JP2841219B2 - How to apply anti-chipping paint on car bodies - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention prevents chipping damage in which a coating film is damaged by jumping (ie, ston chipping) of gravel or the like spread on a road while a car is running. The present invention also relates to a chipping-resistant paint coating method capable of always maintaining good appearance and quality of a vehicle body.

[Conventional technology]

When a car travels on an unpaved road, especially in a salt-damaged area, especially in the winter, dents due to flying stones often occur at the tip of the hood of the vehicle body, around the tire house, etc.
If left unattended, chipping corrosion will occur from that part.
Therefore, it is necessary to protect the painted surface of the vehicle body from this chipping damage, and various means have been conventionally proposed. For example, Japanese Unexamined Patent Publication (Kokai) No. 63-171681 discloses a urethane-based clear coat containing a specific amount of a polyester resin, a melamine resin, and a cellulose acetate butyrate resin in a portion of a vehicle body which is susceptible to ston chipping after top coating of the vehicle body. A coating method for applying a paint is described, and it is disclosed that the urethane-based clear paint is baked and cured, and the cured coating film protects a coating film layer below a top coating film of the vehicle body and improves the appearance. .

[Problems to be solved by the invention]

However, in the prior art exemplified, even if the top coat is protected by a cured coating of a urethane-based clear paint, if it suffers chipping damage over time, even if it does not reach the top coat, Since the dents remain on the cured coating film of the urethane-based clear coating, there is a problem that the external appearance is impaired. Also, the urethane-based clear coating that has been baked and hardened once is very difficult to peel off from the top coating in terms of its characteristics, so it is not possible to wipe out the remaining dents, and as a result, There is also a problem that the coating film with impaired properties cannot be recovered to its original state.

The present invention solves the above-mentioned conventional problems, and by imparting a releasability to the coating film of the chipping-resistant paint on the top coat, after a lapse of a predetermined period, peels off the paint film damaged by chipping, and provides a new coating. An object of the present invention is to provide a coating method capable of forming a chipping-resistant coating film.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a composition for a chipping-resistant paint, which is a urethane lacquer 10 to 20 as a main ingredient.
And an anti-chipping paint containing 60 to 75 parts of isopropyl alcohol as a solvent, 7 to 12 parts of toluene, and 7 to 10 parts of ethyl acetate in a portion of the automobile body which has been overcoated, which is susceptible to ston chipping. A means for applying and drying so as to have the above-mentioned dry film thickness, peeling it off after a predetermined period, and applying and drying the paint again is adopted.

[Action]

A coating film with a specific composition and a chipping-resistant paint applied to a specific dry film thickness or more protects the coating layers below the top coat of the car body and provides good interfacial adhesion to the top coat. At the same time, releasability from the top coat is also provided.

〔Example〕

Each of the strippable paints prepared by blending urethane lacquer, isopropyl alcohol, toluene, and ethyl acetate at the composition ratios shown in the upper row of Table 1 as known chipping-resistant paints (hereinafter, referred to as strippable paints) was used. Enclose in a spray can with dimethyl ether aerosol gas. The viscosity of the strippable paint at this time is 90 poise at 25 ° C. On the other hand, on a rectangular steel plate of 150 mm length and 70 mm width,
A test piece was formed by spraying the strippable paints having the respective composition ratios described above onto a substrate having a coating thickness of 130μ by applying 3 coats of 3 coats and baking to a coating thickness of 30μ to obtain a dry coating thickness of 30μ. .

The lower part of Table 1 shows the result of the characteristic test for each test piece. In the test items, the visual appearance inspection is the quality of the smoothness and sagging of the coated surface of the strippable paint coating film. The interface adhesion of the top coat is
Using a gravelometer, temperature -20 ℃, test piece angle
90 °, discharge pressure 4kg / cm ² , crushed stone directly hit the surface of the strippable paint film under the condition of 50g of No. 7 crushed stone specified in JIS as a discharged stone, low temperature chipping test After the test, the interfacial adhesion between the strippable paint coating film and the substrate (whether or not there is floating) is visually determined. Next, the releasability is the ease of peeling when a part of the strippable paint film after the low-temperature chipping test is cleaved with a nail and this film is pulled and peeled off with a finger from the defective portion, and completely peeled off. It is to determine whether or not. Further, the spray applicability is to determine the occurrence of a tail on a coated surface when a strippable paint is spray-applied to a substrate and the presence or absence of poor atomization. In the results of the characteristic test, the mark ○ indicates excellent, and the mark X indicates defective.

As is clear from the characteristic test results, urethane lacquer
A test piece using a strippable paint having a composition within the range of 10 to 20 parts, 60 to 75 parts of isopropyl alcohol, 7 to 12 parts of toluene, 7 to 10 parts of ethyl acetate in a limited number of parts is visually inspected for the appearance, and a top coat is applied. All of the properties of adhesion, peelability, and spray application properties are good. However, if the urethane lacquer blending number is less than 10 parts, it is difficult to obtain a desired film thickness due to poor film-forming ability,
On the other hand, when the number of parts exceeds 21 parts, as shown in Comparative Example 1, a problem arises in spray application properties. Comparative Example 2 with less than 60 parts of isopropyl alcohol
As shown in (1), the smoothness of the coated surface of the strippable paint coating film deteriorates, and when the blending number exceeds 75 parts, the coated surface similarly sags as shown in Comparative Example 3.
On the other hand, if the blending amount of toluene is less than 7 parts, the quick-drying property is poor, and if it exceeds 12 parts, the drying is too fast and the smoothness of the coated surface of the strippable paint coating film is too high as shown in Comparative Example 4. Gets worse. Further, when the number of parts of ethyl acetate is less than 7 parts, as shown in Comparative Example 5, the interfacial adhesion with the coated surface of the top coat film is deteriorated. As shown in FIG. 6, a problem arises in the releasability of the top coat from the coated surface.

Next, the relationship between the film thickness of the strippable paint and the chipping resistance will be described. Urethane lacquer 15 parts as main agent, isopropyl alcohol 64 as solvent
Parts, 9 parts of toluene and 9 parts of ethyl acetate are sealed in a known spray can together with dimethyl ether aerosol gas. The viscosity of the strippable paint at this time is 90 poise at 25 ° C. This strippable paint was coated and dried on the coated surface of the top coat of the substrate so that the dried film thickness was 20 μm, 25 μm, 30 μm, and 60 μm, respectively, while covering approximately half the area. A total of 16 test pieces were prepared. Therefore, approximately half of each test piece is formed with a strippable paint film, and the rest of the test piece is not formed, and the overcoated surface remains as it is. For each test piece, a low-temperature chipping test was performed under the same conditions as described above, and the number of dents having a size of 1 mmφ or more generated in the overcoat film was measured. The graph shows the measurement results in the drawing. In the low-temperature chipping test, the parts of each test piece where the strippable paint is not applied are directly hit by the discharged crushed stones, causing direct chipping damage to the top coating film. Since the film protects the topcoat, the larger the thickness of the strippable paint, the less crushed stones reach the topcoat and the number of dents received by the topcoat I do.

As is evident from the drawing, where the number of dents received on the part where the strippable paint is not applied is about 15 on average, the dry film thickness of the strippable paint is 30μ, and the chipping damage of the top coat film Became 0. Therefore, when the dry film thickness of the strippable paint is formed to be 30 μm or more on the top coat, a reliable chipping resistance can be obtained. In addition, about each test piece from which the dry film thickness of a strippable paint coating film differs, as a result of having carried out the characteristic test about the interface adhesion and peeling property with a top coating film similarly to the above, Table-2 and Table- As shown in FIG. 3, good characteristics were obtained in each case.

As is clear from the characteristic test results of the strippable paint film, the portion of the automobile body that has been overcoated is susceptible to ston chipping, and the dry film thickness of the strippable paint film having the above composition is 30 μ or more. By forming as described above, it is possible to prevent the occurrence of dents reaching the top coat, but with the running of the vehicle for a considerable period, the strippable paint coat naturally deteriorates, and
Since many dents remain on this coating film, the appearance becomes unsightly. Therefore, usually every three to four weeks, the strippable paint film is peeled off to expose the top coat film, and the stripped paint is newly applied to the peeled portion and dried to improve the appearance and quality. Can be maintained.

In this example, the method of atomization by a spray can was used for applying the strippable paint.
Needless to say, the same chipping resistance can be obtained by brush coating or by using an ordinary spray gun.

〔The invention's effect〕

According to the coating method of the present invention having the above-described structure, a specific chipping-resistant paint is applied to a portion of the vehicle body that is susceptible to ston chipping to a thickness equal to or greater than a predetermined dry film thickness, and reaches the top coat. The chipping damage is not received so much that a reliable chipping resistance is obtained. In addition, since the urethane lacquer is used as the main agent, the chipping-resistant coating film is rich in elasticity, so it has excellent interfacial adhesion to the top coating film, and has good releasability, so it can be easily handled by hand without using a rim bar. Can be peeled off. Therefore, after a predetermined period of time has passed since the chipping-resistant paint has been applied to the finished car body and dried, the chipping-resistant paint film has deteriorated, or when many dents have formed on the paint film, the paint film is peeled off. If the procedure of applying and drying the anti-chipping paint again on the peeled portion is repeated, there is an effect that the new anti-chipping coating can reproduce a beautiful appearance and maintain good quality by simple means.

[Brief description of the drawings]

The drawing is a graph showing the anti-chipping effect when the thickness of the anti-chipping coating film in the examples of the present invention is changed.

Claims (1)

(57) [Claims] 1. A urethane lacquer 10 is provided on a portion of an automobile body that has been overcoated to be easily subjected to ston chipping.
~ 20 parts, 60-75 parts of isopropyl alcohol as solvent,
An anti-chipping paint containing 7 to 12 parts of toluene and 7 to 10 parts of ethyl acetate is applied and dried so as to have a dry film thickness of 30 μ or more. After a predetermined period, the coating film of the applied and dried anti-chipping paint is peeled off. And repeating the procedure of applying and drying the chipping-resistant paint on the peeled portion again.