Electrodeposition coating composition and water-based electrodeposition coating containing the same

Abstract

To provide a composition for electrodeposition coating that can form an electrodeposition coating layer having excellent voltage resistance, and an aqueous electrodeposition coating containing the same.SOLUTION: A composition for electrodeposition coating contains an aromatic polyamide imide resin, a flexibility enhancer and a hydrophilic cationic polymer. For the contents, for example, the aromatic polyamide imide resin is 75-90 wt.%, the flexibility enhancer is 5-15 wt.%, and the hydrophilic cationic polymer is 5-15 wt.% relative to the total amount of the three components.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an electrodeposition coating composition and a water-based electrodeposition coating containing the same. [Background technology]

[0002] Electrodeposition coating compositions are required to have a wide range of properties depending on their application, such as insulation, heat resistance, and abrasion resistance. For heat-resistant applications, improved properties are achieved by using polyimide resins and amide-imide resins. In particular, there has been an increasing demand for coating film flexibility, such as vibration resistance and bendability during post-processing, for automotive applications.

[0003] To meet these demands, there is an anionic composition (Patent Document 1) in which a polyamide resin or polyimide resin having terminal OH groups or SH groups is neutralized with an alkali such as an amine.

[0004] There is also a cationic composition (Patent Document 2) obtained by copolymerizing a compound having OH groups at the 3,3-positions of a benzene ring and then adding a benzoic acid compound having an amino group to the OH groups. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-268235 [Patent Document 2] Japanese Patent Application Publication No. 2019-094404 [Patent Document 3] Japanese Patent Application Publication No. 2019-218433 Summary of the Invention [Problem to be solved by the invention]

[0006] However, all of the above compositions have room for improvement. For example, the anionic type of Patent Document 2 causes dissolution of the coated object, which is the anode, and therefore cannot be applied to metals used in electronic components, such as copper and silver plating.

[0007] In addition, because it is difficult to disperse or dissolve in water, it must be used in combination with a large amount (50% or more) of organic polar solvents with high dissolving power, such as NMP (N-methylpyrrolidone) and DMF (N,N-dimethylformamide), which poses safety and environmental problems.

[0008] In the case of the cationic composition of Patent Document 3, the polyimide varnish is reacted with the hydrophilic cationic polymer, so the reaction must be controlled. In addition, when reactivity is taken into consideration, there is a problem in that the types of materials that can be selected are limited.

[0009] Furthermore, although Patent Document 1 describes a coating composition with excellent heat-resistant insulation properties and flexibility, there are problems in that when the polycondensation polyimide content is up to 60%, flexibility decreases when the thermally crosslinked imide content exceeds 10%, and heat resistance decreases when the hydrophilic cationic polymer content exceeds 10%.

[0010] As a result of extensive research, the present inventors have discovered that an electrodeposition coating composition containing an aromatic polyamideimide resin, a flexibility enhancing agent, and a hydrophilic cationic polymer can form an electrodeposition coating film having excellent heat resistance and flexibility, and have thus completed the present invention. [Means for solving the problem]

[0011] That is, the present invention is an electrodeposition coating composition comprising an aromatic polyamideimide resin, a flexibility enhancing agent, and a hydrophilic cationic polymer.

[0012] The present invention is also characterized in that the composition contains 75 to 90% by weight of aromatic polyamideimide resin, 5 to 15% by weight of flexibility enhancer, and 5 to 15% by weight of hydrophilic cationic polymer relative to the total amount of the aromatic polyamideimide resin, flexibility enhancer, and hydrophilic cationic polymer.

[0013] The present invention also provides a water-based electrodeposition paint, characterized in that the above electrodeposition paint composition is contained in a dispersed state in a medium containing an acid neutralizer. [Effects of the Invention]

[0014] The electrodeposition coating composition of the present invention forms a coating film on a substrate by electrodeposition coating and cures it, exhibiting excellent heat resistance and flexibility, making it ideal for use in coating automotive equipment, which requires flexibility of the coating film, such as properties against vibration and flexibility during post-processing. Furthermore, while electrodeposition coatings made from only a hydrophilic cationic polymer and an aromatic polyamideimide will result in separation and sedimentation, the inclusion of a flexibility enhancing agent that is compatible with the hydrophilic cationic polymer and aromatic polyamideimide resin prevents reaction and stabilizes the electrodeposition coating composition.

[0015] Furthermore, the aqueous electrodeposition paint of the present invention contains the electrodeposition paint composition in a dispersed state in a medium containing an acid neutralizer, thereby blending the aromatic polyamideimide resin, flexibility enhancing agent, and hydrophilic cationic polymer, and the entanglement and compatibility between the resins makes it possible to disperse the hydrophilic cationic polymer and aromatic polyamideimide resin in water without causing them to react with each other.

[0016] Furthermore, the properties of the composition improve heat resistance and insulation, and the reduced amount of organic solvent used allows for good uniform coating, and the product also has excellent safety and environmental properties.

[0017] Furthermore, the aqueous electrodeposition paint of the present invention has excellent heat resistance and insulating properties due to the inclusion of an aromatic polyamideimide resin, and by including a flexibility enhancing agent, the aromatic polyamideimide resin is incorporated into the hydrophilic cationic polymer to achieve cationization, thereby achieving further improvements in heat resistance and insulating properties.

[0018] Furthermore, by incorporating the aromatic polyamideimide resin with the flexibility enhancing agent and the hydrophilic cationic polymer, it is not necessary to react the aromatic polyamideimide resin with the hydrophilic cationic polymer, and the coating material can be easily produced.

[0019] Furthermore, by including a hydrophilic cationic polymer, the aromatic polyamide-imide resin can be dispersed or dissolved in water, and the reduced amount of organic solvent used provides excellent safety and environmental properties. DETAILED DESCRIPTION OF THE INVENTION

[0020] The electrodeposition coating composition of the present invention contains an aromatic polyamideimide resin, a flexibility enhancing agent, and a hydrophilic cationic polymer, and the respective contents of these components are, for example, 75 to 90% by weight of the aromatic polyamideimide resin, 5 to 15% by weight of the flexibility enhancing agent, and 5 to 15% by weight of the hydrophilic cationic polymer, relative to the total amount of the aromatic polyamideimide resin, the flexibility enhancing agent, and the hydrophilic cationic polymer.

[0021] In the present invention, the aromatic polyamide-imide resin is not particularly limited, but may be, for example, Examples of the average molecular weight include those of 5,000 or more, and even those of 10,000 or more.

[0022] The aromatic polyamide-imide resin may have a molecular weight of 50,000 or less, or 30,000 or less.

[0023] Preferred aromatic polyamideimide resins include those having an average molecular weight of 5,000 or more and 50,000 or less, and more preferred aromatic polyamideimide resins include those having an average molecular weight of 10,000 or more and 30,000 or less.

[0024] If the average molecular weight is less than 5,000, the coating may not form a continuous film when formed, resulting in the risk of coating cracks. If the average molecular weight is more than 50,000, the solubility of the resin in solvents decreases. If the resin solids content is less than 30%, the amount of solvent required when preparing the paint increases, which may reduce the paint stability.

[0025] Such aromatic polyamideimide resin may be a known aromatic polyamideimide resin, and may be one produced by a known method, if necessary.

[0026] The aromatic polyamide-imide resin may be, for example, a polyamide-imide resin represented by the general formula (1): [ka] [ka] Examples of the amide-imide resin include the amide-imide resin represented by the following formula:

[0027] Such aromatic polyamideimide resins may be newly synthesized or may be known.

[0028] As an example of producing an aromatic polyamide-imide resin by a known method, a case of producing it from trimellitic anhydride and an aromatic isocyanate by the isocyanate method will be described.

[0029] Specifically, examples of aromatic diisocyanates include tolylene diisocyanate, diphenylmethane diisocyanate, and 1,5-naphthalene diisocyanate. Diphenylmethane diisocyanate is preferred.

[0030] The reaction between trimellitic anhydride and aromatic isocyanate can be carried out by a known method of the isocyanate method. For example, an aromatic polyamide-imide resin can be produced by reacting trimellitic anhydride and aromatic isocyanate in a solvent at 120 to 180°C for 1 to 5 hours with stirring.

[0031] Examples of the reaction solvent include aprotic polar solvents such as N-methylpyrrolidone, dimethylformamide, and 1,3-dimethyl-2-imidazolidinone.

[0032] The aromatic polyamide-imide resin produced by the above reaction may have a terminal carboxyl group or an isocyanate group which may be converted to a hydroxyl group by reacting with a diol compound.

[0033] The flexibility enhancing agent is not particularly limited as long as it can prevent the electrodeposition coating from breaking when the aromatic polyamideimide resin is bent at a tensile pressure that is the safe tension of a soft copper wire at room temperature. For example, a flexibility enhancing agent having a melting point of 100°C or less can be suitably used.

[0034] Examples of such flexibility enhancing agents include trimellitic tricarboxylic acid esters, sulfonamide compounds, phosphate ester compounds, and imide compounds. Examples of trimellitic tricarboxylic acid esters include tributyl trimellitate and tris(2-ethylhexyl) trimellitate.

[0035] Examples of sulfonamide compounds include o-toluenesulfonamide, p-toluenesulfonamide, N-ethyl-o / p-toluenesulfonamide, Nn-butylbenzenesulfonamide, and N-cyclohexyl-p-toluenesulfonamide.

[0036] Further, examples of the phosphate ester compounds include trimethyl phosphate, triethyl phosphate, tributyl phosphate, tris(2-ethylhexyl) phosphate, triphenyl phosphate, 2-ethylhexyldiphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, and cresyldiphenyl phosphate.

[0037] The imide compound may be a polycondensate obtained by reacting either a diisocyanate compound or a diamino compound with a carboxylic acid anhydride, and the diisocyanate compound may be an aromatic diisocyanate.

[0038] Examples of aromatic diisocyanates include phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, 1,4-dinaphthalene diisocyanate, 4,4'-diphenylenemethane diisocyanate, 2,4- or 2,6-tolylene diisocyanate or a mixture thereof, 4,4'-toluidine diisocyanate, and 1,4-xylylene diisocyanate compounds.

[0039] Among these, compounds in which an isocyanate group is bonded to a phenyl skeleton, such as 4,4'-diphenylenemethane diisocyanate and phenylene diisocyanate, or 1,4-xylylene diisocyanate are preferred.

[0040] The diamine compound may be an aromatic diamine, specifically, for example, phenylenediamine, 2,4-diaminotoluene, 4,4'-diamino-3,3'-dimethyl-1,1'-biphenyl, 4,4'-diamino-3,3'-dihydroxy-1,1'-biphenyl, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfide, 2,2-bis(4-aminophenyl)propane, 2,2-bis(4-aminophenyl)hexafluoropropane, 1,3-bis(4-aminophenoxy)benzene, 1,4 ... benzene, 4,4'-bis(4-aminophenoxy)biphenyl, 1,3-bis[2-(4-aminophenyl)-2-propyl]benzene, 1,4-bis[2-(4-aminophenyl)-2-propyl]benzene, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(4-aminophenoxy)phenyl]sulfone, 2,6-diaminopyridine, 2,6-diamino-4-methylpyridine, 4,4'-(9-fluorenylidene)dianiline, α,α-bis(4-aminophenyl)-1,3-diisopropylbenzene, and the like.

[0041] Of these, phenylenediamine, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfide, and bis[4-(3-aminophenoxy)phenyl]sulfone are preferred.

[0042] The carboxylic acid anhydride is not particularly limited, but is preferably an anhydride of an alicyclic carboxylic acid, which is a low-viscosity liquid and easy to handle, and from the viewpoint of the heat resistance and mechanical properties of the cured product.

[0043] Examples of such alicyclic carboxylic acid anhydrides include 6-membered alicyclic carboxylic acid anhydrides such as hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, 1,2,3,6-tetrahydrophthalic anhydride, and methyl-1,2,3,6-tetrahydrophthalic anhydride; nadic anhydride, methylnadic anhydride, hydrogenated nadic anhydride, hydrogenated methylnadic anhydride, decylsuccinic anhydride, hexadecylsuccinic anhydride, dodecylsuccinic anhydride, tetradecylsuccinic anhydride, glutaric anhydride, 3-methylglutaric anhydride, 3,3-dimethylglutaric anhydride, 2,2-dimethylglutaric anhydride, 3,3-tetramethyleneglutaric anhydride, and 3,3-pentamethyleneglutaric anhydride.

[0044] Of these, hydrogenated methylnadic anhydride, hexahydrophthalic anhydride, methylhexahydrophthalic anhydride, etc. are preferred.

[0045] The imide compound can be produced by a known method such as an isocyanate method or a high-temperature solution polymerization method. For example, the imide compound can be produced by reacting either a diisocyanate compound or a diamino compound with a carboxylic acid anhydride in a solvent at 150 to 220°C for 1 to 12 hours under stirring.

[0046] Examples of the reaction solvent include aprotic polar solvents such as N-methylpyrrolidone, dimethylformamide, and 1,3-dimethyl-2-imidazolidinone. In the reaction, the molar ratio of the diisocyanate compound or the diamino compound to the carboxylic acid anhydride is 0.49 to 0.55 mol when the diisocyanate compound is used, and 0.48 to 0.52 mol when the diamino compound is used, relative to 1 mol of the carboxylic acid anhydride, so that an imide compound can be produced.

[0047] The flexibility enhancing agent is compatible with the aromatic polyamideimide resin and the hydrophilic cationic polymer resin, and is codeposited in the electrodeposition coating film.

[0048] If the composition ratio of the flexibility enhancing agent is less than 5% by weight, the compatibility between the resins decreases, making it difficult for the resin to disperse or dissolve in water. As a result, the appearance smoothness and insulating properties also decrease. If it is more than 15% by weight, crosslinking becomes insufficient, and sufficient coating strength cannot be obtained. As mentioned above, the composition ratio of the flexibility enhancing agent is preferably 5 to 15% by weight, and more preferably 5 to 10% by weight.

[0049] Examples of hydrophilic cationic polymers include acrylic copolymers and epoxyamine adduct resins.

[0050] Examples of acrylic copolymers include copolymers of alkylamino derivatives, hydroxyalkyl derivatives, and vinyl derivatives of acrylic acid or methacrylic acid.

[0051] Examples of the alkylamino derivatives of acrylic acid or methacrylic acid include dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, and ethyltrimethylammonium chloride acrylate.

[0052] Examples of alkylhydroxy derivatives of acrylic acid or methacrylic acid include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate, and 2-hydroxy-3-phenoxypropyl acrylate.

[0053] Vinyl derivatives include methyl acrylate, methyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, n-butyl acrylate, and n-methacrylate. -butyl, isobutyl acrylate, isobutyl methacrylate, benzyl acrylate, benzyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, isobornyl acrylate, 2-(perfluorooctyl)ethyl methacrylate, trifluoromethyl methacrylate, styrene, and the like.

[0054] The copolymer may be a known copolymer or may be one obtained by copolymerizing the acrylic acid or methacrylic acid derivative as appropriate. The copolymerization can be carried out by a known method, for example, by dissolving the acrylic acid or methacrylic acid derivative in a solvent and reacting the resulting mixture under heating and reflux in the presence of a polymerization initiator.

[0055] Furthermore, examples of epoxy amine adduct resins include those in which the epoxy groups of an epoxy resin have been modified with primary and secondary amines.

[0056] Examples of epoxy resins include bisphenol A type epoxy resins (trade names: Epicoat 828, Epicoat 834, Epicoat 1001, Epicoat 1004, Epicoat 1007, Epicoat 1009 (manufactured by Mitsubishi Chemical Corporation)) and novolac phenol type epoxy resins (trade names: Epicoat 152, Epicoat 154 (manufactured by Mitsubishi Chemical Corporation)).

[0057] Examples of primary amines that can be used include monomethanolamine, monoethanolamine, mono-n-propanolamine, monoisopropanolamine, dimethylaminoethylamine, diethylaminoethylamine, and diethylaminopropylamine. Examples of secondary amines that can be used include dimethanolamine, diethanolamine, di-n-propanolamine, diisopropanolamine, methylethanolamine, methylpropanolamine, and di-n-butylamine.

[0058] The epoxy amine adduct resin may be produced by a known method, and can be produced by appropriately modifying the epoxy groups of the epoxy resin with primary and secondary amines. For example, the epoxy amine adduct resin can be easily produced by dissolving the epoxy resin in a solvent, gradually adding the amine while heating and stirring, and then heating.

[0059] The hydrophilic cationic polymer is prepared by dispersing an aromatic polyamideimide resin and a flexibility enhancing agent in acidic water, and then depositing the aromatic polyamideimide resin and the flexibility enhancing agent on the substrate by electrodeposition coating.

[0060] If the hydrophilic cationic polymer content is less than 5% by weight, the resin is less soluble in water, and if it is more than 15% by weight, the co-deposition rate of the polyimide resin and the flexibility enhancing agent decreases, making it difficult to obtain heat resistance and insulating properties. As described above, the composition ratio of the hydrophilic cationic polymer is preferably 5 to 15% by weight, and more preferably 5 to 10% by weight.

[0061] As a neutralizing agent for dispersing the resin mixture in water, organic acids such as lactic acid, acetic acid, formic acid, succinic acid, and butyric acid can be used. The amount used is 0.2 to 8 g, more preferably 0.5 to 7 g, and even more preferably 1 to 6 g per liter of paint.

[0062] The substrate in the present invention can be any electrically conductive conductor, including metals, semiconductors such as silicon and indium titanate, and electrically conductive ceramic particles. That is, the target substrate is not limited as long as it can be electrodeposited, but can also be stainless steel (SUS304), aluminum or anodized aluminum materials, plated materials or plated articles, die-casting, etc.

[0063] Any of the plating materials commonly used in this field can be used, such as pure iron, carbon steel, high-tensile steel (low-alloy steel, maraging steel), magnetic steel, non-magnetic steel, high-manganese steel, stainless steel (martensitic stainless steel, ferritic stainless steel, austenitic stainless steel, austenitic-ferritic stainless steel, precipitation-hardened stainless steel, etc.), iron-based metals such as superalloy steel, copper and copper alloys (oxygen-free copper, phosphor bronze, tough pitch copper, aluminum bronze, beryllium copper, high-strength brass, red brass, nickel silver, brass, free-cutting brass, Nevar brass, etc.), iron-nickel alloys, nickel-chromium alloys, nickel, chromium, aluminum and aluminum alloys, magnesium and magnesium alloys, titanium, zirconium, hafnium and their alloys, molybdenum, tungsten and their alloys, niobium, tantalum and their alloys, and ceramic fine particles (alumina, zirconium core, etc.).

[0064] There are no particular limitations on the type of plating applied to the surface of the plated material, and any plating commonly used in this field can be used.

[0065] Examples include various alloy platings such as copper-nickel-chrome plating, nickel-boron-tungsten plating, nickel-boron plating, brass plating, bronze plating, gold plating, silver plating, copper plating, tin plating, rhodium plating, palladium plating, platinum plating, cadmium plating, nickel plating, chrome plating, black chrome plating, zinc plating, black nickel plating, black rhodium plating, zinc plating, industrial (hard) chrome plating, etc. Also, examples of die casting include zinc die casting, aluminum die casting, magnesium die casting, and sintered alloy die casting.

[0066] Furthermore, in the present invention, the substrate to be coated is not particularly limited as long as it can be subjected to electrodeposition coating. For example, electronic components, specifically semiconductor elements such as transistors and diodes, passive elements (chip components) such as resistors, capacitors, inductors and transformers, electromagnet-related components such as electromagnets, solenoids, electric motors, relays, speakers and meters, piezoelectric elements such as crystal oscillators and ceramic oscillators, wiring-related components such as electric wires, printed wiring boards, connectors, sockets, plugs and switches, electronic component inspection device components such as test probes, probe guides, inspection test pins, inspection base materials and electrical contacts, LEDs, light bulbs, fluorescent lamps, heaters, heating wires, fuses, antennas, heat sinks, nickel-metal hydride batteries, etc. Examples of products include batteries, secondary batteries such as lithium-ion batteries, AC motors such as DC motors, universal motors, synchronous motors, and induction motors, motors such as stepping motors, coil-related parts such as toroidal coils, choke coils, edgewise coils, and reactor coils, exhaust passages and intake passages of automobile internal combustion engines, exhaust gas recirculation passages connecting them, exhaust gas recirculation flow control valves installed in the passages, metal exhaust gas recirculation housings that house them, piping parts used in these, electronic parts such as pressure sensors, exhaust gas recirculation (EGR) units such as electronic devices, cases and cover parts for protecting electronic devices, radiators, intercoolers, oil coolers (for engine oil, steering, transmission, differential, and power take-off), heat exchangers such as evaporators, condensers, heater cores, and heat exchangers (exhaust gas heat exchangers for heating) for air-cooled engines, bearings used in electrical equipment such as motors and generators, cases, cover parts, and inspection parts for housing these electronic parts and electronic devices, etc.

[0067] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. A-1 was used as the aromatic polyamide-imide resin, eight types of flexibility enhancers B-1 to B-8, and C-1 was used as the hydrophilic cationic polymer.

[0068] Reference example 1 Synthesis of aromatic polyamide-imide resin A-1 A mixture of 127 g of N-methylpyrrolidone (NMP), 69 g (0.28 mol) of 4,4-diphenylmethane diisocyanate, and 58 g (0.3 mol) of trimellitic anhydride was reacted at 150°C for 3 hours with stirring to obtain an aromatic polyamideimide (PAI) solution (PAI / NMP = 50 / 50%) having -COOH groups at the terminals.

[0069] Reference example 2 Preparation of hydrophilic cationic polymer C-1 60 g of isopropyl alcohol was heated to reflux, and 2,2,2-trifluoromethylmethylsilane was added to it. A mixture of 25 g of methacrylate, 20 g of methyl methacrylate, 30 g of 2-hydroxyethyl acrylate, 25 g of n-butyl acrylate, 15 g of dimethylaminoethyl methacrylate, 25 g of styrene, and 1 g of benzoin peroxide as a polymerization initiator is divided into eight portions and added dropwise in succession at 10-minute intervals.

[0070] The mixture was then reacted at 70-80°C for 5-6 hours, and 0.1 g of benzoin peroxide was added to the reaction mixture. The mixture was then refluxed for approximately 1 hour until the odor of the monomer disappeared, yielding a yellow, transparent resin solution with a solids concentration of 70%, a viscosity of 20,000 cps (25°C), and MEQ63.

[0071] Reference example 3 Preparation of imide compound 1 A mixture of 193.8 g of N-methylpyrrolidone, 125.1 g (0.50 mol) of 4,4'-diphenylmethane diisocyanate, 155.7 g (1.01 mol) of hexahydrophthalic anhydride, and 23.7 g of xylene was gradually heated from room temperature to 180°C with stirring, and the mixture was allowed to react for 2 hours to obtain imide compound 1. After cooling, N-methylpyrrolidone was added to obtain a 50% solids solution (imide / NMP = 50 / 50%). The melting point of the polycondensate was 87°C. The melting point was measured using a DSC-60 (Shimadzu Corporation) after drying at 180°C for 1 hour to remove the solvent.

[0072] Reference example 4 Preparation of imide compound 2 A mixture of 215.2 g of N-methylpyrrolidone, 231.2 g (0.50 mol) of bis[4-(3-aminophenoxy)phenyl]sulfone, 155.7 g (1.01 mol) of hexahydrophthalic anhydride, and 30.7 g of xylene was stirred and gradually heated from room temperature to 180 °C while distilling off water using a Dean-Stark reactor. The reaction time was 2 hours, yielding imide compound 2. After cooling, N-methylpyrrolidone was added to a solids content of 50%, yielding an imide solution (imide / NMP = 50 / 50%). The melting point of the imide molecule was 98 °C. The melting point was measured using a DSC-60 (Shimadzu Corporation) after drying at 180°C for 1 hour to remove the solvent.

[0073] Reference example 5 Preparation of imide compound 3 A mixture of 164.0 g of N-methylpyrrolidone, 99.1 g (0.50 mol) of 4,4′-diaminodiphenylmethane, 101.1 g (1.01 mol) of succinic anhydride, and 18.2 g of xylene was reacted in the same manner as in Reference Example 2 to obtain imide compound 3. The melting point of the imide molecule was 210°C. The melting point was measured using a DSC-60 (Shimadzu Corporation) after drying at 180°C for 1 hour to remove the solvent.

[0074] <Evaluation method> The evaluation items and evaluation methods are as follows: Film thickness: According to the JIS test method (K5600-1-7), the thickness of the test piece was measured using a micrometer before and after painting, and the difference was calculated to be the film thickness.

[0075] Paint stability: Paint stability was evaluated by leaving 100 g of paint at room temperature for one week, shaking it gently, and then visually checking for the presence of sediment. <Judgment criteria> ○: Indicates that there is no separation or sedimentation of the paint. △: Indicates that sediment has occurred in the paint.

[0076] Withstand voltage (breakdown voltage): A copper wire with a diameter (φ) of 1.0 mm was electro-deposited to a film thickness of 30 μm, and then bent (tension bending) while pulling with a force of 50 N so that R = 1.0. An AC / DC withstand voltage tester (MODEL 8526, Tsuruga Electric Co., Ltd.) was used to measure the voltage (AC) at which dielectric breakdown occurred in the film, and this was taken as the withstand voltage.

[0077] Aromatic polyamide-imide resin A-1: Aromatic polyamide-imide resin produced in Reference Example 1 Flexibility Reinforcement Agent B-1: Tris(2-ethylhexyl) trimellitate B-2: p-toluenesulfonamide B-3: Tricresyl phosphate B-4: Imide compound 1 prepared in Reference Example 3 B-5: Imide compound 2 prepared in Reference Example 4 B-6: N,N'-4,4'-diphenylmethane bismaleimide (melting point 159°C) B-7: N,N'-m-xylenebisnadimide (melting point 170°C) B-8: Imide compound 3 prepared in Reference Example 5 Hydrophilic Cationic Polymer C-1: Hydrophilic cationic polymer produced in Reference Example 2

[0078] (1) Preparation of paints for Examples 1 to 8 and Comparative Examples 1 to 3 Appropriate amounts of aromatic polyamide-imide resin, flexibility enhancer, and hydrophilic cationic polymer were mixed together as shown in Table 1. Lactic acid was added as an acid neutralizer, and the mixture was mixed and neutralized at 60°C for 2 hours. Pure water was then added and the mixture was dispersed in water to produce the aqueous electrodeposition coatings of Examples 1 to 6 and Comparative Examples 1 to 4.

[0079] (2) Electrodeposition coating Next, electrodeposition coating was performed on the test pieces to evaluate the properties of the coating film. The paints of Examples 1 to 8 and Comparative Examples 1 to 3 listed in Table 1 were placed in a 2-liter tank, and the liquid temperature was maintained at 25° C. Electrodeposition coating was carried out using a carbon plate as the anode and a copper wire test piece (diameter 1.0 mm, length 150 mm) as the cathode.

[0080] First, the copper wire is degreased with a weak alkali at 50°C for 5 minutes, then washed with water. Neutralize with 1% nitric acid at room temperature for 1 minute, and then wash with water.

[0081] Next, the plate is washed with ion-exchanged water, and then electrodeposition coating is performed for 1 minute at a voltage of 100 V using the paints of Examples 1 to 8 and Comparative Examples 1 to 3. After washing with water and drying (at 100°C for 15 minutes), the plate is baked at 180°C for 30 minutes.

[0082] The test pieces were subjected to various measurements and tests to evaluate the properties of the coating film. The evaluation results are shown in Table 1.

[0083] [Table 1]

[0084] [Table 2]

[0085] First, as is clear from Table 1, Examples 1 to 8 have high breakdown voltages of 2.1 to 3.1 KV, whereas Comparative Examples 1 and 2 have very low breakdown voltages of 0.2 to 0.3 KV. This indicates that the electrodeposition paint of the present invention has high flexibility and does not break when subjected to tension bending. In addition, in Comparative Examples 1 and 2, the terminal allyl groups reacted with each other, increasing the crosslink density of the coating film, which is thought to have reduced flexibility and caused the breakage. In Comparative Example 3, it is believed that the melting point of B-8 was so high that it aggregated with itself, making it unable to embrace the aromatic amide-imide resin and failing to emulsify.

[0086] As described above, the electrodeposition coating composition of the present invention and the aqueous electrodeposition coating containing the same impart excellent heat resistance and insulating properties to the coating film when the coating film is formed, and also improves flexibility, and has excellent properties in terms of safety and the environment.

[0087] According to the present invention, by blending three components, namely, a flexibility enhancing agent, a hydrophilic cationic polymer, and an aromatic polyamideimide resin, the entanglement and compatibility between the resins enables dispersion in water without causing reaction between the hydrophilic cationic polymer and the aromatic polyamideimide resin. That is, when an electrodeposition coating is made using only a hydrophilic cationic polymer and an aromatic polyamideimide, separation and sedimentation occur, but by adding a flexibility enhancing agent that is compatible with the hydrophilic cationic polymer and the aromatic polyamideimide resin, reaction does not occur and the electrodeposition coating composition becomes stable.

[0088] Furthermore, due to the characteristics of its composition, it has good voltage resistance and is also excellent in terms of safety and the environment.

Claims

1. An electrodeposition coating composition comprising an aromatic polyamideimide resin, a flexibility enhancing agent, and a hydrophilic cationic polymer.

2. 2. The electrodeposition coating composition according to claim 1, characterized in that it contains 75 to 90% by weight of aromatic polyamideimide resin, 5 to 15% by weight of flexibility enhancing agent, and 5 to 15% by weight of hydrophilic cationic polymer, based on the total amount of aromatic polyamideimide resin, flexibility enhancing agent, and hydrophilic cationic polymer.

3. 3. A water-based electrodeposition paint comprising the electrodeposition paint composition according to claim 1 or 2 dispersed in a medium containing an acid neutralizer.

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