JPH08165386A - Polypropylene resin composition - Google Patents

Abstract

PURPOSE: To obtain a polypropylene resin composition having physical properties similar to those of propylene/ethylene block copolymers and improved in chalking resistance. CONSTITUTION: A polypropylene resin composition is made up of (A) a matrix phase of a homopolypropylene and (B) a random copolymer phase of propylene and ethylene. The copolymer phase (B) has an ethylene content of 30 to 90wt.% and an inherent viscosity of 2dl/g or less and amounts to 1 to 30wt.% in the composition. The composition has a melt flow rate of 1 to 100g/10min.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polypropylene resin composition, and more particularly to a polypropylene resin composition having excellent choking resistance.

[0002]

2. Description of the Related Art Polypropylene is widely used as an inexpensive material having excellent mechanical properties and chemical resistance.

However, since a large amount of tertiary carbon is contained in the structure, there is a problem in weather resistance (particularly light resistance), and the appearance is impaired due to the generation of minute cracks on the surface of the molded product, which reduces the product value. I may lose. It is well known that a phenomenon called choking (powder) appears as a phenomenon associated with the surface deterioration of the molded product.

In order to solve these problems, measures such as adding an antioxidant, a light stabilizer, an ultraviolet absorber, etc. to polypropylene have been taken, but there is a limit to the improvement effect due to addition and the product. This leads to an increase in cost and is a problem.

As one of the polypropylene resins, the mechanical properties are well-balanced and the low temperature resistance is excellent, so that the propylene-ethylene block copolymer, which is often used in industrial materials, has the above-mentioned properties. The peculiar choking of polypropylene occurred, and the advent of means for improving it.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polypropylene resin composition having physical properties similar to those of a propylene-ethylene block copolymer and having improved chalking resistance.

[0007]

As a result of intensive studies, the inventors of the present invention found that a composition of homopolypropylene serving as a matrix phase and a random copolymerization phase of propylene and ethylene having a specific composition was found to be the present invention. The present invention has been completed by finding that the object of can be achieved.

That is, the present invention is a polypropylene resin composition comprising a matrix phase (A) made of homopolypropylene and a random copolymerization phase (B) of propylene and ethylene, wherein the copolymerization phase (B) is A gist of a polypropylene resin composition having an ethylene content of 30 to 90% by weight, an intrinsic viscosity of 2 dl / g or less, a ratio in the composition of 1 to 30% by weight, and a melt flow rate of 1 to 100 g / 10 min. And

The homopolypropylene used as the matrix phase (A) in the present invention may be any homopolymer of propylene, but in particular, the boiling n-heptane insoluble content is 80% by weight or more, preferably 90% by weight. % Or more of a highly crystalline homopolypropylene is preferable, and such a homopolypropylene can be produced by polymerizing propylene using a highly stereoregular Ziegler-Natsuta type catalyst.

Many such Ziegler-Natsuta type catalysts with high stereoregularity are known, and any one may be selected from them, but typically, titanium trichloride and ethers, carboxylic acid esters and the like are used. A catalyst component obtained by contacting with an electron-donating compound, or a catalyst component in which an electron-donating compound such as titanium tetrachloride and a carboxylic acid ester or an alkoxysilane is supported on a magnesium compound, and diethylaluminum chloride, triethylaluminum or the like. Organoaluminum compounds, more preferably, a catalyst in combination with the above-mentioned electron-donating compound as the third component can be mentioned.

The random copolymerization phase (B) of propylene and ethylene in the present invention is a component obtained by randomly copolymerizing propylene and ethylene simultaneously, and the component has an ethylene content of 30 to 30. 90% by weight, preferably 40-80% by weight, and an intrinsic viscosity of 2 dl /
g or less, preferably 1 to 2 dl / g.

If the ethylene content and the intrinsic viscosity in the component are out of the above ranges, the improvement of the choking resistance, which is the object of the present invention, cannot be achieved.

The intrinsic viscosity ([η]) is 135 ° C.
It is the value measured in decalin.

The above-mentioned copolymerization component can be produced by copolymerizing propylene and ethylene in the presence of a polymerization catalyst so as to have the above-mentioned properties. The polymerization catalyst is not particularly limited, and the above-mentioned catalyst that can be used when polypropylene is produced by polymerizing propylene can be used.

The composition of the present invention comprises 1 to 30% by weight of the matrix phase (A) composed of the homopolypropylene, and the random copolymer phase (B) of propylene and ethylene,
It is preferably composed of 5 to 20% by weight.

When the proportion of the copolymerization phase (B) in the composition is less than 1% by weight, impact resistance is lowered, and when it exceeds 30% by weight, rigidity is lowered, both of which are not preferable.

Further, the composition of the present invention has a melt flow rate (MFR; JIS K7210; load 2.16k).
g, measured at 230 ° C.) is 1 to 100 g / 10 minutes, preferably 3 to 50 g / 10 minutes. If the MFR is less than 1 g / 10 minutes, moldability will be poor, and if it exceeds 100 g / 10 minutes, problems will occur in mechanical strength.

The composition of the present invention is preferably one in which the homopolypropylene and the copolymerization component are uniformly mixed, which can be obtained by strongly kneading the both, but a more preferable production method is the above-mentioned propylene. Is a method for continuously producing a polypropylene and a step for producing a random copolymerization component of propylene and ethylene by copolymerizing the propylene and ethylene. The order of these steps may be either, but it is more preferable to precede the step for producing polypropylene.

More specifically, propylene is polymerized using the above-mentioned highly stereoregular Ziegler-Natsuta type catalyst,
It is a method of randomly copolymerizing propylene and ethylene in the presence of the obtained polypropylene and the catalyst to obtain a copolymerization component thereof.

Although the composition of the present invention can be produced by doing so, the composition of the present invention can be used in an amount within the range not impairing the purpose of the present invention. Additives such as a light stabilizer, an ultraviolet absorber, a neutralizing agent, an inorganic filler, an antifogging agent, an antiblocking agent, a lubricant and a dye can be added.

Generally, the amount of the antioxidant used is preferably 0.01 to 1 part by weight per 100 parts by weight of the polypropylene resin.

The amount of the neutralizing agent used is usually 0.01 to 1 part by weight based on 100 parts by weight of the polypropylene resin.

[0023]

EXAMPLES The present invention will now be described in more detail with reference to examples. The percentages (%) in the examples are by weight unless otherwise specified.

The physical properties of the composition were measured according to the following test methods.

Chalking generation cycle (Chokin resistant
Weatherability acceleration tester; manufactured by Iwasaki Electric Co., Ltd. Eye super UV
Tester test conditions: 83 ° C, temperature 50%, illuminance 100 mW / cm
² , 16 hours room temperature, 100% humidity, final irradiation, 8 hours
1-cycle flexural modulus JIS K7203 (Example 1) Anhydrous magnesium chloride, dioctyl phthalate and titanium tetrachloride were contacted by the method described in Examples of JP-A-57-63310 to obtain a titanium content of 2.0. % Catalyst component was prepared.

In a 5 liter stainless steel autoclave equipped with a stirrer, under a nitrogen gas atmosphere, 3 liters of liquid propylene, 2.4 liters of hydrogen gas, 35 mg of the catalyst component obtained above, and 0.1 liter of n-heptane were added. Charge a polymerization catalyst consisting of 3 ml of a solution containing 4 mol of triethylaluminum and 3 ml of a solution containing 0.08 mol of phenyltriethoxysilane in 1 l of n-heptane, 70
Polymerization of propylene was carried out at 0 ° C for 1 hour.

Purge unreacted propylene and hydrogen,
After charging 5.4 liters of hydrogen gas, a mixed gas of propylene and ethylene with an ethylene / propylene molar ratio of 1.3 was fed to the autoclave for 69 minutes while maintaining the partial pressure of 6 kg / cm ^2. Then, propylene and ethylene were copolymerized at 70 ° C., unreacted materials were removed and then dried to obtain a composition of the present invention.

As a result of the analysis of the composition obtained by the polymerization experiment conducted in parallel with the above, the composition had a melt flow rate (MFR) of 10.0 g / 10 min. The content of boiling n-heptane-insoluble matter was 95.5%, the proportion of the random copolymerization phase (B) of propylene and ethylene obtained in the latter stage was 15%, the ethylene content was 50.0%, and The viscosity ([η]) is 1.
It was 0 dl / g.

100 parts by weight of the composition obtained above, 0.05 part by weight of a phenolic antioxidant, 0.05 part by weight of a phosphorus antioxidant, 0.15 part by weight of a light stabilizer, and 0. After 15 parts by weight and 0.10 parts by weight of calcium stearate (neutralizing agent) were dry blended with a super mixer, pellets were obtained using a twin-screw extruder (45 mmφ). A test piece conforming to the above test method was molded from the pellets by an injection molding machine, and physical properties were measured according to the test method. The results are shown in Table 1.

(Examples 2 to 6 and Comparative Example 1) In the production of the composition of Example 1, the composition of the composition shown in Table 1 was obtained by changing the conditions during the copolymerization of propylene and ethylene.

Example 1 except that these compositions were used
Dry blending was carried out in the same manner as above to obtain pellets. Physical properties of the test pieces obtained from these pellets were measured in the same manner as in Example 1, and the results are shown in Table 1.

The composition of Comparative Example 1 has the following composition:
It corresponds to a propylene-ethylene block copolymer generally used as an industrial material.

[0033]

[Table 1]

[0034]

The composition of the present invention has significantly improved choking resistance without impairing mechanical strength such as rigidity.
In particular, it is suitable as a material for injection-molded products such as containers and exterior parts that place importance on appearance.

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Claims (2)

[Claims] 1. A polypropylene resin composition comprising a matrix phase (A) composed of homopolypropylene and a random copolymerization phase (B) of propylene and ethylene, wherein the copolymerization phase (B) has an ethylene content of 30 to 90% by weight, an intrinsic viscosity of 2 dl / g or less, a ratio in the composition of 1 to 30% by weight, and a melt flow rate of 1 to 10
0 g / 10 min polypropylene resin composition. 2. The copolymer phase (B) has an ethylene content of 40 to 80% by weight, an intrinsic viscosity of 1 to 2 dl / g, a ratio of 5 to 20% by weight in the composition, and a melt flow rate. The polypropylene resin composition according to claim 1, wherein the rate is 3 to 50 g / 10 minutes.