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
2000-07-11
2002-08-27
Jagannathan, Vasu (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...
C524S505000, C525S088000, C525S240000
Reexamination Certificate
active
06441081
ABSTRACT:
TECHNICAL FIELD
This invention relates to a polypropylene resin composition and an injection-molded article thereof. Particularly, it relates to a polypropylene resin composition characterized by being excellent in rigidity and impact resistance in respect of physical properties, having a short molding cycle in respect of injection moldability and by surface quality such as neither flow mark nor weld line being developed, no surface strain being caused, and the like and to an injection-molded article thereof. More particularly, it relates to a polypropylene resin composition which comprises a specific polypropylene resin as the main component, a specific ethylene-1-octene copolymer rubber component and talc, which is excellent in physical properties and injection moldability as mentioned above, and to an injection-molded article excellent in dimensional stability formed by molding the same by an injection molding method, particularly to an injection-molded article for exterior automotive trim (bumper or the like).
BACKGROUND ART
Recently, as a material for exterior automotive trim, there have been widely used propylene-ethylene block copolymer materials in view of weight-saving, cost reduction and the like.
However, the propylene-ethylene block copolymer is low in impact strength, and in order to improve this impact strength, it has been proposed to blend a propylene-ethylene block copolymer with an ethylene-propylene copolymer rubber, an ethylene-1-octene copolymer rubber or the like as stated in JP-A-53-22552, JP-A-6-192500, JP-A-6-248156, JP-A-6-192506 and JP-A-53-40045. However, when an ethylene-propylene copolymer rubber, an ethylene-1-octene copolymer rubber or the like is blended, impact strength is improved but, contrarily, thermal properties such as heat distortion temperature and the like and rigidity are deteriorated, and as a material for exterior automotive trim, it has a fault.
In order to solve this, further compounding the above composition with an inorganic filler such as calcium carbonate, barium sulfate, mica, crystalline calcium silicate, talc or the like is proposed in, for example, JP-A-51-136735, JP-A-53-64256, JP-A-53-64257, JP-A-57-55952, JP-A-57-207630, JP-A-58-17139, JP-A-58-111846, JP-A-59-98157, JP-B-55-3374 and the like.
However, a conventional material of a system consisting of a propylene-ethylene block copolymer/ethylene-propylene copolymer rubber or ethylene-1-octene copolymer rubber/inorganic filler has still been insufficient as a material for exterior automotive trim in respect of injection moldability and balance between impact strength and rigidity.
DISCLOSURE OF INVENTION
Under such circumstances, this invention aims at providing a polypropylene resin composition which is good in balance between impact strength and rigidity and excellent in injection moldability such as no flow mark being developed or the like and providing an injection-molded article thereof.
The present inventors have found that a polypropylene resin composition satisfying the above object and an injection-molded article thereof are obtained by using mainly a polypropylene resin and adding thereto a specific rubber component at a specific composition ratio and have reached this invention. That is to say, this invention relates to a polypropylene resin composition which comprises:
(1) 55 to 75% by weight of (A) a polypropylene resin consisting of a mixture of the following polymers (i) and (ii):
(i) a propylene-ethylene block copolymer having a propylene homopolymer part which is the first segment and having a propylene-ethylene random copolymer part which is the second segment and
(ii) a propylene homopolymer having an intrinsic viscosity [&eegr;]P of 0.8 to 1.8 dl/g as measured in tetralin at 135° C.,
(2) 21 to 30% by weight of (B) an ethylene-1-octene copolymer rubber having a melt flow rate (JIS-K-6758 at 190° C.) of 2 to 10 g/10 min. and having a 1-octene component content of 20 to 25% by weight, and
(3) 5 to 20% by weight of (C) talc having an average particle diameter of not more than 3 &mgr;m, wherein when the amount of the second segment contained in the propylene-ethylene block copolymer of the polypropylene resin (A) is designated as (A)′ and the ethylene-1-octene copolymer rubber content is designated as (B)′, the following expression is satisfied:
0.10≦{(
A
)′/[(
A
)′+(
B
)′]}≦0.30,
and when the above composition is subjected to a tensile test according to ASTM D638 at 23° C., it exhibits an ultimate elongation of at least 400%, and wherein the melt flow rate (JIS-K-6758 at 230° C.) of the composition is at least 30 g/10 min., and also to an injection-molded article obtained by injection molding the above polypropylene resin composition.
This invention is explained in detail below.
In this invention, the polypropylene resin (A) means a polypropylene resin which comprises mainly a polymer mixture of the above propylene-ethylene block copolymer (i) having a propylene homopolymer part which is the first segment and having a propylene-ethylene random copolymer part which is the second segment with the above propylene homopolymer (ii) having an intrinsic viscosity [&eegr;]P of 0.8 to 1.8 dl/g as measured in tetralin at 135° C. As to the ratio between (i) and (ii) , there is usually used one having a ratio of 90% by weight-60% by weight of (ii) to 10% by weight-40% by weight of (i) (provided (i)+(ii)=100% by weight).
The polypropylene resin (A) in this invention has a Q value, which is the weight average molecular weight (Mw)
umber average molecular weight (Mn) ratio which represents the molecular weight distribution according to the gel permeation chromatography (GPC) of the propylene homopolymer part of the polypropylene resin (A), of preferably 3.0 to 5.0, more preferably 3.5 to 4.5. When the Q value is less than 3.0, the flow properties are deteriorated, and when the Q value exceeds 5.0, no preferable result is obtained with respect to balance between rigidity and impact property in some cases.
Here, the propylene homopolymer part of the polypropylene resin (A) means both the first segment part of the propylene-ethylene block copolymer (i) and the propylene homopolymer (ii).
Particularly preferable physical properties, compositions and the like of the propylene homopolymer (ii) in the polypropylene resin (A) are as follows:
That is, the Q value is preferably 3.0 to 5.0, more preferably 3.5 to 4.5 and, in addition, the isotactic pentad fraction calculated by
13
C-NMR is at least 0.97, preferably at least 0.98. When the isotactic pentad fraction is less than 0.97, it is difficult in some cases to satisfy the objective rigidity, heat resistance and the like.
Moreover, the intrinsic viscosity [&eegr;]P is 0.8 to 1.8 dl/g, preferably 0.9 to 1.6 dl/g, as measured in tetralin at 135° C. When the intrinsic viscosity [&eegr;]P is less than 0.8 dl/g, the impact strength becomes low and no preferable result is obtained in respect of physical properties. Furthermore, when the intrinsic viscosity exceeds 1.8 dl/g, the flow properties are deteriorated.
In the case of the propylene-ethylene block copolymer (i) in the polypropylene resin (A) which copolymer has the propylene homopolymer part as the first segment and the propylene-ethylene random copolymer part as the second segment, those physical properties, compositions and the like which are particularly preferably required are as follows:
In the propylene-ethylene block copolymer (i) the physical properties of the propylene homopolymer part which is the first segment are the same as those of the above-mentioned propylene homopolymer (ii). That is, the Q value is 3.0 to 5.0, preferably 3.5 to 4.5 and the isotactic pentad fraction calculated by
13
C-NMR is at least 0.97, preferably at least 0.98. Moreover, the intrinsic viscosity [&eegr;]P is 0.8 to 1.8 dl/g, preferably 0.9 to 1.6 dl/g, as measured in tetralin at 135° C.
The propylene homopolymer part which is the first segment of the propylene-eth
Ichikawa Shoichi
Iwai Hisayuki
Kanzaki Susumu
Nomura Takao
Ohkawa Kenichi
Birch & Stewart Kolasch & Birch, LLP
Jagannathan Vasu
Shosho Callie E.
Sumitomo Chemical Company Limited
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