JPH0246386B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a multilayer baked coating film with improved interlayer adhesion. BACKGROUND OF THE INVENTION Conventionally, baking-type top coat paints as industrial paints have been widely used for automobiles, colored galvanized iron, light electrical appliances, fixtures and fittings, etc., and include solid color paints, metallic color paints, clear paints, etc. These coating systems include the 1-coat, 1-bake type, and the 2-coat type, in which metallic color paint and clear paint are applied wet-on-wet and then baked.
There is a 1-bake type. Recently, a painting system called two-tone color has been used from a design standpoint, but each paint may be the same paint or different types of paint. Furthermore, recently, solid color coatings, 2 coats, 1 bake type metallics, etc.
An over clear coating method is also used to form another layer of clear coating on top of the clear coating to improve the finished appearance and weather resistance. In paint films finished by one-coat, one-bake type painting or two-coat, one-bake type painting, it is necessary to repair defects on the paint film. Generally, repair involves sanding the defective area using sandpaper, etc. to adjust the paint surface, then repainting the defective area and its surrounding area or the entire surface using the same paint, and post-adjustment with wax or compound. A process is being followed. In this way, in repair painting, two-tone painting, over clear painting, etc., the lower layer paint film (a paint film relative to the upper layer paint film and does not necessarily mean the first layer paint film) formed from the same paint or different paints. , the primary coating film) and the upper coating film (hereinafter referred to as the primary coating film)
It is unavoidable that the 2nd coating film (hereinafter referred to as the 2nd coating film) overlaps (the 2nd coating film is formed on top of the baked primary coating film). There is almost no problem with the interlayer adhesion between the primary coating film and the secondary coating film in areas where the primary coating has been polished or otherwise adjusted, but delamination is likely to occur in unadjusted areas. In other words, in areas where the primary coating has been adjusted by polishing, etc., contaminants on the coating surface are removed and a new coating surface is exposed, improving adhesion, and the adhesion area increases as the surface area increases due to surface scratches. interlayer adhesion is hardly a problem since the second coating film has an anchoring effect on the scratched area.
On the other hand, in areas where the primary coating film has not been adjusted, the physical properties between the primary coating film and the secondary coating film determine the interlayer adhesion, and the primary coating film and secondary coating film are of the same type. Delamination is likely to occur even if the paint is of a different type; in the former case, the primary paint film is exposed to the air until it is repaired, so the paint surface becomes contaminated and surface properties such as surface tension change; Moreover, since the primary coating film is subjected to baking twice, including during repairs, it is thought that differences in polar groups and cohesive strength occur between the primary coating film and the secondary coating film, and in the latter case (for example, This is because the adhesion between the layers of the paint film is more likely to be poor than in the case of the former case, since the physical properties related to the adhesion of the paint film itself are different in the case of tone painting or over clear coat painting. Furthermore, as is well known, the primary coating film is baked under conditions (hereinafter referred to as
If the secondary coating is baked under conditions (hereinafter referred to as overbaking conditions) and the secondary coating is baked at a lower temperature and/or shorter time than the standard baking conditions (hereinafter referred to as underbaking conditions), the interlayer adhesion of the coating film becomes even worse. Particularly in paint baking lines for industrial paints, objects to be coated may remain in the baking oven and be baked under overbaking conditions, and the secondary coating side is usually subjected to repair baking using an infrared lamp, etc. Since there are many cases where the product is baked for a short time on the line, it may be under baking conditions. Under these baking conditions, the difference in physical properties related to intercoat adhesion between the primary and secondary coatings will be greater than under standard baking conditions, resulting in poor intercoat adhesion. be. Other factors that worsen interlayer adhesion of paint film include 1.
Environmental conditions at the time when the paint for the second coat is applied on the second coat are mentioned. For example, repair coatings applied in winter are prone to interlayer delamination, but this is because winter is a low temperature and low humidity, so there is less moisture adsorbed on the surface of the primary coating, and the Juan der Waals effect mainly due to hydrogen bonding forces. This is thought to be because the force becomes smaller. As a method for improving the interlayer adhesion of the coating film, 1
Next, the method of polishing the entire surface of the paint film has traditionally been used, but since it takes too much man-hours, recently only the necessary areas are polished, so the above-mentioned adhesion problem remains in the unadjusted areas, so the paint side has to take countermeasures. has become necessary. Additionally, heating and humidification using steam or the like is used as a countermeasure against low temperature and low humidity in winter, but this is not desirable from the standpoint of energy conservation. As a countermeasure to improve interlayer adhesion from the paint side, the conventional approach has been to increase the amount of polar groups in the resin in the paint, such as hydroxyl groups and carboxyl groups, to increase the Van der Waals force on the paint film surface. However, as a result, polar groups remain in the coating film, and there is a risk that coating film performance such as water resistance and weather resistance may deteriorate. In addition, as a measure against adhesion under overbaking conditions between the primary and secondary coatings, we have increased the reactivity of the secondary coating to bring its cohesive force closer to that of the primary coating. Acid catalysts such as phosphoric acid esters and para-toluenesulfonic acid are sometimes added, but the paint may react and thicken during storage, or acid catalysts remaining in the paint film may cause poor water resistance. Undesirable. The present invention has been made in order to solve the above-mentioned problems related to interlayer adhesion of baked paint films, and its gist is that one type of paint film contains bentonites and organic bentonites selected from the group consisting of bentonites and organic bentonites. It consists in a multilayer baked coating film having at least one coating layer containing one or more types of additives. The bentonites and organic bentonites used in the present invention are not particularly limited and may be any commercially available ones, such as Benton #38 and Benton #34 manufactured by Nasional, Organite manufactured by Toyosun Yoko Co., Ltd., Esben, Examples include Bengel et al. Additives used in the invention may optionally include other conventional additives such as inorganic silica, such as finely divided silicic acid and diatomaceous earths, silicates such as magnesium silicate, aluminum silicate, sodium silicate, lithium silicate and potassium silicate, and pigments. may be blended as appropriate. The amount of additive used in the present invention is usually 0.01 to 5
In terms of weight percent, if the amount is more than 5 percent by weight, the gloss and weather resistance of the top coat film will be reduced, and if it is less than 0.01 percent by weight, it will be difficult to achieve the intended purpose of the present invention. The above-mentioned additives may be contained only in the primary coating film side, or may be contained in both the primary coating film side and the secondary coating film side. Furthermore, when the primary coating side is polished, the interlayer adhesion of the coating film is further improved. The paints containing the above additives are not particularly limited, and include conventional baking-type top coat paints, such as alkyd/melamine type paints, acrylic, melamine type paints, oil-free polyester/melamine type paints, oil-free polyester/isocyanate type paints, It may be a solid color paint such as an acrylic isocyanate type paint, a metallic color paint, a clear paint, or the like. The reason why the interlayer adhesion of the multilayer baked coating film according to the present invention is improved is not clear, but all of the above additives contain a large amount of oxygen atoms in their structures, so hydrogen between the primary coating film and the secondary coating film is It strengthens the bonding force and also has a higher rate of adsorption of moisture in the air than titanium dioxide or zinc oxide, so it is estimated that the Van der Waals force between the coatings will increase and interlayer adhesion will be significantly improved. . According to the present invention, all of the above-mentioned problems related to interlayer adhesion, which have conventionally been a concern in multilayer baked coatings, are solved. The present invention will be explained below using Examples and Comparative Examples. "Part" and "%" in the following descriptions
are all based on weight. Paint manufacturing example Paint 1 14.3 parts of alkyd varnish (“Betsukosol-1323” manufactured by Dainippon Ink Co., Ltd.) in a glass container (500 c.c.),
Titanium oxide (Sakai Chemical Co., Ltd. "R-5N") 80.0 parts, xylol/n-butanol (weight ratio 4/1) 28.3
and 100.0 parts of glass beads (1.5 mmΦ), stirred uniformly, and dispersed for 1 hour. '') and 14.7 parts of xylene/n-butanol (weight ratio 4/1) were added and dissolved to produce Paint 1. Paint 2 In a glass container (500 c.c.), 14.3 parts of alkyd varnish (Betsukozol-1323), 80.0 parts of titanium oxide ("R-5N" manufactured by Sakai Chemical Co., Ltd.), 2.4 parts of organite (organic bentonite manufactured by Hojun Yoko Co., Ltd.) , xylol/n
- 28.3 parts of butanol (weight ratio 4/1) and 100.0 parts of glass beads (1.5 mmΦ) were charged, stirred uniformly, and then dispersed for 1 hour.
35.5 parts of varnish and 14.7 parts of xylene/n-butanol (weight ratio 4/1) were added and dissolved to produce paint 2 (containing 1% organic bentonite). Paint 3 Acrylic 44-179 in a glass container (300 c.c.)
Varnish (acrylic resin manufactured by Nippon Reichhold)
122 parts, 44 parts of Super Betsukamine L-117-60 varnish (melamine resin manufactured by Nippon Reichhold),
0.6 parts of Modaflow (manufactured by Monsanto) and 28.0 parts of xylol were added and stirred uniformly to produce paint 3 (clear paint). Paint 4 Acrylic in stainless steel container 44-179 40
Part, Bengel (bentonite manufactured by Toyojun Yokosha) 12
After adding 48 parts of xylol and 150 parts of glass beads for dispersion (1.5 mmΦ) and dispersing for 1 hour,
Remove the glass beads and add acrylic 44-
179 Add 500 parts and stir evenly to make bentonite 2.
% containing paste was prepared. Mix 8 parts of the paste into 100 parts of paint 3,
Paint 4 (clear paint containing 0.15% bentonite) was produced by uniformly stirring. Paint 5 Acrylic 50- in the same way as for paint 3
612 (Acrylic varnish manufactured by Nippon Reichhold)
122 parts, Super Bethcomin L-117-60 varnish 44
Paint 5 (clear paint) was prepared from 1 part, 0.6 parts of Modaflow, and 28.0 parts of xylol. Paint 6 In the same way as for paint 4, apply acrylic 50
A paste containing 2% organic bentonite was prepared from 40 parts of -612 varnish, 12 parts of Bentone #38 (organic bentonite manufactured by Nacional), 48 parts of xylol, and 500 parts of Acrydik 50-612 varnish. Paint 6 (a clear paint containing 0.3% organic bentonite) was prepared by mixing 20 parts of the paste, 100 parts of Paint 5, and 6.0 parts of Supervecamine L-117-60. Paint 7 Acrylic 47-712 in a glass container (300 c.c.)
(Acrylic resin varnish manufactured by Nippon Reichhold)
65 parts, Super Bethcomin L-117-60 varnish
13.6 parts, aluminum paste 1109MA (manufactured by Toyo Aluminum Co., Ltd.) 5.5 parts, n-butanol 4.6 parts, ethyl acetate 3 parts, butyl acetate 4 parts, xylol 3.4 parts,
and 0.5 part of triethylamine were charged and stirred uniformly for 30 minutes to produce paint 7 (metallic paint). Comparative Example 1 of improving interlayer adhesion between coatings of the same paint system (Solid Color/Solid Color)
Paint 1 (solid color paint) diluted to NO4/20 seconds (paint temperature 20℃) was applied to the test piece (A,
B, C and D) [Pieces prepared by degreasing and cleaning commercially available JIS.G3141 (SPCC-SD steel plate manufactured by Nippon Test Panel Co., Ltd.) with xylol and then wiping off the solvent using commercially available gauze] Using a commercially available kap gun, 20℃, 75% The primary coating film was applied using a normal coating method under RH conditions.
After setting for 10 minutes before baking,
Test pieces A and B were baked at 140°C for 30 minutes, and test pieces C and D were baked at 160°C for 90 minutes. 40% at 20℃ using silica gel immediately after baking
The test piece was left in a container at RH for 30 minutes, and at the same time, the test piece was taken out and the same paint as the first coat was applied as a second coat on the unadjusted first coat. After setting for 10 minutes, test pieces A and C were heated to 140℃ for 30 minutes, and test pieces B and D were heated to 130℃.
After baking them for 20 minutes each, they were left in a room environment for 24 hours. The primary coating thickness and secondary coating thickness of the four test pieces were 35μ and 30μ, respectively. 100 squares were made by cross-cutting the coating film at 1 mm intervals, and a normal tape peeling test was conducted to evaluate the interlayer adhesion between the primary coating film and the secondary coating film. The results are shown in Table-1. Example 1 (Solid Color/Solid Color) Test plates E, F, G, and H were prepared using Paint 2 according to the procedure of Comparative Example 1. The primary and secondary coating thicknesses were 35μ and 30μ, respectively. The baking conditions for the coating film were as follows.

[Table] The interlayer adhesion of the coating film was evaluated in the same manner as in Comparative Example 1 for the obtained test plate. The results are shown in Table-1. Comparative Example 2 (Clear/Clear) Thinner [xylol: Solbetsuso 100 (manufactured by Etsuso): Solbetsuso 150 = 70:15:15 (weight ratio)] in a food cup NO4/20 seconds (paint liquid temperature 20°C)
A test plate was prepared according to the procedure of Comparative Example 1 using Paint 3 diluted to . However, the primary coating film and the
The baking conditions for the next coating were 160℃, 90 minutes and
The temperature was 130°C for 20 minutes. Both the primary coating film thickness and the secondary coating film thickness were 30μ. The interlayer adhesion of the coating film was evaluated in the same manner as in Comparative Example 1 for the obtained test plate. The results are shown in Table-1. Example 2 (Clear/Clear) A test plate was prepared using Paint 4 according to the procedure of Comparative Example 2. Both the primary coating film thickness and the secondary coating film thickness were 30μ. The interlayer adhesion of the coating film was evaluated in the same manner as in Comparative Example 1 for the obtained test plate. The results are shown in Table-1.

[Table] Comparative example 3 of improving interlayer adhesion between coatings of different paint systems (solid color/metallic clear) Paint 1 was used as the primary coating under the same conditions as Comparative Example 1, and after baking at 160℃ for 90 minutes. , leave it in a container containing dry silica gel for 30 minutes, then remove it.
Immediately use thinner (ethyl acetate: butyl acetate: xylol: cardotol acetate = 20:20:
Paint 7 (metallic paint) diluted to food cup NO4/15 seconds (paint liquid temperature 20℃) with
After an interval of 3 minutes, the same clear paint as that prepared in Comparative Example 2 was applied. At 130℃ after setting
Bake for 20 minutes. The thickness of the primary coating was 35μ, the thickness of the metallic coating on the secondary coating was 20μ, and the thickness of the clear coating was 30μ. The interlayer adhesion of the coating film was evaluated in the same manner as Comparative Example 1, and the results are shown in Table 2. Example 3 (Solid Color/Metallic Clear) A test plate was prepared according to the procedure of Comparative Example 3 using the solid color used in Example 1 as the primary coating and the metallic clear used in Comparative Example 3 as the secondary coating. It was created. The interlayer adhesion of the coating film was evaluated on the obtained test plate in the same manner as in Comparative Example 1, and the results are shown in Table 2. Comparative Example 4 (Clear/Clear) Paint 3 was used as the primary coating and applied according to the clear paint coating conditions described in Comparative Example 2, baked at 160°C for 90 minutes, and then placed in a container containing silica gel for 30 minutes. After leaving it for a while, immediately take it out, apply paint 5 according to the clear paint coating conditions, and set 30.
After that, it was baked at 130°C for 20 minutes to form a secondary coating film.
Both the primary coating film thickness and the secondary coating film thickness were 30μ. The interlayer adhesion of the coating film was evaluated in the same manner as Comparative Example 1, and the results are shown in Table 2. Example 4 According to the procedure of Comparative Example 4, a primary coating film was formed using Paint 4 (clear paint), and then Paint 6 was applied.
A test plate was prepared by forming a secondary coating film using (clear paint). The interlayer adhesion of the coating film was evaluated on the obtained test plate in the same manner as in Comparative Example 1, and the results are shown in Table 2. Comparative Example 5 Based on the procedure of Comparative Example 2, a primary coating film was formed using Paint 3 (clear paint), and then Paint 1
A test plate was prepared by forming a secondary coating film using (solid color paint). The interlayer adhesion of the coating film was evaluated on the obtained test plate in the same manner as in Comparative Example 1, and the results are shown in Table 2. Example 5 Based on the procedure of Comparative Example 5, paint 6 (clear paint) was formed as a primary coating film, and then paint 2 was formed.
(solid color paint) was formed as a secondary coating film to prepare a test plate. The interlayer adhesion of the coating film was evaluated on the obtained test plate in the same manner as in Comparative Example 1, and the results are shown in Table 2. Comparative Example 6 In accordance with the procedure of Comparative Example 3, a first coating film was formed using Paint 1 (solid color paint), a second coating film was formed using Paint 3 (clear paint), and a test plate was prepared. Created. The interlayer adhesion of the coating film was evaluated on the obtained test plate in the same manner as in Comparative Example 1, and the results are shown in Table 2. Example 6 A test plate was prepared by forming a primary coating using paint 2 (solid color paint) and then forming a secondary coating using paint 4 (clear paint) in the same manner as in comparative example 6. . The interlayer adhesion of the coating film was evaluated on the obtained test plate in the same manner as in Comparative Example 1, and the results are shown in Table 2.

[Table] * Judgment criteria are the same as in Table-1

Claims (1)

[Scope of Claims] 1. A composite material having at least one adjacent layer a coating film containing one or more additives selected from the group consisting of bentonites and organic bentonites. Layer baked coating. 2. The coating film according to item 1, wherein only the primary coating film contains an additive. 3. The coating film according to item 1, wherein the first coating film and the second coating film contain an additive. 4. The coating film according to item 1, wherein the additive is organic bentonite. 5. The coating film according to item 1, containing 0.01 to 5% by weight of the additive.