JPH06340832A - Electrodeposition coating composition - Google Patents

Abstract

PURPOSE:To obtain an electrodeposition coating compsn. excellent in pigment sedimentation inhibition and capable of forming a coating film excellent in surface finish and chipping resistance by using a specific amt. of a high-purity spherical amorphous silica powder in an electrodeposition coating. CONSTITUTION:An electrodeposition coating material in an amt. of 100 pts.wt. in terms of resin solids is blended with 0.1-40 pts.wt. high-purity spherical amorphous silica powder obtd., e.g. by cooling a silicon oxide vapor formed by burning a metallic silicon powder. The electrodeposition coating material is pref. cationic. If necessary, it may be blended with a curing agent, a pigment, a curing catalyst, an org. solvent, a pigment-dispersed resin, a coating surface modifier, etc., in addition to the silica powder. The pigment is usually titanium white and/or a rust-proofing pigment, and if necessary, other pigment in combination. The total amt. of the pigments including the silica powder is pref. at most 50 pts.wt. per 100 pts.wt. resin solids.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an electrodeposition coating composition containing spherical high-purity amorphous silica powder, which is capable of forming a coating film having excellent pigment settling-preventing property, coating surface finish and chipping resistance. Regarding things.

[0002]

2. Description of the Related Art Electrodeposition paints can form a coating film having excellent throwing power and rust-prevention property, so that it is suitable for coating members having many bag structures, such as automobiles and electric appliances. Widely used in practice.

Generally, electrodeposition paints are mixed with a large amount of rust preventive pigments, titanium white, etc. for the purpose of sufficient anticorrosion effect and improvement of coating film physical properties, but these pigments have a large specific gravity in the paint. There is a problem that the control of the electrodeposition bath is difficult because it easily settles, and there is also a problem that the effect of rust prevention gradually decreases. Further, since pigment settling occurs in the horizontal part of the object to be coated during electrodeposition coating, there is a problem that the coating film has defects such as rough skin and uneven coating.

In order to prevent the pigmentation of the electrodeposition paint, it is common to add fine synthetic silica powder by a conventionally known dry method, wet method, gelation of silicic acid or the like to impart thixotropic property to the paint. However, in order to sufficiently exert the prevention of sedimentation of the large specific gravity pigment, a large amount of fine silica powder is required, and as a result, the gloss of the electrodeposition coating film is reduced, and the surface is rough due to a decrease in heat fluidity, There are problems that coating film defects such as the escape of hydrogen gas during electrodeposition coating, deterioration of coating film physical properties, and pigment dispersibility decrease.

Further, in recent years, in the automobile industry field, there is an increasing demand for improvement of durability in a corrosive environment of a vehicle body outer panel (for example, rock salt spraying in a cold region). That is, when rock salt particles or pebbles collide with the coating film surface of the vehicle body when the vehicle is running, there is a problem that the coating film peels off, so-called chipping occurs, and especially in a low temperature environment, the coating film becomes hard and loses elasticity. Since the impact cannot be alleviated and the above-mentioned peeling is likely to occur, there is an urgent need to consider measures against chipping in a low temperature environment.

As a countermeasure against this, the present applicant has proposed a coating method in which an electrodeposition coating is applied to an object to be coated, a chipping sealer having a low static glass transition temperature is applied, and then an ordinary intermediate coating and top coating are applied ( For example, JP-A-62-65765). The coating thickness of this chipping sealer is 3 to 10
μm is a preferable range, and if it is less than this range, the effect of chipping resistance cannot be expected so much, and if it is more than this range, the finished appearance after top-coating tends to be deteriorated. However, in the spray coating method which is usually used, it is difficult to control the film thickness, and there is a problem in dealing with the mass production coating line. Further, increasing the number of steps for applying the chipping sealer to the conventional coating step is a reverse step from the viewpoint of saving steps, and is not economically preferable.

[0007]

Therefore, the inventors of the present invention have earnestly studied to obtain an electrodeposition coating composition which is capable of forming a coating film having excellent pigment settling-preventing property, coating surface finish and chipping resistance. As a result, by using spherical high-purity amorphous silica powder in the electrodeposition coating, it is possible to prevent sedimentation of titanium white and rust-preventive pigments in the electrodeposition coating bath, and to prevent horizontal and vertical portions of the coated object. The inventors have found that there is almost no difference in the smoothness of the coating film and that a coating film having excellent coating surface finish and chipping resistance can be formed, thus completing the present invention.

That is, the present invention relates to an electrodeposition coating composition characterized by containing spherical high-purity amorphous silica powder in the electrodeposition coating.

The spherical high-purity amorphous silica powder used in the present invention (hereinafter abbreviated as "spherical silica powder") may be spherical high-purity amorphous silica fine powder containing 98% or more of silica. For example, it can be obtained by cooling vapor silicon oxide generated by burning metal silicon powder (Japanese Patent Laid-Open No. 60-255).
No. 602, JP-A-2-289404, JP-A-3-17
0319).

In this production method, the particle size of the silica powder obtained by controlling the combustion and cooling conditions can be changed as appropriate, and the particle size is usually 0.01 micron to 10 micron. It is possible to obtain spherical fine particles having a uniform shape.

The specific gravity of the spherical silica powder is not particularly limited, but it is possible that the rust preventive pigment component in the paint settles on the horizontal portion of the object to be coated and causes defects such as rough skin on the coating film. From the viewpoint of prevention, 3.0 g / cm ³ or less, further 2.0 to
It is preferable that the specific gravity is in the range of 2.8 g / cm ³ ,
The average particle size is 10 μm or less, preferably 0. 0, from the viewpoints of bath control, coating finish and pigment dispersibility of the electrodeposition paint.
Suitably the range is from 1 to 1.0 micron. The oil absorption is usually 10 to 50 ml / 100 g, preferably 15 to 35 ml / 100 g. The spherical silica powder is spherical and has a uniform shape and is extremely excellent in pigment dispersibility, as compared with conventional ground silica powder.

In the present invention, the electrodeposition coating containing the above-mentioned spherical silica powder can be electrodeposition coated, and conventionally known anion type and cation type electrodeposition coatings can be used. .

As the film-forming resin component of such an electrodeposition paint, in the case of an anion type, an anionic resin having a carboxyl group can be mentioned. This resin is caustic soda,
It is used after being neutralized with a neutralizing agent which is a base such as caustic potash, ammonia and amine, and dispersed or dissolved in water. Examples of the anionic resin include maleated polybutadiene, carboxyl group-containing oil-modified epoxy ester resin,
Examples thereof include a carboxyl group-containing acrylic resin and a carboxyl group-containing alkyd resin.

Further, as the film forming resin component in the case of the cationic electrocoating material, a cationic resin having an amino group may be mentioned. This resin is an acid such as hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid, propionic acid or lactic acid. It is used after being neutralized with a neutralizing agent, and dispersed or dissolved in water. Examples of the above-mentioned cationic resin include amine-added epoxy resins, polyamide-modified epoxy resins, polyester-modified epoxy-amine addition resins, amino group-containing polyptadiene resins, amino group-containing acrylic resins and the like.

In the present invention, as the electrodeposition paint, a cationic type is generally preferable because it is excellent in corrosion resistance.

In the present invention, an amino resin, depending on the functional group of the anionic resin or the cationic resin,
It is preferable to add a curing agent such as polyisocyanate.

In the electrodeposition coating composition of the present invention, in addition to water, a neutralizing agent, a film-forming resin component and spherical silica powder, if necessary, the above curing agent, a pigment, a curing catalyst, an organic solvent, A pigment-dispersed resin, a coating surface adjusting agent and the like can be added.

As the above-mentioned pigment, a pigment which has been generally used as a pigment for electrodeposition paints can be used.
Titanium white and / or rust preventive pigments and, if necessary, other pigments are used in combination.

Examples of the rust preventive pigment include lead silicate, zinc chromate, strontium chromate, lead hydroxide and aluminum tripolyphosphate. Further, as the above-mentioned other pigments, coloring pigments such as carbon black; clay,
Examples include extender pigments such as talc, calcium carbonate, barium sulfate, and aluminum silicate.

In the present invention, even if a pigment having a high specific gravity such as titanium white and / or a rust preventive pigment is blended in the electrodeposition coating composition, since the spherical silica powder is blended, the pigment precipitation can be prevented. It is possible to obtain a coating film having good coating surface finish properties and no coating film defects such as rough skin, uneven coating, and hydrogen gas escape, and good coating film properties.

In the present invention, the content of the spherical silica powder is 100 parts by weight of the resin solid content of the electrodeposition coating material.
It is 0.1 to 40 parts by weight. If the compounding amount of the spherical silica powder is less than 0.1 part by weight, the effect due to the compounding is not sufficient, while if it exceeds 40 parts by weight, the coating surface finish property, coating film physical properties, chipping resistance and the like are deteriorated. Further, from the viewpoint of chipping resistance, the amount of the spherical silica powder is 0.1 to 35 parts by weight, more preferably 5 to 30 parts by weight, based on 100 parts by weight of the resin solid content of the electrodeposition coating material. The total amount of pigment including powder is preferably 50 parts by weight or less, and more preferably 40 parts by weight or less.

In the method for coating the electrodeposition coating composition of the present invention, when the composition is a cation type, the material to be coated is used as a cathode and the counter electrode such as stainless steel or carbon is used as an anode for electrodeposition coating. On the other hand, when the composition is an anionic type, electrodeposition coating is performed using the article to be coated as the anode and the counter electrode as the cathode. The electrodeposition coating is usually performed at a bath temperature of 15 ° C to 35 ° C and a coating voltage of 50 to 400 V, and usually for 1 minute to 20 minutes. The electrodeposition-coated object is washed with water and then usually 150 to 20.
Heating is performed at 0 ° C. for 5 to 60 minutes to form a cured coating film.

[0023]

EFFECTS OF THE INVENTION In the electrodeposition coating composition of the present invention, since the spherical silica powder to be blended is a spherical fine powder, the oil absorption is lower than that of ground silica powder, and the pigment itself can be incorporated into the resin. The dispersibility is good, and even if it is added in a large amount, it can be added in a large amount because the deterioration of the coating film physical properties is small, and the reason is not clear, but it effectively prevents the precipitation of titanium white or anticorrosion pigment. Therefore, bath management is facilitated, and an electrodeposition coating film having a good coating surface finish can be stably formed.

The chipping resistance of the electrodeposition coating film generally tends to become worse as the pigment content increases, but when spherical silica powder is blended in the present invention, titanium white, ground silica, clay, talc, etc. are blended. Compared with the above case, the decrease in chipping resistance with respect to the increase in the compounding amount is very small, and when compared with the same pigment amount, an electrodeposition coating film having extremely good chipping resistance can be obtained. Further, even if a large amount of spherical silica powder is blended, it is possible to form an electrodeposition coating film having a good coating surface finish as described above.

[0025]

EXAMPLES The present invention will be described more specifically with reference to Examples and Comparative Examples below. In the following, "parts" and "%" indicate "parts by weight" and "% by weight".

Example 1 315 parts of "Electron 2000 clear" (solid content 35%, thermosetting water-borne polyamide modified epoxy polyamino resin-blocked isocyanate type cationic electrodeposition coating resin clear) manufactured by Kansai Paint Co., Ltd. was put in a high-speed stirrer. A pigment paste having a composition (part) shown in Table 1 obtained by dispersing glass beads as a dispersion media for 3 hours was added, and the mixture was stirred at a low speed for 15 minutes and then diluted with deionized water to obtain a cationic type having a nonvolatile content of 20%. An electrodeposition coating composition was prepared.

Examples 2 to 9 and Comparative Examples 1 to 8 In Example 1, the pigment paste formulation (parts) is shown in Table 1 below.
Each cation-type electrodeposition coating composition was prepared in the same manner as in Example 1 except that the composition shown in each example was used.

An object to be coated at the cathode portion (a cold-rolled zinc phosphate-treated steel sheet having a thickness of 0.8 mm) horizontally set in the bath of the cationic electrodeposition coating obtained in each of the above examples, and a stainless steel plate serving as the anode portion Between the electrodes with an applied voltage of 250 V for 3 to 4 minutes,
An electrodeposition coating film having a dry film thickness of about 20 μm was obtained. Then, excess paint was removed by washing with water and then baked at 170 ° C. for 30 minutes.

The obtained baked electrodeposition coated plate was tested for electrodeposition coating finish, impact resistance, corrosion resistance and chipping resistance. The pigment particles used in each of the examples and comparative examples, which were obtained by dispersing glass beads with a high-speed stirrer for 3 hours as a dispersion media, were examined for dispersed particles. Furthermore, the pigment precipitation properties of the electrodeposition coatings obtained in each example were also investigated. The test results are shown in Table 1 below.

The tests in Table 1 were carried out according to the following test methods.

Pigment settling property of electrodeposition paint: 2.5 l of paint was placed in a 3 l square polyvinyl chloride container, allowed to stand for 5 hours, and then stirred with a stirrer for 5 minutes at a rotation speed of 120 rpm. The sedimentation state of the pigment at the bottom of the container was visually evaluated.

◯: Almost no sediment, ×: a large amount of sediment remained, and the sediment was hard.

Finishing property of the electrodeposition coating film: The state of the coating surface of the electrodeposition coating film in the horizontal portion was visually evaluated.

⊚: No abnormality, ◯: Slight shine was observed, Δ: Slight sensation was observed, X: Species and shine were noticeable.

Impact resistance: JIS K5400 8.3.
According to the DuPont type impact resistance test of 2 (1990), the test was conducted with the weight of the falling weight of 1 kg and the tip diameter of the wick of 1/2 inch, with the coated surface facing upward, and the coating film showed cracks or peeling. The minimum height of falling weight is displayed.

Corrosion resistance: A cross cut is put on the coated surface and JI
A salt spray test according to S Z 2371 was carried out for 240 hours. When the rust width on one side of the cross-cut of the coated plate at that time was 2 mm or less, it was evaluated as ◯ (good).

Chipping resistance: Preparation of test coated plate; baked Electrodeposited coated plate was coated with amino alkyd intermediate coating [Kansai Paint Co., Ltd., "Amilac TP37 sealer"] to a film thickness of 25-35.
It was coated so as to have a thickness of μm, and heated at 140 ° C. for 30 minutes to be cured. Further, a top coat paint was applied to the surface coated with the intermediate coat. This topcoat is "Neo Amillac # 6000"
[Kansai Paint Co., Ltd., amino alkyd paint] was applied to a cured film thickness of 30 to 40 μm, and 1
A test coated plate was obtained by baking at 40 ° C. for 30 minutes to cure.

Chipping resistance test condition: No. 7 crushed stone 5 using Q-G-R-gravel meter (product of Q panel company)
Crushed stones were blown onto the test coated plate to give an impact to the coated film under the conditions of an air pressure of 4 kg / cm ² and a temperature of −20 ° C. Then, an adhesive gum tape was adhered to this coating film, which was rapidly peeled off, and then the appearance of the coating film was visually evaluated.

⊚ (very good): A scratch on a part of the top coating film, or very little peeling between the top coating film and the intermediate coating film or between the intermediate coating film and the electrodeposition coating film. It was observed, but no peeling of the electrodeposition coating film was observed.

◯ (Good): Some peeling was observed between the top coating film and the intermediate coating film or between the intermediate coating film and the electrodeposition coating film,
A slight peeling of the electrodeposition coating film is observed.

Δ (Poor): A large amount of peeling was observed between the overcoat coating film and the intermediate coating film or between the intermediate coating film and the electrodeposition coating film, and considerable peeling of the electrodeposition coating film was also observed.

[0042]

[Table 1]

[0043]

[Table 2]

(Note) in Table 1 is as follows.

(Note 1) Admafine SO-25R:
Spherical high-purity amorphous silica powder manufactured by Admatechs Co., Ltd., SiO ₂ purity 99.8%, average particle size 0.5 μ.
m, specific gravity by Beckmann method 2.36, oil absorption 26 ml /
100 g.

(Note 2) Admafine SO-25H:
Spherical high-purity amorphous silica powder manufactured by Admatechs Co., Ltd., SiO ₂ purity 99.99%, average particle size 0.5.
μm, Beckman method specific gravity 2.34, oil absorption 24ml
/ 100g.

(Note 3) Syloid 244: Synthetic silica manufactured by Fuji Davison Chemical Co., Ltd., obtained by gelation of silicic acid, and has a highly porous network structure in which primary particles are three-dimensionally connected by chemical bonds. Average particle size 3.5μm, oil absorption 300ml / 100g.

Front page continuation (72) Inventor Abe No. 1 Toyota-cho, Toyota-cho, Aichi Prefecture, inside Admatex Co., Ltd. (72) Inventor Masafumi Kume 4-17-1, Higashi-Hachiman, Hiratsuka-shi, Kanagawa Kansai Paint Co., Ltd.

Claims (5)

[Claims] 1. A spherical high-purity amorphous silica powder in an amount of 0.1 to 40 relative to 100 parts by weight of a resin solid content of an electrodeposition coating composition.
An electrodeposition coating composition, characterized in that it contains a part by weight. 2. The electrodeposition coating composition according to claim 1, wherein the spherical high-purity amorphous silica powder is a silica powder obtained by cooling vapor silicon oxide produced by burning metallic silicon powder. . 3. The electrodeposition coating composition according to claim 1 or 2, wherein the electrodeposition coating is a cationic type electrodeposition coating. 4. The electrodeposition coating composition contains, in addition to spherical high-purity amorphous silica powder, titanium white and / or rust preventive pigment as a pigment component and, if necessary, other pigments. The electrodeposition coating composition according to 2 or 3. 5. The content of spherical high-purity amorphous silica powder is 0.
5. The total pigment amount including the spherical high-purity amorphous silica powder is 50 parts by weight or less.
The electrodeposition coating composition described.