JPH1143630A - Cation type electrodeposition paint composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electrodeposition paint having excellent hardenability and long-time-storage-stability which gives an electrodeposition paint film having excellent adhesion at the initial condition and after a humidity test even on a smooth metal substrate surface. SOLUTION: An electrodeposition paint contains (1) the primary emulsion particles in which a resin (A) having hydroxide groups and cationic groups, and an imidazole compound having a molecular weight per an imidazole ring of 68-300 are neutralized by an acid and dispersed stably in an aqueous medium and (2) the secondary emulsion particles containing the resin (A) and a curing agent having two or more functional groups, per a molecule in average, containing an epoxy group in which an epoxy group is bonded to an aliphatic or cyclic structure and/or a bridged aliphatic or cyclic structure, in which secondary emulsion the resin (A) is neutralized by an acid and dispersed stably in an aqueous medium. In the resin (A), the cationic group content is 3-200, on the basis of KOH (mg/g-solid content), and the hydroxide group equivalent is 20-5,000.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cationic electrodeposition coating composition capable of forming a coating film having excellent adhesion to a substrate, and having excellent curability and storage stability.

[0002]

2. Description of the Related Art Conventionally, as a curing agent for epoxy resin in organic solvent type paints and powder paints,
It is known to use imidazole-based compounds.

However, imidazole compounds are:
In general, an imidazole compound has not been used as a curing agent for an epoxy resin in a water-based paint because it has high crystallinity and is hardly miscible with a paint resin in an aqueous paint, and precipitates and separates.

As a method of incorporating an imidazole compound into a water-based paint resin in a water-based paint, a method in which the imidazole compound is heated and dissolved, mixed with the paint resin, and dispersed in an aqueous medium to form an emulsion is considered. However, originally, the imidazole compound is poorly miscible with the aqueous paint resin and also poorly soluble in the aqueous medium, so that it gradually precipitates during storage, and the precipitates become nuclei to aggregate the emulsion particles, There were problems such as sedimentation and a decrease in the curability of the coating film. In addition, there is also a problem that a polymerization and curing reaction of the epoxy resin may occur during heating and melting to cause gelation.

The applicant of the present invention has proposed, in Japanese Patent Application Laid-Open No. 2-255874, an aqueous coating composition containing a resin containing a hydroxyl group and a cationic group, a curing agent containing an epoxy group, and a metal compound as a curing catalyst. . This composition generally shows excellent coating performance, but when used as an electrodeposition coating composition, the adhesion of the electrodeposition coating is not sufficient when the surface of the metal substrate is smooth, especially after the moisture resistance test. However, there has been a problem that the adhesion of the electrodeposition coating film to the metal substrate surface tends to decrease, and further, the curability of the electrodeposition coating film is not sufficient.

Accordingly, the present inventors have proposed to add a neutralized imidazole compound to the aqueous coating composition as a method for solving the above-mentioned problem (Japanese Patent Application No. 9-6).
No. 9396). This composition has excellent adhesion and curability of the coating film, but has a problem that the long-term storage stability is insufficient.

An object of the present invention is to provide an electrodeposition coating containing a resin containing a hydroxyl group and a cationic group and an epoxy resin, which shows a sufficient adhesive force even when the surface of a metal substrate is smooth, and shows a good adhesion after a moisture resistance test. In addition, it is possible to obtain an electrodeposition coating having excellent adhesion to the metal substrate surface, and to obtain an electrodeposition coating having excellent curability of the electrodeposition coating and excellent storage stability for a long time. It is.

The present inventors have conducted intensive studies to achieve the above object. As a result, in the above resin system, an imidazole compound serving as a curing catalyst and an epoxy resin serving as a curing agent were mixed in separate emulsion particles. The present inventors have found that the above object can be achieved by separating and presenting in the present invention, and have completed the present invention.

[0009]

That is, the present invention provides:
(1) a resin (A) having a hydroxyl group and a cationic group,
A first emulsion particle in which an imidazole compound (B) having a molecular weight of 68 to 300 per imidazole ring is neutralized with an acid and stably dispersed in an aqueous medium; and (2) the resin (A) and an epoxy group-containing curing agent (C) having an average of two or more epoxy group-containing functional groups in which an epoxy group is bonded to an alicyclic skeleton and / or a bridged alicyclic skeleton per molecule. Characterized in that the resin (A) is neutralized with an acid and contains second emulsion particles which are stably dispersed in an aqueous medium. To provide.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The electrodeposition coating composition of the present invention contains first and second emulsion particles which are stably dispersed in an aqueous medium. The respective emulsion particles will be described below.

First Emulsion Particles The first emulsion particles are obtained by neutralizing a resin (A) having a hydroxyl group and a cationic group and an imidazole compound (B) with an acid and stably dispersing the resin in an aqueous medium. Emulsion particles. Hereinafter, each component in the first emulsion particles will be described.

Resin containing hydroxyl group and cationic group
(A) The resin (A) contains a hydroxyl group capable of reacting with the epoxy group in the epoxy group-containing curing agent (B), and has a sufficient number of cationic groups to form a stable aqueous dispersion. Optional resins are included. Examples of the resin (A) include the following.

(A) a reaction product obtained by reacting a polyepoxy resin with a cationizing agent; (b) a polycondensate of a polycarboxylic acid and a polyamine (see US Pat. No. 2,450,940) ) Is protonated with an acid; (c) is a protonated polyisocyanate or polyol and a mono- or polyamine adduct with an acid; and (d) a copolymer of an acrylic or vinyl monomer having a hydroxyl group and an amino group. A product obtained by protonating the union with an acid (JP-B-45-12395, JP-B-45-12396).
(E) protonated acid adduct of a polycarboxylic acid resin and an alkyleneimine (US Pat. No. 3,403,
No. 088); and the like.

Specific examples and production methods of these cationic resins are described, for example, in JP-B-45-12395, JP-B-45-12396, and JP-B-49-23.
No. 087, U.S. Pat. No. 2,450,940, U.S. Pat. No. 3,403,088, U.S. Pat. No. 3,891,529, U.S. Pat.
No. 3,663, and the like.

Particularly desirable as the resin (A) in the present invention is a reaction of a cationizing agent with an epoxy group of a polyepoxide compound excellent in corrosion resistance obtained from a polyphenol compound and epichlorohydrin, which is included in the above (a). It is a reaction product obtained at least.

The polyepoxide compound is a compound having two or more epoxy groups in one molecule and generally has a number average molecular weight of at least 200, preferably 400 to 4,000, more preferably 800 to 2,000. Those having are suitable. As such a polyepoxide compound, those known per se can be used,
For example, a polyglycidyl ether of a polyphenol compound which can be produced by reacting a polyphenol compound with epichlorohydrin in the presence of an alkali is included. Examples of the polyphenol compound that can be used here include bis (4-hydroxyphenyl)
-2,2-propane, 4,4'-dihydroxybenzophenone, 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, 1,5-dihydroxynaphthalene, bis (2,4-dihydroxyphenyl) methane, tetra (4
-Hydroxyphenyl) -1,1,2,2-ethane,
4,4'-dihydroxydiphenyl ether, 4,4 '
-Dihydroxydiphenyl sulfone, phenol novolak, cresol novolak and the like. Among the above-mentioned polyepoxide compounds, those particularly suitable for producing the base resin (A) have a number average molecular weight of at least about 38.
0, more preferably about 800 to about 2,000, and an epoxy equivalent of 190 to 2,000, preferably 400 to 1.0.
00 is a polyglycidyl ether of a polyphenol compound in the range of

[0017]

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## EQU1 ## The polyepoxide compound may be partially reacted with a polyol, a polyether polyol, a polyester polyol, a polyamidoamine, a polycarboxylic acid, a polyisocyanate, or the like, and may further be subjected to graft polymerization of ε-caprolactone, an acrylic monomer, or the like. .

On the other hand, as a cationizing agent for introducing a cationic group into the polyepoxide compound, an aliphatic or alicyclic or aromatic-aliphatic primary or secondary amine salt or tertiary amine salt is used. , Secondary sulfide salts, tertiary phosphine salts and the like. These react with epoxy groups to form cationic groups. Further, a tertiary aminomonoisocyanate obtained by a reaction between a tertiary amino alcohol and diisocyanate can be reacted with a hydroxyl group of an epoxy resin to form a cationic group.

Examples of the amine compound in the cationizing agent include the following.

(A) methylamine, ethylamine, n-
Or iso-propylamine, monoethanolamine, n
Primary amines such as-or iso-propanolamine; (i) secondary amines such as diethylamine, diethanolamine, di-n- or iso-propanolamine, N-methylethanolamine, N-ethylethanolamine; Polyamines such as ethylenediamine, diethylenetriamine, hydroxyethylaminoethylamine, ethylaminoethylamine, methylaminopropylamine, dimethylaminoethylamine and dimethylaminopropylamine.

Of these, alkanolamines having a hydroxyl group are preferred. Alternatively, the primary amino group may be reacted with a ketone in advance and blocked, and then reacted with the epoxy group with the remaining active hydrogen.

Further, in addition to the above-mentioned amine compounds, basic compounds such as ammonia, hydroxylamine, hydrazine, hydroxyethylhydrazine and N-hydroxyethylimidazoline can also be used. The basic group formed by using these compounds can be protonated with an acid, particularly preferably a water-soluble organic carboxylic acid such as formic acid, acetic acid, glycolic acid, or lactic acid to be a cationic group.

Further, tertiary amines such as triethylamine, triethanolamine, N, N-dimethylethanolamine, N-methyldiethanolamine, N, N-diethylethanolamine and N-ethyldiethanolamine can also be used. To form a quaternary salt by reacting with an epoxy group in advance.

In addition to the amino compound, a tertiary compound is formed by reacting a salt of a sulfide such as diethyl sulfide, diphenyl sulfide, tetramethylene sulfide or thiodiethanol with boric acid, carbonic acid or organic monocarboxylic acid with an epoxy group. It may be a sulfonium salt.

Further, a salt of a phosphine such as triethylphosphine, phenyldimethylphosphine, diphenylmethylphosphine or triphenylphosphine with the above-mentioned acid may be reacted with an epoxy group to form a quaternary phosphonium salt.

The hydroxyl group of the resin (A) includes, for example, an alkanolamine in the above-mentioned cationizing agent, a primary hydroxyl group which can be introduced from a ring-opened product of caprolactone which may be introduced into an epoxide compound and a polyol; Secondary hydroxyl group in the resin; Among them, the primary hydroxyl group introduced by the alkanolamine is preferable because of its excellent crosslinking curing reactivity with the epoxy group-containing curing agent (B). Such alkanolamines are preferably those exemplified above for the cationizing agent.

The content of the hydroxyl group in the resin (A) is from 20 to 50,000 in terms of the hydroxyl equivalent from the viewpoint of the crosslinking and curing reactivity with the epoxy group contained in the epoxy group-containing curing agent (B).
00, particularly preferably in the range of 100 to 1,000, and particularly preferably the primary hydroxyl group equivalent is in the range of 200 to 1,000. The content of the ionic group is preferably at least the minimum necessary for stably dispersing the resin (A), and is generally 3 to 200 in terms of KOH (mg / g solid content).
In particular, it is preferably in the range of 10 to 80. However, even when the content of the ionic group is 3 or less, it is also possible to use the composition after dispersing it in an aqueous solution using a surfactant or the like.

The resin (A) has a hydroxyl group and an ionic group, and desirably does not contain a free epoxy group in principle.

Imidazole compound (B) The imidazole compound (B) functions as a catalyst for a curing reaction between the resin (A) and the epoxy group-containing curing agent (C), or as a curing agent for the curing agent (C).

The imidazole compound (B) is an imidazole compound having a molecular weight of 68 to 300 per imidazole ring. In the case of one imidazole ring, the molecular weight must be in the range of 68 to 300. For example, when it has two imidazole rings, the molecular weight is 136.
It must be in the range of ~ 600.

Specific examples of the imidazole compound (B) include imidazole, 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-phenylimidazole and 2-phenyl -4-methylimidazole,
1-benzyl-2-methylimidazole, 2-ethylimidazole, 2-isopropylimidazole, 2-phenyl-4-benzylimidazole, 1-cyanoethyl-
2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-
Undecylimidazole, 1-cyanoethyl-2-isopropylimidazole, 1-cyanoethyl-2-phenylimidazole, 2,4-diamino-6- [2'-methylimidazolyl- (1) ']-ethyl-S-triazine, 2 , 4-Diamino-6- [2′-ethyl-4-methylimidazolyl- (1) ′]-ethyl-S-triazine, 2-methylimidazolium isocyanuric acid adduct,
2-phenylimidazolium isocyanuric acid adduct, 1
-Aminoethyl-2-methylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4-benzyl-5-hydroxymethylimidazole and the like Compound having one imidazole ring in one molecule; 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-
Hydroxymethylimidazole or 2-phenyl-4-
A compound having two or more imidazole rings in one molecule obtained by condensing a hydroxymethyl group-containing imidazole compound such as benzyl-5-hydroxymethylimidazole by dehydration and deformaldehyde reaction, for example, 4,4'-
Methylene-bis- (2-ethyl-5-methylimidazole) and the like can be mentioned.

In the imidazole compound (B), if the molecular weight per imidazole ring exceeds 300, the dispersion stability in the electrodeposition coating composition of the present invention is not sufficient even when neutralized and dispersed in water. The imidazole compound easily precipitates in the coating composition.

In the electrodeposition coating composition of the present invention, the resin (A) and the imidazole compound (B) are neutralized by an acid to form first emulsion particles which are stably dispersed in an aqueous medium.

In the present invention, the term "aqueous medium" refers to a medium in which water is infinitely soluble, preferably 50% by weight of water.
Above, more preferably a medium containing 80% by weight or more of water. The remainder of the aqueous medium excluding water includes a hydrophilic organic solvent, a neutralizing agent, and the like.

As the acid used for the neutralization, hydrochloric acid,
Mineral acids such as sulfuric acid and phosphoric acid; acetic acid, formic acid, propionic acid, trimethylacetic acid, acrylic acid, methacrylic acid, lactic acid, hydroxyacetic acid, crotonic acid, monochloroacetic acid, maleic acid monoethyl ester, fumaric acid monoethyl ester, itaconic acid Organic acids such as monomethyl ester can be mentioned. These neutralizing agents can be used alone or as a mixture of two or more.

The first emulsion particles can be obtained by mixing, neutralizing and dispersing the resin (A), the imidazole compound (B) and the acid for neutralization in an aqueous medium. The neutralization equivalent of the resin (A) and the imidazole compound (B) by this acid is 0.2 to 1.2 with respect to the total of the cationic group in the resin (A) and the imidazole ring of the imidazole compound (B). It is preferably in the range of equivalents,
More preferably, it is in the range of 0.3 to 1.0. The ratio between the resin (A) and the imidazole compound (B) in the first emulsion particles is not particularly limited, but usually, the weight ratio of the former to the latter is 100: 0.1.
It is used in the range of ~ 20.

Second Emulsion Particle The second emulsion particle contains a resin (A) having a hydroxyl group and a cationic group and a curing agent (C) containing an epoxy group, and the resin (A) is mixed with an acid. Emulsion particles obtained by dispersing the resin (A) and the curing agent (C) stably in an aqueous medium. Hereinafter, each component in the second emulsion particles will be described.

Resin containing hydroxyl group and cationic group
(A) As the resin (A), the same resin as the resin (A) having a hydroxyl group and a cationic group in the first emulsion particles can be used.

Epoxy group-containing curing agent (C) Epoxy group-containing curing agent (C) (hereinafter sometimes referred to as “curing agent (C)”) mainly reacts with resin (A) by the etherification reaction as described above. A curing agent for forming a crosslinked cured coating film, etc., comprising an average of two or more, preferably 3 or more, specific “epoxy group-containing functional groups” per molecule.
Or more.

That is, the epoxy group-containing functional group in the curing agent (C) comprises an alicyclic skeleton and / or a bridged alicyclic skeleton and an epoxy group.
Member, preferably a 5- to 6-membered saturated carbocyclic ring or
And the bridged alicyclic skeleton has a linear or branched C _1-6 between two carbon atoms constituting the cyclic or polycyclic ring. (Preferably C _1-4 )
Alkylene group [for example _{-CH 2 -, - CH 2 CH} 2 -,
_{-CH (CH 3) -, -} CH (CH 3) CH 2 -, - C (C
H ₃ ) ₂ —, —CH (C ₂ H ₅ ) CH ₂ — and the like] (endmethylene, endethylene, etc.).

On the other hand, an epoxy group

[0043]

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Is that one of the carbon atoms in the epoxy group is directly bonded to a ring carbon atom in the alicyclic skeleton or bridged alicyclic skeleton (see, for example, the following formulas [1] and [2]). ) Or
Alternatively, two carbon atoms of the epoxy group and two adjacent carbon atoms constituting a ring in the alicyclic skeleton or bridged alicyclic skeleton are common (for example, the following formula [3],
It is important to refer to [4]).

Specific examples of such an epoxy group-containing functional group include those represented by the following formulas [1] to [4].

[0046]

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[0047]

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[0048]

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[0049]

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(Wherein R ₁ , R ₂ , R ₃ , R ₅ , R ₆ ,
R ₇ , R ₁₀ and R ₁₁ are each H, CH ₃ or C ₂ H ₅
And R ₄ , R ₈ and R ₉ each represent H or CH ₃ . The curing agent (C) may have an average of at least two, preferably three or more, more preferably four or more epoxy group-containing functional groups represented by the above formulas [1] to [4] per molecule. it can. The epoxy group-containing functional groups in the curing agent (C) may be the same or different, and the curing agent (C) may be used alone or as a mixture of two or more.

Of the above, epoxy group-containing groups represented by the formulas [1] and [3] are preferable, and particularly, the following formula [5]

[0052]

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An epoxy group-containing functional group represented by the following formula [6]

[0054]

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The epoxy group-containing functional group represented by the following formula is preferred.

The epoxy equivalent and molecular weight of the curing agent (C) are not strictly limited, and can be changed according to the production method, required performance of the final coating composition, and the like. , Epoxy equivalent is usually 100 ~
2,000, preferably between 150 and 500, more preferably between 150 and 250;
The number average molecular weight is usually 400 to 100,000, preferably 700 to 50,000, more preferably 700 to 3
Suitably, it is in the range of 0.000.

The curing agent (C) having two or more epoxy group-containing functional groups in one molecule is described in, for example,
6-8016, JP-A-57-47365,
JP-A-60-166675, JP-A-63-221
No. 121, JP-A-63-234028 and the like, and those known per se can be used.

Alternatively, the above-mentioned curing agent (C) having an epoxy group-containing functional group can be obtained by a method known per se, and its main production methods are listed below, but are not limited thereto.

First Production Method: Part of an alicyclic compound having two or more carbon-carbon double bonds in a molecule is partially epoxidized and the epoxy group is subjected to ring-opening polymerization. A method of epoxidizing the double bond remaining in the polymer.

Second production method: a method in which an alicyclic compound having two or more epoxy groups in the same molecule is subjected to ring-opening polymerization based on the epoxy group to such an extent that all of the epoxy groups are not erased.

Third production method: a method of polymerizing a compound having an epoxy group-containing functional group and a polymerizable unsaturated bond in the same molecule.

Hereinafter, these production methods will be described more specifically.

First Production Method: An alicyclic compound having two or more carbon-carbon double bonds in one molecule (hereinafter abbreviated as “alicyclic compound (a)”) has an alicyclic skeleton or an alicyclic skeleton. The alicyclic ring or bridged alicyclic ring structure described above for the bridge alicyclic skeleton is used as a basic skeleton, and a double bond is present between two adjacent carbon atoms constituting the ring, or the ring structure Is a compound containing at least two or more double bonds based on other carbon atoms directly bonded to the carbon atom constituting

Typical examples of the alicyclic compound (a) are as follows.

[0065]

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A part of the carbon-carbon double bond contained in the alicyclic compound (a) is modified into an epoxy group with a peroxide or the like (partial epoxidation). The partially epoxidized product is obtained by modifying a part of a plurality of double bonds contained in the alicyclic compound (a) to an epoxy group. In each molecule, an epoxy group and a carbon-carbon double bond are formed. The double bond is present between two adjacent carbon atoms constituting the ring, or a double bond based on another carbon atom is bonded to the carbon atom of the ring. It is necessary to be.

Next, a polymer of the alicyclic compound (a) is obtained by ring-opening polymerization based on the epoxy group in the partially epoxidized product. It is preferable to use an initiator for this ring-opening polymerization, and the terminal of the curing agent (C) is a residue X due to the initiator component.
May be bonded. Here, X is an organic compound residue having active hydrogen, and examples of the organic compound having active hydrogen as a precursor thereof include alcohols, phenols, carboxylic acids, amines, and thiols. .

At the time of ring-opening polymerization, it is obtained by causing a partially epoxidized product alone or, if necessary, other epoxy compounds to co-exist and subjecting the epoxy groups contained therein to ring-opening polymerization (ether bond).

The composition ratio of the other epoxy compounds in the ring-opened polymer can be arbitrarily selected depending on the purpose. Specifically, the structural formulas [1] to [1] per molecule of the obtained ring-opened copolymer can be used. It is desirable to select any one or more of [4] in a range having an average of 2 or more, preferably 3 or more, and more preferably 4 or more.

The number average molecular weight of the (co) polymer thus obtained is generally from 400 to 100,000, especially 7
It is preferably in the range of 00 to 50,000, more preferably 700 to 30,000.

The ring-opening polymer has a double bond based on the alicyclic compound (a), and a curing agent (C) can be obtained by epoxidizing all or a part of the double bond. Epoxidation of the double bond can be carried out using an epoxidizing agent such as peracids and hydroperoxides.

The epoxy equivalent of the curing agent (C) thus obtained is generally from 100 to 2,000, especially from 150 to 2,000.
Preferably, it is in the range of 500, more preferably 150 to 250.

Commercial products of such a curing agent (C) include, for example, EHPE-3150, EHPE-3100,
EHPE-1150 (trade name, manufactured by Daicel Chemical Industries, Ltd.) and the like, and these are epoxy resins of the following structural formula having a cyclohexane skeleton using 4-vinylcyclohexene-1-oxide.

[0074]

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(Wherein n is 2 or more, preferably 3
The number is preferably 4 or more, and X is the residue of the initiator component. 2 ) Second production method: obtained by, for example, epoxidizing at least two of the double bonds contained in the alicyclic compound (a), and then subjecting the alicyclic compound to ring-opening polymerization so that the epoxy group remains.

As the alicyclic compound having an average of two or more epoxy groups per molecule, the following monocyclic or condensed cyclic compounds are representatively shown.

[0077]

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In the ring-opening polymerization, one or more alicyclic compounds having an average of two or more epoxy groups per molecule can be prepared by reacting one or more alicyclic compounds as described in the first production method, if necessary, with an initiator, The curing agent (C) can be obtained by performing a ring-opening polymerization reaction using a catalyst and stopping the reaction at a predetermined reaction point where the epoxy group remains.

The ring-opened polymer [curing agent (C)] thus obtained generally has a number average molecular weight of 400 to 100,0.
And preferably in the range of from 700 to 50,000, and the epoxy equivalent is generally from 100 to 2,000.
Conveniently in the range of 00, especially 150-500, even 150-250.

Third production method: As a compound having at least one epoxy group-containing functional group and at least one polymerizable unsaturated bond in the same molecule (hereinafter sometimes abbreviated as “polymerizable epoxy monomer”) Are, for example, those represented by the following general formulas.

[0081]

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[0082] (wherein, R ₁₂ represents a hydrogen atom or a methyl group, R ₁₃ represents. A divalent aliphatic saturated hydrocarbon group having 1 to 6 carbon atoms) in the polymerizable epoxy monomers, the R ₁₃ Examples of the divalent aliphatic hydrocarbon group having 1 to 6 carbon atoms include linear or branched alkylene groups such as methylene, ethylene, propylene, tetramethylene, ethylethylene, pentamethylene and hexamethylene. And the like.

Specific examples of the polymerizable epoxy monomer represented by the above general formula (1) include 3,4-epoxycyclohexylmethyl acrylate and 3,4-epoxycyclohexylmethyl methacrylate. Further, 4-vinylcyclohexene oxide can be used as the polymerizable epoxy monomer.

A curing agent (B) is obtained by polymerizing one or more kinds selected from polymerizable epoxy monomers.
Can be produced, but other polymerizable unsaturated monomers can be copolymerized at that time.

The other polymerizable unsaturated monomers include:
A wide selection can be made according to the desired performance of the (co) polymer obtained, and representative examples thereof are as follows. (A) esters of acrylic acid or methacrylic acid; for example, methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, lauryl acrylate, methyl methacrylate, methacrylic C1-C18 alkyl esters of acrylic acid or methacrylic acid such as ethyl acrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, hexyl methacrylate, octyl methacrylate, lauryl methacrylate; hydroxyethyl acrylate, hydroxyethyl methacrylate C2-8 hydroxyalkyl esters of acrylic acid or methacrylic acid such as hydroxypropyl acrylate and hydroxypropyl methacrylate.

(B) Vinyl aromatic compounds; for example, styrene, α-methylstyrene, vinyltoluene, p-chlorostyrene.

(C) a polyolefin compound; for example,
Butadiene, isoprene, chloroprene.

(D) Others: acrylonitrile, methacrylonitrile, beoba monomer (product of Shell Chemical Company),
Vinyl compounds having polycaprolactone chains (for example, F
M-3X monomer; trade name, manufactured by Daicel Chemical Industries).

The composition ratio of the polymerizable epoxy monomer and the other polymerizable unsaturated monomer can be arbitrarily selected according to the purpose, and the curing agent (C) obtained by the copolymerization reaction in one molecule of the curing agent (C) is used. Per epoxy group-containing functional group on average, preferably 3 or more on average, more preferably 4 or more on average, but it is used as a functional group that imparts sufficient curability. In order to do so, it is particularly preferable that the content of the polymerizable epoxy monomer in the solid content of the curing agent (C) is in the range of 5 to 100% by weight, more preferably 20 to 100% by weight.

The curing agent (C) obtained by the third production method can be produced by the same method and under the same conditions as in the polymerization reaction based on a polymerizable unsaturated bond of an ordinary acrylic resin or vinyl resin. it can.

The curing agent (C) of the third production example preferably has a number average molecular weight generally in the range of about 3,000 to about 100,000, and particularly preferably 4,000 to 10,000.
Those within the range of 00 are more preferred.

Among the above-mentioned curing agents (C), preferred ones have an average of epoxy group-containing functional groups of 3 per molecule.
Or more, more preferably 4 or more on average, and most preferably 5 or more on average, and the epoxy equivalent is preferably 100 to 2,000, more preferably 150 to 500, and particularly preferably 150 to 500. 250 and the number average molecular weight is preferably 400-100,
000, more preferably 700 to 50,000, particularly preferably 700 to 30,000.

The second emulsion particles can be obtained by stably dispersing a mixture of the resin (A) and the curing agent (C) in an aqueous medium. The mixture can be dispersed by neutralizing the resin (A) with an acid to impart water dispersibility. As the acid used for the neutralization, those mentioned as the acid used for the neutralization of the resin (A) and the imidazole compound (B) in the formation of the first emulsion particles can be used.

The neutralization equivalent of the resin (A) with an acid during the formation of the second emulsion particles is in the range of 0.2 to 1.2 equivalents to the cationic group in the resin (A). It is preferable that it is in the range of 0.3 to 1.0. The ratio between the resin (A) and the curing agent (C) in the second emulsion particles is not particularly limited, but usually, the weight ratio of the former to the latter is 100: 25 to 100%.
It is used in the range of 200.

In the composition of the present invention, the mixing ratio between the first emulsion particles and the second emulsion particles is not particularly limited.
In general, the weight ratio of the solid content of the curing agent (C) to the resin (A) is from 0.2 to 0.2
1.0, particularly 0.25 to 0.85, more preferably 0.25 to 0.65, and the imidazole compound based on the total solid content of the resin (A) and the curing agent (C) The solid content weight ratio of (B) is 0.0005 to
It is desirable to select and use it in the range of 0.10, particularly 0.001 to 0.05, more preferably 0.002 to 0.03.

The method for preparing the electrodeposition coating composition of the present invention is not particularly limited as long as the electrodeposition coating composition in which the first emulsion particles and the second emulsion particles are stably dispersed over time can be obtained. It is not something to be done. The electrodeposition coating composition of the present invention is, for example, a first emulsion particle dispersion stably dispersed in an aqueous medium, and a first emulsion particle dispersion stably dispersed in an aqueous medium are mixed, If necessary, it can be carried out by mixing a coloring pigment such as carbon black, titanium white, lead white, lead oxide, and red iron oxide; an extender pigment such as clay and talc; or other additives. Other additives that can be incorporated include, for example, a small amount of a surfactant as a dispersant or an anti-cissing agent, an ultraviolet absorber, an antioxidant, and the like.

[0097]

The present invention will be described more specifically with reference to the following examples. Hereinafter, “parts” and “%” are based on weight. Production Example 1 of Resin (A) Having Hydroxyl Group and Cationic Group 155 parts of EHPE3150 (* 1), 70 parts of diethanolamine, 475 parts of bisphenol A diglycidyl ether having an epoxy equivalent of 190 in advance, and bisphenol A2
85 parts, 53 parts of diethanolamine and carbitol 80
And a mixture consisting of the entire reaction product obtained by reacting the mixture at 130 ° C. for 3 hours and reacting at 160 ° C. for 5 hours. Then, 692 parts of methylpropanol was added, the solid content was 60%, and the amine value was 63. Thus, a cationic resin solution (A-1) having a primary hydroxyl group equivalent of 443 was obtained.

(* 1) EHPE3150: an epoxy resin having a repeating unit represented by the following formula and having an epoxy equivalent of about 175 to 195, manufactured by Daicel Chemical Industries, Ltd.

[0099]

Embedded image

In the formula, m represents an integer of 2 or more.

Production Example 2 of Epoxy Group-Containing Curing Agent (B) Duranate TPA-100 [trade name, manufactured by Asahi Kasei Corporation;
Isocyanurate of hexamethylene diisocyanate, isocyanate equivalent 185] 14.5 parts and 3,4-
10.5 parts of epoxy tetrahydrobenzyl alcohol [manufactured by Daicel Chemical Industries, Ltd., epoxy equivalent: 135]
The mixture was reacted at 20 ° C. for 3 hours. After confirming that the isocyanate value was 0, 6.3 parts of methylpropanol was added to obtain a curing agent solution (B-2) having a solid content of 80%. This curing agent resin had a number average molecular weight of 970 and an epoxy equivalent of 325.
Had.

Production Example 3 of Resin Emulsion (Production of First Emulsion Particles) Into 8.3 parts of the above 60% cationic resin solution (A-1) was added:
1 part of 2-phenylimidazole and 0.1 part of formic acid are added,
With sufficient stirring, 20.6 parts of deionized water was added to obtain a first emulsion particle dispersion (E-1-1) having a solid content of 20%, a pH of 6.5, and an emulsion particle diameter of 0.1 μm.

Production Example 4 (Production of First Emulsion Particles) To 8.3 parts of the above 60% cationic resin solution (A-1),
2-undecyl imidazole (2 parts) and formic acid (0.15 parts) were added, and while sufficiently stirring, deionized water (20.55 parts) was added to give a solid content of 20%, pH 6.0, and an emulsion particle size of 0.0
5 μm first emulsion particle dispersion (E-1-2)
I got

Production Example 5 (Production of Second Emulsion Particles) 75 parts of the above 60% cationic resin solution (A-1) and the above EHPE-3150 were dissolved in ethylene glycol monoethyl ether to give a solid content of 80%. Hardener solution (B-
1) 62.5 parts and formic acid 0.6 part were added, and with sufficient stirring, 336.9 parts of deionized water was added to obtain a solid content of 20%.
%, PH 6.6, emulsion particle size 0.05 μm
(E-2-1) was obtained.

Production Example 6 (Production of Second Emulsion Particles) 75 parts of the above 60% cationic resin solution (A-1) and the curing agent solution (B-2) having a solid content of 80% obtained in the above Production Example 2 6
Add 2.5 parts and 0.5 part of formic acid, add 337 parts of deionized water with sufficient stirring, solid content 20%, pH 6.
3. A second emulsion particle dispersion (E-2-2) having an emulsion particle diameter of 0.1 μm was obtained.

Production Example 7 (Production of Comparative Emulsion) The above-mentioned EHPE-3150 was dissolved in 83.3 parts of the above 60% cationic resin solution (A-1) in ethylene glycol monoethyl ether, and the solid content was 80%. 62.5 parts of a curing agent solution (B-1) and 0.6 part of formic acid are added, and 312 parts of deionized water are added with sufficient stirring to obtain a solid content of 2 parts.
An emulsion particle dispersion (EC-1) having 0%, pH 6.2, and an emulsion particle diameter of 0.10 μm was obtained.

Production Example 8 (Production of Comparative Emulsion) 83.3 parts of the above 60% cationic resin solution (A-1) was mixed with the curing agent solution (B) having a solid content of 80% obtained in Production Example 2 above.
-2) 62.5 parts and formic acid 0.6 part were added, and 312 parts of deionized water was added with sufficient stirring to obtain a solid content of 20%.
An emulsion particle dispersion (EC-2) having a pH of 6.2 and an emulsion particle diameter of 0.10 μm was obtained.

Example 1 30 parts of the first emulsion particle dispersion (E-1-1) having a solid content of 20% obtained in Production Example 3 was added to the second emulsion particle dispersion having a solid content of 20% obtained in Production Example 5 above. Emulsion particle dispersion (E-2
-1) 475 parts were mixed and stirred, pH 6.1, solid content 2
0% of the cationic electrodeposition paint-1 was obtained.

Example 2 35 parts of the first emulsion particle dispersion (E-1-2) having a solid content of 20% obtained in Preparation Example 4 was added to the second emulsion particle dispersion having a solid content of 20% obtained in Preparation Example 6. Emulsion particle dispersion (E-2
-2) 475 parts were mixed and stirred, pH 6.3, solid content 2
0% of a cationic electrodeposition paint-2 was obtained.

Example 3 The cationic resin solution (A-1) 10 obtained in Production Example 1 was used.
0 parts of titanium white 50 parts, clay 50 parts, formic acid 3.0 parts,
After adding 55 parts of deionized water and kneading, the glass beads 8
Add 00 parts and disperse with a paint shaker, remove the glass beads, and obtain a pigment dispersion (P-1) having a solid content of about 62%.
I got

The dispersion of the second emulsion particles having a solid content of 20% obtained in Preparation Example 5 was dispersed in 30 parts of the first emulsion particle dispersion (E-1-1) having a solid content of 20% obtained in Preparation Example 3. 475 parts of the liquid (E-2-1) and the pigment dispersion (P-
1) 7.1 parts and 14.9 parts of deionized water were mixed and stirred to obtain a cationic electrodeposition paint-3 having a pH of 6.1 and a solid content of 20%.

Comparative Example 1 To 1 part of 2-phenylimidazole was added 1 part of a 10% aqueous solution of formic acid obtained by dissolving 0.1 part of formic acid in 0.9 part of water and 3.5 parts of water, followed by stirring. An imidazole compound neutralized dispersion (C-1) was obtained. This dispersion liquid (C-1) was a uniform cloudy colloidal dispersion having a solid content of 20%.

To 500 parts of the emulsion particle dispersion (EC-1) having a solid content of 20% obtained in Preparation Example 7, 5 parts of the imidazole compound neutralized dispersion (C-1) was mixed.
The mixture was stirred to obtain a cationic electrodeposition coating material-4 (comparative) having a pH of 6.2 and a solid content of 20%.

Comparative Example 2 0.1 part of formic acid was added to 1 part of 2-undecylimidazole.
1 part of a 10% aqueous formic acid solution obtained by dissolving the above-mentioned parts in 0.9 parts of water and 3.5 parts of water were added thereto, followed by stirring to obtain an imidazole compound neutralized dispersion liquid (C-2). This dispersion liquid (C-2) was a uniform cloudy colloidal dispersion having a solid content of 20%.

To 500 parts of the emulsion particle dispersion (EC-2) having a solid content of 20% obtained in Production Example 8, 10 parts of the imidazole compound neutralized dispersion (C-1) was mixed and stirred. , PH 6.2, and a solid content of 20%, to obtain a cationic electrodeposition paint-5 (for comparison).

Comparative Example 3 The neutralized dispersion of the imidazole compound (C-1) used in Example 1 was added to 500 parts of the emulsion particle dispersion (EC-1) having a solid content of 20% obtained in Production Example 7 above. 5) 5 parts and the pigment dispersion (P-1) 7.1 used in Example 3 above.
The parts were mixed and stirred to obtain a cationic electrodeposition paint-6 (comparative) having a pH of 6.2 and a solid content of 20%.

Comparative Example 4 The second emulsion particle dispersion (E
-2-1) Cationic electrodeposition paint-7 itself (for comparison)
And

Comparative Example 5 The second emulsion particle dispersion (E
2-1) 10 parts of a 20% solids aqueous solution of lead acetate in 500 parts
The parts were mixed and stirred to obtain a cationic electrodeposition paint-8 (comparative) having a pH of 6.2 and a solid content of 20%.

Comparative Example 6 The second emulsion particle dispersion (E
-2-1) 500 parts, 2-phenylimidazole 1 part, and pigment dispersion (P-1) 7.1 used in Example 3 above
The parts were mixed and stirred to obtain a cationic electrodeposition coating material 9 having a pH of 6.2 and a solid content of 20% (for comparison).

Regarding the electrodeposition paints obtained in Examples 1 to 3 and Comparative Examples 1 to 6, the gel fraction of the coating film, the elongation percentage of the coating film, the adhesion, the coating film hardness, and the coating stability with respect to open agitation. The test was performed based on the following test method. The test results are shown in Table 1 below.

Preparation of Test Coated Plate (1) Regarding the gel fraction and elongation of the coating film, each electrodeposition coating material was applied to a tin plate by cationic electrodeposition coating under a condition of an applied voltage of 150 V so that the coating film thickness was about 20 μm. After washing with water, 2
The test was performed using painted tinplates baked at 00 ° C for 20 minutes.

(2) Regarding the adhesion and hardness of the coating film, cationic electrodeposition coating was performed on a cold-rolled polished steel plate under the condition of an applied voltage of 170 V so that the coating film thickness was about 20 μm. After washing with water, the test was performed using a painted polished steel plate baked at 200 ° C. for 20 minutes.

Test method Gel fraction: The coating film of the painted tin plate was peeled from the tin plate, placed in a stainless steel mesh container of 300 mesh, and refluxed at a reflux temperature of 6 with a solvent of acetone / methanol = 1/1. After the time extraction, the gel fraction was calculated according to the following equation.

Gel fraction (%) = (weight of coating film after extraction) /
(Coating weight before extraction) x 100 Coating elongation: Cut the coating film peeled from the painted tin plate,
For a coating film having a width of 5 mm and a length of 20 mm, an autograph (manufactured by Shimadzu Corporation) was used at a temperature of 20 ° C. and a tensile speed of 20 mm /
The coating film elongation was measured under the conditions of minutes. The coating film elongation is the ratio (%) of elongation to the original length when the coating film is cut.

Adhesion: Initial painted polished steel plate and about 100
A coating film adhesion test was carried out on a polished steel plate immersed in boiling water at 30 ° C. for 30 minutes. The adhesion test is based on JIS K
-5400 8.5.2 (1990) In accordance with the cross cut tape method, cuts reaching the substrate were made in the coating film, 100 squares of 1 mm x 1 mm were created, and a cellophane adhesive tape was adhered to the surface, The evaluation was made based on the number of squares remaining without being peeled off after abrupt peeling. 100 means that peeling of the coating film was not observed and adhesion was good.

Coating film hardness: JIS
A pencil scratch test specified in K-5400 8.4.2 (1990) was performed, and evaluation was performed by the blurring method.

Coating stability: The electrodeposition coating composition was kept at 30 ° C., covered lightly with an aluminum foil, stirred for 1 week and 3 weeks, and the state of the coating composition was examined. Those in which no significant change was observed in the paint state were indicated by ○. Agglomeration in paint,
Those in which gelation was observed were indicated by x.

[0128]

[Table 1]

[0129]

According to the electrodeposition coating composition of the present invention, in an electrodeposition coating system containing a resin having a hydroxyl group and a cationic group, an epoxy resin and an imidazole compound, the epoxy resin and the imidazole compound are different from each other. It is present in the emulsion and is stably dispersed. Since the electrodeposition coating composition of the present invention does not contain a metal catalyst, it exhibits sufficient adhesion even when the surface of the metal substrate is smooth, and has excellent adhesion to the surface of the metal substrate even after the moisture resistance test. A coating film can be obtained. Since the epoxy resin and the imidazole compound are separated from each other, the electrodeposition coating composition of the present invention has excellent long-term storage stability and excellent curability.

Claims (3)

[Claims] (1) A resin (A) having a hydroxyl group and a cationic group and a resin having a molecular weight of 6 per imidazole ring.
A first emulsion particle obtained by neutralizing an imidazole compound (B) of 8 to 300 with an acid and stably dispersing in an aqueous medium; and (2) the resin (A) and an alicyclic compound An epoxy group-containing curing agent (C) having an average of two or more epoxy group-containing functional groups per molecule in which an epoxy group is bonded to a skeleton and / or a bridged alicyclic skeleton; A second emulsion particle, which is neutralized with an acid and is stably dispersed in an aqueous medium. 2. The resin (A) has a cationic group content of 3 to 200 in terms of KOH (mg / g solid content) and a hydroxyl equivalent of 20 to 5,000. Item 7. The coating composition according to Item 1. 3. The epoxy group-containing functional group in the curing agent (C) is represented by the following formulas [1] to [4]: Embedded image Embedded image Embedded image Wherein R ₁ , R ₂ , R ₃ , R ₅ , R ₆ , R ₇ , R ₁₀ and R ₁₁ each represent H, CH ₃ or C ₂ H ₅ ;
R ₄ , R ₈ and R ₉ each represent H or CH ₃ . 3. The coating composition according to claim 1, which is at least one member selected from the group consisting of: