JPS60203437A - Metallic coated metallic plate - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a metallic coated metal plate. More specifically, the present invention relates to a metallic coated metal plate that is particularly suitable for automobile exterior panels and is characterized by high durability and guaranteed appearance quality.

Today, automobile painting lines are becoming more energy-saving each year, and in particular, the baking and drying ovens used in each painting process are often converted from combustion-type indirect hot-air ovens to direct hot-air ovens.

In this case, the backing of NOx (nitrogen oxides) in the furnace shows an extremely high concentration in the direct furnace, and the difference between the baked paint film (for example, between the intermediate coat and the top coat) is thought to be caused by this NOx. There is a tendency for frequent delamination of paint films). This delamination phenomenon frequently occurs when solvent-based aminoacrylic 4M resin paints are used. The present invention prevents the occurrence of the delamination phenomenon, especially the delamination phenomenon of the paint film obtained by direct baking drying in a hot air oven, and establishes a highly durable coating system, and also has a high quality appearance. The objective is to provide a coating system that makes it possible to

Conventional metallic coated metal sheets for automobile exterior panels aimed at high appearance quality are coated with a chemical conversion coating (for example, a zinc phosphate chemical conversion coating) on a metal plate 1 such as a cold-rolled steel sheet or a galvanized steel sheet, as shown in FIG. ) 2, Baked coating film 3 of electrodeposition paint (for example, cationic electrodeposition paint whose main component is amino-modified epoxy resin), and intermediate coating paint (for example, solvent-based oil-free alkyd 'O (oil-free) with amino resin as a crosslinking agent). A metallic base paint (for example, a solvent-based thermosetting acrylic resin metallic base paint using an amino resin as a crosslinking agent) 5a and a clear paint (A) (
For example, a coating film 5 by wet-on-wet coating with a solvent-based thermosetting acrylic resin clear paint (5b) using an amino resin as a crosslinking agent, and the above-mentioned clear paint (A)
It is constructed by sequentially laminating baked coating films 6 of the same type of clear paint (B).

Although the coated plate having such a configuration exhibits excellent performance in terms of appearance quality, it has the following problems.

(i) For coated boards obtained under baking conditions such as staying in a baking furnace for as long as 1 hour or at a temperature 20°C or more higher than the standard temperature (usually about 140°C), the coating film 5b
-6 often causes transom peeling phenomenon.

(ii) Particularly in painted panels that have been directly baked in a hot air oven, delamination may occur between the coating films 5b and 6.
There are many directions.

(iii) In coating film secondary performance evaluation such as hot water resistance test,
7 creases (blister) often occur between the coating films 5b and 6.

Such problems (i) to (iii) are often discovered immediately after the coated board is manufactured, but they may also be discovered after a certain period of time has elapsed. As a countermeasure against this problem, sanding treatment has conventionally been adopted in many cases.

In addition, in the above conventional coating system, clear paint (A)
It has been proposed to improve the decrease in coating film adhesion caused by over-baking by using different types of paints and (B) (Japanese Unexamined Patent Publication No. 105266/1982). According to this proposal, an acrylic resin with a high acid value and a high total number of 01-1 valences (in the example, a resin with an acid value of 10 and an OH value of 65 to 110) is used in the clear paint (A) to coat II Mo51. In the clear paint (B), the coating film 6 can be formed using an acrylic resin with a low total number of acid value and O0 value (in the example, a resin with an acid value of 10 to 20.08 and a valence of 63 to 65). It is a requirement.

In this coating system, it is difficult to expect much from high weather resistance performance because the final upper coating film is formed by a coating film with a low total number of OH values (including M resin).

The present invention solves the above-mentioned problems of the prior art, and its key points are a solvent-based thermosetting acrylic resin metallic base paint using Aztjl resin as a crosslinking agent and a solvent using 7mino resin as a crosslinking agent. On top of the wet-on-wet coating film with the thermosetting acrylic resin clear paint (I), a solvent-based thermosetting acrylic resin clear paint (II) containing amino ljj fat as a crosslinking agent and amino O (oil) were added. A metallic coated metal plate characterized by having a coating film formed by wet-on-wet coating with a solvent-based thermosetting acrylic resin clear paint (III) using as a crosslinking agent.

Next, an example of the coated plate of the present invention will be specifically explained with reference to FIG. Note that 1.2.3 and 4 respectively indicate a metal plate, a chemical conversion coating, an electrodeposited fired paint film, and an intermediate fired paint film, as in FIG. 3 is usually 15-25μ, 4 is usually 20
It has a film thickness of ~40μ, or 50 to 60μ as necessary.

The coating film 15 is an important coating film for the appearance quality as a metallic coating and the weather resistance performance of the overall coating film, and is formed by wet-on-wet coating of a metallic base paint and a clear paint (1). Usual metallic base paints may be used. For example, as a base resin, the acid value is 10 to 25, preferably 12 to 20.08, and the acid value is 25.
~60, preferably 30-50, Fang 11 (number average molecular weight) 10 (100-2500'0. Preferably 150
00 to 22000, a thermosetting acrylic resin having a special value of SP value 10.5 to 11.3, preferably 10°7 to 11.2, and an amino resin (e.g., butyl etherified melamine resin) as a crosslinking agent. The solid content weight ratio of the latter is 8t3
:20, and a solvent, aluminum powder pigment, and if necessary, a coloring pigment and additives may be blended according to a conventional method to form a metallic base paint. This metallic base paint is uniformly applied to the coated surface of the intermediate baked paint film 4 according to a conventional method so that the dry film thickness is 15 to 20μ,
After setting for about 2 to 4 minutes, apply clear paint (1)
Paint.

The clear paint (1) has an acid value of 10 to 30, preferably 12 to 25.08 and a valence of 60 to 95 as a base resin.
, preferably 66-90, Mn 7000-10000,
Preferably 7500-9()00, SPPO23-10
．． 5. A thermosetting acrylic resin preferably having a characteristic value of 9.5 to 10.2, and an amine resin (e.g., butyl etherified melamine resin) as a crosslinking agent in a solid content weight ratio of 70:30. A clear paint prepared by adding a solvent and, if necessary, additives according to a conventional method, may be used.

This clear paint (1) is coated uniformly on the undried coated surface of the metallic base paint according to a conventional method so that the dry film thickness is 25 to 30 μm, and after setting for about 10 minutes, it is baked and dried. The standard conditions for drying are 140°C and 30°C.
A minute is enough. In the coating film 15 obtained in this way, the coating film 15a is made of a metallic base paint;
b shows a coating film made of clear paint (1).

Coating film 16 is the most important coating film in the coated board of the present invention, and the formation of this coating significantly improves the appearance quality of the metallic coating.It also improves durability in all aspects, including coating adhesion. The properties (especially weather resistance) are also significantly improved. This coating film consists of clear paint (II) and clear paint (
III) is formed by wet-on-wet painting.

The clear paint (II) has an acid value of 10 to 25, preferably 12 to 20.00, and an acid value of 25 as the base resin.
-6+'), preferably 30-50, Mn10000~
2 S OOO1 preferably 15000-22000,
SP value 10.5-11.3, preferably 10.7-11
．． A thermosetting acrylic resin having a special value of 2 and a resin (e.g., butyl etherified melamine resin) as the third component are used at a solid content weight ratio of 80:20, and a solvent is added according to a conventional method. A clear paint containing additives as necessary may be used.

The clear paint (11) is applied uniformly to the coated surface of the coating film 15, which has been left to cool for at least 30 minutes, preferably for at least 1 hour, in a conventional manner so that the dry film thickness is 5 to 15 μm, After setting for ~4 minutes, clear paint (III
) to paint.

The clear paint (III) has an acid value of 10 to 30, preferably 12 to 25, and an Ol (value of 60) as a base resin.
~95, preferably 66-90, W117000-1o
ooo, preferably 7500-9000% sp value 963
~10.5, preferably a thermosetting acrylic resin having a special value of 9.5 to 10.2, an amino resin (
For example, a clear paint may be used in which a butyl etherified melamine resin (butyl etherified melamine resin) is used in a solid weight ratio of 70:30, and a solvent and, if necessary, additives are blended according to a conventional method.

This clear paint (m>) is applied uniformly on the undried surface of the clear paint (II) according to a conventional method so that the dry film thickness is 25 to 30 μm, and after setting for about 10 minutes, it is baked and dried. Baking drying The standard condition is 140'C13
() minutes is sufficient. In the coating film 16 obtained in this way, the coating film 16a is a coating film made of clear paint (11),
161] shows a coating film made of clear paint (III).

The coating film IGa ensures adhesion between the coating films 15 and 16, and the coating film 161] maintains the weather resistance of the coating film.
be done.

In addition, for the clear paints (1) and (III), acrylic resins having the same characteristic values may be used (or resins may be used), and acrylic resins having different characteristic values within the above range may be used. It's okay.

According to the coated plate of the present invention having the above-described configuration, the requirements for high durability and appearance quality can be guaranteed.

Next, the present invention will be specifically explained with reference to Reference Examples, Examples, and Comparative Examples. In the examples, "parts" and "%" mean "parts by weight" and "% by weight."

Reference Example 1 A monomer having a composition shown in Table 1 and 1% of 7zobisisobutyronitrile based on the total amount of monomers were mixed in a solvent having a composition shown in Table 1, and the mixture was reacted at 100 to 120°C for 6 hours. Resins A-1 to A-8 (solid content 50%) having the special values shown in Table 1 are shown in Table 1.

Reference Example 2 160 parts of resin A-6 obtained in Reference Example 1, 33.3 parts of melamine resin (Mitsui Toatsu Co., Ltd. 7-thyl etherified melamine resin "Niepan 20SE-60J, solid content 60%)" and aluminum powder pigment (Toyo Aluminum "Aluminum Paste #1109MAJ") was mixed with 10 parts of toluene/acetic acid 1]-butyl/7 tyl cellosolve/Tsurupetsu #150 = 5 (1/30/10/10 (weight ratio) solvent). Dilute with water and mix with 7-odd cup #4 for 15 seconds (29
°C) and use it as a base metallic paint.

Reference Example 3 Each of the resins A-1 to A-5 obtained in Reference Example 1 and the melamine resin used in Reference Example 2 were mixed in a solid content ratio of 70/30.
(weight ratio) and mix the mixture with Tsurpets #1
Dilute with 0.00 and dilute with 7-odd cup #4 for 25 seconds (
20℃) and apply clear paint TCA-1~']
'CA-5.

Reference Example 4 Each of the resins A-6 to A-8 obtained in Reference Example 1 and the melamine resin used in Reference Example 2 were mixed in a solid content ratio of 80/2.
0 (weight ratio), and the mixture was mixed with toluene/1-dobutyl acetate/butyl cellosolve/Tsurpetsu #15O.
= 50/30-/1(')/10 (weight ratio) diluted with a solvent and washed in a 7 odometer #4 for 20 seconds (20').
Adjust to C) and clear paint BCA-6~B CA
-8.

Examples 1 to 4 and Comparative Examples 1 to 3 The base metallic paint of Reference Example 2 was applied to a coated mild steel plate which was subjected to degreasing treatment → zinc phosphate treatment → cationic electrodeposition primer coating → intermediate coating and surface coating according to the conventional method. After spray painting to a dry film thickness of 15 to 20μ, and setting at room temperature for 3 minutes, as shown in Table 2, clear paint (1) of Reference Example 3 was applied to a dry film thickness of 25 to 30μ. The first step is to spray paint wet-on-wet.
After setting for 10 minutes at room temperature, dry in an electric drying oven in a NOx-free atmosphere or with NOx.
30 at 141)'C in an atmosphere containing xS±2ppm
A first baking τj drying is carried out for 90 minutes at 150'C or 150'C.

After the coated plate was taken out of the drying oven and left for one hour, as shown in Table 2, the dry film thickness of the clear paint (II) of Reference Example 4 was 5 to 5.
After setting at room temperature for 3 minutes, apply the clear paint (III) of Reference Example 3 to a dry film thickness of 25 to 30 μm as shown in Table 2. 3rd stage clear coating (wet-on-wet spray coating), set at room temperature for 10 minutes, then baked 12 times for 30 minutes at 140°C in an electric drying oven in an NOx-free atmosphere (;J drying) .

However, in Comparative Example 1, the second stage clear coating is omitted.

Table 2 shows the results of coating film performance evaluation for the coated plates thus obtained. However, regarding coating film performance other than adhesion, after drying mi times in an NOx-free atmosphere,
The evaluation was performed at 140° C. for 30 minutes.

The evaluation method for coating film performance is as follows.

(1) Adhesion Make a cross-scratch on the painted surface with a knife that reaches the base material, and apply adhesive tape (width 25m + Il) with sufficient pressure to paste it (tl
After applying the coating, peel it off suddenly at '+'A'i and evaluate the condition of the painted surface.

○: No peeling of the paint film △ Peeling of the paint film in a small area along the varnish scratch line ×: Peeling of the paint film of 1 fil& was observed when adhesive tape was applied (=50% or more of the area of 1 part).

(2) Resistance) Using gauze impregnated with the three-component Kijiroru, rub the same coated surface 8 times and evaluate the resistance of the coated film to wiping.

○: No change observed △: Slight resistance felt when rubbed ×: Significant resistance and dissolution of the coating film observed (3) Plastic with an inner diameter of 38 mm and a height of 15 mm on a chemical-resistant painted surface Place the cylinder and seal it with liquid. 5m of 0.1N sulfuric acid in the cylinder
1 and leave it at 20°C for 24 hours.

Thereafter, the coated surface was washed with water, and the contact surface with sulfuric acid was evaluated.

O: No abnormality is observed on the painted surface. Δ: Some gloss and sink marks are observed. ×: Significant gloss and sink marks are observed. (4) The water-resistant coated plate is immersed in a constant temperature water bath at 50°C for 240 hours. For the coated plates that were then taken out, (a) evaluate the condition of the coated surfaces for gloss and sink marks;

○: No reduction in gloss observed ×: Significant reduction in gloss (b) Close contact Test and evaluate in the same manner as the adhesion test in (1) above.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of a conventionally known coated plate, and FIG. 2 is a sectional view showing an example of the coated plate of the present invention, in which 1 is a metal plate, 2 is a chemical conversion coating, and 3 is an electrodeposited coating. 11 coating film, 4 is intermediate coating (11 coating film, 5a + ISa is metallic base coating film, 5b, 15b, 6. 16a, 16b is clear coating film. Patent applicant Toyo Kogyo Co., Ltd. Nippon Paint Co., Ltd. Agent) Benrito Ao 1+ Ao and 1 other person Figure 1 Figure 2

Claims (6)

[Claims] (1) Wet-on-wet coating of a solvent-based thermosetting acrylic resin metallic base paint using Ami7 resin as a crosslinking agent and a solvent-based thermosetting acrylic resin clear paint (I) using 7Mino resin as a crosslinking agent. On top of the film, a wet-on coating of a solvent-based thermosetting acrylic resin clear paint (II) using an amino resin as a crosslinking agent and a solvent-based thermosetting acrylic resin clear paint (III) using a 7mino resin as a crosslinking agent is applied. A metallic coated metal plate characterized by having a wet coating film. (2) Clear paints (1) and (III) have a relatively high acid value, an acrylic resin with a relatively low total number of OH values, and a relatively low number average molecular weight, and a clear paint (II) with a relatively low acid value and The metallic coated metal plate according to item 1 above, which is obtained using an acrylic resin having a number average molecular weight that is relatively high in terms of the total number of OH values. (3) Clear paints (1) and (III) have an acid value of 12 to 2.
5.08 valence 66-90, number average molecular weight 7500-900
0, acrylic resin with sp value of 9.5 to 10.2, clear paint (II) with acid value of 12 to 2 (), OH
Value 30-50, number average molecular weight 15000-22000,
The metallic coated metal plate according to item 2 above, which is obtained using an acrylic resin having a special sp value of 10.7 to 11.2. (4) The metallic coated metal plate according to item 3 above, which is obtained by using acrylic resins having the same time value as the clear paints (1) and (III). (5) The metallic coated metal plate according to item 3 above, which is obtained by using acrylic resins having different special values as the clear paints (1) and (III). (6) The metallic coated metal plate according to any one of items 1 to 5 above, which is obtained by baking and drying the coating directly in a hot air oven.