JP6012744B2 - Cationic electrodeposition coating composition - Google Patents

Description

[Cross-reference of related applications]
This application claims priority based on Japanese Patent Application No. 2012-220323, the entire disclosure of which is incorporated herein by reference, filed on October 2, 2012. The present invention relates to a cationic electrodeposition coating composition having good coating stability and excellent throwing power and corrosion resistance.

  Cationic electrodeposition coating compositions are widely used as primer coatings for conductive metal products such as automobile bodies that require these performances due to excellent coating workability and good corrosion resistance of the formed coating film. Yes.

Conventionally, the strength of an automobile body has been increased from the viewpoint of improving collision safety, and a reinforcing material is further added to a member welded by spot welding, so that the number of objects to be coated having a complicated bag portion has increased. In such a structure, since the current density (mA / cm ² ) at the time of electrodeposition coating decreases, the coating film hardly deposits and the bag portion is unpainted. The deterioration of the anticorrosion property was remarkable under the severe environment.

  For this reason, when the coating voltage is increased to ensure the film thickness (μm) of the bag portion (improvement of so-called “throwing power”), the finishing performance is reduced, or the thickness of the outer plate of the object to be coated (μm) There was a problem that the amount of paint used increased as the thickness of the film increased.

  For this reason, various electrodeposition paints have been proposed for the purpose of improving paint stability, throwing power and anticorrosion.

  For example, a hydroxyl group-containing carboxylic acid (B) and an amino group-containing compound (C) obtained by reacting a hydroxyl group of hydroxymonocarboxylic acid (b1) with caprolactone (b2) to an epoxy resin (A) having an epoxy equivalent of 400 to 2500 A cationic electrodeposition coating composition using an amino group-containing epoxy resin obtained by reacting as a resin component is disclosed (Patent Document 1).

  An amino group obtained by reacting an epoxy resin having an epoxy equivalent of 180 to 2,500 with an alkylphenol compound, a polyol obtained by adding caprolactone to a compound containing a plurality of active hydrogen groups, and an amino group-containing compound. A cationic electrodeposition coating composition containing a contained epoxy resin as a resin component is disclosed (Patent Document 2).

  However, the cationic electrodeposition coating compositions described in Patent Literature 1 and Patent Literature 2 have good coating stability and cannot satisfy throwing power and corrosion resistance.

JP 2002-161232 A JP 2004-307871 A

  The problem to be solved by the invention is to provide a cationic electrodeposition coating composition having good paint stability, excellent throwing power and anticorrosion properties, and providing a coated article excellent in these various coating film performances. It is.

    As a result of intensive studies in order to solve the above problems, the inventors of the present invention have developed a cationic electrodeposition containing a specific modified epoxy resin (A), an amino group-containing epoxy resin (B), and a blocked polyisocyanate curing agent (C). It has been found that the above-mentioned problems can be solved by the coating composition, and the present invention has been completed.

That is, the present invention
1. A cationic electrodeposition coating composition containing the following modified epoxy resin (A), amino group-containing epoxy resin (B), and blocked polyisocyanate curing agent (C), comprising (A) component, (B) component and (C) 3-40 mass% of modified epoxy resin (A), 20-60 mass% of amino group-containing epoxy resin (B), blocked polyisocyanate curing agent (C) 10 based on the total solid content of component (C) Cationic electrodeposition coating composition containing -40% by mass.

Modified epoxy resin (A):
At least one acidic compound selected from the carboxylic acid-containing compound (a21) of the following formula (1) and the phenol compound (a22) of the following formula (2) in the epoxy resin (a1) having an epoxy equivalent of 180 to 4,000 A modified epoxy resin (A) obtained by reacting (a2), [[carboxyl group of carboxylic acid-containing compound (a21) and / or hydroxyl group of phenol compound (a22)] / epoxy group of epoxy resin (a1) ] Is an epoxy resin having an equivalent ratio of 0.8 to 1.15

(X represents a hydrocarbon group having 1 to 23 carbon atoms which may have a substituent selected from the group consisting of —OH, —OR, —SH and —SR, and R represents an alkyl group)

(Y represents a hydrogen atom or optionally a hydrocarbon group having 1 to 23 carbon atoms which may have a substituent selected from the group consisting of —OR, —SH and —SR, and R represents an alkyl group. Represent)
A coated article obtained by electrodeposition-coating a metal coating using the cationic electrodeposition coating composition described in Section 2.1 as an electrodeposition coating bath;
A method for forming a coating film, comprising: using the cationic electrodeposition coating composition according to Section 3.1 as an electrodeposition coating bath; immersing the coating object in the bath; and energizing the immersed coating object. About.

  The cationic electrodeposition coating composition of the present invention has good coating stability, and the coating film obtained by electrodeposition coating of the cationic electrodeposition coating composition is excellent in throwing power and corrosion resistance.

  Specifically, an automobile coated with the product of the present invention has little corrosion deterioration of the paint film on the automobile body even when running for a long time in an environment where snow melting salt is dispersed. Furthermore, in the coating line, since the paint stability is excellent, there is little blockage of the ultrafiltration membrane (UF filter).

It is a model figure of the jig | tool for a throwing power test with 4 boxes used for a throwing power test. The electrodeposition coating state in the throwing power test is shown.

  The present invention relates to a cationic electrodeposition coating composition containing a specific modified epoxy resin (A), an amino group-containing epoxy resin (B), and a blocked polyisocyanate curing agent (C). Details will be described below.

[Modified epoxy resin (A)]
The modified epoxy resin (A) used in the cationic electrodeposition coating composition of the present invention is obtained by adding the carboxylic acids (a21) of the following formula (1) and the following formula (A1) to the epoxy resin (a1) having an epoxy equivalent of 180 to 4,000. 2) A resin obtained by blending at least one acidic compound (a2) selected from phenols (a22) and, if necessary, a modifier (a3) and reacting them.

(X represents a hydrocarbon group having 1 to 23 carbon atoms which may have a substituent selected from the group consisting of —OH, —OR, —SH and —SR, and R represents an alkyl group)

(Y represents a hydrogen atom or optionally a hydrocarbon group having 1 to 23 carbon atoms which may have a substituent selected from the group consisting of —OR, —SH and —SR, and R represents an alkyl group. Represent)
In addition, in this specification, the acidic compound of the carboxylic acid (a21) of the said Formula (1) is shown as the carboxylic acid containing compound (a21) of the said Formula (1). Similarly, the phenols (a22) of the above formula (2) are referred to as phenol compounds (a22) of the above formula (2).

Epoxy resin (a1)
The epoxy resin (a1) used for the production of the modified epoxy resin (A) is:
It is a compound having at least one, preferably two or more epoxy groups in one molecule, its number average molecular weight is in the range of 400 to 4,000, preferably 800 to 2,500, and the epoxy equivalent is 180 to 2, Those having a range of 500, preferably 400 to 1,500 are suitable, and those obtained by the reaction of a polyphenol compound and epihalohydrin are particularly preferred.

  Examples of the polyphenol compound used for forming the epoxy resin (a1) include bis (4-hydroxyphenyl) -2,2-propane [bisphenol A] and 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, , It may be mentioned 4'-dihydroxydiphenyl sulfone, phenol novolak, and cresol novolak.

  Moreover, as an epoxy resin (a1) obtained by reaction of a polyphenol compound and epichlorohydrin, the resin of the following formula induced | guided | derived from bisphenol A is suitable especially.

  Here, what is shown by n = 1-8 is suitable.

  Examples of such commercially available epoxy resin (a1) include those sold by Mitsubishi Chemical Corporation under the trade names jER828EL, jER1001, jER1002, jER1004, and jER1007.

  The epoxy resin (a1) is, for example, a resin obtained by condensing epichlorohydrin and bisphenol up to a high molecular weight in the presence of a catalyst such as an alkali catalyst, if necessary, and epichlorohydrin and bisphenol, if necessary. Any of resins obtained by condensation in the presence of a catalyst such as a catalyst to form a low molecular weight epoxy resin and a polyaddition reaction of the low molecular weight epoxy resin and bisphenol may be used.

  The epoxy resin (a1) may be modified as required by reacting with a modifier. Such a modifier is not particularly limited as long as it is a resin or compound having reactivity with the epoxy resin. For example, polyol, polyether polyol, polyester polyol, polyamidoamine, polycarboxylic acid, fatty acid, polyisocyanate compound, Examples include lactone compounds such as ε-caprolactone, compounds obtained by reacting lactone compounds such as ε-caprolactone and polyisocyanate compounds, acrylic monomers, compounds obtained by polymerization reaction of acrylic monomers, and xylene formaldehyde compounds.

Acidic compound (a2)
According to the present invention, the acidic compound (a2) that reacts with the epoxy resin (a1) is at least one selected from the carboxylic acid-containing compound (a21) of the following formula (1) and the phenolic compound (a22) of the following formula (2). It is a compound of this.

(X represents a hydrocarbon group having 1 to 23 carbon atoms which may have a substituent selected from the group consisting of —OH, —OR, —SH and —SR, and R represents an alkyl group)

(Y represents a hydrogen atom or optionally a hydrocarbon group having 1 to 23 carbon atoms which may have a substituent selected from the group consisting of —OR, —SH and —SR, and R represents an alkyl group. Represent)
In the above formula (1), the hydrocarbon group having 1 to 23 carbon atoms represented by X can be linear, branched or cyclic, and examples thereof include methyl, ethyl, n-propyl, An alkyl group having 1 to 23 carbon atoms, particularly 4 to 20 carbon atoms, more preferably 5 to 12 carbon atoms such as isopropyl, n-butyl, tert-butyl, hexyl, heptyl, nonyl, icosyl and tricosyl group; vinyl, 1-propenyl, C2-C23 alkenyl group such as 3-hexenyl, 7-hexadecenyl, 7-icocenyl, etc., especially 4-20 Cyl; C6-C23 such as phenyl group, naphthyl group, biphenyl group, especially 6-20 aryl Groups etc. are preferred. Of these, the alkyl group and aryl group are particularly preferable, and an alkyl group is more preferable. These groups may optionally be substituted with a group selected from the group consisting of a hydroxyl group (—OH), an alkoxy group (—OR), a mercapto group (—SH), and an alkylthio group (—SR). When there are a plurality of substituents, these substituents may be the same or different. When the hydrocarbon group having 1 to 23 carbon atoms represented by X has a substituent, the number of the substituent is not particularly limited, but for example, at least 1, preferably 1 to 3, more preferably 1 to It is preferred to have two substituents.

  When the hydrocarbon group represented by X has an alkoxy group (—OR) and / or an alkylthio group (—SR) as a substituent, the alkyl group represented by R is not particularly limited, but for example, methyl, ethyl , Propyl, isopropyl, butyl, pentyl, hexyl group and the like, and a linear or branched alkyl group having 1 to 8 carbon atoms.

  The carboxylic acid-containing compound (a21) of the above formula (1) is, for example, acetic acid, propionic acid, butyric acid, valeric acid, acrylic acid, oleic acid, glycolic acid, glyceric acid, lactic acid, dimethylolpropionic acid, dimethylolbutyric acid, dimethylol. Examples include valeric acid, benzoic acid, gallic acid and the like. Among these, valeric acid, octylic acid, oleic acid, dimethylolpropionic acid, dimethylolbutyric acid, dimethylolvaleric acid, and benzoic acid are preferable.

  The carboxylic acid-containing compound (a21) of the above formula (1) may be used alone or in combination of two or more.

  Examples of the phenol compound (a22) of the above formula (2) include phenol, cresol, ethylphenol, para-tert-butylphenol, and nonylphenol, and alkylphenol is particularly preferable.

  In the above formula (2), the hydrocarbon group having 1 to 23 carbon atoms represented by Y can be linear, branched or cyclic. Specifically, for example, methyl, ethyl , N-propyl, isopropyl, n-butyl, hexyl, heptyl, nonyl, icosyl, tricosyl group, etc., alkyl having 1 to 23 carbon atoms, particularly 4 to 20 carbon atoms, more preferably 7 to 11 (for example, 8 to 10). Groups; alkenyl groups such as vinyl and oleyl groups; aryl groups such as phenyl groups, and the like.

  These groups may optionally be substituted with at least one, preferably 1 to 3 groups selected from the group consisting of a hydroxyl group, an alkoxy group, a mercapto group and an alkylthio group. Examples of the hydrocarbon group substituted with such a group include 1-hydroxyethyl, 1,1-dimethylolethyl, 1,1-dimethylolpropyl, 3,4,5-trihydroxyphenyl group, and the like.

  The phenol compound (a22) of (2) may be used alone or in combination of two or more.

  The reaction between the epoxy resin (a1) and the acidic compound (a2) described above is carried out by [the carboxyl group of the carboxylic acid-containing compound (a21) and / or the hydroxyl group of the phenol compound (a22)] / epoxy resin (a1). It is possible to react (a1) component with (a2) component so that the equivalent ratio of [epoxy group] is 0.8 to 1.15, preferably 0.9 to 1.11. It is important in terms of electrodeposition characteristics and anticorrosive properties of the coating film. When the blending ratio is exceeded, a part of the carboxyl group and / or hydroxyl group of the component (a21) and / or the component (a22) remains without reacting, which may affect the dispersibility and electrodeposition characteristics of the resin. is there.

Denaturant (a3)
As the modified epoxy resin (A), if necessary, a modified epoxy resin (A3) may be used by blending a modifier (a3). Such a modifier (a3) is not particularly limited as long as it is a resin or compound having reactivity with an epoxy resin. For example, polyol, polyether polyol, polyester polyol, polyglycidyl ether, polyisocyanate compound, polyisocyanate compound A lactone compound such as ε-caprolactone, an acrylic monomer, a compound obtained by polymerizing an acrylic monomer, or a xylene formaldehyde compound can also be used as a modifier.

  The modified epoxy resin (A) used as a resin component in the cationic electrodeposition coating composition of the present invention contains the acidic compound (a2) and, if necessary, the modifier (a3) in the epoxy resin (a1). And it can manufacture by making it react by a method known per se.

  The reaction with the epoxy resin (a1), the acidic compound (a2), and the modifying agent (a3) blended as necessary is usually about 60 to about 60 to about 5 to about 5 in an appropriate solvent. The reaction can be performed at a temperature of about 250 ° C., preferably about 70 to about 200 ° C. for about 1 to 25 hours, preferably about 1 to 12 hours.

  Examples of the organic solvent include hydrocarbon solvents such as toluene, xylene, cyclohexane, and n-hexane; ester solvents such as methyl acetate, ethyl acetate, and butyl acetate; acetone, methyl ethyl ketone, methyl isobutyl ketone, and methyl amyl ketone. Ketone solvents; amide solvents such as dimethylformamide and dimethylacetamide; alcohol solvents such as methanol, ethanol, n-propanol, and iso-propanol; or a mixture thereof. Examples thereof include titanium compounds such as tetrabutoxy titanium and tetrapropoxy titanium; organotin compounds such as tin octylate, dibutyltin oxide and dibutyltin laurate; metal compounds such as stannous chloride; and organic amine compounds. . In this way, a reaction product in which the acidic compound (a2) is added to the skeleton of the epoxy resin (a1) is obtained.

  The above addition reaction is usually carried out in an appropriate solvent as described above 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. The proportion of each reaction component used in the above reaction can be appropriately changed depending on the application of the coating composition, etc., but the epoxy resin (a1), the acidic compound (a2), and, if necessary, the modifier (a3) The epoxy resin (a1) is generally 60 to 85% by mass, preferably 64 to 82% by mass, and the acidic compound (a2) is generally 15 to 40% by mass, preferably 17 to 17%, based on the total solid content. The content of 26% by mass and the modifier (a3) is generally 25% by mass or less, preferably 1 to 10% by mass.

  The number average molecular weight of the modified epoxy resin (A) is more than 1,000 and not more than 7,000, preferably in the range of 1,050 to 3,500, from the viewpoint of throwing power and corrosion resistance. It is preferred to have a number average molecular weight.

  In this specification, the number average molecular weight and the weight average molecular weight are values obtained by converting the number average molecular weight and the weight average molecular weight measured using a gel permeation chromatograph (GPC) based on the molecular weight of standard polystyrene. is there. Specifically, “HLC8120GPC” (trade name, manufactured by Tosoh Corporation) is used as a gel permeation chromatograph, and “TSKgel G-4000HXL”, “TSKgel G-3000HXL”, “TSKgel G-2500HXL” are used as columns. ”And“ TSKgel G-2000HXL ”(trade names, all manufactured by Tosoh Corporation), and can be measured under the conditions of mobile phase tetrahydrofuran, measurement temperature 40 ° C., flow rate 1 mL / min, and detector RI. it can.

[Amino group-containing epoxy resin (B)]
The amino group-containing epoxy resin (B) used in the present invention is a resin obtained by blending an epoxy resin (b1), an amine compound (b2), and, if necessary, a modifier and reacting them.

  The amino group-containing epoxy resin (B) includes, for example, (1) an adduct of an epoxy resin and a primary amine compound, a secondary amine compound, or a primary and secondary mixed amine compound (for example, US Pat. No. 3, 984, 299); (2) Adducts of epoxy resins and secondary amine compounds obtained by ketiminization of primary amine compounds (see, for example, US Pat. No. 4,017,438) And (3) a reaction product obtained by etherification of an epoxy resin and a ketiminated hydroxy compound having a primary amino group (for example, see JP-A-59-43013).

Epoxy resin (b1):
The epoxy resin (b1) used for the production of the amino group-containing epoxy resin (B) is a compound having at least one, preferably two or more epoxy groups in one molecule, and its number average molecular weight is 400. ˜4,000, preferably in the range of 800 to 2,500, and epoxy equivalent having a range of 180 to 2,500, preferably in the range of 400 to 1,500, particularly suitable for the reaction between polyphenol compounds and epihalohydrins. The epoxy resin obtained by is preferable.

  Examples of the polyphenol compound used for forming the epoxy resin (b1) include bis (4-hydroxyphenyl) -2,2-propane [bisphenol A] and 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, , It may be mentioned 4'-dihydroxydiphenyl sulfone, phenol novolak, and cresol novolak.

  Moreover, as an epoxy resin (b1) obtained by reaction of a polyphenol compound and epichlorohydrin, the resin of the following formula induced | guided | derived from bisphenol A is suitable especially.

  Here, what is shown by n = 0-8 is suitable.

  Examples of such commercially available epoxy resin (b1) include those sold by Mitsubishi Chemical Corporation under the trade names jER828EL, jER1001, jER1002, jER1004, and jER1007.

  The epoxy resin (b1) is, for example, a resin obtained by condensing epichlorohydrin and bisphenol up to a high molecular weight in the presence of a catalyst such as an alkali catalyst, if necessary, and epichlorohydrin and bisphenol, if necessary. Any of resins obtained by condensation in the presence of a catalyst such as a catalyst to form a low molecular weight epoxy resin and a polyaddition reaction of the low molecular weight epoxy resin and bisphenol may be used.

  As the epoxy resin (b1), an epoxy resin (b1) that has undergone internal modification by reacting with a modifying agent (b3) may be used as necessary. Such a modifier (b3) is not particularly limited as long as it is a resin or compound having reactivity with the epoxy resin. For example, polyol, polyether polyol, polyester polyol, polyamidoamine, polycarboxylic acid, fatty acid, poly Examples thereof include isocyanate compounds, lactone compounds such as ε-caprolactone, compounds obtained by reacting lactone compounds such as ε-caprolactone with polyisocyanate compounds, acrylic monomers, compounds obtained by polymerizing acrylic monomers, and xylene formaldehyde compounds.

Amine compound (b2):
Examples of the amine compound (b2) used in the production of the amino group-containing epoxy resin (B) include monomethylamine, dimethylamine, monoethylamine, diethylamine, monoisopropylamine, diisopropylamine, monobutylamine, and dibutylamine. Mono- or di-alkylamines; monoethanolamine, diethanolamine, mono (2-hydroxypropyl) amine, di (2-hydroxypropyl) amine, monomethylaminoethanol, N- (2-hydroxypropyl) ethylenediamine, 3-methyl Alkanolamines such as amine-1,2-propanediol, 3-tert-butylamino-1,2-propanediol, N-methylglucamine, N-octylglucamine; ethylenediamine, propylenediamine Alkylene diamines such as butylenediamine, hexamethylenediamine, diethylenetriamine, dipropylenetriamine, bis (hexamethylene) triamine, triethylenetetramine; polyamines having heterocycles such as 3-pyrrolidinol, 3-piperidinol, 4-pyrrolidinol; Methyl isobutyl ketone, methyl ethyl ketone, amine compounds such as monoethanolamine, mono (2-hydroxypropyl) amine, N- (2-hydroxypropyl) ethylenediamine, diethylenetriamine, dipropylenetriamine, bis (hexamethylene) triamine, triethylenetetramine, Examples thereof include ketiminated amine compounds obtained by reacting a ketone compound such as cyclohexanone.

  The amino group-containing epoxy resin (B) may be modified by blending a modifier (b3) as necessary.

  Such a modifier (b3) is not particularly limited as long as it is a resin or compound having reactivity with the epoxy resin (b1). For example, diol, polyol, polyether polyol, polyester polyol, polyamidoamine, polycarboxylic acid are used. Acids, fatty acids, polyisocyanate compounds, lactone compounds such as ε-caprolactone, compounds obtained by reacting lactone compounds such as ε-caprolactone with polyisocyanate compounds, acrylic monomers, compounds obtained by polymerizing acrylic monomers, xylene formaldehyde compounds, etc. Can be used.

  The use ratio of the above modifier is not strictly limited and can be appropriately changed depending on the use of the cationic electrodeposition coating composition, etc., but from the viewpoint of improving finish and anticorrosion, an amino group-containing A suitable range is 0 to 50% by mass, preferably 5 to 30% by mass, based on the solid content of the epoxy resin (B).

  The reaction with the epoxy resin (b1), the amine compound (b2), and a modifier used as necessary is usually about 80 to about 170 ° C., preferably about 90 to about 90 ° C. in a suitable organic solvent. It is carried out at a temperature of 150 ° C. for about 1 to 6 hours, preferably about 1 to 5 hours.

  Examples of the organic solvent include hydrocarbon solvents such as toluene, xylene, cyclohexane, and n-hexane; ester solvents such as methyl acetate, ethyl acetate, and butyl acetate; acetone, methyl ethyl ketone, methyl isobutyl ketone, and methyl amyl ketone. Ketone solvents such as amide solvents such as dimethylformamide and dimethylacetamide; alcohol solvents such as methanol, ethanol, n-propanol and iso-propanol; ether alcohol compounds such as ethylene glycol monobutyl ether and diethylene glycol monoethyl ether; Or the mixture of these organic solvents is mentioned.

  The amine value of the amino group-containing epoxy resin (B) thus obtained is 40 to 80 mg KOH / g resin solid content, preferably 45 to 65 mg KOH / g resin solid content. From the viewpoints of safety and corrosion resistance. The number average molecular weight of the amino group-containing epoxy resin (B) is preferably 1,500 to 5,000, more preferably 2,000 to 4,000 from the viewpoint of throwing power and corrosion resistance.

[Blocked polyisocyanate curing agent (C)]
The blocked polyisocyanate curing agent (C) is a product resulting from an addition reaction between a polyisocyanate compound and an isocyanate blocking agent. As the polyisocyanate compound used in the blocked polyisocyanate curing agent (C), known compounds can be used, such as tolylene diisocyanate, xylylene diisocyanate, phenylene diisocyanate, diphenylmethane-2,2′-diisocyanate. , Diphenylmethane-2,4′-diisocyanate, diphenylmethane-4,4′-diisocyanate, crude MDI [polymethylene polyphenyl isocyanate], bis (isocyanate methyl) cyclohexane, tetramethylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate, isophorone diisocyanate, etc. Aromatic, aliphatic or alicyclic polyisocyanate compounds; cyclized polymers or polymers of these polyisocyanate compounds Let thereof; 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 are more preferable for corrosion resistance.

  On the other hand, the isocyanate blocking agent is added and blocked to the isocyanate group of the polyisocyanate compound, and the blocked polyisocyanate compound produced by the addition reaction is stable at normal temperature, but the coating baking temperature (usually When heated to about 100 to about 200 ° C., it is desirable that the blocking agent dissociates to regenerate free isocyanate groups.

  Examples of the isocyanate blocking agent used in the blocked polyisocyanate curing agent (C) include oxime compounds such as methyl ethyl ketoxime and cyclohexanone oxime; phenol compounds such as phenol, para-t-butylphenol and cresol; n-butanol Alcohol compounds such as 2-ethylhexanol, phenyl carbinol, methyl phenyl carbinol, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, ethylene glycol, propylene glycol; lactam compounds such as ε-caprolactam and γ-butyrolactam; Active methylenes such as dimethyl acid, diethyl malonate, dipropyl malonate, ethyl acetoacetate, methyl acetoacetate, acetylacetone Compounds and the like.

Production of cationic electrodeposition coating composition The blending ratio of the modified epoxy resin (A), amino group-containing epoxy resin (B) and blocked polyisocyanate curing agent (C) in the cationic electrodeposition coating composition of the present invention is as described above. Based on the total solid content of component (A), component (B) and component (C), component (A) is 3 to 40% by mass, preferably 10 to 37% by mass, and component (B) is 20 to 20%. 60 mass%, preferably 28-55 mass%, and component (C) is in the range of 10-40 mass%, preferably 15-35 mass%.

  If the blending amount of the modified epoxy resin (A) is less than 3% by mass, corrosion resistance and corrosion resistance may be impaired, and if it exceeds 40% by mass, corrosion resistance and paint stability may be impaired. When the blending amount of the amino group-containing epoxy resin (B) is less than 20% by mass, the coating stability may be impaired, and when it exceeds 60% by mass, the anticorrosion and the corrosion resistance may be impaired.

  If the blending amount of the blocked polyisocyanate curing agent (C) is less than 10% by mass, the corrosion resistance and paint stability may be impaired, and if it exceeds 40% by mass, the stability of the paint may be impaired.

  The cationic electrodeposition coating composition of the present invention is prepared by thoroughly mixing various additives such as a surfactant and a surface conditioner, an organic solvent, and the like in addition to the above components to obtain a compounded resin. An emulsion is obtained by water-solubilization or water-dispersion with carboxylic acid or the like. In addition, generally publicly known organic carboxylic acid can be used for neutralization of compound resin, but especially acetic acid, formic acid, lactic acid, or a mixture thereof is preferred. Subsequently, it can adjust by adding a pigment dispersion paste and water to an emulsion.

  The above-mentioned pigment dispersion paste is prepared by dispersing colored pigments, rust preventive pigments and extender pigments in fine particles in advance. For example, a pigment dispersing resin, a neutralizing agent and a pigment are blended, and a ball mill, sand mill, pebble mill, etc. A pigment dispersion paste can be prepared by dispersing in a dispersion mixer.

  As the pigment dispersion resin, known resins can be used, for example, epoxy resins and acrylic resins having a hydroxyl group and a cationic group, surfactants, etc., or tertiary amine type epoxy resins, quaternary ammonium salt type epoxy resins, A tertiary sulfonium salt type epoxy resin can be used.

  The above pigments can be used without particular limitation, for example, colored pigments such as titanium oxide, carbon black, bengara, etc .; extender pigments such as clay, mica, barita, calcium carbonate, silica; aluminum phosphomolybdate, aluminum tripolyphosphate, oxidation Anticorrosive pigments such as zinc (zinc white) can be added.

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

  In addition, for the purpose of improving coating film curability, organic tin compounds such as dibutyltin dibenzoate, dioctyltin oxide, and dibutyltin oxide can be used.

  Examples of the coated article of the cationic electrodeposition coating composition thus obtained include automobile bodies, motorcycle parts, household equipment, and other equipment.

  As the substrate to be coated, cold rolled steel sheet, galvannealed steel sheet, electrogalvanized steel sheet, electrogalvanized steel double layer plated steel sheet, organic composite plated steel sheet, Al material, Mg material, etc., and these metal plates Examples include those obtained by cleaning the surface such as alkali degreasing as necessary and then performing surface treatment such as phosphate chemical conversion and chromate treatment. If it is a metal, there will be no restriction | limiting in particular.

  The cationic electrodeposition coating composition of the present invention can be applied to a desired substrate surface by cationic electrodeposition. Cationic electrodeposition coating is generally diluted with deionized water or the like to have a solid content concentration of about 5 to 40% by mass, preferably 10 to 25% by mass, and a pH of 3.5 to 9.0. Preferably, the cationic electrodeposition coating composition adjusted in the range of 4.0 to 7.0 is used as a bath, 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. The current is applied by using the object to be coated as a cathode. After electrodeposition, usually ultrafiltrate (UF filtrate), reverse osmosis permeate (RO water), industrial water, pure water, etc. are sufficient to remove the cationic electrodeposition paint that has adhered to the object. Wash with water.

  Although the film thickness of an electrodeposition coating film is not specifically limited, Generally, it can be in the range of 5-40 micrometers based on a dry coating film, Preferably it can be in the range of 10-30 micrometers. The coating film is baked and dried using a drying facility such as an electric hot air dryer or a gas hot air dryer at a surface temperature of the coated material of 110 to 200 ° C., preferably 140 to 180 ° C. for 10 minutes to The heating is performed for 180 minutes, preferably 20 minutes to 60 minutes. A cured coating film is obtained by 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, “parts” indicates mass parts, and “%” indicates mass%.

Production Synthesis Example 1 of Modified Epoxy Resin (A) Production of 1 300 parts of ε-caprolactone was added to 400 parts of PP-400 (manufactured by Sanyo Chemical Industries, trade name, polypropylene glycol molecular weight 400), and the temperature was raised to 130 ° C. Thereafter, 0.01 part of tetrabutoxytitanium was added and the temperature was raised to 170 ° C. Sampling was carried out over time while maintaining this temperature, the amount of unreacted ε-caprolactone was traced by infrared absorption spectrum measurement, and when the reaction rate reached 98% or more, cooling was performed. 1 was obtained.

Synthesis Example 2 Modifier No. Production of 2 400 parts of ε-caprolactone was added to 660 parts of BPE-100 (manufactured by Sanyo Chemical Co., Ltd., trade name, bisphenol A polyethylene glycol, number average molecular weight 660), and the temperature was raised to 130 ° C. Thereafter, 0.01 part of tetrabutoxytitanium was added and the temperature was raised to 170 ° C. Sampling was carried out over time while maintaining this temperature, the amount of unreacted ε-caprolactone was monitored by infrared absorption spectrum measurement, and when the reaction rate reached 98% or more, cooling was performed. 2 was obtained.

Production Example 1 Modified Epoxy Resin No. 1 1
After adding 385 parts of nonylphenol, 68 parts of benzoic acid, and 0.2 part of dimethylbenzylamine to 1,000 parts of jER1001 (Note 1), the mixture was reacted at 140 ° C. until the epoxy equivalent reached 60,000 or more. 360 parts of ethylene glycol monobutyl ether was added to the modified epoxy resin No. 80 having a resin solid content of 80% by mass. One solution was obtained. Modified epoxy resin no. The resin solid content of one solution had a number average molecular weight of 1100.
(Note 1) jER1001: manufactured by Mitsubishi Chemical Corporation, trade name, epoxy resin, epoxy equivalent 475

Production Example 2 Modified Epoxy Resin No. 2
To 1,050 parts of jER828EL (Note 2), 400 parts of bisphenol A and 0.2 part of dimethylbenzylamine were added and reacted at 140 ° C. until an epoxy equivalent of 750 was reached. 140 parts of nonylphenol was added thereto, and reacted at 130 ° C. until an epoxy equivalent of 1,150 was reached.

Subsequently, after adding 145 parts of octylic acid and making it react until an epoxy equivalent becomes 9,000 or more, 430 parts of ethylene glycol monobutyl ether is added, and the modified epoxy resin solution No. 80 of resin solid content 80 mass% is added. Two solutions were obtained. Modified epoxy resin no. The resin solids of the two solutions had a number average molecular weight of 1700.
(Note 2) jER828EL: manufactured by Mitsubishi Chemical Corporation, trade name, epoxy resin, epoxy equivalent 190

Production Example 3 Modified Epoxy Resin No. 3
To 1,050 parts of jER828EL (Note 2), 400 parts of bisphenol A and 0.2 part of dimethylbenzylamine were added and reacted at 140 ° C. until an epoxy equivalent of 750 was reached. After adding 530 parts of nonylphenol and allowing the epoxy equivalent to reach 60,000 or more, 500 parts of ethylene glycol monobutyl ether was added and modified epoxy resin solution No. 80 having a resin solid content of 80% by mass was added. Three solutions were obtained. Modified epoxy resin no. The resin solid content of the three solutions was a number average molecular weight of 1800.

Production Example 4 Modified Epoxy Resin No. 4
To 1,050 parts of jER828EL (Note 2), 400 parts of bisphenol A and 0.2 part of dimethylbenzylamine were added and reacted at 140 ° C. until an epoxy equivalent of 750 was reached. Among them, 350 parts of nonylphenol, 50 parts of benzoic acid, and the modifier No. obtained in Synthesis Example 1 were used. 30 parts were added and reacted at 140 ° C. for 4 hours, and then 470 parts of ethylene glycol monobutyl ether was added to make modified epoxy resin No. 1 having a resin solid content of 80% by mass. Four solutions were obtained. Modified epoxy resin no. The resin solid content of the four solutions was a number average molecular weight 1850.

Production Example 5 Modified Epoxy Resin No. 5
To 1,000 parts of jER1001 (Note 1), 245 parts of benzoic acid and 0.2 part of dimethylbenzylamine were added and reacted at 140 ° C. until the epoxy equivalent reached 5,500. Subsequently, the modifier No. obtained in Synthesis Example 2 was used. 130 parts were added and reacted at 120 ° C. for 4 hours, and then 340 parts of ethylene glycol monobutyl ether was added to make a modified epoxy resin no. Five solutions were obtained. Modified epoxy resin no. The resin solid content of the five solutions had a number average molecular weight of 1150.

Production Example 6 Modified Epoxy Resin No. 6
To 1,000 parts of jER1001 (Note 1), 60 parts of dimer acid (a dimer of unsaturated fatty acid having 18 carbon atoms, CAS 61788-89-4) and 0.2 part of dimethylbenzylamine were added, and the epoxy equivalent was 1, The reaction was continued at 140 ° C. until 200. Subsequently, after adding 245 parts of benzoic acid and reacting at 140 ° C. until the epoxy equivalent reached 50,000 or more, 325 parts of ethylene glycol monobutyl ether was added, and modified epoxy resin No. 80 having a resin solid content of 80% by mass was added. 6 solutions were obtained. Modified epoxy resin no. The resin solid content of 6 solutions had a number average molecular weight of 1100.

Comparative Production Example 1 Modified epoxy resin no. 7
To 1,050 parts of jER828EL (Note 2), 400 parts of bisphenol A and 0.2 part of dimethylbenzylamine were added and reacted at 140 ° C. until an epoxy equivalent of 750 was reached. Into that, 170 parts of benzoic acid was added and reacted at 140 ° C. until the epoxy equivalent reached 2,700. Seven solutions were obtained. Modified epoxy resin no. The resin solid content of 7 solutions had a number average molecular weight of 1700.

Comparative Production Example 2 Modified Epoxy Resin No. 8
To 1,050 parts of jER828EL (Note 2), 400 parts of bisphenol A and 0.2 part of dimethylbenzylamine were added and reacted at 140 ° C. until an epoxy equivalent of 750 was reached. Into this, 320 parts of nonylphenol was added and reacted at 140 ° C. until the epoxy equivalent reached 2,900, and then 440 parts of ethylene glycol monobutyl ether was added to give modified epoxy resin No. 80 having a resin solid content of 80% by mass. 8 solutions were obtained. Modified epoxy resin no. The resin solid content of 8 solutions is the number average molecular weight
1850.

Comparative Production Example 3 Modified Epoxy Resin No. 9
To 1,000 parts of jER1001 (Note 1), 250 parts of nonylphenol, 190 parts of benzoic acid and 0.2 part of dimethylbenzylamine were added and reacted at 140 ° C. until the epoxy equivalent reached 65,000 or more. 360 parts of monobutyl ether was added to the modified epoxy resin No. 80 having a resin solid content of 80% by mass. Nine solutions were obtained. Modified epoxy resin no. The resin solid content of 9 solutions had a number average molecular weight of 1100.

  Modified epoxy resin no. 1-No. Table 1 shows the contents of 9 blends.

Production synthesis example 3 of amino group-containing epoxy resin (B) Production of 3 Into the flask, 600 parts of 50% formalin, 137.5 parts of phenol, 252.5 parts of 98% industrial sulfuric acid and 530 parts of metaxylene were allowed to react at 84 to 88 ° C. for 4 hours. After completion of the reaction, the mixture was allowed to stand to separate the resin phase and the sulfuric acid aqueous phase, and then the resin phase was washed with water three times. 3 was obtained.

Production Example 7 Amino group-containing epoxy resin no. Production of 1 solution To a flask, 1,000 parts of jER828EL (Note 2), 400 parts of bisphenol A and 0.2 part of dimethylbenzylamine were added and reacted at 130 ° C. until an epoxy equivalent of 750 was reached.

  Next, the modifier No. obtained in Synthesis Example 3 was added to this reaction product. 3 parts 300 parts, diethanolamine 137 parts and diethylenetriamine methyl isobutyl ketone ketimine compound 95 parts, reacted at 120 ° C. for 4 hours, ethylene glycol monobutyl ether 403 parts, solid content 80% amino group-containing epoxy resin No. One solution was obtained.

  Amino group-containing epoxy resin no. The resin solid content of one solution had a number average molecular weight of 2,000 and an amine value of 57 mgKOH / g.

Production Example 8 Amino group-containing epoxy resin 2 Solution Production Example 1140 parts of jER828EL (Note 2), 456 parts of bisphenol A and 0.2 part of dimethylbenzylamine were added to a flask and reacted at 130 ° C. until an epoxy equivalent of 820 was reached.

  Next, 420 parts of methyl isobutyl ketone was added, and then the modifier No. obtained in Synthesis Example 3 was added to this reaction product. 3 and then 95 parts of diethanolamine and 127 parts of a methyl isobutyl ketone ketiminate of diethylenetriamine (purity 84%, methyl isobutyl ketone solution) were reacted at 120 ° C. for 4 hours, and the resin solid content was 80%. Amino group-containing epoxy resin no. Two solutions were obtained.

  Amino group-containing epoxy resin no. The resin solid content of the two solutions had an amine value of 47 mgKOH / g and a number average molecular weight of 2,500.

Production Example 9 of Blocked Polyisocyanate Curing Agent (C) Production Example of Curing Agent In a reaction vessel, 270 parts of Cosmonate M-200 (trade name, manufactured by Mitsui Chemicals, Crude MDI) and 127 parts of methyl isobutyl ketone The temperature was raised to 70 ° C. In this, 236 parts of ethylene glycol monobutyl ether was added dropwise over 1 hour, and then the temperature was raised to 100 ° C., sampled over time while maintaining this temperature, and absorption of unreacted isocyanate groups by infrared absorption spectrum measurement It was confirmed that there was no more, and a curing agent having a resin solid content of 80% was obtained.

Production and production example 10 of emulsion Production Example 1 Modified resin No. 1 obtained in Production Example 1 17.5 of a solution (solid content 30 parts), amino group-modified epoxy resin No. 1 obtained in Production Example 7. Mix 50.0 parts (solid content 40 parts) of 1 solution, 37.5 parts (solid content 30 parts) of the curing agent obtained in Production Example 9, and further mix 13 parts of 10% acetic acid. After stirring, 156 parts of deionized water was added dropwise over about 15 minutes while stirring vigorously, and emulsion No. 34 having a solid content of 34% was added. 1 was obtained.

Production Examples 11 to 20 Emulsion No. 2-No. Production Example No. 10 Emulsion No. 10 was prepared in the same manner as in Production Example 10 except that the contents shown in Table 2 were used. 2-No. 11 was obtained.

Comparative Production Examples 4-12
Emulsion No. 5 was prepared in the same manner as in Production Example 10 except that the contents of Table 2 were used. 12-No. 17 was obtained.

Production Example 21 Production Example of Resin for Dispersing Pigment In a flask equipped with a stirrer, thermometer, dropping funnel and reflux condenser, 450 parts of nonylphenol and 960 parts of CNE195LB (Note 3) were charged and gradually heated while mixing and stirring. , Reacted at 160 ° C. Thereafter, 430 parts of ε-caprolactone was charged, and the temperature was raised to 170 ° C. for reaction. Further, 105 parts of diethanolamine and 124 parts of N-methylethanolamine were reacted to confirm that the epoxy value was 0, and the solid content was adjusted by adding ethylene glycol monobutyl ether to obtain a pigment-dispersed resin having a solid content of 60%. A solution was obtained. The resin solid content of this pigment-dispersed resin solution had an amine value of 70 mgKOH / g and a number average molecular weight of 2,200.
(Note 3) CNE195LB: manufactured by Changchun Japan Co., Ltd., trade name, cresol type novolac epoxy resin, glycidyl ether of novolac type phenol resin Production Example 22 Production Example of Pigment Dispersion Paste Pigment dispersion of 60% solid content obtained in Production Example 21 Resin 8.3 parts (solid content 5 parts), titanium oxide 14.5 parts, refined clay 7.0 parts, carbon black 0.3 parts, dioctyltin oxide 1 part, bismuth hydroxide 1 part and deionized water 20 3 parts was added and dispersed in a ball mill for 20 hours to obtain a pigment dispersion paste having a solid content of 55%.

[Create test plate]
Cold-rolled steel sheet (150 mm (length) x 70 mm (width) x 0.8 mm (thickness)) subjected to chemical conversion treatment (Palbond # 3020, manufactured by Nippon Parkerizing Co., Ltd., trade name, zinc phosphate treatment agent) Using a steel plate (0.8 mm × 150 mm × 70 mm) as an object to be coated, each of the cationic electrodeposition paints obtained in Examples and Comparative Examples was electrodeposited to a dry film thickness of 15 μm, and 170 ° C. for 20 minutes. A test plate was obtained by baking and drying.

[Cation electrodeposition paint]
Example 1 Cationic Electrodeposition Paint No. Production of emulsion No. 1 obtained in Production Example 10 1 is 294 parts (solid content 100 parts), 55% of the pigment dispersion paste obtained in Production Example 22 is added 52.4 parts (solid content 28.8 parts), deionized water 350 parts, and the solid content is 20%. Cationic electrodeposition paint no. 1 was produced.

Examples 2 to 11 Cationic electrodeposition paint No. 2-No. In the same manner as in Example 1, the cationic electrodeposition coating material No. 2-No. 11 was produced. The test results are also shown.

Comparative Examples 1-6 Cationic electrodeposition paint No. 12-No. In the same manner as in Example 1, the cationic electrodeposition paint no. 12-No. 17 was produced. The test results are also shown.

[Create test plate]
Cold-rolled steel sheet (150 mm (length) x 70 mm (width) x 0.8 mm (thickness)) subjected to chemical conversion treatment (Palbond # 3020; manufactured by Nippon Parkerizing Co., Ltd., trade name, zinc phosphate treatment agent) Using steel plate (0.8 mm × 150 mm × 70 mm) as an object to be coated, electrodeposition coating was performed using each of the cationic electrodeposition paints obtained in Examples and Comparative Examples.

  (Note 4) Throwing power: A “four-box box throwing power test jig” (see FIG. 1) in which a hole of 8 mm in diameter is drilled and four steel plates are installed at intervals of 2 cm is as shown in FIG. Wired. Of the four steel plates in FIG. 2, the left-hand surface toward the leftmost steel plate is referred to as “A surface”, and the right-hand surface is referred to as “B surface”. Similarly, the left and right surfaces of the second steel plate from the left are “C-plane” and “D-plane”, respectively, and the left and right surfaces of the third steel plate from the left are “E-plane” and “F-plane”, respectively. The right and left surfaces of the rightmost steel plate are the “G surface” and “H surface”, respectively. Among these, the A surface is an “outer plate”, and the G surface is an “inner plate”.

  In the apparatus of FIG. 2, electrodeposition coating was performed at a coating bath temperature of 30 ° C., a distance of 10 cm between the A surface and the electrode, and a current-carrying time of 3 minutes, with a voltage of 15 μm on the dried outer plate. The throwing power was evaluated by the outer plate dry film thickness, the inner plate dry film thickness, and the throwing power (%) (= inner plate dry film thickness / outer plate dry film thickness × 100).

About [Evaluation] A: G plane (film thickness) / A plane (film thickness) = 70% or more, throwing power is quite good.
B: G plane (film thickness) / A plane (film thickness) = 65% or more and less than 70%, and throwing power is good.
C: G plane (film thickness) / A plane (film thickness) = 60% or more and less than 65%, and the throwing power is slightly poor.
D: G plane (film thickness) / A plane (film thickness) = less than 60%, throwing power is poor.

(Note 5) Anticorrosion:
The coating film was cross-cut with a cutter knife so as to reach the base of the 15 μm dry electrodeposition coating film test plate obtained in Examples and Comparative Examples, and this was 35 ° C. according to JIS Z-2371. A salt spray test was conducted for 840 hours, and evaluation was made based on the following criteria based on the scratches from the cut portion and the blister width.
For A, the maximum width of rust and blisters is 2.0 mm or less from the cut part (one side)
B is the maximum width of rust and blisters exceeds 2.0 and 3.0mm or less (one side)
C, the maximum width of rust and blisters exceeds 3.0mm from the cut and 3.5mm or less (one side)
In D, the maximum width of rust and swelling exceeds 3.5 mm from the cut portion.

(Note 6) Corrosion resistance:
WP-306 (trade name, aqueous intermediate coating) manufactured by Kansai Paint Co., Ltd. is applied to the cationic electrodeposition coating film test plate having a dry film thickness of 15 μm obtained in Examples and Comparative Examples so that the cured film thickness becomes 25 μm. After spray coating, baking was performed at 140 ° C. for 30 minutes with an electric hot air dryer. Furthermore, on the above-mentioned intermediate coating film, neo-amylac 6000 (manufactured by Kansai Paint Co., Ltd., trade name, top coating) is spray-coated so that the cured film thickness is 35 μm, and then heated at 140 ° C. for 30 minutes with an electric hot air dryer. Baking and blank test coating plates were prepared.

The coating film on the obtained exposure test coating plate was cross-cut with a knife so as to reach the substrate, exposed to the horizontal in Chikura Town (shore area), Chiba Prefecture for one year, and then rust and swelling from the cut area. Evaluation was made according to the following criteria according to the width.
For each evaluation, the maximum width of rust or swelling is
A is the maximum width of rust or swelling is less than 2mm on one side from the cut part,
B is the maximum width of rust or blisters from 2mm to 3mm on one side from the cut part,
C has a maximum width of rust or blisters of 3 mm or more and less than 4 mm on one side from the cut part.
For D, the maximum width of rust or swelling is 4 mm or more from one side of the cut.

(Note 7) Paint stability:
Each cationic electrodeposition paint was stirred at 35 ° C. for 30 days with the container sealed (700 rpm, diameter 3 cm blade). Thereafter, the entire amount of the cationic electrodeposition coating material was filtered through a 400 mesh filter, and the amount of the residue (mg / L) was measured, which was used as a criterion for determining the water dispersibility of the cationic electrodeposition coating material.
A is less than 10 mg / L,
B represents 10 mg / L or more, and less than 20 mg / L. C represents 20 mg / L or more, and less than 30 mg / L D represents 30 mg / L or more.

  In the field of the cationic electrodeposition coating to which the present invention belongs, a coating excellent in all throwing power, corrosion resistance, black corrosion resistance, and coating stability is desirable.

  A coated article having excellent throwing power, anticorrosion, and resistance to exposure can be provided.

1. The outer plate (A surface) in the jig for throwing power test of the 2.4-sheet box method with a diameter of 8 mm is shown.
3 shows an inner plate (G surface) in a jig for testing throwing power of the four-sheet box method.
4). An electrodeposition paint bath is shown.

Claims (3)

A cationic electrodeposition coating composition containing the following modified epoxy resin (A), amino group-containing epoxy resin (B), and blocked polyisocyanate curing agent (C), comprising (A) component, (B) component and (C) 3-40 mass% of modified epoxy resin (A), 20-60 mass% of amino group-containing epoxy resin (B), blocked polyisocyanate curing agent (C) 10 based on the total solid content of component (C) Cationic electrodeposition coating composition containing -40% by mass.
Modified epoxy resin (A):
At least one acidic compound selected from the carboxylic acid-containing compound (a21) of the following formula (1) and the phenol compound (a22) of the following formula (2) in the epoxy resin (a1) having an epoxy equivalent of 180 to 4,000 A modified epoxy resin (A) obtained by reacting (a2), [[carboxyl group of carboxylic acid-containing compound (a21) and / or hydroxyl group of phenol compound (a22)] / epoxy group of epoxy resin (a1) ] Is an epoxy resin having an equivalent ratio of 0.8 to 1.15

(In the formula, X represents a hydrocarbon group having 1 to 23 carbon atoms which may have a substituent selected from the group consisting of —OH, —OR, —SH and —SR, and R represents an alkyl group. Represents)

Wherein Y represents a hydrogen atom or optionally a hydrocarbon group having 1 to 23 carbon atoms which may have a substituent selected from the group consisting of —OR, —SH and —SR; Represents an alkyl group) A coated article obtained by electrodeposition-coating a metal coating using the cationic electrodeposition coating composition according to claim 1 as an electrodeposition coating bath. A method for forming a coating film, comprising: using the cationic electrodeposition coating composition according to claim 1 as an electrodeposition coating bath; immersing the coating object in the bath; and energizing the immersed coating object.

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