Cationic electrodeposition coating composition

Abstract

To provide a cationic electro-deposition coating composition which is excellent in corrosion resistance and finishing properties of an edge part and a plane part even in a thin film, and a coated article which is excellent in various coated film performances.SOLUTION: A cationic electro-deposition coating composition contains an amino group-containing epoxy resin (A) and a blocked polyisocyanate compound (B), further contains 0.1-40 mass% of epoxy resin crosslinked particles (C) and 0.1-40 mass% of clay mineral (D) based on the total mass of solid contents of the amino group-containing epoxy resin (A) and the blocked polyisocyanate compound (B), and has a number average molecular weight of the epoxy resin crosslinked particles (C) of 100,000 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a cationic electrodeposition coating composition comprising an amino group-containing epoxy resin, a blocked polyisocyanate compound, and epoxy resin crosslinked particles. [Background technology]

[0002] Cationic electrodeposition coating compositions have excellent coating workability and the coating films they form have good corrosion resistance, and therefore are widely used as primer coatings for conductive metal products such as automobile bodies, automobile parts, electrical equipment parts, and other equipment, which require these properties.

[0003] When a substrate has sharp edges, the coating film at the edges may become thin during heat curing, resulting in poor corrosion protection. Therefore, when coating substrates with edges, there is a need for a method to improve the corrosion protection of the edges.

[0004] Patent Document 1 discloses that the electrodeposition paint contains a polyacrylamide resin as a method for improving the rust prevention properties of edges. It is believed that the inclusion of this resin can control shrinkage caused by heating or inhibit the decrease in edge covering due to flow caused by interaction with the coating film components. However, since the paint contains a highly polar, soluble resin, the corrosion prevention properties of flat surfaces can sometimes be inferior.

[0005] Patent Documents 2 and 3 disclose that electrodeposition paint contains a cationic microgel dispersion (epoxy viscosity modifier). By including the resin, it is possible to suppress the flow of the electrodeposition coating film due to heat flow at the edge, but there are cases where sufficient corrosion protection at the edge cannot be obtained under severe corrosion conditions. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2017-214572 [Patent Document 2] Japanese Patent Application Publication No. 2018-159032 [Patent Document 3] Japanese Patent Application Publication No. 7-268063 Summary of the Invention [Problem to be solved by the invention]

[0007] The problem to be solved by the invention is to provide a cationic electrodeposition coating composition which has excellent corrosion resistance and finish on edge and flat surfaces even when the coating is thin, and to provide a coated article which has these excellent coating film properties. [Means for solving the problem]

[0008] As a result of intensive research into solving the above-mentioned problems, the inventors have found that the above-mentioned problems can be solved by a cationic electrodeposition coating composition containing an amino group-containing epoxy resin (A), a blocked polyisocyanate compound (B), epoxy resin crosslinked particles (C) and a clay mineral (D), and have thus completed the present invention.

[0009] That is, the present invention provides the following cationic electrodeposition coating composition and coated articles obtained by the method for coating a cationic electrodeposition coating film. Item 1. A cationic electrodeposition coating composition containing an amino group-containing epoxy resin (A) and a blocked polyisocyanate compound (B), further containing 0.1 to 40 mass% of crosslinked epoxy resin particles (C) and 0.1 to 40 mass% of a clay mineral (D) based on the total mass of the solid contents of the amino group-containing epoxy resin (A) and the blocked polyisocyanate compound (B), wherein the number average molecular weight of the crosslinked epoxy resin particles (C) measured by the following method is less than 100,000. <Method for measuring number average molecular weight> The epoxy resin crosslinked particles (C) were diluted with N,N'-dimethylformamide to a solids concentration of 1% by mass and allowed to stand at room temperature for 24 hours. Insoluble components were then removed by filtration, and the number average molecular weight was measured using gel permeation chromatography (GPC). Item 2. The cationic electrodeposition coating composition according to Item 1, wherein the proportion of insoluble components (crosslinked components) in the epoxy resin crosslinked particles (C) is 10 mass % or more when measured by the following method. <Method for measuring the proportion of insoluble components (cross-linked components)> The epoxy resin crosslinked particles (C) were diluted with N,N'-dimethylformamide to a solids concentration of 1% by mass and allowed to stand at room temperature for 24 hours. The insoluble components (crosslinked components) were then filtered using a Myshori filter for GPC (pore size: 0.2 microns). The residue was dried at 130°C for 3 hours, and the solid mass of the residue was measured. The proportion (mass%) of the insoluble components (crosslinked components) was calculated using the following formula: Proportion of insoluble components (cross-linked components) (mass%) = A / B x 100 A: Solid mass of filtration residue B: Mass of epoxy resin crosslinked particle (C) solution diluted to 1% by mass solids / 100 Item 3. A cationic electrodeposition coating composition according to Item 1 or 2, wherein the epoxy resin crosslinked particles (C) are a reaction product of an amino group-containing epoxy resin (C-1) and an epoxy resin (C-2). Item 4. A cationic electrodeposition coating composition according to Item 3, wherein the amino group-containing epoxy resin (C-1) is a reaction product of an epoxy resin (C-1-1) and an amine compound (C-1-2), and the amine compound (C-1-2) contains a ketiminated amine compound (C-1-2-1) in an amount of 2 mol % or more and less than 40 mol %. Item 5. The cationic electrodeposition coating composition according to Item 1 or 2, wherein the epoxy resin crosslinked particles (C) contain a reaction product of an amino group-containing epoxy resin (C-1) and a crosslinking agent other than the epoxy resin (C-2). Item 6. The cationic electrodeposition coating composition according to any one of Items 1 to 5, wherein the crosslinked epoxy resin particles (C) have a polymer ratio (peak area for molecular weights of 100,000 or more) of less than 40%. Item 7. The cationic electrodeposition coating composition according to any one of Items 1 to 6, wherein the number average molecular weight of the epoxy resin crosslinked particles (C) is 9,000 or less. Item 8. The cationic electrodeposition coating composition according to any one of Items 1 to 7, wherein the clay mineral (D) is contained in an amount of 0.1 to 30 mass % based on the total mass of the solid contents of the amino group-containing epoxy resin (A) and the blocked polyisocyanate compound (B), and has at least one shape selected from the group consisting of plate-like, scale-like, layer-like, rod-like, needle-like, fibrous, and chain-like. Item 9. The cationic electrodeposition coating composition according to Item 8, wherein the clay mineral (D) has at least one shape selected from the group consisting of rod-like, needle-like, fibrous, and chain-like shapes. Item 10. The cationic electrodeposition coating composition according to any one of Items 1 to 9, wherein the clay mineral (D) is dispersed using a shear disperser. Item 11. A coating method for electrodeposition coating by immersing a metal substrate in an electrodeposition coating bath containing the cationic electrodeposition coating composition according to any one of items 1 to 10. Item 12. A method for producing a coated article, comprising forming a coating film by the coating method according to Item 11, and then heat-curing the coating film. [Effects of the Invention]

[0010] The cationic electrodeposition coating composition of the present invention has excellent corrosion resistance and finish on edges and flat surfaces, and is particularly good in finish and corrosion resistance when used in thin films, and exhibits good corrosion resistance on edges even under severe corrosive conditions. Automobile bodies coated with the product of the present invention are less susceptible to corrosion deterioration even when driven in an environment where snow-melting salt is sprayed. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention relates to a cationic electrodeposition coating composition containing an amino group-containing epoxy resin (A), a blocked polyisocyanate compound (B), epoxy resin crosslinked particles (C) and a clay mineral (D). This will be explained in detail below.

[0012] Amino group-containing epoxy resin (A) Examples of the amino group-containing epoxy resin (A) that can be used in the present invention include (1) adducts of an epoxy resin with primary mono- and polyamines, secondary mono- and polyamines, or mixed primary and secondary polyamines (see, for example, U.S. Pat. No. 3,984,299); (2) adducts of an epoxy resin with secondary mono- and polyamines having a ketiminated primary amino group (see, for example, U.S. Pat. No. 4,017,438); and (3) reaction products obtained by etherification of an epoxy resin with a hydroxy compound having a ketiminated primary amino group (see, for example, JP-A-59-43013).

[0013] The epoxy resin (A-1) used in the production of the amino group-containing epoxy resin (A) is a compound having at least one, preferably two or more, epoxy groups per molecule, and suitably has a number average molecular weight of at least 300, preferably 400 to 4,000, and more preferably 800 to 2,500, and an epoxy equivalent of at least 160, preferably 180 to 2,500, and more preferably 400 to 1,500. Examples of such epoxy resins that can be used include those obtained by reacting a polyphenol compound with an epihalohydrin (e.g., epichlorohydrin).

[0014] Examples of polyphenol compounds used to form the epoxy resin include bis(4-hydroxyphenyl)-2,2-propane [bisphenol A], bis(4-hydroxyphenyl)methane [bisphenol F], bis(4-hydroxycyclohexyl)methane [hydrogenated bisphenol F], 2,2-bis(4-hydroxycyclohexyl)propane [hydrogenated bisphenol A], 4,4'-dihydroxybenzophenone, bis(4-hydroxyphenyl)-1,1-ethane, bis(4-hydroxyphenyl)-1,1-isobutane, bis(4-hydroxy-3-tert-butyl-phenyl)-2,2-propane, bis(2-hydroxynaphthyl)methane, tetra(4-hydroxyphenyl)-1,1,2,2-ethane, 4,4'-dihydroxydiphenyl sulfone, phenol novolac, and cresol novolac.

[0015] Also, epoxy resins obtained by reacting polyphenol compounds with epihalohydrins are As the resin, an epoxy resin derived from bisphenol A and represented by the following formula (1) is particularly suitable. Furthermore, it is also possible to use an epoxy resin having a high molecular weight and / or a multifunctionality obtained by reacting an epoxy resin of the following formula (1) with a polyphenol compound, and among these, bisphenol A is preferred as the polyphenol compound.

[0016] [ka]

[0017] Here, n=0 to 8 is preferred.

[0018] Commercially available examples of such epoxy resins include those sold by Mitsubishi Chemical Corporation under the trade names jER828EL, jER1002, jER1004, and jER1007.

[0019] The epoxy resin (A-1) may be an epoxy resin containing a polyalkylene oxide chain in its resin skeleton. Typically, such an epoxy resin can be obtained by (α) reacting an epoxy resin having at least one, preferably two or more, epoxy groups with an alkylene oxide or polyalkylene oxide to introduce a polyalkylene oxide chain, or (β) reacting the polyphenol compound with a polyalkylene oxide having at least one, preferably two or more, epoxy groups to introduce a polyalkylene oxide chain. Alternatively, an epoxy resin already containing a polyalkylene oxide chain may be used (see, for example, the specification of JP-A-8-337750). The alkylene group in the polyalkylene oxide chain is preferably an alkylene group having 2 to 8 carbon atoms, more preferably an ethylene group, a propylene group or a butylene group, and particularly preferably a propylene group. From the viewpoint of improving paint stability, finish and corrosion resistance, the content of the polyalkylene oxide chain is generally within the range of 1.0 to 15 mass%, preferably 2.0 to 9.5 mass%, more preferably 3.0 to 8.0 mass%, as the content of the polyalkylene oxide as a constituent component, based on the solid mass of the amino group-containing epoxy resin.

[0020] Examples of the primary mono- and polyamines, secondary mono- and polyamines, or mixed primary and secondary polyamines used in the production of the amino group-containing epoxy resin (A) above (1) include mono- or di-alkylamines such as monomethylamine, dimethylamine, monoethylamine, diethylamine, monoisopropylamine, diisopropylamine, monobutylamine, and dibutylamine; alkanolamines such as monoethanolamine, diethanolamine, mono(2-hydroxypropyl)amine, and monomethylaminoethanol; and alkylenepolyamines such as ethylenediamine, propylenediamine, butylenediamine, hexamethylenediamine, diethylenetriamine, and triethylenetetramine.

[0021] Examples of the secondary mono- and polyamines having ketiminated primary amino groups used in the production of the amino group-containing epoxy resin (A) described above in (2) include ketimines produced by reacting a ketone compound with diethylenetriamine, dipropylenetriamine, or the like, among the mixed primary and secondary polyamines used in the production of the amine-added epoxy resin described above in (1).

[0022] Examples of the hydroxy compound having a ketiminated primary amino group used in the production of the amino group-containing epoxy resin (A) described above in (3) include hydroxyl group-containing ketimines obtained by reacting a compound having a primary amino group and a hydroxyl group, such as monoethanolamine or mono(2-hydroxypropyl)amine, among the primary mono- and polyamines, secondary mono- and polyamines, or mixed primary and secondary polyamines used in the production of the amino group-containing epoxy resin (A) described above in (1), with a ketone compound.

[0023] The amine value of such an amino group-containing epoxy resin (A) is preferably in the range of 30 to 80 mg KOH / g resin solid content, more preferably 40 to 70 mg KOH / g resin solid content, from the viewpoint of improving water dispersibility and anticorrosion properties.

[0024] Furthermore, the amino group-containing epoxy resin (A) can be modified with a modifier, if necessary. Such modifiers are not particularly limited as long as they are resins or compounds reactive with epoxy resins. For example, polyols, polyether polyols, polyester polyols, polyamidoamines, polycarboxylic acids, fatty acids, polyisocyanate compounds, compounds obtained by reacting polyisocyanate compounds, lactone compounds such as ε-caprolactone, acrylic monomers, compounds obtained by polymerizing acrylic monomers, xylene formaldehyde compounds, and epoxy compounds can also be used as modifiers. These modifiers can be used alone or in combination of two or more. Among these, it is preferable to use at least one saturated and / or unsaturated fatty acid as the modifier, particularly from the viewpoint of throwing power and / or corrosion prevention. Fatty acids that can be used are preferably long-chain fatty acids having 8 to 22 carbon atoms, such as caprylic acid, capric acid, octanoic acid, nonanoic acid, decanoic acid, lauric acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, oleic acid, linoleic acid, and linolenic acid. Among these, long-chain fatty acids having 10 to 20 carbon atoms are more preferable, and long-chain fatty acids having 13 to 18 carbon atoms are even more preferable.

[0025] The addition reaction of the above amine compound and modifier to the epoxy resin (A-1) can usually be carried out in an appropriate solvent at a temperature of about 80 to about 170°C, preferably about 90 to about 150°C, for about 1 to 6 hours, preferably about 1 to 5 hours.

[0026] Examples of the solvent include hydrocarbons such as toluene, xylene, cyclohexane, and n-hexane; esters such as methyl acetate, ethyl acetate, and butyl acetate; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and methyl amyl ketone; amides such as dimethylformamide and dimethylacetamide; alcohols such as methanol, ethanol, n-propanol, and isopropanol; and ether alcohol compounds such as ethylene glycol monobutyl ether and diethylene glycol monoethyl ether; and mixtures thereof.

[0027] The proportion of the modifier used is not strictly limited and can be varied as appropriate depending on the intended use of the coating composition, but from the viewpoint of improving the finish and corrosion resistance, it is generally appropriate that the proportion be in the range of 0 to 50 mass %, preferably 3 to 30 mass %, and more preferably 6 to 20 mass %, based on the solid mass of the amino group-containing epoxy resin.

[0028] Blocked polyisocyanate compound (B) The blocked polyisocyanate compound (B) is an addition reaction product of a polyisocyanate compound and an isocyanate blocking agent in approximately stoichiometric amounts. The polyisocyanate compound used in the blocked polyisocyanate compound (B) may be a known compound, such as aromatic, aliphatic, or alicyclic polyisocyanate compounds such as tolylene diisocyanate, xylylene diisocyanate, phenylene diisocyanate, diphenylmethane-2,2'-diisocyanate, diphenylmethane-2,4'-diisocyanate, diphenylmethane-4,4'-diisocyanate, crude MDI (polymethylene polyphenylisocyanate), bis(isocyanatomethyl)cyclohexane, tetramethylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate, and isophorone diisocyanate; cyclized polymers or biuret products of these polyisocyanate compounds; or combinations thereof.

[0029] In particular, aromatic polyisocyanate compounds such as tolylene diisocyanate, xylylene diisocyanate, phenylene diisocyanate, diphenylmethane-2,4'-diisocyanate, diphenylmethane-4,4'-diisocyanate, crude MDI, etc. (preferably crude MDI, etc.) are more preferred for their corrosion prevention properties.

[0030] On the other hand, the isocyanate blocking agent is added to the isocyanate groups of the polyisocyanate compound to block them, and the blocked polyisocyanate compound produced by the addition is stable at room temperature, but it is desirable that when heated to the baking temperature of the coating film (usually about 100 to about 200°C), the blocking agent dissociates to regenerate free isocyanate groups.

[0031] Examples of blocking agents used in the blocked polyisocyanate compound (B) include oxime-based compounds such as methyl ethyl ketoxime and cyclohexanone oxime; phenol-based compounds such as phenol, para-t-butylphenol, and cresol; alcohol-based compounds such as n-butanol, 2-ethylhexanol, phenyl carbinol, methylphenyl carbinol, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, ethylene glycol, and propylene glycol; lactam-based compounds such as ε-caprolactam and γ-butyrolactam; and active methylene-based compounds such as dimethyl malonate, diethyl malonate, ethyl acetoacetate, methyl acetoacetate, and acetylacetone (preferably, alcohol-based compounds).

[0032] Epoxy resin crosslinked particles (C) The epoxy resin crosslinked particles (C) that can be used in the cationic electrodeposition coating composition of the present invention generally contain 0.1 to 40 mass %, preferably 1 to 30 mass %, and more preferably 5 to 15 mass %, of the epoxy resin crosslinked particles (C) based on the total mass of the solid contents of the resin (A) and compound (B). Furthermore, the upper limit of the number average molecular weight measured under the conditions described below is typically less than 100,000, preferably 9,000 or less, and more preferably 5,000 or less, and the lower limit is typically 100 or more, preferably 150 or more, and more preferably 200 or more, from the viewpoint of finish and corrosion resistance of the edge portion.

[0033] <Method for measuring number average molecular weight> The epoxy resin crosslinked particles (C) were diluted with N,N'-dimethylformamide to a solids concentration of 1% by mass and allowed to stand at room temperature for 24 hours. The insoluble components (crosslinked components) were then filtered out using a Myshori filter for GPC (pore size: 0.2 microns), and the number average molecular weight was measured using gel permeation chromatography (GPC) as described below. In gel permeation chromatography (GPC) measurements, the presence of insoluble components (in the present invention, cross-linked components that are not dissolved in the solvent) can cause clogging within the device and lead to breakdowns, so it is common to prepare samples by filtering using a filter.

[0034] <Gel permeation chromatography (GPC)> Apparatus: "HLC8120GPC" (product name, manufactured by Tosoh Corporation), Columns: four columns: "TSKgel G-4000HXL", "TSKgel G-3000HXL", "TSKgel G-2500HXL" and "TSKgel G-2000HXL" (product names, all manufactured by Tosoh Corporation); Mobile phase: N,N'-dimethylformamide, Conditions: measurement temperature 40℃, flow rate 1mL / min, Detector: RI.

[0035] In this specification, the number average molecular weight and weight average molecular weight are values ​​calculated by converting the retention time (retention volume) measured using the gel permeation chromatograph (GPC) into the molecular weight of polystyrene using the retention time (retention volume) of a standard polystyrene of known molecular weight measured under the same conditions.

[0036] The epoxy resin crosslinked particles (C) have a poor finish when their molecular weight increases. Therefore, in the molecular weight measurement data measured by gel permeation chromatography (GPC), the peak area (polymer ratio) at a molecular weight of 100,000 or more is preferably less than 40%, more preferably less than 30%, of the total peak area. In this specification, the peak area corresponding to a molecular weight of 100,000 or more is sometimes referred to as the "polymer ratio."

[0037] The proportion of the insoluble component (crosslinked component) in the epoxy resin crosslinked particles (C) is preferably 10% by mass or more, more preferably 10 to 90% by mass, even more preferably 10 to 60% by mass, and particularly preferably 15 to 45% by mass, from the viewpoints of corrosion resistance of the edge and flat surface portions and finish quality. If the insoluble components are too high, the finish quality will deteriorate, and if the insoluble components are too low, the corrosion resistance of the edge portion will deteriorate. Therefore, by keeping the content within this range, it is possible to achieve both corrosion resistance and finish quality at the edge portion. The proportion of the insoluble component (crosslinked component) can be calculated by the following method. <Method for measuring the proportion of insoluble components (cross-linked components)> The crosslinked epoxy resin particles (C) were diluted with N,N'-dimethylformamide to a solids concentration of 1% by mass and allowed to stand at room temperature for 24 hours. The insoluble components were then filtered using a Myshori filter for GPC (pore size: 0.2 microns). The insoluble residue was dried at 130°C for 3 hours, and the solid mass of the residue was measured. The proportion (mass%) of the insoluble components (crosslinked components) can be calculated using the following formula: Proportion of insoluble components (cross-linked components) (mass%) = A / B x 100 A: Solid mass of filtration residue B: Solid mass of epoxy resin crosslinked particle (D2-1) solution before filtration

[0038] The epoxy resin crosslinked particles (C) that can be used in the cationic electrodeposition coating composition of the present invention are not particularly limited as long as they are particles obtained by crosslinking an epoxy resin with a crosslinking agent. Examples of crosslinking agents include compounds having one or more reactive functional groups such as epoxy groups, isocyanate groups, hydroxyl groups, carboxyl groups, amino groups, and silyl groups. Preferred examples include one or more compounds selected from the group consisting of epoxy resins, polyisocyanate compounds, polyol compounds, polycarboxylic acid compounds, and polyamine compounds. Furthermore, the crosslinking agent may be one that crosslinks the epoxy resin by a Michael addition reaction. For example, an amino group-containing epoxy resin is produced by reacting an epoxy resin with an amine compound, the amino group-containing epoxy resin is neutralized with an acid compound, the resulting resin is dispersed in an aqueous solvent, and the resulting dispersion is mixed and reacted with a polyfunctional epoxy resin and / or a polyisocyanate compound to produce crosslinked epoxy resin particles. Alternatively, the epoxy resin may have at least one functional group reactive with the epoxy group, and the crosslinked particles may be obtained by reacting them.

[0039] As one embodiment of the epoxy resin crosslinked particles (C), the production process includes the following steps: step (I) of producing an amino group-containing epoxy resin (C-1) by reacting an epoxy resin (C-1-1) with an amine compound (C-1-2); step (II) of neutralizing the amino group-containing epoxy resin (C-1) with an acid compound and dispersing it in an aqueous solvent; and step (III) of mixing and reacting the resulting dispersion with an epoxy resin (C-2) to obtain the epoxy resin crosslinked particles (C). The epoxy resin (C-2) may be replaced with a polyisocyanate compound or other crosslinkable component.

[0040] <Process (I)> The step of producing the amino group-containing epoxy resin (C-1) obtained by reacting the epoxy resin (C-1-1) with the amine compound (C-1-2) can be carried out by the same production method as that for the amino group-containing epoxy resin (A) described above.

[0041] As the epoxy resin (C-1-1), the same as the epoxy resin (A-1) described above can be used, and among these, the epoxy resin of the formula (1) derived from bisphenol A can be preferably used. Furthermore, an epoxy resin obtained by reacting the epoxy resin of the formula (1) with a polyphenol compound to increase the molecular weight and / or to make it multifunctional can be preferably used, and the polyphenol compound is preferably bisphenol A. The number average molecular weight of the epoxy resin (C-1-1) is preferably 400 to 5,000, more preferably 700 to 3,000.

[0042] As the amine compound (C-1-2), the amine compounds listed for the amino group-containing epoxy resin (A) can be suitably used, but it is particularly preferred to include a ketiminated amine compound (C-1-2-1), and particularly preferred to include a secondary mono- or polyamine (C-1-2-2) having a ketiminated primary amino group. Examples of the secondary mono- and polyamines (C-1-2-2) having the ketiminated primary amino group include ketimines of amine compounds represented by the following formula (2). Specific examples include diketimines of diethylenetriamine, dipropylenetriamine, dibutylenetriamine, bis(hexamethylene)triamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexaamine.

[0043] [ka]

[0044] (In the formula, R1 and R2 are hydrocarbon groups having 1 to 8 carbon atoms and may be different or the same, and n is an integer of 1 to 5.) The ketiminated amine compound (C-1-2-1) is contained in the amine compound (C-1-2) in an amount of preferably 0.1 mol % or more and less than 80 mol %, more preferably 1 mol % or more and less than 50 mol %, even more preferably 2 mol % or more and less than 40 mol %, and particularly preferably 5 mol % or more and less than 30 mol %. In this specification, the content of the ketiminated amine compound (C-1-2-1) may be referred to as the "ketimine compound content."

[0045] The ketimine-blocked primary amino group of the amine compound (C-1-2-1) is hydrolyzed in the water dispersion step (II) described below to reveal a primary amino group. Then, in step (III), the primary amino group reacts with the epoxy group of the epoxy resin (C-2), resulting in a polymer-polymerization and / or crosslinking reaction. Therefore, by adjusting the amount of the amine compound (C-1-2-1) within the above range, the molecular weight, particle size, and / or degree of crosslinking (proportion of insoluble components) of the epoxy resin crosslinked particles (C) can be optimized.

[0046] <Process (II)> The amino group-containing epoxy resin (C-1) obtained in the above step (I) is then neutralized with an acid compound and further dispersed in an aqueous solvent to obtain a dispersion. Here, the aqueous solvent refers to a solvent containing water and other solvents that can be contained as necessary. Examples of other solvents include ester-based solvents, ketone-based solvents, amide-based solvents, alcohol-based solvents, and ether alcohol-based solvents, or mixtures thereof. As the acid compound, any known acid compound can be used without any particular limitation, and among them, organic acids are preferred, and formic acid, lactic acid, acetic acid, or a mixture thereof is more preferred. The neutralization equivalent of the acid compound is preferably 0.2 to 1.5 equivalents, more preferably 0.5 to 1.0 equivalents, per equivalent of amino group. In addition to the acid compound, additives such as an emulsifier may also be contained.

[0047] The dispersion of the resin (C-1) in the aqueous solvent may be carried out by adding the aqueous solvent to the neutralized amino group-containing epoxy resin (C-1) while stirring, or by adding the neutralized amino group-containing epoxy resin (C-1) to the aqueous solvent while stirring, or by mixing the aqueous solvent and the neutralized amino group-containing epoxy resin (C-1) and then stirring. The dispersion temperature is preferably less than 100°C, more preferably 40 to 99°C, and even more preferably 50 to 95°C. The resin solid content concentration of the dispersion is preferably from 5 to 80% by mass, more preferably from 10 to 50% by mass.

[0048] <Process (III)> The dispersion obtained in the above step (II) can then be mixed with a crosslinking agent such as an epoxy resin (C-2) and further reacted to obtain epoxy resin crosslinked particles (C). The epoxy resin (C-2) may be the same as the epoxy resin (A-1) described above, and preferably used is an epoxy resin of the formula (1) derived from bisphenol A. The epoxy equivalent of the epoxy resin (C-2) is preferably 180 to 2,000, more preferably 180 to 500.

[0049] In the above reaction step, the primary amino group of the amino group-containing epoxy resin (C-1) from which the ketimine block has been removed by hydrolysis reacts with the epoxy group of the epoxy resin (C-2), resulting in a polymerization and / or crosslinking reaction. The equivalent ratio of the primary amino group to the epoxy group is preferably 0.5 to 2.0 equivalents, more preferably 0.7 to 1.5 equivalents, of the epoxy group per equivalent of the primary amino group. The reaction temperature is preferably less than 100°C, more preferably 40 to 99°C, and even more preferably 50 to 95°C. Furthermore, during or after the polymerizing and / or crosslinking reaction, a solvent removal step can be carried out by reducing the pressure at a temperature of 40 to 99°C.

[0050] The volume-average particle diameter of the crosslinked epoxy resin particles (C) obtained in step (III) is generally within the range of 30 nm to 1,000 nm, preferably greater than 100 nm, more preferably greater than 150 nm, even more preferably greater than 200 nm, and particularly preferably greater than 300 nm, from the viewpoints of corrosion resistance at the edges and flat surfaces and finish quality, and is preferably smaller than 800 nm, more preferably smaller than 700 nm, even more preferably smaller than 600 nm, and particularly preferably smaller than 500 nm. The volume average particle size can be measured using a laser diffraction / scattering measurement device, and the particle sizes herein were measured using a Microtrac UPA250 (product name, manufactured by Nikkiso Co., Ltd., particle size distribution measurement device). The amine value of the resin crosslinked particles (C) is preferably within a range of 25 to 200 mgKOH / g, and more preferably within a range of 50 to 180 mgKOH / g. By adjusting the content within the above range, the dispersibility of the particles in the aqueous solvent and the water resistance of the coating film are excellent.

[0051] Clay Minerals (D) The clay mineral (D) that can be used in the cationic electrodeposition coating composition of the present invention is typically contained in an amount of 0.1 to 40 mass %, preferably 1 to 25 mass %, and more preferably 3 to 15 mass %, based on the total mass of the solid contents of the resin (A) and compound (B).

[0052] Clay minerals (D) are the main components of clay, including layered silicate minerals (phyllosilicates), calcite, dolomite, feldspars, quartz, zeolites, and others with chain structures (attapulgite, sepiolite, etc.), fibrous structures (palygorskite, etc.), and those without a clear crystalline structure (allophane). Clay minerals include silica, magnesium, iron, potassium, and sodium extracted from clay layers, and also include refined clay. Refined clay is clay that has had its impurities dissolved and removed using acid or other methods. Kaolin clay, containing kaolinite (chemical formula: Al2O3·2SiO2·2H2O2), is commonly used in paint applications.

[0053] The clay mineral (D) of the present invention preferably contains at least one clay mineral (D2) other than clay (D1) (usually 0.1 to 40 mass%, preferably 1 to 25 mass%, more preferably 3 to 15 mass%), and more preferably contains at least one clay mineral (D2) other than clay in combination with clay (D1) (usually 0.1 to 40 mass%, preferably 1 to 25 mass%, more preferably 3 to 15 mass%).

[0054] The shape of the clay mineral (D2) other than the clay is preferably at least one selected from the group consisting of plate-like, scaly, layer-like, rod-like, chain-like, needle-like, and fibrous shapes, but it is particularly preferable to include a clay mineral other than layer-like shapes, and it is more preferable to include a clay mineral having at least one shape selected from the group consisting of rod-like, needle-like, fibrous, and chain-like shapes.

[0055] The clay mineral (D2) is preferably organically treated. The organic treatment is not particularly limited, but is generally carried out using an alkyl quaternary ammonium compound to hydrophobize the surface of the clay mineral, thereby improving the dispersion stability of the resulting clay mineral.

[0056] The average particle size of the clay mineral is preferably 0.1 to 30 μm, more preferably 0.2 to 20 μm, and even more preferably 0.3 to 10 μm.

[0057] The average particle size of the clay mineral can be measured by laser diffraction (volume basis). The average particle size of the clay mineral is measured based on primary particles. However, to minimize the influence of secondary particles, which are aggregates of primary particles, the particle size is measured after ultrasonic re-dispersion for approximately 3 to 5 minutes (dissolving the secondary particles, which are aggregates of primary particles, and separating them back into primary particles). This minimizes the influence of secondary particles, which are aggregates of primary particles, and allows the average particle size to be measured for something consisting almost entirely of primary particles. Therefore, the average particle size of the clay mineral in this invention is the volume-based average particle size of the primary particles of the clay mineral.

[0058] Since the clay mineral (D2) is destroyed by media dispersion (dispersion using a ball mill or the like), it is preferable to disperse the clay mineral (D2) in a resin or solvent using a shear-type disperser and then mix it into the coating material, and / or to add the clay mineral (D2) to the coating material while stirring the coating material using a shear-type disperser. Examples of the shear-type disperser include, but are not limited to, a disper, a homomixer, and a homogenizer.

[0059] The clay mineral (D2) may be mixed into a coating material by, for example, adding it to an aqueous dispersion of the amino group-containing epoxy resin (A) and the blocked polyisocyanate compound (B) when the aqueous dispersion is produced; adding it to a pigment paste together with a pigment and a dispersing resin when the pigment paste is produced; or adding it to a coating material in which the aqueous dispersion and the pigment paste are mixed while stirring. Any of these methods may be suitably used.

[0060] Cationic electrodeposition coating composition The proportions of the amino group-containing epoxy resin (A) and the blocked polyisocyanate compound (B) in the cationic electrodeposition coating composition of the present invention are preferably within the ranges of 5 to 95 mass %, preferably 50 to 80 mass %, of component (A) and 5 to 95 mass %, preferably 20 to 50 mass %, of component (B), based on the total mass of the solid contents of components (A) and (B), in order to obtain coated articles with good paint stability, excellent finish, and corrosion resistance. A ratio outside these ranges is undesirable, as it may impair either the paint properties or the coating film performance. As mentioned above, the cationic electrodeposition coating composition of the present invention also contains component (C) and component (D).

[0061] The method for producing the cationic electrodeposition coating composition of the present invention is not particularly limited, but for example, the composition can be obtained by thoroughly mixing the above-mentioned resin (A) and compound (B) with various additives such as surfactants and surface conditioners, as necessary, to prepare a compounded resin, which is then dispersed in water, and then thoroughly mixing this with epoxy resin crosslinked particles (C), a pigment dispersion paste, water, an organic solvent, a neutralizer, etc. The method for adding the clay mineral (D) is as described above. As the neutralizing agent, any known organic acid can be used without any particular limitation, and among them, formic acid, lactic acid, or a mixture thereof is preferred.

[0062] The pigment dispersion paste is a pigment such as a color pigment, an anti-rust pigment, or an extender pigment that has been dispersed into fine particles in advance. For example, the pigment dispersion paste can be prepared by blending a pigment dispersing resin, a neutralizing agent, and a pigment, and dispersing the mixture in a dispersing mixer such as a ball mill, a sand mill, or a pebble mill.

[0063] As the pigment dispersing resin, any known resin can be used without any particular limitation, and examples thereof include epoxy resins or acrylic resins having a hydroxyl group and a cationic group, surfactants, tertiary amine-type epoxy resins, quaternary ammonium salt-type epoxy resins, tertiary sulfonium salt-type epoxy resins, tertiary amine-type acrylic resins, quaternary ammonium salt-type acrylic resins, and tertiary sulfonium salt-type acrylic resins.

[0064] As the pigment, any known pigment can be used without any particular limitation, and examples of pigments that can be added include coloring pigments such as titanium oxide, carbon black, and red iron oxide; extender pigments such as mica, baryta, calcium carbonate, and silica; and rust-preventive pigments such as aluminum phosphomolybdate, aluminum tripolyphosphate, and zinc oxide (zinc white).

[0065] Furthermore, for the purpose of corrosion inhibition or rust prevention, a bismuth compound may be contained, such as bismuth oxide, bismuth hydroxide, basic bismuth carbonate, bismuth nitrate, bismuth silicate, or organic acid bismuth.

[0066] Furthermore, for the purpose of improving the curability of the coating film, organic tin compounds such as dibutyltin dibenzoate, dioctyltin oxide, and dibutyltin oxide can be used. By using (increasing the amount of) and / or micronizing the above-mentioned anti-rust pigments such as zinc oxide (zinc white) and / or bismuth compounds, it is possible to improve the curability of the coating film without containing these organic tin compounds. The blending amount of these pigments is preferably within the range of 1 to 100 parts by mass, particularly 10 to 50 parts by mass, per 100 parts by mass of the total resin solids content of resin (A) and compound (B).

[0067] Paint film formation method The present invention provides a method for forming a cationic electrodeposition coating film, which comprises the steps of immersing a substrate in an electrodeposition bath containing the above-mentioned cationic electrodeposition coating composition, and passing a current through the substrate using it as a cathode.

[0068] The substrates to be coated with the cationic electrodeposition coating composition of the present invention include automobile bodies, motorcycle parts, household appliances, other appliances, etc., and are not particularly limited as long as they are made of metal.

[0069] Examples of metal steel sheets to be coated include cold-rolled steel sheets, galvannealed steel sheets, electrogalvanized steel sheets, electrolytic zinc-iron double-layer plated steel sheets, organic composite plated steel sheets, Al materials, Mg materials, and the like, as well as these metal sheets whose surfaces have been cleaned by alkaline degreasing or the like, as necessary, and then subjected to surface treatments such as phosphate conversion treatment and chromate treatment.

[0070] The cationic electrodeposition coating composition can be applied to the surface of the desired substrate by cationic electrodeposition coating. The cationic electrodeposition method generally involves preparing a bath containing the cationic electrodeposition coating composition, which has been diluted with deionized water or the like to a solids concentration of approximately 5 to 40% by mass, preferably 10 to 25% by mass, and further adjusted to a pH of 4.0 to 9.0, preferably 5.5 to 7.0. The bath temperature is typically adjusted to 15 to 35°C, and a voltage load of 100 to 400 V, preferably 150 to 350 V, is applied to the substrate as the cathode at least once, preferably once. After electrodeposition coating, the substrate is typically thoroughly washed with ultrafiltrate (UF filtrate), reverse osmosis water (RO water), industrial water, pure water, or the like to remove any excess cationic electrodeposition coating.

[0071] The thickness of the electrodeposition coating is not particularly limited, but can generally be within the range of 5 to 60 μm, preferably 10 to 35 μm, based on the dried coating. The bake drying of the coating is carried out by heating the electrodeposition coating using drying equipment such as an electric hot air dryer or a gas hot air dryer at a surface temperature of 110 to 200°C, preferably 140 to 180°C, for 10 to 180 minutes, preferably 20 to 50 minutes. A cured coating can be obtained by the bake drying. [Example]

[0072] The present invention will be described in more detail below with reference to Production Examples, Examples, and Comparative Examples, but the present invention is not limited thereto. In each example, "parts" means parts by mass, and "%" means % by mass.

[0073] Preparation of amino group-containing epoxy resin (A) Manufacturing Example 1 Into a flask equipped with a stirrer, a thermometer, a nitrogen inlet tube, and a reflux condenser, 1,200 parts of jER828EL (trade name, epoxy resin manufactured by Japan Epoxy Resins Co., Ltd., epoxy equivalent 190, number average molecular weight 350), 500 parts of bisphenol A, and 0.2 parts of dimethylbenzylamine were added, and the mixture was allowed to react at 130°C until the epoxy equivalent reached 850. Next, 160 parts of diethanolamine and 65 parts of a ketimine compound of diethylenetriamine and methyl isobutyl ketone were added, and the mixture was allowed to react at 120°C for 4 hours. After that, 480 g of ethylene glycol monobutyl ether was added to obtain an amino group-containing epoxy resin A-1 solution with a solids content of 80%. The amino group-containing epoxy resin A-1 had an amine value of 59 mgKOH / g and a number average molecular weight of 2,100.

[0074] Production of blocked polyisocyanate compound (B) Manufacturing Example 2 Into a reaction vessel, 270 parts of Cosmonate M-200 (trade name, manufactured by Mitsui Chemicals, Inc., crude MDI, NCO group content 31.3%) and 127 parts of methyl isobutyl ketone were added and heated to 70° C. 236 parts of ethylene glycol monobutyl ether was added dropwise over 1 hour, and then the temperature was raised to 100° C. Sampling was performed over time while maintaining this temperature, and infrared absorption spectroscopy confirmed that the absorption of unreacted isocyanate groups had disappeared, yielding a blocked polyisocyanate compound B-1 with a resin solids content of 80%.

[0075] Manufacture of pigment dispersion resins Manufacturing Example 3 A flask equipped with a stirrer, thermometer, dropping funnel, and reflux condenser was charged with 1010 parts of jER828EL (trade name, epoxy resin manufactured by Japan Epoxy Resins Co., Ltd., epoxy equivalent weight 190, number average molecular weight 350), 390 parts of bisphenol A, 240 parts of PLACCEL 212 (trade name, polycaprolactone diol manufactured by Daicel Chemical Industries, Ltd., weight average molecular weight approximately 1250), and 0.2 parts of dimethylbenzylamine, and the mixture was reacted at 130°C until the epoxy equivalent reached approximately 1090. Next, 134 parts of dimethylethanolamine and 150 parts of a 90% lactic acid aqueous solution were added, and the mixture was reacted at 90°C until the epoxy groups disappeared. Next, propylene glycol monomethyl ether was added to adjust the solids content, resulting in a pigment dispersion resin containing a quaternary ammonium salt group with a solids content of 60%.

[0076] Pigment dispersion paste manufacturing Manufacturing Example 4-1 8.3 parts (solids content 5 parts) of the pigment dispersion resin containing a quaternary ammonium base and having a solids content of 60% obtained in Production Example 3, 14.5 parts of titanium oxide, 7 parts of refined clay, 0.3 parts of carbon black, 2 parts of bismuth hydroxide, and 20.3 parts of deionized water were added and dispersed in a ball mill for 20 hours to obtain a pigment dispersion paste P-1 having a solids content of 55%.

[0077] Manufacturing Example 4-2 8.3 parts (solids content: 5 parts) of the pigment dispersion resin containing a quaternary ammonium base and having a solids content of 60% obtained in Production Example 3, 21.5 parts of titanium oxide, 0.3 parts of carbon black, 2 parts of bismuth hydroxide, and 20.3 parts of deionized water were added and dispersed in a ball mill for 20 hours to obtain a pigment dispersion paste P-2 having a solids content of 55%.

[0078] Preparation of epoxy resin crosslinked particles (C) Manufacturing Example 5 A reaction vessel equipped with a stirrer, thermometer, dropping funnel, and reflux condenser was charged with 527 parts of jER828EL, 160 parts of bisphenol A, and 0.1 parts of dimethylbenzylamine. The temperature inside the reaction vessel was maintained at 160°C, and the reaction was continued until the epoxy equivalent reached 490 g / mol. The temperature inside the reaction vessel was then cooled to 140°C, and 1.7 parts of dimethylbenzylamine was added. The reaction was continued until the epoxy equivalent reached 890 g / mol. After that, 220 parts of methyl butyl ketone was added, and the temperature inside the reaction vessel was cooled to 100°C. A mixture of 45 parts of N-methylethanolamine and 45 parts of diethylenetriamine diketimine (ketimine compound content: 22 mol%) was then added, and the mixture was allowed to react at 115°C for 1 hour to obtain an amino-containing epoxy resin solution. 204 parts of the obtained amino group-containing epoxy resin solution was added to a new reaction vessel, and the temperature inside the reaction vessel was maintained at 90°C. Next, 16 parts of 88% lactic acid was added to neutralize the acid, and 664 parts of deionized water was added to dilute and disperse the solution. Next, 16 parts of a jER828EL solution adjusted to an 80% solids content with propylene glycol monomethyl ether was added, and the reaction was carried out at 90°C for 3 hours. After that, methyl isobutyl ketone was removed under reduced pressure, and the mixture was diluted with deionized water to obtain a solution of epoxy resin crosslinked particles (C-1) with a solids content of 18%.

[0079] Manufacturing Example 6 A reaction vessel equipped with a stirrer, thermometer, dropping funnel, and reflux condenser was charged with 478 parts of jER828EL, 238 parts of bisphenol A, and 0.1 parts of dimethylbenzylamine. The temperature inside the reaction vessel was maintained at 160°C and the reaction was continued until the epoxy equivalent reached 1540 g / mol. Next, 233 parts of methyl butyl ketone was added while the temperature inside the reaction vessel was cooled to 100°C. A mixture of 23 parts of N-methylethanolamine and 28 parts of diethylenetriamine diketimine (ketimine compound content: 25 mol%) was then added, and the mixture was allowed to react at 115°C for 1 hour to obtain an amino group-containing epoxy resin solution. 217 parts of the obtained amino group-containing epoxy resin solution was added to a new reaction vessel, and the temperature inside the reaction vessel was maintained at 90° C. Next, 10 parts of 88% lactic acid was added to neutralize the acid, and 662 parts of deionized water was added to dilute and disperse the solution. Next, 11 parts of jER828EL solution prepared as an 80% solids solution with propylene glycol monomethyl ether was added, and the mixture was allowed to react at 90°C for 3 hours. After that, methyl isobutyl ketone was removed under reduced pressure, and the mixture was diluted with deionized water to obtain a solution of epoxy resin crosslinked particles (C-2) with a solids content of 18%.

[0080] Manufacturing Example 7 A reaction vessel equipped with a stirrer, thermometer, dropping funnel, and reflux condenser was charged with 472 parts of jER828EL, 253 parts of bisphenol A, and 0.1 parts of dimethylbenzylamine. The temperature inside the reaction vessel was maintained at 160°C and the reaction was continued until the epoxy equivalent reached 2450 g / mol. Next, 235 parts of methyl butyl ketone was added while the temperature inside the reaction vessel was cooled to 100°C. A mixture of 16 parts of N-methylethanolamine and 24 parts of diethylenetriamine diketimine (ketimine compound content: 30 mol%) was then added, and the mixture was allowed to react at 115°C for 1 hour to obtain an amino group-containing epoxy resin solution. 220 parts of the obtained amino group-containing epoxy resin solution was added to a new reaction vessel, and the temperature inside the reaction vessel was maintained at 90° C. Next, 7 parts of 88% lactic acid was added to neutralize the acid, and 662 parts of deionized water was added to dilute and disperse the solution. Next, 11 parts of jER828EL solution prepared as an 80% solids solution with propylene glycol monomethyl ether was added, and the mixture was allowed to react at 90°C for 3 hours. After that, the methyl isobutyl ketone was removed under reduced pressure, and the mixture was diluted with deionized water to obtain a solution of epoxy resin crosslinked particles (C-3) with a solids content of 18%.

[0081] Manufacturing Example 8 A reaction vessel equipped with a stirrer, thermometer, dropping funnel, and reflux condenser was charged with 472 parts of jER828EL, 253 parts of bisphenol A, and 0.1 parts of dimethylbenzylamine. The temperature inside the reaction vessel was maintained at 160°C and the reaction was continued until the epoxy equivalent reached 2450 g / mol. Next, 230 parts of methyl butyl ketone was added while the temperature inside the reaction vessel was cooled to 100°C. A mixture of 13 parts of N-methylethanolamine and 32 parts of diethylenetriamine diketimine (ketimine compound content: 40 mol%) was then added, and the mixture was allowed to react at 115°C for 1 hour to obtain an amino group-containing epoxy resin solution. 214 parts of the obtained amino group-containing epoxy resin solution was added to a new reaction vessel, and the temperature inside the reaction vessel was maintained at 90° C. Then, 6 parts of 88% lactic acid was added to neutralize the acid, and 662 parts of deionized water was added to dilute and disperse the solution. Next, 18 parts of jER828EL solution prepared as an 80% solids solution with propylene glycol monomethyl ether was added, and the mixture was allowed to react at 90°C for 3 hours. After that, methyl isobutyl ketone was removed under reduced pressure, and the mixture was diluted with deionized water to obtain a solution of epoxy resin crosslinked particles (C-4) with a solids content of 18%.

[0082] Manufacturing Example 9 A reaction vessel equipped with a stirrer, thermometer, dropping funnel, and reflux condenser was charged with 477 parts of jER828EL, 237 parts of bisphenol A, and 0.1 parts of dimethylbenzylamine. The temperature inside the reaction vessel was maintained at 160°C and the reaction was continued until the epoxy equivalent reached 1540 g / mol. Next, 223 parts of methyl butyl ketone was added while the temperature inside the reaction vessel was cooled to 100°C. A mixture of 19 parts of N-methylethanolamine and 44 parts of diethylenetriamine diketimine (ketimine compound content: 40 mol%) was then added, and the mixture was allowed to react at 115°C for 1 hour to obtain an amino group-containing epoxy resin solution. 210 parts of the obtained amino group-containing epoxy resin solution was added to a new reaction vessel, and the temperature inside the reaction vessel was maintained at 90° C. Next, 11 parts of 88% lactic acid was added to neutralize the acid, and 663 parts of deionized water was added to dilute and disperse the solution. Next, 16 parts of jER828EL solution prepared as a 80% solids solution with propylene glycol monomethyl ether was added, and the mixture was allowed to react at 90°C for 3 hours. After that, the methyl isobutyl ketone was removed under reduced pressure, and the mixture was diluted with deionized water to obtain a solution of epoxy resin crosslinked particles (C-5) with a solids content of 18%.

[0083] Manufacturing Example 10 A reaction vessel equipped with a stirrer, thermometer, dropping funnel, and reflux condenser was charged with 470 parts of jER828EL, 252 parts of bisphenol A, and 0.1 parts of dimethylbenzylamine. The temperature inside the reaction vessel was maintained at 160°C and the reaction was continued until the epoxy equivalent reached 2450 g / mol. Next, 226 parts of methyl butyl ketone was added while the temperature inside the reaction vessel was cooled to 100°C. A mixture of 3 parts of diethylenetriamine, 9 parts of N-methylethanolamine, and 39 parts of diethylenetriamine diketimine (ketimine compound content: 50 mol%) was then added, and the mixture was allowed to react at 115°C for 1 hour to obtain an amino-containing epoxy resin solution. 211 parts of the obtained amino group-containing epoxy resin solution was added to a new reaction vessel, and the temperature inside the reaction vessel was maintained at 90° C. Next, 9 parts of 88% lactic acid was added to neutralize the acid, and 663 parts of deionized water was added to dilute and disperse the solution. Next, 18 parts of jER828EL solution prepared as an 80% solids solution with propylene glycol monomethyl ether was added, and the mixture was allowed to react at 90°C for 3 hours. After that, the methyl isobutyl ketone was removed under reduced pressure, and the mixture was diluted with deionized water to obtain a solution of epoxy resin crosslinked particles (C-6) with a solids content of 18%.

[0084] Manufacturing Example 11 A reaction vessel equipped with a stirrer, a thermometer, a dropping funnel, and a reflux condenser was charged with 1,023 parts of DER-331J (trade name, bisphenol A-type epoxy resin manufactured by The Dow Chemical Company), 365 parts of a bisphenol A-ethylene oxide adduct, 297 parts of bisphenol A, and 88.7 parts of methyl isobutyl ketone, and the mixture was heated to 140°C under a nitrogen atmosphere. 1.4 parts benzyldimethylamine was added and the reaction mixture was allowed to exotherm to about 185°C and refluxed to remove water, then cooled to 160°C, held for 30 minutes, further cooled to 145°C and 4.2 parts benzyldimethylamine was added. The reaction was continued at 145°C until the Gardner-Holdt viscosity (measured by dissolving in 50% resin solids in 2-methoxypropanol) was O to P. At this point, the reaction mixture was cooled to 125°C and a mixture of 131 parts diethylenetriamine diketimine (60 mole % ketimine content) and 85.2 parts N-methylethanolamine was added. The mixture was heated to 140°C, cooled to 125°C, and kept at this temperature for 1 hour to obtain an amino group-containing epoxy resin solution. After 1 hour, the amino group-containing epoxy resin was dispersed in a solvent consisting of 227.7 parts of 88% lactic acid and 1293 parts of deionized water, and then further diluted with deionized water to a solids content of 31%. Then, 2258.1 parts of the dispersion obtained above and 1510.8 parts of deionized water were mixed and stirred, and a mixed solution of 71.7 parts of DER-331J (trade name, bisphenol A type epoxy resin manufactured by Dow Chemical Company) and 17.9 parts of methyl isobutyl ketone was added with stirring, and the mixture was then heated to 90°C and kept at that temperature for 3 hours. At the end of the incubation, the reaction mixture was diluted with 598.7 parts of deionized water, methyl isobutyl ketone was removed under reduced pressure, and deionized water was added to obtain a solution of epoxy resin crosslinked particles (C-7) with a solids content of 18%.

[0085] Manufacturing Example 12 A reaction vessel equipped with a stirrer, a thermometer, a dropping funnel, and a reflux condenser was charged with 940 parts of DER-331J (trade name, bisphenol A-type epoxy resin manufactured by The Dow Chemical Company), 388 parts of bisphenol A, and 2 parts of dimethylbenzylamine, and the temperature inside the reaction vessel was maintained at 140°C. The reaction was carried out until the epoxy equivalent reached 800 g / eq, and then the temperature inside the reaction vessel was cooled to 120°C. Next, a mixture of 258 parts (ketimine compound content: 50 mol%) of diethylenetriamine diketimine (a methyl isobutyl ketone solution with a solid content of 73%), 21 parts of N-methylethanolamine, and 45 parts of diethylenetriamine was added, and the mixture was allowed to react at 120°C for 1 hour to obtain an amino group-containing epoxy resin solution. Next, after cooling to 90°C, deionized water and acetic acid were added to neutralize the acid so that the neutralization rate of the amino groups in the amino group-containing epoxy resin was 18%, and deionized water was added to dilute and disperse the mixture so that the solid content was 20%. Thereafter, 188 parts of DER-331J (trade name, bisphenol A-type epoxy resin manufactured by Dow Chemical Company) was added, and the mixture was allowed to react for 3 hours at 90° C. Methyl isobutyl ketone was removed under reduced pressure, and deionized water was added to obtain a solution of epoxy resin crosslinked particles (C-8) with a solids content of 18%.

[0086] Manufacturing Example 13 A reaction vessel equipped with a stirrer, thermometer, dropping funnel, and reflux condenser was charged with 413 parts of jER828EL, 126 parts of bisphenol A, and 0.1 parts of dimethylbenzylamine. The temperature inside the reaction vessel was maintained at 160°C, and the reaction was continued until the epoxy equivalent reached 490 g / mol. The temperature inside the reaction vessel was then cooled to 140°C, and 1.3 parts of dimethylbenzylamine was added. The reaction was continued until the epoxy equivalent reached 890 g / mol. After that, 177 parts of methyl isobutyl ketone was added, and the temperature inside the reaction vessel was cooled to 100°C. Next, a mixture of 44 parts of diethanolamine, 4 parts of N-methylethanolamine, and 35 parts of a diketimine compound of diethylenetriamine and methyl isobutyl ketone (ketimine compound content: 22 mol%) was added, and the reaction was continued for 1 hour at 115°C, yielding an amino group-containing epoxy resin solution. 305 parts of the obtained amino group-containing epoxy resin solution was added to a new reaction vessel, and the temperature inside the reaction vessel was maintained at 90°C. Next, 26 parts of 88% lactic acid was added to neutralize the acid, and 1,146 parts of deionized water was added to dilute and disperse. Next, 24 parts of jER828EL solution, which had been adjusted to an 80% solids content with propylene glycol monomethyl ether, was added, and the reaction was carried out at 90°C for 3 hours. After that, methyl isobutyl ketone was removed under reduced pressure, and the mixture was diluted with deionized water to obtain a solution of epoxy resin crosslinked particles (C-9) with an 18% solids content.

[0087] Manufacturing Example 14 A reaction vessel equipped with a stirrer, thermometer, dropping funnel, and reflux condenser was charged with 527 parts of jER828EL, 160 parts of bisphenol A, and 0.1 parts of dimethylbenzylamine. The temperature inside the reaction vessel was maintained at 160°C, and the reaction was continued until the epoxy equivalent reached 490 g / mol. The temperature inside the reaction vessel was then cooled to 140°C, and 1.7 parts of dimethylbenzylamine was added. The reaction was continued until the epoxy equivalent reached 890 g / mol. After this, 220 parts of methyl isobutyl ketone was added, and the reaction vessel was cooled to 100°C. A mixture of 45 parts of N-methylethanolamine and 45 parts of a diketimine compound of diethylenetriamine and methyl isobutyl ketone (ketimine compound content: 22 mol%) was then added, and the mixture was allowed to react at 115°C for 1 hour, yielding an amino-containing epoxy resin solution. 221 parts of the resulting amino-containing epoxy resin solution was added to a new reaction vessel, and the temperature inside the reaction vessel was maintained at 90°C. Next, 9 parts of 88% formic acid was added to neutralize the acid, and 662 parts of deionized water was added to dilute and disperse the mixture. Next, 7.8 parts of a hexamethylene diisocyanate solution with methyl isobutyl ketone to make a 80% solids solution was added, and the mixture was reacted at 90°C for 3 hours. After that, the methyl isobutyl ketone was removed under reduced pressure, and the mixture was diluted with deionized water to obtain a solution of epoxy resin crosslinked particles (C-10) with a solids content of 18%.

[0088] Manufacturing Example 15 A reaction vessel equipped with a stirrer, thermometer, dropping funnel, and reflux condenser was charged with 527 parts of jER828EL, 160 parts of bisphenol A, and 0.1 parts of dimethylbenzylamine. The temperature inside the reaction vessel was maintained at 160°C, and the reaction was continued until the epoxy equivalent reached 490 g / mol. The temperature inside the reaction vessel was then cooled to 140°C, and 1.7 parts of dimethylbenzylamine was added. The reaction was continued until the epoxy equivalent reached 890 g / mol. After this, 220 parts of methyl isobutyl ketone was added, and the reaction vessel was cooled to 100°C. A mixture of 45 parts of N-methylethanolamine and 45 parts of a diketimine compound of diethylenetriamine and methyl isobutyl ketone (ketimine compound content: 22 mol%) was then added, and the mixture was allowed to react at 115°C for 1 hour, yielding an amino-containing epoxy resin solution. 221 parts of the resulting amino-containing epoxy resin solution was added to a new reaction vessel, and the temperature inside the reaction vessel was maintained at 90°C. Next, 9 parts of 88% formic acid was added to neutralize the acid, and 662 parts of deionized water was added to dilute and disperse the mixture. Next, 10.4 parts of a 1,6-hexanediol diacrylate solution with methyl isobutyl ketone to make an 80% solids solution was added, and the mixture was allowed to react (Michael addition reaction) at 90°C for 3 hours. After that, the methyl isobutyl ketone was removed under reduced pressure, and the mixture was diluted with deionized water to obtain a solution of epoxy resin crosslinked particles (C-11) with a solids content of 18%.

[0089] The number average molecular weight, polymer ratio, insoluble component ratio, and volume average particle size of the crosslinked epoxy resin particles obtained in Production Examples 5 to 15 are shown in Table 1 below.

[0090] [Table 1]

[0091] (Note 1) Number average molecular weight: The crosslinked epoxy resin particles were diluted with N,N'-dimethylformamide to a solids concentration of 1% by mass and allowed to stand at room temperature for 24 hours. The insoluble components (crosslinked components) were then filtered out using a Myshori filter for GPC (pore size: 0.2 microns), and the number average molecular weight was measured using a gel permeation chromatography (GPC) [HLC8120GPC (trade name, manufactured by Tosoh Corporation)]. (Note 2) Polymer ratio (%): In the above molecular weight measurement data, this indicates the ratio (%) of the peak area with a molecular weight of 100,000 or more to the total peak area. (Note 3) Insoluble component ratio (mass %): The crosslinked epoxy resin particles were diluted with N,N'-dimethylformamide to a solids concentration of 1 mass % and allowed to stand at room temperature for 24 hours. The solution was then filtered through a Myshori filter for GPC (pore size: 0.2 microns), and the insoluble component ratio (crosslinked component ratio) was calculated using the following formula: Percentage of insoluble components (mass%) = A / B x 100 [A: solid content mass of the filtration residue, B: mass of the epoxy resin crosslinked particle (C) solution diluted to 1 mass % solid content / 100]. (Note 4) Volume average particle size (nm): Epoxy resin crosslinked particles were measured using a Microtrac UPA250 (product name, manufactured by Nikkiso Co., Ltd., particle size distribution analyzer).

[0092] Preparation of cationic electrodeposition coating composition Example 1 87.5 parts (solid content: 70 parts) of the amino group-containing epoxy resin (A-1) obtained in Production Example 1 and 37.5 parts (solid content: 30 parts) of the blocked polyisocyanate compound (B-1) obtained in Production Example 2 were mixed, and 13 parts of 10% acetic acid was further added and stirred uniformly. Deionized water was then added dropwise over a period of about 15 minutes with vigorous stirring to obtain an emulsion with a solid content of 34%. Next, 294 parts (solid content 100 parts) of the above emulsion, 52.4 parts of the pigment dispersion paste P-1 obtained in Production Example 4-1, 33.3 parts (solid content 6 parts) of the epoxy resin crosslinked particle (C-1) solution obtained in Production Example 5, and deionized water were added to produce a cationic electrodeposition coating composition (X-1) with a solid content of 20%.

[0093] Examples 2 to 19, Comparative Examples 1 to 6 Cationic electrodeposition coating compositions (X-2) to (X-25) were produced in the same manner as in Example 1 except for using the formulations shown in Table 2 below. The clay mineral GARAMITE 1958 was prepared by mixing the amino group-containing epoxy resin (A-1), the blocked polyisocyanate compound (B-1), and acetic acid, and then gradually adding the clay mineral while vigorously stirring the resin solution with a disperser. The results of the evaluation tests (edge ​​corrosion resistance, flat surface corrosion resistance, and finish) described below are also shown in the table. The cationic electrodeposition coating composition of the present invention is required to pass all three types of evaluation tests.

[0094] [Table 2]

[0095] All blend amounts in the table are solid content values. (Note 5) GARAMITE 1958: Product name, manufactured by BYK Japan, clay mineral (organically treated sepiolite / palygorskite / smectite). <Corrosion resistance at edges> Test panels were prepared by electrodeposition coating a cutter blade (blade angle 20 degrees, length 10 cm, zinc phosphate treated) at a bath temperature of 28°C, adjusting the energization time, so that the film thickness on the general surface was 15 μm. Next, this was subjected to a 96-hour salt spray resistance test in accordance with JIS Z-2371, and the edge portion at the tip of the cutter blade was evaluated according to the following criteria. The evaluations are "◎", "○", "○△" and "△" for pass, and "×" for fail. ◎: No rust 〇: Rust count is 10 or less per 10cm 〇△: Number of rust spots is 11-25 / 10cm △: Number of rust spots is 26-40 / 10cm ×: Number of rust spots is 41 or more per 10cm.

[0096] Creating test panels Cold-rolled steel sheets (150 mm (length) × 70 mm (width) × 0.8 mm (thickness)) that had been subjected to a chemical conversion treatment (product name: Palbond #3020, manufactured by Nippon Parkerizing Co., Ltd., zinc phosphate treatment agent) were used as the substrates. Each of the cationic electrodeposition paints obtained in the Examples and Comparative Examples was electrodeposited to a dry film thickness of 15 μm, and the sheets were baked and dried at 170°C for 20 minutes to obtain test panels.

[0097] <Corrosion resistance of flat parts> A cross-cut was made in the coating film with a cutter knife so as to reach the base material of the test plate, and this was subjected to a 35°C salt spray test for 840 hours in accordance with JIS Z-2371. The rust and blister width on one side of the cut were evaluated according to the following criteria. The evaluations are "◎", "○", "○△" and "△" for pass, and "×" for fail. ◎: The maximum width of rust and blisters is 2.0 mm or less on one side of the cut. ○: The maximum width of rust and blisters is more than 2.0mm and 3.0mm or less on one side of the cut. △: The maximum width of rust and blisters is more than 3.0 mm on one side of the cut and is 3.5 mm or less. ×: The maximum width of rust and blisters exceeds 3.5 mm on one side of the cut portion.

[0098] <Finishing quality (surface roughness)> The surface roughness (Ra) of the coated surface of the obtained test plate was measured at a cutoff of 0.8 mm using a Surftest 301 (trade name, manufactured by Mitutoyo Corporation, surface roughness meter) and evaluated according to the following criteria. The evaluations are "◎", "○", "○△" and "△" for pass, and "×" for fail. ◎: Surface roughness value (Ra) is less than 0.2, ○: Surface roughness value (Ra) is 0.2 or more and less than 0.24; ○△: Surface roughness value (Ra) is 0.24 or more and less than 0.28; △: Surface roughness value (Ra) is 0.28 or more and less than 0.32, ×: The surface roughness value (Ra) is 0.32 or more.

Claims

1. A cationic electrodeposition coating composition comprising an amino group-containing epoxy resin (A) and a blocked polyisocyanate compound (B), further comprising 0.1 to 40 mass% of epoxy resin crosslinked particles (C) and 0.1 to 40 mass% of a clay mineral (D) based on the total mass of the solid contents of the amino group-containing epoxy resin (A) and the blocked polyisocyanate compound (B); the epoxy resin crosslinked particles (C) are a reaction product of an epoxy resin (C-2) and a dispersion obtained by neutralizing an amino group-containing epoxy resin (C-1) obtained by reacting an epoxy resin with an amine compound with an acid compound and dispersing the neutralized resin in an aqueous solvent, the number average molecular weight of the crosslinked epoxy resin particles (C) measured by the following method is less than 100,000, A cationic electrodeposition coating composition characterized in that the proportion of insoluble components (crosslinked components) in the epoxy resin crosslinked particles (C) is 10 mass % or more when measured by the following method. <Method for measuring number average molecular weight> The epoxy resin crosslinked particles (C) were diluted with N,N'-dimethylformamide to a solids concentration of 1% by mass and allowed to stand at room temperature for 24 hours. Insoluble components were then removed by filtration, and the number average molecular weight was measured using gel permeation chromatography (GPC). <Method for measuring the proportion of insoluble components (crosslinked components)> The crosslinked epoxy resin particles (C) were diluted with N,N'-dimethylformamide to a solids concentration of 1% by mass and allowed to stand at room temperature for 24 hours. The insoluble components (crosslinked components) were then filtered using a Myshori filter for GPC (pore size: 0.2 microns), and the residue was dried at 130°C for 3 hours to measure the solid mass of the residue. The proportion (% by mass) of the insoluble components (crosslinked components) can be calculated using the following formula: Proportion (mass%) of insoluble component (crosslinked component) = A / B x 100 A: solid mass of filtration residue B: Mass of epoxy resin crosslinked particle (C) solution diluted to 1% by mass solids / 100

2. The cationic electrodeposition coating composition according to claim 1, characterized in that the amino group-containing epoxy resin (C-1) is a reaction product of an epoxy resin (C-1-1) and an amine compound (C-1-2), and the amine compound (C-1-2) contains a ketiminated amine compound (C-1-2-1) in an amount of 2 mol % or more and less than 40 mol %.

3. 3. The cationic electrodeposition coating composition according to claim 1, wherein the epoxy resin crosslinked particles (C) have a polymer ratio (peak area for molecular weights of 100,000 or more) of less than 40%.

4. 4. The cationic electrodeposition coating composition according to claim 1, wherein the number average molecular weight of the epoxy resin crosslinked particles (C) is 9,000 or less.

5. The cationic electrodeposition coating composition according to any one of claims 1 to 4, characterized in that the clay mineral (D) is contained in an amount of 0.1 to 30 mass % based on the total mass of the solid contents of the amino group-containing epoxy resin (A) and the blocked polyisocyanate compound (B), and has at least one shape selected from the group consisting of plate-like, scale-like, layer-like, rod-like, needle-like, fibrous and chain-like.

6. 6. The cationic electrodeposition coating composition according to claim 5, wherein the clay mineral (D) has at least one shape selected from the group consisting of rod-like, needle-like, fibrous and chain-like shapes.

7. 7. The cationic electrodeposition coating composition according to any one of claims 1 to 6, wherein the clay mineral (D) is dispersed using a shear disperser.

8. A coating method comprising immersing a metal substrate in an electrodeposition coating bath comprising the cationic electrodeposition coating composition according to any one of claims 1 to 7, and carrying out electrodeposition coating.

9. A method for producing a coated article, comprising the steps of forming a coating film by the coating method according to claim 8 and then heat-curing the coating film.

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