JP2003286434A - Water-based coating composition and method for forming multilayer coating film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water-based coating composition which gives a coating film exhibiting good visual external appearances and excellent flip-flop properties, and a method for forming a multilayer coating film. <P>SOLUTION: A monomer mixture A having an acid value of 30-150 and a hydroxy value of 10-100 is subjected to solution polymerization in an organic solvent to synthesize a copolymer solution. The copolymer solution is converted into an aqueous solution and then the organic solvent is removed under reduced pressure to give an aqueous resin solution for emulsion polymerization. A monomer mixture B having an acid value of at most 20 and a hydroxy value of at most 100 is subjected to emulsion polymerization using the resin in an aqueous solution for emulsion polymerization as a protective colloid thereby synthesizing a core resin in the protective colloid to give a water-based resin dispersion. The water-based coating composition comprises the water-based resin dispersion and a glittering material. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-based coating composition applied to automobile bodies and the like, and a method for forming a multilayer coating film formed on automobile bodies and the like.

[0002]

2. Description of the Related Art Conventionally, paints used for industrial use are called solvent-type paints and use an organic solvent as a diluting solvent. Therefore, a large amount of organic solvent was contained in the paint, but in consideration of the environment in recent years, water-based paints have been developed in which the contained organic solvent is reduced and water is used as a diluting solvent. As such a water-based paint, for example,
JP-A-7-53913 discloses a polymer obtained by neutralizing at least a part of a polymer containing an amide group-containing ethylenically unsaturated monomer, an acidic group-containing ethylenically unsaturated monomer and a hydroxyl group-containing ethylenically unsaturated monomer. Disclosed is an aqueous coating composition containing the above resin and an aqueous dispersion of carboxyl group-containing acrylic resin particles.

Generally, a coating film obtained from a conventional water-based paint has a problem that the smoothness and the appearance are poor as compared with the conventional solvent-based paint. Particularly, a coating film obtained from a water-based paint containing a glittering material as a coloring component, which is used for an automobile body requiring high appearance, has a visual appearance, a flip-flop property, etc., as compared with a solvent-based base paint. There was a problem of being extremely defective.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide an aqueous coating composition having a good visual appearance of the obtained coating film and excellent flip-flop property, and a method for forming a multilayer coating film. It is in.

[0005]

The present invention has an acid value of 30 to 30.
At 150, a monomer mixture solution A having a hydroxyl value of 10 to 100 is solution-polymerized in an organic solvent to synthesize a copolymer solution, the copolymer solution is converted into an aqueous solution, and the organic solution is reduced under reduced pressure. After the solvent is removed to obtain an aqueous solution resin for emulsion polymerization, the aqueous solution resin for emulsion polymerization is used as a protective colloid to emulsion-polymerize a monomer mixture B having an acid value of 20 and a hydroxyl value of 100. An aqueous coating composition comprising an aqueous resin dispersion obtained by synthesizing a core resin in the protective colloid, and a glittering material.

The present invention further includes the general formula (1) or (2):

[Chemical 3] (In the formula (1), R ¹ , R ² and R ³ represent hydrocarbon groups which may be the same or different from each other, R ¹ represents a hydrocarbon group which may have a urethane bond, R ^{1 3} represents a branched chain or secondary hydrocarbon group, j is a number of 1 or more,
k is a number within the range of 1 to 500. )

[Chemical 4] (In the formula (2), R ¹ , R ² , R ³ , R ⁴ and R ⁵ represent hydrocarbon groups which may be the same or different from each other;
¹ represents a hydrocarbon group which may have a urethane bond, R ³ represents a branched or secondary hydrocarbon group, and n represents 2
The above numbers, j is a number of 2 or more, and k and m are numbers in the range of 1 to 500, respectively. ) At least one of the urethane-based compound represented by, the content of the urethane-based compound is 0.01 to 20% by weight in terms of solid content with respect to the resin solid content in the coating composition, It is the above-mentioned aqueous coating composition.

In the present invention, the monomer mixed liquid A and the monomer mixed liquid B are at least one selected from the group consisting of (meth) acrylic acid esters, styrene monomers, (meth) acrylonitrile and (meth) acrylamide. The above-mentioned aqueous coating composition containing the polymerizable unsaturated monomer of.

In the present invention, the weight A of the monomer mixed liquid A is
w and the weight Bw of the monomer mixture B are 10/1.
The above water-based coating composition satisfies the relationship of 00 ≦ Aw / (Aw + Bw) ≦ 50/100.

The present invention is the above aqueous coating composition, wherein the monomer mixture liquid A further contains a crosslinking monomer as a copolymerization component.

The present invention is the above aqueous coating composition, wherein the monomer mixture liquid B further contains a crosslinking monomer as a copolymerization component.

In the present invention, the average number of primary hydroxyl groups contained in one molecule is 0.02 or more, and the number average molecular weight is 30.
The above water-based coating composition contains a polyether polyol having a water tolerance value of 0 to 3,000 and 2.0 or more. The present invention is the aqueous coating composition, wherein the polyether polyol has at least one primary hydroxyl group in one molecule and has a hydroxyl value of 30 to 700.

Further, the present invention is a method for forming a multilayer coating film by coating a water-based base coating composition on an object to be coated, applying a clear coating composition thereon, and then heating and curing the coating composition. The aqueous base paint is any one of the aqueous paint compositions described above, which is a method for forming a multilayer coating film.

Further, the present invention is a multilayer coating film formed by the above-mentioned method for forming a multilayer coating film.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION First, the aqueous coating composition of the present invention will be described. The aqueous coating composition of the present invention is characterized by containing an aqueous resin dispersion obtained by synthesizing an aqueous resin for emulsion polymerization as a protective colloid and a core resin in the protective colloid, and a glittering material. is there.

The aqueous resin dispersion contained in the aqueous coating composition of the present invention is obtained by synthesizing a core resin in the protective colloid using an aqueous solution resin for emulsion polymerization as a protective colloid.

Specifically, the above aqueous resin dispersion is obtained by obtaining a water-soluble resin for emulsion polymerization, using it as a protective colloid, and synthesizing a core resin in this protective colloid.

In the step of obtaining the water-soluble resin for emulsion polymerization, first, the acid value is 30 to 150 and the hydroxyl value is 10 to 10.
The monomer mixed solution A of 100 is solution polymerized in an organic solvent to obtain a copolymer solution, and then the copolymer solution is converted into an aqueous solution, and the organic solvent is removed under reduced pressure.

The method of solution polymerization is not particularly limited and may be carried out by a conventional method, specifically, a method of polymerizing while dropping the above-mentioned monomer mixture A in an organic solvent in the presence of a radical polymerization initiator. Can be mentioned.

The acid value of the above-mentioned monomer mixed liquid A has a lower limit of 3
0, the upper limit 150, preferably the lower limit 40, the upper limit 130, the hydroxyl value is the lower limit 10, the upper limit 100, preferably the lower limit 30,
The upper limit is 80. When the above acid value is less than 30, when an alkali is added to the obtained aqueous resin dispersion, sufficient viscosity does not occur, and desired viscosity and structural viscosity cannot be obtained. Further, when the acid value exceeds 150, the water resistance of the coating film obtained after being made into a paint is lowered. On the other hand, when the hydroxyl value is less than 10, the coating film obtained after being made into a coating has insufficient curability. On the other hand, when the hydroxyl value exceeds 100, the compatibility with other components such as a curing agent decreases, and the resulting coating film becomes non-uniform.

The acid value and hydroxyl value in the present specification are
It is a value obtained by calculation from the blending amount of each polymerizable unsaturated monomer contained in the monomer mixed liquid.

The above-mentioned monomer mixed solution A contains an acid group-containing polymerizable unsaturated monomer and a hydroxyl group-containing polymerizable unsaturated monomer as essential components, and optionally contains other polymerizable unsaturated monomers.

The acid group-containing polymerizable unsaturated monomer is 1
A compound having one or more unsaturated double bonds and one or more acid groups in the molecule, and specifically, acrylic acid, methacrylic acid, crotonic acid, propylacrylic acid, isopropylacrylic acid, itaconic acid, maleic anhydride and Carboxylic acid group-containing polymerizable unsaturated monomers such as fumaric acid; Sulfonic acid group-containing polymerizable unsaturated monomers such as t-butylacrylamide sulfonic acid; Phosphoric acid group-containing polymerizable unsaturated monomers such as light ester PM (manufactured by Light Ester Co.) A saturated monomer etc. can be mentioned. You may use 2 or more types of these.

As the hydroxyl group-containing polymerizable unsaturated monomer, specifically, 2-hydroxyethyl acrylate,
2-hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, N-methylol acrylamide, allyl alcohol, Praxel FA series, Praxel FM series (all are from Daicel Chemical Industries Ltd. ) -Caprolactone-modified acrylic monomer and the like. You may use 2 or more types of these.

As the above-mentioned other polymerizable unsaturated monomer, for example, a monoester of a monohydric alcohol having 1 to 24 carbon atoms and acrylic acid or methacrylic acid is preferable, and examples thereof include methyl (meth) acrylate and ethyl (meth). Acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, lauryl (meth) (Meth) acrylic acid esters such as acrylate and stearyl (meth) acrylate; styrene-based monomers such as styrene and α-methylstyrene; and (meth) acrylonitrile and (meth) acrylamide. You may use 2 or more types of these.

The above organic solvent is not particularly limited, and ester solvents such as ethyl acetate, n-butyl acetate, isobutyl acetate, methyl cellosolve acetate, butyl carbitol acetate; methanol, ethanol, isopropanol, n-butanol, sec- Lower alcohol solvents such as butanol and isobutanol; ether solvents such as n-butyl ether, dioxane, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether and the like can be mentioned.

The above radical polymerization initiator is not particularly limited, and specific examples thereof include peroxide compounds such as t-butyl hydroperoxide and t-butyl peroxy-2-ethoxyhexanoate; azobisiso Examples thereof include azo compounds such as butyronitrile, azobis (2-methylbutyronitrile), and azobisdimethylvaleronitrile.

Subsequently, the obtained copolymer solution is converted into an aqueous solution, and the organic solvent is removed under reduced pressure. The conversion method is not particularly limited, and examples thereof include a method of neutralizing the acidic groups contained in the copolymer with a neutralizing base, and then adding water to dissolve the resin in water. The neutralizing base is not particularly limited, for example, monomethylamine, dimethylamine, trimethylamine, monoethylamine, triethylamine, monoisopropylamine,
Diethylenetriamine, triethylenetriamine, triethylenetetramine, monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine, dimethylethanolamine, 2-aminomethylpropanol, morpholine, methylmorpholine, piperazine, ammonia, sodium hydroxide , Potassium hydroxide, lithium hydroxide and the like.

As a method for removing the organic solvent under the above reduced pressure, an ordinary reduced pressure distillation method can be used. For example, a reduced pressure of 50 to 200 mmHg and a temperature of 40 to 80 ° C.
It can be performed in 1 to 10 hours. The organic solvent is preferably removed almost completely.

The weight average molecular weight of the aqueous solution resin for emulsion polymerization thus obtained is not particularly limited and is generally about 10,000 to 50,000, for example, about 20,000 to 30,000.

In the step of obtaining the above-mentioned aqueous resin dispersion, the obtained aqueous solution resin for emulsion polymerization is used as a protective colloid, and the monomer mixture B is emulsion-polymerized to synthesize the core resin in the protective colloid.

Examples of the emulsion polymerization method include a method of dropping the monomer mixture solution B in the presence of the emulsion polymerization aqueous solution resin and the free radical polymerization initiator. The monomer mixture B has an acid value of upper limit 20, preferably upper limit 10, and a hydroxyl value of 100, preferably lower limit 20 and upper limit 70. When the acid value is more than 20, the viscosity of the dispersion after the alkali is added to the prepared aqueous resin dispersion to increase the viscosity is largely changed with time, and the stability is lacking. On the other hand, when the hydroxyl value exceeds 100, the water resistance of the coating film obtained after being made into a paint is lowered, or the compatibility with other components such as a curing agent is poor and the coating film obtained becomes non-uniform.

Like the monomer mixture solution A, the monomer mixture solution B contains the acid group-containing polymerizable unsaturated monomer, the hydroxyl group-containing polymerizable unsaturated monomer and the other polymerizable unsaturated monomer. There is. Unlike the monomer mixture liquid A, the monomer mixture liquid B does not necessarily have to include the acid group-containing polymerizable unsaturated monomer and the hydroxyl group-containing polymerizable unsaturated monomer. Also,
A chain transfer agent may be included if necessary.

As the above free radical polymerization initiator,
Persulfates such as potassium persulfate, sodium persulfate, ammonium persulfate, which decompose in water to generate free radicals, and reduction of these and hydrogen peroxide and acidic sodium sulfite, sodium thiosulfate, rongalit, ascorbic acid, etc. So-called redox type initiators can be mentioned in combination with the agent.

During the emulsion polymerization, other emulsifiers may be supplementarily used in addition to the aqueous solution resin for emulsion polymerization. Examples of the other emulsifiers include, for example, micelle compounds having a hydrocarbon group having 6 or more carbon atoms and a hydrophilic moiety such as carboxylate, sulfonate or sulfate partial ester in the same molecule. Anionic or nonionic emulsifiers selected from Among these, as anionic emulsifiers, specifically, alkali metal salts or ammonium salts of sulfuric acid half esters of alkylphenols or higher alcohols; alkali metal salts or ammonium salts of alkyl or allyl sulfonates; polyoxyethylene alkylphenyl ethers,
Examples thereof include alkali metal salts or ammonium salts of sulfuric acid half esters of polyoxyethylene alkyl ether or polyoxyethylene allyl ether. Specific examples of the nonionic emulsifier include polyoxyethylene alkylphenyl ether, polyoxyethylene alkyl ether, polyoxyethylene allyl ether, and the like. In addition to these general-purpose anionic emulsifiers and nonionic emulsifiers, they have a radical-polymerizable unsaturated double bond in the molecule, that is, acrylic, methacryl, propenyl, allyl, allyl ether, maleic acid Examples thereof include various anionic and nonionic reactive emulsifiers having groups such as
You may use 2 or more types of these.

The weight average molecular weight of the core resin thus obtained is not particularly limited, but generally 50,000 to
It is about 1,000,000, for example, about 100,000 to 1,000,000.

Here, in the above aqueous resin dispersion,
The weight Aw of the monomer mixed solution A and the weight Bw of the monomer mixed solution B are 10/100 ≦ Aw / (Aw + B
w) It is preferable to use each polymerizable unsaturated monomer so as to satisfy the relation of ≦ 50/100. Aw / (Aw +
When Bw) is less than this range, the resulting aqueous resin dispersion may have insufficient alkali thickening. When it is large, a sufficient alkali thickening can be obtained, but the coating film obtained after being made into a paint Water resistance may decrease. More preferably, 20/100 ≦ Aw / (Aw + Bw) ≦ 4
It is to satisfy the relationship of 0/100.

In the present invention, one or both of the monomer mixed liquid A and the monomer mixed liquid B are the above-mentioned acid group-containing polymerizable unsaturated monomer, the above hydroxyl group-containing polymerizable unsaturated monomer and the above-mentioned other polymerizable unsaturated. In addition to the monomer, it is also preferable to further include a crosslinkable monomer as a copolymerization component. By copolymerizing a crosslinkable monomer, the resin has a crosslinked structure, or depending on the type of the crosslinkable monomer, it has a crosslinked structure due to the reaction with a crosslinking auxiliary agent during the formation of a coating film, which is excellent in solvent resistance. A coating film is obtained.

There is a great advantage in improving the solvent resistance of the coating film. For example, when the aqueous coating composition of the present invention is used as an aqueous base coating when forming a multi-layer coating in an automobile or the like, a clear coating is applied on the formed base coating, but a clear coating is applied. Since the surface of the base coating film is not attacked or the altered layer is not generated by the solvent contained therein, interlayer diffuse reflection between the base coating film and the clear coating film is reduced, and as a result, the appearance is excellent. A multilayer coating film is obtained. In addition, the water-based coating composition of the present invention can be used for various coating applications such as exposure to or contact with a solvent.

As the crosslinkable monomer, it is possible to use a carbonyl group-containing monomer, a hydrolyzable silyl group-containing monomer, a glycidyl group-containing monomer, a crosslinkable monomer having a polymerizable unsaturated group such as various polyfunctional vinyl monomers, and the like. it can. N-methylol (meth) acrylamide and N-methoxymethyl (meth) acrylamide also have crosslinkability but are weak.

As the carbonyl group-containing monomer, for example, acrolein, diacetone (meth) acrylamide, acetoacetoxyethyl (meth) acrylate, formyl styrene, vinyl alkyl ketone having 4 to 7 carbon atoms (for example, vinyl methyl ketone, Examples thereof include monomers having a keto group such as vinyl ethyl ketone and vinyl butyl ketone). Of these, diacetone (meth) acrylamide is preferred. When such a carbonyl group-containing monomer is used, a hydrazine compound is added to the aqueous resin dispersion as a crosslinking aid,
A cross-linking structure is formed during coating film formation. Alternatively, the hydrazine-based compound may be added after mixing the aqueous resin dispersion and the glittering material. The aqueous coating composition of the present invention may contain a hydrazine compound.

Examples of hydrazine compounds include oxalic acid dihydrazide, malonic acid dihydrazide, glutaric acid dihydrazide, succinic acid dihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, and the like, saturated aliphatic carboxylic acid dihydrazide having 2 to 18 carbon atoms. ; Monoolefinic unsaturated dicarboxylic acid dihydrazides such as maleic acid dihydrazide, fumaric acid dihydrazide, itaconic acid dihydrazide; phthalic acid dihydrazide, terephthalic acid dihydrazide, isophthalic acid dihydrazide, pyromellitic acid dihydrazide, trihydrazide or tetrahydrazide; nitrile trihydrazide; , Citric acid trihydrazide, 1,2,4-benzene trihydrazide, ethylenediaminetetraacetic acid tetrahydrazide, 1,4,5,8-naphthoic acid tetrahydrazide, carbo Polyhydrazide obtained by reacting a low polymer having an acid lower alkyl ester group with hydrazine or hydrazine hydrate (hydrazine hydrate); carbonic acid dihydrazide, bissemicarbazide;
Examples include diisocyanates such as hexamethylene diisocyanate and isophorone diisocyanate, and polyisocyanate compounds derived therefrom, and hydrazine compounds and water-based polyfunctional semicarbazides obtained by excessively reacting the above-exemplified dihydrazides.

Examples of the hydrolyzable silyl group-containing monomer include γ- (meth) acryloxypropylmethyldimethoxysilane, γ- (meth) acryloxypropylmethyldiethoxysilane and γ- (meth) acryloxypropyltriethoxy. Examples thereof include monomers containing an alkoxysilyl group such as silane.

As the glycidyl group-containing monomer, glycidyl (meth) acrylate, β-methylglycidyl (meth) acrylate, (3,4-epoxycyclohexyl) methyl (meth) acrylate, 3-chloro-2-hydroxypropyl (meth) Acrylate etc. are mentioned.

Examples of polyfunctional vinyl monomers include divinylbenzene, ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, hexanediol di (meth) acrylate, diethylene glycol di (meth) acrylate, polyethylene glycol di (meth). ) Acrylate, polypropylene glycol di (meth) acrylate, allyl (meth) acrylate, neopentyl glycol di (meth) acrylate,
Examples thereof include divinyl compounds such as pentaerythritol di (meth) acrylate, and pentaerythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and the like.

The above crosslinkable monomers may be used alone or in combination of two or more. Among the above-mentioned crosslinkable monomers, a carbonyl group-containing monomer and a hydrolyzable silyl group-containing monomer are preferable from the viewpoint of the effect of improving the solvent resistance of the obtained coating film.

When a crosslinkable monomer is used, in both the monomer mixture A and the monomer mixture B,
The crosslinkable monomer is added in an amount of 0.5 to 10 relative to the total amount of the acid group-containing polymerizable unsaturated monomer, the hydroxyl group-containing polymerizable unsaturated monomer and the other polymerizable unsaturated monomer.
It may be used in an amount of 1% by weight, preferably 1 to 8% by weight. Although it depends on the kind of the monomer, a cross-linking structure of the resin A for emulsion polymerization or the core resin B can be obtained in the amount used within this range, and the effect of improving the solvent resistance of the coating film can be obtained. When the amount used is less than this range, it is difficult to obtain the effect of improving the solvent resistance of the coating film. On the other hand, when the amount used is more than this range, there is a problem such as gelation in the resin production process, or the production of the resin. Even if there is no problem in the process, there is a case where the formation of the coating film becomes nonuniform.

The crosslinked structure may be introduced into both the resin A for emulsion polymerization or the core resin B, or only one of them may be introduced. In order to introduce a crosslinked structure into only one of them, when Bw ≧ Aw, introducing a crosslinked structure into the resin B has a larger effect of improving solvent resistance of the coating film than introducing a crosslinked structure into the resin A. To be In the case of introducing a crosslinked structure into both the resin A and the resin B, when a carbonyl group-containing monomer is used as the crosslinkable monomer, the hydrazine-based compound acts between the resin A and the resin B during the coating film formation. Also, a crosslinked structure is easily formed.

Thus, the aqueous resin dispersion contained in the aqueous coating composition of the present invention can be obtained.

Further, the aqueous coating composition of the present invention contains a glitter material. The glittering material imparts aesthetics and design to the resulting coating film. The shape of the glittering material is not particularly limited and it may be colored, for example, the average particle diameter (D ₅₀ ) is 2 to ₅₀ μm,
A scaly luster color material having a thickness of 0.1 to 5 μm is preferable. Further, those having an average particle diameter in the range of 10 to 35 μm are more preferable because they are excellent in glitter feeling. Specific examples thereof include uncolored or colored metallic luster pigments such as metals or alloys such as aluminum, copper, zinc, iron, nickel, tin, and aluminum oxide, and mixtures thereof. Besides, interference mica pigments, white mica pigments, graphite pigments, etc. are also included in this. The concentration of the glittering material is generally 18.0% by weight, 0.01% by weight, and 15% by weight with respect to the solid content of the coating resin (solid content of all the resins contained in the coating material). It is preferably 0.0% by weight, more preferably 0.01% by weight as the lower limit and 13.0% by weight as the upper limit.

When the glittering material is a scale-like glittering material, the aqueous coating composition of the present invention preferably further contains a phosphoric acid group-containing acrylic resin. This phosphoric acid group-containing acrylic resin is an acrylic resin obtained by copolymerizing a polymerizable unsaturated monomer represented by the following general formula (3) with another polymerizable unsaturated monomer.

[0051]

[Chemical 5]

(In the formula (3), X represents a hydrogen atom or a methyl group, Y represents an alkylene group having 2 to 4 carbon atoms, and h represents an integer of 3 to 30.)

The phosphoric acid group-containing acrylic resin is used for favorably dispersing the scaly luster color material. The phosphoric acid group-containing acrylic resin has a number average molecular weight of 100 as the lower limit.
It is preferably 0 and the upper limit is 50,000. When the number average molecular weight is less than 1000, the flaky glitter may not be sufficiently dispersed, and when the number average molecular weight exceeds 50,000, the appearance of the resulting coating film may be deteriorated.

The phosphoric acid group-containing acrylic resin is
The solid content has an acid value of 15 as a lower limit and 200 as an upper limit, and the acid value of the phosphoric acid group is 10 as a lower limit and 150 as an upper limit.
Is preferred. If the acid value is less than 15, the scale-like brightening agent may not be sufficiently dispersed, and if the acid value is more than 200, the storage stability of the aqueous coating composition may decrease. . Further, the phosphoric acid group-containing acrylic resin may have a hydroxyl value for ensuring curability, and the value is preferably 20 as the lower limit and 200 as the upper limit.

The phosphoric acid group-containing acrylic resin is preferably contained in a lower limit of 0.01 parts by weight and an upper limit of 5 parts by weight, more preferably in a lower limit of 0.1 parts by weight, based on 100 parts by weight of the coating resin solid content. The upper limit is 4 parts by weight, particularly preferably the lower limit is 0.2 parts by weight and the upper limit is 3 parts by weight. If the content of the phosphoric acid group-containing acrylic resin is too low, the performance of the coating film may deteriorate. Further, if the content of the phosphoric acid group-containing acrylic resin is too large, the storage stability of the coating composition deteriorates.

Examples of the polymerizable unsaturated monomer represented by the above general formula (3) include acid phosphooxyhexa (oxypropylene) monomethacrylate and acid phosphooxide deca (oxypropylene) monomethacrylate. . The other polymerizable unsaturated monomer is a polymerizable unsaturated monomer copolymerizable with the polymerizable unsaturated monomer represented by the general formula (3), and two or more kinds may be used. Further, since the obtained copolymer, that is, the acrylic resin can be cured by the curing agent, it may be a polymerizable unsaturated monomer having an acidic group such as a carboxylic acid group or a sulfonic acid group or a hydroxyl group.

When the aqueous coating composition of the present invention contains a metallic luster colorant as a coloring component, it serves as a corrosion inhibitor for the luster pigment or improves the wettability of the luster pigment to obtain a multilayer coating film. In order to improve the physical properties of, it is preferable to include a phosphoric acid group-containing compound having an alkyl group. The alkyl group preferably has a lower limit of 8 and an upper limit of 18 and more preferably has a lower limit of 10 and an upper limit of 14. When the number of carbon atoms is less than 8, the wettability is lowered and the adhesiveness is lowered, and when the number of carbon atoms is more than 18, the compound crystals may be precipitated in the paint to cause a problem.

Further, the hydrophilic-lipophilic balance HL of the above compounds
B preferably has a lower limit of 3 and an upper limit of 12, and more preferably a lower limit of 4 and an upper limit of 8. If the HLB is out of the above range, the wettability may decrease. HLB is a Griffin formula based on the weight fraction:
HLB = 20 × (MH / M) [wherein, MH means the molecular weight of the hydrophilic group portion, and M means the molecular weight of the activator]. Further, the molecular weight of the hydrophilic group portion can be determined by using the molecular weight of phosphoric acid ester, sulfonic acid and carboxylic acid.

As such a compound, specifically, 2
-Ethylhexyl acid phosphate, mono- or di-diisodecyl acid phosphate, mono- or di-
Examples thereof include tridecyl acid phosphate, mono- or di-lauryl acid phosphate, mono- or di-nonylphenyl acid phosphate, and the like.

When the aqueous coating composition of the present invention contains the above compound, the content of the above compound is preferably 0.1% by weight as the lower limit and 5% by weight as the upper limit based on the solid content of the coating resin, and the lower limit is 0%. More preferably, it is 0.2% by weight and the upper limit is 2% by weight. When the content is less than 0.1% by weight,
If the adhesion is reduced and the content exceeds 5% by weight, the water resistance may be reduced.

The aqueous coating composition of the present invention may contain the urethane compound represented by the above general formula (1) or (2). By including this urethane compound, the flip-flop property of the obtained coating film can be further improved. Here, in the formula (1) or (2),
R ¹ , R ² , R ³ , R ⁴ and R ⁵ represent hydrocarbon groups which may be the same or different from each other, R ¹ represents a hydrocarbon group which may have a urethane bond, R ³ Represents a branched chain or secondary hydrocarbon group, n is a number of 2 or more, j is 1 or more in the general formula (1), and 2 in the general formula (2).
It is the above number, and k and m are numbers in the range of 1 to 500, respectively.

The urethane compound represented by the above general formula (1) is, for example, an aliphatic, aromatic or alicyclic R compound.
^One or more mono- or polyisocyanates represented by 1- (NCO) _j and HO- (R ² -O) _k -R ³
It can be obtained by reacting one or more polyether monoalcohols represented by In this case, R ^{1 to} R ³ in the formula are the above R ¹ −
It is determined by (NCO) _j and HO- (R ² —O) _k —R ³ .

As a method for obtaining the urethane compound represented by the general formula (1), for example, R ^1- (NCO) _j
And a mono- or polyisocyanate represented by HO- (R
^2- O) _k -R ³ and a polyether monoalcohol are blended so that the ratio of the hydroxyl value and the isocyanate value from each compound is 1.05 / 1 to 1.4 / 1,
As in the case of the usual reaction between polyether and isocyanate, for example, a method of heating at 80 to 90 ° C. for 1 to 3 hours to carry out the reaction can be mentioned.

The urethane compound represented by the general formula (2) is, for example, a mono- or polyisocyanate represented by R ^1- (NCO) _j which is a raw material for obtaining the general formula (1). and polyisocyanate j is 2 or more, and a polyether monoalcohol represented by _{^{HO- (R 2 -O) k -R}} 3, ^{further, R 4 - [(O-} R 5) m -
It can be obtained by reacting one or more polyether polyols represented by OH] _n as a raw material. In this case, R ^{1 to} R ⁵ in the formula are the above R ⁴ −
_{^{[(O-R 5) m}} -OH] n, R 1 - (NCO) j, H
It is determined by _{^{O- (R 2 -O) k -R}} 3.

Among the mono- or polyisocyanates represented by R ^1- (NCO) _j , the polyisocyanate in which j is 2 or more has two or more isocyanate groups in one molecule, and In the above general formula (1)
The polyisocyanate represented by R ^1- (NCO) _j (wherein j is 2 or more) mentioned above can be mentioned. Further, the polyether monoalcohol represented by _{^{HO- (R 2 -O) k -R}} 3 is not particularly limited as long as it is a polyether monohydric alcohol branched or secondary, specifically, The thing mentioned in the said General formula (1) can be mentioned.

Examples of the polyether polyol represented by R ⁴ -[(O-R ⁵ ) _m -OH] _n include those described in the polyether polyol described later. Here, R ⁵ is determined by the alkylene oxide or styrene oxide to be added, but from the viewpoint of easy industrial availability, alkylene oxide or styrene oxide having 2 to 4 carbon atoms is preferable. The alkylene oxide or styrene oxide to be added may be homopolymerized, two or more kinds of polymerized or block polymerized. The degree of polymerization m is 1 to 500
Is preferable, 1 to 200 is more preferable, and 10 to 200 is further preferable. The ratio of ethylene to total R ^5, from the viewpoint of the appearance of the resulting coating film is preferably 50 to 100 wt% of the total R ^5, and more preferably 65 to 100 wt%. The molecular weight of such a polyether polyol is preferably 500 to 50,000,
It is more preferably 1000 to 20000.

As a method for obtaining the urethane compound represented by the above general formula (2), for example, the above R ^1- (NC
O) _j , one or more polyisocyanates represented by HO- (R ² —O) _k —R ³ , and 1 or 2
At least one polyether monoalcohol and R ⁴ -[(O
-R ⁵⁾ _m -OH] and one or more polyether polyols represented by _n, the ratio of the hydroxyl value and the isocyanate value from each compound 1.05 / 1 to 1.4 / 1 As in the case of the usual reaction between polyether and isocyanate, for example, a method of heating at 80 to 90 ° C. for 1 to 3 hours and reacting can be mentioned.

When the water-based coating composition of the present invention contains the urethane compound represented by the above general formula (1) or (2), its content is lower than the lower limit of 0.
It is preferable that the upper limit is 01% by weight and the upper limit is 20% by weight, and the lower limit is 0.1% by weight and the upper limit is 10% by weight. When the content is less than 0.01% by weight, the appearance of the resulting coating film is insufficiently improved, or when the aqueous coating composition contains a glittering agent as a coloring component described below, If the improvement of the flip-flop property is insufficient, or if it exceeds 20% by weight, various properties of the obtained coating film may be deteriorated.

The aqueous coating composition of the present invention may further contain a polyether polyol. Such a polyether polyol has an average lower limit of 0.02, preferably a lower limit of 0.04, and more preferably a lower limit of 1 primary hydroxyl group in one molecule. When the number of primary hydroxyl groups is less than 0.02, various properties of the obtained coating film are deteriorated. Further, the above polyether polyol may have secondary and tertiary hydroxyl groups in addition to the primary hydroxyl group, and from the viewpoint of various properties of the coating film obtained, all of the hydroxyl groups in one molecule including these may be included. The number is preferably 3 or more. The hydroxyl value of the above polyether polyol is preferably a lower limit of 30 and an upper limit of 700, more preferably a lower limit of 50 and an upper limit of 500.
If the hydroxyl value is out of the above range, the storage stability of the coating composition may be deteriorated, and various properties of the resulting coating film may be deteriorated.

Further, the number average molecular weight of the above polyether polyol has a lower limit of 300 and an upper limit of 3000, and a lower limit of 4
00 and an upper limit of 2000 are preferable. When the number average molecular weight is out of the above range or is less than 300, various properties of the obtained coating film are deteriorated. The number average molecular weight can be determined by GPC (gel permeation chromatography) using polystyrene as a standard.

Further, the water tolerance value of the above polyether polyol has a lower limit of 2.0 and preferably a lower limit of 3.0. When the water tolerance value is less than 2.0, the stability of the coating composition is deteriorated and the appearance of the resulting coating film is deteriorated. The water tolerance value is for evaluating the degree of hydrophilicity, and the higher the value, the higher the hydrophilicity. The above water tolerance measurement method is
0.5 g of the above polyether polyol was mixed and dispersed in 10 ml of acetone in a 100 ml beaker under the condition of 25 ° C., and ion-exchanged water was gradually added to the mixture using a buret until the mixture became cloudy. Measure the amount (ml) of ion-exchanged water required for. The amount (ml) of this ion-exchanged water is taken as the water tolerance value.

In this method, for example, when the polyether polyol is hydrophobic, initially the polyether polyol and acetone were in a good compatible state, but the addition of a small amount of ion-exchanged water caused an incompatible state. And white turbidity occurs in the measurement system. On the contrary, when the polyether polyol is hydrophilic, the more hydrophilic the polyether polyol is, the more ion-exchanged water is required before cloudiness occurs. Therefore, the hydrophilic / hydrophobic degree of the polyether polyol can be measured by this method.

When the aqueous coating composition of the present invention contains the above polyether polyol, the content thereof is preferably 1% by weight and 40% by weight in the solid content of the coating resin, and the lower limit is 3% by weight. It is more preferable that the upper limit is 30% by weight. If the content is less than 1% by weight, the appearance of the obtained coating film may be deteriorated, and if it exceeds 40% by weight, various properties of the obtained coating film may be deteriorated.

Specific examples of such a polyether polyol include compounds in which an alkylene oxide is added to a compound containing an active hydrogen atom. As the active hydrogen atom-containing compound, a polyhydric alcohol,
Examples thereof include polyhydric phenols and polyhydric carboxylic acids. Examples thereof include water; polyhydric alcohol components such as 1,6-hexanediol and neopentyl glycol, and tetrahydric alcohols such as diglycerin and sorbitan; adonitol and arabitol. , Xylitol, triglycerin and other pentahydric alcohols; dipentaerythritol, sorbitol, mannitol, iditol, inositol, dulcitol, talose, allose and other hexahydric alcohols, sucrose and other octahydric alcohols, polyglycerin and other polyhydric alcohols, Polyhydric phenols such as pyrogallol, hydroquinone and phloroglucin, and polyhydric phenols such as bisphenols such as bisphenol A and bisphenol sulfone; polycarboxylic acid components such as adipic acid and maleic anhydride, and mixtures of two or more thereof. Thing, and the like.

Particularly, trihydric or higher alcohols used to form a polyether polyol having 3 or more total hydroxyl groups in one molecule include glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, sorbitan, Sorbitol and the like are preferable.

Specific examples of the alkylene oxide include ethylene oxide, propylene oxide,
Examples thereof include alkylene oxides such as butylene oxide, and these can be used in combination of two or more kinds. When two or more kinds are used together, the addition format may be either block or random.

Such polyether polyols commercially available include, for example, Prime Pole P.
X-1000, Sannix SP-750, PP-40
0 (both manufactured by Sanyo Chemical Industry Co., Ltd.), PTMG-65
0 (manufactured by Mitsubishi Chemical Corporation) and the like can be mentioned. The polyether polyol is usually obtained by carrying out an addition reaction of the alkylene oxide with the active hydrogen-containing compound in the presence of an alkali catalyst at a temperature of 60 to 160 ° C. under ordinary pressure or pressure. .

Further, the above-mentioned polyether polyol is used in order to improve the pigment dispersibility in JP-A-59-138269.
As described in the publication, amino resins and hydroxyethylethyleneimine, which will be described later (for example, “HE
A "), 2-hydroxypropyl-2-aziridinylethylcarboxylate (eg, mutual medicinal product" HPAC ")
Basic substances such as can be modified as a modifier. The amount of the modifier is preferably 1 to 10% by weight based on the polyether polyol. When the amount of the modifier is less than 1% by weight, a sufficient modifying effect cannot be obtained, and when it exceeds 10% by weight, the stability of the modified polyether polyol may be deteriorated.

The water-based coating composition of the present invention may optionally contain other film-forming resin. Such a material is not particularly limited, and examples thereof include an acrylic resin, a polyester resin, an alkyd resin, an epoxy resin, and a urethane resin. In particular, the water-based coating composition of the present invention contains a scaly luster color material. In this case, it is preferable to contain a polyester resin and / or an alkyd resin for the purpose of improving the flip-flop property of the obtained coating film.

Such polyester resin and alkyd resin have a number average molecular weight of lower limit 3000 and upper limit 50000.
Is preferable, and the lower limit is 3000 and the upper limit is 30,000.
Is more preferable. The number average molecular weight is 300
If it is less than 0, the coating workability and curability are not sufficient, and if it exceeds 50,000, the nonvolatile content during coating becomes too low, which may adversely affect the coating workability.

The above polyester resin and alkyd resin preferably have an acid group, and the acid value of the resin solid content is preferably 10 as a lower limit and 100 as an upper limit, and more preferably 20 and 80 as a lower limit. preferable. When the acid value is less than 10, the water dispersibility of the resin is reduced and
If it exceeds the range, various properties of the obtained coating film may be deteriorated. The polyester resin and alkyd resin preferably have a hydroxyl group, and the hydroxyl value is lower than 1
0 and the upper limit of 180 are preferable, and the lower limit of 20 and the upper limit of 160 are more preferable. The hydroxyl value is 10
If it is less than 18, the curability of the resulting coating film decreases, and
When it exceeds 0, various properties of the obtained coating film may be deteriorated. A method for obtaining such a polyester resin and an alkyd resin is not particularly limited, and it can be obtained by polycondensing a polyvalent carboxylic acid component, a polyhydric alcohol component, and, if necessary, an oil and fat component by a conventional method.

When the polyester resin and / or alkyd resin is contained, the compounding ratio of the aqueous resin dispersion / polyester resin and alkyd resin based on the weight of the resin solid content is 5/95 as the lower limit and 95/5 as the upper limit. The lower limit is preferably 10/90, the upper limit is 85/15, and the lower limit is 20/80 and the upper limit is 70/30. If it is out of the above range, sagging at the time of coating may be suppressed or the appearance of the coating film may be deteriorated. When the above-mentioned polyester resin and / or alkyd resin is blended, it is preferable that the polyester resin and / or alkyd resin be dissolved or dispersed in an aqueous medium in advance with a neutralizing base from the viewpoint of storage stability.

Further, the aqueous coating composition of the present invention may contain a curing agent. Examples of the curing agent include those generally used in coating materials, and specific examples thereof include amino resins, blocked isocyanates, epoxy compounds, aziridine compounds, carbodiimide compounds, oxazoline compounds, and metal ions. However, amino resins and / or blocked isocyanates are preferred from the viewpoints of various properties and cost of the resulting coating film.

The amino resin as the curing agent is not particularly limited, and a water-soluble melamine resin or a water-insoluble melamine resin can be used. Further, from the viewpoint of stability of the water-based coating composition, it is preferable to use a melamine resin having a water tolerance value of 3.0 or more. The water tolerance value can be measured in the same manner as the method described above for the polyether polyol.

The above-mentioned blocked isocyanate can be obtained by adding a blocking agent having active hydrogen to a polyisocyanate such as trimethylene diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, isophorone diisocyanate, etc. As a result, the blocking agent is dissociated to generate an isocyanate group, which reacts with the functional group in the resin component and is cured.

When these curing agents are contained in the aqueous coating composition of the present invention, the content is 20 parts by weight as a lower limit from the viewpoint of curability with respect to 100 parts by weight of the resin solid content in the aqueous coating composition. The upper limit is preferably 100 parts by weight.

The aqueous coating composition of the present invention may further contain a pigment in addition to the above components. Examples of the pigment include organic azo chelate pigments, insoluble azo pigments, condensed azo pigments, phthalocyanine pigments, indigo pigments, perinone pigments, perylene pigments, dioxane pigments, quinacridone pigments, isoindolinone pigments. Pigments, metal complex pigments and the like can be mentioned. Inorganic pigments such as yellow lead, yellow iron oxide, red iron oxide, carbon black, titanium dioxide and the like and talc, clay, barium sulfate, calcium carbonate and the like extender pigments can be mentioned. .

The concentration of the pigment in the solids contained in the aqueous coating composition is 0.1% by weight as the lower limit and 50 as the upper limit.
The upper limit is preferably 0.5% by weight, more preferably the lower limit is 0.5% by weight and the upper limit is 40% by weight, further preferably the lower limit is 1.0 and the upper limit is 30% by weight.

In the water-based paint composition of the present invention, in addition to the above-mentioned components, additives usually added to the paint, such as surface modifiers, thickeners, antioxidants, UV inhibitors, antifoaming agents, etc. You may mix | blend. The blending amount of these is within the range known to those skilled in the art. The method for producing the water-based coating composition of the present invention is not particularly limited, and is well known to those skilled in the art such as kneading a compound such as a pigment using a kneader, a roll, or the like, and dispersing using a sand grind mill, a disper, or the like. All methods can be used.

Next, the method for forming a multilayer coating film of the present invention will be described. The method for forming a multilayer coating film of the present invention comprises applying an aqueous base paint to an object on which an electrodeposition coating film and an intermediate coating film have been formed, if necessary, and then applying a clear paint thereon, followed by heat curing. A method of forming a multilayer coating film by carrying out the above, wherein the above-mentioned water-based base coating material is the above-mentioned water-based coating material composition.

The above-mentioned article to be coated can be used for various base materials such as metal moldings, plastic moldings, foams and the like, but is applicable to metal moldings capable of cationic electrodeposition coating. preferable. Examples of the metal molded product include, for example, iron, copper, aluminum, tin, zinc, etc., and plates made of alloys containing these metals, and molded products. Specifically, passenger cars, trucks, motorcycles,
Examples include automobile bodies such as buses and parts. It is preferable that these metals have been previously subjected to chemical conversion treatment with phosphate, chromate, or the like.

An electrodeposition coating film may be formed on the metal molded article that has been subjected to the chemical conversion treatment. As such an electrodeposition coating, a cation type and anion type can be used, but from the viewpoint of anticorrosion property, a cation type electrodeposition coating is preferable.

The above-mentioned plastic molded products include polypropylene resin, polycarbonate resin, urethane resin,
Examples thereof include plates and molded products made of polyester resin, polystyrene resin, ABS resin, vinyl chloride resin, polyamide resin, and the like. Specific examples include automobile parts such as spoilers, bumpers, mirror covers, grilles, door knobs, and the like. be able to. Further, it is preferable that these plastic molded products are washed with trichloroethane by steam or washed with a neutral detergent. Further, a primer coating may be applied to enable electrostatic coating.

If necessary, an intermediate coating film may be formed on the above substrate. An intermediate coating material is used for forming the intermediate coating film. This intermediate coating material contains a film-forming resin, a curing agent, various organic or inorganic coloring components, extender pigments, and the like. The coating film-forming resin and the curing agent are not particularly limited, and specifically, the coating film-forming resin and the curing agent mentioned in the above-mentioned aqueous coating composition can be mentioned, in combination. Is used. From the viewpoint of various properties and cost of the obtained intermediate coating film, an acrylic resin and / or a polyester resin and an amino resin and / or an isocyanate are used in combination.

As the coloring component contained in the above-mentioned intermediate coating composition, those described in the above aqueous coating composition can be mentioned. Generally, it is preferable to use a gray intermediate coating mainly composed of carbon black and titanium dioxide, a set gray in which the hues of the top coating are matched, and a so-called color intermediate coating in which various coloring components are combined. Further, flat pigments such as aluminum powder and mica powder may be added. In addition to the above components, these intermediate coating materials may contain additives that are usually added to the coating material, such as surface modifiers, antioxidants and defoaming agents.

The clear paint used in the method for forming a multilayer coating film of the present invention is not particularly limited, and a clear paint containing a film-forming resin and a curing agent can be used. Further, a coloring component may be contained as long as it does not impair the design of the base. Examples of the form of this clear paint include solvent type, aqueous type and powder type.

Preferred examples of the above-mentioned solvent-type clear coating material include a combination of an acrylic resin and / or a polyester resin with an amino resin and / or an isocyanate, or a carboxylic acid / epoxy, from the viewpoint of transparency or acid etching resistance. An acrylic resin and / or a polyester resin having a curing system may be used.

Further, as an example of the above water-based clear coating material, there is included a resin obtained by neutralizing a coating film-forming resin contained in the above-mentioned solvent-based clear coating material with a base to make it water-based. I can list things. This neutralization can be carried out before or after the polymerization by adding a tertiary amine such as dimethylethanolamine and triethylamine.

On the other hand, as the powder type clear paint, usual powder paints such as thermoplastic and thermosetting powder paints can be used. A thermosetting powder coating is preferable because a coating film having good physical properties can be obtained. Specific examples of the thermosetting powder coating include epoxy-based, acrylic-based, and polyester-based powder clear coatings, and acrylic-based powder clear coatings having good weather resistance are particularly preferable.

Further, it is preferable that a viscosity control agent is added to the clear paint in order to ensure coating workability. As the viscosity control agent, those which are well known by those skilled in the art and generally exhibit thixotropic properties can be used.

In the method for forming a multilayer coating film of the present invention, the base coating film formed by coating the above-mentioned aqueous coating composition used as an aqueous base coating composition on an article to be coated has a beautiful appearance and a good design. It is what imparts sex.

As a method of coating the above-mentioned water-based base coating on the automobile body, from the viewpoint of improving the appearance, multi-stage coating by air electrostatic spray coating, preferably 2
Examples of the coating method include coating on a stage or a combination of air electrostatic spray coating and a rotary atomization type electrostatic coating machine called metallic bell.

The film thickness of the coating film when coated with the aqueous base coating material in the method for forming a multilayer coating film of the present invention varies depending on the desired use, but it is generally 10 to 30 μm in dry film thickness. preferable. When the dry film thickness is less than 10 μm, the underlayer cannot be hidden and film breakage occurs,
If it exceeds 30 μm, the sharpness may be deteriorated, or defects such as unevenness or sagging may occur during coating.

In the method for forming a multilayer coating film of the present invention, the base coating film obtained by coating this aqueous base coating composition may be baked and then the clear coating composition may be coated thereon. By coating a clear paint on the film to form a clear paint film, the baking and drying step of the base paint film can be omitted, which is preferable from the economical and environmental viewpoints. In order to obtain a good finished coating film,
Before applying clear paint, apply uncured base coating 4
It is desirable to heat at 0 to 100 ° C. for 2 to 10 minutes.

In the method for forming a multilayer coating film of the present invention, the clear coating film applied after forming the above base coating film is
It is intended to smooth and protect irregularities, flicker and the like caused by the base coating film, and further to give a beautiful appearance. Specific examples of the method of applying the above-mentioned clear coating to the above base coating film include a coating method using a rotary atomization type electrostatic coating machine called micro-microbell or microbell.

The dry film thickness of the clear coating film formed by applying the above clear paint is generally 10-8.
It is preferably about 0 μm, more preferably about 20 to 60 μm. If the dry film thickness is less than 10 μm, it is impossible to hide the irregularities of the base, and if it exceeds 80 μm, defects such as cracking or sagging may occur during coating.

The clear coating film thus formed is preferably baked together with the uncured base coating film as described above, that is, so-called 2-coat 1-baking is performed to form the coating film. The baking temperature is 80 to 180 ° C. from the viewpoint of the crosslink density and the physical properties of the obtained multilayer coating film.
Is preferably set to 120 ° C., more preferably 120 to 160 ° C. Although the baking time can be arbitrarily set according to the baking temperature, the baking time is 120 to 160 ° C. and the baking time is 10 to 3
Suitably 0 minutes.

The film thickness of the multilayer coating film formed by the method for forming a multilayer coating film of the present invention is generally 30 to 300 μm, preferably 50 to 250 μm. When the film thickness is less than 30 μm, the strength of the film itself decreases,
If it exceeds 300 μm, the physical properties of the film such as cooling and heating cycles may deteriorate.

[0109]

The present invention will be described in more detail with reference to the following examples, which should not be construed as limiting the invention. In the following, all "parts" and "%" are based on weight unless otherwise specified.

[Production Example 1: Production of Aqueous Resin Dispersion 1] 0.5 parts of AMBN (2,2′-azobis (2-methylbutyronitrile)) as a polymerization initiator and IPA were placed in a reaction vessel.
100 parts of (isopropyl alcohol) was charged and the temperature was raised to 80 ° C. with stirring. Then, with stirring, 55 parts of methyl methacrylate, 40 parts of n-butyl acrylate,
A monomer mixture A (acid value 52, hydroxyl value 69) consisting of 20 parts of 2-hydroxyethyl methacrylate and 10 parts of methacrylic acid was added dropwise over 5 hours.

After completion of dropping, 0.3 part of AMBN was added to IPA.
What was melt | dissolved in 15 parts was added to the reaction container, and reaction was continued at 80 degreeC for 2 hours. After completion of the polymerization, while continuing stirring, 5 parts of 25% ammonia water was added to the reaction container, and 350 parts of water was dropped into the reaction container over about 2 hours to form an aqueous solution. After being made into an aqueous solution, IPA was evaporated using a rotary evaporator to obtain an aqueous solution resin for emulsion polymerization.

Next, 225 parts of the above aqueous solution resin for emulsion polymerization, 560 parts of water and Newcol 707SF were placed in a reaction vessel.
Charge 1 part (manufactured by Nippon Emulsifier), heat and stir to 75
After reaching 0 ° C., 5 parts of a monomer mixture B (acid value 3, hydroxyl value 41) consisting of 90 parts of methyl methacrylate, 100 parts of n-butyl acrylate, 20 parts of 2-hydroxyethyl methacrylate and 1 part of methacrylic acid. % By weight and 0.5 part of ammonium persulfate were dissolved in 5 parts of water and added, and the mixture was stirred for 20 minutes. Then, the remaining portion 9 of the monomer mixture liquid B for core resin
5% by weight was added dropwise at 80 ° C. over 2 hours, and after the addition was completed, the temperature was further maintained at 80 to 85 ° C. for 1 hour and then cooled.

After cooling, a mixed solution of 1 part of dimethylaminoethanol and 10 parts of water was added to obtain an aqueous resin dispersion 1 having a nonvolatile content of 30% by weight.

[Production Example 2: Production of water-soluble acrylic resin]
Dipropylene glycol methyl ether 2 in the reaction vessel
3.9 parts and propylene glycol methyl ether 1
Add 6.1 parts and mix with stirring in a nitrogen stream for 120
The temperature was raised to ° C. Next, 54.5 parts of ethyl acrylate,
A mixed solution of 12.5 parts of methyl methacrylate, 14.7 parts of 2-hydroxyethyl acrylate, 10.0 parts of styrene and 8.5 parts of methacrylic acid, 10.0 parts of dipropylene glycol methyl ether and t-butylperm. Oxy-
An initiator solution consisting of 2.0 parts of 2-ethylhexanoate was added dropwise to the reaction vessel in parallel over 3 hours. After completion of dropping, aging was carried out at the same temperature for 0.5 hour.

Further, an initiator solution consisting of 5.0 parts of dipropylene glycol methyl ether and 0.3 part of t-butylperoxy-2-ethylhexanoate was added dropwise to the reaction vessel over 0.5 hours. After completion of dropping, aging was carried out at the same temperature for 1 hour.

Then, the solvent was removed under reduced pressure (70
Torr) After distilling off 16.1 parts of the solvent at 110 ° C., 187.2 parts of ion-exchanged water and 8.8 parts of dimethylaminoethanol were added to obtain a nonvolatile content of 31%, a weight average molecular weight of 27,000 and a number average molecular weight. Is 9000, solid acid value is 5
A water-soluble acrylic resin having a hydroxyl value of 6 and 70 was obtained.

[Production Example 3: Production of phosphoric acid group-containing acrylic resin] 23 parts of methoxypropanol was added to a reaction vessel,
The temperature was raised to 120 ° C while mixing and stirring in a nitrogen stream. Next, 22 parts of a solution prepared by dissolving 15 parts of phosmer PP (acid phosphooxyhexa (oxypropylene) monomethacrylate manufactured by Unichemical Co., Ltd.) in 7 parts of methoxypropanol, 12.3 parts of 2-ethylhexyl acrylate,
A mixed solution of 7.0 parts of 2-hydroxyethyl methacrylate, 7.5 parts of lauryl methacrylate, 4.4 parts of styrene and 3.8 parts of methacrylic acid, and methoxypropanol of 4.
An initiator solution consisting of 5 parts and 0.9 part of azobisisobutyronitrile was added dropwise to the reaction vessel in parallel over 3 hours. After completion of dropping, aging was carried out at the same temperature for 0.5 hour.

Further, an initiator solution consisting of 0.5 part of methoxypropanol and 0.5 part of azobisisobutyronitrile was added dropwise to the reaction vessel over 0.5 hours. After completion of the dropping, the mixture was aged for 1.5 hours at the same temperature, 13.7 parts of methoxypropanol was added, and the nonvolatile content was 50%, the solid content acid value was 61, the hydroxyl value was 60, and the phosphoric acid group had a number average molecular weight of 5000. An acrylic resin containing was obtained.

[Production Example 4: Preparation of glitter paste] 2-
Alpaste MH8801 in 40 parts of ethylhexanol
(Asahi Kasei Co., Ltd. aluminum pigment paste) 21 parts was dissolved, then, while stirring with a tabletop disper, 10 parts of Prime Pole PX-1000 (bifunctional polyether polyol, Sanyo Kasei Co., Ltd.), the phosphorus obtained in Production Example 3 5 parts of an acid group-containing acrylic resin and 0.3 part of lauryl acid phosphate were gradually added to obtain a bright material paste containing aluminum.

Example 1 200.0 parts of the aqueous resin dispersion 1 obtained in Production Example 1, 32.3 parts of the water-soluble acrylic resin obtained in Production Example 2 were obtained in Production Example 4. 66.3 parts of glitter paste, 25.3 parts of Cymel 204, 1.7 parts of Adecanol SDX-1014 (urethane compound manufactured by Asahi Denka Co., Ltd., active ingredient 30% by weight), and 40 parts of 2-ethylhexanol. After mixing and stirring, a 10 wt% aqueous solution of dimethylaminoethanol was added to adjust the pH to 8, to obtain a uniformly dispersed aqueous coating composition 1. This paint was diluted with ion-exchanged water for 45 seconds (measured with a No. 4 Ford cup at 20 ° C.).

Zinc phosphate treated 300 × 400 × 0.
Power Top U-50 (Cationic electrodeposition paint manufactured by Nippon Paint Co., Ltd.) was electro-deposited on an 8 mm dull steel plate so that the dry film thickness was 20 μm, and the coated plate was baked at 160 ° C. for 30 minutes for 25 seconds (No. .4 Ford Cup, 20
Olga P-2 (a melamine curable polyester resin-based gray intermediate coating made by Nippon Paint Co., Ltd.) which has been pre-diluted in (measured at ℃) was coated with air spray for 2 stages to a dry film thickness of 35 μm, and at 140 ° C. After baking for 30 minutes and cooling, an electrodeposited substrate was obtained.

The above aqueous coating composition 1 was applied to an electrodeposited substrate under the conditions of a room temperature of 25 ° C. and a humidity of 85% so as to have a dry film thickness of 15 μm. Atomization type electrostatic coating machine) was applied for 2 stages. An interval setting of 1.5 minutes was performed between the two applications. After the second application, the setting was performed with an interval of 5 minutes. afterwards,
Preheating was performed at 80 ° C. for 3 minutes.

After preheating, the coated plate was allowed to cool to room temperature,
As a clear paint, Olga TO-563 clear (Nippon Paint Co., Ltd. melamine curing type acrylic resin clear paint) is used, and Micro Micro Bell (rotating atomizing electrostatic coating machine made by ABB Lansberg Co., Ltd.) so that the dry film thickness is 40 μm. I painted it for 1 stage and set it for 7 minutes.
Further, the coated plate obtained is heated at 140 ° C. in a hot air drying oven for 30 minutes.
After baking for a minute, a multilayer coating film was obtained on the substrate.

[Production Examples 5-9: Production of Aqueous Resin Dispersions 2-6] Except that the polymerizable unsaturated monomer mixture A and the polymerizable unsaturated monomer mixture B are blended as shown in Table 1, respectively. In the same manner as in Production Example 1
Got 6. The acid value and hydroxyl value of each monomer mixture are shown in Table 1.
It was shown to.

Examples 2 to 6 Aqueous coating compositions 2 to 6 were obtained in the same manner as in Example 1 except that the aqueous resin dispersions 2 to 6 were used instead of the aqueous resin dispersion 1. It was Further, it was diluted in the same manner as in Example 1. Further, coating was carried out in the same manner as in Example 1 to obtain a multilayer coating film.

[Production Example 10: Production of aqueous resin dispersion liquid 7]
In a reaction vessel charged with 130.0 parts of ion-exchanged water, ADEKA REASOAP NE-20 (α- {1-[(allyloxy) methyl] -2- (nonylphenoxy) ethyl} -ω-hydroxyoxy manufactured by Asahi Denka Co., Ltd. was used. Ethylene, solid content 80% by weight aqueous solution) 0.2 parts, and Aqualon HS-10 (Daiichi Kogyo Seiyaku Co., Ltd. polyoxyethylene alkylpropenyl phenyl ether sulfate) 0.2 parts were added, and mixed and stirred in a nitrogen stream. Meanwhile, the temperature was raised to 80 ° C. Then, 90.0 parts of methyl methacrylate, butyl acrylate 10
0.0 parts, 2-hydroxyethyl methacrylate 20.0
Parts, methacrylic acid 1.0 parts, ADEKA REASOAP NE-2
0, 0.3 parts, AQUALON HS-10, 0.2 parts, and ion-exchanged water, 70 parts, and a first-stage monomer mixture solution (acid value 3, hydroxyl value 41) and ammonium persulfate 0.
An initiator solution consisting of 2 parts and 7 parts of ion-exchanged water was added dropwise to the reaction vessel in parallel over 2 hours. After the dropping is completed,
Aging was carried out at the same temperature for 1 hour.

Further, at 80 ° C., methyl methacrylate 5 was added.
5.0 parts, n-butyl acrylate 40.0 parts, 2-hydroxyethyl methacrylate 20.0 parts, methacrylic acid 1
0.0 parts, 0.3 parts of Aqualon HS-10, and 30 parts of ion-exchanged water in the second stage monomer mixture liquid (acid value 52, hydroxyl value 69) and ammonium persulfate 0.1.
And an initiator solution consisting of 3 parts of ion-exchanged water and 0.5 parts of
It was added dropwise to the reaction vessel in parallel over time. After completion of the dropping, aging was carried out for 2 hours at the same temperature.

Then, it was cooled to 40 ° C. and filtered through a 400 mesh filter. Further, a 10 wt% dimethylaminoethanol aqueous solution was added to adjust the pH to 7 to obtain an aqueous resin dispersion liquid 7 having a nonvolatile content of 30%.

[Production Examples 11 to 15: Aqueous resin dispersion liquid 8 to
Production of 12] Aqueous resin dispersions 8 to 12 were obtained in the same manner as in Production Example 1, except that the respective monomer mixture liquids in the first and second stages were mixed as shown in Table 2. The acid value and hydroxyl value of each monomer mixture are shown in Table 2.

Comparative Examples 1 to 6 Aqueous coating compositions 7 to 12 were obtained in the same manner as in Example 1 except that the aqueous resin dispersions 7 to 12 were used instead of the aqueous resin dispersion 1. It was Further, it was diluted in the same manner as in Example 1. further,
The same coating was performed to obtain a multilayer coating film.

(Evaluation Test) Examples 1 to 6 and Comparative Examples 1 to 1
The IV value of the multilayer coating film obtained in 6 was measured using an IV meter (manufactured by Kansai Paint Co., Ltd.) to evaluate the flip-flop property of the coating film. 220 or more was passed. In addition, the appearance of each multilayer coating film was visually evaluated and found to be good.

[0132]

[Table 1]

[0133]

[Table 2]

From Tables 1 and 2, all of the aqueous coating compositions of Examples 1 to 6 contained the aqueous resin dispersions synthesized by the predetermined steps, so that they had good visual appearance and were obtained. It was found that the flip-flop property of the coating film was extremely high. However, it has been found that the flip-flop property is insufficient when an aqueous resin dispersion obtained by a conventional general emulsion polymerization method is used.

[Production Example 16: Production of aqueous resin dispersion 13] AMBN (2,2 ') was used as a polymerization initiator in a reaction vessel.
-Prepare 0.5 parts of azobis (2-methylbutyronitrile) and 100 parts of IPA (isopropyl alcohol),
The temperature was raised to 80 ° C. with stirring. Then, with stirring, a monomer mixture A (acid value 5: 55 parts of methyl methacrylate, 40 parts of n-butyl acrylate, 20 parts of 2-hydroxyethyl methacrylate and 10 parts of methacrylic acid) was used.
2, hydroxyl value 69) was added dropwise over 5 hours.

After completion of dropping, 0.3 part of AMBN was added to IPA.
What was melt | dissolved in 15 parts was added to the reaction container, and reaction was continued at 80 degreeC for 2 hours. After completion of the polymerization, while continuing stirring, 5 parts of 25% ammonia water was added to the reaction container, and 350 parts of water was dropped into the reaction container over about 2 hours to form an aqueous solution. After being made into an aqueous solution, IPA was evaporated using a rotary evaporator to obtain an aqueous solution resin for emulsion polymerization.

Next, 225 parts of the above aqueous solution resin for emulsion polymerization, 560 parts of water and Newcol 707SF were placed in a reaction vessel.
Charge 1 part (manufactured by Nippon Emulsifier), heat and stir to 75
After reaching ℃, 87 parts of methyl methacrylate, 97 parts of n-butyl acrylate, 6 parts of diacetone acrylamide,
5% by weight of a monomer mixture liquid B (acid value 3, hydroxyl value 41) consisting of 20 parts of 2-hydroxyethyl methacrylate and 1 part of methacrylic acid and 0.5 parts of ammonium persulfate in 5 parts of water.
It was melted into a part and added, and stirred for 20 minutes. Then, the remaining 95% by weight of the monomer mixture liquid B for core resin is
Add dropwise over 2 hours, then 80-85 after completion of addition
It was kept at ℃ for 1 hour and then cooled.

After cooling, a mixed solution of 1 part of dimethylaminoethanol and 10 parts of water was added, and further 3 parts of adipic dihydrazide was added to obtain an aqueous resin dispersion 13 having a nonvolatile content of 30% by weight.

[Production Example 17: Production of Aqueous Resin Dispersion Liquid 14] The composition of the polymerizable unsaturated monomer mixture liquid B was changed as shown in Table 3 except that the amount of adipic dihydrazide added was 5 parts. An aqueous resin dispersion 14 was obtained in the same manner as in Production Example 16. The acid value and the hydroxyl value of the monomer mixed solution B are shown in Table 3.

[Production Examples 18 to 22: Aqueous resin dispersion liquid 15]
Production of -19] Aqueous resin dispersion 15 was prepared in the same manner as in Production Example 16 except that the composition of polymerizable unsaturated monomer mixture B was changed as shown in Table 3 and that adipic acid dihydrazide was not added. ~ 19 were obtained. The acid value and hydroxyl value of each monomer mixture B are shown in Table 3.

[Examples 7 to 13] Aqueous coating compositions 13 to 13 were prepared in the same manner as in Example 1 except that the aqueous resin dispersions 13 to 19 were used instead of the aqueous resin dispersion 1.
I got 19. Further, it was diluted in the same manner as in Example 1. Further, coating was carried out in the same manner as in Example 1 to obtain a multilayer coating film.

The IV values of the multilayer coating films obtained in Examples 7 to 13 were measured using an IV meter (manufactured by Kansai Paint Co., Ltd.) to evaluate the flip-flop property of the coating film. 22
0 or more was passed. In addition, the appearance of each multilayer coating film was visually evaluated and found to be good.

[0143]

[Table 3]

The abbreviations in Table 3 are as follows. Other abbreviations are the same as in Tables 1 and 2. DAAAm: diacetone acrylamide KBM-502: manufactured by Shin-Etsu Chemical Co., Ltd., alkoxysilyl group-containing monomer KBM-503: manufactured by Shin-Etsu Chemical Co., Ltd., alkoxysilyl group-containing monomer N-MAM: N-methylolacrylamide GMA: glycidyl Methacrylate

From Table 3, since all the aqueous coating compositions of Examples 7 to 13 contained the aqueous resin dispersions synthesized by the predetermined steps, the visual appearance was good and the coating films obtained were good. It was found that the flip-flop property of was extremely high. In particular, the coating films of Examples 7 to 11 using diacetone acrylamide or a hydrolyzable silyl group-containing monomer as the crosslinkable monomer showed a very good appearance.

[0146]

The aqueous coating composition of the present invention contains an aqueous resin dispersion synthesized by a predetermined process,
The flip-flop property of the obtained coating film becomes high.

Furthermore, according to the present invention, excellent solvent resistance can be imparted to the coating film by using a crosslinkable monomer as a copolymerization component in the preparation of the emulsion polymerization resin and / or core resin. As a result, a multilayer coating having a very good appearance is obtained.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C09D 4/00 C09D 4/00 5/00 5/00 Z 5/29 5/29 171/00 171/00 175/04 175/04 175/08 175/08 (72) Inventor Chiharu Senoo 19-17 Ikedanaka-cho, Neyagawa-shi, Osaka Japan Paint Co., Ltd. (72) Inventor Tadahiko Nishi 19-19 Ikedanaka-cho, Neyagawa-shi, Osaka No. 17 Nippon Paint Co., Ltd. in the F-term (reference) 4D075 AE03 BB26Z CB06 CB13 DA06 DA23 DB02 DB05 DB06 DB07 DB35 DB36 DB37 DB38 DB43 DB48 DB50 DB53 DC12 DC13 EA06 EA07 EA10 EA13 EA43 EB14 EB20 EB22 EB32 EB33 EB35 EB37 EB38 EB45 EB51 EB52 EB55 EB56 EC10 EC60 4J034 DG02 DG14 DG16 HA07 HC03 HC12 HC17 HC22 HC46 HC52 HC71 HC73 MA22 RA07 4J038 CE051 CG002 CG141 CG171 CH121 CH141 DF012 DG132 FA042 FA092 FA102 FA112 FA152 FA212 GA03 GA06 GA14 HA15 HA026 HA02 HA11226. HA546 KA03 KA08 KA09 MA03 MA08 MA10 PB07 PC02 PC08

Claims (10)

[Claims] 1. An acid value of 30 to 150 and a hydroxyl value of 10.
Solution polymerization of a monomer mixture A of 100 to 100 to synthesize a copolymer solution, the copolymer solution is converted into an aqueous solution, and the organic solvent is removed under reduced pressure to perform emulsion polymerization. After obtaining an aqueous solution resin for use as a protective colloid, the aqueous solution resin for emulsion polymerization is used,
An aqueous resin dispersion obtained by emulsion-polymerizing a monomer mixture liquid B having an acid value of upper limit of 20 and a hydroxyl value of upper limit of 100 to synthesize a core resin in the protective colloid, and a glittering material. An aqueous coating composition characterized by the above. 2. Further, the compound represented by the general formula (1) or (2): (In the formula (1), R ¹ , R ² and R ³ represent hydrocarbon groups which may be the same or different from each other, R ¹ represents a hydrocarbon group which may have a urethane bond, R ^{1 3} represents a branched chain or secondary hydrocarbon group, j is a number of 1 or more,
k is a number within the range of 1 to 500. ) [Chemical 2] (In the formula (2), R ¹ , R ² , R ³ , R ⁴ and R ⁵ represent hydrocarbon groups which may be the same or different from each other;
¹ represents a hydrocarbon group which may have a urethane bond, R ³ represents a branched or secondary hydrocarbon group, and n represents 2
The above numbers, j is a number of 2 or more, and k and m are numbers in the range of 1 to 500, respectively. ) At least one of the urethane-based compound represented by, the content of the urethane-based compound is 0.01 to 20% by weight in terms of solid content with respect to the resin solid content in the coating composition, Claim 1
The water-based coating composition according to 1. 3. The monomer mixed liquid A and the monomer mixed liquid B are at least one polymerization selected from the group consisting of (meth) acrylic acid esters, styrene-based monomers, (meth) acrylonitrile and (meth) acrylamide, respectively. The aqueous coating composition according to claim 1 or 2, which contains a water-unsaturated monomer. 4. The weight Aw of the monomer mixed solution A and the weight Bw of the monomer mixed solution B are 10/100 ≦ A.
The aqueous coating composition according to any one of claims 1 to 3, which satisfies the relationship of w / (Aw + Bw) ≦ 50/100. 5. The monomer mixture liquid A further contains a crosslinkable monomer as a copolymerization component.
The aqueous coating composition according to any one of the above. 6. The monomer mixture liquid B further contains a crosslinkable monomer as a copolymerization component.
The aqueous coating composition according to any one of the above. 7. The average number of primary hydroxyl groups in one molecule is 0.02 or more, and the number average molecular weight is 300 to 30.
The water-borne coating composition according to any one of claims 1 to 6, which contains a polyether polyol having a water tolerance value of 2.0 or more. 8. The aqueous coating composition according to claim 7, wherein the polyether polyol has at least one primary hydroxyl group in one molecule and has a hydroxyl value of 30 to 700. 9. A method of forming a multi-layer coating film by applying a water-based base paint to an object to be coated, applying a clear paint thereon, and then heat-curing the water-based base paint, the water-based base paint comprising: A method for forming a multilayer coating film, which is the aqueous coating composition according to any one of claims 1 to 8. 10. A multilayer coating film formed by the method according to claim 9.