JP2022129794A - Cationic electro-deposition coating composition - Google Patents

Abstract

To provide a cationic electro-deposition coating composition which enables formation of an aminated epoxy resin obtained by reacting an amine compound and an epoxy resin without introducing an ester bond, enhances flexibility of a coated film, further improves adhesion and blocking property of the coated film compared to a conventional coated film, and enhances rust prevention.SOLUTION: A cationic electro-deposition coating composition contains an aminated epoxy resin and a blocked polyisocyanate curing agent, where the aminated epoxy resin is an aminated epoxy resin obtained by reacting an amine compound and an epoxy resin, the epoxy resin is a reaction product of a bisphenol type epoxy resin (a1), diglycidyl ether (a2) of a polyalkylene oxide diol compound and a bisphenol compound (a3), a solubility parameter (SP) of the aminated epoxy resin is 10.2-11.5, and an elongation rate after the cationic electro-deposition coating composition is coated onto a steel plate with a dry film thickness of 20 μm, and is baked at 160°C for 15 minutes is 0.1-5.6%.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a cationic electrodeposition coating composition, particularly to a cationic electrodeposition coating composition having excellent flexibility.

Cationic electrodeposition paints are often used as undercoat paints to impart corrosion resistance to industrial products such as automobiles, and contain aminated epoxy resins and blocked polyisocyanate curing agents. Cationic electrodeposition paints require high adhesion, high hydrophobicity (barrier property), flexibility, etc., in addition to high rust resistance. Flexibility is a performance necessary for adhering to a substrate having a complicated structure, and is always required for cationic electrodeposition coating compositions.

In Japanese Patent No. 6681691 (Patent Document 1), the epoxy resin used for the amino group-modified epoxy resin of the cationic electrodeposition coating composition is (a) a propylene oxide-added diepoxy resin, (b) a bisphenol compound, (c) the above It is described to be the reactant of a diepoxy resin different from the propylene oxide adducted diepoxy resin and (d) a dicarboxylic acid in which the carboxyl group is attached through at least one carbon atom. In this cationic electrodeposition coating composition, the amino group-modified epoxy resin has an ester bond due to the reaction with a dicarboxylic acid, and hydrolysis of the ester bond leads to a decrease in corrosion resistance and a decrease in paint stability over time. be.

Japanese Patent No. 6681691

In the present invention, an aminated epoxy resin obtained by reacting an amine compound with an epoxy resin is formed without introducing an ester bond to increase the flexibility of the coating film, and the adhesion and barrier properties of the coating film. To provide a cationic electrodeposition coating composition which further improves rust prevention properties by further improving the above than conventional ones.

Specifically, the present invention provides the following aspects:
[1]
A cationic electrodeposition coating composition containing an aminated epoxy resin and a blocked polyisocyanate curing agent,
The aminated epoxy resin is an aminated epoxy resin obtained by reacting an amine compound with an epoxy resin,
The epoxy resin is a reaction product of a bisphenol type epoxy resin (a1), a diglycidyl ether of a polyalkylene oxide diol compound (a2) and a bisphenol compound (a3),
The solubility parameter (SP) of the aminated epoxy resin is 10.2 to 11.5,
A cationic electrodeposition coating composition having an elongation of 0.1 to 5.6% after coating a steel plate with the cationic electrodeposition coating composition to a dry film thickness of 20 μm and baking at 160° C. for 15 minutes. .
[2]
According to [1], wherein the diglycidyl ether (a2) of the polyalkylene oxide diol compound is selected from the group consisting of polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, polybutylene glycol diglycidyl ether and mixtures thereof. Cationic electrodeposition coating composition.
[3]
the amine compound is a combination of two types of primary amine and secondary amine;
The primary amine has the formula:
NH2-( _CH2 )n _- ^NR1R2 ( ¹ )
(In formula (1), R ¹ and R ² are the same or different and represent an alkyl group having 1 to 6 carbon atoms which may have a terminal hydroxyl group, and n represents an integer of 2 to 4.)
has
A secondary amine of the formula:
^R3R4NH ( ² )
(In formula (2), R ³ and R ⁴ represent an alkyl group having 1 to 4 carbon atoms and having a terminal hydroxyl group.)
The cationic electrodeposition coating composition according to [1] or [2].
[4]
A cationic electrodeposition coating film coated using the cationic electrodeposition coating composition according to any one of [1] to [3].

In the present invention, when producing an aminated epoxy resin, a diglycidyl ether of a polyalkylene oxide diol compound is used as part of the epoxy resin to synthesize the aminated epoxy resin, and the flexibility due to the alkylene oxide is obtained by adding an ether group. It is introduced into the epoxy resin skeleton via and introduced into the cationic electrodeposition coating composition without using a highly hydrolyzable ester bond as in the conventional method, and the cationic electrodeposition coating composition is made to have a cured film thickness of 20 μm. It is characterized by an elongation rate of 0.1 to 5.6% after coating on a steel plate and baking at 160° C. for 15 minutes. By using the diglycidyl ether of the alkylene oxide diol compound, the elongation rate of the electrodeposition coating film can be increased, and corrosion resistance, adhesion and barrier properties can be exhibited.

The cationic electrodeposition coating composition of the present invention is a cationic electrodeposition coating composition containing an aminated epoxy resin and a blocked polyisocyanate curing agent, wherein the aminated epoxy resin reacts the amine compound with the epoxy resin. and the epoxy resin is a reaction product of a bisphenol type epoxy resin (a1), a diglycidyl ether of a polyalkylene oxide diol compound (a2) and a bisphenol compound (a3) The solubility parameter (SP) of the aminated epoxy resin is 10.2 to 11.5, and the cationic electrodeposition coating composition is applied to a steel plate so as to have a dry film thickness of 20 μm and baked at 160° C. for 15 minutes. It has an elongation rate of 0.1 to 5.6% after it is applied. In this specification, when a numerical range is expressed as "a to b" (both a and b represent numerical values), it means from a to b.

<Amine epoxy resin>
Aminated epoxy resins are film-forming resins that constitute electrodeposition coatings. An aminated epoxy resin is obtained by reacting an amine compound with an epoxy resin, and is obtained by modifying the oxirane ring (also referred to as "epoxy group") of the epoxy resin with an amine compound, i.e., amination. In the present invention, the epoxy resin is a reaction product of a bisphenol type epoxy resin (a1), a diglycidyl ether of a polyalkylene oxide diol compound (a2) and a bisphenol compound (a3).

The bisphenol type epoxy resin (a1) is, for example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, 3,3′,5,5′-tetramethyl-4,4′-diglycidyloxy diphenylmethane and the like. Examples of bisphenol A type epoxy resins or bisphenol F type epoxy resins include Epicoat 807, 815, 825, 827, 828, 834, 1001, 1004, 1007 and 1009 (manufactured by Mitsubishi Chemical Corporation, trade names), DER -330, DER-301, DER-361 (manufactured by Dow Chemical Co., Ltd., trade names), YD-8125, YDF-170, YDF-170, YDF-175S, YDF-2001, YDF-2004, YDF-8170 (these are trade names manufactured by Nippon Steel Chemical & Materials Co., Ltd.), etc. are available.

Examples of glycidyl ethers (a2) of polyalkylene oxide diols include polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and polybutylene glycol diglycidyl ether. These are commercially available as EP400P from Sanyo Kasei Co., Ltd., for example.

The bisphenol compound (a3) is not particularly limited as long as it is a compound having two phenolic OH groups in one molecule. , bisphenol BP and the like. Among them, bisphenol A and bisphenol F are preferred.

The reaction conditions for the bisphenol-type epoxy resin (a1), the glycidyl ether of polyalkylene oxide diol (a2) and the bisphenol compound (a3) can be appropriately selected according to the stirrer and reaction scale used. The reaction conditions include, for example, 85 to 180° C. for 0.1 to 8 hours, more preferably 100 to 150° C. for 2 to 8 hours. As the stirrer to be used, a stirrer generally used in the paint field can be used.

The epoxy resin used in the present invention is a reaction product of a bisphenol-type epoxy resin (a1), a diglycidyl ether of a polyalkylene oxide diol compound (a2), and a bisphenol compound (a3), and the amount necessary for the reaction of each component is is expressed in terms of equivalents, since each component (a1), (a2) and (a3) is a necessary component of the epoxy resin of the present invention, one equivalent is required for a total of 3 equivalents, and the flexibility of the coating film is improved. Each component is added according to the conditions such as molecular weight and amine value, which will be described later. It's easy to do. Increasing the equivalent weight of the polyalkylene oxide diol glycidyl ether (a2) increases the flexibility of the coating film, while increasing the equivalent weight of the bisphenol compound (a3) tends to make it harder.

In the case of the present invention, an aminated epoxy resin is obtained by reacting the oxirane ring of the epoxy resin with an amine compound. As the amine compound, an amine compound that is generally used for producing an aminated epoxy resin is used. Examples of commonly used amine compounds include primary amines such as butylamine, octylamine, monoethanolamine; secondary amines such as diethylamine, dibutylamine, methylbutylamine, diethanolamine, N-methylethanolamine; complex amines such as diethylenetriamine; Amines are mentioned. The above primary amine can control the reaction by forming a ketimine group using a ketone compound and by so-called blocking. Amine compounds having a ketimine group or a diketimine group that can be used include ketimine such as aminoethylethanolamine and diketimine such as diethylenetriamine. Ketimine-forming ketone compounds include methyl isopropyl ketone (MIPK), diisobutyl ketone (DIBK), methyl isobutyl ketone (MIBK), diethyl ketone (DEK), ethyl butyl ketone (EBK), ethyl propyl ketone (EPK), di Examples include propyl ketone (DPK) and methyl ethyl ketone (MEK), and methyl isobutyl ketone (MIBK) is preferably used. As the amine compound, a tertiary amine may be used, and specific examples thereof include triethylamine, N,N-dimethylbenzylamine, N,N-dimethylethanolamine, and the like. These amines may be used individually by 1 type, and may use 2 or more types together.

In the present invention, the reaction of the aminated epoxy resin can be easily controlled by using a specific amine compound. Specifically, the amine compound is a combination of two types, a primary amine and a secondary amine, and the primary amine has the formula:
NH2-( _CH2 )n _- ^NR1R2 ( ¹ )
(In formula (1), R ¹ and R ² are the same or different and represent an alkyl group having 1 to 6 carbon atoms which may have a terminal hydroxyl group, and n represents an integer of 2 to 4.)
has
A secondary amine of the formula:
^R3R4NH ( ² )
(In formula (2), R ³ and R ⁴ represent an alkyl group having 1 to 4 carbon atoms and having a terminal hydroxyl group.)
is preferably used. When these amine compounds are used, the primary amino group of the primary amine is first reacted with the epoxy resin and consumed, leaving only the secondary amino group, which reacts with the epoxy group of the epoxy resin. We believe that there is no superiority in reactivity, and the reaction progresses evenly, and the reaction can be controlled. A tertiary amino group or a tertiary amino group produced by the reaction of a secondary amino group present in the primary amine may also react with an epoxy group to form a quaternary ammonium group, but this reaction is thought to be rare. be done.

The primary amine has the above formula (1), and R ¹ and R ² are specifically methyl, ethyl, propyl or butyl, and may have a terminal hydroxyl group. Further, n is 2 to 4, preferably 3. Specific examples of primary amines include aminopropyldiethanolamine, dimethylaminopropanediamine, diethylaminopropanediamine, dibutylaminopropanediamine and the like. The above secondary amine is a secondary amine having the above formula (2), and is obtained by bonding R ³ and R ⁴ to a nitrogen atom, and both R ³ and R ⁴ have 1 to 1 carbon atoms each having a hydroxyl group. It has 4 alkyl groups. Specific examples of secondary amines include dimethanolamine and diethanolamine.

In the amination step, the amount of the amine compound to be reacted with the epoxy resin is preferably 0.9 to 1.2 equivalents with respect to 1 equivalent of the epoxy group of the epoxy resin. When a primary amine and a secondary amine are used as the amine compound as described above, the amount of the primary amine is 30-80% by weight, more preferably 40-70% by weight of the total amine compound. When the amount of the primary amine exceeds 80% by weight of the total amine compound, the viscosity of the resin becomes high and stirring becomes difficult.

The reaction conditions for reacting the epoxy resin with the amine compound for amine modification can be appropriately selected according to the reaction scale and the like. The reaction conditions include, for example, 80 to 150° C. for 0.1 to 5 hours, more preferably 120 to 150° C. for 0.5 to 3 hours.

The aminated epoxy resins of the present invention are required to have a solubility parameter (SP) of 10.2-11.5. The solubility parameter (SP) is an index representing the solubility of the resin, and can be obtained by turbid point titration using water, which is a poor solvent with a high SP value, and n-hexane, which is a poor solvent with a low SP value. can. Details of the solubility parameter (SP) are provided in the Examples of this specification. The solubility parameter (SP) value is preferably 10.2-11.3, more preferably 10.2-10.9. It is difficult to make the solubility parameter (SP) of the aminated epoxy resin of the present invention smaller than 10.2 from the viewpoint of compatibility with the number of adhesion functional groups. The hydrophobicity of the resin is insufficient.

The aminated epoxy resin preferably has a number average molecular weight in the range of 1,000 to 7,000. When the number average molecular weight is 1,000 or more, physical properties such as solvent resistance and corrosion resistance of the resulting cured electrodeposition coating film are improved. On the other hand, when the number average molecular weight is 7,000 or less, the viscosity of the aminated epoxy resin can be easily adjusted, smooth synthesis becomes possible, and the resulting aminated epoxy resin can be easily emulsified and dispersed. become easier. More preferably, the aminated epoxy resin has a number average molecular weight in the range of 1,500 to 4,000.

The amine value of the aminated epoxy resin is preferably in the range of 20-100 mgKOH/g. When the amine value of the aminated epoxy resin is 20 mgKOH/g or more, the emulsification dispersion stability of the aminated epoxy resin in the electrodeposition coating composition is improved. On the other hand, when the amine value is 100 mgKOH/g or less, the amount of amino groups in the cured electrodeposition coating film becomes appropriate, and there is no risk of lowering the water resistance of the coating film. More preferably, the aminated epoxy resin has an amine value in the range of 20-80 mgKOH/g.

The hydroxyl value of the aminated epoxy resin is preferably within the range of 150-650 mgKOH/g. When the hydroxyl value is 150 mgKOH/g or more, the cured electrodeposition coating film can be cured well, and the coating film appearance is also improved. On the other hand, when the hydroxyl value is 650 mgKOH/g or less, the amount of hydroxyl groups remaining in the cured electrodeposition coating film becomes appropriate, and there is no risk of lowering the water resistance of the coating film. More preferably, the hydroxyl value of the aminated epoxy resin is in the range of 150-400 mgKOH/g.

In the electrodeposition coating composition of the present invention, the number average molecular weight is in the range of 1,000 to 7,000, the amine value is 20 to 100 mgKOH/g, and the hydroxyl value is 150 to 650 mgKOH/g. By using an aminated epoxy resin, preferably 150 to 400 mg KOH/g, there is an advantage that excellent corrosion resistance can be imparted to the article to be coated.

As the aminated epoxy resin, if necessary, aminated epoxy resins having different amine values and/or hydroxyl values may be used in combination. When two or more types of aminated epoxy resins with different amine values and hydroxyl values are used in combination, the average amine value and average hydroxyl value calculated based on the mass ratio of the aminated epoxy resins used are within the above numerical range. is preferred. In addition, as the aminated epoxy resin to be used in combination, an aminated epoxy resin having an amine value of 20 to 50 mgKOH/g and a hydroxyl value of 50 to 300 mgKOH/g, and an aminated epoxy resin having an amine value of 50 to 200 mgKOH/g. Moreover, combined use with an aminated epoxy resin having a hydroxyl value of 200 to 500 mgKOH/g is preferred. The use of such a combination has the advantage that the core of the emulsion is more hydrophobic and the shell is more hydrophilic, providing excellent corrosion resistance.

The aminated epoxy resin may contain an amino group-containing acrylic resin, an amino group-containing polyester resin, or the like, if necessary.

<Blocked polyisocyanate curing agent>
A blocked polyisocyanate curing agent (hereinafter sometimes simply referred to as a "curing agent") is a coating film-forming resin that constitutes an electrodeposition coating film. A blocked polyisocyanate curing agent can be prepared by blocking a polyisocyanate with a capping agent.

Examples of polyisocyanates include aliphatic diisocyanates such as hexamethylene diisocyanate (including trimers), tetramethylene diisocyanate and trimethylhexamethylene diisocyanate; Aromatic diisocyanates such as polyisocyanate, 4,4'-diphenylmethane diisocyanate, tolylene diisocyanate and xylylene diisocyanate can be mentioned.

Examples of sealants include monohydric alkyl (or aromatic) alcohols such as n-butanol, n-hexyl alcohol, 2-ethylhexanol, lauryl alcohol, phenol carbinol, methylphenyl carbinol; cellosolves such as hexyl ether and ethylene glycol mono-2-ethylhexyl ether; polyether type double-ended diols such as polyethylene glycol, polypropylene glycol and polytetramethylene ether glycol phenol; ethylene glycol, propylene glycol, 1,4-butanediol and the like and polyester type double-ended polyols obtained from dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, suberic acid and sebacic acid; phenols such as para-t-butylphenol and cresol; dimethyl ketoxime and methyl ethyl keto Oximes such as oxime, methyl isobutyl ketoxime, methyl amyl ketoxime and cyclohexanone oxime; and lactams represented by ε-caprolactam and γ-butyrolactam are preferably used.

The blocked polyisocyanate curing agent preferably has a blocking rate of 100%. This has the advantage of improving the storage stability of the electrodeposition coating composition.

The blocked polyisocyanate curing agent combines a curing agent prepared by blocking an aliphatic diisocyanate with a blocking agent and a curing agent prepared by blocking an aromatic diisocyanate with a blocking agent. is preferred.

The blocked polyisocyanate curing agent preferentially reacts with the primary amine of the aminated epoxy resin and further reacts with hydroxyl groups to cure. As the curing agent, at least one curing agent selected from the group consisting of organic curing agents such as melamine resins and phenolic resins, silane coupling agents, and metal curing agents may be used in combination with the blocked isocyanate curing agent.

<Preparation of resin emulsion>
The resin emulsion is prepared by dissolving each of the aminated epoxy resin and the blocked polyisocyanate curing agent in an organic solvent to prepare a solution, mixing these solutions, and then neutralizing with a neutralizing acid. can be prepared. Examples of neutralizing acids include organic acids such as methanesulfonic acid, sulfamic acid, lactic acid, dimethylolpropionic acid, formic acid, and acetic acid. More preferably, in the present invention, the resin emulsion containing the aminated epoxy resin and the curing agent is neutralized with one or more acids selected from the group consisting of formic acid, acetic acid and lactic acid.

The content of the blocked polyisocyanate curing agent reacts with active hydrogen-containing functional groups such as primary amino groups, secondary amino groups or hydroxyl groups in the aminated epoxy resin during curing to give a good cured coating film. is required in an amount sufficient for The content of the curing agent is preferably 90/10 to 50/50, more preferably 80/20 to 65/, expressed as a solid content mass ratio of the aminated epoxy resin to the curing agent (aminated epoxy resin/curing agent). 35 range. By adjusting the solid content mass ratio between the aminated epoxy resin and the blocked polyisocyanate curing agent, the fluidity and curing speed of the coating film (deposited film) during film formation are improved, and the appearance of the coating is improved.

The solid content of the resin emulsion is usually 25 to 50% by mass, preferably 35 to 45% by mass, based on the total amount of the resin emulsion. Here, the term "solid content of the resin emulsion" means the mass of all the components contained in the resin emulsion that remain solid even after the solvent is removed. Specifically, it means the total weight of aminated epoxy resin, curing agent and other solid components added as necessary, contained in the resin emulsion.

The neutralizing acid is preferably used in an amount of 10 to 100%, more preferably 20 to 70%, as the equivalent ratio of the neutralizing acid to the amino group equivalents of the aminated epoxy resin. preferable. In the present specification, the equivalent ratio of the neutralizing acid to the amino group equivalent of the aminated epoxy resin is defined as the neutralization ratio. When the neutralization rate is 10% or more, affinity for water is ensured, and water dispersibility is improved.

<Pigment dispersion paste>
The cationic electrodeposition coating composition of the present invention may optionally contain a pigment dispersion paste. The pigment dispersion paste is a component optionally contained in the electrodeposition coating composition, and generally contains a pigment dispersion resin and a pigment.

Pigment Dispersing Resin The pigment dispersing resin is a resin for dispersing the pigment, and is used by being dispersed in an aqueous medium. As the pigment dispersing resin, a pigment dispersing resin having a cationic group such as a modified epoxy resin having at least one or more selected from quaternary ammonium groups, tertiary sulfonium groups and primary amino groups can be used. Specific examples of pigment dispersion resins include quaternary ammonium group-containing epoxy resins and tertiary sulfonium group-containing epoxy resins. As the aqueous solvent, ion-exchanged water or water containing a small amount of alcohol is used.

Pigment A pigment is a pigment generally used in an electrodeposition coating composition. As pigments, e.g. commonly used inorganic and organic pigments, e.g. colored pigments such as titanium white (titanium dioxide), carbon black and red iron oxide; kaolin, talc, aluminum silicate, calcium carbonate, mica and clay. extender pigments; iron phosphate, aluminum phosphate, calcium phosphate, aluminum tripolyphosphate, and rust preventive pigments such as aluminum phosphomolybdate and aluminum zinc phosphomolybdate.

Preparation of Pigment Dispersion Paste A pigment dispersion paste is prepared by mixing a pigment dispersion resin and a pigment. The content of the pigment-dispersing resin in the pigment-dispersing paste is not particularly limited.

The solid content of the pigment dispersion paste is usually 40 to 70% by mass, preferably 50 to 60% by mass, based on the total amount of the pigment dispersion paste.

As used herein, the term “solid content of the pigment dispersion paste” means the mass of all the components contained in the pigment dispersion paste that remain solid even after the solvent is removed. Specifically, it means the total weight of the pigment dispersion resin and the pigment and other solid components added as necessary, which are contained in the pigment dispersion paste.

<Other ingredients, etc.>
The cationic electrodeposition coating composition of the present invention may further contain a nitrite metal salt in addition to the above components. The nitrite metal salt is preferably an alkali metal nitrite or an alkaline earth metal nitrite, more preferably an alkaline earth metal nitrite. Nitrite metal salts include, for example, calcium nitrite, sodium nitrite, potassium nitrite, magnesium nitrite, strontium nitrite, barium nitrite, and zinc nitrite.

When the cationic electrodeposition coating composition contains a nitrite metal salt, there is an advantage that the corrosion resistance is improved, and in particular the corrosion resistance of the edge portion (edge rust prevention) is further improved. When the cationic electrodeposition coating composition contains a nitrite metal salt, the content is 0.001 to 0.2% by mass in terms of the metal element of the metal component with respect to the total mass of the coating film-forming resin. is preferred.

The nitrite metal salt can be added to the cationic electrodeposition coating composition by any method. For example, a method of preparing an aqueous solution of the nitrite metal salt in advance and adding it to the cationic electrodeposition coating composition can be used. It is also possible to mix the nitrite metal salt with the pigment in advance and disperse it in the same manner as the pigment.

<Production of cationic electrodeposition coating composition>
The cationic electrodeposition coating composition of the present invention is prepared by mixing a resin emulsion containing an aminated epoxy resin and a blocked polyisocyanate curing agent, a pigment dispersion paste, additives, etc. by a commonly used method. can be done.

As used herein, the term "solid content of the electrodeposition coating composition" means the mass of all the components contained in the electrodeposition coating composition that remain solid after removal of the solvent. . Specifically, the total solid mass of the aminated epoxy resin, the blocked polyisocyanate curing agent, and optionally the pigment dispersing resin, pigment, and other solid components contained in the electrodeposition coating composition means

The solid content of the cationic electrodeposition coating composition of the present invention is preferably 1 to 30% by mass based on the total amount of the electrodeposition coating composition. If the solid content of the cationic electrodeposition coating composition is less than 1% by mass, the amount of deposition of the electrodeposition coating film is reduced, which may make it difficult to ensure sufficient corrosion resistance. If the solid content of the cationic electrodeposition coating composition exceeds 30% by mass, the throwing power or coating appearance may deteriorate.

The cationic electrodeposition coating composition of the present invention preferably has a pH of 4.5-7. When the pH of the cationic electrodeposition coating composition is less than 4.5, the amount of acid present in the cationic electrodeposition coating composition becomes excessive, which may result in poor paint film appearance or coating workability. be. On the other hand, if the pH exceeds 7, the filterability of the cationic electrodeposition coating composition may deteriorate, and the horizontal appearance of the cured electrodeposition coating film may deteriorate. The pH of the cationic electrodeposition coating composition can be set within the above range by adjusting the amount of neutralizing acid used, the amount of free acid added, and the like. More preferably, the pH is 5-7.

The pH of the cationic electrodeposition coating composition can be measured using a commercially available pH meter with a temperature compensation function.

The milligram equivalent (MEQ(A)) of the acid to 100 g of the solid content of the cationic electrodeposition coating composition is preferably 10-50. The milligram equivalent (MEQ(A)) of the acid per 100 g of the resin solid content of the cationic electrodeposition coating composition can be adjusted by adjusting the amount of neutralized acid and the amount of free acid.

Here, MEQ (A) is an abbreviation for mg equivalent (acid), which is the sum of mg equivalents of all acids per 100 g of solid content of the paint. This MEQ (A) is obtained by precisely weighing about 10 g of the solid content of the electrodeposition coating composition, dissolving it in about 50 ml of a solvent (THF: tetrahydrofuran), and performing potentiometric titration with a 1/10 N NaOH solution. , the amount of acid contained in the cationic electrodeposition coating composition can be quantified and measured.

The cationic electrodeposition paint composition of the present invention contains additives commonly used in the paint field, such as ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monoethylhexyl ether, propylene glycol monobutyl ether, and dipropylene. Organic solvents such as glycol monobutyl ether and propylene glycol monophenyl ether, anti-drying agents, surfactants such as antifoaming agents, viscosity modifiers such as acrylic resin fine particles, anti-repellent agents, vanadium salts, copper, iron, manganese, magnesium , inorganic rust inhibitors such as calcium salts, etc., may optionally be included. In addition to these, known auxiliary complexing agents, buffering agents, smoothing agents, stress relieving agents, brightening agents, semi-brightening agents, antioxidants, UV absorbers, and the like may be blended depending on the purpose. These additives may be added during the production of the resin emulsion, during the production of the pigment dispersion paste, or during or after mixing the resin emulsion and the pigment dispersion paste. good.

The cationic electrodeposition coating composition of the present invention may contain other coating film-forming resin components in addition to the aminated epoxy resin. Examples of other coating film-forming resin components include acrylic resins, polyester resins, urethane resins, butadiene resins, phenol resins, and xylene resins. Phenol resins and xylene resins are preferred as other coating film-forming resin components that can be contained in the electrodeposition coating composition. Examples of phenolic resins and xylene resins include xylene resins having 2 to 10 aromatic rings.

In the cationic electrodeposition coating composition of the present invention, the solubility parameter (SP) of the mixture obtained by mixing the aminated epoxy resin and the blocked polyisocyanate curing agent is also an index for evaluating the performance of the electrodeposition coating. In the present invention, the solubility parameter (SP) of the mixture obtained by mixing the aminated epoxy resin and the blocked polyisocyanate curing agent is 10.2 to 11.5, preferably 10.2 to 11.3, more preferably 10. .2 to 10.9. If the solubility parameter (SP) of the mixture obtained by mixing the aminated epoxy resin and the blocked polyisocyanate curing agent is less than 10.2, the adhesion decreases, and conversely, if it is greater than 11.5, the hydrophilicity increases. increase, and the barrier property of the coating decreases.

<Electrodeposition coating and electrodeposition coating film formation>
An electrodeposition coating film can be formed by subjecting an article to be coated to electrodeposition coating using the cationic electrodeposition coating composition of the present invention. In electrodeposition coating using the cationic electrodeposition coating composition of the present invention, a voltage is applied between the object to be coated as a cathode and an anode. As a result, an electrodeposition coating film is deposited on the object to be coated.

As the object to be coated with the cationic electrodeposition coating composition of the present invention, a variety of electrically conductive objects can be used. Examples of usable objects to be coated include cold-rolled steel sheets, hot-rolled steel sheets, stainless steel, electrogalvanized steel sheets, hot-dip galvanized steel sheets, zinc-aluminum alloy plated steel sheets, zinc-iron alloy plated steel sheets, and zinc-magnesium alloy plated steel sheets. Steel plate, zinc-aluminum-magnesium alloy plated steel plate, aluminum plated steel plate, aluminum-silicon alloy plated steel plate, tin plated steel plate and the like.

In the electrodeposition coating step, the electrodeposition coating is performed by immersing the object to be coated in the electrodeposition coating composition and then applying a voltage of 50 to 450V. If the applied voltage is less than 50 V, the electrodeposition may become insufficient, and if it exceeds 450 V, the appearance of the coating film may deteriorate. At the time of electrodeposition coating, the bath liquid temperature of the coating composition is usually adjusted to 10 to 45°C.

The voltage application time varies depending on the electrodeposition conditions, but can generally be 2 to 5 minutes.

In the electrodeposition coating using the cationic electrodeposition coating composition of the present invention, the film thickness of the deposited electrodeposition coating film is preferably 5 to 60 μm, and the thickness of the electrodeposition coating film finally obtained by heat curing is preferably 5 to 60 μm. More preferably, the film thickness is 10 to 25 μm. If the film thickness of the electrodeposition coating film is less than 5 µm, there is a risk that the rust prevention will be insufficient.

The electrodeposition coating film deposited as described above can be cured by, for example, washing with water as necessary and heating at 120 to 260° C., preferably 140 to 220° C., for 10 to 30 minutes. . Thereby, a cured electrodeposition coating film is formed.

In the present invention, the elongation rate of the cured coating film is controlled. The elongation is obtained by coating the cationic electrodeposition coating composition on a steel plate so that the cured film thickness is 20 μm, baking the coating at 160° C. for 15 minutes, and then measuring the elongation of the electrodeposition coating. . Specifically, the elongation rate is obtained by calculating the ratio (%) of the length of the coating film stretched until it breaks to the length of the coating film before measurement. The elongation by this measurement is 0.1-5.6%, preferably 2.0-4.5%. If the elongation percentage is less than 0.1%, there is a drawback that the impact resistance test is deteriorated, and if it exceeds 5.6%, there is a drawback that the coating film swells greatly during the corrosion resistance test.

With the cationic electrodeposition coating composition of the present invention, even when a cured electrodeposition coating film is provided on an object to be coated having edges, it is possible to provide a cured electrodeposition coating film with excellent edge rust prevention properties. There are advantages to be had. Since the cationic electrodeposition coating composition of the present invention has a function of allowing the deposited electrodeposition coating film to remain, it is suitable for providing a cured electrodeposition coating film on an object having edges. can be used.

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these. In the examples, "parts" and "%" are based on mass unless otherwise specified.

Production Example 1-A Production of aminated epoxy resin (resin A ) 900 parts of bisphenol A type epoxy resin (trade name DER-331J, manufactured by Dow Chemical Co., Ltd.), 320 parts of bisphenol A, polypropylene glycol diglycidyl ether (from Sanyo Chemical Co., Ltd.) Add 60 parts of commercially available EP400P), 30 parts of phenol, and 2 parts of dimethylbenzylamine, keep the temperature in the reaction vessel at 120 ° C., and react until the epoxy equivalent reaches 600 g / eq. was cooled to 110°C. Then, a mixture of 110 parts of diethanolamine (DETA) and 70 parts of diethylaminopropylamine (DEAPA) was added and allowed to react at 140° C. for 1 hour to obtain an aminated epoxy resin (resin A).

Production Example 1-B Production of aminated epoxy resin (resin B) Bisphenol A type epoxy resin (trade name DER-331J, manufactured by Dow Chemical Co.) 380 parts, polypropylene glycol diglycidyl ether 870 parts, bisphenol A 320 parts, phenol 30 parts and 2 parts of dimethylbenzylamine were added, the temperature in the reaction vessel was maintained at 120°C, and the reaction was allowed to proceed until the epoxy equivalent reached 620 g/eq. Then, a mixture of 110 parts of diethanolamine (DETA) and 70 parts of diethylaminopropanediamine (DEAPA) was added and allowed to react at 140° C. for 1 hour to obtain an aminated epoxy resin (resin B).

Production Example 1-C Production of aminated epoxy resin (resin C) Bisphenol A type epoxy resin (trade name DER-331J, Dow Chemical Co.) 900 parts, polypropylene glycol diglycidyl ether 60 parts, bisphenol A 320 parts, phenol 130 parts and 2 parts of dimethylbenzylamine were added, the temperature in the reaction vessel was maintained at 120°C, and the reaction was allowed to proceed until the epoxy equivalent reached 620 g/eq. Then, a mixture of 85 parts of diketimine, 60 parts of diethanolamine (DETA) and 25 parts of N-methylethanolamine (MMA) was added and allowed to react at 140° C. for 1 hour to obtain an aminated epoxy resin (resin C).

Production Example 1-D Production of aminated epoxy resin (resin D) Bisphenol A type epoxy resin (trade name DER-331J, Dow Chemical Co.) 380 parts, polypropylene glycol diglycidyl ether 880 parts, bisphenol A 75 parts, phenol 130 parts , Add 2 parts of dimethylbenzylamine, 100 parts of diketimine, 30 parts of N-methylethanolamine (MMA) Keep the temperature in the reaction vessel at 120 ° C., react until the epoxy equivalent becomes 650 g / eq, then react It cooled until the temperature in a container became 110 degreeC. Then, a mixture of 100 parts of diethanolamine (DETA), 30 parts of N-methylethanolamine (MMA) and 100 parts of diketimine was added and reacted at 160° C. for 1 hour to obtain an aminated epoxy resin (resin D).

Production Example 1-E Production of aminated epoxy resin (resin E) Bisphenol A type epoxy resin (trade name DER-331J, Dow Chemical Co.) 900 parts, polybutylene glycol diglycidyl ether 60 parts, bisphenol A 320 parts, phenol 30 and 2 parts of dimethylbenzylamine were added, the temperature in the reaction vessel was maintained at 120°C, and the reaction was allowed to proceed until the epoxy equivalent reached 620 g/eq. Then, a mixture of 110 parts of diethanolamine (DETA) and 70 parts of diethylaminopropanediamine (DEAPA) was added and allowed to react at 140° C. for 1 hour to obtain an aminated epoxy resin (resin E).
Production Example 1-F Production of aminated epoxy resin (resin F)
380 parts of bisphenol A type epoxy resin (trade name DER-331J, manufactured by Dow Chemical), 870 parts of polybutylene glycol diglycidyl ether, 320 parts of bisphenol A, 30 parts of phenol, and 2 parts of dimethylbenzylamine were added, and the temperature in the reaction vessel was was maintained at 120°C and reacted until the epoxy equivalent reached 620 g/eq, and then cooled until the temperature in the reaction vessel reached 110°C. Then, a mixture of 110 parts of diethanolamine (DETA) and 70 parts of diethylaminopropanediamine (DEAPA) was added and allowed to react at 140° C. for 1 hour to obtain an aminated epoxy resin (resin F).

Production Example 1-G Production of aminated epoxy resin (resin G) Bisphenol A type epoxy resin (trade name DER-331J, manufactured by Dow Chemical Co.) 640 parts, polypropylene glycol diglycidyl ether 100 parts, bisphenol A 160 parts, dimer acid 100 and 2 parts of dimethylbenzylamine were added, the temperature in the reaction vessel was maintained at 120°C, and the reaction was allowed to proceed until the epoxy equivalent reached 1100 g/eq. 80 parts of diketimine and 20 parts of diethanolamine (DETA) were added and reacted at 140° C. for 1 hour to obtain an aminated epoxy resin (resin G).

Production Example 1-H Production of aminated epoxy resin (resin H ) 940 parts of bisphenol A type epoxy resin (trade name DER-331J, manufactured by Dow Chemical Co.), 380 parts of bisphenol A, 60 parts of phenol and 2 parts of dimethylbenzylamine were added. , the temperature in the reaction vessel was kept at 120°C, and the reaction was allowed to proceed until the epoxy equivalent reached 1100 g/eq, and then the temperature in the reaction vessel was cooled to 110°C. 60 parts of diethanolamine (DETA), 25 parts of N-methylethanolamine (MMA), and 80 parts of diethylenetriamine diketimine (diketimine: methyl isobutyl ketone solution with a solid content of 73%) are added and reacted at 140° C. for 1 hour, An aminated epoxy resin (resin H) was obtained.

Production Example 2 Production of blocked polyisocyanate curing agent (1) 1370 parts of polymethylene polyphenyl polyisocyanate (MDI) and 732 parts of MIBK were placed in a reactor and heated to 60°C. 300 parts of butyl diglycol ether and butyl cellosolve 1330 were added dropwise thereto at 60° C. over 2 hours. After further heating at 75° C. for 4 hours, it was confirmed by IR spectrum measurement that the absorption based on the isocyanate group had disappeared. .

Production Example 3 Preparation of Pigment Dispersion Resin 2220 parts of isophorone diisocyanate and 342.1 parts of methyl isobutyl ketone were charged into a reaction vessel equipped with a stirrer, a cooling tube, a nitrogen inlet tube and a thermometer, and the temperature was raised to 50° C. to obtain dibutyltin laurate. 2.2 parts were added, and 878.7 parts of methyl ethyl ketone oxime was charged at 60°C. After that, the temperature was maintained at 60° C. for 1 hour, and after confirming that the NCO equivalent was 348, 890 parts of dimethylethanolamine was added. After incubating at 60°C for 1 hour and confirming by IR that the NCO peak has disappeared, 1872.6 parts of 50% lactic acid and 495 parts of deionized water are added while cooling so that the temperature does not exceed 60°C for quaternization. got the drug. Next, 870 parts of tolylene diisocyanate and 49.5 parts of methyl isobutyl ketone were charged into a different reactor, and 667.2 parts of 2-ethylhexanol was added dropwise over 2.5 hours so as not to exceed 50°C. After completion of dropping, 35.5 parts of methyl isobutyl ketone was added and the temperature was maintained for 30 minutes. After confirming that the NCO equivalent was 330 to 370, a half-blocked polyisocyanate was obtained.

In a reaction vessel equipped with a stirrer, a condenser, a nitrogen inlet tube and a thermometer, 940.0 parts of bisphenol A type epoxy resin (trade name DER-331J, manufactured by Dow Chemical Co.) was diluted with 38.5 parts of methanol, 0.1 part of dibutyltin dilaurate was added thereto. After raising the temperature to 50° C., 87.1 parts of tolylene diisocyanate was added and the temperature was further raised. At 100°C, 1.4 parts of N,N-dimethylbenzylamine was added and the mixture was kept at 130°C for 2 hours. At this time, methanol was fractionated with a fractionating tube. This was cooled to 115°C, methyl isobutyl ketone was charged until the solid content concentration reached 90%, then 270.3 parts of bisphenol A and 39.2 parts of 2-ethylhexanoic acid were charged, and the mixture was heated and stirred at 125°C for 2 hours. 516.4 parts of the above half-blocked polyisocyanate was added dropwise over 30 minutes, followed by heating and stirring for 30 minutes. 1506 parts of polyoxyethylene bisphenol A ether was gradually added and dissolved. After cooling to 90°C, the above quaternizing agent was added, and the acid value was confirmed to be 2 or less while maintaining at 70 to 80°C to obtain a pigment dispersion resin (resin solid content: 30%).

Production Example 4 Preparation of Pigment Dispersion Paste 106.9 parts of the pigment dispersion resin obtained in Production Example 3, 1.6 parts of carbon black, 40 parts of kaolin, 55.4 parts of titanium dioxide, and 3 parts of aluminum phosphomolybdate were added to a sand grind mill. , 13 parts of deionized water was added and dispersed until the particle size became 10 μm or less to obtain a pigment dispersion paste (resin solid content: 60%).

Production Example 5-A Production of electrodeposition coating resin emulsion (EmA ) 400 g (solid content) of the aminated epoxy resin (resin A) obtained in Production Example 1-A and the blocked polyisocyanate curing agent obtained in Production Example 2 (1) 160 g (solid content) were mixed, and ethylene glycol mono-2-ethylhexyl ether was added so that the solid content was 3% (15 g). Next, formic acid was added so as to give a neutralization rate of 40% for neutralization, and deionized water was added to slowly dilute to obtain an electrodeposition paint resin emulsion (EmA).

Production Examples 5-B to H Production of electrodeposition paint resin emulsions (EmB to H) Production Example 5- A for aminated epoxy resins (resins B to H) obtained in Production Examples 1-B to 1-H Electrocoating resin emulsions (EmB to EmH) were obtained in the same manner as in the above.

Example 1
1394 g of ion-exchanged water, 560 g of the resin emulsion (EmA) and 41 g of the pigment dispersion paste obtained in Production Example 4 were added to a stainless steel container and then aged at 40° C. for 16 hours to form an electrodeposition coating composition.

Examples 2-6 and Comparative Examples 1-2
In Examples 2 to 6 (EmB, EmC, EmD, EmE and EmF) and Comparative Examples 1 and 2 (EmG, EmH), electrodeposition coating compositions were obtained in the same manner as in Example 1.

An electrodeposition coated cold-rolled steel sheet (JISG3141, SPCC-SD) was degreased by immersing it in Surf Cleaner EC90 (manufactured by Nippon Paint Surf Chemicals Co., Ltd.) at 50° C. for 2 minutes. Next, zirconium chemical conversion treatment was performed by immersing it at 40° C. for 90 seconds in a zirconium chemical conversion treatment solution containing 0.005% ZrF and adjusted to pH 4 using NaOH. Next, a required amount of 2-ethylhexyl glycol was added to the electrodeposition coating composition obtained in Examples or Comparative Examples so that the film thickness of the electrodeposition coating film after curing was 20 μm, and then a steel plate was immersed. A voltage was applied under the condition that the voltage reached 180 V for 30 seconds and was maintained for 150 seconds to deposit an uncured electrodeposition coating film on the object to be coated.

The uncured electrodeposition coating film thus obtained was cured by baking at 160° C. for 15 minutes to obtain an electrodeposition coating plate having a cured electrodeposition coating film. The following evaluations were performed on the obtained cured electrodeposition coating film. Table 1 shows the results. Table 1 shows the composition (parts by weight of components) of the aminated epoxy resin used in the electrodeposition coating composition of each example, the solubility parameter (SP) of the aminated epoxy resin, and the physical properties of the coating film (curability (rubbing properties), elongation, salt water immersion test (SDT), cyclic corrosion test (CCT) and paint stability) are also described. Describe each evaluation method and evaluation criteria

The following evaluation tests were carried out using the electrodeposition coating compositions and coated plates obtained in the above Examples.

<Solubility parameter (SP) of aminated epoxy resin>
A solubility parameter (SP value) can be actually measured by the following method.
Reference SUH, CLARKE [J. P. S. A-1, 5, 1671-1681 (1967)]
・Measurement temperature: 20°C
- Sample: 0.5 g of resin is weighed in a 100 ml beaker, 10 ml of a good solvent is added using a whole pipette, and dissolved with a magnetic stirrer.
• Solvent: good solvent: dioxane, acetone • Poor solvent: n-hexane, ion-exchanged water • Turbidity point measurement: Using a 50 ml burette, the poor solvent is added dropwise, and the point at which turbidity occurs is defined as the drop amount.
• Calculation: The SP value δ of the resin is given by the following formula.
δ = ( _Vml ^1/2 _δml + _Vmh ^1/2 _δmh )/( _Vml ^1/2 + _Vmh ^1/2 )
Vm _{= V1V2 /} ( _{φ1V2 + φ2V1} )
_{δm =} φ1 _{δ1 +} φ2 δ2
V _i : Molecular volume of solvent (ml/mol)
φ _i : volume fraction of each solvent at turbid point δ _i : SP value of solvent ml: low SP poor solvent mixture mh: high SP poor solvent mixture

<Curability (rubbing property)>
The coating film was rubbed 50 times with gauze soaked in methyl isobutyl ketone (MIBK), and the curability was determined from the surface condition of the coating film. The evaluation criteria are as follows.
◯: No change in coating film.
Δ: There are coating film streaks.
x: Gauze is colored.

<Elongation rate (%)>
A stress-strain curve of the coating film is prepared, and the ratio (%) of the length stretched until the sample breaks to the initial sample length is obtained by calculation.

<Cycle Corrosion Test (CCT)>
A cross-cut scratch was made with a knife so as to reach the base material in the coating film of the electrodeposition coated plate after curing using a cold-rolled steel plate, and JASOM609-91 "Methods for Corrosion Test of Automobile Materials" was performed for 100 cycles. After that, we observed the occurrence of rust and blisters from the cross-cut part, and evaluated the corrosion resistance in accordance with the actual corrosive environment. Evaluation criteria are as follows.
Evaluation criteria ○: The maximum width of rust or blisters is less than 7.5 mm from the cut part (both sides) No blisters other than the cut part ○△: The maximum width of rust or blisters is 5 mm or more and less than 7.5 mm from the cut part (both sides) Cut Blisters also exist outside the part △: The maximum width of rust or blisters is 7.5 mm or more and less than 10 mm from the cut part (both sides)
△×: The maximum width of rust or blisters is 10 mm or more and less than 12.5 mm from the cut part (both sides)
×: The maximum width of rust or blisters is 12.5 mm or more from the cut part (both sides)
A grade of ◯△ or higher is acceptable.

<Salt Dipping Test (SDT)>
A cold-rolled steel sheet (JIS G 3141: SPCC-SD) was degreased using Surf Cleaner 53 manufactured by Nippon Paint Co., Ltd. The obtained steel plate was subjected to chemical conversion treatment using a zircon oxide treatment agent (Surfdyne EC3200, manufactured by Nippon Paint Co., Ltd.). Using the cationic electrodeposition coating compositions of Examples and Comparative Examples, electrodeposition coating was applied to the chemically treated steel plate so that the film thickness of the dry coating film was 20 μm, and this was baked at 160° C. for 20 minutes. It was cured to obtain a cured electrodeposited coating film. Two parallel cuts were made in the resulting coating film with a knife so as to reach the substrate, and the film was immersed in a 5% sodium chloride aqueous solution at 55° C. for 240 hours. After that, a tape was attached around the cut portion, and the peeled width of the paint film was measured when the tape was peeled off. The evaluation results are shown in Tables 1-3.
○: The maximum width of tape peeling is less than 2 mm on both sides of the cut part △: The maximum width of tape peeling is 2 mm or more and less than 4 mm on both sides of the cut part ×: The maximum width of tape peeling is 4 mm or more on both sides of the cut part During the above evaluation, ○ pass.

Stability of electrodeposition paint composition (paint stability)
The state of the electrodeposition coating composition was visually observed in a state where the electrodeposition coating composition was left standing or in a state where it was stirred, and the stability of the coating was evaluated. The evaluation criteria were as follows. The term "stable" as used herein means that the pigment does not settle within 15 minutes after the coating composition is left to stand for 4 weeks and then stirred again.
Evaluation criteria ○: Stable when the electrodeposition coating composition is left standing ○△: Not stable when the electrodeposition coating composition is left standing, but stabilizes immediately by stirring again △: Electrodeposition Stable when the coating composition is continuously stirred ×: Not stabilized even when the electrodeposition coating composition is continuously stirred

As is clear from Table 1 above, corrosion resistance (cycle Corrosion test and saltwater immersion test) have shown good results, and other performances (physical properties of the coating film and aging stability of the coating) are also excellent. On the other hand, in Comparative Examples, when the SP value of the aminated epoxy resin and the elongation rate of the electrodeposition coating film deviate from their ranges, the results of corrosion resistance are not sufficient, and the stability of the paint over time is also insufficient. I'm getting results.

Claims (4)

A cationic electrodeposition coating composition containing an aminated epoxy resin and a blocked polyisocyanate curing agent,
The aminated epoxy resin is an aminated epoxy resin obtained by reacting an amine compound with an epoxy resin,
The epoxy resin is a reaction product of a bisphenol type epoxy resin (a1), a diglycidyl ether of a polyalkylene oxide diol compound (a2) and a bisphenol compound (a3),
The solubility parameter (SP) of the aminated epoxy resin is 10.2 to 11.5,
A cationic electrodeposition coating composition having an elongation of 0.1 to 5.6% after coating a steel plate with the cationic electrodeposition coating composition to a dry film thickness of 20 μm and baking at 160° C. for 15 minutes. . 2. The method of claim 1, wherein the diglycidyl ether (a2) of the polyalkylene oxide diol compound is selected from the group consisting of polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, polybutylene glycol diglycidyl ether and mixtures thereof. Cationic electrodeposition coating composition. the amine compound is a combination of two types of primary amine and secondary amine;
The primary amine has the formula:
NH2-( _CH2 )n _- ^NR1R2 ( ¹ )
(In formula (1), R ¹ and R ² are the same or different and represent an alkyl group having 1 to 6 carbon atoms which may have a terminal hydroxyl group, and n represents an integer of 2 to 4.)
has
A secondary amine of the formula:
^R3R4NH ( ² )
(In formula (2), R ³ and R ⁴ represent an alkyl group having 1 to 4 carbon atoms and having a terminal hydroxyl group.)
The cationic electrodeposition coating composition according to claim 1 or 2, having A cationic electrodeposition coating film coated with the cationic electrodeposition coating composition according to any one of claims 1 to 3.