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
2003-02-11
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
06518363
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polypropylene resin composition containing two kinds of specified propylene-ethylene block copolymers having mutually different structures. More particularly, it relates to a polypropylene resin composition providing a molded article excellent in appearance when formed into a molded article because few flow marks are generated. For example, the die swell is high and few fish eyes are generated. Further, the present invention relates 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 widely 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 07-157626A discloses a thermoplastic resin composition containing a propylene-ethylene block copolymer obtained by multi-stage polymerization and a polyolefin rubber. The propylene-ethylene block copolymer is composed of a propylene-ethylene block copolymer in which the ethylene content of a propylene-ethylene random copolymer phase is from 5 to 50% by weight and the intrinsic viscosity of the copolymer phase is from 4.0 to 8.0 dl/g, and a propylene-ethylene block copolymer in which the ethylene content of a propylene-ethylene random copolymer phase is more than 50% by weight to 98% by weight and an intrinsic viscosity of the copolymer phase is 2.0 to less than 4.0 dl/g. Further, it is disclosed that the thermoplastic resin composition having an extremely large ductility can be obtained.
JP 07-157627A discloses a thermoplastic resin composition containing a propylene-ethylene block copolymer obtained by multistage polymerization and a polyolefin rubber. The propylene-ethylene block copolymer is composed of a propylene-ethylene block copolymer in which the intrinsic viscosity of a propylene-ethylene random copolymer phase is from 4.0 to 8.0 dl/g, and a propylene-ethylene block copolymer in which the intrinsic viscosity of a propylene-ethylene random copolymer phase is 2.0 to less than 4.0 dl/g excluding the propylene-ethylene block copolymer of JP 07-157626A. Further, it also discloses that the thermoplastic resin composition having a extremely large ductility can be obtained.
Moreover, JP 07-233305A discloses a polypropylene resin composition improved in flowability, containing a polypropylene, an inorganic filler, and a metallic soap composed of a fatty acid of 15 to 20 carbon atoms and zinc, and having an improved flowability. As the polypropylene, a block copolymer containing a propylene-ethylene copolymer portion having an [&eegr;] of 2 to 6 dl/g and having an [&eegr;] of 7 to 15 dl/g is disclosed. As the preferred embodiment, it discloses the composition composed of 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, and being suitable for manufacturing a thin-walled molded article because of its improved flowability.
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. If the intrinsic viscosity of the propylene-ethylene random copolymer portion is set high, granular structures generate, whereby the appearance of the molded article becomes poor.
As a method for solving such a problem of the appearance, for example, JP 07-286075A 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, it has been desired to develop a polypropylene resin composition without generating flow marks on its surface when formed into a molded article. In other words, it is desired to improve appearance, and ensure practical use even when granular structures are generated.
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, i.e., having few flow marks. In other words, die swell is high and few fish eyes are generated.
Further, another object of the present invention is to provide a molded article made of a polypropylene resin composition.
In view of the present situation, the present inventors as a result of intensive study, 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.
Namely, the present invention relates to a polypropylene resin composition comprising:
(A) 95 to 80% by weight of a polypropylene resin selected from the group consisting of a propylene-ethylene block copolymer (i) having a propylene homopolymer portion and propylene-ethylene random copolymer portion, and (ii) a mixture of the propylene-ethylene block copolymer (i) and a propylene homopolymer, wherein an intrinsic viscosity [&eegr;]
A
P
of the propylene homopolymer portion when the resin (A) is the copolymer (i), or of the total of the propylene homopolymer portion and the propylene homopolymer when the resin (A) is the mixture (ii) is not more than 1.3 dl/g, and an intrinsic viscosity [&eegr;]
A
EP
of the propylene-ethylene random copolymer portion is not more than 3.0 dl/g; and
(B) 5 to 20% by weight of a propylene-ethylene block copolymer composed of a propylene homopolymer portion and propylene-ethylene random copolymer portion wherein an intrinsic viscosity [&eegr;]
B
EP
of the propylene-ethylene random copolymer is 8.0 to 15 dl/g, and 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.
Below, the present invention will be described in detail.
DETAILED DESCRIPTION OF THE INVENTION
The propylene-ethylene block copolymer (i) used in the present invention is a propylene-ethylene block copolymer having a propylene homopolymer portion (hereinafter, sometimes referred to as “first segment of the copolymer (i)”), and a propylene-ethylene random copolymer portion (hereinafter,
Kanzaki Susumu
Shimojo Moriyasu
Tsuji Mitsuji
Nutter Nathan M.
Sumitomo Chemical Company Limited
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