JPH0693215A - Aqueous pigment dispersion for electrodeposition coating - Google Patents

Abstract

PURPOSE:To obtain a dispersion, comprising a pigment and a specific aqueous dispersion and excellent in storage stability, dispersibility and surface glossiness. CONSTITUTION:The dispersion comprises (A) preferably 0.1-90wt.% (based on the solid content of the dispersion) pigment such as zinc flower or a nitroso pigment-based pigment, (B) an aqueous dispersion such as an aqueous substance prepared by dispersing a neutralized substance obtained by neutralizing a copolymer containing (i) preferably 3-10 pts.wt. carboxyl group-containing vinylic monomer (e.g. acrylic acid), (ii) preferably 5-25 pts.wt. basic group-containing vinylic monomer such as 1-vinyl-2-pyrrolidone, (iii) preferably 5-20 pts.wt. vinylic monomer modified with polyoxyalkylene glycol or its monoether derivative (e.g. diethylene glycol acrylate) and (iv) preferably 5-30 pts.wt. vinylic monomer having a >=8C alkyl group such as 2-ethylhexyl (meth)acrylate as essential monomer components with a neutralizing agent in water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous pigment dispersion for electrodeposition paint.

[0002]

2. Description of the Related Art Conventionally, materials such as aluminum and iron have been coated with electrodeposition paint for the purpose of beauty and protection.

Usually, a color pigment, an extender pigment or the like is blended in the electrodeposition paint depending on the application, and when the pigment is blended, a pigment paste in which the pigment is previously dispersed with a pigment dispersant is generally used.

The pigment dispersant has defects such as difficulty in dispersing the pigment at the time of production, agglomeration / sedimentation of the pigment during storage, resulting reduction in gloss of a coating film, color separation, floating, and deterioration of coating film performance. It is formulated to prevent

As the dispersant, a resin solution in which a part of the base resin used in the electrodeposition coating is dissolved in an organic solvent is generally used from the viewpoints of dispersibility in pigments, storage stability of the coating and the like. For this reason, the organic solvent has come to be contained in the electrodeposition coating material, which poses a problem in terms of environmental pollution and safety.

Further, as a pigment dispersant which does not use an organic solvent, an ethylenically unsaturated nitrogen-containing monomer, an ethylenically unsaturated carboxylic acid and a (meth) acrylic acid ester monomer of a C _{8 to} C ₂₄ monoalcohol are used. The use of a water-soluble copolymer as an aqueous pigment dispersion is disclosed in JP-A-60-9236.
No. 0 publication.

However, the stability of the dispersion is poor because the aqueous pigment dispersion has insufficient dispersibility for various pigments. When this product is used for electrodeposition coating, the pigment in the bath coating (diluted to a solid content of about 8%) separates from the dispersant while circulating in the electrodeposition tank, clogging the filter and coating the filter. There is a problem that causes defects such as gloss on the film surface. Further, in the electrodeposition coating, when the dispersibility of the dispersant and the pigment component in the bath coating is insufficient, the dispersant and the pigment component are easily separated during the electrodeposition coating, so that the bath coating stability, There is a defect that the surface gloss of the coating film decreases.

[0008]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that
The use of a copolymer containing a vinyl monomer modified with polyoxyalkylene glycol or a derivative thereof as an essential monomer component as a resin for a pigment dispersion liquid of an electrodeposition coating can solve all the above-mentioned problems. The present invention has been completed and the present invention has been completed.

That is, in the present invention, an aqueous pigment dispersion for electrodeposition coating composition containing a pigment and an aqueous dispersant (hereinafter, this may be simply referred to as "dispersant") (hereinafter, this is simply referred to as "aqueous"). Abbreviated as "pigment dispersion"), the dispersant is a carboxyl group-containing vinyl monomer (a) or a basic group-containing vinyl monomer (b), polyoxyalkylene glycol or a monoether thereof. Derivative-modified vinyl-based monomer (c) (hereinafter abbreviated as modified vinyl-based monomer (c)) and vinyl-based monomer (d) having an alkyl group of C ₈ or more (hereinafter, long-chain vinyl-based Abbreviated as monomer (d).)
Relates to an aqueous pigment dispersion for electrodeposition coatings, which is an aqueous product obtained by dispersing a neutralized product obtained by neutralizing a copolymer having an essential monomer component with a neutralizing agent in water .

The aqueous pigment dispersion of the present invention will be described below. The copolymer, which is the dispersant component used in the aqueous pigment dispersion of the present invention, is a carboxyl group-containing vinyl monomer (a) or a basic group-containing vinyl monomer (b), a modified vinyl monomer (c). ), A long-chain vinyl-based monomer (d) and, if necessary, another vinyl-based monomer (e).

Carboxyl group-containing vinyl-based monomer (a): The carboxyl group-containing vinyl-based monomer (a) used in the present invention comprises a carbon atom to which a carboxyl group is bonded and a carbon atom adjacent to the carbon atom. Unsaturated aliphatic mono- or polycarboxylic acid of the type having a radically polymerizable double bond, containing 3 to 8 carbon atoms and having 1 or 2 carboxyl groups and the carboxyl group via an alkylene bond. And those bonded to a (meth) acryloyl group.

Examples of such α, β-ethylenically unsaturated carboxylic acid include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, maleic anhydride, fumaric acid, 2-carboxyethyl (meth) acrylate, 2-
Carboxypropyl (meth) acrylate etc. are mentioned, These can be used individually or in combination of 2 or more types.

Basic group-containing vinyl monomer (b): The basic group-containing vinyl monomer (b) used in the present invention contains one or more basic nitrogen atoms in one molecule. A monomer containing one ethylenically unsaturated bond is included, and typical examples thereof include an unsaturated monomer having a nitrogen-containing heterocycle and a nitrogen-containing derivative of (meth) acrylic acid. Hereinafter, these monomers will be specifically described.

[1] As the unsaturated monomer having a nitrogen-containing heterocycle, a monocyclic or polycyclic heterocycle containing 1 to 3, preferably 1 or 2 ring nitrogen atoms is bonded to a vinyl group. The above-mentioned monomers are included, and in particular, the monomers shown below can be mentioned. (I) Vinylpyrrolidones: For example, 1-vinyl-2-
Pyrrolidone, 1-vinyl-3-pyrrolidone and the like. (II) Vinylpyridines: For example, 2-vinylpyridine, 4-vinylpyridine, 5-methyl-2-vinylpyridine, 5-ethyl-2-vinylpyridine and the like. (III) Vinylimidazoles: For example, 1-vinylimidazole, 1-vinyl-2-methylimidazole and the like. (IV) Vinylcarbazoles: For example, N-vinylcarbazole and the like. (V) Vinylquinolines: For example, 2-vinylquinoline and the like. (VI) Vinylbiperidines: For example, 3-vinylpiperidine, N-methyl-3-vinylpiperidine and the like. (VII) Vinylmorpholines: For example, N- (meth) acryloylmorpholine and the like. (VIII) Vinylpyrrolidines: For example, N- (meth) acryloylpyrrolidine and the like.

[2] Nitrogen-containing derivatives of (meth) acrylic acid include those containing a substituted or unsubstituted amino group in the ester portion of (meth) acrylic acid ester, and amides and acrylonitrile of (meth) acrylic acid. Is included. Specifically, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate,
Tertiary butylaminoethyl (meth) acrylate, (meth)
Acrylamide, N-methylol (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N-
Methoxy (meth) acrylamide, N-ethoxy (meth) acrylamide, N-dimethylacrylamide, N
-Propyl acrylamide and the like.

[3] Macromonomers of [1] and [2] The above-mentioned [1] to [3] can be used alone or in combination of two or more. Among the above, vinylpyrrolidones are particularly preferable.

Modified vinyl-based monomer (c): The modified vinyl-based monomer (c) used in the present invention is 1 in one molecule.
A monomer containing at least one ether bond and one ethylenically unsaturated bond is included, and in particular, the following general formula (1) or (2)

[0018]

[Chemical 1]

(Wherein R ₁ represents a hydrogen atom or a methyl group, R ₂ represents a C ₁ -C ₁₈ alkyl group, a cycloalkyl group, an aryl group or an aralkyl group, and n is 2 or 3).
, M is 2 to 50 integers, and p is 1 to 50 integers. ) Is preferable.

Examples of the modified vinyl monomer (c) include diethylene glycol (meth) acrylate, triethylene glycol (meth) acrylate, polyethylene glycol (meth) acrylate, dipropylene glycol (meth) acrylate and tripropylene glycol. (Meth) acrylate, polypropylene glycol (meth) acrylate, polyethylene polypropylene glycol (meth) acrylate, methoxyethylene (meth) acrylate, ethoxyethylene (meth) acrylate, butoxyethylene (meth) acrylate,
Hexyloxyethylene (meth) acrylate, ethoxypropylene (meth) acrylate, ethoxydiethylene (meth) acrylate, butoxydiethylene (meth)
Examples thereof include acrylate, dodecyloxydiethylene (meth) acrylate, phenoxydipropylene (meth) acrylate, and benzyloxydiethylene (meth) acrylate. These can be used alone or in combination of two or more.

Among the above, polyethylene and / or polypropylene glycol (meth) acrylate having m or p of 5 to 30 and its methyl ether have various pigment dispersibility, storage stability of dispersion, and high surface gloss of the final coating film. It is desirable to use this because it has advantages such as.

Long-chain vinyl-based monomer (d): The long-chain vinyl-based monomer (d) used in the present invention contains a C ₈ or more alkyl group and an ethylenically unsaturated bond in one molecule. monomers are included, include (meth) acrylic acid ester of a C ₉ -C ₂₅ vinyl esters of monocarboxylic acids and C ₈ -C ₂₄ monoalcohols. Examples of the vinyl ester include vinyl 2-ethylhexanate, vinyl laurinate, Veova monomer (manufactured by Shell Chemical Co.),
Examples thereof include vinyl stearate. Examples of the (meth) acrylic acid ester include 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, and 2-hydroxystearyl (meth) acrylate. These can be used alone or in combination of two or more.

Other vinyl-based monomer (e): In addition to the above-mentioned monomers (a) to (d), other vinyl-based monomer (e) may be appropriately used, if necessary. it can.

Examples of the other vinyl-based monomer (e) include esters of (meth) acrylic acid: for example, methyl (meth) acrylate, ethyl (meth) acrylate, (meth)
C ₁ -C ₇ alkyl or cycloalkyl ester of (meth) acrylic acid such as propyl acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, cyclohexyl (meth) acrylate; Glycidyl (meth) acrylate, acetoacetoxyalkyl (meth) acrylate: C _{2 to} C ₁₈ of (meth) acrylic acid such as methoxybutyl (meth) acrylate, methoxyethyl (meth) acrylate and ethoxybutyl (meth) acrylate. alkoxyalkyl ester; allyl (meth) (meth) C ₂ -C ₈ alkenyl esters of acrylic acid acrylate; hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate of (meth) C ₂ -C acrylic acid ₇ hydroxyalkyl esters, A Yloxy (meth) acrylate of (meth) C ₃ -C ₁₈ alkenyloxy alkyl esters of acrylic acid.

Vinyl aromatic compounds: for example, styrene, α-methylstyrene, vinyltoluene, p-chlorostyrene. Polyolefin compound: For example, butadiene, isoprene, chloroprene. Others: methyl isopropenyl ketone, vinyl acetate,
Vinyl propionate, vinyl pivalate, etc. These monomers can be used alone or in combination of two or more.

According to the present invention, the above-mentioned monomer (a),
A combination of (c) and (d) or (b), (c)
If necessary, the monomer (e) is copolymerized with those of (d) and (d). The copolymerization is carried out by a method known per se, for example, an inert organic solvent (further preferably a water-miscible cellosolve type, alcohol type, carbitol type, glyme type,
In the presence of a polymerization catalyst (for example, a peroxide-based compound, an azo-based compound, a diazo-based compound, etc.) in a solvent such as cellosolve acetate-based compound), usually about 4-1 at about 40 to about 180 ° C.
It is carried out by continuing the reaction for 2 hours.

The monomers (a) to form the copolymer
The compounding ratio of (e) can be compounded in the following ratios.

Carboxyl group-containing vinyl monomer (a): about 2 to 20 parts by weight, preferably about 3 to 10 parts by weight. If the proportion is less than about 2 parts by weight, the storage stability and the pigment dispersibility will be deteriorated, while if it exceeds about 20 parts by weight, the pigment dispersibility and the coating film performance (water resistance etc.) will be deteriorated.

Basic group-containing vinyl monomer (b): about 1
The desired range is from -30 parts by weight, preferably about 5-25 parts by weight. When the ratio is less than about 1 part by weight, storage stability and pigment dispersibility are deteriorated, while when it exceeds about 30 parts by weight, storage stability, pigment dispersibility, coating film curability, coating film performance (water resistance, etc.). And so on are not preferable.

Modified vinyl-based monomer (c): about 4 to 30 parts by weight, preferably about 5 to 20 parts by weight.
When the proportion is less than about 4 parts by weight, storage stability and pigment dispersibility are deteriorated, while when it exceeds about 30 parts by weight, coating hardness and coating performance (water resistance etc.) are reduced, which is not preferable.

Long-chain vinyl monomer (d): about 4 to 40 parts by weight, preferably about 5 to 30 parts by weight.
When the proportion is less than about 4 parts by weight, the pigment dispersibility is lowered, while when it exceeds about 30 parts by weight, the coating film hardness is lowered, which is not preferable.

Other vinyl-based monomer (e): about 80 parts by weight or less, preferably about 30 to 75 parts by weight.

The copolymer, which is the dispersant component, is about 50.
0 to 200,000, preferably about 1,000 to 10
It is desirable to have an average molecular weight in the range of 10,000.

Further, the above-mentioned copolymer having a hydroxyl group introduced therein can also be used. When the copolymer having a hydroxyl group is used in combination with, for example, a coating material that forms a cured coating film using a hydroxyl group (such as an electrodeposition coating material using an amino or block polyisocyanate curable resin), When the resin component is cured, the copolymer of the dispersant component is also cured at the same time, and there is an advantage that the coating film performance (water resistance, weather resistance, process resistance, etc.) is further improved.

As a method for introducing a hydroxyl group into the copolymer, a vinyl monomer having a hydroxyl group (for example, one represented by the general formula (1) and C _{2 to} C ₇ of the (meth) acrylic acid) can be used.
Hydroxyalkyl ester etc.) can be used as a monomer component. The hydroxyl group has a hydroxyl equivalent of about 20 to 200, preferably about 30 to 180.

The copolymer thus produced is hydrated as it is or after the solvent is distilled off. This hydration is carried out by a conventional method, for example, in the carboxyl groups present in the copolymers (a), (c) and (d) or in the copolymers (b), (c) and (d). The basic group can be neutralized with a neutralizing agent such as a conventionally known basic compound (or acidic compound). Examples of the basic compound that can be used include ammonia, amines, alkali metal hydroxides, alkali metal carbonates and bicarbonates, and the like. The amine may be a primary, secondary or tertiary alkylamine; primary
Grade, secondary or tertiary alkanolamines; and cycloalkylamines and the like can be used. Further, potassium hydroxide, sodium hydroxide and the like can be used as alkali metal hydroxides; potassium carbonate, sodium carbonate, sodium bicarbonate and the like can be used as alkali metal carbonates and bicarbonates. Of these basic compounds, amines are particularly preferable. Further, as the acidic compound, for example, acetic acid, hydroxyacetic acid and the like can be mentioned as preferable ones.

The neutralization treatment can be easily carried out by a conventional method by adding the above-mentioned neutralizing agent or its aqueous solution to the copolymer or its solution obtained as described above. The amount of the neutralizing agent used is generally 0.1 to 2.0 equivalents, preferably 0.3 to 2.0, with respect to the carboxyl group or basic group in the copolymer.
It is 1.0 equivalent.

The aqueous product thus obtained is used as a dispersant in an aqueous pigment dispersion liquid composed of a pigment and a dispersant.

The amount of the dispersant used is generally about 1 to 2,000 parts by weight, preferably about 1 to 100 parts by weight per 100 parts by weight of the pigment.
It can be 1,000 parts by weight. If the upper limit of this range is exceeded, the balance between the coloring power and the viscosity of the aqueous pigment dispersion tends to be unbalanced, while if the lower limit is not reached, the dispersion stability of the pigment tends to decrease.

The pigment used in the aqueous pigment dispersion of the present invention may be an inorganic or organic pigment usually used in this type of pigment dispersion, and examples of the inorganic pigment include (1) Oxide type (zinc white, titanium dioxide,
Red iron oxide, chromium oxide, cobalt blue, iron black, etc.);
(2) Hydroxide type (alumina white, yellow iron oxide, etc.); (3) Sulfide, selenide type (zinc sulfide, vermilion, cadmium yellow, cadmium red, etc.); (4) Ferrocyanide type (dark blue, etc.) ); (5) Chromate system (yellow lead,
(Zinc chromate, molybdenum red, etc.); (6) Sulfate system (precipitable barium sulfate, etc.); (7) Carbonate system (precipitable calcium carbonate, etc.); (8) Silicate system (hydrous silicate,
(Clay, ultramarine, etc.); (9) Phosphate type (manganese violet, etc.); (10) Carbon type (carbon black, etc.);
(11) Metal powder type (aluminum powder, bronze powder, zinc powder, etc.) and the like, and as organic pigments, (1) nitroso pigment type (naphthol green B etc.); (2) nitro pigment type (naphthol yellow) S, etc.); (3) Azo pigment type (resole red, lake red C, fast yellow,
(Naphthol red, red, etc.); (4) Dyeing lake pigment system (alkali blue lake, rhodamine lake, etc.);
(5) Phthalocyanine pigments (phthalocyanine blue, fast sky blue, etc.); (6) Condensed polycyclic pigments (perylene red, quinacridone red, dioxazine violet, isoindolinone yellow, etc.) and the like.

The content of the pigment in the aqueous pigment dispersion of the present invention is not particularly limited, but it is generally about 0.1 to 90% by weight based on the weight (solid content) of the dispersion. Is.

The aqueous pigment dispersion of the present invention can be prepared by mixing together the above-mentioned components in a suitable dispersing device, and the dispersing device which can be used is usually used in the paint industry. Ball mill,
Roll mills, homomixers, sand grinders, shakers, attritors, etc. are mentioned.

If necessary, conventionally known surfactants and protective colloids may be added to the aqueous pigment dispersion of the present invention.

The aqueous pigment dispersion liquid of the present invention contains a conventionally known electrodeposition coating material such as an acrylic resin type, a fluororesin type or a polyester resin as a base resin, and a melamine resin, a blocked polyisocyanate or the like as a curing agent. It can be used for glossy or matte paints. Further, the carboxyl group-containing aqueous pigment dispersion composed of the copolymers of the above-mentioned components (a), (c) and (d) is used for anionic electrodeposition paints (b), (c) and (d).
A basic group-containing aqueous pigment dispersion composed of a copolymer of components is used for a cationic electrodeposition coating composition.

As the above-mentioned anionic and cationic electrodeposition coatings, conventionally known ones can be used. Representative examples of these include thermosetting resins having an acrylic resin, an epoxy resin, a polyester resin, a fluorine resin, or a polybutadiene resin as a base resin. Among these, it is preferable to use anionic or cationic electrodeposition coating of acrylic resin, which has good compatibility with the dispersant and has excellent storage stability of the electrodeposition coating and excellent finish appearance of the coating. .

The mixing ratio of the aqueous pigment dispersion liquid of the present invention can be varied within a wide range depending on the kind of pigment in the dispersion liquid and the degree of coloring required for the final paint. The aqueous pigment dispersion (solid content) can be blended in the range of 2 to 100 parts by weight based on 100 parts by weight of the resin content of the electrodeposition coating composition.

[0047]

In the present invention, the dispersant conventionally used in the aqueous pigment dispersion has an acidic group derived from an unsaturated carboxylic acid and a basic group derived from a nitrogen-containing monomer, and has a C Properties by introducing a hydrophobic group and a hydrophilic group (the acidic group or the basic group) derived from the (meth) acrylic acid ester of an _8- C ₂₄ monoalcohol (the surface of the pigment is acidic or basic, the pigment is The dispersibility of various pigments (inorganic or organic, etc.) was improved. However, when the hydrophobic group is strengthened, the water solubility decreases, and therefore the dispersant If the hydrophilicity is increased, the copolymer adsorbed on the pigment will be separated from the pigment during storage and the sediment due to the pigment aggregation will increase, and both will be balanced. It was difficult. The dispersant used in the present invention uses a vinyl monomer modified with a polyoxyalkylene glycol or a monoether derivative thereof as a monomer component, so that the dispersant is imparted with appropriate hydrophilicity, As a result, it is presumed that the pigment dispersibility, the storage stability of the aqueous pigment dispersion, and the gloss of the coating film finally formed are improved.

[0048]

EXAMPLES The present invention will be described in detail with reference to examples.
In the examples, "part" and "%" are based on weight.

Dispersant 1 Production Example 100 parts of n-butyl cellosolve was placed in a reaction vessel and heated to 120 ° C. Next, the mixture in the ratio shown below,
This solution was added dropwise over about 2 hours. The reaction was carried out under nitrogen injection.

2-ethylhexyl methacrylate 20 parts N-butyl methacrylate 15 parts Acrylic acid 6 parts

[0051]

[Chemical 2]

Bremmer AE-350 ^{* 1} 10 parts Methyl methacrylate 10 parts Styrene 16 parts Azobisisobutyronitrile 2 parts (* 1: manufactured by NOF CORPORATION, trade name, polyethylene glycol monoacrylate, weight average molecular weight approx. 380)

While maintaining the reaction temperature at 120 ° C., the above mixture was added dropwise while stirring the reaction solution. After 1 hour from the end of the dropping, 2.5 parts of azobisisobutyronitrile was added to the reaction solution, and after 2 hours, 2.5 parts of azobisisobutyronitrile was added to the reaction solution, and then the temperature was kept at 120 ° C. for 2 hours. The reaction was carried out as it was. A copolymer solution having a heating residue of 50% and a number average molecular weight (copolymer) of 20,000 was obtained. Further, this copolymer was neutralized with triethanolamine (1.0 equivalent neutralization) and water was added to obtain a dispersant consisting of an aqueous solution with a heating residue of 15%.

Dispersant 2 Production Example Dispersant 2 was obtained in the same composition and method as Dispersant 1, except that the total amount of the monomer component Bremmer AE-350 used in the copolymer in Dispersant 1 was replaced with methyl methacrylate.

Preparation Example of Dispersant 3 In Dispersant 1, 10 parts of styrene was used as the monomer component, and
-Ethylhexyl methacrylate 10 parts, methyl methacrylate 20 parts, n-butyl acrylate 25 parts, Bremmer AE-350 ^{* 1} 10 parts, dimethylaminoethyl methacrylate 10 parts, hydroxyethyl acrylate 1
A copolymer solution having a heating residue of 50% and a number average molecular weight (copolymer) of 20,000 was obtained in the same manner as in Dispersant 1 except that the amount was replaced with 5 parts. Further, this copolymer solution was neutralized with hydroxyacetic acid (1.0 equivalent neutralization) and water was added to obtain a dispersant consisting of an aqueous solution with a heating residue of 15%.

Dispersant 4 Production Example Dispersant 3 was heated in the same manner as Dispersant 3 except that 10 parts of Bremmer AE-350 ^{* 1} was replaced by styrene in the monomer component used in the copolymer.
%, A copolymer solution having a number average molecular weight (copolymer) of 20,000 was obtained. Further, this copolymer solution was neutralized with hydroxyacetic acid (1.0 equivalent), water was added, and the heating residue 15
% Dispersant was obtained.

[0057]

[Examples and Comparative Examples] The dispersant and pigment obtained in the above Production Example were mixed in the composition (solid content, parts) described in Table 1, water was added, and titanium white was used for 30 minutes using a shaker disperser. Dispersion was carried out for 2 hours to obtain an aqueous pigment dispersion. The properties of the pigment dispersion are shown in Table 1.

Next, Table 1 shows the aqueous pigment dispersions in the clear coating (I) (Kansai Paint Co., Ltd., trade name, Electron AG200, 8% anion type electrodeposition coating "acrylic melamine curing type"). After mixing according to the above formula (solid content, parts), a 6063S aluminum alloy plate treated with alumite (film thickness 9 μm) was subjected to anion electrodeposition coating to a dry film thickness of about 20 μm, and then at 180 ° C. for 30 minutes.
It was heated for a minute to obtain a colored coating film. Table 1 shows the surface gloss of the coating film.

Further, clear coating (II) [acrylic copolymer (styrene / methyl methacrylate / n-butyl acrylate / dimethylaminoethyl methacrylate /
Hydroxyethyl acrylate = 30/20/25/1
0/15 (parts) number average molecular weight 20,000 75 parts / hexa methylene diisocyanate 25 parts oxime block compound was neutralized with hydroxyacetic acid and then dispersed in water to 8%] After mixing in the indicated composition (solid content, parts), cation electrodeposition was performed on a zinc phosphate-treated steel plate so that the dry film thickness was about 20 μm, followed by heating at 180 ° C. for 30 minutes to obtain a colored coating film. . The surface gloss of the coating film is shown in Table 1.

[0060]

[Table 1]

(* 1) Pigment A: Titanium white CR-97 (trade name, manufactured by Ishihara Sangyo Co., Ltd.) B: Carbon MA-100B (Mitsubishi Chemical Industry Co., Ltd.)
Trade name: C: Cyanine Green TK (Toyo Ink Mfg. Co., Ltd.,
Trade name) D: Phthalocyanine blue 5240K (trade name, Dainichi Seika Kogyo Co., Ltd.)

(* 2) Properties Particle size: Measured according to JIS K 5400 A method. Storability: The state of the dispersion after being left at 40 ° C. for 2 weeks was compared with that of the initial state, and the presence or absence of sedimentation or separation was observed. Color mixing stability: The aqueous pigment dispersions used in the examples and comparative examples are diluted with deionized water until the pigment concentration reaches 1% by volume, and then the pigment A / B becomes 8/2 (volume ratio). After mixing as described above, this product was placed in a test tube, allowed to stand at room temperature for 2 days, and then observed for color separation.

(* 3) Coating surface gloss: 60 degree specular reflectance

Claims (1)

[Claims] 1. A water-based pigment dispersion for electrodeposition paint, comprising a pigment and an aqueous dispersant, wherein the dispersant is a carboxyl group-containing vinyl monomer (a) or a basic group-containing vinyl monomer (b). , A polyoxyalkylene glycol or a monoether derivative thereof modified vinyl monomer (c) and a copolymer containing as an essential monomer component a vinyl monomer (d) having a C ₈ or more alkyl group are neutralized. An aqueous pigment dispersion for electrodeposition coatings, which is an aqueous product obtained by dispersing a neutralized product obtained by neutralizing with an agent in water.