JPH04354564A - Surface treatment of resin molding - Google Patents

Abstract

PURPOSE:To provide the method for the surface treatment of a resin molding which can improve the adhesion of a coated film and does not adversely affect environment. CONSTITUTION:This method for the surface treatment of the thickness consists of a washing stage for washing the surface of the thickness of polypropylene, etc., to be used as a side mold, etc., with an alcoholic solvent, such as isopropyl alcohol, a corona treatment stage for subjecting the surface of the resin molding washed in this washing stage to a corona discharge treatment and a coating stage for coating the surface of the resin molding subjected to the corona discharge treatment with a coating material, such as urethane coating material of a two pots type.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for surface treatment of resin molded articles, particularly polyolefin resin molded articles with poor paint adhesion.

0002

2. Description of the Related Art Conventionally, when painting polypropylene resin molded products such as side moldings attached to both sides of an automobile, the process is as follows. That is, first, the surface of the resin molded article is washed with 1,1,1-trichloroethane, and then the surface is degreased. Through this degreasing treatment, oil components such as mold release agents and rust preventive agents that are thinly attached to the surface of the resin molded product are dissolved in 1,1,1-trichloroethane.
remove from its surface. Then, this resin molded product was
Dry for 15 minutes at °C.

[0003] Next, a chlorine-based primer is applied in advance to the surface of the degreased resin molded product in order to improve the adhesion of the paint, and the product is dried. Next, a two-component urethane paint is sprayed onto the surface of the resin molded product using a spray gun. Then, it is dried at 80° C. for 30 minutes. In this way, a coating layer having a predetermined color tone is formed on the surface of the resin molded article.

0004

[Problem to be Solved by the Invention] Generally, the surface of a resin molded product made of polyolefin such as polypropylene has low polarity and is inert, so when paint is applied to the surface of a resin molded product, the adhesion of the paint is poor. Inferior. Therefore, as mentioned above, the surface of the resin molded product is cleaned with 1,1,1-trichloroethane in advance and degreased to remove oil adhering to the surface of the resin molded product, and then a primer is applied.
Needs to dry. This primer has the function of improving the adhesion between the surface of the resin molded article and the coating layer formed by the paint, and promoting the curing of the paint.

However, this primer is still insufficiently effective in improving the adhesion of the paint layer, and furthermore, if the degreasing treatment is insufficient, this primer has the problem that its effectiveness is further reduced. Ta. In addition, 1,1,1-trichloroethane, which is used to clean the surface of resin molded products, is effective for removing oil and other substances adhering to the surface of resin molded products, but it is also effective in degreasing, especially in the ozone layer. It is a substance whose use is being regulated as it has an adverse effect on the human body, and there is a desire for a substance that can replace it.

The present invention has been made to solve the above-mentioned problems, and its purpose is to improve the adhesion of the coating film and to improve the surface of resin molded products with less negative impact on the environment. The purpose is to provide a processing method.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a cleaning process in which the surface of a resin molded product is cleaned with an alcohol-based solvent, and a cleaning process in which the surface of the resin molded product that has been cleaned in the same cleaning process is washed with an alcohol-based solvent. The gist is a method for surface treatment of resin molded products, which consists of a corona treatment step in which a corona discharge treatment is performed, and a coating step in which a paint is applied to the surface of the resin molded product that has been subjected to the corona discharge treatment in the same corona treatment step.

[0008]

[Operation] In the cleaning process, the surface of the resin molded product is cleaned with an alcohol solvent. This alcohol-based solvent can dissolve oil and other substances on the surface of resin molded products and sufficiently remove them from the surface, and it does not have the risk of deteriorating the environment like conventional 1,1,1-trichloroethane. do not have.

In the corona treatment step, carbonyl groups and carboxyl groups are generated and activated by ozone generated by corona discharge on the surface of the cleaned resin molded article. In the painting process, paint is applied to the surface of the corona discharge-treated resin molded product to form a coating layer. This coating layer has good adhesion to the surface of the resin molded product due to the reaction between the carbonyl and carboxyl groups generated on the surface of the resin molded product during the corona treatment process and the functional groups in the paint. .

0010

[Examples] Examples embodying the present invention will be described below. The material constituting the resin molded product targeted by the present invention is polypropylene (polypropylene), which has poor adhesion to paints.
(hereinafter referred to as PP), thermoplastic polyolefin as a thermoplastic elastomer (hereinafter referred to as TPO), styrene-
Ethylene-butylene-styrene copolymer resin (SEB)
(referred to as S). As the TPO, for example, the product name 9070B manufactured by Mitsui Petrochemical Co., Ltd. can be mentioned. Examples of resin molded products using these materials include side moldings, bumpers, mudguards, etc. as automobile parts.

Now, among the surface treatment methods for such resin molded articles, the cleaning step will first be explained. In this process, oil and fine dust on the surface of the resin molded product are removed by wiping the surface of the resin molded product using isopropyl alcohol as an alcohol-based solvent, or by immersing the resin molded product in isopropyl alcohol or cleaning it with steam. remove. This alcohol-based solvent has excellent cleaning effects and has little effect on the ozone layer. As the alcohol solvent, in addition to isopropyl alcohol, lower alcohols such as ethanol and methanol may be used.

Next, the corona treatment step will be explained. Corona discharge is a phenomenon in which when a high voltage is applied between two conductors, a discharge occurs accompanied by light emission immediately before a spark discharge occurs. Therefore, the resin molded product cleaned in the cleaning step is placed on an insulating plate on which a counter electrode is provided, and corona discharge is caused between the counter electrode and the main electrode located above the counter electrode. In this state, corona discharge treatment is performed over the entire resin molded product while moving the main electrode along the resin molded product. The conditions for this corona discharge treatment are, for example, a corona discharge output of 125 W and a treatment speed of 100 mm/min. For details of this corona treatment process, please refer to JP-A-62-
It is described in No. 106935, Japanese Unexamined Patent Publication No. 115039/1983, and the like.

[0013] By performing this corona discharge treatment,
The surface of the resin molded product is chemically activated. That is, on the surface of the resin molded product, carbonyl groups, carboxyl groups, etc. are generated by ozone generated by corona discharge, and these functional groups react with the functional groups in the paint, which will be described later, to form a coating layer on the surface of the resin molded product. Improves adhesion. Next, in the painting process, for example, a two-component urethane paint is applied to the surface of the resin molded product. Specifically, this is carried out by mixing a solution consisting of a polyisocyanate compound and a pigment having a predetermined color tone with a solution consisting of a polyol compound, and spray-coating the mixture onto a resin molded article using a spray gun. Then, it is dried at 80° C. for 30 minutes.

[0014] In this way, a coating layer having a predetermined color tone can be formed on the surface of the resin molded article. As mentioned above, this coating layer is coated with corona discharge treatment on the surface of the resin molded product, so the surface of the resin molded product is activated, and as a result, the adhesion of the coating layer to the resin molded product is improved. improves. In order to compare the adhesion of the coating layer to the resin molded article with a conventional method, the 180 degree peel strength of the coating layer was measured. The results are shown in Table 1. The measurement conditions are as follows.

(1) Material of resin molded product: TPO or SE
BS (2) Cleaning step: TCE represents a cleaning treatment using 1,1,1-trichloroethane. IPA represents a product washed with isopropyl alcohol.

[0016]

[Table 1]

As shown in Table 1 above, Example 1 of the present invention
and Example 2 both exhibit high 180 degree peel strength. From this result, even if the material is TPO, S
It can be seen that even with EBS, the adhesion of the coating layer to the surface of the resin molded product is excellent. On the other hand, although Comparative Example 1 has high peel strength, it is inappropriate because it uses 1,1,1-trichloroethane as a cleaning agent. Comparative Example 2 shows that the primer treatment is inferior to the corona discharge treatment of Comparative Example 1. Comparative Example 3 shows that the primer treatment is considerably inferior to the corona discharge treatment of Example 1. Comparative Example 4 shows that the primer treatment is considerably inferior to the corona discharge treatment of Example 2 even when the material is SEBS.

As described above, in the cleaning process, the surface of the resin molded product is washed with an alcohol-based solvent to sufficiently remove oil from the surface of the resin molded product, and in the corona treatment process, the surface of the resin molded product is chemically cleaned. , it is possible to significantly improve the adhesion of the coating film to the resin molded product. Therefore, superior adhesion can be obtained compared to the case of using a conventional primer, and the effect can be exhibited without being greatly affected by the state of the cleaning treatment with the alcohol solvent. Furthermore, alcoholic solvents such as isopropyl alcohol are less likely to have an adverse effect on the environment than conventional 1,1,1-trichloroethane.

The present invention is not limited to the above embodiments, and for example, acrylic paints, epoxy paints, etc. may be used as the paint used in the painting process.

[0020]

[Effects of the Invention] As detailed above, according to the surface treatment method for resin molded products of the present invention, it is possible to significantly improve the adhesion of the coating film, and it is said that there is little negative impact on the environment. be effective.

Claims (1)

[Claims] Claim 1: A cleaning process in which the surface of the resin molded product is cleaned with an alcohol-based solvent, a corona treatment process in which the surface of the resin molded product that has been cleaned in the cleaning process is subjected to corona discharge treatment, and a corona treatment process in which the surface of the resin molded product is subjected to corona discharge treatment. A method for surface treatment of resin molded products, which comprises a painting process of applying paint to the surface of the resin molded products that have been subjected to corona discharge treatment.