JPH10204338A - Cationic electrodeposition coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a coating compsn. that gives a coating film having a high kaolin content and a low metal ion content and excellent in external appearance and corrosion resistance, by dispersing a cationic amine-modified epoxy resin, a blocked polyisocyanate curing agent, and a pigment paste contg. baked kaolin having a specified acidity parameter into a water-base medium contg. a neutralizer. SOLUTION: Baked kaolin occupies 10-90wt.% of the pigments contained in the pigment paste, and the metal ion content of the compsn. is set at 500ppm or lower. Pref. the acidity parameter of the baked kaolin is -3 to +8μmol/m<3> . The cationic amine-modified epoxy resin is pref. one obtd. by the ring-opening with an amine compd., esp. one contg. oxazolidone rings and obtd. by reacting a bisurethane with a difunctional epoxy resin. The curing agent is a blocked alicyclic diisocyanate (e.g. a blocked hydrogenated TDI, hydrogenated MDI, or norbornane diisocyanate) or a dimer thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION The present invention relates to a cationic electrodeposition coating composition, and more particularly to a cationic electrodeposition coating composition of the type which forms a cured coating film by crosslinking a cationic amine-modified epoxy resin with a blocked polyisocyanate curing agent. About things.

[0002] Cationic electrodeposition coatings generally contain various additives such as a film-forming cationic resin, a curing agent, a pigment component, an aqueous medium and a surfactant. The pigment component contained in such an electrodeposition paint usually contains a color pigment, a rust preventive pigment and an extender pigment. Of these, kaolin is used for the extender pigment in order to enhance the rust prevention and repellency of the electrodeposition film.

[0003] The pigment component contained in the electrodeposition paint is prepared by preparing a pigment-dispersed paste previously dispersed at a high concentration in an aqueous medium, and is then added to the electrodeposition paint and mixed. Pigment dispersion paste, the above-described pigment component, a pigment dispersing resin for efficiently and stably dispersing the pigment component,
Contains aqueous medium. In such a pigment dispersion paste, as the content of kaolin increases, the dispersion stability decreases. If the dispersion stability of the pigment-dispersed paste is reduced, the stability of the electrodeposition paint containing the same is also reduced, which complicates the management of the electrodeposition bath, and the electrodeposition coating in terms of smoothness and rust prevention. The quality of the film may be degraded.

[0004] Further, since the electrodeposition paint usually contains metal ions such as lead, it becomes a water-insoluble metal compound during storage, which lowers the storage stability and may cause poor appearance of the formed coating film. is there. For this reason, it is desirable to eliminate or reduce the concentration of metal ions in the paint.

Accordingly, the present invention provides a cationic coating composition containing kaolin, which has excellent coating film appearance and corrosion resistance and is free of metal ions or capable of reducing its concentration.

According to the disclosure the present invention [0006] The present invention, in an aqueous medium containing a neutralizing agent, and a cationic amine-modified epoxy resin, a blocked polyisocyanate curing agent, a cationic electrodeposition paint obtained by dispersing pigment paste A cationic electrodeposition coating composition, wherein calcined kaolin accounts for 10 to 90% by weight of the pigment component in the pigment dispersion paste, and the metal ion concentration in the coating composition is 500 ppm or less. Things are provided.

In a preferred embodiment, the calcined kaolin has an acidity parameter of −3 to +0.8 μmol / m ² . Preferably, the amine-modified epoxy resin and the curing agent are each an oxazolidone ring-containing amine-modified epoxy resin and an alicyclic polyisocyanate, particularly 2,5- or 2,6-bis (isocyanatomethyl).
Bicyclo [2.2.1] heptane-based curing agent. By combining these requirements, the dispersion stability of kaolin in the paint is improved, and a coating film having excellent smoothness and corrosion resistance is obtained. At the same time, the disadvantages encountered when the metal ion concentration of the system using the non-yellowing block polycyanate curing agent is at least low are avoided.

Detailed Discussion Amine-Modified Epoxy Resins Amine-modified epoxy resins for use in cationic electrodeposition coatings are known. Japanese Patent Publication Nos. 55-34238 and 56-341
86, 59-15929, and the like.

Typically, the entire epoxy ring of the bisphenol type epoxy resin is opened with an active hydrogen compound capable of introducing a cationic group, or a part of the epoxy ring is opened with another active hydrogen compound. And the remaining epoxy ring is opened with an active hydrogen compound capable of introducing a cationic group.

A typical example of the bisphenol type epoxy resin is a bisphenol A type or bisphenol F type epoxy resin. The former commercial product is Epikote 828
(Yuika Shell Epoxy Co., Ltd., epoxy equivalent 180-1
90), Epicoat 1001 (same as above, epoxy equivalent 450
~ 500), Epicoat 1010 (same as above, epoxy equivalent 3
000-4000), and the latter commercially available products include Epikote 807 (same as above, epoxy equivalent: 170). Further, as disclosed in Japanese Patent Application Laid-Open Nos. 5-306327, 6-329755, and 7-33848 of the present applicant, starting from an epoxy resin containing an oxazolidone ring in the chain. Good.

Active hydrogen compounds into which a cationic group can be introduced include primary amines and secondary amines. Examples include butylamine, octylamine, diethylamine,
In addition to dibutylamine, methylbutylamine, monoethanolamine, diethanolamine, N-methylethanolamine and the like, there are secondary amines in which primary amines such as aminoethylethanolamine ketimine and diethylenetriamine diketimine are blocked. The amines may be used in combination of two or more.

Other active hydrogen compounds that can be used to open the epoxy ring include phenol, cresol,
Monophenols such as nonylphenol and nitrophenol; monoalcohols such as hexyl alcohol, 2-ethylhexanol, stearyl alcohol, monobutyl- or monohexyl ether of ethylene glycol or propylene glycol; aliphatic monocarboxylic acids such as stearic acid and octylic acid Acids; aliphatic hydroxycarboxylic acids such as glycolic acid, dimethylolpropionic acid, hydroxypivalic acid, lactic acid, and citric acid; and mercaptoalkanols such as mercaptoethanol.

For the purpose of the present invention, it is preferred to use an amine-modified epoxy resin containing an oxazolidone ring.

It is known that a chain-extended epoxy resin containing an oxazolidone ring can be obtained by reacting a bifunctional epoxy resin with a diisocyanate compound blocked with a monoalcohol, ie, bisurethane. An amine-modified epoxy resin obtained by opening the epoxy ring of this epoxy resin with an amine is one example. Also,
According to the method disclosed in Japanese Patent Application Laid-Open No. Hei 7-33848 of the present applicant, one isocyanate group of a diisocyanate compound is reversibly blocked with a monoalcohol, and the other isocyanate group is a hydroxyl group-containing compound serving as a soft segment. When a bifunctional epoxy resin is reacted with a reversibly blocked asymmetric bisurethane compound, a modified epoxy resin containing an oxazolidone ring and a soft segment is obtained. When the epoxy ring of the modified epoxy resin thus obtained is opened with an active hydrogen compound capable of introducing a cationic group such as an amine, a cationic modified epoxy resin is obtained.

In this method, the hydroxyl compound which irreversibly blocks the other isocyanate group of the diisocyanate compound is an aliphatic monoalcohol having 4 or more carbon atoms such as butanol and 2-ethylhexanol, a long-chain alkylphenol such as nonylphenol, ethylene Glycol monoether such as mono-2-ethylhexyl ether of glycol or propylene glycol.

The cationically modified epoxy resin can also be produced by the method described in Japanese Patent Application Laid-Open No. Hei 6-329755 of the present applicant. In this case, instead of the diisocyanate compound blocked with the monoalcohol, a prepolymer obtained by reacting the difunctional isocyanate compound with the difunctional isocyanate compound serving as a soft segment is obtained by difunctionally blocking the terminal isocyanate group of the prepolymer. React with the epoxy resin and then open the remaining epoxy ring with an active hydrogen compound capable of introducing a cationic group. Examples of the bifunctional active hydrogen compound serving as a soft segment include polyether diol, polyester diol, polyoxyalkylenediamine, bifunctional long-chain fatty acid, terminal carboxyl group nitrile rubber oligomer, terminal hydroxyl group polybutadiene oligomer, and the like.

The curing agent thus obtained amine modified epoxy resin is crosslinked with a blocked polyisocyanate as a curing agent and cured. Blocked polyisocyanates that can be used are well known in the art and include tolylene diisocyanate (TDI),
4,4'-diphenylmethane diisocyanate (MD
I), aromatic diisocyanate compounds such as xylylene diisocyanate (XDI); hexamethylene diisocyanate (HMDI), isophorone diisocyanate (IPDI), 2,5- or 2,6-bis (isocyanatomethyl) bicyclo [2,2 1] An aliphatic or alicyclic diisocyanate compound such as heptane (norbornane diisocyanate NBDI); or a polyisocyanate compound such as a dimer, trimer and trimethylolpropane adduct of these diisocyanate compounds is used.

Preferred curing agents used in the present invention are hydrogenated TDI, hydrogenated MDI, hydrogenated XDI, IPDI, 2,5-
Or an alicyclic diisocyanate such as 2,6-bis (isocyanatomethyl) -bicyclo [2.2.1] heptane (also referred to as norbornane diisocyanate);
Their dimers (biurets), trimers (isocyanurates) and their aliphatic polyhydric alcohols such as ethylene glycol, propylene glycol, trimethylolpropane, hexanetriol and NCO / OH ratio of 2
The adduct or prepolymer obtained by the above reaction is blocked.

The blocking agent is one which is added to an isocyanate group and is stable at ordinary temperature, but can regenerate a free isocyanate group when heated to a temperature higher than the dissociation temperature.

Specifically, phenolic blocking agents such as phenol, cresol, xylenol, chlorophenol and ethylphenol; ε-caprolactam,
lactam blocking agents such as δ-palerolactam, γ-butyrolactam and β-propiolactam; active methylene blocking agents such as ethyl acetoacetate and acetylacetone; methanol, ethanol, propanol,
Butanol, amyl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, propylene glycol monomethyl ether, benzyl alcohol, methyl glycolate, butyl glycolate, diacetone alcohol, methyl lactate and ethyl lactate Alcohol blocking agents such as formaldoxime, acetoaldoxime, acetoxime, methyl ethyl ketoxime, diacetyl monooxime, cyclohexane oxime and the like; butyl mercaptan, hexyl mercaptan, t-butyl mercaptan, thiophenol,
Mercaptan blocking agents such as methylthiophenol and ethylthiophenol; acid amide blocking agents such as acetate amide and benzamide; imide blocking agents such as succinimide and maleic imide; imidazole blocks such as imidazole and 2-ethylimidazole. Agents; and the like. Of these, when low-temperature curing (160 ° C. or lower) is desired, lactam-based and oxime-based blocking agents are preferably used.

The pigment components used in the pigment-dispersed paste electrodeposition paint include coloring pigments such as titanium dioxide, carbon black and red iron oxide, rust preventive pigments such as basic lead silicate and aluminum phosphomolybdate, kaolin, clay, and the like. It is an extender pigment such as talc.

In the present invention, no lead-based rust-preventive pigment is used at all to reduce the lead content, or even if used, the total metal ion concentration of the diluted paint (the state added to the electrodeposition bath) is 500 ppm.
It should be used in the following amounts: If the metal ion concentration is high, the smoothness may decrease.

Further, in the present invention, calcined kaolin is used so as to account for 10 to 90% by weight of all the pigment components in the pigment dispersion paste. The calcined kaolin preferably has an acidity parameter of −3 to 0.8 μmol / m ² .

The acidity parameter of calcined kaolin is represented by the difference between the acid amount and the base amount of kaolin (acid amount-base amount). In addition, the acid amount and the base amount of kaolin can be determined as follows.

(Amount of acid) 5 g of kaolin and N /
50 ml of a 100 methyl isobutyl ketone solution is added to an Erlenmeyer flask, which is tightly sealed and dispersed by stirring at 20 ° C. This was allowed to stand for 24 hours, and the dispersion was centrifuged to remove the supernatant liquid for 10 hours.
Collect ml. The supernatant is diluted with 50 ml of methyl isobutyl ketone and back titrated with N / 100 perchloric acid. The amount of pyridine consumed in this way is determined, and this value is converted into the unit area of kaolin to obtain the acid amount.

(Amount of base) 5 g of kaolin and N / 1 of acetic acid
50 ml of a 00 methyl isobutyl ketone solution is added to an Erlenmeyer flask, sealed tightly, and dispersed by stirring at 20 ° C. This is 2
After leaving for 4 hours, the dispersion was centrifuged and the supernatant was
Collect 1 This supernatant solution is treated with methyl isobutyl ketone /
Dilute with 50 ml of a mixture of methanol at a volume ratio of 3/2 and back titrate with N / 100 potassium methoxide. The amount of acetic acid thus consumed is determined, and this value is converted into the unit area of kaolin to obtain the amount of base.

As is well known, a pigment dispersion paste is prepared by dispersing a pigment component, a dispersing resin, and an aqueous medium into a paste using a mill such as a sand grind mill.

As the resin for dispersing the pigment for the cationic electrodeposition paint, a quaternary ammonium salt type water-soluble cationic resin obtained by ring-opening an epoxy resin with a tertiary amine salt, or an epoxy resin comprising an acid / sulfide A tertiary sulfonium salt type water-soluble cationic resin obtained by ring opening with a mixture is usually used.

Both are well known to those skilled in the art,
Tertiary sulfonium salt type cationic resins are preferred. For example, a bisphenol-type epoxy resin is directly opened with an acid / sulfide mixture, or a half-blocked isocyanate is added to a secondary alcoholic hydroxyl group in the epoxy resin by a urethane bond, and then the ring is opened with an acid / sulfide mixture. Manufactured by Various carboxylic acids and sulfides can be used,
Preference is given to carboxylic acids and sulfides having hydroxyl groups, such as dimethylolpropionic acid and 1- (2-hydroxyethylthio) -2-propanol. When a half-block diisocyanate is added, it is preferable to use a non-yellowing alicyclic diisocyanate.

The pigment dispersing resin is suitably used as a solid content in an amount of 0.1 to 1.0 times the total weight of the pigment component and 0.4 to 1.8 times the calcined kaolin. The nonvolatile content of the paste is generally 20 to 80% by weight, preferably 50 to 80% by weight.
６０60% by weight.

In a system using a non-yellowing blocked polyisocyanate curing agent, the performance including the corrosion resistance of the coating film may be reduced when the lead-free or low-lead content is used. In such a case, a water-soluble cerium, antimony, bismuth or cobalt compound is preferably added to the pigment dispersion paste to adjust the concentration of all metal ions including lead in the coating composition to an appropriate level of 500 ppm or less. Examples of such compounds include cerium acetate, triphenylantimony, bismuth nitrate and cobalt acetate.

Electrodeposition paint The electrodeposition paint of the present invention is prepared by dispersing the above-mentioned cationic epoxy resin, curing agent and pigment dispersion paste in an aqueous medium containing a neutralizing agent. Neutralizing agents are inorganic or organic acids such as hydrochloric, nitric, phosphoric, formic, acetic, lactic acids. The amount is that which achieves a neutralization of at least 20%, preferably 30-60%.

The amount of the curing agent must be sufficient to react with active hydrogen-containing functional groups such as primary and secondary amino groups and hydroxyl groups in the resin during curing to give a good cured coating film. It is generally 95/5 to 45/50, preferably 85/1, expressed as a weight ratio of solid content to resin curing agent.
It is in the range of 5 to 70/30.

The electrodeposition paint is dibutyltin dilaurate,
It can include tin compounds such as dibutyltin oxide, and conventional urethane cleavage catalysts. The amount is usually 0.1 to 5% by weight of the blocked polyisocyanate compound.

The electrodeposition paint can contain conventional paint additives such as a water-miscible organic solvent, a surfactant, an antioxidant and an ultraviolet absorber. Do not use lead-based antirust pigments,
Or diluted paint even when used (in the state of being added to the electrodeposition bath)
Should be used in such an amount that the total metal ion concentration, including lead, is below 500 ppm. In particular, when the lead ion concentration is high, not only is it harmful to the environment, but also the smoothness may decrease.

The following preparations and examples are given by way of illustration and not limitation. In these, "parts" and "%" are based on weight unless otherwise specified.

[0037] Production Example 1 oxazolidone ring-containing cationic resin Part. Production of resin denaturant Coronate 1104 (MDI, NCO equivalent 133.5, manufactured by Nippon Polyurethane) 46.73 in a flask equipped with a stirrer, condenser, nitrogen injection tube, thermometer and dropping funnel.
And 21.93 parts of MIBK, nitrogen was bubbled while stirring, and 6.42 parts of methanol was added dropwise. The temperature rose from room temperature to 60 ° C. At that temperature 3
After stirring for 0 minutes, the temperature was raised to 100 ° C., 20.88 parts of ethylene glycol mono-2-ethylhexyl ether was added dropwise, and the mixture was stirred for 1 hour. Thereafter, 0.01 parts of dibutyltin dilaurate, BP-5P (bisphenol A manufactured by Sanyo Chemical Industries, Ltd.)
13.7 parts of propylene oxide (5 mol adduct) was added, the reaction was continued at 120 ° C. until the isocyanate group disappeared by an infrared spectrometer, and the mixture was cooled. Non-volatile content 80%

Part 2. Oxazolidone ring-containing cationic
Synthesis on the same flask resin, DER-331J (Mitsubishi Dow bisphenol A diglycidyl ether having an epoxy equivalent of 188) 357.2 parts, MIBK21.32 parts, 17.98 parts of methanol, dibutyltin dilaurate 0.0
One part was taken and nitrogen was bubbled while stirring. During that time, 47.85 parts of TDI-80 (Tolylene diisocyanate manufactured by Nippon Polyurethane, NCO equivalent 87) was added dropwise.
The temperature was raised from room temperature to 60 ° C. The reaction was continued at that temperature until the isocyanate group disappeared by infrared spectroscopy. Thereafter, 0.743 parts of dimethylbenzylamine was added, the temperature was raised to 130 ° C., and the reaction was continued for 3 hours. At this time, absorption at 1750 cm ^-1 due to the carbonyl group of the oxazolidone ring was observed by an infrared spectrometer.

Thereafter, the mixture was cooled to 120 ° C., 52.13 parts of 2-ethylhexanoic acid was added, and the reaction was continued for 1 hour.
The reaction was continued for hours. Thereafter, the mixture was cooled to 120 ° C., 30.78 parts of bisphenol A was added, and the reaction was continued for 3 hours.

Thereafter, the mixture was cooled to 100 ° C., and 21 parts of ethylene glycol mono-2-ethylhexyl ether, 24.03 parts of N-methylethanolamine, 10.84 parts of di-n-butylamine, and diethylenetriamine MIBK ketimine (73% MIBK solution) 31.67 parts were added. The temperature rose to 120 ° C. The reaction was continued at the same temperature for 2 hours to obtain an oxazolidone ring-containing cationic resin. Non-volatile content 85%

Production Example 2 In a flask equipped with a block isocyanate curing agent stirrer, a condenser, a nitrogen inlet tube, a thermometer and a dropping funnel, 2,5- and 2,6-bis (isocyanatomethyl) -bicyclo [2. 2.1] Heptane (manufactured by Mitsui Toatsu, NCO equivalent = 103) 723
Parts, 333 parts of methyl isobutyl ketone, and 0.01 of dibutyltin silaurate were weighed and heated to 70 ° C. After homogeneous dissolution, methyl ethyl ketoxime 61
0 parts were added dropwise over 2 hours. Reaction temperature 70 after completion of dropping
The reaction was continued until the NCO group disappeared by IR analysis while maintaining the temperature at ℃ to obtain a curing agent.

Production Example 3 A reaction vessel equipped with a pigment dispersion resin stirrer, a nitrogen inlet tube and a cooling tube was prepared, and 222.2 parts of isophorone diisocyanate was added thereto. This isophorone diisocyanate was diluted with 39.1 parts of methyl isobutyl ketone, and 0.2 part of dibutyltin dilaurate was further added. The temperature was raised to 50 ° C., and 2-ethylhexanol 1 was placed in a dry nitrogen atmosphere.
31.5 parts of the mixture were dropped and reacted over 2 hours with stirring. Further, when the reaction temperature was maintained at 50 ° C., 2-
Ethylhexanol half-blocked isophorone diisocyanate (solid content = 90%) was obtained.

Next, a reaction vessel equipped with a stirrer, a nitrogen introducing pipe, and a cooling pipe was prepared, and epicoat 828 (epoxy resin manufactured by Shell Chemical Co., Ltd .: epoxy equivalent = 19) was added thereto.
0) 382.0 parts and 118.0 parts of bisphenol A were charged. This was heated to 130 ° C. under a nitrogen atmosphere, and 0.15 parts of dimethylbenzylamine was added to the mixture.
The reaction was performed at 0 ° C. for about 1 hour. As a result, a bisphenol-type epoxy resin having an epoxy equivalent of 500 was obtained.

The mixture was cooled to 140 ° C., and 210.0 parts of the previously prepared 2-ethylhexanol half-blocked isophorone diisocyanate was added and reacted for 1 hour. After diluting with 210.0 parts of dipropylene glycol monobutyl ether and cooling to 100 ° C., 408.0 parts of 1- (2-hydroxyethylthio) -2-propanol (136.0 parts of solid content), 134.0 parts of methylolpropionic acid and 14 deionized water
Add 4.0 parts, and add 70 to 7 until the acid value becomes 3.0 or less.
The reaction was carried out at 5 ° C. to obtain a resin having a sulfonium conversion rate of 70.6%. 13.0 parts of lactic acid and 156 of deionized water
8.0 parts were added and diluted to obtain a pigment-dispersed resin varnish.
30% solids

Examples 1 to 9 and Comparative Examples 1 to 4 365.0 parts of the oxazolidone ring-containing cationic resin of Production Example 1 and 130.0 parts of the curing agent of Production Example 2 were uniformly mixed as main emulsion solids. The mixture was neutralized by adding 1.1 parts of glacial acetic acid and 6.3 parts of formic acid, and further slowly diluted by adding 663.6 parts of deionized water. Then, the solvent was removed under reduced pressure so that the solid content became 36.0%, to prepare a main emulsion.

Pigment-dispersed paste According to the formulations shown in Tables 1 and 2, the pigment component, the water-soluble metal compound, the pigment-dispersed resin varnish of Production Example 3 and deionized water were dispersed in a sand grind mill until the particle size became 10 μm or less. A pigment dispersion paste was prepared.

Paint composition and evaluation 890 parts of main emulsion, pigment dispersion paste 250
Parts and solids were mixed with 1% dibutyltin oxide, and deionized water was added to adjust the nonvolatile content to 20% to obtain a cationic electrodeposition paint.

These coatings were tested by the following method. The results are shown in Tables 1 and 2.

Test Method 1. Metal ion concentration The paint was centrifuged at 1200 rpm for 1 hour, and the supernatant was quantified for metal ions (total of lead, cerium, antimony, bismuth, and cobalt) by X-ray fluorescence. Unit ppm 2. Horizontal test piece A test piece having a size of 7 × 15 cm is placed horizontally at a depth of 10 cm in the paint, and allowed to stand for 3 minutes.
After electrodeposition, washed with water and baked at 160 ° C. for 10 minutes. The number of bumps on the painted surface was counted visually. ：: 3 or less; Δ: 4 to 10; ×: 11 or more Finishing property of top coat The Nippon Paint Co., Ltd. super rack M95 silver as a base coat and Super Lack O-100-2 Clear as a top coat are applied to the coating film obtained in the test 2 in two coats and one bake. Was examined for the degree of yellowing. ：: no yellowing; Δ: slight yellowing; ×: marked yellowing Corrosion resistance The paint was electrodeposited on a test piece to a dry film thickness of 20 μm.
Bake at 0 ° C for 10 minutes, and apply 10
cm, and dipped in 5% saline at 55 ° C for 240 hours.
The peel width of the coating film is measured. ：: <2 mm; Δ: 2-4 mm; ×:> 4 mm

[0050]

[Table 1]

[0051]

[Table 2]

Continued on the front page (72) Inventor Mitsuo Yamada 19-17 Ikedanakamachi, Neyagawa-shi, Osaka Inside Nippon Paint Co., Ltd.

Claims (8)

[Claims] 1. A cationic electrodeposition coating composition comprising a cationic amine-modified epoxy resin, a blocked polyisocyanate curing agent, and a pigment dispersion paste dispersed in an aqueous medium containing a neutralizing agent, wherein the pigment is A cationic electrodeposition coating composition, wherein calcined kaolin accounts for 10 to 90% by weight of the pigment component in the dispersion paste, and the metal ion concentration in the coating composition is 500 ppm or less. 2. The pigment dispersion paste according to claim 1, wherein the calcined kaolin, the remaining pigment component, and the total pigment component are contained in an amount of 0.1% by weight.
2. The cationic electrodeposition coating composition according to claim 1, which contains the dispersing resin in an amount of 1 to 1.0 times and 0.4 to 1.8 times of calcined kaolin. 3. The cationic electrodeposition coating composition according to claim ² , wherein the calcined kaolin has an acidity parameter of −3 to +0.8 μmol / m ² . 4. The cationic electrodeposition coating composition according to claim 2, wherein said dispersing resin is a water-soluble modified epoxy resin having a tertiary sulfonium group. 5. The cationic electrodeposition coating composition according to claim 1, wherein said amine-modified epoxy resin contains an oxazolidone ring in the chain. 6. The cationic electrodeposition coating composition according to claim 1, wherein the blocked polyisocyanate curing agent is an alicyclic blocked polyisocyanate curing agent. 7. The cationic electrode according to claim 6, wherein the alicyclic blocked polyisocyanate curing agent is a 2,5- or 2,6-bis (isocyanatomethyl) bicyclo [2.2.1] heptane-based curing agent. Coating composition. 8. The coating composition further comprises at least one metal ion selected from the group consisting of lead, cerium, antimony, bismuth and cobalt, wherein the total metal ion concentration in the coating is 5%.
The cationic electrodeposition coating composition according to any one of claims 1 to 7, which has a content of 00 ppm or less.