Cationic electrodeposition coating composition and electronic component having coating film

Abstract

The present invention addresses the problem of providing: a cationic electrodeposition coating composition which is excellent in terms of insulation properties and edge covering properties applicable to electronic components; and an electronic component which has a coating film by being coated with the cationic electrodeposition coating composition. The problem is solved by a cationic electrodeposition coating composition which contains a cationic epoxy resin (A), an organic acid zinc compound (B), and a phenolic compound (C).

Description

Cationic electrodeposition coating composition and electronic parts having coating film

[0001] The present invention relates to a cationic electrodeposition coating composition and an electronic part having a coating film.

[0002] In electronic components, insulation has been imparted by painting to prevent electrical conduction. In recent years, other functions have also been required for coatings such as paints. For example, electronic components used in automobiles are required to maintain performance such as insulation for a long period of time even in high-temperature environments (high-temperature durability). Patent Document 1 discloses an electronic component that satisfies the requirement for high-temperature durability by including a specific amino-modified epoxy resin in the coating.

[0003] Japanese Patent Application Laid-Open No. 2023-154458

[0004] In recent years, there has been a demand for even higher performance electronic components, and highly reliable insulation properties are required. To achieve highly reliable insulation properties, it is important to coat not only the flat surfaces of electronic components but also their edge portions (end faces and pin corners) without defects, thereby providing insulation. This requires a coating material with excellent edge covering properties. Therefore, an object of the present invention is to provide a cationic electrodeposition coating composition that is applicable to electronic components and has excellent insulation properties and edge covering properties, and an electronic component having a coating film coated with the cationic electrodeposition coating composition.

[0005] The present invention, which achieves the above-mentioned object, may include the following: [1] A cationic electrodeposition coating composition comprising a cationic epoxy resin (A), an organic acid zinc compound (B), and a phenolic compound (C). [2] The cationic electrodeposition coating composition according to [1], wherein the organic acid zinc compound (B) is contained in an amount of 10 ppm to 1,000 ppm in terms of divalent zinc ions. [3] The cationic electrodeposition coating composition according to [1] or [2], wherein the phenolic compound (C) is contained in an amount of 1 part by mass to 20 parts by mass per 100 parts by mass of the cationic epoxy resin (A). [4] The cationic electrodeposition coating composition according to any one of [1] to [3], wherein the phenolic compound (C) comprises a Mannich reaction product of a phenol and / or a phenolic resin, formaldehyde, and an amine. [5] The cationic electrodeposition coating composition according to [4], wherein the Mannich reaction products of the phenols and / or phenolic resin, formaldehyde, and amines include those cationized with an organic acid, the amines include at least one selected from N-methylethanolamine and diethanolamine, and the organic acid includes a monovalent organic acid. [6] The cationic electrodeposition coating composition according to any of [1] to [5], wherein the cationic epoxy resin is an amino group-modified epoxy resin obtained by reacting an epoxy resin (A1) with an amine compound (A2), and the epoxy resin (A1) is a resin having: structural units derived from a propylene oxide-added diepoxy resin (a1) represented by formula (1), structural units derived from a bisphenol compound (a2), structural units derived from a diepoxy resin (a3) ​​different from formula (1), and structural units derived from a dicarboxylic acid (a4) in which two carboxyl groups are bonded via at least one carbon atom. [In formula (1), R １represents an alkylene group having 3 to 10 carbon atoms which may have a substituent, a cyclohexylene group which may have a substituent, a phenylene group which may have a substituent, or -Ra-Rb-Rc-, where Ra and Rc are cyclohexylene groups or phenylene groups, Rb is a methylene group which may have one or two substituents, and m and n are each independently an integer of 1 to 20.] [7] The cationic electrodeposition coating composition according to any one of [1] to [6], further comprising a blocked polyisocyanate curing agent (D). [8] An electronic part having a coating film coated with the cationic electrodeposition coating composition according to any one of [1] to [7].

[0006] According to the present invention, it is possible to provide a cationic electrodeposition coating composition that is applicable to electronic components and has excellent edge covering and insulating properties, and electronic components having a coating film coated with the cationic electrodeposition coating composition.

[0007] The present invention will be described in detail below with reference to specific embodiments. <Cationic Electrodeposition Coating Composition> A cationic electrodeposition coating composition according to one embodiment of the present invention comprises a cationic epoxy resin (A), an organic acid zinc compound (B), and a phenol compound (C).

[0008] <Cationic Epoxy Resin (A)> The cationic epoxy resin (A) is not particularly limited as long as it is a cationized epoxy resin, but for example, an amino group-modified epoxy resin obtained by reacting an epoxy resin (A1) with an amine compound (A2) and then cationizing it with an organic acid can be used. Bisphenol-type and novolac-type epoxy resins are particularly suitable as the epoxy resin (A1), and among bisphenol-type epoxy resins, the modified epoxy resins shown below are more suitable.

[0009] <Modified Epoxy Resin> The modified epoxy resin preferably has, for example, a structural unit derived from a propionoxide-added diepoxy resin (a1) represented by formula (1), a structural unit derived from a bisphenol compound (a2), a structural unit derived from a diepoxy resin (a3) ​​different from formula (1), and a structural unit derived from a dicarboxylic acid (a4) in which two carboxyl groups are bonded via at least one carbon atom. [In formula (1), R １ represents an alkylene group having 3 to 10 carbon atoms which may have a substituent, a cyclohexylene group which may have a substituent, a phenylene group which may have a substituent, or -Ra-Rb-Rc-, where Ra and Rc are cyclohexylene groups or phenylene groups, Rb is a methylene group which may have one or two substituents, and m and n are each independently an integer of 1 to 20.

[0010] Here, R in the above formula (1) １ The "substituents" that can be contained in are independent of each other, and examples thereof include an alkyl group, a phenyl group, a hydroxyl group, and an alkoxyl group. Furthermore, these substituents may be substituted with another functional group (e.g., an alkyl group, a phenyl group, etc.). Furthermore, the alkyl group may be linear, branched, or cyclic.

[0011] The propylene oxide-added diepoxy resin (a1) of the above formula (1) can be obtained by a known method. １ The polyether compound can be obtained by subjecting propylene oxide to addition or addition polymerization to a polyol compound having hydroxyl groups at both ends, and then reacting the resulting polyether compound (having hydroxyl groups at both ends) with epichlorohydrin to diepoxidize it.

[0012] The above R １Examples of polyol compounds having hydroxyl groups at both ends include: linear or cyclic alkylene glycols having hydroxyl groups bonded to carbon atoms at both ends, such as 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, and 1,4-cyclohexanediol; polyhydric phenols having two or more hydroxyl groups, such as catechol, resorcinol, hydroquinone, and pyrogallol; polyphenol compounds such as 2,2-bis(4-hydroxycyclohexyl)propane (hydrogenated bisphenol A), hydrogenated bisphenol F, hydrogenated bisphenol E, hydrogenated bisphenol B, hydrogenated bisphenol AP, hydrogenated bisphenol BP, bisphenol A, bisphenol F, bisphenol E, bisphenol B, bisphenol AP, and bisphenol BP, or hydrogenated products thereof.

[0013] The propylene oxide-added diepoxy resin (a1) of formula (1) may be used alone or in combination of two or more in the production of a modified epoxy resin. When two or more propylene oxide-added diepoxy resins (a1) of formula (1) are used to produce a modified epoxy resin, they may be added separately or simultaneously.

[0014] Examples of the bisphenol compound (a2) include bisphenol A, bisphenol F, bisphenol E, bisphenol B, bisphenol S, bisphenol AP, and bisphenol BP. Among these, bisphenol A and bisphenol F are preferred. In producing the modified epoxy resin, the bisphenol compound (a2) may be used alone or in combination of two or more. When producing the modified epoxy resin using two or more bisphenol compounds (a2), they may be added separately or simultaneously.

[0015] The diepoxy resin (a3) ​​is a compound having two epoxy groups in one molecule, different from the propylene oxide-added diepoxy resin (a1). The diepoxy resin (a3) ​​is not particularly limited, but preferably has an epoxy equivalent in the range of 170 to 500, more preferably 170 to 400. The diepoxy resin (a3) ​​is not particularly limited, but is preferably a compound represented by the above formula (2). In formula (2), R ３ and R ４ may be the same or different, and may be, for example, a single bond, an alkylene group, a phenylene group, or a cyclohexylene group. １ and Y １ are each independently a hydrogen atom or an alkyl group. １ and Y １ The alkyl group as is not particularly limited as long as it is linear or branched, but is preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms.

[0016]

[0017] The diepoxy resin (a3) ​​can be obtained by diepoxidizing two hydroxyl groups in a polyol compound by reacting them with epihalohydrin (for example, epichlorohydrin). Examples of the polyol compound include: linear or cyclic alkylene glycols having hydroxyl groups bonded to carbon atoms at both ends, such as 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, and 1,4-cyclohexanediol; polyhydric phenols having two or more hydroxyl groups, such as catechol, resorcinol, hydroquinone, and pyrogallol; 2,2-bis(4-hydroxycyclohexyl)propane (hydrogenated bisphenol A), hydrogenated bisphenol F, hydrogenated bisphenol E, hydrogenated bisphenol B, hydrogenated bisphenol AP, hydrogenated bisphenol BP, bisphenol A, bisphenol F, bisphenol E, bisphenol B, bisphenol AP, bisphenol BP, 4,4'-dihydroxybenzophenone, and bis(4-hydroxyphenyl)-2,2- ... Polyphenol compounds or hydrogenated products thereof, such as tetrakis(4-hydroxyphenyl)-1,1-isobutane, bis(4-hydroxy-2-tert-butylphenyl)-2,2-propane, bis(4-hydroxy-3-tert-butylphenyl)-2,2-propane, bis(2-hydroxynaphthyl)methane, tetrakis(4-hydroxyphenyl)-1,1,2,2-ethane, 4,4'-dihydroxydiphenyl sulfone, 2,2-bis(4-hydroxyphenyl)hexafluoropropane, bis(4-hydroxyphenyl)-2,2-dichloroethylene, and 2,2-bis(3-methyl-4hydroxyphenyl)propane; alkylene glycols in which two hydroxyl groups are bonded to the same carbon atom, such as 1,1-dihydroxyethane, 1,1-dihydroxypropane, and 2,2-dihydroxypropane; alkylene glycols in which one hydroxyl group and one hydroxyalkyl group are bonded to the same carbon atom, such as 2-hydroxypropanol and 2-hydroxybutanol;Alkylene glycols in which one or two hydroxyalkyl groups are bonded to the same carbon atom, such as 2,2-(dihydroxymethyl)ethane, 2,2-(dihydroxyethyl)propane, 2,2-dimethyl-1,3-propanediol, 2,2-dimethyl-1,4-butanediol, and 3,3-diethyl-1,6-hexanediol; alkylene glycols in which one hydroxyl group and one phenol group are bonded to the same carbon atom, such as 4-(1-hydroxyethyl)phenol, 3-(1-hydroxyethyl)phenol, and 4-(1-hydroxypropyl)phenol; alkylene glycols in which one hydroxyl group and one cyclohexanol group are bonded to the same carbon atom, such as 4-(1-hydroxyethyl)cyclohexanol and 2-(1-hydroxyethyl)cyclohexanol; 4 alkylene glycols in which one hydroxyalkyl group and one phenol group are bonded to the same carbon atom, such as 4-hydroxyphenyl-2-propanol and 4-hydroxyphenyl-2-butanol; alkylene glycols in which one hydroxyalkyl group and one cyclohexanol group are bonded to the same carbon atom, such as 2-(4-hydroxycyclohexyl)-1-propanol and 2,2-dimethyl-2-(4-hydroxycyclohexyl)-1-ethanol; alkylene glycols in which one phenol group and one cyclohexanol group are bonded to the same carbon atom, such as 2-(4-hydroxyphenyl)-2-(4-hydroxycyclohexyl)propane and 1-(4-hydroxyphenyl)-1-(4-hydroxycyclohexyl)propane; and the like.

[0018] In the production of the modified epoxy resin, the diepoxy resin (a3) ​​may be used alone or in combination of two or more. When two or more diepoxy resins (a3) ​​are used to produce the modified epoxy resin, they may be added separately or simultaneously.

[0019] The dicarboxylic acid (a4) is a compound in which two carboxyl groups are bonded via at least one carbon atom. A suitable dicarboxylic acid is a compound in which the two carboxyl groups are bonded to a linear alkylene group (R ２In the compound of formula (6), the alkylene group (R ２ The alkylene group (R ) in the compound of formula (6) may have one or more substituents selected from an alkyl group, an alkenyl group, an alkadienyl group, and a methylene group, or may have one or more substituents selected from two or more substituents selected from an alkyl group, an alkenyl group, an alkadienyl group, and a methylene group. ２ When the alkylene group (R) has 2 to 20 carbon atoms, it may form a ring via adjacent carbon atoms of the alkylene group. The ring may have one or more substituents selected from alkyl groups and alkenyl groups, and preferably has two substituents of alkyl groups and / or alkenyl groups. When the ring has two substituents, the two substituents may be the same or different. Examples of the ring include a cyclohexane ring, a cyclohexene ring, a benzene ring, and a bicyclo ring in which two carbon-carbon bonds in a decalin ring are double bonds (e.g., bicyclo[4.4.0]decane-1,7-diene, etc.). ２ The alkyl group, alkenyl group, or alkadienyl group that may be present on the ring may be linear or branched.

[0020]

[0021] More preferred dicarboxylic acids (a4) are compounds having a cyclic and / or unsaturated bond. Particularly preferred dicarboxylic acids (a4) are compounds of formula (6) that do not contain an alkylene group (R ２ ) has 2 to 18 carbon atoms, and ２ ) may have one methylene group, one or two alkyl groups having 5 to 9 carbon atoms, or two substituents of one or two kinds selected from alkyl groups, alkenyl groups, and alkadienyl groups having 5 to 9 carbon atoms, or an alkylene group (R ２) constitutes any one of the above rings via adjacent carbon atoms, and the rings may each have two substituents independently, each of which is an alkyl group, an alkenyl group, or an alkadienyl group having 5 to 9 carbon atoms.

[0022] Examples of the dicarboxylic acid (a4) include malonic acid, succinic acid, glutaric acid, 2,2-dimethylglutaric acid, 3,3-dimethylglutaric acid, adipic acid, 2,2-dimethyladipic acid, pimelic acid, suberic acid, azelaic acid, 2-ethylazelaic acid, sebacic acid, 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid, 1,11-undecanedicarboxylic acid, 1,12-dodecanedicarboxylic acid, and 1,13-tridecanedicarboxylic acid. Examples of the dicarboxylic acid (a4) include carboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,15-pentadecanedicarboxylic acid, 1,16-hexadecanedicarboxylic acid, 1,17-heptadecanedicarboxylic acid, 1,18-octadecanedicarboxylic acid, 1,19-nonadecanedicarboxylic acid, 1,20-icosanedicarboxylic acid, itaconic acid, phthalic acid, dimer acid, 1,2-cyclohexanedicarboxylic acid, and 1,2-cyclohexenedicarboxylic acid. In the production of the modified epoxy resin, the dicarboxylic acid (a4) may be used alone or in combination of two or more. When two or more dicarboxylic acids (a4) are used to produce the modified epoxy resin, they may be added separately or simultaneously.

[0023] Examples of dimer acids that can be used as raw materials for the modified epoxy resin include commercially available Haridimer 200, 250, or 270S (Harima Chemical Group Co., Ltd.); Tsunodyme 205, 216, 228, 395, or 346 (Chikuno Foods Co., Ltd.); Unidyme 14, 14R, T-17, 18, T-18, 22, T-22, 27, 35, M-9, M-15, M-35, or 40, Century D-75, D-77, D-78, or D-1156, or Sylvatal 7001 or 7002 (Arizona Chemical Co., Ltd.); 1016, 1003, 1026, 1028, 1061, 1062, 1008, or 1012 (each manufactured by BASF); hydrogenated dimer acid (average Mn of about 570; Sigma-Aldrich); and the like.

[0024] <Amine Compound (A2)> The amine compound (A2) is a raw material for introducing an amino group into the epoxy resin (A1). Therefore, the amine compound (A2) contains at least one active hydrogen capable of reacting with an epoxy group. The amine compound (A2) is not particularly limited as long as it can introduce an amino group, and for example, an alkylamine, an alkanolamine, etc. can be used. Examples of alkylamines include monomethylamine, dimethylamine, monoethylamine, diethylamine, monoisopropylamine, diisopropylamine, monobutylamine, dibutylamine, ethylenediamine, propylenediamine, butylenediamine, hexamethylenediamine, tetraethylenepentamine, pentaethylenehexamine, diethylaminopropylamine, and diethylenetriamine. Examples of alkanolamines include monoethanolamine, diethanolamine, mono(2-hydroxypropyl)amine, di(2-hydroxypropyl)amine, monomethylaminoethanol, and monoethylaminoethanol. Of these, alkanolamines are preferred. It is to be noted that primary amines may also be ketiminated. These amine compounds may be used alone or in combination of two or more. When two or more amine compounds (A2) are used to produce the cationic epoxy resin (A), they may be added separately or simultaneously.

[0025] <Method for producing epoxy resin (A1)> Next, the method for producing the epoxy resin (A1) will be described in detail. The epoxy resin (A1) can be produced, for example, by stirring a mixture of raw materials, namely, a propylene oxide-added diepoxy resin (a1), a bisphenol compound (a2), a diepoxy resin (a3), and a dicarboxylic acid (a4), at a predetermined temperature to cause the mixture to react. In order to promote the reaction, it is preferable to further add a reaction catalyst to the mixture.

[0026] The reaction catalyst is not particularly limited as long as it promotes the reaction, and examples of the reaction catalyst that can be used include tertiary amines such as dimethylbenzylamine, triethylamine, tributylamine, etc., and quaternary ammonium salts such as tetraethylammonium bromide, tetrabutylammonium bromide, etc. The reaction temperature is desirably controlled to be between 70°C and 200°C in consideration of the progress of the reaction.

[0027] The epoxy equivalent of the epoxy resin (A1) obtained by the above-mentioned production method is, for example, preferably from 1,000 to 5,000, more preferably from 1,250 to 4,000, and particularly preferably from 1,500 to 3,000. When an epoxy resin (A1) within this range is used as a raw material for the cationic epoxy resin (A), it becomes possible to produce a cationic electrodeposition coating composition that can achieve better liquid stability and efficiently form a predetermined film thickness. The epoxy equivalent can be measured according to the potentiometric titration method of JIS K7236. The measurement can be performed using a commercially available potentiometric titrator (e.g., the AT-610 manufactured by Kyoto Electronics Manufacturing Co., Ltd.).

[0028] In the production of epoxy resin (A1), the blending ratios of propylene oxide-added diepoxy resin (a1), bisphenol compound (a2), diepoxy resin (a3), and dicarboxylic acid (a4) relative to the total mass of each raw material (a1) to (a4) are as follows: The blending ratio of propylene oxide-added diepoxy resin (a1) is preferably 1 to 50 mass%, more preferably 5 to 45 mass%, and most preferably 10 to 40 mass%. The blending ratio of dicarboxylic acid (a4) is preferably 1 to 20 mass%, more preferably 5 to 20 mass%, and most preferably 10 to 20 mass%. The remaining blending ratios are accounted for by the bisphenol compound (a2) and diepoxy resin (a3), and the bisphenol compound (a2) and diepoxy resin (a3) ​​are preferably 1 mass% or more.

[0029] The above reaction may be carried out in a solvent by adding each raw material to the solvent as appropriate. The solvent is not particularly limited as long as it is one that is commonly used in the production of resins, and examples thereof include hydrocarbon solvents such as toluene, xylene, and hexane; ester solvents such as methyl acetate and ethyl acetate; ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; amide solvents such as dimethylformamide and dimethylacetamide; alcohol solvents such as methanol, ethanol, and isopropanol; and ether alcohol solvents such as ethylene glycol monobutyl ether and ethylene glycol monohexyl ether; and the like. These may be used alone or in combination of two or more.

[0030] <Method for Producing Cationic Epoxy Resin (A)> Next, the method for producing the cationic epoxy resin (A) will be described in detail. First, the epoxy resin (A1) is reacted with the amine compound (A2). The reaction temperature and time are preferably within the range of 70°C to 110°C for 1 to 5 hours. In producing the resin, the amount of the amine compound (A2) is preferably adjusted so that the amine value of the resin is within the range of 5 mgKOH / g to 30 mgKOH / g. Therefore, the amine value of the resulting resin is preferably within the range of 5 mgKOH / g to 30 mgKOH / g, more preferably within the range of 5 mgKOH / g to 20 mgKOH / g, and particularly preferably within the range of 10 mgKOH / g to 20 mgKOH / g. The amine value, i.e., the total amine value of the resin, can be measured according to the potentiometric titration method of JIS K7237.

[0031] If unreacted epoxy groups remain even after adjusting the amine value, a compound capable of reacting with epoxy groups may be used to react with the unreacted epoxy groups. The compound to be reacted with the unreacted epoxy groups is not particularly limited, and examples thereof include phenol compounds, carboxylic acids, xylene formaldehyde resins, and ε-caprolactone.

[0032] For the reaction of the epoxy resin (A1) with the amine compound (A2), the same solvents as those used in producing the epoxy resin (A1) can be used, but the solvent is not limited thereto, and other solvents may also be used.

[0033] A cationic epoxy resin (A) can be obtained by cationizing the amino groups contained in the structure of an amino-modified epoxy resin obtained by reacting an epoxy resin (A1) with an amine compound (A2) with an organic acid. The organic acid is not particularly limited as long as it can cationize the amino groups in the amino-modified epoxy resin. Examples of the organic acid include organic carboxylic acids such as formic acid, acetic acid, and lactic acid; and organic sulfonic acids such as sulfamic acid and methanesulfonic acid. Among these, methanesulfonic acid is preferred because it can produce a more stable low-amine value resin emulsion. These acids can be used alone or in combination of two or more. When two or more acids are used, they can be added separately or simultaneously. Cationization can be performed on all or a portion of the amino groups. The amount of organic acid used for cationization is, for example, 0.1 to 1.0 equivalent, preferably 0.25 to 0.75 equivalent, relative to the number of moles of amino groups.

[0034] The content of the cationic epoxy resin (A) contained in the cationic electrodeposition coating composition is not particularly limited, but is preferably 50 g / L or more and 250 g / L or less, and more preferably 100 g / L or more and 200 g / L or less.

[0035] <Blocked Polyisocyanate Curing Agent (D)> The blocked polyisocyanate curing agent (D) is an addition reaction product of a polyisocyanate compound and a blocking agent, preferably an addition reaction product of a polyisocyanate compound and a blocking agent in approximately stoichiometric amounts. Examples of polyisocyanate compounds include tolylene diisocyanate, xylylene diisocyanate, phenylene diisocyanate, diphenylmethane-2,4'-diisocyanate, diphenylmethane-4,4'-diisocyanate, polymeric MDI (crude MDI), bis(isocyanatomethyl)cyclohexane, tetramethylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate, and isophorone diisocyanate. These compounds can be used alone or in combination of two or more.

[0036] The blocking agent is added to the isocyanate group of the polyisocyanate compound to block other compounds from reacting with it. The blocked polyisocyanate compound produced by blocking the isocyanate group with a blocking agent is stable at room temperature. It is desirable that the blocked polyisocyanate compound be one in which the blocking agent dissociates when the coating film formed from the cationic electrodeposition coating composition of the present invention is baked. The baking temperature is usually about 100 to 200°C.

[0037] Examples of blocking agents that satisfy these requirements include lactam compounds such as ε-caprolactam and γ-butyrolactam; oxime compounds such as methyl ethyl ketoxime and cyclohexanone oxime; phenolic compounds such as phenol, para-t-butylphenol, and cresol; alcohols such as n-butanol and 2-ethylhexanol; and ether alcohol compounds such as ethylene glycol monobutyl ether and ethylene glycol monohexyl ether. These blocking agents can be used alone or in combination of two or more. In order to efficiently carry out the addition and dissociation reactions of the blocking agent and to efficiently obtain the intended addition reaction product, the hydroxyl groups in the modified epoxy resin may be reacted with the isocyanate groups in the polyisocyanate compound in advance, and some or all of the other isocyanate groups in the polyisocyanate compound may be blocked with a blocking agent.

[0038] Furthermore, in order to make the addition and dissociation reactions of the blocking agent more efficient, it is also possible to appropriately contain a curing catalyst. As the curing catalyst, commercially available catalysts can be appropriately used. The content of the blocked polyisocyanate curing agent (D) contained in the cationic electrodeposition coating composition is not particularly limited, but is preferably 15 g / L or more and 75 g / L or less, and more preferably 30 g / L or more and 60 g / L or less.

[0039] <Method for producing resin emulsion> The cationic epoxy resin (A) may be dispersed in water to form a resin emulsion. The resin emulsion can be produced by diluting a resin cationized with an organic acid with water while stirring.

[0040] The amount of acid used for cationization is not particularly limited, but if the amount is too small, the amount of cationization that imparts water dispersibility will be reduced and an emulsion may not be formed, so it is preferable to adjust the amount of acid appropriately.

[0041] The resin emulsion may contain other raw materials, such as a blocked polyisocyanate curing agent (D), a liquid medium (preferably water), a pigment paste (containing a pigment and a resin for dispersing the pigment), an organic solvent, a surfactant, an antifoaming agent, an antibacterial agent, and other additives used in cationic electrodeposition paints.

[0042] <Organic Zinc Compound (B)> The cationic electrodeposition coating composition contains at least one organic zinc compound. Specific examples of the organic zinc compound include zinc formate, zinc acetate, zinc lactate, zinc gluconate, zinc tranexamate, zinc dipropionate, and zinc methanesulfonate. Among these, it is preferable to use at least one selected from the group consisting of zinc lactate, zinc acetate, and zinc methanesulfonate, and zinc acetate is most suitable.

[0043] The content of the organic acid zinc compound contained in the cationic electrodeposition coating composition is not particularly limited, but is preferably 10 ppm to 1,000 ppm, more preferably 100 ppm to 500 ppm, and even more preferably 150 ppm to 350 ppm, calculated as divalent zinc ions. The divalent zinc ions contained in the composition can be quantified using an ICP atomic emission spectrometer.

[0044] <Phenol Compound (C)> The cationic electrodeposition coating composition contains a phenol compound (C). Examples of the phenol compound (C) include phenols and phenol resins. Examples of phenols include phenol, alkyl-substituted phenols, polyhydric phenols, α-naphthol, bisphenol, and polyvinylphenol. Examples of alkyl-substituted phenols include cresol, xylenol, butylphenol, and amylphenol. Examples of polyhydric phenols include resorcinol and catechol. Examples of bisphenols include bisphenol A and bisphenol F. Examples of phenol resins include reaction products of the above phenols with formaldehyde. The form of the reaction product of the above phenols with formaldehyde is not particularly limited, and examples include novolak and resol. The phenol compound (C) may be a Mannich reaction product of the above phenols and / or phenol resins, formaldehyde, and amines. The Mannich reaction products of the phenols and / or phenolic resins, formaldehyde, and amines may be used as they are, or may be cationized with an organic acid. The phenolic compounds (C) may be used alone or in combination of two or more. Of the above, as the phenolic compound (C), it is preferable to use the Mannich reaction products of the phenols and / or phenolic resins, formaldehyde, and amines, and it is more preferable to use the Mannich reaction products of the phenols and / or phenolic resins, formaldehyde, and amines cationized with an organic acid.

[0045] As the formaldehyde, formaldehyde, a compound that generates formaldehyde, etc. can be used. Examples of compounds that generate formaldehyde include aldehyde derivatives, aliphatic aldehydes, aromatic aldehydes, heterocyclic aldehydes, etc. Examples of aldehyde derivatives include paraformaldehyde and hexamethylenetetramine. Examples of aliphatic aldehydes include acetaldehyde and propionaldehyde. Examples of aromatic aldehydes include benzaldehyde, and examples of heterocyclic aldehydes include furfural. These may be used alone or in combination of two or more. Among these, formaldehyde is preferred.

[0046] Examples of the amines that can be used include primary amines and secondary amines. Examples of primary amines include primary alkylamines, primary hydroxyalkylamines, and primary aromatic amines. Examples of primary alkylamines include methylamine, ethylamine, propylamine, isopropylamine, and butylamine. Examples of primary hydroxyalkylamines include ethanolamine, propanolamine, and isopropanolamine. Examples of primary aromatic amines include aniline. Examples of secondary amines include secondary alkylamines and secondary hydroxyalkylamines. Examples of secondary alkylamines include dimethylamine, diethylamine, ethylpropylamine, dipropylamine, diisopropylamine, and dibutylamine. Examples of secondary hydroxyalkylamines include N-methylethanolamine, N-ethylethanolamine, diethanolamine, dipropanolamine, and diisopropanolamine. These may be used alone or in combination of two or more. Among these, secondary hydroxyalkylamines are preferred, and N-methylethanolamine and diethanolamine are more preferred.

[0047] The Mannich reaction can be carried out using conventional methods. For example, phenols and / or phenolic resins, formaldehyde, and amines can be mixed, and optionally, alcohols, glycol ethers, ketones, or the like can be used as a solvent. The reaction can be carried out at 20°C to 100°C for several minutes to several hours. The amounts of the phenols and / or phenolic resins, formaldehyde, and amines used in the Mannich reaction are not particularly limited, and the formaldehyde and amines are consumed in equimolar amounts during the Mannich reaction. The progress of the Mannich reaction can be confirmed by quantifying the remaining formaldehyde. There are no particular limitations on the method for confirming formaldehyde, but for example, the acetylacetone absorptiometry method described in Japanese Agricultural Standard JAS 6000 established by the Ministry of Agriculture, Forestry and Fisheries can be used.

[0048] The organic acid used to cationize the Mannich reaction product of the phenols and / or phenolic resins, formaldehyde, and amines can be, for example, a monovalent organic acid or a polyvalent organic acid. Examples of the monovalent organic acid include formic acid, acetic acid, propionic acid, lactic acid, methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, benzenesulfonic acid, toluenesulfonic acid, and nitrobenzenesulfonic acid. Examples of the polyvalent organic acid include citric acid, lactic acid, malic acid, fumaric acid, and maleic acid. Among these, monovalent organic acids are preferred, with acetic acid and methanesulfonic acid being particularly preferred. The content of the phenol compound (C) contained in the cationic electrodeposition coating composition according to the present invention is not particularly limited, but is preferably 10 g / L or more and 200 g / L or less, and more preferably 50 g / L or more and 100 g / L or less. The phenol compound (C) is preferably contained in an amount of 1 part by mass or more and 20 parts by mass or less per 100 parts by mass of the cationic epoxy resin (A).

[0049] <Method for producing cationic electrodeposition coating composition> The cationic electrodeposition coating composition can be produced, for example, by stirring and mixing the above-mentioned resin emulsion, organic acid zinc compound (B), and water-soluble phenolic compound (C), and, if necessary, the above-mentioned liquid medium, pigment paste, organic solvent, surfactant, antifoaming agent, etc. The concentration of the cationic electrodeposition coating composition can be adjusted by appropriately diluting it with deionized water.

[0050] The pH of the cationic electrodeposition coating composition is not particularly limited, but is preferably in the range of 2.0 to 8.0, and more preferably in the range of 3.0 to 6.0. By ensuring that the pH of the composition is within this range, even if a chemical conversion treatment is performed with a chemical conversion treatment solution before cationic electrodeposition coating using the cationic electrodeposition coating composition, adverse effects due to contamination of the chemical conversion treatment solution and metals etched by the chemical conversion treatment can be prevented. There are no particular limitations on the pH adjusters that can be used to adjust the pH, and known acids and bases can be used. For example, acids such as formic acid, acetic acid, lactic acid, nitric acid, sulfamic acid, methanesulfonic acid, and benzenesulfonic acid, and bases such as aqueous ammonia, monoethanolamine, diethanolamine, and triethanolamine can be used as appropriate. Note that the pH in this specification refers to a value measured at 25°C using a commercially available pH meter.

[0051] The electrical conductivity of the cationic electrodeposition coating composition is not particularly limited, but is preferably 1000 μS / cm or more and less than 2000 μS / cm. If it is less than 1000 μS / cm, deposition of the coating film during electrodeposition coating may be delayed, making it difficult to obtain a sufficient film thickness. If it is 2000 μS / cm or more, the appearance of the coating may deteriorate and sufficient insulation may not be obtained. The electrical conductivity can be measured using a commercially available electrical conductivity meter (for example, Toa DKK's Multi Water Quality Meter MM-60R).

[0052] <Cationic Electrodeposition Coating Method> Cationic electrodeposition coating using a cationic electrodeposition coating composition can be carried out by applying a current of 10 to 400 V, preferably 50 to 250 V, to the substrate as the cathode. The temperature of the paint bath containing the cationic electrodeposition coating composition during cationic electrodeposition coating is typically between 10 and 50°C, preferably between 15 and 40°C, but is not limited to these temperatures. After cationic electrodeposition coating, a drying step is carried out to harden the formed coating film. The drying of the coating film is preferably carried out at a temperature of about 100 to about 300°C, for example, at the surface temperature of the coated object, and more preferably between about 150 and about 250°C. By drying and hardening the coating film in this way, an article having a coating film coated with the cationic electrodeposition coating composition is obtained. A water-washing step may be carried out between the cationic electrodeposition coating step and the drying step, if necessary. The water-washing step can be carried out using, for example, ultrafiltrate, reverse osmosis permeated water, industrial water, pure water, or the like.

[0053] The thickness of the coating film formed by the cationic electrodeposition coating method is not particularly limited, but is preferably 5 μm to 50 μm, more preferably 10 μm to 40 μm. By keeping the thickness within this range, excellent corrosion resistance can be obtained. The coating thickness can be measured with an electromagnetic induction type film thickness meter if the base metal is a magnetic metal, or with an eddy current type film thickness meter if the base metal is a non-magnetic metal.

[0054] <Electronic Components> There are no particular limitations on the articles to which the cationic electrodeposition coating composition can be applied, but electronic components are preferred. The electronic components are not particularly limited as long as they can be electrodeposited, and can be applied to, for example, electronic components constituting motors (cores, stators, rotors), lead wires, rectangular wires, copper wires, reactor coils, resolvers, bus bars, bobbins, inductors, capacitors, transformers, sintered magnets, component housings, adhesives, optical materials (e.g., imaging lenses), resists, liquid resists, printing plates, insulating varnishes, insulating sheets, laminates, printed circuit boards, sealants (e.g., for semiconductor devices, LED packages, liquid crystal injection ports, organic electroluminescence devices, optical elements, electrical insulation, electronic components, separation membranes, etc.), passivation films (e.g., for semiconductors, solar cells, etc.), interlayer insulating films, protective films, etc. The metal material constituting the electronic component is not particularly limited, and examples thereof include cold-rolled steel, zinc-plated steel (e.g., galvannealed steel, hot-dip galvanized steel, and electrogalvanized steel), aluminum steel, aluminum, copper (oxygen-free copper and brass), and magnesium. These metal materials may be subjected to a surface cleaning treatment such as alkaline degreasing, or may be subjected to a surface treatment such as zinc phosphate conversion treatment or zirconium conversion treatment after the surface cleaning treatment. These electronic components may also be used in, for example, automobile parts and household appliances.

[0055] <Other Uses> Examples of applications of the present invention to materials other than electronic components include eyeglasses, lining agents, inks, molding materials, putties, glass fiber impregnating agents, sealing agents, lens portions of lens sheets such as prism lens sheets (for example, those used in the backlights of liquid crystal display devices), Fresnel lens sheets (for example, those used in the screens of projection televisions and the like), lenticular lens sheets, and the like, or backlights using such sheets, optical lenses (for example, microlenses, and the like), optical elements, optical connectors, optical waveguides, and casting agents for optical shaping.

[0056] <Examples> The present invention will be explained in more detail below with reference to Production Examples, Examples, and Comparative Examples, but the present invention is not limited thereto. The metal plates and degreasing agents used in the examples were arbitrarily selected from commercially available materials, and do not limit the actual use of the cationic electrodeposition coating composition of the present invention. Unless otherwise specified, % and parts mean % by mass and parts by mass, respectively. The raw materials used in the formulations are listed in Tables 1 to 4 below.

[0057] <Production of Amino-Modified Epoxy Resin> <Production Example 1> A 2-liter separable flask equipped with a thermometer, reflux condenser, and stirrer was charged with 77.25 g of diepoxy resin (Epolite 3002NN), 96.79 g of bisphenol A, 549.5 g of bisphenol A diglycidyl ether (jER828EL), 63.24 g of dicarboxylic acid (Haldimer 270S), and 1.0 g of triethylamine, and the mixture was reacted at 160°C until an epoxy equivalent of 1500 was reached. 194.86 g of butyl cellosolve was added to terminate the reaction. The temperature was then adjusted to 100°C, and 14.63 g of diethanolamine was added. The mixture was reacted for 5 hours to obtain an amino-modified epoxy resin.

[0058] <Production Example 2> 114.7 g of bisphenol A, 286.94 g of bisphenol A diglycidyl ether (jER828EL), and 1.0 g of triethylamine were placed in a 2-liter separable flask equipped with a thermometer, a reflux condenser, and a stirrer, and the mixture was allowed to react at 160°C until an epoxy equivalent of 1,500 was reached. The reaction was then terminated by adding 194.86 g of butyl cellosolve. The temperature was then adjusted to 100°C, and 52.93 g of diethanolamine was added. The mixture was allowed to react for 5 hours to obtain an amino-modified epoxy resin.

[0059] <Production of Blocked Polyisocyanate Curing Agent (D)> <Production Example 3> In a reaction vessel, 115.6 g of methyl isobutyl ketone was added to 678.4 g of Cosmonate M-200 (trade name, crude MDI manufactured by Mitsui Chemicals, Inc.), and the temperature was raised to 70°C. Then, 706.0 g of butyl cellosolve was slowly added dropwise, and after completion of the dropwise addition, the temperature was raised to 90°C. The reaction was carried out at 90°C for 12 hours to obtain a blocked polyisocyanate curing agent. When infrared absorption spectroscopy was performed, no absorption due to unreacted isocyanate groups was observed, confirming that the isocyanate was completely blocked.

[0060] <Production of Cationic Epoxy Resin (A) Emulsion> <Production Example 4> 649.54 g of the amino group-modified epoxy resin obtained in Production Example 1 and 216.51 g of the blocked polyisocyanate obtained in Production Example 3 were mixed, and then 6.69 g of methanesulfonic acid was added and stirred uniformly. Then, 1,116.79 g of deionized water was added over a period of about 10 minutes with vigorous stirring, to obtain a cationic epoxy resin (A) emulsion with a solids content of 33%.

[0061] <Production Example 5> 649.54 g of the amino group-modified epoxy resin obtained in Production Example 2 and 216.51 g of the blocked polyisocyanate obtained in Production Example 3 were mixed, and then 24.19 g of methanesulfonic acid was added and stirred uniformly. Then, 1099.30 g of deionized water was added thereto over a period of about 10 minutes with vigorous stirring, to obtain a cationic epoxy resin (A) emulsion with a solids content of 33%.

[0062] <Production of Water-Soluble Phenol Compound (C)> <Production Example 6> 228.3 g of bisphenol A and 500.0 g of ethanol were placed in a 2-liter separable flask equipped with a thermometer, a reflux condenser, and a stirrer, and the temperature was raised to 60°C. Then, 162.3 g of formalin and 150.2 g of methylethanolamine were added dropwise, and the mixture was allowed to react for 5 hours. Then, while maintaining the temperature at 60°C, 120.1 g of acetic acid was added, and the mixture was allowed to react for 1 hour. Then, 1572.8 g of water was added, and a water-soluble phenol compound with a solids content of 20% was produced.

[0063] <Production Examples 7 to 13> Water-soluble phenolic compounds with a solid content of 20% (Production Examples 7 to 13) were produced in the same manner as in Production Example 6 using the raw materials shown in Table 1.

[0064]

[0065] <Preparation of Cationic Electrodeposition Coating Composition> <Example 1> 910.61 g of the resin emulsion produced in Production Example 4, 3.72 g of zinc lactate, 78.88 g of the water-soluble phenol compound produced in Production Example 6, and 1006.79 g of deionized water were mixed and stirred to prepare a cationic electrodeposition coating composition with a solids content of 16%.

[0066] Examples 2 to 23 and Comparative Examples 1 to 4 In the same manner as in Example 1, cationic coating compositions with a solids content of 16% were produced using the raw materials shown in Table 2.

[0067]

[0068] <Preparation of Test Plates> To prepare the test plates, first, a metal plate (cold-rolled steel plate: CRS (150 mm (length) × 70 mm (width) × 0.8 mm (thickness) in the table), aluminum alloy plate: Al (A5051) in the table, oxygen-free copper plate: Cu (C1020) in the table, or galvanized steel plate: GA in the table) was degreased (Fine Cleaner E6400, product name, manufactured by Nippon Parkerizing Co., Ltd., 60°C × 3 minutes dipping treatment) and then washed with water to clean it. Next, the cleaned metal plate was used as a substrate and electrodeposited using the cationic electrodeposition coating compositions of Examples 1 to 23 and Comparative Examples 1 to 4 to a dry film thickness of 20 μm, to obtain a test plate for each Example and Comparative Example.

[0069] <Various Evaluations> The test plates (electrodeposition coated plates) obtained by the above method were subjected to various evaluations as follows. The results are shown in Table 3.

[0070] <Breakdown Voltage> The breakdown voltage (breakdown voltage per unit film thickness) of each test panel was measured using a voltage resistance tester (TOS9201, manufactured by Kikusui Electronics Co., Ltd.). The measurement was performed under conditions of an initial voltage of 0 V, a voltage increase rate of 50 V / sec, and a cutoff current of 1.0 mA. Evaluation was performed according to the following criteria, with B or higher being considered a pass. S: 120 V / μm or higher A: 100 V / μm or higher and less than 120 V / μm B: 80 V / μm or higher and less than 100 V / μm C: Less than 80 V / μm

[0071] <Edge Coverage> The coating thickness of each test panel was measured using an electromagnetic induction coating thickness meter if the base metal was magnetic, or an eddy current coating thickness meter if the base metal was non-magnetic, to determine the coating thickness at the center of the surface of the test panel. Next, the edge of each test panel was cut out and embedded in a cup containing epoxy resin, the resin was cured, and the coating cross section was polished. The coating cross section was then observed using a Keyence VHX-6000 digital microscope at a magnification of 300x. The edge thickness was calculated by image analysis using data analysis software compatible with this device, and the calculated value was used as the edge thickness. The edge coverage rate was defined as the ratio of the edge thickness to the center thickness of the test panel, and was evaluated according to the following criteria, with a score of B or higher being considered a pass. S: 90% or more; A: 70% or more and less than 90%; B: 50% or more and less than 70%; C: Less than 50%

[0072] <Pinhole Test> Referring to JIS3261-5:2019, the test plate was immersed in 0.2% saline solution, with the sample as the cathode and the saline solution as the anode, and a 12V DC power supply was applied for 1 minute. If there were no pinholes, nothing would happen, but if there were pinholes, bubbles generated by the electrolysis of water would emerge from them, so the number of bubbles was counted and evaluated according to the following criteria, with B or higher being considered a pass. S: No bubbles generated A: 1 or 2 bubbles generated B: 3 to 5 bubbles generated C: 6 or more bubbles generated

[0073]

[0074] Although the present invention will be described in detail with reference to specific examples, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention.

Claims

1. A cationic electrodeposition coating composition comprising a cationic epoxy resin (A), an organic acid zinc compound (B), and a phenol compound (C).

2. The cationic electrodeposition coating composition according to claim 1, wherein the organic acid zinc compound (B) is contained in an amount of 10 ppm or more and 1000 ppm or less in terms of divalent zinc ions.

3. The cationic electrodeposition coating composition according to claim 1, wherein the phenol compound (C) is contained in an amount of 1 part by mass to 20 parts by mass per 100 parts by mass of the cationic epoxy resin (A).

4. The cationic electrodeposition coating composition according to claim 1, wherein the phenolic compound (C) comprises a Mannich reaction product of a phenol and / or a phenolic resin, formaldehyde, and an amine.

5. The cationic electrodeposition coating composition according to claim 4, wherein the Mannich reaction products of the phenols and / or phenolic resins, formaldehyde, and amines include those cationized with an organic acid, the amines include at least one selected from N-methylethanolamine and diethanolamine, and the organic acid includes a monovalent organic acid.

6. The cationic electrodeposition coating composition according to claim 1, wherein the cationic epoxy resin is an amino-modified epoxy resin obtained by reacting an epoxy resin (A1) with an amine compound (A2), and the amino-modified epoxy resin is cationized with an organic acid, and the epoxy resin (A1) is a resin having: a structural unit derived from a propylene oxide-added diepoxy resin (a1) represented by formula (1); a structural unit derived from a bisphenol compound (a2); a structural unit derived from a diepoxy resin (a3) ​​different from formula (1); and a structural unit derived from a dicarboxylic acid (a4) in which two carboxyl groups are bonded via at least one carbon atom. [In formula (1), R １ represents an alkylene group having 3 to 10 carbon atoms which may have a substituent, a cyclohexylene group which may have a substituent, a phenylene group which may have a substituent, or -Ra-Rb-Rc-, where Ra and Rc are cyclohexylene groups or phenylene groups, Rb is a methylene group which may have one or two substituents, and m and n are each independently an integer of 1 to 20.

7. The cationic electrodeposition coating composition according to claim 1, further comprising a blocked polyisocyanate curing agent (D).

8. An electronic part having a coating film coated with the cationic electrodeposition coating composition according to any one of claims 1 to 7.

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