JPS62223278A - Cathodic deposition type electrodeposition coating composition - Google Patents

Abstract

PURPOSE:To provide the titled compsn. which is low temperature-curable and gives a coated surface having excellent smoothness, etc., by blending a reaction product of a high-molecular compd. with an amine compd. and an alpha,beta-unsaturated carboxylic acid with a specified epoxy resin derivative and a polyisocyanate. CONSTITUTION:100g of a high-molecular compd. (A) having an MW of 500-5,000, and C=C double bonds having an iodine value of 50-500 and contg. 1-12wt% oxirane oxygen is reacted with 30-500mmol of an amine compd. (B) of formula I (wherein R1 and R2 are each a member selected from the group consisting of 1-20C hydrocarbon groups, etc.) and 20-200mmol of an alpha,beta-unsaturated carboxylic acid (C) of formula II (wherein R3 and R4 are each H or methyl). 100pts.wt. reaction product is blended with 10-150pts.wt. product obtd. by reacting the epoxy groups of an epoxy resin of formula III (wherein R5 and R6 are each H or a 1-10C alkyl; and n is a number of 0-20) with the component B and/or the component C and 5-200pts.wt. blocked polyisocyanate compd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a cathodically deposited electrodeposition coating composition that is curable at low temperatures, has excellent coated surface smoothness and corrosion resistance, and can be formed into a thick film.

[Problems to be solved by conventional technology and invention]

Resins with basic groups of the following form form cationic resins in water, and when this is used for electrodeposition coating, the resin is deposited on the cathode. Solved the essential drawbacks of conventional anodic electrodeposition paints, in which the resin is neutralized with a base and made water-soluble, namely the elution of metals from the coated object into the paint bath and various problems caused by this. can do.

Various proposals have been made regarding such cathodic deposition type paints.

In recent years, in order to save energy and labor, it has become desirable to bake at a lower temperature, make the electrodeposited coating thicker and eliminate the intermediate coating process, and smooth the surface of the electrocoated coating and eliminate the wet polishing process. It is rare.

In particular, as an acid compound for cathode-deposited electrodeposition coatings with excellent low-temperature curing properties, unsaturated group-containing polymer compounds such as volbutazine are epoxidized, and acrylic (methacrylic) double-layers are highly reactive with amino groups. A type that introduces bonds has been proposed (Japanese Patent Application Laid-Open No. 56-15L777), but with this oxidative polymerization curing type, when the electrodeposited coating is made thick, the internal curing of the coating is insufficient, and corrosion resistance is not practical. , does not satisfy characteristics such as physicality.

As a result of various studies, the present inventors have found that by mixing a blocked isocyanate compound with a resin having a specific oxidative polymerization ability and using a combination of oxidative polymerization curing and isocyanate curing, the internal curability of the coating film can be improved, and it can be cured at low temperatures. The inventors have discovered that it is possible to obtain a cathode-deposited electrodeposition coating material that is hardenable, has excellent coating film slipperiness and corrosion resistance, and can be formed into a thick film.

An object of the present invention is to provide a cathodically deposited electrodeposition paint that is curable at low temperatures, has excellent coated surface smoothness and corrosion resistance, and can be formed into a thick film.

[Means to solve the problem]

That is, the present invention provides (A) a polymer compound 10 having a molecular weight of 500 to 5000 and an iodine value of 50 to 500, a carbon-carbon double bond, and oxirane oxygen in an amount of 1 to 12% by weight.
per 0 g, the general formula H-N (in the formula, R1 and R2 represent a hydrocarbon having 1 to 20 carbon atoms, a part of which may be substituted with a hydroxyl group; however, R1 and R2 can have a ring structure. , the ring structure may contain an unsaturated group.]
30 to 500 mmol of an amine compound represented by and 20 to 200 mmol of an α,β unsaturated carboxylic acid represented by the general formula CH=C-C-OH [wherein R3 and R4 represent a hydrogen atom or a methyl group] The reaction product lOO heavy blue part (B) general formula [wherein R9 and R6 are hydrogen atoms or carbon atoms 1 to 10]
an alkyl group, n is an integer from 0 to 20. ] R2 of the epoxy group of the epoxy resin represented by has a carbon number of 1, which may be partially substituted with a hydroxyl group.
~20 hydrocarbons, provided that R1 and R2 can have a ring structure, and the ring structure can contain an unsaturated group. The amine compound and/or the general formula represented by ] represents a hydrogen atom or a methyl group. ]
, 10 to 150 parts by weight of a reaction product of a β-unsaturated carboxylic acid.

(C) A cathodically deposited electrodeposition coating composition containing 5 to 200 parts by weight of a polyisocyanate compound completely or partially blocked with a compound having two or more active isocyanate groups in one molecule.

500 to 5.00, which is the starting material for the component (^) of the present invention.
A polymer compound having a carbon-carbon double bond with a molecular weight of 0 and an iodine number of 50 to 500 is produced by a conventionally known method.

That is, using an alkali metal or an organic alkali metal compound as a catalyst, a conjugated diolefin having 4 to 10 carbon atoms alone, these diolefins together, or an aromatic vinyl monomer such as styrene in an amount of 50 mol% or less based on the conjugated diolefin. , α-methylstyrene, vinyltoluene, or divinylbenzene at a temperature of 0° C. to 100° C. is a typical manufacturing method. In this case, in order to control the molecular weight and obtain a light-colored low polymer with a low gel content, an organic alkali metal compound such as sodium benzyl is used as a catalyst, and a compound having an alkylaryl group, such as toluene, is used as a chain transfer agent. chain transfer polymerization method (US Pat. No. 37890)
No. 90) or a living polymerization method using a polycyclic aromatic compound such as naphthalene as an activator and an alkali metal such as sodium as a catalyst in a tetrahydrofuran solvent (
(Japanese Patent Publication No. 42-17485, No. 43-27432) or using an aromatic hydrocarbon such as toluene or xylene as a solvent, a dispersion of an alkali metal such as sodium as a catalyst, and an ether such as dioxane and san. Preferred production methods include polymerization methods in which the molecular weight of molecules is controlled by addition (Japanese Patent Publications Nos. 32-7446, 38-1245, and 34-10188). Produced by coordination anion polymerization using an acetonate compound and an alkyl aluminum halide as a catalyst (Japanese Patent Publication No. 45-507, No. 46-8)
No. 0300) low polymers can also be used.

The component (^) of the present invention is to replace the unsaturated compound with hydrogen peroxide,
After epoxidizing by a known method using a peroxide such as peracid to introduce 1 to 12% by weight of oxirane oxygen groups as oxygen, an amine compound represented by [wherein R1 and R2 are the same as above] was added to the solvent. After reacting at a temperature of 50 to 200°C in the presence or absence, α, β unsaturated carboxylic acid represented by the general formula % formula % [wherein R3 and R4 are the same as above] is reacted at a temperature of 100 to 200°C. C
It is produced by reacting with

Oxyrane oxygen content is 1-12%, preferably 2-10%
If the amount is less than this, the addition of amine and α,β unsaturated carboxylic acid is insufficient, resulting in insufficient water solubility and curability, making it undesirable as a paint.

If the amount is more than this, a large amount of unreacted epoxy groups will remain and the stability of the paint will be deteriorated.

Examples of amines used in the reaction are dimethylamine,
Examples include aliphatic amines such as diethylamine, alkanolamines such as methylethanolamine and jetanolamine, and cyclic amines such as morpholine and piperidine.

The amount of amine to be added is 100g of epoxidized polymer compound.
30 to 500 mmol, preferably 50 to .300 mmol.

Examples of α,β unsaturated carboxylic acids include acrylic acid, methacrylic acid and crotonic acid.

The amount of α, β unsaturated carboxylic acid to be added is 20 to 200 as the amount of carboxylic acid per 100 g of the epoxidized polymer compound.
mmol, preferably 50 to 150 mmol.

Component (B) of the present invention is a diglycidyl compound represented by the general formula [wherein R1 and R6 are the same as above] at a temperature of 0 to 200°C, preferably 50°C.
At ~150°C, the amine compound represented by the general formula H-N [wherein R and R2 are the same as above] was added to substantially 2% of the glycidyl compound per mol of the glycidyl compound.
It can be obtained by reacting moles (1, δ~2°0).

Examples of amines used in the reaction are dimethylamine,
Examples include aliphatic amines such as diethylamine, alkanolamines such as methylethanolamine and jetanolamine, and cyclic amines such as morpholine and piperidine.

Further, the above diglycidyl compound may be added at a temperature of 0 to 200°C, preferably 50 to 150°C, α represented by CH=C-C-〇H [wherein R3 and R4 are the same as above],
Component (B) can also be produced by reacting substantially 2 moles (1.8 to 2.0) of β-unsaturated monocarboxylic acid, such as acrylic acid, methacrylic acid, crotonic acid, etc., to 1 mole of diglycidyl compound. can.

Alternatively, after the above glycidyl compound is partially reacted with an amine compound, the remaining glycidyl group may be reacted with an α,β unsaturated molar carboxylic acid.

When carrying out reactions with α, β, and unsaturated molar carboxylic acids, hydroquinone, methoquinone,
By adding 0.01-1.0% of a radical polymerization inhibitor such as N-phenyl/N'-iso10vinyl-P-phenyl diamine and P-benzoquinone, tertiary amines and quaternary ammonium It is preferable to use a suitable catalyst such as a salt, and these reactions can be carried out in the presence or absence of a solvent, but when a solvent is used, it is inert to the reaction. It is possible to use an appropriate amount of a solvent that can be used in electrodeposition paints, such as ethyl cellosolve acetate, MIBK, etc., and mix it with components (A) and (C) as is for use in electrodeposition paints without removing them after the reaction. Although it is practically advantageous, when a completely blocked isocyanate compound is used as component (C), a solvent such as ethyl cellosolve or butyl cellosolve, which is commonly used in electrodeposition coatings, may be used.

In the present invention, it is preferable to react with a carboxylic acid group so that the diglycidyl compound is not present.

If so, this group will react unfavorably with the basic group of the resin (A) or (B) when it is made water-soluble by adding an acid later, causing gelation, resulting in an excessively high viscosity. It interferes with water solubilization. For example, even if water-solubilization is achieved, the aqueous solution changes over time, resulting in disadvantages such as unsteady electrodeposition characteristics or an inability to obtain an electrodeposited coating.

The content of component (B) is in the range of 10 to 150 parts by weight, preferably 30 to 100 parts by weight, based on 100 parts by weight of component (A).

If the content of component (B) is less than this, the smoothness and corrosion resistance of the coating film will not be improved sufficiently, and if it is more than this, the water dispersibility will deteriorate. One is a partially blocked polyisocyanate containing in one molecule a blocked incyanate group and an unblocked active incyanate group that can be thermally dissociated during baking of the coating to regenerate the active incyanate groups. The compound is reacted with the above components (A) and (B), or another component (C), a blocked isocyanate group that can regenerate the active incyanate group by thermal dissociation during baking of the coating film, is added. The completely blocked polyisocyanate compound having two or more molecules in one molecule is
) and (B), the curability of the coating film, particularly the internal curability of the coating film, is improved, and particularly favorable results are obtained in coating film performance such as corrosion resistance and physical properties when the film is thickened.

The content of component (C) is 5 to 200 parts by weight, preferably 2
The content of component (C) is in the range of 0 to 100 parts by weight,
If the amount is less than this, the improvement in internal curability will not be sufficient, and if it is more than this, the water dispersibility will deteriorate.

The above component (C) is a partially blocked or completely blocked compound obtained by reacting a blocking agent in a range of 0.5 to 1.0 mol with respect to 1 mol of NCO groups of the polyisocyanate compound, and hexamethylene diisocyanate. Examples include aromatic or aliphatic diisocyanates such as m- or p-phenylene diisocyanate and 4,4'-diphenylmethane diisocyanate, or reactants of these with polyol components such as ethylene glycol, propylene glycol, and trimethylolpropane. , as blocking agents methanol, ethanol, butanol,
Oximes such as hexanol, cyclohexanol, benzyl alcohol, ethyl cellosolve, butylnoalcohols, methyl ethyl ketoxime, acetoxime, tertiary hydroxyamines such as diethylethanolamine, other phenols, creso/ε-caplactam, etc. Particularly preferable examples include aliphatic alcohol oximes, phenols, and ε-caprolactam.The reaction of this polyisocyanate compound with a blocking agent is carried out using incyanate groups and an inert solvent such as cellosolve acetate, MI BK, MEK, etc. 100 in the presence of
It is prepared by mixing at a temperature below 0.5°C.

In the present invention, after reacting or mixing component (A), component (B), and component (C) in advance, component (A)
) 0.1 to 2.0 preferably 0.2 to the amine group of
It is preferable to neutralize and solubilize with a water-soluble organic acid such as formic acid, acetic acid, propionic acid, lactic acid or the like in an amount of 1.0 molar equivalent.

When dissolving or dispersing the compositions (A), (B) and (C) of the present invention in water, it is possible to facilitate dissolution or dispersion, improve the stability of the aqueous solution, and improve the fluidity of the resin.
For the purpose of improving the smoothness of the coating film, we use ethyl cellosolve, propyl cellosolve, butyl cellosolve, ethylene glycol dimethyl ether, diacetone alcohol, 4-methoxy-4-
It is preferable to use 10 to 100 parts by weight of an organic solvent such as methylpentanone-2 or methyl ethyl ketone per 100 parts by weight of each resin composition.

The cathodically deposited electrodeposition coating composition of the present invention may further contain a metal such as a salt or complex of lead, zinc, iron, tin, manganese, or cobalt as a curing catalyst.

Suitable examples include octyl[i, lead naphthenate, dibutyltin dilaurate, lead acetate, manganese acetate, manganese lactate, cobalt acetate, cobalt lactate, and the like.

The cathodically deposited electrodeposition coating composition of the present invention may further contain suitable pigments such as iron oxide, lead oxide, strontium chromate, carbon black, titanium dioxide, talc, aluminum silicate, and barium sulfate. One or more can be blended.

These pigments can be added as they are to the composition of the present invention, but a large amount of the pigments is added to a portion of component (A) that has been neutralized and dispersed in water or made into an aqueous solution, and then mixed to form a paste-like masterbatch. This paste-like pigment can be added to the composition.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples. The physical properties of the coating films of Examples and Comparative Examples were tested according to JIS-5400.

Production Example 1 [Production of component (A)] Nisseki Polybutadiene B-2000 (number average molecular weight 200
0.1.2 bond (65%) was epoxidized using peracetic acid to form an epoxidized 71-” with an oxirane oxygen content of 6.4%.
j? Diene (E+) was produced. 2.000 g of this epoxidized polybutadiene (E t ) and 711.7 g of ethyl cellosolve were added to 31! ;After charging the autoclave, add 140.0g of dimethylamine and heat at 150°C.
After reacting for 5 hours, unreacted amine was distilled off to produce a solution (EA) of an amine adduct of polybutadiene.

Next, a mixture of 1423.5 g of the above solution (E A ), 79.3 g of acrylic a, 7.6 g of hydroxene and 26.4 g of ethyl cellosolve was added, and further 12 g of ethyl cellosolve was added.
A resin solution (A+) of the component (^) of the present invention was prepared by reacting at 0°C for 3 hours and 45 minutes. The amine value of this product is 9
8.1 mmol/100g, acid value 5.3 mmol/
100 g and the solids concentration was 75.0% by weight.

Production Example 2 [Production of component (A)] Nisseki Polybutadiene B-1800 (number average molecular weight 180
0.1.2 bond 64%) is epoxidized using peracetic acid and contains oxirane oxygen! A 6.5% epoxidized bobutadiene (E2) was produced.

1.000 g of this epoxidized polybutadiene (E2) and 131.0 g of methylethanolamine were charged into a 3Y^ separable flask and reacted at 170°C for 6 hours.

After the reaction, it was cooled to 120°C, and cellosolve acetate 404.
Add 1g, acrylic acid 81.4g, Hydroki Juku 8
．． 8 g of the mixture was added and reacted at 120'C for 5 hours to prepare a resin solution (A2) of component A of the present invention.

The amine value of this product is 108. Immol/100g,
The acid value was 1.3 mmol/100 g, and the solid content concentration was 75% by weight.

Production Example 3 [Production of component (B)] The following compound cH was obtained by reacting bisphenol A and epichlorohydrin in the presence of an alkali catalyst.

As a result, 1.000 g of bisphenol type epoxy resin (trade name: Pico) 1004 Yuka Ciel Epoxy Special Product with an epoxy equivalent of 950 was added to ethyl cellosolve 34
Add 72 g of acrylic acid, 10 g of hydroquinone and 5 g of N,N dimethylaminoethanol, heat to 120°C and react for 3 hours to obtain a resin solution (B1) of component (B) of the present invention. Synthesized. .

Production Example 4 [Production of component (B)] The following compound co, 0 obtained by reacting bisphenol A and epichlorohydrin in the presence of an alkali catalyst was used as a bisphenol type epoxy resin having an epoxy equivalent of 450 [trade name Epicote 1001 oil] Made by Chemical Shell Epoxy■ 1.000gt-M I B K 40
7 g, and added 221 g of jetanolamine and reacted at 100° C. for 3 hours to produce a resin solution (B2) of component (B) of the present invention.

The amine content of this product was 129 mmol/100 g, and the solid content concentration was 75.0% by weight.

Production Example 5 [Component (C) Production of completely blocked polyisocyanate compound] 222 g of n-butanol was added dropwise over 1 hour to a mixture of 504 g of hexamethylene diisocyanate and 286 g of cellosolve acetate at a temperature of 50°C or less, and then at 70°C. 134 g of trimethylolpropane was added to the partially blocked isocyanate synthesized by holding for 1 hour and reacted at 90° C. for 3 hours to produce a resin solution (C1) of component C of the present invention.

This is a completely blocked isocyanate compound with virtually no unreacted incyanate groups, 2 mmol 17100 g of unreacted isocyanate groups, and a solid content concentration of 75.0.
% by weight.

Production Example 6 [Production of component (C) partially blocked polyisocyanate compound] Tolylene diisocyanate (80% 2.4-lylene diisocyanate = mixture of 0% 2,6-tolylene diisocyanate) 174 g 113 g of ε-caprolactam was added to a mixture of 96 g of cellosolve acetate, the temperature was raised to 60° C. in 1 hour, and the temperature was then maintained at 60° C. for 2 hours to produce a resin solution (C2) of component (C) of the present invention.

This product was a partially blocked isocyanate compound, had unreacted incyanate groups of 260 mmol/100 g, and had a solid content concentration of 75.0% by weight.

Production Example 7 [Production of Pigment Paste] 31.6 g of acetic acid was added to 1000 g of the solution (E A ) of the amine adduct of polybutadiene produced in Production Example 1 for neutralization, and then deionized water was added to prepare a 25% by weight aqueous solution. did.

400 g of this 25% by weight aqueous solution, 1 carbon black
0g basic lead silicate 30g, titania 110g, aluminum silicate 100g and glass beads 500g for 1 yen;
The mixture was placed in a stainless steel beaker and stirred vigorously for 2 hours using a high-speed rotating mixer, and then the glass peas were filtered to prepare a pigment paste (pp) having a solid content concentration of 53.8% by weight.

Example 1 400 g of (A r ) produced in Production Example 1, 200 g of (B+) produced in Production Example 3, and (A r ) produced in Production Example 5.
CI ) 200g was mixed at 60℃ for 1 hour to make it homogeneous, then cooled to room temperature and mixed with 6g of dibutyltin dilaurate and vinegar!
After 10.8 g was added and neutralized, deionized water was added with vigorous stirring to prepare a 25% by weight aqueous solution.

Next, 433 g of the pigment paste (pp) manufactured in Production Example 7 and 1.0 g of manganese acetate were added to 2400 g of this aqueous solution.
1,334 g of deionized water was added and thoroughly mixed to prepare an electrodeposition coating liquid having a solid content concentration of 20% by weight.

Using the above electrolyte paint solution, a carbon electrode was used as an anode, and a zinc phosphate treated plate (Japan Test Panel Co., Ltd., Bt3004,0
．． 8X 70X 150mm> was used as a cathode, and cathodic deposition type electrodeposition coating was performed. The test results are shown in Table-1.

Comparative Example 1 After mixing 300 g of (A + > 600 g, B+) produced in Production Example 3 at 60'C for 1 hour to make it homogeneous, it was cooled to room temperature and 12.2 g of acetic acid was added. After mixing, add deionized water while stirring vigorously for 25 minutes.
A wt% aqueous solution was prepared.

Next, 2400 g of this aqueous solution was prepared and mixed on the far side 7 of G:"A to prepare a 20% by weight electrodeposition coating liquid.

Using the above electrodeposition coating liquid, a carbon electrode was used as an anode, and a zinc phosphate treated plate (Japan Test Panel, Bt3θ04,0.
8X 70X 150mm> was used as a cathode, and cathodic deposition type electrodeposition coating was performed. The test results are shown in Table-1.

This Comparative Example 1 is an example in which there is no C component (C,) in Example 1.6 Table 1 [Test Results] Note 1) Rubbing test with methyl isobutyl ketone (1
50 times per minute) Judgment is as follows.

○Unchanged, ΔThe rubbed area becomes cloudy, ×Substrate exposed.

Note 2) Judgment is made as follows based on the maximum rust width from the cut part made on the paint film.

◎1ma+ or less, 01~2■, Δ2~3mII, ×3f
lII11 or more (5% NaCl aqueous solution spray) Note 3)
The coating film was soaked in a 1:1 mixed solution of methanol and acene at 40°C.
After immersion for 24 hours, it is dried and expressed as a percentage of the remaining coating film.

Example 2 500 g of (A 2 ) produced in Production Example 2, 300 g of (B2) produced in Production Example 4, and (2) produced in Production Example 6 were added.
After adding 200 g of Cz) and reacting at 80'C for 1 hour, the mixture was cooled to room temperature, neutralized by adding 6 g of 20% lead octylate and 18 g of acetic acid, and deionized with vigorous stirring to give a solid concentration of 25% by weight. An aqueous solution was prepared.

Next, 346 g of the pigment paste (pp) manufactured in Production Example 7 and 1.5 g of cobalt acetate were added to 2400 g of this aqueous solution.
1,631 g of deionized water was added thereto and thoroughly mixed to prepare an electrodeposition coating liquid having a solid content concentration of 18% by weight.

Using the above electrodeposition coating liquid, a carbon electrode was used as an anode, and a zinc phosphate treated plate (Japan Test Panel Co., Ltd., Bt3004,0
．． (8 x 70 x 160 mm) All cathodes were used and cathodic deposition type electrodeposition coating was performed.

The test results are shown in Table-2.

Comparative Example 2 500g of (A2) produced in Production Example 2 and 300g of (B2) produced in 11M4 were mixed at 80°C for an hour, cooled to room temperature, neutralized by adding 14.4g of acetic acid, and stirred vigorously. inside? An electrodeposition coating solution was prepared by adding deionized water to give a solid content concentration of 25% by weight and 2%, and a test was conducted under the same conditions as in Example 2, and the results are shown in Table 24.

Comparative Example 2 is an example in which the C component (C2) in Example 2 is not present.

Table 2 [Test results] Note 1) Rubbing test with methyl isobutyl getone (1
50 times per minute) Judgment is as follows.

O unchanged, Δ The rubbed area becomes cloudy, Note 2) Judgment is made as follows based on the maximum rust width from the cut part made on the paint film.

01mm or less, 01~2IIIal, 62~3111m
, ×3I1m or more (5% NaCl aqueous solution spray) Note 3
) The coating film was soaked in a 1:l mixed solution of methanol and acene for 40 minutes.
It was immersed at ℃ for 24 hours and then dried and expressed as a percentage of the remaining coating film.

〔Effect of the invention〕

The composition of the present invention has low-temperature curability and superior coating surface smoothness and corrosion resistance compared to conventional cathodic deposition type electrodeposition paints, and can be made into a thick film, making it suitable for use in the automobile industry and all other industrial fields. can be used.

Claims (1)

[Scope of Claims] (A) (B) Molecular weight of 500 to 5000 and 50 to 500
A polymer compound having a carbon-carbon double bond with an iodine value of 1 to 12% by weight of oxirane oxygen. (b) General formula of 30 to 500 mmol per 100 g of the polymer compound ▲ Numerical formula, chemical formula, table, etc. ~20 hydrocarbons, where R_1 and R_2 can have a ring structure, and the ring structure can contain an unsaturated group. ] and (c) 20 to 100 g of the polymer compound of (a) above.
General formula for 200 mmol ▲ Numerical formulas, chemical formulas, tables, etc. are available ▼ [In the formula, R_3 and R_4 represent a hydrogen atom or a methyl group. ] 100 parts by weight of a reaction product of an α,β unsaturated carboxylic acid represented by: (B) General formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [In the formula, R_5 and R_6 are hydrogen atoms or have 1 to 10 carbon atoms.
, where n is an integer from 0 to 20] Substantially all of the epoxy groups of the epoxy resin are converted into amines represented by the general formula ▲ There are numerical formulas, chemical formulas, tables, etc. ▼ [same as (b) above] 10 to 150 parts by weight of a product reacted with an α, β unsaturated carboxylic acid represented by a compound and/or general formula ▲ Numerical formula, chemical formula, table, etc. ▼ [same as above (c)]. (C) A cathodically deposited electrodeposition coating composition containing 5 to 200 parts by weight of a polyisocyanate compound completely or partially blocked with a compound having two or more active isocyanate groups in one molecule.