JPH06228795A - Method for cation electrodeposition - Google Patents

Abstract

PURPOSE:To obtain weather resistance even for the inside of a bag-like structure by performing electrodeposition coating of high weather resistance and further performing electrodeposition coating of good adhesion property. CONSTITUTION:A cation electrodeposition coating material essentially consisting of cation electrodepositing vinyl copolymer containing hydroxyl groups of 50-150 hydroxylic value is applied to form a 25mum thick film and baked. Then a cation electrodeposition coating material containing gelled fine particles is applied and baked. This coating material containing gelled fine particles is obtd. by dispersing amine-added epoxy resin in water and crosslinking in particles. The amine-added epoxy resin contains hydrolytic alkoxysilane groups as the gelled fine particles having strong corrosion preventing effect for edges. Thereby, even a bag-like part which is not covered with the first electrodeposition coating material or an edge part not coated because of a thermal flow during baking can be coated with the second electrodeposition film. Thereby, enough weather resistance, finished state and corrosion resistance can be obtd. for each part of the body to be coated.

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 method, and in particular, it applies two types of cationic electrodeposition coatings having different functions to an object having a complicated structure such as an automobile body.
The present invention relates to a cation electrodeposition coating method in which high weather resistance of a general outer plate portion and throwing power of a bag-shaped structure portion can be made compatible by baking the coat 2.

[0002]

2. Description of the Related Art Cationic electrodeposition coating is performed by applying a voltage between an object to be coated and a counter electrode in an electrodeposition bath by using an object to be coated as a cathode. It is a method of forming a film, and a coating film having excellent smoothness is obtained by heat flow in the baking process. As a cationic electrodeposition coating, a cationic electrodeposition coating composed of an epoxy resin is generally used, but a cationic electrodeposition coating composed of an epoxy resin is excellent in throwing power and corrosion resistance but inferior in weather resistance. On the other hand, a cationic electrodeposition coating made of an acrylic resin has excellent weather resistance, but has poor throwing power with respect to an object to be coated having a complicated structure, and it is difficult to obtain anticorrosion property because an unpainted portion remains.

In recent years, with the desire to shorten the coating process and save resources, the intermediate coating is omitted in the coating system for automobile bodies.
There is an increasing demand for high weather resistance of the electrodeposition coating film so that the overcoating can be directly applied on the electrodeposition coating film. However, as described above, it is difficult to achieve both high throwing power and weather resistance, and it is necessary to have sufficient throwing power as in the inside of the bag-shaped structure of the automobile body (hereinafter referred to as “bag portion”). In the article to be coated having such a structure, throwing power is prioritized, and weather resistance has not been sufficiently satisfied.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have applied an electrodeposition coating having excellent weather resistance in the first electrodeposition coating and baked it to form a bag portion or the like. A bag part that has high weather resistance of general parts other than complicated structure parts, and is painted unpainted after the first baking by coating and baking the electrodeposition paint with good throwing power in the second electrodeposition coating. The present invention has been completed by discovering that it is sufficiently related to such parts.

That is, according to the present invention, an object to be coated having a complicated structure is coated with a cationic electrodeposition coating composition (A) containing a hydroxyl group-containing cationic electrodeposition vinyl copolymer as a main component and baked, It is intended to provide a cationic electrodeposition coating method characterized by coating and baking a cationic electrodeposition coating composition (B) containing a cationic electrodeposition epoxy resin as a main component.

In the present invention, cationic electrodeposition paint (A)
Is an electrodeposition paint which is electrodeposited for the first time, and contains a cationic electrodeposition vinyl copolymer containing a hydroxyl group as a main component.

As the above-mentioned cationic electrodeposition vinyl-based copolymer, conventionally known ones can be used, and examples thereof include those obtained by copolymerizing an amino group-containing monomer with a hydroxyl group-containing monomer and other vinyl monomers. .

The amino group-containing monomer is preferably an amino group-containing acrylic monomer, for example, aminoethyl (meth) acrylate, N-tert-butylaminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate. , N, N-diethylaminoethyl (meth) acrylate, N, N-dipropylaminoethyl (meth) acrylate, N, N-dibutylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N , N-dimethylaminobutyl (meth) acrylate and other aminoalkyl acrylic acid esters or methacrylic acid esters; N, N
-Dimethylaminoethyl (meth) acrylamide, N,
N-diethylaminoethyl (meth) acrylamide,
Examples thereof include aminoalkyl acrylamides such as N, N-dipropylaminoethyl (meth) acrylamide and N, N-dimethylaminopropyl (meth) acrylamide, or methacrylamides. These may be used alone or in combination of two or more. The amino group-containing monomer is 3 to 20% by weight of the total amount of the monomers,
It is suitable to use it in a range of preferably 5 to 18% by weight.

[0009] As the hydroxyl group-containing monomers such as hydroxyethyl (meth) acrylate, hydroxyalkyl esters of C ₁ ~ ₈ of the acrylic acid or methacrylic acid such as hydroxyethyl (meth) acrylate can be preferably used.

The other vinyl monomer is not particularly limited as long as it is a monomer copolymerizable with the amino group-containing monomer or the hydroxyl group-containing monomer, and examples thereof include methyl (meth) acrylate, ethyl (meth) acrylate,
n-butyl (meth) acrylate, iso-butyl (meth) acrylate, tert-butyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, etc. alkyl or cycloalkyl esters of C ₁ ~ ₂₄ of acrylic acid or methacrylic acid; styrene, vinyl toluene, alpha
-Methylstyrene, vinyl propionate, vinyl acetate,
(Meth) acrylonitrile, vinyl propionate,
Vinyl monomers such as (meth) acrylamide, N, N-diethyl (meth) acrylamide, and veova monomer (shell chemical product) can be mentioned, and each can be used alone or in combination of two or more kinds. These monomers can be appropriately selected depending on the desired properties of the electrodeposition coating composition and the required performance of the coating film formed therefrom.

The copolymer containing the above-mentioned monomers can be produced by a conventionally known method, generally by a solution polymerization method.

As the cationic electrodeposition vinyl copolymer, an amine is added to a copolymer of a glycidyl group-containing monomer and a hydroxyl group-containing monomer and a copolymer of any other vinyl monomer that is copolymerizable therewith and does not react with the glycidyl group. There are also things that consist of.

As the glycidyl group-containing monomer,
Examples thereof include glycidyl (meth) acrylate, vinylcyclohexene monoepoxide, N-glycidyl acrylamide, and allyl glycidyl ether. The glycidyl group-containing monomer is used in an amount of 5 to 50% by weight, preferably 10 to 40% by weight, based on the total amount of the monomers.

As the hydroxyl group-containing monomer and the other vinyl monomer which is copolymerizable therewith and does not react with the glycidyl group, the above-mentioned ones can be similarly used. Also, the production of a copolymer composed of such monomers can be carried out by a conventionally known method.

The addition reaction of the glycidyl group-containing copolymer obtained as described above with an amine can be carried out by a conventionally known method, for example, a secondary amine is added to the copolymer solution and the reaction is carried out at about 50 to 120 ° C. Examples of the method include reacting at the temperature of about 1 to 20 hours. Examples of the amine used include alkylamines such as propylamine, butylamine, dimethylamine, diethylamine and di-n-propylamine; alkanolamines such as diethanolamine, diisopropanolamine and N-methylethanolamine; piperidine, morpholine, N-methyl piperazine etc. are mentioned. The amount of the amine used is usually in the range of about 0.1 to 1 mol per mol of the glycidyl group.

The hydroxyl value of the cationic electrodeposition vinyl copolymer obtained as described above is not particularly limited, but is usually 30 to 200, preferably 50 to 150. If the hydroxyl value is less than 30, the coating film obtained tends to be poor in curability, and if it exceeds 200, the weather resistance and corrosion resistance tend to be poor.

The molecular weight of the cationic electrodeposition vinyl copolymer is usually in the range of about 5,000 to 100,000, preferably 10,000 to 50,000.

The above cationic electrodeposition vinyl copolymer is
It can be neutralized with an organic acid such as acetic acid, propionic acid, lactic acid, and hydroxyacetic acid to provide water dispersibility. Further, the copolymer can be cured with a crosslinking agent such as a block polyisocyanate compound or a melamine resin. The blocked polyisocyanate compound is an addition reaction product of a polyisocyanate compound and an isocyanate blocking agent (for example, an alcohol compound, an oxime compound, a phenol compound, etc.). Aromatic, alicyclic and aliphatic polyisocyanate compounds such as diisocyanate, xylylene diisocyanate, phenylene diisocyanate, bis (isocyanatomethyl) cyclohexane, tetramethylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate and isophorone diisocyanate, and these Add ethylene glycol, propylene glycol, trimethylolpropane, or hexanetriol to excess polyisocyanate compound. Include a terminal isocyanate-containing compounds obtained by reacting a low molecular weight active hydrogen-containing compounds such as castor oil. Further, it is desirable from the viewpoint of anticorrosion that a small amount of a conventionally known amine-added epoxy resin as another cationic electrodeposition resin is used in combination with the above cationic electrodeposition vinyl copolymer.

The above-mentioned cationic electrodeposition coating (A) is an ordinary coating additive as required, for example, a coloring pigment such as carbon black, titanium white, red iron oxide; clay, talc,
An extender pigment such as calcium carbonate; a rust preventive pigment such as strontium chromate, lead chromate, and lead silicate; or other additives can be added. Other additives include, for example, dispersion aids (nonionic surfactants); anti-repellent agents for coating surfaces (acrylic resins, fluororesins, silicone resins, etc.); hardening accelerators (eg lead, bismuth, tin, etc.). Metal salts); organic solvents and the like. The cationic electrodeposition coating (A) may be mixed with conductive powder such as conductive carbon (graphite etc.) or metallic powder, if necessary. In that case, the cationic electrodeposition coating (A)
The coating film formed by is 1 × 10 at 20 ℃ and 20V.
Volume specific electrical resistance value in the range of ⁷ to 10 ¹³ Ω · cm (film thickness 2
5 .mu.m), which allows sufficient formation of a coating film at the boundary between the first electrodeposition coating film and the second electrodeposition coating film.

The cationic electrodeposition coating composition (A) is appropriately diluted with deionized water so that the solid content concentration is about 5 to 25% by weight and the pH is about 5.5 to 8. You can

As a method and apparatus for performing electrodeposition coating on an object to be coated with the above-mentioned cationic electrodeposition coating (A), a method and apparatus known per se which has been conventionally used in cationic electrodeposition coating is used. be able to. At that time, the uncoated material was used as the cathode and stainless steel # 316 was used as the anode.
It is preferable to use a plate or a ferrite metal plate. The electrodeposition coating conditions that can be used are not particularly limited, but generally bath temperature: 15 to 35 ° C. (preferably 20 to 30 ° C.).
C), voltage: 100 to 400 V (preferably 200 to 3)
00V), 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, electrodeposition under stirring condition is desirable.

The thickness (dry state) of the electrodeposition coating film of the cationic electrodeposition coating composition (A) is 10 to 90 μm, preferably 20 to 90 μm.
It is preferably in the range of 70 μm.

The electrodeposition coating film formed on the article to be coated is washed with deionized water or the like and then washed at about 100 to 200 ° C., preferably 10 ° C.
It can be baked and cured at 0 to 180 ° C. Such curing can be performed to the extent that the paint by the second electrodeposition coating is not applied to the coating film.

In the present invention, cationic electrodeposition paint (B)
Is an electrodeposition paint that is electrodeposited a second time, and contains a cationic electrodeposition epoxy resin as a main component. When the second electrodeposition coating is carried out, the electrodeposition coating film is selectively applied to the unpainted portion such as the bag portion which has not been stuck in the first electrodeposition coating or the edge portion where the substrate is exposed due to heat flow during baking. Is formed. This is because the coating film portion formed by the first electrodeposition coating has a higher electric resistance value than the exposed substrate, so that the second electrodeposition coating film is formed on the coating film portion by the second electrodeposition coating. This is because it is not formed. In the ultra-thin film part formed near the unpainted part, etc. by the first electrodeposition coating and baking, it is presumed that the film itself is not a continuous layer but the substrate is exposed with pores. This can be regarded as an unpainted portion, and the electrodeposition coating film is selectively formed by the second electrodeposition coating.

Examples of the above-mentioned cationic electrodeposition epoxy resin include amine-added epoxy resins. The amine-added epoxy resins are polyamine resins usually used in electrodeposition paints, such as (i) polyepoxide compound and primary grade. Mono- and polyamines, secondary mono- and polyamines or adducts with primary and secondary mixed polyamines (see, for example, U.S. Pat. No. 3,984,299); (ii) polyepoxide compounds and ketiminated primary Addition products with secondary mono- and polyamines having amino groups (see, for example, US Pat. No. 4,017,438); (iii) Polyepoxide compounds and hydroxy compounds having ketiminated primary amino groups. A reaction product obtained by etherification (see, for example, JP-A-59-43013) may be included.

The polyepoxide compound used for producing 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 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 amine-added epoxy resin can be cured with a crosslinking agent such as a polyisocyanate compound blocked with alcohols or a melamine resin, if necessary.

It is also possible to use a self-crosslinking type amine-added epoxy resin which can be cured without using the above-mentioned cross-linking agent.
-A resin having a hydroxyalkyl carbamate group introduced therein (see, for example, JP-A-59-155470); a resin which can be cured by a transesterification reaction (see, for example, JP-A-55-80436); a block in a base resin It is also possible to use a resin having an isocyanate group introduced therein.

Further, the cationic electrodeposition coating composition (B) may be blended with gelled fine particles and / or particulate components such as pigments when edge corrosion resistance is strongly required, and gelled fine particles are particularly preferable. is there.

As the above-mentioned gelled fine particles, conventionally known ones can be used without particular limitation as long as they are fine particle polymers gelled by a crosslinking reaction in the particles. For example, acryl containing an alkoxysilane group and a cationic group. A copolymer in which the copolymer is dispersed in water and crosslinked within particles (Japanese Patent Application No. 62-54).
No. 141); Internally crosslinked gelled fine particles having an alkoxysilane group, a hydroxyl group and a cationic group (see JP-A-2-47173); An internally crosslinked gel having an alkoxysilane group, a urethane bond, a hydroxyl group and a cationic group. And the like (see JP-A-3-62860).

Further, as the above-mentioned gelled fine particles, cationic electrodepositable gelled fine particles obtained by water-dispersing an epoxy resin amine adduct containing a hydrolyzable alkoxysilane group and cross-linking within the particles are particularly effective in terms of corrosion resistance. Can be preferably used. The gelled fine particles will be described below.

The above-mentioned "epoxy resin amine adduct containing a hydrolyzable alkoxysilane group" is a product obtained by introducing a hydrolyzable alkoxysilane group into an epoxy resin amine adduct, and is a cationic group, especially an acid. The hydrated amino group is stably dispersed in water as a water-dispersing group, and the silanol group produced by hydrolysis of the alkoxysilane group is condensed with both silanol groups and, if there is a hydroxyl group, the hydroxyl group. The term refers to an adduct that can be gelled by intra-particle crosslinking.

The epoxy resin amine adduct which is a constituent of the gelled fine particles includes a polyamine resin and the like as described in the section of the cationic electrodeposition epoxy resin.

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 of 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 the following.

[0037]

[Chemical 1]

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

[0039]

[Chemical 2]

(3) Method of adding an alkoxysilane group-containing epoxy compound 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.

[0041]

[Chemical 3]

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

[0043]

[Chemical 4]

In each of the above formulas, R may be exemplified by the following: (i) Alcohol residues such as methyl group, ethyl group, propyl group, butyl group and hexyl group;
(Ii) Ether alcohol residues such as methoxyethyl group, ethoxyethyl group and methoxypropyl group; (iii) Ester alcohol residues such as acetoxyethyl group; (iv)
Examples thereof include cycloalkyl or aralkyl alcohol residues such as cyclohexyl group and benzyl group; and (v) oxime alcohol residue.

R in the above formula has a smaller number of carbon atoms and is more easily hydrolyzed, but is inferior in stability, so that 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

When the gelled fine particles are blended in the cationic electrodeposition coating composition (B), the blending amount is 3 with respect to the total resin solids (the total of the cationic electrodepositable epoxy resin and the gelled fine particles). It is suitable that the content is ˜50% by weight, preferably 7 to 35% by weight. If necessary, as other particulate components, coloring pigments such as titanium white, carbon black, red iron oxide, and yellow lead; extender pigments such as talc, calcium carbonate, mica, clay, and silica; strontium chromate, lead chromate, You may use together antirust pigments, such as lead silicate.

Further, when only the pigment is blended without using the gelled fine particles as the particulate component, the above-mentioned pigment can be added in a larger amount than usual, but the oil absorption is 10
It is suitable to add 0 or more pigments, for example, silicon dioxide pigments such as anhydrous silicon dioxide and hydrous amorphous silicon dioxide, and carbon pigments in an amount of 5% by weight or more based on the total pigment content.

The cationic electrodeposition coating composition (B) thus obtained
Is appropriately diluted with deionized water to obtain a solid concentration of about 3 to 25.
% By weight, preferably 5-20% by weight, pH about 5.5-8
It is appropriate to adjust it so that it falls within the range.

In the present invention, the above-mentioned cationic electrodeposition coating composition (A) is used to form a coating film on an unpainted portion such as a bag portion or an edge portion of an article to which an electrodeposition coating film has already been formed on a general portion. The method and apparatus for performing electrodeposition coating using the cationic electrodeposition coating (B) is the above-mentioned cationic electrodeposition coating (A).
Can be used in the same manner as the method and apparatus used in. Among them, the energization time and the like are 1/4 to 1 / the time required for the cationic electrodeposition coating (A).
Even 2 is sufficient to form an electrodeposition coating film of the cationic electrodeposition coating composition (B) on the unpainted portion of the coated object. Thus, cationic electrodeposition coating (A) and cationic electrodeposition coating (B)
The electrodeposition coating film formed by the above can be finished by appropriately applying an intermediate coating and a top coating, if necessary.

In the present invention, the article to be coated having a complicated structure has a bag portion or an edge portion like an automobile body, and is preferably made of a rust-proof treated steel plate from the viewpoint of rustproof property. . As the steel sheet, hot-dip galvanized steel sheet,
After cleaning the surface of base materials such as electrogalvanized steel sheets, electrogalvanized / iron double-layered steel sheets, organic composite plated steel sheets, cold-rolled steel sheets, if necessary, such as alkali degreasing, phosphate chemical treatment, chromate chemical treatment, etc. Examples include those that have undergone pretreatment.

[0054]

According to the method of the present invention, the first and second
When the electrodeposition coating of the first time is performed, selectively the bag part where the electrodeposition coating film applied the first time is not stuck, and the unpainted part such as the edge part which is not formed due to heat flow during baking, The electrodeposition coating film applied the second time is formed. Therefore, by using the method of the present invention, it is possible to sufficiently obtain high weather resistance and finish of the general part for the object to be coated having a complicated structure. ,
The throwing power and the anticorrosion property of the bag portion and the edge portion can be secured, and the required performance can be satisfied at a high level for each portion of the article to be coated.

[0055]

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.

Production Example of Vinyl Copolymer Solution Production Example 1 27 parts of n-butyl alcohol and 27 parts of isopropyl alcohol were placed in a reaction vessel and heated to 90 ° C. 30 parts of styrene, 35 parts of 2-ethylhexyl methacrylate, 20 parts of 2-hydroxyethyl acrylate
Part, N, N-dimethylaminoethyl acrylate 15
Part, and a mixture of 3.5 parts of azobisisobutyronitrile were added dropwise over about 2 hours. The reaction was carried out under nitrogen injection.
The reaction temperature was kept at 90 ° C., and the reaction was further continued for 4 hours to obtain a vinyl copolymer solution (I) having a solid content of 65%.

Production Example 2 20 parts of n-butyl alcohol and 20 parts of isopropyl alcohol were placed in a reaction vessel and heated to 90 ° C. 15 parts of methyl methacrylate, 30 parts of n-butyl acrylate, 20 parts of styrene, 20 parts of glycidyl methacrylate, 15 parts of hydroxypropyl methacrylate
Part, a mixture of 3 parts azobisisobutyronitrile, about 2 parts
It dripped over time. The reaction was carried out under nitrogen injection. The reaction temperature was maintained at 90 ° C., and the reaction was further performed for 4 hours to obtain a copolymer solution. Next, 9 parts of diethanolamine and 14 parts of isopropyl alcohol were added to this copolymer solution, and the reaction was carried out at 90 ° C. for 3 hours to obtain a vinyl copolymer solution (II) having a solid content of 65%.

Preparation of Cationic Electrodeposition Coating (A) Preparation Example 1 Vinyl Copolymer Solution (I) 12 Obtained in the Above Production Example
Acetic acid 4.8 parts was added to 3 parts (solid content 80 parts) and deionized water was further added to prepare an aqueous dispersion, to which 15 parts of 60% polyester-modified epoxy resin aqueous dispersion was added and mixed by stirring. Further, 6.4 parts of ethylene glycol mono-2-ethylhexyl ether diblock of 4,4′-diphenylmethane diisocyanate, 23 parts of methyl ethyl ketoxime diblock of isophorone diisocyanate,
1 part of dibutyltin dilaurate and 0.5 part of polypropylene glycol 4000 were added and mixed uniformly, and deionized water was added with stirring to obtain a clear emulsion having a nonvolatile content of 32%. Table 1 was added to 320 parts of the clear emulsion.
Pigment paste (P-1) having a solid content of 43% as shown in 95.3
Parts with stirring and diluted with deionized water to obtain a solid content of 2
A 0% cationic electrodeposition coating composition (A-1) was obtained.

Preparation Example 2 Vinyl-based copolymer solution (II) 13 obtained in the above Production Example
Acetic acid (3.0 parts) was added to 8.5 parts (solid content: 90 parts), and deionized water was further added to prepare an aqueous dispersion.
In the same manner as above, 4,4'-diphenylmethane diisocyanate diblock product, isophorone diisocyanate diblock product, dibutyltin dilaurate and polypropylene glycol 4000 were added in the same amounts as in Preparation Example 1 and uniformly mixed, and deionized water was added while stirring. In addition, a clear emulsion having a nonvolatile content of 32% was obtained. A cationic electrodeposition coating composition (A-2) having a solid content of 20% was obtained by the same operation as in Preparation Example 1 using the clear emulsion.

Production Example 3 of Gelled Fine Particles Production Example 3 Epon 8 was blown into a reaction vessel equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen gas blowing port while blowing nitrogen gas.
28EL (Note 1) 1,045 parts, bisphenol A17
12 parts by adding 1 part and 52.2 parts of diethanolamine
After heating to 0 ° C, the epoxy equivalent (Note 2) is the theoretical value (31
The reaction was allowed to proceed to 7). Thereafter, the mixture was cooled to 80 ° C., 221 parts of KBE-903 (Note 3) and 157.5 parts of diethanolamine were added, and the reaction was continued until the tertiary amine value (Note 4) reached the theoretical value (102). Then, the mixture was diluted with 706 parts of 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.

100 parts of the epoxy resin amine adduct containing the hydrolyzable alkoxysilane group obtained above and 11 parts of 10% acetic acid were added to a 21 flask and stirred at 30 ° C. for 5 minutes, and then 239 parts of deionized water. Was dripped over about 30 minutes with strong stirring, the temperature was raised to 50 ° C., and stirring was carried out for about 3 hours. Thus, a milky white intraparticle crosslinked gelled fine particle dispersion (G-) 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.

(Note 1) Diglycidyl ether of bisphenol A having an epoxy equivalent of about 190 (manufactured by Yuka Shell Co., Ltd.) (Note 2) In accordance with JIS-K-7236. However, the amino group is also added as an epoxy group. (Note 3) γ-aminopropyltriethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) (Note 4) After acetylation with acetic anhydride, titration with perchloric acid using crystal violet as an indicator.

Production Example 4 A reactor similar to that of Production Example 1 was charged with 950 parts of Epon 828EL, 342 parts of bisphenol A and 96.5 parts of amine A (Note 5) under nitrogen gas blowing and heated to 160 ° C. to obtain an epoxy equivalent. The reaction was allowed to reach the theoretical value (694). Then, the mixture was cooled to 100 ° C., 193 parts of amine A (post-addition) and 159 parts of amine B (note 6) were added, and 3 parts were added.
The reaction was carried out until the primary amine value reached the theoretical value (97).
Then, 36 parts of deionized water was added at 100 ° C. to carry out a deketimination reaction, and then KBE was also carried out at 100 ° C.
-402 (Note 7) (496 parts) was added and the reaction was continued until the epoxy group disappeared. Then diluted with 486 parts of ethylene glycol monobutyl ether to give a number average molecular weight of 1,900.
A 70% solids solution of the epoxy resin amine adduct containing the hydrolyzable alkoxysilane group was obtained.

100 parts of the epoxy resin amine adduct containing the hydrolyzable alkoxysilane group obtained above and 11 parts of 10% acetic acid were added to a flask 21 and stirred at 30 ° C. for 5 minutes, and then 239 parts of deionized water. Was dripped over about 30 minutes with strong stirring, the temperature was raised to 50 ° C., and stirring was carried out for about 3 hours. Thus, solid content 20%, average particle size in ethylene glycol monobutyl ether 0.15 μm
The milky white particles of the crosslinked gelled fine particle dispersion (G-
)was gotten.

(Note 5) Methylisobutylketone solution of ketimine of 74% monoethanolamine and methylisobutylketone of active ingredient (Note 6) Methylisobutylketone solution of diketimine of diethylenetriamine of 84% of active ingredient in methylisobutylketone (Note) 7) γ-glycidoxypropylmethyldiethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.).

Production Example 5 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 (Note 8) 50 parts (Note 8) γ-methacryloxypropyltrimethoxysilane (Shin-Etsu Chemical) (Industrial company)

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 fine particle (G-) dispersion was obtained. (See Japanese Patent Laid-Open No. 2-47173)

Preparation of Cationic Electrodeposition Paint (B) Table 2 shows a cationic emulsion for cationic electrodeposition (manufactured by Kansai Paint Co., Ltd., Elektron 9450) having a solid content of 35% and comprising a polyamide-modified epoxy resin and a completely blocked diisocyanate. Pigment paste (P-2) having a solid content of 43% and / or gelled fine particle dispersion liquids (G-) to (G-) having a solid content of 20% were added with stirring in a formulation shown in Table 2 and deionized water was added. The mixture was diluted to obtain cationic electrodeposition coatings (B-1) to (B-4) having a solid content of 20%.

[0069]

[Table 1]

[0070]

[Table 2]

Examples and Comparative Examples The cationic electrodeposition coating composition (A-1) or (A-
2) was used as the first electrodeposition paint, and electrodeposition coating was performed under the conditions shown in Table 3 to form an electrodeposition coating film having a film thickness of 50 μm (dry film thickness) in the general part other than the bag part and the edge part. Then wash the coating with water,
Baked at 170 ° C. for 20 minutes (however, only in Example 4,
It was baked at 120 ° C. for 10 minutes. ). Further, the combinations of the coated plates shown in Table 4 were used for cationic electrodeposition coatings (B-1) to (B-
4) and electrodeposition coating under the conditions shown in Table 3, washing with water,
A coated plate was obtained by baking at 170 ° C. for 20 minutes. The performance test results of this coated plate are shown in Table 4. In Comparative Example 1, only the electrodeposition coating (A-1) was used, in Comparative Examples 2 and 3, the electrodeposition coating (B-1) was used.
Electrodeposition coating was performed on only (B-2).

[0072]

[Table 3]

[0073]

[Table 4]

(Note 9) to (Note 13) in Table 4 are as follows. (Note 9) Finishability: The surface roughness of the electrodeposition coating film was measured with a surface roughness meter Surf Test No. 402 (manufactured by Mitoyo Co., Ltd.). (Measurement condition λc = 0.8 mm) Numerical values are shown by Ra value: μ.

(Note 10) Weather resistance: The coated plate was sunshine weatherometer (light intensity 1,100K · Joule / m ² · hr) to 1
After accelerated exposure for 00 hours and 500 hours, the rate of change (%) in gloss (60 degree specular reflectance) from before exposure (initial) was examined. For gloss measurement, a digital gloss meter GM-26D type (sold by Murakami Color Research Laboratory) was used. The gloss retention rate (%) was calculated from the following formula. Gloss retention = (Measured gloss after 100 hours or 500 hours exposure / Measured gloss before exposure) × 100

(Note 11) Edge corrosion resistance: A salt spray test was conducted on an object to be electrodeposited according to JIS-Z-2371, and the number of rust points generated in the punched burr portion after 240 hours was measured. Then, the number was evaluated.

(Note 12) Anticorrosion property: For an electrodeposition-coated object, a cross-cut flaw was made with a knife in the electrodeposition coating film to reach the base in the general part, and this was JIS-Z.
A salt fog test for 840 hours according to 2371;
The rust from knife scratches and the blister width (mm) were measured.

(Note 13) Bag part coatability: The object to be tested for bag part coatability test was immersed in an electrodeposition bath so that the immersion depth was 90 mm, the distance from the counter electrode was 110 mm, and a hole of 8 mmφ was opened. The surface was immersed so that the opposite surface faces the counter electrode, and electrodeposition coating was performed as described above. The thickness of the electrodeposited coating film on the portion corresponding to the inner surface of the box-shaped body of the steel sheet having no holes among the four steel sheets arranged in parallel to the object to be coated forms the box-shaped body. The ratio of the steel plate closest to the counter electrode among the perforated steel plates to the film thickness of the electrodeposition coating film of the portion corresponding to the outer surface of the box-shaped body was expressed by (%). The higher the ratio, the better the bag coatability.

Claims (4)

[Claims] 1. A cationic electrodeposition coating composition (A) containing a cationic electrodeposition vinyl copolymer containing a hydroxyl group as a main component is applied to an article to be coated having a complicated structure, baked and then subjected to cationic electrodeposition. Electrodeposition coating method comprising coating and baking a cationic electrodeposition coating composition (B) containing a water-soluble epoxy resin as a main component. 2. The cationic electrodeposition coating method according to claim 1, wherein the cationic electrodeposition coating composition (B) contains gelled fine particles and / or pigments. 3. The cation according to claim 2, wherein the gelled fine particles are cation electrodepositable gelled fine particles obtained by dispersing an epoxy resin amine adduct containing a hydrolyzable alkoxysilane group in water and crosslinking the particles. Electrodeposition coating method. 4. The cationic electrodeposition coating method according to claim 1, 2 or 3, wherein the article to be coated is a rust-proof treated steel plate.