JP2008266400A - Cationic electrodeposition coating material composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coated article giving a semigloss coating film having excellent weather resistance, corrosion resistance, long-term corrosion resistance especially exposure resistance, etc., and finish and having 60° specular gloss of 15-55. <P>SOLUTION: The cationic electrodeposition coating material composition contains an aqueous dispersion containing a resin component (A) and a pigment-dispersed paste containing a novolac epoxy resin pigment-dispersed resin (B) and a pigment component (C), and gives a coating film having a sea-island structure on the cross-section of the baked and dried coating film. The total dibutyl phthalate absorption of the pigment component (C) in the pigment-dispersed paste is 300-1,000 ml/100 g, and the 0.1-3 pts.mass of a body pigment having a dibutyl phthalate absorption of 200-400 ml/100 g is used based on 100 pts.mass of the resin component in the cationic electrodeposition coating material composition produced by using the pigment-dispersed paste. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is excellent in long-term corrosion resistance such as weathering resistance, anticorrosion, especially galling resistance, and finish, and can obtain a semi-glossy coating film with 60 specular gloss of 15 to 55. The present invention relates to a cationic electrodeposition coating composition characterized in that the surface side forms a sea-island structure.

  Conventionally, cationic electrodeposition paints are widely used in automobile parts, electrical equipment parts, and other equipment because they can form a coating film excellent in weather resistance, corrosion resistance, and finish. Due to such characteristics of the cationic electrodeposition coating, its use as a product by one-time electrodeposition coating has increased, and a semi-glossy coating having weather resistance and corrosion resistance has been demanded for the cationic electrodeposition coating.

  For example, an amine-modified epoxy cationic resin, a self-crosslinking acrylic cationic resin obtained by adding a block diisocyanate to a cationic acrylic resin having a solubility parameter at least 0.5 lower than that of an amine-modified epoxy cationic resin, and block isocyanate curing A cationic electrodeposition coating composition containing an agent is disclosed (Patent Document 1).

  Also, a pigment-dispersed paste and a block poly which are blended with an amine-modified epoxy resin and a cationic acrylic resin at a solid weight ratio of 7/3 to 3/7 and dispersed with a quaternary ammonium or sulfonium cation type epoxy pigment dispersing resin. A matte cationic electrodeposition coating composition obtained by dispersing an isocyanate crosslinking agent in an aqueous medium containing a neutralizing agent is disclosed (Patent Document 2).

However, the matte cationic electrodeposition coating composition described in Patent Document 2 has a problem in stability over time because a constant coating gloss cannot be obtained during running use in a coating line.
In addition, the cationic electrodeposition coating composition contains a plurality of emulsions, and the difference in the amount of electricity (a) required for starting deposition of a coating composed of two types of emulsions selected from the plurality of emulsions is 50 to 400C. A method for forming a multilayer coating film using a cationic electrodeposition paint having a thickness of / m ² is disclosed (Patent Document 3).

  Moreover, as an electrodeposition coating composition capable of forming such a semi-glossy coating film, the difference in solubility parameter between the cationic emulsion (A) and the cationic emulsion (B) is 0.5 to 1.5, An invention relating to an electrodeposition coating composition capable of obtaining a cured electrodeposition coating film having a low specular gloss and a good finished appearance by an emulsion having a difference in curing start temperature of 20 to 60 ° C. is disclosed (patent) Reference 4).

  However, with these conventional techniques, a semi-glossy coating film having excellent coating performance such as long-term corrosion resistance such as weather resistance, adhesion, anticorrosion, and particularly exposure resistance, and a 60 ° specular gloss of 15 to 55 is obtained. For this purpose, it is necessary to increase the pigment concentration, and the coating film performance and finish are reduced.

JP-A-8-333528 JP-A-9-87554 JP 2003-328192 A Japanese Patent Laid-Open No. 2006-2001

  The problem to be solved by the present invention is to obtain a semi-glossy coating film having excellent long-term corrosion resistance and finish properties such as weather resistance and corrosion resistance, particularly exposure resistance, and a 60-degree specular gloss of 15 to 55. It is to provide a cationic electrodeposition coating composition.

  As a result of intensive studies to solve the above-mentioned problems, the inventors have obtained an aqueous dispersion containing a resin component (A) having the following characteristics, and a novolac epoxy resin pigment dispersion resin (B) and a pigment component (C). A cationic electrodeposition paint comprising a pigment-dispersed paste comprising a coating film after baking and drying, and found to be achieved by a cationic electrodeposition paint composition characterized in that the film cross-section forms a sea-island structure; The present invention has been completed.

  “Aqueous dispersion: As resin component (A), it contains at least two types of resins, an amino group-containing polyol-modified epoxy resin (A1) and an amino group-containing acrylic resin (A2).

  Pigment dispersion paste: Novolac epoxy resin pigment dispersion resin (B) obtained by reacting glycidyl etherified product (b1), cyclic ester compound (b2), amine compound (b3) and phenol compound (b4) of novolac type phenol resin, In addition, the total amount of dibutyl phthalate oil absorption of the pigment component (C) in the pigment dispersion paste is 300 to 1,000 ml / 100 g, and 100 parts by mass of the resin component in the cationic electrodeposition coating composition using the pigment dispersion paste. 0.1 to 3 parts by mass of extender pigment having a dibutyl phthalate oil absorption of 200 to 400 ml / 100 g based on the standard "

  Like the cationic electrodeposition paint of the present invention, the cationic electrodeposition paint having a sea-island cross-section is excellent in long-term corrosion resistance and finish properties such as weather resistance, corrosion resistance, especially exposure resistance, and 60 ° specular gloss. Is a matte coating film of 15 to 55, and a coated article excellent in finish is obtained.

  The reason why the above effect is obtained is that a part (island part) having a different pigment concentration is intentionally formed in the coating film due to the compatibility of the resin component (A) and the novolac epoxy resin pigment dispersion resin (B). An electrodeposition coating film having a sea-island structure at least on the coating film surface side in the coating film section can be formed. In this electrodeposition coating film, volume shrinkage at the time of thermosetting occurs locally and microscopic unevenness can be formed on the surface of the coating film, so that a low gloss coating film is obtained.

  The present invention contains an aqueous dispersion containing a specific resin component (A), and a pigment dispersion paste containing a novolac epoxy resin pigment dispersion resin (B) and a pigment component (C), The present invention relates to a cationic electrodeposition coating composition characterized by forming a sea-island structure on the surface of a coating film. Details will be described below.

[Water dispersion]
The aqueous dispersion used in the cationic electrodeposition coating composition of the present invention contains at least two kinds of amino group-containing polyol-modified epoxy resin (A1) and amino group-containing acrylic resin (A2) as the resin component (A). It is characterized by.

Amino group-containing polyol-modified epoxy resin (A1):
The amino group-containing polyol-modified epoxy resin (A1) used as the resin component (A) in the cationic electrodeposition coating composition of the present invention is a specific alkylphenol in the epoxy resin (a1) having an epoxy equivalent of 180 to 2,500. The compound (a2) is reacted to add the alkylphenol (a2) to the epoxy resin (a1) of the above formula, and then the caprolactone (a32) is added to the compound (a31) containing a plurality of active hydrogen groups. A resin obtained by simultaneously reacting a polyol compound (a3) and an amine compound (a4) obtained by adding one end of the polyol compound (a3) to the skeleton of the epoxy resin (a) It is.

Epoxy resin (a1):
As the epoxy resin (a1), the epoxy resin used as a starting material is particularly preferably an epoxy resin obtained by a reaction between a polyphenol compound and an epihalohydrin, for example, epichlorohydrin, from the viewpoint of the corrosion resistance of the coating film.

  A conventionally well-known thing can be used as a polyphenol compound which can be used for formation of this epoxy resin. Examples of such polyphenol compounds include bis (4-hydroxyphenyl) -2,2-propane (bisphenol A), 4,4-dihydroxybenzophenone, bis (4-hydroxyphenyl) methane (bisphenol F), bis (4 -Hydroxyphenyl) -1,1-ethane, bis (4-hydroxyphenyl) -1,1-isobutane, bis (4-hydroxy-tert-butyl-phenyl) -2,2-propane, bis (2-hydroxynaphthyl) ) Methane, tetra (4-hydroxyphenyl) -1,1,2,2-ethane, 4,4-dihydroxydiphenylsulfone (bisphenol S), phenol novolac, cresol novolac and the like.

  Moreover, bisphenol A obtained by reaction of a polyphenol compound and epichlorohydrin, the following formula

, N = 0 to 8 are preferable.
The epoxy resin (a1) can have an epoxy equivalent weight in the range of 180 to 2,500, preferably 200 to 2,000, more preferably 400 to 1,500, and generally 200 to 8, Those having a number average molecular weight in the range of 000, especially 400 to 4,000, more particularly 800 to 2,500 are suitable.
Examples of such commercially available epoxy resins include those sold by Japan Epoxy Resins Co., Ltd. under the trade names of Epicoat 828EL, 1002 on the left, 1004 on the left, and 1007 on the left.

Alkylphenols (a2):
The alkylphenols (a2) are represented by the following formula (1).

Formula (1)
(Wherein X is a hydrogen atom, —OH, —OR, —NHR, —SH and —SR, a hydrocarbon group having 1 to 15 carbon atoms which may have a substituent selected from the group consisting of —SR, R is Specific examples of the above formula (1) (which represents an alkyl group) include, for example, phenol, cresol, ethylphenol, para-tert-butylphenol, nonylphenol and the like.

Polyol compound (a3):
The polyol compound (a3) is obtained by adding caprolactone to a compound containing a plurality of active hydrogen groups. Here, the active hydrogen group means an atomic group containing at least one active hydrogen, and includes, for example, an alcoholic hydroxyl group, a primary amino group, a secondary amino group, and the like.

  The compound containing a plurality of active hydrogen groups in one molecule generally has a number average molecular weight in the range of 62 to 5,000, preferably 62 to 4,000, and more preferably 62 to 1,500. In addition, the active hydrogen-containing compound preferably has an average of at least 2 and less than 30, particularly 2 to 10 active hydrogen groups per molecule.

  Specifically, as a compound containing a plurality of active hydrogen groups in one molecule, (1) a polyol compound, (2) a primary amino group and / or a secondary amino group, or a primary amino group and And / or amine compounds having secondary amino groups and hydroxyl groups, (3) linear or branched polyether polyols, and (4) linear or branched polyester polyols.

  The (1) polyol compound is a compound containing at least two alcoholic hydroxyl groups in one molecule, such as ethylene glycol, propylene glycol, 1,3-butylene glycol, 1,4-butanediol, Diols such as 1,6-hexanediol, diethylene glycol, dipropylene glycol, cyclohexane-1,4-dimethylol, neopentyl glycol, triethylene glycol, hydrogenated bisphenol A; triols such as glycerin, trimethylolethane, trimethylolpropane Tetrols such as pentaerythritol and α-methyl glucooxide; hexols such as sorbitol and dipentaerythritol; octols such as sucrose;

  Examples of the amine compound (2) include butylenediamine, hexamethylenediamine, monoethanolamine, diethanolamine, diethanolamine, triethanolamine, isophoronediamine, ethylenediamine, propylenediamine, diethylenetriamine, and triethylenetetramine.

  The (3) linear or branched polyether polyol is usually an alkylene oxide (for example, ethylene oxide, propylene oxide) having a number average molecular weight within the range of 62 to 10,000, preferably 62 to 2,000. , Butylene oxide, tetrahydrofuran, etc.), which are produced by ring-opening addition reaction of polyethylene glycol, polypropylene glycol, polytetramethylene glycol, poly (ethylene / propylene) glycol, bisphenol A ethylene glycol ether, bisphenol A polypropylene glycol ether etc. are mentioned.

  The (4) linear or branched polyester polyol can usually have a number average molecular weight in the range of 200 to 10,000, preferably 200 to 3,000. Examples thereof include those obtained by a polycondensation reaction of an acid or an anhydride thereof and an organic diol under an excess of organic diol.

  Examples of the organic dicarboxylic acid used herein include fatty acid-based, alicyclic or aromatic dicarboxylic acids having 2 to 44 carbon atoms, particularly 4 to 36, such as succinic acid, adipic acid, azelaic acid, sebacic acid and maleic acid. Examples include acid, fumaric acid, glutaric acid, hexachloroheptanedicarboxylic acid, cyclohexanedicarboxylic acid, o-phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, and tetrachlorophthalic acid. In addition to these dicarboxylic acids, a small amount of polycarboxylic acid anhydrides or unsaturated fatty acid adducts having three or more carboxyl groups can be used in combination. Examples of the organic diol include polypropylene, polyethylene glycol, and polylactone.

  On the other hand, examples of caprolactone that can be added to a compound containing a plurality of active hydrogen groups include γ-caprolactone, ε-caprolactone, and δ-caprolactone, and ε-caprolactone is particularly preferable.

  The above addition reaction of a compound containing a plurality of active hydrogen groups and caprolactone can be carried out by a method known per se. Specifically, for example, titanium compounds such as tetrabutoxy titanium and tetrapropoxy titanium; organotin compounds such as tin octylate, dibutyltin oxide, and dibutyltin laurate; presence of a catalyst such as a metal compound such as stannous chloride A compound containing a plurality of active hydrogen groups and caprolactone can be heated by heating at a temperature of about 100 to about 250 ° C. for about 1 to about 15 hours.

  In general, the catalyst can be used in an amount of 0.5 to 1,000 ppm based on the total amount of the compound containing a plurality of active hydrogen groups and caprolactone. Caprolactone is generally 1 to 30 mol, preferably 1 to 20 mol, more preferably 1 to 15 per active hydrogen group equivalent of a compound containing a plurality of active hydrogen groups (that is, per active hydrogen). It can be used within the molar range.

  The polyol compound (a3) thus obtained combines high plasticization performance based on a compound having a plurality of active hydrogen groups, high compatibility with an epoxy resin based on (poly) caprolactone, and high reactivity due to a terminal hydroxyl group. It is extremely useful as a plasticizer for epoxy resins for paints.

  The polyol compound (a3) can generally contain a total of 20 to 95% by weight, preferably 25 to 90% by weight, of units derived from caprolactone, and generally 300 to 10,000, preferably Can have a number average molecular weight in the range of 400 to 5,000.

Amine compound (a4):
The amine compound (a4) may be of any kind as long as it contains at least one active hydrogen that reacts with an epoxy group and can cationize the epoxy resin, and is particularly capable of introducing a primary amino group. Is preferably used.

  Examples of the primary amine compound capable of introducing the primary amino group include ethanolamine, propanolamine, 2- (2-aminoethylamino) ethanol, hydroxyethylaminopropylamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and Examples thereof include ketimine compounds such as pentaethylenehexamine.

  As the amine compound that can be used in combination with the primary amine, those conventionally used for cationization of epoxy resins can be used, and secondary amines are particularly preferred. Examples include diethylamine, diisopropylamine, diethanolamine, di (2-hydroxypropyl) amine, monomethylaminoethanol, monoethylaminoethanol and the like.

  The reaction between the epoxy resin (a1) and the alkylphenols (a2) is usually carried out at a temperature of about 60 to about 250 ° C., preferably about 70 to about 200 ° C. in a suitable solvent, optionally in the presence of a catalyst. It can be performed for about 1 to 25 hours, preferably about 1 to 12 hours. Examples of the solvent include hydrocarbons such as toluene, xylene, cyclohexane, and n-hexane; esters such as methyl acetate, ethyl acetate, and butyl acetate; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and methyl amyl ketone. Examples thereof include amide systems such as dimethylformamide and dimethylacetamide; alcohol systems such as methanol, ethanol, n-propanol, and iso-propanol; or mixtures thereof. Examples of the catalyst used as appropriate include tetrabutoxy Examples include titanium compounds such as titanium and tetrapropoxy titanium; organic tin compounds such as tin octylate, dibutyltin oxide, and dibutyltin laurate; metal compounds such as stannous chloride; and organic amine compounds. Thus, a reaction product in which alkylphenols (a2) are added to the skeleton of the epoxy resin (a1) is obtained.

  The addition reaction of the polyol compound (a3) and the amine compound (a4) to this reaction product is usually performed at a temperature of about 80 to about 170 ° C., preferably about 90 to about 150 ° C. in a suitable solvent as described above. It can be performed for about 1 to 6 hours, preferably about 1 to 5 hours.

  The use ratio of each reaction component in the above reaction is not strictly limited and can be appropriately changed according to the use of the coating composition, etc., but it can be changed by epoxy resin (a1), alkylphenols (a2), polyol. The following ranges are suitable based on the total solid weight of the four components of the compound (a3) and the amine compound (a4).

  Epoxy resin (a1): generally 60 to 85% by weight, preferably 62 to 83% by weight, alkylphenols (a2): generally 0.5 to 15% by weight, preferably 1 to 10% by weight, polyol compound (a3): Generally 5 to 20 wt%, preferably 5 to 18 wt%, amine compound (a4): generally 5 to 25 wt%, preferably 6 to 19 wt%. An amino group-containing polyol-modified epoxy resin (A1) can be obtained by reacting by a known method.

Amino group-containing acrylic resin (A2):
The resin component (A) of the present invention is characterized by containing at least two kinds of amino group-containing polyol-modified epoxy resin (A1) and amino group-containing acrylic resin (A2). The acrylic resin can be obtained by radical copolymerization of a hydroxyl group-containing acrylic monomer, an amino group-containing acrylic monomer, and other monomers as monomer components constituting the acrylic resin.

  Examples of hydroxyl group-containing acrylic monomers include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and addition of 2-hydroxyethyl (meth) acrylate and caprolactone. (For example, Plaxel FA-2 and FM-3 as trade names manufactured by Daicel Corporation) and the like. These can be used alone or in combination of two or more.

  Examples of amino group-containing acrylic monomers include N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, and N, N-di. -T-butylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylamide, etc. are mentioned.

  Examples of other monomers include aromatic vinyl monomers such as styrene, vinyl toluene, and α-methyl styrene, such as methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, Examples include n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, cyclohexyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate.

  The acrylic resin can be obtained by subjecting the above monomers to radical copolymerization by a known method. The hydroxyl value of the acrylic resin is usually in the range of 10 to 300 mgKOH / g, preferably 50 to 200 mgKOH / g, and the number average molecular weight is in the range of 2,000 to 100,000, preferably 3,000 to 50, Within the range of 000 is appropriate. The amine compound (a4) similar to that used for the amino group-containing polyol-modified epoxy resin (A1) can be used as the amine compound that is a water-dispersing group for water-dispersing the acrylic resin.

  Specifically, primary mono- and polyamines, secondary mono- and polyamines, or primary and secondary mixed polyamines, secondary mono- and polyamines having ketimized primary amino groups, ketiminated primary aminos Examples thereof include hydroxy compounds having a group. Specifically, diethylamine, diethanolamine, diethyltriamine ketimine compound, and the like are preferably used.

  As the resin component (A), conventionally known amino group-containing epoxy resins can be used as other resin components in addition to the amino group-containing polyol-modified epoxy resin (A1) and amino group-containing acrylic resin (A2).

  As such an amino group-containing epoxy resin, it can also be modified using a plastic modifier, for example, a polycaprolactone polyol compound-modified amino group-containing epoxy resin plastic-modified with a caprolactone polyol compound having reactivity with an epoxy group. Alternatively, an xylene-formaldehyde resin-modified amino group-containing epoxy resin can be used.

As the amine compound to be reacted with the epoxy resin, the same amine compound (a4) as that used for the amino group-containing polyol-modified epoxy resin (A1) or amino group-containing acrylic resin (A2) can be used. An amino group-containing epoxy resin can be obtained by reacting the epoxy resin with an amino group-containing compound by a known method.
Furthermore, a blocked polyisocyanate compound can also be used as the resin component (A). Examples of such a blocked polyisocyanate compound include those obtained by blocking an aromatic, alicyclic or aliphatic polyisocyanate compound with a blocking agent, and these may be used alone or in combination of two or more. Can do.

  Specific examples of the aromatic polyisocyanate include 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, crude TDI, and 2,4′-diphenylmethane diisocyanate. 4,4′-diphenylmethane diisocyanate, crude MDI [mixture of 2,4′-diphenylmethane diisocyanate and 4,4′-diphenylmethane diisocyanate], 4,4′-diisocyanatobiphenyl, 3,3′-dimethyl-4, 4′-diisocyanatobiphenyl, 3,3′-dimethyl-4,4′-diisocyanatodiphenylmethane, 1,5-naphthylene diisocyanate, 4,4 ′, 4 ″ -triphenylmethane triisocyanate, m- Or p-isocyanatopheny Such as sulfonyl isocyanate.

  Examples of the aliphatic polyisocyanate include ethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), dodecamethylene diisocyanate, 1,6,11-undecane triisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and lysine diisocyanate. 2,6-diisocyanatomethylcaproate, bis (2-isocyanatoethyl) fumarate, bis (2-isocyanatoethyl) carbonate, 2-isocyanatoethyl-2,6-diisocyanatohexanoate, p -Xylylene diisocyanate (XDI), α, α, α ′, α′-tetramethylxylylene diisocyanate (TMXDI) and the like.

  Examples of the alicyclic polyisocyanate include isophorone diisocyanate (IPDI), dicyclohexylmethane-4,4′-diisocyanate (hydrogenated MDI), and cyclohexylene diisocyanate. Of these polyisocyanate compounds, aliphatic polyisocyanates and alicyclic polyisocyanates are preferred from the viewpoints of weather resistance and corrosion resistance.

  The blocking agent is to block by adding to the isocyanate group of the polyisocyanate compound, and the blocked polyisocyanate compound produced by the addition of the blocking agent is stable at ordinary temperature and at a general electrodeposition coating baking temperature. It is desirable that the isocyanate group can be regenerated by dissociating the blocking agent when heated to a temperature of about 100 ° C. to about 200 ° C.

Examples of the blocking agent satisfying such requirements include lactam compounds such as ε-caprolactam and γ-butyrolactam; oxime compounds such as methyl ethyl ketoxime and cyclohexanone oxime; phenol compounds such as phenol, para-t-butylphenol and cresol. Aliphatic alcohols such as n-butanol and 2-ethylhexanol; aromatic alkyl alcohols such as phenyl carbinol and methyl phenyl carbinol; ether alcohol compounds such as ethylene glycol monobutyl ether and diethylene glycol monoethyl ether; propylene glycol; Dipropylene glycol, 1,3-butanediol, 1,2-butanediol, 3-methyl-1,2-butanediol, 1,2-pentanediol 1,4-pentanediol, 3-methyl-4,3-pentanediol, 3-methyl-4,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,5-hexane Examples thereof include hydroxyl group-containing compounds such as diol, 1,4-hexanediol, 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, dimethylolvaleric acid and glyceric acid. As the block polyisocyanate compound, isophorone diisocyanate blocked with methyl ethyl ketoxime is particularly preferable.

The blending ratio of the blocked isocyanate compound in the resin component (A) is 10 to 50% by weight, preferably 15 to 30% by weight, based on the total solid mass of the base resin component (A). Can be within the range.
Resin component (A) comprising the above-described amine-added polyol-modified epoxy resin (A1) and amine-added acrylic resin (A2) and appropriately blended with other amino group-containing epoxy resin or blocked polyisocyanate is used as a carboxylic acid. An aqueous dispersion obtained with a neutralizing agent such as an acid and deionized water can be used in the production of a cationic electrodeposition coating composition.

[Pigment dispersion paste]
The cationic electrodeposition coating composition of the present invention is characterized by using a pigment dispersion paste containing a novolac epoxy resin pigment dispersion resin (B) and a pigment component (C).

Novolac epoxy resin pigment dispersion resin (B):
The novolak epoxy resin-based pigment dispersion resin (B) comprises a glycidyl etherified product (b1), a cyclic ester compound (b2), an amine compound (b3), and a phenol compound (b4) of a novolak type phenol resin. Based on the total solid content mass of the etherified product (b1), the cyclic ester compound (b2), the amine compound (b3), and the phenol compound (b4), (b1) 30 to 70 mass%, (b2) 5 to 45 mass %, (B3) 5 to 15% by mass, and (b4) 1 to 30% by mass.

Glycidyl etherified product of novolac type phenol resin (b1):
As the glycidyl etherified product (b1) of the novolak type phenol resin, a compound represented by the following formula (2) can be preferably used.

Formula (2)
(In the above formula, R ₁ and R ₂ are the same or different and each represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, an aryl group, an aralkyl group or a halogen atom, and R ₃ is an alkyl having 1 to 10 carbon atoms. Group, aryl group, aralkyl group, allyl group or halogen atom, R ₄ and R ₆ are the same or different and each represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms or a glycidyloxyphenyl group, and R ₅ represents A hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group, an aralkyl group, an allyl group or a halogen atom, and n is an integer of 1 to 38)
In the above general formula (2), the “alkyl group” is linear or branched, for example, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isoamyl. Hexyl, heptyl, octyl, 2-ethylhexyl, nonyl, decyl group and the like.

  The “aryl group” may be either monocyclic or polycyclic, and examples thereof include phenyl and naphthyl groups. Particularly, the phenyl group is preferable, and the “aralkyl group” is an aryl-substituted alkyl group. And includes, for example, benzyl, phenethyl and the like, and benzyl is preferred.

  “Halogen atom” includes fluorine, chlorine, bromine and iodine atoms.

The “glycidyloxyphenyl group” represented by R ₄ or R ₆ is a group represented by the following formula (3).

Formula (3)
(In the above formula, W represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms)
In the general formula (2), as R ₁ and R ₂ , a hydrogen atom, a methyl group, a chlorine atom and a bromine atom are preferable, and a hydrogen atom, a methyl group and a bromine atom are particularly preferable.

Further, as R ₃ and R ₅ , a methyl group, a tert-butyl group, a nonyl group, a phenyl group, a chlorine atom and a bromine atom are preferable, and a methyl group, a tert-butyl group, a phenyl group and a bromine atom are particularly preferable. is there. Furthermore, R ₄ and R ₆ are preferably hydrogen atoms, and n is particularly preferably 1-8.

  The number average molecular weight (Note 1) of the novolak epoxy resin pigment dispersing resin (B) is generally preferably in the range of about 400 to about 8,000, particularly 600 to 2,000. The novolac epoxy resin pigment dispersion resin (B) preferably has 3.5 to 10 glycidyl groups per molecule, and the epoxy equivalent of the novolac epoxy resin pigment dispersion resin (B). Is preferably in the range of about 180 to about 2,000, in particular 200 to 600.

  (Note 1) Number average molecular weight: according to JIS K 0124-83, 4 of separation columns “TSK GEL4000HXL”, “TSK G3000HXL”, “TSK G2500HXL”, “TSK G2000HXL” (above, manufactured by Tosoh Corporation) Using a book, using tetrahydrofuran for GPC as an eluent at 40 ° C. and a flow rate of 1.0 ml / min, a chromatogram obtained with an RI refractometer and a standard polystyrene calibration curve are used.

  The novolac epoxy resin pigment dispersion resin (B) is, for example, the following formula (4):

(In the above formula (4), R ₁ , R ₂ and R ₃ are as defined above)
And a bifunctional phenol compound (b-1) represented by the following formula (5)
R ₄ —CHO Formula (5)
(Wherein R ₄ has the same meaning as above)
The aldehyde compound (b-2) and / or the following formula (6)
R ₄ —CO—R ₆ formula (6)
(Wherein R ₄ and R ₆ are as defined above)
It is produced by introducing a glycidyl ether group by further reacting an epihalohydrin (b-5) with a novolak-type phenol resin (b-4) obtained by subjecting a ketone compound (b-3) represented by can do.

  In addition, during or after the reaction for obtaining the novolac type phenol resin (b-4), the following formula (7)

Formula (7)
(Wherein R ₇ represents an alkyl group having 1 to 10 carbon atoms, an aryl group, an aralkyl group, an allyl group or a halogen atom, and R ₁ and R ₂ are as defined above).
A monofunctional phenol compound (b-6) represented by the formula (1) may be used in combination as a terminal blocking agent.

Specific examples of the group R ₇ in the formula (7) include methyl group, ethyl group, propyl group, n-butyl group, tert-butyl group, pentyl group, hexyl group, nonyl group, ethylene group, propylene group, phenyl Group, benzyl group, chlorine atom, bromine atom and iodine atom, etc., preferably methyl group, tert-butyl group, nonyl group, phenyl group, chlorine atom and bromine atom, especially methyl group, tert-butyl group A phenyl group and a bromine atom are preferred.

  The term “bifunctional” used for the phenolic compound (b-1) above means that in formula (4), two hydrogen atoms are directly bonded to the ortho and / or para positions based on the hydroxyl group. Means that These hydrogen atoms undergo a dehydration condensation reaction with the carbonyl group (C═O) in the above components (b-2) and (b-3) to produce a novolak type phenol resin (b-4).

In addition, the term “monofunctional” used for the phenolic compound of component (b-6) means that in formula (7), one hydrogen atom is directly bonded to the ortho or para position based on the hydroxyl group. Means that
This hydrogen atom undergoes a dehydration condensation reaction with the carbonyl group (C═O) in the component (b-2) or (b-3) to form the end of the novolak type phenol resin (b-4).

  Examples of the bifunctional phenol compound (b-1) represented by the formula (4) include phenol, p-propenylphenol, o-benzylphenol, 6-n-amyl-n-cresol, o-cresol, p -Cresol, o-ethylphenol, o-phenylphenol, p-phenylphenol, p-tert-pentylphenol, p-tert-butylphenol, o-chlorophenol, p-chlorophenol, 4-chloro-3,5-xylenol O-allylphenol, nonylphenol, o-bromophenol, p-cumylphenol, and the like.

  Examples of the aldehyde compound (b-2) represented by the formula (5) include acetaldehyde and formaldehyde. Alternatively, m- (or p-) hydroxybenzaldehyde may be used as the aldehyde compound (b-2), and after reaction with the component (b-1), this hydroxybenzaldehyde may be glycidyl etherified with epihalohydrin (b-5). . In addition, the benzene nucleus of the hydroxybenzaldehyde may be substituted with an alkyl group having 1 to 10 carbon atoms.

  Examples of the ketone compound (b-3) represented by the formula (6) include acetone, methyl ethyl ketone, and methyl isobutyl ketone.

  Furthermore, examples of the epihalohydrin (b-5) include epichlorohydrin and epibromohydrin.

  A novolak-type phenol resin (b-4) is obtained by subjecting the component (b-1) to a condensation polymerization reaction of the component (b-2) and / or the component (b-3). This polycondensation reaction can be carried out according to a known method for producing a novolak type phenol resin.

In the production of the novolak type phenol resin (b-4), during the polycondensation reaction between the component (b-1) and the component (b-2) and / or the component (b-3) as necessary or Thereafter, the monofunctional phenol compound (b-6) represented by the formula (5) can be reacted as an end-capping agent.
Specific examples of the monofunctional phenol compound (b-6) represented by the formula (7) include 2-tert-butyl-4-methylphenol, 2,4-xylenol, 2,6-xylenol, 2 , 4-dichlorophenol, 2,4-dibromophenol, dichloroxylenol, dibromoxylenol, 2,4,5-trichlorophenol, 6-phenyl-2-chlorophenol, and the like. The polycondensation reaction between the component (b-6) and the component (b-1), the component (b-2) and / or the component (b-3) can be performed in the same manner as described above.

Glycidyl etherified product of novolac type phenol resin (b):
The glycidyl etherified product (b) of the novolac type phenol resin can be obtained by reacting the phenolic hydroxyl group in the novolac type phenol resin (b-4) with the epihalohydrin (b-5) to glycidyl ether. Specifically, for example, a novolac type phenol resin (b-4) is dissolved in epihalohydrin (b-5) to form a solution, and an aqueous solution of an alkali metal hydroxide is continuously added to the solution. Of water and unreacted epihalohydrin (b-5). The component (b-5) can be separated from this distilled liquid and reused. This reaction is preferably carried out in the presence of an ether solvent such as dioxane or diethoxyethane.

  In addition, although the glycidyl etherification product (b1) of a novolak-type phenol resin can be manufactured as described above, a commercially available product may be used. As polyglycidyl etherified products, DEN-438 and DEN-439 (manufactured by Dow Chemical Japan Co., Ltd., trade name); as polyglycidyl etherified products of cresol type novolak resin, EPICRON N-695 (manufactured by Dainippon Ink Co., Ltd.) (Trade name), CNE195LB (Changchun Japan Co., Ltd.), EOCN-102S, EOCN-1020 and EOCN104S (Nippon Kayaku Co., Ltd., trade name); BREN- S (Nippon Kayaku Co., Ltd., trade name) An example of a polyglycidyl etherified product of a long-chain alkyl-modified phenol type novolak resin is ESMB-260 (trade name, manufactured by Sumitomo Chemical Co., Ltd.);

Cyclic ester compound (b2):
The cyclic ester compound (b2) has the following formula (8)

Formula (8)
(In the above formula, R ₈ represents a hydrogen atom or CH ₃ , and n is an integer of 3 to 6)
Specifically, for example, δ-valerolactone, ε-caprolactone, ζ-enalactone, η-caprolactone, γ-valerolactone, δ-caprolactone, ε-enalactone, ξ- Caprolactone is exemplified, and ε-caprolactone is particularly preferable. The methylene chain portion derived from the lactone of the cyclic ester compound (b2) imparts storage stability and weather resistance to the novolak epoxy resin pigment dispersion resin (B).

Amine compound (b3):
The amine compound (b3) may be a primary or secondary amine compound having at least one primary hydroxyl group in one molecule. This is useful for introducing a primary hydroxyl group and a basic group into the pigment dispersing resin (A).

  A cationic resin is formed by a reaction between the amino group of the amine compound (b3) and the glycidyl group of the glycidyl etherified product (b1) of the novolak type phenol resin represented by the formula (1), and the primary resin in the cationic resin is produced. Hydroxyl group and basic group are produced by reaction with conventional bisphenol A type epoxy resin, but water dispersibility is remarkably superior to those groups, and pigment dispersion paste and cation using the pigment dispersion paste are used. Contributes to improving the stability of electrodeposition paints. Furthermore, in the formed coating film, it contributes also to the improvement of anticorrosion property, especially corrosion resistance. Specific examples of the amine compound (b3) include the compounds exemplified below.

(1) Primary alkanolamines such as monoethanolamine, monopropanolamine, monobutanolamine (2) N-methylethanolamine, N-ethylethanolamine, diethanolamine, di-n- (or iso) -propanolamine, Secondary alkanolamines such as dibutanolamine (3) Adducts (secondary alkanolamines) of the above primary alkanolamines with α, β-unsaturated carbonyl compounds, such as monoethanolamine and N, N- Adducts with dimethylaminopropylacrylamide, adducts of monoethanolamine and hydroxyethyl (meth) acrylate, adducts of monoethanolamine and hydroxypropyl (meth) acrylate, monoethanolamine and hydroxybutyl (meth) acrylate (4) Primary and secondary alkanolamines such as hydroxyethylaminoethylamine (5) One or more selected from hydroxyamine, hydroxyethylhydrazine and hydroxybutylhydrazine and ketone compounds such as dimethyl ketone , Methyl ethyl ketone, methyl isobutyl ketone, dibutyl ketone, dipropyl ketone and other condensates (secondary alkanolamine)
(6) Following formula (9)

Formula (9)
(In the above formula, n is an integer of 1 to 6, and R ₉ represents a hydrocarbon chain having 4 to 36 carbon atoms which may contain a hydroxyl group and / or a polymerizable unsaturated group).
An amine compound in which a primary hydroxyl group, a secondary amino group, and an amide group coexist in one molecule represented by the formula (9) is exemplified by N-hydroxyalkylalkylenediamine and C5-C37 amine compound. It can be obtained by dehydrating condensation reaction with a monocarboxylic acid. Examples of such diamines include primary hydroxyl groups such as hydroxyethylaminoethylamine, N-hydroxyethylpropylenediamine, N-hydroxyethylbutylenediamine, N-hydroxyethylpentylenediamine, N-hydroxyethylhexylenediamine, and the like. First and second diamines are preferred, and examples of monocarboxylic acids include coconut oil fatty acid, castor oil fatty acid, rice bran oil fatty acid, soybean oil fatty acid, tall oil fatty acid, dehydrated castor oil fatty acid, safflower oil fatty acid, linseed oil Mixed fatty acids such as fatty acids and tung oil fatty acids, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, ricinoleic acid, linoleic acid, linolenic acid, eleostearic acid, 12-hydroxystearic acid, Behe Such as acid, and the like.

  The reaction of the diamine with the monocarboxylic acid to obtain the amine compound represented by the above formula (9) is usually performed by mixing both components in an approximately equimolar ratio and using an organic solvent such as toluene or methyl isobutyl ketone. It can be carried out by removing a specified amount of reaction product water, and an amine compound can be obtained by removing the residual organic solvent by a reduced pressure method or the like.

  The amine compound thus obtained generally has an amine value (secondary amine) in the range of 88 to 350 mgKOH / g, particularly 120 to 230 mgKOH / g, and a hydroxyl value (preferably a primary hydroxyl group) of 44. It is preferable to be within the range of -350 mgKOH / g, particularly 60-230 mgKOH / g.

  Of the compounds (1) to (6) described above as the amine compound (c), the primary alkanol secondary amines (2), (3) and (6) are preferred. In particular, it is preferable to use an amine compound represented by the formula (9) (particularly hydroxyethylaminoethyl fatty acid amide) and diethanolamine in order to improve finish and anticorrosion properties.

Phenol compound (b4):
As the phenol compound (b4), one having at least one, preferably 1 to 5, phenolic hydroxyl groups in one molecule can be used. Specifically, for example, 2,2-bis (p-hydroxyphenyl) propane, 4,4′-dihydroxybenzophenone, 1,1-bis (p-hydroxyphenyl) ethane, 1,1-bis (p-hydroxy) Phenyl) isobutane, 2,2-bis (4-hydroxy-3-tert-butylphenyl) propane, bis (2-hydroxynaphthyl) methane, 1,5-dihydroxynaphthalene, bis (2,4-dihydroxyphenyl) methane, Examples thereof include polyhydric phenol compounds such as 1,1,2,2-tetra (p-hydroxyphenyl) ethane, 4,4-dihydroxydiphenyl ether, 4,4-dihydroxydiphenyl sulfone, phenol novolac, and cresol novolac. Furthermore, monophenol compounds such as phenol, nonylphenol, α- or β-naphthol, p-tert-octylphenol, o- or p-phenylphenol can also be used.

  In order to form a coating film having more excellent anticorrosion properties, the phenol compound (c4) is particularly preferably bisphenol A [2,2-bis (p-hydroxyphenyl) propane] or bisphenol F [bis (p-hydroxyphenyl). It is preferable to use a reaction product of bisphenols such as) methane] and epichlorohydrin.

  Among these reaction products, in particular, the number average molecular weight is at least 200, preferably in the range of about 800 to about 3,000, and an average of 2 or less, preferably 0. Those represented by the following formulas containing 8 to 1.2 phenolic hydroxyl groups are suitable.

(In the above formula (10), n is an average number of 0 to 7, and R ₁₀ represents a residue of an active hydrogen compound)
In the above formula, the active hydrogen-containing compound which is a precursor of R ₁₀ in the general formula (10) includes, for example, amines such as secondary amines; phenols such as nonylphenol; organic acids such as fatty acids. Thiols; ethers or alcohols such as alkyl alcohol, ethylene glycol monobutyl ether and carbitol; and compounds such as inorganic acids. Of these, dialkanolamine which is a secondary amine having a primary hydroxyl group, and monophenol such as nonylphenol, phenylphenol and phenol are particularly preferred. In particular, when a primary hydroxyl group-containing amine is used, curability is improved, and when monophenol is used, stability is improved.

  Further, as the phenol compound, for example, 1 mol of a bisphenol A diglycidyl ether type polyepoxide having a molecular weight of 200 or more, preferably 380 to 2,000, and a molecular weight of 200 or more, preferably 200 to 2,000. Reaction of 1 mol of bisphenol A polyphenol within the range of 1 and 1 mol of a compound having active hydrogen in the presence of a catalyst or a solvent, if necessary, at a temperature of 30 to 300 ° C., preferably 70 to 180 ° C. Let

  In addition, as the phenol compound (b4), polyols such as dimer diol, ethylene glycol, propylene glycol and butylene glycol; polyether glycols such as polyethylene glycol, polypropylene glycol and polybutylene glycol; polyester polyols such as polycaprolactone; Polycarboxylic acids; polyisocyanates; monoisocyanates; oxides of unsaturated compounds such as ethylene oxide, propylene oxide, butylene oxide, styrene oxide; allyl glycidyl ether, polypropylene glycol diglycidyl ether, 2-ethylhexyl glycidyl ether, methyl glycidyl Has hydroxyl groups such as ether, butyl glycidyl ether, and phenyl glycidyl ether. Glycidyl esters of organic acids such as fatty acids; that glycidyl ether compounds alicyclic oxirane-containing compounds and the like may also be used those obtained by reacting bisphenol A. Further, a compound obtained by graft polymerization of δ-4-caprolactone, an acrylic monomer or the like to this compound can also be used.

  The novolak epoxy resin pigment dispersion resin (B) is, for example, a method in which a glycidyl etherified product (b1), a cyclic ester compound (b2), an amine compound (b3), and a phenol compound (b4) of a novolak type phenol resin are reacted simultaneously. Alternatively, it can be obtained by reacting a cyclic ester compound (b2) and an amine compound (b3) with a glycidyl etherified product (b1) of a novolak-type phenol resin, and then reacting the phenol compound (c4).

  The reaction temperature in the reaction of the glycidyl etherified product (b1), cyclic ester compound (b2), amine compound (b3) and phenolic compound (b4) of the novolak type phenol resin is usually 50 to 300 ° C. in the presence of an organic solvent, The inside of the range of 70-200 degreeC is especially preferable.

  The resulting novolac epoxy resin pigment dispersing resin (B) has a number average molecular weight of generally 1,000 to 20,000, particularly 1,500 to 10,000, and a hydroxyl value of 10 to 1000 mgKOH / g. In particular, a range of 50 to 300 mgKOH / g and an amine value of 10 to 300 mgKOH / g, particularly 30 to 100 mgKOH / g are also preferable for coating film performance and paint stability.

  In addition to the novolak epoxy resin pigment dispersion resin (B), other tertiary amine type amino group-containing epoxy resins, quaternary ammonium salt type epoxy resins, quaternary ammonium salts are used as the pigment dispersing resin. A type acrylic resin can also be used in combination.

Pigment component (C):
The pigment dispersion paste used for the cationic electrodeposition paint of the present invention is prepared by blending the above-described novolac epoxy resin pigment dispersion resin (B) with a neutralizer and a pigment component (C), and using a ball mill, pebble mill, sand mill, It can be produced by dispersing using a conventionally used disperser such as a shaker and setting the particle size to 15 μm or less, preferably 8 μm or less. Among these, a ball mill is preferable from the viewpoint of workability, and a dispersion time by the ball mill is preferably 1 to 96 hours, and more preferably 10 to 48 hours from the viewpoint of pigment particle size and production man-hour.

  In this specification, the particle size is dispersed based on the degree of dispersion according to JIS K-5400-4.7.1 (1990) distribution diagram, and the distribution density of the particles is observed using a tube gauge. This is a reading of the scale where the grain began to appear.

  Dibutyl phthalate oil absorption (Note 2) of pigment components (colored pigment, extender pigment and rust preventive pigment) used in the cationic electrodeposition coating composition of the present invention is 300 to 1,000 ml / 100 g, preferably Is 350 to 800 ml / 100 g, more preferably 400 to 750 ml / 100 g, and based on 100 parts by mass of the resin component in the cationic electrodeposition coating composition using the pigment dispersion paste, the dibutyl phthalate oil absorption It is a semi-glossy coating that contains 0.1 to 3 parts by mass, preferably 0.5 to 2 parts by mass, and more preferably 0.7 to 1.5 parts by mass of extender pigments having a mass of 200 to 400 ml / 100 g It is suitable for achieving both finish and finish.

  If the total amount of dibutyl phthalate oil absorption is less than 300 ml / 100 g, the 60 ° specular glossiness tends to be over 55, and if the total amount of dibutyl phthalate oil absorption exceeds 1,000 ml / 100 g, the finishing performance is lowered.

  The total DBP oil absorption amount of the pigment components (colored pigment, extender pigment and rust preventive pigment) in the pigment dispersion paste used in the cationic electrodeposition coating composition is “oil absorption amount of the colored pigment × blending amount = DBP oil absorption amount”. , Oil absorption amount of extender pigment x blending amount = DBP oil absorption amount, oil absorption amount of rust preventive pigment x blending amount = DBP oil absorption amount ".

  For example, the sum of the dibutyl phthalate oil absorption amount of the color pigment is 20.5 (oil absorption amount of titanium white) × 24 (blending amount) = 492. The total amount of the dibutyl phthalate oil absorption of the extender pigment is obtained from the oil absorption amount of the extender pigment x the blending amount. For example, 230 (oil absorption amount of extender pigment) × 1 (blending amount) = 230. Moreover, the sum total of the dibutyl phthalate oil absorption amount of a rust preventive pigment is calculated | required by the oil absorption amount x compounding amount of a rust preventive pigment. 30 (oil absorption amount of rust preventive pigment) × 2 = 60. Therefore, the total DBP oil absorption amount is 782.

(Note 2) Dibutyl phthalate oil absorption:
A dry sample of 1000 mg is accurately weighed and transferred onto a smooth glass plate or stone plate having a size of 300 mm × 300 mm or more, and if it is granular, it is crushed by applying an appropriate pressure with a spatula. Gently pour about 1/2 of the expected amount of dibutyl phthalate required from the burette onto a glass or stone plate, and add dibutyl phthalate (hereinafter abbreviated as “DBP oil absorption”) to a circle. After spreading the sample evenly, the sample is gradually transferred onto dibutyl phthalate to disperse it, and kneaded carefully by drawing a small circle with a spatula. The sample adhering to the spatula is removed with another spatula, and the required amount of DBP of about 1/3 to 1/4 is added, and the same operation is repeated until the mixture becomes uniform. When it is close to the end point, add one drop at a time. This operation is finished in 10 to 15 minutes, and after 3 minutes from the end of the operation, the dripping amount of dibutyl phthalate in the burette is read, and the oil absorption amount: OA (ml / 100 g) is calculated by the following equation (1). calculate.
OA = (V / W) × 100 (1)
[Wherein V is the amount of DBP used (ml) used up to the end point, and W is the weight (g) of the dried sample].

  As the pigment component (C), examples of the color pigment include titanium white, carbon black, red pepper, yellow iron oxide (ocher), copper phthalocyanine blue, and copper phthalocyanine green. Examples of extender pigments include clay (kaolin), talc, calcium carbonate, barium sulfate, silica, diatomaceous earth, and magnesium carbonate. As the rust preventive pigment, rust preventive pigments such as aluminum phosphomolybdate, aluminum tripolyphosphate, zinc oxide, bismuth oxide, and bismuth hydroxide can be appropriately used.

  In particular, in order to obtain a gray semi-gloss electrodeposition coating film or a beige semi-gloss electrodeposition coating film, titanium white is added to 100 parts by mass of the solid content of the resin component (A) in the cationic electrodeposition coating composition. It is preferable to contain 10 to 40 parts by mass in order to form a sea-island structure in the cross section of the coating film. A gloss electrodeposition coating can be easily obtained.

  The pigment component (C) is a novolac epoxy resin pigment dispersed by adjusting the type and amount of pigment used according to the desired coating performance and the desired semi-gloss (60 degree specular gloss value). Add a curing catalyst such as resin (B), dibutyltin oxide, dioctyltin dioxide and the like, surfactant, neutralizing agent and water and stir well with a stirrer, or using a ball mill, sand mill, etc. A pigment dispersion paste can be obtained by dispersing for 1 to 96 hours, preferably 10 to 48 hours.

[Production of cationic electrodeposition coating composition]
The cationic electrodeposition coating composition can be produced by preparing a pigment dispersion paste in advance and mixing it with an aqueous dispersion containing the resin component (A).
The cationic electrodeposition coating composition of the present invention can be applied to the surface of a desired substrate by cationic electrodeposition coating. The electrodeposition coating is generally diluted with deionized water or the like so that the solid content concentration is about 5 to 40% by weight, preferably 15 to 25% by weight, and the pH is in the range of 5.5 to 9.0. An electrodeposition bath composed of a cationic electrodeposition coating composition adjusted inside is usually adjusted to a bath temperature of 15 to 35 ° C. and can be performed under a load voltage of 100 to 400V.

  Examples of the substrate to which the cationic electrodeposition coating composition of the present invention can be applied include, for example, a cold-rolled steel sheet, a hot dip galvanized steel sheet, an electrogalvanized steel sheet, an electrogalvanized iron double-layer plated steel sheet, an organic composite plated steel sheet, and aluminum. Examples of the steel plate such as a plate include those obtained by cleaning the surface by alkali degreasing as necessary, and then performing surface treatment such as phosphate chemical treatment and chromate treatment.

  The film thickness of the cationic electrodeposition coating film is not particularly limited, but in general, it is preferably in the range of 10 to 50 μm, particularly 15 to 45 μm based on the cured coating film. The baking temperature of the coating film is generally about 120 to about 200 ° C., preferably about 140 to about 180 ° C. on the surface of the object, and the baking time is preferably about 5 to 60 minutes. Can be about 10 to 30 minutes.

[About electrodeposition coating cross section]
The coating film after electrodeposition coating of the cationic electrodeposition coating composition of the present invention and baking and drying is as shown in FIG. 1. The resin component (A), the novolac epoxy resin pigment dispersion resin (B) and the pigment component (C) as shown in FIG. The ratio of the pigment component (C) to the total solid content (hereinafter sometimes referred to as “pigment content (Note 3)”) is 10% by mass or more and 40% by mass or less. The ratio of the pigment component (C) “pigment content (Note 3)” dispersed in the “sea part” is less than 10% by mass, and the domain size is 0.1 to 40 μm, preferably 2 to 20 μm. It is characterized by comprising “islands” in the range of

(Note 3) Pigment content: In the cross section of the coating film having a sea-island structure, the pigment content of “sea part” and “island part” is a standard using an electronic probe microanalyzer (model number EMAX-500, manufactured by Horiba Seisakusho). Create a calibration curve for the relationship between the counting rate (counts per unit time) on the vertical axis of the element (Ti) and the pigment content of the cationic electrodeposition paint (see Note 12). The pigment content of “Kaibe” and “Shimbe” was determined.
Note that FIG. 2 is a chart of the sea, but a Ti peak is clearly recognized. On the other hand, FIG. 3 is an island chart, but the Ti peak is very weak and difficult to recognize.

[Reason for semi-glossy coating]
The reason why a “semi-glossy coating film” can be obtained by forming a sea-island structure on at least the coating film surface side in the coating film cross section is considered as follows.

For example, in Example 1 of Table 6, in the case of “pigment content of electrodeposition paint = 20.5 mass%, ratio of island portion in coating film cross section = 25%, pigment content of island portion = 5%”. ,
(1) Amount of pigment in the island:
Since the proportion of the island portion is 25% (cross-sectional area), the volume fraction of the island portion is 125 / 1,000 = 0.125, and the pigment content of the island portion is 5%.
That is, the amount of the pigment in the island portion is 0.125 × 5 = 0.63 mass%.
(2) Pigment distribution in a coating film with a sea-island structure:
The pigment content of the electrodeposition paint is distributed at a ratio of “island portion: sea portion = 0.63 mass%: 19.9 mass%” out of 20.50 mass%.
(3) Amount of pigment in the sea:
The pigment content of the sea part = 19.9 / (1-0.125) (ratio of the sea part) = 22.7% by mass.
(4) Shrinkage ratio of “island part” and “sea part” in the coating film having a sea-island structure: The shrinkage ratios of “island part” and “sea part” were determined in the section of the coating film having a sea-island structure.
[Before baking hardening]
The island is 99.37% by mass (resin content) + 0.63% by mass (pigment content)
Sea part is 77.30% by mass (resin content) + 22.70% by mass (pigment content)
(5) The resin content in the coating film is assumed to cause 8% loss on heating due to volatilization of the blocking agent used in the cross-linking agent, for example, in baking and drying at 170 ° C. for 20 minutes.
[After baking and curing]
Therefore, the island part: 99.37% by mass (resin content) × 0.92 (8% loss on heating) + 0.63% by mass (pigment content) = 92.05%, and the shrinkage is 100-92.05. = 8.0%. On the other hand, sea part: 77.30% by mass (resin content) × 0.92 (8% loss on heating) + 22.70% by mass (pigment content) = 93.8%, and the shrinkage is 100-93.8 = 6.2%.
As described above, the shrinkage rate of the “island” is 8.0%, the shrinkage of the “sea” is 6.2%, and the shrinkage difference is 1.8%. Is considered to form a semi-glossy coating.

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 Example 1 Amino group-containing epoxy resin No. 1 Preparation of 1 solution 697 parts of ε-caprolactone was added to 103 parts of diethylenetriamine, and the temperature was raised to 130 ° C. Thereafter, 0.01 part of tetrabutoxy titanium was added and the temperature was raised to 170 ° C. Sampling was performed over time while maintaining this temperature, the amount of unreacted ε-caprolactone was monitored by infrared absorption spectrum measurement, and the reaction was cooled when the reaction rate reached 98% or more to synthesize modifier 1.
Separately, 400 parts of bisphenol A and 0.2 part of dimethylbenzylamine are added to 1000 parts of Epicoat 828EL (trade name, epoxy resin, epoxy equivalent 190, molecular weight 350, manufactured by Japan Epoxy Resin Co., Ltd.), and the epoxy equivalent becomes 750 at 130 ° C. Reacted until.
120 parts of nonylphenol was added thereto, and the mixture was reacted at 130 ° C. until the epoxy equivalent was 1000.
Next, 200 parts of modifier 1, 95 parts of diethanolamine and 65 parts of diethylenetriamine ketiminate were added and reacted at 120 ° C. for 4 hours. Then, 414 parts of ethylene glycol monobutyl ether was added, and the amine value was 40 mg KOH / g, the resin solid content. 80% amino group-containing epoxy resin no. One solution was obtained.

Production Example 2 Amino group-containing epoxy resin No. 1 2 Production of Solution 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, molecular weight 660), and the temperature was raised to 130 ° C. Thereafter, 0.01 part of tetrabutoxy titanium 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 higher, the modifier 2 was synthesized.
Separately, 400 parts of bisphenol A and 0.2 part of dimethylbenzylamine are added to 1000 parts of Epicoat 828EL (trade name, epoxy resin, epoxy equivalent 190, molecular weight 350, manufactured by Japan Epoxy Resin Co., Ltd.), and the epoxy equivalent becomes 750 at 130 ° C. Reacted until.
120 parts of nonylphenol was added thereto, and the mixture was reacted at 130 ° C. until the epoxy equivalent was 1000.
Next, 300 parts of modifier 2, 95 parts of diethanolamine and 65 parts of diethylenetriamine ketiminate were added and reacted at 120 ° C. for 4 hours, and then adjusted with ethylene glycol monobutyl ether to give an amine value of 40 mg KOH / g, resin solid content of 80 % -Containing nonylphenol-added amino group-containing epoxy resin no. Two solutions were obtained.

Production Example 3 Amino group-containing epoxy resin Production of 3 solutions
A separable flask having an internal volume of 2 liters equipped with a thermometer, reflux condenser, and stirrer, Epicoat 828EL (trade name, epoxy resin manufactured by Japan Epoxy Resin Co., Ltd.), 1010 parts, 390 parts of bisphenol A and dimethylbenzyl 0.2 parts of amine was added and reacted at 130 ° C. until the epoxy equivalent was 800.
Next, 160 parts of diethanolamine and 65 parts of ketimine compound of diethylenetriamine were added and reacted at 120 ° C. for 4 hours, 355 parts of ethylene glycol monobutyl ether was added, and an amino group having an amine value of 67 mg KOH / g and a resin solid content of 80% by mass was added. Containing epoxy resin no. Three solutions were obtained.

Production Example 4 Amino group-containing epoxy resin (4) 525 parts of propylene oxide-modified bisphenol A diglycidyl ether (note 4), 342 parts of bisphenol A, and 342 parts of bisphenol A under a nitrogen gas blowing to a reaction vessel equipped with a thermometer, stirrer, reflux condenser, and nitrogen gas blowing port 36 parts of a methyl isobutyl ketone solution of ketimine with ethanolamine and methyl isobutyl ketone was charged and reacted at 160 ° C. until the epoxy group disappeared.
Further, 665 parts of bisphenol diglycidyl ether having an epoxy equivalent weight of about 190 and 232 parts of a methyl isobutyl ketone solution of ketimine of monoethanolamine and methyl isobutyl ketone were added to this product and reacted at 130 ° C. until an epoxy equivalent of 800 was reached. It was. As a result, an epoxy resin liquid having a number average molecular weight of about 1,500 was obtained.
Next, dilute and cool with 365 parts of ethylene glycol monobutyl ether. When the temperature reaches 100 ° C, add 167 parts of methyl isobutyl ketone diketimine solution of diethylenetriamine and methyl isobutyl ketone, and react at 100 ° C until the increase in viscosity stops. Amino group-containing epoxy resin No. 45 mgKOH / g, resin solid content 80%. Four solutions were obtained.

  (Note 4) Propylene oxide-modified bisphenol A diglycidyl ether (manufactured by Sanyo Kasei Co., Ltd., trade name, Glicier BPP-350, epoxy equivalent of about 340).

Production Example 5 Amino group-containing acrylic resin no. Production Example of 1 Solution 246 parts of propylene glycol monomethyl ether was charged into a 2-liter four-necked flask with a volume of 2 liters, and maintained at 110 ° C. after purging with nitrogen. In this, the mixture shown below was dripped over 3 hours.
30 parts of styrene
6 parts methyl methacrylate
n-butyl acrylate 6 parts
24 parts of 2-ethylhexyl methacrylate
PLACCEL FM-3 (trade name, manufactured by Daicel Chemical Industries) 24 parts
10 parts of dimethylaminoethyl methacrylate 1 hour after the completion of dropping, a solution of 8 parts of 2,2′-azobis (2-methylbutyronitrile) in 56 parts of propylene glycol monomethyl ether was added over 1 hour. It was dripped. After completion of the dropwise addition, this was further maintained at 110 ° C. for 1 hour, methylisobutylketone was added, and amino group-containing acrylic resin No. 1 having a hydroxyl value of 80 mgKOH / g, a number average molecular weight of 16,000 and a resin solid content of 80% was added. One solution was obtained.

Production Example 6 Amino group-containing acrylic resin Production Example of 2 Solution The same operation as in Production Example 5 was carried out except that the mixture to be dropped was blended as shown in Table 1, and amino group-containing acrylic resin No. 1 was prepared. Two solutions were obtained.

Production Example 7 Amino group-containing acrylic resin no. Production Example 3 Solution The same operation as in Production Example 5 was performed except that the mixture to be dropped was mixed as shown in Table 1, and amino group-containing acrylic resin No. 3 was prepared. Three solutions were obtained.

(Note 5) Plaxel FM3: a product name manufactured by Daicel Chemical Industries, Ltd. Methacrylic acid ester having a polyester chain in which ε-caprolactone is opened.

Production Example 8 Production Example of Curing Agent A 4-liter flask having a volume of 2 liters was charged with 50 parts of isophorone diisocyanate, 40 parts of methyl ketoxime was added dropwise at 55 ° C., and then heated at 80 ° C. for 1 hour to obtain a resin solid content of 90 % Curing agent was obtained.

Production Example 9 Pigment Dispersing Resin No. Production Example 1 Into a flask equipped with a stirrer, thermometer, dropping funnel and reflux condenser, 450 parts of nonylphenol and 960 parts of CNE195LB (Note 6) were charged and gradually heated with mixing and stirring, and allowed to react at 160 ° C. . Thereafter, 430 parts of ε-caprolactone is charged, and the temperature is raised to 170 ° C. for reaction. Furthermore, 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, for pigment dispersion having a solid content of 60%. Resin No. One solution was obtained. This pigment dispersing resin No. The hydroxyl value of 1 was 150 mgKOH / g, the amine value was 70 mgKOH / g, and the number average molecular weight was 2,200.

(Note 6) CNE195LB: manufactured by Changchun Japan Co., Ltd., trade name, cresol-type novolac epoxy resin, glycidyl etherified product of novolac-type phenol resin Production Example 10 Pigment Dispersion Resin No. Production Example 2 A flask equipped with a stirrer, thermometer, dropping funnel and reflux condenser was charged with 450 parts of nonylphenol and 960 parts of CNE195LB (Note 6), and gradually heated with mixing and stirring, and reacted at 160 ° C. . Thereafter, 430 parts of ε-caprolactam is charged, and the temperature is raised to 170 ° C. to cause the reaction. Further, 278 parts of diethanolamine was reacted, and it was confirmed that the epoxy value was 0, and ethylene glycol monobutyl ether was added to adjust the solid content. Two solutions were obtained. The pigment dispersion resin No. The hydroxyl value of 2 was 200 mgKOH / g, the amine value was 70 mgKOH / g, and the number average molecular weight was 2300.

Production Example 11 Pigment Dispersing Resin No. 3 Production Example Epicoat 828EL (trade name, epoxy resin, manufactured by Japan Epoxy Resin Co., Ltd.) 1010 parts, 390 parts of bisphenol A, 240 parts of polycaprolactone diol (number average molecular weight of about 1,200) and 0.2 parts of dimethylbenzylamine And is reacted at 130 ° C. until the epoxy equivalent is about 1,090.
Next, 134 parts of dimethylethanolamine and 90 parts of acetic acid were added and reacted at 120 ° C. for 4 hours. Then, ethylene glycol monobutyl ether was added to adjust the solid content, and an ammonium salt type resin system having a resin solid content of 60% was prepared. Resin for pigment dispersion No. Three solutions were obtained. This pigment dispersing resin No. 3 had an ammonium salt value of 44 mg KOH / g and a number average molecular weight of 3,000.

Production Example 12 Emulsion No. Production of 80% amino group-containing epoxy resin No. 1 obtained in Production Example 1 above. No. 1 solution 43.8 parts (solid content 35 parts), 75% amino group-containing acrylic resin No. 1 Three solutions (43.8 parts) (solid content 35 parts), 33.3 parts (solid content 30 parts) of the curing agent obtained in Production Example 8 and 8.2 parts of 10% formic acid were mixed and stirred uniformly. Thereafter, 164.9 parts of deionized water was added dropwise over about 15 minutes while stirring vigorously, and emulsion No. 3 having a solid content of 34.0% was obtained. 1 was obtained.

Production Examples 13 to 20 Emulsion No. 2-No. No. 9 Emulsion No. 9 having the formulation shown in Table 2 was prepared in the same manner as in Production Example 12. 2-No. 9 was obtained.

Production Example 21 Pigment Dispersion Paste No. Production Example 1 Resin No. 1 for pigment dispersion having a solid content of 60% obtained in Production Example 9 1 is 8.3 parts (solid content 5 parts), JR-600E (note 7) 25 parts, tripolyaluminum dihydrogen phosphate 2 parts, dioctyltin oxide 1 part, deionized water 23.7 parts into a ball mill. For 20 hours, and a pigment dispersion paste No. 1 was obtained.

Production Examples 22 to 24 Pigment dispersion paste No. 2-No. Production Example 4 Pigment Dispersion Paste No. 4 In the same operation as in No. 1, the pigment dispersion paste No. 2-No. 4 was created.

  (Note 7) JR-600E: manufactured by Teika Co., Ltd., trade name, titanium oxide, dibutyl phthalate oil absorption 20.5 ml / 100 g.

  (Note 8) Carplex FPS-5: DSL Japan Co., Ltd., trade name, hydrous amorphous silicon dioxide, dibutyl phthalate oil absorption 230 ml / 100 g.

  (Note 9) Total DBP oil absorption of color pigments: Total dibutyl phthalate oil absorption of color pigments = Oil absorption of color pigments x blending amount. For example, pigment dispersion paste No. In case of 1, 20.5 × 24.0 = 492.

  (Note 10) Total amount of DBP oil absorption of extender pigment: Total of DBP oil absorption amount of extender pigment = Oil absorption amount of extender pigment x blending amount. For example, pigment dispersion paste No. In case of 1, 230 × 1 = 230.

  (Note 11) Total DBP oil absorption amount of rust preventive pigment: Total DBP oil absorption amount of rust preventive pigment = Oil absorption amount of rust preventive pigment x blending amount. For example, pigment dispersion paste No. In case of 1, 30 × 2 = 60.

  (Note 12) Total dibutyl phthalate (DBP) oil absorption: Total dibutyl phthalate oil absorption of colored pigments (Note 9) + Total dibutyl phthalate oil absorption of body pigments (Note 10). For example, pigment dispersion paste No. 4, [(20.5 × 24) + (230 × 1) + (30 × 2 = 60)] = 782.

Example 1 Cationic Electrodeposition Paint No. 1 Production of 34% emulsion No. obtained in Production Example 12 No. 1 294 parts (solid content 100 parts), 55% pigment paste No. obtained in Production Example 21 60 parts (33 parts) of 1 and 311 parts of deionized water were added, and the cationic electrodeposition paint No. 1 having a solid content of 20% was added. 1 was obtained.

Examples 2 to 9 Cationic electrodeposition paint No. 2-No. 9 in combination with production table 4 of cationic electrodeposition coating No. 2-No. 9 was created.

(Note 12) Pigment content of electrodeposition paint:
The pigment content was determined according to the following procedure and equation (1).
The mass of the crucible as a container was measured. (1)
2 g of each cationic electrodeposition coating material was collected, dried by heating at 105 ° C. for 3 hours, then cooled in a dehumidifier desiccator, and after reaching a constant weight at room temperature, the solid content in the cationic electrodeposition coating material was determined. . (2)
The crucible containing each sample was heated in an electric furnace at 800 ° C. for 5 hours, then cooled in a desiccator that had been dehumidified, and the mass was measured after reaching a constant weight at room temperature. (3)
Pigment content = [(3) − (1) / (2) − (1)] × 100 (1).

Comparative Examples 1-9 Cationic electrodeposition paint No. 10-No. Production examples of No. 18 Cationic electrodeposition paint Nos. 10-No. 18 was created.

Preparation of test plate Using each of the cationic electrodeposition paints obtained in the above examples and comparative examples, the dry film thickness is 20 μm on a cold-rolled steel plate (0.8 mm × 70 mm × 150 mm) subjected to zinc phosphate treatment. Thus, electrodeposition coating was applied, and baking was performed at 170 ° C. for 20 minutes to prepare a test plate, which was tested according to the following test method. The results are shown in Tables 6 and 7.

(Note 13) Observation of cross section of coating film: The cross section of the coating film obtained by cutting the test plate was confirmed with a scanning electron microscope (500 times magnification) for the sea-island structure.
A: The sea-island structure could be observed. B: The sea-island structure could not be observed.

  (Note 14) Ratio of island part in coating film cross section (%): Cut the test plate, scan the cross section of the coating film with a scanning electron micrograph, and determine the occupied area (%) of the island part of the sea island structure in the coating film cross section. It was determined using LUZEX III (trade name, image analyzer manufactured by Nikon Instech Co., Ltd.).

(Note 15) Pigment content in the island:
It was determined according to the method described in (Note 3).

(Note 16) Weather resistance: A 1 mm square goblet on the surface of a test plate that was subjected to an accelerated weather resistance test using a sunshine carbon arc lamp type specified in JIS K-5400 9.8.1 until the irradiation time reached 200 hours. 100 pieces were put and the adhesion test was done with vinyl tape.
◎: Good with no peeling chipping ○: Good with no peeling, but chipping △: 90-99 / 100 peeling ×: 89/100 or less peeling.

(Note 17) Anticorrosion: A test plate obtained by electrodeposition coating on a cold-rolled steel plate was subjected to crosscut scratches with a knife so as to reach the substrate, and this was 840 hours according to JIS Z-2371. The salt spray resistance test was conducted, and the following criteria were evaluated based on the rust and blister width from the knife scratch.
◎ indicates that the maximum width of rust and blisters is less than 2 mm from the cut part (one side)
○: The maximum width of rust and blisters is 2 mm or more from the cut part and less than 3 mm (one side)
△ indicates that the maximum width of rust and blisters is 3 mm or more from the cut part and less than 4 mm (one side)
X indicates that the maximum width of rust and swelling is 4 mm or more from the cut part.

(Note 18) Exposure resistance:
After spraying the test plate with WP-300 (manufactured by Kansai Paint Co., Ltd., water-based intermediate coating) so as to have a cured film thickness of 25 μm, it is baked at 140 ° C. for 30 minutes with an electric hot air dryer. I did it. Furthermore, neo-amylac 6000 (manufactured by Kansai Paint Co., Ltd., top coating) is applied onto the intermediate coating film by spray coating so that the cured film thickness is 35 μm, and then baked at 140 ° C. for 30 minutes in an electric hot air dryer. The exposure test board was produced.
The coating film on the obtained exposure test plate was cross-cut with a knife so as to reach the substrate, and this was exposed horizontally in Chikura Town, Chiba Prefecture for one year, then rust and blister width from knife scratches. Based on the following criteria.
◎ indicates that the maximum width of rust or swelling is less than 2 mm from the cut part (one side)
○ indicates that the maximum width of rust or blister is 2 mm or more from the cut part and less than 3 mm (one side)
△ indicates that the maximum width of rust or blisters is 3 mm or more and less than 4 mm from the cut part (one side)
X: The maximum width of rust or blisters is 4 mm or more (one side) from the cut part.
It shows that.

(Note 19) Finishing property: The surface roughness of the test plate is determined according to JIS B 0651, using surf test 301 (trade name, surface roughness measuring machine, manufactured by Mitutoyo Corporation), centerline average roughness. The (Ra) value was evaluated.
For each evaluation,
A: Ra value is less than 0.23 μm,
○: Ra value is 0.23 or more and less than 0.30 μm,
Δ: Ra value is 0.30 or more and less than 0.40 μm ×: Ra value is more than 0.40 μm.

  (Note 20) 60 degree specular glossiness: When the degree of gloss of the multilayer coating film is 60 degrees according to the 60 degree specular glossiness of JIS K-5400 7.6 (1990), respectively. The reflectance was measured and expressed as a percentage when the glossiness of the reference surface of the specular glossiness was taken as 100.

  INDUSTRIAL APPLICABILITY The present invention can provide a coated article having a semi-glossy coating film with a 60 specular gloss of 15 to 55 and excellent finish, which is excellent in long-term corrosion resistance such as weather resistance, anticorrosion, and particularly resistance to exposure.

It is an electron micrograph (500-times multiplication factor) of the halftone of the electrodeposition coating film cross section which forms sea island structure. It is the chart of the X-ray microprobe analyzer of "sea part" in the cross section of the electrodeposition coating film which forms a sea island structure. Ti peaks are clearly visible. FIG. 3 is a chart of an “island” X-ray microprobe analyzer in a cross-sectional view of an electrodeposition coating film forming a sea-island structure. Ti peak is not observed.

Claims (6)

A cationic electrodeposition paint comprising a water dispersion containing a resin component (A) having the following characteristics, and a pigment dispersion paste containing a novolac epoxy resin pigment dispersion resin (B) and a pigment component (C), after baking and drying A cationic electrodeposition coating composition characterized in that the cross section of the coating forms a sea-island structure.
“Aqueous dispersion: As resin component (A), it contains at least two types of resins, an amino group-containing polyol-modified epoxy resin (A1) and an amino group-containing acrylic resin (A2).
Pigment dispersion paste: Novolac epoxy resin pigment dispersion resin (B) obtained by reacting glycidyl etherified product (b1), cyclic ester compound (b2), amine compound (b3) and phenol compound (b4) of novolac type phenol resin, In addition, the total amount of dibutyl phthalate oil absorption of the pigment component (C) in the pigment dispersion paste is 300 to 1,000 ml / 100 g, and 100 parts by mass of the resin component in the cationic electrodeposition coating composition using the pigment dispersion paste. 0.1 to 3 parts by mass of extender pigment having a dibutyl phthalate oil absorption of 200 to 400 ml / 100 g based on the standard " The amino group-containing polyol-modified epoxy resin (A1) is converted into an epoxy resin (a1) having an epoxy equivalent of 180 to 2500 by the following formula (1).

Formula (1)
(Wherein X is a hydrogen atom, —OH, —OR, —NHR, —SH and —SR, a hydrocarbon group having 1 to 15 carbon atoms which may have a substituent selected from the group consisting of —SR, R is Represents an alkyl group)
Is reacted with the epoxy resin (a1) of the above formula to add the alkylphenol (a2) to the compound (a31) containing a plurality of active hydrogen groups. ), A resin obtained by adding one end of the polyol compound (a3) to the skeleton of the epoxy resin (a1), which is obtained by simultaneously reacting the polyol compound (a3) obtained by adding an amine compound (a4) The cationic electrodeposition coating composition in which the coating film cross section according to claim 1 forms a sea-island structure.   The novolac epoxy resin pigment dispersion resin (B) is a glycidyl ether product (b1), a cyclic ester compound (b2), an amine compound (b3) and a phenol compound (b4) of a novolac type phenol resin. Based on the total solid content mass of the etherified product (b1), the cyclic ester compound (b2), the amine compound (b3), and the phenol compound (b4), (b1) 30 to 70 mass%, (b2) 5 to 45 mass %, (B3) 5 to 15% by mass, and (b4) 1 to 30% by mass of a resin for dispersing pigments, wherein the cross section of the coating film according to claim 1 or 2 forms a sea-island structure. Electrodeposition paint composition.   A cationic electrodeposition coating composition according to any one of claims 1 to 3 is electrodeposited and the cross section of the coating after baking and drying forms a sea-island structure, and the resin component (A) and a novolac epoxy resin pigment The sea part in which the ratio of the pigment component (C) is 10% by mass or more and 40% by mass or less with respect to the total solid content of the dispersion resin (B) and the pigment component (C), and the pigment dispersed in the sea The electrodeposition coating film which consists of an island part whose major axis of the domain whose ratio of a component (C) is less than 10 mass% is 0.1-40 micrometers. A coating obtained by electrodeposition-coating the cationic electrodeposition coating composition according to any one of claims 1 to 3 on a metal substrate and baking and drying it is semi-gloss with a 60 ° specular glossiness of 15 to 55 Electrodeposition coating. 5. The 60 ° specular glossiness according to claim 4, wherein the cationic electrodeposition coating composition contains 10 to 40 parts by mass of titanium white with respect to 100 parts by mass of the solid content of the resin component (A). 15-55 gray or beige semi-gloss electrodeposition coating.

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