JPH0811774B2 - Method for coating polypropylene resin composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polypropylene-based resin composition, and more particularly to a method for coating a polypropylene-based resin composition whose molded article has excellent coatability after plasma treatment.

[Prior Art] Since polypropylene resins are excellent in weight reduction, durability, safety, designability, economy, etc., their molded products are widely used in various industrial parts such as automobile parts. However, many are colored black or black based on the color tone and weather resistance. However, as a recent market demand, there is an increasing demand for higher quality by coating from the viewpoint of design and the like, and it is indispensable to impart paintability.

At present, as a method for coating polypropylene resin molded products, the surface treatment of the resin molded products is carried out with a halogen-containing organic solvent such as trichloroethylene, trichloroethane, etc., and then primer coating and top coating are often carried out. For the purpose of solving environmental pollution problems caused by halogen-based organic solvents and reducing costs by omitting steps, a method of performing topcoating after surface treatment of a molded product by plasma treatment has come to be implemented.

In most cases, the polypropylene resin before painting is often colored with a coloring agent composed of an inorganic type, an organic type or a combination thereof, regardless of whether it is a full-scale painting or a partial painting, especially outdoors. It is common to add carbon black or a black pigment mainly composed of carbon black to the parts to be used in consideration of the method of use and improving the weather resistance. At present, the amount of carbon black added to the polypropylene resin is also increasing.

[Problems to be Solved by the Invention] However, it becomes clear that when the molded product of the polypropylene resin in which a large amount of carbon black is added as described above is applied after the plasma treatment, the coating property is significantly reduced. As a result of intensive studies on polypropylene resin compositions with good coatability when coated after plasma treatment, the paintability of molded products dramatically improved by specifying the type and addition amount of carbon black to be used. The inventors have found that they are improved and have completed the present invention.

[Means for Solving the Problems] That is, the present invention comprises a polypropylene resin and carbon black, and 0.01 to 0.6 part by weight of carbon black is added to 100 parts by weight of the polypropylene resin, Has a mean particle size of 5 to 40 μm and a specific surface area of 50 to 1100 m ² / g.

[Embodiment of the Invention] The polypropylene resin used for constituting the polypropylene resin composition of the present invention means ethylene-
Means a propylene copolymer or a copolymer of propylene and other α-olefin, various polyethylene,
It also includes those in which 50% by weight or less of the copolymer is replaced with other crystalline resins and various rubbers (EPR, EPDM, etc.).

Examples of the carbon black in the present invention include furnace black, thermal black, channel black, acetylene black, etc., which are generally used after coloring a polypropylene-based resin black, but the color tone, heat resistance, weather resistance, etc. And the average particle size is 5-40 μm,
A specific surface area of 50 to 1100 m ² / g is used. Of these, furnace black and channel black are preferable. Of course, these carbon blacks can be used in combination of two or more kinds.

The amount of carbon black added is 0.01 to 0.6 parts by weight, preferably 0.
It should be 05 to 0.5 parts by weight. 0.01 added
If the amount is less than parts by weight, the weather resistance of the resin composition decreases, and heat and weather resistance stabilizers that are generally used for improvement can be used, but weather resistance such as exterior parts is particularly required. Since it is necessary to use a considerably large amount of these stabilizers in parts, the cost is very high, and in addition to the drawbacks such as the stabilizers protruding to the surface of the molded product after molding, the paintability and appearance are degraded. Yes Not practical. On the other hand, the added amount is 0.
If it exceeds 6 parts by weight, the peel strength of the coating film when the molded product is applied after plasma treatment is significantly reduced, and blister is likely to occur in the hot water resistance test, which is not preferable.

Further, the average particle size of carbon black needs to be in the above range from the viewpoint of dispersibility, color tone, weather resistance, etc. When the particle size is small, the particles cause secondary aggregation and dispersibility. In addition to lowering the cost, the cost is also high, and on the other hand, when the average particle size is large, not only the color tone deteriorates, but also the weather resistance decreases, which is not preferable. The average particle size of carbon black is measured directly by an electron microscope, and the specific surface area is determined by the adsorption amount of nitrogen and iodine.

In the polypropylene-based resin composition of the present invention, in addition to the polypropylene-based resin and carbon black,
As long as the effect of the present invention is not significantly impaired,
Antioxidants, heat stabilizers, ultraviolet absorbers, flame retardants, nucleating agents, organic / inorganic pigments, etc., which are usually added to polypropylene resins, may be used alone or in combination as required.

The polypropylene-based resin composition of the present invention comprises the polypropylene-based resin, carbon black and, if necessary, the above-mentioned additives, and various known means can be used for the blending. For example, if it is desired to obtain the resin composition of the present invention as pelletized, after mixing the above components using a Henschel mixer or the like generally used in the art, a single-screw extruder, FC
It can be easily obtained by kneading using a twin-screw extruder such as M or ICM, a roll, or a Banbury mixer. The resin composition thus obtained can be molded into a desired molded article by a commonly used molding method such as an injection molding method, an extrusion molding method, and a compression molding method.

The surface treatment of the molded product with plasma is performed by, for example, high frequency,
This can be carried out by contacting the surface of the molded product with plasma generated by exciting oxygen, nitrogen, another inert gas or a mixed gas of these by microwave discharge or the like. The condition varies slightly depending on the type of gas, but normally the pressure is 0.1 to 5 Tor
A suitable processing time is about 5 to 600 seconds. However, depending on the shape of the molded product, it may be necessary to lengthen the processing time or change the shape of the processing tank.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples.

[Examples 1 to 4] As a polypropylene resin, an ethylene-propylene copolymer (PP-A) having an ethylene content of 8% was used.
0 parts by weight of 2,6-di-tert-butyl-4-methylphenol 0.05 parts by weight, calcium stearate 0.1 parts by weight, tetrakis [methylene-3- (3 ', 5'-di-te]
rt-Butyl-4'-hydroxyphenyl) propionate] methane 0.2 parts by weight, bis (2,2,6,6-tetramethyl-
0.4 parts by weight of 4-piperidyl) sebacate, 2- (3-ter
t-butyl-5-methyl-2-hydroxyphenyl)-
0.2 parts by weight of 5-chlorobenzotriazole and furnace black (hereinafter referred to as carbon black A) having an average particle size of 18 μm and a specific surface area of 200 m ² / g or an average particle size of 14 μm
m and a specific surface area of 280 m ² / g, channel black (hereinafter referred to as carbon black B) was blended at the respective addition amounts shown in Table 1. After mixing each of the blends with a Henschel mixer, a resin composition of the present invention was obtained which was pelletized with a 40 mmφ extruder set at 230 ° C. Each of the obtained resin compositions was molded by injection molding to obtain a test piece for coating (80 × 160 × 2 mm flat plate).

Plasma treatment was applied to each of these test pieces under the following conditions, and then a two-component urethane-based topcoat paint was applied to a film thickness of 50 μm.
After drying for 1 minute, the coated article was obtained by leaving it at room temperature for 48 hours.

For each of the coated products obtained in this manner, a notch having a width of 1.0 cm was made in the coating film of the coated product with a cutter, and the 180 ° peel strength of the coating film was measured using an Instron tensile tester. Each of these coated products was dipped in warm water at 40 ° C., and the coatability was evaluated by visually determining the state of the coating film after 240 hours. The results are shown in Table 1.

Plasma processing conditions 1) Plasma processing device; Toshiba microwave plasma processing device (TMZ-2026M) 2) Processing gas; oxygen 3) Processing time; 30 seconds 4) Gas pressure; 1.0 Torr 5) Gas flow rate; 480cc / min 6 ) Microwave output: 1500 W [Example 5] An ethylene-propylene copolymer having a propylene content of 26% by weight and a Mooney viscosity of 24 at 100 ° C relative to 80 parts by weight of PP-A used in Example 1. Combined rubber (EPR-A) 20
Tests were conducted in the same manner as in Example 1 except that the polypropylene resin blended in parts by weight was used, and the results obtained are shown in Table 1.

[Examples 6 to 8] The carbon black of Example 1 was prepared to have an average particle size of 6 mμ,
Carbon black C with a specific surface area of 1000 m ² / g, average particle size 35
μm and a specific surface area of 600 m ² / g of carbon black D,
Tests were conducted in the same manner as in Example 1 except that the amount added was as shown in Table-1, and the results obtained are shown in Table-1.

[Comparative Examples 1 and 2] Tests were conducted in the same manner as in Example 1 except that the amount of carbon black A added in Examples 1 and 2 was 1.0 part by weight.
Table 1 shows the obtained results.

As is clear from the above Examples and Comparative Examples, the resin composition of the present invention has excellent coating film peel strength and water resistance,
Shows extremely good paintability.

[Effects of the Invention] As described above, with the polypropylene resin composition of the present invention, it is possible to obtain a molded article having extremely good coatability after plasma treatment.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Katsumi Sekiguchi 2070 Iijima-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture (56) References JP-A-59-219352 (JP, A) JP-A-59-217737 (JP, A) JP-A-59-184237 (JP, A) JP-A-57-200954 (JP, A)

Claims (1)

[Claims] 1. A polypropylene-based resin and carbon black are included, and 0.01 per 100 parts of the polypropylene-based resin is included.
~ 0.6 parts by weight of carbon black is added, and the carbon black has an average particle size of 5 to 40 µm and a specific surface area of 50 to 1100.
A method for coating a polypropylene resin composition, which comprises molding a polypropylene resin composition of m ² / g, subjecting the molded product to plasma treatment, and then coating.