JPH11124545A - Aqueous coating composition and finish coating method therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aq. coating compsn. which can form a coating film excellent in water resistance by incorporating a water-soluble resin and/or a water-dispersible resin, a pigment, and a specific neutralizing agent into the same. SOLUTION: An acrylic copolymer obtd. by copolymerizing 1-30 wt.% alkylene oxide group-contg. (meth)acrylate of the formula (wherein R is H or methyl; m is 1-10; and n is 2 or 3), 0.5-80 wt.% (meth)acrylate having a cyclic satd. hydrocarbon group, 10 wt.% or lower acid group-contg. monomer, and 0-98.5 wt.% other unsatd. monomers and having a number average mol.wt. of 3,000-200,000 is neutralized with a neutralizing agent comprising an amine having a b.p. of 150 deg.C or lower and at least one hydroxyl group per molecule, giving a water-soluble resin. A film-forming component comprising 5-50 wt.% above-obtd. water-soluble resin and 95-50 wt.% water-dispersible resin comprising an acrylic resin emulsion and/or a urethane resin emulsion is compounded with a pigment and optionally a crosslinker, a thickener, a surface modifier, an antifoaming agent, a cure catalyst, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous coating composition capable of forming a coating having excellent water resistance.

[0002]

2. Description of the Related Art Conventionally, organic solvent-based paints have been frequently used for coating automotive exterior panels and the like, but the use of water-based paints has been shifting from the viewpoint of air pollution and resource saving. In particular, various types of water-based basecoat paints have been proposed for finish coating in which a basecoat paint is applied and then a clear paint is applied (for example, Japanese Patent Application Laid-Open No. Sho 62-193).
676 etc.). Generally, resins such as an acrylic resin emulsion, a urethane resin emulsion, and a water-soluble acrylic resin are mainly used for the aqueous paint for the basecoat.

[0003] In the water-based paint, ammonia, amine or the like is generally used as a neutralizing agent for obtaining the stability of the resin emulsion or for making the resin water-soluble. However, since the amine forms a salt with an acid group in the resin, the amine is likely to remain in the coating film particularly when the coating film is formed by drying at room temperature or forcibly drying at 80 ° C. or lower, and the water resistance is lowered. Could not be improved.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that the water resistance is improved by using a specific amine as a neutralizing agent in a paint. The invention has been reached.

That is, the present invention relates to an aqueous coating composition comprising a water-soluble resin (A) and / or a water-dispersible resin (B) and a pigment (C) as main components, wherein a neutralizing agent in the coating is used. (D) An aqueous coating composition characterized by using an amine having a boiling point of 150 ° C. or lower and having one or more hydroxyl groups in one molecule, and the base coating surface of the aqueous coating composition The present invention provides a coating method for coating as a paint and then applying a top clear paint.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a water-soluble resin (A)
Any of those known in the art can be used. Usually, an aqueous solution obtained by neutralizing an acrylic copolymer into which an acid group such as a carboxyl group has been introduced with a neutralizing agent, particularly a neutralizing agent (D) described below. Acrylic resin.

The acrylic copolymer is a monomer containing an acid group.
And other acrylic monomers, but from the viewpoint of water resistance, the acrylic copolymer contains (a) an alkylene oxide group-containing (meth) acrylate, and (b) a cyclic saturated hydrocarbon. Those obtained by copolymerizing (meth) acrylate having a group, (c) an acid group-containing monomer and (d) another unsaturated monomer can be suitably used.

The alkylene oxide group-containing (meth) acrylate (a) has the following general formula (1)

[0009]

Embedded image

Wherein R is a hydrogen atom or a methyl group, R ₁
Is a hydrogen atom, an alkyl group or an acyl group, and m is 1 to 100
And n represents an integer of 2 or 3. When R ₁ is an alkyl group or an acyl group, it preferably has about 1 to 8 carbon atoms. It is not desirable because copolymerizability and compatibility are reduced.

Examples of the monomer (a) include diethylene glycol (meth) acrylate, triethylene glycol (meth) acrylate, and polyethylene glycol.
(Meth) acrylate, dipropylene glycol (meth) acrylate, tripropylene glycol (meth)
Acrylate, polypropylene glycol (meth) acrylate, polyethylene polypropylene glycol (meth) acrylate, methoxyethylene glycol (meth) acrylate, ethoxyethylene glycol (meth) acrylate Ethoxydiethylene glycol (meth) acrylate, ethoxytriethylene glycol (meth) acrylate, ethoxy polyethylene glycol
(Meth) acrylate, propoxytriethylene glycol (meth) acrylate, methoxypropylene glycol (meth) acrylate, ethoxypropylene glycol (meth) acrylate, ethoxydipropylene glycol (Meth) acrylate, ethoxytripropylene glycol (meth) acrylate, ethoxy polypropylene glycol (meth) acrylate, propoxytripropylene glycol (meth) acrylate, and the like. These can be used alone or in combination of two or more.

The cyclic saturated hydrocarbon group-containing (meth) acrylate (b) includes a monocyclic hydrocarbon group, a bridged alicyclic hydrocarbon group, and a bicyclic terpene group, for example, isobornyl. (Meth) acrylate, adamantyl (meth) acrylate, bicyclo [3,3,1] nonyl (meth) acrylate, cyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate
And these can be used alone or in combination of two or more. Particularly, isobornyl (meth) acrylate, adamantyl (meth) acrylate and the like are preferable.

Examples of the acid group-containing monomer (c) include acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, β-carboxyethyl acrylate,
2-acrylamido-2-methylpropanesulfonic acid,
Allylsulfonic acid, styrenesulfonic acid sodium salt,
And sulfoethyl methacrylate and its sodium and ammonium salts, and phosphoric acid group-containing monomers such as "Light Ester PM" (manufactured by Light Ester Co., Ltd.).
These can be used alone or in combination of two or more. At least one of which has a carboxy group
It is preferred to use parts.

Examples of the other unsaturated monomers (d) include hydroxyl group-containing unsaturated monomers other than the above-mentioned (a) monomers. For example, 2-hydroxyethyl (meth) acrylate, hydroxypropyl ( (Meth) acrylic acid such as hydroxyalkyl esters of (meth) acrylic acid having 2 to 8 carbon atoms; N-methylolacrylamide, allyl alcohol, and ε-caprolactone-modified acrylic monomer. Further, as (d),
For example, methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, lauryl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate C1-C20 alkyl esters of (meth) acrylic acid such as isopropyl methacrylate, butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, lauryl methacrylate; dimethylaminoethyl acrylate, dimethylamino Nitrogen-containing monomers such as ethyl methacrylate, N-butoxymethyl acrylamide, N, N-dimethyl acrylamide; acryl such as glycidyl acrylate and glycidyl methacrylate And these monomers can be used alone or in combination of two or more. Further, vinyl monomers other than acrylic monomers such as vinyl acetate, vinyl propionate, styrene, α-methylstyrene, vinyl toluene, acrylonitrile, methacrylonitrile, butadiene and isoprene can be used.

The copolymerization reaction of the above monomers can be carried out by a known method, for example, using a radical polymerization catalyst such as azobisisobutyronitrile, benzoyl peroxide, ammonium persulfate, etc. It is performed in an organic solvent. The reaction ratio of the monomers is (a) 1 to 30% by weight of the monomer, preferably 5 to 20% by weight, and (b) 0.5 to 80% of the monomer.
% By weight, preferably 5 to 50% by weight, (c) 10% by weight
In the following, the ratio is preferably 0.5 to 5% by weight, and (d) monomer to 0 to 98.5% by weight, and more preferably 25 to 85% by weight.

The obtained acrylic copolymer has an acid value of about 20.
About 150, number average molecular weight about 3,000 to about 200,0
00, preferably 10,000 to 100,000.

The present invention provides a neutralizing agent (D) in a paint,
An amine having a boiling point of 150 ° C. or lower and having one or more hydroxyl groups in one molecule is used, and it is desirable to use the neutralizing agent (D) also for neutralizing the acrylic copolymer.

The amine of the neutralizing agent (D) has a boiling point of 150
C. or less, preferably 30-140.degree. If the boiling point exceeds 150 ° C., it is not preferable because the amine remains in the resulting coating film at room temperature and the water resistance decreases, which is not preferable. The amine of the neutralizing agent (D) has one or more hydroxyl groups in one molecule, and a tertiary amine is particularly preferable.

Examples of the amine include dimethylethanolamine, dimethylpropanolamine, dimethylisopropanolamine, and the like. In particular, dimethylethanolamine is preferred in terms of water resistance and drying property.

In the present invention, as the water-dispersible resin (B), conventionally known ones can be used, and usually an acrylic resin emulsion and / or a urethane resin emulsion.

The acrylic resin emulsion is obtained by uniformly dispersing acrylic resin particles in an aqueous medium.
For example, a fine-particle acrylic resin emulsion having an average particle diameter of 0.05 to 1.0 μm obtained by subjecting a vinyl monomer to emulsion polymerization in one or more stages in the presence of a dispersion stabilizer such as a surfactant may be used. . The vinyl monomer to be emulsion-polymerized is preferably appropriately selected from the monomers exemplified for the water-soluble resin (A), and if necessary, a polyvinyl compound having two or more polymerizable unsaturated bonds in one molecule. When a small amount of is used, an acrylic resin emulsion crosslinked in the particle is obtained, and the coating film performance is improved, so that it is preferable.

Examples of the dispersion stabilizer include a nonionic surfactant such as polyoxyethylene nonylphenyl ether, an anionic surfactant such as polyoxyethylene alkyl allyl ether sulfate, and an acid value of 20 to 20. 1
For example, a water-soluble resin such as an acrylic resin having a number average molecular weight of about 5,000 to 30,000 is used.

Examples of the polyvinyl compound include ethylene glycol diacrylate, ethylene glycol dimethacrylate, and triethylene glycol diacrylate.
, Tetraethylene glycol dimethacrylate, 1,
6-hexanediol diacrylate, divinylbenzene, trimethylolpropane triacrylate and the like can be mentioned.

The acrylic resin emulsion produced here is also preferably adjusted in pH with the amine of the neutralizing agent (D).

As the urethane resin emulsion, an emulsion obtained by reacting an isocyanate group-containing prepolymer with a polyisocyanate, a polyol and a hydroxy acid in the presence of water can be used.

Examples of such an emulsion include (I) an aliphatic and / or alicyclic polyisocyanate (e), a high molecular weight polyol (f), a dimethylol alkanoic acid (g), and if necessary, a chain. Carboxyl group-containing polyurethane resin emulsified and dispersed in water by adding an excess isocyanate group-containing prepolymer (i) obtained by polymerizing an elongating agent (h) by one-step or multi-step method, monoamine (j) and water in any order. Emulsions and (II) carboxyl group-containing polyurethane resin emulsions in which a chain extender (k), an emulsifier and water as required, are added to the above-mentioned prepolymer (i) in any order, and emulsified and dispersed in water.

Examples of the aliphatic and / or alicyclic polyisocyanate (e) include hexamethylene diisocyanate, 2,2,4-trimethylhexane diisocyanate and lysine diisocyanate. 2 to 12 carbon atoms such as
Aliphatic diisocyanates; 1,4-cyclohexane diisocyanate, isophorone diisocyanate, 4,4
Alicyclic diisocyanates having 4 to 18 carbon atoms such as '-dicyclohexylmethane diisocyanate, methylcyclohexylene diisocyanate, and isopropylidenecyclohexyl-4,4'diisocyanate; diisocyanates thereof; Modified products (carbodiimide, uretdione,
Uretoimine-containing modified products); and mixtures of two or more of these. Of these, 1,4-cyclohexane diisocyanate, isophorone diisocyanate
G, 4,4'-dicyclohexylmethane diisocyanate
And alicyclic diisocyanates such as

The above-mentioned high molecular weight polyol (f) preferably has a number average molecular weight of 500 to 5,000, preferably 1,0 to 1,0.
Polyetherdiol and polyesterdiol having a molecular weight of 00 to 3,000. For example, those obtained by polymerizing or copolymerizing (block or random) alkylene oxide (ethylene oxide, propylene oxide, butylene oxide, etc.) and / or heterocyclic ether (tetrahydrofuran, etc.), for example, polyethylene glycol, polypropylene glycol -Polyethylene-propylene (block or random) glycol, polytetramethylene ether terglycol, polyhexamethylene ether terglycol, polyoctamethylene ether terglycol; dicarboxylic acids (adipic acid, succinic acid) , Sebacic acid, glutaric acid, maleic acid, fumaric acid, phthalic acid, etc.) and glycols (ethylene glycol, propylene glycol, 1,4)
-Butanediol, 1,6-hexanediol, 3-methyl-1,5-pentaneditol, neopentylglycol, bishydroxymethylcyclohexane, etc.), for example, polyethylene adipate Polybutylene adipate, polyhexamethylene adipate,
Polyneopentyl adipate, poly-3-methylpentyl adipate, polyethylene / butylene adipate, polyneopentyl / hexyl adipate; polylactone diols such as polycaprolactone diol, poly-3
-Methylvalerolactonediol; polycarbonate-diol; and mixtures of two or more thereof.

Examples of the above dimethylolalkanoic acid (g) include dimethylolacetic acid, dimethylolpropionic acid, dimethylolbutyric acid and the like, and dimethylolpropionic acid is particularly preferred. The dimethylolalkanoic acid (g) is suitably used as a carboxyl group in the prepolymer (i) in an amount of 0.5 to 20% by weight, preferably 1 to 10% by weight.

The chain extender (h) is preferably a low molecular weight (number average molecular weight less than 500) polyol, polyamine or the like. Examples of the low molecular weight polyol include, for example, glyco-
And low-alkylene oxide adducts thereof, and trivalent alcohols such as glycerin, trimethylolethane, and trimethylolpropane, and low-alkylene oxide adducts thereof. Examples of polyamines include ethylenediamine and tetramethylenediamine. , Monohydroxyethyldiethylenediamine, isophoronediamine and the like. The chain extender (h) is used in an amount of from 0 to 20% by weight, preferably from 0.
Suitably, it is used in an amount of 5 to 10% by weight.

The above-mentioned prepolymer (i) comprises the above (e) to
(G) and, if necessary, (h) can be synthesized by a one-step or multi-step method. The components (e) to (h) may be blended so as to have an isocyanate group in the prepolymer (i). Usually, the equivalent ratio of isocyanate group / hydroxyl group is 1.1 to 1.0. It is desirable to be within the range of 1.9. The synthesis reaction of the prepolymer (i) can be performed based on a conventionally known method.

The emulsion (I) can be produced by adding the above-mentioned prepolymer (i), monoamine (j) and water in an arbitrary order and self-emulsifying and dispersing in water.

As the monoamine (j), a conventionally known amine can be used, but it is preferable to use the amine of the neutralizing agent (D).

The emulsion (II) can be produced by adding the above-mentioned prepolymer (i), chain extender (k), if necessary, an emulsifier and water in an arbitrary order, and emulsifying and dispersing in water. As the chain extender (k), the polyamine described for the chain extender (h) can be used. Examples of the emulsifier include nonionic surfactants such as higher alcohols and alkylene oxide adducts and anionic surfactants such as alkylbenzene sulfonates.

In the present invention, the water-soluble resin (A) and / or
Alternatively, the water-dispersible resin (B) is used as a vehicle component, and these can be used alone or in combination. Preferably, the water-soluble resin (A) and the water-dispersible resin (B) are preferably used in a weight ratio of solid content of 5/95 to 50/50.

Further, if necessary, other water-soluble and / or water-dispersible resins which are usually used as a film-forming component of an aqueous paint may be appropriately selected and used in combination. Examples of such other water-soluble and / or water-dispersible resins include water-soluble or water-dispersible alkyd resins, polyester resins, cellulose resins, and the like.

In the present invention, a crosslinking agent can be contained as required. Examples of the crosslinking agent include water-soluble or water-dispersible amino resins, (block) polyisocyanates, epoxy resins and the like.

In the present invention, as the pigment (C), metallic pigments and / or coloring pigments usually used in the field of coatings can be used. For example, aluminum paste, pearl powder, graphite, MIO, titanium white, caramel Bonblack, phthalocyanine and the like. In addition, extenders can be blended.

The composition of the present invention may further contain, if necessary, other components commonly used in the preparation of aqueous paints such as thickeners, surface conditioners, defoamers, curing catalysts, water and organic solvents. May be. At the time of blending the pigment, a pigment paste may be prepared using the water-soluble resin (A) of the present invention as a pigment dispersing resin.

In the composition of the present invention, when the above components are blended to form a coating, the pH is adjusted using the amine of the neutralizing agent (D).

The coating film obtained by the composition of the present invention can be dried under normal temperature drying and forced drying (80 ° C. or lower), and can be applied to baking at a high temperature.

The present invention also relates to a method of applying a basecoat paint on a substrate surface and then applying a top clear paint, wherein the basecoat paint is used as the aqueous paint of the present invention. The present invention provides a coating method using the composition.

Examples of the base material surface include those obtained by applying a usual primer to a metal or plastic material. For example, an automobile body subjected to electrodeposition coating or intermediate coating or an automobile body Repair painted surface.

The aqueous coating composition of the present invention is usually applied to the surface of the substrate so that the dry film thickness is in the range of 10 to 30 μm to obtain a base coat. The basecoat coating may be cured before the top clear coating is applied, or the top clear coating may be applied wet-on-wet on the basecoat coating.

As the top clear paint used in the method of the present invention, conventionally known paints can be used without particular limitation.
Examples thereof include organic solvent type paints (including non-aqueous dispersion type paints) and powder paints. For example, acrylic resin or fluorine resin having a crosslinkable functional group such as a hydroxyl group and a crosslinking agent such as (block) polyisocyanate or melamine resin And a lacquer coating mainly composed of a cellulose acetate-butyrate-modified acrylic resin. When a urethane-curable paint is used, a part of the isocyanate component permeates into the basecoat paint film from the top clear paint film, so that the water-soluble paint used in the base paint paint is used. Even if the water-dispersible resin (A) contains a hydroxyl group, it is preferable because the crosslinking agent component is not used in the basecoat paint or the weight can be reduced.

The top clear paint further contains paint additives such as pigments, cellulose derivatives, additional resins, ultraviolet absorbers, light stabilizers, surface conditioners, and curing catalysts, if necessary. be able to.

The film thickness of the top clear paint is suitably in the range of 20 to 100 μm in dry film thickness. As a coating method, a normal spray coating, an electrostatic coating, or the like is adopted for both the base-coat paint and the top clear paint, but other paint methods are not particularly limited.

[0048]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples.

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

Production Example 1 Production of Water-Soluble Resin 75 parts of butyl cellosolve was added to a reaction vessel, and the temperature was raised to 115 ° C. in a nitrogen stream. After reaching 115 ° C., 20 parts of methyl methacrylate, 20 parts of n-butyl methacrylate, 30 parts of isobornyl acrylate, 11 parts of styrene, 5 parts of hydroxyethyl acrylate, 4 parts of acrylic acid, RMA
-450 (Note 1) 10 parts and azobisbutyronitrile 1
Of the mixture was added over 3 hours, and the mixture was aged for another 2 hours. After completion of the reaction, dimethylethanolamine (b.
p. Neutralized at 134 ° C.) and further added with 25 parts of butyl cellosolve to obtain a water-soluble acrylic resin solution (A-A) having an acid value of 31, a viscosity of Z4 (Gardona foam viscometer) and a solid content of 50%.
1) was obtained.

(Note 1) RMA-450M: Nippon Emulsifier Co., Ltd., methoxypolyethylene glycol monomethacrylate
G (45-mer) Preparation Example 2 Preparation Example 1 was repeated, except that dimethylethanolamine was changed to triethylamine (bp 90 ° C.) as a neutralizing agent. (Ga
(Donner-foam viscometer) to obtain a water-soluble acrylic resin solution (A-2) having a solid content of 50%.

Production Example 3 In Production Example 1, dimethylethanolamine was replaced with ammonium methylpropanol (bp 16) as a neutralizing agent.
5 ° C.) except that the acid value is 3
1. A water-soluble acrylic resin solution (A-3) having a viscosity of Z3 (Gardona foam viscometer) and a solid content of 50% was obtained.

Production Example 4 of Water-Dispersible Resin A reaction vessel was charged with 140 parts of deionized water and "Newcol-70".
7SF "(manufactured by Nippon Emulsifier Co., Ltd., surfactant, solid content 30
%) And a monomer mixture (methyl methacrylate)
55 parts, styrene 8 parts, n-butyl acrylate 9
Part, 2-hydroxyethyl acrylate 5 parts, 1,6-
Hexanediol diacrylate (2 parts) and methacrylic acid (1 part) were added, and the mixture was stirred and mixed in a nitrogen stream.
At 0 ° C., 3 parts of 3% ammonium persulfate were added. Then 8
Raise the temperature to 0 ° C. and leave the remaining 79 parts of the monomer mixture,
A pre-emulsion comprising 2.5 parts of "Newcol-707SF", 4 parts of 3% ammonium persulfate and 42 parts of deionized water was added to the reaction vessel over 4 hours using a metering pump, and the mixture was aged for 1 hour after the addition was completed. .

Further, at 80 ° C., a monomer mixture (5 parts of methyl methacrylate, 7 parts of n-butyl acrylate, 5 parts of 2-ethylhexyl acrylate, 3 parts of methacrylic acid and “Newcol-707SF”) "0.5 parts)
20.5 parts and 4 parts of 3% ammonium persulfate were simultaneously dropped in parallel over 1.5 hours, aged for 1 hour after the addition was completed, diluted with 30 parts of deionized water, and dried at 30 ° C. with 200 mesh nylon cloth. Filtered. Deionized water was further added to the filtrate, and the pH was adjusted to 7.5 with dimethylethanolamine to obtain an acrylic resin emulsion (B-1) having an average particle diameter of 0.1 μm and a solid content of 20%.

Preparation Example 5 Preparation Example 4 was repeated, except that dimethylethanolamine was changed to triethylamine as a neutralizing agent. The pH was 7.6, the average particle size was 0.15 μm, and the acryl was 23% solid. A resin emulsion (B-2) was obtained.

Production Example 6 Production Example 4 was carried out in the same manner as in Production Example 4 except that dimethylethanolamine was changed to ammonium methylpropanol as a neutralizing agent, and the pH was 7.4 and the average particle diameter was 0.1.
Acrylic resin emulsion with a solid content of 22 μm (B-
3) was obtained.

Production Example 7 Polybutylene adipate 11 having a number average molecular weight of 2,000
5.5 parts, 115.5 parts of polycaprolactone diol having a number average molecular weight of 2000, dimethylolpropionic acid 2
3.2 parts, 6.5 parts of 1,4-butanediol and 1-isocyanato-3-isocyanatomethyl-3,5,5
120.1 parts of trimethylcyclohexane was charged into a polymerization vessel and reacted at 85 ° C. for 7 hours in a nitrogen stream with stirring to obtain a terminal NCO prepolymer having an NCO content of 4.0%. Next, the prepolymer was cooled to 50 ° C., and 165 parts of acetone was added and uniformly dissolved. Then, 15.7 parts of dimethylethanolamine was added with stirring, and 600 parts of deionized water was added while keeping the temperature at 50 ° C. or lower. The obtained aqueous 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 obtain a urethane resin emulsion (B-4) having a solid content of 39%. Was.

Preparation Example 8 The same procedure as in Preparation Example 7 was carried out except that dimethylethanolamine was changed to triethylamine as a neutralizing agent, and a urethane resin emulsion having a solid content of 39% (B
-5) was obtained.

Preparation Example 9 The same procedure as in Preparation Example 7 was carried out except that dimethylethanolamine was changed to ammonium methylpropanol as a neutralizing agent, to produce a urethane resin emulsion (B-6) having a solid content of 40%. ) Got.

Adjustment of Aluminum Paste An aluminum pigment paste “MG-5” was added to a stirring and mixing vessel.
17 parts of "1" (manufactured by Asahi Kasei Corporation, metal content: 66.3%) and 20 parts of butyl cellosolve were added and mixed by stirring to obtain an aluminum paste (C-1).

Adjustment of Titanium White Paste In a stirring and mixing vessel, 20 parts of titanium white "CR-95" (manufactured by Teica) and "BYK-184" (manufactured by BYK-Chemie, Inc.)
10 parts of a pigment dispersant) and 100 parts of deionized water,
Further, the mixture was dispersed in a sand mill for 30 minutes to obtain titanium white paste (C-2).

Preparation of basecoat paint Example 1 Aluminum paste (C-1) obtained above 1100.1
Part and the water-soluble acrylic resin solution obtained in Production Example 1 (A-
1) Add 60 parts to a stirring and mixing vessel, and after stirring for 1 hour, 350 parts of an acrylic resin emulsion (B-1), "Primal ASE-60" (manufactured by Rohm and Haas Company, thickener) 17.9 Was added and stirring was continued for another hour. The resulting mixture was diluted with dimethylethanolamine to pH 8.0.
Then, deionized water was added to obtain a metallic base paint having a solid content of 15%.

Examples 2 to 4 and Comparative Examples 1 to 4 Each base coat paint was obtained in the same manner as in Example 1 except that the components and formulations shown in Table 1 were used. still,
Table 1 shows the solid content, wherein a is dimethylethanolamine, b is trimethylamine, and c is ammonium methylpropanol as neutralizing agents for pH adjustment.

[0064]

[Table 1]

Coating Examples 5-8 and Comparative Examples 5-8 A commercially available lacquer was applied on a 300 × 100 × 0.8 mm mild steel plate.
The primer surfacer was coated with a dry film thickness of 40 μm, dried at room temperature for 30 minutes, and polished with # 400 water-resistant abrasive paper to obtain a coated plate. On the plate to be coated, a coating film of “TC-71 Clear” (manufactured by Kansai Paint Co., Ltd., aminoacrylic resin) was formed as an old coating film of an automobile outer panel, and the base coat obtained above was formed thereon. -Paint was applied with a spray gun to a dry film thickness of 15 µm, left standing for 10 minutes,
"Retane PG2KM Clear" (Kansai Paint Co., Ltd., urethane-cured clear)
Was coated with a spray gun so as to have a dry film thickness of about 40 μm, and was forcibly dried at 60 ° C. for 20 minutes to obtain each test coated plate.

The test coated plate obtained was subjected to the following performance tests. Table 2 shows the results.

(1) Adhesion: Each coated plate was placed in water at 20 ° C. for 7 minutes.
After dipping for a day and taking out, the coating film was cross-cut so as to reach the base material, and an adhesive cellophane tape was stuck to the coated surface and the coated film surface after strong peeling was evaluated (（: no peeling,
Δ: slight peeling, ×: significant peeling).

(2) Water resistance: Each coated plate was immersed in a constant temperature water bath at 40 ° C. for 14 days, taken out, and left standing for 1 hour to visually evaluate the state of the coating film. (○: no abnormality, Δ: slightly glossy, ×: glossy, blistering)

[0069]

According to the present invention, by using a specific amine as a neutralizing agent in a paint, a coating film having excellent water resistance and adhesion can be formed even at room temperature drying such as for automobile repair. The composition of the present invention is very useful as a waterborne basecoat paint.

[0070]

[Table 2]

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C09D 133/06 C09D 133/06 175/04 175/04

Claims (6)

[Claims] 1. A water-based coating composition comprising a water-soluble resin (A) and / or a water-dispersible resin (B) and a pigment (C) as main components, wherein a neutralizing agent (D) in the coating is used. And the boiling point is 1
An aqueous coating composition using an amine having one or more hydroxyl groups in one molecule at 50 ° C. or lower. 2. The aqueous coating composition according to claim 1, wherein the neutralizing agent (D) is dimethylethanolamine. 3. The water-soluble resin (A) may be an alkylene oxide group-containing (meth) acrylate, a cyclic saturated hydrocarbon group-containing (meth) acrylate, an acid group-containing monomer, or another unsaturated monomer. The aqueous coating composition according to claim 1 or 2, which is a water-soluble acrylic resin obtained by neutralizing an acrylic copolymer obtained by copolymerizing-with a neutralizing agent. 4. The aqueous coating composition according to claim 1, wherein the water-dispersible resin (B) is an acrylic resin emulsion and / or a urethane resin emulsion. 5. The use ratio of the water-soluble resin (A) and the water-dispersible resin (B) is from 5/95 to 50/5 in terms of solids weight ratio.
The aqueous coating composition according to any one of claims 1 to 4, which is 0. 6. A base coat is coated with a base coat paint,
Next, in a method of applying a top clear paint, the base paint contains a water-soluble resin (A) and / or a water-dispersible resin (B) and a pigment (C) as main components, and A coating method using an aqueous coating composition comprising an amine having a boiling point of 150 ° C. or lower and having one or more hydroxyl groups in one molecule as a neutralizing agent (D) therein.