JPH0212511B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a matte electrodeposition coating method capable of coating a metal article with a specific water-based paint to form a uniform matte coating film.

Conventionally, many methods have been proposed for forming an electrodeposited coating film in a matte state. For example, (1)
A method of treating an electrodeposited coating film with an alcohol solution or an alcohol-containing aqueous solution (see Japanese Patent Publication No. 46-22351), (2) Treating an electrodeposition coating film before baking with hot water or heated steam containing or not containing an acid. (Refer to Japanese Patent Publication No. 47-51927), (3) A method of cleaning the electrodeposited coating with a cationic surfactant (Refer to Japanese Patent Publication No. 48-4447), (4) Electrodeposition before baking. A method of treating a coating film with an aqueous solution of an organic acid or an inorganic acid (see Japanese Patent Publication No. 14159-14160 of 1983), (5) A method of treating an electrodeposited coating film with an aqueous solution of a salt after cleaning it (Japanese Patent Publication No. 56-14159-14160). −
9392), etc.), or (6) a method of dispersing a matting agent in the electrodeposition paint and performing electrodeposition coating after forming an electrodeposition coating film (see Japanese Patent Publication No. 9392). (Refer to Publication No. 16569/1983) etc. are known.

However, the method of treating the coating film with chemicals etc. after forming the electrodeposited coating film does not produce a sufficient matting effect, and the degree of matting changes with changes in the condition of the treatment solution, resulting in uniform matting. There is a problem that a stable coating film cannot be obtained. Furthermore, since this method adds one step to the conventional electrodeposition coating process, there is the problem of reduced work efficiency, and for these reasons, it has not yet been implemented on a practical scale. .

However, the method of blending a matting agent into a paint to make the coating film matte has been practiced for many years in coating methods other than electrodeposition coating.

However, it is difficult to use this method as is in electrodeposition coating. For example, when using an electrodeposition paint in which fine silica powder is dispersed as a matting agent, the fine silica powder tends to settle, resulting in a significant difference in the degree of matting between the top and bottom surfaces of the object being coated. However, there was a problem that the paint became unstable.

On the other hand, it is known from (6) above that a solvent-insoluble particulate polymerization reaction product is added to a paint as a matting agent.

This method has the advantage that the conventional mechanical refining process such as crushing or dispersing the matting agent is not required, but as in the case of adding the matting agent described above, particulate polymerization occurs in the paint. The tendency of the reaction products to settle is unavoidable, so that the problem still remains that uniform matte coatings cannot be obtained.

Unlike these known techniques, the present inventors have achieved a matte coating by simply performing ordinary electrodeposition coating without dispersing a matting agent or treating the electrodeposition coating with chemicals or the like. The present invention was completed as a result of research into a matte electrodeposition coating method that can form a film.

That is, the object of the present invention is to provide a matte electrodeposited coating film that can form a matte electrodeposited coating film on a metal article by a method completely different from conventional methods, which has no difference in gloss or unevenness in gloss, and has a uniform and unique texture. An object of the present invention is to provide an electrodeposition coating method.

To summarize the present invention, the matte electrodeposition coating method of the present invention comprises (a) an α,β-ethylenically unsaturated polycarboxylic acid resin and (b) an epoxy compound, or the (a) component,
A water-based paint prepared by diluting a resin composition containing component (b) and (c) alkoxylated methylolmelamine as film-forming components and a reaction product obtained by heating a water-based emulsion containing these components as an active component. A metal article is immersed therein as an anode, and a voltage is applied between the metal article and the cathode to perform electrodeposition coating, followed by washing with water and then heat treatment.

In the matte electrodeposition coating method of the present invention, a water-based paint prepared by diluting a water-based emulsion of the specific resin composition with water is used.

The α,β-ethylenically unsaturated polycarboxylic acid resin in the present invention is obtained by reacting an α,β-ethylenically unsaturated carboxylic acid with a monomer copolymerizable therewith.

To explain the present invention in detail, the α,β-ethylenically unsaturated polycarboxylic acid resin used in the present invention includes (a) α,β-ethylenically unsaturated carboxylic acid 3-
30% by weight, (b) hydroxyalkyl-containing ester or amide or amide derivative of α,β-ethylenically unsaturated carboxylic acid 5 to 30% by weight (c) Alkyl ester of α,β-ethylenically unsaturated carboxylic acid 30
~80% by weight, (d) other copolymerizable monomers 0 to 20% by weight, and is obtained by reacting a monomer composition blended so that the total amount is 100% by weight, Those with a value of 10 to 200 are preferred.

Suitable (a) α,β-ethylenically unsaturated carboxylic acids include acrylic acid, α-chloroacrylic acid,
Methacrylic acid, itaconic acid, maleic anhydride, maleic acid, fumaric acid, crotonic acid, citraconic acid, mesaconic acid, etc. alone or in mixtures, or their functional derivatives having at least one carboxyl group, such as unsaturated polymerizable Partial esters or amides of di- or poly-carboxylic acids.

(b) As the hydroxyalkyl-containing ester or amide or amide derivative of α,β-ethylenically unsaturated carboxylic acid, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate,
2-hydroxypropyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, diethylene glycol monoacrylate, diethylene glycol monomethacrylate, acrylamide, methacrylamide, methylol acrylamide, methylol methacrylamide, alkoxymethylol acrylamide, alkoxymethylol Examples include methacrylamide, diacetone acrylamide, and diacetone methacrylamide.

(c) Examples of alkyl esters of α,β-ethylenically unsaturated carboxylic acids include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate, n-propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, butyl acrylates, butyl methacrylate, lauryl acrylate, lauryl methacrylate, stearyl acrylate, stearyl methacrylate, hexyl acrylate, 2-ethylhexyl methacrylate, heptyl acrylate, heptyl methacrylate, and similar esters having up to about 20 carbon atoms in the alkyl group are used. can. (d) Other copolymerizable monomers include styrene, α-alkylstyrene, α-chlorostyrene, vinyltoluene, acrylonitrile, vinyl acetate, and the like.

On the other hand, as the epoxy compound, any compound having at least one epoxy group in the molecule can be used, but it is particularly preferable to use an epoxy resin since excellent effects can be obtained.

Epoxy resins include bisphenol epoxy resins, resorcinol epoxy resins, tetrahydroxyphenylmethane epoxy resins, novolac epoxy resins, polyalcohol epoxy resins, polyglycol epoxy resins, glycerin triether epoxy resins, and polyolefin epoxy resins. Type epoxy resin, epoxidized soybean oil, alicyclic type epoxy resin, etc. can be used.

On the other hand, the alkoxylated methylol melamine may be one in which at least a portion of the methylol group is alkoxylated with a lower alcohol. As the lower alcohol, one or more of methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, etc. is used.

The above α and β in the water-based paint used in the present invention
- Regarding the composition ratio of ethylenically unsaturated polycarboxylic acid resin and epoxy compound, the amount of epoxy compound added is limited depending on the amount of acid in the polycarboxylic acid resin, and even when the amount of acid is constant, the amount of epoxy compound added is limited. The amount that can be added varies depending on the epoxy equivalent of. Therefore, it is necessary to select an appropriate polycarboxylic acid resin and add an epoxy compound having an appropriate epoxy equivalent in an amount commensurate with the amount of acid. Generally, the composition ratio of the polycarboxylic acid resin and the epoxy compound is preferably 3 to 70 parts by weight of the epoxy compound per 100 parts by weight of the polycarboxylic acid resin.

In addition, epoxy equivalent refers to the value obtained by dividing the molecular weight of an epoxy compound by the number of epoxy groups.

The method of the present invention includes using an aqueous emulsion of a resin composition obtained by further adding alkoxylated methylolmelamine to the composition of the polycarboxylic acid resin and epoxy compound.

In this case, each composition ratio is polycarboxylic acid resin:
Epoxy compound: alkoxylated methylolmelamine is preferably in the range of 100:5 to 40:5 to 60 (wt%).

In the present invention, when an epoxy compound and an alkoxylated methylol melamine are used together, it is preferable that the reaction with the polycarboxylic acid resin is quick.

The resin composition used in the present invention can be produced, for example, by the following method.

In a reaction vessel equipped with a stirrer, a thermometer, and a reflux condenser, (a) α,β-ethylenically unsaturated polycarboxylic acid resin, (b) epoxy resin, or/and (c) alkoxylated methylol melamine were added in an organic solvent. Mix in the presence of. During or after this mixing, a hydrophilic base is added while stirring, and water is further added to form an emulsion. Next, the temperature is raised to 40°C to reflux temperature, and stirring is continued to complete the reaction. The lower the heating temperature, the longer the reaction time and/or the room temperature standing time.

Examples of organic solvents include alcohols such as methanol, ethanol, n-propanol, isopropyl alcohol, n-butanol, isobutanol, sec-butanol, t-butanol, pentanol, methyl cellosolve, ethyl cellosolve, isopropyl cellosolve, Use cellosolves such as butyl cellosolve, sec-butyl cellosolve, etc.

Examples of hydrophilic bases include ammonia, monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monoisopropylamine, diisopropylamine, triisopropylamine, monobutylamine, dibutylamine, tributylamine, and other alkylamines; ethanolamine,
Diethanolamine, triethanolamine, mono(2-hydroxypropyl)amine, di(2-
Alkanolamines such as hydroxypropyl)amine, tri(2-hydroxypropyl)amine, dimethylaminoethanol, and diethylaminoethanol; alkylene polyamines such as ethylenediamine, propylenediamine, diethylenetriamine, and triethylenetetramine; and alkylenes such as ethyleneimine and propyleneimine. In addition to imines, piperazine, morpholine, pyrazine, pyridine, sodium hydroxide, potassium hydroxide,
Examples include metal hydroxides such as lithium hydroxide.

The hydrophilic base may be added at a molar ratio of 0.1 to 0.8 with respect to the carboxyl groups of the α,β-ethylenically unsaturated polycarboxylic acid resin.

In the production of the resin composition used in the present invention, when an acid is added, the reaction time and coating baking time are shortened, and favorable results can be obtained.
This is because the acid promotes the reaction between α,β-ethylenically unsaturated polycarboxylic acid resin and epoxy compound or/and alkoxylated methylol melamine, and also acts as a crosslinking catalyst during baking of the coating film. It is presumed that this is because of this.

Acids that can be blended into the resin composition include organic acids and/or inorganic acids. Examples of organic acids include formic acid,
Includes acetic acid, oxalic acid, sulfonic acid compounds, etc.
On the other hand, examples of inorganic acids include sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid.

In the present invention, at least one of an organic acid or an inorganic acid
More than one species or a mixture of organic and inorganic acids can be used.

In the present invention, it is preferable to use a sulfonic acid compound because it exhibits particularly excellent effects. Sulfonic acid compounds include aliphatic sulfonic acids and aromatic sulfonic acids. Examples of aliphatic sulfonic acids include alkanesulfonic acids such as methanesulfonic acid and ethanesulfonic acid; examples of aromatic sulfonic acids include
Alkylbenzenesulfonic acids such as m-nonylbenzenesulfonic acid, p-decylbenzenesulfonic acid, p-undecylbenzenesulfonic acid, p-dodecylbenzenesulfonic acid, p-toluenesulfonic acid, dinonylnaphthalenesulfonic acid, dinonylnaphthalene disulfone Acid, dialkylnaphthalenesulfonic acid or disulfonic acid such as dihexylnaphthalenedisulfonic acid, dihebutylnaphthalenedisulfonic acid, dioctylnaphthalenedisulfonic acid, didecylnaphthalenedisulfonic acid, etc. is used.

The acid may be added as desired, and may be added at the time of mixing the coating film-forming components or after mixing, for example, before adding the hydrophilic base. In addition, when adding an acid, a hydrophobic base may be added simultaneously or separately, and in some cases, a salt-containing substance containing a reaction product with the base may be added. In these cases, the acid may be added alone. The same effect can be obtained.

The reason why a hydrophobic base is used to neutralize an acid in the resin composition of the present invention is that an acid is normally neutralized by a base and becomes water-soluble, but when a hydrophobic base is used, the acid remains hydrophobic even after being neutralized. Such hydrophobized neutralized products are included in the resin of the paint film forming component, so they are not removed even if the paint is subjected to ion exchange treatment.
Therefore, the purpose is to keep fluctuations in the amount of acid in the paint small even during continuous operation. The acid or salt-containing substance is within 10% by weight, preferably within 5% by weight, particularly preferably within 5% by weight, based on the coating film forming components of the resin composition.
It is appropriate to add the amount within 1.0% by weight.

This is necessary in order to preserve the excellent physical properties of the resulting matte coating.

The hydrophobic base is particularly preferably one that is sparingly soluble or insoluble in water. Examples include long chain alkyl amines or amines containing aralkyl groups.

In the present invention, the aqueous emulsion of the resin composition obtained by the method described above is used after being diluted with water to an appropriate resin solid content concentration. In this case, colorants and other coating additives commonly used in electrodeposition coating may be mixed and used. Further, the gloss of the coating film can be adjusted as desired by mixing this electrodeposition paint with another electrodeposition coating composition that forms a coating film with excellent gloss.

When a metal article is electrocoated in the aqueous paint prepared in this way, a uniform matte electrocoated film can be obtained regardless of the shape or size of the article.

The water-based paint in the present invention is a water-based emulsion containing the above-mentioned components (a) and (b), or a water-based emulsion containing the components (a) and (b).
As described above, water is added to a resin composition containing a reaction product obtained by heating an aqueous emulsion containing component (c) to obtain a resin solid content concentration of 3 to 35% by weight, preferably 5% by weight. By adjusting and using it after diluting it to ~25% by weight, and by incorporating an inorganic acid and/or an organic acid or an acid salt into this water-based paint composition, the heating temperature can be lowered and desired results can be obtained. can get.

Next, electrodeposition coating is achieved by immersing the metal article in the water-based paint as an anode, providing a cathode, and applying a voltage of about 10 to 300 V for about 10 to 300 seconds between the two electrodes (direct current). Ru.

After the electrodeposition coating is completed, the metal objects in the water-based paint are pulled up and drained, and then washed. Various types of water can be used for cleaning, for example deionized water,
Although tap water and well water are usually used, acids, bases, salts,
Water added or containing surfactants, organic solvents, etc. can also be used. After washing, heat treatment is performed to crosslink the electrodeposition coating. This heat treatment is accomplished at a temperature of about 130-220°C for about 10-80 minutes. During this heat treatment, it is desirable to pre-dry the electrodeposited coating film as this tends to further reduce the gloss value.

Further, in the present invention, the metal article to be coated may be any metal that has conductivity, and its type, size, and shape are not particularly limited. Examples of such metals include iron, copper, aluminum,
Examples include magnesium, aluminum subjected to anodization treatment or chemical conversion treatment, and further aluminum made into boehmite. In particular, in the case of anodized aluminum, it is also possible to use an oxide film that has been colored in advance with dyes, pigments, electrolysis, or the like.

As described above, the method described above is always stable and eliminates gloss differences and gloss unevenness, which is not possible with the conventional method of using electrodeposition paint containing a matting agent on metal articles or the method of post-treating the electrodeposition coating film with chemicals. A matte electrodeposition coating film with a uniform and unique texture is formed. In particular, by optimally blending each component, the gloss value can be made very small.

Furthermore, the coating films obtained by the present invention have excellent adhesion to the object to be coated, and some also have excellent coating film properties such as acid resistance, alkali resistance, and boiling water resistance.

In the present invention, in order to prevent as much as possible changes in the bath composition of the water-based paint caused by continuous coating, it is desirable to control the bath composition by subjecting the paint to various known treatments. As the treatment means, ion exchange treatment, ultrafiltration treatment, reverse osmosis treatment, replenishment treatment of thick paint with low amine concentration, etc. can be carried out alone or in appropriate combinations.

Next, the present invention will be explained with reference to Examples, but the present invention is not limited to these in any way. Note that parts in the following text mean parts by weight.

Example 1 10 parts of acrylic acid, 15 parts of 2-hydroxyethyl methacrylate, and 5 parts of ethyl acrylate were placed in a reaction vessel equipped with a stirrer, a thermometer, and a reflux condenser.
10 parts of styrene, 15 parts of 2-ethylhexyl acrylate, 45 parts of methyl methacrylate, 1.5 parts of azobisisobutyronitrile, 12 parts of ethylene glycol monobutyl ether, and 35 parts of isopropyl alcohol were stirred under reflux for 6 hours. A carboxylic acid resin solution (acid value 78) was prepared. 100 parts of this polycarboxylic acid resin solution, methoxybutoxy mixed methylolmelamine (trade name MX
−40 (manufactured by Sanwa Chemical Co., Ltd.) 30 parts and bisphenol type epoxy resin (trade name Epicote 834)
10 parts (manufactured by Ciel Chemical Co., Ltd.) were added and mixed by stirring.

Next, while stirring, 3.7 parts of dimethylmonoethanolamine was added, followed by further addition of 130 parts of deionized water to form an emulsion. This emulsion-formed internal solution was heated to about 90°C, and
Stirring was continued for a period of time to complete the reaction, and a resin composition was prepared.

Then, add deionized water to bring the resin solids concentration to 10.
A % by weight water-based paint was prepared.

This water-based paint was placed in an electrodeposition tank and kept at 20°C, and a degreased aluminum plate was immersed therein as an anode, and a direct current was applied between it and the stainless steel plate at a voltage of 100V for 2 minutes. Next, the aluminum plate was lifted out of the electrodeposition bath, the liquid was sufficiently drained, and then washed with tap water. After washing, the coating film was air-dried and then heat-treated at 160° C. for 30 minutes to cure the coating film. As a result, a uniform matte electrodeposited coating film with a gloss value of 8% (60° specular reflectance) was formed on the surface of the aluminum plate.

The water-based paint in the electrodeposition tank was optionally passed through an anion exchange resin and a cation exchange resin to keep the liquid composition stable at all times.

Example 2 In a method similar to Example 1, acrylic acid 5
parts, 25 parts of 2-hydroxyethyl methacrylate,
Stirring 10 parts of styrene, 15 parts of butyl acrylate, 45 parts of methyl methacrylate, 1.5 parts of azobisisobutyronitrile, 12 parts of ethylene glycol monobutyl ether, and 35 parts of isopropyl alcohol at reflux temperature (approximately 90°C) for 6 hours, A polycarboxylic acid resin solution (acid value approximately 40) was prepared. 100 parts of this polycarboxylic acid resin solution, 25 parts of methoxybutoxy mixed methylol melamine (product name MX-40 manufactured by Sanwa Chemical Co., Ltd.), and 5 parts of diglycidyl ether type polyethylene glycol (product name Epolite 400E manufactured by Kyoeisha Yushi Co., Ltd.) After mixing p
-0.8 part of dodecylbenzenesulfonic acid was added and mixed. Next, while stirring, 2.3 parts of dimethylmonoethanolamine was added, followed by further addition of 120 parts of deionized water to form an emulsion. The emulsion-formed contents were heated to about 90°C, and
Stirring was continued for a period of time to complete the reaction, and a resin composition was prepared.

Then add deionized water to bring the resin solids concentration to 10.
A % by weight water-based paint was prepared.

An extruded aluminum profile that has been anodized and inorganic electrolytically colored (amber color) is immersed in the electrodeposition tank containing this water-based paint as an anode, and a voltage is applied between it and the cathode stainless steel plate. 170V
DC current was applied for 2 minutes. Next, the extruded aluminum profile was taken out of the electrocoating tank, thoroughly washed with water, and then heat treated at 170°C for 30 minutes, resulting in a uniform matte electrodeposition with excellent adhesion and an even gloss value of 5%. A coating was formed.

Example 3 In a method similar to Example 1, acrylic acid 15
parts, 10 parts of 2-hydroxyethyl acrylate, 2 parts
- 5 parts of hydroxyethyl methacrylate, 5 parts of ethyl acrylate, 10 parts of styrene, 10 parts of octyl acrylate, 35 parts of methyl methacrylate, 1.5 parts of azobisisobutyronitrile, 12 parts of ethylene glycol monobutyl ether, and 35 parts of isopropyl alcohol at reflux temperature. (approx. 90°C) for 6 hours, and the polycarboxylic acid resin solution (acid value
117) was prepared. This polycarboxylic acid resin solution
100 parts, methoxybutoxy mixed methylolmelamine (trade name MX-40 manufactured by Sanwa Chemical Co., Ltd.) 30 parts, p-
With 0.2 parts of dodecylbenzenesulfonic acid
0.2 part of n-butylamine is simultaneously mixed, and further,
After mixing 10 parts of a novolac type epoxy resin (trade name Epicote 152, manufactured by Shell Chemical Co., Ltd.), 4.2 parts of dimethylmonoethanolamine was added, and further 130 parts of deionized water was added to form an emulsion.
This emulsion was heated to about 90° C. and stirred for about 3 hours to complete the reaction, and a resin composition was prepared.

Then add deionized water to bring the resin solids concentration to 10.
% by weight, and further dispersed 25 parts by weight of titanium white per 100 parts by weight of the resin solid content to prepare a white water-based paint. An iron plate treated with zinc phosphate was immersed as an anode in the electrodeposition tank containing this water-based paint, and a direct current was applied between it and the stainless steel cathode at a voltage of 100 volts for 2 minutes. Next, the iron plate was taken out of the electrodeposition tank, thoroughly washed with water, and then heated at 170°C for 30 minutes, resulting in a white, uniform, matte electrodeposition coating with excellent adhesion and an even gloss value of 6%. A film was formed.

Example 4 Anodized aluminum with inorganic electrolytic coloring
The same method as in Example 2 was carried out except that it was immersed in an aqueous nickel sulfate solution at 95° C. for 2 minutes and subjected to a semi-sealing treatment. As a result, a uniform matte electrodeposited coating film with a gloss value of 5% was similarly formed.

Example 5 When carrying out the method of Example 2 continuously, in order to replenish the resin solid content that decreases in the water-based paint composition, the resin solid content concentration was increased to 40% by weight and neutralized every time the resin solid content decreased to 0.2% or less. A replenishment paint with a concentration of 0.25 (same as the above water-based paint except that the degree of neutralization was changed) was added to the paint bath at a rate of 5 g per paint bath to minimize fluctuations in the resin solid content and amine concentration of the paint. I kept it. As a result, a homogeneous matte electrodeposited coating (gloss value 5
~8%) were stably formed.

Example 6 In continuously carrying out the method of Example 2 (PH8.9), a portion of the water-based paint was passed through the cation exchange resin every time the pH in the water-based paint increased by 0.4. As a result, the PH fluctuation range of the water-based paint could be suppressed to a small extent, and a homogeneous matte electrodeposition coating film with a gloss value of 5 to 8% was stably obtained. As explained above, according to the present invention, by using a specific water-based paint, it is possible to form a uniform matte electrodeposited coating film on various metal articles without differences in gloss or unevenness in gloss.

Claims (1)

[Scope of Claims] 1. 3 to 70 parts by weight of (b) an epoxy compound is blended with 100 parts by weight of (a) α, β-ethylenically unsaturated polycarboxylic acid resin to form a coating film forming component; Contains as an active ingredient a reaction product obtained by mixing components and component (b) in the presence of an organic solvent, and heating an aqueous emulsion obtained by sequentially adding a hydrophilic base and water at a temperature of 40°C to reflux. A metal article is immersed as an anode in a water-based paint containing a diluted resin composition.
After performing electrodeposition coating by applying a voltage between the metal article and the cathode, it is washed with water, and then heated at 130 to 220℃ for 10 minutes.
A matte electrodeposition coating method characterized by heat treatment for ~80 minutes. 2 The resin composition is prepared by adding and mixing an inorganic acid and/or an organic acid at the time of mixing or after mixing components (a) and (b), adding a hydrophilic base and water to this, emulsifying it, and then heating it. The matte electrodeposition coating method according to claim 1, which is a composition containing a reaction product obtained by. 3. The resin composition is emulsionized by adding and mixing an inorganic acid and/or an organic acid and a hydrophobic base during or after mixing components (a) and (b), and adding a hydrophilic base and water to this. The matte electrodeposition coating method according to claim 1, which is a composition containing a reaction product obtained by heating after heating. 4 The resin composition is prepared by adding and mixing a salt-containing material obtained from an inorganic acid and/or an organic acid and a hydrophobic base during or after mixing components (a) and (b), and adding and mixing a salt-containing material obtained from an inorganic acid and/or an organic acid and a hydrophobic base. The matte electrodeposition coating method according to claim 1, which is a composition containing a reaction product obtained by adding water to emulsion and then heating. 5 to 100 parts by weight of (a) α, β-ethylenically unsaturated polycarboxylic acid resin, (b) 5 to 40 parts by weight of epoxy compound
parts by weight and (c) 5 to 60 parts by weight of alkoxylated methylolmelamine to form a coating film forming component.
A water-based emulsion obtained by mixing components (a), (b) and (c) in the presence of an organic solvent and sequentially adding a hydrophilic base and water is obtained by heating the aqueous emulsion at 40℃ to reflux temperature. A metal article is immersed as an anode in a water-based paint diluted with a resin composition containing a reaction product containing the reaction product as an active ingredient, and a voltage is applied between the metal article and the cathode to perform electrodeposition coating, followed by washing with water. A matte electrodeposition coating method characterized by applying heat treatment at 130 to 220°C for 10 to 80 minutes. 6 The resin composition is emulsionized by adding and mixing an inorganic acid and/or an organic acid during or after mixing components (a), (b) and (c), and adding a hydrophilic base and water to this. The matte electrodeposition coating method according to claim 5, which is a composition containing a reaction product obtained by heating after heating.