JPS608319B2 - Method of forming matte electrodeposition coating film - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for forming a matte electrodeposited coating film.

For details, see ■ Equilibrium moisture content at 90% relative humidity is 20%.
Electrodeposition of a matte coating film-forming electrodeposition paint on a conductor by dispersing fine silica powder in an aqueous or water-soluble electrodeposition paint with the following conditions and: The present invention relates to a method for forming a matte electrodeposited coating film, which is characterized by coating. The open-deposition coating method uses water-based paint, so it has excellent fire safety, and it also has many advantages, such as mass production through automation and the ability to achieve a uniform coating film thickness. It has been used in many fields as an industrial painting method for over 10 years.

Evening However, the surface of the article obtained by Kameyuki coating is
Most of them are shiny.

However, recently there has been a demand for a matte type with a calm texture and poor gloss that does not peel off, especially in the field of one-coat finishing using lightning coating, such as building materials. Conventionally, many methods have been proposed for matting an exposed coating film.

For example, a method of cleaning a '11 electrodeposition coating film with a cationic surfactant (see Japanese Patent Publication No. 48-4447);
'2} A method of treating an electrodeposited coating film with an alcoholic acid solution or an alcohol-containing aqueous solution (see Japanese Patent Publication No. 46-22351), '31 Treating an electroplated coating film before baking with an aqueous solution of an organic acid or an inorganic acid. Method (Tsubaki Kaisho 52-137444
There are known methods such as '4) treating the lightning coated coating before brazing with hot water or heated steam containing or not containing an acid (see Japanese Patent Publication No. 47-51927). be. However, with these methods, which involve some kind of treatment after forming a tortoise coating, a sufficient matting effect may not be obtained, and if the treatment solution is not strictly controlled, the matte state may vary from lot to lot, and the matte texture may vary. There are problems such as differences in color, uneven matting, and loss of luster, and the addition of one step to the decoating coating line reduces work efficiency, so it has not yet been operated on a practical scale. This is the current situation. On the other hand, as a method for forming a matte coating film, a method of dispersing a matting agent in the paint is widely practiced in general painting, and its application has also been considered and has been conducted in decoat coating.

However, with this method, the matting agent tends to settle in the paint, making the haze-deposited paint unstable in continuous electrodeposition coating methods, and there are also problems with the matting effect and coating performance. At present, it is not put into practical use. When a koji matte coating is formed by lightning-coating a paint with a matting agent added and dispersed therein, there are few changes in the composition of the wind-electrodeposited coating, {b} coating appearance, 'c} coating performance (boiling water resistance, It is required to have excellent alkali resistance) and {d) matting effect. The technical problem of the present invention is to establish a method that satisfies all the conditions necessary for forming these matte electrodeposition coatings, and by selecting fine silica powder with specific characteristics as a matting agent, This was achieved by frost coating using an electrodeposition coating material for forming a matte coating film which is added and dispersed in the coating material.

In summary, the present invention is made by dispersing fine silica powder in a water-based or water-soluble electrodeposition paint, which has an equilibrium moisture content of 20% or less at a relative humidity of 90%, and a pH of the aqueous suspension of 5.5 or more. This is a method for forming a matte electrodeposition coating film, which is characterized in that the electrodeposition paint 3 for forming a matte coating film is electrodeposited onto a conductor. To explain the present invention in more detail, the paint used for mist coating contains a polycarboxylic acid resin and an amino resin as film-forming components.

4. As the polycarboxylic acid resin, use is made of one or a mixture of two or more of the above, such as saturated or unsaturated alkyd resins, oil modified products thereof, acrylic polymers having carboxyl groups, vinyl polymers, and acrylic vinyl copolymers. . This polycarboxylic acid resin is
At least a portion of the carboxyl group is neutralized with an organic amine or ammonia to make it dilutable in water to a transparent or emulsified state. Organic amines used for neutralizing polycarboxylic acid resin include monomethylamine, dimethylamine,
Trimethylamine, diethylamine, triethylamine, monoisopropylamine, diisof.

Examples include lopylamine, dimethylaminoethanol, and diethylaminoethanol, and ammonia can also be used. By using polycarboxylic acid resin in combination with amino resin, it is necessary to improve the physical and chemical properties of the coating film as a thermosetting electrodeposition paint.

As the amino resin, melamine resin, urea resin, benzoguanamine resin, acetoguanamine resin, etc. can be used, but in the present invention, among the melamine resins, one or more monovalent resins such as methanol, ethanol, propanol, and butanol are used. Suitable are sparingly water-soluble methylolmelamines which have been at least partially etherified with alcohols such as

The composition ratio of polycarboxylic acid resin and amino resin as coating film forming components is polycarboxylic acid resin: amino resin = 30 to 9.
A suitable weight ratio is 0:70 to 10 (weight ratio).

The lightning coating is used after being diluted so that the coating film-forming components are 3 to 2% by weight. The fine silica powder added as a matting agent has an equilibrium moisture content of 20% or less at a relative humidity of 90%.

This is a necessary condition for imparting chemical performance to the coating film, especially boiling water resistance and alkali resistance, and the equilibrium water content is 20
% or more of silica fine powder is undesirable because a large number of silanol groups will be present on the silica surface, making it easier to absorb water and causing deterioration of the performance of the coating film.
Furthermore, the silica fine powder used is one whose aqueous suspension has a pH value of 5.5 or more. This is because when silica whose pH value of an aqueous suspension of silica fine powder is 5.5 or less is dispersed in an electrodeposition paint, the pH of the electrodeposition liquid becomes
tends to be in the acidic range, which tends to cause gelation of the paint, and when this haze-deposited paint is exposed, the silica content in the electrodeposited film increases more than the amount of silica in the exposed paint. This is because when electrocoating is performed, the amount of silica dispersed in the haze paint varies greatly, and the matte state of the matte coating film obtained with each treatment is not constant. Furthermore, excessive silica is present on the surface of the electrodeposition coating, and the pH value near the coating surface is low, resulting in agglomeration of silica and paint, forming white blobs on the coating. It is also recognized that the appearance of the paint is significantly deteriorated, which is not desirable. In the present invention, since fine silica powder having the above-mentioned specific properties is used, the co-advance property during mist coating is constant, and a mist coating film with excellent coating appearance, chemical performance, and matting effect is produced. You can get it. In the present invention, an electrodeposition paint in which specific fine silica powder is dispersed as a matting agent is coated with a military coating so that the above-mentioned four conditions necessary for forming a matte electrodeposition film are simultaneously provided. The amount to be blended varies depending on the desired degree of matting and the silica particle size, but the appropriate amount is 0.1 to 4 parts by weight, preferably 1 to 3 parts by weight, per 10 parts by weight of the film-forming component of the electrodeposition paint. be.

This is because if the amount of silica added is extremely small, almost no matting effect can be obtained, whereas if it is added in a large amount, the coating film tends to whiten and the water resistance is also poor. In any case, a formulation suitable for the desired level of matteness may be used. Incidentally, in the present invention, a matte coating film refers to a coating film having a value of 90 or less when measured with a gloss meter.

The particle size of the fine silica powder used in the present invention is not particularly specified, but according to experiments conducted by the present inventors, the smaller the particle size is, the easier it is to handle and the more uniformly matte the coating can be obtained. . However, if ultrafine particles are used, the matting effect will be reduced, so it is necessary to select an appropriate particle size. From the results of experiments using commercially available silica fine powder, it was found that the average particle diameter (secondary) is preferably 5 or less. The method for dispersing fine silica powder in an electrodeposition paint is to mix the fine silica powder, water and a solvent as necessary with the stock solution of the lightning coating paint, and uniformly disperse the powder using a method such as a sand mill, ball mill, or roll kneading method. It is possible to further dilute the product with deionized water, or to mix fine silica powder into a pre-diluted lightning coating and disperse it using a high-speed disperser, such as a homomixer.

To form a matte coating film, a conductor is used as an anode and immersed in a matte electrodeposition paint, and a counter electrode is provided and a voltage of 15 to 300 volts is applied for 30 to 30 minutes.
This is done by applying a direct current for 300 seconds.

If the conductor is a long material, it may be held at an angle of 30 to 900 degrees with respect to the horizontal and then electrodeposited. The conductor may be of any type, and its size and shape are not limited. For example, iron, copper, aluminum, anodized or chemically treated aluminum, and boehmite aluminum can be used. These conductors can be colored by dyeing or electrolysis. In the present invention, washing with water is usually performed after decoating, but it is also possible to omit this washing process.

In particular, when painting the longest material by hanging it vertically (900 degrees with respect to the horizontal), it is advantageous to omit the water washing process. Examples will be shown below to more specifically explain the present invention.

Examples 1 to 6 Fine silica powder (with the characteristics shown below) was added to a commercially available acrylic-melamine electrocoating paint stock solution (resin solid content: 5% by weight).
Product name: NIPSEAL E-200A, manufactured by Nippon Silica Kogyo Co., Ltd.)
was added and sufficiently mixed and dispersed using a sand mill.

Next, deionized water was added to this dispersion to reduce the resin solid content to 1
A matte electroplating coating was prepared with a weight percent of . The amount of the electrodeposition paint stock solution and the amount of fine silica powder added (parts by weight, the same hereinafter) are as shown in Table 1. The characteristics of the fine silica powder used as a matting agent are as follows.

Equilibrium moisture at 90% relative humidity 10% pH of 4% water suspension 6.5 Average particle size (secondary) 2.5 Anodized aluminum elongated shape in each paint prepared on the surface (
2 m) was held horizontally at an angle of 10 mm with respect to the horizontal, and with this as an anode and a stainless steel plate as a cathode, a DC current was applied at a voltage of 180 V across 15 sand gaps.

After the painting was completed, the long aluminum strip was taken out of the paint rack, washed with water, and then placed in a hot air circulation drying oven and dried by heating at 18 psi for 30 minutes. The thickness, gloss, appearance, boiling water resistance, and alkali resistance of the resulting lightning coating are top-notch.
It was as shown in the table. Table 1 Boiling water resistance and alkali resistance test of matte electrodeposited coating film is JISK
The test was conducted according to the test method of -5400.

However, boiling water resistance is determined by the presence or absence of any abnormality in the paint film after being immersed in boiling water for one field, and alkali resistance test is determined by the presence or absence of any abnormality in the paint film after being immersed in an alkaline aqueous solution for 24 hours. did. Comparative Examples 1 to 4 The same method as in Example 4 was carried out except when fine silica powder was not added (Comparative Example 1) and fine silica powder with different characteristics was added (Comparative Examples 2 to 4). did.

The resulting matte electrodeposited coating was as shown in Table 2.

The contents of the commercially available silica used in Comparative Examples 2 to 4 are as follows. Comparative Example 2 Product name Cyroid 244 Comparative Example 3 manufactured by Fuji Davison Co., Ltd. Comparative Example 4 manufactured by Nippon Aerosil Co., Ltd. Product name Ae.

Zeal 200 Table 2 Example 7 The same method as in Example 3 was carried out except that the long aluminum profile was held in a vertically suspended state in the longitudinal direction and washing with water after coating was not performed.

The resulting matte electrodeposition coating film was as shown in Table 3.

Table 3 Example 8 16 parts of a commercially available acrylic-alkyd-melamine electrocoating paint stock solution (resin solids content 50%) was diluted with 84 parts of deionized water to create a haze coating with a resin solids content of 8%. did.

Next, fine silica powder (trade name Nipseal E-2) was added to this.
20 (manufactured by Nippon Silica Kogyo Co., Ltd.) was gradually added and mixed and dispersed using a homomixer to prepare a matte electrodeposition paint. A chemically treated steel plate is immersed in this paint as an anode, and a stainless steel plate is used as a cathode.
A direct current was applied at a voltage of 90V for 120 seconds.

After the electrodeposition was completed, the steel plate was taken out from the rack, washed with water, and then placed in a hot air circulation drying oven and dried by heating at 180° C. for 30 minutes. As a result, a matte electrodeposition coating film with a coating thickness of 12 mm and excellent coating film matte effect, coating appearance, and coating performance was formed. Experimental Example In Example 4 and Comparative Example 3, the copropagation properties of fine silica powder were compared.

Co-progressivity refers to the ratio of the amount of silica in the military uniform paint to the amount of silica in the decoated coating, and in the present invention, the silica content in the silkworm coating is 100%, and the silica content in the lightning coating is The silica content was indicated.

The results are shown in Table 4.

Table 4: To measure the silica content in a film, scrape a certain weight of the electrodeposited film with a knife, place it in a crucible, and place the crucible in a
It was heated to 0°C, and when the weight reached a constant value, the remaining amount was determined and the silica content was calculated.

Claims (1)

[Scope of Claims] 1. A fine silica powder having (a) an equilibrium moisture content of 20% or less at a relative humidity of 90%, and (b) an aqueous suspension having a pH of 5.5 or more, is prepared using an aqueous or water-soluble electrolyte. 1. A method for forming a matte electrodeposition coating film, which comprises electrodepositing an electrodeposition paint for forming a matte coating film, which is dispersed in a coating material, onto a conductor. 2. The method according to claim 1, wherein the water-based or water-soluble electrodeposition paint contains a polycarboxylic acid resin and an amino resin that are at least partially neutralized with amine or ammonia as film-forming components. 3. Claim No. 3 in which the polycarboxylic acid resin is a mixture of an acrylic polymer, a vinyl polymer, an acrylic vinyl copolymer, a saturated or unsaturated alkyd resin, and one or more oil modified products thereof having a carboxyl group. The method described in any one of paragraphs 1 to 2. 4. The method according to any one of claims 1 to 3, wherein the conductor is iron, copper, aluminum, or an alloy thereof, or aluminum that has been anodized, chemically treated, or boehmited, or an alloy thereof. . 5. The method according to any one of claims 1 to 4, wherein the conductor is electrodeposited at an angle of 3 to 90 degrees with respect to the horizontal. 6. Claims 1 to 5, in which the conductor is electrodeposited in a vertically suspended state and then heated and dried without washing with water.
The method described in either of the above.