JPS60150871A - Method for improving adhesiveness of coated film in multicolor painting system - Google Patents

Abstract

PURPOSE:To omit surface roughing operations and finish polishing operations by coating a paint having excellent adhesiveness to the underlayer on the underlayer coated film by using a vehicle of the same color and vehicle series as the underlayer, and then coating a paint having excellent finishing quality and durability. CONSTITUTION:A paint A having excellent adhesiveness to the underlayer coated film and a paint B having excellent finishing quality and durability are coated on the underlayer coated film to form an upperlayer coated film by using a vehicle of the same color and vehicle series as the underlayer as the vehicle of the paint A. The paint A is firstly coated, and then the paint B is coated on the paint A. Both paints are simultaneously cured. The surface roughing operation and the finish polishing operation can be omitted in this way.

Description

[Detailed Description of the Invention] Regarding the Method: In painting automobile bodies, multicolor painting such as two-tone painting is performed.

Conventionally, two-tone painting of automobile bodies has generally been carried out as follows.

■ The first color of paint is applied to the base coated body and baked to form a completely cured undercoat.

(2) Roughen the surface of the lower coating film by sanding or the like at the area where the upper coating film of the second color is to be applied and at the boundary between the lower coating film and the upper coating film (hereinafter referred to as the "parting part").

■ Apply masking to the parting section.

■ Apply a second color of paint to the area on the lower layer where the upper layer will be applied, and bake to form a completely cured upper layer.

■ Remove masking.

■ Finish polishing the parting area where the masking has been removed.

In the above, the reason why the lower layer coating film is roughly solidified in step (2) is to improve the adhesion of the upper layer coating film provided thereon. In this case, in order to ensure the adhesion of the upper layer coating near the parting part, it is necessary to roughen the parting part as well as the area overlapping with the upper layer coating. Therefore, it is necessary to finish polish the parting part in step (2).

However, the above-mentioned surface roughening work and final polishing work are very similar, leading to a decrease in productivity. The purpose of this invention is to provide a multicolor painting method that eliminates or simplifies these operations.

That is, the present invention provides two types of paints: a paint (A) that has good adhesion to the underlayer paint film and a paint (B) that has good finish quality and durability, which consists of a lower paint film and a vehicle underneath. Apply the paint (A) to the area where the upper layer coating will be applied on the lower layer coating.
This invention relates to a method for improving paint film adhesion in a multicolor paint system, characterized in that an upper layer paint film is formed by applying a paint (B) (B) on top of the paint (B) and then curing both paint films.

The present invention uses two types of paint (A) and paint (B) to form the upper layer coating, and the paint (A) is applied on the lower layer coating.
Use a material that has good adhesion to the underlying paint film, and use a paint that has the same finish quality and durability as a regular top coat paint for the paint (B) that is overcoated on top of the paint (A). As a result, an upper layer coating with excellent adhesion to the lower layer coating can be replaced without roughening the lower layer coating, and there is no effect on the finish quality or durability of the resulting upper layer coating. No problem.

As described above, in the present invention, the surface roughening process can be omitted, and the final polishing process can also be omitted, thereby improving productivity. Note that in the present invention, a surface roughening step may also be used, but even in that case, since a coating material (A) with good adhesion is used, the surface roughening work can be simplified, and the finish of the parting portion can also be improved. Polishing work can also be simplified.

Furthermore, since the paint (A) and paint (B) used in the present invention are composed of the same type of vehicle, and the upper layer coating film is formed using two coats and one bake using these two paints, the paint (
Problems such as poor adhesion do not occur between the coating film of A) and the coating film of (in the paint).

Furthermore, since the present invention does not require any special steps other than forming the upper coating film using two types of paints, it can be adequately handled using conventional coating equipment.

In the present invention, as the paint (Bl), top coat paints used in conventional multicolor painting can be used as they are without any particular limitations.

As the paint (A), a paint having the same color and the same vehicle as the paint (B) is used. Examples of paints that have excellent adhesion to the underlying coating include the following.

(1) Paint with a higher pigment concentration The pigment concentration is 10% (weight%,
(same below) high in the range below 5 to 10
% is preferably used.

(2) Melamine-based curable paint with high melamine resin content When a melamine-based curable paint such as melamine-alkyd resin paint is used for paint (A) and (B), melamine resin is used as paint (A). The content is higher than the melamine resin content of paint (B) by about 10% or less, especially 3~
It is preferably used that is about 6% higher.

(8) Paints containing additives that promote coating film curing Examples of such additives include dinonylnatutale disulfonic acid sulphate.

In the present invention, the above-mentioned paint (A) 'E is applied on top of the lower layer paint film, and the paint (B) is overcoated thereon, and both the paint films (paint body) and (B) are cured by baking at the same time. The coating state of the coating material (A) when coating the coating material (B) may be any coating state between a completely wet coating film and a semi-cured coating film.

In the present invention, the method of forming the lower layer coating film, the method of masking, etc. may be the same as conventional methods.

In the above, the present invention was mainly explained using two-tone coating as an example, but the present invention is not limited to such an example, and a third color coating is further provided on the second color upper layer coating. It is applicable to three-color painting and multi-color painting.

Next, the present invention will be explained in detail with reference to Examples and Comparative Examples.

Example 1 Polybutadiene-based electrodeposition paint was electrodeposited on a dull steel plate with a thickness Q of 8 mm that had been subjected to phosphoric acid zinc chemical conversion treatment.
Baking was carried out at 0°C for 25 minutes to obtain an electrodeposited film with a thickness of 20 μm.

On top of the electrodeposited coating film, an automotive intermediate coating Cer 7 Acer and a black melamine-alkyd resin paint were applied.
A first color lower layer coating film with a thickness of 50 μm (intermediate coat thickness 20 μm, top coat thickness 30 μm) was formed by baking under the conditions shown in the table.Next, paint (A ) as a red melamine-alkyd resin paint (red pigment concentration in the solid content: 15%, melamine resin content in the resin content: 30%) with a film thickness of 10% after curing.
μm), then red melamine-alkyd resin paint as paint (B) (red pigment concentration in solid content: 10%, melamine resin content in resin content: 60%)
) was coated with a film thickness of 2 [lpm] after curing, and then baked under the conditions shown in Table 1 to form an upper layer coating film of the second color with a thickness of 30 μm.

The resulting coating film was examined for adhesion between the lower coating film and the upper coating film according to a goblin adhesion test. The results are shown in Table 1. In the results of the goblin adhesion test in Table 1, 0/100 represents that the upper layer coating does not peel off at all, 100/100 represents that the upper layer coating completely peels off, and 0/100 and 100/100 represent that the upper layer coating completely peels off. Values between 100 represent intermediate states.

Table 1 Comparative Example 1 A coating was applied in the same manner as in Example 1 except that the upper coating film was formed using only paint (B), and an adhesion test was conducted. The results are shown in Table 2.

Table 2 Example 2 In Example 1, the lower layer coating film was formed using a white melamine-alkyd resin paint, and the upper layer coating film was used as paint (A). Melamine resin in the paint (B) used in Example 1 An adhesion test was performed by coating in the same manner as in Example 1 except that the same paint (B) as in Example 1 was used and the content was increased to 35%. The results are shown in Table 6.

Table 3 In Example 2, coating was carried out in the same manner as in Example 2, except that the upper coating film was formed using only paint (B), and an adhesion test was conducted. The results are shown in Table 4.

Table 4 Example 3 In Example 1, the lower coating film was formed using a white melamine-alkyd resin paint, the upper coating film was used as paint (A), and the solid content was added to the paint (E) used in Example 1. An adhesion test was carried out using a paint to which 2% dinonylnatutale disulfonic acid was added and in the same manner as in Example 1, except that the same paint as in Example 1 was used as the paint (Bl). Table 5

Claims (1)

[Claims] 1. When forming an upper coating film of a different color from the lower coating film on the lower coating film, the lower coating film and the lower coating film, which are mutually similar in color and made of the same type of vehicle, are used to form the upper coating film. Using two types of paint: a paint (A) with good adhesion and a paint (B) with good finish quality and durability, paint (A) is applied to the area where the upper layer coating will be applied on the lower layer coating. A method for improving paint film adhesion in a multicolor paint system, characterized by forming an upper layer paint film by coating both paint films and then curing both paint films.