JPH06173089A - Coating method - Google Patents

Abstract

PURPOSE:To enable pollution prevention, resource economization and a sufficient improvement in the appearance of the coating by applying the first layer coating having corrosion-protectiveness to edges, the second layer coating having weather resistance and further an aq. based coating and a powder coating on a substrate. CONSTITUTION:The following coating is applied on an uncured electrodeposition- coating film of a cationic electrodeposition coating contg. 5 to 50wt.% cationic- electrodepositing gelatinized particulates per the total resinous solid content. Firstly, the amounts of the epoxy-based cationic-electrodepositing resin (B) which has 40 to 60dyne/cm surface tention and forms an aq. bath that can be electrodeposited on the cathode at the time of neutralizing it with an acid, and the nonionic coating film forming resin (C) having 25 to 45dyne/cm surface tension are selected so that the B:C ratio is within the range of 60:40 to 98:2. Then the cationic electrodeposition coating having surface tension of B greater than that of C, a <=0.7mA/cm<2> minimum electrodeposition current density and a >=80wt.% degree of emulsification, is applied on the above film. Thereafter, the aq. based coating contg. a metallic pigment and/or a color pigment, and further the powder clear coating are applied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention provides a coating method which is particularly low in coating cost, has excellent weather resistance, edge corrosion resistance, and finished appearance of the coating film, and is advantageous for resource saving and pollution prevention. Regarding

[0002]

2. Description of the Related Art Conventionally, the outer panels of automobiles, motorcycles, electric appliances, etc., for which cosmetic appearance is particularly important, form organic films that form a coating film excellent in smoothness, sharpness and weather resistance. Finished with solvent-diluted thermosetting top coat.
The coating process is usually carried out by applying a cationic electrodeposition coating once for the purpose of imparting anticorrosion property, then applying an intermediate coating for ensuring weather resistance, and heating and curing each of these coatings. , As an overcoat, an organic solvent type thermosetting enamel paint (hereinafter abbreviated as "base coat") containing a color pigment and / or a metallic pigment is applied, and the organic solvent type thermosetting transparent clear paint is not cured. In many cases, it is a two-coat one-bake system in which both coating films are heated and cured simultaneously after being repeatedly applied.

However, in recent years, there has been a strong demand for improvement in anticorrosion property of edges and finish appearance (for example, smoothness, sharpness, and feeling of flesh), and further improvement of weather resistance, resource saving and pollution prevention measures. It is also desired that the coating cost be low. Here, the "edge portion" refers to a portion having a sharp angle shape such as a corner portion such as a cut surface of a metal coated object, a bent portion, a curved surface portion and a protrusion portion.

Among them, in order to improve the corrosion resistance of the edge portion, for example, an anticorrosive steel plate is used, or after the electrodeposition coating and baking, the edge portion is subjected to repair coating with a roller or brush. However, the cost and the number of steps are enormous. In addition, various attempts have been made such as adding a large amount of pigment to the electrodeposition paint and reducing the amount of plastic component.
To form a thick electrodeposition coating film on the edge part (hereinafter,
It is difficult to achieve both "edge cover") and obtaining the smoothness of the coating film. In addition, double electrodeposition coating has been attempted. Edge coating is achieved by increasing the pigment concentration of the electrodeposition coating used for the first layer or using a pigment with a high oil absorption, and smoothing the second layer. Although a method for achieving the above has been proposed, this method has a problem that a finish defect due to pigment sedimentation occurs particularly in the horizontal portion of the bag structure of the article to be coated. Therefore, improvement of the finished appearance is dealt with by adding a rheology control agent to the top coating and polishing the surface of the intermediate coating, but the former is fundamental because there is a limit to improving smoothness and sharpness. It cannot be said that this is a countermeasure, and the latter has the problem that the number of man-hours and the sufficient improvement in appearance cannot be obtained. On the other hand, even in high-solid paints (containing high solids content), which were developed as a measure against pollution, there is a limit to the reduction of organic solvent, and when this is used as a metallic base coat, a light metallic such as silver is sufficient whiteness. Is difficult to obtain. In addition, since the intermediate coating and top coating (base coat, clear coating) in the above conventional coating process usually contain a large amount of organic solvent, it is not preferable from the viewpoint of pollution prevention and resource saving, and the total cost in the coating process is low. Some point out that the cost is high.

[0005]

SUMMARY OF THE INVENTION The inventors of the present invention have solved the above-mentioned various defects and significantly improved the anticorrosion property of the edge portion and the finished appearance, reduce the coating cost, have excellent weather resistance, and save energy. As a result of diligent study on a coating method for forming a coating film that is advantageous in preventing resources and pollution, a specific cationic electrodeposition coating having excellent corrosion resistance at the edge was coated (first layer), and then a coating with good weather resistance was applied. A cationic electrodeposition paint having a specific composition that can form a layer coating film is applied (second layer), and an aqueous base coat and a clear powder paint are applied as an overcoating process without intermediate coating. The inventors have found that the above-mentioned objects can be achieved thereby, and completed the present invention.

That is, according to the present invention, (i) a cationic electrodeposition coating composition (I) containing 5 to 50% by weight of the cationic electrodeposition gelling fine particles (A) with respect to the total resin solid content is electrodeposited on an object to be coated. On the uncured electrodeposition coating film obtained by coating, (ii) a surface tension of 40 to 60 dyne / cm and an aqueous bath capable of electrodeposition on the cathode can be formed by neutralizing with an acid Epoxy cationic electrodeposition resin (B), and surface tension of 25 ~
Non-ionic film-forming resin (C) with 45 dyne / cm 2
Resin (B): resin (C) = 60: 40 to 98: 2 in a weight ratio within the range, the surface tension of the resin (B) is larger than the surface tension of the resin (C), and the minimum electric Deposition current density 0.7 mA / cm ² or less and emulsification degree 80% by weight
The above cationic electrodeposition coating composition (II) is electrodeposited and then heated to cure both coating films (i) and (ii), and then (iii) metallic pigment is applied to the electrodeposition coated surface. And / or a water-based base coating material containing a coloring pigment is applied, and (iv) a powder clear coating material is further applied on the coated surface without curing, and then heated to (iii) and (iv) above. The present invention provides a coating method characterized by curing both coating films.

A feature of the present invention is that the cationic electrodeposition coating composition of the above-mentioned step (i) and step (ii) is repeatedly applied by a wet-on-wet method, both the electrodeposition coating films are heated and cured, and then an intermediate coating composition is applied. Without performing the above, the top coat paint of the above step (iii) and step (iv) is applied. That is, first, the cationic electrodeposition coating composition (I) containing a specific amount of the gelled fine particles (A) in the step (i) can form a thick coating film on the edge portion as well, so that the edge portion is protected against corrosion. In particular, the corrosion resistance of the edge portion is remarkably improved and the coating workability is also excellent, and pinholes, uneven coating, and skin roughness are hardly observed. next,
The cationic electrodeposition coating composition (II) in the step (ii) contains a resin (B) and a resin (C) having different surface tensions as main components, and the nonionic coating film is formed by the difference in the surface tensions of the resins (B) and (C). The forming resin (C) floats to the upper layer portion, while the epoxy resin (B) moves to the coated surface side, that is, the electrodeposition coated surface side of the step (i), and as a result, the upper layer portion mainly has good weather resistance. It is possible to form a multi-layer film having a concentration gradient such that the non-ionic film-forming resin occupies the lower layer part and the epoxy resin mainly having good anticorrosion property occupies the lower layer part, and as a result, the lower layer can be formed by one electrodeposition coating. It is possible to form a multi-layer electrodeposition coating film having a concentration gradient consisting of a layer excellent in anticorrosion property and an upper layer having excellent weather resistance, and a cured coating film of the coating material (II) alone,
The 60% specular reflectance retention after irradiation with a light beam of 1,100 K.Joule / m ² · hr for 40 hours is usually 50% or more, and preferably 60% or more.

Therefore, in the multi-layer electrodeposition coating film (consisting of approximately three layers) formed in the above steps (i) and (ii), the electrodeposition coating film in the step (i) is mainly used for coating the object. The corrosion resistance of the edge portion of, and the multi-layer electrodeposition coating film of the step (ii) can further improve the corrosion resistance and also significantly improve the weather resistance and the thread rust resistance, and as a result, The electrodeposition coating film obtained in the steps (i) and (ii) above,
Edge edge corrosion resistance, general corrosion resistance and weather resistance are remarkably excellent, and further smoothness, interlayer adhesion and thread rust resistance are also good. Therefore, even if the ordinary intermediate coating is omitted and the top coating is directly applied to the electrodeposition coated surface in the steps (i) and (ii), the weather resistance and the like are not deteriorated.

The coating method of the present invention will be described in more detail below.

Step (i) : This is a step of performing the first cationic electrodeposition coating by using the cationic electrodeposition coating (I) with the object to be coated as a cathode, and its main purpose is to improve the corrosion resistance of the edge portion.

The cationic electrodeposition coating composition (I) contains the cationic electrodeposition gelling fine particles (A) in an amount of 5 to 50 relative to the total resin solid content.
It is a coating material containing wt%.

As the above-mentioned cation electrodepositable gelled fine particles (A), any conventionally known one can be used without particular limitation as long as it is a fine particle polymer gelled by a crosslinking reaction in the particles.
For example, an acrylic copolymer containing an alkoxysilane group and a cationic group is dispersed in water and crosslinked within the particle (see Japanese Patent Application No. 62-54141); having an alkoxysilane group, a hydroxyl group and a cationic group. Internally crosslinked gelled fine particles (see JP-A-2-47173); Internally crosslinked gelled fine particles having an alkoxysilane group, a urethane bond, a hydroxyl group and a cationic group (Japanese Patent Laid-Open No. 3-62).
860) and the like.

Further, in the present invention, as the above-mentioned gelled fine particles (A), a cationic electrodeposition gelation is obtained by water-dispersing an epoxy resin amine adduct containing a hydrolyzable alkoxysilane group and crosslinking the particles. Fine particles
It can be preferably used from the viewpoint of corrosion resistance. The gelled fine particles will be described below.

The "hydrolyzable alkoxysilane group-containing epoxy resin amine adduct" is obtained by introducing a hydrolyzable alkoxysilane group into an epoxy resin amine adduct, and is neutralized with a cationic group, particularly an acid. Stable dispersion of the amino group as a water-dispersing group in water, and the silanol group produced by hydrolysis of the alkoxysilane group is condensed with silanol groups and, if there is a hydroxyl group, the hydroxyl group to condense the particles. This refers to an addition product that is internally crosslinked and can be gelled.

The epoxy resin amine adduct which is a constituent of the gelled fine particles is a polyamine resin usually used in cationic electrodeposition coatings, for example, (i) polyepoxide compound and primary mono- and polyamine, secondary mono. −
And a polyamine or an adduct with a mixed primary and secondary polyamine (see, for example, US Pat. No. 3,984,299); (ii) a polyepoxide compound and a secondary mono-containing a ketiminated primary amino group, and Addition products with polyamines (see, for example, US Pat. No. 4,017,438); (iii) Reaction products obtained by etherification of polyepoxide compounds and hydroxy compounds having ketiminated primary amino groups (eg, Japanese Patent Laid-Open No. 59-43013
(See Japanese Patent Laid-Open Publication) and the like.

The polyepoxide compound used in the production of the above polyamine resin is a compound having two or more epoxy groups in one molecule, and is generally at least 200, preferably 400 to 4,000, and more preferably 800 to.
Those having a number average molecular weight within the range of 2,000 are suitable, and those obtained by reacting a polyphenol compound with epichlorohydrin are particularly preferable. Examples of the polyphenol compound that can be used for forming the polyepoxide compound include bis (4-hydroxyphenyl) -2,2-propane, 4,4′-dihydroxybenzophenone and 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,
Examples thereof include bis (2,4-dihydroxyphenyl) methane, tetra (4-hydroxyphenyl) -1,1,2,2-ethane, 4,4'-dihydroxydiphenyl sulfone, phenol novolac and cresol novolac.

The polyepoxide compound may be a compound partially reacted with a polyol, a polyether polyol, a polyester polyol, a polyacid amine, a polycarboxylic acid, a polyisocyanate compound or the like, and further, ε-caprolactone or an acrylic monomer. And the like may be graft-polymerized.

The method of introducing the hydrolyzable alkoxysilane group into the epoxy resin amine adduct is not particularly limited, and it depends on the kind of the hydrolyzable alkoxysilane group to be introduced from a method known per se. However, it is preferable to employ a method that does not generate a by-product such as water-soluble salts that adversely affects electrodeposition coating. For example, the following method can be exemplified.

(1) Method for adding an alkoxysilane group-containing amine compound to an epoxy group in a base resin: Examples of amine compounds that can be used here include those represented by the following formula.

[0020]

[Chemical 1]

(2) Method of adding an alkoxysilane group-containing mercaptan to an epoxy group in a base resin: Examples of mercaptans that can be used here include the following.

[0022]

[Chemical 2]

(3) Method for adding an alkoxy compound containing an alkoxysilane group to an amino group in a base resin: Examples of the epoxy compound that can be used here include those represented by the following formula.

[0024]

[Chemical 3]

(4) Method of adding an alkoxysilane group-containing isocyanate compound to the hydroxyl group and amino group in the base resin: Examples of the isocyanate compound that can be used here include those of the following formula.

[0026]

[Chemical 4]

In each of the above formulas, R may be exemplified as follows: (i) --CH ₃ , --CH ₂ H ₅ , --C ₃ H ₇ , --C ₄ H.
_9, an alcohol residue such as _{-C 6 H 13, -C 8 H} 17: (ii) -C 2 H 4 OCH 3, -C 2 H 4 OC 2 H 5, -
_{C 2 H 4 OC 3 H 7} , -C 2 H 4 OC 4 H 9, -C 3 H
₆ OCH ₃ , -C ₃ H ₆ OC ₂ H ₅ , -C ₄ H ₈ OCH
_{3, -C 2 H 4 OC 2} H 4 OCH 3, -C 2 H 4 OC 2
H ₄ OC ₂ H _5, ether alcohol residue such as _{-C 2 H 4 OC 2 H 4} OC 4 H 9:

(Iii)

[Chemical 5]

(Iv) Cycloalkyl or aralkyl alcohol residue such as phenyl group and benzyl group:

(V)

[Chemical 6]

Oxime alcohol residue such as: (vi) Other

[0032]

[Chemical 7]

Etc.

R in the above formula has a smaller number of carbon atoms and is more easily hydrolyzed, but it is inferior in stability, and therefore, a carbon number of about 2 to 7 is advantageous in terms of balance. Further, ones having 2 or less carbon atoms and those having 7 or more carbon atoms may be combined and balanced.

Water dispersion of the above epoxy resin amine adduct containing a hydrolyzable alkoxysilane group can be carried out by a method known per se. For example, an epoxy resin amine adduct containing the above hydrolyzable alkoxysilane groups can be added to the amine group present at about 0.
By neutralizing with 1 to 1 equivalent of an acid, for example, a water-soluble carboxylic acid such as formic acid, acetic acid, lactic acid, hydroxyacetic acid, etc., and then dispersing in water so that the solid content concentration is about 40% by weight or less. Can be done.

The dispersed particles of the epoxy resin amine adduct containing hydrolyzable alkoxysilane groups thus obtained can then be intraparticle crosslinked. Intraparticle crosslinking may proceed to some extent by simply storing the dispersion for an extended period of time, but it is advantageous to heat the aqueous dispersion to a temperature of about 50 ° C. or higher to effect intraparticle crosslinking. It is desirable to promote. Alternatively, when water-dispersing the epoxy resin amine adduct containing the hydrolyzable alkoxysilane group, tin octylate, zinc octylate, zirconium octylate, dibutyltin dilaurate, etc. in the resin solution or in the aqueous medium are used. By adding a silanol group condensation catalyst and performing water dispersion in the presence of the catalyst, intraparticle crosslinking can be performed simultaneously with water dispersion.

The gelled fine particle aqueous dispersion thus produced is usually about 10 to 40% by weight, preferably 15 to 40% by weight.
It may have a resin solids content of 30% by weight. The particle size of the dispersed particles is generally 0.5 μm or less, preferably 0.01 to 0.3 μm, more preferably 0.05 to
It can be in the range of 0.2 μm. The particle size can be adjusted by adjusting the amount of the cationic groups in the epoxy resin amine adduct containing the hydrolyzable alkoxysilane group, thereby easily obtaining the particle size within the desired range. You can

The cationic electrodeposition coating (I) can be composed of the same component composition as in a normal cationic electrodeposition coating except that the gelled fine particles (A) are additionally contained.

Thus, the above cationic electrodeposition coating (I)
Is a resin component other than the gelled fine particles (A),
It may contain a resin usually used in a cationic electrodeposition coating (hereinafter sometimes referred to as a cationic electrodeposition coating resin), such as an amine-added epoxy resin. As the amine-added epoxy resin, those mentioned in the description of the epoxy resin amine-added product which is a constituent component of the gelled fine particles (A) can be appropriately used.

The above-mentioned amine-added epoxy resin can be cured by using a polyisocyanate compound blocked with alcohols, if necessary. Further, an amine-added epoxy resin that can be cured without using a blocked isocyanate compound can also be used. For example, a resin obtained by introducing β-hydroxyalkyl carbamate into a polyepoxide substance (for example, JP-A-59-155470). (See Japanese Laid-Open Patent Publication); a resin of a type that can be cured by a transesterification reaction (for example, JP-A-55-8
No. 0436) and the like can also be used.

The above-mentioned cationic aqueous solution or aqueous dispersion of the cationic electrodeposition coating resin is usually prepared by neutralizing the resin with a water-soluble organic acid such as formic acid, acetic acid or lactic acid.
It can be carried out by dispersing in water.

The thus obtained cationic electrodeposition coating resin solution or water dispersion and the aqueous dispersion of the gelled particles (A) are mixed with the gelled fine particles (A) in the total resin solid content (cationic electrodeposition coating resin and 5 for the total of gelled fine particles (A))
The cationic electrodeposition coating composition (I) can be obtained by mixing in an amount of -50% by weight, preferably 10-35% by weight. When the content of the gelled fine particles (A) in the cationic electrodeposition coating composition (I) is less than 5% by weight based on the total solid content of the resin, the edge coverage of the electrodeposition coating film becomes insufficient, while 50 When the content exceeds 5% by weight, there is a problem that the leveling effect of the coating film of the second layer of the cationic electrodeposition coating composition (II) due to heat flow becomes insufficient and the smoothness of the electrodeposition coating film becomes poor.

The cationic electrodeposition coating composition (i) further includes, if necessary, conventional coating additives, for example, color pigments such as carbon black, titanium white, lead white, lead oxide and red iron oxide; clay, talc and mica. , Extenders such as silica; strontium chromate, lead chromate, basic lead chromate, red lead, lead silicate, basic lead silicate, lead phosphate,
Basic lead phosphate, lead tripolyphosphate, lead silicochromate, yellow lead, cyanamide lead, calcium calcium zincate, lead sulfate,
Can contain anticorrosion pigments such as basic lead sulfate,
Further, other additives such as a dispersion stabilizer and a curing accelerator may be included.

The cationic electrodeposition coating composition (I) can be applied to a desired substrate surface by cationic electrodeposition coating.
Cationic electrodeposition coating is generally diluted with deionized water or the like so that the solid content concentration is about 5 to 40% by weight, and the pH is adjusted within the range of 5.5 to 8.0. It can be carried out using an electrodeposition bath consisting of I).

In the present invention, it is not always necessary to wash with water after the first electrodeposition coating is performed, but it is usually preferable to wash the electrodeposition coating film with a shower (washing with a shower or washing with immersion). By this washing with water, the corrosion resistance of the edge portion is further improved, and an electrodeposition coating film having substantially no pinhole defects is formed.

Step (ii) : The cation electrodeposition coating (II) is used as the second cation electrodeposition on the uncured coating surface of the cation electrodeposition coating film by the cation electrodeposition coating (I) of the above step (i). A step of coating and then heating to cure both coating films formed by the steps (i) and (ii), further improving the anticorrosion property of the electrodeposition coating film of the step (i),
Moreover, the main purpose is to improve weather resistance and the like.

The cationic electrodeposition paint (II) has a surface tension of 4
Epoxy-based cationic electrodeposition resin (B) having a surface tension of 25 to 45 dyne / c, which is 0 to 60 dyne / cm and is capable of forming an aqueous bath capable of electrodeposition on the cathode by neutralizing with an acid.
The nonionic film-forming resin (C), which is m, is contained at a weight ratio within the range of resin (B): resin (C) = 60: 40 to 98: 2, and the surface tension of the resin (B) is Resin (C)
Larger than the surface tension of, and the minimum electrodeposition current density is 0.7
It is a cationic electrodeposition paint having a mA / cm ² or less and an emulsification degree of 80% by weight or more.

The resin (B) in the cationic electrodeposition coating (II) has a surface tension of 40 to 60 dyne / cm, preferably 4
It is necessary to be within the range of 5 to 55 dyne / cm,
Specifically, for example, among the resins described in the cationic electrodeposition coating (I), those having a surface tension in the above range can be preferably used. The surface tension of the resin (B) is 40 dyne / c
If it is lower than m, the nonionic film-forming resin (C) described later
The compatibility with and becomes too good, making it difficult to form a multilayer film having a desired concentration gradient, and the electrodeposition coating film has poor weather resistance and corrosion resistance. On the other hand, the surface tension is 6
If it exceeds 0 dyne / cm, the concentration gradient will be extremely advanced, and the resin (B) and the resin (C) will be completely separated into two layers, and the interlayer adhesion between the resin (B) and the resin (C) will be increased. Results in poor results.

In the present specification, an epoxy cationic resin (B) and a nonionic film forming resin (C) described later are used.
"Surface tension" is measured as follows: Resin (B) or resin (C) was diluted with a solvent and dried on a degreased smooth tin plate with a bar coater to a dry coating film thickness of 10 μm. Paint so that. The coating film was air-dried at room temperature for 1 day, further dried at 50 ° C./0.1 atm for 1 hour, and after 10 minutes at room temperature, deionized water was added dropwise to give a contact angle (θ) with the dried resin. taking measurement. Then with Sell
Neumann's empirical formula

[Equation 1] In the formula, γ _L : surface tension of water (72.8 dyne / cm), γ _S :
The surface tension (dyne / cm) of the resin (B) or the resin (C) determines the surface tension of the resin (B) or the resin (C).

Next, the nonionic film-forming resin (C) used in the cationic electrodeposition coating (II) is a thermosetting resin or a thermosetting resin as long as it has excellent weather resistance for the purpose of the present invention. Any of the plastic resins, acrylic resin,
Polyester resin, polyester modified resin and silicon modified resin are preferably used. It is important and essential that the resin (C) is nonionic, that is, it does not have a functional group that produces a cationic group upon neutralization of an acid or the like. That is, when the resin (C) is ionic, the surface tension thereof becomes large. Therefore, in order to obtain a multilayer coating film having an ideal concentration gradient, the skeleton part (nonionic part) of the resin (C) Must be designed to have a low surface tension, and the resulting multilayer coating film tends to have poor interlayer adhesion and corrosion resistance.

The preferred resin (C) will be described in more detail below. First, as the nonionic acrylic resin, for example, methyl (meth) acrylate,
Alkyl esters of (meth) acrylic acid such as ethyl (meth) acrylate, butyl (meth) acrylate, propyl (meth) acrylate, 2-ethylhexyl (meth) acrylate; hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, etc. Hydroxyalkyl ester of (meth) acrylic acid; glycidyl (meth) acrylate; acrylic monomers such as (meth) acrylic acid, and styrene and its derivatives (for example, α-methylstyrene), (meth) acrylonitrile, butadiene, etc. Examples thereof include those obtained by appropriately selecting one kind or two or more kinds of other unsaturated monomers according to the physical properties, and (co) polymerizing according to a conventional method.

The acrylic resin has a number average molecular weight of about 3,
000 to about 100,000, preferably about 4,000 to
Those in the range of about 50,000 are suitable. Further, when the acrylic resin contains a hydroxyl group as a functional group, it can be crosslinked and cured by reacting with a polyisocyanate compound which is a crosslinking agent of the resin (B).

Examples of the nonionic polyester resin used as the resin (C) include phthalic acid and its acid anhydride, isophthalic acid, terephthalic acid, trimellitic acid and its acid anhydride, pyromellitic acid and its acid anhydride. , Hexahydrophthalic acid and its acid anhydride, succinic acid, adipic acid, pimelic acid, sebacic acid, brassic acid, and other polybasic acid components, and ethylene glycol, diethylene glycol, propylene glycol, neopentyl glycol, 1,6- Those which can be produced by condensation polymerization with a polyol component such as hexanediol, trimethylolpropane, glycerin, pentaerythritol and tricyclodecanedimethanol according to a conventional method are included. At that time, for example, benzoic acid or p-t-butylbenzoic acid may be used as the end-capping agent to control the molecular weight.

As the resin (C), a blend of the above-mentioned acrylic resin and polyester resin can be used, and further, polyester modified (graft) acrylic resin and acrylic modified (graft) polyester resin are combined with the above-mentioned raw materials. By synthesizing them, they can also be used as the resin (C) (these are collectively referred to as “polyester-modified resin” in the present specification).

Furthermore, the nonionic silicone-modified resin used as the resin (C) includes a base resin such as the above-mentioned acrylic resin or polyester resin, or an alkyd resin modified with a silicone resin. The amount of the silicone resin used is 50% by weight or less, preferably 3 to 45% by weight, based on the whole resin. When the content of the silicone resin exceeds 50% by weight, the interlayer adhesion with the top coat film deteriorates. In addition, resin (B) and resin (C)
Tend to be completely separated into two layers, and the adhesion between layers tends to deteriorate.

The silicone resin used to modify the base resin usually has a number average molecular weight preferably in the range of about 500 to about 2,000. An organopolysiloxane resin having two or more reactive groups such as a hydroxyl group and an alkoxy group in the molecule, for example, Z-6018 (Dow Cornin
g company product, molecular weight 1,600), Z-6188 (DowCor
ning products, molecular weight 650), Sylkyd50,
DC-3037 (Dow Corning product) KR-216,
KR-218, KSP-1 [Shin-Etsu Silicone Products],
TSR-160, TSR-165 [product of Tokyo Shibaura Electric Co., Ltd.], SH5050, SH6018, SH6188 [product of Toray Silicone Co., Ltd.] and the like can be used.

The silicon-modified resin is obtained by co-condensing the above-mentioned silicon resin and a base resin having a hydroxyl group and / or a carboxyl group, for example, an acrylic resin, a polyester resin, etc., in the above-mentioned use ratio by a method known per se. It can be manufactured.

The nonionic film-forming resin (C) has a surface tension of 25 to 45 dyne / cm, preferably 28 to 40 dyne / c.
Must be within m. Surface tension is 25 dy
If it is less than ne / cm 2, the adhesion between the formed coating film and the top coating film is deteriorated, and the resin (B) and the resin (C) are completely separated into two layers, and the adhesion between layers is deteriorated. On the other hand, when the surface tension exceeds 45 dyne / cm 2, the compatibility with the resin (B) becomes so good that it becomes difficult to form a multilayer film having a desired concentration gradient, and the weather resistance and corrosion resistance of the coating film are both high. Results inferior.

In the cationic electrodeposition coating composition (II), the surface tensions of the resin (B) and the resin (C) are within the respective specific ranges, and the surface tension of the resin (B) is the surface tension of the resin (C). If it is larger, a multilayer film having a concentration gradient can be formed, but the difference in surface tension between the resin (B) and the resin (C) is preferably 5 dyne / cm or more, more preferably 10 to 20 dyne / cm. It is easy and rapid to form a multilayer film and practical to select and combine both components so as to be within the range.

In the preparation of the cationic electrodeposition coating (II), the resin (B) and the resin (C) can be used alone or in combination of two or more kinds. The ratio of the resin (B) to the resin (C) used is (B) :( C) = 60: 40-
It should be within the range of 98: 2, preferably 70:30 to 95: 5. A blending ratio outside the above range is not preferable because a multilayer film having an effective concentration gradient cannot be obtained and the weather resistance or anticorrosion property becomes poor.

Further, in the cationic electrodeposition coating composition (II), in addition to the above-mentioned resins (B) and (C), if necessary, a coloring pigment, an anticorrosive pigment, and a constitution generally used in the field of coating composition may be used. Pigments, additives and the like can be added.

[0062] Cationic electrodeposition paint (II) is made mainly of a resin (B) and the resin (C), the minimum electric析電current density 0.7 mA / cm ² or less, preferably 0.5 mA / cm ² The following is more preferably 0.3 mA / cm ² or less and the degree of emulsification is 80% by weight or more, preferably 85% by weight, more preferably 90% by weight or more.

The above-mentioned "minimum electrodeposition current density" is a value measured by the following method; platinum plates having a surface area of 1 cm ^{2 and having} a back surface insulated are used as a counter electrode and an object to be coated so that their surfaces face each other. Place in the electrodeposition paint bath at a distance of 15 cm. A constant current was applied at 28 ° C without stirring and the time and voltage were recorded. The current density was changed every 0.05 mA / cm ² , and the voltage surge due to resistance increase due to electro-deposition of the paint was 3 Min or the current density when it occurs in the vicinity of more than 3 min is the minimum electrodeposition current density.

The "degree of emulsification" is an index showing the proportion (% by weight) of the particles truly suspended as particles in the electrodeposition coating, and is determined by the following procedure;
First, about 35 to about 20 to 20% by weight of clear emulsion.
The cc is placed in a cell, sealed, and centrifuged at 28,000 RPM for 60 minutes. The supernatant 2 cc of the separated sample is pipetted and dried at 120 ° C. for 1 hour to measure the nonvolatile content N ₁ (%). Then, the cell is turned upside down to allow the supernatant to flow away, and then inverted for another 10 minutes to remove the supernatant layer. After homogenizing the remaining sedimentation layer with a glass rod, weigh precisely 1.5 to 2.0 g,
Non-volatile content N ₂ (%) is measured by drying at 120 ° C. for 1 hour. Next, we precisely weigh about 2 cc of clear emulsion and 120 ° C.
After drying for 1 hour, the nonvolatile content N ₀ (%) is measured. The emulsification degree is a value obtained by the following formula.

[0065]

[Equation 2]

In the present invention, if the minimum electrodeposition current density of the cationic electrodeposition coating composition (II) exceeds 0.7 mA / cm ² , it will be difficult to secure a film thickness that imparts smoothness to the coated surface. When the degree of emulsification is less than 80% by weight, the second electrodeposition coating film is mixed with the first electrodeposition coating film, resulting in both edge corrosion resistance and surface smoothness. Tends to decline.

Electrodeposition coating method : In the present invention, the method and apparatus for performing the electrodeposition coating on the object to be coated with the cationic electrodeposition coatings (I) and (II) are those conventionally used in cathodic electrodeposition coating. It is possible to use methods and devices known per se. At this time, it is desirable to use the object to be coated as a cathode and the carbon plate as an anode. The electrodeposition coating conditions that can be used are not particularly limited, but generally, bath temperature: 20 to 30 ° C., voltage: 100 to 400 V
(Preferably 200 to 300 V), current density: 0.01 to
3 A / dm ² , energization time: 30 seconds to 10 minutes, pole area ratio (A /
C): 6/1 to 1/6, distance between electrodes: 10 to 100 cm, and it is desirable to electrodeposit in a stirring state.

The film thickness (dry state) of the electrodeposition coating film of step (i) formed by using the above-mentioned electrodeposition coating method is 5 to 30 μm.
Preferably, it is in the range of 10 to 25 μm, and the film thickness (dry state) of the electrodeposition coating film of step (ii) formed thereon is in the range of 5 to 70 μm, preferably 10 to 50 μm. Is convenient.

In the present invention, the electrodeposition coating of step (ii) may be carried out in the uncured state of the electrodeposition coating film of step (i) in order to form a composite coating film, and also to improve the adhesive property. Is preferable and is a necessary condition, the electrodeposition coating film of step (i) may be heated, for example, at 120 ° C. for about 10 minutes, or may be heated to remove water with hot air. It should be understood that the term "uncured state" in the present invention also includes a semi-cured state.

Steps (i), (ii) formed on the article to be coated
The cationic electrodeposition coating according to is about 150 to about 180 after washing.
It is baked and hardened at ℃. The total electrodeposition coating film thickness can be the total film thickness of the first electrodeposition coating film thickness and the second electrodeposition coating film thickness described above. The coating thickness is generally desired to be within the range of 15 to 80 μm.

Step (iii) : A step of applying a water-based base coating on the coating surface of the heat-cured cationic electrodeposition coating (II). In the present invention, the water-based base coating material belongs to a top coating material, and contains a base resin, a curing agent, a metallic pigment and / or a coloring pigment, and water as main components, and an organic solvent or the like is added as necessary. It is a thermosetting paint.

The base resin is a main component for forming a coating film by the aqueous base coating material, and a coating resin which has good weather resistance and is soluble or dispersible in water is suitable. For example, it is usually used as a vehicle for an aqueous coating material. Type of acrylic resin, polyester resin, epoxy resin, urethane resin,
And the like are water-soluble or water-dispersed. These water-soluble or water-dispersible resins are
In principle, a sufficient amount of hydrophilic groups, such as carboxyl groups (-COOH), to be water-soluble or water-dispersible,
A hydroxyl group (-OH), a methylol group (-CH ₂ OH), amino group (-NH _2), sulfone group (-SO ₃ H), polyoxyethylene bond _{- (CH 2 CH 2 O)} n - introducing the like,
Of those containing, the most common one is to contain a carboxyl group, which can be made water-soluble by neutralizing it to form an alkali salt. The amount of carboxyl group that can be made water-soluble depends on the skeleton of the resin, the content of other hydrophilic groups, the type of neutralizing agent, and the neutralization equivalent, but an acid value of at least 30 is required. Generally, such a water-soluble resin can be made completely water-soluble by neutralizing with an alkaline substance such as sodium hydroxide and various amines.

Examples of the acrylic resin include α and β
-(Meth) acrylic acid ester having a functional group such as ethylenically unsaturated carboxylic acid, hydroxyl group, amide group and methylol group, and acid value obtained by copolymerizing other (meth) acrylic acid ester, styrene, etc. 30-1
And those having a hydroxyl value of about 20 to 200.

The polyester resin is obtained by subjecting a polybasic acid, a polyhydric alcohol and a modified oil to a condensation reaction by a conventional method. As the epoxy resin, for example, a method of synthesizing an epoxy ester by reacting an epoxy group with an unsaturated fatty acid and adding α, β-unsaturated acid to the unsaturated group, a hydroxyl group of the epoxy ester, and a phthalic acid And an epoxy ester resin obtained by a method of esterifying with a polybasic acid such as trimellitic acid.

Examples of the urethane resin include those obtained by reacting the above acrylic resin, polyester resin or epoxy resin with a diisocyanate compound to have a high molecular weight, which is mainly used as a water-dispersible resin.

The water dispersion of the above resin can be achieved by polymerizing the above monomer component by emulsion polymerization in the presence of a surfactant or a water-soluble resin. Further, it can be obtained by dispersing the above resin in water in the presence of an emulsifier or the like. In this water dispersion,
The base resin may not contain the hydrophilic group at all, or may contain less than the water-soluble resin.

Among these, as an aqueous dispersion of an acrylic resin, for example, nonionic surfactants such as polyoxyethylene nonyl phenyl ether and anionic surfactants such as polyoxyethylene alkyl allyl ether sulfate ester salt which have been conventionally known are used. Agent, an acid value of about 20 to 150, and a dispersion stabilizer such as a water-soluble resin such as an acrylic resin having a number average molecular weight of about 5,000 to 30,000, in the presence of an acrylic monomer and, if necessary, other additives. Average particle size prepared by polymerizing copolymerizable monomer: 0.05-1.0 μm
Aqueous dispersions in the range of degrees are preferred.

Examples of the monomer to be subjected to polymerization include α, β-ethylenically unsaturated compounds such as (meth) acrylic acid, maleic acid, fumaric acid, itaconic acid, maleic acid or a half-esterified product of fumaric acid. Carboxylic acid; methyl (meth)
Acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate,
(Meth) such as 2-ethylhexyl (meth) acrylate
Acrylic acid ester; hydroxy group-containing (meth) acrylic acid ester such as hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate; N-propoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, glycidyl (meth ) Polymerizable unsaturated monomers such as acrylate, styrene and vinyl acetate.

If necessary, the polymerizable unsaturated monomer may be a polyfunctional monomer such as ethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate or trifunctional monomer. A small amount of methylolpropane di (meth) acrylate, allyl (meth) acrylate, trimethylolpropane triacrylate, etc. can also be used together.

The dispersion is preferably obtained by a multistage polymerization method. That is, first, a monomer containing no or small amount of α, β-ethylenically unsaturated acid is polymerized,
Next, the multi-stage polymerized emulsion obtained by copolymerizing a monomer containing a large amount of α, β-ethylenically unsaturated acid thickens by neutralizing with a neutralizing agent. It is preferable from the aspect. The neutralizing agent used is ammonia or a water-soluble amino compound such as
Monoethanolamine, ethylamine, dimethylamine, diethylamine, triethylamine, propylamine, dipropylamine, isopropylamine, diisopropylamine, triethanolamine, butylamine,
Dibutylamine, 2-ethylhexylamine, ethylenediamine, propylenediamine, methylethanolamine, dimethylethanolamine, diethylethanolamine, morpholine and the like are used, but tertiary amine triethylamine, dimethylethanolamine and the like are particularly preferable. Further, the one obtained by increasing the viscosity by adding a high acid value acrylic resin or a thickener is also useful for the purpose of the present invention.

In terms of mechanical stability, storage stability and other properties of the acrylic resin in the aqueous dispersion, it is advantageous to crosslink the dispersed particles. Further, if necessary, a polyester-based or polyurethane-based water-dispersible resin produced by a conventionally known method can be used in combination with this aqueous dispersion.

The curing agent is for three-dimensionally crosslinking and curing the above-mentioned base resin by heating, and specifically,
An amino resin obtained by condensation or cocondensation of melamine, benzoguanamine, urea or the like with formaldehyde, or etherification with a lower monohydric alcohol is preferably used.

On the other hand, examples of the metallic pigment that can be blended in the aqueous base coating material include aluminum flakes and copper bronze flakes, and examples of the coloring pigments include titanium dioxide, iron oxide, chromium oxide and chromium. Inorganic pigments such as lead acid and carbon black;
Phthalocyanine blue, phthalocyanine green, carbazole violet, anthrapyrimidine yellow,
Organic pigments such as flavanthuron yellow, isoindoline yellow, indusulon blue, quinacridone violet and the like can be mentioned. An extender pigment such as talc or kaolin can be further added to the aqueous base paint.

The ratio of each of the above components in the above water-based base coating material can be arbitrarily selected according to the purpose. For example, the base resin and the curing agent are based on the total weight of the two components.
The former is preferably in the range of 60 to 90% by weight, particularly 70 to 85% by weight, the latter is preferably in the range of 40 to 10% by weight, particularly 30 to 15% by weight, and the pigment is appropriately selected depending on the desired metallic feel, color and the like. It is sufficient to mix the above components in an amount of about 1 to 250 parts by weight with respect to 100 parts by weight of the resin solid content, which is the sum of both components.

The above-mentioned water-based base coating composition is prepared by adding the above-mentioned base resin, curing agent and pigment to the solid content in a conventional manner by adding deionized water and, if necessary, additives such as an organic solvent, a thickener and a defoaming agent. 10-40% by weight, viscosity 800-5,0
It is obtained by adjusting to about 00 cps / 6 rpm (B-type viscometer).

The above-mentioned water-based base paint of step (iii) can be used very suitably as a base coat in the case of coating with a two-coat one-bake system. Then, the step (i),
On the surface of the cationic electrodeposition heat-cured coating film according to (ii), the step (ii
The aqueous base coating material i) can be applied by spray coating or the like so as to have a film thickness of, for example, about 10 to 50 μm (dry film thickness).

Step (iv) : A step of applying a powder clear paint to the surface of the uncured coating film obtained by applying the aqueous base paint in the above step (iii).

The powder clear coating composition may be a thermosetting powder coating composition known per se, and as a general rule, a transparent coating film capable of seeing through the metallic coating film or the colored coating film of the above aqueous base coating composition. A powder coating material capable of forming a resin, which basically does not include a coloring pigment or a metallic pigment, and contains a base resin and a curing agent as main components.

The base resin is a main component for forming a coating film of the powder coating material, for example, an acrylic resin having one or more crosslinkable functional groups selected from a hydroxyl group, a carboxyl group, a glycidyl group and the like. Examples thereof include resins, polyester resins, fluororesins, urethane resins, and modified products thereof (for example, graft polymers), but these are merely examples and the present invention is not limited thereto. The glass transition temperature of the base resin is generally 50 ° C. or higher, preferably 60 to 120 ° C., and
The composition and molecular weight can be arbitrarily selected according to the purpose,
There is no particular limitation.

The curing agent is a component for three-dimensionally crosslinking and curing the above-mentioned base resin by heating, and examples thereof include alkoxymethylolmelamine, blocked polyisocyanate compound, epoxy compound, isocyanurate compound and aliphatic dibasic acid. Etc. can be used.

Most preferably, the molar ratio of the functional group in the base resin to the functional group in the curing agent is substantially equimolar.

If desired, coating additives such as a flow control agent, an ultraviolet absorber and a light stabilizer may be added to the above powder clear coating material.

The powder clear coating material is usually obtained by melt-kneading the above-mentioned components, cooling and pulverizing, and these steps and particle sizes may be conventional.

Further, the powder clear coating composition of the step (iv) is obtained by coating the water-based base coating composition of the step (iii) without heating and curing most or all of the water contained in the coating film. At room temperature or 100 ° C to remove
After air-drying in the following, it is applied to the uncured coating surface of the aqueous base coating material of the step (iii). The coating method is not particularly limited, and any powder coating method such as electrostatic spray coating or fluidized dipping method can be used.

The coating film thickness of the powder clear coating composition of step (iv) is not particularly limited, but generally, for example, 4
The range of 0 to 200 μm is suitable, and among them, in order to improve the smoothness, sharpness, gloss, and feeling of flesh of the finished coating film, it is preferable to apply the coating to a thickness of 60 to 120 μm. .

Then, after applying both the coating materials of the above steps (iii) and (iv), the curing temperature of the both coating films, for example, 120 to 1
Both coatings are cured simultaneously by heating to 70 ° C.

[0097]

The above-described method of the present invention is a coating method in which the coating process is simplified, the edge corrosion resistance and the finish appearance of the coating are extremely excellent, and resource saving and pollution control are advantageous. It can be widely used for painting automobiles, motorcycles, electric appliances and the like.

[0098]

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the examples and comparative examples, "parts" and "%" indicate "parts by weight" and "% by weight", respectively.

Containing Hydrolyzable Alkoxysilane Group
Production Example of Epoxy Resin Amine Adduct Production Example 1 An epoxy resin amine adduct containing a hydrolyzable alkoxysilane group was produced with the following formulation.

Raw material parts by weight Epon 828EL ¹⁾ 1,045 Bisphenol A 171 Diethanolamine 52.2 KBE-903 ²⁾ 221 Diethanolamine 157.5 Ethylene glycol monobutyl ether 706 Note 1) Diglycidyl ether of bisphenol A having an epoxy equivalent of about 190 (Yukaka Shell Co., Ltd.) Note 2) γ-aminopropyltriethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) Nitrogen gas was added to a reaction vessel equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen gas blowing port. Epon 8 under blowing
28 EL, bisphenol A and diethanolamine were charged and heated to 120 ° C. and reacted until the epoxy equivalent ³⁾ reached the theoretical value (317). Then cool to 80 ° C., add KBE-903 and diethanolamine,
The reaction was continued until the tertiary amine value ⁴⁾ reached the theoretical value (102). Then, it was diluted with ethylene glycol monobutyl ether to obtain an ethylene glycol monobutyl ether solution having a solid content of 70% of an epoxy resin amine adduct containing a hydrolyzable alkoxysilane group having a number average molecular weight of about 1,650.

Note 3) According to JIS-K-7236. However, the amino group is also added as an epoxy group.

Note 4) After acetylation with acetic anhydride, titration with perchloric acid using crystal violet as an indicator.

Production Example 2 An epoxy resin amine adduct containing a hydrolyzable alkoxysilane group was produced with the following formulation.

Raw material parts by weight Epon 828EL 950 Bisphenol A 342 Diethanolamine 52.5 X-12-636 ⁵⁾ 289.5 Ethylene glycol monobutyl ether 700 Note 5) N-methyl-γ-aminopropyltrimethoxysilane (Shin-Etsu Chemical Co., Ltd. )) Epon 828EL, bisphenol A and diethanolamine were charged into a reactor similar to that of Production Example 1 while blowing nitrogen gas, heated to 120 ° C., and reacted until the epoxy equivalent reached a theoretical value (672). Then, it cooled to 80 degreeC, X-12-636 was added, and it was made to react until the tertiary amine value reached a theoretical value (69). Then, it was diluted with ethylene glycol monobutyl ether to obtain a solution having a solid content of 70% of an epoxy resin amine adduct containing a hydrolyzable alkoxysilane group having a number average molecular weight of about 1,600.

Production Example 3 An epoxy resin amine adduct containing a hydrolyzable alkoxysilane group was produced with the following formulation.

Raw material parts by weight Epon 828EL 950 Bisphenol A 342 Amine A ⁶⁾ 96.5 Amine A (post-added) 193 Amine B ⁷⁾ 159 Deionized water 36 KBE-402 ⁸⁾ 496 Ethylene glycol monobutyl ether 486 Note 6) Effective A methyl isobutyl ketone solution of ketimine with 74% monoethanolamine and methyl isobutyl ketone.

Note 7) Methyl isobutyl ketone solution of diethylenetriamine of 84% active ingredient in methyl isobutyl ketone of diketimine.

Note 8) γ-glycidoxypropylmethyldiethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) Epon 828EL, bisphenol A and amine A were charged into a reactor similar to that of Production Example 1 under nitrogen gas blowing to prepare 160 Heated to ℃, Epoxy equivalent is theoretical value (694)
It was made to react until it reached. Then, the mixture was cooled to 100 ° C., amine A (post-added) and amine B were added, and the reaction was continued until the tertiary amine value reached the theoretical value (97). After that, deionized water was added at 100 ° C. to carry out a deketimination reaction, and subsequently, KBE-402 was added at 100 ° C. to react until the epoxy group was eliminated. Then, it was diluted with ethylene glycol monobutyl ether to obtain a 70% solid content solution of an epoxy resin amine adduct containing a hydrolyzable alkoxysilane group having a number average molecular weight of about 1,900.

Production Example of Gelled Fine Particles (A) Production Example 4 100 parts of the epoxy resin amine adduct containing the hydrolyzable alkoxysilane group obtained in Production Example 1 and 11 parts of 10% acetic acid were added to a 21-flask. After stirring at 30 ° C for 5 minutes, 239 parts of deionized water was added dropwise over about 30 minutes while stirring strongly, and the temperature was raised to 50 ° C and stirring was performed for about 3 hours.

Thus, a milky white intraparticle crosslinked gelled fine particle dispersion having a solid content of 20% was obtained, and the average particle diameter of the fine particles in ethylene glycol monobutyl ether was 0.15 μm.

Production Example 5 To a 21-flask, 100 parts of the epoxy resin amine adduct containing the hydrolyzable alkoxysilane group obtained in Production Example 2 and 7.5 parts of 10% acetic acid were added and stirred at 30 ° C. for 5 minutes. Thereafter, 242.5 parts of deionized water was added dropwise over about 30 minutes while stirring vigorously, the temperature was raised to 50 ° C., and stirring was performed for about 3 hours.

Thus, the solid content is 20%, the average particle size in ethylene glycol monobutyl ether is 0.15 μm.
A milky white intra-particle cross-linked gelled fine particle dispersion liquid was obtained.

Production Example 6 To a 21-flask was added 100 parts of the epoxy resin amine adduct containing the hydrolyzable alkoxysilane group obtained in Production Example 3 and 11 parts of 10% acetic acid, and the mixture was stirred at 30 ° C. for 5 minutes. 239 parts of deionized water was added dropwise over about 30 minutes with strong stirring, the temperature was raised to 50 ° C., and stirring was carried out for about 3 hours.

Thus, the solid content is 20% and the average particle size in ethylene glycol monobutyl ether is 0.15 μm.
A milky white intra-particle cross-linked gelled fine particle dispersion liquid was obtained.

Production Example 7 1 equipped with a stirrer, thermometer, cooling tube and heating mantle
In a liter flask, deionized water 3,507.5 parts and Latemur K-180 (manufactured by Kao Corporation, 25% aqueous solution)
80 parts was added and the temperature was raised to 90 ° C. with stirring. To this was added 20% of an aqueous solution mixture prepared by dissolving 12.5 parts of a polymerization initiator VA-086 (manufactured by Wako Pure Chemical Industries, Ltd.) in 500 parts of deionized water. After 15 minutes, 5 percent of the following monomer mixture was added. Styrene 430 parts n-butyl acrylate 440 parts 1,6-hexanediol diacrylate 40 parts 2-hydroxyethyl acrylate 40 parts KBM-503 ⁹⁾ 50 parts Note 9) γ-methacryloxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd. )

Then, after stirring for another 30 minutes, dropwise addition of the remaining monomer mixture and polymerization initiator aqueous solution was started. The monomer mixture was supplied for 3 hours, and the polymerization initiator aqueous solution was supplied for 3, 5 hours, respectively, and the polymerization temperature was kept at 90 ° C. Even after the dropping of the aqueous solution of the polymerization initiator, it was heated for 30 minutes, kept at 90 ° C., cooled to room temperature, filtered with a filter cloth, and taken out. Thus, solid content 20%, average particle size 0.07
A micronized gelled particle dispersion was obtained. (JP-A-2-471
(See Publication No. 73)

Preparation Example of Cationic Electrodeposition Coating (I) Preparation Example 1 572 parts of a cationic electrodeposition clear emulsion (Kansai Paint Co., Ltd., Elektron 9450) having a solid content of 35% and comprising a polyamide-modified epoxy resin and a completely blocked diisocyanate. And the solid content of 20 obtained in Production Example 4
% Gelled fine particle dispersion liquid and 139.4 parts of the following pigment paste A having a solid content of 43% are added with stirring and diluted with 588.5 parts of deionized water to obtain the cationic electrodeposition coating (I) -1. Obtained.

[0118]

[Table 1]

Preparation Example 2 Cationic electrodeposition paint (I) -2 was prepared in the same manner as in Preparation Example 1, except that 300 parts of the dispersion obtained in Preparation Example 5 was used as the gelled fine particle dispersion. Got

Preparation Example 3 Preparation Example 6 was prepared in the same manner as Preparation Example 1 as a gelled fine particle dispersion liquid.
A cationic electrodeposition coating composition (I) -3 was obtained in the same manner as in Preparation Example 1 except that 200 parts of the dispersion liquid obtained in (2) was used.

Preparation Example 4 Preparation Example 1 was prepared in the same manner as Preparation Example 7 except that the gelled fine particle dispersion was prepared.
A cationic electrodeposition coating composition (I) -4 was obtained in the same manner as in Preparation Example 1 except that 200 parts of the dispersion liquid obtained in (2) was used.

Comparative Preparation Example 1 A cation electrodeposition coating material G was obtained in the same manner as in Preparation Example 1 except that the gelled fine particle dispersion liquid was not added.

Production of Epoxy Cationic Electrodepositable Resin (B)
Manufacturing Production Example 8 Bisphenol-type epoxy resin (Chirageigy "Araldite # 6071") 930 parts Bisphenol-type epoxy resin (Ciba-Geigy "Araldite GY2600") 380 parts Polycaprolactone diol (Daicel "Plaxel # 205") 550 parts Dimethylbenzylamine acetate 2.6 parts p-Nonylphenol 79 parts Monoethanolamine methylisobutylketone ketiminide 71 parts Diethanolamine 105 parts Butylcellosolve 180 parts Cellosolve 525 parts After the components and components are combined and reacted at 150 ° C for 2 hours,
Ingredients ~ are mixed and reacted at 80 to 90 ° C for 3 hours,
A resin solution (B-1) having a solid content of 75% was obtained. The surface tension of this resin was 53 dyne / cm 2.

Production of Nonionic Film-Forming Resin (C) Production Example 9 Butyl Cellosolve 26 parts 80% Polyester Monomer ("FM-3X" manufactured by Daicel) 37.5 parts Styrene 40 parts Hydroxyethyl methacrylate 25 parts n-Butyl Methacrylate 5 parts AIBN (azobisisobutyronitrile) 4 parts Butylcellosolve 5 parts Azobisdimethylvaleronitrile 0.5 parts Cellosolve 23 parts The components are heated to 130 ° C.
After dropping over a period of time, maintain at 130 ° C for 2 hours and
The ingredients are added dropwise over 2 hours at 130 ° C.
Hold for time, then add ingredients and cool. Thus, a resin solution (C-1) having a solid content of 62% and a number average molecular weight of about 5,000 and a surface tension of 40 dyne / cm was obtained.

Production Example 10 Butylcellosolve 26 parts 80% Polyester monomer ("FM-3X" manufactured by Daicel) 87.5 parts Styrene 25 parts Hydroxyethyl acrylate 5 parts AIBN (azobisisobutyronitrile) 4 parts Butylcellosolve 5 parts Azo Bisdimethylvaleronitrile 0.5 parts Cellosolve 23 parts The components are heated to 130 ° C., and at 130 ° C.
After dripping over a period of time, maintain at 130 ° C for 2 hours, and
Ingredients were added dropwise at 0 ° C over 2 hours, then at 130 ° C
Maintained for 2 hours, then added ingredients and cooled. Thus, a resin solution (C-2) having a solid content of 62% and a number average molecular weight of about 5,000 and a surface tension of 35 dyne / cm was obtained.

Production Example 11 Epicoat # 828EL (manufactured by Yuka Shell Co., Ltd.) 1,425 parts Benzoic acid 458 parts Cyclohexanone 209 parts Silicone resin SH-6018 (manufactured by DOW CORNING) 1,684 parts Tetraisopropyl titanate (10) % Toluene solution) 16 parts Cyclohexanone 856 parts Toluene 344 parts After reacting the components ~ at 170 ° C for 5 hours, the components are cooled to 80 ° C, the components ~ are blended, reflux dehydration is performed at 150 ° C, and the dehydration amount is 17 parts by weight. Was reacted for about 5 to 8 hours. Thus, a resin solution (C-3) having a silicone resin content of 46%, a solid content of 71% and a surface tension of 30 dyne / cm.
Got

Preparation Example of Cationic Electrodeposition Paint (II) Resin Solution (B-1) and Resin Solution (C-1)
(C-3) was mixed with the combination and formulation (solid content ratio) shown in Table 2 below (resin content of 82.6 as solid content).
Part), 5 parts of ethylene glycol mono-2-ethylhexyl ether diblock of 4,4'-diphenylmethane diisocyanate, 12.4 parts of methyl ethyl ketone ketoxime diblock of isophorone diisocyanate,
Polypropylene glycol 4000 0.5 parts were added and mixed uniformly, then 1 part of lead acetate and 9.3 parts of 10% acetic acid were added and stirred, and further 185.75 parts of deionized water were added and uniformly stirred and mixed to obtain a solid. 32% min of each emulsion was made. To 626 parts of this emulsion was added 139.4 parts of a pigment paste A having a solid content of 43%, and 550 parts of deionized water were added.
Diluted with 1 part, and cationic electrodeposition paint (II) -1 to (II) -6
Got

Preparation Example of Aqueous Base Paint Metallic aqueous paint (M-1) : Acrylic resin aqueous dispersion W-1 (Note 10) 275 parts Acrylic resin aqueous solution W-2 (Note 11) 40 parts Cymel 350 (Mitsui Toatsu 25 parts aluminum paste AW-500B (manufactured by Asahi Kasei Metals Co., Ltd.) 20 parts butyl cellosolve 20 parts deionized water 253 parts and mixed with Tikusol K-130B (thickener manufactured by Kyoeisha Oil and Fat Chemical Co., Ltd.). After addition, the viscosity was adjusted to 3,000 cps with a B-type viscometer (rotor rotation speed 6 rpm) to obtain a metallic aqueous base coating material (M-1). Nonvolatile content about 19%.

White water-based paint (S-1) : Acrylic resin aqueous solution W-2 (Note 11) 40 parts Titanium white 100 parts Butyl cellosolve 20 parts Dispersed to 5 μm or less with a peple mill to prepare acrylic resin aqueous solution W-1 (Note 10). ) 275 parts Cymel 350 25 parts deionized water 111 parts were added and the viscosity was adjusted to 2,500 cps in the same manner as in the preceding paragraph to obtain a white aqueous base paint (S-1). Nonvolatile content about 30
%.

(Note 10) Acrylic resin aqueous dispersion (W-
1): 140 parts of deionized water and 30% Newc in the reaction vessel
ol 707SF (Nippon Emulsifier, surfactant) 2.5
Parts and 1 part of the following monomer mixture (1) were added, and the mixture was stirred and mixed in a nitrogen stream, and 3% ammonium persulfate 3% was added at 60 ° C.
Added parts. Then, after raising the temperature to 80 ° C., 79 parts of the following monomer mixture (1), 30% Newcol 707
A monomer emulsion consisting of SF (2.5 parts), 3% ammonium persulfate (4 parts) and deionized water (42 parts) was added to the reaction vessel using a metering pump over 4 hours. After completion of the addition, aging was carried out for 1 hour.

Further, at 80 ° C., 20.5 parts of the following monomer mixture (2) and 4 parts of a 3% ammonium persulfate aqueous solution are simultaneously dropped in parallel to the reaction solution over 1.5 hours. After the completion of the addition, the mixture was aged for 1 hour and filtered at 200C with 200mesh nylon cloth. Deionized water was further added to this product to adjust the pH to 7.5 with dimethylaminoethanol, and a 20% non-volatile acrylic resin water dispersion (W-1) having an average particle size of 0.1 μm and a Tg (glass transition temperature) of 46 ° C. Got

[0132] monomer mixture (1) 1 part monomer mixture of methyl methacrylate 55 parts Styrene 10 parts of acrylic acid n- butyl 9 parts of 2-hydroxyethyl acrylate 5 parts of methacrylic acid (2) methyl methacrylate 5 parts Acrylic Acid n-butyl 7 parts 2-Ethylhexyl acrylate 5 parts Methacrylic acid 3 parts 30% Newcol 707SF (Nippon Emulsifier Co., Ltd., surfactant) 0.5 parts

(Note 11) Acrylic resin aqueous solution (W-
2): 60 parts of butyl cellosolve and 15 parts of isobutyl alcohol were added to a reaction vessel and heated to 115 ° C. in a nitrogen stream. When the temperature reaches 115 ° C, n-butyl acrylate 26
Parts, 47 parts of methyl methacrylate, 10 parts of styrene, 10 parts of 2-hydroxyethyl methacrylate, 6 parts of acrylic acid and 1 part of azoisobutyronitrile are added over 3 hours, and after the addition is completed, at 115 ° C. for 30 minutes. Aged, 1 part azobisisobutyronitrile and butyl cellosolve 115
5 parts of the mixture are added over 1 hour and after aging for 30 minutes 5
It was filtered through a 200 mesh nylon cloth at 0 ° C. The acid value of the obtained reaction product was 48, the viscosity Z ₁ (Gardner foam viscometer), the nonvolatile content was 55%, and the Tg was 45 ° C. This product was neutralized with dimethylaminoethanol in an equivalent amount, and deionized water was added to obtain a 50% acrylic resin aqueous solution (W-2).

Example of Preparation of Powder Clear Paint 40 parts of methyl methacrylate and acrylic acid-2 were placed in a flask.
-Ethylhexyl 30 parts, glycidyl methacrylate 30
Parts, 10 parts of styrene, 1 part of t-butyl peroxide (polymerization initiator), and 2 parts of potassium oleate soap (surfactant) were charged and subjected to heat polymerization by a suspension polymerization method to obtain a particulate copolymer ( The glass transition temperature was about 60 ° C). 100 parts of the obtained copolymer, 25 parts of decamethylene dicarboxylic acid, and 1 part of the coating surface adjusting agent were melt-kneaded at 120 ° C. for 10 minutes using a heating kneader. Then, the kneaded product is cooled and then crushed using a crusher to obtain a particle size of 20 to 150.
A powder clear paint (P-1) having a size of about μm was obtained.

Examples and Comparative Examples SPC mild steel treated with zinc phosphate was dipped in a bath (28 ° C.) of a cationic electrodeposition coating composition (I) adjusted to a solid content of 20% with deionized water. Soft steel as cathode, 150 ~
Energize at 250 V so that the film thickness after heating and curing will be 20 μm, wash the coating film with deionized water, and then wash it on the uncured coating film.
The cationic electrodeposition coating composition (II) adjusted to a solid content rate of 20% with deionized water was applied at a voltage of 250 to 350 V and an energizing time of 2 to 3
The film thickness after heat curing is 20 to 2 under the condition of the minute and the bath temperature of 28 ° C.
After coating so as to have a thickness of 5 μm and washing with water, the electrodeposition coating film was cured by heating at 180 ° C. for 30 minutes in an atmosphere having a nitrogen dioxide temperature of 10 ppm. Next, a water-based base paint (M-1) or (S-1) was sprayed onto the electrodeposition coated surface as a first overcoat (Devilpis SGA502,
10 at 25 ° C, 70% humidity) and cured film thickness (M-1)
˜20 μm, (S-1) 25 to 40 μm, and then 8 to remove water in the coating film.
After heating and drying at 0 ° C. for 5 minutes, an uncured coating surface of the water-based base coating material was coated with a powder clear coating material (P-
The cured coating thickness of 1) is 70 to 10 by electrostatic powder coating method.
The coating was applied so as to have a thickness of 0 μm and heated at 150 ° C. for 30 minutes to simultaneously cure both coating films of the above coating materials. Table 2 also shows these coating steps and their evaluation.

[0136]

[Table 2]

(* 1) to (* 5) in Table 2 are as follows. (* 1) Intermediate coating N-1: Amino-alkyd resin intermediate coating, which is applied on the cured electrodeposition coated surface by a spray coater to a thickness of 30 μm based on the cured coating film.
It was heated at 160 ° C. for 30 minutes to be cured.

(* 2) Gloss retention of electrodeposition coating film: A coating plate coated with the electrodeposition coating material as described above and heat-cured was used as a sunshine weatherometer (light intensity was 1,100K Joule / m ² · hr).
Accelerate for 100 hours in the gloss, gloss with the front (60 °
The specular reflectance) change rate (%) was examined. A digital gloss meter GM-26D type (sold by Murakami Color Research Laboratory) was used for initial and 40-hour irradiation gloss measurement. The gloss retention is calculated by the following formula.

[0139]

[Equation 3]

(* 3) Horizontal part finish: The finish of the coated plate that had been subjected to the top coat was measured by the image clarity measuring device JCRI-PG.
Evaluation was performed using a D-166 type Gd meter (sold by: Japan Color Research Institute). The larger the value, the better the sharpness.

(* 4) Weather resistance: The coated plate which had been subjected to the overcoating was subjected to accelerated exposure for 4,000 hours in the same manner as in (* 2) and then immersed in warm water at 40 ° C. for 20 hours to reach the substrate. The coating film was cross-cut on and the peeling test was performed using cellophane adhesive tape. If there is no peeling on the electrodeposition coated surface, it is ○, and if there is peeling, it is ×.

(* 5) Rust resistance at the edge part: Cutter replacement blade (Olfa LB-10, Olfa LB-10, shape width 10 cm,
The blade edge angle of 22 °) was subjected to electrodeposition coating in the above Examples and Comparative Examples and heated at 180 ° C. for 30 minutes to form an electrodeposition coating film. Then, a salt spray tester was used to perform a test for 1,680 hours, and the rust generation score at the edge was evaluated. ○: The number of rust points is 9 or less △: 〃 10 to 15 ×: 〃 16 or more

Claims (2)

[Claims] 1. (i) A cationic electrodeposition coating composition (I) containing 5 to 50% by weight of the cationic electrodeposition gelling fine particles (A) with respect to the total resin solid content is electrodeposited on an object to be coated. On the resulting uncured electrodeposition coating film, (ii) an epoxy cation having a surface tension of 40 to 60 dyne / cm and capable of forming an aqueous bath capable of electrodeposition on the cathode by neutralizing with an acid. The electrodepositable resin (B) and the nonionic film-forming resin (C) having a surface tension of 25 to 45 dyne / cm are used as resin (B): resin (C) = 60: 40 to 9
It is contained in a weight ratio within the range of 8: 2, the surface tension of the resin (B) is larger than that of the resin (C), and the minimum electrodeposition current density is 0.7 mA / cm ² or less and the degree of emulsification. Of 80% by weight or more is applied by electrodeposition coating of a cationic electrodeposition coating composition (II), followed by heating to cure both coating films of (i) and (ii). iii) A water-based base coating material containing a metallic pigment and / or a coloring pigment is applied, and (iv) a powder clear coating material is applied on the coated surface without curing, and then heated ((iii) above). And (iv) both coating films are cured. 2. The cationic electrodeposition gelling fine particles (A) in the cationic electrodeposition coating composition (I) are water-dispersed epoxy resin amine adducts containing a hydrolyzable alkoxysilane group and crosslinked within the particles. The coating method according to claim 1, wherein