Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Composite having voids in a component
Reexamination Certificate
2001-02-15
2002-12-17
Nakarani, D. S. (Department: 1773)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Composite having voids in a component
C428S319700, C428S319900, C428S516000, C428S519000, C428S521000, C428S523000
Reexamination Certificate
active
06495249
ABSTRACT:
BACKGROUND OF INVENTION
The present invention relates to a layered product having a skin layer of a thermoplastic elastomer composition which comprises a specific ethylene-&agr;-olefin copolymer and a propylene resin, said ethylene-&agr;-olefin copolymer being partially or completely crosslinked.
Hitherto, flexible thermoplastic resins have been used for automotive interior parts such as instrument panels, head linings and door trims, bags, trunks, furniture such as chairs, and sheets for seats of various vehicles. For these uses, since flexible thermoplastic resins are generally expensive, in many cases, the flexible thermoplastic resin is used as a skin material, and a cushioning material such as a foamed polyolefin resin or a reinforcing material such as a polyolefin resin is used as a substrate, and the skin material and the substrate are laminated to obtain the desired articles. Among the flexible thermoplastic resins used as the skin material, flexible polyvinyl chloride has such features that it is hardly flawed and it can provide articles having high quality feeling of soft touch, and for these reasons, the flexible polyvinyl chloride has been mainly used for the above uses.
However, the flexible polyvinyl chloride used as the skin material has suffered from the problems in long-term weathering resistance, low-temperature resistance, bleeding out of plasticizers and high gravity. Moreover, recently, it has been ascertained that harmful dioxin is produced if organic chlorine compounds such as polyvinyl chloride is burnt by improper equipment in the waste incineration stage. As a result, use of polyvinyl chloride is being gradually avoided.
On the other hand, flexible thermoplastic polyolefin resins are light in weight, excellent in low-temperature resistance, relatively high in weathering resistance, furthermore, generates no harmful gases when incinerated, and can be recycled, and thus are the most useful as substitute materials for polyvinyl chloride.
For obtaining the flexible thermoplastic polyolefin resins, namely, polyolefin thermoplastic elastomers, there is known a method for producing so-called dynamically crosslinked polyolefin thermoplastic elastomers which comprises crosslinking under melt kneading a radical crosslinkable elastomer and an olefin resin having no radical crosslinkability in the presence of a radical initiator in an extruder. Representative examples of the elastomers are dynamically crosslinked polyolefin thermoplastic elastomers of an ethylene-propylene-non-conjugated diene copolymer (EPDM) and a polypropylene resin. However, although EPDM is excellent in crosslinkability because of the presence of a diene component in the polymer chain, it has such problems that it is insufficient in mechanical strength, inferior in abrasion resistance and readily flawed, and inferior in environmental resistance. Therefore, improvement of quality of EPDM has been demanded, and layered products comprising a polyolefin thermoplastic elastomer as a skin layer which can stand practical use are desired.
SUMMARY OF THE INVENTION
Under the circumstances, the object of the present invention is to provide a layered product which comprises a skin layer and a cushioning layer and/or a reinforcing layer (substrate) and which has no problems as mentioned above, namely, is excellent in mechanical strength, abrasion resistance and environmental resistance (weathering resistance).
As a result of intensive research conducted by the inventors, it has been found that the above problems can be solved by using, as the flexible thermoplastic resin of the skin layer, a polyolefin thermoplastic elastomer which uses as a rubber component an ethylene-&agr;-olefin copolymer comprising ethylene and an &agr;-olefin and having a specific structure, specifically, an ethylene-&agr;-olefin copolymer produced using a metallocene catalyst.
That is, the layered product of the present invention is characterized by being formed of a skin layer and a cushioning layer and/or a reinforcing layer, said skin layer being a thermoplastic elastomer composition which comprises (A) 1-99 parts by weight of an ethylene-&agr;-olefin copolymer produced by polymerizing ethylene and an &agr;-olefin of 3-12 carbon atoms using a metallocene catalyst and (B) 1-99 parts by weight of a propylene resin [total amount of (A) and (B) being 100 parts by weight], said ethylene-&agr;-olefin copolymer being partially or completely crosslinked.
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be explained in detail below.
The ethylene-&agr;-olefin copolymer which is the component (A) in the thermoplastic elastomer composition which is a skin layer of the layered product of the present invention is a rubber-like ethylene-&agr;-olefin copolymer comprising ethylene and an &agr;-olefin of 3-12 carbon atoms.
The &agr;-olefins of 3-20 carbon atoms include, for example, propylene, butene-1, pentene-1, hexene-1, 4-methylpentene-1, heptene-1, octene-1, nonene-1, decene-1, undecene-1 and dodecene-1. These &agr;-olefins may be used each alone or in combination of two or more. Furthermore, they may contain a copolymer component as a third component. As the copolymer component of the third component, mention may be made of, for example, conjugated dienes such as 1,3-butadiene and isoprene, and non-conjugated dienes such as dicyclopentadiene, 1,4-hexadiene, cyclooctadiene, methylenenorbornene and ethylidenenorbornene. A typical example thereof is EPDM (ethylene-propylene-diene copolymer).
As mentioned above, the present invention includes also ethylene-&agr;-olefin copolymers in which a conjugated diene or non-conjugated diene is copolymerized, and does not exclude these copolymers, but ethylene-&agr;-olefin copolymers containing no conjugated diene or non-conjugated diene are superior in environmental resistance and weathering resistance to ethylene-&agr;-olefin copolymers containing conjugated diene or non-conjugated diene, and, hence, the former are more preferred.
In the present invention, the ethylene-&agr;-olefin copolymers are produced using known metallocene catalysts.
The metallocene catalysts generally comprise a promoter and a cyclopentadienyl derivative of a metal of Group IV, such as titanium or zirconium, and they are not only high in activity as polymerization catalysts, but also, as compared with conventional Ziegler catalysts, give copolymers which are narrower in molecular weight distribution and which have a more uniform distribution of &agr;-olefin of 3-12 carbon atoms as a comonomer. Therefore, the ethylene-&agr;-olefin copolymers produced using metallocene catalysts greatly differ in properties from those obtained using Ziegler catalysts and the like.
The features of the ethylene-&agr;-olefin copolymers produced using metallocene catalysts are enumerated below.
1. Because of the high activity of the polymerization catalysts, composition of &agr;-olefin as a comonomer can be conspicuously enhanced, and elastomer-like polymers high in flexibility can be obtained even in the state of containing no plasticizers.
2. The copolymers have more uniform distribution of the comonomers as compared with polymers obtained using Ziegler catalysts.
3. The copolymers have a very sharp molecular weight distribution, contain little low-molecular weight components, are excellent in mechanical strength and workability and have high quality as compared with polymers obtained using Ziegler catalysts.
4. In spite of the highly sharp molecular weight distribution, in the case of introducing a long chain branching, the copolymers have a high ratio (I10/I2) of a melt index (I10) at 190° C./10 kgf and a melt index (I2) at 190° C./2.16 kgf as specified by ASTM D1238, and thus the copolymers are excellent in workability.
5. The copolymers hardly show blocking even if the copolymerization ratio of the &agr;-olefin is high, and can have the form of pellets.
In the ethylene-&agr;-olefin copolymers produced using Ziegler catalysts, the melt index ratio (I10/I2) and the molecular weight distribution show nearly linear proport
Shibayama Shinichi
Uchida Kensuke
Asahi Kasei Kabushiki Kaisha
Nakarani D. S.
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