Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1999-11-22
2001-03-20
Michl, Paul R. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
active
06204328
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention relates to polyolefin resin compositions, and more particularly, to the resin compositions having a good flowability and high-temperature rigidity, and a well-balanced combination of the properties such as rigidity and impact resistance, which are suitable for the manufacture of molded articles, especially interior automotive trim parts.
BACKGROUND ART
Polypropylene resins have been extensively used in automotive applications and in various fields such as electrical appliances, miscellaneous goods or films, because the articles molded therefrom are excellent in rigidity and high-temperature rigidity. However, conventional polypropylene resins have been limited in the use range, since the articles molded therefrom are deficient in impact resistance.
As typical polypropylene resins having improved impact resistance are known a polypropylene resin comprising propylene/ethylene block copolymers wherein propylene and ethylene are block copolymerized, and polypropylene resin compositions wherein polypropylene is incorporated with an ethylene/&agr;-olefin copolymer rubber. Since such polypropylene resins have lower rigidity than a propylene homopolymer, these resins are incorporated with inorganic fillers such as talc to make up for lowered rigidity, as the occasion demands, and used mainly as molding materials for exterior automotive trim parts including automotive bumpers and interior automotive trim parts including instrument panels, console boxes, resin pillars and trims. However, inorganic fillers should be incorporated in a large amount so as to enhance the rigidity of the resin composition, which leads to a lowered flowability of the resultant composition and an increased specific gravity of the resultant molded article, resulting in an increased weight of the products.
With a view to improving the impact resistance and stress-whitening resistance of &agr;-olefin polymers such as polypropylene and polyethylene, the resin compositions wherein hydrogenated diene copolymers are incorporated therein have been proposed.
For example, JP-B-59-37294 discloses a resin compositions wherein a hydrogenated 1,2-polybutadiene is incorporated in polymers or copolymers of &agr;-olefin with 2 to 20 carbons, especially ethylene homopolymer, propylene homopolymer or propylene/ethylene copolymer.
JP-B-62-45883 and JP-A-4-342752 disclose a resin composition wherein a hydrogenated diblock copolymer of polybutadienes consisting of 1,2-block and 1,4-block is incorporated in &agr;-olefin polymers or copolymers, in particular polypropylene.
JP-A-5-132606 discloses a resin composition wherein a hydrogenated product of polybutadiene/conjugated diene block copolymers is incorporated in a crystalline propylene/ethylene block copolymer. JP-A-1-168743 and JP-A-1-168744 disclose a resin composition wherein a hydrogenated product of isoprene/butadiene copolymers is incorporated in polyolefins. These resin compositions are improved in both stress-whitening resistance and impact resistance, but remarkably lowered in rigidity and high-temperature rigidity. Thus a practical use of such resin compositions is limited to the field of soft materials.
In order to enhance the reduced rigidity and high-temperature rigidity in the above-described resin compositions wherein the hydrogenated diene block copolymers are incorporated in the propylene/ethylene block copolymers, it is considered that high stereoregular polypropylenes disclosed in JP-A-1-254706 and JP-A-62-187707 may be used instead of said propylene/ethylene block copolymers, whereby the rigidity and the high-temperature rigidity of the molded articles are improved without any increase in the specific gravity. However, a reduction in impact resistance of the molded articles is also anticipated.
As mentioned above, the impact resistance of the polypropylene resin compositions is improved by the incorporation of the ethylene/&agr;-olefin copolymer rubber or the hydrogenated polybutadiene polymer or copolymer. However, the incorporation of these rubber components in a large amount brings about another problem of lowering the rigidity, the high-temperature rigidity and the flowability of the resulting molded articles. Thus, it has been desired to develop a polypropylene resin composition capable of improving the impact resistance of the molded articles without reducing the rigidity and the high-temperature rigidity of the molded articles as well as the flowability of the resin compositions.
Accordingly, an object of the present invention is to provide a polyolefin resin composition having good flowability of the resin composition, good rigidity, high-temperature rigidity and impact resistance of the molded article as well as a well-balanced combination of these properties.
SUMMARY OF THE INVENTION
The above-mentioned object of the invention can be attained by incorporation of a specific hydrogenated diene block copolymer into a composition comprising a specific high rigid polypropylene/ethylene-propylene copolymer composition and a specific ethylene/&agr;-olefin copolymer rubber.
The present invention provides a polyolefin resin composition comprising
(a) 50-94% by weight of a polypropylene/ethylene-propylene copolymer composition,
(b) 5-40% by weight of an ethylene/&agr;-olefin copolymer rubber and
(c) 1-10% by weight of a hydrogenated diene block copolymer, the sum of components (a), (b) and (c) being 100% by weight,
wherein the polypropylene/ethylene-propylene copolymer composition (a) comprises 60-95% by weight of a polypropylene component and 5-40% by weight of an ethylene-propylene copolymer component having an ethylene content of 30-80% by weight, the polypropylene component has an isotactic pentad ratio (P) of not less than 0.96 and a M
w
/M
n
(Q value) of not more than 6, and a ratio of the maximum melt flow rate (MFR
max
) to the minimum melt flow rate (MFR
min
) has the following relationship
0.1≦Log(
MFR
max
/MFR
min
)≦1
and further the polypropylene/ethylene-propylene copolymer composition (a) has the following relationship between the melt flow rate of the polypropylene component (MFR
PP
) and the melt flow rate of the ethylene-propylene copolymer component (MFR
EP
)
3≦Log(
MFR
PP
/MFR
EP
)≦7
the ethylene/&agr;-olefin copolymer rubber (b) is a copolymer of ethylene and an &agr;-olefin of 4 or more carbons, has an ethylene content of 25-90% by weight and contains a polyethylene crystal having a long period of 6-14 nm as determined by a small angle X-ray scattering, and
the hydrogenated diene block copolymer (c) is A-B or A-B-A block copolymer wherein A segment is a 1,4-polybutadiene block and B segment is a 1,2-polybutadiene block, a polyisoprene block or a butadiene/isoprene copolymer block, not less than 85% of unsaturated bonds therein being hydrogenated.
The present invention also provides a polyolefin resin composition comprising 70-95% by weight of the above polyolefin resin composition and (d) 5-30% by weight of talc.
The present invention further provides an interior automotive trim part which is molded from the above polyolefin resin composition having a melt flow rate of not less than 20 g/10 min and has a flexural modulus of not less than 2200 MPa at 23° C., a heat distortion temperature of not lower than 70° C. and an Izod impact strength of not less than 300 J/m at room temperature.
MODE FOR CARRYING OUT THE INVENTION
The polyolefin resin composition of the invention comprises:
(a) 50-94% by weight of a polypropylene/ethylene-propylene copolymer composition,
(b) 5-40% by weight of an ethylene/&agr;-olefin copolymer rubber, and
(c) 1-10% by weight of a hydrogenated diene block copolymer.
The present invention also includes a polyolefin resin composition wherein
(d) 5-30% by weight of talc, based on the total weight of the composition, and
(e) a desired additive
are further incorporated in the above-mentioned polyolefin resin composition.
Each component constituting the polyolefin resin composition of the present invention is fully described below.
(a) Polypropylene/ethylene-prop
Sanpei Akihiko
Shimomura Yozo
Chisso Corporation
McDermott & Will & Emery
Michl Paul R.
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