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...
Reexamination Certificate
2000-12-22
2004-07-06
Cain, Edward J. (Department: 1714)
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...
C525S088000, C525S095000, C525S240000, C525S242000
Reexamination Certificate
active
06759465
ABSTRACT:
TECHNICAL FIELD
This invention relates to a thermoplastic resin composition having excellent characteristic features in rigidity, impact resistance and moldability and to injection moldings excellent in dimensional stability formed therefrom by an injection molding method, particularly injection moldings for automobile if interior and exterior trims.
BACKGROUND ART
In recent years, propylene-ethylene block copolymers have been used as automobile materials from the view points of weight reduction and cost reduction. However, previous propylene-ethylene block copolymer materials are low in impact resistance; to improve the impact resistance, it has been proposed to compound into propylene-ethylene block copolymers an ethylene-propylene copolymer rubber, ethylene-&agr;-olefin copolymer rubber or the like. When an ethylene-propylene copolymer rubber, ethylene-&agr;-olefin copolymer rubber or the like is compounded, however, though the resulting composition is improved in impact strength, the composition conversely shows a lowered rigidity and deteriorated thermal properties such as heat distortion temperature, and hence has difficulties for use as automobile interior and exterior trim materials. To solve the problems, it has been proposed to compound additionally into the composition inorganic fillers, such as calcium carbonate, barium sulfate, mica, crystalline calcium silicate and talc.
For example, JP-A-51-136735 discloses a thermoplastic resin composition comprising an ethylene-block copolymer mainly based on propylene, an ethylene-propylene rubber and talc, and describes the physical properties thereof. It also describes, only in general, that styrene-butadiene rubbers can be used similarly to the ethylene-propylene rubber, but it describes nothing about the structure and state of the product obtained by melt-kneading the rubber and about the molecular weight distribution, melt flow rate, styrene content, etc. of the rubber.
JP-A-6-192,500 discloses a propylene-based resin composition comprising a propylene-ethylene block copolymer and an ethylene-1-hexene copolymer. It further describes as additional compounding ingredients, the blend of talc or the like, which are auxiliary additive components conventionally used in the process for producing resin compositions, and styrene-butadiene type rubbers or the like. However, it describes nothing about the structure and state of the product obtained by melt-kneading the rubber and about the molecular weight distribution, melt flow rate, styrene content, etc. of the rubber.
JP-A-6-192506 discloses a polypropylene composition comprising polypropylene, ethylene-1-octene random copolymer and talc, but it describes nothing of the use of vinyl aromatic compound-containing rubbers.
As described above, previous resin compositions comprising a propylene-ethylene block copolymer, ethylene-propylene copolymer rubber or ethylene-&agr;-olefin copolymer rubber and inorganic filler have been, as automobile interior and exterior trim materials, still insufficient in the balance of impact strength with rigidity and in injection moldability. Further, prior technologies for using styrene-butadiene type rubbers or the like have also been unsatisfactory.
DISCLOSURE OF THE INVENTION
Under such circumstances, the object of this invention is to provide a polypropylene-based resin composition comprising a crystalline polypropylene-based resin, elastomer and talc which satisfies, in respect of physical properties, the impact resistance and rigidity required for automobile interior and exterior trim materials and is excellent in injection moldability and to provide injection moldings thereof, particularly injection moldings for automobile interior and exterior trim uses.
The present inventors have found that a polypropylene-based resin composition and injection moldings thereof which can meet the above-mentioned objects can be obtained by using a specific crystalline polypropylene-based resin as the main component and melt-kneading therewith, in specific compounding ratios, a specific elastomer component and talc, and resultantly attained this invention.
Thus, this invention relates to a thermoplastic resin composition which is obtained by melt-kneading a mixture comprising (1) 55-75% by weight of a crystalline polypropylene-based resin, (2) 10-30% by weight of an elastomer comprising a vinyl aromatic compound-containing rubber or comprising a vinyl aromatic compound-containing-rubber and an ethylene-&agr;-olefin random copolymer rubber and (c) 15-25% by weight of talc having an average particle diameter of not more than 3 &mgr;m, and which satisfies the following conditions (a)-(c):
(a) when the crystalline polypropylene-based resin (1) has been melt-kneaded with the elastomer (2) comprising a vinyl aromatic compound-containing rubber or comprising a vinyl aromatic compound-containing rubber and an ethylene-a-olefin random copolymer rubber, the long period obtained by small angle X-ray scattering attributable to the vinyl aromatic compound-containing rubber is 12-24 nm,
(b) when the crystalline polypropylene-based resin (1) has been melt-kneaded with the elastomer (2) comprising a vinyl aromatic compound-containing rubber or comprising a vinyl aromatic compound-containing rubber and an ethylene-&agr;-olefin random copolymer rubber, elastomer particles which undergo micro phase separation to have the form of particle, and are present in the vicinity of the interface between particles of the elastomer and the crystalline polypropylene-based resin as matrix, have a particle diameter of not more than 30 nm, and
(c) the difference between the glass transition point (Tg
1
) assigned to the crystalline propylene homopolymer portion of the crystalline polypropylene-based resin (1) and the glass transition point (Tg
2
) assigned to the crystalline propylene homopolymer portion of a composition obtained by melt-kneading the crystalline polypropylene-based resin (1) with the elastomer (2) comprising a vinyl aromatic compound-containing rubber or comprising a vinyl aromatic compound-containing rubber and an ethylene-&agr;-olefin random copolymer rubber and talc (3) (that is, &Dgr;Tg=Tg
1
−Tg
2
) is 4.0-7.0° C.
This invention also relates to injection moldings formed from the above-mentioned polypropylene-based resin composition by an injection molding method.
This invention further relates to injection moldings for automobile interior and exterior trim uses.
BEST MODE FOR CARRYING OUT THE INVENTION
This invention is described in detail below.
The thermoplastic resin composition of this invention is a composition obtained by melt-kneading a mixture comprising (1) 55-75% by weight of a crystalline polypropylene-based resin, (2) 10-30% by weight of an elastomer comprising a vinyl aromatic compound-containing rubber or comprising a vinyl aromatic compound-containing rubber and an ethylene-&agr;-olefin random copolymer rubber and (3) 15-25% by weight of talc having an average particle diameter of not more than 3 &mgr;m.
The crystalline polypropylene-based resin (1) used in this invention is not particularly limited so long as it is crystalline and may be, for example, propylene homopolymers, propylene-ethylene copolymers and propylene-&agr;-olefin copolymers. The &agr;-olefin in the copolymer has at least 4 carbon atoms and may be, for example, butene, pentene, hexene, heptene, octene, decene and the like.
Particularly preferably used crystalline polypropylene-based resin (1) is a crystalline polypropylene selected from a crystalline ethylene-propylene block copolymer (1A) or a mixture (1B) of the crystalline ethylene-propylene block copolymer (1A) with a crystalline propylene homopolymer.
The crystalline ethylene-propylene block copolymer (1A) herein referred to is a crystalline ethylene-propylene block copolymer consisting essentially of a propylene homopolymer portion (hereinafter referred to as the first segment) and an ethylene-propylene random copolymer portion (hereinafter referred to as the second segment).
The propylene homopolymer portion, which is th
Iwai Hisayuki
Kanzaki Susumu
Matsuda Masatoshi
Nagai Takayuki
Nomura Takao
Cain Edward J.
Sughrue & Mion, PLLC
Sumitomo Chemical Company Limited
Wyrozebski Katarzyna
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