P-1).

Water-based Colored Coatings (S-1) to (S-5) The components obtained in the above Production Examples 1 to 5 were blended and stirred in the proportions shown in Table 2 to obtain compositions of "Acrysol ASE". -60 "(made by Rohm and Haas, thickener) and diethanolamine are added to give an apparent viscosity of 3.
000 cps / 6 rpm (B type viscometer), pH was adjusted to 7.80 to obtain an aqueous paint. In Table 2, the compounding amounts shown in the table are all solid contents.

Further, although the component (K-1) also contains the component (M-5), the blending amount of the crosslinking agent component in the table shows only the hydrophobic melamine resin, and (M-5) Ingredient is (M)
It is included in the blended amount of ingredients. Therefore, the blending amount described in the column of the (M) component is a mixture of the (M-5) component from the (K-1) component and the (M) component described in the same column, and from the blending amount thereof, The amount of the component (M) is the amount excluding the amount of the component (M-5).

[0158]

[Table 2]

2) Organic solvent-based clear coating acrylic resin (A-1) Styrene 100 g n-Butyl acrylate 450 g 2-Ethylhexyl methacrylate 200 g 2-Hydroxyethyl methacrylate 150 g γ-methacryloxypropyltrimethoxysilane 100 g Azobisisobutyro A mixture of 20 g of nitrile was added to 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.

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

Acrylic Resin (A-3) Styrene 200 g n-Butyl Acrylate 600 g 2-Hydroxyethyl Methacrylate 200 g Azobisisobutyronitrile A mixture of 20 g was added dropwise to the same amount of xylene at 120 ° C. for 3 hours. It was aged at the same temperature for 2 hours. The number average molecular weight of the obtained transparent polymer was 18,000.

Non-Aqueous Polymer Particles (C-1) 1) Synthesis of Dispersion Stabilizer Resin (N) Isobutyl acetate 40 parts Toluene 40 parts are heated to reflux and the following monomers and polymerization initiators are added dropwise over 3 hours. After dripping, the mixture was aged for 2 hours. Methacryloxypropyltrimethoxysilane 5 parts Styrene 10 parts Isobutyl methacrylate 49 parts 2-Ethylhexyl methacrylate 25 parts 2-Hydroxyethyl methacrylate 11 parts 2,2'-Azobisisobutyronitrile 2 parts The resulting acrylic resin varnish is non-volatile. The content was 55%, the viscosity (Gardner, 25 ° C., the same below) G, and the weight average molecular weight was 16,000.

2) Preparation of Non-Aqueous Dispersion (N-1) Heptane 93 parts 55% Dispersion stabilizer resin (N) varnish 98 parts was charged in a flask and heated to reflux, and the following monomers and polymerization initiator were added to 3 parts. The mixture was dropped over a period of time and aged for 2 hours. Styrene 15 parts Methyl methacrylate 40 parts Acrylonitrile 30 parts 2-Hydroxyethyl methacrylate 15 parts tert-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 an electron microscope, the same applies hereinafter) 0.
It was a milky white stable low-viscosity polymer particle dispersion of 2 to 0.3 μm. No precipitation or coarse particles were observed even after standing still for 3 months at room temperature.

Clear paint (T-1) (A-1) solution 140 parts Cymel 303 (Note 1) 30 parts Nacure 5225 0.5 parts Surface conditioner (BYK-300 solution manufactured by Big Chem Co., Ltd.) 0.1 part UV absorption Agent (Tinubin 900, manufactured by Ciba-Geigy) 1.0 part The above mixture was diluted with Swazol # 1000, and the viscosity (Ford cup # 4, 20 ° C) was adjusted to 25 seconds. The coating solids were 45%. (Note 1) Cymel 303: Mitsui Cyanamid, full-methoxylated melamine resin

Clear paint (T-2) (A-2) solution 160 parts Cymel 303 (Note 1) 20 parts Nacure 5225 0.5 parts Surface conditioner 0.1 parts UV absorber 1.0 part Using the above mixture It adjusted like T-1. The coating solid content was 46%.

Clear coating (T-3) (A-2) solution 140 parts 60% U-ban 20SE (Muthi Toatsu Co., Ltd. butylated melamine) 50 parts Surface conditioner 0.1 part UV absorber 1.0 part The above mixture Was adjusted in the same manner as in T-1. The coating solid content was 40%.

Clear coating (T-4) (A-1) solution 120 parts Cymel 303 30 parts (N-1) dispersion 18.8 parts Nacure 5225 0.5 parts Surface conditioner 0.1 parts UV absorber 1. 0 part It adjusted like T-1 using the above-mentioned mixture. The coating solids were 55%.

Clear coating (T-5) (A-2) solution 160 parts Cymel 303 20 parts Surface modifier 0.1 part UV absorber 1.0 part Catalyst Ca-4 1.0 part T using the above mixture It adjusted like -1. The coating solid content was 46%.

II. Examples and Comparative Examples Using the water-based paint (base coat) and the clear paint obtained in the above-mentioned Production Examples, coating was carried out by the 2-coat 1-bake system as follows.

As the coated product of the steel plate, one subjected to the following pretreatment was used. That is, "Bondelight # 3030"
"Elektron No. 9200" (Kansai Paint Co., Ltd., epoxy resin-based cationic electrodeposition paint) is applied as a primer to the steel plate surface-treated with (Nihon Parker Rising Co., Ltd., zinc phosphate treatment agent). Then, "Amilak N-2 Sealer" (Kansai Paint Co., Ltd., aminopolyester resin-based intermediate coating material) applied thereon and cured, was used as an article to be coated.

The water-based paint was treated at a temperature of 25 ° C. and a relative humidity of 65.
% Spraying environment and spray coating with a spray gun twice each. A setting of 2 minutes was performed between two applications. The air pressure in the spray gun was 5 kg / cm ² , the flow rate of the paint was 350 ml / min, and the distance to the object to be coated was 35 cm. The position of the article to be coated was kept vertical during the whole process. After being applied twice, it was left in the coated environment for 2 minutes and air dried at a temperature of 80 ° C. for 10 minutes. After cooling to room temperature, apply clear paint using an electrostatic gun, set for 5 minutes,
It was baked at 120 to 140 ° C. for 30 minutes. The dry film pressures of the base coat and the clear coating were 15 μm and 40 μm, respectively. Thus, the coating was performed by the two-coat one-bake method.

The coatability and the performance of the resulting coating film were evaluated by the following tests (1) to (12). The results are shown in Table 3.

[0173]

[Table 3]

[Test Method] 1. Finished appearance: visually evaluated. ◯: Both smoothness and luster are good. X: Tint is generated on the coated surface, and the luster is significantly impaired.

2. Acid resistance: A test coated plate is soaked 1/2 in a 40% sulfuric acid solution, left at 50 ° C. for 5 hours, and then washed with water,
The coated surface was observed and evaluated according to the following criteria. ○: No change at all ×: Whitened coating surface

3. Scratch resistance: An automobile having a test coated plate adhered to the roof was washed 5 times with a car washing machine and the coated surface state of the coated plate was observed. The car wash is made by Yasui Sangyo "PO 2
0FWRC "was used. The evaluation criteria are as follows. ◯: Almost no scratches were found by visual observation and passed × Visually marked scratches were clearly found and failed

4. Interfacial adhesion: A test coated plate was immersed in warm water at 80 ° C. for 8 hours, 100 crosscuts were placed at 2 mm intervals, and the presence / absence of peeling of the base / clear interface was determined with an adhesive cellophane tape. ◯: No peeling was observed at all ×: Some peeling was observed

5. Gel fraction of multi-layer coating film: The released multi-layer coating film was placed in a 300 mesh stainless steel mesh container and acetone / methanol = 1 with a Soxhlet extractor.
After extraction with a / 1 solvent for 6 hours, the gel fraction was calculated according to the following formula.

[0179]

[Equation 1]

6. Storability: The viscosity of the paint before and after storage at 40 ° C. for 10 days was measured and evaluated. ◯: Ratio of change in viscosity is less than 10% of initial viscosity x: Significant increase in viscosity or gelation

Claims (1)

[Claims] 1. A water-based colored paint is applied, and then an organic solvent-based clear paint containing an acrylic resin having an alkoxysilane group and a hydroxyl group as a main component and an amino resin is applied to the coated surface and then heated. A method for forming a multilayer coating film by a two-coat one-bake system in which both coating films are simultaneously cured, wherein the aqueous colored coating composition is obtained by adding a catalyst for hydrolysis of an alkoxysilane group. Coating method.