Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Patent
1998-12-11
2000-07-11
Michl, Paul R.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
524491, C08K 501
Patent
active
060874317
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an olefinic thermoplastic elastomer composition comprising a specific olefinic elastomer.
BACKGROUND ART
Thermoplastic elastomer compositions produced by so called dynamic crosslinking, i.e. crosslinking of a radical crosslinkable, olefinic elastomer with a non-radical crosslinkable olefinic resin such as polypropylene (PP), etc. in the presence of a radical initiator, while melt-kneading them through an extruder belongs to the well known art and have been already widely used in automobile parts, etc.
For the thermoplastic elastomer compositions, ethylene-propylene-diene rubber (EPDM) has been so far used as an olefinic elastomer, where the diene component in the polymer chain is necessary for improving the crosslinkability, but the elastomer is not satisfactory yet with respect to the environment-caused deterioration resistance due to the diene component and their quality improvement has been keenly desired.
JP-A-8-120127 and JP-A-9-137001 disclose the art of using olefinic elastomers produced in the presence of a metallocene catalyst, but the elastomers are not satisfactory yet with respect to the quality and improvement of its quality has been desired.
An object of the present invention is to improve the processability and the environment-caused deterioration resistance, which have been problems of the conventional olefinic elastomers, and to provide an olefinic thermoplastic elastomer composition having distinguished mechanical characteristics, particularly a composition capable of having a low hardness and substantially free from such problems as oil bleed, etc.
DISCLOSURE OF THE INVENTION
Many attempts have been recently made to develop various polymers by a metallocene catalyst. The present inventors have found that olefinic elastomers having a specific structure of ethylene and .alpha.-olefin produced by a metallocene catalyst have a much, distinguished radical crosslinkability and can solve all of the above-mentioned problems and thus have accomplished the present invention.
That is, the present invention provides an olefinic thermoplastic elastomer composition, which comprises a mixture comprising: least one .alpha.-olefin having 6 to 12 carbon atoms, and having an .alpha.-olefin copolymerization ratio of 26 to 30% by weight, a density of 0.8 to 0.9 g/cm.sup.3 and a molecular weight distribution (Mw/Mn) of less than 3.0 in terms of a ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) calculated by gel permeation chromatography (GPC), crosslinked by a radical initiator or both of a radical initiator and a crosslinking promoter.
BEST MODE FOR CARRYING OUT THE INVENTION
The olefinic elastomer as the main component of the present thermoplastic elastomer composition is a copolymer comprising ethylene and at least one .alpha.-olefin having 6 to 12 carbon atoms and have a specific copolymerization ratio, a specific density and a specific molecular weight distribution.
.alpha.-Olefins having 6 to 12 carbon atoms include, for example, hexene-1, 4-methylpentane-1, heptene-1, octene-1, nonene-1, decene-1, undecene-1, dodecane-1, etc., among which hexene-1, 4-methylpentene-1 and octene-1 are preferable, and octene-1 is particularly preferable. Even a small amount of octene-1 has a distinguished effect of softening the polymer, and also the resulting copolymers have a distinguished mechanical strength.
The olefinic elastomers for use in the present invention are produced preferably by a well known metallocene catalyst.
Metallocene catalyst comprises a cyclopentadienyl derivative of Group IV metals such as titanium, zirconium, etc. and a promoter and is characterized not only by a high activity as a polymerization catalyst, but also by a narrower molecular weight distribution of the resulting polymers and more uniform distribution of .alpha.-olefins having 6 to 12 carbon atoms as a comonomer of the copolymers than those of polymers obtained by the conventional catalyst, for example, a Ziegler catalyst.
That is, the ol
REFERENCES:
patent: 4212787 (1980-07-01), Matsuda
patent: 4440911 (1984-04-01), Inoue
patent: 5391629 (1995-02-01), Turner
patent: 5520975 (1996-05-01), Inoue
Shibayama Shinichi
Uchida Kensuke
Asahi Kasei Kagyo Kabushiki Kaisha
Michl Paul R.
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