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
1998-02-24
2002-05-07
Mulcahy, Peter D. (Department: 1713)
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
Reexamination Certificate
active
06384122
ABSTRACT:
TECHNICAL FIELD
This invention relates to a thermoplastic resin composition which is excellent in rigidity and impact resistance in respect of physical properties, has a short molding cycle and characteristic features in surface quality such as no generation of flow mark or weldline, no surface strain or the like in respect of injection moldability, and to an injection molded article excellent in dimension stability molded therefrom by an injection molding method, particularly an automobile interior trim material.
More particularly, this invention relates to a thermoplastic resin composition which comprises a specific crystalline polypropylene as a main component and is excellent in rigidity and impact resistance in respect of physical properties and has a short molding cycle and excellent surface quality in respect of injection moldability; and to an injection molded article excellent in dimension stability prepared therefrom by an injection molding method, particularly an injection molded article for automobile interior trim.
BACKGROUND ART
Crystalline ethylene-propylene copolymer/ethylene-propylene copolymer rubber/talc compositions (referred to hereinafter as the ethylene-propylene copolymer rubber type composition) has been widely used as an automobile interior trim material because they are inexpensive, good in moldability and the like. The ethylene-propylene copolymer rubber type resin composition is usually molded into an automobile interior trim material by an injection molding method. As to the injection moldability thereof, it is required firstly that the molding cycle of the present composition be shortened for increasing the productivity; secondly that the present composition give, by an injection molding, an interior trim molded article which has such excellent surface qualities that neither flow mark nor weldline is generated and no surface strain is caused; and the like.
However, conventional ethylene-propylene copolymer rubber type compositions have such problems that when the fluidity thereof is simply increased, the impact strength which is required for an interior trim material is not satisfied though the surface quality is improved in the injection molding and the filling time is shortened but the plasticizing time becomes long and hence the molding cycle is consequently not shortened.
DISCLOSURE OF INVENTION
Under such circumstances, this invention aims at providing a themoplastic resin composition which comprises a crystalline polypropylene as a main component, and which, in respect of physical properties, satisfies the impact strength and rigidity required for an interior trim material and has high flow and good balance between impact strength and rigidity as compared with conventionally used ethylene-propylene copolymer rubber compositions, and in respect of injection moldability, has a short molding cycle and good surface quality, and further providing an injection molded article using the composition, particularly an injection molded article for automobile interior trim.
This invention relates to a thermoplastic resin composition comprising (A) a crystalline polypropylene, (B) an ethylene-butene-1 copolymer rubber, (C) an ethylene-propylene copolymer rubber and (D) a vinyl aromatic compound-containing rubber (at least one of the above (B), (C) and (D) is used), (E) talc and (F) fibrous magnesium oxysulfate and to an injection molded article obtained by molding the above thermoplastic resin composition by an injection molding method.
That is to say, this invention relates to a thermoplastic resin composition which comprises:
(1) 57 to 71% by weight of a crystalline polypropylene (A) selected from the following (i) or (ii):
(i) a crystalline ethylene-propylene copolymer in which the propylene homopolymer portion which is the first segment has a Q value of 3 to 5 which is the weight average molecular weight (Mw)
umber average molecular weight (Mn) ratio according to a gel permeation chromatography (GPC) method, an isotactic pentad fraction of not less than 0.98 as calculated by
13
C-NMR and an intrinsic viscosity of 0.9 to 1.1 dl/g as measured at 135° C. in tetralin; and the ethylene-propylene random copolymer portion which is the second segment has an intrinsic viscosity of 4.5 to 5.5 dl/g as measured at 135° C. in tetralin and an ethylene/propylene ratio of 25/75 to 35/65 (weight % ratio), and
(ii) a mixture of the crystalline ethylene-propylene block copolymer of (i) with a crystalline propylene homopolymer having a Q value of 3 to 5 according to the GPC method, an isotactic pentad fraction of not less than 0.98 as calculated by
13
C-NMR and an intrinsic viscosity of 0.9 to 1.1 dl/g as measured at 135° C. in tetralin;
(2) 14 to 18% by weight of at least one rubber component selected from the group consisting of the following (B), (C) and (D):
0 to 5% by weight of the following ethylene-butene-1 copolymer rubber (B):
an ethylene-butene-1 copolymer rubber having a Q value of not more than 2.7 according to the GPC method, a butene-1 content of 15 to 20% by weight, an intrinsic viscosity of 1.1 to 2.1 dl/g as measured at 70° C. in xylene and a Mooney viscosity at 100° C. (ML
1+4
100° C.) of 7 to 90,
0 to 5% by weight of the following ethylene propylene copolymer rubber (C):
an ethylene-propylene copolymer rubber having a Q value of not more than 2.7 according to the GPC method, a propylene content of 20 to 30% by weight, an intrinsic viscosity of 1.8 to 2.2 dl/g as measured at 70° C. in xylene and a Mooney viscosity at 100° C. (ML
1+4
100° C.) of 35 to 100, and
10 to 18% by weight of the following vinyl aromatic compound-containing rubber (D):
a vinyl aromatic compound-containing rubber in which a vinyl aromatic compound is bonded to an olefinic copolymer rubber or a conjugated diene rubber, and which has a vinyl aromatic compound content of 1 to 50% by weight and a melt viscosity at 230° C. at a shear rate of 10 sec
−1
of not more than 10
4
as measured by a capillary flow tester, and which is characterized in that in a blend prepared by adding 10% by weight of the vinyl aromatic compound-containing rubber to a crystalline propylene homopolymer having an isotactic pentad.fraction of 0.98 as calculated by
13
C-NMR and an intrinsic viscosity of 1.55 dl/g as measured at 135° C. in tetralin, the difference (&Dgr;Tg, Tg shift) in glass transition point (Tg) attributed to the crystalline propylene homopolymer portion before and after the blending is less than 3° C.;
(3) 15 to 25% by weight of talc having an average particle size of not more than 4 &mgr;m (E); and
(4) 0 to 10% by weight of fibrous magnesium oxysulfate having a fiber diameter of 0.3 to 2 &mgr;m and an average fiber length of 5 to 50 &mgr;m (F),
and which thermoplastic resin composition satisfies the following equations 1) to 4):
(
A
)+(
B
)+(
C
)+(
D
)+(
E
)+(
F
)=100 1)
0.20≦{[(
A
)×(
A
)′+(
B
)+(
C
)+(
D
)]/100}≦0.25 2)
0.1≦{(
A
)×(
A
)′/[(
A
)×(
A
)′+(
B
)+(
C
)+(D)]} 3)
15≦[(
E
)+(
F
)]≦25 4)
wherein (A), (B), (C), (D), (E) and (F) indicate weight % of the respective components and (A)′ indicates the weight fraction of the second segment in the crystalline polypropylene (A), and has a melt flow index (JIS-K-6758, 230° C.) of 25 to 35 g/10 minutes and a flexural modulus at 23° C. of not less than 20,000 kg/cm
2
; and to an injection molded article obtained from the thermoplastic resin composition, particularly a molded article for automobile interior trim.
This invention is explained below in detail.
In this invention, the crystalline polypropylene (A) means (i) a crystalline ethylene-propylene copolymer having a crystalline propylene homopolymer portion as the first segment and an ethylene-propylene random copolymer portion as a second segment (referred to as the block copolymer in some cases) or (ii) a mixture of such a crystalline ethylene-propylene c
Doi Teruhiko
Hirakawa Manabu
Hisayama Tetsuya
Miyake Yuichi
Nishio Takeyoshi
Mulcahy Peter D.
Sughrue & Mion, PLLC
Sumitomo Chemical Company Limited
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