JP3287643B2 - Cationic electrodeposition coating composition and preparation method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cationic electrodeposition coating composition, and more particularly, to a method for dispersing an epoxy resin-amine adduct containing a hydrolyzable alkoxysilane group in a resin for dispersing a pigment. The present invention relates to a cationic electrodeposition coating composition containing a pigment-dispersed paste prepared by adding the same, particularly having excellent smoothness and capable of forming a thick coating film on edges such as corners and projections.

[0002]

2. Description of the Related Art Cationic electrodeposition coatings, which are widely used mainly in the automobile industry, have excellent anticorrosion properties, but the coating film thickness at the edge portion of the object to be coated is not increased. There is a drawback that the coverability is inferior, and improvement thereof is desired. Therefore, conventionally, various methods for imparting rheological control properties by, for example, adding gelling fine particles to a cationic electrodeposition coating have been proposed, and the present applicant has also previously proposed an alkoxysilane group and a hydroxyl group and a cationic group. And a method for producing the same having an internally crosslinked gelled fine particle polymer (see JP-A-2-47173).
Further, an internally crosslinked gelled fine particle polymer having an alkoxysilane group, a urethane bond, a hydroxyl group and a cationic group, and a method for producing the same have been proposed (see JP-A-3-62860). These previously proposed internally crosslinked gelled fine particle polymers have cationic electrodeposition properties, so that bath stability and electrodeposition characteristics are not impaired even when added to a cationic electrodeposition paint, and the baked coating film Is particularly excellent in edge cover properties, but has a drawback that it is slightly inferior in general anticorrosion properties because it is based on an acrylic resin, and has a practically insufficient point.

On the other hand, gelled fine particles using an epoxy resin which is excellent in anticorrosion properties have also been known. For example, a cationic microgel dispersion in which a mixture of a cationic polyepoxide-amine reaction product and a polyepoxide crosslinking agent is dispersed in water and crosslinked in a particle (JP-A-4-226)
No. 171) has been proposed, but the dispersion is inferior in rheological control, so that it is necessary to use a large amount in order to impart sufficient edge coverage. There is a disadvantage that the smoothness of the coated surface is impaired.

[0004]

[Means for Solving the Problems] Accordingly, the present inventors
As a result of intensive research to develop a rheology control agent that is superior to conventional gelled fine particles in corrosion protection and smoothness of the coating film and is useful in cationic electrodeposition coatings,
At the time of dispersing the pigment used in the cationic electrodeposition coating, using an epoxy resin amine adduct containing a hydrolyzable alkoxysilane group, adding this to the pigment and the dispersing resin, dispersing and mixing to prepare a pigment dispersion paste, When this pigment dispersion paste is mixed with a cationic electrodeposition resin emulsion or the like, the resulting cationic electrodeposition coating composition can be obtained without impairing bath stability, electrodeposition properties, water resistance of the coating film, and corrosion resistance. In order to complete the present invention, it has been found that a decrease in the viscosity of a molten coating film during baking and curing of an electrodeposition coating film is controlled, and that a cationic electrodeposition coating film having both excellent coating surface smoothness and edge coverage is provided. Reached.

Thus, the present invention provides a cationic electrodeposition coating composition characterized by comprising a pigment dispersion paste containing an epoxy resin-amine adduct containing a hydrolyzable alkoxysilane group. Is what you do.

Further, according to the present invention, a pigment-dispersed paste is prepared by adding an epoxy resin-amine adduct containing a hydrolyzable alkoxysilane group to a pigment and a dispersing resin, and dispersing and mixing the pigment-dispersed paste. The present invention provides a method for preparing a cationic electrodeposition coating composition, which is mixed with an adhesive resin emulsion.

In the present invention, the epoxy resin-amine adduct containing a hydrolyzable alkoxysilane group added at the time of preparing the pigment dispersion paste is adsorbed on the pigment surface together with the dispersing resin, and the resin adsorbed on the pigment surface is Cross-linking, such as condensation of silanol groups generated by hydrolysis of alkoxysilane groups in the resin prior to thermal fluidization during baking of the coating film with hydroxyl groups if silanol groups and / or hydroxyl groups are present. It is considered that a reaction occurs to exhibit rheological control properties, that is, the pigment acts as a rheological control agent having a gel layer formed on the surface.

Therefore, rheology controllability can be exhibited with a smaller amount of resin than the amount of conventional gelled fine particles, etc., by blending the pigment dispersion paste with the cationic electrodeposition paint.

In the present invention, "epoxy resin-amine adduct containing a hydrolyzable alkoxysilane group"
Cationic groups, especially amino groups which can be neutralized with an acid, are dispersed in water stably in water, and silanol groups formed by hydrolysis of the alkoxysilane groups are silanol groups, and hydroxyl groups. Refers to an adduct that can also condense with its hydroxyl group when is present.

The above-mentioned epoxy resin-amine adduct includes polyamine resins commonly used in cationic electrodeposition coatings, and includes, for example, (i) polyepoxide compounds and primary mono- and polyamines, secondary mono- and polyamines. Or adducts of primary and secondary mixed polyamines (see, for example, US Pat. No. 3,984,299); (ii) a polyepoxide compound and a secondary mono- or polyamine having a ketiminated primary amino group. Adducts (see, for example, U.S. Pat. No. 4,017,438); (iii) polyepoxide compounds and ketiminated 1
And a reaction product obtained by etherification with a hydroxy compound having a secondary amino group (for example, see JP-A-59-43013).

The polyepoxide compound used for producing the above polyamine resin is an epoxy group.

[0012]

Embedded image Is generally a compound having a number average molecular weight of at least 200, preferably 400 to 4,000, more preferably 800 to 2,000, and particularly preferably polyphenol. Those obtained by reacting a compound with epichlorohydrin are preferred. Examples of the polyphenol compound that can be used for forming the polyepoxide compound include, for example, bis (4-
(Hydroxyphenyl) -2,2-propane, 4,4′-
Dihydroxybenzophenone, bis (4-hydroxyphenyl) -1,1-ethane, bis- (4-hydroxyphenyl) -1,1-isobutane, bis (4-hydroxy-tert-butyl-phenyl) -2,2 -Propane,
Bis (2-hydroxynaphthyl) methane, 1,5-dihydroxynaphthalene, bis (2,4-dihydroxyphenyl) methane, tetra (4-hydroxyphenyl)-
1,1,2,2-ethane, 4,4'-dihydroxydiphenyl sulfone, phenol novolak, cresol novolak and the like.

The polyepoxide compound may be partially reacted with, for example, a polyol, a polyether polyol, a polyester polyol, a polyacid amine, a polycarboxylic acid, a polyisocyanate compound, and the like. Further, ε-caprolactone, It may be obtained by graft polymerization of an acrylic monomer or the like.

The method for introducing the hydrolyzable alkoxysilane group into the epoxy resin-amine adduct as described above is not particularly limited, and the type of the hydrolyzable alkoxysilane group to be introduced by a method known per se. Although it can be arbitrarily selected according to the method, it is preferable to adopt a method that does not generate by-products such as water-soluble salts that adversely affect the 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 the amine compound that can be used here include the following compounds.

[0016]

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(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.

[0018]

Embedded image (3) Method of adding an alkoxysilane group-containing epoxy compound to an amino group in a base resin: The following compounds are exemplified as epoxy compounds that can be used here.

[0019]

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(4) Method of adding an alkoxysilane group-containing isocyanate compound to a hydroxyl group or an amino group in the base resin: The following formulas are exemplified as the isocyanate compound that can be used here.

[0021]

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In each of the above formulas, R can be exemplified as follows:

[0023]

Embedded image _{(i) -CH 3, -C 2} H 5, -C 3 H 7, -C 4 H
_9, an alcohol residue such as _{-C 6 H 13, -C 8 H} 17;

[0024]

Embedded image _{(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, -C
Ether alcohol residue, such as _{2 H 4 OC 2 H 4 OC} 4 H 9;

[0025]

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[0026]

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[0027]

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[0028]

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In the above formula, R having a smaller number of carbon atoms is more liable to be hydrolyzed. However, R having a carbon number of about 2 to 7 is advantageous in terms of balance because it is easily condensed after hydrolysis and has poor stability in an aqueous system. . Moreover, you may balance by combining what has a carbon number 2 or less and what has a carbon number more than 7.

The amount of the hydrolyzable alkoxysilane group introduced into the epoxy resin-amine adduct as described above is not particularly limited, but is usually an alkoxysilane equivalent (converted to one alkoxysilane group). Molecular weight)
Is 500 to 200,000, preferably 1,000 to 4
0000, more preferably 2,000 to 20,000
It is appropriate to choose so as to be within the range of 0.

In the present invention, a pigment-dispersed paste is produced by adding the above-mentioned epoxy resin amine-containing adduct containing a hydrolyzable alkoxysilane group at the time of dispersing the pigment, and dispersing and mixing with the pigment and the dispersing resin. Can be.
These dispersions can be performed in a conventionally known manner,
Specifically, a pigment, a dispersing resin, and an epoxy resin amine adduct containing a hydrolyzable alkoxysilane group, if necessary, together with a paint additive such as a neutralizing agent, etc., and a dispersion mixer such as a ball mill. It can be prepared in the form of a paste by dispersing in water.

As the above-mentioned pigments, any pigment can be used without particular limitation as long as it is a pigment usually used for an electrodeposition paint. For example, titanium white, carbon black, red iron,
Color pigments such as graphite; extenders such as talc, clay, mica, calcium carbonate, silica, and barita; strontium chromate, zinc chromate, basic lead silicate,
Rust prevention pigments such as lead chromate are exemplified.

As the above-mentioned dispersing resin, those listed as base resin components for a cationic electrodeposition paint described later can be used. In particular, they are epoxy tertiary amine type, epoxy quaternary ammonium salt type, It is suitable to use as an acrylic quaternary ammonium salt type resin.

The amount of the epoxy resin amine adduct containing a hydrolyzable alkoxysilane group added during the production of the pigment dispersion paste is 1 to 35% by weight, preferably 2 to 35% by weight, based on the total resin solids in the electrodeposition paint. It is desirable to adjust so as to be within the range of 15% by weight. When the addition amount is less than 1% by weight, the effect of controlling the decrease in the melt viscosity of the coating film during baking of the electrodeposition coating film is small, and the edge coverage of the electrodeposition coating film tends to be insufficient. If it exceeds, the smoothness of the electrodeposition coating film tends to be inferior.

According to the present invention, there is provided a cationic electrodeposition coating composition comprising the pigment-dispersed paste produced as described above. In the cationic electrodeposition coating composition, the components other than the pigment dispersion paste are not particularly limited, and may be the same as the usual cationic electrodeposition coating composition.

The cationic electrodeposition coating composition of the present invention comprises, as a base resin component, a resin usually used in a cationic electrodeposition coating, for example, a polyamine resin represented by an amine-added epoxy resin, for example, the above-mentioned hydrolyzable alkoxy resin. It may contain an epoxy resin-amine adduct as described in the description of the epoxy resin-amine adduct containing a silane group.

In the case where good weather resistance is required for a cured coating film formed using the composition of the present invention,
An amino group-containing acrylic resin or a nonionic acrylic resin having excellent weather resistance is used alone, or it is convenient to use it in combination with the amine-added epoxy resin.

The above amine-added epoxy resin can be cured, if necessary, using a polyisocyanate compound blocked with an alcohol or the like.

Further, an amine-added epoxy resin which can be cured without using a blocked isocyanate compound can also be used. For example, a resin in which a β-hydroxyalkyl carbamate group is introduced into a polyepoxide substance (for example, JP-A-59-1984) A resin which can be cured by transesterification (see, for example, JP-A-55-80436) can also be used.

Preparation of the cationic aqueous solution or aqueous dispersion of the cationic electrodeposition coating resin is usually carried out 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 a water dispersing treatment, whereby a cationic electrodeposition resin emulsion is obtained.

The cationic electrodeposition coating composition of the present invention can be prepared by mixing the above-mentioned cationic electrodeposition resin emulsion with the pigment dispersion paste. The cationic electrodeposition coating composition of the present invention may optionally contain paint additives such as an organic solvent, a curing catalyst, a pigment dispersant, and a coating surface adjuster.

The cationic electrodeposition coating composition of the present invention can be applied to a desired substrate surface by cationic electrodeposition coating. The cationic electrodeposition is carried out according to a method known per se, and 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 further adjusted to 5.5 to 5.5% by weight.
The electrodeposition bath comprising the cationic electrodeposition coating composition of the present invention adjusted to a range of 8.0 is usually adjusted to a bath temperature of 15 to 35 ° C., and the object to be coated is subjected to a cathode under the condition of a load voltage of 100 to 400 V. Can be performed as

The film thickness of the electrodeposition coating that can be formed using the coating composition of the present invention is not particularly limited, but is generally preferably in the range of 10 to 40 μm based on the cured coating film. The baking and curing temperature of the coating film is generally 100 to 2
A temperature in the range of 00 ° C is suitable.

[0044]

According to the present invention, a pigment dispersion paste containing an epoxy resin-amine adduct containing a hydrolyzable alkoxysilane group is blended into a cationic electrodeposition paint to adsorb it on the pigment. The applied resin acts as a flow control agent at the time of baking of the electrodeposition coating film, and exhibits excellent cissing prevention effect, surface smoothness, edge covering effect, and the like. It is considered that the above effect is obtained in the present invention because a crosslinking reaction occurs before the resin adsorbed on the pigment heat-flows at the time of baking of the electrodeposition coating film, so that a decrease in melt viscosity can be controlled.

The cationic electrodeposition coating composition of the present invention has good bath stability and electrodeposition properties, and also has excellent edge cover properties as a result of suppressing a decrease in viscosity of the coating film during heat curing. It is possible to improve the rust-preventive properties of the part and to form a coating film having good smoothness on the coated surface.

[0046]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. In Examples and Comparative Examples, “parts” and “%” indicate “parts by weight” and “% by weight”, respectively.

Contains a hydrolyzable alkoxysilane group
The epoxy resin amine adduct containing Production Example 1 hydrolyzable alkoxysilane groups in the epoxy resin amine adduct prepared in the following formulation.

Raw material parts by weight Epon 828EL ¹⁾ 1045 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 (oil) Note 2) γ-aminopropyltriethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) Blowing nitrogen gas into a reaction vessel equipped with a thermometer, stirrer, reflux condenser and nitrogen gas inlet In Epon 8
28EL, bisphenol A and diethanolamine are charged and heated to 120 ° C. until the epoxy equivalent ³⁾ reaches the theoretical value (317). Thereafter, the mixture was cooled to 80 ° C., and KBE-903 and diethanolamine were added.
The reaction is continued until the tertiary amine value ⁴⁾ reaches the theoretical value (102). Thereafter, the mixture was diluted with ethylene glycol monobutyl ether to obtain an ethylene glycol monobutyl ether solution (I) having a 70% solid content of an epoxy resin-amine adduct containing a hydrolyzable alkoxysilane group having a number average molecular weight of about 1650.

Note 3) Based on JIS K-7236. However, amino groups are also included as epoxy groups.

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

Production Example 2 An epoxy resin-amine adduct containing a hydrolyzable alkoxysilane group is produced with the following composition.

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 solution of ketimine in 74% by weight of monoethanolamine and methyl isobutyl ketone in methyl isobutyl ketone.

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

Note 8) γ-glycidoxypropylmethyldiethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) 160 parts of Epon 828EL, bisphenol A and amine A were charged into the same reactor as in Production Example 1 while blowing nitrogen gas. ℃, epoxy equivalent is theoretical value (694)
React until reaching. Thereafter, the mixture is cooled to 100 ° C., amine A and amine B are added, and the mixture is reacted until the tertiary amine value reaches the theoretical value (97). Then 100 ° C
Then, deketimination reaction is carried out by adding deionized water, and then KBE-402 is added at 100 ° C. until the epoxy group disappears. After that, the mixture was diluted with ethylene glycol monobutyl ether to obtain a number average molecular weight of about 19
Thus, a solution (II) having a solid content of 70% of an epoxy resin amine adduct containing a hydrolyzable alkoxysilane group of 00 was obtained.

Production of Pigment Dispersion Paste Each of the components shown in Table 1 below was added to a ball mill and subjected to dispersion treatment for 40 hours to obtain Pigment Pastes A to D having a solid content of 43%. In the table, the compounding amount of the resin is represented by solid content.

[0056]

[Table 1]

Production of Cationic Electrocoating Composition Example 1 572 parts of a cationic electrocoating clear emulsion composed of a polyamide-modified epoxy resin and a completely blocked diisocyanate and having a solid content of 35% (trade name: Electron 9450, manufactured by Kansai Paint Co., Ltd.) 43% of solid content obtained above
Was added with stirring, and diluted with 605.4 parts of deionized water to obtain a cationic electrodeposition paint.

Examples 2 and 3 and Comparative Example 1 A cationic electrodeposition paint was obtained in the same manner as in Example 1, except that pigment pastes B, C and D were used as the pigment paste, respectively.

Example 4 632 parts of a clear emulsion for cationic electrodeposition (Electron 9600, manufactured by Kansai Paint Co., Ltd.) consisting of a polyester-modified epoxy resin, a completely blocked diisocyanate and a nonionic acrylic resin and having a solid content of 32% was added to 626 parts of the above. Pigment paste A153 having a solid content of 43% was obtained.
Five parts were added with stirring, and diluted with 552 parts of deionized water to obtain a cationic electrodeposition paint.

Examples 5 and 6 and Comparative Example 2 A cationic electrodeposition paint was obtained in the same manner as in Example 4, except that pigment pastes B, C and D were used as the pigment paste.

Test Example (Electrodeposition Test) In the cationic electrodeposition coatings obtained in Examples 1 to 6 and Comparative Examples 1 and 2, Pearl Bond # 3030 (Zinc phosphate type, manufactured by Nippon Parkerizing Co., Ltd.) was used. 0.8 × 3 with chemical treatment
A cold rolled steel sheet of 00 × 90 mm (the angle between the end face and the flat portion was 45 °) was immersed, and electrodeposition coating was performed using the cold cathode steel sheet as a cathode. The conditions of electrodeposition coating were as follows: bath temperature of electrodeposition paint 30 ° C, pH
An electrodeposition coating film having a voltage of 300 V and a voltage of 300 V and a thickness (based on the dry film thickness) of 20 μm was formed. After the electrodeposition, the coating film was washed with water and baked at 185 ° C. for 20 minutes. The performance test results of this coated plate are shown in Table 1 below. Table 1 also shows the measurement results of the viscosity of the coating solution.

Performance Test Method (* 1) Melt Viscosity of Coating Film
-Z-0237) and evaluated from the heat fluid appearance of the scratch mark. The numerical values indicate the lowest viscosity (centipoise).

(* 2) End surface coverage Under the condition that the cured film thickness of the flat portion is 20 μm, a steel plate having an edge portion angle of 45 ° is electrodeposited and cured under predetermined baking conditions to prepare a test plate. . Set to the salt spray device so that the edge of the test plate is vertical, and JIS-Z
The corrosion resistance of the edge portion after 168 hours is evaluated by a -2371 salt water film test.

A: No rust was generated. A: Rust was slightly generated. X: Rust was significantly generated.

A: Good B: Almost good C: Slightly poor (* 4) Impact resistance Performed in an atmosphere of 20 ° C. in accordance with JIS-K-5400 8.3.2-1990. Weight 500g,
The maximum height at which the coating radius does not cause damage under the condition that the tip radius of the hammer is 1/2 inch is shown (cm). 50 cm was the highest value.

(* 5) Chipping resistance The baking electrodeposition plate is further coated with a thermosetting intermediate coating material and a top coating material and subjected to the following test with respect to a cured product obtained by heating.

Test equipment: QGR Graperometer (Q panel company product) Blowing stone: Crushed stone with a diameter of about 15 to 20 m / m Blowing stone volume: about 500 ml Blowing air pressure: about 4 kg / cm ² during the test of temperature: about 20 ° C. specimen mounted on specimen holder, after allowed fired crushed rock about 500ml in spraying air pressure of about 4 kg / cm ² on the test piece, the coated surface state evaluated. The state of the painted surface is visually observed and evaluated according to the following criteria.

(Evaluation) （(good): Slight scratches due to impact were observed in a part of the top coat, and no peeling of the electrodeposited coat was observed.

（(Slightly poor): scratches due to impact were observed in the overcoated and intermediate coating films, and peeling of the electrodeposited coating film was slightly observed.

△ (poor): Many scratches due to impact were observed in the top coat and the intermediate coat, and peeling of the electrodeposited coat was also considerably observed.

(* 6) Secondary adhesion in hot water After immersion in water at 40 ° C. for 20 days, JIS-K-540
0 8.5-2. According to 8.5.2-1990, the coating film is provided with a crepe, and an adhesive cellophane tape is adhered to the surface thereof, and the coated surface after being rapidly removed is evaluated.

：: Good without any abnormality △: Slight peeling of the edge of the gobang ×: Partially peeling of the gobang (* 7) Salt water spray resistance Crossed the electrodeposition coating film with a knife so as to reach the substrate A cut flaw was inserted, and this was cut into 100 according to JIS-Z-2371.
A 0 hour salt spray test is performed to measure rust from knife scratches and blister width.

(* 8) Two-coat weather resistance An amino alkyd resin paint Amiratkuya (manufactured by Kansai Paint Co., Ltd.) was further coated on the electrodeposition-coated plate at 35 μm, and baked at 140 ° C. for 15 minutes. The coated plate is placed on a sunshine weatherometer for 20 hours and placed in water at 40 ° C.
After soaking for 0 hours, a cross cut is made on the coated plate, and a peeling test is performed with a cellophane adhesive tape. This test was repeated to examine the time at which peeling occurred.

[0074]

[Table 2]

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Jiro Nagaoka 4-171-1, Higashi-Hachiman, Hiratsuka-shi, Kanagawa Inside Kansai Paint Co., Ltd. (58) Field surveyed (Int. Cl. ⁷ , DB name) C09D 5/44

Claims (1)

(57) [Claims] 1. A pigment dispersion paste obtained by dispersing and mixing an epoxy resin-amine adduct containing a hydrolyzable alkoxysilane group together with a pigment and a dispersing resin in an aqueous medium, and a cationic electrodeposition resin emulsion. comprise Ri name et containing hydrolyzable alkoxysilane groups
The oxy resin-amine adduct was added to all resin solids in the coating composition.
Based on the solid content, the cationic electrodeposition coating composition characterized that you containing in the range of 2 to 15 wt%.