JPS6141274B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a cationic electrodeposition coating method. Although the rust prevention of automobile bodies has been considerably improved with the introduction of cationic electrodeposition paints, it has not yet reached a fully satisfactory level. In particular, physical properties of the coating film, such as secondary adhesion, chipping resistance, and corrosion resistance, are in need of improvement. Furthermore, conventional blocked isocyanate-curing cationic electrodeposition paints have inherent disadvantages such as higher baking temperatures and higher amounts of smoke and tar than anionic electrodeposition paints. There is. In order to solve such problems and drawbacks, the present inventors continued their intensive research, and as a result, they discovered a new crosslinking and thermosetting reaction (Michael type addition reaction) technology that is completely different from the conventional technology. The inventors have discovered that the above-mentioned problems can be significantly improved by applying the method, and have completed the present invention. That is, the present invention provides a primary amine group or a secondary amine group.
A cationic electrodeposition paint bath consisting of a polyamine resin solution having an amine group is used to electrodeposit the conductive object as a cathode, and then a spray paint consisting of a resin solution having one or more acryloyl or methacryloyl groups in the molecule. This invention relates to a cationic electrodeposition coating method characterized in that the cationic electrodeposition paint film and the spray paint film are simultaneously baked and cured. The polyamine resin having a primary amine group or a secondary amine group (hereinafter simply referred to as polyamine resin) used in the present invention includes, for example, a reaction product of polyepoxide and a primary amine, a polyepoxide and a ketimine-blocked primary amine group. Examples include reaction products with polyamines contained therein. Polyepoxides are compounds having one or more 1,2 epoxy functional groups, such as polyglycidyl ethers of polyphenols (by etherifying polyphenols with epichlorohydrin or dichlorohydrin in the presence of an alkali). etc.). Here, examples of polyphenols include 2,2-bis(4-hydroxyphenyl)propane (referred to as bisphenol A), 1,1-bis(4-hydroxyphenyl)ethane, 2-methyl-1,1 -bis(4-hydroxyphenyl)propane, 2,2-bis(4-hydroxy-3-t-
butylphenyl)propane, bis(2-hydroxynaphthyl)methane, 1,5-dihydroxy-naphthalene, and the like. Also used are oxyalkylated adducts (for example, ethylene oxide adducts or propylene oxide adducts of polyphenols), novolac type phenolic resins, and polyphenolic resins similar to these. Next, as for other polyepoxides,
Examples include epoxidized polyalkadiene resins, glycidyl (meth)acrylic copolymer resins, polyglycidyl ethers of hydroxyl group-containing resins, and polyglycidyl esters of carboxyl group-containing resins. The polyepoxide may be further reacted to undergo chain extension and increase its molecular weight. In this case, chain extenders include active hydrogen-containing compounds that are reactive with epoxy groups, such as compounds containing hydroxyl groups, thiol groups, carboxyl groups, secondary amine groups, etc. (for example, dimer acids, polyether polyols, polyester polyols, etc.). , hydantoin, bisphenol A, polyamide, amino acid, etc.). Polyepoxides are amines (primary amines, ketimine-blocked polyamines containing primary amine groups)
reacts with to form a polyamine resin. Primary amines include monoamines (e.g. propylamine, butylamine, amylamine,
-ethylhexylamine, monoethanolamine, etc.) are preferred. The primary amine reacts with the epoxy group to form a secondary amine group that is useful for subsequent crosslinking reactions. As the ketimine-blocked primary amine group-containing polyamine, the primary amine group in the polyamine (for example, diethylenetriamine, dipropylenetriamine, dibutylenetriamine, triethylenetetramine, etc.) is a ketone (for example, acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.). Examples include those converted to ketimine by reaction with After the ketimine-blocked polyamine containing a primary amine group reacts with an epoxy group, the ketimine group is hydrolyzed by addition of water to form a primary amine group useful for the subsequent crosslinking reaction. By neutralizing the amine group with an acid, polyamine resin can be converted into a cationic base and an aqueous dispersion (cationic electrodeposition paint) can be formed. Here, the acid is an organic acid or an inorganic acid, such as formic acid, acetic acid, lactic acid, and phosphoric acid. The amount of acid used is 30 to 100 of the theoretical total neutralization equivalent.
% amount. The proportion of cationic base in the polyamine resin,
The molecular weights and structures of the various components must be mutually adjusted, taking into consideration the dispersion stability when the polyamine resin is mixed with an aqueous medium, the electrodeposition properties described below, cross-curing properties, coating performance, etc. . If the anode and cathode (conductive coating material) are immersed in an aqueous dispersion of polyamine resin (cationic electrodeposition paint) and a voltage is applied between the two electrodes, the conductive resin will be deposited on the surface of the cathode. . Such cationic electrodeposition coating techniques are well known in the art; however, the deposited coating is one that is not redissolved in the aqueous dispersion (cationic electrodeposition) bath and is removed from the bath. It must be insensitive to moisture to the extent that it will not be washed off by subsequent washing. The molecular weight of the polyamine resin, the type and amount of the cationic base, and the concentration of the aqueous dispersion of the polyamine resin (cationic electrodeposition paint) are all dependent on each other, so their selection is important. In the crosslinking and thermosetting reactions in the present invention, the active hydrogen atoms of the primary amine or secondary amine group of the cationic electrodeposition paint film are carbon-carbon of the (meth)acryloyl group of the spray paint film of the next step. It is mainly a Michael type addition reaction that adds to the double bond of
If necessary, a conventionally known curing method using blocked isocyanate may be used in combination. Polyamine resin is produced by a conventional method, and an example of the basic process is as follows. Part or all of the polyepoxide is charged into a reaction vessel and mixed under a stream of inert gas to form a uniform liquid. If necessary in this step, heating, addition of a suitable organic solvent, preliminary reaction of the polyepoxide with other components such as bisphenol A, etc. can be carried out. The amines are added to the above homogeneous liquid while stirring it at an appropriate temperature under a stream of inert gas. The amines are added by a method such as whole amount charging, divided charging, or dropwise charging, and the type and amount of amines can be changed depending on the timing in the process.
At this stage, heating, cooling, refluxing of volatile components, addition of part of the polyepoxide, solvent, etc. can be carried out. After the addition of amines is completed, the reaction is continued at an appropriate temperature and time, and if necessary,
Add other ingredients and react, dilute with solvent,
A polyamine resin solution is obtained by performing processes such as distillation and filtration. Polyamine resin solution contains neutralizing agent (acid), solvent,
Mixing machines such as resolvers, homo mixers, sand grind mills, attritors, roll mills, etc. that are commonly used for the production of paints with water, pigments, etc.
Mix uniformly using a disperser or the like to create a cationic electrodeposition paint bath that is an aqueous dispersion with a solid content (polyamine resin content) of approximately 10% by weight or more and 25% by weight or less. Next, an electric current is passed between the anode and the cathode (conductive object to be coated) through the obtained cationic electrodeposition paint bath to deposit a coating layer on the cathode. Here, the solvent is a hydrophilic or semi-hydrophilic solvent conventionally used in electrodeposition paints, such as isopropyl alcohol, butyl alcohol, ethyl cellosolve, butyl cellosolve, diacetone alcohol, etc. For example, titanium dioxide, carbon black,
Examples include talc, kaolin, silica, and lead silicate. Resin having one or more acryloyl group or methacryloyl group in the molecule used in the present invention [hereinafter referred to as (meth)acryloyl group-containing resin]
For example, reaction products of polyepoxides (similar to the polyepoxides used in the above-mentioned polyamine resins) and acrylic acid or methacrylic acid, carboxyl group-containing resins (for example, carboxyl group-containing acrylic polymers, carboxyl group-containing polybutadiene, high acid hydroxyl group-containing resins (e.g., reaction products of polyepoxide and monoalcohol or phenol, epoxy groups obtained by reacting polyepoxide with excess polyhydric alcohol) transetherification reaction product of N-alkoxymethylacrylamide or N-alkoxymethylmethacrylamide, terminal isocyanate prepolymer and hydroxyalkyl acrylate or hydroxyalkyl methacrylate. The molecular weight, structure, composition, content of acryloyl group or methacryloyl group, etc. of the (meth)acryloyl group-containing resin should be determined depending on the desired properties of the final product. For example, the content of acryloyl or methacryloyl groups may be set to 1, in order to obtain sufficient crosslinking density when curing.
It should contain one or more per molecule, but
When the number exceeds 6, it tends to gel during the reaction of introducing an acryloyl group or a methacryloyl group, so 1 to 6 is preferred, and 2 to 3 is particularly preferred. The reaction product of polyepoxide and acrylic acid or methacrylic acid is usually prepared by heating 2 moles of acrylic acid or methacrylic acid in the presence of 1 mole of polyepoxide, a tertiary amine catalyst, and a known polymerization inhibitor at 100°C. It can be obtained by carrying out the reaction at different temperatures. In this reaction, a suitable organic solvent is added and the whole amount, portions, or
Heating, cooling, and refluxing volatile components are performed by methods such as dripping. Among the reaction products of polyepoxide and acrylic acid or methacrylic acid, those represented by the following general formula are preferred. (wherein R is H or _CH3 , _R1 is H or _CH3 , _R2 is H, _CH3 or _C2H5 , and n is _1-16 . ) A reaction product of a carboxyl group-containing resin and glycidyl acrylate or glycidyl methacrylate can also be obtained by a method similar to the method used to obtain the reaction product of polyepoxide and acrylic acid or methacrylic acid. The reaction product of the hydroxyl group-containing resin and N-alkoxymethylacrylamide or N-alkoxymethylmethacrylamide is usually prepared at 50 to 200°C in the presence of a polymerization inhibitor and preferably an acid catalyst such as p-toluenesulfonic acid. Preferably 80-160℃
and the transetherification reaction (to carry out the reaction completely, the alcohol formed is distilled off at atmospheric or reduced pressure or as an azeotrope with a solvent, preferably a hydroxyl-free solvent). ). The (meth)acryloyl group-containing resin is mixed with a hydrophilic solvent, pigment, etc. in a mixer such as a resolver, homomixer, sand grind mill, attritor, or roll mill, which are commonly used in the production of paints.
Mix uniformly using a disperser or the like to obtain a hydrophilic solvent dispersion. An aqueous dispersion can also be obtained by a method similar to the method for obtaining a hydrophilic solvent dispersion, but at least a portion of the tertiary amine group is neutralized with an acid and converted to a cationic base, and then dispersed in water. It is preferable to support sex. Examples of pigments include titanium dioxide, carbon black, talc, kaolin, silica, red lead, cyanamide lead, basic lead citrate, basic lead sulfate, zinc chromate, barium chromate, strontium chromate, and chromium. Examples include calcium acid, zinc phosphate, and zinc molybdate. The present invention is carried out as follows using a cationic electrodeposition paint made of the above-mentioned polyamine resin solution and a spray paint made of a (meth)acryloyl group-containing resin solution (hydrophilic solvent dispersion or water dispersion). be done. That is, electrodeposition is applied in a cationic electrodeposition paint bath consisting of a polyamine resin solution using the conductive substrate as a cathode in the same manner as normal cationic electrodeposition painting, and immediately after washing with water, the undried cationic electrodeposition paint is applied. On the paint film, or on the cationic electrodeposition paint film that has been pre-dried at 50-120℃ for 5-60 minutes after washing with water.
A spray paint consisting of a (meth)acryloyl group-containing resin solution (hydrophilic solvent dispersion or water dispersion) is sprayed, and the cationic electrodeposition paint film and the spray paint film are heated at 150 to 190°C for 10 to 40 minutes. By simultaneously baking and curing, a cured coating film that is thick (30 to 50μ) and has excellent adhesion, flexibility, chipping resistance, water resistance, alkali resistance, acid resistance, etc. can be obtained. . Next, the present invention will be explained in further detail by giving production examples, examples, and comparative examples. In the examples, parts are parts by weight, and % is weight %. Production Example 1 (Cationic electrodeposition paint A consisting of polyamine resin solution) Polyepoxide (manufactured by Yuka Ciel Epoxy Co., Ltd., Epicoat #1001, obtained by the reaction of bisphenol A and epichlorohydrin) was placed in a reaction vessel.
epoxy resin with an epoxy equivalent of 450 to 500) 507 parts,
24 parts of xylene was charged and the temperature was gradually raised to 140 to 150°C to remove water present in the resin. Next, 145 parts of dimer acid (Versatime #216, manufactured by Daiichi General Co., Ltd.) and 1 part of dimethylethanolamine were added, and the mixture was maintained at 120°C for about 2 hours. After the acid value became 1 or less, it was cooled to 80℃ and diketimine (made from 1 mole of diethylenetriamine and 2 moles of methyl isobutyl ketone)126
Added a section. Then, after holding it at 80-100℃ for about 1 hour,
The temperature was raised to 120°C, xylene was removed under reduced pressure, 222 parts of ethyl cellosolve was added, and the mixture was cooled to room temperature to obtain a polyamine resin solution. For 1000 parts of the obtained polyamine resin solution,
6.8 parts of acetic acid and 405.0 parts of deionized water were added to obtain cationic electrodeposition paint A having a polyamine resin content of 13%. Production Example 2 (Cationic electrodeposition paint B consisting of polyamine resin solution) Polyepoxide in the reaction vessel (Preparation Example 1)
532 parts of resin and 28 parts of xylene were charged, and the temperature was gradually raised to 140 to 150°C to remove water present in the resin. Next, 66 parts of xylene, dimethylhydantoin
Add 34 parts and hold at 140℃ for 3 hours, then heat to 80℃
92 parts of diketimine (preparation example 1 above) and 59 parts of monoethanolamine were added. Then, after holding at 80 to 100°C for 1 hour, 252 parts of butyl cellosolve was added, and the mixture was cooled to room temperature to obtain a polyamine resin solution. For 100 parts of the obtained polyamine resin solution,
8 parts of acetic acid and 392 parts of deionized water were added to obtain a cationic electrodeposition paint B having a polyamine resin content of 13%. Production Example 3 (Cationic electrodeposition paint C consisting of polyamine resin solution) Using the polyamine resin solution obtained in Production Example 1, the following mixture was dispersed with a sand grind mill, and then 258.0 parts of deionized water was added to form a solid. A cationic electrodeposition paint C having a content of 18% was obtained. Polyamine resin solution 100.0 parts Titanium dioxide 17.0 Carbon black 1.2 Kaolin 8.0 Acetic acid 7.0 Deionized water 123.0 Production example 4 (Cationic electrodeposition paint D consisting of polyamine resin solution) Polyamine resin solution obtained in Production example 2 After dispersing the following mixture using a sand grind mill, 366.0 parts of deionized water was further added to obtain a cationic electrodeposition paint D having a solid content of 17%. Polyamine resin solution 100.0 parts Titanium dioxide 15.0〃 Carbon black 0.5〃 Kaolin 7.0〃 Acetic acid 8.0〃 Deionized water 117.0〃 Production example 5 [Spray paint A consisting of (meth)acryloyl group-containing resin solution] Polyepoxide (as described above) -Manufacturing example 1)
413 parts of methyl isobutyl ketone, 112 parts of methyl isobutyl ketone, 5 parts of a 30% methanol solution of tetramethylammonium chloride, and 53 parts of acetic acid were heated at 110° C. for 4 hours to defunctionalize and form a polyol. Next, after adding 7 parts of a 40% solution of p-toluenesulfonic acid (transetherification catalyst) in ethyl cellosolve, the pressure inside the reaction vessel was reduced to approximately 25 to 27 mm.
I changed it to Hg. Then, N-butoxymethylacrylamide
141 parts and 9 parts of a 30% solution of hydroxy (polymerization inhibitor) in ethyl cellosolve were added at 130 to 135°C over 1 hour. Then, the butanol produced by the transetherification reaction was distilled off under reduced pressure for about 5 hours, and the pressure inside the reaction vessel was returned to atmospheric pressure with nitrogen gas. ) An acryloyl group-containing resin solution (hydrophilic solvent dispersion, resin content 58%) was obtained. Obtained (meth)acryloyl group-containing resin solution
Spray paint A was obtained by diluting 100 parts with 37 parts of ethyl cellosolve and 56 parts of isopropyl alcohol. Production Example 6 [Spray paint B consisting of (meth)acryloyl group-containing resin solution] Polyepoxide (previous Production Example 1) was placed in the reaction vessel.
606 parts, ethyl cellosolve 280 parts, acrylic acid 94 parts
Part, ethyl cellosolve 30% solution of hydroquinone 13
1 part, 7 parts of a 30% methanol solution of tetramethylammonium chloride was charged, and under nitrogen gas,
Heating at 130°C for 5 hours to defunctionalize the (meth)acryloyl group-containing resin solution (hydrophilic solvent dispersion,
Resin content: 70%) was obtained. Obtained (meth)acryloyl group-containing resin solution
Spray paint B was obtained by diluting 100 parts with 53 parts of ethyl cellosolve and 80 parts of isopropyl alcohol. Production Example 7 [Spray paint C consisting of (meth)acryloyl group-containing resin solution] Epoxidized polybutadiene resin (a liquid with a number average molecular weight of 1100, 87.8% of 1,2-bonds, and 10.2% of trans-1,4-bonds) was placed in a reaction vessel. Epoxidized polybutadiene with oxirane oxygen content
8.3%) 500 parts, butyl cellosolve 300
A 40% aqueous solution of dimethylamine was added dropwise over 30 minutes while stirring and maintaining the temperature at 70°C. Next, 2 parts of hydroquinone was added, and 130 parts of acrylic acid was gradually added dropwise while maintaining the temperature at 90°C, and the addition reaction was continued for 4 hours to introduce an acryloyl group to obtain a resin solution (resin content: 70%). The obtained resin solution was neutralized with acetic acid in an equimolar amount to the amine group in the resin solution, and then diluted with deionized water to obtain a (meth)acryloyl group-containing resin solution (water dispersion, resin content 50%). I got it. Obtained (meth)acryloyl group-containing resin solution
Spray paint C was obtained by diluting 100 parts with 29 parts of ethyl cellosolve and 36 parts of deionized water. Example 1 The cationic electrodeposition paint A obtained in Production Example 1 was electrodeposited (film thickness 22μ) using a zinc phosphate treated steel plate as the cathode under the conditions of bath temperature 27°C, applied voltage 120V, and current application time 2 minutes. ), then washed with water and sufficiently air-blown to obtain an undried coating film. Spray paint A obtained in Production Example 5 was spray-coated and baked (160℃ for 20 minutes, 170℃ for 20 minutes). Test specimens were obtained (in two different ways for 20 minutes). The obtained test pieces were tested for acetone resistance, pencil hardness, impact resistance, bending resistance, etc. The test results are shown in Table 1. Example 2 The cationic electrodeposition paint B obtained in Production Example 2 was electrocoated (film thickness 21μ) using a zinc phosphate-treated steel plate as the cathode under the conditions of bath temperature 27°C, applied voltage 140V, and current application time 2 minutes. ), then washed with water and thoroughly blown with air. Spray paint B obtained in Production Example 6 was spray-coated on the undried coating film obtained, and baked in the same manner as in Example 1 to form a test piece. Obtained. The obtained test piece was subjected to the same test as in Example 1. The test results are shown in Table 1. Example 3 The cationic electrodeposition paint A obtained in Production Example 1 was electrodeposited (film thickness 21μ) using a zinc phosphate treated steel plate as the cathode under the conditions of bath temperature 27°C, applied voltage 120V, and current application time 2 minutes. ), then washed with water, thoroughly blown with air, and pre-dried at 110°C for 25 minutes. Spray paint C obtained in Production Example 7 was spray-coated and baked in the same manner as in Example 1. A test piece was obtained. The obtained test piece was subjected to the same test as in Example 1. The test results are shown in Table 1. Example 4 The cationic electrodeposition paint C obtained in Production Example 3 was electrocoated (film thickness 20μ) using a zinc phosphate treated steel plate as the cathode under the conditions of bath temperature 28°C, applied voltage 200V, and energization time 3 minutes. ), washed with water and sufficiently air-blown to obtain an undried coating film, and then added the (meth)acryloyl group-containing resin solution obtained in Production Example 5.
For 100.0 parts, butyl cellosolve 46.0 parts, titanium dioxide 63.6 parts, kaolin 27.0 parts, silica 5.0 parts
Spray paint (gray color) D obtained by adding 63.0 parts of isopropyl alcohol to a mixture of 0.4 parts of carbon black and 4.0 parts of strontium chromate separated using a sand grind mill was applied.
A test piece was obtained by baking at 170°C for 25 minutes. Regarding the obtained test pieces, the appearance of the coating film, corrosion resistance,
Adhesion, impact resistance, flexibility (Erichsen value),
Tests were conducted on chipping resistance, water resistance, alkali resistance, acid resistance, etc. The test results are shown in Table 2. Example 5 The cationic electrodeposition paint D obtained in Production Example 4 was electrodeposited (film thickness 21μ) using a zinc phosphate treated steel plate as the cathode under the conditions of bath temperature 28°C, applied voltage 240V, and energization time 3 minutes. ), then washed with water and sufficiently air-blown to obtain an undried coating film, and then spray-painted the spray paint (gray color) D obtained in Example 4,
A test piece was obtained by baking at 170°C for 25 minutes. A test similar to that in Example 4 was conducted on the obtained test piece. The test results are shown in Table 2. Example 6 55.0 parts of butyl cellosolve and 49.0 parts of titanium dioxide were added to the undried coating film of the cationic electrodeposition paint D obtained in Example 5, based on 100.0 parts of the (meth)acryloyl group-containing resin solution obtained in Production Example 6. part, talc
34.0 parts, 3.8 parts of silica, 1.2 parts of carbon black,
Spray paint (gray color) E obtained by adding 13.0 parts of butyl cellosolve and 46.0 parts of isopropyl alcohol to 8.0 parts of zinc phosphate dispersed in a sand grind mill was spray-coated and baked at 170°C for 25 minutes to prepare a test piece. I got it. A test similar to that in Example 4 was conducted on the obtained test piece. The test results are shown in Table 2. Comparative example 1 2,4-tolylene diisocyanate in the reaction vessel
652 parts and 50 parts of methyl isobutyl ketone were charged.
While stirring and keeping the temperature below 30°C, 488 parts of 2-ethylhexanol was added dropwise over about 5 hours to obtain a semi-blocked product of 2-ethylhexanol of 2,4-tolylene diisocyanate. In addition, polyepoxide (previously described) was added to another reaction vessel.
Production example 1) Prepare 507 parts and 24 parts of xylene, 140~
The temperature was gradually raised to 150°C to remove water present in the resin. Then, it was cooled to 110°C, and 50 parts of methyl isobutyl ketone and the 2-ethylhexanol semi-blocked product of the above 2,4-tolylene diisocyanate were added.
180 parts were added and heated at 120°C for 1 hour. Next, 130 parts of polycaprolactone diol (manufactured by Union Carbide, PCP0200) and 0.4 parts of benzyldimethylamine were added, and after heating at 130°C for 4 hours, 260 parts of methyl isobutyl ketone was added. Then, it was cooled to 80°C and diketimine (previously mentioned) was added.
Production example 1) Add 35 parts and 31 parts of diethylamine,
After heating at 115℃ for 3 hours, ethyl cellosolve
157 parts were added and cooled to room temperature to obtain a polyamine resin solution. For 100.0 parts of the obtained polyamine resin solution, 1.1 parts of dibutyltin dilaurate, 7.0 parts of acetic acid,
Add 426.0 parts of deionized water to polyamine resin: 13
% cationic electrodeposition paint was obtained. The obtained cationic electrodeposition paint was applied at a bath temperature of 27°C and an applied voltage of 120V using a zinc phosphate treated steel plate as a cathode.
Electrodeposition coating (film thickness 21μ) under the condition of 2 minutes of current application.
After that, it was washed with water, thoroughly blown with air, and then baked in the same manner as in Example 1 to obtain a test piece. The obtained test piece was subjected to the same test as in Example 1. The test results are shown in Table 1. Comparative Example 2 Using the polyamine resin solution obtained in Comparative Example 1, the following mixture was dispersed using a sand grind mill, and then 258.0 parts of deionized water was added to obtain a cationic electrodeposition paint with a solid content of 18%. Polyamine resin solution 100.0 parts Dibutyltin dilaurate 1.1〃 Titanium dioxide 17.0〃 Carbon black 1.2〃 Kaolin 8.0〃 Acetic acid 7.0〃 Deionized water 122.0〃 The obtained cationic electrodeposition paint was heated to bath temperature using a zinc phosphate treated steel plate as a cathode. 28℃, applied voltage 240V,
Electrodeposition coating (film thickness 21μ) under the condition of 3 minutes of current application.
After that, it was washed with water, thoroughly blown with air, and then baked at 170°C for 25 minutes to obtain a test piece. The obtained test piece was subjected to the same test as in Example 4. The test results are shown in Table 2.

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Claims (1)

[Claims] 1 Electrodeposition is applied to a conductive object using a cationic electrodeposition paint bath consisting of a polyamine resin solution having a primary or secondary amine group as a cathode, and then one or more acryloyl or methacryloyl groups in the molecule is applied. 1. A cationic electrodeposition coating method, which comprises spraying a spray paint made of a resin solution having a cationic electrodeposition paint film and simultaneously baking and curing the cationic electrodeposition paint film and the spray paint film.