JP6714752B1 - Cationic electrodeposition coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cationic electrodeposition coating composition excellent in anticorrosion property and finish property of edge portion and flat surface portion even in a thin film, and a coated article excellent in various coating film performances thereof. A cationic electrodeposition coating composition having an amino group-containing epoxy resin (A), a blocked polyisocyanate compound (B), and epoxy resin crosslinked particles (C), which comprises the resin (A) and the compound ( The epoxy resin crosslinked particles (C) are contained in an amount of 0.1 to 40 parts by mass, and the number average molecular weight of the epoxy resin crosslinked particles (C) is less than 100,000, based on the total mass of the solid content of B). A cationic electrodeposition coating composition comprising: [Selection diagram] None

Description

The present invention relates to a cationic electrodeposition coating composition having an amino group-containing epoxy resin, a blocked polyisocyanate compound, and epoxy resin crosslinked particles.

The cationic electrodeposition coating composition has excellent coating workability and the formed coating film has good anticorrosion properties, so that the performance of these is required for automobile bodies, automobile parts, electric equipment parts and other equipment. It is widely used as an undercoat paint for conductive metal products such as.

When the article to be coated has a sharp edge portion, the coating film on the edge portion may become thin during heat curing of the paint, resulting in poor corrosion resistance. Therefore, in coating an object to be coated having an edge portion, a means for improving the corrosion resistance of the edge portion is required.

As a method for improving the rust preventive property of the edge portion, Patent Document 1 discloses that a polyacrylamide resin is contained in the electrodeposition coating composition. By containing the above-mentioned resin, it is considered that the shrinkage caused by heating can be controlled or the edge covering reduction due to the flow can be suppressed by interacting with the coating film components, but it contains a highly polar soluble resin. Therefore, the corrosion resistance of the flat portion may be poor.

Patent Documents 2 and 3 disclose that a cationic microgel dispersion (epoxy viscosity agent) is contained in an electrodeposition coating composition. By containing the above resin, the flow of the electrodeposition coating film due to the heat flow at the edge portion can be suppressed, but the corrosion resistance of the edge portion may not be sufficiently obtained under severe corrosion conditions.

JP, 2017-214572, A JP, 2018-159032, A JP-A-7-268063

The problem to be solved by the invention is to provide a cationic electrodeposition coating composition excellent in corrosion resistance of edge portions and flat portions even in a thin film, and finish, and a coated article excellent in these various coating film performances. Is.

As a result of intensive studies conducted by the inventors to solve the above-mentioned problems, a cationic electrodeposition coating composition having an amino group-containing epoxy resin (A), a blocked polyisocyanate compound (B), and epoxy resin crosslinked particles (C). The inventors have found that the above problems can be solved depending on the product, and have completed the present invention.

That is, the present invention provides a cationic electrodeposition coating composition, a method for forming a cationic electrodeposition coating film, and a coated article which has been electrodeposition coated by the coating film forming method described below.
Item 1. A cationic electrodeposition coating composition comprising an amino group-containing epoxy resin (A), a blocked polyisocyanate compound (B), and epoxy resin crosslinked particles (C), wherein the amino group-containing epoxy resin (A) and the blocked resin composition are blocked. Based on the total solid content of the polyisocyanate compound (B), the coating composition contains 0.1 to 40 parts by mass of the epoxy resin crosslinked particles (C), and the epoxy resin crosslinked particles measured by the following method ( A cationic electrodeposition coating composition, wherein the number average molecular weight of C) is less than 100,000.
<Method of measuring number average molecular weight>
The epoxy resin crosslinked particles (C) were diluted with N,N'-dimethylformamide to a solid content concentration of 1% by mass, and allowed to stand at room temperature for 24 hours. Then, insoluble components were 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 ratio of the insoluble component (crosslinking component) when the epoxy resin crosslinked particles (C) is measured by the following method is 10% by mass or more.
<Method of measuring insoluble component (crosslinking component) ratio>
The epoxy resin crosslinked particles (C) were diluted with N,N'-dimethylformamide to a solid content concentration of 1% by mass, and allowed to stand at room temperature for 24 hours. Next, the insoluble component (crosslinking component) was filtered through a Gishory filter for GPC (pore size: 0.2 micron), and the residue was dried under the condition of 130° C. for 3 hours to measure the solid content mass of the residue. The proportion (mass %) of the insoluble component (crosslinking component) can be calculated by the following formula.
Insoluble component (crosslinking component) ratio (mass %)=A/B×100
A: Solid content mass of filtration residue B: Mass of epoxy resin crosslinked particle (C) solution diluted to 1 mass% solid content/100
Item 3. The cationic electrodeposition according to item 1 or 2, wherein the crosslinked epoxy resin particles (C) is a reaction product of an amino group-containing epoxy resin (C-1) and an epoxy resin (C-2). Coating composition.
Item 4. The amino group-containing epoxy resin (C-1) is a reaction product of the epoxy resin (C-1-1) and the amine compound (C-1-2), and the amine compound (C-1-2) Contains the ketiminated amine compound (C-1-2-1) in an amount of 2 mol% or more and less than 40 mol%, the cationic electrodeposition coating composition according to item 3 above.
Item 5. The cationic electrodeposition coating composition according to any one of items 1 to 4, which has a high molecular weight (peak area having a molecular weight of 100,000 or more) of less than 40%.
Item 6. A coating method in which a metal article is immersed in an electrodeposition coating bath comprising the cationic electrodeposition coating composition according to the above items 1 to 5 and electrodeposition coating is performed.
Item 7. Item 7. A method for producing a coated article, which comprises the steps of forming a coating film by the coating method according to Item 6 and then heat curing.

The cationic electrodeposition coating composition of the present invention is excellent in corrosion resistance of the edge portion and the flat surface portion, and excellent in finishability, and particularly has good finishability and corrosion resistance in a thin film, and corrosion resistance of the edge portion even under severe corrosive conditions. Is good. An automobile body coated with the product of the present invention is less likely to be corroded and deteriorated even when it is run in an environment in which snow melting salt is sprayed.

The present invention relates to a cationic electrodeposition coating composition having an amino group-containing epoxy resin (A), a blocked polyisocyanate compound (B), and epoxy resin crosslinked particles (C). The details will be described below.

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) epoxy resin and primary mono- and polyamines, secondary mono- and polyamines, and primary and secondary mixed polyamines. (See, for example, U.S. Pat. No. 3,984,299); (2) Addition product of epoxy resin and secondary mono- and polyamine having ketiminated primary amino group (for example, , U.S. Pat. No. 4,017,438); (3) A reaction product obtained by etherification of an epoxy resin and a ketiminated hydroxy compound having a primary amino group (see, for example, JP-A-59). -43013 gazette) etc. can be mentioned.

The epoxy resin (A-1) used for producing the above amino group-containing epoxy resin (A) is a compound having at least one, and preferably two or more epoxy groups in one molecule, and its molecular weight is A number average molecular weight in the range of at least 300, preferably 400 to 4,000, more preferably 800 to 2,500 and at least 160, preferably 180 to 2,500, more preferably 400 to 1,500. Those having an epoxy equivalent are suitable. As such an epoxy resin, for example, a resin obtained by reacting a polyphenol compound with epihalohydrin (eg, epichlorohydrin etc.) can be used.

Examples of the polyphenol compound used for forming 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, cresol novolac and the like can be mentioned.

Further, as the epoxy resin obtained by the reaction of the polyphenol compound and epihalohydrin, the epoxy resin of the following formula (1) derived from bisphenol A is particularly preferable.
Further, an epoxy resin having a high molecular weight and/or a polyfunctionalization obtained by reacting an epoxy resin represented by the following formula (1) with a polyphenol compound can be used, and among them, bisphenol A is preferable as the polyphenol compound.

Here, those represented by n=0 to 8 are preferable.

Examples of commercially available products of such epoxy resins include those sold by Mitsubishi Chemical Corporation under the trade names of jER828EL, jER1002, jER1004, and jER1007.

Further, as the epoxy resin (A-1), an epoxy resin containing a polyalkylene oxide chain in the resin skeleton can be used. Usually, such an epoxy resin is prepared by reacting an epoxy resin having at least one (α) epoxy group, preferably two or more with an alkylene oxide or polyalkylene oxide to introduce a polyalkylene oxide chain, (β ) It can be obtained by a method of reacting the above polyphenol compound with a polyalkylene oxide having at least one, and preferably two or more epoxy groups to introduce a polyalkylene oxide chain. Moreover, you may use the epoxy resin which already contains the polyalkylene oxide chain. (For example, refer to the specification of JP-A-8-337750)
As the alkylene group in the polyalkylene oxide chain, an alkylene group having 2 to 8 carbon atoms is preferable, an ethylene group, a propylene group or a butylene group is more preferable, and a propylene group is particularly preferable.
The content of the polyalkylene oxide chain, in terms of coating stability, finish and corrosion resistance improvement, based on the solid content mass of the amino group-containing epoxy resin, the content as a constituent component of the polyalkylene oxide. In general, 1.0 to 15% by mass, preferably 2.0 to 9.5% by mass, more preferably 3.0 to 8.0% by mass is suitable.

Examples of the primary mono- and polyamines, secondary mono- and polyamines or primary and secondary mixed polyamines used in the production of the amino group-containing epoxy resin (A) of the above (1) include monomethylamine, Mono- or di-alkylamines such as dimethylamine, monoethylamine, diethylamine, monoisopropylamine, diisopropylamine, monobutylamine, dibutylamine; monoethanolamine, diethanolamine, mono(2-hydroxypropyl)amine, monomethylaminoethanol, etc. Alkanol amines; alkylene polyamines such as ethylene diamine, propylene diamine, butylene diamine, hexamethylene diamine, diethylene triamine, triethylene tetramine and the like can be mentioned.

Examples of the secondary mono- and polyamine having a ketiminated primary amino group used in the production of the amino group-containing epoxy resin (A) of the above (2) include, for example, the amine-added epoxy of the above (1). Among the primary and secondary mixed polyamines used in the production of resins, for example, ketimine compounds formed by reacting a ketone compound with diethylenetriamine, dipropylenetriamine and the like can be mentioned.

Examples of the hydroxy compound having a ketiminized primary amino group used in the production of the amino group-containing epoxy resin (A) of the above (3) include, for example, the amino group containing epoxy resin (A) of the above (1). Among the primary mono- and polyamines, secondary mono- and polyamines or primary and secondary mixed polyamines used for the production of the above, compounds having a primary amino group and a hydroxyl group, for example, monoethanolamine, Examples thereof include a hydroxyl group-containing ketimine compound obtained by reacting a ketone compound with mono(2-hydroxypropyl)amine.

The amine value of such an amino group-containing epoxy resin (A) is in the range of 30 to 80 mgKOH/g resin solids, and more preferably in the range of 40 to 70 mgKOH/g resin solids. It is preferable from the viewpoint of improving the property.

The amino group-containing epoxy resin (A) can be modified with a modifying agent, if necessary. Such a modifier is not particularly limited as long as it is a resin or compound having reactivity with an epoxy resin, and examples thereof include polyol, polyether polyol, polyester polyol, polyamidoamine, polycarboxylic acid, fatty acid, polyisocyanate compound, and polyisocyanate compound. A compound obtained by reacting an isocyanate compound, a lactone compound such as ε-caprolactone, an acrylic monomer, a compound obtained by polymerizing an acrylic monomer, a xylene formaldehyde compound, and an epoxy compound can also be used as the modifier. These modifiers can be used alone or in combination of two or more.
Among them, as the modifier, it is preferable to use at least one saturated and/or unsaturated fatty acid from the viewpoint of throwing power and/or corrosion resistance. As the fatty acid that can be used, a long-chain fatty acid having 8 to 22 carbon atoms is preferable, and examples thereof include caprylic acid, capric acid, octanoic acid, nonanoic acid, decanoic acid, lauric acid, myristic acid, pentadecyl acid, palmitic acid, and margaric acid. , Stearic acid, oleic acid, linoleic acid, linolenic acid and the like. Among them, a long chain fatty acid having 10 to 20 carbon atoms is more preferable, and a long chain fatty acid having 13 to 18 carbon atoms is further preferable.

The addition reaction of the above amine compound and the modifier to the epoxy resin (A-1) is usually 1 to 6 at a temperature of about 80 to about 170° C., preferably about 90 to about 150° C. in a suitable solvent. It can be performed for about an hour, preferably about 1 to 5 hours.

Examples of the solvent include hydrocarbon solvents such as toluene, xylene, cyclohexane, and n-hexane; ester solvents such as methyl acetate, ethyl acetate, and butyl acetate; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and methyl amyl ketone. System; amide system such as dimethylformamide, dimethylacetamide; alcohol system such as methanol, ethanol, n-propanol, iso-propanol, ether alcohol system compound such as ethylene glycol monobutyl ether, diethylene glycol monoethyl ether; or a mixture thereof. Can be mentioned.

The use ratio of the above modifier is not strictly limited and can be appropriately changed depending on the application of the coating composition and the like, but from the viewpoint of improving finishability and anticorrosion property, the amino group-containing epoxy resin It is suitable to be in the range of usually 0 to 50% by mass, preferably 3 to 30% by mass, and more preferably 6 to 20% by mass, based on the mass of the solid content.

Blocked polyisocyanate compound (B)
The blocked polyisocyanate compound (B) is an addition reaction product of the polyisocyanate compound and the isocyanate blocking agent in almost stoichiometric amounts. As the polyisocyanate compound used in the blocked polyisocyanate compound (B), known compounds can be used, for example, tolylene diisocyanate, xylylene diisocyanate, phenylene diisocyanate, diphenylmethane-2,2′-diisocyanate, Diphenylmethane-2,4'-diisocyanate, diphenylmethane-4,4'-diisocyanate, crude MDI [polymethylene polyphenyl isocyanate], bis(isocyanatomethyl)cyclohexane, tetramethylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate, isophorone diisocyanate, etc. Aromatic, aliphatic or alicyclic polyisocyanate compounds; cyclized polymers or bullets of these polyisocyanate compounds; or combinations thereof.

In particular, aromatic polyisocyanate compounds such as tolylene diisocyanate, xylylene diisocyanate, phenylene diisocyanate, diphenylmethane-2,4'-diisocyanate, diphenylmethane-4,4'-diisocyanate and crude MDI (preferably crude MDI) are anticorrosive. Therefore, it is more preferable.

On the other hand, the above-mentioned isocyanate blocking agent blocks by adding to the isocyanate group of the polyisocyanate compound, and the blocked polyisocyanate compound formed by the addition is stable at room temperature, but the baking temperature of the coating film (usually about 100). It is desirable for the blocking agent to dissociate to regenerate free isocyanate groups when heated to ~200°C).

Examples of the blocking agent used in the blocked polyisocyanate compound (B) include oxime compounds such as methylethylketoxime and cyclohexanone oxime; phenol compounds such as phenol, para-t-butylphenol and cresol; n-butanol, 2 -Ethylhexanol, phenylcarbinol, methylphenylcarbinol, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, ethylene glycol, propylene glycol and other alcohol compounds; ε-caprolactam, γ-butyrolactam and other lactam compounds; dimethyl malonate , And active methylene compounds such as diethyl malonate, ethyl acetoacetate, methyl acetoacetate, and acetylacetone (preferably alcohol compounds).

Epoxy resin crosslinked particles (C)
The epoxy resin cross-linked particles (C) that can be used in the cationic electrodeposition coating composition of the present invention are the epoxy resin cross-linked particles (C) based on the total solid mass of the resin (A) and the compound (B). It is suitable to contain 0.1 to 40 parts by mass, preferably 1 to 30 parts by mass, and more preferably 5 to 15 parts by mass.
The number average molecular weight measured under the following conditions is usually less than 100,000, preferably 100 or more and less than 100,000, more preferably 150 or more and less than 10,000, and particularly preferably. Is preferably 200 or more and less than 5,000 from the viewpoint of finishability and corrosion resistance of the edge portion.

<Measurement method of number average molecular weight>
The epoxy resin crosslinked particles (C) were diluted with N,N'-dimethylformamide to a concentration of 1% by mass of solid content, and allowed to stand at room temperature for 24 hours. Next, the insoluble component (crosslinking component) was removed by filtration through a Gishory filter for GPC (pore size: 0.2 micron), and the number average molecular weight was measured using the following gel permeation chromatography (GPC).
In addition, in gel permeation chromatography (GPC) measurement, if an insoluble component (a cross-linking component that does not dissolve in the solvent in the present invention) is present, clogging occurs in the device and causes a failure. Therefore, use a filter. It is common to filter and prepare the sample.

<Gel permeation chromatography (GPC)>
Device: "HLC8120GPC" (trade name, manufactured by Tosoh Corporation),
Column: Four of "TSKgel G-4000HXL", "TSKgel G-3000HXL", and "TSKgel G-2000HXL" (trade name, all manufactured by Tosoh Corporation),
Mobile phase: N,N'-dimethylformamide,
Conditions: measurement temperature 40° C., flow rate 1 mL/min,
Detector: RI.

In the present specification, the number average molecular weight and the weight average molecular weight are the retention time (retention capacity) measured using the above gel permeation chromatograph (GPC), and the retention of standard polystyrene of known molecular weight measured under the same conditions. It is a value obtained by converting the molecular weight of polystyrene by time (retention capacity).

The epoxy resin crosslinked particles (C) have a poor finish when they have a high molecular weight. Therefore, in the molecular weight measurement data measured by gel permeation chromatography (GPC), a peak area (high molecular weight) having a molecular weight of 100,000 or more. Is preferably less than 40% of the total peak area, and more preferably less than 30%.
In the present specification, the peak area having a molecular weight of 100,000 or more may be referred to as “high molecular weight”.

Further, the proportion of the insoluble component (crosslinking component) of the epoxy resin crosslinked particles (C) is preferably 10% by mass or more, and 10 to 90% by mass, from the viewpoint of corrosion resistance of the edge portion and the flat surface portion and finishability. % Is more preferable, 10 to 60% by mass is further preferable, and 15 to 45% by mass is particularly preferable.
When the amount of the insoluble component is large, the finish property is deteriorated, and when the amount of the insoluble component is small, the anticorrosion property of the edge part is deteriorated.Therefore, if it is within this range, both the anticorrosion property of the edge part and the finish property can be compatible. obtain.
The ratio of the insoluble component (crosslinking component) can be calculated by the following method.

<Method of measuring insoluble component (crosslinking component) ratio>
The epoxy resin crosslinked particles (C) were diluted with N,N'-dimethylformamide to a solid content concentration of 1% by mass, and allowed to stand at room temperature for 24 hours. Next, the insoluble component (crosslinking component) was filtered through a Gishory filter for GPC (pore size: 0.2 micron), and the residue was dried under the condition of 130° C. for 3 hours to measure the solid content mass of the residue. The ratio (mass %) of the insoluble component (crosslinking component) can be calculated by the following formula.
Insoluble component (crosslinking component) ratio (mass %)=A/B×100
A: Solid content mass of filtration residue B: Mass of epoxy resin crosslinked particle (C) solution diluted to 1 mass% solid content/100

The epoxy resin crosslinked particles (C) that can be used in the cationic electrodeposition coating composition of the present invention are obtained by reacting an epoxy resin (C-1-1) with an amine compound (C-1-2). A step (I) of producing an amino group-containing epoxy resin (C-1), a step (II) of neutralizing the amino group-containing epoxy resin (C-1) with an acid compound, and dispersing in an aqueous solvent, It can be produced by a step including a step (III) of mixing and reacting the dispersion and the epoxy resin (C-2) to obtain the epoxy resin crosslinked particles (C).

<Process (I)>
The step of producing the amino group-containing epoxy resin (C-1) obtained by reacting the epoxy resin (C-1-1) and the amine compound (C-1-2) is as described above. The same manufacturing method as in (A) can be used.

As the epoxy resin (C-1-1), the same epoxy resin (A-1) as described above can be used, and among them, the epoxy resin of the formula (1) derived from bisphenol A is preferable. Can be used for. Furthermore, a high molecular weight and/or polyfunctionalized epoxy resin obtained by reacting the epoxy resin of the formula (1) with a polyphenol compound can be preferably used, and bisphenol A is preferable as the polyphenol compound.
The number average molecular weight of the epoxy resin (C-1-1) is preferably 400 to 5,000, more preferably 700 to 3,000.

As the amine compound (C-1-2), the amine compounds mentioned in the above-mentioned amino group-containing epoxy resin (A) can be preferably used, but particularly ketiminized amine compounds (C-1-2). -1) is preferable, and above all, it is preferable to include a secondary mono- and polyamine (C-1-2-2) having a ketiminated primary amino group.
Examples of the secondary mono- and polyamines (C-1-2-2) having a ketiminated primary amino group include, for example, ketimine compounds of amine compounds represented by the following formula (2): Specific examples thereof include diketiminide compounds such as diethylenetriamine, dipropylenetriamine, dibutylenetriamine, bis(hexamethylene)triamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine.

(In the formula, R ₁ and R ₂ are hydrocarbon groups having 1 to 8 carbon atoms and may be different or the same. n is an integer of 1 to 5.)
The ketiminated amine compound (C-1-2-1) may be contained in the amine compound (C-1-2) in a range of 0.1 mol% or more and less than 80 mol %. Preferably, it is contained in a range of 1 mol% or more and less than 50 mol%, more preferably 2 mol% or more, and further preferably contained in a range of less than 40 mol%, and 5 mol% or more, and It is particularly preferable that the content is less than 30 mol %.
In addition, in this specification, the content rate of the ketimine-ized amine compound (C-1-2-1) may be called "ketimine compound content rate."

The ketiminization-blocked primary amino group contained in the amine compound (C-1-2-1) is hydrolyzed in a water dispersion step (II) described below, and a primary amino group appears. Then, in the step (III), the primary amino group reacts with the epoxy group of the epoxy resin (C-2) to cause a high molecular weight and/or a crosslinking reaction. Therefore, by adjusting the amine compound (C-1-2-1) within the above range, the molecular weight, particle diameter, and/or degree of crosslinking (ratio of insoluble components) of the epoxy resin crosslinked particles (C) are optimized. It can be within the range.

<Step (II)>
The amino group-containing epoxy resin (C-1) obtained in the above step (I) is subsequently neutralized with an acid compound and further dispersed in an aqueous solvent to obtain a dispersion.
Here, the aqueous solvent is a solvent containing water and other solvent that can be contained as necessary, and as the other solvent, for example, an ester solvent, a ketone solvent, an amide solvent, an alcohol solvent, And an ether alcohol solvent, or a mixture thereof.
As the above-mentioned acid compound, known acid compounds can be used without particular limitation, and among them, organic acids are preferable, and formic acid, lactic acid, acetic acid, or a mixture thereof is preferable. The neutralization equivalent is preferably 0.2 to 1.5 equivalents, more preferably 0.5 to 1.0 equivalents of the acid compound with respect to 1 equivalent of the amino group.
In addition to the above acid compounds, additives such as emulsifiers may be included.

For the dispersion of the resin (C-1) in the aqueous solvent, the aqueous solvent may be added to the neutralized amino group-containing epoxy resin (C-1) while stirring, or the aqueous solvent may be added. The neutralized amino group-containing epoxy resin (C-1) may be added with stirring, or the aqueous solvent and the neutralized amino group-containing epoxy resin (C-1) may be mixed and then stirred. May be.
The dispersion temperature is preferably lower than 100°C, more preferably 40 to 99°C, and further preferably 50 to 95°C.
The resin solid content concentration of the dispersion is preferably 5 to 80% by mass, more preferably 10 to 50% by mass.

<Step (III)>
The dispersion obtained in the above step (II) is subsequently mixed with an epoxy resin (C-2) and further reacted to obtain epoxy resin crosslinked particles (C).
As the epoxy resin (C-2), the same epoxy resin (A-1) as described above can be used, and among them, the epoxy resin of the formula (1) derived from bisphenol A is preferably used. be able to. The epoxy equivalent of the epoxy resin (C-2) is preferably 180 to 2000, more preferably 180 to 500.

In the above reaction step, the primary amino group of the amino group-containing epoxy resin (C-1) from which the ketiminated block is removed by hydrolysis reacts with the epoxy group of the epoxy resin (C-2) to increase the molecular weight and / Or a crosslinking reaction occurs.
As the equivalent ratio of the primary amino group and the epoxy group, the epoxy group is preferably 0.5 to 2.0 equivalents, more preferably 0.7 to 1.5 equivalents, relative to 1 equivalent of the primary amino group. ..
The reaction temperature is preferably lower than 100°C, more preferably 40 to 99°C, and further preferably 50 to 95°C.

The volume average particle diameter of the epoxy resin crosslinked particles (C) obtained in the step (III) is usually in the range of 80 nm to 1000 nm from the viewpoint of corrosion resistance of the edge portion and the flat portion, and finishability. It is preferably larger than 100 nm, more preferably larger than 150 nm, further preferably larger than 200 nm, particularly preferably larger than 300 nm. Further, it is preferably smaller than 800 nm, more preferably smaller than 700 nm, further preferably smaller than 600 nm, particularly preferably smaller than 500 nm.
The volume average particle diameter can be measured by a laser diffraction/scattering measuring device, and the particle diameter in this specification was measured by Microtrac UPA250 (trade name, manufactured by Nikkiso Co., Ltd., particle size distribution measuring device).
The amine value of the resin crosslinked particles (C) is preferably in the range of 25 to 200 mgKOH/g, more preferably in the range of 50 to 180 mgKOH/g.
Within the above range, the dispersibility of particles in an aqueous solvent and the water resistance of the coating film are excellent.

Regarding Cationic Electrodeposition Coating Composition As the compounding ratio of the amino group-containing epoxy resin (A) and the blocked polyisocyanate compound (B) in the cationic electrodeposition coating composition of the present invention, the above components (A) and (B) are included. Within the range of 5 to 95 mass% of component (A), preferably 50 to 80 mass%, and 5 to 95 mass% of component (B), preferably 20 to 50 mass%, based on the total solid content of It is also preferable that the coating stability is good, and a coated article having excellent finish and corrosion resistance is obtained. If the amount is out of the above range, any of the above-mentioned coating properties and coating film performance may be impaired, which is not preferable.
Moreover, as a compounding ratio of a component (C), 0.1-40 mass parts is normally contained on the basis of solid content total mass of the said resin (A) and a compound (B), Preferably 1-30 mass parts is contained. However, it is more preferable to contain 5 to 15 parts by mass also in order to obtain a coated article excellent in both corrosion resistance and finish of the edge portion.

The method for producing the cationic electrodeposition coating composition of the present invention is not particularly limited, but, for example, in addition to the resin (A) and the compound (B), a surfactant and/or a surface adjusting agent may be added if necessary. After sufficiently mixing various additives such as an agent to prepare a prepared resin, it is dispersed in water, and the epoxy resin crosslinked particles (C), pigment dispersion paste, water, an organic solvent, a neutralizing agent, etc. are sufficiently mixed. Can be obtained. As the neutralizing agent, a known organic acid can be used without particular limitation, and among them, formic acid, lactic acid or a mixture thereof is preferable.

The above-mentioned pigment dispersion paste is a pigment such as a color pigment, a rust preventive pigment and an extender pigment which is previously dispersed in fine particles. For example, a pigment dispersing resin, a neutralizing agent and a pigment are blended, and a ball mill and a sand mill are used. A pigment dispersion paste can be prepared by dispersion treatment in a dispersion mixer such as a Pebble mill.

As the above-mentioned pigment-dispersing resin, known ones can be used without particular limitation. For example, epoxy resins having a hydroxyl group and a cationic group, acrylic resins, surfactants, etc., tertiary amine type epoxy resins, quaternary ammonium salt type epoxies. Resin, tertiary sulfonium salt type epoxy resin, tertiary amine type acrylic resin, quaternary ammonium salt type acrylic resin, tertiary sulfonium salt type acrylic resin and the like can be used.

As the above-mentioned pigment, known pigments can be used without particular limitation. For example, coloring pigments such as titanium oxide, carbon black and red iron oxide; extender pigments such as clay, mica, barita, calcium carbonate and silica; aluminum phosphomolybdate, tripolyphosphorus. A rust preventive pigment such as aluminum acid salt or zinc oxide (zinc white) may be added.

Furthermore, a bismuth compound can be contained for the purpose of corrosion inhibition or rust prevention. Examples of the bismuth compound that can be used include bismuth oxide, bismuth hydroxide, basic bismuth carbonate, bismuth nitrate, bismuth silicate, and bismuth organic acid.

Further, an organic tin compound such as dibutyltin dibenzoate, dioctyltin oxide or dibutyltin oxide can be used for the purpose of improving the curability of the coating film. By using (increasing) and/or refining the rust preventive pigment such as zinc oxide (zinc white) and/or bismuth compound, the curability of the coating film can be improved without containing these organotin compounds. It can also be planned. The content of these pigments is preferably 1 to 100 parts by mass, and particularly preferably 10 to 50 parts by mass per 100 parts by mass of the total resin solid content of the resin (A) and the compound (B).

Coating film forming method The present invention includes a step of immersing a coating object in an electrodeposition bath composed of the above-mentioned cationic electrodeposition coating composition, and a step of energizing the coating object as a cathode, forming a cationic electrodeposition coating film Provide a way.

Examples of the object to be coated with the cationic electrodeposition coating composition of the present invention include automobile bodies, two-wheeled vehicle parts, household appliances, and other appliances, and there is no particular limitation as long as it is a metal.

Examples of the metal steel sheet as an object to be coated include cold rolled steel sheet, galvannealed steel sheet, electrogalvanized steel sheet, electrogalvanized-iron double-layer plated steel sheet, organic composite plated steel sheet, Al raw material, Mg raw material, and the like The plate may be subjected to surface treatment such as phosphate conversion treatment and chromate treatment after cleaning the surface such as alkali degreasing as necessary.

The cationic electrodeposition coating composition can be applied to the desired surface of the substrate to be coated by cationic electrodeposition coating. The cation electrodeposition method is generally diluted with deionized water or the like to a solid content concentration of about 5 to 40% by mass, preferably 10 to 25% by mass, and a pH of 4.0 to 9.0. As a bath, the cationic electrodeposition coating composition adjusted to preferably in the range of 5.5 to 7.0 is usually adjusted to a bath temperature of 15 to 35° C. and a load voltage of 100 to 400 V, preferably 150 to 350 V. Then, the object to be coated is used as a cathode and electricity is applied. After electrodeposition coating, ultrafiltration liquid (UF filtrate), reverse osmosis permeation water (RO water), industrial water, pure water, etc. are usually sufficient to remove excess cationic electrodeposition coating on the object to be coated. Wash with water.

Although the film thickness of the electrodeposition coating film is not particularly limited, it can generally be in the range of 5 to 40 μm, preferably 10 to 30 μm based on the dry coating film. Further, the baking and drying of the coating film is carried out at 110 to 200° C., preferably 140 to 180° C. at the temperature of the surface of the coated article by using a drying facility such as an electric hot air drier or a gas hot air drier. The time is 10 to 180 minutes, preferably 20 to 50 minutes by heating the electrodeposition coating film. A cured coating film can be obtained by the baking and drying.

Hereinafter, the present invention will be described in more detail with reference to Production Examples, Examples, and Comparative Examples, but the present invention is not limited thereto. In each example, "part" means mass part and "%" means mass %.

Production of amino group-containing epoxy resin (A) Production Example 1
In a flask equipped with a stirrer, a thermometer, a nitrogen introduction tube and a reflux condenser, jER828EL (trade name, epoxy resin manufactured by Japan Epoxy Resin Co., epoxy equivalent 190, number average molecular weight 350) 1200 parts, bisphenol A 500 parts and dimethyl. Benzylamine (0.2 parts) was added, and the mixture was reacted at 130° C. until the epoxy equivalent became 850.
Next, after adding 160 parts of diethanolamine and 65 parts of a ketiminized product of diethylenetriamine and methyl isobutyl ketone and reacting at 120° C. for 4 hours, 480 g of ethylene glycol monobutyl ether was added, and an amino group-containing epoxy resin A having a solid content of 80% was added. -1 solution was obtained. 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.

Production Example 2 of Blocked Polyisocyanate Compound (B)
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 to the reaction vessel, and the temperature was raised to 70°C. To this, 236 parts of ethylene glycol monobutyl ether was added dropwise over 1 hour, then heated to 100° C., sampled over time while maintaining this temperature, and absorption of unreacted isocyanate groups by infrared absorption spectrum measurement. Was confirmed to have disappeared, and a blocked polyisocyanate compound B-1 having a resin solid content of 80% was obtained.

Production Example 3 of pigment dispersion resin
In a flask equipped with a stirrer, a thermometer, a dropping funnel and a reflux condenser, jER828EL (trade name, epoxy resin manufactured by Japan Epoxy Resin Co., epoxy equivalent 190, number average molecular weight 350) 1010 parts, bisphenol A 390 parts, 240 parts of Praxel 212 (trade name, polycaprolactone diol, Daicel Chemical Industries, Ltd., weight average molecular weight of about 1250) and 0.2 part of dimethylbenzylamine were added and reacted at 130° C. until the epoxy equivalent became about 1090. Next, 134 parts of dimethylethanolamine and 150 parts of a 90% strength aqueous lactic acid solution were added and reacted at 90° C. until the epoxy groups disappeared. Then, propylene glycol monomethyl ether was added to adjust the solid content to obtain a pigment dispersion resin containing a quaternary ammonium salt group having a solid content of 60%.

Manufacturing Example 4 of Pigment Dispersion Paste
8.3 parts of pigment dispersing resin containing 60% solid content quaternary ammonium salt obtained in Production Example 3 (solid content 5 parts), titanium oxide 14.5 parts, purified clay 7 parts, carbon black 0.3 Part, bismuth hydroxide 2 parts, and deionized water 20.3 parts were added and dispersed in a ball mill for 20 hours to obtain a pigment dispersion paste P-1 having a solid content of 55%.

Production Example 5 of Epoxy Resin Crosslinked Particles (C)
To a reaction vessel equipped with a stirrer, a thermometer, a dropping funnel and a reflux condenser, jER828EL527 parts, bisphenol A 160 parts, dimethylbenzylamine 0.1 parts were added, and the temperature in the reaction vessel was maintained at 160°C to obtain an epoxy equivalent. Was reacted up to 490 g/mol. Then, the temperature in the reaction vessel was cooled to 140° C., 1.7 parts of dimethylbenzylamine was added and reacted so that the epoxy equivalent was 890 g/mol, and then the temperature in the reaction vessel was adjusted to 100 while adding 220 parts of methylbutylketone. Cooled to °C. Then, a mixture of 45 parts of N-methylethanolamine and 45 parts of diethylenetriaminediketimine (ketimine compound content rate: 22 mol %) was added and reacted at 115° C. for 1 hour to obtain an amino group-containing epoxy resin solution.
204 parts of the obtained amino group-containing epoxy resin solution was added to a new reaction container, and the temperature inside the reaction container 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. Then, 16 parts of a jER828EL solution having a solid content of 80% solution with propylene glycol monomethyl ether was added and reacted at 90° C. for 3 hours, then methyl isobutyl ketone was removed under reduced pressure and diluted with deionized water to give a solid. A 18% epoxy resin crosslinked particle (C-1) solution was obtained.

Production Example 6
To a reaction vessel equipped with a stirrer, a thermometer, a dropping funnel, and a reflux condenser, jER828EL 478 parts, bisphenol A 238 parts, and dimethylbenzylamine 0.1 part were added, and the temperature in the reaction vessel was maintained at 160° C. The reaction was performed up to an equivalent weight of 1540 g/mol. Then, the temperature in the reaction vessel was cooled to 100° C. while adding 233 parts of methyl butyl ketone. Next, a mixture of 23 parts of N-methylethanolamine and 28 parts of diethylenetriaminediketimine (ketimine compound content rate: 25 mol%) was added and reacted 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 container, and the temperature inside the reaction container 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 and diluted and dispersed.
Then, 11 parts of a jER828EL solution having a solid content of 80% solution with propylene glycol monomethyl ether was added and reacted at 90° C. for 3 hours, then methyl isobutyl ketone was removed under reduced pressure and diluted with deionized water. An epoxy resin crosslinked particle (C-2) solution having a solid content of 18% was obtained.

Production Example 7
To a reaction vessel equipped with a stirrer, a thermometer, a dropping funnel and a reflux condenser, 472 parts of jER828EL, 253 parts of bisphenol A and 0.1 part of dimethylbenzylamine were added, and the temperature in the reaction vessel was maintained at 160° C. The reaction was performed up to an equivalent weight of 2450 g/mol. Then, the temperature in the reaction vessel was cooled to 100° C. while adding 235 parts of methyl butyl ketone. Then, a mixture of 16 parts of N-methylethanolamine and 24 parts of diethylenetriaminediketimine (ketimine compound content rate: 30 mol %) was added and reacted 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 container, and the temperature inside the reaction container 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 and diluted and dispersed.
Then, 11 parts of a jER828EL solution having a solid content of 80% solution with propylene glycol monomethyl ether was added and reacted at 90° C. for 3 hours, then methyl isobutyl ketone was removed under reduced pressure and diluted with deionized water. An epoxy resin crosslinked particle (C-3) solution having a solid content of 18% was obtained.

Production Example 8
To a reaction vessel equipped with a stirrer, a thermometer, a dropping funnel and a reflux condenser, 472 parts of jER828EL, 253 parts of bisphenol A and 0.1 part of dimethylbenzylamine were added, and the temperature in the reaction vessel was maintained at 160° C. The reaction was performed up to an equivalent weight of 2450 g/mol. Then, the temperature in the reaction vessel was cooled to 100° C. while adding 230 parts of methyl butyl ketone. Next, a mixture of 13 parts of N-methylethanolamine and 32 parts of diethylenetriaminediketimine (ketimine compound content rate: 40 mol%) was added and reacted 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 container, and the temperature inside the reaction container was maintained at 90°C. Next, 6 parts of 88% lactic acid was added to neutralize the acid, and 662 parts of deionized water was added to dilute and disperse.
Then, 18 parts of jER828EL solution having a solid content of 80% solution with propylene glycol monomethyl ether was added and reacted at 90° C. for 3 hours, then methyl isobutyl ketone was removed under reduced pressure and diluted with deionized water. An epoxy resin crosslinked particle (C-4) solution having a solid content of 18% was obtained.

Production Example 9
477 parts of jER828EL, 237 parts of bisphenol A, 0.1 part of dimethylbenzylamine were added to a reaction container equipped with a stirrer, a thermometer, a dropping funnel and a reflux condenser, and the temperature in the reaction container was kept at 160° C. The reaction was performed up to an equivalent weight of 1540 g/mol. Then, the temperature in the reaction vessel was cooled to 100° C. while adding 223 parts of methyl butyl ketone. Next, a mixture of 19 parts of N-methylethanolamine and 44 parts of diethylenetriaminediketimine (ketimine compound content rate: 40 mol %) was added and reacted 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 container, and the temperature inside the reaction container 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 and diluted and dispersed.
Then, 16 parts of a jER828EL solution having a solid content of 80% solution with propylene glycol monomethyl ether was added and reacted at 90° C. for 3 hours, then methyl isobutyl ketone was removed under reduced pressure and diluted with deionized water. An epoxy resin crosslinked particle (C-5) solution having a solid content of 18% was obtained.

Production Example 10
470 parts of jER828EL, 252 parts of bisphenol A, and 0.1 part of dimethylbenzylamine were added to a reaction container equipped with a stirrer, a thermometer, a dropping funnel and a reflux condenser, and the temperature in the reaction container was kept at 160° C. The reaction was performed up to an equivalent weight of 2450 g/mol. Then, the temperature in the reaction vessel was cooled to 100° C. while adding 226 parts of methyl butyl ketone. Next, a mixture of 3 parts of diethylenetriamine, 9 parts of N-methylethanolamine and 39 parts of diethylenetriaminediketimine (content ratio of ketimine compound: 50 mol %) was added and reacted at 115° C. for 1 hour to give an amino group-containing epoxy resin solution. Got
211 parts of the obtained amino group-containing epoxy resin solution was added to a new reaction container, and the temperature inside the reaction container was maintained at 90°C. Next, 88 parts of 88% lactic acid was added to neutralize the acid, and 663 parts of deionized water was added and diluted and dispersed.
Then, 18 parts of jER828EL solution having a solid content of 80% solution with propylene glycol monomethyl ether was added and reacted at 90° C. for 3 hours, then methyl isobutyl ketone was removed under reduced pressure and diluted with deionized water. A solution of crosslinked epoxy resin particles (C-6) having a solid content of 18% was obtained.

Production Example 11
In a reaction vessel equipped with a stirrer, a thermometer, a dropping funnel and a reflux condenser, 1023 parts of DER-331J (trade name, bisphenol A type epoxy resin manufactured by Dow Chemical Company), 365 parts of bisphenol A-ethylene oxide adduct, bisphenol A 297. And 88.7 parts of methyl isobutyl ketone were added and heated to 140° C. under a nitrogen atmosphere.
1.4 parts of benzyldimethylamine were added and the reaction mixture was left to exotherm to about 185° C. and refluxed to remove water. Then, it was cooled to 160° C., kept for 30 minutes, further cooled to 145° C., and 4.2 parts of benzyldimethylamine was added.
The reaction was continued at 145° C. until the Gardner-Holdt viscosity (measured in 2-methoxypropanol 50% resin solids) was O-P. At this point, the reaction mixture was cooled to 125° C. and a mixture of 131 parts diethylenetriaminediketimine (ketimine compound content: 60 mol %) and 85.2 parts N-methylethanolamine was added.
The mixture exothermed to 140° C., cooled to 125° C. and kept at this temperature for 1 hour to obtain an amino group-containing epoxy resin solution.
One hour later, 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. Then, it was further diluted with deionized water, and diluted and dispersed so that the solid content was 31%.
Thereafter, 2258.1 parts of the above-obtained dispersion and 1510.8 parts of deionized water were mixed and stirred, and 71.7 parts of DER-331J (trade name, bisphenol A type epoxy resin manufactured by Dow Chemical Co.) and methyl. A mixed solution of 17.9 parts of isobutyl ketone was added with stirring. Then, it was heated to 90° C. and kept warm 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 give a solution of crosslinked epoxy resin particles (C-7) having a solid content of 18%. Obtained.

Production Example 12
To a reaction vessel equipped with a stirrer, a thermometer, a dropping funnel and a reflux condenser, 940 parts of DER-331J (trade name, bisphenol A type epoxy resin manufactured by Dow Chemical Co.), 388 parts of bisphenol A, and 2 parts of dimethylbenzylamine were added. The temperature in the reaction vessel was maintained at 140° C., and the reaction was performed until the epoxy equivalent reached 800 g/eq, and then the temperature in the reaction vessel was cooled to 120° C.
Then, a mixture of 258 parts of diethylenetriamine diketimine (a solution of methylisobutylketone having a solid content of 73%) (ketimine compound content: 50 mol %), 21 parts of N-methylethanolamine and 45 parts of diethylenetriamine is added, and the mixture is added at 120° C. for 1 hour. By reacting, an amino group-containing epoxy resin solution was obtained.
Then, after cooling to 90° C., deionized water and acetic acid are added so that the amino group neutralization rate of the amino group-containing epoxy resin is 18% to acid-neutralize, and deionized water is added to solidify. It was diluted and dispersed so that the content was 20%.
Then, 188 parts of DER-331J (trade name, bisphenol A type epoxy resin manufactured by Dow Chemical Co.) was added and reacted at 90° C. for 3 hours. Methyl isobutyl ketone was removed under reduced pressure, and deionized water was added to obtain a solution of crosslinked epoxy resin particles (C-8) having a solid content of 18%.

The number average molecular weight, high molecular weight, insoluble component ratio, and volume average particle diameter of the epoxy resin crosslinked particles obtained in Production Examples 5 to 12 are shown in Table 1 below.

(Note 1) Number average molecular weight: Epoxy resin crosslinked particles were diluted with N,N'-dimethylformamide to a concentration of solid content of 1% by mass, and allowed to stand at room temperature for 24 hours. Then, the insoluble component (crosslinking component) is removed by filtration through a Gishory filter for GPC (pore size: 0.2 micron), and gel permeation chromatography (GPC) [“HLC8120GPC” (trade name, manufactured by Tosoh Corporation)] is used. The number average molecular weight was measured.
(Note 2) High molecular weight (%): In the above molecular weight measurement data, the ratio (%) of the peak area having a molecular weight of 100,000 or more to the total peak area is shown.
(Note 3) Insoluble component ratio (mass %): The epoxy resin cross-linked particles were diluted with N,N′-dimethylformamide to a solid content concentration of 1 mass %, and allowed to stand at room temperature for 24 hours. Subsequently, the mixture was filtered through a Gishory filter for GPC (pore size: 0.2 micron), and the proportion of the insoluble component (crosslinking component) was calculated by the following formula.
Insoluble component ratio (mass %)=A/B×100
[A: mass of solid content of filtration residue, B: mass of epoxy resin crosslinked particle (C) solution diluted to 1 mass% solid content/100].
(Note 4) Volume average particle diameter (nm): Epoxy resin crosslinked particles were measured with Microtrac UPA250 (trade name, manufactured by Nikkiso Co., Ltd., particle size distribution measuring device).

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

Examples 2-11, Comparative Examples 1-5
Cationic electrodeposition coating compositions (X-2) to (X-16) were produced in the same manner as in Example 1 except that the formulations shown in Table 2 below were used.
Further, the results of the evaluation tests (edge part anticorrosion property, flat part anticorrosion property, finish property) described later 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.

The compounding amounts in the table are all solid content values.

<Corrosion resistance of edge>
A test plate with a cutter blade (blade angle of 20 degrees, length of 10 cm, zinc phosphate treatment) at a bath temperature of 28° C., with the energization time adjusted and electrodeposition coating to give a film thickness of 15 μm on the general surface It was created.
Next, this was subjected to a salt water spray resistance test for 96 hours according to JIS Z-2371, and the edge portion was evaluated according to the following criteria.
In the evaluation, “⊚”, “◯”, “◯Δ” and “Δ” are acceptable, and “x” is not acceptable.
⊚: No rust generated ◯: Number of rust generated was 10 or less/10 cm
○ △: The number of rusts generated is 11 to 25/10 cm
Δ: The number of rust generated is 26 to 40/10 cm
X: The number of rust generated is 41/10 cm or more.

Preparation of test plate Cold-rolled steel sheet (150 mm (length) x 70 mm (width) x 0.8 mm (thickness)) subjected to chemical conversion treatment (trade name, Palbond #3020, manufactured by Nippon Parkerizing Co., Ltd., zinc phosphate treatment agent) Each of the cationic electrodeposition coating materials obtained in Examples and Comparative Examples was used as an article to be coated, and electrodeposition coating was performed so that the dry film thickness was 15 μm, and the coating was baked and dried at 170° C. for 20 minutes to obtain a test plate.

<Flat part anticorrosion>
Cross-cut scratches were made on the coating film with a cutter knife so as to reach the base of the test plate, and this was subjected to a 35°C salt spray test for 840 hours according to JIS Z-2371, and rust and blisters on one side from the cut part The width was evaluated according to the following criteria.
In the evaluation, “⊚”, “◯”, “◯Δ” and “Δ” are acceptable, and “x” is not acceptable.
⊚: The maximum width of rust and blisters is 2.0 mm or less on one side from the cut part,
◯: The maximum width of rust and blistering exceeds 2.0 on one side of the cut portion and 3.0 mm or less,
Δ: The maximum width of rust and blisters exceeds 3.0 mm on one side of the cut portion and 3.5 mm or less,
X: The maximum width of rust and blisters exceeds 3.5 mm on one side of the cut portion.

<Finishability (surface roughness)>
The surface roughness value (Ra) of the coated surface of the obtained test plate was measured at a cutoff of 0.8 mm using Surftest 301 (trade name, manufactured by Mitutoyo Corporation, surface roughness meter). It was evaluated according to the standard.
In the evaluation, “⊚”, “◯”, “◯Δ” and “Δ” are acceptable, and “x” is not acceptable.
⊚: Surface roughness value (Ra) is less than 0.2,
◯: Surface roughness value (Ra) is 0.2 or more and less than 0.24,
B: Surface roughness value (Ra) is 0.24 or more and less than 0.28,
Δ: Surface roughness value (Ra) is 0.28 or more and less than 0.32,
X: Surface roughness value (Ra) is 0.32 or more.

Claims (6)

A cationic electrodeposition coating composition comprising an amino group-containing epoxy resin (A), a blocked polyisocyanate compound (B), and epoxy resin crosslinked particles (C), wherein the amino group-containing epoxy resin (A) and the blocked resin composition are blocked. The coating composition contains 0.1 to 40 parts by mass of the epoxy resin crosslinked particles (C) based on the total solid content of the polyisocyanate compound (B), and the epoxy resin crosslinked particles (C) contains an amino group. It is a reaction product of the epoxy resin (C-1) and the epoxy resin (C-2), and the number average molecular weight of the epoxy resin crosslinked particles (C) measured by the following method is 8,000 or less. A characteristic cationic electrodeposition coating composition.
<Measurement method of number average molecular weight>
The epoxy resin crosslinked particles (C) were diluted with N,N'-dimethylformamide to a solid content concentration of 1% by mass, and allowed to stand at room temperature for 24 hours. Then, insoluble components were removed by filtration, and the number average molecular weight was measured using gel permeation chromatography (GPC). The cationic electrodeposition coating composition according to claim 1, wherein the ratio of the insoluble component (crosslinking component) when the epoxy resin crosslinked particles (C) is measured by the following method is 10% by mass or more.
<Method of measuring insoluble component (crosslinking component) ratio>
The epoxy resin crosslinked particles (C) were diluted with N,N'-dimethylformamide to a solid content concentration of 1% by mass, and allowed to stand at room temperature for 24 hours. Next, the insoluble component (crosslinking component) was filtered through a Gishory filter for GPC (pore size: 0.2 micron), and the residue was dried under the condition of 130° C. for 3 hours to measure the solid content mass of the residue. The ratio (mass %) of the insoluble component (crosslinking component) can be calculated by the following formula.
Insoluble component (crosslinking component) ratio (mass %)=A/B×100
A: Solid content mass of filtration residue B: Mass of epoxy resin crosslinked particle (C) solution diluted to 1 mass% solid content/100 The amino group-containing epoxy resin (C-1) is a reaction product of the epoxy resin (C-1-1) and the amine compound (C-1-2), and the amine compound (C-1-2) Contains the ketiminated amine compound (C-1-2-1) in an amount of 2 mol% or more and less than 40 mol%, the cationic electrodeposition coating composition according to claim 1 or 2. Stuff. The cationic electrodeposition coating composition according to any one of claims 1 to 4 , which has a high molecular weight (peak area having a molecular weight of 100,000 or more) of less than 40%. Claim 1 of the metal object to be coated was immersed in comprising electrodeposition coating bath from a cationic electrodeposition coating composition 4, electrodeposition coating painting method. A method for producing a coated article, comprising the steps of forming a coating film by the coating method according to claim 5 and then heat curing.