JPS6228812B2 - - Google Patents

Description

[Detailed description of the invention]

This invention uses an ethylene-propylene block copolymer or a polyethylene-polypropylene mixture as a raw material resin, and treats the surface of the molded product obtained by molding the resin with low-temperature discharge plasma, thereby improving the paintability and printability of the molded product. and a method for improving adhesion and the like. Surface treatment technology for resins is essential for commercializing resins and for increasing the versatility of products. However, in the case of polypropylene resin, etc., since its properties are crystalline and non-polar,
It has been considered difficult to paint (paintability), print (printability), or adhere objects (adhesiveness) to the surface of the molded product. Subsequently, surface treatment technology for polypropylene resin was also researched and developed, leading to gradual improvements in paintability, printability, and adhesion. Surface treatment technologies that have been established so far include:
The main methods known are chromic acid treatment, corona treatment, and flame treatment, but each has its own problems.
The application of the processing technology is limited. For example, in chromic acid treatment, there is a problem in waste liquid treatment, in corona treatment, the surface treatment target is limited to membrane-like objects such as films and sheets, and in frame treatment, surface treatment There is a problem that the object is limited to a simple shape. The low-temperature plasma treatment according to the present invention is a surface treatment technology that has been developed to solve these problems and be applicable to a wide range of applications. However, even in low-temperature plasma treatment, there is a problem in that the effect is not so pronounced depending on the resin to be treated. For example, even if the surface of a homo-polypropylene resin molded product was treated with low-temperature plasma, the paintability, printability, and adhesion properties were not significantly improved, and the product was impractical. The purpose of this invention is to provide a solution to the above-mentioned problems, and it is found that when low-temperature plasma treatment is applied to a specific resin composition, the paintability, printability, and adhesion improve compared to conventional examples. The object of the present invention is to provide a surface treatment method that significantly increases the amount of carbon dioxide and has excellent practical effects. The details of this invention will be explained below. In this invention, the pressure is 100 mmHg or less, preferably 0.1
~10 mmHg gas such as oxygen, nitrogen, argon, helium, etc., preferably oxygen, is excited by discharge such as glow discharge or high-frequency discharge to generate low-temperature plasma, and in this atmosphere, 1 to 35% by weight of ethylene is contained. An ethylene-propylene block copolymer or a polyethylene-polypropylene mixture is used as a raw material resin, and a molded product obtained by molding the resin is placed and subjected to the low-temperature plasma treatment, or the plasma is sprayed onto the surface of the molded product. related to the method of Here, as the above-mentioned block copolymer, for example, Japanese Patent Publication No. 40-11623, No. 43-11230, or No. 44-1973
16668, and preferably has an ethylene content of 3 to 30% by weight, an MI (melt index) of 0.8 to 3.0, and an elastic modulus of 6000 to 12000 Kg/ ^cm2. Particularly preferably, the ethylene content is 15-25% by weight and the MI is 2.0.
~3.0, and an ethylene/propylene copolymer having an elastic modulus of 7,000 to 10,000 Kg/cm ² is used. Furthermore, regarding the material of the resin, other monomers such as butene, hexene, maleic anhydride,
A copolymer of vinyl acetate or the like and ethylene or propylene, other resins, fillers, antioxidants, and other additives may be blended. Further, the molded product made of such a resin may be an injection molded product, a blow molded product, an extrusion molded product, etc., and is not limited to a specific product. Next, the plasma processing conditions, such as the type of gas, pressure, processing amount, processing time, temperature, pressure, etc., are not particularly limited, and the processing can be performed using normal conditions, but as a result of the inventors' investigation, , the processing amount is
It was found that this had a significant effect on the surface texture. That is, plasma treatment requires a certain amount of treatment or more in order to improve surface activity, but when the treatment amount is increased, the contact angle and gloss level decrease in accordance with the treatment amount. However, it has been found that paintability, printability, and adhesion are improved at a certain range of processing amount, but are conversely reduced when the processing amount exceeds that range. Focusing on this phenomenon, as a result of various studies, we found that the processing amount depends on the effective output wattage (W) of the discharge section and the processing time t.
(sec) and the processing chamber volume V(), it can be expressed by the following equation. Processing amount = W × t/V [W・sec/] The surface activity improvement effect is achieved when the processing amount is “100~
60000W・sec/” Preferably “200~30000W・
It was found that it was large in the range of 1.sec/'. In order to clarify this relationship, a case will be described in which a resin molded article made of a propylene/ethylene block copolymer having an ethylene content of 8% by weight is subjected to plasma treatment. That is, the activation output is 25W, 50W, 100W, 200W
The elapsed processing time is 8 seconds and 15 seconds.
A test was conducted to see how the shear peel strength of the molded product changes after treatment for 30 seconds, 30 seconds, 60 seconds, 120 seconds, 300 seconds, and 900 seconds. The test results are shown in Figure 1. Table 1 shows the relationship between processing time and processing amount for each output. The test results show that when the output was 25W, high peel strength was exhibited when the treatment time was 8 seconds or more. In this case, the processing amount calculated using the above formula (see Table 1) is 100 W·sec/or more. Similarly output
In the case of 200W, high peel strength was exhibited at a processing amount of 60,000W·sec/or less. Here, high peel strength refers to a strength of about 10 Kg/cm ² or more, and the plasma processing amount that indicates this high peel strength is "100 to 60000 W・sec/" preferably 200 to 60,000 W・sec/in the entire output range.
It is 30000W・sec/. Therefore, even if the processing amount is increased to 60,000 W・sec/or more, or even if it is decreased to 100 W・sec/or less, the peel strength will decrease. ~
It shows high peel strength at 60,000 W·sec/''. The plasma processing conditions shown in FIG. 1 are as follows. (a) Plasma treatment machine LFE plasma equipment (frequency 13.56MHz)
Model PDS-302 (a) Plasma processing method Gas body: Oxygen gas flow rate: 10c.c./min Plasma activation output: 25-200W Processing chamber volume: 2

[Table] The above peel strength was determined by the shear peel test method in the epoxy adhesive strength test of Example 1 described below. Next, examples of the present invention will be shown, and will show that when the resin molded product of the present invention is subjected to low-temperature plasma treatment under desired conditions, the resin surface not only becomes polarized, but also exhibits a surface roughening phenomenon. It is revealed that the paintability, printability, and adhesion of resin molded products are significantly improved. Example 1 (Including Comparative Example 1) This example describes a test piece of a molded product according to the present invention obtained by injection molding an ethylene propylene block copolymer (MFR6) with an ethylene content of 8% by weight. On the other hand, in Comparative Example 1, a molded test piece obtained by injection molding of homopolypropylene was subjected to plasma treatment in the same manner as in Example 1. Both Examples and Comparative Examples were subjected to plasma treatment under the same conditions, and by the test method described below,
An experiment was conducted to examine how the differences in the materials of both materials affect the processing effect. (1) Plasma treatment conditions (a) Plasma treatment machine IPC-2005 high frequency plasma treatment equipment (b) Plasma treatment method Gas body: Oxygen gas flow rate: 300c.c./min Gas pressure: 1mmHg Temperature: 50 to 80℃ Output: 100W Processing time: 0 to 15 minutes (C) Molding test piece Injection molding machine: Meiki Seisakusho SJ45C Test piece: 100mm x 100mm x 3mmt (plate shape) (2) Measurement items (A) After treatment, the test pieces were treated with epoxy After adhesion with resin and curing, the shear peel strength was measured. (b) In order to investigate the surface activity due to low-temperature plasma treatment, the contact angle of the treated specimen with water was measured. (c) In order to investigate the unevenness of the surface, the glossiness of the treated product was measured and observed using a scanning electron microscope (SEM). (3) Measurement method (a) Epoxy adhesive strength test method Adhesive: Konishiku Bond (two-component curing epoxy resin adhesive) Adhesion method Two pieces of 15 mm width x 50 mm length were prepared from the treated test piece. Cut out two test pieces, apply adhesive to one longitudinal end of one of the two test pieces, attach one end of the other test piece to it, and adhere by applying a force of 0.6 kg/cm ² .
At this time, the overlapping part should be 15 mm x 15 mm. Next, heat is continued for 1 hour at a temperature of 70°C to harden. Shear peel test Tensile tester (Autograph IS-500)
Perform a shear peeling test at a speed of 5 mm/min using a 5 mm/min, and determine the maximum stress. The value obtained by converting this determined maximum stress to 1 cm ² is the epoxy peel strength. (a) Method for measuring contact angle One drop of distilled water was dropped on the surface of the treated test piece, and the contact angle was measured using a contact angle measuring device (manufactured by Erma). (C) Glossiness measurement method The 60°/60° specular gloss of the surface of the treated test piece was measured using a glossmeter (manufactured by Toyo Rika). (d) SEM observation Au was vacuum-deposited on the surface of the treated test piece, and 1000~
Observed at 10,000x magnification. (4) Test results The above test results are shown in Table 2 and Figures 2 to 5.

[Table] From the above results, the epoxy peel strength of the ethylene propylene copolymer of Example 1 reached saturation in 5 minutes, and the strength was sufficiently greater than that of the homopolypropylene of Comparative Example 1. Yes, it has more than doubled. Although there is no difference in the contact angle, which is a measure of surface activity, between Example 1 and Comparative Example 1, there are significant differences in the change in glossiness, which is a measure of surface roughness, and in the SEM photographs. That is, in FIGS. 2 to 5, FIG. 2 shows the untreated test piece of the example, and FIG. 3 shows the test piece treated for 15 minutes, showing considerable convex portions.
Moreover, FIG. 4 shows an untreated test piece of a comparative example, and FIG. 5 shows the test piece treated for 15 minutes, and there is not much change compared to the untreated test piece. As described above, in the examples, considerable convex portions were formed, but this convex portion was observed by another phase contrast microscope (not shown) and was found to be a polyethylene phase. As mentioned above, the reason why the ethylene propylene block copolymer of Example 1 has a significantly higher processing effect, especially adhesive strength, than the homo-polypropylene of Comparative Example 1 is that between polyethylene and polypropylene,
The stability against oxidation is different, and polypropylene is more easily oxidized, which is the reason why in the case of ethylene/propylene block copolymer, the propylene copolymer part escapes first due to plasma irradiation, and the ethylene polymer part It is presumed that this is because the actual surface that contributes to adhesion increases because it remains in a convex shape, and an anchoring effect appears due to the formation of a large number of irregularities. Example 2 (Including comparative and reference examples) In this example, a molded article of an ethylene-propylene block copolymer or a polyethylene polypropylene mixture containing 1 to 35% by weight of ethylene was subjected to plasma treatment. On the other hand, in Comparative Examples, the above-mentioned copolymers or mixtures contain less than 1% by weight or more than 35% by weight of ethylene, or molded articles of homopolypropylene or the like that do not contain any ethylene are subjected to plasma treatment. As described above, in this example and comparative example, resin molded articles with different ethylene components were subjected to plasma treatment and the effects of the treatment were observed. Both Examples and Comparative Examples were subjected to plasma treatment under the same conditions, and the following tests were conducted to examine how the difference in ethylene-containing components would affect the treatment effect. Incidentally, as a reference example, the following test was conducted on a sample that was not subjected to plasma treatment, and the effect of plasma treatment was also investigated. (1) Plasma processing conditions (a) Plasma processing machine Toshiba TMW-7470 microwave plasma processing equipment (b) Plasma processing method Gas body: Oxygen gas flow rate: 100c.c./min Gas pressure: 0.5mmHg Temperature: 30℃ Output : 1KW Time: 15 seconds (2) Test method (a) The epoxy peel strength test is the same as in Example 1, so the explanation will be omitted. (a) Urethane coating test Paint: Two-component urethane paint (Dainippon Paint V Top) Coating method: Apply to a film thickness of approximately 30μ by spraying, and apply at a temperature of 70°C.
The test was carried out after being stored indoors for 3 days after baking. Paint Film Test Adhesion (Substrate Test) Use a razor to make cuts in the paint film to make 100 squares of 1 mm square. then 25
Nichiban cello tape with a width of mm was attached to the paint film, and the tape was strongly peeled off at an angle of 45°, and the number of grid lines of peeled paint was counted. Hot water resistance A grid test was conducted after boiling in boiling water for 2 hours.

[Table] From the above results (see Table 3), the epoxy peel strength of the example and the comparative example due to plasma treatment is approximately twice as high as that of the comparative example, and the adhesion of the example is significantly improved. It turns out that it does. The difference in initial adhesion of the coating films was relatively small, but there was a significant difference in hot water resistance. As shown in the reference example, in the case of a test piece that was not subjected to plasma treatment, the epoxy peel strength, coating adhesion, and hot water resistance were all almost zero. From the above results, it was found that the effects of the present invention are significantly exhibited when the ethylene component is 1 to 35% by weight. Example 3 (Including Comparative Examples) In this example, an automobile radiator grille made by injection molding of an ethylene propylene block copolymer with an ethylene component of 8% by weight was treated with plasma and sprayed with urethane paint. , the adhesion and impact resistance of this coating were tested. On the other hand, in a comparative example, an automobile radiator grille made by injection molding of a homopolypropylene resin containing no ethylene component was subjected to plasma treatment, and the same test as in the example was conducted. Plasma treatment and other tests in Examples and Comparative Examples were all conducted under the same conditions. (1) Plasma processing conditions (a) Plasma processing machine Toshiba microwave plasma processing equipment model TMZ-9602-A (b) Plasma processing method Processing gas: Oxygen gas pressure: 0.5mmHg Output: 2KW Time: 20 seconds (2) Measurement Method (a) Urethane coating Paint: Cashew two-component curing type Stron Ace #8000 Film thickness: Approximately 30μ (b) Adhesion test Cross-cut test (c) Impact resistance test Using a Dupont impact tester, load 0.5Kg
The product was struck from the back side of the flat part at a height of 50 cm, and the state of peeling of the paint film was observed.

[Table] From the results of this test (Table 4), it was found that the coating films of Examples had considerably high practical adhesion performance, and the coating films of Comparative Examples had poor practical adhesion performance. That is, it has been demonstrated that when an ethylene propylene block copolymer containing 8% by weight of ethylene is subjected to plasma treatment, the coating properties are significantly improved.

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between plasma treatment time and shear peel strength, Figure 2 is a SEM photograph of the surface of the molded test piece in Example 1 when untreated, and Figure 3 is the plasma treatment in Example 1. SEM photograph of the surface of the molded test piece after 15 minutes, and Figure 4 shows the surface of the molded test piece in Comparative Example 1 when untreated.
The SEM photograph, Figure 5, shows the surface of the molded test piece after 15 minutes of plasma treatment in Comparative Example 1.
It is a SEM photograph diagram.

Claims (1)

[Claims] 1. Oxygen, nitrogen, argon,
It is characterized by irradiating a gaseous body such as helium with a low-temperature plasma generated by exciting a gas such as a glow discharge, and improving the surface performance of the molded product when the plasma treatment amount is in the range of 100 to 60,000 W·sec/. surface treatment method.