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
2001-04-26
2003-07-15
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...
C524S451000
Reexamination Certificate
active
06593409
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thermoplastic resin composition excellent in rigidity and impact resistance, and provides, when molded, a molded article having a excellent appearance, particularly few flow marks. Further, the present invention relates to an injection-molded article of the thermoplastic resin composition.
2. Description of Related Arts
Polypropylene-based resins have been widely used in materials requiring rigidity, impact strength and the like. Recently, polypropylene-based resins are increasingly used, particularly, as automobile materials, and especially, ethylene-propylene block copolymers are used increasingly. Though ethylene-propylene block copolymers have been conventionally produced by a solvent method, the ethylene-propylene block copolymers are recently produced by a continuous gas phase method which is simple in a production process and can produce the ethylene-propylene block copolymer at low cost.
However, the ethylene-propylene block copolymer produced by the gas phase method has, in general, problems that, due to lower intrinsic viscosity [&eegr;]
EP
of an ethylene-propylene copolymer portion, swelling ratio (SR) is low, flow marks are many and appearance of a molded article deteriorates, further that when the intrinsic viscosity [&eegr;]
EP
of an ethylene-propylene copolymer portion of the ethylene-propylene block copolymer produced by a gas phase method is increased, a granular structure is generated and appearance of a molded article deteriorates.
For solving the problems regarding appearance as described above, for example, JP-A-07-286022 discloses a propylene-based block copolymer produced by a batch-wise solvent method, which has a intrinsic viscosity of an n-decane-insoluble component at 23° C. of 0.1 to 20 dl/g, has a intrinsic viscosity of an n-decane-soluble component at 23° C. of 5 to 15 dl/g, and can form a molded article without generating a gel on the appearance. However, as disclosed in Comparative Example 3 thereof, an ethylene-propylene block copolymer showing higher intrinsic viscosity of an n-decane-soluble component at 23° C. which is supposed to correspond to an ethylene-propylene block copolymer portion contains a lot of rubber granules causing gels.
Further, JP-A-07-286075 discloses a propylene polymer composition which contains a propylene polymer produced according to continuous mode and an ethylene-propylene block copolymer showing a intrinsic viscosity of an n-decane-soluble component at 23° C. of 5 to 12 dl/g, and can form a molded article generating no gels on appearance. However, the amount of the ethylene-propylene block copolymer compounded is as high as 12% by weight or more.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a thermoplastic resin composition having an excellent stiffness, impact resistance and flowability, and providing, when molded, a molded article having a excellent appearance, particularly few flow marks, and an injection-molded article obtained by using the thermoplastic resin composition.
Under the situations, the present inventors have intensively studied, and resultantly found that the above-mentioned problems can be solved by a thermoplastic resin composition comprising a polypropylene-based resin, elastomer, inorganic filler, and an extremely small amount of a resin having specific melt tension (MT), specific swelling ratio (SR) and specific time required until the ratio of the relaxation modulus G(t) to the relaxation modulus G(0.02) in a time of 0.02 sec. reaches 0.01, and an injection-molded article obtained by using the resin composition, leading to completion of the present invention.
Namely, the present invention relates to a thermoplastic resin composition comprising:
(A) a polypropylene-based resin of 35 to 85% by weight;
(B) an elastomer of 10 to 35% by weight;
(C) an inorganic filler of 2 to 30% by weight; and
(D) a resin of 0.1% by weight or more and less than 5% by weight, wherein (1) the melt tension of the resin (D) measured at a temperature of 190° C. and a winding rate of 15.7 m/min. is 0.1 N or more, (2) the swelling ratio of the resin (D) measured at a temperature of 220° C., an L/D ratio of an orifice of 40 and a shear rate of 1.2×10
3
sec
−1
is 1.8 or more, and (3) the time required until the ratio (G(t)/G(0.02)) of the relaxation elastic modulus G(t) measured at 210° C. to there laxation elastic modulus G(0.02) in a time of 0.02 sec. reaches 0.01, of the resin (D) is 10 sec. or more, and wherein the sum of the (A), (B), (C) and (D) is 100% by weight.
Further, the present invention relates to an injection-molded article obtained by using the above-mentioned thermoplastic resin composition.
The present invention will be illustrated in detail below.
DETAILED DESCRIPTION OF THE INVENTION
The propylene-based resin (A) used in the present invention is not particularly restricted, and preferably, is a crystalline polypropylene-based resin, and examples thereof include a crystalline propylene homopolymer, crystalline ethylene-propylene copolymer, crystalline propylene-&agr;-olefin copolymer and the like, and these may be used alone or in a combination of two or more.
The &agr;-olefin used in the crystalline propylene-&agr;-olefin copolymer is an &agr;-olefin having 4 or more carbon atoms, preferably 4 to 20 carbon atoms, more preferably 4 to 12 carbon atoms, and examples thereof include butene-1, pentene-1, hexene-1, heptene-1, octene-1, decene-1 and the like. Examples of the crystalline propylene-&agr;-olefin copolymer include a crystalline propylene-butene-1 copolymer, crystalline propylene-hexene-1 copolymer and the like.
Further, the crystalline polypropylene-based resin is preferably a crystalline propylene homopolymer, a crystalline ethylene-propylene block copolymer or a mixture of thereof, more preferably a crystalline ethylene-propylene block copolymer or a mixture of a crystalline propylene homopolymer and a crystalline ethylene-propylene block copolymer.
The crystalline ethylene-propylene block copolymer used in the present invention is a crystalline ethylene-propylene block copolymer composed of a propylene homopolymer portion (referred to as “first segment”) and an ethylene-propylene random copolymer portion (referred to as “second segment”).
The propylene homopolymer portion as the first segment has a Q value which is a ratio of weight average molecular weight (Mw)
umber average molecular weight (Mn) according to a gel permeation chromatography (GPC) method of preferably from 3.0 to 5.0, more preferably from 3.5 to 4.5. The first segment has preferably an isotactic pentad fraction calculated based on
13
C-NMR of preferably 0.98 or more, more preferably 0.99 or more. Further, the intrinsic viscosity [&eegr;]
P
of a tetralin solution at 135° C. of the first segment is preferably from 0.7 to 1.1 dl/g, more preferably from 0.8 to 1.0 dl/g.
The ethylene-propylene random copolymer portion as the second segment, has an intrinsic viscosity [&eegr;]
EP
of a tetralin solution at 135° C. of from 1.0 or more and less than 8.0 dl/g, preferably from 1.5 to 7.5 dl/g. Further, the second segment has an ethylene content [(C2′)
EP
] of preferably from 25 to 35% by weight, more preferably from 27 to 33% by weight.
The weight ratio of the ethylene-propylene random copolymer portion (second segment) to the propylene homopolymer portion (first segment) (second segment/first segment ratio) is preferably 8/92 to 35/65.
The crystalline propylene homopolymer used in the above-mentioned mixture with the crystalline ethylene-propylene block copolymer is a polymer having physical properties similar to those of the propylene homopolymer portion which is the first segment of the crystalline ethylene-propylene block copolymer, and specifically having a Q value which is ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) according to a gel permeation chromatography (GPC) method of preferably from 3.0 to
Kondo Shin-ichi
Ohkawa Kenichi
Shimojo Moriyasu
LandOfFree
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