JPH1036718A - Electrodeposition coating composition and method for producing the same - Google Patents

Abstract

(57) [Problem] To provide an electrodeposition coating composition from which an electrodeposition coating film having good weather resistance and workability and having a high matting effect can be obtained. A resin having a carboxyl group and an alkoxysilane compound having a resin solid content of 1.5% by weight or more and / or
Alternatively, an electrodeposition coating composition containing the hydrolyzate thereof is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrodeposition coating composition, and more specifically, it comprises (a) a resin having a carboxyl group and (b) an alkoxysilane compound and / or a hydrolyzate thereof. The present invention relates to an electrodeposition coating composition wherein the content of the alkoxysilane compound and / or its hydrolyzate is 1.5% by weight or more of the solid content of the resin having the carboxyl group (a).

[0002]

2. Description of the Related Art Hitherto, many methods have been proposed for obtaining a matte electrodeposition coating film. For example, (1)
A method of washing the electrodeposited film with a cationic surfactant (see Japanese Patent Publication No. 48-4447), and a method of treating the electrodeposited film with an alcohol solution or an alcohol-containing aqueous solution (Japanese Patent Publication No. 46-22351). (3) a method of treating an electrodeposited coating film before baking with an aqueous solution of an organic acid or an inorganic acid (see JP-A-52-137444-6), and (4) an electrodeposition coating before baking. A method of treating the membrane with hot water or steam (Japanese Patent Publication No. 47-
A method is known in the art.

However, in the method of performing some treatment after forming the electrodeposition coating film, a sufficient matting effect cannot be obtained, or if the treatment liquid is not strictly controlled, the matting state varies from lot to lot, and Differences in texture, uneven matting, and mattness occur. In addition, since one step is added in the electrodeposition coating line, problems such as a decrease in work efficiency occur.

[0004] Further, as a method of obtaining a matte coating film in general coating, a method of dispersing a matting agent in a paint is widely practiced, and (5) a matting agent is added to an aqueous or water-soluble electrodeposition paint. (See JP-B-60-8318) and (6) a method of dispersing silica fine powder in an aqueous or water-soluble electrodeposition coating (see JP-B-60-8319). The application of was considered.

However, the method of dispersing the matting agent in the paint is liable to cause the matting agent to settle in the paint, and has a matting effect such as uneven matting state, difference in matte texture, and uneven matting. At present, there is a problem with the performance of the coating film, and operation on a practical scale has not yet been achieved.

[0006] When a matte coating film is formed by electrodeposition coating a paint in which a matting agent has been added and dispersed, (A) the change in the composition of the electrodeposition paint is small, (B) the appearance of the coating film, and (C) the coating film. Excellent performance (boiling water resistance, alkali resistance, acid resistance) and (D) excellent matting effect are required. However, in the method of adding and dispersing a matting agent, it is difficult to satisfy the above requirements (A), (B) and (C) because a third component different from the resin component is mixed.

In recent years, there has been proposed an invention in which a molecule having an alkoxysilane group in a side chain is introduced into a resin having a carboxyl group to form a microgel, thereby producing a matte effect (Japanese Patent Publication No. Sho 62-24519). ), The mainstream of matte electrodeposition paint. In this method, when a resin having a carboxyl group is produced for the purpose of introducing an alkoxysilane group into a side chain of the resin, an alkoxysilane compound of 2 to 7% by weight of a resin component is added.
An alkoxysilane group could not be introduced into a side chain of a resin molecule as expected, and there were problems such as not only necessity for devising the polymerization reaction of the resin but also adversely affecting the properties of the resin.

Further, even when an alkoxysilane group can be introduced into a side chain of a resin having a carboxyl group, the alkoxysilane group cannot sufficiently stabilize paint particles (resin molecules) forming a microgel. Was.

Further, attempts have been made to disperse the resin having a carboxyl group by adding a small amount (less than 1% by weight) of an alkoxysilane compound. Was not.

As described above, an electrodeposition coating film having good weather resistance, acid resistance, workability and high matting effect has not yet been obtained.

[0011]

Accordingly, there has been a demand for an electrodeposition coating composition which is excellent in weather resistance, acid resistance, workability, and provides an electrodeposition coating film having a high matting effect.

[0012]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object while making use of the characteristics of the resin having a carboxyl group. As a result, 1.5% by weight or more of the resin having a carboxyl group was obtained. It has been found that by including an alkoxysilane compound and / or a hydrolyzate thereof in an electrodeposition coating composition, an electrodeposition coating film having good weather resistance, acid resistance, workability and a high matting effect can be obtained. Invented the invention.

That is, the present invention provides (a) a resin having a carboxyl group, (b) an alkoxysilane compound and / or
Or a hydrolyzate thereof, wherein the content of the (b) alkoxysilane compound and / or its hydrolyzate is (a) 1.5% by weight of the solid content of the resin having a carboxyl group. % Or more.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The electrodeposition coating composition of the present invention contains an alkoxysilane compound and / or a hydrolyzate of 1.5% by weight or more of the solid content of a resin having a carboxyl group.

The alkoxysilane compound of the present invention is a compound having a Si-OR structure and / or a Si-OH structure in a molecule. Further, the alkoxysilane compound can be used as a partial hydrolyzate and / or a complete hydrolyzate. Further, it is also preferable to use silica fine particles as an auxiliary additive of the alkoxysilane compound and / or its hydrolyzate.

These alkoxysilane compounds include, for example, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane,
Examples include aminopropyltrimethoxysilane and aminopropyltriethoxysilane. When a silane compound having an epoxy group such as a γ-glycidoxyalkylalkoxysilane compound is used, a curing catalyst such as an aluminum chelate compound can be added.

In order to increase the hardness of the coating film surface, improve weather resistance and acid resistance, and reduce the defects of the coating film, it is necessary to silanolize some or all of the alkoxyl groups under acidic conditions. Preferably, silanol groups can be condensed by neutralizing the acid.

The condensation reaction of the silanol group can be performed before or after the addition to the resin having a carboxyl group.
When the silanol group is condensed before being added to the resin having a carboxyl group, the system is preferably acidified.
If the system is made basic before the addition, the mixing efficiency of the alkoxysilane compound and / or its hydrolyzate and the resin may be reduced.

It is preferable to use a part or all of an alkoxysilane compound having high compatibility with a resin having a carboxyl group, since a stable electrodeposition coating film can be obtained at an early stage after the production of the electrodeposition coating material. The siloxane bond (Si-O-Si) bond formed by the condensation reaction may be formed from an alkoxysilane compound, but preferably, the surface of the silica fine particles is treated with the alkoxysilane compound in the presence of a catalytic amount of an amine. And generate it. In this case, it is preferable to use silica fine particles of about 10 times the amount of the alkoxysilane compound.

The alkoxysilane compound and / or its hydrolyzate is contained in an amount of 1.5% by weight or more based on the resin solid content of the resin having a carboxyl group,
It is preferred that the content be contained by weight. When the content is 1.5% by weight or more, the resin molecules and the alkoxysilane compound and / or a hydrolyzate thereof form entanglement of molecular chains, and the paint particles are stabilized. On the other hand, if the amount exceeds 30 parts by weight, for example, the coating particles may be enlarged, the surface may be roughened at the time of coating film formation, and further, sedimentation may occur due to secondary aggregation.

Examples of the resin having a carboxyl group according to the present invention include a saturated or unsaturated alkyd resin and an oil-modified resin thereof, an acrylic polymer having a carboxyl group, a vinyl polymer, an acrylic vinyl copolymer, and a hydroxyl group-containing fluoropolymer. Examples thereof include a fluorinated polymer having a carboxyl group, such as one obtained by reacting a dibasic acid anhydride to introduce a carboxyl group, and a mixture thereof. Further, the resin having a carboxyl group of the present invention preferably has a number average molecular weight of 10,000.
-30000, acid value 5-200, hydroxyl value 1
0 to 200.

It is also possible to add an appropriate amount of a melamine resin to the resin having a carboxyl group to improve the boiling water resistance and alkali resistance of the electrodeposition coating film.

At the time of coating (dispersion in water), the electrodeposition composition of the present invention is preferably dispersed in water in the presence of an organic base. Organic bases improve emulsification and do not adversely affect coating performance. When neutralized with salts other than organic bases,
Even after thermal drying, salt remains in the coating film, and the coating film performance tends to deteriorate.

Further, at the time of coating (dispersion in water), it is preferable to add amines or ammonia in order to impart ionicity to the resin having a carboxyl group. In this case, 60% of the resin acid value of the resin having a carboxyl group
It is more preferable to add amines or ammonia corresponding to a neutralization of 90%. If the neutralization ratio is out of this range, the alkoxysilane compound and / or hydrolyzate thereof added to the resin during coating may not be separated from the resin or may not be well dispersed in water.

When an alkoxysilane compound and / or a hydrolyzate thereof, amines or ammonia is mixed with a resin having a carboxyl group, the temperature is from 0 ° C. to 100 ° C.
It is preferred to mix at a temperature of When the temperature is low, the dispersing efficiency of the alkoxysilane compound and / or its hydrolyzate, amines or ammonia in a resin having a carboxyl group decreases, and when the temperature is high, the alkoxysilane compound and / or its hydrolyzate , Amines or ammonia, and a resin having a carboxyl group may deteriorate.

After mixing the alkoxysilane compound and / or its hydrolyzate, amines or ammonia, and a resin having a carboxyl group, it is preferable to form a coating within one week immediately after mixing. If left for a long time after mixing, the paint particles at the time of forming the paint may undergo secondary aggregation and settle.

[0027]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto.

Example 1 At 25 ° C., γ-glycidoxypropyltrimethoxysilane (trade name: KBM-40) was used as an alkoxysilane compound.
3, 3 parts by weight of Shin-Etsu Chemical Co., Ltd.) and 0.1N HCl aqueous solution (0.1 ml per 1 g of the silane compound) were sufficiently mixed with a chemister. After mixing, triethylamine was gradually added to the mixture so that the system became weakly basic, and the mixture was allowed to stand for 1 hour. Acrylic resin (acid value 50.5, hydroxyl value 86.0, solid content 53.4% by weight, solvent composition normal butanol 18.3% by weight, isopropanol 28.3% by weight) 100% by solid weight
Parts by weight of the mixed solution, and after standing for 3 hours, triethylamine was added corresponding to 60% neutralization of the resin acid value, and deionized water was gradually added to prepare a stock solution for electrodeposition paint having a resin solid content of 30% by weight. .

Next, the dispersion was allowed to stand for 1 week immediately after mixing in a temperature range of 0 ° C. to 100 ° C., and then deionized water was gradually added to adjust the resin solid content to 10% by weight.

An anodized aluminum test plate (trade name: A6063S, manufactured by Nippon Test Panel Kogyo Co., Ltd.), which was anodized in the prepared paint, was held in a vertically suspended state, and this was used as an anode, and the coating thickness was 14 μm. The voltage was adjusted so as to obtain a DC current for 150 seconds. After painting, remove the test plate from the paint bath, drain for 90 seconds, wash with water,
Then, it was placed in a hot-air circulation oven and dried by heating at 180 ° C. for 30 minutes. Table 1 shows the weather resistance, acid resistance, and pencil hardness of the obtained electrodeposition coating film.

Example 2 An electrodeposition paint was prepared in the same manner as in Example 1 except that the amount of γ-glycidoxypropyltrimethoxysilane (trade name: KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.) was changed to 3 parts by weight. Adjust
The coating film performance was evaluated in the same manner as in Example 1. Performance is first
It is shown in the table.

Example 3 An electrodeposition paint was prepared in the same manner as in Example 1 except that the amount of γ-glycidoxypropyltrimethoxysilane (trade name: KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.) was changed to 30 parts by weight. Was adjusted, and the coating film performance was evaluated. The performance is shown in Table 1.

Example 4 At 25 ° C., 3 parts by weight of γ-glycidoxypropyltrimethoxysilane (trade name: KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.) and silica sol (trade name: Snowtex IPA-ST,
10 parts by weight of Nissan Chemical Co., Ltd. and 0.1N HCl aqueous solution (0.1 ml per 1 g of silane compound) were sufficiently mixed with a chemister stirrer.
A 10% by weight electrodeposition paint was prepared, and the coating film performance was evaluated in the same manner as in Example 1. The performance is shown in Table 1.

Example 5 An electrodeposition paint was prepared in the same manner as in Example 4 except that γ-glycidoxypropyltriethoxysilane (trade name: KBE-403, manufactured by Shin-Etsu Chemical Co., Ltd.) was used as the alkoxysilane compound. The coating film performance was evaluated in the same manner as in Example 1. The performance is shown in Table 1.

Example 6 A coating material for electrodeposition was prepared in the same manner as in Example 4 except that aminopropyltrimethoxysilane was used as the alkoxysilane compound, and the coating film performance was evaluated in the same manner as in Example 1. The performance is shown in Table 1.

Example 7 A coating material for electrodeposition was prepared in the same manner as in Example 4 except that aminopropyltriethoxysilane was used as the alkoxysilane compound, and the coating film performance was evaluated in the same manner as in Example 1. The performance is shown in Table 1.

Example 8 The same procedure as in Example 1 was carried out except that a melamine resin (trade name: Nikalac MX-57, manufactured by Sanwa Chemical Co.) was added simultaneously with triethylamine to prepare an electrodeposition paint. And the coating film performance was evaluated. The performance is shown in Table 1.

Comparative Example 1 The coating film performance was evaluated in the same manner as in Example 1 except that γ-glycidoxypropyltrimethoxysilane and 0.1N HCl aqueous solution were not mixed and neutralized with triethylamine. did. Table 1 shows the weather resistance, acid resistance, and pencil hardness of the obtained electrodeposition coating film.

Comparative Example 2 The coating film performance was evaluated in the same manner as in Example 4 except that γ-glycidoxypropyltrimethoxysilane was not mixed. Table 1 shows the weather resistance, acid resistance, and pencil hardness of the obtained electrodeposition coating film.

[0040]

[Table 1]

[0041]

The electrodeposition coating composition of the present invention is excellent in matting effect, weather resistance, and acid resistance, and is excellent in the hardness of the coating film surface without mixing a crosslinking agent such as melamine resin. Paint.

Claims (9)

[Claims] (1) a resin having a carboxyl group, and (b) a resin having a carboxyl group.
In an electrodeposition coating composition containing an alkoxysilane compound and / or a hydrolyzate thereof, the content of (b) the alkoxysilane compound and / or the hydrolyzate thereof is (a) the solid content of the resin having a carboxyl group. An electrodeposition coating composition characterized in that the content is 1.5% by weight or more. 2. The method according to claim 1, wherein the content of the (b) alkoxysilane compound and / or its hydrolyzate is 1.5 to 30% by weight of the solid content of the resin (a) having a carboxyl group. Item 7. The electrodeposition coating composition according to Item 1. 3. The electrodeposition coating composition according to claim 1, wherein the alkoxyl group of the (b) alkoxysilane compound and / or a hydrolyzate thereof is silanolized. 4. A resin having a carboxyl group (a) having a number average molecular weight of 10,000 to 30,000 and an acid value of 5
The electrodeposition coating composition according to claim 1, wherein the composition has a hydroxyl value of 10 to 200. 5. The electrodeposition coating composition according to claim 1, comprising (c) an amine or ammonia. 6. The electrodeposition coating composition according to claim 5, wherein (c) an amine or ammonia is contained in an amount equivalent to 60% to 90% neutralization of the resin acid value. 7. The electrodeposition coating composition according to claim 1, comprising silica fine particles. 8. A method for producing an electrodeposition coating composition, comprising dispersing the electrodeposition coating composition according to claim 1 in water in the presence of an organic base. 9. The electrodeposition coating composition according to claim 5,
A method for producing an electrodeposition paint, which comprises mixing at a temperature of from 100 ° C to 100 ° C.