JPS63172758A - Polypropylene resin composition for bumper - Google Patents

Abstract

PURPOSE:To provide the title compsn. which has excellent rigidity, low- temperature impact resistance and coatability and gives products having excellent appearances, consisting of a crystalline ethylene.propylene block copolymer, a specified copolymer rubber and talc having a surface treated with an organosilane compd. CONSTITUTION:100pts.wt. talc (a) is treated with 0.01-5pts.wt. organosilane compd. (b) in a (semi)drying crusher (e.g., a fluidized bed type jet crusher) to obtain a component (A) wherein the surface of the component (a) has been treated with the component (b). 65-55% (by weight; the same applies hereinbelow) crystalline ethylene.propylene block copolymer (A) having an ethylene content of 4-8%, a boiling heptane insoluble content not lower than 85% and an MI of 10-15g/10min is blended with 30-35% ethylene.propylene(.diene ter)polymer (B) having a propylene content of 45-60% and a Mooney viscosity (100 deg.C) of 20-50, composed of ethylene, propylene and optionally a third component selected from the group consisting of dicyclopentadiene, ethylidenenorbornene and 1,4-hexadiene and 5-10% component C.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a polypropylene resin composition for bumpers that has high rigidity, low-temperature impact γ resistance, and has excellent paintability and product appearance.

(Prior art) A resin composition composed of polypropylene resin, ethylene-propylene copolymer rubber, and various inorganic fillers has a good balance of physical properties such as rigidity and impact resistance, and has good paintability and excellent moldability. Currently, it is widely used in large parts for automobile exteriors, especially bumpers (Japanese Patent Laid-Open No. 57-55
No. 952, No. 57-159842, No. 58-
213043, etc.).

[Problem that the invention seeks to solve]

However, when a conventional polypropylene resin composition is used to mold a product shaped like a bumper, the weld lines are very noticeable, and when painted, the weld lines become even more noticeable, resulting in a poor appearance and poor product value. was lowered.

The present invention was made to solve the above problems, and an object of the present invention is to provide a polypropylene resin composition for a bumper that has a good appearance without impairing various physical properties as a bumper material.

[Means for solving problems]

That is, the present invention consists of the following components a) to C), and the blending ratio of each component is 65 to 55% by weight of a) and 30 to 35% of b), taking the total amount of a) to C) as 100% by weight. A polypropylene resin composition for a bumper, characterized in that C) is 5 to 10% by weight.

a) Ethylene content 4-8% by weight, boiling an-hebutane insoluble content 85% by weight or more, melt flow index (M
I) 10-15 g/min crystalline ethylene-propylene block copolymer.

b) Ethylene-propylene copolymer rubber having a propylene content of 45 to 60% by weight and a Mooney viscosity (ML100°C 1+4) of 20 to 50 and/or a third component having a similar propylene content and Mooney viscosity; is dicyclopentadiene, ethylidene norbornene or 1,4-hexadiene.

C) Talc surface-treated with a silane-based organic compound in a dry or semi-dry grinder.

In a preferred embodiment of the present invention, the pulverizer is a jet stream type pulverizer, and furthermore, it is a fluidized bed type jet pulverizer.

The ethylene/propylene block copolymer used in the present invention is limited to one having an ethylene content of 4 to 8% by weight, a boiling n-bebutane insoluble content of 85% by weight or more, and a MIION of 15g/10ml.

Polypropylene homopolymers and random copolymers have low impact resistance and are not preferred.

If the ethylene content in the ethylene/propylene block copolymer is less than 4% by weight, the impact resistance will be low, and if it exceeds 8% by weight, the rigidity will be low and the scratch resistance will be poor. boiling 1
If the 1n-heptane insoluble content is less than 85% by weight, the rigidity will be low and the scratch resistance will be poor, which is not preferable. M.I.
If it is less than lOg / 10m1n, the moldability will decrease and flow marks will easily occur on the product.
If it exceeds n, the impact resistance will deteriorate and the product will be more likely to be dented, which is not preferable.

The rubber component used in the present invention has a propylene content of 4
Ethylene Pro 1 having a Mooney viscosity of 5 to 60% by weight and a Mooney viscosity of 100°C (ML) of 20 to 50.
+4 and ren copolymer rubber (EPR) and/or have similar propylene content and Mooney viscosity, and the third component is dicyclopentadiene, ethylidene norbornene or 1
．． It is limited to ethylene-propylene-che 23-component copolymer rubber (EPDM), which is 4-hexadiene.

If the propylene content in the EPR or EPDM is less than 45% by weight, the dispersion of the EPR or EPDM will be poor, resulting in poor appearance and also poor #mildew resistance. On the other hand, when it exceeds 60 fifi%, scratch resistance decreases.

4- If EPR or EPDM with a knee viscosity (Mt, 100°C 1+4) of less than 20° is used, the peeling strength of the coating will decrease, and weld lines will be more noticeable.
If it exceeds the above range, moldability decreases, flow marks are more likely to occur, and weld lines become more noticeable, which is undesirable in either case.

Talc is surface-treated by being ground together with a silane-based organic compound in a dry or semi-dry grinding machine, or surface-treated with a silane-based organic compound in the above-mentioned grinding machine. Such talc can be prepared by pre-mixing talc with a silane-based organic compound such as an organosilane-based coupling agent, silicone oil, modified silicone oil, or various silane compounds, or by supplying the talc separately to a grinder. Obtained by processing.

Here, the ratio of talc and silane-based organic compound is usually 0.00 parts per 100 parts by weight of talc. About 1 to 5 parts by weight of O is preferable. In other words, 0.0 in terms of increasing the surface treatment effect.
The amount is preferably 1 part by weight or more, while the amount is preferably 5 parts by weight or less in terms of improving the balance of physical properties such as rigidity, impact resistance, heat resistance, and surface properties of the resulting resin composition. If the amount exceeds 5 parts by weight, not only the rigidity, impact resistance, etc. may deteriorate, but also the cost will increase, which is not preferable in any case.

The above-mentioned pulverizer may be one that can perform fine pulverization using a dry or semi-dry method, such as a micron mill, a jet stream pulverizer, a ball mill, a micronizer, a turbo mill, an atomizer, etc. Micronizer type in terms of grinding efficiency, grinding time, and workability.
Jet-flow type mills such as reductionizer type, impact type, opposing type, and fluidized bed type are preferred, and among them, fluidized bed type jet mills are particularly preferred because surface treatment can be performed more uniformly.

By using such talc, not only the appearance (flow marks, welt lines) of the resulting molded product is improved, but also the impact resistance is greatly improved. The blending ratio of each component in the present invention is 65 to 55% by weight of a), 30 to 35% by weight of b), and 5 to IO% by weight of C) based on 100% by weight of the total amount of components a) to C). be.

If a) exceeds 65% by weight, impact resistance and coating peel strength will decrease, and if it is less than 55% by weight, rigidity will decrease, which is not preferable.

If b) is less than 30% by weight, the impact resistance and coating peel strength will decrease, and if it exceeds 35% by weight, the rigidity will be low and the product appearance will deteriorate (dents, flow marks, weld lines), so it is preferable. do not have.

When C) is less than 5% by weight, the rigidity is low, and when it exceeds 10% by weight, impact resistance and product appearance (flow marks, weld lines) are also deteriorated, so both cases are unfavorable.

In the present invention, antioxidants, lubricants, ultraviolet absorbers,
Various additives such as ultraviolet stabilizers, heat stabilizers, antistatic agents, and organic or inorganic pigments may be added alone or in combination. Examples of these various additives include those commonly added to polyolefin resins, and they may be used within a range that does not significantly impair the effects of the present invention. Further, if necessary, resins other than the polypropylene resin used in the present invention (for example, polyethylene) and inorganic fillers other than talc may be used in combination as long as they do not significantly impair the effects of the present invention.

The resin composition of the present invention is usually obtained by premixing each component in a mixer such as a Henschel mixer, and then melt-kneading it into pellets using a single-screw or twin-screw presser. The material is then molded into a product using extrusion molding, injection molding, rotational molding, compression molding, or other molding methods.

〔Example〕

The present invention will be specifically explained below using Examples.

In the following description, Ml is ASTMD-1
238, flexural modulus was measured according to ASTM D-790, and Izod impact value was measured according to ASTM D-256. The components used in the Examples and Comparative Examples are as follows.

Talc-A Talc 1 having a normal particle size distribution with an average particle size of about 10p
0 (1 part by weight) and 1.0 part by weight of dimethylpolysiloxylazan were separately supplied to a fluidized bed counterjet mill "400A F G type" pulverizer manufactured by Albine, West Germany, and subjected to pulverization surface treatment under the following conditions. Ta.

Processing conditions Air flow rate 1B20tn3/Hr Grinding pressure 6kg/crn'' (compressed air used) Classifier rotation speed 4000rpm Talc-B Talc-A using r-aminopropyltriethoxysilane instead of dimethylpolysiloxysilazane.

Talc-C A type that only performs pulverization without using a surface treatment agent.

Talc-D 100 parts by weight of Talc-C and 1.0 parts by weight of dimethylpolysiloxysilazane were mixed in a Henschel mixer.

Examples 1 to 4 The aforementioned components a) to C) were blended in the proportions shown in Table 4,
To 100 parts by weight of the same, 0.05 part by weight of 2,6-C-Lert-butyl-4-methylphenol, 0.1 part by weight of calcium stearate, and 0.1 part by weight of 2,6-C-Lert-butyl-4-methylphenol, -Butyl-4-hydroxyphenyl)propionate] After adding 0.1 part by weight of methane and mixing with a Henschel mixer, 40 mm
Complete extrusion was performed using a φ single-screw extruder, and pelletization was performed at 210°C. The obtained pellets were molded into predetermined test pieces at 210° C. using an injection molding machine, and the physical properties of each test piece were measured. Table 4 shows the results.
Shown below.

The weld line was evaluated by the following method.

The above pellets were injection molded using a 100 ton injection molding machine under conditions of a molding temperature of 210°C, an injection pressure of 800 kg/crn', and a mold temperature of 50°C.
A flat test piece with a size of 3 mm was molded. This test piece is 80 mm from the gate part on one side of 80 mm and 2
It has a hole with a diameter of 201 m centered at a point located at a distance of 40 m+n from a 40 mm side. The weld line generated in the longitudinal direction from this hole was visually observed and evaluated according to the following criteria.

○: Niraeld line is not substantially observed.

△: Niraeld line is slightly observed.

×: Weld lines are considerably observed.

Paintability was evaluated by measuring peel strength and hot water resistance using test pieces obtained by the following painting method.

Coating method: A flat plate of AOX 160 x 2 mm obtained using an injection molding machine was used as a test piece. It was washed with trichloroethane vapor for 60 seconds, and then a two-component acrylic-chlorinated polypropylene base coat was applied to a film thickness of 15 μm. After drying at 90°C for 30 minutes, apply a two-component urethane top coat to a film thickness of approximately 100°C, dry at 90°C for 40 minutes, and then leave at room temperature. A paintability test piece was obtained after being left for 48 hours.

Peel strength The test piece obtained by the above method was peeled with a cutter knife to a width of 1.
A cut of 0 cm was made and the film was pulled at a speed of 30 mm/min using an Instron tensile tester to measure the 180° peel strength of the coating film.

Hot Water Resistance The test piece obtained by the above method was immersed in hot water at 40°C for 240 hours, and then the state of the coating surface was observed.

○: No blistering of the coating film.

△: There is some blistering in the coating film.

×: There was considerable blistering of the coating film.

Comparative Examples 1 to II Components a) to C) were tested in the same manner as in Example 1 using the types and blending amounts shown in Table 4. The obtained results are shown in the same table.

〔Effect of the invention〕

The polypropylene resin composition according to the present invention has high rigidity and impact resistance, has a good balance of physical properties, and has good moldability, paintability,
Due to its excellent product appearance, it is suitable for large exterior parts such as automobile bumpers and side moldings.

Patent applicant: Mitsui Toatsu Chemical Co., Ltd. Honda motor industry stock company

Claims (1)

[Scope of Claims] 1. Consisting of the following components a) to c), where the blending ratio of each component is 65% by weight, assuming that the total amount of a) to c) is 100% by weight.
~55 wt%, b) 30-35 wt% and c) 5
A polypropylene resin composition for a bumper, characterized in that the content thereof is 10% by weight. a) Ethylene content 4-8% by weight, boiling n-heptane insoluble content 85% by weight or more, melt flow index (MI
) 10-15 g/10 min of crystalline ethylene/propylene block copolymer. b) Ethylene-propylene copolymer rubber with a propylene content of 45 to 60% by weight and a Mooney viscosity (ML^1^0^0^℃_1_+_4) of 20 to 50 and/or a similar propylene content and a Mooney viscosity of ethylene-propylene-diene terpolymer rubber, wherein the third component is zinclopentadiene, ethylidenenorbornene or 1,4-hexadiene. c) Talc surface-treated with a silane-based organic compound in a dry or semi-dry grinder. 2. The resin composition according to claim 1, wherein the pulverizer is a jet stream type pulverizer. 3. The resin composition according to claim 2, wherein the jet stream type pulverizer is a fluidized bed type jet pulverizer.