Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Reexamination Certificate
2000-06-09
2002-06-04
Kiliman, Leszek (Department: 1773)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
C428S515000, C428S520000, C525S193000, C525S194000, C525S232000
Reexamination Certificate
active
06399200
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a thermoplastic elastomer composition, powder, pellets and a molded article. More specifically, the present invention relates to a thermoplastic elastomer composition having an excellent powder moldability and resistance at lower temperature and providing a molded article of a thermoplastic elastomer, being hardly whitened on bending, and powder, pellets and a molded article obtained by using said thermoplastic elastomer composition.
BACKGROUND ARTS
Hitherto, a sheet-like molded article having complicated uneven patterns such as leather grain, stitch and the like on its surface is used as a skin material of interior parts of an automobile, and the like. As such molded article, a molded article obtained by powder molding powder obtained by pulverizing an olefin-based thermoplastic elastomer is proposed as a replacing article of a conventional vinyl chloride-based resin molded article (for example, refer to Japanese Patent Publication (Kokai) Hei Nos.3-199579 and 3-199589). However, the molded article obtained by powder molding powder obtained by pulverizing such thermoplastic elastomer has problems that resistance at lower temperature and whitening resistance on bending are insufficient.
For example, when said molded article is used as a skin material of an instrument panel housing an air bag, it is required that it is not brittlely fractured at a lower temperature (−30° C. to −40° C.) and an extremely high expanding speed (1 to 100 m/sec.). When the resistance at lower temperature is insufficient, not only the air bag does not accurately expand on collision, but also there is a dangerousness that the broken pieces of the skin material are scattered on the face and the like of a driver to cause injury.
Further, because of being easily whitened on bending, there has been a problem that the bent portion of said molded article is apt to be easily whitened when said molded article is taken out from a mold at the production of said molded article or when said molded article is preliminarily molded before laminating said molded article on a substrate.
To solve such problems, a thermoplastic elastomer hardly whitening the bent portion of said molded article and a molded article thereof are proposed (refer to WO/97-00911). However, although the whitening resistance on bending is sufficient, the resistance at lower temperature was insufficient yet.
DISCLOSURE OF THE INVENTION
Under these circumstances, the object to be solved by the present invention is to provide a thermoplastic elastomer composition providing a molded article of a thermoplastic elastomer having an excellent powder moldability and resistance at lower temperature, and being hardly whitened on bending, pellets obtained by using said thermoplastic elastomer composition, and a molded article thereof.
Namely, the first invention among the present invention relates to a thermoplastic elastomer composition containing (A), (B-1) and (B-2) described below and having a total content of (B-1) and (B-2) of 10 to 250 parts by weight per 100 parts by weight of the content of (A), a complex dynamic viscosity &eegr;*(1) at 250° C. of 1.5×10
5
poise or less and a Newtonian viscosity index n of 0.67 or less;
(A): a polyolefin-based resin,
(B-1): a conjugated diene-based thermoplastic elastomer or its hydrogenated product providing two tan &dgr; peaks within a temperature range of −70 to 30° C. in a temperature dependence curve of tan &dgr; determined by a solid viscoelasticity measurement of the composition obtained by being kneaded with (A), and
(B-2): a conjugated diene-based thermoplastic elastomer or its hydrogenated product providing a new single tan &dgr; peak at a temperature which is different from both the tan &dgr; peak temperature of (A) and the tan &dgr; peak temperature of (B-2) within a temperature range of −70 to 30° C. in a temperature dependence curve of tan &dgr; determined by a solid viscoelasticity measurement of the composition obtained by being kneaded with (A).
Further, the second invention of the present invention relates to powder prepared from the thermoplastic elastomer composition of the fore-mentioned first invention.
Further, the third invention of the present invention relates to pellets prepared from the thermoplastic elastomer composition of the fore-mentioned first invention, the thermoplastic elastomer composition having a complex dynamic viscosity &eegr;*(1) at250° C. of 5×10
4
poise or less and a Newtonian viscosity index n of 0.28 or less.
Further, the fourth invention of the present invention relates to a molded article obtained by powder molding the powder or the pellets comprising the thermoplastic elastomer composition of the fore-mentioned second or third invention.
BEST MODE FOR PRACTICING THE INVENTION
The component (A) of the present invention is a polyolefin-based resin, and at least one kind selected from a homopolymer or copolymer of at least one olefin having a high crystallinity. Said olefin includes olefins having 2 to 8 carbon atoms such as ethylene, propylene, 1-butene, 1-hexene, 1-octene and the like. The crystallinity of said (A) is preferably 50% or more. Examples of said (A) include a polyethylene, a polypropylene, a poly(1-butene) and a copolymer of propylene with an &agr;-olefin other than propylene (e.g. 1-butene-1). When (A) is a propylene-ethylene copolymer or a propylene-1-butene copolymer, it is preferable since the thermoplastic elastomer composition of the present invention provides a molded article excellent in heat resistance and flexibility.
Further, a copolymer obtained by copolymerizing 2 or more of monomers selected from ethylene and &agr;-olefins having 3 to 8 carbon atoms at two steps or more can be used. For example, a copolymer obtained by homopolymerizing propylene at the first step and copolymerizing propylene with ethylene or an &agr;-olefin other than propylene at the second step can be used.
Further, when a molded article is produced by a powder molding method using the powder of the thermoplastic elastomer composition of the present invention, a melt flow rate (MFR) of (A) which was measured at 230° C. under a load of 2.16 kgf according to JIS K-7210 is usually within a range of 20 to 500 g/10 min., preferably 50 to 300 g/10 min., and preferably 100 to 300 g/10 min. in particular.
The component (B-1) of the present invention is a conjugated diene-based thermoplastic elastomer or its hydrogenated product providing two tan &dgr; peaks within a temperature range of −70 to 30° C. in a temperature dependence curve of tan &dgr; determined by a solid viscoelasticity measurement of the composition obtained by being kneaded with (A).
Further, the component (B-2) of the present invention is a conjugated diene-based thermoplastic elastomer or its hydrogenated product providing a new single tan &dgr; peak at a temperature which is different from both the tan &dgr; peak temperature of (A) and the tan &dgr; peak temperature of (B-2) within a temperature range of −70 to 30° C. in a temperature dependence curve of tan &dgr; determined by a solid viscoelasticity measurement of the composition obtained by being kneaded with (A).
It can be determined by being previously kneaded with (A) and carrying out a solid viscoelasticity measurement whether the conjugated diene-based thermoplastic elastomer or its hydrogenated product belongs to either (B-1) or (B-2).
The conjugated diene-based thermoplastic elastomer of (B-1) and (B-2) or its hydrogenated product includes a conjugated diene-based rubbery polymer, a hydrogenated conjugated diene-based rubbery polymer and the like.
The conjugated diene-based rubbery polymer is a conjugated diene polymer rubber or a conjugated diene-based copolymer rubber.
The conjugated diene polymer rubber is a polymer rubber prepared by polymerizing or copolymerizing at least one conjugated diene. Examples of the conjugated diene include conjugated dienes having 4 to 8 carbon atoms such as butadiene, isoprene, pentadiene, 2,3-dimethylbutadiene and the
Ejiri Susumu
Nakatsuji Yoshihiro
Sugimoto Hiroyuki
Birch & Stewart Kolasch & Birch, LLP
Kiliman Leszek
Sumitomo Chemical Company Limited
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