Land vehicles – Wheeled – Attachment
Patent
1998-06-03
2000-08-22
Sellers, Robert E.
Land vehicles
Wheeled
Attachment
524505, 525 89, B60R 2120, C08L 5302, C08K 501
Patent
active
061060119
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to a thermoplastic elastomer composition and a cover for an air bag device. More particularly, the present invention is concerned with a thermoplastic elastomer composition comprising, in specific amount relationships, a mixture of two different specific hydrogenated block copolymers which are different in molecular structure and number average molecular weight, a polyolefin resin having a specific melt flow rate, and optionally a hydrocarbon oil; and also concerned with a cover for use in releasably holding an air bag device, which comprises a molded body formed by molding the thermoplastic elastomer composition.
The thermoplastic elastomer composition of the present invention has excellent softness, heat resistance, low-temperature characteristics, weatherability, mechanical strength, moldability and scratch resistance (resistance of the surface of a molded article to scratching) and, therefore, can be advantageously used as a material for various types of articles, such as parts of automobiles or electrical appliances, toys, miscellaneous goods and the like. Especially, by virtue of the excellent scratch resistance, the elastomer composition can be advantageously used as a material for articles which require maintenance of good appearance. Examples of such articles include interior parts of automobiles, such as an instrument panel, an arm rest, a steering wheel and a horn pad, and exterior parts of automobiles, such as a window molding and a bumper. In addition, it is noted that a cover for use in releasably holding an air bag device, which comprises a molded body formed by molding the above-mentioned thermoplastic elastomer composition, exhibits not only the above-mentioned excellent properties, but also excellent break-opening characteristics in a wide temperature range of from -40 to 90 .degree. C. without occurrence of tearing at unintended portions of the cover and without scattering of broken pieces of the cover. Further, since the thermoplastic resin composition of the present invention exhibits excellent scratch resistance and excellent moldability, it becomes possible to omit cumbersome coating processes, which have been conventionally required for obtaining molded articles having good appearance. Therefore, using the thermoplastic elastomer composition of the present invention, the molded articles can be obtained with high productivity at low cost.
2. Background Art
In the fields of parts for automobiles as well as electrical appliances and medical instruments, miscellaneous goods and the like, in which a vulcanized rubber has conventionally been used as a main material therefor, a recent tendency is noted, wherein thermoplastic elastomers are widely used as materials due to the high productivity which can be achieved by thermoplastic elastomers. Examples of such thermoplastic elastomers include a polyolefin elastomer comprising an ethylene/propylene copolymer and a propylene homopolymer; a polyurethane elastomer; and a soft polyvinyl chloride.
However, when these materials are used for obtaining molded articles, they have disadvantages in that all of the desired characteristics for materials for producing molded articles, such as scratch resistance, softness, moldability, economical efficiency and recyclability, cannot be satisfied simultaneously. For example, polyolefin elastomers are relatively cheap and have excellent weatherability and excellent heat resistance, but they are poor in softness and scratch resistance. Polyurethane elastomers have excellent scratch resistance, but have disadvantages in that they are not only poor in softness and weatherability but also expensive. Soft polyvinyl chloride products are relatively cheap and have excellent weatherability and excellent scratch resistance, but they are poor in softness at low temperatures and in recyclability.
With respect to materials for molded articles, in addition to the above-mentioned materials, some proposals were made, in which attention was direct
REFERENCES:
patent: 4892903 (1990-01-01), Himes
patent: 4985499 (1991-01-01), Nishikawa et al.
patent: 5068138 (1991-11-01), Mitchell et al.
patent: 5093422 (1992-03-01), Himes
patent: 5358986 (1994-10-01), Onafusa et al.
patent: 5750612 (1998-05-01), Zyagawa et al.
Masubuchi Tetsuo
Tanaka Mitsuhiro
Asahi Kasei Kogyo Kabushiki
Sellers Robert E.
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