JPS6234058B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a propylene-based copolymer resin composition, and more specifically, it is made by blending a specific inelastic copolymer and an elastic copolymer in a certain ratio, and has excellent low-temperature impact resistance and rigidity, as well as surface gloss of molded products. The present invention relates to providing a propylene copolymer resin composition with excellent properties. Many attempts have been made to improve the physical properties of polypropylene by blending various polymers into it, but most of these attempts have focused on improving low-temperature impact resistance.
Not much has been done to improve other physical properties, such as surface gloss. In general, resin compositions with improved low-temperature impact resistance have defects in appearance, such as uneven surface gloss or visible welds when molded into objects by injection molding, for example. Although there was no problem in terms of strength, it could not be used as an interior or exterior material as it was. Therefore, it was used as a material for invisible parts or as an interior and exterior material after surface treatment such as graining or painting. The present inventors have developed a propylene-based copolymer resin composition that not only greatly improves the physical properties of polypropylene, such as low-temperature impact resistance, but also significantly improves the surface gloss of molded products, and can be used as is as an interior and exterior material. We conducted extensive research to develop it. As a result, a mixture of an ethylene-propylene random copolymer and a block copolymer was used as the inelastic copolymer, and an elastic copolymer of ethylene-propylene was blended in a certain proportion. The present inventors have discovered that the resin composition has physical properties suitable for the above-mentioned purpose, and have completed the present invention. That is, the present invention provides an inelastic copolymer comprising (A) 10 to 80% by weight of an ethylene-propylene thermoplastic inelastic random copolymer and 90 to 20% by weight of an ethylene-propylene thermoplastic inelastic block copolymer.
The present invention provides a propylene copolymer resin composition comprising 10 to 50 parts by weight of (B) an amorphous ethylene-propylene elastic copolymer mixed with 100 parts by weight. As mentioned above, the composition of the present invention is produced by blending an elastic copolymer with an ethylene-propylene non-elastic copolymer. Random copolymer (hereinafter abbreviated as "RPEP")
It is necessary to use 10 to 80% by weight of ethylene-propylene thermoplastic inelastic block copolymer (hereinafter abbreviated as "BPEP") for the remainder. Note that RPEP in the above inelastic copolymer
should be used in an amount of 10% by weight or more, preferably 20% by weight or more. If the amount of RPEP in the inelastic copolymer is less than 10% by weight, the resulting composition will not have sufficient gloss. Although there are no particular restrictions on the physical properties of the RPEP, it is usually preferable to have a density of 0.89 to 0.92 g/cm ³ and a melt index of 5 to 10. There are also no restrictions on the physical properties of BPEP, but the density is between 0.89 and 0.92.
g/cm ³ and a melt index of 0.4 to 10 are preferred. Next, in the composition of the present invention, the above-mentioned inelastic copolymer
10 parts by weight of amorphous ethylene-propylene elastic copolymer (hereinafter referred to as "EPR")
It is blended in a proportion of ~50 parts by weight, preferably 10 to 30 parts by weight. If the blending ratio of EPR is less than 10 parts by weight, the resulting composition will not have sufficient low-temperature impact resistance, while if it is more than 50 parts by weight, the low-temperature impact resistance of the composition will be insufficient depending on the amount added. This is not preferred because it is not very effective in improving physical properties such as rigidity and fluidity. There are no particular restrictions on the physical properties of the above EPR, but for example, torsional rigidity (according to ASTM D1043) 10 to 100 Kg/cm ² , Mooney viscosity ML ₁₊₄ (100
℃) 20 to 100 is preferred. Furthermore, as the EPR used in the present invention, a so-called ethylene-propylene-diene elastic copolymer obtained by copolymerizing ethylene, propylene, and a small amount of a diene compound can also be used. The composition of the present invention is prepared by blending the above-mentioned components in predetermined proportions by various methods including a melt mixing step such as a single-stage melt mixing method, a combined dry blending/melt mixing method such as a multi-stage melt mixing method, and further It can be produced by sufficiently kneading it using various kneading machines such as a Banbury mixer or a co-kneader or an extruder. The various molded products molded using the thus obtained resin composition of the present invention have extremely excellent appearance, such as a sharp reduction in surface gloss unevenness and suppressed appearance of weld areas, and can be used at low temperatures. It also has sufficient physical properties such as impact resistance, rigidity, and fluidity. Therefore, molded products made from the composition of the present invention can be used as interior and exterior materials as they are without surface treatment such as graining or painting.
Furthermore, in the case of injection molding, the composition of the present invention can be used in RPEP.
Since the minimum filling pressure, which is one of the criteria that indicates the ease of flow of molten resin, is small, the molding operation can be simplified. Therefore, the resin composition of the present invention can be used in a wide range of applications such as automobile bumpers, flexible front and guardrail materials, cushioning materials such as fenders, as well as freezing boxes, refrigeration equipment materials, and outer shells of small ships. can be used. Next, the present invention will be explained in more detail with reference to Examples. Examples 1 to 25 and Comparative Examples 1 to 4 A predetermined part by weight of EPR was blended with 100 parts by weight of an inelastic copolymer consisting of a predetermined weight % of RPEP and a predetermined weight % of BPEP, and using a 40 mmφ pelletizer, Granules were obtained by kneading at a set temperature of 220°C.
Test pieces necessary for various measurements were obtained by molding or cutting from the molded product, and the test pieces were used to measure the respective physical properties. The results are shown in Table 1. In addition, each measurement item was performed by the following method. Glossiness: According to ASTM-D-523. The gloss level is preferably 70 or higher, particularly 80 or higher. Izotsu impact strength: According to JIS-K-6781 (-
For Izod impact strength at 30°C, test pieces were immersed in dry ice-ethanol maintained at the same temperature for about 5 hours). In terms of numerical values, a value of 10 kg/cm or more is sufficient for practical use. Stiffness: According to ASTM-D-747. If the molded product is intended to be a rigid structure, the appropriate amount is 7000 Kg/cm ² or more, and if the molded product is intended to be a flexible structure, the appropriate value is 5000 to 7000 Kg/cm ² . Minimum filling pressure: The minimum pressure required to fill the entire specified mold volume with resin during injection molding. Note that the smaller the value, the easier it is to mold. The physical properties of each resin component used are as follows. RPEP: Melt index 7.2, density 0.90g/
cm ³ , ethylene with ethylene unit content 3.4% by weight
Propylene thermoplastic inelastic random copolymer. BPEP-1: Melt index 2.5, density 0.90
g/cm ³ , an ethylene-propylene thermoplastic inelastic block copolymer with an ethylene unit content of 9.0% by weight. BPEP-2: Melt index 4.7, density 0.90
g/cm ³ , an ethylene-propylene thermoplastic inelastic block copolymer with an ethylene unit content of 8.9% by weight. BPEP-3: Melt index 9.0, density 0.90
g/cm ³ , an ethylene-propylene thermoplastic inelastic block copolymer with an ethylene unit content of 8.1% by weight. EPR: Amorphous ethylene-propylene elastic copolymer with a torsional rigidity of 30 Kg/cm ³ and a propylene unit content of 27% by weight.

[Table] Example 26 Predetermined weight % of RPEP same as that used in the above example and predetermined weight % of BPEP-1 or BPEP-3
EPR for 100 parts by weight of an inelastic copolymer consisting of
A predetermined amount of the composition was added, and the glossiness of the test piece of each composition was measured in the same manner as in the above example. The results are shown in Tables 2 and 3.

【table】

[Table] Considering Tables 1 to 3 above, the product containing only BPEP and EPR has good low-temperature impact resistance, but
The surface gloss is not sufficient. In this case further
It can be seen that by blending RPEP, it is possible to significantly improve the surface gloss while maintaining low-temperature impact resistance and rigidity within a range that does not cause any practical problems.

Claims (1)

[Scope of Claims] 1 (A) 10 to 80% by weight of ethylene-propylene thermoplastic inelastic random copolymer and ethylene-
Propylene thermoplastic inelastic block copolymer 90
(B) Amorphous ethylene-propylene elastic copolymer 10 to 100 parts by weight of an inelastic copolymer consisting of ~20% by weight
A propylene copolymer resin composition containing ~50 parts by weight. 2. Claims in which the inelastic copolymer is comprised of 20 to 80% by weight of an ethylene-propylene thermoplastic inelastic random copolymer and 80 to 20% by weight of an ethylene-propylene thermoplastic inelastic block copolymer. The composition according to item 1. 3. The composition according to claim 1, wherein the proportion of the amorphous ethylene-propylene elastic copolymer is 10 to 30 parts by weight.