Cationic electrodeposition coating composition and method for forming cured electrodeposition coating film

Abstract

To provide a cationic electro-deposition coating composition from which a cured electro-deposition coating film having excellent corrosion resistance and appearance can be obtained.SOLUTION: A cationic electro-deposition coating composition contains an amine-modified epoxy resin (A), a blocked polyisocyanate curing agent (B), and a coordination polymer catalyst (C) having a metal complex containing a metal ion (C1) and an organic ligand (C2) as a constituent unit, wherein the metal ion (C1) contains at least one metal element ion selected from the group consisting of Bi, Zn, Zr, Cs and lanthanoid, and the organic ligand (C2) contains at least one selected from the group consisting of amine compounds represented by general formulae (1) to (5).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a cationic electrodeposition coating composition and a method for forming a cured electrodeposition coating film. [Background technology]

[0002] Cationic electrodeposition coating compositions are generally used as undercoats for automobiles, etc. Cationic electrodeposition coating compositions form coatings with high corrosion resistance.

[0003] Patent Document 1 discloses a cationic electrodeposition coating composition containing a bismuth compound as a catalyst, and Patent Document 2 discloses an electrodeposition coating composition containing a cyclic guanidine. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-187198 [Patent Document 2] US Patent Application Publication No. 2011 / 0005937 Summary of the Invention [Problem to be solved by the invention]

[0005] Bismuth compounds can lose their catalytic activity over time due to hydrolysis, whereas organic amine catalysts such as cyclic guanidines are highly water-soluble and have poor electrodeposition efficiency, making them difficult to incorporate into the deposited film and therefore difficult to demonstrate their catalytic activity.

[0006] An object of the present invention is to provide a cationic electrodeposition coating composition which gives a cured electrodeposition coating film having excellent corrosion resistance and appearance. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides the following aspects. [1] Amine-modified epoxy resin (A), a blocked polyisocyanate curing agent (B), and a coordination polymer catalyst (C) having, as a constituent unit, a metal complex containing a metal ion (C1) and an organic ligand (C2); the metal ion (C1) contains an ion of at least one metal element selected from the group consisting of Bi, Zn, Zr, Cs, and lanthanoids; The organic ligand (C2) is represented by the following general formula (1): [ka] (In the formula, R11, R21, and R31 each independently represent a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, a nitro group, a halogen atom, or an amino group.) an amine compound (C2-1) represented by the formula: The following general formula (2): [ka] (In the formula, R12 and R22 each independently represent a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, a nitro group, a halogen atom, or an amino group.) an amine compound (C2-2) represented by the formula: The following general formula (3): [ka] (In the formula, R13 and R23 each independently represent a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, a nitro group, a halogen atom, or an amino group.) an amine compound (C2-3) represented by the formula: The following general formula (4): [ka] (In the formula, R14, R24, R34, R44, and R54 each independently represent a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, a nitro group, a halogen atom, or an amino group.) and an amine compound (C2-4) represented by the formula: The following general formula (5): [ka] (In the formula, R15 to R125 each independently represent a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, a nitro group, a halogen atom, or an amino group.) A cationic electrodeposition coating composition comprising at least one selected from the group consisting of amine compounds (C2-5) represented by the following formula: [2] The cationic electrodeposition coating composition of [1] above, which contains the coordination polymer catalyst (C) in an amount of 0.1 to 3 parts by mass per 100 parts by mass of the resin solid content of the cationic electrodeposition coating composition. [3] The cationic electrodeposition coating composition of the above [1] or [2], wherein in the coordination polymer catalyst (C), the molar ratio of the metal ion (C1) to the organic ligand (C2) (metal ion:organic ligand) is 1:0.5 to 1:5. [4] The cationic electrodeposition coating composition of the above [1] or [2], wherein in the coordination polymer catalyst (C), the molar ratio of the metal ion (C1) to the organic ligand (C2) (metal ion:organic ligand) is 1:1 to 1:2.8. [5] The cationic electrodeposition coating composition according to the above [1] or [2], wherein the coordination polymer catalyst (C) is a solid. [6] The cationic electrodeposition coating composition according to the above [1] or [2], further comprising an inorganic pigment (D). [7] The cationic electrodeposition coating composition according to the above [1] or [2], wherein the blocked polyisocyanate curing agent (B) comprises a reaction product of a blocking agent and an aromatic polyisocyanate. [8] Immersing an object to be coated in the cationic electrodeposition coating composition of [1] above to perform electrodeposition coating, thereby forming an uncured electrodeposition coating film; and A method for forming a cured electrodeposition coating film, comprising heating the uncured electrodeposition coating film to form a cured electrodeposition coating film on the substrate. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a cationic electrodeposition coating composition which can give a cured electrodeposition coating film having excellent corrosion resistance and appearance. DETAILED DESCRIPTION OF THE INVENTION

[0009] In the present disclosure, a polymer having as a constituent unit a metal complex in which one or more amine compounds are coordinated to a metal ion is used as a catalyst. Coordinating an amine compound to a catalytically active metal inhibits its hydrolysis and enhances its stability. Fixing a catalytically active amine compound to a metal reduces its water solubility. The polymer catalyst can maintain high catalytic activity (high stability). Furthermore, the polymer catalyst is uniformly and finely present in the deposit film, allowing the deposit film to harden densely and smoothly. The resulting cured electrodeposition coating film has excellent corrosion resistance and appearance.

[0010] Hereinafter, the number average molecular weight and weight average molecular weight can be measured by gel permeation chromatography (GPC) using a polystyrene standard sample standard after removing water by drying under reduced pressure or the like.

[0011] The average particle size is the 50% average particle size (D50) in the volumetric particle size distribution measured using a laser diffraction / scattering particle size distribution analyzer, such as the UPA-150 (Microtrac particle size distribution analyzer, manufactured by Nikkiso Co., Ltd.).

[0012] The solid content is the component remaining as a solid after the solvent is removed. The solid content of the resin emulsion (i) described below is specifically the amine-modified epoxy resin (A), the curing agent (B), and other solid components added as needed. The solid content of the pigment dispersion paste (ii) is specifically the coordination polymer catalyst (C), the inorganic pigment (D), the pigment dispersion resin (E), and other solid components added as needed.

[0013] The resin solid content is the resin component of the above solid content. The resin solid content of the resin emulsion (i) is specifically the amine-modified epoxy resin (A) and the curing agent (B). The resin solid content of the pigment dispersion paste (ii) is specifically the pigment dispersion resin (E). The resin solid content of the cationic electrodeposition coating composition is specifically all the resin solid content contained in the resin emulsion (i) and the pigment dispersion paste (ii).

[0014] Cationic electrodeposition coating composition The cationic electrodeposition coating composition contains an amine-modified epoxy resin (A), a blocked polyisocyanate curing agent (B), and a coordination polymer catalyst (C).

[0015] The cationic electrodeposition coating composition may further contain an inorganic pigment (D). The cationic electrodeposition coating composition may further contain a pigment dispersing resin (E). The cationic electrodeposition coating composition may be a mixture of a resin emulsion (i) and a pigment dispersing paste (ii). The resin emulsion (i) contains an amine-modified epoxy resin (A) and a blocked polyisocyanate curing agent (B). The pigment dispersing paste (ii) contains a coordination polymer catalyst (C), an inorganic pigment (D), and a pigment dispersing resin (E).

[0016] Hereinafter, a cationic electrodeposition coating composition (hereinafter sometimes simply referred to as electrodeposition coating) which is a mixture of resin emulsion (i) and pigment dispersion paste (ii) will be described as an example, although the cationic electrodeposition coating composition used in the present disclosure is not limited to this. First, the coordination polymer catalyst (C) will be explained.

[0017] Coordination polymer catalyst (C) The coordination polymer catalyst (C) is a polymer having, as a constituent unit, a metal complex containing a metal ion (C1) and an organic ligand (C2).

[0018] The coordination polymer catalyst (C) has a structure similar to that of materials known as MOFs (Metal Organic Frameworks). MOFs are metal complexes containing metal ions and organic ligands, and are highly regular, porous structures in which the metal ions (or metal clusters) that serve as nodes are bridged by organic ligands.

[0019] Coordination polymer catalyst (C) has a large surface area and high catalytic activity. In addition, coordination polymer catalyst (C) has excellent stability, allowing it to maintain this high catalytic activity. Because coordination polymer catalyst (C) exists in a solid (powder) form in the electrodeposition paint, it is easily electrodeposited and can be present uniformly and finely in the deposited film. Therefore, coordination polymer catalyst (C) can harden the deposited film densely and smoothly.

[0020] For information on MOFs, see, for example, (1) Kitagawa Susumu, editor, "Porous Materials Made by Nanoscience," CMC Publishing, March 2010, and (2) Japan Chemical Society, edited, "Creation of Functional Substances with Innovative Porous Material Space," Kagaku Dojin, December 2010.

[0021] The coordination polymer catalyst (C) may have a one-dimensional structure, a two-dimensional structure, or a three-dimensional structure, and typically has a three-dimensional structure.

[0022] The coordination polymer catalyst (C) can be dispersed using a pigment dispersing resin (E) in the same manner as the inorganic pigment (D).

[0023] The size of the coordination polymer catalyst (C) before being blended into the electrodeposition coating is not particularly limited. The average particle diameter of the coordination polymer catalyst (C) is, for example, 0.001 μm or more and 10 μm or less. The average particle diameter of the coordination polymer catalyst (C) may be 0.01 μm or more. The average particle diameter of the coordination polymer catalyst (C) may be 5 μm or less.

[0024] The organic ligand (C2) is coordinately bonded to the metal ion (C1) via an amino group. The coordination number of the organic ligand (C2) is not particularly limited. The molar ratio of the metal ion to the organic ligand (metal ion:organic ligand) may be, for example, 1:0.5 to 1:5. When the number of moles of the organic ligand per mole of the metal ion is 0.5 or more, stability can be further improved. When the number of moles of the organic ligand per mole of the metal ion is 5 or less, the appearance of the coating film can be further improved. The number of moles of the organic ligand per mole of the metal ion may be 1.0 or more, 1.5 or more, or 2.0 or more. The number of moles of the organic ligand per mole of the metal ion may be 2.8 or less, or 2.5 or less. In one embodiment, the molar ratio (metal ion:organic ligand) is, for example, 1:1 to 1:2.8.

[0025] The molar ratio (metal ion / organic ligand) is calculated from the amounts of raw materials (e.g., metal salts as raw materials for the metal ions (C1) and amine compounds as raw materials for the organic ligands (C2)) charged when producing the coordination polymer catalyst (C), the yield, atomic weights (or molecular weights), etc.

[0026] The content of the coordination polymer catalyst (C) may be 0.1 parts by mass or more and 3.0 parts by mass or less per 100 parts by mass of the resin solid content of the cationic electrodeposition coating composition. When the content of the coordination polymer catalyst (C) is 0.1 parts by mass or more, curability is improved. When the content of the coordination polymer catalyst (C) is 3.0 parts by mass or less, the appearance of the coating film is improved. The content of the coordination polymer catalyst (C) may be 0.5 parts by mass or more, or may be 1.0 parts by mass or more. The content of the coordination polymer catalyst (C) may be 2.5 parts by mass or less, or may be 2.0 parts by mass or less.

[0027] The coordination polymer catalyst (C) can be obtained by reacting a metal salt with an amine compound at room temperature or under heating. Examples of the metal salt include nitrates, acetates, and hydrochlorides. Examples of the amine compound include the amine compounds (C2-1) to (C2-5) described below.

[0028] Metal ions (C1) The metal ion (C1) includes an ion of at least one metal element selected from the group consisting of Bi (bismuth), Zn (zinc), Zr (zirconium), Cs (cesium), and lanthanoids. The metal element may be Bi (bismuth) or Zn (zinc).

[0029] Lanthanides is a collective term for 15 elements with atomic numbers from 57 to 71 (lanthanum to lutetium on the periodic table). Lanthanides include lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

[0030] The metal element may be included as a cluster, which is an aggregate of metal atoms having metal-metal bonds.

[0031] ·Organic ligand (C2) The organic ligand (C2) includes at least one selected from the group consisting of amine compounds (C2-1) to (C2-5) represented by the following general formulas (1) to (5).

[0032] In the general formulae (1) to (5), some or all of the hydrogen atoms of the alkyl group, aryl group, and alkoxy group may be substituted with halogen atoms or may be unsubstituted. Some or all of the hydrogen atoms of the aryl group may be substituted with alkyl groups and / or alkoxy groups or may be unsubstituted. Some or all of the hydrogen atoms of the amino group may be substituted with at least one group selected from the group consisting of alkyl groups, aryl groups, and alkoxy groups or may be unsubstituted.

[0033] In the general formulas (1) to (5), the alkyl group, aryl group, and alkoxy group may have, for example, one or more N, O, or carbonyl groups at the end or in the molecular chain.

[0034] In the general formulas (1) to (5), the alkyl group may be linear or branched, and may contain one or more ring structures. The number of carbon atoms in the alkyl group is not particularly limited, and is, for example, 1 to 20.

[0035] In the general formulae (1) to (5), the aryl group is not particularly limited as long as it has at least one aromatic ring. The number of carbon atoms in the aryl group is not particularly limited, and is, for example, 6 to 20.

[0036] In the general formulas (1) to (5), the alkyl group constituting the alkoxy group may be linear or branched, and may contain one or more ring structures. The number of carbon atoms in the alkyl group is not particularly limited, and may be, for example, 1 to 20.

[0037] Examples of the alkyl group include unsubstituted alkyl groups such as methyl, ethyl, propyl, isopropyl, n-butyl, and isobutyl groups; and substituted alkyl groups such as chloromethyl groups.

[0038] The organic ligand (C2) may not contain an S atom. A group containing an S atom (for example, an —SH group) may reduce the corrosion resistance of the cured electrodeposition coating film.

[0039] Amine compounds (C2-1) The amine compound (C2-1) is represented by the following general formula (1): Specifically, the amine compound (C2-1) is imidazole or a derivative thereof.

[0040] [ka] (In the formula, R11, R21, and R31 each independently represent a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, a nitro group, a halogen atom, or an amino group.)

[0041] At least one of R11, R21, and R31 may be a hydrogen atom or a methyl group. R11, R21, and R31 may all be hydrogen atoms. R11 and R21 may be hydrogen atoms, and R31 may be an alkyl group having 1 to 3 carbon atoms.

[0042] Amine compounds (C2-2) The amine compound (C2-2) is represented by the following general formula (2): Specifically, the amine compound (C2-2) is triazole and its derivatives.

[0043] [ka] (In the formula, R12 and R22 each independently represent a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, a nitro group, a halogen atom, or an amino group.)

[0044] At least one of R12 and R22 may be a hydrogen atom. Both R12 and R22 may be hydrogen atoms.

[0045] Amine compounds (C2-3) The amine compound (C2-3) is represented by the following general formula (3): Specifically, the amine compound (C2-3) is triazole and its derivatives.

[0046] [ka] (In the formula, R13 and R23 each independently represent a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, a nitro group, a halogen atom, or an amino group.)

[0047] At least one of R13 and R23 may be a hydrogen atom. Both R13 and R23 may be hydrogen atoms.

[0048] Amine compounds (C2-4) The amine compound (C2-4) is represented by the following general formula (4): Specifically, the amine compound (C2-4) is benzimidazole and its derivatives.

[0049] [ka] (In the formula, R14, R24, R34, R44, and R54 each independently represent a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, a nitro group, a halogen atom, or an amino group.)

[0050] At least one of R14, R24, R34, R44 and R54 may be a hydrogen atom. R14, R24, R34, R44 and R54 may all be hydrogen atoms.

[0051] Amine compounds (C2-5) The amine compound (C2-5) is represented by the following general formula (5): Specifically, the amine compound (C2-5) is 1,57-triazabicyclo[4,4,0]dec-5-ene (TBD) and its derivatives.

[0052] [ka] (In the formula, R15 to R125 each independently represent a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, a nitro group, a halogen atom, or an amino group.)

[0053] At least one of R15, R25, R35, R45, R55, R65, R75, R85, R95, R105, R115, and R125 may be a hydrogen atom, and all of R15, R25, R35, R45, R55, R65, R75, R85, R95, R105, R115, and R125 may be a hydrogen atom.

[0054] Resin emulsion (i) The resin emulsion (i) contains an amine-modified epoxy resin (A) and a blocked polyisocyanate curing agent (B). The resin emulsion (i) may further contain other components, if necessary.

[0055] Amine-modified epoxy resin (A) The amine-modified epoxy resin (A) is a film-forming resin that constitutes the electrodeposition coating film.

[0056] The amine-modified epoxy resin (A) may have an oxirane ring in the epoxy resin skeleton modified with an amine compound. The amine-modified epoxy resin (A) is prepared, for example, by ring-opening the oxirane ring in the raw material epoxy resin skeleton through a reaction with an amine compound such as a primary amine, a secondary amine, or a tertiary amine and / or an acid salt thereof.

[0057] A typical example of the starting epoxy resin is polyphenol polyglycidyl ether epoxy resin, which is obtained by reacting polycyclic phenolic compounds such as bisphenol A, bisphenol F, bisphenol S, phenol novolac, and cresol novolac with epichlorohydrin.

[0058] Other raw material epoxy resins include, for example, the oxazolidone ring-containing epoxy resins described in JP-A-5-306327, which are prepared by reacting epichlorohydrin with a diisocyanate compound or a bis-urethane compound obtained by blocking the isocyanate group of a diisocyanate compound with a lower alcohol such as methanol or ethanol.

[0059] The raw material epoxy resin may be chain-extended with a difunctional polyester polyol, polyether polyol, bisphenol, dibasic carboxylic acid, or the like.

[0060] The starting epoxy resin may have an oxirane ring to which a monohydroxy compound such as 2-ethylhexanol, nonylphenol, ethylene glycol mono-2-ethylhexyl ether, ethylene glycol mono-n-butyl ether, or propylene glycol mono-2-ethylhexyl ether or a monocarboxylic acid compound such as octylic acid is added. This allows the molecular weight or amine equivalent of the epoxy resin to be adjusted, thereby improving its thermal flow properties.

[0061] Amine compounds include primary amines and secondary amines. Reaction of a raw epoxy resin with a secondary amine yields an amine-modified epoxy resin with a tertiary amino group. Reaction of a raw epoxy resin with a primary amine yields an amine-modified epoxy resin with a secondary amino group. Using a secondary amine with a blocked primary amine yields an amine-modified epoxy resin with a primary amino group. For example, to prepare an amine-modified epoxy resin with primary and secondary amino groups, a ketimine in which the primary amino group is blocked with a ketone can be used as the amine compound. After introducing the ketimine into the raw epoxy resin, deblocking produces primary and secondary amino groups. If necessary, a tertiary amine may be used in combination as the amine to react with the oxirane ring.

[0062] Specific examples of primary and secondary amines include butylamine, octylamine, diethylamine, dibutylamine, methylbutylamine, monoethanolamine, diethanolamine, and N-methylethanolamine. Specific examples of secondary amines having blocked primary amines include the ketimine of aminoethylethanolamine and the diketimine of diethylenetriamine. Specific examples of tertiary amines include triethylamine, N,N-dimethylbenzylamine, and N,N-dimethylethanolamine. These may be used alone or in combination of two or more.

[0063] As the amine compound, a combination of 50 to 100 mass % of a secondary amine, 0 to 30 mass % of a secondary amine having a blocked primary amine, and 0 to 20 mass % of a primary amine may be used.

[0064] The number average molecular weight of the amine-modified epoxy resin (A) is, for example, 1,000 to 5,000. When the number average molecular weight is 1,000 or more, solvent resistance and corrosion resistance are further improved. When the number average molecular weight is 5,000 or less, viscosity adjustment of the amine-modified epoxy resin (A) becomes easy, and synthesis proceeds smoothly. In addition, the amine-modified epoxy resin (A) is easily emulsified and dispersed, and handleability is improved. The number average molecular weight of the amine-modified epoxy resin (A) may be 2,000 or more. The number average molecular weight of the amine-modified epoxy resin (A) may be 3,500 or less.

[0065] The amine value of the amine-modified epoxy resin (A) may be 20 to 100 mgKOH / g. When the amine value is 20 mgKOH / g or more, the dispersion stability of the amine-modified epoxy resin (A) in the electrodeposition coating is improved. When the amine value is 100 mgKOH / g or less, the water resistance of the electrodeposition coating film is enhanced. The amine value of the amine-modified epoxy resin (A) may be 80 mgKOH / g or less.

[0066] The hydroxyl value of the amine-modified epoxy resin (A) may be 150 to 650 mgKOH / g. When the hydroxyl value is 150 mgKOH / g or more, the curability and appearance of the electrodeposition coating film are improved. When the hydroxyl value is 650 mgKOH / g or less, the water resistance of the electrodeposition coating film is enhanced. The hydroxyl value of the amine-modified epoxy resin (A) may be 180 mgKOH / g or more. The hydroxyl value of the amine-modified epoxy resin (A) may be 300 mgKOH / g or less.

[0067] The amine-modified epoxy resin (A) may have a number average molecular weight of 1,000 to 5,000, an amine value of 20 to 100 mgKOH / g, and a hydroxyl value of 150 to 650 mgKOH / g, which further improves corrosion resistance.

[0068] Two or more amine-modified epoxy resins having different amine values ​​and / or hydroxyl values ​​may be used in combination as the amine-modified epoxy resin (A). In this case, the average amine value and average hydroxyl value calculated based on the mass ratio of the amine-modified epoxy resins used should be within the above-mentioned ranges.

[0069] The electrodeposition paint may contain other film-forming resins, such as acrylic resins, polyester resins, urethane resins, olefin resins, phenolic resins, and xylene resins.

[0070] As the coating film-forming resin, for example, an amino group-containing acrylic resin and an amino group-containing polyester resin may be used together with the amine-modified epoxy resin (A) as needed.

[0071] Blocked polyisocyanate curing agent (B) The blocked polyisocyanate curing agent (B) (hereinafter sometimes referred to simply as "curing agent (B)") is also a film-forming resin. The curing agent (B) reacts preferentially with the amino groups of the amine-modified epoxy resin (A) and then with the hydroxyl groups to form a crosslinked structure.

[0072] The curing agent (B) is prepared by blocking a polyisocyanate with a blocking agent, for example, by adding the blocking agent dropwise to the polyisocyanate at 40 to 50°C while stirring, optionally in the presence of a curing catalyst (e.g., a tin catalyst).

[0073] The polyisocyanate may include at least one selected from the group consisting of aromatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates. The polyisocyanate may be an aromatic polyisocyanate or an aliphatic polyisocyanate. The polyisocyanate may be an aromatic polyisocyanate.

[0074] Examples of aromatic polyisocyanates include 4,4'-diphenylmethane diisocyanate, tolylene diisocyanate, and xylylene diisocyanate. Examples of aliphatic polyisocyanates include aliphatic diisocyanates such as hexamethylene diisocyanate, tetramethylene diisocyanate, and trimethylhexamethylene diisocyanate. Examples of alicyclic polyisocyanates include alicyclic diisocyanates such as isophorone diisocyanate and 4,4'-methylenebis(cyclohexyl isocyanate).

[0075] In the curing agent (B), the polyisocyanate may form an adduct such as a biuret, uretdione, isocyanurate or allophanate.

[0076] Preferred examples of blocking agents include monohydric alkyl (or aromatic) alcohols such as n-butanol, n-hexyl alcohol, 2-ethylhexanol, lauryl alcohol, phenol carbinol, and methylphenyl carbinol; cellosolves such as ethylene glycol monohexyl ether and ethylene glycol mono 2-ethylhexyl ether; polyether-type diols terminated at both ends such as polyethylene glycol, polypropylene glycol, and polytetramethylene ether glycol phenol; polyester-type polyols terminated at both ends obtained from diols such as ethylene glycol, propylene glycol, and 1,4-butanediol and dicarboxylic acids such as oxalic acid, succinic acid, adipic acid, suberic acid, and sebacic acid; phenols such as para-t-butylphenol and cresol; oxime compounds such as dimethyl ketoxime, methyl ethyl ketoxime, methyl isobutyl ketoxime, methyl amyl ketoxime, and cyclohexanone oxime; and lactams represented by ε-caprolactam and γ-butyrolactam. Among others, the blocking agent may be an oxime compound.

[0077] The blocking rate of the curing agent (B) may be 100%, which improves the storage stability of the electrodeposition coating.

[0078] As the curing agent (B), a combination of a blocked aliphatic diisocyanate and a blocked aromatic diisocyanate may be used.

[0079] As the curing agent, at least one selected from the group consisting of organic curing agents (such as melamine resins and phenolic resins), silane coupling agents and metal curing agents may be used together with the curing agent (B).

[0080] Preparation of resin emulsion (i) The resin emulsion (i) can be prepared as follows: The amine-modified epoxy resin (A) and the curing agent (B) are dissolved in an organic solvent to prepare a solution. After mixing these solutions, the mixture is neutralized with a neutralizing acid.

[0081] Examples of the neutralizing acid include organic acids such as methanesulfonic acid, sulfamic acid, lactic acid, dimethylolpropionic acid, formic acid, acetic acid, etc. The neutralizing acid may be at least one selected from the group consisting of formic acid, acetic acid, and lactic acid.

[0082] The ratio of the equivalent weight of the neutralizing acid to the equivalent weight of the amino groups in the amine-modified epoxy resin (A) (neutralization rate) may be 10 to 100%. When the neutralization rate is 10% or more, the affinity of the amine-modified epoxy resin (A) for water is improved, and the water dispersibility is enhanced. The neutralization rate may be 20% or more. The neutralization rate may be 70% or less. The neutralizing acid is used in an amount that satisfies the above neutralization rate.

[0083] The curing agent (B) is used in an amount sufficient to react with active hydrogen-containing functional groups such as primary amino groups, secondary amino groups or hydroxyl groups in the amine-modified epoxy resin (A) during curing.

[0084] The solid mass ratio (A / B) of the amine-modified epoxy resin (A) to the curing agent (B) may be 90 / 10 to 50 / 50. A / B may be 80 / 20 to 65 / 35. By adjusting A / B, the fluidity and curing speed of the deposited film can be controlled, improving the appearance of the coating film.

[0085] The solid content of the resin emulsion (i) may be 25% by mass or more and 50% by mass or less, 35% by mass or more, or 45% by mass or less.

[0086] Pigment dispersion paste (ii) The pigment dispersion paste (ii) contains a coordination polymer catalyst (C), an inorganic pigment (D), and a pigment dispersing resin (E).

[0087] Inorganic pigments (D) The inorganic pigment (D) is one that is commonly used in electrodeposition paints and is not particularly limited. Examples of the inorganic pigment (D) include color pigments such as titanium white (titanium dioxide), carbon black, and red iron oxide; extender pigments such as kaolin, talc, aluminum silicate, calcium carbonate, mica, and clay; and rust-preventive pigments such as iron phosphate, aluminum phosphate, calcium phosphate, aluminum tripolyphosphate, aluminum phosphomolybdate, and aluminum zinc phosphomolybdate. These pigments may be used alone or in combination of two or more.

[0088] The total content of the inorganic pigment (D) may be 1% by mass or more and 37% by mass or less of the resin solid content of the electrodeposition paint. The content of the inorganic pigment (D) may be 5% by mass or more, 10% by mass or more, 12% by mass or more, 15% by mass or more, or 16% by mass or more. The content of the inorganic pigment (D) may be 30% by mass or less, 27% by mass or less, or 25% by mass or less.

[0089] Pigment dispersing resin (E) The pigment dispersing resin is a resin for dispersing pigments and is dispersed in an aqueous medium before use. For example, a pigment dispersing resin having a cationic group can be used as the pigment dispersing resin. For example, an amine-modified epoxy resin (e) having at least one or more groups selected from a quaternary ammonium group, a tertiary sulfonium group, and a primary amino group can be used as the pigment dispersing resin. Ion-exchanged water or water containing a small amount of alcohol is used as the aqueous solvent.

[0090] The amine-modified epoxy resin (e) can be prepared, for example, by reacting a half-blocked isocyanate with the hydroxyl groups of a raw epoxy resin having hydroxyl groups to introduce blocked isocyanate groups. The introduction of blocked isocyanate groups is carried out by reacting the raw epoxy resin having hydroxyl groups with the half-blocked isocyanate at 140°C for about 1 hour.

[0091] Polyepoxides can be used as the raw material epoxy resin. Polyepoxides have an average of two or more 1,2-epoxy groups per molecule. Examples of polyepoxides include the raw material epoxy resins exemplified for the amine-modified epoxy resin (A).

[0092] Half-blocked isocyanates are prepared by blocking some of the isocyanate groups of a polyisocyanate with a blocking agent. Examples of polyisocyanates include the polyisocyanates exemplified as curing agent (B). Examples of blocking agents include lower aliphatic alkyl monoalcohols having 4 to 20 carbon atoms. Specific examples of blocking agents include butyl alcohol, amyl alcohol, hexyl alcohol, 2-ethylhexyl alcohol, and heptyl alcohol.

[0093] The carbon number of the tertiary amine may be 1 to 6. Specific examples of the tertiary amine include dimethylethanolamine, trimethylamine, triethylamine, dimethylbenzylamine, diethylbenzylamine, N,N-dimethylcyclohexylamine, tri-n-butylamine, diphenethylmethylamine, dimethylaniline, and N-methylmorpholine.

[0094] The neutralizing acid is not particularly limited. Examples of the neutralizing acid include inorganic acids or organic acids such as hydrochloric acid, nitric acid, phosphoric acid, formic acid, acetic acid, and lactic acid. The neutralizing acid may be at least one selected from the group consisting of formic acid, acetic acid, and lactic acid.

[0095] others The electrodeposition paint may contain an organic solvent, such as ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monoethylhexyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, or propylene glycol monophenyl ether.

[0096] The electrodeposition paint may contain additives commonly used in the paint field. Examples of additives include surfactants, viscosity modifiers, anti-repellents, inorganic rust inhibitors, auxiliary complexing agents, buffers, leveling agents, stress relaxation agents, gloss agents, semi-gloss agents, antioxidants, and ultraviolet absorbers. The additives are added during the preparation of the resin emulsion (i) and / or the pigment dispersion paste (ii).

[0097] Formation of cured electrodeposition coating film The cured electrodeposition coating film is formed by a method including immersing an object to be coated in the above-mentioned cationic electrodeposition coating composition to perform electrodeposition coating to form an uncured electrodeposition coating film, and heating the uncured electrodeposition coating film to form a cured electrodeposition coating film on the object to be coated.

[0098] Electrodeposition coating The object to be coated is immersed in a bath containing electrodeposition paint, and a current is passed between the object as the cathode and a separately installed anode, applying a voltage. This causes the components of the electrodeposition paint to deposit on the object, forming a deposit film (uncured electrodeposition coating film).

[0099] The applied voltage may be 50 V or more and 450 V or less. The bath temperature is, for example, 10° C. or more and 45° C. or less. The application time is, for example, 2 minutes or more and 5 minutes or less.

[0100] The substrate to be coated is not particularly limited as long as it has electrical conductivity, and examples of the substrate include cold-rolled steel sheets, hot-rolled steel sheets, stainless steel, electrogalvanized steel sheets, hot-dip galvanized steel sheets, zinc-aluminum alloy-plated steel sheets, zinc-iron alloy-plated steel sheets, zinc-magnesium alloy-plated steel sheets, zinc-aluminum-magnesium alloy-plated steel sheets, aluminum-plated steel sheets, aluminum-silicon alloy-plated steel sheets, and tin-plated steel sheets.

[0101] heating The substrate is then removed from the bath and heated, forming a cured electrodeposition coating. The substrate may be rinsed with water before heating.

[0102] The heating temperature is, for example, 120° C. or higher and 260° C. or lower. The heating temperature may be 140° C. or higher. The heating temperature may be 220° C. or lower. The heating time may be, for example, 10 minutes or higher and 30 minutes or lower.

[0103] The thickness of the cured electrodeposition coating film is, for example, 5 μm or more and 40 μm or less. This provides sufficient corrosion resistance. The thickness of the cured electrodeposition coating film may be 10 μm or more. The thickness of the cured electrodeposition coating film may be 25 μm or less. [Example]

[0104] The present invention will be described in more detail with reference to the following examples, but is not limited thereto. In the examples, "parts" and "%" are by weight unless otherwise specified.

[0105] [Production Example A] Production of amine-modified epoxy resin (A) A mixture of 92 parts of methyl isobutyl ketone (MIBK), 940 parts of bisphenol A epoxy resin (trade name: DER-331J, manufactured by The Dow Chemical Company), 382 parts of bisphenol A, 63 parts of octylic acid, and 2 parts of dimethylbenzylamine was added, and the temperature inside the reaction vessel was maintained at 140°C. The reaction was continued until the epoxy equivalent reached 1110 g / eq, and then the reaction vessel was cooled to 120°C. Next, a mixture of 78 parts of diethylenetriamine diketimine (a methyl isobutyl ketone solution with a solids concentration of 73%) and 92 parts of diethanolamine was added, and the mixture was allowed to react at 120°C for 1 hour to obtain an amine-modified epoxy resin (A).

[0106] [Production Example B1] Production of blocked polyisocyanate curing agent (B1) A reaction vessel was charged with 1,680 parts of hexamethylene diisocyanate (HDI) and 732 parts of MIBK, and the mixture was heated to 60°C. A solution of 346 parts of trimethylolpropane dissolved in 1,067 parts of methyl ethyl keto (MEK) oxime was added dropwise at 60°C over 2 hours. After further heating at 75°C for 4 hours, IR spectroscopy confirmed that the absorption due to the isocyanate group had disappeared, and the mixture was allowed to cool. Then, 27 parts of MIBK was added to obtain a blocked polyisocyanate curing agent (B1) with a solids concentration of 80%.

[0107] [Production Example B2] Production of blocked polyisocyanate curing agent (B2) A reaction vessel was charged with 1,340 parts of 4,4'-diphenylmethane diisocyanate and 277 parts of MIBK, and the mixture was heated to 80°C. A solution of 226 parts of ε-caprolactam in 944 parts of butyl cellosolve was added dropwise at 80°C over 2 hours. After further heating at 100°C for 4 hours, IR spectroscopy confirmed that the absorption due to the isocyanate group had disappeared, and the mixture was allowed to cool. Then, 349 parts of MIBK was added to obtain a blocked isocyanate curing agent (B2) with a solids concentration of 80%.

[0108] [Production Example C1] Production of Coordination Polymer Catalyst (C-1) 29.1 parts of a metal salt (bismuth nitrate pentahydrate) was dissolved in 29.1 parts of N,N-dimethylformamide (DMF). Separately, 8.2 parts of an organic compound (imidazole) was dissolved in 25.4 parts of DMF, and then 0.6 parts of triethylamine was added and stirred for 15 minutes. Next, the imidazole solution was added to the DMF solution containing the metal salt (bismuth nitrate pentahydrate) and stirred at room temperature for 48 hours. The pH was then adjusted to 9.0 with 10 M NaOH solution, and the mixture was filtered through a 1 μm filter. The solid obtained after filtration was dried at 80 °C for 12 hours to obtain the coordination polymer catalyst (C-1).

[0109] [Production Example C2] Production of Coordination Polymer Catalyst (C-2) A coordination polymer catalyst (C-2) was obtained in the same manner as in Production Example C1, except that 14.3 parts of triazole was used as the organic compound.

[0110] [Production Example C3] Production of Coordination Polymer Catalyst (C-3) A coordination polymer catalyst (C-3) was obtained in the same manner as in Production Example C1, except that 14.2 parts of benzimidazole was used as the organic compound.

[0111] [Production Example C4] Production of Coordination Polymer Catalyst (C-4) A coordination polymer catalyst (C-4) was obtained in the same manner as in Production Example C1, except that 16.7 parts of TBD was used as the organic compound.

[0112] [Production Example C5] Production of Coordination Polymer Catalyst (C-5) A coordination polymer catalyst (C-5) was obtained in the same manner as in Production Example C1, except that 17.9 parts of zinc nitrate hexahydrate was used as the metal salt.

[0113] [Production Example C6] Production of Coordination Polymer Catalyst (C-6) A coordination polymer catalyst (C-6) was obtained in the same manner as in Production Example C2, except that 17.9 parts of zinc nitrate hexahydrate was used as the metal salt.

[0114] [Production Example C7] Production of Coordination Polymer Catalyst (C-7) A coordination polymer catalyst (C-7) was obtained in the same manner as in Production Example C3, except that 17.9 parts of zinc nitrate hexahydrate was used as the metal salt.

[0115] [Production Example C8] Production of Coordination Polymer Catalyst (C-8) A coordination polymer catalyst (C-8) was obtained in the same manner as in Production Example C4, except that 17.9 parts of zinc nitrate hexahydrate was used as the metal salt.

[0116] [Production Example C9] Production of Coordination Polymer Catalyst (C-9) A coordination polymer catalyst (C-9) was obtained in the same manner as in Production Example C1, except that 13.9 parts of zirconium nitrate hydrate was used as the metal salt.

[0117] [Production Example C10] Production of Coordination Polymer Catalyst (C-10) A coordination polymer catalyst (C-10) was obtained in the same manner as in Production Example C2, except that 13.9 parts of zirconium nitrate hydrate was used as the metal salt.

[0118] [Production Example C11] Production of Coordination Polymer Catalyst (C-11) The same procedure as in Production Example C3 was repeated except that 13.9 parts of zirconium nitrate hydrate was used as the metal salt. In this manner, the coordination polymer catalyst (C-11) was obtained.

[0119] [Production Example C12] Production of Coordination Polymer Catalyst (C-12) The same procedure as in Production Example C4 was repeated except that 13.9 parts of zirconium nitrate hydrate was used as the metal salt. In the same manner, the coordination polymer catalyst (C-12) was obtained.

[0120] [Production Example C13] Production of Coordination Polymer Catalyst (C-13) A coordination polymer catalyst (C-13) was obtained in the same manner as in Production Example C1, except that 11.7 parts of cesium nitrate was used as the metal salt.

[0121] [Production Example C14] Production of Coordination Polymer Catalyst (C-14) A coordination polymer catalyst (C-14) was obtained in the same manner as in Production Example C2, except that 11.7 parts of cesium nitrate was used as the metal salt.

[0122] [Production Example C15] Production of Coordination Polymer Catalyst (C-15) A coordination polymer catalyst (C-15) was obtained in the same manner as in Production Example C3, except that 11.7 parts of cesium nitrate was used as the metal salt.

[0123] [Production Example C16] Production of Coordination Polymer Catalyst (C-16) A coordination polymer catalyst (C-16) was obtained in the same manner as in Production Example C4, except that 11.7 parts of cesium nitrate was used as the metal salt.

[0124] [Production Example C17] Production of Coordination Polymer Catalyst (C-17) A coordination polymer catalyst (C-17) was obtained in the same manner as in Production Example C1, except that 26.1 parts of cerium nitrate hexahydrate was used as the metal salt.

[0125] [Production Example C18] Production of Coordination Polymer Catalyst (C-18) A coordination polymer catalyst (C-18) was obtained in the same manner as in Production Example C2, except that 26.1 parts of cerium nitrate hexahydrate was used as the metal salt.

[0126] [Production Example C19] Production of Coordination Polymer Catalyst (C-19) A coordination polymer catalyst (C-19) was obtained in the same manner as in Production Example C3, except that 26.1 parts of cerium nitrate hexahydrate was used as the metal salt.

[0127] [Production Example C20] Production of Coordination Polymer Catalyst (C-20) A coordination polymer catalyst (C-20) was obtained in the same manner as in Production Example C4, except that 26.1 parts of cerium nitrate hexahydrate was used as the metal salt.

[0128] [Production Example C21] Production of Coordination Polymer Catalyst (C-21) A coordination polymer catalyst (C-21) was obtained in the same manner as in Production Example C1, except that 26.0 parts of lanthanum nitrate hexahydrate was used as the metal salt.

[0129] [Production Example C22] Production of Coordination Polymer Catalyst (C-22) A coordination polymer catalyst (C-22) was obtained in the same manner as in Production Example C2, except that 26.0 parts of lanthanum nitrate hexahydrate was used as the metal salt.

[0130] [Production Example C23] Production of Coordination Polymer Catalyst (C-23) A coordination polymer catalyst (C-23) was obtained in the same manner as in Production Example C3, except that 26.0 parts of lanthanum nitrate hexahydrate was used as the metal salt.

[0131] [Production Example C24] Production of Coordination Polymer Catalyst (C-24) A coordination polymer catalyst (C-24) was obtained in the same manner as in Production Example C4, except that 26.0 parts of lanthanum nitrate hexahydrate was used as the metal salt.

[0132] [Production Example C25] Production of Coordination Polymer Catalyst (C-25) A coordination polymer catalyst (C-25) was obtained in the same manner as in Production Example C1, except that 26.3 parts of neodymium nitrate hexahydrate was used as the metal salt.

[0133] [Production Example C26] Production of Coordination Polymer Catalyst (C-26) A coordination polymer catalyst (C-26) was obtained in the same manner as in Production Example C2, except that 26.3 parts of neodymium nitrate hexahydrate was used as the metal salt.

[0134] [Production Example C27] Production of Coordination Polymer Catalyst (C-27) A coordination polymer catalyst (C-27) was obtained in the same manner as in Production Example C3, except that 26.3 parts of neodymium nitrate hexahydrate was used as the metal salt.

[0135] [Production Example C28] Production of Coordination Polymer Catalyst (C-28) A coordination polymer catalyst (C-28) was obtained in the same manner as in Production Example C4, except that 26.3 parts of neodymium nitrate hexahydrate was used as the metal salt.

[0136] [Production Example C29] Production of Coordination Polymer Catalyst (C-29) A coordination polymer catalyst (C-29) was obtained in the same manner as in Production Example C1, except that 2.0 parts of imidazole was used as the organic compound.

[0137] [Production Example C30] Production of Coordination Polymer Catalyst (C-30) A coordination polymer catalyst (C-30) was obtained in the same manner as in Production Example C2, except that 3.6 parts of triazole was used as the organic compound.

[0138] [Production Example C31] Production of Coordination Polymer Catalyst (C-31) A coordination polymer catalyst (C-31) was obtained in the same manner as in Production Example C3, except that 3.5 parts of benzimidazole was used as the organic compound.

[0139] [Production Example C32] Production of Coordination Polymer Catalyst (C-32) A coordination polymer catalyst (C-32) was obtained in the same manner as in Production Example C4, except that 4.2 parts of TBD was used as the organic compound.

[0140] [Production Example C33] Production of Coordination Polymer Catalyst (C-33) A coordination polymer catalyst (C-33) was obtained in the same manner as in Production Example C1, except that 20.4 parts of imidazole was used as the organic compound.

[0141] [Production Example C34] Production of Coordination Polymer Catalyst (C-34) A coordination polymer catalyst (C-34) was obtained in the same manner as in Production Example C2, except that 35.7 parts of triazole was used as the organic compound.

[0142] [Production Example C35] Production of Coordination Polymer Catalyst (C-35) A coordination polymer catalyst (C-35) was obtained in the same manner as in Production Example C3, except that 35.4 parts of benzimidazole was used as the organic compound.

[0143] [Production Example C36] Production of Coordination Polymer Catalyst (C-36) A coordination polymer catalyst (C-36) was obtained in the same manner as in Production Example C4, except that 41.8 parts of TBD was used as the organic compound.

[0144] [Production Example C37] Production of Coordination Polymer Catalyst (C-37) A coordination polymer catalyst (C-37) was obtained in the same manner as in Production Example C1, except that 17.9 parts of zinc nitrate hexahydrate was used as the metal salt and 2.0 parts of imidazole was used as the organic compound.

[0145] [Production Example C38] Production of Coordination Polymer Catalyst (C-38) A coordination polymer catalyst (C-38) was obtained in the same manner as in Production Example C2, except that 17.9 parts of zinc nitrate hexahydrate was used as the metal salt and 3.6 parts of triazole was used as the organic compound.

[0146] [Production Example C39] Production of Coordination Polymer Catalyst (C-39) A coordination polymer catalyst (C-39) was obtained in the same manner as in Production Example C3, except that 17.9 parts of zinc nitrate hexahydrate was used as the metal salt and 3.5 parts of benzimidazole was used as the organic compound.

[0147] [Production Example C40] Production of Coordination Polymer Catalyst (C-40) A coordination polymer catalyst (C-40) was obtained in the same manner as in Production Example C4, except that 17.9 parts of zinc nitrate hexahydrate was used as the metal salt and 4.2 parts of TBD was used as the organic compound.

[0148] [Production Example C41] Production of Coordination Polymer Catalyst (C-41) A coordination polymer catalyst (C-41) was obtained in the same manner as in Production Example C1, except that 17.9 parts of zinc nitrate hexahydrate was used as the metal salt and 20.4 parts of imidazole was used as the organic compound.

[0149] [Production Example C42] Production of Coordination Polymer Catalyst (C-42) A coordination polymer catalyst (C-42) was obtained in the same manner as in Production Example C2, except that 17.9 parts of zinc nitrate hexahydrate was used as the metal salt and 35.7 parts of triazole was used as the organic compound.

[0150] [Production Example C43] Production of Coordination Polymer Catalyst (C-43) A coordination polymer catalyst (C-43) was obtained in the same manner as in Production Example C3, except that 17.9 parts of zinc nitrate hexahydrate was used as the metal salt and 35.4 parts of benzimidazole was used as the organic compound.

[0151] [Production Example C44] Production of Coordination Polymer Catalyst (C-44) A coordination polymer catalyst (C-44) was obtained in the same manner as in Production Example C4, except that 17.9 parts of zinc nitrate hexahydrate was used as the metal salt and 41.8 parts of TBD was used as the organic compound.

[0152] [Production Example C45] Production of Coordination Polymer Catalyst (C-45) A coordination polymer catalyst (C-45) was obtained in the same manner as in Production Example C1, except that 9.9 parts of 2-methylimidazole was used as the organic compound.

[0153] [Production Example C46] Production of Coordination Polymer Catalyst (C-46) A coordination polymer catalyst (C-46) was obtained in the same manner as in Production Example C1, except that 11.5 parts of 2-ethylimidazole was used as the organic compound.

[0154] [Production Example C47] Production of Coordination Polymer Catalyst (C-47) A coordination polymer catalyst (C-47) was obtained in the same manner as in Production Example C1, except that 1.6 parts of imidazole was used as the organic compound.

[0155] [Production Example C48] Production of Coordination Polymer Catalyst (C-48) A coordination polymer catalyst (C-48) was obtained in the same manner as in Production Example C1, except that 24.5 parts of imidazole was used as the organic compound.

[0156] [Comparative Production Example C49] Production of Coordination Polymer Catalyst (C-49) A coordination polymer catalyst containing an S atom (C-49) was obtained in the same manner as in Production Example C1, except that 20.1 parts of 2-mercaptobenzthiazole was used as the organic compound.

[0157] [Production Example E] Production of pigment dispersing resin (E) Preparation of 2-ethylhexanol half-blocked isophorone diisocyanate A reaction vessel equipped with a stirrer, a condenser, a nitrogen inlet, and a thermometer was charged with 222.0 parts of isophorone diisocyanate (IPDI) and diluted with 39.1 parts of MIBK. 0.2 parts of dibutyltin dilaurate was added. After heating to 50°C, 131.5 parts of 2-ethylhexanol were added dropwise over 2 hours under stirring in a dry nitrogen atmosphere to obtain 2-ethylhexanol half-blocked IPDI (solids concentration 90.0% by mass).

[0158] Preparation of quaternizing agents To a reaction vessel were added 87.2 parts of dimethylethanolamine, 117.6 parts of a 75% aqueous lactic acid solution, and 39.2 parts of ethylene glycol mono-n-butyl ether in that order, and the mixture was stirred at 65°C for 30 minutes to prepare a quaternizing agent.

[0159] ·Manufacturing pigment dispersion resin A reaction vessel was charged with 10.0 parts of bisphenol A epoxy resin (trade name: DER-331J, manufactured by The Dow Chemical Company) and 289.6 parts of bisphenol A, and the mixture was reacted at 150-160°C for 1 hour under a nitrogen atmosphere. After cooling to 120°C, 498.8 parts of the previously prepared 2-ethylhexanol half-blocked IPDI (MIBK solution) was added. The reaction mixture was stirred at 110-120°C for 1 hour. Subsequently, 463.4 parts of ethylene glycol mono-n-butyl ether was added, and the mixture was cooled to 85-95°C. 196.7 parts of the previously prepared quaternizing agent was then added. The reaction mixture was maintained at 85-95°C until the acid value reached 1. Then, 964 parts of deionized water was added to obtain a pigment dispersion resin (amine-modified epoxy resin (e)) (solids concentration: 50% by mass).

[0160] [Preparation Example 1] Preparation of pigment dispersion paste Ion-exchanged water and 60 parts of a pigment dispersion resin (amine-modified epoxy resin (e)) were mixed and stirred at room temperature for 1 hour. Then, 8.2 parts of a coordination polymer catalyst (C-1), 1 part of carbon, 40 parts of titanium dioxide, and 59 parts of Satenton (calcined kaolin) were added, and the mixture was stirred at 40°C for 1 hour using a sand mill to obtain a pigment dispersion paste (solid concentration: 47% by mass).

[0161] [Preparation Example 2] Preparation of resin emulsion (Em) 350 parts (solids) of amine-modified epoxy resin (A) were mixed with 75 parts (solids) of blocked polyisocyanate curing agent (B1) and 75 parts (solids) of blocked polyisocyanate curing agent (B2). Ethylene glycol mono-2-ethylhexyl ether was added to the mixture at 3% (15 parts) of the solids. Formic acid was then added to a neutralization rate of 40% to neutralize the amine-modified epoxy resin (A), followed by slow dilution with ion-exchanged water. MIBK was then removed under reduced pressure until the solids content reached 40%, yielding a resin emulsion (Em).

[0162] [Example 1] 516 parts of ion-exchanged water, 393 parts of resin emulsion (Em), and 91 parts of pigment dispersion paste were added to a stainless steel container, followed by aging at 40°C for 16 hours to obtain a cationic electrodeposition coating composition.

[0163] [Examples 2 to 54, Comparative Example 1] Cationic electrodeposition coating compositions were obtained in the same manner as in Example 1, except that the types of coordination polymer catalysts were as shown in Tables 1 to 9. The contents of the coordination polymer catalyst (C) shown in the tables are values ​​relative to 100 parts by mass of the resin solid content of the cationic electrodeposition coating composition.

[0164] Comparative Example 2 A cationic electrodeposition coating composition was obtained in the same manner as in Example 1, except that a metal compound (bismuth nitrate pentahydrate) and an amine compound (imidazole) were added instead of the coordination polymer catalyst.

[0165] Comparative Example 3 A cationic electrodeposition coating composition was obtained in the same manner as in Example 1, except that a metal compound (zinc nitrate hexahydrate) and an amine compound (imidazole) were added instead of the coordination polymer catalyst.

[0166] Comparative Example 4 A cationic electrodeposition coating composition was obtained in the same manner as in Example 1, except that only a metal compound (bismuth nitrate pentahydrate) was added instead of the coordination polymer catalyst.

[0167] Comparative Example 5 A cationic electrodeposition coating composition was obtained in the same manner as in Example 1, except that only an amine compound (imidazole) was added instead of the coordination polymer catalyst.

[0168] [evaluation] The cationic electrodeposition coating compositions obtained in the Examples and Comparative Examples were evaluated as follows.

[0169] (1) Curability Using the electrodeposition paint immediately after preparation, a coating film was deposited on a tin plate whose mass had been measured in advance, so that the dried coating film had a thickness of 20 μm. The plate was then heated at 160°C for 15 minutes to form a cured electrodeposition coating film on the tin plate. After measuring the mass of the coated plate, it was immersed in acetone and refluxed for 6 hours, and then dried at 105°C for 20 minutes. The mass of the coated plate after drying was measured, and the gel fraction was calculated using the following formula (1).

[0170] Gel fraction (%) = (W2 - W0) / (W1 - W0) × 100 In the formula, W0 is the mass of the tin plate, W1 is the mass of the coated plate after curing, and W2 is the mass of the coated plate after immersion in acetone.

[0171] Separately, after preparation, the electrodeposition paint was left to stand at 40°C for 30 days, and a coated plate was prepared in the same manner as above, and the gel fraction was determined. The higher the gel fraction, the higher the curability. A gel fraction of 85% or more can be evaluated as having excellent curability.

[0172] (2) Catalyst stability The difference between the gel fraction immediately after the preparation and the gel fraction after standing for 40 days was determined and evaluated according to the following criteria: A rating of C or higher indicates that the catalyst has excellent stability.

[0173] (Evaluation criteria) A: The difference in gel fraction is 2% or less B: The difference in gel fraction is more than 2% and less than 4% C: The difference in gel fraction is more than 4% and less than 9% D: The difference in gel fraction is 9% or more

[0174] (3) Corrosion resistance A cold-rolled steel sheet (JIS G3141, SPCC-SD) was degreased by immersion in Surf Cleaner EC90 (Nippon Paint) at 50°C for 2 minutes. Next, the cold-rolled steel sheet was immersed in Surf Fine GL 1 (Nippon Paint) at room temperature for 30 seconds, and then in Surfdyne 6350 (Nippon Paint) at 35°C for 2 minutes. The sheet was then rinsed with deionized water.

[0175] A required amount of 2-ethylhexyl glycol was added to the electrodeposition paint so that the thickness of the cured electrodeposition coating film would be 15 μm. After the above cold-rolled steel sheets were all immersed in the diluted electrodeposition paint, voltage application was immediately initiated. The voltage was increased for 30 seconds, reached 180 V, and then maintained for 150 seconds, depositing an uncured electrodeposition coating film on the cold-rolled steel sheet. The resulting uncured electrodeposition coating film was heat-cured at 140°C for 15 minutes to obtain a coated plate with a cured electrodeposition coating film.

[0176] A cross-cut was made in the cured electrodeposition coating with a cutter knife so that the cut reached the cold-rolled steel plate. The coated plate was then subjected to a 35°C salt spray test for 1000 hours in accordance with JIS Z-2371. The maximum width of rust or blisters on one side of the cut was measured and evaluated according to the following criteria. A rating of C or higher indicates excellent corrosion resistance.

[0177] (Evaluation criteria) A: 2.0mm or less B: More than 2.0mm and less than 3.5mm C: More than 3.5mm and less than 5.0mm D: More than 5.0mm

[0178] (4) Coating appearance (surface roughness Ra) For the coated panels prepared in the same manner as above, the arithmetic mean roughness (Ra) of the roughness curve of the cured electrodeposition coating was measured using an evaluation type surface roughness measuring instrument (Mitsutoyo, SURFTEST SJ-201P) according to a method conforming to JIS-B0601. Seven measurements were taken using a sample with a 2.5 mm wide cutoff (5 sections), and the Ra value (μm) was obtained by averaging the top and bottom erase results. The obtained average Ra value was evaluated according to the following criteria. A rating of C or higher was considered to be excellent in appearance.

[0179] (Evaluation criteria) A: Average Ra value is less than 0.20 μm B: Average Ra value is 0.20 μm or more and less than 0.25 μm C: Average Ra value is 0.25 μm or more and less than 0.30 μm D: Average Ra value is 0.30 μm or more

[0180] [Table 1]

[0181] [Table 2]

[0182] [Table 3]

[0183] [Table 4]

[0184] [Table 5]

[0185] [Table 6]

[0186] [Table 7]

[0187] [Table 8]

[0188] [Table 9]

[0189] In order to solve the above problems, the present invention provides the following aspects. [1] Amine-modified epoxy resin (A), a blocked polyisocyanate curing agent (B), and a coordination polymer catalyst (C) having, as a constituent unit, a metal complex containing a metal ion (C1) and an organic ligand (C2); the metal ion (C1) contains an ion of at least one metal element selected from the group consisting of Bi, Zn, Zr, Cs, and lanthanoids; The organic ligand (C2) is represented by the following general formula (1): [ka] (In the formula, R11, R21, and R31 each independently represent a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, a nitro group, a halogen atom, or an amino group.) an amine compound (C2-1) represented by the formula: The following general formula (2): [ka] (In the formula, R12 and R22 each independently represent a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, a nitro group, a halogen atom, or an amino group.) an amine compound (C2-2) represented by the formula: The following general formula (3): [ka] (In the formula, R13 and R23 each independently represent a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, a nitro group, a halogen atom, or an amino group.) an amine compound (C2-3) represented by the formula: The following general formula (4): [ka] (In the formula, R14, R24, R34, R44, and R54 each independently represent a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, a nitro group, a halogen atom, or an amino group.) and an amine compound (C2-4) represented by the formula: The following general formula (5): [ka] (In the formula, R15 to R125 each independently represent a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, a nitro group, a halogen atom, or an amino group.) A cationic electrodeposition coating composition comprising at least one selected from the group consisting of amine compounds (C2-5) represented by the following formula: [2] The cationic electrodeposition coating composition of [1] above, which contains the coordination polymer catalyst (C) in an amount of 0.1 to 3 parts by mass per 100 parts by mass of the resin solid content of the cationic electrodeposition coating composition. [3] The cationic electrodeposition coating composition of the above [1] or [2], wherein in the coordination polymer catalyst (C), the molar ratio of the metal ion (C1) to the organic ligand (C2) (metal ion:organic ligand) is 1:0.5 to 1:5. [4] The cationic electrodeposition coating composition of any one of the above [1] to [3], wherein in the coordination polymer catalyst (C), the molar ratio of the metal ion (C1) to the organic ligand (C2) (metal ion:organic ligand) is 1:1 to 1:2.8. [5] The cationic electrodeposition coating composition according to any one of the above [1] to [4], wherein the coordination polymer catalyst (C) is a solid. [6] The cationic electrodeposition coating composition according to any one of the above [1] to [5], further comprising an inorganic pigment (D). [7] The cationic electrodeposition coating composition according to any one of the above [1] to [6], wherein the blocked polyisocyanate curing agent (B) comprises a reaction product of a blocking agent and an aromatic polyisocyanate. [8] immersing an object to be coated in any one of the cationic electrodeposition coating compositions [1] to [7] above to perform electrodeposition coating, thereby forming an uncured electrodeposition coating film; and A method for forming a cured electrodeposition coating film, comprising heating the uncured electrodeposition coating film to form a cured electrodeposition coating film on the substrate. [Industrial Applicability]

[0190] The present invention can provide a cured electrodeposition coating film having excellent corrosion resistance and appearance, and is particularly suitable for electrodeposition coating of automobile bodies.

Claims

1. amine-modified epoxy resin (A), a blocked polyisocyanate curing agent (B), and a coordination polymer catalyst (C) having, as a constituent unit, a metal complex containing a metal ion (C1) and an organic ligand (C2); the metal ion (C1) contains an ion of at least one metal element selected from the group consisting of Bi, Zn, Zr, Cs, and lanthanoids; The organic ligand (C2) is represented by the following general formula (1): 【Chemistry 1】 (In the formula, R11, R21, and R31 each independently represent a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, a nitro group, a halogen atom, or an amino group.) an amine compound (C2-1) represented by the formula: The following general formula (2): 【Chemistry 2】 (In the formula, R12 and R22 each independently represent a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, a nitro group, a halogen atom, or an amino group.) an amine compound (C2-2) represented by the formula: The following general formula (3): 【Transformation 3】 (In the formula, R13 and R23 each independently represent a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, a nitro group, a halogen atom, or an amino group.) an amine compound (C2-3) represented by the formula: The following general formula (4): 【Chemistry 4】 (In the formula, R14, R24, R34, R44, and R54 each independently represent a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, a nitro group, a halogen atom, or an amino group.) and an amine compound (C2-4) represented by the formula: The following general formula (5): 【Transformation 5】 (In the formula, R15 to R125 each independently represent a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, a nitro group, a halogen atom, or an amino group.) A cationic electrodeposition coating composition comprising at least one amine compound (C2-5) selected from the group consisting of:

2. 2. The cationic electrodeposition coating composition according to claim 1, wherein the coordination polymer catalyst (C) is contained in an amount of 0.1 to 3 parts by mass per 100 parts by mass of the resin solid content of the cationic electrodeposition coating composition.

3. 3. The cationic electrodeposition coating composition according to claim 1, wherein in the coordination polymer catalyst (C), the molar ratio of the metal ion (C1) to the organic ligand (C2) (metal ion:organic ligand) is 1:0.5 to 1:

5.

4. 3. The cationic electrodeposition coating composition according to claim 1, wherein in the coordination polymer catalyst (C), the molar ratio of the metal ion (C1) to the organic ligand (C2) (metal ion:organic ligand) is 1:1 to 1:2.

8.

5. 3. The cationic electrodeposition coating composition according to claim 1, wherein the coordination polymer catalyst (C) is a solid.

6. The cationic electrodeposition coating composition according to claim 1 or 2, further comprising an inorganic pigment (D).

7. 3. The cationic electrodeposition coating composition according to claim 1, wherein the blocked polyisocyanate curing agent (B) comprises a reaction product of a blocking agent and an aromatic polyisocyanate.

8. immersing an object to be coated in the cationic electrodeposition coating composition according to claim 1 to carry out electrodeposition coating to form an uncured electrodeposition coating film; a step of heating the uncured electrodeposition coating film to form a cured electrodeposition coating film on the substrate.

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