JPH0546849B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method for coating colored polypropylene resin molded articles. [Prior Art] Polypropylene resin has traditionally been widely used in industrial parts due to its excellent chemical, physical, and electrical properties. Also, because it is highly crystalline, it has poor solubility in active agents and has very low paintability. To this end, various surface treatments have been carried out on the surface of polypropylene resin molded articles to improve paintability. The surface treatment methods include flame treatment, corona discharge treatment, etc., but there are problems such as restrictions on the shape of the molded product, reduced sustainability of surface activity, and restrictions on painting. Treatment methods using halogen-containing organic solvents are also used, but
Due to problems such as the necessity of a priming process and environmental pollution caused by halogen-containing organic solvents, a method of applying a topcoat after surface treatment with plasma has become widely used. Many polypropylene resin molded products that are subject to painting are colored with inorganic or organic pigments, or a combination of these, regardless of whether they are fully or partially painted.Particularly for those used outdoors, etc. Considering the method of use, carbon black or a black pigment mainly composed of carbon black is often added to improve weather resistance, and the amount of carbon black added is also increasing. This is the current situation. However, it has become clear that when a polypropylene resin molded article to which a large amount of carbon black has been added is painted after plasma treatment, the paintability is significantly reduced. [Problems to be Solved by the Invention] An object of the present invention is to provide a method for coating colored polypropylene resins that does not have the various drawbacks of conventional methods. [Means for Solving the Problems] As a result of intensive research on the method of coating colored polypropylene resin molded products, the present inventors found that after plasma treatment, polypropylene resin molded products with a specified amount of carbon black added The present inventors have discovered that painting improves the paintability dramatically. That is, the present invention uses polypropylene resin (A) 100
parts by weight, thermoplastic elastomer (B) 0 to 100 parts by weight,
Inorganic filler (C) 0 to 100 parts by weight ((B) + (C) / (A)
A polypropylene resin composition obtained by adding 0.01 to 0.6 parts by weight of carbon black to 100 parts by weight of a resin consisting of 1.0 or less) is coated after plasma treatment. This is a painting method. The polypropylene resin used in the present invention means a propylene homopolymer, an ethylene/propylene copolymer, or a copolymer of propylene and other α-olefins, to which various polyethylenes and other crystalline resins are added. But it's okay. Further, if necessary, it may be partially or entirely modified with an unsaturated carboxylic acid such as maleic anhydride. Thermoplastic elastomers include ethylene/propylene copolymer rubber, ethylene/propylene copolymer rubber,
Examples include diene copolymer rubber, styrene/butadiene copolymer rubber, isobutylene/isoprene copolymer rubber, and the like. The inorganic filler is a powdered fibrous inorganic filler, such as calcium oxide, magnesium oxide, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, magnesium carbonate, calcium silicate, magnesium silicate, calcium sulfate, magnesium sulfate, carbonate. Calcium, barium sulfate, calcium sulfite, potassium titanate,
Examples include talc, clay, mica, glass, basic magnesium carbonate, dolomite, and the like. These various inorganic fillers may be surface-treated with various coupling agents, surfactants, etc., and these surface treatments contribute to improving the rigidity and impact resistance of the resin composition. The amounts of the thermoplastic elastomer and inorganic filler used in the present invention are 0 to 100 parts by weight of the thermoplastic elastomer and 0 to 100 parts by weight of the inorganic filler, based on 100 parts by weight of the polypropylene resin.
Further, it is desirable that the total amount of the thermoplastic elastomer and the inorganic filler is in the range of 0 to 100 parts by weight,
If the thermoplastic elastomer or inorganic filler or the total amount thereof exceeds 100 parts by weight, the balance of mechanical properties such as rigidity and impact resistance and paintability of the resulting polypropylene resin composition will deteriorate. Undesirable. A carbon black-free polypropylene resin composition obtained by adding or not adding a thermoplastic elastomer and/or an inorganic filler to the above-mentioned polypropylene resin is hereinafter referred to as a base resin. Examples of the carbon black used in the present invention include furnace black, thermal black, channel black, acetylene black, etc., which are generally used to color polypropylene resin black. In this respect, furnace black and channel black with an average particle diameter of 5 to 40 mμ are preferable.
Moreover, two or more types of these carbon blacks can also be used in combination. The average particle size of carbon black is preferably within the above range; if the average particle size is small, the particles will cause secondary aggregation and the dispersibility will decrease, and the price will also increase; Either case is unfavorable since the color tone becomes poor and the weather resistance also decreases. The value of the average particle diameter of carbon black is determined not only by direct measurement using an electron microscope, but also by the value obtained as a sphere based on the specific surface area determined from the adsorption amount of nitrogen, iodine, etc. The amount of carbon black added above is based on the base resin.
0.01 to 0.6 parts by weight per 100 parts by weight, preferably
It is necessary that the amount is 0.05 to 0.5 parts by weight, and the amount added is
If it is less than 0.01 part by weight, weather resistance will decrease. To improve this, commonly used heat-resistant and weather-resistant stabilizers can be used, but especially for parts that require weather resistance, such as exterior parts, it is necessary to use quite a large amount of these stabilizers. This makes it extremely expensive, and it is not practical because the stabilizer stands out on the surface of the molded product after molding, reducing paintability and appearance. Furthermore, if the amount of carbon black added exceeds 0.6 parts by weight, the peel strength of the coating film applied after plasma treatment will be markedly reduced, and blistering will easily occur in the hot water resistance test, which is not preferable. In addition, various antioxidants, heat stabilizers, ultraviolet absorbers,
Ultraviolet stabilizer: Flame retardant, nucleating agent, organic or inorganic pigment, etc. may be used alone or in combination. The polypropylene resin composition of the present invention is mixed using a Henschel mixer or the like commonly used in the industry, and then mixed using a single-screw extruder.
It is often kneaded and pelletized using a twin-screw extruder such as FCM or CIM, rolls, or a Banbury mixer. The molded article used in the present invention is obtained by a commonly used molding method such as an injection molding method, an extrusion molding method, or a compression molding method using the resin composition obtained by the above method. The surface treatment method for molded products using plasma usually involves bringing plasma excited by oxygen, nitrogen, other inert gases, or a mixture of these gases into contact with the surface of the molded product using high frequency, microwave discharge, etc. can be done. The processing conditions vary slightly depending on the type of gas, but the normal pressure is 0.1 to 5 Torr, and the processing time is 5 to 600 Torr.
It is about seconds. Depending on the shape of the molded product, it may be necessary to lengthen the treatment time or change the shape of the treatment tank. The present invention will be specifically explained below using Examples. [Example] Examples 1 to 5 0.05 part by weight of 2,6-di-tert-butyl-4-methylphenol and 0.1 part by weight of calcium stearate per 100 parts by weight of polypropylene homopolymer (PP-A) having a melt flow index of 4.0. Parts by weight, tetrakis [methylene-3-(3',5'-di-
tert-butyl-4'-hydroxyphenyl)propionate] 0.2 parts by weight of methane, bis(2,2,6,
6-tetramethyl-4-piperidyl) sebacate
0.4 parts by weight, 0.2 parts by weight of 2-(3-tert-butyl-5-methyl-2-hydroxyphenyl)-5-chlorobenzotriazole, and an average particle size of 24
A furnace black (carbon black A) with an average particle diameter of 18 mμ and a channel black (carbon black B) with an average particle diameter of 18 mμ were mixed in the amounts shown in Table 1, and after mixing with a Henschel mixer, the temperature was set to 230 °C.
The resin composition was pelletized using a 40 mmφ extruder set at ℃, and the resulting resin composition was injection molded to obtain a test piece (80 x 160 x 2 mm flat plate). This test piece was subjected to plasma treatment under the following conditions, then coated with a two-component urethane topcoat to a film thickness of 50 μm, dried at 90°C for 40 minutes, and then kept at room temperature for 48 hours. I left it alone and got a painted product. The width of the cutter is applied to the coating film of this painted product.
A 1.0 cm cut was made and the 180° peel strength of the coating film was measured using an Instron tensile tester. In addition, the coated product was immersed in warm water at 40°C and the state of the coating film was visually determined after 240 hours. ●Plasma processing conditions (1) Plasma processing equipment Toshiba microwave plasma processing equipment (TMZ-2026M) (2) Processing gas Oxygen (3) Processing time 30 seconds (4) Gas pressure 1.0Torr (5) Gas flow rate 480c.c ./min (6) Microwave output 1500W ●Judgment criteria for paint film condition ○: No blisters in the paint film △: Some blisters in the paint film ×: Quite a few blisters in the paint film The results are shown in Table-1. Example 6 Instead of PP-A in Example 1, ethylene content was 8
Weight%, melt flow index 3.8/10min
Ethylene-propylene block copolymer (PP)
-B) was used, and the test was conducted in the same manner as in Example 1, except that the amount of carbon black A added was set to the value shown in Table 1, and the obtained results are shown in Table 1. Examples 7 and 8 In Example 6, ethylene-propylene copolymer rubber (EPR) with a propylene content of 26% and a Mooney viscosity of 24 at 100°C was used with respect to 100 parts by weight of PP-B.
Table 1 shows the results obtained by testing in the same manner as in Example 6, except that 20 parts by weight and 40 parts by weight of -A) were added. Examples 9 and 10 In Example 6, for 100 parts by weight of PP-B,
The test was carried out in the same manner as in Example 6, except that 10 parts by weight and 20 parts by weight of talc having an average particle diameter of 3.2 μm were added, and the results obtained are shown in Table 1. Example 11 Tests were carried out in the same manner as in Example 6, except that 20 parts by weight of calcium carbonate having an average particle size of 2.5 μm were added to 100 parts by weight of PP-B, and the results are shown in Table 1. Examples 12 to 14 Tests were conducted in the same manner as in Example 6, using the proportions of PP-B, EPR-A, talc, and calcium carbonate shown in Table 1. The results obtained are shown in Table-1. Comparative Examples 1 to 5 In Examples 1, 4, 6, 7, and 12, the addition amount of carbon black-A or -B was changed to the ratio shown in Table 1 to 100 parts by weight of each base resin. The results obtained by testing in the same manner as in Example 1 are shown in the table below.
Shown in 1.

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【table】

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〔Effect of the invention〕

By the method of the present invention, it has become possible to coat molded articles of colored polypropylene resin compositions, which have conventionally had various problems, with extremely excellent peel strength and moisture resistance.

Claims (1)

[Claims] 1. 100 parts by weight of polypropylene resin (A), 0 to 100 parts by weight of thermoplastic elastomer (B), inorganic filler (C)
Add carbon black to 100 parts by weight of resin consisting of 0 to 100 parts by weight (however, (B) + (C) / (A) = 1.0 or less).
A method for coating a polypropylene resin molded article, which comprises coating a molded article obtained from a polypropylene resin composition containing 0.01 to 0.6 parts by weight after plasma treatment.