JPS6228813B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for improving the paintability, printability, adhesion, etc. of a molded product by treating the surface of a molded product made of a composite resin in which a propylene polymer is filled with inorganic fine powder with low-temperature discharge plasma. Resin surface treatment technology is useful in commercializing resin products and in increasing the versatility of products.
It is essential. However, in the case of polypropylene resin, etc., its properties are crystalline and non-polar, so the surface of the molded product can be painted (paintability), printed (printability), or printed. It was considered difficult to bond (adhesive). 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 flame treatment, There is a problem in that the objects to be processed are limited to objects with simple shapes. 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 homopolypropylene resin molded product was subjected to low-temperature plasma treatment, 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 of a gas such as oxygen, nitrogen, argon, helium, etc., preferably oxygen, is excited by a desired discharge such as glow discharge or high-frequency discharge to generate low-temperature plasma, and in this atmosphere, inorganic fine powder is added to the propylene polymer. For example, a molded product obtained by molding a composite resin filled with 5 to 60% by weight of talc clay, calcium carbonate, or barium sulfate, etc. is placed and subjected to the low temperature plasma treatment, or the low temperature plasma is blown onto the surface of the molded product. This is a method of attaching and processing. Here, the propylene polymer may be homopolypropylene, ethylene-propylene copolymer, copolymer of propylene with a small amount of other monomer, polyethylene, polypropylene mixture, or homopolypropylene, ethylene-propylene copolymer. , a copolymer of propylene with a small amount of other monomers, polypropylene, a polypropylene mixture, etc., mixed with rubber or other fillers, or added with antioxidants, pigments, etc. may also be used. Furthermore, 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, output, etc., are not particularly limited and the processing can be performed using normal conditions, but as a result of the studies conducted by the present inventors. It was found that the amount of treatment had a significant effect on the surface quality. 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 improve with a certain range of processing amount, but conversely decrease when the processing amount exceeds that range. After focusing on this phenomenon and conducting various studies, we found that the processing amount is
Discharge unit output wattage (W) and processing time t (sec)
and the processing chamber volume V( ) 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~
60000Wsec/” Preferably, “200~
It was found that it was large in the range of 30000Wsec/''. Next, examples of the present invention will be shown, and when the resin molded article according to 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) In this example, 20% by weight of talc was added to polypropylene.
Regarding the molded product test piece according to this invention obtained by injection molding a composite resin containing such that
On the other hand, in Comparative Example 1, a molded test piece obtained by injection molding was subjected to plasma treatment in the same manner as in Example 1 for a resin containing only polypropylene without talc. 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 (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: Each machine manufacturing company SJ45C Test piece: 100mm x 100mm x 3mmt (plate shape) (2) Measurement items (A) Test piece comrades after processing After adhering with epoxy 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 test piece with water was measured. (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 ³ .
At this time, the overlapping part should be 15 mm x 15 mm. Next, heating 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). (4) Test results The results of the above tests are shown in Table-1.

[Table] From the above results, when the epoxy peel strength was filled with talc in Example 1, the plasma treatment significantly improved the epoxy peel strength and reached saturation in 5 minutes. This is approximately twice as large as in the case of . Regarding the degree of decrease in the contact angle, there is a tendency for the surface activity to become larger in Example 1, and according to the results of observation of the treated surface using a scanning electron microscope (not shown), in the case of Example 1, Without treatment, talc is hardly exposed on the surface, but with plasma treatment, talc is exposed and the surface unevenness becomes extremely noticeable, whereas in the case of Comparative Example 1, with plasma treatment, The unevenness only increases slightly. In this way, when polypropylene filled with talc is plasma treated, the adhesion is improved not only by the polarization effect of the polypropylene surface due to the plasma treatment, but also by the volatilization and escape of the surface polypropylene layer, which improves the adhesion of the filler from the surface. It is presumed that this is due to the increase in surface activity due to exposure to water, the increase in the actual adhesion area due to the formation of surface irregularities, and the anchoring effect. Example 2 (including comparative examples and reference examples) In this example, 50% of talc was added to homopolypropylene.
A composite resin containing ~6% by weight of talc, a composite resin containing 20% by weight of talc in an ethylene propylene block copolymer containing 8% by weight, and a homopolypropylene containing heavy carbonate. Composite resin containing 20% by weight of calcium, composite resin containing 20% by weight of colloidal calcium carbonate in homopolypropylene, homopolypropylene with average particle size
Moldings of composite resin containing 20% by weight of barium sulfate (0.5μ) were subjected to low-temperature plasma treatment, whereas comparative examples were made using homopolypropylene containing 3% by weight or 70% by weight of talc. A composite resin containing 70% by weight of heavy calcium carbonate in homopolypropylene was subjected to low-temperature plasma treatment. As described above, in this example and comparative example, resin molded articles having different types and concentrations of inorganic fine powders were subjected to plasma treatment and the treatment effects were observed. Plasma treatment was carried out under the same conditions for both Examples and Comparative Examples, and the following tests were conducted to examine how the differences in the components of the inorganic fine powders of both cases affected the treatment effects. 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-7407 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: Sprayed to a film thickness of approximately 30 μm and baked for 1 hour at a temperature of 70°C. The test was carried out after being stored indoors for 3 days. Paint Film Test Adhesion (Checkerboard Test) Use a razor to make cuts in the paint film to create 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 in boiling water for 2 hours after boiling.

【table】

[Table] Regarding the above results, Example 2 and Comparative Example 2,
It was found that the epoxy peel strength of the Examples due to plasma treatment was about twice as high as that of the Comparative Examples, and that the adhesiveness of the Examples was significantly improved. Although the difference in initial adhesion of the coating films was relatively small, there was a significant difference in hot water resistance. Furthermore, when the material in Example 2 (in Table 2) is an ethylene propylene block copolymer resin, the adhesion properties are greatly improved, in addition to the effect caused by mixing the filler. This is thought to be due to the effect of the heterogeneous structure of the resin phase. The effect of the heterogeneous structure is that the two resin phases, polyethylene and polypropylene, have different stability against oxidation, with polypropylene being more susceptible to oxidation and the polypropylene part escaping earlier when exposed to plasma. However, the ethylene portion remains in a convex shape, resulting in an uneven resin surface. Next, the adhesion was effective up to 60% filler content, but the effectiveness decreased significantly when the amount exceeded 70%. The reason for this is that when the filler filling amount reaches 70%, the filler itself peels off and falls off. From the above results, the effect of the present invention is that the content of talc, calcium carbonate, or barium sulfate is 5 to 60%.
It was found that the effect was significantly exhibited when the weight percentage was increased. Example 3 (Including Comparative Example) In this example, a composite resin in which polypropylene was filled with talc at a concentration of 20% by weight was molded using a molding machine (Toshiba
IS515B) was used to manufacture an automobile furnace body, plasma-treated it, sprayed and applied urethane paint onto the surface of the treated automobile furnace body, and tested the adhesion and impact resistance of this coating film. This is what I did. On the other hand, in a comparative example, an automobile furnace body made of a single resin of polypropylene that does not contain talc was subjected to plasma treatment, and the same test as in the example was conducted. Plasma treatment and other tests in this example and comparative example were 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) ) Measuring method (a) Urethane coating method Paint: Cashew two-component curing type Stron Ace #8000 Film thickness: Approximately 30μ (a) Adhesion test Cross-cut test (c) Impact resistance test The product was tested using a Dupont impact tester. The back side of the flat part was struck from 50 cm above with an object with a load of 0.5 kg, and the state of peeling of the paint film was observed.

[Table] From the above test results (Table 3), it was found that the coating film of Example 3 had considerably high practical adhesion performance, and the coating film of Comparative Example 3 had poor practical adhesion performance. In other words, it has been demonstrated that when a polypropylene composite material filled with 20% by weight of talc is subjected to plasma treatment, its paintability is significantly improved.

Claims (1)

[Claims] 1. On the surface of a molded product made of a composite resin made of propylene polymer filled with 5 to 60% by weight of inorganic fine powder,
The molded article is irradiated with low-temperature plasma generated by exciting a gas such as oxygen, nitrogen, argon, helium, etc. under a pressure of 100 mmHg or less by an electric discharge such as a glow discharge, and the plasma processing amount is in the range of 100 to 60,000 Wsec/. A surface treatment method characterized by improving surface performance.