JPH0588262B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to a method for pre-painting a polyolefin resin product such as polyethylene (PE) or polypropylene (PP). (Prior Art) Since polyethylene, polypropylene, etc. can be colored themselves, there is generally no need to paint them. However, for example, if an automobile bumper is obtained by molding the above-mentioned resin, it may be necessary to paint or color code a part of the automobile bumper in relation to other parts. . On the other hand, olefin resins have low surface energy and extremely weak coating film adhesion. Therefore, conventional methods have been to treat the surface of resin products with a chlorinated organic solvent such as trichlorethylene and then apply a primer, or to treat the surface with trichlorethylene as disclosed in JP-A-57-15870. A pre-painting treatment method has been proposed in which surface treatment is carried out using oxidizing low-temperature plasma treatment. (Problems to be Solved by the Invention) In the method described above, that is, the method of treating the surface of a polyolefin resin with a chlorinated organic solvent such as trichlorethylene, trichlorethylene is highly toxic and Careful attention must be paid to drainage and operational management.Furthermore, if the surface is treated with an organic solvent such as trichlorethylene, the surface of the resin product will become too rough, and if plasma treatment is applied, This results in so-called over-etching, which has the disadvantage of decreasing the peel strength of the coating film. (Means for Solving the Problems) In order to solve the above problems, the present invention uses a degreasing agent made of a water-soluble inorganic solvent instead of a chlorinated organic solvent such as trichlorethylene to produce polyolefin resin products. After degreasing the surface of O ₂
The surface was treated with plasma to increase the adhesion of the coating on the surface of the resin product. (Function) By treating the surface of polyolefin resin products with a degreasing agent made of a water-soluble inorganic solvent, oils on the surface of the resin product can be easily removed, and problems caused by treatment with organic solvents can be avoided. In other words, over-etching due to extreme surface roughening can be avoided. In addition, wastewater treatment is easy because it only requires neutralizing the washing water, and there is no danger of air pollution or ignition caused by evaporation of organic solvents, and operational management is also easy. be.
In addition, there is no need to resupply the shortage due to evaporation, and so-called running costs are low. (Example) Examples of the present invention will be described below with reference to the accompanying drawings. In the examples, an automobile bumper is shown as a polyolefin resin product. First, in the present invention, as shown in FIG. 1, a molded automobile bumper 1 is immersed in a degreasing tank 2 to degrease the surface of the bumper 1. Here, the polyolefin resin constituting the bumper 1 includes, for example, polyethylene, polypropylene, polyethylene homopolymer, polypropylene homopolymer, ethylene vinyl acetate copolymer, ethylene acrylate copolymer, ethylene propylene copolymer, and a thermoplastic elastomer in a single substance or a mixture thereof. Examples include those mixed with inorganic fillers, glass fibers, etc. Further, as the degreasing agent, a degreasing agent made of a water-soluble inorganic solvent, specifically, sodium metasilicate or the like is used. In the example, the bumper 1 was suspended and supported by the hanger 3 and immersed in the degreasing tank 2, but a degreasing agent was sprayed onto the surface of the bumper 1 using a spray gun or the like. You can do it like this. When the degreasing process on the surface of the bumper 1 is completed in this way, as shown in FIG.
The bumper 1 surface is treated with O ₂ plasma. Then, a polymer that does not contain oxygen, such as a polyolefin resin, incorporates a large amount of active oxygen radicals into the polymer as carbonyl bonds, increasing the surface energy and greatly increasing the adhesive strength of the coating film. The conditions for plasma processing here vary depending on the plasma processing tank, the shape of the product being processed, etc., but when using oxygen gas as the processing gas, the degree of vacuum is 0.3 to 5.0 Torr, and the frequency is 2450±.
It is preferable to use 10 MHz and a processing time of 5 to 300 seconds. Thereafter, as shown in FIG. 3, a two-component urethane paint 7 is applied as a top coat using a spray gun 6 to obtain a product. Next, specific experimental results are shown in a table and compared with conventional examples.

[Table] The conditions for plasma treatment in the experiment are as follows. Microwave output…2450MHz×1.5Kw Processing gas…O ₂ 97%, N ₂ 3% Processing gas flow rate…2/min Processing time…20sec Pressure…0.8~1.0Torr Also, the coating peel strength (Kg/cm) is as follows: This is called peeling strength, and is the force required to peel off a 1cm wide coating at a speed of 30mm/min after 48 hours of baking drying, measured using a horizontal load measuring machine. As is clear from the table, according to the method of the present invention, the peel strength of the paint film is comparable to that of the conventional method, which was prepared by applying a primer in advance to improve adhesion. It can be seen that this is a significant improvement compared to the conventional method. (Effects of the Invention) As is clear from the above description, according to the painting pretreatment method according to the present invention, the surface treatment of polyolefin resin products is performed using a degreasing agent made of a water-soluble inorganic solvent. There is no over-etching when plasma treatment is performed later, and the adhesion of the coating film on the surface of the resin product is improved. Furthermore, it is extremely advantageous in terms of wastewater treatment, operational management, safety management, etc. compared to the case of using trichlorethylene or the like.

[Brief explanation of the drawing]

Figure 1 shows the degreasing process for resin products, Figure 2
The figure shows the degreased resin product being carried into the plasma processing apparatus, and FIG. 3 shows the resin product being painted. In addition, 1 in the drawing is a bumper which is a resin product, 2
5 is a degreasing tank, and 5 is a plasma processing device.

Claims (1)

[Claims] 1. After treating the surface of a polyolefin resin product with a degreasing agent made of a water-soluble inorganic solvent, the resin product is placed in a plasma treatment chamber with a treatment gas atmosphere mainly consisting of oxygen gas, and then the inside of the plasma treatment chamber is A pre-painting treatment method characterized in that the surface of a resin product is treated by activating a treatment gas by reducing the pressure and generating plasma.