JPH07316477A - Resin composition for cationic electrodeposition coating material - Google Patents

Abstract

PURPOSE:To obtain the title composition which can give a coating film showing a small heating loss when baked and improved in low-temperature curability, dye stability, corrosion resistance, solvent resistance and mechanical properties by mixing a cationic-group-containing resin with a specified blocked isocyanate. CONSTITUTION:A blocking agent comprising a sec. amine of the formula: R1-NH-R2 (R1 is 1-10C alkyl or cycloalkyl; and R2 is 3-10C alkyl or cycloalkyl, provided that they may be combined with each other to form a ring) is reacted with a polyisocyanate at 30-100 deg.C to obtain a blocked polyisocyanate. 90-10wt.% cationic-group-containing resin is mixed with 40-60wt.% above blocked polyisocyanate.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel resin composition for cationic electrodeposition coating. More specifically, the present invention has excellent low-temperature curability and excellent bath liquid stability of a paint, has a small amount of heat loss component during baking, and has good corrosion resistance, solvent resistance, mechanical properties, etc. The present invention relates to a resin composition for cationic electrodeposition coating having a film performance.

[0002]

2. Description of the Related Art Electrodeposition coating is superior to air spray coating and electrostatic spray coating for members having a bag structure, such as automobiles and electric appliances, and has excellent throwing power and less environmental pollution. Widely used as a primer coating. As the resin used for electrodeposition coating, a cationic resin is currently in the mainstream, and a resin obtained by cationizing the amino group of a modified epoxy resin having an amino group in the molecule is used as a base resin, and tolylene diisocyanate is used. A typical example thereof is a resin composition containing a blocked polyisocyanate as a curing agent, which is obtained by reacting an aromatic isocyanate such as diphenylmethane diisocyanate with a blocking agent. Examples of the blocking agent used include aliphatic alcohol compounds such as methanol, ethanol, n-butanol and 2-ethylhexanol, cellosolve compounds such as methyl cellosolve, ethyl cellosolve, butyl cellosolve and hexyl cellosolve, acetone oxime, methyl etiketone. There are oxime compounds such as oxime and cyclohexanone oxime, and lactam compounds such as ε-caprolactam.

[0003]

One of the recent problems in electrodeposition coating is the close-up of the problem of low temperature curability. This problem is due to the reduction of energy consumption.
This is an issue that will become even more important in the future. Regarding the curability, the blocked polyisocyanate is the largest contributor, but the existing blocked polyisocyanates currently used are those with good bath liquid stability of the paint, when the baking temperature becomes low, Sufficient coating performance cannot be obtained due to insufficient curability, and on the other hand, those capable of low temperature baking have a problem that good stability cannot be obtained.

[0004]

From the above, the inventors of the present invention can sufficiently bake at a temperature of 150 ° C. or lower, have excellent paint stability, have a small heating loss during baking, and As a result of diligent studies on the development of a resin composition for cationic electrodeposition coatings, which has good coating performance in terms of corrosion resistance, solvent resistance, mechanical properties, etc., a specific secondary amine was identified as a blocking agent for blocked polyisocyanates. It was found that the above object can be achieved by using

That is, the present invention provides a resin composition for a cationic electrodeposition coating composition containing a resin having a cationic group (base resin) and a blocked polyisocyanate (curing agent), represented by the general formula R ₁ -NH-R ₂ ( In the formula, R ₁ has 1 to ₁ carbon atoms.
An alkyl group having 10 or a cycloalkyl group, R
₂ represents an alkyl group having 3 to 10 carbon atoms or a cycloalkyl group, and R ₁ and R ₂ can form a covalent ring in some cases), and a secondary amine represented by A resin composition for a cationic electrodeposition coating, characterized by using a blocked polyisocyanate.

Regarding the resin having a cation group used as the base resin of the present invention, an amino group is introduced into an epoxy resin, an epoxy group-containing acrylic resin, an epoxy group-free acrylic resin, a polyurethane resin or the like, and the amino group is acidified. It is obtained by protonating at. Particularly preferred acids include formic acid, acetic acid, lactic acid, propionic acid, citric acid, malic acid, sulfamic acid and the like. The amount of amino groups is not particularly limited, but usually 0.5 to 3 equivalents per 1000 g of resin is suitable. Particularly preferred resins having a cationic group are epoxy resins and acrylic resins.

The epoxy resin is preferably an epoxy resin having two epoxy groups per molecule on average, and its molecular weight is 400 to 7,000, particularly 400 to 7,000.
4000 is preferred. To give a concrete example, one is 1
It is a glycidyl ether of polyphenol having two phenolic hydroxyl groups in the molecule, and preferable polyphenols are resorcin, hydroquinone, and 2,2.
-Bis- (4-hydroxyphenyl) -propane (commonly called bisphenol A), 4,4'-dihydroxybenzophenone, 1,1-bis- (4-hydroxyphenyl)-
Examples thereof include methane, 1,1-bis- (4-hydroxyphenyl) -ethane, 4,4′-dihydroxybiphenyl and the like. Others are glycidyl ethers of diols having two alcoholic hydroxyl groups in one molecule, and preferable diols are ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol and neo. Pentyl glycol, diethylene glycol, triethylene glycol,
Low molecular weight diols such as 1,4-cyclohexanediol,
Polyethylene glycol, polypropylene glycol,
Examples thereof include oligomer diols such as polytetramethylene glycol, but are not limited thereto, and a mixture of the above epoxy resins is also possible.

In order to obtain a suitable molecular weight, the epoxy resin is made to have a high molecular weight by using a linking agent. Preferred linking agents include the above polyphenols or diols, and further dicarboxylic acids having two carboxyl groups in one molecule, such as adipic acid, azelaic acid, sebacic acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, Examples thereof include isophthalic acid, dimer acid, a butadiene polymer containing a carboxyl group, and a butadiene / acrylonitrile copolymer. As the amine, ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine,
Examples thereof include primary amines such as monoethanolamine, dimethylaminopropylamine and diethylaminopropylamine, and diamines in which each amino group of hexamethylenedimine is secondaryized. It is also possible to extend the chain length with polyisocyanate.

Regarding the epoxy group-containing acrylic resin,
It is obtained by copolymerizing an epoxy group-containing unsaturated monomer, an acrylic monomer and, if necessary, an unsaturated monomer other than the acrylic monomer in the presence of a polymerization initiator. Examples of the epoxy group-containing unsaturated monomer include glycidyl acrylate, glycidyl methacrylate, and allyl glycidyl ether. As the acrylic monomer,
Ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate,
2-hydroxyethyl acrylate, methyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate, cyclohexyl methacrylate, acrylamide, methacrylamide, N-methylol acrylamide, N- (n-butoxymethyl)-
Examples of acrylamide and the like and unsaturated monomers other than the acrylic monomer include styrene, α-methylstyrene, vinyltoluene, cyclohexyl vinyl ether, and acrylonitrile.

As the aminating agent for aminating the epoxy group of the epoxy resin or the epoxy group-containing acrylic resin, methylamine, ethylamine, n-propylamine, isopropylamine, monoethanolamine, n-propanolamine, isopropanolamine is used. , Diethylamine, diethanolamine, N-methylethanolamine, n-ethylethanolamine, ethylenediamine, diethylenetriamine, hydroxyethylaminoethylamine, ethylaminoethylamine, methylaminopropylamine, dimethylaminopropylamine and the like or a mixture thereof.
Among these, alkanolamines having a hydroxyl group are particularly preferable. Alternatively, the primary amino group may be reacted with a ketone in advance to form a block, and then the remaining active hydrogen may be reacted with the epoxy group. As a specific method of amination,
U.S. Pat. No. 3,984,299, U.S. Pat. No. 4,017,438, JP-A-59-40301.
Reference is made to No. 3, etc.

Regarding the epoxy group-free acrylic resin,
Dimethylaminoethyl acrylate, diethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, dimethylaminopropyl acrylamide, an amino group-containing unsaturated monomer such as diallylamine and the above acrylic monomer and optionally an unsaturated monomer other than an acrylic monomer, It is obtained by copolymerization in the presence of a polymerization initiator.

With respect to the polyurethane resin, a diisocyanate having two isocyanate groups per molecule is reacted with a diol having two hydroxyl groups per molecule, and an amino alcohol having a tertiary amino group as a terminal isocyanate group is reacted. And an epoxy group of a polyurethane resin obtained by reacting a terminal isocyanate group with glycidol or the like by an amination by the method described above.

The blocking agent used in the curing agent of the present invention reacts with the isocyanate group of the polyisocyanate shown below to form a blocked polyisocyanate which is a curing agent. In the present invention, as the blocking agent, a secondary amine represented by the general formula R ₁ —NH—R ₂ is used, where R ₁ is an alkyl group or cycloalkyl group having 1 to 10 carbon atoms, and R ₂ is a carbon atom. It represents an alkyl group or a cycloalkyl group having the number 3 to 10, and R ₁ and R ₂ represent a group capable of forming a covalent ring in some cases. R ₁ is a methyl group, an ethyl group, n
-Propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, cyclohexyl group, alkyl-substituted cyclohexyl group and the like can be exemplified, and R ₂ is n-propyl group, isopropyl group, n-butyl group. ,
Examples thereof include an isobutyl group, a tert-butyl group, a cyclohexyl group, and an alkyl-substituted product of a cyclohexyl group. As the shared _{ring, -C 5 H 10 -, -} C 4 H
_{8 -, - C 2 H 4} OC 2 H 4 - or may illustrate these alkyl substituted derivatives.

Specific examples of the secondary amine used in the present invention include ethylisopropylamine, di-n-propylamine, diisopropylamine and isopropyl-te.
rt-butylamine, di-n-butylamine, diisobutylamine, dicyclohexylamine, di- (3,5,5
5-trimethylcyclohexyl) amine, piperidine,
2,6-dimethylpiperidine, pyrrolidine, 2,5-dimethylpyrrolidine, 2,2,6,6-tetramethylpiperidine, morpholine, 2,6-dimethylmorpholine, isopropylcyclohexylamine and the like, or a mixture thereof, It is not limited to these. It is not clear why the blocked isocyanate of the present invention can be baked at a low temperature, but it is considered that one factor is steric hindrance of the substituent of the secondary amine used.

The polyisocyanate used in the present invention is an aromatic or aliphatic (including alicyclic) polyisocyanate. For example, 2,4- or 2,6-toluylene diisocyanate or a mixture thereof, p-
Phenylene diisocyanate, diphenylmethane-4,
4'-diisocyanate, polymethylene polyphenyl isocyanate, tetramethylene diisocyanate, hexamedidiisocyanate, isophorone diisocyanate,
Cyclohexylmethane-4,4'-diisocyanate,
m- or p-xylylene diisocyanate, further a buret modified product or an isocyanurate modified product of the above-mentioned isocyanate, or a part of the isocyanate group of the above-mentioned isocyanate, ethylene glycol, propylene glycol, 1,4-butanediol, 1,6 -Low-molecular diols such as hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol, and 1,4-cyclohexanediol, polyisocyanates linked with oligomer diols such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and polylactone diol. Examples thereof include, but are not limited to, mixtures thereof.

The reaction between the polyisocyanate and the blocking agent can be carried out in a solvent or in a solvent-free melt. As the solvent used in the reaction, a solvent that does not react with polyisocyanate, for example, acetone, methyl etiketone, methyl isobutolketone, cyclopentanone, cyclohexanone, ketone compounds such as isophorone,
Examples thereof include aromatic hydrocarbons such as benzene, toluene, xylene, chlorobenzene, and nitrobenzene, cyclic ether compounds such as tetrahydrofuran and dioxane, and halogenated hydrocarbons such as chloroform and carbon tetrachloride. The reaction temperature is not particularly limited, but is preferably 30 to 100 ° C.

Regarding the blocking agent, the secondary amine is an essential component, but it is also possible to partially use other known blocking agents in combination. To illustrate, aliphatic alcohol compounds such as methanol, ethanol, n-butanol and 2-ethylhexanol, cellosolve compounds such as methyl cellosolve, ethyl cellosolve, butyl cellosolve and hexyl cellosolve, acetone oxime,
There are oxime compounds such as methyl etiketone oxime and cyclohexanone oxime, and lactam compounds such as ε-caprolactam. Regarding the ratio of the secondary amine of the present invention to the other blocking agent, the equivalent amount of the secondary amine of the present invention in all the blocking agents is preferably 70% or more, and more preferably 80% or more.

In the present invention, the mixing ratio of the resin having a cation group (base resin) and the blocked polyisocyanate (curing agent) is 90 to 40/10 to 60, preferably 85 to 50 /. It is 15 to 50, and more preferably 80 to 55/20 to 45.

The acid-neutralized composition for cationic electrodeposition coating composition of the present invention is usually used for electrodeposition coating in a state of being dispersed in water. It is also possible to use an organic solvent other than water together if necessary. For example, isopropanol,
Examples include n-butanol, isobutanol, 2-ethylhexanol, methyl cellosolve, ethyl cellosolve, butyl cellosolve, hexyl cellosolve, methoxypropanol, phenoxypropanol, butylcarbitol, isophorone, toluene, xylene.

The cationic electrodeposition coating resin composition of the present invention may further contain a conventional coating additive, for example, if necessary.
Coloring pigments such as titanium white, carbon black, red iron oxide, and yellow lead, extenders such as kaolin, talc, calcium carbonate, mica, clay, silica, strontium chromate, zinc chromate, lead silicate, basic lead silicate, Lead chromate, basic lead chromate, lead phosphate, red lead, cyanamide lead, lead zincate, lead sulfate, basic lead sulfate,
A rust preventive pigment such as aluminum phosphomolybdate or aluminum tripolyphosphate, an antifoaming agent, a cissing inhibitor, or a curing catalyst may be contained.

The resin composition for a cationic electrodeposition coating composition of the present invention can be coated on a desired substrate surface by a known cationic electrodeposition coating. Specifically, the solid content concentration of the paint is preferably about 5 to 40% by weight, more preferably 15% by weight.
-25%, PH is adjusted to 5-8 depending on the amount of acid used, and the object to be coated can be applied as a cathode under the conditions of a bath temperature of 15-35 ° C and a load voltage of 100-450V, but this condition is not limiting. It is not something that will be done. The coating film thickness obtained from the coating resin composition of the present invention is not particularly limited, but in the cured coating film, 5 to 60 μm, preferably 10 to 40 μm is suitable.

The present invention will be described in more detail below with reference to production examples and examples, but the present invention is not limited thereto.

Production of Blocked Polyisocyanate Production Example 1 Production of Curing Agent A Polymethylene polyphenyl isocyanate having an isocyanate equivalent weight of 140 (Millionate manufactured by Nippon Polyurethane Co., Ltd.) was placed in a four-neck flask equipped with a reflux condenser, a thermometer and a stirrer. MR-400) 812 g, isophorone 249 g, and xylene 541 g were charged and the temperature was raised to 40 ° C. After the temperature was raised, 748 g of di-n-butylamine was added dropwise over 1 hour while maintaining the temperature at 40 to 50 ° C. After the dropwise addition was completed, the reaction was continued for 1 hour, and after the reaction was completed, 249 g of butyl cellosolve was added to adjust the concentration to obtain a curing agent A having a solid content of 60%.

Production Example 2 Production of Curing Agent B The same reaction was carried out by using diisobutylamine instead of di-n-butylamine of Production Example 1 to obtain a curing agent B having a solid content of 60%.

Production Example 3 Production of Curing Agent C The same reaction was carried out by using 655 g of 2,6-dimethylpiperidine instead of di-n-butylamine of Production Example 1 to obtain a curing agent C having a solid content of 60%. .

Production Example 4 Production of Curing Agent D Isophorone 227, 106 g of toluene and 328 g of ε-caprolactam were charged in a four-necked flask equipped with a reflux condenser, a thermometer and a stirrer, and the temperature was raised to 45 ° C. and ε- Dissolve caprolactam. After the dissolution, 812 g of polymethylene polyphenyl isocyanate used in Production Example 1 was charged over 1 hour, and the mixture was reacted at 40 to 50 ° C. for 3 hours. After the reaction, 483 g of butyl cellosolve was added dropwise over 1 hour while maintaining the same temperature, and after the addition, the temperature was raised to 90 ° C. and kept for 2 hours to obtain a curing agent D having a solid content of 75%.

Production Example 5 Production of Base Resin A A bisphenol A type epoxy resin having an epoxy equivalent of 950 (Sumiepoxy ESA-014 manufactured by Sumitomo Chemical Co., Ltd.) was placed in a four-necked flask equipped with a reflux condenser, a thermometer and a stirrer.
Charge 1805g, 855g methoxy propanol,
Heat up to 90 ° C. Next, while maintaining the same temperature, diethanolamine was added dropwise over 1 hour, and after the addition, the temperature was kept for 2 hours to obtain a base resin A having a solid content of 70%.

Production Example 6 Production of Base Resin B In a four-necked flask equipped with a reflux condenser, a thermometer and a stirrer, 145 g of ethyl cellosolve and 1 of butyl cellosolve were added.
Charge 45g and 110g isopropanol, 105 ℃
After heating up to 450 g of butyl acrylate, 100 g of methyl methacrylate, 150 g of styrene, 200 g of 2-hydroxyethyl methacrylate, 100 g of dimethylaminopropyl acrylamide, and 30 g of azobisisobutyronitrile under reflux, the mixture was added dropwise over 2 hours. Then, the temperature was kept for 4 hours to obtain a base resin B having a solid content of 70%.

Production Example 7 Production of Dispersion Resin A bisphenol A type epoxy resin having an epoxy equivalent of 186 (Sumiepoxy ELA-128 manufactured by Sumitomo Chemical Co., Ltd.) was placed in a four-necked flask equipped with a reflux condenser, a thermometer and a stirrer.
372 g, bisphenol A type epoxy resin having an epoxy equivalent of 475 (Sumiepoxy ESA-01 manufactured by Sumitomo Chemical Co., Ltd.
1) 950 g, methoxypropanol 779 g, diethanolamine 105 g, and diethylaminopropylamine 390 g were charged, the temperature was raised to 120 ° C., and the reaction was carried out at the same temperature for 3 hours to obtain a dispersion resin having a solid content of 70%.

Production Example 8 Production of Pigment Paste In a stainless steel cylindrical container, 286 g of the dispersion resin of Production Example 7,
Charge 9.2 g of formic acid, 983 g of deionized water, 2.6 g of carbon black, 300 g of titanium oxide, 300 g of kaolin, 50 g of basic lead silicate, 40 g of butyl carbitol, stir with a dissolver for 30 minutes, then granulate with a horizontal sand mill. Dispersion was performed until the gauge particle size became 10 μm or less, and a pigment paste having a solid content of 45% was obtained.

Examples 1 to 5 and Comparative Examples 1 and 2 Production of Aqueous Dispersion of Resin Composition for Cationic Electrocoating Composition A clear resin for cationic electrocoating composition was prepared according to the formulation shown in Table 1. Manufacturing Example 5 for producing clear resin,
The base resin of Example 6, the curing agent of Production Examples 1, 2, 3, and 4 and phenoxypropanol were mixed, and the mixture was poured into a mixed solution of deionized water and formic acid at a constant speed with sufficient stirring to emulsify and electrodeposition. It was used as a clear resin for paints.

Test Examples 1 to 7 Production of Cationic Electrodeposition Paint and Paint Evaluation As shown in Table 2, a container made of polyethylene was used and Examples 1 to 1 were prepared.
5328 and 3328 g of the cationic electrodeposition coating clear resin obtained in Comparative Examples 1 and 2 were charged, and 563 g of the pigment paste obtained in Production Example 8 and 2.3 g of the curing catalyst dibutyltin oxide were added with sufficient stirring, and the mixture was thoroughly mixed. The mixture was stirred and mixed to obtain an electrodeposition paint.

Coating Method The cationic electrodeposition coating compositions obtained in Test Examples 1 to 7 were coated on an object to be coated under the condition that the average film thickness after baking was 20 μm.
An untreated cold-rolled steel sheet (150 × 70 × 0.
8 mm) was used.

Test method (1) Heat loss: The coating film dried at 105 ° C. for 3 hours was baked at 160 ° C. for 20 minutes and then evaluated for weight loss. (2) Curability The coating film baked at each temperature for 10 minutes was ethanol. The solvent is wiped with a mixed solvent having a weight ratio of / acetone of 1/1. ◯: No change in coating film after 10 continuous runs ×: Partial dissolution of coating film within 10 cycles (3) Corrosion resistance A coating film baked at 150 ° C. for 20 minutes was sprayed with salt water according to JIS-Z-2731. The test was conducted according to the test method. A scratch reaching the substrate is put on the electrodeposition coated surface with a cutter knife, and the peeled state and rust width of the coating film after 500 hours are evaluated.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

According to the present invention, a resin having a cation group is used as a base resin, and a secondary amine having an alkyl group or a cycloalkyl group (one substituent has 1 to 1 carbon atoms).
0, the other substituent has 3 to 10 carbon atoms, or is blocked with a secondary amine forming a ring structure), by using a polyisocyanate as a curing agent,
Cationic electrodeposition paint that can be baked sufficiently at temperatures below or below, has excellent paint stability, has little loss on heating during baking, and has good coating performance in terms of corrosion resistance, solvent resistance, mechanical properties, etc. A resin composition for use can be provided.

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[Procedure amendment]

[Submission date] May 18, 1995

[Procedure Amendment 1]

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The polyisocyanate used in the present invention is an aromatic or aliphatic (including alicyclic) polyisocyanate. For example, 2,4- or 2,6-tri
Diisocyanate or mixtures thereof, p- phenylene diisocyanate, diphenylmethane -4,
4'-diisocyanate, polymethylene polyphenyl isocyanate, tetramethylene diisocyanate, hex
Samethylene diisocyanate , isophorone diisocyanate, cyclohexylmethane-4,4'-diisocyanate, m- or p-xylylene diisocyanate,
Furthermore, a buret modified product or an isocyanurate modified product of the above-mentioned isocyanate, or a part of the isocyanate group of the above-mentioned isocyanate, ethylene glycol,
Propylene glycol, 1,4-butanediol, 1,
6-hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol, 1,4-
Examples thereof include, but are not limited to, low molecular weight diols such as cyclohexanediol, polyisocyanates linked with oligomeric diols such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polylactone diol, and mixtures thereof. .

[Procedure Amendment 2]

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Production Example 4 Production of Curing Agent D A four-necked flask equipped with a reflux condenser, a thermometer and a stirrer was charged with 227 g of isophorone , 106 g of toluene and 328 g of ε-caprolactam and heated to 45 ° C. to obtain ε-.
Dissolve caprolactam. After dissolution, 1 part of 812 g of polymethylene polyphenyl isocyanate used in Production Example 1 was dissolved.
It was charged over time and reacted at 40 to 50 ° C. for 3 hours.
After the reaction, while maintaining the same temperature, butyl cellosolve 483 g
Was dropped over 1 hour, the temperature was raised to 90 ° C. after the dropping, and the temperature was kept for 2 hours to obtain a curing agent D having a solid content of 75%.

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0027

[Correction method] Change

[Correction content]

Production Example 5 Production of Base Resin A A bisphenol A type epoxy resin having an epoxy equivalent of 950 (Sumiepoxy ESA-014 manufactured by Sumitomo Chemical Co., Ltd.) was placed in a four-necked flask equipped with a reflux condenser, a thermometer and a stirrer.
Charge 1805g, 855g methoxy propanol,
Heat up to 90 ° C. Then, while maintaining the same temperature, di
190 g of ethanolamine was added dropwise over 1 hour, and after the addition, the temperature was kept for 2 hours to obtain a base resin A having a solid content of 70%.

Claims (1)

[Claims] 1. A resin composition for a cationic electrodeposition coating composition containing a resin having a cationic group (base resin) and a blocked polyisocyanate (curing agent), wherein R ₁ —NH—R ₂ Wherein R ₁ is an alkyl group or cycloalkyl group having 1 to 10 carbon atoms, and R ₂ is 3 carbon atoms
Blocking was carried out using a secondary amine represented by an alkyl group having 10 to 10 or a cycloalkyl group, wherein R ₁ and R ₂ can form a covalent ring as a blocking agent, A resin composition for a cationic electrodeposition coating, characterized by using a blocked polyisocyanate.