JP7752411B2 - Electrodeposition coating composition and method for producing article - Google Patents

Description

This disclosure relates to an electrodeposition coating composition and a method for producing an article.

Electrodeposition coating is a coating method in which a coating film is deposited on the surface of a substrate by immersing the substrate in an electrodeposition coating composition and applying a voltage. This method is capable of applying a uniform coating to even the smallest details of substrates, even those with complex shapes, with high coating efficiency, and can be applied automatically and continuously, making it widely used as a primer coating method for a variety of substrates. Electrodeposition coating also has the advantage of providing excellent protection for the substrate, such as providing high corrosion resistance. Furthermore, because electrodeposition coating compositions are water-based coating compositions, they have the advantage of being less environmentally hazardous than solvent-based coating compositions.

In recent years, there has been a demand for smaller, more powerful motors for automobiles, particularly the drive motors used in electric vehicles (EVs) and hybrid vehicles (HVs). To achieve this, a high current density in the coil is desirable, but at the same time, the heat generated by the coil also increases. For this reason, even higher levels of insulation and heat resistance are required for the insulating coatings that cover the enameled wire used in the coils of automobile motors.

Polyimide resins are a promising candidate for achieving these high insulation and heat resistance requirements. Polyimide resins have a rigid and strong molecular structure in which multiple aromatic groups are bonded via imide bonds, and the imide ring structure has strong intermolecular forces. Therefore, compared to ordinary polymer compounds (resin compositions), polyimide resins exhibit superior electrical insulation, heat resistance, mechanical properties, solvent resistance, chemical resistance, and more. However, due to their molecular structure, polyimide resins can only be dispersed in specific organic solvents, such as amide-based solvents, and film formation is difficult, making their application in paints difficult.

In light of this situation, electrodeposition coating using polyimide resins that are soluble in specific organic solvents is being considered for use in electrodeposition coating (Patent Documents 1 and 2).

On the other hand, as mentioned above, polyimide resins are insoluble in the organic solvents commonly used in coating applications. Therefore, a method has been investigated in which electrodeposition coating is performed using an electrodeposition coating composition in which its precursor, polyamic acid (also known as polyamic acid), is dispersed in water, and the electrodeposition coating film is then heated at a high temperature of 250 to 300°C to dehydrate and cyclize the polyamic acid to form a polyimide coating film (Patent Documents 3 to 6).

Japanese Patent Application Laid-Open No. 2003-327905 Japanese Patent Application Laid-Open No. 2005-187914 JP 63-111199 Publication Japanese Patent Application Publication No. 6-252003 Japanese Patent Application Publication No. 9-124978 Japanese Patent Application Publication No. 3-6397

However, as noted in Patent Documents 1 and 2, polyimide resins are insoluble in water, and therefore when used as electrodeposition paints, they must be dispersed in water in a colloidal state to form an electrodeposition solution. This makes it easy for defects to occur in the electrodeposition coating film, and the uniformity of the resulting electrodeposition coating film cannot be fully guaranteed, preventing the excellent properties of polyimide resins from being fully utilized.

In addition, in the methods disclosed in Patent Documents 3 to 6, the polyamic acid in the polyimide precursor is easily hydrolyzed, resulting in poor storage stability of the coating composition. Furthermore, in order to dehydrate and ring-close the polyamic acid contained in the electrodeposition coating film to convert it to imidization, heat treatment at a high temperature above a certain level and for a long period of time is required, which also poses productivity problems.

The present disclosure aims to provide an electrodeposition coating composition that has excellent storage stability, can be cured and dried at lower temperatures and in shorter times than conventional coating compositions, and can produce a coating that has good coating appearance, excellent heat resistance, insulating properties, and excellent adhesion to the substrate. It also aims to provide a method for manufacturing an article using the electrodeposition coating composition.

The present disclosure includes the following.
[1] An electrodeposition coating composition comprising a film-forming resin (A), a basic compound (B), an organic solvent (C), and water (D),
The coating film-forming resin (A) contains a polyamic acid derivative (A1) having a structural unit represented by formula (2):
the content of carboxy ester groups in the polyamic acid derivative (A1) is less than 75 mol % of the total of carboxy groups and carboxy ester groups in the polyamic acid derivative (A1),
the basic compound (B) includes a hydrophobic amine compound (B1) and a hydrophilic amine compound (B2),
the solubility of the hydrophobic amine compound (B1) in water at 20°C is more than 5 μg/100 mL and less than 10 g/100 mL, and the solubility of the hydrophilic amine compound (B2) in water at 20°C is 10 g/100 mL or more;
The electrodeposition coating composition, wherein the organic solvent (C) comprises an aprotic solvent (C1).

[In formula (2),
Ar represents an aromatic hydrocarbon group having 6 to 20 carbon atoms;
L represents a single bond, —O—, an alkylene group having 1 to 3 carbon atoms, a fluoroalkylene group having 1 to 3 carbon atoms, or —CO—;
Each R ¹ independently represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, provided that at least one R ¹ is an alkyl group having 1 to 5 carbon atoms.
[2] The electrodeposition coating composition according to [1], wherein the content of carboxy ester groups contained in the polyamic acid derivative (A1) is more than 10 mol % of the total of carboxy groups and carboxy ester groups contained in the polyamic acid derivative (A1).
[3] The electrodeposition coating composition according to [1] or [2], wherein the content of the hydrophobic amine compound (B1) in the basic compound (B) is 50 mass% or more.
[4] The electrodeposition coating composition according to any one of [1] to [3], wherein the aprotic solvent (C1) contains at least one solvent selected from the group consisting of amide solvents, sulfone solvents, sulfoxide solvents, ester solvents, and ketone solvents.
[5] The electrodeposition coating composition according to any one of [1] to [4], wherein the content of the aprotic solvent (C1) in the organic solvent (C) is 50 mass% or more.
[6] The electrodeposition coating composition according to any one of [1] to [5], wherein the content of the organic solvent (C) is more than 100 parts by mass and less than 300 parts by mass per 100 parts by mass of the water (D).
[7] The electrodeposition coating composition according to any one of [1] to [6], which is used for coating a copper wire coil.
[8] A method for producing an article comprising a substrate and an electrodeposition coating film provided on the surface of the substrate,
An electrodeposition coating process in which the substrate is immersed in the electrodeposition coating composition according to any one of [1] to [7] and a voltage is applied to form a deposition coating film on the surface of the substrate; and
The method for producing an article includes a drying step of drying the deposition coating film at 100 to 300°C for 10 to 180 minutes to obtain the electrodeposition coating film.
[9] The method for manufacturing an article according to [8], wherein the substrate is a copper wire coil.

The present disclosure provides an electrodeposition coating composition that has excellent storage stability, cures and dries at lower temperatures and in shorter times than conventional coating compositions, and produces a coating film with good coating appearance, heat resistance, and insulating properties. It also provides a method for manufacturing an article using the electrodeposition coating composition.

The electrodeposition coating composition of the present disclosure contains a film-forming resin (A), a basic compound (B), an organic solvent (C), and water (D). As described below, the film-forming resin (A) contains a polyamic acid derivative (A1), and by neutralizing the carboxyl groups of the polyamic acid derivative (A1) with the basic compound (B), an electrodeposition coating composition can be obtained in which the film-forming resin (A) is dispersed in the organic solvent (C) and water (D).

[Coating film-forming resin (A)]
The coating film-forming resin (A) contains a polyamic acid derivative (A1) having a structural unit represented by formula (2) (hereinafter also referred to as "structural unit (2)").

[In formula (2),
Ar represents an aromatic hydrocarbon group having 6 to 20 carbon atoms;
L represents a single bond, —O—, an alkylene group having 1 to 3 carbon atoms, a fluoroalkylene group having 1 to 3 carbon atoms, or —CO—;
Each R ¹ independently represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, provided that at least one R ¹ is an alkyl group having 1 to 5 carbon atoms.

In the polyamic acid derivative (A1), the content of carboxy ester groups (i.e., —COOR ¹ when R ¹ is other than a hydrogen atom) (hereinafter also referred to as the “esterification rate”) is less than 75 mol %, preferably 70 mol % or less, more preferably 60 mol % or less, even more preferably 50 mol % or less, and preferably more than 10 mol %, more preferably 15 mol % or more, even more preferably 25 mol % or more, and particularly preferably 35 mol % or more, based on the total content of carboxyl groups (—COOH) and the carboxy ester groups. When the polyamic acid derivative (A1) has both carboxy ester groups and carboxy groups and the esterification rate is within the above range, there is an advantage that the dispersibility of the polyamic acid derivative (A1) in water is improved.

The esterification rate can be calculated from the acid value of a reference polyamic acid derivative in which all R ^1s contained in the polyamic acid derivative (A1) are hydrogen atoms and the acid value of the polyamic acid derivative (A1) using the following formula:
Esterification rate (%) = acid value of polyamic acid derivative (A1) / acid value of reference polyamic acid derivative × 100
In the present disclosure, the acid value is expressed as a value converted into solid content, and can be measured by a method in accordance with JIS K 0070. The reference polyamic acid derivative may be a raw material for the polyamic acid derivative (A1) described later (a reaction product of an aromatic tetracarboxylic dianhydride (X1) and an aromatic diamine (Y)).

When heated, the polyamic acid derivative (A1) forms imide bonds, becoming a polyimide resin. Specifically, the amide bond and carboxy group in the structural unit (2) react, resulting in dehydration and ring closure to form an imide bond. Furthermore, the amide bond and carboxy ester group in the structural unit (2) react, resulting in dealcoholization and ring closure to form an imide bond (hereinafter, both of these reactions are also referred to as "imidization reactions"). Therefore, after the electrodeposition coating composition of the present disclosure is electrodeposited onto the surface of a substrate to form a polyamic acid coating film (deposition coating film), the amide bond and the carboxy group or carboxy ester group can be reacted and ring-closed by heating to form polyimide bonds, converting the polyamic acid coating film (deposition coating film) into a polyimide resin coating film.

Without being bound by any particular theory, the inventors have found that, in the present disclosure, the inclusion of a carboxyl group in the structural unit (2) of the polyamic acid derivative (A1) ensures the dispersibility of the film-forming resin (A) in water, allowing the electrodeposition coating composition of the present disclosure to function as an electrodeposition coating. Similarly, the inventors have found that, in the present disclosure, the inclusion of a carboxy ester group (i.e., -COOR ¹ ) in the structural unit (2) of the polyamic acid derivative (A1) inhibits hydrolysis of the film-forming resin (A) even when dispersed in water, thereby improving the storage stability of the electrodeposition coating composition.

The polyamic acid derivative (A1) may further have a unit represented by formula (1) (hereinafter also referred to as "structural unit (1)") in addition to structural unit (2).

[In formula (1),
Ar represents an aromatic hydrocarbon group having 6 to 20 carbon atoms;
L represents a single bond, —O—, an alkylene group having 1 to 3 carbon atoms, a fluoroalkylene group having 1 to 3 carbon atoms, or —CO—.]

In structural unit (1), as in structural unit (2), an imidization reaction can occur in which an amide bond reacts with a carboxy group, resulting in dehydration and ring closure to form an imide bond. When the polyamic acid derivative (A1) contains structural unit (1), the carboxy group contained in structural unit (1) is also included in the carboxy group contained in polyamic acid derivative (A1) when calculating the esterification rate.

When the polyamic acid derivative (A1) contains structural unit (1), the content of carboxy ester groups contained in structural unit (2) is preferably less than 75 mol%, more preferably 70 mol% or less, even more preferably 60 mol% or less, and especially preferably 50 mol% or less, based on the total content of carboxy groups and carboxy ester groups contained in structural unit (1) and structural unit (2), and is preferably more than 10 mol%, more preferably 15 mol% or more, even more preferably 25 mol% or more, and especially preferably 35 mol% or more.

In formulas (1) and (2), examples of the aromatic hydrocarbon group represented by Ar include monocyclic aromatic hydrocarbon groups such as benzenetetrayl, thiophenetetrayl, and pyridinetetrayl; and polycyclic aromatic hydrocarbon groups such as naphthalenetetrayl, biphenyltetrayl, bisphenylethertetrayl, benzophenonetetrayl, biphenylethertetrayl, bisphenylpropanetetrayl, ethylidenediphenyltetrayl, and isopropylidenediphenyltetrayl. The aromatic hydrocarbon group represented by Ar may have a substituent such as a fluorine atom, trifluoromethyl, or methyl. The aromatic hydrocarbon group represented by Ar has 6 to 20 carbon atoms, preferably 6 to 18, and more preferably 6 to 12. The Ars in formulas (1) and (2) may be the same or different. Furthermore, multiple Ars within multiple structural units (1) may be the same or different, and multiple Ars within multiple structural units (2) may be the same or different.

In formula (1) and formula (2), L each independently represents a single bond, -O-, an alkylene group having 1 to 3 carbon atoms, a fluoroalkylene group having 1 to 3 carbon atoms, or -CO-, preferably -O-, -CH ₂ -, or -CO-, and particularly preferably -O-. L in formula (1) and formula (2) may be the same or different from one another. Furthermore, among multiple structural units (1), multiple Ls may be the same or different from one another, and among multiple structural units (2), multiple Ls may be the same or different from one another.

In formula (2), the groups represented by R ¹ are each independently an alkyl group having 1 to 5 carbon atoms, and preferably an alkyl group having 1 to 3 carbon atoms. Among multiple structural units (2), multiple R ¹ may be the same or different.

The portion of the polyamic acid derivative (A1) having the structural unit (1) can be produced by reacting an aromatic tetracarboxylic dianhydride (X1) with an aromatic diamine (Y).

The aromatic tetracarboxylic dianhydride (X1) is pyromellitic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 3,3',4,4'-biphthalic dianhydride, 2,3,3',4'-biphthalic dianhydride, 3,4,3',4'-biphenyltetracarboxylic dianhydride, 3,4,3',4'-benzophenonetetracarboxylic dianhydride, 2,3,3',4'-biphenylethertetracarboxylic dianhydride, bis(dicarboxyphenyl)propane dianhydride, 4,4'-[2,2,2-trimethylsilyl]propanedi ... Examples of aromatic acid dianhydrides include bis(1,2-fluoro-1-(trifluoromethyl)ethylidene)bis(1,2-benzenedicarboxylic acid dianhydride), 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), bistrifluoromethylated pyromellitic acid, bis(dicarboxylphenyl)ether dianhydride, thiophenetetracarboxylic acid dianhydride, pyromellitic acid dianhydride, 1,2,5,6-naphthalenetetracarboxylic acid dianhydride, and 2,3,5,6-pyridinetetracarboxylic acid dianhydride. The aromatic tetracarboxylic acid dianhydride (X1) may be used alone or in combination.

Examples of the aromatic diamine (Y) include 4,4'-diaminophenyl ether, 4,4'-diaminophenylmethane, 2,2'-trifluoromethylbenzidine, 4,4'-diamino-3,3'-dimethyl-1,1'-biphenyl, 4,4'-diamino-3,3'-dimethoxy-1,1'-biphenyl, 4,4'-methylenebis(benzenamine), 4,4'-oxybis(benzenamine), 3,4'-oxybis(benzenamine), 3,3'-carboxylbis(benzenamine), and 1-methylethylidine-4,4' Examples of aromatic diamines include 4,4'-bis(benzeneamine), 3,3'-diaminobenzophenone, 1-trifluoromethyl-2,2,2-trifluoroethylidine-4,4'-bis(benzeneamine), 1,1,1,3,3,3-hexafluoro-2-bis-4(4-aminophenyl)propane, 4,4'-diamino-3,3',5,5'-tetramethylbiphenyl, 2,2-bis[4(4-aminophenoxy)phenyl]propane, and 4,4-(or 3,4'-, 3,3'-, 2,4'-)diamino-biphenyl ether. The aromatic diamine (Y) may be used alone or in combination with multiple types. It may also be combined with a diamine and/or acid anhydride having a carboxyl group. When selecting these combinations, it is necessary to select a composition that allows the combination to be soluble in a solvent.

When the aromatic tetracarboxylic dianhydride (X1) and aromatic diamine (Y) are reacted, succinic anhydride, phthalic anhydride, or maleic anhydride may be present as an end-capping agent.

The reaction solvent used in the reaction between the aromatic tetracarboxylic dianhydride (X1) and the aromatic diamine (Y) is preferably an organic solvent, more preferably a polar organic solvent, such as N-methylpyrrolidone (NMP), dimethylacetamide (DMAC), dimethylformamide (DMF), dimethylformaldehyde, and dimethyl sulfoxide (DMSO). The reaction solvent may be used alone or in combination.

The temperature when reacting the aromatic tetracarboxylic dianhydride (X1) with the aromatic diamine (Y) may be, for example, 0 to 100°C, or even 0 to 60°C. The reaction time may be 10 minutes to 50 hours, or even 20 minutes to 30 hours. The number average molecular weight can be controlled by adjusting the reaction time.

The moiety having structural unit (2) can be produced by introducing an alkyl group having 1 to 5 carbon atoms into the carboxy group contained in structural unit (1) using an alkylating agent. Examples of the alkylating agent include hydrochloric acid-alcohol reagents such as hydrochloric acid-methanol reagent and hydrochloric acid-butanol reagent; boron halide-alcohol reagents such as boron oxychloride-methanol reagent, boron trifluoride-methanol reagent, boron trifluoride-propanol reagent, boron trifluoride-isopropyl alcohol reagent, boron trifluoride-butanol reagent, and boron trichloride-chloroethanol reagent; alkyl halides having 1 to 5 carbon atoms such as methyl iodide, methyl bromide, ethyl iodide, propyl bromide, butyl iodide, butyl bromide, pentyl iodide, and pentyl bromide; N,N-dimethylformamide dimethyl ether acetals such as N,N-dimethylformamide diethyl acetal, N,N-dimethylformamide dipropyl acetal, N,N-dimethylformamide dibutyl acetal, N,N-dimethylformamide di-tert-butyl acetal, N,N-dimethylformamide dineopentyl acetal, and acetone dimethyl acetal; diazomethane derivatives such as trimethylsilyldiazomethane, N-methyl-N-nitrosoparatoluenesulfonamide, N-methyl-N-nitrosourethane, and 1-methyl-3-nitro-1-nitrosoguanidine; trimethyl orthoformate, triethyl orthoformate, ortho orthoformic acid alkyl esters such as tripropyl formate and tributyl orthoformate; alkylisoureas such as N,N'-diisopropyl-O-methylisourea, N,N'-diisopropyl-O-ethylisourea, O,N,N'-triisopropylisourea and N,N'-diisopropyl-O-tert-butylisourea; triazenes such as 1-methyl-3-paratolyltriazene, 1-ethyl-3-paratolyltriazene and 1-isopropyl-3-paratolyltriazene; carbonates such as dimethyl carbonate, diethyl carbonate, dipropyl carbonate, diisopropyl carbonate and dibutyl carbonate; dimethyl sulfate, fluorosulfuric acid Examples of suitable sulfuric acid esters include dimethyl, methyl methanesulfonate, methyl trifluoromethanesulfonate, methyl paratoluenesulfonate, diethyl sulfate, ethyl methanesulfonate, ethyl paratoluenesulfonate, dipropyl sulfate, propyl methanesulfonate, propyl paratoluenesulfonate, diisopropyl sulfate, isopropyl methanesulfonate, dibutyl sulfate, butyl paratoluenesulfonate, 2-chloroethyl methanesulfonate, 2,2,2-trifluoroethyl methanesulfonate, and 1,1,1,3,3,3-hexafluoroisopropyl paratoluenesulfonate; and alkyl orthoacetates. If necessary, a base such as sodium carbonate, potassium carbonate, triethylamine, pyridine, or diazabicycloundecene (DBU) may be used in combination.

The moiety having structural unit (2) may also be produced by reacting a compound (X2) in which the carboxyl group of an aromatic tetracarboxylic dianhydride (X1) is esterified with an aromatic diamine (Y). The compound (X2) is preferably an alkyl ester of the aromatic tetracarboxylic dianhydride (X1) having 1 to 5 carbon atoms.

The number average molecular weight of the polyamic acid derivative (A1) is preferably 10,000 to 100,000, more preferably 20,000 to 90,000, from the viewpoints of storage stability and uniformity of the coating film (deposited coating film) obtained by electrodeposition coating.
In the present disclosure, the number average molecular weight is a polystyrene equivalent value determined by gel permeation chromatography.

The content of the polyamic acid derivative (A1) in the coating film-forming resin (A) is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, with the upper limit being 100% by mass.

The film-forming resin (A) may contain other polyamic acid derivatives in addition to the polyamic acid derivative (A1). Examples of other polyamic acid derivatives include reaction products of tetracarboxylic dianhydrides with diamines other than the polyamic acid derivative (A1) (specifically, reaction products of aromatic tetracarboxylic dianhydrides with other diamines; reaction products of other tetracarboxylic dianhydrides with aromatic diamines or other diamines). Examples of the tetracarboxylic acid include the aromatic tetracarboxylic acid dianhydrides described above; and other tetracarboxylic acid dianhydrides such as 3,4,3',4'-biphenylsulfonetetracarboxylic acid dianhydride, bis(dicarboxylphenyl)sulfonic acid dianhydride, 1,2,3,4-butanetetracarboxylic acid dianhydride, cyclopentanetetracarboxylic acid dianhydride, bicyclooctenetetracarboxylic acid dianhydride, bicyclo(2,2,2)-oct-7-ene-2,3,5,6-tetracarboxylic acid dianhydride, and 5(2,5-dioxotetrahydrofuryl)3-methyl-3cyclohexene-1,2-dicarboxylic acid dianhydride. Examples of the diamine include the aromatic diamines: 4,4'-diaminophenyl sulfone, 2,4 (or 2,5)-diaminotoluene, 1,4-benzenediamine, 1,3-benzenediamine, 6-methyl-1,3-benzenediamine, 4,4'-thiobis(benzeneamine), 4,4'-sulfonyl(benzeneamine), 3,3'-sulfonyl(benzeneamine), 3,3'-dichloro-4,4'-diaminobiphenyl, 1,5-diaminonaphthalene, 4,4'-diaminobenzanilide, 2,6- Other diamines include diaminopyridine, 3,3'-dinitro-4,4'-diaminobiphenyl, bis[4(3-aminophenoxy)phenyl]sulfone, bis[4(4-aminophenoxy)phenyl]ethyl, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 9,9-bis(4-aminophenyl)fluorene, bis[4(4-aminophenoxy)phenyl]sulfone, benzidine-3,3-dicarboxylic acid, and diaminosilane compounds.

The coating composition of the present invention may optionally contain a film-forming resin other than the polyamic acid derivative (A1). Examples of other film-forming resins include polyimide resins, acrylic resins, polyester resins, urethane resins, epoxy resins, phenolic resins, and acrylic-modified epoxy resins. Epoxy resins are preferred from the viewpoint of improving the heat resistance and insulating properties of the cured electrodeposition coating film. Furthermore, when such other film-forming resins are used, their content is preferably less than 10 mass% and more preferably less than 5 mass% based on the resin solids contained in the coating composition. In one embodiment, the other film-forming resin may be water-soluble or water-dispersed and then mixed with the polyamic acid derivative (A1), basic compound (B), and organic solvent (C). In another embodiment, the other film-forming resin may be mixed with the polyamic acid derivative (A1), then mixed with the basic compound (B) and organic solvent (C), and dispersed using a dispersing device such as a disperser, thereby dispersing it in the electrodeposition coating composition.

The content of the film-forming resin (A) in the electrodeposition coating composition is preferably 0.1% by mass or more, more preferably 1% by mass or more, and preferably 20% by mass or less, more preferably 10% by mass or less.

[Basic compound (B)]
The basic compound (B) includes a hydrophobic amine compound (B1) and a hydrophilic amine compound (B2). In the present disclosure, the amine compounds including the hydrophobic amine compound (B1) and the hydrophilic amine compound (B2) refer to compounds having one or more amino groups in the molecule.

In the present disclosure, the hydrophobic amine compound (B1) refers to an amine compound having a water solubility of more than 5 μg/mL and less than 10 g/100 mL at 20°C. Without being bound by any particular theory, the inventors' studies have shown that the hydrophobic amine compound (B1) has low water solubility, which gives it a high affinity with the film-forming resin (A). It remains in the formed electrodeposition coating film (deposited coating film) and can effectively function as a catalyst when forming a polyimide resin from a polyamic acid derivative. Furthermore, despite its hydrophobicity, the hydrophobic amine compound (B1) possesses a certain amount of water solubility, which can improve the storage stability of the resulting electrodeposition coating composition. The water solubility of the hydrophobic amine compound (B1) at 20°C is preferably 10 μg/100 mL or more, more preferably 1 mg/100 mL or more, and even more preferably 5 mg/100 mL, and preferably 8 g/mL or less, more preferably 1 g/mL or less, and even more preferably 100 mg/100 mL.

Examples of the hydrophobic amine compound (B1) include trialkylamines to which an alkyl group having a relatively large number of carbon atoms is bonded, and specifically include compounds represented by formula (b1) (hereinafter also referred to as "compound (b1)") that have the above-mentioned solubility in water.
NR ² R ³ R ⁴ (b1)
[In formula (b1),
R ² , R ³ and R ⁴ each independently represent an alkyl group having 1 to 10 carbon atoms, a phenyl group or a phenylalkyl group.
However, the total number of carbon atoms in R ² , R ³ and R ⁴ is 6 or more and 20 or less.]

Examples of the alkyl group represented by ^R2 , ^R3 , and ^R4 include a linear or branched alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, and a decyl group, or a phenyl group or a benzyl group. ^R2 , ^R3 , and ^R4 may be the same or different from each other.

The total number of carbon atoms in R ² , R ³ and R ⁴ is preferably 6 to 15, more preferably 6 to 12.

As the hydrophobic amine compound (B1), from the viewpoint of the imidization reaction of the polyamic acid derivative (A1), dimethyldecylamine, triethylamine, tripropylamine, tributylamine, aniline, benzylamine, phenethylamine, dimethylaniline, and dimethylbenzylamine are preferred, and dimethyldecylamine, triethylamine, and tributylamine are more preferred.

The hydrophobic amine compound (B1) may be used alone or in combination.

The boiling point of the hydrophobic amine compound (B1) is preferably 80°C or higher, more preferably 150°C or higher, and even more preferably 180°C or higher, and may be, for example, 260°C or lower, even more preferably 250°C or lower, and particularly preferably 240°C or lower. Having a boiling point within the above range has the advantage of ensuring that the imidization reaction of the polyamic acid derivative (A1) proceeds smoothly.

The content of the hydrophobic amine compound (B1) in the basic compound (B) is preferably 50 mol% or more, more preferably 60 mol% or more, even more preferably 70 mol% or more, and preferably 95 mol% or less, more preferably 92 mol% or less, and even more preferably 88 mol% or less. Having the content of the hydrophobic amine compound (B1) within the above range has the advantage of improving the reactivity of the imidization reaction of the polyamic acid derivative (A1).

In the present disclosure, the hydrophilic amine compound (B2) refers to the amine compounds described above that have a water solubility of 10 g/100 mL or more at 20°C. Without being bound by any particular theory, the inventors' studies have shown that the high water solubility of the hydrophilic amine compound (B2) neutralizes the carboxyl groups contained in the film-forming resin (A), thereby improving the storage stability of the resulting electrodeposition coating composition and suppressing residue in the electrodeposition coating. The water solubility of the hydrophilic amine compound (B2) is preferably 15 g/100 mL or more, and more preferably 20 g/100 mL or more, at 20°C. In the present disclosure, the water solubility of a water-miscible compound is considered to be infinite.

Examples of the hydrophilic amine compound (B2) include alkanolamines and trialkylamines to which an alkyl group having a relatively small number of carbon atoms is bonded. Specific examples include compounds represented by formula (b2) (hereinafter also referred to as "compound (b2)") that have the above-mentioned solubility in water.
NR ⁵ R ⁶ R ⁷ (b2)
[In formula (b2),
R ⁵ , R ⁶ and R ⁷ each independently represent an alkyl group having 1 to 3 carbon atoms or a hydroxyalkyl group having 1 to 10 carbon atoms.
However, R ⁵ , R ⁶ and R ⁷ are all alkyl groups and the total number of carbon atoms in these alkyl groups is 5 or less, or at least one of R ⁵ , R ⁶ and R ⁷ is a hydroxyalkyl group having 1 to 10 carbon atoms.]

Examples of the alkyl group represented by R ⁵ , R ⁶ and R ⁷ include a methyl group, an ethyl group and a propyl group. The number of carbon atoms in the alkyl group represented by R ⁵ , R ⁶ and R ⁷ is preferably 1 to 2.

Examples of the hydroxyalkyl group represented by R ⁵ , R ⁶ , and R ⁷ include a hydroxymethyl group, a hydroxypropyl group, a hydroxybutyl group, a hydroxypentyl group, etc. The number of carbon atoms in the hydroxyalkyl group represented by R ⁵ , R ⁶ , and R ⁷ is preferably 1 to 10, and more preferably 1 to 4.

Of R ⁵ , R ⁶ and R ⁷ , preferably one or more are hydroxyalkyl groups, more preferably two or more are hydroxyalkyl groups, and even more preferably all are hydroxyalkyl groups.

R ⁵ , R ⁶ and R ⁷ may be the same or different.

Preferred hydrophilic amine compounds (B2) are trimethylamine, diethylmethylamine, N,N-dimethylaminoethanol, and triethanolamine, with triethanolamine being more preferred.

The hydrophilic amine compound (B2) may be used alone or in combination.

The content of the hydrophilic amine compound (B2) is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 12 parts by mass or more, per 100 parts by mass of the hydrophobic amine compound (B1), and is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 25 parts by mass or less. Having the content of the hydrophilic amine compound (B2) within the above range has the advantage of improving the storage stability of the resulting electrodeposition coating composition.

The total content of the hydrophobic amine compound (B1) and the hydrophilic amine compound (B2) in the basic compound (B) is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and preferably 100% by mass or less.

The basic compound (B) may contain other basic compounds in addition to the amine compound. Examples of such other basic compounds include alkali metal hydroxides and alkaline earth gold hydroxides.

In the present disclosure, the content of the basic compound (B) is such that the neutralization rate of the polyamic acid derivative (A1) by the basic compound (B), i.e., the neutralization rate calculated in molar terms by the following formula, is preferably 50% or more, more preferably 70% or more, even more preferably 90% or more, and is preferably 200% or less, more preferably 120% or less.
Neutralization rate (%)=[(basic valence of basic compound (B)×number of moles of basic compound (B))/(number of moles of carboxy groups in polyamic acid derivative (A1)]×100

When the amount of basic compound (B) used is at least the above lower limit, the manufacturability (emulsification ability) of the electrodeposition coating composition is good, and when it is at most the above upper limit, the manufacturability (emulsification ability) and storage stability of the electrodeposition coating composition are good.

[Organic solvent (C)]
The organic solvent (C) includes an aprotic solvent (C1). In the present disclosure, the aprotic solvent (C1) refers to a solvent that is not proton-donating. The aprotic solvent (C1) preferably includes at least one solvent selected from the group consisting of amide solvents, sulfone solvents, sulfoxide solvents, ester solvents, and ketone solvents. The inclusion of the aprotic solvent (C1) has the advantages of improving the storage stability of the resulting coating composition and improving the continuity and smoothness of the resulting coating film.

Examples of the amide solvents include N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), dimethylacetamide (DMAc), 1,3-dimethyl-2-imidazolidinone (DMI), N,N-dimethylpropyleneurea, N,N-2-trimethylpropionamide, and 3-methoxy-N,N-dimethylpropanamide. Examples of the sulfone solvents include cyclic sulfone solvents, such as sulfolane. Examples of the sulfoxide solvents include dimethyl sulfoxide. Examples of the ester solvents include cyclic ester solvents, such as gamma-butyrolactone. Examples of the ketone solvents include cyclic ketone solvents, such as cyclohexanone. The organic solvent (C) is preferably an amide solvent, more preferably N-methyl-2-pyrrolidone, N,N-dimethylformamide, 1,3-dimethyl-2-imidazolidinone (DMI), N,N-dimethylpropyleneurea, N,N-2-trimethylpropionamide, or 3-methoxy-N,N-dimethylpropanamide, and even more preferably N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone (DMI), N,N-dimethylpropyleneurea, N,N-2-trimethylpropionamide, or 3-methoxy-N,N-dimethylpropanamide. The amide solvents may be used alone or in combination. Other aprotic solvents (C1) include ether solvents such as tetrahydrofuran, and nitrile solvents such as acetonitrile.

The content of the aprotic solvent (C1) in the organic solvent (C) is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and preferably 100% by mass or less. Having the content of the aprotic solvent (C1) within this range has the advantages of improving the storage stability of the resulting coating composition and improving the continuity and smoothness of the resulting coating film.

The organic solvent (C) may contain an organic solvent (C) other than the aprotic solvent (C1). The other organic solvent is preferably a polar solvent, such as an alcohol such as methanol or ethanol.

The content of the organic solvent (C) is preferably 100 parts by mass or more, more preferably 120 parts by mass or more, and preferably 300 parts by mass or less, more preferably 250 parts by mass or less, per 100 parts by mass of water (D), which will be described later. Having the content of the organic solvent (C) within this range has the advantage of improving the film-forming properties of the resulting coating film.

[Water (D)]
As water (D), any water commonly used in the art can be used as appropriate, and ion-exchanged water is preferably used. The total content of the organic solvent (C) and water (D) in the electrodeposition coating composition is preferably 80% by mass or more and preferably 98% by mass or less.

[Pigment]
The electrodeposition coating composition may contain a pigment as needed, such as coloring pigments including titanium oxide, yellow iron oxide, red iron oxide, carbon black, phthalocyanine blue, phthalocyanine green, azo red, quinacridone red, and benzimidazolone yellow; extender pigments including silica compounds, silica-alumina compounds, aluminum compounds, calcium compounds (e.g., calcium carbonate), nitrides, barium sulfate, layered silicate compounds (e.g., kaolin, clay, and talc), layered double hydroxides, lime charcoal, zirconia, yttria, and zinc oxide; and rust-preventive pigments including iron phosphate, aluminum phosphate, calcium phosphate, aluminum tripolyphosphate, aluminum molybdate, calcium molybdate, and aluminum phosphomolybdate.

When the electrodeposition coating composition contains a pigment, from the viewpoint of ease of pigment dispersion, it is preferable to disperse the pigment in advance in an anionic pigment dispersing resin and use the resulting pigment dispersion paste in the production of the electrodeposition coating composition. The pigment dispersion paste may contain an aqueous medium and, if necessary, a neutralizing base.

The anionic pigment dispersing resin may be a modified acrylic resin prepared using an acrylic ester, acrylic acid, an azonitrile compound, or the like.

Examples of the neutralizing base include ammonia; organic amines such as diethylamine, ethylethanolamine, diethanolamine, monoethanolamine, monopropanolamine, isopropanolamine, ethylaminoethylamine, hydroxyethylamine, diethylenetriamine, and triethylamine; and alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. The solids content of the raw material dispersion paste may be, for example, 35 to 70% by mass, or even 40 to 65% by mass.

The aqueous medium may be a mixture of the organic solvent (C) and water (D).

The pigment dispersion paste can be produced by mixing an anionic pigment dispersion resin, pigment, aqueous medium, and, if necessary, a neutralizing base, and dispersing the mixture using a dispersing device such as a ball mill or sand grinding mill until the particle size of the pigment in the mixture is, for example, 15 μm or less.

The pigment dispersion paste may be, for example, a commercially available product such as WAJ-AAT-907 Black, WAJ-AAT-825 Violet, or WAJ-AAT-731 Blue (all manufactured by Toyochem Co., Ltd.), or Emacol NS Ochre 4622 (manufactured by Sanyo Pigment Co., Ltd.).

When the electrodeposition coating composition contains a pigment, the pigment content is preferably 2 to 50 mass % of the total solid content of the electrodeposition coating composition, which not only allows for the production of a good electrodeposition coating film but also improves the storage stability of the electrodeposition coating composition.
In the present disclosure, the total solid content of the electrodeposition coating composition refers to the portion of the electrodeposition coating composition excluding the organic solvent (C) and water (D).

[Additives]
The electrodeposition coating composition may contain other additives as required, such as dispersants, viscosity modifiers, surface modifiers, antifoaming agents, film-forming aids, ultraviolet absorbers, antioxidants, pH adjusters, and catalysts.

[Method of manufacturing electrodeposition coating composition]
The electrodeposition coating composition of the present disclosure can be prepared by mixing the respective components. Specifically, the electrodeposition coating composition of the present disclosure can be produced by adding and mixing the film-forming resin (A), the basic compound (B), the organic solvent (C), and other components (pigments, additives, etc.) used as needed, and then mixing the resulting mixture with water (D) to disperse them. More specific methods for producing the electrodeposition coating composition include, for example, the following method.

First, the film-forming resin (A) and the organic solvent (C) are mixed, and then the basic compound (B) is mixed in. The resulting mixture is added dropwise to water (D), or an aqueous medium is added to the resulting mixture, followed by dispersion or dissolution, to obtain an aqueous dispersion.
As an example of another production method, first, the coating film-forming resin (A), basic compound (B) and organic solvent (C) are mixed, and the resulting mixture is added dropwise to water (C), or water (C) is added to the resulting mixture, followed by dispersion or dissolution, to obtain an aqueous dispersion.

In addition, other components used as needed in the production of the electrodeposition coating composition can be added at any appropriate time. Furthermore, mixing, dispersion, or dissolution can be carried out using, for example, a mixer/disperser, kneader, or the like, such as a roller mill, ball mill, bead mill, pebble mill, sand grind mill, pot mill, paint shaker, or disperser.

A method for manufacturing an article comprising a substrate and an electrodeposition coating film formed from the electrodeposition coating composition of the present disclosure is also included within the technical scope of the present disclosure.

[Article manufacturing method]
The method for producing the article includes an electrodeposition coating step of immersing the substrate in the electrodeposition coating composition of the present disclosure and applying a voltage to form a deposition coating film on the surface of the substrate;
The method includes a drying step of drying the deposited coating film for 10 to 180 minutes at 80 to 300° C. to form an electrodeposition coating film. In one embodiment, the drying step may be performed by setting the drying temperature and/or drying time in a stepwise manner, for example, by drying at 80 to 120° C. for 10 to 30 minutes, followed by drying at 140 to 180° C. for 10 to 30 minutes, and then drying at 200 to 240° C. for 10 to 30 minutes.

The substrate to be coated with the electrodeposition coating composition is not particularly limited as long as it is electrically conductive. Examples include metals (iron, steel, copper, aluminum, magnesium, tin, zinc, etc., and alloys containing these metals), iron plates, steel plates, aluminum plates, and those that have been surface-treated (for example, with phosphoric acid, chromate, or zirconium-based chemical conversion treatments), as well as molded products of these.

In the electrodeposition coating process, the bath temperature of the coating composition is preferably 10°C to 40°C, more preferably 10°C to 30°C. The applied voltage is preferably 10V to 200V, more preferably 30V to 100V. The voltage application time is preferably 1 second to 300 seconds, more preferably 30 seconds to 180 seconds.

After the electrodeposition coating process and before the drying process, a process of rinsing the deposited coating with water or solvent may be carried out. The purpose of the water rinsing is to wash the substrate to which the electrodeposition paint has adhered and remove the electrodeposition liquid. There are no particular limitations on the water rinsing method, and a conventional washing device can be used. For example, a device can be used to wash the electrodeposition-coated substrate using the filtrate obtained by ultrafiltration of the electrodeposition liquid as the washing liquid.

In the drying step, the drying temperature may be, for example, 5 to 180 minutes, preferably 10 to 180 minutes, and particularly preferably 10 to 120 minutes. The baking and drying means may be a conventional heating and drying device, and specific examples include a hot air drying oven, near-infrared heating oven, far-infrared heating oven, and induction heating oven.

The thickness of the resulting electrocoated coating is preferably 5 to 25 μm.

The electrodeposition coating composition and article manufacturing method disclosed herein can be preferably used on substrates with complex shapes, such as segmented copper wire, specifically copper wire coils. They can also be preferably used on substrates that require insulation and heat resistance, such as generator coils.

The present invention will be further explained in detail using the following examples, but the present invention is not limited to these.

(Production Example 1)
Production example of film-forming resin (A1: polyamic acid derivative)
A reaction vessel equipped with a stirrer, reflux condenser, and thermometer was charged with 73.2 parts by mass of 4,4'-diaminodiphenyl ether and 823.6 parts by mass of N-methyl-2-pyrrolidone, and the mixture was heated to 50°C with stirring to dissolve. Next, 107.6 parts by mass of 3,4,3',4'-diphenyltetracarboxylic dianhydride was gradually added to the dissolved mixture. After the addition was completed, stirring was continued for 1 hour, and finally, 0.2 parts by mass of phthalic anhydride was added and stirred for an additional 30 minutes to obtain 1,004.4 parts by mass of polyamic acid (I-1) (solids concentration: 18.0% by mass).

Next, 1,004.4 parts by mass of polyamic acid (I-1) and 300.0 parts by mass of N-methyl-2-pyrrolidone were added to a reaction vessel equipped with a stirrer, reflux condenser, and thermometer, and 37.6 parts by mass of potassium carbonate was added while stirring. 56.0 parts by mass of iodopropane was then added, and the mixture was heated to 45°C and stirred for 7 hours. The mixture was then cooled to room temperature and filtered to obtain 1,360.4 parts by mass of a reaction product in which a portion of the carboxy groups of polyamic acid (I-1) had been esterified. The resulting reaction product was poured into a large volume of acetone in a stainless steel vessel and reprecipitated, followed by filtration to separate the solid. The resulting solid was then heated and vacuum dried at 40°C for 24 hours to obtain polyamic acid derivative (A1-1) (esterification rate: 45 mol%).

(Production Examples 2 to 13)
Polyamic acid derivatives (A1-2) to (A1-10) and (a1-1) to (a1-3) were obtained in the same manner as in Production Example 1, except that the types and amounts of tetracarboxylic dianhydride (X1) and aromatic diamine compound (Y1) in Production Example 1 were changed as shown in Table 1, and the types and amounts of polyamic acid and alkylating agent were changed as shown in Table 2. The number average molecular weights of polyamic acids (I-4) and (I-5) were adjusted by setting the reaction times of tetracarboxylic dianhydride (X1) and aromatic diamine compound (Y1) to 30 minutes and 1,440 minutes, respectively.

Example 1
Preparation example of electrodeposition coating composition
100.0 parts by mass of the polyamic acid derivative (A1), 34.6 parts by mass of tributylamine as the hydrophobic amine compound (B1), 5.3 parts by mass of triethanolamine as the hydrophilic amine compound (B2), and 1,740 parts by mass of N-methyl-2-pyrrolidone as the solvent (C1) were mixed (polyamic acid derivative mixture), and 1,160 parts by mass of deionized water was gradually added while stirring with a disper, to obtain an electrodeposition coating composition.

(Examples 2 to 17, 19 to 20, Comparative Examples 1 to 8, 10)
An electrodeposition coating composition was obtained in the same manner as in Example 1, except that the film-forming resin (A), basic compound (B), organic solvent (C), water (D) and other resins (z) used as needed were changed as shown in Table 3.

(Example 18)
95.0 parts by mass of the polyamic acid derivative (A1-1) and 5.0 parts by mass of the other resin (z1) were mixed and dispersed using a disper, and then 34.6 parts by mass of tributylamine as the hydrophobic amine compound (B1), 5.3 parts by mass of triethanolamine as the hydrophilic amine compound (B2), and 1,740 parts by mass of N-methyl-2-pyrrolidone as the solvent (C1) were mixed, and 1,160 parts by mass of deionized water was gradually added while stirring with a disper, thereby obtaining an electrodeposition coating composition.

(Comparative Example 9)
A 2L reaction vessel equipped with a stirrer, a cooling tube, a nitrogen inlet tube, and a thermometer connected to a temperature regulator was charged with 700 parts by weight of isopropyl alcohol and heated to 80 ° C. under a nitrogen atmosphere. Into this reaction vessel, 322 parts by weight of methyl methacrylate, 140 parts by weight of butyl acrylate, 105 parts by weight of styrene, 84 parts by weight of 2-hydroxyethyl methacrylate, 49 parts by weight of acrylic acid and azoisobutyronitrile 7 parts by weight of the mixed solution was added dropwise at a constant rate over 3 hours, and then, by holding at 80 ° C. for 2 hours, an acrylic resin (solid concentration: 50% by weight, acid value: 55 mg KOH / g, hydroxyl value: 52 mg KOH / g, number average molecular weight: 30,000) was obtained.

328 parts by weight of the acrylic resin, 86 parts by weight of Cymel 235 (manufactured by Allnex Japan Co., Ltd., solids concentration: 100%), and 11 parts by weight of triethylamine were mixed with 3.75 parts by weight of dinonylnaphthalenesulfonic acid while stirring with a disper. The resulting mixture was diluted with deionized water to a solids content of 10% by weight to obtain an electrodeposition coating composition.

Details of the materials used in the examples and comparative examples are as follows.
Raw materials for polyamic acid derivatives: aromatic tetracarboxylic dianhydride (X1)
Tetracarboxylic acid (X1-1): 3,3',4,4'-biphenyltetracarboxylic dianhydride Tetracarboxylic acid (X1-2): pyromellitic dianhydride Aromatic diamine compound (Y)
Aromatic diamine compound (Y-1): 4,4'-diaminodiphenyl ether Aromatic diamine compound (Y-2): p-phenylenediamine Alkylating agent Iodomethane; number of carbon atoms in the alkyl group of R1 in formula (2): 1
Iodopropane: Number of carbon atoms in the alkyl group of R1 in formula (2): 3
Iodopentane: Number of carbon atoms in the alkyl group of R1 in formula (2): 5
Iodohexane: Number of carbon atoms in the alkyl group of R1 in formula (2): 6
Other diamine compounds: Diamine compound (y-1): 1,3-bis(4-aminopropyl)-1,1,3,3-tetramethyldisiloxane basic compound (B)
Hydrophobic amine compound (B1)
Hydrophobic amine compound (B1-1): tributylamine; solubility in water (20°C): 300 mg/100 mL, boiling point: 215°C
Hydrophobic amine compound (B1-2): N,N-dimethyldecylamine; solubility in water (20°C): 8.6 mg/100 mL, boiling point: 235°C
Hydrophobic amine compound (B1-3): triethylamine; solubility in water (20°C): 17 g/100 mL, boiling point: 89°C
Hydrophobic amine compound (B1-4): trioctylamine; solubility in water (20°C): 0.005 mg/100 mL, boiling point: 365°C
Hydrophilic amine compound (B2)
Hydrophilic amine compound (B2-1): triethanolamine; solubility in water (20°C): 10 g/100 mL, boiling point: 335°C
Hydrophilic amine compound (B2-2): N,N-diethylmethylamine; solubility in water (20°C): 311 g/100 mL, boiling point: 64°C
Organic solvent (C)
Aprotic Solvent (C1)
Aprotic solvent (C1-1): N-methylpyrrolidone (amide solvent)
Aprotic solvent (C1-2): N,N-dimethylformamide (amide solvent)
Other solvents Other solvents (c-1): Methanol water (D)
Deionized water and other resins (z1) jER-825 (epoxy resin, manufactured by Mitsubishi Chemical Corporation)

Preparation of electrodeposition coating (test plate) An oxygen-free copper plate (C1100P) to be coated was immersed in an 18% by mass aqueous solution of sodium persulfate at 40°C for 1 minute, removed and rinsed with deionized water. Next, it was immersed in a 4% by mass aqueous solution of sulfuric acid at room temperature for 2 minutes, removed and rinsed with deionized water, and then used for the test.

After immersing the entire substrate in an electrodeposition bath containing the electrodeposition coating composition obtained above at a liquid temperature of 30°C, voltage application was initiated immediately, increased over 30 seconds, and maintained at 80V for 150 seconds, forming a deposition coating film on the substrate. The resulting deposition coating film was dried by heating at 100°C, 150°C, and 200°C for 15 minutes each, yielding an electrodeposition-coated plate with an electrodeposition coating film thickness of 18 μm.

(3) Evaluation item [Manufacturability of electrodeposition coating composition]
In the preparation of the electrodeposition coating composition, the state of the coating composition when pure water was added to the polyamic acid derivative mixture was visually observed to evaluate the manufacturability of the electrodeposition coating composition. The evaluation criteria are as follows. A score of 0 or higher was considered to be pass.
⊚: No precipitation of polyamic acid derivative was observed.
◯: slight precipitation of polyamic acid derivative observed;
×: Precipitation of polyamic acid derivative observed

[Storage stability]
The electrodeposition coating compositions obtained in the above Examples and Comparative Examples were allowed to stand at 23°C. Every day, an electrodeposition coating film was produced using the above-mentioned method for preparing an electrodeposition coating film (test plate). The state of the obtained electrodeposition coating film (deposited coating film) was visually observed, and the storage stability of the electrodeposition coating composition was evaluated. The evaluation criteria were as follows. A score of △ or higher was considered to be acceptable.
◎: The electrodeposition coating film did not become cloudy for 15 days or more. ○: The electrodeposition coating film did not become cloudy for 10 days or more but less than 15 days. △: The electrodeposition coating film did not become cloudy for 2 days or more but less than 10 days. ×: The electrodeposition coating film became cloudy in less than 2 days.

[Coating film appearance]
The appearance of the electrodeposition coating films obtained in the above Examples and Comparative Examples was visually observed and evaluated. The evaluation criteria were as follows: A score of △ or higher was considered to be acceptable.
⊚: A coating film having continuity and a smooth and uniform thickness is obtained.
◯: A continuous and smooth coating film was obtained.
△: Continuity is observed, but a smooth coating film is not obtained (added for adjustment of Comparative Examples 9 and 10)
×: There is no continuity and a smooth coating film cannot be obtained.

[Adhesion (cross-cut test)]
The coating film of the test plate obtained in the above Examples and Comparative Examples was cut with a cutter at 1 mm intervals, 11 lines vertically and horizontally, and Cellophane Tape ^{(registered trademark)} (manufactured by Nichiban Co., Ltd.) was applied on the cuts and then peeled off. The number of remaining squares out of 100 squares was counted to evaluate adhesion (cross-cut test). 100/100 indicates that the coating film peeled off 0% of the area, for example, 80/100 indicates that the coating film peeled off 20% of the area, and 50/100 indicates that the coating film peeled off 50% of the area. The evaluation criteria are as follows:
◎: 100/100
〇: 90/100 to 99/100
△: 80/100 to 89/100
×: 79/100 or less

[Heat resistance]
The test plates obtained in the above Examples and Comparative Examples were subjected to a heat resistance test at 220°C for 500 hours using a Perfect Jet Oven (manufactured by ESSPEC). The thickness of the coating film after the test was measured, and the remaining rate of the coating film was calculated according to the following formula to evaluate the heat resistance of the coating film. The evaluation criteria are as follows: A score of △ or higher was considered to be pass. The coating film thickness was measured using an eddy-current film thickness meter LH-370 (manufactured by Kett).
Residual rate of coating film (%) = coating film thickness after test / coating film thickness before test × 100
⊚: The remaining rate of the coating film is 97% or more.
Good: The remaining rate of the coating film is 95% or more and less than 97%.
Δ: The remaining rate of the coating film is 90% or more but less than 95%.
×: The remaining rate of the coating film is less than 90%.

[Insulation]
The dielectric breakdown strength of the test plates obtained in the examples and comparative examples was measured by a method in accordance with JIS C 2110-1:2016.
That is, using a voltage resistance tester MODEL 8504 (manufactured by Tsuruga Electric Co., Ltd.; electrode size: 10 mmφ), the test plate was immersed in glycerin, and a voltage was continuously applied while increasing the voltage at a detection current of 50 mA and a voltage increase rate of 100 V/sec to evaluate the insulating properties of the coating film. The voltage at which dielectric breakdown of the coating film occurred, i.e., the voltage at which a current of 50 mA was detected, was taken as the dielectric breakdown voltage. The evaluation criteria were as follows. A rating of 0 or higher was considered to be a pass. The test was conducted at a temperature of 23°C.
⊚: The voltage at which breakdown occurred was greater than 1.5 kV.
Good: The voltage at which breakdown occurred was 1.0 kV or more and less than 1.5 kV.
×: The voltage at which breakdown occurred was less than 1.0 kV.

Examples 1 to 20 are examples of the present invention, and it was confirmed that the electrodeposition coating composition had good storage stability, could be cured and dried at low temperatures in a short time, and the resulting coating film had good appearance, heat resistance, and insulation properties.

In Comparative Example 1, the film-forming resin did not have the structural unit represented by formula (2), and the heat resistance and insulating properties of the electrodeposition coating were not fully satisfactory.
Comparative Example 2 is an example in which the coating film-forming resin does not have the structural unit represented by formula (1) or the structural unit represented by formula (2), and the heat resistance and insulating properties of the electrocoated coating film were not fully satisfactory.
In Comparative Example 3, the esterification rate of the coating film-forming resin was 75% or more, and the heat resistance and insulating properties of the electrodeposition coating film were not fully satisfactory.
In Comparative Example 4, the solubility of the hydrophobic amine compound in water was 5 μg/100 mL or less, and the manufacturability of the electrodeposition coating composition was poor. The storage stability of the electrodeposition coating composition was also not fully satisfactory. Because film formation was difficult, no tests on coating film performance were conducted.
Comparative Example 5 is an example that does not contain a hydrophobic amine compound, and the appearance, heat resistance and insulating properties of the electrodeposition coating film were not fully satisfactory.
Comparative Example 6 is an example that does not contain an aprotic polar solvent, and the electrodeposition coating composition had poor manufacturability and storage stability. Since film formation was difficult, no tests on coating film performance were conducted.
Comparative Example 7 was an example containing no water, and the electrodeposition coating composition was poor in manufacturability and had insufficient storage stability. In addition, the coating film obtained had insufficient appearance and adhesion.
Comparative Example 8 is an example in which the coating film-forming resin (A) did not contain the polyamic acid derivative (A1), and the resulting coating film was not fully satisfactory in adhesion, heat resistance and insulating properties.
Comparative Example 9 is an example that does not contain the hydrophilic amine compound (B2), and the electrodeposition coating composition was poor in manufacturability and storage stability. Since film formation was difficult, no tests on coating film performance were conducted.

Claims (8)

An electrodeposition coating composition comprising a film-forming resin (A), a basic compound (B), an organic solvent (C), and water (D),
The film-forming resin (A) is a compound represented by formula (2) :
[In formula (2),
Ar represents an aromatic hydrocarbon group having 6 to 20 carbon atoms;
L represents a single bond, —O—, an alkylene group having 1 to 3 carbon atoms, a fluoroalkylene group having 1 to 3 carbon atoms, or —CO—;
Each R ¹ independently represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, provided that at least one R ¹ is an alkyl group having 1 to 5 carbon atoms.
The polyamic acid derivative (A1) has a structural unit represented by
the content of carboxy ester groups in the polyamic acid derivative (A1) is less than 75 mol % of the total of carboxy groups and carboxy ester groups in the polyamic acid derivative (A1),
the basic compound (B) includes a hydrophobic amine compound (B1) and a hydrophilic amine compound (B2),
the solubility of the hydrophobic amine compound (B1) in water at 20°C is more than 5 μg/100 mL and less than 10 g/100 mL, and the solubility of the hydrophilic amine compound (B2) in water at 20°C is 10 g/100 mL or more;
The organic solvent (C) includes an aprotic solvent (C1),
An electrodeposition coating composition , wherein the content of carboxy ester groups contained in the polyamic acid derivative (A1) is more than 10 mol % of the total of carboxy groups and carboxy ester groups contained in the polyamic acid derivative (A1) . 2. The electrodeposition coating composition according to claim 1 , wherein the content of said hydrophobic amine compound (B1) in said basic compound (B) is 50 mass % or more. 3. The electrodeposition coating composition according to claim 1 , wherein the aprotic solvent (C1) comprises at least one solvent selected from the group consisting of amide solvents, sulfone solvents, sulfoxide solvents, ester solvents, and ketone solvents. 4. The electrodeposition coating composition according to claim 1 , wherein the content of said aprotic solvent (C1) in said organic solvent (C) is 50 mass % or more. 5. The electrodeposition coating composition according to claim 1 , wherein the content of said organic solvent (C) is more than 100 parts by mass and less than 300 parts by mass per 100 parts by mass of said water (D). The electrodeposition coating composition according to any one of claims 1 to 5 , which is used to coat a copper wire coil. A method for manufacturing an article comprising a substrate and an electrodeposition coating film provided on the surface of the substrate, comprising:
an electrodeposition coating step of immersing the substrate in the electrodeposition coating composition according to any one of claims 1 to 6 and applying a voltage to form a deposition coating film on the surface of the substrate; and
The method for producing an article includes a drying step of drying the deposition coating film at 100 to 300°C for 10 to 180 minutes to obtain the electrodeposition coating film. The method for manufacturing an article according to claim 7 , wherein the object to be coated is a copper wire coil.