JPS61215643A - Polypropylene resin composition for coated bumper - Google Patents

Abstract

PURPOSE:To provide a resin compsn. which has high rigidity and high impact resistance and is excellent in coatability after plasma treatment, by blending a crystalline ethylene/propylene block copolymer, a thermoplastic elastomer, an inorg. filler and carbon black in a specified ratio. CONSTITUTION:A resin compsn. consists of a polypropylene resin (a) contg. a crystalline ethylene/propylene block copolymer, 7-60wt% thermoplastic elastomer and 3-30wt% inorg. filler and 0.01-0.6wt% (based on the quantity of polypropylene resin) carbon black (b). As said block copolymer, one having an ethylene content of 7-30wt% and a boiling n-heptane-insolubles content of 65wt% or above is preferred from the viewpoints of impact resistance and flexural modulus of moldings. When the quantity of carbon black is less than 0.01wt%, weather resistance is lowered, while when the quantity exceeds 0.6wt%, the peel strength of a coating film coated after plasma treatment is greatly lowered and further blistering is liable to occur in a hot water-resisting test.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to an improved polypropylene resin composition for painted bumpers.

[Conventional technology]

Polypropylene resin is lightweight, durable, and safe.

Due to its excellent design and economic efficiency, it is often used in automobile parts and other industrial parts, and in recent years, its use in automobile bumpers has been particularly remarkable. Most of the bumpers were also painted in black or black-like colors in consideration of color tone, weather resistance, etc., but recent market needs include: □There is a desire to make the bumpers more luxurious by painting them in terms of design. With increasing demand, it has become essential to provide paintability.

Currently, thermoplastic elastomers are added to polypropylene resins for bumpers to improve impact resistance and paintability, and inorganic fillers are added to improve rigidity.

The coating method is to treat the surface of the molded product with a nitrogen-containing organic solvent such as trichlorethylene or trichloroethane, and then apply a primer coat.

In many cases, a top coat is applied, but in order to prevent environmental pollution caused by organic solvents containing nitrogen and chlorides, and to reduce costs by omitting processes, a method of applying a top coat after surface treatment with plasma treatment has begun to be implemented. There is.

In most cases, the entire surface of the bumper molded product made of polypropylene resin is painted.

Regardless of partial painting, it is often colored with inorganic, organic, or a combination of these colorants for design purposes, and especially for bumper materials, weather resistance may be improved by considering how they are used. In many cases, carbon black, or a black pigment mainly composed of carbon black, is added, and as a result, the amount of carbon black added is currently large.

[Problem that the invention seeks to solve]

However, it has become clear that when a bumper made of polypropylene resin containing a large amount of carbon black is painted after plasma treatment, the paintability is significantly inferior, and there is a need for a polypropylene resin composition for painted bumpers with good paintability. There is.

Therefore, the object of the present invention is to have high rigidity and high impact resistance,
Another object of the present invention is to provide a polypropylene resin composition for bumpers that has excellent paintability after plasma treatment.

[Means for Solving the Problems] The present invention provides the following polypropylene resin composition for painted bumpers.

a) a crystalline ethylene-propylene block copolymer;
b) A polypropylene resin comprising a thermoplastic elastomer and an inorganic filler in an amount of 7 to 60% by weight and 3 to 30% by weight, respectively;
A polypropylene resin composition for painted bumpers consisting of carbon black having a weight ratio of 01 to 0.6.

The crystalline ethylene-propylene block copolymer used in the present invention has an ethylene content of 7 to 80% by weight and a boiling n-hebutane insoluble content, considering the impact resistance 1 flexural modulus of the molded product obtained. The content is preferably 65% by weight or more.

Examples of thermoplastic elastomers include ethylene-propylene copolymer rubber, ethylene-propylene-diene copolymer rubber, styrene-butadiene copolymer rubber, isobutylene-isoprene copolymer rubber, etc. Considering low-temperature impact properties, etc., ethylene-propylene copolymer rubber and ethylene-propylene-diene copolymer rubber are preferred, especially those with a propylene content of 20 to 90%.
Mooney viscosity at 0-90 parts by weight 00'O is 15-1
00 ethylene propylene copolymer rubber, and/
′! or monoethylene-propylene-diene copolymer rubber is preferred.

The inorganic filler used in the present invention is calcium oxide or magnesium oxide having a particle size of substantially 10 μm or more and a weight ratio of 5 μm or less, and an average particle size of 6 μm or less, preferably 5 μm or less.

Calcium hydroxide, magnesium hydroxide, aluminum hydroxide, calcium carbonate, magnesium carbonate, barium sulfate, magnesium sulfate, potassium titanate, talc,
Examples include clay, glass powder, dolomite, and wollastonite. Among these, particularly preferred are calcium carbonate, barium sulfate, and talc. These inorganic fillers can be used alone or in combination of two or more.

When the particle size of the inorganic filler exceeds 6 μm, the impact resistance of the resulting polypropylene resin composition decreases.

The average particle size in the present invention is an equal area diameter measured by a light transmission method, and is a value determined as a particle size at a coefficient of 50 of a particle size cumulative distribution (generally referred to as Dso).

The blending ratio of the crystalline ethylene-propylene block copolymer, thermoplastic elastomer, and inorganic filler used in the present invention is determined by considering the rigidity, impact resistance, paintability, etc. of the resulting resin composition. The amount of the thermoplastic elastomer is 7 to 60 parts by weight and the inorganic filler is 3 to 30 parts by weight per 100 parts by weight of the block copolymer.

If the amount of thermoplastic elastomer is less than 7 parts by weight, the low-temperature impact resistance of the bumper molded product will decrease when it is coated after plasma treatment, while if it exceeds 60 parts by weight, the surface layer of the bumper molded product will peel off. This tends to occur, resulting in poor peel strength of the coating film and a decrease in the rigidity of the molded product, both of which are unfavorable.

If the amount of inorganic filler added is less than 3%, the rigidity of the molded product will decrease, making it less practical as a bumper, while if it exceeds 30 parts by weight, the molded product will be less practical due to the moisture contained in the inorganic filler. In particular, the hot water resistance and moisture resistance of the paint film after painting are reduced, blisters are likely to occur between the resin layer and the paint film, and the low-temperature impact resistance of the molded product is reduced, so it is preferable in both cases. do not have.

Carbon blacks that are blended into polypropylene resin consisting of crystalline ethylene-propylene block copolymer, thermoplastic elastomer, and inorganic filler include furnace black, thermal black, which is generally used to color polypropylene/resin black, Examples include channel black, acetylene black, etc., and color tone, heat resistance,
From the viewpoint of weather resistance, furnace black and channel black having an average particle diameter of 5 to 40 m[mu] are preferable, and two or more of these carbon blacks can also be used in combination.

The amount of carbon black added is 0.01 to 0.6 parts by weight, preferably 0.05 to 0.5 parts by weight, per 100 parts by weight of the polypropylene resin. If the amount added 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 bumpers, it is necessary to use quite a large amount of these stabilizers. This makes it very expensive, and it is not practical because the stabilizer looms on the surface of the bumper after molding, reducing paintability and appearance. On the other hand, if it is added in an amount exceeding 0.6 parts by weight, it is not preferable because it not only significantly reduces the peel strength of the coating film applied after plasma treatment, but also tends to cause blisters in the hot water resistance test.

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, resulting in poor dispersibility and will also be expensive.On the other hand, if the average particle size is large, In this case, the color tone deteriorates and the weather resistance also decreases, which is not preferable in either case.

The value of the average particle diameter of carbon black is determined by direct measurement using an electron microscope, or by calculating the spherical shape from the specific surface area value determined from the amount of nitrogen, iodine, etc. adsorbed.

Antioxidants, heat stabilizers, ultraviolet absorbers, flame retardants, nucleating agents, organic/inorganic pigments, etc. that are normally added to polypropylene resins may be used alone as long as they do not significantly impair the effects of the present invention. Or they can be used together.

The polypropylene resin composition of the present invention is mixed using, for example, a Henschel mixer commonly used in the industry, and then mixed using a single-screw extruder.

It is produced by kneading and venting using a twin-screw extrusion machine such as FCM or CIM, rolls, Banbury mixer, etc.

The resin composition thus obtained can be molded into a predetermined molded article by commonly used molding methods such as injection molding, extrusion molding, and compression molding.

Surface treatment using plasma is carried out by bringing into contact the surface of a molded article with plasma excited with inert gas such as oxygen, nitrogen, or a mixture thereof using high frequency, microwave discharge, or the like. Processing conditions vary somewhat depending on the type of gas, but are usually a pressure of 0.1 to 5 Torr and a processing time of about 5 to 600 seconds. Needless to say, depending on the shape of the molded product, it may be necessary to lengthen the processing time or to vary the shape of the processing tank.

〔Example〕

The present invention will be specifically explained below using Examples.

Examples 1 to 3 Ethylene content 12.5% by weight, boiling n-hebutane
Solvent content 94.2 weight ratio, melt flow index 13.
5 t/l Omin's crystalline ethylene-propylene/block copolymer (hereinafter referred to as PP-A) 75 parts by weight, propylene content 59 weight 1100'0 ethylene-propylene copolymer rubber (hereinafter referred to as EPR) with a Teno Mooney viscosity of 27 -A) 20 parts by weight and an average particle size of 1.1
For a total of 100 parts by weight of 5 parts by weight of Merck of μm, 2
．． 0.05 parts by weight of 6-tert-butylphenol, 0.1 parts by weight of calcium stearate, tetrakis-
[0.2 parts by weight of methylene-3-(8',5'-di-tart-butyl-4'-hydroxyphenyl)propionate cometaph, bis(2,2,6,6-titramethyl-4-piperdyl)sebacate 0.4 parts by weight, 2-
(8-tert-butyl-5-methyl-2-hydroxyphenyl)-5-chloropenttriazole 0.2
Furnace black (carbon black A) with a weight part and average particle size of 22 mμ and channel black (carbon black B) with an average particle size of 16 mμ were blended in the amounts shown in Table 1. After mixing with a shell mixer, 280
The resin composition was pelletized using a 40al diameter extruder set to 'O', and the resulting resin composition was injection molded to obtain a test piece (80x160x2fi flat plate).

After plasma treatment was performed on this test piece under the following conditions, a two-component urethane top coat was applied to a film thickness of 50.
The coated product was coated so as to have a thickness of μ, dried at 90°0 for 40 minutes, and then left at room temperature for 48 hours to obtain a coated product. The coating film of this painted product is cut to a width of 1. A notch of Om was made and the 180° peel strength of the coating film was measured using an Instron tensile tester.

Further, the coated product was immersed in warm water at 40° 0, 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) ■ Processing gas Oxygen ■ Processing time 30 seconds (42 gas pressure 1. Q Torr (5)
Gas flow rate 439 cc/m1n (6)
Microwave output: 1500W Judgment criteria for the state of the coating film ○: No blisters in the coating film Δ: Some blisters in the coating film X: Considerable blisters in the coating film The results are shown in Table 1.

Example 4 In Example 1, the average particle size was 1.9 mμ instead of talc.
The test was conducted in the same manner as in Example 1, except that calcium carbonate was used, and the results are shown in Table 1.

Example 5 Propylene content 2 instead of EPR-A in Example 1
6 weight 1. Example 1 except that an ethylene-propylene copolymer rubber having a Mooney viscosity at 100°O of 24 was used.
The test was conducted in the same manner as above, and the results are shown in Table 1.

Example 6 In Example 1, BPR-A was replaced with BPR-A, which had a Mooney viscosity of 88 at a propylene content of 27 and a weight of 1,100"C.
EPDM whose component is ethylidene norbornene (EP
The test was conducted in the same manner as in Example 1 except that DM-A) was used, and the results are shown in Table 1.

Examples 7 and 8 PP-A and EPR-A used in Example 1.

The test was conducted in the same manner as in Example 1, except that the amount of talc was changed to the amount shown in Table 1, and the obtained results are shown in Table 1.

Example 9 In Example 1, a crystalline ethylene-propylene block with an ethylene content of 14% by weight, a boiling n-hebutane insoluble content of 85% by weight, and a melt flow index of 3.5JF/10ml was used instead of PP-A. Polymer (PP-18
) was used, but the test was conducted in the same manner as in Example 1, and the obtained results are shown in Table 1.

Comparative Examples 1 to 5 In Examples 1.2 and 4 to 6, tests were conducted in the same manner as in Example 1, except that the amount of carbon black A or B added was changed as shown in Table 2, and the obtained results are shown in Table 2. -2.

Comparative Examples 6 to 8 The blending amounts of PP-A, EPR-A, and talc were set to the values shown in Table 2, pelletization was performed in the same manner as in Example 1, and the obtained pellets were subjected to prescribed tests using an injection molding machine. When a piece was molded and its physical properties were measured, it was found that the physical properties of the resin composition for a bumper had a poor balance of rigidity and impact resistance compared to Example 1, so the coating properties were not evaluated.

The results of each physical property side chamber are shown in Table 3 in comparison with Example 1.

The melt flow index (MI) is based on ASTM
D-1238, flexural modulus was measured according to ASTM D-790, and Izod impact value was measured according to A8TM D-256.

〔Effect of the invention〕

With the polypropylene resin composition for bumpers of the present invention,
It is possible to provide a bumper molded product that has high rigidity, high impact resistance, and has good paintability after plasma treatment.

Patent applicant: Mitsui Toatsu Chemical Co., Ltd. Procedural amendment (voluntary) March 2, 1986

Claims (1)

[Claims] 1, a) Crystalline ethylene-propylene block copolymer and 7-60% and 3-30% by weight thereof, respectively
A polypropylene resin composition for a painted bumper, comprising a polypropylene resin comprising a thermoplastic elastomer and an inorganic filler, and b) carbon black in an amount of 0.01 to 0.6% by weight of the polypropylene resin.