Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2001-06-27
2002-10-29
Nutter, Nathan M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
active
06472477
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polypropylene resin composition comprising a propylene homopolymer, and a propylene-ethylene block copolymer. More particularly, it relates to a polypropylene resin composition excellent in appearance when formed into a molded article because flow marks hardly generate, in other wards, a die swell is high and few fish eyes generate, and to a molded article made of the polypropylene resin composition.
2. Description of Related Arts
Polypropylene resin compositions are materials excellent in rigidity, impact resistance, and the like, and they have been used in wide fields as molded articles such as automobile internal and external trim materials, electrical parts housings, and the like. It is well known that, among these polypropylene resin compositions, a polypropylene resin composition containing propylene-ethylene block copolymers, for example, a polypropylene resin composition containing a propylene-ethylene block copolymer and a propylene homopolymer, or different two kinds of propylene-ethylene block copolymers is preferably used because of its excellent rigidity, impact resistance, and the like.
For example, JP 7-157626A discloses a thermoplastic resin composition containing a propylene-ethylene block copolymer obtained by multistage polymerization and a polyolefin rubber. As the propylene-ethylene block copolymer, there is used a propylene-ethylene block copolymer wherein the ethylene content of a propylene-ethylene random copolymer phase is from 5 to 50% by weight, the intrinsic viscosity of the copolymer phase is from 4.0 to 8.0 dl/g, and the propylene-ethylene block copolymer having an ethylene content of more than 50% by weight to not more than 98% by weight, and an intrinsic viscosity of from not less than 2.0 to less than 4.0 dl/g. Further, it discloses that the thermoplastic resin composition having a extremely large ductility can be obtained.
Further, JP 7-157627A discloses a thermoplastic resin composition containing a propylene-ethylene block copolymer obtained by multistage polymerization and a polyolefin rubber. As the propylene-ethylene block copolymer, there is used a propylene-ethylene block copolymer wherein the intrinsic viscosity of a propylene-ethylene random copolymer phase is from 4.0 to 8.0 dl/g, and the propylene-ethylene block copolymer has an intrinsic viscosity of from not less than 2.0 to less than 4.0 dl/g excluding the propylene-ethylene block copolymer of JP 7-157626A. Further, it also discloses that the thermoplastic resin composition having a extremely large ductility can be obtained.
Moreover, JP 7-233305A discloses a polypropylene resin composition improved in flowability, containing a polypropylene, an inorganic filler, and a metallic soap composed of a fatty acid composed of 15 to 20 carbon atoms and zinc, and having an improved melt index. As the polypropylene, a block copolymer containing a propylene-ethylene copolymer portion having an [&eegr;] of 2 to 6 dl/g and that of 7 to 15 dl/g. As the preferred embodiment, it discloses the composition containing at least two kinds of block copolymers. And, it discloses that there can be obtained a polypropylene resin composition having, in practical use, no problem of reduction of impact strength, rigidity, heat resistance, and the like, being suitable for manufacturing a thin-walled molded article because of its improved flowability, and less causing to discolor into yellow or pink due to pelletizing, and to bleed on the surface of a mold and an injection molded article.
Incidentally, in recent years, a propylene-ethylene block copolymer, which is preferably used because of its excellent rigidity, impact resistance, and the like, has become manufactured by a continuous gas phase process whereby the manufacturing step is simple, and manufacturing can be performed at a low cost. However, in general, the propylene-ethylene block copolymer manufactured by the gas phase process has the following problems. That is, if the intrinsic viscosity of the propylene-ethylene random copolymer portion is set high, granular structures generate whereby appearance of a molded article becomes poor.
As a method for solving such a problem of the appearance, for example, in JP 7-286075A discloses a propylene polymer composition which comprises a propylene polymer manufactured by a continuous polymerization method, wherein the propylene polymer has a content of a 23° C. n-decane soluble component of from 0 to less than 15% by weight, the 23° C. n-decane soluble component contains a structural unit derived from ethylene in an amount of from 30 to 60 mol % and has an intrinsic viscosity [&eegr;] of from 3 to 7.5 dl/g, and a propylene block copolymer produced by a batch-wise or continuous solvent polymerization method, wherein the propylene block copolymer has a content of a 23° C. n-decane soluble component of from 15 to 40% by weight, the 23° C. n-decane soluble component contains a structural unit derived from ethylene in an amount of from 30 to 60 mol %, and has an intrinsic viscosity [&eegr;] of from 5 to 12 dl/g. It also discloses that the propylene polymer composition is obtainable that is excellent in rigidity and impact resistance, and is capable of being formed into a molded article without generating granular structures on its surface.
However, there has been desired a development of a polypropylene resin composition hardly generating flow marks on its surface when formed into a molded article, in other words, being more excellent in appearance than ever, and having no problem in practical use even when it generates granular structures.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a polypropylene resin composition providing a molded article excellent in appearance when formed into a molded article because flow marks hardly generate, in other wards, a die swell is high and few fish eyes generate.
Further, another object of the present invention is to provide a molded article made of the polypropylene resin composition.
In view of the present situation, the present inventors have intensively studied, and as a result, they have found that a polypropylene resin composition obtained by using two kinds of specific propylene-ethylene block copolymers which are mutually different in structure, can solve the foregoing problems. Thus, they have completed the present invention.
That is, the present invention relates to a polypropylene resin composition comprising:
95 to 50% by weight of a propylene homopolymer (A) having an intrinsic viscosity [&eegr;]
A
of not more than 1.3 dl/g; and
5 to 50% by weight of a propylene-ethylene block copolymer (B) having a propylene homopolymer portion having an intrinsic viscosity [&eegr;]
B
P
of from 1.4 to 2.0 dl/g, and a propylene-ethylene random copolymer portion having an intrinsic viscosity [&eegr;]
B
EP
of from 4.0 to 15 dl/g, wherein the polypropylene resin composition has a melt flow rate (MFR) of from 5.0 to 150 g/10 min. and the sum of the (A) and (B) is 100% by weight.
The present invention will be described in detail below.
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, one ore more kinds of propylene homopolymers may be used.
The intrinsic viscosity [&eegr;]
A
of the propylene homopolymer (A) is not more than 1.3 dl/g, preferably 0.7 to 1.3 dl/g. When the intrinsic viscosity [&eegr;]
A
exceeds 1.3 dl/g, the melt flow rate (MFR) of the polyolefin resin composition may be reduced, resulting in a reduction in flowability.
The isotactic pentad fraction of the propylene homopolymer (A), calculated by
13
C-NMR is preferably not less than 0.95, more preferably not less than 0.97 from the viewpoints of rigidity, heat resistance, and the like.
The molecular weight distribution (Q value) of the propylene homopolymer (A) is preferably from 3 to 6 from the viewpoint of the flowability and the balance between impact resistance and rigidity.
The propylene-ethylene bl
Atarashi Kenji
Kanzaki Susumu
Tsuji Mitsuji
Nutter Nathan M.
Sughrue & Mion, PLLC
Sumitomo Chemical Company Limited
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